System for detecting the clamping between disc and brake caliper, and method for adjusting the braking action applied on a brake disc by a brake caliper equipped with such system

Abstract

A system for detecting the clamping between disc and brake caliper, in a braking system, comprises a brake caliper (10) of a floating type, comprising a brake caliper body configured to support a pair of brake pads (12), adapted to engage a brake disc (14) from opposite sides thereof, and a proximity sensor (16), mounted to said brake caliper body on the reaction side of the brake caliper (10), i.e., on the side of said body configured to support the brake pad (12) intended to come into contact with the brake disc (14) secondly, said proximity sensor (16) being adapted to measure the relative displacement between said reaction side of the brake caliper (10) and the brake disc (14).

Description

[0001] System for detecting the clamping between disc and brake caliper, and method for adjusting the braking action applied on a brake disc by a brake caliper equipped with such system

[0002] Technical field

[0003] The present invention relates, in general, to the field of braking systems for vehicles; in particular, the invention relates to a system for detecting the clamping between disc and brake caliper, and to a method for controlling and adjusting the braking action applied on a brake disc by a brake caliper equipped with such system.

[0004] Prior art

[0005] In the background art, various solutions are provided for detecting the contact between caliper and brake disc. This contact is defined as the moment in which both pads of the caliper come into contact with the disc, a condition which is also referred to as “caliper-disc bite” or, equivalently, “caliper-to-disc touch”. For a caliper of the floating type, such a condition conventionally provides that the outer side of the caliper (the so-called reaction side) comes into contact with the disc slightly after the inner pad.

[0006] An electromechanical caliper is a caliper of the floating type, designed for the braking of vehicles, wherein the braking force actuation is generated by an electric motor that mechanically couples to a motion transmission system. The motion is transmitted from the electric motor to the caliper piston, which, in turn, transfers the braking action to the pad and then to the disc. The pad in contact with the piston is defined as inner pad. When the inner pad comes into contact with the disc, the floating part of the caliper, named reaction side, is drawn, taking the outer pad into contact with the disc in turn. The step of motion transmission from the electric motor to the piston, and the consequent drawing of the reaction side, is called approach step. During the approach step, the force applied by the caliper remains substantially constant. The approach step ends when the outer pad comes into contact with the disc. This is called the “caliper-disc bite” instant. From this moment onward, the braking force may increase with respect to the force required for the braking of the vehicle. For electro-mechanical type calipers, controlling and consequently detecting the clamping force is extremely important for performing the braking action, and there is an extensive literature mainly focused on the development of a sensorless electro-mechanical caliper, i.e., without a sensor dedicated to such detection, wherein, in general, the topic of the detection of caliper-disc contact and clamping is addressed by software algorithms.

[0007] For example, documents CN117681839A and CN117681839A implement an estimation of the “clamping force-caliper deformation” characteristic during parking operations.

[0008] KR20220086144 A provides the removal of the force sensor and the implementation of motor current measurement for estimating the clamping force, including additional stiffness in the transmission of motion between motor and piston.

[0009] CN117681840A suggests to estimate the force-deformation characteristic from the motor angle and motor current measurement.

[0010] There are also various scientific publications that address the sensorless control of by-wire brake calipers, for example:

[0011] Putz, M.H.; Seifert, H.; Zach, M.; Schiffer, M.; Peternel, J.: “Accuracy of Sensor-Less Control of an Electro-Mechanical Brake” - SAE Technical Paper Series; SAE World Congress & Exhibition: Detroit, MI, USA, 2015;

[0012] Schwarz, R.; Isermann, R.; Bohm, J.; Nell, J.; Rieth, P.: “Clamping Force Estimation for a Brake-by-Wire Actuator” - SAE Technical Paper Series; SAE World Congress & Exhibition: Detroit, MI, USA, 1999;

[0013] Ki, Y.-H.; Ahn, H.-S.; Cheon, J.S.: “Fault-Tolerant Control of EMB Systems” - SAE Int. J. Passeng. Cars Electron. Electr. Syst. 2012, 5, 579-589;

[0014] Hoseinnezhad, R.; Saric, S.; Bab-Hadiashar, A.: “Estimation of Clamp Force in Brake-by- Wire Systems: A Step-by-Step Identification Approach” - SAE Technical Paper Series; SAE World Congress & Exhibition: Detroit, MI, USA, 2006;

