JPH1073018A - Temperature control device for exhaust gas purifying catalyst of internal combustion engine - Google Patents

Abstract

(57) [Problem] To improve exhaust gas purification performance by adjusting exhaust gas temperature and controlling catalyst temperature within an active temperature range without deteriorating the driving feeling. SOLUTION: When the catalyst temperature is lower than the activation temperature range, the engine torque should not exceed the allowable limit value,
The fuel supply amount is corrected to the increasing side by the temperature-raising fuel supply amount map, and the speed ratio is corrected to the decreasing side by the temperature-raising gear ratio map, and the engine is operated at a low speed and a high torque.
The temperature of the exhaust gas is raised to raise the catalyst temperature to the activation temperature range (steps 102 → 103 → 105). When the catalyst temperature is higher than the activation temperature range, the fuel supply amount is corrected to the decreasing side within the range where the engine speed does not exceed the permissible limit value, and the speed ratio is corrected and controlled to the increasing side by using the temperature reduction gear ratio map. Operating the engine at high speed and low torque,
The exhaust gas temperature is lowered to lower the catalyst temperature to the activation temperature range (steps 102 → 104 → 106).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying catalyst for an internal combustion engine which controls the temperature of an exhaust gas purifying catalyst mounted on a vehicle equipped with an automatic transmission so as to maintain a good exhaust gas purification rate. The present invention relates to a control device.

[0002]

2. Description of the Related Art Conventionally, a catalyst has been widely used as a means for purifying exhaust gas of an internal combustion engine. However, purifying exhaust gas with this catalyst has the following problems.

At low temperatures when the catalyst is not active, harmful substances cannot be purified. When a catalyst is used at a high temperature, the catalyst is deteriorated and the purification rate is reduced. In an internal combustion engine (such as a gasoline lean burn engine, a gasoline direct injection engine, or a diesel engine) in which the ratio of air to fuel in the cylinder (air-fuel ratio) is leaner than the theoretical equivalent, the exhaust gas is more exhausted than a normal gasoline engine Since the oxygen concentration of the NOx is high, a NOx catalyst capable of purifying NOx in excess of oxygen is used. However, this NOx
As shown in FIG. 2, the catalyst is N 2 only in a predetermined activation temperature range.
Ox can be purified, and NOx cannot be purified if the catalyst temperature is higher than the activation temperature range. In a diesel engine, when the temperature rises, sulfur in the fuel is oxidized by the catalyst, and this sulfur oxide (sulfate) degrades the catalyst or particulates (fine particles).
Causes increased emissions.

As described above, in order to maintain a good exhaust gas purification rate, it is necessary to keep the catalyst temperature within the activation temperature range. Therefore, as disclosed in Japanese Patent Application Laid-Open No. 7-259544, when the catalyst temperature becomes higher than a predetermined temperature, the fuel injection amount is corrected to increase or decrease and the air-fuel ratio is excessively changed to rich or lean, Techniques have been proposed to lower the temperature of the catalyst by lowering the temperature of the exhaust gas.

[0005]

However, if the air-fuel ratio is excessively changed in order to lower the exhaust gas temperature,
The engine output also changes, and there is a possibility that acceleration and deceleration different from the accelerator operation by the driver may be performed, and the driving feeling is impaired.

The present invention has been made in view of such circumstances, and accordingly, it is an object of the present invention to adjust the exhaust gas temperature to keep the catalyst temperature within a predetermined activation temperature range without deteriorating the driving feeling. An object of the present invention is to provide a temperature control device for an exhaust gas purifying catalyst of an internal combustion engine that can maintain the temperature and improve the exhaust gas purifying performance.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a fuel supply system for increasing or decreasing the amount of fuel supplied to an internal combustion engine (hereinafter referred to as "engine") when a catalyst temperature is out of an active temperature range. By performing the correction in combination with the change of the gear ratio of the automatic transmission, the engine speed (engine speed) and the engine torque are changed while maintaining the engine output (= speed × torque) constant, thereby changing the exhaust gas temperature. To raise or lower the catalyst temperature to within the activation temperature range. In this catalyst temperature control, since the engine output is kept constant, the driving force of the vehicle is kept constant, and acceleration and deceleration unlike driver's accelerator operation does not occur, impairing driving feeling There is no.

According to the present invention, the catalyst temperature is judged by the catalyst temperature judging means. If the catalyst temperature is lower than the activation temperature range of the catalyst, the fuel supply amount control means increases the fuel supply amount of the fuel supply means. And the shift control means corrects the speed ratio of the automatic transmission to the decreasing side. This allows
The engine is operated at a higher torque and a lower rotation speed than before the correction while the engine output remains constant, and the exhaust gas temperature rises due to the increase correction of the fuel supply amount, and the catalyst temperature rises within the activation temperature range.

