Transmission mechanism with at least two speed ratios

Abstract

A transmission mechanism (18) comprises: a drive shaft (22), an epicyclic gear train (20) including a first input member (24), a second input member (26) and an output member (28), a first permanent kinematic linkage (L1) between the input shaft (22) and the first input member (24) of the epicyclic gear train (20), and a commutator mechanism (17). In a first position of the commutator mechanism (17), a second kinematic linkage (L2) is established between the drive shaft (22) and the second input member (26) of the epicyclic gear train (20), and the first input member (24) is able to rotate relative to the second input member (26). In a second position of the switching mechanism (17), the second kinematic link (L2) is interrupted and the first input member (24) is coupled to the second input member (26) of the epicyclic gear train (20). (Shorthand figure: 1)

Description

Title of the invention: Transmission mechanism with at least two speed ratios. TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to a transmission mechanism, intended, for example, for driving a motorized vehicle, such as a motor vehicle, a motorcycle, a motorized personal mobility device (PMD), a vehicle for transporting persons with reduced mobility, or an autonomous vehicle, or a piece of equipment, such as a power take-off (PTO) of a construction vehicle or an agricultural vehicle. PRIOR TECHNOLOGY

[0002] Document EP3632728 describes a transmission mechanism comprising: a drive shaft linked to an electric machine, a driven member which is an input member of a differential driving two half-shafts of drive wheels of a motor vehicle, an epicyclic gear train comprising a first input member, a second input member and an output member fixed to the rotating driven member, a first permanent kinematic link between the input shaft and the first input member of the epicyclic gear train, and a movable switching mechanism between at least a first position and a second position to ensure, in the first position, a first speed ratio between the drive shaft and the driven member, and, in the second position, a second speed ratio between the drive shaft and the driven member.The switching mechanism includes a clutch to rotationally link the two input members of the epicyclic gear train, and a brake to stop the second input member of the epicyclic gear train. The speed ratios obtained between the driving shaft and the driven member are relatively low. Description of the invention

[0003] The invention aims to remedy the drawbacks of the prior art and to propose a compact transmission mechanism with at least two speed ratios different from each other and with a high ratio.

[0004] To this end, according to a first aspect of the invention, a transmission mechanism is proposed comprising: a drive shaft, an epicyclic gear train having a first input member, a second input member and an output member rotating about a principal axis of rotation of the epicyclic gear train, a first permanent kinematic linkage between the input shaft and the first input member of the epicyclic gear train, and a movable commutation mechanism between at least a first position and a second position to ensure, in the first position, a first speed ratio between the drive shaft and the output member, and, in the second In the first position of the switching mechanism, a second kinematic linkage is established between the drive shaft and the second input element of the epicyclic gear train, and the first input element is able to rotate relative to the second input element. In the second position of the switching mechanism, the second kinematic linkage is broken, and the first input element is coupled to the second input element of the epicyclic gear train.

[0005] The epicyclic gear train comprises three main rotating elements which have a common main axis of rotation. The rotating elements of the epicyclic gear train and the commutation mechanism preferably have the same axis of rotation.

[0006] In one embodiment, the first input member is a planet carrier, preferably with a row of planet gears, the second input member is an internal planet gear, and the output member is a ring gear. In an alternative embodiment, the first input member is a ring gear, the second input member is a central planet gear, and the output member is a planet carrier, preferably with a row of planet gears. Other configurations are possible.

[0007] According to one embodiment, the drive shaft has an axis of rotation coaxial with the main axis of rotation of the epicyclic gear train. Alternatively, the drive shaft has an axis of rotation parallel to the main axis of rotation of the epicyclic gear train and at a distance from the main axis of rotation of the epicyclic gear train.

[0008] According to one embodiment, the transmission mechanism further comprises a receiving member kinematically linked in rotation to the output member of the epicyclic train.

[0009] The epicyclic gear train is arranged between the switching mechanism and the receiving member of the transmission mechanism.

[0010] According to one embodiment, the receiving member has an axis of rotation coaxial with the main axis of rotation of the epicyclic gear train. Alternatively, the receiving member has an axis of rotation parallel to the main axis of rotation of the epicyclic gear train and at a distance from the main axis of rotation of the epicyclic gear train.

