CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 61/081,868, filed July 18, 2008, entitled "PROTECTION SYSTEM", the contents of which are incorporated herein in their entirety.

BACKGROUND

[0002] Compound transmissions of the range or combined range/splitter type are known. Such transmissions typically comprise a multiple speed main transmission section connected in series with a range type auxiliary section wherein the range step is greater than the total ratio coverage of the main transmission section.

[0003] In such transmissions, the main section is typically shifted by means of a shift housing assembly controlled by a manually operated shift lever or the like. In contrast, the auxiliary range section is shifted by means of a button or switch. It is known that a switch operated by the main section shift mechanism controls a remote slave valve/actuator mechanism. The valve/actuator mechanism controls operation of a range selection actuator. The range selection actuator includes a fluid-actuated piston that divides an actuator cylinder into two chambers. The piston is made to move in response to selective pressurization of one chamber while simultaneously exhausting a second chamber. Since the auxiliary range section often utilizes synchronized jaw clutches, a range shift is typically initiated and completed while the main transmission section is shifted to, or at least towards, a neutral condition to address shift quality and to minimize undue transmission performance degradation including undue wear to the synchronized jaw clutches.

[0004] Known compound range type transmissions usually include a control system such as a pneumatic control system having at least one interlock device, which allows a range shift to be preselected using a selector button or switch at a master control valve, but prevents shift initiation until the main transmission section is at least approaching the neutral condition. One approach for preventing shift initiation utilizes mechanical type interlock devices on the range section actuator mechanical linkage that physically prevent movement of the range section shift fork until the main section is shifted into neutral. A second approach for preventing shift initiation utilizes logic-based interlock devices of the type wherein the valve supplying pressurized fluid to the range section cylinder is either disabled or not provided with pressurized fluid until a shift to main section neutral is sensed, or is only activated and provided with pressurized fluid while the main section is shifted to and remains in neutral. Examples of such transmissions and related control systems may be seen by reference to U.S. Pat. Nos. 2,654,268; 3,138,965, 4,060,005 and 4,974,474, the disclosures of which are hereby incorporated by reference in their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 is a schematic illustration of an exemplary compound transmission having a range type auxiliary section and utilizing a pneumatic control system.

[0006] FIG. 2 is a schematic illustration of an exemplary shifting mechanism that may be used with the transmission of FIG. 1.

[0007] FIG. 3 is a schematic illustration of an exemplary shift pattern for use with the transmission of FIG. 1.

[0008] FIG. 4 is a perspective view of a shift housing assembly of the transmission of FIG. 1.

[0009] FIG. 5 is a block schematic diagram of the exemplary pneumatic control system for the transmission of FIG. 1 with the auxiliary section in high range.

[0010] FIG. 6 is a block schematic diagram of a protection system that may be used with the transmission of FIG. 1.

[0011] FIG. 7 is a schematic illustration, in flow chart format, of the protection system of FIG. 6. [0012] FIGS. 8A - B are schematic illustrations, in flow chart format, of the logic that may be used by an exemplary control module for controlling the diagnostic tools and the protection system of FIG. 6.

[0013] FIG. 9 is a schematic illustration, in flow chart format, of the logic that may be used by an exemplary control module for controlling auxiliary range shifts and a bypass system for the transmission of FIG. 1.

DETAILED DESCRIPTION

[0014] Referring to FIG. 1 and FIG. 2, an exemplary range type compound transmission 10 is illustrated. Compound transmission 10 comprises a multiple speed main transmission section 12 connected in series with a range type auxiliary section 14. Transmission 10 is housed within a 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.

[0015] In main section 12, the input shaft 16 carries an input gear 24 for simultaneously driving a pair of countershaft assemblies 26 at substantially the same rotational speeds. The two countershaft assemblies 26, which may be substantially identical, are illustrated on diametrically opposite sides of a mainshaft 28 which is generally coaxially aligned with the input shaft 16. Each of the countershaft assemblies 26 comprises a countershaft 30 supported by bearings 32 and 34 in the housing H. Each of the countershaft assemblies 26 is provided with a grouping of countershaft gears 38, 40, 42, 44, 46 and 48, fixed for rotation therewith. A plurality of mainshaft gears 50, 52, 54, 56 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. 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. [0016] As best shown in FIG. 2, clutch collars 60, 62 and 64 may be axially positioned by means of shift forks 6OA, 62A and 64A, respectively, associated with the shift housing assembly 70 and controlled by a shift lever 72. In one illustrative approach clutch collars 60, 62 and 64 may be synchronized or nonsynchronized double acting jaw clutch type mechanisms.

