JPH0114079B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power unit suspension system for a motorcycle.

[Prior Art and Problems to be Solved by the Invention] In a power unit suspension system for a small motorcycle such as a scooter, the front part of the power unit, which is integrally equipped with an engine and a means for transmitting power to the rear wheels, is mounted on a front and rear support shaft. A system in which the upper part of the power unit is swingably connected to the vehicle body via a link having a shock absorber and the upper part of the power unit is connected to the vehicle body via a shock absorber is disclosed in Japanese Patent Publication No. 38-12215 and Japanese Patent Application Laid-Open No. 54-53438, etc. It is publicly known.

In such a power unit suspension system, the direction of the main excitation force passing through the crankshaft of the engine determines the direction of the excitation force at the power unit side support shaft of the link.

However, as is known from the above-mentioned Japanese Patent Publication No. 38-12215 and Japanese Patent Application Laid-open No. 54-53438, conventionally, the direction of the engine's main excitation force is orthogonal to the axis passing through the front and rear support shafts of the link. It is becoming.

Therefore, at the pivot connection point (rear support shaft) between the power unit and the link, the vibration direction of the power unit due to the engine's main excitation force is inclined with respect to the link axis. A tensile or pressing force acts on the support shaft, and the link does not swing smoothly around the vehicle body side support shaft (front support shaft), resulting in a considerable amount of vibration being transmitted to the vehicle body via the link. was.

Furthermore, the instantaneous center of the power unit vibration system caused by the engine's main excitation force is determined by the intersection of the link axis and a line perpendicular to the direction of the engine's main excitation force at the center of the crankshaft.
The position of the instantaneous center determines the degree of action of the engine's main excitation force on the rear wheels.

However, in the conventional ones disclosed in Japanese Patent Publication No. 38-12215 and Japanese Patent Application Laid-Open No. 54-53438, the link axis and the line perpendicular to the engine main excitation force direction at the center of the crankshaft are parallel; In other words, since they do not converge, the intersection position cannot be found.

Therefore, the instantaneous center of the power unit vibration system caused by the engine main excitation force cannot be determined, and the engine main excitation force acts considerably on the rear wheels.

Therefore, an object of the present invention is to change the vibration direction caused by the main excitation force of the engine of the power unit to the pivot shaft on the power unit side of the link to the axis passing through the front and rear shafts of the link on the vehicle body side and the power unit side. By tilting the main excitation force direction of the engine rearward with respect to the above-mentioned axis of the link so that it is orthogonal to the axis, the link can smoothly swing around the pivot shaft on the vehicle body side. This makes it possible to minimize the transmission of vibration caused by the engine main excitation force of the power unit to the vehicle body via the link, and also to align the momentary center of the power unit vibration system caused by the engine main excitation force with the axis of the shock absorber. By moving it closer to the downward extension line, the effect of the engine's main excitation force on the rear wheels can be reduced.
This makes it possible to minimize the transmission of vibration caused by the vibration of the rear wheels in contact with the vehicle body through the shock absorber, thereby increasing the effect of suppressing vibration transmission to the vehicle body and improving ride comfort. An object of the present invention is to provide a power unit suspension system for a motorcycle.

[Means for Solving the Problems] In order to achieve the above-mentioned problems, the present invention connects the front part of a power unit that integrally includes an engine and a means for transmitting power to rear wheels via a link having a support shaft at the front and rear. In a power unit suspension system for a motorcycle, the power unit is swingably connected to the vehicle body, and the upper part of the power unit is connected to the vehicle body via a shock absorber. The front and rear spindles are arranged so that a line perpendicular to the center of the crankshaft and a line passing through the front and rear spindles of the link intersect at the rear of the link, so that the main power of the engine of the power unit is The vibration direction of the support shaft of the link due to the vibration force is
The shock absorber is configured to be perpendicular to the link, and a position where a line perpendicular to the direction of the main excitation force of the engine at the center of the crankshaft and a line passing through the front and rear support shafts intersect is determined. It is characterized by being placed close to the downward extension of the axis.

[Operation] First, the front and rear support shafts are arranged so that a line that is perpendicular to the direction of the main excitation force passing through the engine crankshaft at the center of the crankshaft and a line that passes through the front and rear support shafts of the link intersect at the rear of the link. The vibration direction of the rear support shaft of the link caused by the main excitation force of the engine of the power unit is perpendicular to the axis of the link, so that the link swings smoothly around the support shaft on the vehicle body side. Therefore, vibration transmission due to the engine main excitation force of the power unit to the vehicle body via the link is suppressed to a minimum.

Then, the position where the line perpendicular to the engine main excitation force direction at the center of the crankshaft intersects with the line passing through the front and rear support shafts of the link, that is, the instantaneous center of the power unit vibration system caused by the engine main excitation force, is Since the shock absorber axis is brought closer to the downward extension line, the effect of the main excitation force of the engine on the rear wheels is reduced, and therefore the vibration caused by the rear wheels contacting the vehicle body via the shock absorber is reduced. Vibration transmission is also minimized.

