JP2013217212A - Gas fuel injection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas fuel injection system having improved durability of a fuel injection valve, the system being to be applied to a direct injection type and spark ignition type internal combustion engine.SOLUTION: In an engine 10 with a gas fuel direct injection system as well as a spark ignition system, a fuel injection valve 30 is mounted on a cylinder block 12 of the engine. The fuel injection valve 30 is disposed in such a manner that when a piston 13 of the engine is positioned at a top dead center TDC, a nozzle hole 31b is sealed by an outer circumferential face 13a of the piston and that while the piston 13 is positioned apart from the top dead center TDC by a predetermined distance L or more, the nozzle hole 31b is in an open state released from the outer circumferential face 13a.

Description

  The present invention relates to a gas fuel injection system applied to a direct injection and spark ignition internal combustion engine.

  A general fuel injection valve mounted on an ignition engine has an injection hole formed at the tip of a cylindrical body. The body includes a valve body that opens and closes the nozzle hole and a seat portion on which the valve body is seated (see Patent Document 1). When the fuel injection valve is mounted on a direct injection engine that directly injects fuel into the combustion chamber, the tip of the fuel injection valve is exposed in the fuel chamber (see Patent Document 2).

  Accordingly, the tip of the fuel injection valve including the seat portion is exposed to the high temperature in the combustion chamber during a period in which the combustion chamber is at a high temperature from the latter stage of the compression stroke to the first half of the combustion stroke.

JP 2006-348842 A JP 2000-73840 A

  When liquid fuel is injected from the fuel injection valve, the tip of the fuel injection valve is cooled by the liquid fuel itself or its vaporization heat. However, when gas fuel is injected from the fuel injection valve, the tip of the fuel injection valve is not cooled by the liquid fuel itself or the heat of vaporization thereof. Therefore, when the gas fuel is directly injected from the fuel injection valve into the fuel chamber, the tip of the fuel injection valve including the seat portion becomes high temperature, and there is a concern about the durability of the fuel injection valve.

  The present invention has been made to solve the above problems, and provides a gas fuel injection system with improved durability of a fuel injection valve, which is applied to a direct injection and spark ignition internal combustion engine. Objective.

  In order to solve the above-described problems, in the invention according to claim 1, a fuel injection valve that directly injects gaseous fuel into a combustion chamber of an internal combustion engine, gas fuel injected from an injection hole of the fuel injection valve, and air It is assumed that the present invention is applied to an internal combustion engine that includes an ignition plug that ignites an air-fuel mixture. The fuel injection valve is attached to a cylinder block of the engine. Further, the fuel injection valve has the nozzle hole formed by the outer peripheral surface of the piston when the piston of the engine is at the top dead center position. The nozzle hole is disposed so as to be blocked and when the piston is located at a position more than a predetermined distance from the top dead center position, the nozzle hole is opened from the outer peripheral surface.

  According to the first aspect of the present invention, when the piston of the internal combustion engine is between the top dead center and a position separated from the top dead center by a predetermined distance, the sealed state in which the nozzle hole is blocked by the outer peripheral surface of the piston. It becomes. For this reason, the injection hole of the fuel injection valve can be blocked including the period in which the piston is in the vicinity of the top dead center, that is, the high temperature period in which the temperature in the combustion chamber increases. Therefore, it can suppress that the front-end | tip of a fuel injection valve is exposed to the high temperature in a combustion chamber, and can improve the durability of the fuel injection valve which injects gaseous fuel.

  On the other hand, the nozzle hole of the fuel injection valve is opened from the outer peripheral surface of the piston during a period in which the piston is at a predetermined distance or more from the top dead center position, that is, a period excluding a period in which the piston is in the vicinity of the top dead center. It becomes the released state. For this reason, in the period when the temperature in the combustion chamber is lower than the high temperature period, it becomes possible to directly inject gas fuel from the nozzle hole into the combustion chamber.

