JPH0559940A - Catalytic conversion device of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve catalytic conversion performance by controlling a secondary air amount in accordance with temperature of a catalytic converter furnished with a heater function. CONSTITUTION:A temperature sensor 3 to detect temperature of a catalytic converter 1, a means 4 to judge a supply territory of a secondary air by way of comparing this detected temperature with a specified value and a means to control supply of the secondary air in accordance with a judgment result are furnished. Additionally, a means 5 to compute temperature change per hour on the basis of that detected value and a means to control supply of the secondary air in accordance with that computed value are furnished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst purifying device for an internal combustion engine.

[0002]

2. Description of the Related Art In some catalytic converters used to prevent air pollution of automobiles and the like, secondary air is supplied upstream of the catalytic converter to promote the oxidation reaction of HC and CO ( See JP-A-62-90919).

However, in the case of the conventional device having the heater function for heating the catalytic converter, the heat of the catalyst is rather taken away by the secondary air when the temperature of the catalytic converter is considerably low, including during the warm-up of the engine. There is a problem that it takes a lot of time for the catalyst to reach the activation temperature. Also, even when the temperature of the catalytic converter is high,
Since a constant amount of secondary air is supplied irrespective of the temperature, there is a problem that the purifying ability of the catalyst cannot always be fully exerted.

In view of these conventional problems, the present invention has an object to control the amount of secondary air based on the temperature of a catalytic converter having a heater function to enhance the catalytic purification performance.

[0005]

According to the present invention, as shown in FIG. 1, a catalytic converter 1 having a heater function is provided in the middle of an exhaust pipe, and a secondary air supply means is provided upstream of the catalytic converter 1. In a catalyst purifying apparatus for an internal combustion engine equipped with 2, a temperature sensor 3 for detecting the temperature of the catalytic converter 1
And means 4 for comparing the detected temperature with a predetermined value to determine the supply area of the secondary air, and means 6 for controlling the supply of the secondary air according to the determination result.

Further, a temperature sensor 3 for detecting the temperature of the catalytic converter 1, a means 5 for calculating a temperature change per time based on the detected value, and a supply of secondary air according to the calculated value are controlled. And means 6.

[0007]

[Function] When the temperature of the catalytic converter is lower than the predetermined value, by stopping the supply of the secondary air to the catalytic converter, the amount of heat generated by the oxidation reaction is greater than the amount of heat taken by the secondary air passing through the catalytic converter. It can be prevented from becoming small, and the temperature rise of the catalytic converter heated by the heater function can be accelerated.

In the operating state in which the secondary air is supplied,
When the temperature rises corresponding to the temperature change of the catalytic converter, the oxygen concentration of the catalytic converter is sufficiently increased by increasing the amount of secondary air in accordance with the rising speed, so that the HC and CO contained in the exhaust gas are reduced. When the temperature of the catalytic converter falls by sufficiently promoting the oxidation reaction of, the secondary air amount is reduced according to the falling speed to prevent the temperature from being excessively lowered due to the excessive supply of the secondary air amount. , Keep the catalyst active.

[0009]

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

As shown in FIG. 2, the exhaust pipe 12 of the engine 11
A catalytic converter 1 is interposed in the middle of the above, and an electric air pump 15 is connected upstream of the catalytic converter 1 as a secondary air supply means. The catalytic converter 1 is provided with an electric heater 14 as a heater function for heating the catalytic converter 1.

The controller 16 turns off when the engine 11 is started.
The signal of the ignition switch 17 which becomes N and the detection signal from the temperature sensor 3 which detects the temperature T of the catalytic converter 1 are respectively inputted to control the energization of the heater 14 through the transistor 19 during engine operation and The secondary air amount is adjusted by controlling the rotation of the electric air pump 15 based on the temperature T.

On the basis of the temperature T detected by the temperature sensor 3 and the signal from the ignition switch 17, the controller 16 raises the detected temperature T above a first predetermined value T ₁ and at the same time a first predetermined value T 1. _It is determined that the secondary air supply region is below the second predetermined value T ₂ which is lower than ₁ , and the temperature change dT / dt of the detected temperature T per time is calculated, and this calculated value dT / dt is calculated. The electric air pump 15 is controlled to supply the proportional secondary air amount Q.

