Reduced-length, high-capacity compound transmission

Abstract: A high-capacity compound transmission (200/400) of lighter weight and/or shorter axial length than comparable prior art transmissions is provided. In one embodiment, the compound transmission of the present invention utilizes main and auxiliary section countershafts (324, 362) which are coaxial and define a countershaft assembly supported solely by bearings in the transmission housing (214) forward and rearward end walls (214A, 214B) and by intermediate bearing means (324B) carried by a partial intermediate housing wall (214C) axially aligned with the axial travel space (380) of a mainshaft clutch (64). The mainshaft (346) is supported solely at the forward and rearward ends thereof on or by the rearward end of the input shaft (16) and forward end of the output shaft (358).

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an improved high-capacity compound mechanical change gear transmission structure, preferably for vehicular compound transmissions of the multiple substantially identical countershaft type. In particular, the present invention relates to an improved high-capacity compound mechanical transmission structure allowing, for a given transmission capacity and life, the provision of a lighter, axially shorter and/or less costly transmission as compared to comparable prior art high-capacity transmission structures. More particularly, in one of the preferred embodiments, the reverse mainshaft and countershaft gears are of a reduced pitch diameter to provide ease of bearing assembly and assembly of the mainshaft into a front-opening, tub-type housing. Description of the Prior Art Compound change gear transmissions, usually vehicular transmissions for heavy duty vehicles, of the type having one or more auxiliary sections connected in series with a main transmission section are well 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, at least in theory, a compound change gear transmission comprising a 4-forward-speed main section connected in series with a 3-speed auxiliary section will provide twelve (4 ' 3 = 12) available forward ratios. Auxiliary transmission sections are of three general types: range type, splitter type or combined range/splitter type. In compound transmissions having a range type auxiliary section the auxiliary section ratio step or steps are greater than the total ratio coverage of the main transmission section ratios used in both ranges 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. Pats. No. 3,105,395; 2,637,222; 2,637,221 and 4,807,493. 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 a splitter-type auxiliary sections may be seen by reference to U.S. Pats. No. 4,290,515; 3,799,002; 4,440,037 and 4,527,447. 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 one or more of the main section ratios to be split in at least one range. One example of a compound transmission having a single combined range/splitter-type auxiliary section may be seen by reference to U.S. Pats. No. 3,283,613; 3,648,546. Another example is the "Ecosplit" model of transmission sold by Zahnradfabrik Friedrichshafen Aktiengesellshaft of Friedrichshafen, Federal Republic of Germany, which utilizes a separate splitter auxiliary section in front of, and a separate range auxiliary section behind, the main transmission section. Another example of a compound vehicular transmission having a single combined 3-gear-layer, 4-speed combined splitter/range transmission may be seen by reference to U.S. Pats. No. 4,754,665 and 4,944,197. US-A-4807493 describes a multispeed twin counter-shaft transmission according to the preamble of claim 1, having a floating main shaft with no internal or external bearings or other supporting device at or adjacent its ends. Positioning and supporting of the mainshaft is by the gears on it and the corresponding gears on the countershafts. It should be noted that the terms main and auxiliary sections 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 4-speed main section with 2-speed range-type auxiliary section, if the normally designated auxiliary is considered the main section, the normally designated main section would be considered a 4-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 forwards 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. The prior art compound change gear transmissions, especially, the prior art compound transmissions of the type having both range- and splitter-type auxiliary section gearing, such as the "Roadranger" and "Super 10" offered by Eaton Corporation and the "Ecosplit" offered by Zahnradfabrik Friedrichshafen Aktiengesellshaft, are well received and widely used in manually shifted, heavy-duty vehicles. However, these and other types of prior