JPH02283808A - Valve system of engine - Google Patents

Abstract

PURPOSE:To enable arrangement of both valve stems, in mutual close proximately, by constituting a rocker arm by which rotation of a valve system cam is transmitted to the valve stems of the intake/exhaust valves, with one end which is supported pivotally on the diagonal location of a cylinder head part and the other end which is abutted on the valve stem end. CONSTITUTION:In a four-cycle vertical single cylinder engine, an exhaust port 14 and an intake port 15 which are open to a combustion chamber 13, are formed on a cylinder head part 12 formed integratedly on the left side part of a cylinder block 2, and respective ports 14, 15 are opened and closed by an exhaust valve 24 and an intake valve 25. In this case, a pair of rocker shafts 27a, 27b are supported axially in parallel with a cam shaft 20 at the diagonal location to a cylinder boa center inside a rocker chamber R, and respective rocker arms 28a, 28b are axially supported swingably on respective rocker shafts 27a, 27b. Moreover, cam slippers provided on the one-side ends of a respective rocker arms 28a, 28b are fit slidably, cams 26a, 26b, and the other end surfaces are respectively abutted on the valve stem ends of the valves 24, 25.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the invention] Field of application in the industrial industry> The present invention relates to a valve train for an engine, and in particular to a valve train that is improved so that the valve layout can be freely set. Regarding.

Conventional technology> In recent years, there has been a strong trend toward higher performance in general-purpose engines used in work equipment such as lawn mowers and portable generators.
There is a tendency to adopt i'lOHc type engines in which the valve train including the camshaft is arranged centrally on the cylinder head side.

In such a general-purpose engine, it is desirable to be able to promote miniaturization, and at the same time, it is also desirable to be able to simplify the structure as much as possible and reduce the number of parts. Therefore, the carburetor and muffler are generally mounted directly on the side of the cylinder block.

However, in order to promote miniaturization and maintain maintainability of spark plugs, etc., the mounting position of the carburetor or muffler is subject to considerable restrictions. especially,"
If a structure is adopted in which the carburetor and muffler are directly attached to the side surface of the cylinder block as described in Section 2, their positions will be greatly affected by the arrangement of the intake port and exhaust port. Therefore, one of the requirements for this type of general-purpose engine is a high degree of freedom in the arrangement of intake ports and exhaust ports.

Now, based on this viewpoint, a structure in which both the intake and exhaust valves are arranged offset from each other with respect to the axis of the crankshaft is disclosed in Japanese Patent Laid-Open No. 189330/1989. According to this structure, the spark plug can be installed from the side of the cylinder block while avoiding the carburetor or muffler, which reduces the dimension of the cylinder head in the crankshaft direction and ensures maintainability of the spark plug. I can do it.

<Problems to be Solved by the Invention> By the way, the same structure has a camshaft extending parallel to the crankshaft in the center of the cylinder, supports rocker arms in four sections in a seesaw manner on the cylinder head, and connects the camshaft to the camshaft. When one end of the rocker arm is pushed away by the formed cam, the valve stem ends of both the intake and exhaust valves that are in contact with the other end of the rocker arm are pushed down and opened. According to this structure, since the camshaft is disposed between the valve stems of both the intake and exhaust valves, both valves are arranged in a V-shape. Therefore, the cylinder head width tends to be relatively large, and in addition, the combustion chamber becomes a so-called pent-roof type, which is not necessarily advantageous in securing the desired compression ratio, especially for small displacement engines. It's hard to say.

The present invention was made in view of the problems of the prior art, and its main purpose is to provide an engine valve train that promotes compactness around the cylinder head and improves the degree of freedom in valve layout. The goal is to provide equipment.

[Structure of the Invention] Means for Solving the Problems According to the present invention, it is an object of the present invention to A valve operating device consisting of an intake valve, an exhaust valve, a camshaft, and a rocker arm arranged on the head side, wherein the rocker arm has one end pivoted at a diagonal position of the cylinder head, and the intake/exhaust valve. the other end abutting the valve stem ends of both the valves, and the intake and exhaust valves are sandwiched between a cam formed on the camshaft and the valve stem ends of the intake and exhaust valves. This is achieved by providing an engine valve operating device characterized in that the lift of the cam is transmitted to the engine. In particular, it is preferable that cams corresponding to the intake valve and the exhaust valve are formed on a common camshaft, and that the valve stems of both the intake and exhaust valves extend in line 1a with the cylinder axis.

