Fuel injection control device

Abstract

To provide a fuel injection control device capable of performing suitable calculation of drive pulse width with reduced time.SOLUTION: A relation between an electric conduction start time and a valve closing time is acquired. A first valve closing time and a first electric conduction time when a change amount of the valve closing time relative to an increase amount of a request electric conduction time corresponds to a point spanning from a higher side to a lower side of a preset threshold value are acquired. A second valve closing time and a second electric conduction time when the change amount of the valve closing time relative to the increase amount of the request electric conduction time corresponds to a point spanning from the lower side to the higher side of the set threshold value are acquired. Drive command pulse width in a region where drive pulse width is smaller than in the first electric conduction time and when the valve closing time is shorter than the second valve closing time is acquired as a third electric conduction time. Whether or not a value of the request electric conduction time based on a request fuel injection amount corresponds to a section from the third electric conduction time to the second electric conduction time is determined, and the section from the third electric conduction time to the second electric conduction time is set as ineffective pulse width.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a fuel injection control device. [Background technology]

[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 cylinders by increasing the pressure of the fuel supplied to the engine cylinders, atomizing the injected fuel, and forming a uniform air-fuel mixture.

[0004] In order to improve the pressure of fuel supplied into the engine cylinder, for example, the amount of fuel required for one combustion stroke can be divided and injected to achieve homogenization and improve exhaust performance. To achieve this, the fuel injection valve needs to be able to measure the injection amount with high precision. Patent Document 1 describes a fuel injection device that detects individual information and corrects the drive pulse width to suppress injection amount variations in the nonlinear region and improve the injection amount measurement accuracy. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-134689 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the fuel injection device described in Patent Document 1 sequentially changes the drive pulse width to achieve the target injection amount in a region where the injection amount is nonlinear with respect to the drive command pulse width to the fuel injection valve. As a result, the fuel injection device described in Patent Document 1 has the problem of taking a long time to achieve the target injection amount. Here, the region where the injection amount is nonlinear refers to a region where there is a mixture of a region where the injection amount has a positive correlation with the injection pulse width and a region where the injection amount has a negative correlation with the injection pulse width. If it takes a long time to achieve the target injection amount, engine performance will deteriorate during that time. Also, if it takes a long time to achieve the target injection amount, there is a problem that the exhaust emitted from the engine will deteriorate.

[0007] An object of the present invention is to provide a fuel injection control device that can calculate a suitable drive pulse width in a short amount of time. [Means for solving the problem]

[0008] In order to solve the above problems, for example, the configurations described in the claims are adopted. The present application includes a plurality of means for solving the above-mentioned problems, and one example thereof is a fuel injection control device that includes a control unit that controls the drive command pulse width of a fuel injection valve having a solenoid coil based on a required fuel injection amount, a voltage detection unit that detects a back electromotive force value of the solenoid coil, and a valve closing detection unit that detects the valve closing time of the fuel injection valve based on the back electromotive force value. Here, the control unit acquires the relationship between the start of current flow and the valve closing time from the valve closing detection unit, acquires a first valve closing time and a first current flow time corresponding to the point where the change in the valve closing time relative to the increment of the required current flow time crosses from higher to lower than a predetermined threshold, acquires a second valve closing time and a second current flow time corresponding to the point where the change in the valve closing time relative to the increment of the required current flow time crosses from lower to higher than a predetermined threshold, acquires as a third current flow time a drive command pulse width in a region where the drive pulse width is smaller than the first current flow time and when the valve closing time is smaller than the second valve closing time, determines whether the value of the required current flow time based on the required fuel injection amount falls within the section from the third current flow time to the second current flow time, and sets the section from the third current flow time to the second current flow time as an invalid pulse width. [Effects of the Invention]

