JPH0754927A - Balancer of crank shaft - Google Patents

Abstract

PURPOSE:To prevent generation of the gear strike sound from a crank shaft balancer by forming it in a simple structure, with less number of component parts, and with less man-hours in assembly, by heightening the balance amount relative to the weight, and by setting small the starting torque. CONSTITUTION:A cam 20 is formed at the tip of a shaft member 12 rotating together with a crank shaft 2, and the tip is fitted in the center hole of a weight 13, and a resilient member with a stopper is mounted in the center of the weight 13, and the cam 20 and resilient member are coupled together in such a way as capable of transmitting the torque and also absorbing excessive torque.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crankshaft balancer for reducing engine vibration and noise.

[0002]

2. Description of the Related Art In an engine, vibration and noise are generated by an unbalanced mass of a rotating portion. Therefore, a balancer for reducing the unbalanced mass has been incorporated. As one form of this type of engine balancer, a balancer configured to directly rotate the eccentric weight member in synchronization with a crankshaft is used.
Also, as a balancer for this type of crankshaft,
It is divided into a driven member that is directly driven to rotate by the crankshaft and a weight member that is connected to the driven member so as to be able to transmit a rotational force, and both are separated by a fixed angle (for example, about 30 mm) via an elastic member.
It has been proposed to provide a cushioning effect by relatively rotationally displacing the same. A document disclosing a crankshaft balancer having such a cushioning action is, for example, Japanese Patent Application Laid-Open No. 60-192145.

[0003]

However, in the conventional crankshaft balancer of this type, the drive gear (or drive sprocket) rotated by the crankshaft and the weight (weight) with the shaft are divided, and the above-mentioned drive is performed. Since a buffer mechanism consisting of springs, stoppers, holders, etc. is provided between the gear and the shaft part, the structure is complicated and the number of parts is large.In addition, it is necessary to process the engagement groove of the snap ring and caulking. Yes, there is a lot of processing man-hours and assembly man-hours.

The present invention has been made in view of the above technical problems, and an object of the present invention is to simplify the structure, reduce the number of parts, and reduce the number of processing and assembling steps. The moment of inertia effect can be increased,
It is an object of the present invention to provide a crankshaft balancer capable of preventing the generation of gear hammering noise by setting a small initial torque for buffering.

[0005]

According to the present invention, there is provided a drive member which is rotationally driven by a crankshaft, and a weight member which is connected to the drive member via an elastic member so as to be capable of transmitting a rotational force and relatively rotationally displaceable. In a balancer for a crankshaft, the drive member is formed of a shaft member that is axially supported in parallel with the crankshaft, and the drive member is fitted to the center of rotation of the weight member, and a cam portion is provided at the tip end portion of the shaft member. The above-mentioned object is achieved by mounting an elastic member with a stopper at the center of rotation of the weight member and providing a cushioning action by elastically displacing the elastic member by the cam portion when torque is transmitted. It is a thing.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view showing an embodiment of a crankshaft balancer to which the present invention is applied. In FIG. 1, a crankshaft 2 is rotatably supported inside a crankcase 1 of the engine. The illustrated engine has a two-cylinder structure, and crank pins 4 are fixed at two axial positions of the crankshaft 2 via crank webs 3 and 3, respectively. Connecting rods (not shown) are connected to the respective crankpins 4, and the other ends of these connecting rods are connected to pistons (not shown) in the corresponding cylinders.

The crankshaft 2 is supported by bearings provided at a total of four positions on both side surface parts 5, 6 of the crankcase 1 and two central wall parts 7, 7. Also,
The illustrated crankshaft 2 has an output gear 8 for extracting the engine output, a cam gear 9 for driving a cam for operating the intake and exhaust valves, and an auxiliary device for driving an auxiliary machine such as an oil pump or a water pump. A machine gear 10 and the like are provided.

