EP2128629B1 - Method and device for detecting the operating condition of a combustion engine - Google Patents

Description

TECHNICAL AREA

The invention relates to a method and a device for detecting the operating state of an internal combustion engine.

STATE OF THE ART

Various electrical consumers on board a motor vehicle, such as navigation devices, driver assistance systems for the active support of the driver in the operation of the motor vehicle and automatic toll collection devices need information about the current operating state of the entire vehicle for proper operation. In addition, the function of some electrical consumers should always be available when the engine of the motor vehicle is in operation and thus moves the motor vehicle. In contrast to the above-mentioned consumers, such as navigation device, driver assistance system and toll collection device, it is the same for example for on-board music systems, whether the vehicle is in operation or not, because the music system makes sense both at standstill of the engine as well as in the operation of the vehicle can be used. In particular, the above-mentioned automatic toll collection devices must be activated during operation of the vehicle and should pull when possible with the engine off little to no electrical power.

The operating state of the motor vehicle is usually determined by means of available control signals in the electrical system, these control signals are usually available only in electrical on-board bus systems, which is located behind the dashboard for built-in appliances. If an electrical load, such as a navigation device, a driver assistance system, a toll collection device or other device that should always be available while driving, subsequently and / or temporarily used in the vehicle, so it is not permanently installed, this system is usually exclusively the cigarette lighter, at best a standardized plug for power supply available. Located next to this power source usually no externally accessible electrical signal sources in the interior of a motor vehicle. Even plug contacts, which provide electric power only when the ignition is switched off, are not available in conventional motor vehicles. In order to switch off an electrical load in a motor vehicle automatically when driving interrupted and turn on again when driving, it is therefore necessary to switch off the consumer manually and turn on again.

From the US-A-5 599 636 is a device for improving the battery current of a rechargeable battery at low ambient temperatures known. This includes a battery heater comprising a temperature sensor and a heating element in a liquid and acid protected arrangement. The heating element comprises a power transistor supplied by the battery and arranged on a cooling plate. The emitter of the power transistor is driven by a temperature control circuit when the battery temperature drops below a reference temperature and the battery voltage is between a first, lower, and a second, upper threshold. A trigger circuit responds to a rise in the battery voltage after a high load current has been turned off and starts a timer that will conduct the power transistor for a predetermined period of time when the battery voltage is at or below the lower threshold.

DISCLOSURE OF THE INVENTION

The invention provides a method and a device for detecting the operating state of an internal combustion engine. According to the invention, the time course of an existing on-board voltage is monitored and characteristic patterns of the on-board voltage profile are derived by the method and the device when the internal combustion engine is in operation and when this internal combustion engine is at rest.

The method according to the invention for detecting the operating state of an internal combustion engine comprises the following steps: a) measuring the standby voltage of a vehicle electrical system, b) detecting a sudden voltage drop in the vehicle electrical system, c) detecting a voltage increase beyond the level of the open circuit voltage to a stable level of an operating voltage d) measuring the operating voltage, e) detecting a gradual voltage drop over a period of more than half a second to a stable rest voltage for the detection of an idle state internal combustion engine. Further advantageous embodiments of the method according to the invention are specified in the subclaims to claim 1.

The object of the invention is defined in the claims. The device according to the invention for detecting the operating state of an internal combustion engine comprises: a) at least one device for electrical connection to a vehicle electrical system, b) at least one device for measuring and storing a measured voltage, c) at least one device for measuring the time and d) at least one device for performing a comparison of different measured values at different times, preferably a microcontroller. Further advantageous embodiments of the device according to the invention are specified in the subclaims to claim 10.

The invention requires that the electrical voltage of the vehicle electrical system of a motor vehicle is provided by a starter battery, which is usually the case, the electrical voltage in the electrical system is dependent on the operating condition of the motor vehicle. Resting and operating voltages of approx. 6V are usual today for small vehicles, approx. 12V for passenger vehicles (Passenger car) and about 24V for trucks and large construction, traction or drive machinery, such as excavators, tractors for agriculture, ships or aircraft. In addition to these voltages, voltages of approx. 9V, approx. 18V, approx. 28V and approx. 32V DC are provided in exceptional cases, depending on the configuration of a starter battery on board. An electrical load, which should be available during operation of the vehicle and should be switched off when the engine to save power, uses the method of the invention to derive the operating state of the motor vehicle from the exact time course of the vehicle electrical system voltage.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail with reference to the accompanying figures.

Figur 1

ein Diagramm eines Spannungsverlaufes eines Bordnetzes in einem Personen-KFZ während der Anlassphase,

Figur 2

ein Diagramm eines Spannungsverlaufes eines Bordnetzes in einem Personen-KFZ während der Abstellphase,

Figur 3

zwei Flussdiagramme zur Verdeutlichung des Verfahrens zur Detektion der Betriebszustände des Verbrennungsmotors,

Figur 4

ein einfaches Blockschaltbild einer Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens.

