JPS634054B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a balancer device for a three-cylinder engine. In general, in a three-cylinder engine in which the crank arms are arranged at equal intervals of 120 degrees, the sliding of the piston is Due to the primary inertia force generated in the reciprocating direction, an unbalanced primary inertia couple is generated. By the way, as a balancer device for removing this unbalanced primary inertia couple, the ones shown in Figs.
No. 38814). This balancer device is provided with balance weights W _c1 ′, W _c2 ′, and W _c3 ′ in opposite extension directions of crank arms 2, 3, and 4 for each cylinder crank journal of a crankshaft 1, respectively. The weight of each balance weight W _c1 ′, W _c2 ′, W _c3 ′ above corresponds to the sum of the weights of each cylinder's crank arms 2, 3, 4, crank pins 5, 6, 7, the large end of the connecting rod, etc. _The weight ₍ W _R +1/2W ₀ ), and the balance weights W _c1 ′, W _c2 ′, and W _c3 ′ are set at a crank radius r with respect to the axis of the crankshaft 1, and each cylinder is set to a so-called half balance. Then, a synthetic couple of the primary inertia couple due to the reciprocating weight W ₀ and the inertia couple generated by the balance weights W _c1 ′, W _c2 ′, W _c3 ′ is applied to the crankshaft, while the crankshaft 1 A pair of balance weights that generate a constant inertial force P (=γω ² /g×1/2W ₀ × cos30°) on the balancer shaft 15 that rotates in parallel with and at the same angular velocity ω.
W _A and W _A are provided in opposite directions and at a distance of 2L, which is twice the pitch L between the cylinders, in the axial direction, and the inertia couple due to the above balance weights W _A and W _A

By balancing [Formula] and the above composite couple, the primary inertial couple due to the above reciprocating mass W ₀ can be canceled out relatively easily. However, since the balancer device described above half-balances each cylinder, the counterweights W _c1 ′, W _c2 ′,
The total weight of W _c3 ′ is {3×(W _R +1/2W ₀ )}, which has the disadvantage that it is heavy and the crankshaft 1 as a whole becomes heavy. For this reason, the balancer device goes against today's idea of reducing the weight of the engine and improving fuel efficiency and driving performance. Therefore, a balancer device has been proposed in which a crankshaft that is equivalent to the crankshaft 1 of the balancer device, that is, generates the same couple as the crankshaft 1, is constructed to be lighter than the conventional example (Japanese Patent Laid-Open No. 55-11111).
−6035). This balancer device removes the counterweight to be added to the second cylinder, and removes the counterweight to be added to the first and third cylinders W″ _c1 , W″ _c3 (not shown)
, relative to the center of rotation of the crankshaft,
on the opposite sides of the crank arms of the first and third cylinders, respectively, in a direction perpendicular to the crank arms of the second cylinder, and relative to the center of rotation of the crankshaft.
The counterweights W _c1 ″ of the first and third cylinders are provided in the opposite direction of 180° and at the position of the crank radius r.