[0017] Returning to FIG. 1, mainshaft gear 58 is the reverse gear and is shown in continuous meshing engagement with countershaft gears 48 by means of conventional intermediate idler gears (not shown). While main section 12 does provide five selectable forward speed ratios, the lowest forward speed ratio, namely that provided by drivingly connecting mainshaft drive gear 56 to mainshaft 28, is often of such a high gear reduction it has to be considered a low or "creeper" gear which is utilized only for starting of a vehicle under severe conditions and, is not usually utilized in the high transmission range. Accordingly, while main section 12 does provide five forward speeds, in the exemplary illustration it is usually referred to as a "four plus one" main section.

[0018] Auxiliary transmission range section 14 includes two substantially identical auxiliary countershaft assemblies 74 each comprising an auxiliary countershaft 76 supported by bearings 78 and 80 in housing H and carrying three auxiliary section countershaft gears 82, 84 and 85 for rotation therewith. Auxiliary countershaft gears 82 are constantly meshed with and support a range input/main section output gear 86 that is fixed to mainshaft 28. Auxiliary section countershaft gears 84 and 85 are constantly meshed with auxiliary section output gears 88 and 89 respectively that surround transmission output shaft 90.

[0019] A two-position synchronized jaw clutch assembly 92, which is axially positioned using a shift fork 92A and a range section shifting actuator assembly 93, is provided for clutching either gear 86 to mainshaft 28 for deep range operation or gear 88 to mainshaft 28 for low range operation of the compound transmission 10. Synchronized jaw clutch assembly 94, which is axially positioned using a shift fork 94A, is provided for clutching gear 89 to mainshaft 28 for high range operation of the compound transmission 10.

[0020] The five forward speeds provided by main section 12 in the exemplary illustration are compounded by the deep range of the auxiliary section 14. Then, the four forward speeds not including the lowest forward speed are compounded by the low range of the auxiliary section 14. Finally, the four forward speeds are then used without being compounded by the auxiliary section 14 while the auxiliary section 14 is in the high range.

[0021] Clutch collars 60, 62 and 64 are three-position clutches in that they may be positioned in a centered, nonengaged position as illustrated, or in a fully rightwardly engaged or fully leftwardly engaged position by means of shift lever 72 as shown in FIG. 2. As is known, only one of the clutch collars 60, 62 and 64 is engageable at a given time and main section interlock mechanisms (not shown) may be provided to lock the other clutches in the neutral condition.

[0022] In one illustrated approach shown in FIG. 2, selection of low or high range operation of the transmission 10 is by means of an operator actuated low/high range switch or button 98, and selection of deep range operation of the transmission 10 is by means of an operator actuated deep range switch or button 99. Alternatively, a three-way range switch can be used in place of low/high range switch 98 and deep range switch 99 to enable selection between the deep, low and high range operations of the transmission 10. Low/high range switch 98 and deep range switch 99, or alternatively a three-way range switch, are typically located at the shift lever 72, and are connected to a control module 100, which will be described in more detail below.

[0023] The shift pattern for compound range type transmission 10 is schematically illustrated in FIG. 3. The reverse gear, R, is available in any of the ranges of auxiliary section 14. As noted above, main transmission section 12 provides five forward speeds that are compounded by auxiliary transmission section 14. The lowest forward speed, Lo, is available only when auxiliary section 14 is in the deep range. Thus, the vehicle operator has access to four forward speeds for each of the ranges of the auxiliary section 14, with one forward speed for each range accessible at each of the shift lever 72 forward speed positions, resulting in twelve available forward speeds. In the deep range, the available forward speeds are 1 ^st through 4 ^th ; in the low range, the available forward speeds are 5 ^th through 8 ^th ; and in the high range, the available forward speeds are 9 ^th through 12 ^th . By way of example, when shift lever 72 is in the center, forward position, the vehicle can be operated in the 1 ^st , 5 ^th or 9 ^th speeds, depending on the engaged range of the auxiliary section 14. The vehicle would operate in 1 ^st speed if the deep range were engaged, 5 ^th speed if the low range were engaged, or 9 ^l speed if the high range were engaged.

