Segmented Balancer Shaft for Engine Layout Flexibility
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Solution Overview
Problem
The conventional balancer apparatus for internal combustion engines has a limited design flexibility due to the elongated axial length of the balancer shaft, which is constrained by the bearing portion's inner diameter, restricting the layout of other components.
Innovation Solution
A balancer apparatus with a dual-housing design, where a first housing supports a first shaft portion and a second housing supports a second shaft portion of the balancer shaft, allowing independent setting of the outermost diameter of the shafts and inner diameters of the bearing portions, thereby reducing axial dimensions and constraints on component layout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the balancer shaft is inserted into the housing via a single bearing portion, then the structure is simple, but the outermost diameter of the balancer shaft is limited by the inner diameter of the bearing portion, requiring an elongated axial length to secure the required unbalance amount
Solution Approach 1:
The housing is divided into a first housing and a second housing, with the balancer shaft segmented into a first shaft portion and a second shaft portion. Each shaft portion is supported by a separate bearing portion in its corresponding housing. This segmentation allows the outermost diameter of the balancer shaft to be determined by the larger of the two bearing portion inner diameters, rather than being constrained by a single bearing portion, thereby reducing the required axial length while maintaining the unbalance amount.
2Quantity of substance
If the balancer shaft has an elongated axial length to secure the required unbalance amount, then the unbalance amount is sufficient, but the constraints on layout among other components increase, limiting design flexibility
Solution Approach 1:
By segmenting the housing and balancer shaft into two portions each, supported by separate bearing portions, the invention allows the outermost diameter of the balancer shaft to be increased (determined by the larger bearing portion inner diameter) without increasing the axial length. This enables sufficient unbalance amount to be achieved while maintaining compact axial dimensions, thereby improving layout flexibility and design adaptability.
3Ease of manufacture
If the balancer shaft outermost diameter is limited by the bearing portion inner diameter, then the structure is constrained, but manufacturing is simpler, whereas increasing the outermost diameter requires an elongated axial length
Solution Approach 1:
The invention segments the housing into two separate housings, each with its own bearing portion supporting a corresponding shaft portion. This allows the outermost diameter of the balancer shaft to be determined by the larger of the two bearing portion inner diameters, enabling a larger shaft diameter without elongating the axial length, thus resolving the contradiction between ease of manufacture and axial length.
Data Source
AI summary
An object of the present invention is to provide a balancer apparatus for an internal combustion engine that can improve design flexibility in the internal combustion engine. The balancer apparatus includes left and right balancer shafts 21L and 21R each including a balancer weight 21a and a rear-side shaft portion 19b and a front-side shaft portion 19a provided on both sides of the weight portion 21a in a rotational axis direction, a rear-side housing 22R including a bearing holding portion 22Rd surrounding an outer periphery of the rear-side shaft portion 19b and rotatably supporting the rear-side shaft portion 19b, and a front-side housing 22F including a bearing holding portion 22Fd rotatably supporting the front-side shaft portion 19a.