Patent Application
20090240414
This invention relates generally to vehicle braking systems and, more particularly, to suppression of brake noise via brake system pressure modulation.
Brake noise is a result of the excitation of a brake corner component, e.g. a brake rotor, a brake drum, a caliper bracket, etc., by the friction material. This phenomenon is also known as friction-induced vibration or friction instability, the onset of which is typically attributed to an increase in the friction between a brake pad and a brake rotor under a certain set of conditions, e.g. low ambient temperatures, light brake applies, high humidity, etc. The energy from the friction instability is dissipated through the brake corner component, in the form of a squeal, or through a chassis component, in the form of a groan.
One known technique of brake noise suppression includes a brake system that detects an ideal squeal condition and, if certain conditions are met during a brake apply, partially relieves the brake system pressure and then reapplies the brake system pressure as a one-time occurrence. Further, if the ideal squeal conditions are met in an off-brake condition, this known technique lightly activates the brake so as to minimize the possibility of the onset of stick/slip.
Other known techniques of brake noise suppression attempt to suppress brake squeal via control of the friction forcing function using piezoelectric stacks, e.g. dither control, or closed-loop hydraulic pressure control to avoid particular conditions that can cause brake squeal.
Further, other known techniques of brake noise suppression include physical modifications of the brake system, e.g. the addition of lining chamfers and/or pad shims, or the use of low coefficient friction linings and/or damped iron rotors, which can be costly and represent some measure of additional risk to implement.
A method of brake noise suppression via brake system pressure modulation is disclosed including the steps of: detecting a brake apply and modulating a brake system pressure to disrupt formation of a friction instability upon detection of the brake apply.
In one example embodiment, the brake system pressure is modulated at each brake apply detected.
In another example embodiment, the method further includes the steps of: determining whether the brake apply detected is of a brake apply type that is indicative of brake noise; and modulating the brake system pressure to disrupt formation of the friction instability only when the brake apply type is indicative of brake noise, for example but not limited to, light brake applies, low vehicle speeds and/or low ambient temperature.
In yet another example embodiment, the method further includes the steps of: identifying a limit cycle associated with a noise-inducing friction instability; determining whether the brake apply is associated with a noise-inducing friction instability; and modulating the brake system pressure to disrupt formation of the noise-inducing friction instability by hindering development of the limit cycle associated with the noise-inducing friction instability.
In yet another example embodiment, the method further includes the steps of: detecting a brake noise; and modulating the brake system pressure only upon detection of the brake noise.
The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.
Referring to the drawings, wherein like reference numbers refer to like components,
As a driver (not shown) exerts pressure on the brake pedal 16, hydraulic pressure within the master cylinder 12 increases. The hydraulic brake unit or ABS modulator 14 sends the hydraulic pressure through brake lines 18 to wheels RF, LF, RR, and LR located at each of the four corners of the vehicle.
Each of the two front wheels, RF and LF, of the vehicle are equipped with disk brake systems 20. Each of the two rear wheels, RR and LR, of the vehicle are equipped with drum brake systems 22.
Each of the two front disk brake systems 20 includes a brake rotor or disk 24 mounted to a hub 26. A caliper 28 includes brake pads 30, which interact with the brake rotor 24 to cause the rotation of wheels RF and LF to slow and/or eventually stop. Each of the calipers 28 engages and/or disengages their respective brake pads 30, exerting and/or relieving an applied braking force, based on a change in the hydraulic pressure received through brake lines 18.
Each of the two rear drum brake systems 22 includes a brake drum 40 and a pair of brake shoes 42. A brake pad 44 is mounted to each of the brake shoes 42 and the brake pads 44 interact with an inner surface 46 of each of the brake drums 40 to cause the rotation of wheels RR and LR to slow and/or eventually stop. A hydraulic brake cylinder 48 is operable to receive the hydraulic pressure from the brake lines 18 and to deliver hydraulic pressure to each of the brake shoes 42.
In response, each of the brake shoes 42 engages and/or disengages their respective brake pads 44, exerting and/or relieving an applied brake force, based on a change in the hydraulic pressure received through the brake lines 18.
