Holding device for an electromechanical vehicle brake device

Abstract

The invention relates to a holding device (10) for an electromechanical vehicle brake device (12). Such a holding device (10) comprises a control device provided with a control program and at least one movably mounted plastic holding element (18). The element (18) fixes an electromechanical vehicle brake device (12) connected to the holding device (10) in at least one braking force holding position by means of a control device configured with a control program. Furthermore, a control device equipped with a control program changes an end position of the plastic holding element (18) relative to the electromechanical vehicle brake (12), which end position is necessary for a braking fastening process of the electromechanical vehicle brake device (12), in this way, during the entire service life of the holding device (10), a load state that remains unchanged on the plastic holding element (18) as a result of the braking fastening process can be avoided.

Description

Technical Field

[0001] The invention relates to a holding device for an electromechanical vehicle brake system. Background Art

[0002] Conventional electromechanical vehicle brake systems for conventional vehicles with internal combustion engines or for electric vehicles typically use an electric motor with a rotary transmission and a rotational / translational converter to generate the actuating force for the friction brakes. For the rotary transmission, a cost-effective solution is to use plastic gears in the individual transmission stages (e.g., worm gear stages), which offers good NVH (Noise, Vibration, Harshness) characteristics.

[0003] When used as a service brake, the transmission of an electromechanical vehicle brake system is generally not designed to be self-locking, so that additional mechanisms are 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, which prevents the transmission or the electric motor from rotating in a form-fitting manner. For this purpose, for example, a switchable overrunning clutch or an actuable pin is known, which prevents rotation when the parking brake is engaged.

[0005] These elements are usually arranged as far as possible in the step-up gear part of the drive train, for example directly on the motor pinion, since the torque is lowest there and they can be realized in a particularly small and cost-effective manner.

[0006] In modular electromechanical vehicle brake systems, such components can also be considered independent units. Creep problems are known to occur when using components made of plastic products, such as plastic gears. Creep problems can occur particularly when the locking mechanism for the parking function is arranged upstream of a plastic transmission stage in the transmission. This results in a high, static, and constant load on the plastic gear, particularly on one or a small number of teeth, during parking. This load can promote undesirable deformations due to creep. Summary of the Invention

[0007] The invention provides a holding device for an electromechanical vehicle brake system according to claim 1 and a method for operating a holding device according to claim 10 .

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

[0009] Preferred developments are the subject matter of the dependent claims.

[0010] The present invention is based on the idea of providing a holding device for an electromechanical vehicle brake system and a method for operating such a holding device, wherein components of the holding device that are loaded during a braking securing process of the electromechanical vehicle brake system adopt different end positions during different braking securing processes, so that constant load states on the components due to the braking securing processes can be avoided over the entire service life of the holding device. The constant end positions known from the prior art in rigid systems result in very static and constant loads acting on the holding element, leading to premature material fatigue over the entire service life of the holding device and, therefore, no longer ensuring a smooth functioning of the braking securing process of the electromechanical vehicle brake system.

[0011] According to the present invention, a holding device for an electromechanical vehicle brake system comprises a control device equipped with a control program and at least one movably supported plastic holding element. The element secures the electromechanical vehicle brake system, which is connected to the holding device, in at least one braking force holding position using the control device equipped with the control program. Furthermore, the control device equipped with the control program changes the end position of the plastic holding element relative to the electromechanical vehicle brake required for the brake securing process of the electromechanical vehicle brake system, thereby preventing a constant load state on the plastic holding element caused by the brake securing process throughout the 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 brake system. The term "holding device" is understood herein to mean a holding force for providing a sufficient parking torque of the electromechanical vehicle brake system, ie a corresponding safe braking holding process.

