JP2008057334A - Catalyst temperature estimating device and catalyst temperature estimating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly and easily estimate the temperature of a catalyst. <P>SOLUTION: This catalyst temperature estimating device comprises a fuel cut execution means 22 for executing the fuel cut of an engine 2, a theoretical temperature rise amount calculation means 34 for calculating the rise amount of temperature of a catalyst 13 by cutting a fuel by the fuel cut execution means 22, a critical rise amount storage means 41 for storing the critical rise amount of temperature which is the limitation of temperature rise amount for each fuel cut, a temperature lowering amount calculation means 35 for calculating the lowering amount of the temperature of the catalyst 13 due to the stoppage of fuel cut, and catalyst temperature estimating means 37 for estimating the temperature of the catalyst 13 according to the theoretical temperature rise amount, the critical rise amount, and the temperature lowering amount. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus and a method for estimating the temperature of a catalyst for purifying exhaust gas discharged from an engine mounted on a vehicle.

Conventionally, there are various techniques for purifying exhaust gas discharged from the engine of a vehicle with a catalyst, and there are also various techniques for detecting or estimating the temperature of the catalyst. In addition, as an example of a technique for detecting or estimating such a catalyst temperature, there is a technique disclosed in Patent Document 1 below.
JP 2002-122018 A

By the way, in recent years, when a predetermined condition is satisfied, control for stopping fuel supply to a running vehicle engine and improving fuel efficiency has been frequently used. Such control is generally known as “fuel cut” control.
However, when the fuel cut is performed, the exhaust gas atmosphere becomes lean, so that the oxidation of fuel components adhering to the catalyst (hereinafter simply referred to as unburned components) is promoted, and the temperature of the catalyst rapidly increases. A phenomenon occurs. However, since the catalyst has a certain degree of heat resistance, even if the temperature is raised by oxidation of unburned components, it can withstand a predetermined heat-resistant temperature. In other words, a temperature increase exceeding the heat resistant temperature must be avoided in order to avoid melting of the catalyst.

On the other hand, if the fuel cut can be executed more frequently, it will be possible to further improve the fuel consumption. Therefore, the fuel cut should not be stopped as much as possible within the range that does not exceed the heat resistance temperature of the catalyst. Is required.
However, it is difficult to accurately estimate the temperature of the catalyst, and in particular, it is difficult to estimate the catalyst temperature in a situation where fuel cuts are frequently performed.

Of course, there is no way to directly detect the temperature of the catalyst by providing a temperature sensor in the catalyst, but the cost increases due to the addition of the temperature sensor, and replacement work when the temperature sensor itself deteriorates. In view of the cost and labor required for this, it is not a preferable method.
The present invention has been devised in view of such problems, and even when a fuel cut is performed, the temperature of the catalyst can be estimated more accurately, quickly and at a low cost. An object of the present invention is to provide an estimation device and a catalyst temperature estimation method.

  In order to achieve the above object, a catalyst temperature estimation device according to the present invention (Claim 1) is a vehicle catalyst temperature estimation device having a catalyst for purifying exhaust gas from an engine, and performs fuel cut of the engine. Fuel cut execution means and temperature rise estimation means for estimating the temperature rise of the catalyst due to the fuel cut execution means executing the fuel cut based on the reaction calculation on the catalyst or the reaction calculation and heat transfer calculation It is characterized by comprising.

A catalyst temperature estimation device according to a second aspect of the present invention is the content of the first aspect, wherein a limit increase amount that is a limit of a temperature increase amount of the catalyst due to execution of the fuel cut per time is determined. It is characterized by comprising a limit increase amount defining means for defining.
The temperature estimation device for a catalyst according to the present invention described in claim 3 is the temperature according to claim 1 or 2, wherein the temperature decrease amount of the catalyst due to the stop of the fuel cut is estimated based on the temperature increase amount. It is characterized by comprising a reduction amount estimating means.

According to a fourth aspect of the present invention, there is provided the catalyst temperature estimating apparatus according to the first or second aspect of the present invention, wherein the temperature decrease amount estimation means includes the temperature increase amount and a temperature decrease rate according to the exhaust gas flow rate. The temperature drop amount is estimated based on the above.
The catalyst temperature estimation device of the present invention according to claim 5 is the content of claim 3 or 4, wherein the temperature increase amount of the catalyst estimated by the temperature increase amount estimation means and the limit increase Catalyst temperature estimating means for estimating the temperature of the catalyst based on the limit increase amount defined by the amount defining means and the temperature decrease amount of the catalyst estimated by the temperature decrease amount estimating means, The catalyst temperature estimating means obtains an exothermic temperature amount of the catalyst based on the temperature increase amount and the limit increase amount while the fuel cut is being executed by the fuel cut executing means, and based on the exothermic temperature amount, While estimating the temperature of the catalyst, and while the fuel cut by the fuel cut execution means is stopped, the fuel cut stop reference temperature, which is the temperature of the catalyst when the fuel cut is stopped, and the temperature decrease amount, Based on the catalyst It is characterized by estimating the temperature.

  A catalyst temperature estimation device according to a sixth aspect of the present invention is the fuel cut according to any one of the first to fifth aspects, wherein the fuel cut is executed by the fuel cut execution means. A fuel cut execution period detecting means for detecting an execution period; and a temperature increase rate storage means for storing a temperature increase rate which is a temperature increase amount of the catalyst per unit time during the fuel cut execution period, and the temperature The increase amount estimation means obtains the temperature increase amount based on the temperature increase rate stored in the temperature increase rate storage means and the fuel cut execution period detected by the fuel cut execution period detection means. Yes.

  A catalyst temperature estimation device according to a seventh aspect of the present invention is the content of any one of the fourth to sixth aspects, wherein the fuel cut by the fuel cut execution means is stopped and Fuel cut stop period detecting means for detecting a non-operation period of the fuel cut execution means as a fuel cut stop period, and a temperature for storing the temperature decrease rate as a temperature decrease rate of the catalyst per calculation cycle during the fuel cut stop period A temperature drop amount estimating means, wherein the temperature drop amount estimating means comprises the temperature drop rate stored in the temperature drop rate storage means, the fuel cut stop period detected by the fuel cut stop period detecting means, and the fuel. The temperature reduction amount is obtained based on the cut stop reference temperature.

