JPH08159995A - Exhaust heat quantity calculating apparatus - Google Patents

Abstract

PURPOSE: To accurately calculate the exhaust heat quantity. CONSTITUTION: A cumulative intake air mass SGan is calculated (step 2), a cumulative fuel mass GFn is calculated (step 9), and the exhaust gas components are represented by carbon dioxide (CO2 ), moisture (H2 O) and nitrogen (N2 ) to obtain the specific heat at constant pressure cp . An enthalpy Hn is calculated based on an equation Hn =(SGan +GFn )×tE×cp (step 11). The exhaust heat quantity is calculated based on the enthalpy Hn .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust heat quantity computing device, and more particularly to a technique for computing the enthalpy of exhaust gas of an internal combustion engine in order to estimate the inlet temperature of a catalyst installed in an exhaust system.

[0002]

2. Description of the Related Art Conventionally, there has been known an exhaust heat quantity calculation device for calculating an exhaust heat quantity by obtaining a temperature change.

[0003]

However, in the conventional exhaust gas heat quantity calculation device, the concept of enthalpy is not introduced and the calculation is performed by obtaining the temperature change. Therefore, the heat transfer term due to the change in the flow velocity of the exhaust gas is ignored. Therefore, an error was generated in the calculated exhaust heat amount. The present invention has been made in view of such conventional problems, and an object of the present invention is to provide an exhaust heat amount calculation device that can accurately calculate the exhaust heat amount.

[0004]

Therefore, in the exhaust heat quantity computing device according to the invention of claim 1, as shown in FIG.
Intake air mass detection means for detecting the intake air mass to the engine, engine speed detection means for detecting the engine speed, and fuel mass detection means for detecting the fuel mass injected and supplied to the engine at regular intervals. A cumulative intake air mass calculating means for calculating a cumulative intake air mass in a predetermined period based on the detected intake air mass, and an average engine speed in a predetermined period based on the detected engine speed. Average rotation speed calculation means, cumulative fuel mass calculation means for calculating a cumulative fuel mass in a predetermined period based on the fuel mass detected by the fuel mass detection means, average rotation speed of the engine and cumulative intake air in the predetermined period An exhaust temperature estimating means for estimating the exhaust temperature based on the mass, and an exhaust temperature based on the cumulative intake air mass, the cumulative fuel mass, the exhaust temperature, and the specific heat of the exhaust. Enthalpy calculation means for calculating enthalpy of equipped with an exhaust heat quantity calculating means for calculating the amount of heat of the exhaust based on the enthalpy of the computed evacuated by the enthalpy calculation means.

[0005] In such exhaust heat arithmetic unit to a second aspect of the invention, the enthalpy calculation means, means for calculating the enthalpy H _n by the following equation _{(1) H n = (SG} an + G Fn) × t E × c p ··· (1) SG _an: cumulative intake air mass during a predetermined period G _Fn: cumulative fuel mass t _E: a specific heat at constant pressure: exhaust temperature c _p.

In the exhaust heat quantity computing device according to the third aspect of the present invention, as shown in FIG. 2, the engine is an air-fuel ratio controlled to a target air-fuel ratio, and intake air mass detection for detecting intake air mass to the engine is performed. Means, engine speed detecting means for detecting the engine speed, cumulative intake air mass calculating means for calculating a cumulative intake air mass in a predetermined period based on the detected intake air mass, and the detected engine Average rotation speed calculation means for calculating the average rotation speed of the engine in a predetermined period based on the rotation speed, and exhaust temperature estimation means for estimating the exhaust temperature based on the average rotation speed of the engine and the cumulative intake air mass in the predetermined period An enthalpy calculating means for calculating an enthalpy of exhaust gas based on the target air-fuel ratio, cumulative intake air mass in a predetermined period, exhaust gas temperature, and specific heat of exhaust gas; An exhaust heat quantity calculating means for calculating the amount of heat of the exhaust based on the enthalpy of the exhaust gas calculated by the peak calculating means, with a.

In the exhaust heat quantity computing device according to the invention of claim 4, the enthalpy computing means computes the enthalpy H _n by the following equation (2): H _n = SG _an (1+ (1 / target air-fuel ratio) _{) × t E × c p ···} (2) SG an: cumulative intake air mass t _E in a predetermined period: a specific heat at constant pressure: exhaust temperature c _p.

