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Email required Address never made public. Name required. Follow Following. Out of The Box. Still others in this category offer a synchronized shuttle shift or reverser. The shuttle shift gives you a second hand lever to easily switch from forward to reverse without coming to a full stop. Other subtle variations of these combinations exist, but in general you operate the clutch to make the shift, and the clutch is often a dry design, meaning it is not bathed in oil and can wear more quickly.
An upgrade to the relatively simple gear transmission is the power shuttle transmission. This gear transmission features a forward-reverse shuttle lever that, when moved from one position, through neutral to the other, will automatically clutch the tractor, make the shift and reengage the clutch, based on tractor speed and rpm.
To the novice, this may seem absurd, but power shuttle is wonderful if you do a lot of forward and reverse shifting, such as with a loader. The clutches in these machines are usually bathed in oil and hydraulically actuated for smooth control and long life.
The hydrostatic transmission, which, also, is usually coupled to a gear-type range transmission, relies on high-pressure hydraulic oil to spin the rear output shaft and, subsequently, the wheels. Although not part of the illustrated routine of FIG. When the gearshift lever is shifted from reverse to forward, the microprocessor detects, at step FIG.
At step , PG is tested to see if it has been cleard. If it has, a table is addressed at step to read out the forward gear value FG and at step the microprocessor uses this value of FG to energize the transmission clutches. On the other hand, if the test at step shows that the PG register has not been cleared, then FG is set equal to PG. From the foregoing description it is seen that the routine illustrated in FIGS.
The selection of reverse gear is made according to Table I. Shuttle shifting of the transmission 10 from forward to reverse gear, or from reverse to forward gear results in an energy load on the transmission oil, and loading of the vehicle engine with a consequent increase in fuel consumption.
The energy load placed on the clutches increases at a rate proportional to the square of the vehicle speed so that when the vehicle speed reaches about 4 MPH the clutches in the transmission are overloaded by shuttle shifting. Thus, larger and more expensive clutches become necessary for shuttle shifting even at moderate vehicle speeds. However, several methods have been developed for controlling transmission 10 to prevent clutch overloading and, for a given clutch sizing, permit shuttle shifting at moderate or high vehicle speeds without overloading the clutches.
Assume that the vehicle has been in some forward gear and the operator moves the gearshift lever 6 FIG. At step , the microprocessor senses that the gearshift lever is in the R position the program proceeds to step where the microprocessor applies signals to the clutches in the initial and intermediate clutch sets 70 and 75 FIG.
At step a modulating signal is applied to the low speed clutch 82 or the reverse clutch 83 in the final clutch set The output shaft 20 is rotating, being driven at this time because of forward vehicle movement. Application of the modulating signal to the clutch in the final clutch set causes the output shaft 20 to begin driving the transmission and this load begins slowing the output shaft The modulating signal is a pulse width modulated current signal that is applied to the solenoid which controls the valve that in turn controls the pressure applied to the torque transmitting element of the clutch.
At step , the speed of the output shaft 20 is sensed by sensor 5 FIG. If the speed is greater than the threshold value, the microprocessor decreases the modulating signal at step and waits for a short interval of time at step before looping back to again execute steps and The decreased modulating signal causes a higher hydraulic pressure to be applied to the torque transmitting element of clutch When the speed of shaft 20 has been reduced so that the sensed speed is less than the threshold value, this condition is detected at step and the program moves to step where the microprocessor 1 applies signals to the clutch sets 70, 75 and 80 to select the desired reverse gear speed.
When shifting takes place from reverse to forward gear, the microprocessor 1 executes a sequence of steps like steps with the exception that the forward gear clutches are set to select the desired forward gear at step The method just described permits shuttle shifting of transmissions at low and moderate speeds even without torque converters.
However, this method is not satisfactory for use when shuttle shifting at higher speeds been. An incremental increase in efficiency in such operation can be gained in the following manner. It has been found that, with proper clutch control, clutch energy loads can be reduced thus allowing shuttle shifting to take place at higher speeds while resulting in lower oil temperatures and lower clutch energy loads.
Furthermore, by sharing the energy load between two or more clutches, shifting may be accomplished at even higher speeds. Also, there is a reduced engine load and a greater economy of fuel use. To gain all of these advantages, the transmission 10 illustrated in FIG. At step , all of the clutches 71, 72 and 73 in the initial clutch set 70 are released thereby disconnecting the engine 7 from the transmission. Gearing within the transmission continues to rotate. Next, two or more of the clutches 76, 77 and 78 in the intermediate clutch set 75 are energized at step thereby locking up the transmission and stopping rotation of the internal transmission parts.
