JP4671887B2 - Internal combustion engine with a balancer - Google Patents

Description

  The present invention relates to a single-cylinder internal combustion engine comprising a piston that is reciprocally fitted to a cylinder having a cylinder axis that is offset laterally with respect to the rotation center line of the crankshaft, and a balancer that is rotationally driven by the crankshaft. The in-phase two-cylinder internal combustion engine having the same phase is mounted on a vehicle, for example.

2. Description of the Related Art An internal combustion engine including a piston that is reciprocally fitted to a cylinder having a cylinder axis that is offset laterally with respect to a rotation center line of the crankshaft (hereinafter referred to as an “offset cylinder”). A technique for reducing vibration using an inertial force acting on a moving part as an oscillating force is known (see, for example, Patent Document 1).
JP 2005-331006 A

  An internal combustion engine having an offset type cylinder is different from an internal combustion engine having a cylinder with no offset (hereinafter referred to as “normal type cylinder”) in the form of vibration generated by an inertial force acting on a reciprocating motion unit. For this reason, in an internal combustion engine having an offset type cylinder, a balancer having a complicated mechanism is often used, such as a reciprocating balancer, compared to a rotary type balancer widely used in an internal combustion engine having a normal type cylinder. , The freedom of placement of the balancer is reduced, the internal combustion engine is enlarged in a specific direction like a reciprocating balancer, the weight is increased by a complicated drive mechanism, and the rotary balancer is manufactured. Costs may increase due to the inability to use equipment.

  The present invention has been made in view of such circumstances, and in an internal combustion engine equipped with an offset cylinder, by using a rotary balancer, the vibration reduction effect is excellent and the degree of freedom in arranging the balancer is increased. An object of the present invention is to reduce the size and weight of an internal combustion engine and reduce the cost.

ここで、δ：シリンダ軸線のオフセット量
Ｌ：コンロッド長
ｒ：クランク半径 According to the first aspect of the present invention, a cylinder having a cylinder axis that is offset laterally with respect to the rotation center line of the crankshaft, and a cylinder shaft that is reciprocally fitted to the cylinder and connected to the crankshaft to rotate the crankshaft. In a single-cylinder or in-phase two-cylinder internal combustion engine that includes a piston that performs a reciprocating motion, the balancer is rotationally driven by a crankshaft and includes a piston and reciprocates in conjunction with the crankshaft. meet balancer weight of the mass m _b and the following formulas _p and the mass m _c and the balancer counterweight of the crankshaft (a), the phase difference alpha ₁ and the rotation angle and the crank angle of the counterweight around the crankshaft set so that the phase difference alpha ₂ satisfy the following formula (B) between the rotational angle and the crank angle of the balancer weight around balancer shaft An internal combustion engine, characterized in that it is.

Where δ: cylinder axis offset
L: Connecting rod length
r: Crank radius

  According to this, in the internal combustion engine provided with the offset type cylinder, the balancer, which is a rotary balancer similar to the internal combustion engine provided with the conventional normal type cylinder, considers the offset amount and the mass of the counterweight and the balancer weight and the counterweight. And the vibration which generate | occur | produces by a reciprocating motion part reduces by setting the phase difference of balancer weight to the specific value based on Formula (A), (B). Further, since it is a rotary balancer, the balancer itself and the balancer drive mechanism can be reduced in size and structure, and the sliding resistance of the balancer can be reduced. In addition, since the rotary balancer manufacturing equipment widely used in the internal combustion engine having the normal type cylinder can be used, there is almost no new equipment investment and the manufacturing cost is reduced.

  According to the first aspect of the present invention, in the internal combustion engine provided with the offset type cylinder, by using the rotary balancer, the vibration reduction effect is excellent, and the balancer itself and the balancer drive mechanism are downsized and the structure is simplified. This makes it possible to increase the degree of freedom in arranging the balancer and to reduce the size and weight of the internal combustion engine, and further to reduce costs and improve fuel efficiency.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
Referring to FIG. 1, an internal combustion engine 2 to which the present invention is applied is a water-cooled single-cylinder four-stroke internal combustion engine that is mounted on a motorcycle 1 as a vehicle in a lateral arrangement in which a crankshaft C is oriented in the vehicle width direction. The power unit 4 is configured together with the power transmission device 3 that extends rearward from the internal combustion engine on the left side of the vehicle body.
In this embodiment, the up and down, front and rear, and left and right are based on the motorcycle 1.

