FR2779498A1 - Hydraulic clutch control for motor vehicle - Google Patents

Abstract

The motor vehicle hydraulic clutch control has a cylinder (17) with a piston (21) shaped to receive the head (40) of the piston rod (33). The piston is surrounded by a secondary skirt (42) with the piston seal ring (41) positioned between the external periphery of the piston and the internal periphery if the skirt.

Description

Clutch hydraulic control device, in particular for a vehicle

automobile,

  comprising improved mounting means.

  The invention relates to a hydraulic control device for a clutch, in particular for a motor vehicle, comprising at least one emitting or receiving cylinder provided with a piston. The invention relates more particularly to a hydraulic control device for a clutch of a motor vehicle comprising at least one control cylinder of the type in which the cylinder comprises a substantially tubular cylinder body in which axially slides a piston which delimits, by a face transverse front, a hydraulic chamber and which cooperates, by a rear transverse face, with a piston rod, in which a connection orifice of a pipe or pipe opens into the hydraulic chamber and in which the cylinder body is made of material moldable, such as plastic. Such a device is described, for example in the

document DE-U-295 16 488.

  In this one, the piston belongs to a set

  comprising a metallic piston jacket.

  More specifically, the piston liner has a protuberance at its front end on which the piston is molded. The shirt serves as a receptacle for two half-shells

  shaped to receive the head of the piston rod.

  In addition, the piston carries a piston seal designed to cooperate with a metal guide sleeve mounted in the internal bore of the cylinder body and delimiting the hydraulic chamber, while the cylinder body carries a secondary seal of sealing intended to cooperate with the piston jacket. The cylinder body is, to do this, internally stepped in diameter to present a larger section at the rear so as to be able to accommodate the secondary seal. An immobilization shirt is housed in favor of this plus

  large section to hold the secondary seal.

  The object of the present invention is to propose a control device the design of which allows precise mounting using a simple tool ensuring in particular the coaxiality and alignment of the various guide bores of the piston. To this end, the invention provides a hydraulic control device for a clutch, in particular for a motor vehicle, comprising at least one control cylinder comprising a first jacket, a cylinder body having a bottom at the front and open to the rear to receive the first liner for fixing, a piston sliding axially in the cylinder body, a piston liner, said second liner, axially integral with the piston and sliding axially in the first liner, a worn piston seal by the piston, a second seal carried by the cylinder body to cooperate with the second jacket, a piston rod having at the front a head to cooperate * with the piston, in which the cylinder body, the first jacket and the piston are made of plastic, while the second jacket is metallic and in which the piston has a front face delimiting the hydraulic chamber and a rear face cooperating with the piston rod, characterized in that the first jacket has externally access openings to the second jacket for the passage of a mounting and centering tool According to other characteristics of the invention: - Said openings are formed in the rear section of the first jacket; - Said openings are slots of axial orientation; - Said slots are closed axially at the front end of the first jacket; - Said slots are open axially at the rear end of the first jacket; - Said openings are distributed angularly in a regular manner around the axis of the first jacket; - The number of said openings is greater than or equal to three; - Said openings allow the passage of projections belonging to a mounting and centering tool which pass through them to engage with the second jacket; - Said tool is centered externally around the first jacket; - Said tool is centered internally in the first jacket; - The first jacket has at its rear end at least one stop intended to cooperate with the rear end of the second jacket to limit the displacement of the piston; - The front section of the first jacket is fitted into the cylinder body by being fixed to said body by a tight fixing, such as ultrasonic welding, welding by indirect heat or bonding; - the cylinder body, the first jacket and the piston are made of plastic, while the second jacket is metallic; the piston is shaped to receive the head of the piston rod, in that the piston is surrounded by the second sleeve, in that the piston seal intervenes between the external periphery of the piston and the internal periphery of the second sleeve, and in that the second shirt enters

the hydraulic chamber.

  The description which follows illustrates the invention in

  look at the accompanying drawings in which: - Figure 1 is an axial sectional view of a master cylinder produced in accordance with the teachings of the invention and in which the piston is shown respectively in a first advanced position and in a second retracted position; - Figures 2 to 4 are views respectively along the arrows 2, 3 and 4 of Figure 1, Figures 5 and 6 are partial views on a larger scale respectively of the front and rear part of Figure 1; - Figure 7 is a partial view of Figure 6 of the piston groove for securing the piston liner of the piston; - Figures 8 to 10 are figures similar to Figure 1 for other embodiments. In all the figures, the common elements will be

  affected by the same reference signs.

  In Figures 1 and 8 to 10, there is shown a control cylinder in the form of a transmitter of a

  motor vehicle clutch control.

  Such a device (not shown) comprises a sending cylinder connected by a pipe to a receiving cylinder of

  structure similar to the master cylinder.

  Each receiving or emitting cylinder comprises a piston movable axially inside a cylinder body to delimit a hydraulic chamber of variable volume. A connection orifice, to which the pipe is connected, opens out

in the hydraulic chamber.