On the other hand, when the temperature of the catalyst is higher than the activation temperature range, the fuel supply amount is corrected to the decreasing side and the speed ratio of the automatic transmission is corrected to the increasing side. As a result, the engine is operated at a low torque and a high speed as compared with before the correction while the engine output is kept constant, and the exhaust gas temperature is lowered by the correction of the decrease in the fuel supply amount, and the catalyst temperature is lowered to the activation temperature range. In this way, in the present invention, the exhaust gas temperature is changed by changing the engine speed and the engine torque while keeping the engine output constant, so that the catalyst temperature can be maintained without deteriorating the driving feeling. Can be maintained in a predetermined activation temperature range, and the exhaust gas purification performance can be improved.

In this case, the change of the gear ratio of the automatic transmission is as follows.
In an automatic transmission without a lock-up clutch mechanism, the change can be performed by changing the gear ratio of the transmission gear mechanism. In an automatic transmission with a lock-up clutch mechanism, in addition to the change in the gear ratio of the transmission gear mechanism, lock-up can be performed. Lock-up slip control of the clutch mechanism may be used. in this case,
The change of the gear ratio of the transmission gear mechanism and the lock-up slip control may be used together, or one of them may be used alone. When a belt-driven continuously variable transmission is used as the automatic transmission, the diameter of the effective pulley around which the belt is stretched may be controlled. In any of these cases, the general control of the automatic transmission can be used,
There is no need to add a special mechanism (claim 2).

By the way, at the time of deceleration, since the fuel supply amount is reduced or the fuel is cut, the exhaust gas temperature is lowered. Therefore, the exhaust gas at the time of deceleration is convenient for cooling a high-temperature catalyst, but when the temperature of the catalyst is low, it causes an increase in the temperature of the catalyst.

Therefore, in the third aspect, when the vehicle is in a deceleration state and the catalyst temperature is lower than the activation temperature range, the lock-up control of the lock-up clutch mechanism is released. As a result, the engine speed rapidly decreases to the idle speed, and the amount of low-temperature exhaust gas passing through the catalyst (proportional to the engine speed) decreases quickly, so that the catalyst temperature can be prevented from lowering.

On the other hand, when the vehicle is in a deceleration state and the temperature of the catalyst is higher than the activation temperature range, the lock-up control is activated. As a result, the engine speed decreases slowly, and the amount of low-temperature exhaust gas passing through the catalyst (proportional to the engine speed) decreases slowly, during which the catalyst temperature falls within the activation temperature range.

According to a fourth aspect of the present invention, when the catalyst temperature is determined to be lower than the activation temperature range when the vehicle is in a decelerating state, the lockup control is released and the speed ratio of the automatic transmission is corrected to a reduction side. I do. As a result, the engine speed rapidly decreases to the idle speed, and the amount of low-temperature exhaust gas passing through the catalyst quickly decreases. In addition to this, by reducing the fuel cut region where the fuel supply amount is zero, the discharge time of the low-temperature exhaust gas after the fuel cut is shortened. As a result, a decrease in the temperature of the catalyst is suppressed.

On the other hand, when the catalyst temperature is determined to be higher than the activation temperature range when the vehicle is in a deceleration state, the lock-up control is activated and the speed ratio of the automatic transmission is corrected to an increasing side. As a result, the engine speed slowly decreases, and the amount of low-temperature exhaust gas passing through the catalyst decreases slowly. In addition to this, by expanding the fuel cut area, the low-temperature exhaust gas discharge time after the fuel cut is extended. As a result, the catalyst temperature surely falls to within the activation temperature range.

Further, in claim 5, a NOx catalyst capable of reducing and purifying NOx under an excess of oxygen is used as a catalyst.
This catalyst has a narrow active temperature range in which NOx can be reduced and purified (for example, 200 ° C. to 300 ° C. for a Pt-based catalyst). By maintaining the catalyst temperature in the active temperature range according to the present invention, the effect of improving exhaust gas purification performance is great.

Further, in the present invention, the exhaust gas discharged from the diesel engine is purified. Diesel engine fuel, light oil, contains sulfur. At high temperatures, sulfur is oxidized by the catalyst, and this sulfur oxide (sulfate) degrades the catalyst and increases the emission of particulates (particulates). Since this is a cause, the effect of keeping the catalyst temperature within the activation temperature range is great.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] FIG. 1 shows a first embodiment in which the present invention is applied to a NOx catalyst system for a diesel engine.
A description will be given based on FIGS. An intake manifold 12 for introducing air into each cylinder is connected to an intake side of a diesel engine 11 which is an internal combustion engine, and an exhaust pipe 13 is connected to an exhaust side via an exhaust manifold 14. A NOx catalyst 15 that can reduce and purify NOx under excess oxygen is provided in the exhaust pipe 13. This NOx
An exhaust gas temperature sensor 16 that detects exhaust gas temperature near the downstream side of the NOx catalyst 15 is installed downstream of the catalyst 15. The exhaust gas temperature detected by the exhaust gas temperature sensor 16 is used to determine the temperature of the NOx catalyst 15 (hereinafter simply referred to as “catalyst”). Temperature). Therefore, the exhaust gas temperature sensor 16
It is used as a catalyst temperature determining means described in the claims.

