Elements of the Ministry of Agriculture
Elements of the Ministry of Agriculture

Design scheme of elements MA


(EN) The invention relates to machine building. The mechanical stepless transmission comprises a drive shaft and a driven shaft mounted on the drive shaft, an eccentric transducer with an eccentricity adjustment mechanism (16), a freewheel mechanism (MOX) and coaxial gears (10) arranged coaxially with the central gear (11) Mounted on the driven shaft (18). The driving elements (7) of the MAX are connected to the inverter, and the slave units (8) are connected to the gear wheels (9) via torsion shafts (10). The converter crank is mounted on an intermediate shaft (2) mounted inside the drive shaft with an eccentricity equal to the crank radius and is able to rotate about its axis with the eccentricity control mechanism. This allows the crank neck to be made with a sufficiently small diameter in order to connect it to the axles of the driving elements (7) of the MAX by means of a crank mechanism. The invention makes it possible to provide additional control enabling to obtain any desired engine load in a wide range of the gear ratio change, to increase the potential reliability of the converter.

The angle between the tangents drawn through the point of contact between the roller and cage assembly and an asterisk is called a wedge angle.

To reduce the influence of errors of manufacture and wear and tear on the angle of jamming the rollers work surfaces with an asterisk are not recommended to perform flat and cylindrical with guides in the form of a circle, Archimedes or logarithmic spiral.

Wedging and wedged state Ministry of Agriculture

By wedging MA refers to the process of rolling rollers in the tapered portion of the wedge of space between the sprocket and the ring as a result of the friction forces caused by the movement of the driving member relative to the driven in the direction of torque transmission. This process is characterized by the growth and strength of the normal pressure friction force between the clutch yoke and the sprocket, the energy loss due to friction of rollers rolling on the working surfaces, loss of energy to break the oil film and the accumulation of strain energy.

The process is preceded by jamming the time corresponding to the end of the period of free running when the angular velocity of the cage from the 1 and 2 with an asterisk are equal.

It has assumed that all of the rollers, placed in the separator, the same force and effect wedging rollers occurs simultaneously.

Method of calculation and diagram of the forces acting on the roller during the seizure MA, shown in [3]. At the present time it has not yet adopted any unified theory of jamming USDA.


Wedging MA


The wedging period of the MCA is characterized by a decrease in the torque transmitted by the clutch from the value corresponding to the wedged state to zero. As the torque decreases, the main links become free from deformations. 


Under the action of the elastic roller are moved into the wider part of the wedge space. Simultaneously, the driving and driven members are rotated relative to each other.


Free wheeling MA


Under the period of freewheel USDA understand the movement of the mechanism in which the driven member moves at a higher angular velocity than the master. Rasklineny the rollers and by the forces of friction in contact with the yoke rotate in cage windows. Free running is continued after the end of the process of propping USDA before the start of a period of jamming.

Selection of the main design parameters of the Ministry of Agriculture

The main criteria of efficiency USDA are:

  • - the ability of the clutch to jam without slipping;
  • - contact strength and fatigue endurance of the most loaded elements;
  • - absence of increased wear of working surfaces of parts at high relative angular velocities of movement of the links during the period of free running.

Reliable jamming USDA possible under the conditions:

  • - contact of rollers with a cage and an asterisk at the initial moment of jamming;
  • - self-jamming of rollers in the initial stage of their jamming period;
  • - but slipping of the coupling in the presence of deformation of the loaded elements.

Implementation of the first and second conditions is provided mainly by the action of the pressure forces on the rollers, the value of which is selected based on the dynamics of movement of the main units of the Ministry of Agriculture and the properties of the lubricating oil.


Selecting a wedge angle


The choice of the angle of wedge roller in designing roller MOA usually decided on the basis of experimental data of their design and operation. For selfwedging MA

the wedging angles are selected in the range 3 ° <a <5 ° 30 ', and the tolerance for the wedging angle is ± 15'.


Requirements for the construction of parts MA


To reduce the dimensions of the Ministry of Agriculture is necessary to use the maximum possible number of rollers and ensure a more uniform contact with the yoke of an asterisk. The uniformity of the pressure distribution along the length of the rollers can be achieved by making the rollers is slightly convex (with Bombino) or rollers are slightly tapered at the ends.

A great influence on the uniformity of load distribution between the rollers and along the length of each of them is provided by the accuracy of manufacturing the separator and sprocket, and in the course of long-term operation, the wear resistance of the separator material. The use of separators from aluminum alloys has shown that they have unsatisfactory wear resistance. Better performance is provided by bronze and steel separators. Operational experience and results of research of high-speed MAX helicopters show the advisability of using steel lightweight separators and the need to improve the quality of their dynamic balancing.

Particular attention in the design of the Ministry of Agriculture should be paid to the accuracy of centering stars, cage and cage. In eccentric disposition relative to the cage sprocket rollers wedged at different angles and that can lead to considerable overloading of some clips, while others may not transmit torque.

Blog and articles