Patent Publication Number: US-2005130790-A1

Title: Planetary gearset mechanism of double sun gear type

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to a planetary gear mechanism of a double sun gear type having two sun gears.  
      A double sun gear type planetary gear mechanism includes two sun gears disposed axially in a row, engaged with pinions, and connected, respectively, with two different rotating members. Even in an layout in which one sun gear is surrounded by a carrier, the other sun gear can be connected to a housing through a brake.  
      Japanese Patent Application Publication No. H11(1999)-037230 shows a double sun gear type planetary gear mechanism including a rotation member located radially inside two sun gears, and connected with a pinion carrier through a space between the sun gears, so that a wide variety of speed ratios can be attained.  
      However, it is not achieve to embody this planetary gear mechanism of the double sun gear type.  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide a construction implementing a double sun gear planetary gear mechanism.  
      According to one aspect of the present invention, a double-sun-gear planetary gear mechanism comprises: a first sun gear; a second sun gear; a first rotation member connected with the first sun gear; a second rotation member connected with the second sun gear; third rotation member disposed radially inside the first rotation member and the second rotation member; a plurality of pinions each engaging with both the first sun gear and the second sun gear; and a planetary carrier supporting each of the pinions at both ends rotatably. The planetary carrier includes; a plurality of pinion shafts each supporting one of the pinions, and each extending axially from a first end to a second end; a first support portion supporting the first ends of the pinion shafts; a second support portion supporting the second ends of the pinion shafts; a plurality of connecting portions connecting the first and second support portions, each of the connecting portions being located radially outside the first sun gear and the second sun gear, and circumferentially between adjacent two of the pinions; and an inner center portion extending radially inwardly between the first sun gear and the second sun gear, and connecting the planetary carrier with the third rotation member.  
      According to another aspect of the invention, a double-sun-gear planetary gear mechanism comprises: a first sun gear; a second sun gear; a plurality of pinions each engaging with both the first sun gear and the second sun gear; a ring gear engaging with the pinions; and a planetary carrier supporting each of the pinions at both ends rotatably. The planetary carrier includes; a first carrier plate including a first annular plate portion supporting first ends of the pinions; a second carrier plate including a second annular plate portion supporting second ends of the pinions. The first and second carrier plates are joined together by a plurality of fastening devices each extending axially at a position circumferentially between two of the pinions. One of the first and second carrier plates includes a center disk portion which is located axially between the first and second annular plate portions and which is formed with a plurality of pinion receiving holes each receiving one of the pinions. The center disk portion extends radially inwards between the first and second sun gears. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic view showing an automatic transmission provided with a planetary gear mechanism of a double sun gear type according to one embodiment of the present invention.  
       FIG. 2  is a table showing an engagement logic of friction engagement elements to select one of gear speeds.  
       FIG. 3  is a speed diagram in each gear speed of the automatic transmission.  
       FIG. 4  is a perspective view showing a third carrier C 3  of the automatic transmission of  FIG. 1  as viewed from a front side.  
       FIG. 5  is a perspective view showing the third carrier C 3  of the automatic transmission of  FIG. 1  as viewed from a rear side.  
       FIG. 6  is a rear view showing the third carrier C 3  of the automatic transmission of  FIG. 1 .  
       FIG. 7  is a sectional view taken along a section line S 7 -S 7  of  FIG. 6 .  
       FIG. 8  is an enlarged view showing the pinion support structure of the third carrier C 3 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIG. 1  schematically shows an automatic transmission including a planetary gear mechanism of a double sun gear type according to one embodiment of the present invention.  
      Rotation of an engine  1  is transmitted through an engine output shaft E 1  to a torque converter  2  to increase torque. The rotation with increased torque is transmitted through an input shaft INPUT to a transmission mechanism. The torque converter  2  has a lockup clutch mechanism to directly connect the engine output shaft E 1  with the input shaft INPUT when the efficiency in transmission of torque is decreased.  
