CA1056677A - Four cylinder in-line engine with secondary balancer system - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A four cylinder in-line engine is disclosed with a secondary balancer system, wherein at least one pair of balancer elements are arranged substantially at an identical horizontal distance from the longitudinal axes of the engine cylinders and on lines which are substantially parallel to the plane of the longitudinal axes. The distance taken between the axes of the paired balancer elements in the direction of the cylinder axes is determined at such desired values as to satisfy the engine usage and design. The paired balancer elements are rotated in the opposite directions to each other with a speed of rotation twice as high as that of the engine crankshaft, such that the lower balancer element is rotated in the opposite direction to that of the engine crankshaft.

Description

i77 FIEl~D OF THE INVENTION

The present invention relates to a four cylinder in-line engine with a secondary balance system, by which not only vertical secondary vibromotive forces but also secondary moments due to the reciprocating masses and the internal combustion explosion are eliminated.

DESCRIPTION OF THE DRAWINGS
__ ____---------- , 1 O Fig. 1 shows a schematic diagram of the forces acting on the components of a reciprocating engine utilizing the prior art secondary balancer system;
Fig. 2 shows a schematic diagram of the forces acting on the components of a reciprocating engine utilizing a secondary , balancer system according to the present invention; ;
' Figs. 3 - 37 show graphical illustrations of equi-!, vibromotive moment diagrams for selected parameters; ~ `
. ~ .
' Fig. 38 is a graph showing harmonic coefficients for ' the torque generated by the combustion explosion;
Fig. 39a shows a second embodiment of a balancer system according to the present invention; and ~' Fig. 39b shows a third embodiment of a balancer system according to the present invention.
' Prior Art Z ,: -, In a four cylinder in-line engine, the following forces are well known in the art to cause vibration of the engi~le due to the reclprocating masses including: -(a~ a vibromotive force (mainly of secondary order);
(b) a vibromotive moment due to the reciprocating masses ;
1 30 (mainly of the secondary order); and .: . .:

:

1 (c) a vibromotive moment due to the internal explosion (mainly of the secondary order).
.` , ; For an engine in an automotive vehicle of smaller or medium size, the vibromotive force is estimated about one ton, while the vibromotive moments are about one-half oE the vibromotive force. ;;~
In order to damp the vibrations of such four cylinder in-line engine, there has been proposed and put into actual ~
practice a system, by which the secondary component of the ~ ;
vibromotive force of the above item (a) or of the vertical vibro- ~ ;
motive force due to the reciprocating masses can be eliminated.
In an example of this system, a pair of balancer elements 2' and

2' are, as shown in Fi~. 1, arranged substantially symmetrically ~-relative to a cylinder axis 3'. The paired balancer elements 2' and 2' are rotated in the opposite directions to each other `1 with a speed of rotation twice as high as that of an engine crankshaft, thus eliminating the vertical vibromotive forces.

First, the balance will be theoretically examined in ~ ;
!
the following. Here, if the vertical vibromotive force due to the reciprocating masses is assumed to be F'l while the vertical `
vibromotive force due to the balancer system F'2, then in order to damp the vertical vibromotive force the two forces are required to satisfy the equation:
.

~ F ' l + F ' 2 = -If, moreover, the forces are assumed to be positive in the vertically upward direction, then the force can be ex-pressed by the following equation:
, ~
F'l = 4mr~2 (C2cos 29 + C4COS 4~ +----)1 ' .

;

. !

~ ' :

0~6g~7 1 where ; C = 1 ~ , and 2 ~ 4~~3 C~ 3 4~ 316~ 5 The letter A ordinarily takes a value of 3 to 4, and the terms subsequent to 1 exert a small influence on the above equations.
' ~ 3 Thus, the equation for F'l can be simplified as follows:

