JPH059453Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a secondary air supply device for an engine.

[Prior art]

In general, an engine's secondary air supply device supplies secondary air from the air cleaner to the exhaust passage, promotes the reaction between the catalyst and exhaust gas in the catalytic converter, and purifies the exhaust gas efficiently. One example is the conventional Japanese Patent Application Laid-open No. 54-9319.
There is something shown in the publication No.

In such a secondary air supply device, if there are variations in the amount of secondary air supplied, this will cause variations in the exhaust gas purification efficiency and the durability of the catalyst. For example, the amount of secondary air supplied is set so that the purification rate of the catalytic converter is close to a predetermined value when the vehicle has traveled 50,000 km, thereby ensuring the purification performance and durability of the catalyst.

[Purpose of invention]

This invention aims to provide a secondary air supply device for an engine that can further improve the durability of the catalyst under such circumstances.

[Structure of the idea]

As a result of intensive research to further improve the durability of the catalytic converter as described above, the inventor of this case found that by skillfully controlling the supply amount of secondary air, the durability of the catalyst can be improved without significantly impairing the purification performance of the catalyst. We have discovered that it can significantly improve your sexual performance. In other words, when the vehicle has traveled only a short distance, the catalyst has hardly deteriorated, and even if the secondary air supply amount is increased and the catalyst temperature is lowered, the purification efficiency does not deteriorate much. If the amount is increased, catalyst deterioration can be reduced due to the so-called cooling effect, which lowers the catalyst temperature, and if the amount of secondary air supplied is decreased as the vehicle travels longer, Purification efficiency can be improved by raising the reaction temperature of the catalyst, thereby increasing the distance traveled by the vehicle until the catalyst purification efficiency reaches a predetermined value, that is, improving durability.

Therefore, this invention provides an engine equipped with a catalytic converter disposed in an exhaust passage of the engine to purify exhaust gas, and a secondary air supply device that supplies secondary air to the exhaust passage upstream of the catalytic converter. When the value indicating deterioration of the converter is less than a predetermined value, the amount of secondary air supplied is greater than the amount required for appropriate exhaust purification, and after the value indicating deterioration of the catalytic converter reaches a predetermined value. is designed to supply an amount necessary for appropriate exhaust gas purification.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Figure 1 shows two parts of an engine according to an embodiment of the present invention.
Next shows the air supply device. In the figure, reference numeral 1 denotes an engine. A throttle chamber 3 is formed on the downstream side of an intake passage 2 of the engine 1, and a throttle valve 4 is disposed within the chamber 3. An air flow meter 5 is provided in the intake passage 2 on the upstream side of the throttle chamber 3, and the upstream end of the intake passage 2 is connected to an air cleaner 6. Further, a catalytic converter 8 is interposed in the exhaust passage 7 of the engine 1, and a silencer 9 is provided downstream of the converter 8.

The engine 1 is provided with a secondary air supply device 10. In this secondary air supply device 10, one end of the secondary air supply passage 11 is connected to the air cleaner 6, and the other end is connected to the upstream exhaust passage 7 of the catalytic converter 8. An air pump 12 is disposed in the middle of this secondary air supply passage 11, and an air control valve 13 is disposed downstream of the air pump 12 to cut off the supply of secondary air during high load and high rotation.

In addition, an air pump 12 is provided in the secondary air supply passage 11.
A bypass passage 14 is branched by bypassing the
is provided. In the figure, numeral 16 indicates deterioration of the catalytic converter 8 and detects the distance traveled, which is a parameter of the accumulated operating time of the engine 1. 17 receives the output of the odometer 16, and This control unit outputs a close signal to the relief valve 15 when the distance is less than the set value α, and outputs an open signal to the relief valve 15 when the distance is more than the set value α.
Reference numeral 7 denotes secondary air increasing means for increasing the amount of secondary air supplied when the cumulative operating time detected by the engine cumulative operating time detecting means does not reach a predetermined cumulative operating time.

Next, the operation will be explained using FIG. 2. Here, FIG. 2 shows the relationship between travel distance and secondary air supply amount.

