JP3120558B2 - Fuel injection valve - Google Patents

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 used for a diesel engine, and more particularly to a fuel injection valve for detecting abnormal combustion in a combustion chamber.

[0002]

2. Description of the Related Art Conventionally, in a fuel injection valve for a diesel engine, since a nozzle is arranged protruding into a combustion chamber, the strength of the nozzle exposed to high-temperature combustion gas is easily reduced by heat, and the strength is reduced. If the fuel injection valve continues to be used, cracks will occur. In particular, when cracks occur in the members that maintain oil tightness, the oil tightness is not maintained, and fuel leaks into the combustion chamber, causing overrunning and flame generation of the diesel engine. Also, if the broken parts scatter in the combustion chamber, the engine will be locked.

As described above, since the decrease in the strength of the fuel injection valve may cause a fatal trouble to the diesel engine, the engine performance and the nozzle characteristics are determined so that the nozzle temperature is kept below the limit temperature. ing.

[0004]

However, during abnormal combustion of a diesel engine, the temperature of the fuel injector rises excessively, so that there is a problem that the above-mentioned problems tend to occur. The present invention has been made in order to solve such a problem, and it is an object of the present invention to provide a fuel injection valve which detects an abnormality in the nozzle temperature of the fuel injection valve and prevents the occurrence of the problem. With the goal.

[0005]

A fuel injection valve according to the present invention for solving the above-mentioned problems comprises a reciprocally movable valve member,
A guide hole that can move the valve member in the axial direction and guides it in an oil-tight manner, a valve seat that can be brought into contact with the valve member, and an injection hole that can be opened and closed by separating the valve member from the valve seat. A valve body having, a biasing means for biasing the valve member in a closing direction, a magnet fixed to the valve member and capable of reciprocating with the valve member, and disposed via an air gap with respect to the magnet, When the temperature of the magnet is below the Curie point, a voltage corresponding to the magnetic flux density of a magnetic circuit formed according to the position of the magnet is generated, and when the magnet exceeds the Curie point,
And a magneto-electric conversion element that detects an abnormality by interrupting a magnetic circuit by utilizing a relative decrease in the magnetic flux density of the magnet.

[0006]

According to the fuel injection valve of the present invention, when the temperature of the combustion chamber becomes high and the magnet exceeds the Curie point due to the heat transmitted from the nozzle body, the magnetic flux density of the magnet itself decreases and the lift of the valve member increases. Since the magnetic circuit is interrupted regardless of the amount, the abnormality of the combustion chamber is detected from the electric signal generated from the magnetoelectric conversion element.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a cylindrical housing 4 of a fuel injection valve 3 is screwed to a cylinder head 2 of a diesel engine 1. Inside the housing 4, the large diameter portion 5a of the nozzle body 5 is positioned on the step portion 4a, and an annular spacer 6 is mounted on the upper portion thereof.
The holder 8 has a screw portion 8a and a screw portion 4 of the housing 4
b.

A nozzle needle 10 is slidably provided on an inner peripheral wall of a guide hole 5e formed in an axial direction of the nozzle body 5, and a front end inclined portion 10a of the nozzle needle 10 can be separated from and connected to a valve seat 5f. And the nozzle needle 1
The pin 12 is connected to the protrusion 10b at the rear of the zero. Compression coil spring 14 for urging pin 12 to the valve closing side
The one end 14a urges the pin 12 toward the valve closing side, and the other end 14a
b urges the hole bottom 8b via the first annular shim 16, the flange portion 18a of the sensor housing 18, and the second annular shim 20. Thereby, the oil tightness of the nozzle body 5 and the nozzle needle 10 is maintained.

At the end of the cylindrical sensor housing 18,
A search coil 22 is provided.
Is wound by an extra-fine wire magnet wire, and its periphery is molded with resin. One end 24 a of the wire 24 is electrically connected to the lead wire 24. The search coil 22 is arranged to face a solid cylindrical magnet 28 fixed to the pin 12 via an air gap 26. The axial length of the air gap 26 is preferably equal to or greater than the lift amount of the nozzle needle 10, and for example, about 0.1 mm is suitable. The air gap 26 can be adjusted by changing the thickness of the first shim 16 or the second shim 20.

The above-mentioned magnet 28 is fixed to the inner peripheral wall of the cylinder of the pin 12 with an adhesive having good heat resistance, and the magnet itself is made of a material having a Curie point at a temperature of about 130 ° C. The characteristics of the magnet 28 are, for example, as shown in the schematic diagram of the magnetic hysteresis curve shown in FIG. When the temperature of the magnet 28 is equal to or lower than the Curie point, a relatively large magnetic flux density is obtained as the magnetomotive force increases as shown by the solid line. On the other hand, when the magnet 28 is placed in a state where the temperature of the magnet 28 exceeds the Curie point, the magnetic flux density does not become sufficiently large even if the magnetomotive force increases.