On the upstream side of the NOx catalyst 15, NO
A light oil addition device 17 for adding light oil (fuel) as a reducing agent for reducing and purifying the x catalyst 15 to exhaust gas is provided. The light oil addition device 17 includes a fuel injection pump 18
Is supplied with fuel. The fuel injection pump 18 uses the power of the diesel engine 11 as a drive source, and a belt 21 that transmits engine power is stretched between a crank pulley 19 and a pulley 20 of the fuel injection pump 17.
Fuel discharged from the fuel injection pump 17 at high pressure is supplied to a fuel injection nozzle 23 (fuel supply means) of each cylinder of the diesel engine 11 through a high-pressure fuel pipe 22.

The power of the diesel engine 11 is shifted by an automatic transmission 24 and transmitted to a wheel drive system. The automatic transmission 24 includes a torque converter 26 having a built-in lock-up clutch mechanism 25, a transmission clutch / brake mechanism 27, a transmission gear mechanism 28 including a planetary gear mechanism, and a hydraulic control device 29 for controlling the operation of each part. It is configured. The torque converter 26 is a diesel engine 1
1 acts as a fluid coupling for transmitting the rotational force of the crankshaft 30, which is the output shaft, to the transmission gear mechanism 28, the torque converter input shaft 31 is connected to the crankshaft 30, and both rotate integrally. I have.

A pump impeller 32 is provided on the input shaft 31 of the torque converter.
The turbine runner 33 is rotationally driven by the hydraulic power, and a stator 34 for returning oil from the turbine runner 33 to the pump impeller 32 is provided between the two. The one-way clutch 3
5, and is supported by a stator shaft (not shown). Torque converter input shaft 31 and turbine runner 3
, A lock-up clutch mechanism 25 is provided between the torque converter input shaft 31 and the turbine runner 33.
The rotational speed difference (slip amount) with respect to the torque converter output shaft 37 connected to is controlled by the lock-up clutch mechanism 25.

The torque converter output shaft 37 serves as an input shaft of the transmission clutch / brake mechanism 27, and the hydraulic pressure of each part of a hydraulic circuit (not shown) provided in the transmission clutch / brake mechanism 27 is controlled by a hydraulic control device 29. By performing the control, the gear ratio (speed ratio) of the transmission gear mechanism 28 is switched. The output shaft 38 of the transmission gear mechanism 28 is connected to a wheel drive system.

On the other hand, the control circuit 39 controls the injection amount of the fuel injection nozzle 23 based on various engine operation state signals output from the exhaust gas temperature sensor 16, an accelerator sensor (not shown), an engine speed sensor, a water temperature sensor, and the like. Controlling fuel injection amount control circuit 40 (fuel supply amount control means)
And a catalyst temperature control circuit 41 for controlling the NOx catalyst 15 to an active state, and a shift control circuit 42 (shift control means) for controlling switching of the speed ratio of the automatic transmission 24.

Here, the purification characteristics of the NOx catalyst 15 are shown in FIG.
This will be described with reference to FIG. FIG. 2 is a graph showing a purification rate a of nitrogen oxide NOx, a purification rate b of light oil (HC) as a reducing agent, and a production rate c of sulfate (sulfur oxide) with respect to a catalyst temperature. When the catalyst temperature is lower than T1, neither nitrogen oxides nor HC are purified, and when the catalyst temperature is higher than T1, purification of nitrogen oxides and HC starts. When the catalyst temperature is around T2, the purification rate of nitrogen oxides becomes maximum, The purification rate of the purification becomes almost 100%. When the catalyst temperature is equal to or higher than T2, the purification rate of nitrogen oxides decreases as the catalyst temperature increases. When the catalyst temperature is equal to or higher than T3, the purification rate of nitrogen oxides greatly decreases and becomes almost zero. Therefore, nitrogen oxides can be purified only when the catalyst temperature is in the range of T1 to T3, which is the activation temperature range.

When the temperature is higher than T4, sulfate, which is a particulate matter of controlled substances, starts to be formed. Therefore, in order to suppress the formation of sulfate, the catalyst temperature needs to be lower than T4. Generally, for a NOx catalyst in which Pt is supported on zeolite, T1 in FIG.
00 ° C, T2 is about 250 ° C, T3 is about 300 ° C, and T4 is about 400 ° C. NOx catalyst 1 having such purification characteristics
In No. 5, in order to improve the purification rate of nitrogen oxides and suppress the production of sulfate, it is necessary to keep the catalyst temperature in the active temperature range of T1 (200 ° C.) to T3 (300 ° C.).