art compound change-gear transmissions are not totally satisfactory, as it is an ongoing objective, especially for vehicular transmissions, to provide transmissions of equal or improved capacities and reliability which use fewer parts and/or are axially shorter and/or lighter in weight as compared to prior art transmissions of comparable capacity and reliability. U.S. Pats. No. 5,370,013 and 5,390,561, disclose transmissions of an improved structure which use fewer parts and/or are axially shorter and/or of a lighter weight as compared to comparable prior art compound transmissions of equivalent capacity and reliability. This was accomplished by providing a compound transmission wherein (i) the main and auxiliary section countershafts form a coaxial assembly of countershafts supported solely by bearings in the front and rear end walls of the transmission housing, and/or (ii) the mainshaft is supported, preferably in a radially floating manner, solely by the input and/or output shafts without intermediate bearings joumalled in an intermediate housing wall. The above structure eliminated the requirement of all or a large portion of the intermediate housing wall(s) and the various shaft support bearings associated therewith which allowed the provision of compound change gear transmissions of relatively lighter weight, shorter axial length and/or fewer parts as compared to comparable prior art transmissions. While the above-described improved transmission structure is an advancement in the art, to provide a compound transmission having a relatively equal or greater reliability and a relatively large capacity without providing some intermediate support for the countershaft assemblies requires an undesirable increase in transmission center distances (the distance between the axes of rotation of the input shaft/main shaft/output shaft and the countershaft assemblies) and/or diameters of the countershafts. SUMMARY OF THE INVENTION In accordance with the present invention, which is described in claim 1, a reduced axial length, high-capacity compound transmission is provided which utilizes substantially fewer parts and/or is axially shorter and/or of a lighter weight as compared to comparable prior art compound transmissions of equivalent capacity and reliability. In a preferred embodiment of the present invention, the foregoing is accomplished in a high-capacity compound transmission by utilizing (i) main and auxiliary section countershafts which form a coaxial assembly of countershafts each supported solely by bearings in the front and rear end walls of the transmission housing and by a bearing in a relatively small partial intermediate wall axially aligned with a mainshaft clutch, such as the low-speed and/or reverse mainshaft clutch, and/or (ii) a mainshaft which is supported, preferably in a radially floating manner, solely by the input and/or output shafts without intermediate bearings journalled. in an intermediate housing wall. In another embodiment, the main and auxiliary section countershafts are offset and supported at their inner ends by separate bearing means received in a partial intermediate wall aligned with a main section clutch. The above structures eliminate the requirement of a large portion of the intermediate housing wall(s) and various shaft support bearings associated therewith which allows the provision of high-capacity compound change gear transmissions of relatively lighter weight, shorter axial length and/or fewer parts as compared to comparable prior art transmissions. As the partial intermediate wall and associated bearing are axially aligned with a mainshaft clutch, no additional axial space is required therefor. To provide ease of assembly, especially if a front-opening, tub-type housing is utilized, one of the preferred embodiments utilizes a reverse idler of relatively enlarged pitch diameter and reverse mainshaft and/or countershaft gears of relatively reduced pitch diameter. Accordingly, it is an object of the present invention to provide a new and improved reduced axial length, high-capacity compound change-gear transmission. 