WO2018162380A1

WO2018162380A1 - Actuator for hydraulic or pneumatic control device

Info

Publication number: WO2018162380A1
Application number: PCT/EP2018/055289
Authority: WO
Inventors: Guillaume ALBERT; Christophe Mollier; Jean-Philippe Voisin
Original assignee: Psa Automobiles Sa; Valeo Passive Hydraulic Actuators S.R.L.
Priority date: 2017-03-06
Filing date: 2018-03-05
Publication date: 2018-09-13
Also published as: CN110494657B; CN110494657A; DE112018001186T5; FR3063526B1; FR3063526A1

Abstract

The invention relates to an actuator for a hydraulic or pneumatic control device comprising: - a cylindrical body (8), - a piston (10) sliding in the body (8), - a control rod (12) movable between an extended position and a retracted position, a stop (28) projecting radially from the control rod (12) and designed to interact with a stop surface (30) on the cylindrical body (8), - a protective envelope (16) surrounding the control rod (12) and comprising successively: - a first end (17) attached to the body (8), - a rigid portion (21) inside which the stop (28) moves, - a deformable portion (22) having a compressed state and an extended state, and - a second end (19) attached to the control rod (12), the piston (10) defining with the body (8) a third, variable-volume chamber (39) the volume of which varies to receive fluid from or supply fluid to the deformable portion (22).

Description

ACTUATOR FOR A HYDRAULIC CONTROL DEVICE OR

PNEUMATIC

Technical field of the invention

The invention relates to the field of actuators for control devices, hydraulic or pneumatic, intended to equip a motor vehicle. The invention thus relates, for example, to a cylinder for a control system of a motor vehicle clutch or for a braking control system.

State of the art

It is known in the state of the art a hydraulic or pneumatic cylinder for a control device comprising a cylindrical body provided with an internal bore in which is slidably housed a piston, thus defining a hydraulic or pneumatic chamber with variable volume of the actuator. The hydraulic or pneumatic cylinder comprises a control rod connected on the one hand to the piston and, on the other hand, to an actuating member for controlling the movement of the piston. Such an actuating member is, for example in the context of a control cylinder transmitter in a clutch system, a clutch pedal of the vehicle.

In order to limit the displacement of the control rod with respect to the cylinder body, the control rod has a stop, for example in the form of a stop disk projecting radially around the control rod. This stop cooperates with the body of the cylinder, an end of the body of the cylinder traversed by the control rod forming a stop surface with which the stop carried by the control rod cooperates.

In addition, in order to protect the cylindrical body and the piston from the dust present in the environment, a bellows surrounds the control rod. Indeed, such dust could degrade the seal between the piston and the body or degrade the piston and / or the cylinder body. A first end of the bellows is mounted on the cylinder body and a second end of the bellows is mounted on the control rod. When moving the control rod relative to at the cylinder body, the bellows compresses or expands, depending on the direction of movement of the control rod, so as to remain around the control rod and prevent dust from entering the bore of the cylinder body housing the piston.

However, to protect the cylinder, the bellows must have dimensions allowing it to completely surround the control rod. The stop protruding radially from the control rod thus imposes large minimum dimensions of the bellows. However, because of these large minimum dimensions, the bellows has a large variation in its internal volume during compression or development related to the displacement of the control rod.

In order to allow this great variation of the internal volume of the bellows, the internal volume of the bellows is put into communication with its external environment. For this, it is known to make an orifice in the bellows allowing air to circulate between the outside environment of the bellows and the internal volume of the bellows. However, even if this communication is limited to a single orifice, it nevertheless constitutes an intake of outside air, and therefore of dust, into the internal volume of the bellows.

The document US2004 / 0188199 A1 describes a control device actuator limiting the risks of dust penetration into the internal volume of the bellows by putting the internal volume of the bellows in communication with an external environment chosen for its low dust content. Thus, in this document, the communication between the internal volume of the bellows and the air source is via a pipe passing through the fastening of the bellows on the control rod, this pipe opening into an environment having a limited exposure to dust. However, this solution only limits the penetration of dust into the internal volume of the bellows and does not prevent the dust from entering the internal volume of the bellows. DE102013202767 discloses an actuator according to the preamble of claim 1.

Object of the invention

One aspect of the invention is based on the idea of solving at least some disadvantages of the prior art by providing a control device actuator having good reliability and wear resistance over time. In particular, the invention starts from the idea of providing a control device actuator whose internal space is protected from external contaminations.

