JP5395622B2 - Engine and pre-chamber plug attached to the engine - Google Patents

Description

  The present invention comprises a plug body with a cover provided on a plug body that covers an ignition point and forms an ignition chamber. The plug body with a cover is attached to a cylinder head, and the combustion faces the ignition chamber and the piston. The present invention relates to an engine in which a communication portion that communicates with a chamber is provided in the plug cover, and a pre-chamber plug that is attached to the engine.

In a spark ignition engine, in order to ensure stable ignition of a lean air-fuel mixture, a pre-chamber plug having a plug cover that covers an ignition point of the spark plug body and forms an ignition chamber may be provided in the cylinder head.
The pre-chamber plug is configured by providing one or a plurality of communication holes in the plug cover, and the communication holes are configured to communicate the ignition chamber and the combustion chamber. The communication hole allows the air-fuel mixture of combustion air and fuel sucked into the combustion chamber in the intake stroke to flow into the ignition chamber from the combustion chamber mainly in the compression stroke, and the air-fuel mixture in the ignition chamber in the combustion expansion stroke. A combustion flame formed by spark ignition is ejected from the ignition chamber to the combustion chamber. In the combustion chamber, the air-fuel mixture is combusted by the combustion flame ejected from the communication hole (see Patent Documents 1 and 2).

  Further, in the spark ignition engine similarly provided with the pre-chamber plug, as an arrangement of the communication path in the pre-chamber plug, the opening area of the communication hole provided toward the intake valve side is provided toward the exhaust valve side. What is comprised larger than the opening area of a communicating hole is known (refer patent document 3).

JP 2007-77902 A JP 2007-40174 A JP-A 51-55813

  In the engine provided with the pre-chamber plug described in Patent Documents 1 and 2, the air-fuel mixture introduced from the combustion chamber to the ignition chamber through the communication hole in the compression stroke is due to a small opening area of the communication hole. There is a problem that the inflow of the air-fuel mixture into the ignition chamber is limited, it is difficult to sufficiently mix with the exhaust gas remaining in the ignition chamber, the fuel concentration around the ignition point is lowered, and the ignitability is deteriorated. Further, when the air-fuel mixture is diluted, this problem becomes remarkable, and the lean limit (limit of air-fuel mixture dilution) is limited.

  In the engine provided with the pre-chamber plug described in Patent Document 3, since the opening area of the communication hole provided toward the intake valve side is large, mixing from the combustion chamber to the ignition chamber via the communication hole is performed. The inflow of qi can be promoted. However, since the opening area between the communicating portion provided on the intake bubble side and the communicating portion provided on the exhaust valve side has a size relationship, the flow rate and flow velocity of the combustion flame that is ejected from the ignition chamber to the combustion chamber through the communicating portion, etc. Is different between the intake valve side and the exhaust valve side, and the ejection of the combustion flame to the combustion chamber becomes uneven, and there is a problem that the state of the flame ejection to the combustion chamber cannot be made uniform.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an engine having a plug body with a cover in which a plug cover that covers an ignition point and forms an ignition chamber is provided on the plug body. An engine that can promote the inflow of the air-fuel mixture from the combustion chamber to the ignition chamber through the communication hole provided in the combustion chamber, and can make the flame injection state to the combustion chamber uniform and a desired state The point is to provide a chamber plug.

The engine of the present invention for achieving the above object comprises a plug body with a cover provided on a plug body that covers an ignition point and forms an ignition chamber, and the plug body with a cover is attached to a cylinder head, The plug cover is provided with a communication portion that communicates the ignition chamber and the combustion chamber facing the piston,
The characteristic configuration is that the position of the plug body with the cover is switched between a protruding posture in which the tip of the plug main body protrudes to the inside of the combustion chamber and a retracted posture in which the protruding amount is reduced from the position in the combustion chamber in the protruding posture. Having means,
The opening area of the communicating portion in the protruding posture is set larger than the opening area of the communicating portion in the retracted posture ;
The cover-attached plug body is provided so as to be movable in a retreating direction with respect to the combustion chamber by a pressure change of the combustion chamber,
The exit / retreat posture switching means is provided with a biasing means for biasing the plug main body with the cover toward the protruding side in the retracting direction with respect to the combustion chamber .

According to the above characteristic configuration, the tip of the plug body with cover, that is, the tip of the plug cover, is switched between a protruding posture in which the tip protrudes to the inside of the combustion chamber and a retracted posture in which the protruding amount is reduced from the position in the combustion chamber in the protruding posture. Thus, the opening area of the communicating portion in the protruding posture is larger than the opening area of the communicating portion in the retracted posture.
Thus, for example, in the intake stroke or compression stroke in which the air-fuel mixture flows into the ignition chamber, the cover body with the cover is in a protruding posture to increase the opening area of the communication portion, so that the air-fuel mixture is appropriately transferred from the combustion chamber to the ignition chamber. The mixture can be sufficiently mixed with the exhaust gas remaining in the ignition chamber. As a result, the ignitability in the ignition chamber can be improved, and even when the air-fuel mixture is diluted, the air-fuel mixture can be ignited relatively well, so that the lean limit (the limit of air-fuel mixture dilution) can be extended.
On the other hand, in the combustion expansion process in which the combustion flame is ejected from the ignition chamber, the cover body with the cover is retracted to reduce the opening area of the communication portion, and the flow velocity of the combustion flame ejected from the ignition chamber to the combustion chamber is increased. And misfire during the propagation of the combustion flame can be suppressed.
From the above, in an engine provided with a plug body with a cover provided with a plug cover that covers the ignition point and forms an ignition chamber, the plug cover flows into the ignition chamber from the combustion chamber through the communication hole provided in the plug cover. The mixture can be properly mixed with the exhaust gas remaining in the ignition chamber to expand the lean limit of the mixture, and misfiring can be achieved by increasing the flow rate of the combustion flame that is ejected from the ignition chamber to the combustion chamber through the communication hole. Therefore, it is possible to realize an engine that can suppress the occurrence of the above and can make the jet state of the flame to the combustion chamber uniform and desired.

