JP2009185649A - Valve train structure for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve train structure for an engine capable of reducing the weight and size of the engine, of opening and closing an intake valve and an exhaust valve at accurate timing even when the engine is driven at high speed, and of reducing load resistance when the intake valve and the exhaust valve are opened and closed. <P>SOLUTION: This valve train structure for the engine is provided with pulleys 40a, 40b (rotors) rotating with interlocking with rotation of a crankshaft and having annular cam grooves 43a, 43b formed thereon. Rocker arms 50a, 50b are connected to the intake valve 20 or the exhaust valve 30 at one ends and attached into the cam grooves 43a, 43b at another ends. The rocker arms 50a, 50b are guided by the cam grooves 43a, 43b and are inclined when the pulleys 40a, 40b are rotated to open and close the intake valve 20 and the exhaust valve 30. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a valve operating structure of an engine for operating an intake valve or an exhaust valve.

  The four-cycle engine has a valve operating structure in which one end of a rocker arm provided in the cylinder head is connected to an intake valve and an exhaust valve, and the other end slides on a cam surface provided on a camshaft. There is something that has been. In such a valve operating structure, when the camshaft is rotated, the other end of the rocker arm is guided to the cam surface, and the rocker arm tilts to open and close the intake valve and the exhaust valve. (For example, refer to Patent Document 1).

  In the conventional valve operating structure described above, a valve spring is provided for the intake valve or the exhaust valve. When the intake valve or the exhaust valve is closed, the intake valve or the exhaust valve is pushed up by the biasing force of the valve spring, and the intake valve When opening the exhaust valve, the rocker arm pushes down the intake valve and the exhaust valve against the biasing force of the valve spring.

JP-A-5-163914 (paragraphs 0016 to 0018, FIG. 1)

In the conventional valve train described above, the number of parts provided in the cylinder head, such as a camshaft and a valve spring, is large, so that the weight of the engine increases and the engine becomes large.
In addition, when closing the intake and exhaust valves, the biasing force of the valve spring is used, so when the engine is driven at high speed, the opening and closing timing of the intake and exhaust valves follows the rotation of the crankshaft. There is a problem that valve surging disappears.
Also, when opening the intake and exhaust valves, the rocker arm must depress the intake and exhaust valves against the biasing force of the valve spring, increasing the load resistance when opening and closing the intake and exhaust valves. There is a problem that it ends up.

  Therefore, in the present invention, the above-described problems can be solved, the engine can be reduced in weight and size, and the intake valve and the exhaust valve can be opened and closed with accurate timing even when the engine is driven at a high speed. Further, it is an object of the present invention to provide a valve operating structure for an engine that can reduce load resistance when opening and closing an intake valve and an exhaust valve.

  In order to solve the above-described problems, the present invention provides an engine valve operating structure in which a rocker arm for operating an intake valve or an exhaust valve is provided in a cylinder head, and is interlocked with rotation of a crankshaft. It has a rotating body that rotates and has an annular cam groove formed around the center of rotation, and the rocker arm is attached with one end connected to an intake valve or exhaust valve and the other end slidable within the cam groove When the rotating body is rotated, the other end of the rocker arm is guided by the cam groove, and the rocker arm is tilted to open or close the intake valve or the exhaust valve. It is a feature.

  In order to solve the above problems, another configuration of the present invention is an engine valve operating structure in which a connecting member for operating an intake valve or an exhaust valve is provided in a cylinder head, and a crankshaft And a rotating body having an annular cam groove formed around the center of rotation. One end of the connecting member is connected to the intake valve or the exhaust valve, and the other end is slid into the cam groove. It is attached in a movable state, and when the rotating body is rotated, the other end of the connecting member is guided by the cam groove, and the connecting member is displaced so that the intake valve or the exhaust valve opens and closes. It is characterized by being composed.

  In these configurations, the intake valve and the exhaust valve are forcibly opened and closed by operating the rocker arm and the connecting member while being guided by the annular cam groove formed in the rotating body. Therefore, in the present invention, the camshaft and the valve spring for operating the rocker arm and the connecting member are not necessary, and the number of components provided in the cylinder head is reduced as compared with the conventional valve operating structure. And miniaturization.