[0024] As best seen in FIG. 4, shift forks 6OA, 62A, and 64A are integrated into a shift housing assembly 70, which is disposed within and connected to housing H. The shift forks 60A, 62A, and 64A extend from the shift housing assembly 70 and are controlled by shift lever 72.

[0025] As also shown in FIG. 4, the main section 12 may be controlled by axial movement of three shift rails 120, 122 and 124 contained within the shift housing assembly 70, which in turn are operated using the shift lever 72 as shown in FIGS. 2 and 4. Alternative mechanisms to the three rail shift arrangement may be employed, with such mechanism having more shift rails, or just a single shift rail such as the one shown in U.S. Pat. No. 4,621,537, which is incorporated herein in its entirety.

[0026] Returning to FIG. 1, transmission 10 may also include an output shaft speed sensor 91 for sensing the output shaft 90 rotational speed. Output shaft speed sensor 91 is connected to control module 100 which receives a signal from output shaft speed sensor 91 and processes the signal according to predetermined logic rules.

[0027] Control module 100 monitors parameters of transmission 10, including the output shaft 90 rotational speed and the range state of auxiliary section 14. Control module 100 includes the logic for controlling the overall operation of auxiliary section 14.

[0028] FIG. 5 illustrates a pneumatic control system 200, which controls shifting between the deep, low and high ranges of the auxiliary section 14. The auxiliary section 14 of FIG. 5 is shown in the high range. Control module 100 is connected to, and selectively controls, pneumatic control system 200. Pneumatic control system 200 includes a master control valve 202, which is typically located in proximity to shift lever 72. When a range shift is initiated, master control valve 202 receives a signal indicative of the desired range shift. Pneumatic control system 200 also includes a range valve 210 and a deep range valve 220, which are in fluid communication with master control valve 202. Range valve 210 and deep range valve 220 are used with master control valve 202 to enable a desired range shift. Range valve 210 includes a range solenoid 212 and deep range valve 220 includes a deep range solenoid 222. Range solenoid 212 and deep range solenoid 222 are in communication with, and controlled by, control module 100.

[0029] Master control valve 202 operates range valve 210 and deep range valve 220 by sending pneumatic signals 230, 232 to the range valve 210 and the deep range valve 220 upon initiation of a range shift. Range valve 210 is connected to a range piston cylinder 214, and deep range valve 220 is connected to a deep range piston cylinder 224. The range piston cylinders 214 and 224 each include a right or high range side 215, 225 and a left or low range side 216, 226 separated by a range piston 217, 227 which is sealingly and slideably received within the cylinders 214, 224.

[0030] Pneumatic control system 200 also includes an air regulator 234 in communication with master control valve 202 and an exhaust valve 236 in communication with air regulator 234. When the pneumatic signals 230, 232 are pressurized from the master control valve 202, range valve 210 and deep range valve 220 are both in a first valve state. Air regulator 234 provides pressurized air at a predetermined pressure to exhaust valve 236, which selectively provides the pressurized air to range valve 210 and deep range valve 220. When a pneumatic signal 230, 232 is pressurized, the left or low range side 216, 226 of cylinders 214, 224 is pressurized and the right or high range side 215, 225 of cylinders 214, 224 is exhausted. When a pneumatic signal 230, 232 is at or sufficiently close to zero pressure, range valve 210 and deep range valve 220 are both in a second valve state, during which the right or high range side 215, 225 of cylinders 214, 224 is pressurized, and the left or low range side 216, 226 is exhausted. The pressurization of the left or low range sides 216, 226 and/or the right or high range sides 215, 225 causes range pistons 217, 227 to move either to the left or to the right of cylinders 214, 224. As range pistons 217, 227 move, actuator shafts 218, 228 also move, causing a corresponding range shift. When both pneumatic signals 230, 232 are pressurized, the pistons 217, 227 both move to the right of cylinders 214, 224, and the deep range is selected. The low range is selected when the deep range valve pneumatic signal 232 is exhausted, causing piston 227 to move to the left of cylinder 224, and the range valve pneumatic signal 230 is pressurized, causing piston 217 to move to the right of cylinder 214. When both pneumatic signals 230, 232 are exhausted, the pistons 217, 227 both move to the left of cylinders 214, 224, and the high range is selected.

