Abstract:
The drum supporting structure comprises larger and smaller diameter portions and a radially raised wall portion which are defined by the aluminum drum support, the radially raised wall portion being arranged at an axially base end of the larger diameter portion and the larger diameter portion having seal rings concentrically mounted thereon; a first steel sleeve coaxially fitted to a cylindrical inner wall of the larger diameter bore, the first steel sleeve including a cylindrical major portion which is slidably put on the seal rings and a cylindrical end portion which is slidably and directly supported on the larger diameter portion of the drum support and a second steel sleeve coaxially fitted to a cylindrical outer wall of the smaller diameter portion of the drum support to bear a cylindrical inner wall of the smaller diameter bore of the drum.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to automotive automatic transmissions, and more particularly to a drum supporting structure installed in the automatic transmission for rotatably supporting an aluminum drum on an aluminum drum support. More specifically, the present invention is concerned with a bearing arrangement installed in the drum supporting structure, by which an undesired centrifugal whirling of the drum about the drum support is suppressed during rotation of the drum. 
     2. Description of the Prior 
     In automotive automatic transmissions of a type wherein an aluminum drum is rotatably supported by an aluminum drum support, various drum supporting structures have been hitherto proposed and put into practical use. One of them is such a structure as shown in FIG.  13 . 
     That is, in such a conventional drum supporting structure, a first steel sleeve  104  is press-fitted in a larger diameter bore of the aluminum drum  103 , a second steel sleeve  105  is press-fitted on a smaller diameter portion of the aluminum drum support  102  and a steel ring  111  is fitted to a raised wall of the drum support  102 . Upon assembly, the first steel sleeve  104  is carried on three seal rings  102   a ,  102   b  and  102   c  mounted on a larger diameter portion of the drum support  102 , the second steel sleeve  105  carries thereon a cylindrical inner wall of a smaller diameter bore of the drum  103 , and the steel ring  111  bears an axial base end of the drum  103 , as shown. 
     That is, in the illustrated conventional drum supporting structure, three steel members, which are the first and second steel sleeves  104  and  105  and the steel ring  111 , are interposed between the aluminum drum support  102  and the aluminum drum  103 . However, practical supporting of the aluminum drum  103  on the aluminum drum support  102  is carried out by only the second steel sleeve  105 . That is, due to presence of the three seal rings  102   a ,  102   b  and  102   c  between the first steel sleeve  104  and the aluminum drum support  102 , the first steel sleeve  104  does not participate in supporting the drum  103  on the drum support  102 . That is, a so-called one point supporting is employed in the illustrated conventional drum supporting structure. 
     However, the one point supporting tends to bring about undesired centrifugal whirling of the drum  103  relative to the drum support  102  when the drum  103  rotates about the drum support  102 . This phenomenon becomes much severe when the axial length of the drum  103  increases. 
     Furthermore, usage of the three steel members  104 ,  105  and  111  has brought about a time-consumed and troublesome assembling work. Particularly, fixing the steel ring  111  to the raised wall of the drum support  102  has needed a very skilled technique. These have caused a costly assemblage of the transmission. Furthermore, in such drum supporting structure, it has been difficult to feed a sufficient amount of lubrication oil to an end clearance  110  which inevitably appears between the drum support  102  and the drum  103  at a position between the first steel member  104  and the steel ring  111 . In fact, even when an oil passage “O” is provided in the larger diameter portion of the drum support  102  to lubricate such end clearance  110  by using a lubrication oil flowing in a lubrication oil passage formed in an output shaft OUT, adequate oil feeding to the clearance  110  is not expected. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a drum supporting structure for an automotive automatic transmission, which is free of the above-mentioned drawbacks. 
