EP0809021B1 - Glow plug preheating control method and device for diesel engine - Google Patents

Description

The present invention relates to a method for operating a Diesel engine by controlling a glow operation of a glow plug, at which of the glow plug initially during the heating phase until reaching a target temperature, an electric heating power is fed, whose Amount is higher than the continuous power of the glow plug in continuous operation without Damage can be supplied, the duration of the heating phase so is dimensioned that no damage to the glow plug takes place, and in which after the heating phase, the heating power of the glow plug maximum of Continuous power corresponds and is regulated by the fact that the temperature of Incandescent filament of the glow plug measured and compared with a setpoint temperature and the heating power is regulated.

To ignite the fuel when starting diesel engines (diesel) by means of glow plugs, the temperature of the glow plug in a heating phase be heated to a target temperature at which the fuel ignites. At the Starting the diesel engine must therefore wait a certain time Vorglühzeit become.

From US 4,934,349 is a method of operating a diesel engine known in this process, on the one hand during the heating up supplied to achieve a desired temperature, an electrical heating power and then the heating power of the glow plug is controlled, this by measuring the temperature of the filament of the glow plug and comparison with a set temperature and appropriate control of the heating power he follows.

For this purpose, US 4,934,349 two circles for the provision of the Heating power, namely a "stable preheating circuit" and a "quick preheating circuit "which are both driven accordingly.

EP 0 315 934 A1 discloses a method for controlling glow plugs Diesel engines, in which the flow of current to the glow plug through Pulse width modulation periodically off and on.

During the shutdown breaks, the ohmic resistance of the Determined glow plug representing physical quantity. After this Measurement result has exceeded a predetermined setpoint, is a Initiated control process, which adjusts the temperature of the glow plug, that a predetermined operating temperature is maintained.

DE 693 04 586 discloses a method for operating a diesel engine, in which in a so-called preheating the filaments of the Glow plugs of all cylinders are supplied. Further, if necessary the start of the engine still provided a reheating by means of the candles.

US 4,444,160 also discloses a control for glow plugs of a Diesel engine, whereby the control also provides that before starting of the engine during a first heating period the glow plugs higher current is supplied, until a desired temperature is reached and then the heating power is reduced to the desired Keep temperature until the engine is safely started.

US 4,137,885 discloses a circuit for driving glow plugs, where two input variables generate a control time for the glow plugs will not damage the candles and too long a pre-heat time avoid.

US 5,144,922 discloses a circuit for driving glow plugs in Heating intervals, wherein between the heating intervals with a measuring current the Glow plug temperature is determined.

Object of the present invention is to provide a generic method create, with which diesel engines can be operated optimally.

This object is achieved in a method of the type mentioned According solved according to the invention that quickly heating up as glow plugs Stabglühkerzen be used that of a glow plug control the Temperature of the filament of the glow plugs is measured that the Glow plug temperature data from glow plug states of the glow plug control of a motor control are transmitted that the Set temperature specified by the engine control of the glow plug control and that of the glow plug control each glow plug with a separate power output stage is controlled.

In order to enable an advantageous quick start, it is provided that the Glow plug is designed as a fast-heating rod glow plug, which of an electrical control unit can be heated up quickly such that at a given on-board voltage, they supply a certain current for a measured current Can absorb time so that they do not get a candle in no time can absorb harmful heating energy, where it is for applying the large current is advantageous, the rated voltage, i. the for the Continuous operation of the candle suitable voltage to which these are connected can be, without causing damage to the glow plug, smaller than to choose the rated voltage of the ship, and that after reaching the limit for the Ignition necessary candle temperature the energy input advantageously by a clocked power supply up to her Rated continuous power is throttled until the engine is started or the Annealing process is interrupted.

It is also envisaged that a Data transmission of Glühkerzenzustands, in particular the temperature of Glow plug, between a motor control or an engine management of Diesel engine and the glow plug control takes place.

It is advantageous in the inventive method when the temperature the filament of the glow plug control is determinable and the Glow plug control comprises a control unit, the heating power of Supply unit as a function of the temperature difference between the actually prevailing temperature of the filament and a predetermined set temperature controls.

It is advantageous if the glow plug control an interrupter unit comprises for determining the temperature of the filament, the one of a Supply unit of the filament supplied heating power interrupts.