The hydraulic brake unit 14 includes a controller, shown generally as 50, which is operable to detect the brake apply received from the brake pedal 16 and to modulate the hydraulic pressure delivered through the brake lines 18 to each of the wheels RF, LF, RR and LR, to modulate the applied brake force.
As a driver (not shown) exerts pressure on the brake pedal 116, the electronic controller 150 is operable to transmit the electronic input to wheels RF, LF, RR, and LR located at each of the four corners of the vehicle.
Each of the two front wheels, RF and LF, of the vehicle are equipped with disk brake systems 120. Each of the two rear wheels, RR and LR, of the vehicle are equipped with drum brake systems 122.
Each of the two front disk brake systems 120 includes a brake rotor or disk 124 mounted to a hub 126. A caliper 128 includes brake pads 130, which interact with the brake rotor 124 to cause the rotation of wheels RF and LF to slow and/or eventually stop. Each of the calipers 128 engages and/or disengages their respective brake pads 130, exerting and/or relieving an applied braking force, based on the electronic input received from the electronic controller 150.
Each of the two rear drum brake systems 122 includes a brake drum 140 and a pair of brake shoes 142. A brake pad 144 is mounted to each of the brake shoes 142 and the brake pads 144 interact with an inner surface 146 of each of the brake drums 140 to cause the rotation of wheels RR and LR to slow and/or eventually stop. A hydraulic brake cylinder 148 is operable to receive the electronic input from the electronic controller 150 and to exert hydraulic pressure to each of the brake shoes 142.
In response, each of the brake shoes 142 engages and/or disengages their respective brake pads 144, exerting and/or relieving an applied brake force, based on the electronic input received from the electronic controller 150.
The electronic controller 150 is operable to detect the brake apply received from the brake pedal 116 and to modulate a hydraulic pressure at each of the wheels RF, LF, RR and LR, to modulate the applied brake force.
At each applied brake force interface, i.e. between the brake pads 30, 130 and the brake rotor 24, 124 and between the brake pads 44, 144 and the brake drums 40, 140, there exists an opportunity for brake noise, which is the excitation of a brake corner component, for example but not limited to, a brake rotor, a brake drum, a brake caliper bracket or the like, by the friction material, i.e. the brake pad. This phenomenon is known as friction-induced vibration or friction instability. The energy from the friction instability is dissipated through the brake rotor or the caliper bracket as brake noise, in the form of a groan.
As a driver (not shown) exerts pressure on the brake pedal 116, the electronic controller 150 is operable to transmit the electronic input to wheels RF, LF, RR, and LR located at each of the four corners of the vehicle.
Each of the two front wheels, RF and LF, and each of the two rear wheels RR and LR, of the vehicle are equipped with disk brake systems 120. Each of the disk brake systems 120 includes a brake rotor or disk 124 mounted to a hub 126. A caliper 128 includes brake pads 130, which interact with the brake rotor 124 to cause the rotation of wheels RF and LF to slow and/or eventually stop.
An electric motor 162 is mounted in electrical communication with each of the calipers 128 and the electronic controller 150. Each caliper 128 is operable to engage and/or disengage their respective brake pads 130, exerting and/or relieving an applied braking force, based on the electronic input received from the electronic controller 150.
The electronic controller 150 is operable to detect the brake apply received from the brake pedal 116 and to control each of the electric motors 162 located at each of the wheels RF, LF, RR and LR, to modulate the applied brake force.
In one example embodiment, as illustrated in
In another example embodiment, as illustrated in
In yet another example embodiment, as illustrated in
In yet another example embodiment, as illustrated in
In each of the disclosed example embodiments discussed above, the brake system pressure modulation results in modulation of a normal force on the brake lining and the friction force, thereby disrupting the formation of friction instabilities. The modulation is of a small enough magnitude that the driver is unaware of any modulation.
Further, as discussed above, in the hydraulic braking system illustrated in
Finally, as discussed above, in the electric braking system illustrated in
While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.
