FR3072939A1 - ROTOR NOT COLLECTIVE VARIABLE AND AIRCRAFT - Google Patents

Abstract

The present invention relates to a variable collective pitch rotor rotatable about an axis of rotation (AXROT). Said variable collective pitch rotor comprises a plurality of blades mounted individually movable on the hub (10) around a pitch variation axis (AXPAS). An operating mechanism comprises a control rod (31) mounted in translation relative to the hub (10) and a control plate rotatably mounted on the control rod (31). Pitch rods (60) are hinged to arms (42) of the control plate and pitch levers of the blades. At least one said step rod (60) is articulated to a said arm (42) by a pivot connection (70) and to a said step lever by a ball joint (63), the control plate being free to rotate around said axis of rotation (AXROT) relative to the hub (10).

Description

Variable collective pitch rotor and aircraft

The present invention relates to a rotor provided with blades with variable collective pitch and an aircraft provided with this rotor.

The project leading to this patent application received funding from the European Union's Horizon 2020 research and innovation program, under the CleanSky 2 grant agreement No. "GAM-FRC-2014-001 Issue E ".

Such a rotor can for example be a rotor participating at least partially in the control of the yaw movement of a rotorcraft. Such a rotor can also, for example, be a propeller propeller of an aircraft or of a ship. By way of illustration, the rotor can thus be a propeller propeller of an aircraft, and for example of a hybrid aircraft provided with at least one lift rotor and at least one propeller propeller.

The expression "variable collective pitch rotor" can designate such a rotor for convenience.

A variable collective pitch rotor can be provided with a hub which is mechanically connected to a power plant. More specifically, this hub is fixed to a rotor mast set in motion by the power plant. The power plant then rotates the rotor mast and the hub around an axis of rotation of the rotor.

Blades are articulated to this hub so as in particular to be movable in rotation relative to the hub around axes of variation of respective substantially radial pitches. Consequently, the blades are on the one hand movable in rotation jointly with the hub around the axis of rotation of the rotor and, on the other hand, movable in rotation relative to the hub around their respective axes of variation of pitch.

The thrust generated by the variable collective pitch rotor can then be controlled by a collective variation of the pitch of the blades. To this end, the variable collective pitch rotor is equipped with an operating mechanism for maneuvering the blades in the same manner and at the same time around their respective pitch variation axes.

According to an embodiment present on the helicopter known under the name 332MK1, such an operating mechanism is sometimes qualified as a "spider". This operating mechanism comprises a control rod mounted movable in translation in the rotor mast. This control rod is controlled by commands actuable by a pilot and / or an automatic piloting system.

The control rod can pass longitudinally through a central hole in the hub to reach a control plate. The control plate is rotatably mounted on the control rod. This control plate includes a central body and multiple arms forming a star. Each arm is articulated by a ball joint to a pitch rod, the pitch rod being articulated by another ball joint to a pitch lever of a blade.

In addition, the operating mechanism includes a guide tube which extends around the control rod. This guide tube extends from a first extreme zone to a second extreme zone. The first end zone is secured to the control plate. The second extreme zone extends in the central hole of the hub to be integral in rotation with the hub. Thus, the second extreme zone has grooves engaged with grooves in the hub.

These provisions are such that a translational operation of the control rod by a pilot causes a collective variation in the pitch of the blades.

Furthermore, the efforts to collectively pivot the blades can be significant. These efforts are all the more important on a propeller propeller requiring a variation of pitch of the blades over a wide range.

Indeed and due to the ball joints, the translation of the control plate tends to induce an inclination of the pitch rods. This inclination tends to induce the creation of tangential parasitic forces which generate a moment. This moment tends to rotate the control plate around the axis of rotation. This rotary movement is nevertheless stopped by the grooves of the hub against which the grooves of the guide tube bear. However, the grooves of the hub then rub strongly against the grooves of the guide tube. This results in the creation of significant friction forces between the hub and the operating mechanism which can only be overcome by exerting a relatively large control force on the control rod.

