JP2016008525A - Engine control unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce irregularities in generated torque among cylinders of an engine.SOLUTION: An engine control unit comprises: heat generation gravity center calculation means 23 for detecting a heat generation gravity center G of combustion in each of a plurality of cylinders of an engine; and combustion control means 24 for comparing the heat generation gravity centers G of the respective cylinders calculated by the heat generation gravity center calculation means 23, and correcting fuel injection so that the heat generation gravity centers G are close to one another. The fuel injection is corrected by advancing or retarding fuel injection timing per cylinder, and the combustion control means 24 corrects the fuel injection so as to make the heat generation gravity center G of each cylinder closer to a preset heat generation gravity center reference value G. The heat generation gravity center calculation means 23 calculates the heat generation gravity center G in each cylinder on the basis of a numerical value of a combustion pressure sensor 34 provided in each cylinder or on the basis of a rotation angular velocity of the crankshaft C.

Description

  The present invention relates to an engine control device having a function of suppressing variation in combustion between cylinders.

  In general, when the engine has a plurality of cylinders, the generated torque may vary among the cylinders. This variation in torque is caused by a small difference in compression ratio due to dimensional error between cylinders, a difference in intake state amount due to differences in intake passage handling and shape, variation in fuel injection state due to injector dimensional error, It occurs due to the difference of various conditions such as the difference of the inner wall temperature.

  It is desirable to avoid the variation in torque between the cylinders as much as possible because it leads to deterioration of drivability, fuel consumption, and in some cases, increased emission of unburned hydrocarbons.

  Adjustment of the variation in torque between the cylinders is often performed by increasing or decreasing the fuel injection amount by the injector, that is, the fuel injection period so that the rotational speed of each cylinder is constant under stable conditions such as idling. For example, a cylinder with a large torque reduces the fuel injection amount, and a cylinder with a small torque increases the injection amount.

  Further, as another method for suppressing the variation in torque between the cylinders, a fuel injection amount that causes a known generated torque under a stable condition such as an idle, a fuel injection period, a current generated torque and a fuel injection amount, a fuel injection The learning control etc. which hold | maintain the deviation | shift with a period as a learning value of an injector is also considered.

  Patent Document 1 discloses a technique for correcting the fuel injection amount after correcting the ignition timing by fuel injection timing control so that the generated torque approaches the target torque.

Japanese Patent Laid-Open No. 2002-21613

  However, in such a learning method, if the combustion timing of the fuel is different, the corresponding generated torque is also different. For this reason, there is a problem that an appropriate correction value cannot be obtained when the generated torque changes under other conditions not related to the fuel injection amount.

  For example, there is a case where the amount of fuel injection is not so large but the torque is sufficiently generated, or conversely, a case where the amount of generated fuel is small but the amount of fuel injection is sufficiently large. In addition, due to the difference in combustion timing, even if the fuel injection amount is the same, there may be a case where the difference in torque occurs due to the combustion timing being biased forward or backward.

  Accordingly, an object of the present invention is to effectively reduce variation in torque generated between cylinders of an engine.

  In order to solve the above-described problems, the present invention provides a heat generation time for detecting a predetermined time at which a heat generation amount of combustion in a plurality of cylinders of an engine is a predetermined range ratio with respect to a total heat generation amount of one cycle. And a combustion control means for comparing the predetermined timings of the respective cylinders calculated by the heat generation timing calculating means and correcting fuel injection to bring the predetermined timings closer to each other. For the correction, an engine control device for advancing or retarding the fuel injection timing for each cylinder is employed.

  Here, the predetermined time may be a heat generation center of gravity, and the heat generation time calculation unit may be a heat generation center of gravity calculation unit.

  Here, the combustion control means may be configured to correct the fuel injection so that the heat generation center of gravity of each cylinder approaches a predetermined heat generation center of gravity reference value.

  The combustion control means compares the generated torque of each cylinder with the target torque with the fuel injection timing corrected, and if the generated torque is different from the target torque, the fuel is controlled so that the generated torque matches the target torque. It can be set as the structure which correct | amends injection quantity.

  The heat generation center of gravity calculation means may be configured to calculate the heat generation center of gravity in the cylinder based on a numerical value of a combustion pressure sensor provided in each cylinder.

  Further, in each of the above-described configurations, an angular velocity detection unit that detects an angular velocity of a rotating shaft that is driven in accordance with an output of the engine, and an angular acceleration calculation unit that calculates an angular acceleration based on the angular velocity detected by the angular velocity detection unit And the heat generation center of gravity calculation means calculates the heat generation center of gravity in the cylinder based on the change in angular acceleration calculated by the angular acceleration calculation means.

  Here, the change of the angular acceleration is calculated based on two reference angular accelerations obtained along the time series, and the value of the angular acceleration preceding the time series among the two angular acceleration values is: It is desirable that the detection is made in a range of a crank angle straddling the top dead center in the initial stage of the expansion stroke.

  The angular acceleration value preceded by the time series is the angular velocity detected in the crank angle range straddling the top dead center in the early stage of the expansion stroke, and the crank angle after the crank angle range straddling the top dead center. It can be set as the structure calculated based on the angular velocity detected in the range.

  Further, the heat generation center of gravity can be obtained based on a difference between two angular acceleration values obtained along a time series and a generated torque of the engine.

