JPS6236915B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an engine suspension method that is applied to a chain-driven vehicle that transmits the driving force of the engine to the drive wheels via a chain, and that suppresses transmission of engine vibrations to the vehicle body.

Conventionally, in many chain-driven vehicles such as motorcycles and tricycles, the engine is directly fixed to the frame to prevent the engine from "dancing" due to fluctuations in the driving force applied to the chain. However, as engines become larger, engine vibrations also increase, and ride comfort is also required to be improved. Therefore, an engine suspension method that can effectively prevent the transmission of engine vibrations to the vehicle body and that also reduces engine movement is needed. It was wanted.

This invention was made in view of the above circumstances, and it significantly reduces the transmission of engine vibrations to the vehicle body, improving ride comfort, and also reduces engine movement due to fluctuations in driving force, etc., and reduces engine mounting space. The object of the present invention is to provide an engine suspension method that allows for a very small amount of spare space.

According to the present invention, the object is to provide a chain-driven vehicle in which an engine is swingably mounted on a frame of a vehicle body, in which the engine is provided with an extension portion extending in the tension direction of the drive chain, and the engine is provided with an extension portion extending in the tension direction of the drive chain. locating the instantaneous center of the engine and pivotally supporting the engine near this instantaneous center;
This is achieved by a method for suspending an engine in a chain-driven vehicle, characterized in that the shaft fulcrum is located near the tension side of the drive chain. The present invention will be explained in detail below based on the drawings.

FIG. 1 is a side view showing an embodiment in which the present invention is applied to a motorcycle, and FIG. 2 is a partial front view thereof. In these figures, reference numeral 1 is a cradle type frame, and this frame 1 has a steering wheel.
Head pipe 2, left and right pair of down tubes 3
(3a, 3b), backstay 3', tank rail 4, seat pillar tube 4', seat rail 5
Equipped with. Note that the back stay 3' is integrated with the down tube 3, and the seat pillar tube 4' is integrated with the down tube 3.
is integrated with the tank rail 4. A stay 6 is welded approximately horizontally within the triangle formed by the back stay 3', seat pillar tube 4', and seat rail 5.
A bracket 7 is welded to the position between the two. A shaft fulcrum C, which will be described later, is located on this bracket 7.

10 is a rear wheel as a driving wheel, and this rear wheel 1
0 is suspended by a swing arm suspension system. That is, the rear wheel 10 is held by a rear arm 11 whose front end is pivotally supported by the frame 1 so as to be movable up and down, and is given a downward return habit by a cushion unit 12. The front end of the rear arm 11 is pivotally supported between a pair of left and right brackets 13 (only one of which is shown in the figure) fixed to the backstay 3'.

Reference numeral 20 denotes an engine, and a transmission mechanism (not shown) and the like are housed in a crankcase 21 of the engine 20. In other words, engine 20 here
includes not only the original engine in the strict sense of the word, such as the piston, crankshaft, cylinder block, etc.
The engine 20 includes parts that vibrate together with the original engine, and the transmission inside the crankcase 21, the carburetor 22, a part of the exhaust pipe 23, etc. are included in the engine 20. The piston of this engine 20 is arranged to move up and down in a substantially vertical direction, and the primary inertial force f is generated in the up and down direction of the crankshaft center A. G is the center of gravity of the engine, and this center of gravity G is located above and rearward of the crankshaft center A.

25 is an extension member, which is connected to the crankcase 2.
It is fixed to the rear part of the seat pillar tube 4' so as to straddle the seat pillar tube 4'. This extension member 25
extends rearward along an orthogonal line B that passes through the center of gravity G and is orthogonal to the direction of the primary inertial force f, and its rear end is pivotally supported by a pivot point C located on the bracket 7. Note that this pivot point C is located near the instantaneous center on the orthogonal line B, which will be described later. That is, the position of this shaft fulcrum C is determined so as to satisfy the following equation.

I/m≒｜l・e｜……(1) Here I is the engine inertia rate m is the engine mass l is the distance between the engine center of gravity G and the primary inertia force f e is the distance between the engine center of gravity G and the shaft fulcrum C shall represent.

Reference numeral 30 denotes a protruding member fixed to the front end of the crankcase 21. The protruding member 30 extends between the pair of left and right down tubes 3a, 3b, and there is a round shape between the left and right side surfaces and each down tube 3a, 3b. They are connected via shaped vibration isolating rubber 31 (31a, 31b).