On a helicopter, the pitch of the blades is relatively small. As a result, the use of splines can have a limited impact on control efforts. On the other hand, these control forces can be more appreciably increased on a propeller with propeller.

As an alternative to the splines, an operating mechanism may include a compass to link the control plate and the hub in rotation. A compass is used to transmit torque without significantly increasing the control effort required to translate the control rod. Nevertheless, a compass tends to wear down, which induces regular maintenance operations. In addition, the mass of a compass can be relatively high.

The helicopter known under the brand squirrel® has a variable collective pitch rotor distant from the rotor of the 332MK1 helicopter. Indeed, the squirrel® helicopter includes a balance rotor and not a rigid rotor. In addition, the squirrel® helicopter includes a maneuvering mechanism which is not of the "spider" type since it does not have a control plate but is fitted with two pitch rods hinged to a control cylinder. This control cylinder surrounds the rotor mast. The control cylinder is connected to a control by a return means and a ball bearing.

The documents FR 2050019 and FR 2589817 are also known and distant from the invention.

The document FR 2050019 describes an installation for varying the pitch of a propeller of a boat.

The document FR 2589817 describes a device for feathering the blades of a propeller plane.

The object of the present invention is therefore to provide a variable collective pitch rotor with an innovative control plate tending to reduce the control forces to be supplied in order to vary the pitch of the rotor blades collectively.

According to one aspect of the invention, a variable collective pitch rotor is mobile in rotation about an axis of rotation, the variable collective pitch rotor comprising a hub, the variable collective pitch rotor comprising a plurality of blades, each blade said plurality of blades being individually movable mounted on the hub at least in pivoting about an axis of variation of pitch. The variable collective pitch rotor comprises an operating mechanism for simultaneously varying or even of the same amplitude a pitch of each blade of said plurality of blades around its pitch variation axis, the operating mechanism comprising a control rod mounted movably in translation relative to the hub, for example along said axis of rotation. The operating mechanism comprises a control plate mounted to rotate, for example around the axis of rotation, on the control rod by a rolling mechanism. The operating mechanism comprises a plurality of pitch rods, each pitch rod of said plurality of pitch rods being articulated to an arm of the control plate and to a pitch lever of a said blade.

At least one said pitch rod of said plurality of pitch rods is articulated to a said arm by a pivot link and to a said lever by a ball joint, said control plate being free to rotate about said axis of rotation relative to the hub.

Optionally, said pivot link comprises a pivot axis tangent to a circle centered on said axis of rotation. Such a circle can pass substantially through the ends of the arms of the control plate.

The expression “mounted individually movable on the hub at least in pivoting around a pitch variation axis” signifies in particular that each blade is carried by the hub while being free to rotate around its own axis of variation of not, and possibly other movements.

The pivot link has between at least one pitch rod and the control plate prevents an inclination of the pitch rod, unlike a ball joint. Therefore, when the pitch rod tends to tilt, this pitch rod exerts a force on the control plate. This control plate being free to rotate relative to the hub, unlike the helicopter

332MK1, this control plate then rotates around the axis of rotation of the rotor, relative to the hub until it reaches a new equilibrium position.

As a result, this rotor has at least one pitch link articulated by a pivot connection to a freely rotating control plate. This particular arrangement makes it possible to modify the angular orientation of the control plate relative to the hub to maintain the pitch rods in a privileged position in order to at least minimize the parasitic forces.

In the absence of parasitic forces or reduced parasitic forces, the control forces required to move the control rod can be reduced.

This architecture can then have an optimized mass following the elimination or reduction of the parasitic forces. In the presence of significant parasitic forces, it may indeed be necessary to add parts or to oversize certain parts to withstand the consequences of these parasitic forces. The invention tends to avoid or limit these consequences.

In addition, this architecture allows the use of an actuator positioned in the axis of rotation to operate the control rod, unlike architectures requiring return levers subjected to control forces.

This variable collective pitch rotor may have one or more of the following characteristics.

