WO2022025782A1

WO2022025782A1 - Precession transmission

Info

Publication number: WO2022025782A1
Application number: PCT/RS2021/000009
Authority: WO
Inventors: Milutin Smiljanic; Petar Smiljanic
Original assignee: Milutin Smiljanic; Petar Smiljanic
Priority date: 2020-07-27
Filing date: 2021-06-25
Publication date: 2022-02-03
Also published as: RS20200892A1

Abstract

The present invention relates to a precession transmission which is a mechanical transmission for transfer of rotation and torque where the relative motion of coupled bevel gears or friction disks (1-2, 3-4,...) is achieved by precessional movement of the first and other odd bevel gears (1, 3). The tooth numbers of the gears coupled to each other are different. The first bevel gear or friction gear (1) is fixed on an eccentric shaft (6) of the input shaft (7) by which it is forced to move precessively around the input shaft (7), rolling along the coupled second bevel gear or friction gear (2) fixed to the housing (14). The rotation of the first bevel gear or friction gear (1) is transferred to the output shaft (8) by a spherical joint (23) or by a third bevel gear (3) fixed on the first bevel gear or friction gear (1) coupled to a fourth bevel gear (4) fixed to the output shaft (8). The number of coupled gears or friction discs can be two or more.

Description

PRECESSION TRANSMISSION

TECHNICAL FIELD

The invention belongs to the gearing with gears or friction discs for changing the circumferential speed, ie. number of revolutions and circumferential torque.

According to the international Patent Classification (IPC), it is designated as:

F16H 1/04 - Toothed gearings for conveying rotary motion involving only two intermeshing members.

F16H 1/04 -Toothed gearings for conveying rotary motion involving more than two intermeshing members.

F16H 1/12 - Toothed gearings for conveying rotary motion with non-paralel axes.

F16H 13/00 - Gearing for conveying rotary motion with constant gear ratio by friction between rotary members.

BACKGROUND ART:

With each transmission, is theoretically possible to achieve any transmission ratio and to transfer any power, where the real values depend on several elements. These are: The number of gears or friction elements in coupled the freewheeling of the output shaft caused by the backlash between the elements, the load capacity of the transmission elements and so on.

The technical problem has been solved by so-called, standard gears, with various gear tooth profiles. Large gear ratios require a multi-staged gearbox with large gears, resulting in a bulky and heavy product with a large output shaft freewheeling.

Worm gears allow higher gear ratios and are self-braking, in the absence of vibration, but due to the presence of friction caused by worm sliding on worm wheel, the efficiency is significantly reduced. The position of the worm relative to the worm wheel can be adjusted to eliminate the backlash between the teeth and thus reduce the freewheeling of the output shaft. This leads to more intense wear and an increase in the freewheeling of the output shaft during the service life.

The most common transmission for large gear ratios are epicycloid gears and their special case - the so-called planetary gears, (as: KR20130002131A-2013-01-07), which have smaller dimensions and large available torque on the output shaft, but the need for multi-stage transmission is not eliminated. This type of transmission is characterized by an increased number of elements, and thus the price of the transmission, as well as the backlash causing freewheeling of the output shaft increases.

Cycloid gears (US-A-4909102, CN 108869641 A) are characterized by a geometry that is specific and demanding in construction. In addition, there are vibrations that cannot be fully balanced, which makes it difficult to apply large input speeds. The good sides are the large transmission ratios and the compactness of the design, i.e. small transmission dimensions, as well as small backlash and freewheeling of the output shaft.

Harmonic drive (US906143, JPS9166747A), are newer transmissions, which are characterized by large gear ratios, small dimensions and small backlash. Production is expensive and complicated. They are also characterized by low rigidity of the transmission, as well as the vibrations present in the work, due to the influence of the deformable element, which achieves the transmission of rotational motion and power. The efficiency is significantly reduced and we can compare it with worm gears.

DISCLOSURE OF INVENTION

Invention is based on the precession movement of one bevel gear, or friction element, on another, which is similar to the movement of Euler's disk, or a rotated coin which has precession movement around the own coordinate origin when falling.

