JP5555030B2 - Engine and spark plug provided therein - Google Patents

Description

The present invention provides an engine in which a spark plug having an ignition chamber inside a plug cover that covers an ignition point is mounted on a cylinder head, and a communication hole that communicates the ignition chamber and a combustion chamber facing a piston is provided in the plug cover. And a spark plug for realizing the engine.

In an engine including an ignition plug having a communication hole between an ignition chamber (referred to as a pre-chamber or a sub chamber) and a combustion chamber, combustion (particularly combustion in the combustion chamber) proceeds in the following manner.
That is, in the compression stroke, the mixture of fuel and combustion air flows into the ignition chamber due to the rise of the piston. In the expansion stroke, the mixture in the ignition chamber is spark-ignited, and the combustion flame formed in the ignition chamber is Through the communication hole, the fuel is ejected from the ignition chamber to the combustion chamber, and the air-fuel mixture in the combustion chamber is ignited (see Patent Documents 1 and 2).
Thus, in an engine equipped with an ignition chamber, the air-fuel mixture that has entered the ignition chamber is spark-ignited, the air-fuel mixture in the ignition chamber is once burned, and the combustion flame is ejected from the communication hole into the combustion chamber. Qi can be burned well. At this time, the combustion flame ejected from the communication hole spreads rapidly in the combustion chamber, so that stable combustion can be realized even when lean combustion is performed using, for example, city gas having low combustibility.

JP 2007-77902 A JP 2007-40174 A

In an engine using a pre-chamber type spark plug as described above, the temperature of the plug cover head (sometimes called a cup) is low when the engine is in a cold state, so that the temperature that inhibits combustion near the ignition point. Therefore, there are cases where it is harder to ignite than a normal spark plug.
Therefore, at the time of cold start, there is a high ratio of misfire cycles, and engine start may fail, making it difficult to ensure stable start. Further, during such cold start, combustion is likely to be unstable, and there is room for improvement in terms of combustion efficiency, and there is also room for improvement in terms of unburned hydrocarbon emissions.

  The present invention has been made paying attention to such a point, and an object of the present invention is to obtain an engine that can be stably started even when the engine is provided with a pre-chamber spark plug, and to prepare for it. The point is to provide a spark plug.

In order to achieve the above object, an ignition plug having an ignition chamber inside the plug cover covering the ignition point is mounted on the cylinder head, and a communication hole that connects the ignition chamber and the combustion chamber facing the piston is formed in the plug cover. The characteristic configuration of the engine is
When the spark plug is mounted on the cylinder head, the spark cover is provided on the plug cover head facing the combustion chamber and on the base end side of the plug cover head, and the spark plug is mounted on the cylinder head. With a plug cover base end that bears
A heating means capable of heating the plug cover head;
Control means for controlling one or both of the cranking start timing and the ignition start timing at the time of starting the engine based on the temperature of the plug cover head that is heated with heating by the heating means. That is.

In this engine, the plug cover head is heated by the heating means when the engine is started and before the cranking start timing and ignition start timing. Then, one or both of the cranking start timing and the ignition start timing is adjusted according to the temperature of the plug cover head. As a result, ignition can be started with the plug cover head heated to some extent. Therefore, the air-fuel mixture entering the ignition chamber is heated even during cold start, the cooling loss in the plug cover head is reduced, and the temperature of the air-fuel mixture in the ignition chamber at the ignition timing after compression is higher than before. can do. As a result, ignition with the spark plug is facilitated. Further, in a state where a flame kernel is formed in the vicinity of the ignition position immediately after ignition, it is difficult to extinguish the flame because the temperature of the surrounding wall surface is high.
As a result, it is possible to reduce the ratio of the cycle that misfires even during the cold start, and it is possible to perform a stable start without failing the engine start even during the cold start. Moreover, since combustion is stabilized, combustion efficiency is improved, and unburned hydrocarbon emissions are also reduced.
In the engine of this configuration, when the cranking is started according to the temperature of the plug cover head, as a starting method, the plug cover head facing the combustion chamber in the mounted state mounted on the cylinder head, With respect to the spark plug provided on the base end side of the plug cover head, and provided with a plug cover base end portion for mounting the spark plug to the cylinder head,
Performing a heating step of heating the plug cover head by a heating means;
After the temperature of the plug cover head, which is raised with the heating in the heating process, reaches the cranking start temperature, a cranking process for performing cranking is performed, and then by spark discharge between the electrodes of the spark plug. It will shift to the spark ignition stroke to ignite.