     According to the present invention, there is provided a drum supporting structure for use in an automatic transmission. The automatic transmission includes a transmission case, an aluminum drum support fixed to the transmission case, an aluminum drum rotatably held by the drum support, a piston installed in the drum, a hydraulic fluid passage formed in the drum to feed the piston with a hydraulic work, a lubrication oil passage formed in the drum support to feed the piston with a lubrication oil, and seal rings for hermetically separating the lubrication fluid passage and the lubrication oil passage. The drum supporting structure comprises larger and smaller diameter portions and a radially raised wall portion which are defined by the aluminum drum support, the radially raised wall portion being arranged at an axially base end of the larger diameter portion, the larger diameter portion having the seal rings concentrically mounted thereon; larger and smaller diameter bores defined by the aluminum drum to respectively receive therein the larger and smaller diameter portions of the drum support allowing an axially base end of the drum to face the radially raised wall portion of the drum support; a first steel sleeve coaxially fitted to a cylindrical inner wall of the larger diameter bore, the first steel sleeve including a cylindrical major portion which is slidably put on the seal rings and a cylindrical end portion which is slidably and directly supported on the larger diameter portion of the aluminum drum support, the cylindrical major portion and the cylindrical end portion being integrally connected to constitute a single unit; and a second steel sleeve coaxially fitted to a cylindrical outer wall of the smaller diameter portion of the drum support to bear a cylindrical inner wall of the smaller diameter bore of said drum. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying, in which: 
     FIG. 1 is a sectional view of an automotive automatic transmission to which the present invention is practically applied; 
     FIG. 2 is a power train possessed by the automatic transmission to which the present invention is practically applied; 
     FIG. 3 is a table showing various conditions taken by various friction elements used in the automatic transmission to which the invention is practically applied; 
     FIG. 4 is a view similar to FIG. 2, but showing a torque transmission path that is established when the automatic transmission assumes First gear; 
     FIG. 5 is a view similar to FIG. 2, but showing a torque transmission path that is established when the automatic transmission assumes Second gear; 
     FIG. 6 is a view similar to FIG. 2, but showing a torque transmission path that is established when the automatic transmission assumes Third gear; 
     FIG. 7 is a view similar to FIG. 2, but showing a torque transmission path that is established when the automatic transmission assumes Fourth gear; 
     FIG. 8 is a view similar to FIG. 2, but showing a torque transmission path that is established when the automatic transmission assumes Fifth gear; 
     FIG. 9 is a view similar to FIG. 2, but showing a torque transmission path that is established when the automatic transmission assumes Reverse gear; 
     FIG. 10 is an enlarged sectional view of an upper half of a part of the automatic transmission where a drum supporting structure of the present invention is installed; 
     FIG. 11 is an enlarged sectional view of the entirety-of the part of the automatic transmission where the drum supporting structure of the present invention is installed; 
     FIG. 12 is a view similar to FIG. 11, but showing a modification of the drum supporting structure of the present invention; and 
     FIG. 13 is an enlarged sectional view of an upper half of a conventional drum supporting structure. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 and 2, there is shown an automotive automatic transmission to which the present invention is practically applied. 
     In the drawings, particularly in FIG. 2, designated by G 1 , G 2  and G 3  are first, second and third planetary gear units, designated by M 1  and M 2  are first and second connecting members, designated by C 1 , C 2  and C 3  are first, second and third clutches, designated by B 1 , B 2 , B 3  and B 4  are first, second, third and fourth brakes, designated by F 1 , F 2  and F 3  are first, second and third one-way clutches and designated by “IN” and “OUT” are input and output shafts respectively. 
     The first planetary gear unit G 1  is of a single pinion type that comprises a first sun gear S 1 , a first ring gear R 1 , a first pinion (not shown) engaged with both the first sun gear S 1  and the first ring gear R 1  and a first carrier PC 1  carrying the first pinion. 
     The second planetary gear unit G 2  is also of a single pinion type that comprises a second sun gear S 2 , a second ring gear R 2 , a second pinion (not shown) engaged with both the second sun gear S 2  and the second ring gear R 2  and a second carrier PC 2  carrying the second pinion. 
     The third planetary gear unit G 3  is also of a single pinion type that comprises a third sun gear  53 , a third ring gear R 3 , a third pinion engaged with both the third sun gear S 3  and the third ring gear R 3  and a third carrier PC 3  carrying the third pinion. 
     The first connecting member M 1  integrally connects the first carrier PC 1  and the third ring gear R 3 . 
     The second connecting member M 2  integrally connects the second ring gear R 2  and the third carrier PC 3 . 
     The first clutch C 1  selectively establishes connection or disconnection between the first ring gear R 1  and the second ring gear R 2 . 
