JPH116468A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress rising of a temperature of a coil and a super magnetostrictive element by mounting the coil in a casing, and fitting the casing so as to be brought into close contact with an inner wall surface of an injection valve body, in a device formed in such a constitution that a nozzle is opened/closed by an actuator provided with the coil for expanding-driving the super magnetostrictive element. SOLUTION: When current-carrying to a coil 12c is stopped from a condition in which a needle valve 13 is closing held, a super magnetostrictive element 12a is contracted and a piston 18 is retreated, and thereby, the volume of a pressure chamber 21 is enlarged and pressure is reduced. The needle valve 13 is lift-operated in a back direction on the basis of a difference between front and rear pressure of a piston part 24, and fuel is injected from an injection hole 23. In such a fuel injection valve 1, the coil 12c is enclosed by the casing 10, and the outer peripheral surface of the casing 10 is fitted to a fuel injection valve main body 11 so as to tightly fit to the inner circumferential surface of the main body 11, and thereby, heat generated from the coil 12c is efficiently transferred from the casing 10 to the injection valve main body 11, so as to suppress a rise of temperature of the coil 12c and the super magnetostrictive element 12c.

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 for an internal combustion engine using a giant magnetostrictive element as an actuator.

[0002]

2. Description of the Related Art A fuel injection valve applied to an in-cylinder fuel injection type spark ignition type internal combustion engine is required to have high responsiveness and high opening / closing accuracy. As a fuel injection valve that meets such demands, there is known a fuel injection valve that controls the opening and closing of a needle valve by supplying a signal current to an actuator using a giant magnetostrictive element and causing the actuator to expand and contract (for example, Japanese Patent Application Laid-Open No. HEI 9-103572). 4-8
No. 1565).

[0003]

An actuator using a giant magnetostrictive element is provided with an electromagnetic coil so as to surround the giant magnetostrictive element, and expands and contracts the giant magnetostrictive element by the action of a magnetic field when the coil is energized. Since the nozzle is opened and closed, if the temperature of the giant magnetostrictive element rises due to the heat generated by the coil, there is a problem that the magnetostriction decreases and the fuel injection quantity becomes inaccurate.

As a countermeasure against this, for example, Japanese Unexamined Patent Publication No.
In the case of No. 2, the passage for circulating the refrigerant is formed in the actuator, but the structure is complicated because a passage for the fuel injection valve, a seal for the refrigerant, and a pipe for circulating the refrigerant are required. .

[0005]

According to a first aspect of the present invention, an actuator including a giant-magnetostrictive element and a coil for driving the giant-magnetostrictive element to expand and contract is housed in an injection valve main body, and based on the expansion and contraction operation of the actuator. In a fuel injection valve that opens and closes a nozzle, the coil is housed in a casing having an outer wall surrounding the coil, and the casing is so arranged that its outer peripheral surface is in close contact with the inner wall surface of the injector main body. It shall be fitted.

According to a second aspect of the present invention, the casing of the first aspect of the present invention comprises an inner cylindrical portion through which a rod-shaped giant magnetostrictive element penetrates, and an outer cylindrical portion which accommodates a coil between the inner cylindrical portion. And an end member for connecting the inner cylindrical portion and the outer cylindrical portion at the ends.

According to a third aspect of the present invention, the casing according to the second aspect of the present invention comprises two casing members divided at an intermediate portion in the axial direction, and accommodates a coil therein and is connected to each other. The coil was held in this state.

According to a fourth aspect of the present invention, the casing of the first aspect of the present invention is formed by folding an end of an inner cylindrical portion having a coil fitted on the outer periphery so as to surround the coil outer periphery.

According to a fifth aspect of the present invention, the casing of the first aspect of the present invention is formed by molding, and a coil is cast inside the casing at the time of molding.

[0010]

According to the first and second aspects of the invention, since the outer peripheral surface of the casing surrounding the coil is in close contact with the inner surface of the injection valve body, heat generated from the coil when the injection valve is driven is injected from the casing. The heat is efficiently transmitted to the valve body and is radiated to the periphery of the injection valve body. As a result, the temperature rise of the coil and the giant magnetostrictive element is suppressed, so that the displacement characteristics and the fuel injection amount of the giant magnetostrictive element caused by the temperature rise can be prevented.

In addition, since it is not necessary to set an extra displacement amount in the giant magnetostrictive element in consideration of the variation of the displacement amount at the time of temperature change, it is possible to provide a small actuator having a necessary minimum displacement amount characteristic. .

Further, since the outer peripheral portion of the coil is protected by the casing, a problem that the insulating film on the coil surface comes off due to contact with the inner surface portion of the injection valve body when assembled into the injection valve may occur. Absent.

