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.