  According to the present invention, the fuel injection is performed in order to detect the predetermined time and the heat generation center of gravity at which the heat generation amount of combustion in the plurality of cylinders of the engine is within the predetermined range ratio and bring the predetermined time and the heat generation center of gravity close to each other. Since the correction is made to advance or retard the timing for each cylinder, it is possible to effectively reduce the variation in torque generated between the cylinders of the engine regardless of the cause of the occurrence.

It is a schematic diagram which shows the structure of the control apparatus of the engine of this invention. It is a schematic diagram which shows the structure of the rotation sensor which detects rotation of the crankshaft of an engine. It is a schematic diagram which shows the example of the pulse for detecting rotation of a crankshaft. It is a schematic diagram which shows the example of a setting of the crank angle for calculating the rotation angular velocity and rotation angle acceleration of a crankshaft. It is a graph which shows the relationship between the variation | change_quantity of the rotational angular acceleration of a crankshaft, and a heat generation gravity center. It is a flowchart of control by the engine control apparatus of one Embodiment of this invention. It is a graph which shows the relationship between a cylinder pressure and a crank angle, and the relationship between a heat release rate and a crank angle. It is a graph which shows the relationship between the time which a crankshaft rotates 30 degree | times, and a crank angle, and the relationship between the rotation angle acceleration of a crankshaft, and a crank angle. It is a graph which shows the relationship between the change of the rotational angular acceleration of a crankshaft, and a heat generation gravity center. (A) to (c) are graphs showing the relationship between generated torque and heat generating center of gravity, noise and heat generating center of gravity, crankshaft rotation angular acceleration change and heat generating center of gravity, respectively (c) to (f) FIG. 5 is a graph showing the relationship between generated torque and heat generation center of gravity, noise and heat generation center of gravity, crankshaft rotation angular acceleration change, and heat generation center of gravity.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram conceptually showing the control device for the engine of this embodiment.

  The engine E of this embodiment is an automobile diesel engine. As shown in FIG. 1, the engine E has an intake port for sending intake air into the cylinder containing the piston P, an intake passage 1 leading to the intake port, an exhaust passage 2 drawn from the exhaust port, and a fuel injection device D. Etc. The intake port and the exhaust port are opened and closed by valves 1a and 2a, respectively.

  In this embodiment, a multi-cylinder engine having a plurality of cylinders is assumed, and FIG. 1 shows one of them, but the present invention can be applied regardless of the number of cylinders.

  The intake passage 1 has a high-pressure throttle valve 5 that adjusts the flow area of the intake port upstream from the intake port, an intake air cooling device (intercooler) 6 that cools the intake air flowing through the intake passage 1, and a turbocharger. In the intake passage 11 further upstream of the compressor 17, a low-pressure throttle valve 15, an air cleaner 16, and the like for adjusting the flow passage area are provided.

  In the exhaust passage 2, a turbocharger turbine 7, an exhaust purification unit 8 including a catalyst for removing unburned hydrocarbon (HC) and the like in the exhaust, and the like, a muffler (muffler) from the exhaust port toward the downstream side 12 is provided.

  A midway portion between the turbine 7 and the exhaust port of the exhaust passage 2 and a midway portion between the intake port of the intake passage 1 and the first throttle valve 5 are communicated by a high pressure exhaust gas recirculation passage 3 constituting a high pressure exhaust gas recirculation device. doing. A part of the exhaust gas discharged from the engine E returns to the intake passage 1 as a recirculation gas via the high-pressure exhaust recirculation passage 3. A high-pressure exhaust gas recirculation valve 4 is provided in the high-pressure exhaust gas recirculation passage 3. The recirculated gas merges with the intake air in the intake passage 1 according to the pressure state in the intake passage 1 that is associated with the opening and closing of the high-pressure exhaust gas recirculation valve 4 and the opening and closing of the first throttle valve 5.

  Further, midway portions of the exhaust purification unit 8 and the silencer 12 in the exhaust passage 2 and midway portions of the compressor 17 and the low pressure throttle valve 15 in the intake passage 11 are low pressure exhaust gas recirculation passages constituting a low pressure exhaust gas recirculation device. 13 communicates. A part of the exhaust gas discharged from the engine E returns to the upstream side of the compressor 17 of the turbocharger in the intake passage 11 as the recirculation gas via the low pressure exhaust recirculation passage 13. The low pressure exhaust gas recirculation passage 13 is provided with a low pressure exhaust gas recirculation valve 14. The recirculated gas merges with the intake air in the intake passage 11 according to the pressure state in the intake passage 11 that is associated with the opening and closing of the low pressure exhaust recirculation valve 14 and the opening and closing of the low pressure throttle valve 15. Reference numeral 10 in the figure is a recirculation gas cooler that cools the recirculation gas in the low-pressure exhaust recirculation passage 13.

  A vehicle equipped with the engine E includes an electronic control unit 20 for controlling the engine.

  The electronic control unit 20 includes fuel injection execution means 25 that executes fuel injection by the fuel injection device D based on the operating state of the engine. In addition, control means 26 is provided for controlling the supercharging pressure, controlling the opening of the first throttle valve 5 and the low-pressure throttle valve 15, and other commands necessary for engine control.

