Shift mechanism of outboard engine

Information

  • Patent Grant
  • 6401560
  • Patent Number
    6,401,560
  • Date Filed
    Thursday, June 29, 2000
    24 years ago
  • Date Issued
    Tuesday, June 11, 2002
    22 years ago
Abstract
A shift mechanism of an outboard engine has a shift cam which is remotely-operable to effect change-over of the direction of rotation of a propeller shaft in a gear case. A shift cam support member is a member separate from and detachably secured to the gear case. The shift mechanism permits use of a single design of the gear case adapted to either a rotary shift cam or a vertically-movable shift cam.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to a shift mechanism of an outboard engine.




2. Description of the Related Art




A conventional outboard engine has a shift mechanism which is remotely-operable to change the direction of rotation of a propeller shaft between “forward” and “reverse” passing through a “neutral” state in the process. To enable such a change-over of direction of rotation, the propeller shaft has a push rod incorporated therein. The push rod is moved back and forth to bring a shift dog into and out of engagement with the propeller shaft. This arrangement is generally known as a “shift-in and shift-out” structure. A shift cam is typically used as means for effecting the back-and-forth movement of the push rod.




The shift cam has a cam profile which is defined by three curved recesses that are smoothly connected one to another. These three recesses correspond to three shift positions, i.e., the “forward”, “reverse” and “neutral” states, of the shift mechanism. The above-mentioned push rod is normally spring-biased towards the cam, so as to rest in one of the three recesses, thus selecting one of the three shift positions.




There are two types, of the shift cam: a vertically-movable shift cam which moves up and down to bring different recesses into engagement with the push rod; and a rotational shift cam which rotates within a horizontal plane. The rotational shift cam imparts to the operator a better feel of manipulation and is used mainly for large-sized outboard engines.




The shift cam is supported by a shift cam support portion which is disposed in, and formed integrally with, a gear case, regardless of the type of the shift cam.




The rotational shift cam and the vertically-movable shift cam have different structures and, hence, require different designs of the shift cam supporting structure. This means that one design of the gear case cannot be used commonly both for the rotational shift cam and the vertically-movable shift cam, due to the difference of the design of the shift cam supporting structure which is formed integrally with the gear case. Thus, manufacturers are obliged to prepare two types of gear case of different designs. This in turn requires troublesome work for the administration of the gear cases in the production process.




For instance, the following problems are encountered due to the difference between the two types of the shift cam. A vertically-movable shift cam is generally provided with a link mechanism in an engine room covered by an engine cover. It may be impossible to find space for accommodating such a link mechanism within the engine room, due to, for example, a change in the design specifications of the outboard engine. One solution to this problem could be to replace the vertically-movable shift cam with a rotational shift cam which does not require any link mechanism such as that used for the vertically-movable shift cam. This solution, however, imposes additional cost due to the necessity for a gear case which is designed exclusively for the rotary shift cam.




In general, the shift cam supporting portion is formed on the innermost portion of a gear case. This makes it difficult to mount and demount the shift cam.




OBJECTS AND SUMMARY OF THE INVENTION




In view of the foregoing, it is an object of the present invention to provide a shift mechanism of an outboard engine which permits the use of a single type of gear case either with a vertically-movable shift cam or a rotational shift cam.




To this end, according to the present invention, there is provided a shift mechanism of an outboard engine, comprising: a remotely-operable shift cam for effecting change-over of the direction of rotation of a propeller shaft within a gear case; and a shift cam support member disposed in the gear case and detachably secured to the gear case and supporting the shift cam.




The shift cam support member may be a forward gear bearing housing for holding a bearing which supports a forward driven gear.




Alternatively, the shift cam support member may be a shift cam housing which is a member formed separately from and detachably secured to the gear case.




The shift mechanism may further comprise a detent mechanism provided on the shift cam support member.




The shift mechanism may also further comprise a bearing which is provided in the shift cam housing and which supports a shift rod for rotating the shift cam.




Preferably, the shift cam mechanism has been assembled by inserting the shift cam housing together with the shift can mounted therein, forwardly into the gear case and detachably securing the shift cam housing to the gear case.




The above and other objects, features and advantages of the present invention will become clear from the following description of a preferred embodiment with reference to the accompanying drawings.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a side view of an outboard engine incorporating an embodiment of the shift mechanism of the present invention, as viewed from the port side, with certain internal elements shown in dashed line.





FIG. 2

is an enlarged sectional view of a gear case used in the embodiment of FIG.


1


.





FIG. 3

is a sectional view taken along the line III—III of FIG.


2


.





