Power transmission box
The power transmission box with a roller bearing design addresses the challenge of secure axial load transfer in rotor blade systems by facilitating continuous operation through controlled force distribution and assembly simplicity.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- NTN EUROPE
- Filing Date
- 2023-12-22
- Publication Date
- 2026-06-12
Smart Images
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Abstract
Description
Title of the invention: Power transmission box
[0001] The invention relates to a power transmission box comprising an assembly intended to be driven in rotation by a transmission pinion, said assembly comprising a rotor carrying in rotation a variable geometry unit.
[0002] It applies in particular to power transmission boxes for a rotor of a gyroplane carrying variable pitch blades, such as a rear rotor of a helicopter.
[0003] In order to adjust the pitch of the blades, the box includes a control rod which is actuated in translation, said rod being connected to a control shaft by means of a bearing to transform a translation of said rod into a modification of the pitch of the blades.
[0004] Given the high axial stresses to which the bearing is subjected, document EP-3 587 845 describes the use of a bearing comprising two rows of angular contact balls which are mounted so that in the event of degradation of one, the other remains operational in order to secure the blade pitch control function.
[0005] To limit the complexity of mounting the bearing according to this prior art, document EP-4 166 803 provides a bearing design comprising two rows of angular contact balls in a raceway respectively, in which a clearance is formed between the tracks of said raceways and said rows, said clearances being arranged so that axial forces in one direction are transmitted exclusively through one of said raceways and that, in the event of degradation of said raceway, the transmission of said axial forces is transferred to the other raceway.
[0006] The invention aims to improve the prior art by proposing in particular a transmission box comprising two rows of angular contact balls in a rolling race respectively, in which the design of said races is improved to secure the transfer of the axial load from one degraded race to the other race, and this in a bearing whose manufacture and assembly are facilitated.
[0007] To this end, the invention proposes a power transmission box comprising an assembly intended to be driven in rotation by a transmission pinion, said assembly comprising a rotor carrying in rotation a variable geometry unit, said box comprising a control rod for a mechanism for adjusting the geometry of said unit, said rod being actuated in translation and said mechanism comprising a control shaft connected to said rod by means of a roller bearing, said mechanism being arranged to transform a translation of said rod into a modification of the geometry of the unit, said bearing comprising a driving member fixed in rotation to the rod and a driven member fixed in rotation to the shaft. control, each of said components having two axially spaced running tracks forming with the tracks of the other component two running paths in each of which a row of spherical rolling bodies is arranged to guide the relative rotation of said components, the rows of spherical rolling bodies being arranged opposite an upstream - respectively downstream - portion of the driving - respectively driven - running tracks along a direct load line to transmit the translational force in a principal direction extending from a first to a second of said rows, the driving component comprising a driving ring on which the first driving running track is formed and the driven component comprising two driven rings on each of which a portion of the first driven running track is formed, said driven rings being axially joined to form said first driven running track,The osculation rates of the upstream portion of the first leading track and the downstream portion of the first led track being each between 0.51 and 0.57, the sum of the osculation rates of the upstream portion of the second leading track and the downstream portion of the second led track being less than the sum of the osculation rates of the upstream portion of the first leading track and the downstream portion of the first led track.
[0008] Other objects and advantages of the invention will become apparent from the following description, made with reference to the accompanying figures, in which:
[0009] [Fig. 1] schematically represents a longitudinal section of a transmission box according to an embodiment of the invention;
[0010] [Fig.2],
[0011] [Fig.3] and
[0012] [Fig.4] each represent in longitudinal section one side of a bearing for a transmission box, according respectively to an embodiment of the invention.
[0013] In relation to these figures, a power transmission box is described below comprising an assembly intended to be driven in rotation by a transmission pinion 1, said assembly comprising a rotor 2 carrying in rotation a variable geometry unit 3.
[0014] According to one envisaged application, the box allows power transmission to a rotor 2 of a gyroplane carrying variable pitch blades 3a, such as a rear rotor 2 of a helicopter.