In the exhaust heat quantity computing device according to the fifth aspect of the present invention, the exhaust temperature estimating means is configured to estimate the exhaust temperature by using a look-up table. In the exhaust gas heat quantity computing device according to the invention of claim 6, the specific heat of the exhaust gas is a value when the exhaust gas components are represented by carbon dioxide, water and nitrogen. In the exhaust heat quantity computing device according to the invention of claim 7, the exhaust temperature is set to the exhaust temperature of the front tube inlet or the manifold catalyst inlet.

In the exhaust heat quantity computing device according to the invention of claim 8, the predetermined period is a period in which all cylinders burn at least once.

[0010]

According to the structure of the exhaust heat quantity computing device of the first aspect of the present invention, the intake air mass to the engine, the engine speed and the fuel mass are detected, and the accumulated intake air mass in the predetermined period and the engine The heat quantity of the exhaust gas is calculated by calculating the average rotation speed and the cumulative fuel mass, further estimating the exhaust gas temperature, and calculating the enthalpy of the exhaust gas based on these.
Since the exhaust heat quantity is calculated in this way, the exhaust heat quantity is not affected by the change in the exhaust flow rate, so that no error occurs in the exhaust heat quantity.

According to the configuration of the exhaust heat quantity computing device of the second aspect of the invention, specifically, the enthalpy H _n is the cumulative intake air mass SG _an , the cumulative fuel mass G _Fn , the exhaust temperature t _E ,
It is calculated from the constant pressure specific heat c _p by the above equation (1). According to the configuration of the exhaust heat quantity computing device of the third aspect of the present invention, in the engine in which the air-fuel ratio is controlled to the target air-fuel ratio, the stoichiometric air-fuel ratio is used instead of calculating the cumulative fuel mass in the predetermined period. Can be calculated, and since the air-fuel ratio is constant, the enthalpy of the exhaust gas can be easily calculated.

According to the configuration of the exhaust heat quantity computing device of the fourth aspect of the present invention, specifically, in an engine in which the air-fuel ratio is controlled to the target air-fuel ratio, the enthalpy H _n is the target air-fuel ratio, the cumulative intake air mass SG _{From an} , exhaust temperature t _E , constant pressure specific heat c _p ,
It is calculated by the equation (2). According to the exhaust heat quantity computing device of the invention of claim 5, the exhaust temperature is estimated by using the look-up table based on the average engine speed and the cumulative intake air mass in the predetermined period. It is possible to easily estimate the exhaust temperature.

According to the configuration of the exhaust heat quantity computing device of the sixth aspect of the present invention, since the constant pressure specific heat of carbon dioxide, water and nitrogen is large, these can be represented as the specific heat of the exhaust. According to the configuration of the exhaust heat calculation device of the invention of claim 7, the exhaust temperature is set to the exhaust temperature of the front tube inlet or the manifold catalyst inlet, so that the estimation accuracy of the catalyst inlet temperature is improved.

According to the configuration of the exhaust heat quantity computing device of the eighth aspect of the present invention, since the predetermined period is a period in which all the cylinders burn at least once, there is no influence of variations among the cylinders.

[0015]

Embodiments of the present invention will be described below with reference to FIGS. First, the first embodiment will be described. FIG.
FIG. 1 is a diagram showing a system of this embodiment. Intake air is
It is supplied into the engine 1 through an intake passage 2 of the engine 1. The intake passage 2 is provided with an air flow meter 3 for detecting the intake air mass. Fuel is supplied into the engine 1 by the injector 4 and ignited by the spark plug 5. The engine 1 is provided with a crank angle sensor 6 that detects the rotation speed of the engine 1, and a cooling water temperature sensor 7 that detects the cooling water temperature of the engine 1.

The exhaust passage 8 has a pre-catalyst 9 and a main catalyst.
10 are installed. In this embodiment, in order to reduce NO _X , an EGR passage 12 is arranged by connecting the downstream side of the throttle valve 11 of the intake passage 2 and the upstream side of the pre-catalyst 9 of the exhaust passage 8 to the EGR passage 12. A step motor type EGR control valve 13 for adjusting the EGR amount is provided, and an exhaust pressure sensor 14 for detecting the exhaust pressure is provided.