In addition , according to the above characteristic configuration, the urging means urges the plug main body with the cover toward the protruding side in the retracting direction with respect to the combustion chamber, so that the urging force of the urging means is larger than the pressure of the combustion chamber. Then, the cover main body with the cover is maintained in the state of moving to the side protruding from the combustion chamber by the urging force of the urging means, and is switched to the protruding posture. On the other hand, when the pressure in the combustion chamber rises and becomes larger than the urging force of the urging means, the plug body with the cover moves to the retreating side with respect to the combustion chamber and is switched to the retreat posture. As a result, the plug body with cover can be switched to the protruding position at the later stage of the compression stroke or at the initial stage of the intake stroke or the compression stroke where the pressure in the combustion chamber becomes smaller than the combustion expansion stroke, and the compression stroke in which the pressure in the combustion chamber increases. In the later stage and the combustion expansion stroke, the plug body with the cover can be switched to the retracted posture.

  According to a further characteristic configuration of the engine of the present invention, the urging force of the urging means is set to be larger than the pressure in the combustion chamber in the middle to late period of the exhaust stroke, the intake stroke, and the initial to middle period of the compression stroke. In addition, the pressure is set to be smaller than the pressure in the combustion chamber from the middle stage to the latter stage of the compression stroke, from the early stage to the middle stage of the combustion expansion stroke, and the exhaust stroke.

According to the above characteristic configuration, the urging force of the urging means is set to be larger than the pressure of the combustion chamber during the period from the middle stage to the latter stage of the exhaust stroke, the intake stroke, and the initial stage to the middle stage of the compression stroke. Therefore, the plug body with the cover can be accurately maintained in the protruding posture. As a result, the opening area of the communication portion can be increased from the initial stage to the middle stage of the compression stroke as well as the intake stroke, and the air-fuel mixture can be appropriately guided from the combustion chamber to the ignition chamber via the communication portion.
On the other hand, since the urging force of the urging means is set to be smaller than the pressure of the combustion chamber during the middle to late period of the compression stroke, the initial period to the middle period of the combustion expansion stroke, and the exhaust stroke, a cover is attached. The plug body can be accurately maintained in the retracted position. As a result, when the combustion flame is ejected from the ignition chamber to the combustion chamber, the opening area of the communication portion can be reduced, and the flow rate of the combustion flame ejected from the ignition chamber to the combustion chamber via the communication portion can be reduced. Can be fast.

  A further characteristic configuration of the engine according to the present invention is that the urging means has an urging member disposed between the support member fixed to the cylinder head and the plug body with the cover.

  According to the above characteristic configuration, the cover body with the cover can be switched between the projecting posture and the retracted posture by the biasing means having a relatively simple configuration including the support member and the biasing member, so that the structure can be simplified. Effects such as easy design can be expected. Moreover, the urging member can be set in an appropriate direction for urging the plug main body with the cover, although it has a simple configuration of being arranged between the support member and the plug main body with the cover.

  According to a further characteristic configuration of the engine of the present invention, the communication portion is configured such that, in the retracted position, a portion provided on the base end side of the plug body with the cover is closed by the wall surface of the cylinder head and is in a non-communication state. It is in.

  According to the above characteristic configuration, in the retracted posture, the communication portion is closed by the wall surface of the cylinder head at the base end side of the plug body with the cover and becomes in a non-communication state, and the opening area of the communication portion can be reduced. That is, the part provided on the base end side of the plug body with the cover of the communication portion is appropriately closed even if the plug body with the cover is in the retracted position, even if the valve body is not provided separately. , It becomes a non-communication state.

According to a further characteristic configuration of the engine of the present invention, the communication portion is provided on a distal end side from a distal end side of the plug body with cover and a distal end side communication hole provided on a distal end side of the plug body with cover. A proximal end side communication hole,
In the retracted position, the distal end side communication hole maintains a communication state in which the ignition chamber communicates with the combustion chamber, and the proximal end side communication hole is closed by a wall surface of the cylinder head, and the ignition chamber and the combustion chamber are closed. It is in the point which maintains the non-communication state which does not connect with a combustion chamber.

According to the above characteristic configuration, when the plug body with the cover maintains the projecting posture, the distal end side communication hole and the proximal end side communication hole maintain the communication state in which the ignition chamber and the combustion chamber communicate with each other. That is, in the projecting posture, the communication portion has a larger opening area because the distal end side communication hole and the proximal end side communication hole are opened. Thus, in the projecting posture, the air-fuel mixture flowing from the ignition chamber to the combustion chamber can be appropriately guided, and the air-fuel mixture and the exhaust gas remaining in the ignition chamber can be sufficiently mixed.
On the other hand, when the plug body with the cover is maintained in the retracted posture, the distal end side communication hole maintains a communication state in which the ignition chamber and the combustion chamber communicate with each other, and the proximal end side communication hole includes the ignition chamber and the combustion chamber. Maintain a non-communication state that does not communicate. That is, in the retracted posture, the communication portion opens the distal end side communication hole and closes the proximal end side communication hole, thereby reducing the opening area. Thereby, in a retreat posture, the combustion flame guided from the ignition chamber to the combustion chamber can be ejected at high speed only from the front end side communication hole.