[0031] There is a fourth range cylinder position that results in the deep range being repeated when the deep range valve pneumatic signal 232 is pressurized, and the range valve pneumatic signal 230 is exhausted. Operation in the indicated state results in loading between the range mainshaft and interfacing components, which may result in undesirable transmission performance degradation. The control module 100 monitors low/high range switch 98 and deep range switch 99 to ensure that the transmission does not operate in this condition. If the potentially debilitating condition is detected, however, the control module 100 will automatically shift the auxiliary transmission to the high range to minimize potential long-term transmission performance degradation.

[0032] Due to the characteristics of the transmission shift cycle, a false indication of this condition can be detected by control module 100. By way of example, a false indication of this condition can occur if the vehicle were started in the high range, and the transmission was subsequently shifted to deep range to start moving the vehicle. Range piston cylinder 214 and deep range piston cylinder 224 may not shift at exactly the same speed, such that the deep range piston cylinder 224 could shift faster than the range piston cylinder 214. During this transition state of auxiliary section 14, control module 100 would detect the fourth range cylinder position and automatically shift auxiliary section 14 into the high range. To prevent this from occurring during the transition state, control module 100 requires this condition to be present for a predetermined amount of time, such as for five (5) of more seconds in one exemplary illustration, and requires the output shaft speed sensor 91 to indicate that the output shaft speed is greater than a predetermined value, to indicate that the vehicle is not stationary. This prevents the potentially debilitating condition from being used, and also allows for the transition state to pass without causing an automatic shift into the high range.

[0033] Potentially debilitating, high-speed downshifts occur when a gear shift is attempted from a gear high in the shift pattern of one range to another gear that is low in the shift pattern in another range. This type of shift can potentially hinder long-term transmission performance. Control module 100, output shaft speed sensor 91, range solenoid 212 and deep range solenoid 222 form a protection system 250, illustrated in FIG. 6, to prevent such a high-speed downshift.

[0034] Control module 100 monitors the speed of output shaft 90, the engaged range of auxiliary section 14, and the positions of low/high range switch 98 and the deep range switch 99 to determine the current transmission operating condition. The output shaft speed is measured by output shaft speed sensor 91, and is then compared by control module 100 to a pre-set frequency table of acceptable speed for the deep range and the low range.

[0035] The high speed downshift limit for the deep and low ranges can be calculated using the maximum ratio of the intended range and the clutch burst speed, hi an exemplary illustration with 4750 revolutions per minute (rpm) as the maximum clutch speed allowed to prevent burst (e.g., a 5000 rpm burst minimum), the set point for inhibiting a shift to deep range is calculated based on ensuring that the worst case 5 ^th speed to 1 ^st speed downshift will not result in over speed. Using a sample first gear ratio of 12.051, the set point for the deep range can be calculated by dividing the maximum clutch burst by the first gear ratio, or 4750/12.051, which equals 394 rpm. To account for hysteresis, a range of values above and below the set point are determined. In this exemplary illustration, deep range values of 420 rpm and 388 rpm may be used. Accordingly, if the output shaft speed is greater than 420 rpm, the maximum acceptable speed for allowing a shift to the deep range is 388 rpm. Once the output shaft speed has dropped below 388 rpm, downshifts to the deep range will be allowed until the output shaft speed reaches 420 rpm. A similar calculation is performed to determine the set point for the low range, which is approximately 1000 rpm. In this exemplary illustration, low range values of 1033 rpm and 984 rpm may be used to account for hysteresis. This is just one exemplary method by which the acceptable speeds can be determined, as the acceptable speeds can be determined in a variety of manners and according to both hardware and environmental considerations, such as differences in engine models.