According to one embodiment, the invention provides an actuator for a hydraulic or pneumatic control device comprising

a cylindrical body provided with an internal bore,

a piston capable of sliding inside said internal bore along an axis (X) of sliding,

a control rod having a first end coupled to the piston and a second end intended to be coupled to an actuating element so as to move the piston inside the internal bore when the element is displaced; actuator, the control rod being movable between an extended position and a retracted position, a stop member projecting radially from the control rod and being arranged to cooperate with an abutment surface carried by the cylindrical body when the rod of control is in the retracted position,

- a protective envelope of the control rod surrounding the control rod and comprising successively:

a first end sealingly attached to the cylindrical body,

a rigid portion delimiting a first chamber inside which the stop member moves during the displacement of the control rod between its deployed position and its retracted position, a deformable portion able to deform along the control rod during the movement of the control rod and delimiting a second variable volume chamber communicating with the first chamber, said deformable portion being deformable between a compressed state when the control rod is in the retracted position and a developed state when the rod control is in the deployed position; and

a second end sealingly attached to the control rod, the piston defining with the internal bore of the body a third variable volume chamber which is in communication with the first chamber and whose volume varies according to the position of the piston so as firstly to receive a volume of fluid resulting from a reduction in the volume of the second chamber during the displacement of the control rod towards its retracted position and, secondly, supplying fluid to the second chamber during the displacement of the control rod towards its deployed position .

By rigid portion is meant a portion which has sufficient rigidity so that said rigid portion does not deform during the movement of the control rod between its retracted position and its deployed position, thus maintaining an internal volume of the first substantially constant chamber.

Thus, such an actuator has a protective envelope with variable volume whose variation of the internal volume is independent of the dimensions of the stop member of the control rod. Thus, it is possible to minimize the size of the second chamber and thus to minimize the variation of volume of the protective envelope during the movement of the control rod. By minimizing the variable volume of the protective envelope, it is no longer necessary to provide communication between the internal volume of the protective envelope and its external environment. In particular, it is not necessary to supply external air to the internal volume of the protective envelope when it increases or to evacuate the air contained in said internal volume of the protective envelope when it decreases. . Indeed, the volume of air displaced by the change of state of the second chamber can be advantageously absorbed or supplied, according to the direction of movement of the control rod, by the third chamber formed in the cylinder body whose volume varies according to the displacement of the piston in the cylinder.

According to other advantageous embodiments, such an actuator may have one or more of the following characteristics:

According to one embodiment, the second chamber has an internal volume when the deformable portion is in the developed state which is between + 30% and -30% of the internal volume of the third chamber in the retracted position of the control rod, in particular between + 10% and -10%, and preferably between + 5% and -5%. According to one embodiment, the internal volume of the second chamber when the deformable portion is in the developed state is equal to the internal volume of the third chamber in the retracted position of the control rod.

According to one embodiment, the decrease in the internal volume of the second chamber when the deformable portion deforms from the developed state to the compressed state corresponds to the increase in the internal volume of the third chamber when the control rod moves. from the deployed position to the retracted position. Conversely, the increase in the internal volume of the second chamber when the deformable portion deforms from the compressed state to the developed state corresponds to the decrease in the internal volume of the third chamber when the control rod moves from the retracted position. towards the deployed position.

According to one embodiment, the abutment member is an abutment disc projecting radially around the control rod.

According to one embodiment, the deformable portion of the envelope has a diameter smaller than the diameter of the rigid portion.

According to one embodiment, the deformable portion of the protective envelope comprises a bellows having an average diameter which is less than a maximum radial dimension of the stop member.

According to one embodiment, the deformable portion of the protective envelope comprises a bellows having a minimum diameter which is less than a maximum radial dimension of the stop member.

According to one embodiment, the average diameter of the bellows is smaller than the diameter of the stop disc.

According to one embodiment, the maximum diameter of the bellows is smaller than the maximum radial diameter of the stop member.

According to one embodiment, the bellows has a plurality of successive folds, the diameter of each fold of the bellows being increasing from the second end of the protective envelope to the rigid portion. Thanks to these characteristics, the deformable portion of the envelope remains coaxial with the control rod, including when the control rod has a slight inclination relative to the axis of the piston. According to one embodiment, the deformable portion of the protective envelope is made of an elastomeric material. Thanks to these characteristics, the deformable portion has good deformation characteristics allowing simple modification of the internal volume of the second chamber of the envelope.

