Epicyclic reducer comprising at least one axial force transmission component forming a radial eccentric force path

Abstract

The present invention relates to an epicyclic reducer (1) for an electric parking brake, the reducer (1) comprising a drive shaft (3), at least one reduction stage and a cylindrical member (14), the cylindrical member and the outer planetary gear (2) of the reducer forming a screw / nut system. The reducer (1) comprises at least one axial force transmission component (16, 11), the at least one axial force transmission component being positioned between a support ring (20) of the drive shaft (3) and the cylindrical member (14) to transmit an axial force applied via one of the support ring (20) or the cylindrical member (14) to the other of the support ring (20) and the cylindrical member (14). The axial force transmission component (16, 11) prevents the drive shaft (3) from buckling by defining a radially eccentric axial force transmission path.

Description

Technical Field

[0001] The present invention relates to an epicyclic reducer, for example, an epicyclic reducer for an electric parking brake actuator of an automobile. Background Art

[0002] A conventional floating caliper electric parking brake is disclosed in FR 3 031 058 A1 and FIG. 1 thereof.

[0003] In a manner known per se, the brake of FIG. 1 comprises an epicyclic reducer whose external sun gear forms a piston 100 movable in translation along a longitudinal axis A100. The input torque generated by the electric motor is transmitted to this piston 100 via a drive shaft 200 (individually represented in FIG. 2 ), and to a series-connected planetary gear train. The output planet carrier 300 of the reducer comprises an external thread that cooperates with an internal thread formed by an internal toothing 400 of the piston 100, so as to convert the rotation of the planet carrier 300 into a translation of the piston 100 along the longitudinal axis A100, such translation making it possible to press the brake pad against the brake disc by cooperating with a finger 500 of the caliper arranged facing the piston 100.

[0004] In this conventional speed reducer, the drive shaft 200 carries a sun gear 600, which meshes with the planetary gears 700 of the first gear train. The planetary carrier 900 of the first gear train carries a sun gear 950, which meshes with the planetary gears 970 of the second gear train. The drive shaft 200 includes a downstream portion 800, which passes through openings in the planetary carrier 900 and the sun gear 950 so that one end of the downstream portion 800 is accommodated in the cavity of the output planetary carrier 300, so that the shaft 200 can rotate relative to the planetary carriers 300 and 900 and relative to the sun gear 950.

[0005] In this configuration, the application of mechanical forces on the piston 100 during braking causes these forces to be recovered by the drive shaft 200 , which may result in buckling of this shaft 200 . Summary of the invention

[0006] One object of the invention is to limit the risk of buckling of the drive shaft of such an epicyclic reducer, in particular in order to be able to reduce the diameter of the drive shaft.

[0007] More generally, the invention aims to reduce the mass and costs of such an epicyclic reducer.

[0008] To this end, an object of the present invention is a revolving reducer comprising:

[0009] a drive shaft which can be driven in rotation about a longitudinal axis by a motor and which comprises an internal sun gear having said longitudinal axis as its axis of rotation,

[0010] an external sun gear provided with an internal toothing forming an internal thread, the external sun gear being rotationally fixed about a longitudinal axis,

[0011] a transmission comprising one or more planet carriers and one or more planet gears carried by the planet carrier or carriers,

[0012] - A cylindrical member, which is configured to be driven rotationally around the longitudinal axis through the transmission device when the drive shaft rotates around the longitudinal axis. The cylindrical member includes an external thread that cooperates with the internal thread of the external sun gear so that the rotation axis of the cylindrical member around the longitudinal axis can drive the external sun gear translationally along the longitudinal axis.

[0013] According to the present invention, the drive shaft includes a shoulder on the radial outside of the inner sun gear, which shoulder forms a support ring, and the reducer includes at least one axial force transmission component, which is arranged between the support ring and the cylindrical member to transmit the axial force applied to one of the support ring and the cylindrical member to the other of the support ring and the cylindrical member.

