JP2015175373A - Method of limiting current consumption in glow time controller, and glow time controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid damage to a glow time controller, in particular, damage to a field effect transistor that realizes polarity reversal protection.SOLUTION: The present invention provides a method of limiting the current consumption in a glow time controller in which a predetermined number of glow plugs are controlled with pulse-width modulated control signals derived from a battery voltage, and a method of reducing the number of simultaneously operated glow plugs in a glow time controller provided with a device limiting the current consumption.

Description

  The present invention relates to a method for limiting the current consumption of a glow time control device, which controls a predetermined number of glow plugs by a control signal derived from an operating voltage and subjected to pulse width modulation, and a glow time control device.

In a recent glow time control device, the glow plug is controlled by pulse width modulation of the battery voltage U _Batt supplied to the glow time control device. In this case, the power transistor has a switching function, and one power transistor is provided for each glow plug in order to control the glow plug. By adjusting the duty cycle (DC) of the pulse width modulation control, the plug voltage effective value U_eff or the plug current effective value l_eff can be set flexibly.

  A glow time control device incorporating a battery voltage compensation function is known. According to this apparatus, the effective voltage value U_eff supplied to the glow plug is kept as constant as possible by adjusting the duty cycle, and in this way, the deviation of the battery voltage is compensated.

  In order to heat the glow plug as rapidly as possible during the preheating phase, also called the push phase, after the glow time control device is activated, the effective current consumption value is set to be large. Thus, during this preheat phase, a high duty cycle is set (U_eff is typically about 11V) and after the glow plug reaches the target glow temperature, the duty cycle is reduced during the steady glow operation period ( U_eff is generally about 7V or 4.4V).

  Depending on the type of glow plug used (ceramic or metal), especially when the temperature is low (−40 ° C.) and the battery voltage is relatively high (16 V), the remarkably large on during the preheating phase Current may flow. This places high demands on the current capacity of the electronic components used. In particular, it is extremely difficult to guarantee such a current capacity when the reverse polarity protection (IPP) realized by the field effect transistor is required. The reason is that a particularly large current flows during the preheating phase, especially in the case of low-voltage ceramic plugs. The maximum plug current of the glow plug is determined only by the resistance of the plug and the battery voltage when the switch is turned on for the first time, that is, the maximum plug current cannot be changed.

  The problem on which the present invention is based is therefore to avoid damaging the glow time control device, in particular to avoid damaging the voltage effect transistor that implements polarity reversal protection.

  According to the present invention, the object is to reduce the number of glow plugs to be operated simultaneously, a method for limiting the current consumption of a glow time control device, and a glow time control with a device for limiting the current consumption Solved by the device.

  By reducing the number of glow plugs that are operated simultaneously, the current consumption of the glow time control device is reduced as a whole, thereby preventing the field effect transistor that realizes polarity protection from being damaged. The deviation between the target value and the effective voltage is taken into account in the glow control by the glow time control device or the engine control device, so that the strategy of the glow control can be matched according to the deviation.

  Advantageously, the number of glow plugs operated simultaneously is reduced depending on the battery voltage and / or depending on a measured value representing the plug temperature of the glow plug. In this way, by limiting the glow plug control channels that are operated simultaneously, the total current consumption of the glow time control device is reduced.

  According to one embodiment, the reduction of the number of glow plugs to be operated simultaneously is performed during the glow plug preheating phase. During this preheating phase, also called the push phase, the resistance of the plug is particularly small, especially when the temperature is low, and therefore a very large current flows through the glow plug in order to rapidly heat the glow plug. Therefore, the current consumption is limited by reducing the number of glow plugs operated simultaneously, and the glow time control device is protected from damage.

  According to one embodiment, depending on the battery voltage and / or depending on the measured value representing the plug temperature of the glow plug, all the glow plugs are operated simultaneously during the glow plug preheating phase, Alternatively, it is determined whether to reduce the number of glow plugs to be operated simultaneously. Therefore, heating as fast as possible is always ensured while avoiding damage to the glow time control device, thereby ensuring operation of the glow plug.

