JPH02221645A - Governor mechanism of OHC type engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention <Industrial Application Field> The present invention relates to a governor mechanism for controlling the rotational speed of an OHC type engine, and particularly to a drive structure of a centrifugal governor mechanism.

<Prior Art> Engines used in pumps, generators, lawn mowers, etc. are provided with a governor mechanism, such as a centrifugal governor, in order to maintain a constant rotational speed.

Such a centrifugal governor mechanism consists of a governor holder that is rotatably supported on the engine body and driven by a crankshaft or balancer shaft via a gear, and a governor holder that is pivotally attached to the governor holder and that responds to the rotational speed of the engine. a governor arm that expands and opens in the centrifugal direction; a governor slider that is slidably inserted into a shaft that protrudes from the center of the governor holder; and a governor slider that moves by contacting the arm of the governor weight; and a governor arm that transmits the amount to the throttle valve. Because such a governor mechanism is driven by the engine, even when the load on the engine fluctuates, it maintains a constant rotational speed so that the centrifugal force applied to the governor weight and the spring restoring force linked to the throttle valve are balanced. (For example, see Japanese Utility Model Application Publication No. 59-40536).

However, although such engines are usually selected with the intention of making them smaller and lighter, the governor mechanism described above has the problem of noise since the governor holder meshes with the crankshaft. However, since the number of gears is relatively large and the location of the governor holder is limited, it is difficult to reduce the size and weight of the engine.

On the other hand, in order to improve the performance of the above-mentioned engines, there is a tendency for OHC engines to be adopted instead of conventional OHV engine engines. The inventor noticed that the shaft is connected to a crankshaft connected to the proximal end side of the piston that slides in the cylinder using a timing belt to drive the shaft.

<Problem to be solved by the invention> In view of the problems of the prior art and the knowledge of the present inventor,
A main object of the present invention is to provide a governor mechanism for an OHC type engine that reduces noise, is smaller in size, and is lighter in weight.

[Structure of the Invention (Means for Solving the Problems)] According to the present invention, such an object is achieved by connecting a crankshaft connected to the proximal end side of a piston that slides together in a cylinder, and a crankshaft disposed on the cylinder head side. A governor mechanism for rotating the crankshaft of an OHC type engine at a constant speed, the governor mechanism comprising a camshaft and a timing belt connecting the two shafts via a pulley so as to interlock the two shafts. This is achieved by providing a governor mechanism for an OHC type engine, which is characterized in that it is driven by the timing belt.

In this way, by driving the governor holder with a timing belt, noise is reduced compared to gear drive, there is no need to provide a gear on the crankshaft side, and there is a high degree of freedom in the location of the governor holder. Become.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 and 2 show a single cylinder OHC type vertical crankshaft engine constructed according to the present invention. A crankcase 3 is integrally coupled to the right side opening of the cylinder block 2 constituting the engine body 1.
The crankshaft 5 is supported along the vertical direction by a pair of ball bearings 4a and 4b provided at the joint with the crankshaft 5.

A piston 8 that slides into a cylinder bore 7 provided inside the cylinder block 2 is connected to a crank pin 6 formed approximately at the center of the crankshaft 5 via a connecting rod 9.

A balancer shaft 10 is pivotally supported in parallel to the crankshaft 5 at the joint between the cylinder block 2 and the crankcase 3. This balancer shaft 10 is used to offset the primary vibrational force generated due to the eccentricity of the crank pin 6, and is connected to the crankshaft 5 via a gear means 11. It is rotated at the same speed and in opposite directions.

A head cover 12 is integrally coupled to the left side opening of the cylinder block 2. A pair of upper and lower journal parts 13a and 13b are formed at the joint between the cylinder block 2 and the head cover 12, and these journal parts 13a and 13b form a camshaft extending parallel to the crankshaft 5. 14 are supported at both ends thereof. The camshaft 14 is connected to the crankshaft 5 via a timing belt 17 wound between a large timing pulley 15 integrally formed on the lower end side and a small timing pulley 16 fixed to the crankshaft 5. It is driven at 1/2 rotation speed.

On the left side of the cylinder block 2, an intake valve 19 and an exhaust valve 20 are provided which are normally biased in the valve closing direction by valve springs 18a and 18b, respectively. These two valves 19 and 20 are arranged in parallel at appropriate intervals in a plane parallel to the rank shaft 5, and a direct lifter 22a is connected to a pair of cams 21a and 21b formed on the camshaft 14.・They are engaged with each other via 22b,
It is driven to open and close at appropriate timing according to the rotation of the crankshaft 5.

A flywheel 23 is fixed to the upper end of the crankshaft 5. A blade 24 that functions as a cooling fan is integrally formed on the outer circumference of the axial end surface of the flan wheel 23. Further, a permanent magnet 25 is fixed to a part of its outer periphery, and works together with an ignition device 26 fixed to the cylinder block side to generate the required ignition spark at a predetermined timing. . Furthermore, a recoil starter 27 is connected to the shaft end of the crankshaft 5.

A lubricating oil tank 28 is provided on the right side of the crankcase 3. At the second end of this lubricating oil tank 28,
One end of the passage 34 opens opposite the lower wall of the crankcase 3, and the other end of the passage 34 opens through a reed valve 33. This passage 34 allows the lubricating oil to flow only from the bottom of the crankcase 3 to the top of the lubricating oil tank 28 . In addition, at the bottom of the lubricating oil tank 28,
A passage 35 is provided which is connected to the hose port 36 and has a one-way valve 39 interposed therein which allows only the inflow of lubricating oil from the lubricating oil tank 28.
7, the lubricating oil is branched to the cam journal part 13a located above the cylinder block 2 and the crank bearing part 4a also located above.

