Abstract:
A self adjusting wet brake positioned interior of a transaxle or transmission casing. The self adjusting brake assembly utilizes a brake pad having a cooperating ramp surface which is contacted by a brake cam for brake actuation. The cooperating ramp surface allows the brake mechanism of the current invention to automatically account for brake pad wear and the attendant decrease in brake pad thickness. As the brake pad wears and decreases in thickness, the brake cam progressively contacts ramp surface of the brake pad to effect brake actuation. In one exemplary embodiment, the ramp surface is integral with the brake pad.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a transmission or transaxle, and, more particularly, to a brake apparatus for braking a transmission or transaxle which automatically compensates for brake pad wear 
     2. Description of the Related Art 
     Transmissions and transaxles typically include a brake assembly operable to apply braking force thereto. Typically, braking force is applied to the speed reduction mechanism of the transmission or transaxle. In one typical brake apparatus, a brake pad is axially displaced a predetermined distance to frictionally engage a component (e.g., a brake disc) rotationally fixed to a shaft of the speed reduction mechanism to effect braking of the transmission or transaxle. Additionally, a friction backing pad may be utilized to engage the side of the brake disk opposite the brake pad when the brake is engaged. Repeated engagement of the brake assembly causes the material of the brake pad to wear away and, consequently, the axial displacement which formerly engaged the brake is no longer sufficient to effect braking activity. It is therefore desirable that the brake assembly be adjusted to account for brake pad wear and the consequent decrease in brake pad thickness. Prior brake mechanisms required manual adjustment to account for brake pad wear. Such manual adjustments are time consuming to perform and lead to operational down time. 
     Mechanisms of the prior art have sought to provide a self adjusting brake system to eliminate manual adjustment and the associated problems. Prior art self adjusting brake systems typically utilize a nut threaded to a shaft together with a ratchet mechanism. Typically, a disc having ratchet teeth is connected to the nut and operably engaged with a pawl affixed to the brake lever, with the nut determining the axial position of the brake lever. The brake lever includes a cam surface whereby actuation of the brake lever actuates the brake pad to effect braking. As the brake apparatus is utilized, and the brake pad wears, the nut is axially displaced along the shaft supporting the brake pad and thereby axially displaces the brake lever. Self adjusting brakes of this type are mounted exterior to the transmission or transaxle upon which they act, and, therefore, require additional space, and can be damaged by debris. 
     What is needed in the art is a self adjusting brake system which eliminates manual adjustment to compensate for brake pad wear and which does not require additional apparatus exterior to the transmission or transaxle housing. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved self adjusting brake for use with a transmission or transaxle, wherein it is desired to provide a self adjusting brake mechanism which does not require additional apparatus exterior to the transmission or transaxle housing and which brake apparatus comprises an internal “wet” type brake. The current invention utilizes a brake pad or brake pad assembly having a ramp surface cooperating with the brake pad and an actuator for engaging the ramp surface and thereby actuating the brake pad. The ramp surface of the current invention allows for self adjustment of the brake mechanism. As the brake pad wears and consequently decreases in thickness, the actuator will progressively engage the ramp surface to effect braking activity. In one exemplary embodiment, the actuator includes a ramp surface which mates with the ramp surface cooperating with the brake pad. The self adjusting brake of the current invention is internally positioned in the transmission or transaxle casing and is therefore lubricated by the transmission or transaxle which advantageously mitigates part wear. 
     The invention, in one form thereof, comprises a transaxle including a hydrostatic transmission module housed in a hydrostatic transmission module casing. The hydrostatic transmission module includes an output shaft. An axle module is housed in an axle module casing and includes a pair of axles, a reduction gear train and a gear train input shaft detachably connectable to the output shaft of the hydrostatic transmission. The axle module casing is separable into a plurality of axle casing components along a split line substantially perpendicular to the axles. A brake assembly for braking the axle module is mounted internally in the axle casing. 
     The invention, in another form thereof, comprises a transmission including a housing with a speed reduction mechanism operably positioned therein. A brake assembly is supported by the housing and is operable to selectively apply braking force to the speed reduction mechanism. The brake assembly includes a brake pad, a stepped ramp surface, and an actuator for selectively engaging the stepped ramp surface and thereby actuating the brake pad. 
