JP2875897B2 - Spark ignition gas internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sub-chamber combustion type spark ignition gas internal combustion engine using a gas fuel such as natural gas.
In particular, the engine startability has been improved.

[0002]

2. Description of the Related Art In recent years, a spark ignition gas internal combustion engine using a gaseous fuel such as liquefied natural gas which is more advantageous in terms of thermal efficiency and emission pollution than a spark ignition internal combustion engine mainly comprising gasoline or the like as a fuel has been reviewed. It is getting. The basic structure of this spark ignition gas internal combustion engine is almost the same as that of a gasoline engine, except that it is necessary to incorporate a safety device such as a gas shutoff valve to prevent explosion due to gas leakage or air mixing. It is different from a fuel supply method in a gasoline engine.

[0003] As such a conventional spark ignition gas internal combustion engine, there is a sub-chamber combustion type as shown in FIG.

That is, as shown in FIG. 2 showing the concept of the spark ignition gas internal combustion engine of the sub-chamber combustion system, a connecting rod 10 is used.
A cylinder head 107 that slidably holds an intake valve 106 and an exhaust valve (not shown) is attached to a cylinder block 105 that slidably accommodates a piston 104 that is connected to a crankshaft 103 of an engine 102 through a cylinder 1. ing. This cylinder head 107 and cylinder block 1
A main combustion chamber 108 surrounded by the main combustion chamber 108 and the piston 104 is provided with the intake valve 10 facing the main combustion chamber 108, respectively.
The intake pipe 109 and an exhaust pipe (not shown) communicate with each other via the exhaust valve 6 and the exhaust valve.
Is provided.

[0005] A fuel supply pipe 112 serving as a passage for gas fuel from a fuel storage cylinder (not shown) communicates with the gas mixer 111. A flow control valve 113 for adjusting the flow rate of the fuel is provided. Further, in the middle of the fuel supply pipe 112, a booster 114 for increasing the pressure of the gas fuel flowing through the fuel supply pipe 112 to, for example, several kilograms per square centimeter, and an engine 102
An openable manual shutoff valve 115 functioning as a safety device for stopping supply of gaseous fuel to the fuel supply pipe, a fuel flow meter 116 for detecting a flow rate of gaseous fuel in the fuel supply pipe 112, And a fuel pressure regulator 117 capable of adjusting the pressure of the gaseous fuel are interposed in order from the upstream side.

On the other hand, a sub-chamber 118 facing the main combustion chamber 108 is formed in the center of the cylinder head 107. The sub-chamber 118 facing the tip of the ignition plug 119 communicates with a sub-chamber fuel supply pipe 120 branched from the fuel supply pipe 112 between the manual shutoff valve 115 and the fuel flow meter 116. In the middle of the sub-chamber fuel supply pipe 120, an openable / closable manual shut-off valve 121 functioning as a safety device for stopping the supply of gas fuel to the sub-chamber 118, and the gas fuel in the sub-chamber fuel supply pipe 120. 2, and a check valve 123 for preventing the backflow of gas fuel during the compression stroke in which the piston 104 rises in FIG. I have.

The flow control valve 113 has a crankshaft 1
The controller 124 sets a fuel supply amount based on the engine speed 03 (hereinafter referred to as the engine speed) and the opening degree of the throttle valve 110, and gives an opening period corresponding to the fuel supply amount to the flow regulating valve 113. The controller 124 is connected to the fuel pressure regulator 117 on the fuel supply pipe 112 side.
And the fuel pressure regulator 122 on the side of the sub-chamber fuel supply pipe 120, and the pressure of the gas fuel by the fuel pressure regulators 113 and 122 is optimally controlled based on the opening degree of the throttle valve 110 and the like.

Accordingly, the gas fuel flowing through the fuel supply pipe 112 is adjusted to an appropriate pressure by the fuel pressure regulator 117 controlled by the controller 124, and the engine speed and the opening of the throttle valve 110 are adjusted so as to obtain the stoichiometric air-fuel ratio. Is set by the controller 120, and an opening period corresponding to this is given to the flow regulating valve 113.
As a result, the air and the gas fuel are uniformly mixed in the gas mixer 111 and pass through the intake pipe 109 to the main combustion chamber 1.
08.

On the other hand, the gas fuel flowing through the sub-chamber fuel supply pipe 120 is adjusted to an appropriate pressure by a fuel pressure regulator 122 controlled by a controller 124, and a check valve is provided during the compression stroke in which the piston 104 rises. This gas fuel is pumped into the sub chamber 118 via 123. In the middle of the compression stroke, a part of the air-fuel mixture set to the stoichiometric air-fuel ratio in the main combustion chamber 108 flows into the sub-chamber 118,
It mixes with the gas fuel supplied into the sub-chamber 118 from the sub-chamber fuel supply pipe 120 side. The spark discharge of the ignition plug 119 occurring before the end of the compression stroke causes the sub-chamber 1
18 ignites the gas fuel in the main combustion chamber 108
Propagating to the side.