According to a first embodiment, each pitch rod of said plurality of pitch rods can be articulated to a said arm by a said pivot connection and to a said lever by a said ball joint.

All pivot connections can have a pivot axis tangent to the same circle centered on the axis of rotation of the rotor. The pivot axes of the pivot connections can be favorably coplanar.

This architecture allows, in the event of wear or rupture of one of the pivot connections, to continue to control the angular position of the control plate via the other pivot connections.

The pitch rods can possibly be reinforced. Indeed, this hyperstatic architecture can stress the pitch rods in bending if the pivot axes of the pivot connections are not coplanar. The pitch rods can then be reinforced to support this bending.

According to a second embodiment, at least one pitch rod is not articulated to the control plate by a pivot link.

For example, a single pitch rod of said plurality of pitch rods is articulated to a said arm by a pivot link and to a said lever by a ball joint, the other pitch rods of said plurality of pitch rods being each articulated to a said arm by a ball joint and to said lever by a ball joint.

In this case, the assembly becomes isostatic.

According to one aspect, the pivot link of a connecting rod can comprise two bearings each having a row of balls or two bearings each having a row of tapered rollers, or a bearing with two rows of balls or a bearing with two rows of tapered rollers ...

According to one aspect, the pivot connection of a connecting rod can include one or two plain bearings.

According to one aspect, the pivot connection of a connecting rod may include an elastomeric bearing.

For example, when all the pitch rods are fitted with a pivot link at the interface with the control plate, elastomeric bearings can be used. Indeed, the deformation of these elastomeric bearings makes it possible to ensure the mounting of the system and its operation.

Optionally, these various variants can be combined with one another.

According to one aspect, the operating mechanism may comprise a guide tube integral in rotation with said control plate, said guide tube extending from a first end zone integral with the control plate to a second end zone, said second end zone being inserted into an orifice of the hub or even guided in translation by the hub, said hub and the guide tube not being secured in rotation to allow rotation of the guide tube relative to the hub about said axis of rotation.

For example, at least one bearing and / or at least one ball or roller bearing means is interposed between the guide tube and the hub. For example, two bearings are spaced from one another along the axis of rotation and are each placed at the interface between the hub and the guide tube.

The guide tube makes it possible to correctly position the control plate with respect to the hub.

In one aspect, the guide tube and the control rod can be coaxial and centered on said axis of rotation.

In one aspect, the guide tube can surround the control rod, at least locally.

According to one aspect, the guide tube can be fixed to the control plate and / or to an external cage of said rolling mechanism.

For example, at least one bolt passes through the control plate, a lip of the guide tube and a lip of an outer cage of a rolling mechanism.

In the absence of a guide tube, at least two guide bearings or the like can be interposed between the control rod and the hub to guide a translation of the control rod.

In one aspect, the rolling mechanism can be a ball or roller rolling mechanism. Several configurations are possible: a double row ball bearing, a double row taper roller bearing, two single row ball bearings, two single row taper roller bearings.

According to one aspect, at least one said pitch rod of said plurality of pitch rods is a variable length rod.

Such a variable length connecting rod offers the possibility of adjusting the operating mechanism.

The invention also relates to an aircraft which comprises at least one variable collective pitch rotor according to this invention.

For example, the aircraft may be a helicopter, the collective pitch rotor being a rotor participating in the control of the yaw movement of this helicopter. Such a rotor participating in the control of the yaw movement can be a rotor commonly called rear rotor.

For example, the aircraft may be a hybrid aircraft which is provided with a main rotor participating at least in the lift of this hybrid aircraft and at least one propeller propeller, said at least one variable collective pitch rotor being a says propeller.