  The master cylinder has a piston rod connected for example to a clutch pedal on which the driver acts or an actuator which is started up.

  according to predetermined programs.

  The piston of the master cylinder is intended to expel a fluid, such as oil, contained in the hydraulic chamber in the direction of the pipe or pipe which connects the

  master cylinder to master cylinder.

  When the clutch is engaged, the volume of the hydraulic chamber of the master cylinder is maximum while the volume of the control chamber of the master cylinder is

minimum.

  During the declutching operation, the volume of the hydraulic chamber of the master cylinder decreases, while the volume

  of the slave cylinder control chamber increases.

  The piston of the receiving cylinder then acts on a rod acting, for example, on the clutch release clutch actuating

  the clutch release bearing, which includes the friction clutch.

  Each transmitter and receiver cylinder has a spring

  acting between the piston and the bottom of the cylinder body.

  When the driver releases his action on the clutch pedal or when the actuator returns to its initial clutch position, the return spring of the master cylinder relaxes to return the piston to its initial position while the return spring of the cylinder transmitter is compressed by the clutch spring, such as a diaphragm, which thus brings the

  piston of the receiving cylinder to its initial position.

  In FIGS. 1 and 8 to 10, the emitter cylinder is shown in the delivery position and comprises a cylinder body 17 provided with an inlet orifice 18 closed by a plug 19. It is by means of this orifice input that the pipe or pipe, connecting the receiving cylinder to the emitting cylinder, opens into the hydraulic chamber 20 of the

master cylinder.

  The chamber 20 is of variable volume and is delimited by the body 17 and the piston 21 mounted axially movable at

  inside the cylinder body 17.

  In the examples shown, the cylinder bodies 17

  and the piston 21 are made of moldable plastic.

  This plastic material is possibly reinforced by glass fibers, kevlar fibers etc. to confer resistance

desired in parts 17, 21.

  The cylinder body 17 has a generally tubular shape.

  This body 17 has an internal bore 22, 23 of blind form better visible in FIG. 5. The body 17 is a form of internally stepped tube with an axis of axial symmetry XX (FIG. 1) with a bottom 24 d at the front. transverse orientation, into which opens the inlet orifice 18 belonging to a connector for connecting the aforementioned pipe for example by pinout, the connector 25 having for this purpose internally passages not referenced for the passage of a pin 48 allowing to connect the above-mentioned pipe to the master cylinder. Alternatively, the connector is of the screw type. The body 17

is open at the back.

  The connector 25 and the bottom 24 belong to the front part 26 of the cylinder body 17; while the other open end of the cylinder body belongs to the rear part 27

of this body.

  The front part 26 is of smaller diameter than that of the rear part 27 because the body 17 is in the form of a stepped tube. The internal bore 22, 23 therefore has a rear portion 23 belonging to the rear part 27 of larger diameter than the front part 22 belonging to the front part 26. Rigidification ribs can be provided on

  the front part 26 delimited by the bottom 24.

  The piston 21 is capable of sliding in the body 17, more precisely in the internal bore 22, 23 thereof, between an advanced clutch position shown in the upper part of Figures 1, 5, 6, and 8 to 10 and a retracted disengagement position shown in the lower part of these FIGS. 1, 5, 6, and 8 to 10. In the retracted position, the chamber 20 and the control fluid are pressurized, while in the advanced position the

  chamber 20 and the control fluid are depressurized.

  It will be noted that a projection 28 of frustoconical shape is

after molding the bottom 24.

  The projection 28 extends axially and serves at its base as a centering device for the return spring 29, here a helical spring acting in the aforementioned manner between the body 17 and the piston 21, more precisely here between the transverse bottom 24 and the front

of piston 21.

  The piston 21 has (FIGS. 5 and 6) a transverse wall 30 whose front face 31 defines the hydraulic chamber 20 and whose rear face 32 cooperates with the rod

piston 33, here metallic.

  The transverse wall 30 is extended forward by a chimney 34, externally of frustoconical shape, with a

  blind central hole 35 of cylindrical shape.

  The bottom of the hole 35, of axial orientation, is formed by

the front face 31 of the wall 30.

  -7 The helical return spring 29 is mounted around the chimney 34, the base of which serves as a centering device for the return spring, the rear end of which rests on the front face 31 of the

transverse wall 30 of the piston 21.

  The spring 29 therefore intervenes axially between the bottom 24 and the front face 31. Of course, the orifice 18 crosses the bottom 24 and opens laterally relative to the projection 28 after molding of the bottom 24 and serving through its base of

  centering device at the front end of the spring 29.

  The top face 36 of the projection 28, according to a characteristic

  ristic, serves as a stop for the front face 37 of the chimney 34.

  More specifically, in the retracted position, the piston 21 comes into contact through the front face 37 of the chimney 34 with the top face 36 of the projection 28. The body 17 therefore has a

  stop 28 limiting the forward movement of the piston 21.

  The chimney 34 is rigid and is allowed to come into contact with a projection 28 forming the abovementioned stop. The

  chimney 34 stiffens the plastic piston 21.