  According to one embodiment, in order to reduce the number of glow plugs that are operated simultaneously, synchronization of pulse width modulated control signals for the glow plugs is performed. Such synchronization makes it possible to minimize fluctuations of the total current consumption of the glow time control device over time. In this case, when the glow plug control channel n is switched off, the next glow plug control channel n + 1 is switched on in synchronization therewith.

  Advantageously, after the glow time control device is switched on, the battery voltage is measured and / or a measured value representing the plug temperature of the n glow plugs is measured, the battery voltage being above the first voltage threshold. And / or if the measured value representing the plug temperature of the n glow plugs is below the first temperature threshold, so that no more glow plugs than n-1 glow plugs are powered simultaneously. The glow plug is controlled by pulse width modulation. When only n-1 glow plugs are used for the purpose of reducing the total current consumption, the duty cycle of the pulse width modulated control signal is reduced.

  For example, if the battery voltage exceeds an mth voltage threshold that is higher than the first voltage threshold, and / or a measured value representing the plug temperature of n glow plugs is lower than the first temperature threshold. When the temperature is below the mth temperature threshold, the glow plugs are controlled by pulse width modulation so that a larger number of glow plugs than nm glow plugs are not supplied at the same time, where n> m. By such a method, the number of glow plugs operated simultaneously can be further reduced, but the duty cycle of the pulse width modulated control signal for the glow plugs operated is also reduced at the same time.

  According to one embodiment, a ceramic low voltage plug is used as the glow plug. In particular, this type of low-voltage ceramic plug is subjected to a high on-current during the preheating phase at low temperatures or when the battery voltage is relatively high. By reducing the number of glow plugs to be fed, the level of glow plug on-current is reduced, which can reliably prevent damage to the glow time control device.

  According to one embodiment, when the set period of the preheating phase has elapsed, the reduction of the number of glow plugs that are simultaneously operated is terminated.

  As another option, if the measured value representing the plug temperature of the glow plug exceeds a predetermined measured plug temperature and / or if the current plug current falls below a predetermined measured plug current, The reduction of the number of glow plugs to be operated ends. In this way, a current consumption limitation is introduced only when the current consumption is too high, ie only when the glow time control device is to be prevented from being damaged.

  The described method can always be used advantageously when the current consumption of the glow time control device is limited.

  The invention also relates to a glow time control device comprising a device for limiting current consumption. In this case, a predetermined number of glow plugs are controlled by a control signal derived from the operating voltage and pulse width modulated. This glow time control device is provided with means for adjusting the effective voltage applied to the glow plug by reducing the number of glow plugs to be operated simultaneously. The advantage of this is that excessively high currents avoid damage to the glow time controller when the battery voltage is high and / or when the ambient temperature is low, in particular the glow time controller. The damage to the field effect transistor that is provided inside and implements polarity protection is avoided.

  Advantageously, at least one polarity protection element for limiting the current capacity of the glow time control device is arranged between the battery voltage input terminal and the power transistor for controlling the glow plug.

  Many embodiments are possible according to the invention. Next, two of them will be described in detail with reference to the drawings. In the drawings, the same reference numerals are assigned to the same elements or members.