The Precession Transmission is based on coupled two bevel gears or two friction discs (1 and 2), are set at an angle, with a tendency to be as close as possible to 180°. The first bevel gear (friction disk) (1) fixed on bearings on an eccentric input shaft (6) and (7), by which rotation the gear (friction disk) (1) is forced to precessively move around the input shaft axis, rolling along the second, coupled gear (friction disk) (2), which is stationary and attached to the housing (14). During rolling, gear (friction disk) (1) rotation about own axis is proportional to tooth number difference of the coupled gears, i.e. by the pitch cone circumference of the elements coupled. Rotation of gear (friction disk) (1) is transferred on output shaft (8) by a spherical joint (23) or in case of transmission with tree or more gears, by bevel gear (3), attached on rotated gear (1), coupled with bevel gear (4), fixed on output shaft (8).

The number of coupled gears, or friction discs, can be two, or more.

Coupled elements transmission ratio depends on the gears teeth number, or friction elements diameters ratio.

The Precession Transmission combines the good properties of all the solutions listed in Background Art. The Precession Transmission has a transmission ratio similar to a harmonic drive, or cycloid transmission, which makes it possible to achieve large transmission ratios (i > 500,000), with a small mass and dimensions gearbox in only one stage of the Precession Transmission. It is possible to couple a Precession Transmission in a multi-staged transmission, without increasing the backlash of the output shaft. Gears with any tooth profiles could be used. The Precession Transmission has possibility of backlash adjusting, or neutralization system implementation and thus reducing the freewheeling of the output shaft, which has been possible so far with worm gears and bevel gears. The housing is cylindrical, similar to an epicycloid, cycloid or harmonic drive transmission.

The elements of the Precession Transmission are calculated by standardized calculation methods for gears or friction disks. There are no restrictions on power transmission. The degree of gears coupling in Precession Transmission increases with coupling angle and always is: ε ≥ 2; Wherein : ε - degree of gear coupling , for gears with straight teeth. Such a high degree of gear coupling enables the reduction of gearbox dimensions and weight, compared to other types of transmission from 30 ÷ 70%, depending on the required characteristics.

BRIEF DESCRIPTION OF DRAWINGS

The invention is described by means of detailed embodiment examples with reference to accompanying Figures. 1, 2, 3, wherein:

Figure 1 : Cross section of a Precession Transmission

Figure 2: Cross section of a Precession Transmission with a spherical joint

Figure 3: Cross section of a Precession Transmission with multiple output shafts

BEST MODE FOR CARRYING OUT OF THE INVENTION

The Precession Transmission is shown in Figure 1. Its main purpose is to transform the rotational movement by changing the number of revolutions and torque. Applying input torque at the eccentric input shaft, consisting of the eccentric (7), and the eccentric shaft (6), forces the gear (friction disk) (1) to move according to the kinematics of the Euler disk, (where the Euler disk is bevel gear (friction disk) (1), around the coordinate origin (16), placed on the outer gear pair, bevel gears (friction disks) (1) and (2), pitch cones axes intersection simultaneously rolling along the paired conical gear (friction disk) (2). Gear ratio of gear pair, bevel gears (friction disks) (1) and (2), is defined as: Wherein:

i₁ - gear pair 1-2 transmission ratio z₂ - gear 2 teeth number z₁ - gear 1 teeth number or by the friction discs diameter difference: Wherein:

i₁ - friction pair 1-2 transmission ratio d₂ - friction disc 2 diameter d₁ - friction disc 1 diameter

The gear (friction disk) (1), is mounted by bearings (12) on the input shaft subassembly (6) and (7), around which it rotates freely. Gear (friction disk) (2) is fixed - fastened with screws (5), to the lower part of the housing (14). On gear (friction disk) (1), a concentric bevel gear (friction disk) (3) is fixed. The processional motion of both gears (friction discs) (1) and (3) is around the common coordinate origin (16).

Bevel gear (friction disk)3 is coupled to bevel gear (friction disk)4. The gear ratio of gear pairs (friction discs) (3) and (4) is calculated in the same way as the gear ratio of the first gear pair (1) and (2): Wherein: i₂ - gear pair 3-4 transmission ratio Z₄ - gear 4 teeth number Z₃ - gear 3 teeth number

Or for friction discs: Wherein: i₂ - friction pair 3-4 transmission ratio d₄ — friction disc 4 diameter d₃— friction disc 3 diameter

The bevel gear (friction disk) (4), is fastened with screws 15, to the output shaft 8 and together they are supported by a bearing 11, for the lower part of the gearbox housing 14.

