JPH08326527A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PURPOSE: To prevent the generation of a problem caused by keeping on heating an electrically heated catalyst due to the abnormality or the like of a control circuit. CONSTITUTION: The fail-safe function of forcibly cutting off power supply to the electric heater of an electrically heated catalyst(EHC) separately from a signal from an engine control system(ECM) 16, that is, a cut-off relay switch 17 switched on/off by a temperature switch 18, is interposed in the power circuit 11 of the electric heater 10. Accordingly, in the case of the ECM 16 ending in abnormality due to the influenece of noise or the like so as to continue to output current-on signals to the electric heater 10, that is, even in the case of a current being applied to the electric heater 10 outside of the operating condition of the electric heater 10, power supply to the electric heater 10 is forcibly cut off by the cut-off relay switch 17 so as to impede such a situation as to keep on heating the EHC.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly to an exhaust gas purification apparatus in which an electrically heated catalyst heated by an electric heater is installed in an exhaust passage of the internal combustion engine.

[0002]

2. Description of the Related Art When an exhaust gas temperature is low immediately after a cold start of an internal combustion engine (hereinafter referred to as an engine), it is almost impossible to purify the exhaust gas by a three-way catalyst provided in an exhaust passage.
Therefore, conventionally, for the purpose of activating the catalyst early, as shown in FIG. 3, an electrically heated catalyst (hereinafter, referred to as EHC) 2 having an electric heater 1 for heating the catalyst is used as an engine 3
An exhaust emission control device has been proposed, which has an EHC system configured to be installed in the exhaust passage 4 of Japanese Patent Laid-Open No. 4-2797.
(See Japanese Patent Publication No. 18).

In the conventional EHC system, the EH
The internal temperature of C2 is detected by the temperature detecting means 5, and when the detected temperature reaches a certain temperature, it is judged that the catalyst 2 is sufficiently activated and heating is unnecessary, and the engine control module (hereinafter, The control signal from the ECM) 6 stops the energization of the electric heater 1. Also, the energization time to the electric heater 1 required to activate the electrically heated catalyst 2 is calculated from the cooling water temperature of the engine 3 and the like,
When the actual energization time reaches the calculated time, it is determined that the electrically heated catalyst 2 is sufficiently activated and heating is unnecessary, and the energization to the electric heater 1 is stopped.

[0004]

However, such a conventional EHC system has the following problems. That is, in the past, the power supply control (energization ON-OFF) of the EHC system is performed based on the control signal output from the ECM 6.
The ECM6 becomes abnormal due to the influence of noise, etc., and the power is turned on.
There is a possibility that the signal may be continuously output to the electric heater 1.

When such a situation occurs, the electrically heated catalyst 2 continues to be heated, especially when the exhaust gas is hot.
Since the component allowable temperature is exceeded, the components of the system including the electrically heated catalyst 2 are thermally deteriorated, and there is a concern that the vehicle may be thermally adversely affected. Therefore, in view of the conventional problems as described above, the present invention adds a fail-safe function of forcibly shutting off the power supply to the electrically heated catalyst separately from the signal from the control circuit. It is intended to prevent the occurrence of problems due to the electrically heated catalyst being continuously heated due to abnormality or the like.

[0006]

Therefore, according to the invention of claim 1, an electrically heated catalyst heated by an electric heater is provided in an exhaust passage of an internal combustion engine, and a power supply circuit of the electric heater is provided with an engine. An exhaust gas purification apparatus for an internal combustion engine, comprising an energization control circuit for controlling energization of an electric heater according to operating conditions, wherein an electric heater for an electrically heated catalyst is provided in the power supply circuit and in a system separate from the energization control circuit. An energization stop circuit is provided to detect an out-of-conduction condition and forcibly stop energization of the electric heater.

According to a second aspect of the present invention, the energization control circuit controls opening and closing of a relay switch provided in a power supply circuit and an energization circuit of a relay coil of the relay switch according to engine operating conditions. And means.
According to a third aspect of the present invention, a relay switch in which the energization stop circuit is interposed in a power supply circuit and an energization circuit of a relay coil of the relay switch are opened by detecting outside an electric heater energization condition of an electrically heated catalyst. And a switch means for switching.