[0011] According to one embodiment, the receiving member is an input member of an output differential driving two output half-shafts. Assuming that the receiving member is coaxial with the main axis of the epicyclic gear train, it can advantageously be provided that the receiving member has an axis of rotation coaxial with the main axis of rotation of the epicyclic gear train, one of the output half-shafts or of the output differential passing through the epicyclic gear train.

[0012] According to one embodiment, each kinematic linkage comprises at least one drive gear fixed to the drive shaft meshing with a wheel A driven gear is integral with a clutch of the commutating mechanism or the first input component of the epicyclic gear train. The gear system ensures precise transmission of the forces exerted by the drive shaft. Alternatively, each kinematic linkage includes at least one driving gear integral with the drive shaft, driving a chain which in turn drives a driven gear integral with a clutch of the commutating mechanism or the first input component of the epicyclic gear train; or a driving pulley integral with the drive shaft, driving a belt which in turn drives a driven pulley integral with a clutch of the commutating mechanism or the first input component of the epicyclic gear train.

[0013] According to various embodiments, one or more of the following conditions are satisfied: • the speed ratio between the drive shaft and the first input element of the epicyclic gear train is strictly greater than 1; • the speed ratio between the drive shaft and the second input element of the epicyclic gear train, in the second position, is equal to 1; • the speed ratio between the drive shaft and the second input element of the epicyclic train, in the second position, is less than the speed ratio between the drive shaft and the first input element of the epicyclic train, which is a planet carrier; • The speed ratio between the drive shaft and the second input element of the epicyclic gear train, in the second position, is greater than the speed ratio between the drive shaft and the first input element of the epicyclic gear train, the second input element being a planet carrier.

[0014] According to one embodiment, the switching mechanism comprises at least one first clutch for coupling and uncoupling the first input element and the second input element or one of the first and second input elements and the output element, and at least one second clutch for establishing and breaking the second kinematic linkage.When the first clutch is closed and the two input members of the epicyclic gear train are coupled, or when one of them is coupled to the output member, the epicyclic gear train rotates as a single unit, and the gear ratio achieved in the second position of the switching mechanism is entirely determined by the first kinematic linkage. The second clutch is then necessarily open. In the first position of the switching mechanism, the first clutch is open, allowing the two input members to rotate relative to each other, and the second clutch is closed, so that the torque is transmitted in parallel through the first permanent kinematic linkage and the second kinematic linkage passing through the closed second clutch.

[0015] Two clutch arrangements are possible. For increased axial compactness In this system, one of the first or second clutches at least partially surrounds the other. A more radially compact alternative is to have the first and second clutches axially separated along a main axis of rotation of the epicyclic gear train. In this embodiment, the distance between the first and second kinematic links is greater to ensure the insertion and rotational operation of both clutches.

[0016] According to one embodiment, the two clutches are multi-disc clutches, each containing a row of inner discs and a row of outer discs. The first clutch includes an actuator which, in the engaged position, engages the inner and outer discs of the first clutch and, in the disengaged position, disengages the inner and outer discs of the first clutch. The second clutch includes an actuator which, in the engaged position, engages the inner and outer discs of the second clutch and, in the disengaged position, disengages the inner and outer discs of the second clutch.

[0017] Two speed ratios are possible: - the first actuator is engaged and the second actuator is disengaged to perform a first gear ratio, or - the first actuator is disengaged and the second actuator is engaged to perform a second gear ratio different from the first gear ratio.

[0018] When stopped, the simultaneous engagement of the two actuators makes it possible to achieve a stopping brake.

[0019] The switching mechanism can offer a third speed ratio different from the first two speed ratios. In one embodiment, there is then at least one third clutch to establish and break a third kinematic link between the drive shaft and the second input element of the epicyclic gear train, the third kinematic link having a speed ratio different from the second kinematic link.

[0020] Two alternatives are possible for the positioning of the third clutch relative to the first two clutches: - the third clutch surrounds at least partially one of the first and second clutches; or - the third clutch is positioned axially at a distance from the first and second clutches.

[0021] The third clutch is preferably a multi-disc clutch, each disc containing a row of inner discs and a row of outer discs. The third clutch includes an actuator which, in the engaged position, locks the inner and outer discs of the third clutch and which, in the disengaged position, separates the inner and outer discs of the third clutch.