In the above configuration, cranking was started on the condition that the temperature of the plug cover head reached the cranking start temperature, but heating by the heating means was performed for a predetermined time, and the plug cover head was heated to some extent. Even if cranking is started in the state, the same operation and effect as described above can be obtained.
When this configuration is adopted, an ignition plug having an ignition chamber inside the plug cover that covers the ignition point is attached to the cylinder head, and a communication hole that connects the ignition chamber and the combustion chamber facing the piston is provided in the plug cover. To the engine
When the spark plug is mounted on the cylinder head, the spark cover is provided on the plug cover head facing the combustion chamber and on the base end side of the plug cover head, and the spark plug is mounted on the cylinder head. With a plug cover base end that bears
A heating means capable of heating the plug cover head;
Control means for starting cranking when the engine is started after heating by the heating means for a certain period of time may be provided.

In the configurations described so far, the heating means includes a heating mechanism provided at the plug cover head and a heating mechanism provided at the base end of the plug cover that is thermally connected to the plug cover head. Either one or both can be used.
More specifically, the heating means can be a heating mechanism including a resistance heating element provided on the plug cover head. On the other hand, the purpose of heating can also be achieved by providing a resistance heating element at the base end portion of the plug cover and heating the plug cover head by heat transfer from this portion.

An ignition plug capable of exhibiting the above-described operations and effects includes a plug body having an ignition point, and a plug cover attached to the plug body so as to cover the ignition point, and a cylinder head of an engine to be mounted A spark plug in which a plurality of communication holes are formed in the plug cover for connecting the combustion chamber facing the piston and the ignition chamber formed in the plug cover in a state where the plug body and the plug cover are mounted on the plug cover. As
With the spark plug mounted on the cylinder head, the plug cover head facing the combustion chamber is provided on the base end side of the plug cover head, and the spark plug is mounted on the cylinder head. With a plug cover base end to carry,
A heating means capable of heating the plug cover head;
The heating means may be a spark plug configured as a heating element provided across the plug cover head.

  Further, the engine described above is provided with temperature detecting means for detecting the temperature of the plug cover head, and the control means is based on the temperature of the plug cover head detected by the temperature detecting means. Thus, if one or both of the cranking start timing and the ignition start timing at the time of starting the engine are controlled, the temperature of the plug cover head is directly detected and the cranking at the time of starting the engine is appropriately performed. Either or both of the ranking start timing and the ignition start timing can be controlled.

Schematic configuration diagram of an engine of the present invention and a spark plug provided therein Cross-sectional view in the horizontal plane passing through the communication hole of the plug cover Bottom view of plug cover head Time chart showing temperature change, cranking and ignition start of the plug cover head when the engine starts Diagram showing control flow at engine startup

[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 spark plug 11 that is attached to the cylinder head 6. And is configured. 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. Thus, the reciprocating motion of the piston 2 is output as the rotational motion of the crankshaft C by the connecting rod. Such a configuration is the same as that of a normal four-stroke engine. The crankshaft C is provided with a cell motor M for ensuring the rotation of the crankshaft without causing combustion in the combustion chamber 3 in the initial stage of startup.

