Hydraulic cylinder device and boat propelling apparatus including the same

A trim device includes a trim cylinder, a piston, a piston rod and a support member. The piston is slidable inside the trim cylinder, in the axial direction of the trim cylinder. The piston rod is connected with the piston and moves in the axial direction of the trim cylinder following the movement of the piston. The support member is slidable relative to the piston rod and arranged to support the piston rod so that the piston rod's axial center can become tilted with respect to the axial center of the cylinder.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to hydraulic cylinder devices and boat propelling apparatuses. More specifically, the present invention relates to a hydraulic cylinder device for use in adjusting a slant angle of the propelling apparatus main body, and a boat propelling apparatus including the hydraulic cylinder device.

2. Description of the Related Art

In boats equipped with a boat propelling apparatus, a slant angle of the propelling apparatus main body with respect to the boat body is adjusted in accordance with the mode of travel. Specifically, during a high speed travel mainly, the adjustment in the slant angle of the propelling apparatus main body is performed within a trim range, which is a range of small slant angles, for keeping an appropriate cruising attitude. During a slow speed travel or when the boat is stopping, the adjustment in the slant angle of the propelling apparatus main body is performed within a tilt range, which is a range of large slant angles, in order to prevent the propelling apparatus main body from hitting an underwater object. Such an adjustment of the slant angle of the propelling apparatus main body is performed, generally, by means of a power tilt and trim system.

For example, JP-A Hei 7-81678 discloses a hydraulic power tilt and trim system, in which a trim cylinder is slidably provided inside a tilt cylinder, and a piston rod is provided inside the trim cylinder. The piston rod has a tip connected with a swivel arm which is provided pivotably on the boat body, and a propelling apparatus main body is mounted on this swivel arm.

When adjusting the slant angle of the propelling apparatus main body in the trim range in this hydraulic power tilt and trim system, a hydraulic pressure in the tilt cylinder is adjusted in order to adjust the trim cylinder's position in the tilt cylinder. In this process, the piston rod moves (rises or lowers) inside the tilt cylinder together with the trim cylinder, and the swivel arm pivots with the piston rod as the rod rises or lowers. In this way, the adjustment is made of the slant angle of the propelling apparatus main body in the trim range. When adjusting the slant angle of the propelling apparatus main body in the tilt range, the trim cylinder is moved to its upper end of stroke in the tilt cylinder, and in this state, a hydraulic pressure inside the trim cylinder is adjusted. This adjusts the piston rod's position in the trim cylinder. In this process, the swivel arm pivots with the piston rod as the piston rod rises or lowers, adjusting the slant angle of the propelling apparatus main body in the tilt range.

In the hydraulic power tilt and trim system disclosed in JP-A Hei 7-81678, the piston rod moves linearly in an axial direction of the tilt cylinder and trim cylinder. On the other hand, the swivel arm is arranged to pivot with respect to the boat body. Because of this arrangement, there is a rubbing action where the piston rod's tip portion makes contact with the swivel arm. Specifically, the swivel arm rubs against the piston rod along a direction in which the piston rod travels. The rubbing action causes a sharp increase of a frictional force at a place of contact between the piston rod tip portion and the swivel arm, giving rise to a stick-slip phenomenon and an accompanying noise from the place of contact between the piston rod tip portion and the swivel arm.

SUMMARY OF THE INVENTION

In view of the above, preferred embodiments of the present invention provide a hydraulic cylinder device and a boat propelling apparatus capable of reducing the stick-slip phenomenon.

According to a preferred embodiment of the present invention, a hydraulic cylinder device includes a cylinder, a piston provided inside the cylinder and arranged to be slidable in an axial direction of the cylinder, a piston rod connected with the piston, and a support member arranged to be slidable relative to the piston rod to support the piston rod so that an axial center of the piston rod can be tilted with respect to an axial center of the cylinder.

In a preferred embodiment of the present invention, the support member arranged to support the piston rod allows the piston rod to tilt so that its axial center is tilted with respect to the cylinder's axial center. Therefore, when the piston rod is subjected to an external radial force, the center axis of the piston rod is tilted with respect to the center axis of the cylinder. Thus, when the piston rod's tip portion makes contact with another member and generates a frictional force, the center axis of the piston rod tilts with respect to the center axis of the cylinder in a direction in which an increase in the frictional force is reduced. In this case, since the arrangement prevents the frictional force from increasing rapidly at the place of contact between the piston rod and the other member, it is possible to prevent the stick-slip phenomenon. Also, since the support member allows the piston rod to tilt, it is possible to absorb impact energy and vibration of the piston rod, and thereby to prevent a large impact force from reaching other constituent members of the hydraulic cylinder device.

Preferably, the support member urges the piston rod for substantial axial alignment of the piston rod with the cylinder. In this case, the arrangement provides automatic adjustment so that the piston rod will take an appropriate position. Therefore, it is possible to make more appropriate contact of the piston rod's tip portion with the other member.

Preferably, the support member includes an elastic member. In this case, it is possible to sufficiently absorb the impact energy and vibration from the piston.

More preferably, the support member includes an inner circumferential metal which is fixed inside the elastic member and is slidable to the piston rod, and an outer circumferential metal which is provided on an outer circumferential side of the elastic member. Further, the inner circumferential metal, the elastic member and the outer circumferential metal are in substantial axial alignment with each other. In this case, even if the axial center of the inner circumferential metal is moved off of the axial center of the outer circumferential metal, the elastic member urges the inner circumferential metal so that the inner circumferential metal will become aligned with the outer circumferential metal. This provides automatic position adjustment of the piston rod.

