EP1460255A2 - Control apparatus and computer program for driving a fuel valve in an internal combustion engine - Google Patents

Abstract

The computer (50) contains a memory (52) which may be a diskette, a CD or a flash memory. The computer sends control signals to a piezoelectric valve actuator (100) and to a direct fuel injection system. The piezoelectric actuator drives the valve (300) via a hydraulic adjuster (200) which consists of a piston and cylinder unit.

Description

The invention relates to a control device and a computer program for controlling at least one fuel valve with a piezo drive of an internal combustion engine with gasoline direct injection via a coupling element.

State of the art

It is known from the prior art that, in the case of fuel valves with a piezo drive, the needle stroke on the valve seat can be adjusted by means of charge or voltage applied to the piezo element as an actuator. In the prior art, the fuel valve is usually not controlled by a direct connection to the actuator, but by a hydraulic coupling element connected between the actuator and the fuel valve. This serves to compensate for temperature expansions and strains due to pressure forces and wear.

However, the behavior of this hydraulic coupling element is disadvantageously dependent on the period of the activation, that is to say in particular on the speed of the internal combustion engine, on the activation duration of the Fuel valve (injection duration), the load force of the fuel valve, which depends on the pressure in a fuel accumulator, and the damping constant of the hydraulic coupling element, which not least depends on the temperature of the hydraulic medium used.

Depending on the above-mentioned negative influences, a so-called "steady stroke loss" occurs during the operation of the hydraulic coupling element, which, if not taken into account, leads to incorrect control of the fuel valve. More specifically, it can lead to an incorrect setting of the needle lift of the fuel valve and thus to an incorrect setting of the injection quantity of the fuel valve.

Based on this prior art, it is the object of the invention to develop a known control device for controlling a fuel valve via a coupling element and a computer program for such a control device so that they enable more precise control of the fuel valve.

This object is achieved by the subject matter of patent claim 1. Accordingly, the problem for the known control device is achieved in particular in that it is designed to compensate for a steady stroke loss as a fault variable characteristic of the coupling element when the fuel valve is actuated.

Advantages of the invention

Advantageously, this compensation ensures according to the invention that the stationary Stroke loss has no negative effects on the accuracy of the control of the fuel valve. Any errors or inaccuracies resulting from the stationary stroke loss are compensated according to the invention by the control device prior to activation.

According to one exemplary embodiment of the invention, it is advantageous to include the effects of the stationary stroke loss as an error variable on the stroke of the fuel valve and / or on the injection quantity in the formulas, characteristic curves or characteristic diagrams stored in the control unit for controlling the fuel valve. By calculating the coupling behavior in the control parameters of the fuel valve, the effects of the stationary error due to speed, injection time, system pressure or valve temperature on the needle stroke and / or the injection quantity are minimized. The valve lift and the injection quantity can therefore be set more precisely.

Further advantageous refinements of the control device are the subject of the dependent claims.

The above-mentioned object is further achieved by a computer program for a control device. The advantages of this computer program correspond to the advantages mentioned above with reference to the control device.

drawings

Figur 1

ein hydraulisches Kopplungselement;

Figur 2

den zeitlichen Zusammenhang zwischen vorgenannten Einspritzungen und der Größe des Spaltes des Kopplungselementes; und

Figur 3

ein Steuergerät gemäß der Erfindung

zeigt.A total of three drawings are attached to the invention, wherein

Figure 1

a hydraulic coupling element;

Figure 2

the temporal relationship between the aforementioned injections and the size of the gap of the coupling element; and

Figure 3

a control device according to the invention

shows.

Description of the embodiments

FIG. 1 shows the arrangement on which the invention is based, of a control device 50, a piezo drive 100 for controlling a fuel valve 300 in accordance with injection commands issued by the control device 50. It can be seen in FIG. 1 that the piezo drive 100 is not directly on the fuel valve 300 acts, but that a hydraulic coupling element 200 is connected between these two components. This hydraulic coupling element is used to compensate for temperature expansions and expansions as a result of compressive forces and to compensate for wear.