[0014] At least one transmission element makes it possible to recover some of the applied axial forces to which the retarder is subjected (for example during braking when the retarder is part of a brake actuator) in order to relieve the drive shaft.

[0015] The invention thus makes it possible to reduce the mass and costs of a conventional reducer, in particular by reducing the diameter of the portion of the drive shaft adjacent to the bearing ring of the shaft.

[0016] In one embodiment, the at least one axial force transmission element can be supported on the one hand, preferably via a friction washer, against the support ring and on the other hand against one of the planetary carriers of the gearbox.

[0017] In one embodiment, at least one axial force transmission component can comprise one or more radial openings, each of which forms a receptacle for a respective planetary gear of the transmission.

[0018] In an embodiment, the at least one axial force transmitting component may include a plurality of arms, the radial opening being defined between the plurality of arms.

[0019] In one embodiment, the transmission device may include a first planetary carrier and a second planetary carrier, and the reducer includes a first axial force transmission component, which is arranged between the supporting ring and the first planetary carrier to transmit the axial force applied to one of the supporting ring and the first planetary carrier to the other of the supporting ring and the first planetary carrier; the second planetary carrier forms a second axial force transmission component, which is arranged between the first planetary carrier and the cylindrical member to transmit the axial force applied to one of the first planetary carrier and the cylindrical member to the other of the first planetary carrier and the cylindrical member.

[0020] In one embodiment, the reducer may include a ring gear that rotates integrally with the outer sun gear around the longitudinal axis, and the second planet carrier may form a free retaining frame that carries planetary gears that are meshed with both the inner tooth portion of the ring gear and the inner tooth portion of the cylindrical member, the inner tooth portion of the ring gear including a number of teeth different from the number of teeth of the inner tooth portion of the cylindrical member.

[0021] In one embodiment, the second axial force transmission component may be supported against the first planet carrier, preferably via a friction washer, on the one hand, and may be supported against a support surface of the cylindrical element, preferably via a friction washer, on the other hand.

[0022] Another object of the invention is an electric brake actuator comprising a reduction gear as defined above and an electric motor configured to drive said drive shaft in rotation about said longitudinal axis.

[0023] Another subject of the invention is a disc brake, preferably a floating caliper brake, such as a parking brake or a service brake, comprising an actuator as defined above.

[0024] Another object of the invention is a motor vehicle comprising a disc brake as defined above.

[0025] Other advantages and characteristics of the invention will become apparent from the following detailed, non-limiting description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The following detailed description refers to the accompanying drawings, in which:

[0027] [ Fig. 1 ] is a partial schematic perspective view in longitudinal section of an electric parking brake including an epicyclic reducer of a known type;

[0028] [FIG. 2] is a schematic perspective view of a drive shaft of a speed reducer of the brake of FIG. 1;

[0029] [ Figure 3 ] is a partial schematic longitudinal cross-sectional view of an epicyclic reducer according to the present invention;

[0030] [ Figure 4 ]yes Figure 3 A schematic perspective view of an axial force transmission component of a reducer;

[0031] [ Figure 5 ]yes Figure 3 Schematic perspective exploded view of a part of a reducer. DETAILED DESCRIPTION

[0032] Figure 3 and Figure 5 An epicyclic reducer 1 according to the invention is shown. This reducer 1 can be used in the automotive field, for example in electric brakes fitted to disc brakes, in particular of the floating calliper type, or more generally in electromechanical actuators for converting a rotational motion into a translational motion.

[0033] Reference Figure 3 The reducer 1 comprises an outer sun gear 2 forming a piston which is movable in translation along a longitudinal axis A1. The piston 2 is fixed in rotation about this longitudinal axis A1 by any conventional means, for example by inserting a pin (for example belonging to a brake caliper) into a corresponding recess formed in the piston 2.

[0034] The translational displacement of the piston 2 along the longitudinal axis A1 is caused by an electric motor (not shown) which transmits an input torque to the drive shaft 3 of the reducer 1. The rotational movement of this shaft 3 about the axis A1 is converted into a translational movement of the piston 2 by means of a transmission and a motion conversion member, as described below.

