JP2003120429A - Fuel injection valve, diesel engine having this valve and fuel injection valve cooling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection valve capable of a stable operation, when using a low boiling fuel in a fuel supply system of relatively low pressure. SOLUTION: In the fuel injection valve of a diesel engine which generates power by using gas energy of a high temperature and high pressure generated by burning the supplied low boiling fuel in a combustion chamber, a leak hole 12 and a leak passage 13 are provided as leak flow paths which vaporizes by blowing off a portion of the low boiling fuel flowing into the fuel injection valve body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection valve for injecting fuel into a combustion chamber of a diesel engine, a diesel engine equipped with the fuel injection valve, and a method for cooling the fuel injection valve, and more particularly to a low boiling point fuel. It relates to a technique suitable for use.

[0002]

2. Description of the Related Art A diesel engine is an engine that obtains power by driving a piston or the like with high-temperature and high-pressure gas energy generated by burning fuel. Since this diesel engine needs to inject fuel into the combustion chamber (cylinder) in a liquid state, the fuel supply system and the fuel injection system are pressurized. That is, there is provided a fuel injection valve for injecting the high-pressure liquid fuel sent from the fuel injection pump into the combustion chamber in a liquid state, and the fuel supplied into this fuel injection valve is It is atomized by passing through a fuel injection nozzle (injection hole) provided in the fuel injection nozzle and is injected into the combustion chamber.

Here, an example of a conventional fuel injection valve is shown in FIG. In FIG. 5, reference numeral 01 in the drawing is a nozzle hole, and 0
Reference numeral 2 is a nozzle tip, 03 is a needle valve, 04 is a nozzle tip retainer, 05 is a nozzle holder, 06 is a needle valve retainer spring, 07 is a holder for attaching an injection pipe, 08 is an injection pipe, 09 is an oil passage,
Reference numeral 010 is an oil sump, and 011 is a fuel valve sack portion. This fuel injection valve includes a nozzle tip 02 and a nozzle holder 05.
In the body integrated by the nozzle tip holder 04,
The needle valve 03 biased toward the injection hole 01 by the needle valve pressing spring 06 is slidably accommodated. The tip of the needle valve 03, which is biased by the needle valve pressing spring 06, comes into close contact with the inner wall of the nozzle tip 02 and the oil sump 01
The line between 0 and the nozzle hole 01 is blocked.

The fuel injection valve receives a high pressure supply of liquid fuel from a fuel injection pump (not shown) via an injection pipe 08. This liquid fuel is guided through the oil passage 09 to the oil sump 010 in the space formed between the needle valve 03 and the nozzle tip 02. The pressure of the liquid fuel accumulated in the oil sump 010 acts on the needle valve 03, and when the pressure becomes larger than the biasing force of the needle valve pressing spring 06, the needle valve 03 is pushed up. As a result, the liquid fuel in the oil sump 010 flows into the fuel valve suck portion 011 and is injected into the combustion chamber (not shown) in a liquid state from the injection hole 01 opened in the fuel valve suck portion 011.

[0005]

By the way, the above-mentioned conventional fuel injection valve has a long history of use when a liquid fuel having a high boiling point such as light oil is used, and there is no particular problem. That is, since the fuel injection valve is thermally affected by the engine body such that the nozzle tip 05 provided with the injection hole 01 is installed in a high temperature combustion chamber, the temperature of the fuel injection valve rises to a high temperature (particularly the nozzle tip 05). There is no particular problem when a liquid fuel that does not vaporize even when it passes through and its vicinity (for example, the injection pipe 08) is used.

On the other hand, in recent years, development of a diesel engine that operates using a new fuel other than the above-mentioned light oil has been advanced. Some of these new fuels include
For example, synthetic fuel dimethyl ether (hereinafter referred to as “D
A fuel having a lower boiling point than light oil (hereinafter abbreviated as “ME”), liquefied petroleum gas (hereinafter abbreviated as “LPG”), liquefied natural gas (hereinafter abbreviated as “LNG”), and liquid hydrogen (hereinafter abbreviated as “LNG”) , "Low boiling point fuel").

Such a low boiling point fuel is a liquid fuel pumped from a storage tank to a fuel injection valve, and has a low boiling point so that it may be vaporized by the thermal influence of the fuel injection valve and its vicinity. It is fuel. When such a low boiling point fuel is used as a fuel for a diesel engine, gas fuel vaporized due to heat may exist in the fuel supply system and the fuel injection system. In this way, when the compressible fluid gas fuel is present in the fuel supply system and the fuel injection system, it is not possible to raise the pressure by the pump so as to pressurize the incompressible fluid liquid fuel only, and the appropriate fuel injection pressure is applied. Will not be obtained.

That is, since the pressure increase of the liquid fuel by the pump is absorbed by the compression of the gas fuel, it becomes impossible to perform an appropriate pressure increase at the time of fuel injection, and the desired discharge pressure at the injection hole 01 cannot be obtained. is there. As a result, a phenomenon such as a decrease in fuel injection amount or inability to inject fuel occurs, which causes a serious obstacle to smooth operation of the diesel engine. This kind of phenomenon can be avoided by keeping the pressure of the fuel supply system high enough, but it usually causes an increase in size and weight, and therefore the structure of the fuel supply system is not practical in terms of strength and cost. Not at all.

The present invention has been made in view of the above circumstances, and a fuel injection valve and a fuel injection valve capable of performing stable operation even when a low boiling point fuel is used in a fuel supply system of relatively low pressurization. It is an object of the present invention to provide a diesel engine equipped with and a method for cooling a fuel injection valve.

