JP2020041504A - Control device of internal combustion engine - Google Patents

Abstract

To suppress erroneous detection of knock and to prevent degradation of knock detectability.SOLUTION: A control device of an internal combustion engine includes a plurality of cylinders, and at least a first cylinder and a second cylinder include receiving portions for receiving knock signals from knock sensors disposed on the same bank and mounted on the internal combustion engine, and a knock detecting portion for detecting knocking in the internal combustion engine by using the knock signals in a knock detection window in a period to take the knock signal. The knock detection portion detects whether noise in opening and closing a first fuel injection valve, is included in the knock detection window of the second cylinder or not on the basis of boost voltage boosted by a battery for operating a first fuel injection valve as the fuel injection valve for injecting a fuel to the first cylinder.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a control device for an internal combustion engine.

  Generally, in a spark ignition type internal combustion engine which compresses a mixture of air and fuel and ignites with a spark plug, a knock control device for suppressing generation of knock is mounted. As is well known, this knock control device performs feedback control of the ignition timing to an ignition timing at which no knock occurs based on a knock signal of a predetermined level output from a knock sensor.

  For example, the following method is known as a knock detection method in the knock control device. First, the signal of the knock sensor is A / D-converted in a section defined by a predetermined crank angle range (hereinafter, referred to as a "knock detection window") so as to take in a specific section in which knock may occur. Next, the background level is calculated by filtering the AD conversion value when knock does not occur, for example, by performing weighted averaging. Then, an evaluation value is calculated using the background level and the AD conversion value in a section where knock may occur, and when the evaluation value exceeds a threshold value, it is determined that knock is present.

  By the way, the A / D conversion value of the knock sensor signal when knock does not occur means so-called background noise, and this background noise is mainly caused by valve seating of a valve operating system such as an intake valve and an exhaust valve. Noise, injector opening / closing valve noise, other mechanical noise, vibration noise due to combustion, and the like.

  It has been generally known that the knock controllability is largely affected by the seating noise of the intake valve, and a number of avoiding means have been disclosed as a known technique. In recent years, an in-cylinder internal combustion engine that directly injects fuel into a cylinder has been used in order to reduce fuel consumption and exhaust gas harmful components. In the in-cylinder injection type internal combustion engine, the injected fuel pressure is set high to inject fuel into the cylinder. In addition, the set pressure of the valve-closing spring of the injector is set to be large in accordance with this, so that the on-off valve noise of the injector greatly affects the background noise.

  Further, in an in-cylinder injection type internal combustion engine, split injection is performed in which the number of times of fuel injection is divided from one to a plurality of times (for example, one to three times) during one combustion cycle. . For example, in the case of the first injection mode for generating a homogeneous mixture, the fuel is injected once or twice in the intake stroke, and in the second injection mode for generating the stratified mixture, the fuel is injected in the intake stroke. The fuel is injected once or twice, and the fuel is injected once or twice in the subsequent compression stroke. The adoption of the injection mode in which the fuel is injected also in the compression stroke following the intake stroke has a great effect on knock determination.

  Specifically, in a horizontally opposed four-cylinder internal combustion engine in which the combustion cycle is performed in the order of the first cylinder, the third cylinder, the second cylinder, and the fourth cylinder, fuel is injected in the intake stroke of the first cylinder. If it is, the knock detection window is open for the second cylinder. At this time, in the horizontally opposed four-cylinder internal combustion engine, the first cylinder and the third cylinder are in the same bank, the second cylinder and the fourth cylinder are in the same bank, and a knock sensor is provided in each bank. I have. For this reason, the valve closing noise of the injector during the intake stroke of the first cylinder is hardly transmitted to the bank of the second cylinder, and is taken into the knock detection window of the second cylinder and does not adversely affect it. The term “bank” refers to a row of cylinders, and is also called a “cylinder row” or a “cylinder bank”.

  However, when fuel is injected in the first half of the compression stroke following the intake stroke of the third cylinder, the knock detection window is opened in the first half of the expansion stroke of the first cylinder. At this time, since the first cylinder and the third cylinder are in the same bank, the knock detection window set in the first half of the expansion stroke of the first cylinder and the fuel injection timing in the first half of the compression stroke of the third cylinder overlap each other. The valve closing noise of the injector in the compression stroke of the three cylinders is taken into the knock detection window of the first cylinder.

  Therefore, the AD conversion value of the knock sensor signal taken in the knock detection window section of the first cylinder reflects the valve closing noise of the injector in the first half of the compression stroke of the third cylinder. May cause detection. Of course, the erroneous detection of knock may similarly occur in other cylinders.

  In order to avoid such an influence of the injector opening / closing valve noise, for example, in Patent Document 1, the vibration intensity during the knock determination period and the vibration intensity during the operation of the injector are calculated, and the knock determination value is calculated based on the larger magnitude. There have been proposed means for calculating, and means for learning the vibration intensity of the injector noise when there is no knock, and calculating a knock determination value based on the learned value. As another avoiding means, the influence of the injector opening / closing valve noise is avoided by switching the knock determination value or the background noise value to a set value corresponding to the mode in accordance with the switching between the first injection mode and the second injection mode. Means have been proposed.

JP 2013-15105 A

  On the other hand, in a system for fuel injection, in a fuel injection device having an electromagnetically driven fuel injection valve, a boosting power supply generally includes a boosting circuit including an inductive element and a switching element, and a capacitor for storing boosted power. It is composed of When the fuel injection valve is energized from the boost power supply, power is supplied by discharging from the capacitor. For this reason, when a current is supplied from the step-up power supply, the voltage of the capacitor drops due to discharge.

  The voltage of the capacitor lowered by the discharge is charged by the booster circuit after the discharge, and returns to the boosted predetermined voltage.However, when performing a plurality of injections in a relatively short time, the charge is applied to the second and subsequent injections. May not be in time. If the next injection is performed before the charging of the boosted voltage is completed, since the voltage is lower than the rating, the suction energy of the plunger of the fuel injection valve decreases, and the operation of the on-off valve of the fuel injection valve is delayed from the rating. Therefore, for example, the AD conversion value of the knock sensor signal taken in the section of the knock detection window of the first cylinder includes the opening / closing valve noise of the injector in the first half of the compression stroke of the third cylinder. Detection may occur. Therefore, even when performing fuel injection a plurality of times in one combustion cycle, it is required that erroneous knock detection be suppressed and that knock detection performance be not deteriorated.

