JP2010236462A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To high-dimensionally achieve both suppression of overheat and EGR requirement in an internal combustion engine provided with an EGR system. <P>SOLUTION: In this control device for the internal combustion engine performing cooling of the internal combustion engine and cooling of the EGR system in the same cooling system, a water temperature threshold Tw2 for preventing the water temperature of the cooling system from being raised to a predetermined overheating temperature when EGR is stopped and a predetermined threshold Tw1 lower than the threshold Tw2 are set based on required heat dissipation Qw with respect to the cooling system of the internal combustion engine and heat dissipation Qr of the cooling system of the internal combustion engine. When the water temperature of the internal combustion engine reaches the threshold Tw1, the amount of EGR is reduced. After that, when the water temperature of the internal combustion engine reaches the threshold Tw2, the EGR is stopped. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine having an EGR system.

  Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-51566, in an internal combustion engine having an external EGR device, a system has been proposed that stops external EGR when the temperature of engine cooling water exceeds a predetermined temperature. ing. In this system, the engine coolant does not exchange heat with the high-temperature exhaust gas by the EGR cooler, so that the temperature rise of the engine coolant can be suppressed and the engine can be prevented from overheating.

JP 2007-51566 A JP-A-9-287525

  During high load operation of the internal combustion engine, it is conceivable that the coolant temperature rises and overheats. In the conventional system described above, in order to suppress this overheating, the external EGR is immediately stopped when the temperature of the engine cooling water exceeds a predetermined temperature. However, the EGR request is issued from a request related to emission, fuel consumption, etc., and it is desirable to satisfy the required amount as much as possible. For this reason, the above-described conventional system that stops the external EGR when the coolant temperature exceeds a predetermined temperature still leaves room for improvement from the viewpoint of achieving both EGR requirements and suppression of overheating. It was.

  The present invention has been made to solve the above-described problems, and provides an internal combustion engine control device capable of achieving both overheat suppression and EGR requirements at a high level in an internal combustion engine having an EGR system. The purpose is to do.

In order to achieve the above object, a first invention provides a control device for an internal combustion engine that performs cooling of the internal combustion engine and cooling of an EGR system included in the internal combustion engine in the same cooling system.
A first water temperature for preventing the water temperature of the cooling system from rising to a predetermined overheat temperature when the EGR is stopped based on a required heat radiation amount for the cooling system of the internal combustion engine and a heat radiation amount of the cooling system of the internal combustion engine; Water temperature setting means for setting a predetermined second water temperature lower than the first water temperature;
EGR reduction means for reducing the amount of EGR when the water temperature of the internal combustion engine reaches the second water temperature;
It is characterized by providing.

  According to the first invention, based on the required heat release amount and the heat release amount for the cooling system of the internal combustion engine, the first water temperature for preventing the water temperature of the cooling system from rising to a predetermined overheat temperature when the EGR is stopped, A predetermined second water temperature lower than the first water temperature is set. Then, when the water temperature of the internal combustion engine exceeds the second water temperature, the EGR amount is reduced. For this reason, according to the present invention, since the EGR is continued while reducing the EGR amount, the period until the water temperature reaches the first water temperature can be lengthened. Thereby, since the possibility that the water temperature reaches the first water temperature can be effectively reduced, the occurrence of overheating can be effectively suppressed and the EGR request can be satisfied as much as possible.

It is a simplified diagram for explaining a system configuration as an embodiment of the present invention. FIG. 2 shows an example of a timing chart during high-speed towing climbing of the internal combustion engine. The map which prescribes | regulates the relationship between the heat dissipation amount Qr and the required heat dissipation amount Qw, and the threshold value Tw is shown. The map which prescribes | regulates the relationship between threshold value Tw and an EGR rate coefficient is shown.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a simplified diagram for explaining a system configuration as a first embodiment of the present invention. The internal combustion engine of the present embodiment is an internal combustion engine having an EGR system, and the cooling system for cooling the internal combustion engine and the cooling system for cooling EGR gas are configured by the same cooling system. . As shown in FIG. 1, the system of the present embodiment includes various means for acquiring the operating state of the internal combustion engine and external information. More specifically, the system of the present embodiment includes vehicle speed detection means 10 for detecting the vehicle speed, outside air temperature detection means 12 for detecting the outside air temperature, and engine speed detection for detecting the engine speed. Means 14, engine load detection means 16 for detecting the engine load, and air-fuel ratio detection means 18 for detecting the air-fuel ratio are provided.

