JP2012246879A - Fuel injection valve drive control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection valve drive control device capable of effectively suppressing the generation of a high-rising current caused by a holding current resulting from the remaining energy of a fuel injection valve after a current supplied to the fuel injection valve is sharply lowered to the holding current from a peak current.SOLUTION: When a supply current 20B reaches Ip, all of first, second and third switching elements 2, 4 and 6 are turned off, the supply current is sharply lowered to a holding-current lower limit threshold L, and when the supply current is lowered to value lower than the holding-current lower limit threshold L, the holding current 20B is raised by carrying electricity to the second and third switching elements 4, 6 while turning off the first switching element 2. After that, when the supply current reaches a holding-current upper limit threshold H, the first and second switching elements 2, 4 are turned off, and when the supply current 20B exceeds the holding-current upper limit threshold H even if peak post-processing for lowering the supply current 20B is performed by carrying electricity to the third switching element 6, the third switching element 6 is turned off until the supply current 20B is lowered to the holding-current lower limit threshold L.

Description

  The present invention relates to a fuel injection valve drive control device used in a fuel supply system of an automobile.

  In the technical field of automobile engines, in-cylinder injection engines that inject fuel directly into the cylinder (combustion chamber) have been put into practical use. In this in-cylinder engine, improvement of exhaust emission characteristics and fuel consumption due to lean combustion are particularly problematic.

  A conventional control device for controlling a direct injection type fuel injection valve in a cylinder is provided with a booster circuit that boosts the voltage to a voltage higher than the battery voltage, and the booster voltage generated by the booster circuit supplies the fuel injector in a short time. Many employ a method of increasing the current.

  A typical current waveform uses a boosted voltage during a peak current energization period in the initial energization, and raises the fuel injection valve supply current to a predetermined peak current in a short time. This peak current is about 5 to 20 times larger than the fuel injection valve supply current of the method of injecting into the intake port.

  After the energization period of the peak current ends, the energy supply source to the fuel injection valve shifts from the boosted voltage to the battery power source. Through the first holding current controlled by the first holding / stopping current of about 1/2 to 1/3 of the peak current, and further with the second holding / stopping current of about 2/3 to 1/2 Transition to the controlled second holding current. The fuel injection valve is opened by the peak current and the first holding current, and the fuel is injected into the cylinder.

  At the end of injection, in order to quickly close the fuel injection valve, it is necessary to sharply drop the current supplied (energized) to the fuel injection valve (hereinafter referred to as supply current) and to cut off the supply current. .

  As described above, since a large amount of energy is required to drive the fuel injection valve, various drive current patterns exist in order to suppress heat generation of the fuel injection valve and its drive circuit.

  For example, as described in Patent Document 1, when switching from the peak current to the holding current, the current is sharply lowered to change to the holding current, or the switching current is slowly switched from the peak current to the first holding current. When the combination is changed, such as a pattern in which the current is sharply lowered and switched from the first holding current to the second holding current, there are a great many patterns.

JP 2010-106847 A

  Here, when driving with the fuel injection valve driving current pattern as described in Patent Document 1, immediately after the sharp change from the peak current to the holding current, due to the residual energy of the fuel injection valve, the target holding current A rising swell current is generated.

  In this way, the rising current generated immediately after the supply current sharply falls from the peak current to the holding current varies due to various factors such as battery voltage and ambient temperature, so the current flowing through the fuel injection valve becomes unstable, This also affects the injection characteristics of the fuel injection valve.

  For example, in a region where the fuel injection amount is small near the idle, the injection time is such that the fuel injection valve is closed immediately after switching from the peak current to the holding current. At this time, if the current flowing through the fuel injection valve becomes unstable due to the residual energy of the fuel injection valve, the time required to close the valve also varies in proportion thereto, so the fuel injection amount varies accordingly.

