JP2002256863A - Device for suppressing deterioration of catalyst in internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst deterioration-suppressing device capable of ensuring an engine brake force which can compensates the lowering of engine brake brought by the inhibition of fuel cut while restraining the heat deterioration of the catalyst. SOLUTION: This catalyst deterioration-suppressing device has a structure such that when the temperature of the catalyst is a prescribed one or higher at the deceleration of a vehicle by a fuel cut, the fuel cut is inhibited and also an exhaust path is narrowed down. Thereby, when the catalyst 19 is environmentally apt to deteriorate in the deceleration operation of the vehicle, there is no concern of combustion under a low pressure, and the large engine brake force coping with the torque generated with combustion by the exhaust loss brought by throttling an exhaust pipe 20 can be obtained while continuing the combustion of an engine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst deterioration device for an internal combustion engine that generates engine braking force while suppressing catalyst deterioration.

[0002]

2. Description of the Related Art In an engine (internal combustion engine) mounted on an automobile (vehicle), a catalyst such as a three-way catalyst, a lean NOx catalyst, and an HC adsorption catalyst is attached to an exhaust passage in order to purify exhaust gas. I have.

[0003] Such a catalyst has a characteristic that it is easily degraded in a high-temperature state and in an oxidizing atmosphere. Specifically, the situation in which the catalyst is in a high temperature state is, for example, a high-speed operation (high-load rich operation). In this state, the catalyst is not in an oxidizing atmosphere. However, when the catalyst becomes an oxidizing atmosphere, the catalyst is thermally degraded.

[0004] In order to suppress such thermal degradation of the catalyst, restrictions are imposed on the engine of an automobile when decelerating from high-speed operation.

[0005] In this respect, the engine is usually operated in a fuel cut operation in which the fuel supplied to the cylinder is cut in order to accelerate deceleration and obtain a feeling of deceleration during deceleration during deceleration operation in which the vehicle decelerates. Done. This is because if the fuel is not cut off during deceleration, torque will be generated from the engine even during deceleration, and the engine braking force will be reduced.

However, when the catalyst is decelerated from a high-speed operation (high-load operation), if the fuel of the engine is cut off,
Since it is in an oxidizing atmosphere in addition to being in a high temperature state,
Thermal degradation is promoted.

For this reason, in deceleration from high-speed operation (high-load operation), in order to protect the catalyst (suppress deterioration), the operation in which the fuel is cut so as not to be in an oxidizing atmosphere is prohibited, and the fuel supply is continued. It is required that other means generate a large engine braking force that can compensate for the decrease in engine braking caused by fuel supply.

For this reason, conventionally, during the intake stroke of the engine, the throttle valve in the intake passage is throttled, and the throttle loss at this time, that is, the intake loss, causes a decrease in speed from high-speed operation.
An engine braking force is generated to compensate for the reduced engine braking performance.

[0009]

However, in order to generate a large engine braking force that compensates for a decrease in engine brake caused by fuel supply only by a throttle loss in the suction stroke, the throttle valve must be considerably throttled. Must be increased.

However, when the throttle amount increases, the pressure in the manifold serving as the intake port of the engine decreases, and the engine burns at a low pressure, so that the combustion state may deteriorate.

For this reason, it is difficult to set the throttle amount to a large value in order to secure good combustion, and there is a situation in which satisfactory engine braking performance cannot be secured.

The present invention has been made in view of the above circumstances. It is an object of the present invention to secure a large engine braking force capable of compensating for a decrease in engine brake caused by prohibition of fuel cut while suppressing thermal deterioration of a catalyst. An object of the present invention is to provide a catalyst deterioration suppressing device for an internal combustion engine for a vehicle.

[0013]

According to a first aspect of the present invention, there is provided a catalyst deterioration suppressing device for inhibiting a fuel cut when a temperature of a catalyst is equal to or higher than a predetermined temperature during deceleration of a vehicle in which a fuel cut is performed. At the same time, a structure that restricts the exhaust path has been adopted so that a large engine braking force that can counteract the torque at which combustion occurs can be obtained.

