JPH1054251A - Internal combustion engine controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve fuel consumption, exhaust emission control capability, and driverability. SOLUTION: A bypass air quantity control valve 19 is fitted at an intake bypass passage 18 which bypasses an intake passage 12 on more downstream side than a turbo supercharger 13 and an exhaust passage 14 on more upstream side of a catalyst 17, and a bypass displacement control valve 22 is fitted at an exhaust bypass passage 21 which bypasses the upstream side and the downstream side of an exhaust gas turbine 15. When catalyst temperature is below target catalyst temperature, the bypass air quantity control valve 19 is opened completely and cooling of the catalyst 17 is stopped. The opening of the bypass displacement control valve 22 is controlled to ensure necessary engine output. When the catalyst temperature is above the target catalyst temperature, the opening of the bypass air quantity controlling valve 19 is controlled, with necessary engine output ensured, according to a difference between the catalyst temperature and the target catalyst temperature within the range of sufficient supercharging performance of the turbo supercharger 13, and a part of supercharging air is bypassed to the exhaust passage 14 side to cool down the catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine control device provided with a supercharger and an exhaust gas purifying catalyst.

[0002]

2. Description of the Related Art For example, a catalyst for purifying nitrogen oxides (NOx) contained in exhaust gas from a diesel engine is disclosed in US Pat.
It is generally known that the NOx purification rate is high only in a predetermined activation temperature range (for example, 200 to 400 ° C.) as shown in FIG. Therefore, in order to reduce NOx emission, it is effective to maintain the catalyst temperature within the activation temperature range. However, in practice, the exhaust gas temperature greatly changes depending on the operation state of the engine, and the catalyst temperature may be out of the activation temperature range, so that stable NOx purification performance cannot be obtained.

Therefore, in an engine equipped with a turbocharger, as disclosed in Japanese Patent Application Laid-Open No. 7-189720, an intake passage on the upstream side of the turbocharger and an exhaust passage on the downstream side of the turbocharger are provided. A passage opening / closing valve that opens and closes by a boost pressure is provided in the middle of the bypass passage, and when the boost pressure becomes a predetermined value or more, the passage opening / closing valve is opened to reduce the supercharged air. By partially bypassing the exhaust passage, the exhaust gas temperature is lowered to cool the catalyst. However, if a part of the supercharged air is bypassed to the exhaust passage, the engine output is reduced and the drivability is deteriorated. Therefore, in Japanese Patent Application Laid-Open No. Hei 7-189720, a part of the supercharged air is bypassed. Attempts have been made to solve the accompanying decrease in engine output by installing an auxiliary machine for amplifying the supercharging pressure in the turbocharger.

[0004]

However, in the configuration disclosed in the above publication, the passage opening / closing valve of the bypass passage is opened / closed by the supercharging pressure. Therefore, even if the catalyst temperature is high, if the supercharging pressure is low, the passage opening / closing valve is opened. It is not opened and the catalyst cannot be cooled. Therefore, in the configuration of the above publication, even when the engine load is small, when the catalyst temperature (exhaust gas temperature) is high,
It is necessary to drive the auxiliary machine with the output of the engine to increase the supercharging pressure, which deteriorates fuel efficiency. In addition, when the engine load is large, the supercharging pressure increases,
Even when the catalyst temperature is appropriate, the passage opening / closing valve is opened due to the supercharging pressure, so that the catalyst temperature falls below the appropriate temperature, and the exhaust gas purification capacity is reduced. Further, by providing the auxiliary machine, the whole apparatus becomes large in size, and it is not possible to satisfy the demand for downsizing and cost reduction.

[0005] The present invention has been made in view of such circumstances, and an object of the present invention is to achieve both exhaust purification performance and drivability while realizing improved fuel economy, compactness, and low cost. It is an object of the present invention to provide an internal combustion engine control device that can achieve the above.

[0006]

According to a first aspect of the present invention, there is provided an internal combustion engine control apparatus comprising: an intake passage downstream of a supercharger and an exhaust passage upstream of a catalyst; Is provided, and a bypass air amount control valve is provided in the intake bypass passage.
Then, the oxygen amount of the intake air supplied to the internal combustion engine (hereinafter referred to as “supplied oxygen amount”) is estimated by the supplied oxygen amount estimating means, and the oxygen amount of the intake air required to burn the fuel supplied to the internal combustion engine is estimated. (Hereinafter referred to as "target oxygen amount")
Is calculated by the target oxygen amount calculating means. Then, the control unit controls the opening degree of the bypass air amount control valve based on the difference between the catalyst temperature and the target catalyst temperature determined by the catalyst temperature determination unit and the difference between the supplied oxygen amount and the target oxygen amount. I do. Here, “controlling the opening degree” means not only controlling the valve opening degree with a motor or the like, but also controlling the degree of time for opening and closing the valve by controlling the ON / OFF duty of the solenoid valve. Including.

