JP2002147308A - Fuel/water injection internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel/water injection internal combustion engine capable of executing highly accurate water injection control with a comparatively simple control method, of reducing the device cost of a control operation apparatus for water injection and of reducing NOx. SOLUTION: This fuel/water injection internal combustion engine is so structured that a high-pressure fuel from a fuel injection pump and water fed via a water passage are injected into a combustion chamber from one fuel injection valve. The internal combustion engine is provided with a water injection valve mounted in the water passage for connecting the water passage to a fuel passage, a solenoid valve for fuel for opening and closing a fuel feeding passage, an amount regulating piston device provided with a water chamber whose volume is changed by the axial movement of a piston, and a selector valve for switching over the connection of the water chamber to the water injection valve. When the selector valve connects the water chamber to the water injection valve, the water in the water chamber is fed to the water injection valve side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is configured to inject high-pressure fuel supplied from a fuel injection pump through a fuel passage and water supplied from a water pump into a combustion chamber from one fuel injection valve. More particularly, the present invention relates to a fuel / water injection internal combustion engine in which water is supplied to the fuel injection valve by using a metering piston device.

[0002]

2. Description of the Related Art In a diesel engine, a fuel / water injection diesel engine in which fuel and water are injected from a fuel injection valve into a combustion chamber has been proposed as an effective technique for reducing nitrogen oxides (NOx). . One such technique is the invention of Japanese Patent No. 2772114 filed by the present applicant. FIG. 4 shows the structure of the invention, in which 001 is a fuel injection pump, 3 is a fuel injection valve, 01 is a fuel tank, 02 is a fuel supply pump, 019 is a water tank, 018 is a water supply pump, and 016 is fuel. A control valve 020 controls the supply of water to the injection valve 3, and a control device 020 controls opening and closing of the control valve 016.

In this fuel / water injection diesel engine, water pumped from a water tank 019 by a water supply pump 018 is sent to the control valve 016 through a water supply pipe 017. During the fuel discharge suspension period of the fuel injection pump 001, the control valve 0 is controlled via the control device 020.
The valve 16 is opened and sends a predetermined amount of water to the water supply path 21 of the fuel injection valve 3 through the supply pipe 015. At this time, the valve opening pressure P of the check valve 07 of the fuel injection pump 001
r, opening pressure Pp of the fuel valve in the check valve 013 of the water supply path 021, when the opening pressure _{P 0} of the needle valve 011 of the fuel injection valve 3 is set _P 0> _Pr, and P 0> Pp Therefore, the water supplied to the water supply passage 021 in the fuel injection valve 3 passes through the water passage 030 and the fuel / water junction portion 031 via the fuel valve check valve 013 and enters the fuel passage 022. Inflow.

[0004] The fuel located on the fuel injection pump 001 side of the converging portion 031 in the fuel passage 022 is pushed back toward the fuel injection pump 001 through the high-pressure fuel pipe 08. As a result, the fuel injection valve 3 is filled with the oil reservoir 012 and the fuel corresponding to the volume from the oil reservoir 012 to the junction 031, and the fuel passage 022 on the upstream side of the junction 031.
Is filled with a predetermined amount of water, and the upstream side thereof is again in a layered state filled with fuel.

Next, the discharge of the fuel injection pump 001 is started, the fuel in the fuel injection valve 3 is compressed, and the pressure rises and becomes equal to or higher than the valve opening pressure P ₀ of the fuel injection valve 3.
The needle valve 011 is opened and injection is started. In the injection, among the fuel and water in the stratified state as described above, the fuel is first injected, and after the ignition delay period, the combustion is started. Subsequently, water is injected at the preceding fuel spray flame during combustion. The water injected at this time also becomes a spray and takes in the air in the combustion chamber into the inside thereof, so that air is supplied to the fuel previously injected, and combustion is activated.
Finally, the remaining fuel is injected into the preceding water spray and burns. Due to the thermal effect of the fuel and water injection, the temperature rise of the flame is suppressed, and the generation of NOx is suppressed.

[0006]

In the invention of Japanese Patent No. 2772114 shown in FIG. 4, after fuel and water are filled into the fuel injection valve 3 in layers, the fuel is injected into the combustion chamber by high-pressure fuel and injected. Due to the thermal effect of the fuel and water injection, the temperature rise of the flame is suppressed, and the generation of NOx is suppressed. However, in such a conventional technique, the amount of water injected into the fuel injection valve 3 is controlled by the control device 02.
Since the control is performed by changing the stroke and the valve opening timing of the control valve 016 according to 0, it is necessary to maintain the control accuracy of the control valve 016 high in order to obtain the required water injection amount and the water injection timing. With difficulty.

