JPS6256645A - Crank balancing device for engine - Google Patents

Abstract

PURPOSE:To simplify the construction by furnishing a balancer weight between a balancer con-rod, which is coupled with an eccentric part of a crank shaft, and a yoke which is installed with rotatability with respect to a crank case. CONSTITUTION:A balance weight 3a is furnished in the place 180 apart from a crank pin 6 on a crank shaft 3. A crank balance device 11 consists of a balancer con-rod 12, a yoke 13 and a balancer weight 14. This balancer weight 14 has one end of yoke 13 which is coupled rotatably. This ensures that balancer weight functions without play even during high-speed operation, and the construction can be simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a crank balance device that is suitably used in a two-stroke engine or the like and reduces engine vibration.

``Conventional technology'' Generally speaking, a balance weight is attached to the crankshaft to reduce the vibration of a piston type engine.
A method is used to cancel the inertial force at the top and bottom dead centers of the piston. However, when a balance weight heavy enough to cancel out the inertial force of the balance weight is attached, there is a problem in that lateral vibrations are newly generated due to the centrifugal force of the balance weight.

Therefore, by reciprocating a balancer weight of approximately the same weight as the piston in the opposite direction to the piston,
Various crank balance devices have been developed to offset the inertial force at the top and bottom dead centers of the piston as described above, and one known example of this type of balance device is the one shown in Japanese Patent Application Laid-open No. 1221.0/1983. . This balancer weight is connected to the free end of a balancer connecting rod which is pivotally connected to an eccentric shaft part having a phase difference of 180 degrees with respect to the crankshaft part of the engine crankshaft, The weight is configured to move approximately linearly reciprocating along the cylinder axis through relative sliding between the pin and the elongated hole in the cylinder axis, and the inertia force at the top and bottom dead center of the piston is approximately reduced. It was something that could be canceled out.

"Problems to be Solved by the Invention" The present invention aims to solve the following problems in the above-mentioned conventional technology.

In other words, in the above-mentioned crank balance device, since the bottle is configured to slide in a long hole formed in the balancer weight, this sliding movement occurs especially when the engine is operated at high speed. There were concerns about durability, such as parts becoming worn and rattling.

In addition, in the conventional crank balance device described above, the balancer connecting rod is connected to the inside of the two crank bearings that support the crankshaft, so it is necessary to place both crank bearings a certain distance apart. There was some dissatisfaction with the bending strength in the vicinity.

Furthermore, in the above-mentioned crank balance device, since the balancer weight is provided in the crank chamber that accommodates the crankshaft of the crankcase, the internal capacity of the crank chamber becomes large. Therefore, the two-legged crank balance device has the problem of being unsuitable for a two-stroke engine that introduces the air-fuel mixture into the cylinder through the crank chamber.

"Means for Solving the Problems" The engine crank balance device of the present invention includes a balancer conrod having one end rotatably connected to the eccentric shaft of the crankshaft outside the crank bearing, and the other end of the balancer conrod. a yoke, one end of which is rotatably connected to the crankcase, and the other end rotatably attached to the crankcase, and a balancer weight attached to the connection between the balancer connecting rod and the yoke. It is something.

``Example'' Hereinafter, the engine crank balance device of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a sectional view of the main parts of a two-stroke engine 1 to which an embodiment of the present invention is applied, and reference numeral 2 indicates a crankcase. A crankshaft 3 is provided inside the crank chamber 2a of the crankcase 2, and the crankshaft 3 is rotatably supported by the crankcase 2 via a bearing 4.5. A crank bin 6 is formed in the center of the crankshaft 3, eccentric from the central axis of the crankshaft 3, and at a position 180° apart from the crank bin 6.
A balance weight 3a is formed. One end of a piston connecting rod 7 is rotatably connected to the crank bin 6, and the other end of the piston connecting rod 7 is connected to a piston pin 9 inside a piston 8. In addition, a balancer bin IO is attached to the crankshaft 3 on the outside of the bearing 4, and the balancer bin IO is eccentric with a phase difference of 180° with respect to the crank pin 4.
: Market J! The crank balance device IT described above consists of a balancer connecting rod 12, a yoke 13, and a balancer weight 14.

One end of the balancer connecting rod 12 is rotatably connected to the balancer bin IO of the crankshaft 3, and the other end of the balancer connecting rod 12 is rotatably connected to a cylindrical balancer weight 14. .

The balancer weight I4 is formed to have a weight that balances the weight of the piston 8 and the piston connecting rod 7. One end of a yoke 13 is rotatably connected to the balancer weight 14, and the other end of the yoke 13 is rotatably supported on a part of the crankcase 2 by a yoke pin 15. . As shown in FIG. 2, the balancer connecting rod 12 is arranged so that it is approximately parallel to the crankshaft 7 when the piston 8 is located at the vertical dead center. 2 and 7:1
．． .