[0009] According to the present invention, the drive pulse width for achieving a target injection amount can be determined without trial and error calculation even in the region where the injection amount is nonlinear, so that an appropriate drive pulse width can be calculated in a short time. As a result, the present invention can suppress deterioration of engine performance that occurs in the process of sequential calculation, and can improve exhaust emissions from the engine. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an overall configuration diagram showing an example of the basic configuration of an internal combustion engine equipped with a fuel injection control device according to an embodiment of the present invention; [Figure 2] 1 is a cross-sectional view showing a fuel injection device according to an embodiment of the present invention; [Figure 3] 1 is a diagram showing details of a drive circuit and an engine control unit (ECU) of a fuel injection control device according to an embodiment of the present invention. [Figure 4]3 is a diagram showing the drive command injection pulse (injection pulse), drive voltage, detection filter, filtered signal, drive current, valve body displacement, and movable core displacement for the fuel injection device shown in FIG. 2 when the drive command pulse width is long. [Figure 5] FIG. 4 is a diagram showing the relationship between the valve closing time and the injection amount. [Figure 6] 1A is a diagram showing the relationship between the drive pulse width and the valve closing time, and FIG. 1B is a diagram showing the relationship between the drive pulse width and the slope of the valve closing time relative to the drive pulse width. [Figure 7] 10 is a flowchart showing a process flow for calculating a control invalid pulse width according to an embodiment of the present invention. [Figure 8] 10A and 10B are diagrams illustrating an example of a process for deriving the slope of the valve closing time relative to the drive pulse width and the intercept of the valve closing time relative to the drive pulse width for a target valve closing time. [Figure 9] FIG. 10 is a diagram showing an example of variations in individual characteristics of injection amounts when the present invention is not applied. [Figure 10] FIG. 10 is a diagram showing an example of variations in individual characteristics of injection amount when an embodiment of the present invention is applied. [Figure 11] FIG. 10 is a diagram showing a comparison between a conventional example of a valve closing detection value versus an injection amount and an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] A fuel injection control device according to an embodiment of the present invention will be described below. 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 to 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 has passed through the throttle valve 119 is drawn into a collector 115, which is a branching section, and is 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] A solenoid-driven open / close valve 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 (ECU: Electronic Control Unit) 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.

[0017] As shown in Fig. 2, the 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. The ECU 109 calls up a program from the RAM 261 based on a control command, and controls a solenoid based on the data stored in the ROM 260. This drives an on-off valve so that the pressure of the fuel discharged from the high-pressure fuel pump 125 (fuel pressure) becomes a desired pressure.

[0018] 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. When a drive current is supplied (energized) to a coil 208 (described later), the fuel injection device 200 operates a valve body to inject fuel.

[0019] 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 by the fuel pressure sensor 126, the ECU 109 sends a control command to a fuel injection control device 127 to adjust the fuel pressure in the high-pressure fuel pipe 129 to a desired pressure. That is, the ECU 109 performs so-called feedback control to adjust the fuel pressure in the high-pressure fuel pipe 129 to the desired pressure.

[0020] Furthermore, each combustion chamber 121 of the internal combustion engine 101 is provided with an ignition 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.

[0021] 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.

[0022] 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 concentration of oxygen 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 injection supplied from the fuel injection device 200 becomes a target air-fuel ratio.

[0023] 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 result 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.

[0024] 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 indicating the opening of the accelerator operated by the driver, a fuel pressure sensor 126, and the like.

[0025] The ECU 109 calculates the torque required for the internal combustion engine 101 based on the signal supplied from the accelerator opening 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.

[0026] 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 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 after the internal combustion engine 101 is started, etc.

[0027] 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 ignition plug 106.

[0028] [Configuration of fuel injection system] 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. 2, 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 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 supply unit 212 is disposed at the upper end of the drawing, and fuel injection holes 215 and valve seat 202 are disposed at the lower end. Moving iron core 206, valve element 201, and intermediate member 214 are disposed between fuel supply unit 212 and valve seat 202.

[0030] The end of fuel injection device 200 on the opposite side (fuel supply unit 212 side) of fuel injection hole 215 and valve seat 202 is connected to high-pressure fuel pipe 129 (see FIG. 1), not shown. The end of fuel injection device 200 on the opposite side of fuel supply unit 212 (fuel injection hole 215 side) is inserted into a mounting hole (insertion hole) formed in a member such as a cylinder block or cylinder head 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 207 and the housing 209. The fixed iron core 207, the coil 208, and the housing 209 form a magnetic circuit. In a closed valve state in which the coil 208 is not energized, the valve element 201 abuts against the valve seat 202 due to 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 that bias the valve element 201 in the valve closing direction. This state in which the valve element 201 abuts against the valve seat 202 is referred to as a stable closed valve state. In the stable closed valve state, the movable iron core 206 abuts against the intermediate member 214 and is disposed in the closed valve position. The valve element 201 is driven via a transmission surface 219 that transmits the load from the movable iron core 206.

[0033] 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 element 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. 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 element 201 and the movable iron core 206.

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

[0035] The ECU 109 receives signals indicating the engine state 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. The ECU 109 communicates with the fuel injection control device 127 through a communication line 222, and can switch 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 can change its control constant by communicating with the ECU 109, and the current waveform changes depending on 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. FIG. 3 is a diagram showing the details of the drive circuit of the fuel injection control device 127 and the ECU 109. The ECU 109 (see FIG. 2) includes a CPU (Central Processing Unit) 501 built therein. CPU 501 receives various signals indicating the state of the engine from fuel pressure sensor 126, air flow meter 120, oxygen sensor 113, crank angle sensor 116, etc. In response to these signals, CPU 501 calculates the width of a drive command pulse (injection pulse) and injection timing for controlling the amount of fuel injected from fuel injection device 200 in accordance with the operating conditions of the internal combustion engine.

[0038] Furthermore, CPU 501 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 drive IC 502 of fuel injection device 200 through signal line 223. CPU 501 represents a specific example of a control unit in fuel injection control device 127 of the present embodiment. The injection amount is determined by the pulse width of the drive command pulse. Thereafter, CPU 501 supplies a drive current to fuel injection device 200 by switching switching elements 505, 506, and 507 between energized and de-energized states using drive IC 502.

[0039] 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 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, for example, FETs (Field Effect Transistors) or transistors, and can switch between energizing and de-energizing the fuel injection device 200.

[0040] The boost 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 with 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.

[0041] In the boost circuit 514, when the transistor 531 is turned on, the battery voltage VB shifts to the ground potential 534 side. On the other hand, when the transistor 531 is turned off, the high voltage generated in the coil 530 flows through the diode 532 and accumulates charge in the capacitor 533. Then, this transistor is repeatedly turned on and off, increasing the voltage of the capacitor 533 until it reaches the boosted voltage VH. The transistor 531 is connected to a driving IC (Integrated Circuit) 502 or a CPU 501, and the boosted 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 by a DC / DC converter or the like.

[0042] Switching element 507 is connected between a low voltage source and a high voltage terminal of solenoid 540. Low voltage source VB is, for example, a battery voltage, and its voltage value is about 12 to 14 V. Switching element 506 is connected between a low voltage side terminal of fuel injection device 200 and ground potential 515.

[0043] Drive IC 502 detects the value of the current flowing through fuel injector 200 using current detection resistors 508, 512, and 513. Then, drive IC 502 switches switching elements 505, 506, and 507 between energized and de-energized states based 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.

[0044] CPU 501 communicates with drive IC 502 through communication line 222, and drive IC 502 can switch the drive current it generates depending on the pressure of the fuel supplied to fuel injection device 200 (see FIG. 2) and operating conditions. In addition, both ends of resistors 508, 512, and 513 are connected to the A / D conversion port of IC 502, and drive IC 502 can detect the voltage applied across resistors 508, 512, and 513.

[0045] Note that data acquisition processing, calculation processing, and control processing required for executing target pulse width correction control processing, which will be described later in this embodiment, are executed by a program prepared in the ECU 109 or the CPU 501. That is, by executing the program prepared in the ECU 109, the fuel injection control device 127 is configured with a control unit that controls the drive command pulse width of the fuel injection valve based on the required fuel injection amount. Also, the circuit configuration shown in FIG. 3 constitutes a voltage detection unit that detects the back electromotive force value of the solenoid 540. Also, the ECU 109 or the CPU 501 is configured with a valve closing detection unit that detects the valve closing time of the fuel injection valve based on the energization start time of the fuel injection valve, which is based on the detected back electromotive force value.

[0046] [Fuel injection system operation] 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 is a diagram showing the drive command pulse (ejection pulse), drive voltage, drive current, valve element displacement, and movable iron core displacement. The displacement of the valve element movable element shown in the bottom part of FIG. 4 is shown by the dashed line as the displacement of the valve element 201 and the solid line as the displacement of the movable iron core 206.

