JP2001021061A - Fluid injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the responsiveness of a fluid injection valve without enlarging it. SOLUTION: A fluid injection valve is provided with a valve element 3 and an actuator 4, and when the actuator 4 drives the valve element 3 to open an injection port 2, supplied fluids are injected. The actuator 4 is made of a shape memory alloy 4s, and elongated when cooled to a deformation temperature or lower to hold the valve element 3 in the position of closing the injection port 2. It is contracted when heated to the transformation temperature or higher, and the valve element 3 is displaced to the position of opening the injection port 2. Since the contraction rate of the shape memory alloy 4s is large, a sufficient amount of stroke is secured even without setting its axial length so large, and the responsiveness of the fluid injection valve is improved without enlarging it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid injection valve such as an engine fuel injection valve.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 11-50932 discloses a fuel injection valve for an engine using a piezoelectric element (piezo element) which generates a distortion by energization as an actuator for driving a valve element for opening and closing an injection port. ing.

[0003]

[Problems to be solved by the invention]
When a piezoelectric element is used as an actuator, the amount of change per unit length, that is, the distortion rate is small, so in order to secure a sufficient stroke amount of the actuator, it is necessary to use the piezoelectric element as a laminated structure. There is a problem that the size of the fuel injection valve cannot be avoided.

[0004] The present invention has been made in view of the above-mentioned problems of the prior art, and has an object to improve the responsiveness of a fluid injection valve without increasing the size thereof.

[0005]

According to a first aspect of the present invention, there is provided a valve element for opening and closing an injection port, and an actuator for driving the valve element, and the actuator drives the valve element to open the injection port. In the fluid injection valve from which the supplied fluid is injected, the actuator is made of a shape memory alloy,
It is configured to extend when cooled below the transformation temperature and hold the valve at the position where the injection port is closed, but to contract when heated above the transformation temperature and displace the valve to the position where the injection port is opened. It is characterized by the following.

In a second aspect based on the first aspect, the transformation temperature of the shape memory alloy constituting the actuator is set to a temperature higher than the temperature of the fluid, and the fluid is guided around the actuator. The cooling is performed.

According to a third aspect of the present invention, in the second aspect, the actuator is constituted by arranging a plurality of rod-shaped shape memory alloys so as to form a space inside with a gap therebetween, and the fluid is provided in the space. , And are configured to pass through the gap.

According to a fourth aspect, in the third aspect, the actuator is formed by twisting a wire made of a shape memory alloy into a rod shape.

[0009]

According to the first aspect of the present invention, the actuator for driving the valve element of the fluid injection valve is made of a shape memory alloy, so that a high response can be achieved without increasing the size of the fuel injection valve. That is, the shape memory alloy constituting the actuator contracts instantaneously when heated to the transformation temperature due to resistance heating or the like. However, since the contraction rate at this time is much larger than the distortion rate of the piezoelectric element, Even if the length in the direction is reduced, a sufficient stroke amount can be secured.

In order to use the shape memory alloy as an actuator, it is necessary to change the temperature across the transformation temperature. According to the second invention, the transformation temperature of the shape memory alloy constituting the actuator is supplied. By setting the temperature to be equal to or lower than the temperature of the fluid to be cooled and using the fluid to cool the actuator to a temperature equal to or lower than the transformation temperature, it is not necessary to provide a means for cooling the actuator, and the injection valve can be further downsized. There is.

According to the third aspect, the contact area between the supplied fluid and the actuator is increased, and according to the fourth aspect, the contact area is further increased. As a result, the cooling efficiency of the actuator is improved, so that the actuator can be rapidly cooled to the transformation temperature or lower, and the valve closing response of the fuel injection valve is improved.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a schematic configuration of a fuel injection valve according to the present invention, wherein 1 denotes an injector housing, 2 denotes a fuel injection opening which opens into an intake port or a combustion chamber of an engine (not shown), and 3 denotes an injection opening / closing opening. A needle-shaped valve element (needle valve), 4 is a rod-shaped shape memory alloy actuator (SMA actuator) that drives the needle valve 3 in the axial direction, and 5 is a cap that connects the needle valve 3 and the SMA actuator 4 while insulating them. .

Here, the SMA actuator 4 is made of Ti-N
i, made of an alloy 4s having a shape memory effect such as Cu-Zn-Al, which contracts in the axial direction when the temperature exceeds the transformation temperature, and expands to the original length when the temperature falls below the transformation temperature. The shrinkage of the shape memory alloy 4s when the temperature exceeds the transformation temperature is about 2%, which is larger than the distortion (about 0.1%) of the piezoelectric element. The transformation temperature depends on the metal composition, and is set here to a value higher than the temperature of the fuel supplied to the fuel injection valve.

Reference numeral 6 denotes a circular member provided with a plurality of through holes 7 for passing fuel in the axial direction. The SMA actuator 4 and the circular member 6 are fixed together by a needle valve holder 8.

Reference numeral 9 denotes the needle valve holder 8 and the housing 1
It is a plug for fixing to. Fuel pressurized by a fuel pump (not shown) is supplied to a fuel supply port 10 of the plug 9. Reference numeral 11 denotes a power supply line for applying a voltage to the SMA actuator 4, which is connected to a controller (not shown).

The axial positional relationship between the needle valve 3, the SMA actuator 4, the cap 5, the circular member 6, and the needle valve holder 8 and the housing 1 is defined by the interference of the plug 9. 9, the tip of the needle valve 3 is connected to the injection port 2 when the SMA actuator 4 is in the extended state.
Is fixed so as to close off.

