JP2867776B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas system for an internal combustion engine, and more particularly to an exhaust gas purifying system for an internal combustion engine in which the heater of a catalyst with a heater is energized to promote warming-up of the catalyst.

[0002]

2. Description of the Related Art Generally, a catalyst for purifying exhaust gas of an internal combustion engine is not activated unless a predetermined temperature is reached, and a purifying function cannot be obtained. The catalyst in the internal combustion engine is heated by the exhaust gas. However, the exhaust gas temperature is low particularly during a cold start, and the internal combustion engine body has not been warmed up yet.

Therefore, a heater for heating the catalyst and a thermostat for detecting the temperature of the catalyst are provided, the heater is energized to forcibly heat the catalyst, and the temperature of the catalyst is maintained in a predetermined temperature range by the thermostat. An exhaust gas purifying apparatus in which the power supply to the heater is controlled as described above is conventionally known (Japanese Utility Model Laid-Open No. 48-32714).

[0004]

However, in the above-mentioned conventional exhaust gas purifying apparatus, when the thermostat is defective, the heater is energized even when the catalyst bed temperature exceeds a predetermined temperature range, so that the catalyst bed temperature is reduced. May become abnormally high temperature and may deteriorate the catalyst. Also, if the heater is defective, there is a possibility that the predetermined exhaust gas purification performance may not be obtained,
Since the thermostat operates according to the exhaust gas temperature, it is not possible to judge a failure with high accuracy only by the presence or absence of the operation of the thermostat.

The present invention has been made in view of the above points, and an object of the present invention is to provide an exhaust gas purifying apparatus for an internal combustion engine which determines a failure based on a change in temperature of a catalyst.

[0006]

FIG. 1 is a block diagram showing the principle of the present invention. The present invention includes a heater-equipped catalyst 12, which is provided in an exhaust passage 11 of an internal combustion engine 10 and includes a catalyst 12a and a heater 12b for purifying exhaust gas, and an energizing means 13 for energizing the heater 12b to heat the catalyst 12a. The exhaust gas purifying apparatus includes a load detecting unit 14, a temperature detecting unit 15, a control unit 16, and a determining unit 17.

Here, the load detecting means 14 detects that the internal combustion engine 10 is in a low load operation state. Also,
The temperature detecting means 15 detects the temperature of the catalyst 12a. When the load detecting means 14 detects the low load operation state and the temperature detecting means 15 detects that the temperature of the catalyst 12a is equal to or lower than a predetermined value, the control means 16
Operation control. Further, the determining means 17 determines that the system has failed when the temperature of the catalyst 12a is equal to or less than the predetermined value for a predetermined time while the energizing means 13 is in the operating state.

[0008]

When the control means 16 is in a low-load operation state and the operation of the energizing means 13 is controlled when the temperature of the catalyst 12a is equal to or lower than a predetermined value, if the heater 12b and the temperature detecting means 15 are normal, respectively, As the temperature elapses, the temperature of the catalyst 12a rises, and when the predetermined time has elapsed, the temperature becomes higher than a predetermined value.

However, if the heater 12b is defective, the amount of heat generated by the heater 12b is extremely small even if the energizing means 13 is activated. Therefore, the temperature of the catalyst 12a must be increased to the predetermined value even after the predetermined time has elapsed. If the temperature detection means 15 is defective, the heater 12b
Since the temperature of the catalyst 12a cannot be accurately detected even if the temperature of the catalyst 12a is heated, a detection result that the temperature of the catalyst 12a is equal to or higher than the predetermined value cannot be obtained even if the power is supplied for the predetermined time. Therefore, in the present invention, the determining means 17 determines whether the energizing means 13
If the temperature of the catalyst 12a is equal to or lower than the predetermined value at the time when the power supply operation continues for a predetermined time, it is determined that the system has failed.

[0010]

FIG. 2 is a block diagram showing one embodiment of the present invention. In the figure, reference numeral 21 denotes an engine, which corresponds to the internal combustion engine 10. The combustion chamber of the engine 21 is connected to an exhaust manifold 22 (corresponding to the exhaust passage 11) via an exhaust valve (neither is shown). The exhaust manifold 22 is provided with an AI (air injection) inlet 23 at an outlet thereof, and is further connected to a heater-equipped catalyst 24 (corresponding to the heater-equipped catalyst 12) downstream of the AI inlet 23. On the downstream side of the heater-equipped catalyst 24, a start cat 25 and a main catalyst 26 are sequentially arranged. The start cat 25 is a small-capacity catalyst,
Together with the heater-equipped catalyst 24 and the main catalyst 26, each of them purifies exhaust gas by catalytic action.

The heater-equipped catalyst 24 is provided with a positive electrode 27 and a negative electrode 28. Near the catalyst 24 with heater,
A temperature detector 29 for detecting a heater temperature, for example, using a thermocouple.
Is provided. The temperature detector 29 corresponds to the temperature detecting means 15. The negative electrode 28 is connected to a negative terminal of the battery 30, and the positive electrode 27 is connected to a positive terminal of the battery 30 via a controller 31.
The battery 30 and the controller 31 constitute the above-mentioned energizing means 13.

The controller 31 receives the terminal voltage of the catalyst with heater 24 via a line 32 and
, The terminal voltage of the battery 30 is input. Also,
The controller 31 is connected to a diagnostic lamp 34 provided in the driver's seat to control lighting thereof, and an idle switch which is turned on when a throttle valve (not shown) provided in the intake manifold 37 is fully closed. 3
5 is input. The idle switch 35 constitutes the load detecting means 14.

