WO2016027024A1

WO2016027024A1 - Speed reducer for a turbomachine

Info

Publication number: WO2016027024A1
Application number: PCT/FR2015/052178
Authority: WO
Inventors: Antoine MATHIEU
Original assignee: Hispano-Suiza
Priority date: 2014-08-19
Filing date: 2015-08-07
Publication date: 2016-02-25
Also published as: FR3025010B1; FR3025010A1

Abstract

A speed reducer for a turbomachine, such as a turboprop, comprising rotating parts meshed with each other, characterised in that a first rotating part (16') comprises a helical-tooth pinion (26') meshed with a helical-tooth pinion of a second rotating part, said first rotating part being provided with means (34) for measuring the axial forces to which it is subjected as a result of the transmission of a rotational torque by said second rotating part, said measurement means being configured to be linked to means (38) for calculating said rotational torque from an output signal from said measurement means.

Description

Speed reducer for a turbomachine

TECHNICAL AREA

The present invention relates to a speed reducer for a turbomachine such as a turboprop.

STATE OF THE ART

A turbomachine may comprise one or more mechanical speed reducers. This is particularly the case of a turboprop engine whose propeller (not faired) is rotated by a turbine shaft via a speed reducer, commonly called PGB which is the acronym for Propeller Gear Box .

There are several types of speed reducers such as planetary, chain, worm gear, intermediate drive gear reducers, and so on. All these reducers comprise rotating parts intermeshed with each other. The present invention is preferably but not exclusively applicable to the transmission line intermediate reducer (also called compound reducer).

In the present art, such a speed reducer comprises an input line and an output line driven by the input line through two intermediate transmission lines. The power transmitted by the input line is separated between the intermediate lines before being transferred to the output line. The intermediate transmission lines are parallel and each comprise a shaft carrying an input gear engrained with the input line and an output gear engrained with the output line. The input gears of the two intermediate transmission lines are identical and include straight teeth.

It has already been proposed to equip a turbomachine gearbox means for measuring or calculating the torque transmitted to a rotating part by another rotating part. The accuracy of the torque control of rotation influences in particular the precision of the power supplied by the turbomachine and makes it possible to optimize the lifetime of the gearbox. However, the currently proposed technologies are complex and cumbersome and therefore difficult to use in the aforementioned type of reducer.

For example, there is known a technology in which the rotational torque is calculated from torsion forces which are determined from a torsion angle measured between a transmission shaft between two rotating parts, and a control shaft. The torsion angle is measured by means of a tone wheel associated with each shaft and an inductive sensor. This technology is complex to implement and cumbersome. SUMMARY OF THE INVENTION

The present invention proposes in particular to regulate the power supplied by a turbomachine, by a precise measurement of a torque in a speed reducer.

The invention proposes a speed reducer for a turbomachine, such as a turboprop, comprising intermeshing rotating parts, characterized in that a first rotating part comprises a helical gear gear meshing with a toothed gear. a second rotating part, said first rotating part being equipped with means for measuring the axial forces to which it is subjected due to the transmission of a rotational torque by said second rotating part, said measuring means being mounted on a rolling bearing for guiding said first rotating part and being configured to be connected to means for calculating said rotational torque from an output signal of said measuring means, by the following mathematical relationship:

with C: the rotation torque (in Nm), r _p : the pitch radius of the bearing toothing of the first rotating part (in m), β: the helix angle of this toothing (in rad), and Fa: the axial force induced by this toothing (in N).

In the present application, the term "rotating part" in particular refers to a part intended for a mechanical power transmission.

The invention thus proposes to calculate the rotational torque from a measurement of axial forces. Indeed, as will be explained in more detail in the following, the axial forces to which a rotating part in operation is directly proportional to the torque applied to it. The axial forces are here generated by the co-operation of the helical teeth of the rotating parts. The invention thus proposes to replace straight teeth of the prior art by helical teeth to ensure the generation of axial forces. Although some prior art gearboxes already include helical gear teeth, they are used for other reasons (efficiency, noise reduction, etc.). During rotation of the second rotating part, it causes the first rotating part and applies axial forces due to the cooperation of their helical teeth. In this case, the second rotating part is a driving part and the first rotating part is a driven part. The axial forces are measured by the measuring means which are configured to emit an output signal corresponding to the level of axial forces detected and intended to be transmitted to means for calculating the torque.

