KR20040058618A - balancing structure for 3-cylinder offset engines - Google Patents

Abstract

PURPOSE: A balanced structure is provided to minimize the vibration and the noise by offsetting the change of the inertia and the inertia moment through the reset of an installed angle of a balance weight. CONSTITUTION: The weight center of a balance weight for a rotary inertia moment is arranged outside toward the lengthwise center of a crankshaft and arranged in the faced position toward the radius of the crankshaft at 150degrees from the weight center of first and third crank arms(12,12'). The balance weight for a rotary inertia moment balances the rotary inertia moment from a rotary weight of a crank device. The weight center of a balance weight for a primary reciprocation inertia moment is arranged inside toward the lengthwise center of the crankshaft and arranged in the faced position toward the radius of the crankshaft within 150degrees plus/minus a certain angle from the weight center of first and third crank arms. The balance weight for the primary reciprocation inertia moment balances the primary reciprocation inertia moment as a primary component of a reciprocation inertia moment from a reciprocation weight of the crank device. Thereby, an engine balance from the change of the inertia and the inertia moment is devised.

Description

Balancing structure for 3-cylinder offset engines}

The present invention relates to an equilibrium structure of a three-cylinder offset engine, and more particularly, in accordance with the reciprocating mass and rotational mass of the engine in the offset design between the center of the crankshaft and the center of the cylinder bore to reduce the side force between the cylinder bore and the piston. This invention relates to a balanced structure of a three-cylinder offset engine capable of achieving an engine balance by resolving an unbalance of an inertia moment resulting from a change in inertia force by changing a mounting angle of a balance weight.

Internal combustion engines, commonly referred to as engines, are connected to each other by a piston that reciprocates through the explosive force generated by combustion of a mixer in which fuel and air are mixed at an appropriate ratio in the combustion chamber, and the piston and the connecting rod are connected to each other. It is comprised by the crank mechanism which performs a rotational motion.

Among them, in the three-cylinder engine having three cylinder bores, the configuration of the crank mechanism is three first, second and third crank arms sequentially on the crank shaft 10 as shown in FIG. 12, 12 'and 12 "are radially equidistantly spaced (120 [deg.]), Respectively, and the balance weights 14 of predetermined weight are respectively applied to the first and third crank arms 12 and 12". Bars are attached in pairs, and the balance weights 14 are provided on the first and second balance weights 14a and 14b provided on the first crank arm 12 side, and on the third crank arm 12 side. And third and fourth balance weights 14c and 14d.

Here, the plurality of balance weights 14 is the crank shaft 10 in the first to third crank arms (12, 12 ', 12 ") is rotated by receiving the driving force through the connecting rod during the explosion stroke of the piston, It will serve to balance the dynamic balance that occurs over the entire battlefield.

In addition, the four balance weights 14 have their centers of gravity from the centers of gravity of the first and third crank arms 12, 12 ", respectively, as shown in FIG. 2 with respect to the crankshaft 10. FIG. It is arranged at an angle of 150 °, which is set from the concept of design taking into account the dynamic balance of the crankshaft 10.

That is, the first and second balance weights 14a and 14b are disposed at an angle of 150 ° from the first crank arm 12, and are spaced apart at an angle of 120 ° from the first crank arm 12. The third and fourth balance weights 14c and 14d are arranged on the third crank arm 12 "at an angle of 150 degrees therefrom.

However, in the conventional three-cylinder engine having the above-described structure, more specifically in the non-offset engine where the center of the crankshaft 10 and the center of the cylinder bore coincide with each other, In the explosion stroke, the piston reciprocates the inside of the cylinder, causing a lateral force to press against the thrust wall of the cylinder bore, which in turn causes a loss of driving force due to friction between the piston and the cylinder bore, resulting in worse fuel economy. do.

Accordingly, as shown in FIG. 3, the center O of the crankshaft 10 is eccentric by a predetermined amount e from the center O 'of the cylinder bore 16. Thus, a so-called three-cylinder offset engine has been proposed, in which the piston 18 reduces the side force (Fs) that pushes the thrust-side wall of the cylinder bore 16 during an explosion stroke of the engine. In the engine, the lateral force (Fs) that pushes the thrust wall of the cylinder bore 16 of the cylinder bore 16 during the explosion stroke is reduced compared to the engine that is not offset, thereby reducing frictional losses. Through the effect of promoting combustion (shortening of the main combustion period) by reducing the moving speed of the piston 18, the fuel economy can be improved.

