CZ2017245A3 - Planetary continuously variable transmission with mechanical gear ratio control - Google Patents

Abstract

The rigid friction members of this CVT form a non-toothed planetary gear, whose springed satellites (1) have the shape of double-cones. They engage with them symmetric pairs of mirror-displaceable central wheels (2) and, in opposite directions, crown-wheels (3) that can be moved in a mirror-like manner. Shifting and changing satellites (1) from CVT axis. To the axes of the satellites (1), the gears (9) attached thereto, engaging the toothed racks (8) attached to the CVT housing, hold parallel to the radial cuts (5) in the walls of the stationary cage of the satellite intended for the projecting ends of the axes. Both the central wheels (2) and the crown (3) are provided with circumferential grooves for tapered pins (16) and (17) rotatable in shifters (13) mounted on screws with right and left threads (14) and (15). The same helical gears (18) with slanted teeth are attached to them, which engage in a closed circuit. An external gear control is connected to one. Each second bolt is terminated by a groove connection for axially displacing the gear, the hub of which has a recess for the fork of the device controlling the friction element pressure.

Description

The present invention is one of the friction continuously variable transmissions, referred to as Continuously Variable Transmission (CVT). In a narrower definition, the present invention is one of the variators with rigid friction members.

BACKGROUND OF THE INVENTION

In the group of continuously variable transmissions with rigid friction members, several principles have been applied, such as a pulley on a flat plate, a pulley on the outer conical surface, a ring between two inverted cones, Kopp ball variator, but also variators according to the author PV 20004474, PV 2002-2548 and PV 2003-1788 and in accordance with its patent No. 305972. This patent follows the present invention.

Planetary CVTs with rigid friction members are also produced, but, unlike the above-mentioned patent, they exhibit significantly greater frictional losses, mainly due to considerably different trajectories of the interface. Their disc-shaped, slightly conical satellites are clamped by spring force on the outside between the two stator rims and on the inside between the rotary jaws on the input shaft. The output shaft is connected to the satellite carrier. The transmission is changed by moving the satellites in the radial direction. The disadvantages of these CVTs are low efficiency and relatively fast wear of the friction surfaces.

Of all rigid frictional members CVT, toroidal CVT and its modifications: semitoroid, and especially double semitoroid, were the most important. Its advantage is, besides the relatively favorable geometry, limiting the unavoidable slip on the contact pads, in particular, that the high contact forces on the friction members do not pass over the bearings, which not only saves the sizing of the bearings but also less energy losses therein. However, it is necessary to ensure as accurately as possible the alignment of the pulleys transmitting forces in parallel between the semitoroid disks.

However, if really large tangential forces are to be transmitted, it is necessary to strive for as large a real contact area as possible (without increasing the geometrically caused slip). In this, even the semitoroid CVT has only limited possibilities. For example, it is hardly applicable to heavy goods vehicles and earth moving machines where a continuously variable transmission would be highly desirable.

Although the CVT of U.S. Patent No. 305972 permits the transmission of considerable tangential forces, its problem is the undesirable effect of centrifugal force on the pressure in the rollers whose pistons move the outer friction elements (rims) in contact with the double cones. This is a source of imbalance in the gear ratio adjusting system, since the pressure in the central roller feed system in contact with the twin cones is not affected by the rotation speed. Feedback compensation of centrifugal force is therefore necessary. In addition, it is necessary to ensure their perpendicular perpendicularity to the axis of rotation during axial displacement of the rims, which requires a more complex series connection of the rollers.

The unresolved problem of CVT according to Patent No. 305972 is also the static uncertainty of the parallel-connected double-cones in contact with the rims and the central pulleys, which can cause unacceptable uneven load on them.

Another disadvantage of the solution according to the patent No. 305972 is also the attachment of the double cones on the swinging arms. Their deflection angle undesirably affects the contact forces of the double cones on the rims and the central pulleys.

The use of continuously variable gears is quite common in scooters and cars. If these CVTs have good mechanical efficiency, a reduction in fuel consumption can be expected, even

- 1 GB 2017 - 245 A3 compared to manual transmission. Indeed, with suitable automatic control, the CVT ratio can be varied continuously so that the torque / engine combination that has the lowest value for specific power consumption is selected for the power required in the driving situation.

Also, acceleration times for a vehicle equipped with a continuously variable transmission should be shorter, since not only the shift shifts are eliminated, but the engine speed can be maintained at maximum power during acceleration.

