JPH0128301Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection valve capable of detecting needle valve lift.

2. Description of the Related Art In order to electrically control the operating state of an engine, fuel injection valves are provided with a detector for detecting needle valve lift.

Conventional needle valve lift detection involves providing an iron core at the tip of a pressing member that moves together with the needle valve, and installing a winding group consisting of primary and secondary windings through which the iron core is inserted inside the fuel injection valve body. The winding group and the iron core constitute a differential transformer, and this is performed by detecting the output voltage of the secondary winding due to movement of the iron core.

Another method is to provide a search coil at the tip of a fixed member opposite to the tip of the pressing member, and use the search coil to detect eddy currents generated by movement of the pressing member to detect needle valve lift.

However, when using the above-mentioned conventional method, the primary and secondary windings and search coils are constructed by winding thin electric wires, so they are easily disconnected due to vibrations caused by engine operation and thermal expansion caused by temperature rise. ,
It had some drawbacks that made it unsuitable for long-term use.

Furthermore, as shown in Japanese Unexamined Patent Publication No. 56-113044, it is known that a spring force generated by movement of a needle valve is applied to a piezoelectric element, and displacement of the needle valve is detected by the output of the piezoelectric element. ing. However, since this method uses a piezoelectric element, the internal impedance of the detecting section is high and noise is easily discarded.

The present invention has been developed in view of the above, and aims to provide a fuel injection valve that eliminates the above drawbacks and is highly durable and capable of stably detecting needle valve lift over a long period of time. .

According to the present invention, this object is achieved by providing a pressure-sensitive conductive rubber that receives pressure as the needle valve moves, and by providing derivation means for deriving the resistance value of the pressure-sensitive conductive rubber.

The present invention will be explained below with reference to examples.

FIG. 1 is a sectional view showing an embodiment of the present invention.

The fuel injection valve 1 includes a nozzle body 2 in which a valve seat 3 is formed, a needle valve 4 that is inserted so as to be able to advance and retreat in the axial direction within the nozzle body 2 to control opening and closing of injection, a nozzle holder 5, and the nozzle body 2. and a cap nut 7 that fixes the nozzle body 2, the nozzle holder 5, and the intermediate member 6 to each other and integrates them. On the rear end side of the needle valve 4, one end is connected to a spring chamber 5' inside the nozzle holder 5.
A pressing member 8 extending up to 100 mm is fitted therein. A pressure sensitive conductive rubber 9 is detachably fixed to one end of the pressing member 8. Here, the pressure-sensitive conductive rubber is one in which conductive particles are dispersed in a non-conductive rubber base material, as disclosed in JP-A No. 53-67856 (Japanese Patent Publication No. 56-10764). The resistance value it exhibits changes depending on the applied pressure. In addition, an insulating bush 1 is inserted into the nozzle holder 5 at one end and whose lower end projects into the spring chamber 5'.
0 is installed. A spacer 11 is fixed to the lower end surface of the insulating bush 10. A coil spring 12 is housed in the spring chamber 5', and the coil spring 12 is elastically inserted between the pressing member 8 and the spacer 11. It passes through the spacer 11 and the insulating bushing 10, and one end is attached to the nozzle holder 5.
An electrode 14 is fixed to the insulating bushing 10, protruding outward and having its other end abutted against the pressure-sensitive conductive rubber 9. The length of the electrode 14 is set so that the other end surface of the electrode 14 is in light contact with the pressure-sensitive conductive rubber 9 when the fuel injection valve 1 is in the closed state. The spacer 11 is preferably an insulating member, but may also be a conductive member, in which case a gap is provided between the spacer 11 and the electrode 14.
and the electrode 14 are insulated.