In US Pat. No. 6,490,935, it is the axial component of a resistance force which is measured. This axial component is obtained thanks to a tapered roller bearing. The document thus makes it possible to determine the axial forces on a bearing and not the axial forces to which a shaft is directly subjected because of the transmission of a torque. In US-A-2,899,822, the measuring means are not located on a rolling bearing and do not use the mathematical relationship above.

The reducer according to the invention may comprise one or more of the following characteristics, taken separately or in combination with each other:

said rolling bearing is a ball bearing,

said measuring means are mounted on an outer ring of said rolling bearing;

said measuring means are mounted between the outer ring of the rolling bearing and a housing of the gearbox;

said measuring means are integrated with said guide bearing;

said first rotating part is an input, intermediate or output line of the reducer.

The present invention also relates to a turbomachine, characterized in that it comprises at least one gear as described above.

The reducer may include an output line configured to drive an unducted propeller of the turboprop.

Preferably, the turbomachine comprises a computer comprising said calculating means.

The turbomachine is preferably an aircraft turboprop.

DESCRIPTION OF THE FIGURES

The invention will be better understood and other details, characteristics and advantages of the invention will emerge more clearly on reading the following description given by way of nonlimiting example and with reference to the appended drawings in which:

FIG. 1 is a schematic perspective view of a speed reducer with two intermediate transmission lines,

FIG. 2 is a schematic view of an intermediate transmission line, according to the prior art, FIG. 3 is a schematic view of an intermediate transmission line, according to one embodiment of the invention, and

- Figure 4 is a schematic view of an intermediate transmission line, according to an alternative embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 schematically represents a speed reducer with two intermediate transmission lines, this reducer comprising essentially 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.

The different parts 12, 14, 16 of the gearbox form rotating parts and are generally mounted in a housing of the gearbox which is not shown here, this casing having a first port for the passage of the input line and its connection. to a first element of a turbomachine for example, and a second orifice for the passage of the output line and its connection to a second element of the turbomachine. The first element is for example a turbine shaft of the turbomachine and the second element is a drive shaft of a propeller of this turbomachine in the case where the latter is a turboprop.

The input line 12 comprises a shaft 18 carrying a pinion 20 with external external teeth. The pinion 20 and the shaft 18 are coaxial and rotate around the same axis noted B.

The output line 14 comprises a shaft 22 carrying a pinion 24 with external external teeth. The pinion 24 and the shaft 22 are coaxial and rotate about the same axis noted A. They rotate here in the same direction of rotation as the pinion 20 and the shaft 18 of the input line.

The input and output lines 12, 14 are parallel. Their axes of rotation A, B are therefore parallel. The intermediate transmission lines 16 are substantially parallel and identical. Each line 16 has a shaft 25 which carries 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 pinion 24 of the output line 14. The input gears 26 are meshing with the pinion 20 of the input line 12. The pinions 26, 28 are with straight external gears. Each shaft 25 and its gears 26, 28 are coaxial and rotate about the same axis noted C, parallel to the axes A and B.

Figure 2 shows an intermediate transmission line 16 according to the prior art, the gears 26, 28 are straight teeth. References 30 and 32 denote guide bearings of the transmission line, which are mounted between the shaft 25 of the line and the housing of the gear (not shown). The bearings 30, 32 are here rolling bearings, the bearing 30 being a ball bearing located at one end of the shaft 25 and the bearing 32 being a roller bearing located at the opposite end of the shaft.

FIG. 3 represents an embodiment of the invention which is here applied to an intermediate transmission line 16 'but which can be applied to any rotating part of the gearbox.

