U.S. patent application number 09/793297 was filed with the patent office on 2002-02-28 for tilt device for marine propulsion unit.
Invention is credited to Nakamura, Tamotsu, Sekikawa, Shinsuke.
Application Number | 20020025735 09/793297 |
Document ID | / |
Family ID | 18689641 |
Filed Date | 2002-02-28 |
United States Patent
Application |
20020025735 |
Kind Code |
A1 |
Nakamura, Tamotsu ; et
al. |
February 28, 2002 |
Tilt device for marine propulsion unit
Abstract
In a tilt device for a marine propulsion unit, a cylinder is
constituted by a double pipe having an outer cylinder and an inner
cylinder, a rod guide sealing the outer cylinder and the inner
cylinder is provided at an end portion of the cylinder, a free
piston is arranged in a space between the outer cylinder and the
inner cylinder, a liquid discharging chamber is formed in a rod
guide side from the free piston of the space, and an absorber valve
which can be opened at a time when a pressure of a fluid in the rod
side chamber is increased to a level equal to or more than a
predetermined value and can feed the fluid in the rod side chamber
to the liquid discharging chamber and a return valve which can feed
the fluid in the liquid discharging chamber to the rod side chamber
are provided in the rod guide.
Inventors: |
Nakamura, Tamotsu; (Saitama,
JP) ; Sekikawa, Shinsuke; (Saitama, JP) |
Correspondence
Address: |
ORUM & ROTH
53 West Jackson Boulevard
Chicago
IL
60604-3606
US
|
Family ID: |
18689641 |
Appl. No.: |
09/793297 |
Filed: |
February 26, 2001 |
Current U.S.
Class: |
440/61F |
Current CPC
Class: |
B63H 20/10 20130101 |
Class at
Publication: |
440/61 |
International
Class: |
B63H 005/125 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 23, 2000 |
JP |
2000-190118 |
Claims
What is claimed is:
1. A tilt device for a marine propulsion unit comprising: a
cylinder connected to one of a hull and a main body of a propulsion
unit which is arranged and constructed to receive a working fluid;
a piston rod connected to another and inserted into the cylinder so
as to freely compress and expand; a piston connected to an inserted
end to the cylinder of the piston rod, and defining a rod side
chamber in a piston rod receiving side within the cylinder and a
piston side chamber in a side which does not receive a piston rod
within the cylinder; a switching valve capable of communicating the
rod side chamber with the piston side chamber; and a pressure
accumulating chamber capable of applying a gas pressure to the
piston side chamber, wherein the cylinder is has a double pipe
having an outer cylinder and an inner cylinder, the piston rod and
the piston are received in the inner cylinder, a rod guide
supporting the piston rod seals the outer cylinder and the inner
cylinder at an end portion of the cylinder, a free piston is
arranged in a space between the outer cylinder and the inner
cylinder, the pressure accumulating chamber is formed in an
opposite rod guide side to the free piston in said space, a liquid
discharging chamber is formed in a rod guide side, and an absorber
valve which can be opened at a time when a pressure of a fluid in
the rod side chamber is increased to a level equal to or more than
a predetermined value and can feed the fluid in the rod side
chamber to the liquid discharging chamber and a return valve which
can be opened at a time when the pressure of the fluid in the
liquid discharging chamber is increased to a level equal to or more
than a predetermined value and can feed the fluid in the liquid
discharging chamber to the rod side chamber are provided in the rod
guide.
2. A tilt device for a marine propulsion unit as claimed in claim
1, wherein said switching valve is provided in the piston rod or
the piston, a switching operation rod operating said switching
valve is installed in the piston rod, and an operating portion of
said switching operation rod is provided in a portion protruding
from the cylinder of the piston rod.
3. A tilt device for a marine propulsion unit as claimed in claim
1, wherein a gas-liquid separating means is arranged between said
pressure accumulating chamber and the piston side chamber.
4. A tilt device for a marine propulsion unit as claimed in claim
2, wherein a gas-liquid separating means is arranged between said
pressure accumulating chamber and the piston side chamber.
5. A tilt device for a marine propulsion unit as claimed in claim
3, wherein said gas-liquid separating means is a free piston.
6. A tilt device for a marine propulsion unit as claimed in claim
4, wherein said gas-liquid separating means is a free piston.
