Tilting apparatus with a cylinder piston assembly

Abstract: A tilting apparatus of an outboard engine has a propulsion unit (6) that is affixed to the boat (1) by a clamp bracket (3), allowing tilting the unit (6) up and down by extending and retracting a cylinder rod (11,25) of a cylinder piston assembly (8,24). The cylinder-piston assembly (8,24) comprises a piston (14,29) attached to a piston rod (11,25) slidably accommodated in a cylinder (10,26), having a first chamber (12,27) and a second chamber (13,28,53) being divided by the piston (14,29), whereby at least one valve chamber (15,30) is formed inside the piston (14,29), said at least one valve chamber (15,30) connecting the first chamber (12,27) and the second chamber (13,28) through connecting passages (14a,29a,29c) and housing a flow control means (16,31) for opening and closing fluid communication through the piston (14,29). By incorporating a shock-absorbing valve structure, it is possible to design cylinders which are particularly suitable in tilting apparatus of small, lightweight outboard engines.

Description: The present invention relates to a tilting apparatus in particular for an outboard engine according to the preamble of claim 1. In a conventional marine propulsion unit as e.g. shown in Figs. 1 to 3 and 11, a propulsion unit 6 of an outboard engine is attached to the stern plate 2 of a boat 1 by a clamp bracket 3 and a swivel bracket 4 which are joined by a horizontal shaft 5 to allow the propulsion unit 6 to be tilted up and down, and further this swivel bracket 4 supports the propulsion unit around a steering shaft (not shown) disposed approximately perpendicularly to the horizontal shaft 5 to allow turning the propulsion unit 6 left and right. This propulsion unit 6 incorporates an internal combustion engine 36 which rotates a propeller 7 by a drive shaft 35a, a gear apparatus 35b, and a propeller shaft 35c. The bottom of a tilt cylinder 8 is connected to a shaft 3a of the foregoing clamp bracket 3 while the top of a tilt rod 8a of the tilt cylinder is connected to a shaft 4a of the swivel bracket 4. The extension and-retraction of the tilt rod 8a of the tilt cylinder 8 controls the tilting of the propulsion unit 6. Further, lower shafts (not shown) of a pair of trimming cylinders 9 disposed on each side ofthe tilt cylinder 8 are connected to the foregoing clamp bracket 3, and the trim control of the propulsion device 6 is accomplished by extending and retracting trim rods 9a of the trimming cylinders 9. Among the foregoing cylinders 8 and 9, the purpose of the tilt cylinder 8 in particular is to allow tilting up the propulsion unit 6 to avoid damage to the propeller 7 before landing the boat or when obstacles in the water are realized while cruising. However, when, as shown in Figure 11, the propulsion unit 6 accidentally comes into contact with an obstacle 20, such as a piece of floating wood, the propeller, etc. may be damaged. In other words, the struck obstacle 20 exerts an upwardly rotating reaction force P on the propulsion unit, and jointly the rod and the piston in the tilt cylinder 8 is trying to move upward. The piston cannot move upward due to the oil pressure inside the tilt cylinder 8 and the propulsion unit 6 is unable to tilt up. In mid-sized or larger outboard engines the propulsion unit 6 must be able to be quickly tilted upward for collisions with floating wood would greatly damage the propulsion unit 6. Therefore, it has been proposed (e.g. in US-A-4,786,263) as it is shown in Figs. 1 and 2 to design the tilt cylinder 8 to allow automatically quickly tilting up the propulsion unit 6 to avoid damage to the propeller 7 when obstacles in the water are struck while cruising. The basic structure of the foregoing tilt cylinder 8 is such that the bottom end 10b of each cylinder unit 10 is connected to the clamp bracket 3, while each rod 11 is connected at its top end 11a to the swivel bracket 4. The bottom 11b of each rod 11 is connected to piston 14, which is free to move up and down inside the cylinder unit 10, and which divides each cylinder into an upper chamber 12 and a lower chamber 13. Reference 10a denotes a plug formed on the top end area of the cylinder unit 10. By controlling the oil pressure resp. exerted and reduced through an inlet/outlet hole 12a located at the side of the upper chamber 12 and an inlet/outlet hole 13 located at the side of the lower chamber 13 of the cylinder unit 10, the resulting up/down motion of the piston causes the extension and retraction of the rod 11 to tilt the outboard engine 6 up or down. A plurality of valve chambers 15 (six in this embodiment) are formed in the bottom of the piston 14 to connect to the upper chamber 12 and to the lower chamber 13 in the cylinder 10, these valve chambers being apart at equidistant angles (45° in this embodiment) along the circumference of a concentric circle so as to lie approximately half-way between the outside circumference of the rod 11 and the piston 