A pre-chamber plug for achieving the above object includes a plug body with a cover in which a plug cover that covers an ignition point and forms an ignition chamber is provided on the plug body, and the plug body with the cover is mounted on a cylinder head of an engine to be mounted. In the state where is mounted, the plug cover is formed in the plug cover to communicate the combustion chamber facing the piston and the ignition chamber formed in the plug cover,
The characteristic configuration is such that the tip of the plug main body with the cover is switched between a protruding posture protruding inward of the combustion chamber and a retracted posture in which the protruding amount is reduced from the position in the combustion chamber in the protruding posture. Having means,
The opening area of the communication portion in the protruding posture is set to be larger than the opening area of the communication portion in the retracted posture.

According to the above characteristic configuration, when the plug body with cover is attached to the cylinder head of the engine to be attached, the tip of the plug body with cover, that is, the tip of the plug cover protrudes to the inside of the combustion chamber. Thus, the retraction posture in which the protrusion amount is reduced from the position in the combustion chamber in the protruding posture is changed, and the opening area of the communicating portion in the protruding posture is larger than the opening area of the communicating portion in the retracting posture.
Thus, for example, in the intake stroke or compression stroke in which the air-fuel mixture flows into the ignition chamber, the cover body with the cover is in a protruding posture to increase the opening area of the communication portion, so that the air-fuel mixture is appropriately transferred from the combustion chamber to the ignition chamber. The mixture can be sufficiently mixed with the exhaust gas remaining in the ignition chamber. As a result, the ignitability in the ignition chamber can be improved, and even when the air-fuel mixture is diluted, the air-fuel mixture can be ignited relatively well, so that the lean limit (the limit of air-fuel mixture dilution) can be extended.
On the other hand, in the combustion expansion process in which the combustion flame is ejected from the ignition chamber, the cover body with the cover is retracted to reduce the opening area of the communication portion, and the flow velocity of the combustion flame ejected from the ignition chamber to the combustion chamber is increased. And misfire during the propagation of the combustion flame can be suppressed.

According to a further characteristic configuration of the pre-chamber plug of the present invention, the cover-attached plug body is provided so as to be movable in a retracting direction with respect to the combustion chamber by a change in pressure of the combustion chamber.
The exit / retreat posture switching means is provided with a biasing means for biasing the plug main body with the cover toward the protruding side in the retracting direction with respect to the combustion chamber.

  According to the above characteristic configuration, the urging means urges the plug main body with the cover toward the protruding side in the retracting direction with respect to the combustion chamber. The attached plug body is maintained in a state of moving to the side protruding from the combustion chamber by the urging force of the urging means, and is switched to the protruding posture. On the other hand, when the pressure in the combustion chamber rises and becomes larger than the urging force of the urging means, the plug body with the cover moves to the retreating side with respect to the combustion chamber and is switched to the retreat posture. As a result, the plug body with cover can be switched to the protruding position at the later stage of the compression stroke or at the initial stage of the intake stroke or the compression stroke where the pressure in the combustion chamber becomes smaller than the combustion expansion stroke, and the compression stroke in which the pressure in the combustion chamber increases. In the later stage and the combustion expansion stroke, the plug body with the cover can be switched to the retracted posture.

  The pre-chamber plug of the present invention is further characterized in that the urging force of the urging means is such that the urging force of the combustion chamber is from the middle stage to the late stage of the exhaust stroke, the intake stroke, and the initial stage to the middle stage of the compression stroke. The pressure is set to be larger than the pressure, and is set to be smaller than the pressure in the combustion chamber from the middle to the latter stage of the compression stroke, the combustion expansion stroke, and the early to middle of the exhaust stroke in the engine to be mounted.

According to the above characteristic configuration, the biasing force of the biasing means is greater than the pressure of the combustion chamber during the period from the middle to the late period of the exhaust stroke of the engine to be mounted, from the initial period to the middle period of the intake stroke, and the compression stroke. Since it is set large, the plug body with the cover can be accurately maintained in the protruding posture. As a result, the opening area of the communication portion can be increased from the initial stage to the middle stage of the compression stroke as well as the intake stroke, and the air-fuel mixture can be appropriately guided from the combustion chamber to the ignition chamber via the communication portion.
On the other hand, the energizing force of the energizing means is set to be smaller than the pressure of the combustion chamber in the period from the middle to the latter of the compression stroke of the engine to be mounted, the period from the early stage to the middle of the combustion expansion stroke, and the exhaust stroke. Therefore, the plug body with the cover can be accurately maintained in the retracted position. As a result, when the combustion flame is ejected from the ignition chamber to the combustion chamber, the opening area of the communication portion can be reduced, and the flow rate of the combustion flame ejected from the ignition chamber to the combustion chamber via the communication portion can be reduced. Can be fast.

  A further characteristic configuration of the pre-chamber plug of the present invention is that the urging means has an urging member disposed between the support member fixed to the cylinder head and the plug body with cover.