  According to a sixth aspect of the present invention, a fuel injection valve that directly injects gaseous fuel into a combustion chamber of an internal combustion engine, and an ignition plug that ignites a mixture of gaseous fuel and air injected from the nozzle hole of the fuel injection valve And is applied to an internal combustion engine comprising: A cylinder chamber or a cylinder block of the engine is formed with a storage chamber for storing a portion including the injection hole in the fuel injection valve, and the storage chamber has a communication port communicating with the combustion chamber. A low-temperature period that is formed and includes an on-off valve that opens and closes the communication port, the on-off valve is closed during a high-temperature period in which the combustion chamber is at or above a predetermined temperature, and the combustion chamber is below the predetermined temperature In the above, the on-off valve is opened and gas fuel is directly injected from the nozzle hole into the combustion chamber through the communication port.

  According to the sixth aspect of the present invention, during the high temperature period in which the combustion chamber is equal to or higher than the predetermined temperature, the communication port that connects the storage chamber and the combustion chamber is in a sealed state that is blocked by the on-off valve. For this reason, there is no possibility that the nozzle hole accommodated in the accommodating chamber is exposed to the high temperature in the combustion chamber. Therefore, durability of the fuel injection valve that injects the gas fuel can be improved.

  On the other hand, in a low temperature period in which the combustion chamber is lower than a predetermined temperature, the communication port that connects the storage port and the combustion chamber is opened by the on-off valve. For this reason, in the low temperature period in which the combustion chamber is lower than the predetermined temperature, it becomes possible to directly inject gas fuel from the injection hole accommodated in the accommodation chamber to the combustion chamber through the communication port.

The figure which shows the fuel-injection system concerning 1st Embodiment. Sectional drawing which shows the fuel injection valve of FIG. The time chart which shows 1 combustion cycle in 1st Embodiment. The figure which shows the state by which the communicating port was sealed in the fuel-injection system concerning 2nd Embodiment. The figure which shows the state by which the communicating port was open | released in 2nd Embodiment. The time chart which shows 1 combustion cycle in 2nd Embodiment. The figure which shows the fuel-injection system concerning other embodiment.

  Hereinafter, specific embodiments of a gas fuel injection system applied to an ignition type and direct injection type gas engine will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings, and the description of the same reference numerals is used.

(First embodiment)
FIG. 1 is a cross-sectional view schematically showing an engine 10 (internal combustion engine) to which the present embodiment is applied. The engine 10 is mounted on a vehicle and functions as a travel drive source. The engine 10 is a spark ignition type gas engine having an ignition plug 20 and a direct injection engine that directly injects fuel into the combustion chamber 10a. is there. Further, the engine 10 is a reciprocating engine that includes a cylinder head 11, a cylinder block 12, a piston 13, and the like.

  The cylinder head 11 forms a wall surface of the combustion chamber 10 a that faces the top surface 13 b of the piston 13. The cylinder head 11 includes an ignition plug 20, an intake valve 21 that circulates and blocks intake air to and from the combustion chamber 10 a, an exhaust valve 22 that discharges and blocks exhaust gas from the combustion chamber 10 a, and the intake chamber 21 through the intake valve 21. An exhaust pipe 24 connected to the combustion chamber 10a via a connected intake pipe 23 and an exhaust valve 22 is attached. Further, the intake pipe 23 includes a throttle valve 25 that adjusts the intake flow rate in the intake pipe 23. By controlling the throttle valve 25, a desired amount of intake air is drawn into the combustion chamber 10a within a predetermined period.

  On the other hand, the cylinder block 12 forms a cylinder in which the piston 13 slides. The cylinder block 12 is provided with a fuel injection valve 30 that injects gaseous fuel into the combustion chamber 10a.

