ELECTRONIC PARKING BRAKE ACTUATION SYSTEM

Abstract

An electronic parking brake system (100), comprising: a brake caliper (102); a first brake pad (106) and a second brake pad (106) disposed on either side of a brake rotor (110) and enclosed within the brake caliper (102); an actuating piston (103) enclosed within the brake caliper (102) and configured to act on the first brake pad (106); and a two-stage actuating mechanism (120) coupled to the actuating piston (103), the two-stage actuating mechanism (120) comprising: a first lead screw (122) having a first plurality of thread flanks; a second lead screw (124) having a second plurality of thread flanks; a preloaded torsion spring (128); andan actuating assembly (104) having an input shaft (130) coupled to the preloaded torsion spring (128) of the two-stage actuating mechanism (120);wherein the preloaded torsion spring (128) is configured to activate a first stage of movement of the two-stage actuation mechanism (120) via rotation of the first lead screw (122), and a size and a pitch of each of the first and second lead screws (122, 124) are configured to minimize power consumption by the actuation assembly (104) and to meet a desired actuation time with low power consumption and a high actuation gear ratio; wherein the input shaft (130) has a slot (131) and the preloaded torsion spring (128) has a first end that engages the slot (131) in a first configuration, and wherein the preloaded torsion spring (128) transmits input shaft torque from the actuation assembly (104) to rotate the first lead screw (122) a predetermined angular distance;wherein the actuating piston (103) has a notch (132) and the first end of the preloaded torsion spring (128) is directed radially from the slot (131) in the input shaft (130) to the notch (132) in the actuating piston (103) to hold the preloaded torsion spring (128) in a second configuration to prevent reverse rotation of the first lead screw (122) and to allow rotation of the second lead screw (124) in a second stage of movement of the two-stage actuating mechanism (120);

Description

INTRODUCTION

[0001] The present disclosure relates generally to the actuation of the electronic parking brake (EPB) for a vehicle.

[0002] Parking brakes (also called "emergency brakes") were historically manually operated mechanical devices configured to pull a cable, causing a mechanism to tighten a vehicle's rear brake calipers. Parking brakes were traditionally used to ensure a vehicle did not roll out of position, such as when parked on an incline.

[0003] Conventional electronic parking brakes (EPBs) cannot generate sufficient clamping force to hold the vehicle on steep or extreme gradients, both at gross vehicle weight (GVW) and gross combined vehicle weight (GCVW). Therefore, it would be desirable to achieve the desired clamping force with a faster application time while reducing the number of components of the EPB system.

[0004] JP 2010 - 190 348 A describes a disc brake with an electric parking mechanism. It comprises a brake caliper, brake pads, and a piston acting on one of the brake pads. A mechanical pressure-generating device has an adjusting screw and an input screw. A torsion spring and a coupled input shaft are also provided.

[0005] DE 10 2006 022 388 A1 describes an electromechanical disc brake as a service and parking brake for a motor vehicle. The brake is designed with a differential as a transfer case and an energy storage device, for example, in the form of a spring-loaded brake, which can be preloaded via the differential with an electromechanical actuation device and keeps the brake applied as a parking brake via the differential.

[0006] DE 10 2014 002 484 A1 describes a motor vehicle brake, in particular a combined hydraulically and electromechanically actuated motor vehicle brake, with an actuator assembly comprising: a housing, an actuator that is displaceable relative to the housing along a longitudinal axis for hydraulically or electromechanically displacing a brake pad, a motor drive, and a displacement mechanism arranged between the motor drive and the displaceable actuator for displacing the actuator.In order to achieve a rapid feed movement, it is provided that the displacement mechanism has a multi-stage spindle-nut arrangement with a first spindle-nut pairing with a first thread pitch and a second spindle-nut pairing with a second thread pitch, wherein the first thread pitch is greater than the second thread pitch, wherein in an electromechanical actuation of the motor vehicle brake, the first spindle-nut pairing is effective in a first actuation phase and the second spindle-nut pairing is effective in a second actuation phase. DESCRIPTION

[0007] Embodiments according to the present disclosure provide a number of advantages. For example, embodiments according to the present disclosure enable desired stresses of an electronic parking brake (EPB) system by using an actuator with a higher torque ratio without compromising the actuation time of the EPB system.

