JP2011163156A - Fuel injection control device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device capable of controlling a fuel injection amount at high accuracy by significantly reducing a minimum injection amount without changing a structure of a solenoid valve (fuel injection valve). <P>SOLUTION: This fuel injection control device for controlling a fuel injection valve comprises energization control means for estimating a lift amount after energization of the fuel injection valve starts, and completing energization of the fuel injection valve when the lift amount reaches a required lift amount. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

 The present invention relates to a fuel injection control apparatus and method.

  In order to deal with engine controllability and emissions, it is one of the items to be considered that the fuel injection amount is finely controlled. One technique for reducing the minimum injection amount in order to finely control the fuel injection amount is to reduce the bounce (plunger bounce phenomenon) of the electromagnetic valve used as the fuel injection valve. Generally, since the period from the start of energization of the solenoid valve until the rise bounce is stabilized is set as the minimum fuel injection period, reducing the bounce directly leads to a reduction in the minimum injection amount. Controllability of the fuel injection amount can be improved. For this reason, techniques for reducing bounce have been developed in the past by improving the structure of the solenoid valve and improving the control method.

 In the following Patent Document 1, as a technique for reducing bounce by structural improvement of a solenoid valve, an annular recess is formed at a position corresponding to a coil of the fixed core on the surface of a movable core (plunger) facing the fixed core of the solenoid valve. A technique for increasing the volume of the space formed between the movable iron core and the fixed iron core is disclosed. Further, in Patent Document 2 below, as a technique for reducing bounce by improving the control method of the electromagnetic valve, after a predetermined level of suction current is passed through the coil of the solenoid valve, the current is once reduced to zero or lower than the suction current. There is disclosed a technique for switching to a current whose level is temporarily higher than the holding current immediately before the switching and the plunger collides with the stopper.

JP 2002-168362 A Japanese Patent Publication No. 3-7834

 With the technique of the said patent document 1, the rise in manufacturing cost accompanying the complexity of a solenoid valve structure will be caused. Further, since the technique of Patent Document 2 is intended to reduce bounce after the valve opening operation (after the full lift of the plunger), the minimum injection period shorter than the valve opening period cannot be obtained, and the reduction of the minimum injection amount is not possible. Have difficulty.

   The present invention has been made in view of the above-described circumstances, and achieves a significant reduction in the minimum injection amount without changing the structure of the electromagnetic valve (fuel injection valve). It is an object of the present invention to provide a fuel injection control device and method capable of realizing control.

 In order to achieve the above object, a fuel injection control device according to the present invention is a fuel injection control device that controls a fuel injection valve, and estimates a lift amount after energization of the fuel injection valve is started, and the lift amount Is provided with energization control means for terminating energization of the fuel injection valve when the required lift amount is reached.

In the fuel injection control device according to the present invention, the energization control means estimates the lift amount based on an inductance of the fuel injection valve.
In the fuel injection control device according to the present invention, the fuel injection control device further includes storage means for previously storing a correspondence relationship between the inductance and the lift amount, and the energization control means uses the correspondence relationship between the inductance and the lift amount. The lift amount corresponding to the calculated value of the inductance is obtained.
In the fuel injection control device according to the present invention, the fuel injection control device further includes a current measurement unit that measures a drive current flowing through the fuel injection valve, and the energization control unit acquires the current measurement unit from the current measurement unit at regular intervals after the energization is started. A change amount of the drive current is calculated using a measured value of the drive current, and the inductance is calculated based on the change amount of the drive current.
In the fuel injection control device according to the present invention, the energization control means estimates the lift amount based on at least one of a lift speed and a lift acceleration of the fuel injection valve.

  On the other hand, the fuel injection control method according to the present invention estimates the lift amount after the start of energization of the fuel injection valve, and ends energization of the fuel injection valve when the lift amount reaches the required lift amount. And

  In the present invention, the lift amount after the start of energization of the fuel injection valve is estimated, and when the lift amount reaches the required lift amount, the energization of the fuel injection valve is terminated, whereby the fuel injection valve is being opened. It is possible to switch to the valve closing operation at an arbitrary timing. As a result, the minimum injection amount can be greatly reduced, and as a result, highly accurate control of the fuel injection amount can be realized. Further, in the present invention, it is not necessary to make structural improvements to the fuel injection valve for the purpose of reducing bounce in order to reduce the minimum injection amount, which leads to a reduction in manufacturing cost.

