Gearbox

Abstract

A gearbox comprises a high-speed shaft (1) with a gear pinion (2), a low-speed shaft (6) with a low-speed gear wheel (7) and at least two branches of split power containing a shaft (3) of the split power. A supporting disc (9) is located in the gearbox, which is connected to the shaft (1), (6) and / or the pinion gear (2) and / or the low-speed gear wheel (7) via a flexible element (10) or a joint (11) to tilt axis of the supporting disc (9). Each of the split power branch shafts (3) is provided with a first portion of a sliding fit and a circumference of the supporting disc (9) is provided with corresponding second portion of the sliding fit to create a sliding connection and to capture axial forces by the supporting disc (9) and split power branch shafts (3). Axial force generated by the gearing increases when one branch is loaded by more load. This force causes axial displacement of more loaded branch, and thereby tilting of the supporting disc (9). Thereby, less loaded branch retracts more into engagement at the same time, which results in its higher loading.

Description

[0001] Gearbox

[0002] Field of the invention

[0003] The present invention relates to the field of geared transmissions for transmission of rotary motion, in particular the field of the split power gearbox design.

[0004] Background of the invention

[0005] One of the known gearbox types is a split power gearbox. In the gearbox of this type, the power is transmitted by multiple branches at the same time, usually by two or three ones. A branch refers to a shaft with two gear wheels of various diameter. One of the gear wheels engages with a gear wheel on the input shaft and the other gear wheel engages with a gear wheel on the output shaft. From the gearbox design’s point of view, it is favourable but not necessary so that the input and output shafts are mutually coaxial, and the branches are rotated 180° each other for the gearbox with two branches, or 120° for the gearbox with three branches.

[0006] To equalize the power being transmitted across the branches, differentiation between or among the branches is needed. This is usually provided using a floating high-speed shaft that radially floats into an optimum position in which the power is split equally. However, the radial highspeed shaft may be unstable, in particular when not loaded.

[0007] Summary of the invention

[0008] The present invention provides the split power gearbox design. The gearbox comprises a highspeed shaft provided with a gear pinion and fitted in at least one radial bearing. Furthermore, the gearbox comprises a low-speed shaft provided with a low-speed gearwheel. The low-speed shaft may be fitted in at least one radial bearing, or it may be hung on the downstream shaft only.

[0009] Furthermore, the gearbox comprises two or three split power branches. Each of the split power branches includes a split power shaft. This is fitted in the radial bearings and provided with firmly attached gear wheel of larger diameter, and firmly attached gear wheel of smaller diameter. The larger gear wheels of the split power branches are coupled with the pinion gear of the highspeed shaft, and they form a high-speed gear stage in combination. The smaller gear wheels of the split power branches are coupled with the low-speed gear wheel of the low-speed shaft, and they form a low-speed gear stage in combination. Either the high-speed gear stage and / or low- speed gear stage is provided with a helical gearing. Helix angle of the high-speed gear stage differs from the helix angle of the low-speed gear stage. Therefore, when the split power branch shaft moves axially, the high-speed stage and low-speed gear stage will rotate differently in angular direction. The power is differentiated thereby.

[0010] A supporting disc is fitted coaxially with the shaft of said at least one gear with the helical gearing. A flexible element or a joint is used to connect the supporting disc to the high-speed or low-speed shaft and / or gear pinion of said coaxially arranged gear with the helical gearing. The flexible element or joint is capable of providing inclination of axis of the supporting disc with respect to the axis of said coaxially arranged gear with the helical gearing. Furthermore, the flexible element or joint prevents from mutual rotation of the supporting disc and an element to which it is connected via the flexible element (i.e., to the shaft and / or gear pinion and / or low- speed gear wheel of the said coaxially arranged gear with the helical gearing). Axial position of the supporting disc centre remains unchanged.

[0011] The joint will provide equal distribution of the power into individual branches. However, this design is more complex from the manufacturing point of view, and requires lubrication. The joint may be a ball joint where both portions thereof are secured against mutual rotation along the longitudinal axis (the axis parallel to the shaft of the gear with the helical gearing). The flexible connection does not provide fully equal power distribution because the power splitting is influenced by rigidity of the connection. Compared to the joint, it is easier from the manufacturing point of view and no lubrication is required. To achieve the power splitting as most even as possible, the flexible connection needs to be designed to have low flexural rigidity but sufficient rigidity in axial direction. The flexible connection shows high rigidity in moving in all axes and in rotation around the longitudinal axis (the axis parallel to the shaft of the gear with helical gearing), but low rigidity when rotating around axes perpendicular to the longitudinal axis. Said may be achieved by e.g., various diameter and material parameters, the flexible connection may be hollow, etc.

[0012] Each split power branch shaft is provided with a first portion of a sliding fit and a circumference of the supporting disc is provided with corresponding second portion of the sliding fit. A technical effect of the sliding fit is forming of a slide connection and capturing axial forces between the supporting disc and the split power branch shafts.

[0013] In a favourable embodiment, the low-speed gear stage is the one being provided with the helical gearing. This is favourable as it generates higher axial forces than the high-speed gear stage. The supporting disc captures the axial forces and the forces are not transmitted to a driving and driven machine.

