Power tilt device, in particular for lifting and lowering a marine propulsion unit

Abstract: A power tilt device (10), in particular to tilt a marine propulsion unit (5), comprising a cylinder device (12) having a tilt piston (15) provided at one side with a piston rod (18) and dividing said cylinder device (12) into a first chamber (S1) and a second chamber (S2): Said first and second chambers (S1,S2) being supplyable with working fluid from a working fluid pump (11) via twin main valves (13A,13B), one (13A) of which being connected with said first chamber (S1) and said working fluid pump (11), the other (13B) being connected with said second chamber (S2) and said working fluid pump (11), said twin main valves (13A,13B) being operable in cooperation with respective first and second shuttle piston units (23A,23B). Said shuttle piston units comprising shuttle pistons (23A,23B) wherein one of said shuffle pistons (23A,23B) being accommodated in a sealing condition, whereas the other of said shuttle pistons (23A,23B) being adapted to allow the working fluid to flow in both directions between the working chambers of said shuttle piston unit.

Description: This invention relates to a power tilt device, in particular to tilt a marine propulsion unit, according to the preamble part of the independent claim 1. Such a type of power tilt device is interposed between the clamp bracket for securing the marine propulsion unit to the hull and the swivel bracket pivoted for up and down rotary movements about the tilt shaft on the clamp bracket, so that the marine propulsion unit disposed at the stern of a vessel can be tilted. The tilting operations are made to lift the marine propulsion unit above the water surface when the marine vessel is stopped and moored, or when the marine propulsion unit is lowered back into the water. Here, such a conventional power tilt device comprises: a tilt cylinder device for tilting up and down movements while receiving working oil supply from a hydraulic pump respectively into a tilt lower chamber and a tilt upper chamber; and conventional twin main valves, with one valve being provided in a tilt up side oil passage interconnecting the tilt lower chamber of the tilt cylinder device and the hydraulic pump, and the other valve being provided in a tilt down side oil passage interconnecting the tilt upper chamber of the tilt cylinder device and the hydraulic pump, with each of the main valves being opened and closed with a shuttle piston. In this configuration, the paired twin cylinders, with each of which including a sliding shuttle piston, are interconnected through a communication passage, so that both of the shuttle pistons are interlocked through hydraulic pressure supplied to one of the cylinders and that the other main valve is simultaneously pushed open. However, the conventional power tilt device described above has problems as shown in FIGs. 5 and 6. That is to say, in the conventional arrangement, both of the shuttle pistons 123A, 123B for opening and closing the twin main valves 113A, 113B are provided with seal members 127A, 127B. If air (A) is present in the middle of the communication passage 125 in an initial, stationary state shown in FIG. 5(a) when working oil is supplied from a hydraulic pump 111 to the oil chamber Sb of one cylinder 124B in a tilt action state shown in FIG. 5(b), one main valve 113A is opened, working oil is supplied to a tilt cylinder device (not shown). At the same time, working oil is supplied to the other cylinder 124A through a check valve 126 provided in the shuttle piston 123B and a communicating passage 125, and the other shuttle piston 123A is lowered. Then, a projection 123a provided on the shuttle piston 123A pushes open the main valve 113A, and working oil from the tilt cylinder device (not shown) is returned through the main valve 113A to the hydraulic pump 111. Here, the air (A) stagnant in the communication passage 125 is in a compressed state due to hydraulic pressure. When the supply of the working oil from the hydraulic pump 111 is stopped at the end of the tilt action, since the communication passage 125 is tightly sealed with the seal members 127A, 127B provided at the shuttle pistons 123A, 123B, the air (A) compressed in the communication passage 125 cannot be discharged out of the communication passage 125, and expands in the communication passage 125, presses down the shuttle pistons 123A, 123B as shown in FIG. 5(c). As a result, the main valves 113A, 113B remain open, raising a problem of inability of holding a tilted up state for example. A similar problem occurs as shown in FIG. 6 when excessive amount of working oil collects in the communication passage 125 after an extended period of use. The oil pressure in the communication passage 125 increases and presses down the shuttle pistons 123A, 123B. As a result, the main valves 113A, 113B remain open. A tilt cylinder for tilting an outboard engine as indicated above is also shown from US-A-5,444,979, wherein the tilt cylinder is connected to two fluid passages, two on/off valves, and a valve block comprising two shuttle valves with a gear