Further, the nozzle body 2 is provided with an oil reservoir chamber 15, and the nozzle holder 5 and the intermediate member 6 are provided with an oil passage hole 16 extending through the nozzle holder 5 and the intermediate member 6.
_A and 16 _C are drilled. The nozzle body 2 is provided with an oil passage hole _16D that communicates the oil reservoir chamber 15 with the oil passage hole _16C . The nozzle holder 5 is provided with an oil passage hole 17 for guiding fuel oil returning through the gap between the nozzle body 2 and the needle valve 4 to an oil tank (not shown).

On the other hand, the electrode 14 is connected to a voltage source 1 whose one end is grounded.
A voltage of 8 is supplied via a resistor 19 to the electrode 14.
The voltage at the connection point between the resistor 19 and the resistor 19 is detected as the output voltage. Here, electrode 14, power supply 1
8 and the resistor 19 constitute a derivation means for taking out the resistance value of the pressure-sensitive conductive rubber 9 to the outside.

In the embodiment of the present invention constructed as described above, the fuel injection valve 1 is grounded when in use, and the pressing member 8 is grounded. Therefore, an equivalent circuit as shown in FIG. 2 is obtained in which the voltage of the voltage source 18 is electrically divided by the resistor R of the pressure-sensitive conductive rubber 9 and the resistor 19 and output. Further, the resistance value-pressure characteristic of the pressure-sensitive conductive rubber 9 is as shown in FIG.

Now, when fuel oil is not being supplied from the fuel injection pump (not shown), the needle valve 4 is pushed down via the pressing member 8 by the pressing force of the coil spring 12 as shown in FIG. The injection port formed by is in a closed state and no fuel injection is performed. At this time, the electrode 14 is in light contact with the pressure-sensitive conductive rubber 9 and a pressure P _S is applied thereto, and the resistance R of the pressure-sensitive conductive rubber 9 exhibits a resistance value R _S .

When fuel oil is supplied from the fuel injection pump, the fuel oil is guided to the oil reservoir chamber 15 through the oil passage holes 16 _A , 16 _C , and 16 _D. Therefore, the needle valve 4 is connected to the oil reservoir chamber 1.
The fuel injection valve 1 moves upward in FIG. 1 against the pressure of the fuel oil in the coil spring 12, and the fuel injection valve 1 becomes open, and fuel oil is injected from the injection port. On the other hand, in accordance with the amount by which the needle valve 4 moves upward in _FIG. The resistance value of the pressure-sensitive conductive rubber 9 decreases. When the injection port is fully open, pressure P _O (P _O > P _S ) is applied to the pressure-sensitive conductive rubber 9, and the resistance of the pressure-sensitive conductive rubber 9 is the resistance value R _O
(R _S > R _O ).

As a result, the output voltage obtained by dividing the voltage of the voltage source 18 by the resistor R of the pressure-sensitive conductive rubber 9 and the resistor 19 changes monotonically according to the lift of the needle valve 4, and the output voltage value of the needle valve 4 changes monotonically according to the lift of the needle valve 4. Lift detected.

Next, a modification of one embodiment of the present invention will be described.

FIG. 4 is a sectional view showing a modification of one embodiment of the present invention.

In FIG. 4, the same components as those in the embodiment of the present invention shown in FIG. 1 are denoted by the same reference numerals.

A modification of the embodiment of the present invention is that the electrode 14 is replaced with the pressure-sensitive conductive rubber 9 in the embodiment of the present invention.
A pressure-sensitive conductive rubber _9A is removably fixed to the other end. Further, the length of the electrode 14 is set so that the lower end surface of the pressure-sensitive conductive rubber _9A is in light contact with one end surface of the pressing member 8 when the fuel injection valve 1 is in the closed state.

Therefore, the operation of the modified example of the embodiment of the present invention is the same as that of the embodiment of the present invention, and detailed explanation thereof will be omitted.

Next, other embodiments of the present invention will be described.

FIG. 5 is a sectional view showing another embodiment of the present invention.

In FIG. 5, the same components as those in the embodiment of the present invention shown in FIG. 1 are designated with the same reference numerals.