7. A tilt device for a marine propulsion unit as claimed in claim
1, wherein a communicating passage communicating the piston side
chamber with the rod side chamber is provided in an inserted end
side to the inner cylinder of said piston rod, and said switching
valve is provided in the communicating passage.
8. A tilt device for a marine propulsion unit as claimed in claim
2, wherein a communicating passage communicating the piston side
chamber with the rod side chamber is provided in an inserted end
side to the inner cylinder of said piston rod, and said switching
valve is provided in the communicating passage.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a tilt device for a marine
propulsion unit.
[0003] 2. Description of the Related Art
[0004] There is a structure described in Japanese Patent No.
2945071 as a tilt device with a gas assist function for assisting a
tilt up load applied to a main body of a propulsion unit by a gas
pressure in a pressure accumulating chamber.
[0005] The tilt device is structured such that a piston is fixed to
the piston rod inserted to the cylinder. The inner portion of the
cylinder is separated into a rod side chamber and a piston side
chamber by the piston. A switching valve for communicating the rod
side chamber with the piston side chamber and an operating portion
thereof are provided in a side portion of the cylinder. A pressure
accumulating chamber for applying a gas pressure for a gas assist
to the piston side chamber is arranged within the cylinder and on
the piston side chamber. Accordingly, the gas pressure in the
pressure accumulating chamber is applied to both sides of the
piston via a working fluid when opening the switching valve,
whereby the gas assist force corresponding to a cross sectional
area of the rod can be generated in a tilting up direction.
[0006] Further, an absorber valve can be opened when the fluid
pressure in the rod side chamber is increased to a level equal to
or more than a predetermined value in order to absorb an impact
force applied to the propulsion unit main body. When a collision
with drifting wood occurs, the fluid in the rod side chamber can be
discharged and a return valve can return the temporarily discharged
fluid mentioned above from the absorber valve to the rod side
chamber. This series of events will return the propulsion unit main
body after rising up. The absorber valve, rod side chamber and
return valve are provided in the piston. Further, a free piston for
coinciding the return position of the propulsion unit main body
after rising up with a staying position before rising up is
provided in the piston close to the piston side chamber, whereby it
is possible to form a liquid discharging chamber for the fluid
discharged from the absorber valve between the piston and the free
piston.
[0007] (1) Since the absorber valve and the return valve are
provided in the piston, it is hard to make the diameter of the
piston small and further, it is unavoidable that the cylinder is
enlarged.
[0008] (2) Since the pressure accumulating chamber is within the
single cylinder type cylinder and on the piston side chamber, in a
recessed portion in a side of the closed end of the cylinder, it is
hard to increase a capacity of the pressure accumulating
chamber.
[0009] (3) Since the switching valve and the operating portion
thereof are provided in the side portion of the cylinder, the
lateral size of the tilt device becomes too large.
SUMMARY OF THE INVENTION
[0010] An object of the present invention is to provide a tilt
device for a marine propulsion unit with a gas assist function
which can increase the capacity of the pressure accumulating
chamber while being compact and can secure a rising up performance
of a propulsion unit main body caused by a collision of drifting
wood.
[0011] In accordance with the present invention, the tilt device
for a marine propulsion unit contains a cylinder connected to one
of a hull and a main body of a propulsion unit and receiving a
working fluid, and a piston rod connected to another and inserted
into the cylinder so as to freely compress and expand. A piston
connected to an inserted end to the cylinder of the piston rod and
defines a rod side chamber in the receiving side of a piston rod
and a piston side chamber in a non-receiving side of the piston rod
within the cylinder. A switching valve which is capable of
communicating the rod side chamber with the piston side chamber,
and a pressure accumulating chamber capable of applying a gas
pressure to the piston side chamber are contained in the marine
propulsion unit. The cylinder is constituted by a double pipe which
has an outer cylinder and an inner cylinder, and receives the
piston rod and the piston in the inner cylinder. The outer cylinder
and the inner cylinder are sealed at an end portion of the
cylinder, a rod guide supporting the piston rod is provided, a free
piston is arranged in a space between the outer cylinder and the
inner cylinder, the pressure accumulating chamber is formed in an
opposite rod guide side to the free piston in said space, and a
liquid discharging chamber is formed in a rod guide side. An
absorber valve which can be opened when the fluid pressure in the
rod side chamber is increased to a level equal to or more than a
predetermined value can feed the fluid in the rod side chamber to
the liquid discharging chamber. A return valve which can be opened
when the pressure of the fluid in the liquid discharging chamber is
increased to a level equal to or more than a predetermined value
can feed the fluid in the liquid discharging chamber to the rod
side chamber are provided in the rod guide.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present invention will be more fully understood from the
detailed description given below and from the accompanying drawings
which should not be taken to be a limitation on the invention, but
are for explanation and understanding only.
