JP2011052616A - Device for controlling fuel injection for multiple cylinder internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device which effectively reduces a variation in rotational fluctuation and in combustion condition of cylinders, suppresses vibration, and improves the efficiency of exhaust emission. <P>SOLUTION: This fuel injection control device for a multiple cylinder internal combustion engine includes: a first correction means for detecting the variation in the rotational fluctuation in each cylinder and correcting the amount of fuel injected from each cylinder based on the variation in the rotational fluctuation; and a second correction means for detecting a variation in a cylinder inner pressure parameter of each cylinder and correcting the amount of fuel injected from each cylinder based on the variation in the cylinder inner pressure parameter. Correction by the first correction means and correction by the second correction means are switchable with respect to each operation area of the internal combustion engine. Each correction is performed in a suitable operation area to achieve both the vibration suppression and efficient exhaust emission. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for a multi-cylinder internal combustion engine, and more particularly to a fuel injection control device for a multi-cylinder internal combustion engine capable of controlling the fuel injection amount of each cylinder so as to eliminate variations among cylinders.

  In general, in a multi-cylinder internal combustion engine having a plurality of cylinders, rotation between cylinders due to variations in fuel injection amount among cylinders, variations in EGR gas amount between cylinders, variations in mechanical friction among cylinders, etc. Variation in variation occurs. In order to reduce vibration due to this variation in rotational fluctuation, the change in engine rotation speed for each cylinder is measured by a crank angle sensor attached to the crankshaft, and the fuel for each cylinder is set so that the change in rotation speed is constant for each cylinder. There is a technique for correcting the injection amount (see Patent Document 1).

JP 2004-52620 A

  According to this technique, the rotational fluctuation of each cylinder becomes constant, and the rotational fluctuation of the entire engine can be reduced particularly in a low load region including idling. However, even if the rotational fluctuation can be reduced, the combustion state of each cylinder varies and the exhaust gas performance may not be sufficient. It should be noted that in the middle and high load range, engine rotation fluctuations are naturally reduced, and it is difficult to effectively utilize the technology.

  On the other hand, the combustion state of each cylinder can be grasped from the output of an in-cylinder pressure sensor provided in each cylinder. Therefore, an in-cylinder pressure parameter that is an index value indicating the in-cylinder combustion state is calculated for each cylinder from the output of the in-cylinder pressure sensor, and the fuel injection amount for each cylinder is set so that the value of this in-cylinder pressure parameter is constant for each cylinder It is conceivable to correct this. In this way, the combustion state of each cylinder can be made constant and sufficient exhaust gas performance can be obtained. This technology is considered to be effective in any load range.

  However, with this technology, there is a possibility that variations in rotational fluctuation due to differences in friction between the cylinders cannot be sufficiently reduced. In other words, the former technique has the advantage that it can reduce the variation in rotational fluctuation at low load, but it has the disadvantage that it cannot reduce even the variation in the combustion state, and the latter technique has each drawback regardless of the load range. Although there is an advantage that the variation in the combustion state of the cylinder can be reduced, there is a disadvantage that the variation in the rotational fluctuation at the time of low load cannot be sufficiently reduced.

  Therefore, the present invention has been made in view of such circumstances, and the object thereof is to effectively reduce variation in rotational fluctuation and combustion state of each cylinder and achieve both vibration suppression and exhaust gas performance. Another object of the present invention is to provide a fuel injection control device for a multi-cylinder internal combustion engine.

  According to one aspect of the present invention, there is provided a fuel injection control device for a multi-cylinder internal combustion engine that controls the amount of fuel injected from a fuel injection valve of each cylinder for each cylinder, and the amount of variation in rotational fluctuation of each cylinder is determined. A first correction unit that detects and corrects the fuel injection amount of each cylinder based on the variation amount of the rotational fluctuation; detects the variation amount of the in-cylinder pressure parameter of each cylinder; and detects each variation amount based on the variation amount of the in-cylinder pressure parameter. A second correction unit that corrects the fuel injection amount of the cylinder, and performs the first correction by the first correction unit and the second correction by the second correction unit for each operating region of the internal combustion engine. A fuel injection control device for a multi-cylinder internal combustion engine is provided that is executed by switching.

  According to this, since the first correction and the second correction are performed by switching for each engine operation region, these corrections can be performed in the operation region suitable for each, and vibration suppression and exhaust gas performance can be achieved. It is possible to achieve both.

  Preferably, the first operation region in which the first correction is performed is set to be at a lower rotation and a lower load side than the second operation region in which the second correction is performed.

  According to this, the advantages and disadvantages of both corrections can be compensated, and the variation in rotational fluctuation by the first correction can be realized on the low rotation / low load side, and the combustion state variation can be reduced by the second correction on the high rotation / high load side. Can be realized. Therefore, it is possible to effectively achieve both vibration suppression and exhaust gas performance.

