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Title:
ELECTRICALLY DRIVEN PARKING BRAKE ACTUATION ASSEMBLY
Document Type and Number:
WIPO Patent Application WO/2002/095256
Kind Code:
A2
Abstract:
A parking brake actuation assembly is provided including an electric motor and a first rotatable member operatively connected to the electric motor so as to enable the motor to rotate the first rotatable member in a brake applying rotational direction. The first rotatable member normally is prevented against rotation in a brake releasing rotational direction. A second rotatable member is rotatable relative to the first rotatable member and includes cable attachment structure for affixing a brake activation linkage thereto. A clutch spring is disposed between the first and second rotatable members and is configured to contract upon initiation of rotation of the first rotatable member in the brake applying direction so as to couple the second rotatable member to the first rotatable member for affecting rotation of the second rotatable member in the brake applying direction.

Inventors:
REVELIS PETER
SYKES MICHAEL
Application Number:
PCT/IB2002/003125
Publication Date:
November 28, 2002
Filing Date:
May 24, 2002
Export Citation:
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Assignee:
VENTRA GROUP INC (CA)
International Classes:
B60T7/02; B60T7/10; B60T13/74; F16D65/28; (IPC1-7): F16D65/00
Foreign References:
DE19653961A11998-06-25
US6386338B12002-05-14
US4561527A1985-12-31
Download PDF:
Description:
ELECTRICALLY DRIVEN PARKING BRAKE ACTUATION ASSEMBLY , [ [001]' "e present application claims priority to U. S. Provisional Application Serial . No. 60/2) 2, 914 f led May 24, 2001, and U. S Nonprovisional Application filed May 23, 2002, ! application to be assigned, the entirety of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention i [0002] The present invention relates to a parking brake actuation system for a motor vehicle a d ; more ; particularly, to an improved electrically driven parking brake actuation assembly that car be electric, ally or manually released. 2. escripti'of Related Art [ (10031 S (me automc iles or other motor vehicles are equipped with power-assisted parking brakes. A power-assisted parking brake is an electrically driven brake actuation system that allows remote actuation'of the brakes of the automobile (typically only the rear brakes) to prevent movement of the automobile when parked. These systems include an electric motor and a rotaiior Lal-to-lilear drive mechanism for translating the rotational movement and torque of the motor to linear displacement of a brake cable mechanically connected to the brakes. Upon remote a, tuation, l fthe motor rotates to effect displacement of the brake cable to set the brakes. The brass may similarly be remotely released by effecting reverse rotation of the motor. Additionally, the brakes may be manually released with a manual override in case of automobile zu power fa lure, to low the automobile to be moved (e. g., towed). There are several disadvan ages wi h brake actuation systems of current design. i 0041 The manual overrides usually do not allow unrestricted movement of the brake cable and brakes back to their home (unactuated) positions. This is due to the resistance to ! movement inherent within the brake actuation system itself, such as in the drive mechanism and the motor. Accordingly, use of the manual override does not necessarily ensure complete release of the brakes. Forced movement of the automobile with only partially released brakes can causl wear anLd/or damage to the brakes. [0005] Additionally, in order to maintain actuation of the brakes, with some systems the 0 motor must be continuously energized to maintain a holding torque on the drive mechanism. This continuous use of the motor significantly limits the useable life of the motor and therefore the brake actuation system. Alternatively, a separate locking device may be used to allow the l. motor to be de-er rgized without allowing slippage of the brakes. However, this superfluous , I compon ntry siglificantly increases manufacturing costs of the brake actuation system. ! Moreover, additicn of such 2 separate component increases the size of the brake actuation f such system and correspondingly reduces orientation and space management options available for installation of the brake actuation system into an automobile. [0006] Furthermore, prior brake actuation systems have been integrated with ! componentry of the vehicles themselves and have not been readily available for add-on or retro- fitting to other vehicles. SUMMARY OF THE INVENTION i [ () 0071 A first aspect'of the present invention provides a power-driven parking brake !, h actuating assemb y for actuating a vehicle brake system via a brake activation linkage including an electric motor and a first rotatable member operatively connected to the electric motor so as to enable the motor to rotate the first rotatable member in a brake applying rotational direction. The first rotatable member is normally prevented against rotation in a brake releasing rotational direction. A second rotatable member is rotatable relative to the first rotatable member and includes a brake linkage actuator connectable to the brake activation linkage and movable to actuate the same. A torsion clutch spring is disposed between the first and second rotatable I members and is configured to contract upon initiation of rotation of the first rotatable member by the m tor in the brake applying direction so as to couple the second rotatable member to the i first rotai able member for affecting rotation of the second rotatable member in the brake i applying direction for actuation of the brake activation linkage. The clutch spring is also configured to remain contracted as the actuated brake activation linkage applies a force to the second rotatable 'ember in the brake releasing direction so as to keep the second rotatable ! member oupled to the first rotatable member. This'enables the first rotatable member to ; , I i I prevent rotation of the second rotatable member in the brake releasing direction. A selectively actuable brake release mechanism is operatively connected to the clutch spring such that movement of the release member expands the clutch spring to de-couple the second rotatable member from the first member, thus enabling the second rotatable member to rotate in the brake j releasing direction. [008] The release mechanism may be manually powered or electrically powered, preferably by a source separate from the vehicle's conventional main battery system, so that it can be re eased ii j the event vehicle power is lost and the main battery system is drained. ; [ (009] A) bother aspect of the present invention provides a brake actuation assembly i I including an elec c motor having an output shaft and a drive assembly coupled to the output shaft. Tlle brake actuation assembly also includes a pivot structure coupled to the drive assembly so as to be pivotable by the electric motor via the drive assembly. The pivot structure i, has comi cting sti ucture thereon configured to couple with a brake actuating linkage. The drive assembly is configured to lock in a brake actuated position upon movement thereinto. A release structure is coupled to the drive assembly to release the drive assembly from the locked brake actuated position The release structure includes a pair of connecting portions positioned thereon a : respective relative positions. Each of the connecting portions is configured to connect to a release cable assembly, such that the brake actuating assembly is capable of being disposed ,'I in two di ferent'stallation orientations corresponding to the positions of the connecting J ! ! portions.' i [8010] Tllfese and other aspects of this invention will become apparent upon reading the followin disclosure in accordance with the figures. i, I BRIEF DESCRIPTION OF THE DRAWINGS [0011] Fig. 1 is a schematic view of a vehicle equipped with a brake actuation assembly according to principles of the present invention ; [012] Fig. 2 is a top plan view of one embodiment of the brake actuation assembly shown in Fig. 1 iii a first position ; [013] Fi. 3 is a perspective explod d view of the brake actuation assembly shown in I I, Fig. [014] F s. 3A and 3B are detailed perspective exploded views of the brake actuation li I ; assembl shown in Fig. 3 ; I O15 Fi. 4 is a top plan view of the brake actuation assembly shown in Fig. 2 in a [] g pp Y g second position ;., ! ! [01 016] Figs. 5-5B are cross-sectional views of connecting portions of the brake actuation h assemble shown m Fig 4 ; [(1017] Fig. 6 is a top plan view of the brake actuation assembly shown in Fig. 2 in a third pos tion ; l [ (018] Fi. . 7 is a schematic view of another embodiment of the brake actuation assembly shown m Fig. 1 ; i II' [019] Fi. 8 is a perspective view of a manual release mechanism of the brake actuation . I'I assembly shown in Fig. 7 ; [U020] Fig. 9 is a top plan view of the manual release mechanism shown in Fig. 8 ; I. [0021] Fig. 10 is a cross-sectional view of the manual release mechanism taken along j line I-I in Fig. 9 ; !' [0022] Fig. 11 is a perspective view of a release gear of the manual release mechanism shown in Fig. 8 ; [/023] Figs. 12 and 13 are front and top plan views, respectively, of the release gear i shown in Fig. 11 ; [024] Fi g. 14 is a perspective view of a release lever of the manual release mechanism [ () 0241 Fi, lr shown in Fig. 8 ; and ! I [025] Fi's. 15 and 16 are front and top plan views, respectively, of the release lever shown in Fig. 14. , ! i DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION i [0026] Fig. 1 schematically illustrates a vehicle 10 having a pair of front wheel assemblies 12 and a pair of rear wheel assemblies 14. The rear wheel assemblies 14 each include a brake nbchanism 16, e. g., drum or disk brake mechanisms, which are operable to I apply'a braking force to the wheel assemblies 14 in order to slow and/or stop the vehicle 10 whenmoving, or to prevent movement of the vehicle 10 when stopped. The brake mechanisms i I I 16 are accuable bv a hydraulic brake system including a pedal and master cylinder (not shown) and hydraulic lines 18 connected between the master cylinder and the brake mechanisms. Additionally, the brake mechanisms 16 may be mechanically actuated by a brake actuation linkage including a pair of linkages 20 coupled to a brake actuation assembly 22 via a connecting linkage 24. In the illustrated embodiment, the linkages 20, 24 are wire strand cables ; however they may be rigid linkages, such as rods. The brake actuation assembly 22 is remotely i operable to electrically apply or release the brake mechanisms 16 via the linkages 20, 24 by an occupant of the vehicle 10, e. g., a driver, with an electrical control assembly 26. The electrical , j i control assembly 26 may include, e. g., a pair of push buttons, or a two-position toggle switch t ! ! ).) i I i positioned, e. g\, within a dashboard or console of the vehicle 10 to remotely apply and release , rakc me. a ralce actuation assembly 22. Additionally, a manual release i i mechani m 28 m y be used to release tension within : the linkages 20, 24 to release the brake ' ! ! mechani ms 16, such as when the vehicle 10 is not powered. [0027] Fig. 2 shows the brake actuation assembly 22 in greater detail. The brake actuation assembly 22 includes a housing 30 having a base 32 and side wall portions 34 and 36 and a top plate 37 coupled to the side wall portions 34, 36 to form an enclosure for a drive i assembly 38. Figs. 3 and 3A show the top plate 37 including a pair of slots 39 formed therein. i The slot 39 are configured to receive therein a corresponding pair of upright portions 33 on the p gp p g p side wall portion 36 to secure the top plate 37 to the side wall portion 36. Additionally, the top i plate 37 ncludes a slot 41 formed in an end thereof opposite the slots 39. The slot 41 is i configured to receive therein an upright portion 35 on the side wall portion 34 to secure the top plate 37 o the sic e wall portion 34. The housing 30 may be formed of sheet or plate metal material, or any suitably rigid material, such as a polymer or composite. i., 1, 0281 The drive assembly 38 is configured to be driven by a reversible electric motor 40 to ap ly and release a tension within the connecting linkage 24 to correspondingly apply and release the brake mechanisms 16. The connecting linkage 24 is connected to the drive assembly li 38 via a sensing device 44, which will-be discussed in greater detail below. Additionally, the manual r lease mechanism 28 includes a cable assembly 46 having a pull cable 48 coupled to the drive assembly 38 to allow manual release of tension within the connecting linkage 24 and thereby release tt e brake mechanisms 16 in a manner that will also be discussed below in greater détail. detail.' ; 029] A shown in Fig. 3, the motor'40 is connected to the side wall portion 34 with a spacer member 42 disposed therebetween by, e. g., threaded fasteners (not shown). Alternatively, the ; spacer member 42 may be separately connected to or formed integrally with either of the side wall portion 34 and motor 40. The motor 40 includes an armature 50 that may be coupled to a drive shaft 52 via a coupling structure 54. Alternatively, the armature 50 may be integrally formed with the drive shaft 52. The drive shaft 52 extends through aligned openings within the spacer 42 and side wall portion 34. A worm gear 56 is fixedly mounted to the drive shaft 52 (or may be integrally formed therewith) and an end portion 58 of the drive shaft 52 is !" rotatably supported within a receiving opening 59 formed in the side wall portion 36 such as with a bearing or journal structure 60 to facilitate rotation and flexural support of the drive shaft 52. Add tionally, shafts 62, 64, 66 extend through corresponding shaft receiving openings 68 . : ! within the base 32 and are non-rotatably fixed thereto. As shown, the shafts 62, 64, 66 are ; oriented parallel b one another and perpendicularly to the worm 56. i 1103 01 A st gear structure 70 is rotatably mounted on shaft 62 within the housing 30. i The first gear structure 70 includes a worm gear 72, a pinion gear 74, and a spacer 76 which may be forme separately or integrally as one piece. The worm gear 72, pinion gear 74, and spacer ! 76 are coaxially aligned and at least the wonn gear 72 and pinion gear 74 are non-rotatably ! ! connected to each other (i. e., they are fixed for rotation together). The worm 56, being rotatable ion by the motor 40, is drivingly engaged in an intermeshed relation with the worm gear 72 to drive the first ear ear structure 70. The worm gear 72 rotatably drives the pinion gear 74 due to their integral c r non-ro ratable relation. A second gear structure 78 is similar to the first gear structure i 70 and includes a spur gear 80, a pinion gear 182, and a spacer 84. Although shown separately, I I the spur ear 80, inion gear 82, and spacer 84 may be formed integrally with one another as one thé piece. any case, at least the gears 80, 82 are non-rotatably connected to one another. The i pinion ge ar 74 of the first gear structure 70 drivingly engages the spur gear 80 of the second gear structure in an intermeshed relation, which correspondingly rotates the pinion gear 82. The i pinion gear 82 drivingly engages a main gear 86 in an intermeshed relation, which is rotatably mounted on shaft, 66. The main gear 86 may be of any type or construction and may be generica y referred to as a non-limiting first rotatable member. , I : 1 [0031] The torque at main gear 86, as well as the rotational speed thereof, is generated by the m) tor 40 and is delivered to the main gear 86 via the first and second gear structures 70, 78. The torque and speed of the main gear 86 may be altered by modifying the torque and speed of the, m tor 40 a d/or by altering the relative sizes of the gears 56, 72, 74, 80, 82, and 86. [032] A further shown in Fig. 3, the main gear 86 includes a first shaft element 88 , thereon. The main gear 86 and first shaft eler ent 8 ly integrally formed as one ! piece, however, may be separately formed and subsequently non-rotatably coupled to one another. The first shaft element 88 is oriented concentrically with the main gear 86 and extends coaxially outwardly therefrom. The first shaft element 88 defines a circumferential outer periphery 90. The first shaft element 88 can be coupled to a second shaft element 94 of a second rotatable member to move a cable attachment structure on the second rotatable member 95. The cable attachment structure may include an activation arm 96, which is pivoted with the second i rotatable membel by the coupling of the first and second shaft elements 88, 94, as will be discusse in greater detail below. The second shaft element 94 is coaxially aligned with the first shaft elet nent 88. ind is formed with a diameter equal an outer diameter of the first shaft element [. i I 88. The activation arm 96 extends generally radially outwardly from the second shaft element g Y Y Y n 94. A fi st end 98 of the sensing device 44 is coupled to a radially outward end of the activation arm 96 second end 100 of the sensing device 44 is connected to the connecting linkage 24. Accordingly, when the second shaft element 94 is rotated, the activation arm 96 pivots to apply f (i and release a tension on the connecting linkage 24 thereby applying and releasing the brake n mechanisms 16. Il xi 10331 annular groove 102 is provided within the main gear 86 along the outer periphery 90 of the first shaft element 88. The annular groove 102 includes a tangential leg 104. A clutch spring 106 in the form of a torsion spring having a plurality of circular windings includes a first end 108 that is received within the annular groove 102. A tang 110 is received g within the tangential leg 104 of the annular groove 102. As shown in Fig. 3B, a release gear 112 includes an annular groove 1lu14 formed therein so as to receive a second end 116 of the clutch spring 1 (6. The annular groove 114 includes another tangential leg 118 that receives an opposite extending tang 120 of the second end 116 of the clutch spring 106. The release gear 112 is foLned witlh a circular central opening 121 that extends axially therethrough so as to i receive the second shaft element 94 therein. The release gear 112 is rotatably mounted on the i second shaft element 94 and is non-rotatably coupled to the second end 116 of the clutch spring 106 via the receipt of the tang 120 in the tangential leg 118. !' : [034] A release bracket, or release lever, 122 includes an annular structure 124 defining an axially extendimg circular central opening 126 to rotatably receive therein the second shaft ; element 94. The Felease bracket 122 is axially disposed between the activation arm 96 and the release g ar 112 on the second shaft element 94. The release bracket 122 includes a pair of : j L radially extending connecting portions 128, 1129 that are configured to fixedly receive an end of 9 the pull cable 48. The connecting portions 128, 129 are preferably arranged on the annular t structure 124 to be circumferentially spaced about 90° from one another. Although only one cable ass zmbly 48 is needed for the manual actuator 28, forming the release bracket 122 with the pair of connecting portions 128, 129 at different relative positions provides different configuration options for installation into the vehicle 10. Figs. 3 and 4 show the cable 48 i connecte to respective connecting portions 128, 129. A pivotable pawl structure 130 is mounted to the annular structure 124 adjacent the connecting portion 128. The pawl 130 !' includes a ratchet tooth 132 extending outwardly therefrom for engagement with the release gear 112. [035] As shown in Figs. 3B and 5, the connector portion 128 may have a generally U- shaped configuration providing spaced opposing wall structures 128A, 128B. Each wall structure 128A, 128B is formed with an opening 131A, 131B therein. In a situation such as shown in Figs. 3B and 5, wherein the cable 48 is connected to the connector portion 129, a I. cylindrical retaining pin 131 is disposed within openings 131A, 131B in the wall structures 128A, 128B of the connector portion 128. The pawl structure 130 is disposed between the wall i i : structures 128A, 128B and is pivotally secured to pin 131, which extends through a receiving i, opening L25 within the pawl structure 130. The pin 131 is secured within openings 131A, 131B by e. g., clip or pin, which is indicated at 131C. A spacer 125A is positioned between the pawl structure 130 and the wall structure 128B so as to align the pawl structure 130 with the release gear 112 Refe ng to Fig. 5A in a case wherein the pull cable 48 is connected to connecting portion 128, a st member, or cable stay 133 ion an end of the cable 48 extends through the openings 131A, 131B in the wall structures 128A, 128B and the pawl structure 130 is pivotally mounted thereon ! via opening 125. In this situation, the cable 48 itself replaces the position of the spacer 125A, shown in Fig. 5, to maintain the aligned position of the pawl structure 130 with t) the release gear 112. In the situation wherein the cable 48 is connected to the connector portion j ! 129, suc as shown in Figs. 3B and 5B, the stop member 133 extends through openings 135A, 135B within wall structures 129A, 129B of connector portion 129. A spacer 133A is positioned between the cable 48 and one of the wall structures 129A, 129B on the stop member 133 to limit ! movement of the stop member 133 within the connector portion 129. Alternatively, the spacer , ; 125A of Fig. 5 cc\ild also be employed for connector portion 129 in place of the arrangement in Fig. 5C. I [0036] The second shaft element 94 includes an axially extending stud structure 134. In the illustrated embodiment, the stud structure 134, the activation arm 96, and the second shaft element 4 are formed integrally in one piece with one another. However, it is also possible for these components to be formed separately and subsequently non-rotatably joined to one another. A torsion spring 136 is positioned around the stud structure 134 and includes first and second l torsional Ly biasel ends 138, 140. The first end 138 extends through an oversized opening 142 i within the annular structure 124 of the release bracket 122 and engages within a receiving opening 44 of t e pawl structure 130. The second end 140 is received within a transverse I i I i opening 146 of axially extending stud structure 148 on the outward end of the activation arm 96. The second end 140 of the spring 136 is not only fixed relative to the second rotatable member 95 by it receipt in opening 146, it also serves to axially retain the first end 98 of the I sensing device 44. on the stud structure 148. The first end 138 of the spring 136 biases the i !' ratchet t ooh 132 of the pawl structure 130 into engagement with saw teeth 150 on an outer periphery of the release gear 112. As shown, the saw teeth 150 incline opposite the brake- actuating direction, toward the brake-releasing direction. The ratchet tooth 132 and saw teeth 150 cooperate to permit relative rotational movement of the release gear 112 and release bracket 122 in 01. e rotational direction and prevent such movement in an opposite direction. In particular the ratchet tooth 132 rides over ramped leading edge surfaces 166 of the teeth 150 (see Fig. 2), which effects repeated radially outwardly and inwardly pivotal movement (i. e., ratchet movement) of the pawl structure 130 when the release gear 112 is rotated therepast in i i the brake-actuatii g direction. The ratchet tooth 132 also interlocks with overhanging trailing edge surfaces 16s (see Fig. 2) of the teeth 150 when the release gear 112 is rotated relative thereto i the brake-releasing direction. An optional spring washer 152 is disposed between the stud structure 134 and the top plate 37 to apply an axial retaining force on the components rotatably mounted to the shaft 66. [0037] As will be discussed below, the second end 140 of the torsion spring 136 plays i. the additional role of biasing the activation arm 96. However, separate springs for biasing the pawl 13C and thejactivation arm 96 could be used instead of a single one as shown. 