EP1745203B1 - Method of diagnosis for control circuits - Google Patents

Abstract

The invention relates to a method of diagnosis for control circuits comprising at least one actuator, especially a fuel injection device. According to the invention, the control circuit, before it is used, and the at least one actuator are examined for short circuits. If such a short circuit is detected, an error response is carried out.

Description

State of the art

The invention is based on a method for the diagnosis of drive circuits with at least one actuator, in particular a capacitive actuator of a fuel injection device, according to the preamble of the independent claim.

The present invention also relates to a device for driving drive circuits, in particular a control device of an internal combustion engine, and a computer program product for carrying out the method according to the invention on a computer or control device.

Such actuators, operated capacitively or inductively, are used in fuel injection devices of internal combustion engines, in particular in those with direct fuel injection. When using piezo actuators as capacitive actuators a valve element of the fuel injection device is moved from an open to a closed position and vice versa by a change in length of the piezoelectric actuator. However, if it comes to a short circuit in a supply line to a piezoelectric actuator or in the piezoelectric actuator itself, in a drive circuit or in a control unit which controls the piezoelectric actuator, a proper control of the piezoelectric actuator is no longer possible. In addition, it is also possible that in this way a plurality of piezoelectric actuators is impaired in their function. In the best case this can lead to a loss of comfort, in an unfavorable case to a deterioration of the fuel consumption and the emission behavior of the engine Internal combustion engine, and in extreme cases lead to a risk to the user of the internal combustion engine.

From the EP 1138 907 A1 List already known a method in which the voltage with which a capacitive element of a piezoelectric actuator is charged or discharged, detected and from this the capacitance of the capacitive element is determined. By means of this determined capacity can now be concluded whether there is a short circuit in the investigated piezoelectric actuator.

From the DE 37 01 795 A1 For example, there is known a method for detecting an abnormality in an air-fuel ratio control system in internal combustion engines, in which a proportional control valve is provided which is controlled in response to a sensor output signal for detecting the concentration of oxygen in the exhaust gases for controlling a secondary air amount to be supplied to the engine. Short circuits in a drive circuit for the valve can be detected.

From the DE 40 12 109 A1 a device for monitoring the function of an electrical / electronic switching means, its connected load, its control and its connection line is known, can be detected in the short circuits.

The inventive method with the features of the independent claim has the advantage that before each operation of a respective drive circuit for driving at least one actuator, this drive circuit and the at least one actuator is checked for short circuits, and that occurs in the presence of a short circuit, an error response. This has the particular advantage that before each operation of the Control circuit is ensured that the respectively driven drive circuit is without a short circuit.

According to the invention, a high-side output stage path of the drive circuit is checked for short circuits to ground and battery, and in a low-side output stage path of the drive circuit, each individual actuator is checked for short circuits to ground and battery. This has the particular advantage that a short circuit not only assigned to a specific drive circuit, but also the error path with respect to high or low side can be reliably identified.

According to the invention, it is further provided that before the respective drive circuit is checked for short circuits, a preliminary test is carried out in which first a high-side switching element is closed and thereafter it is checked whether a bank voltage exceeds a threshold value after a pre-test time. If the bank voltage exceeds the operating threshold value until the end of the pre-test time, then it can be assumed that there is no short circuit and further checking for a short circuit is not necessary in principle. However, if the bank voltage has reached the threshold after the pre-test time is not exceeded, there is probably a short circuit in the drive circuit and a more detailed check of the drive circuit for short circuit is to be initiated. This approach has the particular advantage that a thorough short-circuit check is only made if there were any signs in advance; which pointed to a short circuit.

The measures listed in the dependent claims advantageous refinements and improvements of the independent claim method are possible.

According to a further advantageous embodiment, the drive circuit in which a short circuit has been detected is blocked as a fault reaction. By means of this procedure, and in particular a rapid error reaction after detection of a short circuit, it is advantageously possible to dispense with a continuous short circuit strength of the drive output stage. Thus, it is sufficient to build the output stage, although short-circuit-proof but not necessarily permanently short circuit-proof and thus makes it possible to cost-effective components or
To use mechanical components. Furthermore, by eliminating additional components that would be necessary for a permanent short-circuit strength, the dissipated power loss is reduced.