[0010]

The present invention adopts the following means in order to solve the above problems. The fuel injection valve according to claim 1 is a fuel injection valve for a diesel engine that generates power by utilizing high-temperature and high-pressure gas energy generated by burning a low boiling point fuel supplied into a combustion chamber. It is characterized in that a leak flow path is provided to allow a part of the low boiling point fuel that has flowed into the fuel injection valve body to escape and evaporate.

According to such a fuel injection valve, when the low boiling point fuel that has escaped to the leak passage evaporates latent heat of vaporization from the surroundings, the fuel injection valve main body provided with the leak passage can be cooled. it can.

In the fuel injection valve of the first aspect, it is preferable that the leak flow passage is connected to an intake system, whereby the leaked low boiling point fuel is introduced into the combustion chamber together with fresh air and burned. be able to.

In the fuel injection valve according to the first or second aspect of the invention, it is preferable that the low boiling point fuel is allowed to escape only at the fuel injection timing, whereby the flow rate of the low boiling point fuel to be leaked can be minimized.

According to another aspect of the fuel injection valve of the present invention, the leak passage has a space provided in a nozzle tip forming an outer peripheral wall of an oil sump, at least one of the oil sump and an oil passage, and the leak passage. It is preferable to provide a leak hole that communicates with the space portion and a leak pipe line that connects the space portion and the intake system, whereby the oil is supplied to the oil sump or the oil passage. A part of the low boiling point fuel flows into the space through the leak hole and is vaporized, and the vaporized low boiling point fuel gas is guided to the intake system through the leak pipe line.

According to another aspect of the fuel injection valve of the present invention, the leak passage has a space provided in the nozzle tip forming the outer peripheral wall of the oil sump and a fuel valve sack into which the fuel flows when the needle valve is opened. It is preferable that a leak hole communicating between the space portion and the space portion and a leak conduit connecting between the space portion and the intake system are provided, whereby the needle valve is opened and the oil is discharged. A part of the low boiling point fuel that has flowed into the fuel valve sack from the reservoir flows into the space through the leak holes and evaporates, and the vaporized low boiling point fuel gas passes through the leak pipe to the intake system. Be guided.

In the fuel injection valve according to the fourth or fifth aspect, it is preferable that the leak hole is provided with a leak valve that opens at a predetermined pressure or more. As a result, in the case of claim 4, by controlling the pressure at which the leak valve opens, it is possible to leak the low boiling point fuel only during fuel injection and to adjust the leak amount. Further, in the case of claim 5, the amount of combustion gas returning (backflowing) from the leak hole to the intake side can be controlled by appropriately setting the pressure at which the leak valve opens.

According to a seventh aspect of the present invention, there is provided a diesel engine in which power is generated by utilizing high temperature and high pressure gas energy generated by burning a low boiling point fuel supplied into a combustion chamber. Is
The fuel injection valve according to any one of claims 1 to 6 is provided.

In such a diesel engine, the leaked low-boiling point fuel takes away the latent heat of vaporization and cools the fuel injection valve body, so that the low-boiling point fuel supplied to the fuel injection valve evaporates. It is possible to prevent a decrease in the fuel injection amount or to prevent the fuel injection from becoming impossible, so that stable operation can be performed.

According to a eighth aspect of the present invention, there is provided a method for cooling a fuel injection valve for a diesel engine in which power is generated by utilizing high temperature and high pressure gas energy generated by burning a low boiling point fuel supplied into a combustion chamber. A method for cooling a valve, characterized in that a part of the low boiling point fuel that has flowed into the fuel injection valve body is released as a leak fuel to a leak flow path provided in the nozzle tip, and is cooled by the latent heat of vaporization of the leak fuel. To do.

According to such a fuel injection valve cooling method,
A part of the low boiling point fuel is released to the leak flow path as leak fuel and cooled by the latent heat of vaporization, so the fuel injection valve is cooled without using another refrigerant to prevent the vaporization of low boiling point fuel. be able to.

In the fuel injection valve cooling method according to the eighth aspect, it is preferable that the leaked fuel is supplied to the intake system and is absorbed into the combustion chamber together with fresh air, whereby the leaked low boiling point fuel is burned. It is possible to minimize the decrease in thermal efficiency.

In the fuel injection valve cooling method according to the eighth or ninth aspect, it is preferable that the low boiling point fuel is allowed to escape only at the fuel injection timing, whereby the flow rate of the low boiling point fuel to be leaked can be minimized. it can.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a fuel injection valve according to the present invention will be described below with reference to the drawings. <First Embodiment> In the fuel injection valve of the first embodiment shown in FIG. 1, reference numeral 1 in the drawing denotes a nozzle hole, 2 is a nozzle tip, 3 is a needle valve, 4 is a nozzle tip holder, and 5 is a nozzle. Holder, 6 is a needle valve pressing spring, 7 is a holder for attaching an injection pipe,
8 is an injection pipe, 9 is an oil passage, 10 is an oil sump, 11 is a fuel valve sack portion, 12 is a leak hole, 13 is a leak passage, and 14 is a leak pipe.

This fuel injection valve is for injecting mist-like low boiling point fuel into a combustion chamber (not shown) of a diesel engine.
The other end of the injection pipe 8 is connected to a fuel injection pump (not shown). The low boiling point fuel used here is, for example, DM
There are E, LPG, LNG, liquid hydrogen, etc., all of which are stored in liquid form in the fuel tank. This low boiling point fuel is pumped at a high pressure as it is in a liquid state by a fuel injection pump. The fuel supply pressure of the low boiling point fuel is, for example, DME.
In this case, the high pressure is about 2.5 MPa.