More preferably, hydraulic cylinder device further includes an inner stopper which is provided in the inner circumferential metal so as to be movable in an axial direction of the inner circumferential metal, a first stopper portion which is provided in the inner circumferential metal and is arranged to stop the inner stopper, and a second stopper portion which is immovable in an axial direction of the cylinder and is arranged to stop the inner stopper. In this case, the inner stopper moves together with the inner circumferential metal under a capture by the first stopper portion, but then stops its movement in the axial direction of the cylinder when it is captured by the second stopper portion, whereby the movement of the inner circumferential metal in the axial direction of the cylinder stops also. As a result, excessive deformation of the elastic member is prevented. Therefore, the arrangement reduces deterioration of the elastic member.

Preferably, the support member seals the cylinder. In this case, there is no need for a sealing member to be provided separately, so it becomes possible to simplify the structure of the hydraulic cylinder device.

Preferably, the hydraulic cylinder device further includes a sealing member for sealing the cylinder. In this case, there is no need for the support member to seal the cylinder, so it becomes possible to simplify the structure of the support member.

Preferably, hydraulic cylinder device further includes a limiting portion which has a first curved surface. With this arrangement, the piston has a second curved surface arranged to mate with the first curved surface, and a mating contact made by the first curved surface and the second curved surface limits a movement of the piston in an axial direction of the cylinder, and the second curved surface can slip on the first curved surface for pivotal movement of the piston. In this case, the piston is still capable of pivoting even under a situation where the piston's movement in the axial direction of the cylinder is limited, i.e., even when the piston rod is extended to its limit. Therefore, the axial center of the piston rod can still tilt with respect to the axial center of the cylinder rod even when the piston rod is extended to its limit. Thus, the arrangement sufficiently reduces the stick-slip phenomenon. Also, since the contact between the first curved surface and the second curved surface provide stable support to the piston, it is possible to keep the piston rod as tilted even if the piston rod has been extended to its limit while it is tilted with respect to the cylinder.

Preferably, the piston has a first engagement surface which faces the limiting portion, and the limiting portion which has a second engagement surface arranged to stop the first engagement surface to limit the piston in its axial center slant angle with respect to the axial center of the cylinder. In this case, as the first engagement surface is captured by the second engagement surface, the piston stops pivotal movement, and therefore it is possible to prevent the piston rod's slant angle from becoming excessively large. Thus, it becomes possible to make more appropriate contact of the piston rod's tip portion with the other member.

According to another preferred embodiment of the present invention, a boat propelling apparatus includes a swivel bracket that is pivotable in an up-down direction with respect to a boat body, a propelling apparatus main body mounted on the swivel bracket, and the above-described hydraulic cylinder device arranged to allow the swivel bracket to pivot in the up-down direction for a slant angle adjustment of the propelling apparatus main body with respect to the boat body.

In a preferred embodiment of the present invention, the slant angle of the propelling apparatus main body with respect to the boat body is adjusted with the above-described hydraulic cylinder device, and therefore, it is possible to prevent the stick-slip phenomenon when adjusting the slant angle of the propelling apparatus main body. It is also possible to absorb impact energy and vibration of the piston rod with the support member.

The above-described and other elements, steps, features, characteristics, aspects and advantages of the present invention will become clearer from the following detailed description of preferred embodiments of the present invention with reference to the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a conceptual side view showing a configuration of a boat propelling apparatus according to a preferred embodiment of the present invention. In the following paragraphs, description will be made for preferred embodiments where a hydraulic cylinder device according to the present invention is applied to a trim device and to a boat propelling apparatus. In a preferred embodiment of the present invention, an up-down direction is determined from a state where a boat body34(seeFIG. 1) is floating in the water. InFIG. 1, a trim range is indicated by Arrow A1and a tilt range is indicated by Arrow A2.

As shown inFIG. 1, a boat propelling apparatus10includes a propelling apparatus main body12, a bracket unit14and a power tilt and trim system16. It should be noted here that in order to make the description simple and concise, the power tilt and trim system16is shown in a simplified line drawing inFIG. 1as well as inFIG. 2which will be referred to later.

The propelling apparatus main body12has a top cowling18, an upper case20and a bottom case22. An engine24is mounted inside the top cowling18. Inside the upper case20and the bottom case22, a drive shaft26extends in the up-down direction. The drive shaft26has an upper end portion connected with a crankshaft (not illustrated) of the engine24. A propeller28is provided on a rear side of the bottom case22. The propeller28is connected with an end of a propeller shaft30. The propeller shaft30has another end portion connected with a lower end portion of the drive shaft26via a bevel gear32. With such a configuration as the above, a driving force from the engine24is transmitted through the drive shaft26, the bevel gear32and the propeller shaft30, to the propeller28, enabling the propeller28to make normal or reverse rotation thereby generating a propelling force which causes the boat body34to make a forward or a backward travel.

FIG. 2is a side view for describing a relationship between the bracket unit14and the power tilt and trim system16inFIG. 1.FIG. 3is a front view (as viewed from behind the propelling apparatus main body12) of the power tilt and trim system16inFIG. 1.FIG. 4is a right side view of the power tilt and trim system16inFIG. 3.FIG. 5is a plan view of the power tilt and trim system16inFIG. 3.

Referring toFIG. 1andFIG. 2, the bracket unit14includes a pair of clamp brackets36fixed to a rear portion of the boat body34, spaced from each other in a horizontal direction (the widthwise direction of the boat body34); and a swivel bracket38(seeFIG. 2) mounted between the clamp brackets36. It should be noted here that in order to make the description simpler, only one of the two clamp brackets36, i.e., the one closer to the viewer, is shown inFIG. 1whereas only one of the clamp brackets36which is on the far side is shown inFIG. 2. Note also that the swivel bracket38is not illustrated inFIG. 1. A tilt shaft40is mounted to extend in a horizontal direction on upper end portions of the clamp brackets36.

Referring toFIG. 2, the swivel bracket38includes a platy main body portion42which is substantially parallel to a rear end portion of the boat body34(seeFIG. 1); and an arm portions44(FIG. 2shows only one arm portion44on the side closer to the viewer) arranged on an upper portion of the main body portion42, to extend from two respective sides toward the boat body34. The pair of arm portions44are both mounted pivotably around the tilt shaft40. Thus, the swivel bracket38is pivotable to the clamp brackets36in the up-down direction.

