JP2002089328A - Method for controlling piezoelectric actuator of injection valve for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resolve difficulty of starting of an engine, in particular in a starting stage, by more rapidly performing pressure forming in a fuel pipe system. SOLUTION: A control unit 21 detects a system pressure PR and/or different parameters of an internal combustion engine, and when the system pressure PR is not enough, control of a piezoelectric actuator 2 is performed with a given algorithm in association of the current system pressure PR, or stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for controlling a piezo actuator of an injector of an injection system for controlling a nozzle needle via a switching valve having a closing member, that is, a piezoelectric actuator.
The invention relates to a method of determining the minimum control time or the minimum holding time for the closing element by the control unit when a minimum fuel quantity is required.

[0002]

2. Description of the Related Art In known injection valves (injectors), for example in a common-rail system, a defined pressure is created in a pipeline system by a fuel pump. The electronic control operates the switching valve by means of a voltage pulse applied to a piezo-actuator, ie a piezoelectric actuator, which determines a defined fuel quantity to be injected. In particular, when the internal pressure of the internal combustion engine is low, the system pressure may be reduced to such a degree that opening of the valve needle is not always guaranteed. In addition, a defined minimum control or holding time causes the switching valve to be moved in the direction of its second valve seat, which inevitably leads to a return line for the fuel present in the high-pressure system. Some runoff occurs through the road. As a result, rapid pressure build-up or pressure build-up is further delayed, which may cause difficulty in starting the engine. Particularly in cold climates, for example, where diesel engines originally have relatively high starting difficulties, starting can be made more difficult.

[0003]

SUMMARY OF THE INVENTION The object of the invention is to improve a method of the type mentioned at the outset so that the pressure build-up or pressure build-up in the fuel line system takes place more rapidly and thus in particular The aim is to provide a method in which the engine receives a defined amount of fuel during the start-up phase, thereby eliminating the starting difficulties.

[0004]

SUMMARY OF THE INVENTION In order to solve this problem, the method according to the invention provides for the control unit to detect system pressure and / or other operating parameters of the internal combustion engine and to determine if the system pressure is not sufficient. Using a predetermined algorithm, the control of the piezoelectric actuator is performed (freigeben) or interrupted (sperren) in relation to the current system pressure.

[0005]

The method according to the invention for controlling a piezoelectric actuator of an injector has the following advantages over the prior art. This means that the pressure build-up or pressure build-up in the fuel line system takes place more quickly, so that the engine receives a defined fuel quantity, especially during the start-up phase. It is further advantageous that an algorithm can be used to achieve that the execution or continuation (Freigabe) of the control of the piezoelectric actuator can be controlled in relation to the system pressure currently being established.

[0006] Advantageous refinements and improvements of the method according to claim 1 are made possible by the measures described below.
In this case, it is considered particularly advantageous that the measurement and evaluation of the system pressure can suppress the control for the piezoelectric actuator or the associated movement of the switching valve.

It is also advantageous to control the execution or continuation of the control in relation to another parameter, for example the water temperature. Since the water temperature is one of the important parameters for the operating state of the engine, this parameter can be taken into account, for example, to determine an optimal fuel quantity in terms of exhaust gas requirements. The corresponding value can be specified in the form of a characteristic line or a table, so that the application can be easily implemented.

In particular, if the control conditions are embodied in the form of software programs, an advantageous adaptation to the respective engine type is obtained. In this case, an existing software program that already exists can be advantageously used. In that case, it is only necessary to extend the existing software program by the control method according to the invention. This has the advantage that additional effort is minimized.

[0009] During engine operation, the pressure in the fuel system is generally sufficient. This is because at relatively high rotational speeds, sufficient fuel is pumped. Critical cases resulting in low system pressure generally occur during the start-up phase, so that such disadvantages can be advantageously avoided.

[0010] Still another advantage of the present invention is described in the embodiment of the invention.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

The injection valve 1 shown in cross section in FIG. 1 can be regarded as known in terms of its basic structure. First,
In order to facilitate understanding of the present invention, a basic structure of the injector 1 will be briefly described. The injection valve 1 has a central bore, which has different cross sections in different areas. A piezo actuator, ie, a working piston 3 with a piezoelectric actuator 2, is introduced into the upper part of the hole. In this case, the working piston 3 is rigidly connected to the piezoelectric actuator 2.
The working piston 3 is a hydraulic coupler (hydra).
ulisch. The Koppler 4 is closed at the top and an opening at the bottom is provided for the connection passage with the first valve seat 6. The piston 5 with the closing member 12 is arranged in this connection passage. The closing member 12 is formed as a double-switching, ie, double-seat, control valve. Piezoelectric actuator 2
Is in the rest phase, the closing member 12 is closing the first valve seat 6. The piezoelectric actuator 2 has terminals + and-
When electrically controlled by the control voltage applied U _A, the actuator 2 of the piezoelectric operates the working piston 3, hydraulic coupler 4 the second valve seat 7 of the piston 5 with the closure member 12 through Press in the direction of. Second
Below the valve seat 7, a nozzle needle 11 is movably disposed in a corresponding passage. This nozzle needle 11
Is what kind of control voltage U is applied to the piezoelectric actuator 2.
_The outlet provided in the high-pressure passage (common rail pressure) 13 is closed or opened depending on whether _A is applied. In the high-pressure range, the medium to be injected, for example gasoline or diesel fuel for an internal combustion engine, is supplied via the inlet channel 9. Via the inflow restriction 8 and the outflow restriction 10, the supply amount of the medium in the direction toward the nozzle needle 11 and the hydraulic coupler 4 is controlled.
The hydraulic coupler 4 in this case has the task of increasing the stroke of the piston 5 on the one hand and separating the control valve from the static thermal expansion of the piezoelectric actuator 2 on the other hand. The refilling mechanism for the hydraulic coupler 4 is not shown for reasons of clarity of the drawing.

