EP1745203A1

EP1745203A1 - Method of diagnosis for control circuits

Info

Publication number: EP1745203A1
Application number: EP05729778A
Authority: EP
Inventors: Bernd Kudicke; Thoralf Rosahl
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2004-04-30
Filing date: 2005-04-05
Publication date: 2007-01-24
Anticipated expiration: 2025-04-05
Also published as: JP2007534883A; WO2005106227A1; EP1745203B1; DE502005004283D1; DE102004021377A1; US20080278876A1

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

Method for diagnosing a control circuit

State of the art

The invention is based on a method for diagnosing control circuits with at least one actuator, in particular a capacitive actuator of a fuel

Injector, according to the preamble of the independent claim.

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

Actuators of this type, operated capacitively or inductively, are used in fuel injectors of BremilCTafi machines, in particular in those with direct fuel injection. When using piezo actuators as capacitive

Actuators are moved by a change in length of the piezo actuator, a valve element of the K-fuel injector from an open to a closed position and vice versa. However, if there is a short circuit in a supply line to a piezo actuator or in the piezo actuator itself, in a control circuit or in a control device which controls the piezo actuator, this is a proper one

Control of the piezo actuator is no longer possible. In addition, it is also possible for a plurality of piezo actuators to be impaired in their function as a result. In the best case, this can lead to a loss of comfort, in an unfavorable case to a deterioration in the fuel consumption and the emission behavior of the Breruαlcraftairaschine, and in extreme cases lead to a hazard to the user of the internal combustion engine.

A method is already known from EP 1 138 907 A1, in which the voltage with which a capacitive element of a piezo actuator is charged or discharged is detected and the capacitance of the capacitive element is determined from this. Using this determined capacitance, it can now be concluded whether there is a short circuit in the piezo actuator under investigation.

In contrast, the method according to the invention with the features of the independent claim has the advantage that before each operation of a respective control circuit for controlling at least one actuator, this control circuit and the at least one actuator is checked for short circuits, and that an error reaction occurs if a short circuit is present. This has the particular advantage that it is ensured before each operation of the control circuit that the one that is controlled

Control circuit without short circuit is.

Advantageous further developments and improvements of the method specified in the independent claim are possible through the measures listed in the subclaims.

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

It is particularly advantageous that a pre-test is carried out before the respective control circuit is checked for short circuits, in which a high-side

Switching element is closed and it is then checked whether a bank voltage exceeds a threshold value after a pre-test time. If the voltage exceeds the operating threshold by the end of the pre-test period, it can be assumed that there is no short circuit and a further check for a short circuit is in principle not necessary. However, the bank voltage has the threshold after the pre-test time not exceeded, there is probably a short circuit in the control circuit and a further detailed check of the control circuit for a short circuit must be initiated. This procedure has the particular advantage that an in-depth check for a short circuit is only carried out if there were signs in advance that indicated a short circuit.

According to a further advantageous embodiment, the

Control circuit, in which a short circuit was detected, blocked.

This procedure and, in particular, a rapid error reaction after a short circuit has been detected, advantageously makes it possible to respond to a

To dispense with the permanent short-circuit strength of the control output stage. It is therefore sufficient to build the output stage short-circuit-proof but not necessarily permanent-short-circuit-proof, thus making it possible to use inexpensive components or mechanical components. Furthermore, by dispensing with additional components that would be necessary for permanent short-circuit strength, the one to be dissipated

Power loss reduced.

According to a further advantageous embodiment, a device for controlling a control circuit, which has at least one actuator, is provided, the device being designed, for example, as a control device of an internal combustion engine and programmed to use at least one method according to the invention. In this way, the diagnosis of a short circuit can advantageously be carried out centrally by a control unit and, for example, in addition to the fault reactions, further measures can also be initiated.

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

drawings

Further features, possible applications and advantages of the invention result from the following description of exemplary embodiments of the invention, which in the drawings are shown. All of the features described or illustrated, individually or in any combination, form the subject matter of the invention, regardless of their summary in the patent claims or their relationship, and regardless of their formulation or representation in the description or in the drawings.

Show it:

Figure 1 shows schematically a control circuit for two capacitive actuators; FIG. 2 shows a control diagram for a short circuit check according to the invention;

FIG. 3 schematically shows a process 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 control a control circuit with a permanent short circuit.

