JPH0774661B2 - Balancer device for V8 cylinder engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a 4-cycle V-8 cylinder engine,
The present invention relates to a balancer device that realizes a so-called perfect balance in which the secondary inertia force and the couple force based on the secondary inertia force are all zero and that reduces the rolling moment caused by the reciprocating inertia force and the combustion pressure.

(Prior art and its problems) Conventionally, an in-line eight-cylinder engine, 90
It is known that a V-type 8-cylinder engine having a ° V and 90 ° crank arrangement, and a V-type 8-cylinder engine having a 50 ° to 60 ° V and 90 ° crank arrangement with a crank pin offset.

However, in the first in-line 8-cylinder engine, the total length of the engine becomes long, and the supercharger requires a pulse converter or the like.

In addition, in the second V-type 8-cylinder engine with the 90 ° V and 90 ° crank arrangement, in order to obtain the primary unbalanced couple, the balance weight of the crankshaft is overbalanced or the balance weight is set to the crank throw. A so-called outer balancer arranged outside is required, and uneven firing occurs between the cylinders of the V-shaped one bank, resulting in poor supercharging performance.

Further, in the third crankpin offset engine, the secondary balance cannot be perfectly taken, and the V-shaped one bank cannot ignite at equal intervals.

(Object of the Invention) In a four-cycle eight-cylinder V-type engine, when the crank arrangement is a so-called 180 ° arrangement and four cylinders in a single row are ignited at equal intervals, unbalanced reciprocating motion that fluctuates at twice the crankshaft speed. Although the inertial force remains, the present invention provides the unbalanced reciprocating inertial force on one eccentric balancer shaft that rotates at twice the number of revolutions of the crankshaft by providing a balance weight,
An object of the present invention is to provide a balancer device for a V-type 8-cylinder engine that can achieve secondary balance completely and reduce rolling moment due to piston side pressure.

(Structure of the Invention) (1) Technical Means The present invention sets the V angle of a 4-cycle V-type 8-cylinder engine to 60 °, arranges the crankshaft 10 in a so-called 180 °, and rotates the crankshaft at twice the rotational speed. Only one balancer shaft 20 that rotates in the same direction as the crank shaft 10 is provided, and the center of rotation of this balancer shaft 20 is the piston 18 with respect to the center of the crank shaft.
Eccentric to the side opposite to the engine vertical centerline Oe on the opposite side of
Assuming that the center of rotation of the balancer shaft 20 has a deviation angle ψ and a length l, The balancer device for a V-type 8-cylinder engine is characterized in that the rolling moment due to the piston side pressure is reduced.

(2) Action When a 180 ° crank arrangement is adopted in a 60 ° V-type 8-cylinder engine, an unbalanced inertial force that rotates in the same direction as the engine rotation direction and at a double speed remains, but the balancer shaft does not crank. Since it is eccentric with respect to the shaft center and rotates in the same direction at twice the number of rotations, it is possible to cancel this secondary unbalanced inertial force to achieve perfect balance and reduce the rolling moment due to piston side pressure. .

(Example) In FIG. 1, which is a schematic diagram of the structure of a 4-cycle adopting the present invention, Oc is the center of the crankshaft 10 (FIG. 2). As shown in FIG. 2, the crankshaft 10 is arranged at 180 °, and the four crank throws are in the same plane and are plane-symmetric. A piston 18 is connected to the crank pin 12 via a connecting rod 16.

With respect to the crankshaft center Oc, more specifically, a balancer shaft 20 centered on a balancer center Ob that is eccentric to a position with a deviation angle ψ and a length l with respect to an engine vertical centerline Oe described later.
(Fig. 2) is pivotally supported. The balancer shaft 20 is, for example, geared or chain-driven so as to rotate in the same direction as the crankshaft 10 at twice the number of rotations. The balancer shaft 20 is provided with a balancer weight 22 having a predetermined mass.

