JPH03258930A - Internal combustion engine - Google Patents

Abstract

PURPOSE:To stabilize output regardless of the compression ratio in an internal combustion engine forming a combustion chamber loaded with a sparking plug in its cylinder head by constituting a part of the combustion chamber including the sparking plug by a different block capable of being advanced or retracted in a cylinder head body. CONSTITUTION:In a cylinder head 2, a combustion chamber 7 is formed in accordance with a cylinder 1c. The middle part of the combustion chamber 7 is constituted by a block 2b different from a cylinder head body 2a, and a sparking plug 8 is loaded into the center part of the block 2b. On the block 2b, thread parts 9a, 9b in the two, upper and lower steps are provided, and the block is screwed into the cylinder head body 2a with the thread part 9a so that the block can be advanced or retracted, and further the thread part 9b fixes the block 2b positively. When the compression ratio is changed, the block 2b is advanced or retracted with respect to the cylinder head body 2a with the sparking plug 8 held integrally with it, and thereby the relative position of ignition part of the sparking plug 8 and the surrounding wall surface of the combustion chamber is not changed in any way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an internal combustion engine that has a variable compression ratio with a simple configuration.

[Prior art] Conventionally, as an internal combustion engine with variable compression ratio,
As disclosed in Japanese Patent No. 129426, it has been proposed that a rotating rod with a semicircular cross section is installed on the wall of the combustion chamber, and the volume of the combustion chamber is changed by appropriately rotating the rotating rod. . However, in this internal combustion engine, the rod with a semicircular cross section makes the wall surface of the combustion chamber convex or concave near the ignition plug, so there is a difference between the ignition plug (ignition part) and the wall surface of the combustion chamber in the vicinity. Each time the relative position changes and the compression ratio changes, the flame propagation conditions change,
There is a problem that stable output cannot be obtained.

[Problem B to be Solved by the Invention] In view of the above-mentioned problems, an object of the present invention is to provide an internal combustion engine that can stabilize the output by changing the compression ratio so as not to substantially change the flame propagation state. It's about doing.

[Means for Solving the Problems] In order to achieve the above object, the internal combustion engine of the present invention includes a combustion chamber including a spark plug, in which a part of the combustion chamber is formed by a separate block that can move forward and backward with respect to the cylinder head body. It is characterized by the fact that

With this configuration, when changing the compression ratio, the ignition part of the spark plug and the wall surface of the combustion chamber around it move together, and the relative position of the two does not change, so the flame propagation state changes depending on the change in the compression ratio. can be kept from changing too much. Therefore, the output can be stabilized regardless of the compression ratio.

〔Example〕

The figure shows a two-cycle engine according to an embodiment of the present invention.
is a cylinder block, and 2 is a cylinder head. A piston 3 is fitted into the cylinder lc of the cylinder block 1 so as to reciprocate. An intake port is provided at a lower position (not shown), and a scavenging passage 4 and an exhaust passage 5 are provided above. A control valve 6 for adjusting exhaust timing is provided at the entrance of the exhaust passage 5, and protrudes as shown in the figure at low speeds and retracts inward at high speeds.

A combustion chamber 7 is formed in the cylinder head 2 in correspondence with the cylinder IC. The combustion chamber 7 has a central portion formed by a block 2b separate from the cylinder head main body 2a, and an ignition plug 8 is mounted at the center of the block 2b.

The block 2b is provided with two upper and lower threaded portions 9a and 9b, of which the lower threaded portion 9a is screwed into the cylinder head body 2a so that it can move forward and backward. Therefore, by moving this block 2b back and forth, the volume of the combustion chamber 7 changes, thereby making it possible to change the compression ratio.

On the other hand, a lock nut 11 is screwed into the upper screw portion 9b, and by tightening the lock nut 11 when the block 2b is set at a predetermined advance/retreat position, the position can be reliably fixed. Further, an O-ring IO is provided between the upper and lower screw portions 9a and 9b to seal the combustion chamber 7 from the outside.

Further, the block 2b and the lock nut 11 have engagement recesses 12 and 13 formed in their respective outer peripheral ears. A screwing operation can be performed by engaging a tool such as a wrench with each of these.

In the internal combustion engine, when changing the compression ratio as described above, the programmer 2b with the spark plug 8 attached thereto moves forward and backward with respect to the cylinder head body 2a, so the ignition part of the spark plug 8 and its The relative positions of the surrounding combustion chamber walls do not change at all. Therefore, even if the compression ratio is changed, the flame propagation state does not substantially change, and therefore the output can be stabilized regardless of the compression ratio.

In addition, although the above-mentioned embodiment explained the case of a two-cycle engine, the present invention can also be applied to a four-stroke engine.

〔Effect of the invention〕

As mentioned above, in the internal combustion engine of the present invention, a part of the combustion chamber including the ignition plug is constructed as a separate block that can move forward and backward with respect to the cylinder head body, so the compression ratio can be adjusted by moving this block forward and backward. When changing, the relative position between the ignition part of the ignition plug and the wall surface of the combustion chamber around it is not changed, so the state of flame propagation is not changed.

Therefore, the output can be stabilized regardless of the compression ratio.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an internal combustion engine according to an embodiment of the present invention;
FIG. 2 is a view taken in the direction of the ■ arrow in FIG. 1... Cylinder block, 2... Cylinder head,
2a...Cylinder head body, 2b...Block,
7... Combustion chamber, 8... Ignition plug, 9a, 9b... Threaded portion, 11... Lock nut.

Claims (1)

[Claims] In an internal combustion engine in which a combustion chamber is formed in a cylinder head and an ignition plug is attached to the combustion chamber, a part of the combustion chamber including the ignition plug is formed by a separate block that can move forward and backward with respect to the cylinder head main body. Internal combustion engine.