The sensor signals from the air flow meter 3, the crank angle sensor 6, the cooling water temperature sensor 7, and the exhaust pressure sensor 14 are input to the control unit 15, which drives each actuator based on these sensor signals. When a failure occurs, the warning light 16 is turned on to display the failure. Further, the control unit 15 has a built-in software for calculating the exhaust heat amount.

Next, the operation of the control unit 15 is shown in FIG.
A description will be given based on the flowchart. This routine is executed every 10 ms. Step ("S" in the figure)
1), the intake air mass G _an (g / 10 ms) is detected by the air flow meter 3.
This step corresponds to the intake air mass detecting means.

In step 2, a predetermined period, for example 100 mse
The cumulative intake air mass SG _an between c is calculated based on the following equation. SG _an = (G _a1 + G _a2 + ... + G _an ) (n = 10) In order to eliminate the influence of variations among the cylinders, the predetermined period is burned at least once in all cylinders at any rotation speed. Set to do. If the maximum rotation speed is 6000 rpm and four cylinders, a period of 20 msec or more is required, but if the period for obtaining the cumulative value is too long, the responsiveness will deteriorate.
sec is appropriate.

This step corresponds to the cumulative intake air mass calculating means. In step 3, the crank angle sensor 6 detects the rotation speed N _n of the engine 1. This step corresponds to the engine speed detecting means. In step 4, 100m
The average rotation speed N _nAV of the engine 1 during sec is calculated.

N _nAV = (N ₁ + N ₂ + ... + N _n ) /
n (n = 10) This step corresponds to the average rotation speed calculation means. In step 5, the basic fuel mass T _pn (g) injected and supplied to the engine
Is calculated based on the following equation. T _pn = K · Q _an / N _n (K is a constant) This step corresponds to the fuel mass detection means.

In step 6, the cooling water temperature sensor 7 detects the cooling water temperature T _Wn . In step 7, the coolant temperature correction value K _TW of the basic fuel mass T _pn is calculated from the detected coolant temperature T _Wn.
Ask for. FIG. 5 is a diagram showing an example of _{obtaining the} water temperature correction value K _TW , and the water temperature correction value K _TW increases as the water temperature decreases. In step 8, the fuel mass T _En is calculated based on the following equation.

T _En = T _pn × K _{TW In} step 9, the cumulative fuel mass G _Fn is calculated based on the following equation. G _Fn = (T _E1 · N ₁ + ... + T _En · N _n ) / 6000 This step corresponds to the cumulative fuel mass calculation means. In step 10, the average rotation speed N _{nAV for} 100 msec and (SG _an /
N _nAV ) and the exhaust temperature t _E based on a look-up table as shown in FIG. 6, for example. The exhaust temperature t _E is estimated by the operating conditions of the engine 1, and the operating conditions of the engine 1 are the average speed N _nAV and (SG _an /
N _nAV ). This look-up table is used to estimate the exhaust temperature t _E in order to estimate the average speed N
It is a table previously obtained from _nAV and (SG _an / N _nAV ).

This step corresponds to the exhaust temperature estimation means. In step 11, the enthalpy H _n is calculated by multiplying the sum of the cumulative intake air mass SG _an and the cumulative fuel mass G _{Fn by} the exhaust temperature t _E and the constant pressure specific heat c _p . The calculation formula is as follows. H _n = (SG _an + G _Fn ) × t _E × c _p Note that the constant pressure specific heat of the exhaust gas c _p is equal to carbon dioxide (C
O ₂ ), water (H ₂ O), and nitrogen (N ₂ ) are represented as a sum in accordance with the mass ratio of the constant pressure specific heat of each exhaust component. carbon dioxide
Since the constant pressure specific heats of (CO ₂ ), water (H ₂ O) and nitrogen (N ₂ ) are large, the sum of these constant pressure specific heats corresponding to the mass ratio is approximately the exhaust gas specific heat c
_v .

This step corresponds to the enthalpy calculation means. According to this configuration, the cumulative intake air mass SG _an and the cumulative fuel mass G _Fn are added, and the exhaust temperature t
By calculating the enthalpy H _n of the exhaust by multiplying _E and the constant pressure specific heat c _p, it is possible to calculate the heat quantity of the exhaust gas. Since the heat of exhaust gas is calculated in this way,
The heat quantity of the exhaust gas is not affected by the change in the flow rate of the exhaust gas, and the heat quantity of the exhaust gas does not have an error. Therefore, the heat quantity of the exhaust gas can be calculated accurately and easily.

