Patent ID: 12250902

DETAILED DESCRIPTION

As mentioned above, the transmission2, the subject of the invention, is more particularly intended to be applied to a wheeled vehicle1, notably a pedestrian-controlled wheeled vehicle.FIG.1represents the application of such a transmission2to a lawnmower. This lawnmower comprises a wheeled chassis, the rear wheels of the chassis being represented as7A,7B in the figures.

This transmission2can be housed at least partially in a housing generally made of synthetic material. This transmission2comprises a driving member3formed here by a drive pinion. This driving member3could, in an equivalent manner, have been produced for example in the form of a worm screw. This driving member3is a rotary member. This driving member3is driven in rotation by a motor system17for driving the driving member3with which the vehicle1is equipped in rotation. This system17for driving the driving member3in rotation comprises a motor with two directions of rotation and gears coupling the output shaft of the motor with the driving member3for driving the driving member3in rotation in a first direction of rotation, the so-called forward direction of the vehicle, and a second, opposite direction of rotation, called reverse. The driving member3is permanently engaged by meshing with a rotary driven member5produced in the form of a toothed wheel that is holed centrally so to be able to be threaded onto a shaft6which forms the drive shaft of the wheels7A and7B of the vehicle1. This driven member5is mounted to rotate freely on said wheel drive shaft6. The driven member5can be driven in rotation by the driving member3in two directions of rotation, namely a first, so-called forward, rotational driving direction, and a second, so-called reverse, rotational driving direction. The wheel drive shaft6can be produced in a single piece as illustrated inFIG.2B. The wheel drive shaft6can also be formed by at least two coaxial wheel drive shaft sections6A,6B each capable of driving a wheel7A,7B of a same pair of wheels of the vehicle.

These shaft sections6A,6B are kept aligned by holding means and are, in the aligned state, capable of being driven by a relative rotational displacement. The holding means are, for example, formed by a linking pin coupled at each of its ends by fitting to a wheel drive shaft section.

These drive shaft sections6A,6B extend, in the examples represented, parallel to the motor shaft of the motor system17for driving of the driving member3in rotation. At the ends of the wheel drive shaft sections6A,6B there can be disposed, each time, a drive pinion intended to engage with a drive pinion borne by each wheel7A,7B of the vehicle. Obviously, other means for transmitting the movement of the wheel drive shaft section6A or respectively6B to the wheel7A or respectively7B can be provided without departing from the scope of the invention. The production of the wheel drive shaft in the form of two shaft sections allows each wheel of the pair of wheels to turn independently of the other wheel of the pair of wheels.

The transmission2also comprises, disposed between the wheel drive shaft6or each of the wheel drive shaft sections6A,6B and the driven member5, a clutch mechanism8. Thus, in the case of a wheel drive shaft6produced in a single piece, the transmission2comprises only a single clutch mechanism8for transmitting the movement of the driven member5to said shaft6. In the case of a wheel drive shaft6formed by at least two shaft sections6A,6B, the transmission2comprises two clutch mechanisms8, one disposed between the driven member5and the wheel drive shaft section6A, and the other disposed between the driven member5and the wheel drive shaft section6B. These clutch mechanisms8are capable of transmitting, for one of them, the transmission of the movement of the driven member5to the wheel drive shaft section6A, and for the other, the transmission of the movement of the driven member5to the wheel drive shaft section6B. Thus, the toothed wheel, forming the driven member5, disposed coaxially to the wheel drive shaft sections6A,6B, is disposed between two clutch mechanisms8, each clutch mechanism8being borne, at least partially, by one of the wheel drive shaft sections6A or6B.

