JP2998472B2 - Vibration reduction device for 2-cycle 4-cylinder engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration reducing device for a two-cycle four-cylinder engine.

[0002]

2. Description of the Related Art In a single-cylinder two-cycle engine, there is known an engine provided with a balance shaft driven by a crankshaft in order to reduce the vibration of the engine body caused in the movement direction of the piston due to the inertia of the piston (Japanese Patent Laid-Open Publication No. Sho. No. 62-135616).

[0003]

However, when a two-stroke engine is made to be a multi-cylinder engine, vibrations about a transverse axis passing through the center of gravity of the engine body and perpendicular to the longitudinal axis of the engine body, that is, vibrations due to pitching, are generated. Vibration around the vertical axis passing through the center of gravity of the main body, that is, vibration due to yawing occurs. However, even if the balance shaft used in the above-described single-cylinder two-cycle engine is used, it is not possible to prevent such vibration due to pitching and yawing. Can not.

[0004]

According to the present invention, there is provided a two-cycle four-cylinder engine in which the ignition order of the first and fourth cylinders is adjacent to each other. A counterweight that balances the rotational motion mass of the crankshaft is attached to the crankshaft to prevent yawing vibration of the crankshaft, and rotates around the axis parallel to the axis of the crankshaft at the same speed in the opposite direction and the same direction as the crankshaft, respectively. A first shaft and a second shaft are mounted on the engine body symmetrically with respect to a plane passing through the axis of the crankshaft, and a second shaft that rotates in the same direction as the crankshaft.
The first cylinder and 4 from the center of gravity of the engine body
The unbalanced mass is attached to the cylinder number side substantially equidistantly, and the mounting direction of the unbalanced mass of the cylinder number 4 with respect to the second shaft is changed in the direction of the crankshaft pin of the cylinder number 1 with respect to the crankshaft and of the cylinder number 4 The direction in which the unbalanced mass of the first cylinder is attached to the second shaft with respect to the second shaft is 180 degrees from the direction in which the unbalanced mass of the fourth cylinder is attached to the second shaft. , The unbalanced mass of the first shaft is arranged symmetrically with respect to the plane described above with respect to the unbalanced mass of the second shaft.

[0005]

In order to prevent yawing vibration of the engine caused by rotation of the crankshaft, a counterweight is mounted on the crankshaft to balance the rotational motion mass of the crankshaft. Since the shaft and the unbalanced mass are arranged symmetrically, no yawing vibration of the engine occurs. On the other hand, the mounting direction of the unbalance mass of the fourth cylinder with respect to the second shaft rotating in the same direction as the crankshaft is determined from both the direction of the crankshaft pin of the first cylinder and the direction of the counterweight of the fourth cylinder with respect to the crankshaft. The direction of the unbalance mass on the first cylinder side with respect to the second shaft is set to a direction separated by 180 degrees from the direction of the installation of the unbalance mass on the fourth cylinder side with respect to the second shaft, and the direction opposite to the crankshaft. Placing the unbalanced mass of the rotating first shaft with respect to the plane described above relative to the unbalanced mass of the second shaft prevents the occurrence of pitching vibrations caused by the reciprocating mass of the engine.

[0006]

1 to 3 show a four-cylinder two-stroke engine whose ignition sequence is 1-3-2-4. This engine is an in-line four-cylinder engine having four pistons 1 (FIG. 1), and is provided with an intake valve 2 and an exhaust valve 3 (FIG. 1). A first camshaft 5 for driving and a second camshaft 5 for driving the exhaust valve 3
Is mounted. The camshafts 5 and 6 are parallel to the axis of the crankshaft 7 and pass through a plane KK (FIG. 3) passing through the axis of the crankshaft 7.
The camshafts 5 and 6 are provided with gears 8 and 9 that mesh with each other at one end thereof.

A timing pulley 10 is attached to an end of the second camshaft 6 opposite to the gear 9, and a drive pulley 11 is attached to an end of the crankshaft 7. The timing pulley 10 is rotated at the same speed and in the same direction as the crankshaft 7 by a timing belt 13 wound around the timing pulley 10, the driving pulley 11, the idle pulley 12, and the like. Therefore, the second camshaft 6 is also rotated at the same speed in the same direction as the crankshaft 7. On the other hand, the first camshaft 5 is rotated at the same speed in the opposite direction to the second camshaft 6 by the second camshaft 6 via the gears 8 and 9, so that the first camshaft 5 and the crankshaft 7 It will be rotated at the same speed in the opposite direction.

