Power plants – Pressure fluid source and motor – Pulsator
Patent
1994-11-21
1996-11-12
Ryznic, John E.
Power plants
Pressure fluid source and motor
Pulsator
60554, 913692, B60T 1320, F15B 910
Patent
active
055728707
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a boosted brake device for a motor vehicle, comprising, on the one hand, a master cylinder filled with a brake fluid and equipped with a main hydraulic piston intended to receive an actuation force composed of an input force and a boost force both acting in an axial direction, and, on the other hand, a pneumatic booster capable of being activated by applying the said input force to a control rod controlling the opening of a valve, in order to exert the actuation force on the main hydraulic piston, the booster comprising a rigid casing separated in leaktight fashion into two chambers by means of at least one movable partition, capable, under the effect of a pressure difference established between the two chambers by opening the valve, of moving in the same direction as a pneumatic piston carrying the valve and itself also capable of moving with respect to the casing, the input force being transmitted via a reaction disk on which the pneumatic piston also bears in order to supply to it at least part of the boost force.
A device of this type is well known in the prior art and is described in, for example, U.S. Pat. No. 4,491,058.
Such a braking device has the advantage, resulting from the use of a pneumatic piston which can move with respect to the rigid casing, that the total travel available for the control rod, and therefore for the brake pedal, is relatively long, which constitutes a condition necessary for ensuring optimum control of the deceleration of the vehicle during braking.
However, this condition, although necessary, is not sufficient and this control is lessened in current boosted braking devices by the fact that to obtain the minimum pressure necessary to start braking requires a very long initial travel of the control rod.
The object of the present invention is to allow an optimization of the control, by the driver of a vehicle, of the deceleration of the latter by proposing a boosted braking device, the effectiveness of which is manifested right from the onset of braking that is to say after a very short initial travel of the brake pedal.
To this end, the device of the present invention is essentially characterized in that the movable partition is mounted so that it can slide freely with respect to the pneumatic piston, in that the main hydraulic piston of the master cylinder itself includes a hollow movable cylinder which communicates with the master cylinder which is secured to the movable partition, and inside which there slides, in leaktight fashion and in the axial direction, a secondary hydraulic piston capable of receiving at least the said input force coming from the reaction disk, and in that the free sliding of the movable partition with respect to the pneumatic piston is limited, for a movement of this partition toward the master cylinder, by the secondary hydraulic piston being driven in this same direction, by the movable cylinder.
According to a preferred embodiment of the invention, the movable cylinder exhibits an internal stop capable of interacting with the secondary hydraulic piston in order to drive the latter.
Apart from the advantages already outlined and the simplicity of manufacturing and adjustment to which they lead, these features make it possible, on the one hand, to ensure that any failure of the primary hydraulic circuit still has no consequence on the value of the amplification ratio of the booster and, on the other hand, to adjust the respective hydraulic sections of the movable cylinder and of the secondary hydraulic piston independently of the value of this amplification ratio.
Other features and advantages of the invention will emerge clearly from the description which is given hereinafter, by way of indication and without any limitation, with reference to the appended drawings, in which:
FIG. 1 is a partial sectional view of a device in accordance with the invention; and
FIG. 2 is a diagrammatic and partial sectional view of the same device.
Insofar as the invention only relates to an improvement made to braking systems with
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Castel Philippe
Castello Olivier
AlliedSignal Europe Services Techniques
McCormick Jr. Leo H.
Ryznic John E.
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