Holding device for electromechanical vehicle braking devices

Abstract

The present invention provides a holding device (10) for electromechanical vehicle braking devices (12). Such a holding device (10) comprises a control device with a control program and at least one movably mounted plastic holding element (18). This element (18) is designed to fix an electromechanical vehicle braking device (12) connected to the holding device (10) in at least one braking force holding position by means of the control device with the control program. Furthermore, the control device with the control program is designed to vary the end positions of the plastic holding element (18) relative to the electromechanical vehicle brake (12) required for the braking fixing process of the electromechanical vehicle braking device (12), so that constant load conditions on the plastic holding element (18) due to the braking fixing processes can be avoided over the entire service life of the holding device (10).

Description

[0001] The present invention relates to a holding device for electromechanical vehicle braking devices. State of the art

[0002] Conventional electromechanical vehicle braking systems for conventionally powered vehicles with internal combustion engines or for electric vehicles typically use an electric motor with a rotary gearbox and a rotary / translation converter to generate actuating forces for the friction brake. For rotary gearboxes, the use of plastic gears in individual gear stages (e.g., in worm gear stages) is a cost-effective solution that, among other things, offers favorable NVH (noise, vibration, harshness) behavior.

[0003] The gears of electromechanical vehicle braking devices are generally not self-locking as service brakes, so an additional mechanism is required to permanently maintain the braking torque when parking.

[0004] A particularly advantageous implementation is an additional element in the transmission or on the electric motor that positively blocks the rotation of these components. Examples of this include switchable freewheels or actuatable pins that block rotation when the parking brake is applied.

[0005] As a rule, these elements are installed in the highly geared part of the chain, for example directly on the motor pinion, since this is where the torque is lowest, allowing for a particularly small and cost-effective implementation.

[0006] In modular electromechanical vehicle braking systems, such assemblies can also be considered a stand-alone unit. The problem of creep is well known when using components made of plastic products, for example, in the form of plastic gears. This problem can occur particularly when the locking mechanism for the parking function in the transmission is located upstream of the plastic gear stage. This creates a strong, constant static load on the plastic gear during parking, particularly on one or a few teeth of the gear. This load can promote adverse deformation due to creep. Disclosure of the invention

[0007] The present invention provides a holding device for electromechanical vehicle braking devices according to claim 1 and a method for operating a holding device according to claim 10.

[0008] Furthermore, the present invention provides both an electromechanical disc vehicle brake device with a holding device according to one of claims 1 to 7 and an electromechanical drum vehicle brake device with a holding device according to one of claims 1 to 7.

[0009] Preferred further training is the subject of the subclaims. Advantages of the invention

[0010] The idea underlying the present invention is to provide a holding device for electromechanical vehicle brake devices and a method for operating such a holding device, wherein a component of the holding device that is loaded during a brake fixing process of the electromechanical vehicle brake device assumes different end positions during different brake fixing processes, so that constant load conditions on the component due to the brake fixing processes can be avoided during an entire service life of the holding device.Constant end positions, which are known in rigid systems from the state of the art, lead to a highly static and constant load on the holding element, so that premature material fatigue occurs over the entire service life of the holding device and, as a result, smooth functioning of brake fixation processes of the electromechanical vehicle braking device is no longer guaranteed.

[0011] According to the invention, the holding device for electromechanical vehicle brake devices comprises a control device with a control program and at least one movably mounted plastic holding element. This element is designed to fix an electromechanical vehicle brake device connected to the holding device in at least one braking force holding position by means of the control device with a control program. Furthermore, the control device with a control program is designed to vary the end positions of the plastic holding element relative to the electromechanical vehicle brake required for the brake fixing process of the electromechanical vehicle brake device, so that constant load conditions on the plastic holding element due to the brake fixing processes can be avoided over the entire service life of the holding device.

[0012] The plastic retaining element may comprise one or more plastic gears.

[0013] The holding device can be advantageously used, for example, in any vehicle with an electromechanical vehicle braking system. The term "holding device" in this context refers to the holding forces required to provide sufficient parking torque, i.e., the respective safe braking action, of the electromechanical vehicle braking system.

