JPS62199960A - Fuel injection valve - Google Patents

Abstract

PURPOSE:To reduce the influence of thermal expansion depending upon temperature and to improve control precision as high speed properties is effectively utilized, by a method wherein a spacer, having a thermal expansion factor to which consideration is paid, is combined with a piezo-electric element which controls opening and closing of a valve. CONSTITUTION:A fuel injection valve opens and closes a nozzle valve 5 through the force of a return spring 4 through expansion and contraction motion of a piezo-electric element 3 situated in a body 2 of an injection body 1. In which case, the piezo-electric element 3 is a ceramic series element having a low thermal expansion factor alpha1, but an iron series metal is generally used as the material of the body 2. The material of the body has a high thermal expansion factor alpha2, and a valve stroke is decreased by means of a difference in thermal expansion. In which case, in order to compensate for the difference in thermal expansion, a spacer 6 having a high thermal expansion factor alpha3 is situated to the piezo-electric element 3. This constitution decreases the influence of thermal expansion of a fuel injection valve body depending upon temperature and enables precision on control of an amount of injected fuel to be excellently held without damaging high speed properties of opening and closing of a valve.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a fuel injection valve, and particularly to a fuel injection valve using a piezoelectric element.

(Prior art) Conventional fuel injection valves are generally electromagnetic type, and this method closes the valve by pressing the needle against the seat using the pressing force of the return spring.On the other hand, when the valve is closed, the suppressing force of the return spring The needle is attracted by electromagnetic force against the This type of system has the drawbacks of slow operation speed and large size because the valve is operated by electromagnetic force.

Therefore, in recent years, various fuel injection valves using piezoelectric elements have been proposed. That is, as is well known, piezoelectric elements are small in size and have excellent characteristics such as high-speed response, energy efficiency, and power generation. This is because highly accurate flow rate control is achieved.

(Problems to be solved by the invention) However, when piezoelectric elements are applied to fuel injection valves,
There are problems as shown below.

That is, although the piezoelectric element has the above-mentioned characteristics, since the piezoelectric element is formed of a ceramic material, instability in the amount of displacement is inevitable due to internal factors of the element itself (temperature hysteresis, polarization deterioration, etc.).

Furthermore, since the components of the fuel injection valve are made of iron-based metal rot, etc., the difference in temperature expansion coefficient between the piezoelectric element and the body causes the valve lift tail to be inaccurate, resulting in deterioration of flow rate accuracy. arise.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a fuel injection valve that reduces the influence of thermal expansion due to temperature and improves flow mother control accuracy.

Structure of the invention] (Means for solving problems) FIG. 1 is a diagram showing the basic concept of the present invention.

In FIG. 1, a piezoelectric element 3 is provided in a body 2 of a fuel injection valve body, and a nozzle valve 5 is operated via a return spring 4 by utilizing the expansion and contraction movement of this piezoelectric element. The piezoelectric element 3 used here is a ceramic element and has a small coefficient of thermal expansion, and depending on the material of the element, it may shrink as the temperature rises (the coefficient of thermal expansion has a negative sign).

Further, this type of body material generally uses iron-based metal scraps, etc., and has a large coefficient of thermal expansion.

Here, if the thermal expansion coefficient of the piezoelectric element is α1, the thermal expansion coefficient of the body material is α2, and the element length is 1, the nozzle and the element cannot contact each other due to the difference in thermal expansion coefficient, and a gap is created.

Its size Δl is ΔJl=<α2−α1)! 6 guns...(1). Note that 6 points is the temperature increase from the temperature at which contact is maintained. By the way, α
1=-4x10/deg, α2=11xlO/d
eg, 1 = 40 mm.

When AT=50°C, Δ1=30 μra.

However, in general, the stroke of the injection valve is 30 μm to 100 μm.
Since the gap is on the order of μm, a reduction in the valve stroke due to the gap 1 will have a large impact on performance.

Therefore, in the present invention, the piezoelectric element 3 is provided with a spacer 6 made of a material having a large coefficient of thermal expansion.

(Function) Therefore, the shrinkage of the piezoelectric element 3 due to temperature rise can be canceled by the expansion of the spacer 6. in this case,
If the coefficient of thermal expansion of the spacer is α3 and the length is 1', then J l = (Z 2LLLL22'' upper J ... (
2) By incorporating the spacer 6 having a length of α3, almost no gap can be created.