That is, the side force Fs generated when the center O of the crankshaft 10 is offset during the downward movement of the piston 18 according to the explosion stroke of the engine is the center O of the crankshaft 10. It can be seen that as shown by the dashed line and the solid line, respectively, compared to the side force (Fs) generated when the offset is not offset, where the side force (Fs) is the connecting rod ( It corresponds to the horizontal component of the load on the load transmitted to the crank arm 12 through 20).

In addition, since a large part of the loss due to mechanical friction related to fuel economy is known to be caused by the side force (Fs), the reduction of the friction loss caused by the side force (Fs) as described above is a fuel economy when the engine is running. In the case of a normal engine, the center O of the crankshaft 10 is offset by a predetermined amount e from the center O 'of the cylinder bore 16 in the case of a normal engine. It is designed to improve the fuel economy from the reduction of friction loss due to the reduction of the side force Fs between the cylinder bore 16 and the piston 18.

However, in the case where the center O of the crankshaft 10 is offset from the center O 'of the cylinder bore 16 by a predetermined amount e as described above, when the piston 18 moves up, 4, the side force Fs, ie, the explosion stroke, which pushes the piston 18 to the anti-trust side wall of the cylinder bore 16, between the cylinder bore 16 and the piston 18. The side force (Fs), which acts in the opposite direction as compared to the time, increases rather as shown by the dashed line and the solid line, respectively, as compared to the case of non-offset. Thus, according to the direction of the reciprocating motion of the piston 18 The side force (Fs) generated alternately to the thrust side and the anti-trust side wall surface of the cylinder bore 16 is shown according to the rotation amount and the load condition of the engine, as well as the magnitude (solid and dashed lines). ) Is not only different, but also Since it acts as a regular vibration during operation, it may cause undesirable results when considering the NVH side of the engine.

Therefore, in order to set the optimum offset amount in offsetting the center O of the crankshaft 10 and the center O 'of the cylinder bore 16, the piston 18 is raised and lowered. In consideration of the degree of side force (Fs) applied to the thrust side and the anti-trust side wall of the cylinder bore 16, respectively, during the movement, it should be made at an appropriate level.

In this way, in the so-called offset engine in which the center O of the crankshaft 10 is eccentric from the center O 'of the cylinder bore 16 by a predetermined amount e, the cylinder bore 16 from the piston 18 The piston in operation has a structure of another crank mechanism compared to a non-offset engine, although it has the advantage of improving the fuel efficiency as the side force (Fs) transmitted to) is reduced. This results in a noticeable change in the displacement, velocity and acceleration of (18).

In particular, the change in acceleration is the reciprocation mass of the engine (the mass of the portion of the piston 18 including the small end of the connecting rod 20) and the rotation mass (connecting rod 20). The total mass of the crank arm 12 and the balance weight 14 portion, including a part of the large end of the reciprocating mass, which causes a change in the magnitude and direction of the reciprocating inertia force and the reciprocating moment of inertia by the reciprocating mass. The magnitude and direction of the force acting on each connection portion from 18 to crankshaft 10 is different from the existing non-offset engine, for example, causing a change in the swinging motion of the connecting rod 20, Considering the entire engine, the natural frequency of the crankshaft 10 can be changed by changing the inertia and moment of inertia related to engine balancing. Thus, the NVH characteristics of the vehicle are changed.

Therefore, in the application of an offset engine for eccentric the center O of the crankshaft 10 from the center O 'of the cylinder bore 16 by a predetermined amount e, a change in the load acting on each connecting portion. In addition, a review of the engine balance is required, which includes changes in engine balance resulting from changes in the respective inertia forces and moments of inertia with changes in the reciprocating and rotational masses of the engine, from which the power train system includes the engine. This is to reduce the occurrence of abnormal vibrations and noise in the system.

Accordingly, the present invention has been made in view of the above, and improves fuel economy by reducing the side force due to friction between the cylinder bore and the piston during the explosion stroke of the piston by offsetting the center of the crankshaft of the engine from the center of the cylinder bore. In order to reduce the change of the inertia force and moment of inertia caused by the change of the reciprocating and rotational mass of the engine according to the offset of the crankshaft center offset by resetting the installation angle of the balance weight, The purpose is to provide a balanced configuration of a three-cylinder offset engine that can minimize the generation of vibration and hence noise.