      The transmission mechanism includes a first planetary gear set G 1  and a planetary gear system GS, and transmits the rotation from the input shaft INPUT to an output gear OUTPUT.  
      The first planetary gear set G 1  is a planetary gear set of a single pinion type serving as a reduction device. The single pinion type first planetary gear set G 1  includes a first sun gear S 1 , a first ring gear R 1 , and a first carrier C 1  supporting first pinions P 1  engaging with both the sun gear S 1  and the ring gear R 1 .  
      The planetary gear system GS includes a second planetary gear set G 2  and a third planetary gear set G 3 .  
      The second planetary gear set G 2  is a planetary gear set of a single pinion type including a second sun gear S 2 , a second ring gear R 2 , and a second carrier C 2  supporting second pinions P 2  engaging with both the sun gear S 2  and the ring gear R 2 .  
      The third planetary gear set G 3  is a double sun gear type planetary gear set or double sun gear type planetary gear mechanism including a third sun gear (a first sun gear of the double sun gear type planetary gear mechanism G 3 ) S 3 ; a fourth sun gear (a second sun gear in the double sun gear type planetary gear mechanism) S 4 ; third pinions P 3  (pinions in the double sun gear type planetary gear mechanism) each engaging with both the third and fourth sun gears; a third carrier (a planetary carrier or planet carrier in the double sun gear type planetary gear mechanism) C 3  supporting the third pinions P 3 ; and a third ring gear R 3  (a ring gear in the double sun gear type planetary gear mechanism) engaging with the third pinions P 3 .  
      The planet carrier C 3  includes a center member CM serving as a center disk portion. The center member extends radially between the sun gears S 3  and S 4 .  
      The input shaft INPUT Is connected with the first ring gear R 1  to transmit driving force from the engine  1  as a driving source through the torque converter  2 .  
      The output gear OUTPUT is connected with the second carrier C 2  to transmit output driving force through a final gear (not shown) to driving wheels of a vehicle.  
      In this example, the second sun gear S 2  is integrally connected with a first connection member (or a first rotation member) M 1 . The fourth sun gear S 4  is integrally connected with a second connection member (or a second rotation member) M 2 .  
      In this example, the center member CM is integrally connected with a third connection member (a third rotation member of the double sun gear type planetary gear mechanism) M 3  located radially inside the first connection member M 1  and the second connection member M 2 . The third carrier C 3  is integrally connected with a fourth connection member M 4 . The second carrier C 2  and the third ring gear R 3  are integrally connected by a fifth connection member M 5 .  
      A low clutch L/C selectively connects and disconnects the first carrier C 1  with the second ring gear R 2 . A 2-6 brake  2 - 6 /B selectively stops rotation of the fourth sun gear S 4 . A 3-5 reverse clutch  3 - 5 R/C selectively connects and disconnects the first carrier C 1  with the second sun gear S 2  and the third sun gear S 3 . A high clutch H/C selectively connects and disconnects the input shaft INPUT with the center member CM. A low reverse brake L&amp;R/B selectively stops rotation of the third carrier C 3 .  
      Each of the clutches L/C,  3 - 5 R/C and H/C and the brakes L&amp;R/B and  2 - 6 /B is connected with a hydraulically-operated shift control apparatus (not shown) to produce engagement pressure (shown by solid line circles) and disengagement pressure (unmarked) in each gear speed of six forward speeds and one reverse speed, as shown in  FIG. 2 . As the shift control apparatus, it is possible to employ an electrically-controlled type, a hydraulically-controlled type, and an electrically and hydraulically controlled type.  
       FIG. 3  is a speed diagram showing the rotating and held states of the members in each gear speed of the six forward speeds and one reverse speed of the automatic transmission shown in  FIG. 1 . The first through sixth speeds and reverse speed can be attained according to the table in  FIG. 2 .  
