JPS5839850A - Balancer for three-cylinder engine - Google Patents

Abstract

PURPOSE:To contrive reducing vibration of an engine and making a balancer into light-weight and compact size in such a way that the balancers which are independent are installed in the parts of a balancer shaft which revolves in the inverse direction to a crankshaft, corresponding to bearings for the first and third cylinders and balancers which are divided into two parts are installed at the part of a second cylinder, corresponding to bearings. CONSTITUTION:Crank arms of a crankshaft 1 for the first and third cylinders are provided with the counter-weights 6a-1, 6a-2; 6c-1, 6c-2 and 6a'-1, 6a'-2; 6c'-1, 6c'-2 to the mass of the reciprocating parts and revolving parts of the engine respectively. Besides, counter-weights 6b-1, 6b-2 to only the mass of the reciprocating parts are installed on the crank arm of the second cylinder. Further, a balancer shaft 7 which revolves in the inverse direction at the same speed as the crankshaft 1 which has been mentioned above, the balancers 8a, 8c are installed at the part of said shaft 7 corresponding to the bearings 9a, 9d of the first and third air culinders and balancers 8b-1, 8b-2 which are divided into two parts are installed at the part corresponding to the bearings 9b, 9c of the second cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a three-cylinder engine for the JII, in which a counterweight is provided on the crankshaft itself, and a balancer shaft that rotates at the same speed and in the opposite direction relative to the crankshaft is provided. The primary inertia force due to the reciprocating and rotating mass of the cylinder and X
A balancer that balances the first-order inertia couple around the shaft and also balances the first-order inertia couple in the longitudinal direction of the crankshaft.
There are things to do.

In each cylinder, there is an inertia force due to the reciprocating mass and a rotating mass.The inertia force due to the rotating mass can be balanced out by installing a counterweight on the opposite side of the crank arm, and the inertia force due to the reciprocating mass is due to the rotating mass. case and 1
- The balance can be half balanced at the same position, and the remaining part can be balanced by a balancer shaft that rotates in the opposite direction at the same speed as the crankshaft. By the way, in the case of a three-cylinder engine, as described above, the inertia cal of each air WJ is balanced, and at the same time
Even if the inertia couple around the shaft is also balanced, an inertia couple occurs in the longitudinal direction, and in order to balance and remove this inertia couple, a counterweight of the crankshaft has been conventionally used, as disclosed in Japanese Patent Application Laid-Open No. 55-6035. A device with a specific separation structure, or a device that generates an inertia couple on the balancer shaft that has the same size and direction as the inertia couple of the rank axis system and cancels it out, as in Japanese Patent Publication No. 54-2333. be.

The above is related to the balance of inertia force and inertia couple that is generally used in three-cylinder engines. In other words, in an engine with an odd number of cylinders, such as a three-cylinder engine, the inertial forces of the first and third cylinders act symmetrically on both sides of the second cylinder, which is located in the middle. The inertial couple must be taken into account, and this has a large effect on engine vibration. On the other hand, the longitudinal eccentric force of swinging due to this inertial force can be balanced by the balancer on the balancer shaft, but in this case, even if the couple is constant, the mass can be changed depending on the distance between the balancers, so the balancer By specifying the mounting position of the balancer shaft, it becomes very advantageous in terms of the structure of the balancer shaft itself, degree of freedom in design, machining relative to the crankshaft, etc.

In view of the above circumstances, the present invention provides a balancer device for a three-cylinder engine that uses a crankshaft weight and a balancer shaft to bring the balancer shaft closer to the crankshaft side and to reduce the size of the balancer shaft. The purpose is to provide

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings. First, to explain the balance system per cylinder in Fig. 1, in the figure, numeral 1 is the crankshaft, 2 is the crank arm sequentially arranged at equal intervals of 120°, 3 is the crank pin, 4 is the connecting rod, and 5 is the piston. A counterweight 6 is provided on the extension line of the crank arm 2 on the opposite side from the crank pin 3 to half balance the entire inertia due to the rotating mass and the inertia due to the reciprocating mass. Also,
One balancer shaft 1 is provided that rotates lightly in the opposite direction at the same speed as the crankshaft 1, and a balancer 8 is provided that half-balances the remaining part of the inertial force due to the reciprocating part. As shown in the figure, when the crank arm 2 is positioned clockwise by θ from the top of the Z-axis, the balancer 8 of the balancer shaft 7 is positioned counterclockwise by the same amount θ from the bottom of the Z-axis. Here, r, the inertial mass of the reciprocating part is Ip, and to make the explanation easier to understand, the equivalent inertial mass of the crank pin 3 of the rotating part is 10, then the mass of the counterweight 6 on the crankshaft side is relative to the reciprocating mass - p It is better to half balance it, so -p
/2, the rotational mass -G rotates in the same direction as the crankshaft 1, so all of them can be balanced, resulting in 10, and the total becomes (sp/2) + ac. Further, the mass of the balancer 8 on the balancer shaft side is the remainder of the above-mentioned reciprocating mass and becomes -1)/2.