FIG. 4

is an enlarged sectional view of a gear case used in a second embodiment of the present invention.





FIG. 5

is an enlarged sectional view of a gear case used in a third embodiment of the present invention.





FIG. 6

is an illustration of the gear case of

FIG. 5

as viewed in the direction of an arrow VI.





FIG. 7

is an enlarged sectional view of a gear case used in a fourth embodiment of the present invention.





FIG. 8

is an illustration of the gear case of

FIG. 7

as viewed in the direction of an arrow VIII.











DESCRIPTION OF THE PREFERRED EMBODIMENT




Preferred embodiments of the present invention will be described with reference to the accompanying drawings.




Referring first to

FIG. 1

an outboard engine, shown generally at


1


, has an engine holder


2


on which is mounted an engine unit


3


. The engine unit


3


is a so-called vertical engine with a crankshaft


4


extending substantially vertically.




An oil pan


5


is disposed beneath the engine holder


2


. A clamp bracket


6


, attached to the engine holder


2


for example, clamps to a transom of the boat's hull (not shown), whereby the outboard engine


1


is secured to the hull. The engine unit


3


and the engine holder


2


are covered by an engine cover


7


.




A drive shaft housing


8


is provided below the oil pan


5


. A drive shaft


9


extends substantially vertically through the engine holder


2


, oil pan


5


and the drive shaft housing


8


. The drive shaft


9


is connected at its upper end to the lower end of the crankshaft


4


. The drive shaft


9


extending downward through the drive shaft housing


8


drives, through bevel gears


11


disposed in a gear case


10


under the drive shaft housing


8


and through a propeller shaft


12


, a propeller


13


which propels a boat or the like.




The outboard engine


1


is provided with a remote-controlled shift mechanism


14


in the four embodiments of the invention. The embodiments are detailed in


14


A (first embodiment of FIG.


3


),


14


B (second embodiment of FIG.


4


),


14


C (third embodiment of FIG.


5


), or


14


D (fourth embodiment of FIG.


7


). The remote-controlled shift mechanism


14


effects change-over of the direction of rotation of the propeller shaft


12


from “forward” to “reverse” via a “neutral” state, and vice versa.




Referring now to

FIGS. 2 and 3

, the shift mechanism


14


A of this embodiment has major parts including a shift rod


15


, a shift rod


16


, an assist device


17


, a shift cam


18


A, a push rod


19


and a shift dog


20


. This shift mechanism is a rotary-type mechanism which effects the change-over of the shift position through horizontal rotation of the shift cam


18


A.




The shift rod


15


extends towards the gear case


10


from, for example, a position in the engine cover


7


near the engine unit


3


. The shift rod


15


is connected to the shift rod


16


via an assist device


17


which is disposed in the portion of the gear case


10


adjoining the drive shaft housing


8


and which incorporates a detent mechanism


21


. When an operator on board manipulates a shift lever (not shown) or the like, the motion of the shift lever is converted into a rotational motion of the shift rod


15


which is then transmitted to the shift rod


16


.




The shift cam


18


A is fixed to the lower end of the shift rod


16


to rotate together with the shift rod


16


. As will be seen from

FIG. 3

, the shift cam


18


A has a cam profile composed of three consecutive curved recesses


22


which respectively correspond to the “forward” (F), “neutral” (N) and the “reverse” ®) shift positions. These recesses have bottoms that are at different radial directions from the axis of rotation of the shift cam


18


A. The push rod


19


is received in a bore formed in the propeller shaft


12


, so as to be movable in the direction of the axis of the propeller shaft


12


. The push rod


19


is always biased by a spring


23


against the shift cam


18


, so that the end of the push rod


19


is urged into one of the recesses


21


of the shift cam


18


A, whereby the shift mechanism


14


is set to one of the three shift positions.




The aforementioned bevel gears


11


include a forward driven gear


24


and a reverse driven gear


25


which are rotatably carried by the propeller shaft


12


through bearings


26


and


27


. These driven gears


24


and


25


are always held in driving engagement with a drive gear


28


fixed to the lower end of the drive shaft


9


. The shift dog


20


on the outer peripheral portion of the propeller shaft


12


drivingly connects either one of the forward driven gear


24


and the reverse driven gear


25


to the propeller shaft


12


, while disconnecting the other from the same, in accordance with the axial position of the push rod


19


. The shift dog


20


also holds the shift mechanism


14


in the neutral state in which both the forward and reverse driven gears


23


and


24


are freed from the propeller shaft


12


.