The figure which shows the Example of the circuit of a glow time control apparatus The figure which illustrates the time characteristic of the on current supplied to the ceramic glow plug of the low temperature state Diagram showing a first embodiment of the method according to the invention Diagram showing a second embodiment of the method according to the invention The figure shown about the Example for synchronizing the glow plug control by a glow time control apparatus

FIG. 1 shows one embodiment of a glow time control device 1, which is connected to a battery voltage U _Batt . Inside the glow time control device 1, the battery voltage U _Batt is applied to two field effect transistors 2 and 3 connected in parallel, and these field effect transistors realize polarity reversal protection according to the battery level. These field effect transistors 2 and 3 are controlled by a microprocessor or ASIC not specifically shown in the figure, and the glow plug power transistors are also controlled by these. According to the glow time control device 1 to be considered here, an internal combustion engine having four cylinders is controlled. In this case, one glow plug 9, 10, 11, 12 is provided for each cylinder. . Each of these glow plugs 9, 10, 11, and 12 is controlled by a single power transistor 5, 6, 7, and 8, respectively, in a pulse width modulation system. Formed by ASIC. The current capacity of the glow time control device 1 described above is generally limited to 200 A by the field effect transistors 2 and 3.

The glow plugs 9, 10, 11, and 12 are formed as low-voltage ceramic plugs. This kind of low-voltage ceramic plug has a temperature characteristic as shown in FIG. 2 during a preheating phase in which the glow plugs 9, 10, 11, 12 in a low temperature state are heated to a predetermined operating temperature by a large on-current. Or it has a current lapse characteristic. In this case, the temperature course characteristics of the glow plugs 9, 10, 11, and 12 are drawn as a curve A for a temperature from −30 ° C. and as a curve B for a temperature from + 25 ° C. As an alternative to these, the temperature rise of the glow plugs 9, 10, 11, 12 is shown on the time axis. In this case, curve C represents the applied operating voltage U _Batt , curve D represents the plug current at −30 ° C., and curve E represents the plug current at 25 ° C.

The method according to the present invention will now be described in detail based on the two embodiments shown in FIGS. After the activation of the glow time control device 1 and before the plug current is _delivered , first the battery voltage U _Batt is measured and / or the measured value M which correlates with the plug temperature is measured. Alternatively, the temperature of the glow time control device 1 can be set. The outside air temperature is not necessarily directly acquired as a measurement value of the glow time control device 1. Therefore, as another option, the temperature inside the glow time control device 1 can be measured, or the outside air temperature can also be measured by an engine control device which is also arranged close to the internal combustion engine, for example LIN or The outside air temperature can be supplied from the engine control device to the glow time control device 1 by transfer via a communication data line such as a CAN bus. The plug temperature itself cannot be measured if no nominal current is supplied, and therefore cannot be obtained before the start of the glow process. Then, according to the evaluation of the measured values described above, the four glow plugs 9, 10, 11, 12 are all operated simultaneously to perform reliable preheating, or the number of glow plugs 9, 10, 11, 12 operated simultaneously is determined. A determination is made as to whether to reduce the on-current and to limit it.

In the following description, it is assumed that the diesel engine is provided with n cylinders and n glow plugs corresponding to the cylinders, and here, n = 4 is selected as an example. When the measured battery voltage U _Batt is above the first voltage threshold U _Battn and / or the measured value M correlated with the plug temperature is below the first temperature threshold T _n , n−1 glow plugs. The glow plugs 9, 10, 11, and 12 are controlled so that more glow plugs than 9, 11, and 12 are not supplied with power simultaneously. FIG. 3 shows the maximum total current l of the glow time control device 1 with respect to the battery voltage U _Batt . The relationship between the total current l of the glow time control device 1 and the battery voltage U _Batt is set for the case of the ceramic glow plugs 9, 10, 11, 12 having a plug resistance of about 200 mΩ and a low temperature of −40 ° C. ing.

The purpose here is to limit the total current consumption of the glow time control device 1 to a value smaller than 200 A so that the operation performance of the field effect transistors 2 and 3 is not restricted. The 4-channel operation 4K is allowed until 11.5 V which is the first voltage threshold U ₁ of the effective voltage U_eff. In this operation, all four glow plugs 9, 10, 11, and 12 are simultaneously supplied with a control signal that is pulse-width modulated with a 100% duty cycle. Until the second threshold value U ₂ of the effective voltage U_eff reaches 15 V, the glow time control device 1 is switched to the three-channel operation 3K. In this operation, only three glow plugs 9, 11, 12 are operated simultaneously, and the allowable duty cycle at this time is 75% of the maximum of the control signal. From 15V, which is the second threshold value U ₂ of the effective voltage U_eff, the glow time control device 1 is switched to the two-channel operation 2K. In this operation, the two glow plugs 9 and 10 are operated simultaneously, and the duty cycle of the pulse width modulated control signal is limited to a maximum of 50%.