According to a further advantageous embodiment, a device for driving control circuit, which have at least one actuator, is provided, wherein the device is designed for example as a control unit of an internal combustion engine and is programmed to use at least one inventive method. Thus, in an advantageous manner, the diagnosis for short circuit can be taken over centrally by a control device and, for example, in addition to the fault realizations, further measures can be initiated.

According to a further advantageous embodiment, the inventive method is stored as a computer program product with program code and stored on a machine-readable carrier, so that the method is carried out in an advantageous manner when the program is executed on a computer or controller.

drawings

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, in the drawings are shown. All described or illustrated features, alone or in any combination form the subject of the invention, regardless of their combination in the claims or their dependency and regardless of their formulation or representation in the description or in the drawings.

• Figur 1 zeigt schematisch eine Ansteuerschaltung für zwei kapazitiven Stellglieder,
• Figur 2 zeigt ein Ansteuerungsschema für eine erfindungsgemäße Überprüfung auf Kurzschluss;
• Figur 3 zeigt schematisch einen erfindungsgemäßen Verfahrensablauf;

Show it:

• FIG. 1 shows schematically a drive circuit for two capacitive actuators,
• FIG. 2 shows a driving scheme for a short-circuit verification according to the invention;
• FIG. 3 schematically shows a method sequence according to the invention;

The invention is based on the consideration that an output stage for the control of actuators does not necessarily have to be permanently short-circuit-proof if it is ensured that the output stage does not drive a control circuit with a permanent short circuit. According to the invention, it is now provided to check the respective drive circuit and the actuators themselves for a short circuit before operating an actuator. If a short circuit is detected, preferably the respective drive circuit for further operation, in particular an output stage control, is disabled.

Typically, actuators that are intended for operation in a Brennläftmaschine summarized into groups in a common drive circuit. These groups of actuators are commonly referred to as a bank or as a bank system for a six-cylinder internal combustion engine, for example, three bank systems can be provided with two actuators.

FIG. 1 schematically shows a drive circuit for two capacitive actuators. First and second actuators are in FIG. 1 marked with actuator 1 and actuator 2. Both actuators (actuator 1, 2) are each connected to a connection on the so-called high side via a common supply line with a throttle, wherein the inductor either via a high-side switching element HSL on a supply line or a low-side switching element LSE on a ground line can be switched. The electrical connection of the actuators (actuator 1, 2) via the common feed line, the throttle and the high-side switching element to the supply line is also referred to as a high-side power stage path.

On the other connection side of the actuators (actuator 1, 2), the so-called Lowside the connection of the first actuator actuator 1 with a first lowside switching element GLS1 and the connection of the second actuator actuator 2 is connected to a second lowside switching element GLS2 wherein the two switching elements GLS1, GLS2, the two actuators actuator 1, 2 switch to a common Lowside supply line. The common low-side supply line is connected to the ground line via a measuring resistor R meas. The electrical path from the connection of a respective actuator actuator 1, 2 via the associated Lowside switching element GLS1,2, the Lowside supply line and the measuring resistor R measurement to the ground line is also referred to as Lowside Endstufenpfad 1, 2

Parallel to the actuators a bridging switching element GSTOP is provided, which connects the high side of the actuators via a shunt resistor Rshunt with the lowside supply line. All switches and switching elements are in the embodiment of FIG. 3 open. The voltage drop across the actuators is referred to as the so-called bank voltage UBANK. The voltage drop across the measuring resistor Rmess is proportional to the piezoelectric current IPIEZO.

In FIG. 2 If the drive circuit is not operated, all the switching elements are open except for the bypass switching element GSTOP.