Referring to FIG. 3A, the first camshaft 5 has a first cylinder cam 14a and a second cylinder cam 14b.
And a third cylinder cam 14c and a fourth cylinder cam 14d. Further, on both sides of the fourth cylinder cam group 14d, unbalance masses 15a and 15c are formed integrally with the first camshaft 5, respectively.
Unbalance masses 16a and 16c are integrally formed on the first camshaft 5 on both sides of the first camshaft 5, respectively. These unbalanced masses 15a, 15c, 16a, 16c are shown in FIG.
3 (E), the same sector shape is formed as shown in FIG. 3 (E), and the mounting direction of the unbalanced masses 15a, 15c with respect to the first camshaft 5 is the same as the unbalanced mass 16a, 16c is 180 degrees apart from the mounting direction. These unbalanced masses 15a, 15c, 16a, and 16c all have the same mass, and further, each unbalanced mass 15a, 1
6c are equally spaced from a transverse axis y passing through the center of gravity G of the engine body, and each unbalanced mass 15c, 16a is also located at an equal distance from a transverse axis y passing through the center of gravity G of the engine body. Have been.

Similarly, the second camshaft 6 is also provided with a first cylinder cam 14e, a second cylinder cam 14f, a third cylinder cam 14g, and a fourth cylinder cam 14h. Further, unbalanced masses 15b and 15d are formed integrally with the second camshaft 6 on both sides of the fourth cylinder cam group 14h, respectively, and unbalanced masses 16b and 16d are also formed on both sides of the first cylinder cam group 14e. Are formed integrally with the second camshaft 6. These unbalance masses 15
b, 15d, 16b and 16d are shown in FIGS.
As shown in (E), the unbalance masses 15a, 15
has the same sector shape as c, 16a, and 16c.
Furthermore, these unbalanced masses 15b, 15d, 16b,
16d is an unbalanced mass 15a with respect to the plane KK,
15c, 16a and 16c are arranged symmetrically. Therefore, the unbalance mass 15 with respect to the second camshaft 6
The mounting directions of the b and 15d are 180 degrees apart from the mounting directions of the unbalance masses 16b and 16d with respect to the second camshaft 6. Also, each unbalanced mass 15b, 16d is arranged at an equal distance from a transverse axis y passing through the center of gravity G of the engine body, and each unbalanced mass 15d, 16b is also equal from a transverse axis y passing through the center of gravity G of the engine body. They will be placed at a distance. In addition, each unbalance mass 15b, 15d, 1
6b and 16d are the unbalanced masses 15a, 15c and 1 respectively.
It has the same mass as 6a, 16c.

Next, pitching vibration occurring around the horizontal axis y and yawing vibration occurring around the vertical axis x passing through the center of gravity G of the engine body will be described with reference to FIG. FIG. 4 shows the first camshaft 5, the second camshaft 6, the crankshaft 7, and the unbalance mass 15a.
15d and 16a to 16d are schematically shown in FIG.
17a is a crankshaft pin for the first cylinder,
17b indicates a crankshaft pin for the second cylinder, 17c indicates a crankshaft pin for the third cylinder, and 17d indicates a crankshaft pin for the fourth cylinder. Also, 18
Represents counterweights provided on the opposite sides of the crankshaft pins 17a, 17b, 17c, 17d with respect to the axis of the crankshaft 7, respectively. 4, the rotational direction of the crankshaft 7 is indicated by R, and the rotational directions of the camshafts 5, 6 are indicated by r.

When the rotational motion mass of the crankshaft 7 and the balance weight 18 are not balanced and the balance weight 18 is overbalanced, that is, the centrifugal force generated by the rotation of the balance weight 18 causes the rotational motion mass of the crankshaft 7 to change. Is greater than the centrifugal force of the crankshaft pin when the piston descends, the centrifugal force of the counterweight 18 causes a force in the direction opposite to the crankshaft pin as shown by a broken line T in FIGS. 4A and 4B to the engine body. When the piston rises, the centrifugal force of the counterweight 18 causes a force T in the direction opposite to the crankshaft pin to act on the engine body, and the couple of forces Mx around the vertical axis x are exerted on the engine body by these forces T. That is, yawing occurs. However, in the present invention, the mass of the balance weight 18 is determined so that the rotational motion mass of the crankshaft 7 and the balance weight 18 are balanced, and therefore, yawing vibration about the vertical axis X does not occur.

On the other hand, when the piston approaches the top dead center, the ascending speed of the piston is rapidly reduced, so that an elastic force in the piston ascending direction shown by F in FIG. On the other hand, when the piston approaches the bottom dead center, the descending speed of the piston is rapidly reduced, so that an inertial force in the piston descending direction as indicated by F in FIG. As a result, the rotational motion mass of the crankshaft 7 and the balance weight 1
Even with the balance of the motor shaft 8, the inertial force F causes a couple My around the horizontal axis y, that is, pitching. In this case, since the crankshaft pins 17b and 17c of the second cylinder and the third cylinder are close to the horizontal axis y, the pitching caused by the second cylinder and the third cylinder is small, and therefore, the first pitching My is generated. Pitching caused by the cylinder and the fourth cylinder is dominant. Therefore, in order to suppress the occurrence of the pitching My, it is necessary to suppress the pitching caused by the first and fourth cylinders.