[0036] If the output shaft speed exceeds the acceptable speed for a particular range downshift, the control module 100 sends a signal to range solenoid 212 and deep range solenoid 222. Range solenoid 212 and deep range solenoid 222 selectively block the range valve 210 and/or deep range valve 220 from changing state during initiation of a range shift upon receipt of the signal from control module 100. In normal operation, range solenoid 212 and deep range solenoid 222 are in the "on" state, which allows the pressurized pneumatic signals 230, 232 from master control valve 202 to pass through the solenoids 212, 222 to change the state of range valve 210 and/or deep range valve 220. When the output shaft speed exceeds the acceptable speed for a particular range downshift, control module 100 sends a signal to range solenoid 212 and deep range solenoid 222, changing the solenoid states to the "off state. When the solenoids 212, 222 are in the "off state, the solenoids 212, 222 block the pressurized pneumatic signals 230, 232 from passing through the solenoids 212, 222 to change the state of the range valve 210 and deep range valve 220. Thus, range solenoid 212 and deep range solenoid 222 selectively eliminate changes in the state of the range valve 210 and deep range valve 220 during initiation of a range shift upon receipt of the signal from control module 100. When the output shaft speed falls below the acceptable speed for a range downshift, the control module 100 will change the solenoid states back to the "on" state, allowing the completion of the range downshift. In this manner, protection system 250 prevents a high-speed downshift when the output shaft speed exceeds an acceptable speed.

[0037] By way of example, if a downshift was attempted from the 11 ^th gear to the 8 ^th gear as shown in the shift pattern of Fig. 3, and the output shaft speed exceeded the acceptable speed for a shift into the low range, the control module 100 would prevent a change in the range state, keeping the auxiliary section 14 in the high range. As auxiliary section 14 is preventing from changing the range state, the attempted downshift would actually result in a shift from the 11 ^th gear to the 12 ^th gear, as the 12 ^th gear is the high range gear that occupies the same shift position as the 8 ^th gear in the shift pattern of FIG. 3. The vehicle operator could then shift back to the 11 ^th gear if so desired, and wait until the output shaft speed falls below the acceptable speed to permit a shift to the low range before properly attempting a shift to the 8 ^th gear.

[0038] With reference to FIG. 7, an illustration of operation of the protection system 250 is as follows. The operation of protection system 250 starts at step 300, where the control module 100 detects an operator desire to downshift from a gear in one auxiliary section range to a gear in a lower auxiliary section range. When the downshift request is detected, the operation moves to Step 310, where the control module 100 detects a value representative of the output shaft 90 rotational speed, and compares this value to an acceptable speed for range the operator desires to shift into. If the value representative of the output shaft 90 rotational speed is less than the acceptable speed for the particular range, control module 100 allows the operator initiated downshift, Step 315.

[0039] If the value representative of the output shaft 90 rotational speed is greater than the acceptable speed for the particular range, the operation proceeds to Step 320, where the control module 100 send a signal to range solenoid 212 and deep range solenoid 222, changing the solenoids 212, 222 from a first state, the "on" state, to a second state, the "off state. The state change of the solenoids 212, 222 prevents the range valve 210 and deep range valve 220 from changing state, thus preventing the range shift.

[0040] In step 330, the control module again detects a value representative of the output shaft 90 rotational speed, and compares this value to the acceptable speed for the desired range shift. If the value representative of the output shaft 90 rotational speed is greater than the acceptable speed, this step will repeat until the value is less than the acceptable speed.

[0041] Once the value is less than the acceptable speed, the operation proceeds to step 340, where control module 100 sends a signal to range solenoid 212 and deep range solenoid 222, changing the solenoids back to the first state. After solenoids 212, 222 have changed back to the first state, control module 100 allows the operator initiated downshift, Step 315.

