JPH0134649Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a secondary air supply device for an internal combustion engine that uses exhaust pulsation to introduce secondary air into an exhaust system via a check valve.

Prior Art In order to promote the reaction of the catalyst installed in the exhaust system at low temperatures and to prevent overheating and burnout at high temperatures, a secondary air cutoff valve is provided upstream of the check valve in the secondary air passage, and the engine When the engine is cold, the shutoff valve is opened to introduce secondary air through the check valve, and when the engine is warm, the shutoff valve is closed to stop the introduction of secondary air. There are secondary air supply devices that
Publication No.).

However, in the conventional configuration in which the secondary air cutoff valve is provided in this way, when the secondary air cutoff valve is closed, exhaust gas enters into the secondary air passage and the check valve casing, etc., and the engine During the warm state, that is, because the exhaust gas remains for a relatively long period of time, moisture and various components in the exhaust gas can cause corrosion to the pipes and metal parts of check valves that make up the secondary air passage. There is a problem in that it is easy to occur.

In order to prevent this corrosion, for example, as shown in Japanese Utility Model Publication No. 57-17050, a small hole is provided in parallel with the secondary air cutoff valve to allow constant flow of secondary air. Some devices are configured to allow some secondary air to flow into the secondary air passage to scavenge exhaust gas even when the secondary air cutoff valve is closed. However, 2
With this configuration, in which some amount of secondary air is constantly supplied even in an operating range where secondary air is not required, there is a risk that overheating and afterburn of the catalyst will occur.

Purpose of the invention This invention was made in view of the conventional problems mentioned above, and its purpose is to eliminate exhaust gas that has entered the secondary air passage without overheating the catalyst or causing afterburn. It is an object of the present invention to provide a secondary air supply device that can effectively scavenge air and prevent the above-mentioned corrosion.

Structure of the invention A secondary air supply device for an internal combustion engine according to the invention includes a secondary air cutoff valve that communicates with the exhaust system via a check valve, a temperature detection means for detecting the temperature state of the engine, and a deceleration device for the engine. deceleration detection means for detecting the state;
Temperature determining means and deceleration determining means for outputting a valve open signal when the engine is cold and at a predetermined time of deceleration, and outputting a valve open signal for a predetermined time when the secondary air cutoff valve is in a closed state for a predetermined time. and a shutoff valve driving mechanism that drives the secondary air shutoff valve to open based on the valve opening signal.

Embodiment FIG. 1 is an explanatory diagram of the configuration of a secondary air supply device according to the present invention, in which a secondary air passage 3 is connected to the side surface of an air cleaner 1 via a check valve 2 consisting of a pair of reed valves. , its tip is the exhaust manifold 4
A secondary air cutoff valve 5 is provided on the upstream side of the check valve 2 and is opened and closed using negative pressure as a driving force. The above secondary air cutoff valve 5
The negative pressure chamber 5a is connected to a negative pressure source such as an intake manifold 8 via a negative pressure delay valve 6 and a solenoid valve 7, and when the solenoid valve 7 is opened and negative pressure is introduced, 2 The secondary air inlet 5b is opened, and when the solenoid valve 7 is closed to introduce atmospheric air, the secondary air inlet 5b is closed. The negative pressure delay valve 6 provides an appropriate delay (approximately 0.2 to 4 seconds) from when the solenoid valve 7 opens until when negative pressure actually acts on the secondary air cutoff valve 5. Conversely, due to this action, there is no delay when the solenoid valve 7 is closed, that is, when the atmosphere is introduced.

On the other hand, numeral 9 is a temperature sensor that detects the engine cooling water temperature, and numeral 10 is a temperature sensor that detects the engine's cooling water temperature.
11 is a neutral switch that detects whether the transmission is in the neutral position; 12 is a throttle valve switch that detects when the throttle valve 13 is fully closed; these detection signals are The signals are input to the control circuit 14, respectively. Further, the rotational speed of the engine is detected from the cycle of the ignition signal of the ignition coil 15. Further, a slow cut solenoid valve 16 is provided in the slow fuel passage of the carburetor.

FIG. 2 shows a functional block diagram of the control circuit 14. Referring to this block diagram, the operation of the secondary air supply device will be explained. First, the temperature determination means 21 detects the temperature detected by the temperature sensor 9. The temperature is compared with the temperature set by the temperature condition setting means 22. When the detected temperature is cold and is lower than the set temperature, a valve open signal is output to the solenoid valve drive determination circuit 23, which turns on the solenoid valve 7 via the solenoid valve drive output circuit 24, and the secondary air cutoff valve 5 is turned on. The valve is opened and secondary air is introduced. Furthermore, when the detected temperature is warmer than the set temperature, the valve opening signal is not output and secondary air is not introduced.

