JP3493986B2 - Diesel engine cylinder intake gas temperature calculation device and EGR control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder intake gas temperature calculation device in a diesel engine equipped with an EGR device equipped with an EGR (exhaust gas recirculation) gas cooling device, and an EGR control device using the same.

[0002]

2. Description of the Related Art Due to the growing interest in environmental improvement in recent years,
Emission regulations for diesel engines are being tightened. In particular, if a large amount of EGR is applied to reduce NOx of a diesel engine, the ignition delay period until the fuel injected into the combustion chamber is ignited becomes longer, the combustion temperature decreases, and the combustion ratio in the latter half of the expansion stroke increases. And the combustion atmosphere becomes oxygen-deficient, so exhaust particulate matter (hereinafter PM; Pa
rticulate Matter) and other exhaust components (HC, C
O) tends to deteriorate.

Therefore, in order to improve this trade-off relationship, a new combustion concept has been proposed in recent years for the conventional direct injection diesel engine mainly composed of diffusion combustion. For example, Japanese Patent Application Laid-Open No. 8-86251 discloses that NOx and PM are simultaneously reduced by prolonging the ignition delay period of injected fuel and lowering the combustion temperature.

Further, if the temperature of the EGR gas is lowered, the charging efficiency in the intake stroke is improved (the operation can be performed under the condition of more oxygen), and the temperature at the end of the compression stroke in the combustion chamber is also lowered, so that NOx is reduced. It has been experimentally clarified that it is possible to reduce both PM and PM at the same time, and the necessity of providing an EGR gas cooling device for cooling EGR gas using engine cooling water as shown in JP-A-8-261072 is increasing. There is.

[0005]

As described above, the EGR gas cooling device is effective as an exhaust gas purifying means for a diesel engine, but when it is applied to an actual vehicle, it has the following problems. FIG. 44 shows the results of measuring various parameters when the vehicle was equipped with a diesel engine equipped with an EGR gas cooling device.

In the case of an actual vehicle, the amount of cooling water increases and decreases depending on the engine speed and load, and the EGR amount also increases and decreases. For this reason, the EGR gas cooling capacity of the EGR gas cooling device greatly changes depending on the operating state of the engine.
Therefore, the temperature of the gas sucked into the cylinder to be managed changes greatly depending on the operating state. Therefore, if the EGR gas cooling device described in JP-A-8-261072 is simply mounted on the vehicle, the exhaust gas reduction effect of the EGR gas cooling device obtained in the steady experiment cannot be obtained.

In addition, the EG on the outlet side of the EGR gas cooling device responds to changes in the cooling water circulation amount and exhaust temperature due to the rotational load.
The change in R gas temperature shows a slow response due to the influence of the thermal inertia of the cooling device. Therefore, for example, when the cooling water temperature is changed under the condition that the opening degree of the EGR valve is constant, the EGR rate changes with a slow response to the change of the cooling water temperature. Therefore,
For example, as disclosed in Japanese Patent Laid-Open No. 6-108925, a sensor is added to the outlet of the EGR gas cooling device so as to measure the EGR gas temperature, and the EGR amount is corrected according to the EGR gas temperature.

However, in the case of measuring the temperature of gas, even if a sensor having a considerably high response is used, the response time constant is on the order of ten and several seconds in consideration of compatibility between durability and responsiveness as an automobile sensor. However, it is difficult to accurately measure the EGR gas temperature of the vehicle. In addition, since the response and accuracy of the sensor deteriorate over time due to soot adhesion to the sensor, it is difficult to apply it to the vehicle considering the life cycle of the vehicle.

On the other hand, for example, as disclosed in Japanese Unexamined Patent Publication No. 5-263717, there is one that estimates the intake air temperature by measuring the operating state of the engine, the intake air amount, and the intake pipe internal pressure. With this configuration,
Compared to the case of actually measuring the gas temperature, there is a merit that there is no response delay due to the estimation by calculation, but the actual intake air temperature has a delay due to the delay of the sensor, actuator, and working gas, and The phase difference becomes a problem.

When a heat exchanger such as an EGR gas cooling device is provided, the intake air temperature prediction model shown in the embodiment does not have a heat exchange model and the intake pipe internal pressure is not lower than the atmospheric pressure. It is difficult to accurately measure the pressure in the intake pipe with the pressure sensor. Therefore, the detection accuracy of the actual EGR amount is insufficient and the intake air temperature cannot be accurately predicted, so that it is difficult to accurately calculate the temperature of the gas sucked into the cylinder.

The present invention has been made by paying attention to such a conventional problem, and in a diesel engine to which an EGR gas cooling device is applied, the EGR is performed even in a transient operation in which the operating condition changes momentarily. An object of the present invention is to provide a cylinder intake gas temperature calculation device that can accurately calculate the cylinder intake gas temperature so that the exhaust gas reduction effect of gas cooling can be enjoyed.

Further, there is provided an EGR control device for a diesel engine which can obtain a desired exhaust gas reduction effect by correcting and controlling EGR according to the cylinder intake gas temperature using this cylinder intake gas temperature calculation device. The purpose is to

[0013]

For this reason, the invention according to claim 1 is configured as follows (see FIG. 1). Intake fresh air amount detection means for detecting the intake fresh air amount to the engine,
Intake fresh air temperature detecting means for detecting intake fresh air temperature, intake system pressure detecting means for detecting intake system pressure, exhaust system pressure detecting means for detecting exhaust system pressure, and exhaust temperature detecting exhaust temperature And detection means.