In this case, the smaller the difference between the supplied oxygen amount and the target oxygen amount, the better the combustion state of the fuel supplied to the internal combustion engine, which leads to improved drivability and reduced emission. If the difference between the catalyst temperature and the target catalyst temperature is small, the catalyst temperature falls within a predetermined activation temperature range, and the NOx purification rate increases. In consideration of such characteristics, as in the present invention, if the opening degree of the bypass air amount control valve is controlled based on the difference between the catalyst temperature and the target catalyst temperature and the difference between the supplied oxygen amount and the target oxygen amount, The exhaust gas purifying performance can be secured by adjusting the bypass amount of the supercharged air (catalyst cooling effect) while ensuring drivability (output of the internal combustion engine). In addition, according to the present invention, the opening degree of the bypass air amount control valve can be controlled by the control means irrespective of the supercharging pressure, so that the supercharging pressure is increased by driving the auxiliary machine with the output of the internal combustion engine as in the prior art. This eliminates the necessity and improves fuel efficiency, and also reduces the size and cost because the auxiliary machine is not required.

When a turbocharger is used as the supercharger, an exhaust bypass passage for bypassing the upstream and downstream sides of the exhaust turbine of the turbocharger is provided. The exhaust bypass passage may be provided with a bypass exhaust amount control valve. In this case,
The degree of opening of the bypass air amount control valve and the bypass exhaust amount control valve may be comprehensively controlled based on the difference between the catalyst temperature and the target catalyst temperature and the difference between the supplied oxygen amount and the target oxygen amount. With this configuration, by controlling the bypass amount of the exhaust gas flowing through the exhaust bypass passage, the amount of the exhaust gas passing through the exhaust turbine is controlled, and the rotation speed (supercharging pressure) of the exhaust turbine is controlled. And control characteristics can be improved.

In this case, when the catalyst temperature is equal to or lower than the target catalyst temperature, that is, when it is not necessary to cool the catalyst, the bypass air amount control valve is closed to move the exhaust passage upstream of the catalyst in the exhaust passage. By cutting off the bypass of the supercharged air, the cooling of the catalyst by the supercharged air is stopped, and the increase of the catalyst temperature is promoted to enhance the exhaust gas purifying ability. At the same time, by controlling the opening of the bypass exhaust amount control valve, the number of revolutions (supercharging pressure) of the exhaust turbine is controlled so that the supplied oxygen amount is adjusted to the target oxygen amount, and the combustion of the internal combustion engine is controlled. Improve efficiency,
Improve fuel efficiency and drivability.

On the other hand, when the catalyst temperature is higher than the target catalyst temperature, that is, when the catalyst needs to be cooled, the bypass air amount control valve and the bypass exhaust amount control valve are opened to adjust the supplied oxygen amount to the target oxygen amount. Control the degree of opening of the bypass air amount control valve within the range where the turbocharger has sufficient supercharging capacity after ensuring the output of the internal combustion engine, and calculating the difference between the catalyst temperature and the target catalyst temperature. By reducing the temperature of the exhaust gas and cooling the catalyst, the exhaust gas purification capacity is increased by bypassing a part of the supercharged air to the exhaust passage side. In this case, bypass of the supercharged air to the exhaust passage side (cooling of the catalyst)
Is performed within a range where the turbocharger has enough supercharging capacity, so that the supply of supercharged air to the internal combustion engine does not become insufficient, the output of the internal combustion engine is secured, and the drivability is reduced. I will not do it.

According to a fourth aspect of the present invention, a first intake bypass passage that bypasses an intake passage downstream of the turbocharger and an exhaust passage upstream of the catalyst, and a downstream of the turbocharger. A second intake bypass passage is provided for bypassing the intake passage and an exhaust passage downstream of the catalyst. The first and second bypass air amount control valves provided in both intake bypass passages are connected to the catalyst temperature and The control means performs comprehensive control based on the difference between the target catalyst temperature and the difference between the supplied oxygen amount and the target oxygen amount. With this configuration, by controlling the first and second bypass air amount control valves, the control of the bypass amount of the supercharging air to the upstream side of the catalyst in the exhaust passage and the control of the supercharging pressure are simultaneously performed. It is possible to achieve both exhaust purification performance and drivability.

In this case, when the catalyst temperature is lower than the target catalyst temperature (when it is not necessary to cool the catalyst), the first bypass air amount control valve is closed, so that the catalyst in the exhaust passage is closed. Shut off the bypass for upstream supercharging,
The cooling of the catalyst due to the supercharging is stopped, and a rise in the catalyst temperature is promoted to enhance the exhaust gas purification ability. At the same time, by controlling the opening degree of the second bypass air amount control valve, the supercharging pressure is controlled by controlling the bypass amount of the supercharged air to the downstream side of the catalyst in the exhaust passage, and the supply oxygen amount is controlled. Control is performed to match the amount of oxygen, thereby improving the combustion efficiency of the internal combustion engine and improving fuel efficiency and drivability.