[0015] Fig. 1 schematically represents a rotor 2 equipped with external teeth 4 for its rotational drive by the transmission pinion 1, said rotor being supported along an axis of rotation A by a set of bearings 5, the blades 3a being mounted with a variable angular pitch on said rotor.
[0016] The box includes a control rod 6 for a mechanism 7 for adjusting the geometry of the variable geometry unit 3, said rod being actuated in translation along the axis A to, in the intended application, control the pitch of the blades 3a of the rear rotor 2, in particular to a value adapted to provide a thrust which balances the reaction torque of the main rotor of the helicopter.
[0017] The adjustment mechanism 7 comprises a control shaft 8 which is connected to the rod 6 by means of a bearing 9, said mechanism being arranged to transform a translation of said rod along the axis of rotation A into a modification of the geometry of the unit 3. [Fig. 1] schematically shows the bearing 9 and a linkage 7a between the control shaft 8 and the blades 3a so that a translation of said shaft induces a rotation of said blades on the rotor 2.
[0018] The bearing 9 comprises a driving member 10 rotationally fixed to the control rod 6 and a driven member 11 rotationally fixed to the control shaft 8. In the figures, the driving member 10 is external, the driven member 11 being internal. However, depending on the structure of the transmission, the reverse configuration may be considered.
[0019] Each of the members 10, 11 has two axially spaced rolling tracks 10a, 10b; lia, 11b forming with the tracks lia, 11b; 10a, 10b of the other member 11, 10 two rolling paths 12, 13 in each of which a row 14, 15 of spherical rolling bodies 16 is arranged to guide the relative rotation of said members around the axis A.
[0020] In the description, the terms for positioning in space are taken in relation to the axis of rotation A of the bearing 9, which coincides with the axis of translation of the rod 6 and control shaft 8. In particular, the terms "inside" and "outside" refer to a location respectively close to and far from the axis A.
[0021] The rows 14, 15 of spherical rolling bodies 16 are in oblique contact in the rolling paths 12, 13 by being arranged opposite an upstream portion lOal, lObl - respectively downstream 1 la2, 1 lb2 - of the leading rolling tracks 10a, 10b - respectively led 1 la, 11b- along a direct load line La to transmit the translational force in a main direction SI extending from a first 14 to a second 15 of said rows.
[0022] In the description, the terms "upstream"; "downstream"; "first" and "second" are defined with respect to the SI principal direction of application of a control force by the rod 6 on the shaft 8, namely from left to right in the figures.
[0023] The driving member 10 comprises a driving ring 17 on which is formed the first driving bearing track 10a, the driven member 11 comprising two driven rings 18, 19 on each of which is formed an upstream portion 1 la4 and the downstream portion 1 la2 of the first driving bearing track 1 la.
[0024] The driven rings 18, 19 are axially joined to form the first track 1 of the driven bearing, in particular by being held axially by means of a connecting ring.
[0025] Each of the portions lOal, lObl, lla2, llb2 of tracks 10a, 10b, lia, 11b of rolling has an osculation rate which is the ratio of the radius of curvature of said portion to the diameter of the spherical rolling bodies 16. The osculation rates of the upstream portion lOal of the first leading track 10a and of the downstream portion 1 la2 of the first led track lia are each between 0.51 and 0.57.
[0026] In particular, these increased osculation rates compared to a standard value of 0.50 make it possible to form a clearance B, C, in particular between 0.1 and 0.5 mm and more precisely between 0.2 and 0.3 mm, between the first row 14 of rolling bodies 16 and each of the portions lOal, lla2 of tracks 10a, lia.
[0027] Furthermore, the sum of the osculation rates of the upstream portion lObl of the second leading track 10b and the downstream portion 1 lb2 of the second led track 11b is less than the sum of the osculation rates of the upstream portion lOal of the first leading track 10a and the downstream portion 1 la2 of the first led track lia.
[0028] Thus, the control effort in the main direction SI is applied to the driving ring 17 to be transmitted to the driven member 11 only by the second row 15 of spherical rolling bodies 16, insofar as a clearance B, C is formed between the rolling bodies 16 and each of the tracks 10a, 1 la of the first rolling path 12.