Further, an EGR passage for returning a part of exhaust gas from the exhaust system to the intake system, an EGR valve provided in the middle of the EGR passage, and a target EGR based on engine operating conditions.
A target EGR amount setting means for setting the amount, and an EGR valve control means for controlling the EGR valve by setting a target opening degree of the EGR valve based on the target EGR amount and the differential pressure between the intake system pressure and the exhaust system pressure. Further, an EGR gas cooling device for cooling the EGR gas is provided.

Here, cylinder intake fresh air amount calculating means for calculating the cylinder intake fresh air amount by delaying the intake fresh air amount detected by the intake fresh air amount detecting means,
EGR valve opening detection means for detecting the opening degree of the EGR valve, EGR amount calculation means for calculating the EGR amount from the differential pressure between the intake system pressure and the exhaust system pressure, and the opening degree of the EGR valve, and the EGR amount delay Based on the cylinder intake EGR amount calculation means for performing processing to calculate the cylinder intake EGR amount, the EGR gas cooling device efficiency setting means for setting the efficiency of the EGR gas cooling device, and the exhaust temperature and the efficiency of the EGR gas cooling device. EGR gas temperature calculating means for calculating the EGR gas temperature on the outlet side of the EGR gas cooling device, and fresh intake air amount of cylinder, fresh intake air temperature, EGR amount of cylinder intake, and E on the outlet side of EGR gas cooling device
A cylinder intake gas temperature calculation means for calculating the cylinder intake gas temperature based on the GR gas temperature is provided to configure a cylinder intake gas temperature calculation device.

According to a second aspect of the present invention, the EGR gas cooling device cools the EGR gas with engine cooling water, and the EGR gas cooling water temperature detecting device detects the temperature of the cooling water passing through the EGR gas cooling device. Means for controlling the EGR gas temperature calculation means to control the exhaust gas temperature and the EGR
The EG on the outlet side of the EGR gas cooling device is based on the temperature of the cooling water passing through the gas cooling device and the efficiency of the EGR gas cooling device.
It is characterized in that the R gas temperature is calculated (see FIG. 1).

In the invention according to claim 3, instead of the intake system pressure detecting means, an intake system pressure predicting means for predicting the intake system pressure based on engine operating conditions is provided, and in place of the exhaust system pressure detecting means. An exhaust system pressure predicting means for predicting the exhaust system pressure based on engine operating conditions is provided. In the invention according to claim 4, an exhaust temperature predicting means for predicting the exhaust temperature based on the engine operating condition is provided in place of the exhaust temperature detecting means.

The invention according to claim 5 is characterized in that intake fresh air temperature correction means for correcting the intake fresh air temperature detected by the intake fresh air temperature detecting means by the intake system pressure is provided (FIG. 1). reference). In the invention according to claim 6, the above-mentioned cylinder intake gas temperature calculation device is used, and the target EGR amount for correcting the target EGR amount according to the cylinder intake gas temperature is used.
An EGR control device for a diesel engine is configured by providing a quantity correction means (see FIG. 1).

The invention according to claim 7 is characterized in that a water temperature adjusting device for adjusting the cooling water temperature of the EGR gas cooling device for cooling the EGR gas with the engine cooling water is provided according to the cylinder intake gas temperature. . The invention according to claim 8 is characterized in that a water amount adjusting device for adjusting the cooling water amount of the EGR gas cooling device for cooling the EGR gas with the engine cooling water is provided according to the cylinder intake gas temperature.

[0020]

According to the invention of claim 1, the cylinder intake fresh air amount, the intake fresh air temperature, the cylinder intake EGR amount, and E
The EGR gas temperature on the outlet side of the GR gas cooling device is appropriately calculated, and the cylinder intake gas temperature can be accurately predicted and calculated based on these, and the EGR can be appropriately corrected and controlled according to the cylinder intake gas temperature. The effect of becoming is obtained.

According to the second aspect of the present invention, when the EGR gas cooling device cools the EGR gas with the engine cooling water, the temperature of the cooling water passing through the EGR gas cooling device is detected and taken into consideration. By calculating the EGR gas temperature on the outlet side of the EGR gas cooling device, the cylinder intake gas temperature can be more accurately predicted and calculated. According to the third aspect of the present invention, it is possible to accurately grasp the intake system pressure and the exhaust system pressure based on the engine operating conditions.

According to the fourth aspect of the present invention, it is possible to accurately grasp the exhaust temperature by predicting the exhaust temperature based on the engine operating conditions. According to the fifth aspect of the present invention, by correcting the detected value of the fresh intake air temperature by the sensor with the intake system pressure, it is possible to accurately grasp the fluctuation of the fresh intake air temperature due to the fluctuation of the intake system pressure.

According to the sixth aspect of the present invention, by using the cylinder intake gas temperature calculation device described above and correcting the target EGR amount according to the cylinder intake gas temperature, for example, exhaust gas due to a delay in EGR gas cooling is exhausted. A desired exhaust gas reduction effect can be obtained, for example, deterioration can be suppressed to a minimum. According to the invention of claim 7, the capacity of the EGR gas cooling device is controlled by adjusting the cooling water temperature of the EGR gas cooling device in accordance with the cylinder intake gas temperature, and the EGR gas is controlled even during the transient operation. The exhaust reduction effect of cooling can be maximized.

According to the invention of claim 8, the capacity of the EGR gas cooling device is controlled by adjusting the amount of cooling water of the EGR gas cooling device according to the cylinder intake gas temperature, and even during transient operation. The exhaust reduction effect by EGR gas cooling can be maximized.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 2 is a system diagram showing the first embodiment of the present invention. In the diesel engine 1, the fuel is
The electronically controlled fuel injection pump 2 directly injects and supplies it into the combustion chamber 4 through the fuel injection nozzle 3.