After the transmission has been locked up, one of the clutches 81, 82 and 83 in the final clutch set is modulated at step to connect the transmission gearing to the output shaft 20 thereby decelerating the vehicle. The output speed is monitored by the output shaft speed sensor 5 FIG. When the vehicle is nearly stopped, the microprocessor outputs signals to the clutches in the transmission 10 to actuate the appropriate clutches to select a desired new gear speed.
At step the microprocessor senses the speed and if the speed exceeds a threshold value the microprocessor computes a new modulating signal value at step and waits a short interval at step The new modulating signal is then applied to the solenoid of the clutch in set 80 when the program loops back to step As described above with respect to step , the transmission may then shift to the selected gear.
The method illustrated in FIG. It allows shuttle shifting at maximum vehicle speed without free wheeling and without excessive clutch loads. The initiation of shifts is based on vehicle speed hence the method automatically adapts to variations in vehicle deceleration due to surface conditions, grades, drawbar loads and operator use of service brakes.
The microprocessor 1 enters the routine of FIG. Actually, the forward speed of the vehicle is determined by the speed sensor 5 which senses the rate of rotation of the transmission output shaft The shaft carries a tooth gear whose rotation is magnetically sensed by the sensor 5 which produces one output pulse for each tooth sensed on the rotating gear.
Table II shows, for an exemplary embodiment, the correlation between each forward gear and the frequency of the output signal from the speed sensor 5. The routine of FIG. If the sensor output frequency is lower than the threshold value it means that another deceleration strategy should be used.
Thus, from step an exit is made from the routine to one of the routines described above for controlling vehicle deceleration. If the test at step shows that the vehicle speed is high enough to invoke the high speed deceleration routine, the program moves to step At this step, the microprocessor successively accesses its memory which stores the values shown in column 2 of Table II, and compares each accessed value with the frequency of the output signal from sensor 5 until it finds the lowest gear that will not overspeed the engine.
That is, it finds the highest frequency value in the table which is still less than the frequency of the output signal from the sensor 5.
For example, if the output from sensor 5 is a HZ signal, the value is the highest frequency in the table which is still less than This corresponds to gear The microprocessor reads this value from the table and sends it to the display at step At step the value 13 is used to energize the clutches in transmission 10 to select forward gear After the transmission is shifted into gear 13 at step , the program enters a loop comprising steps and At step the frequency of the output signal from sensor 5 is compared with the threshold frequency to see if the speed is such that the downshift strategy is still required.
If it is not, the routine exits to another deceleration routine as described above that is suitable for use at lower speeds. If the test at step shows that the speed is still greater than the threshold value the program executes step At this step the microprocessor tests the vehicle speed as measured by the output from sensor 5 and determines if the transmission can be downshifted one gear. This is done by accessing the table for gear 13 to read out frequency value , and then comparing with the output frequency as measured by sensor 5.
If sensor 5 is still producing an output signal greater than HZ, the program loops back to again execute steps and At some point the vehicle will be decelerated so that the output signal from sensor 5 is less than HZ.
When this is determined at an execution of step , the display is updated at step to display gear 12 and at step clutches are energized to select gear 12 so that the engine 7 again becomes a load on the output shaft Steps and are again repeatedly executed and, if the test at step shows the speed as measured by sensor 5 to be less than the value accessed from the table, steps and are executed to update the display and downshift the transmission one gear.
This continues until a test at step shows that the speed of the vehicle is low enough to employ a low or medium speed deceleration routine as described above. At this point an exit is made from the routine of FIG. As explained above, solenoid operated valves control the hydraulic pressure applied to the clutches and thus the torque transferred by the clutches to move the vehicle.
Variations in the current applied to the solenoids, the valve adjustments, and the pressure required to begin to transfer torque all result in inconsistent operation from one tractor to the next, and variations in the operation of a given tractor over a period of time. According to one aspect of the present invention, a calibration program is stored in microprocessor 1 for calibrating the clutches in the final clutch set 80 of transmission This program may be used on each new tractor after assembly, or as required by service or clutch wear, to determine the magnitude of a current which must be applied to a solenoid so that the clutch controlled by the solenoid produces a torque just sufficient to reduce engine speed.