  The motorcycle 1 includes a vehicle body that includes a vehicle body frame F and a vehicle body cover 5 that covers the vehicle body frame F, and a power unit 4 that is supported by the vehicle body frame F. The vehicle body frame F includes a head pipe 6 at the front end, a pair of left and right main frames 7 which are inclined downward from the head pipe 6 and extend rearward, and are bent substantially vertically after extending substantially vertically downward from the head pipe 6. A pair of left and right down tubes 8 extending rearward and connected to the rear portion of the main frame 7, and a pair of left and right connections extending slightly rearward than the central portion of the main frame 7. A seat rail 9 and a pair of left and right rear frames 10 that connect the rear portion of the main frame 7 and the rear portion of the seat rail 9 are provided.

  A front fork 13 having a front wheel 11 pivotally supported at the lower end and a handle 12 attached to the upper end is supported on the head pipe 6 so as to be steerable. A rear wheel 14 is pivotally supported at a rear end portion of a power unit 4 that includes a transmission composed of a V-belt type automatic transmission and a final reduction device and includes a power transmission device 3 that transmits the power of the crankshaft C to the rear wheel 14. The The power unit 4 is swingably supported by a pivot shaft 17 attached to the vehicle body by a hanger 15 provided in the internal combustion engine 2 at a front portion thereof, and a tandem seat for an occupant by a hanger 16 at a rear end portion thereof. 18 is supported by a rear cushion 19 coupled to the rear end portion of the seat rail 9 that supports 18.

Referring also to FIG. 2, the internal combustion engine 2 includes a single cylinder 30 that is greatly inclined forward so that the cylinder axis L <b> 2 is directed slightly upward from the crankshaft C toward the front, and a front end portion of the cylinder 30. The engine main body includes a cylinder head 31 to be coupled, a head cover 32 coupled to the front end portion of the cylinder head 31, and a crankcase 33 coupled to the rear end portion of the cylinder 30. The crankshaft C has a pair of weight portions Cb (FIG. 2 shows one weight portion) constituting the counterweight Wc in a direction parallel to the rotation center line L1 (hereinafter referred to as “axial direction”). ) Is rotatably supported by the crankcase 33 via a pair of main bearings that are arranged with a sandwich in between.
The cylinder axis L2 is offset by a predetermined offset amount δ to the side with respect to the rotation center line L1, in this embodiment, to the rotation direction side of the crankshaft C from the piston top dead center. That is, the cylinder axis L2 is separated from the plane H including the rotation center line L1 and parallel to the cylinder axis L2 by a distance equal to the offset amount δ.

  A piston 34 fitted to the cylinder 30 so as to be reciprocally movable is connected to a piston pin 34a of the piston 34 at a small end portion 35a, and connected to a crank pin Ca of the crankshaft C at a large end portion 35b. It is connected to the crankshaft C through 35. The cylinder head 31 is formed with a combustion chamber 36 facing the piston 34 in the direction of the cylinder axis L2, and an intake port 37 and an exhaust port 38 that open to the combustion chamber 36. Further, the intake port 37 and the exhaust port 38 are opened and closed, respectively. An intake valve 40 and an exhaust valve 41 are provided. The intake valve 40 and the exhaust valve 41 are driven to open and close in synchronization with the rotation of the crankshaft C by an SOHC type valve gear 42 having one camshaft 42a and rocker arms 42b and 42c that are driven to rotate by the power of the crankshaft C. Then, the intake port 37 and the exhaust port 38 are respectively opened and closed.

  During operation of the internal combustion engine 2, the intake air flowing through the intake device of the internal combustion engine 2 is controlled in flow rate by the throttle valve, and then mixed with the fuel injected from the fuel injection valve to form an air-fuel mixture. Flows into the combustion chamber 36 through the intake port 37, and is ignited by the spark plug in the combustion chamber 36 to burn. The piston 34 driven by the pressure of the generated combustion gas and reciprocatingly drives the crankshaft C through the connecting rod 35. The combustion gas flows out to the exhaust port 38 as exhaust gas, and is further discharged to the outside of the internal combustion engine 2 through an exhaust device having an exhaust pipe connected to the exhaust port.