In this way, since the camshafts are provided outside the valve stem ends of both the intake and exhaust valves, both valve stems can be disposed close to each other. Therefore, there is no need to increase the size of the cylinder head.

In addition, the valve position can be set relatively freely depending on the length of the rocker arm or the direction in which it extends.

In particular, if both the intake and exhaust valves are driven by a common camshaft and the valve stems of both valves extend parallel to the cylinder axis, the combustion chamber can be formed more compactly. Further downsizing of the cylinder head can be promoted.

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

FIGS. 1 and 2 show the entirety of a four-cycle vertical crankshaft forced air-cooled single-cylinder engine constructed according to the present invention. The right side opening of the cylinder block 2 that constitutes the engine body 1 has a crankcase 3
are butt-coupled, and a crankshaft 5 is supported along the vertical direction by a pair of ball bearings 4a and 4b provided at the joint between the cylinder block 2 and the crankcase 3. A crank pin 6 formed approximately at the center of the crankshaft 5 is connected via a connecting rod 9 or a piston 8 that is slidably engaged with a cylinder block formed inside the cylinder block 2 in a downward direction.

At the joint between the cylinder block 2 and the crank pin 3, a balancer shaft 10 is supported in a row 51ε with respect to the crankshaft 5. This balancer shaft 10 is for canceling the primary vibrational force caused by the eccentricity of the crank pin 6, and is connected to the crank shaft 5 through a gear means 11.
, and is driven to rotate at the same speed as the crankshaft 5 and in the opposite direction.

On the left side of the cylinder block 2, there is a cylinder head section 1.
2 are integrally formed. This cylinder head part 1
2 has a combustion chamber 13 defined at the left end of the cylinder bore 7.
, an exhaust port 14 and an intake port 15 that open into the combustion chamber 13, and an exhaust passage 16 and an intake passage that extend from these ports 14 and 15 in a direction substantially perpendicular to the crankshaft 5, that is, in the horizontal direction. 17 are formed. The exhaust passage 16 and the intake passage 17 extend in opposite directions across the axis of the cylinder bore 7.

A rocker arm chamber R is formed at the end of the cylinder head portion 12 in the cylinder axial direction, and a head cover 18 is butt-coupled. As shown in FIG. 3, a pair of upper and lower journal parts 19a and 19b are formed at the joint between the cylinder head part 12 and the head cover 18. A camshaft 20 extending parallel to the shaft 5 is supported by its both ends. This camshaft 20 has a large timing pulley 21a integrally formed on its lower end side,
It is driven at 1/2 the rotational speed of the crankshaft 5 via a timing belt 22 wound around a small timing pulley 21b fixed to the crankshaft 5. Note that a transmission mechanism consisting of both timing pulleys 21a, 21b and timing belt 22 is housed in a belt chamber B integrally formed with the cylinder block 2 below the cylinder bore 7.

The cylinder head portion 12 has an exhaust port 14 marked 1-.
In order to open and close the intake port 15, an exhaust valve 24 and an intake valve 25 are provided which are normally biased in the direction of the valve closing force by valve springs 23a and 23b. In addition, a pair of rocker shafts 2 are arranged parallel to the camshaft 20 at a position opposite to ff+ with respect to the center of the cylinder bore in the rocker chamber R.
7a and 27b are extended, and these rocker shafts 27a
- Rocker arms 28a and 28b are pivotally supported by rocker arms 27b, respectively.