According to one embodiment, the rigid portion of the protective envelope has a wall thicker than the thickness of a wall of the deformable portion of the protective envelope.

According to one embodiment, the rigid portion of the protective envelope has at least one reinforcing member.

According to one embodiment, the reinforcing member is at least one axial reinforcing member developing parallel to the control rod.

According to one embodiment, the reinforcing member is an insert associated with the rigid portion.

Thanks to these characteristics, the rigid portion has good mechanical characteristics. In particular, thanks to these features, the rigid portion has a good rigidity ensuring the conservation of the internal volume of the first chamber. Thus, the deformable portion is deformed preferentially to the rigid portion and the variable volume of the envelope is thus determined by the deformable portion.

According to one embodiment, the first end of the control rod is coupled to the piston with a degree of freedom in rotation about a radial axis perpendicular to the axis of sliding (X) of the piston, the envelope further comprising a flexible portion located between the rigid portion and the first end of the casing, said flexible portion being adapted to allow the rigid portion a degree of freedom in rotation about said radial axis. Thanks to these characteristics, the rigid portion of the envelope remains coaxial with the control rod, including when the control rod has a slight inclination relative to the axis of the piston.

Some aspects of the invention start from the idea of making a bellows sealingly surrounding the control rod. Some aspects of the invention start from the idea of minimizing the volume variation of the protective envelope. Certain aspects of the invention start from the idea of dissociating the dimensions of the variable volume of the protective envelope from the dimensions of the stop member of the control rod. Some aspects of the invention start from the idea of dividing the protective envelope between a fixed volume in which the thrust member of the control rod moves and a variable volume allowing the deformation of the envelope when a displacement of the control rod relative to the cylinder body.

Some aspects of the invention start from the idea of not feeding the internal volume of the protective envelope with ambient air. Some aspects of the invention depart from the idea of not allowing dust to enter the internal volume of the protective envelope. Some aspects of the invention start from the idea of facilitating the deflection of the control rod despite the presence of the protective envelope.

Brief description of the figures

The invention will be better understood, and other objects, details, features and advantages thereof will appear more clearly in the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes. with reference to the appended figures.

In these figures:

- Figure 1 is a schematic illustration of a hydraulic control device of a motor vehicle clutch.

- Figure 2 is a schematic perspective illustration of a hydraulic cylinder having a control rod surrounded by a protective envelope according to the invention.

- Figure 3 is a detail sectional view of Figure 2 illustrating the protective envelope of the control rod.

- Figure 4 is an axial sectional view of a portion of the hydraulic cylinder of Figure 2 when the control rod is in an extended position. - Figure 5 is a broken perspective view of a portion of the hydraulic cylinder of Figure 2 when the control rod is in the deployed position.

- Figure 6 is an axial sectional view of a portion of the hydraulic cylinder of Figure 2 when the control rod is in a retracted position.

- Figure 7 is a broken perspective view of a portion of the hydraulic cylinder of Figure 2 when the control rod is in the retracted position.

- Figure 8 is an axial sectional view of a portion of a hydraulic cylinder according to an alternative embodiment when the axis of the control rod is aligned with the axis of sliding of the piston.

- Figure 9 is an axial sectional view of the hydraulic cylinder portion of Figure 8 when the axis of the control rod is inclined relative to the axis of sliding of the piston.

Detailed description of embodiments

In the description and the claims, the terms "external" and "internal" as well as the "axial" and "radial" orientations will be used to denote, according to the definitions given in the description, elements of the device actuator. ordered. By convention, the "radial" orientation is directed orthogonally to the axis X of sliding of the piston in the bore of the cylinder body determining the "axial" orientation and, from the inside to the outside while moving away of said axis. The terms "external" and "internal" are used to define the relative position of one element relative to another, with reference to the X axis, an element close to the X axis is thus described as internal by opposition an outer member located radially peripherally. Furthermore, the terms "back" AR and "forward" AV are used to define the relative position of one element relative to another in the axial direction, an element intended to be placed close to the end of the rod. opposed control to the piston being designated by the rear and an element intended to be placed close to the end of the piston opposite to the control rod being designated by before. The invention is described below in the context of a hydraulic cylinder transmitter hydraulic clutch control device, but applies similarly to any cylinder actuator, hydraulic or pneumatic, control device, such as 'a braking system master cylinder or other.