On the other hand, when the catalyst temperature is higher than the target catalyst temperature, the first oxygen amount is adjusted so that the supplied oxygen amount matches the target oxygen amount.
And controlling the degree of opening of the second bypass air amount control valve to secure the output of the internal combustion engine, and then setting the difference between the catalyst temperature and the target catalyst temperature within a range where the supercharging capacity of the supercharger has a margin. By controlling the opening degree of the first bypass air amount control valve according to the above, a part of the supercharged air is bypassed to the catalyst upstream side of the exhaust passage,
The catalyst is cooled by lowering the exhaust gas temperature on the upstream side of the catalyst. In this case, since the bypass of the supercharged air to the upstream side of the catalyst (cooling of the catalyst) is performed within a range where the supercharging capacity of the supercharger has a surplus, the supercharged air to the internal combustion engine becomes insufficiently supplied. The output of the internal combustion engine is secured, and the drivability does not decrease.

According to a sixth aspect of the present invention, the supply oxygen amount estimating means detects an intake pressure sensor for detecting an intake pressure, an intake air amount sensor for detecting an intake air amount, and detects a recirculation amount of exhaust gas to an intake system. At least one of an exhaust gas recirculation amount sensor and an oxygen sensor for detecting an amount of oxygen sucked into the internal combustion engine;
The supply oxygen amount is estimated based on the output signals of the two sensors. Here, as the intake pressure sensor and the intake air amount sensor, existing sensors mounted on the vehicle for controlling the internal combustion engine may be used, and the cost burden can be reduced. Furthermore, the supply oxygen amount may be estimated by combining the detection value of one of the intake pressure sensor and the intake air amount sensor with the detection value of the exhaust gas recirculation amount sensor. In this way, it is possible to estimate an accurate supply oxygen amount in consideration of oxygen in the exhaust gas recirculated to the intake system. Further, if the oxygen sensor is used, the supplied oxygen amount can be directly detected.

According to a seventh aspect of the present invention, the target oxygen amount calculating means sets the target oxygen amount in an operating state of the internal combustion engine within a range equal to or less than a maximum oxygen amount corresponding to a supercharging pressure limit value of the supercharger. Calculated based on Thus, the target oxygen amount can be set so that the internal combustion engine does not become overloaded, and the durability of the internal combustion engine can be improved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. First, a schematic configuration of the entire engine control system will be described with reference to FIG. A turbocharger 13 is provided in an intake passage 12 of a diesel engine 11 which is an internal combustion engine. This turbocharger 13
Uses an exhaust turbine 15 driven by the kinetic energy of exhaust gas flowing in the exhaust passage 14 as a drive source. A catalyst 17 for purifying exhaust gas is provided in the exhaust passage 14 downstream of the exhaust turbine 15.

Further, an intake bypass passage 18 for bypassing the intake passage 12 downstream of the turbocharger 13 and the exhaust passage 14 upstream of the catalyst 17 is provided. A bypass air amount control valve 19 whose degree can be adjusted is provided. The opening degree of the bypass air amount control valve 19 may be adjusted by a motor (not shown) such as a step motor. Alternatively, when the bypass air amount control valve 19 is formed by an electromagnetic valve, the energization of the solenoid coil of the electromagnetic valve is duty-controlled to control the degree of time for opening and closing the valve and pass through the valve. What is necessary is just to control the amount of air. Controlling the degree of opening and closing the valve by such duty control of the solenoid valve is also included in the concept of "controlling the opening of the bypass air amount control valve" in the claims. An intake pressure sensor 20 for detecting intake pressure is provided in the intake passage 12 downstream of the inlet 18a of the intake bypass passage 18.

On the other hand, in the exhaust passage 14, the exhaust turbine 1
An exhaust bypass passage 21 (a waste gate) for bypassing the upstream side and the downstream side of the exhaust pipe 5 is provided, and the exhaust bypass passage 21 is provided with a bypass exhaust amount control valve 22 whose opening degree can be adjusted. This bypass displacement control valve 22
May be adjusted by a duty control of a motor (not shown) or a solenoid valve, similarly to the adjustment of the opening of the bypass air amount control valve 19. An exhaust temperature sensor 23 for detecting an exhaust gas temperature is provided near the upstream end surface of the catalyst 17, and the temperature of the catalyst 17 is determined from the exhaust gas temperature detected by the exhaust gas temperature sensor 23. Therefore, in the present embodiment, the exhaust gas temperature sensor 23 is used as a catalyst temperature determining means described in the claims.

The accelerator 24 is provided with an accelerator opening sensor 25 for detecting the accelerator opening (accelerator operation amount), and the diesel engine 11 is provided with an engine speed sensor 26 for detecting the engine speed. ing.