[0014] The variable end positions ensure a consistently safe braking and securing process for the electromechanical vehicle brake system. In other words, the parking process required by the provided holding device always generates sufficient holding force based on the respective end position of the plastic holding element to secure the vehicle in a safe parking position. The required end positions are characterized by ensuring a braking torque higher than a threshold value of the minimum parking brake torque required for parking the vehicle, respectively, and the required holding force can be provided based on the respective end position of the plastic holding element. The proposed device offers the advantage of varying the required end positions, thereby avoiding uniform load conditions on the plastic holding element due to the different end positions that occur. This surprisingly conveniently avoids uniform load conditions on the plastic holding element during a braking and securing process of the electromechanical vehicle brake system, resulting in a reliable and more durable mechanism. Consequently, it is possible to avoid the plastic holding element having to maintain a constant end position to provide sufficient holding force for a safe braking and securing process. The proposed holding device advantageously provides a plurality of possible necessary end positions of the plastic holding element, from which changes can be made, so that a constant load state due to a 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 a plastic gear or worm gear. The advantages mentioned above also apply to this embodiment of the proposed holding device. The required end positions to be changed here result in a more uniform load distribution on the teeth of the plastic gear, or correspondingly, a more uniform load distribution on a subsection of the worm gear over the entire service life of the holding device.

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

[0017] In this way, it is ensured that the adaptively required end position of the plastic retaining element always lies within the range required for a safe and reliable brake securing process of the electromechanical vehicle brake system.

[0018] Depending on the intended use of the proposed holding device, this information can be set in a control unit equipped with a control program so that the required end position can be reliably selected from this range. The respective key value can also be considered as a target value for the required end position to be changed. In other words, the first end position or the second end position can also be variably controlled to achieve a reliable braking and holding process of the electromechanical vehicle brake system.

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

[0020] The most recently used end position of the plastic retaining element is determined from the last braking and securing operation of the electromechanical vehicle brake system by means of the retaining device and can be stored accordingly by a control device equipped with a control program. This ensures that the required end position varies sufficiently over the entire service life of the retaining device, thereby avoiding constant load states.

[0021] According to a preferred embodiment of the holding device, a control device equipped with a control program changes a selected end position of the plastic holding element towards at least one further end position different from the already selected end position based on a user-definable parking time interval (time interval) for a current braking securing process of the electromechanical vehicle brake device.

[0022] This ensures that unfavorable uniform load conditions can be avoided even during longer braking and holding processes of the electromechanical vehicle brake system. The user-definable parking interval can, for example, correspond to a two-day parking duration, so that after two days at the latest, different end positions are achieved with the retaining device to avoid the aforementioned constant load on the plastic retaining element. The user-definable parking interval also allows, for example, the required end positions to be regularly adjusted during longer parking periods. Thus, the required end positions are regularly adjusted during longer parking periods. It is therefore conceivable that, during very long parking periods of a vehicle equipped with the proposed retaining device, the required end positions can be changed at regular intervals. In other words, during longer parking periods of a vehicle equipped with the proposed mechanism, unfavorable static, constant loads on the plastic retaining element can be easily avoided.

[0023] According to a preferred embodiment of the holding device, a control device equipped with a control program changes the respective end position by means of a random method.

[0024] Instead of a predetermined variation of the individual end positions in order to avoid a constant load state, a random method can be used to ensure in a simple manner that a sufficiently alternating end position of the plastic retaining element is achieved even over the relatively long service life of the retaining device, so that a constant load state on the plastic retaining element due to a braking securing process can be avoided over the entire service life of the retaining device.

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

[0026] This ensures particularly accurate and precise setting of the individual end positions, allowing for a large number of possible end positions to be used for the desired variable operating functions. The actuator can include all common mechanisms required for this embodiment, such as a motor. Thus, the actuator can include, for example, a component that can be referred to as a parking element, which acts as a locking pawl or a switchable overrunning clutch to prevent the actuator from rotating when the current is off. The plastic retaining element is thus held in the respective end positions by means of a control device and its corresponding design, so that the generated parking brake torque is maintained even when the current is off. For this purpose, such a component can, for example, act on a corresponding pinion or similar component of the actuator.