F'l = 4mr~2 cos 2 : 10 The equation for F'2 above is where the letter m indicates the reciprocating mass for one ~ -cylinder, the letter ~ the angular velocity of rotat.ion of the crankshaft, the letter r one-half of stroke of the piston,~the Y letter a the crack angle, the letter ~ = Q/r the connecting rod ratio, the letter Q the length of the connecting rods, the .
~ letter m~ is the mass of one balancer element, and the letter rB
;,~ the distance between the center of rotation and the centroid of ; i ~o , , . . ~ .
the balancer element. -~
Therefore, the summation of the forces F'l and F'2 yields F'l ~ F'2 = 4mr~2 cos 2~ - 2mBrB(2~) cos 2a, and this summa~
tion has to be zero. Consequently, mB is expressed as mB = mr . ~ -According to this equation, in order to eliminate the vertical vibromotive forces of a four cylinder in-line engine~
it is sufficient that one pair of balancer elements, which have their unbalanced mass mB expressed as mr , are rotated in the opposite directions to each other (in order to balance the horizontal forces) with a speed of rotation twice as high as that j of the engine crankshaft~
~ `, ' ~ ~3~ ~

6~7 1 As is easily understood from the foregoing description, :.
`. in the case of actual practice, the vibromotive force of the ~ ~
item (a) due to the reciprocating masses can be eliminated. ~:
~. However such a balancer system cannot produce moments to counter `i the effects of vibromotive moments due to item (b) and (c). As a result, it has been considered impossible to set the four cylinder straight-type engine free from vibrations.

SUMMARY OF THE INVENTION

It is~ therefore, an object to provide a ~our cylinder . , .
in-line engine of reciprocating type, in which the vibromotive moment of the items (b) and (c) can be balanced to zero with a resultant reduction in vibrations but with the engine performance being maintained at an excellent level.
According to the present invention, there is provided.
a four cylinder in-line engine with a secondary balancer system, which is characterized in that at least one palr ~f balancer ~ `. -elements is arranged substantially at an identical distance .- ~ ;
from a pla.ne contain.ing the lonaitudinal axes of the engine ;~
cylinders and on line which are substantially in parallel with said longitudinal axes, in that the distance taken between the axes of the paired balancer elements in a direction parallel to that of the cylinder axes is determined at such desired values as to satisfy the engine usage and design, and in that the paired .
balancer elements are rotated in the opposite direc~ion to each other with a speed of rotation twice as high as that of the : .
engine crankshaft in a manner that the lower balancer element ~;
:- is rotated in the opposite direction to that of the engine crankshaft. In the engine according to the present invention, moreover, the vibromotive moments due to the-reciprocating masses . ~ and the combustion explosion, as well as the vertical vibromotive force of the conventional engine can be efficiently eliminated.
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~5f~67 7 ~ :

DETAILED DESCRIPTION OF THE INVENTION
. ________~
One embodiment of the present invention will be described in detail with reference to Fig. 2. Designated at ~.
reference numerals 1 and 2 are, respectively, a crankshaft and ...
a connecting rod, the latter having its larger end 3 journaled :~
to a pin 4 of the former and its smaller lend 5 journaled to a ;~
` piston 7 through a pin 6. Reference numeral 8 indicates the "! engine cylinder. Designated at reference numerals 9 and 9' are at least one pair of balancer elements, which are arranged .
substantially at an identical distance from the longitudinal :
axes 10 of the engine cylinders 8 and respectively on such lines :
11 and 11' as are directed substantially in parallel with the longitudinal axes 10. Moreover, designated at reference numerals 13 and 13' are balancer shafts of the balancer elements 9 and 9', which shafts are made coactive with the crankshaft 1 by way of~
gears, sprocket chains or the like so that their speed of rotation ! may be twice as high as that of the crankshaft 1. ~ ~
The four cylinder in-line engine according to the r : ' ~0 present invention has the aforedescribed construction arrangements ~:~ and its resultant effects will be detailed in the following.
If it is assumed for the straight-type four-cylinder ; engine that the moment of item (b) due to the reciprocating ~ ;
masses is Ml, that the moment of item (c) due to the combustion explosion is M2, and that the counter-moment due to the balancers ~ is M3, then these moments Ml, M2 and M3 are obtained from the ~::
following equations: `
(A) As to M~
The moment Ml due to the reciprocating masses of the .
straight-type four-c~linder engine is well known in the art to be expressed as: (Any of the moments will take a 1(~S6~77 1 positive value in ~h~ direction of rotation of the crank~
shaft.) ~1 = ~ 4mr2~2t2sin 2~ - 4mr2~2t4sin 4 where t2 and t4 are harmonic coefficients expressed as:
.' , t2 = ~ 1 - 1 ---: t4 = - 1 - 1 --~ .