FIG. 2 shows a cross section taken along line AA of FIG.

As shown in FIG. 1, the SMA actuator 4 is constituted by arranging a plurality of rod-shaped shape memory alloys 4s around a circular member 6 with an annular gap. The pressurized fuel is supplied from the fuel supply port 10 to the space A surrounded by the shape memory alloy 4s through the through hole 7, and the fuel passes through the gap while being in contact with the surface of the shape memory alloy 4s and cooling. SM
It is guided to the vicinity of the injection port 2 through the outer space B between the A4 actuator 4 and the housing 1.

Next, the operation will be described.

When no voltage is applied to the SMA actuator 4, the temperature of the shape memory alloy 4s constituting the SMA actuator 4 is substantially equal to the fuel temperature and lower than the transformation temperature. Therefore, the SMA actuator 4 is in the extended state, and the needle valve 3 is held at a position where the injection port 2 is closed.

When a voltage is applied to the SMA actuator 4 in this state, the temperature of the shape memory alloy 4 s constituting the SMA actuator 4 rapidly rises due to its own heat generation (heating with electric resistance). When the temperature of the shape memory alloy 4s exceeds the transformation temperature, the SMA actuator 4 contracts in the axial direction, the tip of the needle valve 3 is lifted, and the injection port 2 is opened.

When the supply of voltage to the SMA actuator 4 is stopped, the temperature of the shape memory alloy 4s is substantially reduced to the fuel temperature by the fuel flowing on the surface of the shape memory alloy 4s. Since the fuel passes through the gap between the shape memory alloy 4s, the contact area between the fuel and the shape memory alloy 4s is large, and the shape memory alloy 4s is quickly cooled. When the shape memory alloy 4s is cooled to the transformation temperature or lower, the shape memory alloy 4s, that is, the SMA actuator 4 is again expanded, and the tip of the needle valve 3 closes the injection port 2.

Therefore, in the fuel injection valve according to the present invention, when a voltage is applied to the SMA actuator 4, the valve opens to inject fuel, and when no voltage is applied, the valve closes to stop the fuel injection. As a result, the fuel can be intermittently injected by repeatedly energizing and de-energizing the SMA actuator 4.

When energized, the shape memory alloy 4s is immediately heated to a temperature exceeding the transformation temperature, and when not energized, the fuel introduced to the surface of the shape memory alloy 4s rapidly cools the shape memory alloy 4s below the transformation temperature. Therefore, contraction and extension of the SMA actuator 4, that is, opening and closing of the injection port 2 are performed with high response, and a highly responsive fuel injection valve is realized.

Further, the shrinkage of the shape memory alloy 4s is large, and the SMA actuator 4 can secure a sufficient stroke amount without increasing the axial length of the shape memory alloy 4s so much that high responsiveness can be obtained. It is possible to reduce the size of the fuel injection valve while ensuring it.

Although the shape memory alloy 4s forming the SMA actuator 4 has a rod shape, the shape memory alloy 4s
May be a rod shape formed by twisting a plurality of shape memory alloy wires. In this case, the contact area between the shape memory alloy 4s and the fuel further increases, the cooling efficiency of the shape memory alloy 4s increases, and the fuel injection valve can have a higher response.

The embodiment in which the present invention is applied to the fuel injection valve of the engine has been described above. However, the above-described embodiment is merely illustrative, and the applicable range of the present invention is limited to the configuration of this embodiment. It is not something to be done. INDUSTRIAL APPLICATION This invention can be applied not only to the fuel injection valve of an engine, but can be widely applied to the injection valve which injects a fluid.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a fuel injection valve according to the present invention.

FIG. 2 is a cross-sectional view taken along the line AA of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injector housing 2 Injection port 3 Needle valve 4 SMA actuator 4s Shape memory alloy 5 Cap 6 Circular member 7 Through hole 8 Needle valve holder 9 Plug 10 Fuel supply port 11 Power supply line

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenmei Kubo 2 Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside Nissan Motor Co., Ltd. (72) Inventor Shigeru Kamagaya 2 Takara-cho, Kanagawa-ku Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. Terms (reference) 3G066 BA19 BA67 CC06Z CC14 CD22 CD23 CE01 3H057 AA02 BB02 BB32 CC06 DD13 EE02 FC05 HH04 HH17 5H303 AA13 BB01 BB09 BB11 BB17 DD15 MM02

Claims (4)

[Claims] 1. A fluid ejecting apparatus comprising: a valve element for opening and closing an injection port; and an actuator for driving the valve element. When the actuator drives the valve element to open the injection port, a supplied fluid is injected. In the valve, the actuator is made of a shape memory alloy, and expands when cooled below the transformation temperature, and holds the valve body at a position where the injection port is closed, but contracts when heated above the transformation temperature, causing the valve body to shrink. A fluid injection valve configured to be displaced to a position where the injection port is opened. 2. A transformation temperature of a shape memory alloy constituting the actuator is set to a temperature higher than a temperature of the fluid,
The fluid injection valve according to claim 1, wherein the fluid is guided around the actuator to cool the fluid. 3. The actuator is constituted by arranging a plurality of rod-shaped shape memory alloys so as to form a space inside with a gap therebetween, supplying the fluid into the space, and passing through the gap. The fluid injection valve according to claim 2, wherein the fluid injection valve is configured. 4. The fluid injection valve according to claim 3, wherein the actuator is formed by twisting shape memory alloy wires into a rod shape.