JPH04249637A - Balancer device for three-cylinder engine - Google Patents

Abstract

PURPOSE:To reduce the weight of the whole of an engine by diminishing the inertial couple of force generated on a series three-cylinder engine due to the weight of the smaller weight by specifying the installation positions and weights of three balancer weights installed on a crank counterweight and a balancer shaft. CONSTITUTION:As for a three-cylinder engine in which the crankarms 12a-13c of cylinders #1-#3 are arranged in a phase of 120 deg., a balancer shaft 16 which revolves in the opposite direction in 1:1 for a crankshaft 12 is installed. A weight (a) corresponding to the revolution movement part weight Wr in a crank system and the weights (b) and (c) in consideration of the reciprocating movement weight Wp of the crank system are installed on the crankshaft 12 in correspondence with each cylinder #1-#3. Further, the balancer weight B' and C' having the equal weights to the weights a-c are installed on the balancer shaft 16, at the position of (360 deg.-theta) on the cylinder #1 side, -60 deg. on the cylinder #2 side, and (240 deg.-theta) on the cylinder #3 side, having the cylinder center line as standard.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a balancer device for a three-cylinder engine.

0003

[Prior Art] In an in-line three-cylinder engine, each crank arm of the crankshaft is arranged at equal intervals with a phase of 120 degrees, but the weight of the reciprocating part of the crank system is equivalent to the sum of the masses of the piston, piston pin, etc. As a result, an unbalanced primary inertia couple is generated due to the primary inertia force generated in the sliding direction of the piston.

In order to eliminate this primary inertia couple, in the conventional balancer device for an in-line three-cylinder engine, as schematically shown in FIGS. 5 and 6, a No.
1~No. 3 cylinders #1 to #3 are arranged at equal intervals with a cylinder pitch L with a phase of 120 degrees, and the rotating parts of the crank system (crank arm 2, crank pin 3, etc.) of each cylinder #1 to #3 are Mass (weight of rotating moving part) W
The mass Wr corresponding to r and the mass of the reciprocating part of the crank system (piston, connecting rod, etc.) (reciprocating part weight) Wp
A mass of 0.5 Wp, which is equivalent to 1/2 of
No. 1 for crankshaft systems. 1 cylinder #1 and no.
An inertial couple is generated by a component of the residual combined inertial force generated in cylinder #3. On the other hand, a balancer shaft 4 is provided so as to be parallel to the crankshaft 1 and equally rotate in the opposite direction, and on this balancer shaft 4 there is a No. 1 cylinder #1 and no. 3 cylinder #
A balancer weight E, which is approximately 70% of the weight Wp of the reciprocating part, is installed at the position corresponding to No. 3 at the angle shown in FIGS. There is a method designed to cancel this out (see Japanese Patent Publication No. 54-2333).

[0005]

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, the crank counter weight A and the balancer shaft 4 have a weight of 100% of the weight of the rotary movement part (Wr) and a weight of 50% of the weight of the reciprocating part (Wp). Since the balancer weight E, which is 70% of the reciprocating part weight (Wp), is arranged in the above relationship, the crankshaft 1
Both the weight of the balancer shaft and the weight of the balancer shaft have increased significantly,
There was a problem in that the weight of the entire engine increased, leading to an increase in cost.

[0006] This invention was made in consideration of the above-mentioned circumstances.
It is an object of the present invention to provide a balancer device for a three-cylinder engine that can eliminate the primary inertia couple generated in a cylinder engine and reduce the weight of the entire engine. [Structure of the invention]

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention has a balancer shaft that rotates in the opposite direction on a one-to-one basis with respect to the crankshaft, and has a crank counter whose weight is 100% of the weight of the rotating motion part. The weight is provided in the direction of 180 degrees with respect to the crank pin, and the crank counter weight is set to No. Angle θ = 150 to 180° in the rotation direction from the crank pin of 1 cylinder, No. 180° from the 2nd cylinder crank pin, No. The balancer weight of the balancer shaft is set at a position 360°-θ from the crank pin of the 3rd cylinder, and the weight is determined so that the centrifugal forces generated are balanced. When the first cylinder is at the top dead center, No. 1 is moved in the opposite direction to the balancer rotation direction based on the cylinder center line. 360°-θ on the 1 cylinder side, No. -60° on the 2nd cylinder side, No.
．． It is characterized by being provided at the 240°-θ position on the 3rd cylinder side.