By doing this, the Z of the reciprocating part and the rotating part.

The inertial forces in the Y direction are all balanced. Therefore 3
In a cylindrical engine, if a counterweight 6 and a balancer 8 of each mass are attached to the positions corresponding to each cylinder, then the total number of counterweight layers on the crankshaft side is 3 ((sp/2) + - C). , the total mass of the balancer on the balancer shaft side is (3/2) sp.

Next, the balance due to the mass of the reciprocating part in a three-cylinder engine will be explained with reference to FIG. 2. In FIG. The first cylinder is then rotated 240°, and the third cylinder is 12
It is in a state of 0” rotation position.

Therefore, when the cylinder moves by θ from this state, the excitation force Fp1 of the first cylinder, the excitation force Fp2 of the second cylinder, and the excitation force Fp3 of the third cylinder are as follows.

Fpl-mpr ω2 cos (θ +24
0 ) Fp2=lpr ω2 CO3θ Fp3=mpr ω2 cos (θ+120) Then, the total inertial force is balanced by F pl + F D2+ F I)3=0.

In addition, the inertia couple in the longitudinal direction of the crankshaft is applied to a point P located a distance 1IIIS away from the first cylinder in order to provide membrane properties.
If we look at it from above and let the pitch of each cylinder be L, then Fpl ・S + Fp2(S+L) ・+
-Fp3(S+2L).

That is, −〇− Fpl・S+Fp2(S+L)+Fp3(8+2 1)
=-J'1spr oo2 1 sin θ---
(1), and the reciprocating mass, which is the Z-direction load, causes a longitudinal bias around the Y-axis.

To explain the balance by mass of the counterweights 6a, 6b, and 6c that are half-balanced for each cylinder in Fig. 3, Fig. 2 w44! 2 shows the case where the second cylinder is at top dead center, and the counterweights 6a, 6b, 6c of each cylinder are crank arms 2a, 2b.

It is at a position 180" phase advanced relative to 2C. Therefore, in the two directions when moving by θ from this state, the force due to each h lantern weight mass 1" real, Frec2, F
rec3 becomes as follows.

Freci = (lap/2) r O2C
O8(θ +240 + 180)1': re
c2= (ap/2) r O2cos (θ+1
80) F rec3= (ap/2) r O2co
s (θ+120+180) Therefore, the inertia force in the Z direction is balanced as Frecl Frec2+Frec3-0.

On the other hand, F re in the longitudinal direction due to such two-directional forces
cl −S + F rec2 (S + L) +
F rec3 (S 12) = (j'j/2) mpr O21stn θ--
-(2a), and a longitudinal bias force around the Y axis is also generated.

In addition, the counterweights 6a, 6b, and 6c have a component not only in two directions but also in the Y direction, and the inertia force is balanced in the Y direction, and the inertia couple in the longitudinal direction due to the force in the Y direction is as follows. .

−(m/2) mpr O21cosθ---(2b
) Immediately, a longitudinal bias force around the Z axis is generated due to the force in the Y direction.

Above, the counterweight 6a to 6G on the crankshaft side
The inertia couple in the longitudinal direction generated by is generated around the Y wheel in the Z direction and around the Z wheel in the Y direction, and the combination of the two is as follows.

(5/2) g+pr oa2 1 sin
θ - (j'i/2) apr x ω2L cos θ = (strokes/2) 1 apr ω21 (sin θ-c
osθ)...(3) By the way, in addition to providing the above-mentioned crankshaft side counterweight for each cylinder, it is also possible to separately provide the counterweight on the first and third cylinders on both sides except for the second cylinder in the center. This is also possible, and this case will be explained with reference to FIG. To state the results without explaining the intermediate progress, the counterweight value of the first and third cylinders, 8σ, is the mass of (old/2) (■p/2), and the counterweight value of the first cylinder is: This is a position further 30" phase advanced from the position 180 degrees phase advanced from the crank arm 2a, and the third cylinder counterweight 6
σ is provided at a position 30 degrees behind the position 180@phase ahead of the crank arm 2C. That is, both counterweights u and 6σ are at positions 180'' opposite to the crankshaft 1 and perpendicular to the central crank arm 2b.