Part of the exhaust gas is introduced into the intake system from the exhaust system by the EGR device. The EGR device includes an EGR passage 5, an EGR valve 6 that controls the EGR amount, and a collector 7.
(EGR gas introduction position) The intake throttle valve 8 on the upstream side is included. The EGR passage 5 is supplied with E by the engine cooling water.
An EGR gas cooling device 9 that cools the GR gas is provided.

Further, the swirl control valve 1 is provided downstream of the collector 7.
0 is provided so that swirl can be generated in the combustion chamber 4. Further, in this example, the turbocharger 11 and the intercooler 12 are attached to the intake system, and the exhaust purification catalyst 13 is attached to the exhaust system. Reference numeral 14 is an air flow meter as a fresh intake air amount detecting means for detecting the fresh intake air amount, 15 is an intake air temperature sensor as a fresh intake air temperature detecting means for detecting the fresh intake air temperature, and 16 is an engine cooling water temperature. A water temperature sensor 17 is an EGR gas cooling water temperature sensor as an EGR gas cooling water temperature detecting means for detecting the temperature of the cooling water passing through the EGR gas cooling device 9.

A specific example of the fuel injection device including the electronically controlled fuel injection pump 2 and the fuel injection nozzle 3 is shown in FIG. The electronically controlled fuel injection pump 2 includes a drive shaft 2
Feed pump 22 that rotates by 1 and pre-pressurizes fuel
The pump chamber 23 that stores the fuel pressurized by the feed pump 22 and that lubricates the inside of the pump, and the pump chamber 23 that is rotated by the drive shaft 21 and is reciprocated by the face cam 24 while rotating.
25 for inhaling and pressurizing and distributing the fuel, the delivery valve 26 provided for each cylinder and delivering the fuel distributed by the plunger 25 to the fuel injection nozzle 3 of each cylinder, and the plunger 25 for pressurizing the fuel. A control sleeve 27 that determines the end of injection by leaking the injected fuel into the pump chamber 23,
The rotary solenoid 28 for freely adjusting the fuel injection amount, the fuel cut valve 29 for stopping the engine by stopping the fuel intake of the plunger 25,
Equipped with.

The electronically controlled fuel injection pump 2 is connected to the face cam 24 as a fuel injection timing adjusting mechanism as shown in FIG. 4 in addition to FIG. 3 and moves its position to move the face cam. Timer piston 30 capable of adjusting the fuel injection timing by changing the phase of cam 24
And a timing control valve 31 for adjusting the fuel injection timing by adjusting the timer high pressure chamber pressure by leaking the high pressure fuel in the high pressure chamber that drives the timer piston 30 to the low pressure chamber side.

Further, as various sensors, rotation speed sensors 32 and 33 for detecting engine rotation speed or pump rotation speed are provided.
And an accelerator opening sensor 34 for detecting an accelerator opening (control lever opening) and a nozzle lift sensor 3 for detecting a valve opening timing (actual injection timing) of the fuel injection nozzle 3.
5 and a fuel temperature sensor 3 for detecting the fuel temperature in the pump chamber 23
7, an engine key switch 38 and the like are provided, and these signals are input to the control unit 39.

The air flow meter 1 shown in FIG.
Signals from the intake air temperature sensor 15, the water temperature sensor 16, and the EGR gas cooling water temperature sensor 17 are also input to the control unit 39. The fuel injection pump is not limited to the jerk type injection pump shown in the figure, and may be a common rail injection pump or a unit injector currently being developed by each company.

The control unit 39 performs predetermined arithmetic processing by a built-in microcomputer to drive and control the fuel injection amount control rotary solenoid 28, the fuel cut valve 29, and the fuel injection timing control timing control valve 31. In addition, the EGR valve 6 in FIG.
The swirl control valve 10 and the like are also drive-controlled. A specific example of the EGR device is shown in FIG.

The EGR valve 6 is provided in the EGR passage 5 and is driven by a step motor to adjust the EGR amount. Incidentally, such a step motor drive type EGR valve 6
Alternatively, a negative pressure drive type EGR valve or the like may be used. The intake throttle valve 8 is based on the negative pressure created by the vacuum pump.
The control negative pressure regulated by the on / off control of the two solenoid valves 41, 42 operates in stages to regulate the pressure in the collector 7.

Next, the control content will be described with reference to a flow chart. FIG. 6 is a flowchart of the intake system pressure (collector pressure; hereinafter referred to as intake pressure) Pm calculation. This flow corresponds to the intake system pressure predicting means and is executed in synchronization with the reference crank angle signal. It is also possible to use an intake pressure sensor as the intake system pressure detecting means instead of the predictive calculation.

At S1, the cylinder intake fresh air amount Qac, the cylinder intake EGR amount Qec, the intake fresh air temperature Ta, the EGR gas temperature Te, and the volumetric efficiency equivalent value Kin are read. The method of calculating each parameter will be described later. In S2, the intake pressure Pm is calculated by the following equation using the above parameters, and the process ends.

Pm = ((Qac × Ta + Qec × Te) × R
× Kpm) / (Kin × Kvol) + Opm where R is a gas constant, Kvol is a volume ratio (= 1 cylinder volume Vc / intake system volume Vm), and Kpm and Opm are constants. FIG. 7 is a flow chart of the exhaust system pressure (EGR gas outlet pressure; hereinafter referred to as exhaust pressure) Pexh calculation. This flow corresponds to the exhaust system pressure predicting means and is executed in synchronization with the reference crank angle signal. Instead of the predictive calculation, it is possible to use an exhaust pressure sensor as the exhaust system pressure detecting means.

In S1, the exhaust amount Qexh discharged from the cylinder, the exhaust temperature Texh, and the engine speed Ne are read. The method of calculating each parameter will be described later. S2
Then, using the above parameters, the exhaust pressure Pexh is calculated by the following equation, and the processing is ended. Pexh = (Qexh × Ne / Kcon) ² × Texh × Kpexh
+ Opexh Here, Kcon, Kpexh, and Opexh are constants.

