KR20070055276A - Feedback combustion control method using piezo injector - Google Patents

Abstract

Disclosed is a feedback combustion control method using a piezo injector. In the feedback combustion control method using the disclosed piezo injector, the pressure change in the combustion chamber of the engine is transmitted to the nozzle portion needle of the piezo injector, and acts on the piezo actuator of the piezo injector to generate a potential difference, and the potential difference is generated by the ECU of the engine. It is characterized in that the feedback control for the fuel injection timing of the piezo injector.

According to the present invention, it is possible to accurately detect the fuel injection timing to implement accurate feedback control of the fuel injection timing in the engine combustion mapping. Therefore, it is possible to control the optimum fuel injection timing, it is possible to significantly reduce the exhaust gas through the combustion feedback control by the piezo actuator, there is an advantage that can respond to the exhaust gas regulation.

Piezo injector, feedback combustion control, combustion chamber, ECU

Description

Feedback combustion control method using piezo injector {FEEDBACK COMBUSTION CONTROL METHOD USING PIEZO INJECTOR}

1 is a cross-sectional view showing the configuration of a general piezo injector.

Figure 2 is a control block diagram schematically showing a feedback combustion control method according to the prior art.

Figure 3 is a block control diagram schematically showing a feedback combustion control method using a piezo injector according to the present invention.

4 is a cross-sectional view of a piezo injector applied to a control method according to the present invention.

5 is a graph showing the characteristics of the piezo actuator of the piezo injector.

6 and 7 are graphs showing the pressure difference in the combustion chamber and the potential difference with respect to the crankshaft angle when the fuel is not injected.

8 and 9 are graphs each showing a pressure difference in a combustion chamber and a potential difference with respect to the crankshaft angle during fuel injection.

<Description of the symbols for the main parts of the drawings>

30. Piezo Injector

31.Piezo Actuator

32. Nozzle

33. Control valve

34. High pressure supply

35. Connector

40. ECU

52. Combustion chamber

The present invention relates to a feedback combustion control method using a piezo injector, and more particularly, to a feedback combustion control method using a piezo injector for enabling accurate detection of fuel injection timing.

The combustion control of the common rail system employing a piezo injector, which is used as a next-generation fuel injection system for a diesel engine of a passenger vehicle, is controlled in an open loop manner.

As shown in FIG. 1, the piezo injector 10 utilizes the piezoelectric effect of the piezo ceramic element, and deformation is generated by a high-potential difference, thereby controlling the movement of the nozzle part needle 12 of the piezo injector 10. Inject fuel.

That is, fuel injection according to the operating conditions of the engine is controlled by the ECU 21 in synchronization with the signal of the engine rotation sensor 22, as shown in FIG.

In addition, the piezo injector 10 of the common rail system employs a piezo element-type actuator 11, and thus, the response is very high, and thus, the piezo injector 10 may play a very important role in improving the performance of the diesel engine and reducing the emission gas.

However, despite the advantages of this technology development, the combustion control of the diesel engine, in particular, the control of fuel injection timing, is carried out using the actual combustion chamber (open loop method) implemented using the signal of the engine rotation sensor 22 in the ECU 21. 23) It is not possible to control the optimum injection timing according to the pressure conditions inside.

In addition, the injection timing control method is inevitable in the error caused by the deviation of the hardware, such as the tolerance of the engine rotation sensor 22 and the target wheel (target wheel). This means that the control accuracy of the fuel injection timing, which is very important in diesel combustion, is lowered, and thus there is a limit to stricter exhaust gas regulations.

In addition, an acceleration sensor (G-sensor) is installed on the cylinder block of the engine to measure the condition in the combustion chamber 23 to control the closed loop feedback of the fuel injection time, but the increase in price due to the installation of additional sensors More precise control is required due to the inaccuracy of the acceleration sensor signal.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a feedback combustion control method using a piezo injector capable of controlling the optimum fuel injection timing and enabling the response to the exhaust gas regulation. There is this.

In the feedback combustion control method using the piezo injector of the present invention for achieving the above object, the pressure change in the combustion chamber of the engine is transmitted to the nozzle portion needle of the piezo injector, acting on the piezo actuator of the piezo injector to change the potential difference And detecting the potential difference in the ECU of the engine and performing feedback control on the fuel injection timing of the piezo injector.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a block control diagram schematically showing a configuration of a feedback combustion control method using a piezo injector according to the present invention, and FIG. 4 is a perspective view of a piezo injector applied to the control method according to the present invention.

Referring to the drawings, the feedback combustion control method using the piezo injector according to the present invention, first, the pressure change in the combustion chamber 52 of the engine is transmitted to the needle of the nozzle portion 32 of the piezo injector 30. Then, the potential difference is generated by acting on the piezo actuator 31 of the piezo injector 30, and the ECU 40 of the engine detects the potential difference to perform feedback control on the fuel injection timing of the piezo injector 30.

Meanwhile, reference numeral 33 not described in FIG. 4 denotes a control valve, 34 denotes a high pressure supply unit, and 35 denotes a connector.