According to the second aspect of the present invention, since the coil is surrounded by the casing composed of the inner and outer cylindrical portions and the end members connecting the ends, the heat transfer path is maximized around the coil. And a better cooling performance can be obtained.

According to the third aspect of the present invention, the two wound casing members are put on each other so as to sandwich the coil wound in advance from the front and rear, and are connected to each other.
The invention according to the invention can be easily manufactured.

According to the fourth aspect of the present invention, since the outer cylindrical portion is formed by turning the end of the inner cylindrical portion in which the coil is fitted outward, the number of components is reduced, and the heat transfer path is reduced. Can be formed without interruption.

According to the fifth aspect of the present invention, since the coil is integrated inside the casing by molding,
Due to the close contact between the coil and the casing, a sufficient heat transfer path between them can be ensured, so that good cooling performance can be obtained.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a fuel injection valve. The fuel injection valve 1 has an actuator 12 housed inside a cylindrical main body 11 and a main body 11.
Is provided with a nozzle body 14 in which a needle valve 13 is accommodated.

The actuator 12 includes a columnar giant magnetostrictive element 12a and a coil 12c held around the giant magnetostrictive element 12a via a casing 10.

The end plate 15 provided at the rear end of the giant magnetostrictive element 12a is positioned via a ball 17 with respect to a cap 16 fitted to the main body 11. A piston 18 is provided on the tip side of the giant magnetostrictive element 12a,
The piston 18 has a cylinder portion 19 formed in the main body.
Are slidably fitted through a seal ring 20 in an oil-tight manner.

A pressure chamber 21 is defined in front of the piston 18 and between the cylinder section 19 and the piston 18 is urged rearward by the tension of a disc spring 22 housed in the pressure chamber 21. ing. The pressure chamber 21 communicates with the pressure chamber 26 via the passage 30.

The needle valve 13 for opening and closing the injection hole 23 opened at the tip of the nozzle body 14 is housed therein. The needle valve 13 has a large-diameter piston portion 24 at its base end, and the piston portion 24 is slidably held along a cylinder portion 25 formed on the inner periphery of the holder. A coil spring 27 is interposed in a pressure chamber 26 defined behind the piston portion 24, and the needle valve 13 is urged in a valve closing direction by the tension of the spring 27.

The space inside the nozzle body 14 ahead of the piston portion 24 is a fuel chamber 28, and this fuel chamber 2
The fuel 8 is supplied with fuel adjusted to a predetermined pressure from a fuel system (not shown) through a fuel supply port 29.

The coil 12c of the actuator 12 includes:
An injection signal is supplied from a fuel injection amount control circuit (not shown). The fuel injection amount control circuit determines the fuel injection amount using, for example, the rotation speed of the internal combustion engine and the intake air amount as parameters, and supplies a current having a pulse width corresponding to the fuel injection amount to the coil 12c as an injection signal to supply the fuel. The injection is performed.

The details of the operation of the fuel injection valve 1 when such an injection signal is input are as follows. First, in this fuel injection valve, a predetermined voltage is supplied to the coil 12c at the time of non-injection, and a predetermined amount of initial displacement in the extension direction is given to the giant magnetostrictive element 12a by the action of the magnetic field generated by the coil 12c at this time. ing. Thereby, the actuator 12 keeps the volume of the pressure chamber 21 small.
Since the pressure of the fuel supplied to the fuel chamber 28 also acts on the pressure chamber 26 via the sliding gap between the needle valve piston portion 24 and the cylinder portion 25, the front-rear pressure of the needle valve 13 is reduced. The needle valve 13 is held in a closed state by the tension of the spring 27.

In this state, when the power supply to the coil 12c is stopped, the giant magnetostrictive element 12a contracts and the piston 18 retreats, so that the pressure chamber 21 expands its volume and reduces the pressure. This pressure drop is immediately transmitted to the pressure chamber 26 behind the needle valve via the passage 30. At this time, the sliding gap between the needle valve piston portion 24 and the cylinder portion 25 acts as an orifice. The pressure change in the fuel chamber 28 is delayed with respect to the pressure drop, and the fuel chamber 28 becomes relatively high in pressure. Based on the pressure difference between the front and rear of the piston portion 24, the needle valve 13 is lifted rearward against the spring 27 to open the injection hole 23 and perform fuel injection.

When the energization of the coil 12c is resumed after a lapse of time determined in accordance with the required fuel injection amount at that time, the giant magnetostrictive element 12a of the actuator 12 expands again to increase the pressure in the pressure chambers 21 and 26. Needle valve 1
3 moves in the valve closing direction, and the fuel injection ends. The closed state of the needle valve 13 at the time of non-injection is maintained by the tension of the coil spring 27 in the pressure equilibrium state before and after the piston 24 as described above.

