First-Order Balancer of Internal Combustion Engine

The present invention relates to a first-order balancer of an internal combustion engine by which vertical and horizontal first-order unbalanced moments arising in an internal combustion engine may be simultaneously balanced.

Generally in internal combustion engines, in a four-cylinder diesel engine for example, vertical and horizontal first-order unbalanced moments arise during the driving thereof. Such first-order unbalanced moments have been conventionally balanced by fitting fly-wheels with counterweights placed thereon on the front and rear ends of a shaft of a diesel engine, and allowing the fly-wheels to rotate with the rotation of the shaft.

In the above-mentioned case, however, the sum of the vertical first-order unbalanced moment and the horizontal first-order unbalanced moment is maintained at a constant relationship, and when one of the first-order unbalanced moment is reduced by the compensation thereof, the other first-order unbalanced moment is increased thereby, causing an inconvenience that both vertical and horizontal moments may not be simultaneously balanced.

While chain-balancers or electric balancers have been conventionally used to balance the vertical second-order unbalanced moment and to decrease the vibrating force of one direction, namely the vertical direction, if chain-balancers or electric balancers are applied for balancing vertical and horizontal first-order unbalanced moments, the counterweights or the balancers become too big to be loaded on diesel engines of vessels and so on.

A first-order balancer of an internal combustion engine in accordance with the present invention comprises forward-rotating fly-wheels fitted on both ends of a shaft and allowed to rotate in the same direction as said shaft, backward-rotating fly-wheels fitted respectively on said both forward-rotating fly-wheels and allowed to rotate in the opposite direction from said both forward-rotating fly-wheels, forward-rotational counterweights placed on said both forward-rotating fly-wheels, and backward-rotational counterweights placed on said both backward-rotating fly-wheels and having different weights from said both forward-rotational counterweights.

The present invention will be further described by way of example, with reference to the accompanying drawings, in which:

FIGS. 1a and 1b are front and side views of a first embodiment of a first-order balancer of an internal combustion engine in accordance with the present invention;

FIG. 2 is an enlarged view of a portion in FIG. 1;

FIG. 3 is a perspective view of main portions in FIG. 1;

FIG. 4 is a balancing system of the first embodiment in FIG. 1;

FIGS. 5a and 5b are compensation conditions of vertical and horizontal first-order unbalanced moments, respectively, in the first embodiment in FIG. 1;

FIGS. 6a and 6b are front and plain views of a second embodiment of a first-order balancer of an internal combustion engine in accordance with the present invention; and

FIG. 7 is an enlarged side section view of a portion in FIG. 6.

The description hereinafter will discuss a first embodiment of the present invention with reference to FIGS. 1 to 5.

A crank 2 is installed within a four-cylinder diesel engine 1. A shaft 3 rotates with the rotation of the crank 2. Two forward-rotating fly-wheels 4 and 5 are fitted on both ends of the shaft 3 and rotate in the same direction as the shaft 3. Two forward-rotating gears 6 and 7 are formed on the forward-rotating fly-wheels 4 and 5, respectively. Two backward-rotating fly-wheels 8 and 9 are fitted on the outer sides of forward-rotating fly-wheels 4 and 5, respectively, and two backward-rotating gears 10 and 11 are formed on the backward-rotating fly-wheels 8 and 9, respectively. Two bevel gears 12a and 12b are fitted between the forwarding-rotating gear 6 and the backward-rotating gear 10 at one end of the shaft, and allow the backward-rotating fly-wheel 8 to rotate in the opposite direction from the rotation of the forward-rotating fly-wheel 4. The bevel gears 12a and 12b are holded on a mount 13a. Two bevel gears 14a and 14b are fitted between the forward-rotating gear 7 and the backward-rotating gear 11 at the other end of the shaft, and allow the backward-rotating fly-wheel 9 to rotate in the opposite direction from the rotation of the forward-rotating fly-wheel 5. The bevel gears 14a and 14b are holded on a mount 13b, in a similar manner to the bevel gears 12a and 12b. Two forward-rotational counterweights 15 and 16 are placed on the forward-rotating fly-wheels 4 and 5, respectively, and two backward-rotational counterweights 17 and 18 are placed on the backward-rotating fly-wheels 8 and 9, respectively. The backward-rotational counterweights 17 and 18 have a different weight from the forward-rotational counterweights 15 and 16. It is to be noted that arrows shown in FIG. 3 indicate the respective directions of rotation.

As shown in FIG. 4, by substituting two forward-rotating masses 15' and 16' for the forward-rotational counterweights 15 and 16, respectively, and substituting two backward-rotating masses 17' and 18' for the backward-rotational counterweights 17 and 18, respectively, and by setting the distance from the center of the shaft 3 to each of the masses 15' and 16' as R1 and also setting the distance from the center of the shaft 3 to each of the masses 17' and 18' as R2, the coupling moments for both forward-rotating masses 15' and 16' and both backward-rotating masses 17' and 18', ma and mb, respectively, may be expressed in equations (1) and (2) hereinafter shown:

where W is the weight of the forward-rotational counterweights 15 and 16, w is the weight of the backward-rotational counterweights 17 and 18, .omega. is an angular velocity at which the shaft 3 rotates, L1 is the distance between two forward-rotating masses 15' and 16', and L2 is the distance between two backward-rotating masses 17' and 18'. The vertical first-order unbalanced moment to be compensated arises as ma+mb, while the horizontal first-order unbalanced moment for compensation arises as ma-mb.

