192 clutches and power-stop control – Clutches – Operators
Reexamination Certificate
2000-02-18
2001-10-09
Marmor, Charles A (Department: 3681)
192 clutches and power-stop control
Clutches
Operators
C192S090000
Reexamination Certificate
active
06298968
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a hydraulic circuit, especially for a clutch. More particularly it relates to an emitter device which is adapted to transmit an order for control to a receiver device through a hydraulic path.
2. Description of the Related Art
Such apparatus is known conventionally under the name of a master cylinder. In a traditional configuration, the master cylinder comprises two main parts which are, firstly, a piston and cylinder assembly in which the piston is actuated by a pedal, for example a clutch pedal, and secondly, a hydraulic fluid reservoir which is adapted to compensate for the variations in volume in the fluid due to wear in the clutch liners or due to possible leaks in the hydraulic circuit.
Apparatuses of this kind are for example described in the document FR-A-2 522 757. In general terms they comprise, between the reservoir and the hydraulic chamber defined by the cylinder and in which the piston is displaceable, a non-return means which enables the circuit to be refilled in its rest position and enables the circuit to be put under pressure.
In these traditional apparatuses, the seals which provide sealing of the pressure chamber often consist of a seal carried by the piston or, as in the above mentioned document, a flexible membrane which is disposed between the piston and the cylinder; the central portion of this membrane, which is fixed to the cylinder by its periphery, follows the longitudinal displacements of the piston during engagement and disengagement of the clutch. These seals are subjected on one of their faces to a fluid environment, and on their other faces to an atmospheric environment which results in a dry and often polluted surface. This difference in environment, and the action of pressure, leads to a relatively limited useful life of these seals, which is the source of leaks that are potentially dangerous, in this case for the user of the vehicle.
Receiver devices, located at the end of the hydraulic circuit, for example in line with the clutch release bearing, operate and are designed in principle substantially identically to those of the emitters. They naturally have the same problems in practice in the traditional technology.
SUMMARY OF THE INVENTION
The invention aims to provide an emitter device for a hydraulic circuit which enables optimum conditions to be obtained for reliability of the seals in operation, and also to prevent premature wear and aging of the circuit, and therefore to ensure durable sealing and hence increased operational safety for this critical member, in particular when it is used to equip a traveling vehicle.
According to another object of the invention, the emitter device is simple and inexpensive to manufacture.
To this end, the invention proposes an emitter for a hydraulic control system, adapted to be controlled by a control member and comprising a hydraulic chamber, in which a piston is mounted for sliding movement sealed by a seal which it carries, and defining therein a variable volume pressure chamber connected to a hydraulic pipe, a hydraulic fluid reservoir connected to the said pressure chamber through at least one passage, a means for preventing return of fluid to the reservoir during pressurisation of the pipe, and a means for transmitting movement of the control member to the piston, characterised in that the hydraulic chamber is extended along its longitudinal axis by a reserve space which is adapted to receive the piston in its rest position when the circuit is unpressurised, the said reserve space containing hydraulic fluid up to a level which is sufficient for the seal to be immersed therein, the hydraulic chamber and the reserve space being formed in a common casing, and in that the transmission means consists of at least two parts, one of which is internal to the casing and connected to the piston, while the other one is external to the casing, the two parts being coupled together through means passing through the wall of the casing.
Thanks to this arrangement, the piston, and therefore the seal which it carries, are integrally and durably immersed in the hydraulic liquid.
Preferably, the reserve space is adapted to contain hydraulic fluid up to a normal fluid level so as to constitute the volumetric compensation reservoir of the hydraulic circuit.
Advantageously, the part internal to the casing extends through the free surface of the liquid, and the means extending through the casing extends through the latter above the level of the liquid.
These arrangements have several advantages. In the first place, they lead to a considerable simplification in the manufacture of the emitter device, by grouping elements in a single unit.
In the second place, and much more importantly, the seals which seal the pressure chamber during pressurisation of the circuit are immersed in the hydraulic fluid, on one side within the pressure chamber and on the other side within the reservoir, which ensures perfect lubrication and eliminates pollution and the action of air, and therefore both wear and aging of the seal.
It will also be understood that it is possible here to provide a satisfactory seal closing off the pressure chamber and being of a simple type, with any marginal leaks of fluids out of the pressure chamber being here “recycled” , so that the fluid is then simply returned into the fluid reservoir. It is evident that this contributes to economy in the choice of seals for the emitter device, while increasing general reliability.
It should be noted that this arrangement also prevents the reverse entry of air bubbles and polluting particles into the hydraulic circuit, since the cylinder is totally immersed in the fluid.
This arrangement therefore has a number of intrinsic advantages, both as to simplicity of manufacture and as to safety for the user.
In accordance with particular arrangements, which can if desired be combined:
the means for transmission of the movements of the piston consists of three levers fixed to a shaft, which is free to rotate about a horizontal axis and which extends through the side walls of the casing, with one of the levers, namely an internal lever, being included in the reservoir, while the other two levers, being external levers, are outside the casing on either side of the latter. Such a symmetrical arrangement leads to a symmetry in the forces, thus preventing parasitic reactions on the pivot axis A of the levers;
the hydraulic chamber and the reserve space are incorporated in the casing, which is substantially symmetrical on a vertical plane containing the longitudinal axis of the pressure chamber, the side walls of the casing being mainly vertical, and the three levers having substantially identical geometry;
the three levers are of identical lengths, so as to reduce even further the parasitic reactions on the axis A;
the means fastening the levers on the shaft consists of rings fitted on the shaft between the said levers;
preferably, the rings are ratchet rings of a material harder than that of the levers, and on which the levers are an interference fit;
sealing of the casing in the region of the shaft is provided by means of annular seals which are fitted on the outside of the rings, between the internal lever and the side walls of the casing;
the three levers are fixed to the shaft in the same angular position, which diminishes even more the reaction forces on the axis A;
the casing has, on the outer faces of its side walls, ribs which define abutments for limiting the maximum amplitude of the movements of the levers.
These various arrangements are adapted to permit the simple realisation of a two-part transmission means, in which the coupling between the two parts is disposed outside the hydraulic fluid, in this case above the normal level of the fluid in the reservoir.
The rotary seals ensure sealing between the internal part of the control unit and the external part which works at a low amplitude, which leads to simple manufacture, reduced cost and extended useful life.
In further particular arrangements
Liniak Berenato Longacre & White
Marmor Charles A
Rodriguez Saul
Valeo
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