TEXT OF THE DESCRIPTION

Field of the invention

This invention relates to motor-vehicles of the type comprising:

- a plurality of disc brakes associated with the wheels of the motorvehicle,

- each disc brake including a disc connected in rotation with the respective wheel, and a brake caliper provided with brake pads cooperating with the disc,

- a braking system to control the operation of said disc brakes following the intervention of the driver on a brake pedal or following the intervention of an automatic braking system with which the motor-vehicle provided, and

- an electronic controller of said braking system,

- wherein with each disc brake there is associated at least one sensor suitable for sending a signal indicative of the noise generated by the disc brake to said electronic controller.

Prior art

Motor-vehicles of the type indicated above are known for example from US 7,021 ,727 B2, US 2004/0183366 A1 , US 2010/0066164 A1 , and also from EP 3 640 492 A1 .

Object of the invention

The object of this invention is to provide a system for controlling the noise generated by the disc brakes of a motor-vehicle which is capable of distinguishing between noises of different nature and implementing specific interventions for each type of noise detected.

A further object of the invention is to provide a noise control system which is capable of automatically removing, in whole or in part, the cause of the origin of the noise.

A further object of the invention is to achieve said objectives in a simple way, without constructive complications and without any appreciable increase in the production costs of the motor-vehicle.

Summary of the invention

In view of achieving one or more of said objects, the invention relates to a motor-vehicle having the features which have been indicated at the beginning of the present disclosure and further characterized in that said electronic controller is configured to process the output signals by the sensors associated with the disc brakes of the motor-vehicle in order to distinguish between:

- a multi-frequency noise in a frequency range of 200-1500 Hz, this noise being indicative of an oxidized brake disc,

- a noise in a frequency range of 1500-14000 Hz, this noise being indicative of a whistle generated by an incorrect interaction between the brake pad and the respective brake disc, and

- a periodic noise having a period which is variable as a function of the speed of the vehicle, this noise being indicative of a deformed brake disc, said electronic controller being also configured to implement the following corrective functions:

- controlling the braking system, when during braking a noise due to an oxidized brake disc is detected, in such a way as to superimpose a pressure modulation to the pressure with which the brake pads are pressed against the brake disc, the pressure modulation being such as to cause a partial or total removal of a layer of oxide from this brake disc, while simultaneously operating the other brakes of the vehicle in order not to alter their braking performance,

- controlling the braking system, when during braking a whistle generated by a disc brake is detected, in such a way as to superimpose a pressure modulation to the pressure with which the brake pads are pressed against the brake disc, the pressure modulation being such as to modify the interaction between the brake disc and the brake pads of the disc brake, while simultaneously operating the other brakes of the vehicle in order not to alter their braking performance,

- controlling said braking system when, during braking, a periodic noise is detected which is variable as a function of the speed of the vehicle, this noise being indicative of a deformed brake disc, in such a way as to modulate the braking pressure on this disc, so as to reduce an emergence of vibrations that may affect the motor-vehicle, while simultaneously operating the other brakes of the vehicle in order not to alter their braking performance.

According to a further feature, the electronic controller is configured to receive signals from a plurality of motor-vehicle sensors indicating one or more operating parameters of the motor-vehicle, selected, for example, from steering angle, vehicle speed, rotation speed of each wheel, vehicle yaw angle, operating condition of the transmission, and said electronic controller is characterized in that it is configured to define ranges of values of said operating parameters of the vehicle and/or combinations of said ranges of values which determine a safety priority condition, said electronic controller being also configured to disable said corrective functions when a safety priority condition is detected.