FIG. 1 schematically illustrates a hydraulic control device 1 of a clutch 2. The hydraulic control device 1 comprises a hydraulic transmitter cylinder 3 which is associated with an actuating element, such as a pedal 4, and a hydraulic cylinder receiver 5 which is associated with a clutch 2, for example via an actuating fork 6. The hydraulic transmitter cylinder 3 and the hydraulic receiver cylinder 5 are connected to each other by a hydraulic circuit 7 filled with a fluid . The fluid is for example a brake fluid or an oil, such as a gearbox oil.

The hydraulic cylinders, emitter 3 and receiver 5, each comprise a body 8, 9 having an internal bore and a piston 10, 1 1 able to slide inside said bore and defining with the internal bore a variable volume hydraulic chamber. connected to the hydraulic circuit 7. The piston 10 of the hydraulic transmitter cylinder 3 is connected to a control rod 12 which is articulated on the clutch pedal 4. The piston 1 1 of the hydraulic receiver cylinder 5 is connected to a rod 13 which is resting on the control fork 6 of the clutch 2.

The actuating fork 6 is pivotally mounted on the chassis of the vehicle and cooperates with a clutch abutment 14 so that a pivoting of the actuating fork 6 causes an axial displacement of the clutch abutment 14 and, consequently , a displacement of the clutch 2 between an engaged position and a disengaged position.

When a user presses on the pedal 4, the control rod 12 is moved so as to slide the piston 10 of the hydraulic transmitter cylinder 3 from the rear towards the front, from a deployed position to a retracted position, in the body 8 of the hydraulic transmitter cylinder 3 in order to drive fluid towards the hydraulic receiver cylinder 5. The piston 1 1 of the hydraulic receiver cylinder 5 then slides in the body 9 of the hydraulic receiver cylinder 5, which allows to move the clutch 2 from its engaged position to its disengaged position. Figure 2 is a perspective illustration of the hydraulic transmitter cylinder 3 of Figure 1. The hydraulic transmitter cylinder 3 comprises a control rod 12. A fluid reservoir 15 is mounted on the body 8 of the hydraulic transmitter cylinder 3. This reservoir 15 constitutes a reserve of fluid for the variable volume hydraulic chamber of the hydraulic transmitter cylinder 3 and therefore for the hydraulic circuit 7.

The control rod 12 is surrounded by a protective casing 16 illustrated in greater detail in FIG. 3. A front end 17 of the casing 16 is fixed on a rear end 18 of the body 8. A rear end 19 of the casing 16 is sealingly attached to a rear portion 20 of the control rod 12. The casing 16 comprises, from the front end 17 to the rear end 19, a rigid portion 21 and a deformable portion 22.

The deformable portion 22 has a bellows shape. The deformable portion 22 is of conical shape, the diameter of the folds of the bellows decreasing from the front of the bellows towards the rear of the bellows. The deformable portion 22 is of deformable material, for example elastomer such as ethylene-propylene-diene monomer (EPDM), butadiene-acrylonitrile copolymers (NBR for Nitrile butadiene rubber in English), hydrogenated butadiene-acrylonitrile copolymers (HNBR for Hydrogenated nitrile butadiene rubber in English) or silicone or a thermoplastic elastomer (TPE) such as a vulcanized thermoplastic elastomer (TPV or TPE-V).

The rigid portion 21 is of circular cylindrical shape and surrounds a front portion 27 of the control rod 12. The rigid portion 21 is dimensionally stable. For this, the rigid portion 21 is made in any suitable manner to maintain its shape during a displacement of the control rod 12. For example, the rigid portion 21 may be made of the same material as the deformable portion 22 with a greater wall thickness. In another embodiment, the rigid portion 21 may comprise at least one reinforcing member, such as reinforcing ribs (not shown) developing parallel to the control rod 12. In another embodiment, the material used to the manufacture of the rigid portion 21 may be chosen to have mechanical characteristics suitable for maintaining the shape of the rigid portion 21. In another embodiment, the reinforcing member may be an insert (not shown) associated with the rigid portion 21. These various embodiments for rigidifying the rigid portion may be implemented in alternative or combined ways. The rigid portion 21 and the deformable portion 22 may be manufactured together, that is to say in one-piece form, for example by molding, co-molding or otherwise, or separately and be subsequently associated to form the envelope 16.

The rigid portion 21 delimits a first chamber 23, or front chamber 23, of the envelope 16. The first chamber 23 has a constant volume regardless of the position of the control rod 12. The deformable portion 22 defines a second chamber 24 , or rear chamber 24, of the envelope 16. The second chamber 24 has a variable volume. The first chamber 23 and the second chamber 24 are in communication.