14. A ball valve 16 is inserted into the top of each respective valve chamber 15, and a valve spring 17 below each ball valve 16 biases each upward against a valve seat. The openings 14a are formed in the bottom surface of the piston 14 to allow inserting the ball valves 16 and the valve springs 17 into the respective valve chambers 15; these openings 14a are covered by a washer 19 and a bolt 18 that passes through the piston 14 and threads into the bottom of the rod 11. The valve chambers 15 of the piston 14 in the foregoing tilt cylinder 8 hold ball valves 16 and valve springs 17 that comprise a shock-absorbing valve structure. This shock-absorbing valve structure prevents damaging the propeller 7, etc., when landing the boat or when the propulsion unit 6 accidentally strikes an obstacle 20 in the water while cruising. Accordingly, in case of an impact the rod 11 of the tilt cylinder 8 is pulled to extend in the Q direction, the oil pressure in the upper chamber 12 is increased due to the rod 11 and the piston 14 trying to move upward, and this increased oil pressure then overcomes the resistance of the valve springs 17 for the ball valves 16, causing the ball valves to be dislodged from their valve seats, thereby allowing the upper chamber 12 to transmit pressurized oil into the lower oil chamber 11. Thus, in conjunction with the up-tilting reaction force P that acts upon the propulsion unit 6, the rod 11 is drawn out in the direction Q and both the rod 11 and the piston 14 move upward to tilt the propulsion unit 6 upward as well. In mid-sized or larger outboard engines, since the propulsion unit 6 must be able to be quickly tilted upward, it was necessary for the foregoing tilt cylinder 8 to be large in diameter to accommodate the above described shock-absorbing valve structure formed in a large-diameter piston as a means to compensate for collisions with floating wood. However, since there is less shock when a piece of floating wood strikes a small outboard engine, the tilt cylinder must be of smaller diameter because the larger-diameter tilt cylinders used for mid-sized and larger outboard engines cannot be adapted as-is to such small outboard engines. On the other hand, for reasons of strength, the diameter of the rod 11 of the tilt cylinder 8 cannot be too small. Therefore, it is an objective of the invention to provide a tilting apparatus where the overall structure of which is more compact and being suitable for small size outboard engines. For a tilting apparatus as indicated above, this objective is solved in an inventive manner by the features of the characterizing portion of claim 1. Preferably by forming a single valve chamber on the inside of the piston that is approximately coaxial with the rod, by connecting this valve chamber at its top and bottom through respective passages to the upper chamber and lower chamber, and by assembling a valve, valve spring, etc. into this valve chamber, it is possible to meet the requirements for a compact design of tilt cylinders used on small outboard engines that incorporates a relatively small piston, but a relative broad, coaxial shock-absorbing valve structure. As a result, such small diameter cylinders are optimal for use on small outboard engines. Further, by forming the upper connecting passage and the lower connecting passage in the piston, machining costs can be reduced because no special machining operations are necessary to form the upper connecting passage in the rod. Further, by forming an insertion hole in the valve chamber for the valve and valve spring, and by closing this opening with a plug bolt, it is possible to easily install the valve and valve spring into the valve chamber while the plug bolt is removed. Further advantageous embodiments are laid down in the subclaims. The invention will be described hereinafter in greater detail by means of an example of embodiment, making reference to the accompanying figures, wherein: Figure 1 is a sectional view of a known tilt cylinder of a conventional tilting apparatus, Figure 2 is a sectional view taken along line A-A of Figure 1, Figure 3 is a front view of such a conventional outboard engine, Figure 4 is a sectional view of an embodiment of a tilt cylinder, Figure 5 is an enlarged sectional view of a shock-absorbing valve structure for tilt cylinders according to Figure 4, Figure 6 is an embodiment showing a modification of the structure of Figure 5, Figure 7 is a sectional side view of the important parts of the outboard engine, Figure 8 is a front view of the outboard engine, Figure 9 is a schematic view of the oil circuit operating the tilt cylinder-piston assembly, Figure 10 is a schematic view of an embodiment with an oil circuit operating a two-piston tilt cylinder, and Figure 11 is a side view of an outboard engine with a conventional tilting apparatus. Parts that are identical to or perform the same function as in the conventional apparatus described above bear the same reference numbers and