At a widthwise (horizontal) center portion in the main body portion42, a rotatable steering shaft46extends in the up-down direction. The upper case20(seeFIG. 1) of the propelling apparatus main body12(seeFIG. 1) is attached to an upper end portion and a lower end portion of the steering shaft46. Thus, the propelling apparatus main body12is pivotable horizontally around the steering shaft46.

In a center portion in the up-down direction of the main body portion42, a pair of recesses42a(FIG. 2shows only one recess42aon the side closer to the viewer) are arranged to be spaced from each other in the widthwise direction. In each of the recesses42a,a projection48projects toward the boat body34. Each of the projections48has a lower side where a trim receiver50is attached pivotably. Each trim receiver50has a concavely curved surface52. The arm portions44of the swivel bracket38have a connecting shaft54which extends horizontally through the arm portions44at a side closer to the main body portion42. The connecting shaft54, which is inserted through annular member72to be described later, is moved in the up-down direction as the annular member72moves in the up-down direction. Thus, the swivel bracket38pivots around the tilt shaft40.

Referring toFIG. 1andFIG. 2, the power tilt and trim system16is disposed between the clamp brackets36. Referring toFIG. 3throughFIG. 5, the power tilt and trim system16preferably includes a pair of trim devices56; a tilt device58provided between the trim devices56; a pressure feeder60provided above one of the trim devices56; and a reservoir tank62provided above the other of the trim devices56. The trim device56is a preferred embodiment of the hydraulic cylinder device according to the present invention.

Each trim device56includes a trim cylinder64and a piston rod66. The tilt device58includes a tilt cylinder68and a piston rod70. The piston rod70has a tip provided with the annular member72.

Referring toFIG. 2, each trim cylinder64is fixed to a corresponding one of the clamp brackets36. The tilt cylinder68is mounted pivotably to a connecting shaft68awhich is fixed to the clamp brackets36.

Referring toFIG. 3through toFIG. 5, the pressure feeder60preferably includes, e.g., a hydraulic pump and a motor which drives the hydraulic pump, and feeds a hydraulic fluid to the trim cylinder64and the tilt cylinder68. The reservoir tank62stores the hydraulic fluid which is to be supplied to the trim cylinder64and the tilt cylinder68.

The piston rod66of the trim device56moves in and out based on the hydraulic pressure of the hydraulic fluid supplied from the reservoir tank62to the trim cylinder64whereas the piston rod70of the tilt device58moves in and out based on the hydraulic pressure of the hydraulic fluid supplied from the reservoir tank62to the tilt cylinder68.

Referring toFIG. 2, the piston rod66in each trim device56has a tip which makes contact with the curved surface52of the corresponding trim receiver50when the propelling apparatus main body12(seeFIG. 1) is in the trim range A1(seeFIG. 1). The connecting shaft54of the swivel bracket38is inserted rotatably through the annular member72of the tilt device58.

Next, an operation of the power tilt and trim system16will be described.

Referring toFIG. 1andFIG. 3, when adjusting the slant angle of the propelling apparatus main body12in the trim range A1, the trim devices56of the power tilt and trim system16is operated. Specifically, the pressure feeder60makes an adjustment on the hydraulic pressure of the hydraulic fluid inside the trim cylinder64, to adjust the amount of travel (position) of the piston rod66. Referring toFIG. 2, in the trim range A1(seeFIG. 1), the tip of the piston rod66is in contact with the trim receiver50of the swivel bracket38, so that the swivel bracket38is pivoted around the tilt shaft40in the up-down direction, following the in-and-out movement of the piston rod66. Since the propelling apparatus main body12is mounted on the swivel bracket38as described earlier, a pivoting action of the swivel bracket38causes the propelling apparatus main body12to pivot in the trim range A1. In this way, the slant angle of the propelling apparatus main body12is adjusted in the trim range A1.

Reference is now made toFIG. 1and toFIG. 3. When adjusting the slant angle of the propelling apparatus main body12in the tilt range A2, the tilt device58of the power tilt and trim system16is operated. Specifically, with the piston rod66of the trim device56at its end of extending stroke, the pressure feeder60makes an adjustment on the hydraulic pressure of the hydraulic fluid inside the tilt cylinder68, to adjust the amount of travel (position) of the piston rod70. Referring toFIG. 2, the piston rod70has a tip provided with the annular member72, which is rotatably penetrated by the connecting shaft54that is attached to the swivel bracket38. Hence, as the piston rod70makes an in-and-out movement, and the swivel bracket38is pivoted around the tilt shaft40in the up-down direction, causing the propelling apparatus main body12to pivot in the tilt range A2(seeFIG. 1). This is how the slant angle of the propelling apparatus main body12is adjusted in the tilt range A2.

It should be noted here that when the swivel bracket38pivots, the connecting shaft54moves on an arc which is centered around the tilt shaft40. This requires that the annular member72also has to move like the connecting shaft54, on an arc which is centered around the tilt shaft40. In order to achieve this, the tilt cylinder68is mounted pivotably to the connecting shaft68ain the tilt device58so that the piston rod70can tilt in accordance with the position of the connecting shaft54. This arrangement allows the annular member72to move on the arc which is centered around the tilt shaft40. It should be noted here that while the propelling apparatus main body12is being operated in the trim range A1(seeFIG. 1), the piston rod70makes an in-and-out movement following the up-and-down movement of the connecting shaft54.

It should also be noted here that the power tilt and trim system16(the pressure feeder60) is electrically connected with, e.g., a control unit (not illustrated) installed in the boat body34, and is operated by a human operator who makes control on the control unit.

