FR3151888A1 - PLANET CARRIER FOR DIFFERENTIAL EPICYCLOIDAL REDUCER OF A BRAKE ACTUATOR AND EPICYCLOIDAL REDUCER COMPRISING SUCH A PLANET CARRIER - Google Patents

Abstract

The invention relates to a planet carrier (3, 3') for a differential epicyclic reducer of a brake actuator. It comprises a frame arranged and configured to carry planet pinions (30) distributed angularly around the axis (A) of the planet carrier, said frame being a cylindrical sleeve (32) comprising a first and a second edge (33, 34). The sleeve comprises at least one opening (35) through which a planet pinion (30) projects radially. The first and second edges respectively comprise a first and a second radial collar (36, 37) which extends towards the inside of the cylindrical sleeve, each comprising a notch (38) of circular section, extending from the cylindrical sleeve on either side of one side of said at least one opening (35) in a longitudinal direction (D) parallel to the axis (A) of said planet carrier, the notches supporting a shaft (31) of circular section, ensuring the rotational guidance of said planet pinion. Figure for the abstract: [Fig.4]

Description

PLANET CARRIER FOR DIFFERENTIAL EPICYCLOIDAL REDUCER OF A BRAKE ACTUATOR AND EPICYCLOIDAL REDUCER COMPRISING SUCH A PLANET CARRIER

The present invention relates in particular to a planet carrier for a differential reduction brake actuator.

The field of the invention is that of braking systems for automobiles.

The invention provides a planet carrier comprising a frame arranged and configured to carry planet gears distributed angularly around the axis of the planet carrier.

The frame comprises a single plate arranged and configured to form a cylindrical shell which has openings through which at least one satellite pinion projects radially.

The plate has a notch forming a longitudinal groove on at least one side of the openings, along a direction parallel to the axis of the planet carrier, so as to support one or more rotating guide shafts projecting from said planet gears.

The brake actuator comprising such a planet carrier comprises two radial crowns which overlap at least partially and which each comprise an internal gear which intertwines with the gear of the same planet.

At least one of the two crowns is mobile in translation.

STATE OF THE ART

In a vehicle, particularly a road vehicle, the function of the parking and/or emergency brake consists of applying and maintaining the application of brake pads linked to a fixed part of the chassis, on a rotating mobile part which is linked to one or more wheels, typically a disc or a drum.

In brake assemblies using one or more electric actuators, it is known to use a screw-nut system to exert linear support on the pad, often by means of a piston. This type of configuration exists for electric operation alone, or in combination with hydraulic actuation of this piston or another.

In general, the screw-nut system is actuated by a geared motor. Some gear reduction mechanisms include one or more epicyclic gear trains. An epicyclic gear train includes two planet gears (a first planet gear, called an inner one, and a second planet gear, called an outer one) and satellites carried by a planet carrier. Each satellite meshes with both planet gears which are arranged coaxially. Most often, the outer planet gear is internally toothed, and is often called a "crown". In this case, the inner planet gear is often simply called "the planet gear", without further precision.

Document FR 3 031 154 A discloses a reducer which comprises two reduction stages.

In reference to the , it comprises an upstream reduction stage formed by an upstream epicyclic gear train with satellites 131 and a fixed crown 121.

This upstream train is driven at the input by its inner sun gear 111, itself driven by a toothed shaft carrying a drive imprint 119 and having an axis A. This upstream epicyclic train drives its planet carrier 130 at the output. This upstream planet carrier 130 solidly carries the input sun gear 139 for a second reduction stage called a differential epicyclic reducer (DPR) with double crown.

The second stage comprises an epicyclic gear train driven at the input by the sun gear 139 and whose satellites (or planetary pinions) 141 mesh with a fixed crown 121, here the same as for the upstream epicyclic gear train.

From this fixed crown, by a common planet carrier 140 (or sleeve 140) (also represented by Figures 2a and 2b), the satellites 141 of the differential reducer (DPR) drive at the output a mobile crown 151. On its external surface, this mobile crown 151 carries a thread 152 coaxial with the epicyclic gears, and cooperating with an internal thread 161 of the piston 16 to drive it in translation.

Preferably, the fixed crown 121 is common to the two epicyclic gear trains, and the differential satellites 141 are common to the two crowns 121, 151 of the differential gear train, which generally carry a different number of teeth from one to the other. The planet carrier is generally machined or sintered or even molded, in metal or plastic.