[0015] Schmidt, P.B.; Gasperi, M.L.; Ray, G.; Wijenayake, A.H.: “Initial rotor angle detection of a nonsalient pole permanent magnet synchronous machine” - Proceedings of the IAS’97. Conference Record of the 1997 IEEE Industry Applications Conference, Thirty-Second IAS Annual Meeting, New Orleans, LA, USA, 5-9 October 1997;

[0016] Hwang, W.; Han, K.; Huh, K.: “Fault detection and diagnosis of the electromechanical brake based on observer and parity space” - Int. J. Automot. Technol. 2012, 13, 845-851

[0017] The above solutions relate to the use of sensorless algorithms, which nonetheless are affected by poor control strategy accuracy evaluation, for example, when dealing with braking system variations or braking behavior. The poor control accuracy derives from the error in identifying, via software, the beginning of the step of braking, in other words, the poor accuracy resides in the caliper-disc bite estimation error.

[0018] Summary of the invention

[0019] It is an object of the present invention to overcome the aforementioned problems.

[0020] To obtain such a result, a detection system and an adjustment method according to the present invention are based on the consideration that the reaction side movement, in a floating brake caliper, is subsequent to the inner pad movement, or, more precisely, to the moment at which the inner pad comes into contact with the disc, as described above. Therefore, the caliper-disc bite may be detected by measuring the reaction side displacement, i.e., the occurrence of the condition wherein both pads are in contact with the disc after the approach step is concluded.

[0021] By virtue of this principle, it is possible to couple a low-cost displacement sensor to a conventional sensorless type caliper control strategy, which allows the force sensor to be eliminated, with advantages in terms of layout, dimensions, weight, and costs of the caliper. Furthermore, an increase in the system accuracy is plausible, given the impossibility of having a low-cost force sensor that is particularly accurate over such a wide operating range (in terms of measured force).

[0022] According to the invention, a proximity sensor is mounted on the reaction side of a floating brake caliper (the proximity sensor being preferably of the inductive type, but in any event the control strategy can be implemented by integrating any displacement sensor which ensures, for example, a measurement accuracy lower than one millimeter), adapted to measure the relative displacement between the reaction side of the caliper and the brake disc, i.e., the extent of the displacement of the reaction side of the caliper in the direction of the disc and / or the distance between the reaction side of the caliper and the disc.

[0023] The inductive sensor may be, for example, an eddy current sensor, adapted to be positioned in front of the brake disc and magnetically coupled to the disc itself.

[0024] According to an embodiment, the caliper may be a hydraulic or pneumatic floating caliper, e.g., for applications on trucks, passenger cars or motorcycles. A similar principle is also implementable for the application to fixed calipers, by integrating the sensor on the caliper itself, at the inner or outer side, a principle pertaining to the measurement of deformation of the caliper at the beginning and during braking.

[0025] With respect to the prior art, the solution is effective, low cost and the particular type of sensor described (inductive sensor, capable of magnetically coupling to the brake disc) makes it possible to integrate other functions in the sensor itself (e.g., crack detection, disc wear estimation, etc.), and to enrich the value proposition of an intelligent braking system.

[0026] A solution according to the invention may further be implemented in a hybrid approach, wherein the proximity sensor may be used for detecting the instant in which the pads touch the disc (bite) and the caliper is controlled with a conventional sensorless strategy, as a function of the caliper force-deformation curve.

[0027] The advantage is not only linked to greater reliability with respect to product and use tolerances, but also to a reduction in development times and costs, since a smaller effort is required for calibration, which is necessary to implement a conventional sensorless strategy.

[0028] According to a further aspect of the invention, a method for detecting the clamping between the disc and the brake caliper provides the step of emitting a “disc bite flag” (i.e., a signal indicative of the occurrence of contact by both pads with the disc) as an output of the proximity sensor, to indicate that a bite of the caliper on the disc has occurred. The “disc bite flag” triggers the switch from the position control (performed during the approach step) to the force control (performed during the step of increasing the clamping force and executing the actual braking action) so that, during the position control, the clearance between caliper and disc is taken up in the shortest time possible. During the force control, the brake caliper actuator is controlled with a force feedback loop wherein the force feedback is given by the estimate of the generated force, extrapolated from a caliper stiffness curve.