As described above, the effect of suppressing vibration transmission from the power unit to the vehicle body via the link and shock absorber is enhanced, and ride comfort is improved.

[Example] Examples will be described below based on the accompanying drawings.

In FIG. 1, which is a perspective view of the rear part of a motorcycle to which the present invention is applied, with the front part omitted, the body frame of the motorcycle 1 is composed of a main frame 2 and a rear frame 3, and as shown in the figure, the main frame 2
A seat 4 is attached above a rear frame 3 connected to the rear part of the vehicle, which curves upward and extends rearward, and the periphery of the rear frame 3 is covered with a body cowl 5, and 6 is a rear fender.

The power unit 7 consists of an engine 8 standing upward from the front and a crankcase 9 below it.
A rear wheel 11 is pivotally supported at the rear of the transmission case 10, and a means for transmitting power to the rear wheel 11 is built in the transmission case 10. . Furthermore, the rear part of the upper part of this transmission case 10 and the rear frame 3 above it
It is connected to the rear part by a shock absorber 12 which is a unit of a hydraulic damper and a coil spring, and the axis of the shock absorber 12 is tilted forward in the illustration.

A link 13 is connected between the lower part of the front part of the power unit 7 and the front part of the rear frame 3 in front of it.
are pivotally connected via front and rear support shafts 14 and 16. Reference numeral 7a designates a pivot boss portion provided at the lower part (lower surface of the crankcase 9) of the front portion (engine 8) of the power unit 7, and rubber bushes 15, 17 are interposed around the front and rear support shafts 14, 16, respectively. There is.

4 and 5 show an example of the detailed structure of the link 13 portion, and the link 13 as shown in the figure
Cylindrical members 13a, 13a are fixed to the front left and right sides, respectively, and a front support shaft 14 is installed between the left and right side pieces 3a, 3a at the lower part of the front part of the rear frame 3, as shown in the figure. Inner and outer rings 15 are located on the left and right sides of this support shaft 14.
The cylindrical members 13a are assembled with rubber bushes 15 having rubber bushes 15a and 15b interposed therebetween. Left and right pivot bosses 7a, 7a are protruded from the lower surface of the crankcase 9 of the power unit 7.
Further, a collar 18 is fixed to the rear part of the link 13. Inner and outer rings 17a, 1 on the left and right sides of this support shaft 18
The pivot boss portions 7a of the power unit 7 are respectively assembled with a rubber bush 17 having a diameter 7b interposed therebetween. Reference numeral 7b is a mounting hole for the pivot boss portion 7a, and reference numerals 19 and 20 are mounting holes for the link 13 and the power unit 7.
This is a bump stopper rubber interposed between the Here, each of the rubber bushes 15 and 17 is preloaded in the torsional direction.

In the above, the effect of vibration of the power unit 7 due to the main excitation force of the engine 8 on the link 13 will be considered.

The main excitation force of the engine 8 is generated at the center of the crankshaft, and the direction of the excitation force in each part of the power unit 7 is different. This is because this changes depending on the mass of the power unit 7, the moment around the center of gravity, etc., and as shown in Fig. 2, an extension line N connecting the crankshaft center P of the engine 8 and the center of gravity C of the power unit 7.
The power unit 7 is located around the momentary center O that exists above.
exercise. For example, if the main excitation force direction of the engine is indicated by arrow d, an excitation force in the direction of arrow a will be generated at the upper end of the cylinder head of the engine 8, and the power unit side pivot point by the rear support shaft 16 of the link 13 will be generated at the upper end of the cylinder head of the engine 8. At A, an excitation force is generated in the direction of arrow b.

As described above, the direction of the excitation force of the power unit 7, which momentarily moves around the center O due to the main excitation force of the engine 8, differs in each part.

In Fig. 2, the instantaneous center O of the power unit 7 caused by the engine's main excitation force is the crankshaft center P.
Although the instantaneous center O is generally located on an extended line N passing through the center of gravity C from As shown in FIG. 2, it is not necessarily located on a line passing through the center of gravity C.

The direction of the engine's main excitation force determines the direction of the excitation force at the power unit side pivot point of the link connected to the vehicle body, but the center of gravity of the power unit and the engine's main excitation force Because the crankshaft that generates vibration is largely separated, the direction of vibration caused by the engine's main excitation force at the crankshaft does not necessarily match the direction of vibration at the rear link support shaft of the power unit as a whole, so vibration transmission is not necessarily possible. is difficult to minimize.

FIG. 3 illustrates this. That is, as shown in the figure, if the direction of the main excitation force of the engine is d' and the direction of vibration of the rear support shaft 16 of the link 13 with respect to the power unit 7 is b', then the direction of the main excitation force of the engine with respect to the link 13 is d'. If they are orthogonal to each other, the link rear support shaft 16 has the front and rear support shafts 1 of the link 13 as shown in b'.
Vibration occurs in a direction oblique to the line connecting 4 and 16. As a result, a tensile or pressing force acts on each of the front and rear support shafts 14 and 16 of the link 13, which prevents the link 13 from swinging smoothly around the front support shaft 14 relative to the vehicle body, resulting in increased vibration transmission. Become.