  In addition, by forcibly opening and closing the intake and exhaust valves, the opening and closing timing of the intake and exhaust valves can follow the crankshaft rotation even when the engine is driven at a high speed. Since the exhaust valve can be opened and closed with accurate timing, the allowable engine speed can be increased.

  In addition, the intake valve and exhaust valve are forcibly opened and closed by guiding the rocker arm and the connecting member to the annular cam groove, and there is no need to provide a valve spring on the intake valve or exhaust valve. And load resistance when opening and closing the exhaust valve can be reduced.

  In the above-described valve train structure of the engine, the rotation of the crankshaft can be transmitted to the rotating body by the annular linear body that is stretched between the rotating body and the crankshaft.

  In this configuration, the rotating body is rotated in the same configuration as the cam pulley and cam sprocket for rotating the camshaft in the conventional valve operating structure, and when the valve operating structure of the present invention is applied to a conventional engine, Since it is not necessary to change the structure of the conventional engine significantly, the manufacturing cost can be reduced.

According to the valve operating structure of the engine of the present invention, by forcibly opening and closing the intake valve and the exhaust valve, the camshaft and the valve spring become unnecessary, and the number of parts provided in the cylinder head is reduced, so that the engine is lightweight. And miniaturization.
Further, even when the engine is driven at a high speed, the intake valve and the exhaust valve can be opened and closed with accurate timing, so that the allowable engine speed can be increased.
Further, since it is not necessary to provide a valve spring for the intake valve or the exhaust valve, it is possible to reduce the load resistance when opening or closing the intake valve or the exhaust valve.

Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
In the description of each embodiment, the same constituent elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[First embodiment]
First, after describing the structure of the whole engine using the valve operating structure of the first embodiment, the valve operating structure will be described in detail.
In the following description, the front / rear / left / right direction corresponds to the front / rear / left / right direction shown in each drawing. The front-rear and left-right directions are directions set for convenience in describing the valve train structure of the first embodiment, and do not limit the configuration of the valve train structure.

An engine 1 shown in FIG. 1 is a four-cycle internal combustion engine. A cylinder head 3 is provided above the cylinder block 2, and a crankcase 4 is provided below the cylinder block 2. The engine 1 is an OHC engine in which an intake valve 20 and an exhaust valve 30 and a valve operating structure 10 for opening and closing the intake valve 20 and the exhaust valve 30 are provided in a cylinder head 3.
In addition, in the engine 1 of 1st embodiment, since the structure of a well-known internal combustion engine is used about structures other than the valve operating structure 10, the detailed description is abbreviate | omitted.

The cylinder head 3 includes a cylinder head main body 3a and a rocker arm cover 3b that covers the upper portion of the cylinder head main body 3a.
An intake port 3c and an exhaust port 3d communicating with the combustion chamber 6 are formed in the cylinder head body 3a. Specifically, an intake port 3c is disposed on the left side and an exhaust port 3d is disposed on the right side with respect to the center position of the cylinder head body 3a in the left-right direction.

The cylinder head body 3a is provided with an intake valve 20 and an exhaust valve 30 so as to correspond to the intake port 3c and the exhaust port 3d, and sandwiches the center position in the left-right direction of the cylinder head body 3a. An intake valve 20 is disposed on the left side, and an exhaust valve 30 is disposed on the right side.
As shown in FIG. 2A, when the intake valve 20 moves up and down, the space between the intake port 3 c and the combustion chamber 6 is opened and closed by the umbrella portion 21 formed at the lower end portion of the intake valve 20. Reference numeral 23 denotes a cylindrical guide member that guides the vertical movement of the intake valve 20, and the stem portion 22 of the intake valve 20 is inserted through a through hole formed in the center.
As shown in FIG. 2 (b), when the exhaust valve 30 moves up and down, the exhaust port 3 d and the combustion chamber 6 are opened and closed by the umbrella portion 31 formed at the lower end of the exhaust valve 30. Reference numeral 33 denotes a cylindrical guide member that guides the vertical movement of the exhaust valve 30, and the stem portion 32 of the exhaust valve 30 is inserted into a through hole formed in the center.

