FR2764663A1 - Motor vehicle electronic control unit signal failure compensation method - Google Patents

Abstract

The method is used in conjunction with an engine (2), clutch (4), gearbox (6) and drive shaft (8) which drives the rear wheels (12) through a differential (10) according to the position of the accelerator (14) which has a position sensor (16) connected to a control unit (18) to which several other engine management sensors are also connected. The braking system has a sensor (34) on the brake pedal (32) controlling all the brake cylinders (38) through a control system (36) and wheel rotation sensors (40) connected to a control system (42). A further control unit (44) controls the action of the clutch and gearbox through actuators (46,48,50) and also has an input from a drive shaft sensor (52). The absence of any signal input to the control units is identified and a mean value substituted.

Description

 To prepare ceramic pastes and workpieces, a known method consists in adding to the mixture of ceramic grains, a suitable binder or a combination of binders, in order to obtain sufficient resistance during the transformation of the pasta or workpieces made from these pastes, but also during use.

 Known binders include phosphates, for example aluminum monophosphate, alkali silicates, aluminum sulfate, synthetic resins as well as various inorganic and organic binders.

 For certain applications, it is sufficient to use so-called temporary binders. Their main function is to ensure the green resistance of a blank until, in the firing process, a ceramic bond takes over with regard to the resistance of the product.

 Mainly in the hot forming process, for example injection molding or hot extrusion, the use of thermoplastic binders is known in ceramic pastes. The mixture is brought to a temperature above the melting point of the binder and thus converted into a flowable form (viscous) and then transformed. After forming, the binder must be removed from the preform (paste) again before carrying out the usual sintering process.

 The operation of removing the binder is problematic both from the point of view of the process technique and that of environmental protection. if solvents are used to extract the binders by dissolving them, in addition to the binder itself, additional harmful substances are obtained which must be removed. Details on this subject are given in patent EP 0 362 866 A2. This document further describes a method of manufacturing a sintered part, in which an organic binder is used which is partly composed of a water-soluble thermoplastic organic polymer and partly of a thermoplastic organic polymer insoluble in l 'water. After forming, the formed part is brought into contact with water and the water-soluble polymer is extracted before sintering the shaped part.

 The degree of extraction of the binder which can be obtained by staying in water (treatment with water) is here clearly less than 50%, so that the problems described above remain essentially the same as regards removing the residual binder.

Combinations of special binders for the manufacture of pastes and ceramic shaped parts are also described in the patents
EP 0 517 129 B1, EP 0 599 285 B1, DE 44 38 962 A1 and
EP 0 519 326 B1. In all cases, partial removal of the binder is carried out using water as the solvent.

 Thus, the object of the present invention is to provide a means which respects the environment and which is optimized from the point of view of the process technique which allows at least a temporary connection to be made in pastes and shaped ceramic parts.

 The present invention is based on the observation that this objective can be achieved by the use of a modified sugar or of a sugar alcohol as a binder for pastes and ceramic shaped parts. In this context, the term "sugar" represents mono and oligosaccharides. These low molecular weight carbohydrates are sweet tasting, water soluble, crystalline and amorphous compounds with defined molecular weights.

 The aforementioned carbohydrates should be distinguished from polysaccharides which, like most polymers, have no homogeneous molecular weight and are furthermore very little or not at all soluble in water.

 The term sugar alcohols describes a group of polyhydroxy compounds obtained from monosaccharides by reduction of the carbonyl function.

These sugar alcohols are mainly crystalline but, in a modified form, they can also be amorphous. These are water-soluble polyols. Depending on the number of hydroxyl groups present in the molecule, there are, for example, tetritols, pentitols and hexitols.

Among the sugar alcohols present in the natural state, there are for example glycerol and adonitol.

 The aforementioned sugars and sugar alcohols have in common the fact that they have a "sticky consistency", which makes them particularly suitable for use as binders or as components of binders.

Another essential advantage lies in the fact that both of these substances are very easily soluble in water.

 As a result, they fulfill the following action mechanism during the manufacture of ceramic pastes and their subsequent transformation into shaped parts.

 during the formation of a ceramic paste, for example, the addition of carbohydrates causes adhesion of the ceramic particles. When the temperature is increased to prepare the ceramic paste mixed with the binder in order to then form it in the forming process of the type mentioned above (for example injection molding, hot extrusion), the binder changes to the state of very low viscosity aggregate which makes the dough as a whole plastic, so that it is also possible to obtain ceramic parts of complicated shapes by pressing, injection or casting.