[0027] To engage the parking brake, for example, a defined current can be applied, and / or a specific motor position can be reached, and / or a specific actuating force (if measured by a sensor) can be set, and / or a specific braking torque (if measured by a sensor) can be set. Given the same brake state, i.e., the same wear, the same thermal state, and the same coefficient of friction, all types of actuation result in the same motor position and, therefore, the same transmission position when parking. Because the parking position changes only very slowly due to state changes, such as wear over service life, during prolonged parking, the same teeth of the plastic gear are constantly subjected to high loads if the vehicle remains in the same position.

[0028] In other words, according to at least one embodiment of the present invention, a more even distribution of the load on the teeth of the plastic gear can be achieved by a software function that randomizes the parking position of the motor to a level above the necessary parking brake torque, thereby enabling different positions to be achieved between different parking brake procedures. Furthermore, during longer parking phases, the parking brake torque can be adjusted at regular intervals and different positions can be achieved. This adjustment can, for example, be combined with known functions that are always performed when parking a vehicle (e.g., hot reclamp / relax, operating strategies to prevent shock when releasing the brake).

[0029] According to the invention, an electromechanical disc vehicle brake system is also proposed, which has a holding device according to the invention.

[0030] The advantages mentioned above also apply to the present invention. It is conceivable that the retaining device is functionally coupled to the electromechanical disc vehicle brake system as a separate component. It is also conceivable that the retaining device is already provided as a functional subassembly in the electromechanical disc vehicle brake system.

[0031] Furthermore, according to the invention, an electromechanical drum vehicle brake system is proposed having a holding device according to the invention.

[0032] The advantages mentioned above also apply to the present invention. It is conceivable that the retaining device is functionally coupled to the electromechanical drum vehicle brake system as a separate component. It is also conceivable that the retaining device is already provided as a functional subassembly in the electromechanical drum vehicle brake system.

[0033] According to the present invention, in a method for operating a holding device according to the present invention, the following steps are performed: identifying a parking brake process of an electromechanical vehicle brake device by means of the holding device according to the present invention; determining a first end position of a plastic holding element of the holding device and a second end position of the plastic holding element of the holding device, wherein the first end position has a minimum holding force for a braking holding process of the electromechanical vehicle brake device, and the second end position has a maximum holding force for a braking holding process of the electromechanical vehicle brake device; selecting a current end position of the plastic holding element between the first end position and the second end position by means of a random method, wherein the selected current end position of the plastic holding element is different from at least the end position of the plastic holding element used most recently, so that a constant load state on the plastic holding element due to the holding process can be avoided during the entire service life of the holding device.

[0034] The proposed method offers the advantage of varying the respective required end positions, so that due to the different provided end positions, uniform load conditions on the plastic retaining element can be avoided. In this way, uniform load conditions on the plastic retaining element during a braking and securing process of an electromechanical vehicle brake system can be avoided surprisingly easily, thereby providing a reliable and more durable mechanism.

[0035] According to a preferred embodiment of the method, the time course of a current braking securing process of the electromechanical vehicle brake system is recorded; the current end position of the plastic retaining element is changed according to a user-definable parking time interval towards a new end position of the plastic retaining element, which new end position differs from the current end position of the plastic retaining element used the last time, so that a constant load state of the plastic retaining element due to the current braking securing process of the electromechanical vehicle brake system can be avoided.

[0036] The time course of the current braking process of the electromechanical vehicle brake system begins when the required holding force is set based on the respective end positions of the plastic retaining elements, thereby providing sufficient parking torque for a safe braking process of the electromechanical vehicle brake system. The adjustable time interval can be selected, for example, so that the selected current end position is not maintained for so long that the constant load on the plastic retaining elements causes damage in the material due to creep processes. The user-defined parking time interval also allows, for example, for regular adjustment of the required end position during long parking periods. Thus, the required end position is regularly adjusted during long parking periods. It is therefore conceivable that the required end position be changed at regular intervals if a vehicle equipped with the proposed retaining device is parked for a long period of time.

[0037] In other words, it is possible to easily avoid disadvantageous, static, and constant loads on the plastic retaining element during longer parking phases of a vehicle in which the proposed method is used.