A value representing this magnitude of current is stored in the microprocessor or memory during the calibration program. Subsequently, when the solenoid is to be energized the value is read from the memory to control the magnitude of the current applied to the solenoid. During this method of calibration, the vehicle brakes should be applied so that the output shaft 20 FIG. This assures uniform loading conditions during the calibration procedure. At step , a current corresponding the value of I S is applied to the solenoid of the clutch being calibrated.
It should be remembered that the hydraulic pressure applied to one of the clutches in transmission 10 varies inversely with respect to the current I S applied to the clutch solenoid. This pressure should be low enough such that the clutch is not applied. At step the routine waits for an interval of time sufficient for the engine speed to stabilize after any loading caused by energization of the clutches.
After this interval of time has elapsed, the calibration routine advances to step where the microprocessor 1 determines the engine speed RPM as sensed by the sensor 9 FIG. This reference value of engine speed is saved and the program advances to step where I S is decremented and applied to the clutch being calibrated to thereby increase the pressure to the clutch. At step , the program again waits for a sufficient interval of time for the engine speed to stabilize after any loading caused by application of the decremented value of I S to the clutch solenoid at step At step the engine speed is again sensed and at step the new engine speed RPM1 is compared with the reference engine speed RPM.
The program branches to step where the microprocessor 1 sends signals to the display 2 to display an error code indicating a high I S error. After the display is energized the calibration routine ends. If the comparison at step shows that RPM1 is not less than RPM then at step I S is again decremented and applied to the solenoid of the clutch being calibrated. The program waits at step for the engine speed to stabilize in case the new value of I S applied to the solenoid resulted in a loading of the engine as a result of torque being transmitted by the clutch.
The engine speed is again sensed at step and compared at step with the value RPM saved at step If RPM is greater than RPM1, it means that the engine has slowed as a result of being loaded, and this in turn indicates that the clutch being calibrated has transmitted torque in response to the signal I S generated the last time step was executed. This value of I S is saved at step Subsequently, each time the clutch is to be energized the microprocessor 1 subtracts the saved value of I S from a fixed current value and the difference current is applied to the clutch as a modulating signal.
If, during execution of the loop comprising steps , the test at step proves true, it means that the clutch cannot be calibrated without servicing.
The microprocessor 1 sends signals to display 2 to display a low current error message on the display at step It will be understood that FIG. The routine must be executed for each clutch to be calibrated so that a calibration value of I S is saved for each clutch.
However, as is conventional in measurement systems, a small offset value may be added to RPM before it is compared with RPM1. Also, steps and show I S being decremented by 1. It should be understood that "1" represents an increment of current necessary to change the pressure applied by the clutch torque transmitting element some fixed increment such as 10 psi. In the calibration method illustrated in FIG.
However, it is possible to calibrate the clutches by not applying the vehicle brakes during the calibration procedure, and sensing when the vehicle begins to move. Vehicle movement may be sensed by sensor 5 FIG. At step I S is set equal to I MAX so that maximum current is applied to the solenoid of the clutch being calibrated resulting in minimum hydraulic pressure being applied to the torque transmitting element of the clutch.
Clutch solenoids are then energized at step so that drive power from the engine may be transmitted to the transmission output shaft This may be any combination of clutch solenoids necessary to select a particular gear, so long as the combination includes the solenoid of the clutch being calibrated.
At step the program waits for any torque transmitted by the clutches to be manifested by movement of the vehicle, or more specifically, rotation of the transmission output shaft At step the microprocessor 1 acts with sensor 5 to sense rotation of the shaft There's usually a column shifter that you use to toggle direction after selecting what gear you want to be in.
I also believe you can shift gears "on the fly" without using the foot clutch. Someone jump in if I'm incorrect on this, I don't have a shuttle shift myself. Kind of getting the good qualities of a gear more hp to ground , along with the good qualities of an HST quick and easy back and forth movement.
What it doesn't give you is the infinitley variable speed of an HST. Jan 31, 5. Jan 31, 6. There are a lot of shuttle shift transmissions that you must use the clutch when ever you are shifting F-R, up or down. I would guess that it is usually a higher end option that gets you a shuttle shift trans that does not require manually engaging the clutch.
Jan 31, 7. I have a MF 3e. It is an industrial TLB 49hp. It has a shuttle shift. No manual clutch at all. Brakes on the left. Two pedals on the right one pedal is forward , the other is reverse.
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