JP2008196352A - Fuel injection device for multi-cylinder engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device for a multi-cylinder engine capable of more accurately performing injection amount control. <P>SOLUTION: The fuel injection device for the multi-cylinder engine 1 is provided with fuel injection valves 2 provided in the multi-cylinder engine 1; exhaust temperature detecting means 37 for detecting reference exhaust temperatures Tgb1 to Tgb4 from respective cylinders; a fuel injection control means A0 for injecting, from the fuel injection valves 2, target injection amount set in accordance with the operating state of the engine 1; an additional injection control means A02 for injecting additional injection amount qs1#1 to qs1#4 from the fuel injection valves 2 at predetermined injection timing ts delayed from injection timing of the target injection amount by the fuel injection control means A0 when the engine 1 is in a predetermined operating region; an additional injection amount correcting means A3 for correcting additional injection amount with respect to each cylinder so that detection values of the respective exhaust temperature detecting means 37 are within a predetermined range; and an injection control amount correcting means A4 for correcting injection control amount of each of the fuel injection valves 2 with respect to each cylinder at normal time based on correction results of the additional injection amount correcting means A3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel injection device for a multi-cylinder engine that can perform injection amount control of a fuel injection device with higher accuracy.

  In a direct injection engine, for example, a common rail diesel engine, fuel is increased in pressure by a fuel injection pump, the high pressure fuel is sent to a common rail, and the common rail guides the fuel injection valve provided in each cylinder. Each fuel injection valve includes an electromagnetic injection control valve (needle valve), and the injection control valve is controlled to open and close according to the fuel injection amount, the injection timing, and the number of injections.

  By the way, in order to further improve the exhaust gas performance of the engine or to further suppress the noise generated when the engine is driven, the injection amount is set so that the fuel amount injected from the fuel injection device becomes a target value as intended. It is important to increase accuracy. In particular, the precision of injection quantity is improved by more accurately controlling small injection quantities such as pre-injection and pilot injection, which are performed prior to main injection in normal injection, or after injection and post-injection after main injection. This is very important.

Here, taking the pilot injection as an example, the relationship between the injection amount and the generation of smoke and noise will be described.
FIG. 14 is a graph showing an example of the degree of smoke and noise generation with respect to the pilot injection amount. In this graph, the upper curve shows the noise generation characteristic with respect to the pilot injection amount, and the lower curve shows the smoke generation characteristic with respect to the pilot injection amount.
As shown in FIG. 14, when the pilot injection amount is large, both noise and smoke tend to be deteriorated. Conversely, when the amount is too small, noise tends to be extremely deteriorated. For this reason, in order to suppress smoke and noise, it is necessary to perform injection amount control of sub-injection such as pilot injection and post injection more accurately.

However, sub-injection such as pilot injection and post-injection has a smaller injection amount than main injection, is easily affected by individual differences in fuel injection valves (injectors), deterioration over time, etc., and there is variation in the injection amount for each cylinder. Prone to occur. For this reason, in order to suppress variations among cylinders, the fuel injection amount in normal injection is corrected.
For example, in the fuel injection device disclosed in Japanese Patent Application Laid-Open No. 2003-172185 (Patent Document 1), a numerical value (learning value) that can obtain an optimum temperature rising effect corresponding to each operating condition for the temperature of the exhaust purification catalyst. Therefore, the post-injection amount and the added fuel amount to the engine are feedback-controlled in accordance with detection signals from a plurality of exhaust temperature sensors.

JP 2003-172185 A

Incidentally, the fuel injection device of Patent Document 1 performs feedback control of the post-injection amount according to the temperature information of the exhaust temperature sensor in order to maintain the temperature of the exhaust purification catalyst at an optimum value. This is not to obtain the characteristic fluctuation amount, and it is difficult to control the target injection amount (control injection amount) for each cylinder sufficiently accurately.
The present invention has been made paying attention to the above-described problems, and an object of the present invention is to provide a fuel injection device for a multi-cylinder engine that can perform injection amount control more accurately.