A balancer 11, which is directly connected to the crankshaft 2 and is rotationally driven, is mounted in the crankcase 1. The balancer 11 includes a drive member (shaft member) 12 that is rotationally driven by the crankshaft 2.
And a weight member (weight member) 13 which is connected to the drive member 12 via an elastic member so as to be capable of transmitting a rotational force and capable of relative rotational displacement. The weight member 13 is rotatably supported between the central wall portions 7 by the central wall portions 7 and 7.
Reference numeral 2 is rotatably supported by one side surface portion 5 and is fitted at the tip end thereof to the rotation center of the weight member 13.

A balancer drive gear 14 is formed integrally with the crankshaft 2, and the shaft member 12
The balancer driven gear 15 is formed on the
These gears 14 and 15 are always in mesh. 2 and 3 are sectional views taken along line 2-2 in FIG. 1, FIG. 2 shows a state in which the shaft member 12 and the weight member 13 are not relatively rotationally displaced, and FIG. Weight member 1
3 shows a state of relative rotational displacement. In a two-cylinder engine, the phases of crank rotations of the cylinders are generally different, so that the balancer has a different configuration for each cylinder. Even in the engine shown in the figure, a different balancer 11 is used for each cylinder, but since the configurations thereof are substantially the same except for the rotational position of the inertial mass, one balancer mechanism will be described below.

1 to 3, the weight member 13 has a shape as eccentric as possible with respect to the center of rotation A as shown in the drawing, and the eccentric mass portion 16 and the eccentric mass portion of the crankshaft 2 are rotated with respect to each other. The crankshaft 2 is balanced when the engine is rotating by selecting the proper selection.

The weight member 13 is formed with an internal cavity 17 which is opened on the opposite side of the eccentric mass portion 16 and passes through the central portion to reach the eccentric mass portion side as shown in the drawing. Further, a center hole (bearing hole) 18 communicating with the internal cavity 17 is formed in the weight member. On the other hand, the shaft member 1
The inner cavity 1 is attached to the distal end of the inner cavity 1 in the same manner as the cylindrical portion 19 fitted in the central hole 18 in the assembled state.
A cam portion 20 protruding to 7 is formed. In the illustrated example, the cam portion 20 has a cam shape with a substantially semicircular cross section.

Inside the inner cavity 17 of the weight member 13, the cam shape 20 is engaged to buffer the shock or increased load when the rotation of the crankshaft 2 changes (when the rotation of the balancer 11 changes). Damper mechanism (buffer mechanism) 2
1 is installed. In the illustrated example, this damper mechanism 2
Reference numeral 1 is composed of a compression coil spring 22 and a stopper member 23 that also serves as a spring holder. The compression coil spring (hereinafter, simply referred to as a spring) 22 is compressed by the cam portion 20 via the stopper member 23. In addition, the stopper member 23 is the spring (elastic member) 2
2 is compressed and elastically deformed up to a certain amount (FIG. 3), but even if the spring 22 is further compressed, the internal cavity 17
The shape and dimensions are such that the shaft member 12 and the weight member 13 are integrally rotated by hitting the bottom surface of the spring member to prevent further compression of the spring 22.

Thus, the drive member 12 which is rotationally driven by the crankshaft 2 and the weight which is connected to the drive member 12 via the compression coil spring (elastic member) 22 so as to be able to transmit the rotational force and to be relatively rotationally displaceable. A driving member is formed by a shaft member 12 that is axially supported in parallel with the crankshaft 2, and is fitted in the rotation center portion of the weight member 13, and a cam is provided at the tip end portion of the shaft member 12. The portion 20 is provided, the compression coil spring 22 with the stopper 23 is attached to the center of rotation of the weight member 13, and the cam portion 20 elastically displaces the compression coil spring 22 at the time of transmitting the rotational force to obtain a cushioning action. The balancer 11 of the crankshaft configured as above is obtained.