As shown in Figures 2 to 7, the rear end 18 of the body 8 of the hydraulic transmitter cylinder 3 has on a radially outer face a circular groove. The front end 17 of the casing 16 has a circular front rim 26 projecting radially towards the X axis. The front rim 26 is housed in the groove 25 so as to fix the front end 17 of the casing 16 on the rear end 18 of the body 8. The front flange 26 and the circular groove 25 cooperate with each other sealingly. The rear portion 20 of the control rod 12 has a circular groove 31. The rear end 19 of the casing 16 has a rib 32 projecting radially towards the axis X. The rib 32 is housed in the groove 31 so as to fix the rear end 19 of the casing 16 on the rear portion 20 of the control rod 12. Preferably, the cooperation between the rib 32 and the groove 31 is sealed.

The front portion 27 of the control rod 12 is separated from the rear portion 20 by a disk 28. A front end of the front portion 27 is mounted on a rear end 29 of the piston 10, as explained hereinafter with reference to the figures 4 and 5. A rear end of the rear portion 20 is articulated on the pedal 4. The disc 28 is circular in shape and protrudes radially from the control rod 12.

The rear end 18 of the body 8 has a rear face 30 facing the disc 28. This rear face 30 has a central orifice coaxial with the axis X and traversed by the front portion 27 of the control rod 12. The disc 28 has a diameter greater than the diameter of the orifice of the rear face 30 of the body 8. In other words, the disc 28 forms a stop member of the control rod 12 cooperating with the rear face 30 of the body 8 which forms an abutment surface. The cooperation between the disc 28 and the rear face 30 makes it possible to block the forward displacement of the control rod 12 when the disc 28 bears axially against the rear face 30, as explained below. The disk 28 and the rear face 30 thus make it possible to define the retracted position of the control rod 12.

The disk 28 is housed in the first chamber 23. The internal diameter of the rigid portion 21 is greater than the diameter of the disk 28 to allow the disk 28 to move in the first chamber 23. Moreover, the average diameter of the second chamber 24 is smaller than the diameter of the disk 28, the average diameter being the average arithmetic value between the inner diameter (or minimum diameter) and the outer diameter (or maximum diameter) of the rigid portion. The average diameter of the second chamber 24 is preferably equal to or close to the diameter of the bore in the body 8 of the hydraulic cylinder transmitter 3. In other words, the rigid portion 21 accommodates the stop member of the control rod 12 formed by the disc 28 while deporting the deformable portion 22 of variable volume of the casing 16 with respect to said stop member, thus making it possible to make the dimensions of the deformable portion 22 of the casing 16 independent of the dimensions of the stop member of the control rod 12.

Figures 4 and 5 illustrate the hydraulic cylinder of Figure 2 in an extended position of the control rod.

In the deployed position of the control rod 12, the piston 10 housed in the bore of the body 8 of the hydraulic transmitter cylinder 3 is pushed back by the control rod 12, the rear end 29 of the piston 10 being located in the bore of the body 8 near the rear end 18 of the body 8. A radially inner face 33 of the body 8 defining the bore in which the piston 10 slides comprises a groove in which is housed a seal, here a lip seal 34. This lip seal 34 provides a dynamic seal against the piston 10. In other words, when the piston 10 slides in the bore, this lip seal 34 ensures the sealing of the hydraulic fluid chamber of the transmitter hydraulic cylinder and avoids that said fluid does not escape the hydraulic circuit 7 from the rear of the body 8 of the hydraulic cylinder transmitter 3. It could also be an O-ring. It is important to keep this lip seal 34 dust-free in order to maintain its integrity during the life of the transmitter hydraulic cylinder 3.

The bore of the body 8 of the hydraulic transmitter cylinder 3 defines with the rear end 29 of the piston 10 a third chamber 39. This third chamber 39 is in communication with the first chamber 23 and the second chamber 24 via the orifice of the face 8. In other words, this third chamber 39 is delimited on the one hand axially by the rear end 29 of the piston 10 and the orifice of the rear face 30 of the body 8 and, on the other hand, radially by the radially inner face 33 of the bore formed in the body 8 of the emitter hydraulic cylinder 3.

