JP3551697B2 - Control unit for diesel engine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for controlling an exhaust gas recirculation amount and a fuel injection amount so that a diesel engine has a predetermined excess air ratio.
[0002]
[Prior art]
Various measures have been taken to improve the composition of exhaust gas emitted from diesel engines.Smoke and particulates are controlled by electronically controlling the fuel injection amount and injection timing to target values with high precision according to the operating conditions. By reducing a part of the exhaust gas into the intake air, the combustion temperature and pressure can be reduced, and the emission amount of NOx can be reduced.
[0003]
Also, there is a possibility that the exhaust characteristics are always kept good by appropriately controlling the excess air ratio of the diesel engine, that is, the ratio of fresh air and fuel supplied to the engine to the stoichiometric air-fuel ratio.
[0004]
According to Japanese Patent Application Laid-Open No. 61-176647, an excess air ratio sensor is provided in the exhaust system, and the exhaust gas recirculation amount is feedback-controlled so that the target excess air ratio set according to the operating state matches the actually measured excess air ratio. Further, it is disclosed that when the exhaust gas recirculation is stopped, the fuel injection amount is feedback-controlled.
[0005]
[Problems to be solved by the invention]
However, when the excess air ratio sensor is installed in the exhaust system as described above, the deterioration of the sensor is severe due to the influence of soot in the exhaust gas, and the excess air ratio is measured stably and accurately in consideration of the initial variation of the sensor. It was difficult to control the excess air ratio, and there was a limit in improving the exhaust gas composition.
[0006]
Even when controlling the excess air ratio, since the control of the fuel injection amount and the exhaust gas recirculation amount are not linked, it is necessary to achieve both good power performance and exhaust characteristics, including during transient operation of the engine. Was difficult.
[0007]
The present invention has been proposed to solve such a problem.
[0008]
In the present invention, by maintaining the target excess air ratio according to the operating state and controlling the exhaust gas recirculation amount and the fuel injection amount to be the target excess air ratio, it is possible to always maintain good operability and exhaust characteristics. With the goal.
[0009]
[Means for Solving the Problems]
According to a first aspect of the present invention, there are provided a rotational speed means for detecting a rotational speed of an engine, a load detecting means for detecting a load on an engine, a fuel injection amount detecting means for detecting a fuel injection amount to be supplied to the engine, Intake air amount measuring means for measuring the amount, intake air temperature measuring means for measuring the intake air temperature, an exhaust gas recirculation passage for recirculating a part of the exhaust gas into the intake air, and an exhaust gas recirculation amount recirculated to the exhaust gas recirculation passage. In a diesel engine provided with an exhaust gas recirculation control valve for controlling and an opening degree detecting means for detecting an opening degree of the exhaust gas recirculation control valve, a pressure of an intake system is calculated based on the intake air amount and the intake air temperature. Intake system pressure calculating means, exhaust system pressure calculating means for calculating the exhaust system pressure based on the intake air amount, the intake air temperature and the fuel injection amount, and a differential pressure between the intake system pressure and the exhaust system pressure; exhaust Exhaust gas recirculation amount calculating means for calculating an exhaust gas recirculation amount from the flow control valve opening degree, and excess air ratio calculating means for calculating an actual air excess ratio based on the intake air amount, the fuel injection amount, and the exhaust gas recirculation amount. A target excess air ratio setting means for setting a target excess air ratio according to an engine speed and a load; and controlling an opening degree of the exhaust gas recirculation control valve such that the target excess air ratio and the actual excess air ratio match. Control meansWhen the actual excess air ratio is lower than the target excess air ratio, the actual fuel injection amount is limited so as not to be larger than the fuel injection amount calculated from the target excess air ratio, the intake air amount, and the exhaust gas recirculation amount. Means for limiting the fuel injection amount, and wherein the means for limiting the fuel injection amount cancels the limitation in steady-state operation except for gentle acceleration and acceleration operation.
[0010]
According to a second aspect of the present invention, there is provided a rotational speed detecting means for detecting a rotational speed of the engine, a load detecting means for detecting a load on the engine, a fuel injection amount detecting means for detecting a fuel injection amount supplied to the engine, and an intake air for the engine. Intake air amount measuring means for measuring the amount, intake air temperature measuring means for measuring the intake air temperature, an exhaust gas recirculation passage for recirculating a part of the exhaust gas into the intake air, and an exhaust gas recirculation amount recirculated to the exhaust gas recirculation passage. An exhaust recirculation control valve for controlling, in a diesel engine, a target excess air ratio setting means for setting a target excess air ratio according to the engine speed and the load, and the intake air amount and the fuel injection amount. Means for calculating a target exhaust gas recirculation amount required to obtain a target excess air ratio; intake system pressure calculating means for calculating an intake system pressure based on the intake air amount and the intake air temperature; Exhaust system pressure calculating means for calculating an exhaust system pressure based on the air volume, intake air temperature, and fuel injection amount; and the exhaust gas recirculation control based on a differential pressure between the intake system pressure and the exhaust system pressure and a target exhaust gas recirculation amount. Means for calculating the target valve opening of the valve, means for controlling the opening of the exhaust gas recirculation control valve to match this target valve opening,Means for detecting the opening degree of the exhaust gas recirculation control valve; exhaust gas recirculation amount calculating means for calculating the exhaust gas recirculation amount from the differential pressure between the intake system pressure and the exhaust system pressure and the exhaust gas recirculation control valve opening degree; An excess air ratio calculating means for calculating an actual excess air ratio based on the amount, the fuel injection amount, and the exhaust gas recirculation amount; comparing the actual excess air ratio thus obtained with the target excess air ratio; Means for limiting the actual fuel injection amount to be not larger than the fuel injection amount calculated from the target excess air ratio, the intake air amount, and the exhaust gas recirculation amount when the actual excess air ratio is lower than the excess air ratio; Wherein the means for restricting the fuel injection amount cancels the restriction in steady-state operation and acceleration operation except slow acceleration.
[0015]
[Action and Effect of the Invention]
In the first aspect, the excess air ratio can be calculated based on the intake air amount at that time, the fuel injection amount, and the exhaust gas recirculation amount. Of these, the exhaust gas recirculation amount can be obtained by calculation if the differential pressure between the exhaust system pressure and the intake system pressure and the opening degree of the exhaust gas recirculation control valve are known. Each pressure of the exhaust system and the intake system can be thermodynamically and hydrodynamically calculated based on the intake air amount, the intake air temperature, the fuel injection amount, and the like.
[0016]
For this reason, it is possible to calculate the actual excess air ratio every moment based on these calculated values.
[0017]
On the other hand, the target excess air ratio at which the particulates in the exhaust gas can be suppressed to a predetermined value or less depends on the nature of the engine and its operating conditions.
