JPH0364665A - Needle lift sensor for fuel injection nozzle - Google Patents

Abstract

PURPOSE:To perform high-precise detection of a lift amount of a nozzle needle by a method wherein a coil is situated vertically below the flange part of a pressure pin incorporated in a distance piece, and a non-electromagnetic body is located between the distance piece and a flange part. CONSTITUTION:An injector is formed such that a fuel passage 22 formed in an injector body 20 and communicated to a fuel inflow port 21 is communicated to a nozzle 25 through a high pressure passage 23, and a high pressure passage 24 branched from the fuel passage 22 is communicated to a passage 53a of an outer valve 53 of a solenoid valve part 26. In this case, a pressure pin 31 is coupled to the lower end of a command piston 58 lifted through upward movement of an outer valve 53, and a flange part 31a of the pressure pin is contained in a bobbin 40 formed of a non-magnetic substance and engaged internally of a distance piece 36. A thick annular protrusion part 40b is formed on the bottom of the small part of an annular thin section part 40a of the lower end part of the bobbin 40, and a coil 42 is wound around the outer periphery of the thin section protrusion part to measure a lift amount of a nozzle needle 37.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a needle lift sensor for a fuel injection nozzle that injects and supplies fuel to a diesel engine.

(Prior Art) A needle lift sensor that detects the lift amount of a nozzle needle in order to detect the fuel injection timing in a fuel injection device is conventionally known.

For example, in the conventional one shown in FIG. 4, a gap sensor 2 as shown in FIG. It is loosely inserted around the sensor portion 2b of the sensor 2, and presses the nozzle needle 6 vertically downward via the collar portion 5a of the spacer 5 with the other end 4a of the compression coil spring.

Furthermore, in the conventional devices shown in FIGS. 6 to 8, a spacer 1 is attached to the upper end surface 9a of the flange portion of the pressure pin 9 that pushes out the nozzle needle 8 housed in the nozzle body 7 vertically downward.
0, and a disc-shaped magnet 11 is embedded in the upper surface of the protrusion 10a. A lift sensor 12 is disposed vertically above the magnet 11, and the lift amount of the nozzle needle 8 is detected by measuring the vertical clearance distance with the magnet 11.

Furthermore, as shown in Japanese Patent Application Laid-Open No. 57-93679, a coil is provided vertically below the flange portion of the pressure pin, and this coil is energized to detect the inductance of the coil. A device that detects the lift amount of a needle is known.

(Issues to be Solved by the Invention) However, according to the conventional needle lift sensor of a fuel injection nozzle, in the conventional one shown in FIGS. It is difficult to make the diameter sufficiently small, and in the conventional injector shown in Figs. 6 to 8, the permanent magnet is located eccentrically from the body axis, so the size of the injector body is large. However, there is a problem in that there is a certain limit to reducing the diameter of the injector body.

Furthermore, as shown in Japanese Patent Application Laid-Open No. 57-93679,
In order to avoid collisions between the coil and flange due to jumping of the pressure pin or swinging of the spacer, it is necessary to keep the distance between the flange of the pressure pin and the coil at least a predetermined value, but if this distance is too large, , there is a problem that the detection accuracy of the needle lift amount becomes poor.

The present invention has been made to solve these problems, and a coil is provided inside the distance piece vertically below the flange of the pressure pin connected to the nozzle needle, and the inner peripheral wall of the distance piece and the flange are connected to each other. By interposing a non-magnetic material between the parts and detecting the change in inductance caused by the excitation of the coil, it is possible to miniaturize the injector body of the coil and accurately measure the amount of needle lift. A needle lift sensor for an injection nozzle is provided.