FIG. 8 is a flow chart of the cylinder intake fresh air amount Qac calculation. This flow corresponds to the cylinder intake fresh air amount calculation means and is executed in synchronization with the reference crank angle signal. In S1, the output voltage of the air flow meter (AFM) is read, in S2, the intake fresh air amount is calculated by table conversion from the voltage, and in S3, a value Qas0 obtained by performing a weighted average process on the value is obtained.

At S4, the engine speed Ne is read,
In S5, the intake fresh air amount Qac0 per cylinder is obtained from Qas0, Ne and the constant KCON # by the following equation. In Qac0 = Qas0 / Ne.times.KCON # S6, the delay processing for Qas0 is performed n times, and the intake fresh air amount Qacn at the collector inlet is calculated.

In step S7, the cylinder intake fresh air amount Qac is obtained by performing a delay process shown in the following equation from Qacn using the volume ratio Kvol and the volume efficiency equivalent value Kin, and the process is ended. Qac = Qacn-1 x (1-Kvol x Kin) + Qacn x Kvo
l × Kin FIG. 9 is a flowchart of the cylinder intake EGR amount Qec calculation. This flow corresponds to the cylinder intake EGR amount calculation means and is executed in synchronization with the reference crank angle signal.

At S1 and S2, the EGR amount Qe and the engine speed Ne are read. The method of calculating the EGR amount Qe will be described later. In S3, the intake EGR amount Qecn per cylinder is obtained from the EGR amount Qe, the engine speed Ne and the constant KCON # by the following equation. In Qecn = Qe / Ne × KCON # S4, using the volume ratio Kvol and the volumetric efficiency equivalent value Kin, a delay process as shown in the following equation is performed from Qecn to obtain the cylinder intake EGR amount Qec, and the process is ended. .

Qec = Qecn-1 × (1-Kvol × Kin) +
Qecn × Kvol × Kin FIG. 10 is a flowchart of the intake fresh air temperature Ta calculation. This flow corresponds to the intake fresh air temperature detecting means and the intake fresh air temperature correcting means, and is executed every predetermined time (for example, 10 ms). In S1, the intake fresh air temperature Ta0 detected by the intake temperature sensor and the intake pressure Pmn-1 are read.

In S2 and S3, the temperature change prediction calculation is performed according to the law of thermodynamics as in the following equation, and the intake fresh air temperature T
a is obtained, and the process ends. Pressure correction coefficient Ktmpi = (Pmn-1 / PA #) Intake fresh air temperature Ta = Ta0 * Ktmpi + TOFF # Here, PA # and TOFF # are constants. However, TO
The FF # may be corrected by the water temperature, the vehicle speed, or the like.

FIG. 11 is a flow chart for calculating the EGR gas temperature Te on the outlet side (collector inlet) of the EGR gas cooling device. This flow corresponds to EGR gas temperature calculation means including EGR gas cooling device efficiency setting means, and is executed in synchronization with the reference crank angle signal. In S1, the exhaust temperature Texh
, EGR gas cooling water temperature Twg0 detected by the EGR gas cooling water temperature sensor, the basic heat transmission coefficient κ0 and its correction coefficient κh on the heat transfer surface of the EGR gas cooling device, which corresponds to the efficiency of the EGR gas cooling device, Read in.

The basic coefficient of heat transmission κ0 is, as shown in FIG. 12, the engine speed Ne and the fuel injection amount (load) Qsol.
The map is approximately searched from and the correction coefficient κh is searched from the table based on the EGR amount Qe as shown in FIG. A method of calculating the exhaust temperature Texh and the EGR amount Qe will be described later. In S2, the delay processing of the heat transmission coefficient κ is performed by the calculation shown in the following equation.

Κ = κn -1 × (1−TcK) + κ0 × TcK Here, TcK is a constant. The subscript n-1 is the value one cycle before. In S3, the advance processing of the EGR gas cooling water temperature Twg is performed by the calculation as shown in the following equation. Twg = GKTw * Tw-Twg0n-1 Here, GKTw is a constant. Also, the subscript n-1 is 1
It is the value before the cycle.

In S4, the EGR gas temperature Te at the outlet side of the EGR gas cooling device is calculated by the following equation, and the process is terminated. Te = Texh−Twg × κ × A / (κ × κh × A / 2−Q
e × Cp) Here, A and Cp are constants. The calculation formula of Te is a modification of the following formula based on the heat exchanger model shown in FIG.

Ga × Cp × (Tgin−Tgout) = κ × A
X ((Tgin-Tgout) / 2-Tw) Here, Cp is the gas specific heat (which is originally a function of temperature but is a constant because the change is small in the operating range), and A is the heat transfer surface area. FIG. 15 is a flowchart of the volume efficiency equivalent value Kin calculation. This flow is executed in synchronization with the reference crank angle signal.

At S1, the cylinder intake fresh air amount Qac, the fuel injection amount Qsol, and the engine speed Ne are read. In S2, the volumetric efficiency basic value KinH1 is calculated from the cylinder intake fresh air amount Qac and the engine speed Ne by referring to a map as shown in FIG. 16, for example. At S3, the fuel injection amount Q
From sol and engine speed Ne, referring to a map as shown in FIG. 17, for example, the volume efficiency load correction coefficient KinH2
Is calculated.