As a result, a large engine braking force that compensates for a decrease in engine braking performance caused by the prohibition of fuel cut while securing thermal deterioration of the catalyst is secured.

According to a second aspect of the present invention, in addition to the above object, the catalyst deterioration suppressing device has a structure in which the intake passage of the internal combustion engine is throttle-controlled together with the exhaust passage so that deterioration of combustion under low pressure is suppressed. A large engine brake was easily secured while ensuring combustion stability.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The following describes the present invention based on the first embodiment shown in FIGS.

FIG. 1 shows a peripheral structure of a vehicle internal combustion engine to which the present invention is applied, for example, mounted on an automobile. In FIG. 1, reference numeral 1 denotes an internal combustion engine, for example, a direct injection spark type reciprocating gasoline engine ( (Hereinafter simply referred to as engine).

The engine body 1 has a cylinder block 2 in which a cylinder 2a is formed, a cylinder head 3 mounted on an upper end of the block 2, and an oil pan 4 mounted on a lower end of the cylinder block 2. It is composed.

A piston 5 is reciprocally housed in the cylinder 2a of the cylinder block 2. Further, a combustion chamber 6 which is combined with the cylinder 2a is formed on the lower surface of the cylinder head 3. At the center of the combustion chamber 6 is a spark plug 3a.
Is incorporated. An upright intake port 8 extending from the combustion chamber 6 to the upper end of the cylinder block 2 is formed on one side of the combustion chamber 6 with the ignition plug 3a interposed therebetween. An exhaust port 7 extending to one side in the width direction is formed. These intake and exhaust ports 7,
An intake valve 9 and an exhaust valve 10 of a camshaft drive type are respectively incorporated at ends of a combustion chamber 6 of 8. Further, an electronically controlled injector 11 for injecting fuel into the cylinder 2a is incorporated in a portion near the intake port 8. Then, a predetermined combustion cycle (for example, four cycles of intake, compression, explosion, and exhaust) is performed in the cylinder 2a from the operation of each of the intake valve 9, the exhaust valve 10, and the injector 11.

The inlet of the intake port 8 has an intake manifold 13, a surge tank 14, an electronically controlled throttle valve 15, an air flow sensor (not shown), and an air cleaner (not shown: all of which constitute an intake passage together with the intake port). Are opened to the atmosphere through the passages formed in order, so that combustion air required for combustion can be taken into the cylinder 2a from the atmosphere. The outlet of the exhaust port 7 is formed by an exhaust manifold 17, an exhaust pipe 18, a catalyst 19 (three-way catalyst, lean NOx catalyst, HC adsorption catalyst, etc.), and a tail pipe 20 (all of which constitute an exhaust path together with the exhaust port). The exhaust gas discharged from the engine is discharged to the atmosphere through the passages sequentially opened to the atmosphere. Reference numeral 24 denotes a temperature sensor for detecting the temperature of the catalyst 19 (for example, installed at the catalyst inlet).

Electronic control devices for each part of the engine (injector 11, throttle valve 15, air flow sensor, etc.)
Is an ECU 2 configured by a microcomputer, for example.
1 (corresponding to control means). This ECU 21
An engine opening signal from an accelerator opening sensor (not shown), an engine speed signal from an engine rotation sensor (not shown) for detecting the engine speed, an intake flow rate signal from an air flow sensor, etc. A function of calculating various target values according to the operating state and controlling the opening degree of the throttle valve 15, the fuel injection amount of the injector 11, and the injection timing according to these values is set.

During driving of the automobile, the ECU 21 receives signals such as an accelerator opening signal, an engine speed signal, and a brake signal from a brake switch (not shown) which is turned on / off in conjunction with operation of a brake pedal, for example, from a middle / high speed operation. When a deceleration of the fuel is detected, a fuel cut function (fuel cut mode) for stopping the fuel injection of the injector 11 and a deceleration operation of the deceleration operation in which the catalyst 19 causing the catalyst deterioration is brought into a high temperature state [for example, a high speed operation (high load operation) )), A function (fuel cut prohibition mode) in which fuel cut is prohibited to protect the catalyst 19 from thermal degradation, that is, fuel injection is continued. Note that the fuel cut is canceled when the engine speed decreases to a predetermined recovery injection start speed.