[0022] Three speed ratios are possible: • The first clutch is engaged, the second and third clutches are disengaged, to perform a first gear engagement; or, • the second clutch is engaged, the first clutch and the third clutch are disengaged, to perform a second gear ratio different from the first gear ratio, or; • the third clutch is engaged, the first clutch and the second clutch are disengaged, to perform a third gear ratio different from the first gear ratio and the second gear ratio.

[0023] The switching mechanism also allows a brake to be applied when stopped by engaging two of the clutches.

[0024] In practice, in the first position of the switching mechanism, the first speed ratio between the motor shaft and the output member is greater than 15, preferably greater than 20, preferably greater than 50, preferably greater than 100. BRIEF DESCRIPTION OF THE FIGURES

[0025] Other features and advantages of the invention will become apparent from the following description, with reference to the attached figures.

[0026] [Fig. 1] Fig. 1 illustrates a motor vehicle drive train comprising a propulsion assembly and transmission mechanism according to a first embodiment of the invention.

[0027] [Fig.2] Fig.2 illustrates a motor vehicle drive train comprising a propulsion assembly and transmission mechanism according to a second embodiment of the invention.

[0028] [Fig. 3] Fig. 3 illustrates a motor vehicle drive train comprising a propulsion assembly and transmission mechanism according to a third embodiment of the invention.

[0029] [Fig.4] Fig.4 illustrates a motor vehicle drive train comprising a propulsion assembly and transmission mechanism according to a fourth embodiment of the invention.

[0030] [Fig. 5] [Fig. 5] illustrates a motor vehicle drive train comprising a propulsion assembly and transmission mechanism according to a fifth embodiment of the invention.

[0031] [Fig.6] Fig.6 illustrates a motor vehicle drive train comprising a propulsion assembly and transmission mechanism according to a sixth embodiment of the invention.

[0032] [Fig.7] Fig.7 illustrates a motor vehicle drive train comprising a propulsion assembly and transmission mechanism according to a seventh embodiment of the invention.

[0033] [Fig.8] Fig.8 illustrates a motor vehicle drive train comprising a propulsion assembly and transmission mechanism according to an eighth embodiment of the invention.

[0034] [Fig.9] Fig.9 illustrates a motor vehicle drive train comprising a propulsion assembly and transmission mechanism according to a ninth embodiment of the invention.

[0035] For clarity, functionally identical or similar elements are identified by identical reference numerals throughout the figures, DETAILED description of embodiments

[0036] Figure 1 is illustrated of a motor vehicle drive train 10, comprising a receiving member 33 driven by a propulsion assembly 14.

[0037] This propulsion assembly 14 comprises an electric machine 16 and a transmission mechanism 18 kinematically linking the electric machine 16 to the receiving organ 33 of the vehicle, the transmission mechanism 18 comprising in particular a drive shaft 22 fixed in rotation to the rotor of the electric machine 16, an epicyclic gear train 20, two separate kinematic links L1, L2 between the drive shaft 22 and the epicyclic gear train 20, and a commutation mechanism 17.

[0038] The first kinematic link Ll in this embodiment comprises a first toothed wheel 35 fixed in rotation to the motor shaft 22, and directly meshing with a toothed wheel 37 formed by a first input element 24 of the epicyclic train 20, which is here a planet carrier.

[0039] The second kinematic link L2 includes a second toothed wheel 39 meshing with a toothed wheel 41 fixed in rotation to an input member C21 of a clutch C2 whose output member C22 is fixed in rotation to a second input member 26 of the epicyclic train 20, constituted in this embodiment by a central pinion.

[0040] The clutch C2 of the second kinematic link L2, which will also be referred to as the "second clutch" in the following description, is preferably a wet multi-disc clutch, whose input member C21 is preferably an outer disc carrier and whose output member C22 is an inner disc carrier.

[0041] The output member 28 of the epicyclic gear train 20, here consisting of an outer ring, is rotationally fixed to a toothed wheel 31 which meshes with the member receiver 33, which here is an input element of a differential 32 distributing the torque between two half-shafts of wheel 34, 36. Where appropriate, a second toothed wheel 30 may be provided, fixed to the output element 28 of the epicyclic train 20, meshing with a pinion (not shown) linked to a parking brake.

