Compound transmission having auto range actuation through dual entry first speed gear
TECHNICAL FIELD 
     The present invention relates to compound transmissions including a multispeed main transmission section connected in series with a multispeed auxiliary transmission section, and in particular to such a compound transmission having a combined range and splitter type auxiliary transmission section. 
     BACKGROUND ART 
     Compound change gear transmissions of the type having one or more auxiliary sections connected in series with a main transmission section are known in the prior art. Briefly, by utilizing main and auxiliary transmission sections connected in series, assuming proper sizing of the ratio steps, the total of available transmission ratios is equal to the product of the main and auxiliary section ratios. By way of example, a compound change gear transmission comprising a four (4) speed main section connected in series with a three (3) speed auxiliary section will theoretically provide twelve (4×3=12) available ratios. 
     Auxiliary transmission sections are of three general types: range type, splitter type or combined range/splitter type. In compound transmission having a range type auxiliary section, the ratio step or steps are greater than the total ratio coverage of the main transmission section and the main section is shifted progressively through its ratios in each range. Examples of compound transmissions having range type auxiliary sections may be seen by reference to U.S. Pat. No. 3,105,395; U.S. Pat. No. 2,637,222; and U.S. Pat. No. 2,637,221, the disclosures of which are hereby incorporated by reference. 
     In compound transmissions having a splitter type auxiliary section, the ratio steps of the splitter auxiliary section are less than the ratio steps of the main transmission section and each main section ratio is split, or subdivided, by the splitter section. Examples of compound change gear transmissions having splitter type auxiliary sections may be seen by reference to U.S. Pat. No. 4,290,515; U.S. Pat. No. 3,799,002; U.S. Pat. No. 4,440,037; and U.S. Pat. No. 4,527,447, the disclosures of which are hereby incorporated by reference. 
     In a combined range and splitter type auxiliary section, or sections, both range and splitter type ratios are provided allowing the main section to be progressively shifted through its ratios in at least two ranges and also allowing the main section ratios to be split in at least one range. 
     Examples of a compound transmission having a single combined range/splitter type auxiliary section may be seen by reference to U.S. Pat. No. 3,283,613 and U.S. Pat. No. 3,648,546, the disclosures of which are hereby incorporated by reference. Eaton also produces the &#34;Super 10&#34; compound transmission which has a 2+1 main section and an auxiliary section having both range and splitter gears.. All three forward ratios are used in the low range, while two forward ratios are repeated in the high range. This results in a standard 5 speed shift pattern. 
     Another example of a combined range and splitter type compound transmission is the &#34;Ecosplit&#34; model of transmission sold by Zahnradfabrik Friedrichshafen Aktiengesellschaft of Friedrichshafen, Germany, which utilizes a separate splitter auxiliary section in front of, and a separate range auxiliary section behind, the main transmission section. Still another example is the RMO-13-145A thirteen speed transmission sold by Rockwell Corporation, in which the high range forward ratios are split. 
     It should be noted that the terms main and auxiliary section are relative and that if the designations of the main and auxiliary sections are reversed, the type of auxiliary section (either range or splitter) will also be reversed. In other words, given what is conventionally considered a four-speed main section with two-speed range type auxiliary section, if the normally designated auxiliary is considered the main section, the normally designated main section would be considered a four-speed splitter type auxiliary section therefor. By generally accepted transmission industry convention, and as used in this description of the invention, the main transmission section of a compound transmission is that section which contains the largest (or at least no less) number of forward speed ratios, which allows selection of a neutral position, which contains the reverse ratio(s) and/or which is shifted (in manual or semiautomatic transmissions) by manipulation of a shift bar or shift rail or shift shaft/shift finger assembly as opposed to master/slave valve/cylinder arrangements or the like. 