[0029] Furthermore, in the event of degradation of the second rolling path 13, in particular on a clearance greater than the sum of the clearances B, C of the first rolling path 12, the rolling bodies 16 come into contact on said first path to transmit the force in the main direction SI through the first row 14 of rolling bodies 16.
[0030] According to one embodiment, the osculation rate of the downstream portion 1 lb2 of the second led track 11b and / or the osculation rate of the upstream portion 10b 1 of the second leading track 10b are less than 0.51, in particular being each of the order of 0.50 which corresponds to a standard osculation rate for an oblique contact ball bearing.
[0031] Advantageously, at least one of the osculation rate of the upstream portion lOal of the first leading track 10a and the osculation rate of the downstream portion 1la2 of the first led track 1la is between 0.53 and 0.54. In particular, the osculation rate of the upstream portion lOal of the first leading track 10a is substantially equal to the osculation rate of the downstream portion 1la2 of the first led track 1la, for example being 0.538 to each form a clearance B, C of the order of 0.3 mm for each of said tracks.
[0032] In relation to [Fig.2], the driving member 10 comprises a single ring 17 on which the first 10a and second 10b driving bearing tracks are formed.
[0033] Advantageously with respect to the assembly of the bearing 9, the second leading track 10b extends between two edges respectively front 20 and rear 21 along the main direction SI, said rear edge being inscribed in a diameter which is greater than the diameter in which said front edge is inscribed.
[0034] In particular, the second leading track 10b has a maximum diameter Dmax, the rear edge 21 being inscribed in a diameter which is greater than 90% of said maximum diameter.
[0035] Similarly, the driven member 11 according to [Fig.2] includes a third driven ring 22 on which is formed the second driven bearing track 11b, said second driven track extending between two edges respectively front 23 and rear 24 along the main direction SI, said front edge being inscribed in a diameter which is smaller than the diameter in which said rear edge is inscribed.
[0036] In particular, the second conducted track 11b has a minimum diameter Dmin, the front edge 23 being inscribed in a diameter which is less than 110% of said minimum diameter.
[0037] In relation to figures 3 and 4, the bearing 9 allows the transmission of a translational force in an opposite direction S2 extending from the second 15 to the first 14 row of rolling bodies 16. Thus, depending on the direction SI, S2 of translation of the rod 6, the adjusting mechanism 7 can adjust the pitch in respectively one direction.
[0038] In particular, the driving member 10 shown in these figures 3 and 4 comprises two rings 25, 26 on which respectively the first 10a and the second 10b driving bearing tracks are formed, said rings being axially joined to form the driving member 10.
[0039] Furthermore, the driven member 11 comprises two driven rings 27, 28 on each of which is formed an upstream portion 1 lb4 and the downstream portion 1 lb2 of the second driven bearing track 11b, said driven rings being axially joined to form said second driven bearing track.
[0040] More specifically, the driven member 11 according to [Fig.3] comprises two lateral rings 18, 28 axially joined on either side of a central ring 27, 19, said lateral rings respectively carrying the upstream portion 1 la4 of the first driven bearing track 1 la and the downstream portion 1 lb2 of the second driven bearing track 11b, the downstream portions 1 la2 of said first track and upstream portions 1 lb4 of said second track being formed on either side of the central ring 27, 19.
[0041] In [Fig.4], the driven member 11 comprises two axially joined central rings 19, 27, the downstream portions 1 la2 of the first driven track 1 la and upstream portions 1 lb4 of the second driven track 11b being formed on either side of said central rings respectively, the driven member 11 further comprising two lateral rings 18, 28 axially joined respectively on either side of one of the said central rings, the said lateral rings respectively carrying the upstream portion 1 la4 of the first driven bearing track 1 la and the downstream portion 1 lb2 of the second driven bearing track 11b.