Show it:

FIG. 1

a diagram of a voltage curve of a vehicle electrical system in a passenger vehicle during the starting phase,

FIG. 2

a diagram of a voltage curve of a vehicle electrical system in a passenger car during the parking phase,

FIG. 3

two flow diagrams to illustrate the method for detecting the operating states of the internal combustion engine,

FIG. 4

a simple block diagram of an apparatus for performing the method according to the invention.

DESCRIPTION OF THE EMBODIMENTS

In FIG. 1 is a diagram of a voltage waveform 1 of the electrical voltage in a vehicle electrical system of a passenger car during the start phase abc shown over the time t. Starting with the first phase a, in which the internal combustion engine is in the idle state, the on-board voltage on conventional power supply elements, such as cigarette lighter or board socket, about 12 V, which corresponds to the usual rest voltage of a starter battery for passenger cars. This exemplary voltage can also be 6V, 9V, 18V, 24V, 28V or 32V and also have different voltages depending on the type of vehicle. In the method according to the invention, this voltage, once recognized by a device for carrying out the method according to the invention as a rest voltage, is used as the base voltage in relation to which the further voltage curve during the phases b and c is classified. When an internal combustion engine is started, the voltage of a starter battery suddenly decreases from the higher standby voltage to a lower working voltage, from about 9V to about 10V. The typical sudden drop in voltage at start-up varies between different battery types and capacities between 0.5 and 3V. Typical is the voltage drop of about 1V to 2V. A usual starting process of a conventional internal combustion engine of a passenger car takes between 0.5 seconds to 10 seconds, in exceptional cases or poorly maintained engines even longer. Within this time b and the electrical voltage of the electrical system does not rise by a parallel alternator for power and charge the starter battery, because the required number of revolutions during startup is not enough to increase the on-board voltage. Depending on the circuit layout, in some vehicles, the entire power supply of all electrical loads in the electrical system is interrupted in favor of the electric starter so as not to unnecessarily burden the starter battery during cranking. In this case, the electrical voltage of the vehicle electrical system drops to 0V during phase b.

With the start of the internal combustion engine at the beginning of phase c, the electrical voltage of the electrical system increases to the operating or charging voltage of about 14V. This overvoltage of at least 0.5 V, typically from 1 V to 2 V is maintained by a control electronics in the alternator over a wide speed curve to load the starter battery with the required overvoltage can. It would be possible to stabilize the electrical voltage of the electrical system within a certain interval rule technically, but this is usually not the case, but the electrical voltage of the electrical system is usually removed directly from the starter battery. This circumstance makes it possible for electrical consumers, which are installed subsequently or transitionally in a vehicle, to derive the operating state of the internal combustion engine from the time profile of the electrical voltage of the vehicle electrical system.

The above course of the on-board voltage over time during the starting process of the internal combustion engine is typical and is independent of the type of internal combustion engine. The starter battery has a rest voltage, reduces its voltage under heavy load by the starting process and the voltage applied to the starter battery voltage is increased by the charging operation of the internal combustion engine. Diesel engines, such as diesel or Glühkolbenmotore, but also turbines need during operation except possibly existing control electronics no further electrical energy. On the other hand, spark-ignited engines, such as petrol or gasoline engines, have typical voltage spikes and / or voltage dips 2 of the spark plugs or the ignition coils in the vehicle electrical system. To generate the spark, the charging process of an ignition coil is suddenly interrupted by a breaker contact or by a charging electronics and the spark plug connected to the ignition coil serves as a discharge resistor of the energy present in the ignition coil. The spark with high voltage on the spark plug and also the change of ignition coil charge for charging interruption is possible from the electrical system only with extensive measures for shielding. Usually, however, the ignition processes in the vehicle electrical system can be measured by means of slight voltage peaks with low capacitance. These voltage peaks and / or voltage dips 2 are of short duration and occur synchronously with the ignition frequency of the motor. In a four-stroke engine with four cylinders, the ignition frequency is two sparks per revolution. At typical speeds of 800 min ^-1 to 6000 min ^-1 for passenger car engines with four cylinders which gives a frequency of 1,600 min ^-1 to 12,000 rpm ^-1 (26 2/3 Hz to 200 Hz). For low-speed engines, such as large single-cylinder or marine engines firing frequencies from 50 min ^-1 to 400 min ^-1 (5/6 Hz to 6 2/3 Hz). Optionally for measuring the electrical voltage curve of the vehicle electrical system, the method according to the invention for detecting the operating state of an internal combustion engine can be configured such that these voltage peaks and / or voltage dips 2 are detected, which is equivalent to a gasoline engine with spark ignition in operation. With auto-igniters, this detection is not possible because these voltage spikes do not exist there. Alternatively or cumulatively, the residual ripple 3 of the vehicle electrical system can also be measured. The residual ripple 3 in the electrical system with a frequency that is synchronous to the transmission ratio of the engine speed to alternator speed comes through the power generation by an alternator to conditions. Some alternators generate alternating current, which is first rectified and possibly largely smoothed, other alternators generate three-phase current, which is also converted by appropriate interconnection in a wavy DC. This wavy DC is used to charge the starter battery, the residual ripple 3 is not compensated by the capacitive effect of the starter battery.