  FIG. 1A shows a state when the piston 13 is at the top dead center TDC. Thus, when the piston 13 is within a predetermined range from the top dead center position, the injection hole 31b of the fuel injection valve 30 is in a closed state in which the outer peripheral surface 13a of the piston 13 is blocked. Specifically, when the top surface 13b of the piston 13 exists between the top dead center TDC and the injection hole 31b (range of the predetermined distance L), the sealed state is established.

  FIG. 1B shows a state when the piston 13 is at the bottom dead center BDC. As described above, when the top surface 13b of the piston 13 is at a position separated from the top dead center position by the predetermined distance L or more, the injection hole 31b is opened from the outer peripheral surface 13a of the piston 13. Specifically, when the top surface 13b of the piston 13 exists between the bottom dead center BDC and the nozzle hole 31b, the piston 13 is opened. During the open period, the nozzle hole 31b is exposed to the combustion chamber 10a, so that fuel can be injected from the nozzle hole 31b into the combustion chamber 10a.

  The operation of the spark plug 20 and the fuel injection valve 30 is controlled by an electronic control unit (ECU 40). The ECU 40 controls the amount of fuel to be injected into the combustion chamber 10a per combustion cycle (fuel injection amount), the fuel injection timing, the ignition timing by the spark plug 20, and the like based on detected values such as the engine speed and engine load. To do. As a result, the engine operating state is controlled so that the engine output and the exhaust emission are optimized.

  FIG. 2 is a cross-sectional view showing the structure of the fuel injection valve 30. The fuel injection valve 30 includes a cylindrical body 31, a valve body 32 that opens and closes the injection hole 31 b, and an electric actuator 33 that drives the valve body 32. A nozzle hole 31 b is formed at the tip of the body 31, and a fuel passage 31 a connected to the nozzle hole 31 b is formed inside the body 31. The valve body 32 is accommodated inside the fuel passage 31a. A tapered seat surface 31c having a sealing property is formed on the inner peripheral surface of the front end portion of the body 31. When the valve body 32 is separated from the seat surface 31c, the high-pressure fuel supplied from the high-pressure port 34 is injected from the injection hole 31b through the fuel passage 31a. On the other hand, when the valve body 32 is seated on the seat surface 31c, fuel injection from the injection hole 31b is stopped.

  The electric actuator 33 includes a stator 33b having an electromagnetic solenoid 33a and an armature 33c. When electric power is supplied from the ECU 40 to the electromagnetic solenoid 33a, the armature 33c is attracted to the stator 33b. Then, the valve body 32 connected to the armature 33c is lifted up against the elastic force of the spring 35 and is separated from the seat surface 31c. That is, it is ejected from the nozzle hole 31b during the period when power is supplied to the electromagnetic solenoid 33a. Therefore, the amount of fuel injected by one valve opening is controlled by the power supply time. On the other hand, when the power supply is stopped, the valve body 32 is lifted down by the elastic force of the spring 35 and is seated on the seat surface 31c, and fuel injection from the injection hole 31b is stopped.

  Note that gas fuel in a fuel tank (not shown) is pumped to a pressure accumulating vessel (delivery pipe), and high pressure gas fuel accumulated in the pressure accumulating vessel is distributed to the high pressure port 34 of the fuel injection valve 30 of each cylinder. Has been. Then, fuel injection by the fuel injection valve 30 of each cylinder is started with a phase difference of a predetermined crank angle.

  Next, the fuel injection timing in one combustion cycle will be described with reference to FIG. 3 (a) to 3 (d) are: (a) timing for opening / closing the intake valve 21, (b) timing for opening / closing the exhaust valve 22, (c) timing for switching between the blocked state and the open state, and (d) the combustion chamber. It is a time chart which shows the change of the pressure (cylinder pressure) in 10a. FIGS. 3 (1) to 3 (5) show the state of the engine 10 corresponding to the periods (1) to (5) in FIG. 3 (d), respectively.