In the fuel injection valve, a nozzle tip 2 and a nozzle holder 5 each having a hollow cylindrical portion in the axial (up and down) direction are coaxially overlapped and integrated by a nozzle tip retainer 4 to form a fuel injection valve main body. Movable parts such as the needle valve 3 and the needle valve pressing spring 6 are housed in a hollow cylindrical portion inside the fuel injection valve body. The needle valve 3 is biased downward in the drawing toward the injection hole 1 by a needle valve pressing spring 6 located on the upper end side, and is configured to be vertically slidable in the hollow cylindrical portion.

An oil sump 10 is formed between the lower outer peripheral surface of the needle valve 3 and the wall surface of the hollow cylindrical portion of the nozzle tip 2 as a space for accumulating the low boiling point fuel. The oil sump 10 is in communication with an injection pipe 8 and an oil passage 9, one end of which is connected to a fuel injection pump (not shown). The other end of the injection pipe 8 is connected to the nozzle holder 5 via the injection pipe attachment holder 7 and communicates with one end of an oil passage 9 formed in the nozzle holder 5. The oil passage 9 is a flow path for the low boiling point fuel provided so as to communicate with the nozzle holder 5 and the nozzle tip 2, and the other end of the oil passage 9 is open to the oil sump 10. Therefore, the low boiling point fuel pumped from the fuel injection pump is
It is supplied to the oil sump 10 through the injection pipe 8 and the oil passage 9.

The lower end portion of the needle valve 3 is in close contact with the wall surface (inner peripheral surface) which forms the internal space of the nozzle tip 2 with the seat surface under the bias of the needle valve pressing spring 6. Due to this close contact, the fuel sack portion 1 in which the oil sump 10 and the injection hole 1 are opened
1 is cut off, so that the low boiling point fuel in the oil sump 10 does not flow out from the injection hole 1 formed in the lower end portion of the nozzle tip 2.

However, when the low-boiling point fuel is continuously pumped from the fuel injection pump in such a shut-off state, the low-boiling point fuel is fed from the fuel injection pump (not shown) through the injection pipe 8 to the low-boiling point fuel. To be supplied. This low boiling point fuel is guided to the oil sump 10 through the oil passage 9. The pressure of the low boiling point fuel accumulated in the oil sump 10 is equal to the step 3 of the needle valve 3.
When the push-up force acting on a and generated by the same pressure becomes larger than the biasing force of the needle valve pressing spring 6, the needle valve 3 is pushed up and the oil sump 10 and the fuel sack portion 11 are brought into communication with each other.

As a result, the low boiling point fuel in the oil sump 10 flows into the fuel valve sack portion 11, and liquid (from the injection hole 1 opening in the nozzle tip 2 forming the fuel valve sack portion 11 to the combustion chamber (not shown)) It is sprayed as it is. Note that once fuel injection is performed, the pressure in the oil sump 10 drops, so the biasing force of the needle valve retainer spring 6 becomes greater than the pressure of the low boiling point fuel again, and the needle valve 3 moves to the nozzle tip 2 of the nozzle tip 2. The fuel injection from the injection hole 1 into the combustion chamber is stopped by closely contacting the inner wall.

In the fuel injection valve having the above-mentioned structure, a space portion serving as the leak passage 13 is provided inside the wall member forming the hollow cylindrical portion of the nozzle tip 2 so as to surround the needle valve 3. Has been. This leak passage 1
3 is in communication with the oil sump 10 by the minute diameter leak hole 12, and the leak passage is formed by the leak hole 12 and the leak passage 13. In addition, leak hole 1
A plurality of needles 2 are provided on the outer peripheral portion of the needle valve 3 at an appropriate pitch. Further, the leak passage 13 is connected to the leak pipe 14 by an intake system (for example, an intake pipe line) of the diesel engine.
It is connected to the. That is, the leak fuel, which is a part of the low boiling point fuel that has leaked out from the oil sump 10 through the leak hole 12 to the leak passage 13, evaporates in the leak passage 13 to become a gas fuel. , Leak tube 1
4 and is sucked into the intake pipe.

The operation of the above-described first embodiment will be described below. In this case, a part of the low boiling point fuel supplied to the oil sump 10, that is, a very small amount of the low boiling point fuel (leak fuel) passing through the leak holes 12 having a small diameter is affected by the heat of the engine body and becomes a high temperature. On the way to the leak passage 13 and inside the leak passage 13. This time,
Because the latent heat of vaporization is taken away to cool the fuel injection valve body, the rise in the temperature of the fuel injection valve and its surroundings is suppressed, and the temperature of the fuel injection valve body and the vicinity of the fuel injection valve body are kept so that the low boiling point fuel excluding leak fuel does not evaporate. The injection pipe 8 is cooled. Therefore, even if the pressure of the fuel supply system is set to a relatively low pressure, it is possible to prevent the low boiling point fuel from evaporating and becoming a gas fuel (vapor) of an incompressible fluid in the fuel supply system and the fuel injection system, Injection hole 1
The discharge pressure can be maintained at a desired value and stable operation can be performed.