Further, the electronic control unit 20 detects angular acceleration of the crankshaft C (rotating shaft) driven in accordance with the output of the engine E, and angular velocity based on the angular velocity detected by the angular velocity detection means 21. Based on the angular acceleration calculating means 22 for calculating acceleration and the change in angular acceleration calculated by the angular acceleration calculating means 22, the heat generation amount in the cylinder becomes a predetermined range ratio with respect to the total heat generation amount of one cycle. And a heat generation time calculating means 23 for calculating a predetermined time.
In this embodiment, as the predetermined time calculated by the heat generation time calculation means 23, a heat generation center of gravity G that is a time when the heat generation amount becomes 50% of the total heat generation amount of one cycle is adopted. . Hereinafter, in this embodiment, the predetermined time is referred to as a heat generation center of gravity G, and the heat generation time calculation unit 23 is referred to as a heat generation center of gravity calculation unit 23.

Further, the electronic control unit 20 compares the heat generation center of gravity G calculated by the heat generation center of gravity calculation means 23 with a predetermined heat generation center of gravity reference value G ₀ to control combustion in the cylinder. 24. The combustion control means 24 instructs the fuel injection execution means 25 to correct the necessary fuel injection timing. Further, the combustion control unit 24 commands the fuel injection execution unit 25 to correct the fuel injection amount when necessary in a state where the correction of the fuel injection timing is commanded.

  As shown in FIGS. 1 and 2, the angular velocity detection means 21 acquires information from a crank angle sensor 30 and a cylinder discrimination sensor 33 provided in the engine E.

  The crank angle sensor 30 includes a rotating member 31 that rotates integrally with the crankshaft C of the engine, and a plurality of vanes 31 a that are formed on the periphery of the rotating member 31 and project outward in the radial direction. The vanes 31a are provided at regular intervals along the circumferential direction of the rotating member 31, and the adjacent vanes 31a all have circumferential lengths corresponding to the constant rotation angle of the crankshaft C. A detection unit 32 provided to face the vane 31a optically or electromagnetically detects the passage of the vane 31a accompanying the rotation of the rotating member 31, and outputs a pulse based on the detection. (See (b), (d) and (e) in FIG. 3).

  The cylinder discrimination sensor 33 is provided on the camshaft in the cylinder head. While the crankshaft C rotates twice around the axis and the camshaft rotates once around the axis, a predetermined pulse is output every time the camshaft takes a specific rotational position corresponding to one cylinder. (See (c), (d), and (e) in FIG. 3).

  The detection of the angular acceleration will be described. During the operation of the engine E, the electronic control unit 20 acquires the pulse output from the crank angle sensor 30 and the detection signal of the cylinder discrimination sensor 33, and repeats the calculation continuously. To do.

  The electronic control unit 20 determines what number the pulse output from the crank angle sensor 30 is after the specific pulse output from the cylinder determination sensor 33. Thus, the pulse from the input crank angle sensor 30 can be used to calculate the stroke of intake, compression, expansion, and exhaust of each cylinder, that is, the heat generation gravity center G of the numbered cylinder. Identify whether it is information. Specifically, the number of the cylinder that is executing the expansion stroke (for example, around the top dead center of the expansion stroke) at the time of the pulse acquisition is identified.

  The electronic control unit 20 responds to a pulse from the crank angle sensor 30 with a timer for the identified cylinder (or a group of cylinders including the identified cylinder and proceeding in the same process as the cylinder). Start.

  When a predetermined number of pulses are acquired from the crank angle sensor 30 after the timer is started, the electronic control unit 20 stops the timer and acquires the elapsed time after the timer is started. This time measurement result is a time required for the crankshaft C to rotate by a predetermined rotation angle in a predetermined region around the compression top dead center of the piston P of the identified cylinder. Hereinafter, it is referred to as “predetermined angle elapsed time”.

  In this embodiment, as shown in FIG. 3 (b), the vane 31a is set to 60 teeth every 6 degrees (however, since the identification missing tooth 4 is included, 56 pulses), this predetermined angle elapsed time is The angle corresponding to the passage of the five vanes 31a, that is, the time required for the rotation angle of the crankshaft C to be 30 degrees as shown in FIG. This angle may be other than 30 degrees, for example, 20 degrees, 15 degrees, or the like.

  The angular velocity detection means 21 calculates an average angular velocity during the passage through the predetermined rotation angle (30 degrees) based on the predetermined angle elapsed time.

The calculation formula is, for example,
(Expression 1) Angular velocity ω _n = (π / 6) ÷ (T _{ca (n)} )
It becomes.
Here, T _{ca (n)} is the nth time from the start of the timer among the predetermined angle elapsed time for each predetermined rotation angle (30 degrees = π / 6 rad) acquired corresponding to the identified cylinder. Indicates that

  The angular acceleration calculation means 22 calculates the angular acceleration based on these angular velocity information. The angular acceleration is calculated based on two angular velocities obtained along the time series. In this embodiment, two angular velocities adjacent to each other along the time series are used.

The calculation formula is, for example,
(Expression 2) Angular acceleration α _{n−1 to n}
= D ² θ / dt ²
= 10 ¹² ×
[{(Π / 6) ÷ (T _{ca (n)} )} − {(π / 6) ÷ (T _{ca (n−1)} )}]
/ {( _{Tca (n-1)} ) + ( _{Tca (n)} )} / 2
It becomes.
This is the angular acceleration α _n calculated based on the n−1th predetermined angle elapsed time T _{ca (n−1)} acquired from the timer start and the nth acquired predetermined angle elapsed time T _{ca (n). -1} to _n are shown. That is, α _{n−1 to n} are average angular accelerations from the measurement start end to the measurement end in a range of an angle (60 degrees) twice a predetermined rotation angle (30 degrees = π / 6 rad).

  For example, FIG. 4 is a schematic diagram for calculating a predetermined angle elapsed time, angular velocity, and angular acceleration every 30 degrees in a period in which the piston P of the identified cylinder is in a region of 180 degrees before and after compression top dead center. It is.

Here, the region of the crank angle of 180 degrees from the timer start to the timer stop is divided into six regions every 30 degrees. The angular velocity ω ₄ based on the time T ₄ (T _{ca (4)} ) passing through the region 4 (18 degrees before the top dead center and 12 degrees after the top dead center) that is the fourth region from the timer start, and the region 5 (the top The angular acceleration calculated by the angular velocity ω ₅ based on the time T ₅ (T _{ca (5)} ) passing through 12 degrees after dead center to 42 degrees after top dead center is α ₄₅ (α _4-5 ), and region 5 and the angular velocity omega _5, the angular acceleration is calculated by the angular velocity omega ₆ based on the time _T 6 passing through (72 degrees after top dead center to 42 ° after top dead _{center) (T ca (6))} region 6 alpha ₅₆ (Α _5-6 ). α ₄₅ is an average angular acceleration from the measurement start end s to the measurement end u in the corresponding 60-degree range. α ₅₆ is an average angular acceleration from the measurement start end u to the measurement end v in the corresponding 60-degree range.

  The heat generation center of gravity calculation means 23 calculates the heat generation center of gravity G of the corresponding cylinder based on the change in the angular acceleration based on the information on the angular acceleration calculated by the angular acceleration calculation means 22.

  The heat generation center of gravity G means that when the generated energy (heat) from the start of combustion to the end of combustion in one cycle of one cylinder is 100, the integrated value of the combustion energy (heat) generated from the start of combustion is half. It is the time when it reached 50. That is, the position of the crank angle θ at which the heat generation amount reaches 50% of the total heat generation amount in one cycle of one cylinder is set as the heat generation gravity center G.

The heat generation amount can also be obtained by integrating the heat generation rate (heat generation amount per unit crank angle), but in this embodiment, instead of directly calculating the heat generation amount, the heat generation center of gravity G and _Note that there is a linear correlation between the difference Δα between the values of the two angular accelerations α _{n− 1 to n} and α _{n to n + 1} obtained along the time series of rotation of the crankshaft C, Based on the change in angular acceleration and the torque value of the engine E, the heat generation center of gravity G is obtained.

For example, FIG. 5 is a chart showing a correlation for calculating the heat generation gravity center G. Here, the horizontal axis represents the crank angle θ (deg. CA) of the heat generation center of gravity G, and the vertical axis represents the angular acceleration change, that is, the difference Δα between the values of the two angular accelerations α _{n− 1 to n} and α _{n to n + 1.} Yes. Here, n = 5, and Δα = α _5-6 -α _4-5 is expressed as Δα = α ₅₆ -α ₄₅ .

For example, in the case where the generated torque of the engine is 120 Nm, in FIG. 5, the relationship between the crank angle θ of the heat generation center of gravity G and the angular acceleration change Δα = α ₅₆ −α ₄₅ is represented by Δ mark: a located at the uppermost position. The distribution is as shown. Such information can be acquired in advance by an experiment using the same type of master engine or the like. Based on the distribution of these pieces of information, an approximate expression H ₁₂₀ by the least square method or the like is obtained. The crank angle θ of the heat generation gravity center G can be obtained if the change in angular acceleration Δα = α ₅₆ −α ₄₅ is found from the approximate expression H ₁₂₀ under the condition that the generated torque is ₁₂₀ Nm.

For example, when the generated torque of the engine is 80 Nm, in FIG. 5, the relationship between the crank angle θ of the heat generation center of gravity G and the change in angular acceleration Δα = α ₅₆ −α ₄₅ is indicated at the center □: b It becomes distribution shown by. When the generated torque of the engine is 20 Nm, the relationship between the crank angle θ of the heat generation center of gravity G and the angular acceleration change Δα = α ₅₆ −α ₄₅ has a distribution indicated by a mark “c” located at the center.
If a similar approximate expression is obtained even under other torque conditions, for example, 100 Nm, 60 Nm, 40 Nm, etc., if the angular acceleration change Δα = α ₅₆ −α ₄₅ is found under the torque conditions, The crank angle θ of the generated center of gravity G can be obtained. The pitch of the torque for acquiring data can be freely set every 10 Nm, every 20 Nm, or the like.

However, FIG. 5 shows the _relationship between the crank angle θ of the heat generation center of gravity G under the condition of an engine speed of 1500 revolutions / minute (min ⁻¹ ) and the angular acceleration change Δα = α _{n to n + 1} −α _{n− 1 to n} . It shows the relationship. At other engine speeds, for example, 2000 rpm / min, 2500 rpm / min, 3500 rpm / min, and the like, if a similar map diagram is obtained, the torque condition and angular acceleration change Δα = α ₅₆ -α ₄₅ If it becomes clear, the crank angle θ of the heat generation center of gravity G can be obtained. The pitch of the engine speed at which data is acquired can be freely set at every 500 revolutions / minute, every 100 revolutions / minute, or the like.

