Technical Field

The invention relates to a method for operating a particulate filter arrangement in a vehicle, wherein the particulate filter arrangement features at least one filter medium body in a filter housing and an actively adjustable airflow generator by means of which an air flow to the filter medium body can be generated.

Background Art

W02020/094964 A1 describes a brake dust particulate filter for a brake disc arrangement in a vehicle having an electric or hybrid drive. The brake dust particulate filter is designed as an active extraction system featuring a turbine as vacuum source driven to generate a brake air flow directed towards the particulate filter. The vacuum source is activated via a control unit as soon as the electric motor drive for energy recovery is running in braking mode. In so doing, it is possible to activate the vacuum source and generate a brake air flow even before the friction brake is operated in the vehicle, so that an airflow is already in place to dissipate the friction particles when the friction brake is operated.

EP 1 837 066 A2 describes a particulate filter arrangement for a motor vehicle, via which particles are extracted from various units and from various locations in the vehicle. The particulate filter arrangement features an air flow generator and a filter means in a filter housing, in which suction hoses are introduced. Among others, air is drawn in via the suction hoses from the bottom area of the vehicle and directed to the filter housing.

GB 1 906 14 727 A discloses a particulate filter arrangement in a motor vehicle having a funnel-shaped intake port arranged immediately adjacent to a vehicle wheel and via which dust is directed into a dust collection container.

Summary of Invention

The object of the invention is to effectively extract dust and particles generated when driving and braking a vehicle.

This object is solved according to the invention with the characteristics of the independent claims. The subclaims specify appropriate further developments. The particulate filter arrangement according to the invention can be used in vehicles, in particular in motor vehicles, to collect dust and particles produced, on the one hand, by friction between the brake disc and the brake pad when the vehicle brake is operated and, on the other hand, by tire dust while the vehicle is in motion. Tire dust occurs continuously when the vehicle is in motion due to the rolling of the tires on the road surface, especially when the vehicle is accelerating, braking, and cornering, but also when the vehicle speed is constant and the vehicle is driving straight ahead. The particulate filter arrangement functions as a brake dust particulate filter and additionally as a tire particulate filter; both functions are combined in the particulate filter arrangement.

The particulate filter arrangement features a filter housing and one or more filter medium bodies accommodated in the filter housing, as well as an actively adjustable air flow generator by means of which an air flow can be generated towards the filter medium body. The air flow generator is preferably an electrically drivable unit, in particular an electric pump generating the air flow when operated. However, air flow generators without own drive but having an actuator for changing the state of the air flow generator, for example an electrically adjustable flap on a turbine which is exposed to the wind and generates an air flow from the wind, can be considered, wherein the free cross-sectional area of an opening through which the air flow is introduced into the turbine is adjustable by means of the actuator.

The airflow generated by the air flow generator can be a suction flow, in which the air flow is aspirated towards the filter medium body. A reverse design is also possible as an overpressure flow generated by the air flow generator and directed away from the air flow generator towards the filter medium body. In any case, the generated airflow passes through the filter medium body, where dust and particles are absorbed.

The air flow is made of a first partial air flow associated with a brake disc arrangement in the vehicle, and a second partial air flow guided from at least one tire environment of the vehicle towards the filter medium body. Two partial air flows are thus obtained, via each of which particles are conveyed to the filter medium body. Brake dust generated during brake application can be discharged via the first partial air flow. Both partial air flows can be merged during their course towards the filter medium body and combined to form a common air flow.

The volume flow or "level" of each active partial air flow - measured in unit of mass per unit of time or unit of volume per unit of time - can be set as a function of characteristic and/or state variables of the vehicle. In this connection, various operating modes can be considered. It is possible that both partial air flows are permanently active in braking mode and in the non-braking, moving state, but that the volume flow of each partial air flow and thus the ratio of the partial air flows to one another can be adjusted. An operating mode is also possible in which one partial airflow is temporarily completely deactivated and thus there is no flow, and only the second partial air flow is active. However, in this case, too, an additional setting is possible in which both partial air flows are active, wherein the volume flow of each partial air flow can be adjusted. In any case, the sum of both partial air flows is either constant, so that only the ratio of the partial air flows to each other changes, or the sum of both partial air flows is not constant and can be varied.