In this case, 2 when moving by θ from the state shown in the figure.
Force F recl due to each counterweight in the direction *ii
', F rec3' is Frec1'-(In
/2 ) (-p/2) r ω2xco
s(θ+240 + 180 + 30)9- Frec3' = (Jj/2) (In/
2) r cc>2xcos(θ+120.1
．． 180-30), and the Z-direction inertia force is F real' + F rec3' = 0,
Of course it's balanced.

Next, the longitudinal inertia couple due to this force in the Z direction is Frec1' -3+ Frec3' (S+21
>= (j'N/2) ipr co21. sin
θ, which agrees with equation (2a).

The inertia forces are also balanced in the Y direction, and the longitudinal inertia couple due to the force in the Y direction matches equation (2b).

From this, one counterweight on the crankshaft side should be provided for each cylinder, or one counterweight should be provided only for the 1st and 13th cylinders.As a result, the inertia force would be balanced, and the longitudinal inertia couple tJs It is understood that they will be the same.

Above, we have explained the balance of inertia force due to the reciprocating mass and counterweight on the crankshaft, and the longitudinal inertia couple, that is, whirling, but here 10- (1) 2 and (3) longitudinal bias force remain. and when we synthesize this, we get January spr ω2 L sin θ + (old/
2) spr oo2xi-(sinθ-CO
Sθ) = −(fi/2) gipr w2 L (sin
θ+COSθ...(4) Therefore, how to balance such a longitudinal couple on the balancer shaft side will be explained with reference to FIG. First, on the balancer axis l, the balancer 8 corresponding to each cylinder is
If you half balance with a, 8b, and 8c,
The mass of each balancer 8a to 8C is 2p/2 relative to the reciprocating mass on the crankshaft side. Further, as shown in the figure, when the second cylinder is at the top dead center, the balancer 8b corresponding to the second cylinder is at the opposite position on the bottom dead center side, and the balancer 8b corresponding to the first cylinder is at the opposite position.
a is further 180 degrees from the position where the phase has advanced 240 degrees counterclockwise.
The balancer 8C corresponding to the third cylinder is at a position shifted by 180° in phase from the 120° counterclockwise position.

Therefore, the forces F recl, F rec2 . in the 7 directions when jIA moves by θ from this state. F rec3 is F
recl= (wp/2) r w2
cos (θ +240 + 180)Fre
c2- (sp/2) roo2 co
s (θ +180 )1- rec3= (ap
/2) r oa2 cos (θ4120
+1'80), the Z-direction inertial force is balanced, and the longitudinal couple around the Y-axis due to this Z-direction force is (j"j/2) gipr ω21-sinθ...
(2a') Also, in the Y direction, since it rotates in the opposite direction to the crankshaft, the m-force becomes negative, but the inertia force is similarly balanced, and the longitudinal couple around the two wheels due to this force in the Y direction is ( j'j／
2) spr ω2 L cos θ --- (2b') Therefore, the inertia couple in the longitudinal direction generated by the balancers 8a to 8c of the balancer shaft steel is also generated around the Y ring in the Z direction and around the Y wheel in the Z direction.
This occurs around the Z-axis depending on the direction, and the combined result is as follows using equations (2a') and (2b') above.

(J'j/2)-pr ω2 L (sin
θ + cos θ )...(4') By the way, the balancer on the balancer shaft side can also be separated and assembled in the same way as the crankshaft side in FIG. 4. This case will be explained with reference to FIG. The mass of the equivalent balancer sow and the balance rust equivalent to the third cylinder is -1)/
2 multiplied by VJ/2, the cylinder corresponding to the first cylinder is located further ahead in phase by 30 degrees, and the cylinder corresponding to the third cylinder is positioned further behind in phase by 30 degrees. This gives the same result as in Figure 5, and can be replaced by that.

