JPH0717870Y2 - Noise reduction structure for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a noise reduction structure for an internal combustion engine, and more particularly to a structure for reducing noise generated around the crankshaft of the engine.

[Conventional technology]

In order to suppress the vibration of the crankshaft, especially the journal part, and to reduce the noise around the crankshaft generated during engine operation, it is provided facing the cylinder block bearing part that supports the journal parts located at both ends of the crankshaft. A crankshaft anti-vibration structure has been proposed in which the crank caps are connected with a reinforcing beam, and a radial bearing and a thrust bearing are attached to the bearing portion composed of the crank caps connected to the beam. 69618 publication).

[Problems to be solved by the device]

By the way, in general, a crankshaft is equipped with a crank pulley and a flywheel at both ends thereof, so that the both ends are in a so-called cantilevered state, and both ends of the crankshaft are burned with combustion of each cylinder close to the crank pulley and the flywheel. Noise from bending vibration is generated from the part.
Therefore, even if the rigidity of the support structure at both ends of the crankshaft is increased as in the conventional structure described above, the crankshaft portion on the crank pulley side and the crankshaft portion on the flywheel side have different inertial masses for the crank pulley and the flywheel, respectively. Therefore, they vibrate at different frequencies, and the vibrations of different frequencies are alternately generated due to the different vibration modes. Generally, a sound with discontinuity or intensity (with sound pressure fluctuation) feels rough or noisy even if the noise level is low, whereas a continuous sound has a high noise level. It is known that it is smooth and noisy, and it is not preferable for hearing to alternately generate such vibrations of different frequencies. In view of the above problems, it is an object of the present invention to provide a noise reduction structure that eliminates the intensity component of noise.

[Means for Solving the Problems]

According to the present invention, in order to achieve the above object, the mass of the crank pulley attached to one end of the crankshaft is
m ₁ and the bending stiffness coefficient of the crankshaft that vibrates due to the explosion and combustion of the cylinder adjacent to the crank pulley.
K ₁ , the mass of the flywheel attached to the other end of the crankshaft was m _2, and the flexural rigidity coefficient of the crankshaft portion vibrating due to the explosion and combustion of the cylinder adjacent to the flywheel was K ₂ . Sometimes the masses m ₁ and m ₂ and the bending stiffness coefficients are set so that the relationship of K ₁ / m ₁ ≈K ₂ / m ₂ is satisfied.
In a multi-cylinder internal combustion engine in which K ₁ and K ₂ are defined, a flywheel and a crank pulley are formed such that the flywheel mass m ₂ is larger than the crank pulley mass m ₁ .
Differentiating the pin journal or crank arm size of the crankshaft part belonging to the cylinder adjacent to the flywheel from the pin journal or crank arm size of the crankshaft part belonging to the cylinder adjacent to the crank pulley K ₁ / m ₁ ≈K The bending rigidity coefficient K ₂ of the crankshaft part vibrates with the explosion / combustion of the cylinder adjacent to the flywheel so as to satisfy the relationship of ₂ / m ₂ with the explosion / combustion of the cylinder adjacent to the crank pulley. Provided is a noise reduction structure for an internal combustion engine in which the flexural rigidity coefficient K ₁ of a crankshaft portion vibrating in a vertical direction is made larger.

[Action]

Due to the difference in mass between the crank pulley and the flywheel, the natural frequency of the crankshaft portion caused by the explosion and combustion of the cylinders close to each other caused a difference, and as a result, the frequency range was different (Fig. 4). In the present invention, when the flywheel mass m ₂ is larger than the crank pulley mass m ₂ , the explosion of the cylinder adjacent to the flywheel occurs.
The bending stiffness coefficient K ₂ of the crankshaft part that vibrates with combustion is set to the bending stiffness coefficient K ₁ of the crankshaft part that vibrates with the explosion and combustion of the cylinder adjacent to the crank pulley.
To make K ₁ / m ₁ ≈ K ₂ / m ₂ to make the natural frequencies almost equal, and to make the resulting level of each frequency range even and suppress noise intensity (sound pressure fluctuation). .

〔Example〕

Prior to describing the embodiment of the present invention, each vibration of the crank pulley and the flywheel cylinder will be described with reference to the drawings.