  The transverse wall 30 is extended towards the rear by

  a socket 38 provided with a bore 39 which widens outwards.

  Here, the bore 39 is of frustoconical shape, its bottom being delimited in part by the rear face 32 of the wall

transverse 30 of the piston 21.

  The bottom of the bore 39 is generally semi-shaped

  spherical for reception of the head 40 which has the rod 33 at its front end. The head 40 is generally in the form of a spherical ball which penetrates in a complementary manner into the generally semi-spherical bottom of the internal bore 39 of

the socket 38.

  This socket 38 is fragmented into axial fingers by

  slots according to a characteristic.

  The sleeve 38 has an external cylindrical shape with an external diameter greater than that of the chimney 34. the head 40 of the rod 33 is allowed to spread the fingers of the sleeve 38 by contact with the internal bore, until it engages with

  the semi-spherical part of the bottom of the bore 39.

  The rod 33 is therefore pivotally mounted in the piston 21 more particularly in the bottom of the fragmented bush 38

in axial fingers by slits.

  According to one characteristic, the transverse wall 30, and therefore the piston 21, carries at its outer periphery a seal of

sealing piston 41.

  Here, the seal 41 is an O-ring seal mounted in a groove not referenced, that has the transverse wall 30 at its outer periphery. Other form of seal are

possible.

  This seal 41 is allowed to cooperate, according to one characteristic, with the internal periphery of a metallic piston jacket 42. The piston liner 42 surrounds the piston 21 and here has a tubular shape. The piston 21 therefore penetrates inside the jacket 42. As described below, the rear end of the piston extends in axial projection through

  relative to the rear face of the shirt 42.

  The piston liner 42 is, for example, based on anodized aluminum or treated steel. The piston liner 42 extends at the front in axial projection relative to the chimney 34. In the retracted position, the chimney 34 is in contact with the

  projection 28, while the jacket 42 is spaced from the bottom 24.

  Radially, the piston chimney 42 extends at a distance

  chimney 34 and return spring 29.

  This shirt 42 is in contact with the wall

transverse 30 and the socket 38.

  More specifically, the piston liner 42 is in intimate contact at its internal periphery with the external periphery of the

seal 41.

  The seal 41 therefore immobilizes axially by tightening the

piston liner 41.

  This shirt 42 tends to close the sleeve 38. More specifically, the shirt 42 radially forces the fingers of the sleeve 38 to deform radially inward. So the

  sleeve 38 is mounted under prestress in the jacket 42.

  The socket 38, by tightening, therefore also immobilizes

  axially the piston liner 42 relative to the piston 21.

  This shirt 42 is therefore, according to one characteristic,

axially integral with the piston 21.

  This shirt is also integral in rotation with the

  piston 21 through the seal 41 and the socket 38.

  To perfect this axial immobilization and also in rotation of the jacket 42 relative to the piston 21, it is proposed that one of the elements, piston jacket 42 - piston 21, has one or more notches penetrating into one or more recesses

  in the other of the piston elements 2 - piston jacket 42.

  For example, the jacket 42 may have holes at its rear end into which penetrate radial projections, forming notches, coming from the external periphery of the sleeve 38 at the rear thereof. The jacket is then forced onto the outer periphery of the piston 21 until the radial projections of the sleeve 38 penetrate the holes of

the shirt 42.

  Thus, the shirt 42 is secured by snap-fastening

its piston 21.

  Here, as visible in FIG. 7, the rear end of the sleeve 38 has at its external periphery a fixing groove 43, while the rear end of the piston jacket 42 is locally deformed radially inwardly to form tabs 44 engaging the rear flank

  and the bottom of the fixing groove 43.

  Alternatively, the rear end of the jacket 42 is locally serrated or has lugs for penetration into

the fixing groove 43.

  Alternatively, the rear end of the shirt is attached

by overmolding with the piston 21.

  In any case, a piston 21 - piston jacket 42 subassembly is formed in all cases, forming an axially movable element in the body 17. The jacket 42 and the

  piston 21 are concentric and coaxial parts.

  This piston liner 42 prevents the fingers of the sleeve 38 from deploying radially outwards so that it ensures, without additional parts, an axial locking of the rod 33 inside the piston 21. The rod 33 does not can therefore escape axially relative to the piston 21, while having the possibility of swiveling, thanks to the seat 138, here of generally semi-spherical shape, which has the socket 38 and the rear face 32. Of course, it is possible to control the stress exerted by the piston liner 42 on the sleeve 38 so that the piston rod 33 can be disassembled manually. All of this is made possible by the constitution in

  plastics material of the piston and the flexibility of the sleeve 38.

  Of course, the shirt 42 can be glued on

  the piston 21 after having introduced the rod 33 into the piston.

  In all cases, the piston 21 is internally shaped to receive the head 40 of the piston rod 33. This piston 21 has internally a seat for the head 40. The seat is delimited by the bush 38, flexible thanks to the slots, and the face

rear 32.

  This head 40 can indeed have another shape and it

  the same is true inside the socket 38 and the seat.

