JP5074448B2 - Fuel injection control device - Google Patents

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a fuel injection control device capable of improving the fuel injection amount accuracy and improving the dynamic range of the fuel injection amount.

  The internal combustion engine includes a fuel injection control device that performs an operation of converting an appropriate fuel amount corresponding to an operation state into an injection time of the fuel injection valve, and drives the fuel injection valve that supplies fuel over the injection time. Is provided. The fuel injection valve performs fuel injection by opening and closing a movable valve constituting the fuel injection valve by a magnetic force generated by a current flowing through the coil. The amount of fuel to be injected is determined mainly by the pressure difference between the fuel supply pressure and the ambient pressure around the nozzle nozzle of the fuel injection valve, and the time (period) during which fuel is injected while the valve body is kept open. Is done.

  In recent years, there has been a demand for a reduction in the idling speed of an internal combustion engine from the viewpoint of improving emissions and reducing fuel consumption. For this reason, the request | requirement regarding the reduction | decrease of the minimum injection amount which can be injected by the fuel injection valve is increasing.

  In addition, in order to reduce fuel consumption, there is an increased chance of performing a fuel cut that does not inject fuel when the output of the internal combustion engine is unnecessary, and thus the frequency of restarting fuel injection is also increasing. When resuming fuel injection, it is necessary to inject a small amount of fuel corresponding to no load. Further, split injection is performed for the purpose of increasing output and improving exhaust performance. Split injection is intended to improve the performance of an internal combustion engine by dividing the fuel that is originally required for one injection into multiple times and injecting it at an appropriate time. It is required to reduce the amount of fuel injection.

  In addition, in internal combustion engines, attempts have been made to reduce fuel consumption when the vehicle is mounted by downsizing the displacement. In this case, since the specific output is required to be improved by supercharging or the like, it is required to increase the maximum injection amount without increasing or decreasing the minimum injection amount. For this reason, the dynamic range (a value obtained by dividing the maximum injection amount by the minimum injection amount) required for the fuel injection valve tends to increase.

  In Patent Document 1, when the operating state of the internal combustion engine is an area in which the controllable minimum fuel injection amount characteristic (Qmin characteristic) is important, it is switched to one of the small holding currents among a plurality of different current waveforms. Thus, there is shown an injector control device that can optimally control the injector and maintain the minimum fuel injection amount characteristic even when the inductance of the solenoid of the injector is small.

Japanese Patent No. 4037632

  In order to accurately inject an appropriate amount of fuel from the fuel injection valve, it is necessary to stabilize the opening time and closing time of the movable valve of the fuel injection valve. However, the individual fuel injection valves have electromagnetic variations that are unavoidable in production, for example, variations in the resistance value, inductance value, and the like of the coil, and the resistance values vary depending on the environmental temperature.

  When the fuel injection valve is opened, this electromagnetic variation causes a variation in current rising characteristics and a variation in valve opening response of the movable valve, resulting in variations in the injection amount.

  Due to the variation in the injection amount, the Qmin characteristic cannot be reduced, the dynamic range is lowered, the emission characteristic is deteriorated, and the fuel consumption cannot be further reduced. If it is attempted to use a low injection amount forcibly, there is a concern of rebounding such as deterioration in driving performance.

  The method described in Patent Document 1 cannot sufficiently meet the demand for such fuel injection amount accuracy.

  The present invention has been made in view of such problems, and provides a fuel injection control device that can reduce variations in fuel injection amount and expand the dynamic range of a fuel injection valve.

  In order to solve the above problems, the present invention employs the following means.

  A fuel injection device having a solenoid; means for detecting an operating state of the internal combustion engine; and fuel injection control means for adjusting a pulse width of a fuel injection pulse supplied to the fuel injection device based on the detected operating state of the internal combustion engine. And the fuel injection control means supplies a valve opening current by supplying a high valve opening voltage to the solenoid by a predetermined high voltage valve opening period based on the fuel injection pulse width; and the predetermined high voltage After the voltage valve opening period ends, the solenoid includes a means for applying a low valve opening voltage to the solenoid and supplying a holding current for holding the valve open state to the solenoid, and the solenoid has a high voltage valve opening voltage. Is compared with a preset target value, and the high voltage valve opening voltage is set so that the peak value of the valve opening current coincides with the target value. The fee Back control.

