FR2785648A1 - Hydraulic cylinder to operate clutch or brake of vehicle, with control element, maximum stroke of which is less than that of piston - Google Patents

Abstract

The hydraulic cylinder has a casing (2) with input connection (15) and pressure connection (16), a sprung piston (60) in a compression chamber and a piston rod (8) pivoted to the piston. There is a spring-loaded control element (9a) connected to the piston and able to be displaced relative to it. The maximum stroke of the control element is smaller than that of the piston.

Description

l

  CYLINDER FOR A HYDRAULIC MANEUVER

CLUTCH

  The present invention relates to a jack for a hydraulic system of a vehicle, in particular for operating a clutch arranged between an internal combustion engine and a gearbox with gears. Cylinders of this type have a housing with a hollow cylinder structure forming a space for

  compression with an inlet fitting and a discharge fitting.

  In the compression space is inserted a piston which is arranged with freedom to slide axially and which is sealed relative to the housing. The piston is associated with a compression spring which forcibly constrains the piston towards an end position without play. At the end opposite the compression space, a piston rod is articulated on the piston, with freedom pivot. The other end of the piston rod can for example be fixed to a clutch pedal, for maneuvering

manual clutch.

  From document DE 3713248 C2, a cylinder of the type of construction mentioned at the beginning is known. This cylinder has a piston which is surrounded by a steel sheath. To seal an annular slot located between the piston and the steel sleeve, an annular groove is provided in the piston, on the side of the compression space, to receive a round sealing ring which presses tightly against the steel sheath. To guide the piston, a sheath known as an intermediate sheath is inserted into the casing, the length of which is clearly less than the longitudinal extension of the piston. The positioning of the intermediate sheath is guaranteed by a retaining element, in which, in the mounting position, notching heels, radially preloaded, are notched in the recesses of the casing. On the two front faces of the intermediate sleeve, annular seals with grooves are inserted into recesses which seal the intermediate slot located between the piston and the intermediate sleeve. The compression spring added in the compression space of the housing is supported between a housing bottom and the piston. In the neutral position, due to the elastic force exerted by the compression spring, the piston assumes an end position in the case of which this piston bears, by a radial front plate of piston, against the intermediate sheath. The structure of the known cylinder comprises a plurality of individual components which require a high mounting expense and at the same time increase the manufacturing costs. The known cylinder also has an inlet connection which is arranged perpendicular to the longitudinal axis of the cylinder and which is axially offset with respect to the discharge connection of the cylinder. The arrangement of this fitting does not allow vertical mounting in the case where the inlet fitting is placed above the discharge fitting to allow automatic bleeding of air from the circuit

hydraulic.

  Taking into account the drawbacks of the known device, the object of the present invention is to create a structure for an actuator - optimized from the component point of view; - ensuring self-bleeding of the air even in vertical mounting;

  - with which one can obtain a cost advantage.

  According to the invention, the piston is connected, on the side of the compression space, to a control element which opens or closes the inlet connection according to the position of the piston. The inlet fitting is attached to it in a bottom of the casing, arranged perpendicular to a longitudinal axis of the jack. Such an inlet fitting, in connection with a discharge fitting which is arranged, in a cylindrical section of the casing, axially offset from

  at the inlet connection, guarantees automatic air purging,

  ie the evacuation of air enclosed in the hydraulic circuit, even

  in case of vertical mounting of the cylinder.

  For the control element constrained by the force of the spring and disposed with freedom of sliding relative to the piston, a stroke or displacement is provided, less than the maximum stroke of the piston. Because of this arrangement, in the end position of the piston which corresponds to the engaged position of the clutch, a permanently open inlet connection is guaranteed and by which an automatic air purge can take place. It is also possible an automatic reflux of a hydraulic fluid from a reservoir, connected to the inlet connection, to, if necessary, complete the refueling of the hydraulic circuit with hydraulic fluid. The closing of the inlet connection, necessary for the pressure build-up, takes place automatically after a partial stroke of the piston. The stroke of the piston for closing the inlet channel can be determined there by the length of the control element which at the same time defines the dimension of the slot existing between

  the control element and the inlet fitting, open.