[0008] According to the invention, an electronic parking brake system comprises a brake caliper, a first brake pad, and a second brake pad disposed on either side of a brake rotor and enclosed within the brake caliper, an actuating piston enclosed within the brake caliper and configured to act on the first brake pad, and a two-stage actuating mechanism coupled to the actuating piston. The two-stage actuating mechanism includes a first lead screw having a first plurality of thread flanks, a second lead screw having a second plurality of thread flanks, a preloaded torsion spring, and an actuating assembly having an input shaft coupled to the preloaded torsion spring of the two-stage actuating mechanism.The preloaded torsion spring is configured to activate a first stage of movement of the two-stage actuating mechanism via rotation of the first lead screw. The size and pitch of the first and second lead screws are designed to minimize power consumption of the actuating assembly and achieve the desired actuation time with low power consumption and a high actuation gear ratio. The input shaft includes a slot, and the preloaded torsion spring includes a first end engaging the slot in a first configuration. In the first configuration, the preloaded torsion spring transmits input shaft torque from the actuating assembly to rotate the first lead screw through a predetermined angular travel.The actuating piston includes a notch, and the first end of the preloaded torsion spring is directed radially from the slot in the input shaft to the notch in the actuating piston to maintain the preloaded torsion spring in a second configuration to prevent back-driving of the first lead screw and to allow rotation of the second lead screw in a second stage of movement of the two-stage actuating mechanism.

[0009] In some cases, the second lead screw has a smaller pitch than the first lead screw.

[0010] In some aspects, the two-stage actuating mechanism includes a self-adjusting mechanism to control the displacement of the actuating piston within a predetermined travel.

[0011] In some cases, the actuating piston has a groove formed in an outer surface of the actuating piston, and the self-adjusting mechanism moves within the groove.

[0012] In some cases the groove has a width of about 4 mm.

[0013] In some aspects, the first lead screw is inserted into the actuating piston and the second lead screw is inserted into the first lead screw such that the first lead screw, the second lead screw, and the actuating piston move along a longitudinal axis.

[0014] In some cases, the first plurality of thread flanks of the first lead screw engages corresponding grooves in an inner surface of the actuating piston, and the second plurality of thread flanks of the second lead screw engages corresponding grooves in an inner surface of the first lead screw.

[0015] In some aspects, in the first phase of movement of the two-stage actuating mechanism, the first lead screw rotates via the preloaded torsion spring less than one hundred eighty (180) degrees to a first predetermined clamping load, and in a second phase of movement of the two-stage actuating mechanism, the second lead screw provides an additional clamping load.

[0016] In another aspect of the present disclosure, a two-stage actuation mechanism for a brake system includes an actuation piston configured to apply braking pressure to a brake rotor, a first lead screw having a first plurality of thread flanks, a second lead screw having a second plurality of thread flanks, a preloaded torsion spring, and an actuation assembly having an input shaft connected to the preloaded torsion spring of the two-stage actuation mechanism. The preloaded torsion spring is configured to activate a first stage of movement of the two-stage actuation mechanism via rotation of the first lead screw.The size and pitch of the first and second spindles are designed to minimize the power consumption of the actuating assembly and to achieve the desired actuating time with low power consumption and a high actuating gear ratio.

[0017] In some cases, the second lead screw has a smaller pitch than the first lead screw.

[0018] In some aspects, the two-stage actuating mechanism further includes a self-adjusting mechanism to control the displacement of the actuating piston within a predetermined travel.

[0019] In some aspects, the first lead screw is inserted into the actuating piston and the second lead screw is inserted into the first lead screw such that the first lead screw, the second lead screw, and the actuating piston move along a longitudinal axis.

