F l o r i a n P E T R E S C U\’ s B o o k s S t o r eThe Design of Gearings with High EfficiencyISBN 978-1-4467-9054-0A Short Book Description: Development and diversification of machines and mechanisms with applications in all areas of scientific research requires new systematization and improvement of existing mechanical systems by creating new mechanisms adapted to the modern requirements, which involve more complex topological structures. Modern industry, the practice of engineering design and manufacture increasingly rely more on scientific research results and practical. The processes

via The Efficiency of Gearings – THE DESIGN OF GEARINGS WITH HIGH EFFICIENCY.

 


F l o r i a n   P E T R E S C U’ s   B o o k s   S t o r e

The Design of Gearings with High Efficiency

ISBN 978-1-4467-9054-0


A Short Book Description:

Development and diversification of machines and mechanisms with applications in all areas of scientific research requires new systematization and improvement of existing mechanical systems by creating new mechanisms adapted to the modern requirements, which involve more complex topological structures. Modern industry, the practice of engineering design and manufacture increasingly rely more on scientific research results and practical.

The processes of robotisation of today define and influence the emergence of new industries, with applications in specific environmental conditions, handling of objects in outer space, and are leading teleoperator in disciplines such as medicine, automations, nuclear energetic, etc.

In this context this paper attempts to bring a contribution to science and technology applied in the kinematic and dynamic analysis and synthesis of mechanisms with gearings.

The book presents an original method to determine the efficiency of the gear. The originality of this method relies on the eliminated friction modulus. The work is analyzing the influence of a few parameters concerning gear efficiency. These parameters are: z1 – the number of teeth for the primary wheel of gear; z2 – the number of teeth of the secondary wheel of gear; ?0 – the normal pressure angle on the divided circle; ? – the inclination angle. With the relations presented in this paper, one can synthesize the gear’s mechanisms.

We begin with the right teeth (the toothed gear), with i=-4, once for z1 we shall take successively different values, rising from 8 teeth. One can see that for 8 teeth of the driving wheel the standard pressure angle, ?0=200, is too small to be used (it obtains a minimum pressure angle, ?m, negative and this fact is not admitted; see the first table). In the second table we shall diminish (in module) the value for the ratio of transmission, i, from 4 to 2. We will see how for a lower value of the number of teeth of the wheel 1, the standard pressure angle (a0=200) is too small and it will be necessary to increase it to a minimum value. For example, if z1=8, the necessary minimum value is a0=290 for an i=-4 (see the table 1) and a0=280 for an i=-2 (see the table 2). If z1=10, the necessary minimum pressure angle is a0=260 for i=-4 (see the table 1) and a0=250 for i=-2 (see the table 2). When the number of teeth of the wheel 1 increases, we can decrease the normal pressure angle, a0. We will see that for z1=90 it can take a less value for the normal pressure angle (for the pressure angle of reference), a0=80. In the table 3 we increases the module of i value (the ratio of transmission), from 2 to 6.

In the table 4, the teeth are bended (b?0). The module i takes now the value 2.

The efficiency (of the gear) increases when the number of teeth for the driving wheel 1, z1, increases, and when the pressure angle, ?0, diminishes; z2 and i12 have not so much influence about the efficiency value.

We can easily see that for the value ?0=200, the efficiency takes roughly the value ??0.89 for any values of the others parameters (this justifies the choice of this value, ?0=200, for the standard pressure angle of reference).

But the better efficiency may be obtained only for a ?0?200 (?0<200).

The pressure angle of reference, ?0, can be decreased, when in the same time, the number of teeth for the driving wheel 1, z1, increases, to increase the gears’ efficiency.

Contrary, when we desire to create a gear with a low z1 (for a less gauge), it will be necessary to increase the ?0 value, for maintaining a positive value for ?m (in this case the gear efficiency will be diminished).

When ? increases, the efficiency (?) increases too, but its growth is insignificant. We can see in the last part of the work, that in reality it (? increases) produces a decrease in yield.

The module of the gear, m, has not any influence on the gear’s efficiency value.

When ?0 is diminished one can take a higher normal module, for increasing the addendum of teeth, but the increase of the m at the same time with the increase of the z1 can lead to a greater gauge.

The gears’ efficiency (?) is really a function of ?0 and z1: ?=f(?0,z1); the two angles (?m and ?M) are just the intermediate parameters (intermediate variables).