  A catalyst temperature estimation method according to the present invention (Claim 8) is a catalyst temperature estimation method for a vehicle having a catalyst for purifying exhaust gas from an engine, and a fuel cut execution step for executing a fuel cut of the engine ( Step S11), and a temperature rise estimation step for estimating the temperature rise of the catalyst by executing the fuel cut in the fuel cut execution step based on the reaction calculation on the catalyst or the reaction calculation and heat transfer calculation ( Step S12).

The method for estimating the temperature of the catalyst of the present invention according to claim 9 is characterized in that, in the content of claim 8, a limit increase amount that is a limit of the temperature increase amount of the catalyst due to execution of the fuel cut per time is calculated. A limiting increase amount defining step (step S13) to be defined is provided.
The method for estimating the temperature of the catalyst of the present invention according to claim 10 is the temperature according to claim 8 or 9, wherein the temperature decrease amount of the catalyst due to the stop of the fuel cut is estimated based on the temperature increase amount. A reduction amount estimation step (step S17) is provided.

The temperature estimation method for a catalyst of the present invention according to claim 11 is the content of claim 10, wherein the temperature decrease amount estimation step includes the temperature increase amount estimated in the temperature increase amount estimation step and the exhaust gas. The temperature drop amount is estimated based on the temperature drop rate corresponding to the flow rate.
A temperature estimation method for a catalyst according to a twelfth aspect of the present invention is the content of the tenth or eleventh aspect, based on the temperature increase amount and the limit increase amount while the fuel cut is being executed. The amount of heat generated by the catalyst is obtained, the temperature of the catalyst is estimated based on the amount of heat generated, and while the fuel cut is stopped, the fuel that is the temperature of the catalyst when the fuel cut is stopped A catalyst temperature estimation step (steps S14, S15, S17) for estimating the temperature of the catalyst based on the cut stop reference temperature and the temperature decrease amount is provided.

  A catalyst temperature estimation method according to a thirteenth aspect of the present invention is the content of any one of the eighth to twelfth aspects, wherein the fuel cut is performed during a period in which the fuel cut of the engine is being performed. A fuel cut execution period detection step (step S31) for detecting a period, and a temperature increase rate storage step (step S32) for storing a temperature increase rate which is a temperature increase amount of the catalyst per unit time during the fuel cut execution period The temperature increase estimation step includes the fuel cut execution period detected in the fuel cut execution period detection step and the temperature increase rate stored in the temperature increase rate storage step. And a temperature increase calculation step (step S35) for obtaining the temperature increase of the catalyst.

  Further, the temperature estimation method for a catalyst according to the present invention described in claim 14 is the content described in any one of claims 11 to 13, wherein the period during which the fuel cut is stopped is detected as a fuel cut stop period. A fuel cut stop period detecting step (step S33), and a temperature decrease rate storage step (step S33) for storing the temperature decrease rate as a temperature decrease rate of the catalyst per calculation period during the fuel cut stop period. The temperature decrease amount estimation step is based on the temperature decrease rate stored in the temperature decrease rate storage step, the fuel cut stop period detected in the fuel cut stop period detection step, and the fuel cut stop reference temperature. It is characterized in that the amount of temperature decrease is obtained.

According to the catalyst temperature estimation apparatus and method of the present invention, it is possible to estimate the behavior of the catalyst temperature according to the execution / stop of the fuel cut more quickly and easily. In addition, it is possible to estimate the amount of heat generated more quickly than the actual temperature detection, and to suppress the temporary overheating of the catalyst due to the temperature detection delay, so that the essential protection of the catalyst can be achieved. . (Claims 1-4 and Claims 8-11)
Further, since the temperature of the catalyst can be easily estimated based on the amount of heat generated by the catalyst when the fuel cut is performed and the amount of decrease in the temperature of the catalyst when the fuel cut is stopped, the calculation load required for this estimation can be reduced. (Claim 5 and Claim 12)
Further, by storing in advance a temperature increase rate, which is the temperature increase amount of the catalyst per calculation cycle during the fuel cut execution period, it is possible to reduce the calculation load required for estimating the catalyst temperature. (Claim 6 and Claim 13)
Further, by storing in advance the temperature decrease rate, which is the catalyst temperature decrease rate per calculation cycle during the fuel cut stop period, the calculation load required for estimating the catalyst temperature can be reduced. (Claim 7 and Claim 14)

  Hereinafter, a catalyst temperature estimation device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing an engine and a supply / exhaust system of a vehicle including the overall configuration, and FIG. 3 is a schematic block diagram showing a temperature estimation control and a fuel cut control system, FIG. 3 is a flowchart showing a calculation method for estimating the heat generation temperature of the catalyst, FIG. 4 is a flowchart showing a fuel cut control method, and FIG. FIG. 6 is a time chart showing the relationship between the execution of fuel cut control and the rise in catalyst temperature, and FIG. 7 is a calculation method (catalyst temperature) using a catalyst temperature estimation device. It is a flowchart which shows the outline | summary of an estimation method.

As shown in FIG. 1, a vehicle 1 is equipped with a gasoline engine (hereinafter simply referred to as “engine”) 2. An injector 3 is provided in an intake port (not shown) of the engine 2.
The injector 3 injects fuel into an intake port (not shown) of the engine 2 based on a fuel injection signal transmitted from an ECU 30 described later.

An intake manifold 4 is connected to the intake port of the engine 2, and an exhaust manifold 5 is connected to an exhaust port (not shown).
An air cleaner (A / C) 7, an air flow sensor (AFS) 8, and a throttle body 9 are provided upstream of the intake manifold 4.
A throttle valve 11 is provided in the throttle body 9. The throttle valve 11 is driven by a stepper motor 12 so that the opening degree θ _TH is adjusted.

The air flow sensor 8 detects a flow rate Q _{FR of} fresh air flowing into the intake port of the engine 2. The detection result by the air flow sensor 8 is read by the ECU 30 described later.
An exhaust passage 12 is connected to the downstream side of the exhaust manifold 5, and a three-way catalyst (catalyst) 13 is provided on the downstream side of the exhaust passage 12.

