Abstract:
An electrically powered actuator mechanism for operating a vehicle parking brake including a reversible electrical motor having output gearing driving a sector gear. A wrapped spring clutch drivingly connects the sector gear to an intermediate operator cable wind up wheel. The intermediate cable is connected to the brake cable to set the brakes when the operator cable is wound up by energization of the motor in one direction, with a load sensor turning off the motor when a predetermined tension load is reached. Locking motor gearing holds the brake in the set condition. Reversal of the motor upwinds the cable to release the parking brake. A self adjusting feature is provided by a pretensioned clock spring creating a torsional bias on the wind up wheel tending to maintain a predetermined tension in the brake cable. A spring clutch is released by engagement of a release arm to allow the clock spring to adjust the wind up wheel. A cable operated manual release causes a release lever to engage the clutch spring release arm to allow the cable to release although the clock spring monitoring a minimum tension after release of the winding wheel.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. provisional Ser. No. 60/457,776, filed Mar. 26, 2003. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention concerns electrically powered actuator mechanisms for automobile parking brakes in which an electrical motor is selectively activated to set or release the vehicle brakes by a control switch. Such powered parking brakes add a measure of convenience over the usual manually operated parking brakes.  
         [0003]     However, it would be highly desirable that a manual release be incorporated as well as a powered release to allow vehicle operation in the event of failure of the powered system.  
         [0004]     Another desirable feature would be a self adjusting mechanism which would automatically take up the brake operating cable slack, which typically will increase over time, to avoid the delay in actuating the brake which would otherwise occur. Such self adjust features have heretofore been incorporated in manually operated parking brakes but have not been incorporated in electrically actuated parking brakes.  
         [0005]     Such self adjustment action should desirably eliminate the need for adjustment when the parking brake actuator is installed during vehicle assembly to reduce the labor involved in carrying out the installation.  
         [0006]     Such a parking brake should itself be compact and reliable while providing these features.  
         [0007]     The object of the present invention is to provide an electrically operated actuator mechanism for vehicle parking brakes which can electrically apply and release the brakes but which also allows a manual release of the brakes.  
         [0008]     It is another object of the present invention to provide an electrically powered actuator mechanism for parking brakes which incorporates a self adjustment of the brake operator cable to automatically take up any slack which develops to avoid any delay in applying the parking brake.  
       SUMMARY OF THE INVENTION  
       [0009]     These and other objects of the present invention which will be understood upon a reading of the following specification and claims are achieved by a parking brake actuator mechanism in which a reversible electrical motor is selectively energized in a first direction to apply the brakes, and in a second direction to release the brakes.  
         [0010]     A manual release cable is connected to the parking brake actuation mechanism to release the brakes when the cable is pulled as by a release lever or button in the passenger compartment.  
         [0011]     A prewound clock spring is connected to apply a predetermined tension to the brake operator cable whenever the brake is released, to take up any slack developing in the system prior to the next engagement of the brake.  
         [0012]     A prewound clutch spring establishes a driving connection between a pivot member comprised of a sector gear driven by an electric motor output gearing and a rotary cable track wind up wheel which is freely rotatable on a drive shaft connected to the sector gear to be rotated therewith. The cable wind up wheel has an intermediate operator cable partially wrapped therein in a guide groove in the wind up wheel perimeter which also has a drum clutch surface over which one section of a the clutch spring is received. An auxiliary drum is drivingly engaged with the drive pin to be rotated therewith and receives the other section of the clutch spring.  
         [0013]     When the sector gear is driven by the motor in a direction applying the brakes, the clutch spring, wrapped tightly onto both drum surfaces, causes the operator cable to be wound up on the cable operator track up wheel. This pulls the brake cable connected to the brake via a cable connector and load sensor. When the sensor detects development of a preset cable load, the motor control circuit turns off the motor. The motor output includes irreversible gearing which holds the cable in the brake set position.  
         [0014]     The distribution of the clutch spring engagement stress across both the auxiliary drum and the cable wind up wheel drum surface reduces the concentration of stress over prior uses of a clutch spring in manually actuated brakes which concentrated the stress at the first winding of the clutch spring leading to increased wear.  
