Actuation Responsive Brake Pedal Pad Assembly

The present invention relates to devices for providing electrical indication of user-actuation of vehicle brake servoactuator lever arm. The present invention provides a pad assembly for the pedal provided on the brake servoactuator arm with the pad assembly providing an electrical signal indicative of the vehicle operator applying an actuation force to the brake pedal.

Heretofore it has been common practice to provide an electrical switch having the actuator member thereof disposed to sense movement of the pivoted brake servoactuator arm for actuating a switch to energize the vehicle brake lights or stop lamps or other vehicle accessory. Where brake servo lever arm switches are utilized for sensing movement of the arm a minimum amount of movement of the brake pedal has been required in order that the sensing switch can be properly positioned or calibrated for actuation at the time of installation. This is because of the mechanical motion disadvantage of the switch actuator being installed when it is typically between the brake arm pivot and the pedal which is mounted on the end of the lever arm. If a very sensitive switch actuator, as for example a microswitch, is employed, it is extremely difficult to adjust the switch on its mounting in order to properly sense movement of the brake pedal arm from its at-rest position against a resilient stop as typically employed for quietness of operation. If a relatively long-travel switch actuator is employed to render the installation and switch calibration easier, then a prohibitive amount of brake pedal movement is experienced before the sensing switch can close the circuit and the brake actuation signal is delayed for a prohibitively long period of time.

It has thus long been desired to provide a way or means of providing an electrical signal responsive to initial user application of a brake actuating force to the brake pedal in a manner which eliminates the necessity of calibration of a sensing switch with respect to the at-rest and actuated positions of the brake pedal arm.

The present invention provides a unique and novel pad assembly for application on a vehicle brake pedal provided on the end of a pivoted brake servoactuator lever arm. The pad assembly of the present invention comprises an elastomeric pad having the electrically responsive mechanism embedded in the elastomeric material for providing an electrical indication of user application of an actuating force to the surface of the pad.

In one embodiment the elastomeric pad assembly of the present invention operates as a pair of electrical contacts to close a circuit to provide a signal for actuating the vehicle brake lights, or other vehicle accessory.

In other embodiments the pad assembly employs piezoelectric strips embedded therein which are deformed, upon the application by the user of a force to the surface of the elastomeric pad, to thereby provide an electrical signal indicative of the amount of deformation which is generally proportional to the magnitude of the applied force. The present invention thus provides an electrically responsive brake pedal pad assembly which is highly sensitive to the application of a user actuation force to the surface of the pad for providing an electrical signal indicative thereof.

In one embodiment a pair of plastic film strips having a metallized surface are disposed on opposites of an apertured insulating spacer and are embedded in the elastomeric brake pad. Upon application of a brake pad actuating force to the surface of the pad the metallized strips are deformed into the apertures of the spacer and make contact therein to close a circuit for brake light actuation, or other accessory circuit.

In other embodiments of the invention piezoelectric strips are employed embedded in the elastomeric pad in such a manner that relaxation means adjacent the piezoelectric strips permit ready deformation of the piezoelectric material to provide electrical signal responsive to the applied force to the pad. The relaxation means may comprise a recess on one side of the piezoelectric material or elastomeric material of softer composition than the surrounding material.

The electrical signal output from the pad may be fed directly to electronic circuitry located in the support base for the pad on the pedal arm thereby providing for remote actuation of devices such as vehicle accessories related to the braking effort.

FIG. 1 is a section view of the present invention installed on a brake servoactuator arm;

FIG. 2 is an exploded view of the construction of the electrical switch in the embodiment of FIG. 1;

FIGS. 1 and 2 is a portion of a section view of the electrical contacts of the embodiment of FIGS. 1 and 2 in the closed or actuated condition;

FIG. 4 is an axonometric view of an alternate embodiment of the electrical components for the device of FIG. 1; FIG. 5 is a portion of a section view of the embodiment of FIG. 4;

FIG. 6 is a portion of section similar to FIG. 5 and shows an alternate arrangement thereof; and

FIG. 7 is a view similar to FIG. 1 of another embodiment of the invention.

DETAILED DESCRIPTION

Referring to FIG. 1, the invention is illustrated generally at 10 as a brake pad assembly having a cup-shaped rigid support 12 attached to the end of a brake servoactuator lever arm 14 which is typically pivoted on the vehicle structure about the end thereof (not shown) remote from the end illustrated in the drawings. Arm 14 has a wiring access hole 16 and a wiring harness channel 18 provided therein for routing of electrical leads therein.

A cover plate 22 is rigidly attached by any suitable means over the support 12 and provides a rigid backing for the pressure sensitive pad means indicated generally at 20 which is adapted to have a brake actuating force applied by the user or vehicle operator to the outer surface 24 thereof. In the presently preferred practiced, the pad means 20 is formed generally of resilient flexible material such as elastomeric material and has grooves 26, 28 formed in the end portions thereof which are received over the ends of the cover plate 22 which preferably extend outwardly over the support 12 by a minimum amount necessary to provide retention of the pad means 20.

Pad means 20 has an electrical sensor indicated generally at 30 embedded therein for providing an electrical signal upon application of a brake actuating force to surface 24 of the pad means 20.

