FR2901857A1 - Harmonic reducer for driving shaft of reversible actuator, has reversibility units with external and internal friction disks for authorizing movement of driving shaft without driving displacement of all or part of reducer - Google Patents

Abstract

The reducer has reversibility units with external and internal friction disks (8, 9) for authorizing the movement of a driving shaft without driving the displacement of all or a part of the reducer. The friction disks (9) are connected to a support (11) fixed on an actuating shaft (12), and a flexible belt (3) comprises a metallic insert, where the belt (3) cooperates with a fixed belt (2). The disks (8, 9) slides with respect to each other, when a force higher than a determined threshold is applied directly on the shaft, and the belts are made of plastic.

Description

The present invention relates to a

  reversible harmonic reducer. It applies to all types of actuators and in particular to the actuators of opening, including tailgates and chests.

  At the present time, for the opening actuators, planetary gear trains consisting of a central sun gear are conventionally meshing with a plurality of planet gears, the latter driving a fixed ring gear. An example of conventional epicyclic gear is shown in Figures la and lb of US Patent 6629905.

  The epicyclic gear trains have the advantage of good torque transmission and good accuracy.

  Nevertheless, the planetary gear systems also have significant drawbacks, in particular a high noise level mainly due to the angular play inevitably existing in these systems. In addition, the planetary gear trains require a large number of parts, which increases their cost all the more, not only in the manufacture but also in the assembly of the assembly. Finally, because of the large number of parts required and the risk of wear associated with each of them, the actuating systems 30 using planetary gear trains have an often short service life.

  Harmonic reducers are already known as solutions for actuating systems, but these systems have the main disadvantage of not being reversible, that is to say of not allowing rotation and / or displacement of the shaft. actuating the opposite side of the motor when this opposite side becomes the input of the system, rendering them unusable in a large number of applications; the input being defined then as the side from which the activation of the actuating shaft originates.

  Indeed, in the case where the flexible ring is actuated directly first, by the electric motor of the actuating system, the flexible ring is rotatable in both directions of rotation to rotate the actuating shaft, for example to raise or lower a vehicle tailgate, but the actuating shaft, when a force is directly applied thereto and then transmitted to the harmonic gear, can not cause displacement or rotation harmonic gear.

  Moreover, these systems are extremely expensive, in particular because of their manufacturing process and the materials used.

  The object of the invention is therefore more particularly to eliminate these disadvantages. It has for this purpose a harmonic reducer having means able to make it reversible, that is to say that the actuating shaft is able to move, or to turn, when the actuating force is not coming the motor or motors of the system but of the actuating shaft, or output, for example following a manual actuation of the actuating system.

  Thus, the invention relates to a harmonic reducer, having a fixed ring (2) and a flexible ring (3), the reducer being able to set in motion an actuating shaft (12), characterized in that it comprises means of reversibility (8, 9, 11/33, 34) able to allow the movement of said actuating shaft without causing the displacement of all or part of said harmonic gear.

  The term "harmonic reducer" is intended to mean an assembly consisting of a fixed ring gear comprising n teeth inside which is placed a flexible ring gear and rotatably mounted having (n-2x) teeth with x = integer number. Usually, the flexible crown will have 2 teeth less than the fixed crown. The flexible ring is rotated by an electric motor.

  The term reversibility means that the actuating shaft can be moved, or rotated, by exerting an adequate force from the input and also from the output of the actuator system. For an actuator, the input is defined on the side of the actuating shaft where the electric motor is located and the output is on the side opposite to the input relative to the actuating shaft.

  Thus, in the case of a harmonic reducer, the rollers rotated by the motor, via its shaft, are able to cause the rotation of the flexible ring but the flexible ring, when a force comes directly from the shaft of actuation and is transmitted to the flexible ring, can not cause the rotation of the whole roller / roller holder. Therefore, it is not possible to move, or to rotate, the actuating shaft by a force acting directly on the latter at the output of the actuator.

  Until the present invention, systems using harmonic reducers were not reversible.