  A control device for an internal combustion engine according to a first aspect of the present invention includes a plurality of cylinders, and at least a first cylinder and a second cylinder receive a knock signal from a knock sensor attached to an internal combustion engine arranged in the same bank. And a knock detection unit that detects knocking in the internal combustion engine using the knock signal in a knock detection window that is a period during which the knock signal is captured. The knock detection unit includes the first cylinder. When opening and closing the first fuel injection valve in the knock detection window of the second cylinder based on a boosted voltage that is boosted by a battery that operates a first fuel injection valve that is a fuel injection valve that injects fuel into the second cylinder. It detects whether noise is included or not.

  ADVANTAGE OF THE INVENTION According to this invention, erroneous detection of a knock can be suppressed and knock detectability can be prevented from deteriorating.

Diagram showing the configuration of the fuel injection system The block diagram which shows the outline of a structure and operation | movement of the fuel injection valve control part 127 FIG. 4 is a diagram showing a transition of progress of each stroke of the internal combustion engine 101. The figure which shows transition of the progress of each process at the time of shifting from the 1st injection mode to the 2nd injection mode. Time chart showing an example of boosted voltage during multi-stage injection Timing chart showing the relationship between fuel injector drive current, boost voltage, and boost return time Conceptual diagram showing the relationship between the battery voltage and the reset reference time of the boosted voltage Diagram showing temporal relationship between injector drive signal, knock sensor signal, and knock detection window Conceptual diagram showing the relationship between the insufficient boosted voltage and the angle obtained by converting the delay time of the injector noise into the crank angle of the internal combustion engine 101. The figure which shows the outline | summary of operation | movement of the knock detection part 11 Flow chart showing the operation of the fuel injection valve control unit 127 Flow chart showing the operation of the fuel injection valve control unit 127

-Embodiment-
Hereinafter, an embodiment of an ECU which is a control device of an internal combustion engine will be described with reference to FIGS. However, the present invention is not limited to the following embodiments, and includes various modifications and application examples within the technical concept of the present invention.

  FIG. 1 is a diagram showing a configuration of a fuel injection system for an internal combustion engine according to an embodiment of the present invention. The fuel injection system shown in FIG. 1 includes an internal combustion engine (engine) 101 having four cylinders, a fuel injection valve (injector) 105, and an electronic device that controls overall control of the internal combustion engine including fuel injection by the fuel injection valve 105. An ECU (Engine Control Unit) 109 serving as a control device is provided. Hereinafter, the four cylinders provided in the internal combustion engine 101 will be referred to as first to fourth cylinders. Further, a fuel injection valve 105 that injects fuel into each of the first cylinder, the second cylinder, the third cylinder, and the fourth cylinder includes a first fuel injection valve 105a, a second fuel injection valve 105b, and a third fuel injection valve 105c. , And the fourth fuel injection valve 105d.

  The ECU 109 includes a CPU that is a central processing unit, a ROM that is a read-only storage device, and a RAM that is a readable and writable storage device. The CPU expands a program stored in the ROM into the RAM and executes the program. To implement multiple functions. However, the ECU 109 may be realized by an FPGA (Field Programmable Gate Array), which is a rewritable logic circuit, or an ASIC (Application Specific Integrated Circuit), which is an application-specific integrated circuit, instead of a combination of a CPU, a ROM, and a RAM. . ECU 109 may be realized by a combination of different configurations, for example, a combination of CPU, ROM, RAM and FPGA, instead of the combination of CPU, ROM, and RAM.

  In FIG. 1, air taken into an internal combustion engine 101 passes through an air flow meter (AFM: Air Flow Meter) 120 and is taken into a throttle valve 119 and a collector 115 in that order, and then intake air provided to each of four cylinders The fuel is supplied to the combustion chamber 121 through the pipe 110 and the intake valve 103. Although not shown, the intake pipe 110 is provided with an intake pipe pressure sensor 130 for measuring the pressure inside the intake pipe 110. The fuel is sent from a fuel tank 123 to a high-pressure fuel pump 125 provided in the internal combustion engine 101 by a low-pressure fuel pump 124.

  The high-pressure fuel pump 125 controls the fuel pressure to a desired pressure based on a control command value from the ECU 109. The fuel thus pressurized is sent to the fuel injection valve 105 via the high-pressure fuel pipe 128. The fuel injection valve 105 is an in-cylinder direct injection type that can execute fuel injection into the internal combustion engine 101 in a plurality of times during one cycle. The fuel injection valve 105 receives a command (injection pulse) from the fuel injection valve control unit 127 incorporated in the ECU 109 or the ECU 109 itself, and injects fuel into the combustion chamber 121 by opening the valve for a time specified by the command. I do. The total amount of fuel injected during one cycle (total fuel injection amount) can be determined in advance, and the value of each of the fuel injection amounts of the fuel injection performed a plurality of times (each injection amount) can also be determined in advance.

  The internal combustion engine 101 includes a fuel pressure sensor (pressure detector) 126 that measures the pressure in the high-pressure fuel pipe 128 for the purpose of controlling the high-pressure fuel pump 125. The pressure in the high-pressure fuel pipe 128 is the actual fuel pressure supplied to the fuel injection valve 105, that is, the actual fuel pressure. The ECU 109 controls the fuel pressure in the high-pressure fuel pipe 128 to a desired pressure based on the output value of the fuel pressure sensor 126. So-called feedback control is used for controlling the pressure.

  The internal combustion engine 101 includes an ignition coil 107 and a spark plug 106. The ECU 109 controls the energization of the ignition coil 107 and the ignition control by the ignition plug 106 at a desired timing. As a result, the intake air and the fuel are burned in the combustion chamber 121 by the spark released from the spark plug 106. Exhaust gas generated by the combustion is discharged to an exhaust pipe 111 via an exhaust valve 104, and a three-way catalyst 112 for purifying the exhaust gas is provided on the exhaust pipe 111.

  The ECU 109 includes a crank angle sensor 116 for measuring the angle of a crankshaft (not shown) of the internal combustion engine 101, an AFM 120 for indicating the intake air amount, an oxygen sensor 113 for detecting the oxygen concentration in the exhaust gas, and opening of an accelerator operated by the driver. The signals from the accelerator opening sensor 122 indicating the degree and the fuel pressure sensor 126 are input.

  The ECU 109 calculates the required torque of the internal combustion engine 101 from the signal of the accelerator opening sensor 122, and determines whether or not the engine is in an idle state. The ECU 109 also includes a rotation speed detection unit that calculates the rotation speed of the internal combustion engine (hereinafter, engine speed) based on a signal from the crank angle sensor 116, a cooling water temperature of the internal combustion engine 101 obtained from the water temperature sensor 108, A warm-up state determination unit that detects whether or not the three-way catalyst 112 is in a warm-up state based on an elapsed time from the start of the engine 101, and the number of injections of the injector of each cylinder by using outputs of various sensors. And a number-of-times calculating unit.

  Further, the ECU 109 calculates an intake air amount necessary for the internal combustion engine 101 from the above-described required torque and the like, and outputs an opening signal corresponding to the intake air amount to the throttle valve 119. Further, the fuel injection valve control unit 127 calculates a fuel amount according to the intake air amount, outputs a fuel injection signal to the fuel injection valve 105, and further outputs an ignition signal to the ignition coil 107.

  Further, the ignition timing is controlled based on a knock signal detected by a knock sensor 129 common to the first to fourth cylinders so as to be retarded by a predetermined value each time a knock occurs to avoid knocking. I have. The internal combustion engine 101 has a configuration of four horizontally opposed cylinders. The first cylinder and the third cylinder are in the same bank, and the second cylinder and the fourth cylinder are in the same bank. A knock sensor is provided in each bank. In the internal combustion engine 101, the combustion cycle is performed in the order of the first cylinder, the third cylinder, the second cylinder, and the fourth cylinder.

(Configuration of Fuel Injection Valve Control Unit 127)
FIG. 2 is a block diagram showing an outline of the configuration and operation of the fuel injection valve control unit 127. The fuel injection valve control unit 127 includes a knock detection unit 11, a knock control unit 12, and an ignition timing control unit 13. Knock detecting section 11 includes a timing calculating section 14, a knock signal processing section 15, and a knock index calculating section 16. The timing calculator 14 sets a knock detection window. Knock signal processing section 15 receives and processes a signal from knock sensor 129. That is, knock signal processing section 15 also has a function as a receiving section that receives the signal of knock sensor 129. Knock index calculating section 16 calculates the presence or absence of knock and the magnitude of knock.

  The ignition timing control unit 13 includes an ignition timing calculation unit 18 that corrects the ignition timing map 17 with parameters such as a change in water temperature, a change in the number of revolutions, and a change in the throttle opening. The ignition timing map 17 uses the engine speed as a first variable and the load as a second variable, and shows the relationship between these two variables and the basic timing of ignition. However, the ignition timing map 17 also includes the injection mode and the number of injections. Therefore, the ignition timing, the injection mode, and the number of injections can be obtained using the engine speed and the load as variables. The intake pipe pressure sensor 4b calculates the amount of air flowing into the cylinder based on the output of the sensor, and calculates the engine load from the calculation result and the engine speed.

  Load information, information on the number of revolutions of the internal combustion engine 101, and a retard amount to be described later are input to the ignition timing calculation unit 18 of the ignition timing control unit 13. Load information is input from the intake pipe pressure sensor 4b. Information on the rotation speed of the internal combustion engine 101 is input from the crank angle sensor 116. The retard amount is input from knock control unit 12. The ignition timing calculator 18 outputs an ignition signal to the ignition coil 107 based on the retard amount.

  The timing calculation section 14 of the knock detection section 11 calculates the timing for opening and closing the knock detection window from the angular position signal from the crank angle sensor 116. The timing calculation unit 14 generally receives a signal from the knock sensor 129 over a predetermined angle range from the compression top dead center. In the present embodiment, the range is set to 90 ° after the start of the expansion stroke, and the knock detection window is sent to knock signal processing unit 15.

  Knock signal processing section 15 takes in a signal (hereinafter, referred to as a “knock signal”) output from knock sensor 129 for each cylinder. However, knock signal processing section 15 does not always take in the signal, but takes in the signal of knock sensor 129 over the section of the knock detection window set for each cylinder. Knock signal processing section 15 detects the presence or absence of knock by a known method using the signal of knock sensor 129 taken in. The outline of detecting the presence or absence of knock is as follows. First, a plurality of frequency components included in the signal of knock sensor 129 are extracted by a filter. Next, a weighted average is calculated for each frequency component for each explosion process of the internal combustion engine 101, and a noise level (background level) is determined. Then, for each frequency, a difference between the level value of the frequency component and the average value of the frequency component is obtained, and a knock intensity is calculated based on the result to perform knock determination.

This will be specifically described using mathematical expressions. When there is no knock, the knock signal is subjected to a weighted averaging process (filtering process) as shown in Expression 1 below, and is used for calculating a background level (hereinafter, referred to as “BGL”) value for each cylinder.
BGL = MBGL × KP + (1-MBGL) × B_BGL (Equation 1)
However, in Equation 1, BGL is the background level, B_BGL is the previously calculated background level, KP is the knock signal, and MBGL is the weighted average coefficient (filter value; 0 to 1).

  Since the BGL is calculated only when there is no knock, it is inevitably performed after the knock determination, and the BGL calculated this time is used for the next knock determination. In other words, BGL obtained by the previous calculation is used as B_BGL for the knock determination this time. Knock signal processing section 15 outputs the obtained knock signal KP and the calculated BGL to knock index calculation section 16.

  Knock signal processing section 15 includes an offset value map and a threshold map (not shown). The offset value map is referred to for determining an offset value that is an offset amount of the BGL value. The offset value map is, for example, a look-up table, and the offset value is obtained from the engine speed and the load. The offset value map is determined so that the value of the offset value increases as the engine speed and the load increase. However, the offset value map is merely a conceptual description, and may be information other than a table format such as a mathematical expression.

  The threshold map is referred to for determining a knock determination threshold for performing a knock determination. The threshold map is, for example, a look-up table, and the threshold is determined from the engine speed and the load. The threshold map is determined so that the threshold increases as the engine speed and the load increase. However, the threshold map is only conceptually described, and may be information other than a table format such as a mathematical expression.

Knock index calculating section 16 calculates knock index KS using the output of knock signal processing section 15 as in the following Expression 2.
KS = KP / B_BGL (Expression 2)

  As shown in Expression 2, when the ratio (or difference) to a relatively large knock signal generated when knock occurs, that is, the knock index KS exceeds the knock determination threshold, the cylinder is detected as having knock. This knock index is sent to knock control unit 12, and is converted into a retard amount (retard amount) of the ignition timing. This retard amount is sent to the ignition timing calculation section 18, and the ignition timing calculation section 18 corrects the basic ignition timing in the retard direction.

  Therefore, when the knock index exceeds the knock determination threshold, the ignition timing is retarded by a predetermined amount. Thereafter, if knock does not occur, the ignition angle is gradually advanced. When the knock exceeds the knock determination threshold value again, the ignition timing is retarded by a predetermined amount. By repeating this, the ignition timing is feedback-controlled so that the knock level is constant. The ignition timing feedback control may be performed for all cylinders simultaneously or for each cylinder. In the present embodiment, the ignition timing feedback control is performed for each cylinder.

  The suitability of the basic knock detection is as follows: a knock detection window is set so that a knock signal at the time of knock occurrence in a steady operation state can be reliably acquired and A / D converted, and the A / D conversion value and BGL value of the knock signal The knock index obtained based on the ratio is equal to or less than a predetermined value at the time of knock occurrence (reliably detecting the presence of knock) and equal to or more than a predetermined value at the time of no knock occurrence (prevention of knock detection without knock). May be set to the knock determination threshold. The relationship between the fuel injection timing of the injector and the knock detection window in the above-described fuel injection valve control unit 127 will be described with reference to FIG.

(Injector operation timing)
FIG. 3 is a diagram showing the progress of each stroke when the combustion cycle is performed in the order of the first cylinder, the third cylinder, the second cylinder, and the fourth cylinder in the internal combustion engine 101 that is a horizontally opposed four cylinder. is there. The relationship between the injection timing of the injector and the knock detection window at the timing when the first cylinder advances from the intake stroke to the compression stroke, which is indicated by hatching in FIG. 3, will be described. Hereinafter, a mode in which fuel is injected only in the injection timing section of the intake stroke is referred to as “first injection mode”, and a mode in which fuel is injected not only in the intake stroke but also in the compression stroke is referred to as “second injection mode”.

  Here, knock occurs in a section in which the air-fuel mixture in the cylinder is burning, and the knock detection window Wind is set to a crank angle range in the first half of an expansion stroke in which combustion is performed. On the other hand, the injection timing of the injector has various timings as described above. Here, the injection timing section Iinj for performing the injection in the intake stroke and the injection timing section Cinj for performing the injection in the compression stroke are set.

  Further, in the present embodiment, the injection timing section Iinj of the intake stroke is set between the middle and the end of the intake stroke, and the injection timing section Cinj of the compression stroke is set from the first half to the middle of the compression stroke. ing. During these sections, the injection timing of the injector is appropriately controlled.

  Next, when fuel is injected only in the injection timing section Iinj of the intake stroke of the first cylinder, the knock detection window Wind is open in the second cylinder. At this time, the knock detection window Wind of the second cylinder does not overlap the fuel injection timing section Iinj in the intake stroke of the first cylinder. Therefore, the valve closing noise of the injector during the intake stroke of the first cylinder is not captured in the knock detection window Wind of the second cylinder.

  In case the fuel injection timing section Iinj of the intake stroke of the first cylinder is set to be wide and the knock detection window Wind of the second cylinder overlaps the fuel injection timing section Iinj of the intake stroke of the first cylinder temporally. Is assumed. Also in this case, since the first cylinder and the second cylinder have different banks, the valve closing noise of the second cylinder during the intake stroke of the first cylinder has no effect.

  However, when the injection is performed not only in the intake stroke but also in the compression stroke, the fuel is injected in the injection timing section Cinj in the compression stroke, following the fuel injection timing section Iinj in the intake stroke of the third cylinder. Since the first cylinder and the third cylinder are in the same bank, the following problem occurs when the knock detection window Wind of the first cylinder in the same bank and the fuel injection timing section Cinj in the compression stroke of the third cylinder overlap. That is, there is a problem that valve closing noise of the injector in the compression stroke of the third cylinder is taken into the knock detection window Wind of the first cylinder.

  Similarly, since the knock detection window Wind of the second cylinder in the same bank and the fuel injection timing section Cinj of the compression stroke of the fourth cylinder overlap, the valve closing noise of the injector in the compression stroke of the fourth cylinder is reduced. The knock is detected by the knock detection window Wind. As a result, the A / D converted value of the knock sensor signal taken in the section of the knock detection window Wind becomes large by reflecting the valve closing noise of the injector that is injecting in the compression stroke of the third cylinder. False detection may occur.

  FIG. 4 is a diagram showing the progress of each stroke when the internal combustion engine 101 shifts from the first injection mode to the second injection mode. In the second injection mode, injection is performed once in the injection timing section Iinj of the intake stroke, and then once in the injection timing section Cinj in the compression stroke, that is, two times in total. In the second injection mode, the injection timing in the compression stroke is set in the latter half of the set section Cinj.

  In this case, both the injector injection timing a in the compression stroke of the fourth cylinder and the injector injection timing b in the compression stroke of the third cylinder are timings that do not overlap the knock detection windows Wind of the second cylinder and the first cylinder. Therefore, the injector noise is not taken into the knock detection windows Wind of the second cylinder and the first cylinder, and there is no erroneous knock detection even in the second injection mode, so that the correction of the background value is not necessary. If the background value is corrected in this case, the knock signal level when the knock does not occur is corrected so that the knock signal level increases, and the ratio with the knock signal level when the knock occurs decreases, and the knock detectability deteriorates. I do.

(Time chart of boost voltage)
FIG. 5 is a time chart showing an example of a boosted voltage at the time of multi-stage injection. The boosted voltage is a voltage used to drive the fuel injection valve 105, and is a voltage boosted by a battery (not shown). In FIG. 5, time elapses from left to right in the figure. FIG. 5 shows the injection pulse width, the current waveform of the fuel injection valve, and the boost voltage in order from the top. In the example shown in FIG. 5, the multi-stage injection of the same cylinder is performed twice during a 180-deg predetermined period from time t506 to time t507.

  When the power is turned on, the boosted voltage is boosted by a battery to a reference voltage indicated by reference numeral 501, and is kept constant at the reference voltage. As indicated by the solid line denoted by reference numeral 502, the boost voltage drops at the timing of the first injection at time t503, the second injection at time t504, and the first injection at time t505. When the injection is started, the voltage drops sharply, and thereafter, the voltage is increased toward the reference voltage.

  As in the second injection starting from time t504, if the boosted voltage has returned to the reference voltage, a stable fuel injection amount can be injected. However, since the injection interval changes depending on the driving state of the vehicle and the like, the next injection may be performed before the boosted voltage is raised to the reference voltage, as in the injection starting from time t505. In such a case, the suction energy of the plunger of the fuel injection valve is reduced due to the insufficient voltage, the operation of the on-off valve of the fuel injection valve is delayed, and the valve is opened compared to the time when the boosted voltage has returned to the reference voltage. The time gets longer.

  However, the current and voltage shown in FIG. 5 are conceptual, and it is difficult to measure a detailed change in a real environment because the sampling rate is reduced in order to reduce power consumption. For example, the boosted voltage at time t503 or time t504 has reached the reference voltage, and thus its value is clear. However, when the voltage has not reached the reference voltage as at time t505, actual measurement is difficult. Therefore, the boosted voltage is estimated as described below.

(Estimation of boost voltage)
The estimation of the boosted voltage will be described with reference to FIG. FIG. 6 is a timing chart showing the relationship between the drive current of the fuel injection valve, the boost voltage, and the boost return time. However, in FIG. 6, reference numerals are shown in parentheses. In FIG. 6, the electric charge consumed when one fuel injector is driven is indicated by the area of ΔQ401, and ΔQ can be calculated from dt402 and ip403 using Expression 3.
ΔQ = dt × ip / 2 (Equation 3)

  dt402 is the time from when the drive current of the fuel injector flows to when it reaches the peak current, and is equivalent to the fall time ΔT404 of the boosted voltage (Vboost). The dt 402 is set based on any two or more of the battery voltage, the smoothed value of the battery voltage, the ambient temperature of the ECU, the substrate temperature of the ECU, and the temperature of the booster circuit. Here, the smoothed battery voltage value is a value obtained by applying a weighted average filter to the battery voltage to suppress the fluctuation of the battery voltage.

ip403 is the peak current of the fuel injection valve, and is set in advance as the valve opening current Ipeak according to the used fuel pressure and the like. In the fuel injection valve drive current waveform, the rising portion indicates the effective pulse width w1, and the falling portion and the flatly extending injection current I hold indicate the invalid pulse width w2. Further, from the charge calculation formula (Q = CV), the boosted voltage drop amount ΔV405 per drive of the fuel injection valve 105 can be calculated by the following formula 4. However, ΔV is called “boosted voltage drop amount”.
ΔV = ΔQ / C (Equation 4)

The capacitance C is determined according to the capacitor used inside the booster circuit. However, since the capacitor includes variations due to temperature, it is preferable to correct the capacitance using a temperature sensor. According to the charge calculation formula, when two fuel injection valves are driven at the same time, the charge ΔQ401 consumed is doubled, and the boosted voltage drop ΔV405 is also doubled. Further, dtc 406 is a boost voltage return time, and the current ic charged to the boost circuit can be calculated by Expression 5.
ic = ΔQ / dtc (Equation 5)

From the charge calculation equation, Equation 5 can be converted into the following Equation 6.
ΔV = ic × dtc / C (Equation 6)

Assuming that the charged current ic and the capacitance C are fixed values, if the boosted voltage drop amount ΔV405 doubles, the boosted voltage recovery time: dtc406 also doubles. Then, the boosted voltage can be estimated, for example, as in the following Expression 7.
Boosted voltage estimated value = Boosted voltage at the start of previous injection−Boosted voltage drop + Boosted voltage drop × (Injection interval−dt (402)) / (Reset reference time−dt (402)) (Equation 7)

  The “boosted voltage estimated value” on the left side of Expression 7 is, for example, an estimated value of the boosted voltage in the (N + 1) th injection. Looking at the right-hand side of Equation 7 in order, the “boosted voltage at the start of the previous injection” is the boosted voltage at the time of injecting the Nth fuel, and may be an actually measured value or an estimated value, and varies depending on the situation. The “boosted voltage drop amount” is the boosted voltage drop amount ΔV405 in Expression 4, and is a fixed value as long as the same hardware is used. “Injection interval” is the time interval from the Nth injection to the (N + 1) th injection, in other words, the elapsed time.

  The return reference time is a value determined by the voltage and temperature of the battery as described below. However, the maximum value of the boosted voltage estimation value has the reference voltage as an upper limit. The estimated boosted voltage value of the first fuel injection after the power supply of the battery or the first fuel injection after the idle stop is set as the reference voltage. By setting the maximum value of the boosted voltage estimation value as the upper limit of the reference voltage, erroneous calculation can be avoided. In the formula for calculating the boosted voltage estimated value, the reset reference time is set to a measured value of the reset reference time of the boosted voltage.

  FIG. 7 is a conceptual diagram showing the relationship between the battery voltage and the reference voltage for returning the boosted voltage (boost characteristic). A curve 801 indicated by a broken line in FIG. 7 indicates a case where the substrate temperature of the ECU 9 is high, and a curve 802 indicated by a solid line in FIG. 7 indicates the case where the substrate temperature of the ECU 9 is low. FIG. 7 shows that the lower the battery voltage and the higher the substrate temperature of the ECU 9, the longer the return reference time. Although the substrate temperature of the ECU 9 is used here, any one or more of the ambient temperature of the ECU 9 and the temperature of the booster circuit may be used. Although the battery voltage is used here, the battery voltage may be a smoothed value. By the means described so far, the estimated value of the boosted voltage can be obtained.

  FIG. 8 is a diagram showing a temporal relationship among the injector drive signal, the knock sensor signal, and the knock detection window. As for the injector opening / closing noise, delay times d1 and d2 occur from when a signal for operating the injector is output to when the knock sensor detects the noise. The delay time d1 is a noise delay time when the valve is opened, and the delay time d2 is a noise delay time when the valve is closed. Therefore, the determination as to whether or not the above-described injector noise overlaps the knock detection window is not merely a comparison between the knock detection window and the injection timing, but the suction energy of the plunger of the fuel injection valve is reduced due to the insufficient boost voltage. It is necessary to consider a predetermined offset at the start point of the knock detection window in consideration of the delay in opening and closing the fuel injection valve.

  FIG. 9 is a conceptual diagram showing the relationship between the insufficient boosted voltage and the angle obtained by converting the delay time of the injector noise into the crank angle (T-ANG) of the internal combustion engine 101. If the delay time of the noise is replaced by the crank angle, the response time of the noise is approximately proportional to the boosted voltage. Therefore, it is preferable that the offset angle to the knock detection window be a function of the boosted voltage.

  FIG. 10 is a diagram showing an outline of the operation of knock detection section 11. In the first injection mode in which the injection is performed only in the intake stroke, since the valve closing noise of the injector is not taken into the knock detection window set in the first half of the expansion stroke, the knock is determined using the normal background level calculation and the knock determination threshold. Is detected. In the second injection mode, if the filtering is performed as usual, the follow-up performance becomes slow. Therefore, as described later, the presence or absence of the injector noise in the knock detection window is detected, and the following processing is performed when the presence of the mixing is detected. . That is, the background level is set to a fixed value of a predetermined amount, or an offset value of a predetermined amount is added to the background level to obtain a new background level.

  Thereby, when the injector noise is mixed in the knock detection window in the second injection mode with respect to the BGL value in the first injection mode, the calculated new BGL value is larger than before correction, and the followability is improved. Secured. Also, the ratio between the BGL value and the AD conversion value of the knock sensor signal is calculated with the new large BGL value, so that an appropriate knock index is obtained.

  Further, in the second injection mode, a knock determination threshold value to be compared with the knock index is set to a larger knock determination threshold value than in the first injection mode, regardless of whether noise is mixed into the knock window. This is for avoiding the influence of the change in the combustion noise due to the difference in the injection mode. By setting the determination threshold to be larger than that in the first injection mode, it is possible to perform the appropriate knock determination. However, similarly to the correction of the BGL value, the knock determination threshold may be switched only when it is detected that the injector noise enters the knock detection window.

(flowchart)
FIG. 11 and FIG. 12 are flowcharts showing the operation of the fuel injection valve control unit 127. However, FIGS. 11 and 12 show only the preparation for knock detection, that is, only the change of the threshold value and the offset of the BGL value. The process shown in FIGS. 11 and 12 is started at predetermined time intervals, for example, every 10 ms, using a compare match interrupt of a counter of a microcomputer provided in the fuel injection valve control unit 127 or the like. The execution subject of each step described below is the fuel injection valve control unit 127.

  First, in step S5, the fuel injection valve control unit 127 reads the injection mode, the injection timing, and the number of injections of the injector of each cylinder from the number calculation unit. The number of injections is the sum of the number of injections in the injection timing section Iinj of the intake stroke and the number of injections in the injection timing section Cinj of the compression stroke.

  In the following step S10, the boosted voltage at each injection is calculated. The method of calculating the boosted voltage is as described above. In the following step S11, the fuel injection valve control unit 127 calculates an offset value used for updating the GBL value when the injection mode is switched. Since the injection mode is captured as information for each cylinder, switching of the injection mode is also determined for each cylinder. The fuel injection valve control unit 127 calculates an offset value with reference to the offset value map. When this offset value is obtained, the process moves to step S12. When the BGL value itself is changed for each injection mode, the BGL value for each injection mode is calculated in this step.

  In step S12, the fuel injection valve control unit 127 calculates a knock determination threshold value corresponding to each injection mode with reference to a threshold value map. The knock determination threshold is set larger in the second injection mode than in the first injection mode. When the knock determination threshold is obtained, the process proceeds to step S13.

  In step S13, the fuel injection valve control unit 127 detects, for each cylinder, whether or not switching from the first injection mode to the second injection mode has been performed. This detection can be detected by monitoring the history of step S5. When the fuel injection valve control unit 127 detects that switching from the first injection mode to the second injection mode has been performed, the process proceeds to step S14, and when the fuel injection valve control unit 127 detects that it is not switching from the first injection mode to the second injection mode, the process proceeds to step S15. Transition. In step S14, the fuel injection valve control unit 127 determines that the switching from the first injection mode to the second injection mode has been performed, and thus switches to the knock determination threshold for the second injection mode obtained in step S12 and sets it. Then, the process proceeds to step S16.