Output signals from sensors for detecting various information related to engine control, such as an accelerator opening sensor 25, an engine speed sensor 26, an exhaust temperature sensor 23, and an intake pressure sensor 20, are sent to an electronic control circuit for engine control (hereinafter referred to as an engine control circuit). (Referred to as “ECU”) 27. This ECU 27
Is mainly composed of a microcomputer, controls the operation of a fuel injection device (not shown) based on the various sensor information, and executes a supercharging control program shown in FIGS. It functions as control means for controlling the opening of the bypass air amount control valve 19 and the bypass exhaust amount control valve 22 based on a difference between the temperature and the target catalyst temperature and a difference between a supply oxygen amount and a target oxygen amount described later.

Hereinafter, the flow of processing of the supercharging control program shown in FIGS. 2 and 3 will be described. This program is started by interruption processing at predetermined time intervals (for example, at every one second) or at predetermined crank angle intervals. When this program is started, first, in step S101, the engine speed Ne, the accelerator opening Ac, and the intake pressure output from the engine speed sensor 26, the accelerator opening sensor 25, the intake pressure sensor 20, and the exhaust temperature sensor 23 are output. Read Pq and exhaust temperature T. And
In the next step S102, the read engine speed N
The target intake pressure P1 required to secure the target engine output is calculated from preset map data in accordance with e and the accelerator opening Ac. At this time, the target intake pressure P
1 is set within a range not more than the supercharging pressure limit value of the turbocharger 13 so that the diesel engine 11 is not overloaded.

After calculating the target intake pressure P1, in step S103, the exhaust gas temperature T is compared with the target catalyst temperature T1 to determine the temperature state (active state) of the catalyst 17. In this case, the temperature of the catalyst 17 is increased mainly by the heat of the exhaust gas,
Since the catalyst temperature can be estimated to be substantially equal to the exhaust gas temperature T,
In the present embodiment, the exhaust gas temperature T is used as substitute data for the catalyst temperature. The target catalyst temperature T1 is determined by the N
The catalyst temperature Tmax (see FIG. 4) at which the Ox purification rate is maximized is set.

In step S103, the exhaust gas temperature T (=
If the catalyst temperature is determined to be equal to or lower than the target catalyst temperature T1, the cooling of the catalyst 17 is unnecessary. In this case, the process proceeds to step S104, and the opening degree of the bypass exhaust amount control valve 22 is calculated so that the intake air pressure Pq becomes equal to the target intake air pressure P1, assuming that the bypass air amount control valve 19 is fully closed. After this,
In step S105, a full-close signal of the bypass air amount control valve 19 is output to fully close the bypass air amount control valve 19, and the bypass of the supercharged air to the upstream side of the catalyst 17 in the exhaust passage 14 is cut off, and the exhaust gas is exhausted. The temperature is prevented from lowering, and the temperature of the catalyst 17 is promoted. Further, in step S105, the opening degree signal of the bypass exhaust amount control valve 22 calculated in step S104 is output, the opening degree of the bypass exhaust amount control valve 22 is adjusted, and the exhaust turbine 15 of the turbocharger 13 is controlled. Adjust the amount of exhaust gas to be bypassed. Thereby, the amount of exhaust gas passing through the exhaust turbine 15 is adjusted, and the exhaust turbine 1
5, the supercharging pressure of the turbocharger 13 is adjusted so that the intake pressure Pq becomes the target intake pressure P1, and the combustion efficiency of the diesel engine 11 is improved, thereby improving fuel efficiency and drivability. Let it.

In this case, since the oxygen amount (supply oxygen amount) of the intake air supplied to the diesel engine 11 can be estimated from the intake pressure Pq, the intake pressure Pq is used as substitute data for the supply oxygen amount. Therefore, in the present embodiment, the intake pressure Pq
Is used as the supply oxygen amount estimating means referred to in the claims. Then, the target intake pressure P1 calculated in step S102 is used as substitute data of the oxygen amount (target oxygen amount) of the intake air necessary for burning the fuel supplied to the diesel engine 11. Therefore, in the present embodiment, the process of step S102 for calculating the target intake pressure P1 plays a role as a target oxygen amount calculating means in the claims.

On the other hand, if it is determined in step S103 that the exhaust gas temperature T (= catalyst temperature) is higher than the target catalyst temperature T1, the catalyst 17 needs to be cooled. In this case, the process proceeds to step S106 in FIG.
= The target intake pressure P1 and the opening degree of the bypass air amount control valve 19 is calculated so that the exhaust gas temperature T becomes equal to the target catalyst temperature T1. Thereafter, the process proceeds to step S107, and the opening degree of the bypass exhaust amount control valve 22 is calculated based on the opening degree of the bypass air amount control valve 19 calculated in step S106 so that the intake pressure Pq becomes equal to the target intake pressure P1.