FIG. 1 is a diagram showing a vibration mode at one end of an engine crankshaft, in which the solid line shows the crankshaft state when the explosion load P due to cylinder combustion is not received, and the chain line shows the load P. The deformation state at the time is shown. In the figure, 1 is a crankshaft, 2a and 2b are main journal parts of the crankshaft 1, 3 are same arm parts, 4 is a pin journal part connected to a connecting rod (not shown),
Reference numeral 5 is a crank pulley fixed to the end of the crankshaft 1, 6a and 6b are cylinder block bearings that respectively support the main journals 2a and 2b, and 7 is mounted facing the bearings 6a and 6b. A crank cap that supports the main journal portions 2a and 2b.

The crankshaft portion on the crank pulley side of the illustrated main journal portion 2a receives an explosion load P when a corresponding cylinder located above the pin journal portion 4 burns, and is deformed as shown by a dashed line in the figure. , Then it will vibrate. That is, when this vibration model is simplified, as shown in FIG.
This is equivalent to vibrating the cantilever beam supported by 6a, 6b and the crank cap 7) with force P. The distance between the cylinder block bearings 6a, 6b (or the crank cap 7), which is the fulcrum, is L ₁ , the crank If the distance between the bearing 6b closest to the pulley 5 and the crank pulley 5 is L ₁ ′, the mass of the crank pulley 5 is m ₁ , the section modulus of the crankshaft 1 is I ₁ , and the Young's modulus is E, the load P is The displacement X ₁ of the pulley 5 due to receiving is calculated from the beam deflection calculation formula. It can be expressed as. That is, the bending stiffness coefficient K ₁ of this vibrating part is Therefore, the natural frequency f ₁ is Becomes

By the way, the same thing can be said for the above-described vibration system for the crankshaft portion to which the flywheel is fixed at the other end portion of the crankshaft. That is, suppose the flywheel mass is m ₂ , the cylinder block bearing distance is L ₂ , the distance between the flywheel and the bearing closest to the flywheel is L ₂ ′, and the bending stiffness coefficient of this vibrating part is K ₂ , If the section modulus of the crankshaft is I ₂ , then the natural frequency f ₂
Is Will be expressed as

Generally, in an even-numbered cylinder engine, when each element is simplified, for example, in the case of an in-line four-cylinder engine, it becomes as shown in FIG. The flywheel is shown as 8. Here, assuming that in the above equations (3) and (4), I ₁ =
When I ₂ , L ₁ = L ₂ , L ₁ ′ = L ₂ ′, the vibration of the cylinder # 1 on the crank pulley side is caused by the difference between the masses m ₁ and m ₂ of the pulley 5 and the flywheel 8 (m ₁ <m ₂ ). A difference occurs between the natural frequency f ₁ of the system and the natural frequency f ₂ of the vibration system of the flywheel side cylinder # 4, and a difference is generated in the resonance frequency range as shown in FIG. 4, resulting in noise. The dynamics (sound pressure fluctuation) will occur.

Therefore, in the present invention, in order to suppress the intensity of this noise (sound pressure fluctuation), as shown in FIG. 5, the natural vibration of each vibration system is set so that the frequency range of the vibration on the crank pulley side and the frequency range of the flywheel side vibration are made substantially equal. The numbers f ₁ and f ₂ are made equal.

FIG. 6 shows the current state of an in-line four-cylinder engine, that is, (1) that there is a mass difference between the crank pulley and the flywheel, and (2) the bearing distances L ₁ and L ₂ and the distances L ₁ ′ and L ₂ ′. In consideration of the fact that there are few degrees of freedom in (3) the crankshafts are made of the same uniform material (Young's modulus E is constant), the natural frequencies of the respective vibration systems are almost equal. Is shown.

That is, according to this embodiment, as shown in the drawing, the width w ₂ of the pin journal 4b on the flywheel 8 side is made smaller than the width w ₁ of the pin journal 4a on the crank pulley 5 side, and the crank on the flywheel 8 side is By designing the thickness t ₂ of the arm 3b to be larger than the thickness t ₁ of the crank arm 3a on the crank pulley 5 side, the value of the section modulus I ₂ in the equation (4) is made larger than I _{1 in the} equation (3). , K ₁ / m ₁ ≈ K ₂ / m ₂ (m ₁ <m ₂ ;
Achieving K ₁ <K ₂ ), the natural frequency f ₁ in each vibration system,
f ₂ is made almost equal (see FIG. 5). Separately from this embodiment, as means for changing the section modulus I ₂ , although not shown, when the diameters of the pin journals 4a and 4b are D _4a and D _4b , respectively, the condition of D _4a <D _4b is satisfied. While each value D _4a , D _4b
Can be set appropriately. In addition, if the above-mentioned restrictions are not taken into consideration, each variable L ₁ , L ₁ ′ in Eqs. (3) and (4) should be satisfied in order to satisfy the relationship of K ₁ / m ₁ ≈K ₂ / m ₂ .
It is also possible to appropriately calculate and design L ₂ and L ₂ ′.