  Ideally, the harmonic reducer comprises a module or means of mechanical reversibility (s), that is to say whose operation only uses forces and mechanical interactions. The embodiments and possibilities offered by the invention are defined by the following features: the harmonic reducer is made of plastic. - According to one possibility, the flexible envelope of the harmonic gear 5 comprises a metal insert. according to one embodiment, the reversibility means comprise at least one pair of friction disks able to slide on one another when a force greater than a determined threshold is applied directly on the actuating shaft. . By force applied directly to the actuating shaft is meant a force applied on the opposite side to that of the motor relative to the harmonic reducer, for example a manual force acting on the device actuated by the actuator according to the invention. the flexible ring comprises a plurality of notches intended to drive, during the rotation of said ring gear, at least one disk of the aforementioned pair of friction discs, the actuator then comprises a spring intended to force the discs under pressure; friction between them. - According to a particularly advantageous aspect of the invention, the notches have at least a portion of its contact faces having an angle of between 5 and 40, preferably 15 2. The reversibility means comprise a removable fastening means when a force greater than a determined threshold is applied directly to the actuating shaft. Removable expression is understood to mean that the fixing means is able to disengage when the acting force is greater than the threshold force, or predetermined. To do this, it may be provided that the removable fastening means consists of a pair of teeth placed respectively on the two dissociable parts. the harmonic reducer may comprise a pair of roller carriers, a part of the rollers being intended to ensure rotation of the flexible ring while the other part of the rollers being intended to prevent the vibration of said ring.

  The invention also relates to a reversible actuator incorporating a harmonic reducer according to the invention.

  Thanks to these arrangements, the invention makes it possible to have a reduced-size actuator for optimized efficiency, presenting a significant cost saving while very significantly reducing the noise of the current actuators, and able to perform a greater number of functions. including manual actuation by a user.

  The device of the invention is particularly applicable to a motor vehicle tailgate actuator having one or two spars in which are placed the actuators each consisting of a tube with a diameter of less than 40 millimeters, of the order of 33 millimeters.

  One embodiment of the invention will be described below, by way of non-limiting example, with reference to the appended figures in which:

  Figure 1 is a schematic perspective view of a portion of the actuator according to the present invention; FIG. 2 is a diagrammatic view illustrating the flexible ring, its means for actuating in rotation and the fixed ring according to the invention;

  Figure 3 is a perspective view of the flexible ring according to the invention;

  Figure 4 is a detailed view of a transmission notch of the flexible ring shown in Figure 1 to show the particular embodiment of said notches; Figure 5 is a sectional view illustrating another embodiment of the inverter means according to the invention;

  Fig. 6 is a perspective view illustrating a flexible ring gear, its rotational actuating means and a fixed ring gear in the embodiment related to the inverter means shown in Fig. 5;

  FIG. 7 illustrates another embodiment of the reversibility means for a harmonic reducer according to the invention; FIG. 8 illustrates a last embodiment of the reversibility means for a harmonic reducer according to the invention.

  Figure 1 illustrates the main part of an actuator made according to the invention. The actuator is housed in an envelope 1 ideally made of plastic.

  The actuator has a harmonic reducer assembly. The harmonic reducer according to the invention consists here of a fixed ring 2, 20 fixed on the casing 1 of the actuator, and a flexible ring each 2, 3 of plastic. In the example chosen to illustrate the invention, these rings 2, 3 are polyoxymethylene (POM), such as Delrin.

  These rings 2, 3 cooperate with each other through teeth placed respectively on the outer circumference at one end of the flexible ring 3 and on the inner circumference of the fixed ring 2. In this embodiment, the fixed ring 2 has 64 teeth while the flexible ring 3 has 62 teeth so that the reduction ratio of the harmonic gear of the actuator is here 64/2 = 32. Of course, we can provide a number of different teeth both for the fixed ring 2 and the flexible ring 3 in order to reduce / increase the dimensions of the actuator and / or to present a different reduction ratio, while keeping the physical rules related to a harmonic reducer.

  The flexible ring 3 is at the output of the harmonic reducer so that it transmits the torque. For this purpose, as can be seen in FIG. 3, the flexible ring 3 is substantially in a longitudinal cylindrical shape with a serrated end 4, the teeth being disposed around the circumference or the outer circumference of the ring 3. The flexible ring 3 comprises a central portion 5 slightly flared, that is to say whose diameter increases slightly from the serrated end 4, to reach the other end 6 composed of a plurality of notches 7 transmission, here five notches 7 uniformly distributed, that is to say that each notch is shifted one of the following with a constant angular spacing, on the periphery of this end; said notches 7 extending parallel or along the longitudinal axis X'X of the flexible ring 3.

  These notches 7 are engaged with external friction disks 8 themselves interacting, by friction, with internal friction disks 9.

  Thus, the rotation of the flexible ring 3 under the action of the electric motor and its arm 17 causes the rotation of the outer friction discs 8 which cause the rotation of the inner friction discs 9. The disc 8 is for example bronze while that the disc 9 is steel or vice versa. Of course, any other suitable material to present the desired friction ratio may be used.