The gaseous low boiling point fuel (leak fuel) evaporated in the leak passage 13 is guided to the intake system through the leak pipe 14. Therefore, this gas fuel is sent into the combustion chamber together with the fresh air sucked from the outside air, and is mixed with the fuel injected from the injection hole 1 in the combustion chamber and burned. For this reason,
The leaked fuel is not wasted, contributes to the combustion in the combustion chamber, and the reduction in the thermal efficiency of the diesel engine can be minimized. In the above-described embodiment, the leaked fuel (vapor) that has evaporated is merged into the intake system in consideration of the thermal efficiency of the diesel engine. However, if cooling of the fuel injection valve body is considered, the present invention is not limited to this. It will not be done.

<Second Embodiment> In the fuel injection valve of the second embodiment shown in FIG. 2, reference numeral 1 in the drawing denotes an injection hole, 2 a nozzle tip, 3 a needle valve, 4 a nozzle tip holder, 5 is a nozzle holder, 6 is a needle valve pressing spring, 7 is a holder for attaching an injection pipe, 8 is an injection pipe, 9 is an oil passage, 10 is an oil sump, 11
Is a fuel valve sack portion, 12A is a leak hole, 13 is a leak passage, and 14 is a leak pipe.

This fuel injection valve has the same basic structure as that of the first embodiment described above, and therefore, the same members are denoted by the same reference numerals here. In this fuel injection valve, a nozzle tip 2 and a nozzle holder 5 are coaxially overlapped with each other to be integrated by a nozzle tip retainer 4 to form a fuel injection valve main body, and a needle valve 3 is formed in a hollow cylindrical portion in the fuel injection valve main body. And, the movable parts such as the needle valve pressing spring 6 are stored. Needle valve 3
Is urged downward in the drawing toward the injection hole 1 side by the needle valve pressing spring 6 located on the upper end side, and is slidable vertically in the hollow cylindrical portion.

An oil sump 1 for accumulating low boiling point fuel is provided between the outer peripheral surface of the lower portion of the needle valve 3 and the wall surface of the hollow cylindrical portion of the nozzle tip 2.
0 is formed. An injection pipe 8 connected to a fuel injection pump and an oil passage 9 communicate with the oil sump 10.
The other end of the injection pipe 8 is connected to the nozzle holder 5 via the injection pipe attachment holder 7 and communicates with one end of an oil passage 9 formed in the nozzle holder 5. The oil passage 9 is a low boiling point fuel flow passage, and the other end of the oil passage 9 opens into the oil sump 10. Therefore, the low boiling point fuel pressure-fed from the fuel injection pump is supplied to the oil sump 10 through the injection pipe 8 and the oil passage 9.

At the lower end of the needle valve 3, the seat surface is in close contact with the inner peripheral surface of the nozzle tip 2 under the bias of the needle valve pressing spring 6. Due to this close contact, the oil sump 10 and the fuel sack portion 11 in which the injection hole 1 is opened are blocked, so that the low boiling point fuel of the oil sump 10 does not flow out from the injection hole 1. However, if the low-boiling point fuel is continuously pumped from the fuel injection pump in such a cutoff state, the oil sump 10
The pressure of the low boiling point fuel accumulated in the tank rises. Due to this pressure increase, when the pushing force generated by the pressure acting on the stepped portion 3a of the needle valve 3 becomes larger than the urging force of the needle valve pressing spring 6, the needle valve 3 is pushed up and the oil sump 10 and the fuel sack portion 11 are pushed.
Communication is established between and.

As a result, the low boiling point fuel in the oil sump 10 flows into the fuel valve sack portion 11, and liquid (from the injection hole 1 opening in the nozzle tip 2 forming the fuel valve sack portion 11 to the combustion chamber (not shown)) It is sprayed as it is. Note that once fuel injection is performed, the pressure in the oil sump 10 decreases, the biasing force of the needle valve pressing spring 6 becomes greater than the pressure of the low boiling point fuel again, and the needle valve 3 is pressed down to cause the nozzle tip 2 to move downward. Since it is in close contact with the inner wall, fuel injection from the injection hole 1 into the combustion chamber is stopped.

In the fuel injection valve having the above-described structure, a space portion serving as the leak passage 13 is provided inside the wall member forming the hollow cylindrical portion of the nozzle tip 2 so as to surround the needle valve 3 over the entire circumference. Has been. This leak passage 1
3 is the fuel sack portion 1 due to the minute leak hole 12A.
1, which is in communication with the leak hole 12 and the leak passage 13.
Thereby forming a leak flow path. The plurality of leak holes 12A are radially provided at an appropriate pitch.

The leak passage 13 is connected by a leak pipe 14 to an intake system (for example, an intake pipe line) of the diesel engine. That is, the leak fuel that is a part of the low boiling point fuel that has leaked from the fuel sack portion 11 to the leak passage 13 through the leak hole 12A is
After being vaporized into gas fuel, it is guided to the leak pipe 14 and sucked into the intake pipe line.

The operation of the second embodiment described above will be described below. In this case, a part of the low boiling point fuel supplied to the fuel sack portion 11 when the needle valve 3 is opened, that is, a very small amount of the leaked fuel passing through the leak hole 12A having a small diameter, causes a thermal influence of the engine body. It evaporates on the way to the leak passage 13 that receives and becomes hot and in the leak passage 13. At this time, since the latent heat of vaporization is taken away to cool the fuel injection valve body, the rise in the temperature of the fuel injection valve and its surroundings is suppressed, and the fuel injection valve body is prevented from reaching such a high temperature that low-boiling point fuel other than leaked fuel evaporates. And the nearby injection pipe 8 is cooled. Therefore, even if the set pressure of the fuel supply system is relatively low, it is possible to prevent the low boiling point fuel from evaporating in the fuel supply system and the fuel injection system to become a gas fuel (vapor) of an incompressible fluid. The discharge pressure from the hole 1 can be maintained at a desired value and stable operation can be performed.

