Internal-combustion engines – Vibration compensating device – Balancing arrangement
Reexamination Certificate
2002-10-21
2004-08-10
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Vibration compensating device
Balancing arrangement
Reexamination Certificate
active
06772725
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a balancing system for an engine, and more particularly to a housing adapted to be disposed within an oil pan for accommodating balance shafts, balance shafts for the balancing system which are each provided with a counterweight portion, and an engine oil return passage provided in the engine comprising below a crankshaft, a housing for accommodating rotatably therein balance shafts.
2. Description of the Related Art
A balancing system is publicly known in, for example, JP-A-2001-74104 in which balance shafts are disposed below a crankshaft in an oil pan, so that the rotation of the crankshaft is transferred to the balance shafts via a chain/sprocket mechanism or gear mechanism.
Because the balance shafts in the balancing system are provided below an oil level within the oil pan, the balance shafts are entirely covered with a housing in order to eliminate any inconveniences that would be caused by the agitation of oil by the balance shafts. In addition, because a large amount of oil remaining within the housing constitutes rotational resistance against the balance shafts, oil remaining within the housing must be discharged as soon as possible, and the above Japanese Unexamined Patent Publication discloses a construction in which oil within the housing is discharged by the rotating balance shafts.
In the prior art construction, however, because the oil discharge ports are constituted by slits formed in the joint surface between the upper and lower housing, the slits are submerged below the oil level. Therefore, when this construction is adopted in an engine which is installed such that axes of cylinders are inclined relative to an orientation which is normal to an axis of the crankshaft, it is conceivable that oil flows back into the housing.
In order to secure the designed amount of oil to be discharged with the oil discharge ports being provided at positions that are not submerged below the oil level or in the upper housing, the area of the discharge ports has to be increased. However, such a construction tends to reduce the rigidity of the upper housing.
Further, a balancing system is disclosed in JP-B-3-18761U in which balance shafts each provided with a counterweight portion are disposed below a crankshaft.
With the balance shafts disclosed in the Japanese Examined Utility Model Publication, thrust supporting faces provided at a journal portion of each of the balance shafts for restricting axial movements of the balance shaft are designed to slidably contact with end faces of an opening in a bearing hole. In addition, it is known that thrust supporting faces are integrally formed on the balance shafts in order to reduce the number of components.
Incidentally, because the thrust supporting faces integrally formed on the journal portion are naturally provided with a larger diameter than that of the journal portion, according to the above construction, irrespective of the position of the weight, a part of the thrust supporting face situated on the opposite side of the balance shaft to the side thereof where the weight is provided becomes like a flange, and an outer circumferential side of the part comes to have a cantilever-like construction. Thus, the rigidity of the thrust supporting face at the part tended to be insufficient.
Moreover, while engine oil which has been used to lubricate and cool a valve train provided on a cylinder head is returned to an oil pan via a return passage provided in a cylinder block or the like, it is preferable that return oil is prevented from contacting the crankshaft which rotates at high speed within a crankcase in order that atomized oil is not mixed in blow-by gas.
There are known as a method for this purpose a construction in which a pipe extending to below an oil level in the oil pan is connected to a downstream end of a return passage provided in a cylinder block and a construction in which a return passage extending to the vicinity of an oil level is provided in a crankcase (JP-A-61-113910U).
According to the conventional constructions, with the construction utilizing the pipe, because the pipe comprising a separate member is required, the number of components is increased, and moreover, the number of man hours for mounting the pipe is also increased. In addition, with the construction is which the return passage is provided in the crankcase, because a mold for the crankcase becomes complicated, and it is difficult to provide the oil discharge port at a position where the oil discharge port is always allowed to be submerged below the oil level irrespective of a change in vehicle posture or driving condition.
SUMMARY OF THE INVENTION
The present invention has been made to solve the problems inherent in the prior art.
A first object of the present invention is to provide a housing for balance shafts which can restrain the decrease in rigidity of the upper housing while securing the area of the oil discharge ports and which is improved such that oil is difficult to contact the balance shaft.
A second object of the present invention is to provide balance shafts for a balancing system for an engine which are improved so as to increase the rigidity of the flange-like thrust supporting faces.
A third object of the present invention is to provide balance shafts for a balancing system for an engine which are improved so as to suppress an increase in weight resulting from reinforcement to a minimum level.
A fourth object of the present invention is to provide an engine oil return passage which is constructed to be formed without calling for increases in the number of components and the number of man hours required for production.
In addition, a fifth object of the present invention is to provide an engine oil return passage which is constructed such that an oil discharge port can be provided at a position which is not affected by changes in vehicle posture and driving condition.
With a view to attaining the above objects, according to a first aspect of the present invention, a housing (
14
U,
14
L) for balance shafts adapted to be disposed within an oil pan (
5
) for accommodating therein balance (
13
L,
13
R) shafts comprises an upper housing (
14
U) and a lower housing (
14
L) which are divided vertically along a plane parallel to axes of the balance shafts, and oil discharge ports (
44
a
,
44
b
) and vertical walls (
47
) are provided on the upper housing which vertical walls (
47
) are provided so as to extend from portions at inner edge portions of the oil discharge ports which extend in parallel with the axis of the balance shaft toward a joint surface thereof with the lower housing.
According to the construction, not only can the decrease in rigidity of the upper housing be restrained while securing the area of the oil discharge ports but also the contact of oil flowing in from the oil discharge ports to the balance shafts can be restrained by the vertical walls. Thus, this results in no increase in rotational resistance.
According to a second aspect of the present invention, the vertical walls extend to reach the joint surface with the lower housing.
According to the construction, not only can the decrease in rigidity of the upper housing be restrained further but also the contact of the oil flowing in from the discharge oil ports to the balance shaft can be restrained further.
According to a third aspect of the present invention, there are provided within the housing two balance shafts which have different heights relative to an oil level and which are parallel to each other, the vertical walls are formed on a side of the upper housing where one of the balance shafts is disposed which is easier to contact oil flowing in from the oil discharge ports, and at least part of an oil inlet passage (a tubular passage
26
) communicating from an oil strainer to an oil pump is provided in the lower housing on a side thereof where the other of the balance shafts is disposed in a manner so as to extend in parallel with the axis of the balance shaft.
According
Endo Yusuke
Fujiki Kenji
Inaba Toshiyuki
Kudo Hirotsugu
Murakami Osamu
Ali Hyder
Argenbright Tony M.
Armstrong Kratz Quintos Hanson & Brooks, LLP
Honda Giken Kabushiki Kaisha
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