     SUMMARY OF THE INVENTION 
     The present invention is a compound transmission comprising a main section and an auxiliary section. The main section includes a plurality of forward gears and a reverse gear. A plurality of main section clutches selectively clutch the gears to a mainshaft to establish a reduction ratio between an input shaft and the mainshaft, with one of the main section gears being clutchable by either of two clutches situated on opposite sides of one of the forward gears. The auxiliary section includes an auxiliary drive gear rotationally fixed to the mainshaft, an intermediate shaft having a reduction gear rotatably mounted thereon, and an output shaft having a splitter gear rotatably mounted thereon. Each of the auxiliary section gears is rotatably engaged with a corresponding auxiliary countershaft gear. A range clutch rotatable with the intermediate shaft selectively clutches the auxiliary drive gear or the reduction gear to the intermediate shaft, and a splitter clutch rotatable with the output shaft selectively clutches the intermediate shaft or the splitter gear to the output shaft. 
     Accordingly, it is an object of the present invention to provide a new and improved compound transmission having a three layer, three-speed auxiliary transmission section of the combined range and splitter type. 
     This and other objects and advantages of the present invention will become apparent from a reading of the detailed description of the preferred embodiment taken in connection with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of a compound transmission having a combined range and splitter auxiliary section; 
     FIG. 2 is a partial sectional view of a main transmission section of the transmission of FIG. 1; 
     FIG. 3 is a schematic illustration of a shift pattern for the compound transmission; and 
     FIG. 4 is a schematic illustration of an alternative embodiment of the compound transmission shown in FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Certain terminology will be used in the following description for convenience in reference only and will not be limiting. The words &#34;upwardly&#34;, &#34;downwardly&#34; &#34;rightwardly&#34; and &#34;leftwardly&#34; will designate directions in the drawings to which reference is made. The words &#34;forward&#34; and &#34;rearward&#34; will refer respectively to the front and rear ends of the transmission as conventionally mounted in a vehicle, being respectfully from left and right sides of the transmission as illustrated in FIG. 1. The words &#34;inwardly&#34; and &#34;outwardly&#34; will refer to directions toward and away from, respectively, the geometric center of the device and designated parts thereof. Said terminology will include the words above specifically mentioned, derivatives thereof and words of similar import. 
     The term &#34;compound transmission&#34; is used to designate a change speed or change gear transmission having a multiple forward speed main transmission section and a multiple speed auxiliary transmission section connected in series whereby the selected gear reduction in the main transmission section may be compounded by further selected gear reduction in the auxiliary transmission section. &#34;Synchronized clutch assembly&#34; and words of similar import shall designate a clutch assembly utilized to nonrotatably couple a selected gear to a shaft by means of a positive clutch in which attempted engagement of said clutch is prevented until the members of the clutch are at substantially synchronous rotation. Relatively large capacity friction means are utilized with the clutch members and are sufficient, upon initiation of a clutch engagement, to cause the clutch members and all members rotating therewith to rotate at substantially synchronous speed. 
     FIG. 1 shows a nine speed compound transmission 10 according to the present invention. Compound transmission 10 comprises a multiple speed main transmission section 12 connected in series with an auxiliary transmission section 14. Typically, transmission 10 is housed within a single housing H and includes an input shaft 16 driven by a prime mover such as diesel engine E through a selectively disengaged, normally engaged friction master clutch C having an input or driving portion 18 drivingly connected to the engine crankshaft 20 and a driven portion 22 rotatably fixed to the transmission input shaft 16. 
     In main transmission section 12, the input shaft 16 carries an input gear 24 rotationally fixed thereto for simultaneously driving a plurality of countershaft assemblies at substantially identical rotational speeds. In the transmission 10 illustrated, two substantially identical main section countershaft assemblies 26 and 26A are provided on opposite sides of mainshaft 28, which is generally coaxially aligned with the input shaft 16. Each of the main section countershaft assemblies 26 and 26A comprises a main section countershaft 30 supported by bearings 32 and 34 in housing H, only a portion of which is schematically illustrated. Each of the main section countershafts 30 is provided with an identical grouping of main section countershaft gears 38, 40, 42, 44, and 48 fixed for rotation therewith. 