  In step S15, the fuel injection valve control unit 127 detects whether the required number of injections and the injection timing in the second injection mode have changed from the previous time. In this step, detection is performed using the values read this time and the previous time in step S5. If the injection mode read this time is the first injection mode, or if the injection mode read this time is the second injection mode and there is no change in the number of injections or the injection timing from the previous time, a negative determination is made in step S15 and FIG. The process proceeds to step S18 in FIG. 12 via the lower F2. In other cases, that is, when the injection mode is the second injection mode last time and this time, and at least one of the number of injections and the injection timing is changed, an affirmative determination is made in step S15, and the process proceeds to step S15.

  In step S16, the fuel injector control unit 127 detects whether or not the injection timing in the compression stroke overlaps the knock detection window. For example, it is detected by comparing the two at an angle replaced with the crank angle of the internal combustion engine 101. Specifically, the detection is performed based on whether or not the injection timing angle exists between the crank angle from the knock detection window start point-OFFSET to the end of the window. Note that the value of OFFSET used in this step is obtained by a combination of Equation 7 and FIG. Specifically, first, a boosted voltage estimated value of Expression 7 is calculated, and a difference from the reference voltage is calculated. Next, the difference is used as the value on the horizontal axis in FIG. 9, and the value of the corresponding T-ANG (deg) is read and set as OFFSET.

  The fuel injection valve control unit 127 detects when there is an injection timing angle between the crank angle from the knock detection window start point -OFFSET to the end of the window, that is, when it is detected that the injector noise is mixed in the knock detection window. Move to step S17. When it is detected that there is no injection timing angle between the crank angle from the knock detection window start point-OFFSET to the end of the window, that is, when it is detected that there is no noise, without correcting the BGL value in step S17, The process proceeds to step S18 in FIG. 12 via F2 at the bottom of FIG.

  In step S17, the fuel injection valve control unit 127 adds the offset value obtained in step S11 to the previous BGL value, that is, the BGL value in the first injection mode. As a result, the BGL value increases, so that the influence of noise on the knock index obtained from the change (ratio) of the knock signal level due to the injector noise is reduced, thereby preventing erroneous knock detection. These are used in the knock detection unit 11 shown in FIG. 2 together with the new knock determination threshold value of the second injection mode obtained in step S14. Next, the process proceeds to step S18 in FIG. 12 via F2 in the lower part of FIG.

  In step S18, the fuel injection valve control unit 127 detects whether or not switching from the second injection mode to the first injection mode is performed, contrary to step S13. When the fuel injection valve control unit 127 detects that it is not switching from the second injection mode to the first injection mode, the processing shown in FIG. 12 ends.

  The processes in steps S20 to S22 correspond to the processes in steps S14, S16, and S17 described above, and therefore, only the outline will be described here. In step S20, the fuel injection valve control unit 127 switches and sets the knock determination threshold value for the first injection mode obtained in step S12, and proceeds to step S21. In step S21, the same detection as in step S16 is performed, and if an affirmative determination is made, the processing shown in FIG. 12 is terminated without performing any special processing because the injection mode is changed but the influence is continued. When the fuel injection valve control unit 127 makes a negative determination in step S21, since the fuel injection valve control unit 127 is no longer affected by the change in the injection mode, the offset is subtracted from the GBL value in step S22 to return to the original state. The indicated process ends.

  As described above, according to the present invention, in addition to the means for switching the knock determination value when switching from one injection to multiple injections, it is determined whether the fuel injection timing overlaps the knock detection window, and the overlap is determined. If it is determined that there is noise, it is considered that noise has entered the window, and the BGL value is set to be large. According to this, erroneous detection of knock can be suppressed when the injection timing of the injector overlaps the knock detection window, and when it does not overlap, the BGL value is not corrected, so that more accurate knock controllability can be realized. Become like

According to the above-described embodiment, the following operation and effect can be obtained.
(1) The ECU 109, which is a control device for the internal combustion engine, receives a knock signal from a knock sensor 129 attached to the internal combustion engine 101 in which at least the first cylinder and the third cylinder are arranged in the same bank. A processing unit 15) and a knock detection unit 11 that detects knocking in the internal combustion engine 101 using a knock signal in a knock detection window during which a knock signal is captured. Knock detecting section 11 sets a first knock detection window for the third cylinder based on a boosted voltage that is boosted by a battery that operates first fuel injection valve 105a, which is fuel injection valve 105 that injects fuel to the first cylinder. It is detected whether or not noise when opening and closing the fuel injection valve 105a is included. Therefore, it is possible to achieve both suppression of erroneous knock detection and prevention of deterioration of knock detection.

  Conventionally, there is known a configuration in which the knock determination value or the BGL value is switched to a set value corresponding to the mode in accordance with switching between the first injection mode and the second injection mode, thereby avoiding the influence of injector opening / closing valve noise. In this configuration, when the mode is switched from the first injection mode to the second injection mode, the knock determination value, the BGL value, or both the knock determination value and the BGL value are switched to a set value corresponding to the second injection mode. . However, depending on the setting of the injection timing in the compression stroke, there is a case where the opening / closing noise of the fuel injection valve 105 does not enter the knock detection window of another cylinder. In this case, by using the BGL value for the second injection mode that is set to be larger than that of the first injection mode, knock detection may be deteriorated.

  On the other hand, the method according to the present embodiment detects whether or not the knock detection window of the third cylinder includes the opening / closing noise of the first fuel injection valve 105a, instead of switching the injection mode. For this detection, the voltage value of the boost voltage for operating the fuel injection valve 105 is used. Therefore, the BGL value is not unnecessarily changed, and both suppression of erroneous knock detection and prevention of deterioration of knock detectability can be achieved.

  The knock detection unit 11 includes a noise at the time of opening and closing the third fuel injection valve 105c in the knock detection window of the first cylinder based on the boosted voltage boosted by the battery that operates the third fuel injection valve 105c. Detect whether or not it is Similarly, knock detection unit 11 is configured to open and close second fuel injection valve 105b in the knock detection window of the fourth cylinder based on the boosted voltage boosted by the battery that operates second fuel injection valve 105b. It detects whether noise is included or not. Further, knock detection unit 11 includes a noise at the time of opening and closing fourth fuel injection valve 105d in the knock detection window of the second cylinder based on the boosted voltage boosted by the battery that operates fourth fuel injection valve 105d. Is detected.