     The invention, in a further form thereof, comprises a hydrostatic transaxle including a hydrostatic transmission and a housing with a speed reduction mechanism operatively positioned therein and coupled to the hydrostatic transmission. A brake assembly is supported by the housing and is operable to selectively apply braking force to the speed reduction mechanism. In this form of the current invention, the brake assembly comprises a brake pad having a brake pad ramp surface, and an actuator for selectively engaging the brake pad ramp surface and thereby actuating the brake pad. 
     The invention, in yet another form thereof, comprises a transmission including housing with a speed reduction mechanism operably positioned therein. A brake assembly is supported by the housing and is operable to selectively apply braking force to the speed reduction mechanism. The brake assembly comprises an actuator and a brake pad having mating ramp surfaces so that movement of the actuator in a given direction engages the mating ramp surfaces and transmits movement of the actuator into movement of the brake pad. 
     The invention, in yet a further form thereof, comprises a transaxle including a variable speed transmission and a housing with a speed reduction mechanism and a differential operably positioned therein. The housing rotatably supports a pair of axles drivingly connected to the differential. A brake assembly is supported by the housing and is operable to selectively apply braking force to the speed reduction mechanism. In this form of the current invention, the brake assembly comprises a brake pad having a brake pad ramp surface and a brake cam for selectively engaging the ramp surface and thereby actuating the brake pad. 
     In one form of the current invention, a differential lock is provided so that the differential may be locked and equal power transmitted to each of the axles. 
     An advantage of the present invention is the ability to eliminate manual adjustment of a brake mechanism utilized to apply braking force to a transmission or transaxle. 
     Another advantage of the present invention is the ability to provide a self adjusting wet brake housed in a transmission or transaxle casing. 
     A further advantage of the present invention is the ability to provide a self adjusting brake which does not require additional apparatus exterior to a transmission or transaxle housing. 
     Yet another advantage of the present invention is the provision of a self adjusting brake of relatively simple construction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a sectional top elevational view of a transaxle in accordance with the present invention; 
     FIG. 2 is a top elevational view of a transaxle in accordance with the present invention, including illustration of a hydrostatic transmission module connectable thereto; 
     FIG. 3 is a radial elevational view illustrating a transaxle in accordance with the present invention; 
     FIG. 4 is a perspective view thereof, including a modular hydrostatic transmission module affixed thereto; 
     FIG. 5 is an exploded perspective view of a transaxle in accordance with the present invention; 
     FIG. 6 is an exploded, radial elevational view of a brake assembly in accordance with present invention; 
     FIG. 7 is a perspective view of a brake rod of the present invention; 
     FIGS. 7A and 7B are axial elevational views thereof; 
     FIG. 8 is a perspective view of a brake pad in accordance with the present invention; 
     FIGS. 8A and 8B are axial elevational views thereof; 
     FIG. 9 is an axial elevational view of a retaining ring utilized with a brake assembly in accordance with the present invention; 
     FIG. 10 is an axial elevational view of a washer utilized with a brake assembly in accordance with the present invention; 
     FIG. 11 is an axial elevational view of a wave spring utilized with a brake assembly in accordance with the present invention; 
     FIG. 12 is a perspective view of a self adjusting cam in accordance with the present invention; 
     FIGS. 12A and 12B are axial elevational views thereof; 
     FIG. 13 is a perspective view of a cam driver in accordance with the present invention; and 
     FIGS. 13A and 13B are axial elevational views thereof. 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings and particularly to FIG. 5, there is illustrated axle module  38  having self adjusting brake assembly  100 . As illustrated in FIG. 6, self adjusting brake assembly  100  includes brake pad  102 , a self adjusting actuator including cam  104  and cam driver  106 , and brake rod  108 . In on e exemplary embodiment, brake pad  102 , self adjusting cam  104 , and cam driver  106  are formed from powdered metal, while brake rod  108  is formed from steel. 
     Brake assembly  100  is assembled with brake rod  108  being inserted through aperture  110  of cam driver  106 . When cam driver  106  is properly positioned about brake rod  108 , aperture  110  of cam driver  106  is positioned about cam driver area  112  of brake rod  108 . As illustrated in FIGS. 7 and 7B, cam driver area  112  of brake rod  108  has a square cross section. Similarly, as illustrated in FIGS. 13,  13 A, and  13 B, aperture  110  of cam driver  106  has a square cross section. Therefore, when cam driver  106  is operably positioned about cam driver area  112  of brake rod  108 , cam driver  106  is rotationally fixed to brake rod  108 . While aperture  110  of cam driver  106  and cam driver area  112  are illustrated having square cross sections, it will be understood by those skilled in the art that differing geometries, including, e.g., alternative polygonal cross sections may be utilized to rotationally fix cam driver  106  to brake rod  108 . 