[0042] Control module 100 is an example of an electronic control unit or other device generally capable of executing instructions stored on a computer-readable medium, such as instructions for performing one or more of the processes discussed herein. Control module 100 may be electronically and microprocessor-controlled and for providing output information to an electronic data link DL, preferably conforming to the industry standard SAE Jl 939 or a comparable protocol. A data link, conforming to the SAE J 1939 protocol or a comparable protocol, transmits information by which information associated with the prime mover and related components.

[0043] Control module 100 may be a single controller or one of a series of interconnected controllers. Although not shown, control module 100 may be of general construction having a central processing unit (CPU), various co-processors, a read only memory (ROM), a random access memory (RAM), an input for selectively receiving data via a data link from various vehicle components including the prime movers and related components, an output for selectively transmitting command output signals, and a bi-directional bus interconnecting the components.

[0044] Computer-executable instructions may be compiled or interpreted from computer programs created using a variety of known programming languages and/or technologies, including, without limitation, and either alone or in combination, Java, C, C++, Visual Basic, Java Script, Perl, etc. In general, a processor (e.g., a microprocessor) receives instructions, e.g., from a memory, a computer-readable medium, etc., and executes these instructions, thereby performing one or more processes, including one or more of the processes described herein. Such instructions and other data may be stored and transmitted using a variety of known computer-readable media.

[0045] A computer-readable medium (also referred to as a processor-readable medium) includes any tangible medium that participates in providing data (e.g., instructions) that may be read by a computer (e.g., by a processor of a computer, a microcontroller, etc.). Such a medium may take many forms, including, but not limited to, non-volatile media and volatile medial. Non-volatile media may include, for example, optical or magnetic disks, read-only memory (ROM), and other persistent memory. Volatile media may include, for example, dynamic random access memory (DRAM), which typically constitutes a main memory. Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other tangible medium with patterns of holes, a RAM, a PROM, an EPROM, a FLASH-EEPROM, any other memory chip or cartridge, or any other medium from which a computer can read.

[0046] A transmission media may facilitate the processing of instructions by carrying instructions from one component or device to another. For example, a transmission media may facilitate electronic communication. Transmission media may include, for example, coaxial cables, copper wire and fiber optics, including the wires that comprise a system bus coupled to a processor of a computer. Transmission media may include or convey acoustic waves, light waves, and electromagnetic emissions, such as those generated during radio frequency (RF) and infrared (IR) data communications.

[0047] As shown in FIG. 6, control module 100 may also include diagnostic tools 102 to detect the occurrence of an electrical failure of various transmission components, including output shaft speed sensor 91, range solenoid 212, deep range solenoid 222, low/high range switch 98, deep range switch 99, or the vehicle power supply. The failure of one or more of these components is known as component failure. When control module 100 detects a failure of one of the above components, the control module 100 will alert the vehicle operator of the failure, for example by activating a service light.

[0048] Further, control module 100 will prevent the transmission from shifting unexpectedly during an occurrence of component failure and will default the auxiliary section 14 to the high range. Defaulting the auxiliary section 14 to the high range prevents any high-speed downshifts from occurring during the component failure. However, the vehicle operator may desire to put the transmission in deep range after a component failure occurs, the transmission is in the default high range position, and the vehicle is stopped. Control module 100 can detect that the vehicle is stopped in a number of manners, including detecting the activation of a vehicle parking brake or detecting an output shaft spped of zero or close to zero. Pneumatic control system 200 may include a bypass system 240, which includes a bypass valve 241, a bypass selector switch 242, bypass pilot 243, which includes a range valve bypass pilot 244 and a deep range bypass pilot 245, double check range valve 246, and double check deep range valve 248, FIG. 5. The vehicle operator can use bypass system 240 to bypass the default high range position to utilize a transmission ratio more suited to maneuver the vehicle to a location of choice upon component failure. Bypass pilot 243 is in communication with both the range valve 210 and the deep range valve 220 via range valve bypass pilot 244 and deep range bypass pilot 245. Pressurizing range valve bypass pilot 244 and deep range bypass pilot 245 will actuate range valve 210 and deep range valve 220, resulting in the engagement of the deep range of the auxiliary section 14. Thus, even after a component failure and the default engagement of the high range by control module 100, the default high range can be bypassed, and the deep range engaged. [0049] Control module 100 is equipped to operate using the vehicle power supply, the battery, as its main power supply. However, if the battery fails, and the vehicle ignition is still on, control module 100 will continue to operate using the ignition power (e.g., as provided by the alternator), to prevent inoperability. Thus, even in the event of a failure of the battery, control module 100 will still be able to prevent high-speed downshifts from occurring and prevent the transmission from shifting unexpectedly during an occurrence of component failure.