Here, the time series of the values of the two angular accelerations α _{n− 1 to n} and α _{n to n + 1} (in the embodiment, α ₄₅ and α ₅₆ ) serving as a reference for calculating the heat generation center of gravity G is the previous one. It is desirable that a certain angular acceleration value (α _{45 in the} embodiment) is detected in a range of a crank angle straddling the top dead center in the early stage of the expansion stroke.

That is, the change in angular acceleration Δα = α _{n to n + 1} −α _{n− 1 to n serving as} a reference for calculating the heat generation gravity center G is within a certain time before and after the passage of the top dead center in the initial stage of the expansion stroke. This is because the numerical value at is considered to have the strongest correlation with the position of the heat generation center of gravity G.

This, for example, the angular velocity omega _n initiated acquisition after completely through the top dead center in the expansion stroke initial, subsequent angular velocity omega _{n + 1,} the angular acceleration based on only the information of ω _{n + 2} ··· α n~ _{This is because if n + 1} ... is calculated, the heat generation center of gravity G is already calculated based only on the information after the combustion is partially started. Further, for example, the angular acceleration α _n− is based on only the information of the angular velocity ω _n that has been acquired before completely passing through the top dead center and the angular velocities ω _n−1 , ω _{n−2. This} is because calculating 1 to _n ... Includes a lot of information on a region where combustion is not started.

Also, when calculating the reference become angular acceleration change _{Δα = α n~n + 1 -α n} -1~n for calculating a heat generation center of gravity G, time series of the angular acceleration alpha _{n-1 to n} in front The values are the angular velocity ω _n−1 detected in the crank angle range straddling the top dead center at the initial stage of the expansion stroke, and the angular velocity ω detected in the crank angle range following the crank angle range straddling the top dead center. More preferably, it is calculated based on _n .

Based on the information on the heat generation center of gravity G obtained in this way, the combustion control means 24 of the electronic control unit 20 uses the heat generation center of gravity G calculated by the heat generation center of gravity calculation means 23 and a predetermined heat generation center of gravity. by comparison with a reference value G _0, the proper fuel injection timing, and calculates the information of the fuel injection amount. Then, the combustion control means 24 commands the fuel injection execution means 25 to correct the necessary fuel injection timing. Further, the combustion control means 24 compares the generated torque with the target torque in a state where the correction of the fuel injection timing is commanded. If the generated torque is different from the target torque, the fuel injection is performed so that the generated torque matches the target torque. The execution unit 25 is instructed to correct the required fuel injection amount.

Here, the heat generation centroid reference value G _0, conditions the heat generated center of gravity G of the aforementioned is calculated, i.e., the torque conditions, the value of the angular acceleration change, other values of the engine speed, under various operating conditions , The position of the center of heat generation determined to be appropriate without causing misfire or the like. Information of these heat-release center of gravity reference value G ₀ is the experiment using the master engine or the like of the same type, can be obtained in advance (for example, refer to FIG. 9 below). The same applies to the target torque.

Combustion control means 24, the heat generation centroid G calculated by the heat generation centroid calculating unit 23 is controlled so as to approach the heat generating centroid reference value G _0. In this embodiment, the combustion control in the cylinder by the combustion control means 24 is controlled by adjusting the fuel injection timing.

Specifically, when the heat generating center of gravity G is in the late than the heat generating centroid reference value G ₀ is the heat generation center of gravity G as close to the heat generating centroid reference value G _0, current fuel injection timing More advanced. Conversely, if the heat generated center of gravity G is in the early than the heat generating centroid reference value G ₀ is the heat generation center of gravity G as close to the heat generating centroid reference value G _0, than the current fuel injection timing Retard. Normally, the fuel injection amount is proportional to the fuel injection duration.

  The control of the combustion state in the cylinder by the combustion control means 24 can be performed separately for each identified cylinder, or a group of cylinders including the identified cylinder and proceeding in the same process as the cylinder. It is possible to perform the same control on the group all at once.

The correction of the fuel injection by this method, carried out respectively for all of the cylinders of the engine, close to the heat generation center of gravity G of the combustion of all the cylinders to heat generation centroid reference value G _0. Preferably, to match the heat generation center of gravity G of the combustion of all the cylinders to heat generation centroid reference value G _0. Thereby, the variation in the generated torque between the cylinders of the engine can be effectively reduced.

  The operation of this engine control device and its control method will be described based on the flowchart of FIG.

Step S1 shown in FIG. 6, on the basis of a predetermined angle elapsed time T _4, T _5, T ₆ is a time through the predetermined rotation angle (30 degrees), pass the predetermined rotation angle (30 degrees) In this process, the angular velocities ω ₄ , ω ₅ , ω ₆ are calculated and the angular accelerations α ₄₅ , α ₅₆ calculated based on the angular velocities ω ₄ , ω ₅ , ω ₆ are calculated.

In step S2, based on the angular accelerations α ₄₅ and α ₅₆ calculated in step S1, a change in angular acceleration, that is, a process of calculating a difference Δα = α ₅₆ −α ₄₅ between the two angular accelerations α ₅₆ and α ₄₅ is performed. It is.

Step S3 is a process of estimating the heat generation center of gravity G based on the angular acceleration change Δα = α ₅₆ −α ₄₅ calculated in step S2 and the torque condition and engine speed condition. Step S4 is likewise torque conditions, based on the condition of the engine speed, a step for estimating the heat generation centroid reference value G _0.

Step S5, the steps S3, S4 heat generation center of gravity G which is calculated by, on the basis of the heat generation centroid reference value G _0, a step for calculating a correction amount of the fuel injection timing. Step S6 is a process of commanding the correction. Note that, in step S6, closer to the heat generating center of gravity G to the heat generating centroid reference value G _0, or in a state of being matched, if the generated torque and the target torque of each cylinder are different, or torque are used between the cylinders When there is a variation or the like, it is also possible to perform control to increase or decrease the fuel injection amount for a specific cylinder as necessary.

  FIG. 7 is a graph showing the relationship between the in-cylinder pressure of the cylinder and the crank angle in the upper stage, and the relationship between the heat generation rate and the crank angle in the lower stage.

  In the upper diagram, the amount of exhaust recirculation gas contained in the air-fuel mixture introduced into the cylinder increases in the order of a chain line, a broken line, and a solid line. The fuel injection timing is constant. As the amount of exhaust gas in the exhaust gas increases, the peak height of the in-cylinder pressure after top dead center tends to gradually decrease. Further, the peak position tends to be gradually delayed. Further, it is considered that when the amount of the exhaust recirculation gas is increased, it eventually leads to misfire.

  In the middle diagram, the amount of exhaust recirculation gas contained in the air-fuel mixture introduced into the cylinder similarly increases in the order of a chain line, a broken line, and a solid line. As the exhaust gas flow increases, the peak of the heat generation rate (instantaneous value) per unit angle after top dead center tends to gradually decrease. Further, the peak position tends to be gradually delayed. Further, as the exhaust gas flow increases, the heat generation rate (instantaneous value) tends to move to the retarded side as a whole, and it can be understood that the position of the heat generation center of gravity G is delayed.

  FIG. 8 is a graph showing the relationship between the time required for the crankshaft to rotate 30 degrees and the crank angle in the upper stage, and the relationship between the rotational angular acceleration of the crankshaft and the crank angle in the lower stage.

In the upper diagram, the amount of exhaust recirculation gas contained in the air-fuel mixture introduced into the cylinder similarly increases in the order of a chain line, a broken line, and a solid line. Along with the increase in the amount of exhaust recirculation gas, the decrease in the predetermined angle elapsed times T ₃ and T ₄ immediately before the top dead center (region 3) and in the vicinity of the top dead center (region 4) is remarkable. Conversely, the predetermined angle elapsed times T ₅ and T ₆ slightly increase after the top dead center (regions 5 and 6).

In the lower diagram, the change in the amount of exhaust recirculation gas for each chain line, broken line, and solid line is the same as described in the above example. As the exhaust gas flow increases, the angular acceleration α ₃₄ between the region 3 immediately before the top dead center and the region 4 near the top dead center slightly increases, and conversely, between the region 4 and the region 5 after the top dead center. The angular acceleration α ₄₅ in FIG. 6 decreases, and similarly, the angular acceleration α ₅₆ between the region 5 and the region 6 decreases.

Therefore, the difference Δα = α ₅₆ −α ₄₅ between the angular accelerations α ₅₆ and α ₄₅ tends to become smaller before and after the top dead center as the exhaust gas flow increases. Further, the decrease in angular velocity and the decrease in angular acceleration after the top dead center causes the combustion progress rate to be slow, and it is considered that the heat generation center of gravity G has moved to the retard side.

  FIG. 9 is a graph showing the relationship between the change in the rotational angular acceleration α of the crankshaft C and the heat generation center of gravity G.

Based on the difference Δα = α ₅₆ −α ₄₅ between the angular accelerations α ₅₆ and α _{45 on} the vertical axis, the heat generation gravity center G of that cycle in the cylinder is estimated, and the heat generation gravity center G is the heat generation gravity center reference value. When the timing is later than G ₀ , as shown by the arrow on the right side of the figure, the fuel injection timing is advanced from the current time so that the heat generation gravity center G approaches the heat generation gravity center reference value G _0. I do.

Conversely, if the heat generated center of gravity G is in the early than the heat generating centroid reference value G _0, as indicated by the arrow on the left side of the figure, so as to bring the heat generation center of gravity G to the heat generating centroid reference value G ₀ In addition, control is performed to retard the fuel injection timing from the current state.

  At that time, the required retard amount and advance amount of the fuel injection timing can be calculated by the combustion control means 24 based on a map diagram and the like held by the electronic control unit 20.

  FIGS. 10A to 10C are graphs showing the relationship between the torque generated by the engine E and the heat generating center of gravity, the noise and the heat generating center of gravity G, and the rotational angular acceleration change of the crankshaft C and the heat generating center of gravity G, respectively. is there. FIGS. 10D to 10F are graphs showing the relationship between the torque generated by the engine E and the heat generating gravity center G, the noise and the heat generating gravity center G, and the rotation angular acceleration change of the crankshaft C and the heat generating gravity center G, respectively. It is.

  As indicated by the arrow in FIG. 10A, when the exhaust gas flow rate is increased and the excess air ratio is gradually decreased from 1.37 to 1.31, 1.29, the heat generation center of gravity G is delayed. Move to the corner side. At this time, torque also decreases.

  However, if the fuel injection timing is gradually advanced from the crank angle after top dead center of 6.5 deg to 7.5 deg, 8.5 deg, 9.5 deg, 11.5 deg while the excess air ratio is 1.29. It can be seen that the heat generation center of gravity G is also moved to the advance side. At this time, the torque also increases and recovers to the level before increasing the amount of exhaust reflux gas.

At this time, as shown in FIG. 10 (b), the noise level from the engine decreases with the movement of the heat generation gravity center G toward the retard side, and increases with the movement of the heat generation gravity center G toward the advance side. Yes.
Further, as shown in FIG. 10C, the change in the angular acceleration of the crankshaft C increases as the heat generation center of gravity G moves toward the retard side, and decreases as the heat generation center of gravity G moves toward the advance side. ing.

  Further, as shown by an arrow in FIG. 10 (d), when the supercharging pressure is gradually decreased from 108 kPa to 103 kPa and 101 kPa, the heat generation gravity center G decreases toward the retarded side as the air amount (oxygen amount) decreases. Move. At this time, torque also decreases.

  However, if the fuel injection timing is gradually advanced from the crank angle after top dead center of 6.5 deg to 7.5 deg, 8.5 deg, 9.5 deg, 11.5 deg with the supercharging pressure of 101 kPa, It can be seen that the generated center of gravity G has also moved to the advance side. At this time, the torque also increases and recovers to the level before reducing the supercharging pressure.

At this time, as shown in FIG. 10 (e), the noise level from the engine decreases with the movement of the heat generation center of gravity G toward the retard side, and increases with the movement of the heat generation center of gravity G toward the advance side. Yes.
As shown in FIG. 10 (f), the change in the angular acceleration of the crankshaft C increases with the movement of the heat generation center of gravity G toward the retard side, and decreases with the movement of the heat generation center of gravity G toward the advance side. ing.

In the above embodiments, the heat generation center of gravity G of each cylinder, by approximating the heat generation centroid reference value G ₀ as a target value of the proper operation, closer to the heat generating center of gravity G of the respective cylinders, or match and a control but the control is not set thermogenesis centroid reference value G ₀ is also possible.

  For example, it is conceivable to control the heat generation gravity center G of each cylinder to be close to or coincide with the average value thereof, that is, the average value of the heat generation gravity centers G of all the cylinders. In addition, it is conceivable to control the heat generation gravity center G of each cylinder so as to be close to or coincide with the most forward (advance side) value of the heat generation gravity centers G. Conversely, it is also conceivable that the heat generation center of gravity G of each cylinder is brought close to or coincides with the most rearward (retard side) value of the heat generation center of gravity G.

  In the above-described embodiment, the fuel generation gravity center G of each cylinder is calculated based on the rotational angular velocity ω and the rotation angular acceleration α of the crankshaft C. However, the heat generation gravity center G is calculated by the heat generation gravity center calculation means 23. Is not limited to the above method by the angular velocity detection means 21 and the angular acceleration calculation means 22.

  For example, the heat generation center of gravity calculation means 23 calculates the amount of generated heat and the heat generation center of gravity G of each cylinder by calculation using information acquired from a combustion pressure sensor (in-cylinder pressure sensor) 34 provided in the angular cylinder. Can do.

  Specifically, the amount of generated heat is calculated using the in-cylinder pressure detected by the combustion pressure sensor 34, the in-cylinder volume ratio when the in-cylinder pressure is detected, and the like. The in-cylinder volume can be calculated using information on the crank angle of the crankshaft C when the in-cylinder pressure is detected. The amount of generated heat can be expressed by the amount of heat (heat generation rate) per unit time (unit crank angle). By integrating the heat generation rate, an integrated value of the amount of generated heat can be calculated.

Based on the in-cylinder pressure P detected by the combustion pressure sensor 34, the calculation formula for the generated heat quantity Q in one cycle of the cylinder is, for example,
(Formula 3) Q = ∫ ₀ ^4π (dQ / dθ)

Can be adopted.

  The heat generation center of gravity G is an integrated value of the combustion energy (heat) generated from the start of combustion, assuming that the generated energy (heat) from the start of combustion of the air-fuel mixture in one cycle of one cylinder is 100. Since the time has reached half 50, the position of the crank angle θ at which the integral value (integrated value) of the heat generation amount reaches 50% of the total heat generation amount of one cycle of one cylinder is determined as the heat generation center of gravity. G.

As described above, according to the present invention, in order to detect the heat generation gravity centers G of combustion in a plurality of cylinders of the engine and bring the heat generation gravity centers G close to each other, the fuel injection timing is advanced or Since the correction for retarding is performed, it is possible to effectively reduce the variation in the torque generated between the cylinders of the engine regardless of the cause of the delay. Further, the heat generation center of gravity G so close to the heat generating centroid reference value G _0, the combustion state of each cylinder can be expected an effect that approached all optimum.

  In each of the above embodiments, a diesel engine that is a compression self-ignition engine has been described as an example. However, the present invention is not limited to this embodiment, and the present invention is also applicable to, for example, a two-cycle gasoline engine and a four-cycle gasoline engine. it can. The present invention can also be applied to reciprocating engines used in various transportation equipment other than automobiles and industrial machines.