According to the present invention for achieving the above object, the first, second, and third crank arms are sequentially radially mounted at equal intervals on the crank shaft, respectively, and the first and second crank arms are arranged on the crank arm side. In the three-cylinder offset engine in which the balance weight is arranged and the third and fourth balance weights are arranged on the third crank arm side, the first and fourth balance weights have their centers of gravity first and third, respectively. Placed at an angle of 150 ° from the center of gravity of the crank arm, wherein the second balance weight is disposed at a separation angle of 150 ° + Δθ with respect to the first crank arm, and the third balance weight is placed on the third crank arm It is characterized in that arranged with a separation angle of about 150 ° -Δθ relative to.

1 is a perspective view schematically showing a crank mechanism of a conventional non-offset engine.

FIG. 2 is a conceptual diagram illustrating a separation angle between a crank arm and a balance weight for each cylinder in the crank mechanism of the non-offset engine shown in FIG.

3 is a conceptual view showing the side force generated during the downward movement of the piston in the offset engine.

4 is a conceptual view showing the side force generated during the upward movement of the piston in the offset engine.

5 is a perspective view schematically showing a crank mechanism of a three-cylinder offset engine according to the present invention.

6 is a conceptual diagram illustrating a separation angle between a crank arm and a balance weight for each cylinder in the crank mechanism of the offset engine shown in FIG. 5;

FIG. 7 is a conceptual diagram showing an arrangement state of a balance weight on the crank axis shown in FIGS. 5 to 6.

8 to 16 are graphs showing changes in various physical elements relative to the crank angle in the equilibrium of a three-cylinder offset engine according to the present invention, respectively.

<Description of Symbols for Main Parts of Drawings>

10-crank shaft 12-crank arm

14-balance weight 16-cylinder bore

18-piston 20-connecting rod

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the three-cylinder offset engine according to the present invention, as shown in FIG. 3, the center O of the crankshaft 10 (shown in FIG. 6) is a predetermined amount e from the center O ′ of the cylinder bore 16. Offset so as to reduce the side force Fs applied to the thrust wall surface of the cylinder bore 16 during the explosion stroke.

In such a three-cylinder offset engine, the crank mechanism has three first, second and third crank arms 12, 12 ', 12 "sequentially on the crank shaft 10, as shown in FIG. Are mounted radially at equal intervals (120 °), and a pair of balance weights 14 of predetermined weight are attached to the first and third crank arms 12 and 12 ", respectively. The balance weight 14 includes first and second balance weights 14a and 14b provided on the first crank arm 12 side, and third and fourth balances provided on the third crank arm 12 side. Weights 14c and 14d.

Here, the plurality of balance weights 14 are rotated when the crank arms 12, 12 ', 12 "from 1 to 3 receive the driving force through the connecting rod 20 during the explosion stroke of the piston 18. In order to achieve a dynamic balance occurring over the entire length of the crankshaft 10.

Further, the balance weights 14 are arranged at a predetermined angle with respect to the first and third crank arms 12 and 12 ", respectively, at a predetermined angle. First, the first and third crank arms 12 and 12" are disposed. The first and fourth balance weights 14a, 14d, which are disposed outwardly toward the longitudinal center of the crankshaft 10, respectively, balance the rotational moment of inertia resulting from the rotational mass of the crank mechanism during operation of the engine. Second and third balance weights corresponding to the equilibrium mass for the rotational moment of inertia, which are disposed inward toward the longitudinal center of the crankshaft 10 with respect to the first and third crank arms 12, 12 " 14b and 14c correspond to the equilibrium mass for the primary reciprocating moment of inertia which balances the primary reciprocating moment of inertia, which is the primary component of the reciprocal moment of inertia resulting from the reciprocating mass of the crank mechanism during operation of the engine.

In addition, the first and fourth balance weights 14a and 14d corresponding to the equilibrium mass for the rotational moment of inertia have their centers of gravity centered on the crankshaft 10 as described above. Are arranged at an angle of 150 ° from the center of gravity of (12, 12 "), so that the first and fourth balance weights 14a and 14d, which are the equilibrium masses for the rotational moment of inertia, respectively have a 180 ° phase difference. .