  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 and combusted. In the exhaust stroke, the exhaust valve is opened, and the combustion 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 injection 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 spark plug 11 includes a plug main body 12 and a plug cover 13 that covers an ignition point (not shown) provided at the tip end portion (lower end portion in FIG. 1) of the plug main body 12 and forms an ignition chamber 14. The plug cover 13 and the plug body 12 are integrated. As shown in FIG. 1, with the spark plug 11 mounted on the cylinder head 6, the plug cover head 13a facing the combustion chamber 3 and the base end side of the plug cover head 13a are provided. And a plug cover base end portion 13b for mounting to the cylinder head 6 . The plug cover head portion 13a is formed in a bottomed cylindrical shape, and in a cross-sectional view by a plane passing through the central axis of the combustion chamber 3 (axis along the straight line W in FIG. 1), the distal end side of the plug main body 12 (downward in FIG. It has a dome shape with a vertex on the side.
The plug body 12 is provided so that its central axis coincides with the central axis of the combustion chamber 3 (axis along the straight line W in FIG. 1). The spark plug 11 is provided so that the plug cover head 13 a protrudes into the combustion chamber 3 in a state of passing through the opening 20 that connects the upper portion of the cylinder head 6 formed in the cylinder head 6 and the combustion chamber 3. ing.

  In the plug cover 13 (specifically, the plug cover head portion 13a), a plurality of communication holes 15 for communicating the combustion chamber 3 and the ignition chamber 14 are formed. The spark plug 11 sparks and ignites the air-fuel mixture flowing into the ignition chamber 14 from the combustion chamber 3 through the communication hole 15, and jets the combustion flame formed by the combustion into the combustion chamber 3 through the communication hole 15. It is configured. 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 15, and the fuel G and the air-fuel mixture are supplied to the ignition chamber 14 from other than the combustion chamber 3. Never happen.

  The control device 40 is constituted by a microprocessor or the like that can execute a program for controlling the engine 1. The control device 40 is configured to control the timing of spark discharge between the center electrode 16a of the spark plug 11 and the ground electrode 16b.

[Basic engine operation]
In the engine 1, for example, in a steady operation such as a rated operation, the piston 2 descends from the top dead center with the intake valve 5 being opened, so that an intake stroke for sucking an air-fuel mixture into the combustion chamber 3 is performed. . Next, the piston 2 ascends while the intake valve 5 and the exhaust valve are closed, thereby performing a compression stroke for compressing the air-fuel mixture in the combustion chamber 3. In this compression stroke, the volume of the combustion chamber 3 is reduced by raising the piston 2 from the bottom dead center, so that the air-fuel mixture sucked into the combustion chamber 3 flows into the ignition chamber 14 through the communication hole 15.
The control device 40 that controls the operation of the engine 1 operates the plug main body 12 at the ignition timing (for example, immediately before the top dead center), sparks at the ignition point, 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 communication 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 combustion exhaust gas in the combustion chamber 3 is led to the exhaust port and discharged.
Thus, the engine 1 is configured as a four-stroke engine that repeatedly performs 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 above is the basic configuration of the engine 1 and the spark plug 11 of the present invention.
As described above, the engine 1 of the present invention is configured to start up stably and quickly. Hereinafter, activation control will be described.
(Startup control)
Configuration As shown in FIG. 1, the engine 1 according to the present invention has a plug cover head 13a facing the combustion chamber 3 and a base of the plug cover head 13a in a mounted state in which a spark plug 11 is mounted on a cylinder head 6. A plug cover base end portion 13b provided on the end side and responsible for mounting the spark plug 11 to the cylinder head 6 is provided.
Further, the plug cover head 13a is provided with a heating means capable of heating the portion. This heating means is specifically constituted by a resistance heating element 30 (specifically, a nichrome wire) provided on the plug cover head portion 13a. In the example shown in FIG. 3, a form in which the resistance heating element 30 is crossed over the plug cover head 13 a is shown. The resistance heating element 30 may be provided in the plug cover head 13a or on the surface. In this example, the configuration in which the resistance heating element 30 is provided so as to cross the plug cover head portion 13a is shown. However, in the present invention, the temperature of the plug cover head portion 13a only needs to be controlled at the time of activation. The plug cover base end portion 13b that is thermally connected to the head portion 13a may be provided with a heating mechanism (for example, a resistance heating element wound in a coil inside the cylindrical plug cover base end portion 13b). .

