Method for controlling a disc brake for a vehicle

Abstract

The method for controlling a disc (7) brake (2) for a vehicle is applied to a disc brake comprising brake pads (6) each carrying a lining (10) and an electromechanical actuator (9) intended to move the brake pads in such a way that the respective linings thereof clamp the disc in order to effect braking. According to this method, at the end of a braking operation, a movement of the brake pads is controlled depending on a state of thermal expansion of the disc and of the respective linings of the brake pads in such a way that, after the movement, a stroke length (d1, d2) between the lining of each brake pad and the disc remains greater than 0 mm and less than a predetermined stroke length (d1, d2).

Description

Method of controlling a disc brake for a vehicle Technical field of the invention

[0001] The invention relates to a method for controlling a disc brake for a vehicle. The invention also relates to a disc brake capable of implementing the method. Finally, the invention also relates to a vehicle comprising at least one disc brake according to the invention. Technical background

[0002] An electromechanically actuated disc brake for a vehicle, for example a motor vehicle, typically comprises an electric motor intended to provide a clamping force to a clamping member, such as a piston, in order to move brake pads carrying brake linings towards the disc so that the brake pad linings grip the disc to effect braking. Friction between the disc and the brake pad linings causes their temperatures to increase and consequently causes their respective thermal expansions. This thermal expansion varies depending on several parameters, such as parameters relating to the braking just performed.When braking stops, the disc and brake pad linings gradually cool so that their respective thermal expansions decrease until they return to a normal state at room temperature.

[0003] When braking is stopped, the brake pads are moved by the electromechanical actuator so as to leave a gap between the disc and the brake pad linings located on either side of the disc. If this gap is too small, there is a risk that the brake pad linings will remain in contact with the disc for a certain time after braking due to thermal expansion, thus creating unwanted residual braking which can affect the dynamic behavior of the vehicle. In addition, residual braking unnecessarily generates brake particles which contribute to air pollution. If the gap between the brake pad linings and the disc is too large, the response time between a braking command and the braking being applied and therefore the braking distance is increased, which is not desirable in terms of vehicle operating safety.

[0004] Thus, when manufacturing a disc brake and in particular when determining the space that will be left between the brake pad linings and the disc outside of a braking period, it is necessary to choose between a short response time associated with a significant risk of residual braking and an absence of risk of residual braking associated with a long response time.

[0005] The invention aims in particular to enable a disc brake for a vehicle to have a response time to a braking command which is short while having a reduced risk of residual braking.

[0006] To this end, the invention relates to a method for controlling a disc brake for a vehicle, in which the disc brake comprises brake pads each carrying a lining and an electromechanical actuator intended to move the brake pads so that their respective linings grip the disc to perform braking, characterized in that, at the end of braking, a movement of the brake pads is controlled as a function of a state of thermal expansion of the disc and of the respective linings of the brake pads so that after this movement, a stroke length between the lining of each brake pad and the disc remains greater than 0 mm and less than a predetermined stroke length.

[0007] Thus, the position of the brake pads relative to the disc outside of a braking period is not fixed but varies depending on the state of thermal expansion of the brake pad linings and the disc. By keeping the stroke length between the lining of each brake pad and the disc greater than 0 mm and less than a predetermined stroke length, it is possible to dynamically maintain a gap between the linings of the brake pads and the disc that is large enough not to cause residual braking and small enough to have a short response time following a braking command, thus making it possible to reduce the braking distance.

[0008] Because the stroke length between the lining of each brake pad and the disc is greater than 0 mm, none of the linings of the brake pads, whether the one facing the first face of the disc or the one facing the second face of the disc, is in contact with the disc outside of a braking period.

[0009] The predetermined stroke length is chosen so that the response time to a braking command is as short as possible.

[0010] The invention may include one or more of the following optional features, taken alone or in combination.

[0011] Advantageously, the predetermined stroke length is between 0.002 mm and 0.100 mm. The lengths in this range of stroke lengths are sufficiently high to avoid the occurrence of residual braking and sufficiently low so that the response time to a braking command allows the shortest possible braking distance to be obtained.

[0012] Advantageously, the state of thermal expansion of the disc and brake pad linings is determined during or after braking by determining a temperature of the disc and / or brake pad linings. Determining the temperature of the disc and / or brake pad linings is a reliable indicator of their state of thermal expansion.