If an operation of the drive circuit is provided, the bypass switching element is opened and then the high-side switching element HSL closed after a waiting time T_TRDLY. If the bank voltage UBANK reaches or exceeds an operating threshold value U_HSL after a pre-test time T_HSL, starting from closed high-side switching element HSL, it can be assumed that there is no short circuit in the drive circuit and the drive circuit is enabled and changes to the usual operating mode. The check of the bank voltage UBANK at the start of operation of the drive circuit serves as a kind of pre-test S0 for a short circuit in the drive circuit to be operated.

If the operating voltage value U_HSL was not exceeded in the pretest S0, the first step S1 of the incoming short circuit check is initiated, wherein the highside switching element HSL remains closed and an additional waiting time T_TRDLY follows directly on the pretest time T_HSL of the pretest SO. If the bank voltage UBANK remains below a minimum threshold value ULOW in this additional waiting time T_TRDLY, then there is a "short to ground on highside output stage path" KSMHS and an error reaction is initiated. Without initiating an error reaction, the high-side shadow element HSL is opened again at the end of the waiting time T_TDRLY and the bypass switching element GSTOP is closed after a further subsequent waiting time T_TRDLY.

After that, in a second step S2, a diagnostic waiting time T_DIAGKSUB follows. Since the high side switching element HSL is open during this time, no current should flow from the high side via the bypass switching element GSTOP, the shunt resistor Rshunt and the measuring resistor Rmess. However, if the piezoelectric current IPIEZO measured across the measuring resistor Rmess exceeds a current threshold IPSEL, a so-called "short circuit to Ubat (battery or supply voltage) on the high-side output stage path" KSUBHS is detected and an error reaction is initiated. Without an error reaction, the bypass switching element GSTOP is opened at the end of the diagnostic waiting time T_DIAGKSUB.

Furthermore, in a third step S3, the first low-side switching element GLS1 is closed for a time T_IPSEL. If the current threshold IPSEL is exceeded during this time T_IPSEL, there is a so-called "short circuit against Ubat (battery or supply voltage) on the low-side power stage path 1" KSUBLS1 and an error reaction is initiated.

At the beginning of the following fourth step S4, the first low-side switching element GLS1 is opened again and second low-side switching element GLS2 is closed. Analogous to The third step S3 is a "short circuit against Ubat (battery or supply voltage) on the low-side power amplifier stage 2" KSUBLS2 before when the piezoelectric current IPIEZO the current threshold exceeds IPES.

In the fifth step S5, the high-side switching element HSL is closed in addition to the second low-side switching element GLS2. If the piezoelectric current exceeds IPIEZO after a Piezc drive time T_PIEZO not the current threshold IPSEL, so there is a so-called "short circuit to ground on the low-side power amplifier path 2" KSMLS2 and an error reaction is initiated.

In order to set states defined for the subsequent measurement, the bypass switching element GSTOP is closed in a sixth step S6, and the second low-side switching element GLS2 and the high-side switching element HSL are opened.

After a discharge waiting time T_DIAGWT1, a seventh step S7 starts and the bypass switching element GSTOP is opened again. After an additional waiting time T_TRDLY, the first low-side switching element GLSI and the high-side switching element HSL are closed for a piezo drive time T PIEZO. If the piezoelectric current does not exceed the current threshold value IPSEL after a piezo activation time T_PIEZO, then there is a so-called "short circuit to ground on the low-side output stage path 1" KSMLS1 and an error reaction is initiated.

After the piezo drive time T PIEZO, the first low-side and the high-side switching element GLS1, HSL are opened in an eighth step S8 and after a further waiting time T_TRDLY the bypass switching element GSTOP is closed, so that after completion of the eighth step S8 the switching elements assume a state as before the beginning of the first step S1.

In FIG. 3 schematically shows the flowchart of a short-circuit verification according to the invention. Where the steps S0 to S7 the in FIG. 2 represented and described steps correspond to the corresponding positions of the switching elements.

