Patent Publication Number: US-6220108-B1

Title: Manually shifted transmission with enhanced automatic range shift

Description:
This is a continuation of application Ser. No. 08/626,591 filed on Apr. 2, 1996 now U.S. Pat. No. 5,673,592. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to manually shifted range-type compound transmissions having enhanced automatic range shifting mechanisms and controls. In particular, the present invention relates to manually shifted range-type transmissions of the “H ½ ” or “double-H” type having an “autorange” type shift mechanism of the general kind disclosed in U.S. Pat. Nos. 3,492,202; 4,275,612; 4,455,883; 5,000,060 and 5,193,410, the disclosures of which are incorporated herein by reference, wherein the range shift controller will prevent range shifting at vehicle speeds at which such shifting is predetermined to be inappropriate. 
     2.DESCRIPTION OF THE PRIOR ART 
     Change-gear transmissions of the range type and of the combined range-and-splitter type are well known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,455,883; 4,754,665; 5,193,410; 5,000,060 and 5,390,561, the disclosures of which are incorporated herein by reference. Range-type transmissions having shift controls of the “multiple-H” type, as opposed to the “repeat-H” type, which utilize an automatic range shift mechanism responsive to movement of a shift lever from a first to a second area or portion of the shift pattern, are well known, as may be seen by reference to aforementioned U.S. Pat. Nos. 4,455,883; 4,974,468; 5,000,060 and 5,193,410. 
     While the prior art manually shifted, range-type transmissions utilizing automatic range shifting controls are widely used and commercially successful, they are not totally satisfactory, as, due to error or inattention, an operator may select a range shift inappropriate under current vehicle speed conditions, which shift will be automatically completed by the range actuator and usual synchronized range clutch assembly. 
     SUMMARY OF THE INVENTION 
     According to the present invention, the drawbacks of the prior art are minimized or overcome by the provision of an enhanced automatic range shifting mechanism and control for manually shifted, range-type transmissions which will prevent range shifts from being implemented at inappropriate vehicle speeds, regardless of shift lever movement from one range section to another range section of the manual shift pattern. The foregoing is accomplished in a manually shifted transmission with an automatic range shifting system by providing a controller for sensing the value of a parameter indicative to vehicle speed, as well as sensing shift lever positioning, and for permitting downshifts only if vehicle speed is less than a first reference value and/or permitting upshifts only if vehicle speed is greater than a second reference value. 
     Accordingly, it is an object of the present invention to provide a new and improved automatic range shifting mechanism and control for manually shifted, range-type transmissions. 
     This and other objects and advantages of the present invention will become apparent from a reading of the following description of the preferred embodiment taken in connection with the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of a compound combined range-and-splitter-type transmission utilizing the automatic range shifting mechanism of the present invention. 
     FIG. 2 is a sectional view of the transmission of FIG.  1 . 
     FIG. 3 illustrates a typical shift pattern and typical gear ratios for the transmission of FIGS. 1 and 2. 
     FIG. 4 is a schematic illustration of the range shifting mechanism of the present invention. 
     FIG. 5 is a schematic illustration of a transmission system utilizing the shifting mechanism and control of the present invention. 
     FIG. 6 is a schematic illustration, in flow chart format, of the automatic range shifting control of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIGS. 1,  2  and  3 , manually shifted transmission  110  of the type advantageously utilizing the enhanced automatic range shifting mechanism and control of the present invention is illustrated. Transmission  110  includes a main section  112  and an auxiliary section  114 , both contained within housing  116 . Housing  116  includes a forward end wall  116 A and a rearward end wall  116 B, but not an intermediate wall. input shaft  118  carries input gear  120  fixed for rotation therewith and defines a rearwardly opening pocket  118 A wherein a reduced diameter extension  158 A of output shaft  158  is piloted. A non-friction bushing  118 B or the like may be provided in pocket or blind bore  118 A. The forward end of input shaft  118  is supported by bearing  118 C in front end wall  116 A, while the rearward end  158 C of output shaft  158  is supported by bearing assembly  158 D in rear and wall  116 B. Bearing assembly  158 D may be a pair of opposed taper bearings or a single roller or ball bearing, as is illustrated in FIG.  3 . 