[0013] Preferably, the determination of the state of thermal expansion of the disc and brake pad linings is carried out using a table or a physical correspondence model linking a temperature of the disc and / or the brake pad linings to their state of thermal expansion. This is a simple, reliable and economical way of determining the state of thermal expansion of the disc and the brake pad linings from their temperatures. The table or the physical correspondence model is for example established beforehand according to the characteristics of the brake, such as the composition of the brake pad linings.

[0014] Advantageously, the temperature of the disc and / or brake pad linings is estimated using at least one braking duration and / or one braking force. These are reliable indicators for estimating the temperature of the disc and / or brake pad linings. Thus, it is not necessary to use a temperature sensor to determine these temperatures, which is economical. It is understood that the longer the braking duration and the greater the braking force, the greater the increase in the temperature of the disc and brake pad linings during braking. It is also understood that the shorter the braking duration and the lower the braking force, the lower the increase in temperature during braking.

[0015] Preferably, the temperature of the disc and / or the brake pad linings is estimated by further using at least one parameter chosen from a vehicle speed, a vehicle mass, or brake dimensions. It is understood that these parameters influence the increase in the temperature of the disc and the brake pad linings during braking. Thus, the use of these parameters makes it possible to refine the estimation of the temperature of the disc and the brake pads. It is understood that the higher the vehicle speed during braking, the vehicle mass, or the brake dimensions, the greater the increase in the temperature of the disc and the brake pad linings during braking. According to other embodiments, other parameters are used to refine the estimation of the temperature of the disc and the brake pad linings.

[0016] Advantageously, if, after the movement of the brake pads, the presence of residual braking is detected, a movement of the brake pads is commanded so as to increase the respective stroke lengths between each brake pad lining and the disc. This monitoring and detection of residual braking ensures that if, for any reason, residual braking appears, it is detected and eliminated, thus avoiding the disadvantages associated with it. The detection of residual braking is carried out differently depending on the embodiments.According to a particular embodiment, a force sensor or observer determines the braking force and if the sensor or observer determines the presence of residual braking outside of a desired braking period, a movement of the brake pads is commanded so as to increase the respective stroke lengths between each brake pad lining and the disc.

[0017] According to one embodiment, the presence of residual braking is detected if an unwanted decrease in a rotational speed of a wheel of the vehicle equipped with the disc brake is detected. This is a simple and effective means of detecting residual braking. Furthermore, it is an economical means since it uses a sensor or observer of rotational speed of a wheel of the vehicle which is generally already present or used.

[0018] The invention also relates to an electromechanically actuated disc brake for a vehicle, comprising an electronic control unit capable of controlling the implementation of the method as described above.

[0019] Finally, the invention also relates to a vehicle comprising at least one disc brake as described previously. Brief description of the figures

[0020] The invention will be better understood on reading the following description, given solely as a non-limiting example and with reference to the appended drawings in which:

[0021] is a view of a vehicle according to the invention;

[0022] is a perspective view of a disc brake according to the invention;

[0023] is a schematic representation of the clamping member, the brake pads and the disc of a disc brake according to the invention shown during braking;

[0024] is a schematic representation similar to the one shown after braking. Detailed description

[0025] La represents a vehicle, here a motor vehicle 1, according to the invention, comprising at least two disc brakes 2, here four in number, equipping each wheel 3 of the motor vehicle 1.

[0026] The invention applies to any type of brake, in particular those intended to equip motor vehicles of the passenger car type, SUV (English acronym for "Sport Utility Vehicles"), two-wheelers (in particular motorcycles), airplanes, industrial vehicles chosen from vans, "Heavy Goods Vehicles" - that is to say metros, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles such as agricultural or civil engineering vehicles -, or other transport or handling vehicles. The invention also applies to non-motorized vehicles such as in particular a trailer, a semi-trailer or a caravan.

[0027] The brake 2 is represented, which in this case is of the floating caliper disc type. Thus, it conventionally comprises a caliper 4 mounted to slide relative to a yoke 5 fixed relative to the motor vehicle 1.

[0028] According to other embodiments, the brake 2 is of a different type, for example a fixed caliper disc brake 2 as shown in Figures 3 and 4.

[0029] Thus, as can be seen in Figures 3 and 4, the disc brake 2 comprises at least two brake pads 6 intended to cooperate by friction respectively with opposite faces of a disc 7 integral in rotation with one of the wheels 3 of the motor vehicle 1 in order to carry out the braking.