For a good projection of the gear, it’s necessary a z1 and a z2 greater than 30-60; but this condition may increase the gauge of mechanism; when the numbers of teeth z1 and z2 beyond the 30 value, the efficiency of the gearing are greater, and the values of the two different efficiencies leveled; this can be a great advantage in transmissions, especially in planetary transmissions, where the moments may come from both directions; will result a better and more equilibrated functionality (But these are the subject of a future work).

In the second (and last) part the book presents shortly an original method to obtain the efficiency of the geared transmissions in function of the contact ratio. With the presented relations one can make the dynamic synthesis of the geared transmissions having in view increasing the efficiency of gearing mechanisms in work (the accuracy of calculations will be high).

One calculates the efficiency of a geared transmission, having in view the fact that at one moment there are several couples of teeth in contact, and not just one.

The start model has got four pairs of teeth in contact (4 couples) concomitantly.

The first couple of teeth in contact has the contact point i, defined by the ray ri1, and the pressure angle ai1; the forces which act at this point are: the motor force Fmi, perpendicular to the position vector ri1 at i and the force transmitted from the wheel 1 to the wheel 2 through the point i, Fti, parallel to the path of action and with the sense from the wheel 1 to the wheel 2, the transmitted force being practically the projection of the motor force on the path of action; the defined velocities are similar to the forces (having in view the original kinematics, or the precise kinematics adopted); the same parameters will be defined for the next three points of contact, j, k, l (see fig. 2).

The best efficiency can be obtained with the internal gearing when the drive wheel 1 is the ring; the minimum efficiency will be obtained when the drive wheel 1 of the internal gearing has external teeth. For the external gearing, the best efficiency is obtained when the bigger wheel is the drive wheel; when one decreases the normal angle a0, the contact ratio increases and the efficiency increases as well. The efficiency increases too, when the number of teeth of the drive wheel 1 increases (when z1 increases).

Generally we use gearings with teeth inclined (with bended teeth). For gears with bended teeth, the calculations show a decrease in yield when the inclination angle increases. For angles with inclination which not exceed 25 degree the efficiency of gearing is good (see the table 6). When the inclination angle (?) exceeds 25 degrees the gearing will suffer a significant drop in yield (see the tables 7 and 8).

The calculation relationships (33-35) are general (Have a general nature). They have the advantage that can be used with great precision in determining the efficiency of any type of gearings.

1 Introduction

In this paper the authors present an original method to calculating the efficiency of the gear.

The originality consists in the way of determination of the gear’s efficiency because one hasn’t used the friction forces of couple (this new way eliminates the classical method). One eliminates the necessity of determining the friction coefficients by different experimental methods as well. The efficiency determined by the new method is the same like the classical efficiency, namely the mechanical efficiency of the gear.

Some mechanisms work by pulses and are transmitting the movement from an element to another by pulses and not by friction. Gears work practically only by pulses. The component of slip or friction is practically the loss. Because of this the mechanical efficacy becomes practically the mechanical efficiency of gear.

The paper is analyzing the influence of a few parameters concerning gear efficiency. With the relations presented in this paper, one can synthesize the gear’s mechanisms. Today, the gears are present every where in the mechanical’s world.


 

Author: Florian Ion TIBERIU-PETRESCU Company: UPB POLYTECHNIC UNIVERSITY OF BUCHAREST TMR Department Residence: BUCHAREST – ROMANIA – EUROPE Websites:

dynamics.ro expertdyna Cars

Memorable Quote 1: Drivetrain Expert (Gear And Gearing Expert) Memorable Quote 2: Otto Engines Expert (Powertrain Expert)

 

 

Florian Ion PETRESCU\’s Books and Publications Spotlight.

 

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First Book:

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THE DESIGN OF GEARINGS WITH HIGH EFFICIENCY

Development and diversification of machines and mechanisms with applications in all areas of scientific research requires new systematization and improvement of existing mechanical systems by creating new mechanisms adapted to the modern requirements; the gearing mechanisms are found today everywhere: in the industry of machinery construction, in energy industry, in aeronautics and aerospace, in electronics& Electrical, in oil industry, in mechatronics and robotics, etc. In this context this book attempts to bring a contribution to science and technology applied in the kinematic and dynamic analysis and synthesis of mechanisms with gearings. The book presents an original method to determine the efficiency of the gearing; the originality of this method relies on the eliminated friction modulus. With the relations presented in this paper, one can synthesize the gear’s mechanisms; the best efficiency can be obtained with the internal gearing when the drive wheel 1 is the ring.