In contrast, the second balance weight 14b corresponding to the equilibrium mass for the first reciprocating inertia moment is disposed at a separation angle of 150 ° + Δθ with respect to the first crank arm 12, and the third balance weight ( 14c) is disposed at a separation angle of 150 ° -Δθ with respect to the third crank arm 12 ″, so that the second and third balance weights 14b and 14c which are equilibrium masses for the first reciprocating moment of inertia. Are each 180 degrees out of phase.

Accordingly, the first and fourth balance weights 14a and 14d corresponding to the balance mass for the rotational moment of inertia and the second and third balance weights 14b corresponding to the balance mass for the first reciprocating moment of inertia. 14c are arranged at equal distances outside the 1st and 3rd crank arms 12, 12 ", respectively, in the radial direction about the crankshaft 10 as shown in FIG. Lose.

As a result, when the reciprocating and rotating inertia forces and moments of inertia according to the reciprocating mass and the rotating mass of the crank mechanism occur during the rotation of the crankshaft 10, the plurality of balance weights 14a, 14b, 14c, and 14d balance the engine. It becomes possible to plan.

As such, in the crank mechanism of the three-cylinder offset engine, the second and third balance weights 14b and 14c, which are the equilibrium masses for the first reciprocating inertia moment, among the balance weights 14 are the first and third crank arms 12, respectively. 12 " with a phase angle of 150 ° + Δθ or 150 ° -Δθ, respectively, so that the center O of the crankshaft 10 and the center O 'of the cylinder bore 16 are respectively This is to balance the first reciprocal moment of inertia resulting from the unbalanced force to the unbalanced moment of inertia caused by being offset by a predetermined amount (e), and thus the process of selecting the placement angle for the equilibrium mass for the first reciprocating moment of inertia. Will be described in more detail below.

Prior to this, the crank mechanism including the crank shaft 10, the crank arm 12, and the balance weight 14 is assumed to be a rigid body, and does not consider the in-cylinder combustion pressure, The inertia force and moment of inertia of higher order terms are excluded from equilibrium, respectively.

In the engine configured as described above, the setting of the coordinate system and the setting of the behavior are as follows.

First, the vertical direction is set to the X-axis, the left-right direction to the Y-axis, and the longitudinal direction to the Z-axis, respectively, and the forces acting in the respective axial directions are called Fx, Fy, and Fz. The moments acting in the respective axial directions are called Mx, My, and Mz.

In addition, the condition for perfect equilibrium of the engine is that the sum of the forces acting in each axial direction and the sum of the moments acting in each axial direction are both zero.

First, in the three-cylinder offset engine, the position x of the piston 18 measured from the center O of the crankshaft 10 is the following general formula, i.e., the rotation angle of the crank arm 12. It can be expressed as a function according to (θ).

Here, C = e / l, λ = r / l, and e is an offset amount.

In addition, l is the length of the connecting rod 20, r is the length of the crank arm 12, θ is the rotation angle of the crank arm 12.

Then, in the general formula for obtaining the position (x) of the piston 18 according to the rotation angle (θ) of the crank arm 12, Proceeding to sum up and expand the terms of

here,

_{a 0 = λ (1/4} + 3C 2/8 + 15C 4/32 + ...) + λ 3 (3/64 + 45C 2/128 + ...) + λ 5 (15/256 + ...) + 1 / λ (1 + C ^2/2 + C ⁴ /8…)

_{a 2 = λ (1/4} + 3C 2/8 + 15C 4/32 + ...) + λ 3 (1/16 + 15C 2/32 + ...) + 15λ 5/512 + ...

^{_{a 4 = λ 3 (1/}} 64 + 15C 2/128 + ...) -3λ 3 / 256- ...

^{_{a 6 = λ 5/512 +}} ...

_{b 1 = C (1 + 3λ} 2/8 + 15C 4/64 + ...) + C 3 (1/2 + 15λ 2/16 + ...) + 6C 5/16 ...

^{_{b 3 = -C (λ 2/}} 8 + 15C 4/128 + ...) -C 3 λ 2 / 16- ...

^{_{b 5 = 3Cλ 4/128 +}} ... to be.