[0038] According to another preferred embodiment of the method, the time course of a current braking securing process of the electromechanical vehicle brake system is recorded; time-dependent material property values of the plastic material of the plastic retaining element are provided; and based on the evaluation of the time-dependent material property values, the current end position of the plastic retaining element is changed towards a new end position of the plastic retaining element, which new end position is different from the current end position of the plastic retaining element used the last time, so that a constant load state of the plastic retaining element due to the current braking securing process of the electromechanical vehicle brake system can be avoided.

[0039] When the required holding force is set based on the respective end positions of the plastic retaining element, thereby providing a sufficient parking torque for a safe braking and securing process of the electromechanical vehicle brake system, the time course of the current braking and securing process of the electromechanical vehicle brake system begins. The evaluation of the time-dependent material property values, for example, includes a model-based prediction of creep properties of the plastic material of the plastic retaining element. For example, if the time course of the current braking and securing process of the electromechanical vehicle brake system reaches a point in time at which damage to the plastic retaining element due to creep properties is foreseeable, or at least foreseeable with sufficient probability, based on the evaluation of the time-dependent material property values, then according to this preferred embodiment of the method, a change is made to another end position, achieving a new end position that differs from the current end position, thereby preventing the plastic retaining element from being subjected to a constant load due to the current braking and securing process of the electromechanical vehicle brake system.

[0040] The service brake actuator can therefore be used to park and stop the vehicle. To this end, the driver's "park" request is recognized. The required parking brake level (requested parking brake level MP,req) is calculated and assigned at time 1: MP = MP,req + MP,rand (random component), where MP,rand is randomly selected between the minimum MP,req and the maximum MP,max for parking. This changes the torque, and thus the highly loaded teeth of the plastic gear, with each parking maneuver. The torque MP is then maintained until time 2 by engaging a locking element on the motor pinion.

[0041] Optionally, the vehicle can then be moved to a newly calculated torque at time 2 and then maintained until, for example, time 3. This step can be performed for longer parking phases and can also be repeated regularly. Time 2 can be selected by predicting the creep properties of the plastic based on a model. To change the parking brake level, it may be necessary to actively release the parking pawl and energize the service brake actuator. This step can also be performed in conjunction with another control strategy that ultimately requires "waking up" the vehicle and applying the service brake. An example of this is the well-known drag of disc brakes during parking, the purpose of which is to compensate for the reduced braking torque due to cooling ("hot re-clamping").

[0042] It is conceivable that the preferred embodiments of the method can also be used and performed in combination with one another.

[0043] The holding device may 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 present invention emerge from the following description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The present invention will be explained in more detail below based on the embodiments given in the schematic diagrams, in which:

[0046] Figure 1 A schematic diagram showing a holding device at an electromechanical vehicle brake system;

[0047] Figure 2 An electromechanical disc vehicle brake device having a retaining device according to the invention is shown;

[0048] Figure 3 An electromechanical drum vehicle brake device having a holding device according to the invention is shown;

[0049] Figure 4 A block diagram shows method steps for operating a holding device according to an exemplary embodiment of the present invention.

[0050] In the figures, the same reference signs indicate identical or functionally identical elements. DETAILED DESCRIPTION

[0051] Figure 1 The schematic diagram of the holding device 10 at an electromechanical vehicle brake device 12 is shown. The electromechanical vehicle brake device 12 is shown in the present embodiment as an electromechanically actuated drum brake. Overall, the combined device can also be referred to as a transmission device with a parking brake mechanism.

[0052] The holding device 10 is shown with a control device and an actuator 16, which is equipped with a control program. Furthermore, the holding device 10 is shown with a plastic holding element 18 in the form of a worm gear. This worm gear comprises, for example, at least one plastic worm wheel. The plastic holding element 18 is attached to the actuator 16, and the possible and necessary end positions of the plastic holding element 18 relative to the electromechanical vehicle brake 12 are shown for the brake securing process of the electromechanical vehicle brake system 12.

