WO2010013365A1

WO2010013365A1 - Catalyst temperature estimation method

Info

Publication number: WO2010013365A1
Application number: PCT/JP2008/072738
Authority: WO
Inventors: 謙一谷岡; 黒木　史宏; 宮本　武司
Original assignee: ボッシュ株式会社
Priority date: 2008-08-01
Filing date: 2008-12-15
Publication date: 2010-02-04

Abstract

A catalyst temperature estimation method which can, even if idle stop control is performed, precisely estimate the temperature of a catalyst to accurately determine the amount of supply of an addition agent. A catalyst temperature estimation method for estimating the temperature of a catalyst placed in an exhaust gas path of an internal combustion engine, in which the temperature of the catalyst is estimated by calculation performed based on the temperature of exhaust gas discharged from the engine, the speed of flow of the exhaust gas, the temperature of outside air, and the speed of flow of the outside air. The calculation is performed considering a change in the temperature of the catalyst during a stop of the engine effected by idle stop control which automatically stops the engine.

Description

Catalyst temperature estimation method

The present invention relates to a catalyst temperature estimation method for estimating the temperature of a catalyst disposed in an exhaust passage of an internal combustion engine. In particular, the present invention relates to a catalyst temperature estimation method for estimating the temperature of a catalyst disposed in an exhaust passage of an internal combustion engine having an idling stop function.

The exhaust gas discharged from an internal combustion engine such as a diesel engine contains nitrogen oxides (hereinafter referred to as “NO _x ”) that may affect the environment. As an exhaust gas purification apparatus used to purify the NO _X, additives unburned fuel and urea water solution or the like on the upstream side of the disposed in an exhaust passage catalyst injection supply, NO in the exhaust gas in the catalyst An exhaust gas purification device that causes _X to undergo a reduction reaction is known.

In such an exhaust purification device, when the amount of additive to be supplied is too large, the additive flows out to the downstream side of the catalyst, while when the amount of additive to be supplied is too small, NO _x flows out to the downstream side of the catalyst. It will be. Therefore, the supply amount of the additive is obtained by calculation so that the amount of the additive to be supplied does not become excessive or insufficient. One factor in calculating the supply amount of the additive is the temperature of the catalyst. For example, the temperature of the catalyst affects the reduction efficiency of NO _{x in} the catalyst. In the case of an exhaust gas purification apparatus that uses an aqueous urea solution as an additive, the temperature of the catalyst also affects the amount of adsorption of ammonia produced from the aqueous urea solution to the catalyst.

Therefore, a catalyst temperature estimation device that can accurately estimate the catalyst temperature has been proposed. More specifically, the catalyst device provided in the exhaust passage of the internal combustion engine, the exhaust temperature sensor for detecting the temperature of the exhaust gas flowing into the catalyst device, and the situation of the outside air that affects the detection result of the exhaust temperature sensor Catalyst temperature estimation configured to include an outside air condition detecting means for detecting or estimating, and a catalyst temperature estimating means for estimating the temperature of the catalyst device based on the detection output of the exhaust temperature sensor and the detection output of the outside air condition detecting means. An apparatus is disclosed (see Patent Document 1).

JP 2002-161793 (full text, full diagram)

By the way, in recent years, an idling stop device for automatically stopping the internal combustion engine during a temporary stop of the vehicle has been used in order to reduce exhaust gas from the internal combustion engine for the purpose of environmental protection and noise prevention. In the case of an internal combustion engine having such an idling stop function, the operation time of the internal combustion engine is restarted before the stop time of the internal combustion engine is relatively short and the temperature of the catalyst becomes equal to the exhaust temperature upstream of the catalyst. There is.
For this reason, in the catalyst temperature estimation device as described in Patent Document 1, if this idling stop function is not taken into consideration, the catalyst temperature is reset when the internal combustion engine is automatically stopped by the idling stop control, and the operation of the internal combustion engine is performed. When restarting, the calculation of the catalyst temperature may be restarted with the temperature of the exhaust gas upstream of the catalyst as the initial value. As a result, an error may occur between the estimated value of the catalyst temperature and the actual catalyst temperature, and the amount of additive added may be excessive or insufficient.

Therefore, the inventors of the present invention have made diligent efforts and found that such a problem can be solved by estimating the catalyst temperature in consideration of the temperature change of the catalyst during the stop of the internal combustion engine by the idling stop control. The present invention has been completed. That is, an object of the present invention is to provide a catalyst temperature estimation method capable of accurately estimating the catalyst temperature and accurately determining the supply amount of the additive even when idling stop control is performed. is there.

According to the present invention, there is provided a catalyst temperature estimation method for estimating the temperature of a catalyst disposed in an exhaust passage of an internal combustion engine, wherein the catalyst temperature includes the temperature of exhaust gas discharged from the internal combustion engine, and the exhaust gas. In consideration of changes in the temperature of the catalyst while the internal combustion engine is stopped by idling stop control, which is estimated by performing calculations based on the flow rate of the engine, the temperature of the outside air, and the flow rate of the outside air. A catalyst temperature estimation method characterized by performing computation is provided, and the above-described problems can be solved.

In carrying out the catalyst temperature estimation method of the present invention, it is preferable to continue the calculation while the internal combustion engine is stopped.

In carrying out the catalyst temperature estimation method of the present invention, the calculation is continued while the internal combustion engine is stopped, and the difference between the temperature of the catalyst calculated by the calculation and the temperature of the exhaust gas upstream of the catalyst is predetermined. Preferably, the calculation is interrupted when the value is within the range, and the calculation is restarted when the operation of the internal combustion engine is resumed.

Further, in carrying out the catalyst temperature estimation method of the present invention, the calculation is continued while the internal combustion engine is stopped, the calculation is interrupted when a predetermined time has elapsed from the stop of the internal combustion engine, and the temperature of the catalyst is Is preferably set to the temperature of the exhaust gas upstream of the catalyst, and then the calculation is restarted.