[0014] The varying end positions are designed to ensure consistently safe brake fixation processes of the electromechanical vehicle braking device. In other words, the parking processes to be effected using the presented holding device are always such that sufficient holding forces are established due to a respective end position of the plastic holding element to fix the vehicle in a safe parking position. A respective required end position is characterized by the fact that braking torques above a threshold of a minimum parking brake torque required for parking are ensured for a safe brake fixation process, whereby the holding forces required for this can be provided due to a respective end position of the plastic holding element.The proposed device offers the advantage of varying the required end positions, so that uniform load conditions on the plastic retaining element can be avoided due to the different end positions that arise. In this way, a consistent load condition on the plastic retaining element can be avoided surprisingly easily during the brake application process of the electromechanical vehicle brake device, thus providing a reliable and longer-lasting mechanism. A consistently constant end position of the plastic retaining element for the purpose of providing sufficient holding forces for a safe brake application process can thus be avoided.The presented holding device is advantageously designed to provide a plurality of possible required end positions of the plastic holding element, so that a variation from this plurality is possible, so that constant load conditions due to an always identical end position of the plastic holding element can be avoided.

[0015] According to a preferred embodiment of the holding device, the plastic holding element is designed as a plastic gear or a worm gear device. The aforementioned advantages apply equally to this embodiment of the presented holding device. The required end positions, which can be varied, result in a more even distribution of the load across the teeth of the plastic gear or, correspondingly, a more even distribution of the load across sections of the worm gear device over the entire service life of the holding device.

[0016] According to a preferred embodiment of the holding device, the respective end positions determined by means of the control device with control program can be varied between a first end position with minimum holding force for the brake fixing process of the electromechanical vehicle brake device and a second end position with maximum holding force for the brake fixing process of the electromechanical vehicle brake device.

[0017] In this way, it is ensured that the necessary end positions of the plastic holding element are always within an interval, which is essential for a safe and reliable brake fixing process of the electromechanical vehicle braking device.

[0018] Depending on the application of the proposed holding device, this information can be configured in the control unit with a control program, allowing a reliable selection of the required end positions from this interval. The respective key values ​​can also be viewed as target values ​​for the required end positions to be varied. In other words, the first or second end position can also be variably controlled to ensure reliable brake fixation of the electromechanical vehicle braking device.

[0019] According to a preferred embodiment of the holding device, an end position of the plastic holding element selected by means of the control device with control program differs at least from an end position of the plastic holding element used immediately before.

[0020] The immediately previous end position of the plastic retaining element is derived from the last brake fixation process of the electromechanical vehicle brake system effected by the retaining device and can be stored accordingly by the control unit with the control program. This ensures that the required end positions vary sufficiently throughout the entire service life of the retaining device to avoid constant load conditions.

[0021] According to a preferred embodiment of the holding device, the control device with control program is designed to vary an already selected end position of the plastic holding element for a current brake fixing process of the electromechanical vehicle braking device towards at least one further end position different from the already selected end position depending on a user-defined adjustable time parking interval.

[0022] This ensures that even during longer brake fixation processes of the electromechanical vehicle braking system, unfavorable, uniform load conditions can be avoided. A user-defined, adjustable time-parking interval can, for example, correspond to a parking period of two days, so that after two days at the latest, a different end position is achieved using the holding device to avoid the aforementioned constant load on the plastic holding element. A user-defined, adjustable time-parking interval can, for example, also be set so that, during longer parking periods, the required end positions are regularly adjusted. During longer parking phases, the required end positions are thus regularly modulated.It is therefore conceivable that, during very long periods of inactivity of the vehicle in which the proposed holding device is installed, the necessary end positions could be varied at regular intervals. In other words, this makes it easy to prevent an unfavorable static and constant load on the plastic holding element during extended parking periods of a vehicle in which the proposed mechanism is installed.

[0023] According to a preferred embodiment of the holding device, the control device with control program is designed to vary the respective end positions with the aid of a random process.

[0024] Instead of, for example, a predetermined variation of the respective end positions in order to avoid constant load conditions, it can be easily ensured with the aid of the random method that sufficiently alternating end positions of the plastic holding element are established even over a longer overall service life of the holding device, so that constant load conditions on the plastic holding element due to the brake fixation processes can be avoided during the entire service life of the holding device.