     A plurality of main section drive or mainshaft gears 50, 52, 54 and 58 surround the mainshaft 28 and are selectively clutchable, one at a time, to the mainshaft 28 for rotation therewith by sliding clutch collars 60, 62 and 64 as is well known in the art. Clutch collar 60 may also be utilized to clutch input gear 24 to mainshaft 28 to provide a direct drive relationship between input shaft 16 and mainshaft 28. Preferably, each of the main section mainshaft gears encircles the mainshaft 28 and is in continuous meshing engagement with and is floatingly supported by the associated countershaft gear group, which mounting means and special advantages resulting therefrom are explained in greater detail in U.S. Pat. No. 3,105,395 and U.S. Pat. No. 3,335,616, the disclosures of which are hereby incorporated by reference. 
     As shown in FIG. 2, clutch collars 60, 62 and 64 are axially positioned by means of shift yokes or forks 66, 67 and 68, respectively. The shift forks are associated with a shift bar housing assembly 69, for example as described in U.S. Pat. No. 4,901,600, assigned to the assignee of the present invention and hereby incorporated by reference. Clutch collars 60, 62 and 64 are, in the preferred embodiment, of the well known nonsynchronized double acting jaw clutch type. Jaw clutches 60, 62, and 64 are three-position clutches in that they may be positioned in a centered axially nondisplaced, nonengaged position as illustrated, or in a fully rightwardly engaged or fully leftwardly engaged position by means of the shift levers 66, 67 and 68. As is well known, only one of the clutches 60, 62 and 64 is engageable at a given time and main section interlock means are provided to lock the other clutches in the neutral condition. 
     Although the present invention is illustrated as a multiple identical countershaft, floating mainshaft and floating mainshaft gear type, and while the auxiliary transmission section of the present invention is particularly well suited for such transmission structure, the advantages of the present invention are equally applicable to transmission of the single countershaft or non-identical multiple countershaft type. 
     Main transmission section 12 provides four selectable forward speed ratios. The first and lowest forward speed ratio is provided by drivingly connecting mainshaft drive gear 54 to mainshaft 28. As shown particularly in FIG. 2, the first speed ratio provided by drivingly connecting the gear 54 to the mainshaft 28 is obtainable either by axially positioning the clutch 64 to the left, or by axially positioning the clutch 62 to the right. Thus, a double entry first gear is provided. The other three forward ratios, in descending order of reduction ratio provided, are obtained by drivingly connecting mainshaft gears 52, 50 or 24 to the mainshaft 28. Main section mainshaft gear 58 is the reverse gear and is in continuous meshing engagement with countershaft gears 48 by means of conventional intermediate idler gears (not shown). 
     Auxiliary transmission section 14 is connected in series with main transmission section 12. Mainshaft 28 extends into the auxiliary section 14 and carries an auxiliary drive gear 70 fixed thereto. The auxiliary drive gear 70 constantly and simultaneously drives two substantially identical auxiliary section countershaft assemblies 72 and 72A at equal rotational speeds. Each of the auxiliary countershaft assemblies 72 and 72A comprises an auxiliary countershaft 74 supported by bearings 76 and 78 in housing H and carrying three auxiliary section countershaft gears 80, 82 and 84 for rotation therewith. 
     Auxiliary section countershaft gears 80 are constantly meshed with and support auxiliary section auxiliary drive gear 70. Auxiliary section countershaft gears 82 are constantly meshed with and support a reduction or range gear 86 which is rotatably mounted on an intermediate or stub shaft 87. Auxiliary section countershaft gears 84 constantly mesh with and support a splitter gear 88, which is rotatably mounted on an output shaft 90. Accordingly, auxiliary section countershaft gears 80 and auxiliary drive gear 70 define a first gear layer, auxiliary section countershaft gears 82 and reduction gear 86 define a second gear layer, and auxiliary section countershaft gears 84 and splitter gear 88 define a third layer, or gear group, of the auxiliary transmission section 14. 