Further, the gaseous leak fuel evaporated in the leak passage 13 is introduced into the intake system through the leak pipe 14. Therefore, this gas fuel is sent into the combustion chamber together with the fresh air sucked from the outside air, and is mixed with the fuel injected from the injection hole 1 in the combustion chamber and burned. Therefore, the leaked fuel is not wasted, and it is possible to contribute to the combustion in the combustion chamber and minimize the reduction in the thermal efficiency of the diesel engine.

Further, in this embodiment, the leak hole 12
Since one end of A is communicated with the fuel sack portion 11, leak fuel is generated only at the fuel injection timing when the needle valve 3 is opened. Therefore, the amount of leaked fuel is relatively small, so that the cooling effect tends to be inferior to that of the first embodiment described above.

However, since a part of the high-temperature and high-pressure combustion gas flows from the combustion chamber, this combustion gas is leaked to the leak pipe 14.
Since it is returned to the intake system together with the gas fuel through the exhaust gas, the effect of exhaust gas recirculation (EGR), which is known to be effective in reducing nitrogen oxides in the exhaust gas, can be automatically provided. In the embodiment described above, the evaporated leaked fuel (vapor) is merged with the intake system in consideration of the thermal efficiency and EGR effect of the diesel engine, but if only cooling of the fuel injection valve body is considered, It is not limited to this.

<Third Embodiment> In the fuel injection valve of the third embodiment shown in FIG. 3, reference numeral 1 in the drawing denotes an injection hole, 2 a nozzle tip, 3 a needle valve, 4 a nozzle tip retainer, 5 is a nozzle holder, 6 is a needle valve pressing spring, 7 is a holder for attaching an injection pipe, 8 is an injection pipe, 9 is an oil passage, 10 is an oil sump, 11
Is a fuel valve sack portion, 12 is a leak hole, 13 is a leak passage, 14 is a leak pipe, and 15 is a leak valve.

This fuel injection valve has the same basic structure as that of the first embodiment described above, and therefore, the same members are designated by the same reference numerals here. In this fuel injection valve, a nozzle tip 2 and a nozzle holder 5 are coaxially overlapped with each other to be integrated by a nozzle tip retainer 4 to form a fuel injection valve main body, and a needle valve 3 is formed in a hollow cylindrical portion in the fuel injection valve main body. And, the movable parts such as the needle valve pressing spring 6 are stored. Needle valve 3
Is urged downward in the drawing toward the injection hole 1 side by the needle valve pressing spring 6 located on the upper end side, and is slidable vertically in the hollow cylindrical portion.

An oil sump 1 for accumulating low boiling point fuel is provided between the outer peripheral surface of the lower portion of the needle valve 3 and the wall surface of the hollow cylindrical portion of the nozzle tip 2.
0 is formed. An injection pipe 8 connected to a fuel injection pump and an oil passage 9 communicate with the oil sump 10.
The other end of the injection pipe 8 is connected to the nozzle holder 5 via the injection pipe attachment holder 7 and communicates with one end of an oil passage 9 formed in the nozzle holder 5. The oil passage 9 is a low boiling point fuel flow passage, and the other end of the oil passage 9 opens into the oil sump 10. Therefore, the low boiling point fuel pressure-fed from the fuel injection pump is supplied to the oil sump 10 through the injection pipe 8 and the oil passage 9.

The lower end of the needle valve 3 is biased by the needle valve pressing spring 6 so that the outer peripheral corner thereof is in close contact with the inner peripheral surface of the nozzle tip 2. Due to this close contact, the oil sump 10 and the fuel sack portion 11 in which the injection hole 1 is opened are blocked, so that the low boiling point fuel of the oil sump 10 does not flow out from the injection hole 1. However, if the low-boiling point fuel is continuously pumped from the fuel injection pump in such a cutoff state, the oil sump 10
The pressure of the low boiling point fuel accumulated in the tank rises. Due to this pressure increase, when the pushing force generated by the pressure acting on the stepped portion 3a of the needle valve 3 becomes larger than the urging force of the needle valve pressing spring 6, the needle valve 3 is pushed up and the oil sump 10 and the fuel sack portion 11 are pushed.
Communication is established between and.

As a result, the low boiling point fuel in the oil sump 10 flows into the fuel valve sack portion 11, and the liquid (from the injection hole 1 opening in the nozzle tip 2 forming the fuel valve sack portion 11 to the combustion chamber not shown) It is sprayed as it is. Note that once fuel injection is performed, the pressure in the oil sump 10 decreases, the biasing force of the needle valve pressing spring 6 becomes greater than the pressure of the low boiling point fuel again, and the needle valve 3 is pressed down to cause the nozzle tip 2 to move downward. Since it is in close contact with the inner wall, fuel injection from the injection hole 1 into the combustion chamber is stopped.

In the fuel injection valve having the above-described structure, a space portion serving as the leak passage 13 is provided inside the wall member forming the hollow cylindrical portion of the nozzle tip 2 so as to surround the needle valve 3 over the entire circumference. Has been. This leak passage 1
3 is in communication with the oil sump 10 through a minute diameter leak hole 12 provided with a leak valve 15.
A leak passage is formed by the leak passage 13. The leak valve 15 provided in the leak hole 12 is provided with an oil sump 10
It opens when the inside pressure becomes equal to or higher than a predetermined pressure, and establishes communication between the oil sump 10 and the leak passage 13. The leak holes 12 are radially provided at an appropriate pitch so as to open to the outer peripheral portion of the needle valve 3.

