JPH1113459A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the excessive heating of an electric-heated catalyst converter by interposing a temperature sensing switch for cutting off a current supplied to the electric-heated catalyst converter by sensing the temperature increase of the electric-heated catalyst converter between a shell and an electrode. SOLUTION: An exhaust emission control device includes an electric-heated catalyst converter 5 interposed in a shell 4, a negative electrode 10 installed in the outer peripheral side of this electric-heated catalyst converter 5, a positive electrode installed in the opposite side thereof and an electric heating function for carrying a current to a carrier through these electrodes, electric heater function are provided. In this case, as a temperature sensing switch for cutting off a current supplied to the electric- heated catalyst converter 5 when the temperature of the electric-heated catalyst converter 5 is increased, a bimetal 1 is provided for connecting the negative electrode 10 with the shell 4. The tip part of this bimetal 1 is joined to the outer peripheral surface of the shell 4 when a temperature is equal to a specified level or lower and, when the temperature is increased more than the specified value, the tip part of the same is separated from the outer peripheral surface of the shell 4 and thereby carrying of the current is turned ON/OFF.

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 exhaust gas purifying apparatus for an internal combustion engine having an electrothermal catalytic converter.

[0002]

2. Description of the Related Art There is an exhaust gas purifying apparatus used for measures against air pollution of automobiles and the like, which includes an electrothermal catalytic converter for heating a catalyst carrier so as to quickly raise a catalyst to a temperature higher than its activation temperature.

[0003] As this type of exhaust gas purifying apparatus, there has been a conventional one shown in FIG. 4 (see Japanese Patent Application Laid-Open No. 5-79321).

[0004] This will be described.
In the first embodiment, a cylindrical shell 4 is connected in the middle of an exhaust pipe of an engine, and an electrothermal catalytic converter 5 is interposed inside the shell 4.

A positive electrode 9 is provided on the outer peripheral side of the electrothermal catalytic converter 5 and a negative electrode 10 is provided on the opposite side.
Is installed. The electrothermal catalytic converter 5 has two electrodes 9, 10
Has an electric heater function that generates heat when energized through the.

The electrode 10 is connected to a main cable 23 of a harness 21 and is connected to the negative terminal of the battery via the main cable 23 and a vehicle body (not shown).

A main cable 23 of a harness 21 is electrically connected to the electrode 9, and the main cable 23 is connected to a positive terminal of the battery via a changeover switch (not shown). The control unit (not shown) closes the changeover switch at the time of cold start to energize the electrothermal catalytic converter 5 to shorten the time required for the catalyst of the electrothermal catalytic converter 5 to reach the activation temperature.

Each electrode 9 provided through the shell 4
10 is heated by the heat transfer from the electrothermal catalytic converter 5, a radiating plate 29 is attached to each of the electrodes 9 and 10, and heat is radiated to the outside air via the radiating plate 29.

[0009]

However, in such a conventional apparatus, if the energization of the electrothermal catalytic converter 5 is continued more than necessary due to a failure of the changeover switch, the deterioration of the electrothermal catalytic converter 5 and the like is accelerated. there is a possibility.

[0010] It is an object of the present invention to solve the above-mentioned problems and to prevent overheating of an electrothermal catalytic converter in an exhaust gas purification device for an internal combustion engine.

[0011]

According to a first aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine, which has a cylindrical shell provided in the middle of an exhaust pipe and an electric heater function of being housed inside the shell. An electrothermal catalytic converter and an electrode connected to the electrothermal catalytic converter, and a temperature sensing switch that intercepts the current supplied to the electrothermal catalytic converter by sensing the temperature rise of the electrothermal catalytic converter is interposed between the shell and the electrode. To do.

According to a second aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine according to the first aspect of the present invention, further comprising a bimetal connecting an electrode and a shell as the temperature sensing switch, wherein the temperature of the bimetal rises above a predetermined value. Then, the conduction between the electrode and the shell is interrupted by the deformation of the bimetal.

According to a third aspect of the present invention, in the exhaust gas purifying apparatus for an internal combustion engine according to the second aspect, the electrode includes a nut which penetrates the shell via an insulator and is screwed to the electrode. The base end of the bimetal is fastened between the nut and the nut, and the tip of the bimetal is grounded to the shell when the temperature is below a predetermined value, and is separated from the shell when the temperature rises above the predetermined value.

According to a fourth aspect of the present invention, there is provided the exhaust gas purifying apparatus for an internal combustion engine according to the third aspect, wherein a tip portion of the bimetal is curved into a C shape and is joined to a shell.

[0015]

In the exhaust gas purifying apparatus for an internal combustion engine according to claim 1, the temperature sensing switch is closed during a cold start,
When the electrothermal catalytic converter is energized, activation of the catalyst is promoted.

For example, when the energization of the electrothermal catalytic converter is continued more than necessary due to a failure in the control system, the temperature sensing switch is opened when the temperature rises above a predetermined value due to the heat transfer from the electrothermal catalytic converter, and the electrothermal catalytic converter is opened. Is stopped and overheating of the electrothermal catalytic converter and the like can be prevented.