As mentioned above, the balance of inertia by the balancer on the balancer shaft side,
and the inertia couple in the longitudinal direction, and the result is equation (4'). Therefore, when this equation (4') is combined with the previous equation (4), it becomes zero, and from this, the inertia couple in the longitudinal direction due to the reciprocating mass generated on the crankshaft side and the mass of the counterweight that half-balances it. will be balanced by the balancer on the balancer shaft side.

Next, we will explain the balance due to the mass of the rotating parts of a three-cylinder engine.The configuration is the same as in Figure 12, and θ
The force acting on the 1st to 13th cylinders at the position of movement, Fc
l, Fc2. l”c3 becomes as follows.

13- 13-Fc1= ω2 cos (θ+240
)F C2-scr ω2 cos θFc3=
i+cr ω2 cos (θ+120) As a result, the longitudinal eccentric force around the Y wheel due to the rotating mass is -m g
icr ω2 Lsin θ −= −(5
a) The longitudinal bias around the Z-axis becomes 5-C'ω2Laosθ...(5b), which similarly occurs around the Y-axis in the 7 directions and around the Z-wheel in the Y direction, and when combined, It will look like this:

-4jg+cr ω2 L, (sinθ-cosθ)
--- (6) Next, apply this rotational quality to 1 for each cylinder.
Counterweight 6a or 6G balanced with =1
The balance due to the mass of is the same as the configuration shown in Figure 3, and the force due to each counterweight mass, F
rotl, F rot2. F rot3 becomes k as follows.

Frotl=scr ω2 cos (θ)
240 + 180) FrO12=ICr
(t)2 C01i (θ +180)Fro
t3=scr ω2 cos (θ+120 +18
0) As a result, the longitudinal couple around the Y axis in two directions becomes 14-fjg+cr ω2 Lsin θ-
--(7a) The longitudinal couple around the Z axis due to the Y direction is -5 Kasumi C" ω2 Lco5 θ ・ ・
・(7b) is obtained, and the combined swing of both is as follows.

JTmcr w2L (sinθ-COSθ) --(
8) In the case of such a rotating mass, as shown in Figure 14, the counterweight can be separated and concentrated in the *i cylinder and the 3rd cylinder by multiplying the mass by IC < m/2 ) and advancing or retarding the phase by 30''. It is possible to do so.

Thus, regarding the rotating mass, the combined whirling longitudinal couple around the Y-axis and Z-axis in equation (6) becomes zero by combining with the similar longitudinal bias force in equation (8) due to the counterweight, and the two will be balanced.

The present invention is based on such a technical idea, and a specific embodiment thereof will be explained with reference to FIG. Inertial force and couple force are generated due to the mass of the parts, and when balancing against the mass of the two parts, they are separated and concentrated on each cylinder and on the first and third cylinder sides. Therefore, such 2
Although it is possible to consider the quality of the seeds together and solve the problem using one type of balance method, it is sometimes preferable to use a separate group for each mass and use a different balance method.

First, count the counterweights 6a-1 and 6a-2゜e for the mass of the reciprocating part for each cylinder using the crankshaft 1.
b-1 and 6b-2, 6cm1 and 60-2 are provided on the opposite side of the crank pin of each crank arm as shown in FIG. Next, the fourth value is calculated for the mass of the rotating part.
As shown in the figure, counterweight side -5 and fij-2, [iσ-5 and 6 = 2 are similarly provided at 2m11 locations of the first and third cylinders excluding the second cylinder. In addition, the balancer shaft 7 only needs to balance the unbalanced mass due to umm, and for this reason, it is based on the technical idea as shown in Fig. 5, and in this case, for example, the crank The inner and outer bearings 9a and 9d of the shaft 1 are selected and independent balancers 8a and 8c are installed at these locations, and the two inner bearings 9b and 9c of the crankshaft 1 are used as the second cylinder equivalent part.
Select and place at those locations: Balancer 5b- divided into two parts.
i, 8tL2 is provided.

In such a configuration, when considering the balance on the crankshaft side, the counterweight to the mass of the rotating part is separated and concentrated in two places. Since there is, multiply the composite price on each cylinder side by (5/2) and get 30'
If the pitch of each cylinder is L as in FIG. 2, then the longitudinal bias force can be generated as follows: 5c(ffi/2) x 2L-old-cl.

Therefore, the synthetic material ① of counterweight etr-i, m-2 is MCa', counterweight (t' -t, 1
Letting the combined mass of 3t1'-a be M cc', considering the balance of the inertial force on the crankshaft 1, M ca' -
pJi cc' is retained.