At S4, the volumetric efficiency equivalent value Kin = KinH1 × K from the volumetric efficiency basic value KinH1 and its correction coefficient KinH2.
Calculate inH2 and finish the process. FIG. 18 shows the exhaust temperature Tex
It is a flowchart of h calculation. This flow corresponds to exhaust temperature prediction means and is executed in synchronization with the reference crank angle signal. An exhaust gas temperature sensor can be used as the exhaust gas temperature detecting means instead of the predictive calculation.

At S1, S2 and S3, the cycle processing value Qf0 of the fuel injection amount, the cycle processing value Tn0 of the cylinder intake gas temperature, and the exhaust pressure Pexh are read. The method of calculating Qf0 and Tn0 will be described later. In S4, the exhaust temperature basic value Texhb is calculated from the cycle processing value Qf0 of the fuel injection amount with reference to a table as shown in FIG. 19, for example.

In S5, the intake air temperature correction coefficient Ktexh1 for the exhaust gas temperature is calculated from the cycle process value Tn0 of the cylinder intake gas temperature by the following equation. Ktexh1 = (Tn0 / TA #) ^{KN #} where TA # and KN # are constants. In S6, an exhaust pressure correction coefficient (temperature increase correction coefficient due to exhaust pressure increase) Ktexh2 with respect to the exhaust temperature is calculated from the exhaust pressure Pexh using an equation based on the law of thermodynamics such as the following equation.

Ktexh2 = (Pexhn-1 / PA #) ^{(# Ke-1) / # Ke} Here, PA # and #Ke are constants. In S7, the exhaust temperature Texh = Texhb × K is calculated from the exhaust temperature basic value Texhb, the intake temperature correction coefficient Ktexh1, and the exhaust pressure correction coefficient Ktexh2.
texh1 × Ktexh2 is calculated, and the process ends.

FIG. 20 is a flowchart of the EGR amount Qe calculation. This flow corresponds to the EGR amount calculation means and is executed in synchronization with the reference crank angle signal. In S1, the intake pressure Pm, the exhaust pressure Pexh, and the EGR valve actual lift amount Lifts as the EGR valve opening degree are read. In this case, an EGR valve lift sensor that directly detects the EGR valve actual lift amount Lifts may be provided as the EGR valve opening detection means, but if the EGR valve is given a target value like a step motor, the actual lift amount is In a system driven by an actuator that is uniquely determined, the EGR valve actual lift amount Lifts is set as the EGR to be described later.
The valve target lift amount Mlift can be used.

In S2, E is calculated from the EGR valve actual lift amount Lifts by referring to a table as shown in FIG.
The GR valve passage area Ave is calculated. In S3, the EGR flow rate Qe is calculated by the following equation from the EGR passage valve area Ave and the differential pressure between the intake pressure Pm and the exhaust pressure Pexh, and the process is ended. Qe = Ave * (Pexh-Pm) < ^1/2 > * KR # Here, KR # is a constant and is a value approximately equal to 2 * (rho is exhaust density). KR # may be calculated from a table according to the EGR valve opening.

FIG. 22 shows the cylinder intake fresh air amount (exhaust amount),
7 is a flowchart of a cycle process of a fuel injection amount and a cylinder intake gas temperature. This flow is for a predetermined time (eg 10
every ms). At S1, the cylinder intake fresh air amount Qac, the fuel injection amount Qsol, and the cylinder intake gas Tint are read. The method of calculating the cylinder intake gas temperature Tint will be described later.

In S2, these Qac, Qsol, Tint
Cycle treatment. That is, as in the following equation, Qac
Is processed by delaying by one minus the number of cylinders, and the cycle processing value, that is, the displacement Qexh, is calculated.
For sol, delay processing for the number of cylinders minus 2 is performed to obtain the cycle processing value Qf0, and for Tint, delay processing for the number of cylinders minus 1 is performed to obtain the cycle processing value Tn0, and the processing is performed. finish.

Qexh = Qac * Z- ^{(CYLN # -1)} Qf0 = Qsol * Z- ^{(CYLN # -2)} Tn0 = Tint * Z- ^{(CYLN # -1)} where CYLN # is the number of cylinders. FIG. 23 is a flowchart of the fuel injection amount Qsol calculation. This flow is executed in synchronization with the reference crank angle signal.

At S1, the engine speed Ne and the accelerator opening (control lever opening) CL are read. S2
Then, from the engine speed Ne and the accelerator opening CL,
For example, the basic fuel injection amount Mqdrv is calculated with reference to the map as shown in FIG. At S3, the basic fuel injection amount M
Various corrections such as water temperature correction are performed on qdrv to obtain the fuel injection amount Qsol1.

In S4, the maximum injection amount Qsol1MAX is determined from the engine speed Ne and the intake pressure Pm by referring to the map shown in FIG. 25, for example, and the maximum injection amount is limited (Qsol1 and Qsol1MAX The smaller one is selected from the above), the result is set as the final fuel injection amount Qsol, and the processing is ended. FIG. 26 shows the command lift amount Lif for the EGR valve.
It is a flowchart of tt calculation. This flow corresponds to the EGR valve control means and is executed in synchronization with the reference crank angle signal.

At S1, the intake pressure Pm, the exhaust pressure Pexh, and the target EGR amount Tqe are read. The method of calculating the target EGR amount Tqe will be described later. At S2, the EGR valve required flow passage area Tav is calculated by using an equation based on the law of fluid dynamics such as the following equation.
Is calculated. Tav = Tqe / (Pexh-Pm) ^1/2 / KR # Here, KR # is a constant and is a value substantially equal to 2 * (rho) is exhaust density. KR # may be calculated from a table according to the EGR valve opening.

In S3, the target lift amount Mlift is calculated from the EGR valve required flow passage area Tav by referring to a table showing the relationship between the flow passage area and the lift amount as shown in FIG. 27, for example. In S4, the target lift amount Mlift is advanced by an amount corresponding to the operation delay of the valve, and the value is set as the command lift amount Liftt, and the process ends.