In the deployed position of the control rod 12 as illustrated in FIGS. 4 and 5, the third chamber 39 has a minimum internal volume, the rear end 29 of the piston 10 being located closest to the orifice of the face In this position, the disk 28 is housed in the first chamber 23 near the junction between the first chamber 23 and the second chamber 24. In addition, in this position, the second chamber 24 has an internal volume. maximum, the bellows being fully deployed. Preferably, the dimensions and in particular the mean diameter of the deformable portion 22 are such that the variation in volume of the second chamber 24 between a compressed state of the deformable portion 22 (see FIGS. 6 and 7) and an expanded state of the deformable portion 22 (Figures 4 and 5) is equivalent to the volume variation of the third chamber 39 between the extended position of the control rod 12 imposing an advanced position of the piston 10 in the body 8 (see Figures 6 and 7) and the retracted position of the control rod 12 (Figures 4 and 5).

The control rod 12 is movable between a deployed position as illustrated in Figures 4 and 5 and a retracted position as illustrated in Figures 5 and 6.

When a user acts by pressing the clutch pedal 4, said clutch pedal 4 pushes the control rod 12 towards the body 8 of the hydraulic cylinder transmitter 3. By pushing the control rod 12 towards the body 8 , the control rod 12 moves axially forwardly so that the front end of the control rod 12 pushes the piston 10 from the rear to the front of the body 8 by sliding it in the bore of the body 8. At this sliding of the piston 10, the lip seal 34 seals the hydraulic chamber of the hydraulic cylinder transmitter. On the other hand, the sliding of the piston 10 moves the rear end 29 of the piston 10 away from the orifice of the rear face 30 of the body 8, consequently increasing the internal volume of the third chamber 39.

Moreover, the advance of the control rod 12 relative to the body 8 causes the axial alignment of the disk 28 and the rear portion 20 of the control rod 12 to the rear face 30 of the body 8.

As illustrated in FIGS. 6 and 7, the disc 28 abuts against the rear face 30 of the body 8 in order to block an additional advance of the control rod 12. The disc 28 moves in the first chamber 23 from the illustrated position in Figures 3 to 5 to the position shown in Figures 6 and 7. The rigid portion 21 of the casing 16 being fixedly mounted on the rear end 18 of the body 8 of the hydraulic cylinder transmitter 3 and the deformable portion 22 the casing 16 being mounted on the rear portion 20 of the control rod 12, the approach between the rear portion 20 of the control rod 12 and the rear face 30 of the body 8 causes the compression of the deformable portion 22 between the rear end 19 of the casing 16 fixed on the rear portion 20 of the control rod 12 and the rigid portion 21 of the casing 16 fixedly mounted on the rear end 18 of the body 8. Due to the rigidity of the part rigid 21, only the deformable portion 22 of the casing 16 is compressed, the internal volume of the casing 16 varying only by the variation of the internal volume of the second chamber 24 delimited by the deformable portion 22. In other words, this compression of the deformable portion 22 causes a decrease in the volume of the second chamber 24, the volume of the first chamber 23 remaining constant due to the rigidity of the rigid portion 21.

The volume of fluid expelled from the second chamber 24 by the compression of the deformable portion 22 of the casing 16 is absorbed by the third chamber 39 whose volume increases because of the advance of the piston 10 in the bore of the body 8 .

Because the disk 28 forming the stop member limiting the displacement of the control rod 12 relative to the body 8 is housed in the first chamber 23, the dimensions of the deformable portion 22 are independent of those of the disk 28. Gold , the volume of fluid displaced by the compression of the deformable portion 22 derives directly from the dimensions of the deformable portion 22. As a result, the variable volume of the envelope 16 depending on the single volume variation of the deformable portion is made independent of the dimensions of the stop member of the rod of 12. Thus, it is possible to minimize the volume of the deformable portion 22 so that the volume of fluid displaced during compression of the deformable portion 22 is absorbed by the volume increase of the third chamber 39 formed in the body 8 of the hydraulic transmitter cylinder 3.

Preferably, the variation in volume of the second chamber 24 between the deployed position and the compressed position of the deformable portion 22 is equal to the volume variation of the third chamber 39 between the retracted position and the deployed position of the control rod. 12. However, depending on the mechanical characteristics of the envelope 16, it is possible that the volume variation of the second chamber 24 is slightly different from the volume variation of the third chamber 39, for example of the order of a difference of plus or minus 30%, preferably of plus or minus 10%, still more preferably of plus or minus 5%, ideally these volume variations being identical. Such a difference in volume variation may for example be absorbed by a slight deformation of the envelope 16 or by the creation of a slight excess pressure or depression in the envelope 16.