     The second clutch C 2  selectively establishes connection or disconnection between the second sun gear S 2  and the third sun gear S 3 . To this second clutch C 2 , there is connected the first one-way clutch F 1  in parallel. 
     The.third clutch C 3  selectively establishes connection or disconnection between the third carrier PC 3  and the third sun gear S 3 . 
     The first brake B 1  selectively brakes rotation of the second connecting member M 2 . 
     The second brake B 2  selectively brakes rotation of the first sun gear S 1 . To this second brake B 2 , there is connected the second one-way clutch F 2  in parallel. 
     The third brake B 3  selectively brakes rotation of the second sun gear S 2 . To this third brake B 3 , there is connected in parallel a unit that includes the fourth brake B 4  and the third one-way clutch F 3  which are arranged in series as shown. 
     The input shaft IN is connected to the first ring gear R 1 , so that an engine torque is applied to the first ring gear R 1  through a torque converter (not shown). 
     The output shaft OUT is connected to the second carrier PC 2 , so that an output torque from the second carrier PC 2  is transmitted to drive wheels (not shown) through a final gear unit (not shown). 
     To the clutches C 1 , C 2  and C 3  and the brakes B 1 , B 2 , B 3  and B 4 , there are connected a hydraulic pressure control device by which engaging pressure and releasing pressure for such friction elements are produced. The hydraulic pressure control device may be of a mechanically controlling type, an electronically controlling type or a combination of these two types. 
     FIG. 3 is a table showing various conditions taken by the various friction elements when the automatic transmission assumes First, Second, Third, Fourth, Fifth and Reverse gears. 
     In the table of FIG. 3, mark “Δ” represents that the corresponding friction element participates in torque transmission when assuming ON condition (viz., power ON), mark “C” represents that the corresponding friction element participates in torque transmission when the corresponding vehicle is under coasting, mark “ 574  ”represents that the corresponding friction element has no effect on the output of the transmission even when applied with a hydraulic pressure, mark “(O)” represents that the corresponding friction element takes an engaged condition under overrun mode, mark “(O)*” represents that the corresponding friction element assumes an engaged condition at the time when the corresponding gear (viz. first gear) is selected and thereafter the friction element takes a disengaged condition in a mode other than the overrun mode, and mark “O” represents that the corresponding friction element takes an engaged condition. 
     FIGS. 4 to  9  are schematic illustrations of power train showing respective torque transmission paths that are established when the automatic transmission assumes First, Second, Third, Fourth, Fifth and Reverse gears. 
     Referring to FIGS. 10 and 11, there is shown a part of the automatic transmission where a drum supporting structure of the present invention is practically arranged. 
     In FIG. 10, denoted by numeral  1  is a transmission case. An aluminum drum support  2  is immovably installed in the transmission case  1 . Rotatably supported by the aluminum drum support  2  is an aluminum drum  3 . Operatively installed in the drum  3  is a piston  6 . The drum  3  is engageable with the above-mentioned first reverse brake B 1  and third clutch C 3  in a known manner, and the drum  3  is connected to the above-mentioned third pinion carrier PC 3  to rotate together, in a known manner. 
     As will be described in detail hereinafter, the aluminum drum  3  has a first steel sleeve  4  press-fitted thereto to be frictionally sustained by the drum support  2 , and the aluminum drum support  2  has a second steel sleeve  5  press-fitted thereto to frictionally sustain the drum  3 . The entire arrangement of the first and second steel sleeves  4  and  5  and the positional relation therebetween are well understood from FIG. 11 which shows in detail the exact portion where the aluminum drum  3  is rotatably supported by the aluminum drum support  2 . 
     As is shown in FIG. 11, the drum support  2  comprises coaxial larger and smaller diameter portions “L 2 ” and “S 2 ” which have a first radially raised wall “R 2 - 1 ” provided therebetween. The drum support  2  further comprises a second radially raised wall “R 2 - 2 ” that is integrally formed on an axially base end of the larger diameter portion “L 2 ”. 
     The larger and smaller diameter portions “L 2 ” and “S 2 ” of the drum support  2  respectively support larger and smaller diameter portions “L 3 ” and “S 3 ” of the drum  3 . More specifically, the larger and smaller diameter portions “L 2 ” and “S 2 ” of the drum support  2  respectively support inner walls of larger and smaller cylindrical bores of the larger and smaller diameter portions “L 3 ” and “S 3 ” of the drum  3 , as shown. 