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 attached drawings. DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic illustration of a prior art high-capacity compound transmission. Fig. 2 is a schematic illustration of one embodiment of a reduced axial length, high-capacity transmission according to the present invention. Fig. 3 is a sectional view of the transmission of Fig. 2. Fig. 4 is a schematic illustration of an alternate embodiment of the present invention. Figs. 5A, 5B and 5C are schematic illustrations of the shift pattern, typical ratios and clutch positions for the transmission of Figs. 1, 2, 3 and 4. Fig. 6 is a partial sectional view of an alternate reverse idler structure for use in the present invention. Figs. 7A and 7B are schematic illustrations of a further example of a transmission, and Figs. 8A, 8B and 8C are schematic illustrations of another example of a transmission. DESCRIPTION OF THE PREFERRED EMBODIMENT Certain terminology in the following description will be used only for convenience and will not be limiting. The words "upwardly," "downwardly," "rightwardly" and "leftwardly" will designate directions in the drawings to which reference is made. The words "forward" and "rearward" will refer, respectively, to the front and rear ends of the transmission as conventionally mounted in the vehicle, being respectively to the left and right sides of the transmission as illustrated in Fig. 1. The words "inwardly" and "outwardly" will refer to directions toward and away from, respectively, the geometric center of the device and designated parts thereof. Said terminology includes the words specifically mentioned above, derivatives thereof and words of similar import. The term "compound transmission" is used to designate a change speed or change gear transmission having a main transmission section and an 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. The term "upshift" as used herein shall mean the shifting from a lower speed gear ratio to a higher speed gear ratio. The term "downshift" as used herein shall mean the shifting from a higher speed gear ratio to a lower speed gear ratio. The terms "low speed gear" or "low gear" as used herein shall designate a gear ratio utilized for relatively lower forward speed operation in a transmission ( i . e ., a set of gears having a higher ratio of reduction of output shaft speed relative to the speed of the input shaft). "Synchronized clutch assembly" 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 and relative large capacity friction means are associated 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 a substantially synchronous speed. Referring now to Fig. 1, there is schematically illustrated a well known and highly commercially successful 18-speed compound transmission 100. Transmission 100 comprises a main transmission section 12A connected in series with an auxiliary transmission section 102 having both range and splitter type gearing. Typically, transmission 100 is housed within a single housing and includes an input shaft 16 driven by a prime mover such as diesel engine E through a selectively disengaged, normally engaged master friction clutch C having an input or driving section 18 drivingly connected to the engine crank shaft 20 and a driven portion 22 rotatably fixed to the transmission input shaft 16. In the main transmission section 12A, the input shaft 16 carries an input gear 24 for simultaneously driving a plurality of substantially identical main section countershaft assemblies 26 and 26a at substantially identical rotational speeds. In the transmission 100 illustrated, two substantially identical main section countershaft assemblies are provided on diametrically opposite sides of a mainshaft 28A, which mainshaft 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, 46 and 48, fixed for rotation therewith. A plurality of main section drive or mainshaft gears 50, 52, 54, 56 and 58 surround the mainshaft 28A and are selectively clutchable, one at a time, to the mainshaft 28A for rotation therewith by sliding clutch collars 60, 62 and 64, as is well known in the art. Clutch collar 60 also may be utilized to clutch input gear 24 to mainshaft 28A to provide a direct drive relationship between input shaft 16 and mainshaft 28A. Preferably, each of the main section mainshaft gears encircles the mainshaft 28A and is in continuous meshing engagement with and is floatingly supported by the associated countershaft gear group, which mounting means and a special advantages resulting therefrom are explained in greater detail in U.S. Pat. Nos. 3,105,395 and 3,335,616. Typically, clutch collars 60, 62 and 64 are axially positioned by means of shift forks (not illustrated) associated with a shift bar housing assembly (not illustrated), as is well known in the prior art. Clutch collars 60, 62 and 64 are of the well known nonsynchronized double acting jaw clutch type. 