JP4513416B2 - Apparatus for estimating catalyst temperature or gas temperature in the vicinity of catalyst and method for estimating the same - Google Patents

Description

  The present invention relates to estimation of a catalyst temperature of an exhaust purification catalyst provided in an exhaust passage of an engine or a gas temperature in the vicinity of the catalyst.

An exhaust gas purification catalyst for removing HC, CO, and NOx in the exhaust gas is provided in the exhaust passage of the engine. Since the purification efficiency of the exhaust purification catalyst is affected according to the catalyst temperature, it is necessary to monitor whether the catalyst temperature is within a predetermined temperature range in order to obtain the optimum conversion efficiency. In the apparatus described in Patent Document 1, the catalyst temperature is estimated based on a plurality of engine parameters including the engine speed and the engine load. According to this method, there is no need to attach a temperature sensor to the catalyst in order to obtain the catalyst temperature, and there is an advantage that estimation of the catalyst temperature can be realized at low cost.
JP 2002-138822 A

  However, in the above prior art, the catalyst temperature is directly estimated from a plurality of engine parameters including the engine rotation speed and the engine load. Therefore, the intermediate process from the engine cylinder to the catalyst is not considered, and the catalyst temperature accuracy is not considered. There was a problem of low.

  The present invention has been made in view of such technical problems, and an object of the present invention is to provide an apparatus and method for estimating the catalyst temperature or the gas temperature in the vicinity of the catalyst with high accuracy.

The gas temperature in the cylinder part of the engine is estimated based on the operating state of the engine, and at the inlet of the catalyst based on the estimated gas temperature in the cylinder part and the heat transfer characteristics of the gas flow path from the cylinder part to the catalyst. The gas temperature is estimated, and the catalyst temperature or the gas temperature in the vicinity of the catalyst is calculated based on the estimated gas temperature at the catalyst inlet and the response characteristics of the catalyst temperature or the gas temperature in the vicinity of the catalyst with respect to the gas temperature at the catalyst inlet. presume.
Further, the second estimating means estimates the gas temperature at the inlet of the catalyst based on the estimated gas temperature of the cylinder portion and the heat transfer characteristic considering the outside air temperature of the gas flow path from the cylinder portion to the catalyst. To do.

  Exhaust gas generated by combustion in the engine flows into the catalyst via an exhaust manifold or the like connecting the engine and the catalyst, and affects the catalyst temperature or the gas temperature in the vicinity of the catalyst. According to the present invention, instead of directly obtaining the catalyst temperature from the parameter indicating the operating state of the engine, the gas temperature at the cylinder portion of the engine is estimated, and this is used to estimate the gas temperature at the catalyst inlet. Is used to estimate the catalyst temperature or the gas temperature in the vicinity of the catalyst, that is, the estimation is performed by dividing the engine to the catalyst into multiple parts, so that the exhaust gas affects the catalyst temperature or the gas temperature in the vicinity of the catalyst. Is taken into consideration, and the catalyst temperature or the gas temperature in the vicinity of the catalyst can be estimated with high accuracy.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Although the description here assumes that the catalyst temperature is estimated, the “catalyst temperature” in the following description can be used as it is for estimating the catalyst temperature if it is read as “the gas temperature in the vicinity of the catalyst”. Alternatively, since the gas temperature in the vicinity of the catalyst is close to the catalyst temperature, the estimated catalyst temperature can be used as it is as the gas temperature in the vicinity of the catalyst. Therefore, only the estimation of the catalyst temperature will be described here, and the description of the gas temperature estimation in the vicinity of the catalyst will be omitted.

  FIG. 1 shows a schematic configuration of an engine system to which a catalyst temperature estimating apparatus and method according to the present invention are applied. The air introduced into the cylinder 4 through the intake passage 2 and the intake port 3 is mixed with the fuel injected from the fuel injection valve 5 provided in the intake port 3 and compressed by the rising piston 6. Thereafter, the ignition plug 7 ignites and burns. The gas expanded by combustion works to push down the piston 6 and is then discharged to the exhaust manifold 9 through the exhaust port 8 by the piston 6 rising again. The intake port 3 and the exhaust port 8 are opened and closed at a predetermined timing by an unillustrated intake valve and exhaust valve, respectively.