In the above embodiment, as the heat generation timing calculation means 23, the heat generation gravity center calculation means 23 for calculating the heat generation gravity center G in the cylinder based on the change in angular acceleration calculated by the angular acceleration calculation means 22 is adopted. Control was performed based on the heat generation center of gravity G calculated by the heat generation center of gravity calculation means 23. However, as a base for the control calculated by the heat generation timing calculation means 23, other than the heat generation center of gravity G is adopted. Also good.
For example, based on the change in angular acceleration calculated by the angular acceleration calculating means 22, the heat generation amount in the cylinder is a predetermined range ratio of 30% or 40% with respect to the total heat generation amount of one cycle. The predetermined time may be calculated by the heat generation time calculation means 23.
At this time, the combustion control means 24 controls the combustion in the cylinder by comparing the predetermined time calculated by the heat generation time calculation means 23 with a predetermined heat generation time reference value.
If the integrated value of the heat generation amount in the cylinder of the cycle is 30% with respect to the total heat generation amount of one cycle, the heat generation time reference value also corresponds to the predetermined time of 30%. If the integrated value of the heat generation amount in the cylinder of the cycle is 40% of the total heat generation amount of one cycle, the heat generation time reference value also corresponds to the predetermined time of 40%. The reference value to be used.

  In the case of a gasoline engine, the configuration of the engine is provided with a spark plug for igniting the fuel in the combustion chamber at the upper part of the cylinder shown in FIG. The ignition timing of the spark plug is controlled by the control means 26 of the electronic control unit 20.

In the case of a gasoline engine as well, for example, based on the difference Δα = α ₅₆ −α ₄₅ between the angular accelerations α ₅₆ and α ₄₅ of the crankshaft C, heat generation for that cycle in that cylinder is performed, for example. The center of gravity G is estimated. When the heat generated center of gravity G is in the late than the heat generating centroid reference value G ₀ is the heat generation center of gravity G as close to the heat generating centroid reference value G _0, from the current fuel injection timing and the ignition timing, etc. Control to advance the angle.

Conversely, if the heat generated center of gravity G is in the early than the heat generating centroid reference value G ₀ is the heat generation center of gravity G as close to the heat generating centroid reference value G _0, the fuel injection timing and the ignition timing, etc. Control is performed to retard the angle from the current level.

Necessary fuel injection timing and retard amount and advance amount of the ignition timing can be calculated by the combustion control means 24 based on a map diagram held by the electronic control unit 20. Electronic control unit 20, the heat generated centroid reference value G ₀ and heat generated timing reference value, is the same point that holds calculated data related to the target torque.

1, 11 Intake passage 2 Exhaust passage 3 High-pressure exhaust recirculation passage 4 High-pressure exhaust recirculation valve 5 High-pressure throttle valve 6 Intake cooling device (intercooler)
7 Turbine 8 Exhaust gas purifier 12 Silencer 13 Low pressure exhaust gas recirculation passage 14 Low pressure exhaust gas recirculation valve 15 Low pressure throttle valve 20 Electronic control unit 21 Angular velocity detection means 22 Angular acceleration calculation means 23 Heat generation center of gravity calculation means (heat generation timing calculation means)
24 Combustion control means 25 Fuel injection execution means 26 Control means 30 Crank angle sensor 33 Cylinder discrimination sensor 34 Combustion pressure sensor

Claims (9)

Heat generation timing calculation means for detecting each predetermined timing at which the heat generation amount of combustion in a plurality of cylinders of the engine is a predetermined range ratio to the total heat generation amount of one cycle;
Combustion control means for comparing the predetermined timings of the respective cylinders calculated by the heat generation timing calculating means and correcting fuel injection for bringing the predetermined timings closer to each other;
The fuel injection correction is an engine control device that advances or retards fuel injection timing for each cylinder. The predetermined time is a center of heat generation,
The engine control device according to claim 1, wherein the heat generation time calculation means is heat generation gravity center calculation means.   The engine control device according to claim 2, wherein the combustion control unit corrects fuel injection so that the heat generation center of gravity of each cylinder approaches a predetermined heat generation center of gravity reference value.   The combustion control means compares the generated torque of each cylinder with the target torque with the fuel injection timing corrected, and if the generated torque is different from the target torque, the fuel is controlled so that the generated torque matches the target torque. The engine control device according to claim 2 or 3, wherein the injection amount is corrected.   The engine control device according to any one of claims 2 to 4, wherein the heat generation center of gravity calculation means calculates a heat generation center of gravity in a cylinder based on a numerical value of a combustion pressure sensor provided in each cylinder. Angular velocity detection means for detecting the angular velocity of the rotating shaft driven in accordance with the output of the engine;
Angular acceleration calculation means for calculating angular acceleration based on the angular velocity detected by the angular velocity detection means,
The engine control device according to any one of claims 2 to 5, wherein the heat generation center of gravity calculation unit calculates a heat generation center of gravity in a cylinder based on a change in angular acceleration calculated by the angular acceleration calculation unit. .   The change of the angular acceleration is calculated based on two reference angular accelerations obtained along the time series, and the value of the angular acceleration preceding the time series among the two angular acceleration values is the initial stage of the expansion stroke. The engine control device according to claim 6, wherein the engine control device is detected in a range of a crank angle straddling the top dead center.   The angular acceleration value preceded by the time series is the angular velocity detected in the crank angle range straddling the top dead center in the early stage of the expansion stroke, and the crank angle after the crank angle range straddling the top dead center. 8. The engine control device according to claim 7, wherein the engine control device is calculated based on an angular velocity detected in a range.   The engine control device according to any one of claims 6 to 8, wherein the heat generation center of gravity is obtained based on a difference between two angular acceleration values obtained along a time series and a generated torque of the engine.

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