[0042] In relation to figures 3 and 4, the rows 14, 15 of spherical rolling bodies 16 are arranged opposite a downstream portion 10a3, 10b3 - respectively upstream 1 la4, 1 lb4 - of the leading rolling tracks 10a, 10b - respectively led 1 la, 11b-along an indirect load line Lb to transmit the translational force in the opposite direction S2.
[0043] The osculation rates of the downstream portion 10b3 of the second leading track 10b and of the upstream portion 1 lb4 of the second led track 1 lb are each between 0.51 and 0.57, the sum of the osculation rates of the downstream portion 10a3 of the first leading track 10a and of the upstream portion 1 la4 of the first led track lia being less than the sum of the osculation rates of the downstream portion 10b3 of the second leading track 10b and of the upstream portion 1 lb4 of the second led track 1 lb.
[0044] Thus, symmetrically to the forward direction SI, the control effort in the reverse direction S2 is applied to the driving member 10 to be transmitted to the driven member 11 only by the first row 14 of spherical rolling bodies 16, insofar as a clearance B', C' is formed between the rolling bodies 16 and each of the tracks 10b, 11b of the second rolling path 13.
[0045] And, in the event of degradation of the first rolling track 12, in particular on a clearance greater than the sum of the clearances B', C' of the second rolling track 13, the rolling bodies 16 come into contact on said second track to transmit the force in the opposite direction S2 through the second row 15 of rolling bodies 16.
[0046] Advantageously, the downstream portion 1 la2 of the first track led 1 la and the upstream portion 1 lb4 of the second track led 1 lb have the same osculation rate. Similarly, the upstream portion 1 la4 of the first track led 1 la and the downstream portion 1 lb2 of the second track led 1 lb have the same osculation rate.
[0047] Similarly, a symmetry can be foreseen between the first 12 and second 13 rolling paths with first 10a and second 10b leading tracks having the same osculation rate.
Claims
1. Demands A power transmission unit comprising an assembly intended to be driven in rotation by a transmission pinion (1), said assembly comprising a rotor (2) rotating a variable geometry unit (3), said unit comprising a control rod (6) for a mechanism (7) for adjusting the geometry of said unit, said rod being actuated in translation and said mechanism comprising a control shaft (8) connected to said rod by means of a bearing (9), said mechanism being arranged to transform a translation of said rod into a modification of the geometry of the unit (3), said bearing comprising a driving member (10) rotationally fixed to the rod (6) and a driven member (11) rotationally fixed to the control shaft (8), each of said members having two axially spaced bearing tracks (10a, 10b; 11a, 11b) forming two paths with the tracks (11a, 11b; 10a, 10b) of the other member (11, 10). (12,13) of bearings in each of which a row (14, 15) of spherical rolling bodies (16) is arranged to guide the relative rotation of said members, the rows (14, 15) of spherical rolling bodies (16) being arranged opposite an upstream (10a, 10b) - respectively downstream (11a, 11b) - portion of the driving raceways (10a, 10b) - respectively driven (11a, 11b) - along a direct load line (1a) to transmit the translational force in a principal direction (11) extending from a first (14) to a second (15) of said rows, the driving member (10) comprising a driving ring (17) on which the first driving raceway (10a) is formed and the driven member (11) comprising two driven rings (18, 19) on each of which is formed a portion (lla4, 1 la2) of the first driven bearing track (lia), said driven rings being axially joined to form said first driven bearing track,said transmission being characterized in that the oscillation rates of the upstream portion (lOal) of the first leading track (10a) and of the downstream portion (lla2) of the first driven track (lia) are each between 0.51 and 0.57, the sum of the oscillation rates of the upstream portion (lObl) of the second leading track (10b) and of the downstream portion (llb2) of the second driven track (11b) being less than the sum of the rates, of osculation of the upstream portion (lOal) of the first leading track (10a) and of the downstream portion (1 la2) of the first led track (lia).
2. Transmission box according to claim 1, characterized in that the oscillation rate of the downstream portion (1 lb2) of the second driven track (11b) and / or the oscillation rate of the upstream portion (1Obl) of the second driving track (10b) are less than 0.
51.