5 is a graph showing the characteristics of the piezo actuator 31 of the piezo injector 30.

This will be described in more detail.

A closed loop feedback control of the fuel injection timing of a common rail system employing a piezo injector 30, which is a next generation fuel injection system of a diesel engine for a passenger vehicle, is a bidirectional characteristic of voltage-displacement of the piezo actuator 31. After the fuel injection, by detecting the potential difference of the piezoelectric element generated by the force acting on the piezo actuator 31 of the piezo injector 30 according to the pressure of the combustion chamber 52 to control the fuel injection timing.

On the other hand, in order to optimize combustion according to each operating condition of the engine, a method of variably controlling the injection timing by feeding back the conditions in the combustion chamber 52 to the ECU 40 is required.

As described above, the explosion is caused by the fuel injection into the combustion chamber of the current engine, and the method of measuring the combustion chamber pressure and controlling it in the engine ECU evaluates the vibration level by attaching an acceleration sensor (G-sensor) to the engine cylinder block. The method is generally used. However, this method is also not reliable in terms of the increased cost and accuracy of the additional mounting of the acceleration sensor.

Recently, the common rail system has been generally applied as a fuel injection system for a diesel engine for a passenger vehicle, and a piezo injector having improved fuel injection amount and injection timing has been developed and mass produced.

The common rail system to which the piezo injector 30 as shown in FIG. 4 is applied has emerged as a next generation fuel injection system in the future for enhanced emission control and improved engine output performance.

The piezo injector 30 is a method of controlling the movement of the nozzle unit 32 by using the characteristic that the displacement occurs by the high voltage in the device.

Therefore, the control method according to the present invention, as shown in Figure 3, using the bi-directional characteristics of the voltage-displacement of the piezo actuator 31, after the fuel injection of the piezo injector 30 according to the pressure of the combustion chamber 52 The potential difference of the piezoelectric element generated by the force acting on the piezo actuator 31 is sensed to feedback control the fuel injection timing.

After the fuel injection, the signal processing method according to the bidirectional characteristic of the voltage-displacement of the piezoelectric element in the pressure change in the combustion chamber 52 according to the combustion explosion by compression ignition is as follows.

As shown in the graphs of FIGS. 6 and 7 at the time of no fuel injection of the piezo injector 30, the pressure change in the cylinder combustion chamber 52 is shown by the vertical movement of the piston, and as shown in FIGS. 8 and 9. In the same manner, the ignition explosion occurs during atomization and injection of the atomized and injected fuel in the piezo injector 30, thereby causing a rapid pressure increase in the cylinder.

The pressure change in the combustion chamber 52 is transmitted to the needle of the nozzle portion 32 of the piezo injector 30 to act as a force on the piezo actuator 31 inside the piezo injector 30 to generate a potential difference. By detecting the potential difference at 40, feedback control is performed on the fuel injection timing of the piezo injector 30.

When the fuel injection timing is detected by the ECU 40, the ECU 40 detects a threshold value of a constant value of the voltage applied to the piezoelectric element and a slope of the potential change with respect to the pressure change generated by the combustion explosion of the fuel injected into the piezo injector 30. Accurate detection of is possible.

Therefore, accurate feedback control of fuel injection timing is realized in engine combustion mapping.

According to the present invention, in the combustion control of a diesel engine, similarly to a gasoline engine, the combustion feedback control by the piezo actuator 32 makes it possible to reliably control the exhaust gas and to maintain it after durability.

As described above, the feedback combustion control method using the piezo injector according to the present invention has the following effects.

Accurate sensing of fuel injection timing enables accurate feedback control of fuel injection timing in engine combustion mapping. Therefore, the optimum fuel injection timing can be controlled.

In addition, through the combustion feedback control by the piezo actuator, it is possible to significantly reduce the exhaust gas to cope with the exhaust gas regulation.

There is no need to install a sensor such as an acceleration sensor, which does not cause a price increase and enables precise control.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent embodiments are possible. Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

Claims (4)

The pressure change in the combustion chamber of the engine is transmitted to the nozzle portion needle of the piezo injector, Acting on the piezo actuator of the piezo injector to generate a potential difference, The potential difference is detected by the ECU of the engine, Feedback combustion control method using a piezo injector, characterized in that for controlling the fuel injection timing of the piezo injector. The method of claim 1, The fuel injection timing feedback control, After fuel injection, the feedback combustion control method using a piezo injector, characterized in that by detecting the potential difference of the piezoelectric element generated by the force acting on the piezo actuator of the piezo injector according to the pressure of the combustion chamber. The method of claim 1, And the piezo injector controls the movement of the nozzle unit by using a characteristic in which displacement occurs due to a high voltage in the element. The ECU of the engine detects a threshold value of a constant value of a voltage applied to a piezo element of the piezo injector and a slope of a potential change with respect to a pressure change in the combustion chamber of the engine caused by a combustion explosion of fuel injected into the piezo injector. Feedback combustion control method using a piezo injector, characterized in that for detecting the fuel injection timing.

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