FIG. 28 is a flow chart for calculating the target EGR amount Tqe. This flow is the same as the flow shown in FIG.
It corresponds to the GR amount calculation means and is executed in synchronization with the reference crank angle signal. At S1, engine speed Ne and target E
Read GR rate Megr and cylinder intake fresh air amount Qac. The method of calculating the target EGR rate Megr will be described later.

In S2, the target intake EGR amount TqecO = Qac × Megr is obtained by multiplying the cylinder intake fresh air amount Qac by the target EGR rate Megr. In S3, the target intake EGR amount TqecO is advanced by an amount corresponding to the intake system capacity to obtain Tqec as in the following equation. Tqec = Tqecn-1 x (1-Kin x Kvol) + Tqec x K
in × Kvol S4, target intake EGR amount Tqec and engine speed N
From e and the constant KCON #, the target EGR amount Tqe is calculated by the following equation, and the process is ended.

Tqe = Tqec × Ne / KCON # FIG. 29 is a flowchart of the calculation of the target EGR rate Megr. This flow corresponds to the target EGR amount calculation means and the target EGR amount correction means, and is executed in synchronization with the reference crank angle signal. At S1, the engine speed Ne and the fuel injection amount Q
Read sol and cylinder intake gas temperature Tint. The method of calculating the cylinder intake gas temperature Tint will be described later.

In S2, the target EGR rate basic value Megr0 is calculated from the engine speed Ne and the fuel injection amount Qsol with reference to a map as shown in FIG. 30, for example. In S3, the correction coefficient Hegr is calculated from the cylinder intake gas temperature Tint with reference to a table as shown in FIG. 31, for example. In S4, the target EGR rate basic value Megr0 is multiplied by the correction coefficient Hegr to obtain the target EGR rate Megr = Meg
r0 × Hegr is obtained, and the processing is ended. This part is target E
It corresponds to a GR amount (target EGR rate) correcting means.

FIG. 32 is a flow chart for calculating the cylinder intake gas temperature Tint. This flow corresponds to the cylinder intake gas temperature calculation means and is executed in synchronization with the reference crank angle signal. In S1, the cylinder intake fresh air amount Qac, the cylinder intake EGR amount Qec, the intake fresh air temperature Ta, and the EGR gas temperature Te are read.

In S2, the cylinder intake gas temperature Tint is calculated from the above by the following equation, and the process is terminated. Tint = (Qac × Ta + Qec × Te) / (Qac + Qec) Thus, the intake fresh air amount and the intake fresh air temperature are measured, and the intake pressure is predicted according to the laws of thermodynamics and fluid dynamics.
The exhaust pressure is predicted in the same manner as the intake pressure, and the target EGR amount is calculated from the differential pressure between the intake pressure and the exhaust pressure and the opening area information for the lift amount of the EGR valve according to the law of fluid dynamics. By predicting the EGR gas temperature on the outlet side of the EGR gas cooling device according to the amount and the operating state of the engine, it is possible to accurately predict the temperature of the gas taken into the cylinder.

Further, the cylinder intake gas temperature can be accurately predicted by predicting the delay of the sensor, the actuator and the working fluid and performing the advance processing so as to compensate for this delay. As a result, in the diesel engine to which the EGR gas cooling device is applied, the exhaust gas reduction effect by the EGR gas cooling can be enjoyed even in the transient operation in which the operating condition changes momentarily. Also, since the cylinder intake gas temperature can be predicted accurately,
The EGR amount can be corrected and controlled according to the cylinder intake gas temperature, and a desired exhaust gas reduction effect can be obtained.

Another embodiment of the present invention will be described below. FIG. 33 is a diagram showing the configuration of the second embodiment. In the second embodiment, the EGR gas cooling device 9 is provided with a radiator 41 and a thermostat 42 of the engine cooling system.
And a radiator fan 4 as a water temperature adjusting device, which is arranged between the engine cooling water and the coolest water.
It is characterized by adjusting the water temperature in 3. 44 is a water pump.

Although not shown, the EGR gas cooling device 9
A water cooling system may be separately provided for adjusting the water temperature. In terms of control, the second embodiment is different from the first embodiment in that the flow of FIG. 34 is added. FIG. 34 is a flowchart of the EGR gas cooling water temperature control by the radiator fan. This flow is executed in synchronization with the reference crank angle signal.

At S1, the cylinder intake gas temperature Tint,
Further, as shown in FIG. 35, the target cylinder intake gas temperature Mtint set by the engine speed Ne and the fuel injection amount (load) Qsol is read. At S2, the difference dT between the cylinder intake gas temperature Tint and the target cylinder intake gas temperature Mtint
int = Tint-Mtint is calculated.

In S3, the number of operating stages of the radiator fan (Off, Low, Mid, Hi) is set from the temperature difference dTint with reference to the table shown in FIG. 36, and the corresponding radiator fan control command is output. , The process ends.
That is, in the second embodiment, the operation of the radiator fan is controlled to control the EGR gas cooling water temperature, thereby controlling the heat exchange amount and controlling the cylinder intake gas temperature.

FIG. 37 is a diagram showing the configuration of the third embodiment of the present invention. In the third embodiment, the EGR gas cooling device 9 is connected to the water pump 4 downstream of the thermostat 42.
4 and the intake side of the engine 1 for cooling with water kept at a constant temperature and for adjusting the amount of water passing through the EGR gas cooling device 9 as a water amount adjusting device. The valve 45 is provided to adjust the amount of water. As the water amount adjusting valve 45, a solenoid valve of a proportional solenoid type or a control valve driven by a step motor or the like is used.