The engine 1 of the present embodiment is configured to lubricate each part in the engine 1 with an air-fuel mixture containing lubricating oil.
The cylinder block 2 of the engine 1 shown in FIG. 1 is provided with a supply path 2b that leads from the carburetor 5 into the cylinder 2a. The opening on the cylinder 2a side of the supply path 2b is opened when the piston 7 moves to the top dead center, and is closed by the outer peripheral surface of the piston 7 when the piston 7 moves to the bottom dead center. It is formed in the position.
Further, a communication path (not shown) leading from the crank chamber 4a to the cylinder head 3 is formed in the crankcase 4 of the engine 1 and the wall of the cylinder block 2, and the crank chamber 4a side of this communication path is formed. A reverse flow prevention mechanism such as a reed valve is provided at the opening of the gas passage so that the air-fuel mixture flows only from the crank chamber 4a side.

In the compression stroke and exhaust stroke of the engine 1, an air-fuel mixture of mixed fuel mixed with lubricating oil and air is generated by the carburetor 5, and this air-fuel mixture is sucked into the cylinder 2a and the crank chamber 4a.
In the intake stroke and the combustion stroke, the air-fuel mixture in the crank chamber 4a is sent out from the crank chamber 4a to the communication path by the pressure due to the lowering of the piston 7.
The air-fuel mixture sent from the crank chamber 4a to the communication path is jetted into the cylinder head 3 from the communication path, blown to the valve operating structure 10 in the cylinder head 3, and then sucked into the combustion chamber 6 for combustion. It is burned in the combustion chamber 6 in the stroke.
Further, the combustion gas in the combustion chamber 6 is sent into the muffler 8 from the exhaust port 3d in the exhaust stroke, and is exhausted to the outside from the muffler 8.

  As described above, in the engine 1, the air-fuel mixture containing the lubricating oil passes through the cylinder 2 a, the crank chamber 4 a, and the cylinder head 3, whereby each part in the engine 1 is lubricated. Therefore, the lubricating performance can be maintained even when the engine 1 is inclined at various angles. For example, when the engine 1 of the present embodiment is applied to a small work machine such as a blower or a chain saw, the lubrication performance of the engine 1 is maintained even if the worker carries the small work machine and uses it in various postures. Thus, the small work machine can be driven stably.

  As shown in FIG. 1, the valve operating structure 10 is provided in the cylinder head 3, and pulleys 40a and 40b, which are rotating bodies that rotate in conjunction with the rotation of the crankshaft 4b, and one end of the intake valve 20 or Rocker arms 50a and 50b connected to the exhaust valve 30 and attached to the pulleys 40a and 40b at the other end are provided.

  As shown in FIG. 4, the pulleys 40a and 40b are disk-shaped members having through-holes 41a and 41b formed in the center and tooth surfaces formed on the outer peripheral surface, and both planes are directed in the front-rear direction. In the state, it is attached to the upper part of the cylinder head body 3a. A first pulley 40a is disposed on the left side and a second pulley 40b is disposed on the right side with the center position in the left-right direction of the cylinder head body 3a (see FIG. 1) interposed therebetween.

On the upper left side of the cylinder head body 3a, as shown in FIG. 2 (a), a rotation support shaft 42a having an axial direction arranged in the front-rear direction is attached. The rotation support shaft 42a is inserted through the through hole 41a of the first pulley 40a, and the first pulley 40a is rotatable around the rotation support shaft 42a.
On the upper right side of the cylinder head body 3a, as shown in FIG. 2 (b), a rotation support shaft 42b having an axial direction arranged in the front-rear direction is attached. The rotation support shaft 42b is inserted through the through hole 41b of the second pulley 40b, and the second pulley 40b is rotatable around the rotation support shaft 42b.

  As shown in FIG. 4, a timing belt 9, which is an annular linear body, is stretched between the left and right pulleys 40 a and 40 b and the crankshaft 4 b (see FIG. 1). The rotation of the crankshaft 4b is transmitted to the pulleys 40a and 40b.