         [0015]     To power release the parking brake, the motor is driven in a reverse direction to drive the sector gear so as to cause unwinding of the operator cable from the groove on the cable wind up wheel. The clutch spring at this time continues to maintain a driving connection to the cable track wind up wheel until a release leg of the clutch spring is driven sufficiently far to engage a fixed post, causing the clutch spring to be expanded to disengage from both clutch drum surfaces, releasing the rotary connection between the cable wind up wheel and the sector gear. This allows the torsion developed by the clock spring to act on the released cable wind up wheel to exert a pull on the brake operator cable and establish a predetermined pretensioning therein which is not sufficient to operate the brake but sufficient to eliminate any slack. The motor is then stopped by the control circuit when a rotary position sensor detects sufficient sector gear travel to insure that release of the clutch spring has occurred.  
         [0016]     To effect a manual release, a manual release cable wire is pulled by manipulation of a lever or button in the passenger compartment, which causes rotation of a manual release lever pivoted on one end of the drive pin. In one embodiment, a separate release cam also pivoted on the drive pin, engages a first tab on the manual release lever and rotates the release lever to cause a second tab to be engaged with the release leg of the clutch spring to again release the cable track wind up wheel. In a second embodiment, the manual release cable wire is directly attached to the manual release lever.  
         [0017]     A release lever positioner spring holds that lever in proper position. A release cam positioner spring on the manual release cable holds the release cam in position retracted away from the tab on the release lever when the release cam is used.  
         [0018]     The pretensioning system includes the clock spring which is received within a cavity within the cable wind up wheel, which has one end connected to the inside of the cable track wind up wheel cavity and anchored at its other end to the drive pin. The clock spring is prewound at assembly when the sector gear is driven by the drive motor to release the clutch spring and allowing free rotation of the cable wind up wheel, the brake operator cable is pulled to prewind the clock spring to create a stored torsional energy. The operator cable connector is then held fixedly in that position by insertion of a tension lock pin or clip.  
         [0019]     After the mechanism is assembled into an automobile, the lock pin or clip is removed. The prewound clock spring then acts to rotate the cable track wind up wheel to take up any slack in the brake cable.  
         [0020]     As soon as the spring clutch is again engaged with the wind up wheel at its new position, there is no lost motion from cable slack to delay brake engagement.  
         [0021]     Thus every time the cable track wind up wheel is released, the clock spring automatically acts to reestablish proper cable tension and repositions the wind up wheel if any slack develops prior to the next brake application.  
         [0022]     An alternate sensor installation may provide an indirect measurement of the force in the brake apply cable by mounting a load sensor to measure the reaction force at the drive pin generated by the cable tension. This reaction force is used to determine the cable load being generated by the motor. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0023]      FIG. 1  is a side view of a parking brake actuator mechanism according to the present invention.  
         [0024]      FIG. 2  is a top view of the actuator mechanism shown in  FIG. 1 .  
         [0025]      FIG. 3  is an end view of the actuator mechanism shown in  FIGS. 1 and 2 .  
         [0026]      FIG. 4  is an exploded pictorial view of a parking brake actuator mechanism according to the present invention.  
         [0027]      FIG. 5  is a pictorial view of the actuator mechanism with the housing cover removed to show the interior components of the actuator mechanism at the start of the powered brake apply condition.  
         [0028]      FIG. 6  is a pictorial view of the actuator mechanism components shown in  FIG. 5  at the start of the powered brake release operation.  
         [0029]      FIG. 7  is a pictorial view of the actuator mechanism components shown in  FIGS. 5 and 6  with the manual release of the brakes completed.  
         [0030]      FIG. 8  is a pictorial view of the interior actuator mechanism components viewed from below to show the self adjust function components.  
         [0031]      FIG. 9  is a pictorial view of actuator mechanism interior components with a cable wind up wheel, auxiliary drum and clutch spring partially broken away to show the clutch spring engagement therewith.  
         [0032]      FIG. 10  is a diagram depicting an alternate form of load sensor arrangement incorporated in the actuator mechanism according to the invention, depicting the force loading.  
         [0033]      FIG. 11  is a side view of an alternate embodiment of the actuator mechanism according to the invention.  
         [0034]      FIG. 12  is a view of the section  12 - 12  taken in  FIG. 11 .  
         [0035]      FIG. 13  is an exploded pictorial view of the components of the actuator mechanism shown in  FIGS. 11 and 12 .  
         [0036]      FIG. 14  is a pictorial view from the top of the actuator mechanism shown in  FIGS. 11 and 12  at the beginning of the brake apply cycle.  
         [0037]      FIG. 15  is a pictorial view from the top of the actuator mechanism shown in  FIGS. 11 and 12  at the beginning of the powered release cycle.  
         [0038]      FIG. 16  is a pictorial view from the bottom of the actuator mechanism shown in  FIGS. 11 and 12  prior to operation of the manual release.  