[0013] The drawings
[0014] FIG. 1 is a schematic view showing a marine propulsion
unit;
[0015] FIG. 2 is a cross sectional view of a main portion showing a
tilt device in accordance with a first embodiment;
[0016] FIG. 3 is a cross sectional view along a line III-III in
FIG. 2;
[0017] FIG. 4 is a cross sectional view along a line IV-IV in FIG.
2;
[0018] FIG. 5 is a cross sectional view showing a tilt down
state;
[0019] FIG. 6 is a cross sectional view showing a middle tilt
state;
[0020] FIG. 7 is a cross sectional view showing a tilt up state;
and
[0021] FIG. 8 is a schematic view showing a hydraulic circuit.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] A marine propulsion unit 10 is, for example, an outboard
motor (or an inboard outboard motor) mounted to a hull 11, as shown
in FIG. 1, and is structured such that a clamp bracket 12 is fixed
to the hull 11 and a swivel bracket 14 is pivoted to the clamp
bracket 12 via a tilt shaft 13. A propulsion unit main body 15 of
the marine propulsion unit 10 is pivoted to the swivel bracket 14
via a steering shaft (not shown). An engine unit 16 is mounted on
an upper portion of the propulsion unit main body 15 and a
propeller 17 is provided in a lower portion of the propulsion unit
main body 15. The marine propulsion unit 10 is held at a down
position by a tilt device 20 mentioned below, and normally or
reverse rotates the propeller 17 in accordance with an operation of
the engine unit 16 so as to move hull 11 forward or rearward.
[0023] The tilt device 20 is structured, as shown in FIGS. 2 to 8,
such that a mounting portion 26 provided in the cylinder 21 is
connected by a pin to one of the clamp brackets 12 and the swivel
bracket 14, to the clamp brackets 12 in the present embodiment. A
mounting portion 27 is screwed and attached to a piston rod 22
inserted to the cylinder 21 so as to freely expand and compress is
connected by a pin to another of the clamp bracket 12 and the
swivel bracket 14; to the swivel bracket 14 in the present
embodiment. A piston 23 is fixed to an inserted end to the cylinder
21 of the piston rod 22. The cylinder 21 is constituted by a double
pipe (a complex cylinder structure) having an outer cylinder 21A
and an inner cylinder 21B and is structured such that the outer
cylinder 21A and the inner cylinder 21B are sealed at an end
portion of the cylinder 21. A rod guide 24 for supporting the
piston rod 22 is provided. That is, the structure is made such that
the inner cylinder 21B and the rod guide 24 are held in an inner
portion of the outer cylinder 21A by abutting one end portion of
the inner cylinder 21B to a recess portion in a closed end of the
casting outer cylinder 21A. Another end portion of the inner
cylinder 21B is fitted to a small diameter portion at an inner end
of the rod guide 24 fitted to an opening portion of the outer
cylinder 21A and caulking and holding the rod guide 24 by an outer
end portion of the outer cylinder 21A. Reference numeral 24A
denotes an oil seal, and reference numerals 24B to 24D denote an
O-ring. Reference numeral 25 denotes a cap.
[0024] The piston rod 22 and the piston 23 are received within the
inner cylinder 21B of the cylinder 21. The piston 23 defines a rod
side chamber 31 in a side which receives the piston rod 22 and a
piston side chamber 32 in a side which does not receive the piston
rod 22 in an inner portion of the inner cylinder 21B. The rod side
chamber 31 and the piston side chamber 32 receive an oil as a
working fluid. Reference numeral 23A denotes an O-ring.
