JPH0511289Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a decompression device for an overhead valve engine, and provides one that can ensure stable decompression performance without rattling of the rocker arm during decompression operation.

<Prior art> As shown in Fig. 4, the conventional decompression device
Of the boss-type rocker arm 52 pivotally supported on the bracket 50, the point of action 58 that contacts the intake and exhaust valves 54 is pushed down from above with the decompression tool 53 to open the intake and exhaust valves 54 and decompress the combustion chamber. Was.

However, recently, there has been an increasing demand for engines that are small and inexpensive to manufacture, so there have been many attempts to use a boat-shaped rocker arm 2 made of sheet metal in place of the boss-shaped rocker arm 52.

That is, the valve-opening point 8 of the boat-shaped rocker arm 2 is pushed down by the decompression tool 3 to decompress the valve.

<Problems to be solved by the invention> However, in the above configuration, the boat-shaped rocker arm 2 is rocked with its fulcrum 7 being pressed from above by the lens-shaped support rod 10 and sliding against the lens-shaped receiving surface of the support rod 10. Because it moves dynamically, there is no pressure from below, unlike conventional boss-type rocker arms.

Therefore, as shown in FIG. 3, when the valve opening application point 8 is pressed with the decompression tool 3, the boat-shaped rocker arm 2 becomes sandwiched between the decompression tool 3 and the intake/exhaust valve 4, and the push rod 12 is pressed. When the lifting force decreases, the rocker arm 2 rises from the fulcrum 7 and the movement of the rocker arm 2 becomes unstable, causing the points where the push rod 12 acts on the rocker arm 2, the points where the lens-shaped support rod 10 acts on the rocker arm 2, and There is a risk of wear and tear on the valve mechanism 1, including the surface where the lens support rod 10 contacts the rocker arm 2.

The technical problem of the present invention is to stabilize the movement of the boat-shaped rocker arm 2 and suppress wear and tear on the valve mechanism.

<Means for Solving the Problems> Means for achieving the above-mentioned problems will be described below with reference to FIGS. 1 and 2, which correspond to embodiments.

That is, in the present invention, the decompression pressing point 6 where the decompression tool 3 presses the rocker arm 2 toward the valve opening side is located at a point beyond the point of action 8 where the decompression tool 3 contacts the intake/exhaust valve 4 when viewed from the fulcrum 7 of the rocker arm 2. It is characterized by being set to .

<Operation> Since the decompression pressure point 6 is set beyond the valve opening application point 8 when viewed from the fulcrum 7, when the boat-shaped rocker arm 2 is pressed with the decompression tool 3, this pressure is The pressure generates a moment that tends to rotate the fulcrum 7 side of the boat-shaped rocker arm 2 upward about the valve opening application point 8.

Therefore, due to this moment, the boat-shaped rocker arm 2 continues to contact the globe-shaped support rod that supports the rocker arm from above, and can be prevented from lifting off from the support rod.

<Effects of the invention> Since the boat-shaped rocker arm continues to be in contact with the support rod that supports itself even during decompression operation, stable decompression performance can be ensured and wear and tear on the valve mechanism can be suppressed.

<Example> Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 is a longitudinal sectional front view of the main parts around the rocker arm chamber of an overhead valve diesel engine, and FIG. 2 is a schematic explanatory diagram of a boat-shaped rocker arm.
, and the piston 16 is fitted into the cylinder 15 so as to be vertically slidable.

A cylinder head 17 and a head cover 18 are sequentially assembled above the cylinder block 14, an intake and exhaust port 19 is opened on the left side of the cylinder head 17, and an intake and exhaust valve 4 is attached to the opening facing the combustion chamber 5 so as to be openable and closable.

An auxiliary combustion chamber 20 is formed on the right side of the cylinder head 17, and its lower end is communicated with the combustion chamber 5, and a combustion injection nozzle 21 is inserted from above the cylinder head 17 so that its lower part faces the auxiliary combustion chamber 20.