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Gear Expert

January 15, 2011

Gear Expert.

 

 

© 2010 Florian Ion PETRESCU and Relly Victoria PETRESCU – Gears Design

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Gears

 

 

 

V Engines Design

January 15, 2011

V Engines Design.

 

V Engines

Otto’s Engines

V Engines Design

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V Engine Design

ABSTRACT:

V engines in a characteristic aside, their reply kinematics-dynamic (operating in a dynamic viewpoint) is closely linked to constructive parameters of the engine, especially the constructive angle. For this reason, as generally constructive value angle was chosen randomly, after various technical requirements constructive or otherwise, inherited or calculated by various factors (more or less essential), but never got to discuss crucial factor (which takes account of the intimate physiology of the mechanism) angle that is constructive with his immediate influence on the overall dynamics of the mechanism, the actual dynamics of the mechanism with the main engine in the V suffered, the noise and vibration are generally higher compared with the similar engines in line. This paper aims to make a major contribution to remedy this problem so that the engine in V can be optimally designed and its dynamic behavior in the operation to become blameless, higher than that of similar engines in line. Theoretical calculations are difficult and complex, but the alteration constructive required of them is simple, consisting of the imposition of a list of constructive values of the angle alpha from which you can select the most convenient for each engine builder in V.

 

  1. INTRODUCTION

Kinematics and dynamic synthesis of V engines can be done according to the constructive alpha angle (a). This constructive angle alpha (see Figure 1) was elected in generally follow different criteria or design requirements (it is determined by the number of cylinders and the condition for obtaining the ignitions uniformly distributed). This work proposes aggregating this angle after rigorous kinematics-dynamic criteria, so that the V engine obtained works silently, with vibration and noise much lower. It is even mainly disadvantage of a motor in V namely that it works with higher vibrations compared with a same power engine in line [1, 6-12].

The authors have studied this works for several years together with a collective joint research (UPB-Autobuzul plant) and dynamic behavior of the V engines [6-8], the level of vibration and noise produced, the level of vibration transmitted inside the vehicle, the possibility of limiting them through various solutions of gripping and containment of the engine. Results were good but not very good. After similar measurements done on other types of engines it was decided the use of engines in line, much quieter than the V. Meanwhile engines have improved but also international standards that limit vibration and noise levels have become more demanding. The engine in V has many fans, it is more compact, more dynamic, more robust, stronger, and higher operating efficiency compared to similar engines in line. But its fans are not only racing fans, motor and habit, there are a wide audience of consumers who want only cars equipped with nerve in V. As to conciliate them well and those who make rules to limit emissions of cars, it was thought that paper aims to provide an equitable solution regarding engines in V.

 

 

 

 

 

 

 

 

 












Fig. 1


  1. THE BASIC IDEA

After decades of work in the mechanisms and machinery field, through experience, I noticed an interesting fact. At the engines in line forces and velocities transmission is normal from the driver (motor) shaft (from the crank shaft) to the pistons (through the rods), and vive versa (in the engine times). The engine in V transmission forces and velocities between elements is forced and unequal regardless of the meaning of transmission (from crank to pistons or from pistons to crank). Dynamics imposed to the main piston is one, and the secondary piston is required other, so that dynamic speeds (actual speeds required) differ, and with them and pistons to crank feedback (to crank shaft), as each would require another main shaft speed. If that’s a pair of pistons, for more pairs of pistons jerk resultant operation will be more and more powerful. Obvious solution is to optimize the dynamic of each pair of pistons in hand. This optimization was based on dynamic coefficients of each piston. Dynamic coefficient of a piston showing the actual crank angular velocity varies compared to required average angular velocity imposed by the motor shaft rotation speed. This variation [3, 4] is due to several factors, kinematics and dynamic, being itself a function and of engine constructive parameters.

The usual mechanisms have a single dynamic factor (coefficient), as is the case and in-line engines.

At the engine in V appear two dynamic factors imposed to the crank (and to the crank shaft) by the two pistons linked together (secondary piston rod link to the main piston rod; see the figure 1). The two dynamic factors differ among themselves and changes their values permanently depending on the crank angle position (crank shaft position).