       FIG. 4  is a perspective view showing the third carrier C 3  as viewed from a front side (the third sun gear S 3 &#39;s side).  FIG. 5  is a perspective view showing the third carrier C 3  as viewed from a rear side (the fourth sun gear S 4 &#39;s side).  FIG. 6  is a rear view showing the third carrier C 3 .  FIG. 7  is a sectional view taken along a section line S 7 -S 7  of  FIG. 6 .  
      The third carrier C 3  is composed of a first carrier plate  3  and a second carrier plate  4 . Four third pinions P 3  are disposed between the first carrier plate  3  and the second carrier plate  4  which are fastened with fastening devices  5  from the second carrier plate  4 &#39;s side. In this example, the fastening devices are bolts  5 .  
      The first carrier plate  3  has a center disk portion including an outer center portion extending radially outwards to an outer circumference which is located radially outside the meshing position of the third pinions P 3  and the third ring gear R 3 , and formed with a toothed portion or rack portion  3   a  engaging with the fourth connection member M 4 . The center disk portion of the first carrier plate  3  includes an inner center portion formed with an inner flange or boss portion  32  projecting at the center of the first carrier plate  3  toward the third gear S 3 . The inner flange  32  has a center spline hole  32   a  into which the third connection member M 3  is inserted. The inner flange  32  has an outside diameter sized to avoid interference with the third sun gear S 3  and the fourth sun gear S 4 .  
      The first carrier plate  3  includes four pinion holes  3   c  formed, in the center disk portion. The four pinion holes  3   c  are arranged circumferentially at 90° intervals. The diameter of the pinion holes  3   c  is greater than the diameter of the third pinions P 3 . Each of the pinions P 3  extends axially through one of the pinion holes  3   c.    
      The first carrier plate  3  includes an annular plate portion  31  covering the third pinions P 3  from the sun gear S 3 &#39;s side, and supported by four plate support portions (or connecting portions)  33  each formed between adjacent two of the pinion holes  3   c . The four plate support (connecting) portions  33  are arranged at 90° intervals in the circumferential direction, The four connecting portions  33  and the four pinion holes  3   c  are arranged alternately in a circle. The annular plate portion  31  serves as a support portion for supporting the pinions.  
      Each of the plate support (connecting) portions  33  is located at a position radially outside the sun gear S 3  and the sun gear S 4 , circumferentially between adjacent two of the third pinions P 3 , and formed with a screw hole  33   a  into which one of the bolts  5  is screwed.  
      The outside diameter of the annular plate portion  31  and the plate support portions  33  are arranged to avoid interference with the meshing locations of the third pinions P 3  and the third ring gear R 3 . The first carrier plate  3  is formed with circumferential cutout portions  31   a  each receiving a radial outer portion of one of the third pinions P 3 . Each of the third pinions P 3  protrudes radially outwards from one of the cutout portions  31   a . The four cutout portions  31   a  and the four plate support portions (or connecting portions)  33  are arranged alternately around the centre axis of the first carrier plate  3 .  
      The annular plate portion  31  is formed with four pinion support holes  31   b  each supporting a first end  6   a  of a pinion shaft  6  supporting one of the third pinions P 3 , and a center opening  31   c  into which the third sun gear S 3  is inserted. The center opening  31   c  is formed at the center of the annular plate portion  31  and sized to avoid interference with meshing locations of the third pinions P 3  and the third sun gear S 3 .  
      The second carrier plate  4  is substantially identical in shape to the annular plate portion  31  of the first carrier plate  3 . The second carrier plate  4  and the annular plate portion  31  of the first carrier plate  3  serve as support portions supporting the third pinions P 3  on both sides. The second carrier plate  4  is formed with circumferential cutout portions  4   a  substantially identical in shape to the cutout portions  31   a  of the annular plate portion  31 , and four pinion support holes  4   b  equal in shape to the pinion support holes  31   b  of the first carrier plate  3 . Each of the pinion support holes  4   b  supports a second end  6   b  of the corresponding pinion shaft  6 . The second carrier plate  4  includes a center opening  4   c  formed at the center of the second carrier plate  4 , and arranged to receive the fourth sun gear S 4 .  