In the prior art, since the control valve 016 is controlled with high control accuracy as described above, the control device 020 performs high-precision timing control of the control valve 016. , The control valve 01
Since control operating devices such as an operating hydraulic pressure generating device and an electric drive device for applying an operating force to the device 6 are required, the device cost increases.

Furthermore, in the prior art, the control device 020 and the control valve 016 are combined to control the water injection, and the control device 020 is not provided with a treatment means when a failure occurs. Therefore, at the time of such a failure, there is a possibility that the injection amount of water becomes excessive and combustion failure occurs. And the like.

The present invention has been made in view of the problems of the prior art,
It is an object of the present invention to provide a fuel-water injection internal combustion engine that can perform high-precision water injection control with a relatively simple control method, reduce the equipment cost of water injection control operation equipment, and realize NOx reduction. Aim.

[0010]

In order to solve the above-mentioned problems, the present invention is directed to a first aspect of the present invention, wherein high-pressure fuel supplied through a fuel passage by a fuel injection pump and water from a water tank to a water pump are provided. In a fuel / water injection internal combustion engine configured to inject water supplied through a passage from one fuel injection valve into a combustion chamber, the water passage is connected to the fuel passage, and a fuel tank and the fuel A fuel solenoid valve provided in a fuel supply passage connecting the fuel inlet of the injection pump to open and close the fuel supply passage; and a pressure in the fuel passage provided in the water passage being higher than a pressure in the water passage. The water injection valve that opens when the pressure drops, the piston reciprocally fitted in the cylinder, and the top surface or back surface of the piston faced, and the volume changes due to the axial movement of the piston. A metering piston device having a water chamber, and a water supply path connecting the water chamber and the water pump outlet, or a water supply path connecting the water chamber and the water injection valve, and connection of the water chamber. A switching valve for switching between the water chamber and the water injection valve when the switching valve is connected to the water chamber and axially moving the piston so that water in the water chamber can be supplied to the water injection valve side. A characteristic fuel / water injection internal combustion engine is proposed.

In claim 1, preferably, as in claim 4, the switching valve is connected to the water chamber side, the water supply path side connected to the water pump, and the water supply path side connected to the water injection valve. It is composed of a three-way solenoid valve capable of switching in three directions.

The invention according to claim 2 relates to a specific configuration of the metering piston device. In claim 1, in the metering piston device, a top surface of the piston faces the water chamber and a back surface of the piston is the same as the piston. A water supply passage at the outlet of the water pump is connected to the second water chamber, and the piston is connected to the water chamber and the second water chamber. It is characterized in that it is configured to be movable in the axial direction by a pressure difference caused by water supplied to the chamber.

According to a third aspect of the present invention, in the first aspect, a stopper device is provided at an end of the piston, the stopper device being configured to limit the axial movement of the piston and adjust a locking position of the piston. It is characterized by the following.

According to this invention, the metering piston device in which the volume of the water chamber is changed by the axial movement of the piston, and the connection between the water chamber of the metering piston device and the water injection valve to the fuel injection valve are switched. It is possible to control the water injection with high accuracy by using a device that is extremely simple and low-cost compared with the prior art, which is combined with a switching valve.

[0015] Further, by changing the locking position of the piston by the stopper and changing the relative position between the stopper and the piston, the stroke of the piston, that is, the volume of the water chamber displaced by the piston is changed. Thus, the amount of water supplied to the fuel injection valve via the water injection valve by the piston can be adjusted.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an embodiment shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not merely intended to limit the scope of the present invention, but are merely illustrative examples unless otherwise specified. Absent.

FIG. 1 is a configuration diagram of a fuel / water injection system for a diesel engine according to an embodiment of the present invention, FIG. 2 is a sectional view of a metering piston device in the embodiment, and FIG. 3 is a fuel injection pump in the embodiment. FIG. 2 is a cross-sectional view illustrating a structure of a fuel injection valve.