In addition, the derivative of the piston 18 according to the general formula for obtaining the position (x) of the piston 18 according to the rotation angle (θ) of the crank arm 12 to obtain the speed (u) of the piston 18, and by differentiating again The general formula for obtaining the acceleration α of the piston 18 can be derived as follows.

Where ω is the rotational speed of the engine (rad / sec).

In the above relation, in the case of the three-cylinder offset engine, the displacement of the piston 18 relative to the rotation angle θ of the crank arm 12 is higher than that of the non-offset engine, as shown in FIG. 8. It can be seen that the positions of the top dead center and the bottom dead center of 18) are moved in the rotational direction of the crank arm 12 at 0 ° and 180 °, respectively.

And, in the single cylinder engine reciprocating inertia force (X _re ) can be defined as follows.

Where m _re is the reciprocating mass and α is the acceleration of the piston 18.

Unlike non-offset engines where the offset amount is zero in this case

According to the addition of the sin term located on the right side, the change of the reciprocal inertia force in the offset single-cylinder engine relative to the rotation angle θ of the crank arm 12 is larger than that of the non-offset single-cylinder engine as shown in FIG. 9. It can be seen that the and directions differ in almost all areas.

In contrast, the rotational inertia force due to the rotational mass is not different between the offset engine and the non-offset engine. In this case, the rotational inertia force X _ro is as follows.

Where m _ro is the rotational mass.

On the other hand, the inertial force generated in each cylinder acts as an inertial moment with respect to the center of the engine to vibrate the entire engine, which in turn causes a vibration of the power train as one rigid body. As shown in FIG. 10, it may be defined as follows based on the crankshaft 10, which is the central axis of the engine.

Here, the reference axis in the direction perpendicular to the crankshaft 10 is set to X, the reference axis crossing the crankshaft 10 in the front-rear direction is set to Y, and the crankshaft 10 is set to Z. .

In this case, the force in each axial direction corresponds to the inertia force in the up-down direction, the left-right direction and the front-rear direction of the engine, respectively, and the moment in each axial direction is the yawing moment (Mx; yawing moment) and the pitching moment (My; pitching moment) and It corresponds to a rolling moment (Mz; rolling moment).

As such, the inertia force and moment of inertia in each axial direction that cause the vibration of the engine are called unbalanced or unbalanced moment, respectively, and these cause the vibration of the engine and wear and noise of the supporting parts such as bearings. .

Minimization of these unbalanced forces and unbalanced moments by examining them at any location in the engine (usually at the center of the engine) is called engine equilibrium, in which the force and moment due to combustion pressure in the engine are discussed in the preceding preceding article. It is common not to consider as one.

In this case, the equilibrium conditions for achieving full equilibrium of the engine are as follows.

Where i is the number of the cylinder bores 16.

On the other hand, the engine has an inertial force due to the reciprocating and rotating masses and the moment of inertia caused by the engine, so that each of them must be balanced.

The reciprocating inertia force (X _re ) in the case of non-offset is

It is a function of the form cosθ. Generally, higher order terms of 4th order or higher are small and are ignored. Only the first term (cosθ), the second term (cos2θ) and the third term (cos3θ) are considered as equilibrium targets. .

On the other hand, in the case of the offset engine,

Since the same sin term is added, the first term (sinθ) and the third term (sin3θ)... Equilibrium should also be reviewed.

In the present invention, a simulation program that can meet the engineering and performance requirements as much as possible by generating, evaluating, and optimizing the motion of the assembly in a real environment at the time of designing together with the water calculation for the in-line three- and four-cylinder engines to examine the engine balance. The interpretation through pro-mechanica motion can be complemented in parallel.

In addition, the 3D model and specifications for motion analysis are as follows, the length of the crank arm 12 is 40.1 mm, the length of the connecting rod 20 is 134.3 mm, the reciprocating mass is 0.389 kg, the rotational mass is 1.005 kg, offset The amount e was 20.0 mm, the pitch of the cylinder bore 16 was 85.0 mm, the rotation speed of the engine was 6000 rpm, and the load state was set to no load, respectively.

In addition, in the present invention, since the sum of the inertia force and the moment of inertia at the center of the engine is of interest, one ground plane is formed at the center of the crankshaft and connected to the pin joint, so that the redundancy = 0, which is an overconstraint index, is achieved. The reliability of the value of the result was secured.

