JP3166345B2 - engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine and, more particularly, to a reciprocating engine in which vibrations which cause noise in a vehicle cabin are reduced.

[0002]

2. Description of the Related Art It is known that an engine vibration is a cause of generation of vehicle interior noise, and this engine vibration is transmitted to the interior of the vehicle to produce unpleasant noise.

[0003] Japanese Patent Application Laid-Open Nos. 3-168439 and 3-168438 have proposed a device for reducing vehicle interior noise due to such engine vibrations. In order to reduce the vibration transmitted to the mount that connects to the vehicle body, when the high frequency micro-vibration is detected from the engine speed or the engine vibration, the voltage is not applied to the electromagnetic fluid and the viscosity is low, so that the mount is mainly configured. The volume change of the main fluid chamber in the body chamber and the sub-fluid chamber is allowed with the deformation of the rubber film, and the rubber elastic body can be deformed, the spring constant is reduced, and the high frequency vibration is reduced.

Further, in an operation state in which low and medium frequency vibrations are applied, a voltage is applied to the electromagnetic fluid to increase the viscosity thereof, and a large amount of fluid moves between the main fluid chamber and the sub fluid chamber. Due to the resistance that the fluid receives at the orifice, the loss factor is increased and low and medium frequency vibrations are attenuated.

[0005] In this manner, high-frequency micro-vibrations and low-medium-frequency vibrations generated according to the driving state and the running state are effectively reduced.

[0006]

As described above, in the prior art, the vehicle interior noise is reduced by reducing the vibration transmitted from the engine. However, this vehicle interior noise provides a good feeling for the driver. And a component that gives a bad feeling are included, and it is not good that the interior sound of the vehicle is low.

That is, in recent luxury cars and the like, when the door is closed, there is a feeling that it is almost isolated from the outside, which is not comfortable for the driver, and listens only to such a car. Then, there was a problem that an unpleasant engine sound such as Huhlühl was heard.

[0008] Such a problem is attributable in part to the improvement of the engine other than the engine serving as a vibration source. Japanese Patent Laid-Open No. 59-73540 discloses the first
By making the combustion chamber volume of the cylinder larger than that of the other cylinders, the compression ratio of the first cylinder is made lower than that of the other cylinders, and the combustion pressure is relatively lowered. Since the fuel consumption and output of the engine are deteriorated and the vibration is merely reduced as a whole, the effect of improving the feeling is insufficient.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce vibrations that adversely affect the feeling of the engine itself without sacrificing the fuel efficiency and output of the engine.

[0010]

For example, the main component of the vibration of an in-line four-cylinder engine is a frequency component of 2n times (n is an integer 1, 2, 3,...) The engine speed, and is usually an even number ( 2n) It is called the next component.

On the other hand, the components that cause unpleasant sound are:
It is known that there are half (0.5 + n) -order components such as 1.5, 2.5, 3.5,... And odd-order components such as 1, 3, 5,.

Of these, it was also found that the 2.5 order component, the 3.5 order component, and further the 3rd order component caused the unpleasant sound.

[0013] Then, based on the calculations and the experimental results so far,
It has been found that the generation of the half-order component and the odd-order component is caused by a difference in response when each engine cylinder is vibrated.

That is, the vibration (displacement) transmitted from the engine to the vehicle body (not shown) is largest in the first cylinder as shown in FIG. 1 (a), and is larger in the second cylinder, the third cylinder, and the fourth cylinder. It was determined that such a difference between the cylinders was the cause of the above-mentioned half-order component and odd-order component, and as shown in FIG. The difference (displacement difference) can reduce the occurrence of half-order components and odd-order components.

Referring to FIG. 2, the magnitudes of vibrations A1, A2, A3, and A4 at the engine foot point A due to the explosion of each of the cylinders # 1 to # 4 of the engine 1 are determined by the engine 1 (power The magnitude of the vibration differs as shown in FIG. 2 in proportion to the distances L1, L2, L3, and L4 from the center of gravity B of the plant (plant) to the respective cylinders. The vibration of the component and the odd-order component can be obtained as follows.

First, the vibration acceleration a at the engine foot point A
= A (ωt) is the sum of vibrations generated from the cylinders. The vibrations generated from the cylinders have a phase (time) difference by the explosion interval Δt, and the amplitudes are different as follows because the transmission paths are different. Vibration generated from the first cylinder: A1 sinωt Vibration generated from the second cylinder: A2 sinω (t + 3Δ
t) Vibration generated from the third cylinder: A3 sinω (t + Δt) Vibration generated from the fourth cylinder: A4 sinω (t + 2Δ)
t) However, the firing order is # 1 → # 3 → # 4 → # 2 cylinder.