  Preferably, the in-cylinder pressure parameter is an indicated mean effective pressure calculated based on a detection value of the in-cylinder pressure sensor within a predetermined period. By doing so, the combustion state in the cylinder can be expressed well, and the second correction can be suitably performed.

  Preferably, each of the first correction unit and the second correction unit calculates and corrects the correction amount during steady operation of the internal combustion engine, and the calculated correction amount corresponds to the operating state of the internal combustion engine. Then, it is stored as a learned value, and correction is executed using the learned value during non-steady operation of the internal combustion engine.

  Since the correction amount is learned during the steady operation of the internal combustion engine, and the first correction and the second correction are executed using the learned values during the non steady operation of the internal combustion engine, an inappropriate value detected during the steady operation is obtained. Based on this, no correction is performed, and control reliability can be ensured.

  Preferably, when the first correction and the second correction are switched during unsteady operation of the internal combustion engine, the first learning value stored in the first correction means and the second correction means The learning value is gradually changed from one of the stored second learning values to the other.

  According to this, when the first learning value and the second learning value are greatly different, it is possible to prevent a sudden change in the correction amount at the time of switching, that is, the fuel injection amount, and further a torque shock.

  According to another aspect of the present invention, there is provided a fuel injection control device for a multi-cylinder internal combustion engine that controls the amount of fuel injected from a fuel injection valve of each cylinder for each cylinder, wherein the amount of variation in rotational fluctuation of each cylinder is determined. A first correction unit that detects and corrects the fuel injection amount of each cylinder based on the variation amount of the rotational fluctuation; detects the variation amount of the in-cylinder pressure parameter of each cylinder; and detects each variation amount based on the variation amount of the in-cylinder pressure parameter. A second correction unit that corrects the fuel injection amount of the cylinder, and the first correction by the first correction unit and the second correction by the second correction unit change the operating state of the internal combustion engine. A fuel injection control device for a multi-cylinder internal combustion engine is provided, which is executed while changing the weighting according to the above.

  According to this, the weighting of one correction can be increased and the weighting of the other correction can be decreased according to the change in the operating state of the internal combustion engine. Therefore, correction suitable for the operating state of the internal combustion engine can be applied more strongly, and vibration suppression and exhaust gas performance can both be achieved.

  Preferably, the weight of the second correction is increased and the weight of the first correction is decreased as the operating state of the internal combustion engine becomes higher or higher.

  As a result, the first correction works more strongly on the low rotation or low load side, and the second correction works more strongly on the high rotation or high load side, compensating for the advantages and disadvantages of both corrections, and suppressing vibration and exhaust gas performance. It is possible to achieve both effectively.

  The present invention exhibits an excellent effect that it is possible to effectively reduce variations in rotational fluctuation and combustion state of each cylinder, and to achieve both vibration suppression and exhaust gas performance.

1 is a schematic view showing an internal combustion engine according to an embodiment of the present invention. It is a figure which shows area division of an engine operation area | region. It is a time chart which shows the change of each value according to a crank angle. The learning map for rotation fluctuation correction is shown. The learning map for cylinder pressure correction is shown. It is a time chart which shows the content of learning value gradual change control. 4 is a flowchart illustrating an example of a fuel injection amount calculation routine.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows an internal combustion engine (engine) according to an embodiment of the present invention. The engine of this embodiment is a compression ignition type internal combustion engine for automobiles and multi-cylinder (4 cylinders in this embodiment), that is, a diesel engine. The engine has an engine body 1 including a plurality (four) of cylinders 7 and pistons, a cylinder block, a crankshaft, and the like. The engine body 1 is provided with a fuel injection valve (injector) 4 for directly injecting fuel into the cylinder 7 for each cylinder, and a common rail 6 for storing fuel injected from each fuel injection valve 4 in a high pressure state. ing. The engine main body 1 is provided with an in-cylinder pressure sensor 5 for detecting the pressure in the cylinder 7, that is, the in-cylinder pressure, for each cylinder. Each cylinder 7 is made into # 1 cylinder, # 2 cylinder, # 3 cylinder, and # 4 cylinder in order from the engine front side. However, the fuel injection order and the combustion order are different, and the order is # 1 cylinder, # 3 cylinder, # 4 cylinder, # 2 cylinder.

  An intake passage 2 and an exhaust passage 3 are connected to the engine body 1. A turbocharger 8 is provided for supercharging the intake air. The turbocharger 8 includes a turbine 9 provided in the exhaust passage 3 and driven by exhaust gas, and a compressor 10 provided in the intake passage 2 and driven by the turbine 9 to supercharge intake air.

  An EGR device 31 for returning a part of the exhaust gas, that is, EGR gas to the intake side is also provided. The EGR device 31 includes an EGR passage 32 for recirculating a part of the exhaust gas in the exhaust passage 3 into the intake passage 2, an EGR cooler 34 for cooling the EGR gas flowing in the EGR passage 32, and the flow rate of the EGR gas. And an EGR valve 33 to be adjusted.

  In the intake passage 2, an electronically controlled throttle valve 12 is provided on the downstream side of the compressor 10 and on the upstream side of the joining portion of the EGR passage 32 and the intake passage 2. An air cleaner 14 is provided at the upstream end of the intake passage 2.

  The exhaust passage 3 upstream of the turbine 9 is provided with a bypass valve 11 that appropriately bypasses exhaust gas to the turbine 9 for supercharging pressure control. An exhaust purification device 13 is provided in the exhaust passage 3 on the downstream side of the turbine 9. The exhaust purification device 13 is an oxidation catalyst that oxidizes and purifies unburned components (hydrocarbon HC and carbon monoxide CO) in exhaust gas, a NOx catalyst that purifies nitrogen oxide NOx in exhaust gas, and exhaust gas Consisting of at least one particulate filter that collects PM.

  Further, the engine is provided with an electronic control unit (hereinafter referred to as ECU) 15 as control means. The ECU 15 includes a CPU, a ROM, a RAM, an input / output port, a storage device, and the like (not shown). The fuel injection valve 4, the EGR valve 33, the throttle valve 12 and the bypass valve 11 are controlled by the ECU 15. Further, detection signals for the accelerator opening, crank angle, in-cylinder pressure, and water temperature are input to the ECU 15 from an accelerator opening sensor (not shown), a crank angle sensor 16, an in-cylinder pressure sensor 5, and a water temperature sensor 17, respectively. The ECU 15 calculates the engine rotation speed based on the crank angle detection signal.

  In particular, the ECU 15 controls the amount of fuel injected from the fuel injection valve 4 of each cylinder individually for each cylinder according to a method described later. The ECU 15 corrects the basic injection amount determined based on the engine operating state by using the correction amount so as to reduce the variation in rotational fluctuation and the variation in the combustion state of each cylinder.

  Next, the contents of the fuel injection control in this embodiment will be described.

  In this embodiment, the first correction means for detecting the variation amount of the rotational fluctuation of each cylinder and correcting the fuel injection amount of each cylinder based on the variation amount of the rotational variation, and the variation amount of the in-cylinder pressure parameter of each cylinder And a second correction means for correcting the fuel injection amount of each cylinder based on the variation amount of the in-cylinder pressure parameter. Then, the first correction by the first correction means (hereinafter referred to as rotation fluctuation correction) and the second correction by the second correction means (hereinafter referred to as in-cylinder pressure correction) are switched for each operation region of the internal combustion engine. To run. Here, the in-cylinder pressure parameter is a value based on the in-cylinder pressure, and refers to an index value representing the in-cylinder combustion state in any one cylinder. Specifically, the first correction unit and the second correction unit are configured by the ECU 15.

  Prior to specific description of both corrections, the area division for these corrections will be described. FIG. 2 shows an engine operation region in which the engine speed and the fuel injection amount, which is a substitute value for the engine load, are parameters. Basically, the rotational fluctuation correction is performed in a first operation region I (hereinafter simply referred to as region I), and the in-cylinder pressure correction is performed in a second operation region II (hereinafter simply referred to as region II). Region I is set at a lower rotation and lower load than region II. Region I includes an idling region I '. Between the region I and the region II, a hysteresis region III for preventing control hunting is provided.

  The fuel injection amount here is a basic injection amount Qb described later determined based on the operating state of the engine. The engine rotation speed is represented by Ne. The region I is a region where Ne ≦ Ne1 and Qb ≦ Qb1. The region II is a region where Ne2 ≦ Ne or Qb2 ≦ Qb, Ne ≦ Ne3, and Qb ≦ Qb3. However, Ne1 <Ne2 <Ne3 and Qb1 <Qb2 <Qb3. The hysteresis region III is a region where Ne1 <Ne or Qb1 <Qb and Ne <Ne2 and Qb <Qb2. Note that the region on the high rotation or high load side from the region II is a region near the maximum rotation or maximum load that deviates from the normal region, that is, a region near the upper limit, and no correction is performed.

  The ECU 15 stores in advance each region as shown in FIG. 2 as a map, compares the actually detected or calculated values of the engine speed Ne and the basic injection amount Qb with the map, and appropriately switches the correction. That is, when the actual value is a value belonging to the region I, the rotation fluctuation correction is executed, and when the actual value is a value belonging to the region II, the in-cylinder pressure correction is executed.