In so-called uncompensated conditions, vertical and horizontal first-order unbalanced moments, Mva and Mha, respectively may be expressed in simple equations (3) and (4) hereinafter shown:

where mv and mh are vertical and horizontal maximum first-order unbalanced moments, respectively, .theta. is the rotational angle and .epsilon. is the initial phase.

Therefore, both first-order unbalanced moments Mva and Mha shown in equations (3) and (4) as being the vibrating moments in uncompensated conditions should be compensated by means of the forward-rotational counterweights 15 and 16 and the backward-rotational counterweights 17 and 18, and the both first-order unbalanced moments Mva and Mha in uncompensated conditions may be balanced out by said both first-order unbalanced moments for compensation so that both compensated vertical and horizontal first-order unbalanced moments Mvb and Mhb become zero.

Here the compensated vertical and horizontal first-order unbalanced moments Mvb and Mhb may be expressed in equations (5) and (6) hereinafter shown respectively:

where mv' and mh' are the maximum first-order unbalanced moments for compensation by means of the forward-rotational counterweights 15 and 16 and the backward-rotational counterweights 17 and 18, respectively, and .gamma. is the initial phase of said mv' and mh'.

Therefore, by adjusting the weight W of the forward-rotational counterweights 15 and 16, the weight w of the backward-rotational counterweights 17 and 18, and the placing positions of the counterweights 15, 16, 17 and 18 on the respective fly-wheels 4, 5, 8 and 9 so that the following equalities may be achieved:

equations (5) and (6) may be transformed to equations (7) and (8) hereinafter shown respectively: ##EQU1##

Furthermore, from the fact that equations (7) and (8) always become zero, equations (9) and (10) are derived:

From equations (9) and (10), equations (11) and (12) are derived:

Against the vertical first-order unbalanced moment Mva arising in uncompensated conditions as shown by a solid line in FIG. 5a, a vertical first-order unbalanced moment for compensation as shown by a dotted line in FIG. 5a acts as a counteracting moment, and the vertical first-order unbalanced moment in uncompensated conditions is balanced out by the vertical first-order unbalanced moment for compensation to be zero. Similarly, against the horizontal first-order unbalanced moment arising in uncompensated conditions as shown by a solid line in FIG. 5b, a horizontal first-order unbalanced moment for compensation as shown by a dotted line in FIG. 5b acts as a counteracting moment, and the horizontal first-order unbalanced moment in uncompenstated conditions is balanced out by the horizontal first-order unbalanced moment for compensation to be zero.

The description hereinafter will discuss a second embodiment of the present invention with reference to FIGS. 6 and 7.

The second embodiment is different from the first embodiment shown in FIGS. 1 to 3 in that two forward-rotating fly-wheels 4' and 5' are fitted on both ends of the shaft 3 of an engine 1, forward-rotating gears 6' and 7' are formed on the forward-rotating fly-wheels 4' and 5', respectively, two backward-rotating fly-wheels 8' and 9' are fitted in parallel with the forward-rotating gears 6' and 7', backward-rotating gears 10' and 11' are formed on the backward-rotating fly-wheels 8' and 9' and engage with the forward-rotating gears 6' and 7', respectively, to rotate in the opposite direction from the rotation of the shaft 3, forward-rotational counterweights 15' and 16' with a weight of W are placed on the forward-rotating fly-wheels 4' and 5', respectively, and backward-rotational counterweights 17' and 18' with a weight of w are placed on the backward-rotating fly-wheels 8' and 9'. It is to be noted that arrows shown in FIG. 7 indicate the respective directions of rotation.

When the forward-rotating fly-wheels 4' and 5' rotate in the same direction as the rotation of the shaft 3, the backward-rotating fly-wheels 8' and 9' rotate in the opposite direction from the rotation of the shaft 3 and the vertical and horizontal first-order unbalanced moments arising in uncompensated conditions are simultaneously balanced out by the vertical and horizontal first-order unbalanced moments for compensation by means of the respective counterweights 15', 16', 17' and 18', in a similar manner as hereinbefore described.

According to the first-order balancer of an internal combustion engine of the present invention, vertical and horizontal first-order unbalanced moments arising during the driving of a diesel engine may be simultaneously balanced to zero, by placing forward-rotational counterweights with a weight of W on both forward-rotating fly-wheels, placing backward-rotational counterweights with a weight of w on both backward-rotating fly-wheels, and providing gear-wheel mechanisms comprising forward-rotating gears, backward-rotating gears and level gears.