JPH0624228U - Bearing structure of general-purpose engine - Google Patents

Abstract

(57) [Abstract] [Purpose] To ensure the lubricity of the support part that supports the thrust load and bending load at the end of the shaft by the metal bearing method, and reduce the surface pressure in the circumferential direction with a compact structure. [Structure] Lubricating means 30 by means of splash oil is provided on the fitting portion and the contact portion of the bearing boss 27, and the end surface 27 of the bearing boss 27 is provided.
The surface pressure reducing means 35 is provided in the direction in which the load such as the thrust of "a" is most applied in relation to the oil groove 33 of the lubricating means 30, and the flange 17b at the end of the shaft 17 and the end surface 27a of the bearing boss 27 are brought into contact with each other. The portion is satisfactorily lubricated by the lubrication means 30, and the end surface 27a of the bearing boss 27 enables the surface pressure reduction means 35 to support a load such as thrust with a substantially uniform surface pressure on the circumference.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a bearing structure for supporting a thrust load and a bending load acting on various shafts by a metal bearing system by abutting contact in a general-purpose engine including a 4-cycle engine.

[0002]

[Prior art]

 In general, a general-purpose engine has a single cylinder or a small number of cylinders and has a large vibration. Therefore, a balancer shaft having a balancer is connected to the crankshaft, and a camshaft of a valve train is connected to the crankshaft. Then, when these shafts are connected so as to rotate synchronously with a helical gear, or when a belt is mounted on the output side shaft and bending load is applied, a thrust load is applied. For this reason, in a shaft subject to this thrust load, a bearing is configured to support the thrust load as well as to be rotatably supported at the shaft end, but a ball bearing or the like is used for the thrust load bearing because of cost considerations. It tends to be supported by the metal bearing system without using it. This metal bearing type thrust load bearing structure is designed to directly support the thrust load by directly abutting the shaft flange on the end surface of the bearing boss. It is required to take measures such as effectively reducing the pressure.

Conventionally, as a bearing structure of a metal bearing type against the thrust load of the engine, there is, for example, a prior art of Japanese Utility Model Laid-Open No. 2-1409. Here, it is shown that an oil sump is provided on the thrust receiving surface of the cam shaft or the opposite surface thereof, and the oil is pressure-fed to the oil sump.

[0004]

[Problems to be solved by the device]

 By the way, in the above-mentioned prior art, since the oil sump is thickly formed on the entire circumference of the thrust receiving surface of the cam shaft, the lubricity is improved, but the contact area is reduced and the surface pressure is increased. . Therefore, in order to reduce the contact surface pressure of the thrust receiving surface below the set value, it is necessary to enlarge the shape of the flange and the like. In addition, since the surface pressure of the end surface of the bearing boss is evenly formed over the entire circumference, if the bending load acts on the shaft and it abuts unevenly in the circumferential direction, ensure the set surface pressure. Therefore, it is necessary to make the shape of the bearing boss large, and both of them have problems such as an increase in the size of the thrust bearing structure.

The present invention has been made in view of this point, and ensures the lubricity of the support portion that supports the thrust load and the bending load at the end portion of the shaft by the metal bearing method, and has a compact structure with a circular shape. The purpose is to reduce the surface pressure in the circumferential direction.

[0006]

[Means for Solving the Problems]

 According to the present invention, a crankshaft, a balancer shaft, and a camshaft are arranged in parallel in a crankcase, and one of these shafts is rotatably supported by fitting an end portion thereof to a bearing boss. In a general-purpose engine in which the flange is abutted against the end surface of the bearing boss and the load such as thrust is supported, a lubricating means with splash oil is provided at the fitting part and the contact part of the bearing boss. The surface pressure reducing means is provided in the direction in which the largest load such as thrust is applied in relation to the oil groove of the lubricating means.

[0007]

[Action]

 Based on the above configuration, the part where the flange of the shaft end where the load such as thrust load and bending load acts during engine operation and the end surface of the bearing boss are well lubricated by the lubricating means, and the end surface of the bearing boss is Since the surface pressure reducing means is applied in the direction in which the load such as thrust acts most, the load such as thrust is supported with a substantially uniform surface pressure on the circumference, and it is possible to support compactly and satisfactorily. .