In the preferred embodiment, the electronic controller is configured for:

- calculating a parameter indicative of a noise level when during braking a noise due to an oxidized brake disc is detected,

- comparing the calculated value of this parameter with a predetermined threshold value, and

- activating said corrective function as long as the calculated value of this parameter is above said threshold value, and for:

- calculating a parameter indicative of a whistle noise level when a disc brake whistle is detected during braking,

- comparing the calculated value of this parameter with a predetermined threshold value, and

- activating said corrective function as long as the calculated value of this parameter is above said threshold value, and for:

- calculating a parameter indicative of a degree of deformation of the brake disc when a noise due to a deformed brake disc is detected during braking,

- comparing the calculated value of this parameter with a predetermined threshold value, and

- activating said corrective function as long as the calculated value of this parameter is above said threshold value.

In the case where the brake calipers are of the conventional hydraulically operated type, the electronic controller is configured to control the braking system so as to apply modulation to the pressure with which the pressurized fluid is supplied to the brake calipers.

The pressure modulation can consist in a “pressure dither”, i.e. a pressure oscillation having predetermined frequency and amplitude, which is added to the normal pressure signal determined by the braking system.

The invention also relates to the method implemented through the system described above.

Detailed description of the invention

Further features and advantages of the invention will emerge from the following description with reference to the attached drawings, provided purely by way of non-limiting example, in which:

- figure 1 is a scheme of a braking system of a motor-vehicle to which the control system of this invention is applied,

- figure 2 is a schematic sectional view of an embodiment of a disc brake,

- figures 3-5 are flow-charts illustrating different strategies implemented with the control method of this invention, and

- figure 6 shows a series of diagrams relating to the strategies implemented with the method according to the invention.

In figure 1 , the references R1 , R2 respectively indicate the two front wheels and the two rear wheels of a motor-vehicle, each of which is associated with a disc brake, respectively indicated with F1 , F2, F3, F4. Each of the disc brakes F1 -F4 can be made according to any known technique and comprises a disc D rigidly connected to the wheel hub, so as to rotate with the wheel, and a brake caliper C carried by the motor-vehicle structure (not shown) and suitable for engaging the disk D to slow down its rotation.

This invention is applicable to any type of disc brake. By way of a non-limiting example only, figure 2 shows a disc brake with a floating type caliper. However, it should be understood that the invention described herein is of general application and is not limited to any specific type of disc brake. With reference to figure 2, the disc D (of which only the peripheral portion is shown) cooperates with a caliper C including a body C1 , on which a brake pad BP1 is rigidly connected, suitable for engaging one face of the disc D. The opposite face of the disc D is intended to be engaged by a second brake pad BP2 carried by a piston P of the fluid actuator of the brake caliper. The piston P is slidably mounted within a chamber CH defined by the body C1 of the brake caliper. The chamber CH is intended to be supplied with fluid under pressure in such a way as to push the piston P to the left (with reference to the drawing) in such a way as to press the pad BP2 against one face of the disc D. At the same time, the supply of pressurized fluid inside chamber CH also causes the entire body C1 of the brake caliper to move to the right (with reference to the drawing), so that the brake pad BP1 is pressed against the left face (with reference to the drawing) of the disc brake D.

Still according to the prior art, the motor-vehicle is equipped with a braking device 1 (figure 1 ) actuated by a brake pedal 2 and hydraulically connected to a pressure modulator unit 3 which controls the supply of the fluid under pressure to the fluid actuators of the brake calipers C, each fluid actuator being defined, in the example of figure 2, by the chamber CH and by the piston P sliding inside it.

Still according to the prior art, the braking system comprises an electronic controller E connected to the modulator 3 for controlling the operation of the braking system.

At least one of the brake pads BP1 , BP2 of at least some of the disc brakes is associated with a sensor suitable for detecting a parameter indicative of a noise level generated by the disc brake. Figure 2, purely by way of example, shows the use of three sensors S1 , S2, S3 associated with the body C1 of the caliper and with the two supports of the brake pads BP1 , BP2, in the form of accelerometers or sensors of any other known type (for example piezoelectric sensors) suitable for detecting the vibrations of the body with which they are associated.

In figure 1 , the dashed lines are the lines with which the output signals from the sensors associated with the disc brakes are sent to the electronic controller E, which in turn is connected to the modulator 3.