Next, description will cover a construction of the trim device56.FIG. 6is an exploded perspective view of the trim device56.FIG. 7is a sectional view showing an internal structure of the trim device56.FIG. 8is an enlarged sectional view showing a rear-end side (a bottom-end side of the trim cylinder64) of the trim device56inFIG. 7whereasFIG. 9is an enlarged sectional view showing a tip-portion side (an open-end side of the trim cylinder64) of the trim device56inFIG. 7.

As shown inFIG. 6, the trim device56preferably includes a circlip74, a dust seal76, a support member78, an O ring80, an outer stopper82, an inner stopper84, a circlip86, a cylinder cap88, an O ring90, a piston rod66, a piston92, a backup ring94, an O ring96, a bolt98and a trim cylinder64. It should be noted here that in the following description of these constituent elements, the up-down direction will be determined in reference to the trim device56as a completed assembly. More specifically, the side closer to the tip of trim device56(the open-end side of the trim cylinder64) will be called the up side whereas a rear-end side of the trim device56(the bottom-end side of the trim cylinder64) will be called the down side.

Referring toFIG. 6throughFIG. 8, the trim cylinder64has an inner circumferential surface which preferably has a circular cross-section. The piston rod66preferably has a circular columnar shape, having a spherically curved tip portion (upper end portion). The piston92preferably is generally circular columnar, and is slidable inside the trim cylinder64in an axial direction of the trim cylinder64. The piston92has a hole100for insertion of a lower end portion of the piston rod66. The piston rod66is inserted in the hole100and under this state, fixed to the piston92with the bolt98. The trim cylinder64has an upper end portion and a lower end portion, each having a fluid inlet/outlet port (not illustrated) for hydraulic fluid to move in and out. The piston92moves axially of the trim cylinder64based on a hydraulic pressure of the hydraulic fluid which is charged and discharged via these fluid inlet/outlet.

The piston92has an outer circumferential surface which preferably includes, naming from its top end and downward, a partial spherical surface102, the engagement surface104, a partial spherical surface106, a groove108and a partial conical surface110. The partial spherical surface102is curved spherically at a curvature which is substantially equal to a curvature of a virtual sphere R (seeFIG. 13to be described later) which is centered around a pivot center C (seeFIG. 13to be described later) of the piston92. The engagement surface104is arranged to face the cylinder cap88. The partial spherical surface106is curved spherically. The groove108is formed in the outer circumferential surface of the piston92, circumferentially thereof. The partial conical surface110is conically curved.

Referring toFIG. 8, the backup ring94and the O ring96are fitted into the groove108. The O ring96provides sealing between the inner circumferential surface of the trim cylinder64and the outer circumferential surface of the piston92. The backup ring94prevents the O ring96from being pushed out of the groove108by the hydraulic pressure of the hydraulic fluid when the pressure has increased on the bottom end side of the trim cylinder64.

In the present preferred embodiment, a diameter of the partial spherical surface106at its lower end provides a maximum diameter of the piston92. The piston92is capable of making its sliding movement smoothly, with the partial spherical surface106staying in contact with the inner circumferential surface of the trim cylinder64.

Referring toFIG. 6,FIG. 7andFIG. 9, the support member78includes a generally annular tilt allowance member112; a generally cylindrical inner circumferential metal114which is fixed on an inner circumferential side of the tilt allowance member112; and a cylindrical outer circumferential metal116(seeFIG. 7andFIG. 9) which is fixed on an outer circumferential portion of the tilt allowance member112. In the support member78, all of the tilt allowance member112, the inner circumferential metal114and the outer circumferential metal116are axially in alignment with the trim cylinder64when there is no load applied. The tilt allowance member112may be made of an elastic material such as rubber and fiber (fabric), for example. The inner circumferential metal114and the outer circumferential metal116may be made of such a metal as aluminum and stainless steel, for example.

Referring toFIG. 9, the tilt allowance member112includes a protruded portion118protruding circumferentially on a lower end portion of its outer circumferential surface. The tilt allowance member112allows the outer circumferential metal116to expose its bottom surface and a lower portion of its inner circumferential surface.

The support member78is manufactured so that it will provide axial alignment of the tilt allowance member112, the inner circumferential metal114and the outer circumferential metal116. Specifically, for example, the support member78is produced by first disposing the inner circumferential metal114and the outer circumferential metal116in predetermined respective places in a metal mold, then injecting a material (e.g., rubber) into the mold, and then allowing the material to set to form the tilt allowance member112.

The inner circumferential metal114has a ridged portion120, a bulged portion122, an inner circumferential groove124and an outer circumferential groove126. The ridged portion120is like a circular wall rising in the upward direction on an upper end portion of the inner circumferential metal114. The bulged portion122is a circumferential bulge in a substantially intermediate portion of the outer circumferential surface of the inner circumferential metal114. The inner circumferential groove124is formed in a lower portion of an inner circumferential surface of the inner circumferential metal114, along the circumferential direction. The outer circumferential groove126is formed in a lower portion of the outer circumferential surface of the inner circumferential metal114, in the circumferential direction.

The inner circumferential metal114is slidable with respect to the piston rod66. The dust seal76is pressed into the ridged portion120. The dust seal76prevents foreign matters (dust, etc.) from entering the trim cylinder64while preventing leakage of the hydraulic fluid from the trim cylinder64. The O ring80is fitted into the inner circumferential groove124, providing a sealing between the inner circumferential metal114and the piston rod66.

The annular outer stopper82and the inner stopper84are provided on the lower end side of the inner circumferential metal114. The inner stopper84is slidable with respect to the inner circumferential metal114. The circlip86, which is fitted into the outer circumferential groove126, prevents the inner stopper84from falling off. The bulged portion122has an outer diameter which is greater than an inner diameter of the inner stopper84. Therefore, the inner stopper84has a limited stroke of travel, which is between the bulged portion122and the circlip86. It should be noted here that the outer stopper82and the inner stopper84may be made of such a material as a metallic material (aluminum, stainless steel, etc.) and a resin material, for example.