According to the invention, it is now provided to check the respective control circuit and the actuators themselves for a short circuit before operating an actuator. If a short circuit is detected, the respective control circuit is preferably blocked for further operation, in particular for an output stage control.

Typically, actuators which are intended for operation in a Brennlcraft machine are combined into groups in a common control circuit. These groups of actuators are commonly referred to as a bank or a banking system. For example, three bench systems, each with two actuators, can be provided for an O-cylinder Brenrikrafi machine.

Figure 1 shows schematically a control circuit for two capacitive actuators. A first and a second actuator are identified in FIG. 1 by actuator 1 and actuator 2. Both actuators (actuator 1, 2) are each connected to a throttle with a connection on the so-called highside, with the

Throttle can either be switched to a supply line via a high-side switching element HSL or to a ground line via a low-side switching element LSE. The electrical connection of the actuators (actuator 1, 2) via the common supply line, the choke and the highside switching element to the supply line is also referred to as the ffighside output 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 is connected to a first lowside switching element GLS1 and the connection of the second actuator actuator 2 to a second lowside switching element GLS2, wherein the two switching elements GLS1, GLS2 switch the two actuators actuators 1, 2 to a common low-side feed line. The common low-side feed line is connected to the ground line via a measuring resistor R ess. The electrical path from the connection of a respective actuator actuator 1, 2 via the associated low-side switching element GLS1, 2, the low-side supply line and the measuring resistor Rmess to the ground line is also called low-side

Power stage path 1, 2 designated.

A bridging switching element GSTOP is provided parallel to the actuators and connects the highside of the actuators to the low-side feed line via a shunt resistor Rshunt. All switches and switching elements are in the exemplary embodiment of the

Figure 3 opened. 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 piezo current IPIEZO.

In Figure 2, the timing of the control of the various switching elements is the

Control circuit shown for checking for a short circuit. If the control circuit is not operated, all switching elements except the bypass switching element GSTOP are open.

If the control circuit is intended to be operated, the bypass switching element is opened and then the highside switching element HSL is closed after a waiting time T_TRDLY. If the bank voltage UBANK reaches or exceeds an operating threshold value UJHSL after or during a pre-test time T HSL, starting from the closed highside switching element HSL, it can be assumed that there is no short circuit in the control circuit and the control circuit is enabled and goes into the normal operating mode about. The checking of the bank voltage UBANK at the start of operation of the control circuit serves as a pretest SO for a short circuit in the control circuit to be operated. If the operating threshold U HSL was not exceeded in the pre-test SO, the first step S1 of the incoming short-circuit check is initiated, the high-side switching element HSL remaining closed and a further waiting time T_TRDLY immediately following the pre-test time T HSL of the pre-test SO. If the bank voltage UBANK remains below one during this additional waiting time T TRDLY

Minimum threshold ULOW, there is a "short circuit to ground on highside power amplifier path" KSMHS and an error reaction is initiated. Without initiating an error reaction, the highside switching element HSL is opened again at the end of the waiting time T TDRLY and after a further subsequent waiting time T TRDLY the bypass switching element GSTOP closed.

This is followed by a diagnosis waiting time T DIAGKSUB in a second step S2. Since the highside switching element HSL is open during this time, no current should flow from the highside via the bridging switching element GSTOP, the shunt resistor Rshunt and the measuring resistor Rmess. However, if the piezocurrent EPIEZO measured via the measuring resistor Rmess exceeds a current threshold IPSEL, a so-called "short circuit against Ubat (battery or supply voltage) is determined on the highside power amplifier path" KSUBHS and an error reaction is initiated End of the diagnostic waiting time T DIAGKSUB open.

Furthermore, in a third step S3, the first low-side switching element GLS1 is closed for a time TJPSEL. If & TJPSEL exceeds the current threshold IPSEL during this time, there is a so-called short circuit against Ubatt (battery or supply voltage) on the low-side power amplifier path 1 "KSUBLS1 and one

Error response is initiated.

At the beginning of the subsequent fourth step S4, the first low-side switching element GLS1 is opened again and the second low-side switching element GLS2 is closed. Analogous to the third step S3, there is a short circuit against Ubatt (battery or

Supply voltage) on the low-side power amplifier path 2 "KSUBLS2 before if the piezo current IPEEZO exceeds the current threshold IPES.