further explanation of them will be omitted. According to an embodiment (as shown in Figs. 4 and 5), an internal combustion engine (not shown) operates the propulsion unit 6 by rotating the propeller 7 by a drive shaft 21. The tilt control for the propulsion unit consists of a cylinder 24 that is pivotally attached to the upper horizontal shaft 22 and the lower horizontal shaft 23 and between the foregoing clamp bracket 3 and swivel bracket 4 wherein the tilting is performed by extending and retracting the tilt rod 25 from the tilt cylinder 24. In the embodiment shown in Figures 7 and 8, there are no trimming cylinders 9 such as were employed in the structure of Figs. 3, 11, but for small-size outboard engines for small boats, there is little need for such trim control. However, it is of course possible to incorporate trimming cylinders 9 if desired. It would be further possible to use the foregoing tilt cylinder to control the boat's trim as well. Mounted onto the foregoing clamp bracket 3 are a motor 36 for the hydraulics, and an oil pump 37 driven by the motor 36, an oil reservoir 38, and a switchable valve that allows the output from the hydraulic pump 37 to apply hydraulic pressure to the upper chamber 27 or the lower chamber 28 of the foregoing tilt cylinder 24. As shown in Figure 4, the foregoing tilt cylinder 24 is linked at its bottom 26a by the lower horizontal shaft 23 to the clamp bracket 3, and it is linked at its top 25a to the upper horizontal shaft 33 to the swivel bracket 4 by the tilt rod 24 which is connected at its bottom 25b by threads. Accordingly, the piston slidably inserted into the foregoing cylinder unit 26 is free to move up and down and it divides the inside of the cylinder unit 26 into an upper chamber 27 and lower chamber 28. Reference 26b denotes a plug bolt that closes the top end of the cylinder unit 26. By controlling the application/relieving of the hydraulic pressure from the inlet/outlet opening 27a of the upper chamber 27 and the inlet/outlet opening 28a of the lower chamber, the extension or retraction of the tilt rod 25 in conjunction with the up/down motion of the piston 29 causes the outboard engine unit 6 to be tilted up and down. As shown in detail in Figure 5 for the foregoing tilt cylinder 24, a valve chamber 30 has been formed in the piston and is approximately coaxial with the foregoing tilt rod 25, and this valve chamber 30 is connected at its top to the upper chamber 27 by a "T"-shaped upper connecting passage 25c formed in the foregoing tilt rod 25. The bottom of the valve chamber 30 connects to the bottom chamber through a diagonal, downward sloping lower connecting passage 29a. The top of the foregoing valve chamber 30 contains a ball valve 32 held by a retainer 31a, while the bottom of the valve chamber 30 contains a valve spring 32 which presses the ball valve 31 by its retainer 31a against the upper valve seat 30a. A female threaded opening 29b is formed in the bottom surface of the foregoing piston 29 to facilitate inserting the ball valve 31, the retainer 31a and the valve spring 32 into the foregoing valve chamber 30, and this female threaded hole 29b is closed by a plug bolt 33. The valve chamber 30, ball valve 31, retainer 31a and the valve spring 32 of the piston 29 compose the shock absorbing structure for the foregoing tilt cylinder 24. As an alternative structure of this embodiment, as shown in Figure 6, it is further possible to use an upward sloping connecting passage 29c formed in the piston that connects to the upper chamber 27 instead of employing the "T"-shaped upper connecting passage 25c in the foregoing tilt cylinder 25. With the foregoing structure, should the propulsion unit 6 accidentally strike an obstacle 20 while cruising, an upwardly rotating reaction force P would be applied to the propulsion unit 6. In conjunction, as shown in Figure 4 the tilt rod 25 of the tilt cylinder 24 is pulled in the Q direction and the piston 29 and the tilt rod 25 try to move upward, increasing the hydraulic pressure inside the upper chamber. This increased hydraulic pressure overcomes the resistance of the valve spring 32 and displaces the ball valve 31 downward and off its valve seat 30a to allow pressurized oil to be expelled from the upper chamber 12, through the upper connecting passage 25c of the valve chamber, through the lower connecting passage 29a, and into the lower chamber 28, thereby causing the hydraulic pressure to be relieved from the upper chamber 27 into the lower chamber 28. Accordingly, when an upward tilting reaction force P acts upon the propulsion unit 6, the piston 29 and the tilt rod are pulled upward in the Q direction to allow the propulsion unit 6 to rotate upward as well. This makes it possible to prevent damage to the propeller 7 when landing the boat or when accidentally striking an obstacle 20 with the propulsion unit 7. In the above structure, a single valve chamber 30 is formed approximately coaxially with the tilt rod 25 in the