  On the other hand, when the actual value changes from the value belonging to the region I to the high rotation or high load side, when the actual value is a value belonging to the hysteresis region III, the actual change is not performed from the rotation fluctuation correction to the in-cylinder pressure correction. Only when the value becomes a value belonging to the region II, switching from the rotation fluctuation correction to the in-cylinder pressure correction is performed. Conversely, when the actual value changes from the value belonging to the region II to the low rotation or low load side, when the actual value is a value belonging to the hysteresis region III, the switching from the in-cylinder pressure correction to the rotation fluctuation correction is not yet performed. Switching from the in-cylinder pressure correction to the rotation fluctuation correction is performed only after the actual value becomes a value belonging to the region I. As described above, the hysteresis region III becomes an intermediate region that belongs to the region I or the region II according to how the actual value changes.

  Next, rotation fluctuation correction of the fuel injection amount will be described. FIG. 3 shows changes in values according to the crank angle relating to the correction of the present embodiment. (A) to (D) respectively show the in-cylinder pressures of the # 1 cylinder, # 3 cylinder, # 4 cylinder, and # 2 cylinder in the order of combustion. (E) shows the engine speed Ne. (F) shows the state of the in-cylinder pressure flag generated by the ECU 15. This in-cylinder pressure flag is high (Hi) within a predetermined period including the compression top dead center of each cylinder, and low (Lo) during other periods. It becomes. In this embodiment, the in-cylinder pressure flag becomes high within a range of ± 60 ° with respect to the compression top dead center of each cylinder. As will be described in detail later, the in-cylinder pressure parameter is calculated based on the in-cylinder pressure data sampled during the period in which the in-cylinder pressure flag is high.

  (G) shows the state of the rotational fluctuation flag generated by the ECU 15, and this rotational fluctuation flag is high (Hi) between the compression top dead center of each cylinder where the engine rotational speed is the lowest and the passage of a predetermined period. It becomes low (Lo) in other periods. In the present embodiment, the rotation fluctuation flag becomes high within a range from the compression top dead center of each cylinder to 60 °. As will be described in detail later, the value of the rotational fluctuation of each cylinder is detected based on the engine speed of the timing at which the rotational fluctuation flag switches from low to high and the timing at which the rotational fluctuation flag switches from high to low.

Now, as shown in FIGS. 3E and 3G, the engine speed detected at the timing when the rotation fluctuation flag switches from low to high is Ne4, and is detected at the timing when the rotation fluctuation flag switches from high to low. If the engine rotation speed is Ne5, the engine rotation speed change amount (that is, the rotation fluctuation amount) W between these timings is calculated by the following equation.
W = Ne5-Ne4 (1)

Further, assuming that the amount of change in engine rotation speed of each cylinder is Wn (where n is the cylinder number), the average value Wm is as follows.
Wm = (W1 + W2 + W3 + W4) / 4 (2)

Incidentally, the fuel injection amount Qfn of each cylinder (that is, the command injection amount for the fuel injection valve 4) Qfn is calculated by adding the rotation fluctuation correction amount dQen of each cylinder to the basic injection amount Qb common to each cylinder. Here, the basic injection amount Qb is calculated according to a predetermined map based on the actual engine operating state, in particular, the detected values of the engine speed Ne and the accelerator opening Ac. The fuel injection amount Qfn for each cylinder is obtained by the following equation.
Qfn = Qb + dQen (3)

Further, the rotation fluctuation correction amount dQen of each cylinder is calculated as follows based on, for example, a PI control (proportional integral control) or I control (integral control) method. First, the target value is set to the average value Wm of the rotational speed change amount of each cylinder, and the deviation En of the rotational speed change amount Wn of each cylinder with respect to the average value Wm is calculated based on the following equation.
En = Wm−Wn (4)

  This deviation En is a value representing the amount of variation in the rotational fluctuation of each cylinder. This is because the variation in rotational fluctuation with respect to the target value Wm increases as the rotational speed change amount Wn becomes farther from the target value Wm in a certain cylinder. Thus, the rotational speed change amount Wn of each cylinder is detected, and the deviation En of each cylinder is detected based on these.

Next, the rotational fluctuation correction amount dQen of each cylinder is calculated by the following equation according to the PI control method. Kp and Ki are predetermined feedback gains.
dQen = Kp × En + Ki × ∫En · dt (5)

  The rotational fluctuation correction amount dQen of each cylinder is a value that brings the deviation En of each cylinder close to zero, in other words, a value that eliminates variations in rotational fluctuation of each cylinder.

  Using the rotation fluctuation correction amount dQen calculated for each cylinder in this way, the basic injection amount Qb for the next fuel injection is feedback-corrected to obtain the fuel injection amount Qfn for each cylinder. By actually injecting this fuel injection amount Qfn, the variation in rotational fluctuation of each cylinder is reduced, the rotational fluctuation of each cylinder becomes constant, and the rotational fluctuation of the engine itself, and hence vibration, is reduced.

  In this example, two points of compression top dead center and 60 ° after compression top dead center are adopted as the timing for calculating the engine rotational speed change amount of each cylinder. It can be arbitrarily set within the expansion stroke section including the point, and may be changed according to the fuel injection pattern.

  Next, in-cylinder pressure correction of the fuel injection amount will be described.

  First, in-cylinder pressure data detected by the in-cylinder pressure sensor 5 of the corresponding cylinder is sampled during a period in which the in-cylinder pressure flag is high. Here, the corresponding cylinder is a cylinder including a compression top dead center within a period in which the in-cylinder pressure flag is high. The data sampling period is, for example, 0.5 ° or 1 °. If the crank angle sensor 16 is larger than this, for example, can detect the crank angle only every 5 °, the multiplication processing etc. is executed inside the ECU 15 so that sampling can be performed every 0.5 ° or 1 °. do it. Alternatively, in-cylinder pressure data may be sampled at regular intervals, and an angle index may be created at each sampling time.

  It is preferable to perform a filtering process such as a moving average on the sampled in-cylinder pressure data. It is also preferable to perform drift correction in the absolute pressure direction on the sampled in-cylinder pressure data as necessary. At this time, the detection value of the absolute pressure sensor provided in the intake passage is used. It is also preferable to perform top dead center correction using motoring data in advance.

Next, from the sampled in-cylinder pressure data (preferably data after the above-mentioned various processes are performed), the indicated mean effective pressure Pin (where n is the cylinder number) as the in-cylinder pressure parameter is calculated by the following equation. The
Pin = ∫ (Pθ × dVθ) · dθ (6)

  Here, P is the in-cylinder pressure, V is the in-cylinder volume, and θ is the crank angle. Pθ means the in-cylinder pressure at the time when the crank angle is θ, and dVθ is the change in the in-cylinder volume when the crank angle changes from θ by a minute angle dθ (for example, 0.5 ° or 1 ° as described above). means.

  Since the relationship between the crank angle θ and the in-cylinder volume V is physically determined in advance, the relationship between the two is stored in advance in the ECU 15 in the form of a map or the like, and the in-cylinder volume corresponding to the detected crank angle θ. V is calculated from a map or the like. The change amount dVθ of the in-cylinder volume when the crank angle changes by a minute angle dθ is also calculated by the ECU 15 in the same manner.

The average value Pim of the indicated average effective pressure Pin of each cylinder is as follows.
Pim = (Pi1 + Pi2 + Pi3 + Pi4) / 4 (7)

Incidentally, the fuel injection amount Qfn of each cylinder is calculated by adding the in-cylinder pressure correction amount dQpn of each cylinder to the basic injection amount Qb common to each cylinder, as in the case of rotational fluctuation correction. That is, the fuel injection amount Qfn of each cylinder is obtained by the following equation.
Qfn = Qb + dQpn (8)

The in-cylinder pressure correction amount dQpn of each cylinder is calculated as follows based on, for example, the PI control or I control method, as in the case of rotational fluctuation correction. First, the target value is the average value Pim of the indicated average effective pressure of each cylinder, and the deviation Epn of the indicated average effective pressure Pin of each cylinder with respect to the average value Pim is calculated based on the following equation.
Epn = Pim−Pin (9)

  This deviation Epn is a value representing the variation amount of the in-cylinder pressure parameter of each cylinder. This is because the variation in the indicated mean effective pressure Pin with respect to the target value Pim, that is, the variation in the combustion state, increases as the indicated mean effective pressure Pin deviates from the target value Pim in a certain cylinder. Thus, the indicated mean effective pressure Pin of each cylinder is detected, and the deviation Epn of each cylinder is detected based on these.

Next, the in-cylinder pressure correction amount dQpn of each cylinder is calculated by the following equation according to the PI control method. Kp and Ki are predetermined feedback gains.
dQpn = Kp × Epn + Ki × ∫Epn · dt (10)

  The in-cylinder pressure correction amount dQpn of each cylinder is a value that brings the deviation Epn of each cylinder close to zero, in other words, a value that eliminates variations in the combustion state of each cylinder.

  Using the in-cylinder pressure correction amount dQpn calculated for each cylinder in this way, the basic injection amount Qb for the next fuel injection is feedback-corrected to obtain the fuel injection amount Qfn for each cylinder. By actually injecting this fuel injection amount Qfn, variation in the combustion state of each cylinder is reduced, the combustion state of each cylinder becomes constant, exhaust gas performance is improved, and deterioration of exhaust gas emission is suppressed.

  Here, as the in-cylinder pressure data sampling period for calculating the indicated mean effective pressure Pin of each cylinder, a period within a range of ± 60 ° with respect to the compression top dead center of each cylinder is adopted, but this period is arbitrary. And may be changed according to the fuel injection pattern.

  In the present embodiment, both the rotational fluctuation correction and the in-cylinder pressure correction as described above are performed during the steady operation of the engine, and are not performed during the unsteady operation such as during transient operation of the engine (acceleration or deceleration). That is, during the engine non-steady operation, the above-described feedback control of the fuel injection amount accompanied with the rotation fluctuation correction and the in-cylinder pressure correction is substantially stopped.

  However, as will be described below, in the present embodiment, the correction amounts dQen and dQpn calculated during steady operation are stored in the ECU 15 as learning values in association with the operating state of the engine, and during unsteady operation of the engine. The correction is executed using the stored learning value. Whether or not the engine is in a steady operation state is calculated by, for example, calculating the rate of change of the engine speed or fuel injection amount (amount of change per predetermined time), and when the rate of change is equal to or less than a predetermined threshold value It can be determined that it is in a state.

  FIG. 4 and FIG. 5 show learning maps for such learning, and these learning maps are stored in advance in the memory of the ECU 15. A learning map is prepared for each cylinder and each type of correction. In the case of this embodiment, 4 maps × 2 types = 8 maps are prepared. FIG. 4 is a learning map for one cylinder for correcting rotational fluctuation, and FIG. 5 is a learning map for one cylinder for correcting in-cylinder pressure. The initial value of the map data is 0, and some learned values are input in the illustrated example.

  However, since the rotation variation correction and the in-cylinder pressure correction are executed in different operating regions, the maps may be shared without being separated. In this case, the correction amount is calculated by any correction in the hysteresis region, but the calculated correction amount corresponds to the operation state at that time regardless of whether the correction amount is calculated by any correction. It may be saved as a learning value.

In these maps, two parameters of an engine speed (engine speed (rpm)) and a fuel injection amount (basic injection amount Qb (mm ³ / st)) are employed as values representing the operating state of the engine. During execution of either the rotational fluctuation correction or the in-cylinder pressure correction, the calculated correction amount is stored in a lattice corresponding to the engine speed and the fuel injection amount at the time of calculating the correction amount. The values in the grid may always be updated during correction execution. Alternatively, during the execution of correction within one grid, a plurality of correction amounts are separately stored in the buffer memory, and when the operating state deviates from the grid, the values stored in the buffer memory are averaged and You may preserve | save as a learning value of a grid | lattice. Depending on the actual driving situation, there may be an unlearned region (lattice), but at this time, a learned value may be calculated by interpolating from surrounding regions that have already been learned.

  The map may be defined by, for example, the fuel injection amount and the common rail pressure instead of the engine rotation speed and the fuel injection amount.

When the engine is in an unsteady operation, a learning value corresponding to the actual engine speed and the fuel injection amount is acquired from the map of FIG. 4 or FIG. 5, and the acquired learning value is replaced with the correction amount to perform correction. For example, when the rotational fluctuation correction is performed during the non-steady operation in the region I shown in FIG. 2, the actual engine speed (ex. 800 (rpm)) and the fuel injection amount (ex. 10 (mm ³ / st)) 4 is acquired from the map of FIG. 4 and correction is executed using the acquired learning value as the correction amount dQen.

  By the way, since the operation state changes during the unsteady operation of the engine, the operation region as shown in FIG. 2 may be switched and the type of correction may be switched. Then, the learning value or the correction amount is switched from one correction learning value to the other correction learning value.

  At this time, if there is not much difference between the learning values of one and the other, there is no problem, but if there is a large difference between the learning values of one and the other, the correction amount and thus the fuel injection amount may change suddenly at the time of switching, and torque shock may occur There is sex.

  Therefore, in the present embodiment, the learning value is gradually changed from one learning value to the other learning value in order to prevent such a correction amount and thus a sudden change in the fuel injection amount, and further a torque shock. That is, the learning value is not switched from one learning value to the other learning value at once, but these learning values are connected slowly and smoothly.

  For example, as shown in FIG. 6, when the operating state of the engine changes so as to sequentially pass through the regions I, III, and II, the learning value becomes the in-cylinder pressure from the rotation variation correction amount dQen when the learning value enters the region II from the region III. The correction amount changes to dQpn. At this time, the learning value is not changed from the rotation fluctuation correction amount dQen to the in-cylinder pressure correction amount dQpn at once, but is gradually changed from the rotation fluctuation correction amount dQen to the in-cylinder pressure correction amount dQpn. In the illustrated example, it is changed linearly at a constant speed, but it may be changed curvedly by applying a first-order lag filter. You may make it perform gradual change only when the difference of the learning value before and behind switching is more than predetermined value.

  Next, the fuel injection amount calculation routine of this embodiment will be described based on the flowchart of FIG. The illustrated routine is executed by the ECU 15.

  First, in step S1, an engine operating region to which the current engine operating state belongs is determined.

  Next, in step S2, it is determined whether or not the current engine operating state belongs to region I. It should be noted that even if the state of rotation fluctuation correction in the region I is changed to the hysteresis region III, correction is not switched, so that it is treated as belonging to the region I.

  When it is determined that it belongs to the region I, the process proceeds to step S3, and it is determined whether or not the current engine operating state is in a steady state. When it is determined that the engine is in the steady state, the process proceeds to step S4, and the rotation fluctuation correction amount dQen is calculated. On the other hand, when it is determined that the engine is in the unsteady state, the process proceeds to step S5, and the learning value corresponding to the current engine operating state is acquired from the learning map as shown in FIG. After steps S4 and S5, the process proceeds to step S11.

  On the other hand, if it is determined in step S2 that the current engine operating state does not belong to region I, the process proceeds to step S6, and it is determined whether or not the current engine operating state belongs to region II. In addition, even if it transfers to the hysteresis area | region III from the state which is performing the cylinder pressure correction | amendment in the area | region II, since switching of correction | amendment does not arise, it treats as what belongs to the area | region II.

  When it is determined that it belongs to the region II, the process proceeds to step S7, and it is determined whether or not the current engine operating state is in a steady state. When it is determined that the engine is in the steady state, the process proceeds to step S8, and the in-cylinder pressure correction amount dQpn is calculated. On the other hand, when it is determined that the engine is in the unsteady state, the process proceeds to step S9, and a learning value corresponding to the current engine operating state is acquired from the learning map as shown in FIG. After steps S8 and S9, the process proceeds to step S11.

  If it is determined in step S6 that the current engine operating state does not belong to region II, the process proceeds to step S10. In this case, the current engine operating state does not belong to any of the regions I to III (that is, it belongs to the region near the upper limit on the high rotation and high load side from the region II), so the correction amount or the learning value is set. Both corrections used are stopped. After step S10, the process proceeds to step S11.

  In step S11, the correction amount processing at the time of area switching as shown in FIG. 6 is executed. That is, when the current engine operating state is an unsteady state and immediately after the transition from the region III to the region I or II, the learning value is corrected so as to gradually change the learning value.

  Thereafter, in step S12, the fuel injection amount Qfn is calculated using the correction amounts dQen, dQpn or the learning value as necessary.

  As described above, according to the present embodiment, the rotation fluctuation correction and the in-cylinder pressure correction are performed by switching each engine operation region. Therefore, these corrections can be executed in an operation region suitable for each, and vibration suppression and exhaust gas performance can both be achieved.

  In particular, the rotational fluctuation correction has an advantage that variation in rotational fluctuation of each cylinder at low load can be reduced, but there is a disadvantage that variation in combustion state of each cylinder cannot be reduced. In-cylinder pressure correction has an advantage that variation in the combustion state of each cylinder can be reduced regardless of the rotational load range, but there is a disadvantage that variation in rotation fluctuation of each cylinder at low load cannot be sufficiently reduced. As the engine rotational speed increases, the engine rotational fluctuation itself decreases and the rotational fluctuation detection resolution decreases, and sufficient accuracy cannot be expected. Therefore, it is difficult to apply the rotational fluctuation correction to the middle and high rotational speed range. is there. On the other hand, at an extremely low load, an error in the measurement result increases depending on the accuracy of the in-cylinder pressure sensor, so that it is difficult to apply the in-cylinder pressure correction at an extremely low load.

  In the present embodiment, the region I (which may also include the region III) in which the rotation variation correction is performed is set on the lower rotation and lower load side than the region II (which may also include the region III) in which in-cylinder pressure correction is performed. Therefore, the advantages and disadvantages of both corrections can be compensated for, and the variation in rotation fluctuation can be reduced by correcting the rotation fluctuation on the low rotation / low load side, and the combustion state variation can be reduced by correcting the in-cylinder pressure on the high rotation / high load side. . Therefore, it is possible to effectively achieve both vibration suppression and exhaust gas performance.

  In this embodiment, since the illustrated mean effective pressure is used as the in-cylinder pressure parameter, the in-cylinder combustion state can be satisfactorily expressed, and in-cylinder pressure correction can be suitably performed. However, other values can be used as the in-cylinder pressure parameter.

  In the present embodiment, the correction amount is learned during the steady operation of the engine, and the rotation fluctuation correction and the in-cylinder pressure correction are performed using the learned value during the transient operation of the engine. It is possible to ensure control reliability without executing correction based on the value.

  Next, another embodiment of the present invention will be described.

  In the embodiment, the rotation fluctuation correction and the in-cylinder pressure correction are clearly switched for each engine operating region. On the other hand, in the present embodiment, both corrections are always executed while changing the weight according to the change in the engine operating state.