Thereafter, in step S108, it is determined whether or not the opening of the bypass displacement control valve 22 is greater than 0 (= fully closed). If it is, the process proceeds to step S109, and in step S106. The calculated opening signal of the bypass air amount control valve 19 and the calculated opening signal of the bypass exhaust amount control valve 22 calculated in step S107 are output.
Adjust the opening of 9, 22. Thereby, the intake pressure Pq =
The supercharging pressure is controlled so as to reach the target intake pressure P1 to secure a necessary engine output, and at the same time, the bypass air amount control valve 19 is controlled so that the exhaust gas temperature T (= catalyst temperature) matches the target catalyst temperature T1. By controlling the opening degree, a part of the supercharged air is bypassed to the exhaust passage 14 side and mixed with the exhaust gas, thereby lowering the exhaust gas temperature, cooling the catalyst 17, and bringing the catalyst temperature to the target catalyst temperature T1. Decrease quickly.

On the other hand, if it is determined in step S108 that the opening degree of the bypass exhaust amount control valve 22 is equal to or less than 0 (= fully closed), the process proceeds to step S110, where the bypass exhaust amount control valve 22 is fully closed. , The opening of the bypass air amount control valve 19 is calculated so that the intake pressure Pq becomes equal to the target intake pressure P1. After that, in step S111, the opening degree signal of the bypass air amount control valve 19 and the fully closed signal of the bypass exhaust amount control valve 22 calculated in step S110 are output,
By fully closing the bypass exhaust amount control valve 22 and adjusting the opening of the bypass air amount control valve 19, the intake pressure Pq = the target intake pressure P
After controlling the supercharging pressure so as to attain the necessary engine output, a part of the supercharging is reduced to the exhaust passage 14 within a range where the supercharging capacity of the turbocharger 13 has a margin. By lowering the exhaust gas temperature, the catalyst 17 is cooled and the catalyst temperature is lowered.

According to the supercharging control described above, when the catalyst temperature (exhaust gas temperature T) is equal to or lower than the target catalyst temperature T1, that is, when cooling of the catalyst 17 is unnecessary, the bypass air amount control valve 19 is fully closed. By doing so, the bypass of the supercharged air to the exhaust passage 14 side is shut off, the cooling of the catalyst by the supercharged air is stopped, and a rise in the catalyst temperature is promoted to enhance the exhaust gas purification capability.
At the same time, by controlling the opening degree of the bypass exhaust amount control valve 22, the rotation speed (supercharging pressure) of the exhaust turbine 15 is controlled to reduce the intake pressure Pq (supply oxygen amount) to the target intake pressure P1 (target oxygen amount). ) To improve the fuel efficiency and drivability by improving the combustion efficiency of the diesel engine 11.

On the other hand, if the catalyst temperature (exhaust temperature T) is higher than the target catalyst temperature T1, that is, if the catalyst 17 needs to be cooled, the intake pressure Pq (supply oxygen amount) is reduced to the target intake pressure P1.
By controlling the opening degree of the bypass air amount control valve 19 and the bypass exhaust amount control valve 22 so as to match the (target oxygen amount),
After the output of the diesel engine 11 is secured, the bypass air amount control valve is controlled according to the difference between the catalyst temperature (exhaust temperature T) and the target catalyst temperature T1 within a range in which the supercharging capacity of the turbocharger 13 has a margin. By controlling the opening of the valve 19 and bypassing a part of the supercharged air to the exhaust passage 14, the exhaust gas temperature is reduced, the catalyst 17 is cooled, and the exhaust gas purifying capability is enhanced.

The behavior of the supercharging control described above will be described with reference to a time chart shown in FIG. The time chart of FIG. 5 is an example of a traveling pattern of acceleration → constant speed traveling → deceleration that frequently occurs when traveling in an urban area. Time t during idle operation
At 0, since the catalyst temperature is lower than the target catalyst temperature T1,
The bypass air amount control valve 19 is fully closed, and the catalyst 17 is not cooled. Also, during idling operation, the output of the diesel engine 11 may be the lowest, so that the bypass exhaust amount control valve 22 is fully opened, the amount of exhaust gas passing through the exhaust turbine 15 is minimal, and the turbocharger 13 Work volume (supercharging pressure) is minimized.

Thereafter, when acceleration is started at time t1, the engine output needs to be increased, so that the bypass displacement control valve 22 is fully closed, the work of the turbocharger 13 is increased, and the supercharging pressure is reduced. Enhanced. Almost simultaneously with the start of the acceleration, the exhaust gas temperature rises. However, since the catalyst 17 has a heat capacity, the increase in the catalyst temperature is later than the increase in the exhaust gas temperature. Accordingly, if the acceleration time (t1 -t2) is relatively short, the catalyst 17 does not need to be cooled during the acceleration because the catalyst temperature is lower than the target catalyst temperature T1. In this case,
During acceleration (t1 -t2), the bypass air amount control valve 19 is continuously maintained in the fully closed state, the bypass of the supercharging air to the exhaust passage 14 side is cut off, and the supercharging all increases the supercharging pressure. The engine output is effectively increased, and good acceleration is ensured.