      The second carrier plate  4  is formed with bolt holes (or fastener holes)  4   d  each aligned with a unique one of the screw holes  33   a  in the plate support portion  33 . Each of the bolts  5  is inserted through one of the bolt holes  4   d  into a corresponding one of the screw holes  33   a . The second carrier plate  4  is formed with a spot facing portion  4   e  around each of the bolt holes  4   d  so that the head of each bolt  5  is sunk under the surface of the second carrier plate  4  when the bolt is tightened into the screw hole  33   a.    
       FIG. 8  shows the support structure for the third pinions P 3  disposed between the first career plate  3  and the second career plate  4 .  
      Each of the third pinions P 3  is rotatably mounted through pinion needles  7   a  on the corresponding pinion shaft (pinion axle)  6 . A pinion washer  7   b  is interposed between each of the third pinions P 3  and the annular plate portion  31 , and another pinion washer  7   b  is interposed between each of the third pinions P 3  and the second carrier plate  4 .  
      Each of the pinion shafts  6  is fixed unrotatable by a pin  8  inserted through a pin receiving hole  41   a  formed in a pin receiving portions  41  of the second carrier plate  4 , into a pin hole  6   c  formed in the pinion shaft  6 , as shown in  FIG. 8 , The pin  8  is inserted through the pin receiving hole  41   a  into the pin hole  6   c  by press fit, so that the pinion shaft  6  is held stationary relative to the second carrier plate  4 .  
      An oil passage  6   d  is formed inside each of the pinion shafts  6  to supply lubricating oil to the pinion shaft  6  and the pinion needles  7   a . The annular plate portion  31  of the first carrier plate  3  is formed with oil holes  31   d  each communicating with one of the oil passages  6   d  of the pinion shafts  6 .  
      The first carrier plate  3  and the second carrier plate  4  are assembled as follows. First, the pinion washers  7   b , the third pinions P 3 , the pinion shafts  6 , the pinion needles  7   a , and the pinion washers  7   b  are set to the second carrier plate  4 . Second, the first carrier plate  3  is set to the first ends of the pinion shafts  6  so as to cover the third pinions P 3  and to position the first end  6   a  of each pinion shaft  6  at the correct position of the corresponding pinion support hole  31   b . Third, the first carrier plate  3  and the second carrier plate  4  are fastened by tightening bolts  5 .  
      The first carrier plate  3  and the second carrier plate  4  can be formed with pin holes receiving a pin for positioning the first and second carrier plates  3  and  4 , before fastening.  
      As mentioned above, in the planetary gear set of the double sun gear type according to the embodiment, the plate support (or connecting) portions  33  are arranged, alternately with the third pinions P 3 , around the third sun gear S 3  and the fourth sun gear S 4 , and thereby connects the first and second carrier plates  3  and  4  with no interference with the third sun gear  53 , the fourth sun gear S 4 , and the third pinions P 3 . With these connecting portions  33 , it is possible to achieve the double sun gear type planetary gear mechanism.  
      The third carrier C 3  has two part structure Including the first carrier plate  3  and the second carrier plate  4  each formed with pinion support holes  31   b  and  4   b  supporting the pinion shafts  6  of the pinions P 3 . The first and second carrier plates  3  and  4  are joined together by fastening devices such as bolts. Therefore, as compared with a three part structure of earlier technology, this structure is advantageous for the assembly operation, and the reduction of the number of parts.  
      The first carrier plate  3  includes the circular center disk portion formed with the rack portion  3   a  engaging with the fourth connection member M 4 . Therefore, it is possible to attain various gear speeds.  
      This application is based on a prior Japanese Patent Application No. 2003-398906. The entire contents of the Japanese Patent Application No. 2003-398906 with a filing date of Nov. 28, 2003 are hereby incorporated by reference.  
      Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described is above. Modifications and variations of the embodiments described above will occur to those skilled in the art in light of the above teachings. The scope of the invention is defined with reference to the following claims.