Further, in carrying out the catalyst temperature estimation method of the present invention, the calculation is interrupted when the internal combustion engine is stopped, and the calculation is restarted after estimating the temperature change of the catalyst while the internal combustion engine is stopped when the operation of the internal combustion engine is resumed. It is preferable.

In carrying out the catalyst temperature estimation method of the present invention, the calculation is interrupted when the internal combustion engine is stopped, and the measurement of the stop time is started. When the operation of the internal combustion engine is resumed, the temperature change of the catalyst corresponding to the stop time is estimated. It is preferable to do.

In carrying out the catalyst temperature estimation method of the present invention, the calculation is interrupted when the internal combustion engine is stopped and the measurement of the stop time is started. When the stop time exceeds a predetermined time, the measurement is stopped and the operation of the internal combustion engine is stopped. When restarting, it is preferable to restart the calculation after setting the temperature of the catalyst to the temperature of the exhaust gas upstream of the catalyst.

According to the catalyst temperature estimation method of the present invention, since the temperature change of the catalyst while the internal combustion engine is stopped by the idling stop control is also taken into consideration, the initial value of the catalyst temperature after the restart of operation may greatly deviate from the actual catalyst temperature. The catalyst temperature can be accurately estimated. Therefore, the supply amount of the additive determined with the catalyst temperature as one factor is accurately calculated, and it is possible to reduce the flow of the additive or NO _x to the downstream side of the catalyst.

In carrying out the catalyst temperature estimation method of the present invention, since the engine switch is on while the internal combustion engine is stopped by the idling stop control, the calculation of the catalyst temperature is continued even when the internal combustion engine is stopped. As a result, the temperature change of the catalyst can be continuously grasped, and an increase in the deviation between the estimated value of the catalyst temperature and the actual catalyst temperature can be prevented.

Further, when carrying out the catalyst temperature estimation method of the present invention, the calculation is stopped when the difference between the estimated value of the catalyst temperature and the exhaust temperature upstream of the catalyst falls within a predetermined range while the internal combustion engine is stopped. Thus, since the temperature of the catalyst after the stop can be predicted to match the exhaust temperature on the upstream side of the catalyst, the value of the exhaust gas temperature on the upstream side of the catalyst is used as the initial value of the catalyst temperature when restarting the operation of the internal combustion engine. To resume the calculation.

In carrying out the catalyst temperature estimation method of the present invention, the calculation is interrupted after a predetermined time has elapsed from the stop of the internal combustion engine, and the exhaust gas temperature on the upstream side of the catalyst is set as the catalyst temperature when the internal combustion engine is restarted. By doing so, waste of battery power can be reduced while suppressing the occurrence of a deviation between the estimated value of the catalyst temperature and the actual catalyst temperature.

In carrying out the catalyst temperature estimation method of the present invention, after the internal combustion engine is stopped by the idling stop control, the calculation is restarted after estimating the change in the catalyst temperature during the stop of the internal combustion engine when the operation of the internal combustion engine is restarted. Thus, it is possible to prevent an increase in the difference between the estimated value of the catalyst temperature and the actual catalyst temperature.

Further, when the catalyst temperature estimation method of the present invention is performed, the change in the catalyst temperature during the stop of the internal combustion engine is estimated in consideration of the stop time of the internal combustion engine by the idling stop control. The deviation between the estimated value of the catalyst temperature and the actual catalyst temperature can be kept small.

Further, in carrying out the catalyst temperature estimation method of the present invention, when a predetermined time has elapsed since the stop of the internal combustion engine, the exhaust temperature on the upstream side of the catalyst is set without estimating the temperature change of the catalyst when the operation of the internal combustion engine is resumed. By setting the catalyst temperature and restarting the calculation, waste of battery power can be reduced while suppressing the occurrence of a deviation between the estimated value of the catalyst temperature and the actual catalyst temperature.

It is a figure which shows the structural example of the exhaust gas purification apparatus with which the estimation method of the catalyst temperature concerning embodiment of this invention is implemented. It is a block diagram which shows the structural example of the control apparatus (DCU) which can implement the estimation method of the catalyst temperature of the 1st Embodiment of this invention. It is a figure for demonstrating the estimation method of the catalyst temperature performed by dividing | segmenting a catalyst into a some brick. It is a figure which shows the flow of the estimation method of the catalyst temperature concerning 1st Embodiment. It is a block diagram which shows the structural example of the control apparatus (DCU) which can implement the estimation method of the catalyst temperature of 2nd Embodiment. It is a figure which shows the flow of the estimation method of the catalyst temperature concerning 2nd Embodiment.

Embodiments relating to the catalyst temperature estimation method of the present invention will be specifically described below with reference to the drawings. However, this embodiment shows one aspect of the present invention and does not limit the present invention, and can be arbitrarily changed within the scope of the present invention.
In addition, in each figure, what has attached | subjected the same code | symbol has shown the same member, and description is abbreviate | omitted suitably.

[First Embodiment]
1. First, an outline of a configuration of an exhaust gas purification apparatus in which the catalyst temperature estimation method according to the first embodiment of the present invention is performed will be described.
FIG. 1 is a diagram showing an overall configuration of an exhaust purification device 10, in which an additive is injected and supplied to the upstream side of a reduction catalyst 13 disposed in an exhaust passage, and NO contained in exhaust gas in the reduction catalyst 13. An exhaust purification device 10 that selectively reduces and purifies _X is shown. The exhaust purification device 10 is disposed in the middle of an exhaust passage connected to the internal combustion engine 5, and a reduction catalyst 13 for selectively reducing NO _x contained in the exhaust gas, and an upstream side of the reduction catalyst 13. The main component is an additive supply device 20 for injecting and supplying an additive into the exhaust pipe 11.

The additive supply device 20 provided in the exhaust purification device 10 includes an additive injection valve 31 fixed to the exhaust pipe 11 on the upstream side of the reduction catalyst 13, a storage tank 50 in which the additive is stored, and a storage tank 50. In order to control the injection amount of the additive to be injected into the exhaust pipe 11 and the pump module 40 including a pump (not shown) for pumping the additive in the additive injection valve 31, the additive A control device (hereinafter referred to as “DCU: Dosing Control Unit”) 60 that controls the operation of the injection valve 31 and the pump is provided.