[0008]

[Operation] By configuring the installation position and weight of the crank counterweight and the balancer weight provided on the balancer shaft to handle the primary inertia couple generated in an in-line three-cylinder engine, the crank counterweight can be used while maintaining the same performance as before. The weight is significantly reduced, making it possible to significantly reduce the weight of the entire engine.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a balancer device for a three-cylinder engine according to the present invention will be described below with reference to the accompanying drawings.

The present invention is applied to an in-line three-cylinder engine mounted on a snowmobile or the like, and FIG. 1 shows the arrangement relationship of the crank pins 11a, 11b, 11c of this in-line three-cylinder engine 10 and their respective weights. shaft 12
FIG. 2 is a schematic perspective view of FIG. 1.

In FIGS. 1 and 2, #1 to #3 are the numbers of the in-line three-cylinder engine 10. From 1 cylinder to No.
Three cylinders are shown, and each cylinder #1~
#3 is No. Crank arms 13a, 13b, 13c of each cylinder #1 to #3 are arranged at equal intervals of a cylinder pitch L with cylinder #2 as a reference, and with an equal phase of 120 degrees.

Crankshaft 1 of three-cylinder engine 10
2, crank counter weights B and D are attached to, for example, crank radial positions corresponding to each cylinder #1 to #3. Crank counter weights B and D are weights a, which correspond to the weight Wr of the rotating part of the crank system, and weights b, c, which take into account the weight Wp of the reciprocating part of the crank system.
The weight a is 100% of the weight Wr of the rotary moving part and is provided at a position of 180 degrees with respect to the crank pins 11a, 11b, and 11c of each cylinder #1 to #3. This balancer device sets the rotary moving part weight Wr of the crank counter weights B and D to each cylinder #1.
~ As a general rule, the reciprocating part weight Wp should be installed at a rotational position of 180° from the crank pins 11a to 11c of #3.
What percentage of the engine should be placed at which position was calculated using a crank balance optimization program.

On the other hand, the weight b corresponding to the weight Wp of the reciprocating part of the crank counter weight B is No. For cylinder #1, No. 1 is located at an angle θ from the crank pin 11a in the rotation direction of the crankshaft 12. 3 For cylinder #3, crank pin 11c (360°-
θ) It is desirable to provide them at rotated angular positions.

In this case, the angle θ is 150°<
The relationship is θ<180°, and the weight W of the weight b is as follows: W=0.35×Wp to 0.5×Wp (Wp=weight of reciprocating part).

As shown in FIG. 3, the actual weight W of the weight b is determined by considering the magnitude of the couple generated during engine operation, and the weight of the weight b is set to be 45% of the reciprocating groove weight Wp. At this time, the engine couple takes a minimum value, and the graph becomes symmetrical before and after that, so it is desirable that the weight is 45%. However, in practice, when considering a lighter engine, it is preferable to set it between 35% and 45%.

[0016] Also, No. The weight C for cylinder #2 is provided at a position 180 degrees from the crank pin 11b, and its weight is 2×Wp×sin (θ-150 degrees).

Incidentally, the crank counter weights B and D are actually a combination of a weight a and a weight b or c.
are arranged taking into account the weight ratio of

By the way, a balancer shaft 16 is provided in parallel to the crankshaft 12. The balancer shaft 16 rotates equally and in the opposite direction to the crankshaft 12, and balancer weights B' and D' are mounted on the balancer shaft 16 in correspondence with the positions of the cylinders #1 to #3. establish. Each balancer weight B', D
' is placed at the cylinder pitch L, then a weight equal to the crankshaft weight is placed at No. 1 with the cylinder center line as a reference. 1 cylinder #1 side is (360°-θ), No.
．． 2 cylinder #2 side is -60°, No. Cylinder#
Install the third side at the (240°-θ) position.