When the first cylinder is at the top dead center as shown in FIG. 4A, a couple W is generated around the horizontal axis y by the inertial force F, as shown in FIG. 4B. Also, when the fourth cylinder is at the bottom dead center, a couple W is generated around the horizontal axis y by the inertial force F. In order to cancel the couple W, a force shown by a broken line W 'in FIGS. 4 (A) and 4 (B) may be applied. What is necessary is just to determine the mounting direction of the balance masses 15a to 15d and 16a to 16d. In this case, regardless of whether the first cylinder is at the top dead center or the fourth cylinder is at the bottom dead center, in order to generate a couple as shown by a broken line W ′, the first cylinder side with respect to the second camshaft 6 Unbalance mass of 16
The mounting directions of the cylinders b and 16d are set so as to be substantially 135 degrees apart from the direction of the crankpin 17a of the first cylinder with respect to the crankshaft 7 and the direction of the balance weight 18 of the fourth cylinder. The direction in which the unbalance masses 15b and 15d are attached to the crankshaft 7 should be approximately 45 degrees away from the direction of the crank pin 17a of the first cylinder and the direction of the counterweight 18 of the fourth cylinder.

As described above, each of the unbalanced masses 15a-1
When the mounting directions of 5d and 16a to 16d are determined, the unbalance masses 15a to 15d and 16a to 16d generate a couple W 'in the opposite direction to the couple W around the horizontal axis y based on the inertial force F. Unbalance masses 15a to 15d,
If the masses 16a to 16d are selected so as to completely cancel the couple W about the horizontal axis y based on the inertial force F, pitching can be prevented.

In the embodiment shown in FIGS. 1 to 3, the unbalance mass 15 of the fourth cylinder with respect to the second camshaft 6 is set.
The mounting directions of the first and second cylinders b and 15d are approximately 45 degrees away from the direction of the crankpin 7a of the first cylinder with respect to the crankshaft 7 and the direction of the counterweight 18 of the fourth cylinder. The mounting direction of the unbalanced masses 16b, 16d on the side of the first camshaft is 180 degrees away from the mounting direction of the unbalanced masses 15b, 15d on the fourth cylinder side, and the unbalanced masses 15a, 15c, 16a, 16c is the plane K
It is arranged symmetrically with respect to -K with the corresponding unbalance masses 15b, 15d, 16b, 16d of the second camshaft 6. Therefore, the occurrence of pitching vibration can be prevented. As described above, the unbalanced masses 15a, 15c, 16a, 16c of the first camshaft 5 and the unbalanced masses 15b, 15d,
Since the camshafts 16b and 16d are arranged symmetrically with respect to the plane KK, the rotation of the camshafts 5 and 6 does not cause yawing vibration.

It should be noted that the ignition sequence of the present invention has been described as 1-3.
Although the invention has been described based on a two-cycle four-cylinder engine having -2-4, the present invention can be similarly applied to a two-cycle four-cylinder engine having an ignition order of 1-4-2-3.

[0017]

As described above, in a two-cycle four-cylinder engine, it is possible to prevent the occurrence of vibration of the engine main body due to pitching and yawing.

[Brief description of the drawings]

FIG. 1 is a front view of an engine body.

FIG. 2 is a side view of a crankshaft and a camshaft.

3A and 3B are diagrams showing a camshaft, wherein FIG. 3A is a plan view, FIG. 3B is a cross-sectional view taken along line BB, and FIG.
FIG. 3D is a cross-sectional view taken along the line C, FIG. 4D is a cross-sectional view taken along the line DD, and FIG. 4E is a cross-sectional view taken along the line EE.

FIG. 4 is a diagram for explaining the generation of pitching and yawing and a method for suppressing the generation.

[Explanation of symbols]

5 First camshaft 6 Second camshaft 7 Crankshaft 15a, 15b, 15c, 15d, 16a, 16b, 1
6c, 16d: Unbalanced mass

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16F 15/26 F02B 77/00

Claims (1)

(57) [Claims] In a two-cycle four-cylinder engine in which the ignition order of the first cylinder and the fourth cylinder are adjacent to each other, a counterbalanced with the rotational motion mass of the crankshaft to prevent yawing vibration of the engine caused by rotation of the crankshaft. The weight is attached to the crankshaft, and the first shaft and the second shaft that rotate at the same speed in the opposite direction and in the same direction as the crankshaft respectively around an axis parallel to the axis of the crankshaft are placed on a plane passing through the axis of the crankshaft. Symmetrically mounted on the engine main body and rotated on the second shaft rotating in the same direction as the crankshaft, the unbalanced masses are located at substantially equal distances from the center of gravity of the engine main body to the first and fourth cylinders. And the mounting direction of the unbalance mass of the fourth cylinder with respect to the second shaft To the direction of the crankshaft pin of the first cylinder and the direction of the counterweight of the fourth cylinder with respect to the crankshaft, and the direction of attachment of the unbalance mass of the first cylinder to the second shaft. In a direction 180 degrees away from the mounting direction of the unbalance mass on the fourth cylinder side, and the unbalance mass of the first shaft is symmetrically arranged with respect to the plane with the unbalance mass of the second shaft. Vibration reduction device for cylinder engine.