  The body 17 is intended to be fixed on a fixed part of the vehicle and therefore belongs to the fixed part of the emitting cylinder, while the piston 21 and the piston rod 33

  belong to the movable part of said cylinder.

  To do this, the body 17 has, here in one piece, an intermediate plate 45 between the front parts 26

and rear 27 of body 17.

  The plate 45 has two parallel edges connected

  between them by two pointed lateral sides.

  The plate 45 is molded with the front 26 and rear 27 parts of the body 17 and protrudes transversely relative to the parts 26, 27 of tubular shape. The plate 45 here has two radially projecting fixing ears 46

compared to parts 26, 27.

  These ears 46 are perforated at 47 for the passage of fixing members, usually screws, of the body 17 and therefore

  from the master cylinder to a fixed part of the motor vehicle.

  In FIG. 3, the distances D and L respectively represent the distance between the axes of the holes 47 and the

  distance between the tops of the lateral flanks of the plate 45.

  We also see at 48 the pin carried by the connector 25 and used for quick fixing by pinning the end of the

  aforementioned pipe in fitting 25.

  A tube 49 secured to the body 17 is also visible at

Figure 3.

  This tube 49 is used to connect the interior of the body 17 to a main make-up reservoir mounted outside the emitter cylinder, knowing that the hydraulic chambers of the emitter and receiver cylinders are filled with hydraulic fluid, here oil. The reservoir is partially filled with this hydraulic fluid and is connected by a pipe, not visible, to the tube 49 opening into an orifice 50, which is present at the front of the plate 45 coming from the molding of the body 17. The orifice 50 is connected to a channel 51 crossing the plate 45

  (figure 6). Here, several channels 51 are provided.

  These channels 51 open out at the front into a feed groove 52 in communication with the orifice 50 and at the rear, inside the rear part 27 of the body 17,

  more precisely in the bore 23 of the rear part 27.

  The orifice 50 is of annular shape and the tube 49 has at its base a shouldered ring 53, penetrating in a complementary manner in the orifice so that the tube can be

  fixed by waterproof bonding to the plate 45.

  Here, the attachment of the tube 49 to the plate 45 is carried out by fitting the ring 53 into the orifice 50 and then by ultrasonic welding between the annular edge of the orifice 50 and the

  outer periphery of the ring 53.

  Of course, to do this, the tube 49 is made of

  plastic compatible with body 17.

  In all cases, bonding or welding by ultrasound, a tight fixing is obtained without additional joint of the tube 49 on the plate 45, the tube 49 being inclined relative to the plate 45. Thanks to this, the channels 51 and the groove 52 are easily made by molding. As a variant, the tube 49 is replaced as visible in FIG. 9 by a plug 149 blocking the orifice 50 while being fixed by sealed bonding or welding by

  ultrasonic tight to the plate 45 like the tube 45 of FIG. 6.

The body 17 is therefore standardized.

  Here, the inside of the tube is stepped in diameter according to

three bores 22, 23 and 123.

  As mentioned above, the bore 22 of smaller diameter is produced in the front part 26 of the body 17, while the other two bores 23, 123 are produced respectively in

  the rear part 27 and in the plate 45 of the body 17.

  The bore 123 is produced centrally in the plate 45 and has an intermediate diameter relative to the bore 23

  made in the rear part 27.

  Thanks to the bores 23, 123, it is possible to mount in the body 17 an immobilization and guide jacket 54. This jacket 54 is thicker than the piston jacket 42. The jacket 54 is made of plastic and has an internal bore of diameter equal to that of the bore 22 of the front part of the body 17. The jacket 54 is therefore secured to the body 17. This jacket 54 is fixed, while the piston jacket 42 is

axially movable.

  The jacket 54 guides the piston jacket 42. More specifically, the internal periphery of the plastic jacket 54 is in intimate contact with the external periphery of the metal piston jacket 42. Externally, the jacket 54 is stepped in diameter so that this jacket 54 is mounted by fitting in the rear part 27 and in the plate 45, the external periphery of the jacket cooperating with the periphery

  internal of the plate 45 and of the rear part 27 of the body 17.

  This shirt 54 is therefore fitted in a complementary manner

in bores 123, 23.

  The tubular jacket 54 has in one piece a front section 55, an intermediate section 56 and a section

rear 57.

  The front section 55 is received in a complementary manner in the bore 123 while the section 56 is received in a complementary manner

complementary to bore 22.

  After fitting the liner 54 into the body 17, the liner is tightly sealed in the body by ultrasonic welding at the outer periphery of the section 56 and the inner periphery of the rear part 27

  as referenced at 58 in Figure 6.

  As a variant, a waterproof bonding of the jacket 54 is carried out on the body 17. The intermediate section 56 partially surrounds the rear section 57, a large annular space existing between the

sections 56 and 57.

  The rear section 57 has an external diameter less than that of the front section 55, itself of external diameter less than that of the intermediate section 56. The section 57 is axially longer than the section 56 or 55 to ensure good guidance of the movable sleeve 42. The lengths of the sections 55,

  56 are a function of the length of the bores 23, 123.