This indicates that each piston (the primary and secondary) tries to impose its dynamic to the main shaft, so that the end result is an operation to struggle, since the two sets of pistons shoot one at one side and the other somewhere else.

The possible solution (unique solution) is matching the two dynamic factors. More specifically to write a mathematical relationship to match the main piston (main engine) dynamic coefficient expression with that of the secondary piston (secondary motor) (Now you can see that engine in V is built of two engines merged, see the fig. 1). Relations that results are quite complicated [5].

Optimization based on obtained relationship can be made in several ways. The most natural seems to be the optimization parameters in view of the engine builders of the V, particularly based on constructive angle alpha, which appears twice in the cinematic scheme of an engine in V: first he is mounting angle formed by the two axes of the two pistons coupled (angle formed by the axis of the main piston guide axis with the secondary piston guide axis); and the second time this item (constructive angle) appears on the element 2 (the rod of the main piston) between the two arms of the element 2 (AB and AC).

  1. SYNTHESIS OF THE ENGINE IN V

3.1. Presentation

In figure 1 is shown a V engine cinematic scheme.

The crank 1 rotates counterclockwise sense with angular velocity w and acts the rod 2 which moves the main piston 3 along the axis DB; the crank 1 acts and the rod 4 which in turn push or pull the piston 5 along the axis DD. Hence the constructive angle a between the two axes DB and DD. The same angle a consists of two arms of the rods 2; the first arm has a length l, and the second has the length a; this length a, plus the length b of the rods 4 must recompose the length of the first rods, l (a+b=l).

Driving force of the crank Fm is perpendicular to the crank arm r, in A. A part of it (FBm) is transmitted to the first arm of the connecting rods 2 (along l) towards the main piston 3. The second part of the driving force (FCm) is forwarded to the secondary piston 5, by the second arm of the first rod (along a).

3.2. Forces and velocities

A part x of the drive force Fm is transmitted towards the first piston (the element 3) and another part of it y is forwarded through the second piston (the element 5); sum of two parts x and y is 1 or 100% taken as a percentage.

The dynamic velocities have the same direction with forces [3-5], unlike the kinematic velocities imposed by the coupling links.

From the element 2 (the first arm of the first rod) forwarded through the main piston (the element 3) the force FB and the velocity vBD.

The kinematic velocity (imposed by linkages) of the point B has the known value vB [5], generally different from the dynamic value vBD. To force the main piston has a velocity equal to the dynamic (the real velocity) incorporate the dynamic coefficient DB, (DB=x.cos2β with vBD=DB.vB), so the dynamic speed is equal to the product between the cinematic velocity and dynamic coefficient DB.

The driving velocity (with the same direction as the driving force and the same sense with this) is given by the relation (vm=r.w).

In C, FCm and vCm are projected in FCn and vCn. They in turn are projected in D (on the DD axis) in the components FD and vD (dynamic velocity of the second piston). The cinematic (classic) velocity has another expression, D. Now one introduces the second dynamic coefficient (from the second piston), DD [5], (where vD=DD.D).

3.3. Determination of the dynamic coefficient D

The mechanism dynamic coefficient D is imposed to all gear and influences its function varying the crank rotation speed (the crank shaft rotation velocity). Any mechanism must take practical only one dynamic factor, D.

To the engines in V the real dynamic coefficient is the result of a random momentary compromise between the two different dynamic coefficients imposed by the two pistons. For this reason the overall functioning of the V engine loud. The ideal solution (right) is obviously bringing the two dynamic factors to around or possibly even equal values. To this end were the two dynamic factors matched, to see what solutions exist to solve the obtained equation ina. The obtained expression is complex and has many variables (the various builder parameters of the engine in V). It sought an analytical synthesis using a complex computer program, by finding of the system alpha general solutions, regardless of the values of others constructive parameters, so that dynamic factors present equal values, and the engine so constructed to operate high efficiency without shocks and vibrations, without noise and with reduced noxious emissions, achieved with high power and lower fuel consumption. The cinematic chain composed of crankshaft, two pistons and two rods should function normally.


 

Fig. 2







Fig. 3 Fig. 4

  1. DYNAMIC ANALYSIS

Analysis of dynamic system revealed a range of values for angle alpha that the theory exposed are likely to lead to the synthesis of V-optimal engine (see the table 1) [5].