In the example of the exhaust emission control device 10 shown in FIG. 1, a control device (hereinafter referred to as “ECU: Electronic Control Unit”) 70 for controlling the operation state of the internal combustion engine 5 is connected to the DCU 60. Information regarding the operating state of the internal combustion engine, such as the fuel injection amount, injection timing, and rotation speed of the internal combustion engine 5, is output from the ECU 70 to the DCU 60. In addition, the ECU 70 obtains the exhaust gas flow rate Ugas by calculation based on the operating state of the internal combustion engine, and the calculation result is also output to the DCU 60. The flow rate Ugas of the exhaust gas may be detected by providing a known flow rate sensor in the exhaust pipe 11.
In this embodiment, the ECU 70 and the DCU 60 are configured as separate control devices, but the ECU 70 and the DCU 60 may be configured as a single control device. Further, each signal input / output to / from the DCU 60 may be exchanged via the CAN.

An exhaust temperature sensor 15 is provided in the exhaust pipe 11 upstream of the reduction catalyst 13, and the sensor value Ts of the exhaust temperature sensor 15 is read by the DCU 60. The value of the exhaust temperature sensor 15 may be sent to the DCU 60 after being read by the ECU 70.
Further, the exhaust purification device 10 includes an outside air temperature sensor 21 that measures the temperature of outside air around the exhaust purification device 10 and an outside air flow rate sensor 23 that measures the flow rate of outside air. The sensor values Tenv and Uenv of these

sensors

21 and 23 are read by the DCU 60 and used to calculate the temperature of the reduction catalyst 13.
In this embodiment, the detected value of the outside air temperature sensor normally provided in the vehicle is used as the sensor value Tenv, and the detected value of the vehicle speed sensor that detects the speed of the vehicle is used as the sensor value Uenv, which increases the cost. Is suppressed.

2. Additive Injection Control Next, additive injection control performed by the additive supply device 20 provided in the exhaust purification device 10 of FIG. 1 will be described.
During operation of the internal combustion engine 5, the additive in the storage tank 50 is pumped toward the additive injection valve 31 by a pump. At this time, feedback control of the pump is performed so that the pressure on the downstream side of the pump is maintained at a predetermined pressure value. When the additive injection valve 31 is opened while the pressure on the downstream side of the pump is maintained at a predetermined pressure value, the additive is injected into the exhaust passage. The opening / closing control of the additive injection valve 31 is performed by performing energization control to the additive injection valve 31 based on the addition instruction value from the DCU 60.

The DCU 60 passes through the reduction catalyst 13 without being reduced, which is detected by the temperature of the reduction catalyst 13, the operating state of the internal combustion engine 5, the exhaust gas temperature, and the NO _X sensor disposed on the downstream side of the reduction catalyst 13. based on the information of the NO _X amount and the like, it calculates the required injection amount of the additive to be supplied. Of these, the temperature of the reduction catalyst 13, and the amount of adsorbable additives or NO _X in reducing catalyst 13, a large influence to the element to reduction efficiency of the NO _X in the reduction catalyst 13, to know the exact temperature Is required.
The requested injection amount calculated by the DCU 60 is transmitted to the control portion of the additive injection valve 31 as an addition instruction value, and the energization control of the additive injection valve 31 is performed according to the addition instruction value, whereby a predetermined amount of addition is added. The agent is injected and supplied into the exhaust passage. The additive injected into the exhaust passage flows into the reduction catalyst 13 together with the exhaust gas, and is used for the reduction reaction of NO _x contained in the exhaust gas.

3. Idling Stop Control The ECU 70 that controls the operating state of the internal combustion engine has an idling stop function for automatically stopping the internal combustion engine 5. This idling stop function automatically stops the internal combustion engine 5 when a predetermined idling stop condition is satisfied in a state where the engine switch of the internal combustion engine is turned on, thereby preventing air pollution caused by exhaust gas and noise caused by engine noise. It is a function for.

The idling stop condition is, for example, the state where the engine switch is on, the speed of the internal combustion engine is equal to or lower than a predetermined threshold value, and the vehicle speed is equal to or lower than the predetermined threshold value for a predetermined time or longer. However, the present invention is not limited to this.
Further, the ECU 70 restarts the operation of the internal combustion engine when the idling stop condition is once established and the internal combustion engine is automatically stopped and then the accelerator pedal is depressed or a predetermined switch is turned on.
The ECU 70 outputs a signal IS to the DCU 60 when the idling stop condition is satisfied and the internal combustion engine is automatically stopped or when the operation of the internal combustion engine is resumed.

4). Catalyst temperature estimation device (DCU)
(1) Configuration of DCU First, a configuration example of the DCU 60 as a catalyst temperature estimation device will be described.
FIG. 2 is a functional block diagram showing a part related to the temperature estimation of the catalyst in the configuration of the DCU 60.
The DCU 60 is configured around a microcomputer having a known configuration, and includes an output information extraction / generation unit (denoted as “output information extraction”) and an idling stop signal reception unit (denoted as “IS reception”). And a catalyst temperature calculation unit (denoted as “catalyst temperature calculation”) for performing a calculation process of the temperature of the reduction catalyst, etc. Specifically, each of these units is realized by executing a program by a microcomputer.

Among these, the output information extraction and generation unit includes the sensor value Ts of the exhaust temperature sensor 15 provided in the exhaust purification device 10, the sensor value Tenv of the outside air temperature sensor 21, the sensor value Uenv of the vehicle speed sensor 23, and the exhaust gas calculated by the ECU 70. This is the part that reads the gas flow rate Ugas and outputs it to the catalyst temperature calculator.
The idling stop signal receiving unit is a part that receives the signal IS output from the ECU 70 when the automatic stop of the internal combustion engine by the idling stop control is turned on or off, and outputs the signal IS to the catalyst temperature calculating unit.

