MARINE POWER STEERING SYSTEM

Abstract: A marine hydraulic system for operation of a power steering assembly includes a pressure accumulator (20) to provide pressurized hydraulic fluid and valving (60) that permits the transfer of hydraulic fluid within the cylinder (14) to provide efficient use of hydraulic fluid.

Description: MARINE POWER STEERING SYSTEM - 1 - The present invention relates to a marine power steering system and more particularly to a system that utilizes an accumulator or pressurized cylinder to supply hydraulic fluid to the power steer- ing system. Typically, marine power steering systems for outboard motors and stern drives utilize an extendable and contractable steering link connected to the boat transom and to the propulsion unit and the extension and contraction of the piston rod in the steering link causes the propulsion unit to pivot and steer the boat. Such units require a rather large hydraulic pump since rather large volumes of hydraulic fluid are required if the steering is moved .rapidly from one side to the other. Such systems also require that the engine be running in order for the steering system to operate since the hydraulic pump is powered by the engine. In general, the present marine hydraulic system for operation of a power steering assembly includes a pump to provide pressurized hydraulic fluid from a reservoir and a control system to selectively place the pump in an operative or in- operative mode. In particular, the invention provides a marine hydraulic system for operation of a power steering assembly whereby pressurized hydraulic fluid is provided to a hydraulic cylinder containing a pis- ton head and piston rod to cause extension or retrac¬ tion of the piston and thereby cause pivotal movement - 2 - of an outboard propulsion unit, said hydraulic system comprising: pump means to provide pressurized hy¬ draulic fluid from a fluid reservoir, control means to place said pump means in an operative or in- operative mode, pressure accumulating means operatively connected to said pump means for accumulating pres¬ surized hydraulic fluid and maintaining said fluid at a desired pressure, a first port in the hy¬ draulic cylinder communicating with, said pressure accumulating means, and introducing pressurized hy¬ draulic fluid on the rod side of the cylinder so that the rod side of the D iston i s constantly exposed to pressurized fluid from the accumulating means, and first valve means disposed within the cylinder for selectively transferring pressurized fluid from the rod aide of the cylinder to the head side of the cylinder in order to pressurize the head side of the cylinder and cause extension of the piston rod. Advantageously, the marine hydraulic system can operate even when th.e engine is not operating and eliminates the need for a large and continuously operating hydraulic pump. In the drawings: Figure 1 is a perspective view of a marine power steering assemb.ly mounted on the transom of a boat and operatiyely connected to an outboard motor; Figure 2 is a schematic drawing of the hy¬ draulic system and steering assembly of Figure 1; Figure 3 is a side cross sectional view of the valve and cylinder assembly in a neutral position; Figure 4 is a side cross sectional view of the valve and cylinder with the valve in a position to allow extension of the piston rod; Figure 5 is a side cross sectional view of the valve and cylinder with the valve in a position to allow retraction of the piston rod; Figure 6 is a side cross sectional view of the accumulator used in the hydraulic system; and Figure 7 is a schematic of the hydraulic system connecting the hydraulic pump, the accumulator and the flow line to the valve and cylinder. Figure 1 shows an outboard motor 10 pivot- ally mounted to the transom 12 of a boat in a con¬ ventional manner. The outboard motor includes a transom bracket, not illustrated, fixed to the transom 12 of the boat with the propulsion unit 11 pivotally at¬ tached to a swivel bracket, not illustrated, to pro¬ vide a steering axis. The swivel bracket is in turn pivotally attached to the transom bracket to provide a tilt axis. A hydraulic cylinder 14 having an ex¬ tendable and contractable piston rod 16 is fixedly mounted on the swivel bracket to tilt with the drive unit 11 and through linkage 18 the linear movement of piston rod 16 is translated into pivotal movement of drive unit 11. Also mounted on transom 12 is accumulator 20 having a port 22 which supplies pressurized hy¬ draulic fluid to cylinder 14 via hose 24 and a port 26 which receives exhausted hydraulic fluid from cylinder 14 via hose 28. The valving for hydraulic cylinder 14 is contained within the cylinder body and the operation of the valving is controlled and determined by the movement of the steering mechanism consisting of gear 30 operatively connected to the steering wheel and movable rack 32. The movement of rack 32 is communicated to yoke 34 by means of linkage 36. This results in pivotal movement of control stem 38 'which in turn causes linear movement of control rod 40. The remainder ' of the hydraulic system in Figure 2 shows accumulator 20 and its associated control package 42 which operates electrical motor 44 and its associated hydraulic pump 