In use, when the engine starts,
The balancer 11 including the shaft member 12 and the weight member 13 rotates together with the crankshaft 2, and vibration and noise of the engine can be reduced by the balance effect of the crankshaft 2. At this time, if the engine speed does not change rapidly, the elastic force of the spring 22 maintains the relative rotational positions of the shaft member 12 and the weight member 13 in the equilibrium state shown in FIG. When the engine speed suddenly changes in the increasing direction, the inertial load of the weight member 13 causes a relative elastic displacement in the rotational direction between the shaft member 12 and the weight member 13 as shown in FIG. Due to the displacement, shock and load increase at the time of sudden rotation increase are buffered.

According to the embodiment described above, the weight member 13
Since the internal cavity 17 is formed in the central portion of and the damper mechanism 21 is mounted in the internal cavity 17, the damper mechanism 21 is incorporated only by reducing the mass of the central portion that does not contribute much to the rotational inertia force (balance amount). It is possible to reduce the size and weight by effectively using the mass as a whole. Further, since the compression coil spring 22 has a structure in which the spring constant can be freely selected, it is possible to freely set the initial torque to a small value, and it is possible to easily design for eliminating gear noise. Further, compared to the conventional example, the structure is simple, the number of parts is small, there is no step such as caulking, and the number of assembling steps can be reduced, and a compact and inexpensive crankshaft balancer can be obtained.

In the above embodiment, the maximum displacement (maximum torque) of the compression coil spring 22 is regulated by the rigid stopper member 23. However, a rubber-like elastic body (elasticity) as shown in FIG. The maximum displacement may be restricted by the stopper 24 of the member). According to this structure, the damper mechanism 2 is changed by appropriately changing the spring characteristics of the two elastic members of the spring 22 and the rubber-like elastic body 24.
It is possible to set the spring characteristic of No. 1 more easily and freely.

[0017]

As is apparent from the above description, according to the present invention, a driving member that is rotationally driven by a crankshaft, and a rotational force can be transmitted to the driving member via an elastic member and a relative rotational displacement is possible. In a balancer for a crankshaft having a weight member connected to the crank member, the drive member is formed of a shaft member that is axially supported in parallel with the crankshaft, and the drive member is fitted to the rotation center of the weight member. Since the cam portion is provided at the tip portion, the elastic member with the stopper is attached to the rotation center portion of the weight member, and the cam portion elastically displaces the elastic member at the time of transmitting the rotational force, the cushioning action is obtained. , Simplification of structure,
It is possible to reduce the number of parts and the number of processing and assembling steps, further improve the moment of inertia effect, and prevent the occurrence of gear hammering noise by setting a small initial torque for buffering. A crankshaft balancer is provided.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of a crankshaft balancer to which the present invention is applied.

2 is a cross-sectional view showing a balanced state of the balancer taken along line 2-2 in FIG.

FIG. 3 is a cross-sectional view showing a maximum displacement state of the balancer taken along line 2-2 in FIG.

FIG. 4 is a cross-sectional view showing a main part configuration of another embodiment of the balancer in FIG.

[Explanation of symbols]

 1 Crankcase 2 Crankshaft 11 Balancer 12 Drive Member (Shaft Member) 13 Weight Member 14 Balancer Drive Gear 15 Balancer Driven Gear 16 Eccentric Mass 17 Inner Cavity 18 Center Hole 20 Cam Part 21 Damper Mechanism (Cushion Mechanism) 22 Compression Coil Spring (Elastic member) 23 Stopper member 24 Rubber-like elastic stopper member (elastic member)

Claims (1)

[Claims] 1. A balancer for a crankshaft, comprising: a drive member that is rotationally driven by a crankshaft; and a weight member that is connected to the drive member via an elastic member so that rotational force can be transmitted and relative rotational displacement is possible. , The drive member is formed of a shaft member that is axially supported in parallel with the crankshaft, and is fitted into the rotation center portion of the weight member, and a cam portion is provided at the tip end portion of the shaft member, and the rotation center of the weight member is provided. Attach an elastic member with a stopper to the part,
A balancer for a crankshaft, wherein the cam portion elastically displaces the elastic member at the time of transmitting a rotational force to obtain a cushioning action.