Fig. 3 Allowable Energy Dissipation
The engine type determines engine stall limit torque. If the transmission is shifted from forward acceleration to backward acceleration under the condition of no-slip control, engine stall may occur because torque Qo for acceleration of a hull generally exceeds the engine stall limit torque.
Qo is proportional to the hydraulic pressure and friction coefficient of the clutch as shown in formula (5).
Qo =P0・μ0・A (5)
P0: Clutch hydraulic pressure (MPa)
μ0: Static friction coefficient of friction plate
A: Constant for each clutch
Therefore, during crash astern, the transmitted torque must not exceed the engine stall torque, and is to be set to the hydraulic pressure below the seizure limit of the friction plate.
3. TEST RESULT
3.1 Test instruments and method
Fig.4 shows a picture of a ship used in the test that is equipped with instruments for optimum control described in this thesis. Fig.5 shows a controller system, and Fig.6 shows the hydraulic route of the marine transmission.
The test was conducted in Miyazu Bay in Kyoto prefecture, in which DGPS was used for the evaluation of ship responsiveness, such as boat speed.
Fig. 4 Boat of Trial
Fig. 5 Transmission Control System
Fig. 6 The hydraulic system
3.2 Test results in the actual ship
(1) Improvement in acceleration using automatic shifting with two reduction gear ratios
In this test, an actual transmission system was used (Reduction gear ratio of Low gear: 3.08, Reduction gear ratio of High gear: 2.46), providing shift revolutions with approximate 80% of the engine rated revolutions from the study result. Fig.7 shows changes in boat speed when automatic shift is performed by quickly accelerating from fine forward acceleration during the actual sailing.
Fig. 7 Boat Speed Properties