When the engine operates, intake air from the air cleaner 6 flows through the intake passage 2, mixes with fuel,
The gas is supplied to the engine 1 and combusted, and the combustion gas generated at that time is discharged from the engine 1 to the exhaust passage 7 as exhaust gas. If the engine mileage is less than the set value α, control unit 1
7 determines from the output of the odometer 16 that the travel distance is less than the set travel distance α, outputs a close signal, and closes the relief valve 1.
5 is closed, and when the air pump 12 pumps the secondary air from the air cleaner 6 toward the exhaust passage 7, all of the secondary air is supplied to the exhaust passage 7 via the secondary air supply passage 11 (the (See part A of Figure 2). The exhaust gas is then sent to the catalytic converter 8 together with the secondary air, where it reacts with the catalyst and is purified, before being released into the atmosphere.

Furthermore, when the running distance of the engine exceeds the set value α, the control unit 17 outputs an open signal, the relief valve 15 is opened, and a part of the secondary air from the air pump 12 is transferred to the bypass passage 14.
The secondary air is relieved to the upstream side of the air pump 12 through the
(See section B in Figure 2).

The inventor also conducted a comparative experiment on the durability of this device and a conventional device. In the experiment, changes in the residual rate of unpurified components in exhaust gas were investigated in order to compare changes in exhaust purification rate with respect to mileage. FIG. 3 shows the results. In the figure, the solid line A shows the change in the residual rate of unpurified components of the present device, and the dashed line B shows the change in the residual rate of unpurified components of the conventional device.

According to this, in the conventional device, the survival rate increases monotonically as the traveling distance increases, as shown by the dashed line B, and at a predetermined traveling distance β, a predetermined survival rate a
has reached. On the other hand, with this device, the survival rate is higher than that of the conventional device when the mileage is short, and this also increases as the mileage increases.
The residual rate is kept sufficiently lower than a. Then, when a predetermined mileage α is reached, this residual rate decreases significantly and becomes less than the residual rate of the conventional device.After that, this purification rate increases as the mileage increases, and at a predetermined mileage β, it becomes lower than the predetermined residual rate a. The survival rate is obtained.

Therefore, in this device, the durability of the catalyst is greatly improved compared to the conventional device, and even when the traveling distance is less than the predetermined distance α, the residual rate of unpurified components remains at the predetermined value a.
It can be seen that the value is below, which is sufficiently satisfactory.

In the above embodiment, in order to obtain a value indicating the deterioration of the catalytic converter, the cumulative operating time of the engine was detected from the distance traveled by the vehicle. Alternatively, the deterioration state of the catalyst may be directly obtained, for example, by detecting the catalyst temperature while keeping the amount of secondary air supplied constant.

[Effect of idea]

As described above, the present invention includes a catalytic converter that is disposed in the exhaust passage of an engine to purify exhaust gas, and a secondary air supply device that supplies secondary air to the exhaust passage upstream of the catalytic converter. In the engine, when the value indicating the deterioration of the catalytic converter is less than a predetermined value, the amount of secondary air supplied is greater than the amount required for appropriate exhaust purification, and the value indicating the deterioration of the catalytic converter is less than the predetermined value. After reaching this value, an amount sufficient to properly purify the exhaust gas is supplied, which has the effect of significantly improving the durability of the catalyst without impairing the purification performance.

[Brief explanation of drawings]

Figure 1 shows two parts of an engine according to an embodiment of the present invention.
A configuration diagram of the secondary air supply device, Fig. 2 is a diagram showing the relationship between the traveling distance and the amount of secondary air supply to explain the operation of the above device, and Fig. 3 is a comparison of the durability of the above device and the conventional device. It is a figure showing the result of an experiment. DESCRIPTION OF SYMBOLS 1...Engine, 7...Exhaust passage, 8...Catalytic converter, 16...Odometer (deterioration detection means), 17...Control unit (secondary air increase means).

Claims (1)

[Scope of Claim for Utility Model Registration] In an engine equipped with a catalytic converter that is disposed in the exhaust passage of the engine to purify exhaust gas, and a secondary air supply device that supplies secondary air to the exhaust passage upstream of the catalytic converter. , a deterioration detection means for detecting a value related to deterioration of the catalytic converter, and when the value detected by the deterioration detection means is less than or equal to a predetermined value, the actual purification rate of the catalytic converter is determined as compared to when the value is greater than or equal to the predetermined value. 1. A secondary air supply device for an engine, comprising: secondary air increasing means for increasing the supply amount of the secondary air in a direction that reduces the difference between the amount of the secondary air and the allowable purification rate.