[0018]
Therefore, by controlling the exhaust gas recirculation amount such that the actual excess air ratio matches the target excess air ratio, the particulate matter in the exhaust gas is appropriately suppressed, and the operating performance of the engine and the NOx emission amount are reduced. Both can be maintained in a well-balanced manner as required.
[0019]
In addition, in this case, a sensor for measuring the excess air ratio is not required, and the excess air ratio can be accurately calculated every moment even in a transient operation state, so that stable high-performance controllability over a long period is guaranteed. Is done.
[0020]
In the second aspect, the target exhaust gas recirculation amount can be calculated from the target excess air ratio based on the intake air amount and the fuel injection amount at that time. Further, if the differential pressure between the upstream and downstream of the exhaust gas recirculation control valve, that is, the differential pressure between the exhaust system and the intake system is known, the valve opening of the exhaust gas recirculation control valve required to obtain the exhaust gas recirculation amount can be calculated.
[0021]
Therefore, by controlling the opening degree of the exhaust gas recirculation control valve so as to have the calculated valve opening degree, NOx can be reduced without deteriorating the driving performance and the particulates in the exhaust gas.
[0022]
In this case, since the control target value of the exhaust gas recirculation control valve is also determined based on the physical model, it is necessary to adjust the control constant when using the classical PID control method during normal feedback control. Therefore, practical use can be relatively easily realized only by examining the design specifications of the exhaust gas recirculation control valve.
[0023]
In the first or second invention,When the actual excess air ratio becomes lower than the target excess air ratio, the fuel injection amount is limited to prevent the excess air ratio from lowering and prevent the particulates from deteriorating.
[0024]
In this case, the fuel injection amount is limited only at the time of moderate acceleration, which often occurs in general driving in urban areas.by doing,The effect of the rebound on the driving performance can be reduced while avoiding deterioration of the exhaust gas composition. It should be noted that stable and good drivability can be maintained by releasing the restriction at the time of steady state or acceleration other than gentle acceleration.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings.
[0026]
First, FIG. 1 shows a fuel injection system for a diesel engine.
[0027]
In FIG. 1, a feed pump 6 for pre-pressurizing fuel is attached to an input shaft 6a of a fuel injection pump 1 which is driven to rotate in synchronization with engine rotation, and further coaxially rotates with the input shaft 6a. At the same time, a plunger 2 connected so as to reciprocate in the axial direction is arranged.
[0028]
The feed pump 6 sends out the pressurized fuel to the pump chamber 7, and the excess fuel is returned to a fuel tank (not shown) to keep the pressure in the pump chamber 7 constant.
[0029]
A face cam 2a having cam lobes corresponding to the number of cylinders is coaxially provided on the plunger 2, and the plunger 2 reciprocates in the axial direction each time the face cam 2a rides on the roller 8a. For example, in the case of a six-cylinder engine, when the input shaft 6a makes one rotation, the face cam 2a rides on the roller 8a six times during this time, and the plunger 2 reciprocates six times. Each time the plunger 2 reciprocates, the fuel is sucked into the plunger chamber 2b and pressurized. A return spring 2k pushes back the plunger 2 against the face cam 2a.
[0030]
In the extension stroke of the plunger 2, the fuel from the pump chamber 7 is sucked into the plunger chamber 2b through the fuel stop valve 10 and the slit 2j provided in the plunger 2.
[0031]
On the other hand, in order to feed the pressurized fuel in the plunger chamber 2b to the fuel injection nozzle in the compression stroke of the plunger 2, a communication passage 2c communicating with the plunger chamber 2b is formed along the axis of the plunger 2. The communication passage 2c has a high-pressure passage 2d that branches in the radial direction on the way, and a discharge passage 2e that also penetrates in the radial direction at the end.
[0032]
Ports 2g of a number corresponding to the number of engine cylinders are equally arranged on the inner periphery of the cylinder 2f around the plunger 2 so as to be selectively connected to the high-pressure passage 2d according to the rotational position of the plunger 2. A delivery valve 2h (only one is shown) is connected to each of the ports 2g, and fuel is pressure-fed from the delivery valve 2h to a fuel injection nozzle (not shown).
[0033]
The plunger 2 reciprocates six times each time it rotates, and pressurizes the inhaled fuel each time. The pressurized fuel is pushed into the high-pressure passage 2d from the communication passage 2c, and at this time, the port 2g communicates depending on the rotation position of the plunger 2. Pressurized fuel is supplied to the fuel injection nozzle via a corresponding delivery valve 2h.
[0034]
On the other hand, a control sleeve 3 is slidably fitted on the outer periphery of the plunger 2 and normally covers and closes the discharge passage 2e. However, due to the movement of the plunger 2 in the compression direction, the discharge passage 2e is eventually formed. release. As a result, the pressure in the plunger chamber 2b is released, and the pressure feed of the fuel from the delivery valve 2h to the fuel injection nozzle 11 ends.
[0035]
Therefore, the amount of fuel sent to the fuel injection nozzle changes depending on the position of the control sleeve 3. If the release passage 2e is released early when the plunger 2 moves in the compression direction, the fuel injection amount is small, and conversely, When the release time of the passage 2e is delayed, the fuel injection amount increases.
[0036]
In order to control the fuel injection amount, a rotary solenoid 4 for freely changing the position of the control sleeve 3 is provided, and a fuel injection signal from a fuel injection amount control unit 18 is supplied to the rotary solenoid 4, and this is supplied to the rotary solenoid 4. The position of the control sleeve 3 is changed accordingly. The position of the control sleeve 3 is detected by the position sensor 5 and is fed back to the control unit 18.
[0037]
Next, the position of the roller 8a on which the face cam 2a rides is controlled by the timer piston 8 in the circumferential direction of the face cam 2a. The illustrated timer piston 8 is rotated by 90 degrees from the actual position for convenience of explanation. A low-pressure chamber 8b and a high-pressure chamber 8c are provided on both sides of the timer piston 8, and the pressure in the high-pressure chamber 8c is adjusted by controlling the amount of a part of the high-pressure fuel released to the low-pressure chamber 8b by the control valve 9. Thus, the position of the timer piston 8 changes.
[0038]
When the position of the timer piston 8 changes and the position of the roller 8a advances in the direction of rotation of the face cam 2a, the position at which the face cam 2a rides on the roller 8a is relatively delayed, and the time when the pressurization of the fuel by the plunger 2 starts, that is, If the fuel injection timing is delayed, and conversely, if the position of the roller 8a is delayed in the direction opposite to the rotation of the face cam 2a, the pressure start timing by the plunger 2 is advanced, and the fuel injection timing is advanced.
[0039]
The signal from the control unit 18 controls the operation of the control valve 9 in accordance with the operation state, adjusts the position of the timer piston 8, and controls the advance and retard of the fuel injection timing.