pump. Furthermore, at least one of the shuttle valves comprises an auxiliary passage which serves to open the ball valve body of said shuttle valve, in order to connect the two shuttle valves with each other through a communication passage and to quickly reduce the high working oil pressure in the valve chamber of said shuttle valve. Accordingly, it is an objective of the present invention to provide a power tilt device as indicated above capable of performing stabilized tilt action as required while securing reliable action of the twin type main valves. According to the present invention, this objective is solved by a power tilt device, in particular to tilt a marine propulsion unit, comprising a cylinder device having a tilt piston provided at one side with a piston rod and dividing said cylinder device into a first chamber and a second chamber, said first and second chambers being supplyable with working fluid from a working fluid pump via twin main valves, one of which being connected with said first chamber and said working fluid pump, the other being connected with said second chamber and said working fluid pump, said twin main valves being operable in cooperation with respective first and second shuttle piston units, wherein said first shuttle piston unit comprises a first shuttle piston and said second shuttle piston unit comprises a second shuttle piston, said first shuttle piston being accommodated in a sealing condition, and wherein said second shuttle piston is adapted to allow the working fluid to flow in both directions between working chambers of said second shuttle piston unit. According to the preferred embodiment, said first shuttle piston being provided with the sealing member. However, it is still possible that the second shuttle piston is provided with said sealing member. In order to ensure bypass of a working fluid, it is advantageous when said other shuttle piston being dimensioned such that a gap being provided between the outer surface of said shuttle piston and the inner surface of an associated cylinder accommodating said other shuttle piston. For an improved control of the system, it is still advantageous when said shuttle pistons each are provided with check valves allowing working fluid transfer in a direction opposite to said twin main valves. This may be further improved when respective cylinders accommodating said shuttle valves are connected via a communication passage. According to an advantageous embodiment of the present invention, said twin main valves being respectively disposed in the middle of working fluid passages connecting said pump with the first and second chambers. To apply the invention to a main propulsion unit, there may be provided a power tilt device for a marine propulsion unit comprising: a tilt cylinder device for tilting up and down movements while receiving working fluid supply from a hydraulic pump respectively into a tilt lower chamber and a tilt upper chamber of the tilt cylinder, and twin main valves, with one valve being provided in a tilt up side oil passage interconnecting the tilt lower chamber of the tilt cylinder device and the hydraulic pump, and the other valve being provided in a tilt down side oil passage interconnecting the tilt upper chamber of the tilt cylinder device and the hydraulic pump, with each of the main valves being opened and closed with a shuttle piston, wherein a seal member is attached to only one of the shuttle pistons. In that case, it is advantageous when said seal member is attached to the shuttle piston that opens and closes the main valve provided in the tilt down side oil passage. With the invention, since one shuttle piston is not provided with a seal member and a gap is left between the shuttle piston and the cylinder holding the shuttle piston, even if air remains in the communication passage before a tilt action, the air is discharged during the tilt action. It has also an advantage that the working oil does not collect excessively in the communication passage even after an extended period of use. Therefore, a state does not occur in which the main valves remain open as both of the shuttle pistons are kept pressed. As a result, the main valves are reliably operated and the tilt action is performed as required securely in a stabilized manner. Other preferred embodiments of the present invention are laid down in further dependent claims. In the following, the present invention is explained in greater detail with respect to several embodiments thereof in conjunction with the accompanying drawings, wherein: FIG. 1 is a side view of an outboard motor in the tilted down state; FIG. 2 is a side view of the outboard motor in the tilted up state; FIG. 3 shows a hydraulic circuit constitution for a power tilt device of the invention; FIG. 4 shows the constitution in cross-section of the twin main valves for the power tilt device; FIG. 5 is a conceptual drawing of part of a conventional power tilt device including main valves, and FIG. 6 is a conceptual drawing of part of a conventional power tilt device including main valves. A power tilt device according to the present invention will