     The larger diameter portion “L 2 ” of the drum support  2  is  15  formed at its cylindrical outer wall with two annular grooves  21  and  22  for flowing hydraulic work fluid. Each groove  21  or  22  is hermetically sealed by seal rings  2   a  and  2   b  (or,  2   b  and  2   c ) operatively disposed on the cylindrical outer wall of the larger diameter portion “L 2 ”. 
     As shown in FIG. 11, the annular groove  22  is connected with a working fluid passage  22 A that extends axially in the drum support  2 . Although not shown in the drawing, another working fluid passage is formed in the drum support  2 , which is connected with the other annular groove  21 . 
     The drum support  2  is further formed with an axially extending oil passage  2   g  that has first and second branch passages  2   h  and  2   i . The first branch passage  2   h  leads to the bottom of the first radially raised wall “R 2 - 1 ” and the second branch passage  2   i  leads to the outer wall of the larger diameter portion “L 2 ”, as shown. Through these oil passages  2   g ,  2   h  and  2   i , lubrication oil is led to various portions between the drum support  2  and the drum  3  where lubrication is needed. Although not shown in the drawings, the transmission case  1  is formed with passages through which the lubrication oil is conveyed to the oil passage  2   g.    
     It is to be noted that the cylindrical outer wall of the larger diameter portion “L 2 ” has near the axially base end thereof an annular bearing ridge  2   f . The annular bearing ridge  2   f  lies between two smaller lubrication oil grooves  2   d  and  2   e  formed at the outer wall of the larger diameter portion “L 2 ”. As shown, the groove  2   e  is provided at the axially base end of the larger diameter portion “L 2 ”. 
     The smaller diameter portion “S 3 ” of the drum  3  is formed at the cylindrical inner wall thereof with an oil passage  31  and an annular oil groove  32 . The oil passage  31  serves to convey the lubrication oil from the first branch passage  2   h  to the annular oil groove  32 . 
     The drum  3  is further formed with passages  33 ,  34  and  35  which serve to feed the piston  6  with the hydraulic work fluid. 
     The first steel sleeve  4  is press-fitted on the cylindrical inner wall of the larger diameter portion “L 3 ” of the drum  3  and rotatably sustained on the larger diameter portion “L 2 ” of the drum support  2 . 
     As shown, the first steel sleeve  4  is of a single member which comprises a cylindrical major portion  4   a , a cylindrical end portion  4   b  and an annular flange portion  4   c  which are coaxially arranged. As shown, the cylindrical major portion  4   a  and the cylindrical end portion  4   b  are integrated and arranged to entirely cover the cylindrical inner wall of the larger diameter portion “L 3 ” of the drum  3 , and the annular flange portion  4   c  is integrally connected to the cylindrical end portion  4   b  and arranged to cover a radially raised wall of the axially base end of the larger diameter portion “L 3 ”, as shown. 
     It is to be noted that the cylindrical major portion  4   a  of the first steel sleeve  4  is slidably put on the three seal rings  2   a ,  2   b  and  2   c  and the cylindrical end portion  4   b  of the sleeve  4  is directly supported on the annular bearing ridge  2   f  of the drum support  2 . In other words, in the first steel sleeve  4 , the cylindrical major portion  4   a  does not participate in supporting the drum  3  on the drum support  2 . That is, only the cylindrical end portion  4   b  of the sleeve  4  does such supporting function. For lubrication of the cylindrical end portion  4   b  and the annular bearing ridge  2   f , lubrication oil is fed to such portions through the second branch passage  2   i  of the axially extending oil passage  2   g  of the drum support  2 . 
     The annular flange portion  4   c  bears the second radially raised wall “R 2 - 2 ” of the drum support  2 . The annular flange portion  4   c  is formed with radially extending oil grooves  4   d . These oil grooves  4   d  are communicated with the second branch passage  2   i.    
     The first steel sleeve  4  is further formed with openings  41  and  42  for feeding the hydraulic work fluid to hydraulic work chambers  6   a  and  6   b  of the piston  6 . 