         [0039]      FIG. 17  is a pictorial view from the bottom of the actuator mechanism shown in  FIGS. 11 and 12  after operation of the manual release.  
         [0040]      FIG. 18  is a plan view of the cross brace showing one form of the load sensor used to control operation of the motor. 
     
    
     DETAILED DESCRIPTION  
       [0041]     In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims.  
         [0042]     Referring to  FIGS. 1-3 , the electrically powered parking brake actuator mechanism  10  includes a housing  12  adapted to be mounted to a structure within an automotive vehicle by mounting ears  14 . The housing  12  is of a two piece construction including an enclosure  16  and a cover  18  with gasket  19  held together with socket head screws  20 .  
         [0043]     A brake operating cable  22  passes out of the housing  12  and extends to vehicle rear brakes  24 , used as parking brakes when operated by the actuator mechanism  10  according to the present invention.  
         [0044]     A manual brake release cable  26  also extends out of the housing  12  and extends to a suitable operating lever or button  25  located in the passenger compartment of the vehicle.  
         [0045]      FIGS. 4 and 4   a  show the components of the actuator mechanism  10  which includes an electric motor-gearing unit  28  which includes an electric motor  30  and a rotary output comprising a right angle gear unit  32  including an output pinion gear  34  rotated by self locking worm gearing (not shown) which locks the pinion gear  34  whenever the motor  30  is not energized. The motor-gearing unit  28  is mounted within the main housing  16 .  
         [0046]     A drive shaft  36  is rotatably mounted in a bearing  38  at one end thereof and extends through a clock spring  40 , an intermediate operator cable wind up wheel  42 , and an auxiliary drum  44 . A clutch spring  46  is received over a drum surface  48  on one end of the wind up wheel  42  and completely over the auxiliary drum  44 . Normally the clutch spring  46  tightly grips both the auxiliary drum  44  and the drum surface  48 .  
         [0047]     The drive shaft  36  also passes through a pivot member, here comprised of a sector gear  50  having gear teeth  52  formed therein in mesh with the pinion gear  34 , a manual release lever  54 , and a locator spring  56 . The end of the drive shaft  36  is rotatably mounted in a bearing  58  in a bearing seat  62  formed in a cross brace  60  mounted in the housing  12 .  
         [0048]     A manual release cam  64  has a bore  68  at one corner rotatable on the bearing seat  62  on the opposite side of the cross brace  60 , and has a manual release cable  26  attached to one corner  66  thereof.  
         [0049]     The drive shaft  36  has a segment  37  formed round but with flats  35  formed on either side to create a driving relationship with complementary flat sided bore  45  in the auxiliary drum  44  and flat sided bore  51  in the sector gear  50 . The wind up wheel  42  has a round bore  73  allowing free rotation on the drive shaft segment  37 . Manual release lever  54  is also rotatable thereon by receiving the drive shaft segment  37  in a round hole  55 .  
         [0050]     The clock spring  40  is received within a circular cavity  70  inside the cable wind up wheel  42 , having an inner formed over end  41  secured to the drive shaft  36  and on outer formed over end  43  secured to the inside of the cavity  70  ( FIGS. 8, 9 ). Thus, when the spring  40  is prewound, the cable wind up wheel  42  is urged to rotate so as to partially wind up an intermediate operator cable  72  having one end held in an anchor  75  by a cross pin  74  and received in a groove track  76 .  
         [0051]     The other end of the intermediate operator cable  72  is connected to a load sensor  78  and cable coupling  80  to which the brake operating cable  22  is attached.  
         [0052]     The intermediate operator cable  72  is pulled to prewind the clock spring  40  to be tensioned to a predetermined level prior to installation of the actuator mechanism  10 , and a temporary locking pin  82  thereafter installed in holes in the housing enclosure  16  ( FIG. 4 ) to maintain the torsional tension in the now wound clock spring  40 .  
         [0053]     Upon installation of the actuator mechanism  10 , the locking pin  82  is removed. The clock spring torsional tension then acts on the cable wind up wheel  42  to pull on the cable  72  and provide the self adjusting feature as described below, since a predetermined cable tension in the brake operating cable  22  is thereby created.  
         [0054]     The clutch spring  46  has a tangential drive leg  47  fixed to the sector gear  50  by a clamping plate  84  attached thereto with screws  86 . A release leg  49  is used to expand and controllably disengage the clutch spring  46  from the drum surface  48  as will be described below.  
