Appointing the efficiency of the arrangement of moving the drive

BOGDAN ĩÓŁTOWSKI

University of Technology and Life Sciences

Summary

It is possible to characterize discussed energy losses with the help of mechanical efficiency of individual elements of the arrangement of moving the drive, as well as total efficiency of the arrangement of moving the drive.

Keywords: efficiency, coupled, gearbox, propeller shaft, main transmission gear 1. Introduction

Mechanical efficiency of machines is determined as the ratio of energy exploited in a machine to the energy supplied to this machine at the same time. Increasing efficiency is tantamount to reducing power consumption. Such aspirations require the highest efficiency of loss reduction. It is carried out through the selection of structural machines of the right characterization (parameters).

It is possible to raise efficiency by selecting working agreements, limiting periods of work in neutral gear, accumulation and recuperation of energy etc. [1,3,5,8].

A large number of factors affects the efficiency of a machine, for example the speed of the move and burdens. An increase in speed, i.e. with regard to the bung at a given amount of charge, causes efficiency reduction; however, the height of a burden, i.e. useful work, at given speed, leads to an increase in efficiency. Zero-dimensional efficiency takes into account the quantitative side of the issue of efficiency. It is expressed in the following manner:

(1) where:

Ș – mechanical efficiency, W_d – delivered work, W_o – useful work.

2. EFFICIENCY OF THE ARRANGEMENT OF MOVING THE DRIVE

A product of individual sub-assemblies determines: transmission gear, embankment with wrists and driving bridge [3,9]. Sailing across the stream of power through each of these mecha-nisms is reduced, which is caused by the appearance of stand-bys there:

η

=

η

⋅

η

⋅

η

⋅

η

W

Ș =

W

Friction clutch during normal operation of a motor vehicle works without skid, then it only loses energy coming from the turnover of the clutch in the centre of air inside the casing. A part of mechanical energy is exchanged for thermal energy. This loss is dependent on the rotation speed, and together with the height, speed rises. In this mechanism levelling speed while driving, another kind of loss (coupling) occurs; this process takes a long this time until a car reaches speed at which the equinox takes place of angle speed at the entry and at the exit. The clutch is a booster of speed, and it is characterized by the value of the torque accessing M1 and, at the exit, M2 and, for itself, equal to different values of angle speed at the entry Ȧ1 and at the exit Ȧ2:

M1 = M2 , Ȧ1  Ȧ2 (3)

Next, power at the entry N1 and at the N2 exit is calculated respectively:

(4) Hence, efficiency coupled:

(5)

While touching the car right away, levelling the angle speed Ȧ1 and Ȧ2 takes place and the ef-ficiency of the clutch increases linearly with increasing angle speed, achieving the unity at Ȧ1 = Ȧ2. The slide of the clutch is expressed, similarly to the slide of wheels, in a relative way [4]:

(6)

So, the efficiency of the clutch is a linear function of the relationship of the angle speed, as well as a linear function of the skid. The efficiency of the included clutch friction is calculated:

ηs = 0,998

Efficiency of the run box. In toothed gear transmissions the following factors decide about the value of energy loss: structural factors (the number of gears moving the drive, engaged pa-rameters, correlations, the number of rollers, the number and kinds of applied bearings and draughtproofings), motor factors (the angle speed of rollers and the moved torque) and tempera-ture, the amount and properties of spreadable oil included in the value of plumbing loss. Since these parameters in the process of vehicle move change, Șb efficiency of the run box also changes. Generally, the efficiency of run boxes is calculated in the following manner:

(7)

N1

= M

Ȧ1 ,

N2

= M

Ȧ2 ,

N

η

=

N

Ȧ

– Ȧ

Ss

=

= 1 -

_η

Ȧ

N

N

N

N

N

−

=

−

=

1

η

NS– engine power sent to the run box, NT – power lost in the run box.

Plumbing resistance in the gearbox is from 20% to 75% of total resistance and grows rapidly at great rotation speed. It depends largely on the amount and quality of the used oil. The influence of the amount of oil in four runs of a gearbox on the power amount lost is shown in fig. 1 [3].

Fig. 1 Dependence of the power lost in the gearbox on the amount of oil

Fig. 2. Influence of the viscosity of oil on the size of the moment of oppositions in a gearbox Temperature and viscosity of oil also enjoy considerable influence of power loss.

Reducing the viscosity of oil and increasing temperature cause a significant reduction of op-positions. For example, a rise in temperature of oil from around 30° to 70° C causes a triple reduc-tion of the moment of opposireduc-tion. Since the temperature of oil in the box is also dependent on the temperature of surroundings, it means that efficiency is lower in winter conditions [1].

However, an explicit analysis is hampered on the account of the fact that the viscosity of oil is adverse lying affected on one hand because of the plumbing friction, and on the other hand fa-vourably because enlarging thickness causes the layers of oil and provokes an exchange of semi fluid friction to fluid.

Fig. 3. Influence of the temperature of oil on the size of the moment of oppositions of the

gearbox

Fig. 4. Momentary Șb efficiency of the gearbox while dispersing the car by a gear change:

curve 1 – and = 0.2 m/sec. 2, vp = 4000 obr/min; curve 2 – and = 1.5 m/sec. 2, vp =

3500 obr/min

The parameters of the operation of the gradual gearbox depend on car speed, oppositions of the move and the changed jerkily correlation, causing a widening of the range of efficiency values for it. They stated experimentally that in the established move the efficiency of the gearbox grew jerkily just enough to decline the value of correlation. For example, for a car with an engine located at the front and with a drive to the back pivot, the efficiency of the gearbox grows jerkily from 0.815 – 0.903 on gear l to 0.970 – 0.981 on gear 4 (direct) [5].