[0047] As shown in FIG. 4, when a drive command pulse Ti is input at time Ts, a high voltage 304 is applied 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 (see FIG. 2).

[0048] 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. This magnetomotive force causes a magnetic flux to flow around a magnetic path formed by the fixed core 207, the housing 209, and the movable core 206 so as to surround the coil 208. At this time, a magnetic attraction force acts between the movable core 206 and the fixed core 207, displacing the movable core 206 and the intermediate member 214 toward the fixed core 207. Thereafter, the movable core 206 displaces until the transmission surface 219 of the valve element 201 abuts against the transmission surface 218 of the movable core 206. The valve element 201 continues to abut against the valve seat 202.

[0049] 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. Then, the valve element 201 is pulled upstream by the energy of the movable iron core 206 and separated from the valve seat 202. As a result, a gap is formed at the valve seat, the fuel passage opens, and fuel is injected from the fuel injection hole 215. In this way, the valve element 201 is suddenly displaced by the movable iron core 206 having kinetic energy.

[0050] The fuel injection control device 127 applies a high voltage 304 to the valve element 201 and causes a drive current 308 to flow through the coil 208 until the movable iron core 206 and the valve element 201 collide with each other at time Ts and sufficient kinetic energy is accumulated to open the valve element 201. 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 fuel injection control device 127 to make the movable iron core 206 respond quickly.

[0051] Furthermore, by quickly responding the movable iron core 206, the fuel injection control device 127 can reduce the effect of the variation on the injection amount, even if the gap 250, which serves as the preliminary stroke, varies from one individual to another. Furthermore, even when the fuel pressure is high, the fuel injection control device 127 can drive the valve element 201 toward the movable iron core 206 by using the kinetic energy of the movable iron core 206 obtained by idle running within the gap 250.

[0052] The drive current flowing through the coil 208 rises sharply as indicated by peak current 308 due to the application of high voltage 304. When the drive current reaches peak current value Ip, the high voltage 304 is switched to battery voltage 305.

[0053] In this embodiment, the current is set to reach a peak current value Ip at the valve opening start timing, and when the current reaches the peak current value Ip, the current is switched to the battery voltage 305, and the battery voltage 305 is controlled by switching on and off so that the current falls within a predetermined current threshold range. While the battery voltage 305 is being switched on and off, a drive current 331 that changes in response to the on and off is obtained.

[0054] After the movable core 206 and the fixed core 207 collide, the valve disc 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 disc 201 and the movable core 206 separate, and the movable core 206 is displaced downstream, but eventually comes to rest and stabilize at the target lift position. This state is called the stable open valve state.

[0055] The movable iron core 206 and the valve element 201 are configured to be capable of relative movement, so when the movable iron core 206 collides with the fixed iron core 207, the valve element 201 and the movable iron core 206 separate from each other, and the valve element 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 the drive voltage in the reverse direction (applies a reverse voltage). This cuts off the current supply to the coil 208, and the magnetic flux generated in the magnetic circuit disappears, causing the magnetic attraction force to disappear. As a result, the movable iron core 206, which has lost its magnetic attraction force, is pushed back to the closed position where the valve element 201 contacts the valve seat 202 by the load of the first spring member 210 and the force due to the fuel pressure.

[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. At time Teoi, when the valve closing required time has elapsed from time Te when the drive command pulse Ti is turned off until the valve closing is completed, 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 the time Teoi when the valve is completely closed, the movable iron core 206 and the valve element 201 become separated as shown in FIG. 2. At this time, a bend-like change appears in the drive voltage, as shown by inflection point 310. From this change, the time Teoi 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, causing an inflection point 310 to occur in the drive voltage.

[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. In this case, the valve-closing time Teoi can be detected by detecting the maximum or maximum value of the filtered signal within a preset range from the filtering start time Tss to the filtering end time Tse.

[0061] The filtered voltage signal in Figure 4 is a waveform obtained by second-order differentiation of the drive voltage. As described above, the waveform obtained by second-order differentiation of the voltage changes in value after digital filtering as the slope of the voltage changes. That is, when the valve element 201 closes, the acceleration of the movable iron core 206 changes, which results in a change in voltage. Therefore, by calculating the maximum value of the digital filtering process, 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, which is the valve closing time Teoi of the valve element 202.

[0062] [Relationship between valve closing time and injection amount] Fig. 5 is a graph showing the valve closing time Teoi (horizontal axis) and the fuel injection amount (vertical axis) injected at that time from fuel injection device 200. As shown in Fig. 5, it is known that a linear relationship exists between the valve closing time Teoi and the injection amount, and the target valve closing time Teoi_tar can be calculated from the target injection amount Q_tar using a previously calculated relational expression (Equation 1). That is, the valve closing time at the drive pulse width, the injection amount injected by the fuel injector, and the pressure supplied to the fuel injector are stored as constants in advance. Next, the required injection amount is used as an input to obtain the required valve closing time, and the target injection pulse width is calculated from the relationship between the obtained required valve closing time, the change amount, and the intercept. a1 and b1 in the formula (1) are the same as a1 and b1 shown in FIG. 5, and may be set as a function of the fuel pressure.

[0063]

number

[0064] [Calculation processing of injection pulse width] Next, a method for calculating the injection pulse width Ti_tar will be explained. Fig. 6(a) is a diagram showing the relationship between the injection pulse width (horizontal axis) and the valve closing delay time (vertical axis). Fig. 6(b) is a diagram showing the relationship between the drive pulse width (horizontal axis) and the slope a_0 (vertical axis) of the valve closing time relative to the pulse width. The drive pulse widths in Fig. 6(a) and Fig. 6(b) are shown with the same time axis.

[0065] As shown in FIG. 6(a), at a predetermined drive pulse width, the valve closing Teoi is detected from the inflection point obtained from the voltage after filtering, and the relationship shown in FIG. 6(a) is obtained. Here, as shown in Figure 6(b), the slope a_0 is calculated from the drive pulse width and the valve closing time Teoi. This can be calculated using, for example, an equation such as the one shown in [Equation 2]. Here, i indicates the order of the drive pulse width, and i+1 indicates a drive pulse that is one step larger than the drive pulse width of i.

[0066]

number

[0067]

number

[0068] As shown in Figure 6(b), there is a section where the slope a_0 of the valve closing time Teoi with respect to the drive pulse width Ti changes from a positive value above zero to a negative value below zero. This is known to be due to the effect of the bounding that occurs when the valve disc 201 collides with the fixed iron core 207. In the region where the bounding between the valve disc 201 and the fixed iron core 207 occurs, there is a region where the slope of the valve closing time Teoi with respect to the drive pulse width changes from a negative value to a positive value. In this region where positive and negative characteristics coexist, there is a risk of instability in feedback control, which calculates the difference between the target valve closing time and the actual valve closing time and determines the control amount based on the difference, making it extremely difficult to converge to the target valve closing time and making the control of the injection pulse width unstable.

[0069] To solve the above problem, in this embodiment, as will be described below, the gradient a_0 of the valve closing time Teoi with respect to the injection pulse width is derived, the region where the characteristic is negative is detected, and the control invalid pulse width is set based on the detected result. Here, in this embodiment, as will be described in the flowchart of Fig. 7, the drive pulse width Ti_e in the region where the characteristic changes from negative to positive and the drive pulse width Ti'_s where the characteristic changes from positive to negative are calculated.

[0070] [Processing to calculate control invalid pulse width] Hereinafter, a method for calculating the injection pulse width Ti_tar with respect to the target time Teoi_tar will be described with reference to FIGS. FIG. 7 is a flowchart showing the flow of calculating the control invalid pulse width. When the calculation of the control invalid pulse width is started, the ECU 109 detects the valve closing time Teoi at a plurality of pulse widths (step S701). Alternatively, the ECU 109 reads the valve closing time Teoi stored in the RAM 261.

[0071] Next, the ECU 109 calculates the gradient a_0 between the drive pulses using the formula (1), and temporarily stores the calculated gradient a_0 in the RAM 261 (step S702). Thereafter, the ECU 109 reads the slope a_0 from the RAM 261 and determines whether or not there is a region where the slope a_0 is negative (step S703).