  According to the above characteristic configuration, the cover body with the cover can be switched between the projecting posture and the retracted posture by the biasing means having a relatively simple configuration including the support member and the biasing member, so that the structure can be simplified. Effects such as easy design can be expected. Moreover, the urging member can be set in an appropriate direction for urging the plug main body with the cover, although it has a simple configuration of being arranged between the support member and the plug main body with the cover.

  In the pre-chamber plug of the present invention, the communicating portion is configured such that, in the retracted position, the portion provided on the base end side of the plug body with the cover is closed by the wall surface of the cylinder head and is not in communication. It is in the point.

  According to the above characteristic configuration, in the retracted posture, the communication portion is closed by the wall surface of the cylinder head at the base end side of the plug body with the cover and becomes in a non-communication state, and the opening area of the communication portion can be reduced. That is, the part provided on the base end side of the plug body with the cover of the communication portion is appropriately closed even if the plug body with the cover is in the retracted position, even if the valve body is not provided separately. , It becomes a non-communication state.

According to still another feature of the prechamber plug of the present invention, the communication portion is provided on a distal end side communication hole provided on a distal end side of the plug body with the cover and on a proximal end side from a distal end side of the plug body with the cover. A proximal end side communication hole,
In the retracted position, the distal end side communication hole maintains a communication state in which the ignition chamber communicates with the combustion chamber, and the proximal end side communication hole is closed by a wall surface of the cylinder head, and the ignition chamber and the combustion chamber are closed. It is in the point which maintains the non-communication state which does not connect with a combustion chamber.

According to the above characteristic configuration, when the plug body with the cover maintains the projecting posture, the distal end side communication hole and the proximal end side communication hole maintain the communication state in which the ignition chamber and the combustion chamber communicate with each other. That is, in the projecting posture, the communication portion has a larger opening area because the distal end side communication hole and the proximal end side communication hole are opened. Thus, in the projecting posture, the air-fuel mixture flowing from the ignition chamber to the combustion chamber can be appropriately guided, and the air-fuel mixture and the exhaust gas remaining in the ignition chamber can be sufficiently mixed.
On the other hand, when the plug body with the cover is maintained in the retracted posture, the distal end side communication hole maintains a communication state in which the ignition chamber and the combustion chamber communicate with each other, and the proximal end side communication hole includes the ignition chamber and the combustion chamber. Maintain a non-communication state that does not communicate. That is, in the retracted posture, the communication portion opens the distal end side communication hole and closes the proximal end side communication hole, thereby reducing the opening area. Thereby, in a retreat posture, the combustion flame guided from the ignition chamber to the combustion chamber can be ejected at high speed only from the front end side communication hole.

It is sectional drawing of an engine when the plug main body with a cover exists in a protrusion attitude | position. It is sectional drawing of an engine when the plug main body with a cover exists in a retraction position. It is a graph which shows the relationship between each driving | running state of an engine, and the opening area of a communicating hole.

[Overall engine configuration]
As shown in FIG. 1, the engine 1 of the present invention includes a piston 2, a cylinder 4 that houses the piston 2 and forms a combustion chamber 3 together with the top surface 2 a of the piston 2, and a plug with a cover that is attached to the cylinder head 6. The main body 11 is provided. The piston 2 is reciprocated in the cylinder 4 and the intake valve 5 and the exhaust valve (not shown) are opened and closed to open and close the intake stroke, the compression stroke, the combustion expansion stroke, and the exhaust stroke in the combustion chamber 3. Are performed sequentially. Thereby, although illustration is abbreviate | omitted, it is comprised so that the reciprocating motion of piston 2 may be output as a rotational motion of a crankshaft by a connecting rod. Such a configuration is the same as that of a normal four-stroke internal combustion engine.

  The engine 1 uses, for example, city gas (13A), which is gaseous fuel, as the fuel G. In the intake stroke, the intake valve 5 is opened and air and fuel G are supplied from the intake port 8 to the combustion chamber 3. An air-fuel mixture (for example, a lean air-fuel mixture) is sucked. In the compression stroke and the combustion expansion stroke, the air-fuel mixture sucked into the combustion chamber 3 is compressed to burn and expand the fuel G. In the exhaust stroke, the exhaust valve is opened and exhaust gas is discharged from the combustion chamber 3 to an exhaust port (not shown).

  A recess 7 is formed on the top surface 2 a of the piston 2 facing the cylinder head 6. As a result, the combustion chamber 3 is constituted by a space formed by the recess 7 in addition to the space between the top surface 2 a of the piston 2 and the inner surface of the cylinder 4. By forming the combustion chamber 3 in this way, when the piston 2 rises in the compression stroke, a vortex flow from the periphery of the recess 7 toward the center of the recess 7, a so-called squish can be generated.

  The intake port 8 provided in the cylinder head 6 is provided with a fuel supply unit 9 that injects the fuel G with respect to the intake air, and generates an air-fuel mixture (for example, a lean air-fuel mixture). Is configured to do. By opening the intake valve 5, a mixture of air and fuel G (for example, a lean mixture) is sucked into the combustion chamber 3. Here, the fuel ejection amount from the fuel supply unit 9 can be changed, and the mixing ratio of air and fuel G can be changed according to the operating state of the engine 1.