' (B) As to M
:~ 10 2 ~ .
', As is also well known in the art, a torque curve is . derived from an indicator diagram of the engine cylinder, and the curve -thus obtained is then expanded into Fourier series, .~ to yield the torque T, as follows~
~'f , T = To = ~D2r ~(a2sin 2~ + b2cos 2~) ~ (a4sin 43 -t b4CoS 4~) +~] ' `I where .
, ~ To denotes an average torque; a2, a4, b2 and b4 harmonic ' ~;;
~ coefficients; and D a bore diameter~of the engine '. ' cylinders.
Since the amount M2 due to the explosion is a reaction 7., of the torque variation, it can be written as:.

M2 = ~ ~D2r[(a2sin 2~ + b2cos 2~) + (a4sin 4~ + b4cos 49) -t ~

(C) As to M3 ,, The positions and rotational directions of the,balancers ;~
; are taken as shown in Fig. 2, and an unbalanced mass of one `~
~, balancer is assumed to be mB = mr so as to acquire the "J ~ ~ :
second-order halance o~ the vibromotive force of item (a).
~, If the centrifugal force of one balancer is denoted by F, ~, , then F is expressed by the following equation~
:
1 : :
;:

~ 6 '~
~.
~: :

~ ~3566~7'7 1 F = mBrB~2~ 2 .
Then, the rolling moment of the r.ighthand balancer g' about the crankshaft is a summation of:
Moment due to the force in x direction which is:
-Fylsin 2~; and Moment due to the force in y direction which is:
Fxlcos 23. :
Therefore, the rolling moment M3right of the righthand 1~ balancer 9' becomes: ~:

3 ht = ~ Fy sin 2~ + Fx cos 2 -. rlg Likewise, the rolling moment of the lefthand balancer 9 about the crankshaft is a summation of:
Moment due to the force in x direction which is: ~.
Fy2sin 2~; and ~
;~t Moment due to the force in y direction which is: ~ -.

-Fx cos 2 :~ Thus, the rolling moment M31eft of the lefthand balancer i-s becomes:

31eft Fy2sin 2~ - Fx2cos 2a.
Therefore, the rolling moment M3 of the both balancers `~
can be expressed as follows:

3 ~3right + M31ef-t = -F[(Yl - Y2)sin2~ -~ (x2 - xljcos2a] .
. Here, if the relation Yl ~ Y2 = Y(Y~0) is substituted : into the above equation, then the equation of M3 is rewritten as follows:

M3 = -F[y sin2a + (x2 - xl)cos 2~]
= ~ ~ 2~ [Y sin 2a + (x2 - xl)cos 2~].
; 30 As a result, the summed vibromotive moment M of the :, :
engine as a whole is obtained~
, :

. ' ',,' ~s~7 ;
1 M - M~ 2 + M3 ( - 4mr2~2t2sin2 û- 4mr2~2t4sin4 ~
- 7rD2r [(a2sin2~ -~ b2cos2~) + (a~sin43 -~ b4cos49) + - - -- 2mr~2 [y sin2~ + ~x2 - xl)cos2~].
In the above equation, only the terms of the second order are taken into consideration, because the terms of the higher orders have less influences and accordingly are omitted.
From this consideration, the equation of the vibromotive ;
moment M is obtained in a simplified form: ~ ~
., , 2 ':' M = (2mr2~2- 7rD2ra2 ~ 2mr~L2y)sin2~ + ~-7rD2rb2 - ~m~L(x2-xl)]cos2~ ~
~ ~ ~ ~ ~ ~ 2 ~
= ~(2mr ~ -~D a2- 2mr~2y)2 + E-7r~ rb2- 2mr~2(x2-xl)] x sin(2~+a), - where a - tan2 ~~~ (x2-xl) ~ 2mr ~ - 7rD ra2 ~ 2mr~2 ... . .

