JPS60153465A - Controller for piezo fuel injection valve - Google Patents

Abstract

PURPOSE:To promote spray of injection fuel by driving a Piezo element through output signal from an adder for combining the pulse signals corresponding with the fuel injection and high frequency signal. CONSTITUTION:Fuel flowed through fuel inlet 9 is partially fed through a gap between injection nozzle 7 and needle valve body 6 into pump chamber 5. Upon application of drive pulse signal, piezo element 2 will expand to push down a piston 3 thus to increase pressure of fuel oil in pump chamber 5 and to close the injection nozzle 7 through needle valve body 6. Upon application of high frequency voltage, the valve body 6 will vibrate with high frequency through fuel oil in the chamber 5 while being pushed up, thereby injected fuel will produce cavitation to inject fine fuel through injection hole 8.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a piezoelectric valve that controls the amount of fuel injected into a combustion chamber by supplying a drive signal corresponding to the amount of fuel injection set according to operating conditions to a fuel injection valve. The present invention relates to a control device for a fuel injection valve.

[Prior art]

In electronically controlled fuel injection systems used in diesel engines, a drive signal is sent to the fuel injection valve in response to the fuel injection amount set according to operating conditions such as intake air amount, engine speed, and cooling water temperature. By supplying the fuel, the amount of fuel injected into the combustion chamber is controlled.

Conventionally, a piezoelectric drive element made of ceramic or the like is known as a driving element for opening and closing a fuel injection valve, which has an important function in controlling the fuel injection amount.

For this reason, the responsiveness to the pulse waveform used as a drive signal is improved, and the control function of the drive element used in electronic control systems has been improved. In order to improve the atomization state and obtain fine atomized particulate fuel, there are the following problems.

In other words, the atomization state of the fuel injected from the fuel injection valve changes depending on the fuel feed pressure, but there are constraints such as increasing the size of the pump in order to increase the feed pressure, so conventional piezoelectric fuel Significant improvements in atomization cannot be expected with injection valves.

[Purpose of the invention]

In view of the above problems, an object of the present invention is to promote atomization of the injected fuel by applying high frequency vibration to the injected fuel from the needle valve element when the fuel injection valve is opened. It is.

[Structure of the invention]

In order to achieve such an object, the present invention provides a pulse signal generation circuit that outputs a pulse signal corresponding to the amount of fuel injection;
a high-frequency signal generation circuit that outputs a high-frequency signal for atomizing the injected fuel; an adder circuit that combines the pulse signal and the high-frequency signal; and a piezoelectric device that is disposed in the fuel injection valve and driven by the output signal of the adder circuit. It is characterized by comprising an element.

[Operations and Effects of the Invention] When the fuel injection valve is opened, high-frequency vibration in the ultrasonic frequency range is applied to the needle valve body to cause cavitation in the injected fuel, so that the injected fuel is atomized by atomization. Significant improvement in the condition is possible.

〔Example〕

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

FIG. 1 is a sectional view showing a fuel injection valve according to an embodiment of the present invention. A piezoelectric element 2 made of ceramics or the like is disposed inside a housing case 1. One end of the piezoelectric element 2 A piston h that operates by following the vertical expansion and contraction vibration of the piezoelectric element 2 is fixed to the other end, and the piezoelectric element 2 is attached to the other end.
An electrode 4 is attached for supplying a drive signal to.

Further, a needle valve body 6 that receives vertical expansion and contraction vibrations of the piezoelectric element 2 through changes in the pressure of fuel oil in the pump chamber 5 is received on the side of the injection nozzle 7 in the housing case 1.
The nozzle injection hole 8 is opened and closed.

On the other hand, high-pressure fuel sent from an injection pump (not shown) is taken in from a fuel port 9 and flows into the injection nozzle 7, and a part of it flows between the injection nozzle 7 and the needle valve body 6. It is supplied to the pump chamber 5 through the gap. An O-ring 10 is installed on the lower side of the piston 3 to prevent fuel from leaking to the piezoelectric element 2 side.