The leak passage 13 is connected by a leak pipe 14 to an intake system (for example, an intake pipe line) of the diesel engine. That is, the leak fuel, which is a portion of the low boiling point fuel that has leaked from the oil sump 10 through the leak hole 12 and the leak valve 15 to the leak passage 13, is evaporated in the leak passage 13 to become a gas fuel, and then the leak pipe. 14
Is sucked into the intake pipe.

The operation of the above-described third embodiment will be described below. In this case, when the pressure in the oil sump 10 rises and the leak valve 15 opens, part of the low boiling point fuel supplied to the oil sump 10 passes through the leak holes 12 having a small diameter, and a very small amount of leak fuel is generated. Become. The leak fuel evaporates on the way to the leak passage 13 and in the leak passage 13 where the leak fuel is heated to a high temperature due to the heat of the engine body. At this time, since the latent heat of vaporization is taken away to cool the fuel injection valve body, the rise in the temperature of the fuel injection valve and its surroundings is suppressed, and the fuel injection valve body is prevented from reaching such a high temperature that low-boiling point fuel other than leaked fuel evaporates. And the nearby injection pipe 8 is cooled. Therefore, even when the set pressure of the fuel supply system is relatively low, it is possible to prevent the low boiling point fuel from evaporating in the fuel supply system and the fuel injection system to become a gas fuel (vapor) of an incompressible fluid. The discharge pressure from 1 can be maintained at a desired value and stable operation can be performed.

In particular, by providing the leak valve 15, it becomes possible to arbitrarily control the leak amount in accordance with the pressure set value at which the valve is opened, and for example, control is performed so that leak fuel is generated only at the fuel injection timing. It is possible to control the flow rate of the leaked fuel, for example, by controlling the cooling rate with a minimum amount of the leaked fuel. In this case, since the leak hole 12 opens in the oil sump 10 which is far from the injection hole 1, the above-mentioned second
Unlike the above embodiment, the high temperature and high pressure combustion gas rarely flows from the combustion chamber.

The gaseous leak fuel vaporized in the leak passage 13 is guided to the intake system through the leak pipe 14. Therefore, this gas fuel is sent into the combustion chamber together with the fresh air sucked from the outside air, and is mixed with the fuel injected from the injection hole 1 in the combustion chamber and burned. For this reason, the leaked fuel is not wasted, contributes to combustion in the combustion chamber, and suppresses a decrease in thermal efficiency of the diesel engine. In addition,
In the above-described embodiment, the leaked fuel (vapor) evaporated in consideration of the thermal efficiency of the diesel engine is merged with the intake system, but the present invention is not limited to this if only the cooling of the fuel injection valve body is considered. There is no.

<Fourth Embodiment> In the fuel injection valve of the fourth embodiment shown in FIG. 4, reference numeral 1 in the drawing denotes an injection hole, 2 a nozzle tip, 3 a needle valve, 4 a nozzle tip retainer, 5 is a nozzle holder, 6 is a needle valve pressing spring, 7 is a holder for attaching an injection pipe, 8 is an injection pipe, 9 is an oil passage, 10 is an oil sump, 11
Is a fuel valve sack portion, 12A is a leak hole, 13 is a leak passage, 14 is a leak pipe, and 15 is a leak valve.

This fuel injection valve is obtained by adding the same leak valve 15 as that used in the third embodiment to the structure of the above-described second embodiment. Therefore, the same members are designated by the same reference numerals here. Is attached. In this fuel injection valve, a nozzle tip 2 and a nozzle holder 5 are coaxially overlapped with each other to be integrated by a nozzle tip retainer 4 to form a fuel injection valve main body, and a needle valve 3 is formed in a hollow cylindrical portion in the fuel injection valve main body. And, the movable parts such as the needle valve pressing spring 6 are stored. The needle valve 3 is biased downward in the drawing toward the injection hole 1 by a needle valve pressing spring 6 located on the upper end side, and is configured to be vertically slidable in the hollow cylindrical portion.

An oil sump 1 for accumulating low boiling point fuel between the outer peripheral surface of the lower portion of the needle valve 3 and the wall surface of the hollow cylindrical portion of the nozzle tip 2.
0 is formed. An injection pipe 8 connected to a fuel injection pump and an oil passage 9 communicate with the oil sump 10.
The other end of the injection pipe 8 is connected to the nozzle holder 5 via the injection pipe attachment holder 7 and communicates with one end of an oil passage 9 formed in the nozzle holder 5. The oil passage 9 is a low boiling point fuel flow passage, and the other end of the oil passage 9 opens into the oil sump 10. Therefore, the low boiling point fuel pressure-fed from the fuel injection pump is supplied to the oil sump 10 through the injection pipe 8 and the oil passage 9.

The lower end portion of the needle valve 3 is biased by the needle valve pressing spring 6 and its outer peripheral corner portion is in close contact with the inner peripheral surface of the nozzle tip 2. Due to this close contact, the oil sump 10 and the fuel sack portion 11 in which the injection hole 1 is opened are blocked, so that the low boiling point fuel of the oil sump 10 does not flow out from the injection hole 1. However, if the low-boiling point fuel is continuously pumped from the fuel injection pump in such a cutoff state, the oil sump 10
The pressure of the low boiling point fuel accumulated in the tank rises. Due to this pressure increase, when the pushing force generated by the pressure acting on the stepped portion 3a of the needle valve 3 becomes larger than the urging force of the needle valve pressing spring 6, the needle valve 3 is pushed up and the oil sump 10 and the fuel sack portion 11 are pushed.
Communication is established between and.