be described as a device for lifting and lowering, respectively, a marine propulsion unit. However, this power tilt device is not limited to this application. This power tilt device may be used for other purposes, i.e. moving doors, flaps etc. First, general constitution of an outboard motor as a marine propulsion unit will be described in reference to FIGs. 1 and 2. FIG. 1 is a side view of an outboard motor in a tilted up state. FIG. 2 is a side view of the outboard motor in a tilted down state. As shown in FIG. 1, an outboard motor 1 is secured to the transom 50a of a hull 50 using paired right and left clamp brackets 2. On the clamp brackets 2 is pivoted a swivel bracket 3 for up and down rotary movements about a tilt shaft 4. A propulsion unit 5 is supported for rotation about a steering shaft 6 on the swivel bracket 3. The marine propulsion unit 5 is provided with an engine 7 as a driving source and a propeller 8. A power tilt device 10 of the invention is interposed between the clamp bracket 2 and the swivel bracket 3 so that the outboard motor 1 can be rotated about the tilt shaft 4 by the tilting action with the power tilt device 10. Next, basic constitution of the power tilt device 10 of the invention will be described in reference to FIGs. 3 and 4. FIG. 3 shows the hydraulic circuit constitution of the power tilt device 10 of the invention. FIG. 4 shows the constitution in cross-section of the twin main valves for the power tilt device. FIG. 3 shows; a hydraulic pump 11, a tilt cylinder device 12 for tilting action with working oil received from the hydraulic pump 11, and twin main valves 13A, 13B. The tilt cylinder device 12 comprises; a tilt piston 15 and a free piston 16 disposed for free sliding in the vertical (horizontal in FIG. 3) direction within a tilt cylinder 14. The lower end of the tilt cylinder 14 is connected through a lower pin 17 to paired right and left clamp brackets 2 (refer to FIGs. 1 and 2). The upper end of a piston rod 18 extending upward from the tilt piston 15 is connected to the swivel bracket 3 through an upper pin 19. The interior of the tilt cylinder device 12 is divided with the tilt piston 15 into a tilt upper chamber S1 and a tilt lower chamber S2. The tilt piston 15 is provided with a damper valve 20 and a check valve 21. The tilt upper chamber S1 of the tilt cylinder device 12 and the hydraulic pump 11 are interconnected through a tilt down side oil passage 22A. The tilt lower chamber S2 of the tilt cylinder device 12 and the hydraulic pump 11 are interconnected through a tilt up side oil passage 22B. The main valves 13A, 13B and shuttle pistons 23A, 23B for opening and closing the main valves 13A, 13B are respectively disposed in the middle of the tilt down side oil passage 22A and the tilt up side oil passage 22B. The shuttle pistons 23A, 23B are fitted for free sliding respectively within cylinders 24A, 24B, and their ends on one side are respectively provided with projections 23a, 23b. As shown in FIG. 4, the main valves 13A, 13B are respectively forced toward closing direction with springs 25A, 25B, so that they constitute check valves for permitting working oil to flow toward the tilt cylinder device 12. The interior of one cylinder 24A is divided into shuttle chambers Sa1 and Sa2 by the shuttle piston 23A. The interior of the other cylinder 24B is also divided into shuttle chambers Sb1 and Sb2 by the shuttle piston 23B. The shuttle chambers Sa2, Sb2 of the cylinders 24A, 24B are interconnected through a communication passage 25. The tilt down side oil passage 22A is connected to the shuttle chamber Sa1 of the cylinder 24A on one side. The tilt up side oil passage 22B is connected to the shuttle chamber Sb1 of the cylinder 24B on other side. The shuttle pistons 23A, 23B are respectively provided with check valves 26A, 26B for permitting oil flow from the shuttle chambers Sa1, Sb1 on one side to the shuttle chambers Sa2, Sb2 on the other side. In this embodiment, a sealing member 27 such as an O-ring is fitted on the outside circumference of the shuttle piston 23A for opening and closing the main valve 13A provided on one side in the tilt down side oil passage 22A, so that reliable sealing function is maintained between the shuttle piston 23A and the cylinder 24A. On the other hand, no sealing member is provided on the other shuttle piston 23B. Instead, a small gap is left between the shuttle piston 23B and the cylinder 24B. FIG. 3 also shows; a manual valve 28, thermal protection valves 29A, 29B, a down relief valve 30A, and an up relief valve 30B. Now the function of the power tilt device 10 of the invention will be described. In the tilted down state with the piston rod 18 located at the bottom end, the outboard motor 1 keeps an almost upright attitude as shown in FIG. 1. When a tilt up operation is started from the tilted down state by driving the hydraulic pump 11, oil delivered out of the hydraulic pump 11 flows through the tilt up side oil passage 22B shown in FIG. 3 into the shuttle chamber Sb1 of the cylinder 24B on one side, its pressure opens the main valve 13B on one side. At the same time, the oil passes