JPH05306664A - Fuel injection valve - Google Patents

Abstract

PURPOSE:To provide a fuel injection valve with which the generation of defects such as cracking of parts, leak of fuel, overrun, fire, etc., can be prevented preliminarily by detecting abnormal combustion of a diesel engine. CONSTITUTION:A nozzle needle 10 provided in a guide hole 5e of a nozzle body 5 to slide reciprocatorily gets apart from/closer to a valve seat part 5f to open and close an injection hole 5d. When pressure of fuel exceeds a set pressure of a compression coil spring 14, the nozzle needle 10 is opened. A magnet 28 to move with the nozzle needle 10 reciprocatorily is disposed facing a coil 22 through an air gap 26. When temperature of a combustion chamber 30 becomes high, and if temperature of the magnet 28 exceeds a Curie point by heat transmitted from the nozzle body 5, etc., magnetic flux of the magnet 28 is reduced extremely, and a magnetic circuit becomes disconnected regardless of lift quantity of the nozzle needle, thereby abnormality in the combustion chamber 30 is detected based on an output voltage generated by the coil 22.

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 in 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 the nozzle is arranged so as to protrude into the combustion chamber, the strength of the nozzle exposed to high temperature combustion gas is apt to be lowered by heat, and the strength is lowered. If you continue to use the fuel injection valve, a crack will occur. In particular, when a member that maintains oil tightness is cracked, oil tightness is not maintained and fuel leaks into the combustion chamber, causing overrun and flame generation of the diesel engine. Also, if the cracked parts scatter in the combustion chamber, it causes an engine lock.

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

[0004]

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

[0005]

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

[0006]

According to the fuel injection valve of the present invention, when the temperature of the combustion chamber becomes high and the heat transferred from the nozzle body causes the magnet to exceed the Curie point, the magnetic flux density of the magnet itself decreases and the valve member lifts. Since the magnetic circuit is cut off regardless of the amount, abnormality in 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 stepped portion 4a, the annular spacer 6 is placed on the upper portion thereof, and the spacer 6
The holder 8 is screwed on the screw part 8a of the housing 4
It is screwed to b.

A nozzle needle 10 is provided slidably on an inner peripheral wall of a guide hole 5e formed in the axial direction of the nozzle body 5, and a front tip inclined portion 10a of the nozzle needle 10 can be contacted with and separated from a valve seat portion 5f. And the nozzle needle 1
The pin 12 is connected to the rear convex portion 10b of 0. Compression coil spring 14 for urging the pin 12 toward the valve closing side
One end 14a biases the pin 12 toward the valve closing side, and the other end 14a
b urges the hole bottom portion 8b through the annular first shim 16, the flange portion 18a of the sensor housing 18, and the annular second 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, and the search coil 22 is provided.
Is wound with an ultrafine magnet wire, and its periphery is resin-molded. 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 with an air gap 26 in between. The axial length of the air gap 26 is preferably equal to or larger than the lift amount of the nozzle needle 10, and for example, about 0.1 mm is suitable. The adjustment of the air gap 26 is possible by changing the thickness of the first shim 16 or the second shim 20.

The aforementioned 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.degree. 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 below 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 situation 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 structure, the magnetic circuit is the magnet 2
8, the pin 12, the spacer 6, the holder 8, the sensor housing 18, the search coil 22, and the air gap 26. From this, even if the needle lift amount of the nozzle needle 10 is increased to some extent, the output of the search coil 22 hardly rises above 0V because the magnetic circuit remains in a substantially cut-off state. This detects an abnormality. According to the experiment, when the temperature of the tip of the nozzle body 5 is 200 ° C., the temperature of the magnet 28 is about 80.
It was ℃.

The 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 a nozzle body 5. The fuel passage 5b, the fuel reservoir 5c, and the injection hole 5d. High-pressure fuel is supplied to the fuel inlet hole 8e formed in the holder 8 of the fuel injection valve 3, and when the pressure of this high-pressure fuel overcomes the set pressure of the compression coil spring 14, the nozzle needle 10 is pushed up. Then, the fuel is injected from the injection hole 5d into the combustion chamber 30 via the linear 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 is seated on the valve seat portion 5f, the injection hole 5d is closed, and the injection is terminated.

Next, FIG. 2 shows the relationship between the lift amount of the nozzle needle 10 and the output voltage of the search coil 22. During normal operation, as shown in FIG. 2, when the needle lift amount of the nozzle needle 10 changes as shown in FIG. 2, the output of the search coil 22 changes substantially in proportion to this. That is,
When the pin 12 rises and the air gap 26 shrinks,
The magnetic flux flowing through the magnetic circuit increases, and the output voltage of the search coil 26 increases. At this time, if the output voltage of the search coil 22 exceeds the reference voltage, the processing signal of the control circuit 31 shown in FIG. 1, for example, 5V is output.

When the nozzle body 5 reaches a high temperature of, for example, about 200 ° C. when abnormal combustion occurs, the heat is generated by the nozzle body 5.
Is transmitted to the pin 12 via the nozzle needle 10 and is transmitted to the magnet 28 via an adhesive having good heat conductivity, and the magnet 28 has a Curie point of, for example, 130 ° C. or higher. Then, the magnetic flux generated by the magnet 28 is extremely reduced. Therefore, the magnetic circuit is cut off regardless of the amount of needle lift of the nozzle needle 10,
The output voltage of the search coil 22 is as shown in FIG. 3, and since the output voltage of the search coil 22 does not exceed the reference voltage,
The processing signal of the control circuit 31 shown in FIG. 1 outputs a constant value of 1 V, for example. Therefore, unlike the case where the output voltage of the search coil 22 is normal as shown in FIG. 2, abnormal combustion in the combustion chamber 30 can be detected from this.

Abnormal combustion can be understood by comparing FIGS. 2 and 3, for example. For example, in a normal state, as shown in FIG. 2, when the output voltage of the search coil 22 exceeds the reference value in accordance with the needle lift amount, the processing signal becomes 5 V, and below the reference value, the processing signal becomes 0 V. On the other hand, when an abnormality occurs, as shown in FIG. 3, the output voltage of the search coil 22 does not exceed the reference value regardless of the value of the needle lift amount. Therefore, the processing signal of the control circuit 31 has a constant value of 0V. Therefore, the abnormality is detected from this.

[0016]

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

[Brief description of 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 diagram showing a needle lift, a search coil output, and a processing signal in a normal state.

FIG. 3 is a time chart diagram 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 history curve of a magnet.

[Explanation of symbols]

 3 Fuel Injection Valve 5 Nozzle Body (Valve Main Body) 5d Injection Hole 5e Guide Hole 5f Valve Seat 10 Nozzle Needle (Valve Member) 12 Pins (Valve Member) 14 Compression Coil Spring (Biasing Means) 22 Search Coil (Magnetic-electric Conversion Element) ) 28 magnets

Claims (1)

[Claims] 1. A reciprocating valve member, a guide hole for axially moving and oil-tightly guiding the valve member, a valve seat portion with which the valve member can come into contact, and the valve seat of the valve member. A valve body having an injection hole that can be opened and closed by being brought into and out of contact with a valve portion, an urging means that urges the valve member in a closing direction, and a magnet that is fixed to the valve member and can reciprocate together with the valve member. When the temperature of the magnet is below the Curie point, a voltage corresponding to the magnetic flux density of the magnetic circuit formed according to the position of the magnet is generated, and the magnet is arranged. A fuel injection valve including a magnetoelectric conversion element that detects an abnormality when the magnetic circuit is cut off by utilizing the fact that the magnetic flux density of the magnet relatively decreases when the Curie point is exceeded. ..