  As shown in the drawing, at the time t1, the piston 13 descends from the top dead center TDC position and the intake stroke is started, and the intake valve 21 is opened. At time t2, the piston 13 is lowered by a predetermined distance L and reaches the position of the injection hole 31b. In this period t1 to t2, the nozzle hole 31b is blocked by the outer peripheral surface 13a of the piston 13, and the sealed state shown in FIG. Therefore, fuel cannot be injected into the combustion chamber 10a during the period t1 to t2.

  The piston 13 descends to the bottom dead center BDC position at time t3, and the intake stroke is completed. The intake valve 21 is closed by time t3. Subsequently, the piston 13 rises from the bottom dead center BDC position, and the compression stroke is started. At time t4, the piston 13 rises to a position that is a predetermined distance L away from the top dead center TDC position, and reaches the position of the nozzle hole 31b again. In this period t2 to t4, the nozzle hole 31b is opened by the outer peripheral surface 13a of the piston 13, and the open state shown in FIG. Therefore, in the period t2 to t4, fuel can be injected into the combustion chamber 10a.

  Here, in order to suppress the blow-back of the intake air due to the injection of the gas fuel, the fuel is injected after the intake valve 21 is closed and the intake of the intake air is finished. That is, the intake of the intake air is finished before the piston 13 is lowered to the bottom dead center BDC position. Then, fuel is injected into the combustion chamber 10a during the period t3 to t4 until the piston 13 rises from the bottom dead center BDC position to the injection hole 31b position.

  Therefore, the opening degree of the throttle valve 25 is controlled so that the required amount of intake air is drawn into the combustion chamber 10a during the period t1 to t3 when the intake valve 21 is open. Further, during the period t3 to t4, the valve body 32 is opened for the time corresponding to the target injection amount (injection period Tq) so that the desired fuel amount is supplied to the combustion chamber 10a, and the fuel is injected. As a result, at the time point t4, the required amount of intake and gas fuel mixture exists in the combustion chamber 10a. Note that the end point of the injection period Tq coincides with the start point t4 of periods t4 to t5 described later, and the length of the injection period Tq (corresponding to the injection amount) is adjusted by adjusting the start point of the injection period Tq. It is adjusting.

  The piston 13 continues to rise after time t4. Then, at the timing when the piston 13 reaches the vicinity of the top dead center TDC, the air-fuel mixture is ignited by the spark plug 20, and the combustion stroke is started. The piston 13 rises to the top dead center TDC position and then descends again, and reaches the position of the nozzle hole 31b that is a predetermined distance L below the top dead center TDC position at time t5. In the period t4 to t5, the piston 13 exists between the top dead center TDC and a position away from the top dead center TDC by a predetermined distance L, and is in a sealed state shown in FIG. This period t4 to t5 corresponds to a period from the latter half of the compression stroke to the first half of the combustion stroke, and includes a high temperature period in which the inside of the combustion chamber 10a is at a high temperature and a high pressure. Therefore, in the period t4 to t5 including the high temperature period, the nozzle hole 31b of the fuel injection valve 30 is blocked, so that the tip of the fuel injection valve 30 is prevented from being exposed to the high temperature in the combustion chamber 10a.

  Thereafter, when the piston 13 descends to the bottom dead center BDC position, the piston 13 rises again from the bottom dead center BDC position. At that time, the exhaust valve 22 is opened and the exhaust stroke is started. At time t6, the piston 13 rises to a position separated by a predetermined distance L from the top dead center TDC position. In the period t5 to t6, the open state shown in FIG. This period t5 to t6 corresponds to a period from the latter half of the combustion stroke to the first half of the exhaust stroke, and is a low temperature period in which the inside of the combustion chamber 10a is at a low temperature and a low pressure.

  When the piston 13 further rises, the sealed state shown in FIG. When the piston 13 rises to the top dead center TDC position, one combustion cycle ends.

  The first embodiment described above has the following effects.