     After cam driver  106  is positioned about brake rod  108 , self adjusting cam  104  is positioned about brake rod  108 . Aperture  188  of self adjusting cam  104  accommodates distal end  114  of brake rod  108  and, in use, is generally positioned about circular self adjusting cam area  116  of brake rod  108 . Aperture  188  is circular and is sized so that self adjusting cam  104  is rotationally moveable relative to brake rod  108 . After cam driver  106  and self adjusting cam  104  are positioned about brake rod  108 , wave spring  118  and washer  120  are positioned over distal end  114  of brake rod  108 . As illustrated in FIGS. 10 and 11, washer  120  and wave spring  118  include central apertures  136  and  138 , respectively. Central apertures  136  and  138  are sized to accommodate distal end  114  of brake rod  108 . Wave spring  118  is placed over distal end  114  of brake rod  108  and positioned directly adjacent recess  133  (FIGS. 12 and 12A) of self adjusting cam  104 . Washer  120  is then placed over distal end  114  of brake rod  108  and abuts wave spring  118 . Recess  133  of self adjusting cam  104  is radially sized to accommodate washer  120 . After positioning wave spring  118  and washer  120 , retaining ring  122  (FIG. 9) is positioned over distal end  114  of brake rod  108  and locked in place about groove  124  of brake rod  108 . Retaining ring  122  includes inner diameter  182  sized to snugly fit about the outer diameter of groove  124 . As will be understood by those skilled in the art, ends  184  of retaining ring  122  will be spread (i.e., moved away from each other) to allow retaining ring  122  to fit about distal end  114  of brake rod  108 . After being positioned about groove  124 , retaining ring  122  will return to its undeformed position and fit snugly about groove  124 . When retaining ring  122  is positioned about groove  124 , it abuts washer  120 . Thus retaining ring  122  limits the axial movement of cam driver  106  and self adjusting cam  104 . 
     After placement of retaining ring  122  about groove  124  of brake rod  108 , distal end of brake rod  108  is inserted through central aperture  126  of brake pad  102  to complete brake assembly  100 . In operation, proximal end  186  (FIGS. 6,  7 , and  7 A) of brake rod  108  is rotated to actuate brake assembly  100 . As described above, cam driver  106  is rotationally fixed to brake rod  108  for rotation therewith. As illustrated, e.g., in FIGS. 6,  13 ,  13 A,  12 , and  12 B, cam driver  106  and self adjusting cam  104  include cooperative, toothed ratchet and pawl surfaces  128  and  130  respectively. Cooperative ratchet and pawl surfaces  128 ,  130  operate to transmit rotational movement of cam driver  106  into rotational movement of self adjusting cam  104  in one direction of movement and allow relative rotational movement between cam driver  106  and self adjusting cam  104  in the opposite direction of rotational movement. As is known in the art, ratcheting mechanisms of this type produce axial movement of one of the members as ratcheting takes place. Wave spring  118  is provided to absorb this axial movement. Cooperating surfaces  128 ,  130  are provided so that brake assembly  100  may be actuated by rotational movement of brake rod  108  in one and so that brake rod  108  can experience limited rotational movement and still actuate brake assembly  100 . FIG. 1 illustrates brake assembly  100  actuated to provide frictional engagement with brake disc  180 . 
     Referring again to FIG. 6, self adjusting cam  104  includes stepped ramp or cam surfaces  132 . Additionally, brake pad  102  includes stepped ramp surfaces  134  (See also FIGS. 8, and  8 A). In operation, cam surfaces  132  of self adjusting cam  104  contact ramp surfaces  134  of brake pad  102  such that rotational movement of self adjusting cam  104  causes axial displacement of brake pad  102 . Brake pad  102  will be configured so as to resist rotational movement so that brake pad  102  will not rotate with self adjusting cam  104 . In one embodiment, brake pad  102  will have a square cross sectional area (with the exception of the portion of brake pad  102  which comprises ramp surfaces  134 , which will have a circular cross section), as illustrated in FIG.  8 . As illustrated in FIG. 1, brake pad  102  abuts a portion of primary axle casing  48  (discussed below) so that a side of brake pad  102  will engage primary axle casing  48  and thereby prohibit rotational movement of brake pad  102 . In this embodiment, brake assembly  100  is no longer operable after the square cross section portion of brake pad  102  is worn away by repeated frictional engagements with brake disc  180 . After the portion of brake pad  102  having a square cross section is worn away, ramp surfaces  134  will simply rotate with self-adjusting cam  104 . The present invention also contemplates an embodiment in which ramp surfaces  134  are not integral with brake pad  102 . The brake mechanism of such an embodiment will function such that the ramp surfaces will cooperate with the brake pad for actuation thereof. 