Hereinafter, the functional form of the injection valve will be described in detail. During each control of the piezoelectric actuator 2, the working piston 3 is moved in the direction of the hydraulic coupler 4. At this time, the piston 5 also moves together with the closing member 12 in the direction of the second valve seat 7. At this time, a part of the fuel existing in the hydraulic coupler 4 is pushed out through the leak gap. Therefore, in order to obtain the functional reliability of the hydraulic coupler 4, each of
Between each injection, the hydraulic coupler 4 must be refilled.

A high pressure is generated in the inflow passage 9. This pressure may be for example 200 to 1600 bar in the case of a common rail system. This pressure acts against the nozzle needle 11 and keeps the nozzle needle 11 closed, so that no fuel flows out. Then, controlled by the voltage U _A is applied, it is controlled actuator 2 of the piezoelectric type is, when thus the closure member 12 is brought into motion in the direction of the second valve seat 7,
The pressure P _R in the high pressure range is reduced, the nozzle needle 11 opens the injection passage or the high-pressure passage 13. When the voltage application to the piezoelectric actuator 2 is released, the closing member 1
2 again moves in the direction of the first valve seat 6.

FIG. 2 shows an injection valve or an injector 1.
Control unit 2 that generates a voltage necessary to control the
1 is a block circuit diagram. The control unit 21 has a voltage generator with a corresponding current source. The current source is a piezoelectric actuator 2 of the injector 1.
This is suitable for applying a voltage to the actuator or canceling the voltage application to the piezoelectric actuator 2. The control unit 21 further has a computer that is program-controlled, and the program of this computer
5 files. In addition, the memory 25 contains characteristic lines or tables for operating parameters of the engine and an algorithm with a defined hysteresis. The control unit 21 is further connected to an input unit 24 for inputting an offset value. Another connection portion is provided, for example for connection with a pressure sensor 22 for detecting the rail pressure P _R in the case of the common rail system. Furthermore, a temperature sensor 23 is provided, the temperature sensor 23 measures the temperature T _W of the internal combustion engine, to notify the information to continuously control unit 21. A further sensor for the speed, for example, can likewise be connected. On the output side, a plurality of injection valves 1 can be connected to the control unit 21 in the form of a group and can be controlled by a corresponding electronic switch. Therefore,
These injection valves 1 can correspond to the respective cylinders of the internal combustion engine, whereby the injection valves 1
1 enables accurate control.

[0016] FIG. 3 is a control diagram is shown having a voltage pulse U _A for controlling the injection valve 1. For example, at time t ₀ , a voltage U ₁ is applied to the piezoelectric actuator 2, which causes the closing member 12 to move from the first valve seat 6 to the second valve seat 7. Next, while the engine is running, the piezoelectric actuator 2
Voltage U ₁ it will remain applied to between the time t ₁ is the t ₂ in. The application time is related to the operating state of the internal combustion engine. To achieve the desired pressure increase pressure for the rail pressure P _R during the minimum control time voltage U ₁ in accordance with the operation state of the internal combustion engine must be maintained. After a time t _2, the nozzle needle 11 opens the injection passage or the high-pressure passage 13, which fuel is injected by. In order to be able to inject the minimum amount of fuel,
Closure member 12 constituting the control valve must be held at a voltage U ₂ during at least a minimum retention time t ₃ ~t _4. During this time, a return passage (not shown) (FIG. 1)
And a portion of the fuel flows out through the, thus the rail pressure P _R
Decrease. After a time t _4, the voltage applied to the actuator 2 of the piezoelectric type is released, the closure member 12 is positioned in the first valve seat 6 again at time point t _5.

