JPH108982A - Crankshaft supporting structure for small engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for highly precisely machining a housing bore for a rolling bearing and reduce the number of machining manhours by providing an elastic material on all periphery of the outer diameter of the outer ring of the rolling bearing by which a crankshaft for a small engine is supported. SOLUTION: For a small engine 22 for a trimming machine, a crankshaft 29 is provided in a housing 28 as a crank room where a cylinder 27 is set up, the crank-shaft 29 having both ends supported on a pair of rolling bearings 1. The bearings 1 are pressed and fitted in cylindrical bearing fittings 28a formed on both side walls of the housing 28. In this case, the rolling bearing 1 is made into deeply grooved ball bearing with a seal on the single side and an elastic material 7 is provided on all periphery of the outer diameter of outer ring 3 to be thick 2-6% of the outer diameters of the outer ring. The crosswise face at the single side is covered with seal 6 which is mounted on the inner diameter of the outer ring 3 and slid on the outer diameter of an inner ring 2. The bearing 1 is set up for the seal 6 to be located at the bottm side of the bearing fitting 28a of the housing 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crankshaft support structure for a small engine applied to a brush cutter, a lawn mower, and other agricultural machines.

[0002]

2. Description of the Related Art Generally, when a bearing is used, the inside diameter of a housing requires high-precision turning or grinding. If a housing is used that has a bad inner diameter shape and a part of the bearing may be tightly fitted (for example, a split housing or a housing that has a poor cylindricity even when integrated), the outer ring deforms following the housing shape Then, problems such as uneven torque occur. Conversely, if the housing is loose from the bearing, the shaft center fluctuates or creeps by the gap between the bearing and the housing due to a change in the load direction, which hinders a longer life of the bearing.

[0003] However, if turning or grinding with high precision is performed on the inner diameter of the housing, the processing cost becomes high. There are also thermal expansion compensating bearings and anti-creep bearings, but they are expensive and are cumbersome to incorporate. Especially,
With a simple small engine used for a brush cutter or the like, the cost is severely restricted, and it is difficult to use such a high-priced bearing. Rubber bearings and resin-wound bearings are available as bearings, and we considered that these could be diverted to crankshaft support bearings for small engines.Rubber-wound bearings are mainly used as feed rollers for sending cards and paper. Because it is used, the thickness of the rubber is
It is as large as 0.07 to 0.22 (rubber thickness / outer diameter of single bearing). Therefore, when a rubber-wound bearing is used for the housing, the axial center fluctuates due to the load. Further, when a resin wound bearing is used, the resin portion may be permanently deformed or have insufficient strength due to a fitting force or a load with the housing.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a crankshaft support structure for a small engine capable of reducing the number of steps for processing the inner diameter of the housing and facilitating the installation of the bearing.

[0005]

A crankshaft support structure according to the present invention is a support structure for supporting a crankshaft of a small engine by a rolling bearing fitted in a housing, wherein the rolling bearing is an outer ring. It is characterized in that a bearing having an elastic body on the entire circumference of the radial surface is used. The elastic body is, for example, rubber or a resin material. According to this configuration, with respect to dimensional tolerance, roundness, cylindricity, etc., even if the bearing is incorporated into a housing that has not been machined to the recommended fitting accuracy of the bearing, the elastic body of the bearing outer ring has an inner diameter at the bearing mounting portion of the housing. It deforms according to its shape, filling the gap between the bearing and the housing. Thereby, fluctuation and creep of the shaft center can be prevented. In addition, the poor roundness of the inner diameter of the housing is also absorbed by the elastic deformation of the elastic body, and is less likely to be transmitted to the bearing as it is.