Referring toFIG. 10, the cylinder cap88includes a generally cylindrical large-diameter portion128, and a small-diameter portion130which has an outer diameter that is smaller than that of the large-diameter portion128. The large-diameter portion128has, on its inner circumferential surface and naming from the top, a cylindrical surface132which has a circular cross-section, an annular engagement surface134, a cylindrical surface136which has a circular cross-section, and an annular engagement surface138. The cylindrical surface136has a diameter which is smaller than that of the cylindrical surface132. The engagement surface134and the engagement surface138are perpendicular or substantially perpendicular to the up-down direction (the axial direction of the cylinder cap88). The cylindrical surface132has grooves140and142respectively on its upper side and lower side. The grooves140,142are formed circumferentially of the cylindrical surface132.

The small-diameter portion130includes an annular engagement surface144provided at a lower end thereof; a partial spherical surface146extending continuously from an inner edge of the engagement surface144and curving spherically in the upward direction; and an outer circumferential groove148formed in the circumferential direction. The partial spherical surface146has a curvature which is substantially equal to that of the partial spherical surface102(seeFIG. 8) in the piston92.

Referring toFIG. 9andFIG. 10, the cylinder cap88has an inner circumferential surface which has a minimum diameter larger than the diameter of the piston rod66. The engagement surface134has an inner diameter which is smaller than an outer diameter of the outer stopper82. The outer stopper82is supported by the engagement surface134. The cylindrical surface132has a diameter which is substantially equal to an outer diameter of the outer stopper82.

The cylindrical surface132prevents radial movement of the outer stopper82. The engagement surface138has an inner diameter which is smaller than an outer diameter of the inner stopper84. The engagement surface138prevents downward movement of the inner stopper84. The cylindrical surface136has a diameter which is larger than an outer diameter of the inner stopper84. The inner stopper84is movable inside the cylindrical surface136radially of the cylinder cap88. The cylindrical surface136has a height (a length in the up-down direction) which is greater than a thickness of the inner stopper84. The inner stopper84is movable between the outer stopper82and the engagement surface138in the up-down direction.

The tilt allowance member112in the support member78is pressed into the cylindrical surface132so that the outer circumferential metal116has its bottom surface contacting an upper surface of the outer stopper82and the protruded portion118sits in the groove142. Thus, the outer circumferential metal116secures the outer stopper82while the protruded portion118prevents the tilt allowance member112from moving upward. For assured prevention of the tilt allowance member112from moving upward, the circlip74is fitted into the groove140in the cylindrical surface132.

A screw thread (not illustrated) is formed in an upper end portion of the inner circumferential surface of the trim cylinder64, as well as in the outer circumferential surface of the small-diameter portion130of the cylinder cap88. In the present preferred embodiment, the small-diameter portion130and the trim cylinder64are threaded together with each other so that the upper end surface of the trim cylinder64makes contact with the large-diameter portion128. In the small-diameter portion130, the groove148is fitted with the O ring90, which provides sealing between the trim cylinder64and the cylinder cap88.

It should be noted here that the support member78is assembled to the cylinder cap88as follows. First, a lower end side of the inner circumferential metal114is inserted into the outer stopper82and the inner stopper84, and the circlip86is attached to the inner circumferential metal114. This completes an assembly of the outer stopper82and the inner stopper84to the inner circumferential metal114. Next, the tilt allowance member112(the support member78) is pressed into the cylindrical surface132, and the circlip74is attached. This completes the assembling process of the support member78to the cylinder cap88.

In the present preferred embodiment, the trim cylinder64preferably defines the cylinder according to a preferred embodiment of the present invention, the tilt allowance member112defines the elastic member, the circlip86or the bulged portion122represents the first stopper portion, the outer stopper82or the engagement surface138represents the second stopper portion, the cylinder cap88serves as the limiting portion, the partial spherical surface146represents the first curved surface, the partial spherical surface102represents the second curved surface, the engagement surface104represents the first engagement surface, and the engagement surface144represents the second engagement surface.

Next, description will cover functions and advantages of the present preferred embodiment. In the trim device56and the boat propelling apparatus10which are preferred embodiments of the present invention, the piston rod66has its lower end portion fixed to the pivotable piston92, and the piston rod66has its outer circumferential surface supported by the support member78which includes the tilt allowance member112that is made of an elastic material. As shown inFIG. 11andFIG. 12therefore, when an external force F is applied radially to the piston rod66, the tilt allowance member112makes an elastic deformation, allowing the axial center of the piston rod66to tilt (lean) with respect to the axial center of the trim cylinder64. For example, when a frictional force is generated at a place of contact between the tip of the piston rod66and the trim receiver50(seeFIG. 2), the axial center of the piston rod66tilts with respect to the axial center of the trim cylinder64in a direction where an increase in the frictional force is reduced. This prevents the frictional force from increasing rapidly at the place of contact between the piston rod66and the trim receiver50, preventing the stick-slip phenomenon.

Also, when an impact is applied to the piston rod66, the impact energy is absorbed by the elastic tilt allowance member112, so it is possible to prevent a large impact force from reaching other constituent members of the trim device56. Likewise, if there is vibration in the piston rod66, the vibration is absorbed by the tilt allowance member112, so it is possible to prevent a large vibration from reaching other constituent members of the trim device56.

The outer circumferential metal116is provided on an outer circumference side of the tilt allowance member112. This reduces deformation of an outer circumferential portion of the tilt allowance member112(especially an outer-side portion of the outer circumferential metal116). As shown inFIG. 12, therefore, even when the tilt allowance member112makes deformation, the outer circumferential surface of the tilt allowance member112does not come off the inner circumferential surface of the cylinder cap88, thereby preventing leakage of the hydraulic fluid from inside the cylinder cap88to the outside.