[0029] These and other objects and advantages are achieved, according to an aspect of the invention, by a system and a method having the features defined in the appended claims.

[0030] Brief description of the drawings

[0031] The functional and structural features of some preferred embodiments of a system and method according to the invention will now be described. Reference is made to the accompanying drawings, wherein: figure l is a perspective view of a proximity sensor, according to an embodiment of the present invention; figure 2 is a perspective view of a brake caliper equipped with the proximity sensor in figure 1, associated with a brake disc, according to an embodiment of the present invention; figure 3 is a diagrammatic perspective view of a brake caliper and disc assembly, according to an embodiment of the present invention; figure 4 is a diagram of the proximity sensor output voltage, as a function of the clamping force applied by the caliper on the disc, measured under static bench test conditions in the absence of disc rotation, according to an embodiment of the present invention; and figure 5 is a diagram indicative of the steps of a method for adjusting the braking action applied by a brake disc and brake caliper assembly equipped with a system for detecting the clamping between the disc and the caliper, according to an embodiment of the invention.

[0032] Detailed description Before explaining a plurality of embodiments of the invention in detail, it is worth noting that the application of the invention is not limited to the constructive details and to the configuration of the components presented in the following description or shown in the drawings. The invention can take other embodiments and may be implemented or made in practice in different manners. It must also be understood that the phraseology and the terminology are only descriptive and must not be understood as limitative.

[0033] By way of example, with reference to the figures, a system for detecting the clamping between a disc and a brake caliper in a braking system comprises a brake caliper 10 of floating type (e.g., a hydraulic or electromechanical brake caliper), which includes a brake caliper body configured to support a pair of brake pads 12 adapted to engage a brake disc 14 on opposite sides thereof, and a proximity sensor 16, mounted to said brake caliper body on the reaction side of the brake caliper 10, i.e. on the side of said body configured to support the pad 12 intended to come into contact with the brake disc 14 secondly. According to an embodiment, the reaction side of the brake caliper 10 is the side of the brake caliper 10 which, in a condition of mounting to the vehicle, is facing towards the outside of the latter.

[0034] The proximity sensor 16 is adapted to measure the relative displacement between said reaction side of the brake caliper 10 and the brake disc 14.

[0035] Preferably, the proximity sensor 16 is an inductive eddy current sensor, adapted to be positioned so as to face the brake disc 14 and to be magnetically coupled to the disc itself.

[0036] In the illustrated example, the proximity sensor 16 is mounted in a groove made in the body of the brake caliper 10.

[0037] Proximity sensors of a suitable type are, for example, described and illustrated in the following documents, the contents of which are to be considered incorporated in the present description: IT102023000028050, IT102023000028032, IT102023000028017,

[0038] IT102023000028044, EP3452348A1, US11167741B2; US2019152463 Al,

[0039] W02017191601A1. According to a preferred embodiment, the proximity sensor 16 is mounted integrally to the brake caliper body 10 so as to be at an appropriate distance from the brake disc.

[0040] Preferably, the proximity sensor 16 is configured to detect relative displacements between the reaction side of the brake caliper 10 and the brake disc 14 measuring less than 1 mm.

[0041] An electronic processing unit may also be present, supported by the brake caliper body 10 and connected to the proximity sensor 16.

[0042] The electronic processing unit is adapted to receive, from the proximity sensor 16, signals indicative of the displacement of the reaction side of the brake caliper 10 in the direction of the brake disc 10 and / or of the distance between said reaction side of the brake caliper 10 and the brake disc 14. The electronic processing unit is further configured to process and / or impart and / or receive an actuation command of the brake caliper 10, adapted to adjust the braking action of said caliper 10 on the disc 14, based on said signal of the proximity sensor 16.

[0043] According to an aspect of the invention, a braking assembly comprises a detection system according to any one of the embodiments described and illustrated above, a brake disc 14 coupled to said detection system, and a pair of brake pads 12, supported by the brake caliper body so as to engage the brake disc 14 from opposite sides thereof.

[0044] According to a further aspect of the invention, a method for adjusting the braking action applied by a brake disc and brake caliper assembly comprises the steps of providing a braking assembly as described above, and acquiring a characteristic curve of the braking force expressed by the brake caliper 10 on the disc 14 as a function of the current absorbed by the actuator of said brake caliper 10.