Conventionally, when starting a sub-chamber combustion type spark ignition gas internal combustion engine as shown in FIG. 2, the opening degree of the throttle valve 110 and the flow regulating valve 113 and the opening of the sub-chamber 118 by the fuel pressure regulator 122 are controlled. The gas fuel supply pressure is adjusted to a value empirically set in advance in the controller 124 for starting.

[0011]

In the spark ignition gas internal combustion engine in the sub-chamber combustion system shown in FIG. 2, although a part of the air-fuel mixture on the main combustion chamber 108 side flows into the sub-chamber 118,
Since only gaseous fuel is pumped from the sub-chamber side fuel supply pipe 120, the air-fuel ratio in the sub-chamber 118
The air-fuel ratio is higher than the air-fuel ratio inside the fuel cell, which is a so-called rich state, and has an advantage that the concentration of nitrogen oxides in the combustion exhaust gas can be reduced.

However, in the spark ignition gas internal combustion engine of the sub-chamber combustion system, inexpensive liquefied natural gas (hereinafter, referred to as LNG) mainly composed of methane is mainly used as a main gas fuel. It is well known that methane has a flammable range of only about 5% to 15% in terms of an air ratio, and has a property that ignitability is not so good.

Therefore, when the spark ignition gas internal combustion engine of the sub-chamber combustion system using LNG is cold-started, the sub-chamber 1
It is desirable that the air-fuel ratio in 18 is also set to a stoichiometric air-fuel ratio or a value close thereto. Therefore, conventionally, the opening degree of the throttle valve 110 and the flow regulating valve 113 and the fuel pressure regulator 1
The supply pressure of the gas fuel to the sub-chamber 118 side by 22 is adjusted in advance to a value empirically set for starting in the controller 124, but the intake air temperature decreases as in winter or the like, If the properties of gas fuel change,
Alternatively, when there is a change in the specification of the shape of the sub-chamber 118, the concentration distribution of the gas fuel in the sub-chamber 118 may vary, and the ignitability of the gas fuel may become unstable. In particular, when the energy of the spark discharge is weakened due to the poor state of the ignition plug 119, the temperature around the ignition plug 119 in the sub chamber 118 is low, the engine speed is extremely low, and the compressed gas temperature is low. The above-mentioned tendency becomes more conspicuous, and the starting of the engine becomes difficult in some cases, in combination with the adverse conditions overlapping.

[0014]

An object of the present invention is to improve the ignitability of gaseous fuel such as LNG and the like by setting the stoichiometric air-fuel ratio in the sub-chamber at the time of a cold start of the engine, etc. It is an object of the present invention to provide a spark ignition gas internal combustion engine of a sub-chamber combustion system excellent in the above.

[0015]

SUMMARY OF THE INVENTION A spark ignition gas internal combustion engine according to the present invention has an intake pipe provided with a throttle valve which communicates with a main combustion chamber and adjusts an amount of intake air to the main combustion chamber, and the intake pipe. A fuel supply pipe for supplying gaseous fuel into the main combustion chamber through the fuel supply pipe, and a fuel flow control valve provided in the middle of the fuel supply pipe and capable of changing the supply amount of gas fuel to the main combustion chamber. A spark-ignited gas internal combustion engine having a sub-chamber communicating with the main combustion chamber, a spark plug having a front end portion facing the sub-chamber and igniting the gaseous fuel, and the fuel upstream of the fuel flow control valve. A fuel supply pipe for a sub-chamber that branches off from a supply pipe and supplies the gas fuel to the sub-chamber, and is provided in the middle of the fuel supply pipe for the sub-chamber and stops the supply of the gas fuel to the sub-chamber. Possible opening And shut-off valve capable, in which and control means for controlling the opening and closing of the shut-off valve.

[0016]

When the supply of gas fuel from the sub-chamber fuel supply pipe to the sub-chamber is cut off, the air-fuel ratio in the sub-chamber corresponds to the air-fuel ratio of the air-fuel mixture sucked into the main combustion chamber from the intake pipe side. I do.
Therefore, when the engine is started, the control means operates the shut-off valve to stop the supply of gas fuel from the sub chamber fuel supply pipe to the sub chamber, and is supplied to the main combustion chamber via the intake pipe. A part of the air-fuel mixture set to the stoichiometric air-fuel ratio is sent into the sub chamber. As a result, the air-fuel mixture in the sub-chamber has the stoichiometric air-fuel ratio with the best ignitability. The air-fuel mixture is ignited by spark discharge from a spark plug, and the flame is propagated to the air-fuel mixture on the main combustion chamber side. Start up.