Next, the crank balance device W of the engine of this embodiment
I, I will explain the action of I. When the engine 1 is operated, as shown in FIG. 2, the balancer weight 14 reciprocates substantially linearly in conjunction with the rotation of the crankshaft 3, symmetrical to the vertical movement of the piston 8. As described above, the balancer weight 14 has a weight that balances the weight of the piston 8 and the piston connecting rod 7, so the balancer weight 14 has a weight that is approximately the same as the inertia force generated by the piston 8 at the vertical dead center. , and generates an inertial force in the opposite direction at the same time as the piston 8 generates an inertial force,
These inertial forces cancel each other out and reduce the vibration of the piston 8.

Crank balance device 1 for an engine having such a configuration
In No. 1, the balancer weight 14 is supported by the rotatable yoke I3, so even when the engine is operated at high speed, the balancer weight 14 is less likely to wobble due to wear etc. Excellent durability.

In addition, the balancer connecting rod 12 is connected to the crank bearing 4.
Since the crankshaft 3 is connected to the outside of the crankshaft 4, the length of the crankshaft 3 between both bearings 4.5 can be shortened, and therefore the bending strength in the vicinity of the crankbin 6 can be increased.

Furthermore, since the crank balance device 11 is disposed outside the crank chamber 2a of the crankcase 2, the internal capacity of the crank chamber 2a can be made smaller compared to conventional devices. Therefore, this crank balance device 11 can also be suitably used for a two-stroke engine that introduces the air-fuel mixture into the cylinder through the crankcase 2.

The layout of the crank balance device 11 shown in the first embodiment is merely an example, and can be modified in various ways depending on design requirements, the type of engine to be applied, etc. For example, FIG. 3 shows a second embodiment of the present invention. In this embodiment, the balancer bin IO is arranged in the same radial direction from the crankshaft center axis 0 as the crank bin 6, and They are assumed to have the same rotational phase. A balancer connecting rod 12 connected to the balancer bin 10 is arranged to be approximately perpendicular to the crank connecting rod 7, and a yoke 13 is arranged to be substantially perpendicular to the balancer connecting rod 12.

The crank balance device of this second embodiment reduces the horizontal vibration of the engine due to the centrifugal force generated by the balance weight 3a formed on the crankshaft 3. FIGS. 4(a) and 4(b) are schematic diagrams showing the operation of this second embodiment.

Figure 4(a) shows the moment when the balance weight 3a is positioned to the left of the central axis O in the figure when the engine is in operation, and at this time the balance weight 3a is generating centrifugal force in the direction of arrow q. . On the other hand, since the balancer weight 14 is located at the right dead center of the stroke at this time, an inertial force is generated in the direction of the arrow p. Therefore, as a result, the centrifugal force (in the q direction) of the balance weight 3a and the inertial force (in the p direction) of the balancer weight 14 cancel each other out, thereby reducing the horizontal vibration of the engine. The same applies to FIG. 4(b), and the centrifugal force (
(S direction) and the inertial force (R direction) generated by the balancer weight 14 cancel each other out, reducing horizontal vibration of the engine. Also in this second embodiment, the first
The same excellent effects as in the example can be obtained.

"Effects of the Invention" As explained above, the engine crank balance device of the present invention is rotatable at the 8 eccentric parts of the crankshaft outside the crank bearing. a balancer connecting rod having one end connected to the balancer connecting rod; a yoke having one end rotatably connected to the other end of the balancer connecting rod and the other end rotatably attached to the crankcase; It consists of a balancer weight attached to the connecting part between the balancer connecting rod and the yoke, and has the following excellent effects.

■Since the balancer weight is supported by a rotatable yoke, even when the engine is operated at high speed, the balancer weight does not wobble due to wear etc., and has excellent durability.

■Since the balancer connecting rod is connected to the outside of the crank bearing, the length of the crankshaft between both bearings can be shortened, and therefore the bending strength in the vicinity of the crankshaft can be increased.

■This crank balance device can be placed outside the crank chamber, and the internal capacity of the crank chamber can be made smaller compared to conventional devices, so it is suitable for use with 2-cycle engines as well. is possible.

[Brief explanation of the drawing]

Figure 11 is a sectional view of the main parts of a two-stroke engine l to which the first embodiment of the engine crank balance device of the present invention is applied, Figure 2 is a side view of the first embodiment of the present invention, and Figure 3 is a Side view of the second embodiment of the present invention, FIGS. 4(a) and 4(b)
) is a schematic diagram showing the operation of the second embodiment. 3... Crankshaft 4.5... Crank bar)'' ring 6... Crank bin IO... Balancer bin 12... Balancer connecting rod 13... Yoke ■4... Balance weight

Claims (1)

[Claims] A balancer connecting rod has one end rotatably connected to the eccentric shaft of the crankshaft outside the crank bearing, and one end of the balancer connecting rod is rotatably connected to the other end of the balancer connecting rod, and the other end is connected to the crankcase. An engine crank balance device comprising a yoke rotatably attached to the yoke, and a balancer weight attached to a connecting portion between the balancer connecting rod and the yoke.