Systems of Hydro Mechanical Drives  Tractiondynamic analysis of transmissions of cranes KS63 and KS100
Tractiondynamic analysis of hydro mechanical transmissions
of the jib selfpropelled cranes KS63 and KS100
The wide nomenclature of jib selfpropelled cranes in a range of lift capacities from 25 up to 400 tons requires for their completion of
a plenty of models of diesel engines.
With objective of unification, restriction of the nomenclature of engines the transmissions elements applied in cranes, maintenance of
fuel profitability and an effective utilization of the installed power the search of various designlayout decisions [8 – 9] is conducted.
One of the most perspective directions in this area is use of socalled power modules, each of which consists of a diesel engine, a hydraulic
torque converter and a reduction gear of the pump drive, collected in one unit. If only one such module is installed on the chassis it is
possible to drive either of the chassis mechanisms, or of the rotary part mechanisms. At installation on the chassis of two such modules for
the chassis mechanisms their total power is used, for the rotary part mechanisms – power of one of them. Thus the total power of engines at
use of twomodular structure of hydro mechanical transmission of crane is below about in 1.4 times for cranes carrying power 63 t and above.
Besides designs of rotary parts without own powerplants (this is one of traditional circuit diagrams) become essentially simpler, configuration
and aesthetic forms of the crane improve. Instead of seven models of engines for all number of cranes it is possible to apply only three models
of serially let out engines (power 132, 177, 235 kW) and four gearboxes for total input power 177, 264, 354, 470 kW. However the modular
principle of creation of powerplants puts forward the certain number of questions, requiring detailed study on the basis of analytical and
experimental researches (at installation of two power modules on a crane).
Major of them are:
– a maintenance of high tractiondynamic properties at movement on various transfers on a crosscountry terrain and roads with various coverings;
– a minimal dynamic loads in elements of transmission at dispersal and braking;
– an effective utilization of positioning power of powerplants.
The decision of the abovelisted problems is interfaced to the closer approach to overlapping characteristics of engines and hydraulic torque
converters, a choice of parameters of system of a joint control of powerplants, to the account of possible circulation of power at availability
of asymmetry of characteristics of power modules and separate branches of transmission.
With this objective the program DRIVE of the computeraided dynamic calculation of hydro mechanical drives of any structure has been
used [10].
The dynamic analysis of power modules of the specified cranes has originally been executed.
Fig. 1.
The rated diagram (Fig. 1, a) included two engines, two hydraulic torque converters, the general gearbox with the reduced load on
its outlet axle. Such rated model allowed estimating:
– a fuel profitability and a stock of power of engines at the maximal resistance to movement of the machine,
– an efficiency of hydraulic torque converters and duration of their work in a stop mode,
– a degree of circulation of power in the power modules of transmission.
Rated oscillograms of transients in the power modules, arising at dispersal are resulted as an example on Fig. 1. Characteristics of engines
(dependence of rotating moments on angular speeds) differ on 10% (Fig. 1, b). The same order mismatch has been given in characteristics
of hydraulic torque converters (Fig. 1, c). Thus real conditions, in which actual characteristics of engines and hydraulic torque
converters (dotted curves on Fig. 1) can differ from passport (continuous lines in the same place) on 5 % in this or that side were simulated.
It can bring to the power circulation effect in power modules, as was observed, the truth, in an insignificant degree.
However at such statement of a problem it is impossible to estimate the effects connected with dynamics wheel propelling and elastic elements
of transmission at dispersal and braking. At the same time tractiondynamic calculation of hydro mechanical transmissions is a necessary stage
of creation of cranes on the chassis of the raised passableness.
With this objective rated diagrams of hydro mechanical transmissions of cranes KS63 (Fig. 2) and KS100 (Fig. 3), containing besides powerplants
(Fig. 1, a) such elements, as elastic shafts, differentials, tires have been considered. In view of the specified characteristics
(of frictional clutches, elastic properties of shaft, slipping of wheels, etc.) have been received fuller and more authentic dispersal
characteristics of hydro mechanical transmissions of cranes at various road conditions.
Fig. 2.
Fig. 3.
Each of the rated circuit diagrams according to requirements of the program DRIVE is presented in the form of set of elements and connecting
nodes and contains two diesel engines with centrifugal regulators (nodes 133 and 234), two hydraulic torque converters (nodes 35, 46),
a gearbox (nodes 912131415161718192021), summarizing both of power streams, which outlet shafts (nodes 20 and 21) are connected
through elastic shafts with wheel bridges. In the diagram of hydro mechanical transmission of crane KS63 (the wheel formula 8х6) one interbridge
differential (nodes 222728) is available; in the diagram of hydro mechanical transmission of crane KS100 (the wheel formula 10х8) two
interbridge differentials (with nodes 222728 and 233536) are available. Each wheel bridge is represented on the diagrams in the form of an
equivalent wheel with the double parameters (a moment of inertia, circular effort, rigidity, etc.).
Work of hydro mechanical transmission on I (V) transfer was simulated by inclusion of a friction clutch 1517, on II (VI) transfer – inclusion
of a friction clutch 1416. Work of hydro mechanical transmission on different transfers (I and V, II and VI, etc.) was defined by the
assignment of various transfer numbers of reducers of the gearbox.