CVT should be very positive for earth moving machines. As is known, they achieve a much higher working performance when equipped with a hydrodynamic transmission instead of a manual, manual transmission. At the same time, the hydrodynamic transmission is unable to utilize the maximum engine power under any of the operating loads, as can be done with CVT. Moreover, its efficiency is much worse due to the predominance of modes using a hydrodynamic converter. The use of CVT in these machines should therefore significantly reduce fuel consumption and further increase their working performance. The same applies to off-road vehicles, especially tracked vehicles.

For these vehicles, it would be advantageous to combine CVT with a differential to create an infinitely variable transmission range (IVT). It can therefore be reduced to zero (neutral) or negative (reverse). Unfortunately, the existing fluent continuous variable transmissions are not capable of transmitting sufficient power for these and similar applications at reasonable dimensions.

SUMMARY OF THE INVENTION

The above-mentioned disadvantages of rigid friction variators are overcome by a planetary continuously variable transmission with mechanical gear ratio control according to the invention, which consists in that:

the shifters, which provide mirror axial displacement of the pair of toothed central and crown gears rolling on the double-spherical satellites, are mounted on half-right and half-left threaded bolts, with the center-wheel bolts adjacent to each other circumferential grooves for conical pins rotatable in the shifters and abutting the respective sides of the grooves are formed on the hubs of the non-toothed central and crown gears. to the CVT casing parallel to the cut-outs made in it, which protrude the protruding ends of the satellites axes, with a flexible material with a very low elastic modulus When the space between the cylindrical bore and the smaller diameter tube is filled there, which is equipped with bearings allowing the rotation of the satellite around the axis that passes freely through the tube, the right and left-hand threaded bolts are fitted with identical helical gears that engage each other in a closed circuit one of which is connected to an external gear ratio control device, on the gearless bolts for displacement of the toothed sun gears, the gears are mounted without axial movement, while the gearless bolts of the toothed crown wheels terminate in a splined connection they have recesses for the forks of the device controlling the mutual pressure of the friction elements.

-2GB 2017 - 245 A3

In addition to the common advantages of planetary CVTs (particularly compact construction and high torque transmission), the advantages of the CVTs according to the invention are high efficiency as well as simple adjustment of the transmission ratio and thrust required for the actual torque value.

Transmitted torque and power can be multiplied by each of the two sunwheels consisting of a rigid center disc and side discs interconnected by front differentials, and each of the two crown gears consisting of a hard center disc and side discs, also interconnected differentials that provide the same peripheral speed.

Clarification of drawings

Figure 1 is an axial section A-A of a planetary CVT housing which illustrates a mechanism for mirroring and counter-directional movement of the crown wheels and sun wheels in contact with both bevel and satellites, as well as measures to allow radial movement of satellites when changing the transmission ratio. Furthermore, FIG. 1 shows one of the meshing gear wheels mounted on right and left-hand threaded screws. These wheels ensure parallel movement of crown wheels and central wheels when changing gear ratio.

Fig. 2 is a cross-sectional view of B-B, in which engagement of the racks with the sprockets at the ends of the axes of the double-cone satellites are seen, which are thus forced to move parallel to the respective grooves when changing the transmission ratio. The shape of the webs of the cage of the satellites (in section) and the location of the bolts and guide pins in the displacers of the central and crown wheels are evident in this figure.

Figure 3 is a cross-sectional view of a C-C satellite cage with toothed racks attached.

DETAILED DESCRIPTION OF THE INVENTION

As can be seen from the figures, the rigid friction members of this CVT are arranged as a planetary spur gear, the non-toothed satellites 1 having a double-cone shape. The non-toothed central wheels 2 and the non-toothed crown wheels 3 are engaged therewith. The central wheels 2 are mirror-sliding in the axial direction in the grooves of the input shaft 4. The crown wheels 3 are also mirror-sliding in the axial direction on sliding guide bars 10 but sliding in opposite directions (when they approach each other, the crown wheels move away from each other).

The opposite movement of the crown wheels and sun wheels requires a change in the distance of the satellites 1 from the CVT axis. This is made possible by radial slots 5 in the walls of the cage 6, which carries the satellites 1 and is part of the housing 7.

The shafts of the satellites 1 are supported on the sides of these slots 5, without adversely affecting the thrust forces between the friction members (for example, the crank suspension would have an effect).

Preservation of the parallelism of the axes of the satellites 1 with the axis of the shaft 4 during their radial displacement is ensured by toothed racks 8 with which the gear wheels 9 are attached to the protruding shafts of the satellites 1.

The static uncertainty caused by the unequal load of the parallel-connected and slightly different friction elements differing in size from each other is alleviated by rubber tubes vulcanized in cylindrical cavities of the double cones to their smaller diameter tubes equipped with rolling bearings enabling rotation of the satellites 1 about axes passing through these tubes.

-3 2017 - 245 A3

From the crown wheels 3, the torque is transmitted via the sliding guide rods 10 to the drum 13 and from there to the shaft 12.