The total gear ratio is defined as follows:

Wherein: i - total transmission ratio i_v8 - transmission ratio on shaft 8, in relation to input shaft 6, 7. i₁ - gear pair 1-2 transmission ratio z₂ - gear 2 teeth number z₁- gear 1 teeth number i₂ — gear pair 3-4 transmission ratio Z₄ - gear 4 teeth number Z₃ - gear 3 teeth number or for friction discs respectively: Wherein:

i - total transmission ratio i_v8 - transmission ratio on shaft 8, in relation to input shaft 6, 7. i₁ - friction pair 1-2 transmission ratio d₂ -friction disc 2 diameter d₁- friction disc 1 diameter i₂ - friction pair 3-4 transmission ratio d₄ - friction disc 4 diameter d₃- friction disc 3 diameter

The input shaft subassembly (6-7) is supported by bearings (18) and (10). The bearing (18) is positioned in the subassembly (9) which allows axial movement of the input shaft (6-7) and thus neutralizes transmission gear pairs (friction discs) back-lash and free-wheeling of the output shaft (8). The movable support of the input shaft is in the bearing (10), which is located in the upper part of the gearbox housing (13). The gearbox housing consisting of upper part (13) and lower part (14), which are connected by screws (17).

With the Precession Transmission, it is possible to transfer the movement to the output shaft via any machine element, or elements that enables precession movement around the point. In Figure 1, this movement is achieved by the subassembly eccentric shaft (6-7) and two pairs of gears outer (1- 2) and inner (3-4), while Figure 2. shows a Precession Transmission with a spherical joint (5). The body of the spherical joint (23) becomes also the second output shaft (19), which has a separately defined transmission ratio compared to the output shaft (8). A Precession Transmission can have n (arbitrary integer number) output shafts, on spherical joints, pairs of gears or friction disks. Figure 3. shows a Precession Transmission with two output shafts (8) and (19) on bevel gears.

The gear ratio of the shaft on the spherical joint shown in Figure 2. is calculated as: Wherein:

i_v1 - transmission ratio on shaft (19) i_v1 = i₁ - gear pair 1-2 transmission ratio z₂ - gear 2 teeth number z₁ - gear 1 teeth number

The gear ratio of shaft 8 shown in Figure 2. is calculated as:

Wherein:

i_v8 - transmission ratio on shaft 8 i₁ - gear pair 1-2 transmission ratio z₂ — gear 2 teeth number z₁ - gear 1 teeth number i₂ - gear pair 3-4 transmission ratio z₄ - gear 4 teeth number z₃ — gear 3 teeth number Similarly, the transmission ratio of the output shafts of the Precession Transmission in Figure 3. is given by the expressions: For shaft 8:

Wherein:

i_v8 - transmission ratio on shaft 8 i₁ — gear pair 1-2 transmission ratio z₂ - gear 2 teeth number z₁- gear 1 teeth number i₂ — gear pair 3-4 transmission ratio Z₄ — gear 4 teeth number Z₃ — gear 3 teeth number

For shaft 19: Wherein:

i_v19 - transmission ratio on shaft 19 i₁ -gear pair 1-2 transmission ratio z₂ - gear 2 teeth number z₁ - gear 1 teeth number i₂ — gear pair 21-22 transmission ratio z₂₂ -gear 22 teeth number z₂₁ - gear 21 teeth number

Respectively, it also applies to friction discs, as well as to evolutionary gears with 3, 4, 5,... n output shafts with appropriate changes in the bearing construction. For dynamic balancing, a balancing mass (9), is added to fully balance the inertial moment of the eccentric masses. The balancing mass (9), is attached to the input shaft (6-7).

INDUSTRIAL APPLICABILITY

The invention can be applied in all areas of industry where mechanical transmissions are used. Single staged Precession Transmission with transmission ratio ranges, i = 3 ÷ >10⁶, enables application in places where other transmissions have been used so far in a multi-stage design. It is particularly suitable for use in robotics and servomechanisms, where large gear ratios are required, along with back-lash close to zero. The possibility of back-lash compensation is enabled by the compensation subassembly (9).

Another usage is in heavy construction and agricultural machines and transportation vehicle wheels rotation reduction ratio, where gearboxes are used in drive-wheel heads.

Claims

CLAIMS I. Precession Transmission categorized with precession movement of the bevel gear (1) along the fixed bevel gear (2), or friction disks, achieving primary rotation and torque transmission ratio by means of a spherical joint (23), to the output shaft (19) and additional n spherical joints, and/or n pairs of bevel gears (friction disks) (3-4), 21-22,..,, n-n + 1, which provides additional change of rotation and torque, in the same or different direction, and the same or different transmission ratio, to n output shafts used as reducer, or multiplicator in opposite direction.