Product: Variable Twin Planet Variable Gear (VTP)
Custom configuration – keyword: Variable Twin Planet. short VTP.
Drive safely, maintain function. Keyword: hard practice. Our VTP stepless transmissions think along and direct your focus to the actual task – operation of the accelerator pedal and steering.
High efficiency and wear-free operation appeal to the fleet manager, the driver benefits from the simplest operation and unrestricted mobility with maximum driving safety, even in the most difficult terrain.
Keyword: Safety through full concentration on the task.
The perfect stepless gearbox for…
- Municipal vehicles
- Road vehicles
- Forestry machines
- Mining Trucks
- Special vehicles
VTP product family
AEBI. In 2012, the AEBI Schmidt Group was the first vehicle with a VTP transmission to present the AEBI VT450 Vario transporter at the Agrama trade fair in Bern. The simple operation and functionality of the innovative VTP drive system convinces even under extreme operating conditions.
The AEBI Transporter was able to win the title “Tractor of the Year 2014” in the class of special tractors.
Test in the off-road. VDS equips Land Rover Defender with the VTP450 CVT transmission. The “Off-road vehicle” project demonstrates the highest level of functionality, mobility and safety in challenging driving situations.
I was impressed by the ease of use in extreme terrain. Go off the gas and the vehicle stops, whether uphill or downhill. Simultaneous coupling, braking and shifting are a thing of the past.
Landini/McCormick. At EIMA 2014 in Bologna, the Power Mondial tractor from Landini/McCormick with VTP transmission was presented.
Variable Twin Planet, General
On the Royal Route
The motive. In search of the ideal configuration of mechanical components and variators, VDS has developed the modular transmission system VTP.
The principle. The VTP transmission system works with hydrostatic-mechanical power branching: in the purely hydrostatic power range and, depending on the design, with up to three overlay ranges.
The core element. The core element is a double planetary set at the gear output. The reverse planet set is only active at low speeds in purely hydrostatic operation, in the second set of planets the superimposition of mechanically and hydrostatically transmitted power takes place.
The advantages. The arrangement and transmission ratios cause high tensile force and large transmission spread with low mechanical effort, even with small Hydrostat units.
In niche segments
Variety for small series. Thanks to its modular design, availability in several sizes and combinability with different variators, VTP transmissions can also be offered for small quantities at reasonable costs.
The big lot for small lot sizes.
Sizes. The VTP transmission system includes additional sizes. The mechanical, hydraulic and electronic components required to achieve the infinitely variable transmission are integrated in a “basic module” in all sizes.
VTP - Variable Twin Planetstepless entry, stepless driving pleasure
Variable Twin Planet, technical description
Stepless entry. Stepless driving pleasure.
VTP in all variants.
Versions. As hydrostatic variators, compact units integrated into the housing in back-to-back design or separate hydro pumps and hydromotors in the closed circle can be used. In all cases, hydro pumps are provided in swivel disc design in combination with constant or adjustment motors in inclined disc or in inclined axis design.
Comments. In order to achieve the best transmission function and switching quality, requirements for control characteristics, response behaviour, etc. must be met. Compact units are on the market with displacement volumes from 28 cc to 175 cc. Depending on the application and the application profile, differential pressures of up to 480 bar are permissible.
For the use of hydro-pumps and motors in a dissolved design, there is a wide range of hydrostatic units available as standard for a wide range of applications.
Functional description. At low speeds or downforce speeds, the power transmission is only carried out via the variator. By connecting the hollow wheel H2 with the housing in the planetary set 2, the force flow from the hydromotor via the solar wheel S2 and the planet carrier to the drive wheels is closed. The transmission components in the mechanical power path do not transfer load in this operating range. Their speeds on the output side are defined by the kinematic coupling in the planet set 1 and on the input side by the coupling to the gear input shaft. In the planet set 2, a high ratio is chosen to achieve high tensile forces with small hydrostat units.
Switching without loss of traction. The rotational movement on the solar wheels S1 and S2 or on the planet carrier forces the hollow wheel H1 a speed, which leads to synchronous speeds at sufficiently high speed on the solar wheels at the couplings K1 during forward driving or on the clutch KR when driving backwards.
When the synchronous speed is reached, the pure hydrostatic drive is switched to the adjacent power-branched area without interruption of the traction force. The switching is carried out by overlapping closing of the corresponding clutch and subsequent opening of the hollow wheel brake. The couplings or brakes are provided as slat couplings. The use of claw couplings is also conceivable, but requires special control properties in the variator.
Performance branch 1. After switching, the mechanical drive power is transmitted via the hollow wheel H1, which is coupled to the gear input shaft and rotates at a constant speed. Due to continuous change in the speed in the hydrostatic branch, the gear ratio is infinitely adjusted. Immediately after switching to the power-branched area, the solar wheel rotates in the planetary set 1 in the opposite direction of rotation of the hollow wheel and thus reduces the speed of the web. In this operating range, the gearbox works with reactive power, which means that the hydromotor works as a pump and delivers via the hydrostatic circuit back into the mechanical path. With a change in the swivel angle in the hydro pump, the speed of the hydromotor is adjusted from maximum speed to the maximum speed of the hollow wheel via swivel angle zero to maximum rotational direction as the hollow wheel H1. At swivel angle zero, the gearbox works with maximum efficiency, because the entire drive power is transmitted purely mechanically. The hydromotor only has to be used to transfer the power dissipation to support the moment on the Solar Wheel S1.
With further adjusting of the swivel disc, the speed of the solar wheel S1 is increased in the same direction to the hollow wheel H1 until maximum travel speed is reached in the first power-branched range.
Performance branch 2. The switching from the first to the second power-branched area is carried out by means of a load circuit with compensation of the step jump by the variator unit. In this special switching function, a continuous speed increase is forced on the hollow wheel H1 via an overlapping circuit of the couplings K1 and K2 and during the acceleration of the hollow wheel by adjusting the speed of the solar wheel the overall translation is kept constant or adapted to the respective driving conditions. After completion of the switching, the gear ratio in the second overlay area is approximately equal to the transmission before the changeover in the first overlay area. This procedure causes a stepless
the gear ratio can be set in two overlay areas with a high overall spread.
The translation in the planet set 1 is chosen much smaller than in the planet set 2 in order to achieve a high gear spread in the power-branched areas on the one hand and to place the pressure level in the hydrostatic circle in areas where the hydro pump and the hydromotor with good effiums.
Speed and efficiency. Figure (speed diagram) shows the speed ratios in a VTP gearbox with an overlay range for return travel, a purely hydrostatic driving range at low speeds and two overlay ranges for forward travel.
In the image (transmission efficiency) the efficiency curve is shown depending on the driving speed at a constant input speed. The characteristic camel humps in the middle of the overlay areas are striking, where the entire drive power is transmitted purely mechanically and the gearbox has the best efficiencies.