     As illustrated in FIG. 8, ramp surfaces  134  of brake pad  102  comprise progressively stepped ramp surfaces. In one exemplary embodiment, ramp surfaces  134  are stepped in twenty degree intervals. In operation, cam surfaces  132  of self adjusting cam  104  progressively contact stepped ramp surfaces  134  of brake pad  102  as brake pad  102  wears and consequently decreases in thickness. When brake pad  102  is new, self adjusting cam  104  will contact the ramp surface of brake pad  102  of the least height. As the brake pad wears, cam surface  132  of self adjusting cam  104  will progressively contact ramp surfaces of brake pad  102  of increasing height, thus automatically compensating for brake pad wear. In use, as the brake pad deteriorates, the brake mechanism will experience a gradual loss of effectiveness which will signal to the user that a replacement pad is required. 
     Reference will now be made to a particular embodiment of a hydrostatic transaxle utilizing the self adjusting brake of the current invention. Referring to FIG. 4, there is illustrated hydrostatic transmission  30 , which is a transaxle including hydrostatic transmission module  32  fastened to axle module  38 . Hydrostatic transmission module  32  is the subject of pending U.S. patent application Ser. No. 09/498,692 entitled “Hydrostatic Transaxle Having Axial Piston Motor and Method for Manufacturing Transaxles,” assigned to the assignee of the present invention, the disclosure of which is herein explicitly incorporated by reference. Hydrostatic transmission module  32  receives power from a power source (not shown), such as, e.g., an internal combustion engine. As illustrated in FIG. 2, hydrostatic transmission module  32  includes pulley  74  operably connected thereto. Pulley  74  is engaged with a belt (not shown) which is further engaged with the power source. Pulley  74  is affixed to input shaft  42  of hydrostatic transmission module  32 . Power is transmitted from the power source to the hydrostatic transmission module  32 , axle module  38  and thereafter to axles  34 ,  36 . 
     As illustrated, e.g., in FIGS. 2 and 4, axle module  38  includes a plurality of apertures  40  through which bolts may pass to affix axle module  38  to a vehicle frame (not shown). Axle module  38  is formed of primary axle casing  48  having split line  46  which is substantially perpendicular to axles  34 ,  36  and secondary axle casings  54 ,  56 . Bolts  58  join secondary axle casings  54 ,  56  to primary axle casing  48  with gasket  178  (FIG. 5) positioned therebetween. Similarly, bolts  52  join first half  50  and second half  60  of primary axle casing  48 . The orientation of split line  46  (i.e., substantially perpendicular to axles  34 ,  36 ) of axle casing  48  advantageously allows the use of full bearings  90  to support axles  34 ,  36 . FIG. 3 illustrates axle module  38  in assembled form. 
     FIG. 2 illustrates piloting of hydrostatic transmission module  32  to axle module  38 . Hydrostatic transmission module  32  includes output shaft  64  having central bore  62 . Gear train input shaft  66  (FIG. 1) includes end  68  sized for insertion into bore  62  of output shaft  64 . End  68  of gear train input shaft  66  (FIG. 5) is recessed into second half  60  of primary axle casing  48 . Output shaft  64  protrudes from hydrostatic transmission casing  76  so that end  68  of gear train input shaft  66  may be piloted to bore  62  of output shaft  64  to guide placement of hydrostatic transmission module  32  in operative engagement with axle module  38 . Hydrostatic transmission module  32  includes protrusions  80  having apertures  70 . Similarly, axle module  38  includes protrusions  82  having apertures  72 . Apertures  70  axially align with apertures  72  after output shaft  64  is piloted to end  68  of gear train input shaft  66 . After piloting of hydrostatic transmission module  32  to axle module  38 , bolts (not shown) are placed through apertures  70 ,  72  and are utilized to affix hydrostatic transmission module  32  to axle module  38 . Output shaft  64  is supported by sleeve and bearing assembly  84 . Sleeve and bearing assembly  84  extends into recess  86  of axle module  38  with oil seal  87  therebetween. However, the piloting of hydrostatic transmission module  32  to axle module  38  is accomplished solely via end  68  of gear train input shaft  66  and bore  62  of output shaft  64 . 