  An air flow meter 11 for detecting the intake air amount and an electronically controlled throttle valve 14 for adjusting the intake air amount of the engine 1 by controlling the opening degree according to the accelerator operation amount are provided in the intake passage 2. Yes. The intake air amount detected by the air flow meter 11 is input to an engine controller (not shown) as a signal indicating the load of the engine 1.

  The exhaust manifold 9 is provided with a temperature sensor 12 for detecting the outside air temperature in the vicinity of the outer wall, and the detected value is input to the catalyst temperature estimating device 20. Further, a three-way catalyst 13 for purifying HC, CO, and NOx in the exhaust gas is provided at the outlet of the exhaust manifold 9, and the exhaust from the engine 1 is further purified by the three-way catalyst 13 and then further downstream. The exhaust gas flows into the exhaust passage 10 and is discharged to the atmosphere via an underfloor catalyst (not shown).

  In addition to the temperature of the outside air in the vicinity of the outer wall of the exhaust manifold 9 detected by the temperature sensor 12, the catalyst temperature estimation device 20 receives the rotational speed, throttle valve opening, and fuel injection amount of the engine 1 from an engine controller (not shown). Various signals indicating the operating state of the engine 1 are input. The catalyst temperature estimation device 20 estimates the gas temperature of the cylinder portion of the engine 1 based on these inputted various signals. Then, the gas temperature at the inlet of the exhaust manifold 9 is set as the gas temperature at the cylinder portion, and the gas temperature at the outlet of the exhaust manifold 9 is estimated based on this and the heat transmissivity of the exhaust manifold 9. Further, the catalyst temperature estimating device 20 is based on the estimated gas temperature at the outlet of the exhaust manifold 9, that is, the gas temperature at the inlet of the catalyst 13, and the response characteristic of the temperature of the catalyst 13 corresponding thereto, (the catalyst bed temperature (catalyst). Temperature).

  In this embodiment, the value detected by the temperature sensor 12 is directly input to the catalyst temperature estimating device 20, but this is once input to the engine controller, and the catalyst temperature estimating device 20 inputs this value via the engine controller. You may make it obtain. Further, instead of providing the temperature sensor 12, the temperature in the vicinity of the outer wall of the exhaust manifold may be estimated by referring to a map from other parameters, and the estimated value may be used instead of the detected value. Further, the catalyst temperature estimating device 20 may not be an independent device from the engine controller, but the catalyst temperature estimating device 20 may be incorporated in the engine controller. In this case, the detected value of the temperature sensor 12 is the catalyst temperature estimating device. To the engine controller.

  Next, the contents of the catalyst temperature estimation performed by the catalyst temperature estimation device 20 will be described in detail.

  FIG. 2 is a flow showing the contents of the catalyst temperature estimation process. This flow is repeated at predetermined time intervals, or is executed in the catalyst temperature estimating device 20 at a timing when it is necessary to obtain the catalyst temperature. As shown in this flow, the estimation of the catalyst temperature is roughly divided into a stage for estimating the gas temperature of the cylinder portion of the engine 1 (step S1), a reading of the heat permeability K of the exhaust manifold 9 (step S2), A step of estimating the gas temperature at the outlet of the exhaust manifold 9 (inlet of the catalyst 13) based on the heat permeability K and the estimated gas temperature of the cylinder portion (step S3), the gas temperature and the catalyst temperature at the inlet of the catalyst 13 The transfer function G (q) is read out (Step S4), and the catalyst temperature is estimated based on the transfer function G (q) and the estimated gas temperature at the catalyst inlet (Step S5). . Therefore, in the following description, the catalyst temperature estimation will be described in each stage.

1. Estimation of gas temperature in the cylinder part (first estimation means)
Gas temperature theta ₁ of the cylinder portion, as shown in FIG. 3, the cylinder portion as the waste heat amount Q increases gas temperature theta ₁ is increased, and the cylinder portion relative increment of the waste heat Q gas temperature theta ₁ of Based on the relationship that the increment gradually decreases, the following equation (1):

θ _mx : exhaust gas temperature at maximum calorific value θ _mn : exhaust gas temperature at zero calorific value k: sensitivity of calorific value to exhaust gas temperature Q: estimated by waste heat quantity. Equation (1) is a regression equation of the characteristics shown in FIG. The exhaust gas temperature θ _mx at the maximum amount of waste heat, the exhaust gas temperature θ _mn at the time of zero waste heat amount, and the sensitivity k of the waste heat amount to the exhaust gas temperature are obtained in advance by experiments. According to this estimation method, the gas temperature θ ₁ of the cylinder portion can be estimated regardless of whether the engine 1 is performing fuel cut.