  The cover-attached plug body 11 attached to the cylinder head 6 is provided so that the central axis thereof coincides with the central axis W of the combustion chamber 3. The plug main body 11 with the cover is provided so that the tip end portion thereof is located in the combustion chamber 3 in a state of passing through the communication hole 23 that connects the upper portion of the cylinder head 6 formed in the cylinder head 6 and the combustion chamber 3. Thus, the pressure in the combustion chamber 2 is slidable in the communication hole 23 in the direction in which the combustion chamber 3 is extended and retracted (the vertical direction in FIGS. 1 and 2). A plurality of seal members 21 are provided on the inner wall of the communication hole 23 with a gap between the outer peripheral portion of the plug body 11 with cover and the inner wall of the communication hole 23.

  The plug main body 11 with a cover includes a plug main body 11a and a plug cover 11b that covers the ignition point 22 disposed at the tip end (the lower end in FIGS. 1 and 2) of the plug main body 11a and forms an ignition chamber 14. The plug cover 11b is formed integrally with the plug body 11a. The plug cover 11b is formed in a bottomed cylindrical shape having a base end side as a cylindrical portion 11c and a distal end side as a bottom portion 11d, and is integrally formed with the plug body 11a. Incidentally, the bottom portion 11d on the front end side is formed to have an arc shape in a cross section by a plane passing through the central axis W of the cylinder 4. The plug main body 11 with cover is moved up and down along the central axis W by the exit / retreat attitude switching means 10 described later, and the protruding attitude shown in FIG. 1 and the retraction position shown in FIG. It is possible to switch between postures.

  The plug cover 11b is formed with a plurality of communication holes 15 (an example of a communication portion) for communicating the combustion chamber 3 and the ignition chamber 14. The plug body 11 with a cover sparks and burns the air-fuel mixture flowing into the ignition chamber 14 from the combustion chamber 3 through the communication hole 15, and the combustion flame formed by the combustion is ejected to the combustion chamber 3 through the communication hole 15. It is configured to let you. In this way, the inflow of the air-fuel mixture from the combustion chamber 3 to the ignition chamber 14 and the ejection of the combustion flame from the ignition chamber 14 to the combustion chamber 3 are performed by the plurality of communication holes 15, thereby The intake air-fuel mixture is burned. Here, the air-fuel mixture flowing into the ignition chamber 14 is all the air-fuel mixture flowing from the combustion chamber 3 through the communication hole, and the fuel G and the air-fuel mixture are supplied to the ignition chamber 14 from other than the combustion chamber 3. There is nothing.

As shown in FIG. 1, the communication hole 15 includes a base end side communication hole 15a provided in the cylindrical portion 11c of the plug cover 11b and a front end side communication hole 15b provided in the front end portion 11d of the plug cover 11b. . The opening direction of the base end side communication hole 15a on the side opened to the combustion chamber 3 is configured such that the piston 2 side (the lower side in FIG. 1) faces the opening direction of the front end side communication hole 15b. In addition, the opening direction of the base end side communication hole 15 a and the front end side communication hole 15 b on the side that opens to the ignition chamber 14 is a direction toward the ignition point 22.
A flange 20 is provided at the end of the plug base end of the plug cover 11b, and the top surface of the cylinder head 6 (on the upper side in FIG. The movement of the plug main body 11 with the cover to the lower side is restricted.

[Basic engine operation]
In the engine 1, the piston 2 descends from the top dead center with the intake valve 5 being opened, whereby an intake stroke is performed in which the air-fuel mixture is taken into the combustion chamber 3. Next, when the piston 2 moves up with the intake valve 5 closed, a compression stroke is performed to compress the air-fuel mixture in the combustion chamber 3. In this compression stroke, the volume of the combustion chamber 3 is reduced by the rise from the bottom dead center of the piston 2, so that the air-fuel mixture sucked into the combustion chamber 3 flows into the ignition chamber 14 through the communication hole 15.
The engine 1 operates the plug body 11a at the ignition timing (for example, immediately before top dead center), sparks at the ignition point 22, and ignites the air-fuel mixture in the ignition chamber 14. Then, the combustion in the ignition chamber 14 proceeds, and the combustion flame is ejected to the combustion chamber 3 through the nozzle hole 15. Thereby, the air-fuel mixture in the combustion chamber 3 is combusted and a combustion expansion stroke is performed. Next, when the piston 2 rises with the exhaust valve opened, an exhaust stroke is performed in which the exhaust gas in the combustion chamber 3 is led to the exhaust port and exhausted.
Thus, the engine 1 is configured to repeatedly perform a series of operations for performing each stroke in the order of the intake stroke, the compression stroke, the combustion expansion stroke, and the exhaust stroke.

The pre-chamber plug of the present invention includes a plug body 11 with a cover and an exit / exit posture switching means 10 for switching the posture. Below, the structure and function of the leaving / exiting posture switching means 10 will be described.
[Exit and exit posture switching means]
As shown in FIG. 1, a protruding posture in which the tip of the plug main body 11 with the cover protrudes to the inside of the combustion chamber 3 and a retracted posture in which the protruding amount is reduced from the position in the combustion chamber 3 in the protruding posture as shown in FIG. 2. The exit / exit posture switching means 10 is provided.
Here, the protruding posture is a posture in which the cylindrical portion 11c of the plug cover 11b protrudes to the inside of the combustion chamber 3, and the retracting posture is a cylinder head from the inside of the combustion chamber 3 to the cylinder head 11c. The posture is retired toward the 6th side.