As described above, since current is constantly supplied to the coil 12c when the fuel injection valve is used, the coil 12c generates heat and raises the temperature of the giant magnetostrictive element 12a.
It fluctuates its operating characteristics.

As a countermeasure against this, in the present invention, the casing 1
0 surrounds the coil 12c, and the body 1
Fit into 1. With this configuration, heat generated from the coil 12c when the injection valve is driven is transferred from the casing 10 to the injection valve body 1
1 and is efficiently transmitted to the periphery of the injection valve body 11. Therefore, the coil 12c and the giant magnetostrictive element 1
The temperature rise of 2a is suppressed, the operating characteristics of the actuator are stabilized, and the fuel injection amount does not vary.

Further, since there is no need to set an extra displacement in anticipation of variation due to a temperature rise, the actuator 12 can be miniaturized by using a giant magnetostrictive element having a necessary minimum displacement characteristic. is there.

Further, since the inner and outer surfaces of the coil 12c are protected by the casing 10, there is no problem that the insulating film on the coil surface is peeled off by the contact with the inner surface of the injection valve body or the like at the time of assembly.

By the way, the casing 1 of this embodiment
Reference numeral 0 denotes an inner cylindrical portion 10a fitted inside the coil 12c as shown, an outer fitting portion 10b fitted outside the coil 12c, and an annular end member 10c connecting both ends thereof. The coil 12c
As a result, a maximum heat transfer path is ensured around the periphery, so that good cooling performance can be obtained. The outer fitting portion 10b forms an outer wall surrounding the coil 12c.

The casing 10 comprises two casing members 10A and 10B having the same shape and divided into front and rear portions as shown in FIG. The casing members 10A and 10B are covered with each other so as to be sandwiched between them. With such a configuration, it is possible to easily manufacture a casing structure that entirely surrounds the coil 12c.

The structure of the casing 10 is not limited to the above-described one. For example, as shown in FIG. 3, the outer cylindrical portion 10b is formed by turning the end of the inner cylindrical portion 10a in which the coil is fitted to the outside. According to this, the number of components constituting the casing can be reduced, and the heat transfer path can be formed without interruption.

Further, the casing 10 may be formed by molding a resin or a metal having excellent heat conductivity. At this time, the actuator 12 may be formed by coating the coil 12c with a heat-resistant insulating film and then casting. Good. In this case, at the time of casting, the casing material is the coil 12c.
, The heat transfer between the coil 12c and the casing 10 is improved, and more excellent cooling performance can be expected.

[Brief description of the drawings]

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

FIG. 2 is an external perspective view of a casing member of the embodiment.

FIG. 3 is an external perspective view of a casing member according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel injection valve 10 Casing 10a Inner cylindrical part of casing 10b Outer cylindrical part of casing 10c End member of casing 11 Main body of fuel injection valve 12 Actuator 12a Giant magnetostrictive element 12c Coil 13 Needle valve 14 Nozzle body 15 End plate 16 Cap 17 Ball Reference Signs List 18 piston 19 cylinder part 20 seal ring 21 pressure chamber 22 disc spring 23 injection hole 24 piston part 25 cylinder part 26 pressure chamber 27 coil spring 28 fuel chamber 29 fuel supply port 30 passage

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takashi Fukuda Nissan Motor Co., Ltd., 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa

Claims (5)

[Claims] 1. A fuel injection valve in which a giant magnetostrictive element and an actuator having a coil for driving the giant magnetostrictive element to expand and contract are housed in an injection valve body, and a nozzle is opened and closed based on the expansion and contraction operation of the actuator. Wherein the coil is housed in a casing having an outer wall surrounding the coil, and the casing is fitted so that an outer peripheral surface of the casing closely contacts an inner wall surface of the injector main body. . 2. A casing, comprising: an inner cylindrical portion through which a bar-shaped giant magnetostrictive element penetrates; an outer cylindrical portion accommodating a coil between the inner cylindrical portion; and the inner cylindrical portion and the outer cylindrical portion. The fuel injection valve according to claim 1, further comprising an end member connected at a portion. 3. The casing according to claim 1, wherein the casing is divided at an intermediate portion in the axial direction, and the coil is housed inside the casing to hold the coil in a mutually coupled state. Item 3. The fuel injection valve according to Item 2. 4. The fuel injection valve according to claim 1, wherein the casing is formed by folding an end of an inner cylindrical portion having a coil fitted on the outer periphery so as to surround the outer periphery of the coil. 5. The fuel injection valve according to claim 1, wherein the casing is formed by molding, and a coil is cast inside the casing.