The internal combustion engine 2 during operation is vibrated based on an unbalanced force generated in a crank mechanism N1 that is composed of a piston 34, a connecting rod 35, a crankshaft C, and the like and converts the rotational motion of the piston 34 into the rotational motion of the crankshaft C. appear. The main component of this unbalanced force is an inertial force that acts on the reciprocating motion part D1, which includes the piston 34 and reciprocates in conjunction with the crankshaft C. Here, the reciprocating part D1 is composed of a reciprocating part of the piston 34 and the connecting rod 35, and the like. The vibration occurring in the internal combustion engine 2, is of major vibrations by vibratory force F _p consisting of inertial force acting on the reciprocating portion D1. (For the sign of the excitation force, see the formula below.)

On the other hand, the internal combustion engine 2, the excitation force F _p suppressing damping mechanism N2 vibration due is provided. The vibration damping mechanism N2 is provided integrally with the crankshaft C and is provided with a counterweight Wc that rotates integrally with the crankshaft C, and a rotation center line L3 that is rotated by the crankshaft C and parallel to the rotation center line L1. And one balancer shaft B as a balancer arranged so as to have
The balancer shaft B includes a shaft portion Ba that is rotatably supported by the crankcase 33, and a balancer weight Wb that is integrally formed with the shaft portion Ba. The balancer weight Wb is disposed between the pair of weight portions Cb in the axial direction. Balancer shaft B as a primary balancer to suppress the primary vibration by the excitation force F _p via the balancer driving mechanism 45 for transmitting the power of the crankshaft C to the balancer shaft B, the crank shaft C and constant velocity And rotated in the opposite direction. The drive mechanism 45 includes a drive gear 45a provided outside the main bearing on the right side, and a driven gear 45b provided on the shaft portion Ba and meshing with the drive gear 45a. The vibration generating force for vibration control generated by the vibration control mechanism N2 during the operation of the internal combustion engine 2 includes the vibration generating force F _c composed of the inertia force generated in the counterweight Wc and the inertial force generated in the balancer weight Wb. composed of a vibratory force F _b consisting. Here, the counterweight Wc and the balancer weight Wb constitute a rotational motion part D2 for vibration suppression.

Hereinafter, the principle of damping vibration generated by the reciprocating motion of the reciprocating motion part D1 by the exciting forces F _b and F _c in the damping mechanism N2 will be described with reference to FIG.
The meanings of the symbols in FIG. 3 and the following equations are as follows.
L: connecting rod length r: crank radius λ: connecting rod ratio (L / r)
δ: Offset (the direction of rotation of the crankshaft C from the piston top dead center is the positive direction)
m _p: mass _{m c} reciprocating portion D1: counterweight Wc mass _{m b:} the balancer mass of the weight Wb alpha _1: phase difference between the rotation angle and the crank angle of the counterweight Wc crankshaft periphery C (crankshaft C Direction of rotation is positive)
α ₂ : Phase difference between the rotation angle of the balancer weight Wb around the balancer axis B and the crank angle (the direction opposite to the rotation direction of the crankshaft C is the positive direction)
ω: rotational speed of crankshaft C

同様に、カウンタウエイトＷｃによる起振力Ｆ_ｃおよびバランサウエイトＷｂによる起振力Ｆ_ｂは、それぞれ次式で表される。

Vibratory force F _p by the reciprocation unit D1 is expressed by the following equation by x and y components in an orthogonal coordinate consisting of x-axis and y-axis to the rotational center line L1 as the origin (see also FIG. 2).

Similarly, excitation force F _b by excitation force F _c and the balancer weight Wb by counterweight Wc are respectively expressed by the following equation.