The three-way catalyst 13 purifies the exhaust gas. More specifically, the three-way catalyst 13 converts NOx out of carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx) contained in the exhaust gas. NOx is changed to nitrogen (N ₂ ) by removing the contained O, and carbon dioxide (CO ₂ ) and water (H ₂ O) are reacted by reacting the removed O with CO and HC. .
Further, the vehicle 1 is provided with an engine speed sensor 14, an accelerator position sensor (APS) 15, a vehicle speed sensor 16, and an exhaust gas temperature sensor 17.

Of these, an engine rotational speed sensor 14 is for detecting the speed N _e of the engine 2, the detection result is adapted to be read by later-described ECU 30.
An accelerator position sensor 15, the amount of depression of the accelerator pedal (not shown) which is depressed by the driver be one that detects a (accelerator opening) theta _AP, the detection result is adapted to be read by ECU 30.

Vehicle speed sensor 16, an electronic speed sensor provided in a transmission (not shown), vehicle speed V _s, which is detected by the vehicle speed sensor 16 is adapted to be read by ECU 30.
The exhaust gas temperature sensor 17 is provided in the exhaust passage 12 in the vicinity of the upstream side of the three-way catalyst 13 and detects the temperature T _EX of the exhaust gas supplied to the three-way catalyst 13. The exhaust gas temperature T _EX detected by the exhaust gas temperature sensor 17 is read by the ECU 30.

The vehicle 1 is provided with an electronic control unit (ECU) 30 including an interface unit, a CPU, a memory, and the like (all not shown).
The ECU 30 includes a fuel control unit (fuel control unit) 31, a fuel cut execution unit (fuel cut execution unit) 32, a fuel cut prohibition unit (fuel cut stop unit) 33, a theoretical temperature increase calculation unit (theoretical temperature). A rise amount calculation means) 34, a temperature decrease amount calculation section (temperature decrease amount calculation means) 35, a temperature outline estimation section 36, and a temperature detail estimation section (catalyst temperature estimation means) 37 are all provided as software.

Further, the ECU 30 is provided with a fuel cut execution counter / timer (fuel cut execution period detection means) 38 and a fuel cut stop counter / timer (fuel cut stop period detection means) 39 as hardware. Yes.
Further, a memory (not shown) of the ECU 30 includes a temperature increase gradient storage unit (temperature increase rate storage unit) 41, a temperature decrease gain storage unit (temperature decrease gain storage unit) 42, and a temperature increase limit storage unit (limit increase amount storage unit). 43) are set as storage areas.

Among these, as shown in FIG. 2, the fuel control unit 31 includes a fresh air flow rate Q _FR detected by the air flow sensor 8, an accelerator opening θ _AP detected by the accelerator position sensor 15, and an engine speed sensor. depending on parameters such as the detected engine speed N _e by 14, a fuel injection signal is a pulse signal by transmitting relative injector 3, controls the fuel injection by the injector 3.

Also, the fuel control unit 31, a fuel cut unit 32 (details will be described later), when receiving the fuel cut signal S _FC is a signal including a fuel cut flag, the fuel injection by the injector 3 It is supposed to be paused.
Further, when the fuel control unit 31 receives a fuel cut prohibition signal _SFS , which is a signal including a fuel cut prohibition flag, from the fuel cut prohibition unit 33 (described later in detail), the fuel control unit 31 receives a fuel cut prohibition signal _SFS from the fuel cut execution unit 32. even if you received the fuel cut signal S _FC, ignore this fuel cut signal S _FC (i.e., in preference to the fuel cut signal S _FC) prohibits the fuel cut, normal Fuel injection control is executed.

Fuel cut unit 32, a predetermined fuel cut condition is satisfied, as shown in FIG. 2, by transmitting the fuel cut signal S _FC is a signal including a fuel cut execution flag to the fuel control unit 31, fuel cut is controlled to stop the fuel supply to the engine 2 is performed in the fuel control unit 31, on the other hand, when the fuel cut condition is not satisfied, by stops transmitting the fuel cut signal S _FC, The fuel cut execution is stopped (that is, fuel injection is permitted).

In this embodiment, the fuel cut execution condition is set in advance after the engine speed _Ne is equal to or higher than the predetermined speed and the accelerator pedal opening θ _AP becomes substantially zero. It is set under the condition that the delay time t _DR has elapsed.
When a predetermined fuel cut prohibition condition is satisfied, the fuel cut prohibition unit 33 transmits a fuel cut prohibition signal _SFS , which is a signal including a fuel cut prohibition flag, to the fuel control unit 31, as shown in FIG. The fuel control unit 31 is prohibited from executing the fuel cut.

Note that the fuel cut prohibition condition is that the temperature T _CAT1 of the three-way catalyst 13 estimated by the temperature approximate estimation unit 36 described later in detail is a predetermined specified temperature T _TH0 (T _{TH0 ≈700} ° C. in the present embodiment). As described above, the temperature T _CAT2 of the three-way catalyst 13 estimated by the temperature detail estimation unit 37 is set to be equal to or higher than the fuel cut prohibition temperature T _TH2 that is a predetermined threshold value. The fuel cut prohibition temperature T _TH2 is set to about 120 ° C. (an example).

These temperatures T _CAT1 and T _CAT2 are referred to as “approximately temperature T _CAT1 ” and “detailed temperature T _CAT2 ”, respectively. Further, the sum of “approximately temperature T _CAT1 ” and “detailed temperature T _CAT2 ” corresponds to the final estimated catalyst temperature. In addition, the “stop” of the fuel cut here means “stop” of the fuel cut due to the fact that the fuel cut condition is not satisfied, and the forced fuel cut by the fuel cut prohibition unit 33. It is meant to include both “prohibited”.

The theoretical temperature increase calculation unit 34 calculates the theoretical temperature increase ΔT _aCAL of the three-way catalyst 13 when the fuel cut execution unit 32 transmits the fuel cut execution signal S _FC and the fuel control unit 31 executes the fuel cut. To do.
More specifically, as shown in FIG. 2, the theoretical temperature increase calculation unit 34 includes a temperature increase gradient R _UP (described later) stored in the temperature increase gradient storage unit 41, and a fuel cut execution counter / timer. The theoretical temperature rise amount ΔT _aCAL of the three-way catalyst 13 is calculated by multiplying by the fuel cut execution period t _FC detected by 38 (that is, by calculating using the following equation (1A)). is there.