[0008]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings. Referring to FIG. 1, a general-purpose engine is a single-cylinder, 4-cycle, air-cooled engine. The splash oil lubrication type engine is described. Reference numeral 1 is a crankcase, 2 is a single-cylinder cylinder, and the crankcase 1 The wind guide case 3 is attached. A crankshaft 4 is rotatably supported horizontally by a ball bearing 5 inside the crankcase 1, a balance weight 4a is provided in the middle of the crankshaft 4, and a connecting rod 6 is connected to connect the cylinder 2 to the cylinder 2. It is connected to the piston side of. A front end of the crankshaft 4 projects into the wind guide case 3 and a flywheel 8 having a cooling fan 7 and a starting wheel 9 are integrally fixed, and a rear end of the crankshaft 4 is inside the crankcase 1 to operate the engine. It has a configuration of. Further, a balancer shaft 10 having a balancer 10a is arranged in parallel next to the crankshaft 4, and both ends of the balancer shaft 10 are rotatably supported by ball bearings 11. The balancer shaft 10 is connected to the crankshaft 4 via a pair of gears 12 and 13, and rotates at a constant speed in opposite directions to balance the inertial force of the piston by the combined force of the balance weight 4a and the balancer 10a to vibrate. Has been reduced. The balancer shaft 10 is also connected via a gear 14 to a governor holder 16 of a governor device 15 mounted on the crankcase 1 side, and operates the governor device 15 in accordance with the engine speed.

Further, a cam shaft 17 is arranged parallel to the upper part of the balancer shaft 10. The cam shaft 17 is connected to the crank shaft 4 via a pair of gears 18 and 19, and is connected to the crank shaft 4. Synchronous rotation is always performed at 1/2 rotation. As shown in FIG. 2, a tappet 21 is brought into contact with the cam 20 of the camshaft 17, and the tappet 21 is connected to the valve side via a push rod 22 to lift the valve. Here, since the rotation of the cam shaft 17 is decelerated by the pair of gears 18 and 19 and the driving torque is large as described above, the use of the cam shaft 17 eliminates the need for the reduction gear and increases the power of the torque. Can be output. Therefore, the pair of gears 18 and 19 have a predetermined rigidity and also serve as an output gear, and the cam shaft 17 also has a predetermined rigidity and also serves as an output shaft to form a power transmission system. The output side end of the shaft 17 is supported by a ball bearing 23 so as to be integrated with the PTO shaft 24 outside the crankcase 1. Then, it is configured to be transmitted to the working machine via a belt 26 mounted on the pulley 25 of the PTO shaft 24, and drives the working machine. The other end 17a of the camshaft 17 is fitted into the bearing boss 27 of the crankcase 1 and is rotatably supported, and the flange 17b abuts against the end surface 27a of the bearing boss 27 to make thrust load and PTO. The belt 26 of the shaft 24 supports the bending load M applied to the cam shaft 17, and the supporting portion of the metal bearing is provided with a lubricating means 30 using splash oil.

2 and 3, the lubricating means 30 will be described. An oil inflow groove 31 is formed in the upper part of the end surface 27a of the bearing boss 27, and an oil inflow groove 31 is formed in the upper axial direction of the inner circumference of the boss hole 27b. An oil groove 32 which communicates with the cam shaft end portion 17a is formed so that oil can be supplied to the fitting portion. An oil groove 33 is also formed on the circumference of the middle of the end surface 27a so that oil can be supplied to the contact portion with the flange 17b. On the other hand, since a bending load is applied to the cam shaft 17 in the direction of arrow F in FIG. 3, the surface pressure reducing means 35 is provided in the bending load acting direction of the end surface 27a of the bearing boss 27. In this surface pressure reducing means 35, the oil groove 33 is formed on the circumference to have a uniform width, and in order to reduce the surface pressure, the bending load acting direction of the end face 27a is locally wide and uneven. It has a circular shape.