In the present embodiment, the fuel injection amount Qf is calculated by the following equation.
Qf = Qb + k * dQen + (1-k) * dQpn (11)

  k is a weighting factor and can take a value in the range of 0 ≦ k ≦ 1 depending on the engine operating state. A value representing the engine operating state, for example, the relationship between the engine rotation speed, the fuel injection amount (basic injection amount Qb), and the weight coefficient k is stored in advance in the ECU 15 in the form of a map. The ECU 15 obtains a weighting factor k corresponding to the actual engine speed and the fuel injection amount from the map, and uses this weighting factor k to calculate the fuel injection amount Qf according to the previous equation.

  The weighting factor k is set so as to decrease as the engine operating state becomes higher or higher, and conversely increase as the engine operating state becomes lower or lower. Therefore, the higher the engine operation state is, the higher the in-cylinder pressure correction, the more the in-cylinder pressure correction weight is increased, and the rotation fluctuation correction weight is decreased. On the contrary, as the engine operating state becomes the low rotation or low load side, the weighting for rotational fluctuation correction is increased and the weighting for in-cylinder pressure correction is decreased.

  Therefore, the rotation fluctuation correction can be applied more strongly than the in-cylinder pressure correction on the low rotation / low load side, and the in-cylinder pressure correction can be applied more strongly than the rotation fluctuation pressure correction on the high rotation / high load side. Therefore, the same effect as that of the above embodiment can be obtained.

  Note that such control using weighting can be applied to the above-described gradual change switching control of the learning value. In this case, the weighting coefficient k is changed as time elapses from the start of switching.

  As mentioned above, although embodiment of this invention was described in detail, this invention can also employ | adopt other embodiment. For example, the deviations En and Epn representing the variation amount of each cylinder are based on the average values Wm and Pim of each cylinder, but instead may be based on the values of a predetermined specific cylinder. Further, a value other than the deviations En and Epn can be adopted as the value representing the variation amount of each cylinder.

1 Engine Body 4 Fuel Injection Valve 5 Cylinder Pressure Sensor 7 Cylinder En Deviation Epn Deviation Qb Basic Injection Amount Qf Fuel Injection Amount Pin Average Mean Effective Pressure k Weighting Factor

Claims (7)

A fuel injection control device for a multi-cylinder internal combustion engine that controls the amount of fuel injected from the fuel injection valve of each cylinder for each cylinder,
First correction means for detecting a variation amount of rotation fluctuation of each cylinder and correcting a fuel injection amount of each cylinder based on the variation amount of rotation fluctuation;
A second correction unit that detects a variation amount of the in-cylinder pressure parameter of each cylinder and corrects a fuel injection amount of each cylinder based on the variation amount of the in-cylinder pressure parameter;
A fuel injection control for a multi-cylinder internal combustion engine, wherein the first correction by the first correction means and the second correction by the second correction means are switched for each operation region of the internal combustion engine. apparatus.   The first operation region in which the first correction is executed is set to be at a lower rotation and a lower load side than the second operation region in which the second correction is executed. A fuel injection control device for a multi-cylinder internal combustion engine according to claim 1.   3. The fuel injection control device for a multi-cylinder internal combustion engine according to claim 1, wherein the in-cylinder pressure parameter is an indicated mean effective pressure calculated based on a detection value of an in-cylinder pressure sensor within a predetermined period.   Each of the first correction unit and the second correction unit calculates and corrects the correction amount during steady operation of the internal combustion engine, and learns the calculated correction amount in association with the operating state of the internal combustion engine. The fuel injection control device for a multi-cylinder internal combustion engine according to any one of claims 1 to 3, wherein the fuel injection control device is stored as a value, and correction is performed using the learned value during an unsteady operation of the internal combustion engine.   When the first correction and the second correction are switched during the unsteady operation of the internal combustion engine, the first learning value stored in the first correction unit and the second correction unit are stored. The fuel injection control device for a multi-cylinder internal combustion engine according to claim 4, wherein the learning value is gradually changed from one of the second learning values to the other. A fuel injection control device for a multi-cylinder internal combustion engine that controls the amount of fuel injected from the fuel injection valve of each cylinder for each cylinder,
First correction means for detecting a variation amount of rotation fluctuation of each cylinder and correcting a fuel injection amount of each cylinder based on the variation amount of rotation fluctuation;
A second correction unit that detects a variation amount of the in-cylinder pressure parameter of each cylinder and corrects a fuel injection amount of each cylinder based on the variation amount of the in-cylinder pressure parameter;
A multi-cylinder internal combustion engine that performs the first correction by the first correction unit and the second correction by the second correction unit while changing the weight according to a change in the operating state of the internal combustion engine. Engine fuel injection control device.   The weight of the second correction is increased and the weight of the first correction is decreased as the operating state of the internal combustion engine becomes a higher speed or a higher load side. A fuel injection control device for a cylinder internal combustion engine.

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