[0035] More specifically, in this example, the drive shaft 3 is adapted to be connected to an electric motor so as to be driven in rotation about the axis A1 when the shaft of the motor rotates about the axis A1 .

[0036] The drive shaft 3 is provided with a first internal sun gear 4 which rotates integrally with the shaft 3 about the axis A1. In this example, the sun gear 4 is formed as a single piece with the shaft 3.

[0037] The outer sun gear 2 comprises an inner toothing 5 which forms on the one hand circumferentially spaced longitudinal grooves for meshing with the planetary gears and on the other hand an inner thread which is configured to cooperate with an outer thread of the motion conversion member (see below).

[0038] The reducer 1 comprises a first planet carrier 6 having three openings 7 eccentric to the axis A1 at 120°, each of which receives a journal 8 carrying a corresponding planet gear 9 to ensure the rotational guidance of the planet gear 9 (see Figure 5 ).

[0039] The planetary gears 9 are meshed with both the first inner sun gear 4 and the longitudinal groove formed by the inner tooth portion 5 of the outer sun gear 2, so that the rotation of the shaft 3 around the axis A1 and therefore the rotation of the sun gear 4 around the axis A1 can, on the one hand, drive each planetary gear 9 in rotation around the journal 8 of the planetary gear 9 and, on the other hand, along a circular trajectory around the axis A1, thereby driving the first planet carrier 6 in rotation around the axis A1.

[0040] Therefore, the speed reducer 1 makes it possible to rotationally drive the first planet carrier 6 about the longitudinal axis A1 at a rotation speed lower than the rotation speed of the drive shaft 3 .

[0041] exist Figure 3 and Figure 5 In the example in FIG. 1 , the reducer 1 comprises a second reduction stage, the input of which comprises a second inner sun gear 10 carried by the first planet carrier 6 and rotating integrally with the planet carrier 6 about the axis A1. In this example, the sun gear 10 and the planet carrier 6 are formed as one piece.

[0042] Figure 3 and Figure 5 The reducer comprises a second planet carrier 11 which, in this example, forms a free cage carrying three planet gears 12. In a manner known per se, the cage 11 has a substantially tubular shape and is provided with radial openings which each extend over a central axial portion, so that each radial opening is axially delimited on either side by a respective axial end portion of the cage. Each of these radial openings forms a housing for one of the planet gears 12. In order to carry the planet gears 12 and to ensure their rotational guidance, a respective shaft connected to the cage by being received in a corresponding bore in each axial end portion of the cage passes through each opening, respectively.

[0043] Reference Figure 3 The reducer 1 includes a ring gear 13, which includes external teeth and internal teeth, and the external teeth are engaged in the longitudinal groove formed by the internal teeth portion 5 of the outer sun gear 2, so that the ring gear 13 and the outer sun gear 2 rotate integrally with each other around the axis A1. The internal teeth of the ring gear 13 are configured to mesh with the planetary gears 12 by defining a contact point located radially inside relative to the internal teeth portion 5 of the outer sun gear 2. In other words, the internal teeth of the ring gear 13 are configured to radially offset the longitudinal groove formed by the internal teeth portion 5 of the outer sun gear 2 toward the inside of the reducer 1.

[0044] In this example, this radial offset is necessary due to the fact that the planetary gears 12 also mesh with teeth formed in a cavity of the motion conversion member 14, the radial dimensions of which are smaller than the radial inner dimensions of the outer sun gear 2 (see Figure 3 and below).

[0045] In this example, the motion conversion member 14 takes the form of a cylindrical piece with an external thread 15, which cooperates with the internal thread formed by the internal toothing 5 of the outer sun gear 2. Due to this cooperation, the rotational displacement of the cylindrical piece 14 around the axis A1 causes the outer sun gear 2 to translate along the axis A1. The cylindrical piece 14 and the piston 2 thus form a reversible screw-nut system.