  That is, assuming that the injection time of the fuel injection valve is Ti and the variation in time required for closing the valve is ΔTc, the variation in the fuel injection amount can be expressed as ΔTc / Ti, and the variation in the closing time ΔTc when the fuel injection valve injection time Ti is increased. However, when Ti becomes small, the influence of valve closing variation ΔTc becomes large.

  Further, in the region where the fuel injection valve injection time Ti is small, the current flowing through the fuel injection valve becomes unstable due to the residual energy of the fuel injection valve, so that the valve closing variation ΔTc increases and the fuel injection amount variation further increases.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to reduce the residual energy of the fuel injection valve after the current supplied to the fuel injection valve has sharply dropped from the peak current to the holding current. Accordingly, it is an object of the present invention to provide a fuel injection valve drive control device capable of effectively suppressing the occurrence of a rising current higher than the holding current.

  In order to achieve the above object, the fuel injection valve drive control device according to the present invention basically includes a booster voltage obtained by boosting the battery voltage so that a current flows through the fuel injector. A first switching element arranged on the side, a second switching element arranged on the upstream side of the fuel injection valve in order to flow a current to the fuel injection valve using the battery voltage, A third switching element disposed on the downstream side of the fuel injection valve in order to control a current flowing through the fuel injection valve; and when the current supplied to the fuel injection valve reaches a peak current threshold When all of the first, second, and third switching elements are cut off, the supply current is sharply lowered to the holding current lower limit threshold, and the supply current falls below the holding current lower limit threshold, the first 1 switching element The second and third switching elements are energized while shutting off, and the supply current is increased. Thereafter, when the supply current reaches the holding current upper limit threshold, the first and second switching elements are shut off. In addition, if the third switching element is energized to perform the peak post-processing to decrease the supply current, and the supply current exceeds the holding current upper limit threshold even after the peak post-processing is performed The third switching element is cut off until the supply current falls to the holding current lower limit threshold value.

In the fuel injection valve drive control device according to the present invention, the swell current generated due to the residual energy of the fuel injection valve is effectively suppressed by changing the current control processing content without changing the conventional circuit configuration. be able to. Therefore, variation in the fuel injection amount can be suppressed, the fuel injection amount control accuracy can be maintained high, and the cost effectiveness is excellent.
Problems, configurations, and effects other than those described above will be clarified by the following embodiments.

The circuit block diagram of one Embodiment (1st Example, 2nd Example, and a prior art example) of the fuel injection valve drive control apparatus which concerns on this invention. The time chart which shows changes, such as a fuel injection valve supply current by the conventional electric current control. The time chart which shows the change of the fuel injection valve supply current etc. by the current control of 1st Example of this invention. The time chart which shows changes of fuel injection valve supply current etc. by current control of the 2nd example of the present invention.

  FIG. 1 is a circuit configuration diagram of one embodiment (first embodiment, second embodiment, and conventional example) of a fuel injection valve drive control device according to the present invention, and corresponds to one cylinder of a fuel injection device for an automobile. The circuit is shown. Although the illustrated circuit configuration itself is the same as the conventional one, the contents of the current control processing are different between the embodiment of the present invention and the conventional example.

  The fuel injection valve drive circuit shown in FIG. 1 supplies the fuel injection valve drive current 20B to the battery 1, the fuel injection valve 20, the booster circuit 100 that generates the high voltage 100A from the battery voltage 1A, and the fuel injection valve 20. The fuel injection valve energizing circuit 200 is provided.

  The fuel injection valve energization circuit 200 includes an FET 2 (first switching element) that applies a high voltage 100A to the fuel injection valve 20, a diode 3 for preventing a current backflow to the FET 2, and a battery voltage 1A to the fuel injection valve 20. FET 4 (second switching element) to be applied, diode 5 for preventing current backflow to FET 4, downstream FET 6 (third switching element) of fuel injection valve supply current 20B, and current 6B flowing through FET 6 are detected. A resistor 7 that recirculates the fuel injection valve supply current 20B, a diode 8 that regenerates the fuel injection valve supply current 20B to the booster circuit when the FET 6 is shut off, and a resistor 10 that detects the current during regeneration. , An output signal processing circuit 201 for generating a fuel injection pulse (output signal) 201A for driving the fuel injection valve 20, and fuel supplied It includes elevation pulse gate signals 2A on the basis of the (output signal) 201A, 4A, and a gate control circuit 202 for generating 6A.