[0045] In the presence of a deceleration request, the method comprises the steps of actuating a first (position) control strategy, including the step of operating the brake caliper 10 to move the reaction side of the brake caliper 10 toward the brake disc 14, and verifying, by means of the proximity sensor 16, whether the pad 12 on the reaction side of the brake caliper 10 is in contact with the disc 14, continuing the step of actuating the brake caliper until the contact condition is reached (here defined as caliper-disc bite), upon reaching which a second (force) control strategy is actuated, which includes the steps of measuring the current drawn by the actuator of the brake caliper 10, estimating a value of expected braking effort (extrapolated from the aforesaid characteristic curve as a function of said measured current), and continuing to actuate the brake caliper 10, until said value of expected braking force matches a value of desired braking force.

[0046] Preliminary measurements on a static bench, as shown in the figure 4, have shown that the sensor can detect, with sufficient resolution, a minimum applied force, considered indicative of the occurrence of the caliper-disc bite condition, and the sensor output is almost insensitive to the different force application levels.

[0047] Various aspects and embodiments of a system and a method according to the invention have been described. It is understood that each embodiment can be combined with any other embodiment. Furthermore, the invention is not limited to the embodiments described, but can be varied within the scope defined by the accompanying claims.

Claims

CLAIMS1. A system for detecting the clamping between disc and brake caliper in a braking system, comprising:- a brake caliper (10) of a floating type, comprising a brake caliper body configured to support a pair of brake pads (12), adapted to engage a brake disc (14) from opposite sides thereof; and- a proximity sensor (16), mounted to said brake caliper body on the reaction side of the brake caliper (10), i.e., on the side of said body configured to support the brake pad (12) intended to come into contact with the brake disc (14) secondly, said proximity sensor (16) being adapted to measure the relative displacement between said reaction side of the brake caliper (10) and the brake disc (14).

2. A system according to claim 1, wherein the proximity sensor (16) is an eddy current inductive sensor, adapted to be magnetically coupled to the brake disc (14).

3. A system according to claim 2, wherein the proximity sensor (16) is mounted to the brake caliper body (10) in such a way that it is at a suitable distance from the brake disc (14).

4. A system according to any of the preceding claims, wherein the proximity sensor (16) is configured to detect relative displacements of less than 1 mm between the reaction side of the brake caliper (10) and the brake disc (14).

5. A system according to any of the preceding claims, wherein the brake caliper (10) is an electromechanical brake caliper.

6. A system according to any of the preceding claims, comprising an electronic processing unit, supported by the body of the brake caliper (10) and connected to the proximity sensor (16), said electronic processing unit being adapted to receive from said proximity sensor (16) signals indicative of the displacement of the reaction side of the brake caliper (10) in the direction of the brake disc (10) and / or the distance between said reaction side of the brake caliper (10) and the brake disc (14), said electronic processing unit being furtherconfigured to process and / or impart and / or receive an actuation command of the brake caliper (10), adapted to adjust the braking action of said brake caliper (10) on the disc (14), based on said proximity sensor signal (16).

7. A braking assembly, comprising:- a detection system according to any of the preceding claims;- a brake disc (14), coupled to said detection system; and- a pair of brake pads (12), supported by the brake caliper body so as to be able to engage the brake disc (14) from opposite sides thereof.

8. A method for adjusting the braking action applied by a brake disc and caliper assembly, comprising the steps of a) providing a braking assembly according to claim 7; b) acquiring a characteristic curve of the braking force applied by the brake caliper (10) on the disc (14) as a function of the current absorbed by the actuator of said brake caliper (io); c) when a request for deceleration is made, actuating an initial control strategy, including the step of operating the brake caliper (10) so as to move the reaction side of the brake caliper (10) towards the brake disc (14); d) checking by means of the proximity sensor (16) whether the pad (12) on the reaction side of the caliper brake (10) is in contact with the disc (14), and continuing with step c) up to the contact condition is reached; e) when the contact condition between the pad (12) on the reaction side of the brake caliper (10) and the disc (14) is reached, implementing a second control strategy, including the steps of f) measuring the current absorbed by the brake caliper actuator (10); g) estimating an expected braking force value extrapolated from the characteristic curve in step b) as a function of the current measured in step f); h) continuing to actuate the brake caliper (10), up to the expected braking force value in step g) coincides with a desired braking force value.

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