FR2842267A1 - Cylinder for hydraulic control of clutch in motor vehicle, uses position detector with part on piston and part housed in hollow formed in walls of cylinder pressure chamber - Google Patents

Abstract

The clutch cylinder has a piston (9), a body (1;3,5) formed with a wall (3a) of thickness e defining a pressure chamber (7) inside which the piston moves, and a position detector (11) which has part (11a) on the piston, and part (11b) in the walls of the pressure chamber.

Description

CYLINDER FOR A HYDRAULIC CONTROL DEVICE

  OF A CLUTCH OF A MOTOR VEHICLE

  The present invention relates to a jack for a hydraulic control device of a clutch of an automated gearbox

  or robotic of a motor vehicle.

  The present invention relates more particularly to a cylinder for a hydraulic control device of a motor vehicle clutch which comprises a cylinder body, a piston capable of exerting a force against the clutch fork by moving in translation at inside the cylinder body, under the action of a pressurized fluid, and a

  sensor for the position or displacement of this piston.

  In the case of automatic or robotic gearboxes, it is a computer which causes, in place of the driver of the vehicle, the declutching, for example, when a movement of the gear lever is detected. The clutch condition is determined by the computer by detecting the position of the piston of the hydraulic control cylinder. The document FR 2 746 457 describes a jack for a hydraulic control device of a motor vehicle clutch which comprises a piston displacement sensor, disposed at the end of the jack body crossed by the axis of the piston. This sensor comprises a mark detection element present on the axis of the piston. The presence of this sensor lengthens the cylinder body which in certain uses can

be troublesome.

  Document EP 0 344 714 describes a cylinder of the same type which comprises a piston position sensor placed at the end of the cylinder body opposite the end crossed by the axis of the piston. The detection of the position of the piston requires the presence of a rod which extends the piston 30 towards the end of the cylinder body equipped with the position sensor. Determining the position of the rod provides the position of the piston. As mentioned above, the presence of the position detector poses a problem

cylinder size.

  Document JP-2000-274454 describes a cylinder of the aforementioned type which includes a position sensor disposed inside the cylinder body, that is to say inside the pressure chamber defined by the wall. of

  cylinder body and in which the piston moves.

  The object of the present invention is to provide a jack for a hydraulic control device of a clutch of a motor vehicle of the aforementioned type which in particular has a space requirement.

  reduces so as not to limit the use of this jack.

  This object is achieved by means of a jack for a hydraulic control device of a motor vehicle clutch of the type comprising, in known manner, a piston, a jack body which comprises, in known manner, a wall of thickness e defining a pressure chamber in which the piston moves and a position or displacement sensor which comprises a first element disposed on the piston and a second element. According to the invention, typically, the second element of the position or displacement sensor is arranged in the thickness e of the wall of the jack body, at at least one

portion of the pressure chamber.

  The term "pressure chamber" designates according to the invention the internal cavity of the cylinder body in which the piston is capable of moving; this cavity comprises a portion into which is injected the pressurized fluid which causes the displacement of the piston and a portion

  in which the fluid does not penetrate but which contains the free end of the piston, that is to say, the end which does not include the axis capable of exerting a force on the clutch fork.

  The integration of the second element of the position or displacement sensor into the cylinder body makes it possible to limit the size of the cylinder.

  both from the point of view of its length and from the point of view of its diameter.

  Thus, the jack of the invention has the same size as a jack having no position or displacement sensor. In addition, the sensor is thus perfectly protected from all the external environment at

  cylinder due to the position of its two elements.

  According to the invention, the second element of the position or displacement sensor can be, depending on its nature, either embedded in the thickness of at least a portion of the wall of the jack body, or disposed in a cavity formed in the thickness of the cylinder body. The second element of the position or displacement sensor 35 can thus be separated from the pressure chamber by a layer of material, be flush with the latter or penetrate into the pressure chamber. The position of the second sensor element is not limited according to the invention as long as it does not interfere with the race

piston.

