JP2002030961A - Combustion control device for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve precision of correction of a fuel control parameter responding to the warming-up state of a diesel engine. SOLUTION: Based on a water temperature Twout at the cooling water outlet of an engine and a temperature difference ΔTW between the outlet water temperature Twout and a water temperature Twin at a cooling water inlet, a correction factor HOSW of a fuel injection amount control parameter, such as a fuel injection amount, is calculated and corrected by using the correction factor HOSW. This constitution, since the correction factor HOSW is calculated in consideration of the temperature difference ΔTW, enables accurate grasping of a warming-up state and improves precision of the correction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to correction control of various combustion control parameters from the start of a diesel engine to the completion of warm-up.

[0002]

2. Description of the Related Art In a vehicle engine, reduction of exhaust emission is a permanent problem. In particular, from the start to the completion of warm-up, flammability tends to deteriorate due to low temperature. In order to maintain good conditions, various combustion control parameters are corrected according to the warm-up state.

[0003] In particular, since the exhaust temperature of a diesel engine is extremely lower than that of a gasoline engine, it is difficult to purify the exhaust gas with a catalyst, and it is necessary to reduce the exhaust emission itself from a cylinder. Correction of the corresponding combustion control parameters is important. In order to correct the combustion control parameter with high accuracy, it is necessary to accurately grasp a warm-up state related to flammability.

Conventionally, the correction of the combustion control parameters according to the warm-up state of a diesel engine has been performed based only on the cooling water temperature at the cooling water outlet receiving combustion heat (see Japanese Patent Application Laid-Open No. 11-350068). ).

[0005]

However, the warming-up state of the engine cannot be accurately grasped only from the cooling water temperature at the cooling water outlet (hereinafter referred to as the outlet water temperature). For example, as shown in FIG. 11, even when the vehicle speed is the same and the outlet water temperature is the same, the required fuel injection amount (load) may be different due to the difference in the warm-up state. However, since the warm-up state cannot be accurately grasped only from the outlet water temperature, there is a problem that the combustion control cannot be appropriately corrected.

The present invention has been made in view of such conventional problems, and provides a combustion control apparatus for a diesel engine capable of accurately grasping a warm-up state and appropriately correcting combustion control. The purpose is to do.

[0007]

According to the present invention, a cooling water temperature at a cooling water inlet and an outlet of an engine is detected, and a combustion control parameter of the engine is corrected based on the detected cooling water temperature. It is characterized by doing.
According to the first aspect of the invention, the engine combustion control parameters are corrected based on the detected coolant temperature at the coolant inlet (inlet coolant temperature) and the coolant temperature at the coolant outlet (outlet coolant temperature). .

With this configuration, the warm-up state can be more accurately grasped by the temperature difference between the outlet water temperature and the inlet water temperature while grasping the rough warm-up state based on the outlet water temperature. The combustion control parameters of the engine can be corrected with high accuracy based on the warm-up state. Further, the invention according to claim 2, when the cooling water temperature at the cooling water outlet is equal to or lower than a set temperature, based on a temperature difference between the cooling water temperature at the cooling water inlet and the cooling water and a cooling water temperature at the cooling water outlet. ,
It is characterized in that a correction amount of the combustion control parameter is calculated and the correction is made by the correction amount.

According to the second aspect of the present invention, when the detected outlet water temperature is equal to or lower than the set temperature, the correction amount of the combustion control parameter is determined based on the temperature difference between the inlet water temperature and the outlet water temperature and the outlet temperature. Calculated and corrected by the correction amount. That is, when the outlet water temperature exceeds the set temperature and is in an equilibrium state, it is determined that the correction of the combustion control parameter based on the water temperature is unnecessary, so that no correction is performed. The correction is performed by calculating a correction amount of the combustion control parameter based on the difference and the outlet water temperature.

The invention according to claim 3 is characterized in that the combustion control is performed on the basis of the amount of heat transferred between the cooling water and the engine body calculated based on the temperature difference and the cooling water temperature at the cooling water outlet. It is characterized in that a correction amount of a parameter is calculated, and correction is performed using the correction amount. According to the invention according to claim 3, during the warm-up of the outlet water temperature equal to or lower than the set temperature, the amount of heat transferred between the cooling water and the engine body is calculated based on a temperature difference between the outlet temperature and the inlet temperature. The combustion control parameter is corrected by a correction amount calculated based on the calculated amount of moving heat and the outlet water temperature.