038] As, discussed previously, the brake actuation assembly 22 is operable to apply and release a tension) n the connecting linkage 24 so as to apply and release the brake mechanisms 16. Fig. 2 shows the brake actuation assembly 22 with its componentry in relative positions corresponding to a situation wherein a minimal amo ; rnt of tension is present within the connecting linkage 24, such as when the brake mechanisms 16 are not engaged. As shown in i ; Fig. 2, in this condition, the components of the brake actuation assembly 22 are in corresponding t first positions (also referred to as brake release positions). [0039] In particular, the activation arm 96 is moved into abutting relation with a stop structure 154 mounted to an inwardly extending tang 156 provided by the side wall portion 34. I i The stop structure 154 preferably serves as a bumper and is therefore formed of a resilient material such as er or other resilient material. Additionally, the ratchet tooth 132 of the pawl structure 130 is engaged with the saw teeth 150 of the release gear 112. [(>040] Tc b initiate tension application to the connecting linkage 24, the motor 40 is I I rotated i t a tensic tIn applyingdirection, e. g., clockwise. To accomplish this, the user need only (il e. g., depl ess a bu on or manipulate a switch fI the electrical control assembly 26. The .' electrical control assembly 26 cooperates with the motor 40 such that the motor 40 is driven in the tension applying direction. The rotation of the motor 40 and torque generated thereby is transmitt d through the first and second gear structures 70, 78 to the main gear 86 so as to rotate the main ! gear 86 in a tension applying direction, e. g., clockwise. Because the tang 110 of the clutch spring 1061 IS situated within the leg 104 of the annular groove 102 provided within the I main gear 86, the tang 110 is rotated with the main gear 86. A residual tension within the connecting linkage 24 produced by biasing members (not shown) within the brake mechanisms zizi 16 initially prevent rotation of the second shaft element 94. Rotation of the first shaft element 88 with t ie main gear 86 in the tension applying direction serves to"close"the clutch spring 106. Ìn c ther wo : ! ds, the tension applying direction corresponds with the winding direction of coils of the clutch spring 106 and displacement thereof in the tension applying direction causes a relative decrease in diameter of the clutch spring 106. The decrease in the diameter of the clutch spring 106 causes an interior periphery of the clutch spring 106 to frictionally engage or"grasp" the outer surface 90 of the first shaft element 88 and an outer surface 158 of the second shaft 'j element 94. The clutch spring 106 is configured such that, when in their first positions, the interior periphery. ofthe clutch spring 106 lightly frictionally engages the outer peripheries of I il the first and second shaft elements 88, 94. As the first shaft element 88 rotates relative to the ! : second shaft element 94 in the tension applying direction, the frictional engagement between the clutch spring 106 and the second shaft element 94 causes a portion of the spring 106 engaging the seco d shaft element 94 to"drag"along the outer periphery 158 of the second shaft element : j i 94, there) y causin 1 g deflection of the spring 1'l06 which tightens the windings of the spring 106 in 94, tlier6) y caust.. i a contras ting mal her on the second shaft element 94. When sufficient contraction of the spring 106 is accomplished, the first and second shaft elements 88 and 94 are non-rotatably coupled. Subsequently, the"resistance"of the brake mechanisms 16, i. e., the force generated by the biasing elements,, within the brake mechanisms 16, is overcome and the second shaft element 94 rotates with the first shaft element 88. Consequently, the activation arm 96 is rotated in a brake applying direction, e. g., clockwise, which serves to generate sufficient tension within the pp Yi g connecting linkage 24 to actuate the brake mechanisms 16. [ (041] Fig. 4 shows the components of the brake actuating assembly 22 in relative ! j positions corresponding to a brake actuated condition, wherein the brake mechanisms 16 are applied. As shown, the activation arm 96 is in a second position thereof that is circumferentially ' advance relative to the first position thereof illustrated in Fig. 2. The rotational displacement of !'' the activation arm 96 linearly displaces the sensing device 44 and connecting linkage 24 to apply the brake mechanisms. 