KR100573847B1 - Piezo injector driving apparatus in diesel common rail system - Google Patents

Abstract

The present invention relates to a piezo injector driving apparatus of a diesel common rail system in which a piezo stack used as an injector pressure regulating valve is opened and closed to directly inject fuel into a combustion chamber by an injector driving signal of an engine ECU.

According to the present invention, the piezo stack used as the injector pressure control valve according to the present invention uses only a small amount of charging current. The fast response makes it possible to reduce current and power consumption, eliminate multiple injections, and provide precise and fast control of fuel injection volume and timing, which increases fuel consumption in the combustion chamber. There is an effect that the amount of exhaust gas is reduced.

Diesel, Common Rail, Piezo Injector, Engine Electronic Control Unit, EMS ECU

Description

Piezo Injector Drive of Diesel Common Rail System {PIEZO INJECTOR DRIVING APPARATUS IN DIESEL COMMON RAIL SYSTEM}             

1 is a circuit diagram showing a piezo injector driving apparatus of a diesel common rail system according to the present invention.

FIG. 2 is a circuit diagram illustrating the high voltage regulator of FIG. 1. FIG.

Figure 3 is an embodiment showing the displacement characteristics of the piezo stack used as the injector pressure control valve in accordance with the present invention.

Figure 4 is a graph showing the current and voltage characteristics of the high voltage regulator.

Fig. 5 is a graph showing the relationship between the duty ratio and the input / output voltage ratio of the high voltage regulator.

Figure 6 is a first embodiment showing a graph of the operating characteristics of the piezo injector driving apparatus of the diesel common rail system according to the present invention.

Figure 7 is a second embodiment showing a graph of the operating characteristics of the piezo injector driving apparatus of the diesel common rail system according to the present invention.

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

10: high voltage regulator 11: PWM controller

20: piezo stack 30: transfer coil

Q1: first transistor Q2: second transistor

Q3: 3rd transistor FET: 4th transistor

L: Inductor D1, D2, D3, D4: Rectifier

C2: high voltage capacitor

The present invention relates to a diesel common rail system, and more particularly to a piezo injector drive device of the diesel common rail system.

As is known, the diesel common rail system is a diesel engine system in which an injector driving device driven by an injector driving signal of an engine electronic control unit (EMS ECU) opens and closes the injector pressure regulating valve to directly inject fuel into the combustion chamber. In particular, a solenoid is used as the injector pressure regulating valve.

However, the injector driving apparatus of the conventional diesel common rail system using the solenoid as the injector pressure regulating valve as described above is expensive, bulky, and noises when boosted due to the large consumption of driving current and power for opening and closing the solenoid. There is a drawback to using a large transformer that occurs a lot.

In particular, since the reaction time of the solenoid itself is slow, it is difficult to control the fuel injection amount and the injection timing in detail during the multi-injection control, and thus, the fuel consumption in the combustion chamber is reduced and the exhaust gas amount is increased. have.

The present invention is to solve the above-mentioned conventional problems, an object of the present invention is to open and close the piezo stack used as the injector pressure control valve by the injector drive signal of the engine electronic control device to direct fuel injection to the combustion chamber The present invention provides a piezo injector driving device for a common rail system.

The piezo injector driving apparatus of the diesel common rail system for achieving the object of the present invention, the high voltage regulator for boosting and outputting the battery power of the vehicle to a specific high pressure by the PWM control method; Injector pressure control that extends its length by acting as a charging capacitor when the driving current of the opposite pole is applied and acts as a charging capacitor, and shrinks its length. Piezo stacks used as valves; A first transistor positioned at a front end of the piezo stack and turned on when an injector open driving signal of an engine electronic control device is input to allow a driving current of a reverse pole to flow into the piezo stack to charge a specific driving voltage to the piezo stack; A second transistor positioned at a rear end of the piezo stack and turned on simultaneously with the first transistor when the injector open driving signal of the engine electronic control device is input to ground the piezo stack; Located between the piezo stack and the first transistor, when the piezo stack acts as a charge and discharge capacitor according to the coil capacity to determine the fuel injection rate by setting the drive current flowing through both ends of the piezo stack and the slope of the drive current. Tailoring transfer coil; And a position between the first transistor and the transfer coil so as to be connected in parallel with the second transistor, and when the injector closing drive signal of the engine electronic control device is input, it is turned on so that the same pole driving current flows to the piezo stack. And a third transistor for discharging a specific driving voltage charged in the stack.