According to the invention, especially in the starting phase,
Rail pressure P_ROr another operating parameter, for example
Water temperature T_WIs not enough, the control voltage U_ASuppress
The pressure increase P_RIt is suggested to promote
It is. For this purpose, the existing software of the control unit 21 is advantageously used.
Incorporating hysteresis into software programs
Is proposed. As can be seen further from FIG.
Knit 43 has rail pressure P _RAnd water temperature T_WInput for
Side. For water temperature, characteristic line 41 is preferably used.
Is stored. For this characteristic line 41, for example,
Control voltage U associated with other operating parameters such as number, load, etc.
_AThe corresponding voltage values for are stored. This characteristic
From line 41, the upper hysteresis threshold for pressure and
A lower hysteresis threshold is formed. Furthermore, hiss
The teresis unit 43 has a rail pressure P_RIs supplied
You. Offset to allow alignment to take place
Unit O_SIs provided. This offset unit
Knit O_S, The offset value is supplied to the subtractor 42
It is possible. Therefore, the offset unit O_SThrough
And implement simple adaptations to different engine types
be able to. Therefore, the hysteresis unit 43
Is a signal for operating the switch 44 at the output side, particularly at the time of starting.
To form This switch 44 is, for example, a rail pressure P
_RControl unit 21 is in an inoperable state when
(Inaktiv)
I have. In an alternative configuration of the present invention, the injection valve 1
Supply line is interrupted. this thing
Is the rail pressure P_RIs below the lower threshold of hysteresis
Is always done if On the other hand, rail pressure
P_RIs higher than the upper threshold, the control unit 21
Is switched to an operable state (aktiv), and a normal
An injection operation is performed. Using the offset value,
Adjust hysteresis threshold and lower hysteresis threshold
can do. This is a common rail system
Pressure fluctuations that occur constantly in the
To prevent "Flattern"
Needed to control. Fluttering occurs
Undesired injection is performed, and eventually the internal combustion engine
May interfere with the desired combustion process.

In still another configuration of the present invention, switch 44 is coupled to the ignition lock. Thus, the switch 44 is activated at the time of starting.

[Brief description of the drawings]

FIG. 1 is a sectional view of an injection valve.

FIG. 2 is a block circuit diagram of a control unit.

FIG. 3 is a control diagram showing a relationship between a voltage pulse for controlling an injection valve and time.

FIG. 4 is a circuit diagram of a control unit including a hysteresis unit.

[Explanation of symbols]

Reference Signs List 1 injection valve, 2 piezoelectric actuator, 3 working piston, 4 hydraulic coupler, 5 piston, 6 first valve seat, 7 second valve seat, 8
Inflow restriction, 9 Inflow passage, 10 Outflow restriction, 11
Nozzle needle, 12 closing member, 13 high pressure passage, 21 control unit, 22 pressure sensor, 23 temperature sensor, 24 input unit, 25 memory,
41 characteristic line, 42 subtractor, 43 hysteresis unit, 44 switch

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 45/00 370 F02D 45/00 370B 376 376B F02M 47/00 F02M 47/00 CE EF 47/02 47 / 02 51/06 51/06 N (72) Inventor Michael Schuler Friolzheim Brühlstrasse 24 F-term (reference) 3G066 AA07 AB02 AC09 BA14 BA19 BA23 CC06T CC08T CC08U CC14 CC64T CC64U CC66 CC68T CC68U CC69 CC70 CD25 CD26 CD29 CE13 CE27 DB01 DC14 DC18 3G084 AA01 AA03 BA13 CA01 DA05 DA09 EA11 EA13 EB02 EB08 EB12 EC04 FA00 FA20 3G301 HA02 HA04 HA06 JA03 JA21 JA23 KA01 LB11 LC05 MA11 NA08 NA09 NC02 ND02 ND04 P03N03 NE03 NE03 NE03 P26

Claims (9)

[Claims] 1. Via a switching valve with a closing member (12)
Of the injection system that controls the nozzle needle (11)
Control the piezoelectric actuator (2) of the injector (1)
Control, in which case a minimum amount of fuel is required.
The control unit (21) controls the closing member (12)
Determine minimum control time or minimum hold time for
In a method of the form, the control unit (21)
Pressure (P _RAnd / or other operating parameters of the internal combustion engine
The system pressure (P_R) Is not enough
In addition, using a predetermined algorithm, the piezoelectric actuator
Data (2) is controlled by the current system pressure (P_RRelated to)
Injection, characterized by performing or interrupting
Controls the piezoelectric actuator of the injector in the system
How to control. 2. An algorithm using pressure-related hysteresis so that control of the piezoelectric actuator (2) is suppressed when the rail pressure (P _R ) is below a lower hysteresis threshold. 2. The method of claim 1, wherein forming. 3. The method according to claim 1, wherein an algorithm controls the execution of the control for the piezoelectric actuator in relation to at least one further parameter, preferably the water temperature (T _W ). the method of. 4. The method according to claim 3, wherein the relationship between the system pressure (P _R ) and the water temperature (T _W ) is stored in the form of a characteristic line or a table. 5. The method according to claim 1, wherein the control for the piezoelectric actuator is formed as a software program. 6. The method of claim 5, wherein the software program is an element of an existing control program. 7. The method as claimed in claim 1, wherein the control for the piezoelectric actuator (2) is suppressed during the starting phase of the engine. 8. The method as claimed in claim 1, wherein the piezoelectric injector has a double-seat switching valve. 9. The method as claimed in claim 1, wherein the injector is used in a common rail system.