(Means for Solving the Problems) A needle lift sensor for a fuel injection nozzle to solve the above problems includes a nozzle needle that is housed so as to be able to reciprocate in the axial direction with respect to the nozzle body, and a means for urging the nozzle needle. a pressure pin that presses in the axial direction by a biasing force; a cylindrical distance piece in which a connecting portion between the nozzle needle and the pressure pin is built; and a flange portion located within the distance piece and formed on the pressure pin. a coil located on the nozzle needle side of the flange portion and around the axis of the nozzle needle or the pressure pin and fixed to the distance piece; an inner circumferential wall of the distance piece and an outer circumferential wall of the flange portion; and a non-magnetic material interposed between the two.

(Function) According to the needle lift sensor for a fuel injection nozzle of the present invention, the coil is provided vertically below the flange portion of the pressure pin around the axis of the nozzle needle or pressure pin, so that when the coil is excited, the pressure The inductance of the coil changes according to the vertical movement of the nozzle needle, and the lift amount of the nozzle needle is measured based on the detected inductance value.

Since the coil is provided around the axis of the nozzle needle or pressure pin, the injector body can be made smaller.Moreover, the coil is installed around the flange of the pressure pin and on the inner circumferential wall of the distance piece that houses the flange. Since the configuration includes a non-magnetic material, the magnetic flux that passes through the non-moving parts of the magnetic flux generated when the coil is excited is reduced,
The lift amount of the nozzle needle can be measured with high accuracy based on the distance between the flange portion and the coil.

(Example) Embodiments of the present invention will be described based on the drawings.

1 to 3 show an injector used in a fuel injection device for a diesel engine.

This injector is a fuel injection valve that is fitted between a nozzle body 38 and an injector body 20 with a cylindrical distance piece 36 interposed therebetween and a retaining nut 35. For example, a fuel pipe connected to a discharge port of a high-pressure pump (not shown) is communicated with a fuel inlet 21 of the injector body 20.

A fuel passage 22 communicating with a fuel inlet 21 is formed in the injector body 20, and a first high pressure passage 23 communicating from the fuel passage 22 to a nozzle 25 is formed along the longitudinal direction of the body. A second high-pressure passage 24 branched from the fuel passage 22 is communicated with a passage 53a of an outer valve 53 of the solenoid valve section 26.

In the magnetic valve section 26, an electromagnetic coil 29 is fixed to a valve body 50 built in a cylindrical housing 28.

A cylindrical inner valve 51 is fixed within a cylinder 52 formed in a valve body 50 on an axial line surrounded by the tri coil 29 . A cylindrical outer valve 53 is disposed on the outer periphery of the inner valve S1 on the cylinder inner peripheral wall 5.
2 so as to be slidable. A disc-shaped armature 5 connected to the upper end 53b of this outer valve 53
4 is pressed vertically downward by a coil spring 30 and moves up and down as the input signal to the electromagnetic coil 29 is turned on and off.

A passage 53a opened to the outer valve 53 passes around the inner valve 51 and communicates with the high pressure chamber 56 via a passage 53c, and further communicates with the control chamber 60. When the outer valve 53 lifts vertically upward from the valve seat portion 50a, the high pressure chamber 56 and the low pressure passage 57 communicate with each other, and the high pressure chamber 5
6 pressure is released. Then, injector body 2
The command piston 58, which is slidably housed in the guide hole 20a of 0, is lifted upward.

The flange portion 31a of the pressure pin 31 connected to the lower end of the command piston 58 is connected to the injector body 20.
The guide hole step portion 20b is pressed vertically downward by a spring 34 via an annular spacer 33.

As shown in FIGS. 1 and 3, this flange portion 31a is housed within a cylindrical distance piece 36,
A nozzle needle 37 is provided inside the nozzle body 38 that contacts the lower end of the distance piece 36 so as to be slidable in the axial direction with respect to the guide hole 38a. A projection 37a formed at the upper end of the nozzle needle 37 is fitted into an annular recess 31b formed at the lower end of the flange portion 31a of the pressure pin 31. The protrusion 37a is loosely inserted into an opening hole 36a formed at the bottom of the distance piece.