そして、起振力Ｆのｘ成分Ｆ_ｘは次式で表される。

ここで、

それゆえ、起振力Ｆ_ｐが起振力Ｆ_ｃおよび起振力Ｆ_ｂにより完全に打ち消されるようにするためには、起振力Ｆのｘ成分Ｆ_ｘについてＦ_ｘ＝０であればよく、そのための条件は、前述の式に基づいて、ｍ_ｃ＝ｍ_ｂかつα_１＝α_２であればよい。 If only the primary vibration which is the main component of the vibration in the internal combustion engine 2 is taken into consideration, the above formula is rearranged, and the excitation force F which is the resultant force of these excitation forces F _p , F _c and F _b is expressed by the following equation. Is done.

Then, x component F _x of the excitation force F is expressed by the following equation.

here,

Therefore, in order to completely cancel the vibration force F _p by the vibration force F _c and the vibration force F _b , it is sufficient that F _x = 0 with respect to the x component F _x of the vibration force F. The condition for this may be m _c = m _b and α ₁ = α ₂ based on the above-described equation.

この式に、ｍ_ｃ＝ｍ_ｂかつα_１＝α_２を代入すると、

ここで、

したがって、Ｆ_ｘ＝０である条件の下で、起振力Ｆのｙ成分Ｆ_ｙについてＦ_ｙ＝０であるためには、Ａ _２ ＝０，Ｂ _２ ＝０が成立すればよく、この両式から次式（Ａ）、（Ｂ）が導出される。

Similarly, the y component F _y of the excitation force F is expressed by the following equation.

Substituting m _c = m _b and α ₁ = α ₂ into this equation,

here,

Therefore, in order to _satisfy F _y = 0 for the y component F _y of the excitation force F under the condition of F _x = 0, it is sufficient that A ₂ = 0 and B ₂ = 0 hold. From the equations, the following equations (A) and (B) are derived.

Then, in the internal combustion engine 2, satisfy the mass _{m b} Togashiki mass _{m c} and the balancer weight Wb of the mass _{m p} counterweight Wc reciprocating portion D1 (A), the phase difference of the counterweight Wc alpha ₁ and the balancer phase difference alpha ₂ weights Wb is that are set to satisfy the formula (B), the vibration generated by the vibratory force F _p by the reciprocation unit D1 is effectively reduced.

In the specification and claims, when the damping parameters of mass m _p , mass m _c , mass m _b , phase difference α ₁ and phase difference α ₂ satisfy the formulas (A) and (B) In addition to the case where each damping parameter completely satisfies the formulas (A) and (B), the formulas (A) and (B) are within the range where no significant difference occurs with respect to the vibration reduction effect by the damping mechanism N2. ) Including the case where the value is almost equal to the value when fully satisfied.

An embodiment of the present invention will be described with reference to FIG. The specifications of the internal combustion engine 2 in this embodiment and a comparative example not based on the present invention are as follows.
Example Offset amount δ: 0.005 m
Connecting rod length L: 0.1185m
Crank radius r: 0.0343m
Connecting rod ratio λ: 3.460
Mass m _p : 0.294 kg
Balance ratio of crankshaft C (m _c / m _p ): 50.53%
Balance ratio of balancer shaft B (m _b / m _p ): 50.53%
Phase difference α ₁ : −8.31 °
Phase difference α ₂ : −8.31 °
Comparative example Crankshaft C balance ratio (m _c / m _p ): 50.00%
Balance ratio of balancer shaft B (m _b / m _p ): 50.00%
Phase difference α ₁ : 0.00 °
Phase difference α ₂ : 0.00 °
Other specifications are the same as in the embodiment.

FIG. 4 (A), the as shown (B), the the present invention, for the x component, x component _{F cx} and the excitation force _{F b} in the x component _{F bx} of excitation force _{F c} is cancel each other , x component _{F x} becomes zero, for the y-component, the y-component _{F by} the y component _{F cy} and the excitation force _{F b} in the excitation force _{F c,} generated by the reciprocating motion of the reciprocating portion D1 exciter Since the x component F _px of the force F _p is completely canceled and the y component F _y becomes zero, an excellent vibration reduction effect can be obtained. On the other hand, as shown in FIGS. 4C and 4D, in the comparative example, the x component F _x is zero for the _x component, but the y component F _cy and y for the y component. Even with the component F _by , the y component F _py cannot be completely canceled, and the vibration reduction effect is inferior to that of the present invention.