  When the piston 13 of the engine 10 is between the top dead center TDC and a position away from the top dead center TDC by a predetermined distance L, the injection hole 31b is blocked by the outer peripheral surface 13a of the piston 13. For this reason, the injection hole 31b of the fuel injection valve 30 can be sealed including the period in which the piston 13 is in the vicinity of the top dead center TDC, that is, the high temperature period in which the temperature in the combustion chamber 10a increases. Therefore, it can suppress that the front-end | tip of the fuel injection valve 30 is exposed to the high temperature in the combustion chamber 10a, and can improve the durability of the fuel injection valve 30 which injects gaseous fuel.

  On the other hand, the injection of the fuel injection valve 30 is not performed during a period in which the piston 13 is located at a position more than the predetermined distance L from the top dead center TDC position, that is, a period excluding a period in which the piston 13 is in the vicinity of the top dead center TDC. The hole 31b is opened from the outer peripheral surface 13a of the piston 13. For this reason, in the period when the temperature in the combustion chamber 10a is lower than the high temperature period, it becomes possible to directly inject the gas fuel from the injection hole 31b to the combustion chamber 10a.

  Since the gas fuel is injected after the intake valve 21 is closed and the intake of the intake air is finished, it is possible to suppress the intake air from being blown back by the injected gas fuel. Further, since the intake valve 21 is closed before the piston 13 is lowered to the bottom dead center BDC position, there are periods t3 to t4 during which the gas fuel can be injected after the intake valve 21 is closed. Therefore, it is possible to inject the gas fuel while suppressing the blowback of the intake air.

  By controlling the throttle valve 25, the required amount of intake air can be drawn into the combustion chamber 10a before the intake valve 21 is closed.

(Second Embodiment)
In the first embodiment, the fuel injection valve 30 is attached to the cylinder block 12, and the open state and the sealed state are switched by the outer peripheral surface 13 a of the piston 13. On the other hand, in 2nd Embodiment shown in FIGS. 4-6, the fuel injection valve 30 is attached to the cylinder head 11, and the open state and the blockade state are switched by the on-off valve 50 mentioned later.

  As shown in FIGS. 4 and 5, the cylinder head 11 is formed with a storage chamber 10 b that stores a portion including the injection hole 31 b of the fuel injection valve 30. In addition, a communication port 10c that communicates with the combustion chamber 10a is formed in the storage chamber 10b. When the communication port 10c is blocked by the on-off valve 50, the nozzle hole 31b is shielded from the combustion chamber 10a. On the other hand, when the communication port 10c is opened by the on-off valve 50, the nozzle hole 31b is exposed to the combustion chamber 10a.

  4A shows a closed state where the on-off valve 50 is closed and the communication port 10c is blocked by the on-off valve 50. FIG. 5 shows that the on-off valve 50 is opened and the communication port 10c is connected to the on-off valve 50. The open state opened by means of. In the open state shown in FIG. 4A, gas fuel can be directly injected from the injection hole 31b accommodated in the accommodation chamber 10b into the combustion chamber 10a through the communication port 10c. In addition, the injection hole 31b is arrange | positioned in the vicinity of the communication port 10c so that the injected gas fuel may not contact the communication port 10c.

  FIG.4 (b) is A arrow view of Fig.4 (a). As shown in FIG. 4B, the on-off valve 50 is disposed at the center of the combustion chamber 10a. Further, the on-off valve 50 is mechanically driven by the rotational force of the crankshaft of the engine 10 as in the case of the intake valve 21 and the exhaust valve 22. Therefore, the communication port 10c opens during a predetermined period set in one combustion cycle. The on-off valve 50 has a structure that opens by operating toward the combustion chamber 10a.

  Next, the fuel injection timing in one combustion cycle will be described with reference to FIG. 6A to 6D show (a) timing for opening and closing the intake valve 21, (b) timing for opening and closing the exhaust valve 22, (c) timing for opening and closing the on-off valve 50, and (d) combustion chamber 10a. It is a time chart which shows the change of the internal pressure (cylinder pressure).