In the fifth step S5, in addition to the second low-side switching element GLS2, the high-side switching element HSL is also closed. If the piezo current exceeds EPIEZO after a piezo control time TJPIEZO not the current threshold value EPSEL, there is a so-called "short circuit to ground on the low side power stage path 2" KSMLS2 and an error reaction is initiated.

In order to set defined states 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 begins and the bypass switching element GSTOP is opened again. After an additional

Waiting time T TRDLY, the first low-side switching element GLS1 and the high-side switching element HSL are closed for a piezo control time T PEBZO. If the piezo current does not exceed the current threshold value EPSEL after a piezo control time TJPIEZO, a so-called "short circuit to ground on the low side power amplifier path 1" KSMLS1 is present and an error reaction is initiated.

After the piezo control time TJPIEZO, the first low-side and 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 the eighth step S8, the switching elements a state like before

Take Sl at the beginning of the first step.

FIG. 3 schematically shows the flow diagram of a short-circuit test according to the invention. The steps SO to S7 correspond to the steps shown and described in FIG. 2 with the corresponding positions of the switching elements.

Step SO essentially corresponds to a pre-test, in which a test criterion is used to decide whether the control circuit to be operated has a short circuit or not. Only if the result of the pre-test is short-circuited in the

Indicates control circuit, the further method steps S1 to S7 are carried out. In steps S1 to S5 and S7, a short circuit is then determined and the exact location of the fault is determined by specific settings of the switching elements and corresponding test questions. In step S0 it is checked whether the bank voltage UBANK exceeds an operating threshold U_HSL by the end of the pre-test time TJHSL. If the result of the check is positive, the control circuit is released in step 100. An incoming short circuit check is initiated with a first step S1 only if a negative result is present.

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 amplifier path KSMHS and step 200 becomes the one

Initiates error reaction, branches.

In the second step S2, the error reaction is initiated in step 200 if the piezo current EPIEZO exceeds the current threshold IPSEL and there is a short circuit against Ubat (battery or supply voltage) on the highside power amplifier path KSUBHS.

In the third step S3, a short circuit against Ubat (battery or supply voltage) is determined on the low-end power stage path 1 KSUBLS1 and the error reaction is initiated in step 200 if the piezoelectric current EPIEZO reaches the current threshold

EPSEL exceeds.

In the fourth step S4, a short circuit against Ubat (battery or supply voltage) is determined on the low-side power amplifier path 2 KSUBLS2 and the error reaction is initiated in step 200 if the piezoelectric current IPEEZO

Current threshold exceeds IPSEL.

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

In the sixth step S6, the next step is prepared without the measurement results being checked. In the seventh step S7, a short circuit to ground is determined on the low-side power stage path KSMLS1 and the error reaction is initiated in step 200 if the piezoelectric current IPIEZO remains below the current threshold IPSEL. If there is no short circuit in the last ÜT_ test in the seventh step S7, the switching elements are checked for their state in the following eighth step S8

Start of the first step S1 was present, switched back. The activation circuit is then released in the subsequent step 100.

The procedure according to the invention has the advantage in particular in steps S2 to S5 and S7 that the checking for short circuits is carried out on the basis of current measurements.

This procedure has the particular advantage of being essentially independent of cable lengths or electrical capacitances of the actuators. As a result, aging effects, such as those found in piezo injectors, play only a minor role in the diagnosis of short circuits.

Furthermore, it is provided that when a short circuit is recognized as an error reaction, the control circuit is blocked, and is therefore no longer available for all other controls. In the case of a 6-cylinder motor with three control circuits / banks with 2 actuators each, this circuit would be deactivated in the event of a short circuit in a control circuit, so that the flame regulator with the remaining two control circuits, i.e. that would be to operate with 4 controlled cylinders.

Without short-circuit detection, there is a risk that the output stage for controlling the actuators will be overloaded and destroyed if a control circuit with a short circuit is triggered repeatedly, which would lead to a total failure of the actuator control. It would no longer be possible to operate the Brennlcraft machine and depending on the situation in which the vehicle is located, the driver himself may also be at risk or exposed to unreasonable dangers.

