JPS584221B2 - Balancer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides a four-stroke in-line two-cylinder engine that performs equally spaced explosions.
Or in a two-stroke single-cylinder reciprocating internal combustion engine, 1
This invention relates to a balancer for an internal combustion engine that aims to eliminate or reduce the primary component of a couple generated by unbalanced inertial force and combustion gas pressure.

In the above-mentioned internal combustion engine, the first-order reciprocating partial inertia force remains as an unbalanced force, and together with the first-order component of the couple due to combustion gas pressure, is the main cause of vibration.

Currently, efforts are being made to reduce the vibration of the primary reciprocating inertia force by attaching an appropriate counterweight to the crank web and also providing a balancer shaft. There remains a force couple with a vector parallel to the crankshaft that is proportional to the distance between the centers of the balancer shaft and the crankshaft, and this causes vibration.

The inertia couple generated in the direction perpendicular to the cylinder center axis due to the provision of the balancer shaft accounts for a large proportion of the couple.

Further, if two balancers are provided, this couple can be eliminated, but the structure becomes complicated, space is required, and there are drawbacks such as increased weight and manufacturing cost.

On the other hand, the couple caused by the combustion gas pressure will be explained with reference to FIG.

That is, a component force is generated to the left in the horizontal direction starting from the piston pin, and a reaction force of the same magnitude as this force is also generated to the right in the horizontal direction at the central axis of the crankshaft.

Therefore, a couple is generated due to the gas pressure, with the distance between the piston pin and the central axis of the crankshaft being the arms of the couple.

This couple acts on the non-rotating parts of the engine, such as the engine block, and the direction of this couple is perpendicular to the plane of the paper in Figure 4, in other words, parallel to the crankshaft and perpendicular to the cylinder center axis. It is in the plane direction.

Conventional countermeasures against this problem include, when mounting the engine, installing the engine via an elastic body or the like.

Although this reduces vibration, it also increases the manufacturing cost of the mounting section, and is not a satisfactory solution.

This invention was made to improve the above-mentioned drawbacks, and by arranging one balancer shaft in a phase range with respect to the rotational direction of the engine that is different from that of the conventional balancer shaft, the above-mentioned combustion gas pressure can be adjusted. It is an object of the present invention to provide a balancer for an internal combustion engine that can cancel a force couple and an inertia couple generated by providing a balancer shaft based on both of these couples.

Hereinafter, the present invention will be specifically explained based on illustrated embodiments.

In the figure, numeral 1 is the cylinder center axis, 2 is the crankshaft, 3 is the balancer shaft 4 is the crankshaft center axis, 5 is the balancer center axis, 6 is the cylinder center axis 1 with the crankshaft center axis 4 as one side, and the engine A plane having an angle of 17° in the direction of rotation of , the other side being a straight line passing through the center of the crankshaft, 7 and 8 have the crankshaft center axis 4 as one side, and planes B and -
It is a plane that forms an angle B.

Here, angles are expressed as positive for the engine rotation direction and negative for the opposite direction, and a plane is defined as a plane perpendicular to the plane of the paper.

The rationale for installing a balancer in this internal combustion engine will be explained below.

When the combustion gas pressure acts on the piston in the cylinder due to the explosion of the gas mixture and pushes the piston down, this force is applied to the crankshaft via the connecting rod.

As can be understood by referring to Fig. 4, the force F acting on the above connecting rod is as follows: A: Piston area, P: Gas pressure Here, the product of the right angle component F' of the crank arm and the arm radius is , is the torque T applied to the crank arm.

Now, if the length of the connecting rod is l, then P (gas pressure) and the trigonometric function can both be expressed as a Fourier series.

In addition, the torque fluctuation due to inertia force is added to the final It is well known that it is expressed in the form of

Here, an and bn differ depending on the engine speed and throttle opening, but in a 4-stroke 2-cylinder or 2-stroke single cylinder, an explosion occurs every 360° of the crank angle, and 1
The following components are large and the terms expressed in the Fourier series of quadratic or lower order can be substantially ignored.

Therefore, if the above-mentioned equation is changed for the first-order component, T1 in this equation becomes as shown in FIG. 5, and when the crank angle θ=α, T1 becomes maximum, and its value is.

In addition, it becomes.

At this time, a reaction force is generated in the direction opposite to the crank rotation direction, and this reaction force becomes a force couple that attempts to rotate the engine body in the opposite direction to the crank rotation direction.

This couple is due to combustion gas pressure.

That is, the couple due to gas pressure is as shown in FIG.

Here, by substituting into the above equation, it becomes the same as equation (1), and as mentioned above, T1=a
1 cos θ + b 1 sin θ, and this equation is expressed as follows when α is a positive acute angle.

Therefore, if we consider the inertia force of the piston again, the inertia force of the piston is the product of the acceleration and mass of the piston, and if we express this mathematically, S = (r + l) - (r
cos θ+l cos ψ) Here, S: piston stroke r: crank arm length l: connecting rod length.

Now, if λ=l/r, S=(1-cosθ)+λr(1-cosψ), where,
Since l sin ψ = rsin θ, if we expand this equation, if the speed of the piston is u, (where ω is the angular velocity), the acceleration is, therefore, the values after the second order component are extremely small, and 1 It has less influence than the next component, so it can be omitted.