R _UP × t _FC = ΔT _aCAL (1A)
In addition, when the control cycle is taken into account, the theoretical temperature increase calculation unit 34 calculates the theoretical temperature increase ΔT _aCAL using the following equation (1B). Here, “(n)” indicates a value in the current control cycle, and “(n−1)” indicates a value in the previous control cycle. F is a control cycle.

ΔT _aCAL (n−1) + (R _UP × f) = ΔT _aCAL (n) (* ΔT _aCAL (0) = 0) (1B)
In the temperature decrease amount calculation unit 35, the fuel cut prohibition unit 33 prohibits the fuel cut (that is, the fuel injection is forcibly permitted) or the fuel cut execution unit 32 does not operate (that is, the fuel does not operate). is intended for calculating the temperature drop amount [Delta] T _b of the three-way catalyst 13 by generally they have allowed) that injection.

More specifically, as shown in FIG. 2, the temperature decrease amount calculation unit 35 calculates a temperature decrease rate R _DOWN (more specifically, calculated using the temperature decrease gain G _DOWN stored in the temperature decrease gain storage unit 41. And the fuel cut stop period detected by the fuel cut prohibition counter timer 39 based on the fuel cut stop reference temperature _TFSS (that is, calculated using the following equation (2)). and calculates the temperature decrease amount [Delta] t _b in t _FS.

R _DOWN × ΔT _b (n−1) = ΔT _b (n) (* ΔT _b (0) = T _FSS ) (2)
Here, a method for calculating the temperature decrease rate R _DOWN will be described in detail. Each parameter used here is
h: heat transfer coefficient s: area where the three-way catalyst 13 and exhaust gas are in contact C _cat : heat capacity of the three-way catalyst 13 Q _EX : exhaust gas flow rate G _DOWN : temperature drop gain of the three-way catalyst 13 ΔT: three-way catalyst Each of them is indicated by a symbol of 13 temperature rise total amounts.

  Using these symbols, if the heat transfer amount ΔH between the exhaust gas and the three-way catalyst 13 is ΔH = h · s · ΔT (temperature difference between the three-way catalyst and the exhaust gas ≈ΔT), the three-way catalyst The total temperature rise ΔT of 13 can be expressed by the following equation (3).

Here, assuming 1−h · s / C _cat = R _DOWN and h≈h ′ · Q _EX , the temperature decrease rate R _DOWN can be expressed by the following equation (4).

The reason why h≈h ′ · Q _EX is set is that the heat transfer coefficient (h) is determined by the exhaust gas flow rate Q _EX . In the actual calculation, the fresh air flow rate Q _FR is used instead of the exhaust gas flow rate Q _EX . This is because the relationship of exhaust gas flow rate Q _FR ∝ fresh air flow rate Q _EX is established.
The approximate temperature estimation unit 36 estimates the approximate temperature T _CAT1 of the catalyst 13 by _{performing a} filtering process on the exhaust gas temperature T _EX detected by the exhaust gas temperature sensor 17 provided in the exhaust passage 12. . At this time, the exhaust gas temperature estimated by the estimation process may be used instead of the exhaust gas temperature sensor. In addition, since the method using this filtering process is a well-known method, detailed description is abbreviate | omitted here. The approximate temperature T _CAT1 estimated by the approximate temperature estimation unit 36 is read by the fuel cut prohibition unit 33 as shown in FIG.

The temperature detail estimation unit 37 includes a theoretical temperature increase amount ΔT _aCAL obtained by the theoretical temperature increase amount calculation unit 34, a temperature increase limit amount ΔT _aMAX stored in the temperature increase limit amount storage unit 43, and a temperature decrease amount calculation unit. The detailed temperature T _CAT2 of the three-way catalyst 13 is estimated on the basis of the temperature decrease amount ΔT _b obtained by Step 35.
More specifically, as shown in FIG. 2, the temperature detail estimation unit 37 reads the approximate temperature T _CAT1 estimated by the approximate temperature estimation unit 36 as needed. Then, the outline temperature T _CAT1 predetermined specified temperature T _TH0 (in this embodiment, T _TH0 ≒ 700 ℃) reached, and, in the case where the fuel cut unit 32 has received the fuel cut signal S _FC, adding a stoichiometric amount of temperature rise [Delta] T _aCAL obtained by theoretical temperature increase calculation unit 34, the fuel cut start reference temperature T _FCS in the smaller of the temperature rise limit amount [Delta] T _Amax stored in a temperature rise limit storage unit 43 set the value as a catalyst calorific [Delta] T _a, and outputs the catalytic heating value [Delta] T _a as detailed temperature T _CAT2.

Further, the temperature detailed estimation unit 37, the detailed temperature T _CAT2 at the time when the fuel cut unit 32 has received the fuel cut signal S _FC in a state in which the fuel cut prohibition unit 33 does not receive fuel cut prohibition signal S _FS The fuel cut start reference temperature T _FCS is stored.
Here, the case where the temperature details estimator 37 receives the fuel cut signal S _FC from fuel cut portion 32 in a state not receiving fuel cut prohibition signal S _FS from the fuel cut prohibition unit 33, i.e., The fuel cut has started.

On the other hand, if no longer receive the fuel cut signal S _FC which has been received from the fuel cut unit 32, or, if the fuel cut prohibition unit 33 has received the fuel cut prohibition signal S _FS, the temperature details estimator 37 is the time that no longer receives the fuel cut signal S _FC, or to store the details temperature T _CAT2 at the time when the fuel cut prohibition unit 33 has received the fuel cut prohibition signal S _FS as fuel cut stopping the reference temperature T _FSS It has become.

In this case, the temperature detailed estimation unit 37, if the fuel cut signal S _FC which has been received from the fuel cut unit 32 stops receiving, or the fuel cut prohibition signal S _FS from the fuel cut prohibition unit 33 The case where it is received means that the fuel cut is stopped.
When the fuel cut is stopped, the detailed temperature estimation unit 37 obtains the value obtained based on the temperature decrease rate R _DOWN obtained by the temperature decrease amount calculation unit 35 and the fuel cut stop reference temperature T _{FSS. Is} output as a detailed temperature _TCAT2 .

