EP1984612B1 - Device and method for controlling at least one glow plug of a motor vehicle - Google Patents

Description

State of the art

The invention relates to a method and a device for controlling at least one glow plug of a motor vehicle.

Usually, the glow plugs are used at the start of the internal combustion engine for heating the combustion chambers. The control of the at least one glow plug is dependent on the operating state of the internal combustion engine.

From the JP 03-105043 already a temperature control of a glow plug in dependence on an injection quantity of the internal combustion engine is known. From the US 4639871 is already a high heating a glow plug with different amounts of energy known.

Disclosure of the invention Advantages of the invention

According to the invention, it has been recognized that in certain operating conditions, the exhaust emissions can be significantly reduced if the control of the glow plugs is dependent on a variable that depends on the exhaust gas temperature and / or depends on the fulfillment of a fuel condition.

Thus, especially when changing the thrust when the engine is cooled, the smoke emissions can be significantly reduced. In particular, the white smoke and / or black smoke can be significantly reduced in the transition from overrun to normal driving. According to the invention, it has been recognized that the combustion chambers cool down during longer overrun operation or during prolonged downhill driving, in which, in particular, a small amount of fuel or no fuel is injected at all. Is then followed by an injection with high fuel quantity, so these are associated with increased smoke emissions. According to the invention this cooling is counteracted by the fact that the glow plugs are driven accordingly. Preferably, it is provided that the glow plugs are energized in the presence of certain conditions such that they are preheated. The aim of the preheating is to achieve the operating temperature of the glow plug in a very short time (eg, <0.55) during the thrust change, especially when a sudden increase injection quantity occurs. Preferably, the preheating in height and gradient is designed so moderate that the service life of the glow plugs is impaired as little as possible. As conditions, the exhaust gas temperature and / or the amount of fuel over time is preferably considered. If this exhaust gas temperature falls below a certain threshold, the annealing process is initialized. Accordingly, the annealing process is initialized when the amount of fuel is below a threshold for a certain period of time. The annealing process is preferably initialized when the fuel quantity assumes the value zero for a certain period of time. Alternatively, it can also be provided that both conditions are combined. This can for example be realized such that both conditions are checked for their presence and that the annealing process is initialized if one of the two conditions is met.

During the glow, the control of the glow plug is dependent on the operating parameters of the internal combustion engine such as in particular the engine speed, the amount of fuel, the outside temperature and / or the exhaust gas temperature. This can be achieved that the glow plug sufficient energy is supplied to achieve sufficient thermal support of the burning process. Furthermore, however, it is prevented that unnecessary energy is supplied to the glow plug, which leads to overheating of the glow plugs or even could damage the glow plug.

drawing

Figur 1

wesentliche Elemente einer Vorrichtung zur Steuerung wenigstens einer Glühkerze,

Figur 2

ein Zustandsdiagramm und die Figuren 3 und 5 jeweils ein Flussdiagramm der erfindungsgemäßen Vorgehensweise.

The embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. Show it:

FIG. 1

essential elements of a device for controlling at least one glow plug,

FIG. 2

a state diagram and the Figures 3 and 5 in each case a flow chart of the procedure according to the invention.

Description of the embodiments

In FIG. 1 the essential elements of the device according to the invention are shown. A glow plug 100 is connected in series with a current measuring means 120 and a switching means 110 between the two terminals of a supply voltage. In the illustrated embodiment, a current measuring means 120 and a switching means 110 is provided for each glow plug. An embodiment of the device according to the invention can also be designed such that a common switching means and / or a common current measuring means is provided for a plurality of glow plugs of an internal combustion engine or all glow plugs of an internal combustion engine.

The illustrated embodiment in which each glow plug is associated with a current measuring means 120 and a switching means 110 offers the advantage that the glow plug can be controlled individually and the current flowing through the glow plug can be evaluated. If several glow plugs are combined to form a group, or if all the glow plugs are actuated jointly via a switching means or the current is evaluated jointly, this offers the advantage that expensive elements such as the switching means can be saved, resulting in considerable cost savings. However, this has the disadvantage that only a common control or a joint evaluation of the power of several or all glow plugs is possible.