  The seal of the hydraulic chamber 20 with respect to the outside is ensured by a dynamic seal 59 which is carried by the cylinder body 17 and which cooperates with the external periphery of the piston liner 42, that is to say with

  the external cylindrical surface of this jacket 42.

  This seal 59 is mounted in the bore 123 and is therefore in contact with the internal periphery of the plate 45 delimiting the bore 123. This seal 59 is axially in contact with the front face of the front section of the guide jacket 54 and with axial bosses 60 coming from molding with the shoulder

  transverse 61 connecting the bore 22 to the bore 123.

  Thus the seal 59 said secondary seal, has good support on the bosses 60 and is provided. Indeed, in the case where the seal 59 is in contact with the shoulder 61, a deformation of the seal 59 occurs at the connection roundness, from the shoulder 61 to the internal periphery of the plate 45. The seal 59 is a lip seal. The piston liner 42 has at least one hole for communication between

  the inside and outside of the shirt 42.

  This hole 62 is located as a function of the axial movement of the piston 21 and of the jacket 42 on either side of the lip of the seal 59. This hole 62 therefore ensures, when the clutch is engaged, communication between the hydraulic control chamber 20 and

the main external tank.

  During the operation of the clutch, this communication is interrupted because the hole 62 is moved to the other side of the seal 59. Here, several holes 62 are provided to ensure a greater passage of fluid and avoid orientation during assembly.

  The holes 62 are distributed regularly.

  It will be noted that the jacket 54 axially immobilizes the seal 59 so that it constitutes an immobilization jacket. This jacket 54 has at its internal periphery at least one axial groove 63, which therefore opens at the lip of the seal 59. Here several axial grooves 63 are provided. As visible in the upper part of FIGS. 5 and 6 in the advanced position, clutch engaged (upper part of FIGS. 5 and 6), communication takes place between the chamber 20 and the grooves 63 via the holes 62, the inclined lip of the seal 59 allowing such communication. The holes 62 are intended to move on either side of the second seal 59. All of this allows communication with the

  outdoor tank and recover from leaks.

  More specifically, the external reservoir is connected to the tube 49 in communication with the orifice 50, the groove 52 and the internal bore 23 via the channels 51, which open into a space delimited by the transverse shoulder 64 for connection of the bore 123 to bore 23, by the front face of the intermediate section 56 and by the external periphery of the section 55 and

  the internal periphery of the rear part 27.

  Passages 65 are made axially in the intermediate section 56 to communicate the fluid coming from the external reservoir with the annular space existing between the

  sections 56, 57 and the grooves 63 with closed bottom.

  To prevent the fluid from escaping towards the outside, a sealing bellows 66 is provided which intervenes between the rear part 27 of the body 17 and the rear of the piston rod 33. Here, the liquid can pass through the plate 45 and the immobilization and guide jacket 54 for accessing the axial grooves 63 and communicating with the chamber 20 via the holes in

passage 62.

  According to one characteristic, the jacket 54 limits the axial movement in one direction of the piston 21 - jacket

piston 42.

  To do this, the fixed liner 54 has at its rear end at least one stop 67 (FIG. 7), here several stops, of transverse orientation allowing a

  fluid passage. Thus, the axial movable piston liner 42-

  ment is allowed to come (advanced position) in contact through its rear face with the stops 67. The rear end of the piston 21 projects axially with respect to the rear end of the jacket 42, which undergoes slight forces when it is

  contact with the stops 67 because the chamber 20 is depressurized.

  It will be noted that fluid communication takes place between the grooves 63 and the space outside the jacket 54 thanks to the play

  radial existing between the piston 21 and the stops 67.

  The bellows 66, here made of elastomer, has at each of its ends transverse beads 68, 69 fixed respectively on the body 17 and on the piston rod 33 to

  using fasteners 70, 71, here metallic.

  More specifically, the rear end of the rod 33 has two grooves 72, 73 axially staggered. The groove 72 is intended to receive the bead 69 while the groove 73, the most distant from the body 17, is intended to receive notches 74 belonging to the fixing part 71 of tubular shape better visible in FIG. 2. This part 71 consists of a ring stepped in diameter (Figure 2) with a continuous rear portion extended by a front portion 76 of larger diameter fragmented by slots in legs 77 elastically deformable radially. The notches 74 belong to the legs

  77 and are directed towards the interior of room 71.

  Thus, the rear end of the bellows 66 is surrounded by the front portion 76 of the part while being trapped between this portion 76 and the rod 33, the bead 69 being housed in the

throat 72.

  The notches 74 enter the groove 73 to immobilize

axially the ring 71.

  The part 70 is in the form of a ring with a bottom 78 directed

generally radially.

  The ring 70 has, like the ring 71, lugs 79 with deformations 80 engaged in a groove (not referenced) produced at the external periphery of the part

rear 27 of body 17.

  The bead 68 is trapped tightly in a cavity delimited by the rear face of the body 17, the external periphery

  of the intermediate section 56 and the bottom 78.