Next, a description will be given of the setting of ψ and l so that the balancer shaft 20 and the balancer weight 22 can cancel the secondary unbalanced combined amount of the crankshaft 10 and also reduce the rolling moment due to the lateral pressure of the piston 18.

First, in the case of the crankshaft 10 arranged at 180 °, the couple unbalanced combined component becomes zero, and only the secondary inertial force remains unbalanced.
The value of the residual unbalanced force F1 is expressed by the following equation (1) with reference to FIG.

W _p; reciprocating inertia force gamma; crank radius omega; crankshaft rotation angular velocity _{(2πrpm / 60) g z;} ≒ ρ + ρ 3/4 (ρ = r / L L is the rod length) beta; V angle theta; crank angle (= Ωt) g; Gravitational acceleration From this equation (1), the unbalanced force F1 rotates at twice the engine speed, and in the opposite direction to the component that rotates in the same direction as the engine rotation direction (first term in parentheses). It can be seen that it is composed of a rotating component (second term in parentheses).

Here, when the V angle is set to β = 60 °, the second term of the equation (1) becomes zero, and only the same direction as the engine rotation direction remains. Therefore, equation (1) is become.

In order to cancel this, a balancer that generates a centrifugal force of F2 = -F1 is required, but as shown in Fig. 1, the balancer center Ob is eccentric from the crankshaft center Oc by ψ, l. When it is placed in the position, the unbalanced inertial force of the formula (1-a) disappears.

On the other hand, a new moment M M = ‖F ₁ ‖l sin (2θ + ψ) (2) is generated. Here, if ψ and l are selected as optimum values, it is possible to cancel out the secondary component of the rolling moment due to the lateral pressure of the piston 18. Incidentally, 180
The second component is the largest in the rolling moment of the 4-crank arrangement with the crank arrangement. The second component of this rolling moment is become. From equations (2), (3), and (4) To get Therefore, ψ and l in FIG. 1 are replaced by (5) and (6)
If set by the equation, the secondary component of the rolling moment will also disappear.

(Effects of the Invention) As described above, in the balancer device for the V-type 8-cylinder engine according to the present invention, the V angle of the 4-cycle V-type 8-cylinder engine is adjusted.
The crankshaft 10 is arranged at a so-called 180 ° position as shown in FIG. 1, and the balancer shaft 20 that rotates in the same direction as the crankshaft 10 at twice the rotation speed of the crankshaft is set to 60 °.
Only the book is provided, and the rotation center Ob of the balancer shaft 20 is eccentric to the crankshaft center Oc on the opposite side of the piston 18 from the engine vertical centerline Oe to reduce the swinging moment due to the piston side pressure. In particular, assuming that the rotation center Ob of the balancer shaft 20 has a deviation angle ψ and a length l, Since the secondary balance of the crankshaft 10 is perfectly established, the rolling moment due to the piston side pressure can be reduced. In short, according to the present invention, in a 4-cycle V-type 8-cylinder engine, perfect balance (first and second unbalance forces and unbalance moments are all zero) is realized, and the rolling moment can be reduced.

[Brief description of drawings]

FIG. 1 is a structural schematic diagram of a V-type 8-cylinder engine adopting the present invention,
FIG. 2 is a view on arrow II of FIG. 10 …… Crankshaft,
12 …… Crank pin, 18 …… Piston, 20 …… Balancer shaft, 22 …… Balancer weight

Claims (1)

[Claims] 1. A 4-cycle V-type 8-cylinder engine having a V angle set to 60 ° and a crankshaft (10) arranged at a so-called 180 ° position,
Only one balancer shaft (20) that rotates in the same direction as the crankshaft (10) at twice the crankshaft speed is provided.
The center of rotation of the balancer shaft (20) is laterally eccentric to the crankshaft center on the side opposite to the piston (18) from the engine vertical center line (Oe), and the center of rotation of the balancer shaft (20) is adjusted. , Declination ψ, and length l, The balancer device for a V-type 8-cylinder engine is characterized in that the rolling moment due to the piston side pressure is reduced.