  It is advantageous that the control element is in the form of a plug, with a control cage structure, which has a closed bottom, oriented in the direction of the inlet fitting, and to which are connected holding arms which are distributed over the periphery, and which are axially oriented towards the piston and are fixed

  to the piston by complementarity of form.

  According to the invention is further provided a compression spring between the control element or control cage and the piston. The spring arrangement ensures that the control element is permanently constrained by force towards the inlet connection. The design of the control element in connection with the compression spring ensures that in the neutral position, which corresponds simultaneously to the upper position of the clutch pedal, the inlet fitting is open due to the formation an annular slot defined between the control element and the inlet fitting. In this position of the control element can be made a resumption of full or a breather operation of the hydraulic circuit. Thanks to the use of a spring, with relatively low elasticity, for the control element, it is also possible to envisage reducing the depression by making the pedal play. To operate the clutch, during which the piston of the cylinder slides, the control element, after a partial stroke of the piston, bears tightly against the inlet fitting and therefore allows

  a rise in pressure in the compression space of the jack.

  To avoid the formation of air bubbles inside the control element, it is split laterally or the holding arms are placed at a sufficient distance from each other for a flow hydraulic fluid can flow unhindered through the control element. One embodiment of the control element provides that its retaining arms are guided against an inner wall of the casing and, at the end, are folded inwards at right angles to form retaining heels. For fixing in position, the heels hold, from behind, by complementarity of form, a

  front plate of the piston or a radial projection of the piston.

  The invention further includes a control element, the retaining arms of which engage in longitudinal guides of the casing and the retaining heels, folded at the end, catch on the piston. A guide of this type of the control element allows an elongated guide of the piston because the zones located between the longitudinal guides provided can be used.

  in the housing for guiding the piston.

  The retaining heels of the retaining arms engage in longitudinal grooves of the piston which, at the end, are closed by a shoulder. This design also allows, between the piston and the control element, a relative sliding which is established as soon as the control element is supported, with sealing,

against the inlet fitting.

  To guarantee automatic bleeding of the circuit air, the invention includes an installation position in the case of which the inlet connection always takes the highest static height of the jack. This results in a height difference between the fitting

  inlet and outlet fitting.

  As an advantageous embodiment of the invention, a housing in two parts is provided to receive the piston and the control element. Both the inlet fitting and the discharge fitting are associated with an upper part, an upper part against the inner wall of which the control element is guided alone or in common with the piston. Another lower part

  of the housing is preferably used to guide the piston.

  The structure of the casing also provides for a planned inlet fitting centered in the bottom of the upper part. Concentrically to the inlet fitting is arranged, to form a tight seat, a

  seal fitted at the bottom of the upper part.

  The inlet fitting, centered, in connection with the seal provides a relatively large surface support for the control element and thus avoids an inclined position preventing the

operation.

  According to the invention, the discharge connection is attached in the upper part, perpendicular to the longitudinal axis of the jack, preferably with a slight axial offset relative to the bottom of the upper part. A groove provided on the inner wall of the upper part and going from the compression fitting to the bottom of the upper allows an unimpeded flow of the hydraulic fluid, in neutral position, from the fitting

  inlet to the discharge connection.

  The invention further includes centering for the compression spring inserted between the piston and the control element. At least one end of the spring is centered, internally and externally, on the piston and on the control element, in order to obtain an always identical position of the compression spring and to avoid an inclined position which may adversely affect the operation of the cylinder assembly. It is also advantageous to provide inside the control element a piston stop. Such a piston stop prohibits support against the

  compression spring, compressed to block.

  In another embodiment of the invention, there is provided, for guiding the piston, a guide sleeve which is preferably attached in the lower part of the casing. To optimize wear, the guide sleeve is made of a material which preferably has a fairly high resistance compared to the piston. As an alternative to a two-part casing, the invention also includes a single-part casing in which the piston is directly guided against an internal bore of the casing or, in

  variant, from a guide sleeve added in the casing.