[0042] In this embodiment, the axis of rotation of the drive shaft 22, the main axis of rotation of the epicyclic gear train 20, which is the axis of rotation of the two input members 24 and 26 and of the output member 28 of the epicyclic gear train 20, and the axis of rotation of the receiving member 33 are parallel but distinct, coplanar or preferably non-coplanar.

[0043] It is understood that the rotational link between the drive shaft 22 and the first input member 24 of the epicyclic gear train 20, the rotational link between the drive shaft 22 and the input member C21 of the clutch C2 and the rotational link between the output member 28 of the epicyclic gear train 20 and the receiving member 33 could be achieved by any other means known to those skilled in the art, in particular by belts or transmission chains.

[0044] The axial distance between the second gear 39 and the motor 16 is preferably less than the axial distance between the first gear 35 and the motor 16. Furthermore, the speed ratio of the first kinematic link L1 between the motor shaft 22 and the first input member 24 of the epicyclic train 20 is preferably greater than the speed ratio of the second kinematic link L2 between the motor shaft 22 and the input member C21 of the clutch C2.

[0045] Remarkably, the switching mechanism 17, which includes the clutch C2, also includes a clutch Cl (also referred to hereafter as the "first clutch") to couple the first input member 24 of the epicyclic train 20 to the second input member 26 of the epicyclic train 20.

[0046] The first clutch Cl of the switching system 17 is preferably a wet multi-disc clutch, composed of inner discs rotationally fixed to an inner disc carrier C12 itself rotationally fixed to the second input member 26 of the epicyclic train 20, and outer discs, rotationally fixed to an outer disc carrier Cil, itself rotationally fixed to the first input member 24 of the epicyclic train 20.

[0047] The two clutches Cl, C2 are coordinated to achieve two gear ratios, and optionally a parking brake. The first clutch Cl engages with the second input member 26 of the epicyclic gear train 20 while the second clutch C2 is open, to achieve a first gear ratio between the drive shaft 22 and the output differential 32. The second clutch C2 engages with the second input member 26 of the epicyclic gear train 20 while the first clutch Cl is open, to achieve a second gear ratio between The drive shaft 22 and the output differential 32 are different from those of the first gear. If necessary, transitional modes can be provided in which one of the clutches, C1 or C2, opens progressively while the other closes progressively, allowing for gear changes without interruption of torque. If necessary, both clutches, C1 and C2, can be engaged when stationary to provide a parking brake.

[0048] The embodiment shown in [Fig.2] differs from the first in the spatial positioning of the second clutch C2. In this embodiment, the first clutch Cl and the second clutch C2 are nested within each other, the output member C22 of the second clutch C2 and the output member C12 of the first clutch Cl forming a single common part of revolution fixed to the second input member 26 of the epicyclic gear train 20. The input member C21 of the second clutch C2, which is rotationally fixed with the toothed wheel 41, is here an inner disc carrier.

[0049] This embodiment makes it possible to limit the axial bulk of the switching system 17 and to reduce the axial distance between the first gear 35 and the second gear 39.

[0050] The embodiment shown in [Fig. 3] differs from the previous one in that a third kinematic linkage L3 connects the drive shaft 22 to the second input member 26 of the epicyclic gear train 20 by means of a third wet multi-disc clutch C3. The third kinematic linkage L3 comprises a third gear 43 meshing with a gear 45 which is rotationally fixed to an input member C31 of a clutch C3, the output member C32 of which is rotationally fixed to the second input member 26 of the epicyclic gear train 20.

[0051] In this embodiment, the axial distance between the third gear 43 and the motor 16 is preferably less than the axial distance between the second gear 39 and the motor 16. Furthermore, the speed ratio of the second kinematic link L2 between the motor shaft 22 and the input member C21 of the second clutch C2 is preferably greater than the speed ratio of the third kinematic link L3 between the motor shaft 22 and the input member C31 of the clutch C3.

[0052] The third clutch C3 is coordinated with the two clutches C1 and C2 to achieve three gear ratios, and optionally a parking brake. The first clutch C1 is closed while the second and third clutches C2 and C3 are open, to achieve a first gear ratio between the drive shaft 22 and the output differential 32. The second clutch C2 is closed while the first clutch C1 and the third clutch C3 are open, to achieve a second gear ratio between the drive shaft 22 and the output differential 32, different from the first gear ratio. The third Clutch C3 is closed while the first clutch Cl and the second clutch C3 are open, to establish a third gear ratio between the drive shaft 22 and the output differential 32, different from the first and second gear ratios. If necessary, transitional modes can be provided in which one of the clutches Cl, C2, or C3 opens progressively while another closes progressively, for a gear change without interruption of torque. If necessary, two of the clutches Cl, C2, and C3, or even all three, can be engaged when stationary to provide a parking brake.