(2) The knock detection unit 11 includes noise in opening and closing the first fuel injection valve 105a in the knock detection window of the third cylinder based on the boosted voltage when the first fuel injection valve 105a injects fuel. Detect whether or not it is Since the voltage that drops by injecting the fuel is constant, it is not necessary to know the boosted voltage for the entire section in which the fuel is injected, and by using the boosted voltage at the time of fuel injection, which is an important and easy-to-detect timing. It can be detected efficiently. Note that, instead of the boosted voltage at the time of injecting the fuel, for example, the detection may be performed using the lowest boosted voltage lowered by injecting the fuel.

(3) Knock detecting section 11 calculates the boosted voltage when fuel was previously injected by first fuel injection valve 105a, the voltage drop due to injection, the time interval of injection, the time during which the boosted voltage drops due to injection, and the boosted voltage. Using the time required for boosting, the boosted voltage at the time of fuel injection is estimated. It is not practical to measure the boosted voltage at short time intervals because power consumption increases. Therefore, in the present embodiment, the boosted voltage estimation value is calculated using Equation 7, and the boosted voltage at the time of fuel injection without consuming excessive power can be obtained.

(4) The knock detection unit 11 determines that the timing obtained by adding a delay time based on the difference between the boosted voltage and the predetermined standard voltage to the predetermined opening / closing timing of the first fuel injection valve 105a is the third cylinder. If the knock detection window is included, the threshold value for detecting the occurrence of knock in the third cylinder is corrected so as to increase. Therefore, the threshold can be changed only under appropriate conditions. Instead of changing the knock determination threshold value, it is also possible to obtain substantially the same effect as increasing the threshold value by multiplying the knock index to be evaluated by a coefficient less than 1.

(5) The knock detection unit 11 performs correction so that the threshold value increases as the rotation speed and the load of the internal combustion engine increase. That is, when the offset is performed, the offset amount of the threshold is increased, and when the value itself is changed, a larger value is used.

(6) The fuel injection valve 105 can switch between a first injection mode in which fuel is injected only in an intake stroke and a second injection mode in which fuel is injected in an intake stroke and a compression process. As shown in the flowcharts of FIGS. 11 and 12, knock detection unit 11 determines whether first fuel injection valve 105 a changes at least one of the number of injections and injection timing in second injection mode, and that first fuel injection valve 105 a Detects whether the knock detection window of the third cylinder includes noise when opening and closing the first fuel injection valve 105a when switching between the first injection mode and the second injection mode. That is, the above-described detection is performed only in a necessary situation, and unnecessary processing is reduced.

(Modification 1)
The airflow sensor 4a may calculate the charging efficiency and provide the calculated charging efficiency to the ignition timing calculation unit 18. That is, in the present modified example, information on the charging efficiency, information on the engine speed, and the retard amount are input to the ignition timing calculation unit 18 of the ignition timing control unit 13.

  The above-described embodiments and modifications may be combined with each other. Although various embodiments and modified examples have been described above, the present invention is not limited to these contents. Other embodiments that can be considered within the scope of the technical concept of the present invention are also included in the scope of the present invention.

11 Knock detection unit 12 Knock control unit 13 Ignition timing control unit 14 Timing calculation unit 15 Knock signal processing unit 16 Knock index calculation unit 17 Ignition timing map 18 Ignition timing calculation unit 101 Internal combustion engine 105 Fuel injection valve 127 ... fuel injection valve control unit 129 ... knock sensor

Claims (6)

A receiving unit that includes a plurality of cylinders, wherein at least the first cylinder and the second cylinder receive a knock signal from a knock sensor attached to an internal combustion engine arranged in the same bank;
A knock detection unit that detects knocking in the internal combustion engine using the knock signal in a knock detection window that is a period for capturing the knock signal,
The knock detection unit is configured to generate the knock detection window of the second cylinder based on a boosted voltage that is boosted by a battery that operates a first fuel injection valve that is a fuel injection valve that injects fuel into the first cylinder. A control device for an internal combustion engine, which detects whether or not noise when opening and closing the first fuel injection valve is included. The control device for an internal combustion engine according to claim 1,
The knock detection unit is configured to control the knock detection window of the second cylinder to open and close the first fuel injection valve based on the boosted voltage when the first fuel injection valve injects the fuel. A control device for an internal combustion engine that detects whether or not it is included. The control device for an internal combustion engine according to claim 2,
The knock detection unit includes: the boosted voltage when the fuel was previously injected by the first fuel injection valve; a voltage drop due to the injection; a time interval of the injection; a time during which the boosted voltage is reduced by the injection; and A control device for an internal combustion engine, which estimates the boosted voltage at the time of injecting the fuel using a time required for boosting the boosted voltage. The control device for an internal combustion engine according to claim 1,
The knock detection unit is configured such that a timing obtained by adding a delay time based on a difference between the boosted voltage and a predetermined standard voltage to a predetermined opening / closing timing of the first fuel injection valve is the timing of the second cylinder. A control device for an internal combustion engine, wherein the control unit corrects a threshold value for detecting occurrence of knock in the second cylinder so that the threshold value is included in a knock detection window. The control device for an internal combustion engine according to claim 4,
A control device for an internal combustion engine, wherein the knock detection unit corrects the threshold value so that the threshold value increases as the rotation speed and the load of the internal combustion engine increase. The control device for an internal combustion engine according to claim 1,
The fuel injection valve is switchable between a first injection mode in which fuel is injected only in an intake stroke, and a second injection mode in which fuel is injected in an intake stroke and a compression process,
The knock detection unit is configured to determine whether the first fuel injection valve changes at least one of the number of injections and the injection timing in the second injection mode, and that the first fuel injection valve determines whether the first fuel injection valve is in the first injection mode and the second injection. A control device for an internal combustion engine, which detects whether or not the knock detection window of the second cylinder includes noise when opening and closing the first fuel injection valve when switching between modes.

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