In order to reduce the vibromotive moments as much as possible, the balancers have to be so positioned that the value ~;

M takes its minimum in terms of the parameters y, xl and x2. For .~:
this requirement, a series of experimen-ts were conducted with use of a four-cylinder internal co~bustion engine, which has the total piston displacement of 1,995 cc, the reciprocating mass m of 795 g, the crank radius r of 45 mm, the length Q of the con-necting rods of 166 mm, the bore diameter D of 84 mm, and the connecting rod ratio ~ of 3.688. The results of these experiments are shown, using suitable values for the parameters y, xl and x2, ~ `~
in Figs. 3 to 37, in which the equi-vibromotive-diagrams are . . ~
; drawn for the selected values of the parameters. In Figs. 3 to 3~ 37, the abscissa indicates the rotational speed of the engine, , while the ordinate indicates the engine output power. Here, the ,~
, . . .

, ~6~S6677 harmonic coef~icients of the second order of the combustion explosion torque are determined by reading the desired values for the mean effective pressures Pmi, which are plotted from the experimental data in Fig. 38. In this regard, the relation- ;
ship between the shown mean effec-tive pressures and the shown horse powers is derived from the following equation~

;:~
H = PmiVN
9 x 1~5 where H indicates the shown horse power (PS), V the total piston displacement (cc), N the rotation speed of the engine (r.p.m.), -~and Pmi the shown mean effective pressures (Kg/cm2).
In the equi-vibromotive-moment diagrams of Figs. 3 to 37, j reference letter M indicates the vibromotive moment, p the output power of the four-cylinder internal combustion engine for use in our experiments, and R the curves showing the running resist-ances during the cruising condition of the automobile, on which ~-, the engine is installed. The parenthesized data (y = 0, x2 - xl =0),`~
as appearing below the abscissa of the above drawings, for example, ~, Fig. 35, mean that for y a 0~ the distance between the axes of `~
! 20 the paired balancers in the axial direction of the engine cylinders is zero, namely, that the axes of the balancers are arranged horizontally. FQr x2-xl = 0, the data mean that the paired balancers are arranged at an equal distance from the plane containing the longitudinal axis of the engine cylinder and axis of the crankshaft.
The behavior of the vibromotive moment M will now be -~
examined in conjunction with Fig. 5, by way of example only.
From this examination, it will be found that the vibromotive moment takes its minimum value in the neighborhood of M = 5 and increases sideway in the fashion 10, 15, 20, 25 . ~ ~
', _ 9 . ', , ., , - . . . ~ , ~,: , - . .

1~566~7 In accordance with such examinationl therefore, the most suitable position of the balancers can be determined for the selected running ranges, respectively, of the automobile :
engine and of the moto.r truck engine.
For the automobile engine which is most often used in the running resistance range during the cruising operation, for instance, if the balancers are so posi-tioned that the re-sistance range may fall under range, in which the engine vibra-- tions take their minimum value, then it is possible to obtain an . lO automobile engine, which has remarkably reduced vibrations over ~ ~
a wide driving range from high to low speed ranye, without ~ :-drastically reforming the construction of the conventional re-ciprocating engine.
In a compact automobile having the engine equipped with the balancer device according to the present invention, more , specifically, the most satisfactory balancer positioning is found, from the equi-vibromotive-moment diagrams, to reside in ' that the vertical distance between the paired balancer shafts has a value in the neighborhood of 75~ of the length Q of the ~ connecting rods, and at the same time that the distances of the righthand and lefthand balancers from the center axis of the cylinders are made equal to each other. With reference to Fig. :
20, moreover, the most satisfactory balancer positioning includes the cruising resistance curve R in the area of the minimum vibro-motive moment M = 5 under the condition (Y = 0.75Q, x2 ~ xl = 0).
Therefore, although the values for determining the most satis- `
factory balancer positioning will vary slightly with the variation of the size of the automobilej the type of the engine and the size .~:
of the engine, they can be selected most suitably for the parti-3~ cular purpose ~rom the respective equi-vibromotive-moment diagrams.