46. Electrical power is provided to control package 42 via cable 47. As mentioned above, the valving for hy- draulic cylinder 14 is contained within the cylinder body and is best shown in Figure 3 through Figure 5. In Figure 3, piston head 48 is in its far left position and thus, piston rod 50 in its fully contracted position, in this position there is no flow of hydraulic fluid and the only hydraulic forces experienced by piston head 48 are those caused by hydraulic fluid in chamber 52 acting on surfaces 54 and 56 and tending to cause right to left movement of piston head 48. The pressurized hydraulic fluid in chamber 52 is delivered via port 58 which receives the hy¬ draulic fluid via check valve 60 from accumulator 20. In order to cause left to right movement (Figure 4) of piston head 48, control rod 40 must be moved right to left from its position shown in Figure 3 to that shown in Figure 4. As control rod 40 moves to the right, poppet actuator 62 will ride up incline 64 of recess 66 and will engage the bottom surface of poppet 68 and lift it from its seat 70. With poppet 68 off of seat 70 pressurized hydraulic fluid is allowed to flow from chamber 52 into poppet chamber 72 around poppet 68 and actuator 62 and into recess 66. From there, the hydraulic fluid flows through passage way 74 and eventually to chamber 76 on the head side of the piston assembly. Here, the pressurized hydraulic fluid acts on surface 78 of piston head 48 and since this surface is greater than that of combined surfaces 54 and 56, piston head 48 will be moved in a left to right direction causing extension of piston rod 50. Thus, when moving piston head 48 from left to right, the hydraulic fluid in chamber 52 is utilized in chamber 76 rather than being - 5 - dumped to reservoir. This results in a more efficient use of hydraulic fluid results and in less use of fluid from actuator 20. In order to contract piston rod 50 and thus cause the opposite pivotal movement of marine unit 10, it is necessary to move control rod 40 from its position shown in Figure 4 left to right to its posi¬ tion shown in Figure 5. In its Figure 5 position, poppet actuator 62 returns to its lowest position in recess 66 thus allowing poppet 68 to become reseated while poppet actuator 80 rides up incline 82 of re¬ cess 84 and engages the bottom surface of poppet 86 causing it to lift off of its seat 88. With poppet 36 lifted off seat 88, hydraulic fluid is allowed to flow from chamber 76 along channel 90, through poppet chamber 92, around poppet 86 and actuator 80 and into recess 84. From recess 84, the hydraulic fluid flows through connecting passage 94 leading into passageway 96 which dumps the hydraluic fluid into reservoir 98 by means of hole 100 leading to pas¬ sageway 102 which is in communication with outlet port 104. Thus, in this position, all hydraulic forces on surface 78 are relieved and since poppet 68 is now in its seated position, the constant hydraulic forces from accumulator 20 acting on surfaces 54 and 56 are now unopposed and piston head 48 is moved from right to left. As shown in Figure 6, accumulator 20 includes an outer casing 106 that forms a hydraulic fluid reservoir 108 in the lower portion of accumulator 20. Accumulator 20 is gas charged so that pres¬ surized gas in chamber 110 urges piston 112 into contact with hydraulic fluid in chamber 114. The position of piston 112 is monitored by means of magnetically sensitive switches 116 and 118 - 6 - that are disposed within arm 120 that extends down¬ wardly into chamber 110 and into centrally located cavity 120 in piston 112. Magnets 122 are disposed within walls 124 of cavity 120. Thus, the vertical position of piston 112 is monitored by the inter¬ action of magnets 122 with magnetically sensitive switches 116 and 118. In Figure 7 , piston 112 is near its extreme lower position with only reserve oil below. This position will be detected by magnetic switch 118. Upon detection of this condition, an electrical sig¬ nal is generated by electrical control package 42 and electric motor 44 and associated hydraulic pump 46 are placed into operation. Hydraulic pump 46 will then pump hydraulic fluid from reservoir 108 through filter 126 and upwardly into chamber 114. Reverse flow of hydraulic fluid from chamber 114 back to pump 46 is prevented by check valve 127. Hydraulic pump 46 will continue to pump hydraulic fluid into chamber 114 until cylinder 112 reaches an upper position in which magnets 122 will activate switch 116 resulting in deactivation of electrical motor 44 and pump 46. Accumulator 20 is utilised to provide pressurized hydraulic fluid to hydraulic cylinder 14 via work port 128. Hydraulic fluid exhausted from hydraulic cylinder 14 is returned to reservoir 108 in accumulator 20 by means of work port 130. A sufficient amount of hydraulic fluid is maintained under pressure in chamber 114 of ac- cu ulator 20 so that it is possible to apply pres¬ surized hydraulic fluid to hydraulic cylinder 14 without operating hydraulic pump 46. Since it is possible to cause left to right movement of piston head 48 by means of transferring pressurized hydraulic fluid from the rod side to the head side of piston 48, such movement can be accomplished without external power.