[0020] In some cases, the first plurality of thread flanks of the first lead screw engages corresponding grooves in an inner surface of the actuating piston, and the second plurality of thread flanks of the second lead screw engages corresponding grooves in an inner surface of the first lead screw.

[0021] In some aspects, in the first phase of movement of the two-stage actuating mechanism, the first lead screw rotates via the preloaded torsion spring less than one hundred eighty (180) degrees to a first predetermined clamping load, and in a second phase of movement of the two-stage actuating mechanism, the second lead screw provides an additional clamping load.

[0022] In another aspect of the present disclosure, a braking system includes a brake caliper having an octagonal inner surface, a brake pad enclosed within the housing, an actuating piston configured to act on the brake pad, the actuating piston enclosed within the housing and configured to translate along a longitudinal axis, and a two-stage actuating mechanism coupled to the actuating piston. The two-stage actuating mechanism includes a first lead screw having a first plurality of thread flanks, a second lead screw having a second plurality of thread flanks, a preloaded torsion spring, and an actuating assembly having an input shaft coupled to the preloaded torsion spring of the two-stage actuating mechanism.The preloaded torsion spring is configured to activate a first stage of movement of the two-stage actuating mechanism via rotation of the first lead screw. The size and pitch of the first and second screws are designed to minimize the power consumption of the actuating assembly and achieve the desired actuation time with low power consumption and a high actuation gear ratio.

[0023] In some aspects, the actuating piston includes a linear bearing positioned on an outer surface of the actuating piston and surrounding at least a portion of the actuating piston, the linear bearing including an octagonal bearing surface that cooperates with the octagonal inner surface of the caliper to prevent rotation of the actuating piston.

[0024] In some cases, the first plurality of thread flanks of the first lead screw engages corresponding grooves in an inner surface of the actuating piston, and the second plurality of thread flanks of the second lead screw engages corresponding grooves in an inner surface of the first lead screw.

[0025] In some aspects, in the first phase of movement of the two-stage actuating mechanism, the first lead screw rotates via the preloaded torsion spring less than one hundred eighty (180) degrees to a first predetermined clamping load, and in a second phase of movement of the two-stage actuating mechanism, the second lead screw provides an additional clamping load. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present disclosure is described in conjunction with the following figures, in which like numerals represent like elements. Fig. 1 is a schematic side cross-sectional view of an electronic parking brake system according to one embodiment. Fig. 2 is a schematic side cross-sectional view of a two-phase actuation system of the electronic parking brake system of Fig. 1 according to one embodiment. Fig. 3 is a schematic perspective side view of the brake caliper of the electronic parking brake system of Fig. 1, which shows the actuating piston and a linear bearing according to one embodiment. Fig. 4 is a schematic side cross-sectional view of an electronic parking brake system in a first position, according to an embodiment. Fig. 5 is a schematic side cross-sectional view of an electronic parking brake system in a second position according to an embodiment. Fig. 6 is a schematic side cross-sectional view of an electronic parking brake system in a third position according to an embodiment. Fig. 7 is a schematic partial perspective view of a torsion spring component of a two-phase actuation system of an electronic parking brake system according to one embodiment. Fig. 8 is a schematic cross-sectional view of a shaft of the electronic parking brake system and the torsion spring in a first position according to one embodiment. Fig. 9 is a schematic cross-sectional view of a shaft of the electronic parking brake system and the torsion spring in a second position according to one embodiment. Fig. 10 is a schematic cross-sectional view of an electronic parking brake system shaft and torsion spring in a third position according to one embodiment. Fig. 11 is a flowchart of a method for actuating an electromechanical electronic parking brake system with two-stage actuation according to one embodiment.

[0027] The foregoing and other features of the present disclosure will become more apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings. Recognizing that these drawings illustrate only some embodiments according to the disclosure and are not to be considered limiting its scope, the disclosure will be described with additional specificity and detail through the use of the accompanying drawings. Any dimensions shown in the drawings or elsewhere are for illustrative purposes only. DETAILED DESCRIPTION

[0028] Embodiments of the present disclosure are described herein. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments may take various and alternative forms. The drawings are not necessarily to scale; some features may be exaggerated or reduced to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for showing one skilled in the art how to variously employ the present disclosure.As those skilled in the art will appreciate, various features illustrated and described with reference to one of the figures may be combined with features illustrated in one or more other figures to produce embodiments not explicitly illustrated or described. The illustrated feature combinations represent representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of this disclosure may be desirable for particular applications or implementations.