The heater-equipped catalyst 24 has a known structure (for example, Japanese Utility Model Laid-Open No. 63-67609). For example, a main monolith catalyst in which a catalyst is supported on a ceramic honeycomb monolith carrier in a case, and a heater as a heater are provided. When a metal monolith catalyst is provided adjacent to the exhaust gas passing direction and a current is applied between the positive electrode 27 and the negative electrode 28, the metal monolith catalyst is heated, and the metal monolith catalyst is set to an activation temperature. The temperature of the gas entering the main monolith catalyst also rises, and the hydrocarbons (HC) in the exhaust gas are increased by the main monolith catalyst.
And carbon monoxide (CO).

The controller 31 comprises, for example, a microcomputer, and implements the control means 16 and the determination means 17 by software processing. FIG. 3 shows a catalyst warm-up heater control routine executed by the controller 31. When this catalyst warm-up heater control routine is started,
First, it is determined whether or not the idle switch (IDL switch) 35 is on (step 41).

That is, according to the present embodiment, the heater energization described later is performed only during a light load operation such as an idle state where the idle switch 35 is turned on. In this light load operation, generally, the amount of exhaust gas is small, so that the temperature of the catalyst is greatly reduced, the catalyst is in a deactivated state, and the exhaust emission is easily deteriorated. Therefore, it is often necessary to energize the heater.

When it is determined in step 41 that the idle switch 35 is ON, the catalyst bed temperature is indirectly detected from the heater temperature detected by the temperature detector 29, and it is determined whether or not the detected temperature is lower than a predetermined value. (Step 4
2). When it is determined in step 41 that the idle switch 35 is off, the operation range is such that the catalyst temperature can be kept sufficiently high, so that the power supply to the heater of the catalyst with heater 24 is turned off without detecting the catalyst bed temperature. (Step 4
3).

Even if the idle switch 35 is determined to be on, if the catalyst bed temperature is determined to be equal to or higher than the predetermined value in step 42, if the heater is energized, the catalyst bed temperature will rise too much, Therefore, the power to the heater is turned off (step 4).
3). After the power supply to the heater is turned off, the timer is cleared (step 44), and this routine ends.

On the other hand, when it is determined in step 42 that the catalyst bed temperature is equal to or higher than the predetermined value, a timer is checked to determine whether a predetermined time has elapsed (step 45). The above timer is cleared by, for example, an initial routine, and is incremented only in step 47 described later. Therefore, when step 45 is first executed, a determination result that a predetermined time has not elapsed is obtained. Accordingly, the routine proceeds to step 46, where the energization of the heater of the catalyst with heater 24 to the heater is started.

When energization of the heater is started, the timer is incremented by a predetermined value, and the process exits this routine. Thereafter, the catalyst warm-up heater control routine is started by interruption every predetermined cycle, and when the idle switch 35 is in the ON state, the power supply to the heater is continued (step 47).

When both the heater and the temperature detector 29 are normal, the catalyst bed temperature of the heater-equipped catalyst 24 rises due to the continuous energization of the heater. In order to reach a higher temperature than the value, the process of step 43 is executed via steps 41 and 42, and the power supply to the heater is stopped.

However, if the catalyst bed temperature does not reach a temperature higher than a predetermined value even when the power supply to the heater is continued for the predetermined time while the idle switch 35 is in the on state, the heater of the catalyst with heater 24 is defective. It is considered that the heating of the catalyst is insufficient or that the temperature detector 29 is defective and that the heater temperature cannot be accurately detected.

In this case, if the temperature detector 29 is abnormal, the catalyst bed temperature may have risen to a predetermined value or more due to the heating of the heater. Goes to step 48, the energization of the heater of the heater-equipped catalyst 24 to the heater is stopped (step 48), and the diagnostic lamp 34 is turned on (step 49) to notify the driver of the abnormality of the exhaust gas purification system.

As described above, according to this embodiment, when the amount of exhaust gas is small and the catalyst bed temperature is hardly changed by the exhaust gas as in the case of idling, the catalyst 24 with heater and the temperature detector 2
Since the presence / absence of the failure is determined, accurate failure diagnosis can be performed.

The present invention is not limited to the above-described embodiment. For example, the temperature detector 29 may be mounted so as to directly detect the temperature of the catalyst.

[0025]

As described above, according to the present invention, when energization of the heater is continued for a predetermined time in a light load operation state, when the catalyst bed temperature is lower than a predetermined value, it is determined that the system has failed. In addition to being able to perform a failure diagnosis, the failure diagnosis can promptly take a countermeasure against the failure, so that the catalyst deterioration of the heater-equipped catalyst can be greatly reduced as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a configuration diagram of one embodiment of the present invention.

FIG. 3 is a flowchart illustrating a catalyst warm-up heater control routine that is an embodiment of a main part of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Internal combustion engine 11 Exhaust passage 12a Catalyst 12b Heater 12, 24 Heated catalyst 13 Current supply means 14 Load detection means 15 Temperature detection means 16 Control means 17 Judgment means 31 Controller 35 Idle switch 36 Diag lamp

Claims (1)

(57) [Claims] 1. An exhaust gas purifying apparatus provided in an exhaust passage of an internal combustion engine and having a heater-equipped catalyst comprising a catalyst for purifying exhaust gas and a heater for heating the catalyst when energized by an energizing means. Load detection means for detecting that the engine is in a low load operation state; temperature detection means for detecting the temperature of the catalyst; low load operation state detected by the load detection means; and Control means for controlling the operation of the energizing means when the temperature of the catalyst is detected to be equal to or lower than a predetermined value; and An exhaust gas purifying apparatus for an internal combustion engine, comprising: a judging means for judging.