In order to achieve the above-mentioned object, the invention according to claim 1 is a fuel injection valve provided in each cylinder of a multi-cylinder engine, and is installed corresponding to each cylinder, and detects an exhaust temperature from each cylinder. An exhaust temperature detecting means for performing injection, a fuel injection valve for injecting a target injection amount set in accordance with an operating state of the engine, and an injection control means when the engine is in a predetermined operating range. Additional injection control means for injecting an additional injection amount from each fuel injection valve at a predetermined injection timing retarded from the injection of the target injection amount, and detection values of the respective exhaust temperature detecting means are within a predetermined range. Based on the correction result of the additional injection amount correction means for correcting the additional injection amount for each cylinder so as to be within the range, and the correction result of the additional injection amount correction means, the injection control amount of each fuel injection valve at the normal time is determined for each cylinder. Osamu And injection control amount correction means for, characterized by comprising a.
Preferably, the detected value may be an exhaust temperature increase value with respect to an exhaust temperature before starting control for injecting the additional injection amount.

  According to a second aspect of the present invention, in the fuel injection device for a multi-cylinder engine according to the first aspect, the predetermined injection timing is a retarded timing at which the additional injection amount of fuel can almost completely burn in the cylinder. It is characterized by being.

  According to a third aspect of the present invention, in the fuel injection device for a multi-cylinder engine according to the first or second aspect, the predetermined operating range is an idle operating range.

  According to the first aspect of the present invention, when the engine is in a predetermined operating range, an additional injection amount is injected from each fuel injection valve, and a fluctuation amount of the exhaust temperature corresponding to the additional injection amount for each cylinder is detected (temperature increase amount). The additional injection amount for each cylinder is corrected so that the detected value falls within a predetermined range, and the injection control amount of the fuel injection valve for each cylinder is calculated based on the additional injection amount for each cylinder, which is the control result. Since the correction is made, the accuracy of the injection control amount can be made more accurate. Thereby, since the injection control amount can be stabilized, the generation of noise and smoke can be suppressed.

  According to the second aspect of the present invention, by delaying the additional injection amount of fuel so as not to affect the torque as much as possible at a timing at which the fuel of the additional injection amount can be almost completely combusted, the normal injection control amount is not affected. The correlation between the additional injection amount and the temperature rise amount can be accurately maintained.

  The invention according to claim 3 is additionally injected from the fuel injection valve by calculating an exhaust temperature detection value (a variation amount of the exhaust temperature) for each cylinder in an idle operation region where engine rotation is relatively stable. Variations in the injection amount due to disturbance can be suppressed, and the accuracy of the injection control amount can be made more accurate.

FIG. 1 shows a common rail diesel engine (hereinafter simply referred to as engine 1) provided with a fuel injection device A for a multi-cylinder engine as an embodiment of the present invention.
The engine 1 is a multi-cylinder direct injection type (in this embodiment, an example of four cylinders is described, and only one cylinder among the four cylinders is shown in FIG. 1), and a cylinder equipped with a fuel injection valve 2 for each cylinder. A combustion chamber 7 is formed by the head 3, the cylinder block 4, and the cavity 6 of the piston 5. The engine 1 is provided with an intake passage 8 and an exhaust passage 9 communicating with each cylinder. The intake passage 8 is provided with a compressor 12 (back side in FIG. 1) of the supercharger 11, and the exhaust passage 9 is provided with a turbine 13 of the supercharger 11. The supercharger 11 of this embodiment is a variable capacity turbo (VGT). The supercharger 11 uses the energy of the exhaust gas to rotate the turbine 13 and rotates the compressor 12 located on the same axis to boost the intake air. When the intake air is pressurized, high-density air is sent into the combustion chamber 7 and the fuel injected through the fuel injection valve 2 is mixed and burned, and the output of the engine 1 is increased.

  An air cleaner 14 is disposed upstream of the compressor 12 in the intake passage 8, and an air flow sensor 15 serving as intake air amount detection means is disposed in the casing of the air cleaner 14. An intercooler 16 and an intake throttle valve 20 are provided downstream of the compressor 12. The intercooler 16 performs intake air cooling, thereby improving the volumetric efficiency of the intake air of the engine 1 and thereby increasing the output. The intake throttle valve 20 is a normally open valve that adjusts the intake flow rate in a timely manner, and is used for generating negative pressure for increasing the EGR.