, , . ~

~5gi6~7 For the industrial engine of stationary type in which ;:
the ~orking number of rotation and the loacl range are substan-tially constant, on the other hand, the whole range of -the working number of rotation need not be satisfied as is quite different from the case of the automobile engine Thus, the :most satisfactory balancer positioning can be so determined as to have the minimum engine vibra-tions for the intended working ~ ~
candition. ~.
The same results as above can be obtained even if the 0 present invention is applied to the four-cylinder engine of transverse type.
As has been described in detail, the straight-type : four-cylinder engine according to the present invention is con-structed in any combination of the following items:
(a) The distance y between the paired balancers in the axial direction of the engine cyLinders is determined at ` such desired value in the range of from 15% to 135~ of the length of th~ connecting rods as to satisfy the engine usage and design;
(b) The difference between the distances xl and x2 of the balancer axes from the plane containing the longi-tudinal axis of the cylinders and axis of the crankshaft are also ; :
determined at such desired value in the range of --5Q'X2 ~ xl < +~.5Q (wherein Q: length of connecting rods, x2: distance between the lower balancer element and ., .
a plane containing the longitudinal axis of the cylinder and ~ .
. axis of the crankshaft and xl: distance between the upper ;
balancer element and said plane) as to satisfy the engine :
.~ usage and design;
Ic) The lower one of the paired balancers is rotated in the opposite direction to the crankshaft, whi:Le the upper one is rotated in the same direction of the crankshaft; and : .

1(~56~77 ~
(d) In a normal case, the center of gravity of the balance weight is positioned as close as possible to the longitudinal cen-ter oE the engine so as to obviate genera-tion of the pitching moment. ~ ;
For a modification, however, the balancers may beseparately arranged in the longitudinal direction of the balancer shafts, as sho~n in Figs. 39(a) and 39(b). In these Figures, for example, one of the balancers is divided into halves having ; the same mass, and these halves are arranged equidistantly with 10 respect to the undivided balancer. In another example, one ~;
balancer is divided into portions having different masses, and the portions are arranged in an inversely proportional fashion to the masses with respect to the undivided balancer. In these ;~
ways, the engine design can be changed in a suitable manner.
As has been described in the above, the present inven-tion can be varied in any combination of the above items (a) to ~d) and other two modifications. As a result, it should be appreciated as an advantage of the present invention that ~a) ,1 '. ' ' :
~, the vibromotive force due to the reciprocating masses, gb) the 20 vibromotive moment due to the reciprocating masses and (c) the ;
vibromotive moment due to the combustion explosion can be -eliminated with use of paired balancers without drastically ;` changing the mainbody of the conventional reciprocating engine.
., ~ .
~ Thus, according to the present invention, there can be provided ~
~: 1 ` , an engine which is remarkably simple in construction with a low production cost, and has vlbrations materially reduced without ;~
-~ reducing its performance in comparison to the conventional engine.
;` The engine of the present invention need not be limited to the above examples having one pair of the balancers but can have two or more pairs of the balancers.

' ~
, ' ~ ' '~ .

~(35~ 77 l Of courser it is believed understandable that the sideway relationship may be reversed (but -the relationship between the vertical positioning and the directions oE rotation of the balancers has to be held constant such that the lower balancer is rotated in the opposite direction to the crankshaft) for the similar resultant effects, if such design change is within the range for achieving the objects of the present inven- :
` tion.
: Here, although the foregoing examples are directed solely to the internal combustion engine, it should be understood that the present invention can be applied to other reciprocating engines such as a pump or a compressor with similar resultant effects.