According to a fourth aspect of the present invention, a relay switch in which the energization stop circuit is interposed in an energization control circuit and an energization circuit of a relay coil of the relay switch are provided under conditions for energizing an electric heater of an electrically heated catalyst. Switch means for detecting and opening. The invention according to claim 5 is a temperature switch, wherein the switch means detects any one of an engine cooling water temperature, an electrically heated catalyst temperature, and an exhaust temperature, and opens when the detected temperature is equal to or higher than a predetermined temperature. Composed from.

[0009]

In the invention of claim 1, a fail-safe function for forcibly cutting off the power supply to the electric heater of the electrically heated catalyst separately from the control signal by the energization control circuit is added, that is, the electrically heated catalyst By providing an energization stop circuit that detects the outside of the electric heater energization condition and forcibly stops energization to the electric heater, the energization control circuit etc. becomes abnormal due to the influence of noise etc. In the case of continuing to output to the heater, that is, even when the electric heater is energized outside the operating condition of the electrically heated catalyst, the power supply to the electrically heated catalyst is forcibly cut off,
The situation in which the electrically heated catalyst continues to be heated is prevented.

According to the second aspect of the invention, the control means outputs an ON signal to the relay coil of the main relay switch at the cold start of the engine, excites the ON signal, and closes the main relay switch. This allows
Electricity is supplied from the power supply to the electric heater of the electrically heated catalyst,
The electrically heated catalyst is heated. And the control means
When the electrically heated catalyst is sufficiently activated and it is determined that heating is unnecessary, control to stop energization of the electric heater is executed, so an OFF signal is output to the relay coil of the main relay switch, And the main switch is opened.

In the third and fifth aspects of the invention, the temperature switch is outside the electric heater energization condition of the electrically heated catalyst,
For example, it is turned off when the engine cooling water temperature is above a certain temperature.
Therefore, the excitation of the relay coil of the cut relay switch is released and the switch is opened, and the energization control circuit etc. becomes abnormal due to the influence of noise, etc. Even in the case where the cut relay switch is opened, the power supply from the power source to the electric heater of the electrically heated catalyst is forcibly stopped, and the heating of the electrically heated catalyst is stopped.

In the inventions as claimed in claims 4 and 5, the temperature switch is outside the electric heater energization condition of the electrically heated catalyst,
For example, it is turned off when the engine cooling water temperature is above a certain temperature.
Therefore, the excitation of the relay coil of the cut relay switch is released, which causes the main relay switch to open and the energization control circuit, etc. malfunctions due to noise, etc. Even when the electric heating catalyst continues, the power supply to the electric heater of the electric heating type catalyst is stopped, and the heating of the electric heating type catalyst is stopped.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of the present invention, in which an electric heater 10 is provided in an exhaust passage of an engine and heats a catalyst.
1 shows an EHC power supply circuit 11 provided with the inside. That is, a power supply circuit 11 in which a power supply 12 such as a battery or an alternator and an EHC electric heater 10 are connected in series is provided with an energization control circuit 13 that controls energization of the electric heater 10 in accordance with engine operating conditions. .

Further, the power supply circuit 11 is provided with an energization stop circuit 14 which is separate from the energization control circuit 13 and which detects an electric heater energization condition outside and forcibly stops energization of the electric heater 10. ing. In this embodiment, the energization control circuit 13 controls the opening / closing of the main relay switch 15 provided in the power supply circuit 11 and the energization circuit 15A of the relay coil 15a of the main relay switch 15 according to the engine operating conditions. ECM16 as a control means for controlling
And are included.

Further, the energization stop circuit 14 includes a cut relay switch 17 provided in the power supply circuit 11 and a energization circuit 1 for the relay coil 17a of the cut relay switch 17.
7A, and a temperature switch 18 as a switch means for detecting and opening an electric heater energization condition outside. The main relay switch 15 is of a type in which the switch piece a is normally opened apart from the switch contacts b and c, that is, a so-called normally open type, and when the coil 15a is excited by energizing the relay coil 15a. , The switch piece a is brought into contact with the switch contacts b and c to be closed.