  The sealing of the piston comprises at least one seal. Preferably there is provided for this an annular seal with groove disposed between the upper part and the lower part. The annular groove seal is guided there in the upper part on the outside and bears against the lower part frontally by a seal back. The sealing lips of the grooved annular seal face in the direction of the compression space, its radially inner sealing lip, radially prestressed, sealingly bearing

  against the lateral surface of the piston.

  The embodiment of a junction position between the lower part and the upper part of the housing provides that a

  end section of the upper part widens radially.

  The enlargement encloses an end section of the lower part. The radially enlarged area of the upper part also serves to receive the annular groove seal,

which leans against a shoulder.

  Preferably, the lower part has a bushel structure

  the bottom of which has a central opening for a piston rod.

  The bottom forms at the same time an end stop for the piston

in neutral position.

  In addition to the previously mentioned embodiments of the invention with regard to the structure of the casing as well as the sealing mode, the invention also encompasses all the structures

heretofore known cylinders.

  For the control element according to the invention, it is

  interesting to make it preferably out of a metallic material.

  For example, it is suitable for a sheet of steel which can conform appropriately by a deep drawing process without chips. For the cylinder casing, regardless of whether it is made in one piece or in two pieces, it is interesting to use a plastic, for example a plastic reinforced with glass fibers, such as for example PA66GF. To obtain identical material pairings, a piston made of plastic is also suitable. As a material for the guide sleeve, a metallic material is particularly suitable. Of course, the invention also includes pairings of

  materials that deviate from the previously mentioned materials.

  The invention is explained in detail below in the drawing

comprising a total of two figures.

  Figure 1 shows in longitudinal section a cylinder

according to the invention.

  Figure 2 shows a cylinder with a control element

of variant structure.

  FIG. 1 represents a jack 1a which comprises a casing 2 made of plastic having an upper part 3 as well as a lower part 4. The casing 2 of structure largely with rotation symmetry, forms a compression space 5 and serves to receive and to guide a piston 6a. To guide the piston 6a, is inserted in the lower part 4 a guide sleeve 7 which is preferably made of a metallic material. Starting from the position shown in FIG. 1, in the direction of the arrow, a sliding of the piston 6a is preferably triggered by means of a clutch pedal, not shown in FIG. 1 and to be operated manually, with which the jack is connected by means of the piston rod 8. On the side of the compression space is connected a control element 9a, having the shape of a control cage and placed axially in front of the piston 6a. The control element 9a has a bottom 10 to which are connected holding arms 1a which are arranged symmetrically distributed around the periphery and are oriented in coincidence, axially in the direction of the piston 6a. At the free end, each holding arm Ia is folded perpendicularly inward to form a notching heel 12 which grasps, from behind, an appendage, protruding from the lateral surface of the piston 6a, of a plate 13 of the piston arranged frontally. Between the bottom 10 of the control element 9a and the plate 13 of the piston, a compression spring 14 is inserted which moves the control element 9a in the direction of the inlet fitting 15. The upper part 3 has a fitting d inlet 15 disposed centrally in the bottom 17 of the upper part 3. In addition, the upper part 3 comprises a discharge connection 16 which is arranged perpendicular to a longitudinal axis 18 of the

  cylinder in the cylindrical section of the upper part 3.

  Due to the fact that the holding arms 11a are arranged at a certain distance from each other, longitudinal slots result to form a control element 9a in the form of a cage. The position of the piston 6a in connection with the control element 9a in the neutral position explains the formation of an annular slot which appears between the bottom 10 of the control element 9a and a seal 19 placed in the bottom 17 of the upper part 3, and which is designated by "x". In this neutral position of the piston 6a, hydraulic fluid can, if necessary, flow without obstacle through the inlet connection 15 to pass into the compression space 5 and, through the discharge connection 16, into the hydraulic circuit . In addition, a vertical mounting position of the jack 1a, according to FIG. 1, allows an automatic air purge or an evacuation of the air enclosed in the hydraulic circuit which can escape through the inlet connector 15 disposed at the place

  statically the highest of the jack la.

  During a maneuver of the jack 1a, during which the piston 6 slides in the direction of the arrow, it occurs, after a partial stroke, which corresponds to the annular slot "x", that the bottom 10 of the control element 9a bears against the seal 19 and thus closes the inlet fitting 15. The seal 19, in common with the bottom 10, forms a seat there

waterproof 32.