     The mainshaft  146 , which carries mainshaft clutches  148  and  150 , and the mainshaft splitter clutch  180  is in the form of a generally tubular body  146 A having an externally splined outer surface  146 B and an axially extending through bore  146 C for passage of output shaft  158 . Shift forks  152  and  154  are provided for shifting clutches  148  and  150 , respectively. Mainshaft  146  is independently rotatable relative to input shaft  118  and output shaft  158  and preferably is free for limited radial movements relative thereto. 
     The main section  112  includes two substantially identical main section countershaft assemblies  122  each comprising a main section countershaft  124  carrying countershaft gears  130 ,  132 ,  134 ,  136  and  138  fixed thereto. Gear pairs  130 ,  134 ,  136  and  138  are constantly meshed with input gear  118 , mainshaft gears  140  and  142  and idler  157 , which is meshed with reverse mainshaft gear  144 , respectively. 
     Main section countershaft  124  extends rearwardly into the auxiliary section, where its rearward end  124 A is supported directly or indirectly in rear housing end wall  116 B. 
     The auxiliary section  114  includes two substantially identical auxiliary countershaft assemblies  160 , each including an auxiliary countershaft  162  carrying auxiliary countershaft gears  168 ,  170  and  172  for rotation therewith. Auxiliary countershaft gear pairs  168 ,  170  and  172  are constantly meshed with splitter gear  174 , splitter/range gear  176  and range gear  178 , respectively. Splitter clutch  180  is fixed to mainshaft  146  for selectively clutching either gear  174  or  176  thereto, while synchronized range clutch  182  is fixed to output shaft  158  for selectively clutching either gear  176  or gear  178  thereto. 
     Auxiliary countershafts  162  are generally tubular in shape, defining a through bore  162 A for receipt of the rearward extensions of the main section countershafts  124 . Bearings or bushings  162 B and  162 C are provided to rotatably support auxiliary countershaft  162  on main section countershaft  124 . Bearing  162 D directly or indirectly supports the rear ends of countershafts  124  and  162  in the rear end wall  116 B. 
     The splitter jaw clutch  180  is a two-position, non-synchronized clutch assembly which may be selectively positioned in the rightwardmost or leftwardmost positions for engaging either gear  176  or gear  174 , respectively, to the mainshaft  146 . Splitter jaw clutch  180  is axially positioned by means of a shift fork  184  controlled by a two- or three-position piston actuator, which is responsive to a driver selection switch such as a button or the like on the shift knob, as is known in the prior art. Two-position synchronized range clutch assembly  182  is a two-position clutch which may be selectively positioned in either the rightwardmost or leftwardmost positions thereof for selectively clutching either gear  178  or  176 , respectively, to output shaft  158 . Clutch assembly  182  is positioned by means of a shift fork  188  operated by means of a two-position piston device  189 . 
     As may be seen by reference to FIGS. 2 and 3, by selectively axially positioning both the splitter clutch  180  and the range clutch  182  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  114  is a three-layer auxiliary section of the combined range and splitter type providing four selectable speeds or drive ratios between the input (mainshaft  146 ) and output (output shaft  158 ) thereof. The main section  112  provides a reverse and three potentially selectable forward speeds. However, one of the selectable main section forward gear ratios, the low-speed gear ratios associated with mainshaft gear  142 , is not utilized in the high range. Thus, transmission  110  is properly designated as a “(2+1)×(2×2)” type transmission providing nine or ten selectable forward speeds, depending upon the desirability and practicality of splitting the low gear ratio. 
     The shift pattern for shifting transmission  110  is schematically illustrated in FIG.  3 . Divisions in the vertical direction at each gear lever position signify splitter shifts, while movement in the horizontal direction from the ¾ and ⅚ leg of the H pattern to the ⅞ and {fraction (9/10)} leg of the H pattern signifies a shift from the low range to the high range of the transmission. As discussed above, splitter shifting is accomplished responsive to a vehicle operator-actuated splitter button or the like, usually a button located at the shift lever knob, while operation of the range clutch shifting assembly is an automatic response to movement of the gear shift lever between the central and rightwardmost legs of the shift pattern (i.e., between the low range and high range portions, respectively), as illustrated in FIG. 3, and as will be described in greater detail below. Automatic range shift devices of this general type for manual shift transmissions are known in the prior art and may be seen by reference to U.S. Pat. Nos. 3,429,202; 4,275,612; 4,455,883 and 5,000,060. 