Referring to FIG. 2, one embodiment of the sensor 30 is illustrated in exploded view as comprising an upper contact strip 32 formed of flexible, preferably plastic, material of a relatively thin configuration and disposed in spaced parallel arrangement with a complementary plastic strip 34. The strips 32, 34 each have adjacent surfaces thereof coated with a suitable electrically conductive metallized coating the coated surface of strip 34 being denoted by reference numeral 36 in FIG. 2. The strips may be formed of a suitable plastic such as polyethylene terrephalate polyester material.

Strips 32, 34 are separated by a distance corresponding to the thickness of a insulating spacer 38 which has a plurality of spaced apertures 40 formed therein in a grid pattern. The spacer 38 is formed of any suitable electrically insulating material as for example polyvinyl chloride plastic. The apertures 40 are sufficiently large to permit strips 32 to be deformed and have the metallized surfaces thereof make contact within the aperture.

Referring to FIG. 3, the embodiment of FIG. 2 is shown in the brake actuated condition wherein the

ad means 20 has a braking force applied thereto sufficient to deform elastomeric material to cause the metallized contact surface 36 of lower layer 34 to make contact with the corresponding metallized layer of the upper strip 32 by deformation through one of the apertures 40 in the spacer plate 38.

Referring to FIG. 2, an electrical lead 44 is attached to the metallized surface 36 and a separate lead 42 is attached to the metallized undersurface of strip 32.

Referring to FIG. 1, the leads 42, 44 extend downwardly through an aperture 46 provided in the cover plate 22 for connection to electronic signal processing means indicated generally at 48 potted in the interior of the support 12.

Referring to FIG. 4, an alternate embodiment of the sensor 130 is illustrated as having a relaxation means comprising spacer 138 formed of elastomeric material preferably of a softer composition or lower durometer on the Shore "A" scale than the elastomeric material of the balance of the pad means 20. The embodiment of FIG. 4 has a plurality of strips of piezoelectric material 132 disposed in spaced parallel arrangement on the upper surface of the spacer 138 with the strips connected to suitable electrical leads such as lead 142 for passage through aperture 46 in the support plate 22 (see FIG. 1).

A second layer of strips of piezoelectric material indicated by the reference numeral 134 in FIG. 4 is disposed in spaced parallel relationship on the undersurface of the elastomeric spacer 138. Strips 134 are preferably disposed generally at right angles to the strips 132 on the upper surface of the spacer 138.

A cross-section of the embodiment of FIG. 4 is shown in FIG. 5 wherein the strips 132 are shown in position on the spacer 138 when the sensor 130 is embedded in pad means 120 which has a surface 124 adapted for having a braking force applied thereto.

Referring to FIG. 6, another embodiment of the invention is shown wherein pad means 220 has a sensor 230 embedded therein which comprises a layer of piezoelectric strips disposed in spaced parallel relationship one of which is denoted by reference numeral 232 in FIG. 6 have a plurality of spaced parallel recesses 236 formed in the elastomeric material adjacent the lower surface of the strips 232. The recesses 224 comprise the relaxation means for permitting downward deflection of spaced regions of the strip 232 upon application of a brake actuating force to the surface 224 of the pad means 20. The strips such as strip 232 are shown in the deformed state in FIG. 6 as the strip would appear with the brake actuating force applied to surface 224. It will be understood that although in the embodiment of FIG. 6 only a single layer of strips is illustrated, that a second layer may be provided spaced between the layer 232 and the cover plate 22 similar to the spacing and arrangement of the strips of the embodiment of FIG. 4.

Referring to FIG. 7, another embodiment of the invention is shown wherein the pad means 320 comprises an integral block of elastomeric material having a sensor 330 which comprises a flat undersurface 321 having a plurality of spaced parallel piezoelectric strips 332 disposed thereon. Pad means 320 has the upper surface 324 thereof adapted for receiving a brake actuating force thereon. The support means 312 mounted to a brake servoactuator arm 14 is bridged by a cover 322 which has the edges thereof upturned to form a recess or channel below the strips 332, which channel comprises the relaxation means for the piezoelectric strips 332. Upon application of a brake actuating force to the surface 324 the flat surface 321 is deflected downward into the recess and strips 332 are correspondingly deformed to provide an electrical signal indicative of the brake actuating force applied to surface 324.

The present invention thus provides a novel and convenient way of providing an electrical signal indicative of application of a brake actuating force to a brake pedal by providing pressure-sensitive sensor means embedded in an elastomeric brake pedal pad.

In one embodiment the sensor comprises spaced metallized surfaces on plastic film which are deformed in apertures in a spacer to make contact thereby completing a circuit for brake light or stop lamp illumination or other vehicle accessory.

In another embodiment the sensor comprises upper and lower layers of piezoelectric strips spaced by suitable relaxation means which may be either soft elastomer or recesses provided in the elastomer to permit deformation of the strips upon application of a brake actuating force to the surface of the pad. In another embodiment the cover plate for mounting of the elastomeric pad has the undersurface spaced a slight amount above and bridging a recess in the support plate for providing the relaxation means as a recess to which the elastomeric pad may be deformed thereby causing piezoelectric strips to provide an output signal indicative of the applied brake actuating force. The assembly of the present invention provides a cup-shaped support which may, if desired, have electronic circuitry for signal conditioning potted therein to thereby permit signal conditioning for remote control functions associated with the braking effort. The present invention thus provides a unique electrical brake actuation force sensor which may be attached to the brake servoactuator arm or mounting on the brake pedal attached to the end of the brake actuating arm.

Although the invention has hereinabove been described with respect to the illustrated embodiments, it will be understood that the invention is capable of modification and variation and is limited only by the following claims.