In addition, the catalyst temperature calculation unit determines the temperature of the reduction catalyst based on the sensor value Ts of the exhaust temperature sensor 15, the sensor value Tenv of the outside air temperature sensor 21, the sensor value Uenv of the vehicle speed sensor 23, the exhaust gas flow rate Ugas, and the like. Is a part obtained by calculation.
An example of the calculation process performed by the catalyst temperature calculation unit will be described below.

(2) Calculation logic of catalyst temperature In the catalyst temperature calculation unit of the DCU 60 of this embodiment, as shown in FIG. 3A, the reduction catalyst 13 is evenly divided into a plurality of regions B (i) ( B (1) to B (n)), and the region B (i) is determined from the balance between the amount of heat flowing into each region B (i) (B (1) to B (n)) and the amount of heat released. The temperature T (i) (T (1) to T (n)) for each (B (1) to B (n)) and the average temperature TE of the reduction catalyst 13 are calculated. Hereinafter, each region B (i) (B (1) to B (n)) of the divided reduction catalyst 13 is referred to as “brick”.
The number of bricks B (i) to be divided is arbitrarily set. However, the larger the number of divisions, the higher the accuracy of the estimated value of the catalyst temperature, while the load on the DCU increases. Therefore, considering the processing capacity of the DCU It is preferable to set.
In the following description, the concept of “temperature rise” includes the concept of negative temperature rise (temperature drop), and the concept of “heat inflow” includes inflow of negative heat (outflow of heat). This concept is also included.

As shown in FIG. 3B, the amount of heat used to increase the temperature of brick B (i) is Q (i) and brick B (i) at the i-th brick B (i) from the upstream side in the exhaust flow direction. ) Qgas (i) is the heat quantity of the exhaust gas flowing into the wall), Qwall (i) is the heat quantity flowing into the brick B (i) from the exhaust pipe wall surface, and B (i-1), B (i + 1) are adjacent bricks. If the amount of heat transferred to the brick B (i) due to the temperature difference is Qscr (i), the balance of these four amounts of heat can be expressed by the following equation (1).
Q (i) = Qgas (i) × η + Qwall (i) + Qscr (i) (1)
η: Coefficient due to heat transfer of brick B (i)

Here, the heat quantity Qgas _{t = s} (i) flowing into the i-th brick B (i) from the upstream side in the exhaust flow direction at a certain time t = s can be expressed by the following equation (2).
Qgas _{t = s} (i) = mgas × cgas × (Tgas _{t = s} (i-1) −T _{t = s-1} (i)) (2)
mgas: Mass flow rate of exhaust gas
cgas: Specific heat of exhaust gas
Tgas _{t = s} (i-1): Temperature of exhaust gas at brick B (i-1) on the upstream side at time t = s
T _{t = s-1} (i): Temperature in brick B (i) when t = s-1 at the previous measurement

In this equation (2), Tgas _{t = s} (i-1) when obtaining the temperature of the most upstream brick B (1), that is, Tgas _{t = s} (0) is the catalyst upstream gas temperature, and the exhaust gas temperature sensor Can be replaced with the sensor value Ts _{t = s} .

Further, at a certain time t = s, the amount of heat Qgas _{t = s} (i + 1) flowing into the brick B (i + 1) on the downstream side of the i-th brick B (i) is the brick B (i In consideration of the coefficient η resulting from the heat transfer of), it can be expressed by the following equation (3).
Qgas _{t = s} (i + 1) = (1-η) × Qgas _{t = s} (i) (3)

Further, the exhaust gas temperature Tgas _{t = s} (i) at the i-th brick B (i) at a certain time t = s can be expressed by the following equation (4).
Tgas _{t = s} (i) = (1-η) × Tgas _{t = s} (i-1) (4)
That is, the amount of heat Qgas _{t = s} (i) flowing into each brick B (i) and the temperature Tgas _{t = s} (i) of the exhaust gas at each brick B (i) become smaller toward the downstream side.

Further, the amount of heat Qwall _{t = s} (i) radiated to the outside from the brick B (i) through the exhaust pipe at a certain time t = s can be expressed by the following equation (5).
Qwall _{t = s} (i) = h × A1 × (T _{t = s} (i) −Tenv _{t = s} ) (5)
h: Heat transfer coefficient between brick B (i) and the atmosphere
A1: Surface area of the outer periphery of the brick B (i) Here, the heat transfer coefficient h between the brick B (i) and the atmosphere is a variable depending on the vehicle speed Uenv, and the value of the vehicle speed Uenv read by the vehicle speed sensor 23 is Then, the value of the heat transfer coefficient h is selected.

In addition, since the temperature of the brick on the upstream side of the exhaust is often higher than the temperature of the brick on the downstream side of the exhaust, the brick is determined by the temperature difference between two adjacent bricks B (i-1) and B (i + 1). B heat coming moves to _{(i) Qscr t = s (} i) is the exhaust downstream side of the bricks from the heat Qscr _{t = s} (i) in which come to move from the exhaust upstream side of the brick B (i-1) Since it is a value obtained by subtracting the amount of heat Qscr _{t = s} (i) out that moves to B (i + 1), it can be expressed by the following equation (6). Note that this value may be a negative value.
Qscr _{t = s} (i) = Qscr _{t = s} (i) in−Qscr _{t = s} (i) out
= {A2 × λ / L × (T _{t = s} (i-1) −T _{t = s} (i))} − {A2 × λ / L × (T _{t = s} (i) −T _{t = s} ( i + 1))}
= A2 × λ / L × (T _{t = s} (i-1) −2T _{t = s} (i) + T _{t = s} (i + 1)) (6)
A2: Brick B (i) effective area λ: Thermal conductivity of brick B (i)
L: Distance between the centers of adjacent bricks

In this equation (6), when calculating the temperature of the most upstream brick B (1), there is no upstream brick B (i-1), so it moves from the upstream brick B (i-1). Calculation is performed assuming that there is no heat quantity Qscr _{t = s} (1) in. Similarly, in Equation (6), when the temperature of the most downstream brick B (n) is determined, there is no downstream brick B (i + 1), so the downstream brick B (n + 1) Calculation is performed assuming that there is no amount of heat Qscr _{t = s} (n) out transferred to

Also, if the temperature rise of brick B (i) when time Δt has passed since t = s-1 at the previous measurement is ΔT _{t = s} (i), it is used for the temperature rise of brick B (i) The amount of heat Q _{t = s} (i) can be expressed by the following formula (7).
Q _{t = s} (i) = mscr × cscr × ΔT _{t = s} (i) / Δt (7)
mscr: Effective mass of brick
cscr: Specific heat of brick Note that mscr × cscr indicates the heat capacity of the reduction catalyst.