The temperature of the filament can in the inventive method be determined by the fact that the glow plug control an electrical Resistance of the filament determining and from the resistance value the Temperature of the filament calculating measuring unit comprises.

It is intended that the Glow plug is first operated with a power that keeps it in continuous operation can not withstand, but with whom they would blow. This high However, heating power is supplied to her only over a period of time, the like It is estimated that there is no damage to the gradually warming Glow plug enters. The glow plug is only so long with the high Heating power operated until it has reached its target temperature. The duration the heating phase is thus determined by the amount of heating power and can be fixed for each type of glow plug used be specified.

In one embodiment of the method is provided that one regulates the heating power of the glow plug by repeating the Temperature of a filament of the glow plug determined with a Setpoint temperature compares, and the heating power to reach a Set temperature corresponding to one of the determined temperature difference Value sets.

It is the power supplied to the filament in dependence regulated by the temperature of the filament of the glow plug. That's it possible to heat up the glow plug with a very high power too operate, which is then throttled when the set temperature is reached.

The throttling of the heating power can be done in such a way that you can Amount of practically continuously supplied heating power reduced, or but by supplying the heating power of the glow plug clocked, i. in interrupts certain time intervals, the length of the interrupting Time intervals depending on the actual temperature of the Filament is adjusted.

It is intended that one on the one hand the glow plug in the heating phase with a very high performance operates, so that the glow plug is heated very quickly and that one to another determines the temperature of the filament of the glow plug and so on can determine when the setpoint temperature has been reached. As soon as that happens is throttled, the power supplied to the glow plug and the glow plug is operated at the maximum with the performance of the glow plug in continuous operation can be supplied without damage.

All embodiments allow short energy provision times for Ignition of the fuel when starting diesel engines with glow plugs. The Exhaust emissions and engine wear are reduced during cold start occurs an increase in comfort by shortening the preheating time.

It is advantageous if the candle temperature stabilized by the process is by polling the temperature at the glow plug tip, so that at sinking temperature (low load operation of the engine) by supplying a calculated amount of electrical energy (intermediate annealing) the optimal Candle temperature is reached again, and this scheme during the total working time of the engine. In such an embodiment the device according to the invention additionally comprises an arithmetic unit which in Dependence on the temperature difference between the actual value and the Desired value of the temperature of the filament to reach the Target temperature required amount of energy calculated.

In an implementation of the method, the glow plug is electrically connected to a Supply unit for providing an electric heating power for the Glow plug connected, wherein the heating power of the supply unit means the glow plug control is controllable.

With the help of the supply unit, the glow plug with electrical energy supplied, wherein the glow plug can be configured in such an advantageous manner can be that the value of the electrical voltage with which they are in continuous operation can be operated without damage, the so-called rated voltage, is lower than the on-board voltage, which is present for example in the vehicle. This makes it possible to use the glow plug during the heating phase with the help of Supply unit with the for the continuous operation of the glow plug too high To operate on-board voltage and after the heating phase the Supply voltage of the glow plug with the help of the control unit on the for To reduce the continuous operation of the glow plug appropriate value.

In a particularly preferred embodiment is provided that the nominal voltage of the candles a smaller Voltage is selected as the rated on-board voltage, preferably one Voltage equivalent to about half of the on-board voltage.

It is favorable if the computing unit of Glow plug control device is designed such that at start interruption and restart after a short time Time by checking the candle temperature for the first quick start heat pulse the amount of energy or the exposure time is recalculated and regulated

It can be provided in an advantageous manner that each annealing process in Operation of the engine is characterized in that in each case the current Temperature of the glow plug tip measured and for the achievement of the Set temperature necessary electrical energy with the help of the arithmetic unit is determined.

In an advantageous embodiment of the method is provided that one in continuous operation of the glow plug thereby regulates the heating power of the glow plug, by repeatedly determining the temperature of the filament of the glow plug, compared with the set temperature and the heating power to reach the Set temperature corresponding to one of the determined temperature difference Value sets. In particular, the adjustment of the heating power for Reaching the setpoint temperature take place in that the value of the heating power is reduced in continuous operation or that the heat output clocked is supplied and the length of the clock intervals of the temperature difference between the actual temperature, i. the actual temperature of the Filament, and the setpoint temperature corresponds.