[0029] Certain terms are used in the following description for reference purposes only and should not be considered limiting. For example, terms such as "top" and "bottom" refer to directions in the drawings to which reference is made. Terms such as "front", "back", "left", "right", "rear", and "side" describe the orientation and / or location of parts of components or elements within a consistent, but arbitrary, frame of reference that will become clear by reference to the text and accompanying drawings in which the components or elements discussed are described. In addition, terms such as "first", "second", "third", etc. may be used to describe individual components. This terminology may include the above terms, their derivatives, and terms of similar meaning.

[0030] Current electronic parking brake (EPB) systems cannot generate the desired clamping forces to hold a vehicle on various gradients at both gross vehicle weight (GVW) and gross combined vehicle weight (GCVW). The embodiments discussed here incorporate a two-stage actuation system with two series-connected lead screws to generate the desired clamping force within the desired actuation time. In various embodiments, the two spindles are connected to a preloaded torsion spring that activates the first stage until a certain predetermined clamping force is reached. The second stage lead screw is used for load modulation.

[0031] In the Fig. 1 and Fig. 2 illustrates an electronic parking brake (EPB) system 100 according to one embodiment. The EPB system 100 includes a two-stage actuation mechanism 120 and an actuation assembly 104. The EPB system 100 includes a brake caliper 102. The brake caliper 102 encloses a first brake pad 106 and a second brake pad 108 disposed on either side of a brake rotor 110. The brake caliper 102 also includes an actuation piston 103 and the two-stage actuation mechanism 120. The two-stage actuation mechanism 120 engages the actuation piston 103 to transmit the torque generated by the actuation assembly 104 to the brake pad 108. The actuating piston 103 defines a longitudinal axis A along which the actuating piston 103 translates upon actuation by the two-stage actuating mechanism 120, as described herein.

[0032] As in Fig. 3, the actuating piston 103 includes a linear bearing 150. The linear bearing 150 is arranged on an outer surface of the actuating piston 103, encloses at least a portion of the actuating piston 103, and includes a bearing surface 151. The bearing surface 151 is octagonal and forms an interface with an octagonal inner surface 111 of the brake caliper 102. The linear bearing 150 also includes a plurality of bearing elements 152, 154. In various embodiments, the bearing elements 152, 154 are ball bearings. The actuating piston 103 translates along the longitudinal axis A within the inner chamber 112 of the brake caliper 102. Rotation of the pressure piston 103 is prevented by the interface between the octagonal bearing surface 151 and the octagonal inner surface 111 of the inner chamber 112 of the brake caliper 102.

[0033] With further reference to Fig. 1, in various embodiments, the EPB system 100 also includes a linear position sensor 20 for the actuating piston and an actuator output shaft position sensor 22. Each of the sensors 20, 22 is in electronic communication with or under the control of at least one controller 24. Although shown as a single unit for illustrative purposes, the controller 24 may additionally include one or more other controllers, collectively referred to as a "controller." The controller 24 may include a microprocessor or central processing unit (CPU) that communicates with various types of computer-readable storage devices or media. The computer-readable storage devices or media may include volatile and non-volatile memory, such as read-only memory (ROM), random access memory (RAM), and keep-alive memory (KAM).KAM is a persistent or non-volatile memory that can be used to store various operating variables while the CPU is off. Computer-readable storage devices or media can be implemented using any number of known storage devices, such as PROMs (programmable read-only memory), EPROMs (electrically erasable PROMs), EEPROMs (electrically erasable PROMs), flash memory, or other electrical, magnetic, optical, or combination storage devices capable of storing data, some of which may represent executable instructions used by the control module 24 in controlling the vehicle.