  Since the present invention has the above-described configuration, it is possible to reduce the variation in the fuel injection amount and to expand the dynamic range of the fuel injection valve.

It is a figure explaining the fuel-injection control apparatus concerning embodiment. It is a figure explaining the structure of a fuel injection valve. It is a figure explaining the transition of the change of the voltage which flows into a fuel injection valve, an electric current, and a movable valve position. It is a figure explaining the transition of the change of the voltage which flows into a fuel injection valve, an electric current, and a movable valve position. It is a figure which shows the structure of a fuel-injection control apparatus.

  Hereinafter, embodiments will be described with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a fuel injection control device according to an embodiment. As shown in FIG. 1, the fuel injection control device 27 performs rotation, boost (intake pipe negative pressure), intake air amount, intake air temperature, water temperature, fuel, in order to perform optimal fuel injection adapted to the state of the engine. A sensor capable of detecting pressure or the like is provided, and a sensor value (measured value) detected by the sensor is taken into an ECU (Engine Control Unit) 19. The ECU 19 includes an injection amount calculation device that calculates an optimal injection amount based on the measurement values detected by each sensor, and an injection time calculation device that calculates an injection time based on the result of the calculation. Calculates the injection pulse width Ti.

  Corresponding to the calculated injection pulse width Ti, the injection valve control device 27 opens the valve by attracting the movable valve 7 of the fuel injection valve 1 with magnetic force. For this purpose, the fuel injection control device 27 applies, for example, a valve opening voltage VH over a predetermined energization time Th, and then applies a holding voltage VB that can supply a preset holding current value.

  At this time, when the valve opening voltage VH is applied with the valve opening voltage energization time Th set in advance for each fuel pressure condition, the peak current Ip obtained is detected and compared with the valve opening current target value Ipeak, and (1) Ip If> Ipeak, (VH is VH-Vr), and (2) if Ip <Ipeak, (VH is VH + Vr) [Vr: specified variable voltage unit], feedback control of the valve opening voltage VH is performed in advance. The valve opening voltage VH is controlled so that the valve opening current Ip becomes equal to the target peak current Ipeak during the energized time Th. Thereby, even in the fuel injection valve having variations in electromagnetic characteristics such as coil resistance, it is possible to make the rising characteristics of the valve opening current uniform.

  FIG. 2 is a view for explaining the structure of the fuel injection valve. The fuel injection valve 1 is supplied with pressurized fuel from a fuel pump (not shown). The fuel passage is opened and closed between the movable valve 7 and a valve seat surface (seat surface) 10 formed on the nozzle 3 side to control fuel injection from the orifice 11. The orifice 11 and the valve seat surface 10 are formed in the orifice plate 12.

  The movable valve 7 is attached to the tip of the plunger 6, and the fuel injection valve is provided with a coil 2 as means for generating a driving force on the movable valve 7. When the coil 2 is not energized and there is no suction force, a return spring 9 as a spring member is provided so as to close the valve 6 by pressing the plunger 6 and the movable valve 7 against the valve seat surface 10.

  When the coil 2 is energized, a magnetic flux is generated. The magnetic flux passes through the core 4, the yoke 5, and the plunger 6, and generates a magnetic attractive force between the core 4, the yoke 5, and the plunger 6. As a result, the plunger 6 and the movable valve 7 are displaced in a direction away from the valve seat surface 10 (upper side in the figure), and fuel is injected from the orifice 11.

  Usually, the movable valve 7 is pressed against the valve seat surface 10 by the return spring 9 and the fuel pressure. For this reason, in order to open the valve quickly, it is necessary to quickly generate a large electromagnetic force. For this reason, the supply voltage VH for valve opening is set higher than the battery voltage VB, and after opening the valve, the movable valve 7 is intermittently driven by the battery voltage VB so that a constant holding current value Ihold flows. Control.

  FIG. 3 is a diagram for explaining the transition of changes in the voltage, current, and movable valve position flowing through the fuel injector when the calculated injection pulse width Ti is sufficiently larger than the pulse width for generating the minimum control injection amount. is there. 3A shows the injection pulse Ti, FIG. 3B shows the injection valve drive voltage V, FIG. 3C shows the drive current I, and FIG. ) Indicates the position of the movable valve body of the fuel injection valve.