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). It also should be noted that while main transmission section 12A does provide five selectable forward speed ratios, the lowest forward speed ratio, namely, that ratio provided by drivingly connected mainshaft drive gear 56 to mainshaft 28, is often of such a high gear reduction as to be considered a low or "creeper" gear which is utilized only for starting of a vehicle under severe conditions and is usually not utilized in the high transmission range and/or may not be split in the low transmission range. Accordingly, while the main section 12 illustrated does provide five forward speeds, it is usually referred to as a "4 + 1" main section, as only four of the forward speeds are compounded by the auxiliary transmission section 102. Jaw clutches 60, 62 and 64 are 3-position clutches in that they may be positioned in a centered, non-engaged position, as illustrated, or in a fully rightwardly engaged or fully leftwardly engaged position. Auxiliary transmission section 102 includes two substantially identical auxiliary countershaft assemblies 104 and 104A, each comprising an auxiliary countershaft 106 supported by bearings 108 and 110 in housing H and carrying three auxiliary section countershaft gears 112, 114 and 116 fixed for rotation therewith. Auxiliary countershaft gears 112 are constantly meshed with and support auxiliary section splitter gear 118 which surrounds mainshaft 28A. Auxiliary countershaft gears 114 are constantly meshed with and support auxiliary section splitter/range gear 120 which surrounds the output shaft 122 at the end thereof adjacent the coaxial end of mainshaft 28A. Auxiliary section countershaft gears 116 constantly mesh and support auxiliary section range gear 124, which surrounds the output shaft 122. Accordingly, auxiliary section countershaft gears 112 and splitter gear 118 define a first gear layer, auxiliary section countershaft gears 114 and splitter/range gear 120 define a second gear layer, and auxiliary section countershaft gears 116 and range gear 124 define a third layer or gear group of the combined splitter and range type auxiliary transmission section 102. A sliding 2-position jaw clutch collar 126 is utilized to selectively couple either the splitter gear 118 or the splitter/range gear 120 to the mainshaft 28A, while a two position synchronized assembly 128 is utilized to selectively couple the splitter/range gear 120 or the range gear 124 to the output shaft 122. The structure and function of double acting sliding jaw clutch collar 126 is substantially identical to the structure and function of sliding clutch collar 96 utilized in connection with transmission 10 while the structure and function of double acting synchronized clutch assembly 128 is substantially identical to the structure and function of synchronized clutch assembly 92 utilized in connection with transmission 10. Synchronized clutch assemblies such as assemblies 92 and 128 are well known in the prior art and examples thereof may be seen by reference to U.S. Pats. Nos. 4,462,489; 4,125,179 and 2,667,955. It is noted that gear 118 defines a forwardly extending hub 118A for receipt of a bearing 118B supported in the intermediate housing wall H'. Bearing 118B provides an intermediate support for the mainshaft 28A, as are bearings 34 and 108. Gear 118 surrounds mainshaft 28A and is normally free to rotate relative thereto and is axially retained relative to the mainshaft 28A by means of retainers. Clutch teeth on the gears and clutch collars (not shown) present tapered surfaces 146 and 148 which are inclined at about 350 relative to the axis of the mainshaft 28A which provides an advantageous interaction tending to resist nonsynchronous engagement and further tending to cause a synchronous rotation, as is described in greater detail in U.S. Pat. No. 3,265,173. Clutch teeth 136 and 140 are provided with similar complementary tapered surfaces. Hub 118A of gear 118 receives bearing 118B which is received in the intermediate housing wall H', as is countershaft support bearing 108. By selectively axially positioning both the splitter clutch 126 and the range clutch 128 in the forward and rearward axial positions thereof, four distinct ratios of mainshaft rotation to output shaft rotation may be provided. Accordingly, auxiliary transmission section 102 is a 3-layer auxiliary section of the combined range and splitter type providing four selectable speeds or drive ratios between the input (countershaft 28A) and output (output shaft 122) thereof. The main section 12A provides a reverse and five potentially selectable forward speeds. However, one of these selectable forward gear ratios (gear 56) is often a creeper or low gear not intended to be used in the high range. Thus, transmission 100 is properly designated as a (4+1)'(2)'(2)-type transmission providing 17 or 18 selectable forward speeds, depending upon the desirability and/or practicality of splitting the low or creeper gear. While clutch 128 (the range clutch) should be a synchronized clutch, double-acting clutch collar 126 (the splitter clutch) is not required to be synchronized. Of course, one or both of the clutches defined by collar 126 could be of the synchronized type. The