[0034] In various embodiments, the controller 24 is also in electronic communication with the actuation assembly 104. In some embodiments, the controller 24 includes an engine controller and may be in combination with or in electronic communication with an electronic control unit on board the vehicle.

[0035] As in Fig. 2, the two-stage actuation mechanism 120 includes a first lead screw 122 and a second lead screw 124. The first lead screw 122 includes a plurality of thread flanks 123 that engage corresponding grooves 113 in an inner surface of the actuation piston 103. Similarly, the second lead screw 124 includes a plurality of thread flanks 125 that engage corresponding grooves 127 in an inner surface of the first lead screw 122. The lead angles of the threads 123, 125 are designed to correspond to the desired load profile for a desired actuation time. The second lead screw 124 has a smaller pitch than the first lead screw 122. In various embodiments, the second lead screw 124 is replaced by a ball screw and a brushless motor for actuation, thereby creating an intelligent electromechanical brake actuator.

[0036] In various embodiments, the second threaded spindle 124 is inserted into the first threaded spindle 122, and the first threaded spindle 122 is inserted into the actuating piston 103. The second threaded spindle 124 also includes a shaft portion 130 that engages the actuating assembly 104. The actuating assembly 104 has a high-ratio reduction gear to maintain the clamping load at the actuating planes. The non-returnable threads 125 of the second threaded spindle 124 maintain the clamping force of the actuating piston 103 without any time delay.

[0037] The first and second threaded spindles 122, 124 are connected to a preloaded torsion spring 128. The torsion spring 128 activates the first stage of movement of the two-stage actuating mechanism 120, i.e., the movement of the first threaded spindle 122, until a predetermined clamping force is reached.

[0038] In various embodiments, the two-stage actuation mechanism 120 also includes a self-adjusting mechanism, e.g., a ring 126. The ring 126 controls the displacement of the actuation piston 103 within a predetermined travel. Controlling the displacement of the actuation piston 103 makes it insensitive to the wear of components such as the brake pads 106, 108. As shown in the Fig. 1 and Fig. As shown in Figure 2, the ring 126 slides within a groove 136 formed in an outer surface of the actuating piston 103. In various embodiments, the groove 136 has a width of approximately 4 mm. The self-adjusting mechanism resets only the position of the first lead screw 122 within the two-stage actuating mechanism 120 to account for component wear.

[0039] In the Fig. 4 to 6 illustrate three stages of actuation of the two-stage actuation mechanism 120 of the EPB system 100. As explained in more detail therein, the engagement of the plurality of threads 123 of the first lead screw 122 with the corresponding grooves 113 in the actuation piston 103 in a first actuation stage and the engagement of the plurality of threads 125 of the second lead screw 124 with the corresponding grooves 127 in the first lead screw 122 in a second actuation stage transmit torque from the actuation assembly 104 to move the actuation piston 103 toward the brake pads 106, 108 and exert a braking force on the brake rotor 110. The lead angles of the two screws are designed to correspond to the load profile for a desired actuation time. In various embodiments, the actuation time is approximately 250 ms.

[0040] Fig. Figure 4 shows the EPB system 100 in a disengaged position, meaning the actuating piston 103 is not exerting a clamping force on the brake pad 108 and no braking is occurring. The ring 126 is located at one end of the groove 136 (in the illustrated embodiment, at the left side or end of the groove 136). The ring 126 acts as a wear control mechanism to control the total travel of the actuating piston 103. In various embodiments, the width of the groove 136 is approximately 4 mm, limiting the travel of the actuating piston 103 to approximately 4 mm. A gap 146 is maintained between the actuating piston 103 and the brake pad 108 to limit inadvertent wear of the components. By electrically actuating the actuating arrangement 104, the actuating piston 103 can be completely retracted from the brake pad 108 in order to allow for a larger running clearance and to avoid a drag torque on the disc brake.