Each weight of W _c3 ″, W″ _c1 , W″ _c3 , The weight of the entire counterweights W″ _c1 and W″ _c3 is set to √3(W _R +1/2W ₀ ) to reduce the weight. However, since this balancer device consisting of a crankshaft does not have a _{counterweight} in the second cylinder, the bearing against the crank journal of the second cylinder is A heavy load is placed on the
This has the disadvantage of impairing the durability of the metal of the bearing. Therefore, the purpose of this invention is to eliminate the primary inertia couple due to the reciprocating mass, reduce the weight of the entire crankshaft, and increase the durability of the metal without placing a large load on the bearings of the crankshaft. The goal is to improve. The structure of this invention is to apply an inertial couple of a certain magnitude to a single balancer shaft that rotates at the same speed in the opposite direction and parallel to the crankshaft of a three-cylinder engine in which the crank arms are arranged at equal intervals of 120 degrees. A balance weight is provided to generate the
A constant inertial force is generated in the crankshaft on the opposite side of the crank arm of the first cylinder with respect to the crank journal, and in the intermediate direction between the opposite extension direction of the crank arm and the direction perpendicular to the crank arm of the second cylinder. and a first weight that is constant on the opposite side of the crank arm of the third cylinder with respect to the crank journal of the third cylinder and in the intermediate direction between the opposite extension direction of the crank arm and the direction perpendicular to the crank arm of the second cylinder. A first weight that generates an inertia force of In order to balance the generated inertia couple, and furthermore, a second weight is provided to generate a constant inertia force in the opposite direction of extension of the crank arm of the second cylinder to the crank journal of the second cylinder. The present invention is characterized in that the inertia force due to the second weight and the component of the inertia force due to the two first weights in the direction of the crank arm of the second cylinder are balanced. Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments. In Figures 3 and 4, 1 is the crankshaft;
2, 3, and 4 are the crank arms of the first, second, and third cylinders arranged at equal intervals of 120 degrees; 5, 6, and 7 are the crank pins of the first, second, and third cylinders; 8, 9 ，
10 is each piston of the first, second, and third cylinder; 15
is a balancer shaft, and W _A and W _A are balance weights, whose construction and weight distribution are exactly the same as those of the conventional example shown in FIGS. 1 and 2 (hereinafter referred to as the first conventional example). It projects from the center of rotation of the crankshaft 1 to the opposite side of the crank arm 2 of the first cylinder and at an angle of 15° with respect to the direction orthogonal to the crank arm 3 of the second cylinder, by a crank radius r. A first weight W _c1 is provided at the position, and
From the center of rotation of the crankshaft 1, on the opposite side of the crank arm 4 of the third cylinder, at a position protruding by a crank radius r at an angle of 15 degrees with respect to the direction perpendicular to the crank arm 3 of the second cylinder, Another first weight W _c3 is provided. The weights W _c1 and W _c3 of both the first weights W _c1 and W _c3 are exactly the same. Further, a second weight Wc2 is provided at a position projecting from the rotation center of the crankshaft 1 toward the opposite side (180 degrees opposite side) of the crank arm 3 of the second cylinder by a crank radius _r . Weights W _c1 , W _c3 of the above first weights W _c1 , W _c3
teeth,
W _c1 = W _c3 = rω ² /g (W _R +1/2W ₀ )cos30°/rω ²
/gcos15°… cos30°/cos15° (W _R + 1/2W ₀ )… and the weight W _c2 of the second weight W _c2 is W _c2 =√3tan15° (W _R + 1/2W ₀ )… ... and set. Here, W _R : Rotating weight of each cylinder W ₀ : Reciprocating weight of each cylinder g : Gravitational acceleration ω : Angular velocity of the crankshaft r : Crank radius. Next, it will be explained below that the balancer device for the three-cylinder engine having the above configuration has a lightweight structure, eliminates the primary inertia couple, and does not apply an excessive load to the bearing portion of the crankshaft. This balancer device and the first conventional example differ only in the mounting positions and weights of the counterweights W _c1 ′, W _c2 ′, W _c3 ′ and the first and second weights W _c1 , W _c2 , and W _c3 . However, the other structures are exactly the same. Therefore, the first and second weights W _c1 ,
The system consisting of W _c2 and W _c3 and the counterweight W _c1 ′,
If we prove that the system consisting of W _c2 ′ and W _c3 ′ produces the same inertial couple, that is, they are equivalent, then
It can be seen that in this embodiment, an unbalanced primary inertia couple due to the reciprocating weight does not occur in the engine.
Furthermore, since the pitch L between each cylinder is the same in this embodiment and the first conventional example, if the inertia forces (centrifugal forces) of both systems are equal, the inertia couples of both systems are equal. Therefore, it will be explained with reference to FIG. 5 that the inertial forces of both systems are equal. Each inertial force F ₁ due to the first weight W _c1 , W _c3 ,
_F3 is inclined at 15 degrees with respect to the X-axis direction perpendicular to the crank arm 3 of the second cylinder, and _F1 = _Wc1 / ^grω2 ... _F3 = _Wc3 / ^grω2 .... Substituting each expression into the above equation, F ₁ = rω ² /g・cos30°/cos15° (W _R + 1/2W ₀ )...