The control circuit 39 executes the catalyst temperature control routine shown in FIG. 3 to keep the catalyst temperature within the active temperature range. This routine is repeatedly started at predetermined time intervals or at predetermined crank angles by interrupt processing. When this routine is started, first, in step 101, signals output from the exhaust gas temperature sensor 16, the accelerator sensor, and the engine speed sensor are read. In the next step 102, the catalyst temperature (= exhaust gas temperature) detected by the exhaust gas temperature sensor 16 is compared with the active temperature range, and if it is within the active temperature range, the process proceeds to step 107, where the reference fuel supply amount map and the reference gear ratio The fuel supply amount and the gear ratio are controlled by the map (normal control).

In this case, as shown in FIG. 4, the reference gear ratio map is a transmission gear mechanism 2 according to the vehicle speed and the accelerator opening.
8 to control the gear ratio from first gear to second gear, second gear to third gear,
Shift up from 3rd gear to 4th gear, conversely 1st gear ← 2nd gear, 2nd gear ←
Shift down to 3rd gear, 3rd gear ← 4th gear. Here, the gear ratio means the torque converter input shaft 31 and the transmission gear mechanism 28.
Is the ratio of the rotation speed of the output shaft 38 to the rotation speed of the output shaft 38 and the constant torque.
The diesel engine 11 is operated at low rotation and high torque, and when the transmission ratio is large, the diesel engine 11 is operated at high rotation and low torque. Therefore, even when the engine output (= rotational speed × torque) is constant, that is, the driving force of the vehicle is constant, the gear ratio is selected to determine the engine speed, and the amount of fuel supplied to the diesel engine 11 is controlled to control the torque. By increasing or decreasing, various engine operating conditions can be created.

When the diesel engine 11 is operated at low rotation and high torque, the exhaust gas temperature becomes higher than when it is operated at high rotation and low torque. The reason is as follows. If the engine output is constant, the fuel consumption per unit time is almost constant, but the diesel engine 11
If the engine is running at low speed, one of the engine pistons
The amount of fuel supply per stroke increases, resulting in high torque. However, in the case of the diesel engine 11, the amount of intake air per stroke of the engine piston is constant regardless of the engine speed. The heat of combustion of the fuel is used to raise the temperature of the intake air, which determines the exhaust gas temperature. Under these circumstances, when the diesel engine 11 is operated at a low rotation speed and a high torque, the fuel supply amount is large and a large amount of combustion heat is constant when compared with the case where the diesel engine 11 is operated at a high rotation speed and a low torque. Because it is used to raise the temperature of the air volume, the exhaust gas temperature rises.

In this routine, utilizing this relationship, the speed ratio is selected to determine the engine speed under the condition that the engine output is constant (the driving force of the vehicle is constant), and the fuel supply amount to the diesel engine 11 is determined. By controlling and increasing or decreasing the torque, the exhaust gas temperature is adjusted, and the catalyst temperature is kept within the activation temperature range.

Specifically, when it is determined in step 102 that the catalyst temperature is lower than the activation temperature range,
Proceeding to step 103, when the speed ratio of the automatic transmission 24 is corrected to be reduced by the catalyst temperature raising control described below, and the diesel engine 11 is operated at a low rotation speed and a high torque by the fuel supply amount increase correction control. It is determined whether the engine torque is within the allowable limit value. In other words, when the engine torque is already high, such as during rapid acceleration, if the catalyst temperature rise control is performed, the engine torque exceeds the permissible limit value.
The fuel supply amount and the gear ratio are controlled by the reference fuel supply amount map and the reference gear ratio map. The change of the gear ratio is performed by changing the gear ratio of the transmission gear mechanism 28 (the same applies hereinafter). When the gear ratio is switched, the fuel injection amount and the injection timing are controlled in the same manner as in normal gear shift control to reduce gear shift shock (hereinafter the same).

On the other hand, if the engine torque is within the allowable limit value, the routine proceeds to step 105, where the catalyst temperature increase control is executed, and the fuel supply amount is corrected and controlled to increase according to the temperature increase fuel supply amount map. The speed ratio is corrected to the decreasing side by the temperature-raising speed ratio map, the diesel engine 11 is operated at a low rotation speed and a high torque, the exhaust gas temperature is raised, and the catalyst temperature is raised to the active temperature range. Here, as shown in FIG.
Since the engine 1 is driven at a low rotation speed and a high torque, as compared with the reference gear ratio map shown in FIG. 4, if the accelerator opening is the same, the vehicle shifts up at a low vehicle speed and does not shift down to a low vehicle speed. .