On the other hand, during this warm time, when the engine reaches a predetermined deceleration state, scavenging is performed by introducing secondary air. That is, the engine speed and the throttle valve switch 12
From the fully closed signal of As a result, the solenoid valve 7 is turned ON via the solenoid valve drive output circuit 24,
At the same time, the slow cut solenoid valve drive output circuit 2
7, the slow cut solenoid valve 16 is turned on. As a result, the fuel supply is stopped, and secondary air is introduced with a slight delay after the fuel supply is stopped. Therefore, the secondary air passage 3 and the check valve 2
Exhaust gas and condensed water that remained inside are quickly scavenged. The introduction of this secondary air is stopped at the same time as the fuel supply stoppage is canceled.

If the clutch switch 10 detects that the clutch is "disengaged" or the neutral switch 11 detects that the transmission is in the neutral position, the solenoid valve 7 will not open even in the deceleration state, and the secondary No air is introduced. This is because if secondary air is introduced in response to rapid deceleration due to racing during gear changes, gas that has adhered to the inner wall of the intake manifold will be sucked in, causing afterburn. Therefore, we are trying to prevent this.

Further, if the deceleration state in which scavenging is possible does not occur for a long time, forced scavenging is performed regardless of the operating state. That is, the solenoid valve operation detection means 2
8 detects the falling and rising edges of the drive signal to the solenoid valve 7, and starts and resets the timer 29. As a result, the elapsed time from when the solenoid valve 7 closes to when it next opens is measured, and when this exceeds the elapsed time determined by the elapsed time condition setting means 30 (for example, about 1 to 30 minutes) Then, the forced scavenging determination means 31 outputs a valve opening signal. The output of this valve opening signal is continued for a period of time (for example, several seconds to several minutes) determined by the forced scavenging time setting means 32, during which time the solenoid valve 7 is turned ON and secondary air is introduced. Therefore, even when driving for a long time without decelerating, such as when driving on a highway, the exhaust gas and condensed water in the secondary air passage 3 and check valve 2 can be reliably discharged, and these long-term Retention can be prevented. Further, since this scavenging with secondary air is performed intensively in a short period of time, there is no risk of overheating of the catalyst, unlike in the conventional configuration in which a small amount of secondary air is constantly supplied.

In the above embodiment, the negative pressure delay valve 6 is used to slightly delay the introduction of secondary air during deceleration compared to the fuel cut.
However, instead of this, a delay circuit 33 is provided between the solenoid valve drive output circuit 24 and the solenoid valve 7,
It is also possible to make it function in the same way.

Effects of the invention As is clear from the above explanation, the secondary air supply device for an internal combustion engine according to this invention scavenges the air in the secondary air passage when the engine decelerates when the fuel supply is stopped. There is no risk of overheating or afterburning of the catalyst due to the secondary air, and even if the deceleration is not in a long-term deceleration state, the air is forcibly scavenged at regular intervals, which prevents backlash caused by long-term retention of exhaust gas. Corrosion of valves, etc. can be reliably prevented.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing an embodiment of this invention, and FIG. 2 is a functional block diagram of its control circuit. 2... Check valve, 3... Secondary air passage, 4... Exhaust manifold, 5... Secondary air cutoff valve, 6... Negative pressure delay valve, 7... Solenoid valve, 9... Temperature sensor, 1
2... Throttle valve switch, 14... Control circuit, 15...
...Ignition coil, 16...Solenoid valve for slow cut.

Claims (1)

[Scope of utility model registration request] A secondary air passage communicating with the exhaust system via a check valve, a secondary air cutoff valve provided upstream of the check valve, a temperature detection means for detecting the temperature state of the engine, and a means for decelerating the engine. deceleration detection means for detecting the state;
Temperature determining means and deceleration determining means for outputting a valve open signal when the engine is cold and at a predetermined time of deceleration, and outputting a valve open signal for a predetermined time when the secondary air cutoff valve is in a closed state for a predetermined time. A secondary air supply device for an internal combustion engine, comprising: a forced air scavenging determination means; and a shutoff valve drive mechanism that drives the secondary air shutoff valve to open based on the valve opening signal.