piston 29, and the top and bottom of this valve chamber are connected with upper chamber 27 and lower chamber 28 through the upper and lower connecting passage 25c (or 29c) and 29a. The ball valve 31 and valve spring 21 inside this valve chamber 30 comprise a shock-absorbing valve structure, which can be incorporated compactly, using a relatively small diameter cylinder 25 and a piston 29 in small outboard engines without encountering space problems. Further, by closing the female threaded opening 29b in the bottom surface of the foregoing piston by a plug bolt 33, when the plug bolt 33 is removed, the ball valve 31 and the valve spring 32 can be easily assembled into the valve chamber 30. Figure 9 further shows a structural set-up of an oil circuit, as it is used for operating and controlling the inventive cylinder-piston assembly as part of the inventive tilting apparatus. While in Figure 9 the reference sign 24 denotes the tilt cylinder of a first or a second embodiment of the invention, the numerals 41, 42 stand for an Up-Thermal protection valve and a Down-Thermal protection valve, leading any surplus oil pressure due to thermal expansion into the reservoir 38. Within the piston 14, 29 a flow control valve 31 or a plurality of flow control valves 16 is integrated for allowing oil to flow from the upper chamber 27 to the lower chamber 28. An oil pressure pump 44 , which is preferably constructed as a gear pump, creates alternatively an up-pressure or a down pressure by transporting oil from oil from the upper chamber 27 of the cylinder 24 through said inlet/outlet opening 27a along an upper oil pipeline 47 and a lower pipeline 48 through the lower inlet/outlet opening 28a into the lower chamber 28 or vice versa. With this oil circuit a spring biased manual valve 40 is incorporated parallel to the oil pressure pump 44, When said manual valve is activated, e.g. by pressing a valve operating button (not shown), the upper and the lower inlet/outlet openings are connected to each other directly, so that the position of the piston 29 relative to the cylinder wall 26 of the tilt cylinder 24 can be altered by manually pushing/pulling the piston rod 25, respectively, by moving the propulsion unit 6 combined to the rod 25. On each side of the oil pressure pump 44, there is an oil relief valve 45, 46 incorporated in the oil circuit for controlling the oil pressure. Additionally, a two-line main valve 43 shiftable between a normal operating state and an exceptional operating state is included in each of the upper and lower oil pipelines 47, 48. If set in normal operating state, the tilt cylinder 24 is controllable by the oil pressure pump; if set in exceptional operating state, the tilt cylinder 24 is controllable by using manual force in combination with the operation of the manual valve 40, so the propulsion unit 6 can be trimmed or tilted up/down without the engine running or the oil pressure pump functioning, e.g. when the motor 37 is defect or no electric power is available. For preventing the manual valve 40 from being operated incidentally, the main valve is included within the oil circuit, offering a way to connect both pipelines 47 and 48. A further embodiment of the inventive tilting apparatus especially for an outboard engine propulsion unit is shown in Figure 10. Similar to Figure 9, Figure 10 shows a structural set-up of an oil circuit being part of the tilting apparatus. Identical parts or those performing the same function in both embodiments of Figures 9 and 10 hold the same reference numerals and will not be further explained. In Figure 10, a two-piston tilt cylinder 50 comprises a cylinder 24 and piston rod 25 which is fixed to a main piston 51. This main piston 51 divides the cylinder 24 into an upper chamber 27 and a lower chamber 28 which is further subdivided into a bottom chamber 53 next to the cylinder bottom 26a and a center chamber 54 by a free piston 52. Incorporated into the main piston 51, there is a flow control valve 31 or a plurality of flow control valves 16 as described above. Additionally and parallel thereto, but with opposite flowing direction, at least one one-way check valve 55 is incorporated within said main piston. During normal operating state when the cylinder 50 is operated by the oil pressure pump 44, when the propulsion unit 6 is hit by a floating object 20, it can tilt up because of the flow control valve 31, allowing oil to flow from the upper chamber 27 to the center chamber 54, while the free piston is not moved. Because of the one-way check valve 55, it is possible to set the main piston 51 and such the propulsion unit 6 back to its original position by manual force, without changing a preset trim position of altitude defined by the location of the free piston 52. Preferably the flow diameter of the at least one-way check valve 55 is approximately 1/5 of the flow diameter of the at least one flow control valve 31, so even for small engines a compact structure is guaranteed.