[0046] Said cavity of the cylindrical member 14 is configured to receive a portion of the cage 11 so that the planetary gears 12 mesh with teeth formed in this cavity through a first axial portion of the planetary gears 12 .

[0047] The ring gear 13 is axially adjacent to the cylindrical member 14 , so that the planetary gears 12 mesh with the internal teeth of the ring gear 13 by means of the second axial portions of the planetary gears 12 .

[0048] With this configuration, the rotation of the sun gear 10 about the axis A1 drives each planet gear 12 rotationally about its own rotation axis and along a circumferential path about the axis A1, thereby driving the free cage 11 rotationally about the axis A1.

[0049] If the number of internal teeth of the ring gear 13 is the same as the number of teeth formed in the cavity of the drum 14, the rotation of the sun gear 10 about the axis A1 will not drive the drum 14 in rotation about this axis A1. In fact, in this case, the teeth of the drum 14 will be axially aligned with the internal teeth of the ring gear 13, so that the planetary gears 12 will only roll in the teeth of the drum 14 when rotating.

[0050] In this example, the number of internal teeth of the ring gear 13 is therefore smaller than the number of teeth formed in the cavity of the drum 14 , so that a relatively high reduction rate is achieved.

[0051] Therefore, the speed reducer 1 enables the drum 14 to be rotationally driven about the longitudinal axis A1 at a rotation speed lower than that of the sun gear 10 and not to mention lower than that of the drive shaft 3 .

[0052] Therefore, the speed reducer 1 reduces the rotation speed by increasing the torque.

[0053] The invention makes it possible to recover the axial forces applied in the reducer 1 , for example when the piston 2 applies a braking force.

[0054] To this end, the reducer 1 comprises a force transmission component 16, such as Figure 4 shown.

[0055] In this example, the component 16 has a substantially tubular shape defining a central opening 19 sized to allow the drive shaft 3 to pass therethrough and to enable relative rotation of the shaft 3 with respect to the component 16 .

[0056] In this embodiment, the force transmission member 16 comprises an annular circumferential solid first portion 17 and a second portion comprising three arms 18 extending axially and defining radial openings therebetween, each forming a housing for a respective planet gear 9 .

[0057] In order to provide force recovery, the drive shaft 3 comprises a shoulder 20 radially outside the inner sun gear 4 , which shoulder 20 forms a bearing ring.

[0058] The component 16 is placed between the support ring formed by the shoulder 20 of the shaft 3 and the planet carrier 6 so as to transfer the axial forces applied to the planet carrier 6 to the support ring 20, or from the support ring 20 to the planet carrier 6, while preventing these axial forces from passing through the radial center part of the shaft 3, in particular the parts of the shaft 3 axially located on either side of the shoulder 20. Therefore, the risk of buckling of the drive shaft 3 when the reducer 1 is used is significantly reduced or eliminated.

[0059] More precisely, said first portion 17 of the force transmission part 16 forms a bearing surface 21 which bears against a bearing surface 22 formed by the bearing ring 20 via a friction washer 23. The axial arm 18 of the force transmission part 16 defines a bearing surface 24 which bears against a bearing surface 25 of the planet carrier 6.

[0060] The friction washer 23 makes it possible to limit the wear of the bearing ring 20 and the force transmission part 16 when the bearing ring 20 and the force transmission part 16 are rotated relative to one another.

[0061] In addition, the multiple axial end portions of the free retainer 11 each form a bearing surface 26, one bearing surface is supported against the bearing surface 27 of the planetary carrier 6 through a friction washer 28, and the other bearing surface is supported against the bearing surface formed by the bottom of the cavity of the cylindrical member 14 through a friction washer 29.

[0062] The free cage 11 interposed between the planet carrier 6 and the drum 14 thus forms a second axial force transmission component, making it possible to transmit axial forces exerted on the drum 14 to the planet carrier 6 or vice versa.