[0040]
The control unit 18 has a nozzle lift sensor 12 for detecting the valve opening timing of the fuel injection nozzle 11, a fuel temperature sensor 15 for detecting the temperature of the fuel supplied to the fuel injection pump 1, and a sensor for detecting the engine coolant temperature. From the cooling water temperature sensor 13, the accelerator opening sensor 16 for detecting the accelerator opening, the rotation speed sensor 14 for detecting the pump rotation speed, and the like, and based on these, the fuel injection amount, the injection The timing control signal is calculated and output.
[0041]
FIG. 2 shows an exhaust gas recirculation system, in which 51 is a diesel engine, 52 is an intake passage, 53 is an exhaust passage, and 54 is an exhaust gas recirculation passage for recirculating a part of exhaust gas in the exhaust passage 53 to the intake passage 52. It is.
[0042]
An air flow meter 55 for measuring the amount of intake air is provided in the intake passage 52, and an intake throttle valve 56 for reducing intake air in two stages is provided downstream thereof. The exhaust gas recirculation passage 54 is connected to the downstream side of the intake throttle valve 56, and an exhaust gas recirculation control valve (EGR valve) 57 for controlling the amount of exhaust gas recirculation is interposed in the exhaust gas recirculation passage 54. .
[0043]
Therefore, the recirculation amount of the exhaust gas flowing from the exhaust passage 53 to the intake passage 52 depends on the differential pressure between the suction negative pressure generated according to the opening degree of the intake throttle valve 56 and the exhaust pressure with the exhaust passage 53, and Is determined according to the opening degree of the EGR valve 57 at that time.
[0044]
The opening degree of the intake throttle valve 56 is controlled in two stages by a negative pressure actuator 56a, and a first negative pressure passage for introducing a negative pressure from a vacuum pump (not shown) to the negative pressure actuator 56a via a first solenoid valve 61. 62 is connected to a second negative pressure passage 64 for guiding a negative pressure through a second electromagnetic valve 63, and the opening degree of the intake throttle valve 56 is controlled by the negative pressure regulated by the electromagnetic valves 61 and 63. Is controlled in two stages, and the suction negative pressure generated downstream thereof is controlled.
[0045]
For example, when the first solenoid valve 61 stops introducing the negative pressure, introduces the atmospheric pressure, and the second solenoid valve 63 introduces the negative pressure, the negative pressure of the negative pressure actuator 56a is weak, and the intake throttle is reduced. The opening of the valve 56 is relatively large. On the other hand, when the first solenoid valve 61 is also introducing a negative pressure, the negative pressure is high and the opening of the intake throttle valve 56 is small. When both the first and second solenoid valves 61 and 63 are introducing atmospheric pressure, the intake throttle valve 56 is held at the fully open position by the return spring.
[0046]
The lift amount of the EGR valve 57 is changed by the rotation of the step motor 57a, and its opening is adjusted, and the amount of exhaust gas recirculation flowing into the intake air through the exhaust gas recirculation passage 54 increases or decreases according to the opening. Incidentally, 57b is a means for detecting the opening of the EGR valve 57.
[0047]
A controller 70 controls the operations of the first and second solenoid valves 61 and 63 and the step motor 57a to control the exhaust gas recirculation amount.
[0048]
FIG. 3 shows a block diagram of a system for controlling the exhaust gas recirculation amount according to the operation state.
[0049]
In this embodiment, while the target excess air ratio is set according to the operating state, the actual excess air ratio is calculated from the intake air amount, the fuel supply amount, and the exhaust gas recirculation amount. The exhaust gas recirculation amount is feedback-controlled so that the excess air ratio matches.
[0050]
The excess air ratio indicates the ratio of the air and fuel supplied to the engine to the stoichiometric air-fuel ratio. According to the experiment performed by the inventor, the target excess air ratio is determined by the characteristics of the engine. It was found that there was an approximately constant excess air value at which the particulates did not deteriorate.
[0051]
In FIG. 3, 101 is an engine speed measuring means, 102 is an intake air amount measuring means, 103 is an intake air temperature measuring means, and based on each of these measured values, 111 Predict pressure.
[0052]
Further, the exhaust system pressure predicting means 113 predicts the exhaust system pressure based on the measured values from the engine load measuring means 105, the fuel injection amount detecting means 106, the intake air amount measuring means 102, and the intake air temperature measuring means 103.
[0053]
Reference numeral 112 denotes an exhaust gas recirculation (EGR) amount predicting unit, which predicts an EGR amount from a detection value from the EGR valve opening degree detecting unit 104 and the above-described intake system pressure predicted value and exhaust system pressure predicted value. The exhaust gas recirculation amount is determined according to the differential pressure between the exhaust passage and the intake passage and the opening of the exhaust gas recirculation control valve. Therefore, the exhaust gas recirculation amount can be calculated from both the predicted value and the detected valve opening. .
[0054]
An excess air ratio calculation means 114 calculates an actual excess air ratio from the intake air amount, the EGR amount, and the fuel injection amount. The excess air ratio represents the ratio of fuel to intake air (fresh air) in relation to the stoichiometric air-fuel ratio, and is calculated by subtracting the EGR amount from the fresh air.
[0055]
On the other hand, reference numeral 116 denotes a target excess air ratio calculating means for calculating a target excess air ratio according to the operating state, that is, based on the engine speed and the load. The excess ratio is compared by the comparing unit 115, and the opening of the EGR valve is adjusted by the EGR valve control unit 117 so that the actual excess air ratio matches the target excess air ratio.
[0056]
In this case, when the excess air ratio is smaller than the target excess air ratio, the ratio of fresh air in the intake air is relatively low. Therefore, the opening of the EGR valve is reduced to limit the EGR amount, and conversely. When the excess air ratio is larger than the target excess air ratio, the opening of the EGR valve is increased to increase the EGR amount. In this way, control is performed so that the target excess air ratio is always maintained. Done.
[0057]
The details of these controls will be described in more detail with reference to the flowcharts in FIG.
[0058]
First, FIG. 4 shows a flow for predicting the pressure of the intake system, which is executed in synchronization with the engine rotation (Ref. Job).
[0059]
In step 1, the cylinder intake air amount Qac, the cylinder intake EGR amount Qec, the intake air temperature Ta, the EGR temperature Te, and the volume efficiency equivalent value Kin are read, respectively. This will be described in detail. In step 2, the pressure Pm of the intake system is calculated based on these measured values as follows.
[0060]
Pm = [(Qec × Ta + Qec × Te) × R × Kpm] / [Kin × Kvol] + Opm (1)
Here, R: gas constant, Kvol: 1 cylinder volume / intake system volume, Kpm. Opm: constant
The pressure Pm of the intake system is basically determined based on the amount of intake air, the amount of EGR, and each temperature, and the higher the temperature, the higher the pressure of the intake system.
[0061]
FIG. 5 is a flow for estimating the pressure of the exhaust system (Ref. Job).