Furthermore, a control unit 130 is provided which, in addition to other components not shown, includes an evaluation 133 and a control 135. The driver 135 controls the switching means 110 to supply a desired energy to the glow plug. The evaluation 133 evaluates the voltage drop across the current measuring means 120 in order to determine the current flowing through the glow plug. The current measuring means 120 is preferably designed as an ohmic resistor.

In addition to the intended in normal operation of the glow plug control of the glow plug to shorten the ignition delay at the start of the engine is provided that in certain operating conditions of the internal combustion engine, the glow plugs are driven to prevent cooling of the combustion chambers, according to the invention it was recognized that the longer Pushing operation, in which no fuel is injected, the internal combustion engine cools. As soon as the internal combustion engine for a long time, d. H. between 2 and 3 minutes in overrun, occurs when accelerating, d. H. when injecting fuel an increased smoke emission. This occurs, for example, when the vehicle is traveling downhill for a long time and injected no fuel and then the driver accelerates to accelerate the vehicle on a flat road or uphill or to keep the speed constant. It was recognized that this effect is based essentially on a cooling of the piston walls. This is preferably done in a time range of 2 to 3 minutes after completion of the injection. The cooling of the complete engine block including the cooling water takes place only after a later time, d. H. about 15 minutes instead. This cooling is now counteracted according to the invention as follows: As soon as a corresponding operating state is detected, the glow plugs are vorbestromt to bring them to a low temperature level to bring by applying an increased operating voltage, these preheated glow plugs within a very short time to the required annealing temperature. The pre-tempering is such that the glow plugs can be brought to the maximum annealing temperature within a period of significantly less than half a second. Usually, the internal combustion engine, in particular the piston walls, heats up within a period of 2 to 3 seconds. After this period, the cylinder inner walls are tempered accordingly by the combustion and there are no more smoke emissions. After this period of time, the annealing process can then be stopped or reduced to a distinct low current level.

In FIG. 2 the different states of such a course are shown. In a first step, the program sequence is initialized. In a second state 2 it is determined whether an annealing process is initiated.

This condition 2 is in FIG. 3 shown in detail. In a first step 100, the exhaust gas temperature TA is determined. In a second step 110, a parameter P is determined based on the exhaust gas temperature TA. Subsequent query 120 checks if this parameter P is greater than a threshold SP. If this is not the case, step 100 is repeated. If this is the case, then state 3 is entered. In this embodiment, based on the exhaust gas temperature and possibly other variables, a parameter P is determined, which represents a measure of how much the cylinder walls are cooled. If this parameter P exceeds a certain threshold value SP, state 3 is entered.

This transition to the third state can also be done according to the in FIG. 3b shown embodiment. In a first step 150 it is checked whether the amount of fuel QK injected into the internal combustion engine assumes the value zero. If this is the case, then in step 160, a time counter Z1 is set to zero. The subsequent query 170 checks whether the time counter Z1 is greater than a time threshold SZ1. If this is the case, then in step 180, state 3 is entered. Ie. If it is detected in state 2 that no fuel is being metered for longer than the time period SZ1, then state 3 is entered. As an alternative to querying whether the metered fuel quantity assumes the value zero, it can also be provided that it is checked whether an amount of fuel that is below a minimum value is metered.

In condition 3, the preconditioning of the glow plug takes place, ie it is charged with a low current so that it reaches a certain temperature. Starting from this temperature, the glow plug can be heated very quickly to the final temperature. Usually, the glow plug is heated to a temperature of about 600 ° to 700 °. State 3 is in FIG. 4 shown in more detail. In a first step 300, a time counter Z3 is set to zero. Subsequently, in step 310, the current is determined, with which the glow plug must be energized for preconditioning. This current value with which the conditioning takes place is specified depending on various operating parameters. Such an operating parameter is, for example, the rotational speed of the internal combustion engine, the outside temperature and / or the exhaust gas temperature TA. Subsequent query 320 checks if the value of counter Z3 is greater than one Threshold is SZ3. If this is the case, then in step 330, state 2 is returned. If this is not the case, the query 330 checks whether the fuel quantity QK is greater than zero. If the query 330 recognizes that the fuel quantity is greater than zero, ie neither fuel is metered, then in step 340, the status 4 is entered. If the amount of fuel continues to be less than zero. or less than a minimum value, so again step 310.