  Further, the plug cover head 13a is provided with a temperature sensor (not shown) composed of a thermocouple or the like for detecting the temperature of this part, and the temperature detection output from this temperature sensor is the control device 40 described above. The structure sent to is adopted.

The controller 40 exercising the heating means, the heating control unit 40a for heating control at least plug cover head 13a, based on the detection output of the temperature sensor, the temperature of the plug cover head 13a is predetermined When the cranking start temperature is reached, the cranking start control means 40b for starting the cranking by operating the cell motor M, and after starting the cranking start control, the engine rotational speed reaches a constant speed, An ignition start control means 40c is provided for starting ignition by operating the spark plug 11 when it is detected that the rotation at the rotational speed is maintained for a predetermined time.

  The above is the configuration related to the startup control. The startup control state will be described with reference to FIGS. 4 and 5. Here, FIG. 4 is a diagram showing the relationship between the timing of each operation at the start control, the temperature of the plug cover head 13a, and the engine speed, and FIG. 5 shows the functional means provided in the control device 40. It is a processing flow to be executed.

Activation Control In the activation control, first, the heating control means 40a operates the heating means to heat the plug cover head 13a (step # 1).
With this heating, when the temperature of the plug cover head 13a reaches a predetermined cranking start temperature, the cranking start control means 40b activates the cell motor M to start cranking (step # 2, step # 2). # 3).
In the illustrated example, the case where the cranking start temperature is 200 ° C. is shown.

  After the cranking start control is started, when it is detected that the engine speed has reached a constant speed and the rotation at that speed has been maintained for a predetermined time (in other words, the cell motor M is normally operated for a predetermined time) When it is confirmed that the ignition timing has been reached), the ignition start control means 40c activates the spark plug 11 to start ignition (step # 4, step # 5).

Thereafter, with the engine speed reaching the rated speed, the engine operation is continued at that speed (step # 6, step # 7).
In the illustrated example, the case where the rated rotation speed is 1200 rpm is shown.
The activation control is completed by the above operation.

[Other alternative embodiments]
(A) In the above embodiment, the communication holes formed in the ignition chamber 14 are configured as the plurality of communication holes 15, but may be configured from a plurality of slits or the like. In the above embodiment, as shown in FIG. 1, the case where the plurality of communication holes 15 are provided at one position in the sliding direction of the piston 2 (the direction along the straight line W in FIG. 1) is shown. It may be provided in a distributed manner.

(B) In the above embodiment, the engine 1 of the present invention is shown as an example of a four-stroke engine. However, the four strokes of the intake stroke, the compression stroke, the combustion expansion stroke, and the exhaust stroke are two strokes. The functions of the present invention are also satisfactorily demonstrated as a two-stroke engine performed in step 6 or a six-stroke engine in which two scavenging strokes are added to the above four strokes.

(C) In the activation control of the above embodiment, the cranking start control means 40b starts cranking based on the temperature of the plug cover head 13a. For example, the heating time of the plug cover head 13a by the heating means Based on the above, cranking may be started. In this case, steps # 1 to # 3 of the start control in the above embodiment are as follows.
The heating control means 40a activates the heating means to heat the plug cover head 13a (step # 1).
The cranking start control means 40b uses the heating means to heat the plug cover head 13a for a certain period of time (the time for the plug cover head 13a to reach a predetermined cranking start temperature), and then starts the cranking by operating the cell motor M. (Step # 2, Step # 3).
Even if such a configuration is adopted, the cold start problem which is a problem of the present application can be solved.

