192 clutches and power-stop control – Clutches – Operators
Reexamination Certificate
2000-02-18
2001-12-04
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Clutches
Operators
C192S085060, C029S888060, C072S348000, C072S356000, C072S359000
Reexamination Certificate
active
06325194
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a declutching device for a clutch, in particular for a mechanical diaphragm clutch for a motor vehicle.
More particularly, the invention relates to a hydraulically controlled declutching device comprising a clutch release bearing which is adapted to act on the declutching device of the clutch, such as a diaphragm, and carried by a piston which is mounted for axial movement, an axially oriented blind cavity defined between a part, referred to as the fixed part and comprising an external body and an internal tube guide which are mounted concentrically, wherein the piston slides axially along the tube guide and penetrates into the blind cavity so as to define with the piston a variable volume chamber.
The invention also relates to a method of making the tube guide.
2. Description of the Related Art A declutching device of this kind with hydraulic control through the piston is described in the document FR-A-2 730 532.
In the latter, the blind cavity is bounded by the tube guide, or guide tube, and by the external body.
The said tube has a plate portion at its rear end. The plate portion is gripped between the external body and the fixed part.
A seal is interposed between the plate portion of the tube guide and the external body, so as to seal the cavity. The axially oriented annular blind cavity is therefore difficult to standardise. In order to overcome this drawback in a simple and inexpensive way, recourse may be considered to a solution of the same type as that described in the document FR-A-2 531 164, that is to say delimiting the axially oriented blind annular cavity by the guide tube, which for this purpose has a base portion that joins an outer tube to an inner tube, which has the greater length.
This may be achieved by press-forming from sheet metal.
Such an arrangement is not entirely satisfactory because the coaxiality between the outer tube and the inner tube is not as good as is desired. In addition, the inner and outer faces of the inner and outer tubes respectively are not as smooth as desired.
SUMMARY OF THE INVENTION
An object of the present invention is to overcome these disadvantages in a simple and inexpensive way. It is therefore an object of the invention to provide good coaxiality between the outer and inner tubes.
Yet another object of the invention is to obtain good quality in the faces of the inner and outer tubes for guiding the piston. According to the invention, the guide tube is obtained by a method of impact drawing from a slug, which is preferably of an aluminium based material. In another version, the slug is of a magnesium based material or mild steel, or brass, or copper or any other malleable material. The method calls for at least one punch and a die for deforming the slug, which is solid, or which in another version has a central hole, in order to cause the metal of the latter to flow in a guided manner.
In this way, good coaxiality between the inner tube and the outer tube are obtained, the respective outer and inner faces of these tubes having a low roughness which enables the seal of the piston to be protected.
In general terms, a guide tube is obtained with good precision and with good geometrical quality without any repeat operation on the component.
It is possible easily to obtain a difference in thickness between the outer tube and the inner tube by adjusting the size of the punch and the die. The base of the cavity may have the desired form and the desired thickness, especially by deforming the slug to a greater or lesser extent with the aid of the punch and by profiling the die.
The base portion may then have a greater thickness than the inner and outer tubes. The external body may be separate from the guide tube. In another version, using the method according to the invention, the body is integral with the guide tube, which includes means for fastening it to the fixed part of the vehicle.
In a first embodiment, the drawing operation consists of a first operation, which produces a cylindrical cup, and then a second operation of deep drawing the base of the cup so as to obtain a tube guide with an axially oriented annular blind cavity delimited by concentric outer and inner tubes. In this case the slug is solid. In a second embodiment, the slug has a central hole so that the guide tube can be obtained in a single operation, with the die being then caused to penetrate into the hollow punch with the aid of a second punch which surrounds the first punch, and a collar portion can be formed for fastening on the guide tube. The declutching device is inexpensive. The guide tube may have an outer tube the length of which is smaller or the same as that of the inner tube.
Thus, thanks to the invention, the blind cavity can be standardised in a simple and inexpensive way.
In this connection it is enough to modify the external body according to each application, and in particular according to the form of the casing on which the external body is fixed.
The external body may be standardised and be mounted, by a bayonet type fitting, on a soleplate for adapting it to the casing. Such a mounting is described for example in the document FR-A-2 745 616, the contents of which are considered as being annexed to the present invention. It is thus possible to standardise both the tube guide and the body at the same time.
In general terms, thanks to the invention, the supplementary seal interposed in the prior art between the body and the plate element of the tube guide is omitted. The dangers of leaks are thus reduced.
The blind cavity is deformed less under the effect of variations of pressure that occur during the engaging and disengaging operations of the clutch, due to the fact that the said cavity is defined by a single member.
In this way improved guidance of the piston is obtained because the deformations of the inner tube of the tube-guide for guiding the piston are reduced. The declutching device according to the invention is thus more robust.
In addition, the seal which is included in the piston at its rear end, cooperates only with the tube guide according to the invention; that is to say with a single material, so that the choice of material for the seal is easier. This seal is more reliable. The useful life of the device is also increased and the dangers of leaks are reduced.
The external body is of a mouldable material, for example one based on aluminium, or plastics material, so that in all cases an inexpensive solution is obtained which is light in weight. The mounting of the body on the tube guide is easy. The body is for example of plastics material formed by moulding on the tube guide.
In another version, the body is of plastics material and is mounted by snap-fitting on the tube guide.
The tube guide may be provided with recesses or projecting elements for preventing it form rotating with respect to the body. For example, during the applied moulding operation, the material of the body enters into the recesses or coats the projecting elements of the tube, such as press-formed elements. Because of the impact drawing process, the projecting elements or recesses, for example in the form of notches, are easily obtained.
Axial arrest of the tube guide is easily achieved, the material of the body matching the base of the tube guide and coming into engagement with the front end of the outer tube of the tube guide.
In all cases, with clipping or applied moulding, the body matches the form of the base portion and of the outer tube of the tube guide.
The body stiffens the tube guide even more, because it is in contact with a surface area of the tube which is larger than that in the prior art.
Deformations of the blind cavity are therefore further reduced. The feed duct to the cavity can be perforated before the body is mounted, for example by applied moulding, on the tube guide.
This operation also leads to perforation of the tube guide to put the cavity into communication with the blind cavity.
The body carries an inlet into which the feed duct extends. The inle
Liniak Berenato Longacre & White
Lorence Richard M.
Rodriguez Saul
Valeo
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