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Claims (13)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In an internal combustion engine of the reciprocating piston type having four cylinders wherein a piston reciprocates in each cylinder, each of the pistons being connected to a rotatable crankshaft by way of a connecting rod such that the reciprocating movement of said pistons causes rotation of said crankshaft, an improved balancer system to dampen the secondary vibromotive force due to reciprocating masses and the secondary vibromotive moments due to the reciprocating masses and the combustion forces comprising:
a) at least one pair of balancer elements rotatably supported on said engine, an upper balancer element of said each pair being disposed laterally of an upper portion of said engine and a lower balancer element of each pair being disposed laterally of a lower portion of said engine such that the balancer elements are located on opposite sides of the cylinders and the axes of rota-tion of the balancer elements are parallel to the axis of rota-tion of the crankshaft and are located in a first plane which is disposed obliquely to a second plane containing the longitudinal axes of said cylinders and the axis of rotation of said crankshaft wherein the difference between the distance of said upper and lower balancer elements from said second plane is in the range of -0.5? ? x2 - x1 ? +0.5?
where ?: length of the connecting rod;
x2: distance between the lower balancer element and said second plane; and x1: distance between the upper balancer element and said second plane, 14 .
1. Claim 1 continued .....
   
   and wherein the distance between the axes of rotation of the balancer elements measured in a direction parallel to the second plane is in the range of from 15% to 135% of the length between the points at which the connecting rods are connected to the pistons and the crankshaft; and b) means driven by said engine to rotate said upper and lower balancer elements in opposite directions at twice the angular velocity of the crankshaft such that said lower balancer element is rotated in a direction opposite that of the crankshaft.
2. 2. An internal combustion engine as claimed in claim 1 wherein each of said balancer elements comprises a body whose center of mass is displaced from its axis of rotation.
3. 3. An internal combustion engine as claimed in claim 1 wherein the moment about the axis of rotation of the crankshaft due to the rotation of said lower balancer element is out of phase with the moment due to the movement of the piston, connect-ing rod and crankshaft and the moment due to the rotation of the upper balancer element is in the opposite direction from the moment due to the movement of the piston, connecting rod and crankshaft.
4. 4. An internal combustion engine as claimed in claim 1 wherein said pair of balancer elements are located at the approximate longitudinal midpoint of the mechanism.
5. 5. An internal combustion engine as claimed in claim 1 wherein all of the pistons are located on the same side of the crankshaft.
6. 6. An internal combustion engine as claimed in claim 1 wherein one of the balancer elements is divided into halves having equal masses and these halves are disposed along the axis of rotation of said balancer element equidistantly from the undivided, balancer element.
7. 7. An internal combustion engine as claimed in claim 1 wherein one of the balancer elements is divided into portions having unequal masses, and the portions are disposed along the axis of rotation of said balancer element such that the distance between each portion and the undivided balancer element is inversely proportioned to the ratio of their masses.
8. 8. An internal combustion engine as claimed in claim 1 wherein said distance between said upper balancer element and said second plane is shorter than the length of the connecting rods, and the distance between the lower balancer element and said second plane is larger than half of the bore diameter of said cylinder.
9. 9. An internal combustion engine as claimed in claim 1 wherein the sum of the distance between said upper balancer element and said second plane and between said lower balancer element and the second plane is approximately twice the length of said connecting rods.
10. 10. An internal combustion engine as claimed in claim 1 wherein the distance between said lower balancer element and said second plane and the distance between said upper balancer element and said second plane are approximately equal to the length of the connecting rods, and the vertical distance between the axis of said upper balancer element and the axis of said lower balancer element is approximately equal to the length of the connecting rods.
11. 11. An internal combustion engine as claimed in claim 1 wherein said distance between said upper balancer element and said second plane is shorter than the length of the connecting rods, and the distance between said lower balancer element and said second plane is larger than half of the bore diameter of said cylinder, and wherein the sum of the distances between the upper balancer element and said second plane and between the lower balancer element and said second plane is approximately twice the length of the connecting rods.
12. 12. An internal combustion engine as claimed in claim 1 wherein the distance between said upper balancer element and said second plane and the distance between the lower balancer element and said second plane is longer than half of the bore diameter of the engine cylinders and the balancer elements are disposed on opposite sides of the cylinders outside of the moving locus of the connector rod.
13. 13. An internal combustion engine as claimed in claim 1 wherein the center of gravity of each of the balancer elements is centrally located along the longitudinal axis of the engine.