[0014] Depending on a specific embodiment of the gearbox, the low-speed gear wheel may have either internal or external gearing.

[0015] The supporting disc may be located between the high-speed shaft and the low-speed shaft. It means the length of the shafts do not interfere with the supporting disc, and the supporting disc is located in a free space between them.

[0016] In another embodiment, the supporting disc may be provided with a central hole through which the high-speed or low-speed shaft goes. Then, the supporting disc looks like a ring being pulled on one of the shafts. This embodiment permits selecting a different design arrangement of a machine.

[0017] The flexible element may have form of an axial projection of the supporting disc in fixed connection with the high-speed or low-speed shaft and / or the gear pinion and / or low-speed gear wheel of said axially arranged gear with the helical gearing.

[0018] In another embodiment, the flexible element may have form of at least one spring arranged around the central axis of the supporting disc. The spring must be firmly attached to the supporting disc on the first side and to the shaft and / or gear pinion and / or low-speed gear wheel of said axially arranged gear with the helical gearing on the other side.

[0019] The described principle of power splitting using the tilting supporting disc may be used for the gearboxes where the power is transmitted by a plurality of branches at the same time. Optimized differentiation occurs only when the branches are in optimized axial position. This is provided by the supporting disc that captures axial forces of each split power branch, and provides mutual axial positions of the gears with simple helical gearing. The tilting supporting disc provides for optimized branch position of individual branches in relation to each other and to the output shaft. Should one branch be loaded more, the axial force generated by the gearing increases This force causes axial displacement of more loaded branch, and thereby tilting of the supporting disc. Thereby, less loaded branch retracts more into engagement at the same time, which results in higher loading. The uneven loading of particular branches is continuously and repeatedly balanced.

[0020] Explanation of drawings

[0021] The exemplary embodiments of the present invention is described with reference to the drawings, in which:

[0022] Fig. 1 - shows schematic longitudinal cross-section of the gearbox according to the present invention;

[0023] Fig. 2 - shows schematic longitudinal cross-section of the supporting disc provided with a joint connected to a low-speed gear wheel;

[0024] Fig. 3 - shows schematic longitudinal cross-section of the supporting disc provided with a flexible element in the form of an axial projection firmly connected to the low-speed gear wheel; Fig. 4 - shows schematic longitudinal cross-section of the supporting disc provided with a central hole and a flexible element in the form of a spring arranged around the central hole of the supporting disc, connected to the low-speed gear wheel.

[0025] Exemplary embodiments of the invention

[0026] Example 1

[0027] A split power gearbox comprises a high-speed shaft 1 provided with a gear pinion 2 fitted in radial bearings 8. Furthermore, the gearbox includes a low-speed shaft 6 provided with a low- speed gear wheel 7 fitted in the radial bearings 8. The high-speed shaft 1 and the low-speed shaft 6 are coaxial. The low-speed gear wheel 7 has external gearing.

[0028] Furthermore, the gearbox comprises two split power branches. Each of the split power branches includes a split power shaft 3 being fitted in the radial bearings 8. Each split power shaft 3 is provided with two firmly attached gears - a larger gear wheel 4 (having a relatively larger diameter) and a smaller gear wheel 5 (having a relative smaller diameter).

[0029] The larger gear wheels 4 of the split power branches are coupled with the pinion gear 2 of the high-speed shaft 1, and they form a high-speed gear stage in combination. The smaller gear wheels 5 of the split power branches are coupled with the low-speed gear wheel 7 of the low- speed shaft 6, and they form a low-speed gear stage in combination. The high-speed gear stage and low-speed gear stage are provided with a helical gearing. Helix angle of the high-speed gear stage is smaller in this embodiment than the helix angle of the low- speed gear stage. Relatively larger helix angle in the gear means that the gear is the one of which gearing provide axial movement of split power branches. In doing so, there are undesired axial forces occurring in the gear that need to be captured, otherwise, the forces would undesirably transmit to the technology downstream the gearbox. Due to lower speed, it is easier to capture undesired axial forces by the supporting disc 9 from the low-speed gear stage.

[0030] Coaxially with the high-speed shaft 1 as well as the low-speed shaft 6, the gearbox houses the supporting disc 9 (the supporting disc 9 axis of rotation is identical to the axis of rotation of both shafts 1, 6). The supporting disc 1 is located between the high-speed shaft 1 and the low- speed shaft 6.

[0031] The supporting disc 9 is connected to the low-speed gear wheel 7 of the low-speed gear stage via a flexible element 10 to tilt axis of the supporting disc 9 with respect to the axis of the low- speed gear stage. Axial position of the supporting disc 9 centre remains unchanged. The flexible element 10 is an axial projection of the supporting disc 9 firmly attached to the low-speed gear wheel 7 of the low-speed gear stage. The flexible element 10 prevents mutual rotation of the supporting disc 9 with respect to the low-speed gear wheel 7 of the low-speed gear stage.