When these values are added, a (ωt) = sinωt + A3sinω (t + Δt) + A4sinω (t + 2Δt) + A2sinω (t + 3Δt).
When limited to (5, 1, 1.5, 2, 2.5), the rotation frequency is 2π / 2Δt in the case of a four-cylinder engine, so that ω = (2π / 2Δt) = nπ / Δt, and therefore, a (ωt) = A1 sinωt + A3 sin (ωt + nπ) + A4 sin (ωt + 2nπ) + A2 sin (ωt + 3nπ) Then, n can be divided as follows.

1) When n is an odd number a (ωt) = A1sinωt−A3sinωt + A4sinωt−A2sinωt Therefore, | a | = A1 + A4− (A2 + A3) Equation (1)

2) When n is an even number a (ωt) = A1sinωt + A3sinωt + A4sinωt + A2sinωt Therefore, | a | = A1 + A4 + A2 + A3 Equation (2)

3) When n is a half-order (n = m / 2, m: odd number) a (ωt) = A1sinωt + A3sin (ωt + mπ / 2) + A4sin (ωt + mπ / 2) + A2sin (ωt + mπ / 2 + mπ) Therefore, | a | = ({A1-A4) ² + (A3-A2) ² }) ^1/2 equation (3)

From the above equations (1) to (3), the following conditions are obtained. Condition where the odd-order component disappears: A1 + A4 = A2 + A3 Equation (4) Condition where the half-order component disappears: A1 = A4 and A2 = A3 Equation (5)

FIG. 3 shows the calculated values of A1 to A4 of the actual engine. A1 to A4 vary depending on the frequency, but are 100 to 200H which are important for the feeling.
In z, it turned out that A1 = 92.3 A2 = 67.5 A3 = 40.4 A4 = 11.2.

A1 to A4 change the explosive power when the compression ratio of each cylinder is changed, and thus change. Therefore, it is considered that A1 to A4 are changed by changing the compression ratio of each cylinder, and the expressions (4) and (5) are satisfied, thereby reducing the harmful components in feeling.

Here, the compression ratios of the first to fourth cylinders are α, β,
If γ and δ are multiplied, the explosive power is also about α, β, γ and δ times.

First, when examining the possibility that the expression (4) is satisfied, it is found that (A1 + A4) = 103.52 (A2 + A3) = 107.99, and it is apparent that the expression (4) is easily satisfied.

The inputs of the first to fourth cylinders are α, β, γ,
Assuming that δ (the initial value is 1.0), Equation (4) is used as the following behavior constraint condition equation. 92.3 <α + 11.2 × δ = 67.5β + 40.4 × γ Equation (6) α + β + γ + δ = 4 (the sum of the inputs of the first to fourth cylinders is unchanged) Equation (7)

If the change range of the input is within 30%, the following constraint condition expression is obtained. 0.7 ≦ α, β, γ, δ ≦ 1.3 Equation (8)

Further, assuming that the square of the half-order component is W,
The objective function W is expressed as follows: W = (92.3 × α-11.2 × δ) ² + (67.5 × β-40.4 × γ) Equation (9)

Α, β, γ, and δ may be determined so that the objective function W is minimized under each of these constraint conditions. This problem is a nonlinear optimal design problem and cannot be easily solved. Therefore, we devise the following.

If the values of α and β can be selected appropriately, γ and δ can be calculated from the behavior constraint equations (6) and (7).
Further, the objective function W can be calculated from α, β, γ, and δ.
Therefore, by setting the initial values of α and β to 0.8, and then looking at the results of varying each of α and β by a small amount, the human determines the change direction and satisfies the side constraint condition equation (8). By repeating the calculation until it becomes, convergence is achieved in eight iterations, and α, β, γ, and δ satisfying each constraint condition can be obtained.
Table 2 below shows the progress of the repeated calculation.

[0031]

[Table 1]

As a result, α = 0.86 (the compression ratio of the first cylinder is 0.86 times the original) β = 0.7 (the compression ratio of the second cylinder is 0.7 times the original) γ = 1. 1 (the compression ratio of the third cylinder is 1.1 times the original) δ = 1.3 (the compression ratio of the fourth cylinder is 1.3 times the original), the equations (4) and (5) are most satisfied. It is a shape that is closer.