The invention and its advantages will appear in more detail in the context of the description which follows with examples given by way of illustration with reference to the appended figures which represent:

- Figures 1 and 2, views illustrating a rotor with variable collective pitch according to the invention,

- Figure 3, a section of a variable collective pitch rotor according to the invention,

FIG. 4, a diagram showing a control rod guided by the hub,

- Figures 5 and 6, two figures illustrating pivot connections,

- Figure 7, a diagram showing pivot connections provided with pivot axes tangent to a circle,

FIG. 8, a diagram showing a control plate having a single pivot connection, and

- Figures 9 and 10, diagrams showing examples of vehicles fitted with a variable collective pitch rotor according to the invention.

The elements present in several separate figures are assigned a single reference.

Three directions X, Y ^an d Z orthogonal to each other are shown in some figures.

The first direction X is said to be longitudinal. The second direction Y is said to be transverse. Finally, the third direction Z is said to be in elevation.

Figures 1 and 2 show a variable collective pitch rotor 1 according to the invention.

With reference to FIG. 1, this variable collective pitch rotor 1 comprises a rotor head 5 secured to a rotor mast 20. Consequently, the rotor mast 20 is mechanically connected to a power plant 6 by a kinematic chain. As a result, the power plant makes it possible to drive the kinematic chain to rotate the rotor head 5 around an axis of rotation AXROT.

This rotor head 5 is provided with a hub 10 which is fixed to the rotor mast 20. For example, the rotor mast 20 is fixed to a plate of the hub 10 by screws or the like which are screwed into holes 11 of this plate. Thus, the rotor mast 20 and the hub 10 are integral in rotation about the axis of rotation AXROT.

Furthermore, the rotor head 5 comprises a plurality of blades 15 each carried by the hub 10, for example six blades. Thus, each blade 15 has an aerodynamic surface 17 and a foot 16. The aerodynamic surfaces 17 are not shown for convenience so as not to unnecessarily burden the figures. The aerodynamic surface 17 of a blade 15 can be attached to the foot 16 of this blade, or the foot and the aerodynamic surface of a blade can form two sections of the same piece.

The foot 16 of a blade is also articulated to the hub 10 to at least confer freedom of movement in rotation to the blade relative to the hub around an axis of variation of pitch AXPAS.

For example, the hub 10 is a rigid hub, that is to say devoid of flexible arms which are deformed in beat in particular. For example, the hub 10 has a hollow enclosure provided with a circular radial opening 12 per blade. According to the illustration in Figure 1, the hub 10 has a bottom 13 secured to the rotor mast 20 and an upper plate 14, the bottom 13 being connected to the upper plate 14 by a side wall 9 comprising the radial orifices 12. The bottom 13, the side wall 9 and the upper plate 14 can form one or more mechanical parts fixed to each other. Consequently, each leg 16 is inserted into such a circular radial orifice 12 of the hub. Optionally, a plain or elastomeric bearing, a ball or roller bearing, or the like is interposed between the base and the periphery of a radial orifice.

Under these conditions, the variable collective pitch rotor 1 is provided with an operating mechanism 30. This operating mechanism 30 has the function of varying simultaneously, or even in the same way, the pitch of each blade 15 around its own axis. step variation AXPAS. Each AXPAS pitch variation axis can be substantially radial with respect to a circle centered on the axis of rotation AX.

FIG. 3 illustrates such an operating mechanism 30.

This operating mechanism 30 comprises a control rod 31 mounted movable in translation relative to the hub 10. The control rod 31 can extend from a first end 32 to a second end 33 along the axis of AXROT rotation, this axis of AXROT rotation being able to be an axis of symmetry of the control rod 31.

In addition, the second end 33 of the control rod 31 is mechanically connected to a control able to move in translation the control rod 31 along the axis of rotation AX or parallel to this axis of rotation AX. For example, a linear actuator 7 arranged along the axis of rotation AX is in mechanical engagement on the control rod 31. This linear actuator can be controlled by commands from a pilot and / or an automatic pilot system. Such an actuator can be a servo control, an electric actuator, etc.

Furthermore, the control rod 31 can pass right through the hub 10 in a direction going from the bottom 13 to the upper plate 14. For example, the control rod 31 passes through an orifice 45 of the substantially centered hub on the AXROT axis of rotation.