On the other hand, an exhaust path, for example, a tail pipe 20 downstream of the catalyst 19 is provided with, for example, a normally-open electronically-controlled throttle valve 25 (corresponding to an exhaust throttle section) constituting a catalyst deterioration suppressing device 23. I have. The throttle of the throttle valve 25 is changed, for example, from a position where the passage of the tail pipe 20 is fully opened to a position where it is almost fully closed, and the throttle of the throttle valve 25 enables an increase in engine exhaust loss.

When the throttle valve 25 is decelerated by the ECU 21 during a deceleration operation in which the temperature of the catalyst 19 becomes high (fuel cut prohibition operation), that is, when the catalyst temperature detected by the temperature sensor 24 is a predetermined temperature (for example, When the temperature is equal to or more than the optimal value determined from the heat resistant temperature), the aperture is largely controlled to the aperture side.

Specifically, the ECU 21 determines a predetermined value A1 for determining the opening of the throttle valve 25 used in the fuel cut-off mode and an opening of the throttle valve 25 for use in the fuel cut mode. A predetermined value A2 is defined.
Each of these predetermined values A1 and A2 corresponds to the engine operating conditions (engine speed, volumetric efficiency, net average effective pressure,
A map value optimized in advance according to the intake air amount, the manifold pressure, the exhaust volume flow rate, the exhaust mass flow rate, the fuel cut duration, the exhaust pressure, or a condition obtained from one or more of the indexes correlated with these. (Including fixed values). For example, the predetermined value A1 is an opening degree that causes an exhaust loss that performs deceleration suitable for the deceleration state while canceling torque generated by combustion during deceleration operation, specifically, a fully closed position or a closed position near the fully closed position. Is set. The predetermined value A2 is set to an opening that causes an exhaust loss that performs deceleration suitable for the deceleration state in combination with the fuel cut, specifically, for example, a value that is a position that is more open than the predetermined value A1 (A1 ≦ A2). ). A2 may be fully open.

The ECU 21 controls the throttle valve 25 in accordance with the predetermined value A2 during normal deceleration operation, that is, in the fuel cut mode, and performs deceleration operation with protection of the catalyst 19, that is, in fuel cut inhibition mode. At this time, a function of restricting the throttle valve 25 according to the predetermined value A1 is set.

With this control, in the fuel cut prohibition mode in which the catalyst 19 is protected by utilizing the exhaust loss of the engine, a load that causes deterioration of combustion in the intake system is not imposed.
Sufficient engine braking force is generated. FIG. 2 shows a control flow of the engine brake utilizing the exhaust loss.

The engine brake control will be described with reference to this control flow. It is assumed that the vehicle is now running normally.

At this time, the ECU 31 determines the accelerator opening,
The engine speed, the brake switch signal, and the like are monitored (step S1). If the operation is not the deceleration operation, the fuel injection amount and the injection timing of the injector 11 and the injection timing according to various target values obtained according to the operation state of the engine are further determined. The throttle valve 15 is controlled (step S2; normal control). At this time, the throttle valve 25 is fully opened.

On the other hand, it is assumed that during driving, the driver operates the brake and shifts to deceleration driving.

During this deceleration, the catalyst temperature falls below a predetermined temperature value (for example, 800 ° C.) (step S3) and the ECU 21
Determines that the situation will not result in thermal degradation,
The mode is switched to the fuel cut mode (step S4), and the fuel injection from the injector 11 is stopped. Then, the throttle valve 25 is set to a predetermined value A determined from a map value corresponding to the operating condition.
Control is performed so that the throttle opening becomes 2 (step S5).