The planet carrier comprises a frame of generally tubular shape, or approximately so, and open at its axial ends.

In reference to the (2a and 2b), the frame of the planet carrier 140 has the shape of a tube whose wall thickness is such that the wall encompasses the rotation shaft of each satellite. The planet carrier is machined radially along its circumference so as to produce several windows 149 (or housings), of substantially rectangular shape, each window being provided to receive a satellite.

Each window is delimited longitudinally at each end by a support part of the tube forming a rotation support for each satellite.

A bore is machined on each transverse face of a support part to receive a rotation shaft of a satellite. Thus machined, the planet carrier constitutes a cage for the satellites.

Each support part forms a transverse flange for each satellite end and the satellites project radially from the circumference of the satellite carrier.

Each guide shaft is crimped into a bore of the planet carrier, each planet being freely rotatably mounted on a guide shaft. Each planet has a longitudinal through bore which opens onto each transverse face and is arranged and configured to receive a guide shaft.

However, it remains interesting to facilitate assembly and lower the manufacturing cost.

For this purpose, document FR 3 074 242 proposes a satellite carrier which comprises a plate 20 ( ) arranged and configured to form a cylindrical envelope, the plate 20 having openings 21 through which a satellite pinion 30 projects radially.

The plate 20 has a longitudinal groove 25 which extends on at least one side of the openings, along a direction parallel to the axis of the planet carrier, so as to support one or more rotating guide shafts 31 projecting from the planet gears 30.

The satellites are thus inserted radially on the cylindrical plate 20 of the satellite carrier and the plate 20 of the satellite carrier is made in a single piece: these two characteristics ensure a reduction in assembly time and a reduction in manufacturing costs.

However, it is still interesting to facilitate assembly, lower the manufacturing cost and reduce the size of the planet carrier, or even of the assembly comprising the planet carrier and the fixed and mobile crowns.

According to a first aspect of the invention, at least one of the aforementioned aims is achieved with a planet carrier for a differential epicyclic reducer of a brake actuator, for actuating a vehicle parking brake, in particular a motor vehicle, which planet carrier comprises a frame arranged and configured to carry planet pinions distributed angularly around the axis of the planet carrier, said frame being a cylindrical sleeve comprising a first and a second edge, said sleeve comprising at least one opening through which a planet pinion projects radially.

The planet carrier according to the invention is remarkable in that said first and second edges respectively comprise a first and a second radial collar which extends towards the inside of the cylindrical sleeve, the first and second collars comprising a notch of circular section, extending from the cylindrical sleeve on either side of one side of said at least one opening in a longitudinal direction parallel to the axis of said planet carrier, the notches supporting a shaft of circular section, ensuring the rotational guidance of said satellite pinion projecting through said at least one opening.

According to an advantageous embodiment, the notch comprises a notch depth which corresponds, or which substantially corresponds, to the radius of said shaft.

According to an alternative embodiment, the notch comprises a notch depth which corresponds, or which substantially corresponds, to the diameter of said shaft.

Advantageously, the planet carrier comprises at least three notches and three planet pinions equidistant from each other, preferably four notches and four planet pinions equidistant from each other.

Furthermore, said cylindrical sleeve of said frame is made in one piece, preferably by molding.

Preferably, said satellite pinion and said shaft are made in one piece, more preferably by molding.

The invention also relates to a differential epicyclic reducer of a brake actuator, comprising a double crown and at least one planet carrier as defined above.

Advantageously, the double crown comprises a first fixed crown and a second crown mobile in rotation about its axis, said fixed and mobile crowns each having an internal gear and being coaxial, said at least one satellite pinion meshing at least partially in the internal gear of said first crown and in the internal gear of said second crown.

Furthermore, the first and second crowns overlap at least partially and said movable crown is partially inserted into said fixed crown, said movable crown comprising a radial wall which is crossed at its center by an opening having a gear or a thread, to drive in rotation respectively a toothed pinion or a worm screw.

The invention finally relates to a brake actuator comprising a reducer as defined above.