In determining whether to operate the two glow plugs 9, 10 or the three glow plugs 9, 11, 12, the battery voltage U _Batt is higher than the first threshold U _Battn. or exceeds the _Battn-1, and / or the measured value M that is correlated with the plug temperature, or below the temperature threshold value T _n-1 of the lower second than the first temperature threshold value T _n, checks. If this condition is true, power is not supplied to more plugs than two plugs 9 and 11 simultaneously. Similarly, this method can be continued for the next voltage threshold U _Battn-m and temperature threshold T _nm .

FIG. 4 shows the characteristics of the effective voltage U_eff of the glow plugs 9, 10, 11, 12 with respect to the battery voltage U _Batt during the reliable preheating operation. This figure clearly shows the deviation ΔU_eff of the target effective voltage U_eff by applying the method according to the invention.

  For the purpose of minimizing the fluctuation of the total current consumption l of the glow time control device 1 with the passage of time, control synchronization for the glow plugs 9, 10, 11, and 12 is executed. In this case, when the first control channel of the glow plugs 9, 10, 11, 12 is cut off, the next control channel of the glow plugs 9, 10, 11, 12 is switched on in synchronization with the cutoff. .

  FIG. 5A shows a four-channel operation 4K of a control signal subjected to pulse width modulation of the glow plugs 9, 10, 11, and 12. For 4-channel operation 4K, the duty cycle is between 100% and 75% and all four glow plugs 9, 10, 11, 12 are activated simultaneously. Here, the characteristic curve F represents the total current l of the glow time control device 1 over one period, and power is supplied to all four glow plugs 9, 10, 11, 12 in the region F1. On the other hand, only three glow plugs 9, 11, 12 are operated in the region F2.

  FIG. 5B shows a three-channel operation 3K in which up to three glow plugs 9, 11, and 12 are operated simultaneously. In the case of 3 channel operation 3K, the duty cycle of the pulse width modulated control signal of the glow plugs 9, 11, 12 is 75% to 50%. Also in this figure, the total current l is represented by the characteristic curve F, the current flowing through the three plugs 9, 11, 12 is represented by the region F1, and the current flowing through the two plugs 9, 11 is represented by the region F2. Yes. In order to realize the two-channel operation 2K executed when the effective voltage U_eff is higher than 15V, the duty cycle is 50% to 25% as shown in FIG. 5C. In this operation, current flows through the two glow plugs 9 and 11 in the region F1, whereas what is represented by the region F2 is that only one glow plug 9 is supplied with power.

  Depending on the identified glow plug type being used, the method for limiting the current consumption of the glow time control device 1 may be cut off. If comprised in this way, when a metal plug is used, it can be made not to carry out electric current limitation, for example. This is because the current consumption of a metal glow plug is generally smaller than that of a ceramic glow plug at a critical or high risk low temperature. The operating period for limiting the current consumption can be terminated after a preset preheating period (for example, 100 ms) has elapsed, or the measured plug temperature (by measuring the resistance value of the plug depending on temperature) is a predetermined value. Or after the plug current measurement exceeds a predetermined value. The effective voltage U_eff can be reduced by applying the method described above. The deviation from the target effective voltage U_eff can be transmitted to the glow control unit of the glow time control device 1, whereby the glow control strategy can be matched according to the deviation. For example, the preheat phase period can be extended to reach a predetermined push energy.