1 is a schematic configuration diagram of an engine control system in the present embodiment. It is a block block diagram of the fuel-injection control apparatus (ECU3) in this embodiment. It is a flowchart showing the operation | movement regarding the fuel-injection control in this embodiment. 6 is a time chart showing a temporal relationship among a drive voltage V applied to a solenoid coil 22a, a drive current I flowing through the solenoid coil 22a, and a plunger lift amount X after the energization of the injector 22 is started. It is an example of the LX conversion map showing the correspondence of the inductance L of the injector 22 (solenoid coil 22a) and the lift amount X of a plunger in this embodiment. It is a 1st flowchart showing the operation | movement regarding the fuel-injection control in a modification. It is a 2nd flowchart showing the operation | movement regarding the fuel-injection control in a modification. It is supplementary explanatory drawing regarding a modification.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an engine control system including a fuel injection control device (ECU) in the present embodiment. As shown in FIG. 1, the engine control system in the present embodiment is schematically configured from an engine 1, a fuel supply unit 2, and an ECU (Electronic Control Unit) 3.

   The engine 1 is a four-cycle engine, and includes a cylinder 10, a piston 11, a connecting rod 12, a crankshaft 13, an intake valve 14, an exhaust valve 15, an ignition plug 16, an ignition coil 17, an intake pipe 18, an exhaust pipe 19, an air cleaner 20, A throttle valve 21, an injector (fuel injection valve) 22, an intake pressure sensor 23, an intake air temperature sensor 24, a throttle opening sensor 25, a coolant temperature sensor 26, and a crank angle sensor 27 are roughly configured.

   The cylinder 10 is a hollow cylindrical member for reciprocating the piston 11 provided therein by repeating four strokes of intake, compression, combustion (expansion), and exhaust, and is a mixture of air and fuel. Intake port 10a that is a flow path for supplying the combustion chamber 10b to the combustion chamber 10b, the air-fuel mixture is stopped, the combustion chamber 10b that is a space for burning the air-fuel mixture compressed in the compression stroke in the combustion stroke, and combustion in the exhaust stroke An exhaust port 10c, which is a flow path for exhausting exhaust gas from the chamber 10b to the outside, is provided. Further, a cooling water passage 10 d for circulating the cooling water is provided on the outer wall of the cylinder 10.

   A crankshaft 13 for converting the reciprocating motion of the piston 11 into a rotational motion is connected to the piston 11 via a connecting rod 12. The crankshaft 13 extends in a direction orthogonal to the reciprocating direction of the piston 11 and is connected to a flywheel, a transmission gear, etc. (not shown). The crankshaft 13 is coaxially connected with a rotor 13a used for detecting a crank angle. A plurality of protrusions are provided on the outer periphery of the rotor 13a so that the rear ends of the protrusions are equiangularly spaced (for example, 20 ° apart) with respect to the rotation direction.

   The intake valve 14 is a valve member for opening and closing an opening on the combustion chamber 10b side in the intake port 10a, and is connected to a camshaft (not shown) and is driven to open and close by the camshaft according to each stroke. . The exhaust valve 15 is a valve member for opening and closing the opening on the combustion chamber 10b side in the exhaust port 10c, and is connected to a camshaft (not shown) and is driven to open and close by the camshaft according to each stroke. .

   The spark plug 16 is installed in the upper part of the combustion chamber 10b so that the electrode is exposed inside the combustion chamber 10b, and generates a spark between the electrodes by a high voltage signal supplied from the ignition coil 17. The ignition coil 17 is a transformer composed of a primary winding and a secondary winding, boosts an ignition voltage signal supplied from the ECU 3 to the primary winding, and supplies the boosted voltage signal to the ignition plug 16 from the secondary winding.

  The intake pipe 18 is a pipe for supplying air, and is connected to the cylinder 10 so that the internal intake flow path 18a communicates with the intake port 10a. The exhaust pipe 19 is a pipe for exhaust gas discharge, and is connected to the cylinder 10 so that the internal exhaust passage 19a communicates with the exhaust port 10c. The air cleaner 20 is provided on the upstream side of the intake pipe 18, cleans the air taken in from the outside, and sends it to the intake passage 18a.