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

Referring to FIG. 1, the high voltage regulator 10 charges or discharges a piezo stack 20 below by using a pulse width modulation (PWM) control method of a vehicle battery power supply (VB). It is a transformer that boosts and outputs a specific high pressure (for example, 80V) for contracting or expanding the length of a.

Referring to FIG. 2, the high voltage capacitor C2 of the high voltage regulator 10 charges and outputs a specific high pressure for contracting or expanding the length of the piezo stack 20.

The PWM controller 11 of the high voltage regulator 10 uses the battery power VB of the vehicle as an old coin source, and output voltage of the high voltage capacitor C2 fed back through the output terminal of the high voltage capacitor C2 is sensed. If it is lower than the set voltage, it is driven to output PWM on / off signal.

The fourth transistor (FET) of the high voltage regulator 10 is a field effect transistor, the drain is connected to the battery side of the vehicle, the source is connected to the ground terminal, the PWM on / off signal of the PWM controller 11 is gated When is input, repeats the on / off operation.

The inductor L of the high voltage regulator 10 is positioned between the battery side of the vehicle and the drain, and generates a reverse voltage to the battery power source VB of the vehicle while the fourth transistor FET is turned off. The high voltage is charged to the high voltage capacitor C2.

The rectifier D4 of the high voltage regulator 10 is positioned between the connection point (see FIG. 2) of the fourth transistor FET and the inductor L and the high voltage capacitor C2, and the fourth transistor FET. Is conducted by the reverse voltage generated in the inductor L during the off operation, causing the reverse voltage of the inductor L to be charged to a specific high voltage in the high voltage capacitor C2.

Referring to FIG. 3, the piezo stack 20 represents an inverse piezoelectric effect in which the length of the stack changes according to its pole and size when a voltage is applied from the outside, and the capacitor having an internal resistance R1 ( It has the property of C1).

When the piezo stack 20 is applied with a driving current of the opposite pole and a specific driving voltage is applied, the piezo stack 20 acts as a charging capacitor C1 and shrinks. When the driving current of the same pole is applied and a specific driving voltage is applied, the discharge capacitor is applied. It acts as a (C1) and is used as an injector pressure regulating valve whose length is expanded.

The piezo stack 20 is made to have a permanent polarity and its driving voltage is proportional to the thickness of each layer, the displacement (Pd) of the stack as shown in Equation 1 below the tensile coefficient (C _s = m / V ), The number of layers (N) of the stack, and the driving voltage (V).

Pd = C _s · N · V

In Fig. 3, (a) shows a piezo stack 20 having a specific polarity, (b) shows a piezo stack 20 in which the current of the same pole flows and (c) shows the opposite pole. The piezo stack 20 which contracted by the electric current is shown.

The first transistor Q1 is positioned at the front end of the piezo stack 20 (see FIG. 1), and is turned on when an injector open driving signal output from an engine ECU (EMS ECU) of a known diesel common lane system is input. Then, the driving current of the opposite pole flows to the piezo stack 20 to charge the piezo stack 20 with a specific driving voltage.

The rectifier D1 connected to the emitter output terminal of the first transistor Q1 is a circuit stabilization diode.

The second transistor Q2 is positioned at the rear end of the piezo stack 20. When the injector open driving signal is input from the engine electronic control device, the second transistor Q2 is turned on at the same time as the first transistor Q1 to open the piezo stack 20. Ground it.

The second transistor Q2 is simultaneously turned on or simultaneously turned off with the first transistor Q1 to ground the piezo stack 20 so that the driving current of the high voltage regulator 10 flows through the piezo stack 20. .

The rectifier D2 connected to the emitter and the collector of the second transistor Q1 is a circuit stabilization diode.

Transfer coil 30 is located between the piezo stack 20 and the first transistor (Q1), the piezo stack 20 when the piezo stack 20 acts as a charge and discharge capacitor (C1) according to the coil capacity The fuel injection rate is determined by setting the drive current flowing through both ends and the slope of this drive current.

The third transistor Q3 is positioned between the first transistor Q1 and the transfer coil 30 so as to be connected in parallel with the second transistor Q2, and is turned on when an injector closing driving signal is input from the engine electronic controller. As a result, a driving current of the same pole flows to the piezo stack 20 to discharge a specific driving voltage charged in the piezo stack 20.

When the second transistor Q2 and the first transistor Q1 are turned on or turned off, the third transistor Q3 is turned off or turned on to serve as a charging capacitor C1 by grounding the piezo stack 20. The discharge current flows through the piezo stack 20 which is charging a specific driving voltage.

The rectifier D3 connected to the collector of the third transistor Q3 is a circuit stabilization diode.