Further, the ECM 16 calculates, for example, the energization time to the electric heater 10 required to activate the EHC from the engine cooling water temperature and the like, and when the actual energization time reaches the calculated time. , The EHC is sufficiently activated and it is judged that heating is unnecessary, and the relay coil 15 of the main relay switch 15 should be stopped to stop the energization of the electric heater 1.
The control for opening the energization circuit 15A of a is executed.

On the other hand, the cut relay switch 17 is
Similar to the main relay switch 15, it is a normally open type switch, and when the coil 17a is excited by energizing the relay coil 17a, the switch piece a is brought into contact with the switch contacts b and c to be closed. The temperature switch 18 is turned on / off based on the engine cooling water temperature, the bed temperature of the electrically heated catalyst, or the exhaust gas temperature downstream of the electrically heated catalyst in the exhaust passage. That is, the temperature switch 18 is configured to be turned on under the operating condition of the electric heater 10 and turned off outside of the operating condition. To be configured.

In such a configuration, the ECM 16 outputs an ON signal to the relay coil 15a of the main relay switch 15 when the engine cold starts. As a result, the relay coil 15a is excited and the switch piece a is brought into contact with the switch contacts b and c to be closed. On the other hand, the temperature switch 18 has, for example, an engine coolant temperature of 400 or the like.
When the temperature is less than ° C, it is turned on, and the relay coil 17a of the cut relay switch 17 is excited by this,
The switch piece a is brought into contact with the switch contacts b and c to be closed.

Therefore, the electric heater 10 is energized from the power source 12 to heat the EHC. And ECM16
Is the EHC when the actual energization time reaches the calculated time.
Is activated sufficiently, it is determined that heating is unnecessary, and control for stopping the energization of the electric heater 10 is executed to turn it off.
Relay coil 15a of the main relay switch 15
Output to. As a result, the excitation of the relay coil 15a is released, and the switch piece a separates from the switch contacts b and c and opens.

Here, it is assumed that the ECM 16 becomes abnormal due to the influence of noise or the like and continues to output the energization ON signal to the electric heater 10 outside the electric heater operating condition. in this case,
The temperature switch 18 is set outside the electric heater operating condition, for example,
It turns off when the engine cooling water temperature is 400 ° C or higher. As a result, the excitation of the relay coil 17a of the cut relay switch 17 is released, the switch piece a is separated from the switch contacts b and c and opened, and the ECM 16 outputs the ON signal. With the opening of 17, the energization of the electric heater of the EHC from the power source 12 is stopped, and the heating of the EHC is stopped.

As described above, a fail-safe function for forcibly cutting off the power supply to the electric heater of the EHC separately from the signal from the ECM 16 is added, that is, the cut relay switch 17 which is turned on / off by the temperature switch 18 is added. Since it is provided in the power supply circuit 11 of the electric heater 10, E
CM16 becomes abnormal due to the influence of noise, etc.
Even when the N signal is continuously output to the electric heater 10, that is, even when the electric heater 10 is energized outside the electric heater operating condition, the cut relay switch 17 supplies power to the electric heater 10. The situation where the EHC is forcibly shut off and the EHC is continuously heated is prevented.

Therefore, in particular, when the exhaust gas is at a high temperature, there is no possibility of exceeding the allowable temperature of the parts, and the thermal deterioration of the components of the system including the EHC and the thermal adverse effects on the vehicle are prevented. Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, the energization stop circuit 14 is provided in the energization control circuit 13, and a cut relay switch 17 is provided.
The energizing circuit 17A of the relay coil 17a of the cut relay switch 17 is configured to include a temperature switch 18 that detects and opens an electric heater energization condition outside.

In such a structure, the temperature switch 18
However, for example, when the cooling water temperature of the engine is 400 ° C. or higher, the relay coil 17a of the cut relay switch 17 is deenergized, and the switch piece a is separated from the switch contacts b and c to open. As a result, even when the main relay switch 15 is opened and the ECM 16 outputs the ON signal, the power supply 12 stops the energization of the electric heater 10 and stops the heating of the EHC.

