JPH09166017A - Exhaust emission control device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diagnose the failure time of a first switch precisely by comparing and detecting voltage supplied to an electrothermal catalyst converter through a first switch which is closed according to an operating condition with a prescribed value voltage. SOLUTION: An electrothermal catalyst converter 4 has a heater function heated by carrying out current-carrying to a catalyst carrier, and the converter 4 is arrange don the way of the exhaust passage of an engine. Voltage VEHC supplied to the converter 4 through a first switch 1 is detected, and an operating condition in which voltage VEHC detected in an operating condition in which the converter 4 is not carried out current-carrying is higher than a prescribed value voltage VEHCFS is judged as the failure time of the first switch. When the failure time of the first switch is judged, control for opening a second switch 9 is carried out when operation of the engine is stopped. It is thus possible to prevent current from supplying from a battery 18 to the converter 4 so as to prevent over heat of the converter 4 and discharge of a battery 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an engine exhaust gas purification apparatus provided with a first switch for connecting and disconnecting electricity to an electrothermal catalytic converter by an alternator.

[0002]

2. Description of the Related Art In a catalytic converter used to prevent air pollution of an automobile engine or the like, an electrothermal catalytic converter that heats a catalyst to a temperature equal to or higher than its activation temperature during cold start or the like.
Some are equipped with (alyst)
191347 publication).

An exhaust gas purification apparatus of this type is provided with a first switch for connecting and disconnecting electricity to the electrothermal catalytic converter by an alternator and directly supplying the electric current generated by the alternator to the electrothermal catalytic converter to rapidly raise the temperature of the catalyst. is there. This is itself filed by the applicant in Japanese Patent Application No. 7-17506.
It has already been proposed as No. 9 and so on.

[0004]

However, in such a conventional engine exhaust emission control device, when the first switch cannot be opened due to welding or the like, the battery can be operated from the battery even after the engine is stopped. Since the electric current is supplied to the electrothermal catalytic converter, the electrothermal catalytic converter may be overheated or the battery may be discharged.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to accurately diagnose a failure of the first switch in the engine exhaust purification system.

[0006]

As shown in FIG. 5, an engine exhaust gas purification apparatus according to a first aspect of the present invention heats the catalytic converter a by energizing the catalytic converter a interposed in the middle of the exhaust passage. An electric heating means b, an alternator c that is driven by an engine to generate electric power, a battery i that stores a current supplied from the alternator c, a first switch j that interrupts a current supplied from the alternator c to the electric heating means b, Energization control means f that closes the first switch j according to operating conditions, and electric heating means b via the first switch j.
Voltage detecting means h for detecting the voltage VEHC supplied to the
And a failure diagnosis means k for diagnosing a failure of the first switch j when the voltage VEHC detected in an operating state in which the electric heating means b is not energized is higher than a predetermined value VEHCFS.

According to a second aspect of the present invention, there is provided an exhaust emission control device for an engine according to the first aspect of the present invention, wherein a second switch m for interrupting the current supplied from the alternator c to the battery i is provided as shown in FIG. , Fail-safe means n for opening the second switch m when the engine is stopped and it is diagnosed that the first switch j has failed.

According to a third aspect of the present invention, in the exhaust gas purifying apparatus for an engine according to the first aspect of the present invention, as shown in FIG. 7, a third switch p for interrupting the current supplied from the alternator c to the electric heating means b is provided. And fail-safe means q for opening the third switch p when it is diagnosed that the first switch j has failed.

[0009]

In the exhaust gas purifying apparatus for an engine according to claim 1, the output current of the alternator c is directly supplied to the electric heating means b through the first switch j in the inactive region of the catalyst to rapidly raise the catalyst. Let it warm.

In the operating state in which the electric heating means b is not energized, the voltage VEHC supplied to the electric heating means b is a predetermined value VEHC.
When it is higher than FS, it is diagnosed that the first switch j has failed.

In the engine exhaust emission control device according to the second aspect of the present invention, the second switch m is opened when the engine is stopped when it is diagnosed that the first switch j has failed.
It is possible to prevent the battery i from energizing the electric heating means b when the engine is stopped, and it is possible to prevent the electrothermal catalytic converter a from overheating or the battery i from being discharged.

In the exhaust gas purifying apparatus for an engine according to claim 3, the alternator c is opened by opening the third switch p when it is diagnosed that the first switch j has failed.
Alternatively, it is possible to prevent the electric heating means b from being energized by the battery i and prevent the electrothermal catalytic converter a from being overheated or causing the battery i to be discharged.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In the electric power supply system diagram of the vehicle shown in FIG. 1, 4 is an electrothermal catalytic converter (EHC). The electrothermal catalytic converter 4 is installed in the middle of an exhaust passage of an engine (not shown). The electrothermal catalytic converter 4 oxidizes HC and CO in the exhaust gas and reduces NOx.