[0063] The friction washers 28 and 29 make it possible to limit the wear of the planet carrier 6 , the free cage 11 and the component 14 when these are caused to rotate relative to one another.

[0064] therefore, Figure 3The embodiment of the invention makes it possible to transmit axial forces applied to the cylindrical member 14 (for example when the piston 2 is subjected to braking forces) to the supporting ring 20 by means of two axial force transmission components 11 and 16 placed between the supporting ring 20 and the cylindrical member 14, while preventing these axial forces from passing through the longitudinal axis A1 and therefore through the portion of the drive shaft 3 having a relatively small diameter compared to the diameter of its shoulder 20. This force transmission function via the eccentric force path is also ensured in the other direction, i.e. when an axial force is applied to the supporting ring 20. In the case when an axial force is applied to the supporting ring 20, the two axial force transmission components 11 and 16 enable the axial force applied to the supporting ring 20 to be transmitted to the cylindrical member 14.

[0065] The foregoing description is given by way of example and is by no means restrictive. For example, in an embodiment not shown, the reducer 1 may include a single reduction stage. In this case, the planet carrier 6 does not include the second inner sun gear 10, but is directly connected to the cylindrical member 14 so that the cylindrical member 14 and the planet carrier 6 rotate integrally with each other around the axis A1. Of course, in this single-stage reduction embodiment, the reducer 1 does not include the free cage 11, the planetary gears 12, and the friction washers 28 and 29.

[0066] In another embodiment not shown, the reducer 1 includes Figure 3 1 and 14. For example, the planetary gear 12 is not carried by the free cage 11, but directly by the component 14. In order to ensure the recovery of the axial force between the planetary carrier 6 and the component 14, the reducer 1 can include an additional axial force transmission component, which is similar to the component 16 and is placed between the planetary carrier 6 and the component 14.

[0067] Glossary

[0068] A100 Longitudinal axis

[0069] 100 Outer sun gear / piston

[0070] 200 Drive shaft

[0071] 300 Output planet carrier

[0072] 400 Internal teeth of external sun gear

[0073] 500 Caliper Finger

[0074] 600 Sun gear

[0075] 700 Planetary gear

[0076] 800 Downstream section of drive shaft

[0077] 900 Planet carrier for first gear train

[0078] A1 Longitudinal axis

[0079] 1 Epicyclic reducer

[0080] 2 Outer sun gear / piston

[0081] 3 Drive shaft

[0082] 4 First inner sun gear

[0083] 5 Internal teeth of the outer sun gear

[0084] 6 First planet carrier

[0085] 7 Opening for the journal of the first planet carrier

[0086] 8 First planet carrier journal

[0087] 9 Planetary gears of the first planet carrier

[0088] 10 Second inner sun gear

[0089] 11 Second planet carrier / free cage / second axial force transmission component

[0090] 12 Planetary gears of the second planet carrier

[0091] 13 Ring gear

[0092] 14 Cylindrical part / motion conversion member / screw

[0093] 15 External thread of cylindrical parts

[0094] 16 (First) Axial force transmission component

[0095] 17 First part of the axial force transmission component / solid part

[0096] 18 Second part / arm of axial force transmission element

[0097] 19 Central opening for axial force transmission

[0098] 20 Drive shaft shoulder / support ring

[0099] 21 Bearing surface of axial force transmission component

[0100] 22 Support surface of support ring

[0101] 23 Friction washer

[0102] 24 Bearing surface of axial force transmission component

[0103] 25 Support surface of first planet carrier

[0104] 26 Second planet carrier bearing surface

[0105] 27 Support surface of first planet carrier

[0106] 28 Friction washer

[0107] 29 Friction washer.