[0025] The tilt device 20 has a tilt operating apparatus 40 which
makes it possible to tilt the propulsion unit 15 between a tilt
down position and a tilt up position in accordance with a manual
operation. The tilt operating apparatus 40 pierces a communicating
passage 41 for communicating the piston side chamber 32 with the
rod side chamber 31 in the inserting end side to the inner cylinder
21B of the piston rod 22, and is provided with a switching valve 42
in the communicating passage 41. The switching valve 42 is pressed
to a valve seat 45 disposed in a middle portion of the
communicating passage 41 by a spring 43B backed up by a spring
bearing 43A attached to an opening of the communicating passage 41
in the side of the piston side chamber 32, and a spring holder 43C
so as to close the communicating passage 41. A switching operation
rod 46 is inserted to a center portion of the piston rod 22 from an
external portion so as to be installed therein. A front end small
diameter portion of the switching operation rod 46 abuts the
switching valve 42, and a base end portion of the switching
operation rod 46 abuts a cam 48 of an operating portion 47 provided
in a bearing portion 28 mounted to the mounting portion 27 attached
to a portion protruding outward from the cylinder 21 of the piston
rod 22 (FIG. 3). Reference numeral 29 denotes a cap, reference
numeral 28A denotes an O-ring, reference numerals 46A and 47A
denote an O-ring, and reference numeral 49 denotes a connecting
pin. The switching operation rod 46 is switched and set to a
closing operation position (an upper end position) of the
communicating passage 41 by the switching valve 42 and an opening
operation position (a lower end position) by rotating the cam 48 of
the operating portion 47 by means of a handle engaged and attached
to a handle engaging portion 47B of the operating portion 47,
thereby opening and closing the switching valve 42 against an
elastic force of the spring 43B.
[0026] The tilt device 20 has a pressure accumulating chamber 50
capable of applying a gas pressure to the piston side chamber 32,
for the purpose of assisting a tilt-up load applied to the
propulsion unit main body 15. This occurs when communicating the
rod side chamber 31 with the piston side chamber 32 in accordance
with an opening operation of the switching valve 42 of the tilt
operating apparatus 40 so as to manually tilt the propulsion unit
main body 15. In the present embodiment, an annular space between
the outer cylinder 21A and the inner cylinder 21B and a bottom side
space of the inner cylinder 21B communicated with the annular space
by a communicating passage 51 form a series of pressure
accumulating chambers 50 in the inner portion of the cylinder 21. A
free piston 52 constituting gas-liquid separating means is arranged
between the pressure accumulating chamber 50 and the piston side
chamber 32 in the inner portion of the inner cylinder 21B.
Reference numeral 52A denotes an O-ring. The pressure accumulating
chamber 50 may be wholly formed as a gas chamber 50A, however, in
accordance with the present embodiment, the structure is made such
that an oil chamber 50B is provided in a lower portion of the gas
chamber 50A and the whole of the gas chamber 50A and the oil
chamber 50B constitutes the pressure accumulating chamber 50. The
pressure accumulating chamber 50 applies a gas pressure generated
in the gas chamber 50A when opening the switching valve 42 of the
tilt operating apparatus 40 to both sides of the piston 23 via the
working fluid, and reduces the tilt-up load by an assist force
obtained by multiplying a cross sectional area of the piston rod 22
by the gas pressure. The cross sectional area corresponds to a
difference between both side pressure receiving areas of the piston
23. Further, the pressure accumulating chamber 50 compensates a
capacity change of the rod side chamber 31 and the piston side
chamber 32 caused in accordance with forward and rearward movements
of the piston rod 22 with respect to the rod side chamber 31 and
the piston side chamber 32 of the cylinder 21, on the basis of
expansion and compression of the gas chamber 50A (upward and
downward movements of the free piston 52).