[0062]
In step 1, the exhaust amount Qexh discharged from the cylinder, the EGR amount Qe (different from the cylinder intake EGR amount Qec), the exhaust temperature Texh, and the engine speed Ne are read. However, the calculation of each parameter will be described later in detail with another flow.
[0063]
In step 2, the exhaust pressure Pexh is calculated by the following equation.
[0064]
Pexh = (Qexh + Qe) × Texh × Ne × Kpexh + Opexh (2)
Where Ne: engine speed, Kpexh. Opexh: constant
The exhaust system pressure Pexh basically increases as the engine displacement increases and as the temperature increases.
[0065]
Next, a method of calculating each of the above parameters will be described with reference to FIGS. First, FIG. 6 is a flowchart for calculating the cylinder intake air amount Qec (Ref. Job).
[0066]
In step 1, the output voltage of the air flow meter AMF provided in the intake passage is read, and in step 2, the intake air amount is calculated from this output voltage by table conversion. In step 3, a load averaging process of the calculated intake air amount is performed to calculate Qas0.
[0067]
In step 4, the engine speed Ne is read, and in step 5, the intake air amount Qac0 per cylinder is calculated as Qac0 = Qas0 / Ne × KCON # from Qas0 and Ne and the constant KCON #.
[0068]
In step 6, the fresh air amount Qacn at the inlet of the intake collector is calculated by performing the above-described delay processing of Qas0 for n times. This takes into account the delay of the intake air from the air flow meter to the collector inlet.
[0069]
In step 7, the delay process of Qacn is performed using the volume ratio Kvol and the volume efficiency equivalent value Kin as in the following equation to obtain the cylinder intake fresh air amount Qac.
[0070]
Qac = Qac_n-1× (1-Kvol × Kin) + Qacn × Kvol × Kin (3)
FIG. 7 is a flowchart for calculating the cylinder intake EGR amount (Ref. Job).
[0071]
In step 1, the EGR amount Qe obtained as described later (see FIG. 15) is read, and in step 2, the engine speed Ne is read. In step 3, Qe load averaging processing is performed to obtain Qe0.
[0072]
In step 4, the intake EGR amount per cylinder Qecn is calculated from Qe0 and Ne and the constant KCON #. Further, in step 5, this Qecn delay processing is performed. This delay processing is calculated by the following equation by using the volume ratio Kvol and the volume efficiency equivalent value Kin.
[0073]
Qec = Qec_n-1× (1-Kvol × Kin) + Qecn × Kvol × Kin (4)
Next, FIG. 8 is a flow for calculating the temperature of the intake fresh air (10 msec. Job).
[0074]
In step 1, the intake pressure Pm_n-1And the intake pressure Pm_n-1In step 2, the pressure correction coefficient Ktmpi is calculated based on_n-1× Calculate as PA #. Here, PA # is a constant.
[0075]
Then, in step 3, based on the pressure correction coefficient Ktmpi, the intake air temperature Ta is calculated as Ta = TA × Ktmpi + TOFF #.
[0076]
The intake air temperature can be calculated based on a comparison between the intake pressure in the standard state and the intake pressure at that time, and the temperature increases as the comparison pressure increases.
[0077]
However, the intake air temperature may be measured by an intake air temperature sensor other than by calculation.
[0078]
FIG. 9 is a flowchart for calculating the temperature Te of EGR (recirculated exhaust gas) recirculated to the intake system (Ref. Job).
[0079]
In step 1, the exhaust gas temperature Texh is read, and in step 2, the EGR temperature Te is calculated as Te = Texh × KTLOS # using the constant KTLOS #.
[0080]
The EGR temperature corresponds to the exhaust gas temperature, and the higher the exhaust gas temperature, the higher the EGR temperature. The calculation of the exhaust gas temperature Texh will be described later.
[0081]
FIG. 10 is a flowchart for calculating the above-mentioned volume efficiency equivalent value Kin (Ref. Job).
[0082]
In step 1, the intake air amount Qac, the fuel injection amount Qsol, and the engine speed Ne are read (however, the fuel injection amount Qsol will be described later). In step 2, based on Qac and Ne, a basic volume efficiency value KinH1 is calculated from the map shown in FIG. Further, in step 3, a volume efficiency load correction value KinH2 is calculated from the map shown in FIG. 12 based on Ne and Qsol.
[0083]
Then, in step 4, a volume efficiency equivalent value Kin is calculated from these KinH1 and KinH2 as Kin = KinH1 × KinH2.
[0084]
FIG. 13 is a flowchart for calculating the exhaust gas temperature Texh (Ref. Job).
[0085]
First, in step 1, the fuel injection amount cycle delay processing value Qf0 is read, and in step 2, the intake air temperature cycle delay processing value Tn0 is read (both will be described later with reference to FIG. 17). Further, in step 3, the exhaust pressure Texh is read.
[0086]
In step 4, the exhaust temperature basic value Texhb is read from the table shown in FIG. 14 based on the fuel injection amount cycle delay processing value Qf0.
[0087]
Note that the exhaust gas basic value increases as the fuel injection amount increases.
[0088]
In step 5, the exhaust temperature intake temperature correction coefficient Ktexh1 is calculated from the intake temperature cycle delay processing value Tn0 described above. That is, Ktexh1 = (Ta0 / TA #)^KN#. Here, TA # and KN # are constants.
[0089]
Next, at step 6, the exhaust gas exhaust pressure correction coefficient Ktexh2 is calculated based on the exhaust pressure Pexh. That is, Ktexh2 = (Pexh / PA #)⁽#^{Ke-1) /}#^KeIs calculated as Here, PA # and #Ke are constants.
[0090]
The higher the intake air temperature, the higher the exhaust temperature, and the higher the exhaust pressure, the higher the exhaust temperature. Therefore, the above-described correction coefficients increase as the intake air temperature and the exhaust pressure increase, respectively.
[0091]
Then, in step 7, the exhaust gas temperature Texh is calculated by multiplying the exhaust gas basic value by each correction coefficient. That is, the exhaust gas temperature becomes Texh = Texhb × Ktexh1 × Ktexh2.
[0092]
FIG. 15 is a flowchart for calculating the EGR amount Qe (Ref. Job).
[0093]
In step 1, the intake pressure Pm, the exhaust pressure Pexh, and the actual lift amount Lifts of the EGR valve are read. Note that Lifts will be described later.
[0094]
In step 2, the opening area (EGR effective flow path area) Ave of the EGR valve is calculated from the table in FIG. 16 based on the lift amount Lifts.
[0095]
Then, in step 3, the EGR amount Qe is calculated from the intake pressure, the exhaust pressure, and the EGR valve opening area as follows.
[0096]
Qe = Ave × (Pexh-Pm)^1/2× KR # ... (5)
Here, KR # is a constant.
[0097]
The EGR amount increases as the differential pressure between the intake pressure and the exhaust pressure increases, and if the differential pressure is the same, increases as the EGR valve opening area increases.
[0098]
FIG. 17 is a flowchart for calculating the fuel injection amount Qsol (Ref. Job).
[0099]
In step 1, a control lever opening CL for controlling the engine speed Ne and the fuel injection amount is read, and in step 2, a map shown in FIG. 18 is searched based on these Ne and CL to obtain the basic fuel injection amount Mqdrv. Ask for. Note that Mqdrv increases as CL increases.
[0100]
In step 3, various corrections are made to the basic fuel injection amount based on the engine coolant temperature and the like to calculate the fuel injection amount Qsol. In step 4, the Qsol is limited based on the maximum value of the fuel injection amount based on a map as shown in FIG. 19 to obtain a final Qsol.
[0101]
The maximum upper limit value QsolMAX increases according to the supercharging pressure (intake pressure Pm). However, when the fuel injection amount is larger than the upper limit value, the upper limit value is limited to the maximum value.
[0102]
FIG. 20 is a flow of a cycle process of the intake air amount, the fuel injection amount, and the intake air temperature (10 msec. Job).
[0103]
In step 1, the intake air amount Qac, the fuel injection amount Qsol, and the cylinder intake air temperature Tn are read. The cylinder intake air temperature Tn is obtained as follows as an average temperature of a mixed gas of fresh air and EGR sucked into the cylinder.
[0104]
Tn = (Qac × Ta + Qec × Te) / (Qac + Qec) (6)
In step 2, cycle processing is performed on these Qac, Qsol, and Tn, and these are for correcting the reading timing of the air flow meter based on the phase difference.
[0105]
Qexh = Qac · Z^-(CYLN#^-1), Qf0 = Qsol · Z^-(CYLN#^-2), Tn0 = Tn · Z^-(CYLN#^-1)It becomes. Here, CYLN # is the number of cylinders.
[0106]
It should be noted that delay processing is performed by subtracting 1 from the number of cylinders for the intake air temperature and by subtracting 2 from the number of cylinders for the fuel injection amount.
[0107]
Next, referring to FIGS. 21 to 24, the excess air ratio is calculated based on the intake fresh air amount, the fuel injection amount, the EGR amount, and the like thus obtained, and the EGR ratio is set so as to match the target excess air ratio. A control operation for feedback-controlling the amount (EGR valve opening) will be described.
[0108]
FIG. 21 is a flowchart for calculating the target excess air ratio Mlamb (Ref. Job).
[0109]
In step 1, the engine speed Ne and the fuel injection amount Qsol are read, and in step 2, a map of the target excess air ratio as shown in FIG. 22 is searched based on these Ne and Qsol to calculate Mlamb.
[0110]
Note that the target excess air ratio Mlamb decreases as the engine speed and the fuel injection amount increase.
[0111]
FIG. 23 is a flowchart for calculating the actual excess air ratio Rlamb (Ref. Job).
[0112]
In step 1, the intake fresh air amount Qac, the EGR amount Qec, and the fuel injection amount Qf0 are read, and in step 2, the actual excess air ratio Rlamb is obtained by the following equation.
[0113]
Rlamb = (Qac-Qec) / Qf0 (6)
In this case, as described above, it is assumed that the stoichiometric air-fuel ratio to be compared is included in Rlamb.
[0114]
Next, FIG. 24 is a flowchart for controlling the opening degree of the EGR valve based on the target excess air ratio and the actual excess air ratio obtained as described above so that they match (Ref. Job).
[0115]
In step 1, the target excess air ratio Mlamb and the actual excess air ratio Rlamb are read, and in step 2, dlamb, which is the difference between the target value and the actually measured value, is determined as dlamb = Mlamb-Rlamb.
[0116]
In step 3, the lift amount of the target EGR valve is calculated as Mlift by performing PID processing according to the difference dlamb.
[0117]
Further, in step 4, a process of advancing the operation delay of the EGR valve for this Mlift is performed, and the command lift amount Liftt of the EGR valve is set. This advance processing is performed on the advance side in anticipation of the delay of the actual operation of the EGR valve.
[0118]
In this way, the opening degree (lift amount) of the EGR valve is corrected and controlled so that the target excess air ratio and the actual excess air ratio match, whereby the target excess air ratio is always obtained. To do.
[0119]
Next, the overall operation will be described.
[0120]
As shown in FIG. 25, when the particulate PM discharged from the engine falls within the allowable limit, the excess air ratio is substantially constant by the engine, and therefore, the excess air ratio is set to this constant value. If controlled, the exhaust composition can be maintained well.
[0121]
The excess air ratio is determined based on the amount of fresh air sucked into the engine, the amount of EGR recirculated to reduce NOx in exhaust gas, and the amount of fuel injection supplied to the engine, and is expressed as follows: You.
[0122]
Excess air ratio = (new intake air amount−EGR amount) / (theoretical air-fuel ratio × fuel injection amount)
Therefore, even with the same fuel supply amount, if the EGR amount changes, the excess air ratio fluctuates, and if the excess air ratio decreases, the amount of particulate emissions increases.
[0123]
The fuel injection amount is limited so that the maximum injection amount does not overload the engine. However, in order to achieve the specified driving performance, basically, the fuel injection amount is determined based on the accelerator opening (control lever opening) and the engine speed. , Required characteristics are determined.
[0124]
In order to maintain a good exhaust gas composition while ensuring the operation performance of the engine, it is important to accurately control the EGR amount so that the excess air ratio accurately keeps a target constant value.
[0125]
Therefore, in the present invention, the target excess air ratio is set according to the operating state, and the actual excess air ratio is calculated from the intake air amount, the fuel injection amount, and the EGR amount, and the target excess air ratio is measured. The EGR amount is feedback-controlled so that the excess air ratio matches.
[0126]
The measured values are used for the intake air amount and the fuel injection amount. The EGR amount is obtained by estimating each pressure of the intake system and the exhaust system, and is obtained by calculation from the EGR valve opening at that time, and from these, the actual excess air ratio is calculated. Is calculated.
[0127]
Therefore, the intake air amount and the intake air temperature are measured first, and the intake pressure is predicted according to the laws of thermodynamics and fluid dynamics. In this case, as shown in FIG. 4, the intake pressure is basically determined based on the amount of fresh air sucked into the cylinder, the amount of EGR, and each gas temperature at that time. If the air flow meter is a hot wire type, it can measure not the volume flow rate but the weight flow rate, so by comparing the measured value of the intake fresh air volume with the measured value of the standard condition, the EGR gas can be measured in a state that does not include the EGR gas. Can be converted to the intake pressure.
[0128]
Therefore, by taking the EGR amount and the EGR temperature into consideration, it is possible to calculate the intake pressure including the above as described above.
[0129]
By comparing the pressure of the intake system with the pressure in the standard state, it is possible to calculate the intake air temperature as a comparison with the intake air temperature in the standard state.
[0130]
On the other hand, the pressure of the exhaust system can be calculated from the exhaust amount from the cylinder, the EGR amount, the exhaust temperature, and the engine speed at that time.
[0131]
The exhaust temperature is obtained from the intake air temperature, the fuel injection amount, and the like. Therefore, the exhaust pressure can be predicted as described above from the measurement result of the intake air amount in the same manner as the intake pressure.
[0132]
The amount of EGR recirculated from the exhaust system to the intake system depends on the pressure difference between the exhaust system and the intake system and the opening area of the EGR valve. The actual EGR amount can be calculated from the opening area of the EGR valve converted from the detected value of the actual lift amount of the EGR valve.
[0133]
As a result, if the excess air ratio is calculated from the EGR amount, the intake fresh air amount, and the fuel injection amount obtained by the calculation, the instantaneous excess air ratio can be calculated in real time even if the operating state changes every moment. Can be calculated.
[0134]
On the other hand, as for the target excess air ratio, a value necessary to suppress the particulates in the exhaust gas within a predetermined range is set based on an engine load and a rotation speed from experimental values and the like. This is read out according to the operating conditions.
[0135]
Then, the opening degree of the EGR valve is feedback-controlled so that the excess air ratio calculated every moment coincides with the target excess air ratio, whereby the particulates in the exhaust gas can always be suppressed to a set value or less. It is.
[0136]
In this case, as compared with the conventional example in which a sensor for measuring the excess air ratio is provided in the exhaust system, it is not affected by the soot in the exhaust gas, and it is possible to control the excess excess air ratio stably and accurately over a long period of time. Further, since the EGR amount can be controlled in relation to the fuel injection amount, there is no problem that the driving performance is significantly reduced.
[0137]
Also, since the calculation of the EGR amount and the adjustment of the opening of the EGR valve are executed every moment, there is no need to correct for the control delay of the EGR amount even during a transient operation or the like. Is maintained.
[0138]
Next, a second embodiment will be described with reference to FIGS.
[0139]
In this embodiment, a target EGR amount is set from a target intake air amount and a fuel injection charge based on a target excess air ratio, and the intake system at that time is set so as to achieve the target EGR amount. The opening degree of the EGR valve is calculated from the differential pressure between the pressure and the exhaust system pressure, and the opening degree of the EGR valve is controlled. A physical model is applied to the control target value of the EGR valve, and a classical model is applied. The adaptation of the control constant by PID control becomes unnecessary.
[0140]
As shown in FIG. 26, the target excess air ratio is calculated by the target excess air ratio calculating means 116, and the intake air amount from the intake air amount measuring means 102 and the fuel injection amount from the fuel injection amount detecting means 106 at that time are calculated. Based on this, the target EGR amount calculation means 118 calculates a target value of the EGR amount necessary for achieving the target excess air ratio.
[0141]
Then, the EGR valve opening calculating means 119 opens the EGR valve for obtaining the target EGR amount from the intake system pressure from the intake system pressure predicting means 111 and the exhaust system pressure from the exhaust system pressure predicting means 113. Calculate the degree.
[0142]
Since the EGR amount can be calculated from the opening degree of the EGR valve and the pressure difference between the front and rear passages thereof, the opening degree of the EGR valve is obtained by giving the target EGR amount and the pressure difference before and after.
[0143]
The EGR valve control means 117 controls the EGR valve opening (lift amount) based on the EGR valve opening thus obtained.
[0144]
The point of this control will be described with reference to the flowcharts of FIGS.
[0145]
FIG. 27 is a flowchart for calculating the EGR amount required according to the operation state (Ref. Job).
[0146]
In step 1, the engine speed Ne, the target excess air ratio Mlamb, the cylinder intake fresh air amount Qac, and the fuel injection amount Qf0 are respectively read.
[0147]
In step 2, the target EGR amount Tqec0 is calculated as Tqec0 = Qac-Mlamb × Qf0.
[0148]
In this case, as described above, the excess air ratio is determined by comparison with the stoichiometric air-fuel ratio (A / F). However, since the stoichiometric air-fuel ratio is a constant value determined according to the type of fuel, this is set to Mlamb in advance. The A / F display is omitted by taking in and converting the data.
[0149]
Then, in step 3, advance processing corresponding to the volume of the intake system is performed, and Tqec is calculated as the processing value. In step 4, the required EGR amount (target EGR amount) Tqe is calculated as Tqe = Tqec × Ne / KVOL #.
[0150]
It should be noted that the target excess air ratio is determined according to the operating state, and the required EGR amount is such that the larger the fuel injection amount at that time, the smaller the required EGR amount.
[0151]
FIG. 28 is a flowchart for calculating the command lift amount Lift of the EGR valve (Ref. Job).
[0152]
First, in step 1, the intake system pressure Pm, the exhaust system pressure Pexh, and the required EGR amount Teq are read.
[0153]
Then, in step 2, based on these, the flow path area Tav of the EGR valve is calculated as follows.
[0154]
Tav = Teq / (Pexh-Pm × KR #)^1/2… (7)
Here, KR # is a correction coefficient.
[0155]
The EGR amount is calculated in relation to the passage area of the EGR valve and the passage pressures before and after the passage area, that is, the differential pressure between the exhaust system pressure and the intake system pressure.
[0156]
Then, in step 3, the target lift amount Mlift of the EGR valve is calculated from the EGR valve lift table as shown in FIG. 29 based on the EGR valve flow path area Tav thus obtained. In step 4, advance processing is performed on the target lift Mlift with respect to the operation delay of the EGR valve, and this is set as a commanded lift amount Liftt.
[0157]
When the target excess air ratio is set according to the operating state in this way, the target EGR amount can be calculated from the intake air amount and the fuel injection amount at this time, as described above.
[0158]
Since the EGR amount is obtained from the opening degree of the EGR valve and the pressure difference before and after the opening degree, the opening degree of the EGR valve necessary for controlling the target EGR amount is determined by the respective upstream and downstream pressures of the EGR valve, that is, the exhaust gas. Back calculation is performed from the system pressure Pexh and the intake system pressure Pm. After the EGR valve opening degree, that is, the lift amount is calculated in this way, the EGR valve is controlled so as to achieve the lift amount.
[0159]
In this case, since the actual differential pressure before and after the EGR valve is calculated, if the opening of the EGR valve is controlled to the target opening, the EGR amount can be accurately controlled to the target EGR amount. Become.
[0160]
Since the EGR amount is determined in relation to the fuel injection amount so as to have a target excess air ratio set in accordance with the operation state, the particulate matter in the exhaust gas is always set to a predetermined value without deteriorating drivability. Below the level.
[0161]
Since the opening degree of the EGR valve is controlled in this manner, it is necessary to adjust the control constant in the feedback control mode using the conventional classical method, that is, in the PID control. By applying the physical model also to the value, it can be adapted only by the design specifications of the EGR valve, and the adaptation to the actual engine can be easily performed.
[0162]
Next, the embodiment shown in FIGS. 30 and 31 will be described.
[0163]
That is, a target EGR amount is obtained based on the target excess air ratio, and control is performed so that the target EGR amount becomes equal to the target excess air ratio. When the rate is smaller than the rate, the amount of fuel is determined to be too large, and the maximum injection amount is limited.
[0164]
In FIG. 30, the maximum fuel injection amount calculating means 120 compares the target excess air rate calculated by the target excess air rate calculating means 116 with the actual excess air rate calculated by the actual excess air rate calculating means 114. When the excess air ratio is smaller (lower) than the target excess air ratio, the maximum fuel injection amount is calculated backward from the target excess air ratio, the EGR amount at that time, and the intake air amount. Then, the actual fuel injection amount at that time is compared with the maximum fuel injection amount. When the actual fuel injection amount is larger than the maximum fuel injection amount, the fuel injection amount is limited so that the excess air ratio does not become too small.
[0165]
Other configurations are the same as those in FIG. However, this embodiment can also be applied to the case of FIG.
[0166]
FIG. 31 is a flowchart for calculating the maximum injection amount Qful (Ref. Job).
[0167]
First, in step 1, the intake air amount Qac, the EGR amount Qec, the fuel injection amount Qsol, and the target excess air ratio Mlamb are read.
[0168]
In step 2, the maximum fuel injection amount Qful is calculated from the definition of the excess air ratio as follows.
[0169]
Qful = Kq × (Qac−Qec) / Mlamb (8)
Here, Kq is a correction coefficient of 1.0 or more.
[0170]
The maximum fuel injection amount Qful is obtained by multiplying the fuel injection amount obtained from the target excess air ratio, the EGR amount, and the intake air amount by a correction coefficient, and relates to the supercharging pressure obtained from FIGS. Is different from the fuel injection amount Qsol for which the maximum value is regulated.
[0171]
Then, in step 3, the Qful thus obtained is compared with the actual fuel injection amount Qsol at that time. If the fuel injection amount Qsol is larger than the maximum fuel injection amount Qful, the fuel injection amount Qsol = The maximum value of the injection amount is limited as Qful.
[0172]
Otherwise, in step 4, the fuel injection amount Qsol is used, and the aforementioned Qsol is directly used as the target injection amount.
[0173]
Here, when the fuel injection amount Qsol becomes larger than the maximum fuel injection amount Qful, it is when the actual excess air ratio is smaller than the target excess air ratio. Therefore, in this case, instead of reducing the EGR amount, By limiting the fuel injection amount, a decrease in the excess air ratio is prevented.
[0174]
As described above, when the maximum value of the fuel injection amount is regulated from the relation of the excess air ratio, the decrease of the excess air ratio in the operation region where the fuel injection amount increases is prevented, and the occurrence of particulates and the like in the exhaust gas is equal to or less than the specified value. Can be suppressed. Also in this case, since the fuel injection amount is limited while maintaining the relationship with the EGR amount, the NOx emission amount does not deteriorate and the driving performance is not significantly impaired.
[0175]
A fourth embodiment shown in FIGS. 32 to 35 will be described.
[0176]
This is different from the third embodiment in that the transient operation state of the engine is determined and the fuel injection amount is limited only under predetermined conditions.
[0177]
As shown in FIG. 32, the transient determination means 122 for determining the transient operation state based on the engine speed, the load, and the fuel injection amount releases the restriction on the fuel injection amount during acceleration and steady operation, and restricts only during slow acceleration. are doing.
[0178]
During acceleration, the driver's intention is respected, and in order to avoid danger, the restriction on the fuel injection amount based on the excess air ratio is released to generate the maximum output of the engine. In order to avoid the occurrence of the periodic fluctuation (hunting) of the engine torque expected due to the repeated limitation of the injection amount, the limitation is also released.
[0179]
Specific control contents will be described below with reference to FIG.
[0180]
FIG. 33 is a flow for judging the transient operation state (Ref. Job).
[0181]
In step 1, the fuel injection amount Qsol, the accelerator opening TVO, and the engine speed Ne are read. In step 2, the fuel injection amount QsolZ several cycles before is set in advance.^-K, Accelerator opening TVOZ^-M, Engine speed NeZ^-NRead.
[0182]
Then, in step 3, a difference between the fuel injection amount, the accelerator opening, the engine speed, dQsol, dTVO, and dNe is calculated.
[0183]
In step 4, based on the obtained AND of dQsol, dTVO, and dNe, a transient determination flag is retrieved from a table as shown in FIG.
[0184]
In this case, when the added value of dQsol, dTVO, and dNe is larger than the first value v1, the slow acceleration flag is set to 0; when the added value is larger than the second value v2, the acceleration flag is set to 1; When the value is larger than the value v3 of 3, the rapid acceleration flag is set to 2.
[0185]
Next, FIG. 35 shows a flow for limiting and correcting the fuel injection amount (Ref. Job).
[0186]
First, in step 1, an intake air amount Qac, an EGR amount Qec, a fuel injection amount Qsol, and a target excess air ratio Mlamb are read. In step 2, the maximum value Qful of the fuel injection amount is calculated as Qful = (Qac-Qec) / Mlamb based on the target excess air ratio.
[0187]
In step 3, under the operating condition of the transient flag = 0, when the fuel injection amount Qsol is larger than the maximum value Qful, the fuel injection amount Qsol is set to Qsol = Qfull, and the maximum value of the fuel injection amount is set at the time of gentle acceleration. Restrict.
[0188]
In step 4, when the fuel injection amount Qsol is larger than the maximum value Qful under the operating condition of the transient flag = 1, the maximum value of the fuel injection amount is increased by setting Qsol = Qful × Kq (where Kq> 1.0). . This makes it possible to secure a high output of the engine during acceleration or the like.
[0189]
In step 5, under the operating condition of the transient flag = 2, when the fuel injection amount Qsol is larger than the maximum value Qful, the fuel injection amount is set to Qsol = Qfull × Ktr (where Ktr <1.0). In this case, the maximum value of the fuel injection amount is regulated, but during this rapid acceleration, it is assumed that normal operation such as engine idling is impossible and the injection amount is limited to protect the engine. I have.
[0190]
Next, in step 6, during normal operation other than the above, Qsol is output as it is as the fuel injection amount, and the maximum value is not limited.
[0191]
In this way, the limitation of the maximum value of the fuel injection amount is executed only at the time of gentle acceleration, and at other accelerations, the limitation of the maximum injection amount is released to secure a good feeling of acceleration. In addition, it is possible to prevent the engine torque from periodically fluctuating near the limit value.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention.