  Particularly advantageously, as can be seen in FIG. 4, the lateral portions 10 of the notches 7, that is to say the contact portions 10 with the external friction discs 8 intended to transmit to them the rotation of the crown flexible 3, are oriented at an angle of between 5 and 40, and preferably 15, relative to the right angle, or zero, formed in Figure 4 by the radius OR. It is indeed essential that the notches 7 do not move towards the outside of the part 3 when the torque is transmitted to the outer friction discs 8.

  The inner friction disks 9 are connected to a support 11, for example made of steel, rigidly connected to the actuating shaft 12. Thus, the rotation of the flexible ring 3 ultimately drives the rotation of the actuating shaft 12, the direction of rotation of the actuating shaft 12 being determined by the direction of rotation of the motor and thus of the flexible ring gear 3. The connection between the inner disks 9 and the support 11 may take place for example by realizing a central bore in the inner disks 9 of substantially complementary shape, for example a square section as shown in Figure 1, to a portion of the support 11 so that a movement / displacement of said inner disks 9 causes the movement / displacement corresponding support 11 and therefore the actuating shaft 12.

  The use of plastic crowns 2, 3, obtained by injection molding, makes it possible to very significantly reduce the cost of the actuator according to the invention. The present invention also draws a particular advantage from the production of a maximum of plastic parts, not only in terms of manufacturing cost but also for the assembly of all the parts forming the actuator according to the invention.

  The flexible ring 3 is set in motion by the motor, not shown in the accompanying figures, via a set of rollers 15 / roller holder (s) 16 fixed (s) to the shaft 17 of the motor, the rollers 15 and the or the roller holder (s) 16 being ideally also plastic. The roller holder (s) 16 is / are rotated by the electric motor of the actuator so that the rollers 15, rotatably mounted, compressing a part of the flexible ring gear 3 against the fixed ring gear 2 are capable of transmitting the rotational torque to the flexible ring gear 3. Thus, in the example chosen to illustrate the invention, when the roller carrier (s) 16 performs (s) a complete turn (360) , the flexible ring 3 is shifted by two teeth by rotation against the fixed ring 2.

  In Figure 2 there is shown a pair of rollers for transmitting the rotation of the flexible ring, the rollers 15 for pressing a portion of the flexible ring 3 against the fixed ring 2 and to allow its rotation.

  According to a possibility offered by the invention, at least two other rollers, not shown in the accompanying figures, for example located on a roller holder 16 perpendicular to the roller holder shown in Figure 2, allow to maintain the spacing of the crown flexible 3 so that the latter 3 does not vibrate, and thus avoids generating noise but also a less good rotation of the flexible ring 3 and thus a degraded power transmission between the two rings 2, 3.

  The spring 20, disposed around the longitudinal actuating shaft 12, is used to constrain the outer friction discs 8 and inner 9 interacting with each other, thanks to the pressure exerted along the axis X'X by said spring 20 on these elements 8, 9, for the transmission of forces. The ends of the spring 20 are housed respectively in two stops 21, 22, for example steel, for locking said spring and to transmit its axial force. In order to absorb the axial forces generated by the spring 20, the actuator may comprise a needle cage 23. Another needle cage 24 may also be provided to absorb the axial forces during the application of the force directly on the spring. actuating shaft 12 or at the output of the actuator, the needle cage (s) also serving as a bearing for the actuating system. In the embodiment shown in Figure 1, these needle cages 23, 24 are positioned on either side of a bearing 25, for example bronze, fixed on the casing 1 of the actuator. It will be noted that the spring 20 can be replaced by Belleville washers without otherwise modifying the device to save space.

  Next to the spring is a ring 26, for example made of steel, for locking in translation the reversibility means 8, 9, 11 on the actuating shaft 12. This ring serves to absorb the axial forces of the transmitted spring 20 via the stop 21.

  In the static position, that is to say when no force is applied to the flexible ring 3, the actuating shaft 12 is kept stationary.