Under a no load situation, the tilt allowance member112, the inner circumferential metal114and the outer circumferential metal116in the support member78are all in axial alignment. Therefore, even if the inner circumferential metal114comes off the axial center of the outer circumferential metal116, the tilt allowance member112urges the inner circumferential metal114so that the inner circumferential metal114will become aligned with the outer circumferential metal116. It should be appreciated that the outer circumferential metal116is designed to be in axial alignment with the trim cylinder64. Therefore, the piston rod66, which is supported by the inner circumferential metal114, is under an urging force from the tilt allowance member112so that the piston rod66is in axial alignment with the trim cylinder64. For this reason, the axial center of the piston rod66is automatically adjusted so that the piston rod66is in axial alignment with the trim cylinder64when the hydraulic pressure of the hydraulic fluid inside the trim cylinder64is not large (when the piston92is not under a large pressure). This prevents such a situation, for example, that the piston rod66starts its travel while it is tilted with respect to the axial center of the trim cylinder64when the trim device56is started (when the piston92is at the lower end of the trim cylinder64). Since this arrangement allows the piston rod66to make appropriate contact with the trim receiver50(seeFIG. 2), an operating force is transmitted efficiently from the piston rod66to the trim receiver50. As a result, a smooth adjustment is possible on the slant angle of the propelling apparatus main body12.

Referring toFIG. 12, the tilting (leaning) movement of the piston rod66is stopped when the outer circumferential surface of the inner stopper84makes contact with the cylindrical surface136of the cylinder cap88. Since this prevents excessive deformation of the tilt allowance member112, the arrangement reduces deterioration of the tilt allowance member112.

Referring toFIG. 13, an upward travel of the piston92is stopped when the partial spherical surface102makes contact with the partial spherical surface146of the cylinder cap88. The curvature of the partial spherical surface102and that of the partial spherical surface146are substantially equal to the curvature of the virtual sphere R which is centered around a pivot center C of the piston92. Therefore, as shown inFIG. 14, while the partial spherical surface102is in contact with the partial spherical surface146, the piston92is pivotable due to a slip action of the partial spherical surface102with respect to the partial spherical surface146. This allows the piston rod66to tilt with respect to the axial center of the trim cylinder64even when the piston rod66is in its fully extended state. Also, since the contact between the partial spherical surface102and the partial spherical surface146provides stable support to the piston, the piston rod66is tilted but is stable even when the piston rod66is in its fully extended state with respect to the trim cylinder64.

Also, the pivotal movement of the piston92is stopped when, as shown inFIG. 14, the engagement surface104of the piston92makes a contact with the engagement surface144of the cylinder cap88. This prevents the piston rod66from assuming an excessively large tilting (leaning) angle under the state where the piston rod66is fully extended. Now, in the boat propelling apparatus10(seeFIG. 1), the trim receiver50(seeFIG. 2) is not in contact with the piston rod66while the propelling apparatus main body12is in operation in the tilt range A2(seeFIG. 1), but comes back into contact again with the piston rod66when the propelling apparatus main body12moves from the tilt range A2to the trim range A1(seeFIG. 1). Therefore, if the piston rod66has an excessively large slant angle when the propelling apparatus main body12moves from the tilt range A2to the trim range A1, the tip of the piston rod66can make incidental contact with a position which is unduly off the center of the trim receiver50. This poses a risk of vibration to be produced when the piston rod66and the trim receiver50make contact with each other. With this in consideration, the slant angle of the trim cylinder64is limited as described above in order to ensure a smooth contact between the piston rod66and the trim receiver50. Preferably, the slant angle of the axial center of the trim cylinder64with respect to the axial center of the piston92is controlled not to become greater than about 10 degrees, for example, through an appropriate determination process of various dimensions in the cylinder cap88and the piston92.

Referring toFIG. 15, when the piston rod66moves upward (in the direction indicated by Arrow A), the inner circumferential metal114of the support member78moves upward, following the movement of the piston rod66. In this process, the inner stopper84moves upward together with the inner circumferential metal114, being captured by the circlip86, but then stops the upward movement when captured by the outer stopper82which is prevented from moving axially of the trim cylinder64. This stops the upward movement of the inner circumferential metal114, preventing the tilt allowance member112from being excessively deformed. As a result, the arrangement reduces deterioration of the tilt allowance member112.

Referring toFIG. 16, when the piston rod66moves downward (the direction indicated by Arrow B), the inner circumferential metal114of the support member78moves downward, following the movement of the piston rod66. In this process, the inner stopper84moves downward together with the inner circumferential metal114, being captured by the bulged portion122of the inner circumferential metal114, but then stops the downward movement when captured by the engagement surface138of the cylinder cap88which is prevented from moving axially of the trim cylinder64. This stops the downward movement of the inner circumferential metal114, preventing the tilt allowance member112from being excessively deformed. Thus, the arrangement reduces deterioration of the tilt allowance member112.

It should be noted here that in the above-described preferred embodiment, the support member78preferably includes the tilt allowance member112, the inner circumferential metal114and the outer circumferential metal116as shown inFIG. 9. However, the constitution of the support member is not limited to those given in the example described above. For example, the support member may not include the inner circumferential metal114and the outer circumferential metal116. In this case, the inner diameter of the tilt allowance member is made smaller than the inner diameter of the above-described the tilt allowance member112in order to allow the tilt allowance member's inner circumferential surface to make contact with the outer circumferential surface of the piston rod66. Another example may be that the inner circumferential metal114may be replaced by a resin member which is formed to have the same shape as the inner circumferential metal114. Likewise, the outer circumferential metal116may be replaced by a resin member that is formed to have the same shape as the outer circumferential metal116.

As shown inFIG. 9, the trim cylinder64and the cylinder cap88are preferably separate members in the above-described preferred embodiment. However, the trim cylinder and the cylinder cap may be provided as single individual pieces. More specifically, the arrangement may be that a trim cylinder has an upper end portion which preferably has the same inner circumferential surface as that of the cylinder cap88, and this trim cylinder preferably includes the support member78, the circlip74, the outer stopper82and the inner stopper84.