[0027] The tilt device 20 has the following structure in order to
secure a rising up performance of the propulsion unit main body 15
due to collision with an obstacle such as drifting wood or the
like. In accordance with the present embodiment, the structure is
made such that a free piston 61 is arranged in an annular space
between the outer cylinder 21A and the inner cylinder 21B of the
cylinder 21. An opposite side of the rod guide 24 with respect to
the free piston 61 in the annular space forms the pressure
accumulating chamber 50, and a side of the rod guide 24 forms a
liquid discharging chamber 60. Reference numerals 61A and 61B
denote an O-ring. Further, an absorber valve 62 (a spring bearing
62A, a spring 62B and a spring holder 62C) and a return valve 63
are provided in the rod guide 24 (FIG. 4). The absorber valve 62
can be opened when the oil in the rod side chamber 31 is increased
to a level equal to or more than a predetermined value such as
under application of an impact force generated by collision with an
obstacle such as drifting wood or the like. The absorber valve 62
can feed the oil in the rod side chamber 31 to the liquid
discharging chamber 60, and can extend the piston rod 22 and the
piston 23 so as to raise the propulsion unit main body 15 up. The
return valve 63 can be opened when the oil in the liquid
discharging chamber 60 is increased to a level equal to or more
than a predetermined value via the piston side chamber 32 and the
pressure accumulating chamber 50 under application of an empty
weight of the propulsion unit main body 15 tilted up after
absorbing the impact force generated by the collision with the
obstacle. Oil in the liquid discharging chamber 60 can return to
the rod side chamber 31, and can compress the piston rod 22 and the
piston 23 so as to return the propulsion unit main body 15 to a
position before rising up. The free piston 61 is brought into
contact with the end surface of the rod guide 24 so as to make the
capacity of the liquid discharging chamber 60 zero before absorbing
the impact force. The free piston 61 moves apart from the end
surface of the rod guide 24 at a degree corresponding to the
capacity of the oil which the absorber valve 62 feeds from the rod
side chamber 31 for absorbing the impact force (the capacity of the
liquid discharging chamber 60 becomes the capacity of the oil). The
free piston 61 returns all of the oil from the return valve 63 to
the rod side chamber 31 after absorbing the impact force so as to
be brought into contact with the end surface of the rod guide 24.
Further, the free piston 61 returns the piston rod 22 and the
piston 23 to the position before absorbing the impact force and
coincides the return position of the propulsion unit main body 15
with the staying position before jumping up.
[0028] In this case, the tilt device 20 is provided with an
operating valve 64 (a spring bearing 64A, a spring 64B and a spring
holder 64C) in the piston 23. The operating valve 64 is opened when
the oil pressure in the piston side chamber 32 is increased to a
level equal to or more than a predetermined value such as a case
that a forward propelling force equal to or more than a
predetermined value is applied under a condition of shipping over a
shoal in which the propulsion unit main body 15 is kept at an
optional middle tilt position. Accordingly, the piston rod 22 moves
forward to the cylinder 21 so as to be compressed, and the
propulsion unit main body 15 is downed to a down position and
becomes a normal shipping state.
[0029] A description will be given below of contents of the
operation of the tilt device 20.
[0030] (A) Normal Shipping
[0031] A description will be given of a reverse lock state keeping
the tilt device 20 at a tilt down position shown in FIG. 5 at a
normal shipping time. In this case, the operating portion 47 of the
tilt operating apparatus 40 sets the switching valve 42 to a closed
position, and the propulsion unit main body 15 abuts the front end
portion of the swivel bracket 14 to the forward movement keeping
portion of the clamp bracket 12, whereby the propulsion unit main
body 15 is kept at the normal shipping position.
[0032] In the case of setting the propulsion unit main body 15 to
the normal shipping position and shipping forward, the forward
movement propelling force is supported by the forward movement
keeping portion of the clamp bracket 12, and the tilt device 20 is
held at the tilt down position. On the other hand, at a rearward
shipping time, a tensile force is applied to the piston rod 22 due
to the rearward movement propelling force and the pressure of the
rod side chamber 31 is increased, however, the absorber valve 62 is
not opened by the pressure increased of this degree, and the tilt
device 20 is held at the tilt down position.
[0033] (B) Shipping over Shoal
[0034] In shipping over the shoal, it is necessary to change the
tilt device 20 from a tilt down position shown in FIG. 5 to a
middle tilt position shown in FIG. 6 so as to prevent the
propulsion unit main body 15 from hitting the bottom of the sea or
river. In this case, the switching valve 42 is opened by the
operating portion 47 of the tilt operating apparatus 40 in the
manner mentioned above so as to communicate the rod side chamber 31
with the piston side chamber 32. Accordingly, the piston rod 22 and
the piston 23 freely move in a vertical direction with respect to
the cylinder 21. Therefore, it is possible to manually set the
propulsion unit main body 15 to a desired middle tilt position. At
this time, the gas pressure in the pressure accumulating chamber 50
assists the tilt-up load as mentioned above, whereby the tilt-up
operation can be easily performed.