If the heating power of the glow plug is also regulated in continuous operation, that is it thereby possible, even during any operating conditions of the engine additionally to perform annealing operations. It is advantageous if you the amounts of energy reaching a given actual temperature the setpoint temperature of the glow plug must be supplied, calculated and then the heating power as long as the glow plug feeds until the Glow plug has received the predetermined amount of energy. Thereby Driving characteristics and exhaust emissions are improved and there is a Reduction of fuel consumption and a reduction in wear of the Motors due to the optimization of combustion.

In a preferred embodiment of the method according to the invention provided that for determining the temperature of the filament the Heating power supply of the glow plug briefly interrupts.

It is favorable, if one the heating power supply until reaching a Temperature equilibrium within the filament interrupts.

The time until, after an interruption of the heating power supply Temperature equilibrium within the glow plug is dependent on each type of glow plug used. At a special preferred embodiment of the method according to the invention is provided that the heating power supply for determining the temperature of Incandescent filament for about 50 to 60 msec interrupts. It turned out that in many cases within such a period of time Temperature equilibrium is achieved within the filament, so that one advantageously at the end of this period, the temperature of the filament determined and used to control the heating power.

It is advantageous to design the glow plug so that they briefly the can withstand double nominal voltage, without causing damage to the Glow plug is done.

The following description of a preferred embodiment of Invention is used in conjunction with the drawings closer Explanation.

Figur 1:

eine schematische Darstellung eines Steuergeräts zur Steuerung des Glühvorgangs der Glühkerzen eines Dieselmotors;

Figur 2:

ein Blockschaltbild des Steuergeräts aus Figur 1;

Figur 3:

den Verlauf der Glühkerzentemperatur und des zugeführten Heizstroms gemäß einer ersten Ausgestaltung der Ansteuerung der Glühkerze;

Figur 4:

eine vergrößerte Darstellung des Details A aus Figur 3 und

Figur 5:

den Verlauf der Glühkerzentemperatur und des zugeführten Heizstroms gemäß einer zweiten Ausgestaltung der Ansteuerung der Glühkerze.

Show it:

FIG. 1:

a schematic representation of a control device for controlling the annealing of the glow plugs of a diesel engine;

FIG. 2:

a block diagram of the controller of Figure 1;

FIG. 3:

the course of the glow plug temperature and the supplied heating current according to a first embodiment of the control of the glow plug;

FIG. 4:

an enlarged view of the detail A of Figure 3 and

FIG. 5:

the course of the glow plug temperature and the supplied heating current according to a second embodiment of the control of the glow plug.

In Figure 1 is a functional diagram in a schematic manner a plant for controlling the annealing process in particular at Quick start of diesel engines (diesel) with adjustable Glow plugs for preheating during startup shown. These includes one with its negative electrode grounded (GND) connected battery, its positive electrode with a Terminal 29 of a controller 32 is connected. The control unit 32 comprises a central control unit in the form of a Micro-controller control and power monitoring with Power output stages, to the terminals G1, G2, G3, G4, G5 and G6 are connected. Both the micro-controller control as well as the current monitoring are to the power supply the connection 29 connected. The micro-controller control is also via a line 12 with the current monitoring and via a line 14 directly to the power output stages connected. In addition, the micro-controller control connected via a line 16 to a terminal 31, to the the common ground (GND) is connected. Besides that is another terminal DL is provided, via which the micro-controller control to a not shown in the drawing Engine control or to an engine management is connectable. To terminals G1 to G6 of the controller 32 glow plugs 20, 22, 24, 26, 28 and 30 are connected, which in addition with the common ground GND in Connection stand.

The structure of the micro-controller control results from the Block diagram of the controller 32 in Figure 2. The micro-controller control comprises a power supply unit, a microprocessor and a driver and protection circuit. The microprocessor and the driver and protection circuit are connected by the connected to the terminal 29 of the controller 32 Power unit with electrical energy provided. The illustrated schematically in Figure 1 as a terminal DL Connection between micro-controller control and Motor control or engine management takes place via a data interface. Here, for example, a single-wire connection or a CAN bus.