 The throttle valve 21 is provided inside the intake passage 18a, and rotates according to a throttle operation (or an accelerator operation). That is, as the throttle valve 21 rotates, the cross-sectional area of the intake passage 18a changes, and the intake air amount changes. The injector 22 is an electromagnetic valve (for example, a solenoid valve) installed in the intake pipe 18 so that the injection port is exposed to the intake port 10a side, and is supplied from the fuel supply unit 2 in accordance with energization control by the ECU 3. Fuel is injected from the injection port. Specifically, the injector 22 injects fuel by performing a valve opening operation and a valve closing operation in accordance with a drive pulse signal supplied from the ECU 3. That is, the fuel injection amount is controlled by the energization time (pulse width) of the drive pulse signal supplied from the ECU 3 to the injector 22.

  The intake pressure sensor 23 is a semiconductor pressure sensor using, for example, a piezoresistive effect, and is installed in the intake pipe 18 so that the sensitivity surface is exposed on the intake flow path 18a side on the downstream side of the throttle valve 21, and the intake pipe An intake pressure signal corresponding to the intake pressure in the engine 18 is output to the ECU 3. The intake air temperature sensor 24 is installed in the intake pipe 18 so that the sensitive portion is exposed on the intake flow path 18a side upstream of the throttle valve 21, and an intake air temperature signal corresponding to the intake air temperature in the intake pipe 18 is sent to the ECU 3. Output to. The throttle opening sensor 25 outputs a throttle opening signal corresponding to the opening of the throttle valve 21 to the ECU 3.

 The cooling water temperature sensor 26 is installed in the cylinder 10 so that the sensitive part is exposed to the cooling water passage 10d side, and outputs a cooling water temperature signal corresponding to the temperature of the cooling water flowing through the cooling water passage 10d to the ECU 3. The crank angle sensor 27 is, for example, an electromagnetic pickup sensor, and outputs a pair of pulse signals having different polarities to the ECU 3 each time each protrusion provided on the outer periphery of the rotor 13a passes in the vicinity of the sensor. More specifically, the crank angle sensor 27 outputs a pulse signal having a negative amplitude when the front end of each protrusion passes in the rotation direction, and the rear end of each protrusion in the rotation direction. When it passes, it outputs a pulse signal having a positive amplitude.

   The fuel supply unit 2 includes a fuel tank 30 and a fuel pump 31. The fuel tank 30 is a container for storing fuel such as gasoline fuel or alcohol fuel. The fuel pump 31 is provided in the fuel tank 30, and pumps out the fuel in the fuel tank 30 in accordance with a pump drive signal input from the ECU 3 and pumps it to the injector 22.

 The ECU 3 controls the overall operation of the engine control system. As shown in FIG. 2, the ECU 3 controls the waveform shaping circuit 40, the rotation speed counter 41, the A / D converter 42, the ignition circuit 43, the injector drive circuit 44, A pump drive circuit 45, a ROM (Read Only Memory) 46, a RAM (Random Access Memory) 47, a timer 48, and a CPU (Central Processing Unit) 49 are provided. The injector drive circuit 44 and the CPU 49 described above constitute the energization control means in this embodiment.

   The waveform shaping circuit 40 converts the crank signal input from the crank angle sensor 27 into a square-wave pulse signal (for example, a negative crank signal is set to a high level and a positive polarity signal and a ground level crank signal are set to a low level). The waveform is shaped and output to the rotation number counter 41 and the CPU 49. That is, this square-wave pulse signal is a signal whose period is the time required for the crankshaft 13 to rotate 20 °. Hereinafter, the square-wave pulse signal output from the waveform shaping circuit 40 is referred to as a crank pulse signal.

 The rotation speed counter 41 calculates the engine rotation speed based on the crank pulse signal input from the waveform shaping circuit 40 and outputs the calculation result to the CPU 49. The A / D converter 42 includes an intake pressure signal input from the intake pressure sensor 23, an intake air temperature signal input from the intake air temperature sensor 24, a throttle opening signal input from the throttle opening sensor 25, and a cooling water temperature sensor. The cooling water temperature signal input from 26 is converted into a digital signal (intake pressure value, intake air temperature value, throttle opening value, cooling water temperature value) and output to the CPU 49.

   The ignition circuit 43 includes a capacitor for accumulating a power supply voltage supplied from a battery (not shown), and in accordance with an ignition control signal input from the CPU 49, the electric charge accumulated in the capacitor is used as an ignition voltage signal for the ignition coil 17. Discharge to the primary winding. The injector drive circuit 44 is electrically connected to the solenoid coil 22a of the injector 22, and generates a drive voltage V in response to an energization start signal input from the CPU 49 and applies it to the solenoid coil 22a (starts energization). On the other hand, in response to the energization end signal input from the CPU 49, the generation of the drive voltage V is stopped (the energization is terminated), thereby generating a drive pulse signal to be supplied to the injector 22.

 The injector drive circuit 44 includes a current measurement circuit 44 a that measures the drive current I flowing through the solenoid coil 22 a by applying the drive voltage V and outputs the measured value to the CPU 49. The pump drive circuit 45 generates a pump drive signal for driving the fuel pump 31 according to the fuel supply control signal input from the CPU 49, and outputs the pump drive signal to the fuel pump 31.

 The ROM 46 is a non-volatile memory that stores in advance an engine control program for realizing various functions of the CPU 49 and various setting data. The ROM 46 stores an L-X conversion map (see FIG. 5) representing a correspondence relationship between the inductance L of the injector 22 (solenoid coil 22a) and the lift amount X of the plunger, which has been experimentally obtained in advance. ing. The RAM 47 is a volatile working memory that is used as a temporary data storage destination when the CPU 49 executes an engine control program and performs various operations. The timer 48 counts time under the control of the CPU 49 and outputs the result to the CPU 49.

   In accordance with the engine control program stored in the ROM 46, the CPU 49 receives the crank pulse signal input from the waveform shaping circuit 40, the engine speed obtained from the speed counter 41, and the intake pressure obtained from the A / D converter 42. Fuel injection control and ignition control of the engine 1 are performed based on the value, the intake air temperature value, the throttle opening value, the coolant temperature value, and the measured value of the drive current I obtained from the current measurement circuit 44a.

 Specifically, the CPU 49 monitors the rotation state of the crankshaft 13 (in other words, the position of the piston 11 in the cylinder 10) based on the crank pulse signal input from the waveform shaping circuit 40, and the piston 11 ignites. When the position corresponding to the timing is reached, an ignition control signal is output to the ignition circuit 43, thereby sparking the spark plug 16.

 Further, the CPU 49 starts energization of the injector 22 (solenoid coil 22a) by outputting an energization start signal to the injector drive circuit 44 when the piston 11 reaches a position corresponding to the fuel injection timing. Here, as a characteristic function in the present embodiment, the CPU 49 uses the measured value of the drive current I acquired at a constant cycle (sampling time Ts) from the current measurement circuit 44a after the start of energization of the injector 22 as a drive current I. Is calculated, and the inductance L of the solenoid coil 22a is calculated based on the calculation result.

Furthermore, CPU 49 obtains the lift X of the plunger corresponding to the calculated value of the inductance L using L-X conversion map stored in the ROM 46, reaches the acquired lift amount X to the required lift amount X _R At this point, the power supply end signal is output to the injector drive circuit 44, so that the power supply to the injector 22 is ended.

  Next, operations related to engine control of the ECU 3 in the engine control system configured as described above, particularly operations related to fuel injection control, will be described in detail with reference to FIGS. FIG. 3 is a flowchart showing operations related to fuel injection control. FIG. 4 is a time chart showing a temporal relationship among the drive voltage V applied to the solenoid coil 22a, the drive current I flowing through the solenoid coil 22a, and the plunger lift amount X after the energization of the injector 22 is started. .

  In FIG. 4, solid lines indicate changes in V, I, and X common to the present embodiment and conventional techniques B1 and B2, dotted lines indicate changes in V, I, and X according to the present embodiment, and alternate long and short dash lines indicate conventional ones. The change of V, I, and X by the technique B1 is shown, and the two-dot chain line shows the change of V, I, and X by the conventional technique B2. Here, the prior art B1 means that after the valve opening operation of the injector 22, the bounce reduction is realized by improving the control method, as in the technique disclosed in Patent Document 2 (Japanese Patent Publication No. 3-7834) described above. This refers to the technology that immediately shifts to the valve closing operation (after the full lift of the plunger). The prior art B2 is a technique for setting the period from the start of energization of the injector 22 until the rise bounce is stabilized as the minimum fuel injection period, and shifting to the valve closing operation after the rise bounce is stabilized (bounce reduction). The method that does not do.

 As described above, the CPU 49 of the ECU 3 constantly monitors the position of the piston 11 based on the crank pulse signal input from the waveform shaping circuit 40, and when the piston 11 reaches a position corresponding to the fuel injection timing. The operation shown in FIG. 3 is performed. As shown in FIG. 3, the CPU 49 first outputs an energization start signal to the injector drive circuit 44 when the piston 11 reaches a position corresponding to the fuel injection timing, whereby the injector 22 (solenoid coil 22 a). Energization is started (step S1).

Thereby, as shown in FIG. 4, the drive voltage V is applied to the solenoid coil 22 a of the injector 22 by the injector drive circuit 44. In FIG. 4, the driving voltage V is the energization start timing of the timing t _0, which is applied to the solenoid coil 22a. On the other hand, as shown in FIG. 4, the drive current I flowing through the solenoid coil 22a is by induction the characteristics of the solenoid coil 22a, will gradually increase from the energization start timing t _0. The injector 22 starts the valve opening operation from the time when the drive current I reaches a predetermined value, and the plunger starts to move in the valve opening direction. That is, as shown in FIG. 4, the plunger lift amount X remains “0” in the period T _nl from the energization start time t ₀ until the drive current I reaches a predetermined value.

Then, CPU 49 is configured to store the RAM47 samples the measured values of the drive current I obtained from the current measuring circuit 44a in the energizing start timing _{t 0} as the drive current _{I 0} of the energization start timing _{t 0,} corresponding to a timer 48 A repeat count operation at the sampling time Ts is instructed (step S2). Thus, thereafter, every time the sampling time Ts elapses, a sampling timing signal is output from the timer 48 to the CPU 49.

Then, the CPU 49 determines whether or not the sampling timing signal is received from the timer 48, that is, whether or not the sampling time Ts has elapsed (step S3). If “Yes”, the variable n (initial value “0”) is determined. ) is incremented (step S4), and stores the measured value of the drive current I obtained from the current measuring circuit 44a to sampling and RAM47 as the drive current _{I n} of the sampling time _{t n} (step S5).

Then, CPU 49 includes a drive current _{I n} of the sampling time _{t n} sampled this time from RAM 47, reads the drive current _{I n-1} sampling time _{t n-1,} which was previously sampled drive current between these adjacent two points A current value (current value) L _n of the inductance L of the solenoid coil 22a is calculated based on the following equation (1) consisting of a change amount of I (I _n −I _n−1 ), a drive voltage V, and a sampling time Ts. (Step S6).

Then, the CPU 49 uses the L-X conversion map (see FIG. 5) stored in the ROM 46 to determine the current value (current value) X of the plunger lift amount X corresponding to the inductance L _n calculated in step S6. get the _n (step S7), and the lift amount X _n that obtained thereof by comparing the required lift amount X _R satisfying fuel injection amount obtained in accordance with the operating conditions were obtained (estimated) lift X _n to determine whether greater than the required lift amount _{X R} (step S8).

If "No" at step S8, CPU 49 repeats the processing of steps S3~S8 returns to the processing in step S3, each time the sampling time Ts has elapsed, sampling of the drive current _{I n,} the calculation of the inductance _{L n} , by performing the acquisition of the lift amount X _n (estimates), to monitor the changes in the lift amount X _n. On the other hand, in the case of "Yes" in the step S8, when the lift amount X _n of words obtained has reached the required lift amount X _R, CPU 49 by outputting the power distribution end signal to the injector drive circuit 44, the injector 22 The energization is terminated (step S9).

In FIG. 4, the lift amount X _k acquired at the sampling timing t _k (n = k) becomes larger than the required lift amount X _R , and energization of the injector 22 is terminated at this timing (the drive voltage V is turned off). Is illustrated. As shown in FIG. 4, the injector 22 starts the valve opening operation from the time (t ₀ + T _nl ) when the drive current I reaches a predetermined value after the energization start timing t ₀ , and the plunger lift amount X gradually increases. Although increases in the opening direction, (estimated) was obtained lift amount X _n has reached the required lift amount X _R, the injector 22 is switched to the closing operation when the driving voltage V is turned off (t _k) It can be seen that the lift amount X of the plunger gradually decreases in the valve closing direction.

Thus, in the present embodiment, after the energization start of the injector 22, the current value of the lift amount X of the plunger to estimate the (X _n lift at the sampling timing t _n), the estimated lift amount X _n is the required lift amount by terminating the energization of the injector 22 when it reaches the X _R, it is possible to switch the valve closing operation at any time during the opening operation. Since the fuel injection amount is represented by the area of the region surrounded by the time transition curve of the lift amount X of the plunger and the time axis, as can be seen from FIG. 4, this embodiment is compared with the conventional techniques B1 and B2. By adopting, the minimum injection amount can be significantly reduced, and as a result, highly accurate control of the fuel injection amount can be realized. Further, in the present embodiment, since it is not necessary to make a structural improvement of the injector 22 for the purpose of reducing the bounce in order to reduce the minimum injection amount, the manufacturing cost is reduced.

On the other hand, in the conventional technique B1, the minimum injection amount is reduced compared to the conventional technique B2 in which bounce reduction is not performed in order to shift to the valve closing operation after the valve opening operation of the injector 22 (after the full lift of the plunger). However, the reduction amount does not reach the present embodiment. On the other hand, the conventional art does not perform bounce reduction B2, since the bounce rising from the energization start timing t ₀ can not be turned off the drive voltage V to stabilize inevitably greatest minimum injection amount, fuel injection amount It is difficult to control with high accuracy.

In addition, this invention is not limited to the said embodiment, The following modifications are mentioned.
(1) Although the case where the lift amount X is estimated based on the inductance L of the injector 22 has been described in the above embodiment, the lift amount X estimation method is not limited to this, and for example, a position sensor that detects the position of the plunger. And the lift amount X may be estimated from the sensor output. In the above embodiment, the case where the inductance L is calculated using the measured value of the drive current I obtained from the current measurement circuit 44a has been described. However, a measurement circuit that directly measures the inductance L may be provided. .

(2) In the above embodiment, the case where the lift amount X is estimated based on the inductance L of the injector 22 has been described. However, when this method is adopted, the sampling amount is increased until the estimated lift amount reaches the required lift amount. In addition, since it is necessary to perform sampling of the drive current, the load on the CPU 49 increases. On the other hand, the load on the CPU 49 can be reduced by estimating the lift amount based on the lift speed of the injector 22. The method will be specifically described below.

 FIG. 6 is a flowchart showing an operation related to fuel injection control in this modification. As shown in FIG. 6, the CPU 49 first starts energization of the injector 22 by outputting an energization start signal to the injector drive circuit 44 when the piston 11 reaches a position corresponding to the fuel injection timing ( Step S11).

Then, CPU 49 is configured to store the RAM47 samples the measured values of the drive current I obtained from the current measuring circuit 44a in the energizing start timing _{t 0} as the drive current _{I 0} of the energization start timing _{t 0,} corresponding to a timer 48 A repeat count operation at the sampling time Ts is instructed (step S12). Thus, thereafter, every time the sampling time Ts elapses, a sampling timing signal is output from the timer 48 to the CPU 49.

Then, the CPU 49 determines whether or not the sampling timing signal is received from the timer 48, that is, whether or not the sampling time Ts has elapsed (step S13). If “Yes”, the variable n (initial value “0”) is determined. ) Is incremented (step S14), and the lift amount _Xn based on the inductance is estimated (step S15).

The process in step S15 is the same as steps S5, S6, and S7 described in the flowchart of FIG. That is, in step S15, CPU 49 samples the measured values of the drive current I obtained from the current measuring circuit 44a as the drive current _{I n} of the sampling timing _{t n,} a drive current _{I n} of the sampling time _{t n} was sampled this time, calculating the inductance L _n with the drive current I _n of the sampling timing t _n-1, which was previously sampled, further obtains the lift amount X _n corresponding to the inductance L _n with L-X conversion map (estimated To do).

Then, the CPU 49 determines whether or not the lift amount _Xn acquired in step S15 is greater than “0” (step S16). If “No”, the process returns to step S13. On the other hand, if “Yes” in step S16, that is, if it is determined that the lift amount X _n is greater than “0” and the injector 22 has shifted to the valve opening operation, the CPU 49 determines the lift amount X _n acquired this time. Then, the current value (current value) V _n of the lift speed V of the plunger is calculated based on the following equation (2) using the previously obtained lift amount X _n−1 (step S17).

Then, the CPU 49 increments the variable c (initial value “0”) (step S18), and determines whether the variable c is “2” or more (step S19). If “No” in step S19, the CPU 49 returns to the process of step S13, whereas if “Yes”, the CPU 49 proceeds to the process of step S20 described later. That is, when it is determined "Yes" in step S19 (they become c ≧ 2), the lift speed V _n calculated for the current sampling timing t _n, was calculated in the previous sampling timing t _n-1 A lift speed V _n-1 is obtained.

Then, CPU 49 in the case of "Yes" at step S19, using a lift speed _{V n} calculated for the current sampling timing _{t n,} and a lift speed _{V n-1} calculated for the previous sampling timing _{t n-1} Based on the following equation (3), the degree of change kV of the lift speed _V is calculated (step S20).

Here, as shown in FIG. 8A, after the valve opening operation of the injector 22 is shifted, the logarithmic value (vertical axis) of the lift speed V shows a substantially linear relationship with the time axis. ) expression by calculating the degree of change k _V of the lift speed V with reference to, or later, without sampling the drive current, calculates a lift X _n with later in (4) and (5) It is possible to perform (estimate).

That, CPU 49, after calculating the degree of change k _V of the lift speed V in step S20, the current sampling timing t _n lift X _n obtained in to determine whether greater than the required lift amount X _R (Step S21). In this case in step S21 is "No", that is, when the lift amount _{X n} does not reach the required lift amount _{X R,} CPU 49 determines whether it has received a sampling timing signal from the timer 48 (step S22), and If “Yes”, the variable n is incremented (step S23).

Then, CPU 49 uses the degree of change _{k V} of the lift speed V calculated in step S20, and calculates the lift speed _{V n} on the basis of the following equation (4) (step S24), and further, the lift speed V and the calculated _n is used to calculate the lift amount _Xn based on the following equation (5) (step S25).

Then, CPU 49, after calculating the lift amount _{X n} in the above step S25, the lift amount _{X n} is re-determined whether the larger the required lift amount _{X R} returns to the processing of step S21, if the "Yes" , that is, when the calculated (estimated) lift X _n has reached the required lift amount X _R, by outputting an energization end signal to the injector drive circuit 44, and terminates the energization of the injector 22 (step S26).

 As described above, according to this modification, after the valve opening operation of the injector 22 is shifted, the lift amount is estimated based on the lift speed of the injector 22, thereby eliminating the need for sampling the drive current and reducing the load on the CPU 49. It becomes possible to reduce.

(3) In the modification (2), the case where the lift amount is estimated based on the lift speed of the injector 22 has been described. However, in order to reduce the load on the CPU 49, after the injector 22 shifts to the valve opening operation, the injector 22 A method of estimating the lift amount based on the lift acceleration may be adopted. As shown in FIG. 8B, after the valve opening operation of the injector 22 is shifted, the logarithmic value (vertical axis) of the lift acceleration A also shows a substantially linear relationship with the time axis. by calculating the k _a, and later, without sampling the drive current, and calculates the lift amount X _n (estimates) it becomes possible.

  FIG. 7 is a flowchart showing the operation related to the fuel injection control in this modification. In the flowchart of FIG. 7, steps that perform the same processing as in the flowchart of FIG. That is, FIG. 7 differs from FIG. 6 in that step S20 in FIG. 6 is replaced with steps S20a to S20d in FIG. 7, and steps S24 and S25 in FIG. 6 are replaced with steps S24a and S25a in FIG. It is only a point. Below, it demonstrates paying attention to a different point in these FIG. 7 and FIG.

First, in step S20a of FIG. 7, CPU 49 uses a lift speed _{V n} calculated for the current sampling timing _{t n,} and a lift speed _{V n-1} calculated for the previous sampling timing _{t n-1,} the following ( 6) The lift acceleration _An is calculated based on the equation (step S20a).

Then, the CPU 49 increments the variable d (initial value “0”) (step S20b), and determines whether or not the variable d is “2” or more (step S20c). If “No” in step S20c, the CPU 49 returns to the process of step S13, whereas if “Yes”, the CPU 49 proceeds to the process of step S20d described later. That is, when it is judged as "Yes" at step S20c (when it becomes d ≧ 2), and the lift acceleration A _n calculated for the current sampling timing t _n, was calculated in the previous sampling timing t _n-1 A lift acceleration _An-1 is obtained.

Then, CPU 49 in the case of "Yes" at step S20c, using a lift acceleration _{A n} calculated for the current sampling timing _{t n,} and a lift acceleration _{A n-1} calculated for the previous sampling timing _{t n-1} The change degree k _A of the lift acceleration _A is calculated based on the following equation (7) (step S20d).

On the other hand, in step S24a, CPU 49 uses the degree of change _{k A} lift acceleration A calculated in step S20d, and calculates the lift acceleration _{A n} in accordance with the following equation (8) (step S24a), further, the calculated Using the lift acceleration _An , the lift amount _Xn is calculated based on the following equation (9) (step S25a).

 As described above, also in this modification, after the valve opening operation of the injector 22 is shifted, the lift amount is estimated based on the lift acceleration of the injector 22, thereby eliminating the need to sample the drive current and reducing the load on the CPU 49. It becomes possible.

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Fuel supply part, 3 ... ECU (Electronic Control Unit), 10 ... Cylinder, 11 ... Piston, 12 ... Connecting rod, 13 ... Crankshaft, 14 ... Intake valve, 15 ... Exhaust valve, 16 ... Spark plug , 17 ... Ignition coil, 18 ... Intake pipe, 19 ... Exhaust pipe, 20 ... Air cleaner, 21 ... Throttle valve, 22 ... Injector, 23 ... Intake pressure sensor, 24 ... Intake temperature sensor, 25 ... Throttle opening sensor, 26 ... Cooling water temperature sensor, 27 ... Crank angle sensor, 30 ... Fuel tank, 31 ... Fuel pump, 40 ... Waveform shaping circuit, 41 ... Revolution counter, 42 ... A / D converter, 43 ... Ignition circuit, 44 ... Injector drive circuit 45 ... Pump drive circuit, 46 ... ROM (Read Only Memory), 47 ... RAM (Random Access Memory), 48 ... Timer, 49 ... CPU (Central Processing Unit)

Claims (6)

A fuel injection control device for controlling a fuel injection valve,
A fuel injection control device comprising: an energization control unit that estimates a lift amount after energization of the fuel injection valve is started and ends energization of the fuel injection valve when the lift amount reaches a required lift amount. .   The fuel injection control device according to claim 1, wherein the energization control unit estimates the lift amount based on an inductance of the fuel injection valve. Storage means for storing in advance the correspondence between the inductance and the lift amount;
The fuel injection control device according to claim 2, wherein the energization control unit acquires a lift amount corresponding to the calculated value of the inductance using a correspondence relationship between the inductance and the lift amount. Comprising current measuring means for measuring a drive current flowing through the fuel injection valve;
The energization control unit calculates a change amount of the drive current using a measurement value of the drive current acquired from the current measurement unit at a constant cycle after the start of energization, and the inductance based on the change amount of the drive current The fuel injection control device according to claim 3, wherein:   The fuel injection control device according to claim 1, wherein the energization control unit estimates the lift amount based on at least one of a lift speed and a lift acceleration of the fuel injection valve.   A fuel injection control method, wherein a lift amount after energization of a fuel injection valve is estimated and energization of the fuel injection valve is terminated when the lift amount reaches a required lift amount.

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