[0025] According to a preferred embodiment of the holding device, the control device comprises at least one actuator device for adjusting respective end positions of the plastic holding element relative to the electromechanical vehicle brake.

[0026] In this way, a particularly accurate and precise adjustment of the respective end positions can be ensured, so that a larger number of possible end positions are available for the intended variable operating function. The actuator device can comprise all common mechanisms, such as a motor, which are necessary for the present embodiment. For example, the actuator device can comprise a component which can be referred to as a parking element, which, as a type of pawl or switchable freewheel, can prevent de-energized rotation of the actuator device. The plastic holding element is thus held in the respective end position by means of the control device and its respective design, so that a built-up parking brake torque can be maintained even in a de-energized state. Such a component can act, for example, on a corresponding pinion or the like of the actuator device for the stated purposes.

[0027] To engage the parking brake, for example, a defined current can be applied and / or a specific motor position can be approached and / or a specific actuating force can be set (if this is measured by a sensor), and / or a specific braking torque can be set (if this is measured by a sensor). If the brake condition is the same, i.e. the same wear, thermal condition and friction coefficient, all types of control result in the motor and therefore the gear position always being the same when parked. Due to changes in condition, e.g. wear over the service life, the parking position only changes very slowly, so that over a longer period of time the same teeth of the plastic gear are always subjected to high levels of stress when parking if the same position is always assumed.

[0028] In other words, at least according to one embodiment of the invention, a more even distribution of the load across the teeth of the plastic gear can be achieved through a software function that randomizes the parking position of the motor above the required parking brake torque level, allowing different positions to be reached between different parking brake applications. Furthermore, during longer parking phases, the parking brake torque can be modulated at regular intervals, allowing different positions to be reached. The modulation can, for example, be combined with known functions that are performed anyway when the vehicle is parked (e.g., hot reclamp / relax, operating strategy to prevent release shock).

[0029] According to the invention, an electromechanical disc vehicle braking device with a holding device according to the invention is also presented.

[0030] The aforementioned advantages apply equally to this presented subject matter. It is conceivable that the holding device is functionally coupled to the electromechanical disc brake device as a separate assembly. It is also conceivable that the holding device is already provided as a functional subassembly in the electromechanical disc brake device.

[0031] In addition, according to the invention, an electromechanical drum vehicle brake device with a holding device according to the invention is presented.

[0032] The aforementioned advantages apply equally to this presented subject matter. It is conceivable that the holding device is functionally coupled to the electromechanical drum vehicle brake device as a separate assembly. It is also conceivable that the holding device is already provided as a functional subassembly in the electromechanical drum vehicle brake device.

[0033] According to the invention, the method for operating a holding device according to the invention includes detecting a parking brake operation of an electromechanical vehicle braking device by means of a holding device according to the invention; determining a first end position of a plastic holding element of the holding device with minimal holding force for a brake fixing operation of the electromechanical vehicle braking device and a second end position of the plastic holding element of the holding device with maximum holding force for the brake fixing operation of the electromechanical vehicle braking device;selecting a current end position of the plastic holding element between the first and second end positions using a random method, wherein the selected current end position of the plastic holding element differs at least from an end position of the plastic holding element used immediately before, so that constant load conditions on the plastic holding element due to the fixing processes can be avoided during the entire service life of the holding device;

[0034] The presented method offers the advantage of varying the required end positions, so that uniform load conditions on the plastic retaining element can be avoided due to the different end positions. In this way, a uniform load condition on the plastic retaining element can be avoided surprisingly easily during the brake fixation process of the electromechanical vehicle brake device, thus providing a reliable and longer-lasting mechanism.

[0035] According to a preferred embodiment of the method, a time profile of a current brake fixing process of the electromechanical vehicle brake device is recorded; the current end position of the plastic holding element is changed as a function of a user-defined adjustable time parking interval to a new end position of the plastic holding element, which differs from the immediately previous current end position of the plastic holding element, so that constant load conditions on the plastic holding element due to a current brake fixing process of the electromechanical vehicle brake device can be avoided.