F ₃ = rω ² /g・cos30゜／cos15゜(W _R +1/2W ₀ )...
becomes. The X-axis direction components F _1x and F _3x of the above inertial forces F ₁ and F ₃ are as follows:
Multiply the inertia forces F ₁ and F ₂ by cos15°, respectively, and get F _1x = rω ² / gcos30° (W _R + 1/2W ₀ )... F _3x = rω ² / gcos30° (W _R + 1/2W ₀ )... becomes. On the other hand, the counterweight W _c1 ′ of the first conventional example,
As is clear from Fig. 2, the X-axis direction components F _1x ′ and F _3x ′ of W _c3 ′ are F′ _1x = rω ² /gcos30° (W _R +1/2W ₀ )…F′ _3x = rω ² / gcos30゜(W _R +1/2W ₀ )... Therefore, from the above equation, the first conventional example and this embodiment are equal in terms of inertia force in the X-axis direction. In addition, the components of the above inertial forces F ₁ and F ₃ in the y-axis direction
F _1y , F _3y are F _1y = F ₁ sin15゜ … F _3y = F ₃ sin15゜ … and by substituting the formula into the above equation, F _1y = rω ² /g (cos30゜) (tan15゜) ( W _R +1/2W ₀ )... F _3y = rω ² /g (cos30°) (tan15°) (W _R +1/2W ₀ )... Therefore, the resultant force of the y-axis components F _1y and F _3y of the above-mentioned inertial force is F _1y +F _3y = rω ² /g√3(tan15°)(W _R +1/2W ₀ )... from the formula. On the other hand, the inertial force F ₂ of the second weight W _c2 is
On the opposite side of the crank arm 3 of the cylinder, that is, in the y-axis direction, F ₂ = rω ² /gW _c2 ..., and substituting the formula into this equation, F ₂ = rω ² /g√3 (tan15°) ( W _R + 1/2W ₀ ) ... becomes. Therefore, from the formula, F _1y +F _3y =F ₂ ..., and the first and second weights W _c1 , W _c2 ,
The component of the inertial force in the y-axis direction of the system consisting of W _c3 is balanced and becomes zero, and since the cylinders are arranged at equal pitches L in the axial direction of the crankshaft 1, no couple is generated. On the other hand, in the first conventional example, the counterweight W _c1 ′,
Since W _c2 ′ and W _c3 ′ are arranged at equal intervals of 120° and each has a weight of (W _R +1/2W ₀ ), it is clear that no component in the y-axis direction is generated, and no couple is generated. According to the above analysis, a system consisting of the counterweights W _c1 ', W _c2 ', and W _c3 ' of the first conventional example and a system consisting of the first and second weights W _c1 , W _c2 , and W _c3 of this embodiment are determined. are equivalent with respect to the couple, so it can be seen that this balancer device is able to cancel the primary inertial couple. On the other hand, the first and second weights W _c1 of this device,
The total weight of W _c2 and W _c3 is calculated from the formula: W = W _c1 + W _c2 + W _c3 = √3 (tan15° + 1/cos15°) (W _R +1/2W ₀ )... On the other hand, the counterweights W _c1 ′, W _c2 ′, of the first conventional example in which each cylinder is half-balanced are
The total weight W' of W _c3 ' is W'=3(W _R +1/2W ₀ )... From the above formula, W/W' = 3/3 (tan15° + ¹ _cps15 °) = 0.74. Therefore, it can be seen that this balancer device can reduce the weight of the weight by about 26% compared to the first conventional example, and can reduce the weight of the entire crankshaft. In addition, since this balancer device is provided with the second weight W _c2 in the second cylinder, it is possible to considerably cancel out the inertia force due to the rotational weight W _R of the second cylinder. Compared to the example (described in JP-A No. 55-6035), the load applied to the bearing portion for the crank journal of the second cylinder can be reduced, and the durability of the metal can be improved. In the above embodiment, the mounting direction of the first weights W _c1 and W _c3 was set at 15 degrees from the x-axis in FIG.