Claims: - 8 - CLAIMS 1. A marine hydraulic system for operation of a power steering assembly whereby pressurized hydraulic fluid is provided to a hydraulic cylinder (14) containing a piston head (48) and piston rod (50) to cause extension or retraction of the piston and thereby cause pivotal movement of an outboard propulsion unit, said hydraulic system comprising: pump means (46) to provide pressurized hydraulic fluid from a fluid reservoir, control means (42) to place said pump means in an operative or inopera¬ tive mode, pressure accumulating means (20) opera- tively connected to said pump means for accumulating pressurized hydraulic fluid and maintaining said fluid at a desired pressure, a first port (58) in the hy¬ draulic cylinder communicating with said pressure accu lating means and introducing pressurized hy¬ draulic fluid on the rod side of the cylinder so that the rod side of the piston is constantly exposed to pressurized fluid from the accumulating means, and first valve means (.68) disposed within the cylinder for selectively transferring pressurized fluid from the rod side of the cylinder to the head side of the cylinder in order to pressurize the head side of the cylinder and cause extension of the piston rod. 2. The hydraulic system of claim 1, in¬ cluding a second port (104) in the hydraulic cylinder communicating with a hydraulic reservoir (98) and a passageway (.92, 94) connecting the head side of the cylinder with said second port, and second valve means (.86) disposed within the cylinder for selectively opening said passageway so that pressurized fluid may be exhausted from the head side of the cylinder to allow retraction of the piston rod. 3. The hydraulic system of Claim 1, wherein - 9 - said accumulating means (.20) comprises: a storage compartment (114) for holding hydraulic fluid, a piston (.112) slidably disposed within said storage compartment and biased into contact with the hy¬ draulic fluid so that the hydraulic fluid is main¬ tained under pressure in said storage compartment, and sensing means (.116, 118) to sense the position of said piston and operatively connected to said control means so that upon detection of a piston position indicative of a low level of hydraulic fluid in said storage compartment said pump is placed in an operative mode so as to supply additional hydraulic fluid to said storage compartment and upon detection of a piston position indicative of an adequate level of hydraulic fluid in said storage compartment said pump is placed in an inoperative mode. 4. The hydraulic system of claim 2, in¬ cluding actuating means (.40) for selectively dis¬ engaging either of said valve means to allow hydraulic fluid to from said rod side to said head side or from said head side to the reservoir. 5. The hydraulic system of claim 3, wherein said sensing means comprises: at least one magnet (122) disposed on said piston so as to follow the movement of said piston, and at least one magnetic field sensitive switch (.116, 118) disposed along the path of movement of said magnet and operatively con¬ nected to said control means.

Inventors: HUNDERTMARK JAMES M, HUNDERTMARK, JAMES, M.
Applicants: BRUNSWICK CORP, BRUNSWICK CORPORATION
Application year: 1988
Main classification: B63H21
IPC codes: B63H20, B63H25, F02B61, F15B1