shift pattern for shifting transmission 100 is schematically illustrated in Fig. 5A, where divisions in the vertical direction illustrate range shifts, while divisions in the horizontal direction illustrate splitter shifts. A method of selecting desirable gear ratios is schematically illustrated by reference to Fig. 5B. Disregarding the creeper (illustrated in dashed lines) and reverse ratios, and assuming that it is desirable that a transmission have generally equal ratio steps, the main section ratio steps should be generally equal, the splitter step should be generally equal to the square root of the main section ratio steps, and the range step should equal about the main section ratio step raised to the N power where N equals the number of main section ratio steps occurring in both ranges ( i . e ., N = 4 in the (4+1)'(2)'(2) transmission). Given the desired ideal ratios, gearing to approximate these ratios is selected. Assuming by way of example that gears 118, 120, 124, 112, 114 and 116, respectively, have 40, 38, 54, 41, 45 and 19 teeth each, respectively, the following four auxiliary section ratios are obtainable: (1) Clutch 126 engaged to gear 120 and clutch 128 engaged to gear 124 provides an auxiliary section reduction of about 3.365:1; (2) Clutch 126 engaged to gear 118 and clutch 128 engaged to gear 124 provides an auxiliary section reduction of about 2,913:1; (3) Clutch 126 engaged to gear 120 and clutch 128 engaged to gear 120 provides an auxiliary section reduction about 1,000:1; and (4) Clutch 126 engaged to gear 118 and clutch 128 engaged to gear 120 provides an auxiliary section reduction of about 0.865:1. In the foregoing example, the splitter steps are about 15.6%, while the range step is about 336.6%, which is generally suitable for a "4+1" main transmission section having about 35% steps, as the square root of 1.35 equals about 1.16, and 1.35 raised to the fourth power ( i.e. , N = 4) equals about 3.32. Fig. 5C illustrates the various gears engaged for the various selectable forward speeds of transmission 100. It is noted that 8-9 and 9-8 shifts are extremely complex because both a main section shift and a combined range and splitter auxiliary section shift are required. A preferred embodiment of the present invention, high-capacity compound transmission 200, is illustrated in Figs. 2 and 3. Transmission 200 includes a main section 212 and an auxiliary section 302 which, except as noted, are functionally identical to main section 12A and auxiliary section 102, respectively, described above. The shift pattern of Fig. 5A, the ratio chart of Fig. 5B and the truth table of Fig. 5C are applicable to both the prior art transmission 100, the preferred embodiment of the present invention transmission 200, and the preferred embodiments 300, 400, 500, 600 and 700 of the present invention to be described in greater detail below. While the present invention is illustrated as an 18-forward-speed compound transmission, it is equally applicable to other compound transmission gearing arrangements, such as those illustrated in aforementioned U.S. Pats. No. 4,944,197 and 5,390,561. Elements of transmission 200, and of transmissions 400, 500, 600 and/or 700 to be described below, which are substantially functionally and structurally identical to elements of transmission 100 will be assigned like reference numerals and will not be redescribed in detail. Transmission 200 is a "(4+1)'(2)'(2)" type compound transmission wherein the main section 212 and auxiliary section 302 are contained within a common housing 214 having a forward end wall 214A, a rearward end wall 214B and a partial intermediate wall 214C. Input shaft 316 carries input gear 24 fixed for rotation therewith and defines an inwardly extending reduced diameter portion 316A which directly or indirectly supports the front end 346A of mainshaft 346. Output shaft 358 extends from the rear end of transmission 200 and carries splines for receipt of an output flange 358A. The inner end 358C of output shaft 358 is provided with a tapered surface for direct or indirect support of the rear end 346B of mainshaft 346. Input shaft 318 is supported in front end wall 316A by taper roller bearing 318B while output shaft 358 is supported in rear end wall 316B by dual taper roller bearing assembly 358E. The mainshaft 346 carries mainshaft clutches 60, 62 and 64 and the splitter clutch 126, and extends generally coaxially between and is supported by the inner ends of the input and output shafts. Mainshaft gears 50, 52, 54, 56 and 58, splitter gear 118 and splitter/range gear 120 surround the mainshaft, preferably for limited radial movement relative thereto, and are selectively clutchable thereto by clutches 60, 62, 64 and 126. Range clutch 128 