An example of controlling the secondary air amount Q will be described with reference to the timing chart of FIG. At the point A where the detected temperature T of the catalytic converter 1 exceeds the first predetermined value T ₁ , the electric air pump 15 is operated to start the supply of secondary air, and the detected temperature T is the first predetermined value T 1. The supply of the secondary air is stopped at the point C, which is lower than the second predetermined value T ₂ lower than ₁ .

The first predetermined value T ₁ is a value corresponding to the activation temperature of the catalyst. When the temperature of the catalytic converter 1 is lower than the first predetermined value T ₁ , the catalytic converter 1 supplies the secondary air. Since the amount of heat taken by the secondary air passing through the catalytic converter 1 is larger than the amount of heat generated by the oxidation reaction by the catalyst, the temperature increase of the catalytic converter 1 heated by the heater 14 is accelerated by stopping the supply of the secondary air. ,
It promotes the activation of the catalyst.

The controller 16 also changes the temperature per unit time dT / based on the temperature T detected by the catalytic converter 1.
dt is calculated, and the secondary air amount Q is adjusted between the first predetermined value T ₁ and the second predetermined value T ₂ in accordance with the temperature change dT / dt.

When the detected temperature T of the catalytic converter 1 rises in the operating state in which the secondary air is supplied, the catalytic converter 1 is increased by increasing the secondary air amount Q according to the rising speed dT / dt. The oxygen concentration of is sufficiently increased to sufficiently accelerate the oxidation reaction of HC and CO contained in the exhaust gas. On the other hand, when the detected temperature T of the catalytic converter 1 decreases, the secondary air amount Q is excessively increased by decreasing the secondary air amount according to the decreasing speed dT / dt. Prevents the temperature from dropping too low and keeps the catalyst active.

In order to ensure the stability of control, the secondary air amount Q is maintained during the period when a predetermined time elapses from the point A at which the detected temperature T of the catalytic converter 1 rises above the first predetermined value T _1.
Keep constant.

[0018]

As described above, according to the present invention, a catalytic converter for an internal combustion engine is equipped with a catalytic converter having a heater function in the middle of an exhaust pipe and an actuator for supplying secondary air upstream of the catalytic converter. In the equipment, when the temperature of the catalytic converter rises above a specified value, the supply of secondary air is started.Therefore, when the temperature of the catalytic converter is low, cooling by the secondary air is prevented and the secondary air is heated by the heater function. Therefore, the temperature rise of the catalytic converter can be accelerated to accelerate the activation.

In the operating state in which the secondary air is supplied, the temperature change per unit time is calculated, and the amount of secondary air is adjusted according to this calculated value. By increasing or decreasing the amount of secondary air, the oxidation reaction of HC and CO can be sufficiently enhanced while maintaining proper activation.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

FIG. 2 is a configuration diagram of a catalyst purification device showing an embodiment.

FIG. 3 is a timing chart showing a control example of the secondary air amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Catalytic converter 2 Secondary air supply means 3 Temperature sensor 4 Secondary air supply area determination means 5 Catalyst temperature change calculation means per hour 6 Control means

Claims (2)

[Claims] 1. A catalyst purifying apparatus for an internal combustion engine, wherein a catalytic converter having a heater function is provided in the middle of an exhaust pipe, and a secondary air supply means is provided upstream of the catalytic converter to detect the temperature of the catalytic converter. An internal combustion engine comprising a temperature sensor, means for comparing the detected temperature with a predetermined value to determine the supply area of the secondary air, and means for controlling the supply of the secondary air according to the determination result. Engine catalyst purification device. 2. The temperature of a catalytic converter is detected in a catalytic converter of an internal combustion engine, wherein a catalytic converter having a heater function is provided in the middle of an exhaust pipe, and a secondary air supply means is provided upstream of the catalytic converter. A catalyst purification method for an internal combustion engine, comprising: a temperature sensor; means for calculating a temperature change per unit time based on the detected value; and means for controlling the supply of secondary air according to the calculated value. apparatus.