In addition, the operating mechanism 30 comprises a control plate 40. This control plate 40 may have a central ring 41 which carries one arm 42 per blade 15. The control plate 40 then has the shape of a star.

The control plate 40 is carried by the first end 32 of the control rod. The control plate 40 is more particularly mounted to rotate on the control rod 31. Consequently, the control plate 40 is fixed at the first end by a rolling mechanism 50.

According to the illustration in FIG. 3, the rolling mechanism 50 is a ball bearing mechanism 51. The rolling mechanism 50 may comprise two internal cages 52 made integral in translation with the control rod. For example, the two inner cages 52 are wedged along the axis of rotation between a lip of the first end 32 and a ring 35 screwed onto the first end 32. The rolling mechanism 50 further comprises an outer cage 53 which surrounds the inner cages 52, two rows of balls 51 being wedged radially between the inner cages 52 and the outer cage 53. The outer cage 53 is also made integral in rotation and in translation with the control plate 40. For example, the outer cage 53 is screwed to the control plate 40.

Several configurations are possible: a bearing with two rows of balls as in Figure 3, a bearing with two rows of tapered rollers, two bearings with a row of balls, two bearings with one row of tapered rollers ...

The control plate 40 is detached from the hub 10 in rotation around the axis of rotation AXROT. Thus, no groove or compass computes in rotation the control plate 40 and the hub 10.

However, the operating mechanism 30 may include a guide tube 80. This guide tube 80 is integral in rotation with the control plate 40. Thus, the guide tube 80 extends along its length by a first end zone 81 integral with the control plate 40 and / or the rolling mechanism 50 up to a second end zone 82.

For example, the central ring 41 is sandwiched in the direction of the axis of rotation AX between a lip of the second end zone 82 and a lip of the outer cage 53. Bolts 200 or equivalent thus each pass through the tube guide 80, the control plate 40 and the outer cage 53 to link them in rotation about the axis of rotation AX and also in translation along this axis of rotation AX.

Furthermore, the second extreme zone 82 is inserted into an orifice 45 of the hub 10. The second extreme zone can pass right through the hub 10.

The hub 10 and the guide tube 80, and in particular its second end zone 82, are not secured in rotation to allow rotation of the guide tube 80 relative to the hub 10 around the axis of rotation AXROT. However, bearings 110 or equivalent can be arranged between the second end zone 82 and the hub 10. For example, two bearings 110 are used for this purpose.

Optionally, the guide tube 80 and the control rod 31 are coaxial and centered on the axis of rotation AXROT. Optionally, the guide tube 80 surrounds the control rod 31.

Alternatively and according to FIG. 4, the control rod 30 can be guided by at least two annular bearings 210 interposed between the hub and this control rod 30.

According to another aspect and with reference to FIG. 3, the operating mechanism 30 is provided with a plurality of pitch rods 60, and for example one pitch rod per blade. At least one pitch rod can be a usual variable length rod for adjustment purposes. Optionally, the projection of a pitch rod 60 in a tangential plane is parallel to the axis of rotation AXROT.

Each pitch link 60 extends from a first end portion 61 articulated to a pitch lever 18 of a blade 15 to a second end portion 62 articulated to an arm 42 of the control plate 40. Such a lever step 18 may be integral with the foot 16 of a blade 15 for example.

According to one aspect, each pitch link 60 can be articulated to a pitch lever 18 by a ball joint 63. For example, such a ball joint 63 comprises a ball 64 which is disposed in a ball joint cage 65 and which is crossed diametrically by a ball joint rod 66. For example, the ball joint cage 65 is secured to the first end portion 61 of a pitch rod 60 and the ball joint rod 66 is secured to a clevis with two branches of the pitch lever 18.

According to one aspect, at least one of the pitch rods is articulated to an arm 42 by a pivot link 70. Such a pivot link 70 may comprise a pivot rod around which an arm 42 rotates relative to each other. and a pitch rod 60. For example, a pivot rod 71 takes the form of a bolt or a pin passing through a two-pronged yoke of an arm 42 to be screwed to a nut.