[0036] A temporal progression of the current brake fixing process of the electromechanical vehicle braking device begins when the necessary holding forces are established due to a respective end position of the plastic holding element, so that a sufficient parking torque can be provided for a safe brake fixing process of the electromechanical vehicle braking device. The adjustable time interval can, for example, be selected such that a selected current end position is never maintained for so long that damage occurs due to creep in the material due to the constant load on the plastic holding element. A user-defined, adjustable time parking interval can, for example, also be set such that during longer parking periods, the required end positions are regularly adjusted. During longer parking phases, the required end positions are therefore regularly modulated.It is therefore conceivable that if the vehicle in which the holding device is provided is stationary for a very long time, the necessary end positions will be varied at regular intervals.

[0037] In other words, it is thus possible to easily avoid an unfavorable static and constant load on the plastic holding element during longer parking phases of a vehicle in which the presented method is applied.

[0038] According to a further preferred embodiment of the method, a temporal progression of a current brake fixing process of the electromechanical vehicle braking device is recorded; time-dependent material characteristics are provided for a plastic material of the plastic holding element; the current end position of the plastic holding element is changed, depending on an evaluation of the time-dependent material characteristics, to a new end position of the plastic holding element that differs from the immediately previous current end position of the plastic holding element, so that constant load conditions on the plastic holding element due to a current brake fixing process of the electromechanical vehicle braking device can be avoided.

[0039] A temporal progression of the current brake fixation process of the electromechanical vehicle brake device begins when the necessary holding forces are established based on a respective end position of the plastic retaining element, so that a sufficient parking torque can be provided for a safe brake fixation process of the electromechanical vehicle brake device. The evaluation of the time-dependent material parameters includes, for example, model-based predictions of the creep behavior of the plastic material of the plastic retaining element.If, for example, the temporal progression of the current brake fixing process of the electromechanical vehicle brake device reaches a point in time which, according to the evaluation of the time-dependent material characteristics, suggests damage to the plastic holding element due to creep behavior or at least suggests it with sufficient probability, then according to this preferred embodiment of the method a change towards a different end position, a new end position different from the current end position, is effected so that constant load conditions on the plastic holding element due to a current brake fixing process of the electromechanical vehicle brake device can be avoided.

[0040] The vehicle can therefore be parked and held using a service brake actuator. For this purpose, a driver request to "park" can be detected. By calculating the desired parking brake level: (Required parking brake level MP,req) and setting MP = MP,req + MP,rand (random component) at time 1, where MP,rand is randomly selected between the minimum MP,req and a maximum value for parking MP,max. This varies the torque and thus the highly loaded teeth of the plastic wheel during each parking maneuver. The torque MP is then maintained by engaging the lock on the motor pinion until time 2.

[0041] Optionally, a new calculated torque can be applied at time 2, which is then maintained, for example, until time 3. This step can be carried out during longer shutdown phases and can also be repeated regularly. The selection of time 2 can be made through a model-based prediction of the plastic's creep behavior. Changing the parking brake level may require actively releasing the parking pawl and energizing the service brake actuator. This step can also be performed in conjunction with other control strategies that require the vehicle to "wake up" and apply the service brake. Examples of this include the well-known re-applying of disc brakes when parking to compensate for decreasing braking torque by cooling down ("hot reclamp").

[0042] It is conceivable that the preferred embodiments of the method are also applied and carried out in respective combinations with one another.

[0043] The holding device can also be characterized by the features and advantages mentioned in connection with the method and vice versa.

[0044] Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings. Short description of the drawings

[0045] The present invention is explained in more detail below with reference to the exemplary embodiments shown in the schematic figures of the drawing.

[0046] They show: Fig. 1 a schematic representation of the holding device on an electromechanical vehicle braking device; Fig. 2 an electromechanical disc vehicle braking device with a holding device according to the invention; Fig. 3 an electromechanical drum vehicle brake device with a holding device according to the invention; Fig. 4 a block diagram of method steps of the method for operating a holding device according to an embodiment of the present invention.

[0047] In the figures, the same reference symbols denote the same or functionally identical elements.

[0048] Fig. Figure 1 shows a schematic representation of the holding device 10 on an electromechanical vehicle braking device 12. The electromechanical vehicle braking device 12 is depicted here as an electromechanically actuated drum brake. This combination can also be collectively referred to as a transmission arrangement with a parking brake mechanism.