As a result, the low boiling point fuel in the oil sump 10 flows into the fuel valve sack portion 11, and the liquid (from the injection hole 1 opening in the nozzle tip 2 forming the fuel valve sack portion 11 to the combustion chamber not shown) It is sprayed as it is. Note that once fuel injection is performed, the pressure in the oil sump 10 decreases, the biasing force of the needle valve pressing spring 6 becomes greater than the pressure of the low boiling point fuel again, and the needle valve 3 is pressed down to cause the nozzle tip 2 to move downward. Since it is in close contact with the inner wall, fuel injection from the injection hole 1 into the combustion chamber is stopped.

In the fuel injection valve having the above-described structure, a space portion serving as the leak passage 13 is provided inside the wall member forming the hollow cylindrical portion of the nozzle tip 2 so as to surround the needle valve 3 over the entire circumference. Has been. This leak passage 1
3 is in communication with the fuel sack portion 11 through a leak hole 12A having a minute diameter and provided with a leak valve 15.
2 and the leak passage 13 form a leak passage. The leak valve 15 provided in the leak passage 12A opens when the pressure inside the fuel sack portion 11 becomes equal to or higher than a predetermined pressure, and establishes communication between the fuel sack portion 11 and the leak passage 13. The plurality of leak holes 12A are radially provided at an appropriate pitch.

The leak passage 13 is connected by a leak pipe 14 to the intake system (for example, the intake pipe line) of the diesel engine. That is, the leak fuel that is a part of the low boiling point fuel that has leaked from the fuel sack portion 11 to the leak passage 13 through the leak hole 12A is
After being vaporized into gas fuel, it is guided to the leak pipe 14 and sucked into the intake pipe line.

The operation of the above-described fourth embodiment will be described below. In this case, a part of the low boiling point fuel supplied to the fuel sack portion 11 when the needle valve 3 is opened, that is, a very small amount of the leaked fuel passing through the leak hole 12A having a small diameter, causes a thermal influence of the engine body. It evaporates on the way to the leak passage 13 that receives and becomes hot and in the leak passage 13. At this time, since the latent heat of vaporization is taken away to cool the fuel injection valve body, the rise in the temperature of the fuel injection valve and its surroundings is suppressed, and the fuel injection valve body is prevented from reaching such a high temperature that low-boiling point fuel other than leaked fuel evaporates. And the nearby injection pipe 8 is cooled. Therefore, even when the set pressure of the fuel supply system is relatively low, it is possible to prevent the low boiling point fuel from evaporating and becoming the incompressible fluid gas fuel (vapor) in the fuel supply system and the fuel injection system. The discharge pressure from the injection hole 1 can be maintained at a desired value and stable operation can be performed.

The gaseous leak fuel vaporized in the leak passage 13 is introduced into the intake system through the leak pipe 14. Therefore, this gas fuel is sent into the combustion chamber together with the fresh air sucked from the outside air, and is mixed with the fuel injected from the injection hole 1 in the combustion chamber and burned. For this reason, the leaked fuel is not wasted, contributes to combustion in the combustion chamber, and suppresses a decrease in thermal efficiency of the diesel engine.

In this embodiment, the leak hole 12
Since one end of A is communicated with the fuel sack portion 11, leak fuel is generated only at the fuel injection timing when the needle valve 3 is opened. Moreover, the leak valve 15 is provided in the middle of the leak hole 12A, and by appropriately setting the valve opening pressure, it becomes possible to control the flow rate of the leak fuel and the combustion gas amount returning to the intake side.

Therefore, not only the cooling effect can be adjusted by controlling the leakage fuel, but also the effect of exhaust gas recirculation (EGR) effective for reducing nitrogen oxides in the exhaust gas is adjusted by controlling the amount of combustion gas returning to the intake side. It also becomes possible. In the embodiment described above, the evaporated leaked fuel (vapor) is merged with the intake system in consideration of the thermal efficiency and EGR effect of the diesel engine, but if only cooling of the fuel injection valve body is considered, It is not limited to this.

If the fuel injection valve having the structure described in each of the above-described embodiments is adopted in the diesel engine, the fuel injection valve can be cooled by the leak fuel to prevent the low boiling point fuel from evaporating. Therefore, the problem that the low boiling point fuel evaporates and the high pressure fuel supply pressure cannot be maintained is solved. Therefore, stable operation is performed by using the gas energy of the high temperature and high pressure combustion gas generated by burning the low boiling point fuel. Can be a diesel engine that continuously generates power.

By adopting the above-mentioned structure of the fuel injection valve, a part of the low boiling point fuel flowing into the fuel injection valve body is leaked to the space from the leak holes 12, 12A provided in the nozzle tip 2. A fuel injection valve cooling method is possible in which the fuel leaks to the leak passage 13 of the other portion and the fuel is cooled by the latent heat of vaporization when the leaked fuel evaporates in the leak passage. That is, a part of the low boiling point fuel is used as the leak fuel, and the leak holes 12 and 12A of the leak passage are formed.
Also, since it is allowed to escape to the leak passage 13 and cooled by its latent heat of vaporization, even if the pressure of the fuel supply system is set to a relatively low level, the fuel injection valve is cooled without using another refrigerant, and Evaporation can be effectively prevented.