In addition, according to the example of FIG. 3, the pivot link 70 may comprise an elastomeric bearing 72 interposed between the pivot rod 71 and the second end zone of the pitch rod. Such an elastomeric bearing 72 comprises a stack of rigid layers 73, for example metallic or composite or plastic, and flexible layers 74, for example made of elastomer.

According to the example of Figure 5, the pivot link 70 has two bearings each with a row of balls 75. For example, the two ball bearings are arranged around the pivot rod 71 between two branches of a yoke an arm. The two ball bearings are attached and are wedged between two rings 76,77. Each ring is then placed between a branch of the yoke of an arm 42 and a ball bearing 75.

Alternatively, the pivot link 70 may comprise two bearings each having a row of tapered rollers, or a bearing with two rows of balls or a bearing with two rows of tapered rollers.

According to the example of FIG. 6, the pivot link 70 comprises one or two smooth bearings 78. For example, the two smooth bearings 78 are arranged around the pivot rod 71 between two branches of a yoke of an arm. The two plain bearings 78 are joined and are wedged between two rings 76,77. Each ring is then placed between a branch of the yoke of an arm 42 and a plain bearing 78.

Furthermore and with reference to FIG. 7, each pivot link 70 of a second end portion 62 of a pitch rod has a pivot axis AXPIV which can be tangent to a circle 100 centered on the axis of rotation AXROT. Consequently, each pivot rod 71 extends along such a pivot axis AXPIV.

This FIG. 7 also illustrates a variant for which each pitch link 60 is articulated to an arm 42 by a pivot link 70 and to a pitch lever 18 by a ball joint 63.

According to this variant, the pivot axes AXPIV of all the pivot connections can be coplanar.

According to FIG. 8, a single pitch rod 60 is articulated to an arm 42 by a pivot link 70. The other pitch rods 60 are each articulated to an arm 42 by a ball joint 63.

Regardless of its construction, the variable collective pitch rotor 1 can be installed on multiple supports. The variable collective pitch rotor 1 can in particular be arranged on multiple vehicles such as ships or aircraft.

According to the example of FIG. 9, a hybrid aircraft 91 comprises a fuselage 92 carrying a main rotor 95 participating at least in the lift of this hybrid aircraft 91. In addition, the fuselage carries at least one half-wing 93 on which is arranged at least one propeller 94. For example, the hybrid aircraft comprises two half-wings, each carrying a propeller. Therefore, at least one propeller 94 can be a variable pitch rotor 1 according to the invention.

According to the example of FIG. 10, an aircraft 90 is a helicopter 96. This helicopter comprises a fuselage 97 which carries at least one main rotor participating at least in its lift. In addition, a tail of the fuselage carries a variable collective pitch rotor 99 according to the invention which participates in the control of the yaw movement of this helicopter 96.

Naturally, the present invention is subject to numerous variations as to its implementation. Although several embodiments have been described, it is understood that it is not conceivable to identify exhaustively all the possible modes. It is of course conceivable to replace a means described by an equivalent means without departing from the scope of the present invention.

Claims (18)