Conversely, during a displacement of the control rod 23 from the retracted position illustrated in FIGS. 6 and 7 to the extended position illustrated in FIGS. 3 to 5, the piston 10 is displaced towards the rear of the cylinder body 8 transmitter 3 by the control rod 12. This displacement of the piston 10 causes a decrease in the internal volume of the third chamber 39. In addition, the rear portion 20 of the control rod 12 is remote from the rear face 30 of the body 8 of the hydraulic cylinder transmitter so that the deformable portion 22 of the casing 16 unfolds, thereby increasing the internal volume of the second chamber 24. This displacement of the control rod 12 further causes the disc 28 to move away from the face rear 30 of the body 8, the disk 28 moving in the first chamber 23 by approaching the deformable portion and remaining in the first chamber 23.

The volume of fluid expelled from the third chamber 39 by the displacement of the piston 10 in the body 8 supplies the second chamber 24 with fluid during its passage from the compressed state to the deployed state without the need for fluid intake from the external environment to the casing 16. In other words, the fluid contained on the one hand in the casing 16, typically in the first chamber 23 and in the second chamber 24, and secondly in the third chamber 39, is a constant volume which does not communicate with the fluid of the external environment of the hydraulic transmitter cylinder 3 and which is preserved in the chambers 23, 24 and 39 during the movements of the control rod 12 and the piston 10.

Thus, the casing 16 constitutes a double-chamber sealed volume 23 and 24 in which the dust from the external environment of the emitter hydraulic cylinder 3 can not penetrate, thus protecting the lip seal 34 housed in the bore of the body 8 of the hydraulic cylinder transmitter 3 and cooperating with the piston 10 to ensure the tightness of the hydraulic cylinder transmitter 3.

FIGS. 8 and 9 illustrate an alternative embodiment of the hydraulic transmitter cylinder 3 in which the casing 16 comprises, between its front end 17 fixed on the rear end 18 of the body 8 and the rigid portion 21, a flexible portion 40. flexible 40 is formed in any suitable manner to allow inclination of the casing 16 relative to the X axis as explained below. In the variant embodiment illustrated in FIGS. 8 and 9, this flexible portion 40 is formed by a fold of the envelope 16.

The front end of the control rod 12 comprises a ball 35 housed in an insert 36. This insert 36 has elastic tabs allowing the insertion of the ball 35 and its holding in position in the insert 36 with a degree of freedom in a direction radial to the axis X, the control rod 12 can thus be inclined relative to the axis X. The rear end 29 of the piston 10 has a cavity 37 in which is depressed the insert 36. The insert 36 comprises a fir-tree pin 38 mounted in force in an axial recess of the cavity 37 to hold the insert 36 in position in the cavity. Therefore, the front end of the control rod 12 is connected to the rear end 29 of the piston 10. Such a cooperation between the control rod 12 and the piston 10 is for example described in the document FR2924185. When the control rod 12 is coaxial with the X axis, for example in the deployed position of the control rod 12, the rigid portion is also coaxial with the X axis and the flexible portion 40 is in a rest position.

When the control rod 12 is inclined relative to the axis X, for example during a displacement of the clutch pedal 4 from an engaged position to a disengaged position or during the installation of the hydraulic transmitter cylinder 3 in the vehicle, the flexible portion is deformed in such a way as to keep the rigid portion 21 coaxial with the control rod 12. This retention of the rigid portion 21 coaxially with the control rod 12 makes it possible to prevent the disk 28 from being at contact of the wall of the rigid wall and thus facilitates the movement relative to the axis X between the control rod 12 and the body 8 of the hydraulic cylinder transmitter 3.

In addition, the conical shape of the bellows facilitates the travel of the control rod 12 when it is displaced by the clutch pedal 4, the bellows remaining coaxial with the control rod 12 having an inclination with respect to the X axis .

Although the invention has been described in connection with several particular embodiments, it is obvious that it is not limited thereto and that it comprises all the technical equivalents of the means described and their combinations if they are within the scope of the invention. In addition, the invention is described above with reference to the figures in the context of a hydraulic cylinder transmitting clutch system but can be applied to any type of cylinder, such as a braking system master cylinder , a hydraulic or pneumatic actuator, an electromechanical actuator or the like.

The use of the verb "to include", "to understand" or "to include" and its conjugated forms does not exclude the presence of other elements or steps other than those set out in a claim.

In the claims, any reference sign in parentheses can not be interpreted as a limitation of the claim.