         [0055]     The manual release lever  54  has an elongated finger  53  which extends to be engagable with the release leg  49  when a tab  65  of the manual release cam  64  engages a tab  57  on the manual release lever upon retraction of the manual release cable  26  as described below.  
         [0056]     Positioner spring  56  holds the lever  54  away from engagement with the release leg  49  until the manual release cable  26  is retracted. A spring  27  on the cable  26  urges the manual release cam  44  to a disengaged position until the movable core wire in the manual release cable  26  is retracted.  
         [0057]      FIG. 5  shows the sector gear  50  at the beginning of a powered parking brake application. A control circuit  90  includes a dash mounted switch (not shown) which may be selectively operated to energize the electric motor  30 , causing the sector gear  50  to be pivoted by rotation of the pinion gear  34  so as to swing the sector gear  50  counter clockwise as viewed in  FIG. 5 .  
         [0058]     Since the clutch spring  46  grips the drum surface  48  on the cable wind up wheel  42 , the rotation of the attached sector gear  50  rotates the wind up wheel  42  to further wrap up the intermediate operator cable  72  thereon.  
         [0059]     This pulls on the brake cable  22  via the connection provided via the load sensor  78  and coupling  80  to apply the brakes  24 .  
         [0060]     The motor  30  continues to operate until a predetermined load is detected by the load sensor  78 , the control circuit  90  then automatically deactivating the motor  30 . The brakes  24  remain applied due to the action of the internal self locking gearing included in the motor drive unit  30 .  
         [0061]      FIG. 6  depicts the brake applied position of the sector gear  50 .  
         [0062]     During this operation, the clutch spring  46  grips both the drum surface  48  and the auxiliary drum  44  so that wear is not concentrated at the first turn on the drum surface  48  but rather over a wider area.  
         [0063]     To release the brakes  24 , the switch included in control circuit  90  is operated to energize the motor in the reverse direction. The clutch spring  46  continues to grip the drum surface  48  since it is designed to normally grip the drum surfaces  48 , and since the wind up wheel  42  is continually urged to rotate counter clockwise as viewed in  FIGS. 5 and 6  by the clock spring  40 , so that rotation of the sector gear  50  clockwise causes clockwise rotation of the wind up wheel  42 , releasing tension in the brake cable  22  and thus releasing the brakes  24 .  
         [0064]     The motor  30  continues to operate, carrying the release leg  49  of the clutch spring  46  into engagement with a fixed post  92  as shown in  FIG. 5 .  
         [0065]     Continued rotation to advance the release leg  49  causes the clutch spring  46  to expand, releasing its engagement with the drum surface  48 .  
         [0066]     The motor  30  continues to rotate until a position sensor  96  adjacent the sector gear  50  perimeter signals the control circuit  90  that the sector gear  50  has reached a position insuring full release of the clutch spring  46 , the control circuit  90  then causing the motor  30  to be deactivated.  
         [0067]      FIG. 7  shows a manual release using the manual release cable  26 , which has a core wire pulled by manipulation of a lever or button  25  accessible from the passenger compartment. The release cam  64  is thereby rotated counter clockwise as seen in  FIG. 7  about its axis of rotation defined by the center of bore  68  (bracket  60  and bearing seat  62  not shown for clarity). The tab  65  engages the tab  57  of the release lever  54 , causing rotation thereof in the same direction. This causes the finger  53  to engage the release leg  49  of the clutch spring  42  and expand the clutch spring  42  releasing its engagement with the drum surface  48  of the wind up wheel  42 . This releases the intermediate operator cable  72  to thereby relax brake cable  22  and allow disengagement of the parking brakes  24 .  
         [0068]     The clock spring  40  however continues to act on the wind up wheel  42  so as to maintain a minimum tension on the intermediate cable  72  to eliminate any slack that has developed.  
         [0069]     Upon the next engagement of the clutch spring  46 , if any rotation of the wind up wheel  42  has occurred to eliminate slack, the clutch spring  46  will engage the drum surface  48  in the rotated position so that only the same travel is necessary to set the brakes, avoiding any cumulative slow down of the actuation time necessary.  
         [0070]      FIG. 10  depicts an alternate form of load sensor, in which a pivot  98  on the end of the drive shaft  36  is held by a slide  100  mounted on the bracket  60 A. A load sensor  102  senses the reaction load on the pivot  98 . The pivot  98  is subjected to part of the reaction force generated by the tension in the cable  22 , and hence the load sensor  102  can be used to detect the level of force causing the motor  30  to be deactivated, since it corresponds to the force applied to the brakes  24 .  