  In a period including a high temperature period in which the combustion chamber 10a is equal to or higher than a predetermined temperature, the on-off valve 50 is closed. On the other hand, during the low temperature period when the combustion chamber 10a is lower than the predetermined temperature, a predetermined period during which the on-off valve 50 is opened is set.

  Specifically, the communication port 10c is blocked by the on-off valve 50 during a period including the high temperature period t9 to t10 from the latter stage of the compression stroke where the combustion chamber 10a is equal to or higher than the predetermined temperature to the first stage of the combustion stroke. On the other hand, in the low temperature period excluding the high temperature period, the period during which the on-off valve 50 is opened is set to the period t7 to t9 corresponding to the first half of the compression stroke from the intake stroke. That is, in the period t7 to t9, the injection hole 31b is exposed to the combustion chamber 10a through the communication port 10c, so that fuel can be injected from the injection hole 31b to the combustion chamber 10a through the communication port 10c. .

  Here, in order to suppress the blow-back of the intake air due to the injection of the gas fuel, the fuel is injected after the intake of the intake air is finished. Specifically, at time t7, the piston 13 descends from the top dead center TDC position, and the intake stroke is started, and the intake valve 21 is opened. Then, the intake valve 21 is closed by time t8 when the piston 13 reaches the bottom dead center BDC position and the intake stroke ends. Thereafter, in a period from t8 to t9, gas fuel is injected into the combustion chamber 10a.

  Therefore, the opening degree of the throttle valve 25 is controlled so that a desired amount of intake air is drawn into the combustion chamber 10a during the period t7 to t8. Further, during the period t8 to t9, the valve body 32 is opened for the time corresponding to the target injection amount (injection period Tq) so that the required amount of fuel is supplied to the combustion chamber 10a, and the fuel is injected. Let The end point of the injection period Tq coincides with the start point t9 of the high temperature period t9 to t10, and the length of the injection period Tq (corresponding to the injection amount) is adjusted by adjusting the start point of the injection period Tq. doing.

  The second embodiment described above has the following effects.

  During the high temperature period in which the combustion chamber 10a is equal to or higher than the predetermined temperature, the communication port 10c that connects the storage chamber 10b and the combustion chamber 10a is blocked by the on-off valve 50. For this reason, there is no possibility that the nozzle hole 31b accommodated in the accommodation chamber 10b is exposed to the high temperature of the combustion chamber 10a. Therefore, durability of the fuel injection valve 30 that injects the gas fuel can be improved.

  On the other hand, in the low temperature period in which the combustion chamber 10a is lower than the predetermined temperature, the communication port 10c that communicates between the storage chamber 10b and the combustion chamber 10a is in an open state in which the on-off valve 50 is opened. For this reason, gas fuel can be directly injected from the injection hole 31b accommodated in the accommodation chamber 10b to the combustion chamber 10a through the communication port 10c in the low temperature period in which the combustion chamber 10a is lower than the predetermined temperature.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be modified as follows. Moreover, you may make it combine the characteristic structure of each embodiment arbitrarily, respectively.

  In each of the above embodiments, the fuel is injected after the intake valve 21 is closed and intake of intake air is finished. However, during high load operation of the engine 10, the gas fuel is injected by the fuel injection valve 30 even before the intake valve 21 is closed within a period in which the piston 13 is located at a predetermined distance L or more from the top dead center TDC position. May be injected. In this way, when the engine 10 is operating at a high load, priority can be given to securing the injection amount of the gas fuel rather than suppressing the return of the intake air. Even in the case where fuel injection is performed before the end of intake of intake air, if the end time of the injection period Tq coincides with the start time of the blocked state, a period in which the intake intake period and the fuel injection period overlap can be minimized. .