35 is a drive sprocket of the engine 20, 36
is a driven sprocket of the rear wheel 10, and a chain 37 is routed around both sprockets 35 and 36. The pivot point C is located near the tension side (upper side in FIG. 1) of the chain 37.

Note that 38 and 39 are stoppers that suppress excessive rocking of the engine 20, and the stopper 38 is attached to the tank rail 4 above the engine 20, and the stopper 38 is attached to the tank rail 4 above the engine 20.
9 are fixed between the pair of down tubes 3a and 3b so as to cross below the protruding member 30.

Figure 3 is a schematic diagram of the embodiment shown in Figure 1;
The figures are diagrams showing the dynamic model, and it will be explained based on these figures that when the above-mentioned equation (1) is established, the transmission of engine vibration to the frame is reduced. The model shown in FIGS. 3 and 4 has an engine 20 supported by a torsion bar at a pivot point C, and is particularly suitable for mounting a small engine.
In FIG. 4, the orthogonal line B is taken as the x-axis, and the direction of the primary inertial force f is taken as the z-axis. Therefore, on the xz plane, point A is (l, o), G
is expressed as (o, o), and C is expressed as (e, o). Note that l and e include positive and negative signs.

Now the engine mass m, the engine inertia factor I,
Let K be the torsion spring constant of the torsion bar, and let θ be the rotation angle around an axis that passes through the fulcrum C and is parallel to the y-axis (positive in the top direction of the paper in Figure 4) (positive in the counterclockwise direction in the figure). For example, the equation of motion of the model in Fig. 4 is (i+me ² )θ¨+Kθ=-f(l-e)...(2). On the other hand, the inertia factor I of the engine 20 can be set as I≡mκ ² (3) if the engine 20 is regarded as a rigid body with a mass m. Here, κ is a quantity having a dimension of length and is called the radius of gyration. Using equation (3), equation (2) becomes as follows.

m(κ ² +e ² )θ¨+Kθ=f(e-l)...(4) To solve equation (4), θ=Θ・exp(iωt), f=F・exp(iωt), ( i = √-1) and by substituting these into equation (4), we get {-ω ² m (κ ² +e ² ) + K}Θ=F(e-l)
...(5) The natural vibration angular velocity ω ₀ can be found from {...}=0 on the left side as follows.

ω ₀ ² =K/m(κ ² +e ² )...(6) Substituting equation (6) into equation (5), {m(κ ² +e ² )(ω ₀ ² −ω ² )}Θ= F(e-
l) ∴Θ=F(e−l)/m(κ ² +e ² )(ω ₀ ² −ω
² )...(7) On the other hand, if the reaction force of the torsion bar at the shaft fulcrum C is r, the balance of the force in the Z-axis direction is mz¨-r=f ∴r=-f+mz...(8) Here, z is the center of gravity G When the entire engine rotates by a minute angle θ, the center of gravity G will move up and down around the shaft support C. Therefore, the center of gravity G
Since the z coordinate of can be expressed as z=eθ, z¨=eθ¨, and by substituting this into equation (8), we get r=-f+meθ¨...(9) To solve equation (9), r= R・exp(iωt), f=F・exp(iωt), θ=Θ・exp(iωt), and substituting them into equation (9), we get −R=F+ω ² meΘ ……(10) Here, (7 ) using the equation -R=F{1+ω ² e(e-l)/(κ ² +e ² )(
ω ₀ ² −ω ² )}…((11) R and F each represent the amplitude, and |R/F| represents the rate at which the periodic inertial force f is transmitted to the frame 1 via the pivot point C. Therefore, we will call it the transmissibility here. This transmissibility is expressed as τ as τ=|R/F|= (κ ² +e ² )ω ₀ ² −(el+κ ² )ω ² /(κ ²
+e ² )(ω ₀ ² −ω ² )...(12).