through the check valve 26B of the shuttle piston 23B, the gap between the cylinder 24B and the shuttle piston 23B, the shuttle chamber Sb2 and the communication passage 25, and into the shuttle chamber Sa2 of the cylinder 24A on the other side. Then, the shuttle piston 23A is pushed up, and the main valve 13A on the other side is pushed open with the projection 23a of the shuttle piston 23A. At this time, even if air remains in the communication passage 25, when the delivery of the working oil from the hydraulic pump 11 stops as the tilting operation is over, air and oil leak through the gap between the shuttle piston 23B and the cylinder 24B and do not remain compressed in the communication passage 25. When the main valve 13B is opened as described above, since the working oil is supplied from the shuttle chamber Sb1 of the cylinder 24B to the tilt lower chamber S2 of the tilt cylinder device 12, the tilt piston 15, the free piston 16, and the piston rod 18 move up like a single body in the tilt cylinder 14. When the piston rod 18 moves up together with the tilt piston 15, the swivel bracket 3 and the outboard motor 1 supported on the swivel bracket 3 swing up about the tilt shaft 4 (refer to FIGs. 1 and 2). Thus, the outboard motor 1 is tilted up as shown in FIG. 2. With this embodiment, since the shuttle piston 23A for opening and closing the main valve 13A provided in the tilt down side oil passage 22A is provided with the sealing member 27, the check valve 26A and the seal member 27 prevent the working oil from leaking to the suction side of the hydraulic pump 11 during the tilt up operation, and thus all the amount of working oil discharged from the hydraulic pump 11 is supplied to the tilt cylinder device 12. As a result, the tilt up operation is performed efficiently within a short period of time. In this connection, if the sealing member 27 were provided on the shuttle piston 23B on the other side, the working oil passing through the check valve 26B during a tilt up operation is drawn through the gap between the shuttle piston 23A and the cylinder 24A into the hydraulic pump 11. Therefore, all the amount of oil discharged from the hydraulic pump 11 is not always used for the tilt up operation, and the tilt up operation is not performed efficiently. On the other hand, the working oil in the tilt upper chamber S1 of the tilt cylinder device 12 is returned to the hydraulic pump 11 as the tilt piston 15 moves up through the tilt down side oil passage 22A, the main valve 13A of an open state, and the shuttle chamber Sa1. When the outboard motor 1 has been tilted up to the trimmed up position shown in FIG. 2 and the drive of the hydraulic pump 11 is stopped, both of the main valves 13A, 13B are closed with urging forces of the springs 25A, 25B, the tilt upper chamber S1 and the tilt lower chamber S2 of the tilt cylinder device 12 are tightly closed, and the working oil filling those chambers is prevented from flowing. As a result, the outboard motor 1 keeps the tilted up attitude shown in FIG. 2. In that case, even if air remains in the communication passage 25 before the tilting operation, the air is discharged as described above through the gap between the shuttle piston 23B on one side and the cylinder 24B. As a result, the deficiency associated with the conventional arrangement that both of the main valves 13A, 13B are kept open (state as shown in FIG. 5(c)) as the air in the communication passage 25 expands and keeps pressing the shuttle pistons 23A, 23B is eliminated, so that the outboard motor 1 is kept in the tilted up state shown in FIG. 2. Also with this embodiment, since the shuttle piston 23B on one side is not provided with a sealing member, and a gap is formed between the shuttle piston 23B and the cylinder 24B, working oil does not collect excessively in the communication passage 25 even after an extended period of time of use. Therefore, a situation does not occur in which both of the main valves 13A, 13B remain open (as shown in FIG. 5 (c)) as the oil pressure in the communication passage 25 increases and keeps pressing both of the shuttle pistons 23A, 23B. As a result, the outboard motor 1 is kept in the tilted up state shown in FIG. 2. Next, when the outboard motor 1 in the tilted up state shown in FIG. 2 is to be tilted down, the hydraulic pump 11 is driven in reverse to supply the working oil delivered from the hydraulic pump 11 through the tilt down side oil passage 22A to the shuttle chamber Sa1 of the cylinder 24A. Then, the working oil supplied with its pressure to the shuttle chamber Sa1 opens the main valve 13A. At the same time, the oil flows into the shuttle chamber Sb2 of the cylinder 24B on the other side through the check valve 26A of the shuttle piston 23A, the shuttle chamber Sa2, and the communication passage 25. As a result, the shuttle piston 23B is pushed up, and the projection 23b of the shuttle piston 23B pushes open the main valve 13B on the other side. When the main valve 13A is opened, since the working oil is supplied from the shuttle chamber Sa1 of the cylinder 24A to the tilt upper chamber S1 of the tilt cylinder device 