With this configuration, the correction amount of the combustion control parameter can be calculated with higher accuracy using the amount of heat transferred between the cooling water and the engine body calculated from the temperature difference as a parameter. The invention according to claim 4 is characterized in that a correction amount of the combustion control parameter is calculated including an engine lubricating oil temperature.

According to the invention according to claim 4, the inlet water temperature,
The correction is performed by calculating a correction amount of the combustion control parameter based on the outlet water temperature and the engine lubricating oil temperature. The temperature of the engine lubricating oil (hereinafter referred to as the oil temperature) has the lowest temperature during warm-up because the temperature rise delay is larger than the inlet water temperature and the outlet water temperature. Therefore, by taking into account the oil temperature, the warm-up state can be grasped more accurately, and the correction amount can be calculated and corrected with higher accuracy in the combustion control parameter.

According to a fifth aspect of the present invention, the correction of the combustion control parameter is stopped when the cooling water temperature at the cooling water outlet is equal to or higher than a set water temperature and the engine lubricating oil temperature is equal to or higher than the set oil temperature. It is characterized by doing. According to the invention of claim 5, when the outlet water temperature and the oil temperature are respectively equal to or higher than the set water temperature and equal to or higher than the set oil temperature, it is determined that the warm-up is completed, and the correction of the combustion control parameters is stopped.

The invention according to claim 6 is characterized in that a heating means for heating the cooling water is provided in the middle of the engine cooling water passage. According to the invention according to claim 6, in an engine provided with a heating means for heating the cooling water for promoting warm-up, when the cooling water is heated by the heating means, and especially when the outlet water temperature rises, the outlet Since it is difficult to grasp the warm-up state only by the water temperature, the effect of calculating and correcting the correction amount including at least the inlet temperature (temperature difference) as in the present invention is large.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 shows an overall configuration of a control device for a diesel engine according to an embodiment of the present invention. In FIG. 1, fuel is supplied to a fuel injection valve 2 provided in a combustion chamber of each cylinder of an engine 1 via a common rail 3 which is a fuel pressure accumulation chamber common to each cylinder.

An inlet water temperature sensor 4 for detecting a water temperature of the inlet portion is provided at an inlet portion of the engine 1 where the cooling water is introduced. An outlet portion from the engine 1 is provided with an outlet water temperature sensor 5 for detecting a water temperature of the outlet portion. The thermostat 6, which operates by sensing the water temperature, closes when the temperature is low and circulates cooling water through the bypass passage 7 to promote warm-up, and opens when the water temperature at the time of warm-up completion is reached. The cooling water is circulated while being cooled by the radiator 8 to cool the engine 1 appropriately.

Further, a heater (including a regenerator) 9 for heating the cooling water, an oil cooler 10 for cooling the lubricating oil with the cooling water, an EGR cooler 11 for cooling the EGR gas with the cooling water, and the like are provided. An oil temperature sensor 12 for detecting an oil temperature is provided before and after the oil pan or oil pump of the engine 1.

Further, a rotation speed sensor 13 for detecting the rotation speed of the engine is provided. The signals from the inlet water temperature sensor 4, the outlet water temperature sensor 5, the oil temperature sensor 12, and the rotation speed sensor 13 are transmitted to the control unit 14
Is output to The control unit 14 determines a fuel injection amount and a fuel injection timing of the fuel injection valve 2, a fuel pressure in the common rail 3, and an E (not shown) based on each of the signals.
The opening degree (EGR rate) of an EGR valve interposed in the GR passage is controlled.

Hereinafter, the correction control during warm-up based on the inlet water temperature, outlet water temperature, oil temperature and the like will be described with reference to a flowchart. FIG. 2 shows a flowchart of control according to the first embodiment. In step 1, the inlet water temperature TWin, the outlet water temperature TWout, and the oil temperature Toil detected by the inlet water temperature sensor 4, the outlet water temperature sensor 5, and the oil temperature sensor 12.
And the engine speed Ne detected by the engine speed sensor 13 is read.