[0041] When the brake is applied as in Fig. As shown in Figure 5, the first threaded spindle 122, which is connected to the input shaft 130 via the torsion spring 128, provides the first stage of actuation. The first threaded spindle 122 rotates less than 180 degrees to close the gap 146 between the actuating piston 103 and the brake pad. In various embodiments, the first threaded spindle 122 generates a clamping force of approximately 250 N.

[0042] In the second stage of activity, which is Fig. As shown in Figure 6, the second lead screw 124 is activated when the torsion spring preload condition is almost overcome. Activation of the second lead screw 124, which has a smaller pitch than the first lead screw 122, provides a greater clamping force of up to approximately 35 kN. The maximum clamping force of the EPB system 100 is achieved in various embodiments within one and a half revolutions of the input shaft 130 of the actuation unit 104.

[0043] Fig. 7 shows the torsion spring 128 coupled to the input shaft 130. The torsion spring 128 includes a first end 129 that engages a gap or slot 131 formed in the input shaft 130.

[0044] The Fig. 8-10 show the position of the first end 129 of the torsion spring 128 when the two-stage actuation mechanism 120 transitions from the first actuation stage to the second actuation stage. As shown in Fig. 8, the first end 129 of the torsion spring 128 engages the input shaft 130 via the slot 131. During the initial application of braking torque from the actuating assembly 104, the preload of the torsion spring 128 transmits the input shaft torque over a predetermined angular path (represented by arrow 141) to the first threaded spindle 122 until the first end 129 of the torsion spring 128 reaches a position where the transition to the second actuation stage begins.

[0045] The transition between the first stage of operation and the second stage of operation is in Fig. 9. As shown by arrow 142, continued angular rotation of the input shaft 130 causes the first end 129 of the torsion spring 128 to be pressed into a notch or groove 132 in the actuating piston 103. The preload of the torsion spring 128 thus holds the first lead screw 122 in a preloaded position and prevents the first lead screw 122 from rotating backward.

[0046] Fig. Figure 10 shows the second stage of actuation. As shown, the first end 129 of the torsion spring 128 is fully seated in the notch 132 of the actuating piston 103. Continued rotation of the input shaft 130 results in the actuation of the second lead screw 124. The second lead screw 124 provides load modulation and additional clamping force over a small travel range.

[0047] The EPB system 100 and two-stage actuation mechanism 120 described herein can be used on the rear wheels of a vehicle as a means of immobilizing the vehicle. In various embodiments, the EPB system 100 and two-stage actuation mechanism 120 are used on the wheels at all four corners of the vehicle, depending on the weight and type of vehicle.

[0048] In various embodiments, the first and second lead screws 122, 124 are configured (size and pitch) to minimize the power consumption of the actuation assembly 104, while ensuring that the EPB system 100 achieves the desired actuation time with low power consumption and the highest possible actuation gear ratio. In various embodiments, the preload and pitch of the torsion spring 128, in conjunction with the lead angles of the first and second lead screws 122, 124, are configured to achieve the maximum possible actuation time across the air gap and ensure a minimum clamp load.

[0049] Fig. 11 illustrates a method 1000 for actuating an electromechanical EPB system with two-stage actuation according to one embodiment. The method 1000 may be used in conjunction with the EPB system 100 and the two-stage actuation mechanism 120 described herein. The method 1000 may be applied in conjunction with the controller 24 as described herein or by other systems connected to or disconnected from the vehicle according to exemplary embodiments. The order of the method 1000 is not limited to sequential execution as described in Fig. 11, but may be performed in one or more varying orders, or the steps may be performed concurrently, as applicable in accordance with the present disclosure.

[0050] Starting at 1002, a braking command is received from the controller 24. In various embodiments, the braking command is initiated by the driver, e.g., by selecting an electronic parking brake or by a vehicle control unit initiating a vehicle braking function. Next, at 1004, the preload of the torsion spring 128 is applied. The preload is applied when the actuation assembly 104 receives an actuation command or signal from the controller 24. The preload transfers the input shaft torque from the actuation assembly 104 to the first lead screw 122 for a predetermined angular travel. The preload initiates rotation of the first lead screw 122 to quickly translate the actuation piston 103 and reduce and / or eliminate the gap 146 under light loads.