The procedure according to the invention ensures that, even if there is a short circuit in the control circuits of the actuators, at least limited operation of the fueling machine is possible, and danger to the driver is avoided. In addition, the type of short circuit is determined by the procedure according to the invention, so that the corresponding information can be called up during a repair and the error can be quickly localized and allows a reliable repair.

Furthermore, it is not absolutely necessary for the procedure according to the invention to design the actuating output stage to be permanently short-circuit proof, since before each operation the actuation circuit is checked for a short circuit and possibly blocked. This ensures that the power amplifier is not operated in a permanent short-circuit condition. However, it can happen that a

Actuator in the corresponding control circuit or by the actuator itself, a short circuit to ground or to the supply voltage occurs. In order to guarantee the operational safety of the entire control system even in such a case, the output stage is advantageously designed such that short-term short circuits are survived by the output stage without damage. If the short-circuit

When the control circuit is activated in the next cycle, the short circuit is recognized by the method according to the invention and the control circuit is blocked. A renewed load on the output stage due to a short circuit is thus advantageously avoided. It is therefore sufficient to design the output stage in such a way that short-term short circuits are withstood. Additional reserves and generous dimensioning of the

Components or mechanical components to maintain a permanent short-circuit strength are not necessary. Through this procedure, in particular, more cost-effective components or mechanical components can be used in the output stage and the output stage can also be made more compact, which also reduces the power loss to be dissipated.

According to a further exemplary embodiment, it is also conceivable to provide the piezo actuators with inductive actuators, 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 actuating control circuits, in particular a control unit of a Brennl raftoiaschine, with means for detecting short circuits, the device being programmed to use the method according to the invention. The program can do this for example as (_tomputeφrogramm product with program code on a machine-readable medium.

Furthermore, it can be provided that all positions of the switch elements, the waiting times, measuring times, threshold values and other data are stored in a map.

Furthermore, it is conceivable to determine the threshold values and also the waiting times / measuring times depending on the operating conditions of the internal combustion engine and / or the mechanical / electrical properties of the actuators. In particular, it is conceivable to individually assign and take these variables into account for each control circuit and also for each actuator.

Furthermore, the method according to the invention can be provided as a program or as a functionality on an electronic component, for example one

EPROM, ASiC or similar to be kept available and operated in a control unit or in particular directly in a power amplifier.

Furthermore, the control circuits themselves can also be understood as part of the output stage, so that functionalities of the control or the power supply are also conceivable in a different form than shown. In particular, the supply line does not necessarily have to be at battery potential and the ground line does not necessarily have to be at ground potential. Power stage solutions are also conceivable in which the actuators are controlled via pulse width modulated current / voltage.

Claims

Expectations

1. A method for diagnosing control circuits with at least one actuator, in particular a fuel injection device, characterized in that prior to the operation of a respective control circuit, this control circuit and the at least one actuator are checked for short circuits, and that an error reaction occurs when a short circuit is present.

2. The method according to claim 1, characterized in that a high-side output stage path of the control circuit is checked for short circuits to ground and battery, and that each individual actuator is checked for short circuits to ground and battery in a lowside output stage path of the control circuit.

3. The method according to claim two, characterized in that before the respective control circuit is checked for short circuits, a high-side switching element HSL is first closed, after which it is checked whether a bank voltage (UBANK) has an operating threshold value after a pretest time (T HSL) (U HSL), and that the control circuit is only checked for short circuits if the bank voltage (UBANK) does not exceed the operating threshold value (U HSL) after the pre-test time (T HSL).

4. The method according to at least one of the preceding claims, characterized in that for checking a short circuit to ground - first a highside switching element (HSL) is closed in the respective control circuit on the highside power amplifier path - and that it is then checked whether after Pre-test time (T HSL) and an additional waiting time (T TRDLY) the bank voltage (UBANK) has exceeded a minimum threshold (ULOW) - and that an error response occurs if the minimum threshold ULOW is not exceeded.

5. The method according to at least one of the preceding claims, characterized in that the control circuit in which a short circuit has been detected is blocked as an error reaction.

6. Device for driving control circuits with at least one StellgUed, in particular a control unit of an internal combustion engine, with means for detecting short circuits, characterized in that it is programmed for use in one of the methods according to one of claims 1 to 5

7. Computer program product with program code, which is stored on a machine-readable carrier, for performing the method according to one of claims 1 to 5 when the program is executed on a computer or control device.