The transmission ratio is changed by moving the crown wheels 3 together while moving the central wheels 2 apart (and vice versa). For this purpose, the shifters 13 on the right and left-hand threads 14 and 15 are used. The shifters 13 are equipped with tapered pins 16 and 17 rotatable on rolling bearings. The pins 16 engage the sides of the circumferential grooves in the hubs of the central wheels 2 and the pins 17 roll along the sides of the circumferential grooves in the crown wheels 3. The pins have the necessary clearance in the circumferential grooves.

If, after increasing the transmission ratio, it is suddenly desired to reduce it (or vice versa), the pins 16 and 17 are pressed against the opposite sides of the circumferential grooves and their rotation is reversed. So slippage will necessarily occur. However, the moment of inertia of the pins and the parts rotating with them is very small, so that the slip phase is short and the wear is minimal.

On the right and left threaded bolts 14 and 15, identical bevel gears 18 are engaged outside the housing 7 (and the cage 6) and engage in a closed circuit, one of which is connected to an external gear ratio control device.

On the bolts 15, the gears are mounted without axial movement, while the bolts 14 terminate in a splined connection for axially displacing the geared wheels, the hubs of which have recesses for the forks of the device controlling the friction element mutual pressure.

Due to its helical toothing, the wheel is rotated by axial displacement and the right-hand and left-hand thread bolts 14 are rotated therewith. This moves the crown wheel shifters while the adjacent bolt 15 controlling the shift of the sun wheels does not move. In this way, prestressing is introduced between the friction elements.

The purpose of said downforce control is to avoid unnecessary stress at low torque values, which in addition is accompanied by greater energy losses.

For friction gears, to minimize slip energy losses, the movement of the contact points on the rigid friction members should not have too different trajectories in the interface, and adjacent contact points should not have a different peripheral speed ratio (transmission ratio) in the real interface. In addition, the thrust forces on the friction members should not go over the bearings in order not to impair their service life or reduce overall efficiency.

In the planetary CVT of this example, the difference in the trajectory of the junction points on the rigid friction members is minimized by the fact that the axes of the satellites 1, the sun wheels 2 and the crown wheels 3 are parallel. The circumferential friction surfaces on the central wheels have the same conicity as the inner friction surfaces of the crown wheels 3 and the satellites 7. All friction members have parallel axes of rotation and their thrust forces compensate for each other due to the symmetrical arrangement, so that they do not go over the bearings.

Industrial applicability

The CVT according to the invention makes it possible to solve a continuous transmission change with a high efficiency even for high power transmission, assuming an extraordinary service life.

Obviously, the CVT according to the invention will also find good application where chain continuously variable transmissions, or articulated CVTs (passenger cars), or wedge-type variators are used, such as in mopeds, scooters, snowmobiles, grain harvesters and the like.

-4GB 2017 - 245 A3

PATENT CLAIMS

Claims (6)

Planetary continuously variable transmission with mechanical gear ratio control, characterized in that the shifters (13) which provide mirror axial displacement of the pair of toothed central and crown gears rolling on the double-spherical satellites are mounted on the screws (14) and (15) a half-right and half-left thread, wherein the center-wheel approach screws (15) are adjacent in a closed circuit to the crown-wheel screws (14) (by reverse screwing, the approach and the distance are interchanged). Planetary continuously variable transmission with mechanical gear ratio control, characterized in that circumferential grooves for bevel pins (16) and (17) rotatable in the sliders (13) and adjacent to respective circumferential sides are formed on the hubs of its non-toothed central and crown wheels. grooves. Planetary continuously variable transmission with mechanical gear ratio control, characterized in that the axes of the double-cone satellites protruding on both sides are provided with gear wheels (9) engaging toothed racks (8) attached to the CVT housing parallel to the radial slots (5) therein. created, into which protruding ends of the axes of the satellites. 4. Planetary continuously variable transmission with mechanical gear ratio control, characterized in that the flexible material of a very low elastic modulus is filled in each double cone with a space between the cylindrical bore and a smaller diameter tube located therein equipped with bearings allowing rotation of the satellite about the axis freely passing through this tube. Planetary continuously variable transmission with mechanical gear ratio control, characterized in that identical right-hand and left-hand threaded bolts (18) with helical teeth are engaged, which engage each other in a closed circuit, one of which is connected to an external gear ratio control device. Planetary continuously variable transmission with mechanical gear ratio control, characterized in that on the screws (15) the gears are fixed without axial movement, while the screws (14) terminate in a splined connection for axial displacement of the mounted gears whose hubs have recesses for the forks of the device controlling the mutual pressure of the friction elements. 3 drawings