[0051] Next, at 1006, the torsion spring 128 engages the actuating piston 103 to maintain the first stage in the preloaded position and prevent the first lead screw 122 from rotating backward. The engagement of the torsion spring 128 with the actuating piston 103 occurs after a predetermined angular travel of the input shaft 130. Finally, at 1008, the second stage is initiated by the rotation of the second lead screw 124, which transmits additional torque from the actuating unit 104 and provides load modulation and additional clamping force.

[0052] In various embodiments, during the various steps 1002, 1004, 1006, 1008 of method 1000, controller 24 receives sensor data from linear position sensor 20 for the actuating piston and position sensor 22 for the actuator output shaft. The data received from one or both sensors 20, 22 is used by controller 24 to control the actuation of actuator assembly 104.

[0053] It should be emphasized that many variations and modifications may be made to the embodiments described herein, with the elements of these embodiments being understood as further acceptable examples. All such modifications and variations are intended to be included within the scope of this disclosure and protected by the following claims. Furthermore, each of the steps described herein may be performed concurrently or in a different order than that given herein. Furthermore, as should be appreciated, the features and characteristics of the specific embodiments disclosed herein may be combined in various ways to form additional embodiments, all of which fall within the scope of the present disclosure.

[0054] Conditional language used herein, such as "may," "could," "e.g.," and the like, unless expressly stated otherwise or understood by context, is generally intended to convey that certain embodiments include certain features, elements, and / or conditions while other embodiments do not include them. Therefore, such conditional language is generally not intended to imply that any features, elements, and / or conditions are in any way required of any embodiment or that any embodiment or embodiments necessarily include logic for determining, with or without input or prompting from the author, whether to include or implement these features, elements, and / or conditions in a particular embodiment.

[0055] Additionally, the following terminology may have been used herein. The singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. For example, reference to an item includes reference to one or more items. The term “one” refers to one, two, or more and generally applies to selecting some or all of a quantity. The term “several” refers to two or more instances of an item. The term “about” or “approximately” means that quantities, dimensions, sizes, wording, parameters, shapes, and other characteristics need not be exact, but may be approximated and / or larger or smaller as desired, taking into account acceptable tolerances, conversion factors, rounding off, errors of measurement, and the like, as well as other factors known to those skilled in the art.The term "substantially" means that the specified characteristic, parameter or value need not be achieved exactly, but that deviations or variations, such as tolerances, measurement errors, limitations of measurement accuracy and other factors known to the person skilled in the art, may occur to an extent that does not preclude the intended effect of the characteristic.

[0056] For convenience, a plurality of items may be listed in a common list. However, these lists should be interpreted as if each member of the list is individually identified as a separate and unique member. Therefore, no individual member of such a list should be construed as the de facto equivalent of any other member of the same list solely by virtue of their presentation in a common group, without any indication to the contrary. When used in connection with a list of items, the terms "and" and "or" should be broadly construed so that any of the listed items may be used alone or in combination with other listed items.The term “alternative” refers to the selection of one of two or more alternatives and is not intended to limit the selection to the alternatives listed or to only one of the alternatives listed at a time, unless the context clearly indicates otherwise.

[0057] The processes, methods, or algorithms disclosed herein may be delivered to or executed by a processing device, controller, or computer, which may include any existing programmable electronic control unit or dedicated electronic control unit. Likewise, the processes, methods, or algorithms may be stored as data and instructions executable by a controller or computer in many forms, including, but not limited to, information permanently stored on non-writable storage media such as read-only devices and information modifiably stored on writable storage media such as floppy disks, magnetic tapes, compact discs, RAM devices, and other magnetic and optical media. The processes, methods, or algorithms may also be implemented in an executable software object.Alternatively, the processes, methods, or algorithms may be embodied, in whole or in part, by suitable hardware components such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), state machines, controllers, or other hardware components or devices, or a combination of hardware, software, and firmware components. Such example devices may be onboard as part of a vehicle computing system or may be located off-board the vehicle and perform remote communication with devices in one or more vehicles.