For some constructive parameters randomly taken (r=0.01 [m], l=0.1 [m], a=0.03 [m], b=0.07 [m]) and for a chosen speed of motor shaft (n=5000 [r/m]), it obtains three different diagrams for the displacement and acceleration of the pistons, corresponding to three alpha angles chosen randomly (50, 750 and 950), (see the figures 2-4).

Value of five degrees are at the beach of values indicated as appropriate, so that acceleration peaks hardly exceed the value of 1000 [m/s2] to both pistons (see the figure 2).

Diagrams in figures 3 and 4 are somewhat similar (but not identical) and present relevant cases also, even if the acceleration peaks have increased at about 3500 [m/s2] for the secondary piston and approximately 30,000 [m/s2] for the main piston. The angles of 75 and 95 degrees can also be used (at least for the indicated constructive parameters), to take into account and ignition requirements uniformly distributed.

A V-engine which reaching local at the primary piston a peak of acceleration of 30000 [m/s2] to a motor shaft speed of 5000 [r/m] (it comes only a local impact) will work similar to engines in line but the power and efficiency higher.

However the use for alpha of constructive values shown in the table 1 may lead to the construction of a V engine quieter than the one in line.

 

 

 

 

 

 

 

 

 

Fig. 5

  1. CONCLUSIONS

SPECIFICATIONS: Acceleration diagrams presented were constructed based on an original method; they are the result of complex calculations with dynamic accelerations and dynamic coefficients which contain the vibrations and pulses; the relationships of calculation can not present classical accelerations known!

A-When shocks are very small, diagrams show even the accelerations.

b-When the shocks are visible the diagrams show the accelerations and their peaks.

c-When the shocks are large or very large, the diagrams will present only the shocks; in this case the accelerations overlapping shocks; accelerations are lower than the shocks and no longer can see (these cases but would not be desirable).

With the values in the table of constructive angle alpha can synthesize a quieter engine in V, regardless of the values of other constructive parameters of the engine.

A first observation arising from reading the values indicated for optimal alpha angle from the table, is that the values close to 90 degrees aren’t present, and in general for these values design software looks a worse dynamics of engine in V. But that these values are used specifically to build engines in V, values determined by the number of cylinders and the condition for obtaining the ignitions uniformly distributed.

For the alpha values who do not appear in table, the built engine works with very large shocks which very difficult can be isolated even with the most modern rubber pads so that vibrations are felt in the vehicle interior, bringing with them uncomfortable and insecure amplified and by the unnatural noises produced by shock.

An important observation would be that today are used “new cinematic schemas of engines in V” (see the figure 5) which to eliminate the vibrations have a single piston mounted on a spindle maneton and have inclined the axes first to right the second to left to give the appearance of the engine in V. It’s a pseudo-engine in V and the added efficiency disappears. The cylinders capacity should be increased to mimic the engine power in V, but also increases fuel consumption.

In this way, and the cylinders in line can be considered an engine in V with alpha of 0 degrees and boxer cylinders may be considered a V engine with alpha of 180 degrees.

REFERENCES

[1] GRUNWALD B., Teoria, calculul şi construcţia motoarelor pentru autovehicule rutiere. Editura didacticã şi pedagogică, Bucureşti, 1980.

[2] Petrescu, F.I., Petrescu, R.V., Câteva elemente privind îmbunătăţirea designului mecanismului motor, Proceedings of 8th National Symposium on GTD, Vol. I, p. 353-358, Brasov, 2003.

[3] Petrescu, F.I., Petrescu, R.V., An original internal combustion engine, Proceedings of 9th International Symposium SYROM, Vol. I, p. 135-140, Bucharest, 2005.

[4] Petrescu, F.I., Petrescu, R.V., Determining the mechanical efficiency of Otto engine’s mechanism, Proceedings of International Symposium, SYROM 2005, Vol. I, p. 141-146, Bucharest, 2005.

[5] Petrescu, F.I., Petrescu, R.V., V Engine Design, Proceedings of International Conference on Engineering Graphics and Design, ICGD 2009, Cluj-Napoca, 2009.


[6]. FRĂŢILĂ, Gh., SOTIR, D., PETRESCU, F., PETRESCU, V., ş.a. Cercetări privind transmisibilitatea vibraţiilor motorului la cadrul şi caroseria automobilului. În a IV-a Conferinţă de Motoare, Automobile, Tractoare şi Maşini Agricole, CONAT-matma, Braşov, 1982, Vol. I, p. 379-388.

