LOAD DISTRIBUTION IN A SPEED REDUCER WITH TWO INTERMEDIATE TRANSMISSION LINES

Abstract

The invention relates to a speed reducer (10) with two intermediate transmission lines (16), in particular for a turbine engine, including an input line (12) and an output line (14) driven by the input line via said intermediate lines, said intermediate lines being substantially parallel, characterised in that it includes load-distribution means between said intermediate lines, said load-distribution means comprising ball-and-socket means (30) for rotatably coupling a first end of the input line, first means (34) for damping the radial movements of said end of the input line, and second means (34) for damping the radial movements of a second opposite end of the input line.

Claims

1. Speed reducer with two intermediate transmission lines, in particular for a turbomachine, comprising an input line and an output line driven by the input line by means of said intermediate lines, these intermediate lines being substantially parallel, wherein it comprises a means of distribution of load between said intermediate lines, this means of load distribution comprising ball-and-socket means for swivel coupling a first end of the input line, first means for damping the radial movements of said first end of the input line, and secondary means for damping the radial movements of a second opposite end of the input line.

2. Reducer according to claim 1, wherein said first and second damping means are configured to allow the input line to move in a direction substantially perpendicular to a plane passing substantially through the axes (C) of the intermediate lines.

3. Reducer according to claim 1, wherein said first and second damping means comprise springs, preferably return springs.

4. Reducer according to claim 3, wherein said springs are identical.

5. Reducer according to claim 1, wherein said first and second damping means comprise roller bearings.

6. Reducer according to claim 5, wherein said springs are identical, and wherein each of said first and second damping means comprises a roller bearing which is mounted on said first or second end of the input line, and which is supported by a spring.

7. Reducer according to claim 1, wherein said first and second damping means are identical.

8. Reducer according to claim 1, wherein said first and second damping means mounted on both sides of a gear of the input line.

9. Reducer according to claim 8, wherein said first and second damping means are situated equidistantly from said gear.

10. Turbomachine, wherein it comprises at least one reducer (10) in accordance with claim 1.

Description

DESCRIPTION OF THE FIGURES

[0025] The invention will be better understood and other details, features and advantages of the invention will become clearer upon reading the following description as a non-limiting example and with reference to the appended drawings of which:

[0026] FIG. 1 is a very schematic view of a speed reducer with two intermediate transmission lines, seen from the side,

[0027] FIG. 2 is a very schematic view of a speed reducer with two intermediate transmission lines, seen from the front,

[0028] FIGS. 3 and 4 are partial schematic views seen from the front of a reducer of the described type, FIG. 3 representing a non-homogeneous distribution of load between the intermediate lines and FIG. 4 a homogeneous distribution of load between the intermediate lines,

[0029] FIG. 5 is a very schematic view of an input line equipped with means of load distribution, and

[0030] FIG. 6 is a very schematic view of an input line equipped with means of load distribution in accordance with the invention.

DETAILED DESCRIPTION

[0031] FIG. 1 very schematically represents a speed reducer 10 with two intermediate transmission lines, said reducer 10 mostly comprising four parts: an input line 12, an output line 14 and two intermediate transmission lines 16 which are driven by the input line 12 and in turn drive the output line 14.

[0032] The different parts 12, 14, 16 of the reducer are in general mounted on a reducer casing which is not represented here, this reducer comprising a first opening for the passage of the input line and its connection to a first component of a turbomachine, for example, and a second opening for the passage of the output line and its connection to a second component of the turbomachine. For example, the first component is a turbine shaft of the turbomachine and the second component is a drive shaft of a propeller of that turbomachine in the case where the latter is a turboprop.

[0033] The input line 12 comprises a shaft 18 bearing a gear 20 with external teeth. The gear 20 and the shaft 18 are coaxial and turn around the same axis marked B.

[0034] The output line 14 comprises a shaft 22 bearing a gear 24 with external teeth. The gear 24 and the shaft 22 are coaxial and turn around the same axis marked A. Here they turn in the same rotational direction as the gear 20 and the shaft 18 of the input line.

[0035] The input and output lines 12, 14 are parallel. Their rotational axes A, B are thus parallel.