[0030] The disc brake 2 illustrated in Figures 3 and 4 further comprises an electric motor 8 intended to provide a clamping force to a clamping member 9, formed here by a piston, in order to move the brake pads 6 towards the disc 7 so that the linings 10 of the brake pads 6 come into contact with the disc 7 and grip it to perform braking as shown in the. During braking, the friction between the linings 10 of the brake pads 6 and the disc 7 causes an increase in the temperature of the linings 10 of the brake pads 6 and the disc 7 and, consequently, their respective thermal expansions.

[0031] At the end of braking, a movement of the brake pads 6 is controlled so that their respective linings 10 are no longer in contact with the disc 7 and, consequently, the wheels 3 of the motor vehicle 1 are no longer slowed down. The disc brake 2 comprises an electronic control unit (not shown) intended to control the operation of the disc brake 2 and in particular to control the movements of the clamping members 9 and therefore of the brake pads 6.

[0032] It will be noted that the floating caliper brake 2 illustrated in la comprises elements not shown but similar to those shown diagrammatically in figures 3 and 4 for the fixed caliper brake, in particular two brake pads intended to cooperate by friction respectively with opposite faces of a disc integral in rotation with one of the wheels 3 of the motor vehicle 1. Similarly, the floating caliper brake 2 illustrated in la comprises an electric motor intended to provide a clamping force to a clamping member in order to move the brake pads towards the disc.

[0033] A method for controlling the disc brake 2 according to the invention is described below, with particular reference to Figures 3 and 4. The electronic control unit is capable of controlling the various steps described below. Although Figures 3 and 4 show a fixed caliper brake comprising a piston 9 on each side of the disc, it is understood that the implementation of the method for controlling a floating caliper brake 2 as shown in the does not depart from the scope of the present invention, this brake 2 being controlled in a manner similar to that described below.

[0034] According to this method, after braking, the movement of the brake pads 6 is carried out as a function of a state of thermal expansion of the disc 7 and the respective linings 10 of the brake pads 6 so that after the movement, a stroke length d1, d2 between the lining 10 of each brake pad 6 and the disc 7 remains greater than 0 mm and less than a predetermined stroke length (see). By maintaining the stroke length d1, d2 between the lining 10 of each brake pad 6 and the disc 7 greater than 0 mm and less than a predetermined stroke length, it is possible to dynamically maintain a space between the linings 10 of the brake pads 6 and the disc 7 which is large enough not to cause residual braking and small enough to allow a short response time following a braking command, thus making it possible to reduce the braking distance.Because the stroke length d1, d2 between the lining 10 of each brake pad 6 and the disc is greater than 0 mm, none of the linings 10 of the brake pads 6, whether that facing the first face of the disc 7 or that facing the second face of the disc 7, is in contact with the disc 7 outside of a braking period (see). According to the present embodiment, the predetermined stroke length is between 0.002 mm and 0.10 mm.

[0035] It is understood that in order to satisfy the condition that the stroke length d1, d2 between the lining 10 of each brake pad 6 and the disc 7 remains greater than 0 mm and less than a predetermined stroke length, the brake pads 6 are moved as the linings 10 of the brake pads 6 and the disc 7 cool. In particular, it is understood that after a first axial movement in the direction opposite to the disc 7, the brake pads 6 are moved axially in the direction of the disc 7 as the cooling and therefore the thermal expansion decreases.

[0036] The state of thermal expansion of the linings 10 of the brake pads 6 and of the disc 7 is determined in different ways depending on the embodiments. In particular, this state of thermal expansion is either measured or estimated, for example using a thermal expansion observer.

[0037] According to the present embodiment, the state of thermal expansion of the disc 7 and the linings 10 of the brake pads 6 is determined during or at the end of braking by determining a temperature of the disc 7 and / or the linings 10 of the brake pads 6. Knowing the temperature of an element is a reliable means of determining its state of thermal expansion. It is noted that, according to the invention, determining only the temperature of the disc 7 makes it possible to determine both the state of thermal expansion of the disc 7 and the linings 10 of the brake pads 6. In the same way, determining only the temperature of the linings 10 of the brake pads 6 makes it possible to determine both the state of thermal expansion of the linings 10 of the brake pads 6 and the disc 7.Indeed, the temperature of the disc 7 and the linings 10 are generally very close so that determining the temperature of one makes it possible to deduce the temperature of the other with an acceptable degree of approximation. Determining the temperature of only one of these elements makes it possible to simplify the process.