The embodiment with variable settings of the partial air flows features various advantages. Due to the use of a common particulate filter arrangement for both brake dust and tire dust, a compact particulate filter arrangement can be realized in which central components such as filter housing, filter medium body and air flow generator can be used together for both partial air flows.

It is also advantageous that the volume flows or heights of the partial air flows can be set as a function of various characteristic and/or state variables. This allows to realize an operation in which dust and particles are extracted in an energy-efficient manner from the location where these particles are generated. The partial airflows can be controlled according to demand and situation.

According to an advantageous embodiment, the setting of the volume flow of the first and the second partial air flow depends on the braking mode of the vehicle. Depending on whether the vehicle is currently in braking mode and a braking torque is generated by means of the vehicle friction brake, or whether no braking is taking place, the volume flow of the first partial air flow, which is guided from the brake disc towards the filter medium body, can be set differently. The volume flow of the second partial air flow can either be maintained or adjusted, in particular reduced, during braking mode. The volume flow of the first partial air flow during braking mode can be made dependent on various brake-related state and/or characteristic variables, in particular on the level of braking torque, vehicle speed and/or vehicle deceleration. With increasing braking torque, increasing vehicle speed and increasing vehicle deceleration, the volume flow of the first partial air flow is also advantageously increased. In an advantageous embodiment, the volume flow of the first partial airflow is increased when the braking mode is initiated. The ratio between the first and second partial air flow in driving situations with brake application is increased due to the increased first partial air flow. The first partial air flow can be reduced again as soon as the braking process is completed.

Without brake application, the second partial airflow can be increased from the at least one tire environment towards the filter medium body. The partial air flows are adjusted in such a way that the ratio between the first and second partial air flow in driving situations without brake application is reduced due to the raised second partial airflow. This approach allows to better discharge tire dust while maintaining the power of the air flow generator.

According to a yet further advantageous embodiment, the volume flow of at least one partial air flow is adjustable between a lower fundamental value and a maximum flow. This ensures that there is a minimum air flow in every operating state and that particles are diverted away from their point of origin. In particular, the first partial air flow from the brake disc arrangement to the filter medium body remains at the minimum level even in phases without braking mode, which corresponds in particular to a base load of the air flow generator. If necessary, the second partial air flow from the tire environment to the filter medium body can be deactivated in phases, in particular during braking mode, and activated only in phases without braking mode. However, it is also possible to design an embodiment having an activation of the second partial air flow during phases with braking mode at the level of the fundamental value.

The particulate filter arrangement in a vehicle according to the invention, with which the method described above can be realized, features at least one filter medium body in a filter housing and an actively adjustable air flow generator for generating an airflow directed towards the filter medium body, wherein the airflow generator can be accommodated in or on the filter housing. Furthermore, the particulate filter arrangement comprises a first flow passage through which a first partial air flow of a brake disc arrangement in the vehicle flows towards the filter medium body, and a second flow passage through which a second partial air flow flows from the environment of at least one tire of the vehicle towards the filter medium body. In this embodiment, brake dust and tire dust are extracted via a common particulate filter arrangement.

Advantageously, the partial airflows through the first and second flow passages are adjustable via a switching unit adjustable as required or according to the situation. As switching element, the switching unit features, for example, a flap or a rotary slide valve designed to be adjustable in order to set the desired volume flows of the partial airflows. Embodiments may be considered, in which exactly one switching element is disposed in the switching unit, wherein the setting of the switching element influences both partial airflows. Embodiments with one switching element each per partial airflow or per flow passage are also possible, so that the partial air flows can be adjusted independently from each other.