[0072] If it is determined in step S703 that there is no region where the gradient a_0 is negative (No in step S703), the ECU 109 ends the process of calculating the control invalid pulse width. Furthermore, if it is determined in step S703 that there is a region where the slope a_0 is negative (Yes in step S703), the ECU 109 acquires the pulse width Ti_e in the region where the slope a_0 changes from negative to positive and the pulse width Ti'_s where the slope a_0 changes from positive to negative (step S704). The pulse width Ti_e in the region where the slope a_0 changes from negative to positive and the pulse width Ti'_s where the slope a_0 changes from positive to negative are values ​​acquired in a state such as that shown in FIG.

[0073] Furthermore, after acquiring the pulse widths Ti_e and Ti'_s in step S704, the ECU 109 acquires the valve closing time Teoi_e at the pulse width Ti_e (step S705). Thereafter, the ECU 109 searches for a region where the drive pulse width is smaller than the injection pulse width Ti'_s and is smaller than the valve closing time Teoi_e, starting from the region where the drive pulse width is larger (step S706). Furthermore, the ECU 109 sets the drive pulse width that is initially shorter than the valve closing time Teoi_e to Ti_s, and sets the ineffective injection pulse width from the drive pulse width Ti_s to the drive pulse width Ti_e (step S707), and the ECU 109 ends the process of calculating the control ineffective pulse width.

[0074] By performing this processing, the control invalid pulse width is excluded from the control drive pulse width, so continuous injection amount control is possible without using the region where the slope of the valve closing time Teoi relative to the injection pulse width Ti is negative.

[0075] The control process by the ECU 109 described above can be summarized as follows. That is, the control unit configured in ECU 109 acquires the relationship between the energization start time and the valve closing time from the valve closing detection unit. When acquiring the relationship between the energization start time and the valve closing time, it is preferable to acquire at least three or more relationships between the energization time and the valve closing time from the output of the valve closing detection unit, for example.

[0076] The control unit configured in ECU 109 then obtains a first valve closing time and a first current supply time corresponding to a point where a change in the valve closing time relative to an increment of the requested current supply time crosses from higher to lower than a preset threshold value. The control unit configured in ECU 109 also obtains a second valve closing time and a second current supply time corresponding to a point where a change in the valve closing time relative to an increment of the requested current supply time crosses from lower to higher than a preset threshold value.

[0077] Furthermore, the control unit configured in ECU 109 acquires, as a third energization time, a drive command pulse width in a region where the drive pulse width is smaller than that at the first energization time and when the valve closing time is smaller than the second valve closing time. Then, the control unit configured in ECU 109 determines whether the value of the requested current supply time based on the requested fuel injection amount falls within the interval from the third current supply time to the second current supply time, and sets the interval from the third current supply time to the second current supply time as the invalid pulse width.

[0078] [Process of deriving the slope and intercept of the valve closing time] FIG. 8 is a diagram showing the process of deriving the slope a_0 and intercept b_0 with respect to the valve closing time, drive pulse width, and target valve closing time Teoi_tar. In FIG. 8, the vertical axis indicates the valve closing time, the slope a_0, and the intercept b_0, and the horizontal axis indicates the drive pulse width. As shown in FIG. 8, the target valve closing time (valve closing time indicated by a black circle) in the region where the slope a_0 is positive can be calculated.

[0079] In this embodiment, once the target injection pulse width Teoi_tar is determined using the relationship between the valve closing time and the fuel injection amount described in Figure 5 and equation [4], the slope a_0 and intercept b_0 corresponding to the target injection pulse width Teoi_tar are calculated. For example, from the slope a_0 and intercept b_0 related to the valve closing time Teoi, the first order k at which the target injection pulse width Teoi_tar exceeds the valve closing time Teoi[k] is calculated, and the slope a_0[k] and b_0[k] are calculated at this time. Because the slope a_0 and intercept b_0 are piecewise linearly approximated, the injection pulse width Ti_tar can be obtained using equation 4.