is carried by output shaft 358 which is surrounded by splitter/range gear 120 and range gear 124. Clutch 128 is effective to clutch either gear 120 or gear 124 to the output shaft 358. The function and operation of transmission 200 is the same as that of transmission 100, discussed above. The countershaft assemblies 322 and 360, respectively, are substantially functionally and operatively identical to the main section and auxiliary countershaft assemblies 26 and 104 of transmission 100, described above. Briefly, main section countershaft(s) 324 carries countershaft gears 38, 40, 42, 44, 46 and 48 fixed thereto, which are constantly meshed with and/or support, mainshaft gears 50, 52, 54 and 56 and, through reverse idler gear 57, mainshaft gear 58. Auxiliary countershaft(s) 362 carries auxiliary countershaft gears 112, 114 and 116, which are constantly meshed with splitter, splitter/range and range gears 112, 114 and 116, respectively. The forward ends 362A of the auxiliary countershaft(s) 362 are generally tubular and telescopically surround the rear end 324A of the main section countershafts and are directly or indirectly rotatably supported by bearings 362B thereon. A bearing 326 supports the forward end of main section countershaft 324 in front wall 214A, while a bearing 362C supports the rearward end of auxiliary section countershaft 362 in the rear end wall 214B. The rearward end 324A of main section countershaft 324 is supported by bearing 324B in partial intermediate wall 214C, while the forward end 362A of auxiliary countershaft 362 is supported by bearing 362B, carried by a cantilevered rearward end of main countershaft 324. The reduced-diameter extension 16A of the input shaft 16 may carry an axial roller bearing and a generally spherical washer of bearing steel, which will abut a generally complimentary radially inwardly and axially rearwardly tapered surface provided on the front end 346A of the mainshaft 346. The hub portion of range/splitter gear 120 surrounds reduced-diameter rearward portion of the mainshaft 346, which also may carry two spherical washers, which interact with generally complimentary inclined surfaces on the mainshaft and on the output shaft, respectively. The advantages of this invention may be appreciated in greater detail by reference to aforementioned U.S. Pat. No. 5,370,013. The mainshaft 346 is thus supported directly or indirectly at its front end by input shaft 16 for a limited amount of radial movement of the mainshaft relative to the axis of rotation of the input shaft. The mainshaft is supported directly or indirectly at its rear end by the output shaft 358 for a limited amount of radial movement of the mainshaft relative to the axis of rotation of the output shaft 358. As with the transmission described in aforementioned U.S. Pat. No. 5,370,013, all or a portion of the gearing of transmissions 200, 400, 500, 600 and/or 700 may be helical. Accordingly, the mainshaft 346 is supported solely by the input and output shafts, preferably with a limited degree of radial freedom or float, requiring no intermediate support to the housing and, if necessary, allowing the transfer of axial forces associated with helical gearing to the housing through appropriate bearings. Further, by eliminating the necessity of an intermediate support for mainshaft 346, the intermediate wall 214C may be of minimal size. Details of the structure of input shaft 16, mainshaft 346 and output shaft 358 may be further understood by reference to aforementioned U.S. Pats. No. 5,370,013 and 5,390,561. It is an important feature of the present invention that the intermediate wall 214C and the bearings 324B supporting the rearward ends of the front or main section countershafts 324 are located within the axial space 380 required for clutch 64 and its forward and/or rearward travel. Accordingly, the addition of the partial intermediate wall 214C and bearings 324B adds little or no axial length to the transmission 200 as compared to transmissions without an intermediate wall, as seen in aforementioned U.S. Pats. No. 5,370,013 and 5,390,561. In transmission 200, the reverse idler 57 is of a relatively enlarged pitch diameter, larger than the pitch diameter of reverse countershaft gear 48, which allows both the reverse mainshaft gear 58 and the reverse countershaft gear 48 to be of a relatively reduced pitch diameter. This allows the inner diameter of bearing 214C to be assembled over the reverse countershaft gear, formed directly on the outer diameter of main section countershaft 324, and permits the main section reverse gear 58 to pass through the central opening in the intermediate wall 214C for assembly purposes. Reverse idler 57 is mounted on an idler shaft 382 cantilever-mounted in housing 