Browse Topic: Transmission valves
Transmission tuning involves adjusting parameters within a vehicle's transmission control unit (TCU) or transmission control module (TCM) to optimize performance, efficiency, and driving experience. Transmission tuning is beneficial for optimizing performance, improving fuel efficiency, smoother shifting and enhancing drivability particularly when a vehicle's power output is increased or for specific driving conditions. Especially in offroad and agricultural machines, transmission tuning is vital to significantly improve vehicle performance during different operations. The process of transmission tuning is quite time consuming as multiple tuning iterations are required on the actual vehicle. A significant reduction in tuning time can be achieved using a simulation environment, which can mimic the actual vehicle dynamics and the real time vehicle behavior. In this paper, tuning during the forward and reverse motion of the tractor is described. A two-level PI control-based shift strategy is designed and implemented. In the two-level PI control, the first level calculates the transmission valve pressure setpoint based on the tractor acceleration error. In addition, the second level identifies the valve current based on the valve pressure error. The dynamics model of the tractor powertrain, which is called the plant model, was developed and a closed loop environment is established with the Simulink model. The tuning of the PI gains and the testing are performed in the plant model environment. The optimum PI gains are identified after multiple test iterations in the mentioned environment. The software then tested on the actual tractor with the optimum values and verified the shuttle shift performance. The results show that quick and comfortable shuttle shifts are achieved during the process of moving from the forward to reverse directions and vice versa.
Interference assessments of a stepped-radius power-train component moving within a deformed stepped bore often arise during engine and transmission development activities. For example, when loads are applied to an engine block, the block distorts. This distortion may cause a cam or crankshaft to bind or wear prematurely in its journals as the part rotates within them. Within an automatic transmission valve body, care must be taken to ensure valve body distortion under oil pressure, assembly, and thermal load does not cause spool valves to stick as they translate within the valve body. In both examples, the mechanical scenario to be assessed involves a uniform or stepped radius cylindrical part maintaining a designated clearance through a correspondingly shaped but distorted bore. These distortions can occur in cross-sections (“out-of-round”) or along the bore (in an “s” or “banana” shaped distortions). To assess clearance in a deformed (stepped or uniform) bore, a new optimization based technique is proposed. This paper defines an optimization process that determines an axis assessed as producing the largest clearance between the stepped surface and points defining the bore surfaces. This clearance is calculated for clouds of points representing undeformed and deformed cylindrical bores. From this clearance, shrinkage (or expansion) of a stepped-bore or single-radius bore is estimated. These clearance data are useful in understanding when a part may stick or bind as a result of projected stepped-bore distortion.
To address an aging agricultural workforce and modern ergonomic guidelines, researchers at Doshisha University and Kubota modeled medium- and large-sized agricultural tractors to reduce vibration and noise and increase comfort. New emphasis is being placed on agricultural vehicles for improved safety, comfort, and functionality. The monocoque-type frame of today's tractors consists of the engine, power transmission case, and differential case in modular assemblies. Main vibration sources are the engine, drive system, and exhaust system. Vibrations travel into the cabin through the frame and are amplified when transmissions from excitation sources coincide with the natural frequency of the frame. To decrease vibration and noise of the tractor, it is necessary to improve the dynamic characteristics of the frame. From measuring tractor part vibration characteristics and cabin noise characteristics, researchers at Doshisha University and Kubota Corp. determined that the bending mode of the frame influences the vibration characteristics of the tractor. Knowing that, the full frame was separated into sub-structures of cases and joint parts, and each was modeled. Model tuning with sensitivity analysis improved accuracy, and a dynamic model for the frame was constructed. Comparing the analytical result with experimental data confirmed the dynamic model. Finally, the design change of the frame was carried out with the object of increasing stiffness while reducing weight.
A new method of testing Automatic Transmission Main Control Assemblies has been developed which provides increased reliability in transmission valve body testing. This method employs an electro-hydraulic test stand sequenced by an IBM 1710 computer system. The computer controls the test cycle, accurately compares test values against test specification parameters, records all test values, and determines whether the transmission Main Control meets all specifications.
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