[0080]

number

[0081] According to this embodiment, it is possible to determine the target drive pulse width Ti_tar from the target injection amount in this manner. That is, as shown in Figure 8, by calculating and storing the change in the valve closing time relative to the increment in the requested energization time for the drive pulse width at which the valve is closed, and then calculating and storing the intercept that appears when the relationship between the increment in the requested energization time and the valve closing time is approximated as a straight line, it is possible to derive the appropriate slope and intercept. In addition, the change amount and intercept closest to the target valve closing time may be referenced, and when the change amount and intercept are referenced in the region of the invalid pulse width, the change amount and intercept at a pulse width greater than the invalid pulse width may be referenced. By using the target pulse width correction control method described above, it is possible to more accurately grasp the individual information of the fuel injector.

[0082] [Effects of this embodiment] 9 and 10 are characteristic diagrams showing examples of the relationship between the fuel injection amount (vertical axis) and the pulse width (horizontal axis). Fig. 9 shows the injection amount characteristics when the target pulse width correction control method of this embodiment is not applied, and Fig. 10 shows the injection amount characteristics when the target pulse width correction control method of this embodiment is applied. The variation in injection quantity at minute pulse widths as shown in Fig. 9 can be suppressed by using control such as correcting the injection pulse width based on the valve closure detection result Teoi, as shown in Fig. 10. This makes it possible to improve the exhaust performance of the engine and reduce fuel consumption.

[0083] 11 is a graph comparing the fuel injection amount (horizontal axis) and the injection amount variation (vertical axis) between the characteristic α of this embodiment and the characteristic β of the conventional embodiment. As shown in this FIG. 11, this embodiment can drastically reduce the injection amount variation. As described above, according to this embodiment, it is possible to suppress variations between individual components, and in turn, it is possible to improve the exhaust performance of the engine and reduce fuel consumption.

[0084] [Variations] The above describes the embodiments of the fuel injection control device of the present invention, including their effects. However, the fuel injection control device of the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the invention described in the claims. Furthermore, the above-described embodiments have 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. [Explanation of symbols]

[0085] 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 injector, 201...valve body, 202...valve seat, 206...moving iron core (moving core), 207...stationary iron core (stator), 208... Coil, 209... Housing, 210... First spring member, 212... Fuel supply portion, 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), 330... Inflection point, 331... Hold current, 501... CPU

Claims

1. a control unit that controls a drive command pulse width of a fuel injection valve having a solenoid coil based on a required fuel injection amount; a voltage detection unit that detects a back electromotive force value of the solenoid coil; a valve closing detection unit that detects a valve closing time of the fuel injection valve based on a time when current is applied to the fuel injection valve that is based on the back electromotive voltage value, The control unit The relationship between the energization time and the valve closing time is obtained from the valve closing detection unit; obtaining a first valve closing time and a first current supply time corresponding to a point where a change in the valve closing time relative to an increment in the required current supply time crosses over from a higher to a lower threshold value; obtaining a second valve closing time and a second current supply time corresponding to a point where a change in the valve closing time relative to an increment in the required current supply time crosses over from a lower to a higher value than a predetermined threshold value; a drive command pulse width in a region where the drive pulse width is smaller than the first energization time and when the valve closing time is smaller than the second valve closing time is acquired as a third energization time; determining whether or not a value of a requested current conduction time based on a requested fuel injection amount falls within a section from the third current conduction time to the second current conduction time, and setting the section from the third current conduction time to the second current conduction time as an invalid pulse width; Fuel injection control device.

2. The control unit calculates and stores a change in the valve closing time relative to an increment in the required current application time in a drive pulse width at which the valve closing detection unit detects that the valve is closed, calculates and stores an intercept that appears when a relationship between the increment in the required current application time and the valve closing time is linearly approximated, and stores the valve closing time such that the change, the intercept, and the drive pulse are paired.

2. The fuel injection control device according to claim 1.

3. the control unit holds the valve closing time at the drive pulse width, the injection amount injected by the fuel injection valve, and the pressure supplied to the fuel injection valve as constants in advance, and obtains the requested valve closing time using the requested fuel injection amount as an input; A target injection pulse width is calculated from the relationship between the obtained requested valve closing time, the change amount, and the intercept.

3. The fuel injection control device according to claim 2.

4. The control unit refers to the change amount and intercept that are closest to the target valve closing time, and when the change amount and intercept are referred to in the region of the invalid pulse width, refers to the change amount and intercept when the pulse width is larger than the invalid pulse width.

4. The fuel injection control device according to claim 3.

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