On the other hand, if the temperature of the catalyst 19 rises to a predetermined temperature (for example, 800 ° C.) or more when the deceleration is a deceleration from, for example, a high-speed traveling (high-load operation), the ECU 21 determines that a situation that causes thermal deterioration is caused. Then, the mode is switched to the fuel cut inhibition mode (step S6), and the fuel injection is continued. Then, the throttle valve 25 is controlled so that the throttle opening has the predetermined value A1 determined from the map value corresponding to the operating condition (step S7).

Then, the engine continues to burn,
The exhaust pressure increases (due to the restriction of the exhaust path). Thus, the engine exhibits a behavior in which the exhaust loss increases.

Here, the predetermined value A1 is set to a throttle value (for example, fully closed) at which the exhaust loss required to cancel the torque generated by combustion and to generate a greater engine braking force is secured. .

That is, the vehicle is decelerated while the engine braking force caused by the exhaust loss is applied (fuel-cut prohibited deceleration).

Therefore, a satisfactory engine brake can be obtained.

FIG. 3 shows a second embodiment of the present invention.

In this embodiment, not only the exhaust loss but also the throttle control of the intake passage, for example, the throttle control of the throttle valve 15 (corresponding to the intake throttle portion) is used in combination to secure a larger engine braking force. Things.

Specifically, the ECU 21 determines a predetermined value B1 which determines the opening of the throttle valve 15 used in the fuel cut inhibition mode, and determines the opening of the throttle valve 15 used in the fuel cut mode. The predetermined value B2 is defined. These predetermined values B1 and B2 are also predetermined values A1 and A2.
As in the case of A2, it is set from map values (including fixed values) optimized according to the operating conditions of the engine. For example, the predetermined value B1 is set to an opening that causes an intake loss that performs deceleration suitable for a deceleration state in combination with an exhaust loss within a range where the combustion state does not deteriorate. The predetermined value B2 is set to an opening that causes an intake loss that performs deceleration suitable for a deceleration condition in combination with a fuel cut and an exhaust loss.

When the fuel cut mode is selected by the ECU 21, the throttle of the throttle valve 25 performed in step S5 is mainly used together with the throttle, and in step S8, the throttle is used as an auxiliary.
The throttle valve 15 is throttled in accordance with the predetermined value B2 shown in FIG. 3 so that a sufficiently large engine braking force is generated from both the generated intake loss and the generated exhaust loss.

In the fuel cut prohibition mode, the throttle of the throttle valve 25 performed in step S7 is mainly used in combination with the predetermined value B shown in step S9 as an auxiliary.
The throttle valve 15 is throttled in a range that does not cause deterioration of combustion according to the above-mentioned formula (1), so that a sufficiently large engine braking force is generated from both the generated intake loss and the generated exhaust loss.

The same effect as that of the first embodiment can be obtained with a structure in which the engine braking force is secured by combining such intake loss and exhaust loss. In particular, the structure that combines the intake loss and the exhaust loss generates the engine braking force by the intake loss due to the restriction of the intake passage that does not have a risk of combustion under low pressure. In addition, there is an advantage that a large engine braking force can be ensured while suppressing deterioration of combustion and supplementing the engine braking performance brought about by the prohibition of fuel cut. Needless to say, even in the fuel cut mode, a larger engine braking force is secured.

In the control flow shown in FIG. 3, steps other than steps S8 and S9 are the same as the control flow of FIG. 2, so that the description other than steps S8 and S9 is omitted.

FIG. 4 shows a third embodiment of the present invention.

In this embodiment, a cooling section, for example, a tail pipe 20 is provided in the tail pipe 20 on the upstream side of the throttle valve 25.
Is formed with a bellows pipe 27a at a part thereof, and the heat of the exhaust gas is transferred immediately before the throttle valve 26.
It has a structure to radiate heat.

With this structure, the thermal burden on the throttle valve 25 is
By the heat radiation of the heat radiation part 27 performed upstream of the throttle valve 25,
The throttle valve 2 has a lower heat resistance temperature.
5 also has the advantage that the engine braking force can be secured using the exhaust loss. Of course, the cooling unit may have a structure other than the heat radiating unit 27 to increase the heat radiating area, such as a structure in which fins are attached to the outer peripheral surface of the pipe, or a structure in which the fins and the bellows pipe 27a are used in combination. , Or other structures.