     A synchronized sliding two position clutch assembly 92 is carried on the intermediate shaft 87. The clutch 92 may be selectively located in the leftwardmost axial position to drivingly couple auxiliary drive gear 70 and mainshaft 28 to the auxiliary intermediate shaft 87 for high range operation, or may be selectively located in the rightwardmost axial position to rotationally couple reduction gear 86 to the auxiliary intermediate shaft 87 for low range operation. To accomplish a shifting of the transmission 10 without requiring the operator to actuate any control device other than the gear lever movements, a range control is provided as described in U.S. Pat. No. 5,000,060, assigned to the assignee of the present invention and hereby incorporated by reference. 
     A sliding two position jaw clutch collar 96 is splined on the output shaft 90 for rotation therewith. Splitter clutch collar 96 may be selectively located in the leftwardmost axial position to rotationally couple the intermediate shaft 87 to the output shaft 90, or may be selectively positioned in the rightwardmost axial position to rotationally couple splitter gear 88 to the output shaft 90. Typically, clutch assembly 96 is axially positioned by means of a shift fork (not shown) controlled by a remotely controlled fluid actuated piston assembly. The piston assembly is operable by a driver selection switch such as a button or the like on the shift knob, for example as described in U.S. Pat. No. 5,000,060. The structure and function of double acting sliding jaw clutch collar 96 is substantially identical to the structure and function of jaw clutch collars 60, 62 and 64 utilized in the main transmission section 12. 
     Synchronized clutch assembly 92 is the range shift clutch utilized for making range shifts in the auxiliary section while sliding jaw clutch collar 96 is the splitter clutch utilized for making splitter shifts in the auxiliary section. When the clutch collar 96 is in the rightwardmost position drivingly coupling splitter gear 88 to output shaft 90, mainshaft 28 drives the output shaft through auxiliary drive gear 70, auxiliary countershaft gears 80, auxiliary countershafts 74, and splitter gear 88 regardless of the position of synchronized clutch assembly 92. Thus, the three-gear-layer auxiliary transmission section 14 provides three selectable gear ratios. 
     FIG. 3 shows the shift pattern for the nine speed compound transmission 10. Divisions in the horizontal direction illustrated by the arrow S represent splitter shifts, while movement by the operator of a gearshift lever between the lower left position and the upper middle position causes the mainshaft gear 58 to be clutched to the mainshaft by clutch 62 instead of clutch 64. This movement also causes the clutch 92 to move from engagement with the reduction gear 86 and into engagement with the auxiliary drive gear 70. This range change is represented by the oscillating line R. 
     Four of the six shift pattern positions provide two selectable ratios, excluding the reverse and low gear positions. In the leftwardmore shift pattern positions, the clutch 96 couples the intermediate shaft 87 to the output shaft 90 for direct drive through the auxiliary section. In the rightwardmore shift pattern positions, the clutch 96 couples the splitter gear 88 to the output shaft 90. 
     The lower left shift pattern position provides the lowest forward speed gear. In this position, the clutch 92 couples the reduction gear 86 to the intermediate shaft, and the clutch 96 couples the intermediate shaft 87 to the output shaft 90. This low range cannot be split due to the auxiliary section 14 only providing three distinct selectable ratios between the mainshaft 28 and output shaft 90. Because the first forward speed gear 54 is used in both low and high range, the shift pattern for the compound transmission 10 has the same configuration as a standard 5 speed, non-repeat, autorange shift pattern. 