  When applying a force directly on the actuating shaft 12, for example in the case where the actuator is used to actuate a tailgate when applying a manual force to lower or raise the tailgate , the actuating shaft 12 can rotate, when the force acting on it exceeds a certain threshold, because the inner friction discs 9 then slide on the outer friction discs 8 without causing them. Thus, the actuating shaft 12 can rotate freely so that the actuator system is reversible since the actuating shaft 12 is able to be movable when a force, greater than a threshold force or a specific force, is applied on the opposite side to the side having the automatic actuating means, namely the electric motor. We can consider that the threshold force is for example 5 Newtons.meter (Nm) and realize / dimension the friction discs, inside 9 and outside 8, and the spring 20 so that the sliding of the disks 8, 9 between them takes place when the force applied directly on the actuating shaft 12 exceeds this threshold of 5 Nm In this embodiment, the reversibility means consist of the inner and outer friction discs 9 and the support 11 attached to the actuating shaft 12.

  According to one possibility offered by the invention, the reversibility means of the actuator may consist of a module without connection with the harmonic gearbox, and in particular the flexible ring gear 3.

  Thus, FIG. 5 shows another embodiment of the reversibility means and FIG. 6 shows the harmonic reducer which could be associated therewith.

  The flexible ring 3 drives during its rotation an insert 30 fixed in the flexible ring 3, always made of plastic. The insert 30 on which the plastic crown 3 is ideally overmoulded serves to mechanically reinforce said ring 3. It may be provided that the insert 30 has irregularities 31 on its circumference or its external periphery so that during overmolding is created a perfect interaction between the flexible ring 3 and the insert 30. This insert 30 is connected to a cylindrical piece 32 fixed to an intermediate member 33 intended to cooperate with a movable connecting piece 34 fixed on the actuating shaft 12 .

  The automatic movement, that is to say thanks to the electric motor, of the actuating shaft 12 via the harmonic reducer is here identical to the first embodiment, except as regards the shape and the specific structure of the the flexible ring 3. Thus, when the flexible ring 3 is rotated, it transmits this rotation, via its metal insert 30, to the cylindrical piece 32, then to the intermediate member 33 which finally communicates its rotation to the piece of link 34 driving the actuating shaft 12 in rotation in one direction or the other, depending on the direction of rotation of the electric motor of the actuator. In the case where a force is applied directly to the actuating shaft 12, this force, beyond a certain threshold, causes the actuating shaft 12 to move along the longitudinal axis X ' X and therefore in the same direction as that of the connecting piece 34, against a pressure means 36, such as for example Belleville washers, acting to bring the connecting piece 34 into contact with the intermediate element 33 so that the rotation of the latter 33 causes the rotation of the connecting piece 34 and vice versa. The contact between the connecting piece 34 and the intermediate element 33 is provided via, for example, teeth disposed on the contact end respectively of said piece 34 and said element 33. Of course, the connection between the connecting piece 34 and the intermediate element 33 may be provided by other conventional systems, such as an electromagnetic clutch, magnetic or other mechanical solutions.

  In this second embodiment, the reversibility means consist of the association of the connecting piece 34 mounted mobile erg translation along the X'X axis thanks for example to the Belleville washers and by means of interaction with the piece of link 34, here the teeth disposed respectively on said workpiece 34 and said intermediate element 33.

  Thus, like the first embodiment, when the force acting on the actuating shaft 12 exceeds a certain threshold, the connecting piece 34 and the intermediate element 33 are no longer in contact so that the actuating shaft 12 can rotate freely.

  These two embodiments, in addition to their structural differences, have in common the use of the non-reversibility of a harmonic reducer to maintain the actuating shaft 12 static or fixed until the force applied directly on the shaft actuation 12 exceeds a threshold force, or reference, which triggers the operation of the reversibility means which then allows the displacement or free rotation of the actuator shaft 12 of the actuator.

  The differences between the two embodiments are related to the possibility of displacement of the actuating shaft 12 itself. Indeed, in the first embodiment, shown in Figures 1 to 4, the actuating shaft 12 is virtually rotatable only while the actuating shaft 12 of the second embodiment has in addition a degree of freedom in translation along the axis X'X. The choice of embodiment is therefore related in part to the application of the actuator and especially to the plausible orientation of the force that can be applied directly to the actuating shaft 12. In fact, in the context of a application of the actuator to a tailgate or trunk actuation of a motor vehicle, the orientation of the manual force applied by the user to the tailgate or the trunk will depend on the angle and the disposition of the actuator (s) on the tailgate or boot.

  Of course, the two embodiments presented above are combinable so that the reversibility means of the first embodiment can be used with the device of the second embodiment, without much structural modification.