In FIG. 1, reference numeral 1 denotes a fuel injection pump, the main part of which is shown in FIG. 3, which is reciprocated by a fuel cam 20 provided on a cam shaft which rotates in conjunction with the crankshaft of the engine. The fuel in the plunger chamber 27 is pressure-fed by the plunger 25. 3
Is a fuel injection valve the details of which are shown in FIG. 1
3 is a fuel tank containing fuel, 31 is the fuel tank 13 and the fuel inlet chamber 28 of the fuel injection pump 1 (FIG. 3).
Reference numeral 12 denotes a fuel supply pump which is provided in the fuel supply pipe 31 and supplies the fuel in the fuel tank 13 to the fuel injection pump 1 side. Reference numeral 4 denotes a fuel solenoid valve provided in the fuel supply pipe 31 for opening and closing the fuel supply pipe. The fuel solenoid valve 4 is a normally open solenoid valve which is normally opened and closed when energized.

Reference numeral 2 denotes a high-pressure fuel pipe connecting the high-pressure fuel outlet of the fuel injection pump 1 and a fuel passage 022 of the fuel injection valve 3 (see FIG. 5). Accordingly, when the fuel solenoid valve 4 closes the fuel supply pipe 31 by energization, the fuel in the plunger chamber 27 is pressurized to a high pressure by the plunger 25 in the fuel injection pump 1, and the fuel is supplied through the high-pressure fuel pipe 2. The fuel injection is terminated when the fuel supply valve 31 is closed and the fuel supply line 31 is closed.

In FIG. 3 showing the details of the fuel injection pump 1 and the fuel injection valve 3, reference numeral 1 denotes a fuel injection pump which is constructed as follows. Reference numeral 25 denotes a plunger which is slidably fitted on the inner periphery of the plunger barrel 24 and is reciprocated by the fuel cam 20. Reference numeral 27 denotes a plunger chamber.
Reference numeral 7 denotes a fuel discharge valve, and reference numeral 18 denotes a fuel check valve. Reference numeral 22 denotes a fuel supply hole connected to the fuel supply pipe 31. Thus, the plunger chamber 2 is moved by the upward movement of the plunger 25.
The fuel supplied to the inside 7 is pressurized to a high pressure, and the high-pressure fuel is pushed to open the fuel discharge valve 17 and discharged to the high-pressure fuel pipe 2. This fuel injection pump 1 is obtained by removing the injection amount control lead of the plunger 25 and the injection amount adjusting mechanism such as a fuel adjustment rack and a pinion from a known jerk type fuel injection pump.

FIG. 3 shows details of the fuel injection valve 3.
, 09 is the main body, 033 is the nozzle tip, 010
Represents a plurality of injection holes formed at the tip of the nozzle tip 033, 011 represents a needle valve fitted in the nozzle tip 033 so as to be able to slide back and forth, and 014 represents a valve opening pressure P _{0 of} the needle valve 011.
012 is an oil reservoir where the tip of the needle valve 011 faces. A fuel passage 022 has an inlet end connected to the high-pressure fuel pipe 2 and an outlet end connected to the oil reservoir 012.

Reference numeral 021 denotes a water passage whose inlet end is connected to a water supply pipe 34 described later and whose outlet end is connected to a horizontal water passage 030 formed below the nozzle tip 033 via a water injection valve 9 described later. . Further, an outlet end of the horizontal water passage 030 is joined to a lower part of the fuel passage 022 at a position upstream of the oil reservoir 012 to form a joining portion 031. Further, the valve opening pressure P of the fuel check valve 18
r, opening pressure Pp of the water injection valve 9, when the opening pressure _{P 0} of the needle valve 011 of the fuel injection valve 3, these relationships, _{P 0>} Pr, as P 0> Pp, Pr> Pp Is set.

In FIG. 1, reference numeral 11 denotes a water tank, 054 denotes a water supply pipe connected to the water tank 11, and 10 denotes a metering piston device provided in the water supply pipe 054 to supply water in the water tank 11 to be described later. Reference numeral 40 denotes a water pump which supplies the fuel to the fuel injection valve 3 via a water solenoid valve 5 or the like. Numeral 40 denotes a metering piston device whose details are shown in FIG. 2, and numeral 5 denotes a water solenoid valve constituted by a three-way solenoid valve. One side of a water supply pipe 49 branched from the outlet of the water pump 10 is connected to the water solenoid valve. The water supply pipe 51 on the other side is connected to the inlet port of the valve 5 and connected to the small water chamber 44 of the metering piston device 40. A water supply pipe 52 has one end connected to the large water chamber 43 of the metering piston device 40 and the other end connected to a switching port of the solenoid valve for water. Reference numeral 34 denotes a water supply pipe connecting the outlet port of the water solenoid valve 5 and a water passage 021 (see FIG. 3) of the fuel injection valve 3. Therefore, the water solenoid valve 5 composed of the three-way solenoid valve is connected to the water supply pipe 52 from the large water chamber 43 of the metering piston device 40 and the water supply pipe 49 from the water pump 10 or the water injection valve 9. The function of switching the connection with the water supply pipe 34 is performed.