  The bellows 66 is stepped in diameter and has a rear part of smaller diameter adapted to bear against the rear face of the section 57 and a front part of larger diameter surrounding the section 57. The rear parts and

  front of the bellows are accordion shaped.

  The section 57 has externally blind slots 83 for receiving a tool for mounting and centering the jacket 54. The slots 83 open axially at the rear of the section 57 and are axially closed at the front by the section 56. Thus, the assembly tool centeringly surrounds the section 57 and centers the piston jacket 42 by means of projections

  passing through the slots 83 to engage the shirt 42.

  Thus, it is possible to fit the jacket 54, jacket 42 and piston 21 assembly into the body 17 and to carry out the fixing by ultrasonic welding of the jacket 54 to the body 17. Of course, it is possible to replace the blind slots 83, of orientation axial, by oblong holes. Generally, the rear section has openings for passage of

mounting tool protrusions.

  We will appreciate the low cost of the control device

  hydraulic according to the invention and ease of assembly.

  In fact, the jacket 42 is fitted onto the piston 21.

  Similarly, the tube 49 and the jacket 54 are fitted

  respectively in the orifice 50 and the bore 23, 123.

  The fastening parts 70, 71 are fitted respectively on the section 57 and on the rod 33. The bellows 66 defines with the body 17 and the rod 33 an integrated booster tank. Ultrasonic welding between the body 17 and

  the fixed liner 54 provides a seal.

  Thus, the master cylinder, according to the invention, uses a single dynamic seal, namely the seal 59 and static seals, namely the seal 41 and the beads 68, 69 of the bellows 66. The seals 59 and 41 are provided because they bathe

in the control fluid.

  Thanks to holes 62, grooves 63 and bellows 66 to

  bead 68, 69 a dynamic joint is removed.

  In FIG. 1, the rear part of the bead 66 is never completely compressed. The initial volume of fluid contained in this rear part is transferred inside the body 17 taking account of the axial displacement of the piston 21. Thus, the external main tank can be eliminated. This is what is achieved in FIG. 9 thanks to the plug 149. Of course, account must be taken of the wear of the friction linings of the clutch in order to have the correct volume in the integrated reservoir delimited by the bellows and intervening between the body 17 and the

  rod 3. This reservoir therefore forms the one and only reservoir.

* In FIG. 8, the rear part of the bellows 6.6 is completely compressed so that the presence of the external tank is essential, the auxiliary tank no longer existing. Only the rear part of the bellows is in the form of an accordion, the front part of the bellows encircling the section 57. Of course, the bellows can be omitted as visible

in Figure 10.

  In this case, a protective cover 166 is provided to withstand impacts. The cover has a cylindrical shape surrounds the fixed jacket 54 and is provided at its rear end with a bottom 167 which is perforated centrally for passage of the rod. At its front end, the cover 166 has an annular radial rim 168

directs outward.

  This rim 168 is fixed to the fixed liner 54 by snap-fastening in favor of a bead engaged in a groove of the

body 17.

  In this case, the fixed liner 54 has only a section

  intermediate 56 and a rear section 57.

  The front section of FIGS. 1 to 9 is replaced by a shim 155 so as to be able to accommodate a second dynamic seal 159 between the shim 155 and the section 56 is notched at its internal periphery for housing the seal 159. The shim 155 has

  radial grooves (not shown) at its rear end.

  Internally, the shim 155 has axial grooves replacing the grooves 63 of Figures 1 to 9. Thus, thanks to

  holes 62, the liquid communicates with the tube 49.

  In FIG. 10, the seal 159 is an additional seal

  preventing leakage to the outside.

  Of course, the cover 166 can surround the bellows 66 of FIGS. 1 to 9. To do this, the fixing piece 70 can be extended at the rear by a tubular part at least partially surrounding the bellows. Alternatively, the fixing piece 71 is extended by a tubular part at the front for

partially surround the bellows.

  Of course, as a variant, the tube 49 and the fixed jacket 54 are mounted in the body 17 by broaching using an elastic pin similar to the elastic pin 48, passages for the pin still being provided respectively in the edge of the orifice 50 and in the rear part 27. As a variant, the parts 49, 54 are mounted by an assembly of the type

bayonet in the body 17.

  In these variants, an additional seal must be provided. Of course, the present invention is applicable to

receiving cylinder.

  In all cases, the piston liner belts the

  piston and forms a sub-assembly therewith.

  The piston liner 42 enters the hydraulic chamber 20 and delimits the latter. More specifically, the jacket 42 enters the bore 22 of the front part 26; the bore 22 being extended axially by the internal bore of the fixed jacket 54, called the first jacket. Thanks to the presence of the projection 28 the inlet 18, forming a connection orifice, may alternatively lead into the front part 26 between the bottom 24 and the piston jacket 42, taking into account that this jacket is at a distance from the background

  when the piston 21 is in the retracted position.

  Of course, the transverse wall 30 of the piston can be thicker so that the seat 138 for receiving the head 40 of the rod 33 (FIG. 6) can be hollowed out in

the transverse wall 30.