  In the first embodiment, one fuel injection valve 30 is provided for one cylinder. However, as shown in FIG. 7, a plurality of fuel injection valves 30 may be provided for one cylinder. Good. If a plurality of fuel injection valves 30 are provided, the injection amount can be increased even if the period during which fuel can be injected is limited. In particular, even when the rotational speed of the engine 10 is fast and the injection period in one combustion cycle is short, a desired amount of gaseous fuel can be injected into the combustion chamber 10a. It should be noted that the position of the cylinder block 12 to which the plurality of fuel injection valves 30 are attached is preferably located at the same distance from the top dead center TDC position. If it does in this way, a blockade state and an open state will change with the same timing to a plurality of fuel injection valves 30.

  In the second embodiment, the fuel injection valve 30 and the on-off valve 50 are attached to the cylinder head 11, but they may be attached to the cylinder block 12.

  DESCRIPTION OF SYMBOLS 10 ... Engine (internal combustion engine), 10a ... Combustion chamber, 10b ... Accommodating chamber, 10c ... Communication port, 11 ... Cylinder head, 12 ... Cylinder block, 13 ... Piston, 13a ... Outer peripheral surface of piston, 30 ... Fuel injection valve, 31b ... nozzle hole, 50 ... on-off valve, L ... predetermined distance.

Claims (6)

A fuel injection valve (30) for directly injecting gaseous fuel into the combustion chamber (10a) of the internal combustion engine (10), and an air-fuel mixture of the gaseous fuel and air injected from the injection hole (31b) of the fuel injection valve are ignited A spark plug (20) that is applied to an internal combustion engine,
The fuel injection valve is attached to a cylinder block (12) of the engine,
Further, the fuel injection valve is in a sealed state in which the nozzle hole is blocked by the outer peripheral surface (13a) of the piston when the piston (13) of the engine is at the top dead center position, and the piston is A gas fuel injection system, wherein the injection hole is disposed so as to be in an open state in which the nozzle hole is open from the outer peripheral surface when the nozzle hole is located at a predetermined distance or more from a dead center position. The engine includes an intake valve (21) for circulating and blocking intake air to the combustion chamber,
In the intake stroke of the engine, the intake valve is closed before the piston descends to the bottom dead center position,
2. The gas fuel injection system according to claim 1, wherein, after the intake valve is closed, the gas fuel is injected by the fuel injection valve within a period in which the piston is located at a position more than the predetermined distance from a top dead center position. . The engine includes an intake pipe (23) connected to the combustion chamber, and a throttle valve (25) for adjusting an intake flow rate of the intake pipe,
The gas fuel injection system according to claim 2, wherein the throttle valve is controlled so that a required amount of intake air is sucked into the combustion chamber before the intake valve is closed.   During high-load operation of the engine, the gas fuel is injected by the fuel injection valve even before the intake valve is closed within a period in which the piston is located at a predetermined distance or more from the top dead center position. The gas fuel injection system according to claim 2 or 3.   The gas fuel injection system according to any one of claims 1 to 4, wherein a plurality of the fuel injection valves are attached to the cylinder block. A fuel injection valve (30) for directly injecting gaseous fuel into the combustion chamber (10a) of the internal combustion engine (10), and an air-fuel mixture of the gaseous fuel and air injected from the injection hole (31b) of the fuel injection valve are ignited A spark plug (20) that is applied to an internal combustion engine,
The cylinder head (11) or the cylinder block (12) of the engine is formed with a storage chamber (10b) for storing a portion including the injection hole in the fuel injection valve,
A communication port (10c) communicating with the combustion chamber is formed in the storage chamber,
An on-off valve (50) for opening and closing the communication port;
During the high temperature period in which the combustion chamber is equal to or higher than a predetermined temperature, the on-off valve is closed.
Gas fuel injection, characterized in that, in a low temperature period in which the combustion chamber is lower than the predetermined temperature, the on-off valve is opened and gas fuel is directly injected from the nozzle hole into the combustion chamber through the communication port. system.

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