During the preconditioning in state 3, the glow plug is pre-energized with a certain current value, which is so dimensioned that the glow plug heats up to about 600 ° to 700 °. This current value is predetermined depending on the operating state of the internal combustion engine such as in particular the engine speed, the outside temperature and / or the exhaust gas temperature. If this condition lasts longer on a time threshold SZ3, then state 2 is entered. As soon as it is detected that fuel is being metered, state 4 is proceeded.

In state 4, which is also referred to as pushing, the glow plug is supplied with so much energy that it reaches its maximum temperature as quickly as possible. This also takes place only for a certain period of time SZ4. The appropriate procedure is in FIG. 5 shown in detail. In a first step 400, a time counter SZ4 is set to zero. Subsequently, in step 410, the current I4 flowing in this state is given depending on the state of the internal combustion engine and / or the state of the glow plugs. Among other things, the already supplied to the glow plug energy is taken into account. Subsequently, in step 420, it is checked whether the time counter Z4 has exceeded a threshold value SZ4. If this is not the case, step 410 is repeated. Otherwise, in step 430, state 5 is entered.

In state 5, the glow plug is operated with nominal voltage. This is done for a certain period of time SZ5. The appropriate procedure is in FIG. 6 shown. In a first step 500, a time counter Z5 is set to zero. Subsequently, in step 510, the current value I5 is specified. The subsequent query 520 checks whether the time period SZ5 has been exceeded. If this is not the case, step 510 occurs again. Otherwise, the transition to state 2 takes place in step 530.

According to the invention it is provided that in a state of the internal combustion engine, in which the risk exists that the combustion chamber cools, the glow plugs are energized according to a predetermined scheme. In a first phase, the glow plugs are preconditioned to reach a certain temperature, from which the final temperature of the glow plugs is rapidly achieved. If the pushing operation, d. H. If fuel is injected again, the glow plugs are energized in such a way that they reach their maximum temperature as quickly as possible, so that the combustion chambers are rapidly heated. After a certain time, the glow plugs are operated for a further period of time with nominal voltage. Ie. they are operated in this time phase so that they maintain their temperature.

According to the invention, it is thus provided that in the overrun mode, a similar annealing process takes place, as at the start of the internal combustion engine. In contrast to the start of the internal combustion engine is a relatively long Vorglühphase in which the glow plugs preconditioned, and as soon as the shear phase ends, the actual annealing process is initiated. The actual annealing process is designed similar to a conventional annealing process. There, the glow plugs at the beginning of a high energy and then a lower energy is supplied so that they quickly reach their temperature and the temperature is then maintained. The longer Vorglühvorgang is possible because the internal combustion engine and the generator is operated and thus sufficient energy is available.

Claims (4)

1. Method for controlling at least one glow plug (100) of a motor vehicle, wherein the at least one glow plug (100) is controlled as a function of an overrun mode of the internal combustion engine, characterized in that an overrun mode of the internal combustion engine is detected if the exhaust gas temperature drops below a threshold value, and/or in that an overrun mode is detected as a function of a fuel quantity (QK) being undershot for a time period which is longer than a time threshold (SZ1), and in that, when an overrun mode is detected, a glow process is started in that the glow plug is pre-heated by applying an operating voltage, wherein the pre-heating is dimensioned in such a way that, after the ending of the overrun mode, the glow plug is heated to the maximum glow temperature within a short time period of less than half a second.
2. Method according to Claim 1, characterized in that the glow plug is controlled as a function of at least one of the operating parameters of the motor rotational speed, external temperature and/or exhaust gas temperature.
3. Method according to Claim 1, characterized in that the control is carried out as a function of the energy supplied to the glow plug.
4. Device for controlling at least one glow plug for a motor vehicle, having means which control at least one glow plug as a function of the operating state of the combustion engine, characterized in that the means detect an overrun mode of the internal combustion engine if the exhaust gas temperature drops below a threshold value, and/or in that the means detect an overrun mode as a function of a fuel quantity (QK) being undershot for a time period which is longer than a time threshold (SZ1), and in that, when an overrun mode is detected, the means start a glow process in that the glow plug is pre-heated by applying an operating voltage, wherein the pre-heating is dimensioned in such a way that, after the ending of the overrun mode, the glow plug is heated to the maximum glow temperature within a short time period of less than half a second.

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