The piezo injector driving device of the diesel common rail system according to the present invention configured as described above operates as follows.

The piezo injector driving apparatus of the diesel common lane system according to the present invention includes the step of boosting the vehicle battery power (VB) to a specific high pressure (for example, 80 V) for charging or discharging the piezo stack 20, and the specific high pressure. The piezo stack 20 is divided into a process of opening and closing the piezo stack 20 which operates as an injector pressure regulating valve by charging or discharging the piezo stack 20 to contract or expand the length thereof.

1. Piezo stack 20 driving voltage step-up process

Referring to FIG. 2, the PWM controller 11 of the high voltage regulator 10 may change the boosting frequency, the PWM duty ratio, etc. using a peripheral resistance, and thus, select the appropriate resistor to drive the voltage of the piezo stack 20. We can get the frequency and duty ratio to optimize the

In practice, the PWM controller 11 drives when the output voltage of the fed-back high voltage capacitor C2 is lower than the set voltage, and outputs a PWM on / off signal at a constant duty ratio, so that current flows in the inductor L. The start up cycle begins.

If the fourth transistor FET is turned off, a reverse voltage is generated across the inductor L so that the rectifier D4 conducts, so that the magnetic energy of the inductor L is a high-capacity high voltage capacitor C2. Accumulate in all.

As such, when the energy of the inductor L is accumulated in the high voltage capacitor C2, the rectifier D4 stops the flow of electricity, and the voltage of the inductor L becomes 0 and is ready for the next boost cycle. At this time, the output of the high voltage capacitor (C2) is multiplied by the frequency per second multiplied by the amount of energy transferred every boost cycle.

Meanwhile, referring to FIG. 4, which is a graph illustrating current and voltage characteristics of the high voltage regulator 10, current is generated in the inductor L while the fourth transistor FET is turned on (t _on ). And the inductor voltage V _L = V _i .

In addition, while the fourth transistor FET is turned off (t _off ), a reverse voltage (V _L = V _i -V _o ) is generated in the inductor L, and the reverse voltage is further added to the input voltage. An output voltage larger than the input voltage is generated and charged in the high voltage capacitor C2.

According to the graph of FIG. 4, since the voltage across the inductor L is 0 during one period T, the voltage drop, the switching, and the rectifier diode of the inductor L and the fourth transistor FET are zero. By ignoring the loss due to the voltage drop, the relationship between the frequency and the duty ratio (D) can be obtained from the following equations (2) and (3).

_{V i · t on - (V} o -V i) · t off = 0

V-D-T-(V _o -V _i ) · (1-D) T = 0

V _o / V _i = 1 / (1-D)

Therefore, based on Equation 4, the relationship between the duty ratio (D) and the input-output voltage ratio (V _o / V _i ) of the high voltage regulator 10 is shown in Figure 5, from which the high voltage regulator 10 of When the frequency and duty ratio are properly selected, it can be seen that the battery power source VB of the vehicle can be easily boosted to a specific high voltage (eg, 80V) for charging or discharging the piezo stack 20.

2. Piezo stack 20 charging and discharging process

Referring to FIG. 3, the piezo stack 20 used as the injector pressure regulating valve basically has the property of a capacitor C1, thereby repeating charging and discharging. Inflate and close Therefore, the fuel injection amount can be adjusted by controlling the closing time of the piezo stack 20.

First, when the first transistor Q1 and the second transistor Q2 are turned on at the same time, a driving current output from the high voltage regulator 10 flows to the piezo stack 20 via the transfer coil 30. Accordingly, the piezo stack 20 is filled.

In this case, the piezo stack 20 is contracted in length by the above-described reverse piezoelectric effect, and in fact, when the piezo stack 20 is used as an injector compression control valve, the piezo stack 20 maintains an open state.

On the other hand, when the first transistor Q1 and the second transistor Q2 are turned off at the same time and the third transistor Q3 is turned on, the driving current output from the high voltage regulator 10 is interrupted and at the same time, the transfer Since the discharge current flows through the third transistor Q3 by the charging voltage of the piezo stack 20 via the coil 30, the piezo stack 20 is discharged.

At this time, the piezo stack 20 is expanded by the above-mentioned reverse piezoelectric effect, and when used as an injector compression control valve, it maintains the valve closed state.

In the charge / discharge process of the piezo stack 20 as described above, the coil capacity of the transfer coil 30 is set to the driving current flowing through both ends of the piezo stack 20 and the slope of the driving current to set the fuel injection rate Decisions are an important factor.