  Further, the system of the present embodiment includes a Qr calculating means 20 for calculating a heat dissipation amount Qr of a cooling system (radiator or the like) of the internal combustion engine, and a Qw calculating means for calculating a required heat dissipation amount Qw for the cooling system. 22 is provided. The Qr calculation unit 20 calculates the heat release amount Qr based on the vehicle speed detected by the vehicle speed detection unit 10 and the outside air temperature detected by the outside air temperature detection unit 12. The Qw calculating means 22 adds the engine speed detected by the engine speed detecting means 14 described above, the engine load detected by the engine load detecting means 16, and the air-fuel ratio detected by the air-fuel ratio detecting means 18. The required heat release amount Qw is calculated based on the EGR rate calculated by the EGR rate correction means 32 described later.

  Further, the system of the present embodiment includes Tw calculation means 24 for calculating the water temperature threshold values Tw1 and Tw2. The Tw calculation unit 24 calculates threshold values Tw1 and Tw2 based on the heat release amount Qr calculated by the Qr calculation unit 20 and the required heat release amount Qw calculated by the Qw calculation unit 22. The threshold value Tw2 indicates a water temperature threshold value at which the water temperature exceeds a predetermined overheat temperature unless the EGR is stopped. The threshold value Tw1 is a temperature lower than the threshold value Tw2, and indicates a water temperature threshold value that will cause the water temperature in the near future to exceed a predetermined overheat temperature if EGR is continued at the current EGR rate. Yes. The threshold values Tw1 and Tw2 are calculated based on a map described later.

  Further, the internal combustion engine of the present embodiment includes an EGR rate calculation means 30, an EGR rate correction means 32, and an EGR opening degree output means 34 as EGR system control. The EGR rate calculating means 30 calculates the EGR rate based on the engine speed detected by the engine speed detecting means 14 described above and the engine load detected by the engine load detecting means 16. The EGR rate calculated by the EGR rate calculating unit is corrected by the EGR rate correcting unit 32. The EGR opening degree output means 34 outputs the EGR opening degree to the actuator based on the corrected EGR rate.

  The internal combustion engine of the present embodiment includes a fuel injection amount calculation means 40 and an injection amount output means 42 as a fuel control system. The fuel injection amount calculating means 40 is based on the engine speed detected by the engine speed detecting means 14 described above, the engine load detected by the engine load detecting means 16, and the air-fuel ratio detected by the air-fuel ratio detecting means 18. Thus, the fuel injection amount is calculated. Further, the injection amount output means 42 outputs the calculated injection amount to the actuator.

[Characteristic Operation of First Embodiment]
Next, the characteristic operation of the internal combustion engine system of the present embodiment will be described with reference to FIGS. The system according to the present embodiment is controlled so that the EGR amount is reduced when the water temperature of the internal combustion engine exceeds the threshold value Tw1 calculated by the Tw calculating means 24. In the following, the functions and operations of each system will be described in more detail along the timing chart shown in FIG.

  FIG. 2 shows an example of a timing chart during high-speed towing climbing of the internal combustion engine. As shown in this figure, the water temperature gradually rises during high load operation. And when the said water temperature exceeds threshold value Tw1 calculated in the Tw calculation means 24, an EGR rate is correct | amended.

  By the way, the threshold value Tw1 is a threshold value of the water temperature at which the water temperature exceeds a predetermined overheat temperature in the near future, and is calculated according to the map shown in FIG. FIG. 3 shows a map that defines the relationship between the heat dissipation amount Qr, the required heat dissipation amount Qw, and the threshold value Tw. As shown in this map, the threshold value Tw is calculated so as to increase as the heat dissipation amount Qr increases and to decrease as the required heat dissipation amount Qw increases. Further, according to this map, Tw1 is calculated to be smaller than Tw2. Thereby, the threshold value Tw reflecting the heat radiation amount Qr and the required heat radiation amount Qw can be calculated.

