JPH0240558B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust pipe system mounting structure applied to a vehicle in which an engine is elastically mounted to a frame.

BACKGROUND ART Conventionally, it has been proposed to mount an engine elastically on a vehicle such as a motorcycle using an elastic material or the like to effectively block transmission of engine vibration to the vehicle body.

For example, as disclosed in Japanese Patent Application No. 54-87457 (Japanese Unexamined Patent Publication No. 56-13266), in an in-line multi-cylinder engine, pistons are arranged at a predetermined angle with the movement direction of the pistons and on a straight line passing through the center of gravity of the engine. Some models have an engine mounted on a frame made of an elastic material with a certain hardness. In this case, by appropriately selecting the hardness and position of the elastic material, engine vibration can be limited to rolling vibration only, and the resonant frequency of this rolling vibration can be made to be outside the normal engine speed range. This prevents vibrations from being transmitted to the frame.

Furthermore, Japanese Patent Application No. 54-172534 (Japanese Unexamined Patent Publication No. 56-95782) discloses a method of rotatably supporting the engine near the instantaneous center of engine vibration (hereinafter referred to as the pivot suspension method). . In this method, if the engine is supported at an instantaneous center that is perpendicular to the direction of piston movement and on a straight line passing through the center of gravity of the engine,
This takes advantage of the fact that the vibration transmissibility is zero.

When mounting an engine elastically, it is necessary to determine the weight, center of gravity, moment of inertia, etc. of the engine, and then calculate the position and hardness of the elastic material. However, since the engine is connected to an exhaust pipe system consisting of a long exhaust pipe and a muffler, the actual vibrations differ from the theory. In particular, in conventional motorcycles, the exhaust pipe system is attached to the frame via rubber, etc., so it is difficult to accurately predict the effect that the hardness and position of this rubber, the weight of the exhaust pipe system, etc. will have on engine vibration. However, there were cases where the vibration reduction effect could not be obtained as theoretically possible.

This invention was developed in view of these circumstances, and takes into account the influence of the exhaust pipe system, ensuring that the theoretical vibration reduction effect can be obtained, and effectively blocking vibration transmission to the frame. The purpose of the present invention is to provide an exhaust pipe system mounting structure suitable for a vehicle.

According to the present invention, this purpose is achieved by providing an engine supported on a frame at a plurality of locations spaced apart in the longitudinal direction;
In a vehicle having an exhaust pipe system consisting of an exhaust pipe and a muffler that extend from the front of the engine to the rear through around the engine, the exhaust pipe system is integrally attached to the engine, and the engine and the entire exhaust pipe system are installed. is approximately one rigid body, the instantaneous center of this rigid body is located near the rear of the engine, and is rotatably supported by a pivot shaft to the frame near this instantaneous center, and the other supporting parts of the rigid body are elastically supported. This is achieved by a vehicle exhaust pipe system mounting structure characterized by supporting the vehicle exhaust pipe system. The present invention will be described in detail below based on the illustrated embodiments.

FIG. 1 is a side view of the main parts of a motorcycle to which a first embodiment of the present invention is applied. In this figure, reference numeral 10 is a down tube, 12 is a seat pillar tube, and 14 is a backstay, and a frame is formed by these, a steering head pipe, a tank rail, etc. (not shown). A bracket 16 is welded to the seat pillar tube 12, and a rear arm 18 that holds a rear wheel (not shown) in a vertically movable manner is pivoted to the bracket 16.
Further, 20 is a footrest similarly fixed to the seat pillar tube 12.

Reference numeral 22 denotes an engine, and a crankcase 24 of this engine 22 accommodates a transmission mechanism (not shown) and the like. That is, the engine 22 here includes not only the engine in the strict sense such as the piston, crankshaft, and cylinder body, but also parts that vibrate together with these, such as the transmission mechanism and carburetor in the crankcase 24. shall be held. However, the engine 22 does not include an exhaust pipe system to be described later.

26 is an exhaust pipe extending from the front of the engine 22 to below the engine, and 28 is a muffler connected to the exhaust pipe 26 and extending rearward. The exhaust pipe 26 and the muffler 28 form an exhaust pipe system 30. The silencer 28 is integrally fixed to the crankcase 24 by a stay 32, and is also connected to the exhaust pipe 2.
Both ends of 6 are fixed to an engine 22 and a muffler 28, respectively. As a result, the engine 22 and the exhaust pipe system 30 form one rigid body.

The engine 22 is elastically mounted on the frame using the aforementioned pivot suspension system. That is, the rear part of the engine 22 is rotatably supported in the vertical direction by a pivot shaft 36 to a bracket 34 welded to the seat pillar tube 12, and the front part of the engine 22 is welded to the down tube 10. It is held by a bracket 38 via elastic rubber. 40 is a support shaft passing through this rubber and the bracket 38. A straight line A connecting the pivot shaft 36 and the support shaft 40 passes through the center of gravity G of the rigid body consisting of the engine 22 and the exhaust pipe system 30, and is perpendicular to the direction of movement of the piston (not shown), that is, the direction of the primary inertial force F. do. Further, the position of the pivot shaft 36 is determined so as to satisfy the following equation.

I/m=l・e where I is the inertia coefficient of the entire rigid body consisting of the engine 22 and the exhaust pipe system 30, m is the mass of this rigid body,
l is the distance from the center of gravity G to the inertial force F, e is the center of gravity G
to the pivot axis 36.

When this formula is satisfied, the vibration transmission rate from the pivot shaft 36 to the frame becomes approximately zero, and the pivot shaft 36 becomes the instantaneous center of this rigid body, as described in the above-mentioned Japanese Patent Application No. 172,534/1989 (Japanese Patent Application Laid-Open No. 56-197). Publication No. 95782)
It is clear from the description.