         [0071]     The components can be arranged differently, as for example in a second embodiment of an actuation mechanism  10 A shown in  FIGS. 11-17 . In this embodiment, the electric drive motor  30 A has its axis oriented parallel to the axis of the cable wind up wheel  42 A and pivot member comprised of sector gear  50 A.  
         [0072]     The motor  30 A is received in a recess  104  in the housing enclosure  16 A secured with screws  106  passing through tabs  108  and received in sockets  110  and has an output gear unit including a pinion gear  34 A meshed with gear teeth  52 A on the sector gear  50 A.  
         [0073]     A drive shaft  36 A has a pin  112  on one end received in a bearing sleeve  38 A in turn held in socket  114  molded in the rear wall of the housing enclosure  16 A.  
         [0074]     The pinion gear  34 A also has a plug end  116  received in a mating hole  111  in a cross brace  60 A having three ends  118 A, B, C, received in corresponding recesses  120 A, B, C and molded into the housing  16 A and secured with screws (not shown).  
         [0075]     The drive shaft  36 A has a reduced diameter end  122  received in a bearing  124  received in a bearing socket  62 A formed in the brace  60 A.  
         [0076]     The drive shaft  36 A has flats  126  on a rounded portion  37 A mating with elongated opening  51 A in the sector gear  50 A and opening  45 A in the auxiliary drum  44 A so as to rotate together.  
         [0077]     The drive shaft  36 A provides rotary support for the cable wind up wheel  42 A. The manual operating lever  54 A is rotatably mounted on an outside diameter  128  of the socket  114  received in a large diameter hole  55 A therein.  
         [0078]     In this second embodiment, the manual release lever  54 A is itself directly connected to the manual release cable  26  by a cross pin  136  on the core wire  135  interfit in a looped end of an arm  131  of a wound wire spring  130 , the wire spring  130  having the formed arm  131  received in notch  132  in the manual release lever  54 A, with the opposite arm  133  anchored against the housing enclosure  16 A, as best seen in  FIGS. 16 and 17 .  
         [0079]     The clock spring  40 A has its inner formed over end  41  A received in a slot  35  in the drive shaft  36 A and its outer formed over end  43 A held in a cylindrical cavity  41  in the cable wind up wheel  42 A.  
         [0080]     The clutch spring  46  is received over a drum surface  48 A of the cable wind up wheel  42 A and also the auxiliary drum  44 A, as in the first described embodiment.  
         [0081]     A spring clip  138  is used to hold the operator cable  72  with the clock spring  40 A in the prewound condition until the actuator  10 A is installed in the vehicle, one edge engaging connector  140 .  
         [0082]     A load sensor  142  is engaged by a slider  138  abutting the plug end  122  of the drive shaft  36 A ( FIG. 14 ) to provide a control signal corresponding to the cable load on the brake cable  22 .  
         [0083]     The actuator  10 A generally operates in the same manner as the first described embodiment.  
         [0084]     The motor  30 A when energized drives the sector gear  50 A, which in turn rotates the cable wind up wheel  42 A by the driving connection created by the spring clutch  46 A. This continues until the load sensor  142  senses a tension load sufficient to set the brakes ( FIG. 14 ) and the control circuit (not shown) turns off the motor  30 A. The brakes  24  are held in the applied condition by the self locking motor gearing.  
         [0085]     To power release, the motor  30 A is activated to drive in the opposite direction to rotate the sector gear  50 A in the opposite direction unwinding the cable  72  until the leg  49 A engages post  92 A to expand and release the clutch spring  46 A ( FIG. 15 ). The motor  30 A is turned off when a sector gear position sensor (not shown) senses that sufficient travel has occurred to insure release of the clutch spring  46 A and then de-energize the motor  30 A as in the first described embodiment.  
         [0086]     Referring to  FIGS. 16 and 17 , the manual release lever  54 A is rotated when the core wire  135  of the manual release cable  26  is drawn back, causing a tab  53 A to engage release arm  49 A of the clutch spring  46 A and disengage the clutch spring  46 A.  
         [0087]      FIG. 18  shows the bracket  60 A which is formed with the seat  62 A receiving a bearing  124  supporting the reduced diameter end  122  of the drive shaft  36 A ( FIG. 12 ). An alternate form of load sensor takes advantage of the fact that the leg  144  of the bracket  60 A is placed in compression by the reaction of drive shaft  36 A to the load of the brake cable  22 . A strain gauge  146  is used to measure the level of that compression to provide the load signal for turning off the motor  30 A at the proper time during the brake apply cycle.