Total of elements in the rated diagrams of hydro mechanical transmissions: 28 for crane KS63, 31 – for crane KS100. The order of mathematical
model is accordingly 22 and 24.
Fig. 4.
As an example the rated oscillograms of transients in hydro mechanical transmission of crane KSH63 at dispersal on I transfer and switching to II
transfer are resulted on Fig. 4. Here it is designated: t – time, s; M – a moment, kN· m; ω – an angular speed, rad/s;
v – speed of forward motion of the crane, m/s; R – a "wheel" (the wheel bridge) circular effort, kN; W – a
road resistance, kN. As well as earlier, the index at a variable means number of node on the rated diagram in which this variable operates
(ω_{1} – an angular speed in node 1, М_{16} – a moment in node 16, etc.).
Simulated dynamics of hydro mechanical transmission at dispersal on a wet ground on I to transfer on a bias 8°, with the subsequent switching to II
transfer with overlapping on time 0.2 s (there is in view of an interval of time when the friction clutch I of transfer 1517 will not open yet
completely, and the friction clutch II of transfer 1416 has already started to become isolated). It is possible to observe this effect on
Fig. 4, a on a relative positioning of dependences of moment М_{17} (t) of friction clutch 1517 and moment
М_{16} (t) of friction clutch 1416. As can be seen from Fig. 4, a, b, dispersal on I transfer at
the specified road conditions lasts approximately 1.5 – 2 s and is characterized by peak values of moments М_{17},
М_{5} and М_{6} at t ≈ 0.6 s. However these processes quickly fade and by the time t = 2 s
about all phase variables become practically constants – there comes a stationary mode of movement on I transfer. At switching on II transfer
dynamics of phase variables is observed again. Especially obviously it is shown at a moment of a friction clutch of II transfer
(М_{16}) and moments of turbine wheels of hydraulic torque converters (М_{5} and М_{6}).
At the same time dynamics of moments on diesel engines shafts (М_{1} and М_{2}) is insignificant and carries
almost aperiodic character with fast transition in statics.
Transients of variation of circular traction efforts R_{26}, R_{31}, R_{32} have similar
character. It is clearly visible, that at switching on II transfer there is a stop of the crane (speed v_{25} reduces to zero),
because total traction effort R_{26} + R_{31} + R_{32} = 80 kN becomes insufficient for
overcoming total resistance W ≈ 120 kN (movement resistance makes ~52 kN, resistance from a bias 8° is approximately equal 68 kN).
It is necessary to note, that as a result of nonuniform weight distribution on axes traction efforts of wheel bridges R_{26},
R_{31}, R_{32} essentially differ (in a stationary mode in ~1.5 times).
On each machine the set of such calculations in which the values has been varied: switching of transfers, a bias of road, a type of a road
covering, overlapping on time of inclusionshutdown of friction clutches of gearbox, as well as deviations of «actual» characteristics of a
diesel engine and a pump wheel of the hydraulic torque converter from their passport characteristics in that and other side (up to 5%), and a
deviation of characteristics of a diesel engine and the appropriating hydraulic torque converter were taken with different signs.
The executed on mathematical models analysis of twomodular system of a drive in view of 5% deviations from nominal characteristics of diesel
engines and hydraulic torque converters, elastic properties of elements of transmission, tires, various factors of grip of the weel, various
time of overlapping of friction clutches of gearbox, in conditions of movement on limiting biases and dispersal on horizontal sites of roads,
at association of streams of power of two power modules has shown:
– the twomotor system of a drive of the cranes 63 and 100 t (with the wheel formulae accordingly 8х6 and 10х8) provides with carrying power
takeoff and dispersal of crane on I transfer at extreme conditions of movement (rising on a wet ground at a bias 8°);
– switching in these conditions on II transfer leads to latching of turbine wheels of hydraulic torque converters and proslipping of friction
clutches with transition to a reversible mode owing to shortage of installed power; diesel engines thus work in a mode close to flameout;
– at movement on dry asphalt on a horizontal site of road dispersal of the crane on V transfer and switching on VI – the accelerated transfer
are provided that testifies to high dynamic qualities of the drive; however speeds of movement of cranes KS63 and KS 100 at transition from
V transfer to VI transfer change differently: the crane KS63 speed practically does not change, and the crane KS100 speed increases in 1.5
times that speaks a different level of specific power and work on various working zones of external characteristics of hydraulic torque
converters.
The analysis of dynamic loads in elements of transmission has allowed establishing an optimum value of overlapping on time of inclusion of
friction clutches of gearbox. For cranes KS63 and KS 100 it makes 0.3 s. Transients on circular efforts of wheels and moments of pump wheels
of hydraulic torque converters in this case become aperiodic, while for other values of overlapping (0.1, 0.2, 0.4 s) oscillatory processes
with significant amplitudes take place.
The comparative analysis of traditional singlemotor system of a drive with the twomodular circuit diagram has shown, that fuel profitability
of the last a little bit above. So, in the established mode on I transfer the difference in values of specific fuel consumption makes 59%.
Carrying out of such calculations provides the foundation for the alternative analysis necessary at creation of new drives and transmissions,
for example, with two modular structure of a drive, and allows estimating correctness schematic decisions at design of hydro mechanical
transmission, to choose its basic elements and to develop on this basis specific requirements to a control system.