Reference numeral 9 denotes a water injection valve provided in a water passage 21 of the fuel injection valve 3 communicating with the outlet side of the water supply pipe 34. The water injection valve 9 is connected to the fuel passage 022 and the junction 031 from the water passage 21 side. permits a flow only toward and as described above, the valve opening pressure Pp is made smaller than the opening pressure Pr of the opening pressure P ₀ and the fuel check valves 18 of the needle valve 011, the The pressure on the fuel passage 022 side in the fuel injection valve 3 connected to the high-pressure fuel pipe 2
The valve is opened when the pressure becomes lower than the pressure in the valve 1.

In FIG. 2 showing the details of the metering piston device 40, reference numeral 41 denotes a cylinder, 42 denotes a piston fitted reciprocally slidably in the cylinder 41, and the inside of the cylinder 41 is It is partitioned into a large water chamber 43 and a small water chamber 44. Reference numeral 042 denotes a seal ring which is inserted into the outer periphery of the piston 42 and seals between the two water chambers 43 and 44. Reference numeral 48 denotes a water inlet / outlet to the large water chamber 43, which is connected to the water supply pipe 52. Reference numeral 47 denotes a water inlet / outlet to the small water chamber 44, which is connected to the water supply pipe 51. As apparent from FIG. 2A, the cross-sectional area A1 of the top surface 42a of the piston 42 facing the large water chamber 43 is
The cross-sectional area A2 of the back surface 42b facing the small water chamber 44 is formed larger. 45 is a piston rod having one end fixed to the piston 42 and penetrating through the small water chamber 44,
The other end of the piston rod 45 is provided with a hydraulic piston 500 as a stopper. The hydraulic piston 5
00 is the other end of the piston rod 45 abutting (5
07 is a contact portion) A stopper piston 501 is reciprocally fitted in a stopper cylinder 506, and pressurized oil is supplied to oil chambers 502 and 503 formed so that both sides of the stopper piston 501 in the stopper cylinder 506 face each other. Supply and discharge. The hydraulic piston 500 controls the amount of pressurized oil into the oil chambers 502 and 503 through oil ports 504 and 505 provided in the stopper cylinder 506 by operating an engine operation system (not shown). Thus, the position of the stopper piston 501 is changed. FIG. 2B shows another embodiment of the stopper 50. In this example, the stopper 50 is screwed into the support member 050 (50a).
Is a screw portion), and the position of the stopper 50 is adjusted by changing the screwing amount. FIG. 2C shows another embodiment of the piston 42. In this embodiment, a spring 045 for returning the piston is interposed between the piston 42 and the inner surface of the cylinder 41.

In such a fuel / water injection diesel engine, the fuel solenoid valve 4, which is a normally open solenoid valve, is energized to close the fuel supply line 31, and is operated by the fuel cam 20 of the fuel injection pump 1. When the plunger 25 which is slid reciprocally is moved upward, the high-pressure fuel pipe 2 becomes a closed space, so that the high-pressure fuel pipe 2 has a high pressure higher than the valve opening pressure P ₀ of the needle valve 011 in the fuel injection valve 3. The fuel pressurized by the plunger 25 acts on the needle valve 011 to open it, and the fuel injection valve 3
Is injected into the combustion chamber from the injection hole 010. When the energization of the fuel solenoid valve 4 is released, the fuel injection pump 1
Is supplied to the plunger chamber 27, and the fuel injection ends. The fuel injection timing at the time of such fuel injection, that is, the fuel injection start timing and the fuel injection end timing, is adjusted by the opening / closing timing of the fuel solenoid valve 4, and the fuel injection amount is adjusted during the period when the fuel solenoid valve 4 is closed and the fuel injection timing. Cam 2
Adjust with a zero lift (cam profile).

Next, the fuel injection suspension period between the fuel injection and the next fuel injection, that is, the fuel supply line 31 is opened by the fuel solenoid valve 4, and the pressure in the fuel passage is reduced by the fuel injection. When water is injected together with fuel from the fuel injection valve 3 during a period in which the pressure of the fuel check valve 18 of the pump 1 is reduced to about the valve opening pressure Pr, the water-side solenoid valve 5 and the metering piston device 40 are next connected. Operate as follows.