LIST OF FIGURES

Other features and advantages of the invention will appear on reading the detailed description of implementations and embodiments which are in no way limiting, and the appended drawings where:

is a longitudinal sectional view of a portion of a brake actuator mechanism, including a planet carrier according to the prior art;

comprises two views 2a and 2b which are views of the planet carrier according to the prior art of the , view 2a being an axial view in slight perspective, view 2b being a perspective view of a section of the satellite carrier showing three of its satellites;

is a computer-generated image seen in perspective of a satellite carrier according to the prior art;

is an axial sectional view of a differential epicyclic reducer of a brake actuator according to the invention;

is a schematic representation of the reducer shown in , illustrating the moving and fixed elements of such a reducer;

is a perspective view of a satellite carrier according to a first embodiment of the invention;

is a perspective view of a satellite carrier according to a second embodiment of the invention;

is an axial sectional view of a part of a reducer according to the invention, illustrating the radial forces that the elements of the reducer apply to each other;

is a radial sectional view of another part of the reducer according to the invention, illustrating the forces exerted by certain elements of the reducer on the satellite pinions; and

is a radial sectional view of a portion of the reducer illustrating the tangential components of the forces that the elements of the reducer apply to each other.

DESCRIPTION OF EMBODIMENTS

The embodiments which will now be described are not limiting: it will be possible in particular to produce variants of the invention comprising only a selection of characteristics described below, isolated from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention in relation to the state of the prior art.

Of course, the invention is not limited to the examples which will be described and many adjustments can be made to these examples without departing from the scope of the invention. In addition, the various characteristics, forms, variants and embodiments of the invention can be associated with each other in various combinations to the extent that they are not incompatible or exclusive of each other.

Figures 1 to 3 illustrate the state of the art and have already been described previously.

There shows a reducer (also called a differential gear) according to the invention.

This is a differential epicyclic reducer of a brake actuator, which has a double crown (references 1 and 2) and a planet carrier (reference 3).

The satellite carrier 3 of the reducer shown in is the one who is represented alone in .

It comprises a frame 32, made in the form of a cylindrical sleeve which, taken in its length L, has a first sleeve edge 33 and a second sleeve edge 34.

The sleeve 32 comprising four openings 35 through which satellite gears 30 project radially.

We see, on the , that the first and second edges 33 and 34 respectively comprise a first collar 36 and a second collar 37 (visible for example in ), radial, each of the collars 36 and 37 extending towards the inside of the cylindrical sleeve 32.

In the example, the sleeve is made by molding: it is a solid piece, of thickness e, each collar corresponding to the lateral edge of the sleeve.

It should be understood that the sleeve 32 could also be made hollow without departing from the scope of the invention.

The difference with the sleeve 20 of the embodiment of the state of the art, presented in , lies in the presence of the collars for the embodiment according to the invention, which gives the sleeve more robustness than that illustrated in . Indeed, the sleeve according to the invention does not include an assembly joint P (the sleeve 20 of the prior art being obtained by folding a sheet metal plate and by joining the two free edges of the plate) and the presence of the collars 36 and 37 forming lateral edges gives the sleeve 32 more rigidity (it is less easily deformable).

The difference between the sleeve 32 according to the invention and the sleeve 140 of the state of the art, illustrated in , lies in the production of the housings: in accordance with this state of the art, the planetary pinions 141 are inserted into the housings in a direction D which is parallel to the axis A of the sleeve 140.

The planetary pinions 141 each comprise a shaft 142, of circular section, ensuring the rotational guidance of the satellite pinion.

The planetary gears 141 are positioned in the housings by inserting the end of their shaft 142 through an opening 143 which is made in the wall of the housing 149.

Then, the assembly is held by a ring 148 of the same diameter and thickness as the sleeve 140, the ring 148 also having through openings allowing the other end of the shafts 142 to be accommodated which provide the rotational guidance of the planetary pinions 141.

The satellite carrier according to the invention, illustrated in particular in , is different: instead of the through openings 143, the sleeve 32 comprises notches 38 of circular section, and which have a diameter slightly greater than the diameter of the shafts 31 of the satellite pinions 30 to accommodate them.

The notches 38 extend on either side of one side of the openings 35 (or housing for a pinion 30) in a longitudinal direction D which is parallel to the axis A of the cylindrical sleeve 32.

The notches 38 thus support the shafts 31 of the pinions 30 which project from the openings 35.

In this way, the satellite pinions 30 are inserted radially into the openings 35: it is therefore not necessary to provide a retaining ring 148 as in the prior art.