Therefore, as shown in FIG. 2, in the present invention, the direction of the excitation force acting on the power unit side pivot portion A of the link 13 is set by the arrow b, taking into account the excitation force distribution of the power unit 7 vibration system. It is set so as to occur in the direction shown by , which is in the vertical direction with respect to the rear support shaft 16 and perpendicular to the axis of the link 13 passing through the front and rear support shafts 14 and 16 . Therefore, as shown by arrow d, the direction of the engine's main excitation force is tilted backward with respect to the axis of link 13, and link 1
An extension of the three axes intersects a line perpendicular to the engine main excitation force direction d at the crank center at the rear of the link 13.

As a result, an excitation force in a direction orthogonal to the axis of the link 13 acts on the rear support shaft 16 of the link 13 as shown by arrow b due to the vibration of the power unit 7 caused by the main excitation force of the engine. Swinging around the front support shaft 14 relative to the side is performed smoothly, and therefore vibration transmission due to the engine main excitation force of the power unit 7 to the vehicle body via the link 13 is suppressed to a minimum. become something that

The position where the line perpendicular to the engine main excitation force direction d at the center of the crankshaft and the extension line of the link 13 axis intersect, that is, the instantaneous center O of the power unit 7 vibration system caused by the engine main excitation force, is ,
As can be easily understood from FIGS. 1 and 2,
Since the shock absorber 12 is positioned close to the downward extension of the axis of the shock absorber 12, the effect of the engine's main excitation force on the rear wheel 11 can also be reduced, preventing the rear wheel 11 from excessively vibrating. Buffer 12
Vibration transmission to the vehicle body via the rear wheel 11 caused by vibration when the rear wheel 11 is in contact with the ground is also suppressed to a minimum.

By the way, regarding the above setting of the engine main excitation force direction, the engine main excitation force direction is mainly influenced by the crank weight, so it is necessary to change the mass distribution ratio and mounting position of the crank weight. The above-mentioned engine main excitation force direction can be set by the following.

[Effects of the Invention] As described above, according to the present invention, first, a line perpendicular to the direction of the main excitation force passing through the engine crankshaft at the center of the crankshaft, and a line passing through the front and rear support shafts of the link, The front and rear support shafts are arranged to intersect at the rear of the link, so that the direction of vibration of the rear support shaft of the link caused by the main excitation force of the engine of the power unit is perpendicular to the axis of the link. The vibrations caused by the main excitation force of the engine of the power unit to the vehicle body via the link can be suppressed to a minimum. .

Then, the position where the line perpendicular to the engine main excitation force direction at the center of the crankshaft intersects with the line passing through the front and rear support shafts of the link, that is, the instantaneous center of the power unit vibration system caused by the engine main excitation force, is Because it is configured to be close to the downward extension of the shock absorber axis,
The effect of the main excitation force of the engine on the rear wheels can be reduced, and therefore the transmission of vibrations caused by vibrations when the rear wheels are in contact with the ground to the vehicle body via the shock absorber can also be suppressed to a minimum.

As described above, the effect of suppressing vibration transmission from the power unit to the vehicle body via the link and shock absorber can be enhanced, and ride comfort can be improved.

[Brief explanation of drawings]

FIG. 1 is a schematic side view of the main parts of a motorcycle to which the present invention is applied, omitting the front part and showing the rear part in perspective;
FIG. 2 is an explanatory diagram of the operation of the present invention, FIG. 3 is an explanatory diagram of the operation of a comparative example, and FIGS. 4 and 5 are enlarged cutaway side views showing the specific structure of the link part in the suspension system of the present invention. FIG. In the drawings, 1 is a motorcycle, 2 and 3 are body frames, 7 is a power unit, 8 is an engine, and 9 is a motorcycle.
10 is a crankcase, 10 is a transmission case, 11 is a rear wheel, 12 is a shock absorber, 13 is a link, 14 and 16 are support shafts, and O is the instantaneous center of the power unit vibration system caused by the engine main excitation force.

Claims (1)

[Scope of Claims] 1. The front part of a power unit that integrally includes an engine and a means for transmitting power to the rear wheels is swingably connected to the vehicle body via a link having a support shaft in the front and rear, and the front part of the power unit is In a power unit suspension system for a motorcycle, the upper part of which is connected to the vehicle body via a shock absorber, a line perpendicular to the direction of the main excitation force passing through the crankshaft of the engine at the center of the crankshaft, and a line between the front and rear of the link. The front and rear support shafts are arranged so that a line passing through the support shaft intersects at the rear of the link, and the rear support shaft portion of the link is The vibration direction is
The shock absorber is configured to be perpendicular to the link, and a position where a line perpendicular to the direction of the main excitation force of the engine at the center of the crankshaft intersects with a line passing through the front and rear support shafts is determined. A motorcycle body power unit suspension system, characterized in that it is arranged close to a downward extension of an axis.