FIG. 2 is a block diagram of an electric circuit for generating a drive signal to be applied to the piezoelectric element 2. The computer 20 generates signals for detecting the operating state of the engine, such as an intake air amount signal, an engine rotation speed signal, and a cooling water temperature signal. are input, and based on these input signals, calculation processing of the fuel injection time is performed to set the fuel injection amount, and from the output side, the calculated injection time is replaced with a pulse width change. A signal is extracted. The circuit for generating this pulse signal is well known, for example, as shown in Japanese Patent Publication No. 47-26567, so its details will be omitted. The pulse signal output from the computer 20 is amplified and shaped by the amplification and shaping circuit 21 as shown in FIG.

On the other hand, a high frequency signal for atomizing the injected fuel is taken out from the high frequency generation circuit 22 as shown in FIG.

The adding circuit 25 is composed of a well-known analog switch 23 and a adding amplifier 24, and the control input terminal of the analog switch 23 receives the pulse signal of the amplification shaping circuit 21, and the input terminal receives the high frequency signal of the high frequency generation circuit 22. As shown in FIG. 3(c), a high frequency signal is taken out from the output side only when the pulse signal is at zero level. The summing amplifier 24 is for combining the signals taken out from the analog switch 23 and the amplifying and shaping circuit 21, and when these two signals are applied to the input terminal, the output side as shown in FIG. 3 (d) is generated. like 2
A signal is obtained by combining the two signals.

The voltage amplification circuit 26 is for amplifying the signal obtained from the addition circuit 25 to a voltage level for driving the piezoelectric element 2, and its output terminal is connected to the electrode 4 of the piezoelectric element 2. In this embodiment, the pulse signal voltage output from the voltage amplification circuit 26 in FIG.
0 Volt, 30 Pol as high frequency signal voltage) (10KH
2) has been obtained.

Next, the operation of this embodiment will be explained.

When the fuel sent from the injection pump reaches a constant feed pressure (approximately 250 kg/cd), it flows into the injection nozzle 7 from the fuel population 9, and a part of it passes through the gap between the injection nozzle 7 and the needle valve body 6. It is supplied to the pump chamber 5. Therefore,
When a drive signal for driving the piezoelectric element 2 is not applied due to the pressure of fuel flowing into the pump chamber 5, the needle valve body 6 is pushed up and fuel is ejected from the nozzle injection hole 8.

When a pulse-like drive signal as shown in FIG. The pressure increases and the needle valve body 6 operates to close the injection nozzle 7. In addition, when a high frequency voltage is applied, the needle valve body 6 is pressed down and
Since high frequency vibrations (approximately 10 microns) occur through the fuel oil in the pump chamber 5, the injected fuel causes cavitation, and fuel with a fine spray diameter is injected from the nozzle injection hole 8. Note that the frequency of the high-frequency signal is preferably in the ultrasonic frequency range of IKHz to IMHz, depending on the shape of the injection nozzle 7 and the size of the piezoelectric element 2.

In the case of this embodiment, a ceramic piezoelectric element 2 having a wide range of frequency response characteristics from low to high frequencies is used, and the piezoelectric element is driven with a waveform as shown in (d) in FIG. When a signal is applied to open the fuel injection valve, high-frequency vibrations in the ultrasonic frequency range are applied to the injected fuel from the needle valve body, resulting in highly responsive fuel injection characteristics and fine atomized fuel particles. can be obtained with a simple control mechanism.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a fuel injection valve that is an embodiment of the present invention, FIG. 2 is an electric circuit configuration diagram, and FIG. 3 is an explanatory diagram of a signal waveform obtained from the electric circuit configuration of FIG. 2. It is. 2------One piezoelectric element 5------Pump chamber 6---Two dollar valve body 7------Injection nozzle 21------Pulse signal generation circuit 22 ------
- High frequency signal generation circuit 25 - - Addition circuit Applicant Toyota Motor Corporation Shiri Hayashi

Claims (1)

[Claims] (1) In a fuel injection valve control device that injects fuel into a combustion chamber by supplying a pulse signal corresponding to a predetermined fuel injection amount to a fuel injection valve according to operating conditions, a pulse signal corresponding to a predetermined fuel injection amount is used. a pulse signal generation circuit that outputs a signal, a high frequency signal generation circuit that outputs a high frequency signal for atomizing the injected fuel, an addition circuit that combines the pulse signal and the high frequency signal, and is disposed in the fuel injection valve, A piezoelectric fuel injection valve control device comprising: a piezoelectric element driven by an output signal of an adder circuit.