[0053] The embodiment shown in [Fig. 4] differs from the previous one in that the three clutches C1, C2, and C3 are arranged axially at a distance from each other. The output member C12 of the first clutch, the output member C22 of the second clutch, and the output member C32 of the third clutch C3 are rotationally fixed, and are rotationally fixed with the second input member 24 of the epicyclic gear train. The input member C21 of the second clutch C2 is rotationally fixed with the gear 41.

[0054] The embodiment shown in [Fig.5] differs from that shown in [Fig.3] in that the third clutch C3 linked to the third kinematic link L3 is arranged axially at a distance from the clutches Cl and C2 which are nested one inside the other.

[0055] The embodiment shown in [Fig.6] differs from that shown in [Fig.3] in that the clutch Cl linked to the first kinematic link L1 is arranged axially at a distance from the clutches C2 and C3, which are nested one inside the other.

[0056] The embodiment shown in [Fig.7] differs from that shown in [Fig.3] in that the second clutch C2 linked to the second kinematic link L2 is arranged axially at a distance from the clutches Cl and C3, which are nested one inside the other.

[0057] In this embodiment, the axial distance between the second gear 39 and the motor 16 is preferably less than the axial distance between the third gear 43 and the motor 16. The axial distance between the third gear 43 and the motor 16 is preferably less than the axial distance between the first gear 35 and the motor 16. Furthermore, the speed ratio of the second kinematic linkage L2 between the motor shaft 22 and the input member C21 of the second clutch C2 is preferably greater than the speed ratio of the third kinematic linkage L3 between the motor shaft 22 and the input member C31 of the clutch C3.

[0058] The embodiment shown in [Fig. 8] differs from that of [Fig. 2] in that the configuration of the epicyclic gear train is modified: the first input member 24 of the epicyclic gear train 20 is a toothed ring, the second input member 26 of the epicyclic gear train 20 is a planet carrier, and the output member 28 of the epicyclic gear train 20 is a planetary gear.

[0059] In this embodiment, the second kinematic link L2 comprises a toothed wheel 39 meshing with a toothed wheel 41 fixed in rotation to the input member C21 of the second clutch C2, whose output member C22 is fixed in rotation to the second input member 26 of the epicyclic train 20. The first clutch Cl is, for its part, disposed between the second input member 26 of the epicyclic train 20 and the output member 28 of the epicyclic train.

[0060] In this embodiment, the clutches have been symbolized as single-disc clutches or as dog clutches, but they can also be, as in previous embodiments, wet multi-disc clutches.

[0061] The embodiment shown in [Fig.9] differs from that of [Fig.1] in that the configuration of the epicyclic train is modified: the first input member 24 of the epicyclic train 20 is a toothed ring, the second input member 26 of the epicyclic train 20 is a planetary pinion and the output member 28 of the epicyclic train 20 is a planet carrier.

[0062] Here too, the Cl and C2 clutches have been illustrated as single-disc or dog clutches, but can where appropriate be replaced by wet multi-disc clutches.

[0063] More generally, across all embodiments, clutches can be of either dry or wet type, single-disc or multi-disc or dog clutches.

[0064] Naturally, the examples shown in the figures and discussed above are given by way of illustration only and are not intended to be limiting. It is explicitly intended that the different embodiments illustrated can be combined to propose others.

Claims

Demands

1. Transmission mechanism (18) comprising: - a drive shaft (22), - an epicyclic gear train (20) comprising a first input member (24), a second input member (26) and an output member (28) rotating about a main axis of rotation of the epicyclic gear train (20), - a first permanent kinematic link (L1) between the input shaft (22) and the first input member (24) of the epicyclic gear train (20), and - a switching mechanism (17) movable between at least a first position and a second position to ensure, in the first position, a first speed ratio between the drive shaft (22) and the output member (28), and, in the second position, a second speed ratio between the drive shaft (22) and the output member (28), different from the first speed ratio;in which: - in the first position of the switching mechanism (17), a second kinematic link (L2) is established between the drive shaft (22) and the second input member (26) of the epicyclic train (20) and the first input member (24) is able to rotate relative to the second input member (26), - in the second position of the switching mechanism (17), the second kinematic link (L2) is interrupted and the first input member (24) is coupled to the second input member (26) of the epicyclic train (20), characterized in that the first kinematic link (L1) comprises a first toothed wheel (35) fixed in rotation to the drive shaft (22), and meshing directly with a toothed wheel (37) formed by the first input member (24) of the epicyclic train (20), which is a planet carrier.