It will be noted that the production of the openings 35 is such that the satellite pinions 30, housed in the openings 35, are distributed angularly equidistantly around the axis A of the satellite carrier.

The notches 38 can have different depths, depending on whether it is desired that the satellite pinions 30 protrude more or less from the surface of the outer wall of the sleeve 32.

According to the embodiment which is illustrated in , the notches 38 comprise a notch depth which corresponds, or which substantially corresponds, to the diameter of the shaft 31.

The satellite gears thus protrude by a height h1 above the surface of the wall of the sleeve 32.

There presents an alternative embodiment 3' of the sleeve 32 of the satellite carrier: according to this alternative, the notches 38 have a depth which corresponds, or which corresponds substantially, to the radius of the shafts 31 of the satellite pinions 30: Thus, the satellite pinions 30 project by a height h2 greater than the height h1.

It will be noted that all the satellite pinions 30 are identical and that their shafts 31 are made in a single piece with the notched roller forming the body of the pinion 30.

Reference will now be made to Figures 4 and 5 to describe the movements of all the elements comprising the reducer according to the invention, as well as the double crown 1 and 2 and its particular arrangement on the satellite pinions 30.

First of all, the reducer comprises a first central pinion 4, also called a “sun”, which comprises a crenellated cylinder secured to a coaxial rotating drive shaft 40.

The planet carrier 3 is fitted around the central pinion 4, so that the planet gears 30 engage with the central pinion 4: thus, when the central pinion is rotated, the planet gears 30 are also rotated, in the opposite direction, and rotate the planet carrier 3.

A first crown 1 is positioned around the satellite carrier 3: it comprises an internal gear 10 which engages with the satellite pinions 30, over a part a of the length L of the satellite pinions 30 (see ).

The first crown 1 is a fixed crown: when the planet carrier 3 is rotated, the first crown 1 does not turn: it is the satellite pinions 30 which move inside the first fixed crown 1.

The second crown 2 is a crown that can rotate around the axis A of the planet carrier: in fact, the second crown 2 is also arranged around the planet carrier 3, has an internal gear 22 which is engaged with the gear of the planet pinions 30, over a part b of the length L of the planet pinions (see also): thus, when the satellite carrier 30 is rotated in one direction, it rotates the crown 2 in the opposite direction. The crown 2 thus rotates in the same direction as that of the central pinion 4.

We notice on the that the fixed crown 1 has a bent part 11 which covers the rotating crown 2: the radial and axial size of the reducer is thus limited.

Furthermore, the movable crown does not have a gear on its outer wall: crown 2 has an internal part 23 ( ) of smaller diameter, with gear and which is axially offset relative to the gear 22 meshing with the satellite pinions 30.

Thus, the movable crown 2 is not capped by a part forming a nut or brake piston, as in the prior art: the part forming a nut or brake piston is provided axially contiguous to the reducer, and it engages in the internal part 23 of the crown 2.

The embodiment according to the invention is thus less radially bulky than the known state-of-the-art solutions.

The fixed 1 and mobile 2 crowns are coaxial.

The rotating crown 2 ensures the movement drive of a screw/nut system (not shown) of the brake system.

Thus designed, the reducer according to the invention is less bulky, more robust and easier to assemble than the reducers of the state of the art.

Figures 8, 9 and 10 will now be described to explain the forces that the elements of the reducer according to the invention produce on each other.

Overall, the assembly of the elements together (double crown, planet carrier, planet pinions and central pinion – or sun) ensures easy assembly and stable operation which makes it possible to reduce the number of planet pinions in the planet carrier:

Indeed, as shown in , the forces F1 and F2 exerted by the two crowns 1 and 2 are greater than the centrifugal force F4 exerted by the central pinion 4 on the satellite pinions

There shows, moreover, that the forces generated by the interlaced teeth of the gears compensate each other: the gears of the two crowns 1 and 2 interlaced in the gears of the pinions 30 generate forces F3 and F5 which are directed towards the inside of the reducer, while the forces F6 and F7 of the gears of the central pinion 4 interlaced in the gear of the satellite pinion 30 are directed towards the outside.

Finally, the shows that the tangential forces F8 to F12 are preponderant compared to the radial forces shown in .

The reducer according to the invention is thus stable and easy to implement.

The invention applies mainly to the braking of motor vehicles.