Independently of the number of clutch mechanisms8, the design and the operation of each clutch mechanism8are similar. The or each clutch mechanism8therefore comprises at least one part9that can be axially displaced on the wheel drive shaft6or the wheel drive shaft sections6A or6B with which said clutch mechanism8cooperates between a position away from the driven member5and a position close to the driven member5. The position of the part9away from the driven member5corresponds to an activated state, that is to say the clutched state of the corresponding clutch mechanism8, a state in which the movement of the driven member5can be transmitted to the wheel drive shaft6. The position of the part9close to the driven member5corresponds to a deactivated state of the corresponding clutch mechanism8, that is to say a declutched state, in which the movement of the driven member5cannot be transmitted to the wheel drive shaft6. Said at least one part9of the or each clutch mechanism8disposed, when the corresponding clutch mechanism8is in the deactivated state, in a position close to the driven member5is disposed, when the corresponding clutch mechanism8is in the activated state, away from the driven member5and engaged with an element12borne by and secured in rotation to the drive shaft6or drive shaft section6A,6B. This part9of the or each clutch mechanism8is also, when the corresponding clutch mechanism8is in the deactivated state, close to the driven member5and uncoupled from the element12borne by and secured in rotation to the wheel drive shaft6or the wheel drive shaft section6A,6B. This part9of the or each clutch mechanism8is therefore axially mobile in the direction of a movement toward and away from the driven member5so as to be able to be moved away from or toward the element12secured in rotation to the wheel drive shaft. The or each so-called automatic clutch mechanism8, that can be activated by driving the driven member5in rotation in a first, so-called forward, rotational driving direction, is therefore configured to allow, when said driven member is in the state driven in forward rotation by bearing contact of the driven member5and of said at least one axially mobile part9of the associated clutch mechanism8, an axial displacement of said axially mobile part9in the direction of a movement away from the driven member5. This axial displacement of said axially mobile part9in the direction of a movement away from the driven member5corresponds to the transition of the associated clutch mechanism from the deactivated state to the activated state. The or each so-called automatic clutch mechanism, that can be deactivated by driving the driven member5in rotation in a second direction of rotation, so-called reverse, counter to said first rotational driving direction, is configured to allow, when said driven member5is in the state driven in reverse rotation, by bearing contact of said at least one part9of the associated clutch mechanism8and of the element12borne by, and secured in rotation to, the wheel drive shaft or drive shaft section, an axial displacement of said axially mobile part9in the direction of a movement close to the driven member5. This axial displacement of said axially mobile part9in the direction of a movement toward the driven member5corresponds to the transition of the associated clutch mechanism8from the activated state to the deactivated state. In the examples represented, said at least one part9of the or each clutch mechanism8disposed, when the corresponding clutch mechanism8is in the deactivated state, in a position close to the driven member5takes the form of a clutch plate91mounted on said wheel drive shaft6or wheel drive shaft section6A,6B, free to rotate and axially mobile. The element12with which the clutch plate91can engage when the corresponding clutch mechanism8is in the activated state also takes the form for example of a plate that is centrally holed so as to be able to be threaded onto the wheel drive shaft6. This element12is secured in rotation to the wheel drive shaft6by a pin or splines or by any other shaft/wheel link type. This element12is axially fixedly mounted on the wheel drive shaft6. To allow an axial displacement of the clutch plate91, the clutch plate91and the driven member5, which here takes the form of a toothed wheel, are provided, for the clutch plate91on each of its faces, and for the driven member5on at least one of its faces, with ramps. These ramps ensure the bearing contact between part9and driven member5so as to allow an activation of the clutch mechanism. The ramps13of one face of the plate91cooperate, when a clutch mechanism8transitions from the deactivated state to the activated state, with the ramps14of the driven member5for an axial displacement of the clutch plate91in a first direction of movement away from the driven member5and securing of the plate91with the element12borne by, and secured in rotation to, the wheel drive shaft section6A or6B which bears with said clutch mechanism8. The ramps15of the other face of the plate91cooperate, when the clutch mechanism transitions from the activated state to the deactivated state, with ramps16of the element12borne by, and secured in rotation to, the wheel drive shaft6A or6B which bears said clutch mechanism8so as to bring about, by axial displacement in an opposite direction of said clutch plate91, the free-wheeling of the wheel drive shaft section6A or6B bearing the clutch mechanism. Once again, these ramps ensure the bearing contact between the part9and the element12so as to allow a deactivation of the clutch mechanism. As the driven member5can comprise ramps on both of its faces, it is capable of cooperating with the clutch plate of each of the clutch mechanisms8.