     Referring again to FIG. 3, and assuming 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 TH  power where N TH  equals the number of main section ratio steps occurring in both ranges (ie., N=2 in the (2+1)×(2×2) transmission  110 ). Given the desired ideal ratios, gearing to approximate these ratios is selected. In the above example, the splitter steps are about 33.3%, while the range step is about 316%, which is generally suitable for a “2+1” main transmission section having about 78% steps, as the square root of 1.78 equals about 1.33 and 1.78 raised to the second power (ie., N=2) equals about 3.16. 
     Transmissions similar to transmission  110  may be seen in greater detail by reference to aforementioned U.S. Pat. Nos. 4,754,665; 5,368,145 and 5,390,561. 
     Although the present invention is illustrated in the embodiment of a compound transmission not having an intermediate wall, the present invention is equally applicable to transmissions of the type illustrated in U.S. Pat. Nos. 4,754,665; 5,193,410 and 5,368,145. 
     As mentioned above, in the prior art, especially for manually shifted, range-type transmissions with an automatic range shifting mechanism, the synchronized range section clutch occasionally would complete range shifts selected in error or due to inattention, even if such shifts were undesirable under current vehicle speed conditions. By way of example, if during an intended 8th-to-9th speed shift at relatively high vehicle speeds, the shift lever is incorrectly moved to the ¾-⅚ leg, or worse yet, to the R L /R H −½ leg, and then moved downwardly into the engaged position, the shift, if completed, will be harsh with potential undue wear and/or damage to the synchronizer, the clutch teeth, the transmission and/or the vehicle. Similarly, if a range upshift is completed at an excessively low vehicle speed, the engine may be stalled and/or the shift undesirably harsh. Such inappropriate range shifting may become more likely if biasing means are not utilized to inhibit movement of the shift lever between legs of the shift pattern. 
     The range clutch  182  is moved by a shift fork  188  attached to an actuator piston  200  of the piston device  189 . The actuator assembly  202  includes the piston device  189  and a valve device  203  operated by command output signals which may be electrical, fluidic and/or mechanical. The valve device  203  controls a selectively pressurized and exhausted chamber  204  to achieve the two positions (H, L) of the shift fork. Alternatively, as seen in aforementioned U.S. Pat. No. 5,000,060, an additional valve.(not shown) responsive to command signals may be provided to selectively pressurize and exhaust the lefthand chamber of the actuator piston/cylinder assembly. 
     FIG. 5 illustrates a vehicular powertrain  206  utilizing the present invention. Powertrain  206  includes an internal combustion engine  208 , a master clutch  210  and manually shifted, range-type transmission  110 . A shift lever  212  operates a shift mechanism  214 , such as a single shift shaft mechanism of the type illustrated in U.S. Pat. No. 4,920,815, the disclosure of which is incorporated herein by reference. 
     The shift lever  214  includes a knob  216  carrying a splitter master valve and selector  218  by which splitter high (H) or splitter low (L) may be selected. 
     A microprocessor-based controller  222  receives input signals  224  and processes same according to predetermined logic rules to issue command output signals  226  to various system actuators, including the range clutch actuator  202 . The microprocessor  222  may be of the type illustrated in U.S. Pat. No. 4,595,986, the disclosure of which is incorporated herein by reference. 
     The engine  208  may include an electronic controller  209  communicating over an electronic data link DL utilizing the SAE J-1922, SAE J-1939 and/or ISO 11898 protocol. Sensors also may be provided to provide input signals indicative of input shaft (IS) and/or output shaft (OS) rotational speeds and/or of the position of the shift lever (GL). Output shaft speed is indicative of vehicle ground speed. 
     As may be seen by reference to FIG. 6, the controller  222  is provided with logic rules under which an automatic range upshift requires that the shift lever be moved into the range-high portion of the shift pattern (⅞-{fraction (9/10)} leg) and that vehicle speed be greater than a reference value (OS&gt;REF 2 ), while an automatic range downshift requires that the shift lever be moved into the range-low portion of the shift pattern (R L /R H −½ or ¾-⅚ leg) and vehicle speed be less than a reference value (OS&lt;REF,). The logic also may require that main section neutral exists prior to commanding a range shift. By way of example, for heavy-duty diesel engines and transmissions of the type illustrated, no automatic range upshift would be permitted below about 5-15 MPH, while no automatic range downshift would be permitted above about 25-35 MPH. 
     Although the present invention has been described with a certain degree of particularity, it is understood that the description of the preferred embodiment is by way of example only and that numerous changes to form and detail are possible without departingr from the spirit and scope of the invention as hereafter claimed.