After that, when the acceleration is completed at time t2 and the vehicle shifts to the constant speed running, the engine output can be smaller than that at the time of acceleration, so that the bypass displacement control valve 22 is opened and the work amount of the turbocharger 13 is increased. (Supercharging pressure) is lower than during acceleration.

At this time, the catalyst temperature continues to rise for a while, even after shifting to the constant speed running, and at time t3, the catalyst temperature exceeds the target catalyst temperature T1. In this case, since the catalyst 17 needs to be cooled, the bypass air amount control valve 19 is opened to an opening corresponding to the difference between the catalyst temperature and the target catalyst temperature T1, and a part of the supercharged air is exhausted through the exhaust passage. Bypassed to the 14 side,
The catalyst 17 is cooled. In this way, when a part of the supercharged air is used for cooling the catalyst 17, the diesel engine 11
To compensate for the decrease in supercharged air supplied to
The opening of the bypass displacement control valve 22 is reduced, the work of the turbocharger 13 is increased, and the engine output required to maintain the constant speed traveling is secured.

After the catalyst temperature reaches the target catalyst temperature T1, the engine temperature is secured and the catalyst temperature is made to coincide with the target catalyst temperature T1 within a range where the supercharging capacity of the turbocharger 13 has a margin. Thus, the opening degree of the bypass air amount control valve 19 is controlled to enhance the exhaust gas purification ability.

When the cooling of the catalyst 17 (bypassing the supercharged air) is not performed as in a conventional general diesel engine, as shown by a dotted line in FIG. Exceeding the catalyst temperature T1, the difference between the catalyst temperature and the target catalyst temperature T1 becomes large, the NOx purification rate decreases, and the NOx emission increases.

On the other hand, in this embodiment, the engine output is ensured, and the bypass is performed in accordance with the difference between the catalyst temperature and the target catalyst temperature T1 within a range where the supercharging capacity of the turbocharger 13 has a margin. Since the opening degree of the air amount control valve 19 is controlled to adjust the bypass amount of the supercharged air for cooling the catalyst 17, N
Ox purification rate can be maintained at a high catalyst temperature, and NOx emission can be effectively reduced. Moreover, the bypass of the supercharged air to the exhaust passage 14 side (cooling of the catalyst 17) is performed by the turbocharger 1
Since the supercharging capacity of 4 is performed within a range where there is a surplus, the supercharging air supply to the diesel engine 11 does not become insufficient, the engine output is secured, the drivability is not reduced, and the exhaust gas is not exhausted. Purification ability and drivability can be compatible.

Incidentally, an intercooler (a heat exchanger for cooling the supercharged air) may be provided in the intake passage 12 on the downstream side of the turbocharger 13 to increase the supercharging efficiency. In this case, it is preferable to provide the inlet 18a of the intake bypass passage 18 downstream of the intercooler. By doing so, a part of the supercharged air cooled by the intercooler is bypassed to the exhaust passage 14 side, so that the cooling effect of the catalyst 17 can be further enhanced.

In the first embodiment, the exhaust bypass passage 21 and the bypass exhaust amount control valve 22 are provided.
The present invention can be applied to a configuration in which these are omitted and can be implemented. In this case, instead of the turbocharger 13, another supercharger such as a mechanical supercharger (supercharger) may be employed.

On the other hand, in the second embodiment of the present invention shown in FIG. 6, the first passage which bypasses the intake passage 12 downstream of the turbocharger 13 and the exhaust passage 14 upstream of the catalyst 17 is used. An intake bypass passage 31 is provided, and a first bypass air amount control valve 32 whose opening is adjustable is provided on the outlet side of the first intake bypass passage 31. Further, a second intake bypass passage 33 for bypassing the first intake bypass passage 31 upstream of the first bypass air amount control valve 32 and the exhaust passage 14 downstream of the catalyst 17 is provided. In the second intake bypass passage 33, a second bypass air amount control valve 34 whose opening degree can be adjusted is provided. The exhaust bypass passage 21 and the bypass exhaust amount control valve 22 provided in the first embodiment are eliminated. Other configurations are the same as those of the first embodiment.