Fuel cut counter timer 38 is for detecting the execution period t _FC of the fuel cut by the fuel cut unit 32, more specifically, Yes in step S11 in the control to be described later with reference to FIG. 3 route (i.e., when fuel is being cut) by counting the number of executions of, so as to detect the fuel cut period t _FC.
Fuel cut prohibiting counter-timer 39, the inhibition period of the fuel cut by the fuel cut prohibition unit 33, and a period during which transmission of the fuel cut signal S _FC from fuel cut portion 32 to the fuel control unit 31 is stopped Is detected as the fuel cut stop period t _FS , and more specifically, the number of executions of the No route of step S11 (that is, when the fuel cut is stopped) in the control shown in FIG. 3 is counted. Thus, the fuel cut stop period _tFS is detected.

The control cycle shown in FIG. 3 is set as 100 ms.
The temperature increase gradient storage unit 41 stores the temperature increase amount ΔT _aCAL of the three-way catalyst 13 per unit time during the fuel cut execution period t _FC as a temperature increase gradient (temperature increase rate) R _UP .
This temperature rise gradient R _UP is a value obtained by taking into account a value obtained by experiment and a value obtained by simulation. Further, this simulation calculates the amount of reaction heat between the unburned components adhering to the three-way catalyst 13 and the oxygen in the exhaust gas flowing into the three-way catalyst 13 during the fuel cut, based on the reaction rate, The heat transfer between the exhaust gas and the three-way catalyst 13, the amount of purification reaction heat of the exhaust gas, the heat conduction amount of the three-way catalyst 13, the oxygen storage capacity of the three-way catalyst 13, etc. are performed. .

In the present embodiment, the temperature increase gradient R _UP is set as a straight line having a gradient that increases by about 100 ° C. in one second, as shown in FIG.
The temperature decrease gain storage unit 42 shown in FIG. 1 stores a temperature decrease gain G _DOWN per calculation cycle during the fuel cut stop period _tFS . This temperature decrease gain G _DOWN is used when calculating the temperature decrease rate R _DOWN as described above.

The temperature increase limit amount storage unit 43 shown in FIG. 1 is a storage area for storing a limit amount ΔT _aMAX of the temperature increase of the three-way catalyst 13 per execution of fuel cut. The limit amount ΔT _aMAX is obtained by the following equation (5).
ΔT _aMAX = upper limit capacity of unburned component of catalyst x amount of reaction heat / heat capacity of catalyst (5)
Moreover, although the upper limit capacity | capacitance of the unburned component adhering to the three-way catalyst 13 changes with specifications of this three-way catalyst 13, it is obtained by using the simulation similar to the simulation mentioned above. In this embodiment, the temperature rise limit amount ΔT _aMAX is set to about 70 ° C. (see FIG. 5).

Further, as shown in this equation (5), the amount of unburned components actually attached to the three-way catalyst 13 is not directly detected or estimated, but the upper limit of unburned components of the catalyst 13 The reason for using the parameter of capacity is as follows.
That is, the three-way catalyst 13 does not actively store unburned components. Therefore, when the exhaust gas in the rich atmosphere flows into the three-way catalyst 13, unburned components with a full upper limit capacity of unburned components are increased. It pays attention that it will adhere to the three-way catalyst 13 immediately.

Since the catalyst temperature estimation device according to an embodiment of the present invention is configured as described above, the following operations and effects are achieved.
First, calculation of the temperature change amount ΔT _CAT2 of the catalyst 13 by the temperature detail estimation unit 37 will be described using the flowchart of FIG.
When the fuel cut is executed by the fuel cut execution unit 32 (Yes route of step S11), the theoretical temperature increase calculation unit 34 uses the above-described equation (1B) to calculate the theoretical temperature increase in the current control cycle. ΔT _aCAL (n) is calculated (step S12). In the first control cycle, the previous theoretical temperature rise ΔT _aCAL (n−1) is calculated as zero.

If the current theoretical temperature rise amount ΔT _aCAL (n) obtained in step S12 is less than or equal to the temperature rise limit amount ΔT _aMAX stored in the temperature rise limit amount storage unit 43 (Yes route in step S13). The value obtained by adding the fuel cut start reference temperature T _FCS to the current theoretical temperature rise amount ΔT _aCAL (n) is set as the current catalyst heat generation amount ΔT _a (step S15).

On the other hand, when the current theoretical temperature rise amount ΔT _aCAL (n) obtained in step S12 is equal to or greater than the temperature rise limit amount ΔT _aMAX (No route in step S13), the current catalyst heat generation amount ΔT _a (n ) _Is set as a value obtained by adding the reference temperature T _FCS and the temperature rise limit amount ΔT _aMAX (step S14).
In other words, the control of the steps S13 to S15, and this theoretical temperature rise ΔT _aCAL (n), of the temperature rise limit amount [Delta] T _Amax, a value obtained by adding the reference temperature T _FCS in the smaller the fuel cut it is a control for regarded as catalytic heating value [Delta] T _a. Thereafter, the detailed temperature estimation unit 37 sets the catalyst heat generation amount ΔT _a as the detailed temperature T _CAT2 .

On the other hand, when the fuel cut is prohibited by the fuel cut prohibition unit 33 (No route in step S11), the temperature decrease amount calculation unit 35 calculates the temperature decrease rate R _DOWN based on the above equation (4). (Step S16) Furthermore, the temperature decrease amount calculation unit 35 obtains the fuel cut stop reference temperature T _FSS (see FIG. 5), which is the detailed temperature T _CAT2 when the previous fuel cut is completed, from the temperature detailed estimation unit 37. The temperature decrease amount ΔT _b (n) due to the fuel cut prohibition is calculated based on the above equation (2) as an initial value of the temperature decrease amount ΔT _b (n), and is output to the temperature detail estimation unit 37 (step S17). . Thereafter, the temperature detailed estimation unit 37 sets the temperature decrease amount [Delta] T _b as detailed temperature T _CAT2.