214. An alternate embodiment of the present invention, transmission 400, may be schematically seen by reference to Fig. 4. Transmission 400 includes a main section 402 and an auxiliary section 404 functionally and structurally identical to main and auxiliary sections 212 and 302 described above, except as specifically indicated below. Briefly, main section 402 differs from main section 212 in that the reverse idler (not shown), reverse countershaft gear 48 and reverse mainshaft gear 58 are of more conventional pitch diameters. Auxiliary section 404 differs from auxiliary section 302 in that only the forward portions 462A of the auxiliary section countershafts 462 are generally tubular and telescopically surround the rearward ends 324A of the main section countershafts 324. An alternate reverse idler construction is illustrated in Fig. 6. Transmission 500 is functionally and structurally identical to above-described transmissions 200 and 400, except for the construction of the reverse idler and related gearing. As in transmissions 200 and 400, mainshaft gears 52 and 54 surround mainshaft 346 and are clutchable thereto by double-acting clutch collar 62, while low gear 56 and reverse gear 58 surround the mainshaft and are clutchable thereto by sliding double-acting clutch 64 controlled by shift fork 64A. Clutch 64 is movable within axle space 380. Mainshaft gears 52, 54 and 56, respectively, are constantly meshed with countershaft gears 42, 44 and 46 carried by main section 502 countershaft 324. In transmission 500, a reverse countershaft gear is deleted and replaced by a reverse idler shaft assembly 504 comprising an idler shaft 506 carrying an idler gear 508 meshed with the low-speed countershaft gear 46 and an idler gear 510 meshed with the reverse mainshaft gear 58. Shaft 506 is supported in housing 214 and may include a hollow shaft 512 supported by needle bearings 514 on a cantilevered fixed shaft 516. Elimination of the reverse countershaft gear allows the bearing 324B to be easily assembled to the rear end of the main section countershaft 324. In the arrangement of transmission 500, if a reduced-pitch-diameter reverse mainshaft gear is required, the pitch diameter of the idler gear 510 should be equal to or greater than the pitch diameter of low-speed countershaft gear 46. Figs. 7A and 7B illustrate an embodiment, of a transmission 600, not utilizing coaxial front and rear countershafts. Transmission 600 includes a main section 602 and an auxiliary section 604 contained in a common housing having a front end wall 214A, a rear end wall 214B, and a modified partial intermediate wall 606. Intermediate wall 606 is axially aligned with the axial space 380 required for operation of the main section clutch 64 and includes two apertures 608 for receiving bearings 324B supporting the rear ends of the main section countershafts 610 and two openings 612 for receiving bearings 614 supporting the forward ends 616 of auxiliary section countershafts 618. A central opening 620 is provided for passage of the mainshaft and clutch 64. A further alternate embodiment of a transmission 700, similar to transmission 600 described above, may be seen by reference to Figs. 8A, 8B and 8C. Transmission 700 includes a main section 602 connected in series with an auxiliary section 702. Transmission 700 differs from transmission 600 in that two separate axially offset partial intermediate walls, 703 and 704, each axially aligned with and in the axial space, 380 and 706, respectively, required for operation of a different mainshaft or output shaft clutch, namely clutches 64 and 126, respectively, are utilized to support the inner ends of the non-coaxial main section and auxiliary section countershafts, 610 and 708, respectively. As may be seen by reference to Figs. 8B and 8C, intermediate wall 703 includes openings 612 for receiving bearings 324B and intermediate wall 704 includes openings 710 for supporting bearings 614. Accordingly, it may be seen that a reduced-length, high-torque-capacity compound change-gear transmission, including the types described in aforementioned U.S. Pats. No. 5,370,013 and 5,390,561, is provided by utilizing a partial intermediate wall 214C or 606 axially aligned with a mainshaft clutch 64 to support a bearing 324B for supporting an inner end of one of the main or auxiliary section countershafts. By locating the partial intermediate wall and bearing in the axial space 380 required for mainshaft clutch travel, little or no additional axial transmission is required. Although the present invention has been described with a certain degree of particularity, it is understood that various changes to form and detail may be made without departing from the scope of the invention as hereinafter claimed.