The way in which a course of the value of gearbox efficiency changes (momentary) deter-mines theoretically the process of car acceleration by gears to the speed of 20 m/sec. (72 km/h) at fixed acceleration and identical initial value of rotation speed of the engine on every gear, is shown in fig. 4. As it can be seen, the range of values of the efficiency of the gearbox changes in a narrow range, and it means that the efficiency is 0.93 – 0.97, depending on the intensity of acceleration and the initial rotation speed of the engine. Switcheroos are a result of the change of the run, i.e. irregular change correlations [2,3].

The process of hastening a car, as well as the original value of rotation speed of an engine ex-ert a distinct influence on an average value of the efficiency of the gearbox. This efficiency grows with an increase in acceleration; in addition to higher intensity of dispersing, this increase is relatively slight.

Fig. 5 Mean of gearbox efficiency % of in the function of hastening rotation speed of an engine for different initial values: 1 — 5000 rotations/min, 2 — 4000 rotations/min, 3 — 3500 rotations/min

Table 1. Mean of the efficiency of boxes of gears of cars at different layouts of gears

Moving the torque.

Direct Through 1 pair of gears Through 2 pairs of gears

Ș = 0,99 Ș = 0,97 Ș = 0,96

The articulated embankment is an element of moving the drive between the run box and the driving bridge. Propeller shafts are most often applied in vehicles with wrists cross.

The efficiency of that kind of articulated embankment depends on: - quantities of wrists,

- structure of the embankment,

- value of the angle of refraction in the wist, - sizes of the moved torque,

- rotation speed of the embankment,

Fig. 6. Two wrists efficiency of a propeller shaft depending on the angle of refraction in wrists It is possible to perform the measurement of the efficiency of the embankment on the position of the circulating power. It demonstrates greater accuracy of measurements than a brake system because it measures only moments or the power of friction. In a brake system, moments and powers are measured at the exit from the embankment [6]. They equal 95% and more at wrists; on the braking position, results of the efficiency comparable to measuring errors are received. Mean of mechanical efficiency with wrists is 0.992 – 0.995.

The main transmission gear for it is characteristic of a function of the resistance moment with a similar course like the efficiency of the gearbox. Since transferring the main transmission gear is permanent, they both depend only on the speed of a vehicle and on oppositions of the move, so efficiency is located in a very narrow period of value and it is on average 0.95 for a hipoidal transmission gear and 0.98 for the transmission gear of the conic section [2].

Generally, the efficiency of the main transmission gear at lower rotation speed is higher, which is caused by shorter friction in gaskets and smaller plumbing resistances. These stand-bys grow with an increase in the rotation speed, and later a fall of efficiency is a result. One should here notice the beneficial occurrence of being found in lower gears of greater efficiency of the main transmission gear, while the efficiency of the gearbox is lower. As a result, the total effi-ciency of these two mechanisms during the ride is approximately permanent.

Average values of efficiency of the main transmission gear are on average 0.95 for the hipoi-dal transmission gear and 0.98 for the transmission gear of the conic section [3].

3. Conclusion

Limiting the flow of the stream influences the amount and types of applied sub-assemblies of the arrangement of moving the drive allowing the flow of energy through the arrangement.

Great entrance legal validity of the arrangement (coming from the engine) by the structure is very much extended, getting the power at the exit causes (measured on wheels) lower than in the agreement at smaller entrance legal validity, but with a less extended agreement.

Bibliography

1. DĊbicki M.: Teoria samochodu, teoria napĊdu, WNT, Warszawa 1976. 2. JaĞkiewicz Z.: Przekładnie stoĪkowe i hipoidalne, WKŁ, Warszawa 1978. 3. Siłka W.: EnergochłonnoĞü ruchu samochodu, WNT, Warszawa 1997. 4. Siłka W.: Teoria ruchu samochodu, WNT, Warszawa 2002.

5. Siłka W., ĝmieszek M.: Wpływ obciąĪenia i prĊdkoĞci na sprawnoĞü mechanicznej skrzyni biegów, Zeszyty Naukowe WSI w Opolu, nr 162, Seria Mechanika z. 39, 1990.

6. ĩółtowski B.: Diagnostic identification of technical objects. Problems of machines exploita-tion. [in Polish] Z.1 (105). PAN. 1996.

7. ĩółtowski B.: Computer enhancement of identification. [in Polish] ZN P.ĝw. nr.49, 1996 (s.55–71).

8. ĩółtowski B.: Machine diagnostics basics. [in Polish] Wyd. ATR, Bydgoszcz, 1996. 9. ĩółtowski B.: Multidimensional monitoring of the track-vehicle interface of a railway

sys-tem. Besanson, 2007.

10. ĩółtowski B.: Elementy dynamiki maszyn, ATR Bydgoszcz 2002.

11. ĩółtowski B., Cempel Cz.: InĪynieria diagnostyki maszyn, Polskie Towarzystwo Diagnosty-ki Technicznej, Warszawa, Bydgoszcz, Radom 2004.

WYZNACZANIE SPRAWNOĝCI UKŁADU PRZENIESIENIA MOCY Streszczenie

W pracy przedstawiono rozpływ energii mechanicznej w poszczególnych ele-mentach układu przeniesienia mocy. Szcegółowy opis podstaw rozpływu pozwala de-finiowaü wstĊpnie efektywnoĞü i sprawnoĞü badanych układów.

Słowa kluczowe: efektywnoĞü, rozpływ, przekładnia, wał napĊdowy, przekładnia główna

*This paper is a part of WND-POIG.01.03.01-00-212/09 project. Andrzej Sadowski

Bogdan ĩółtowski

University of Technology and Life Sciences WIM POIG Bydgoszcz