In step 2, it is determined whether or not the outlet water temperature TWout is higher than a set water temperature TWH for determining whether or not to correct the water temperature. If it is determined that the outlet water temperature TWout is equal to or lower than the set water temperature TWH, the process proceeds to step 3, where the temperature difference ΔTW between the inlet water temperature TWin and the outlet water temperature TWout is calculated. Next, at step 4, the temperature difference ΔTWin and the outlet water temperature T
From Wout, a correction coefficient HOSW based on the water temperature is calculated. Specifically, as shown in FIG. 3, a map of the correction coefficient HOSW calculated according to the temperature difference ΔTW and the outlet water temperature TWout may be set, and the correction coefficient HOSW may be set by searching from the map. Here, the correction coefficient HO
SW indicates that the lower the outlet water temperature TWout is, the more the temperature difference Δ
The smaller the TW is, the larger the value is set. Outlet water temperature T
When Wout is low, the engine temperature is basically low, and when the temperature difference ΔTW is small, the amount of heat transferred from the engine body to the cooling water is small, that is, the temperature of the engine body is relatively lower than the water temperature. It is considered that this is the case. For example, when the temperature difference ΔTW is small even when the outlet water temperature TWout is high to some extent, the outlet water temperature TWout may be increased by the cooling water heating by the heater 9 or the like. Therefore, since the degree of warm-up is lower than estimated only by the outlet water temperature TWout, the correction coefficient HOSW is set to be relatively large in consideration of the temperature difference ΔTW.

Thus, the correction coefficient HO based on the water temperature is obtained.
After setting the SW, the process proceeds to step 7. On the other hand, if it is determined in step 2 that the outlet water temperature TWout is higher than the set water temperature TWH, it is determined that the water temperature has substantially reached the equilibrium temperature, and the process proceeds to step 5, where the water temperature TW of the combustion control parameter (control target) is determined. Is set to zero.

Here, in particular, as shown in FIG. 3, if a map is set including a region where the correction coefficient HOSW is set to 0, the processing of the above steps 2 to 5 is performed for the temperature difference ΔTW and the outlet water temperature TWout. Based on this, it can be set by only one search from the map. The process proceeds from step 5 to step 6 to determine whether or not the oil temperature Toil is higher than the set oil temperature TOH for judging the presence or absence of oil temperature correction. If the oil temperature Toil is equal to or lower than the set oil temperature TOH, the process proceeds to step 7.

In step 7, a correction coefficient HOSO based on the oil temperature Toil of the combustion control parameter is set by, for example, searching from a map as shown in FIG. Here, the correction coefficient HOSO is set to increase as the oil temperature Toil decreases. That is, as shown in FIG. 5, during the warming-up, the temperature of the oil temperature is longer than the inlet water temperature and the outlet water temperature. At this time, the correction coefficient HOSO is increased. FIG. 6 shows a heat transfer relationship between the engine body, the cooling water, and the lubricating oil.

In step 8, a correction coefficient HOS is calculated by adding the correction coefficient HOSW based on the water temperature and the correction coefficient HOSO based on the oil temperature Toil as in the following equation. HOS = HOSW + HOSO On the other hand, if it is determined in step 6 that the oil temperature Toil is higher than the set oil temperature TOH for determining the presence or absence of oil temperature correction, the oil temperature Toil, which has a large temperature rise delay, has also become sufficiently high. It is determined that the engine has been completed, and the routine proceeds to step 9, where the correction coefficient HOS is set to 0 in order to stop the correction of the combustion control parameter according to the warm-up state.

In step 10, the final control amount of the combustion control parameter is calculated by using the correction coefficient HOS corresponding to the warm-up state calculated as described above. Specifically, for example, when the combustion control parameter is the fuel injection amount, as shown in FIG. 7, the basic control is performed based on the engine rotation speed Ne and the control lever position CL of the fuel injection pump according to the accelerator operation amount. The injection amount Qb is searched and set from the map, and the injection correction amount Qhos set by searching from the map based on the water temperature (exit water temperature, etc.) TW is multiplied by the correction coefficient HOS set in step 8 to obtain the final value. And the final correction amount (= Qhos × HOS) is added to the basic injection amount Qb.
Is calculated.

When the combustion control parameter is the EGR rate, as shown in FIG. 8, the target EGR rate Meg is determined based on the engine speed Ne and the load (fuel injection amount Q).
The basic value Megr of r is searched and set from the map, and the correction coefficient basic value Kegr set by searching from the map based on the water temperature (exit water temperature or the like) TW is set to the value in step 8 above.
The final correction amount is calculated by multiplying by the correction coefficient HOS set in step (1), and the final correction amount (= Keg
(r × HOS) is added to calculate the target EGR rate Megr.

The combustion control parameters corrected according to the warm-up state include the fuel pressure in the common rail and the like in addition to the above. Note that the correction coefficient HOS can be set differently (preferably) according to different combustion control parameters. In this way,
By correcting various combustion control parameters based on a correction amount set by accurately grasping the warm-up state, it is possible to improve exhaust emission and fuel efficiency.