In the second embodiment configured as described above, the first intake bypass passage 31 and the first bypass air amount control valve 32 are connected to the intake bypass passage 18 and the bypass air amount control valve in the first embodiment. It plays exactly the same role as the valve 19. Further, the second intake bypass passage 33 and the second bypass air amount control valve 34 adjust the amount of supercharged air bypassed to the downstream side of the catalyst 17 so that the supercharging pressure supplied to the diesel engine 11 is reduced. To adjust, the first
The exhaust gas passage 21 and the bypass exhaust amount control valve 22 in the embodiment have substantially the same functions. Therefore, the first
The control of the bypass air amount control valve 32 and the second bypass air amount control valve 34 is the same as the control of the bypass air amount control valve 19 and the bypass exhaust amount control valve 22 in the first embodiment. In the supercharging control program shown in FIG. 3, “bypass air amount control valve 19” is read as “first bypass air amount control valve 32”, and “bypass exhaust amount control valve 22” is referred to as “second bypass air amount control valve”. The control may be performed by reading as "the valve 34".

In the second embodiment described above, the same effects as those of the first embodiment can be obtained, and even if the exhaust bypass passage 21 (waste gate) is eliminated, the second bypass air amount control valve 34 By adjusting the opening degree, overload on the diesel engine 11 can be prevented, and this is effective when the waste gate cannot be installed due to a problem in the space in the engine room.

In the second embodiment, the second intake bypass passage 33 is configured to be branched from the middle of the first intake bypass passage 31.
The configuration may be such that the components 1 and 33 are completely independent.

Further, in each of the above embodiments, the oxygen amount of the intake air supplied to the diesel engine 11 (the supplied oxygen amount)
Focusing on the fact that can be estimated from the intake pressure Pq, the intake pressure Pq is used as substitute data for the supplied oxygen amount. That is, the intake pressure sensor 20 for detecting the intake pressure Pq is used as the supply oxygen amount estimating means. However, the intake air amount sensor for detecting the intake air amount, and the exhaust gas return for detecting the amount of exhaust gas recirculated to the intake system. Flow sensor, diesel engine 11
The supply oxygen amount may be estimated based on an output signal of at least one of the oxygen sensors that detects the amount of oxygen sucked into the air.

In this case, as the intake pressure sensor 20 and the intake air amount sensor, existing sensors mounted on the vehicle for controlling the diesel engine 11 may be used, and the cost burden can be reduced. Furthermore, the supply oxygen amount may be estimated by combining the detection value of one of the intake pressure sensor and the intake air amount sensor with the detection value of the exhaust gas recirculation amount sensor. With this configuration, it is possible to accurately estimate the supply oxygen amount in consideration of the oxygen in the exhaust gas recirculated to the intake system, and it is possible to improve control accuracy. Further, if an oxygen sensor is used, the supplied oxygen amount can be directly detected, and the control accuracy can be improved.

Further, in each of the above embodiments, the exhaust gas temperature sensor 23 is used as the catalyst temperature determining means, and the exhaust gas temperature T is used as the substitute data of the catalyst temperature. You may make it provide as a temperature determination means. In addition, the present invention can be implemented with various modifications without departing from the gist, such as application to a gasoline engine.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing the flow of processing of a supercharging control program (part 1);

FIG. 3 is a flowchart showing the flow of processing of a supercharging control program (part 2);

FIG. 4 is a diagram showing a relationship between a catalyst temperature and a NOx purification rate.

FIG. 5 is a time chart showing the behavior of supercharging control.

FIG. 6 is a diagram showing a schematic configuration of an entire engine control system according to a second embodiment of the present invention.

[Description of Signs] 11: diesel engine (internal combustion engine), 12: intake passage, 13: turbocharger (supercharger), 14: exhaust passage,
Reference numeral 15: exhaust turbine, 17: catalyst, 18: intake bypass passage, 19: bypass air amount control valve, 20: intake pressure sensor (supply oxygen amount estimating means), 21: exhaust bypass passage,
Reference numeral 22: bypass exhaust amount control valve, 23: exhaust temperature sensor (catalyst temperature determining means), 25: accelerator opening degree sensor, 2
6 engine speed sensor 27 ECU (control means,
Target oxygen amount calculation means), 31 ... first intake bypass passage, 32 ... first bypass air amount control valve, 33 ... second intake bypass passage, 34 ... second bypass air amount control valve.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location F02B 37/00 F02B 37/12 ZAB 37/12 ZAB F02D 23/00 G 37/18 41/02 315 F02D 23 / 00 41/04 330M 41/02 315 45/00 310R 41/04 330 F02B 37/00 303G 45/00 310 37/12 301F (72) Inventor Tsukasa Kuboshima 1-1-1, Showa-cho, Kariya-shi, Aichi Pref. Inside the corporation

Claims (7)