In the above construction, the thickness of the elastic body needs to be determined according to the type of the elastic body and the structure of the housing, but the thickness of the elastic body is two to two times the outer diameter of the outer ring excluding the elastic body part. Preferably it is 6%, and 0.1%.
About 04 is most preferable. With this thickness, both the effect of filling the gap between the inner diameter of the housing and the outer surface of the bearing and the effect of alleviating the poor accuracy of the inner diameter of the housing from being transmitted to the outer ring of the bearing are appropriately obtained. Can be In order to obtain such an effect, when the elastic body is made of a resin material, the hardness is set to D60 in JIS standard.
The following resin materials are preferred. The elastic body may be directly integrated with the outer ring by insert molding, press-fitting, bonding, or the like, or the elastic body is provided on the outer diameter surface of a metal outer ring, and the outer ring is formed on the outer diameter of the outer ring. You may press-fit. The elastic body is integrated with the outer ring by insert molding or bonding. In these configurations, the elastic body may have a tapered end. This makes it easier to insert the bearing into the housing.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIG. 2 shows an example of a brush cutter to which this crankshaft support structure is applied. In this brush cutter, a small engine 22 is provided at one end of a rod 21 and a rotary blade 2 is provided at the other end.
3 and a handle 24 is attached to an intermediate portion. The rotation of the small engine 22 is transmitted to the rotary blade 23 via a transmission shaft 25 inserted into the rod 21 and a transmission mechanism 26 formed of a gear train at the tip thereof.

As shown in the enlarged view of FIG. 1B, the small engine 22 is provided with a crankshaft 29 in a housing 28 serving as a crank chamber in which a cylinder 27 is installed, and the crankshaft 29 is held on both sides of the crank arm. A pair of bearings 1,1
This is supported by The bearing 1 includes a housing 28
Are press-fitted into cylindrical bearing fitting portions 28a formed on both side walls of the bearing. The housing 28 includes the crankshaft 2
9 is divided into two by a dividing surface a along the axial direction, or is divided into two by a dividing surface b along the radial direction, and joined by bolts or the like. The entire small engine 22 is covered with a cover 30.

As shown in FIG. 1A, a bearing 1 is a deep groove ball bearing with a single-sided seal, in which an elastic body 7 is provided on the entire outer circumference of the outer ring 3. The bearing 1 is provided with a rolling element 5 made of a steel ball held by a retainer 4 between an inner ring 2 and an outer ring 3, and has one width surface attached to the inner diameter surface of the outer ring 3 and the outer diameter of the inner ring 2. It is covered with a seal 6 that slides on the surface, and is installed so that the seal 6 is located on the bottom side of the bearing fitting portion 28 a of the housing 28.

The elastic body 7 is made of rubber or resin such as nitrile rubber, and is formed into a predetermined shape by cutting or molding. The thickness t of the elastic body 7 needs to be determined depending on the material of the elastic body 7 and the structure of the housing 28, but in many cases, 2 to 6% of the outer diameter of the outer ring 3 excluding the elastic body 7. , And most preferably about 4%. When the elastic body 7 is made of resin, it is preferable that the hardness is D60 or less according to JIS standard. Even if the width of the elastic body 7 is a width corresponding to the entire width of the outer ring 3 as shown in the figure, the width at which both side edges of the outer diameter surface of the outer ring 3 are exposed as in the example of FIG. It may be. In the case where the width corresponds to the entire width, when both side edges of the outer diameter surface of the outer ring 3 are chamfered as shown in FIG. It is preferable to adopt a chamfered shape such as an arc-shaped cross section along the cross-sectional shape of. The attachment of the elastic body 7 to the outer ring 3 is performed, for example, by press-fitting the annular elastic body 7 manufactured separately from the outer ring 3 into the outer ring 3. In addition, the elastic body 7 may be integrally fixed to the outer ring 3 by insert molding, and may be integrally fixed to the outer ring 3 by bonding the entire surface with an adhesive 8 as in the example of FIG. It is good also as a state.