Note that the balancer shaft 16 may be installed at any position as long as it is parallel to the crankshaft 12.
Also, since the purpose of balancer weight B' (weight WB) is to generate a couple, No. 1 cylinder #1
and no. 3 Cylinder #3 side balancer weight B
' should satisfy WB×L. No. 2 Regarding the balancer weight D' of cylinder #2, No. 1,
No. Since this is to cancel the resultant force of the centrifugal force of the balancer weight B' on the third cylinder side, its weight is 2×WB×sin (θ-150°).

FIG. 4 shows an example of a specific balancer device for a three-cylinder engine when θ=165°, and the weight considering the weight Wp of the reciprocating part of the crank counter weight B is No. 1.No. 3 cylinders #1 and #3 to 0.
45×Wp, No. 2 cylinder #2 by 2 x (0.45
×Wp)×sin15°=0.233×Wp.

On the other hand, the balancer weight on the balancer shaft is arranged in a number opposite to the balancer rotation direction with respect to the cylinder center line. 1 cylinder side is 195°, No. 3
Cylinder side is 45°, No. The 2nd cylinder side is -60°, and its weight is the same as the crank counter weight of 0.
They are 45×Wp, 0.5×Wp, and 0.233×Wp. The total weight of the weights added at this time is (0.45 x Wp x 2 + 0.2329 x Wp) x 2
=2.266×Wp, and in the conventional technology shown in FIG. 1, 0.5×WP×3+0.705×Wp=2.91×Wp
The additional weight has been reduced by approximately 22% compared to the previous model.
Significant weight reduction is achieved.

[0022]

[Effects of the Invention] As described above, according to the present invention, the weight of the weight for canceling the primary inertia couple in a three-cylinder engine can be significantly reduced, so the weight of the entire engine can be significantly reduced. It is possible to reduce costs.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of a balancer device for a three-cylinder engine according to the present invention.

FIG. 2 is a schematic perspective view of FIG. 1;

FIG. 3 is a diagram showing the relationship between engine couple and crank counter weight.

FIG. 4 is a schematic diagram showing a specific application example of the balancer device for a three-cylinder engine of the present invention.

FIG. 5 is a schematic diagram showing a conventional balancer device for a three-cylinder engine.

FIG. 6 is a schematic perspective view of FIG. 5;

[Explanation of symbols]

10 In-line three-cylinder engine 11a, 11b, 11c Crank pin 12 Crankshaft 13a, 13b, 13c Crank arm 16 Counter shaft B, D Crank counter weight a Weight b corresponding to 100% of the weight of the rotating part,
c Weights B', D' for the weight of reciprocating parts Counter weights

Claims (1)

[Claims] [Claim 1] No. 1~No. In a 3-cylinder engine in which the 3-cylinder crank arms are arranged with a 120° phase, there is a balancer shaft that rotates in the opposite direction to the crankshaft on a one-to-one basis. The crank counter weight is installed in the direction of 180 degrees with respect to the crank pin, and the crank counter weight corresponding to the weight of the reciprocating motion is
．． Angle θ = 1 in the rotation direction from the crank pin of 1 cylinder
50~180°, No. 180° from the 2nd cylinder crank pin, No. 3 from the crank pin of the 3 cylinder
The balancer weight of the balancer shaft is set at a position of 60°-θ, and the weight is determined so that the centrifugal forces generated are balanced. When the first cylinder is at the top dead center, No. 1 is moved in the opposite direction to the balancer rotation direction based on the cylinder center line. 360°-θ on the 1 cylinder side, No.
-60° on the 2nd cylinder side, No. 24 on the 3rd cylinder side
A balancer device for a three-cylinder engine, characterized in that it is provided at a 0°-θ position.