042] D'u'n'ng assembly of the brake actuation assembly 22, the torsion spring 136 is pre-loaded so as to have a residual torsional biasing force which correspondingly provides a biasing force at the first and second ends 138, 140 thereof. As such, when the activation arm 96 I is in its f rst position, such as shown in Fig. 2, the spring 136 biases the activation arm 96 and the release bracket 122 rotationally toward one another about the second shaft element 94. In partir,,', in the illustrated embodiment, the spring 136 biases the activation arm 96 in a clockwis directi n, while the release bracket 122 is biased in the counterclockwise direction. A slot 160 s provided within the side wall portion 136, through which the respective connecting portion 128 of the release bracket 122 extends. The slot 160 includes first and second spaced end portions 162, 164 that define first and second positions of the release bracket 122. Figs. 2 ! ! and 4 show the re ease bracket 122 in its first position, wherein the connecting portion 128 abuts the first end portion 162. The spring 136 biases the release bracket 122 into abutting engagem ent with the first end portion 162. Additionally, the biasing of the spring 136 serves to t maintain contact between the ratchet tooth 132 and saw teeth 150 of the pawl structure 130 and l release gear 112, respectively. When the activation arm 96 moves from its first position (i. e., brake release) to its second position (i. e., brake apply), the second end 140 of the spring 136 is moved re lative to the first end 138, thus slightly relieving the torsional bias of the spring 136. However, the pre-loading of the spring 136 is sufficient such that movement of the activation i arm 96 into its second position does not relieve a degree of biasing force on the release bracket j il 122 sufficient to ! ; How the release bracket 122'to pivot out of its first position. In other words, for positions of the activation arm 96 between its first and second positions, the spring 136 resiliently biases the connecting portion 128 into abutting relation with the first end portion 162 of the slJt 160. As the release gear 112 rotates with the second shaft element 94, the pawl i structure 130 undergoes a ratcheting action over the ramped leading edge surfaces 166 of the ll saw teeth 150 (see Fig. 2). 1 0431 the illustrated embodiment, the brake actuating assembly 22 is of a self- i locking c onflgunition, such that when the brake actuating assembly 22 is in the brake engaged condition, there I ! ; no necessity of supplying constant current to the motor 40 to prevent release of the tension within the linkages or for use of an additional locking mechanism to accomplish the same Biasin members within the brake mechanisms 16 themselves serve to apply a torque on the second shaft element 94 in the tension releasing direction. Torque on the second shaft element 94 in the tension releasing direction is relatively equivalent to torque on the first shaft element 8 in the''tension applying direction, either of which maintains constriction of the clutch spring 106 to maintain the non-rotating coupling therebetween. Accordingly, due to torque on If the second shaft'element 94 via the biasing members of the brake mechanisms 16 in the tension releasing direction, the first and second shaft elements 88, 94 remain non-rotatably coupled by 0in the clutch spring lit6. The interaction between the first and second gearing structures 70, 78 and the worm 56 effectively serves to prevent transmission of a significant torque to the motor 40, which w) uld require application of a powered reactant force by the motor 40 to maintain tension I on the lil Ikage 24 land/or prevent relative rotation between the first and second shaft elements 88, 94, which would expand theclutch spring 106, thereby de-coupling the first and second shaft oily elements 88, 94. In particular, respective pitches of the wonn gear 72 and worm 56 are ! i configured such at a torque on the worm gear 72 being applied to the worm 56 predominantly translates into an axial force on the worm 56. The axial force generates a friction between teeth of the w N ruLn gearl 72 and worm 56 that is sufficiently large to prevent movement of the worm 56, vu and the fore the motor 40. ! [0044] To remotely release the brake mechanisms 16, the user need only e. g., depress a button o manipulate a switch on the electrical control assembly 26. The electrical control assembly 26 cooperates with the motor 40 so that the motor 40 is driven in a tension releasing direction (e. g., c unter-clockwise). Rotation, of the motor 40 in the tension releasing direction correspondingly drives the main gear 86 in a tension releasing direction, and thus the first shaft I element 88 therewith. Rotation of the first shaft element 88 in the tension releasing direction correspo dingly'llopens"or expands the clutch spring 106, which thereby"relaxes"the clutch spring's ngagement with the second shaft element 94. The second shaft element 94 is thereby allowed to freely rotate in the tension releasing direction to thereby release the brake mechanisms 16. i [0045] Fig. 6 shows the brake actuating mechanism 22 in a manually released condition. i : As show0, the pull cable 48 has been manually displaced so as to pivot the release bracket 122. As discussed previously, the torsion spring 136 maintains engagement of the tooth 132 of the pawl s cture 130 with saw teeth 150 of the release gear 112. As the release gear 112 rotates i I I, relative 13 the release bracket 122, such as during movement of the activation arm 96 from its first to se cond po sitions, the pawl structure 130 ratchets along the saw teeth 150. However, i whenimc vement if the release bracket 122 is effected by the pull cable 48 relative to the release gear 112 the ratchet tooth 132 engages an overhanging trailing edge surface 168 of one of the i saw teetl 150 an (thereby non-rotatably couples the release bracket 122 and release gear 112. I Because the tang' ; 120 of the clutch spring 106 is disposed within the leg 118 of the annular groove 1 4, rotational movement of the release gear 112 effects relative movement between the tangs 110, 120 of the clutch spring 106. Upon a certain degree of relative movement of the I i tangs 110, 120, the clutch spring 106 is"relaxed"such that an internal diameter of the clutch spring 106 increases and subsequently releases the outer peripheries 90, 158 of the first and second shaft elements 88, 94. Accordingly, the second shaft element 94 and the activation arm 96 are su bsequently free to rotate and are biased toward and into their first positions by the biasing members of the brake mechanisms 16. The second end portion 164 of the slot 160 acts as a seco id position stop to prevent movement of the release bracket 122 past its second position. I i [(1046] Since the brake