Next, operations and effects of the embodiment configured as described above will be described.
In the internal combustion engine 2 provided with an offset-type cylinder 30, the balancer shaft B is rotated by the crankshaft C, mass m _b Togashiki mass m _c and the balancer weight Wb of the mass m _p counterweight Wc reciprocating portion D1 (a) satisfies the phase difference alpha ₂ phase difference alpha ₁ and balancer weight Wb of the counterweight Wc is set to satisfy equation (B). Thereby, in the internal combustion engine 2, the mass m _c , m _b and the phase differences α ₁ , α are taken into account by the balancer shaft B which is a rotary balancer similar to the internal combustion engine having the conventional normal type cylinder in consideration of the offset amount δ. _By setting the vibration damping parameter consisting of ₂ to a specific value based on the equations (A) and (B), vibration generated by the reciprocating motion part D1 is reduced. Further, since the balancer shaft B is a rotary balancer, the balancer shaft B itself and the drive mechanism 45 of the balancer shaft B can be reduced in size and structure, and the sliding resistance of the balancer shaft B can be reduced. In addition, since the balancer shaft manufacturing equipment widely used in the internal combustion engine having the normal type cylinder can be used, there is almost no new equipment investment and the manufacturing cost is reduced.
As a result, in the internal combustion engine 2 having the offset type cylinder 30, the balancer shaft B that is a rotary balancer is used, so that the vibration reduction effect is excellent and the balancer shaft B itself and the drive mechanism 45 of the balancer shaft B are downsized. In addition, the degree of freedom of arrangement of the balancer shaft B can be increased by simplifying the structure, and the internal combustion engine 2 can be reduced in size and weight. Further, cost reduction and fuel consumption improvement can be achieved. Moreover, since the vibration damping effect by the balancer shaft B does not depend on the position of the balancer shaft B with respect to the crankshaft C, this also contributes to an increase in the degree of freedom of the arrangement of the balancer shaft B.

Hereinafter, an embodiment in which a part of the configuration of the above-described embodiment is changed will be described with respect to the changed configuration.
The internal combustion engine may be an in-phase two-cylinder internal combustion engine, in which case the ignition timings in the two cylinders may be shifted by 360 ° in crank angle or at the same time.
An internal combustion engine may be used for machines other than vehicles.

1 is a schematic right side view of a motorcycle on which a power unit including an internal combustion engine to which the present invention is applied is mounted. It is a left sectional view of the important section of the internal-combustion engine of Drawing 1. It is a figure for demonstrating the exciting force which generate | occur | produces in the internal combustion engine of FIG. It is a graph which shows the exciting force of an internal combustion engine, (A) is x component of each exciting force in this invention, (B) is each exciting force y component in this invention, (C) is a comparative example. The x component of each vibration force and (D) indicate the y component of the vibration force in the comparative example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Motorcycle, 2 ... Internal combustion engine, L1, L3 ... Centerline of rotation, L2 ... Cylinder axis, C ... Crankshaft, B ... Balancer shaft, Wc ... Counterweight, Wb ... Balancer weight, D1 ... Reciprocating motion part, D2 ... rotational motion part.

Claims (1)

A cylinder having a cylinder axis that is offset laterally with respect to the rotation center line of the crankshaft, a piston that is reciprocally fitted to the cylinder and that is connected to the crankshaft to rotate the crankshaft, and a balancer. In a single cylinder or in-phase two-cylinder internal combustion engine comprising:
Balancer is rotated by the crankshaft, and the mass m _b a balancer weight of the mass m _c and the balancer counterweight mass m _p and the crankshaft of the reciprocating unit to reciprocate in conjunction with the crankshaft with includes a piston satisfy the following formula (a), the phase difference alpha ₂ is the following formula between the rotational angle and the crank angle of the balancer weight around retardation alpha ₁ and the balancer shaft of the rotation angle and the crank angle of the counterweight around the crankshaft An internal combustion engine set to satisfy (B).

Where δ: cylinder axis offset
L: Connecting rod length
r: Crank radius

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