This characteristic will be described with reference to the time chart of FIG. It is assumed that the vehicle accelerates once and is traveling at point A in FIG. When the catalyst temperature is within the activation temperature range (T1 to T3), the second speed is set according to the reference speed ratio map shown in FIG. Thereafter, when the catalyst temperature decreases to T1 or less, the logic of step 105 shifts up from the second speed to the third speed according to the temperature-raising speed ratio map shown in FIG.
As the engine speed decreases, the fuel injection amount is increased according to the temperature-raised fuel supply amount map. As a result, the diesel engine 11 is operated at low rotation and high torque while maintaining the same output, the exhaust gas temperature rises, and the catalyst temperature also rises. In this way, when the catalyst temperature rises within the activation temperature range, the second speed is controlled by the logic of step 107 according to the reference speed ratio map of FIG. This allows
The catalyst temperature is kept within the activation temperature range.

If it is determined at step 102 in FIG. 3 that the catalyst temperature is higher than the activation temperature range, the routine proceeds to step 104, where the gear ratio of the automatic transmission 24 is increased by the catalyst temperature reduction control described below. And the correction control
Diesel engine 11 by fuel supply reduction control
It is determined whether or not the engine speed is within the allowable limit value when the engine is operated at a high speed and a low torque. In other words, when the engine speed is already high, such as during high-speed running, when the catalyst temperature reduction control is performed, the engine speed exceeds the allowable limit value. The fuel supply amount and the gear ratio are controlled by the supply amount map and the reference gear ratio map.

On the other hand, if the engine speed is within the permissible limit value, the routine proceeds to step 106, in which the fuel supply amount is corrected to the decreasing side by the temperature-lowering fuel supply amount map, and the speed is changed by the temperature-lowering gear ratio map. The diesel engine 11 is operated at a high speed and a low torque by correcting and controlling the ratio to the increasing side, and the exhaust gas temperature is lowered to lower the catalyst temperature to the active temperature range. Here, the temperature reduction gear ratio map is shown in FIG.
As shown in FIG. 4, since the diesel engine 11 is operated at a high rotation speed and a low torque, the vehicle does not shift up to a high vehicle speed if the accelerator opening is the same as compared with the reference gear ratio map of FIG. It is supposed to.

This characteristic will be described with reference to the time chart of FIG. It is assumed that the vehicle is accelerated once and is traveling at the point B in FIG. When the catalyst temperature is within the activation temperature range, the third speed is set according to the reference gear ratio map of FIG. Thereafter, when the catalyst temperature rises and becomes equal to or higher than T3, the logic of step 106 shifts down from third speed to second speed (increase in speed ratio) in accordance with the temperature decreasing speed ratio map shown in FIG. The fuel injection amount is reduced according to the temperature-lowering fuel supply amount map. As a result, the diesel engine 1
1 is operated at high rotation and low torque while maintaining the same output, and the exhaust gas temperature decreases and the catalyst temperature also decreases.
As a result, when the catalyst temperature falls to within the activation temperature range, in step 107, the third speed is controlled in accordance with the reference gear ratio map of FIG.

By controlling the catalyst temperature as described above, the exhaust gas temperature is changed by changing the engine speed and the engine torque while maintaining the engine output (= rotation speed × torque) constant. Without deteriorating the temperature, the catalyst temperature can be kept within the active temperature range where NOx can be purified, and a high NOx purification rate can be obtained. In addition, the generation of sulfate can be suppressed, the emission amount of particulates (fine particles) can be reduced, catalyst deterioration due to sulfate can be prevented, and stable exhaust gas purification performance can be maintained for a long period of time. .

[Second Embodiment] A second embodiment of the present invention will be described with reference to FIGS. In the above-described first embodiment, the gear ratio control is performed by switching the gear ratio of the transmission gear mechanism 28. In the second embodiment, the gear ratio control is performed by lock-up slip control of the lock-up clutch mechanism 25. When the transmission gear ratio is switched by the transmission gear mechanism 28 as in the first embodiment, the transmission ratio is switched stepwise, and the difference between the transmission ratios before and after the switching is large and the transmission shock is large. When the gear ratio is controlled by the lock-up slip control of the lock-up clutch mechanism 25 as in the second embodiment, continuous gear ratio control is performed, and fine gear ratio control can be performed. Shock also has the advantage of being small.

The lock-up clutch mechanism 25 controls the rotational speed difference (lock-up slip amount) between the input shaft 31 and the output shaft 37 of the torque converter. 31,
37 is completely connected, the lock-up slip amount (= input shaft rotation speed / output shaft rotation speed) becomes zero,
The gear ratio is reduced. On the other hand, when the operation of the lock-up clutch mechanism 25 is released, the lock-up slip amount increases, and the speed ratio increases.

Using this characteristic, in the second embodiment,
In step 105 of FIG. 3, when performing the correction control to reduce the gear ratio, the lock-up clutch mechanism 25 is operated to set the lock-up slip amount to zero. Also,
In step 106 of FIG. 3, when the gear ratio is to be controlled to increase, the operation of the lock-up clutch mechanism 25 is released to increase the lock-up slip amount. The other processing is the same as the processing of each step in FIG. 3 of the first embodiment.