  Here, FIG. 5 is a diagram showing a configuration of the fuel injection control device. In FIG. 5, 50.51 and 52 are switching elements, and 56 is a fuel injection valve drive IC. As will be described later, the fuel injection valve drive IC 56 receives the injection pulse width Ti calculated by the ECU 19, drives the switching elements 50 and 52 for the Th time within the received injection pulse width Ti, and then intermittently drives the switching elements 51 and 52. .

  First, as shown in FIG. 3A, at time t0, the injection pulse Ti calculated by the injection amount calculation circuit and the injection pulse calculation circuit of the ECU 19 is transmitted to the drive IC 56. The drive IC 56 simultaneously turns on the switching elements 50 and 52 of the fuel injection control device 27 shown in FIG. 5 at the rising edge of the signal of the drive pulse Ti, and supplies the valve opening voltage VH shown in FIG. As shown in FIG. 3C, the fuel injection valve 53 is supplied with a valve opening current necessary for quick valve opening. At this time, a high voltage power supply VH is applied to the fuel injection valve 1 to supply a valve opening current. The solid line shows the current behavior of standard electromagnetic characteristics.

  As shown in FIG. 3C, when the current reaches the target value Ipeak at time t2 after Th time has elapsed from time t0, the driving IC 56 turns off the switching element 50. The target peak current Ipeak is 11 A, for example. At this time, the current supplied to the fuel injection valve circulates through the diode 59 and the coil 2 of the fuel injection valve, and the energy is dissipated as heat.

  When the current value reaches the second target value Ihold that can keep the fuel injection valve 1 open at the time point t3, the drive IC 56 turns on the switching elements 51 and 52 and switches the low voltage source VB to the fuel injection valve 1. Energize. At this time, the switching element 51 is turned on and off so that the current value is maintained at the second target value Ihold that can maintain the valve opening. For example, the second target value Ihold is 3A.

  At time t4, the supply of current to the fuel injection valve is stopped simultaneously with the fall of the signal of the drive pulse Ti.

  By the way, the opening and closing of the fuel injection valve are caused by the delay in the response of the current caused by the circuit inside the fuel injection control device 27 and the harness up to the fuel injection valve 1 and the response delay of the valve body with respect to the generated magnetic force. This is later than the times t0 and t4 when the injection control device 27 wants to truly open and close the valve.

  As shown in FIG. 3D, when the valve is opened, the movable valve 7 of the fuel injection valve 1 is completely moved to the open position (open) after the response delay time (t20-t0), and when the valve is closed, After the response delay time (t5-t4), the movable valve 7 of the fuel injection valve 1 is completely moved to the closed position (close). Here, the solid line shows the movable valve behavior with standard electromagnetic characteristics. Note that the area surrounded by the line representing the behavior of the movable valve can be regarded as the injection amount.

  FIG. 3 (C) shows the variation of the valve opening current due to electromagnetic variation, and FIG. 3 (D) shows the movable valve behavior of the fuel injection valve accompanying the variation of the valve opening current. Here, the long broken line shows the behavior when the coil resistance of the injection valve is small, and the short broken line shows the behavior when the coil resistance of the injection valve is large.

  When the resistance is small with respect to the peak current arrival point (Ipeak) and the movable valve behavior of the standard electromagnetic characteristics indicated by the solid line, the peak current value increases to Ip1, and the opening time of the movable valve is earlier. The valve opening completion time is also shortened. For this reason, the fuel injection amount varies in the increasing direction.

  Further, when the resistance is large, the peak current value is as low as Ip2, and since the valve opening start time is slow and the valve opening completion time is also slow, the fuel injection amount varies in the decreasing direction.

  That is, variation in electromagnetic characteristics causes variation in valve opening current rising characteristics, opening behavior of the movable valve, and hence fuel injection amount. For this reason, if the rising characteristics of the valve opening current can be matched, it is possible to reduce the variation in the injection amount.