  INDUSTRIAL APPLICABILITY The engine and spark plug of the present invention can be effectively used as an engine and spark plug that can be stably started even when the engine is provided with a pre-chamber spark plug.

1: Engine 2: Piston 3: Combustion chamber 11: Spark plug 13: Plug cover 14: Ignition chamber 15: Communication hole (an example of a communication hole)
40: control device 40a: heating control means 40b: cranking start control means 40c: ignition start control means 40d: transition control means

Claims (9)

An engine in which a spark plug having an ignition chamber inside a plug cover that covers an ignition point is mounted on a cylinder head, and a communication hole that connects the ignition chamber and a combustion chamber facing a piston is provided in the plug cover. ,
When the spark plug is mounted on the cylinder head, the spark cover is provided on the plug cover head facing the combustion chamber and on the base end side of the plug cover head, and the spark plug is mounted on the cylinder head. With a plug cover base end that bears
A heating means capable of heating the plug cover head;
Control means for controlling one or both of the cranking start timing and the ignition start timing at the time of starting the engine based on the temperature of the plug cover head that is heated with heating by the heating means. Engine. A spark plug with an ignition chamber inside the plug cover covering the ignition point is attached to the cylinder head,
An engine in which a communication hole communicating the ignition chamber and a combustion chamber facing the piston is provided in the plug cover,
When the spark plug is mounted on the cylinder head, the spark cover is provided on the plug cover head facing the combustion chamber and on the base end side of the plug cover head, and the spark plug is mounted on the cylinder head. With a plug cover base end that bears
A heating means capable of heating the plug cover head;
An engine comprising control means for starting cranking when the engine is started after being heated by the heating means for a certain period of time.   The heating means is one or both of a heating mechanism provided at the plug cover head and a heating mechanism provided at the base end of the spark plug cover that is thermally connected to the plug cover head. The engine according to claim 1 or 2.   The engine according to any one of claims 1 to 3, wherein the heating means is a heating mechanism including a resistance heating element provided on the plug cover head. Comprising a temperature detecting means for detecting the temperature of the plug cover head;
The control means controls one or both of a cranking start timing and an ignition start timing at the time of engine start based on the temperature of the plug cover head detected by the temperature detecting means. The listed engine. A plug body having an ignition point; and a plug cover attached to the plug body so as to cover the ignition point. A plurality of communication holes communicating with the facing combustion chamber and the ignition chamber formed in the plug cover, the spark plug formed in the plug cover;
When the spark plug is mounted on the cylinder head, the spark cover is provided on the plug cover head facing the combustion chamber and on the base end side of the plug cover head, and the spark plug is mounted on the cylinder head. With a plug cover base end that bears
A heating means capable of heating the plug cover head;
An ignition plug, wherein the heating means is a heating element provided across the plug cover head. The spark plug according to claim 6, wherein the heating means is a heating mechanism including a resistance heating element provided across the plug cover head. An engine starting method in which an ignition plug having an ignition chamber inside a plug cover that covers an ignition point is mounted on a cylinder head, and a communication hole that connects the ignition chamber and a combustion chamber facing a piston is provided in the plug cover Because
A plug cover head facing the combustion chamber in a mounted state attached to the cylinder head, and a plug cover base provided on the proximal end side of the plug cover head and responsible for mounting the spark plug to the cylinder head With respect to the spark plug provided with an end portion, a heating step of heating the plug cover head by heating means is performed,
After the temperature of the plug cover head, which is raised with the heating in the heating process, reaches the cranking start temperature, a cranking process for performing cranking is performed, and then between the electrodes of the spark plug A method for starting an engine that shifts to a spark ignition stroke that is ignited by spark discharge.   9. The engine starting method according to claim 8, wherein when the cranking stroke is shifted to the spark ignition stroke, the engine starts the spark ignition stroke after a predetermined time has elapsed after the cranking stroke is started.

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