3. Transmission box according to any one of claims 1 or 2, characterized in that at least one of the oscillation rate of the upstream portion (lOal) of the first leading track (10a) and the oscillation rate of the downstream portion (lla2) of the first driven track (lla) is between 0.53 and 0.
54.
4. Transmission box according to any one of claims 1 to 3, characterized in that the slewing rate of the upstream portion (10a) of the first leading track (10a) is substantially equal to the slewing rate of the downstream portion (11a2) of the first driven track (1a).
5. Transmission box according to any one of claims 1 to 4, characterized in that the driving member (10) comprises a single ring (17) on which the first (10a) and second (10b) driving raceways are formed, said second driving raceway extending between two edges respectively front (20) and rear (21) along the principal direction (SI), said rear edge being inscribed in a diameter which is greater than the diameter in which said front edge is inscribed.
6. Transmission box according to any one of claims 1 to 4, characterized in that the driving member (10) comprises two rings (25, 26) on which respectively the first (10a) and the second (10b) driving bearing tracks are formed, said rings being axially joined to form the driving member (10).
7. Transmission box according to any one of claims 1 to 6, characterized in that the driven member (11) comprises a third driven ring (22) on which is formed the second driven raceway (11b), said second driven raceway extending between two edges respectively front (23) and rear (24) along the principal direction (SI), said front edge being inscribed in a diameter which is smaller than the diameter in which said rear edge is inscribed.
8. Transmission box according to any one of claims 1 to 6, characterized in that the driven member (11) comprises two driven rings (27, 28) on each of which is formed a portion respectively upstream (1 lb4) and downstream (1 lb2) of the second driven bearing track (11b), said driven rings being axially joined to form said second driven bearing track.
9. Transmission box according to claim 8, characterized in that the driven member (11) comprises two lateral rings (18, 28) axially joined on either side of a central ring (27), said lateral rings respectively carrying the upstream portion (1 la4) of the first driven raceway (1 la) and the downstream portion (1 lb2) of the second driven raceway (11b), the downstream portions (1 la2) of said first raceway and upstream portions (1 lb4) of said second raceway being formed on either side of the central ring (27).
10. Transmission box according to claim 8, characterized in that the driven member (11) comprises two axially joined central rings (19, 27), the downstream portions (1 la2) of the first driven track (1 la) and upstream portions (1 lb4) of the second driven track (11b) being formed on either side of said central rings respectively, the driven member (11) further comprising two axially joined lateral rings (18, 28) respectively on either side of said central rings, said lateral rings carrying respectively the upstream portion (1 la4) of the first driven running track (1 la) and the downstream portion (1 lb2) of the second driven running track (11b).
11. A transmission according to any one of claims 1 to 10, characterized in that the rows (14, 15) of spherical rolling elements (16) are arranged opposite a downstream portion (10a3, 10b3) – respectively upstream (11a4, 11b4) – of the driving raceways (10a, 10b) – respectively driven (11a, 11b) – along an indirect load line (Lb) to transmit the translational force in a reverse direction (S2) extending from the second (15) to the first (14) of said rows, the oscillation rates of the downstream portion (10b3) of the second driving raceway (10b) and of the upstream portion (11b4) of the second driven raceway (11b) are each between 0.51 and 0.57, the sum of the oscillation rates of the downstream portion (10a3) of the first leading track (10a) and of the upstream portion (1 la4) of the first led track (lia) being less than the sum of the osculation rates of the downstream portion (10b3) of the second led track (10b) and the upstream portion (1 lb4) of the second led track (11b).
12. Transmission box according to claim 11, characterized in that the downstream portion (1 la2) of the first driven track (1 la) and the upstream portion (1 lb4) of the second driven track (11b) have the same rate of oscillation.
13. Transmission box according to any one of claims 11 or 12, characterized in that the upstream portion (1 la4) of the first driven track (1 la) and the downstream portion (1 lb2) of the second driven track have the same rate of oscillation.
14. Transmission box according to any one of claims 11 to 13, characterized in that the first (10a) and second (10b) leading tracks have the same rate of oscillation.