[0049] The holding device 10 is shown with a control unit with a control program and an actuator device 16. Furthermore, the holding device 10 is shown with a plastic holding element 18 in the form of a worm gear device. For example, such a worm gear device comprises at least one plastic worm gear. The plastic holding element 18 is mounted on the actuator device 16 and is shown in one of the possible end positions of the plastic holding element 18 relative to the electromechanical vehicle brake 12, which are required for the brake fixing process of the electromechanical vehicle brake device 12.

[0050] An actuator device 16 as a motor can, when energized, generate a rotary movement which can be translated by the gear (for example, two-stage with a worm gear stage (made of plastic) + spur gear stage) and a force can be generated on the brake shoes by a rotation-translation converter. When the brake is applied, the parking element 14 can then be engaged, e.g., by a second small actuator. For example, the parking element 14 could be a pin actuated by a coil, which can thereby block the motor shaft (in the closed state) by the pin blocking a ratchet wheel on this shaft, for example. The power supply to the motor 16 can then be switched off, since the position is held by the parking element. The parking element itself can be designed such that it remains in the engaged position even when the power supply to the small parking actuator is removed.For example, this can be achieved by friction between the pin and the ratchet wheel or a bistable spring.

[0051] This arrangement may result in the entire torque required for parking being permanently maintained via the plastic gear element (worm gear stage). To avoid or reduce creep at this point, the operating strategy is proposed accordingly.

[0052] For example, a pawl or a switchable freewheel can be provided, whereby these elements can also be referred to as a parking element. Actively releasing this component then allows the plastic retaining element to be released for intended variations. In any case, the control device must be designed so that it can maintain the necessary torque for a parking operation, either directly in conjunction with the plastic retaining element or in conjunction with the actuator device and parking element.

[0053] In addition, the plastic holding element 18 can hold a built-up parking brake torque, which in the Fig. 1 is shown in a highly simplified manner by the coupling to a spur gear stage 20 of the electromechanical vehicle braking device 12. When parking, the actuating force F required for parking must be continuously applied to brake shoes in a brake drum 22 of the electromechanical vehicle braking device 12. This creates moments which, among other things, must also or only exclusively be held by the plastic holding element 18. In a gear system, the forces are typically transmitted by only a small portion of the teeth. This results in a high static load on the plastic teeth if the respective end positions are not varied, which can lead to creep over time.

[0054] Because the required end positions of the plastic holding element 18 can be varied while maintaining sufficient function for the brake fixation process of the electromechanical vehicle braking device 12, constant load conditions can be avoided. For example, using the presented holding device 10, a braking torque during a parking process of a vehicle in which the holding device 10 is provided can be randomly varied above a threshold of the minimum parking brake torque required for parking. The differing respective required end positions of the plastic holding element 18 can also be referred to as respective parking brake levels. To change a current parking brake level, it may be necessary to actively release the plastic holding element and simultaneously energize a service brake actuator of the electromechanical vehicle braking device 12.

[0055] Fig. 2 shows an electromechanical disc vehicle braking device 24 with a holding device 10 according to the invention.

[0056] Fig. 3 shows an electromechanical drum vehicle brake device 26 with a holding device 10 according to the invention.

[0057] Fig. 4 shows a block diagram of method steps of the method for operating a holding device according to an embodiment of the present invention.

[0058] In the method for operating a holding device according to the invention according to one of claims 1 to 7, a parking braking operation of an electromechanical vehicle braking device is detected S1 by means of a holding device according to the invention; a first end position of a plastic holding element of the holding device with minimal holding force for a braking fixation operation of the electromechanical vehicle braking device and a second end position of the plastic holding element of the holding device with maximum holding force for the braking fixation operation of the electromechanical vehicle braking device are determined S2;selecting S3 a current end position of the plastic holding element between the first and second end positions with the aid of a random process, wherein the selected current end position of the plastic holding element differs at least from an end position of the plastic holding element used immediately before, so that constant load conditions on the plastic holding element due to the fixing processes can be avoided during the entire service life of the holding device;

[0059] The presented method can be implemented at least partially or even entirely in conjunction with other control strategies, which in any case require a so-called wake-up of the vehicle and a corresponding application of the service brake. Examples of this include the well-known so-called re-applying of disc brakes during parking maneuvers in order to compensate for decreasing braking torque, caused, for example, by cooling processes, also known under the technical term "hot reclamp." In connection with drum brakes, the so-called "hot relax" function should also be mentioned. It is also possible to implement at least partial or even total combinations with methods that provide for regular release of the parking brake in order to avoid a release shock in drum brakes.