[0035] The piston rod 22 and the piston 23 are in an unmovable tilt
lock state with respect to the cylinder 21 by closing the switching
valve 42 in accordance with the operating portion 47 of the tilt
operating apparatus 40 in a state of setting the propulsion unit
main body 15 to the middle tilt position so as to make the rod side
chamber 31 not communicated with the piston side chamber 32.
Accordingly, it is possible to ship over the shoal. In this case,
at a time of landing the hull, it is possible to set the propulsion
unit main body 15 to the middle tilt position in the same manner as
mentioned above.
[0036] In this case, in order to again position the propulsion unit
main body 15 at the tilt-down position, the switching valve 42 is
again opened by the operating portion 47 of the tilt operating
apparatus 40 so that the propulsion unit main body 15 slowly
returns to the tilt-down position due to the empty weight.
[0037] (C) Collision of Drifting Wood at Rearward Shipping over
Shoal
[0038] If an obstacle such as drifting wood or the like collides
with the propulsion unit main body 15 and an impact force directed
towards a front portion of the hull is applied to the lower portion
of the propulsion unit main body 15 at a time of rearward shipping
over the shoal in a state of setting the tilt device 20 to the
middle tilt position shown in FIG. 6, the compressing force is
applied to the piston rod 22, and the pressure of the oil in the
piston side chamber 32 is increased. When the oil pressure reaches
a level equal to or more than a predetermined value, the operating
valve 64 provided in the piston 23 is opened so as to absorb the
impact, the piston rod 22 enters into the cylinder 21 so as to be
compressed, and the propulsion unit main body 15 is downed in a
tilt-down direction.
[0039] (D) Change from Shipping over Shoal to Normal Shipping
[0040] In the case of setting the tilt device 20 to the middle tilt
position shown in FIG. 6 so as to ship over the shoal and
thereafter ship offshore and change the propulsion unit main body
15 to the tilt-down position to perform a normal shipping, the
forward propelling force of the propulsion unit main body 15 is
increased. The propulsion unit main body 15 is applied a force
forward the hull due to the propelling force, so that a compressing
force is applied to the piston rod 22 and the pressure of the oil
in the piston side chamber 32 is increased. When the oil pressure
reaches a level equal to or more than a predetermined value, the
operating valve 64 provided in the piston 23 is opened, the piston
rod 22 enters into the cylinder 21 so as to be compressed, and the
propulsion unit main body 15 is positioned at the tilt-down
position.
[0041] (E) Collision of Drifting Wood at Forward Shipping
[0042] If an obstacle such as drifting wood or the like collides
with the propulsion unit main body 15 and an impact force directed
to a rear portion of the hull is applied to the lower portion of
the propulsion unit main body 15 when shipping forward with the
tilt device 20 set to the tilt-down position shown in FIG. 5 or the
middle tilt position shown in FIG. 6, the tensile force is applied
to the piston rod 22, and the pressure of the oil in the rod side
chamber 31 is increased. When the oil pressure reaches a level
equal to or more than a predetermined value, the absorber valve 62
provided in the rod guide 24 is opened so as to absorb the impact
force, the piston rod 22 moves out of the cylinder 21 so as to be
expanded, the tilt device 20 is upped to the tilt-up position shown
in FIG. 7, and the propulsion unit main body 15 is jumped up. At
this time, the oil which the absorber valve 62 discharges from the
rod side chamber 31 is fed to the liquid discharging chamber 60,
and the free piston 61 moves apart from the end surface of the rod
guide 24 at a degree corresponding to the capacity of the oil.
[0043] After the propulsion unit main body 15 is jumped up, the
pressure of the piston side chamber 32 is increased due to the
empty weight of the tilted-up propulsion unit main body 15, and the
pressure increases the pressure in the liquid discharging chamber
60 via the pressure accumulating chamber 50. When the pressure in
the liquid discharging chamber 60 is increased to a level equal to
or more than a predetermined value, the return valve 63 is opened
so as to return the oil in the liquid pressure chamber 60 to the
rod side chamber 31. Accordingly, when the free piston 61 is
brought into contact with the end surface of the rod guide 24, the
absorber valve 62 returns all of the oils fed to the liquid
discharging chamber 60 due to the impact absorption to the rod side
chamber 31, so that the tilt device 20 returns to the position
before absorbing the impact, and the propulsion unit main body 15
returns to the position before jumping up.