12, the tilt piston 15, the free piston 16, and the piston rod 18 move down like a single body in the tilt cylinder 14. When the piston rod 18 moves down together with the tilt piston 15, the swivel bracket 3 and the outboard motor 1 supported on the swivel bracket 3 swing down about the tilt shaft 4 (refer to FIGs. 1 and 2). Thus, the outboard motor 1 is kept in the tilted down state as shown in FIG. 1. Incidentally, while the invention is explained above as an example application to a power tilt device capable of only the tilting operation, it is a matter of course that the invention may also be applied to a power tilt device capable of both tilting and trimming operations. As is clear from the above explanation of the invention, in the power tilt device for marine propulsion units comprising; a tilt cylinder device for tilting up and down movements while receiving working fluid supply from a hydraulic pump respectively into a tilt lower chamber and a tilt upper chamber, and twin main valves, with one valve being provided in a tilt up side oil passage interconnecting the tilt lower chamber of the tilt cylinder device and the hydraulic pump, and the other valve being provided in a tilt down side oil passage interconnecting the tilt upper chamber of the tilt cylinder device and the hydraulic pump, with each of the main valves being opened and closed with a shuttle piston, a seal member is attached to only one of the shuttle pistons. As a result, an effect is obtained that reliable operation of the twin type of main valves is possible and so the tilting operation is securely performed as required in a stabilized manner.

Claims: A power tilt device (10), in particular to tilt a marine propulsion unit (5), comprising a cylinder device (12) having a tilt piston (15) provided at one side with a piston rod (18) and dividing said cylinder device (12) into a first chamber (S1) and a second chamber (S2), said first and second chambers (S1,S2) being supplyable with working fluid from a working fluid pump (11) via twin main valves (13A,13B), one (13A) of which being connected with said first chamber (S1) and said working fluid pump (11), the other (13B) being connected with said second chamber (S2) and said working fluid pump (11), said twin main valves (13A,13B) being operable in cooperation with respective first and second shuttle piston units, wherein said first shuttle piston unit comprises a first shuttle piston (23A) and said second shuttle piston unit comprises a second shuttle piston (23B), said first shuttle piston (23A) being accommodated in a sealing condition, characterized in that said second shuttle piston (23B) is adapted to allow the working fluid to flow in both directions between working chambers (Sb1,Sb2) of said second shuttle piston unit. Power tilt device according to claim 1, characterized in that said first shuttle piston (23A) is provided with a sealing member (27). Power tilt device according to claim 1 or 2, characterized in that said second shuttle piston (23B) is dimensioned such that a gap is provided between an outer surface of said second shuttle piston (23B) and an inner surface of an associated cylinder (24B) accommodating said second shuttle piston (23B) for allowing working fluid and air leak between said second shuttle piston (23B) and said associated cylinder (24B). Power tilt device according to at least one of the claims 1 to 3, characterized in that said first and second shuttle pistons (23A,23B) are each provided with projections (23a,23b) for operating said twin main valves (13A,13B). Power tilt device according to at least one of the preceding claims 1 to 4, characterized in that said first and second shuttle pistons (23A,23B) are each provided with check valves (26A,26B) allowing working fluid transfer in a direction opposite to said twin main valves (13A,13B). Power tilt device according to at least one of the preceding claims 1 to 5, characterized in that respective cylinders (24A,24B) accommodating said shuttle pistons (23A,23B) are connected via a communication passage (25). Power tilt device according to at least one of the preceding claims 1 to 6, characterized in that said tilt piston (15) is provided with a damper valve (20) and with a check valve (21), wherein said damper valve (20) is adapted to allow working fluid transfer to said second chamber (S2) and said check valve (21) is adapted to allow working fluid transfer to said first chamber (S1). Power tilt device according to at least one of the preceding claims 1 to 7, characterized in that said twin main valves (13A,13B) are respectively disposed in the middle of working fluid passages (22A,22B) connecting said pump (11) with the first and second chambers (S1,S2). Power tilt device according to at least one of the preceding claims 2 to 8, characterized in that said sealing member (27) is an O-ring filled on an outside circumference of said first shuttle piston (23A).

Inventors: SAITO HIDEKI, SAITO, HIDEKI, Saito, Hideki, c/o SOQI Kabushiki Kaisha
Applicants: SOQI K K, SOQI K.K.
Application year: 2000
Main classification: B63H20
IPC codes: F15B21, F15B11, B63H20, F15B7