The invention relates to a brake booster for a manually controlled brake and to a hand brake applying such a booster.
In general, hand brakes known in the field of automotive engineering employ a lever allowing wheel brakes to be operated via a transmission involving cables and/or linkages. These brakes generally act on the rear wheels of the vehicle.
Applying and releasing these brakes are operations that are not necessarily easy for certain users to perform. This is why certain vehicles are now fitted with parking brakes that are motorized or controlled by an actuator. Certain vehicles are even fitted with automatic parking brakes which come into operation as soon as the engine stops.
However, these systems display certain disadvantages. In particular, these systems are unable, except with great difficulty or alternatively are entirely unable, to take account of the conditions in which the vehicle has stopped, such as the inclination of the ground on which the vehicle has stopped. These systems apply a practically standard braking force to the wheel brake devices. This being the case, under certain situations in which the vehicle has come to a standstill, the braking force is excessive. A smaller force could be applied and prove entirely satisfactory. This then results in additional and needless wear and tear on the braking system.
Furthermore, with such brakes, the driver is unable to control the strength of the braking action. In certain circumstances, that may prove to be a disadvantage. For example, in the case of hill starts, the driver is unable to operate the brakes and a complicated electronic control system needs to be provided.
In the case of controlled side skids, the driver is unable to use the hand brake to control the side skid.
Hand brake systems in which the driver maintains control over the strength of the braking still have some advantages. Specifically, the driver is able to meter the strength of the braking according to the lie of the land and avoid applying excessive braking in configurations which do not demand it, thus avoiding needless wear and tear on the braking system. The driver can also use the hand brake to perform a controlled side skid.
Furthermore, under the effect of heat the braking components may expand and the driver can meter the amount of braking according to the feedback he feels through his hand when operating the hand brake. Likewise, when this type of brake is being used as an emergency braking device, the amount of braking can be reduced if the wheels lock up.
By contrast, it is known that conventional hand brakes are sometimes difficult for certain drivers to use. For example, either, through lack of strength, these drivers are unable to apply their vehicle's hand brake firmly enough, or they do not know how to release it.