Hereinafter, the operation of the fuel injection valve drive circuit configured as described above will be described.
FIG. 2 shows (A) fuel injection pulse 201A, (B) current supplied to the fuel injection valve (sometimes abbreviated as supply current) 20B, and (C) upstream side of the fuel injection valve by conventional current control. It is a time chart which shows change of voltage 20A and (D) fuel injection valve downstream side voltage 20C.

  When the fuel injection pulse 201A changes from Low to High (time t1), in order to flow the peak current to the fuel injection valve 20, the FET 2 and FET 6 are turned on (energized), and the high voltage 100A is applied to the fuel injection valve 20, The supply current 20B starts to flow.

  When the supply current 20B reaches Ip (peak current threshold) (time point t2), the FET2, FET4, and FET6 are turned off (cut off) to cut off the energy to the fuel injection valve 20, and the supply current 20B falls sharply. At this time, a back electromotive force is generated from the fuel injection valve 20, and the back electromotive force is regenerated to the booster circuit 100 via the diode 8. During this time, the supply current 20B is monitored using the resistor 10, and the FET2, FET4, and FET6 are kept OFF until the holding current L (holding current lower limit threshold) is reached.

  When the fuel injection valve supply current 20B reaches the holding current L (time t3), the FET 4 and FET 6 are turned on, and the battery voltage 1A is applied to the fuel injection valve 20 to increase the fuel injection valve supply current 20B. At this time, since the fuel injector 20 has residual energy, the fuel injector supply current 20B rapidly increases.

  When the fuel injection valve supply current 20B increases and reaches the holding current H (holding current upper limit threshold value), the FET 4 is turned off, the FET 6 is kept on, the current is recirculated through the diode 9 and the fuel injection valve supply current is lowered. Let However, since there is residual energy in the fuel injection valve 20, the current increases without decreasing (time t3-t4).

  When the residual energy is consumed, the fuel injection valve supply current 20B decreases, and when the holding current L is reached, the FET 4 is turned on, and the battery voltage 1A is applied to the fuel injection valve 20 to increase the fuel injection valve supply current 20B. At this time, since there is no residual energy in the fuel injection valve 20, the fuel injection valve supply current 20B rises slowly.

  The above operation is repeated until the fuel injection pulse 201A switches from High to Low (time t7). When the fuel injection pulse 201A switches from High to Low, the FET2, FET4, and FET6 are turned off. The back electromotive force of the fuel injection valve 20 generated at this time is regenerated to the booster circuit 100 via the diode 8, and the fuel injection valve supply current 20B falls sharply.

<First embodiment>
FIG. 3 shows (A) the fuel injection pulse 201A, (B) the current 20B supplied to the fuel injection valve, (C) the fuel injection valve upstream voltage 20A, and the current control according to the current control of the first embodiment of the present invention. (D) It is a time chart which shows the change of the fuel injection valve downstream voltage 20C.

  When the fuel injection pulse 201A changes from Low to High (time point t1), the FET 2 and the FET 6 are turned on to apply a high voltage 100A to the fuel injection valve 20 in order to flow the peak current to the fuel injection valve 20, and the fuel injection valve The supply current 20B starts to flow.

  When the supply current 20B reaches Ip, the FET2, FET4, and FET6 are turned off, the energy to the fuel injection valve 20 is cut off, and the fuel injection valve supply current 20B falls sharply (time t2). At this time, a back electromotive force is generated from the fuel injection valve 20, and the back electromotive force is regenerated to the booster circuit 100 via the diode 8. During this time, the fuel injection valve supply current 20B is monitored using the resistor 10, and the FET2, FET4, and FET6 are kept OFF until the holding current L (holding current lower limit threshold) is reached.

