BACKGROUND OF THE INVENTION
The invention relates to the design of selectively operable friction clutches in a marine transmission to provide forward and reverse drives to the propeller shaft of a vessel.
U.S. Pat. No. 2,851,895 Aschauer describes a marine gear drive that has been extensively used. It is intended that the gearing and clutch locations shown on U.S. Pat. No. 2,851,895 be utilized for this invention. These gear and shaft locations are shown on end view FIG. 3. Clutches are mounted on the input shaft and countershaft in transverse coplanar relationship are shown on FIGS. 1 and 2 of U.S. Pat. No. 2,851,895.
It is to be noted the clutches utilized in the aforementioned patent are engaged by applying oil pressure to rotating annular pistons housed in their respective cylinders. The engaging system requires numerous components, as a pump, pressure regulating valve, control valve, and seals to transfer oil from the stationary components into the rotating clutches, as shown in FIG. 4 of U.S. Pat. No. 2,851,895. Erratic clutch behavior may result between a control signal and clutch actuation resulting from time and pressure losses between the control valve and clutch cylinders. It is desirable to have a clutch move into engagement quickly and have a torque rise programmed to provide a near constant level of energy absorption instead of potentially damaging peaks.
The pump flow required for optimum clutch engagement and cooling at lower engaging engine speeds rises at full engine speed since the pump is engine driven and results in power loss.
It is planned that the inventions engaging motor provide torque using minimal external power input.
BRIEF SUMMARY OF THE INVENTION
The invention relates to both the engaging and releasing means for a wet multiple plate clutch in a marine gear, using a relatively stationary ball ramp thrust actuator to provide clutch engagement pressure thru a thrust bearing to the rotating plate stack. One element of the ball ramp actuator has numerous gear teeth on its outer diameter meshing with teeth on a smaller pinion driven by an attached motor. The motor provides continuous high level torque for full engine power or lower level varying torque for modulation as in trolling for a vessel. A microprocessor may program engaging conditions. Two springs establish clutch plate release, actuator release, and motor release conditions when the motor is de-energized. An electric motor can be programmed to provide varying or constant torque input to the ball ramp actuator avoiding the hydraulic complexities as discussed earlier.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal section of a marine gear clutch shaft or its clutch countershaft. The only difference between the two is a splined input engine drive shown above and the enclosed countershaft portion shown below the centerline.
FIG. 2 is an enlarged view of the pinion drive used to rotate the geared element of the ball ramp into engagement, and of a torsion spring to provide release.
FIG. 3 is a multiple finger spring used for clutch disengagement as well as ball ramp disengagement positioning.
FIG. 4 shows a typical arcuate recess applied to a ball ramp circular member.
FIG. 5 is a transverse section of the friction plate cooling method to provide uniform plate cooling distribution from the pump blade delivery means.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1 input shaft 10 is appropriately attached to a driving member such as the flywheel of a vessels power plant. (not shown) The shaft is journaled by bearing 13 carried by housing wall 11 at the input and journaled by bearing 14 carried by end plate cover wall 15 detachable from housing 12. Input hub 17 is attached to input shaft 10 by close fitting splines 16 in the conventional manner. Interleaved friction plates 19 and spacer plates 18 make up a friction plate stack package. Input hubs gear teeth 20 support and drive friction plates 19 providing sliding engagement. Spacer plates 18 have lugs 22 that engage with cantilever beams 21 that support and drive the spacer plates 18 and provide sliding engagement. Cantilever beams 21 are integrally attached to output member backplate 23. Pressure plate 24 has lugs 22 that are thicker lengthwise than the lugs on spacer plates 18 and also engage with cantilever beams 21 in like manner. Backplate 23 is integrally attached to drive pinion 25 and supported on shaft 10 by bearing 26. Pressure plate 24 is likewise supported on shaft 10 by bearing 27. A confined annular chamber is bounded by the plate stack inner diameter at its outside, hub 17 at the inside, backplate 23 on the resisting side and pressure plate 24 on the engaging side. Clutch clamping thrust is carried axially by pinion 25 thru plain thrust bearing 28 to transfer gear 29 which is attached to shaft 10 by close fitting splines 30. Clutch clamping thrust from transfer gear 29 is transferred thru anti friction thrust bearing 31 to housing wall 11. Anti friction thrust bearing 32 which may be similar to thrust bearing 31 transfers clutch clamping thrust from the relatively stationary ball ramp engaging system to the rotating clutch elements. Ball and ramp thrust systems are widely used and known to the art. They usually include a pair of circular members having opposed pairs of arcuate recesses receiving load transferring members such as balls, providing thrust when one circular member is rotated with respect to the other.
The invention utilizes a motor producing torque at static output speed after actuating a movable ball ramp rotor a portion of a revolution. Use of an electric motor 34 powered from an external source is shown on FIG. 1. Motor 34 engages and drives shaft 35 in FIG. 2, thru splines on shaft 35. Pinion 38 is rigidly attached to shaft 35. Sleeve 37 acting as a bearing to support shaft and pinion assembly 35 and 38 is pressed rigidly into housing 15. Rotatable ball ramp element 33 has gear teeth 53 meshing with like teeth on pinion 38 to provide a large reduction ratio between the pinion diameter and ball ramp gear pitch diameters. Pinion 38 therefore has large angular rotation compared to that of ramp 33 during engagement. FIG. 4 shows a typical arcuate ball ramp recess 39. Longer recesses allow lower ramp angle and provide greater thrust but require greater ramp rotation readily available thru the electric motor gear reduction means used in the invention.
Two disengaging spring systems are important for clutch release. FIG. 2 shows torsion coil spring 40 used to return pinion 38 and ramp element 33 to their disengaged positions. Each end coil of spring 40 has an axially extending tang positioned to engage a hole in pinion 38 at one end and a hole in housing 15 at the other end, together acting to establish a released position for the gear train made up of pinion 38 and gear and rotatable ramp element 33 when motor 34 is de-energized. FIG. 3 shows finger spring 41 attached to pressure plate 24 by screws 42. The finger tips bear against cantilever beam 21 ends to establish proper clutch plate released clearance. Spring 41 also sets up an overall axial force to maintain proper residual contact for the thrust bearings and ball ramp components when the clutch is disengaged. Stationary ball ramp 43 has threads 44 on its outside diameter to adjust out the numerous axial part tolerances and establish the residual force desired.
Since clutch actuation is controlled by an external power source, clutch cooling and bearing lubrication is visualized as using an external electric motor cooling oil pump drive system. Only low pressure and flow is required since the clutches are not engaged by hydraulic means.
The oil flow required for the invention is used for clutch plate cooling and bearing lubrication only.
Oil is introduced into shaft 10 thru port 45 in housing end cover wall 15. FIG. 5 shows an end view of hub member 17 having external teeth 20, driving friction plates 19. Oil introduced thru inlet 45 flows axially thru shaft longitudinal hole 46 and radially outward thru passages 47 to fill a series of individual cavities, each bounded by drive wall 48, cylindrical top wall 49 and retaining wall 50. During clutch rotation cooling oil flows into the individual cavities 51 inwardly filling them. Added oil then flows under the bottoms of spaced radial walls 50 discharging outwardly thru radial slot passages 52 cut completely thru walls 50. Pump passage 52 delivers pressure and oil flow uniformly across the complete friction pack inner diameter.
During continuous clutch slip utilizing hydroviscous power transmission, the complete confined annular chamber may be filled with oil pressure raised to drive the required oil flow thru the entire stack friction plate face grooving. Operating a released clutch with the oil filled confined annular chamber would provide objectional drag where an air/oil mix does not.
Patent Application
20070199792