The exit / retreat posture switching means 10 for switching the cover-attached plug main body 11 between a projecting posture and a retracted posture is constituted by an urging means that urges the cover-attached plug main body 11 toward the projecting side in the retracting direction with respect to the combustion chamber 3. Yes. The biasing means includes a coil spring 13 (corresponding to a biasing member) disposed between the support member 12 fixed to the cylinder head 6 and the plug main body 11 with a cover. It is composed of The support member 12 is formed in a U shape whose upper side is closed, and is disposed so as to cover the communication hole 23 formed in the cylinder head 6. And the plug main body 11 with a cover is provided in a state where the plug main body 11a penetrates the portion where the support member 12 is closed, and the flange portion 20 of the plug cover 11b of the plug main body 11 with the cover and the support member 12 are closed. A coil spring 13 is disposed between the two parts. The support member 12 and the coil spring 13 can be provided on the top surface side of the cylinder head 6, that is, at a position away from the combustion chamber 3. Thereby, since it can suppress that the heat | fever of the combustion flame inside the combustion chamber 3 propagates with respect to the support member 12 and the coil spring 13, a material with comparatively low heat resistance can also be used, and a design freedom improves. .
In the present invention, the opening area of the communication portion 15 is changed by the exit / retreat posture switching means 10 including the support member 12 and the coil spring 13 disposed outside the combustion chamber 3. For this reason, it is not necessary to provide the components (for example, valve body etc.) for changing the opening area of a communicating part inside the combustion chamber 3. FIG.

  In the direction along the central axis W, the urging force F of the coil spring 13 is set to be larger than the pressure in the combustion chamber 3 in the middle to late period of the exhaust stroke, the intake stroke, and the early to middle periods of the compression stroke, as shown in FIG. In addition, the pressure is set to be smaller than the pressure in the combustion chamber 3 from the middle stage to the latter stage of the compression stroke, from the early stage to the middle stage of the combustion expansion stroke, and the exhaust stroke.

  That is, since the urging force F of the coil 13 is larger than the pressure of the combustion chamber 3 from the middle stage to the latter stage of the exhaust stroke, from the initial stage to the middle stage of the intake stroke, and the compression stroke, the plug main body 11 with the cover acts on the combustion chamber 3. The plug cover 11b moves to the protruding side in the retracting direction, and the plug cover 11b has a limit position on the plug tip side (lower side in FIG. 1) (position where the flange 20 of the plug cover 11b contacts the top surface of the cylinder head 6). It protrudes to a protruding posture. On the other hand, since the biasing force F of the coil spring 13 is smaller than the pressure of the combustion chamber 3 from the middle to the latter of the compression stroke, from the early stage to the middle of the combustion expansion stroke, and from the exhaust stroke, the plug main body 11 with the cover acts on the combustion chamber 3. The plug cover 11b is retracted to the plug base end side (the upper side in FIG. 2) and assumes the retracted position.

As a result, in the protruding posture from the middle stage to the late stage of the exhaust stroke, the intake stroke, and the initial stage to the middle stage of the compression stroke, as shown in FIG. 3, the proximal end side communication holes 15a provided in the cylindrical portion 11c of the plug cover 11b and Both the front end side communication holes 15b provided in the front end portion 11d, that is, all the communication holes 15 are opened. On the other hand, in the retreat posture from the middle to the latter of the compression stroke, the combustion expansion stroke, and the early to middle of the exhaust stroke, as shown in FIG. 3, the proximal communication hole 15a is closed and only the distal communication hole 15b is open. It becomes.
In particular, in the intake stroke or the like, the cover-attached plug body 11 is in a protruding posture, both the base end side communication hole 15a and the front end side communication hole 15b are opened, and the opening area can be increased. The air-fuel mixture flowing into the engine can be appropriately guided, and the air-fuel mixture and the exhaust gas can be appropriately mixed in the ignition chamber 14. Thereby, since the ignitability in the ignition chamber 14 can be improved, even when the air-fuel mixture is diluted, the air-fuel mixture can be ignited relatively well, and the lean limit (limit of air-fuel mixture dilution) can be extended. .
On the other hand, in particular, in the combustion expansion process, the plug body 11 with cover is in a retracted posture, and only the distal end side communication hole 15b is opened, and the opening area can be reduced, so that the combustion flame ejected from the ignition chamber 14 to the combustion chamber 3 It is possible to increase the flow velocity, and to suppress misfiring of the combustion flame in the combustion chamber 3.

[Position in the direction along the central axis W of the communication hole in the protruding posture]
The communication hole 15 in the projecting posture has a base end side communication hole 15 a and a distal end side communication hole 15 b (all communication holes 15) protruding from the lower surface of the cylinder head 6 toward the piston 2 in the direction along the central axis W. Located in position. At this time, all the communication holes 15 are in a communication state.

[Position of the communication hole in the central axis W direction in the retracted position]
The proximal end side communication hole 15a provided in the cylindrical portion 11c of the plug cover 11b in the retracted position is a wall surface of the cylinder head 6, that is, the inner wall of the communication hole 23 in the direction perpendicular to the central axis W as shown in FIG. It will be in the state closed at. A plurality of seal members 21 provided between the inner wall of the communication hole 23 and the plug cover 11b are provided in the direction along the central axis W, but the base end side communication hole 15a is provided in the seal member 21. Of these, it is preferable to retreat to the plug base end side (upward side in FIG. 2) from the same position as that closest to the combustion chamber 3. Thereby, it can prevent much more reliably that a combustion flame ejects to the combustion chamber 3 through the base end side communication hole 15a.