     The second steel sleeve  5  is of a single member that covers a cylindrical outer wall of the smaller diameter portion “ 52 ” of the drum support  2 . The second steel sleeve  5  bears the cylindrical inner wall of the smaller diameter portion “S 3 ” of the drum  3 , as shown. 
     The piston  6  is biased rightward in FIG. 11 by a spring  6   d  installed in a centrifugal force canceling chamber  6   c . The hydraulic work chambers  6   a  and  6   b  are provided at a position opposite to the force canceling chamber  6   c . A passage  61  is formed in the piston  6  to feed the hydraulic work chamber  6   a  with the hydraulic work fluid. 
     In the following, advantageous features of the present invention will be described with reference to the drawings. 
     As is understood from FIGS. 9 and 10, in Reverse gear, the drum  3  connected to the third pinion carrier PC 3  is fixed to the transmission case  1  by means of the first brake B 1 . While, as is seen from FIGS. 4 to  8 , in First, Second, Third, Fourth or Fifth gear, the drum  3  is released from the transmission case  1  and driven by the third pinion carrier PC 3 . That is, when the transmission takes a gear position other than Reverse gear, the drum  3  is always rotated relative to the drum support  2 . To this rotation, the drum supporting structure of the invention exhibits the following advantageous functions. 
     First, to rotatably support the aluminum drum  3  on the aluminum drum support  2 , the first and second steel sleeves  4  and  5  are employed, which are spaced from each other in an axial direction. That is, as has been mentioned hereinabove, in addition to the second steel sleeve  5 , the cylindrical end portion  4   b  of the first steel sleeve  4  is directly supported on the drum support  2 . A so-called two point supporting of the drum  3  on the drum support  2  is achieved. Thus, undesired centrifugal whirling of the drum  3  under rotation of the same is suppressed. Furthermore, due to the same reason, a force inevitably applied to the seal rings  2   a ,  2   b  and  2   c  from the drum  3  is reduced, which protects contacting surfaces of the seal rings  2   a ,  2   b  and  2   c.    
     Second, the first steel sleeve  4  serves to bear a radial force as well as an axial force which are inevitably applied to the drum  3  when the drum  3  is rotated. More specifically, the cylindrical end portion  4   b  of the first sleeve  4  serves to bear the radial force and the annular flange portion  4   c  serves to bear the axial force. The second steel sleeve  5  serves to bear the radial force. 
     Third, the lubrication oil from the first branch passage  2   h  (see FIG. 11) of the drum support  2  is fed to the centrifugal force canceling chamber  6   c  as well as to the second steel sleeve  5 . For the oil feeding to this sleeve  5 , the oil passage  31  and the annular oil groove  32  are effectively used. Furthermore, the lubrication oil from the second branch passage  2   i  is fed to the two smaller oil grooves  2   d  and  2   e  of the drum support  2  and to the oil grooves  4   d  of the annular flange portion  4   c . With this, lubrication at the supporting annular ridge  2   f , the cylindrical end portion  4   b  and the annular flange portion  4   c  is made well. 
     Fourth, the first steel sleeve  4  is fixed to the drum  3  to rotate therewith. Thus, upon rotation of the drum  3 , the lubrication oil in the radially extending oil grooves  4   d  of the annular flange portion  4   c  is forced to flow radially outward due to the centrifugal force. This promotes the lubrication at the annular flange portion  4   c.    
     Referring to FIG. 12, there is shown a modification of the drum supporting structure of the present invention. 
     Since this modification is similar in construction to the above-mentioned drum supporting structure, only different portions will be described in the following. 
     In this modification, a third steel sleeve  7  is further employed in addition to the first and second steel sleeves  4  and  5 . As shown, the third steel sleeve  7  is press-fitted on the larger diameter portion “L 2 ” of the drum support  2  and has structures that correspond to the annular grooves  21  and  22  and the seal rings  2   a ,  2   b  and  2   c.    
     Due to usage of the third steel sleeve  7 , the durability at the portion where the seal rings  2   a ,  2   b  and  2   c  are provided is much assured. 
     The entire contents of Japanese Patent Application 11-296458 (filed Oct. 19, 1999) are incorporated herein by reference. 
     Although the invention has been described above with reference to the embodiments of the invention, the invention is not limited to such embodiments as described above. Various modifications and variations of such embodiments may be carried out by those skilled in the art, in light of the above descriptions.