As shown inFIG. 14, pivotal movement of the piston92is preferably limited by contact between the engagement surface104of the piston92and the engagement surface144of the cylinder cap88in the above-described preferred embodiment. However, pivotal movement of the piston92may be limited by contact between the partial conical surface110of the piston92and the inner circumferential surface of the trim cylinder64.

Also, in the above-described preferred embodiment, the piston92is pivotable in the trim cylinder64. However, the piston rod66may be pivotably connected with the piston92.

The trim device may have a construction as shown inFIG. 17. It should be noted here thatFIG. 17shows a section of an upper end portion of a trim device.FIG. 17shows a trim device150, which differs from the trim device56in the points described in the following paragraphs.

Referring toFIG. 17, in the trim device150, the cylinder cap88(seeFIG. 9) is replaced by a cylinder cap152which is fixed to an upper end portion of the trim cylinder64. The cylinder cap152has a cylindrical surface154on an upper end side of its inner circumferential surface. The cylindrical surface154does not have the grooves140,142(seeFIG. 9) but has a screw thread (not illustrated).

Inside the cylinder cap152, there are provided an inner circumferential metal156, an O ring158,160and an outer circumferential metals162,164, instead of the tilt allowance member112(seeFIG. 9), the inner circumferential metal114(seeFIG. 9) and outer circumferential metal116(seeFIG. 9).

The inner circumferential metal156has an outer circumferential surface formed with a flange portion166which extends radially outward around its circumference. The outer circumferential metal162and the outer circumferential metal164are both cylindrical. The outer circumferential metal162has a lower end portion provided with an annular flange portion168whereas the outer circumferential metal164has an upper end portion provided with an annular flange portion170. Each of the outer circumferential metal162and the outer circumferential metal164has an outer circumferential surface formed with a screw thread (not illustrated) and is threaded to the cylindrical surface154of the cylinder cap152.

The outer circumferential metal162and the outer circumferential metal164sandwich the flange portion166of the inner circumferential metal156by the flange portion168and the flange portion170, and are fixed to the cylinder cap152. The flange portion166has its lower surface spaced from an upper surface of the flange portion168. The flange portion166has its upper surface spaced from a lower surface of the flange portion170.

The flange portion166of the inner circumferential metal156has a diameter which is smaller than an inner diameter of the outer circumferential metal162(inner diameter of a portion above the flange portion168) and is also smaller than an inner diameter of the outer circumferential metal164(inner diameter of a portion below the flange portion170). Thus, the inner circumferential metal156is radially movable.

The O ring158is provided between the flange portion166and the flange portion168. The O ring160is provided between the flange portion166and the flange portion170. These O rings prevent the hydraulic fluid inside the trim cylinder64from leaking outside, by passing between the inner circumferential metal156and the outer circumferential metal162, and between the inner circumferential metal156and the outer circumferential metal164.

Referring toFIG. 17andFIG. 18, the small-diameter portion130has an inner circumferential surface provided with a flat spiral spring172. Referring toFIG. 17, the flat spiral spring172has its inner circumference surface contacted slidably by the piston rod66.

In the trim device150, the flat spiral spring172serves as the support member, whereas the inner circumferential metal156, the O rings158,160, the outer circumferential metal162and the outer circumferential metal164preferably define the sealing members.

Hereinafter, functions and advantages of the trim device150will be described.

In the trim device150, when an external force is applied radially to the piston rod66, the flat spiral spring172makes an elastic deformation, allowing the axial center of the piston rod66to tilt with respect to the axial center of the trim cylinder64. Since this prevents the frictional force from increasing rapidly at the place of contact between the piston rod66and the trim receiver50(seeFIG. 2), the arrangement prevents the stick-slip phenomenon.

Also, when an impact is applied to the piston rod66, the impact energy is absorbed by the flat spiral spring172, so it is possible to prevent a large impact force from reaching other constituent members of the trim device150. Likewise, if there is vibration in the piston rod66, the vibration is absorbed by the flat spiral spring172, so it is possible to prevent a large vibration from reaching other constituent members of the trim device150.

Further, since the piston rod66is urged by the flat spiral spring172so that the piston rod66is in axial alignment with the trim cylinder64, the axial center position of the piston rod66is automatically adjusted in this arrangement.

It should be noted here that the flat spiral spring172may be replaced by other elastic members such as one made of rubber, for example.

In the above-described preferred embodiments, the hydraulic cylinder device according to the present invention is preferably applied to a trim device. However, the hydraulic cylinder device according to preferred embodiments of the present invention may be applied to a tilt device. Specifically, for example, the same constituent members as shown inFIG. 6, i.e., the circlip74, the dust seal76, the support member78, the O ring80, the outer stopper82, the inner stopper84, the circlip86, the cylinder cap88, the O ring90, the piston92, the backup ring94, the O ring96and the bolt98may be used to slidably hold the piston rod70(seeFIG. 3) inside the tilt cylinder68(seeFIG. 3). In this case, the piston rod70makes a tilting movement in accordance with the position of the connecting shaft54(seeFIG. 2) even if the tilt cylinder68is fixed to the clamp brackets36(seeFIG. 1). Therefore, the tilt cylinder68need not be pivotable to the clamp brackets36. This makes it possible to simplify the mounting structure of the tilt cylinder68.

The above-described power tilt and trim system may be replaced by a power tilt and trim system174of a construction as shown inFIG. 19.

FIG. 19show the power tilt and trim system174, which includes a tilt and trim device176, a pressure feeder178and a reservoir tank180. In the power tilt and trim system174, the hydraulic cylinder device according to a preferred embodiment of the present invention is applied to the tilt and trim device176.

The tilt and trim device176includes a tilt and trim cylinder182and a piston rod184. The piston rod184has a tip provided with an annular member186. A connecting shaft54(seeFIG. 2) of a swivel bracket38(seeFIG. 2) is rotatably inserted through the annular member186. The pressure feeder178preferably includes, e.g., a hydraulic pump and a motor which drives the hydraulic pump, and sends pressurized hydraulic fluid to the tilt and trim cylinder182. The reservoir tank180stores the hydraulic fluid to be supplied to the tilt and trim cylinder182.