In the second embodiment, at step 105 in FIG.
The operation in the case where is operated at low rotation and high torque to raise the catalyst temperature to the activation temperature range will be described with reference to the time chart of FIG. When the catalyst temperature is within the activation temperature range, the lock-up slip amount is from 50 rpm to 100 rpm which can absorb the rotation speed fluctuation of the diesel engine 11 and the wheel rotation speed fluctuation.
It is controlled in the range of rpm. Thereafter, when the catalyst temperature decreases to T1 or less, the lock-up clutch mechanism 25
Operates, the input / output shafts 31 and 37 are completely connected, and the lock-up slip amount is controlled to zero. This allows
As the engine speed decreases, the fuel injection amount is increased according to the temperature-raised fuel supply amount map. As a result, the diesel engine 11 is operated at low rotation and high torque while maintaining the same output, the exhaust gas temperature rises, and the catalyst temperature rises within the activation temperature range.

Next, in the second embodiment, in step 106 in FIG. 3, the case where the speed ratio is increased to operate the diesel engine 11 at a high speed and a low torque to lower the catalyst temperature to the active temperature range. The operation will be described with reference to the time chart of FIG. When the catalyst temperature is within the activation temperature range, the lock-up slip amount is changed from the normal 50 rpm to 100 rpm.
pm. Then, the catalyst temperature rises,
When T3 or more, the operation of the lock-up clutch mechanism 25 is released, the lock-up slip amount becomes larger than usual, the engine speed increases, and the fuel injection amount is reduced according to the temperature-lowering fuel supply amount map. As a result, the diesel engine 11 maintains the same output,
The engine is operated at a high rotation speed and a low torque, the exhaust gas temperature decreases, and the catalyst temperature decreases within the activation temperature range.

In the second embodiment, the gear ratio correction control is performed only by the lock-up clutch mechanism 25. However, the lock-up clutch mechanism 25 and the gear ratio switching of the transmission gear mechanism 28 are combined. The gear ratio correction control may be performed.

[Third Embodiment] A third embodiment of the present invention will be described with reference to FIGS. In the third embodiment, the catalyst temperature control of the present invention is applied when the accelerator is fully closed (zero) and the vehicle is decelerated. FIG.
Is a flowchart of a deceleration-time catalyst temperature control routine, FIG.
2 is a time chart showing the behavior of the catalyst temperature rise (warming) control during deceleration, and FIG. 13 is a time chart showing the behavior of the catalyst temperature decrease control during deceleration.

The deceleration-time catalyst temperature control routine of FIG.
It is repeatedly started in the interruption process at every predetermined time or every predetermined crank angle. When this routine is started, first, in step 201, signals output from the exhaust gas temperature sensor 16, the vehicle speed sensor, the accelerator sensor, and the engine speed sensor are read. In the next step 202, it is determined whether or not the accelerator is off (the accelerator is fully closed) and the vehicle is in a deceleration state. If “No”, the condition for executing the catalyst temperature control is not satisfied, and the routine proceeds to step 207. The normal lock-up clutch control, the speed ratio control based on the reference speed ratio map, and the normal fuel cut control (the fuel cut range up to the engine speed 1500 rpm when the vehicle is decelerated) are performed.

On the other hand, if the accelerator is off (the accelerator is fully closed) and the vehicle is in a decelerating state, the condition for executing the catalyst temperature control is satisfied, and the routine proceeds to step 203, where the catalyst temperature is compared with the active temperature range. Is within the activation temperature range, the routine proceeds to step 207, where normal lock-up clutch control, speed ratio control based on the reference speed ratio map, and normal fuel cut control are performed (normal control).

On the other hand, if the catalyst temperature is lower than the activation temperature range, the routine proceeds to step 204, and if the catalyst temperature raising (heating) control described below is performed, is the engine brake torque within the allowable limit value? Determine whether or not. That is, when the engine brake torque becomes extremely high, the allowable limit value is exceeded.
In step 07, normal control is performed.

If the engine brake torque is within the permissible limit value, the routine proceeds to step 206, where the operation of the lock-up clutch mechanism 25 is released, and the speed ratio is controlled to be reduced according to the temperature-raising speed ratio map. In addition, the fuel cut region where the fuel supply amount is zero is reduced.

