US 4,914,916 A · Tandem master cylinder with electromagnetic position sensors for each piston

Abstract

A brake failure warning system for a dual hydraulic master cylinder for use with a motor vehicle. The warning system employs a pair of Hall Effect magnetic sensors which are positioned on the exterior of a plastic cylinder in association with the two pistons mounted within the bore of the cylinder. The pistons have ferrous frustoconical portions which coact with the respective sensors to generate position signals that vary as the pistons move in the bore past the respective sensors. The two position signals are fed to a logic board which compares the signals and generates an error or warning signal in the event that the difference between the two signals exceeds a predetermined amount indicative of failure of one of the two braking systems of the vehicle.

Claims19

Dependent claims

A hydraulic master cylinder assembly comprising:

(A) a cylinder formed of a nonferrous material and defining an axial bore;
(B) first and second pistons, each including a portion formed of a ferrous material, mounted for stroking reciprocal joint axial movement in said bore an coacting with said cylinder to define first and second pressure chambers in said cylinder;
(C) first and second discharge ports in said cylinder communicating respectively with said first and second pressure chambers so that pressurized fluid is delivered through said first and second discharge ports in response to stroking axial movement of said pistons in said bore;
and
(D) sensing means including a magnetic sensor associated with each piston, operative to continuously sense the individual instantaneous axial positions of each piston in said bore as the pistons undergo reciprocal stroking movement in said bore and to continuously generate first and second signals respectively and continuously representing the instantaneous sensed position of said first and second pistons in said bore.

2 more elements

A hydraulic master cylinder assembly comprising:

(A) a cylinder defining an axial bore;
(B) first and second pistons mounted for stroking reciprocal joint axial movement in said bore and coacting with said cylinder to define first and second pressure chambers in said cylinder;
(C) first and second discharge ports in said cylinder communicating respectively with said first and second communicating respectively with said first and second pressure chambers so that pressurized fluid is delivered through said first and second discharge ports in response to stroking axial movement of said pistons in said bore;
and
(D) sensing means operative to sense the individual axial positions of each piston in said bore as the pistons move linearly in said bore;
(E) said sensing means comprising a first sensor associated with said first piston and operative to generate an electrical signal that varies in magnitude in proportion to the axial position of said first piston in said bore and a second sensor associated with said second piston and operative to generate an electrical signal that varies in magnitude in proportion to the axial position of said second piston in said bore;
(F) said sensors being operative to generate electrical signals that remain substantially identical to each other in response to substantially identical joint movement of said pistons in said bore but vary from each other in response to differential movement of said pistons in said bore;
(G) said sensing means being operative to generate a warning signal in response to signals from said first and second sensors that vary from each other by a predetermined amount;
(H) said sensing means further including a first comparator receiving the output signal from said first and second sensors and operative to generate an output signal inlcuding an error signal representing any variations between said sensor output signals, a second comparator receiving the output signal from said first comparator and operative to generate a warning output signal when the received signal exceeds a predetermined maximum threshold signal level and a third comparator and operative to generate a warning output signal when the received signal is less than a predetermined minimum threshold signal level.

6 more elements

A hydraulic master cylinder assembly comprising:

(A) a cylinder formed of a non-ferrous material and defining an axial bore;
(B) first and second pistons mounted for stroking reciprocal joint axial movement in said bore, each including a ferrous portion of varying cross-sectional configuration measured along the axis thereof, and respectively coacting with said cylinder to define first and second pressure chambers in said cylinder;
(C) first and second discharge ports in said cylinder communication respectively with said first and second pressure chambers so that pressurized fluid is delivered through said first and second discharge ports in response to stroking axial movement of said pistons in said bore;
(D) a first magnetic sensor mounted on said cylinder exteriorly of said bore proximate the ferrous portion of said first piston and operative to establish a magnetic field extending through the non-ferrous material of said cylinder and into said bore for coaction with said varying cross-sectional configuration of said first piston ferrous portion to generate a first position signal that varies with variations in the axial position of said first piston in said bore;
and
(E) a second magnetic sensor mounted on said cylinder exteriorly of said bore proximate the ferrous portion of said second piston and operative to establish a magnetic field extending through the non-ferrous material of said cylinder and into said bore for coaction with said varying cross-sectional configuration of said second piston ferrous portion to generate a second position signal that varies with variations in the axial position of said second piston in said bore.

3 more elements

Dependencies are inferred from the claim text.

Tandem master cylinder with electromagnetic position sensors for each piston

Life of this patent

Tandem master cylinder with electromagnetic position sensors for each piston

Life of this patent

Abstract

Claims19