[0060] Although the present invention has been fully described above using the preferred embodiment, it is not limited thereto but can be modified in many ways.

Claims

[1] Holding device (10) for electromechanical vehicle braking devices (12) comprising: - a control device with a control program, at least one movably mounted plastic holding element (18) which is designed to fix an electromechanical vehicle braking device (12) connected to the holding device (10) in at least one braking force holding position by means of the control device (14) with a control program, wherein the control device with a control program is designed to vary the end positions of the plastic holding element (18) relative to the electromechanical vehicle brake (12) required for the braking fixing process of the electromechanical vehicle braking device (12), so that constant load conditions on the plastic holding element (18) due to the braking fixing processes can be avoided during the entire service life of the holding device. [2] Holding device (10) according to claim 1, wherein the plastic holding element (18) is designed as a plastic gear or as a worm gear device. [3] Holding device (10) according to one of claims 1 or 2, wherein the respective end positions determined by means of the control device with control program are variable between a first end position with minimum holding force for the brake fixing process of the electromechanical vehicle brake device (12) and a second end position with maximum holding force for the brake fixing process of the electromechanical vehicle brake device (12). [4] Holding device (10) according to one of the preceding claims, wherein an end position of the plastic holding element (18) selected by means of the control device with control program differs at least from an end position of the plastic holding element (18) used immediately before. [5] Holding device (10) according to one of the preceding claims, wherein the control device with control program is designed to vary an already selected end position of the plastic holding element (18) for a current brake fixing process of the electromechanical vehicle brake device (12) towards at least one further end position different from the already selected end position in dependence on a user-defined adjustable time parking interval. [6] Holding device (10) according to one of the preceding claims, wherein the control device with control program is designed to vary the respective end positions with the aid of a random method. [7] Holding device (10) according to one of the preceding claims, wherein the control device comprises at least one actuator device (16) for adjusting respective end positions of the plastic holding element (18) relative to the electromechanical vehicle brake (12). [8] Electromechanical disc vehicle braking device (24) with a holding device (10) according to one of claims 1 to 7. [9] Electromechanical drum vehicle brake device (26) with a holding device (10) according to one of claims 1 to 7. [10] Method for operating a holding device (10) according to one of claims 1 to 7, comprising the steps: - detecting (S1) a parking braking operation of an electromechanical vehicle braking device (12) by means of a holding device (10) according to one of claims 1 to 7; - determining (S2) a first end position of a plastic holding element (18) of the holding device (10) with minimum holding force for a brake fixing process of the electromechanical vehicle brake device (12) and a second end position of the plastic holding element (18) of the holding device (10) with maximum holding force for the brake fixing process of the electromechanical vehicle brake device (12); - selecting (S3) a current end position of the plastic holding element (18) between the first and second end positions with the aid of a random process, wherein the selected current end position of the plastic holding element (18) differs at least from an end position of the plastic holding element (18) used immediately beforehand, so that constant load conditions on the plastic holding element (18) due to the fixing processes can be avoided during an entire service life of the holding device (10). [11] A method for operating a holding device (10) according to claim 10, comprising the steps: - recording a time course of a current brake fixing process of the electromechanical vehicle braking device (12); - Changing the current end position of the plastic holding element (18) as a function of a user-defined adjustable time parking interval to a new end position of the plastic holding element (18) which differs from the immediately previous current end position of the plastic holding element (18), so that constant load conditions on the plastic holding element (18) due to a current brake fixing process of the electromechanical vehicle brake device (12) can be avoided. [12] A method for operating a holding device (10) according to claim 10, comprising the steps: - recording a time course of a current brake fixing process of the electromechanical vehicle braking device (12); - providing time-dependent material characteristics via a plastic material of the plastic holding element (18), - Changing the current end position of the plastic holding element (18) as a function of an evaluation of the time-dependent material characteristics to a new end position of the plastic holding element (18) which differs from the immediately previous current end position of the plastic holding element (18), so that constant load conditions on the plastic holding element (18) due to a current brake fixing process of the electromechanical vehicle brake device (12) can be avoided.

Images