From the above formula (1) and formula (7), the temperature rise ΔT _{t = s} (i of the brick B (i) when the time Δt has elapsed from the time t = s−1 at the previous measurement of the brick B (i). ) Can be represented by the following formula (8).
ΔT _{t = s} (i) = {(Qgas _{t = s} (i) × η + Qwall _{t = s} (i) + Qscr _{t = s} (i)) / (mscr × cscr)} × Δt (8)

Here, the temperature T _{t = s} (i) of the brick B (i) at the time t = s can be expressed by the following equation (9).

In this equation (9), the temperature T _{t = 0} (i) of each brick B (i) of the reduction catalyst is the exhaust gas immediately after the start of the operation of the internal combustion engine or when a predetermined time has elapsed after the operation of the internal combustion engine is stopped. The initial value T _{t = 0} (i) of the temperature of each brick B (i) is substantially the same as the sensor value Ts of the temperature sensor, so the sensor value Ts _{t = 0} of the exhaust temperature sensor at the start of the internal combustion engine Can be replaced.
Then, ΔT _{t = s} (i) is calculated for each time Δt using the above equations (2) to (8), and integrated to the initial value T _{t = 0} (i) as in equation (9). Thus, the temperature T _{t = s} (i) of each brick B (i) at time t = s can be calculated.

For example, the inlet temperature of the reduction catalyst can be calculated as the temperature T (1) of the brick B (1) at the most upstream in the exhaust flow direction. Further, the outlet temperature of the reduction catalyst can be calculated as the temperature T (n) of the brick B (n) on the most downstream side in the exhaust flow direction when the reduction catalyst is divided into n bricks. As a result, the temperature difference ΔT between the inlet temperature and the outlet temperature of the reduction catalyst can be obtained by subtracting T (n) from T (1).

Also, the average temperature TE of the reduction catalyst at time t = s is obtained by adding the temperatures T (i) of all bricks B (i) and dividing by the number of bricks. Alternatively, if it is assumed that the temperature of the reduction catalyst changes linearly from the inlet to the outlet, simply calculate the average of the inlet temperature T (1) and the outlet temperature T (n) of the reduction catalyst. The value can also be the average temperature TE of the reduction catalyst.

4). Next, a specific example of the catalyst temperature estimation method performed by the DCU 60 described so far will be described. FIG. 4 is a diagram showing a flow of the catalyst temperature estimation method of the present embodiment.
First, immediately after the operation of the internal combustion engine is started, in step S1, the sensor value Tst _{= 0} of the exhaust temperature sensor is read, and the initial value _{Tt = 0} (i) of the temperature of each brick B (i) of the reduction catalyst is set. Is set. Next, after the rotational speed Ne of the internal combustion engine is read in step S2, it is determined whether or not the rotational speed Ne of the internal combustion engine exceeds a threshold value Ne0 in step S3. Until the rotation speed Ne of the internal combustion engine exceeds the threshold value Ne0, steps S2 to S3 are repeated. Then, when the rotational speed Ne of the internal combustion engine exceeds the threshold value Ne0, the process proceeds to step S4. The value of the threshold value Ne0 is set to, for example, the rotational speed at the time of cranking of the internal combustion engine. The reason for waiting until the rotational speed Ne of the internal combustion engine exceeds the threshold value Ne0 is because it is not necessary to consider the amount of heat flowing into the catalyst in estimating the catalyst temperature.

In step S4 in which the rotational speed Ne of the internal combustion engine has advanced beyond the threshold value Ne0, the exhaust temperature Ts _t , the outside air temperature Tenv _t , the vehicle speed Uenv _t , and the exhaust gas flow rate Ugas _t are read, and then in step S5 Based on each value, the temperature T _t (i) of each brick B (i) is calculated using the above equations (1) to (9), and the average temperature TE _{t of the} reduction catalyst is calculated. Is done.

Next, in step S6, it is determined whether or not the internal combustion engine is in an automatic stop state by idling stop control. If the internal combustion engine is not in the automatic stop state, the process returns to step S4, and steps S4 to S6 are repeated until the internal combustion engine is in the automatic stop state.

In step S6, the process proceeds to step S7 when the engine is automatically stopped, if the temperature T _t of each brick B (i) (i) is the same temperature as the sensor value Ts _t of the exhaust gas temperature sensor not Is determined. Returning to step S4 again when the temperature T _t of each brick B (i) (i) is not the same temperature as the sensor value Ts _t of the exhaust gas temperature sensor, while the internal combustion engine is in the automatically stopped state, temperature T _t (i) is the step S4 ~ S7 until the same temperature as the sensor value Ts _t of the exhaust gas temperature sensor is repeated for each brick B (i).

At this time, in obtaining the temperature of the most upstream brick B (1), there is no amount of heat Qscr _{t = s} (1) in transferred from the upstream brick B (i-1) during operation of the internal combustion engine. On the other hand, since the exhaust gas does not flow during the automatic stop of the internal combustion engine, the amount of heat from the most upstream brick B (1) into the upstream exhaust passage Qscr _{t = s} ( 1) In movement is assumed. Therefore, when the catalyst temperature is calculated during the automatic stop of the internal combustion engine, the calculation is performed using T _{t = s} (0) as the sensor value Ts _{t = s} of the exhaust temperature sensor in the above equation (6).