  The waste heat amount Q is a value obtained by subtracting the shaft work W, which is the work extracted from the engine 1, from the fuel heat generation amount Q ′, which is the heat generation amount by burning the fuel (Q = Q′−W). It can be obtained by calculation based on the rotational speed, the fuel injection amount, and the like. The fuel heating value Q 'is expressed by the following equation (2):

CO2: CO ₂ ratio in exhaust gas CO: CO ratio in exhaust gas Hf: Lower calorific value of fuel H _CO : Lower calorific value of _CO Hv: Late heat of vaporization of fuel mf ′: Fuel flow rate (fuel injection amount)
The axis work W can be calculated by the following equation (3):

W ′: illustrated work Wploss ′: pump work Wcross ′: calculation can be performed by cooling loss.

  The illustrated work W ′ and pump work Wploss ′ in the expression (3) are expressed by the following expressions (4) and (5):

Pi: Average effective pressure V0: Displacement N: Engine speed

Pex: Exhaust pressure Pin: Intake pressure VIVC: It can be calculated from the stroke volume from the bottom dead center until the intake valve closes, and the cooling loss Qcross can be calculated from the inlet / outlet water temperature of the engine 1 and the coolant flow rate.

Here, although so as to estimate the gas temperature theta ₁ of the cylinder portion on the basis of the gas temperature theta ₁ of the relationship between the waste heat of the cylinder portion of the engine 1, using other techniques to estimate the gas temperature theta ₁ of the cylinder portion It is also possible. For example, the gas temperature at the exhaust port outlet of the engine 1 (= gas temperature in the cylinder portion) when the rotation speed and load of the engine 1 are changed is measured by experiment, and the engine rotation speed as shown in FIG. An exhaust temperature map that prescribes the relationship of the gas temperature of the cylinder portion with respect to the load (fuel injection amount) is prepared in advance, and the gas temperature θ of the cylinder portion is obtained by referring to the exhaust temperature map based on the rotational speed and load of the engine 1. ₁ may be estimated. In the exhaust temperature map shown in FIG. 4, the fuel injection amount is used as the load of the engine 1, but the intake air amount, the throttle valve opening, the accelerator operation amount, and the like may be used instead of the fuel injection amount. Alternatively, a sensor for detecting the gas temperature at the exhaust port outlet of the engine 1 is attached to the exhaust port outlet of the engine 1, and the gas temperature at the exhaust port outlet is directly detected using this sensor, and this is detected as the gas in the cylinder portion. It is good also as temperature.

2. Estimating the gas temperature at the exhaust manifold outlet (catalyst inlet) (second estimation means)
The gas temperature θ ₂ at the outlet of the exhaust manifold 9 (inlet of the catalyst 13) is the same as that in 1. above. The gas temperature θ ₁ at the cylinder portion estimated by the process described in the above is regarded as the gas temperature at the inlet of the exhaust manifold 9 and is estimated based on the gas temperature θ ₁ at the inlet of the exhaust manifold 9 and the heat transmissivity K of the exhaust manifold 9. .

Further description will be given with reference to FIG. FIG. 5 is a conceptual diagram of the exhaust manifold 9, in which the left side is connected to the exhaust port 8 of the engine 1 and the right side is connected to the three-way catalyst 13. The heat transmissivity K is an index representing the ease of heat transfer, and is a total of the heat conduction of the object body and the heat transfer of the object surface. The unit of the heat transmissivity K is [W / m ² K], and is expressed by the amount of heat per unit area and unit temperature. The heat transfer coefficient is K, the heat transfer coefficient between the exhaust gas and the exhaust manifold inner wall is α1, the heat transfer coefficient between the exhaust manifold outer wall and the outside air near the exhaust manifold outer wall is α2, and the heat conductivity inside the exhaust manifold is Assuming λ, the following equation (6):

