Motors: expansible chamber type – Working member position feedback to motive fluid control – Follower type
Patent
1998-06-03
2000-07-25
Look, Edward K.
Motors: expansible chamber type
Working member position feedback to motive fluid control
Follower type
913692, F15B 910
Patent
active
060924535
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a brake booster according to the preamble of claim 1 and to a method of assembly for a brake booster.
Vehicle brake systems are nowadays, as a rule, equipped with a brake booster which, at least in the case of passenger cars, is usually designed as a vacuum brake booster and which serves for keeping the brake actuating force to be exerted by a driver at a comfortable, that is to say relatively low level. Such a brake booster consists of a multiplicity of individual parts, each of which has a tolerance range. It is therefore impossible to avoid length tolerances occurring in the brake booster along the actuating travel, these length tolerances having to be compensated in order to ensure a uniform characteristic in a series of brake boosters. Particularly critical in this respect is a dimension between an input member of the brake booster, said input member being designed, for example, as a valve piston, and a force transmission member which follows said input member in the actuating direction and which is often a disk made of elastomeric material and is then referred to as a reaction disk. The abovementioned dimension between the input member and the reaction disk is also referred to by specialists as the z-dimension. This determines essentially the behavior of a brake booster in the initial phase of brake actuation, said behavior also being known as the lockin behavior. If the z-dimension is small, the vehicle brake system responds, in the case of a predetermined brake actuating force, to a lesser extent than if the z-dimension is larger. Even small changes in the z-dimension lead to detectable changes in the response behavior of the brake booster, which is why as good a compensation of tolerance as possible is desirable at this point, so that a required characteristic can also be maintained reliably in mass production.
Another important dimension occurs between the output member of a brake booster and a downstream subassembly, for example a brake master cylinder. Here too, the unavoidable length tolerances lead to greater or lesser idle travels which have an undesirable influence on the behavior of the brake system during actuation.
Two different methods have been proposed for achieving tolerance compensation, and both of these are used in practice. The first method establishes the deviation between an actual dimension and a desired dimension by measurements on the partly assembled brake booster and then, by using corresponding distance compensating pieces, for example distance disks, ensures that as close an approximation as possible to a predetermined desirable length is obtained. This presupposes that the distance compensating pieces, disks, rings or the like, are available in a relatively large number of graded sizes. It is nevertheless only ever possible to achieve an approximation to the desired dimension in this way. Furthermore, installing these distance compensating means during the assembly of a brake booster is time consuming and therefore costly on account of the necessary checks of the installed thicknesses and, if appropriate, also of the installation position. If a plurality of distance disks or rings have to be used, the unavoidable waviness of these parts may also result in a spring system which, in turn, has an undesirable influence on the characteristic of the brake booster or the brake system.
The second method is to design specific parts so as to be adjustable in length along the actuating travel of the brake booster, so that a specific desired length can subsequently be set. Such a solution is known, for example, from DE 42 08 384 A1. So that the length of the component of variable length can be set, even when the brake booster is already installed in a vehicle, DE 43 17 490 A1 proposes a tubular sleeve with an extension which allows the sleeve and a part, coupled thereto, of a multipart valve piston to rotate.
The setting work to be carried out for distance compensation is likewise time consuming and, together with the price which in any case is higher for a
REFERENCES:
patent: 3807280 (1974-04-01), Green et al.
patent: 5016520 (1991-05-01), Gautier
patent: 5233905 (1993-08-01), Fecher
patent: 5293808 (1994-03-01), Rueffer et al.
patent: 5452644 (1995-09-01), Bauer et al.
patent: 5518305 (1996-05-01), Jakobi et al.
Look Edward K.
Lucas Industries Public Limited Company
Rodriguez Hermes
LandOfFree
Brake servo unit and method assembling said unit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Brake servo unit and method assembling said unit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Brake servo unit and method assembling said unit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1329152