Step S0 essentially corresponds to a preliminary test in which it is decided on the basis of a test criterion whether or not the drive circuit to be operated has a short circuit. Only if the result of the pretest indicates a short circuit in the drive circuit, the further method steps S1 to S7 are performed. In steps S1 to S5 and S7 is then determined by specific settings of the switching elements and corresponding Prüfabfragen both a present short circuit and determines the exact location of the fault.

In step S0, it is checked whether the bank voltage UBANK exceeds an operating threshold value U_HSL until the end of the pre-test time T_HSL. If the result of the check is positive, the drive circuit is enabled in step 100. Only if a negative result is present, an incoming short-circuit check is initiated with a first step S1.

In step S1, it is checked whether the bank voltage UBANK remains below a minimum threshold value ULOW after an additional waiting time. If the minimum threshold ULOW is not exceeded, there is a short circuit to ground on the highside power stage path KSMHS and a branch is made to step 200, which initiates an error response.

In the second step S2, the error reaction is initiated in step 200, if the piezoelectric current IPIEZO exceeds the current threshold IPSEL and thus there is a short circuit to Ubat (battery or supply voltage) on the high-side output stage path KSUBHS.

In the third step S3, a short circuit to Ubat (battery or supply voltage) is detected on the low-side power stage path 1 KSUBLS 1 and initiated the error response in step 200, if the piezoelectric current IPIEZO exceeds the current threshold IPSEL.

In the fourth step S4, a short circuit to Ubat (battery or supply voltage) is detected on the low-side output stage path 2 KSUBLS2 and the error reaction is initiated in steps 200 if the piezoelectric current IPIEZO exceeds the current threshold IPSEL.

In the fifth step S5, a short circuit to ground is detected on the low-side output stage path 2 KSMLS2 and the error reaction is initiated with step 200 if the piezoelectric current IPIEZO remains below the current threshold IPSEL.

In the sixth step S6, the next step is prepared without checking measurement results.

In the seventh step S7, a short circuit to ground is detected on the low-side output stage path KSMLS1 and the error reaction is initiated in step 200 if the piezoelectric current IPIEZO remains below the current threshold IPSEL. If no short circuit should also be detected in the last check in the seventh step S7, then in the following eighth step S8 the switching elements are switched back to their state which existed before the start of the first step S1. After that, the release of the drive circuit takes place in the following step 100.

The procedure has the advantage in particular in steps S2 to S5 and S7 that the check for short circuits is based on current measurements.

This approach has the particular advantage of being essentially independent of cable lengths or electrical capacities of the actuators. Thus, especially aging effects, as they are present in the piezo injectors play only a minor role in the diagnosis of short circuits.

Furthermore, it is provided that when detecting a short circuit as a fault reaction, the drive circuit is disabled, and thus is no longer available for all other controls. In the case of a six-cylinder internal combustion engine with three drive circuits / banks each having two actuators, this circuit would be put out of action in the event of a short circuit in a drive circuit, so that the internal combustion engine would be connected to the remaining two drive circuits, ie. H. So with 4 controlled cylinders to operate.

Without short-circuit detection, there is the danger that the output stage for controlling the actuators will be overloaded and destroyed in the case of repeated activation of a short-circuited control circuit, which would lead to total failure of the actuator control. Operation of the internal combustion engine would no longer be possible and, depending on the situation in which the vehicle is located, the driver himself might also be endangered or exposed to unreasonable dangers.

With the procedure according to the invention, it is ensured that even in the presence of a short circuit in the control circuits of the actuators at least a limited operation of the internal combustion engine is possible, and a risk to the driver is avoided.

In addition, the type of short circuit is determined by the procedure according to the invention, so that in a repair the corresponding information can be retrieved and the error can be quickly limited and allows a reliable repair.