Similarly, in determining the temperature of the most downstream brick B (n), it is assumed that there is no amount of heat Qscr _{t = s} (n) out transferred to the downstream brick B (n + 1) during operation of the internal combustion engine. Whereas the calculation is performed, the flow of exhaust gas disappears during the automatic stop of the internal combustion engine, so the amount of heat Qscr _{t = s} (n) from the most downstream brick B (n) into the downstream exhaust passage The movement of out is assumed. Therefore, when calculating the catalyst temperature during the automatic stop of the internal combustion engine, when calculating T _{t = s} (n + 1) in the above equation (6), the most upstream brick B (1) is calculated. the temperature difference between the temperature Tgas _t of the exhaust gas temperature Tgas _t of the exhaust gas (1) at the most downstream brick B (n) (n) is taken as _{_{ΔTgas t, T t = s (}} n + 1) = T _{t = s} (0) + ΔTgas _{t = s} .

Further, before the temperature T _t of each brick B (i) (i) is the same temperature as the sensor value Ts _t of the exhaust gas temperature sensor, and the idling stop control is canceled, when the operation of the internal combustion engine is restarted Steps S4 to S6 are repeated as they are, and the calculation of the catalyst temperature is continued.
When the operation of the internal combustion engine is resumed, T _{t = s} (0) = Ts _{t = s} and T _{t = s} (n + 1) = T _{t = s} (0 ) + ΔTgas _{t = s} is canceled.

In step S7, when the temperature T _t of each brick B (i) (i) have the same temperature as the sensor value Ts _t of the exhaust gas temperature sensor, the process proceeds to step S8, operation of the catalyst temperature is interrupted . At the same time, the setting of T _{t = s} (0) = Ts _{t = s} and T _{t = s} (n + 1) = T _{t = s} (0) + ΔTgas _{t = s} in the calculation of the above equation (6) is Canceled. Here, the calculation of the catalyst temperature is interrupted because the catalyst temperature is estimated to be equivalent to the sensor value Ts of the exhaust temperature sensor until the operation of the internal combustion engine is resumed thereafter, and the battery power Savings.

After the calculation of the catalyst temperature is interrupted, in step S9, when it is detected that the automatic stop of the internal combustion engine by the idling stop control is released and the operation of the internal combustion engine is restarted, the process proceeds to step S10, and the exhaust temperature is increased. The sensor value Ts of the sensor is read, and the sensor value Ts is set as the initial value T _{t = 0 ′} (i) of each brick B (i) of the reduction catalyst.
After this, the process returns to step S2 again, and the steps so far are repeated.

In the example of the catalyst temperature estimation method of the present embodiment described above, the calculation is interrupted when each brick temperature becomes the same as the sensor value of the exhaust temperature sensor during the automatic stop of the internal combustion engine by the idling stop control. However, the reference time is set so that each brick temperature becomes the same as the sensor value of the exhaust temperature sensor, and the calculation is interrupted when the elapsed time from the automatic stop exceeds the set reference time. It can also be configured as follows.

As described above, since the calculation of the catalyst temperature is continued even during the automatic stop of the internal combustion engine by the idling stop control, an increase in the deviation between the estimated value of the catalyst temperature and the actual catalyst temperature can be suppressed. In addition, during the automatic stop of the internal combustion engine by idling stop control, the calculation is interrupted when the temperature T (i) of each brick B (i) reaches the same temperature as the sensor value Ts of the exhaust temperature sensor, There is no deviation between the estimated value of the catalyst temperature and the actual catalyst temperature, and battery power is also saved.
As described above, according to the method for estimating the catalyst temperature of the present embodiment, the deviation between the estimated value of the catalyst temperature and the actual catalyst temperature is extremely small, and thus the reduction efficiency according to the catalyst temperature is taken into consideration. Additive injection control can be performed with high accuracy.

[Second Embodiment]
In the catalyst temperature estimation method according to the second embodiment of the present invention, the calculation of the catalyst temperature is not performed during the automatic stop of the internal combustion engine by the idling stop control, but the internal combustion engine is being automatically stopped when the operation of the internal combustion engine is resumed. This is an estimation method in which the calculation of the catalyst temperature is restarted in consideration of the temperature change of the catalyst.
Also in this embodiment, the basic catalyst temperature estimation logic uses the equations (1) to (9) described in the first embodiment. The difference will be mainly described.

1. Configuration of Catalyst Temperature Estimating Device (DCU) FIG. 5 is a functional block diagram showing a portion related to catalyst temperature estimation in the configuration of the DCU 60 ′ of this embodiment.
The DCU 60 ′ is configured with a microcomputer having a known configuration as a center, and includes an output information extraction / generation unit (denoted as “output information extraction”) and an idling stop signal reception unit (denoted as “IS reception”). ), A catalyst temperature calculation unit (denoted as “catalyst temperature calculation”) for calculating the temperature of the reduction catalyst, a timer counter for counting an automatic stop time of the internal combustion engine, and the like as main elements. The timer counter may be provided in the ECU.

Among these, the sensor value extraction generation unit and the idling stop signal reception unit can have the same configuration as that provided in the DCU 60 of the first embodiment.
Further, the catalyst temperature calculation unit is basically configured similarly to the DCU of the first embodiment, and the above-described catalyst temperature calculation process is performed. However, the catalyst temperature calculation unit of the DCU 60 ′ of the present embodiment calculates the temperature change of the reduction catalyst during the automatic stop of the internal combustion engine when the operation is restarted after the internal combustion engine is automatically stopped, and the temperature of each brick B (i). The operation is restarted after initializing T (i). An example of the calculation process at the time of restarting the operation will be described below.

2. Next, a specific example of the catalyst temperature estimation method of the present embodiment performed by the DCU 60 ′ described so far will be described. FIG. 6 is a diagram showing a flow of the catalyst temperature estimation method of the present embodiment.

