Fuel injection control device and fuel injection control method

Abstract

This fuel injection control device comprises: an energization control unit that controls the energization time of a coil on the basis of a pulse width of a drive command pulse; a voltage detection unit that detects a voltage value during energization of the coil; a filter unit that detects inflection points of a waveform of the voltage value; and a valve closing detection unit that detects a valve closing timing of a valve body on the basis of the inflection points of the waveform of the voltage value during the time from a predetermined detection start timing to a detection end timing. The detection end timing with respect to the drive command pulse providing energization at present is determined on the basis of the valve closing timing when the pulse width is longer than the predetermined pulse width.

Description

Fuel injection control device and fuel injection control method

[0001] The present invention relates to a fuel injection control device and a fuel injection control method.

[0002] In recent years, downsized engines have become popular, which are smaller in size and use a turbocharger to generate power. By reducing the displacement, downsized engines can reduce pumping losses, thereby improving fuel efficiency.

[0003] On the other hand, downsized engines tend to have smaller cylinder diameters, which raises concerns that injected fuel may adhere to the cylinder walls, deteriorating exhaust performance. Furthermore, if uneven fuel flow and air occur in a downsized engine, unburned particulate matter is emitted, deteriorating exhaust performance. Therefore, downsized engines aim to homogenize the air and fuel in the engine cylinder by increasing the pressure of the fuel supplied to the engine cylinder, atomizing the injected fuel, and forming a uniform air-fuel mixture.

[0004] In order to improve the pressure of fuel supplied to the engine cylinder, for example, the required amount of fuel can be divided and injected in one combustion stroke to homogenize the air and fuel in the engine cylinder and improve the deterioration of exhaust performance. However, to achieve this, the fuel injection valve needs to be able to measure the injection amount with high accuracy. Patent Document 1 describes a fuel injection device that improves the injection amount measurement accuracy by performing second-order differentiation on the voltage value through filtering and detecting the valve closing position.

[0005] Japanese Patent Application Laid-Open No. 2018-197548

[0006] However, in the fuel injection device described in Patent Document 1, when the width of the drive command pulse to the fuel injection valve is small, the movement amount of the valve disc is small, and the change in acceleration when the valve is closed is small. This makes it easy for erroneous detection of valve closure to occur, and improving robustness has been an issue.

[0007] An object of the present invention is to provide a fuel injection control device and a fuel injection control method for solving the above problems.

[0008] In order to solve the above problem, for example, the configuration described in the claims is adopted. The present application includes a plurality of means for solving the above problem, and one example thereof is a fuel injection control device applied to a fuel injection device including a valve element that opens and closes a fuel passage of the fuel injection device, a movable element that performs opening and closing operation of the valve element, and a stator that has a coil that is excited when energized and biases the movable element, the fuel injection control device including: an energization control unit that controls an energization time of the coil using a pulse width of a drive command pulse; a voltage detection unit that detects a voltage value when the coil is energized; a filter unit that detects an inflection point of a waveform of the voltage value; and a valve close detection unit that detects a valve close timing of the valve element based on an inflection point of the waveform of the voltage value from a predetermined detection start timing to a detection end timing, and the detection end timing for the drive command pulse currently being energized is determined based on the valve close timing when the pulse width is longer than the predetermined pulse width.

[0009] According to the present invention, it is possible to detect valve closure without erroneous detection even with a small pulse width, and to measure the injection amount with high accuracy even in the small injection amount range. It is also possible to improve exhaust emissions from the engine. Problems, configurations, and effects other than those described above will become clear from the description of the following embodiments.

[0010] 1 is an overall configuration diagram showing an example of a basic configuration of an internal combustion engine equipped with a fuel injection control device according to an embodiment of the present invention; FIG. 2 is a cross-sectional view showing a fuel injection device according to an embodiment of the present invention; FIG. 3 is a circuit diagram showing details of a drive circuit and an engine control unit (ECU) of the fuel injection control device according to an embodiment of the present invention; FIG. 4 is a characteristic diagram showing examples of a drive command injection pulse (injection pulse), a drive voltage, a detection filter, a filtered signal, a drive current, a valve element displacement, and a movable iron core displacement when the drive command pulse width is long for the fuel injection device shown in FIG. 5; FIG. 5 is a characteristic diagram showing examples of a drive command injection pulse (injection pulse), a drive voltage, a detection filter, a filtered signal, a drive current, a valve element displacement, and a movable iron core displacement when the drive command pulse width is short for the fuel injection device shown in FIG. 6; 1 is a characteristic diagram showing an example of a correction coefficient relating to fuel temperature with respect to an injection pulse width; FIG. 2 is a characteristic diagram showing an example of a correction coefficient relating to fuel pressure with respect to an injection pulse width; FIG. 3 is a characteristic diagram showing an example of a comparison between a conventional method and an embodiment of a valve closing detection value with respect to an injection pulse width; FIG. 4 is a characteristic diagram showing an example of an injection amount characteristic before injection pulse correction; and FIG. 5 is a characteristic diagram showing an example of an injection amount characteristic after injection pulse correction based on a valve closing detection result.

[0011] A fuel injection control device and a fuel injection control method according to an embodiment of the present invention will be described below with reference to the accompanying drawings. Note that common members in the various drawings are given the same reference numerals.

[0012] [Internal Combustion Engine System] First, the configuration of an internal combustion engine system equipped with a fuel injection control device according to this embodiment will be described. Fig. 1 is a diagram showing the overall configuration of an internal combustion engine system equipped with a fuel injection control device according to this embodiment.

[0013] 1 is a four-stroke engine that repeats four strokes: an intake stroke, a compression stroke, a combustion (expansion) stroke, and an exhaust stroke, and is a multi-cylinder engine having, for example, four cylinders. Note that the number of cylinders that the internal combustion engine 101 has is not limited to four, and it may have, for example, three, six, eight or more cylinders.

