I repair Vario gearbox Fendt JCB Massey, you can write questions, on this material that I know very well and which is globally very resistant and performing, but like any mechanic, nothing is eternal.
Ask your question about box vario fendt at the bottom as a comment
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the explanation of variation is not simple:
according to your schema, we’ll say that the vario transmission combines both mechanical and hydraulic energy, and is a constant balance between action and reaction, of the planetary train, epicyclic train:
as shown in the diagram, the pump is at zero flow. it is driven by the internal combustion engine via 5 and 2 since planetary 4 is at a standstill (4 is the shaft to the wheels), the hydraulic motors do not have a flow rate and therefore block the shaft (4)
so easier to drive the pump flow rate 0, than the impellers.
movement of the tractor:
hydraulic motor max. displacement, the pump gradually discharges, up to its max. displacement = increase of the hydraulic motor speed. at the same time mechanical dimension the resistance created on the crown (3)
by the pump rising in pressure, allows the epicyclic gear (2) to transmit power from the internal combustion engine to the planetary (4).
the crown is the reaction element of the epicyclic train. the planetary is spinning.
the top shaft (8) transmits the hydraulic power from the hydraulic motors and the mechanical power of the planetary (4) to the wheels, the tractor moves forward.
the power transmission is largely achieved by hydraulics, the greater the resistance to forward movement, the higher the pressure.
when the pump (6) reaches the maximum displacement, the motor’s displacement decreases, which leads to an increase in the speed of the motors. the pump pressure is constant and the useful flow rate will decrease as the motors consume less and less since their displacement decreases towards zero. This decrease in the flow rate at constant pressure will lead to a decrease in power in the hydraulic part. on the mechanical side this will result in a decrease in the speed of the crown (3) of the epicyclic gear (2) which will lead to an increase in the speed of the planet (4). (multiplier effect of the train with entry through the satellite carrier)
The acceleration of the engines and the planetary will allow the tractor to accelerate.
when the motors (7) reach their zero displacement they no longer drive the drive shaft (8) and they do not admit any more flow and thus block the pump (6) as the pump is connected to the crown (3) of the epicyclic gear (2) which will also stop.
so the epicyclic gearbox does not transmit any more power to the pump, (locked crown) so all the power of the internal combustion engine passes through the planetary (2) or 100% of power transmitted mechanically.
configuration at max. speed (50 km)
the parts in yellow = front axle and purple = universal joint shaft, there are also two slow and fast ranges I and II
this system is also with small variants on steyr (new holland case) TVT, CVX. on john deere, IVT.
AND the inventor is for me komatsu, on his bull D155ax-3 hydrau mecanical transmission (HMT) of 1989
and I forgot the toyota prius, with an electric motor instead of hydraulics.
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A continuously variable transmission can be built up from an epicyclic gearbox, by following the following assembly:
-motor shaft coupled to the emitting turbine of the hydraulic converter,
-Planetary planetary coupled to a first receiving turbine,
-crown coupled to a second receiving turbine,
-Satellite carrier coupled to the wheels.
In principle, the stepless gearing is varied by adjusting the flow distribution between the two receptor turbines.
Fendt vario gearbox. The gearbox base is a planetary gearbox, with the motor connected to the satellite gate, the crown to a hydraulic pump connected to a hydraulic motor that drives a summing shaft connected by a gear to the planetary gearbox.
The reduction ratio varies according to the inclination of the pump and hydraulic motor. I would like to know how I could find the gear ratio of the train according to the inclinations of the motor and pump (not the same)
You need to find a relationship between the speed of the pump and the hydraulic motor, probably by comparing their respective flow rates, which depend on the inclination of the plates.
With Willis’s relationship, you have 2 equations, and you can find the third one which is the expression of the transmission ratio.
If I understood correctly, you say that the total ratio is « indeterminate » at a given hydraulic ratio.
I find it very strange… A given hydraulic transmission ratio can correspond to only one total ratio.
The hydraulics only allow variable ratio with a torque converter with very average efficiency, except that there is no variable ratio here. And has a given alpha and beta, the hydraulic transmission ratio is fixed.
In my opinion, the system is made in such a way that the hydraulic part allows the variation of the ratio, while transmitting only the variable part of the movement (variable in + or -).
The mechanical train transmits the constant part.
This is why the hydraulic element 6 can be reversed (angle varying from 45° in one direction to 30° in the other). It is this inversion that makes me talk about element rather than motor or pump (and this is as much for element 6 as for elements 7).
By doing so, the poor performance of the hydraulics (compared to a gear train) affects only part of the transmitted power.
So reduced hydraulic, reduced losses, only happiness…
Then, it is only a simple equation of a system in which, it is not necessary to get stuck in the signs…
The strange thing is that the inversion is done on the shaft outside the mechanical transmission chain, so beta must pass at 0° when alpha passes at 0°… Otherwise block 7!!
It’s a constraint I can’t explain.
Is there a coupling between alpha and beta angles in the control?
I’m not just a scientist, I’m not just a technician.
if I understood your sentence above, the pump can be at zero flow so without any flow, and the motors receive nothing, and block the sprockets they drive, and to meet your demand the pump can be at reverse flow; or reverse.
I would like to emphasize that each element, crown, planetary, and satellite, are very often constrained, and that they release their energy for another element, their energy, when they lose their efficiency, and that they are no longer a priority, but they can be complementary….
for motors 7, just like the pump, from the moment there is a zero
When the engine is full, the system locks up and gives way to another function of the tractor’s drive, which is the end result for this function.
I’m not sure I’ve explained it properly.
I forgot to say, there are 2 engines for the small tractor range but for the high range there is only one engine with a large displacement.
the pump can be at zero flow so without any flow, and the motors receive nothing, and blocks the sprockets that they drive
after the pump’s maximum flow rate has increased, the motors decrease their displacement and thus they will end up at zero displacement at a given time,
so the pump is blocked, but the motor shaft is not blocked (8) and moreover, since the crown is blocked (that which drives the pump) the satellites (thermal) always drive but now the planetary which turns the shaft (8) and thus the wheels via sprockets, ranges and axle, etc….
If there is a heavy load on the tractor’s hook, the hydraulic system can resume and help the mechanical part.
I didn’t insist that the pump works at constant power.
because the pump with max. flow rate and max. pressure exceeds the output
the smallest of these tractors (from 120 to 230 HP) so if the pressure is too high in relation to the flow rate, the displacement automatically decreases
so the accelerator at the floor, which is stopped, has no effect on the thermal.
Another advantage of this system is that the tractor remains in position without a hand brake even with heavy loads, whether mounted or lowered.
Hydraulics only allows variable ratio with a torque converter with very average efficiency
a hydrostatic machine that moves on the road from 0 to 30 km/h the pump flows from 0 to 250l/minute, there is no variable ratio! explain me better so that I understand