In another embodiment of the present invention, in one embodiment of the present invention, the pressure-sensitive conductive rubber 9 and the other end of the electrode 14 are made to face each other with a predetermined gap between them. A plate spring 13 having an S-shaped cross section is elastically inserted between the spring 14 and the spring 14.

The other configurations are the same as in the embodiment of the present invention.

In another embodiment of the present invention constructed as described above, when the fuel injection valve 1 is fully closed, the position of the pressing member 8 is moved to the lowest position, and as the needle valve 4 rises, the position of the pressing member 8 is moved to the lowest position. The position of the pressing member 8 also rises, and when the fuel injection valve 1 with the needle valve 4 raised to the highest position is fully open, the position of the pressing member 8 is moved to the highest raised position. As the pressing member 8 moves as described above, the gap between one end of the pressing member 8 and the other end of the electrode 14 changes. As a result, the pressure applied to the pressure-sensitive conductive rubber 9 by the leaf spring 13 changes, and the resistance value exhibited by the pressure-sensitive conductive rubber 9 also changes. As the resistance value of the pressure-sensitive conductive rubber 9 changes, the output voltage also changes, and by detecting the output voltage, the needle valve lift can be detected.

In this case, according to another embodiment of the present invention, the pressure applied to the pressure-sensitive conductive rubber 9 due to the change in the position of the pressing member 8 is determined by the leaf spring 13 and is set independently from the pressing force of the coil spring 12. can do. Furthermore, in the case of another embodiment of the present invention, the deriving means for extracting the resistance value of the pressure-sensitive conductive rubber 9 may be a plate spring 1 in addition to the above-mentioned embodiment.
3 will be added.

As explained above, according to the present invention, the lift of the needle valve is detected by converting it into the resistance value of the pressure-sensitive conductive rubber. The durability is increased compared to the conventional one. Furthermore, it is easy to insert the pressure-sensitive conductive rubber into the fuel injection valve. Furthermore, the output resistance of pressure-sensitive conductive rubber is low, making noise countermeasures easy. Furthermore, since the pressure-sensitive conductive rubber is a passive element, it has the effect of making it difficult for noise to be superimposed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention. Second
The figure is a circuit diagram of an electrical equivalent circuit of an embodiment of the present invention. Figure 3 shows the resistance-pressure characteristic curve of pressure-sensitive conductive rubber. FIG. 4 is a sectional view showing a modification of one embodiment of the present invention. FIG. 5 is a sectional view showing another embodiment of the present invention. 1...Fuel injection valve, 2...Nozzle body, 3...
Valve seat, 4...needle valve, 8...pressing member, 9 and 9
_A ...Pressure-sensitive conductive rubber, 10...Insulating bushing,
12... Coil spring, 13... Leaf spring, 14...
Electrode, 18...voltage source, 19...resistance.

Claims (1)

[Scope of utility model registration request] a nozzle body 2 in which a valve seat 3 is formed; a nozzle holder 5 that is substantially integrated with the nozzle body 2 and has a spring chamber 5' formed therein;
A needle valve 4 is inserted into the nozzle body 2 so as to be able to move forward and backward in the axial direction and cooperates with the valve seat 3 to form an injection port, and a needle valve 4 is fitted to the rear end of the needle valve 4. It is equipped with a pressing member 8 and a coil spring 12 inserted into the spring chamber 5' and urging the needle valve 4 toward the valve seat 3 via the pressing member 8. In the fuel injection valve configured to drive the needle valve 4 in the direction in which the injection port opens against the Pressure-sensitive conductive rubbers 9, 9A installed at positions that receive pressure due to displacement of the needle valve 4, and pressure-sensitive conductive rubbers 9, 9.
A deriving means 1 which is electrically connected to the other end surface of A and is provided electrically insulated from the nozzle holder 5 to derive the resistance value exhibited by the pressure-sensitive conductive rubbers 9 and 9A.
3, 14, 18, and 19.