[0038] The estimated or measured temperature is for example used as input in a correspondence table linking the temperature of the disc 7 and / or the linings 10 of the brake pads 6 to their respective states of thermal expansion. This is a simple and economical way of determining the state of thermal expansion from the temperature.

[0039] According to the embodiments, the temperature of the disc 7 and / or the linings 10 of the brake pads 6 is measured or estimated. In the present case, the temperature of the disc 7 and the linings 10 of the brake pads 6 is estimated using the duration or force of the braking that has just taken place, the speed of the motor vehicle 1 – in particular its evolution during braking -, the mass of the vehicle and the dimensions of the brake 2. The use of all these parameters makes it possible to obtain a precise estimation of the temperature of the disc 7 and the linings 10 of the brake pads 6. According to other embodiments, it is possible to use fewer or more parameters depending on the degree of precision desired for determining the temperature and therefore the state of thermal expansion.

[0040] The method further advantageously comprises an additional step according to which if, at the end of the movement of the pads 6 as described above, the presence of residual braking is detected, then an additional movement of the brake pads 6 is commanded so as to increase the respective stroke length d1, d2 between each lining 10 of brake pad 6 and the disc 7. Thus, if, at the end of the movement of the brake pads 6 taking place at the end of the braking, it is detected that this movement, for whatever reason, was not sufficient to avoid the presence of residual braking, this error is corrected so as to reduce the time during which the residual braking takes place.

[0041] The presence of residual braking is, for example, detected if an unwanted reduction in the rotational speed of a wheel 3 of the motor vehicle 1 equipped with the disc brake 2 is detected. For this purpose, a wheel rotational speed sensor is used, for example, which is generally already present on the motor vehicle 1, which is economical.

[0042] The invention is not limited to the embodiment presented and other embodiments will become apparent to those skilled in the art. List of references

[0043] 1: motor vehicle2: disc brake3: wheel4: caliper5: yoke6: brake pads7: disc8: electric motor9: clamping member10: brake pad liningd1, d2: stroke length between a brake pad lining and the disc

Claims

Method for controlling a disc brake (2) (7) for a vehicle (1), in which the disc brake (2) (7) comprises brake pads (6) each carrying a lining (10) and an electromechanical actuator (9) intended to move the brake pads (6) so that their respective linings (10) grip the disc (7) to perform braking, characterized in that, at the end of braking, a movement of the brake pads (6) is controlled as a function of a state of thermal expansion of the disc (7) and of the respective linings (10) of the brake pads (6) so that after the movement, a stroke length (d1, d2) between the lining (10) of each brake pad (10) and the disc (7) remains greater than 0 mm and less than a predetermined stroke length. Method according to claim 1, wherein the predetermined stroke length (d1, d2) is between 0.002 mm and 0.10 mm. Method according to claim 1 or 2, in which the state of thermal expansion of the disc (7) and the linings (10) of the brake pads (6) is determined during or after braking by determining a temperature of the disc (7) and / or the linings (10) of the brake pads (6). Method according to claim 3, wherein the determination of the state of thermal expansion of the disc (7) and the linings (10) of the brake pads (6) is carried out using a correspondence table linking a temperature of the disc (7) and / or the linings (10) of the brake pads (6) to their state of thermal expansion. Method according to claim 3 or 4, wherein the temperature of the disc (7) and / or the linings (10) of the brake pads (6) is estimated using at least a braking duration and / or a braking force. Method according to claim 5, wherein the temperature of the disc (7) and / or the linings (10) of the brake pads (6) is estimated by further using at least one parameter chosen from a speed of the vehicle (1), a mass of the vehicle (1), or dimensions of the brake (2). Method according to any one of the preceding claims, in which if, at the end of the movement of the brake pads (6), the presence of residual braking is detected, a movement of the brake pads (6) is commanded so as to increase the respective stroke lengths (d1, d2) between each lining (10) of the brake pad (6) and the disc (7). Method according to claim 7, wherein the presence of residual braking is detected if an undesired decrease in a rotational speed of a wheel (3) of the vehicle (1) equipped with the disc brake (2) is detected. Electromechanically actuated disc brake (2) for a vehicle, comprising an electronic control unit capable of controlling the implementation of the method according to any one of claims 1 to 8. Vehicle (1) comprising at least one disc brake (2) (7) according to claim 9.

Images