After setting up the 3D model for the above motion analysis, the equilibrium of the reciprocal inertia force was first considered.

As shown in FIG. 11, the numbers of the cylinder bores 16 are denoted by i = 1, 2, 3,... When N is set and the angle of the crank shaft 10 of each cylinder in the x 'axis is α _i , each crank shaft 10 has a position of (θ + α _i ) with respect to the x axis.

In this case, the reciprocal inertia force in the i-cylinder is expressed as follows, and the cylinder-specific values may be added to the entire engine.

Investigation of the unbalanced reciprocal inertial force of a 3 and 4 cylinder engine using the relation above is as follows.

In the three-cylinder offset engine, the unbalanced force in the x-axis relative to the rotation angle θ of the crank arm 12 is shown. As shown in FIG. 12, the equilibrium of the third component, which is the highest order of the three-cylinder offset engine, is It can be removed with a balance shaft (not shown) that rotates at three times the speed of (10), but the three-cylinder offset engine clearly increases the up and down unbalance because it is almost impossible to adopt in a real engine. However, in terms of engine equilibrium, which ignores relatively small high order terms, at least the secondary components can still be considered balanced.

In contrast, as shown in FIG. 13, in the case of four cylinders, secondary components still exist and increase in size. The difference in magnitude occurs because the constants in the a ₂ term are different, and the increase in the secondary inertia force due to the offset is ΔX ₂ , ignoring the constants C ³ and λ ³ or more in the a ₂ term, as follows.

Where a ' ₂ is the offset is zero and ΔX is approximately 1.04 for the model engine. Since the phase is the same, it can be removed by a balance shaft rotating at twice the speed of the crankshaft 10 as in the conventional method.

Next, the equilibrium of the reciprocating moment of inertia of the 3D model for motion analysis was discussed.

The reciprocating inertia force causes a pitching moment, and the reciprocating moment of inertia in the ith cylinder can be defined from that shown in FIG.

In addition, the reciprocating moment of inertia in the i-th cylinder is expressed as follows by multiplying the general formula for obtaining the reciprocating moment of inertia by the distance l _i to the moment reference point. At this time, all the cylinder-specific values should be added to the entire engine.

In the above relation, the unbalanced reciprocal moment of inertia of a three- and four-cylinder engine is examined as follows.

Actual size is above results Multiplying by. The three cylinders add the sinθ component to the existing components.

When the pitching moment of the 3D model for motion analysis is considered, as shown in FIG. 15, the pitching moment is a combined moment of the rotational moment of inertia and the reciprocating moment of inertia. The rotational moment of inertia will be described later, and the pitching moment of the three-cylinder engine changes the magnitude and phase of the overall pitching moment because the added sin θ primary component and the existing cos θ primary component are converted into a composite function due to the offset.

At this time, when the ratio of the maximum value of the sinθ1st order and the cosθ1st order reciprocal moment of inertia is ΔM ₁ , the following equation is ignored when the constant C ³ , λ ³ or more of the term b _l is ignored.

This is about 0.145 for the 3D model engine for motion analysis according to the present invention.

The phase difference Δθ between the combined moment M _t and the cos θ first order reciprocating moment of inertia is as follows.

Here, θ t is the angle of the maximum value of the combined moment, θ _cosθ is the angle of the _cosθ first order maximum value, and + 8.8 ° for the model engine.

In addition, considering the first reciprocating moment of inertia of the 3D model for motion analysis, as shown in FIG.

That is, in the three-cylinder offset engine, the sinθ1st reciprocal moment of inertia, which is ΔM ₁ times larger than the existing cosθ1 order, is generated with a π / 2 phase difference, which causes the phase of the entire primary reciprocating moment of inertia to move by Δθ. It can be seen that.

At this time, the first reciprocating moment of inertia can be balanced by attaching a balance weight 14 of equilibrium mass to the crankshaft 10.

As shown in the unbalanced reciprocal moment of inertia, the maximum cos θ first order value is θ = 150 ° and the maximum value of the first composite moment is θ = 150 ° + Δθ.

Accordingly, the attachment angles of the second and third balance weights 14b and 14c, which are the primary reciprocal moments of inertia, are respectively 150 ° from the first to third crank arms 12, as shown in FIG. It can be seen that it must be moved by 150 ° + Δθ at.

