JPS643864Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a crankshaft torsional vibration suppression device for an internal combustion engine having a balancer shaft.

For engines with a single cylinder to three cylinders,
For the purpose of eliminating the primary inertia couple, there is a system in which a balancer shaft is arranged in parallel with a crankshaft, and these two shafts are connected by a pair of meshing gears. It is well known that the primary inertia couple is canceled by gears rotating in opposite directions.

Torsional vibrations caused by fire rings occur on the engine crankshaft regardless of the number of cylinders in the engine, but the usual countermeasure is to install a vibration damping system consisting of an inertial mass and a spring on the crankshaft. Conventionally, it has been adopted even in internal combustion engines equipped with a balancer shaft. However, by installing an inertial mass on the crankshaft, the load applied to the crankshaft increases, making it necessary to take measures such as increasing the diameter of the crankshaft. This means that the weight of the engine increases and the structure becomes complicated, which is a problem considering that the engine with the balancer shaft is a small engine.

In view of the drawbacks of the prior art, it is an object of the present invention to provide a structure that can suppress torsional vibrations without setting an inertial mass on the crankshaft. In order to achieve this purpose, in the present invention, the driven gear, which is provided on the balancer shaft and driven by the crankshaft, is divided into two parts, and is connected to the balancer shaft by an annular elastic layer serving as a vibration damping spring. are doing. With this structure, the mass of the driven shaft can be used as an inertial mass, and in combination with the spring action of the annular elastic layer, a vibration damping system is constructed, suppressing the torsional vibration of the crankshaft caused by the firing. be able to.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a three-cylinder internal combustion engine with 10 cylinders.
^-1 , ^10-2 , and ^10-3 indicate pistons, respectively, which are connected to the crankshaft 14 via connecting rods ^12-1 , ^12-2 , and ^12-3 . 16 is a balancer shaft, which is installed in parallel with the crankshaft 14.
A balancer drive gear 18 is provided at the front end 141 of the crankshaft 14 and meshes with a balancer driven gear 20 on the balancer shaft 16 . This driven gear 20 has a two-part structure including a tooth portion 201 that meshes with the driving gear 18 and a core portion 202 that is integrated with the balancer shaft 16.
A rubber layer 24 as an elastic body is interposed between the tooth portion 201 and the core portion 202. The rubber layer 24 can be bonded to the outer periphery of the core portion 202 and the inner periphery of the tooth portion 201 by vulcanization. Alternatively, the tooth portion 201 can be press-fitted with the rubber layer 24 formed around the core portion 202.

In the operation of the present invention described above, the rotation of the crankshaft 14 is transmitted to the balancer shaft 16 via the driving gear 18 and the driven gear 20, and the two shafts 14 and 16 rotate in opposite directions to generate a primary inertial couple. The well-known function of cancellation is obtained. In addition to this operation, a vibration damping system is formed by the mass of the core portion 202 of the driven gear 20 and the spring constant of the rubber layer 24, and suppresses torsional vibrations occurring in the crankshaft 14. It should be noted that the backlash between the gears 18 and 20 must be kept below engine rotational fluctuations, but the rotational speed fluctuations that normally occur in an engine can be sufficiently suppressed by setting the backlash to 0.2 mm or less.

As described above, in the present invention, in an internal combustion engine with a balancer shaft, a tooth part that constantly meshes with the driving gear on the crankshaft with a backlash within the allowable rotational fluctuation range, and a core part that rotates integrally with the balancer shaft. By configuring the driven gear in two parts,
Rotational fluctuations resulting from torsional vibration of the crankshaft can be attenuated within an allowable range. By using the balancer shaft as an inertial mass, the above effects can be obtained without increasing the weight of the crankshaft.

[Brief explanation of drawings]

Fig. 1 is a schematic perspective view showing the configuration of the present invention;
The figure is a front view of the driving gear and the driven gear seen from the direction of FIG. 1, and FIG. 3 is a sectional view taken along the - line of FIG. 2. 10 ^-1 , 10 ^-2 , 10 ^-3 ... piston, 14 ... crankshaft, 16 ... balancer shaft, 18 ... drive gear,
20... Driven gear, 201... Teeth, 202... Core, 24... Rubber layer.

Claims (1)

[Scope of utility model registration request] In an internal combustion engine in which a balancer shaft is provided in parallel with the crankshaft, and a drive gear on the crankshaft and a driven gear on the balancer shaft mesh, the driven gear provides a backlash to the drive gear that is smaller than the allowable rotational fluctuation range. It is composed of two parts: the teeth that constantly mesh with each other, and the core that rotates integrally with the balancer shaft.The teeth and the core are interconnected by an annular elastic layer, and the mass and elasticity of the core are A crankshaft torsional vibration suppression device for an internal combustion engine with a balancer shaft that forms a vibration damping system with the spring constant of the body layer.