[0058] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms encompassed by the claims. The words used in the description are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments may be combined to form other exemplary aspects of the present disclosure that may not be expressly described or illustrated.While various embodiments might be described as advantageous or preferred over other prior art embodiments or implementations with respect to one or more desired characteristics, those skilled in the art will recognize that one or more features or characteristics may be compromised to achieve desired overall system characteristics depending on the specific application and implementation. These characteristics may include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. Therefore, embodiments described as less desirable than other prior art embodiments or implementations with respect to one or more features are not outside the scope of the disclosure and may be desirable for certain applications.

Claims

[1] Electronic parking brake system (100), comprising: a brake calliper (102); a first brake pad (106) and a second brake pad (106) arranged on both sides of a brake rotor (110) and enclosed in the brake caliper (102); an actuating piston (103) enclosed in the brake caliper (102) and configured to that it acts on the first brake pad (106); and a two-stage actuating mechanism (120) coupled to the actuating piston (103), the two-stage actuating mechanism (120) comprising: a first threaded spindle (122) having a first plurality of thread flanks; a second threaded spindle (124) having a second plurality of thread flanks; a preloaded torsion spring (128); and an actuating assembly (104) having an input shaft (130) coupled to the preloaded torsion spring (128) of the two-stage actuating mechanism (120); wherein the preloaded torsion spring (128) is configured to activate a first stage of movement of the two-stage actuation mechanism (120) via rotation of the first lead screw (122), and a size and a pitch of each of the first and second lead screws (122, 124) are configured to minimize power consumption by the actuation assembly (104) and to meet a desired actuation time with low power consumption and a high actuation gear ratio; wherein the input shaft (130) has a slot (131) and the preloaded torsion spring (128) has a first end that engages the slot (131) in a first configuration, and wherein the preloaded torsion spring (128) in the first configuration transmits an input shaft torque from the actuating assembly (104) to rotate the first lead screw (122) a predetermined angular distance; wherein the actuating piston (103) has a notch (132) and the first end of the preloaded torsion spring (128) is directed radially from the slot (131) in the input shaft (130) to the notch (132) in the actuating piston (103) to hold the preloaded torsion spring (128) in a second configuration to prevent reverse rotation of the first lead screw (122) and to allow rotation of the second lead screw (124) in a second stage of movement of the two-stage actuating mechanism (120). [2] Electronic parking brake system (100) according to claim 1, wherein the second threaded spindle (124) has a smaller pitch than the first threaded spindle (122). [3] The electronic parking brake system (100) of claim 1, wherein the two-stage actuating mechanism (120) includes a self-adjusting mechanism for controlling displacement of the actuating piston (103) within a predetermined travel. [4] The electronic parking brake system (100) of claim 3, wherein the actuating piston (103) has a groove (136) formed in an outer surface of the actuating piston (103), and the self-adjusting mechanism moves within the groove (136). [5] The electronic parking brake system (100) of claim 4, wherein the groove (136) has a width of approximately 4 mm. [6] Electronic parking brake system (100) according to claim 1, wherein the first threaded spindle (122) is arranged in the actuating piston (103) and the second threaded spindle (124) is arranged in the first threaded spindle (122) such that the first threaded spindle (122), the second threaded spindle (124) and the actuating piston (103) move along a longitudinal axis. [7] The electronic parking brake system (100) of claim 1, wherein the first plurality of thread flanks of the first threaded spindle (122) engages with corresponding grooves (113) in an inner surface of the actuating piston (103) and the second plurality of thread flanks of the second threaded spindle (124) engages with corresponding grooves (113) in an inner surface of the first threaded spindle (122). [8] The electronic parking brake system (100) of claim 1, wherein in the first stage of movement of the two-stage actuating mechanism (120), the first lead screw (122) rotates via the preloaded torsion spring (128) by less than one hundred and eighty (180) degrees to a first predetermined clamping load, and in a second stage of movement of the two-stage actuating mechanism (120), the second lead screw (124) provides an additional clamping load.

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