Next, the second embodiment will be described. This is for calculating the enthalpy in a system that performs lambda control with the air-fuel ratio A / F as stoichiometry. FIG. 7 is a system diagram of the second embodiment. The difference from the system of the first embodiment is that the oxygen sensor 21 is mounted in the exhaust passage 8 and the control unit 15
Inputs the sensor signal of the oxygen sensor 21 and outputs the air-fuel ratio A / F
This is the point where lambda control with stoichiometry is performed.

Next, the operation of the second embodiment will be described based on the flowchart of FIG. It should be noted that steps that are the same as those in the flowchart of FIG. 4 are denoted by the same reference numerals and description thereof will be omitted. In step 21, the oxygen sensor 21
Measure the output value VO ₂ of. In step 22, the output value VO
Compare ₂ with the comparison value SL.

When the output value VO ₂ exceeds the comparison value SL, the air-fuel ratio A / F is rich, so the routine proceeds to step 23, where the correction coefficient α _n is reduced based on the following equation. Since the air-fuel ratio A / F when α _n = α _n-1 -Δα output value VO ₂ is less than the comparison value SL is lean, the process proceeds to step 24, to increase the correction coefficient alpha _n based on the following equation.

Α _n = α _n-1 + Δα In step 25, the fuel mass T _En is calculated based on the following equation. T _En = T _pn × K _TW × α _{n At} step 26, the stoichiometric air-fuel ratio A / F = 14.6 is used to calculate the cumulative fuel mass G _Fn based on the following equation.

[0030] In G _Fn = SG _an /14.6 step 27, the enthalpy H _n, the cumulative intake air mass SG _an,, the stoichiometric air-fuel ratio A / F = 14.6, calculates by multiplying the exhaust gas temperature t _E and the constant pressure specific heat c _p . The calculation formula is as follows. According to _{H n = SG an · (1+} (1 / 14.6)) × t E × c p such a configuration, the lambda for the A / F stoichiometric
In the control system, the air-fuel ratio A / F is controlled to the stoichiometric air-fuel ratio and is constant, so that the enthalpy H _n can be easily calculated.

In the second embodiment, the air-fuel ratio A / F is set to the stoichiometric air-fuel ratio, but the present invention is not limited to this, and it can be applied to all the lean air-fuel ratio control to the target air-fuel ratio.

[0032]

As described above, according to the exhaust heat quantity computing device of the first aspect of the present invention, since the exhaust heat quantity is calculated, it is not affected by the change in the flow velocity of the exhaust gas. Does not occur, and the amount of exhaust heat can be easily calculated.

According to the exhaust heat quantity computing device of the second aspect of the present invention, the enthalpy H _n is calculated as the cumulative intake air mass S
G _an,, cumulative fuel mass G _Fn, exhaust temperature t _E, specific heat at constant pressure c _p
It can be calculated from the above equation (1). According to the exhaust heat calculation device of the third aspect of the present invention, in an engine in which the air-fuel ratio is controlled to the target air-fuel ratio, the stoichiometric air-fuel ratio is used to calculate the exhaust enthalpy instead of calculating the cumulative fuel mass in a predetermined period. Since the air-fuel ratio is constant, the enthalpy of the exhaust gas can be easily calculated.

According to the exhaust heat quantity computing device of the fourth aspect of the present invention, in an engine in which the air-fuel ratio is controlled to the target air-fuel ratio, the enthalpy H _n is the target air-fuel ratio, the cumulative intake air mass S
G _an,, exhaust temperature t _E, the constant pressure specific heat c _p, wherein (2) can be calculated by the equation. According to the exhaust heat quantity computing device of the fifth aspect of the invention, the exhaust temperature can be easily estimated.

According to the exhaust heat quantity computing device of the sixth aspect of the present invention, since the constant pressure specific heat of carbon dioxide, water and nitrogen is large, these can be represented as the specific heat of the exhaust gas. According to the exhaust heat quantity computing device of the seventh aspect, the exhaust temperature is set to the exhaust temperature of the front tube inlet or the manifold catalyst inlet, so that the estimation accuracy of the catalyst inlet temperature is improved.