According to the crankshaft support structure having this configuration,
Bearing 1 fitted in bearing fitting portion 28a of housing 28
The elastic body 7 is deformed following the inner diameter shape of the bearing fitting portion 28a of the housing 28, and the gap between the bearing 1 and the housing 28 is filled with the elastic body 7. Therefore, fluctuation and creep of the shaft center can be prevented. In addition, the elastic body 7 absorbs poor cylindricity on the inner diameter surface of the bearing fitting portion 28a of the housing 28, so that transmission to the bearing 1 as it is can be reduced. Therefore, it is not necessary to accurately turn or grind the inner diameter surface of the bearing fitting portion 28a of the housing 28, and the number of steps for processing the inner diameter is reduced. Also, bearing 1
Can be easily incorporated into the housing 28. Further, the bearing 1 is not limited to the case where the housing 28 is formed in two pieces as described above, but may be incorporated even if it is of an integral shape. In particular, as shown in the example of FIG. 1 (A), if both sides of the outer diameter surface of the elastic body 7 are chamfered, it is easy to incorporate the elastic body 7 into the integrated housing.

The elastic body 7 has a shape other than these shapes, as shown in FIG.
Both ends 7a may be tapered as shown in FIG.
Thereby, the mounting work by press-fitting into the housing 28 is further facilitated. Thus, both ends 7a of the elastic body 7
Are tapered, slits 10 are provided at regular intervals along the axial direction on the outer diameter surface of the elastic body 7 as shown in the sectional view and the partial front view in FIGS. The diameter surface may be a gear-shaped uneven surface. By providing the slit 10 in this manner, the work of press-fitting the housing 28 is further facilitated.

In addition to the above, the elastic body 7 has a structure shown in FIG.
As shown in (G), the outer ring 11 provided with the elastic body 7 may be formed on the outer diameter surface of the outer ring 11 made of metal by insert molding or bonding, and attached to the outer ring 3 of the bearing by press fitting. . FIG. 1F shows an example of insert molding, and FIG. 1G shows an example of fixation with the adhesive 11. If the elastic body 7 is provided on the outer ring 11 made of metal as in these examples, the work of attaching the elastic body 7 to the bearing outer ring 3 becomes easy, and the quality is stabilized. The fixing of the elastic body 7 to the outer ring 11
Can be manufactured and prepared separately from the main body manufacturing process. Although the above-described embodiment has been described with respect to a case where the invention is applied to a bush cutter, the present invention can also be applied to small engines in general, such as an engine in a lawnmower.

[0014]

According to the crankshaft support structure for a small engine of the present invention, the rolling bearing which is fitted into the housing and supports the crankshaft has an elastic body all around the outer diameter surface of the outer ring. High precision is not required, and processing man-hours are reduced. In addition, there is no need for difficult adjustments or incorporation of separate components into the mounting of the bearing in the housing.
Installation work becomes easy.

[Brief description of the drawings]

FIG. 1A is a sectional view of a bearing in a crankshaft support structure according to an embodiment of the present invention, and FIG. 1B is a cutaway side view of the small engine.

FIG. 2 is a cutaway side view of the brush cutter using the small engine.

FIGS. 3A to 3D are partial cross-sectional views of a modified example of the bearing;
(E) is a partial side view of the bearing of FIG.
(G) is a sectional view and a partial sectional view of still another example of the bearing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Bearing 3 ... Outer ring 7 ... Elastic body 28 ... Housing 28a ... Bearing fitting part 29 ... Crankshaft

Claims (5)

[Claims] 1. A supporting structure for supporting a crankshaft of a small engine by a rolling bearing fitted in a housing, wherein the rolling bearing has an elastic body all around an outer diameter surface of an outer ring. Crankshaft support structure for small engines. 2. The small engine crankshaft support structure according to claim 1, wherein the thickness of the elastic body is 2 to 6% of the outer diameter of the outer race excluding the elastic body portion. 3. The crankshaft support structure for a small engine according to claim 1, wherein the elastic body is a resin material having a hardness of D60 or less according to JIS standards. 4. The crank of a small engine according to claim 1, wherein the elastic body is provided on an outer diameter surface of a metal outer ring, and the outer ring is press-fitted to an outer diameter of the outer ring. Shaft support structure. 5. The crankshaft support structure for a small engine according to claim 1, wherein an end of said elastic body is tapered.