However, in FIG. 4, the same portions as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

The present invention is not limited to the above-described embodiment, and may be implemented with various modifications without departing from the gist of the present invention. For example, in the above-described embodiment, an example in which the exhaust pipe is provided with a throttle valve as the exhaust throttle unit is described. However, the present invention is not limited to this, and a structure in which a valve is provided in another exhaust path portion may be used. Needless to say, the intake throttle section may use a valve provided in another intake path portion instead of the throttle valve. In the above-described embodiment, the example in which the throttle valve is provided on the downstream side of the catalyst has been described. However, the present invention is not limited to this, and the throttle valve may be provided on the upstream side of the catalyst. Since the road volume is reduced, there is an advantage that responsiveness in the fuel cut mode and the fuel cut prohibition mode is improved. Further, in the above-described embodiment, the in-cylinder injection gasoline engine has been described as the internal combustion engine. However, the invention is not limited to this, and may be a gasoline engine or a diesel engine having a structure in which fuel is injected into the intake manifold.

[0049]

As described above, according to the first aspect of the present invention, during deceleration operation of a vehicle with prohibition of fuel cut, a large engine braking force against the torque at which combustion occurs due to exhaust loss caused by the throttle. Can be secured.

Therefore, it is possible to secure a large engine brake that suppresses the deterioration of the engine brake performance caused by the prohibition of the fuel cut while suppressing the thermal deterioration of the catalyst.

According to the second aspect of the present invention, in addition to the above effects, a larger engine brake can be easily secured by the synergistic effect of the engine braking force caused by the intake loss while suppressing the deterioration of combustion under low pressure. This has the effect.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration around an engine in which a catalyst deterioration suppressing device according to a first embodiment of the present invention is incorporated.

FIG. 2 is a flowchart showing control during deceleration running in the catalyst deterioration device.

FIG. 3 is a flowchart showing control during deceleration running, which is a main part of a second embodiment of the present invention.

FIG. 4 is a diagram showing a configuration around an engine which is a main part of a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine body 15 ... Electronic control throttle valve (intake throttle part) 29 ... Catalyst 21 ... ECU (control means) 24 ... Temperature sensor 25 ... Throttle valve (exhaust throttle part).

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) F02D 43/00 301 F02D 43/00 301H 301T 301K F term (reference) 3G065 AA04 AA09 AA10 CA00 CA12 DA04 DA15 EA05 GA05 GA08 GA10 GA29 GA46 HA06 KA02 3G084 BA13 BA24 CA06 DA10 DA37 EB12 FA06 FA10 FA27 FA33 3G091 AA02 AA17 AB03 AB05 AB10 BA07 BA36 CA27 CB02 CB07 DA10 DB11 DC03 EA01 EA03 EA07 EA18 FA19 FB03 BA07 DA09 BA03 BA09 DA08 FA08 FB05 3G301 HA01 JA03 JA33 KA16 LA01 LB01 LC01 MA11 ND06 NE01 NE16 PA11Z PD12Z PE01Z PF03Z PF05Z

Claims (2)

[Claims] 1. A sensor for detecting the temperature of the catalyst of an internal combustion engine having a catalyst in an exhaust passage and capable of operating with fuel supply cut off when the vehicle is decelerated, and an exhaust throttle unit capable of controlling the throttle of the exhaust passage. And control means for prohibiting the fuel cut and restricting the exhaust restrictor when the temperature of the catalyst is equal to or higher than a predetermined temperature at the time of deceleration of the catalyst. apparatus. 2. The internal combustion engine has an intake throttle portion in an intake passage that can be throttled, and the control means inhibits the fuel cut when the temperature of the catalyst is equal to or higher than a predetermined temperature during vehicle deceleration. 2. The catalyst deterioration suppressing device for an internal combustion engine according to claim 1, wherein both the throttle control of the intake throttle unit and the throttle control of the exhaust throttle unit are performed.