Furthermore, the specific heat of the exhaust gas is c [J / kgK], the density of the exhaust gas is ρ [kg / m ³ ], the temperature of the outside air near the exhaust manifold outer wall θf [° C.], and the circumference of the exhaust manifold 9 P [m] and the length of the exhaust manifold 9 in the exhaust gas flow path direction is L [m], the heat transmissivity K is expressed by the following equation (7):

Can be represented by

  The heat transmissibility K changes according to the temperature of the gas flowing into the exhaust manifold 9 and the engine load (for example, intake air amount). Therefore, here, the temperature of the gas flowing into the exhaust manifold 9 and the engine load are changed, and the gas temperature at the outlet of the exhaust manifold is experimentally measured, and the temperature of the gas flowing into the exhaust manifold 9 and the heat transmissivity K with respect to the engine load are measured. And a map as shown in FIG. 6 is prepared in advance. When the gas temperature is actually estimated, the instantaneous heat transmissivity K is obtained by referring to this map based on the gas temperature and the engine load. As shown in FIG. 6, the higher the temperature of the gas flowing into the exhaust manifold 9 and the greater the temperature difference from the vicinity of the outer wall of the exhaust manifold, the easier the heat is transmitted. Therefore, the heat transmissivity K takes a larger value. Become.

When the heat transmissibility K is obtained, the gas temperature θ ₂ at the outlet of the exhaust manifold 9 is calculated by the following equation (8) based on the temperature θf of the outside air near the outer wall of the exhaust manifold 9 detected by the temperature sensor 12 and the heat transmissivity K. ):

Calculate by

  In the above method using the heat transmissibility K, the delay between the gas temperature at the inlet of the exhaust manifold 9 and the gas temperature at the outlet thereof is not considered, but the gas temperature at the inlet of the exhaust manifold 9 and the gas temperature at the outlet thereof are not considered. This is not a problem because there is almost no delay between the two.

3. Estimation of catalyst carrier bed temperature (catalyst temperature) (third estimation means)
As for the catalyst temperature θ ₃ , the gas function θ _{2 at the} outlet of the exhaust manifold, that is, the transfer function G (q) between the gas temperature θ ₂ at the inlet of the catalyst 13 and the catalyst temperature θ ₃ is obtained in advance based on the experimental results. Calculation is performed by multiplying the gas function θ ₂ at the inlet of the catalyst 13 by this transfer function G (q). Various identification methods have been proposed as a method for obtaining a transfer function of a one-input one-output system, and this embodiment uses an ARX model. Specifically, assuming that the gas temperature θ ₂ at the inlet of the catalyst 13 is input u (t) and the catalyst temperature θ ₃ is output y (t), the following equation (9):

H (q) e (t): Disturbance na, nb: Order of polynomial nk: Creates an ARX model represented by input / output delay. Expression (9) is expressed using a linear difference equation representing the ARX model and the shift operator q, and B (q) / A (q) corresponds to the transfer function G (q).

The reason why the ARX model is adopted as the system identification method is that it is advantageous in identifying the system, that is, in reducing the calculation load when obtaining the transfer function G (q) because the ARX model is the simplest model. This is because the solution can always be obtained by the method of least squares. In actually obtaining the transfer function G (q), the gas temperature θ ₂ at the inlet of the catalyst 13 is changed under the condition that the rotational speed of the engine 1 and the load (for example, the intake air amount) are constant, The state of change of the catalyst temperature θ ₃ at that time is actually measured, and the transfer function G (q) is obtained based on this measurement data.

The catalyst temperature θ ₃ is expressed by the following formula (10):

As shown in 2. above. Calculation is performed by multiplying the gas temperature θ ₃ at the inlet of the catalyst 13 calculated by the calculation process described in the above, by a transfer function G (q) obtained in advance using the ARX model. The transfer function G (q) is obtained in advance based on the experimental results by the above method based on the experimental results and stored in the memory of the catalyst temperature estimating device 20, and when the catalyst temperature is estimated, it is simply read and used. Therefore, the calculation load at the time of estimation is low, and the catalyst temperature is estimated quickly.