Next, the fuel cut control will be described using the flowchart shown in FIG.
When the fuel cut is executed by the fuel cut execution unit 32 (Yes route of step S21), the fuel cut prohibition unit 33 determines whether or not the approximate temperature T _CAT1 is _{equal to} or higher than the specified temperature T _TH0. (Step S22).
Here, when it is determined that the approximate temperature T _CAT1 is equal to or higher than the specified temperature T _TH0 (Yes route in step S22), the fuel cut prohibition unit 33 further determines that the detailed temperature T _CAT2 is _equal to or higher than the fuel cut prohibition temperature T _TH2. It is determined whether or not (step S23).

Here, when it is determined that the detailed temperature T _CAT2 is equal to or higher than the fuel cut prohibition temperature T _TH2 (Yes route in step S23), the three-way catalyst 13 may be melted. Then, a fuel cut prohibition signal _SFS , which is a signal including a fuel cut prohibition flag, is transmitted to the fuel control unit 31 to prohibit execution of fuel cut (step S26).
Performing the other hand, in step S23, it is determined that detailed temperature T _CAT2 is less than the fuel cut prohibiting temperature T _TH2 (No route in step S23), and the fuel cut prohibition unit 33 already transmits a fuel cut prohibition signal S _FS If so (Yes route of step S24), the fuel cut prohibition unit 33 determines whether the detailed temperature T _CAT2 is equal to or higher than the fuel cut execution temperature T _TH1 (step S25).

Here, when it is determined that the detailed temperature T _CAT2 is equal to or higher than the fuel cut execution temperature T _TH1 (Yes route in step S25), the fuel cut prohibition unit 33 continues to perform a fuel cut that is a signal including a fuel cut prohibition flag. A prohibition signal _SFS is transmitted to the fuel control unit 31, and execution of fuel cut is prohibited (step S26).
On the other hand, in step S23, it is determined that the detailed temperature T _CAT2 is lower than the fuel cut prohibition temperature T _TH2 (No route of step S23), and the fuel cut prohibition unit 33 transmits the fuel cut prohibition signal _SFS. If no (no route in step S24), and the fuel cut prohibition unit 33 continues, the fuel cut prohibition unit 33 does not perform the transmission of the fuel cut prohibition signal S _FS (step S27).

Further, it is determined that the fuel cut prohibition unit 33 currently although the performed transmission of the fuel cut prohibition signal S _FS (Yes route in step S24), and details the temperature T _CAT2 has become less than the fuel cut execution temperature T _TH1 If (No route in step S25), and the fuel cut prohibition unit 33 stops the transmission of the fuel cut prohibition signal S _FS (step S27).
That is, the control of steps S23 to S25 prevents a phenomenon (so-called hunting) in which the fuel cut by the fuel cut prohibition unit 33 is not frequently prohibited even if the detailed temperature T _CAT2 slightly fluctuates. ing.

Next, a description will be given using the time chart shown in FIG. Here, a case where the approximate temperature T _CAT1 estimated by the approximate temperature estimation unit 36 has already reached the specified temperature T _TH0 is shown.
at time of t _1, fuel cut signal S _FC is a signal including a fuel cut execution flag from fuel cut portion 32 to the fuel control unit 31 is transmitted, the first fuel cut is executed, the theoretical temperature rise The amount calculation unit 34 calculates the temperature increase amount ΔT _aCAL of the catalyst 13. However, this increase in temperature [Delta] T _aCAL is clipped temperature rise limit amount [Delta] T _Amax stored in a temperature rise limit amount storage unit 43 as the upper limit (see arrow A _1).

Then, when the fuel cut-off period t _FC1 from the time of t ₁ has elapsed, the first fuel cut is terminated, in accordance with the temperature decrease rate R _DOWN per unit time (control cycle), details the temperature T of the catalyst 13 _CAT2 is reduced (see arrow A _2).
When the second fuel cut is executed at time t ₂ , the theoretical temperature increase calculation unit 34 calculates the temperature increase ΔT _aCAL of the catalyst 13 again. Also in the execution of the second fuel cut, the temperature rise amount ΔT _aCAL is _set as the upper limit and the temperature rise limit amount ΔT _aMAX is clipped (see arrow A ₃ ).

Thereafter, when the second fuel cut is terminated when the fuel cut-off period t _FC2 has elapsed from the time of t _2, in accordance with the temperature decrease rate R _DOWN, again, it details the temperature T _CAT2 catalyst 13 is reduced (arrow A ₄ ).
When the third fuel cut is executed at time t ₃ , the theoretical temperature increase calculation unit 34 calculates the temperature increase ΔT _aCAL of the catalyst 13 again.

In this third fuel cut execution, since the temperature rise amount ΔT _aCAL exceeds the detailed temperature T _{CAT2 and the} fuel cut prohibition temperature T _TH2 , the fuel cut prohibition unit 33 is a fuel cut prohibition signal that includes a fuel cut prohibition flag. transmitting a signal S _FS to the fuel control unit 31 (see arrow a _5). As a result, execution of fuel cut is prohibited, and the catalyst 13 is prevented from overheating.

Thereafter, the prohibition of fuel cut by decreases gradually details temperature T _CAT2 (see arrow A _6), and becomes equal to or less than the fuel cut permission temperature T _TH1, the fuel cut prohibition unit 33 cancels the prohibition of fuel cut (arrow see a _7), to return to the normal control. At this time, since the fuel cut permission temperature T _TH1 is set to a value lower than the fuel cut prohibition temperature T _TH2 , hunting of the fuel cut prohibition control by the fuel cut prohibition unit 33 is avoided.

Here, with reference to FIG. 6, the prior art and the present invention will be compared by taking as an example a case where execution and prohibition of fuel cut are intermittently performed. In FIG. 6, the alternate long and short dash line indicates the temperature of the three-way catalyst 13 estimated by the prior art, and the solid line indicates the detailed temperature T _CAT2 of the three-way catalyst 13 estimated by the present invention.
In the conventional technique (see the alternate long and short dash line), since the filtering process is used, it cannot be detected that the three-way catalyst 13 has reached the fuel cut prohibition temperature T _TH2 until the time point t ₅ has elapsed.