[0036] The intermediate transmission lines 16 are substantially parallel and identical. Each line 16 comprises a shaft 25 which bears an input gear 26 at a first end and an output gear 28 at a second end. The output gears 28 are meshed with the gear 24 of the output line 14. The input gears 26 are meshed with the gear 20 of the input line 12. The gears 26, 28 have external teeth. Each shaft 25 and its gears 26, 28 are coaxial and turn around the same axis marked C, parallel to axes A and B.

[0037] As previously explained, this type of reducer 10 is a statically indeterminate system and it is possible for an intermediate line 16 to have the majority of the motor power pass through it, while the other intermediate line sees practically no power flow. As seen in FIG. 2, this poor distribution of power or load is mainly due to the fact that, although the gears 26 are in contact with the gear 20 at points C, and the gear 28 of one of the intermediate lines is in contact with the gear 24 at point D, it is difficult to ensure a lack of play at E, between the gear 24 and the gear 28 of the other intermediate line.

[0038] The invention proposes a solution to this problem by equipping the reducer 10 with a means of distributing the load between the intermediate lines 16.

[0039] The general principle of the distribution of load is represented in FIGS. 3 to 5 and FIG. 6 represents an embodiment of the invention.

[0040] The shaft 18 of the input line 12 is susceptible to move radially (with respect to its longitudinal axis). This is made possible by the fact that one of its ends is swivel mounted (FIG. 5), with regard to, for example, the turbine shaft. The end of the shaft 18 comprises, for example, swivelling grooves 30 engaging with complementary grooves of a sleeve 32 connecting the input line of the reducer to the turbine shaft. Radial movements are to be understood here as the swivelling of the input line 12 around a point situated at the level of its swivelling end.

[0041] The opposite end of the shaft 18 of the input line 12 can thus move in a radial direction, these movements being damped by a spring 34.

[0042] If one of the intermediate lines 16 is more loaded (FIG. 3), that is to say the torque passing through this line is greater than that passing through the other line, then the stress f1, produced by this torque, on the input line gear 20 is greater on one side than the other. A force F will thus be applied to the input line gear 20, which will lead to the movement of the input line. This movement allows the plays to be rebalanced at the level of the input line. When balanced, the stress f1, f2 placed on the gear 20 by the torque on the intermediate lines cancels out, which means the torque on the intermediate lines is equal.

[0043] Advantageously, the damping means of spring 34 is combined with a roller bearing 36 guiding the shaft 18 of the input line 12.

[0044] As mentioned above, a gear misalignment can occur as illustrated in FIG. 5. Due to this misaligned operation, a crowning type longitudinal correction of the gear teeth is required. This correction leads to an increase in surface pressure on the teeth. In addition, if the misalignment is significant, it is not necessarily possible to ensure acceptable operation of the reducer, even with the application of crowning.

[0045] The invention allows this problem to be remedied thanks to the overall input line damping.

[0046] FIG. 6 represents an example of an embodiment of the invention, in which the elements described above are indicated by the same reference numerals.

[0047] Two roller bearings 36, of ball-type for example, are mounted on both sides of the gear 20, at the ends of the input line 12.

[0048] Classically, each bearing 36 can comprise two rings, internal and external respectively, between which a row of ball bearing extends which can be maintained by a ring cage. The internal ring of a first bearing 36 is mounted fixedly on an end of shaft 18 of the input line 12, opposite to its end comprising the swivelling grooves 30. The internal ring of the second bearing 36 is mounted fixedly on the end of the shaft 18 comprising the swivelling grooves 30.

[0049] The damping springs 34 support the bearings 36. A first spring 34 supports the first bearing 36, and a second spring 34 supports the second bearing 36. Preferably, the springs 34 are identical. Preferably the springs are return springs. Advantageously, they are situated equidistantly from the gear 20.

[0050] The end of the shaft 18 which comprises the swivelling grooves 30 is engaged with the complementary grooves of a sleeve 32 connecting the input line of the reducer to the turbine shaft.

[0051] The invention works as indicated previously in relation to FIGS. 3 and 4. As is visible in FIG. 6, if one of the intermediate lines 16 is more loaded (FIG. 3), that is to say the torque passing through the line is greater than that passing through the other line, then the stress f1, produced by this torque, on the input line gear 20 is greater than on the other side. A force F will thus be applied to the input line gear 20, which will lead to the movement of the input line, but it does not mean it will misalign thanks to the invention.