[7]. MARINCAŞ, D., SOTIR, D., PETRESCU, F., PETRESCU, V., ş.a. Rezultate experimentale privind îmbunătăţirea izolaţiei fonice a cabinei autoutilitarei TV-14. În a IV-a Conferinţă de Motoare, Automobile, Tractoare şi Maşini Agricole, CONAT-matma, Braşov, 1982, Vol. I, p. 389-398.

[8]. FRĂŢILĂ, Gh., MARINCAŞ, D., BEJAN, N., FRĂŢILĂ, M., PETRESCU, F., PETRESCU, R., RĂDULESCU, I. Contributions a l’amelioration de la suspension du groupe moteur-transmission. În buletinul Universităţii din Braşov, Seria A, Mecanică aplicată, Vol. XXVIII, 1986, p. 117-123.

[9]. Fjoseph L. Stout – Ford Motor Co., I. Engine Excitation Decomposition Methods and V Engine Results. In SAE 2001 Noise & Vibration Conference & Exposition, USA, 2001-01-1595, April 2001.

[10]. D. Taraza, “Accuracy Limits of IMEP Determination from Crankshaft Speed Measurements,” SAE Transactions, Journal of Engines 111, 689-697, 2002.

[11]. FROELUND, K., S.G. FRITZ, and B. SMITH., Ranking Lubricating Oil Consumption of Different Power Assemblies on an EMD 16-645E Locomotive Diesel Engine. Presented at and published in the Proceedings of the 2004 CIMAC Conference, Kyoto, Japan, June 2004.

[12]. Leet, J.A., S. Simescu, K. Froelund, L.G. Dodge, and C.E. Roberts Jr., Emissions Solutions for 2007 and 2010 Heavy-Duty Diesel Engines. Presented at the SAE World Congress and Exhibition, Detroit, Michigan, March 2004. SAE Paper No. 2004-01-0124 , 2004.

Authors:

Florian Ion Petrescu, PhD. Eng. Lecturer at Polytechnic University of Bucharest, TMR Department (Theory of Mechanisms and Robots Department), petrescuflorian@yahoo.com, 0214029632;

Relly Victoria Petrescu, PhD. Eng., Lecturer at Polytechnic University of Bucharest, GDGI Department (Department of Descriptive Geometry and Engineering Graphics), petrescurelly@yahoo.com, 0214029136.

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Otto Engine Design

Cams Dynamics

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Thesis: Contribuţii teoretice şi aplicative privind dinamica mecanismelor plane cu cuple superioare – Florian Ion Tiberiu-Petrescu.

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Contribuţii teoretice şi aplicative privind dinamica mecanismelor plane cu cuple superioare
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Florian Ion Tiberiu-Petrescu, Universitatea “Politehnica”, Bucureşti, 2008
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Tema tezei de doctorat este deosebit de importantă, utilă şi interesantă pentru că abordează o problematică complexă de mare actualitate privind dinamica mecanismelor plane cu came, tacheţi şi angrenaje cu roţi dinţate cu axe paralele. Cercetările s-au efectuat pe baza unei vaste bibliografii, care cuprinde cele mai reprezentative lucrări în acest domeniu.
Conţinutul tezei se ridică la cele mai mari exigenţe impuse unei lucrări de doctorat şi are un înalt nivel ştiinţific. Rezultatele obţinute au fost interpretate corect şi au fost valorificate prin publicarea mai multor lucrări ştiinţifice în străinătate şi în ţară, lucrări ce se bucură de aprecierea specialiştilor din construcţia de maşini.
Teza conţine foarte multe elemente de originalitate ca: rezolvarea ecuaţiei diferenţiale a mişcării, modelul dinamic de integrare, analiza dinamică a mecanismului clasic de distribuţie, dinamica mecanismelor de distribuţie cu tachet translant, respectiv balansier, cu rolă sau plat, calculul randamentului mecanic al cuplei tachet-camă printr-o metodă absolut originală, determinarea randamentului angrenajelor cu roţi dinţate cu axe paralele, randamentul instantaneu, randamentul mediu, calculul angrenajelor interioare, determinarea randamentului angrenajelor ţinând seama de gradul de acoperire, sinteza angrenajelor cu roţi dinţate cu axe paralele pe baza randamentului în funcţionare, etc.
Concluziile la care a ajuns autorul sunt foarte importante atât din punct de vedere teoretic cât şi practic; astfel a stabilit că: tachetul cu rolă permite o mărire a turaţiei motorului până la o valoare dublă faţă de modelul clasic (cu tachet plat), angrenajele cu roţi dinţate pot lucra la turaţii şi momente de torsiune ridicate cu randamente mecanice foarte mari, randamentul cel mai mare se întâlneşte la angrenajele interioare cu roata (inel) având dantură interioară conducătoare, iar la angrenajele cu dantură exterioară randamentul este mai mare când roata mare este conducătoare; cu cât unghiul normal de angrenare scade, creşte gradul de acoperire şi odată cu el şi randamentul angrenării; randamentul mai creşte şi odată cu numărul de dinţi ai roţii conducătoare, etc.
Prin problematica abordată, teza de doctorat a dl. ing. Florian Ion PETRESCU, sub conducerea ştiinţifică a prof. dr. ing. Păun ANTONESCU, se înscrie în contextul sistematizării şi perfecţionării sistemelor mecanice existente, prin crearea de noi mecanisme adaptate cerinţelor moderne, ceea ce implică structuri topologice tot mai complexe.
Scopul lucrării este de a construi modele noi teoretice şi aplicative în analiza şi sinteza dinamică a mecanismelor cu came şi roţi dinţate plane. Teza de doctorat este structurată în trei părţi: prima parte prezintă dinamica mecanismelor plane cu came, tacheţi şi supape, partea a doua prezintă dinamica mecanismelor plane formate din angrenaje cu roţi dinţate cu axe paralele, iar partea a treia conţine concluzii şi enumerarea contribuţiilor originale, cât şi anexe. Bibliografia este ataşată fiecărei părţi. 