Claims: A compound vehicular change gear transmission (200) comprising a multiple speed main transmission section (212) connected in series with a multiple speed auxiliary transmission section (302), said main and auxiliary transmission sections contained within a common transmission housing (214) defining a forward end wall (214A) and a rearward end wall (214B); said main transmission section (200) comprising an input shaft (316) supported for rotation in said housing by input shaft bearing means (318B) carried by said forward end wall, at least one input gear (24) fixable to said input shaft, a mainshaft (346) generally coaxial with said input shaft and extending into said auxiliary transmission section (302), a main section countershaft (324) rotatably supported in said housing and driven by said input shaft, a plurality of main section countershaft gears (38, 40, 42, 44, 46) fixed to said main section countershaft, a plurality of mainshaft gears (50, 52, 54, 56) surrounding said mainshaft and constantly meshed with said main section countershaft gears and main section clutch means (60, 62, 64) carried by said mainshaft for rotation therewith and axial movement relative thereto for selectively fixing said mainshaft gears to said mainshaft for rotation therewith; said auxiliary transmission section comprising at least one auxiliary section countershaft (362) rotatably supported in said housing, an output shaft (358) generally coaxial with said mainshaft and rotatably supported in said housing by output shaft bearing means (358E) carried by said rearward end wall (214B), auxiliary section countershaft gears (112, 114, 116) fixed to each of said one or more auxiliary section countershafts, at least one auxiliary section central gear (124) generally coaxial with said output shaft and constantly meshed with one of each of said auxiliary section countershaft gears (112, 114, 116) and auxiliary section clutch means (126, 128) for selectively clutching at least one of said auxiliary section central gears (118, 120, 124) and said mainshaft to said output shaft; said main section and auxiliary section countershafts being independently rotatable in said housing with the rearward ends of said main section countershafts (324A) and the forward ends (362A) of said auxiliary section countershafts being rotatably supported in said housing by intermediate bearing means mounted in intermediate housing wall (214C) located within the axial space required for one of the main section clutch means (64); and one of said mainshaft gears is a reverse drive ratio gear (58) constantly meshed with an idler gear (57), said idler gear having a greater pitch diameter than at least one of said main section countershaft gears (48), said transmission characterized in that: said mainshaft (346) is supported in said housing solely by said input shaft (316) and said output shaft (358) ; and the countershafts (324 and 362) are coaxial. A transmission according to claim 1, in which said main section clutch means (64) is selectably movable in an axial space (380) to selectively engage and disengage a selected one of a lowest forward drive ratio mainshaft gear (56) and a reverse drive ratio mainshaft gear (58) to said mainshaft (346), said intermediate bearing means and intermediate housing wall being located within said axial space.

Inventors: REYNOLDS JOSEPH DOUGLAS, STINE ALAN CHARLES, REYNOLDS, JOSEPH DOUGLAS, STINE, ALAN CHARLES
Applicants: EATON CORP, EATON CORPORATION
Application year: 1997
Main classification: F16H3
IPC codes: F16H3, F16H61