  On the other hand, as shown in FIGS. 1 and 6, the exhaust passage 9 extends from the exhaust port ep on the cylinder head 3 side, and the exhaust manifold 10, the turbine 13 of the supercharger 11, the exhaust pipe 36, and the exhaust gas purification device. 17 and a muffler (not shown) are sequentially communicated. The exhaust manifold 10 joins exhaust gas from the exhaust ports ep on the cylinder head 3 side through the exhaust gas branch paths es at the exhaust gas joining position et. A turbine 13 of the supercharger 11 is disposed downstream of the exhaust manifold 10.

  Here, each exhaust port ep on the cylinder head 3 side is provided with exhaust temperature sensors 37 as exhaust temperature detecting means for detecting exhaust gas temperatures Tg1 to Tg4 from the respective combustion chambers 7, and the temperature information thereof. Is output to a controller (engine ECU) 18 which is a control means described later. Each exhaust temperature sensor 37 may be provided in each passage of the exhaust manifold 10. An exhaust gas purification device 17 is disposed in the exhaust passage 9 downstream of the supercharger 11.

The fuel injection device A of the engine 1 includes a fuel supply device 19, a fuel injection valve 2 that injects fuel into the combustion chamber 7, and a controller (engine ECU) 18 that serves as these injection control means.
The fuel injection valve 2 attached to the cylinder head 3 has an exciting coil 21 in its main body, a needle valve 22 that opens when the exciting coil 21 is energized, and is opened and closed by the needle valve 22 and fed from the common rail 23. And a nozzle 24 capable of injecting the high-pressure fuel into the combustion chamber 7.
A glow plug 30 is attached to the cylinder head 3 in the vicinity of the fuel injection valve 2. This is connected to the controller 18 and is driven so as to improve combustion at the time of cold start and operation of the engine.

The fuel supply device 19 includes a common rail 23, a fuel injection pump 25 connected to the common rail 23, a fuel tank 26, and an injection pressure sensor 27 that outputs an injection pressure (common rail pressure) Pr.
The fuel stored in the common rail 23 is supplied via a high-pressure pipe 29 from a fuel injection pump 25 that is driven by the rotational force of the engine 1. A fuel injection pressure (common rail pressure) Pr signal stored in the common rail 23 is input to the controller 18 by an injection pressure sensor 27.

  The controller 18 selects one of a plurality of preset rail pressures Pr <b> 1 to Pr <b> 3 (see FIG. 5) set in advance according to the operating condition of the fuel injection pump 25, that is, the engine 1. Then, a control signal is directly transmitted from the controller 18 to the fuel pressure regulator 251 so that the injection pressure (common rail pressure) Pr detected by the injection pressure sensor 27 becomes a set rail pressure (for example, Pr1). Accordingly, the fuel pressure can be adjusted so that the injection pressure Pr in the common rail 23 becomes one of the predetermined rail pressures Pr (for example, Pr1) as shown in FIG. In FIG. 1, reference numeral 31 denotes a fuel return pipe that returns low-pressure oil from the fuel injection valve 2 to the fuel tank 26.

  Here, the controller 18 sets the injection pressure Pr based on the detection information from the above-described sensors, and further calculates an injection control amount (injection pulse width) that realizes the target injection amount. Then, the fuel pressure regulator 251 of the fuel injection pump 25 is controlled to control the injection pressure Pr to a set value. Further, each fuel injection valve 2 is supplied to the steady injection (pilot injection) mode M1 (by the steady injection control means A01) M1 shown in FIGS. 2A and 2B, and the additional injection shown in FIGS. 3A and 3B. It has a function of performing the injection operation in any of the modes (by the additional injection control means A02) M2.

  Specifically, the controller 18 drives the fuel injection valve 2 by selectively using two injection methods. That is, as shown in FIGS. 2A and 2B, in the steady (pilot) injection mode (by the steady injection control means A) M1, the target injection amount set according to the operating state of the engine is set to each fuel injection valve. To make a steady injection. In this case, the main injection (drive pulse width) Tm shown in FIGS. 2A and 2B and the pilot injection Tp preceding this are sequentially performed. This steady (pilot) injection mode (by a steady injection control means A01 described later) M1 is used during low, medium and high load operating ranges and during feedback control that maintains the idle speed N1.

Further, in the additional injection mode (by additional injection control means A02 described later) M2, as shown in FIGS. 3 (a) and 3 (b), the fuel injection valve 2 is operated in a steady injection (pilot) injection mode M1 (see FIG. 2). In the same manner as in the above, the injection drive (Tp + Tm) is performed, and at the predetermined delay time ts thereafter, the additional injection Ts (after injection) is added to increase the exhaust temperature.
This additional injection Ts (after-injection) is performed in a predetermined retardation state (retard amount δθ) set in advance in the expansion stroke, that is, a predetermined retardation timing ts that does not affect the idle speed N1 is a retardation amount. TDCA is performed at 50 ° (an example). As a result, a small quantity of injection qs that does not affect torque generation and that only increases the exhaust temperature is achieved.

Further, the controller 18 performs engine speed feedback control that maintains the idle speed N1, and stores exhaust temperature rise data by additional injection Ts (after injection) at that time. Here, the additional injection amount qs # 1 (corresponding to the injection period (pulse width)) of the additional injection Ts (after injection) is calculated for each cylinder (qs # 1 to qs # 4) as described later. Note that the engine speed feedback control is realized by increasing or decreasing the main injection Tm or the pilot injection Tp regardless of whether the injection mode is the steady injection mode M1 or the additional injection mode M2.
Such additional injection mode M2 is employed only when the engine 1 is operating in a predetermined operating range. The predetermined operating range here is set as a case where the engine load is substantially zero at a predetermined idle speed N1.

  As shown in FIG. 1, the controller 18 includes an input / output device (not shown), a storage device (ROM, RAM, DRAM, etc.) used for storing control programs and control maps, a central processing unit (CPU), a timer counter (not shown). Etc. On the input end side of the controller 18, an accelerator sensor 32 that detects an accelerator operation amount θa, an airflow sensor 15 that detects an intake air amount Qa, a crank angle sensor 21 that detects crank angle information Δθ, and an injection that detects an injection pressure Pr. Various sensors such as a pressure sensor 27, a water temperature sensor 28 for detecting the water temperature wt, a vehicle speed Vc for the vehicle speed sensor 33, an air conditioner switch 40, and an intake pressure sensor 60 for detecting the pressure Pb in the intake pipe are connected. The crank angle information Δθ here is used by the controller 18 to derive the engine speed Ne.

Various devices such as the fuel injection valve 2, the fuel injection pump 25, the glow plug 30, and the intake throttle valve 20 are connected to the output side.
The controller 18 performs a well-known engine control function and functions as a fuel injection device for a multi-cylinder engine that characterizes the present invention. That is, as shown in FIG. 4, the controller 18 as the fuel injection device A includes a steady injection control means A01, an additional injection control means A02, a target injection amount setting means A1, a steady exhaust temperature setting means A2, and an additional injection amount. Correction means A3 and injection control amount correction means A4 are provided. Note that the steady injection control means A01 and the additional injection control means A02 here exhibit a control function in association with each other, and these means constitute the fuel injection control means A0.
The target injection amount setting means A1 of the fuel injection device A takes in the accelerator opening θa, the engine rotational speed Ne, and the like, which are engine operation information, for each cylinder of the engine 1, and obtains the basic fuel injection amount INJb based on these.

Further, the basic fuel injection amount INJb calculated by the target injection amount setting means A1 is also transmitted to the injection control amount correction means A4. The injection control amount correction means A4 appropriately corrects the basic fuel injection amount INJb and transmits it to the fuel injection control means A0.
It should be noted that the basic fuel injection amount INJb is an idling condition in which the engine 1 is in a predetermined operating range that is set in advance, the vehicle is stopped (Vc = 0), the accelerator opening (θa = 0), and the condition of the idle speed N1 is satisfied. It is calculated during control for determining the operating range.
In the fuel injection control means A0 of the controller 18, either the steady injection control means A01 or the additional injection control means A02 selected according to the operation information at that time selectively performs injection control. That is, the fuel injection valve 2 of each cylinder is driven and controlled according to the injection data corresponding to one of the steady injection control means A01 and the additional injection control means A02.
The control as the target injection amount setting means A1 and the fuel injection control means A0 is sequentially performed at predetermined control cycles on the main routine (not shown) side of the controller 18.

  The steady exhaust temperature setting means A2 in the fuel injection device A determines that the engine is in an idle operation range (predetermined operation range) at the initial stage after the start of control, and is in a steady measurement (S1). The fuel injection valve 2 is driven in a pilot injection mode as a predetermined steady injection mode M1. In the pilot injection mode M1, feedback control is performed to maintain the idle speed N1 as a predetermined engine operating state. The exhaust gas temperature Tg of the cylinder at the time of steady measurement (S1) is taken in a plurality of times by the exhaust temperature sensor 37 as the exhaust temperature detection means, and when the exhaust temperature fluctuation is settled, the exhaust temperature is set as reference exhaust temperatures Tgb1 to Tgb4. Capture and store in a predetermined storage area of the controller 18. The reference exhaust temperatures Tgb1 to Tgb4 of the respective cylinders may be taken at the same time, for example, may be taken sequentially into the No. 1 cylinder to the No. 4 cylinder, or taken sequentially from the cylinder where the exhaust temperature fluctuation has converged. You may do it.

As described above, after obtaining the reference exhaust temperatures Tgb1 to Tgb4 as shown in FIGS. 7A to 10A by the steady exhaust temperature setting unit A2, the additional injection amount correcting unit A3 functions as follows. To do.
That is, the additional injection amount correcting means A3 replaces each cylinder with the steady pilot injection mode (reference numeral M1 in FIG. 2), and performs a small amount (1 to 5 mm ³ / st) of additional injection Ts (after injection) during the expansion stroke. Is switched to the additional injection mode (reference numeral M2 in FIG. 3). The additional injection amount qs1 at the time of this additional injection (S2) is adjusted to, for example, around 2 mm ³ / st.

Next, in this additional injection mode (reference M2), the additional injection amount correcting means A3 is the reference exhaust temperature at the time of steady measurement (S1) before injecting the fluctuation amount of the exhaust temperature by each exhaust temperature detecting means, that is, the additional injection amount. The exhaust temperature rise value with respect to Tgb1-Tgb4 is measured. In this case, the additional injection amount qs1 for each cylinder is corrected, as will be described later, so that the detected value (temperature rise amount) falls within a predetermined range.
That is, as shown in FIG. 7A, the reference exhaust temperature Tgb1 previously set in one cylinder is increased by a predetermined temperature increase amount ΔT1 (a value corresponding to the additional injection amount qs1), that is, the detection thereof. The additional injection amount qs1 of one cylinder is corrected to raise the temperature so that the value falls within the predetermined range.

  In this way, the additional injection amount correcting means A3 has the injection timing ts (see FIG. 3) fixed in the operation in the additional injection mode (symbol M2), and the drive pulse width Ts of the additional injection is increased or decreased, that is, the injection The amount (corresponding to the pulse width) qs1 is increased or decreased, and feedback control is performed so as to maintain the target exhaust temperature Tgs1 (= Tgb1 + ΔT1). As shown in FIG. 7 (a), the actual injection amount qs1 # 1 at the additional injection Ts, which is the control result at that time, is obtained in the operating range where the exhaust temperature rises and falls within the target exhaust temperature Tgs1, as shown in FIG. Stored in a predetermined storage area of the controller 18.

As described above, the additional injection Ts is performed at a fixed retard amount δθ, for example, the injection timing ts within the expansion stroke of the retard amount TDCA 50 °, so that the torque generation is not affected, and the additional injection amount qs1 However, this only affects the rise in the exhaust gas temperature of one cylinder.
In addition, since the fuel of the additional injection amount qs1 is almost completely combusted in the cylinder and discharged, the detected value ΔT1 (temperature increase amount) of the exhaust temperature detected by the exhaust temperature sensor 3 as the exhaust temperature detection means is the fuel. Since it corresponds to the actual additional injection amount from the injection valve 2, the correlation between the additional injection amount and the temperature rise amount can be accurately maintained without affecting the normal injection control amount.

Similarly, as shown in FIG. 8, the injection amount of the additional injection Ts required to maintain the target exhaust temperature Tgs2 that has been raised by the temperature increase amount ΔT2 (may be the same value as ΔT1) of one cylinder (for example, the No. 2 cylinder). As shown in FIGS. 9 and 10, learning is performed by correcting qs1 # 2, and in the No. 3 and 4 cylinders, the target exhaust temperature Tgs3 that is raised by the temperature increase amount ΔT3, 4 (here, the same value as ΔT1). , 4 are learned as control results of the actual injection amounts qs1 # 3 and qs1 # 4 of the additional injection Ts required to maintain the value 4, and stored in a predetermined storage area of the controller 18. The temperature increase amounts ΔT1 to ΔT4 of each cylinder may be learned at the same time, or may be learned in order from the No1 cylinder to the No4 cylinder, for example.
Thereafter, based on the additional injection amount qs1 # 1 to qs1 # 4 for each cylinder, which is the control result of the additional injection amount correcting unit A3, the injection control amount correcting unit A4 performs the injection control of each fuel injection valve 2 at the normal time. The amount (injection pulse width) is corrected for each cylinder.

Thereby, the injection amount error of each fuel injection valve 2 in which the combustion reaction result for each cylinder is reflected can be corrected. After this time, the injection control amount (injection pulse width) of each fuel injection valve 2 is always accurate. It can be done in
Next, each control process of the controller 18 of FIG. 1 will be described along the idle control routine of FIG. 11, the steady exhaust temperature setting routine of FIG. 12, and the additional injection amount correction routine of FIG. Here, in a main routine (not shown), one of the plurality of target injection pressures Pr1, Pr2, and Pr3, for example, the injection pressure Pr1 is set in advance. After that, the fuel pressure regulator 251 is driven and controlled so that the injection pressure Pr1 is maintained. These routines are executed at predetermined time intervals by the CPU in the controller 18.

  When the control process of the controller 18 shifts to the idle control routine, first, in step s1, the intake air amount sensor 15, the crank angle sensor 21, the injection pressure sensor 27, the water temperature sensor 28, the accelerator opening sensor 32, the vehicle speed sensor 33, and the air conditioner switch 40. Based on various signals from the exhaust temperature sensor 37 of each cylinder, the intake pressure sensor 60, etc., the intake air amount Qa, the engine speed Ne, the injection pressure Pr, the cooling water temperature wt, the accelerator opening degree θa, the vehicle speed Vc, the air conditioner signal Sa, Each operation information such as the exhaust gas temperatures Tg1 to Tg4 and the intake pressure Pb is read.

Subsequently, in step s2, it is determined whether or not the engine 1 is in an idle operation region that is a predetermined operation region that is set in advance. This determination is made based on the engine speed Ne being a predetermined idle speed N1, the accelerator opening θa being fully closed, the vehicle speed Vc being equal to or less than the stop determination value, and the like. If it is not in the idling operation range, the process proceeds to step s4, the process proceeds to the fuel injection amount control process during non-idle operation, and the process returns to the main routine (not shown). On the other hand, if it is in the idling speed range, the process proceeds to step s3.
In step s3, it is determined whether or not the coolant temperature wt read this time is higher than the warm-up determination value wt1, and if it is lower, it is determined that the warm-up is not yet performed, and the process returns to a main routine (not shown).

On the other hand, when the cooling water temperature wt exceeds the warm air determination value wt1 in step s3, it is determined that the engine is idling after warm air. Here, the process proceeds to step s5 and enters a feedback control (ISC) in which the engine speed Ne is corrected so as to maintain the target idle speed N1 assuming that it is in a predetermined idle operating range. The target idle speed N1 is set in advance to a value that can cope with engine load, for example, driving in the case of air conditioner driving.
Thereafter, when step s6 is reached, it is determined here whether or not the steady exhaust temperature sampling flag is on (FLG1 = 1), initially it is off, the steady measurement time S1 is determined, and the process proceeds to steps s7 and s8. After completion, the process directly proceeds to step s9.

In step s7, a steady exhaust temperature setting process is performed.
As shown in FIG. 12, in step a1 in the steady exhaust temperature setting process, it is determined that the engine has reached the idle operating range (predetermined operating range), and the fuel injection valves 2 of each cylinder are set in the pilot injection mode (FIG. 12). 2, feedback control is performed so as to maintain the idle speed N1. Then, the time point is regarded as the steady measurement time (S1), and the process proceeds to step a2.
Subsequently, in step a2, it is checked again whether the current operating range is in the idling operating range while maintaining the idling speed N1, and when leaving, it returns to the idle control routine, and returns to step a2 after the processing of step a1 again. If YES, the process proceeds to step a3.

In step a3, deviations ΔTgb1 to ΔTgb4 of all cylinders between the previous value and the current value of the reference exhaust temperatures Tgb1 to Tgb4 are obtained. Next, in step a4, the system waits for the deviations ΔTgb1 to ΔTgb4 of all the cylinders to converge to a low level that is equal to or less than the predetermined value h. Proceed to step s8.
In FIG. 12, the reference exhaust temperature is stored in order from the No. 1 cylinder. However, as described above, the reference exhaust temperatures Tgb1 to Tgb4 may be taken in at the same time, or the cylinders whose deviations have converged. You may make it take in sequentially.

In step s8 of the idle control routine, the steady exhaust temperature sampling flag is set to ON (FLG1 = 1), and the process proceeds to step s9.
In step s9, it is determined whether or not the additional injection amount correction flag is (FLG2 = 1) ON. The process proceeds to steps s10 and s11 at the beginning or before correction, and proceeds to step s12.

In step s10, an additional injection amount correction process is performed.
As shown in FIG. 13, in step b1 of the additional injection amount correction process, it is confirmed whether or not the current operation region is in the idle operation region while maintaining the idle rotation speed N1. Return to step b1 again, and proceed to step b2 with a Yes determination.
In step b2, it is determined that the engine has reached the idle operation range (predetermined operation range) at the time of additional injection (S2), and a small amount of additional injection Ts (after injection) is performed during the expansion stroke of the fuel injection valve 2 of each cylinder. ) Including additional injection modes (reference numeral M2 in FIG. 3), and feedback control is performed so as to maintain the same idle speed N1 as in the steady measurement (S1).

  In step b3, in the operation in the additional injection mode, the injection timing ts is fixed, the drive pulse width Ts of the additional injection is increased or decreased, that is, the injection amount (corresponding to the pulse width) qs1 is increased or decreased, and the target exhaust temperature Tgs1. Feedback control is performed so as to maintain (= Tgb1 + ΔT1). Next, in step b4, the exhaust gas temperature fluctuates as shown in FIG. 7A, and the operating region is within the convergence range of the target exhaust temperatures Tgs1 to Tgs4 (the first to fourth cylinders are processed in the same manner). It is determined whether or not. Specifically, it is determined whether or not the exhaust temperature is within a convergence range of the target exhaust temperature in each cylinder with respect to the target exhaust temperatures Tgs1 to Tgs4, that is, a range of Tgs1 ± α to Tgs4 ± α (α is 1 to 3 ° C. as an example). To do.

  When it is determined that the exhaust temperatures of all cylinders have converged to Tgs1 ± α to Tgs4 ± α, in step b5, for example, the actual additional injection Ts required for maintaining one cylinder at the target exhaust temperature Tgs1 (= Tgb1 + ΔT1). The injection amount qs1 # 1 is stored as a control result. Similarly, the actual injection amounts qs1 # 2 to qs1 # 4 of the second to fourth cylinders are stored in the predetermined storage area of the controller 18 as a control result, and the process proceeds to step s16 of the idle control routine. In addition, before the information on all the four cylinders is gathered, for example, when the vehicle is out of the idle operation range, the learning result is reflected based on the information about the cylinder obtained at that time.

Thereafter, the process proceeds to step s11 of the idle control routine, the additional injection amount correction flag is set to ON (FLG2 = 1), and the process proceeds to step s12.
In step s12, the injection control amount (injection pulse width) of the fuel injection valve 2 for each cylinder in the normal state is corrected based on the additional injection amounts qs1 # 1 to qs1 # 4 for each cylinder, which are learning results. End the control. Thereby, the injection amount error of each fuel injection valve 2 reflecting the combustion reaction result for each cylinder can be corrected. After this point, the injection control of each fuel injection valve 2 (for example, the drive time control of each fuel injection valve 2) ) Can always be performed with the accuracy kept appropriate.

Even if a state in which the fuel injection amount fluctuates due to a variation amount of the actual injection amount of each fuel injection valve 2 due to such control, for example, variation in solids of each fuel injection valve 2 or deterioration with time, etc., this It is possible to absorb the fluctuation of the injection amount and perform more accurate fuel injection control.
Note that the temperature increase amounts ΔT1 to ΔT4 of the cylinders described above are set such that the temperature increase amount is set small for a cylinder with relatively high heat dissipation, and the temperature increase amount is set large for a cylinder with relatively low heat dissipation. Thus, the injection amount error can be corrected more accurately, and more accurate fuel injection control can be realized.