Din prezentarea făcută se constată o multitudine de rezultate originale valoroase obţinute de dl. ing. Florian Ion PETRESCU.

Menţionăm câteva din aceste contribuţii:
Partea I-a:
1. Un model dinamic monomasic (cu un singur grad de libertate), translant, cu amortizare internă variabilă. Se determină amortizarea internă a sistemului şi ecuaţiile de mişcare.
2. Cinematica de precizie a mecanismelor de distribuţie, exemplificată pe mecanismul clasic cu camă rotativă şi tachet plat translant, bazată pe un model original de cinematică dinamică. Se determină exact randamentul mecanic, care nu are nici o legătură cu pierderile suplimentare prin frecare (se elimină astfel necesitatea determinării coeficientului de frecare).
3. Un model nou de distribuţie a forţelor şi vitezelor la tachetul translant cu rolă. Se demonstrează performanţele în raport cu modelele clasice.
4. O metodă nouă de determinare a forţelor şi vitezelor la mecanismul cu camă rotativă şi tachet balansier cu rolă. Determinarea randamentului mecanismului.
5. Metode aproximative şi de integrare directă a ecuaţiilor de mişcare.

Partea a II-a:
6. Model nou în dinamica mecanismelor plane formate din angrenaje cu roţi dinţate cu axe paralele.
7. Determinarea randamentului unui angrenaj cu roţi dinţate cu axe paralele pentru dinţii drepţi, în funcţie şi de gradul de acoperire al angrenajului.

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Abstract

 

Relly & Florian PETRESCU : CONTRIBUTIONS TO THE ANALYSIS AND SYNTHESIS OF MECHANISMS WITH BARS AND GEARING | UniBook.

 

CONTRIBUTIONS TO THE ANALYSIS AND SYNTHESIS OF MECHANISMS WITH BARS AND GEARING

Relly & Florian PETRESCU

Short description

Development and diversification of machines and mechanisms with applications in all areas of scientific research requires new systematization and improvement of existing mechanical systems by creating new mechanisms adapted to the modern requirements, which involve more complex topological structures. Modern industry, the practice of engineering design and manufacture increasingly rely more on scientific research results and practical. The processes of robotization of today define and influence the emergence of new industries, with applications in specific environmental conditions, handling of objects in outer space, and are leading teleoperator in disciplines such as medicine, automations, nuclear energetic, etc. In this context this paper attempts to bring a contribution to science and technology applied in the kinematic analysis and synthesis geometro – kinematic of mechanisms with bars and gearing.