The electrothermal catalytic converter 4 has a heater function of generating heat when the catalyst carrier is energized, and constitutes an electric heating means.

In the figure, reference numeral 5 is an alternator. The alternator 5 is rotationally driven by the engine to generate electricity.

Reference numeral 8 in the drawing is a regulator. The higher the rotational speed of the alternator 5, the higher the voltage generated, but the regulator 8 adjusts the output voltage of the alternator 5 to a predetermined value or less by the control duty signal sent from the control unit 16.

The heater circuit 2 which supplies the electric current generated by the alternator 5 to the electrothermal catalytic converter 4 via the first switch 1, and the battery 18 which supplies the generated current via the second switch 9.
A charging circuit 7 for supplying the electric load 6 is provided.
The electric load 6 is, for example, a vehicle headlight, an air conditioner (air conditioner), or the like.

The control unit 16 includes a detection signal from the water temperature sensor 3 for detecting the temperature Tw of the cooling water circulating through the engine, a detection signal from the rotation speed sensor 12 for detecting the engine rotation speed Ne, and the ignition switch 1.
Signals such as 1 are input to control the energization of the electrothermal catalytic converter 4 via the first switch 1 and the second switch 9.

At the time of start-up, when the cooling water temperature Tw is below the predetermined value Tw _0, it is judged that the catalyst is in the inactive region, and the first switch 1 is closed and the second switch 9 is opened to output from the alternator 5. Is supplied to the thermocatalytic converter 4.

In this way, after the electrothermal catalytic converter 4 is energized for a predetermined time t1, the first switch 1 is opened and the second switch 9 is closed, and the thermocatalytic converter 4 is opened.
Is stopped and the current output from the alternator 5 is supplied to the electric load 6 or the battery 18.

By the way, when the first switch 1 fails to open due to welding or the like, the electric current from the battery 18 is supplied to the electrothermal catalytic converter 4 even after the engine is stopped, so that the electrothermal catalytic converter 4 is overheated. Alternatively, the battery 18 may be discharged.

In response to this, the present invention provides the first switch 1
VEH supplied to the electrothermal catalytic converter 4 via
The voltage VEHC detected in the operating state in which C is detected and the electrothermal catalytic converter 4 is not energized is a predetermined value VEHCF.
An operating state higher than S is determined to be when the first switch is out of order. When it is determined that the first switch has failed, control is performed to open the second switch 9 when the engine operation is stopped.

When the first switch 1 fails to open due to welding or the like, the second switch 9 is opened after the engine is stopped, so that the current from the battery 18 is supplied to the electrothermal catalytic converter 4. Is avoided, and the electrothermal catalytic converter 4 can be prevented from being overheated and the discharge of the battery 18 can be prevented.

The flowchart of FIG. 2 shows a program executed by the control unit 16 for controlling the energization of the electrothermal catalytic converter 4, which is executed at regular intervals.

Explaining this, first, when it is determined in step 1 that the ignition switch 11 is turned from OFF to ON, all flags are cleared in step 2, and the first switch 1 is opened in step 3. .

Then, in step 4, the cooling water temperature T
It is determined whether w is an energization condition of a predetermined value Tw ₀ or less.
Further, this energization condition includes that the voltage of the battery 18 is a predetermined value or more.

If it is determined that the condition is the energizing condition, the process proceeds to step 6 through step 5 to close the first switch 1 and open the heater circuit 2.

In step 5, TI is set based on the flag F1.
It is determined whether or not MER1 is being counted. F1
If = 0, proceed to step 7 and enter TIMER
1 is cleared, and then the flag F1 is set to 1 in step 8.

Subsequently, the elapsed time TIMER from when the energization of the electrothermal catalytic converter 4 is started through step 11 and the like.
1 is measured, and if it is determined in step 9 that the elapsed time TIMER1 has exceeded the predetermined time t1, it is considered that the warm-up of the electrothermal catalytic converter 4 has ended, and the process proceeds to step 10 to turn on the first switch 1. It opens and the electricity supply of the electrothermal catalytic converter 4 is stopped. Until TIMER1 exceeds the predetermined time t1 in step 9, TIMER1 in step 11
1 is incremented by ΔT.

As the gist of the present invention, when the electrothermal catalytic converter 4 is in an operation other than the energizing condition, the routine proceeds to step 12, where it is determined whether the voltage VEHC introduced to the electrothermal catalytic converter 4 is higher than a predetermined value VEHCFS. To do.