  Here, the valve opening voltage V supplied to the coil 2 shown in FIG. 3 (B) is made variable, and the valve opening voltage V is feedback-controlled so that a peak current Ipeak is obtained when a specified time Th is applied. For example, in FIG. 3C, when Ip1> Ipeak, a predetermined voltage Vr is subtracted from the valve opening supply voltage VH to obtain VH = VH−Vr, until Ip1 = Ipeak. Repeat feedback control.

  When Ip1 <Ipeak, a specified voltage Vr is added to the valve opening supply voltage VH, VH = VH + Vr, and feedback control is repeatedly performed until Ip1 = Ipeak.

  Thus, when the injection pulse width Ti is a normal value (when the pulse width Ti is sufficiently larger than the pulse width for generating the minimum control injection amount), it is possible to reduce the injection amount variation. Note that when the feedback value of the valve opening voltage exceeds a certain threshold value, it is preferable to stop this processing because the device is in an abnormal state.

  By the way, in the area | region (minimum control injection quantity area | region) with short injection pulse width Ti, the influence degree of injection quantity dispersion | variation becomes large.

  FIG. 4 is a diagram for explaining the transition of changes in the voltage, current, and movable valve position flowing through the fuel injection valve in the region where the injection pulse width Ti is short.

  4A shows the injection pulse Ti, FIG. 4B shows the injection valve drive voltage V, FIG. 4C shows the current I, and FIG. D) shows the position of the movable valve body of the fuel injection valve.

  In the region of the minimum control injection amount in which the injection pulse Ti ends immediately before shifting to the holding current control by the low-voltage power supply VB, the current value at the position where the injection pulse has expired at time t4 in FIG. 4C varies. . For this reason, in addition to the variation in the behavior on the valve opening side of the movable valve in FIG. 4D, the behavior in the valve closing also varies.

  Regarding the behavior of the movable valve shown in FIG. 4D, when the current reaches Ip1 in FIG. 4C, the injection amount is shown as a trapezoidal area surrounded by (t11, t21, t31, t51), and FIG. When the current becomes Ip2 in (C), the injection amount is indicated by a trapezoidal area surrounded by (t12, t22, t32, t52).

  Thus, it can be seen that in the region where the injection pulse width Ti is short, the degree of influence of the variation in the rising characteristics of the valve opening current waveform on the injection amount is extremely increased. That is, the behavior of the movable valve can be matched by matching the rising characteristics of the valve opening current. Thereby, the injection amount variation and the minimum controllable injection region can be reduced, and the dynamic range can be expanded. The fuel injection control device can be arranged for each cylinder.

  As described above, according to the present embodiment, the valve opening current rising characteristic supplied to the fuel injection valve can be adjusted by controlling the supply voltage. For this reason, variation in the fuel injection amount can be reduced, and the dynamic range of the fuel injection valve can be expanded.

1 Fuel Injection Valve 2 Coil 3 Nozzle 4 Core 5 Yoke 6 Plunger 7 Movable Valve 8 Plunger Guide Member 9 Return Spring 10 Valve Seat Surface 11 Orifice 12 Orifice Plate 13 O-ring 14 Filter 15 Connector Mold 16 Adjuster 17 Spacer 19 ECU (Engine Control Unit)
50 to 52 Switching element 53 Fuel injection valve 54 ECU-drive IC communication line 55 Drive pulse transmission line 56 Fuel injection valve drive IC
58, 59 Diode 60 Current detection resistor

Claims (1)

A fuel injection device having a solenoid;
Means for detecting the operating state of the internal combustion engine;
Fuel injection control means for adjusting a pulse width of a fuel injection pulse supplied to the fuel injection device based on the detected operating state of the internal combustion engine,
The fuel injection control means supplies a valve opening current by supplying a high valve opening voltage to the solenoid according to a predetermined high voltage valve opening period based on the fuel injection pulse width;
Means for supplying a solenoid with a holding current for applying a low valve opening voltage to the solenoid to maintain the valve open state after the predetermined high voltage valve opening period is completed ;
The peak value of the valve opening current when a high valve opening voltage is supplied to the solenoid for the predetermined high voltage valve opening period is compared with a preset target value, and the peak value of the valve opening current matches the target value. As described above, a fuel injection control device for an internal combustion engine, which performs feedback control of the high valve opening voltage.

Images