Author Bio

PhD. Eng. Relly Victoria PETRESCU, Senior Lecturer at UPB (Bucharest Polytechnic University), GDGI (Descriptive Geometry and Engineering Graphics) Department, Bucharest, ROMANIA, Europe; PhD. Eng. Florian Ion PETRESCU, Senior Lecturer at UPB (Bucharest Polytechnic University), TMR (Theory of Mechanisms and Robots) Department, Bucharest, ROMANIA, Europe.

http://www.unibook.com/Relly-%2526-Florian-PETRESCU/CONTRIBUTIONS-TO-THE-ANALYSIS-AND-SYNTHESIS-OF-MECHANISMS-WITH-BARS-AND-GEARING

http://www.unibook.com/Relly-%2526-Florian-PETRESCU/CONTRIBUTIONS-TO-THE-ANALYSIS-AND-SYNTHESIS-OF-MECHANISMS-WITH-BARS-AND-GEARING

 

http://www.unibook.com/Relly-%2526-Florian-PETRESCU/CONTRIBUTIONS-TO-THE-ANALYSIS-AND-SYNTHESIS-OF-MECHANISMS-WITH-BARS-AND-GEARING

http://www.unibook.com/Relly-%2526-Florian-PETRESCU/CONTRIBUTIONS-TO-THE-ANALYSIS-AND-SYNTHESIS-OF-MECHANISMS-WITH-BARS-AND-GEARING

 

 

 

Relly & Florian PETRESCU : CONTRIBUTIONS TO THE ANALYSIS AND SYNTHESIS OF MECHANISMS WITH BARS AND GEARING | UniBook.

 

CONTRIBUTIONS TO THE ANALYSIS AND SYNTHESIS OF MECHANISMS WITH BARS AND GEARING

Relly & Florian PETRESCU

Short description

Development and diversification of machines and mechanisms with applications in all areas of scientific research requires new systematization and improvement of existing mechanical systems by creating new mechanisms adapted to the modern requirements, which involve more complex topological structures. Modern industry, the practice of engineering design and manufacture increasingly rely more on scientific research results and practical. The processes of robotization of today define and influence the emergence of new industries, with applications in specific environmental conditions, handling of objects in outer space, and are leading teleoperator in disciplines such as medicine, automations, nuclear energetic, etc. In this context this paper attempts to bring a contribution to science and technology applied in the kinematic analysis and synthesis geometro – kinematic of mechanisms with bars and gearing.

Author Bio

PhD. Eng. Relly Victoria PETRESCU, Senior Lecturer at UPB (Bucharest Polytechnic University), GDGI (Descriptive Geometry and Engineering Graphics) Department, Bucharest, ROMANIA, Europe; PhD. Eng. Florian Ion PETRESCU, Senior Lecturer at UPB (Bucharest Polytechnic University), TMR (Theory of Mechanisms and Robots) Department, Bucharest, ROMANIA, Europe.

http://www.unibook.com/Relly-%2526-Florian-PETRESCU/CONTRIBUTIONS-TO-THE-ANALYSIS-AND-SYNTHESIS-OF-MECHANISMS-WITH-BARS-AND-GEARING

http://www.unibook.com/Relly-%2526-Florian-PETRESCU/CONTRIBUTIONS-TO-THE-ANALYSIS-AND-SYNTHESIS-OF-MECHANISMS-WITH-BARS-AND-GEARING

 

http://www.unibook.com/Relly-%2526-Florian-PETRESCU/CONTRIBUTIONS-TO-THE-ANALYSIS-AND-SYNTHESIS-OF-MECHANISMS-WITH-BARS-AND-GEARING

http://www.unibook.com/Relly-%2526-Florian-PETRESCU/CONTRIBUTIONS-TO-THE-ANALYSIS-AND-SYNTHESIS-OF-MECHANISMS-WITH-BARS-AND-GEARING

 

January 15, 2011

 

This paper is a scientific view, uniform, general, comprehensive and unbiased of the main problems posed by mechanical systems, mobile, serial and parallel. It gives an overview, followed by geometric and kinematic study of the serial and parallel structures. It continues with an introduction in the dynamics these systems. At the serial systems are studied both direct and indirect kinematics, while at the parallel systems is studied only indirect kinematics (this being more useful). Presentation is closely linked of the basic methods of calculating the matrix, which are introduced step by step for a easy understanding of the each sequence.The book is divided into 14 chapters, who have been based on our courses, prepared for our students of the next

via Florian & Relly Petrescu : Mechanical Systems, Serial and Parallel, in movement | UniBook.