The operation at this time will be described with reference to the time chart of FIG. Lock-up clutch mechanism 2 during deceleration
Immediately after releasing the operation of 5, the lock-up slip amount greatly changes from plus to minus. In this state, the rotation speed of the output shaft 37 is higher than the rotation speed of the torque converter input shaft 31, and the torque converter input shaft 31 is driven to rotate by the output shaft 37. Further, at the same time as the release of the lock-up clutch mechanism 25, the speed ratio is corrected and controlled to decrease based on the temperature-raising speed ratio map, and the diesel engine 11 is operated at a low speed. As a result, the engine speed rapidly decreases,
The amount of low-temperature exhaust gas passing through the NOx catalyst 15 (proportional to the engine speed) decreases, and the cooling of the NOx catalyst 15 by the low-temperature exhaust gas amount is reduced. Further, the fuel cut area is reduced from normal, and the fuel supply is restarted from, for example, 1800 rpm. As a result, the time during which the fuel-cut low-temperature exhaust gas passes through the NOx catalyst 15 (fuel cut period) is shortened, and the decrease in the catalyst temperature is suppressed in conjunction with the above-described decrease in the low-temperature exhaust gas amount.

On the other hand, step 203 in FIG.
If it is determined that the catalyst temperature is higher than the activation temperature range, the process proceeds to step 205, where it is determined whether the engine speed is within the allowable limit value when the catalyst temperature reduction control described below is performed. I do. In other words, when the engine speed is already high, such as during high-speed running, the catalyst temperature lowering control causes the engine speed to exceed the permissible limit value. Therefore, the catalyst temperature lowering correction is not performed, and the process proceeds to step 207 to perform normal control. .

If the engine speed is within the permissible limit value, the routine proceeds to step 208, where the lock-up clutch mechanism 25 is operated to connect the input / output shafts 31 and 37 of the torque converter 26 and to reduce the temperature reduction gear ratio. The gear ratio is controlled to be increased in accordance with the map, and the fuel cut area is expanded.

The operation at this time will be described with reference to the time chart of FIG. When the lock-up clutch mechanism 25 is operated, the input / output shafts 31 and 37 of the torque converter 26 are operated.
Are connected, and the lock-up slip amount becomes zero.
Further, the speed ratio is corrected and controlled to be increased according to the temperature drop speed ratio map, and the diesel engine 11 is operated at a high speed.
As a result, the engine speed decreases only gradually, and N
The amount of low-temperature exhaust gas passing through the Ox catalyst 15 (proportional to the engine speed) is maintained at a relatively large amount, and the cooling of the NOx catalyst 15 by the low-temperature exhaust gas is promoted. Further, the fuel cut area is enlarged more than usual to, for example, 1200 rpm.
Restart fuel supply from. As a result, the time during which the fuel-cut low-temperature exhaust gas passes through the NOx catalyst 15 (fuel cut period) is lengthened, the cooling of the NOx catalyst 15 by the low-temperature exhaust gas is continued, and the NOx catalyst 15 is reliably activated in the activation temperature range. Cooled inside.

In the third embodiment, the catalyst temperature control of the first or second embodiment may be executed during an operation other than the time of deceleration.

In each of the first to third embodiments described above,
Although the present invention is applied to a diesel engine, it may be applied to a gasoline lean-burn engine or a direct fuel injection (direct injection) engine. The present invention is not limited to the NOx catalyst, and uses another catalyst such as an oxidation catalyst. If the present invention is applied to the system, it is possible to prevent thermal deterioration of the catalyst and suppress the production of sulfate. Further, the automatic transmission 24 used in each of the above embodiments uses the torque converter 26 that transmits the engine power by a fluid coupling, but transmits the engine power using a belt and a pulley, and reduces the effective radius of the pulley. The present invention may be applied to a continuously variable transmission that controls the gear ratio by making it variable.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an entire system according to a first embodiment of the present invention;

FIG. 2 is a characteristic diagram showing a relationship between a catalyst temperature and a NOx purification rate, an HC purification rate, and a sulfate generation rate.

FIG. 3 is a flowchart showing a processing flow of a catalyst temperature control routine according to the first embodiment;

FIG. 4 is a diagram showing characteristics of a reference gear ratio map;

FIG. 5 is a diagram showing characteristics of a temperature-raising gear ratio map;

FIG. 6 is a diagram showing characteristics of a temperature reduction gear ratio map;

FIG. 7 is a time chart showing the behavior of the catalyst temperature increase control in the first embodiment.

FIG. 8 is a time chart showing the behavior of the catalyst cooling control in the first embodiment.

FIG. 9 is a time chart showing the behavior of the catalyst temperature increase control in the second embodiment.

FIG. 10 is a time chart showing the behavior of the catalyst cooling control in the second embodiment.

FIG. 11 is a flowchart showing a process flow of a catalyst temperature control routine at the time of deceleration in a third embodiment.

FIG. 12 is a time chart showing the behavior of catalyst temperature rise (heat retention) control during deceleration in the third embodiment.

FIG. 13 is a time chart showing the behavior of catalyst temperature decrease control during deceleration in the third embodiment.