For example, as illustrated in FIGS. 6 and 7, when the capacitance of the transfer coil 30 is set differently to 100 uH and 200 uH, the driving current and the driving voltage and the slope of the driving current of both ends of the piezo stack 20 are different. It can be seen that.

Referring to FIG. 6, when the capacity of the transfer coil 30 is set to 100 uH, it can be seen that the driving current and the driving voltage of both ends of the piezo stack 20 change while showing a sharp slope and the maximum current value is also high. In particular, when the maximum current value of the driving current is high and shows an inclined slope, the piezo stack 20 may be impacted to destroy the piezo stack 20 itself due to a fatal effect on durability.

Referring to FIG. 7, when the capacity of the transfer coil 30 is set to 200 uH, which is greater than 100 uH, the slopes of the driving current and the driving voltage at both ends of the piezo stack 20 are relatively gentle and the maximum current value is not only lowered. It can be seen that the shaking of the voltage is also reduced.

As described above, the piezo injector driving device of the diesel common rail system according to the present invention opens and closes the piezo stack used as the injector pressure regulating valve by injector driving signal of the engine electronic control device to directly inject fuel into the combustion chamber. In addition, a low-cost, compact, high-pressure regulator can be used to provide the drive current and power to open and close the piezo stack.

In addition, the piezo stack used as the injector pressure regulating valve according to the present invention uses only a small amount of charging current and is fast in response, thus reducing current and power consumption and easily eliminating multiple injections without time constraints. It is possible to control the fuel injection amount and the injection timing finely and quickly, thereby increasing the fuel consumption in the combustion chamber, thereby reducing the amount of exhaust gas.

What has been described above is just one embodiment for implementing the piezo injector driving apparatus of the diesel common rail system according to the present invention, the present invention is not limited to the above embodiment, the present invention as claimed in the following claims Without departing from the gist of the invention, those skilled in the art to which the present invention pertains to the technical spirit of the present invention to the extent that various modifications can be made.

Claims (2)

delete A high voltage capacitor C2 for outputting a specific high voltage; PWM that uses the battery power (VB) of the vehicle as a driving power and outputs a PWM on / off signal by driving when the output voltage of the high voltage capacitor (C2) sensed through the output terminal of the high voltage capacitor (C2) is lower than a set voltage. A controller 11; A fourth transistor (FET) having a drain connected to a battery side of the vehicle and a source connected to a ground terminal, and repeating on / off operation when a PWM on / off signal of the PWM controller 11 is input to the gate; Located between the battery side of the vehicle and the drain, while generating the reverse voltage for the battery power supply (VB) of the vehicle while the fourth transistor (FET) is off operation to charge a specific high voltage to the high voltage capacitor (C2) Inductor L; And between a connection point of the fourth transistor FET and the inductor L and the high voltage capacitor C2, and by a reverse voltage generated in the inductor L while the fourth transistor FET is turned off. It consists of a rectifier (D4) is conducted so that the reverse voltage of the inductor (L) is charged to a specific high voltage in the high voltage capacitor (C2), by boosting the battery power supply (VB) of the vehicle to a specific high voltage by the PWM control method A high pressure regulator 10 for outputting; When the driving current of the opposite pole is applied and a specific driving voltage is applied, it acts as a charging capacitor C1 and the length is contracted. When the driving current of the same pole is applied and a specific driving voltage is applied, it acts as a discharge capacitor C1. Piezo stack 20 is used as the injector pressure control valve is expanded; Located at the front end of the piezo stack 20, when the injector open drive signal of the engine electronic control device (EMS ECU) is input, it is turned on so that the driving current of the opposite pole flows to the piezo stack 20, the piezo stack 20 A first transistor Q1 which charges a specific driving voltage); A second transistor Q2 positioned at a rear end of the piezo stack 20 and turned on at the same time as the first transistor Q1 when the injector open driving signal of the engine electronic control device is input to ground the piezo stack 20; ); Located between the piezo stack 20 and the first transistor (Q1), the driving flows across both ends of the piezo stack 20 when the piezo stack 20 acts as a charge and discharge capacitor (C1) according to the coil capacity A transfer coil 30 that determines a fuel injection rate by setting a current and a slope of the drive current; And Located between the first transistor Q1 and the transfer coil 30 so as to be connected in parallel with the second transistor Q2, and is turned on when the injector closing driving signal of the engine electronic control device is input, to the piezo stack 20. A third transistor Q3 for discharging a specific driving voltage charged in the piezo stack 20 by allowing a driving current of the same pole to flow; Piezo injector driving device of the diesel common rail system, characterized in that consisting of.

Images