According to this embodiment, engine 22 and exhaust pipe system 30 oscillate in a rotational manner about pivot axis 36. Furthermore, since the weight, moment of inertia, etc. of the exhaust pipe system 30 have already been taken into account when theoretically determining the position of the pivot shaft 36 through calculations, the vibration behavior after mounting the engine 22 on the frame will be significantly different from the theory. never changes. Therefore, it is possible to reliably obtain the vibration reduction effect that is almost in accordance with the theory.

FIG. 2 is a side view of essential parts of a motorcycle to which the second embodiment is applied. In this embodiment, a stay 32A is used in place of the bracket 32 in FIG.
One end of a stay 32A is welded near the center of the silencer 28, and the other end of the stay 32A is held on the pivot shaft 36.

According to this embodiment, the exhaust pipe system 30 is connected to the pivot shaft 36 together with the engine 22 via the stay 32A.
It rotates and vibrates around the center. Further, in this embodiment, since the muffler 28 is held at a position further rearward than in the embodiment shown in FIG. becomes smaller, which is very advantageous in terms of strength. Note that in FIG. 2, the same parts as in FIG. 1 are given the same reference numerals, so the description thereof will not be repeated.

FIG. 3 is a side view of essential parts of a motorcycle to which the third embodiment is applied, and FIG. 4 is a sectional view of the vicinity of the pivot shaft 36. In this embodiment, a rear arm 18 for holding a rear wheel is pivotally attached to a pivot shaft 36A. That is, the weight distribution of the engine 22 and the exhaust pipe system 30 is changed from that of the embodiment shown in FIGS.

In FIG. 4, 42 is a cylinder welded to the front end of the rear arm 18 (FIG. 3), and 44 is a ball bearing interposed between the crankcase 24 and the pivot shaft 36A. The cylinder 42 is held on the pivot shaft 36A between the ball bearing 44 and the bracket 16 via bushes 46 and 48. The stay 32B, which is welded to the silencer 28, is attached to the pivot shaft 36A via a rubber bush 50 on the outside of the bracket 16. 52 is a nut that holds the stay 32B on the pivot shaft 36A, and 54 is a collar that maintains the distance between the ball bearing 44 and another ball bearing (not shown) that pairs with it.

In this embodiment, the only difference is the pivot shaft position from the embodiment shown in FIGS. 1 and 2 due to changes in weight distribution, etc., so the same parts are given the same reference numerals and the explanation thereof will not be repeated.

According to the embodiment of FIGS. 3 and 4, the first,
Compared to the embodiment shown in FIG. 2, there is no need for a bracket 34 for supporting the engine 22 or a support shaft for holding only the rear arm 18, which is suitable for reducing the weight of the vehicle body. Furthermore, compared to the embodiment shown in FIG. 2, by changing the weight distribution etc. so that the position of the pivot shaft 36A is closer to the muffler 28, the stay 32B can be shortened, thereby reducing the weight of the stay 32B and increasing its rigidity. be able to. Furthermore, in the embodiment shown in FIGS. 3 and 4, the stay 32B of the silencer 28 is attached to the pivot shaft 36A via the rubber bushing 50, so that vibrations of the silencer 28 itself, such as vibrations caused by exhaust pulsation or vibrations from the road surface while driving, It can also absorb vibrations received through the frame.

Since each of the above embodiments is applied to the present invention in a pivot suspension system, the center of rotation when the entire engine 22 and exhaust pipe system 30 are viewed as one rigid body is located at the pivot shafts 36, 36A at the rear of the engine 22. In this case, the amplitude at the rear end of the muffler 28 becomes relatively small, which is even more preferable. However, the present invention is of course applicable to other engine suspension systems.

As described above, the present invention supports an engine at a plurality of locations spaced apart in the longitudinal direction, and integrally provides an exhaust pipe system extending from the front of the engine to the rear through the periphery of the engine. It is a rigid body, the instantaneous center of this rigid body is located near the rear of the engine, the arc rigid body is rotatably supported around this instantaneous center, and other supporting parts of this rigid body are elastically supported. Therefore, it is possible to perform vibration analysis with the engine and exhaust pipe system as approximately one rigid body, and it is possible to obtain a vibration reduction effect that substantially matches the theory. That is, by allowing the rigid body to rotate around the instantaneous center, vibration transmission to the frame can be effectively blocked.
Furthermore, since this rigid body is rotatably supported at a position close to its center, the amplitude of the exhaust pipe system is relatively small, making it suitable for vehicles.

[Brief explanation of drawings]

1, 2, and 3 are side views of main parts of a motorcycle to which different embodiments of the present invention are applied, and FIG. 4 is a sectional view of the vicinity of the pivot axis in FIG. 3. 22... Engine, 26... Exhaust pipe, 28... Silencer, 30... Exhaust pipe system, 36, 36A... Pivot shaft.

Claims (1)

[Scope of Claims] 1. An engine supported on a frame at a plurality of locations spaced apart in the longitudinal direction, and an exhaust pipe system including an exhaust pipe and a muffler extending from the front of the engine to the rear through the periphery of the engine. In the vehicle, the exhaust pipe system is integrally attached to the engine so that the engine and the exhaust pipe system as a whole become substantially one rigid body, the instantaneous center of this rigid body is located near the rear of the engine, and the instantaneous center of the rigid body is located near the rear of the engine. An exhaust pipe system mounting structure for a vehicle, characterized in that the exhaust pipe system is rotatably supported on a frame by a pivot shaft, and another support part of the rigid body is elastically supported. 2. The vehicle exhaust pipe system mounting structure according to claim 1, wherein a muffler is held on the pivot shaft.