The intermediate line 16 'differs from that 16 of Figure 2 essentially in that at least one of its teeth is helical and in that it is further associated with means for measuring the axial forces during transmission a couple of rotation.

In the example shown, it is the toothing of the pinion 26 'which cooperates with the input line 12, which is helical. The teeth of the pinion 20 of the input line 12 must have a shape complementary to that of the pinion 26 'of the intermediate line 16' and therefore has a helical shape. Alternatively or additional feature, the other pinion 28 of the line 16 'may have a helical toothing. When transmitting a torque from the input line 12 to the intermediate line 16, the pinion 20 of the input line applies axial forces to the toothing of the pinion 26 'of the intermediate line, by the intermediate helical teeth. These axial forces are directly proportional to the transmitted torque.

According to the invention, the transmitted torque is calculated from a measured value of the axial forces applied to the intermediate line 16 '. For this purpose, the intermediate line 16 'is equipped with means for measuring the aforementioned axial forces.

In the embodiment of FIG. 3, the measurement means

34 are integrated in the guide bearing 30 which is thus of the instrumented type. These measuring means 34 are for example configured to measure the axial forces applied to the line 16 'from the relative axial displacements between the outer and inner rings of the bearing

30.

In the variant embodiment of FIG. 4, the measuring means 34 are mounted between the outer ring of the guide bearing 30 and the casing 36 of the gearbox. The measuring means 34 comprise, for example, a strain gauge-type strain sensor (extensometric or piezoresistive), of the displacement measuring type, of the optical fiber type, etc. They are for example configured to measure the axial forces applied to the line 16 'from the relative axial displacements between the outer ring of the bearing 30 and the housing 36.

The measuring means 34 are configured to emit an output signal which is transmitted to calculation means 38, such as a calculator of the turbomachine, for calculating the torque applied to the line 16 '.

For this, the calculation means 38 use the following mathematical relationship: r * F

C =

with C: the torque transmitted by the toothing (in Nm), r _p : the pitch radius of the pinion (in m), β: the helix angle of the toothing (in rad), and Fa: the axial force induced by the toothing (in N).

Although the invention has been described above in connection with an intermediate line of the gearbox, it could be applied in the same way to the input line or the output line of the gearbox.

Claims

A speed reducer (10) for a turbomachine, such as a turboprop, comprising rotating parts (12, 14, 16 ') meshing with each other, characterized in that a first rotating part (16') comprises a pinion (26 ') with helical gear meshing with a helical gear pinion of a second rotating part (12), said first rotating part being equipped with means (34) for measuring the axial forces to which it is subjected as a result of the transmission of a rotational torque by said second rotating part, said measuring means being mounted on a rolling bearing (30) for guiding said first rotating part (16 ') and being configured to be connected to means (38); ) calculating said rotational torque from an output signal of said measuring means, by the following mathematical relationship:

2. Gearbox (10) according to claim 1, characterized in that said rolling bearing (30) is a ball bearing.

3. Gearbox (10) according to claim 2, characterized in that said measuring means (34) are mounted on an outer ring of said rolling bearing.

4. Gearbox (10) according to claim 3, characterized in that said measuring means (34) are mounted between the outer ring of the rolling bearing and a housing (36) of the gear.

5. Gearbox (10) according to claim 2 or 3, characterized in that said measuring means (34) are integrated with said guide bearing (30).

6. gearbox (10) according to one of the preceding claims, characterized in that said first rotating part is an input line (12), intermediate (16 ') or output (14) of the reducer.

7. Turbomachine, characterized in that it comprises at least one gear (10) according to one of the preceding claims.

8. The turbomachine according to claim 7, characterized in that the gearbox (10) comprises an output line (14) configured to drive an unducted propeller turboprop.

9. The turbomachine according to claim 7 or 8, characterized in that it comprises a computer comprising said calculating means (38).

10. Turbomachine according to one of claims 7 to 9, characterized in that it is a turboprop.