These pair of rocker arms 28a and 28b each extend toward the camshaft 20, and a cam slipper formed on one side of the free end of the rocker arm 28a and 28b is connected to a pair of cams 26a formed on the camshaft 20.・Slides on the outer peripheral surface of 26b, and the other side of the free end is connected to both the intake and exhaust valves 24 and 25.
are in contact with the valve stem ends of each. As a result, according to the rotation of the crankshaft 5, the lift height of both cams 26a and 26b is adjusted to both valves 24 through the two-end hook arms 28a and 28b.
・The signal is transmitted to 25, and both valves 24 are activated at appropriate timing.
・25 is driven to open and close. The axes of the valve stems of both valves 24 and 25 are parallel to the axis of the cylinder bore 7. Therefore, the mutually opposing end surfaces of the valves 24, 25 and the piston 8 are parallel to each other, and the volume of the combustion chamber 13 is suppressed.

On the other hand, a muffler 29 is directly connected to the opening of the exhaust passage 16, and a carburetor 30 is directly connected to the opening of the intake passage 17. The carburetor 30 is connected to a governor mechanism 31 that is gear-driven by the crankshaft 5 and a link mechanism (not shown).
The throttle valve opening is automatically controlled to maintain the set rotational speed.

Further, an air conditioner case 33 having a built-in filter element 32 made of filter paper is connected to the second end of the intake path of the vaporizer 30.

On the other hand, a flywheel 34 is provided at the upper end of the crankshaft 5.
Or it is fixed. A blade 35 that functions as a cooling fan is integrally formed on the outer periphery of the axial end surface of the flywheel 34 .

Further, a permanent magnet 36 is fixed to a part of its outer periphery, and works together with an ignition device 37 fixed to the cylinder block side to generate the required ignition spark at a predetermined timing. . Furthermore, a recoil starter 38 is connected to the shaft end of the crankshaft 5.

A lubricating oil tank 39 is provided on the right side of the crankcase 3. The lubricating oil tank 39 is made of a translucent synthetic resin material, has two-stage bottom walls 40a and 40b, and has a boss portion 41 projecting downward from the shallow bottom portion 40a. It fits into the hole 42 in a fluid-tight manner. Continuing with this boss portion 41, a protrusion 43 extends along the inner surface of one side wall of the lubricating oil tank 39 until it reaches the earthen wall.
A passage 45 is provided therein, which opens opposite to the lower wall of the lubricating oil tank 39 and opens into the upper space of the lubricating oil tank 39 via a reed valve 44 . This passage 45 allows the lubricating oil to flow only from the bottom of the crankcase 3 to the top of the lubricating oil tank 39.

The inner surface of the other side wall of the lubricating oil tank 39 has a deep bottom portion 4Ob.
A second passage 46 opens inward and extends to communicate with the outside of the -1 wall of the lubricating oil tank 39. A hose port 47 is fitted into the opening in the upper wall of the second passage 46, and a lubricating oil supply passage 48 provided inside the cylinder block 2
and is connected via a flexible tube 49.

At the most upstream end of this lubricating oil supply path 48, a lubricating oil tank 3
A one-way valve 50 that only allows lubricating oil to flow in from 9 is interposed.

The lubricating oil supply path 48 extends along the cylinder axis within the 4th wall of the cylinder block 2, and is connected to the cam journal section located on the 2nd side via an oil reservoir chamber 51 formed in the middle part. Similarly to 19a, the lubricating oil is supplied to the crank bearing part 4a located on the second side by branching (7).

According to the above lubricating oil supply device, lubricating oil is sucked into the engine from the lubricating oil tank 39 by the negative pressure generated in the crankcase 3 during the upward stroke of the piston 8, and the positive pressure generated during the downward stroke of the piston 8 The pressure forces the lubricating oil that has flowed down to the lower side inside the cylinder block 2 back into the lubricating oil tank 39 .

The first side of the engine body 1 constructed in this way is covered over substantially the entire surface with a cover 〇 which also serves as a fan shroud.

Now, in the lawn mower engine shown in the above embodiment,
Since it is preferable for the center of gravity to be low in addition to improving maneuverability, it is desirable to be able to reduce the height dimension as much as possible. Therefore, in practice, the intake passage and the exhaust passage are arranged to extend in opposite directions across the cylinder, and a muffler and a carburetor are mounted on both sides of the cylinder block. However, if this is done, the installation position of the spark plug, which is preferably installed in an easily accessible position, may tend to be restricted.