  In the figures illustrated, the seat 138 extends in section over a little more than 180 so as to axially retain the

rod 33.

  Alternatively, seat 138 extends over 180 or less and an attached ring, such as an open circlip, is attached

  in the piston 21 to axially wedge the rod 33.

  This arrangement makes it possible to use a continuous and rigid socket 38. Of course, the formation of a split sleeve 38 facilitates the fitting of the jacket

piston 42 on piston 21.

  This piston 21 is wedged axially at its outer periphery on the piston jacket 42, called the second jacket. For this axial setting, the second jacket 42 may have a single notch, for example in the form of a bead engaged in a continuous groove of the piston produced as a variant in the wall

transverse 30 of the piston 21.

  A single notch and a single hollow can therefore be provided on

  one of the elements, second jacket 42 - piston 21.

  The second metallic jacket 42 is secured at least axially to the piston 21, while the first fixed jacket 54 is secured to the body 17 by being made of moldable plastic. In FIGS. 1 to 9, a flexible element made of material

  elastic, delimits a tank integrated into the emitting cylinder.

  This element consists of an elastomer bellows 66, such as

rubber.

  The second jacket 42 slides axially in the first jacket 54, while the seal 59 cooperates so

  dynamic with the second shirt 42.

  The chimney 34 allows access to the external periphery of the front face 31 of the piston 21, while the bush 38 allows

  to access the central part of the rear face 32.

  The fastening parts 70, 71 tightly cover the ends of the flexible element made of elastic material, here the bellows. In FIG. 8, the bottom 78 of the fixing piece 70

  extends more radially inward.

  In all the figures, axial ribs, not referenced, connect the sections 56, 57 radially to each other, while allowing the fluid coming from the external reservoir to pass

or integrated.

  In FIG. 10, the cover 166 for protecting the first jacket 54 is fixed to the intermediate section of the latter. It can be the same in Figures 1 to 9. For this, it suffices, on the one hand to cut the rear end of the intermediate section 56 to be able to mount the bead 68, and, on the other hand, the receiving groove of the notches of the

  part 70 at the outer periphery of the section 56.

  Of course, a single bead-shaped notch can

  be provided on parts 70 and 71.

  The part 70 is fixed on one of the body elements of

cylinder 17 - first jacket 54.

  It then becomes possible to remove the ears 46 from the plate 45 and fix the cylinder body 17 by a bayonet-type mounting on a fixed part as described in document GB-A-1,539,879 to which we will refer for more

clarifications.

  This mounting can be carried out by means of one of the sections 26, 27 or of the plate 45. The plate 45 can therefore be devoid of fixing means on a fixed part. The plaque

can therefore be annular.

  The openings 83, here in the form of blind slots, produced in the rear section 57 of the jacket 54, are S access openings to the second jacket 42 so that the mounting tool can come into engagement with the second jacket 42 , this tool being engaged with the first jacket 54. All of the

combinations are possible.

  In FIG. 8, the bellows 66 may consist only of a rear accordion-like section fixed at the front on a protective cover surrounding the section 57 and attached so

waterproof on the rear part 27.

  The second folder 54 and the tube can be brought back

by screwing onto the body 17.

  The fixing part 71 can be replaced by a clamp. This part 71 can be fixed by crimping

  on the stem. The same is true of Exhibit 70.

  Alternatively, the attachment of the part 70 is carried out at

using screws.

  In the embodiments described, the cylinder body 17 carries the intermediate plate while being in one piece with it. Alternatively, the 45 plate is attached to the body

cylinder 17.

  Thus, the control device comprises the cylinder body 17, the jacket 54 is an interposed central piece

  between the cylinder body 17 and the jacket 54.

  This central part forms the plate 45.

  The dynamic seal is housed in this room

intermediate.

  The tube 49 is fixed to the plate 45 and it is connected to a transverse conduit produced in the plate. This conduit then opens into a central hole in the plate 45 facing the external part of the jacket 54. It is then possible to accommodate two dynamic seals in the plate. This plate then includes housings for mounting dynamic seals of

conformation similar to seal 59.

  The fixing of the plate 45 on the body of 17 is carried out in a similar manner to the fixing of the jacket 54 on the plate 45, that is to say by a welding of the welding type 58, the plate 45 having a part similar to part 27 for welding. The plate 45 is not used for guiding the jacket 42, a radial clearance existing between the jacket and the outline of the hole in the plate so that the conduit connected to the tube can open into a cavity closed by the two dynamic seals. It is the cylinder body and the jacket 54 which guide the piston jacket 42. For more details, reference may be made to the content of French patent application number 99.02426 filed on 26

February 1999.

  Of course, the ultrasonic type welds can be replaced by local tight seals with indirect

  heat using at least one energy source of the laser type.

  For example, the beam-shaped radiation emitted by the

  laser is in the field of infrared radiation.