  By way of non-limiting examples, there is shown in FIG. 7 another embodiment of the reversibility means. In this case, the reversibility means consist of two parts having identical profiles and intended to be pressed against each other with the aid of at least one spring. Thus, one of the parts 40 is integral with the actuating shaft and the other 41 of the output of the harmonic gear so that the same as the previous embodiments, the torque can be transmitted from the gearbox harmonic to the output shaft. FIG. 7 shows three points 42 defining the profile of the two parts 40, 41. These three points 42 may for example be defined in accordance with the following equations: X = Rsin (t) Y = R cos (t) Z = A sine (wt) In the example chosen to illustrate here the invention, w = 2n / 3, which makes it possible to have 3 undulations, with A = 2 mm being the difference between the highest point and the lower undulations and R = 15 mm, Radius of the circle.

  When the torque becomes too strong, the force coming from the actuating shaft to the workpiece 40, the two parts 40, 41 become detached, thus constituting the disengaging or decoupling system.

  Another embodiment of the means of is illustrated in FIG. 8. In this case, the piece 50 is integral with the flexible ring materialized by the piece 51 in the figure. With the teeth of the workpiece 50, the parts 52 and 53 are rotated. Or, the part 52 is integral with the output shaft or actuation so that the latter 52 rotates with the output shaft. The springs 57 enable the parts 52 and 54 to be pressed onto the part 50 so that the teeth of the parts facing each other, ie the pairs of parts 50-52 and 50-53, are in contact, which makes it possible to transmit the rotation movement.

  It will be noted that the teeth of each of the parts facing each other have complementary geometries. Thus, these teeth may consist of micro triangular facial teeth having a stroke of 1 to 1.5 millimeters (mm) or consist of notches or jaws trapezoidal shape having a stroke of 1 to 1.5mm. When the actuating or output shaft is rotated, the workpiece 54 attempts to rotate. The ball 55 creates a tangential force on the inclined faces of the pieces 52 and 53.

  When the torque applied on the shaft is sufficient, the ball 55 sufficiently pushes the springs 57 which plead the pieces 52 and 53 on the ball 55. At this moment, as can be seen in FIG. 8, the teeth of the piece 50 are no longer in contact with those of the parts 52 and 53. Thus, the decoupling of the harmonic gear and the actuating shaft is realized so that the system is well reversible.

  In this last embodiment, particular importance is given to the inclination of the planes of the parts 52 and 53 which maintain the ball 55 and the stiffness of the springs 57.

Claims (12)

claims   1. harmonic gearbox, having a fixed ring gear (2) and a flexible ring gear (3), the gearbox being able to set in motion an actuating shaft (12), characterized in that it comprises means reversibility device (8, 9, 11/33, 34) adapted to allow the movement of said actuating shaft without causing the displacement of all or part of said harmonic gear.   2. harmonic gear according to claim 1, characterized in that the reversibility means consist of mechanical means.   Harmonic reducer according to claim 1 or 2, characterized in that the harmonic reducer is made of plastic.   4. harmonic gear according to claim 3, characterized in that the flexible envelope (3) comprises a metal insert (30).   5. harmonic gear according to any one of the preceding claims, characterized in that the reversibility means comprise at least one pair of friction discs (8, 9) adapted to slide on one another when a force greater than a determined threshold is applied directly to the actuating shaft (12). 25   Harmonic reduction gear according to claim 5, characterized in that the flexible ring (3) comprises a plurality of notches (7) intended to drive, during the rotation of said ring gear (3), at least one disc (8). of the aforementioned pair of friction discs (8, 9). -17- 2901857   7. harmonic gear according to claim 5 or 6, characterized in that it comprises a spring (20) for compressively compressing the friction discs (8, 9) between them. 5   8. harmonic gear according to claim 6, characterized in that the notches (7) have at least a portion of its contact faces having an angle between 5 and 40, preferably 15 2.   Harmonic reduction gear according to any one of claims 1 to 3, characterized in that the reversibility means comprise a detachable fastening means when a force greater than a determined threshold is applied directly to the actuating shaft ( 12).   10. harmonic gear according to claim 9, characterized in that the removable fastening means consists of a pair of teeth respectively placed on two separable parts (33, 34).   11. harmonic gear according to any one of the preceding claims, characterized in that it comprises a pair of roller carriers (16), a portion of the rollers (15) being intended to ensure the rotation of the flexible ring (3). while the other part of the rollers (15) being intended to prevent the vibration of said ring (3).   12. Actuator comprising a motor and its output shaft (17), an actuating shaft (12) rotated by the motor output shaft (17) by means of a harmonic gear, characterized in that the gearbox harmonic is a harmonic reducer according to any one of the preceding claims.