RU2315215C2 - Gear-ball variable speed drive having gear wheels with end teeth - Google Patents

Abstract

FIELD: machine engineering, possibly mechanisms for changing motion speed without interruption of power transmission process.

SUBSTANCE: gear-ball variable speed drive includes two coaxial gear wheels 1, 4 with end teeth. Set of spherical rolling bodies (balls) is used for transmitting motion from driving gear wheel 1 to driven gear wheel 4. Said balls are free but they are arranged in closed space between teeth of gear wheels, outer and inner rings 7, 8. At rotation of driving wheel lateral surfaces of its teeth provide motion of rolling bodies in circular and axial directions. Balls have different motion paths and motion speeds totally providing rotation motion of some medium called as "third body" for transmitting motion of driving gear wheel to driven gear wheel. Gear ratio depends upon density of said medium that in turn depends upon geometry parameters of gear wheels, diameters and number of rolling bodies and play between teeth of gear wheels. Design of variable speed drive provides possibility of motion of one gear wheel along spines of shaft or on guiding pin along axis.

EFFECT: possibility for varying gear ratio without interrupting power transmission due to using "third body".

6 dwg

Description

The present invention relates to the design of mechanisms that allow you to change the speed during operation without interrupting the flow of power.

In the drives of many machines, there is a need to change the speeds during operation. For this, gearboxes (gearboxes) are used, which are complex mechanisms. The use of gearboxes requires disabling the main movement, for example, clutch in cars or stopping the engine in metal cutting machines, etc.

In modern cars, automatic transmission boxes are used - boxes with automatic gear changes.

“Automatic transmission” is a complex technical system, consisting of:

- a mechanical part comprising a multi-plate clutch and a multi-stage planetary gear;

- a hydraulic part containing a hydraulic pump, a torque converter, a piping and valve system;

- a control unit comprising a control system for power electrics, electromagnetic valves and sensors.

The cost of the automatic gearbox is comparable to the cost of the engine.

While the “automatic boxes” hold their positions, a tendency has been noted for their retreat in front of semi-automatic and continuously variable transmissions (variators).

Specialists from leading automotive companies came to the conclusion that for a continuously variable transmission of existing structures, the most suitable is the design of a V-belt variator with split pulleys such that their halves diverge and converge, due to which the belt works on different diameters. However, the weak point of the V-belt variator is a belt that slips and collapses under heavy loads.

On some models of Nissan and Audi cars, CVTs are installed, where the belt is replaced by a chain of steel tape and trapezoidal segments strung on it.

A V-belt variator with a conventional belt is not a very reliable design, with a chain it is more expensive and difficult to manufacture, so some companies are researching to develop more reliable and compact variator designs. For example, the German company GJT from Alsdorf became interested in the design of a variator consisting of two metal cones and a ring between them. When you move the ring along the cones, the gear ratio changes. The design of the variator was patented in 1902 and is only now being introduced. The developers did not disclose the mechanism for moving the ring and noted that the cones and the ring are in the liquid, which covers the work surfaces with the thinnest light film and this makes it possible to transfer significant loads. The composition of the liquid is also not disclosed.

The proposed technical solution can serve as an alternative to the existing designs of variators used in automotive and other engineering industries.

Known mechanical transmission [1], containing the driving and driven wheels with end teeth, a set of rolling bodies in the form of balls placed uniformly around the circumference in the longitudinal grooves of the housing and the limited space between the teeth of the wheels. The transmission [2] is also known, which differs from [1] in that the rolling bodies (balls) are freely located in the interdental space. A set of free, within a closed interdental space, spherical rolling bodies can be represented in the form of a certain medium - the "third body". When the drive wheel rotates, the lateral surface of the teeth causes the balls to move simultaneously in a circular and axial directions. Rolling bodies have different trajectories and speeds, in total, constituting the rotational movement of the "third body", transmitting the movement from the drive wheel to the follower.