Claims (13)

A predetermined number of glow plugs (9, 10, 11, 12) are controlled by a control signal derived from the operating voltage (U _Batt ) and pulse width modulated;
In a method for limiting the current consumption of a glow time control device,
The number of glow plugs (9, 10, 11, 12) operated simultaneously is reduced,
A method for limiting the current consumption of a glow time control device. The number of glow plugs (9, 10, 11, 12) operated simultaneously depends on the battery voltage (U _Batt ) and / or the plug temperature of the glow plugs (9, 10, 11, 12). Depending on the measured value (M) to be represented,
The method of claim 1. Reduction of the number of glow plugs (9, 10, 11, 12) to be operated simultaneously is performed during the preheating phase of the glow plugs (9, 10, 11, 12).
The method according to claim 1 or 2. Depending on the battery voltage (U _Batt ) and / or depending on the measured value (M) representing the plug temperature of the glow plug, the preheating phase of the glow plug (9, 10, 11, 12) Determining whether all the glow plugs (9, 10, 11, 12) are operated simultaneously or whether the number of glow plugs (9, 10, 11, 12) to be operated simultaneously is reduced;
The method of claim 3. In order to reduce the number of glow plugs (9, 10, 11, 12) operated simultaneously, the pulse width modulated control signals for the glow plugs (9, 10, 11, 12) are synchronized.
5. A method according to any one of claims 1 to 4. After the glow time control device (1) is switched on, the battery voltage (U _Batt ) is measured and / or the measured value (M representing the plug temperature of the n glow plugs (9, 10, 11, 12)). ) And represents the plug temperature of the n glow plugs (9, 10, 11, 12) when the battery voltage (U _Batt ) exceeds the first voltage threshold (U _Battn ) and / or When the measured value (M) falls below the first temperature threshold value (T _n ), more glow plugs than n−1 glow plugs (9, 10, 11, 12) are not supplied at the same time. The glow plug (9, 10, 11, 12) is controlled by pulse width modulation.
6. A method according to any one of claims 1 to 5. When the battery voltage (U _Batt ) exceeds an _mth voltage threshold (U _Battn-m ) higher than the first voltage threshold (U _Battn ) and / or n glow plugs (9, 9) If the measured value representing the plug temperature of 10, 11, 12) (M) falls below the first temperature threshold value (T _n) less than m-th temperature threshold value (T _nm), nm pieces The glow plugs (9, 10, 11, 12) are controlled by pulse width modulation so that a larger number of glow plugs than the other glow plugs (9, 10, 11, 12) are not fed simultaneously, provided that n> m Is,
The method of claim 6. As the glow plug (9, 10, 11, 12), a ceramic low voltage plug is used.
8. A method according to any one of claims 1 to 7. When a predetermined period of the preheating phase has elapsed, the reduction of the number of glow plugs (9, 10, 11, 12) to be simultaneously operated is terminated.
9. A method according to any one of claims 1 to 8. The measured value (M) representing the plug temperature of the glow plug (9, 10, 11, 12) exceeds a predetermined measured plug temperature, and / or the current plug current is a predetermined plug current. When the measured value falls below the value, the reduction of the number of glow plugs (9, 10, 11, 12) to be simultaneously operated is terminated.
9. A method according to any one of claims 1 to 8. Limiting the current consumption of the glow time control device (1);
11. A method according to any one of claims 1 to 10. A predetermined number of glow plugs (9, 10, 11, 12) are controlled by a pulse width modulated control signal derived from the operating voltage (U _Batt ),
In a glow time control device having a device for limiting current consumption,
Means are provided for reducing the number of glow plugs (9, 10, 11, 12) operated simultaneously,
Glow time control device. The current capacity of the glow time control device (1) is limited between the battery voltage input terminal and the power transistors (5, 6, 7, 8) for controlling the glow plug (9, 10, 11, 12). At least one polarity protection element (2, 3) is arranged,
The glow time control device according to claim 11.

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