As will be seen from

FIGS. 2 and 3

, the bearing


26


which supports the forward driven gear


24


of the bevel gears


11


is held by a forward gear bearing housing


29


A which is a supporting member detachably secured to the gear case


10


. Likewise, the bearing


27


which supports the reverse driven gear


25


of the bevel gears


11


is held by a reverse gear bearing housing


30


which is detachably secured to the gear case


10


. The forward gear bearing housing


29


A has an integral support portion


31


A which supports the shift cam


18


A.




Referring now to

FIG. 4

, a shift mechanism


14


B of the second embodiment has major components such as a shift rod (not shown), a shift rod


16


, a shift cam


18


B, a push rod


19


and a shift dog


20


. This shift cam mechanism is a vertical-motion-type mechanism in which the shift cam


18


B is moved up and down.




The shift cam


18


B is integrally attached to the lower end of the shift rod


16


. The shift cam


18


B has a rear face which includes a can profile having three consecutive recesses


22


. An end of the push rod


19


engage one of the three recesses


22


of the shift cam


18


B as the shift cam


18


B is moved up or down.




The bearing


26


, which supports the forward driven gear


24


of the bevel gears


11


, is held by a forward gear bearing housing


19


B which is a support member detachably secured to the gear case


10


. Likewise, the bearing


27


which supports the reverse driven gear


25


of the bevel gears


11


is held by a reverse gear bearing housing


30


which is detachably secured to the gear case


10


. The forward gear bearing housing


29


B includes an integrally formed support portion


31


B which supports the shift cam


18


B. The support portion


31


B is provided with the detent mechanism


21


.




The detent mechanism


21


provided means for holding the shift cam


18


B in the neutral position. For instance, the detent mechanism


21


may include a rigid ball


33


which is urged by a spring


34


into a recess


32


the front side of the shift cam


18


B.




Referring now to

FIGS. 5 and 6

, the shift mechanism


14


C of the third embodiment is a rotary-type mechanism which is similar to the shift mechanism


14


A of the first embodiment. The embodiment of

FIGS. 5 and 6

differs from the first embodiment in the following respects. In the first embodiment, the bearing


26


in support of the forward driven gear


24


of the bevel gears


11


is held by the forward gear bearing housing


29


A which is detachably secured to the gear case


10


, and the support portion


31


A for supporting the shift cam


18


A is integrally formed on the forward gear bearing housing


29


A. In contrast, in the shift mechanism of the third embodiment, the bearing


26


in support of the forward driven gear


24


fits in a mating portion


35


formed in the gear case


10


integrally therewith, while the shift cam denoted by


18


C is supported by a shift cam housing


36


C which is a support member formed as a member separate from the gear case


10


.




For instance, the arrangement may be such that the shift cam housing


36


C is inserted toward the front into the gear case


10


through a shaft hole


37


formed in a rear part of the gear case


10


and is detachably secured to the gear case by means of, for example, bolts


38


.




The shift cam housing


36


C is inserted into the gear case


10


after the shift cam


18


C is mounted in the shift cam housing


36


C. After the insertion and fixation of the shift cam housing


36


C, the shift rod


16


is inserted downward into the gear case


10


and is connected to the shift cam


18


C. The shift cam housing


36


C is provided therein with a bearing


39


that supports the shift rod


16


.




Referring now to

FIGS. 7 and 8

, a shift mechanism of the fourth embodiment, denoted by


14


D, is of the vertical-motion-type mechanism which is similar to shift mechanism


14


B of the second embodiment.




The fourth embodiment is distinguished from the second embodiment in the following respects. In the second embodiment, the bearing


26


in support of the forward driven gear


24


of the bevel gears


11


is held by the forward gear bearing housing


29


B which is detachably secured to the gear case


10


, and the support portion


31


B for supporting the shift cam


18


B is integrally formed on the forward gear bearing housing


29


B. In contrast, in the shift mechanism of the fourth embodiment, the bearing


26


in support of the forward driven gear


24


fits in a mating portion


35


formed in the gear case


10


integrally therewith, while the shift cam denoted by


18


D is supported by a shift cam housing


36


D which is a support member formed as a member separate from the gear case


10


.




For instance, the arrangement may be such that the shift cam housing


36


D is inserted forwardly into the gear case


10


through the shaft hole


37


formed in a rear part of the gear case


10


and is detachably secured to the gear case by means of, for example, bolts


38


.




When the shift cam housing


36


D is inserted into the gear case


10


, the shift cam


18


D has been mounted in the shift cam housing


36


D. After the insertion and fixation of the shift cam housing


36


D, the shift rod


16


is inserted downward into the gear case


10


and is connected to the shift cam


18


D. The shift cam housing


36


D is provided with a detent mechanism


21


which is similar to that used in the second embodiment.