FIG. 2 shows a detailed view of such a coupling element 200. It can be seen that the coupling element is essentially formed by a piston-cylinder arrangement, the piston having the reference symbol 220 and a cylinder for guiding the piston having the reference symbol 210. The piston 220 is guided in the cylinder 210 filled with a hydraulic fluid 220. Forces set by the piezo drive 100 for setting the fuel valve 300 are first transmitted to the piston 220 and from there via the hydraulic fluid 230 to the guide cylinder 210 before they are forwarded from there to the fuel valve 300. To realize a bidirectional power transmission between piezo drive 100 and fuel valve 300, the coupling element 200 is preferably evacuated in its interior.

As already mentioned in the introduction, the behavior of the hydraulic coupling element 200 is dependent on numerous influencing factors mentioned above, which lead to a so-called stationary stroke loss occurring during the operation of the coupling element 200. This stationary stroke loss is designated in FIG. 2 by the reference _symbol h _v.stat . It represents the path error which can occur due to the interposition of the coupling element when the fuel valve 300 is actuated by the piezo drive 100 due to the influences mentioned.

In Figure 3, the behavior of the coupling element 200 during its operation and the steady stroke loss are generally graphically represented as an error. In FIG. 3, the black rectangles represented on the lower timeline represent the actuations of the piezo drive 100 by the control device 50 and consequently also the injections E. The spaces between the injections represent the respective actuation pauses or the fillings B. The graphic in FIG. 3 shows that the coupling gap KS, plotted on the ordinate, drops significantly during the control times due to the pressure exerted on the piston 220 by the piezo drive 100, in order then to rise again with an e-function in the subsequent control pauses. These respective increases therefore result in no pressure being exerted by the piezo drive on the piston 220 and thus on the hydraulic fluid 230 during the control pauses. In Figure 3 it can also be seen that after a certain Operating time sets the already mentioned stationary stroke loss h _V.stat .

wobei

r_k

die Dämpfungskonstante des Kopplungselementes [N/(m/s)];

t_i

die Ansteuerzeit;

F_S

die Schaltkraft;

c_v

die Steifigkeit des Ventils;

t_B

die Dauer der Ansteuerpause (Befüllphase); und

h_v._stat

den stationären Hubverlust

repräsentiert.The stationary stroke loss h _V.stat can be calculated mathematically as follows: $${\text{H}}_{\text{v · stat}}\text{=}\frac{{\text{t}}_{\text{i}}{\text{· F}}_{\text{S}}}{{\text{r}}_{\text{k}}}\text{·}\frac{\text{e}{}^{\text{-}\frac{{\text{c}}_{\text{v}}}{{\text{r}}_{\text{k}}}{\text{· T}}_{\text{B}}}}{\text{1 - e}{}^{\text{-}\frac{{\text{c}}_{\text{v}}}{{\text{r}}_{\text{k}}}{\text{· T}}_{\text{B}}}}$$

in which

r _k

the damping constant of the coupling element [N / (m / s)];

t _i

the control time;

F _S

the switching force;

c _v

the rigidity of the valve;

t _B

the duration of the control pause (filling phase); and

h _v . _stat

the stationary stroke loss

represents.

This steady stroke loss is shown by the fact that with continued operation of the coupling element, the coupling gap KS is no longer able to fully close itself during the control pauses B of the internal combustion engine regenerate, that is, to grow back to its original value h ₀ . This original position h ₀ represents a distance of the piston 220 from the bottom surface of the cylinder 210, see FIG. 2. Because of the steady stroke loss, the piston 220 no longer returns to its original distance h ₀ from the bottom of the cylinder 210, but instead rather, it only manages to _{move away} from the bottom of the cylinder 210 by a distance of h ₀ -h _V.stat during the control _pause B; when he has reached this position, the drive pause for the internal combustion engine has already ended. The piston 220 is then actuated again by the piezo element 100 to reverse its direction of movement and to approach the bottom of the cylinder 210 again, which results in a rapid shortening of the coupling gap KS.