actuating assembly 22 is operated remotely by the user, e. g., from within the vehicle, it is preferable, but not necessary, for the brake actuating assembly 22 to provide for self cut-off when predetermined positions are reached. In particular, the motor 40 I may optionally be de-energized upon applying sufficient tension on the connecting linkage 24 to ensure p loper application of the brake mechanisms 16. Additionally, the motor 40 may i I optionally be de-energized subsequent to release of the brake mechanisms 16. [047] R ferring to Fig. 3B, a general description will now be given of the illustrated embodiment of the sensing device 44. The sensing device 44 includes first and second ti connecting structures 170, 172. The first connecting, structure 170 includes a pair of connecting I,, members 174, ch are secured to one another with a fastener 176, such as, for example, a threaded fastener. The first connecting structure 170 provides a wall member 178 and the i ; 'all member 180. A compression spring 182 is , ; ; disposed between the wall members 178, 180 and is compressed therebetween during relative ! movement between the first and second connecting structures 170, 172. The sensing device 44 l includes pair of switch units 184, one of which determines a maximum displacement position i of the compression spring 182 and the other of which determines a minimum displacement i I position. Referring to Fig. 4, the brake actuating assembly 22 is shown for an applied condition ll of the brake mechanisms 16. The extent of rotational displacement of the activation arm 96 and, therefore, the magnitude of tension applied to connecting linkage 24, is determined by the sensir g evice 4 In particular, when a predetermined displacement of the compression spring in 182 is se ised by ne of the switch units 184"the sensing device 44 communicates with the 'y i electrica control assembly 26 to de-energize the motor 40 and thereby cease rotation of the ! : i activation arm arm 96. Similarly, when a minimum tension within the connecting linkage 24 is I sensed by one of the switch units 184 upon release of the brake mechanisms, 16, the sensing I I device 4 conunumcates with the electrical control assembly 26 to de-energize the motor 40 and thereby cease rotation of the activation arm 96. The use of the sensing device 44 is advantageous to prevent over-tensioning of the connecting linkage 24, as well as under- . gl p, g g g tensioning of the connecting linkage 24. Additionally, the brake actuating assembly 22 is rendered self-adjusting to compensate for gradual stretch of the connecting linkage 24, since the sensing c evice 4 de-energizes the motor 40 based on a measure of tension within the I connecti g linka 24 and not a longitudinal ; displacement thereof. Moreover, it is possible for i the brake actuation assembly 22 to be capable of applying different magnitudes of tension to the y p pp Yl g connecting linkage 24 to correspondingly generate different magnitudes of braking force by i brake mc chanisnis 16. For example, the brake actuation assembly 22 may apply a greater tension to connecting linkage 24 when the vehicle is parked on an incline than when the vehicle is parked on a level surface. The sensing device 44 may be capable of detecting and accordingly de-energizing the motor 40 at different tension levels within the connecting linkage 24. l' Additionally, for this purpose, the electrical control assembly 26 may include an inclination detector (not shown). Ij 0481 Ai iother embodiment of a brake actuation assembly is schematically illustrated in Fig. 7 an is indicated therein at 200. The assembly 200 includes an electric motor 202 which is remotely controlled by the electrical control assembly 26, as with the brake actuation assembly !' !' ! ! ! ! 22 descri bed aboge (i. e., the, electrical control assembly 26 includes push-buttons or a switch to I allows thé user to lectrically drive the motor 202 in forward or reverse directions). A worm 204 ton is coupled to a drive shaft 206 of the motor 202 and worm 204 drivingly engages a worm gear 208. Worm gearl208 is interposed between and intermeshed with the worm 204 and a main gear 210. [0049] The main gear 210 is rotatably mounted on a pivot shaft 212, as are a first shaft element 214 and second shaft element 216. The first shaft element 214 may be welded or j otherwis joined to the main gear 210, or, alternatively, the first shaft element 214 and main gear 210 may be formed as a single, integral unit. The second shaft element 216 and the first shaft element 14 are able to rotate relative to each other about the pivot shaft 212. As also shown, a nut 217, Z zr other suitable retaining structure is affixed to an end of the pivot shaft 212 to prevent substantial relative axial movement between the first and second shaft elements 214, 216. A clutch spring 218 is disposed over the first shaft element 214 and second shaft element 216 in overlapp ng, overlying relation between the two and is configured to permit the first shaft jl element 214 and the second shaft element 216 to rotate relative to each other in one direction (a ! !' tension releasing'direction) but to non-rotatably lock in the opposite direction (a tension i applying direction). [0050] An activation arm 220 extends generally radially outwardly from the second shaft element 16 and may be welded to or integrally formed with the second shaft element 216. The ! : connecti lg linkaje 24 is coupled to cable attachment member 220. vil [1) 051] With this arrangement, the motor 202 drives the worm 204, which, in turn, drives ' ! the worm gear 2 8 and hence the main gear 210. This causes the first shaft element 214 to rotate in the tension applying direction. The rotation of the first shaft element 214 in the tension zoo applying direction causes the clutch spring 218 to close around the second shaft element 216 and thereby non-rotatably couple the second shaft element 216 with the first shaft element 