  According to a particular embodiment, the cylinder body comprises a first part and a second part which cooperate together, said first part or said second part comprising a cavity formed in the thickness of its wall and containing the second element of the detector.

position or displacement.

  The type of position or displacement sensor is not limited according to the invention. According to a particular embodiment, this position or displacement detector comprises a second element which comprises at

minus one winding.

  Likewise, the first element of the position or displacement detector is not limited according to the invention. According to one embodiment

  in particular, the first element comprises an element capable of generating a magnetic field, such as, for example, a ferromagnetic element such as a magnet or a coil traversed by a current.

  The present invention also relates to a vehicle of the type

  automobile which comprises the jack of the invention.

  The present invention, its characteristics and the various advantages

  that it provides will appear more clearly in the light of the description

  which follows from a particular embodiment and which refers to the attached drawing in which: - Figure 1 shows the device of the invention, the piston exerting a force against the clutch fork; Referring to Figure 1, the cylinder of the invention comprises a cylinder body 1 which in the particular example shown is formed of a first part 3 and a second part 5. The first part 3 has a wall cylindrical 3a of axis Ai which defines at least partially the pressure chamber 7. The second part 5 comprises a wall 5a substantially cylindrical, of the same axis Ai, in the thickness e of which is formed a cavity 5b which in the example shown is cylindrical and of axis Al. The second part 5 cooperates by interlocking with the first part 3 and comes

  bear on an annular shoulder 3b formed on the external surface of the first part 3.

  In the example shown, the cavity 5b opens inside the cylinder body, that is to say at the level of the pressure chamber 7, the wall 3a of the first part 3 closing this cavity 5b when the two

parts 3 and 5 are assembled.

  A piston 9 is capable of moving in the pressure chamber 7 under the effect of a pressurized fluid supplied by the conduit 7a. The piston 9 comprises a piston head 9a, a pin 9b capable of exerting a force on the clutch fork E and a support element 9c secured to the piston head 9a. In the particular example shown, the support element 9c is in the form of a cylinder with the same axis AI as the cylinder body 1 and of diameter slightly smaller than the diameter of the pressure chamber 7 so that it can slide inside the latter. One end 9d of the support element 9c is integral with the head of

  piston 9a while its end 9e is free.

  The piston 9 moves in the pressure chamber 7 under the effect of a fluid supplied by the conduit 7a. In the particular example, the duct 7a being arranged laterally, the piston 9 works in traction. It is also possible, according to the invention, to arrange the conduit 7a for supplying the pressurized fluid axially, the piston 9 then working in compression.

  The position or displacement sensor 11 comprises a first element 11a which is, in the particular example shown, an annular magnet 25, disposed on a ring 12 secured to the second end 9e of the support element 9c. The second element 1 lb of the sensor 11 consists of a coil disposed inside the cavity 5b of the second part 5. This coil 1 lb is connected to a motor computer C. When the two parts 3 and 5 are assembled , the winding 1 lb is therefore separated from the chamber 7 by the cylindrical wall 3a of the first part 3. According to a variant not shown, the first part 3 does not have a cylindrical wall 3a extending at the level of the windings Ilb and the pressure chamber 7 is formed by the assembly of the two parts 3 and 5. In this case, the winding 1 lb may or may not be separated from the pressure chamber 7 by a thickness of material formed for example, by a part additional or by a thickness of the wall of the second part; in this case, the cavity formed in the second part opens out at the level of the external surface of the actuator body, which facilitates the introduction of the second element of the sensor, which can possibly be protected by the addition of an external cover on the cylinder body. The cavity can also open both at the level of the external surface of the cylinder body and at the level of the pressure chamber or any other part of the cylinder body allowing the introduction of the second element of the sensor into the thickness of

the wall of the cylinder body.