Claims

1. Actuator for hydraulic or pneumatic control device comprising

a cylindrical body (8) provided with an internal bore,

a piston (10) able to slide inside said internal bore along an axis (X) of sliding,

- a control rod (12) having a first end coupled to the piston (10) and a second end to be coupled to an actuating element (4) so as to move the piston (10) inside the internal bore during a displacement of the actuating element (4), the control rod (12) being movable between an extended position and a retracted position, an abutment member (28) projecting radially from the stem for controlling (12) and being arranged to cooperate with an abutment surface (30) carried by the cylindrical body (8) when the control rod (12) is in the retracted position,

an enclosure (16) for protecting the control rod (12) surrounding the control rod (12) and comprising:

a first end (17) sealingly attached to the cylindrical body (8),

a second end (19) sealingly attached to the control rod (12),

characterized in that

the protective envelope (16) comprises, successively, between its first and second extremities:

a rigid portion (21) delimiting a first chamber (23) inside which the stop member (28) moves during the displacement of the control rod (12) between its deployed position and its retracted position,

a deformable portion (22) able to deform along the control rod (12) during the movement of the control rod (12) and delimiting a second variable volume chamber (24) communicating with the first chamber (23); ), said deformable portion (22) being deformable between a compressed state when the control rod (12) is in the retracted position and a developed state when the control rod (12) is in the deployed position;

the piston (10) defining with the internal bore of the body (8) a third variable volume chamber (39) which is in communication with the first chamber (23) and whose volume varies according to the position of the piston (10). ) so as to firstly receive a volume of fluid resulting from a decrease in the volume of the second chamber (24) during the displacement of the control rod (12) towards its retracted position and secondly , supplying fluid to the second chamber (24) during the displacement of the control rod (12) in the direction of its deployed position.

2. An actuator according to claim 1, wherein the second chamber (24) has an internal volume when the deformable portion is in the developed state which is between + 30% and -30% of the internal volume of the third chamber (39). ) in the retracted position of the control rod (12).

3. Actuator according to one of claims 1 to 2, wherein the decrease in the internal volume of the second chamber (24) when the deformable portion (22) deforms from the developed state to the compressed state corresponds to the increasing the internal volume of the third chamber (39) when the control rod (12) moves from the extended position to the retracted position and the increase of the internal volume of the second chamber (24) when the deformable portion (22) deforms from the compressed state to the expanded state corresponds to the decrease in the internal volume of the third chamber (39) when the control rod (12) moves from the retracted position to the deployed position.

4. Actuator according to one of claims 2 or 3, wherein the internal volume of the second chamber (24) when the deformable portion is in the developed state is equal to the internal volume of the third chamber (39) in the retracted position of the control rod (12).

5. Actuator according to one of claims 1 to 4, wherein the deformable portion (22) of the casing (16) has a diameter less than a diameter of the rigid portion (21) of the casing (16).

6. Actuator according to one of claims 1 to 5, wherein the stop member (28) is an abutment disc projecting radially around the control rod (12).

7. An actuator according to any one of claims 1 to 6, wherein the deformable portion (22) of the protective casing (16) comprises a bellows having an average diameter which is less than a maximum radial dimension of the organ stop.

8. An actuator according to claim 7, wherein the deformable portion (22) of the protective casing (16) comprises a bellows having a minimum diameter which is less than a maximum radial dimension of the stop member.

9. An actuator according to one of claims 7 or 8, wherein the bellows has a plurality of successive folds, the diameter of each fold of the bellows being increasing from the second end of the protective envelope to the rigid portion.

10. Actuator according to one of claims 1 to 9, wherein the deformable portion (22) of the casing (16) of protection is made of an elastomeric material.

1 1. Actuator according to one of claims 1 to 10, wherein the rigid portion (21) of the protective casing (16) has a wall thicker than the thickness of a wall of the deformable portion (22). the protective casing (16).

12. Actuator according to one of claims 1 to 10, wherein the rigid portion of the protective envelope has at least one reinforcing member.

13. An actuator according to one of claims 1 to 12, wherein the first end of the control rod (12) is coupled to the piston (10) with a degree of freedom in rotation about a radial axis perpendicular to the sliding axis (X) of the piston (10), the envelope (16) further comprising a flexible portion (40) located between the rigid portion (21) and the first end (17) of the envelope (16), said flexible portion (40) being adapted to allow the rigid portion a degree of freedom in rotation about said radial axis.