[Operation of exit / exit posture switching means associated with basic engine operation]
Next, the operation of the exit / retreat posture switching means 10 in each of the intake stroke, compression stroke, combustion expansion stroke, and exhaust stroke of the engine 1 is based on the relationship between the biasing force of the coil spring 13 and the pressure of the combustion chamber 3 shown in FIG. I will explain. Incidentally, the pressure in the combustion chamber 3 shown in FIG. 3 illustrates the pressure in the combustion chamber 3 in a general engine.
In the intake stroke, the intake valve 5 opens and maintains the open state, and the mixture of combustion air and fuel G is guided from the intake port 8 to the combustion chamber 3. At this time, since no combustion or the like occurs in the combustion chamber 3, the pressure is relatively low. Therefore, the cover-attached plug body 11 is urged downward by the coil spring 13 and is located at the limit protruding position (position where the flange portion 20 of the plug cover 11b contacts the top surface of the cylinder head 6). At this time, both the base end side communication hole 15a and the front end side communication hole 15b are open (the plug main body 11 with the cover maintains the state shown in FIG. 1). Thus, in the intake stroke in which the air-fuel mixture flows into the ignition chamber 14, the plug body 11 with the cover maintains a protruding posture, increases the opening area of the communication hole 15, and mixes from the combustion chamber 3 to the ignition chamber 14. The air can be guided appropriately, and the air-fuel mixture and the exhaust gas remaining in the ignition chamber 14 can be sufficiently mixed.

From the initial stage to the middle stage of the compression stroke, the intake valve 5 is closed and closed, and the piston 2 moves from the bottom dead center toward the top dead center. Increases gradually as the piston 2 moves. In this case, the urging force F of the coil spring 13 is set to be larger than the pressure inside the combustion chamber 3 as shown in FIG. 3, so that the plug body 11 with the cover maintains the protruding posture (plug body with cover). 11 maintains the state of FIG.
Thereby, in the compression stroke or the like in which the air-fuel mixture flows from the combustion chamber 3 to the ignition chamber 14, the cover body 11 with the cover is made to protrude to increase the opening area of the communication hole 15, and from the combustion chamber 3 to the ignition chamber 14. By appropriately guiding the air-fuel mixture, the air-fuel mixture and the exhaust gas remaining in the ignition chamber 14 can be mixed well.

  In the middle stage of the compression stroke, as shown in FIG. 3, there is a time when the pressure increased in the combustion chamber 3 and the biasing force per unit area of the coil spring 13 are suspended. Then, the pressure inside the combustion chamber 3 becomes higher than the biasing force per unit area of the coil spring 13, and the plug main body 11 with the cover starts to gradually move from the inside to the outside of the combustion chamber 3 (the plug main body with the cover). 11 is a subsequent state from FIG. 1 to FIG.

When the middle stage of the compression stroke passes and the latter stage of the compression stroke starts, the pressure inside the combustion chamber 3 increases and becomes smaller than the urging force per unit area of the coil spring 13. Thereby, the plug main body 11 with a cover will be in a completely retracted posture as shown in FIG. Along with this, the plug base end side communication hole 15a is closed. The plug main body 11 with the cover maintains the retracted posture from the period in which the pressure of the combustion chamber 3 is increased in the combustion expansion stroke to the middle stage of the exhaust stroke, and closes the base end side communication hole 15a (cover). The plug main body 11 is in the state shown in FIG.
Thereby, in a combustion expansion stroke in which a combustion flame is ejected from the ignition chamber 14 to the combustion chamber 3, the plug body 11 with a cover is retracted to reduce the opening area of the communication hole 15, and from the ignition chamber 14 to the combustion chamber. The flow velocity of the combustion flame ejected to 3 can be increased, and the combustion flame can be appropriately propagated to the combustion chamber 3 while suppressing misfire during the propagation of the combustion flame.

After the middle stage of the exhaust stroke, the pressure per unit area of the coil spring 13 again becomes higher than the pressure in the combustion chamber 3, and the plug body 11 with the cover maintains the protruding posture (the plug body 11 with the cover is shown in FIG. 1). Return to state).
[Another embodiment]

(A)
In the above embodiment, the communication hole 15 is shown as comprising the proximal end side communication hole 15a and the distal end side communication hole 15b, but from the plug proximal end side (upper side in FIG. 1) to the plug distal end side (in FIG. 1). It is good also as what consists of a slit-shaped communicating groove | channel provided continuously (lower side). In this case, the slit-shaped communication groove is provided in the cylindrical portion 11c of the slit-shaped communication groove when the plug main body 11 with the cover is in the projecting posture, and all the slit-shaped communication grooves are in the communication state. It is preferable that the provided part is in a communication state, and the part provided in the distal end portion 11d is provided in a position where the connection part is not in communication.

(B)
In the description so far, the installation structure of the plug main body 11 with the cover and the plug main body 11 with the cover is integrally configured by the plug cover 11b and the plug main body 11a. The embodiment in which the posture switching means 10 is switched between the projecting posture and the retirement posture is shown. However, in the installation structure of the plug body 11 with a cover and the plug body 11 with a cover according to the present invention, the plug cover 11b is separated from the plug body 11a, and only the plug cover 11b has a protruding posture by the exit / retreat posture switching means 10. You may comprise so that it can switch to a retirement attitude | position.

