Internal-combustion engines – Vibration compensating device – Balancing arrangement
Reexamination Certificate
2002-12-11
2004-07-06
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Vibration compensating device
Balancing arrangement
C123S1960CP
Reexamination Certificate
active
06758183
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to joint structures for an oil pump shaft and a balancer shaft, and more particularly to a joint structure for an oil pump shaft and a balancer shaft with which a joint thereof can be seen from the outside.
In a conventional joint structure for an oil pump shaft and a balancer shaft, two balancer shafts and an oil pump shaft are arranged in parallel with one another. A driving sprocket fixed on an end portion of a crankshaft of an engine is connected with a driven sprocket fixed on one of the balancer shafts (hereinafter referred to as input-side balancer shaft) through an endless chain, and thereby a driving force from the crankshaft is transmitted to the input-side balancer shaft. Thus-transmitted driving force is in turn transmitted from the input-side balancer shaft to the other balancer shaft (hereinafter referred to as output-side balancer shaft) through gears fixed on the both balancer shafts and engaged with each other to synchronously rotate.
The oil pump shaft that is joined to the output-side balancer shaft is thus driven to rotate together with the output-side balancer shaft, and as the oil pump shaft rotates, an inner rotor of an oil pump provided integrally with the oil pump shaft also rotates accordingly. With the inner rotor of the oil pump rotating, reservoir oil stored in an oil pan is supplied to each section of the engine, which includes the input-side balancer shaft, the output-side balancer shaft, the oil pump shaft, and the crankshaft.
A ratio of the number of teeth of the driving sprocket to that of the driven sprocket is 2:1, whereas a gear ratio of the gears of each balancer shaft is 1:1. Accordingly, the input-side balancer shaft and the output-side balancer shaft are driven to rotate twice as high a rotational speed as the crankshaft.
As a result, plural weights of which the centers of gravity are shifted from the center of rotation of each balancer shaft are driven to rotate at an angular speed twice as fast as the crankshaft, producing a reverse force that serves to cancel a secondary oscillation of the engine derived from reciprocating motion of a piston of the engine.
As shown in
FIG. 8
, an oil pump
110
as one example of the above-described conventional arrangement includes a joint shaft
115
made by integrally joining an input shaft portion
115
a
for driving an inner rotor
111
to rotate, and an output-side balancer shaft
115
b
. The input shaft portion
115
a
of the joint shaft
115
is inserted from the direction of a balancer shaft housing
112
with an upper balancer shaft housing
112
a
thereof detached from a lower balancer shaft housing
112
b
thereof, and is fitted into an bearing hole
113
of an oil pump housing
110
a
. The inner rotor
111
is then mounted on the input shaft portion
115
a
of the oil pump
110
; thereafter, the upper balancer shaft housing
112
a
and an oil pump cover
110
b
are attached to the lower balancer shaft housing
112
b
and the oil pump housing
110
a
, respectively.
However, with the conventional joint structure as discussed above, a joint portion where the inner rotor
111
and the input shaft portion
115
a
are joined together is hidden behind the oil pump housing
110
a
and the balancer shaft housing
112
, and thus disadvantageously cannot be seen from the outside; consequently, the input shaft portion (oil pump shaft)
115
a
and the output-side balancer shaft (balancer shaft)
115
b
could not be joined together with ease.
Therefore, the present invention has been made in order to eliminate the aforementioned disadvantages.
SUMMARY OF THE INVENTION
It is an exemplified general object of the present invention to provide a joint structure for an oil pump shaft and a balancer shaft in which a joint portion of the oil pump shaft and the balancer shaft can be seen from the outside.
According to one exemplified aspect of the present invention, there is provided a joint structure for an oil pump shaft and a balances shaft in which the balancer shaft supported in a bearing portion is coaxially joined to an end portion of the oil pump shaft protruding from an oil pump housing. A housing joint portion that joins the oil pump housing and the bearing portion with a predetermined spacing allowed therebetween is provided below a shaft joint portion where the oil pump shaft and the balancer shaft join together. The above predetermined spacing is set so that the shaft joint portion is disposed between opposed surfaces of the oil pump housing and the bearing portion.
With this joint structure, space between the oil pump housing and the bearing portion is open to an operator, so that the operator can join the oil pump shaft and the balancer shaft together while seeing the end portion of the oil pump shaft from the outside.
Preferably, the shaft joint portion is comprised of a pair of engageable portions of the oil pump shaft and the balancer shaft, and the engageable portions are engageable with each other in a radial direction thereof. A pair of protuberances that guide the engageable portion of the balancer shaft to the engageable portion of the oil pump shaft to make the engageable portions engaged with each other may be provided on the surface of the oil pump housing opposite to the bearing portion of the balancer shaft in such a manner that the protuberances sandwich the end portion of the oil pump shaft.
This structure allows the opposed surfaces of the protuberances to guide the engageable portion of the balancer shaft toward the engageable portion of the oil pump shaft so that these engageable portions may be engaged with each other, and thus facilitates the joining operation of the engageable portions of the oil pump shaft and the balancer shaft.
Moreover, the above pair of protuberances may preferably be designed to lap the engageable portion of the balancer shaft in axial directions of the balancer shaft.
This structure has the oil pump housing formed utilizing space at both sides of the balancer shaft, and thus can realize a compact and lightweight body of the oil pump.
The above bearing portion may preferably be designed to be separable into a first part and a second part, so that only attaching the second part to the first part provided with the housing joint portion after engaging the balancer shaft with the oil pump shaft can finalize a joining operation of the oil pump shaft and the balancer shaft, and thus can considerably improve total operating efficiency.
The above first and second parts of the bearing portion may be fastened together with a bolt fitted in a boss provided outside the protuberances. Provision of the boss outside the protuberances allows the operator to more easily perform the operation of fitting the engageable portion of the balancer shaft into the engageable portion of the oil pump shaft.
The above joint structure for an oil pump shaft and a balancer shaft may further includes a pump cover openably attached to the oil pump housing, a tubular oil discharge port provided in the pump cover, and a tensioner that provides a predetermined level of tension to an endless chain in a gearing for transmitting a driving force from a crank shaft of an engine to the oil pump shaft, whereas a tensioner body of the tensioner is integrally mounted on a tensioner mount portion that is integrally formed on a periphery of the tubular oil discharge port. This construction can serve to reinforce the pump cover, particularly the tubular oil discharge port thereof, thanks to the tensioner mount portion integrally formed with the oil discharge port.
The oil discharge port may preferably be formed to have an outlet thereof oriented in a direction perpendicular to a longitudinal direction of the engine and to have a shape compressed in the longitudinal direction of the engine. With this construction, an amount of overhanging of the endless chain can be reduced, so that a compact structure thereof can be achieved.
Other objects and further features of the present invention will become readily apparent from the following description of pr
Endo Yusuke
Fujiki Kenji
Kudo Hirotsugu
Armstrong Kratz Quintos Hanson & Brooks, LLP
Honda Giken Kogyo Kabushiki Kaisha
Kamen Noah P.
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