  In the first embodiment, the rotating body is constituted by pulleys 40a and 40b, and the timing belt 9 is spanned between the pulleys 40a and 40b and the crankshaft 4b, thereby rotating the crankshaft 4b. However, it is also possible to transmit the rotation of the crankshaft 4b to each sprocket by configuring the rotating body as a sprocket and passing an annular timing chain between each sprocket and the crankshaft 4b.

As shown in FIG. 4, annular cam grooves 43a and 43b are formed around the rotation center on the front surfaces of the first pulley 40a and the second pulley 40b.
As shown in FIG. 2A, the cam groove 43a of the first pulley 40a is a concave guide groove for operating a first rocker arm 50a, which will be described later, and a cam profile that determines the opening / closing timing of the intake valve 20 It has become.
As shown in FIG. 2B, the cam groove 43b of the second pulley 40b is a concave guide groove for operating a second rocker arm 50b described later, and a cam profile that determines the opening / closing timing of the exhaust valve 30. It has become.

  As shown in FIG. 1, the first rocker arm 50a and the second rocker arm 50b are provided on the upper surface of the cylinder head body 3a, and the first rocker arm 50a and the second rocker arm 50b are located on the left side with the center position of the cylinder head body 3a in the left-right direction. An arm 50a is disposed, and a second rocker arm 50b is disposed on the right side.

As shown in FIG. 3, the first rocker arm 50 a has two plate-like members extending in the front-rear direction arranged at a predetermined interval in the left-right direction, and the rear end portion of each plate-like member Are connected to each other.
The front end portion of the first rocker arm 50a sandwiches the upper end portion of the intake valve 20 from the left-right direction, and is formed in the notch groove formed in the front end portion of the first rocker arm 50a and the upper end portion of the intake valve 20. By inserting the joint pin 51a through the through hole (not shown), the front end portion of the first rocker arm 50a and the upper end portion of the intake valve 20 are connected.

The rear end portion of the first rocker arm 50a is attached in a slidable state in the cam groove 43a of the first pulley 40a.
As shown in FIG. 2A, a rod-shaped sliding portion 52a projects rearward from the rear surface of the first rocker arm 50a. The rear end portion of the sliding portion 52a is a portion that slides within the cam groove 43a, and a portion that contacts the inner surface (upper surface, lower surface) of the cam groove 43a is a spherical surface.

On the left and right side surfaces of the first rocker arm 50a, the tilting support shaft 53a protrudes in the left-right direction at a position closer to the rear than the central portion in the front-rear direction. Both left and right ends of the tilting support shaft 53a are rotatably supported by the cylinder head body 3a, and the first rocker arm 50a can tilt around the tilting support shaft 53a.
When the first pulley 40a is rotated around the rotation support shaft 42a, the sliding portion 52a provided at the rear end portion of the first rocker arm 50a is guided by the annular cam groove 43a which is a cam profile. By displacing in the vertical direction, the first rocker arm 50a tilts (oscillates) about the axis of the tilting support shaft 53a.

When the front end side of the first rocker arm 50a is lowered from the state of FIG. 2A, the intake valve 20 is pushed down, and the umbrella portion 21 of the intake valve 20 is separated from between the combustion chamber 6 and the intake port 3c. 6 and the intake port 3c are opened.
Further, when the front end side of the first rocker arm 50a rises from the state in which the intake valve 20 is pushed down, the intake valve 20 is pulled up, and the umbrella portion 21 of the intake valve 20 establishes a gap between the combustion chamber 6 and the intake port 3c. Blocked.

  As shown in FIG. 3, the second rocker arm 50b has a front end portion connected to the upper end portion of the exhaust valve 30 by a joint pin 51b, and a sliding portion 52b provided at the rear end portion is a cam groove of the second pulley 40b. Since it is the same structure as above-mentioned 1st rocker arm 50a except being attached in 43b, the detailed description is abbreviate | omitted.

  The second rocker arm 50b is configured to tilt around the axis of the tilting support shaft 53b protruding from the left and right side surfaces. When the second pulley 40b is rotated about the rotation support shaft 42b, the sliding portion 52b is The second rocker arm 50b is tilted (oscillated) around the tilting support shaft 53b by being guided by the cam groove 43b and displaced in the vertical direction.

When the front end side of the second rocker arm 50b is lowered from the state of FIG. 2B, the exhaust valve 30 is pushed down, and the space between the combustion chamber 6 and the exhaust port 3d is opened.
Further, when the front end side of the second rocker arm 50b rises from the state where the exhaust valve 30 is pushed down, the exhaust valve 30 is pulled up and the space between the combustion chamber 6 and the exhaust port 3d is closed.

  According to the valve operating structure 10 of the first embodiment, as shown in FIG. 3, the rocker arms 50a and 50b are operated by being guided by the annular cam grooves 43a and 43b formed in the pulleys 40a and 40b. Thus, the intake valve 20 and the exhaust valve 30 are forcibly opened and closed. Therefore, in the valve operating structure 10 of the first embodiment, as shown in FIG. 1, camshafts and valve springs for operating the rocker arms 50a and 50b become unnecessary, and compared with the conventional valve operating structure, Since the number of parts provided in the cylinder head 3 is reduced, the engine 1 can be reduced in weight and size.

  In addition, by forcibly opening and closing the intake valve 20 and the exhaust valve 30, the opening and closing timing of the intake valve 20 and the exhaust valve 30 can follow the rotation of the crankshaft 4b even when the engine 1 is driven at a high speed. Since the intake valve 20 and the exhaust valve 30 can be opened and closed with accurate timing, the allowable rotational speed of the engine 1 can be increased.

  In addition, the intake valve 20 and the exhaust valve 30 are forcibly opened and closed by guiding the rocker arms 50a and 50b to the annular cam grooves 43a and 43b, and a valve spring is applied to the intake valve 20 and the exhaust valve 30. Since it is not necessary to provide, load resistance when opening and closing the intake valve 20 and the exhaust valve 30 can be reduced.

  In the valve operating structure 10 of the first embodiment, as shown in FIG. 4, cam grooves 43a and 43b are formed with the same configuration as a cam pulley or cam sprocket for rotating a camshaft in the conventional valve operating structure. The pulleys 40a and 40b are rotated, and when the valve train 10 of the first embodiment is applied to a conventional engine, it is not necessary to significantly change the structure of the conventional engine, thereby reducing the manufacturing cost. can do.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the spirit of the present invention.
For example, in the first embodiment, as shown in FIG. 3, the two rocker arms 50a and 50b are operated by the two pulleys 40a and 40b, respectively, but they are formed as an integral pulley (rotary body). Alternatively, the rear end portions of the two rocker arms 50a and 50b can be guided by the cam grooves. In this configuration, the number of parts can be reduced as compared with the valve train 10 using the two pulleys 40a and 40b (rotating bodies) described above, and the engine can be reduced in weight and size.

  In this embodiment, as shown in FIGS. 2A and 2B, the spherical surfaces formed at the rear ends of the sliding portions 52a and 52b of the rocker arms 50a and 50b are formed in the cam grooves 43a and 43b. However, a rotating part such as a roller is provided at the rear end of each sliding part 52a, 52b, and this rotating part slides while rolling in the cam grooves 43a, 43b. You may comprise as follows.

[Second Embodiment]
Next, the valve operating structure of the second embodiment will be described in detail.
The valve operating structure 10A of the second embodiment shown in FIG. 5 is the valve operating structure 10 of the first embodiment except that the rocker arm is not used to operate the intake valve 20 and the exhaust valve 30 (see FIG. 3). And substantially the same configuration.
In the valve operating structure 10A of the second embodiment, the stem portion 22 of the intake valve 20 and the cam groove 43a of the first pulley 40a are connected via a first connecting member 60a.