Although not shown, the EGR gas cooling device 9
A water cooling system may be separately provided for adjusting the amount of water. In terms of control, the third embodiment is different from the first embodiment in that the flow of FIG. 38 is used instead of the flow of FIG. 11 (strictly, the map of FIG. 40 is used instead of the table of FIG. 13). 41) is added to the flow of FIG. 41.

FIG. 38 is a flowchart of the EGR gas temperature Te calculation routine. This flow corresponds to EGR gas temperature calculation means including EGR gas cooling efficiency setting means, and is executed in synchronization with the reference crank angle signal. At S1, the exhaust temperature Texh and E corresponding to the efficiency of the EGR gas cooling device are obtained.
Basic heat transmission coefficient κ0 on the heat transfer surface of the GR gas cooling device and its correction coefficient κh, EGR amount Qe, EGR gas cooling water temperature Twg0 detected by an EGR gas cooling water temperature sensor
Read in.

Note that the basic coefficient of heat transmission κ0 is, as shown in FIG. 39, the engine speed Ne and the fuel injection amount (load) Qsol.
The map is approximately searched from and the correction coefficient κh is searched from the EGR amount Qe and the water amount adjusting valve opening degree as shown in FIG. In S2, the delay processing of the heat transmission coefficient κ is performed by the calculation shown in the following equation. κ = κn-1 × (1-TcK) + κ0 × TcK Here, TcK is a constant. The subscript n-1 is the value one cycle before.

At S3, the calculation shown in the following equation
A process for advancing the EGR gas cooling water temperature Twg is performed. Twg = GKTw * Tw-Twg0n-1 Here, GKTw is a constant. Also, the subscript n-1 is 1
It is the value before the cycle.

At S4, the EGR gas temperature Te at the outlet side of the EGR gas cooling device is calculated by the following equation, and the process is terminated. Te = Texh−Twg × κ × A / (κ × κh × A / 2−Q
e × Cp) Here, A and Cp are constants. FIG. 41 is a flowchart of the EGR gas cooling water amount control by the water amount adjusting valve.
This flow is executed in synchronization with the reference crank angle signal.

At S1, the cylinder intake gas temperature Tint,
Further, as shown in FIG. 42, the target cylinder intake gas temperature Mtint set by the engine speed Ne and the fuel injection amount (load) Qsol is read. At S2, the difference dT between the cylinder intake gas temperature Tint and the target cylinder intake gas temperature Mtint
int = Tint-Mtint is calculated.

In S3, the water amount adjustment valve opening is set from the temperature difference dTint with reference to the table shown in FIG. 43, a control command is output to the water amount adjustment valve drive actuator, and the process is terminated. . That is, in the third embodiment, the opening degree of the water amount adjusting valve is controlled to control the EGR gas cooling water amount, thereby controlling the heat exchange amount and controlling the cylinder intake gas temperature.

As described above, according to the second embodiment or the third embodiment, E is changed according to the predicted cylinder intake gas temperature.
By controlling the capacity of the GR gas cooling device, it becomes difficult for the cylinder intake gas temperature to fluctuate (especially shift to the high temperature side) even during transient operation, so that the exhaust gas reduction effect by EGR gas cooling can be maximized.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention.

FIG. 2 is a system diagram showing a first embodiment of the present invention.

FIG. 3 is a diagram showing a specific example of a fuel injection device.

FIG. 4 is a detailed diagram of a fuel injection timing adjustment mechanism.

FIG. 5 is a diagram showing a specific example of an EGR device.

FIG. 6 is a flowchart of intake system pressure calculation.

[Fig. 7] Flow chart of exhaust system pressure calculation

FIG. 8 is a flowchart of a cylinder intake fresh air amount calculation.

FIG. 9 is a flowchart of a cylinder intake EGR amount calculation.

FIG. 10: Flowchart of intake fresh air temperature calculation

FIG. 11 is a flowchart of calculating EGR gas temperature.

FIG. 12 is a diagram showing a basic heat transmission coefficient map.

FIG. 13 is a diagram showing a correction coefficient table.

FIG. 14 is a diagram showing a heat exchanger model.

FIG. 15 is a flowchart of a volume efficiency equivalent value calculation.

FIG. 16 is a diagram showing a volume efficiency basic value map.

FIG. 17 is a diagram showing a correction coefficient map.

FIG. 18 is a flowchart of exhaust temperature calculation

FIG. 19 is a diagram showing an exhaust temperature basic value table.

FIG. 20 is a flowchart of EGR amount calculation.

FIG. 21 is a diagram showing an EGR valve flow passage area table.

FIG. 22 is a flowchart of cycle processing.

FIG. 23 is a flowchart of fuel injection amount calculation.

FIG. 24 is a diagram showing a basic fuel injection amount map.

FIG. 25 is a diagram showing a maximum injection amount map.

FIG. 26 is a flowchart of EGR valve command lift amount calculation.

FIG. 27 is a diagram showing a target lift amount table.

FIG. 28 is a flowchart of target EGR amount calculation.

FIG. 29 is a flowchart of target EGR rate calculation.

FIG. 30 is a diagram showing a target EGR rate basic value map.

FIG. 31 is a diagram showing a correction coefficient table.

FIG. 32 is a flowchart for calculating a cylinder intake gas temperature.

FIG. 33 is a diagram showing the configuration of the second embodiment.

FIG. 34 is a flowchart of EGR gas cooling water temperature control.

FIG. 35 is a diagram showing a target cylinder intake gas temperature map.

FIG. 36 is a diagram showing a radiator fan operation stage number table.

FIG. 37 is a diagram showing the configuration of the third embodiment.

FIG. 38 is a flowchart of EGR gas temperature calculation.