Further, unlike the case where the current is cut off in response to a signal from the control unit, the temperature sensing switch itself senses the temperature in the vicinity of the electrothermal catalytic converter and controls the current, so that it is inexpensive and reliable. Highly fail-safe can be realized.

In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, the bimetal is joined to the shell and closed at the time of the cold start, so that the electrothermal catalytic converter is energized and the activation of the catalyst is promoted.

For example, in the case where the energization of the electrothermal catalytic converter is continued more than necessary due to a failure in the control system, the bimetal separates from the shell and opens when the temperature rises above a predetermined value due to heat transfer from the electrothermal catalytic converter. The energization of the catalytic converter is stopped, and the overheating of the electrothermal catalytic converter and the like can be prevented.

Unlike receiving the signal from the control unit and shutting off the power supply, the bimetal itself senses the temperature in the vicinity of the electrothermal catalytic converter and controls the power supply. High failsafe can be realized.

In the exhaust gas purifying apparatus for an internal combustion engine according to the third aspect, the base position of the bimetal is fastened between the insulator and the nut screwed to the electrode, whereby the mounting position accuracy with respect to the shell can be improved. The quality is improved.

In the exhaust gas purifying apparatus for an internal combustion engine according to the fourth aspect, the tip of the bimetal curved in a C-shape is strongly pressed against the shell, and the contact force can be prevented by increasing the grounding force.

[0023]

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

As shown in FIG. 1, in the exhaust gas purifying apparatus 1, a cylindrical shell 4 is connected in the middle of the exhaust pipe of the engine. An electrothermal catalytic converter 5 is provided inside the shell 4. The carrier of the electrothermal catalytic converter 5 carries a catalytic metal such as platinum, and purifies the exhaust gas passing through the narrow path by catalytic action. A downstream catalytic converter (not shown) is provided inside the shell 4 downstream of the electrothermal catalytic converter 5. The downstream catalytic converter promotes oxidation of unburned HC and CO via a three-way catalyst, and reduces NOx. Is to be encouraged.

A negative electrode 10 is provided on the outer peripheral side of the electrothermal catalytic converter 5, and a positive electrode (not shown) is provided on the opposite side. The electrothermal catalytic converter 5 has an electric heater function in which the carrier generates heat when electricity is supplied to the carrier through the cable and these electrodes. As the electric heating means, a structure in which an electric heater provided separately from the carrier inside the catalytic converter may be provided.

In FIG. 2, 15 is an alternator and 18 is a regulator. The alternator 15 is driven to rotate by the engine, and the voltage generated by the alternator 15 increases as the rotation speed increases, but the regulator 18 adjusts the output voltage of the alternator 15 to a predetermined value.

The current output from the alternator 15 is
The electric power is supplied to the electrothermal catalytic converter 5 via the changeover switch 11 or to the battery 17 and the electric load 16. Examples of the electric load 16 include a headlight of a vehicle, an air conditioner (air conditioner), and the like.

The control unit 19 receives a detection signal from the temperature sensor 14 for detecting the temperature T of the electrothermal catalytic converter 5 and a signal from an ignition switch, a starter switch, and the like. To control the energization of

The control unit 19 closes the switch 11 for switching the current output from the alternator 15 to a catalyst inactive region where the catalyst temperature T is equal to or lower than a predetermined value (for example, 350 ° C.) at start-up, and closes the switch 11. And the energization time TIMER2 is set to a predetermined time t2 (for example,
(0 seconds) or more.

The control unit 19 includes the electric load 1
6, the detection signal of the battery voltage VB is input, and the output current of the alternator 5 is duty-controlled.

When the temperature of the catalyst is lower than its activation temperature and the temperature of the catalyst is low, the electrothermal catalytic converter 5 is energized and heated to shorten the time required for the catalyst of the electrothermal catalytic converter 5 to reach the activation temperature. When the catalyst reaches the activation temperature, HC and CO in the exhaust gas are oxidized, and the temperature is further raised by the reaction heat. The exhaust gas whose temperature has increased through the electrothermal catalytic converter 5 hastens the activation of the downstream catalytic converter,
HC and CO emissions during warm-up and the like can be significantly reduced.

The positive electrode of the electrothermal catalytic converter 5 is connected to the output terminal of the alternator 15 via the power cable and the changeover switch 11, and the negative electrode 10 is connected to the metal shell 4 which houses the electrothermal catalytic converter 5. Botty earth.

Even if the temperature of the electrothermal catalytic converter 5 rises beyond a predetermined value due to the failure of the changeover switch 11, the energizing of the electrothermal catalytic converter 5 is continued, and the electrothermal catalytic converter 5 may be overheated. .

To cope with this, the present invention provides a temperature sensing switch for cutting off the current supplied to the electrothermal catalytic converter 5 when the temperature of the electrothermal catalytic converter 5 rises above a predetermined value.

In this embodiment, a bimetal 1 that connects the negative electrode 10 and the shell 4 (that is, the body) is provided as a temperature sensing switch. The bimetal 1 is formed by joining two metal plates having different coefficients of thermal expansion, and is largely curved by a temperature change. Note that a shape memory alloy or the like may be used as the temperature sensing material as the temperature sensing switch.

The cylindrical negative electrode 10 penetrates the shell 4 via the annular insulator 2, and is provided with a nut 3 screwed to the tip of the electrode 10, between the insulator 2 and the nut 3. The base end of the bimetal 1 is fastened. That is, the negative electrode 1
0 is electrically connected to the shell 4 via the bimetal 1.

Since the base end of the bimetal 1 is fastened between the insulator 2 and the nut 3 screwed to the electrode 10, the mounting position accuracy with respect to the shell 4 can be increased, and the quality can be improved.

The tip of the bimetal 1 is formed by bending the crank into a crank shape. When the temperature of the bimetal 1 is lower than a predetermined value, it is surface-bonded to the outer peripheral surface of the shell 4 with a predetermined contact force. The shell 4 is separated upward from the outer peripheral surface in the figure.

A box-shaped waterproof cover 6 is fixed to the outer peripheral surface of the shell 4. The bimetal 1 and the electrode 10 are covered with a waterproof cover 13 so that they can be waterproofed.

The operation will be described below.

At start-up, the changeover switch 11 is closed in a catalyst inactive region where the catalyst temperature T is equal to or lower than a predetermined value, and
The bimetal 1 is closed, the current from the alternator 15 is supplied to the electrothermal catalytic converter 5, and the activation of the electrothermal catalytic converter 5 is promoted.

When the temperature of the electrothermal catalytic converter 5 rises above a predetermined value when the changeover switch 11 is normal, the changeover switch 11 is opened and the electrothermal catalytic converter 5 is not overheated. At this time, the bimetal 1 is kept closed as shown in FIG.

On the other hand, if the switch 11 does not open due to the failure of the switch 11 and the energization of the electrothermal catalytic converter 5 is continued, the temperature of the bimetal 1 becomes a predetermined value due to the heat transfer from the electrothermal catalytic converter 5. When it rises beyond the upper limit, the tip portion curves upward in FIG. 1 and is opened apart from the outer peripheral surface of the shell 4, and the energization of the electrothermal catalytic converter 5 is stopped. As a result, overheating of the electrothermal catalytic converter 5 can be prevented.

Further, unlike the case where the power is cut off by receiving a signal from the control unit, the bimetal 1 itself senses the temperature and controls the power supply in the vicinity of the electrothermal catalytic converter 5, so that the cost is low and the reliability is low. High failsafe can be realized.

Next, as another embodiment, as shown in FIG. 3, the distal end of the bimetal 1 may be formed in a C shape.

In this case, when the temperature of the bimetal 1 is equal to or lower than a predetermined value, the tip of the bimetal 1 is strongly pressed against the outer peripheral surface of the shell 4 to increase the contact force. As described above, it is preferable to increase the grounding force in order to prevent electric contact at the contact point between the bimetal 1 and the shell 4 because large electric power is generally supplied to the electrothermal catalytic converter 5.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an exhaust gas purification apparatus showing an embodiment of the present invention.

FIG. 2 is a system diagram of the same exhaust gas purification apparatus.

FIG. 3 is a longitudinal sectional view of an exhaust gas purification apparatus showing another embodiment.

FIG. 4 is a perspective view of an exhaust gas purifying apparatus showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bimetal 2 Insulator 3 Nut 4 Shell 5 Electrothermal catalytic converter 10 Electrode 11 Changeover switch 19 Control unit

Claims (4)

[Claims] 1. An electrothermal catalytic converter comprising: a tubular shell provided in the middle of an exhaust pipe; an electrothermal catalytic converter housed inside the shell and having an electric heater function; and an electrode connected to the electrothermal catalytic converter. An exhaust gas purifying apparatus for an internal combustion engine, comprising a temperature sensing switch for intercepting a current supplied to an electrothermal catalytic converter by detecting a temperature rise of a catalytic converter, between a shell and an electrode. 2. A temperature sensing switch comprising a bimetal connecting an electrode and a shell, wherein when the temperature of the bimetal rises above a predetermined value, conduction between the electrode and the shell is interrupted by deformation of the bimetal. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1. 3. The electrode includes a nut that penetrates through a shell through an insulator, and is screwed to the electrode. A base end of a bimetal is fastened between the insulator and the nut, and the bimetal has a temperature at a distal end thereof. 3. The exhaust gas purifying apparatus for an internal combustion engine according to claim 2, wherein the device is configured to be grounded to the shell at a predetermined value or less and separated from the shell when the temperature rises above the predetermined value. 4. The exhaust gas purifying apparatus for an internal combustion engine according to claim 3, wherein a tip portion of said bimetal is curved in a C-shape and joined to a shell.