The present invention is not limited to this angle, but the angle is set at the best position depending on the durability of the bearing, the characteristics of the engine, etc., and the angle is approximately 0°. It is possible to set it approximately in the middle of the angle range of more than 30 degrees. Further, in the above embodiment, the first and second weights
Although W _c1 , W _c2 , and W _c3 are provided at a distance of the crank radius r from the center of the crankshaft 1, it goes without saying that the distance is not limited to this as long as an equivalent inertial force is generated. As is clear from the above description, the present invention is directed to a three-cylinder engine in which crank arms are arranged at equal intervals of 120 degrees, on the opposite side of the crank arm with respect to the crank journal of the first cylinder, and on the opposite side of the crank arm. A first weight that generates a constant inertial force is provided in the intermediate direction between the direction and the direction perpendicular to the crank arm of the second cylinder, and
A first element that generates a constant inertial force on the opposite side of the third cylinder's crank arm and in the intermediate direction between the opposite extension direction of the crank arm and the direction perpendicular to the second cylinder's crank arm. A weight is provided, and a synthetic couple of an unbalanced inertia couple generated by the inertia of the two first weights and a primary inertia couple due to the reciprocating weight, and a weight disposed parallel to the crankshaft, is connected to the crankshaft. This is done to balance the inertia couple generated by the balance weight provided on the balancer shaft that rotates in opposite directions at the same angular velocity, and also to maintain a constant inertia in the opposite extension direction of the crank arm relative to the second cylinder crank journal. Since a second weight that generates a force is provided to balance the inertial force due to the second weight and the component of the inertial force due to the two first weights in the direction of the crank arm of the second cylinder, the reciprocating mass In addition to being able to eliminate the primary inertia couple caused by the inertia, the weight of the entire crankshaft can be reduced, and in addition, it is possible to avoid applying a large load to the bearing part of the crankshaft, and the durability of the metal can be improved.

[Brief explanation of the drawing]

FIG. 1 is a simplified perspective view of a conventional balancer device for a three-cylinder engine, FIG. 2 is a simplified view of the crankshaft shown in FIG. 1 viewed from the axial direction, and FIG. 3 is a simplified perspective view of an embodiment of the present invention. , FIG. 4 is a simplified diagram of the crankshaft shown in FIG. 3 viewed from the axial direction, and FIG. 5 is a diagram illustrating inertial forces acting on the first and second weights. 1...Crankshaft, 2,3,4...Crank arm, 5,6,7...Crank pin, 8,9,1
0... Piston, 15... Balance shaft, W _A ,
W _A ...balance weight, W _c1 , W _c3 ... first weight, W _c2 ... second weight.

Claims (1)

[Scope of Claims] 1 In a three-cylinder engine in which crank arms are arranged at equal intervals of 120 degrees, an inertia couple of a certain size is attached to a single balancer shaft that rotates in parallel with the crankshaft and in the opposite direction at the same speed. A balance weight that generates force is provided, and the crankshaft is further provided with a crank arm on the opposite side of the crank journal of the first cylinder and a direction perpendicular to the opposite extension direction of the crank arm and the crank arm of the second cylinder. A first weight that generates a constant inertia force is provided in the intermediate direction between the third cylinder's crank journal and the opposite side of the crank arm of the third cylinder and the opposite extension direction of the second cylinder. A first weight that generates a constant inertia force in a direction midway between the direction perpendicular to the crank arm is provided, and an unbalanced inertia couple generated by the inertia force of the first weights and a primary inertia couple due to the reciprocating weight are provided. The resultant couple with the force and the inertia couple generated by the balance weight are balanced, and furthermore, in the direction of extension of the crank arm opposite to the crank journal of the second cylinder,
A second weight that generates a constant inertial force is provided, so that the inertial force caused by the second weight and the both first weights are
A balancer device for a three-cylinder engine, characterized in that it is configured to balance the component of inertia force in the direction of the crank arm of the second cylinder due to the weight of the engine.