1. Variable collective pitch rotor (1) movable in rotation about an axis of rotation (AXROT), said variable collective pitch rotor (1) comprising a hub (10), said variable collective pitch rotor (1) comprising a plurality of blades (15), each blade (15) of said plurality of blades (15) being individually movably mounted on the hub (10) at least pivoting about a pitch variation axis (AXPAS), said rotor with variable collective pitch (1) comprising an operating mechanism (30) for simultaneously varying a pitch of each blade (15) of said plurality of blades (15) around its pitch variation axis (AXPAS), said operating mechanism (30) comprising a control rod (31) mounted movable in translation relative to the hub (10), said maneuvering mechanism (30) comprising a control plate (40) rotatably mounted on the control rod (31) by a rolling mechanism (50), said operating mechanism (30) comprising a plurality of pitch rods (60), each pitch rod (60) of said plurality of pitch rods (60) being articulated to an arm (42) of the control plate (40) and to a pitch lever (18) of a said blade (15), characterized in that at least one said pitch rod (60) of said plurality of pitch rods (60) is articulated to a said arm (42) by a pivot connection (70) and to a said pitch lever (18) via a ball joint (63), said control plate (40) being free to rotate about said axis of rotation (AXROT) relative to the hub (10). 2. Variable collective pitch rotor according to claim 1, characterized in that each pitch rod (60) of said plurality of pitch rods (60) is articulated to a said arm (42) by a said pivot link (70) and to a said pitch lever (18) by a said ball joint connection (63). 3. Variable collective pitch rotor according to claim 1, characterized in that a single pitch rod (60) of said plurality of pitch rods (60) is articulated to a said arm (42) by a pivot link (70 ) and a said pitch lever (18) by a ball joint (63), the other pitch rods (60) of said plurality of pitch rods (60) each being articulated to a said arm (42) by a bond ball joint (63) and to a said pitch lever (18) by a ball joint connection (63). 4. Variable collective pitch rotor according to any one of claims 1 to 3, characterized in that said pivot link (70) comprises two bearings each having a row of balls (75) or two bearings each having a row of tapered rollers each, or a double row ball bearing or a double row bearing of tapered rollers. 5. Rotor with variable collective pitch according to any one of claims 1 to 4, characterized in that said pivot connection (70) comprises one or two plain bearings (78). 6. Variable collective pitch rotor according to any one of claims 1 to 5, characterized in that said pivot link (70) comprises an elastomeric bearing (72). 7. Variable collective pitch rotor according to any one of claims 1 to 6, characterized in that said operating mechanism (30) comprises a guide tube (80) integral in rotation with said control plate (40), said tube guide (80) extending from a first end region (81) integral with the control plate (40) to a second end region (82), said second end region (82) being inserted in an orifice (45) of the hub (10), said hub (10) and the guide tube (80) not being secured in rotation to allow rotation of the guide tube (80) relative to the hub (10) about said axis of rotation (AXROT ). 8. Variable collective pitch rotor according to claim 7, characterized in that said guide tube (80) and said control rod (31) are coaxial and centered on said axis of rotation (AXROT). 9. Variable collective pitch rotor according to any one of claims 7 to 8, characterized in that said guide tube (80) surrounds said control rod (31). 10. Variable collective pitch rotor according to any one of claims 7 to 9, characterized in that said guide tube (80) is fixed to the control plate (40). 11. Variable collective pitch rotor according to any one of claims 7 to 10, characterized in that said guide tube is fixed to an outer cage of said rolling mechanism. 12. Variable collective pitch rotor according to any one of claims 1 to 6, characterized in that at least two guide bearings (210) are interposed between said control rod and the hub. 13. Variable collective pitch rotor according to any one of claims 1 to 12, characterized in that said rolling mechanism (50) is a ball or roller bearing mechanism (51). 14. Variable collective pitch rotor according to any one of claims 1 to 13, characterized in that said pivot link (70) comprises a pivot axis (AXPIV) tangent to a circle (100) centered on said axis of rotation ( AXROT). 15. Variable collective pitch rotor according to any one of claims 1 to 14, characterized in that at least one said pitch rod (60) of said plurality of pitch rods (60) is a variable length rod. 16. Aircraft (90), characterized in that said aircraft (90) comprises at least one variable collective pitch rotor (1) according to any one of claims 1 to 15. 17. Aircraft according to claim 16, characterized in that said aircraft (90) is a helicopter (96), said collective pitch rotor (1) being a rotor (99) participating in the control of the yaw movement of this helicopter (96 ). 18. Aircraft according to claim 16, characterized in that said aircraft (90) is a hybrid aircraft (91) which is provided with a main rotor (95) participating at least in the lift of this hybrid aircraft (91) and d at least one propeller (94), said at least one variable pitch rotor 5 (1) being a said propeller (94).