Also, the combined center of gravity position of the counterweights u-1° and -2 with respect to the Y axis is L+X', and the counterweight el-1
If the resultant center of gravity position of
Since it is sufficient to satisfy =1jmcL, the following general formula is obtained.

Mca' = MCC' = JjscL/ (2L-+
x' + y' )...(9a) Next, the counterway to the quality of the reciprocating part -6a
-1 and 6a-2, 6b-1 and 6b-2, 6cm1 and 60
-2, the respective combined masses are Mca, ry
lcb, MCC, taking into account the balance of inertial force on the crankshaft, M ca = M cb = M cc
hold.

In addition, the counterweights 6b-1 and 6b-2 of the second kihaku
Counterweight 6 of the first cylinder with respect to the resultant center of gravity position of
If the combined lIc center of gravity position of a-1 and 68-2 is Lx, and the combined center of gravity position of the third cylinder counterweights 6C-1 and 6G-2 is L+y, then Mca (L+X) = Mcc (L+y), x
= Hold y.

Then, for the longitudinal couple, take out the Y direction component, (Mca(Lx) +Mcc(L+y)) co
s30= (I5/2) IpL 18- can be swirled to form the following general formula.

Mca= Mcb-Mcc= (1/2) −
1) L/ (L+
The larger the values of , yl, x, and so are, the smaller the mass will be. To make it easier to understand, counterweights 6a-1 and 6a-2, side-
Combined center of gravity position of 1 and b-a, counterweight 6cm1
and 6cm2.6-1 and 6-2, the counterweight sb-,
By aligning the composite center of gravity of 6b-2 and 6b-2, x'
= y' = x= y -0, the mass of the two counterweights in the first and third cylinders relative to the mass of the rotating part is (m/2)■C, and the mass of the first to third cylinders relative to the mass of the reciprocating part is The mass of the counterweights at the three locations of the air handle is (1/2)-p.

In addition, in the first and third cylinders, counterweights for both the rotating and reciprocating masses are provided at an angle of 30°, but in reality, these are vector-combined and then the balancer shaft 7
Since the reciprocating mass of the engine is balanced for each cylinder equivalent part, the mp
It is sufficient to half-balance with a mass of /2. So balancer 8a.

The masses of the balancers 8C are Mba and Mbc, the synthetic mass of the balancers 8tL, , 8b-2 divided into two is Mbb, and the balancers 8a and 8c are expressed relative to the synthetic center of gravity of the central balancers ab-i, ab-, . Position L+X'',
t-+y'', Mba=Mbb=Mbc x''= Considering the balance of inertial force on the balancer axis
y” is retained.

In addition, for the longitudinal bias, take the Y-direction components of the balancers 8a and 8c on the first and third cylinder sides, and calculate (Mba(L+
x")+Mbc(L+y">)cos
It is sufficient to satisfy the relationship 3°=(j'j/2)spL, resulting in the following general formula.

Mba=Mbb=Mbc=g+l)L/2(L-+
-x'')... (2)) Therefore, even if the pitches of 9C and 9d with respect to the bearings 9a and 9b of the crankshaft 1 are different, the central balancer ab,
and 8b-2, the four balancers 8a, 8L1, 8b-2, 8c are connected to the bearings 9a, 9b.
, 9c, 9d, and if the bearing side has the same pitch, the balancer ab, , 8b-2
This can be easily done by equally dividing the quality of In addition, since the balancers 8a and 8c are shifted outward from the center of the first and third cylinders, the balancer mass can be smaller than if the center were the corresponding part of each cylinder. 8a, 8L1, 8b-2, and 8c aim to make effective use of the bearing space.

In this way, in the crank wheel 1, the first and third cylinders (9a
) The counterweight of the resultant mass of the equation (d-s and d-2,
6('-1 and 6σ-2 are provided at positions perpendicular to the crank arm 2b of the second cylinder, and (
9b) Counterweights 6a-1 and 6a of the combined mass of formula
-2, 6cm1 and 60-2 are provided in position 1 of each crank arm on the opposite side from the crank pin. Further, in the balancer shaft 1, the balancers 8a and 8b are the first and third bearings 9a.

Balancer 8b-1, 8b divided into two parts in the 9d equivalent part
-a is the part corresponding to the bearings 9b and 9c of the 21st-2nd cylinder, and is half-balanced by the mass of equation (2)), and as a result, the inertial force and couple due to the mass of the reciprocating part and rotating part of the 3-cylinder engine are Balance.