When the engine speed has increased to some extent and there is no possibility that the engine will stop, the control means operates the shut-off valve again to start supplying gas fuel from the sub-chamber fuel supply pipe to the sub-chamber side. Then, a normal sub-chamber combustion method is performed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, which shows the concept of an embodiment of a spark ignition gas internal combustion engine of the sub chamber combustion type according to the present invention, a piston 14 connected to a crankshaft 13 of an engine 12 via a connecting rod 11 is provided. A cylinder head 17 that slidably holds an intake valve 16 and an exhaust valve (not shown) is attached to a slidably stored cylinder block 15. In a main combustion chamber 18 surrounded by the cylinder head 17, the cylinder block 15, and the piston 14, an intake pipe 19 and an exhaust pipe (not shown) are provided via the intake valve 16 and the exhaust valve facing the main combustion chamber 18, respectively. A gas mixer 21 having a throttle valve 20 that is linked to the accelerator operation of the driver is provided in the middle of the intake pipe 19 in communication with each other.

The gas mixer 21 has a fuel supply pipe 2 serving as a passage for gas fuel from a fuel storage cylinder (not shown).
The fuel supply pipe 22 facing the gas mixer 21 is provided at its downstream end with a flow control valve 23 for controlling the flow rate of gas fuel. Also, this fuel supply pipe 22
A booster 24 that increases the pressure of gas fuel flowing through the fuel supply pipe 22 to, for example, several kilograms per square centimeter, and an openable / closable device that functions as a safety device for stopping the supply of gas fuel to the engine 12. A manual shut-off valve 25, a fuel flow meter 26 for detecting the flow rate of gaseous fuel in the fuel supply pipe 22,
A fuel pressure regulator 27 capable of adjusting the pressure of gas fuel inside the fuel cell is interposed in order from the upstream side.

On the other hand, a sub-chamber 28 facing the main combustion chamber 18 is formed in the center of the cylinder head 17. A sub-chamber fuel supply pipe 30 branched from the fuel supply pipe 22 between the manual shut-off valve 25 and the fuel flow meter 26 communicates with the sub-chamber 28 facing the tip of the ignition plug 29. In the middle of the sub-chamber fuel supply pipe 30, an openable / closable manual shut-off valve 31 functioning as a safety device for stopping the supply of gas fuel to the sub-chamber 28, and the gas fuel in the sub-chamber fuel supply pipe 30. 2, a fuel pressure regulator 32 capable of adjusting the pressure, an electromagnetic shut-off valve 35 functioning as a shut-off valve of the present invention, and a reverse for preventing a backflow of gas fuel during a compression stroke in which the piston 14 rises in FIG. The stop valve 33 is interposed in order from the upstream side.

The flow regulating valve 23 has a crankshaft 13
The controller 34 sets a fuel supply amount based on the engine speed (hereinafter referred to as the engine speed) and the opening degree of the throttle valve 20, and provides the flow control valve 23 with an opening period corresponding thereto. The controller 34 constituting the control means of the present invention is also connected to the fuel pressure regulator 27 on the fuel supply pipe 22 side, the fuel pressure regulator 32 on the sub-chamber fuel supply pipe 30 side, and the electromagnetic shutoff valve 35. , Throttle valve 2
In addition to optimally controlling the pressure of the gaseous fuel by the fuel pressure regulators 23 and 32 based on the opening degree of 0, the engine 1
The opening and closing of the electromagnetic shut-off valve 35 is controlled so as to stop the supply of gaseous fuel from the sub-chamber fuel supply pipe 30 into the sub-chamber 18 at the time of start-up or the like.

Accordingly, the gas fuel flowing through the fuel supply pipe 22 is adjusted to an appropriate pressure by the fuel pressure regulator 27 controlled by the controller 124, and the fuel supply amount based on the engine speed and the opening of the throttle valve 20. Is set by the controller 30, and a corresponding open period is given to the flow regulating valve 23. Thereby, the gas mixer 11
The air and gas fuel are uniformly mixed in the
Through the main combustion chamber 18.