  After pressing the control element 9a against the seal 19 or against the bottom 17 of the upper part 3, the piston 6a slides in the control element 9a and compresses the compression spring 14. For the positioning of the compression spring T 14, this is internally centered against the bottom 10 of the control element 9a by means of an appendage 21 which projects axially in the direction of the piston 6a and at the same time exerts the function d 'an end stop for the piston 6a. The inlet fitting 15 being closed, the pressure which rises in the compression space 5 with the movement of the piston is transmitted, by the compression fitting 16 and by a hydraulic line which is connected thereto, to another cylinder or slave cylinder not shown in FIG. 1. After the end of the gear change process or of a clutch maneuver and reversal of the movement of the piston in the direction opposite to the direction of the arrow, the inlet fitting 15 remains closed until 'in that the notch heel 12 abuts against the piston plate 13 and that the control element 9a therefore deviates from the seal 19. As an auxiliary measure allowing unimpeded flow of the hydraulic fluid, from the inlet connector 15 to the discharge connector 16, or an air purge in the opposite direction, a longitudinal groove 20, going from the discharge connector 16 to the bottom

  17, is provided in the upper part 3.

  The upper part 3 is connected, in a captive manner, to the lower part 5. For this purpose, the upper part 3 has, at the end, a radial enlargement 22 which is fixed over an end section of the lower part. 4. The components made of plastic, the upper part 3 and the upper part 4 are connected to each other in the overlap area of

  widening 52, preferably by ultrasonic welding.

  Frontally, against the lower part 4 is supported, in the enlargement zone 22, a grooved sealing ring 23 whose radially outer sealing lip 24 bears, in leaktight manner, against the inner wall of the upper part 3 and whose radially inner sealing lip 25 bears in leaktight manner against the lateral surface of the piston 6a. The lower part 4, in the form of a plug, also comprises a bottom 26 which forms, for the piston 6a, in its neutral position, an end stop. In addition, the bottom 26 has a central opening 27 for the rod of

  piston 8 which is fixed to piston 6 with freedom of pivoting.

  2 shows the cylinder 1b and is distinguished from the cylinder 1a of FIG. 1 by another mode of coupling of the control element 9b on the piston 6b as well as by a casing 28 in one piece. A longitudinal guide 29 is associated with each holding arm llb of the control element 9b in the casing 28. The notching heels 12 of the holding arms 1 lb engage in longitudinal grooves 30 of the piston 6b which, on the side compression space, are closed by a shoulder 38. A coupling mode of this type of the control element 9b allows an elongated guide of the piston 6b in the casing 28. For an identical dimensioning of the piston and for a volume identical to the compression space 5, this construction reduces the necessary radial space requirement of the jack 1b and therefore operates an advantageous optimization,

desired, space.

  At the same time, the cylinder 1b shown in FIG. 2 allows the use of a one-piece casing 28 which has, at the end opposite the bottom 17, a closing part 31 to create a stop for the piston and a safety device for the grooved sealing ring 23, the closing part 31 preferably being connected to the casing 28

by a snap connection.

  All the other components provided with markers in FIG. 2 coincide with the corresponding components in FIG. 1,

  so that with regard to their description we can refer to the

  embodiment corresponding to the first exemplary embodiment. l] 1 a Cylinder 1 b Cylinder 2 Housing 3 Upper part 4 Lower part Compression space 6a Piston 6b Piston 7 Guide sleeve 8 Piston rod 9a Control element 9B l Control element Bottom 1i Holding arm 1 1 b retaining 12 Notch heel 13 Piston plate 14 Compression spring 15 Inlet fitting 16 Discharge fitting 17 Bottom 18 Longitudinal axis 19 Seal 20 Longitudinal groove 21 Appendix 22 Widening 23 Groove sealing ring 24 Lip sealing 25 Sealing lip 26 Bottom 27 Opening 28 Housing 29 Longitudinal guide 30 Longitudinal groove 31 Sealing part 32 Watertight seat 33 Shoulder