(Example) Examples will be described below with reference to the drawings.

FIG. 2 is a configuration diagram of an embodiment of a fuel injection valve according to the present invention. FIG. 2 shows an example of a poppet valve type injection valve, in which a piezoelectric element 3-1 in a body 2-1 is held between an engaging element 7 and a temperature compensation spacer 6-1. The holding part 9, which operates in accordance with the movement of the engaging element 7, is subjected to a pressing force by the return spring 4, and the engaging element 7 is further subjected to a compressive force by the extra pressure spring 10, and as a result, the piezoelectric element 3-1 is compressed. It is designed to receive power. Therefore, the valve movable section 8 receives the expansion of the piezoelectric element 3-1 due to voltage application, and the nozzle valve 5 is opened by the movement of the valve movable section 8 against the return spring 4.

On the other hand, when the voltage is no longer applied, the piezoelectric element 3-1 is contracted by the return spring 4 and the extra pressure spring 10, and as a result, the nozzle valve 5 is closed. At this time, the spacer 6-1 cancels the difference in thermal expansion between the piezoelectric element 3-1 and the body 2-1.

FIG. 3 is a block diagram of another embodiment.

In this embodiment, a spacer for temperature compensation and a piezoelectric element are fixed with bolts.

A spacer 6-2 for temperature compensation is fixed inside the body 2,
A cylindrical piezoelectric element 3-2 is attached to the spacer with bolts 11. Extra pressure is applied to the piezoelectric element 3-2 by tightening the bolt 11.

Note that the return spring 4 is supported by a holding section 12 that is integrated with the valve movable section 8.

13 is the bolt tightening section. As a result, piezoelectric element 3
When a voltage is applied to -2, the piezoelectric element 3-2 extends, the bolt 11 also extends, and the tip of the bolt opens the nozzle valve 5. When the valve is closed, the operation is the reverse of the above, and will be omitted.

In this case, by using a material with a large coefficient of thermal expansion for the spacer 6-2, the influence of heat can be reduced.

FIG. 4 shows yet another embodiment.

In this embodiment, the needle valve is moved by the expansion and contraction of the piezoelectric element to open and close the valve.

In FIG. 4, a piezoelectric element 3-3 is supported by an engaging element 7-1 and a spacer 6-3, and the spacer 6-3 is made of a material with large thermal expansion to improve temperature characteristics. 14 is a needle valve, and the explanation of its operation will be omitted.

FIG. 5 shows yet another embodiment.

In this embodiment, the spacer for temperature compensation is omitted, and instead, the same material as the piezoelectric element is used for the body 2-1, 2-2, or a ceramic material with a small coefficient of thermal expansion is used. be. In this case, consideration must be given to making the material of the seat portion 15 metal. Other configurations and operations will be omitted.

[Effects of the Invention] As explained above, according to the present invention, since a spacer having a large coefficient of thermal expansion is inserted into the piezoelectric element, the influence of thermal expansion due to temperature can be reduced, high speed performance can be utilized, and A fuel injection valve with good control accuracy can be provided.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the principle of the fuel injection valve of the present invention, Figure 2 is a diagram explaining the principle of the fuel injection valve of the present invention.
The figure is a configuration diagram of one embodiment of the fuel injection valve of the present invention, FIG. 3 is a configuration diagram of another embodiment, FIG. 4 is a configuration diagram of still another embodiment, and FIG. 5 is a configuration diagram of still another embodiment. FIG. 1...Fuel injection valve body 2.2-1.2-2...
・Body 3.3-1 to 3-4...Piezoelectric element 4...Return spring 5...Nozzle valve 6
．． 6-1 to 6-3...Spacer 7.7-1...Engager 8...Valve movable part 9.12...Holding part 10...Extra pressure spring 11...Bolt 1
3...Tightening part 14...Needle valve 15...Seat part

Claims (1)

[Claims] A fuel injection valve that controls the amount of fuel injected by controlling the opening and closing of a valve using a piezoelectric element as a driving source, characterized in that the piezoelectric element is combined with a spacer that takes into account a coefficient of thermal expansion.