Next, a second embodiment will be described. First
In the embodiment, the inlet water temperature TWin and the outlet water temperature TWout
The correction amount is calculated by combining the temperature difference ΔTW with the outlet water temperature TWout as it is. However, in the second embodiment, the amount of heat dQ transferred between the cooling water and the engine body is calculated based on the temperature difference ΔTW. Is calculated, and the correction amount is calculated based on the calculated moving heat amount dQ and the outlet water temperature TWout.

In the flow chart showing the second embodiment, only the parts different from the flow chart of FIG. 9 will be described. In step 13, the amount of heat transferred dQ between the cooling water and the engine body is calculated by the following equation. I do. dQ = Cc · dm · ΔTW (1) where Cc: specific heat of cooling water [kJ / (kg · K)] dm: mass flow rate of cooling water per unit time (kg / sec)
c) Here, the mass flow rate dm of the cooling water is calculated as a function of the engine rotation speed Ne as follows.

Dm = ρc · dV (Ne) (2) where ρc: density of cooling water (kg / m ³ ) dV (Ne): cooling per unit time calculated as a function of engine speed Ne Volumetric flow rate of water (m ³ / s
ec) From the above equations (1) and (2), dQ = Cc · ρc · dV (Ne) · ΔTW Next, in step, based on the moving heat quantity dQ and the outlet water temperature TWout, the map shown in FIG. A correction coefficient HOSW corresponding to the water temperature is calculated by a search or the like. Here, the correction coefficient HOSW is set to a larger value as the amount of transferred heat dQ is smaller.

The other points are the same as in the first embodiment. That is, in the first embodiment, the temperature difference ΔTW is simply used as a parameter related to the amount of transferred heat.
In the second embodiment, the heat transfer amount dQ is calculated and used with high accuracy by adding the cooling water flow rate to the temperature difference ΔTW, so that the warm-up state can be grasped more accurately, and the exhaust emission, Fuel efficiency can be further improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a system configuration according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a control flow according to the first embodiment;

FIG. 3 is a map in which a correction coefficient HOSW based on water temperature used in the first embodiment is set.

FIG. 4 is a map in which a correction coefficient HOSO based on an oil temperature used in the first embodiment is set.

FIG. 5 is a diagram showing rising changes in inlet water temperature, outlet water temperature, and oil temperature after engine start.

FIG. 6 is a diagram showing a heat transfer relationship between the engine body and cooling water and lubricating oil.

FIG. 7 is a diagram showing a process of calculating a final control amount when applied to correction of a fuel injection amount.

FIG. 8 is a diagram showing a process of calculating a final control amount when applied to correction of a target EGR rate.

FIG. 9 is a flowchart illustrating a control flow according to the second embodiment;

FIG. 10 is a map in which a correction coefficient HOSW based on water temperature used in the second embodiment is set.

FIG. 11 is a diagram illustrating a relationship between a water temperature during warm-up and a fuel injection amount.

[Explanation of symbols]

 1 Engine body 4 Inlet water temperature sensor 5 Outlet water temperature sensor 9 Heater 12 Oil temperature sensor 13 Rotation speed sensor 14 Control unit

Claims (6)

[Claims] 1. A combustion control system for a diesel engine, comprising detecting a coolant temperature at a coolant inlet and an outlet of an engine, and correcting an engine combustion control parameter based on the coolant temperature. 2. The method according to claim 1, wherein when the cooling water temperature at the cooling water outlet is equal to or lower than a set temperature, the combustion control parameter is determined based on a temperature difference between the cooling water temperatures at the cooling water inlet and outlet and the cooling water temperature at the cooling water outlet. The combustion control device for a diesel engine according to claim 1, wherein the correction amount is calculated and the correction amount is corrected by the correction amount. 3. A correction coefficient for the combustion control parameter is calculated based on the amount of heat transferred between the cooling water and the engine body calculated based on the temperature difference and a cooling water temperature at a cooling water outlet. 3. The combustion control device for a diesel engine according to claim 2, wherein the correction is performed by the correction amount. 4. The combustion control device for a diesel engine according to claim 1, wherein a correction amount of the combustion control parameter is calculated including an engine lubricating oil temperature. 5. The correction of the combustion control parameter is stopped when the coolant temperature at the coolant outlet is equal to or higher than a set water temperature and the engine lubricating oil temperature is equal to or higher than the set oil temperature. 5. The combustion control device for a diesel engine according to item 4. 6. The combustion control of a diesel engine according to claim 1, wherein a heating means for heating the cooling water is provided in the engine cooling water passage. apparatus.