  Further, in the present embodiment, the controller 18 has been described as selectively learning one of the plurality of set rail pressures Pr1 to Pr3 (see FIG. 5). First, the rail pressure Pr1 After learning for each cylinder, the learning for each cylinder can be performed sequentially for the rail pressures Pr2 and Pr3. Alternatively, after learning for each rail pressure Pr1 to Pr3 for a specific cylinder, it is also possible to sequentially learn for each rail pressure Pr1 to Pr3 for another cylinder.

1 is a schematic configuration diagram of an internal combustion engine including a fuel injection device for a multi-cylinder engine as one embodiment of the present invention. FIG. 2 is a characteristic explanatory diagram of a steady injection mode performed by the fuel injection device of FIG. 1. It is a characteristic explanatory view of the additional injection mode which performs the additional injection which the fuel-injection apparatus of FIG. 1 performs. It is a functional block diagram of the fuel-injection apparatus of FIG. FIG. 2 is a rail pressure characteristic diagram of the fuel injection device of FIG. 1. FIG. 2 is a schematic plan view of a cylinder head and an exhaust manifold portion of an engine provided with the fuel injection device of FIG. FIGS. 2A and 2B are explanatory diagrams of functions of the fuel injection device of FIG. 1, in which FIG. 1A is an explanatory diagram of exhaust temperature control characteristics in a first cylinder, and FIG. FIG. 2 is a function explanatory diagram of the fuel injection device of FIG. 1, (a) is an explanatory diagram of exhaust temperature control characteristics in a second cylinder, and (b) is an explanatory diagram of a small amount additional injection pattern. FIG. 2 is a function explanatory diagram of the fuel injection device of FIG. 1, (a) is an explanatory diagram of exhaust temperature control characteristics in a third cylinder, and (b) is an explanatory diagram of a small amount additional injection pattern. FIG. 2 is a function explanatory diagram of the fuel injection device of FIG. 1, (a) is an explanatory diagram of exhaust temperature control characteristics in a fourth cylinder, and (b) is an explanatory diagram of a small amount additional injection pattern. 3 is a flowchart of an idle operation control routine of the fuel injection device of FIG. 1. It is a flowchart of the steady exhaust temperature setting process routine of the fuel injection device of FIG. 3 is a flowchart of an additional injection amount correction process routine of the fuel injection device of FIG. 1. It is a noise with respect to the pilot injection quantity in a conventional fuel injection device, and a smoke characteristic diagram.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Fuel injection valve 18 Controller 19 Fuel supply apparatus 37 Waste temperature sensor (exhaust temperature detection means)
qs1 # 1 to qs1 # 4 Additional injection amount A Fuel injection device A0 Fuel injection control means A01 Steady injection control means A02 Additional injection control means A1 Target injection amount setting means A2 Steady exhaust temperature setting means A3 Additional injection amount correction means A4 Injection control Quantity correction means M1 steady injection mode (pilot injection mode)
M2 Additional injection mode Pr Injection pressure (common rail pressure)
S1 During steady measurement S2 During additional injection Tgb1 to Tgb4 Reference exhaust temperature Tgs1 to Tgs4 Target exhaust temperature ΔT1 to ΔT4 Temperature rise ΔTgb1 to ΔTgb4 Deviation Ts Additional injection (after injection)

Claims (3)

A fuel injection valve provided in each cylinder of the multi-cylinder engine;
Exhaust temperature detection means that is installed corresponding to each cylinder and detects the exhaust temperature from each cylinder;
Injection control means for injecting from the fuel injection valve a target injection amount set in accordance with the operating state of the engine;
Additional injection control means for injecting an additional injection amount from each fuel injection valve at a predetermined injection timing retarded from the injection of the target injection amount by the injection control means when the engine is in a predetermined operating range. When,
Additional injection amount correction means for correcting the additional injection amount for each cylinder so that the detection value of each exhaust temperature detection means falls within a predetermined range;
Injection control amount correction means for correcting the injection control amount of each fuel injection valve for each cylinder based on the correction result of the additional injection amount correction means;
A fuel injection device for a multi-cylinder engine. The fuel injection device for a multi-cylinder engine according to claim 1,
The fuel injection device for a multi-cylinder engine, wherein the predetermined injection timing is a retarded timing at which the additional injection amount of fuel can almost completely burn in the cylinder. The fuel injection device for a multi-cylinder engine according to claim 1 or 2,
The fuel injection device for a multi-cylinder engine, wherein the predetermined operating range is an idle operating range.

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