[0044] In accordance with the present embodiment, the following
effects can be obtained.
[0045] (1) Since the pressure accumulating chamber 50 is formed in
the space between the outer cylinder 21A and the inner cylinder 21B
in the cylinder 21, it is possible to form the pressure
accumulating chamber 50 with a large capacity in a wide range in a
longitudinal direction of the cylinder 21, and the capacity of the
pressure accumulating chamber 50 can be increased while the tilt
device 20 is compact, whereby a gas assist performance can be
improved.
[0046] (2) Since the free piston 52 corresponding to the liquid-gas
separating means is interposed between the pressure accumulating
chamber 50 and the piston side chamber 32, the gas in the pressure
accumulating chamber 50 does not feed to the piston side chamber 32
and further to the rod side chamber 31 through the switching valve
42 even when the tilt device 20 takes any mounting attitude such as
a normal or reverse position. Accordingly, the pressure
accumulating chamber 50 can maintain a sufficient gas capacity, no
gas is mixed to the working fluid in the piston side chamber 32 and
the rod side chamber 31, and it is possible to secure a stable gas
assist function at a time of opening the switching valve 42 and
secure a stable tilt-lock function at a time of closing the
switching valve 42. That is, it is possible to secure an improved
operability while keeping a freedom in the mounting direction.
[0047] (3) The absorber valve 62 and the return valve 63 are in the
rod guide 24 and have a diameter larger than that of the piston 23
in the complex cylinder type cylinder 21. Accordingly, since it is
possible to receive the absorber valve 62 and the return valve 63
in the rod guide 24 with room without increasing the diameter of
the rod guide 24 and it is possible to make the diameter of the
piston 23 small, it is possible to jump up the propulsion unit main
body 15 against the collision of drifting wood while making the
cylinder 21 small-diameter and compact.
[0048] (4) In connection with the matter that the absorber valve 62
and the return valve 63 are provided in the rod guide 24, the free
piston 61 for coinciding the returning position after jumping up of
the propulsion unit main body 15 with the staying position before
rising up is provided in the space between the outer cylinder 21A
and the inner cylinder 21B in the cylinder 21. The liquid
discharging chamber 60 for the fluid discharged from the absorber
valve 62 is formed in the rod guide 24 side from the free piston 61
in the space. Accordingly, it is possible to coincide the returning
position of the propulsion unit main body 15 jumped up due to the
collision of drifting wood with the staying position before rising
up.
[0049] (5) Since the switching valve 42 is provided in the piston
rod 22 or the piston 23 and the operating portion 47 of the
switching valve 42 is provided in the portion protruding from the
cylinder 21 of the piston rod 22, it is possible to reduce a
lateral size of the tilt device 20 and make the tilt device 20
compact.
[0050] (6) Since the absorber valve 62 and the return valve 63 in
the items (3) and (4) are not provided in the piston rod 22 or the
piston 23 but in the rod guide 24 at a time of providing the
switching valve 42 in the piston rod 22, it is possible to easily
place the switching valve 42 without increasing the diameter of the
piston 23.
[0051] As heretofore explained, embodiments of the present
invention have been described in detail with reference to the
drawings. However, the specific configurations of the present
invention are not limited to the embodiments but those having a
modification of the design within the range of the present
invention are also included in the present invention.
[0052] As mentioned above, in accordance with the present
invention, the tilt device for a marine propulsion unit provided
with a gas assist function can increase the capacity of a pressure
accumulating chamber while being compact and can secure a jump-up
performance of a propulsion unit main body caused by a collision
with drifting wood.
[0053] Although the invention has been illustrated and described
with respect to several exemplary embodiments thereof, it should be
understood by those skilled in the art that the foregoing and
various other changes, omissions and additions may be made to the
present invention without departing from the spirit and scope
thereof. Therefore, the present invention should not be understood
as limited to the specific embodiment set out above, but should be
understood to include all possible embodiments which can be
embodied within a scope encompassed and equivalents thereof with
respect to the features set out in the appended claims.
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