FIG. 39 is a diagram showing a basic heat transmission coefficient map.

FIG. 40 is a diagram showing a correction coefficient map.

FIG. 41 is a flowchart of EGR gas cooling water amount control.

FIG. 42 is a diagram showing a target cylinder intake gas temperature map.

FIG. 43 is a diagram showing a water amount adjustment valve opening table.

FIG. 44 is a diagram showing changes in various parameters when the vehicle is equipped with a diesel engine equipped with an EGR gas cooling device.

[Explanation of symbols]

1 engine 2 Fuel injection pump 3 Fuel injection nozzle 5 EGR passage 6 EGR valve 7 collector 9 EGR gas cooling device 14 Air flow meter 15 Intake temperature sensor 17 EGR gas cooling water temperature sensor 32 rpm sensor 34 Accelerator position sensor 39 Control unit 41 radiator 42 thermostat 43 radiator fan 44 Water pump 45 Water flow control valve

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02D 45/00 312 F02D 45/00 312R 360 360C 360D 360F (56) Reference JP-A-9-53519 (JP, A) JP-A-9-79092 (JP, A) JP-A-8-284735 (JP, A) JP-A-8-61156 (JP, A) JP-A-8-189407 (JP, A) JP-A-9-14007 (JP , A) JP 9-256914 (JP, A) JP 55-131557 (JP, A) JP 5-263717 (JP, A) JP 8-261072 (JP, A) JP 6-108925 (JP, A) JP-A-8-86251 (JP, A) Actual development Sho 61-66652 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02M 25/07 550 F02M 25/07 570 F02M 25/07 580 F01P 3/20 F02D 45/00 301 F02D 45/00 312 F02D 45/00 360

Claims (8)

(57) [Claims] 1. An intake fresh air amount detecting means for detecting an intake fresh air amount to an engine, an intake fresh air temperature detecting means for detecting an intake fresh air temperature, and an intake system pressure detecting means for detecting a pressure of an intake system. An exhaust system pressure detecting means for detecting the pressure of the exhaust system, an exhaust temperature detecting means for detecting the exhaust temperature, an EGR passage for returning a part of exhaust gas from the exhaust system to the intake system, and an EGR passage in the middle The EGR valve provided, the target EGR amount setting means for setting the target EGR amount based on the engine operating condition, and the target opening degree of the EGR valve from the differential pressure between the intake system pressure and the exhaust system pressure and the target EGR amount. EG to set and control EGR valve
In a diesel engine equipped with an R valve control means and an EGR gas cooling device for cooling the EGR gas, the intake fresh air amount detected by the intake fresh air amount detecting means is subjected to delay processing to obtain a cylinder intake fresh air amount. A cylinder intake fresh air amount calculating means for calculating, an EGR valve opening detecting means for detecting the opening degree of the EGR valve, an EGR amount is calculated from the differential pressure between the intake system pressure and the exhaust system pressure, and the EGR valve opening degree. EGR amount calculation means, a cylinder intake EGR amount calculation means for performing a delay process on the EGR amount to calculate the cylinder intake EGR amount, an EGR gas cooling device efficiency setting means for setting the efficiency of the EGR gas cooling device, and an exhaust gas temperature And EG based on the efficiency of the EGR gas cooler
EG for calculating the EGR gas temperature at the outlet side of the R gas cooling device
R gas temperature calculation means, cylinder intake fresh air amount, intake fresh air temperature and cylinder intake EG
A cylinder intake gas temperature calculation device for a diesel engine, comprising: a cylinder intake gas temperature calculation means for calculating the cylinder intake gas temperature based on the R amount and the EGR gas temperature at the outlet side of the EGR gas cooling device. 2. The EGR gas cooling device cools the EGR gas with engine cooling water.
EGR gas cooling water temperature detecting means for detecting the temperature of the cooling water passing through the gas cooling device is provided, and the EGR gas temperature calculating means is provided to control the exhaust gas temperature, the cooling water temperature passing through the EGR gas cooling device and the efficiency of the EGR gas cooling device. And based on EGR
2. The cylinder intake gas temperature calculating device for a diesel engine according to claim 1, wherein the EGR gas temperature on the outlet side of the gas cooling device is calculated. 3. An intake system pressure predicting means for predicting an intake system pressure based on engine operating conditions is provided in place of the intake system pressure detecting means, and an exhaust system pressure detecting means is provided in place of the exhaust system pressure detecting means. The cylinder intake gas temperature calculation device for a diesel engine according to claim 1 or 2, further comprising exhaust system pressure predicting means for predicting an exhaust system pressure. 4. The exhaust temperature predicting means for predicting the exhaust temperature based on the engine operating condition is provided in place of the exhaust temperature detecting means. Cylinder intake gas temperature calculation device for the diesel engine described. 5. The intake fresh air temperature correction means for correcting the intake fresh air temperature detected by the intake fresh air temperature detecting means by the intake system pressure, according to any one of claims 1 to 4. 1. A cylinder intake gas temperature calculation device for a diesel engine according to any one of the above. 6. A target EGR that includes the cylinder intake gas temperature calculation device according to claim 1 and corrects the target EGR amount according to the cylinder intake gas temperature.
An EGR control device for a diesel engine, characterized in that a quantity correction means is provided. 7. A diesel engine according to claim 6, further comprising a water temperature adjusting device for adjusting the cooling water temperature of the EGR gas cooling device for cooling the EGR gas with the engine cooling water according to the cylinder intake gas temperature. Engine EGR controller. 8. A diesel engine according to claim 6, further comprising a water amount adjusting device for adjusting a cooling water amount of an EGR gas cooling device for cooling the EGR gas with the engine cooling water in accordance with a cylinder intake gas temperature. EGR controller.