And all balancers 8a, 8b-1, 8b-2
, 8c are arranged in the bearing equivalent part of the crankshaft 1 which is shifted from the counterweight position to avoid interference with the counterweight. Therefore, the balancer shaft 1 can be used only as a counterweight without considering the presence of the balancer. Due to the relationship with the crankshaft 1 side, it is possible to place the groove closer to the crankshaft 1 side.

In the above embodiment, the balancer for the part corresponding to the second cylinder is divided into two parts, but one of the crank wheel bearings 9b and 90 is selected as the part corresponding to the second cylinder, and the balancer is divided into two parts for the part corresponding to the second cylinder. A considerable portion of the balancer can also be divided into two parts.

By doing so, vibrations etc. are greatly reduced. Since the reciprocating part and the rotating part are treated separately and each uses a different balancing method, the balance system as a whole will be simplified and clarified. Since the counterweights based on the rotating mass are mutually provided only in the first and third cylinders on the crankshaft 1, the mass of the entire counterweight can be smaller than in the case where the counterweights are provided for each cylinder. By adding generality to the installation of the counterweight and balancer, the degree of freedom in design increases. Furthermore, all the balancers 8a, 8L4,
6b-a.

8C are arranged at a distance from each other in the part corresponding to the crankshaft bearing, so by effectively utilizing the space of the bearing part, it is possible to bring the balancer shaft 1 closer to the crankshaft 1, contributing to miniaturization and reducing the balancer mass. It can also be small.

A specific example of mounting the balancer shaft will be explained with reference to FIGS. 8 and 9. The one in Fig. 8 shows the case where the engine is assembled under the cargo bed in the R-R system, and the engine body 10
is mounted approximately horizontally, and this engine body 1
An air cleaner 11, a carburetor 12, and a suction pipe 13 are horizontally connected and arranged just above the middle of the air conditioner 0, and a cooler compressor 14, ACG 15, etc. are also attached. Therefore, if the balancer shaft 7 is installed on the F side so as not to be submerged in the oil, it will interfere with the carburetor 12, ACG 15, etc., and getting closer to the crankshaft 1 copper will avoid such interference. It will be advantageous to be able to do so.

The one in Fig. 9 is an F-F type, in which the engine body 10 is mounted almost vertically, the air cleaner 11, carburetor 12, and intake pipe 13 are installed on the passenger compartment side, and the exhaust pipe 16 is on the front panel side. If the balancer shaft 7 is placed in front of the engine body 10, it will interfere with the catalytic converter 11 of the exhaust pipe 16. Therefore, in this case as well, if the balancer shaft 1 is moved closer to the crankshaft 1, interference with the catalytic converter 11, etc. can be avoided, and the engine body 10 can be moved closer to the front panel to widen the passenger compartment. Various effects can be obtained, such as the ability to

[Brief explanation of the drawing]

1 to 6 are explanatory diagrams for explaining the present invention in detail,
FIG. 7 is a schematic view showing an embodiment of a balancer device for a three-cylinder engine according to the present invention, and FIGS. 8 and 9 are side views showing a specific example of the case where the present invention is applied to an automatic application. 1... Crank shaft, 2a, 2b, 2c... Crank arm, 6a-1, 6a-2, 6b-1, 6b-2, 6
cm1, 6cm2.61-z, *-a. 6σ-1, 6σ-2...counter weight, 7...
Balancer shaft, 8a, 8L1, 8b-2, 8a-...
Balancer, 9a, 9b, 9c, 9d...crankshaft bearing. Patent Applicant: Fujitarukuri Co., Ltd. Representative Patent Attorney Nobuo Maki Udo Patent Attorney Susumu Murai 25-

Claims (1)

[Claims] The first and third cylinders of the crankshaft, in which the crank arms are sequentially arranged at equal intervals of 120 degrees, have a counterweight for the reciprocating and rotating mass of the engine, and the second cylinder has only a counterweight for the reciprocating mass of the engine. A balancer shaft is provided that rotates at the same speed and in an opposite direction to the crankshaft, and the balancer shaft corresponds to one crankshaft bearing for each of the two rear cylinders of the first to third cylinders. This three-cylinder engine is characterized by having independent balancers installed at two locations in the section, and a split balancer installed at 21 locations corresponding to the two crankshaft bearings in the remaining cylinder for half-balance. balancer device.