Motors: expansible chamber type – Working member position feedback to motive fluid control – Plural input signal means for single motor valve
Reexamination Certificate
2000-05-10
2001-08-14
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
C303S003000, C303S113400
Reexamination Certificate
active
06272969
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic brake booster according to the preamble of claim
1
. Such a brake booster is known, for example, from DE 44 41 913 A1.
Brake boosters of the type described above, on the one hand, to are operable in a conventional manner directly mechanically e.g. by depressing a brake pedal coupled to the input element of the brake booster and, on the other hand, are operable by an integrated electromagnetic actuator which is controllable by an electronic control unit usually disposed outside of the brake booster. Said brake boosters therefore allow not only operation dependent on the request of a driver but also automatic operation independent of the request of the driver as well as a combination of said two types of operation, i.e. a blend of driver-requested and automatic operation of the brake booster (so-called braking-assistant function).
Before a pneumatic brake booster actually boosts the operating force introduced into it, its response force has to be overcome. The response force results from the presence of one or more restoring springs which return the components, which are displaced in operating direction during operation of a brake booster, into their normal position after operation is terminated. This is explained in greater detail using as an example the already cited DE 44 41 913 A1. Upon a manually initiated operation of the brake booster, an input force is introduced via a substantially rod-shaped input element into the control valve of the brake booster, where it is transmitted to an operating piston. The input element and the operating piston are thus displaced in operating direction relative to the control valve housing. As the operating piston is mechanically coupled to the armature of the electromagnetic arrangement, the armature is also displaced in operating direction, with the result that a first sealing seat is opened and allows aeration of the working chamber of the brake booster. The input element and the armature (not shown in DE 44 41 913 A1) are resiliently biased counter to operating direction. This means that a counterforce in operating direction corresponding to the resilient bias first has to be overcome before the input element, the operating piston and the armature are displaced in operating direction and may therefore open the first valve seat. Said counterforce is referred to as the response force of the brake booster and/or control valve.
Frequently the restoring spring of the armature is simultaneously a system resetting spring, which resets the first sealing seat. Said resetting task requires an increased amount of restoring force because the restoring spring of the armature has to be able to work against the restoring spring of the valve element associated with the first sealing seat so that, when the pressure on the brake pedal is eased, said valve element is displaced counter to operating direction and so a second sealing seat is opened, which establishes a connection between the working chamber and the vacuum chamber of the brake booster so that the pressure in the working chamber may be reduced. Said function has to be always guaranteed, i.e. neither frictional forces nor counteracting spring forces may prevent the described opening of the second sealing seat, which is why a specific force surplus in restoring direction is usually provided. Said force surplus ensuring trouble-free functioning of the control valve however leads to an increase of the response force of the control valve. For comfort reasons and also to make the brake system as finely apportionable as possible, a much lower response force is however desirable.
SUMMARY OF THE INVENTION
The object of the invention is to provide a mechanically and electromagnetically operated brake booster, in which the response force to be overcome by a user is noticeably reduced.
On the basis of a brake booster of the type described, said object is achieved according to the invention in that the device for detecting an operation of the control valve effected by means of the mechanical input element, once such an operation has been detected, during said operation prompts an energizing of the electromagnetic arrangement of an intensity sufficient to reduce the response force of the control valve yet not increase the braking force provided by the brake booster in accordance with the operation.
According to the invention, the energizing of the electromagnetic arrangement is therefore, at most, intense enough for the force generated through energizing of the electromagnetic arrangement and acting in operating direction to correspond precisely to the response force acting counter to operating direction. In said case, the operating force summoned up by a driver is fully available as braking force. In dependence upon the response characteristic desired by a vehicle manufacturer, the reduction of the response force of the brake booster and/or its control valve achieved through energizing of the electromagnetic arrangement may however also be less pronounced. According to the invention, a very comfortable brake booster which responds sensitively even to low operating forces is therefore obtained.
In order to realize the apparatus according to the invention, the controller in any case provided in the generic prior art may, for example, have a preset threshold value, from which the energizing of the electromagnetic arrangement in accordance with the invention sets in. The threshold value may be e.g. a specific force, although a predetermined displacement distance which a selected component has to travel may also be used as a threshold value. As a further advantage, the fact that the electromagnetic arrangement is utilized in accordance with the invention during every braking operation prevents the parts of the electromagnetic arrangement from becoming stuck, which may potentially occur in the case of infrequent use.
According to a preferred refinement of the brake booster according to the invention, said energizing of the electromagnetic arrangement ceases during a movement of the input element counter to operating direction, i.e. during a restoring movement. Thus, during a restoring movement the full restoring force of the provided springs acts upon the components which are to be reset.
Advantageously, the intensity of the energizing of the electromagnetic arrangement which reduces the response force is dependent upon the vehicle speed. For example, the reduction of the response force may be less pronounced at relatively low speeds than at high speeds, thereby avoiding a braking system which responds too “harshly” in the bottom speed range.
Said energizing of the electromagnetic arrangement may moreover be dependent upon the type of braking. Thus, for example, the reduction of the response force may be more pronounced when a very quickly initiated braking operation is detected in order to achieve as fast a response of the braking system as possible. On the other hand, in the event of slow, gentle braking the reduction of the response force may be less extreme in order to make the response behaviour of the braking system more comfortable.
According to a development of the brake booster according to the invention, the intensity of said energizing of the electromagnetic arrangement may vary in a driver-specific manner, i.e. the reduction of the response force is geared to the driver's brake operating style, which is established over an extended period. For example, in the case of a driver who operates the brake system predominantly with relatively strong pressure, the reduction of the response force may be less extreme than in the case of a driver who operates the brake system predominantly in a more timid fashion. To said end, the described device for detecting an operation effected by means of the mechanical input element advantageously comprises a learning algorithm, which is stored in a microprocessor. The learning algorithm in cooperation with suitable sensors prepares a driver-specific operating characteristic, as a function of w
Linden Christoph
Zeuner Lothar
Lucas Industries PLC
MacMillan Sobanski & Todd LLC
Ryznic John E.
LandOfFree
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