  When the supply current 20B reaches the holding current L (time point t3), the FET 4 and FET 6 are turned on, and the battery voltage 1A is applied to the fuel injection valve 20 to increase the supply current 20B. At this time, since the fuel injection valve 20 has residual energy, the supply current 20B rapidly increases.

  When the supply current 20B increases and reaches the holding current H (holding current upper limit threshold) (time t4), the FET 4 is turned off, the FET 6 is kept on, the current is circulated through the diode 9 and the fuel injection valve supply current is reduced. Reduce. However, the fuel injection valve 20 has residual energy, and the current increases without decreasing.

  Therefore, the following peak post-processing is performed. That is, when the fuel injection valve supply current 20B increased by the residual energy of the fuel injection valve 20 reaches the holding current HH (holding current limit value) set higher than the holding current H (holding current upper limit threshold) (time point t5). By turning off FET2, FET4, and FET6, the residual energy is regenerated to the booster circuit 100 via the diode 8. During this time, the fuel injection valve supply current 20B is monitored using the resistor 10, and the FET2, FET4, and FET6 are kept OFF until the holding current L is reached.

  When the supply current 20B reaches the holding current L, the FET 4 and FET 6 are turned on, and the battery voltage 1A is applied to the fuel injection valve 20 to increase the fuel injection valve supply current 20B.

  When the supply current 20B increases and reaches the holding current H, the FET 4 is turned off, the FET 6 is kept on, the current is recirculated through the diode 9 and the fuel injection valve supply current is lowered.

  The above operation is repeated until the fuel injection pulse 201A switches from High to Low, and when the fuel injection pulse 201A switches from High to Low (time t7), the FET2, FET4, and FET6 are turned off. The back electromotive force of the fuel injection valve 20 generated at this time is regenerated to the booster circuit 100 via D8, and the fuel injection valve supply current 20B falls sharply.

<Second embodiment>
FIG. 4 shows (A) the fuel injection pulse 201A, (B) the current 20B supplied to the fuel injection valve, (C) the fuel injection valve upstream voltage 20A, and the current control according to the current control of the second embodiment of the present invention. (D) It is a time chart which shows the change of the fuel injection valve downstream voltage 20C.

  When the fuel injection pulse 201A changes from Low to High (time point t1), the FET 2 and the FET 6 are turned on to apply a high voltage 100A to the fuel injection valve 20 in order to flow the peak current to the fuel injection valve 20, and the fuel injection valve The supply current 20B starts to flow.

  When the supply current 20B reaches Ip, the FET2, FET4, and FET6 are turned off, the energy to the fuel injection valve 20 is cut off, and the fuel injection valve supply current 20B falls sharply (time t2). At this time, a back electromotive force is generated from the fuel injection valve 20, and the back electromotive force is regenerated to the booster circuit 100 via the diode 8. During this time, the fuel injection valve supply current 20B is monitored using the resistor 10, and the FET2, FET4, and FET6 are kept OFF until the holding current L (holding current lower limit threshold) is reached.

  When the fuel injection valve supply current 20B reaches the holding current L (t3), the FET 4 and FET 6 are turned on, and the battery voltage 1A is applied to the fuel injection valve 20 to increase the fuel injection valve supply current 20B. At this time, since there is residual energy in the fuel injection valve 20, the fuel injection valve supply current 20B increases rapidly.

  When the supply current 20B increases and reaches the holding current H (holding current upper limit threshold) (time t4), the FET 4 is turned off, the FET 6 remains on, the current is recirculated through the diode 9, and the fuel injection valve supply current Reduce. However, the fuel injection valve 20 has residual energy, and the current increases without decreasing.