Claims (19)

  1. Cylinder for a vehicle hydraulic circuit, in particular for operating a clutch disposed between an internal combustion engine and a gearbox, comprising: - a casing (2) with hollow cylinder structure, forming a compression space , with an inlet fitting and a discharge fitting - a piston (6a) arranged in the compression space with freedom of axial sliding, sealed relative to the casing (2); - a piston rod coming out of the casing (2) articulated to the piston (6a) with freedom of pivoting; - a compression spring acting on the piston (6a), characterized in that, in order to open and close the inlet connection arranged in a bottom of the casing (2), a control element is provided which is connected to the piston (6a), which is arranged with freedom to slide relative to the piston (6a), which is constrained by the force of a spring and whose stroke   maximum is less than that of the piston (6a).   2. Cylinder according to claim 1, characterized by a control element (9a), in the form of a plug, which has the structure of a control cage, which has a closed bottom, oriented towards the inlet fitting and to which are connected holding arms (1a) distributed over the periphery and axially oriented in the direction of the piston. 3. Cylinder according to claim 1, characterized in that the compression spring (14) bears between the bottom (10) of the control element and a front face of the piston 4. Cylinder according to claim 2, characterized in that the holding arms are guided against an inner wall of the housing and, at the end, are folded at right angles inward to form a notching heel (12) , heels which, in the mounting position, grab, from behind, by complementarity of form, a platform of   piston (13) or a radial projection of the piston.   5. Cylinder according to claim 2, characterized in that the holding arms (llb) are guided in longitudinal guides (29) of the casing and that their locking heels, folded perpendicularly inward at the end, come engaged in longitudinal grooves of the piston which, on the space side of   compression, are limited by a shoulder (Figure 2).   6. Cylinder according to claim 1, characterized by a cylinder mounting position in the case of which is provided for the inlet fitting (15) a static height which exceeds a height   corresponding statics of the discharge connection (16).   7. Cylinder according to claim 1, characterized by a two-part casing, comprising: - an upper part (3) with which the inlet fitting and the outlet fitting are associated and against the inner wall of which the element command is guided;   a lower part (4) for guiding the piston.   8. Cylinder according to claim 1, characterized in that with a seal (19), the attached inlet fitting, in the center, in the bottom of the upper part, forms a sealed seat (32).   9. Cylinder according to claim 1, characterized in that the discharge connection (16) is attached in the upper part of the housing or in the housing, perpendicular to a longitudinal axis (18) of the jack.   10. Cylinder according to claim 9, characterized in that the discharge connection is associated with a longitudinal groove (20) which runs against the inner wall of the upper part and goes to the bottom (17) (Figure 1).   11. Cylinder according to claim 3, characterized in that the compression spring (14) is centered, at least by one end,   on the piston (6a) or on the control element.   12. Cylinder according to claim 1, characterized in that to guide the piston (6a) is provided a guide sleeve (7) placed in the lower part.   13. Cylinder according to claim 1, characterized in that for sealing the piston is provided at least one sealing gasket which seals an annular slot located   between the housing (2) and the piston (6a).   14. Cylinder according to claim 13, characterized by a grooved sealing ring (23) which is disposed between the upper part and the lower part, which is enclosed externally by an enlargement (22) of the upper part and which s' presses frontally against the lower part with a seal back, a radially inner sealing lip leaning against the piston.   15. Cylinder according to claim 7, characterized in that the widening (22) of the upper part encloses, by complementarity of form, an end section of the lower part (4) and that the two parts are connected l to each other from   non-detachable in the overlapping area.   16. Cylinder according to claim 7, characterized by a lower part with a valve-shaped structure, the bottom (26) of which has a central opening (27) for the piston rod and forms   further for the piston an end stop.   17. Cylinder according to claim 1, characterized by a control element (9a, 9b) made of a metallic material, made of   preferably by a deep drawing process without chips.   18. Cylinder according to claim 1, characterized in that   the housing (2) and piston (6a) components are made of plastic.   19. Cylinder according to claim 9, characterized in that the piston (6a) is guided in a guide sleeve (7) made of metallic material.