FIG. 2 is a configuration diagram of a fuel injection system.
FIG. 3 is a configuration diagram of an exhaust gas recirculation system.
FIG. 4 is a flowchart for calculating an intake system pressure.
FIG. 5 is a flowchart for calculating an exhaust system pressure.
FIG. 6 is a flowchart for calculating a cylinder intake fresh air amount.
FIG. 7 is a flowchart for calculating a cylinder intake EGR amount;
FIG. 8 is a flowchart for calculating the intake fresh air temperature.
FIG. 9 is a flowchart for calculating an EGR temperature.
FIG. 10 is a flowchart for calculating a volume efficiency equivalent value.
FIG. 11 is a characteristic diagram in which a basic value of volume efficiency is set.
FIG. 12 is a characteristic diagram in which a volume efficiency load correction value is set.
FIG. 13 is a flowchart for calculating an exhaust gas temperature.
FIG. 14 is a characteristic diagram in which basic characteristics of exhaust temperature are set.
FIG. 15 is a flowchart for calculating an EGR amount.
FIG. 16 is a characteristic diagram in which lift characteristics of an EGR valve are set.
FIG. 17 is a flowchart for calculating a fuel injection amount.
FIG. 18 is a characteristic diagram in which fuel injection amount characteristics are set.
FIG. 19 is a characteristic diagram in which a maximum injection amount characteristic is set.
FIG. 20 is a flowchart for calculating cycle processing.
FIG. 21 is a flowchart for calculating a target excess air ratio.
FIG. 22 is a characteristic diagram in which a target excess air ratio is set.
FIG. 23 is a flowchart for calculating an actual excess air ratio.
FIG. 24 is a flowchart for calculating an EGR valve lift amount.
FIG. 25 is an explanatory diagram showing a relationship between an excess air ratio and particulates in exhaust gas.
FIG. 26 is a block diagram of a second embodiment.
FIG. 27 is a flowchart for calculating a required EGR amount.
FIG. 28 is a flowchart for calculating the lift amount of the EGR valve.
FIG. 29 is a characteristic diagram in which lift characteristics of an EGR valve are set.
FIG. 30 is a block diagram of a third embodiment.
FIG. 31 is a flowchart for calculating a maximum injection amount.
FIG. 32 is a block diagram of a fourth embodiment.
FIG. 33 is a flowchart for determining a transient operation state.
FIG. 34 is an explanatory diagram of a transient operation flag.
FIG. 35 is a flow chart for limiting and correcting the fuel injection amount.
[Explanation of symbols]
101 Engine speed measurement means
102 Intake volume measurement means
103 Intake air temperature measuring means
104 EGR valve opening detecting means
105 Engine load measuring means
106 fuel injection amount detecting means
111 Intake system pressure prediction means
112 EGR amount prediction means
113 Exhaust system pressure prediction means
114 Actual excess air ratio calculation means
115 means of comparison
116 Target excess air ratio calculation means
117 EGR valve control means
118 Target EGR amount calculation means
120 Maximum fuel injection amount calculation means
122 Transient operation determination means

Claims (2)

Rotation speed means for detecting the rotation speed of the engine, load detection means for detecting the load of the engine, fuel injection amount detection means for detecting the fuel injection amount supplied to the engine, and intake air for measuring the intake air amount of the engine Intake air temperature measuring means for measuring the intake air temperature, an exhaust gas recirculation passage for recirculating a part of the exhaust gas into the intake air, and an exhaust gas recirculation control valve for controlling the amount of exhaust gas recirculated to the exhaust gas recirculation passage And, in a diesel engine comprising: an opening degree detecting means for detecting an opening degree of the exhaust gas recirculation control valve, an intake system pressure calculating means for calculating an intake system pressure based on the intake air amount and the intake air temperature. Exhaust system pressure calculating means for calculating the exhaust system pressure based on the intake air amount, the intake air temperature and the fuel injection amount; the differential pressure between the intake system pressure and the exhaust system pressure; and the exhaust gas recirculation control valve opening Exhaust gas recirculation amount calculating means for calculating an exhaust gas recirculation amount from the engine; an excess air ratio calculating device for calculating an actual excess air ratio based on the intake air amount, the fuel injection amount, and the exhaust gas recirculation amount; and control means for controlling the target excess air rate setting means for setting a target excess air ratio, the opening degree of the exhaust gas recirculation control valve so that the target excess air ratio and an actual excess air ratio matches in response to the target When the actual excess air ratio is lower than the excess air ratio, means for restricting the actual fuel injection amount from being larger than the fuel injection amount calculated from the target excess air ratio, the intake air amount, and the exhaust gas recirculation amount is provided. A control device for a diesel engine , wherein the means for limiting the amount of fuel injection cancels the limitation in a steady operation and an accelerated operation except for gentle acceleration . Rotation speed means for detecting the rotation speed of the engine, load detection means for detecting the load of the engine, fuel injection amount detection means for detecting the fuel injection amount supplied to the engine, and intake air for measuring the intake air amount of the engine Intake air temperature measuring means for measuring the intake air temperature, an exhaust gas recirculation passage for recirculating a part of the exhaust gas into the intake air, and an exhaust gas recirculation control valve for controlling the amount of exhaust gas recirculated to the exhaust gas recirculation passage And a target excess air ratio setting means for setting a target excess air ratio according to the engine speed and the load, and the target excess air ratio from the intake air amount and the fuel injection amount. Means for calculating a target exhaust gas recirculation amount necessary for the above, intake system pressure calculating means for calculating an intake system pressure based on the intake air amount and the intake air temperature, and the intake air amount and the intake air. Exhaust system pressure calculating means for calculating an exhaust system pressure based on the temperature and the fuel injection amount; and a target valve opening of the exhaust gas recirculation control valve based on a differential pressure between the intake system pressure and the exhaust system pressure and a target exhaust gas recirculation amount. Means for calculating the degree of opening, means for controlling the opening of the exhaust gas recirculation control valve so as to match this target valve opening, means for detecting the degree of opening of the exhaust gas recirculation control valve, intake system pressure and exhaust system An exhaust gas recirculation amount calculating means for calculating an exhaust gas recirculation amount from the pressure differential pressure and the exhaust gas recirculation control valve opening, and an actual excess air ratio based on the intake air amount, the fuel injection amount, and the exhaust gas recirculation amount. Comparing the actual excess air ratio thus obtained with the target excess air ratio. If the actual excess air ratio is lower than the target excess air ratio, the target excess air ratio and the intake Than the fuel injection amount calculated from the air amount and the exhaust gas recirculation amount And means for limiting to the fuel injection amount is not increased when, diesel means for limiting the fuel injection amount, in steady operation and acceleration operation, except for slow acceleration, and cancels the limit Engine control device.

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