[0014] The internal combustion engine 101 includes a piston 102, an intake valve 103, and an exhaust valve 104. The intake air into the internal combustion engine 101 passes through an air flow meter (AFM) 120 that detects the amount of air flowing in, and the flow rate is adjusted by a throttle valve 119. The air that passes through the throttle valve 119 is drawn into a collector 115, which is a branching section, and then supplied to a combustion chamber 121 of each cylinder via an intake pipe 110 and an intake valve 103 provided for each cylinder.

[0015] Meanwhile, fuel is supplied from a fuel tank 123 to a high-pressure fuel pump 125 by a low-pressure fuel pump 124, and the fuel is increased to a pressure required for fuel injection by the high-pressure fuel pump 125. That is, the high-pressure fuel pump 125 moves a plunger provided in the high-pressure fuel pump 125 up and down by power transmitted from an exhaust camshaft (not shown) of an exhaust cam 128, thereby pressurizing (increasing the pressure) the fuel in the high-pressure fuel pump 125.

[0016] An on-off valve driven by a solenoid is provided at the intake port of high-pressure fuel pump 125. The solenoid is connected to a fuel injection device control device 127 provided in an engine control device (Electronic Control Unit: ECU) 109. In the following description, engine control device 109 will be referred to as ECU 109, and fuel injection device control device 127 will be referred to as fuel injection control device 127. Fuel injection control device 127 has a RAM (Random Access Memory) 261 (see FIG. 2) that executes programs and a ROM (Read Only Memory) 260 (see FIG. 2) that stores data. Based on a control command from ECU 109, the program is called from RAM 261, and the solenoid is controlled based on the data stored in ROM 260, thereby driving the on-off valve so that the pressure of the fuel discharged from high-pressure fuel pump 125 (fuel pressure) becomes a desired pressure.

[0017] The fuel pressurized by the high-pressure fuel pump 125 is sent to the fuel injection device 200 via a high-pressure fuel pipe 129. The fuel injection device 200 directly injects fuel into the combustion chamber 121 based on a command from a fuel injection control device 127. The fuel injection device 200 supplies (energizes) a drive current to a coil 208 (described later) to operate a valve body and perform fuel injection.

[0018] The internal combustion engine 101 is also provided with a fuel pressure sensor (fuel pressure sensor) 126 that measures the fuel pressure in a high-pressure fuel pipe 129. Based on the measurement result from the fuel pressure sensor 126, the ECU 109 sends a control command to the fuel injection control device 127 to adjust the fuel pressure in the high-pressure fuel pipe 129 to a desired pressure. In other words, the ECU 109 performs so-called feedback control to adjust the fuel pressure in the high-pressure fuel pipe 129 to the desired pressure.

[0019] Furthermore, each combustion chamber 121 of the internal combustion engine 101 is provided with a spark plug 106, an ignition coil 107, and a water temperature sensor 108. The spark plug 106 exposes an electrode portion inside the combustion chamber 121 and ignites the mixture of intake air and fuel in the combustion chamber 121 by electrical discharge. The ignition coil 107 generates a high voltage for electrical discharge in the spark plug 106. The water temperature sensor 108 measures the temperature of the cooling water that cools the cylinders of the internal combustion engine 101.

[0020] The ECU 109 controls the energization of the ignition coil 107 and the ignition by the spark plug 106. A mixture of intake air and fuel in the combustion chamber 121 is combusted by a spark emitted from the spark plug 106, and the resulting pressure pushes the piston 102 down.

[0021] Exhaust gas generated by combustion is discharged into an exhaust pipe 111 via an exhaust valve 104. A three-way catalyst 112 and an oxygen sensor 113 are provided in the exhaust pipe 111. The three-way catalyst 112 purifies harmful substances contained in the exhaust gas, such as nitrogen oxides (NOx). The oxygen sensor 113 detects the oxygen concentration contained in the exhaust gas and outputs the detection result to the ECU 109. Based on the detection result of the oxygen sensor 113, the ECU 109 performs feedback control so that the amount of fuel injected from the fuel injection device 200 matches the target air-fuel ratio.

[0022] Furthermore, a crankshaft 131 is connected to the piston 102 via a connecting rod 132. The reciprocating motion of the piston 102 is converted into rotational motion by the crankshaft 131. A crank angle sensor 116 is attached to the crankshaft 131. The crank angle sensor 116 detects the rotation and phase of the crankshaft 131 and outputs the detection results to the ECU 109. The ECU 109 detects the rotation speed of the internal combustion engine 101 based on the output of the crank angle sensor 116.

[0023] The ECU 109 receives signals from a crank angle sensor 116, an air flow meter 120, an oxygen sensor 113, an accelerator opening sensor 122, a fuel pressure sensor 126, etc. The accelerator opening sensor 122 is a sensor that indicates the opening of the accelerator operated by the driver.

[0024] The ECU 109 calculates the torque required for the internal combustion engine 101 based on the signal supplied from the accelerator position sensor 122, and determines whether the engine is in an idling state or not. The ECU 109 also calculates the amount of intake air required for the internal combustion engine 101 from the required torque and outputs an opening signal corresponding to the amount of intake air to the throttle valve 119.

[0025] The ECU 109 also has a rotation speed detection unit that calculates the rotation speed of the internal combustion engine 101 (hereinafter referred to as engine rotation speed) based on a signal supplied from the crank angle sensor 116. The ECU 109 also has a warm-up determination unit (not shown) that determines whether the three-way catalyst 112 is warmed up or not based on the temperature of the cooling water obtained from the water temperature sensor 108 and the elapsed time since the internal combustion engine 101 was started, etc.

[0026] The fuel injection control device 127 calculates the amount of fuel (target injection amount) corresponding to the intake air amount, and outputs a corresponding fuel injection signal to the fuel injection device 200. Furthermore, the fuel injection control device 127 outputs an energization signal to the ignition coil 107, and outputs an ignition signal to the spark plug 106.

[0027] [Configuration of the Fuel Injection Device] Next, the configuration of the fuel injection device 200 shown in Fig. 1 will be described with reference to Fig. 2. Fig. 2 is a cross-sectional view showing the fuel injection device 200 shown in Fig. 1.

[0028] 2, the fuel injection device 200 is made up of a fuel supply unit 212 that supplies fuel, a valve seat 202 having fuel injection holes 215 that serve as fuel passages, and a movable iron core (movable element) 206 that drives the valve body 201. In this embodiment, an electromagnetic fuel injection device for an internal combustion engine that uses gasoline as fuel will be described as an example.

[0029] 2, fuel injection device 200 has fuel supply unit 212 disposed at the upper end thereof, and fuel injection holes 215 and valve seat 202 disposed at the lower end thereof. Moving iron core 206, valve body 201, and intermediate member 214 are disposed between fuel supply unit 212 and valve seat 202.

[0030] Fuel injection device 200 is connected to high-pressure fuel pipe 129 (see FIG. 1) at an end (not shown) of fuel injection device 200 on the fuel supply unit 212 side, which is on the opposite side of fuel injection hole 215 and valve seat 202. Furthermore, fuel injection device 200 has an end (fuel injection hole 215 side) on the opposite side of fuel supply unit 212, which is inserted into a mounting hole (insertion hole) formed in a member (cylinder block, cylinder head, etc.) that forms combustion chamber 121 (see FIG. 1).

[0031] Fuel injection device 200 receives fuel from high-pressure fuel pipe 129 (see FIG. 1) through fuel supply unit 212, and injects the fuel into combustion chamber 121 (see FIG. 1) from the tip of valve seat 202. A fuel passage is formed inside fuel injection device 200 so that fuel flows substantially along central axis 200a of fuel injection device 200 from a base end on the fuel supply unit 212 side to a tip end on the fuel injection hole 215 side.

[0032] The coil 208 is disposed between the fixed iron core (stator) 207 and the housing 209. The fixed iron core 207, the coil 208, and the housing 209 constitute an electromagnet. In a valve-closed state in which the coil 208 is not energized, the valve element 201 abuts against the valve seat 202. That is, the valve element 201 is abutted against the valve seat 202 by a force obtained by subtracting the biasing force of the third spring member 217 from the biasing forces of the first spring member 210 and the second spring member 216, which bias the valve element 201 in the valve-closing direction. This state is referred to as a stable valve-closed state (valve-closed standby state). In the stable valve-closed state, the movable iron core 206 abuts against the intermediate member 214 and is disposed in the valve-closed position. The valve element 201 is driven via a transmission surface 219 that transmits the load from the movable iron core 206.

[0033] Furthermore, in the stable valve-closed state, the intermediate member 214 is biased downstream (toward the valve seat 202, in the valve-closing direction) by the second spring member 216, and is stationary in contact with the valve body 201. The movable iron core 206 is biased upstream (toward the fixed iron core 207, in the valve-opening direction) by the third spring member 217, and is in contact with the intermediate member 214. Note that, because the biasing force of the second spring member 216 is greater than the biasing force of the third spring member 217, a gap 250 is formed between the valve body 201 and the movable iron core 206.

[0034] A fuel injection control device 127 and an ECU (engine control device) 109 are connected to the fuel injection device 200. The fuel injection control device 127 has a circuit that receives a drive command pulse (injection pulse) from the ECU 109 and supplies a drive current (drive voltage) to the fuel injection device 200. The ECU 109 and the fuel injection control device 127 may be configured as an integrated component. The fuel injection control device 127 is a device that generates a drive voltage for the fuel injection device 200, and may be integrated with the ECU 109 or configured as a standalone device.

[0035] The ECU 109 receives signals indicating the engine status from various sensors and calculates an appropriate drive command pulse (injection pulse) width and injection timing according to the operating conditions of the internal combustion engine. The drive command pulse output from the ECU 109 is input to the fuel injection control device 127 via a signal line 223.

[0036] The fuel injection control device 127 controls the drive voltage applied to the coil 208 and supplies a drive current to the coil 208. The ECU 109 communicates with the fuel injection control device 127 through a communication line 222. The ECU 109 switches the drive current generated by the fuel injection control device 127 depending on the pressure of the fuel supplied to the fuel injection device 200 and the operating conditions. The fuel injection control device 127 is able to change a control constant through communication with the ECU 109, and changes the current waveform in accordance with the control constant.

[0037] [Configuration of Fuel Injection Control Device] Next, the configuration of the fuel injection control device 127 will be described with reference to Fig. 3. Fig. 3 is a diagram showing the details of the drive circuit of the fuel injection control device 127 and the ECU 109.

[0038] The ECU 109 (see FIG. 2) incorporates a CPU (Central Processing Unit) 501. The CPU 501 receives various signals indicating the state of the engine from the fuel pressure sensor 126, the air flow meter 120, the oxygen sensor 113, the crank angle sensor 116, etc., shown in FIG. 1. In response to these signals, the CPU 501 calculates the width of a drive command pulse (injection pulse) and injection timing for controlling the amount of fuel injected from the fuel injection device 200 in accordance with the operating conditions of the internal combustion engine.

[0039] The CPU 501 also calculates an appropriate pulse width and injection timing of a drive command pulse according to the operating conditions of the internal combustion engine, and outputs the drive command pulse to the drive IC 502 of the fuel injection device 200 via the signal line 223. The drive command pulse is generated and output through a current control process by the current control unit 501a. The CPU 501 represents a specific example of a control unit according to this embodiment, and includes the current control unit 501a, a voltage detection unit 501b, a digital filter unit 501c, and a valve opening detection unit 501d. Although not shown, the valve opening detection unit 501d includes a learning unit that performs a learning process (described later) and stores learned data. These processing units are processing function units configured on a memory by executing a program. The current control unit 501a performs a current control process that outputs a drive command pulse. The voltage detection unit 501b performs a voltage detection process that detects the voltage value when the coil 208 is energized. The digital filter unit 501c, which is an example of a filter unit, performs filtering to detect inflection points in the waveform of the voltage value when current is applied to the coil 208. The valve closing detection unit 501d performs processing to detect the valve closing timing based on inflection points in the waveform of the voltage value during the time from a predetermined detection start timing to a predetermined detection end timing.

[0040] Furthermore, a learning unit included in the valve-close detection unit 501d learns the valve-closing timing when the pulse width of the drive command pulse is longer than a pulse width (predetermined pulse width) for a specific state, which will be described later. This learning unit sets the detection end timing when the drive command pulse has a pulse width longer than the predetermined pulse width in accordance with a first set value, and sets the detection end timing when the drive command pulse has a pulse width shorter than the predetermined pulse width based on a second set value different from the first set value or the learned valve-closing timing of the valve disc. Details of the setting process in this learning process will be described in the flowchart of FIG. 6. The injection amount from the fuel injection device 200 is determined by the pulse width of the drive command pulse. Thereafter, the driving IC 502 switches between energized and de-energized states of the switching elements 505, 506, and 507 to supply a driving current to the fuel injection device 200.

[0041] The switching element 505 is connected between a high voltage source higher than the voltage source VB input to the drive circuit of the fuel injection control device 127 (see FIG. 2 ) and a high-voltage side terminal of the solenoid 540 of the fuel injection device 200. The switching elements 505, 506, 507 are configured by transistors such as FETs (Field Effect Transistors), for example, and switch between energizing and de-energizing the fuel injection device 200.

[0042] The boosted voltage VH, which is the initial voltage value of the high voltage source, is, for example, 65 V, and is generated by boosting the battery voltage using a boost circuit 514. The boost circuit 514 is configured with, for example, a coil 530, a transistor 531, a diode 532, and a capacitor 533.

[0043] In the boost circuit 514, when the transistor 531 is turned ON, the battery voltage VB flows to the ground potential 534. On the other hand, when the transistor 531 is turned OFF, the high voltage generated in the coil 530 is rectified through the diode 532, and a charge is accumulated in the capacitor 533. The transistor is repeatedly turned ON and OFF until the voltage of the capacitor 533 reaches the boost voltage VH, thereby increasing the voltage of the capacitor 533. The transistor 531 is connected to an IC (Integrated Circuit) 502 or a CPU 501. The boost voltage VH output from the boost circuit 514 is detected by the IC 502 or the CPU 501. The boost circuit 514 may be configured with a DC / DC converter or the like. The IC 502 is referred to as a drive IC 502.

[0044] Switching element 507 is connected between a low-voltage power source and a high-voltage terminal of solenoid 540. Low-voltage power source VB is, for example, a battery voltage, and its voltage value is approximately 12 to 14 V. Switching element 506 is connected between a low-voltage terminal of fuel injection device 200 (see FIG. 2) and ground potential 515.

[0045] Driving IC 502 detects the value of the current flowing through fuel injector 200 using current detection resistors 508, 512, and 513, and switches between energized and de-energized states of switching elements 505, 506, and 507 depending on the detected current value, thereby generating the desired drive current. Diodes 509 and 510 apply a reverse voltage to solenoid 540 of fuel injector 200, rapidly reducing the current supplied to solenoid 540.

[0046] The CPU 501 communicates with the drive IC 502 via the communication line 222. The CPU 501 switches the drive current generated by the drive IC 502 depending on the pressure of the fuel supplied to the fuel injection device 200 (see FIG. 2) and the operating conditions. Both ends of the resistors 508, 512, and 513 are connected to the A / D conversion port of the drive IC 502, and the IC 502 is configured to detect the voltage across the resistors 508, 512, and 513.

[0047] [Operation of Fuel Injection Device] Next, the operation of the fuel injection device 200 under the control of the fuel injection control device 127 will be described with reference to Fig. 4. Fig. 4 is a diagram showing the drive command pulse (injection pulse), drive voltage, drive current, valve element displacement, and movable core displacement. The drive voltage also shows the timing of digital filtering and the filtered signal. However, the filtered signal in Fig. 4 is a signal obtained when filtering is performed on the drive voltage for all sections.

[0048] As shown in FIG. 4, when a drive command pulse Ti is input at time Ts, a high voltage 304 is applied to the coil 208 (see FIG. 2) from a high voltage source that has been boosted to a voltage higher than the battery voltage VB, and current begins to be supplied to the coil 208.

[0049] After the coil 208 is energized, a magnetomotive force is generated by the electromagnet formed by the fixed core 207, the coil 208, and the housing 209. A magnetic path is formed by the fixed core 207, the housing 209, and the movable core 206 so as to surround the coil 208, and this magnetomotive force causes magnetic flux to flow around the formed magnetic path. At this time, a magnetic attraction force acts between the movable core 206 and the fixed core 207, and the movable core 206 and the intermediate member 214 are displaced toward the fixed core 207. Thereafter, the movable core 206 is displaced until the transmission surface 219 of the valve element 201 abuts against the transmission surface 218 of the movable core 206. Note that the valve element 201 continues to maintain a state of abutment with the valve seat 202.

[0050] When the movable iron core 206 is displaced by the gap 250 formed between the valve element 201 and the movable iron core 206 and the transmission surface 219 of the valve element 201 collides with the transmission surface 218 of the movable iron core 206, the valve element 201 is pulled upstream by the energy of the movable iron core 206 and the valve element 201 is separated from the valve seat 202. As a result, a gap is formed in the valve seat 202, the fuel passage opens, and fuel is injected from the fuel injection hole 215. Then, the valve element 201 is suddenly displaced by the movable iron core 206 which has kinetic energy.

[0051] The fuel injection control device 127 applies a high voltage 304 to the coil 208 and passes a drive current 308 through the coil 208 from time Ts until time T31 (valve opening start timing) when the movable iron core 206 and the valve disc 201 collide and the valve disc 201 separates from the valve seat 202. As a result, a necessary and sufficient magnetic attraction force is generated between the movable iron core 206 and the fixed iron core 207, allowing the movable iron core 206 to respond quickly. By allowing the movable iron core 206 to respond quickly, for example, even if the gap 250, which serves as the preliminary stroke, varies from one individual to another, the effect of this variation on the injection amount can be reduced.

[0052] The application of high voltage 304 causes the drive current flowing through coil 208 to rise sharply as indicated by peak current 308. When the current reaches peak current value Ip (the peak of current 308), fuel injection control device 127 applies high voltage 304 in the reverse direction (applies a reverse voltage). That is, fuel injection control device 127 turns off all of switching elements 505, 506, and 507 (see FIG. 3). As a result, diodes 509 and 510 are energized by the back electromotive force generated by the inductance of fuel injection device 200, and the current is fed back to voltage source VH. As a result, the drive current flowing through coil 208 rapidly drops and is cut off as indicated by current 317.

[0053] In this embodiment, the valve opening start timing is set when the peak current value Ip is reached, and when the peak current value Ip is reached, the drive voltage of the coil 208 is switched to the battery voltage, and the drive current of the coil 208 is controlled by switching on and off depending on the valve opening start timing so that it falls within a predetermined current threshold range.

[0054] After the movable core 206 and the fixed core 207 collide, the valve element 201 is displaced upstream and the movable core 206 is displaced downward. When the fixed core 207 and the movable core 206 collide, the valve element 201 and the movable core 206 separate, and the movable core 206 is displaced downstream, but eventually comes to rest and stabilizes at the target lift position. This state is the stable open valve state. The stable open valve state in which the valve is stable and comes to rest at the target lift position is the half-lift state. In other words, the pulse width (predetermined pulse width) of the drive command pulse described below is the pulse width at which the valve element 201 is operated to the half-lift state.

[0055] The movable iron core 206 and the valve body 201 are configured to be capable of relative movement, so that when the movable iron core 206 collides with the fixed iron core 207, the valve body 201 and the movable iron core 206 separate from each other, and the valve body 201 is displaced upstream.

[0056] Subsequently, when the drive command pulse Ti is turned OFF at time Te, the fuel injection control device 127 applies a drive voltage in the reverse direction to the coil 208 (applies a reverse voltage). This cuts off the current supply to the coil 208, and the magnetic flux generated in the magnetic circuit disappears, resulting in the disappearance of the magnetic attraction force. As a result, the movable iron core 206, which has lost its magnetic attraction force, is pushed back by the load of the first spring member 210 and the force due to the fuel pressure, and the valve element 201 reaches the closed position in contact with the valve seat 202.

[0057] The biasing force of the first spring member 210 acting on the valve element 201 is transmitted to the movable iron core 206 via a transmission surface 219 on the valve element 201 side and a transmission surface 218 on the movable iron core 206 side. When the valve closing required time has elapsed from time Te when the drive command pulse Ti is turned OFF to time Tb when the valve closing is completed (at time Tb), the valve element 201 comes into contact with the valve seat 202.

[0058] After the valve element 201 comes into contact with the valve seat 202, the transmission surface 218 on the movable iron core 206 side separates from the transmission surface 219 on the valve element 201 side and continues to move downward (in the valve closing direction). After time Tb when the valve is completely closed, the movable iron core 206 and the valve element 201 become separated as shown in Figure 2. At this time, a bend-like change appears in the drive voltage, as shown by inflection point 330. From this change, the time Tb when the valve is completely closed can be detected.

[0059] When the fuel injection device 200 is closed, the third spring member 217 changes from extension to compression when the valve body 201 collides with the valve seat 202, and the direction of movement of the movable iron core 206 is reversed. This changes the acceleration of the movable iron core 206, and the inductance of the coil 208 changes. In other words, when the fuel injection device 200 is closed, the drive current flowing through the coil 208 is cut off, and a back electromotive force is applied to the coil 208. Then, as the drive current converges, the back electromotive force also gradually decreases, and as the back electromotive force decreases, the inductance changes. This causes an inflection point 310 to occur in the drive voltage of the coil 208.

[0060] The inflection point 310 is the timing at which the valve of the fuel injection device 200 is completely closed. For example, the inflection point 310 appears as an extreme value (maximum or minimum value) when the time-series data of the drive voltage applied to the coil 208 is differentiated twice. Therefore, the inflection point 310 can be identified by differentiating the time-series data of the drive voltage twice and detecting the extreme value.

[0061] The digital filter processing of the drive voltage in Figure 4 is a waveform obtained by second-order differentiation of the drive voltage. As described above, the value of the waveform obtained by second-order differentiation of the drive voltage after digital filtering changes as the slope of the drive voltage changes. That is, when the valve element 201 closes, the acceleration of the movable iron core 206 changes, which appears as a change in the drive voltage. Therefore, by calculating the maximum value while the digital filter processing is being performed (while the signal of the detection filter in Figure 4 is at a high level), that is, the maximum value between the predetermined valve close detection start time Tss and the valve close detection end time Tee, it is possible to detect the inflection point 310 corresponding to the valve closing time Tb of the valve element 202.

[0062] FIG. 5 is a diagram showing the drive command pulse, drive voltage, detection filter, filtered signal, drive current, and displacement of the valve disc 201 and the movable iron core 206 when the drive command pulse width Ti is small. As shown in FIG. 5 , when the drive command pulse width Ti is smaller than a certain threshold value Ti_th, the acceleration change when the valve disc 201 seats on the valve seat 202 is small. In such a case, the acceleration change is small, so the maximum value after the digital filter is also small, resulting in a poor S / N ratio. As a result, the valve close detection time may be estimated at a location different from the time when the valve disc 201 seats, i.e., the valve closing time, resulting in an erroneous detection. In such a case, the valve close detection start time Tss and the valve close detection completion time Tse are appropriately set, and the updated valve close completion detection time Tse′ is set. Then, the maximum value is detected within the range from the valve close detection start time Tss to the updated valve close completion detection time Tse′, thereby avoiding erroneous detection. Hereinafter, a method for avoiding erroneous detection when there is a risk that the valve closing detection time may be estimated at a location different from the valve closing time will be described.

[0063] 6 is a flowchart for explaining the process of detecting the valve closing time and the method of setting the updated valve closing completion detection time Tse'. A valve closing detection command is issued by the ECU 109, which is a higher-level controller, and the process of this flowchart is executed by the CPU 501.

[0064] First, the CPU 501 performs initial settings for valve closure detection, such as the valve closure detection start time Tss, the valve closure detection end time Tse, digital filter processing, analog-to-digital conversion, etc. (step S601).

[0065] Next, the CPU 501 acquires the pulse width Ti, the temperature t_fuel, the fuel pressure p_fuel, and the injection interval Tdwell (step S602). Based on the acquired pulse width Ti, temperature t_fuel, fuel pressure p_fuel, and injection interval Tdwell in step S602, the CPU 501 calculates the injection pulse width threshold value Ti_th and the injection interval threshold value Tdw_th used for valve closure detection (step S603).

[0066] The CPU 501 then compares the pulse width Ti with the pulse width threshold Ti_th (step S604). If the pulse width Ti is smaller than the pulse width threshold Ti_th in step S604 (Yes in step S604), it determines that there is a risk of erroneous valve closure detection, and the CPU 501 proceeds to step S605. Conversely, if the pulse width Ti is greater than the pulse width threshold Ti_th in step S604 (No in step S604), the CPU 501 sets initial values ​​for the valve closure detection start time Tss and the valve closure detection end time Tse (step S614). After setting the initial values ​​in step S614, the CPU 501 proceeds to processing in step S615.

[0067] If the pulse width Ti is smaller than the pulse width threshold Ti_th in step S604 (Yes in step S604), the CPU 501 compares the injection interval Tdw with the injection interval threshold Tdw_th (step S605). At this time, it is desirable that Tdw_th determined in step S603 is not a fixed value but is determined by comprehensively determining the valve closing detection data, fuel pressure, fuel temperature, etc.

[0068] If the injection interval Tdw is smaller than the injection interval threshold value Tdw_th in step S605 (Yes in step S605), the process proceeds to step S606. That is, the CPU 501 calculates the estimated Tb_e using a correlation map between the injection interval and the valve closing delay time calculated in advance, and calculates the updated valve closing detection end time Tse' by adding the detection range r1 (step S606). Thereafter, the CPU 501 proceeds to the process of step S615 and subsequent steps.

[0069] Here, the correlation map calculated in advance and stored by the CPU 501 will be described with reference to FIGS. 7 to 10. This correlation map may be learned and stored in advance by a learning unit (not shown) within the CPU 501, for example. FIG. 7 is a correlation map showing an example of the relationship between the injection pulse width and the deviation between the valve opening delay time when the injection interval is sufficiently long and the valve opening delay time when the injection interval is short. The vertical axis of FIG. 7 represents the deviation in the valve opening time, and the horizontal axis represents the pulse width. As shown in FIG. 7, the correlation map has a characteristic t11 for a long injection interval, a characteristic t12 for a sufficiently long injection interval, a characteristic t13 for a medium injection interval, and a characteristic t14 for a short injection interval, and has a deviation for each pulse width.

[0070] Fig. 8 is a characteristic diagram showing an example of the relationship between the deviation of the valve closing delay time when the injection interval is sufficiently long and the valve closing delay time when the injection interval is short, and the injection pulse width. The vertical axis of Fig. 8 represents the valve closing time during multi-stage injection, and the horizontal axis represents the pulse width. As shown in Fig. 8, the correlation map has a characteristic t21 for a short injection interval, a characteristic t22 for a medium injection interval, a characteristic t23 for a sufficiently long injection interval, and a characteristic t24 for a long injection interval, and has a valve closing time for each pulse width.

[0071] 9 is a characteristic diagram showing an example of a correction coefficient relating to fuel temperature with respect to injection pulse width. The vertical axis of FIG. 9 represents the correction coefficient, and the horizontal axis represents the pulse width. As shown in FIG. 9, the fuel temperature with respect to injection pulse width has a high temperature characteristic T31, a medium temperature characteristic T32, and a low temperature characteristic T33, and each pulse width has its own correction coefficient.

[0072] FIG. 10 is a characteristic diagram showing an example of a correction coefficient relating to fuel pressure with respect to injection pulse width. The vertical axis of FIG. 10 represents the correction coefficient, and the horizontal axis represents the pulse width. As shown in FIG. 10, the fuel pressure with respect to the injection pulse width has a low fuel pressure characteristic P11, a medium fuel pressure characteristic P12, and a low fuel pressure characteristic P13, and each pulse width has a correction coefficient. In step S615 (described later), the CPU 501 performs processing to obtain the valve closure detection end time Tse' by multiplying the valve closure detection range Tse' by a preset correction coefficient such as those shown in FIGS. 9 and 10.

[0073] 6, in step S615, the CPU 501 obtains the valve closure detection end time Tse' by multiplying the valve closure detection range Tse' by a preset correction coefficient based on the fuel pressure p_fuel and fuel temperature t_fuel obtained in step S602. Thereafter, the CPU 501 removes noise from the voltage value using a low-pass filter or the like, and then performs digital filtering using a second-order part (step S616) to extract a feature amount of the voltage change.

[0074] The CPU 501 then detects the maximum value of the digital filter 501c within the valve close detection range, i.e., between the valve close detection start time Tss and the valve close detection end time Tse' or the valve close detection end time Tse, and calculates the time when the filter output becomes maximum (step S617).The CPU 501 then sets the obtained time as the valve close detection time Tb and stores the detection result in the ROM 260 (step S618).

[0075] In step S605, if the injection interval Tdw is greater than the injection interval threshold Tdw_th (No in step S605), the process proceeds to step S607. That is, the CPU 501 accesses the data of the valve-close detection result Tb_d stored in the ROM 260 (step S607). Then, the CPU 501 determines whether or not a valve-close detection result exists for the pulse width Ti (step S608).

[0076] If it is determined in step S608 that a valve close detection result exists (Yes in step S608), the CPU 501 sets the updated valve close detection end time Tse' by adding the learned valve close detection result Tb_d to the detection range r2 (step S609). Thereafter, the CPU 501 proceeds to the processing of step S615. If it is determined in step S608 that a valve close detection result does not exist (No in step S608), the CPU 501 determines whether learned valve close data exists between the injection pulse width Ti and Ti + α1 (step S610).

[0077] In step S610, if learned valve-close data exists between the injection pulse width Ti and Ti+α1 (Yes in step S610), the process proceeds to step S611. That is, the CPU 501 acquires the learned valve-close detection result Tb_d and sets the valve-close detection result Tb_d as the valve-close detection end time Tse′ (step S611). Thereafter, the CPU 501 proceeds to step S615.

[0078] In step S615, which is reached after steps S606, S609, and S611, the CPU 501 corrects the fuel pressure and fuel temperature, detects the valve closed position, and saves the result in the ROM 260. Note that if there are multiple valve closed detection results Tb_d, it is desirable to uniquely determine one by averaging, maximum value processing, minimum value processing, or the like. However, the above-described method is merely an example, and the present invention is not limited to this.

[0079] When the injection pulse width Ti is shorter than the injection pulse width Ti at which the movable iron core 206 collides with the fixed iron core 207, the valve closing time Tb has a positive correlation with the injection pulse width Ti. Therefore, the valve closing time Tb at the injection pulse width Ti is earlier than the valve closing position Tb_d detected and stored when the injection pulse width is long. Therefore, by using the valve closing detection end time Tse' as the valve closing detection result Tb_d, the detection range is narrowed in advance, and it becomes possible to detect the valve closing position with high accuracy even when the injection pulse width Ti is short as shown in FIG.

[0080] In step S610, if there is no learned valve-close data between the injection pulse width Ti and Ti+α1 (No in step S610), the CPU 501 proceeds to step S612. That is, the CPU 501 determines whether or not there is one or more learned valve-close detection results Tb_d in the range from Ti+β1 to Ti+β2 (step S612).

[0081] In step S612, if there is one or more learned valve-closed points (Yes in step S612), the process proceeds to step S613. At this time, the ranges β1 and β2 are determined so that a positive correlation is established between the pulse width and the valve-closed time Tb when the pulse width is shorter than the time when the movable iron core 206 collides with the fixed iron core 207. Therefore, the CPU 501 estimates the valve-closed position at the injection pulse width Ti for detecting the valve-closed time by extrapolation from the learned valve-closed detection result Tb_d, and sets the valve-closed detection end time Tse' to the value obtained by adding the estimated valve-closed detection result Tb_e to the allowable range r3 (step S613). This allows the CPU 501 to narrow the detection range in advance, making it possible to accurately detect the valve-closed position even when the injection pulse width Ti is short, as shown in FIG. 5 .

[0082] When calculating the estimated valve closing position Tb_e, if two or more points are extrapolated, the CPU 501 may calculate the estimated valve closing position Tb_e by the least squares method or the like. If only one point is used, the CPU 501 can calculate the estimated valve closing time Tb_e by storing the position in advance in the ROM 260 and using the slope between the injection pulse width and the valve closing time. After the process of step S613, the CPU 501 proceeds to the process of step S615 and subsequent steps, which have already been described.

[0083] In step S612, if there is no learned valve closing time (No in step S612), the detection mode ends. Here, the CPU 501 detects the valve closing time Tb at an injection pulse width greater than Ti_th, and by increasing the number of detection points, detection becomes possible at pulse widths smaller than Ti_th. Note that it is desirable to learn the injection pulse widths for detecting valve closing in order from the largest to the smallest.

[0084] As described above, when the injection pulse width is smaller than Ti_th, the valve close detection start time Tss and the valve close detection end time Tse' are determined based on the estimated valve close position Tb_e, thereby enabling accurate detection of the valve close detection time Tb. That is, as shown in Fig. 9, the valve close detection time Tb can be detected more accurately by determining the valve close detection end time Tse' based on the estimated valve close position Tb_e, compared to when the valve close detection end time Tse is fixed.

[0085] The CPU 501 can accurately detect the valve closing time Tb based on the injection pulse width, injection interval, fuel pressure, and fuel temperature, thereby more accurately grasping the individual information of the fuel injector. As a result, for example, the variation in the injection amount at a small pulse width, as shown in FIG. 10 , can be suppressed by controlling the injection pulse width based on the valve closing detection result Tb, as shown in FIG. 11 , thereby improving the engine's exhaust performance and reducing fuel consumption. That is, FIG. 11 is a characteristic diagram showing the relationship between the valve closing detection value Tb (vertical axis) and the pulse width (horizontal axis). The characteristic x of this embodiment is a better characteristic that suppresses the individual variation compared to the characteristic y of the conventional method. Furthermore, by performing a learning process to store the valve closing time in advance, the optimal pulse width can be obtained through simple processing.

[0086] 12 and 13 are characteristic diagrams showing an example of the relationship between the fuel injection amount (vertical axis) and the pulse width (horizontal axis). Fig. 12 shows the injection amount characteristic before injection pulse correction, and Fig. 13 shows the injection amount characteristic after injection pulse correction based on the valve closure detection result when processing of this embodiment is performed. As can be seen from comparing Figs. 12 and 13, this embodiment can achieve good characteristics with individual variations suppressed.

[0087] In the embodiment described above, the valve closing detection unit 501d detects the maximum value of the voltage value at the detected inflection point. Alternatively, the valve closing detection unit 501d may calculate the maximum values ​​of the voltage value at each of the detected inflection points and detect the inflection point at which the maximum value is greatest during the period from the predetermined detection start timing to the detection end timing as the valve closing timing. This makes it possible to deal with cases where multiple inflection points are detected.

[0088] The above describes one embodiment of the fuel injection control device of the present invention, including its effects. However, the fuel injection control device of the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the invention as defined in the claims. Furthermore, the above embodiment has been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to a system having all of the described configurations.

[0089] REFERENCE SIGNS LIST 101...internal combustion engine, 102...piston, 103...intake valve, 104...exhaust valve, 106...spark plug, 107...ignition coil, 108...water temperature sensor, 109...ECU, 113...oxygen sensor, 116...crank angle sensor, 119...throttle valve, 120...air flow meter, 121...combustion chamber, 122...accelerator opening sensor, 123...fuel tank, 124...low-pressure fuel pump, 125...high-pressure fuel pump, 126...fuel pressure sensor, 127...fuel injection control device, 128...exhaust cam, 129...high-pressure fuel pipe, 131...crankshaft, 200...fuel injection device, 201...valve body, 202...valve seat, 206...moving iron core (mover), 207...stationary iron core (stator), DESCRIPTION OF SYMBOLS 208... Coil, 209... Housing, 210... First spring member, 212... Fuel supply unit, 214... Intermediate member, 215... Fuel injection hole, 216... Second spring member, 217... Third spring member, 218, 219... Transmission surface, 222... Communication line, 223... Signal line, 250... Gap, 260... ROM, 261... RAM, 304... High voltage, 308... Drive current (peak current), 310... Inflection point, 318... Current interruption time, 331... Hold current, 336... Boost voltage, 501... CPU, 501a... Current flow control unit, 501b... Voltage detection unit, 501c... Digital filter unit, 501d... Valve opening detection unit

Claims

1. A fuel injection control device applied to a fuel injection device including: a valve disc which opens and closes a fuel passage; a movable element which opens and closes the valve disc; and a stator which has a coil which is excited when current is applied and which biases the movable element, the fuel injection control device comprising: an energization control unit which controls an energization time of the coil by a pulse width of a drive command pulse; a voltage detection unit which detects a voltage value when the coil is energized; a filter unit which detects an inflection point of a waveform of the voltage value; and a valve close detection unit which detects a valve close timing of the valve disc based on an inflection point of the waveform of the voltage value from a predetermined detection start timing to a detection end timing, wherein the detection end timing for the drive command pulse currently being energized is determined based on the valve close timing when the pulse width is longer than a predetermined pulse width.

2. The fuel injection control device according to claim 1, wherein the predetermined pulse width is set based on the pulse width of the drive command pulse for operating the valve element to the half-lift state.

3. A fuel injection control device as described in claim 2, wherein the valve closing detection unit includes a learning unit which learns the valve closing timing of the valve element when the pulse width is longer than the specified pulse width, and the learning unit sets the detection end timing when the drive command pulse has a pulse width longer than the specified pulse width in accordance with a first set value, and sets the detection end timing when the drive command pulse has a pulse width shorter than the specified pulse width based on a second set value different from the first set value or the learned valve closing timing of the valve element.

4. The fuel injection control device according to claim 1, wherein the valve closing detection unit calculates the maximum value of the voltage value at each of the detected inflection points, and detects the inflection point at which the maximum value is greatest during the period from the specified detection start timing to the detection end timing as the valve closing timing of the valve body.

5. A fuel injection control method applied to a fuel injection device including a valve disc which opens and closes a fuel passage, a movable element which opens and closes the valve disc, and a stator which has a coil which is excited when current is applied and which biases the movable element, the method including: an energization control process which controls an energization time of the coil by a pulse width of a drive command pulse; a voltage detection process which detects a voltage value when the coil is energized; a filter process which detects an inflection point of a waveform of the voltage value; and a valve close detection process which detects a valve close timing of the valve disc based on an inflection point of the waveform of the voltage value during a period from a predetermined detection start timing to a detection end timing, wherein the detection end timing for the drive command pulse currently being energized is determined based on the valve close timing when the pulse width is longer than a predetermined pulse width.

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