The ramps of the driven member5and of the clutch plate9are, here, formed by one of the flanks of crenelations or teeth protruding from said faces.

In the example represented inFIG.3A, the toothed wheel constituting the driven member5has, on each of its faces, a ring of teeth with each tooth having a widened top giving the tooth the overall shape of a T. The horizontal branch of the T is provided, at each of its ends, with a bevel. One of the bevels forms a ramp14of the driven member5for an axial displacement of the clutch plate91in the direction of a movement away from the driven member5.

The clutch plate91comprises, on its face turned toward the driven member5, a ring of teeth with each tooth comprising one flank produced over at least a part of its length parallel to the axis of rotation of the wheel drive shaft sections and one flank produced over at least a part of its length inclined and forming an angle with said axis of rotation. The inclined flank part forms the ramp represented as13in the figures. This flank is the flank stressed in the forward driving of the driven member5by bearing contact with a tooth of the driven member5so as to bring about an axial displacement of the clutch plate in the direction of a movement away from the driven member5. This displacement results from the bearing contact of the ramps13and14. The other face of the clutch plate91, that is to say the one turned toward the element12secured in rotation to the wheel drive shaft section, which in this instance is formed by a wheel or plate with ramps, comprises, likewise, a ring of teeth with flanks, one of them straight and the other inclined. The inclined flank of each tooth is represented as15in the figures and represents the ramp intended to cooperate with the element12for an axial displacement of the clutch plate91in the direction of a movement toward the driven member5.

The element12, secured in rotation to the wheel drive shaft section, also comprises a ring of teeth in which each tooth has one of its flanks inclined, and represented as16in the figures, and the other flank straight. For each tooth of the clutch plate91and of the element12, a straight flank of a tooth of the clutch plate91cooperates with a straight flank of a tooth of the element12secured in rotation to the wheel drive shaft section during forward driving of the driven member5, in the state with the clutch plate91away from the driven member5. This cooperation by bearing contact continues at least as long as the rotational driving speed of the wheel drive shaft section or of the wheel drive shaft is less than the speed of the driven member5.

When the speed of the wheel drive shaft6or of the wheel rotational drive shaft section becomes greater than the speed of rotation of the driven member5, for example when making a turn with the wheel of the shaft forming the outside wheel in said turn, the drive shaft section and the element12become driving such that each tooth of the element12cooperates, on its ramp-forming inclined flank, represented as16in the figures, by bearing contact with the ramp-forming inclined flank represented as15of the teeth of the clutch plate91so as to bring about an axial displacement of the clutch plate91in the direction of a movement toward the driven member5as far as an uncoupled position of said ramps corresponding to the deactivated state of the clutch mechanism8.

When the driven member5is driven in reverse, asFIG.9illustrates, following the reversal of direction of driving of the driving member3in rotation, it is once again the ramps15and16formed by the inclined flanks of the teeth of the clutch plate91and of the element12mounted secured in rotation to the wheel drive shaft section which are in bearing contact and bring about an axial displacement of the clutch plate91in the direction of a movement toward the driven member5as far as an uncoupled position of said ramps of the clutch plate91and of the element12corresponding to the deactivated state of the clutch mechanism8.

This axial displacement is brought about when the rotational driving range of the driven member5extends over one revolution or less than one revolution of driving of said driven member5in rotation depending on the configurations of the ramps.

The relative speed variation between clutch plate9and element12secured in rotation to the wheel drive shaft section therefore automatically allows, when the element12becomes driving, a transition of the clutch mechanism8to the deactivated state when the driven member5is being driven forward, whereas the configuration of the ramps automatically brings about a deactivation when the driven member5is being driven in reverse.