As is clear from FIG. 2, one is for each glow plug separate power output stage provided. To one as possible to obtain a clear representation, are in Figure 2 only four output stages and only two glow plugs 28, 30 shown, in fact, however, just as many power amplifiers as Glow plugs used. The power amplifiers are each with the Driver and protection circuit of the micro-controller control in conjunction with a current measuring unit, which in turn to the driver and protection circuit and to the terminal 29th connected. Instead of each glow plug a separate power amplifier can also be provided, 2 or more Glow plugs in a parallel circuit summarize and a glow plug group formed in this way with one final stage connect.

The connecting lines between the power output stages and the glow plugs 20 to 30 serve on the one hand, the glow plugs to supply with electrical energy. On the other hand the determination of the individual takes place via these lines Resistors and thus the temperature of the glow plugs. For this purpose, their power supply is temporarily interrupted, and instead, a test voltage is applied to the glow plugs applied and the current flowing through the filament of the current Current measuring unit measured. This is done by the controller the power amplifiers by means of the driver and protection circuit, the in turn is coupled to the microprocessor. From the measured current can be at a known test voltage in the usual Way the electrical resistance of the filament determined which in turn is assigned a certain temperature value can be. The thus determined actual temperature is with the Target temperature of the glow plug compared, and from the temperature difference is used by the microprocessor for reaching the desired temperature required heating power calculated, the then fed to the glow plugs via the output stages becomes.

By repeated brief interruption of the heating power supply the glow plugs and determination of the respective Actual temperature is possible, the glow plugs inside heat up in a short time and in a stabilized manner on one To maintain target temperature. The heating power supply is each interrupted for the duration of about 55 ms, so that within the glow plug, a temperature equilibrium established. The current measurement to determine the resistance and therefore the temperature of the glow plug is at the end the interruption interval, the measuring time about 20 microseconds is and with a current measuring range of up to 200 Amp a smallest measurable resolution of about 1 amp is achieved.

The control of the glow plugs by means of the above described controller 32 may be such that the supplied heating current of the respective temperature difference between actual and set temperature corresponds. The result resulting temperature and Heizstromverlauf is in Figure 3 shown. This shows the course in an upper diagram the adjusting Glühkerzentemperatur T depending from time t, with the glow plug temperature T due of the glow plug supplied Heizstromes I changes, its course, also as a function of time t, in Figure 3 is shown in a lower diagram. The Indian respective power output stage associated glow plug is initially a high heating current I supplied, so that the Glow candle heats up considerably. With increasing actual temperature the heating current supply is reduced. This has to Result that the actual temperature of the set temperature of Gradually approaches the glow plug. As already mentioned, takes place the determination of the actual temperature in that the heating power supply, i.e. in the present case, the supply of the corresponding heating current, briefly interrupted and the Resistance of the filament is determined. The in regular Intermittent interruption of Heizstromzufuhr is enlarged in Figure 4, which also shows the course of the heating current I as a function of time t shows. The FIG. 4 shows an enlarged view of that in FIG. 3 dash-dotted drawn details A. The measurement of the Resistance and thus the glow plug temperature takes place each at the end of the interruption interval and is shown in FIG 4 symbolized by the arrows 50.

In the embodiment of the illustrated in FIG Control of the glow plugs is the amplitude of the heating current I according to the temperature difference between actual and Desired temperature of the glow plug is reduced. An alternative Control possibility of the glow plugs by means of the control unit 32 can be seen from FIG. FIG. 5 shows in one upper diagram the adjusting curve of the glow plug temperature T as a function of time t, which is results when the glow plug corresponding to that in a lower Diagram driven in the figure 5 shown control becomes. The lower diagram shows the glow plug control, i.e. the course of the glow plug current, depending on the time t. As can be seen, that of the respective power amplifier associated glow plug during a through the double arrow 55th clarified heating phase consistent with a heating current supplied to maximum amplitude, so that the glow plug, such as seen from the upper diagram of Figure 5, very fast heating up. After reaching the target temperature, the temperature the glow plug during the subsequent holding phase, which is illustrated by the double arrow 60, kept constant. For this purpose, the glow plug is controlled clocked, i.e. the heating current is interrupted regularly, so that the glow plug integrates a total of over time lower heating power is supplied. This way you can the glow plug during the heating up with a very high Heating power to be supplied, they do not in continuous operation would withstand, but their supply is a very fast Heating to the target temperature has the consequence. To Reaching the target temperature is the supplied heating power reduced to a value that is sufficient to to keep the temperature of the glow plug at target temperature, so that destruction of the glow plug is not to be feared.