If this stationary stroke loss of the coupling element 200 is not taken into account when activating the fuel valve 300, this leads to errors in the actuation; more precisely to an imprecise control.

In order to avoid such errors in the actuation of the fuel valve 300 resulting from the stationary stroke loss of the coupling element 200, it is proposed according to the invention to compensate for this stationary stroke loss in the actuation. More specifically, this stationary stroke loss can be taken into account when adjusting the stroke of the fuel valve and / or when adjusting its injection time. Advantageously, the known stationary stroke loss h _{V.stat of} the coupling element 200 used is already stored in the memory _element 52 of the control unit Formulas, characteristic curves or characteristic fields for controlling the fuel valve 300 are taken into account.

The control of the piezo drive 100 and the fuel valve 300 is preferably carried out in accordance with a computer program stored in the control unit 50. This computer program regularly evaluates the formulas and characteristic curves stored in the storage element 52 for controlling the fuel valve. According to the invention, the computer program is designed such that it takes into account the steady stroke loss when the fuel valve is actuated.

The computer program can optionally be stored together with other computer programs for controlling and / or regulating the internal combustion engine 50 on a computer-readable data carrier. The data carrier can be a floppy disk, a compact disc, a flash memory or the like. The program code stored on the data carrier can then be sold to a customer as a product.

In addition, it is possible that the computer program, possibly together with other computer programs, without the aid of an electronic storage medium, is transmitted and sold as a product to a customer via an electronic communication network, in particular the Internet.

Claims (6)

Control device for controlling at least one fuel valve (300) with a piezo drive (100) of an internal combustion engine (50) with gasoline direct injection via a coupling element (200), characterized in that
the control unit (50) is designed to compensate for a steady stroke loss as an error variable characteristic of the coupling element (200) when the fuel valve (300) is activated. Control device according to claim 1, characterized in that the control device is designed to include the stationary stroke loss when controlling the stroke of the fuel valve and / or during the injection time for the fuel valve (300). Control unit according to Claim 1 or 2, characterized in that the effects of the stationary stroke loss on the stroke of the fuel valve and / or on the quantity of fuel to be injected into the internal combustion engine are taken into account in formulas, characteristic curves or characteristic curve fields, such as those for the purpose of controlling the fuel valve (300 ) are stored in a memory element (52) of the control device (50). Control device according to one of the preceding claims, characterized in that the control device (50) is designed to calculate the stationary stroke loss H _{Vstat of} the coupling _element (300) as follows: $${\text{H}}_{\text{v · stat}}\text{=}\frac{{\text{t}}_{\text{i}}{\text{· F}}_{\text{S}}}{{\text{r}}_{\text{k}}}\text{·}\frac{\text{e}{}^{\text{-}\frac{{\text{c}}_{\text{v}}}{{\text{r}}_{\text{k}}}{\text{· T}}_{\text{B}}}}{\text{1 - e}{}^{\text{-}\frac{{\text{c}}_{\text{v}}}{{\text{r}}_{\text{k}}}{\text{· T}}_{\text{B}}}}$$

in which r _k the damping constant of the coupling element [N / (m / s)]; t _i the activation time; F _S the switching force; c _v the rigidity of the overall valve; t _B the duration of the control pause (filling phase); and h _v.stat the stationary stroke loss represents. Computer program for a control device (50) for controlling at least one fuel valve (300) of an internal combustion engine via a coupling element (200), characterized by program code, which is designed to detect a steady stroke loss of the coupling element (200) when the fuel valve (300) is activated compensate. Computer program according to claim 5, characterized in that its program code is stored on a mobile data carrier.

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