In [2], the gear ratio is determined by the density of the “third body”, which depends on the geometric parameters of the gears, the diameters of the rolling elements, their number and the gap between the teeth of the wheels.

The proposed design of the end gear-ball variator provides for a change in the gap between the teeth of the driving and driven wheels during operation by moving one of them along the transmission axis.

Figure 1 shows a structural diagram of a gear-ball variator.

The driving gear 1 is located on the shaft 2 so that it can be moved along the key 3 along the axis of the shaft 2. The driven wheel 4 is fixed to the shaft 5. The wheels 1 and 4 have end teeth and do not directly interact with each other. The transmission of motion is carried out through the "third body" 6 - a set of rolling bodies of a spherical shape. Balls ⌀ 5.6 mm in an amount of 250 pieces, constituting the “third body”, are located in a confined space between the wheels and the rings: inner 7 and outer 8. The outer ring 8 can be replaced by a wall of the housing.

By moving the gear 1 along the transmission axis along the guide key, the distance s between the teeth of the wheels changes, and the properties of the “third body” - its density, on which the gear ratio depends.

To test the possibility of work, a variator model was made, which was investigated on a special stand (Fig. 2).

The variator 9 transmits the movement from the shaft of the engine 10 to the shaft of the generator 11. The engine and the generator are fixed on the slide 12 and 13. The slide 12 is rigidly fixed in the guide 14. In the variator model, the gear is not moved along the guide key (Fig. 1), but by movement the slide 13 together with the generator along the guide using the screw 15 (figure 2).

The crowns of the driven and drive wheels of the variator have the same parameters (figure 3). The number of teeth is z = 6.

The engine, on the shaft of which the driving wheel was placed, has a rotation frequency of 980 rpm, a power of 0.45 kW. The driven wheel is mounted on the generator shaft, which uses a DC motor with independent excitation of the windings. Using a system of rheostats included in the electric circuit of the generator, a load of up to 0.4 kW was applied to the driven transmission wheel.

Figure 4 shows a General view of the stand for the study of the variator. Figure 5 presents the drive wheel mounted on the motor shaft and the outer ring on the driven wheel mounted on the generator shaft; in Fig.6 - driven and driving gears and inner ring.

Studies at the stand confirmed the ability of the transmission of this design to convert rotational motion with any gear ratio, as well as the ability to change speed without stopping the movement (without interrupting the power flow).

At maximum density (the leftmost position of the generator), the drive and driven wheels rotate at the same speed (i = 1). A decrease in the density of the third body with the gear running reduces the speed of the driven wheel to zero. The speed of rotation of the wheels was measured by a tachometer.

Under steady-state operation (constant load), a constant gear ratio was established.

The gear ratio of the variator i depends on the density of the "third body", which is determined by the distance s (Fig. 1) between the ends of the wheels. Given the geometric parameters of the variator links and constant power, an analytical determination of i depending on s is possible.

It is possible to construct these dependencies in the form of calibration graphs, measuring with a tachometer the number of revolutions of the driving and driven wheels for various s.

For a given coefficient of variation and a certain power, you can find the optimal values of the diameters of the wheels, the diameters of the rolling elements and their number, tooth parameters (quantity, height, profile, etc.).

The absence of direct contact of gears in the proposed variator design does not require high precision of their manufacture. The technology of production of gears is simplified by reducing many technological operations that require special equipment. The cost of rolling bodies produced in mass production at bearing factories is very low.

Thus, end gear-ball CVTs can be competitive with CVTs manufactured by both domestic and foreign industry.

Information sources

1. Auth. witness SU 12214180 (G.I. Izmalkov). 03/30/1980

2. Gearing gearing through the "third body". Application No. 2003134115/11 (036642) dated 11.24.2003.

Claims (1)

A gear gearing through the “third body”, containing the drive and driven wheels having end teeth, a set of spherical rolling bodies (balls) freely located in a limited interdental space, characterized in that one of the gears has the possibility of axial movement to vary the gear relationships, including without interrupting the flow of power.

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