Further, if a fuel injection valve cooling method is adopted in which leaked fuel is supplied to the intake system and is absorbed into the combustion chamber together with fresh air, the leaked low boiling point fuel is burned without being wasted. It is possible to minimize the decrease in thermal efficiency. By adopting the fuel injection valve cooling method in which the low boiling point fuel is released only at the fuel injection timing, it is possible to minimize the flow rate of the low boiling point fuel to be leaked and perform efficient cooling.

The structure of the present invention is not limited to the above-described embodiment, but can be appropriately modified within the scope of the present invention.

[0069]

According to the present invention described above, the following effects are exhibited. (1) According to the above-described fuel injection valve and fuel injection valve cooling method, the evaporation latent heat is taken from the surroundings when the low boiling point fuel that has escaped to the leak flow path is evaporated. The injection valve body can be cooled effectively. Therefore, it is possible to prevent the phenomenon that the gas fuel of the compressible fluid formed by the evaporation of the low boiling point fuel is accumulated in the fuel supply system or the fuel injection system and prevents the pressure increase by the fuel injection pump, and the low boiling point fuel is burned. A desired fuel injection pressure is maintained during operation of the diesel engine, and stable operation is possible even with a fuel supply system pressurized to a relatively low pressure. Therefore, in designing a diesel engine using a low boiling point fuel as fuel, restrictions on strength and cost are reduced, and it is possible to provide a diesel engine with high stability and reliability. (2) Since the above-mentioned leaked fuel is guided to the intake system and is sucked into the combustion chamber together with fresh air and burned, the leaked fuel used for cooling is burned without waste, and the decrease in thermal efficiency is minimized. You can

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of a fuel injection valve according to the present invention.

FIG. 2 is a sectional view showing a second embodiment of the fuel injection valve according to the present invention.

FIG. 3 is a sectional view showing a third embodiment of the fuel injection valve according to the present invention.

FIG. 4 is a sectional view showing a fourth embodiment of the fuel injection valve according to the present invention.

FIG. 5 is a cross-sectional view showing a configuration example of a conventional fuel injection valve.

[Explanation of symbols]

1 injection hole 2 nozzle tip 3 needle valve 4 nozzle tip presser 5 nozzle holder 6 Needle valve retainer spring 7 Holder for mounting the injection pipe 8 injection tubes 9 oilways 10 oil sump 11 Fuel sack section 12,12A Leak hole (leak channel) 13 Leak passage (leak passage) 14 leak tube 15 Leak valve

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 19/02 F02D 19/02 Z F02M 21/10 F02M 21/10 61/10 61/10 S (72) Inventor Kawamura Watanabe, Marunouchi 2-chome, Chiyoda-ku, Tokyo Sanryo Heavy Industries Co., Ltd. (72) Inventor Shunichi Mori 5-717, Fukahori-cho, Nagasaki-shi, Nagasaki Nagaryo Engineering Co., Ltd. F-term (reference) 3G066 AA07 AB02 AB04 BA01 BA16 BA31 BA41 CA21 CA23T CC01 CC14 CE13 DA01 DC18 3G092 AA02 AA06 AB05 BB01 DF03 DG05 FA38 HB01Z HB05Z HE01Z HE06Z

Claims (10)

[Claims] 1. A fuel injection valve for a diesel engine, which generates power by utilizing high-temperature and high-pressure gas energy generated by burning a low boiling point fuel supplied into a combustion chamber, wherein A fuel injection valve having a leak passage for allowing a portion of the low boiling point fuel that has flowed into the chamber to escape and evaporate. 2. The fuel injection valve according to claim 1, wherein the leak passage is connected to an intake system. 3. The fuel injection valve according to claim 1, wherein the low boiling point fuel is released only at a fuel injection timing. 4. A leak that connects the space provided in the nozzle tip forming the outer peripheral wall of the oil sump and the space with at least one of the oil sump and the oil passage. 3. The fuel injection valve according to claim 2, further comprising a hole and a leak pipe line connecting the space and the intake system. 5. The leak flow path is provided between a space portion provided in a nozzle tip forming an outer peripheral wall of an oil sump, a fuel valve sack portion into which fuel flows when a needle valve is opened, and the space portion. 4. The fuel injection valve according to claim 3, further comprising a leak hole communicating with the leak hole, and a leak conduit connecting the space and the intake system. 6. The fuel injection valve according to claim 4, wherein the leak hole is provided with a leak valve that opens at a predetermined pressure or more. 7. A diesel engine that generates power by utilizing high-temperature and high-pressure gas energy generated by burning a low-boiling point fuel supplied into a combustion chamber, wherein the diesel engine has any one of claims 1 to 3. Item 7. A diesel engine equipped with the fuel injection valve according to any one of items 6. 8. A method of cooling a fuel injection valve of a diesel engine, which generates power by utilizing high-temperature and high-pressure gas energy generated by burning a low-boiling point fuel supplied into a combustion chamber. A method for cooling a fuel injection valve, characterized in that a part of the low boiling point fuel that has flowed into the main body is released as a leak fuel to a leak flow path provided in a nozzle tip and cooled by the latent heat of vaporization of the leak fuel. 9. The leak fuel is supplied to an intake system and absorbed into a combustion chamber together with fresh air.
The method for cooling a fuel injection valve described. 10. The method of cooling a fuel injection valve according to claim 8, wherein the low boiling point fuel is released only at a fuel injection timing.