According to the invention, the electronic controller E is configured to process the output signals from the sensors S associated with the disc brakes of the motor-vehicle, in such a way as to distinguish between:

- a multi-frequency noise in a frequency range of 200-1500 Hz, this noise being indicative of an oxidized brake disc,

- a noise in a frequency range of 1500-14000 Hz, this noise being indicative of a whistle generated by an incorrect interaction between the brake pad and the respective brake disc, and

- a periodic noise having a period which is variable as a function of the speed of the vehicle, this noise being indicative of a deformed brake disc.

When, during braking, the electronic controller detects, through said sensors, a noise due to an oxidized brake disc, the same controller E controls the braking system in such a way as to superimpose a pressure modulation to the pressure with which the brake pads are pressed against the brake disc, such as to cause a partial or total removal of an oxide layer from the brake disc, while simultaneously operating the other brakes of the vehicle in order not to alter their braking performance.

If the disc brakes are of the conventional hydraulically actuated type, the electronic controller is configured to control the braking system in such a way as to apply said pressure modulation to the pressure with which the pressurized fluid is supplied to the brake calipers.

Similarly, when, during braking, the electronic controller detects, through said sensors, a whistle generated by a disc brake, the controller controls the braking system in such a way as to superimpose a pressure modulation to the pressure with which the brake pads are pressed against the brake disc, such as to modify the interaction between the brake disc and the brake pads of the disc brake, while simultaneously operating the other brakes of the vehicle in order not to alter their braking performance.

Furthermore, according to the invention, when during braking the electronic controller detects, through said sensors, a periodic noise which varies according to the speed of the vehicle, this noise being indicative of a deformed brake disc, the electronic controller controls the braking system in such a way to modulate the braking pressure on the brake disc, so as to reduce the occurrence of vibrations that may affect the motor-vehicle, while simultaneously operating the other brakes of the vehicle in order not to alter their braking performance.

Preferably, the electronic controller is configured to receive signals from a plurality of motor-vehicle sensors indicating one or more operating parameters of the motor-vehicle, selected, for example, from steering angle, vehicle speed, rotation speed of each wheel, vehicle yaw angle, operating conditions of the transmission and said electronic controller is configured to define ranges of values of such operating parameters of the vehicle and/or combinations of said ranges of values which determine a safety priority condition. The electronic controller is configured to disable the corrective functions described above when a safety priority condition is detected.

In the preferred embodiment, the electronic controller is configured for:

- calculating a parameter indicative of a noise level, when a noise due to an oxidized brake disc is detected during braking,

- comparing the calculated value of this parameter with a predetermined threshold value, and

- activating said corrective function as long as the calculated value of this parameter is above said threshold value, and for:

- calculating a parameter indicative of a whistle noise level, when a disc brake whistle is detected during braking,

- comparing the value of this parameter with a predetermined threshold value, and

- activating said corrective function as long as the calculated value of this parameter is above said threshold value, and for:

- calculating a parameter indicative of the degree of deformation of the disc, when a noise due to a deformed brake disc is detected during braking,

- comparing the calculated value of this parameter with a predetermined threshold value, and