In each of the above-described embodiments, the cut relay switch 17 is used by using a type in which the temperature switch 18 is turned on at a temperature lower than a certain set temperature and turned off at the above temperature.
I tried to use a normally open type, but it turned off at less than a certain set temperature as a temperature switch,
It is also possible to use the type that is turned on as described above, and in this case, if the cut relay switch is a type that is normally closed with its switch piece in contact with the switch contact, a so-called normally closed type. good.

[0025]

As described above, according to the first aspect of the invention, the fail-safe function for forcibly shutting off the power supply to the electric heater of the electric heating type catalyst separately from the control signal by the energization control circuit. By adding the, the energization control circuit etc. becomes abnormal due to the influence of noise etc.
Even when the signal is continuously output to the electric heater, that is, even when the electric heater is energized outside the operating condition of the electric heating type catalyst, the power supply to the electric heating type catalyst is forcibly cut off. As a result, the situation in which the electrically heated catalyst continues to be heated is prevented, and as a result, there is no risk of exceeding the component allowable temperature when the exhaust gas is at a high temperature, thermal degradation of the components of the system including EHC, and thermal damage to the vehicle. The adverse effect is prevented.

According to the second aspect of the invention, it is possible to control the energization of the electric heater according to the engine operating conditions. According to the third and fourth aspects of the invention, even when the energization control circuit or the like becomes abnormal due to the influence of noise or the like and the energization control circuit continues to energize the electric heater, the relay switch By the action of the switch means, the power supply to the electric heater of the electrically heated catalyst can be forcibly stopped, and the heating of the electrically heated catalyst can be stopped.

According to the fifth aspect of the invention, the temperature switch can detect the outside of the electric heater energization condition and open the energization circuit of the relay coil of the relay switch.

[Brief description of drawings]

FIG. 1 is a power supply circuit diagram of an EHC electric heater showing an embodiment of the invention described in claims 1, 2, 3 and 5.

FIG. 2 is a power supply circuit diagram of an EHC electric heater showing an embodiment of the invention described in claims 1, 2, 4 and 5.

FIG. 3 is a schematic diagram of an EHC system of a conventional device.

[Explanation of symbols]

 10 Electric Heater 11 Power Supply Circuit 12 Power Supply 13 Energization Control Circuit 14 Energization Stop Circuit 15 Main Relay Switch 16 ECM 17 Cut Relay Switch 18 Temperature Switch

Claims (5)

[Claims] 1. An energization control in which an electrically heated catalyst heated by an electric heater is interposed in an exhaust passage of an internal combustion engine, and a power supply circuit of the electric heater controls energization of the electric heater according to engine operating conditions. In an exhaust gas purification device for an internal combustion engine, which is provided with a circuit, the power supply circuit is provided in a system separate from the energization control circuit, and an electric heater energization condition for an electrically heated catalyst is detected to force energization of the electric heater. An exhaust gas purification device for an internal combustion engine, comprising an energization stop circuit for stopping the internal combustion engine. 2. The energization control circuit includes a relay switch interposed in a power supply circuit, and control means for controlling the opening / closing of the energization circuit of a relay coil of the relay switch according to engine operating conditions. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the exhaust gas purification device is configured. 3. The switch means for opening the energization stop circuit, wherein a relay switch interposed in a power supply circuit and an energization circuit for a relay coil of the relay switch are detected when an electric heater energization condition of an electrically heated catalyst is detected. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1 or 2, wherein the exhaust gas purifying apparatus comprises: 4. The energization stop circuit is a switch for opening a relay switch interposed in an energization control circuit and an energization circuit for a relay coil of the relay switch by detecting a condition outside an electric heater energization condition of an electrically heated catalyst. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1 or 2, further comprising: 5. The switch means comprises a temperature switch that detects any one of an engine cooling water temperature, an electrically heated catalyst temperature, and an exhaust temperature, and opens when the detected temperature is equal to or higher than a predetermined temperature. Item 5. An exhaust gas purification device for an internal combustion engine according to item 3 or 4.