The inside of the head cover 18 is defined as a rocker arm chamber 22 in which the valve train 1 is housed.

The valve train 1 consists of a rocker arm 2, a push rod 12, and an intake/exhaust valve 4.
is made of sheet metal in the shape of a boat, and is configured to be swingable by sliding its center inner wall surface against the lens receiving surface 22 of the lens supporting rod 10 erected on the upper end surface of the cylinder head 17.

The push rod 12 has one end 12a in contact with the input end 24 of the boat-shaped rocker arm 2, that is, the point of push-down action, and the other end 12b in contact with a tappet 25 that moves up and down with the rotation of the valve drive camshaft.

The intake and exhaust valve 4 is normally biased to close by a valve opening spring 26, and is configured such that its upper end 4a can come into contact with the output end of the boat-shaped rocker arm 2, that is, the valve opening point 8.

On the other hand, a decompression rod 27 is rotatably supported on the upper right side of the head cover 18, and a decompression tool 3 made of a threaded rod is screwed into the center of the decompression rod 27.
Due to the rotation of the decompression tool 3, the boat-shaped locking arm 2
is configured to open the intake and exhaust valves 4 by pushing up.

In this case, the decompression pressure point 6 where the decompression tool 3 presses the rocker arm 2 is set at a point beyond the valve opening point 8 when viewed from the fulcrum 7 of the rocker arm 2, and the decompression pressure point 6 where the decompression tool 3 presses the rocker arm 2 is set at a point beyond the valve opening action point 8, so that the decompression force of the decompression tool 3 , so that the rocker arm 2 is pressed against the lens shape receiving surface 23 of the lens shape support rod with the valve opening action point 8 as the center.

Therefore, the functions of the decompression device will be described.

When the decompression shaft 27 is rotated in the decompression operation direction Q, the decompression tool 3 presses down the decompression pressure point 6 and passes the valve opening application point 8 through the boat-shaped rocker arm 2.
The intake and exhaust valves 4 that are pressed open open and decompress the combustion chamber 5.

After starting, when the decompression shaft 27 is rotated in the decompression release direction P, the decompression tool 3 leaves the decompression pressing point 6, the boat-shaped rocker arm 2 stops pressing the intake and exhaust valves 4, and the decompression state is released. Ru.

In the above decompression operation, the rocker arm 2 is pressed against the lens shape receiving surface 23 of the lens shape support rod.
There is no rattling in the Rocker Arm 2, ensuring stable decompression operation.

As described above, the present invention is based on the boat-shaped rock arm 2 made of sheet metal.
When performing a decompression operation via the valve, the decompression pressing point 6 is positioned away from the valve opening application point 8.

Therefore, the present invention can be applied not only to diesel engines but also to electroplated overhead valve engines.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention, FIG. 1 is a longitudinal sectional front view of the main part around the rocker arm chamber of an overhead valve diesel engine, FIG. 2 is a schematic explanatory diagram of the boat-shaped rocker arm, and FIG. FIG. 2 is a view corresponding to an earlier type of boat-shaped rocker arm, and FIG. 4 is a view corresponding to FIG. 2 showing a conventional example of a boss-type rocker arm. 1... Valve gear, 2... Boat-shaped rocker arm, 3
... Decompression tool, 4 ... Intake and exhaust valve, 5 ... Combustion chamber, 6 ... Pressing point for decompression, 7 ... Support point of 2,
8...Point of valve opening action.

Claims (1)

[Scope of utility model registration request] Decompression of an overhead valve engine configured to push open the intake and exhaust valves 4 and decompress the combustion chamber 5 by pushing the boat-shaped rocker arm 2 of the valve train 1 of the overhead valve engine E toward the valve opening side with a decompression tool 3. In the device, the decompression press point 6 where the decompression tool 3 presses the rocker arm 2 toward the valve opening side is set at a point beyond the point of action 8 that contacts the intake and exhaust valve 4 when viewed from the fulcrum 7 of the rocker arm 2. A decompression device for an overhead valve engine, characterized by: