JP2023142635A - Fuel injection device - Google Patents

Abstract

To provide a fuel injection device which can improve durability.SOLUTION: In a fuel injection device 1 for injecting fuel F containing a hydrogen gas toward a combustion chamber 106 of an engine 100, the fuel injection device 1 comprises: a valve seat part (a main body 2, a tip part 21) having a first surface 21s at which an injection hole 21p of the fuel F is opened; a valve body (a needle 3, a valve part 31) having a second surface 31s opposing the first surface 21s, and opening and closing the injection hole 21p by being driven so that a distance between the first surface 21s and the second surface 31s is changed; and a seal part 50 interposed between the first surface 21s and the second surface 31s, and sealing the injection hole 21p by contacting with the first surface 21s and the second surface 31s in a closed state of the injection hole 21p.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a fuel injection device.

Patent Document 1 describes a fuel injection device for a diesel engine. In this fuel injection device, a nozzle needle is housed inside a nozzle body so as to be movable in the axial direction. The nozzle body is formed with a valve seat on which the tip of the nozzle needle is seated. A plurality of fuel injection holes are formed at the tip of the nozzle body. In this fuel injection device, high-pressure auxiliary fuel supplied from a common rail is stored inside a nozzle body, and is injected into a combustion chamber of an engine through a fuel injection hole by movement of a nozzle needle. Further, when the nozzle needle is seated on the valve seat, the nozzle needle closes the valve hole, and the fuel supply section and the fuel injection hole are cut off.

JP2018-193971A

As described above, in conventional fuel injection devices, the valve body, which is the tip of the nozzle needle, opens and closes the fuel injection hole that opens into the valve seat of the nozzle body. This causes wear on the valve body and valve seat. In particular, in engines, fuel injection is required under high pressure, for example several tens of MPa, so the pressing force of the valve element against the valve seat becomes strong. Furthermore, when the fuel is hydrogen gas, no lubricant (light oil or gasoline) is present between the valve body and the valve seat, compared to when the fuel is diesel oil or gasoline. As a result, the wear of the valve body and valve seat becomes significant, which limits the operating time. In other words, it is desired to improve the durability of fuel injection devices under high pressure.

An object of the present disclosure is to provide a fuel injection device that can improve durability.

A fuel injection device according to the present disclosure is a fuel injection device that injects fuel containing hydrogen gas toward a combustion chamber of an engine, and includes a valve seat portion having a first surface through which a fuel injection hole opens; A valve body having a second surface facing the first surface and for opening and closing an injection hole by being driven so that the distance between the first surface and the second surface changes; and the first surface and the second surface. and a sealing member that is interposed between the injection hole and the injection hole and seals the injection hole by contacting the first surface and the second surface when the injection hole is in a closed state.

In this fuel injection device, a sealing member is interposed between a first surface of the valve seat where the injection hole opens and a second surface of the valve body that faces the first surface. Therefore, when the valve body closes the injection hole, the sealing member comes into contact with the first surface of the valve seat and the second surface of the valve body, thereby sealing the injection hole. Therefore, the injection hole is reliably sealed, and wear of the valve body and valve seat portion is suppressed. Thus, according to this fuel injection device, durability is improved under high pressure (when fuel is injected into the combustion chamber of the engine).

In the fuel injection device according to the present disclosure, the seal member may include carbon nanotubes. In this case, it is possible to more reliably suppress wear of the valve body and the valve seat, and improve durability.

In the fuel injection device according to the present disclosure, the seal member may be provided on the first surface. In this case, when improving durability, an increase in the weight of the valve body, which is the driving part, can be avoided.

According to the present disclosure, it is possible to provide a fuel injection device that can improve durability.

FIG. 1 is a schematic cross-sectional view showing a part of an engine according to an embodiment. FIG. 2 is a schematic cross-sectional view of the injector shown in FIG. FIG. 3 is a schematic cross-sectional view of the injector shown in FIG. 1. FIG. FIG. 4 is an enlarged view of the main part of FIG. 2.

Hereinafter, a fuel injection device according to an embodiment will be described with reference to the drawings. In each figure, the same elements or corresponding elements are given the same reference numerals, and redundant explanations are omitted.

FIG. 1 is a schematic cross-sectional view showing a part of an engine according to an embodiment. As shown in FIG. 1, engine 100 is mounted on, for example, a vehicle. The engine 100 includes a cylinder block 102, a cylinder head 103 disposed above the cylinder block 102, a plurality of cylinder liners 104 (only one is shown in FIG. 1) press-fitted into the cylinder block 102, and an inner cylinder liner 104. A piston 105 is arranged to be able to move up and down in a reciprocating manner. A space surrounded by the cylinder head 103, cylinder liner 104, and piston 105 defines a combustion chamber 106.

The cylinder head 103 is provided with an intake port 107 and an exhaust port 108 that communicate with the combustion chamber 106 . The intake port 107 is opened and closed by an intake valve 109. The exhaust port 108 is opened and closed by an exhaust valve 110. Furthermore, a fuel injection device 1 that injects fuel into the combustion chamber 106 is attached to the cylinder head 103 .

2 and 3 are schematic cross-sectional views showing the fuel injection device shown in FIG. 1. FIG. FIG. 4 is an enlarged view of the main part of FIG. 2. The fuel injection device 1 shown in FIGS. 2 to 4 is a device that injects fuel F into the combustion chamber 106 of the engine 100. Fuel F contains hydrogen gas. As an example, the fuel F is hydrogen gas. In this case, engine 100 is a hydrogen engine. Note that FIG. 2 shows the fuel injection device 1 in a state in which the fuel F is not injected, and FIG. 3 shows the fuel injection device 1 in a state in which the fuel F is injected.

The fuel injection device 1 includes a needle 3. The needle 3 is housed inside the main body 2. The needle 3 functions as a valve body for injecting the fuel F from the injection hole 21p. The needle 3 is formed, for example, in a cylindrical shape. The main body 2 is formed in a cylindrical shape and accommodates the needle 3 so as to be slidable in the axial direction. The needle 3 forms a valve portion 31, an enlarged diameter portion 32, and a piston portion 33 from the tip side.

The valve portion 31 has a tapered tip, and the tip functions as a valve body. The valve portion 31 is housed in a first chamber 22 that is larger than the valve portion 31 . The enlarged diameter portion 32 is formed on the proximal end side of the valve portion 31 and has a diameter larger than that of the valve portion 31 . The enlarged diameter portion 32 is accommodated in the first chamber 22 . The outer diameter of the enlarged diameter portion 32 is the same or approximately the same as the inner diameter of the first chamber 22. The enlarged diameter portion 32 is formed so that no gap is created between the outer circumferential surface of the enlarged diameter portion 32 and the inner circumferential surface of the first chamber 22 .

A spring 23 is hooked to the enlarged diameter portion 32 . The spring 23 is a biasing member that applies a reaction force to the main body 2 and biases the needle 3 toward the distal end side. A piston portion 33 is formed on the proximal end side of the enlarged diameter portion 32 . The piston portion 33 is formed in a cylindrical shape and is housed in the second chamber 24 . The outer diameter of the piston portion 33 is the same or approximately the same as the inner diameter of the second chamber 24. The piston portion 33 is formed so that there is no gap between the outer circumferential surface of the piston portion 33 and the inner circumferential surface of the second chamber 24. A control chamber 24a is formed in the second chamber 24. The control chamber 24a is a region of the second chamber 24 defined by the end surface 33a of the piston portion 33.

A fuel F supply path 26 is formed in the main body 2 . The supply passage 26 is a fuel supply passage for supplying the fuel F injected from the outside of the main body 2 to the distal end side of the main body 2. For example, fuel F is supplied to the fuel injection device 1 from a fuel tank (not shown) via a filter, a pump, and a common rail, and is in a high pressure state. The supply path 26 branches in the middle and communicates with the first chamber 22 and the control chamber 24a.

The tip portion 21 of the main body 2 is formed with an injection hole 21p and a sack portion 21a. The injection hole 21p is a hole through which the fuel F is injected from the fuel injection device 1. For example, a plurality of injection holes 21p are formed. The sack portion 21a is a region communicating with the injection hole 21p. The sack portion 21a and the injection hole 21p are cut off from the first chamber 22 by the closing operation of the valve portion 31, and communicated with the first chamber 22 by the opening operation of the valve portion 31. In this way, the tip portion 21 of the main body 2 functions as a valve seat portion that forms a pair with the valve portion 31 as a valve body.

The main body 2 is provided with a control valve 4. The control valve 4 is a valve body that moves the needle 3 by adjusting the pressure of the fuel F in the control chamber 24a. The control valve 4 is housed in the valve chamber 27. The valve chamber 27 communicates with the control chamber 24a through an outflow path 27a. The control valve 4 is biased by a spring 41 and pressed against the entrance of the outflow path 27a. A solenoid 5 is provided in the valve chamber 27 .

The solenoid 5 functions as a drive unit that moves the control valve 4. The solenoid 5 operates according to a control signal from an electronic control unit (not shown). When the solenoid 5 is in an off state, the control valve 4 is in a closed state. In other words, the control valve 4 closes the entrance of the outflow path 27a. On the other hand, when the solenoid 5 is turned on, the control valve 4 is opened. In other words, the control valve 4 moves away from the entrance of the outflow path 27a against the bias of the spring 41, thereby allowing the outflow path 27a and the valve chamber 27 to communicate with each other. A return path 28 is formed in the main body 2. The return passage 28 communicates with the valve chamber 27. The return path 28 is a flow path for returning a portion of the fuel F that has flowed into the supply path 26 to the fuel tank. That is, the return path 28 returns the fuel F that flows into the supply path 26 and is not injected from the injection hole 21p to the fuel tank.

Before the fuel F is injected, the control valve 4 closes the outflow passage 27a. Therefore, no fuel F flows into the valve chamber 27 from the control chamber 24a. Therefore, the control chamber 24a and the first chamber 22 are at the same pressure, and the needle 3 is moved toward the distal end side by the bias of the spring 23 and is in a closed state.

At this time, a control signal is input to the solenoid 5, and the solenoid 5 is turned on for a predetermined period of time. This causes the solenoid 5 to operate and the control valve 4 to move toward the solenoid 5 side. That is, the control valve 4 is separated from the entrance of the outflow path 27a, and the outflow path 27a and the valve chamber 27 communicate with each other. Therefore, the fuel F in the control chamber 24a flows into the valve chamber 27 through the outflow path 27a, and the pressure in the control chamber 24a is reduced. As a result, the needle 3 moves toward the control chamber 24a, and the valve portion 31 separates from the wall surface of the first chamber 22 (first surface 21s, which will be described later). Then, the fuel F flows from the first chamber 22 into the sack portion 21a and is injected from the injection hole 21p.

As described above, in the fuel injection device 1, the main body 2 and the tip end 21 of the main body 2 are valve seat parts having the first surface 21s in which the injection holes 21p of the fuel F are opened, and the needle 3 and the valve part of the needle 3 are 31 has a second surface 31s facing the first surface 21s, and is driven to change the distance between the first surface 21s and the second surface 31s to open and close the injection hole 21p. It is a valve body (see Figure 4).

The first surface 21s is an inner wall surface of the first chamber 22, and has a tapered shape that decreases toward the tip of the first chamber 22. Here, the first surface 21s has a conical shape with its tip portion missing due to the formation of the injection holes 21p. In other words, when viewed from the axial direction (driving direction) of the needle 3, the opening of the injection hole 21p is defined by the inner edge of the first surface 21s.

The second surface 31s is formed within the first chamber 22 so as to have a portion substantially parallel to the first surface 21s. Here, the second surface 31s is the outer surface of the tip 31a of the valve portion 31, and has a tapered shape that decreases toward the tip of the first chamber 22, and specifically has a conical shape.