In the power tilt and trim system174, the pressure feeder178provides adjustment on the hydraulic pressure of the hydraulic fluid inside the tilt and trim cylinder182, to make an adjustment on the amount of travel (position) of the piston rod184. When the power tilt and trim system174is operated, the swivel bracket38(seeFIG. 2) makes a pivotal movement in the up-down direction around the tilt shaft40(seeFIG. 2) as the piston rod184moves in and out. This causes the propelling apparatus main body12(seeFIG. 1) to pivot in the trim range A1(seeFIG. 1) and the tilt range A2(seeFIG. 1). It should be noted here that the power tilt and trim system174does not need the trim receiver50(seeFIG. 2), and therefore it is possible to use a swivel bracket of a simple construction that does not have the recesses42a(seeFIG. 2), the projection48(seeFIG. 2) and the trim receiver50(seeFIG. 2).

FIG. 20is a sectional view which shows an internal construction of the tilt and trim device176. Referring toFIG. 20, a generally columnar piston188is slidably provided inside the generally cylindrical tilt and trim cylinder182. The piston rod184is fixed to the piston188with a bolt190. Inside the tilt and trim cylinder182, a free piston193is slidably provided below the piston188. The tilt and trim cylinder182has an upper end portion and a lower end portion, each having a fluid inlet/outlet port (not illustrated) for hydraulic fluid to move in and out to/from the tilt and trim cylinder182.

Referring toFIG. 21, the piston188includes, like the piston92inFIG. 8, a partial spherical surface102, an engagement surface104, a partial spherical surface106, and a groove108. The groove108is fitted with a backup ring94and an O ring96. Also, the piston188is formed with passages192,194for the hydraulic fluid to flow. The passages192,194are provided with check valves196,198respectively.

Referring toFIG. 22, a cylinder cap200is fixed to an upper end of the tilt and trim cylinder182. The cylinder cap200has the same inner circumferential surface as in the cylinder cap88shown inFIG. 9. On an upper side of the cylinder cap200, there are preferably provided a series of components like inFIG. 9, namely, a circlip74, a dust seal76, a support member78, an O ring80, an outer stopper82, an inner stopper84and a circlip86. The lower end side of the cylinder cap200is, like the cylinder cap88inFIG. 9, includes an engagement surface144and a partial spherical surface146. Also, like the trim device56inFIG. 9, an O ring90is provided between the cylinder cap200and the tilt and trim cylinder182.

Referring toFIG. 20, the free piston193includes a cylindrical portion202and a columnar portion204. The cylindrical portion202has an outer circumferential surface with a groove206formed in a circumferential direction. The groove206is fitted with an O ring208. The cylindrical portion202has its upper end surface contacted by a lower end surface of the piston188.

In the tilt and trim device176, the tilt and trim cylinder182preferably defines the cylinder, the tilt allowance member112preferably defines as the elastic member, the circlip86or the bulged portion122represents the first stopper portion, the outer stopper82or the engagement surface138represents the second stopper portion, the cylinder cap200serves as the limiting portion, the partial spherical surface146represents the first curved surface, the partial spherical surface102represents the second curved surface, the engagement surface104represents the first engagement surface, and the engagement surface144represents the second engagement surface.

In the tilt and trim device176, the free piston193, the piston188and the piston rod184rise together when the hydraulic pressure of the hydraulic fluid increases in the lower side of the free piston193. Also, the piston188, piston rod184and the free piston193lower together when the hydraulic pressure of the hydraulic fluid decreases in the upper side of the free piston193.

Since the tilt and trim device176has the same configuration as the trim device56described earlier except for the free piston193, the piston rod184and the piston188can make the same movement as the piston rod66and the piston92of the trim device56. Therefore, the tilt and trim device176provides the same advantages as the trim device56.

In the tilt and trim device176, when there is a force which acts on the piston rod184to cause the piston rod184to rise rapidly (when, for example, the propelling apparatus main body12(seeFIG. 1) is hit by a piece of driftwood), the check valve198opens, to allow the hydraulic fluid above the piston188to flow via the passage194to between the piston188and the free piston193, causing the piston188to move from the free piston193. Thereafter, when there is a force which acts upon the piston rod184to lower it (e.g., the weight of the propelling apparatus main body12), the check valve196opens, to allow the hydraulic fluid between the piston188and the free piston193to flow through the passage192to above the piston188, causing the piston188to make contact with the free piston193again. As described, according to the tilt and trim device176, it is possible to adjust the hydraulic pressure of the hydraulic fluid between the piston188and the free piston192even when there is a force increasing rapidly on the piston rod184. This makes it possible to sufficiently absorb the impact energy applied to the piston rod184and to prevent a large impact force from reaching other constituent members of the tilt and trim device176.

Also, in the tilt and trim device176, it is possible to fix the tilt and trim cylinder182to the clamp bracket36(seeFIG. 1). As a note, in a tilt and trim device which is constituted by a single cylinder, the cylinder must be mounted pivotably to a clamp bracket as in the tilt cylinder68(seeFIG. 2) described earlier. On the other hand, according to the tilt and trim device176, the piston rod184is tiltable against the tilt and trim cylinder182. Therefore, even if the tilt and trim cylinder182is fixed to the clamp bracket36(seeFIG. 1), the piston rod184can make a tilting movement in accordance with the position of the connecting shaft54(seeFIG. 2). Since it is not necessary to provide a pivotable mounting to the tilt and trim cylinder182on the clamp brackets36, it is now possible to simplify the mounting structure of the tilt and trim cylinder182.

It should be noted here that in the description made so far above, the present invention was described as preferably being applied to a single-cylinder tilt and trim device. However, the present invention may be applied to a double-cylinder tilt and trim device.