Since there is a relationship between time delay and dead time between the gas temperature θ ₂ and the catalyst temperature θ ₃ at the inlet of the catalyst 13, the transfer function G (q) is obtained by system identification using the ARX model in this way. By doing so, time delay and dead time can be expressed, and the catalyst temperature θ ₃ can be estimated with high accuracy.

Strictly speaking, since the transfer function G (q) changes when the rotational speed and load (for example, intake air amount) of the engine 1 change, the same transfer function G (q) is used for all operating states. In such a case, the estimation error is slightly increased. Therefore, when a higher estimation precision is required, the rotational speed of the engine 1, a G (q) the transfer function according to the load preparing a plurality leave mapped, when estimating the catalyst temperature theta ₃ is The transfer function G (q) corresponding to the rotation speed and load of the engine 1 may be read out and used for the estimation calculation. By switching the transfer function G (q) according to the operating state, the catalyst temperature θ ₃ can be estimated with higher accuracy.

Furthermore, although the system is identified using the ARX model here, the catalyst temperature θ ₃ is determined by using a transfer function set without using the ARX model, for example, a combination of a first-order lag and dead time as a transfer function. Alternatively, the estimation may be performed, or another estimation method may be employed as a method for estimating the catalyst temperature. However, the above 2. Since the dead time cannot be expressed well by the calculation method based on the heat transmissivity described in (1), it is not suitable for estimating the catalyst temperature θ ₃ .

  Next, the effect by this invention is demonstrated.

According to the present invention, in estimating the temperature of the catalyst 13 or the gas temperature in the vicinity thereof, the gas temperature θ ₁ of the cylinder portion of the engine 1 is estimated based on the operating state of the engine 1 (first estimating means, step S1). ) To estimate the gas temperature θ ₂ at the inlet of the catalyst 13 based on the estimated gas temperature θ ₁ of the cylinder portion and the heat transfer characteristics of the gas flow path from the cylinder portion to the catalyst (second estimating means). Steps S2 and S3), based on the estimated gas temperature θ ₂ at the inlet of the catalyst 13 and the response characteristics of the catalyst temperature to the gas temperature at the inlet of the catalyst 13 or the gas temperature in the vicinity of the catalyst, or the gas temperature in the vicinity of the catalyst θ ₃ is estimated (third estimation means, steps S4 and S5). According to the present invention, the catalyst temperature or the gas temperature in the vicinity of the catalyst is estimated in consideration of the heat transfer characteristics of the exhaust gas flow path and the response characteristics of the catalyst temperature or the gas temperature in the vicinity of the catalyst with respect to the inflowing exhaust gas temperature. It is possible to improve the estimation accuracy of the catalyst temperature or the gas temperature in the vicinity of the catalyst.

The gas temperature θ ₁ of the cylinder portion is estimated based on, for example, the amount of waste heat of the engine 1 and the sensitivity of the amount of waste heat to the gas temperature of the cylinder portion. As a result, the accuracy in estimating the gas temperature in the cylinder portion is increased, and as a result, the accuracy in estimating the catalyst temperature or the gas temperature in the vicinity of the catalyst can be increased. Since the gas temperature in the cylinder portion can be estimated with the same accuracy even during execution, it is possible to maintain high estimation accuracy even during fuel cut. The cylinder portion gas temperature θ ₁ is estimated by preparing a map (exhaust temperature map, FIG. 4) that defines the relationship between the operating state of the engine 1 and the cylinder portion gas temperature in advance. You may make it do. According to this method, it is possible to reduce the calculation load when actually estimating the catalyst temperature or the gas temperature in the vicinity of the catalyst.

As shown in FIG. 1, when the catalyst 13 is provided at the outlet of the exhaust manifold 9, the gas temperature at the inlet of the catalyst 13 is set to the gas temperature θ ₁ of the cylinder portion and the heat permeability K of the exhaust manifold 9. Based on this, the gas temperature θ ₂ at the catalyst inlet is estimated. By using the heat transmissibility K, the gas temperature θ ₂ at the catalyst inlet can be estimated with high accuracy without increasing the calculation load so much, and this can be used to estimate the catalyst temperature or the gas temperature in the vicinity of the catalyst with high accuracy. it can.