On the other hand, the gas fuel flowing through the sub-chamber fuel supply pipe 30 is adjusted to an appropriate pressure by a fuel pressure regulator 32 controlled by a controller 34, and a check valve is provided during the compression stroke in which the piston 14 rises. This gaseous fuel is pumped into the sub-chamber 28 via 33. In the middle of the compression stroke, a part of the air-fuel mixture in the main combustion chamber 18 flows into the sub-chamber 28, and from the sub-chamber fuel supply pipe 30 to the sub-chamber 28.
Mixes with the gas fuel supplied inside. And, by the spark discharge of the ignition plug 29 occurring before the end of the compression stroke,
The gas fuel in the sub chamber 28 is ignited, and the flame is
Propagation to the 8 side.

During normal operation of the engine 12, the controller 34 holds the electromagnetic shut-off valve 35 in an open state, and feeds gas fuel into the sub-chamber 28 via the sub-chamber fuel supply pipe 30. As a result, a part of the air-fuel mixture set to the stoichiometric air-fuel ratio in the main combustion chamber 18 and the sub-chamber fuel supply pipe 30
Mixed with the gaseous fuel from
It is possible to reduce the concentration of nitrogen oxides in the combustion exhaust gas.

On the other hand, when the controller 34 determines that the engine 12 is at the time of starting, the controller 34 keeps the electromagnetic shut-off valve 35 in the shut-off state, and the fuel supply pipe 3
The supply of gaseous fuel from the zero side into the sub chamber 28 is stopped.
Then, by driving a starting motor (not shown) to drive and rotate the crankshaft 13 of the engine 12, the sub chamber 28
Only a part of the air-fuel mixture set at the stoichiometric air-fuel ratio in the main combustion chamber 18 is supplied to the inside of the main combustion chamber 18. The engine 12 is started by igniting a mixture having good ignitability set to the air-fuel ratio and transmitting the flame to the mixture in the main combustion chamber 18.

At this point, when the engine speed has increased to some extent and there is no possibility that the engine 12 will stop, the controller 34 operates the electromagnetic shut-off valve 35 again to open.
The supply of gaseous fuel from the sub-chamber fuel supply pipe 30 to the sub-chamber 28 side is started, and a normal sub-chamber combustion system is performed.

[0027]

According to the spark ignition gas internal combustion engine of the present invention, the fuel supply pipe for the sub-chamber for supplying gaseous fuel to the sub-chamber communicating with the main combustion chamber is supplied with the fuel upstream of the fuel flow control valve. An open / close shutoff valve is provided in the middle of the sub-chamber fuel supply pipe for stopping supply of gas fuel to the sub-chamber, and control means for controlling the opening / closing of the shut-off valve when the engine is started is provided. As a result, the air-fuel ratio in the sub-chamber can be set to a stoichiometric air-fuel ratio with good ignitability as required, so that good startability can always be ensured even during a cold start of the engine. .

Even if the temperature of the intake air or the properties of the gas fuel changes, or if there is a change in the specifications such as the shape of the sub-chamber, the opening and closing of the shut-off valve by the control device is appropriately controlled. Thus, it is possible to always keep the startability of the engine good.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an embodiment of a spark ignition gas internal combustion engine of a sub-chamber combustion type according to the present invention.

FIG. 2 is a conceptual diagram illustrating an example of a conventional sub-chamber combustion type spark ignition gas internal combustion engine.

[Explanation of symbols]

12 is an engine, 18 is a main combustion chamber, 19 is an intake pipe, 20 is a throttle valve, 22 is a fuel supply pipe, 23 is a fuel flow control valve, 27 and 32 are fuel regulators, 28 is a sub chamber, and 29 is a spark plug. , 30 is a fuel supply pipe for the sub chamber, 33 is a check valve, 3
4 is a controller, 35 is an electromagnetic shutoff valve.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F02M 21/00-21/06 F02B 19/08 F02B 19/10 F02D 19/02

Claims (1)

(57) [Claims] An intake pipe provided with a throttle valve communicating with a main combustion chamber and adjusting an intake air amount to the main combustion chamber, and for supplying gas fuel to the main combustion chamber via the intake pipe. A fuel supply pipe, and a fuel flow control valve provided in the middle of the fuel supply pipe and capable of changing a supply amount of gaseous fuel to the main combustion chamber, in communication with the main combustion chamber. A sub-chamber, a spark plug whose front end faces the sub-chamber and ignites the gaseous fuel, and branches off from the fuel supply pipe upstream of the fuel flow rate regulating valve and transfers the gaseous fuel into the sub-chamber. A fuel supply pipe for the sub-chamber for supplying, a shut-off valve provided in the middle of the fuel supply pipe for the sub-chamber and capable of stopping supply of the gas fuel to the sub-chamber, and opening and closing of the shut-off valve Control means for controlling And a spark ignition gas internal combustion engine.