  Therefore, the following peak post-processing is performed. That is, when a predetermined time (holding current limit time Ta = period from time t4 to time t5) elapses when the supply current 20B increased by the residual energy of the fuel injection valve 20 exceeds the holding current H, FET2, FET4, FET6 Is turned off, and the residual energy is regenerated to the booster circuit 100 via the diode 8. During this time, the supply current 20B is monitored using the resistor 10, and the FET2, FET4, and FET6 are kept OFF until the holding current L is reached.

  When the fuel injection valve supply current 20B reaches the holding current L, the FET 4 and FET 6 are turned on, and the battery voltage 1A is applied to the fuel injection valve 20 to increase the fuel injection valve supply current 20B.

When the supply current 20B increases and reaches the holding current H, the FET 4 is turned off, the FET 6 remains on, the current is recirculated through D9, and the fuel injection valve supply current is lowered.
The above operation is repeated until the fuel injection pulse 201A switches from High to Low (time t7). When the fuel injection pulse 201A switches from High to Low, the FET2, FET4, and FET6 are turned off. The back electromotive force of the fuel injection valve 20 generated at this time is regenerated to the booster circuit 100 via D8, and the fuel injection valve supply current 20B falls sharply.

  As can be understood from the above description, in the embodiment of the present invention, the swell current generated due to the residual energy of the fuel injection valve is changed by changing the current control processing content without changing the conventional circuit configuration. It can be effectively suppressed. Therefore, variation in the fuel injection amount can be suppressed, the fuel injection amount control accuracy can be maintained high, and the cost effectiveness is excellent.

  DESCRIPTION OF SYMBOLS 1 ... Battery, 1A ... Battery voltage, 2 ... High voltage application FET (1st switching element), 2A, 4A, 6A ... Gate signal, 3 ... Backflow prevention diode, 4 ... FET for battery voltage application (second switching element), 5 ... Backflow prevention diode, 6 ... Downstream side FET (third switching element), 6B ... Current flow, 7 ... Current detection resistor, 8 ... regenerative diode, 9 ... recirculation diode, 20 ... fuel injection valve, 20B ... fuel injection valve supply current, 100A ... high voltage, 100 ... booster circuit, DESCRIPTION OF SYMBOLS 200 ... Fuel injection valve electricity supply circuit, 201 ... Output signal processing circuit, 201A ... Fuel injection pulse, 202 ... Gate control circuit, Ip ... Peak current threshold value, L ... Holding current ( Holding current lower threshold) ... holding current (holding current upper threshold), HH ... holding current limit value, Ta ... holding current limit time

Claims (3)

In order to flow a current to the fuel injection valve using the boosted voltage obtained by boosting the battery voltage, the first switching element disposed on the upstream side of the fuel injection valve and the fuel injection valve using the battery voltage A second switching element disposed on the upstream side of the fuel injection valve in order to flow an electric current; and a second switching element disposed on the downstream side of the fuel injection valve in order to control the current flowing in the fuel injection valve. A third switching element, and when the current supplied to the fuel injection valve reaches a peak current threshold, all of the first, second, and third switching elements are cut off to supply the supply current. When the supply current drops below the holding current lower limit threshold, the second and third switching elements are energized while the first switching element is cut off, and the supply current is reduced. After that, when the supply current reaches the holding current upper limit threshold, the first and second switching elements are shut off, and the third switching element is energized to decrease the supply current. A fuel injection valve drive control device configured to perform
If the supply current exceeds the holding current upper limit threshold even after the peak post-processing, the third switching element is shut off until the supply current falls to the holding current lower limit threshold. Fuel injection valve drive control device.   If the supply current exceeds the holding current limit value set higher than the holding current upper limit threshold even after the peak post-processing, all of the first, second and third switching elements are cut off. The fuel injection valve drive control device according to claim 1, wherein the supply current is reduced.   If the supply current exceeds the holding current upper limit threshold for a predetermined time or more even after the peak post-processing, all of the first, second, and third switching elements are shut off, and the supply current is reduced. The fuel injection valve drive control device according to claim 1, wherein the fuel injection valve drive control device is lowered.

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