According to a further advantageous embodiment, the first and second flow passages both open into the switching unit, from which a third flow passage leads to the filter housing with the filter medium body. The partial air flows are joined in the switching unit and then continued as a joint air flow through the third flow passage towards the filter medium body. The partial air flows through the first and second flow passages can be adjusted via the switching unit.

The second flow passage, through which the second partial air flow is guided from the environment of the tire of the vehicle towards the filter medium body, is flow- connected on the tire side to a tire dust collector of funnel-shaped design, for example, wherein the funnel opening of the tire dust collector faces the tire and widens towards the tire. The tire dust collector is preferably attached to the wheel bearing or to axle or steering components which, in the case of steered wheels, move synchronously with the tire to ensure a constant distance to the emission source. The tire dust collector and, where appropriate, other components in the flow path from the tire environment towards the filter medium body are advantageously made of an elastomer or a thermoplastic elastomer (TPE), reducing the risk of damage in case of touchdown or rock fall. The switching unit and/or the air flow generator are advantageously controlled by control signals from a control unit. The control unit can form a constructional unit with the particulate filter arrangement in that the control unit is located, for example, in or on the filter housing of the particulate filter arrangement. The control unit can receive and process state variable signals from a vehicle sensor system for state variable detection and brake signals from the brake signals from the vehicle brake of the vehicle and drive signals from a drive motor of the vehicle. If necessary, the control unit receive and process signals from other units of the vehicle, for example environmental variables such as temperature or humidity.

Furthermore, the invention relates to a computer program product having a program code designed to perform the process steps described above. The computer program product runs in the control device described above.

Brief Description of Drawings

Further advantages and appropriate embodiments can be taken from the claims, the description of the figures and the drawings. It is shown in:

Fig. 1 a perspective view of a particulate filter arrangement for extracting brake dust and tire dust in a vehicle,

Fig. 2 the particulate filter arrangement from a different perspective,

Fig. 3 a flow chart with steps for carrying out a method for operating the particulate filter arrangement.

Identical components in the figures have the same reference numerals.

Description of Embodiments

Figs. 1 and 2 show a brake disc arrangement 1 installed in a motor vehicle. The brake disc arrangement 1 is part of a vehicle brake designed as friction brake and comprises, in addition to a brake disc 2, a brake caliper installed on a brake caliper holder 3 and which is a carrier of brake pads, which frictionally rest against the brake disc 2 during a braking process. The brake disc arrangement 1 is located on a wheel of the vehicle with a tire 4.

A particulate filter arrangement 5 is installed in the vehicle, combining the function of a brake dust particulate filter and additionally the function of a tire particulate filter. The particulate filter arrangement 5 collects brake dust generated by friction between the brake disc and the brake pad when the vehicle brake is operated, and also tire dust generated by contact between the tire 4 and the road surface while the vehicle is in motion. Tire dust is continuously generated when the vehicle is in motion due to the rolling of the tires on the road surface. Tire dust not only increases when the vehicle is accelerating, braking and cornering, but also occurs when the vehicle is traveling at constant speed.

The particulate filter arrangement 5 designed as suction device features a filter housing 6 accommodating a filter medium body in which the brake dust and the tire dust accumulate. An air flow generator 7 designed as an active, electrically drivable unit, in particular as an electric pump, is located on a cover of the filter housing 6. During operation of the air flow generator 7, a suction air flow is generated, which is guided to the filter housing 6. The air flow generator 7 is located on the clean side of the filter medium body accommodated in the filter housing 6, generating a negative pressure on the clean side, which directs the desired air flow towards the filter medium body on the raw side.