When the three-way solenoid valve 5 is turned off by a valve control device (not shown), the water supply pipe 49 from the water pump 10 and the large water chamber 43 of the metering piston device 40 are released. The water from the water pump 10 is sent to the large water chamber 43 by communicating with the water supply pipe 52 from
Filled here. On the other hand, the small water chamber 44 is always supplied with water from the water pump 10, and as described above, the cutoff of the piston 42 of the metering piston device 40 on the side of the top surface 42 a facing the large water chamber 43. Since the area A1 is formed to be larger than the cross-sectional area A2 on the back surface 42b side facing the small water chamber 44, the piston 42 has the cross-sectional area difference (A1-A
The tip of the adjusting screw 46 is moved to the left in FIG. Accordingly, by changing the amount of protrusion of the adjusting screw 46 from the piston rod 45 to change the relative position between the stopper 50 and the piston 42, the stroke of the piston 42, that is, the large water displaced by the piston 42 is reduced. By changing the volume of the chamber 43,
The fuel injection valve 3 passes through the water injection valve 9 by the piston 42.
It is possible to adjust the amount of water supplied to the refrigeration system.

Next, when the water solenoid valve 5 is energized by the valve control device, the water supply pipe 52 from the large water chamber 43 of the metering piston device 40 and the water supply pipe 34 to the water injection valve 9 are connected. The large water chamber 43 communicates with the water supply pipe 52
And the pressure in the water passage reaching the water injection valve 9 via the water supply pipe 34 is reduced to about the residual pressure in the fuel passage, and is lower than the pressure on the small water chamber 44 side on which the supply pressure from the water pump 10 is acting. The piston 42 is moved rightward in FIG. 2 by the pressure difference, and the water filled in the large water chamber 43 is supplied to the water supply pipe 52, the water solenoid valve 5, and the water supply. It is pushed out to the injection valve 9 via the pipe 34. This allows
The water injection valve 9 is opened, and the water is supplied to the water passage 21 of the fuel injection valve 3.

At this time, the fuel reverse of the fuel injection pump 1
The opening pressure Pr of the stop valve 18 and the opening pressure P of the water injection valve 9
p, valve opening pressure P of needle valve 011 of fuel injection valve 3₀, Water supply
Supply pressure P_WThen, these relations become P₀> Pr, P₀> Pp, Pr> Pp, P_W> P_P  The water supply of the fuel injection valve 3 is set as follows.
The water supplied to the water supply line 21 is passed through the water injection valve 9 to be in water flow.
Fuel passage through road 030 and junction 031 of fuel and water
022.

Due to the inflow of the water, the fuel passage 022
The fuel located on the fuel injection pump 1 side of the inner junction portion 031 is pushed back through the high-pressure fuel pipe 2 in the direction of the fuel injection pump 1. As a result, the fuel injection valve 3 is filled with the oil reservoir 012 and the fuel corresponding to the volume from the oil reservoir 012 to the junction 031, and the fuel passage 022 on the upstream side of the junction 031 is filled with a predetermined amount. Of water, and the upstream side thereof is again in a layered state filled with fuel.

[0032] Then, the fuel injection discharge of the pump 1 is started with the fuel in the fuel injection valve 3 is pressurized, the pressure is equal to or greater than the opening pressure P ₀ of the fuel injection valve 3 increases, the needle valve 011 is opened and injection is started. In the injection, among the fuel and water in the stratified state as described above, the fuel is first injected, and after the ignition delay period, the combustion is started. Subsequently, water is injected at the preceding fuel spray flame during combustion. The water injected at this time also becomes a spray and takes in the air in the combustion chamber into the inside thereof, so that air is supplied to the fuel previously injected, and combustion is activated. Finally, the remaining fuel is injected into the preceding water spray and burns. Due to the thermal effect of the fuel and water injection, the temperature rise of the flame is suppressed, and the generation of NOx is suppressed.

[0033]

As described above, according to the present invention, a metering piston device in which the volume of the water chamber is changed by the axial movement of the piston, and water injection into the water chamber and the fuel injection valve of the metering piston device. The water injection can be controlled with high accuracy by a device that is extremely simple and low-cost compared to the related art, in which a switching valve for switching the connection with the valve is combined.

Further, the stopper position of the piston of the metering piston device is changed by the stopper to change the volume of the water chamber in which the piston is pushed away, and the amount of water supplied to the fuel injection valve via the water injection valve by the piston. It is possible to adjust the amount of water supplied to the fuel injection valve by the stopper, even if the switching valve fails to perform its function due to a failure or the like. The amount of water is limited to a volume corresponding to the position of the piston to be regulated, so that it is possible to prevent an excessive amount of water from being supplied to the fuel injection valve and causing a combustion failure.