As shown in FIG. 3, an intake boat 50 is located on one side (lower side in FIG. 2) of the cylinder block 2, and an exhaust port 51 is located on the other side (upper side in FIG. 2). Each is open. That is, the intake boat 50 and the exhaust port 51 are provided so that intake air and exhaust air cross flow in a direction perpendicular to the axis of the crankshaft 5. these,
The intake boat 50 and the exhaust port 51 extend substantially horizontally and substantially parallel to each other, but as described above, the intake valve 19 and the exhaust valve 20 are vertically parallel to each other within a common vertical plane, and the exhaust port 51 extends substantially horizontally and substantially parallel to each other. Since the valve 20 is disposed on the upper side, the exhaust port 51 is disposed on the upper side.

On the other hand, a muffler 52 is directly connected to the opening of the exhaust port 51, and a carburetor 53 is directly connected to the opening of the intake port 50. This carburetor 53 is connected via a link mechanism (not shown) to a governor mechanism 54 driven by a timing belt 17, and automatically adjusts its throttle valve opening to maintain a set rotational speed. Being in control.

The governor mechanism 54 is a centrifugal governor mechanism, and includes a fixed shaft 55 erected in the cylinder block 2 and a
The timing belt 17 is rotatably supported by the timing belt 17.
A governor holder 56 is engaged with a tooth profile formed on the outer circumferential surface of the belt and is driven by the belt. The fixed governor weight 57 and the fixed part protruding from the center of the governor holder 56? ll15
5. The governor weight 5 is slidably inserted into the free end.
The governor slider 58 moves in the axial direction by coming into contact with the arm 57a of No. 7, and the governor arm 59 passes through the cylinder block 2 and transmits the amount of movement of the governor slider 58 to the throttle valve inside the carburetor 53. There is.

By driving the governor holder 56 of the governor mechanism 54 by the timing belt 17, even when the load on the crankshaft 5 fluctuates, the centrifugal force applied to the governor way 157 and the spring restoring force linked to the throttle valve are balanced. A constant rotation speed can be maintained.

In this embodiment, tooth profiles are formed on the outer circumferential surface of the timing belt 17 and on the outer circumferential surface of the governor holder, but they may be omitted if they are not actually required.

On the other hand, at the upstream end of the intake path of the carburetor 53, there is an air cleaner case 6 containing a filter element 60 made of filter paper.
1 is connected. Further, a fuel tank 62 made of synthetic resin is disposed above the carburetor 53 so as to partially overlap the carburetor and the air cleaner case 61. A cover C that also serves as a fan shroud that covers the upper surface of the engine main body 1 is integrally formed on the fuel tank 62.

It goes without saying that the present invention is not limited to the above-mentioned embodiments and can be applied in various ways. For example, in this embodiment, a governor mechanism is provided independently, but it can also be incorporated into a timing belt tensioner and used for both purposes. This will further reduce the number of parts.

[Effects of the Invention] As described above, according to the present invention, by driving the governor holder with a timing belt, noise is reduced compared to gear driving. Furthermore, since it is no longer necessary to provide a gear on the crankshaft side, the number of parts can be reduced, and the degree of freedom in the position of arranging the governor holder is increased, resulting in a reduction in size and weight. From the above, the effects of the present invention are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an engine constructed according to the present invention. FIG. 2 is a partially cutaway top view of an engine constructed according to the present invention. FIG. 3 is an enlarged partial sectional view showing only the essential parts of FIG. 1. 1...Engine body 2...Cylinder block 3
...Crankcase 4a, 4b...Ball bearing 5...
・Crankshaft 6...Crank pin 7...Cylinder bore 8...Piston 9...Conrod
10... Balancer shaft 11... Gear means 12
...Head cover 13a, 13b...Journal portion 14...Camshaft 15...Big timing pulley 16...Small timing pulley 17...Timing belt 18a, 18b...Valve spring 19... Intake valve 20...Exhaust valve 21a, 21b...Cam 22a, 22b...Direct lifter 23...Flywheel 24...Blade 25...Permanent magnet
26... Ignition device 27... Recoil starter 28... Lubricating oil tank 33... Reed valve 34...
・Aisle 35...Aisle 36...Hose port
37... Lubricating oil supply path 38... Three flexible tubes... One-way valve 50... Intake port 51.
... Exhaust port 52 ... Silencer 53 ... Carburetor 54 ... Governor mechanism 55 ... Fixed shaft
56... Governor holder 57... Governor arm 57
a...Arm 58...Governor slider 59...Governor arm 60...Filter element 61...Air cleaner case 62...Fuel tank Q Fig. 3

Claims (2)

[Claims] (1) A crankshaft connected to the proximal end of a piston that slides in the cylinder, a camshaft located on the cylinder head side, and a pulley that connects both shafts so that they interlock with each other. 1. A governor mechanism for an OHC engine, comprising: a timing belt; and a governor mechanism for rotating the crankshaft of an OHC engine at a constant speed, the governor mechanism being driven by the timing belt. (2) The governor mechanism for an OHC type engine according to claim 1, wherein the governor mechanism is driven on the outer peripheral surface side of the timing belt.