A component of the particulate filter arrangement 5 is also a first flow passage 8, through which a first partial air flow flows from the brake disc arrangement 1 towards the filter medium body, and a second flow passage 9, through which a second partial air flow flows from the environment of the tire 4 towards the filter medium body. The first flow passage 8 is connected to a brake dust collector 10 disposed on the brake caliper or on the brake caliper holder 3 and via which brake dust is collected and conveyed to the filter medium body. Specifically the brake dust collector 10 is designed as brake dust exhaust hood. The second flow passage 9 is connected to a funnel- shaped tire dust collector 11 , which faces the tire 4. The tire dust collector 11 is attached, for example, to the wheel bearing or to axle or steering components that move synchronously with the tire when the wheels are steered.

Both flow passages 8 and 9 open into a switching unit 12, from which a further flow passage 13 leads to the filter housing 6 and the filter medium body accommodated therein. The further flow passage 13 receives the two partial air flows fed into the switching unit 12 via the two flow passages 8 and 9, and combines the partial airflows to form a common airflow. The switching unit 12 features a flap or a rotary slide valve as switching element, which are designed to be adjustable in order to set the desired level of the partial air flows through the flow passages 8 and 9. The switching element of the switching unit 12 is set using control signals from a control unit which can form a constructional unit with the particulate filter arrangement 5 and is preferably located in or on the filter housing 6 of the particulate filter arrangement 5. In another embodiment, the control unit can form a constructional unit with the air flow generator. The control unit can receive and process state variable signals from a vehicle sensor system for state variable detection and brake signals from the brake signals from the vehicle brake of the vehicle and drive signals from a drive motor of the vehicle. If necessary, the control unit receive and process signals from other units of the vehicle, for example environmental variables such as temperature or humidity.

The air flow generator 7 is also controlled by control signals from the control unit. Similar to the switching unit 12, the air flow generator 7 can also be set as a function of state, operating and characteristic variables of the vehicle and/or individual units of the vehicle.

The particulate filter arrangement 5 can be used for two different brake disc arrangements and tires at the same time, for example for one brake disc arrangement and one tire in each of the left and right vehicle side areas.

Fig. 3 shows a flow chart with process steps for controlling the switching unit and the airflow generator. The method relates to the vehicle in motion and is applicable both to a driven vehicle at constant speed, to an accelerated vehicle, to a braked vehicle and to a rolling vehicle without delivering a drive torque (sailing).

In the first process step V1 , it is queried whether the vehicle is driving without any brake operation. This state comprises the operating modes driving with drive torque and driving without drive torque, but without braking torque. If the query in process step V1 shows that this driving state - moving vehicle without brake operation - is present, the system advances to the next process step V2 following the yes-branch ("Y").

In process step V2, the switching unit 12 is switched by control signals from the control unit in such a way that the second partial air flow from the environment of the tire to the filter medium body is set to an increased value. At the same time, the first partial airflow from the brake disc arrangement to the filter medium body remains at a fundamental value, from which the first partial airflow can be rapidly increased as soon as a braking process starts. The setting of the switching unit and/or the air flow generator can be made dependent on other state or characteristic variables of the vehicle or of the vehicle environment, for example modified as a function of speed, wherein the fundamental value of the first partial air flow and the increased value of the second partial air flow is raised as the vehicle speed increases. This ensures, on the one hand, that the increased tire dust that occurs at higher speeds is effectively extracted. On the other hand, this ensures that the first partial air flow is also active in driving states of the vehicle without brake operation and that a brake air flow is generated.

However, if the query in process step V1 shows that the vehicle is moving but at the same time the vehicle brake is operated, the system advances to process step V3 following the no-branch ("N"). The switching unit 12 is switched in such a way that the first partial air flow from the brake disc arrangement 1 towards the filter medium body is increased in order to extract the brake dust generated. Furthermore, in step V3, the power of the airflow generator ? can be raised to an increased value, which is higher than the previously set value during driving without brake operation and which depends on various state variables. The increased performance value of the air flow generator 7 depends on the vehicle speed and also on the amount of braking torque applied via the vehicle brake.

During the braking process, the second partial airflow from the tire environment towards the filter medium body can be kept at a low fundamental value.

The entire method, shown in Fig. 3, is run repeatedly at cyclic intervals.