Further, when changing the gas temperature theta ₂ at the inlet of the catalyst of the catalyst temperature to the vicinity of the catalyst based on a change in the gas temperature theta _3, the catalyst temperature to the vicinity of the catalyst to the gas temperature theta ₂ at the catalyst inlet gas temperature theta ₃ A transfer function G (q) indicating response characteristics is obtained in advance by experiment, and the estimated gas temperature θ ₂ at the catalyst inlet is multiplied by the transfer function G (q) to obtain the catalyst temperature or the gas temperature θ _{3 in the} vicinity of the catalyst. If estimated, the catalyst temperature or the gas temperature in the vicinity of the catalyst can be estimated with high accuracy without increasing the calculation load during actual estimation. Further, if the transfer function G (q) is obtained using the ARX model, the system identification procedure is relatively simple, and the change in the gas temperature at the catalyst inlet is the catalyst temperature or the gas temperature in the vicinity of the catalyst. It is possible to perform estimation by taking into account the influence of the time delay until delaying and the influence of dead time, and the estimation accuracy can be further improved.

  In the above-described embodiment, the portion from the cylinder portion of the engine 1 to the catalyst is divided into the cylinder portion, the exhaust manifold portion, and the catalyst portion to estimate the catalyst temperature or the gas temperature in the vicinity of the catalyst. The division method is not limited to this, and the division position and the number of divisions may be changed as necessary. For example, in the above embodiment, the gas temperature in the cylinder portion of the engine is used as it is as the gas temperature at the exhaust manifold inlet. Strictly speaking, after leaving the cylinder, it passes through the exhaust port and reaches the exhaust manifold inlet. Since there is a slight temperature drop, the gas temperature may be estimated by dividing the exhaust port portion. In this case, the second estimating means for estimating the gas temperature at the inlet of the catalyst based on the gas temperature of the cylinder portion and the heat transfer characteristic of the gas flow path from the cylinder portion to the catalyst includes the exhaust port portion and the exhaust manifold portion. The gas temperature is estimated in two stages.

  In the above embodiment, the temperature of the catalyst 13 provided at the outlet of the exhaust manifold 9 or the gas temperature in the vicinity of the catalyst is estimated. However, the temperature of the underfloor catalyst or the gas temperature in the vicinity thereof is estimated using the above method. You can also

  INDUSTRIAL APPLICABILITY The present invention can be widely applied to devices and methods that utilize the catalyst temperature of the exhaust purification catalyst or the gas temperature in the vicinity of the catalyst, such as a device that monitors the catalyst temperature and a control device that controls the engine according to the catalyst temperature. .

1 is a schematic configuration diagram of an engine system to which a catalyst temperature estimation device and method according to the present invention are applied. It is the flowchart which showed the content of the catalyst temperature estimation process which a catalyst temperature estimation apparatus performs. It is the characteristic view which showed the relationship between the waste heat amount of an engine, and the gas temperature of a cylinder part. It is an example of the exhaust temperature map which prescribed | regulated the relationship of the gas temperature of the cylinder part with respect to the engine speed and load (fuel injection amount). It is a conceptual diagram of an exhaust manifold. It is an example of the map which prescribed | regulated the relationship between the temperature of the gas which flows in into an exhaust manifold, and the heat transmissivity with respect to an engine load.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 4 Cylinder 5 Fuel injection valve 6 Piston 7 Spark plug 8 Exhaust port 9 Exhaust manifold 10 Exhaust passage 11 Air flow meter 12 Temperature sensor 13 Three-way catalyst 14 Throttle valve 20 Catalyst temperature estimation apparatus

Claims (12)