[0053] The actuator 16, which is a motor, is capable of generating a rotational motion when energized. This rotational motion can be variable in speed via a transmission (e.g., in two stages using a worm gear stage (made of plastic) and a spur gear stage), and a force acting on the brake pad can be generated via a rotation-translation converter. In the actuated state of the brake, the parking element 14 can be engaged, for example, by a second small actuator. For example, the parking element 14 can be a pin actuated by a coil, and thus the motor shaft can be locked (in the driving state) by causing the pin to, for example, lock a ratchet on the motor shaft. The power supply to the motor 16 can then be stopped because this position is maintained by the parking element. The parking element itself can be designed so that it remains in the engaged position even if the small parking actuator is no longer energized. This can be achieved, for example, by friction between the pin and the ratchet or by a bistable spring.

[0054] This arrangement means that all the torques required for parking should be permanently maintained via the transmission element (worm gear stage) made of plastic. In order to avoid or reduce creep, a corresponding operating strategy is proposed.

[0055] For example, a locking pawl or a switchable overrunning clutch can be provided, wherein these elements can also be referred to as parking elements. Actively releasing this component allows the plastic retaining element to be released for a specific change. In any case, the control device makes it possible to maintain the torque required for the parking process, either directly in conjunction with the plastic retaining element or in conjunction with the actuator and the parking element.

[0056] Furthermore, the built-up parking brake torque can be maintained by the plastic retaining element 18, which is Figure 1 The coupling to the spur gear stage 20 of the electromechanical vehicle brake system 12 is shown in a greatly simplified manner. When the vehicle is parked, the actuating force F required for parking must be permanently applied to the brake pads in the brake drum 22 of the electromechanical vehicle brake system 12. This generates a torque that must also, or only must, be maintained by the plastic retaining element 18. In the meshing, force is typically transmitted via only a small portion of the teeth. If the respective end positions remain unchanged, this results in high static loads on the plastic teeth, which can lead to creep over time.

[0057] By being able to vary the required end position of the plastic retaining element 18, it is possible to avoid a constant load state while maintaining sufficient functionality for the brake holding process of the electromechanical vehicle brake system 12. For example, with the proposed retaining device 10, during the parking process of a vehicle equipped with the retaining device 10, the braking torque can randomly vary above the threshold value of the minimum parking brake torque required for parking. The different required end positions of the plastic retaining element 18 can also be referred to as corresponding parking brake levels. To change the current parking brake level, it may be necessary to actively release the plastic retaining element and simultaneously energize the service brake actuator of the electromechanical vehicle brake system 12.

[0058] Figure 2 An electromechanical disc vehicle brake system 24 is shown having a holding device 10 according to the invention.

[0059] Figure 3 An electromechanical drum vehicle brake system 26 is shown having a holding device 10 according to the invention.

[0060] Figure 4 A block diagram shows method steps for operating a holding device according to an exemplary embodiment of the present invention.

[0061] In a method for operating a holding device according to the present invention according to any one of claims 1 to 7, a parking brake process of an electromechanical vehicle brake device is identified S1 by means of the holding device according to the present invention; a first end position of a plastic holding element of the holding device and a second end position of the plastic holding element of the holding device are determined S2, the first end position having a minimum holding force for the braking holding process of the electromechanical vehicle brake device and the second end position having a maximum holding force for the braking holding process of the electromechanical vehicle brake device; a current end position of the plastic holding element is selected S3 between the first end position and the second end position by means of a random method, wherein the selected current end position of the plastic holding element is at least different from the end position of the plastic holding element used the last time in time, so that a constant load state on the plastic holding element caused by the fixing process can be avoided during the entire service life of the holding device.

[0062] The proposed method can be implemented at least partially or even completely in conjunction with other control strategies that ultimately require a so-called wake-up of the vehicle and associated processes involving the service brakes. An example of this is the well-known dragging of disc brakes during parking, which aims to compensate for reduced braking torque, for example due to cooling processes. This is also known as "hot re-clamping." Regarding drum brakes, the so-called "hot relaxation" function is also mentioned. A combination with a method that provides for periodic release of the parking brake to avoid shock during release in the case of drum brakes is also possible.

[0063] Although the present invention has been fully described above based on the preferred embodiments, the present invention is not limited thereto but can be modified in various ways.