In order to distinguish the short-term voltage drop, possibly also failure, when starting the engine in phase b from a permanent removal of the starter battery, for example during vehicle and / or battery maintenance, it is advantageous if this permanent voltage drop is detected as a fault. Especially those electrical consumers who have their own backup battery, for example to supply an internal system clock or to bridge short-term power outages when starting, the possibility of detecting a fault makes sense, so that the internal backup battery of the electrical load is not unnecessarily discharged. Because the consumer is not turned on in this case.

In FIG. 2 is the electrical voltage waveform 10 of a vehicle electrical system in a passenger car during the shutdown def of the engine shown. Starting at phase d, in which the internal combustion engine is in operation, and the on-board voltage of about 14V is optionally superimposed with voltage peaks and / or voltage dips 2 or a residual ripple 3, follows a phase e, in which the internal combustion engine by interrupting the spark ignition over several Turns to a halt. Within this phase e, the on-board voltage is reduced on the one hand by the elimination of the charging voltage of the alternator, on the other hand, optionally existing smoothing capacitors discharge, so that the electrical voltage of the electrical system not suddenly, but gradually from the operating or charging voltage to the rest voltage of the starter battery by approx. 0.5, typically 1V to 2V, drops. The exact time course of the electrical voltage drop is dependent on the characteristics of the internal combustion engine with alternator, but is not sudden (voltage drop in a few ms range), but gradually (range between 0.1 s to 5 s). After the gradual voltage drop, the voltage of the electrical system stabilizes in phase f on the rest voltage, in the present example, 12V.

In an embodiment of the invention, the detection of an off motor is delayed by 30 s to 10 min, preferably by 2 min to 5 min. This has the advantage that an engine can be switched off for a short time, for example, by a device for gasoline saving in front of a traffic light or in front of a barrier, without that the corresponding consumer is turned off. Navigation devices sometimes take several minutes to initialize, for example, to search for satellites. Driver assistance systems should be available during this time, and automatic toll collection devices should also not be switched off and on again by briefly switching off the engine so as not to interrupt toll collection due to the short break in the journey. By delaying the detection of a switched-off combustion engine thus lead short breaks, such as a refueling, loading and unloading of people or transport goods, getting in and out of passengers of a taxi, but also involuntary interruptions, such as unwanted so-called stalling of an engine when starting , not to an unwanted switching off and on again the corresponding electrical load.

In order to be able to reliably detect the operating state of the internal combustion engine from the course of the electrical voltage of the on-board voltage, it is advantageous if the once-detected open-circuit voltage is temporarily stored for a future comparison with other voltages during starting and during operation. It has proven to be advantageous to wait after once detected AusStation of the engine between 1 min and 30 min, preferably between 5 min and 10 min before the open circuit voltage is measured and stored to wait for a stabilization of the electrical system voltage. The electrical voltage may still vary in the first time after the engine is switched off by a trailing radiator fan, by a trailing fuel pump, by an automatically retracting top, by electric door and window closers, by alarm systems and by slowly discharging electrical consumers.

In FIG. 3 two flowcharts 100 and 200 of the method according to the invention are shown. Flowchart 100 illustrates the flow of steps for detecting an operating one Internal combustion engine. Beginning at start 101, the quiescent voltage of the electrical system is measured in step 102 until a sudden voltage drop is detected. Without a voltage drop, step 102 is repeated until the voltage drop is detected. Alternatively to the repetitive measurement, a differential signal can also be detected so that the falling edge is detected. If a voltage drop has been detected, the method according to the invention proceeds in step 103, in which a reduction in the on-board voltage to 0 V or 1 V to 2 V, depending on the circuit layout of the electrical system is detected. If the voltage drop lasts between 01 and 10 s, the duration is measured in a loop and then rises to a voltage, measurement in step 104, which is above the level of the rest voltage, is the condition for an operating internal combustion engine Fulfills.

Flowchart 200 likewise has, after the start in step 201, a loop in step 202, in which the operating voltage of the vehicle electrical system is measured. Once the on-board voltage changes by a predetermined amount per unit of time, the method proceeds to step 203, in which the gradual voltage drop is detected, advantageously by calculating a quotient of voltage drop per unit time or by measuring a differential signal that must not exceed a predetermined magnitude to detect a gradual voltage drop. Once the on-board voltage has reached a stable level, phase f in FIG. 2 , Measurement in step 204, the condition for an idle state internal combustion engine is met.