The heating phase and then holding the temperature are not on the starting process of the diesel engine or on a maximum glow plug temperature limited, but can also to the so-called intermediate annealing with the engine running and at a determined by the diesel engine control annealing temperature be applied.

To determine if the glow plug is already at its setpoint temperature has reached, can also in the illustrated in Figure 5 Embodiment of the control, the Heizstromzufuhr regularly interrupted for a duration of about 55 ms and on A temperature determination at the end of the interruption interval be carried out as with reference to the Figures 3 and 4 has already been explained. A corresponding Temperature determination can both during the heating 55 as well as during the hold phase 60. Does that have the the respective output stage assigned glow plug not yet theirs Target temperature reached, then the corresponding power amplifier via the driver and protection circuit of the microprocessor so controlled that the glow plug consistently a heating current supplied with maximum amplitude. After reaching the setpoint temperature, the heating current is only clocked, i.e. supplied with interruptions, as is the case from the bottom Diagram of Figure 5 becomes clear. The duration of the interruption times, i.e. the ratio of on / off times The power amplifiers can be used by the microprocessor by comparing the Actual temperature with the target temperature of the respective glow plug be calculated.

Claims (11)

1. Method of operating a diesel engine by controlling a glowing operation of a glow plug, wherein an electric heating-up power is first supplied to the glow plug during the heating-up phase until a set temperature is reached, the amount of the electric heating-up power being higher than the continuous power that can be supplied to the glow plug during continuous operation without damage thereto, and the duration of the heating-up phase being of such length that no damage occurs to the glow plug, and wherein after termination of the heating-up phase, the heating power of the glow plug corresponds at most to the continuous power and is regulated by the temperature of the glow coil of the glow plug being measured and compared with a set temperature and the heating power being regulated,
   characterized in that sheathed glow plugs that heat up quickly are used as glow plugs, in that the temperature of the glow coil of the sheathed glow plugs is measured by a glow plug control device, in that data on glow plug states including the temperature of the glow plugs are transmitted to an engine control device by the glow plug control device, in that the set temperature is predetermined by the engine control device for the glow plug control device, and in that each glow plug is controlled with a separate power output stage by the glow plug control device.
2. Method in accordance with claim 1, characterized in that the regulation to the set temperature is carried out during the entire working time of the engine.
3. Method in accordance with any one of the preceding claims, characterized in that the nominal voltage of the plugs is selected so as to be smaller than the on-board nominal voltage.
4. Method in accordance with claim 3, characterized in that the nominal voltage for reaching the nominal power of the glow plugs is approximately half of the on-board nominal voltage provided.
5. Method in accordance with any one of the preceding claims, characterized in that in the event of interruption of start-up and restart after a short time, the amount of energy or the action time for the first quick-start heating impulse is recalculated and regulated by testing the temperature of the glow plugs.
6. Method in accordance with any one of the preceding claims, characterized in that the current temperature of the glow plug tip is measured and the electrical energy necessary for reaching the set temperature determined for each glowing operation during operation of the engine.
7. Method in accordance with claim 6, characterized in that during continuous operation of the glow plug, the heating power of the glow plug is regulated by the temperature of the glow coil of the glow plug being determined and a temperature difference being formed by comparison with the set temperature, and by the heating power being set at a value corresponding to the temperature difference determined in order to reach the set temperature.
8. Method in accordance with any one of the preceding claims, characterized in that in order to determine the temperature of the glow coil of the sheathed glow plug, the supply of heating power is interrupted for a short time by the glow plug control device and the temperature is then measured.
9. Method in accordance with claim 8, characterized in that the supply of heating power is interrupted practically until a temperature equilibrium within the glow coil is reached.
10. Method in accordance with claim 8 or 9, characterized in that the supply of heating power is interrupted for approximately 50 to 60 msec.
11. Method in accordance with any one of the preceding claims, characterized in that glow plugs which take twice the nominal voltage for a short time without any damage occurring to the plugs are used.

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