Each clutch mechanism8comprises, for its operation, a permanently active brake4on the part9forming the clutch plate91of the or each clutch mechanism8. This brake is, here, formed by a U-shaped leaf spring threaded onto the wheel drive shaft, the branches of said U bearing on the part9forming the clutch plate91of said clutch mechanism8. The presence of this brake generates a permanent braking of the driving of said part9in angular displacement. The result of the design of the clutch mechanisms, as described above, is that each clutch mechanism8is activated by the driving of the driven member5in rotation in a first, so-called forward, rotational driving direction, and axial displacement of the part9of the clutch mechanism forming the clutch plate91in the direction of a movement away from the driven member5so as to engage with the element12secured in rotation to the shaft. In the activated state, the part9of the clutch mechanism8forming the clutch plate91is therefore disposed away from the driven member5, that is to say distanced from the driven member5by a distance greater than that which separates it from the driven member5when the clutch mechanism8is in the deactivated state. The or each clutch mechanism8can be deactivated by driving the wheel drive shaft section6A or6B with which it cooperates in forward rotation, when the speed of rotation of the wheel drive shaft section is greater than the speed of rotation of the driven member5. Greater speed is also understood to mean the case in which the driving member3is not driven in rotation, that is to say stopped.

In fact, during the stopping of the motor driving member3, the inertia of the machine causes a continuation of the displacement of the machine by a value sufficient to drive the wheel drive shaft sections6A and6B of the vehicle in rotation and subsequently generate a deactivation of the clutch mechanisms8.

Likewise, each clutch mechanism is designed to be deactivated, when the speed of rotation of the wheel drive shaft or the wheel drive shaft section which bears the clutch mechanism8is greater than the speed of rotation of the driven member5, for example when taking a turn.

When the clutch mechanism is in the deactivated state, the wheel of the vehicle and the shaft section or the shaft which bears it can turn freely in both directions of rotation. Furthermore, each wheel of a pair of wheels of the vehicle can turn independently of the other wheel of the vehicle in the case of a shaft produced in the form of shaft sections.

The deactivation of the clutch mechanism can also be obtained by driving the driven member5in reverse rotation.

To allow the driven member5to be driven in forward or reverse, using the motor system17for driving the driving member3in rotation, the vehicle comprises a control system18of the motor system17. This control system18comprises at least one manual control member, such as a handle or a lever, that is positioned on the handlebar of the vehicle and that can be actuated manually by the driver of the vehicle. Generally, this control system18is configured to allow manual control of the forward driving of the driven member5by actuation of the manual control member while the reverse driving of the driven member5can be done automatically, for example once the manual control member is released. As a variant, the reverse driving of the driven member5can also be controlled manually. To refine the operation of this transmission2and avoid the transition of the or each clutch mechanism8from the deactivated state to the activated state, when the driven member is in the state driven in reverse, the part9of the or each clutch mechanism8disposed, with the corresponding clutch mechanism8in the deactivated state, in a position close to the driven member5is, in said position, limited in axial displacement in the direction of a movement away from the driven member5when the driven member5is in the state driven in reverse. The transmission comprises an activatable/deactivatable system1000for limiting axial displacement of said at least one part9of the or each clutch mechanism8in the direction of a movement away from the driven member5when said at least one part is in the state positioned in a position close to the corresponding driven member with the clutch mechanism in the deactivated state, this system1000for limiting axial displacement of said at least one part9being active when the driven member5is in the state driven in reverse such that the part9of the or each clutch mechanism8disposed, with the corresponding clutch mechanism8in the deactivated state, in a position close to the driven member5is, in said position, limited in axial displacement in the direction of a movement away from the driven member5when the driven member5is in the state driven in reverse. To that end, the part9forming the clutch plate of the or each clutch mechanism8comprises, for limiting the axial displacement thereof in the direction of a movement away from the driven member5, retaining elements10borne by said part9. These retaining elements10are configured to, when the part9is in a position close to the driven member5, and with the driven member5in the state driven in reverse, engage with complementary retaining elements11borne by the driven member5. In the examples represented, the retaining elements10borne by the part9forming the clutch plate91take the form of hooks. These retaining elements10are disposed protruding from the face of the clutch plate91opposite the driven member5. In particular, the retaining elements10borne by said part9have the overall shape of an L and comprise a first branch100starting on the clutch plate91and extending orthogonally to the clutch plate91in a direction parallel to the wheel drive shaft6and a second branch101orthogonal to the first branch100. The activatable/deactivatable system1000for limiting axial displacement of said at least one part of the or each clutch mechanism in the direction of a movement away from the driven member, when said at least one part is in the state positioned in a position close to the corresponding driven member with the clutch mechanism in the deactivated state, comprises retaining elements10borne by said part9, these retaining elements10being configured to, when said part9is in a position close to the driven member5and with the driven member5in the state driven in reverse, engage with complementary retaining elements11borne by the driven member.