Furthermore, it is not absolutely necessary for the procedure according to the invention to carry out the activating output stage with short-circuit protection, since before each operation the drive circuit is checked for a short-circuit and possibly locked. This ensures that the power amplifier is not operated in a permanent short-circuit condition. However, it may happen that a short circuit to ground or to the supply voltage occurs during the control of an actuator in the corresponding drive circuit or by the actuator itself. In order to guarantee the reliability of the entire control for such a case, the power amplifier is designed in an advantageous manner so that short-term short circuits are survived unscathed by the power amplifier. If the short-circuited drive circuit is activated in the next cycle, then the method according to the invention detects the short circuit and blocks the drive circuit. A renewed load on the output stage by a short circuit is thus avoided in an advantageous manner. It is therefore sufficient to design the output stage in such a way that short-circuiting short circuits are withstood. Additional reserves and generous dimensioning of the components or mechanical components in order to maintain a permanent short-circuit strength are not necessary. In particular, more cost-effective components or mechanical components in the output stage can be used by this procedure, and the output stage can also be made more compact, which additionally reduces the dissipated power dissipation.

According to a further embodiment, it is also conceivable to provide the piezoelectric actuators inductive actuators or in particular also electromechanical actuators. The procedure according to the invention is to be applied analogously here.

Furthermore, it is advantageous to provide a device for driving drive circuits, in particular a control unit of an internal combustion engine, with means for Detection of short circuits, wherein the device is programmed for the application of the method according to the invention. In this case, the program can be stored, for example, as a computer program product with program code on a machine-readable carrier.

Furthermore, it may be provided to store all positions of the switch elements, the waiting times, measurement times, threshold values and other data in a map.

Furthermore, it is conceivable to set the threshold values and also the waiting times / measuring times as a function of operating conditions of the internal combustion engine and / or the mechanical / electrical properties of the actuators. In particular, it is conceivable for each Ansteuerungsschältung and each actuator to assign these variables individually and take into account.

Furthermore, it can be provided to maintain the method according to the invention as a program or as a functionality on an electronic component, for example an EPROM, ASIC or the like, and to operate it in a control unit or, in particular, directly in an output stage.

Furthermore, the drive circuits themselves can be regarded as part of the output stage, so that functionalities of the control or the power supply in another form than imagined are conceivable. In particular, the supply line does not necessarily have to be at battery potential and the ground line is not necessarily at the ground potential. There are also power amplifier solutions are conceivable in which the actuators are controlled by pulse width modulated current or pulse width modulated voltage.

Claims (5)

1. Method for diagnosing drive circuits having at least one actuating element, in particular a fuel injection apparatus, with a respective drive circuit and the at least one actuating element being checked for short circuits before the said drive circuit is operated, and with an error response being made when a short circuit is present, characterized in that a high-side output stage path of the drive circuit is checked for short circuits to earth and the battery, in that each individual actuating element is checked for short circuits to earth and the battery in a low-side output stage path of the drive circuit, in that a high-side switching element HSL is first closed before the respective drive circuit is checked for short circuits, and a check is then made to determine whether a bank voltage (UBANK) exceeds an operating threshold value (U_HSL) after a pretest time (T_HSL), and in that the drive circuit is checked for short circuits only when the bank voltage (UBANK) does not exceed the operating threshold value (U_HSL) after the pretest time (T_HSL).
2. Method according to Claim 1, characterized in that, in order to check for a short circuit to earth, a high-side switching element (HSL) is first closed in the respective drive circuit on the high-side output stage path, and in that a check is then made to determine whether the bank voltage (UBANK) has exceeded a minimum threshold value (ULOW) after the pretest time (T_HSL) and an additional waiting time (T_TRDLY), and in that an error response is made when the minimum threshold value ULOW is not exceeded.
3. Method according to at least one of the preceding claims, characterized in that the drive circuit in which the short circuit was detected is blocked as an error response.
4. Apparatus for driving drive circuits having at least one actuating element, in particular a control device of an internal combustion engine, comprising means for identifying short circuits, characterized in that means for carrying out all the steps of one of the methods according to one of Claims 1 to 3 are present.
5. Computer program product having a program code which is stored in a machine-readable storage medium, in order to carry out all the steps of the method according to one of Claims 1 to 3 when the program is run on a computer or on a control device.

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