[0050] The system also protects the transmission 10 by preventing a range shift from occurring while the main section 12 is in gear. Certain situations may arise when the vehicle operator requests a range shift, but completes a shift of the main section 12 before the auxiliary section 14 completes the range shift. When shift rails 120, 122, 124, Fig. 4, are moved to engage a main section 12 gear, the shift rails 120, 122, 124 actuate an exhaust valve, which in turn exhausts pneumatic control system 200 and prevents air pressure from reaching range piston cylinder 214 and deep range piston cylinder 224. Accordingly, a range shift cannot be executed when the main section 12 is in gear. The pneumatic control system 200 is only pressurized when main section 12 is in neutral. To complete the range shift, the shift lever 72 must be moved to the neutral position, which allows the air pressure to be restored to the range piston cylinder 214 and deep range piston cylinder 224. Then, the main section 12 shift is completed by shift lever 72.

[0051] Control module 100 may also include logic to allow control module 100 to be used with a variety of engine models. An example engine used with control module 100 has a governed engine speed of approximately 2200 rpm. Some engines are considered to be "high rev", where the governed engine speed can approach or exceed 2600 rpm. The "high rev" engine can create a contradiction between the operating limits of the transmission and the required operating speed of the transmission. The operating limits of the transmission are determined from the master clutch burst speed, while the required operating speed of the transmission is determined by the governed engine speed. When the mater clutch burst speed is reduced, and the governed engine speed is increased, it is possible to reach a point at which a range upshift will automatically be performed before the vehicle reaches the governed engine speed in the highest gear of the selected range. By way of example, in this scenario it would be possible to exceed the acceptable speed for the deep range while auxiliary section 14 is still in the deep range. Normally, control module 100 would recognize this and turn solenoids 212, 222 off, resulting in an unexpected range upshift. To prevent this, control module 100 constantly monitors the range state of auxiliary section 14 to allow the vehicle to remain in the lower range after exceeding this point. However, once a range upshift is completed, control module 100 would prevent a range downshift until the output shaft 90 rotational speed falls below the acceptable speed for the downshift.

[0052] FIGS. 8 A - 9 are exemplary schematic illustrations, in flow chart format, of the logic contained in control module 100 for controlling various aspects of the auxiliary section 14. FIGS. 8 A - B illustrate the diagnostic tools logic 400 and the high-speed downshift protection system logic 500, and FIG. 9 illustrates the bypass system logic 600 and the auxiliary section range shift logic 700.

[0053] Although the illustrated approach shown above includes an auxiliary section having deep, low and high ranges, control module 100 can be used with an auxiliary transmission section having only two ranges, such as the low and high ranges. As such an auxiliary section only includes two ranges, the pneumatic control system includes a range switch and one range valve to select between the two ranges, and the control system includes a single solenoid connected to the range valve. In all other aspects, the control module and pneumatic control system used with such an auxiliary section operate in a manner similar to that described in the above illustrated approach and as illustrated in FIGS. 5-7.

[0054] Although the steps of the method of operating the system are listed in an indicated order, the steps may be performed in differing orders or combined such that one operation may perform multiple steps. Furthermore, a step or steps may be initiated before another step or steps are completed, or a step or steps may be initiated and completed after initiation and before completion of (during the performance of) other steps.

[0055] The preceding description has been presented only to illustrate and describe exemplary embodiments of the methods and systems of the present invention. It is not intended to be exhaustive or to limit the invention to any precise form disclosed. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. The invention may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope. The scope of the invention is defined solely by the following claims.