[Explanation of symbols]

Reference Signs List 11: diesel engine (internal combustion engine), 13: exhaust pipe, 15: NOx catalyst, 16: exhaust gas temperature sensor (catalyst temperature determination means), 17: light oil addition device, 18: fuel injection pump, 23: fuel injection nozzle (fuel) Supply means), 24
... automatic transmission, 25 ... lock-up clutch mechanism, 26
... torque converter, 27 ... transmission clutch / brake mechanism, 28 ... transmission gear mechanism, 29 ... hydraulic control device, 30 ...
Crankshaft, 31 torque converter input shaft, 32 pump impeller, 33 turbine runner, 34 stator, 35 one-way clutch, 37 torque converter output shaft, 39 control circuit, 40 fuel injection amount control circuit ( Fuel injection amount control means), 41 ... catalyst temperature control circuit, 42 ...
Shift control circuit (shift control means).

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location F02D 45/00 ZAB F02D 45/00 ZAB 312 312M 312F 360 360C (72) Inventor Tsukasa Kuboshima Kariya, Aichi Prefecture 1-1 1-1 Showa-cho, Nippon Denso Co., Ltd.

Claims (6)

[Claims] 1. A fuel supply means for supplying fuel to each cylinder of an internal combustion engine, a fuel supply amount control means for increasing / decreasing a fuel supply amount of the fuel supply means in accordance with an operation state of the internal combustion engine, Equipped in a vehicle equipped with an automatic transmission provided in a power transmission system of an engine, shift control means for controlling switching of a gear ratio of the automatic transmission, and an exhaust gas purifying catalyst provided in an exhaust system. A catalyst temperature control device for an exhaust gas purifying catalyst of an internal combustion engine, comprising: catalyst temperature determination means for determining a temperature of the catalyst, wherein the catalyst temperature determined by the catalyst temperature determination means is lower than an active temperature range of the catalyst. In this case, the fuel supply amount control means corrects the fuel supply amount of the fuel supply means to the increasing side, and the shift control means corrects the speed ratio of the automatic transmission to the decreasing side, and the catalyst temperature is activated. temperature When the temperature is higher than the range, the fuel supply amount control means corrects the fuel supply amount of the fuel supply means to the decreasing side, and the shift control means corrects the speed ratio of the automatic transmission to the increasing side. A temperature control device for an exhaust gas purifying catalyst of an internal combustion engine. 2. The method according to claim 1, wherein the change ratio of the automatic transmission is changed by the shift control unit by at least one of a change of a gear ratio of a transmission gear mechanism and a lock-up slip control of a lock-up clutch mechanism, or a change of a belt drive system. 2. The temperature control device for an exhaust gas purifying catalyst for an internal combustion engine according to claim 1, wherein the control is performed by controlling the effective pulley diameter of the step transmission. 3. A fuel supply means for supplying fuel to each cylinder of the internal combustion engine, a fuel supply amount control means for increasing / decreasing a fuel supply amount of the fuel supply means in accordance with an operation state of the internal combustion engine, An automatic transmission having a lock-up clutch mechanism provided in a power transmission system of an engine, a shift control means for controlling switching of a gear ratio of the automatic transmission, and an exhaust gas purifying catalyst provided in an exhaust system. A catalyst temperature control device for an exhaust gas purifying catalyst of an internal combustion engine mounted on a vehicle, comprising: catalyst temperature determination means for determining a temperature of the catalyst, wherein the catalyst temperature determination means when the vehicle is in a deceleration state. When the catalyst temperature determined by the above is lower than the catalyst activation temperature range, the shift control means releases the lock-up control of the lock-up clutch mechanism, and the catalyst temperature falls below the activation temperature range. When hot, the shift control unit temperature controller of the exhaust gas purifying catalyst of an internal combustion engine, characterized in that actuating the lock-up control of the lock-up clutch mechanism. 4. When the catalyst temperature is determined to be lower than an activation temperature range when the vehicle is in a deceleration state, the shift control means cancels lock-up control and decreases the speed ratio of the automatic transmission. Side, and the fuel supply amount control means reduces the fuel cut region where the fuel supply amount is zero, and when the catalyst temperature is determined to be higher than the active temperature range when the vehicle is in a deceleration state, 4. The apparatus according to claim 3, wherein said shift control means activates lock-up control, corrects the speed ratio of said automatic transmission to an increasing side, and said fuel supply amount control means enlarges a fuel cut region. The temperature control device for an exhaust gas purifying catalyst for an internal combustion engine according to the above. 5. The catalyst according to claim 1, wherein the catalyst is a NOx catalyst capable of reducing and purifying NOx under excess oxygen.
The temperature control device for an exhaust gas purifying catalyst for an internal combustion engine according to any one of claims 1 to 4. 6. The temperature control device for an exhaust gas purifying catalyst of an internal combustion engine according to claim 1, wherein the internal combustion engine is a diesel engine.