Marine propulsion – Screw propeller – Having transmission
Reexamination Certificate
2002-09-20
2004-07-13
Morano, S. Joseph (Department: 3617)
Marine propulsion
Screw propeller
Having transmission
C192S085060, C192S1030FA
Reexamination Certificate
active
06761600
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a marine gear and a method for preventing a drop in motor speed when engaging a multi-plate clutch of a marine gear.
Marine gear assemblies are known which are arranged between a motor, in particular a diesel motor, and a propeller, which marine gear assemblies comprise hydraulically controllable and selectively activatable multi-plate forward and reverse clutches.
A multi-plate clutch comprises several multi-plate discs of which a first number engages the drive shaft of the motor, while a second number engages the drive shaft or driven shaft of the propeller.
In this arrangement, which comprises several multi-plate discs arranged side by side, alternately one engages the drive shaft of the motor, while the adjacent multi-plate disc engages the driven shaft of the propeller.
In order to engage the multi-plate clutch, the multi-plate discs are pressed against each other by means of specified clutch oil pressure. During such engagement of the multi-plate clutch, the diesel motor operates at partial load until such time as the clutch engagement process is completed, in other words until all multi-plate discs of the multi-plate clutch have been pressed against each other. This can take five seconds or more.
The clutch oil pressure is also referred to as gear change pressure or operating pressure.
Operating pressure build-up takes place according to a so-called pressure build-up curve. The operating pressure is not built up quickly with a steep pressure build-up curve and a possible overswing, but instead, it is built up more slowly so as to be gentle on the diesel motor and the entire drive assembly.
The diesel motor cannot cope with clutch engagement that is too rapid, because the output during partial load operation of the diesel motor is not adequate for this. Rapid engagement of the clutch results in an undesirable drop in motor speed, and in extreme cases, in the motor stalling.
Until now, a pressure build-up curve according to which the clutch oil pressure required for pressing together the multi-plate discs, has been specified theoretically by trial-and-error and in experiments, taking into account existing conditions such as motor output, gyrating mass of the motor, etc.
Once this pressure build-up curve has been determined and set, it is always retained without any changes, irrespective of external factors and parameters.
To disengage the multi-plate clutch, the operating pressure is switched off and the multi-plate discs are relieved by a set spring pressure of a readjusting spring.
It is known to reduce the clutch oil pressure to the extent that a targeted slipping process of the multi-plates is maintained.
With constant motor speed, the propeller speed can be influenced via a slipping multi-plate clutch. This is useful in those cases where at a constant gear transmission the ship's speed is still too high at the lowest motor speed. The propeller speed can then be reduced by slippage of the multi-plates. Such an operating state of the marine gear is referred to as a trolling operation.
For this purpose a pressure-control valve is usually arranged in the pressure-oil line which leads to the multi-plate clutch, with a desired operating pressure being able to be set via said pressure-control valve. If the operating pressure is not at maximum, the multi-plate clutch slips.
From DE 40 19 687 A1, a marine gear is known in which for this purpose a directional control valve is arranged between the pressure-control valve and the multi-plate clutch. In a first operating position of the directional control valve, the operating pressure required for trolling operation is established in the pressure-oil line. By contrast, in a second operating position, the maximum operating pressure required for complete engagement of the multi-plate clutch is established. The directional control valve is hydraulically moved, at a certain minimum control pressure, to the first operating position by the pressure-control valve. Reaching this minimum control pressure depends on the setting of the pressure-control valve. The pressure-control valve is for example a proportional valve which is electrically connected to an electronic control unit. The electronic control unit in turn is connected to a speed sensor with which the present rotational speed of the motor shaft can be detected. A setpoint value or command value can be set at the electronic control unit, with the pressure-reduction valve being operated if said set-point value is exceeded.
With this so-called trolling operation, too, a pressure build-up curve according to which the operating pressure for slipping the multi-plate discs is built up, is theoretically specified by trial and error. Once this pressure build-up curve for trolling operation has been determined and set, it is always retained without any changes. The electronic control unit is only used to monitor the motor speed so that it keeps within a specified range.
SUMMARY
It is the object of the invention to improve a generic marine gear and a method for engaging the multi-plate clutch of a generic marine gear such that a drop in motor speed when engaging the multi-plate clutch is counteracted.
This object is met by a marine gear, and by a method for preventing a drop in motor speed when engaging a multi-plate clutch.
Improvements to, and advantageous embodiments of, the invention are set out in the respective subordinate claims.
The generic marine gear comprises a hydraulic control assembly and an electronic control unit. The hydraulic control assembly comprises variable multi-plate clutches for forward and reverse travel, in which the operating pressure required to engage the multi-plate clutches can be set using control means, depending on selectable parameters. The electronic control unit is used to detect and process at least one operating parameter as well as operating the control means.
According to the invention, the generic marine gear is characterised in that the control means comprises a proportional valve and a pilot-operated pressure-control valve which is located on the pressure-oil line that leads to the multi-plate clutch, for setting the desired operating pressure. The proportional valve can be operated by an electrical control current from the electronic control unit. The pressure control valve can be actuated by a control pressure that is generated by the proportional valve. The electronic control unit is connected to a sensor for detecting the motor speed and/or to a sensor for detecting the load signal of the motor.
The load signal, which is known among those skilled in the art, generally refers to the workload of the motor or the respective power/the respective performance characteristic of the motor.
The invention takes advantage of the fact that manufacturers of marine engines add so-called motor management systems to the respective marine motors, with the load signal being obtained on the basis of said motor management system. The motor management system is used to set the motor speed. If more fuel is added at a higher speed, then the motor also needs more air. All this is organised by the motor management system. The load signal is for example present in the form of a measured variable as a current ranging from 0-200 mA.
A combinatorial arrangement comprising a pilot-operated pressure-control valve and a proportional valve which can be actuated electrically makes it possible to directly transform an electrical control current supplied to the proportional valve by the electronic control unit, into an operating pressure.
In this arrangement, the current operating pressure is proportional to the control pressure present at the control connection of the pressure-control valve.
According to the invention, the control pressure can be set by way of the proportional valve which in turn can be operated by the electronic control unit by way of an electrical control current in direct dependence on the change in motor speed and/or change in the load signal of the motor.
In a marine gear according to the inventi
Daus Jürgen
Lux Hans-Harald
Collard & Roe P.C.
Morano S. Joseph
Olson Larsa
Reintjes GmbH
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