Next, an embodiment of the present invention will be described with respect to an engine having an odd number of cylinders such as a V-type 5-cylinder engine. As shown in FIG. 7, generally in a V-type engine, the crankshaft 10 has a shape in which two pin journals 14 are sandwiched between two main journal bearing portions 16 for the purpose of shortening the overall length of the engine. However, in the case of odd cylinders,
There will be one cylinder left. Therefore, the condition of L ₁ > L ₂ naturally occurs, and therefore, due to the difference in mass between the flywheel 18 and the pulley 15, the difference in natural frequency between the respective vibration systems is caused by a large-mass flywheel on the side of the surplus one cylinder. Installed, the distance L ₂ between the cylinder block bearings on the flywheel side is made smaller than the distance L ₁ on the crank pulley side, and each variable L ₁ ,
L _1, by L _2, set L ₂ I _1, appropriately I _2, etc., it can be more easily reduced than in the case of the even cylinder.

〔effect〕

As described above, according to the present invention, when the mass of the flywheel is larger than that of the crank pulley, the dimensions of the pin journal or crank arm of the crankshaft portion belonging to the cylinder adjacent to the flywheel are adjacent to the crank pulley. Due to the explosion / combustion of the cylinder adjacent to the flywheel so as to satisfy the relationship of K ₁ / m ₁ ≈K ₂ / m ₂ by making it different from the size of the pin journal or crank arm belonging to the cylinder. The bending stiffness coefficient K ₂ of the vibrating crankshaft portion is made larger than the bending stiffness coefficient K ₁ of the crankshaft portion that vibrates due to the explosion and combustion of the cylinder adjacent to the crank pulley. By equalizing the natural frequency and the natural frequency of the flywheel side vibration system,
The vibration frequencies associated with the explosion combustion of the cylinders corresponding to the respective vibration systems can be made equal, so that the generation of noise intensity (sound pressure fluctuation) due to the frequency difference can be suppressed, and the auditory discomfort does not occur.

[Brief description of drawings]

FIG. 1 is an external view showing a vibration form of a crankshaft portion provided with a crank pulley; FIG. 2 is a configuration diagram in which each element in FIG. 1 is simplified; FIG. 3 is a crankshaft and bearings in an in-line four-cylinder engine. FIG. 4 is a graph showing the frequency range generation of each vibration system in a conventional engine over time; FIG. 5 is a graph showing the frequency range of each vibration system according to the present invention over time; FIG. 7 is a partial engine cross-sectional view showing an example in which the noise reduction structure of the present invention is applied to a 4-cylinder in-line engine; FIG. 7 is a schematic configuration diagram showing an arrangement of crankshafts and bearings when the present invention is applied to a V-type 5-cylinder engine. . 1,10 …… Crank shaft, 5,15 …… Crank pulley,
8,18 …… Flywheel.

Claims (1)

[Scope of utility model registration request] 1. A mass of a crank pulley attached to one end of a crankshaft is m _1, and a bending rigidity coefficient of a crankshaft portion vibrating due to explosion and combustion of a cylinder adjacent to the crank pulley is K _1. , The mass of the flywheel attached to the other end of the crankshaft is m ₂ ,
Each mass should satisfy K ₁ / m ₁ ≈K ₂ / m ₂ where K ₂ is the bending rigidity coefficient of the crankshaft portion that vibrates due to the explosion and combustion of the cylinder adjacent to the flywheel.
In a multi-cylinder internal combustion engine in which m ₁ and m ₂ and respective bending stiffness coefficients K ₁ and K ₂ are defined, a flywheel and a crank pulley are formed so that the flywheel mass m ₂ is larger than the crank pulley mass m _1. However, the size of the pin journal or crank arm of the crankshaft portion belonging to the cylinder adjacent to the flywheel is made different from that of the pin journal or crank arm of the crankshaft portion belonging to the cylinder adjacent to the crank pulley, and K ₁ / m ₁ Explosion of the cylinder adjacent to the flywheel so that the relationship of ≈ K ₂ / m ₂ is satisfied. ・ The bending rigidity coefficient K ₂ of the crankshaft part that vibrates with combustion is determined as the explosion of the cylinder adjacent to the crank pulley.
Noise reduction structure for internal combustion engine with bending rigidity coefficient K ₁ of crankshaft part vibrating with combustion increased.