214 such that the E econd staft element 216 also turns in the brake-applying direction, thereby pulling the connecting linkage 24 so as to actuate the brake mechanisms 16. Driving electric power to the i motor 202 may be terminated simply by releasing the brake-actuating button, or, preferably, by i having the connecting linkage 24 include a sensing device, such as sensing device 44 described I above, w uch detects a predetermined maximum tension applied to the connecting linkage 24. i The interconnection between the first shaft element 214 and second shaft element 216 via the ! ! clutch sp ring 218 and the gears 210, 208, 204, provide sufficient rigidity to prevent backward, tension releasing rotation of the second shaft element 216 about the pivot shaft 212. [ (052] The brake actuation system 200 may be released either by driving the motor 202 in a reversed direction to release the spring clutch 218 or may be manually released. That is so that the parking brake can be released even when all power to the system is lost, thereby ! permitting, for example, towing if necessary. A contemplated manual release mechanism 222 is illustrated in Figs.'8-16. [(1053] A release gear 224 is mounted over second shaft element 216 and is rotationally free relative thereto. As illustrated in Fig. 9, a clutch spring-receiving groove 226 is formed in i the botto n surface of the release gear 224. The release gear 224 fits down on top of the clutch spring 218, and ai upper tang (not shown) of the clutch spring 218 fits within tang-receiving p g , pp g () p g g v g i groove extension 228. (The opposite tang of the clutch spring 218 (also not shown), at the opposite end of the clutch spring, is secured relative to the main gear 210 by a post which prevents ! free, unrestrained rotation of the clutch spring 218 relative to the first and second shaft elements 214, 216.) [0054] The release mechanism 222 further includes a ratcheted release lever assembly. In particular, the release lever assembly includes a post 230 with a supporting flange or collar il 232. A toothed release gear 234 is rotationally supported on the post 230 by means of flange or ) collar 232. Teeth 236 of the toothed release gear 234 intermesh with teeth 238 of the release gear 224 such that the two release gears 224, 234 counter-rotate with each other. As shown in Fig. 11, e toothed release gear 234 has ramped ratchet teeth 240 formed on an axially outwardly facing side of the toothed release gear 234 opposite the teeth 236. I [« » 055] Rt ! erring to Figs. 14-16, a release bracket, or release lever, 242 fits rotationally over pos 230 an includes ramped ratchet teeth 244 that interengage with the ramped ratchet , teeth 24 (of the toothed release gear 234. Thus, the release lever 242 and the toothed release gear 234 ! are able to rotate relative to each other in one direction (with the two members moving axially away from each other and back toward each other as their respective ramped teeth slide past each other), but are unable to rotate relative to each other in the opposite direction (by virtue i of flush engagement between the respective"vertical"faces of their respective ramped teeth) such that the two members are forced to rotate together. The release lever 242 further has a release cable connecting portion 246. A compression spring 248 is provided over post 230 (between a retain. washer 250 and the surface of the release lever 242) so as to bias the release ' lever 242 into engagement with the toothed release gear 234. [056] T e release mechanism 222 operates as follows. As the parking brake is being engaged, the clutch spring 218 rotates in an engagement direction, and the release gear 224 rotates in the same direction, i. e., with the clutch spring, by virtue of the clutch spring fitting within the groove, and groove extension 226 and 228. As the release gear 224 rotates, it drives the toothed release gear 234, which is able to rotate past or relative to the release lever 242 as i i I their teeth slide past each other (with the release lever 242 moving axially back and forth along the post 130 against the bias of the compression spring 248). I i' [0057] In order to release the parking brake, the manual actuator 28 (Fig. 1), which is coupled 1o the release cable connecting portion 246 via, e. g., cable assembly 46, is pulled (e. g., from the passenger compartment of the vehicle), which causes the release lever 242 to rotate in the opposite direction. The ratchet-type engagement between the release lever 242 and the toothed release gar 234 causes the release lever 242 to force the toothed release gear 234 to i rotate'in the opposite direction, thereby also causing'the release gear 224 to rotate in its respective opposite direction. This forces the clutch spring 218 to open slightly, thereby releasing its grip on the second shaft element 216 and permitting the second shaft element 216 to rotate on the pivot shaft 212 relative to the first shaft element 214. This allows the parking brake to be released as the second shaft element 216 returns to a"home"position. Preferably, a ' compression spring (not shown) surrounds the release cable (not shown) and is configured to } ! urge the release le, and hence the release lever, back to a neutral position as illustrated. 1 0581 Ail extension spring may be provided between the activation arm 220 and, e. g., i an asse ly hou ing. That extension spring is used to maintain tension in the connecting i linkage 24 when he cable is in its"home"position. Alternatively, tension may be maintained i within the connecjdng linkage 24 via the brake mechanisms 126 themselves. In this case, it is preferable for the assembly housing to provide a stop structure to rigidly limit the movement of the cable attachment member 220. i [0059] Various modifications to and departures from the embodiment disclosed herein will occur to those having skill in the art and are deemed to be within the scope of the following claims.