  One of the elements to be welded is made of material transparent to infrared radiation while the other of the elements is shaped to absorb said radiation. For example, this other element is made of material transparent to said radiation and is provided with at least one additive to absorb the radiation. Of course, this other element may be absorbing said radiation. Thus, the attachment of the tube 49 to the plate 45 can be achieved by this indirect heat welding making the attachment sealed. The tube 49 is shaped to absorb said radiation, being for example made of material transparent to said

  radiation and with an additive to make it transparent.

  The additive which is for example in the form of pigments such as carbon with a content of 1 to 2%. It is the part closest to the laser which is made of transparent material and the other absorbent. Preferably, the laser is rotated relative to the element to be welded. Of course, the reverse is possible. So the plate

is made of transparent material.

  This type of welding is more advantageous than ultrasonic welding because it protects the seal 59 as well as the parts to be welded so that the control cylinder is more reliable. Thanks to this, the channels 51 and the groove 52 are easily produced. The watertight fixing at 58 can be achieved by this

  indirect heat welding.

  The plug 149 can be fixed by this type of welding.

  The attachment of the liner 54 in the body of 17 can therefore be carried out by indirect heat, the plate 45 being made of material transparent to said radiation and the other parts to be welded of material shaped to absorb said radiation. Of course, instead of a sealed ultrasonic weld or by indirect heat supply, it is possible, for example at 58, to produce a sealed friction weld or a sealed high frequency weld. As a variant, the waterproof fixing is a fixing of the type by mirror welding or of the type by welding

  by induction of ferromagnetic joints.

  As is evident from the description and

  Drawings, the jacket 54, called the first jacket, and the piston are made of plastic and the first jacket 54 has at least one stop 67 intended to cooperate with a rear end of the piston to limit the axial displacement of the piston towards the rear. This stop is intended to cooperate with the end

  back of the shirt 42 called the second shirt.

  In reality, the rear axial end of the first jacket has several transverse orientation stops which extend radially inwards. These stops 67 are distributed angularly in a regular manner to allow a

fluid passage.

  Thanks to this design of axial retention of the piston towards the rear, one results in a reduced tolerance on the value of the dead stroke of the piston insofar as it results from the cumulation of the tolerances of three parts, that is to say the shirt of

  piston 42, the outer jacket 54 and the cylinder body.

Claims (14)

  1. Hydraulic control device for a clutch, in particular for a motor vehicle, comprising at least one control cylinder comprising a first jacket (54), a cylinder body (17) having a bottom (24) at the front and open at the rear for reception of the first jacket (54), a piston (21) sliding axially in the cylinder body (17), a piston jacket (42), said second jacket, axially integral with the piston (21 ) and sliding axially in the first jacket (54), a piston seal (41) carried by the piston (21), a second seal (41) carried by the body of the cylinder (17) to cooperate with the second jacket (42), a piston rod (33) having at the front a head (40) for cooperating with the piston (21), in which the cylinder body (17), the first jacket (54) and the piston (21) are made of plastic, while the second jacket (42) is metallic and in which the piston (21) has a front face (31) delimiting the hydraulic chamber (20) and a rear face (32) cooperating with the piston rod (33), characterized in that the first jacket (54) has outward openings ( 83) of access to the second jacket (42) for the passage of an assembly and centering tool 2. Device according to claim 1, characterized in that said openings are formed in the rear section (57) of the first shirt (54).   3. Device according to one of claims 1 or 2,   characterized in that said openings are slots (83 axial orientation.   4. Device according to claim 3, characterized in that said slots are closed axially at the front end of the first shirt (54).   5. Device according to one of claims 3 or 4,   characterized in that said slots (83) are through   axially at the rear end of the first jacket (54).   6. Device according to any one of claims   previous, characterized in that said openings (83) are distributed angularly in a regular manner around the axis of the first shirt (54).   7. Device according to the preceding claim, characterized in that the number of said openings is greater than or equal to three.   8. Device according to any one of claims   previous, characterized in that said openings allow the passage of projections belonging to a mounting and centering tool which pass through them to engage with the second shirt.   9. Device according to any one of claims   previous, characterized in that said tool is centered   externally around the first shirt.   10. Device according to any one of the claims   1 to 8, characterized in that said tool is centered internally in the first jacket   11. Device according to any one of the claims   1 to 10, characterized in that the first jacket (54) has at its rear end at least one stop (67) intended to cooperate with the rear end of the second jacket (42)   to limit the displacement of the piston (21).   12. Device according to any one of claims   previous, characterized in that the front section (55) of the first jacket (54) is fitted into the cylinder body (17) while being fixed to said body (17) by a tight fixing, such as ultrasonic welding , indirect welding heat or bonding.   13. Device according to any one of claims   previous, characterized in that the cylinder body (17), the first jacket (54) and the piston (21) are made of material   plastic, while the second jacket (42) is metallic.   14. Device according to any one of the claims   previous, characterized in that the piston (21) is shaped to receive the head (40) of the piston rod (33), in that the piston (21) is surrounded by the second jacket (42), in that the piston seal (41) intervenes between the external periphery of the piston (21) and the internal periphery of the second jacket (42), and in that the second jacket (42) enters the hydraulic chamber (20) .5