 Another advantage lies in the fact that the adhesive effect of the binder is lost at high temperatures (of the order of 140 to 1500C), due to the low hygroscopic nature, which means that, during this phase, the The forming process is not only unimpeded, but on the contrary is positively influenced.

 Even in the case of the use of crystalline sugars, it has been found that these no longer recrystallize insofar as they have once passed to a viscous state under the effect of the rise in temperature. This property is advantageous because the residual quantities of modified sugar or sugar alcohol possibly present in the green part cannot cause microcracks in the ceramic structure as a result of recrystallization.

 The significantly higher solubility in water compared to that of known binders makes it possible to easily and almost completely remove the binder from the ceramic structure by dissolution, simply by leaving the part to remain in water after forming. This dissolution process is favored when the treatment is done in heated water.

 Since the binder is also a substance which is frequently used in the food industry, it immediately follows that the residual sugar solution does not require any special disposal and, in particular, it does not contain any toxic constituents.

 Depending on whether the binder consists in whole or in part of the aforementioned sugars or sugar alcohols, it is eliminated in whole or in part from the part formed during the extraction carried out thereafter. In this case, extraction rates of 60 to 99% can be obtained immediately depending on the length of stay in the water (generally 1 to 6 hours) and the temperature of the water (preferably between 30 and 700C).

 The use of the aforementioned sugars and sugar alcohols in an amorphous form is an optimal choice.

 The last group includes, for example, sugars or sugar alcohols modified by ethoxylation or propoxylation, alkoxylated carbohydrates, hydrogenated or partially hydrogenated carbohydrates and / or alkoxylated hydrogenated or partially hydrogenated carbohydrates as water soluble component.

 Caramelization of substances during the rise in temperature, negative with regard to their use as binders, is reliably avoided by the choice above.

As indicated, the chosen binders can be used both alone and in combination with other adjuvants. In the latter case, the proportion of sugar or sugar alcohol is generally between 40 and 90% by weight. The additives can be, for example, lubricants, wetting agents or mold release agents which are known as such in the technique of processing ceramics. Among these, we find in particular
polymers of polyethylene, propylene and / or copolymers of ethylene and vinyl acetate and / or ethylene and vinyl ester as lubricants which make it possible to standardize the accumulation of pressure during extrusion, surfactants, in particular nonionic surfactants (for example fatty acid esters with polyglycols), as wetting agents, or wax esters (for example beeswax or grease).

 The proportion of binder in a ceramic paste, for example a porcelain paste, can be up to 20% by weight, reduced to the total mass of the paste.

The present invention will be described in more detail below with reference to an example
85 parts by weight of a ceramic paste based on aluminum oxide are mixed with 15% by weight of a binder having the following composition
75% by weight of propoxylated sorbitol, 15% by weight of ethylene vinyl ester copolymer and 10% by weight of beeswax. After mixing (homogenization) in a conventional ceramic mixer, the paste containing the binder is heated between 160 and 1800C so that the binder passes to the state of low viscosity aggregate. The ceramic paste is then dry pressed to obtain shaped parts such as cups and plates, and as a result it exhibits excellent green resistance.

 The formed parts are then immersed for three hours in hot water at 50 degrees. Under the effect of the diffusion process, the parts of sorbitol, mainly present, are extracted almost entirely. In parallel, the volume of open pores, in particular, increases proportionally, so that the resistance to green nevertheless remains practically unchanged due to the prior forming process.

 In this specific case, the degree of extraction of the binder reached is of the order of 75%.

 The residual content of binder, in connection with the increased (open) porosity after extraction, is not a problem from the point of view of the process technique, during the subsequent baking process. During the temperature increase phase, the residual binder is removed via the open porous structure (removal of the binder), followed by sintering of the product.

 No deterioration of the structure is noted.

 Of course, the present invention is not limited to the exemplary embodiments described and shown above, from which other modes and other embodiments can be provided, without going beyond the ambit of the invention .

Claims (4)

 1. Use of modified sugar or sugar alcohol as a binder or binder component for pastes and shaped ceramic parts.  2. Use according to claim 1, wherein the sugar or the sugar alcohol is used in amorphous form.  3. Use according to claim 1, in which a sugar or a sugar alcohol modified by ethoxylation or propoxylation is used.  4. Use according to claim 1, in which a binder containing 40 to 90% by weight of sugar or sugar alcohol is used, the remainder consisting of lubricants, mold release agents and wetting agents.