These retaining elements10borne by the part9are disposed on a circle with a center situated at the wheel drive shaft6. The center of the circle is in fact disposed on the axis of rotation of the wheel drive shaft6. The complementary retaining elements11of the driven member5with which the retaining elements10borne by the part9of the clutch mechanism8engage when said part9is in a position close to the driven member5and when the driven member5is in the state driven in reverse, take the form of hooks disposed on a circle with a center situated at the wheel drive shaft6. These hooks have the overall shape of a T. For the or at least one of the clutch mechanisms8, the complementary retaining elements11of the driven member5with which the retaining elements10borne by the at least one part9of said clutch mechanism8engage, when said part9is in a position close to the driven member5, and when the driven member5is in the state driven in reverse, take the form of hooks disposed on a circle with a center situated at the wheel drive shaft6. These hooks of the driven member5are configured to interpenetrate with the retaining elements10of said at least one part9of said clutch mechanism8when said retaining elements10are in the state engaged with the complementary retaining elements11.

It will be noted that, for reasons of simplicity, the ramps13of a face of the clutch plate91which cooperate, when the clutch mechanism8transitions from the deactivated state to the activated state, with the ramps14of the driven member5for an axial displacement of the clutch plate91in a first direction of movement away from the driven member5, are formed on the retaining elements10borne by said clutch plate91.

In fact, the teeth of the clutch plate91bearing the ramps13and the hooks of the retaining elements10are, here, produced in a single piece and the ramp13, with which each retaining element10or tooth is equipped, is formed at the base of said retaining element10or of the tooth in the zone of connection of the retaining element10or the tooth to the clutch plate91. Likewise, the ramps14of the driven member5with which the ramps13of a face of the clutch plate91cooperate, when the clutch mechanism8transitions from the deactivated state to the activated state, for an axial displacement of the clutch plate91in a direction of movement away from the driven member5, are formed on the complementary retaining elements11borne by the driven member5. The ramp-holding teeth and the complementary retaining elements11of the driven member5are therefore produced in a single piece.

Thus, one end of the horizontal branch of the T of each tooth constituting the complementary retaining element11of the driven member5is capable of being inserted into the part of the constitutive hook of each retaining element10of the part9forming the clutch plate91in the link zone between the branches of the L-shaped hook such that, in this position, an axial displacement of the part9forming the clutch plate91in the direction of a movement away from the driven member5is prevented. Thus, when the clutch mechanism8is in the clutched state, as illustrated inFIG.8, the reverse driving of the driven member5generates, by cooperation of the ramps15and16of the part9forming the clutch plate91and of the element12secured in rotation to the shaft6, an axial displacement of the part9forming the clutch plate toward the driven member5as far as a position in which the retaining elements10of the part9forming the clutch plate and the complementary retaining elements11of the driven member5interpenetrate as illustrated inFIG.10. In this position, any axial displacement of the part9forming the clutch plate91in the direction of a movement away from the driven member5is prevented.