Steps S1 to S6 are performed in the same manner as steps S1 to S6 in the first embodiment.
In this embodiment, when the internal combustion engine is in the automatic stop state in step S6, the process proceeds to step S17, and the exhaust temperature Ts _{t = stop} at this time and the temperature T _{t = stop} (i) of each brick B (i). Further, the values of the exhaust gas temperature Tgas _{t = stop} (n + 1) and the outside air temperature Tenv _{t = stop} on the downstream side of the catalyst are stored. If the temperature Tt = s (n + 1) in the exhaust passage on the downstream side of the catalyst can be detected, the exhaust gas temperature on the downstream side of the catalyst instead of the exhaust gas temperature Tgas _{t = stop} (n + 1) on the downstream side of the catalyst The temperature Tt = s (n + 1) may be stored. Next, the process proceeds to step S18, and counting of the stop time Tstop of the internal combustion engine by the idling stop control is started.

Next, in step S19, it is determined whether or not the stop time Tstop of the internal combustion engine has passed the reference time Tstop0. This reference time Tstop0 is set to such a time that the temperature T (i) of each brick B (i) becomes the same temperature as the sensor value Ts of the exhaust temperature sensor. If the stop time Tstop of the internal combustion engine has not passed the reference time Tstop0, the process proceeds to step S20, where it is determined whether or not the idling stop control is canceled and the operation of the internal combustion engine is resumed. If the internal combustion engine is in the automatic stop state, the process returns to step S19. If the operation of the internal combustion engine is resumed, the process proceeds to step S21.

In step S21 where the operation of the internal combustion engine is resumed, the exhaust temperature Ts _{t = stop} stored at the time of the automatic stop of the internal combustion engine, the temperature T _{t = stop} (i) of each brick B (i), the exhaust gas downstream of the catalyst The values of the temperature Tgas _{t = stop} (n + 1) and the outside air temperature Tenv _{t = stop} are read, the counter value of the stop time Tstop of the internal combustion engine, the exhaust gas temperature Ts _{t = 0 ''} when restarting the operation, and the outside air temperature Tenv _{t = 0 ''} is read. Then, in step S22, calculation for estimating the temperature T (i) of each brick B (i) during the automatic stop of the internal combustion engine is executed according to the counter value of the stop time Tstop of the internal combustion engine.

At this time, in obtaining the temperature T (1) of the most upstream brick B (1), the amount of heat Qscr _{t = s} (1) transferred from the upstream brick B (i-1) during operation of the internal combustion engine. ) The calculation is performed on the assumption that there is no in, but the exhaust gas does not flow during the automatic stop of the internal combustion engine, so the amount of heat Qscr from the most upstream brick B (1) into the upstream exhaust passage _{t = s} (1) In-movement is assumed. Therefore, in the present embodiment, when the temperature T (1) of the brick B (1) during the automatic stop of the internal combustion engine is calculated, the value of T _{t = s} (0) in the above equation (6) is used. The sensor value Tst _{= s} of the exhaust gas temperature sensor upstream of the catalyst is used. Specifically, assuming that the temperature change indicated by the sensor value Ts _{t = s} from when the internal combustion engine is automatically stopped to when the internal combustion engine is restarted is linear, the sensor value Ts _{t = stop} at the time of automatic _stop Then, T _{t = s} (0) is obtained based on the sensor value Ts _{t = 0 ″} when the operation is resumed and the elapsed time.

Similarly, in determining the temperature T (n) of the most downstream brick B (n), the amount of heat transferred to the downstream brick B (n + 1) during operation of the internal combustion engine Qscr _{t = s} (n) out On the other hand, the calculation is performed on the assumption that there is no exhaust gas, but the exhaust gas flow disappears during the automatic stop of the internal combustion engine, so the amount of heat Qscr _{t =} from the most downstream brick B (n) into the exhaust passage on the downstream side _s (n) out movement is assumed. Therefore, in this embodiment, when calculating the temperature T (n) of each brick B (n) during the automatic stop of the internal combustion engine, in the above equation (6), T _{t = s} (n + 1) As the value, the exhaust gas temperature Tgas _{t = s} (n + 1) on the downstream side of the catalyst is used. Specifically, it is assumed that the change in the temperature Tgas _{t = s} (n + 1) of the exhaust gas downstream of the catalyst from when the internal combustion engine is automatically stopped to when the internal combustion engine is restarted is linear. Based on the temperature Tgas _{t = stop} (n + 1) at the time of _stop , the temperature Tgas _{t = 0 ″} (n + 1) at the time of restarting operation, and the elapsed time, T _{t = s} (n + 1) is obtained.

Also, regarding the outside air temperature Tenv _{t = s} in the equation (5) during the automatic stop of the internal combustion engine, it is assumed that the temperature change from the automatic stop of the internal combustion engine to the restart of the internal combustion engine is linear. Thus, Tenv _{t = s} is obtained based on the outside air temperature Tenv _{t = stop} at the time of automatic stop, the outside air temperature Tenv _{t = 0 ″} at the time of restarting operation, and the elapsed time.
Further, in the present embodiment, T _{t = 0 ''} (0), T _{t = 0 ''} (n + 1) at the time of restarting the operation of the internal combustion engine, the exhaust gas temperature Tgas _{t = s} (n The calculation is performed on the assumption that the value of +1) is the same value as the exhaust gas temperature Tst _{= 0 ″} .

However, the temperature gradient of the exhaust temperature is calculated by a calculation formula (curve change) that takes into account heat transfer from the reduction catalyst to the exhaust and heat transfer from the exhaust to the outside air, and the temperature gradient of the outside air temperature is linearly calculated. It is assumed that the temperature T (i) of each brick B (i) is calculated by deriving the exhaust temperature Ts and the outside air temperature Tenv at the time of each calculation, assuming that it changes. The calculation of the exhaust gas temperature Ts at this time is calculated based on the exhaust gas temperature Tst = stop when the internal combustion engine is automatically stopped and the stop time Tstop of the internal combustion engine. Here, if there is a difference between the calculated exhaust temperature Ts at the time of restarting operation and the value Ts _{t = 0 ''} of the exhaust temperature sensor, the outside air temperature during the automatic stop of the internal combustion engine changes linearly. Assuming that this is the cause, the amount of heat obtained from the temperature difference is added to the amount of heat calculated for each brick B (i), and the temperature T (i) is calculated.