Nomenclature:

A: axis of the planet carrier 3, of the central pinion 4 and of the reducer

h1: height of the satellite gears

h2: height of the satellite gears

D: Direction parallel to axis A passing through the center of the tree 31

a: length of the gear of the satellite pinion meshing with the internal gear of the crown 1

b: length of the gear of the satellite pinion meshing with the internal gear of the crown 2

L: sleeve length 32

e: sleeve thickness 32

P: joint or join

1: fixed crown

2: mobile crown

3, 3’: satellite carrier

4: central pinion

10: internal gear of fixed crown 1

11: bent part of the fixed crown 1 which covers the mobile crown 2

16: piston

20: planet carrier plate

21: openings

22: gear

23: internal part with gear

25: gorges

30: satellites

31: satellite rotation guide shaft

32: frame

33: first edge

34: second edge

35: opening

36: first collar

37: second collar

38: notch

40: central pinion drive shaft 4

111: planetary

119: training footprint

121: fixed crown

130: satellite carrier

131: satellite

139: planetary

140: satellite carrier

141: satellite

142: planetary pinion shaft

143: opening

148: fixing ring

149: window or housing

151: mobile crown

152: thread

161: thread

F1, F2: radial forces exerted by crowns 1 and 2 on satellite pinion 30

F4: radial force exerted by the central pinion on the satellite pinion 30

F3, F5: forces exerted by the crown gears on the gear of the satellite pinion 30

F6, F7: forces exerted by the gear of the central pinion 4 on the gear of the satellite pinion 30

F8, F9, F10, F11 and F21: radial forces exerted by the elements on each other.

Claims (10)

Planet carrier (3, 3') for a differential epicyclic reducer of a brake actuator, for actuating a parking brake of a vehicle, in particular a motor vehicle, which planet carrier (3, 3') comprises a frame arranged and configured to carry planet gears (30) distributed angularly around the axis (A) of the planet carrier, said frame being a cylindrical sleeve (32) comprising a first and a second edge (33, 34), said sleeve (32) comprising at least one opening (35) through which a planet gear (30) projects radially, characterized in that said first and second edges (33, 34) respectively comprise a first and a second radial collar (36, 37) which extends towards the inside of the cylindrical sleeve (32), the first and second collars (33, 34) comprising a notch (38) of circular section, extending from the sleeve (32) cylindrical on either side of one side of said at least one opening (35) in a longitudinal direction (D) parallel to the axis (A) of said planet carrier, the notches (38) supporting a shaft (31) of circular section, ensuring the rotational guidance of said planet pinion (30) projecting through said at least one opening (35). Planet carrier (3') according to claim 1, characterized in that said notch (38) comprises a notch depth which corresponds, or which substantially corresponds, to the radius of said shaft (31). Planet carrier (3) according to claim 1, characterized in that said notch (38) comprises a notch depth which corresponds, or which substantially corresponds, to the diameter of said shaft (31). Planet carrier (3, 3') according to any one of the preceding claims, comprising at least three notches (38) and three planet gears (30) equidistant from each other, preferably four notches (38) and four planet gears (30) equidistant from each other. Planet carrier (3, 3') according to any one of the preceding claims, characterized in that said cylindrical sleeve (32) of said frame is made in a single piece, preferably by molding. Planet carrier (3, 3') according to any one of the preceding claims, characterized in that said satellite pinion (30) and said shaft (31) are made in one piece, preferably by molding. 7. Differential epicyclic reducer of a brake actuator, comprising a double crown (1, 2) and at least one planet carrier (3, 3') according to any one of the preceding claims. 8. Reducer according to claim 7, characterized in that the double crown (1, 2) comprises a first fixed crown (1) and a second crown (2) movable in rotation about its axis, said fixed (1) and movable (2) crowns each having an internal gear (10, 22) and being coaxial, said at least one satellite pinion (30) meshing at least partially in the internal gear (10) of said first crown (1) and in the internal gear (22) of said second crown (2). 9. Reducer according to claim 8, characterized in that said first and second crowns (1, 2) overlap at least partially and in that said movable crown (2) is partially inserted in said fixed crown (1), and in that said movable crown (2) comprises a radial wall which is crossed at its center by an opening having a gear or a thread, to drive in rotation respectively a toothed pinion or a worm screw. Brake actuator comprising a reducer according to any one of claims 7 to 9.