Therefore, acceleration α=ω2rcosθ, inertia force Fi=(W/g)ω2rcosθ (g: gravity, W: reciprocating weight) W/g is half-balanced and expressed as the sum of centrifugal forces that are reversely rotated in the −θ phase.

Now, when a single balancer shaft is provided as in the present invention, a moment M is generated depending on the distance from the center of the crankshaft.

This moment M is a first-order component because it relates to a balancer provided to balance the first-order component of the inertial force.

Since the force couple has a right angle component with respect to the center-to-center distance L, it follows from FIG. 6 that the couple causes the engine to rotate clockwise.

Since the above-mentioned couple of the primary component of the gas pressure is a counterclockwise couple of the engine, by making the above equations (3) and (4) equal, the respective couples can be balanced.

Therefore, since W, r, and ω in equation (4) are constant as described above, (L・W/2g・r・ω2) in equation (4) becomes (3)
So that it is equal to (√(a12+b12)) in the formula, (
4) Once L in the equation is determined, only the cos term remains.

That is, it is sufficient if the following formula holds true.

θ−α=θ−(90−β) That is, α=90−β.

Thus, when α=90−β, the torque T due to the gas pressure and the moment M have the same phase and become moments that cancel each other out.

Here, as is clear from FIG. 6, β is the angle at which the center position of the balancer shaft is measured from the cylinder center axis in the engine rotation direction.

According to the Fourier analysis results from the combustion chamber acupressure diagram based on experimental values, there is a plane 6 whose one side is the crankshaft central axis 4 and the other side is a straight line forming an angle β = 17° with the cylinder central axis 1 in the engine rotation direction. If the balancer shaft 3 that rotates in the opposite direction to the engine rotation is placed above the balancer shaft 3, the phase difference between the couple generated by providing the aforementioned balancer shaft and the couple due to the combustion gas pressure will be 180°.゜, which is the most effective offset.

Now, the relationship between the composite couple and the couple due to gas pressure can be expressed as a dimensionless number Φ
If expressed as , it becomes as follows.

Φ = (Absolute value of composite couple) / (Absolute value of couple due to gas pressure (or couple due to inertia)) Now, with β-17° as the reference, as shown in Figure 1, from there, move in the direction of engine rotation. If we consider B° and -B° in the reverse rotation direction and find the value using B as a parameter, we obtain a curve as shown in Figure 3. When Φ = 0, in other words, the curve of N in Figure 2 is obtained. The ideal effect can be obtained when the rotation speed is high.

Here, B indicates the effective installation range of the panther shaft.

According to experimental values, the above-mentioned value of 17° does not change much in the above-mentioned engine at full throttle or at partial load.

To explain this point with Figure 2, the couple of gas pressure and inertial force determined by the load condition of the engine, the product of the inertial mass of the reciprocating part and the crank radius, and the distance between the centers of the crankshaft 2 and balancer shaft 3. The first component of rotation speed N
, for example, is eliminated at the engine's maximum torque rotation speed, and the greatest effect can be expected around that rotation speed.

Furthermore, even if it is structurally impossible to install the balancer shaft 3 on the plane 6 at 17 degrees from the cylinder center axis 1, the same effect can be obtained in the vicinity, and as shown in FIG. When the balancer shaft 3 is placed in a space surrounded by two planes forming ±60 degrees with the plane 6 with the shaft central axis 4 as one side, Φ<1, that is, B
It is also effective when the angle is <60°.

Generally, in an example where only one conventional balancer shaft 3 is provided, the angle is 90° with respect to the cylinder center axis 1, so from Fig. 3, Φ = 1.2, and Φ becomes 1 or more In the balancer of the present invention, if B=0° (of course, B=60° is also possible), a great improvement can be expected.

As described in detail above, by providing one balancer shaft at a predetermined position, this invention not only functions as a normal balancer that corresponds to the primary component of the reciprocating partial inertia force, but also acts as a balancer based on combustion gas pressure. By canceling out or reducing the force couple with the inertia couple generated by installing a balancer shaft, it is possible to reduce vibrations in engine mounting, especially when operating at a constant load and constant rotation speed. The practical effect is great for institutions that do this.

[Brief explanation of the drawing]

Fig. 1 is a front view of an engine showing one embodiment of the present invention;
The figure is a diagram showing the relationship between the couple, the first-order component, and the rotation speed.
The figure is a diagram showing the relationship between the position of the balancer and its effect.
5 is a diagram showing the crank rotational force, FIG. 5 is a diagram showing the phase of the crank, and FIG. 6 is a diagram showing the relationship with the balancer shaft. 1...Cylinder center axis, 2...Crankshaft, 3...Balancer shaft, 4...
... Crankshaft, 5 ... Balancer center axis, 6 ... Plane, 7 ... Plane,
8...plane.

Claims (1)

[Claims] 1 In a 4-cycle in-line 2-cylinder or 2-stroke single-cylinder reciprocating internal combustion engine that performs evenly spaced explosions, it passes through the crankshaft center axis and is located above the crankshaft at 17° + 6 degrees in the engine rotational direction.
In a space surrounded by two planes forming an angle of 0° and 17°-60°, a central axis of a balancer shaft that rotates at the same speed in the opposite direction as the crankshaft is arranged parallel to the central axis of the crankshaft, A balancer for an internal combustion engine, characterized in that a primary component of the couple due to inertial force on the balancer shaft acts so as to cancel a primary component of the couple due to gas pressure applied to the crankshaft.