  The engine of the present invention and the pre-chamber plug to be mounted on the engine include a plug cover with a cover provided with a plug cover that covers the ignition point and forms an ignition chamber. The air-fuel mixture flowing from the combustion chamber to the ignition chamber through the holes can be appropriately mixed with the exhaust gas remaining in the ignition chamber to extend the lean limit of the air-fuel mixture, and from the ignition chamber to the combustion chamber through the communication holes. The engine can be effectively used as an engine capable of reducing the risk of misfire and a pre-chamber plug attached thereto.

DESCRIPTION OF SYMBOLS 1: Engine 2: Piston 3: Combustion chamber 6: Cylinder head 10: Withdrawing / retreating attitude switching means 11: Plug main body 11a with a cover: Plug main body 11b: Plug cover 11c: Cylindrical part 11d of a plug cover: Tip part 12 of a plug cover : Support member 13: Coil spring 15: Communication hole (an example of a communication part)
15a: Base end side communication hole 15b: Front end side communication hole 22: Ignition point

Claims (10)

A plug cover that covers the ignition point and forms an ignition chamber has a plug body with a cover provided on the plug body, and the plug body with the cover is attached to a cylinder head, and communicates the ignition chamber and the combustion chamber facing the piston. An engine provided in the plug cover,
A retracting posture switching means for switching between a protruding posture in which the tip of the plug main body with the cover protrudes to the inside of the combustion chamber and a retracted posture in which the protruding amount is reduced from a position in the combustion chamber in the protruding posture;
The opening area of the communicating portion in the protruding posture is set larger than the opening area of the communicating portion in the retracted posture ;
The cover-attached plug body is provided so as to be movable in a retreating direction with respect to the combustion chamber by a pressure change of the combustion chamber,
The exit / retreat posture switching means includes an urging means for urging the plug main body with the cover toward a projecting side in a retreat direction with respect to the combustion chamber . The urging force of the urging means is set to be larger than the pressure in the combustion chamber in the middle to late period of the exhaust stroke, the intake stroke, and the initial to middle period of the compression stroke, and is combusted in the middle to late period of the compression stroke. The engine according to claim 1 , wherein the engine is set to be smaller than the pressure of the combustion chamber in the initial stage to the middle stage of the expansion stroke and the exhaust stroke. It said biasing means, an engine according to claim 1 or 2, is disposed a biasing member between the said covered plug body and the support member fixed to the cylinder head. The communication unit is in the retracted position, a portion provided on the proximal side of the cover with the plug body, according to any one of claims 1 to 3 in a non-communicated state is closed by the wall surface of the cylinder head Engine. The communication part has a distal end side communication hole provided on the distal end side of the plug body with cover, and a proximal end side communication hole provided on the proximal side from the distal end side of the plug body with cover,
In the retracted position, the distal end side communication hole maintains a communication state in which the ignition chamber communicates with the combustion chamber, and the proximal end side communication hole is closed by a wall surface of the cylinder head, and the ignition chamber and the combustion chamber are closed. The engine according to any one of claims 1 to 4, wherein a non-communication state in which the combustion chamber is not communicated is maintained. A combustion chamber facing the piston in a state in which the plug cover that covers the ignition point and forms the ignition chamber has a plug body with a cover provided on the plug body, and the plug body with the cover is mounted on the cylinder head of the engine to be mounted A pre-chamber plug formed in the plug cover with a communication portion that communicates with the ignition chamber formed in the plug cover,
A retracting posture switching means for switching a tip end of the plug main body with the cover to a projecting posture projecting inward of the combustion chamber and a retreating posture in which a projecting amount is reduced from a position in the combustion chamber in the projecting posture;
The opening area of the communicating portion in the protruding posture is set larger than the opening area of the communicating portion in the retracted posture ;
The cover-attached plug body is provided so as to be movable in a retreating direction with respect to the combustion chamber by a pressure change of the combustion chamber,
The exit / retreat posture switching means is a pre-chamber plug provided with an urging means for urging the plug main body with cover toward the protruding side in the exit / retreat direction with respect to the combustion chamber. The urging force of the urging means is set to be larger than the pressure of the combustion chamber in the middle to late period of the exhaust stroke in the engine to be mounted, the intake stroke, and the initial to middle of the compression stroke, and the mounting The pre-chamber plug according to claim 6 , wherein the pre-chamber plug is set to be smaller than the pressure of the combustion chamber in the middle to late stage of the compression stroke, the combustion expansion stroke, and the exhaust stroke in the target engine. It said biasing means, pre-chamber plug according to claim 6 or 7 which is disposed a biasing member between the said covered plug body and the support member fixed to the cylinder head. The communication unit is in the retracted position, a portion provided on the proximal side of the cover with the plug body, to any one of claims 6 to 8 in a non-communicated state is closed by the wall surface of the cylinder head The pre-chamber plug as described. The communication part has a distal end side communication hole provided on the distal end side of the plug body with cover, and a proximal end side communication hole provided on the proximal side from the distal end side of the plug body with cover,
In the retracted position, the distal end side communication hole maintains a communication state in which the ignition chamber communicates with the combustion chamber, and the proximal end side communication hole is closed by a wall surface of the cylinder head, and the ignition chamber and the combustion chamber are closed. The pre-chamber plug according to any one of claims 6 to 9, wherein a non-communication state that does not communicate with the combustion chamber is maintained.

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