     Hydrostatic transmission module  32  is described in pending U.S. patent application Ser. No. 09/498,692, incorporated by reference supra. Axle module  38  of the current application is larger than the axle module disclosed in U.S. patent application Ser. No. 09/498,692 and is designed for heavier duty operation. Thus, as described in pending U.S. patent application Ser. No. 09/498,692, hydrostatic transmission module  32  is adaptable for a use in varying applications. As further disclosed in U.S. patent application Ser. No. 09/498,692, hydrostatic transmission modules  32  may be utilized with either a left or right drive transaxle. With this in mind, it is clear that while depicted as a right hand hydrostatic transaxle, the current invention may similarly be configured as a left hand hydrostatic transaxle. 
     Upon piloting of hydrostatic transmission module  32  to axle module  38 , disconnect mechanism  78  is utilized to rotationally fix output shaft  64  to gear train input shaft  66 . Disconnect mechanism  78  is disclosed in U.S. Pat. No. 5,701,738 assigned to the assignee of the present application and herein expressly incorporated by reference. As illustrated, e.g., in FIG. 1, disconnect mechanism  78  includes splined sleeve  88  and lever  91 . Lever  91  is rotationally supported by second half  60  of primary axle casing  48  and is operable to axially displace splined sleeve  88 . For the sake of brevity, disconnect mechanism  78  will not be discussed in further detail, and the reader is directed to U.S. Pat. No. 5,701,738 for further explanation thereof. 
     Referring now to FIGS. 1 and 5, brake pad  102  (FIGS. 8,  8 A, and  8 B) is selectively actuatable by brake assembly  100  for frictional engagement with brake disc  180 . Friction backing pad  140  is held in place by friction backing pad holder  142  and is laterally disposed from brake pad  102 , with brake disc  180  positioned between friction backing pad  140  and brake pad  102 . Brake disc  180  is splined to gear train input shaft  66  such that actuation of brake assembly  100  brings brake disc  180  into frictional contact with friction backing pad  140  and brake pad  102 . Oil plug  94  is affixed to first half  50  of primary axle casing  48  and can be utilized to check the oil level in the axle casing. FIG. 1 illustrates an embodiment of the brake assembly of the current invention wherein friction backing pad  140  is vertically oriented, while FIG. 5 illustrates an embodiment in which friction backing pad  140  is horizontally oriented. These configurations are depicted for illustrative purposes only and are not meant to be limiting in any way. It will be understood by those skilled in the art that various friction backing pad/brake pad placements may be utilized within the teachings of the current invention. 
     As described above, gear train input shaft  66  is selectively connectable to output shaft  64  of hydrostatic transmission module  32 . Power transmitted from hydrostatic transmission module  32  to gear train input shaft  66  is thereafter communicated through a speed reduction mechanism to differential  152 . FIGS.  1  and  5  illustrate embodiments of such a speed reduction mechanism. Input shaft pinion gear  96  is splined to gear train input shaft  66  and is in toothed engagement with intermediate gear  98 . Intermediate gear  98  is splined to intermediate shaft  144  which additionally carries intermediate pinion gear  146  splined thereto. Intermediate pinion gear  146  is in toothed engagement with gear  148 . Gear  148  is splined to differential drive shaft  174 . Differential drive shaft  174  includes differential pinion gear  150  cut therefrom. Differential pinion gear  150  is in toothed engagement with differential ring gear  176 . Differential gear  152  operates to transmit rotational motion to axles  34 ,  36  as is known in the art. Differential  152  includes differential housing  154  with bevel gears  156 ,  158 ,  160 , and  162  rotationally supported therein. In the embodiment illustrated in FIGS. 1 and 5, a differential lock is provided so that upon engagement of the differential lock, axles  34  and  36  receive equal rotational movement. 
     To effect differential locking, differential housing  154  includes apertures  170  sized to accommodate locking pins  166 . Similarly, side bevel gear  162  of differential  152  includes bores  172  sized to accommodate locking pins  166 . Locking pins  166  are affixed to shift collar  164  which is operably connected to differential lock actuator  168 . Bores  172  and apertures  170  are coaxially alignable so that actuation of shift collar  164  by differential lock actuator  168  places locking pins  166  through bores  172  and apertures  170 , thus rotationally engaging side bevel gear  162  with differential housing  154  and locking differential  152 . 
     While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variation, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.