According to the exhaust heat quantity computing device of the eighth aspect of the present invention, the influence of the variation between the cylinders is eliminated.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram showing a configuration of a first invention.

FIG. 2 is a claim correspondence diagram showing a configuration of a second invention.

FIG. 3 is a system diagram of the first embodiment of the present invention.

FIG. 4 is a flowchart showing the operation of FIG.

5 is a characteristic diagram showing the relationship between the water temperature and the correction value of the engine of FIG.

6 is a characteristic diagram showing the relationship between the operating conditions of the engine of FIG. 3 and the exhaust temperature.

FIG. 7 is a system diagram of a second embodiment of the present invention.

8 is a flowchart showing the operation of FIG.

[Explanation of symbols]

 1 Engine 3 Air flow meter 6 Crank angle sensor 7 Cooling water temperature sensor 15 Control unit 21 Oxygen sensor

Claims (8)

[Claims] 1. An intake air mass detecting means for detecting an intake air mass to an engine, an engine speed detecting means for detecting an engine speed, and a fuel mass injected and supplied to the engine at regular time intervals. A fuel mass detection means, a cumulative intake air mass calculation means for calculating a cumulative intake air mass in a predetermined period based on the detected intake air mass, and an engine average in a predetermined period based on the detected engine speed. Average rotation speed calculation means for calculating the rotation speed, cumulative fuel mass calculation means for calculating the cumulative fuel mass in a predetermined period based on the fuel mass detected by the fuel mass detection means, and average rotation of the engine in the predetermined period An exhaust temperature estimating means for estimating an exhaust temperature based on a number and a cumulative intake air mass, and a ratio of the cumulative intake air mass, the cumulative fuel mass, the exhaust temperature, and the exhaust gas. An enthalpy calculation means for calculating exhaust gas enthalpy based on heat, and an exhaust heat quantity calculation means for calculating exhaust gas heat quantity based on the exhaust gas enthalpy calculated by the enthalpy calculation means. Exhaust heat calculation device. 2. The enthalpy calculating means is defined by the following equation (1).
The enthalpy H _n means calculates the _{H n = (SG an + G} Fn) × t E × c p ··· (1) SG an: Cumulative intake air mass during a predetermined period G _Fn: Cumulative fuel mass t _E: exhaust gas temperature c _p: exhaust heat calculation device according to claim 1, characterized in that the specific heat at constant pressure. 3. An engine whose air-fuel ratio is controlled to a target air-fuel ratio, wherein intake air mass detection means for detecting intake air mass to the engine, engine speed detection means for detecting engine speed, and Cumulative intake air mass calculating means for calculating a cumulative intake air mass in a predetermined period based on the detected intake air mass, and average rotation for calculating an average engine speed in the predetermined period based on the detected engine speed. Number calculation means, exhaust temperature estimation means for estimating exhaust temperature based on the average engine speed and cumulative intake air mass in the predetermined period, the target air-fuel ratio, cumulative intake air mass in the predetermined period,
An enthalpy calculating means for calculating the enthalpy of the exhaust based on the exhaust temperature and the specific heat of the exhaust, and an exhaust heat quantity calculating means for calculating the heat quantity of the exhaust based on the enthalpy of the exhaust calculated by the enthalpy calculating means are provided. An exhaust heat quantity computing device characterized by the above. 4. The enthalpy calculation means is defined by the following equation (2).
The enthalpy H means _{H n = SG an · (1+} (1 / target air-fuel ratio)) _n calculates a _{× t E × c p ··· (} 2) SG an: Cumulative intake air mass in a predetermined period t _E: exhaust temperature c _p: exhaust heat calculation device according to claim 3, characterized in that the specific heat at constant pressure. 5. The exhaust heat quantity computing device according to claim 1, wherein the exhaust gas temperature estimating means is configured to estimate the exhaust gas temperature by using a look-up table. 6. The specific heat of the exhaust gas is such that the exhaust gas component is carbon dioxide,
The exhaust calorific value computing device according to any one of claims 1 to 5, wherein the value is a value represented by water and nitrogen. 7. The exhaust heat quantity computing device according to claim 1, wherein the exhaust temperature is set to an exhaust temperature at a front tube inlet or a manifold catalyst inlet. 8. The exhaust heat quantity computing device according to claim 1, wherein the predetermined period is a period in which all cylinders burn at least once.