A description will now be given of the operations of the illustrated embodiments.




An operator of a boat manipulates a shift lever (not shown) of, for example, the shift mechanism


14


A of the first embodiment (FIG.


2


), so that the shift rod


15


and, hence, the shift rod


16


are rotated, thereby rotating the shift cam


18


A fixed to the lower end of the shift rod


16


. As a result of the rotation of the shift cam


18


A, the end of the push rod


19


that has been held in engagement with one of the recesses


22


is caused to engage another recess


22


adjacent to the first-mentioned recess


22


. Since the radial distances of the bottoms of these recesses


22


from the axis of rotation of the shift cam


18


are different, the push rod


19


is moved within the propeller shaft


12


along the axis of the propeller shaft, thereby selectively connecting one of the bevel gears


11


with the propeller shaft or disconnecting these bevels gears


11


from the propeller shaft.




In the first embodiment as described, as well as in the second embodiment, the forward gear bearing housing


29


A (


29


) for holding the bearing


26


in support of the forward driven gear


24


of the bevel gears


11


is detachably secured to the gear case


10


, and the support portion


31


A (


311


B) for supporting the shift cam


18


A (


18


B) is integrally formed on the forward gear bearing housing


29


A (


29


B). With this arrangement, a single gear case


10


can be adapted for either of the two different types of the shift cam, i.e., the rotational shift cam and the vertically-movable shift cam, simply by replacing the forward gear bearing housing


29


A (


29


B).




In the third embodiment as described, as well as in the fourth embodiment, the bearing


26


in support of the forward driven gear


24


fits in the mating portion


35


formed in the gear case


10


integrally therewith, and the shift cam


18


C (


18


D) is supported by the shift cam housing


36


C (


36


D) which is formed as a member separate from the gear case


10


. With this arrangement, a single gear case


10


is adapted for either of the two different types of the shift cam, i.e., the rotational shift cam and the vertically-movable shift cam, simply by replacing the shift cam housing


36


C (


36


D).




As will be understood from the foregoing description, according to the present invention, different types of the shift cam (rotational shift cam and vertically-movable shift cam) are easily assembled with the same design of he gear case


10


, because the shift cam


18


A(


18


B,


18


C,


18


D) is supported by a shift cam support member, i.e., the forward gear bearing housing


29


A(


29


B) or the shift cam housing


36


C(


36


D), which is prepared as a member separate from the gear case


10


and detachably secured to the gear case


10


.




This eliminates the necessity for the two different types of gear case


10


which hitherto have been necessarily prepared corresponding to two types of shift cams


18


A,


18


C and


18


B,


18


D. Thus, the manufacturers are required to prepare only one type of the gear case and, hence, can save the cost that has been incurred for the molding of two types of the gear case. At the same time, it becomes unnecessary to assign two different parts numbers that have been employed to enable identification of the two types of gear case. This also eliminates the necessity for two different storage spaces for the gear case, thus facilitating storage and administration of the gear cases.




As stated before, a problem occurs when the space inside the engine room is reduced by a change in the design specifications of the outboard engine


1


, so that the space for accommodating a link mechanism (not shown) associated with the vertical-motion-type shift cam


18


B(


18


D) is not available in the engine room. This problem, however, is easily overcome by the present invention which permits replacement of the vertical-motion-type shift cam


18


B(


18


D) with a rotary shift cam


18


A(


18


C) simply by the replacement of the forward gear bearing housing


29


A(


29


B) or the shift cam housing


36


C(


36


D). This effectively serves to reduce the production cost.




Furthermore, in accordance with the present invention, a member which is separate from and detachably secured to the gear case


10


, i.e., the forward gear bearing housing


29


A(


29


B) or the shift cam housing


36


C(


36


D), supports the shift cam


18


A(


18


C) or


18


B(


18


D). This simplifies the arrangement of cores of the mold for molding the gear case


10


, thus contributing to further reduction in the production cost.




Referring specifically to the third and fourth embodiments, the assembly of the shift mechanism is facilitated and the time required for the assembly work is shortened, because the shift mechanism can be completed by forwardly inserting the shift cam housing


36


C(


36


D) together with the shift cam


18


C(


18


D) mounted therein and fixing the shift cam housing


36


C(


36


D) to the gear case


10


, through the shaft hole


37


formed in the rear part of the gear case


10


, followed by the insertion and connection of the shift rod


16


to the shift cam


18


C(


18


D) from the upper side of the gear case


10


.