Although such a change in the compression ratio can be devised in various ways, in the present invention, the above-mentioned Japanese Utility Model Application Publication No.
As described in Japanese Patent Publication No. 0, the head shape (thickness of the top land) of the piston of each cylinder is set corresponding to the above α, β, γ, δ.

That is, the thickness of the top lands of the pistons of the first and second cylinders is made smaller than the reference value using the thickness of the top lands of the pistons of the respective cylinders corresponding to the predetermined compression ratio as the reference value , and the third value is obtained . The top lands of the pistons of the cylinders and the fourth cylinder are made thicker than the reference value and at least
Meat of top land of piston of 2nd cylinder from 1st cylinder
The thickness is thinner.

FIG. 4 shows the vibration of each order component of the engine foot at this time, and it can be seen that most of the vibration components are reduced. It should be noted that the second and fourth order components are also reduced.

In the present invention, based on the above results,
It may be thick comb towards the thickness of the top lands of the third of fourth cylinders than cylinders piston.

[0037]

FIG. 5 shows an embodiment of one cylinder in the engine according to the present invention. In this embodiment, the bore × stroke is 80 × 80 mm, and the original compression ratio is set to “10” for each cylinder. " The position of the upper end of the thickness of the top land 3 of the piston 2 in each cylinder corresponding to the original compression ratio “10” is indicated by a dotted line.

Then, the thickness of the top lands of the pistons of the first and second cylinders is made smaller than the reference value while the thickness of the top lands of the pistons of the respective cylinders corresponding to the predetermined compression ratio is made smaller than the reference value. The thickness of the top lands of the pistons of the cylinders and the fourth cylinder is made thicker than the reference value, and the thickness of the top lands of the pistons of the second cylinder is made thinner than that of the first cylinder. for a better thickness Ku towards the wall thickness of the piston top land of the fourth cylinder, the dotted line position of the above, in the case of the first cylinder 1.6 mm in the case of the second cylinder as thin as 4.4mm 0.9m for the third cylinder
m, and in the case of the fourth cylinder, by increasing the thickness by 2.2 mm, the compression ratio ρ corresponding to the above α, β, γ, δ, respectively.
1 = 8.6, ρ2 = 7, ρ3 = 11, ρ4 = 13 are obtained.

The value of each cylinder with respect to the thickness of the top land is determined by the following equation: compression ratio = compression ratio = volume in cylinder at top dead center of piston (TDC) / bottom dead center of piston (BDC) It can be easily obtained from the cylinder internal volume at.

[0040]

As described above, according to the engine of the present invention, the thickness of the top land of the piston of each cylinder corresponding to the predetermined compression ratio is set as the reference value, and the top of the piston of the first cylinder and the second cylinder is used as the reference value. Make the thickness of the land thinner than the reference value ,
The thicknesses of the top lands of the pistons of the third cylinder and the fourth cylinder are made thicker than the reference value, and at least
Reduce the thickness of the top land of the piston of the second cylinder
Since it is configured so that the vibration of the engine foot can be reduced in most order component as shown in FIG. 4, it changes to the driver in the vehicle interior sound based on the half order component and odd order components Since the vibration that gives a bad feeling can be eliminated, the driver can hear a comfortable engine sound according to the amount of depression of the accelerator and can enjoy a comfortable drive.

[Brief description of the drawings]

FIG. 1 is a graph for explaining displacement of each cylinder of an engine according to the present invention.

FIG. 2 is a schematic diagram for explaining a principle of generating a displacement difference for each cylinder of the engine according to the present invention.

FIG. 3 is a graph showing experimentally obtained vibration frequency and amplitude of each cylinder in the engine according to the present invention.

FIG. 4 is a graph showing an improved state of each order component of a vibration frequency in the engine according to the present invention.

FIG. 5 is a view showing an embodiment in which the thickness of the top land of the piston is changed in order to change the compression ratio of each cylinder in the engine according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Piston 3 Top land In a figure, the same code shows the same or equivalent part.

Claims (2)

(57) [Claims] A first cylinder and a second cylinder each having a top land thickness of a piston of each cylinder corresponding to a predetermined compression ratio as a reference value.
The thickness of the top land of the piston cylinder thinner than the reference value, with the thickness of the top lands of the third cylinder and the fourth cylinder piston thicker than the reference value, at least said
Thickness of the top land of the piston of the second cylinder from the one cylinder
An engine characterized by a thinner side . 2. A engine according to claim 1, characterized in that there was thick comb towards the thickness of the top land of the piston of the fourth gas tube than said third air cylinder.