That is, the three-cylinder offset engine according to the present invention is attached to the first to third crank arms 12 as the center between the crankshaft 10 and the cylinder bore 16 is offset by a predetermined amount e. The first and fourth balance weights 14a and 14d, which correspond to the equilibrium mass for the rotational inertia moment, among the plurality of equilibrium masses, are disposed in the same manner as the conventional one for the equilibrium of the rotational inertia moment, and in the equilibrium mass for the first reciprocating inertia moment. It can be seen that the corresponding second and third balance weights 14b and 14c should be arranged in an amount Δθ relative to the existing one to balance the synthetic primary reciprocating moment of inertia.

At this time, since Δθ is changed according to the specifications of the engine determined by the length of the crank arm 12, the length and the offset amount of the connecting rod 20, the setting value for this is a value selected from the above-mentioned equation. In the present invention, as described above, the arrangement of the crank balance mass and the concept thereof will be described in detail through a 3D model for motion analysis.

As described above, according to the equilibrium structure of the three-cylinder offset engine according to the present invention, in the three-cylinder engine, the center O of the crankshaft 10 and the center O 'of the cylinder bore 16 have a predetermined amount ( When offset to e), the general formula expressing the position x of the piston 18 measured from the center O of the crankshaft 10 as a function of the rotational angle θ of the crank arm 12. The change of inertia force is accompanied by the addition of the sin term, compared to the non-offset engine, resulting in a new synthetic first-order reciprocating moment of inertia where the existing cos terms and sin terms are synthesized and their phase is delayed by Δθ. The second and third balance weights 14b and 14c corresponding to the equilibrium mass for the first reciprocating inertia moment on the crankshaft 10 are 150 ° + Δθ to 150 ° -Δθ as compared to the three-cylinder non-offset engine. Loads acting on each connecting portion of the crank mechanism Engine equilibrium can be achieved from each change of inertia and moment of inertia due to changes in the reciprocating and rotational masses of the engine resulting from the change of, thereby reducing the abnormal vibration and noise associated with the powertrain system including the engine. The effect is to reduce the occurrence.

Claims (4)

Crank arms 12, 12 'and 12 "are sequentially mounted on the crank shaft 10 at equal intervals radially, respectively, and are placed on the first crank arm 12 side. In the three-cylinder offset engine in which the first and second balance weights 14a and 14b are arranged and the third and fourth balance weights 14c and 14d are arranged on the third crank arm 12 side. Equilibrium mass for rotational moment of inertia, which balances the rotational moment of inertia resulting from the rotational mass of the crank mechanism, has its center of mass arranged outward toward the longitudinal center of the crankshaft 10, respectively. Placed at radially opposite positions of the crankshaft 10 at an angle of 150 ° from the center of gravity of the third crank arm 12, 12 "; The equilibrium mass for the primary reciprocating moment of inertia, which balances the primary reciprocal moment of inertia, which is the primary component of the reciprocating moment of inertia resulting from the reciprocating mass of the crank mechanism, has its center of mass directed toward the longitudinal center of the crankshaft 10. Respectively disposed inwardly and opposed in the radial direction of the crankshaft 10 at an angle of 150 ° + Δθ to 150 ° -Δθ from the center of gravity of the first and third crank arms 12,12 ″, respectively. Equilibrium structure of a three-cylinder offset engine, characterized in that arranged in a predetermined position. The method of claim 1, The balance mass for the rotational inertia moment is the first and fourth balance weights 14a and 14d, and the balance mass for the first reciprocating moment of inertia is the second and third balance weights 14b and 14c. Equilibrium structure of the cylinder offset engine. The method of claim 2, The three cylinders are characterized in that the first balance weight 14a and the fourth balance weight 14d and the second balance weight 14b and the third balance weight 14c are arranged to have a phase difference of 180 °, respectively. Equilibrium structure of the offset engine. The method of claim 1, [Delta] [theta] is set from the following general formula that measures the position x of the piston 18 from the center O of the crankshaft 10 according to the rotation angle [theta] of the crank arm 12. , Equilibrium structure of the three-cylinder offset engine, characterized in that changed according to the specifications of the engine. Where C = e / l, λ = r / l, e is the offset amount, l is the length of the connecting rod, r is the length of the crank arm, and θ is the rotation angle of the crank arm.