Claims

1. An epicyclic reducer (1), comprising: a drive shaft (3) configured to be driven in rotation about a longitudinal axis (A1) by a motor, the drive shaft (3) comprising an inner sun gear (4) configured to rotate about said longitudinal axis (A1), - an external sun gear (2) provided with an internal toothing (5) forming an internal thread, wherein the external sun gear (2) is rotationally fixed about the longitudinal axis (A1), a transmission comprising at least one planet carrier and at least one planet gear, the at least one planet gear being carried by the at least one planet carrier, - a cylindrical member (14) configured to be driven in rotation about the longitudinal axis (A1) by the transmission device during the rotation of the drive shaft (3) about the longitudinal axis (A1), the cylindrical member (14) comprising an external thread (15) cooperating with the internal thread of the outer sun gear (2) so that the rotation of the cylindrical member (14) about the longitudinal axis (A1) drives the outer sun gear (2) in translation along the longitudinal axis (A1), The reducer (1) is characterized in that the drive shaft (3) includes a shoulder (20) on the radial outside of the inner sun gear (4), the shoulder forming a support ring, and the reducer (1) includes at least one axial force transmission component (16), which is arranged between the support ring (20) and the cylindrical member (14) to transmit the axial force applied to one of the support ring (20) and the cylindrical member (14) to the other of the support ring (20) and the cylindrical member (14).

2. The reducer (1) according to claim 1, wherein: The at least one axial force transmission element (16) bears on the one hand against the bearing ring (20).

3. The reducer (1) according to claim 2, wherein: The at least one axial force transmission component (16) is supported on the one hand against the support ring (20) via a friction washer (23) and on the other hand against one of the planet carriers (6) of the transmission.

4. The reducer (1) according to claim 1, wherein: The at least one axial force transmission component (16) comprises one or more radial openings, wherein each of these radial openings forms a receptacle for a respective planetary gear (9) of the transmission.

5. The reducer (1) according to claim 4, wherein: The at least one axial force transmitting member (16) comprises a plurality of arms (18) defining the radial opening therebetween.

6. The reducer (1) according to claim 1, wherein: The transmission device includes a first planetary carrier (6) and a second planetary carrier (11), wherein the reducer (1) includes a first axial force transmission component (16), which is arranged between the support ring (20) and the first planetary carrier (6) to transmit the axial force applied to one of the support ring (20) and the first planetary carrier (6) to the other of the support ring (20) and the first planetary carrier (6), wherein the second planetary carrier (11) forms a second axial force transmission component, which is arranged between the first planetary carrier (6) and the cylindrical member (14) to transmit the axial force applied to one of the first planetary carrier (6) and the cylindrical member (14) to the other of the first planetary carrier (6) and the cylindrical member (14).

7. The reducer (1) according to claim 6, comprising a ring gear (13) which rotates integrally with the outer sun gear (2) around the longitudinal axis (A1), and wherein: The second planet carrier (11) forms a free cage, which carries planetary gears (12) that mesh with both the internal toothed portion of the ring gear (13) and the internal toothed portion of the cylindrical member (14), wherein the internal toothed portion of the ring gear (13) includes a number of teeth that is different from the number of teeth of the internal toothed portion of the cylindrical member (14).

8. The reducer (1) according to claim 6, wherein: The second axial force transmission component is supported on the first planet carrier (6) on the one hand, and is supported on the supporting surface of the cylindrical element (14) on the other hand.

9. The reducer (1) according to claim 8, wherein: The second axial force transmission component is supported against the first planet carrier (6) through a friction washer (28) on the one hand, and is supported against the supporting surface of the cylindrical member (14) on the other hand.

10. The reducer (1) according to claim 8, wherein: The second axial force transmission component is supported against the first planet carrier (6) on the one hand, and is supported against the supporting surface of the cylindrical member (14) through a friction washer (29) on the other hand.

11. An electric brake actuator, comprising the reducer (1) according to claim 1 and an electric motor configured to rotationally drive the drive shaft (3) about the longitudinal axis (A1).

12. A disc brake comprising the electric brake actuator according to claim 11.

13. The disc brake according to claim 12, wherein: The disc brake is a floating caliper brake.

14. A vehicle comprising the disc brake according to claim 12.

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