A sealing member 50 is interposed between the first surface 21s and the second surface 31s. Here, the seal member 50 is provided on the first surface 21s. The seal member 50 is provided so as to surround the opening of the sack portion 21a that communicates with the injection hole 21p when viewed from the axial direction of the needle 3. Seal member 50 includes carbon nanotubes. As an example, the sealing member 50 is made of heat-resistant viscoelastic carbon nanotubes that have viscoelasticity up to a high temperature range, and is a sheet or coating of a carbon nanotube composite material.

Such a seal member 50 contacts the first surface 21s and the second surface 31s when the injection hole 21p is closed (the second surface 31s is closest to the first surface 21s), thereby sealing the sack portion 21a. The injection hole 21p is sealed by surrounding and sealing the opening. Therefore, in the fuel injection device 1, even when the injection hole 21p is in the closed state, the seal member 50 prevents the first surface 21s and the second surface 31s from coming into direct contact. Note that when the needle 3 is driven so that the distance between the first surface 21s and the second surface 31s is expanded and the injection hole 21p is opened, the seal member 50 remains on the first surface 21s side (see FIG. (See 3).

As explained above, in the fuel injection device 1, the first surface 21s in which the injection hole 21p opens in the tip part 21 (valve seat part) of the main body 2, and the first surface 21s in the valve part 31 (valve body) of the needle 3. A sealing member 50 is interposed between the surface 21s and the opposing second surface 31s. Therefore, when the valve body closes the injection hole 21p, the sealing member 50 contacts the first surface 21s of the valve seat and the second surface 31s of the valve body, sealing the injection hole 21p. .

Therefore, the injection hole 21p is reliably sealed, and wear of the valve body and valve seat is suppressed. Therefore, according to the fuel injection device 1, it is possible to increase the injection pressure to inject the fuel F into a high-pressure atmosphere, and the life and durability are improved. As a result, it will become possible to realize hydrogen engines with higher output, compression ignition, or hydrogen jet spark ignition engines, which is expected to reduce cooling loss and improve thermal efficiency, which will eventually lead to the spread of hydrogen engines in a wide range of fields. is expected.

Furthermore, in the fuel injection device 1, the seal member 50 includes carbon nanotubes. For this reason, it is possible to more reliably suppress wear of the valve body and the valve seat, and improve durability.

Furthermore, in the fuel injection device 1, the seal member 50 is provided on the first surface 21s of the valve seat portion. Therefore, when achieving the above effects, an increase in the weight of the valve body, which is the driving part, can be avoided.

The above embodiment describes one aspect of the present disclosure. Therefore, the present disclosure is not limited to the fuel injection device 1 described above, and may be modified as desired.

For example, in the embodiment described above, the case where the seal member 50 is provided on the first surface 21s of the valve seat portion is illustrated. However, the seal member 50 may be provided on the second surface 31s of the valve body, or may be provided on both the first surface 21s and the second surface 31s. That is, the sealing member 50 may be provided on at least one of the first surface 21s and the second surface 31s so as to seal the injection hole 21p when the injection hole 21p is in the closed state.

Further, the material of the seal member 50 is not limited to those containing carbon nanotubes, and any material can be used.

DESCRIPTION OF SYMBOLS 1... Fuel injection device, 2... Main body (valve seat part), 3... Needle (valve body), 21... Tip part (valve seat part), 21s... First surface, 21p... Injection hole, 31... Valve part (valve body), 31s...second surface, 50...sealing member, 100...engine, 106...combustion chamber, F...fuel.

Claims (3)

A fuel injection device that injects fuel containing hydrogen gas toward a combustion chamber of an engine,
a valve seat portion having a first surface through which the fuel injection hole opens;
a valve body having a second surface opposite to the first surface, and for opening and closing the injection hole by being driven so that the distance between the first surface and the second surface changes;
a sealing member interposed between the first surface and the second surface and sealing the injection hole by contacting the first surface and the second surface when the injection hole is in a closed state;
A fuel injection device comprising: The sealing member includes carbon nanotubes.
The fuel injection device according to claim 1. The sealing member is provided on the first surface.
The fuel injection device according to claim 1 or 2.

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