As is clear from equation (12), as ω becomes larger than ω ₀ , the transmissibility τ decreases, and in a normal vehicle, ω is sufficiently larger than ω ₀ , and τ converges to the following constant value: It can be thought of as a thing.

limτ=κ ² +el/κ ² +e ² ...(13) Figure 7 shows the change in τ based on this equation (13) |
It is a calculation chart shown as a parameter of k/l|. From equation (13), limτ becomes 0 when e=κ ² /l (14), and this point is indicated by a circle in FIG. As is clear from this figure, as |k/l| increases, the slope of the curve representing τ at the point marked with a circle becomes gentler, and even if there is a slight deviation of e/l from this point, τ becomes almost 0. On the other hand, in the engine of a normal motorcycle or the like, |k/l|>1, so if equation (14) is approximately satisfied, τ will be almost 0. Therefore, e≒−κ ² /l If rewritten using equation (3), I/m≒−l・e ...(15) This is the same as equation (1) above, and in this case, engine 2
0 vibration is hardly transmitted to the frame 1. Note that if the equation (7) is satisfied, the point is the instantaneous center, which is the point where the displacement becomes 0 at the moment the engine rotates.

5 and 6 are diagrams showing other schematic diagrams and their dynamic models. This model is more similar to the embodiment shown in FIG. The shaft support C is rotatably supported. In this case, the position of the vibration isolating rubber 31 is (a, o) and its spring constant is k
Then, the coefficient of restoration of this spring in the direction of rotation θ is k(ae) ² , which corresponds to the torsion spring constant K of the torsion bar in FIGS. Therefore, the equations up to equation (14) above are valid as they are by replacing them with K=k(ae) ² (16).

If the reaction force of the shaft fulcrum C is r', the balance of the force in the z-axis direction is meθ¨-k(ae)θ-r'=f ∴-r'=f+k(a-e)θ-meθ ¨ …(17) Here, if we set r′=R′・exp(iωt), f=F・exp(iωt), θ=Θ・exp(iωt), equation (17) becomes −R′=F+{ k(a-e)+ω ² me}Θ...(18) Substituting equation (7) into this and rearranging, -R'=F{m(κ ² +e ² )ω ₀ ² + k(a-e )(e−l)−m(κ ² +el)ω
² }/ {m(κ ² +e ² ) (ω ₀ ² −ω ² )}…(19) Also, by substituting equation (18) into equation (6), ω ₀ ² = k(a-e) ² / m(κ ² +e ² )……(20) If we substitute this ω ₀ ² into the first term of the numerator of equation (19) and rearrange it, we get −R′={k(a−e)(a−l)− m(κ ² +el)ω ² }/ m(κ ² +e ² )(ω ₀ ² −ω ² ) …(21) Therefore, the transfer coefficient τ′ is τ′=|R′/F|={k( a-e) (a-l) - m (κ ² + el) ω ² }/m (κ ² + e ² ) (ω ₀ ² -
ω ² ) …(22) In this equation (22), when ω becomes larger than ω ₀ , τ′ converges to a constant value. That is, limτ'=κ ² +el/κ ² +e ² (23) This equation is the same as equation (13) above. Therefore, similarly to the models shown in FIGS. 3 and 4, when equation (8) holds true, transmission of engine vibration to the frame 1 can be effectively blocked.

In the above embodiment, the extension member 25 is connected to the engine 20.
Although the extension part is formed by fixing to the crankcase 21, this extension part may be formed integrally with the crankcase 21.

In this invention, as described above, the engine is provided with an extension member, and the engine is pivoted near the instantaneous center on the extension member, and this pivot point is located near the tension side of the chain. is less likely to be transmitted to the frame via the shaft fulcrum, improving riding comfort. Furthermore, even if there are fluctuations in the driving force, the engine is less likely to shake because the shaft fulcrum is located near the tension side of the chain, reducing engine movement. Therefore, the extra space for mounting the engine can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a side view showing one embodiment of the present invention, Fig. 2 is a front view of a part thereof, Fig. 3 is a schematic diagram of this embodiment, Fig. 4 is a diagram showing its dynamic model, Fig. 5
FIG. 6 and FIG. 6 are diagrams showing other schematic diagrams and their dynamic models, and FIG. 7 is a diagram showing changes in the transmissibility τ. 20...Engine, 25...Extension member as an extension part, 37...Chain, C...Axis fulcrum.

Claims (1)

[Scope of Claims] 1. In a chain-driven vehicle in which an engine is swingably mounted on a frame of a vehicle body, the engine is provided with an extension extending in the tension direction of the drive chain, and the engine is mounted on the extension. A method for suspending an engine in a chain-driven vehicle, characterized in that an instantaneous center is located, the engine is pivotally supported near the instantaneous center, and the pivot point is located near the tension side of the drive chain.