Claims: Tilting apparatus in particular for an outboard engine comprising a cylinder-piston assembly (24) with a piston (29) attached to a piston rod (25) slidably accommodated in a cylinder (26), having a first chamber (27) and a second chamber (28,53) being divided by the piston (29), wherein at least one valve chamber (30) is formed inside the piston (29), said valve chamber (30) connecting the first chamber (27) and the second chamber (28) through connecting passages (25c,29a,29c) and housing a flow control means (31) for opening and closing fluid communication through the piston (19), wherein an opening (29b) is formed in the surface of the piston (29) at the side opposite to the piston rod (25) to allow inserting one valve (31,31a) and one valve spring (32) in the valve chamber (30), characterized in that the valve chamber (30) is arranged on the central axis (A) of the piston (29), and in that said opening (29b) is closed by a plug bolt (33). Tilting apparatus according to claim 1, characterized in that the connecting passage (29c) leading from the valve chamber (30) to the first chamber (27) on the piston rod side is formed in the piston (29) exclusively, and in that said connecting passage (29c) is inclined with respect to the central axis (A) of the piston (29). Tilting apparatus according to one of claims 1 or 2, characterized in that the connecting passage (29c) leading from the valve chamber (30) to the first chamber (27) on the piston rod side is formed through the piston (29), in particular in that said connecting passage (29c) is formed as an upward sloping passage. Tilting apparatus according to one of claims 1 or 2, characterized in that the connecting passage leading from the valve chamber (30) to the first chamber (27) on the piston rod side is formed through the piston (29) and the piston rod (25), in particular in that said connecting passage (29c) extends axially through the piston (29) and is continued by an axial passage in the piston rod (25), from where it leads to the first chamber (27) via a cross bore (25c) provided on the piston rod (25). Tilting apparatus according to one of claims 1 to 4, characterized in that the connecting passage (29a) leading from the valve chamber (30) to the second cylinder chamber (28) opposite to the piston rod (25) is inclined with respect to the axis (A) of the piston (29). Tilting apparatus according to one of claims 1 to 5, characterized in that the diameter of the valve chamber (30) is at least 75% of the diameter of the piston rod (25) and at least 75% of the radial distance between the piston rod (25) and the inner wall of the cylinder (26). Tilting apparatus according to one of claims 1 to 6, characterized in that the tilting apparatus further comprises an oil circuit, which is connected to the first chamber (27) and to the second chamber (28) via inlet/outlet holes (27a,28a) in the wall of the cylinder (26), and which further comprises an oil pressure pump (44), a main valve (43), a number of thermal protection valves (41,42), a number of oil pressure relief valves (45,46), and a manual valve (40). Tilting apparatus according to claim 7, characterized in that said oil pressure pump (44) is a two-way gear pump, allowing to move oil from said first chamber (27) to said second chamber (28) and vice versa when said main valve (43) is set to a first position. Tilting apparatus according to one of claims 7 or 8, characterized in that said manual valve (40) is a spring biased two-way valve, combining directly said first chamber (27) and said second chamber (28) if activated and when said main valve is set to a second position. Tilting apparatus according to one of claims 1 to 9, characterized in that said second chamber (28) of said cylinder (26) is divided by a second piston (52) being freely slidable within said cylinder (26) in an area between the bottom (26a) of the cylinder (26) and the said first piston (51) in two chambers, a bottom chamber (53) being situated between the bottom (26a) of the cylinder (26) and the second piston (52) and a center chamber (54) being located between the first piston (51) and the second piston (52). Tilting apparatus according to claim 10, characterized in that said first piston (51) further comprises at least one one-way check valve (55) combining said first chamber (27) with said center chamber (54) parallel to said at least one flow control valve (31) but allowing oil flow in opposite direction from said center chamber (54) to said first chamber (27). Tilting apparatus according to claim 11, characterized in that said bottom chamber (53) is connected with said oil circuit via said inlet/outlet hole (28a), and in that said first and said second piston (52) are movable together at the same time by the oil pressure of the oil pressure pump (44) in a normal operation state keeping the center chamber (54) at a minimum size, and in that the first piston (51) is movable individually from the second piston (52) when a pulling force is applied to the piston rod (25), increasing the size of the center chamber while the second piston (52) holds its position relative to the cylinder (26). Tilting apparatus according to one of claims 11 or 12, characterized in that the flow diameter of said one-way check valve (55) is approximately 1/5 of the flow diameter of said at least one flow control valve (31).

Inventors: NAKAMURA DAISUKE, NAKAMURA, DAISUKE, Nakamura, Daisuke, c/o Sanshin Kougho K.K.
Applicants: SANSHIN KOGYO KK, SANSHIN KOGYO K.K.
Application year: 1999
Main classification: B63H20
IPC codes: F02B61, F15B15, F16J1, B63H20