Claims

1. A holding device (10) for an electromechanical vehicle brake system (12), comprising: a control device equipped with a control program, at least one movably mounted plastic retaining element (18), which, by means of the control device (14) equipped with the control program, secures an electromechanical vehicle brake device (12) connected to the retaining device (10) in at least one braking force holding position, wherein A control device equipped with a control program changes the end position of the plastic retaining element (18) relative to the electromechanical vehicle brake (12) that is necessary for a brake securing process of the electromechanical vehicle brake device (12), so that a constant load state on the plastic retaining element (18) caused by the brake securing process can be avoided during the entire service life of the retaining device.

2. The holding device (10) according to claim 1, wherein The plastic retaining element (18) is a plastic gear or worm gear arrangement.

3. The holding device (10) according to claim 1 or 2, wherein: The end position determined accordingly by means of a control device equipped with a control program can be changed between a first end position having a minimum holding force for a braking securing process of the electromechanical vehicle brake device (12) and a second end position having a maximum holding force for a braking securing process of the electromechanical vehicle brake device (12).

4. Holding device (10) according to any one of the preceding claims, wherein The end position of the plastic holding element (18) selected by means of a control device equipped with a control program differs at least from the end position of the plastic holding element (18) used last time.

5. Holding device (10) according to any one of the preceding claims, wherein A control device equipped with a control program changes the end position of the plastic retaining element (18) that has been selected for a current brake fixing process of the electromechanical vehicle brake device (12) towards at least another end position that is different from the already selected end position according to a parking time interval that can be set by the user.

6. Holding device (10) according to any one of the preceding claims, wherein A control device equipped with a control program changes the respective end positions using a random method.

7. Holding device (10) according to any one of the preceding claims, wherein The control device comprises at least one actuator (16) for setting a respective end position of the plastic retaining element (18) relative to the electromechanical vehicle brake (12).

8. An electromechanical disc vehicle brake system (24) having a holding device (10) according to any one of claims 1 to 7.

9. An electromechanical drum vehicle brake system (26) having a holding device (10) according to any one of claims 1 to 7.

10. Method for operating a holding device (10) according to any one of claims 1 to 7, comprising the following steps: - detecting (S1) a parking brake process of an electromechanical vehicle brake device (12) by means of a holding device (10) according to any one of claims 1 to 7; - determining (S2) a first end position of the plastic retaining element (18) of the retaining device (10) having a minimum retaining force for a brake securing process of the electromechanical vehicle brake device (12) and a second end position of the plastic retaining element (18) of the retaining device (10) having a maximum retaining force for a brake securing process of the electromechanical vehicle brake device (12); - selecting (S3) the current end position of the plastic retaining element (18) between the first end position and the second end position by means of a random method, wherein the selected current end position of the plastic retaining element (18) is at least different from the end position of the plastic retaining element (18) used the last time, so that a constant load state at the plastic retaining element (18) caused by the fixing process can be avoided during the entire service life of the retaining device (10).

11. The method for operating a holding device (10) according to claim 10, comprising the following steps: - recording the time course of a current braking holding process of the electromechanical vehicle brake system (12); - changing the current end position of the plastic retaining element (18) towards a new end position of the plastic retaining element (18) according to a user-definable parking time interval, wherein the new end position is different from the current end position of the plastic retaining element (18) used last time, so that a constant load state at the plastic retaining element (18) caused by the current braking fixing process of the electromechanical vehicle brake device (12) can be avoided.

12. The method for operating a holding device (10) according to claim 10, comprising the following steps: - recording the time course of a current braking holding process of the electromechanical vehicle brake system (12); - providing time-dependent material property values of the plastic material of the plastic retaining element (18); - Based on an evaluation of a time-dependent material property value, the current end position of the plastic retaining element (18) is changed towards a new end position of the plastic retaining element (18), which new end position is different from the current end position of the plastic retaining element (18) used last time, so that a constant load state at the plastic retaining element (18) caused by a current braking fixing process of the electromechanical vehicle brake device (12) can be avoided.

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