In contrast, in the present invention (see solid line), since the temperature change amount [Delta] T _CAT2 of the three-way catalyst 13 due to the fuel cut and prohibitions are rapidly estimated, before the time point t ₅ it is possible to three-way catalyst 13 at the time point t ₄ detects that it has reached the fuel cut prohibiting temperature T _TH2.
Finally, the concept of the calculation method (catalyst temperature estimation method) by the catalyst temperature estimation apparatus of the present invention will be described again using a flowchart.

First, a temperature increase gradient R _UP that is the temperature increase amount of the three-way catalyst 13 per unit time during fuel cut execution is stored in advance in the temperature increase rate storage unit 41 (temperature increase rate defining step). A temperature increase limit amount ΔT _aMAX that is a limit of the temperature increase amount of the three-way catalyst 13 due to the fuel cut is stored in the temperature increase limit storage unit 43 in advance (limit increase amount storage step). Further, the temperature decrease gain G _DOWN which is the temperature decrease amount of the three-way catalyst 13 per calculation period during the fuel cut stop period is also stored in the temperature decrease gain storage unit 42 in advance.

Then, first, the fuel cut execution period is detected by the fuel cut execution counter / timer 38 (fuel cut execution step; step S31).
Then, by multiplying the temperature rise gradient R _UP stored in the temperature rise rate storage unit 41 by the fuel cut execution period t _FC detected in step S31, the theory of the three-way catalyst 13 by executing the fuel cut is calculated. A temperature increase amount ΔT _aCAL is calculated (temperature increase amount calculating step; step S32).

Further, a fuel cut stop period _tFS is detected (fuel cut stop period detecting step; step S33).
Then, the temperature decrease rate R _DOWN obtained based on the temperature decrease gain G _DOWN stored in the temperature decrease gain storage unit 43 and the fuel cut that is the detailed temperature T _CAT2 of the three-way catalyst 13 at the time when the fuel cut is prohibited. Based on the stop reference temperature T _FSS , the temperature decrease amount ΔT _b of the three-way catalyst 13 in the fuel cut stop period t _FS detected in step S33 is calculated (temperature decrease amount estimation step; step S34).

Thereafter, based on the theoretical temperature rise amount ΔT _aCAL detected in step S32, the temperature fall amount ΔT _b detected in step S34, and the temperature rise limit amount ΔT _aMAX stored in the temperature rise limit storage unit 43, three The detailed temperature T _CAT2 of the original catalyst 13 is estimated (catalyst temperature estimation step; step S35).
Thus, according to the catalyst temperature estimation device and the catalyst temperature estimation method according to an embodiment of the present invention, the temperature of the catalyst 13 can be estimated more quickly and easily in accordance with the execution / stop of the fuel cut. Can do.

Further, while the fuel cut is being executed, a value obtained by adding the fuel cut start reference temperature T _FCS to the smaller one of the theoretical temperature increase ΔT _aCAL and the limit increase ΔT _aMAX is the heat generation temperature amount ΔT _{a of the} catalyst 13. As a result, the detailed temperature T _CAT2 of the catalyst 13 is estimated. On the other hand, while the fuel cut is stopped, the fuel cut stop criterion which is the detailed temperature T _CAT2 of the catalyst 13 at the time when the fuel cut is stopped. By calculating the temperature decrease amount ΔT _b based on the temperature T _FSS , the calculation load required for estimating the temperature of the catalyst 13 is reduced by using a simple calculation of estimating the detailed temperature T _CAT2 of the catalyst 13. be able to.

Further, by storing in advance a temperature increase gradient R _UP that is the theoretical temperature increase ΔT _aCAL of the catalyst 13 per unit time at t _FC during the fuel cut execution period, the calculation load required for estimating the temperature of the catalyst 13 is reduced. Can be reduced.
Further, by storing in advance the temperature decrease gain G _DOWN of the catalyst 13 at t _FS during the fuel cut stop period, it is possible to reduce the calculation load required for estimating the temperature of the catalyst 13.

Although the embodiment of the present invention has been described above, the present invention is not limited to the embodiment, and various modifications can be made without departing from the spirit of the present invention.
In the above-described embodiment, the fuel cut execution condition is set to a preset delay after the engine speed _Ne is equal to or greater than the predetermined speed and the accelerator pedal opening θ _AP becomes substantially zero. Although the case where the time t _DR has elapsed has been described, the present invention is not limited to such a condition, and various modes can be set depending on the characteristics of the vehicle.

In the above-described embodiment, the case where the fuel cut prohibition temperature T _TH2 is set to about 120 ° C. has been described as an example. However, the present invention is not limited to this and can be variously changed depending on the specifications of the catalyst.
In addition, as described above, the present invention focuses on the point that the upper limit capacity of the unburned component of the catalyst 13 is immediately filled. Therefore, when the fuel cut prohibition is canceled, the air-fuel ratio is rich to reduce exhaust gas. Therefore, the present invention can accurately estimate the temperature of the catalyst 13.

It is a typical block diagram which shows the whole structure of the temperature estimation apparatus of the catalyst which concerns on one Embodiment of this invention. It is a typical block diagram which shows control of the temperature estimation apparatus of the catalyst which concerns on one Embodiment of this invention. It is a flowchart which shows the calculation method which estimates the heat_generation | fever temperature of the catalyst which concerns on one Embodiment of this invention. It is a flowchart which shows the method of the fuel cut control which concerns on one Embodiment of this invention. It is a time chart which shows the relationship between the fuel cut control which concerns on one Embodiment of this invention, and the temperature of a catalyst. It is a time chart which shows the relationship between execution of the fuel cut control which concerns on one Embodiment of this invention, and the raise of a catalyst temperature. It is a flowchart which shows the outline | summary of the calculation method (catalyst temperature estimation method) by the catalyst temperature estimation apparatus which concerns on one Embodiment of this invention.