With the above configuration, when the crankshaft 4 rotates during engine operation, the pair of gears 12, 13 also causes the balancer shaft 10 to rotate at a constant speed in the opposite direction, canceling out the inertial force of the vertical movement of the piston and causing vibration. Will be reduced. Further, the cam shaft 17 is also synchronously rotated by 1/2 by the pair of gears 18 and 19 and is valve-operated by the cam 20 and the like, and a large torque from the PTO shaft 24 integrated with the cam shaft 17 drives the belt 26. It is driven by being transmitted to the working machine side via the machine. At this time, the oil at the bottom of the crankcase 1 is scattered by an oil scraper (not shown) arranged below the connecting rod 6 mounted on the crankshaft 4, and the splashed oil is supplied to the ball bearings 5, 11, 23. Be lubricated. Further, the splashed oil is collected by the oil inflow groove 31 on the end surface 27a of the bearing boss 27 supporting one end 17a of the camshaft 17, and the oil from the oil inflow groove 31 is absorbed by the oil groove 32. 27 and the end of the camshaft 17 and the oil groove 33 having a uniform width supply oil to the abutting contact portions of the end surface 27a and the flange 17b, respectively, and thus the supporting portions of these metal bearings are well lubricated. . On the other hand, the cam shaft 17 is subjected to a thrust load and a bending load by the belt 26 in a predetermined direction, but the end face 27a of the bearing boss 27 has a wide bending load acting direction to reduce the surface pressure. Like Therefore, the surface pressure on the circumference of the contact portion between the end surface 27a and the flange 17b becomes substantially uniform, and the uneven load is favorably supported in terms of strength.

Referring to FIG. 4, a second embodiment of the present invention will be described. The surface pressure reducing means 35 of the end surface 27a of the bearing boss 27 has an oil groove 33 in the bending load acting direction with respect to the end surface 27a having a uniform width. Is formed to be narrow. As a result, the contact area is similarly increased in the bending load acting direction of the end surface 27a, and the surface pressure is reduced.

Referring to FIG. 5, a third embodiment of the present invention will be described. The surface pressure reducing means 35 of the end face 27a of the bearing boss 27 makes an oil flow only to the end face 27a having a uniform width except in the bending load acting direction. It is configured by forming a groove 33. Therefore, in this case, the contact area of the end face 27a in the bending load acting direction is larger than that described above, and the surface pressure is further reduced.

Although the embodiment of the present invention has been described above, the invention can be similarly applied to shafts other than the cam shaft.

[0015]

[Effect of device]

 As described above, according to the present invention, in a general-purpose engine, one end of a shaft such as a cam shaft is rotatably supported by a metal bearing system, and a supporting portion that supports a thrust load and a bending load acting on the shaft is provided. Since the surface pressure reducing means is provided, the thrust load and the bending load can be favorably supported with a uniform surface pressure on the circumference. Since the surface pressure reducing means is configured to increase the contact area of the portion having a large surface pressure due to the relationship between the shape of the end surface of the bearing boss and the shape of the oil groove, the shape of the support portion can be made compact. Further, since the support portion is provided with the lubricating means using the splash oil, it is possible to perform good lubrication.

[Brief description of drawings]

FIG. 1 is an overall plan sectional view showing an embodiment of a bearing structure of an engine according to the present invention.

FIG. 2 is a cross-sectional view showing a support portion and the like of a cam shaft end portion.

FIG. 3 is a front view showing an end surface of a bearing boss.

FIG. 4 is a front view showing an end surface of a bearing boss according to a second embodiment of the present invention.

FIG. 5 is a front view showing an end surface of a bearing boss according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crankcase 4 Crankshaft 10 Balancer shaft 17 Camshaft 17b Flange 27 Bearing boss 27a End surface 30 Lubrication means 33 Oil groove 35 Surface pressure reduction means

Claims (3)

[Scope of utility model registration request] 1. A crankshaft, a balancer shaft, and a cam shaft are arranged in parallel in a crankcase, and one of these shafts is rotatably supported by fitting an end portion to a bearing boss, and a flange is mounted on the bearing boss. In a general-purpose engine in which a load such as thrust is supported by abutting contact with the end face of the bearing, a lubricating oil means is provided at the fitting portion and the contact portion of the bearing boss,
A bearing structure for a general-purpose engine, characterized in that surface pressure reducing means is provided in relation to an oil groove of a lubricating means in a direction in which a load such as thrust on the end surface of the bearing boss is most exerted. 2. The surface pressure reducing means locally increases the contact area of the end surface of the bearing boss in the direction in which the load such as thrust is most applied by the change of the shape of the end surface and the oil groove. The bearing structure for a general-purpose engine according to claim 1. 3. The bearing structure for a general-purpose engine according to claim 1, wherein the one shaft is a cam shaft that also serves as an output shaft.