Therefore, in the present invention, the rocker arm is pivotally supported at a diagonal position of the cylinder, and its free end side extends so as to be inserted between the valve stem end and the cam. As an example of such a configuration, as shown in FIG. 3, if both the intake and exhaust valves 24 and 25 are arranged offset with respect to the axis of the camshaft 20, the diagonal upper right corner in FIG. , and a relatively large space can be obtained in the diagonal lower left corner. Therefore, by installing the spark plug P so that its electrode is located in this portion, the spark plug P can be installed from diagonally above the cylinder block 2, avoiding the carburetor 30.

4 to 6 show modified embodiments of the present invention, and the same reference numerals are given to the parts corresponding to the first embodiment, and the explanation thereof will be omitted.

What is shown in FIG.
4.25, and the one shown in Figure 5 is
Both valves 24 and 25 are arranged on a line perpendicular to the camshaft 20, and the one shown in FIG. 6 has both valves 24 and 25 arranged in symmetrical positions to the one shown in FIG.

In this way, the installation of spark plugs is not just a matter of location; instead, the positions of both the intake and exhaust valves can be freely set, taking into consideration the direction of the intake and exhaust passages and the overall layout of the engine due to other circumstances. can do.

[Effects of the Invention] According to the present invention, as described in detail in Embodiment 1-1, the valve stem can be disposed parallel to the cylinder axis, so the cylinder head including the combustion chamber can be made compact. It has a great effect on achieving In addition,
Depending on the length of the rocker arm and the direction in which it extends, both the intake and exhaust valves can be placed in any position, including "downward to the camshaft, perpendicular to the camshaft, or offset from each other." Therefore, there are fewer restrictions on the mounting position of the spark plug or the mounting position of the carburetor and muffler, and this can have a great effect in partially promoting the downsizing of the engine.

[Brief explanation of drawings]

FIG. 1 is a partially omitted vertical sectional view of an engine configured according to the present invention, FIG. 2 is a partially cut-away - L side view, and FIG. 3 is a head cover FIG. FIGS. 4 to 6 are schematic diagrams showing different embodiments. 1...Engine body 2...Cylinder block 3
..., crankcase 4a, 4b...ball bearing 5.
・Crank i [h 6...Crank pin 7・
... Cylinder bore 8 ... Piston 9 ... Connecting rod 10 ... Balancer shaft 11 ... Gear means
12...Cylinder head part 13...Combustion chamber
14...Exhaust port 15...Intake boat 1
6...Exhaust passage 17...Intake passage 18...
Head cover 19a, 19b...Journal part 20...Cam and shaft 21a...Big timing pulley 21b...Small timing pulley 22...Timing belt 23a, 23b...Valve spring 24...Exhaust valve 25... Intake valves 26a, 26b... Cams 27a, 27b... Cam shafts 28a, 28b... Rocker arm 29... Silencer 30... Carburetor 31...
Governor mechanism 32...filter element 33...
・Air cleaner case 34...Flywheel 35...Blade 36...
・Permanent magnet 37...Ignition device 38...3 recoil starters...Lubricating oil tank 40a, 40b...Bottom wall 4
1...Boss part 42...Through hole 43...Protrusion 44...Reed valve 45...Passage
46...Second passage 47...Hose port 48.
...Lubricating oil supply path 49...Flexible tube 50...One-way valve 51...Ura reservoir chamber Fig. 3

Claims (2)

[Claims] (1) A valve train consisting of an intake valve, an exhaust valve, a camshaft, and a rocker arm arranged on the cylinder head side of the engine in order to control the intake of air-fuel mixture into the combustion chamber of the engine and the discharge of combustion gas. The rocker arm has one end pivotally supported at a diagonal position of the cylinder head portion and the other end abutting the valve stem ends of the intake and exhaust valves, and is formed on the camshaft. A valve operating device for an engine, characterized in that the cam is sandwiched between a cam and a valve stem end of each of the intake and exhaust valves to transmit the lift of the cam to both the intake and exhaust valves. (2) A first method characterized in that cams corresponding to the intake valve and the exhaust valve are formed on a common camshaft, and the valve stems of both the intake and exhaust valves extend parallel to the cylinder axis. A valve train for an engine according to the claims.