Explanation of symbols

1 Vehicle 2 Engine 13 Three-way catalyst (catalyst)
32 Fuel cut execution part (fuel cut execution means)
34 Theoretical temperature rise calculation unit (temperature rise calculation means)
35 Temperature drop calculation unit (Temperature drop calculation means)
36 Temperature detailed estimation part (catalyst temperature estimation means)
38 Fuel cut execution counter / timer (fuel cut execution period detection means)
39 Fuel cut stop counter / timer (fuel cut stop period detection means)
41 Temperature rise gradient storage unit (temperature rise rate storage means)
42 Temperature decrease gain storage unit (temperature decrease rate storage means)
43 Temperature rise limit storage section (limit increase storage means)
G _DOWN Temperature drop gain (Temperature drop rate)
R _DOWN temperature decrease rate (temperature decrease rate)

Claims (14)

A catalyst temperature estimation device for a vehicle having a catalyst for purifying exhaust gas from an engine,
Fuel cut execution means for executing fuel cut of the engine;
The fuel cut execution means comprises temperature increase amount estimation means for estimating a temperature increase amount of the catalyst due to execution of the fuel cut based on a reaction calculation on the catalyst or the reaction calculation and heat transfer calculation. A temperature estimation device for the catalyst. 2. The catalyst temperature estimation device according to claim 1, further comprising a limit increase amount defining means for defining a limit increase amount that is a limit of the temperature increase amount of the catalyst due to execution of the fuel cut per time. . 3. The catalyst temperature estimation device according to claim 1, further comprising a temperature decrease amount estimation unit configured to estimate a temperature decrease amount of the catalyst due to the stop of the fuel cut based on the temperature increase amount. The temperature estimation device for a catalyst according to claim 1 or 2, wherein the temperature decrease estimation means estimates the temperature decrease based on the temperature increase and a temperature decrease rate corresponding to the exhaust gas flow rate. . The temperature increase amount of the catalyst estimated by the temperature increase amount estimation means, the limit increase amount specified by the limit increase amount definition means, and the temperature of the catalyst estimated by the temperature decrease amount estimation means A catalyst temperature estimating means for estimating the temperature of the catalyst based on the amount of decrease;
The catalyst temperature estimating means includes
While the fuel cut is being executed by the fuel cut execution means, the heat generation temperature amount of the catalyst is obtained based on the temperature increase amount and the limit increase amount, and the catalyst temperature is estimated based on the heat generation temperature amount. With
While the fuel cut by the fuel cut execution means is stopped, the temperature of the catalyst is estimated based on the fuel cut stop reference temperature that is the temperature of the catalyst when the fuel cut is stopped and the temperature decrease amount. The temperature estimation device for a catalyst according to claim 3 or 4, characterized in that: Fuel cut execution period detection means for detecting a fuel cut execution period in which the fuel cut is being executed by the fuel cut execution means;
Temperature rise rate storage means for storing a temperature rise rate that is a temperature rise amount of the catalyst per unit time during the fuel cut execution period;
The temperature rise estimation means is
The temperature increase amount is obtained based on the temperature increase rate stored in the temperature increase rate storage means and the fuel cut execution period detected by the fuel cut execution period detection means. The catalyst temperature estimation apparatus according to any one of 5. A fuel cut stop period detecting means for detecting a period during which the fuel cut is stopped by the fuel cut executing means and a non-operation period of the fuel cut executing means as a fuel cut stop period;
Temperature decrease rate storage means for storing the temperature decrease rate as a temperature decrease rate of the catalyst per calculation cycle during the fuel cut stop period;
The temperature drop amount estimation means includes
The temperature decrease amount is obtained based on the temperature decrease rate stored in the temperature decrease rate storage means, the fuel cut stop period detected by the fuel cut stop period detecting means, and the fuel cut stop reference temperature. The temperature estimation device for a catalyst according to any one of claims 4 to 6. A method for estimating a catalyst temperature of a vehicle having a catalyst for purifying exhaust gas from an engine,
A fuel cut execution step for executing a fuel cut of the engine;
And a temperature rise estimation step for estimating a temperature rise amount of the catalyst by executing the fuel cut in the fuel cut execution step based on a reaction calculation on the catalyst or based on the reaction calculation and a heat transfer calculation. A method for estimating the temperature of the catalyst. The catalyst temperature estimation method according to claim 8, further comprising a limit increase amount defining step for defining a limit increase amount that is a limit of the temperature increase amount of the catalyst due to execution of the fuel cut per time. . The catalyst temperature estimation method according to claim 8 or 9, further comprising a temperature decrease amount estimation step for estimating a temperature decrease amount of the catalyst due to the stop of the fuel cut based on the temperature increase amount. The temperature decrease amount estimating step includes:
11. The temperature estimation method for a catalyst according to claim 10, wherein the temperature decrease amount is estimated based on the temperature increase amount estimated in the temperature increase amount estimation step and a temperature decrease rate corresponding to the exhaust gas flow rate. . While the fuel cut is being performed, an exothermic temperature amount of the catalyst is determined based on the temperature increase amount and the limit increase amount, and the catalyst temperature is estimated based on the exothermic temperature amount,
While the fuel cut is stopped, a catalyst temperature estimation step of estimating the temperature of the catalyst based on the fuel cut stop reference temperature that is the temperature of the catalyst when the fuel cut is stopped and the temperature decrease amount The temperature estimation method of the catalyst according to claim 10 or 11, characterized by comprising: A fuel cut execution period detecting step for detecting a fuel cut execution period which is a period during which the fuel cut of the engine is being executed;
A temperature increase rate storage step for storing a temperature increase rate that is an amount of temperature increase of the catalyst per unit time during the fuel cut execution period;
The temperature increase estimation step includes
The temperature for obtaining the temperature increase amount of the catalyst due to execution of the fuel cut based on the fuel cut execution period detected in the fuel cut execution period detection step and the temperature increase rate stored in the temperature increase rate storage step The catalyst temperature estimation method according to any one of claims 8 to 12, further comprising an increase amount calculation step. A fuel cut stop period detecting step for detecting a period during which the fuel cut is stopped as a fuel cut stop period;
A temperature decrease rate storage step for storing the temperature decrease rate as a temperature decrease rate of the catalyst per calculation cycle during the fuel cut stop period;
The temperature decrease amount estimating step includes:
The temperature decrease amount is obtained based on the temperature decrease rate stored in the temperature decrease rate storing step, the fuel cut stop period detected in the fuel cut stop period detecting step, and the fuel cut stop reference temperature. The method for estimating a temperature of a catalyst according to any one of claims 11 to 13.

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