When these calculations are finished, in step S23, the calculated temperature T _{t = 0 ″} (i) of each brick B (i) when the operation is resumed is set as an initial value. After this, the process returns to step S2, and the steps so far are repeated.

On the other hand, when the stop time Tstop of the internal combustion engine has passed the reference time Tstop0 in step S19 described above, the process proceeds to step S24, and the count of the stop time Tstop is stopped. The reason why the stop time Tstop is stopped is that the catalyst temperature is estimated to be equal to the sensor value Ts of the exhaust temperature sensor until the operation of the internal combustion engine is resumed thereafter.

After the count of the stop time Tstop of the internal combustion engine is stopped, in step S25, when it is detected that the automatic stop of the internal combustion engine by the idling stop control is canceled and the operation of the internal combustion engine is restarted, the process proceeds to step S26. The sensor value Ts of the exhaust temperature sensor is read, and the sensor value Ts is set as the initial value T _{t = 0 ′} (i) of each brick B (i) of the reduction catalyst. After this, the process returns to step S2, and the steps so far are repeated.

In the example of the catalyst temperature estimation method of the present embodiment described above, the automatic stop time Tstop of the internal combustion engine by the idling stop control is counted by the timer counter, but the measurement signal of the clock provided in the vehicle or the like May be used. Alternatively, the stop time Tstop may be estimated using the temperature of engine coolant used for cooling the internal combustion engine.
Specifically, cooling is performed to detect the outside air temperature Tenv _{t = stop} when the internal combustion engine is automatically stopped and the temperature of the engine coolant circulating in the engine cooling device provided in the internal combustion engine such as a vehicle. The sensor value Tcool _{t = stop} of the water temperature sensor is read, and the temperature difference ΔTcool _{t = stop} between the outside air temperature Tenv _{t = stop} and the cooling water temperature Tcool _{t = stop} is stored. Further, when the internal combustion engine is restarted, the outside air temperature Tenv _{t = 0 '} and the cooling water temperature Tcool _{t = 0'} are read, and the outside air temperature Tenv _{t = 0 '} and the cooling water temperature Tcool _{t = 0'} The temperature difference ΔTcool _{t = 0 ′} is stored. Then, based on the two temperature differences ΔTcool _{t = stop and} ΔTcool _{t = 0 ′} using a map showing the relationship between the change in temperature difference ΔTcool and the elapsed time, a calculation formula that takes heat transfer into account, etc. The engine stop time Tstop is estimated.

As described above, the stop time Tstop is counted during the automatic stop of the internal combustion engine by idling stop control, and the change in the temperature T (i) of each brick B (i) during the automatic stop is calculated when the operation of the internal combustion engine is resumed. By doing so, the spread of the deviation between the estimated value of the catalyst temperature and the actual catalyst temperature can be suppressed. In addition, when the automatic stop time Tstop of the internal combustion engine by the idling stop control exceeds the reference time Tstop0, the count of the stop time Tstop is stopped, thereby causing a deviation between the estimated value of the catalyst temperature and the actual catalyst temperature. This also saves battery power.
As described above, even in the method for estimating the catalyst temperature according to the present embodiment, the difference between the estimated value of the catalyst temperature and the actual catalyst temperature is extremely small. Therefore, the reduction efficiency according to the catalyst temperature is considered. The injection control of the additive can be performed with high accuracy.

Claims

In a catalyst temperature estimation method for estimating the temperature of a catalyst disposed in an exhaust passage of an internal combustion engine,
The temperature of the catalyst is estimated by performing a calculation based on the temperature of the exhaust gas discharged from the internal combustion engine, the flow rate of the exhaust gas, the temperature of the outside air, and the flow rate of the outside air,
A method for estimating a catalyst temperature, wherein the calculation is performed in consideration of a temperature change of the catalyst while the internal combustion engine is stopped by idling stop control for automatically stopping the internal combustion engine.
The catalyst temperature estimation method according to claim 1, wherein the calculation is continued while the internal combustion engine is stopped.
The calculation is continued while the internal combustion engine is stopped, and the calculation is performed when the difference between the temperature of the catalyst calculated by the calculation and the temperature of the exhaust gas upstream of the catalyst falls within a predetermined range. The catalyst temperature estimation method according to claim 2, wherein the calculation is resumed when the operation of the internal combustion engine is resumed.
The calculation is continued while the internal combustion engine is stopped, the calculation is interrupted when a predetermined time has elapsed from the stop of the internal combustion engine, and when the operation of the internal combustion engine is resumed, the temperature of the catalyst is changed to the upstream side of the catalyst. 3. The catalyst temperature estimation method according to claim 2, wherein the calculation is restarted after the exhaust gas temperature is set.
The calculation is interrupted when the internal combustion engine is stopped, and when the operation of the internal combustion engine is resumed, the calculation is resumed after estimating a temperature change of the catalyst during the stop of the internal combustion engine. The catalyst temperature estimation method according to item 1 of the above.
The calculation is interrupted when the internal combustion engine is stopped and measurement of a stop time is started, and when the operation of the internal combustion engine is resumed, a temperature change of the catalyst according to the stop time is estimated. 6. The catalyst temperature estimation method according to item 5.
When the internal combustion engine is stopped, the calculation is interrupted and measurement of the stop time is started. When the stop time exceeds a predetermined time, the measurement of the stop time is stopped, and when the operation of the internal combustion engine is resumed, The catalyst temperature estimation method according to claim 6, wherein the calculation is resumed after the temperature is set to the temperature of the exhaust gas upstream of the catalyst.