2. Transmission mechanism (18) according to claim 1, characterized in that one of the following features is realized: - the drive shaft (22) has an axis of rotation coaxial with the main axis of rotation of the epicyclic gear train (20); or - the drive shaft (22) has an axis of rotation parallel to the main axis of rotation of the epicyclic gear train (20) and distant from the main axis of rotation of the epicyclic gear train (20).

3. Transmission mechanism (18), according to claim 1 or claim 2, characterized in that the transmission mechanism (18) further comprises a receiving member (33) kinematically linked in rotation to the output member (28) of the epicyclic train (20).

4. Transmission mechanism (18) according to claim 3, characterized in that one of the following features is achieved: - the receiving member (33) has an axis of rotation coaxial with the main axis of rotation of the epicyclic train (20); - the receiving member (33) has an axis of rotation parallel to the main axis of rotation of the epicyclic train (20) and distant from the main axis of rotation of the epicyclic train (20).

5. Transmission mechanism (18), according to claim 3 or claim 4, characterized in that the receiving member (33) is an input member of an output differential (32) driving two output half-shafts (34) and (36).

6. Transmission mechanism (18), according to claim 5, characterized in that the receiving member (33) has an axis of rotation coaxial with the main axis of rotation of the epicyclic train (20), one of the output half-shafts (34) or (36) of the output differential (32) passing through the epicyclic train (20).

7. Transmission mechanism (18), according to any one of the preceding claims, characterized in that one or more of the following conditions are satisfied: - the speed ratio between the drive shaft (22) and the first input element (24) of the epicyclic train (20) is strictly greater than 1; - the speed ratio between the drive shaft (22) and the second input element (26) of the epicyclic train (20), in the second position, is equal to 1; - the speed ratio between the drive shaft (22) and the second input element (26) of the epicyclic train (20), in the second position, is less than the speed ratio between the drive shaft (22) and the first input element (24) of the epicyclic train (20), which is a planet carrier; - the speed ratio between the drive shaft (22) and the second input element (26) of the epicyclic train (20), in the second position, is greater than the speed ratio between the drive shaft (22) and the first input element (24) of the epicyclic train (20), the second input element (26) being a planet carrier.

8. Transmission mechanism (18), according to any one of the preceding claims, characterized in that the switching mechanism (17) comprises at least one first clutch (Cl) for coupling and uncoupling the first input member (24) and the second input member (26) or one of the first (24) and second input members (26) and the output member (28), and at least one second clutch (C2) for establishing and interrupting the second kinematic link (L2).

9. Transmission mechanism (18), according to claim 8, characterized in that one of the first (Cl) or second clutches (C2) at least partially surrounds the other.

10. Transmission mechanism (17), according to claim 8, characterized in that the first (Cl) and second clutches (C2) are axially separated from each other along a main axis of rotation of the epicyclic train (20).

11. Transmission mechanism (18), according to any one of claims 8 to 10, characterized in that the switching mechanism (17) comprises at least one third clutch (C3) for establishing and interrupting a third kinematic link (L3) between the drive shaft (22) and the second input member (26) of the epicyclic train (20), the third kinematic link (L3) having a different speed ratio from the second kinematic link (L2).

12. Transmission mechanism (18), according to claim 11, characterized in that the third clutch (C3) surrounds at least partially one of the first (C1) and second clutches (C2).

13. Transmission mechanism (18), according to claim 12, characterized in that the third clutch (C3) is arranged axially at a distance from the first (Cl) and the second clutch (C2).

14. Transmission mechanism (18) according to any one of the preceding claims, characterized in that in the first position of the switching mechanism (17), the first speed ratio between the drive shaft (22) and the output member (28) is greater than 15, preferably greater than 20, preferably greater than 50, preferably greater than 100.

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