- activating said corrective function as long as the calculated value of this parameter is above said threshold value. Figure 3 shows a flow-chart relating to an example of a strategy implemented in the system according to the invention to reduce or eliminate the noise due to oxidation of the brake disc. Block 101 refers to the operation with which the output signals from the sensors S are received by the electronic controller E. Block 102 indicates the operation with which the electronic controller E calculates a parameter Ri indicative of an oxidized brake disc. In block 103 the system checks whether braking is in progress. If no braking is in progress (output N of block 103) the operations start again from the beginning (therefore without carrying out any corrective function). If the answer in block 103 is affirmative (output Y) it proceeds to block 104, which indicates the operation by which the electronic controller E compares the calculated parameter Ri with a predetermined threshold value Ro. If the calculated parameter is not higher than the threshold value (output N) the operations restart from the beginning. If, on the other hand, the threshold value has been exceeded (output Y), it is checked in block 105 whether the motor-vehicle is in a condition in which priority must be given to safety. If the answer is affirmative (output Y) the operations start again from the beginning, as any corrective function on the brakes is disabled. In the event of a negative response (output N) in block 105, it continues towards the block 106, where it is verified that a number of cycles (“Ne”) greater than a threshold value Nth have not already been performed. In the event of an affirmative response (output Y), an alarm is activated (for example, by turning on a warning light in the motor-vehicle control panel) and the operations start over from the beginning. If the response in block 106 is negative (output N) the system carries out the operation 108 consisting in superimposing a pressure modulation on the braking pressure. Block 109 relates to the increment of the counter of the performed cycles, after which it restarts from the beginning of the operations with a new cycle.

Figure 4 is completely analogous to figure 3 but relates to the strategy that is applied in case a disc brake whistle is detected. In figure 4, the blocks relating to the various operations are indicated with the same reference numbers of figure 3, increased by 100. In block 202 the electronic controller E calculates a parameter Si indicative of a whistle generated by a brake and in block 204 the controller compares the calculated parameter with a threshold value So of that parameter. For the rest, the operations are completely identical to those described with reference to figure 3.

The same applies to the flow-chart of figure 5, where the blocks relating to the various operations have been indicated with the same reference numbers of figure 4, increased by 100. In this case, the electronic controller E processes the signals coming from the sensors to calculate, in block 302, a parameter Oi indicative of the degree of deformation of a brake disc, while in block 305 it compares the calculated parameter with a threshold value Oo of this parameter. In block 308, the electronic controller activates a modulation (in particular a reduction) of the braking pressure, i.e., in the case of a hydraulic system, of the pressure with which the pressurized fluid is supplied to the brake caliper.

The diagram illustrated in figure 6(A) shows the variation over time of the actuating pressure of a brake caliper generated by a driver’s intervention on the brake pedal.

According to the invention, in the case of intervention of the control system, a pressure dither is added to the pressure signal illustrated in the diagram of figure 6(A), for example, which is illustrated in the diagram of figure 6(B). As can be seen, where dither is applied, it consists in pressure oscillations above and below zero, with constant and predetermined amplitude and frequency. The diagram of figure 6(B) shows two different pressure dithers applied in correspondence with the detection of a signal Rll (figure 6(D)) indicative of noise due to an oxidized brake disc, and in correspondence with a signal Fl indicative of a whistle from a brake disc. The system activates the correction function discussed above for each type of noise as long as the presence of the noise is detected. The diagram in figure D shows how following the application of pressure dither, the noise is cancelled. The diagram of figure 6C shows the pressure applied to the brake calipers through the control system of the invention, result of the sum of the pressure signal of the diagram of figure 6(A) and of the pressure signal of the diagram of figure 6(B).

In a preferred embodiment, the pressure dither which is applied by the control system according to the invention has a constant frequency and an amplitude characteristic of the vehicle.

The teachings of this invention are also applicable to motor-vehicles in which drum brakes are provided, in which case at least one sensor of the noise or vibrations generated by the drum brake is associated with each drum brake. The electronic controller E is configured to process the output signal from the sensor associated with the drum brake and to distinguish between the noise generated by an oxidized drum and a whistle generated by an incorrect interaction between the drum and a respective brake shoe.

The electronic controller E is also configured to control the braking system 1 in such a way as to superimpose a pressure modulation to the operating pressure of the brake shoe, in a completely analogous way to what has been described with reference to disc brakes. Naturally, the principle of the invention remaining the same, the details of construction and the embodiments may vary widely with respect to what has been described and illustrated purely by way of example. The sensors associated with the brakes are able to detect both noise and vibration due to oxidation of the drum, and a whistle due to an incorrect interaction between the drum and the respective friction element.