In the third embodiment as described, the shift cam housing


36


C which is in support of the rotary shift cam


18


C is provided therein with the bearing


39


for supporting the shift rod


16


. This ensured smooth rotation of the shift rod


16


, as well as rigidity of the supporting structure, thus offering better feel of the shifting operation.




In the second embodiment, as well as in the third embodiment, the shift cam


18


B(


18


C) can stably be set in the neutral position with a good click feel, by virtue of the detent mechanism


21


which is provided on the support portion


31


B of the forward gear bearing housing


29


B supporting the vertically-movable shift cam


18


B, or on the shift cam housing


36


D which supports the vertically-movable shift cam


18


D.




Although in the third and fourth embodiments the shift cam housing


36


C(


36


D) is inserted into the gear case


10


through the shaft hole


37


formed in the rear portion of the gear case


10


, this is not exclusive and the shift mechanism may be assembled by inserting the shift cam housing


36


C(


36


D) downward into the gear case


10


, through the top end opening of the gear case


10


at which the gear case


10


is adjoined to the drive shaft housing


8


.




As will be understood from the foregoing description, in accordance with the present invention, there is provided a shift mechanism of an outboard engine, comprising: a remotely-operable shift cam for effecting change-over of the direction of rotation of a propeller shaft within a gear case; and a shift cam support member disposed in the gear case and detachably secured to the gear case and supporting the shift cam, the shift cam support member being, for example, a forward gear bearing housing for holding a bearing which supports a forward driven gear, or a shift cam housing which is a member formed separately from and detachably secured to the gear case. With this arrangement, a single design of the gear case can easily be adapted to different types of the shift cam, i.e., a rotational shift cam or a vertically-movable shift cam. This contributes to the reduction in the production cost, while simplifying and facilitating the work for storing the gear cases, as well as the administration of the assembly process.




In a preferred form of the present invention, the shift mechanism further comprises a detent mechanism provided on the shift cam support member. This ensures that the shift mechanism is stably set to and held in the neutral state with good feel of click.




The shift mechanism can further have a bearing which is provided in the shift cam housing and which supports a shift rod for rotating the shift cam. The bearing offers an improved feel in the shifting operation.




Preferably, the shift cam mechanism has been assembled by inserting the shift cam housing together with the shift can mounted therein, forwardly into the gear case and detachably securing the shift cam housing to the gear case. This assembly process improves the efficiency of the assembly work, while shortening the time required for the assembly.




Having described preferred embodiments of the invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.



Claims
  • 1. A shift mechanism of an outboard engine comprising:a gear case; a remotely-operable shift cam for effecting change-over of a direction of rotation of a propeller shaft within said gear case; a shift cam support member disposed in said gear case and detachably secured to said gear case and supporting said shift cam; and said shift cam support member includes a forward gear bearing housing for holding a bearing which supports a forward driven gear.
  • 2. A shift mechanism of an outboard engine according to claim 1, wherein said shift cam support member comprises a shift cam housing which is a member formed separately from and detachably secured to said gear case.
  • 3. A shift mechanism of an outboard engine according to claim 1, further comprising a detent mechanism on said shift cam support member.
  • 4. A shift mechanism of an outboard engine comprising:a gear case; a remotely-operable shift cam for effecting change-over of a direction of rotation of a propeller shaft within said gear case; a shift cam support member disposed in said gear case and detachably secured to said gear case and supporting said shift cam; and a detent mechanism on said shift cam support member.
  • 5. A shift mechanism of an outboard engine comprising:a gear case; a remotely-operable shift cam for effecting change-over of a direction of rotation of a propeller shaft within said gear case; a shift cam support member disposed in said gear case and detachably secured to said gear case and supporting said shift cam; said shift cam support member including a shift cam housing which is a member formed separately from and detachably secured to said gear case; and a bearing in said shift cam housing and said bearing supporting a shift rod for rotating said shift cam.
Priority Claims (1)
Number Date Country Kind
11-280757 Sep 1999 JP
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Number Name Date Kind
2718792 Kiekhaefer Sep 1955 A
3455420 Blanchard, Jr. Jul 1969 A
3919964 Hagen Nov 1975 A
4223773 Croisant et al. Sep 1980 A
4527441 Nakahama Jul 1985 A
4579204 Iio Apr 1986 A
5006084 Handa Apr 1991 A
5059144 Onoue Oct 1991 A
Foreign Referenced Citations (3)
Number Date Country
09216600 Aug 1997 JP
10-114299 May 1998 JP
11165695 Jun 1999 JP