  The EGR rate is corrected based on the threshold value Tw1. More specifically, the EGR rate calculated by the EGR rate calculating means 30 is a value calculated based on the engine speed and the engine load, and no information on the possibility of overheating is reflected. For this reason, if EGR control is executed based on the EGR rate, the required heat release from the EGR system may increase, and the water temperature may rise above a predetermined overheat temperature.

  Therefore, the system according to the present embodiment includes the EGR rate correction unit 32. In the EGR rate correction means, first, it is determined whether or not the current water temperature exceeds the threshold value Tw1 input from the Tw calculation means described above. As a result, when the water temperature does not exceed the threshold value Tw1, it is determined that there is still no possibility of overheating, and the EGR opening degree output means 34 is based on the EGR rate calculated by the EGR rate calculating means 30. The EGR opening is output.

  On the other hand, when the water temperature exceeds the threshold value Tw1, it is determined that there is a possibility of overheating in the near future, and the EGR rate is corrected. Here, specifically, first, an EGR coefficient is calculated. The EGR rate coefficient is a coefficient for correcting the EGR rate by multiplying the input EGR rate, and is calculated according to the map shown in FIG. FIG. 4 shows a map defining the relationship between the threshold value Tw and the EGR rate coefficient. According to this map, the threshold value Tw1 is calculated such that the larger the value, the smaller the EGR coefficient.

  According to the correction of the EGR rate described above, when the water temperature exceeds the threshold value Tw1, the EGR amount is reduced, so that the required heat release amount of the EGR system is reduced. As a result, the rate of increase in the water temperature decreases, so that the period until the water temperature reaches the threshold value Tw2, that is, the period until the EGR rate becomes zero can be lengthened. The longer this period is, the less likely it is to stop EGR. For this reason, according to the system of the present embodiment, it is possible to effectively suppress overheating while satisfying the EGR request as much as possible.

  Further, as shown in the timing chart of FIG. 2, when the operation state of the internal combustion engine does not shift to the light load operation, the water temperature eventually reaches Tw2. In this case, EGR is stopped as shown in FIG. More specifically, the EGR coefficient corresponding to Tw2 is calculated to be zero according to the map shown in FIG. For this reason, the EGR rate is set to zero when the water temperature exceeds Tw2. Thereby, since EGR is stopped and water temperature falls, overheating can be suppressed effectively.

  As described above, according to the system of the present embodiment, the threshold values Tw1 and Tw2 are calculated based on the heat dissipation amount Qr and the required heat dissipation amount Qw, so that the possibility of overheating is effective for the threshold value Can be reflected.

  Further, according to the system of the present embodiment, when the water temperature exceeds the threshold value Tw1, the EGR is reduced and continued, so that the EGR operation time can be extended to improve the fuel consumption. Moreover, since the rate of increase in the water temperature can be reduced by reducing the EGR, the period until the water temperature reaches the threshold value Tw2 can be lengthened. Thereby, while suppressing generation | occurrence | production of overheating, possibility that EGR will be stopped can be reduced effectively.

  In the embodiment described above, the threshold value Tw1 corresponds to the “second water temperature” of the first invention, and the threshold value Tw2 corresponds to the “first water temperature” of the first invention. .

10 vehicle speed detecting means 12 outside air temperature detecting means 14 engine speed detecting means 16 engine load detecting means 18 air-fuel ratio detecting means 20 Qr calculating means 22 Qw calculating means 24 Tw calculating means 30 EGR rate calculating means 32 EGR rate correcting means 34 EGR opening Degree output means 40 Fuel injection amount calculation means 42 Injection amount output means

Claims (1)

In a control apparatus for an internal combustion engine that performs cooling of the internal combustion engine and cooling of the EGR system included in the internal combustion engine in the same cooling system,
A first water temperature for preventing the water temperature of the cooling system from rising to a predetermined overheat temperature when the EGR is stopped based on a required heat radiation amount for the cooling system of the internal combustion engine and a heat radiation amount of the cooling system of the internal combustion engine; Water temperature setting means for setting a predetermined second water temperature lower than the first water temperature;
EGR reduction means for reducing the amount of EGR when the water temperature of the internal combustion engine reaches the second water temperature;
A control device for an internal combustion engine, comprising:

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