  In the particular example shown, the jack comprises means 13 for cohesion between the piston head 9a, the axis 9b and the first element 11a of the sensor 11. In the particular embodiment shown, these means comprise an elastic element 13a in the form of a spring bearing, on the one hand on an internal annular shoulder 3c of the first part 3 of the cylinder body 1 and, on the other hand, on the surface 12a of the ring 12 comprising the first element 11a of the sensor 11. In the example shown, the ring 12 also includes an O-ring 12b ensuring the seal between the portion of the pressure chamber 7 which fills with fluid and the portion which does not come into contact with the fluid. Similarly, a sealing element 15 having a substantially cylindrical shape is interposed between the internal shoulder 3c and the spring 13a and makes it possible to avoid contact of the latter with the fluid entering the pressure chamber 7. The spring 13a makes it possible, due to its elasticity, to hold the piston head 9a, the axis 9b and the first element 1 together.

  of the sensor 11 over the entire length of the stroke of the piston 9.

  The operation of the device of the invention is as follows. Under the effect of the pressurized fluid supplied by the conduit 7a, the piston head 9a moves in the direction of the arrow FI in the pressure chamber 7. The position of the clutch fork E 30 is detected by determining the position of the piston 9. When the piston 9 moves, the magnet 11a which is integral with the piston 9 also moves inside the coil 11a, thus creating an induced current. The sensor 11 can also include two secondary windings. The displacement of the magnet i la generates voltages VI and V2 in each of these secondary windings 35 whose value depends on the position of the magnet 11a. The two secondary windings are connected in series and in phase so that the signal collected is the difference between the voltages VI and V2. At the reference position which corresponds to the middle of the winding 1 lb, the two voltages VI and V2 cancel each other out. The more the magnet moves towards one of the ends of the 1 lb winding, the more the difference VI-V2 increases in absolute value. The output signal is then rectified in order to obtain a DC voltage representative of the position of the magnet 1 a which provides the position of the piston 9 and therefore the position of the clutch fork E. When the fluid leaves through the conduit 7a, the piston 9 then moves 10 along arrow F2 and its movement is detected in the same manner as previously exposed, that is to say due to the movement of the magnet 11a in the winding 1 lb.

Claims (8)

  1. Cylinder for a hydraulic control device of a clutch of a motor vehicle of the type comprising a piston (9), a cylinder body (1; 3, 5) which comprises a wall (3a) of thickness e defining a chamber pressure (7) inside which moves said piston (9) and a position or displacement sensor (11) which comprises a first element (1 la) arranged on the piston (9) and a second element ( 1 lb) characterized in that said second element (1lb) of said position or displacement sensor (11) is disposed in the thickness e of the wall (3a) of the jack body (1; 3, 5), at the level at least a portion of the room pressure (7).   2. Cylinder according to claim 1, characterized in that said cylinder body (1) comprises a first (3) and a second part (5) which cooperate together, said first part (3) and / or said second part (5 ) comprising a cavity (5b) formed in the thickness (e) of their wall and containing the second element (1 lb) of the position or displacement sensor (11). 3. Cylinder according to claim 1 or 2, characterized in that said second element (1 b) of said sensor (11) of position or displacement   has at least one coil (1 lb).   4. Cylinder according to any one of claims 1 to 3, characterized in   that said first element (l a) of said position or displacement sensor (11) includes an element capable of generating a field magnetic.   5. Cylinder according to any one of claims 1 to   4, characterized in that said piston (9) comprises a piston head (9a), an axis (9b) and a support element (9c) which comprises said first element   (1a) of said position or displacement sensor (11).   6. Cylinder according to claim 5, characterized in that it comprises means (13) for ensuring cohesion between the piston head (9a), the axis (9b) and the first element (1 la) of the position or displacement sensor (11). 7. Cylinder according to claim 6, characterized in that said means (13) for ensuring cohesion between the piston head (9a), the axis (9b)   and the first element (11a) of the sensor (11) comprises an elastic element (13a).   8. Vehicle of the automotive type characterized in that it comprises the jack according to any one of claims 1 to 7.