     Disregarding the reverse ratio, it is desirable that the main section ratio steps be generally equal, and the splitter steps be generally equal to the square root of the main section ratio steps. Given these desired ideal ratios, gearing to approximate these ratios is selected. A preferred embodiment of the present invention provides the following relationships: 
     
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Gear       # Teeth  Set Ratio                                             
                             Overall Ratio                                
                                      % Step                              
______________________________________                                    
24 (Drive) 42       1.7380   1                                            
38         73                         89.6                                
50 (3rd)   60       1.0909   1.8961                                       
40         55                         89.4                                
52 (2nd)   62       2.0667   3.5920                                       
42         30                         93.5                                
54 (1st)   44       4        6.9523                                       
44         11                                                             
58 (Reverse)                                                              
           44       4        6.9523                                       
48         11                                                             
70 (Aux Drive)                                                            
           42       0.8809   0.7254                                       
80         37                         37.8                                
86 (Reduction)                                                            
           60       1.875    1                                            
82         32                                                             
88 (Splitter)                                                             
           42       0.8235   1.6517                                       
84         51                                                             
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     The compound transmission 10 thus provides nine forward speeds and one reverse speed as indicated in the chart below: 
     
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Gear Name Ratio       Overall Ratio                                       
                                 % Step                                   
______________________________________                                    
Low       11.48       15.829     --                                       
1         6.952       9.5830     65.2                                     
2         5.043       6.9523     37.8                                     
3         3.592       4.9512     40.4                                     
4         2.606       3.5920     37.8                                     
5         1.896       2.6135     37.4                                     
6         1.375       1.8961     37.8                                     
7         1           1.3783     37.6                                     
8         0.725       1          37.8                                     
Reverse   11.48       15.829                                              
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     FIG. 4 shows an alternative embodiment 100 of the present invention. Compound transmsission 100 comprises a main transmission section 12 substantially similar to the main section shown in FIG. 1, and an auxiliary transmission section 114 connected in series with main transmission section 12. Mainshaft 28 extends into the auxiliary section 114 and carries an auxiliary drive gear 170 and a reduction gear 186 rotatably mounted thereon. When fixed to the mainshaft, the auxiliary drive gear 170 drives auxiliary section countershafts 174 through countershaft gears 180, to which countershaft gears 182 and 184 are rotationally fixed. Auxiliary section countershaft gears 182 and 184 constantly mesh with and respectively support reduction gear 186 and splitter gear 188, which are rotatably mounted on output shaft 190. 
     A synchronized sliding two position clutch assembly 192 is rotatable with the mainshaft 28, and is axially positionable to drivingly couple either auxiliary drive gear 170 or reduction gear 186 to the mainshaft 28. A sliding two position jaw clutch collar 196 is similarly splined on the output shaft 190, and is axially positionable to rotationally couple the mainshaft 28 to the output shaft 190, or to rotationally couple splitter gear 188 to the output shaft 190. 
     In the first forward gear shift pattern position shown in FIG. 3, the range clutch 192 is in the rightwardmost axial position drivingly coupling reduction gear 186 to the mainshaft 28, and the splitter clutch 196 is in the rightwardmost axial position drivingly coupling splitter gear 188 to the mainshaft. When the gearshift lever is thereafter moved to the upper middle position for second forward speed ratio 90 and all subsequent forward speed ratios, the clutch 192 moves to the leftwardmost axial position to couple the mainshaft 28 to the auxiliary drive gear 170. As with the embodiment 10 described above, the splitter clutch 196 is then movable between a position coupling the mainshaft 28 to the output shaft 190 for direct drive and a position coupling the splitter gear 188 to the mainshaft 190 so that the power path is through the reduction gear 186 and the splitter gear 188. The preferred embodiment of the auxiliary section 114 provides the following gear relationships: 
     
         ______________________________________                                    
Gear            # Teeth  Set Ratio                                        
______________________________________                                    
170 (AD)        42       0.8809                                           
180             37                                                        
186 (Red.)      30       2.0333                                           
182             61                                                        
188 (Splitter)  42       0.8235                                           
184             51                                                        
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     The compound transmission 100 thus provides nine forward speeds and at least one reverse speed as indicated in the chart below: 
     
         ______________________________________                                    
Gear Name Ratio       Overall Ratio                                       
                                 % Step                                   
______________________________________                                    
Low       11.64       16.057     --                                       
1         6.952       9.5830     67.6                                     
2         5.043       6.9523     37.8                                     
3         3.592       4.9512     40.4                                     
4         2.606       3.5920     37.8                                     
5         1.896       2.6135     37.4                                     
6         1.375       1.8961     37.8                                     
7         1           1.3783     37.6                                     
8         0.725       1          37.8                                     
Reverse   11.64       16.057                                              
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     Although the present invention has been set forth with a certain degree of particularity, it is understood that various modifications are possible without departing from the spirit and the scope of the invention as hereinafter claimed.