In the above configuration, the magnetic circuit includes the magnet 2
8, a pin 12, a spacer 6, a holder 8, a sensor housing 18, a search coil 22, and an air gap 26. From this, even if the needle lift of the nozzle needle 10 becomes large to some extent, the output of the search coil 22 hardly rises above 0 V because the magnetic circuit remains almost shut off. Thereby, an abnormality is detected. According to experiments, when the temperature of the tip of the nozzle body 5 is 200 ° C., the temperature of the magnet 28 is about 80 ° C.
° C.

A fuel passage is formed in a straight hole 8c formed in the holder 8, a fuel passage 8d communicating with the straight hole 8c and extending in the axial direction, a fuel passage 6a formed in the spacer 6, and formed in the nozzle body 5. A fuel passage 5b, a fuel reservoir 5c, and an injection hole 5d. High-pressure fuel is supplied to a fuel inlet hole 8e formed in the holder 8 of the fuel injection valve 3, and when the pressure of the high-pressure fuel exceeds the set pressure of the compression coil spring 14, the nozzle needle 10 is pushed up. Then, fuel is injected into the combustion chamber 30 from the injection hole 5d via the straight hole 8c, the fuel passage 8d, the fuel passage 6a, the fuel passage 5b, and the fuel reservoir 5c. When the fuel pressure falls below the set pressure of the compression coil spring 10, the nozzle needle 10 sits on the valve seat 5f, closes the injection hole 5d, and terminates the injection.

Next, the relationship between the lift amount of the nozzle needle 10 and the output voltage of the search coil 22 is shown in FIG. In a normal state, as shown in FIG. 2, when the needle lift of the nozzle needle 10 changes as shown in FIG. 2, the output of the search coil 22 changes substantially in proportion thereto. That is,
When the pin 12 is raised and the air gap 26 is reduced,
The magnetic flux flowing through the magnetic circuit increases, and the output voltage of the search coil 26 increases. At this time, when the output voltage of the search coil 22 exceeds the reference voltage, a processing signal of the control circuit 31 shown in FIG.

When abnormal combustion occurs, if the temperature of the nozzle body 5 becomes high, for example, about 200 ° C., the heat is
Is transmitted to the pin 12 via the nozzle needle 10 and to the magnet 28 via an adhesive having good heat transfer properties, and the magnet 28 has a Curie point of, for example, 130 ° C. or higher. Then, the magnetic flux generated by the magnet 28 extremely decreases. For this reason, the above-described magnetic circuit is interrupted regardless of the magnitude of the needle lift of the nozzle needle 10, so that
The output voltage of the search coil 22 becomes as shown in FIG. 3, and since the output voltage of the search coil 22 does not exceed the reference voltage,
As the processing signal of the control circuit 31 shown in FIG. 1, a constant value of, for example, 1 V is output. Therefore, unlike the case where the output voltage of the search coil 22 is normal in FIG. 2, abnormal combustion in the combustion chamber 30 can be detected.

The abnormal combustion can be seen, for example, by comparing FIG. 2 and FIG. For example, when the output voltage of the search coil 22 exceeds the reference value in accordance with the needle lift amount, the processing signal becomes, for example, 5V, and when the output voltage is lower than the reference value, the processing signal becomes 0V, as shown in FIG. On the other hand, when an abnormality occurs, as shown in FIG. 3, the output signal of the search coil 22 does not exceed the reference value regardless of the value of the needle lift amount. Therefore, an abnormality is detected from this.

[0016]

As described above, according to the fuel injection valve of the present invention, heat is transmitted to the magnet via the valve body, the valve member, and the like, and when the magnet temperature exceeds the Curie point due to the heat, the magnet is heated. By utilizing the extremely low magnetic flux, there is an effect that the abnormality of the combustion chamber can be accurately determined regardless of the magnitude of the needle lift.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a fuel injection valve for a diesel engine according to an embodiment of the present invention.

FIG. 2 is a time chart showing a needle lift, a search coil output and a processing signal in a normal state.

FIG. 3 is a time chart showing a needle lift, a search coil output, and a processing signal at the time of abnormality.

FIG. 4 is a schematic diagram showing a magnetic hysteresis curve of a magnet.

[Explanation of symbols]

 Reference Signs List 3 Fuel injection valve 5 Nozzle body (valve body) 5d Injection hole 5e Guide hole 5f Valve seat 10 Nozzle needle (valve member) 12 Pin (valve member) 14 Compression coil spring (biasing means) 22 Search coil (magneto-electric conversion element) ) 28 magnets

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI F02M 63/00 F02M 63/00 C

Claims (1)

(57) [Claims] A valve member capable of reciprocating; a guide hole capable of moving the valve member axially and oil-tightly; a valve seat capable of contacting the valve member; and the valve seat of the valve member. A valve body having an injection hole that can be opened and closed by detaching from the part, a biasing unit that biases the valve member in a closing direction, and a magnet fixed to the valve member and capable of reciprocating with the valve member. The magnet is arranged via an air gap, and when the temperature of the magnet is equal to or lower than the Curie point, generates a voltage corresponding to the magnetic flux density of a magnetic circuit formed according to the position of the magnet. A fuel injection valve having a magnetoelectric conversion element that detects an abnormality by interrupting a magnetic circuit by utilizing a relative decrease in the magnetic flux density of the magnet when exceeding a Curie point. .