In an apparatus that is provided in an engine including a catalyst for purifying exhaust gas and estimates the temperature of the catalyst or the gas temperature in the vicinity of the catalyst,
First estimating means for estimating a gas temperature in a cylinder portion of the engine based on an operating state of the engine;
Second estimating means for estimating a gas temperature at an inlet of the catalyst based on the estimated gas temperature of the cylinder part and a heat transfer characteristic of a gas flow path from the cylinder part to the catalyst;
The temperature of the catalyst or the gas temperature in the vicinity of the catalyst is estimated based on the estimated gas temperature at the catalyst inlet and the response characteristic of the temperature of the catalyst to the gas temperature at the inlet of the catalyst or the gas temperature in the vicinity of the catalyst. Third estimating means for
With
The second estimating means is based on the estimated gas temperature of the cylinder portion and a heat transfer characteristic in consideration of the outside air temperature of the gas flow path from the cylinder portion to the catalyst. An apparatus characterized by estimating a gas temperature . The first estimating means is means for estimating a gas temperature of the cylinder portion based on a waste heat amount of the engine and a sensitivity of the waste heat amount to a gas temperature of the cylinder portion.
The apparatus according to claim 1. Prepare in advance a map that defines the relationship between the operating state of the engine and the gas temperature of the cylinder part,
The first estimating means is means for estimating a gas temperature of the cylinder portion by referring to the map based on an operating state of the engine.
The apparatus according to claim 1. The catalyst is provided at the outlet of the exhaust manifold of the engine;
The second estimating means is means for estimating a gas temperature at an inlet of the catalyst based on the estimated gas temperature of the cylinder portion and a heat flow rate of the exhaust manifold.
An apparatus according to any one of claims 1 to 3, characterized in that The transfer function indicating the response characteristic of the temperature of the catalyst to the gas temperature at the inlet of the catalyst or the gas temperature in the vicinity of the catalyst is expressed as the temperature of the catalyst or the vicinity of the catalyst when the gas temperature at the inlet of the catalyst is changed. Obtained in advance based on changes in gas temperature,
The third estimating means is means for multiplying the estimated gas temperature at the inlet of the catalyst by the transfer function to estimate a temperature of the catalyst or a gas temperature in the vicinity of the catalyst;
An apparatus according to any one of claims 1 to 4, characterized in that The transfer function is a transfer function obtained using an ARX model based on a change in the temperature of the catalyst when the gas temperature at the inlet of the catalyst is changed or the gas temperature in the vicinity of the catalyst. The apparatus according to claim 5. In a method applied to an engine having a catalyst for purifying exhaust gas and estimating a temperature of the catalyst or a gas temperature in the vicinity of the catalyst,
A first stage for estimating a gas temperature in a cylinder portion of the engine based on an operating state of the engine;
A second step of estimating a gas temperature at the inlet of the catalyst based on the estimated gas temperature of the cylinder part and a heat transfer characteristic of a gas flow path from the cylinder part to the catalyst;
The temperature of the catalyst or the gas temperature in the vicinity of the catalyst is estimated based on the estimated gas temperature at the catalyst inlet and the response characteristic of the temperature of the catalyst to the gas temperature at the inlet of the catalyst or the gas temperature in the vicinity of the catalyst. And a third stage
The second estimating means is based on the estimated gas temperature of the cylinder portion and a heat transfer characteristic in consideration of the outside air temperature of the gas flow path from the cylinder portion to the catalyst. A method characterized by estimating a gas temperature . The first estimation step is a step of estimating a gas temperature of the cylinder portion based on a waste heat amount of the engine and a sensitivity of the waste heat amount to a gas temperature of the cylinder portion. Item 7. The method according to Item 7. Prepare in advance a map that defines the relationship between the operating state of the engine and the gas temperature of the cylinder part,
8. The method according to claim 7, wherein the first estimating step is a step of estimating a gas temperature of the cylinder portion with reference to the map based on an operating state of the engine. The catalyst is provided at the outlet of the exhaust manifold of the engine;
The second estimating step is a step of estimating a gas temperature at an inlet of the catalyst based on the estimated gas temperature of the cylinder portion and a heat flow rate of the exhaust manifold.
10. A method according to any one of claims 7 to 9, characterized in that The transfer function indicating the response characteristic of the temperature of the catalyst to the gas temperature at the inlet of the catalyst or the gas temperature in the vicinity of the catalyst is expressed as the temperature of the catalyst or the vicinity of the catalyst when the gas temperature at the inlet of the catalyst is changed. Obtained in advance based on changes in gas temperature,
The third estimating step is a step of estimating the temperature of the catalyst or the gas temperature in the vicinity of the catalyst by multiplying the estimated gas temperature at the inlet of the catalyst by the transfer function.
11. A method according to any one of claims 7 to 10, characterized in that The transfer function is a transfer function obtained using an ARX model based on a change in the temperature of the catalyst when the gas temperature at the inlet of the catalyst is changed or in the vicinity of the catalyst. The method according to claim 11.

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