[0032] Each of the split power branch shafts 3 is provided with a first portion of a sliding fit, which is circumferential groove in this case. The circumference of the supporting disc 9 is provided by corresponding second portion of the sliding fit. Fitting of the circumference of the supporting disc 9 into the circumferential grooves of the split power branch shafts 3 produces a sliding connection being capable of capturing the axial forces between the supporting disc 9 and split power branch shafts 3.

[0033] The exemplary embodiment is shown in Fig. 1 and Fig. 3.

[0034] Example 2

[0035] The split power gearbox differs in this example from Example 1 in that the supporting disc 9 is connected to the low-speed gear wheel 7 of the low-speed gear stage via a joint 11. The joint 11 is capable of providing tilting of the axis of the supporting disc 9 with respect to axis of the low-speed gear stage. Axial position of the supporting disc 9 centre remains unchanged. The joint 11 is a ball joint of which both portions are secured against mutual rotation along the longitudinal axis (i.e., axis parallel to the low-speed shaft 6). Thus, the joint 11 prevents mutual rotation of the supporting disc 9 with respect to the low-speed gear wheel 7 of the low-speed gear stage.

[0036] The exemplary embodiment is shown in Fig. 1 and Fig. 2.

[0037] List of reference numerals

[0038] 1 - high-speed shaft

[0039] 2 - gear pinion of the high-speed shaft

[0040] 3 - split power branch shaft

[0041] 4 - larger gear wheel

[0042] 5 - smaller gear wheel

[0043] 6 - low-speed shaft

[0044] 7 - low-speed gear wheel

[0045] 8 - radial bearing

[0046] 9 - supporting disc

[0047] 10 - flexible element

[0048] 11 - joint

Claims

WO 2025 / 021238 AMENDED CLAIMS PCT / CZ2024 / 050049 received by the International Bureau on 15 January 2025 (15.01 .2025)1. A gearbox comprising a high-speed shaft (1) provided with a gear pinion (2) and fitted in at least one radial bearing (8), a low-speed shaft (6) provided with a low-speed gear wheel (7) and two or three split power branches, wherein each split power branch includes a split power shaft (3) being fitted in radial bearings (8) and provided with two firmly attached gear wheels (4), (5) of different diameters, wherein larger gear wheels (4) of split power branches are coupled with a gear pinion (2) of the high-speed shaft (1) and form a high-speed gear stage in combination, and smaller gear wheels (5) of split power branches are coupled with low-speed gear wheel (7) of the low-speed shaft (6) and form a low-speed gear stage in combination, wherein the high-speed gear stage and / or low-speed gear stage is provided with a helical gearing characterized in that coaxially with the high-speed shaft (1) and / or low-speed shaft (6) of at least one gear with the helical gearing, a supporting disc (9) is fitted in the gearbox and is attached to the high-speed shaft (1) and / or gear pinion (2) or to the low speed shaft (6) and / or low- speed gear wheel (7) of said coaxially arranged gear with the helical gearing via a flexible element (10) or a joint (11) to tilt axis of the supporting disc (9) with respect to axis of said coaxially arranged gear with the helical gearing, axial position of the centre of the supporting disc (9) is fixed and the flexible element (10) or joint (11) is adapted to prevent from mutual rotation of the supporting disc (9) with respect to the shaft (1), (6) and / or gear pinion (2) and / or low-speed gear wheel (7) of said coaxially arranged gear with the helical gearing, and each of the split power branch shafts (3) is provided with a first portion of a sliding fit and a circumference of the supporting disc (9) is provided with corresponding second portion of the sliding fit to create a sliding connection and to capture axial forces by the supporting disc (9) and split power branch shafts (3), wherein, upon the helical gearing being provided both on high-speed gear stage and low-speed gear stage, the helix angle of the high-speed gear stage differs from the helix angle of the low-speed gear stage.10AMENDED SHEET (ARTICLE 19)2. The gearbox according to claim 1 characterized in that the low-speed gear stage is provided with the helical gearing.

3. The gearbox according to claim 1 or claim 2 characterized in that the low-speed gear wheel (7) has internal gearing or external gearing.

4. The gearbox according to any of the previous claims 1 to 3 characterized in that the supporting disc (9) is located between the high-speed shaft (1) and low-speed shaft (6).

5. The gearbox according to any of the previous claims 1 to 3 characterized in that the supporting disc (9) is provided with a central hole through which the high-speed shaft (1) or low-speed shaft (6) goes.

6. The gearbox according to any of the previous claims 1 to 4 characterized in that the flexible element (10) is an axial projection of the supporting disc (9) firmly connected with the high-speed shaft (1) and / or low speed shaft (6) and / or gear pinion (2) and / or low-speed gear wheel (7) of said coaxially arranged gear with the helical gearing.

7. The gearbox according to any of the previous claims 1 to 5 characterized in that the flexible element (10) is at least one spring arranged around the central axis of the supporting disc (9) firmly connected with the supporting disc (9) on the first side, and with the shaft (1), (6) and / or gear pinion (2) and / or low-speed gear wheel (7) of said axially arranged gear with the helical gearing on the other side.11AMENDED SHEET (ARTICLE 19)

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