FIG. 4 Finally, shows a simplified block diagram 300 of a device for detecting the operating state of an internal combustion engine, which monitors the time course of the electrical system voltage and according to the inventive method when the typical patterns of start and / or shutdown are detected, outputs a corresponding signal, for example to turn a connected consumer on or off. The device according to the invention initially has a device for connection to a vehicle electrical system 301, advantageously in the form of a plug or in the form of a contact for the cigarette lighter. About this plug, the electrical consumer located thereon is also supplied with electrical energy.

An arrangement for measuring and storing a measured voltage 302, 303 ideally consists of an A / D converter, which provides a digitally readable value of the measured electrical voltage and which can also be stored in an electronic memory 303. A past time measuring device 304 is necessary to measure the length of the current interruption, voltage drop or voltage spikes to distinguish whether it is a sudden voltage drop in the millisecond range or a gradual voltage drop in the fractional seconds to seconds range. Finally, the device has a device for carrying out an electronic comparison 305 of the measured electrical Tensions over time. This function is best provided by a generic microcontroller, which has its own program memory. In this case, the microcontroller uses the voltage differences measured over time from the A / D converter, forms a quotient of voltage difference and time between two stable electrical voltages and differentiates depending on the numerical values, whether it is a sudden or a negative one gradual voltage drop, or a voltage increase is.

The method according to the invention and the device according to the invention are advantageous for retrofitting devices. Especially in the future used toll collection devices for private vehicle traffic must be installed within a short retrofit time in a larger number of vehicles. For this purpose, such toll collection devices that are powered by the cigarette lighter with power and are otherwise attached to the dashboard or on the windshields, so that these devices are no internal control signals available.

Claims (11)

1. Method for detecting the operating condition of an internal combustion engine, having the following steps:

   a) measuring the open-circuit voltage of an on-board power system (102),

   b) detecting a sudden drop in the voltage in the on-board power system (103),

   c) detecting a rise in voltage above the level of the open-circuit voltage up to a stable level of an operating voltage (104),
   in order to detect an internal combustion engine which is operating, and

   d) measuring the operating voltage (202),

   e) detecting a gradual drop in voltage over the time period of more than half a second up to a stable open-circuit voltage (203, 204)
   in order to detect an internal combustion engine which is in the idle state.
2. Method according to Claim 1, wherein the measured open-circuit voltage is buffered.
3. Method according to one of Claims 1 or 2, wherein the detection of an internal combustion engine which is in the idle state is delayed by 30 seconds to 10 minutes, preferably 2 minutes to 5 minutes.
4. Method according to one of Claims 1 to 3, wherein in order to perform a positive detection of an internal combustion engine which is operating, with external ignition, additionally voltage peaks and/or voltage dips (2) with a frequency of 50 min-1 (5/6 Hz) up to 12 000 min^-1 (200 Hz), preferably with a frequency of 400 min^-1 (5/6 Hz) up to 6000 min^-1 (100 Hz) are detected.
5. Method according to one of Claims 1 to 4, wherein the voltage measurement is performed at the starter battery, at a cigarette lighter or at an on-board power system for supplying power to external power consumers.
6. Method according to one of Claims 1 to 5, wherein the level of the open-circuit voltage is measured 1 to 30 min after the detection of an internal combustion engine which is in the idle state, preferably 5 to 10 min after the detection of an internal combustion engine which is in the idle state, and is buffered.
7. Method according to one of Claims 1 to 6, wherein a sudden drop in voltage of less than 1 min, preferably of less than 30 sec in duration with a subsequent rise in the voltage brings about a positive detection of an internal combustion engine which is operating, and a relatively long sudden drop in voltage brings about a detection of a fault or of removal of the starter battery from the on-board power system.
8. Method according to one of Claims 1 to 7, wherein the sudden drop in voltage is at least 0.5 V, preferably 1 V to 2 V.
9. Method according to one of Claims 1 to 8, wherein the gradual drop in voltage is at least 0.5 V, preferably 1 V to 2 V.
10. Device for detecting the operating condition of an internal combustion engine according to the method according to one of Claims 1 to 9, having

    a) at least one device for electrically connecting to an on-board power system,

    b) at least one device for measuring and storing a measured voltage,

    c) at least one device for measuring the time, and

    d) at least one device for carrying out a comparison of various measured values at various times, preferably a microcontroller, wherein the device for detecting the operating condition of an internal combustion engine is configured in such a way that it is able to carry out the method.
11. Device according to Claim 10, wherein a switch is provided for an electrical load which, when an internal combustion engine which is operating is detected, switches on the electrical load, and, when an internal combustion engine which is in the idle state is detected, switches off the electrical load.

Images