In short, according to the present invention, it is possible to perform water injection control with high accuracy by relatively simple control means, to reduce the equipment cost of a water injection control operation device, and to further reduce water consumption. It is possible to provide a fuel-water injection internal combustion engine that can prevent occurrence of poor combustion at the time of failure of the injection control device, maintain required combustion performance, and realize NOx reduction.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a fuel / water injection system for a diesel engine according to an embodiment of the present invention.

FIG. 2 is a sectional view of a metering piston device in the embodiment.

FIG. 3 is a sectional view showing a structure of a fuel injection pump and a fuel injection valve in the embodiment.

FIG. 4 is a sectional view of a water / fuel injection pump according to the related art. It is sectional drawing of the water / fuel injection pump in a prior art.

[Description of Signs] 1 fuel injection pump 2 high pressure fuel pipe 3 fuel injection valve 4 fuel solenoid valve 5 water solenoid valve 9 water injection valve 10 water pump 010 injection hole 11 water tank 011 needle valve 12 fuel supply pump 012 oil reservoir DESCRIPTION OF SYMBOLS 13 Fuel tank 17 Fuel discharge valve 18 Fuel check valve 20 Fuel cam 22 Filling hole 021 Water passage 022 Fuel passage 24 Plunger barrel 25 Plunger 27 Plunger chamber 31 Fuel supply pipe 031 Junction part 34, 49, 51 Water supply pipe 40 Metering Piston device 42 Piston 43 Large water chamber 44 Small water chamber 46 Adjusting screw 50 Stopper 054 Water supply pipe

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshinori Nagae 5-717-1, Fukahori-cho, Nagasaki-shi Mitsubishi Heavy Industries, Ltd. Nagasaki Research Laboratory Co., Ltd. (72) Inventor Kenichi Iwanaga 5-717-1, Fukahori-cho, Nagasaki-shi No.Mitsubishi Heavy Industries, Ltd.Nagasaki Research Laboratories (72) Inventor Akira Numata 3000 Tana, Sagamihara-shi, Kanagawa Prefecture Mitsubishi Heavy Industries, Ltd.General Purpose Machinery & Special Vehicle Business Division (72) Inventor Takeshi Arai12 Address Mitsubishi Heavy Industries, Ltd. Yokohama Works F-term (reference) 3G066 AA07 AB02 AB08 AC01 AC04 AC06 AD07 BA25 BA51 BA61 CB07U CC06T CC14 CE12 CE22 CE34 DA00

Claims (4)

[Claims] 1. A high-pressure fuel supplied through a fuel passage by a fuel injection pump and water supplied through a water passage by a water pump from a water tank are injected into a combustion chamber from one fuel injection valve. In the fuel / water injection internal combustion engine thus configured, the water passage is connected to the fuel passage, and a fuel supply passage connecting a fuel tank and a fuel inlet of the fuel injection pump is provided in the water passage. A water injection valve which is opened when the pressure in the fuel passage is lower than the pressure in the water passage, a piston fitted reciprocally in the cylinder, and a top surface or a back surface of the piston facing the piston, A metering piston device including a water chamber whose volume is changed by axial movement, and a water supply path connecting the water chamber and the water pump outlet or a water supply connecting the water chamber and the water injection valve. Road And a switching valve for switching connection between the water chamber and the water chamber. When the switching valve connects the water chamber and the water injection valve, water in the water chamber can be supplied to the water injection valve side by axial movement of the piston. A fuel / water injection internal combustion engine characterized in that: 2. The metering piston device is configured such that a top surface of the piston faces the water chamber and a back surface faces a second water chamber formed on the opposite side of the piston.
The water supply path at the outlet of the water pump is connected to the second water chamber, and the piston is configured to be movable in the axial direction by a pressure difference caused by water supplied to the water chamber and the second water chamber. The fuel / water injection internal combustion engine according to claim 1, wherein: 3. The fuel according to claim 1, wherein a stopper device is provided at an end of the piston so as to limit axial movement of the piston and adjust a locking position of the piston. -Water injection internal combustion engine. 4. The switching valve comprises a three-way solenoid valve capable of three-way switching between the water chamber side, the water supply path side connected to the water pump, and the water supply path side connected to the water injection valve. The fuel / water injection internal combustion engine according to claim 1, wherein the internal combustion engine is provided.