Motors: expansible chamber type – Working member position feedback to motive fluid control – Plural input signal means for single motor valve
Reexamination Certificate
2000-01-05
2001-07-03
Ryznic, John E. (Department: 3745)
Motors: expansible chamber type
Working member position feedback to motive fluid control
Plural input signal means for single motor valve
Reexamination Certificate
active
06253656
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a sensor assembly for a vacuum brake booster which is in particular adapted to be actuated electromagnetically, and to a vacuum brake booster which is equipped with such a sensor assembly.
Vacuum brake boosters with an electromagnetic al actuation unit are known, for example, from DE 40 28 290 C1. Brake boosters of the mentioned type are equipped with an electromagnetic actuation unit in order to, additionally or alternatively to the normal, leg force-proportional actuation by the driver of a vehicle, actuate the vehicle brake system by controlling the brake booster. In this manner, on the one hand, fully automatic braking operations, i.e. braking operations without any intervention by the driver, can be realized and, on the other hand, a braking operation initiated by the driver can be assisted, which is of advantage in certain situations, e.g. in an emergency braking operation in order to prevent a collision. Investigations have shown that the majority of the drivers do not press the brake pedal sufficiently vigorously in critical situations so that the braking distance is unnecessarily prolonged. In such a case, the mentioned electromagnetic actuation unit provides the possibility e.g. to fully activate the brake booster independent from the leg activation force of the driver and thus provide the maximum possible brake boost (so-called braking assistant). Solutions of this kind are already employed in production vehicles.
For the detection whether a braking operation is an emergency braking and consequently when the electromagnetic actuation unit of the brake booster is to be activated, as well as for the realisation of completely automatic braking operations, for example in cooperation with a vehicle-to-vehicle distance control system, it is necessary to know the currently prevailing pressure conditions in the brake booster, which are, as a rule, provided to an electronic controller which processes certain parameters of the brake booster and/or a master cylinder connected therewith in order to control the electromagnetic actuation unit in the desired manner. Such a controller is generally arranged remote from the brake booster and is in electrical connection with the latter via electrical lines and is possibly in fluid connection therewith via hoses or tubes. EP 0 306 721 B1 proposes to accommodate the controller in the housing of the brake booster. Such a solution, however, requires a specially designed brake booster housing and therefore opposes an efficient series production of different brake boosters.
The knowledge of the currently prevailing pressure conditions in a vacuum brake booster can also be desired for other reasons, even with a vacuum brake booster which cannot be actuated electromagnetically.
SUMMARY OF THE INVENTION
The invention is based on the object to provide a sensor assembly for a vacuum brake booster the constructive design of which is as compact as possible and the functional and electrical connection of which to a vacuum brake booster is facilitated.
According to the invention, this object is solved by a sensor assembly having the features specified in claim
1
. The sensor assembly according to the invention is characterised in that the entire sensor system and sensor connection technique, which is required for the determination of the pressure conditions currently prevailing in the brake booster, is integrated in the sensor assembly so that the sensor assembly can be flange-mounted directly to the brake booster most easily. The direct flange-mounting of the sensor assembly according to the invention is not only easy to install and in addition space-saving but also results in short connection paths of the electrical lines and the fluid connections which are thus unsusceptible to failure. The sensor assembly according to the invention, when connected to a controller which may be integrated in the sensor assembly, is capable of determining the pressure difference currently prevailing at the or at one of the walls of the brake booster by means of its differential pressure sensor and the two air ducts and establishing the currently effective brake boost therefrom.
In a preferred embodiment of the sensor assembly according to the invention both air ducts are rigid. In such an embodiment the sensor assembly is connected both functionally and mechanically with the brake booster by means of the two air ducts.
The first and/or the second air ducts are advantageously integrally formed with the housing of the sensor assembly so that the entire pre-assembled sensor assembly can be connected with the brake booster in one operation. The mentioned integral configuration can be achieved particularly well if the housing of the sensor assembly is a plastic injection moulded part at which the air ducts are integrally formed.
Preferably, retaining arms for the differential pressure sensor are provided in the housing of the sensor assembly, which according to an configuration advantageous in terms of manufacture are integrally formed with the housing and/or the air ducts. During the installation, the differential pressure sensor locks with the retaining arms so that it is securely held in the locks with of the sensor assembly without requiring further adjusting operations.
According to one embodiment of the sensor assembly according to the invention the two air ducts are arranged one inside the other. For example, the second air duct coaxially surrounds the first air duct. This embodiment is space saving and requires only one single passage in the brake booster housing for both air ducts.
The air ducts are preferably adapted to be locked with the brake booster housing by means of a locking projection, in particular a circumferential one. This enables a simple and secure installation of the sensor assembly at the brake booster, since the air ducts are simply inserted into the brake booster housing until they come into locking engagement, which also secures the sensor assembly itself.
The first air duct which extends as far as into the working chamber of the brake booster is preferably provided, in its end section facing the working chamber, with openings penetrating the duct wall, which provide for a fluid connection of the working chamber with the first air duct. This configuration makes it possible to continue the first air duct e.g. by means of an elastomeric bellows through the brake booster housing so that the first air duct, besides its primary purpose of providing a fluid connection between the working chamber of the brake booster and the differential pressure sensor in the sensor assembly, can also accommodate electrical lines which in this manner can be routed in a space-saving way from the sensor assembly or the controller, respectively, through the brake booster to the electromagnetic actuation unit. Advantageously, the first air duct is dimensioned such that it provides space for the mentioned electrical connecting lines.
According to a further embodiment of the sensor assembly according to the invention, a plug-type or socket-type connector for a further sensor is provided at the housing of same. In this manner, for example, a hydraulic pressure sensor can be connected easily, which supplies the hydraulic pressure in at least one brake circuit of a hydraulic vehicle brake system as a further parameter to the controller. It is thereby possible to improve the activation behaviour of an electronically controlled brake booster and to achieve a more comfortable operational performance.
In a brake booster equipped with the sensor assembly according to the invention, the sensor assembly is preferably secured to the brake booster by means of one or several locking projections which are circumferentially formed on the outer surface of the second air duct (with a coaxial arrangement of the two air ducts) or on the outer surface of both air ducts, these locking projections being sealingly locked behind rubber sleeves inside the brake booster housing. The rubber sleeves are fitted in those passages in the brake bo
Lucas Industries Public Limited Company
MacMillan Sobanski & Todd LLC
Ryznic John E.
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