The front end portion of the first connecting member 60a is externally fitted to the upper portion of the stem portion 22 of the intake valve 20, and the rear end portion of the first connecting member 60a is in the cam groove 43a of the first pulley 40a. It is attached in a slidable state.
The rear end portion of the first connecting member 60a is a portion that slides in the cam groove 43a, and a portion that contacts the inner surface (upper surface, lower surface) of the cam groove 43a is a spherical surface.

  When the first pulley 40a is rotated around the rotation support shaft 42a, the rear end portion of the first connecting member 60a is guided by the annular cam groove 43a that is the cam profile, and the entire first connecting member 60a is vertically moved. By displacing in the direction, the intake valve 20 is also moved in the vertical direction in conjunction with the first connecting member 60a, and the combustion chamber and the intake port are opened and closed.

  Further, in the valve operating structure 10A of the second embodiment, the configuration on the exhaust valve 30 side is the same as the configuration on the intake valve 20 side described above, and the stem portion 32 of the exhaust valve 30 and the cam of the second pulley 40b. The groove 43b is connected via the second connecting member 60b. And when the whole 2nd connection member 60b is displaced to an up-down direction, the exhaust valve 30 moves to an up-down direction in response to the 2nd connection member 60b, and a combustion chamber and an exhaust port are opened and closed.

In the valve operating structure 10A of the second embodiment, similarly to the valve operating structure 10 (see FIG. 3) of the first embodiment, the intake valve 20 and the exhaust valve 30 are forcibly opened and closed, thereby enabling camshafts and valve springs. Is eliminated, and the number of parts provided in the cylinder head is reduced, so that the engine can be reduced in weight and size.
Further, even when the engine is driven at a high speed, the intake valve 20 and the exhaust valve 30 can be opened and closed with accurate timing, so that the allowable engine speed can be increased.
Further, since it is not necessary to provide a valve spring on the intake valve 20 or the exhaust valve 30, the load resistance when opening or closing the intake valve 20 or the exhaust valve 30 can be reduced.

It is a sectional side view showing the engine using the valve gear structure of a first embodiment. It is the figure which showed the valve operating structure of 1st embodiment, (a) is a sectional side view by the side of an intake valve, (b) is a sectional side view by the side of an exhaust valve. It is the perspective view which showed the valve operating structure of 1st embodiment. In the valve operating structure of 1st embodiment, it is the figure which looked at each pulley from the front. It is the perspective view which showed the valve operating structure of 2nd embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Cylinder block 3 Cylinder head 3a Cylinder head main body 3c Intake port 3d Exhaust port 4 Crankcase 4b Crankshaft 6 Combustion chamber 9 Timing belt (striated body)
10 Valve structure (first embodiment)
10A valve operating structure (second embodiment)
20 Intake valve 30 Exhaust valve 40a First pulley (rotating body)
40b Second pulley (rotating body)
43a cam groove 43b cam groove 50a first rocker arm 50b second rocker arm 60a first connecting member 60b second connecting member

Claims (3)

A rocker arm for operating an intake valve or an exhaust valve is a valve operating structure of an engine provided in a cylinder head,
A rotating body that rotates in conjunction with the rotation of the crankshaft and has an annular cam groove formed around the rotation center,
The rocker arm has one end connected to the intake valve or the exhaust valve and the other end attached in a slidable state in the cam groove.
When the rotating body is rotated, the other end of the rocker arm is guided by the cam groove, and the rocker arm tilts to open or close the intake valve or the exhaust valve. The valve operating structure of the engine characterized by this. The connecting member for operating the intake valve or the exhaust valve is a valve operating structure of an engine provided in the cylinder head,
A rotating body that rotates in conjunction with the rotation of the crankshaft and has an annular cam groove formed around the rotation center,
One end of the connecting member is connected to the intake valve or the exhaust valve, and the other end is attached in a slidable state in the cam groove.
When the rotating body is rotated, the other end of the connecting member is guided to the cam groove, and the connecting member is displaced to open or close the intake valve or the exhaust valve. The valve operating structure of the engine characterized by this.   3. The structure according to claim 1, wherein the rotation of the crankshaft is transmitted to the rotating body by an annular linear body that is stretched between the rotating body and the crankshaft. The valve operating structure of the engine described in 1.

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