The flange portion 31a includes a bobbin 4 made of a cylindrical non-magnetic material that is fitted into the inner circumferential wall 36b of the distance piece 36.
It is stored inside 0. A thick annular convex portion 40 is formed on the bottom surface of the small diameter portion of the annular thin wall portion 40a formed at the lower end of the bobbin 40.
b is formed, and a coil 42 is formed on the outer periphery of this annular convex portion 40b.
is wound. This coil 42 is located substantially vertically below the flange portion 31a of the pressure pin. When the coil 42 is energized, the annular thin section 40
This is for the purpose of accurately detecting the vertical distance between the coil 42 and the flange portion 31a via the distance a. The conducting wire 43 of the coil 42 is embedded in a filling material 44 made of non-magnetic resin, and is shielded from the middle! It is protected inside the ji45 and taken out to the outside.

When the coil 42 is excited, lines of magnetic force are generated via the nozzle needle 37, pressure pin 31, and the like. In this case, since the flange portion 31a is arranged almost vertically above the coil 42, the inductance of the coil 42 changes sharply depending on the lift amount of the flange portion 31a, and this detected inductance changes the lift amount of the nozzle needle 37. be measured.

According to such a configuration, since the coil 42 is arranged substantially vertically below the flange portion 31a of the pressure pin 31, the diameters of the nozzle body 38, the distance piece 36, and the injector body 20 can be reduced. By disposing a relatively thick cylindrical bobbin 40 made of a non-magnetic material between the distance piece 36 and the pressure pin 31, when the coil 42 is excited, the magnetic flux passing through the non-movable part is reduced. At the same time,
By interposing a thin annular portion 40a made of a relatively thin non-magnetic material between the pressure pin 31 and the coil 42, the accuracy in detecting the amount of needle lift by the excitation coil is improved.

(Effects of the Invention) As explained above, according to the needle lift sensor for a fuel injection nozzle of the present invention, a coil is provided vertically below the flange portion of the pressure pin built in the distance piece, and the distance piece and the flange portion Since a non-magnetic material is interposed between the two pressure pins, the lift amount of the nozzle needle can be detected with high precision by detecting a change in the inductance of the coil that changes depending on the position of the pressure pin. Since the coil is wound below the flange of the pressure pin,
This has the advantage that it is possible to reduce the diameter of the distance piece and the nozzle body, and it is possible to detect the needle lift amount with high accuracy according to the displacement of the pressure pin.

[Brief explanation of drawings]

FIG. 1 shows a needle lift sensor of a fuel injection nozzle according to an embodiment of the present invention, and is an enlarged sectional view of part B shown in FIG. 2. FIG. 2 is a needle lift sensor of a fuel injection nozzle according to an embodiment of the present invention. 3 is a sectional view taken along the line ■-■ shown in FIG. 1, FIG. 4 is a sectional view showing a conventional example, and FIG. 5 is a perspective view showing the gap sensor shown in FIG. 4. Fig. 6 is a sectional view showing another conventional example, Fig. 7 is an enlarged sectional view of part C shown in Fig. 6, and Fig. 8 is an enlarged sectional view taken along the line ■-■ shown in Fig. 6. . 31...Pressure pin, 31a...Flange portion, 4 6 7 8 0 2 0...Spring (biasing means),...Distance piece,...Nozzle needle,...Nozzle body, ・...bobbin (non-magnetic material), ...coil, ...control room (biasing means).

Claims (1)

[Claims] (1) A nozzle needle that is housed so as to be able to reciprocate in the axial direction with respect to the nozzle body, a pressure pin that presses the nozzle needle in the axial direction by the urging force of a urging means, and a connecting portion between the nozzle needle and the pressure pin. a cylindrical distance piece having a built-in cylindrical distance piece; a flange portion located within the distance piece and formed on the pressure pin; and a flange portion located on the nozzle needle side of the flange portion and around the axis of the nozzle needle or the pressure pin. A fuel injection nozzle comprising: a coil located at and fixed to the distance piece; and a non-magnetic material interposed between an inner circumferential wall of the distance piece and an outer circumferential wall of the flange part. needle lift sensor.