[Claims] 1. An internal combustion engine control device including a supercharger provided in an intake passage and an exhaust purification catalyst provided in an exhaust passage, comprising: catalyst temperature determination means for determining a temperature of the catalyst; An intake bypass passage that bypasses an intake passage downstream of the turbocharger and an exhaust passage upstream of the catalyst, a bypass air amount control valve that controls an amount of air that passes through the intake bypass passage, and an internal combustion engine. Supply oxygen amount estimating means for estimating the oxygen amount of the intake air supplied to the engine (hereinafter referred to as “supply oxygen amount”); and the oxygen amount of the intake air required to burn the fuel supplied to the internal combustion engine (hereinafter “target”). A target oxygen amount calculating means for calculating the oxygen amount), a difference between the catalyst temperature determined by the catalyst temperature determining means and the target catalyst temperature, a supply oxygen amount calculated by the oxygen amount estimating means, and the target oxygen amount calculation hand In an internal combustion engine control apparatus characterized by comprising a control means for controlling an opening degree of the bypass air flow rate control valve based on the difference between the target amount of oxygen determined. 2. The turbocharger is a turbocharger driven by an exhaust turbine driven by exhaust energy, and the exhaust passage bypasses an upstream side and a downstream side of the exhaust turbine. An exhaust bypass passage is provided, and a bypass exhaust amount control valve is provided in the exhaust bypass passage. The control unit includes a difference between a catalyst temperature determined by the catalyst temperature determination unit and a target catalyst temperature, and the oxygen amount estimation unit. And controlling the degree of opening of the bypass air amount control valve and the bypass exhaust amount control valve based on the difference between the supplied oxygen amount obtained in step (a) and the target oxygen amount obtained by the target oxygen amount calculating means. The internal combustion engine control device according to claim 1, wherein 3. The control means, when the catalyst temperature is equal to or lower than the target catalyst temperature, closes the bypass air amount control valve and controls an opening degree of the bypass exhaust amount control valve, thereby controlling the opening degree of the bypass exhaust amount control valve. The supply oxygen amount is controlled to match the target oxygen amount. If the catalyst temperature is higher than the target catalyst temperature, the bypass air amount control valve and the bypass adjust the supply oxygen amount to match the target oxygen amount. The opening degree of the bypass air amount control valve is controlled in accordance with the difference between the catalyst temperature and the target catalyst temperature within a range in which the turbocharger has sufficient supercharging capacity after controlling the opening degree of the displacement control valve. The internal combustion engine control device according to claim 2, wherein the control is performed. 4. An internal combustion engine control device including a supercharger provided in an intake passage and an exhaust purification catalyst provided in an exhaust passage, wherein: a catalyst temperature determining means for determining a temperature of the catalyst; A first intake bypass passage that bypasses an intake passage downstream of the supercharger and an exhaust passage upstream of the catalyst, and a first air passage that controls an amount of air passing through the first intake bypass passage. A bypass air amount control valve, a second intake bypass passage that bypasses an intake passage downstream of the supercharger and an exhaust passage downstream of the catalyst, and passing through the second intake bypass passage. A second bypass air amount control valve for controlling an amount of air to be supplied, an oxygen supply amount estimating means for estimating an oxygen amount of intake air supplied to the internal combustion engine (hereinafter, referred to as an “supply oxygen amount”), and a supply to the internal combustion engine Burning fuel A target oxygen amount calculating means for calculating an oxygen amount of the intake air required to perform the operation (hereinafter, referred to as a “target oxygen amount”); a difference between the catalyst temperature determined by the catalyst temperature determining means and the target catalyst temperature; Control means for controlling the degree of opening of the first and second bypass air amount control valves based on a difference between the supplied oxygen amount obtained by the estimating means and the target oxygen amount obtained by the target oxygen amount calculating means. An internal combustion engine control device comprising: 5. The control means, when the catalyst temperature is lower than a target catalyst temperature, closes the first bypass air amount control valve and adjusts an opening degree of the second bypass air amount control valve. By controlling, the supply oxygen amount is controlled to match the target oxygen amount. When the catalyst temperature is higher than the target catalyst temperature, the first oxygen supply amount is adjusted to the target oxygen amount. And controlling the opening degree of the second bypass air amount control valve, and setting the first bypass according to a difference between the catalyst temperature and a target catalyst temperature within a range in which the supercharging capacity of the supercharger has a surplus. The internal combustion engine control device according to claim 4, wherein the opening degree of the air amount control valve is controlled. 6. The supply oxygen amount estimating means includes an intake pressure sensor for detecting an intake pressure, an intake air amount sensor for detecting an intake air amount, an exhaust gas recirculation amount sensor for detecting a recirculation amount of exhaust gas to an intake system, The internal combustion engine according to any one of claims 1 to 5, wherein the supply oxygen amount is estimated based on an output signal of at least one of the oxygen sensors that detects an oxygen amount taken into the internal combustion engine. Engine control device. 7. The target oxygen amount calculation means calculates the target oxygen amount based on an operation state of an internal combustion engine within a range equal to or less than a maximum oxygen amount corresponding to a supercharging pressure limit value of the supercharger. The internal combustion engine control device according to any one of claims 1 to 6, wherein