If it is determined that the voltage VEHC is higher than the predetermined value VEHCFS, the routine proceeds to step 13, where it is diagnosed that the first switch 1 has a failure, and a warning light (not shown) is turned on to inform the driver of this.

Next, in step 14, it is determined whether the engine speed Ne is lower than a predetermined value N1 (for example, 300 rpm).

When it is determined that the engine speed Ne is lower than the predetermined value N1, the routine proceeds to step 15 to open the second switch 9.

When a failure occurs in which the first switch 1 is stuck in the closed state due to the above configuration, the second switch 9 is opened and the battery 18 energizes the electrothermal catalytic converter 4 when the engine is stopped. To prevent. As a result, the electrothermal catalytic converter 4 is overheated or the battery 1
8 can be prevented from being discharged.

Next, the embodiment shown in FIG. 3 will be described. The parts corresponding to those in FIG. 1 are designated by the same reference numerals.

A first switch 1 and a third switch 10 are provided in series in the heater circuit 2 for supplying the electric current generated by the alternator 5 to the electrothermal catalytic converter 4.

In response to the failure of the first switch 1, the control unit 16 determines the failure of the first switch and controls the opening of the third switch 10.

The flow chart of FIG. 4 shows a program executed by the control unit 16 for controlling energization of the electrothermal catalytic converter 4, which is executed at regular intervals. The parts corresponding to those in FIG. 2 are denoted by the same reference numerals.

When a failure occurs in which the first switch 1 is stuck in the closed state in the processing of steps 1 to 13, the third switch 10 is opened, and the electrothermal catalytic converter 4 is energized by the alternator 5 and the battery 18. To prevent As a result, it is possible to prevent the electrothermal catalytic converter 4 from overheating and prevent the battery 18 from discharging.

[0041]

As described above, in the engine exhaust gas purification apparatus according to the first aspect, it is determined whether the voltage VEHC supplied to the electric heating means is higher than the predetermined value VEHCFS in the operating state in which the electric heating means is not energized by the alternator. By making a determination, it is possible to accurately diagnose when the first switch j has failed.

In the engine exhaust emission control device according to the second aspect of the present invention, the second switch is opened when the engine is stopped when it is diagnosed that the first switch has failed, so that the electric heating means is energized by the battery when the engine is stopped. This is avoided, and it is possible to prevent the electrothermal catalytic converter from being overheated and the battery from being discharged.

In the engine exhaust emission control device according to the third aspect of the present invention, the third switch is opened when it is diagnosed that the first switch has failed, so that the electric heating means is prevented from being energized by the alternator or the battery. Therefore, it is possible to reliably prevent the electrothermal catalytic converter from being overheated and causing the battery to be discharged.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a timing chart showing a control example of the same.

FIG. 3 is a system diagram showing another embodiment.

FIG. 4 is a timing chart showing a control example of the same.

FIG. 5 is a claim correspondence diagram showing the invention according to claim 1;

FIG. 6 is a claim correspondence diagram showing the invention according to claim 2;

FIG. 7 is a claim correspondence diagram showing the invention according to claim 3;

[Explanation of symbols]

 1 1st switch 2 Charge circuit 3 Water temperature sensor 4 Electrothermal catalytic converter 5 Alternator 6 Electric load 7 Charge circuit 8 Voltage regulator 9 2nd switch 10 3rd switch 11 Ignition switch 12 Rotation speed sensor 16 Control unit 18 Battery a Catalytic converter b Electric heat Means c Alternator f Energization control means i Battery j First switch h Voltage detection means k Failure diagnosis means m Second switch n Fail safe means p Third switch q Fail safe means

Claims (3)

[Claims] 1. A catalytic converter installed in the middle of an exhaust passage, an electric heating means for heating the catalytic converter by energization, an alternator driven by an engine to generate electricity, and a battery for storing current supplied from the alternator. A first switch for connecting and disconnecting a current supplied from the alternator to the electric heating means, an energization control means for closing the first switch according to an operating condition, and a voltage VEH supplied to the electric heating means via the first switch.
A voltage detecting means for detecting C, and a failure diagnosing means for diagnosing a failure of the first switch when the voltage VEHC detected in an operating state in which the electric heating means is not energized is higher than a predetermined value VEHCFS. Exhaust purification device for engine. 2. A second switch for connecting and disconnecting a current supplied from an alternator to a battery, and a fail-safe means for opening the second switch when the engine is stopped when it is diagnosed that the first switch has failed. The exhaust emission control device for an engine according to claim 1, wherein: 3. A third switch for connecting and disconnecting a current supplied from the alternator to the electric heating means, and a fail-safe means for opening the third switch when it is diagnosed that the first switch has failed. The exhaust emission control device for an engine according to claim 1.