JPH07180546A - Secondary air feeding device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of defective operation of an air pump and an air cut valve by providing a means to control operation of the air pump based on the operation condition of an internal combustion engine, a means to control operation of the air cut valve, and a means to delay opening operation of the air cut valve from the starting of operation of the air pump. CONSTITUTION:A secondary air passage 5 is connected to the delivery port 1b of an air pump 1 and an air cut valve 6 is located in the middle of the secondary air passage 5. The air pump 1 is switched and controlled by means of an output signal from an engine control unit 15, a negative pressure control valve 13 is switched according to operation and the stop of the air pump 1, and the air cut valve 6 is opened and closed. Further, when operation of the air pump 1 is started, the negative pressure control valve 13 is switched in a delay by a given period to prevent the occurrence of the reverse flow of exhaust gas, and the air cut valve 6 is opened in a delay. This constitution prevents the occurrence of defective operation of the air pump 1 and the air cut valve 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a secondary air supply device for supplying secondary air to an exhaust system of an internal combustion engine by an air pump.

[0002]

2. Description of the Related Art A secondary air supply device for supplying secondary air to an exhaust system has been conventionally known in order to purify exhaust gas of an internal combustion engine. Particularly, in a multi-cylinder internal combustion engine, a reed valve system is not used. A type in which secondary air is forcibly introduced using an electric air pump is widely used.

Further, since it is necessary to control the supply and stop of the secondary air according to the operating conditions such as the load of the engine and the water temperature, in general, a solenoid valve is provided in the secondary air passage from the air pump to the engine exhaust system. The air cut valve is provided, and when the air pump is stopped, the air cut valve is closed at the same time to close the secondary air passage (see, for example, JP-A-56-122012). That is, this type of air cut valve is used to turn the air pump on and off.
Opening and closing was controlled by simply interlocking with.

[0004]

However, if the air cut valve is opened simultaneously with the start of the operation of the air pump as in the prior art, the exhaust system having a high pressure communicates with the air pump before the discharge pressure of the air pump rises sufficiently. Therefore, the exhaust gas may flow back into the secondary air passage and further toward the air pump side, and impurities in the exhaust gas may shorten the life of the air pump and the air cut valve. A check valve may be provided between the air cut valve in the secondary air passage and the exhaust system. However, even in this case, if a large pressure difference is applied at the moment the air cut valve is opened, the check valve is moved to the air pump side. Exhaust easily flows in.

[0005]

Therefore, according to the present invention,
The opening operation of the air cut valve was delayed until the discharge pressure of the air pump increased. That is, the secondary air supply device for an internal combustion engine according to the present invention is provided with an air pump for supplying secondary air, a secondary air passage extending from the air pump to the exhaust system of the internal combustion engine, and the secondary air passage. An air cut valve, a pump control means for controlling the operation of the air pump based on the operating condition of the internal combustion engine, a valve control means for controlling the opening and closing of the air cut valve according to the operation and stop of the air pump, and the air pump. And delay means for delaying the opening operation of the air cut valve from the start of the operation.

[0006]

When the operating condition for supplying the secondary air is reached, the pump control means starts the operation of the air pump, and the valve control means opens the air cut valve. At this time, the opening operation of the air cut valve is executed later than the operation start of the air pump by the delay means. As a result, the secondary air passage is opened when the discharge pressure of the air pump rises to some extent, and backflow of exhaust gas is prevented.

Under the operating conditions where the secondary air should be stopped,
The air pump is stopped and the air cut valve is closed at the same time.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an embodiment of a secondary air supply device according to the present invention. In the figure, reference numeral 1 is an electric air pump, and a muffler 2 is attached to its suction port 1a.
The air cleaner 3 for a pump is connected via. Further, a secondary air passage 5 is connected to the discharge port 1b via a silencer 4, and in the middle of the secondary air passage 5,
An air cut valve 6 composed of a negative pressure type diaphragm valve is interposed. The tip of the secondary air passage 5 is connected to the exhaust system of the internal combustion engine 7, more specifically, the exhaust manifold 8. Note that the illustrated example is applied to a V-type 6-cylinder internal combustion engine 7, and a secondary air gallery 9 is provided for each bank, and a secondary air gallery is provided for each cylinder via the secondary air gallery 9. Will be introduced. A check valve 10 for preventing backflow is provided at the inlet of each secondary air gallery 9.

The air cut valve 6 uses a negative pressure in the intake collector 11 as a working source, and a negative pressure passage 12 connected to the negative pressure chamber of the air cut valve 6 is composed of a three-way solenoid valve. A negative pressure control valve 13 and a check valve 14 are provided. The negative pressure control valve 13 selectively connects the negative pressure chamber of the air cut valve 6 to the side of the intake collector 11 or the atmosphere side, which serves as a negative pressure source.

Reference numeral 15 denotes an engine control unit that comprehensively performs various controls of the internal combustion engine 7. The engine control unit 15 controls the operation of the air pump 1 and the air cut valve 6 based on engine operating conditions. Has been done. The air pump 1 is turned on and off via an air pump relay 16 which is switched by an output signal of the engine control unit 15.
Switching control is performed in an F manner. Further, the negative pressure control valve 13 is switched according to the operation and stop of the air pump 1, and the air cut valve 6 is opened and closed.

Here, when the operation of the air pump 1 is stopped, the negative pressure control valve 13 is switched and the air cut valve 6 is closed at the same time when the air pump 1 is stopped, but when the operation of the air pump 1 is started. The negative pressure control valve 13 is switched with a delay for a predetermined period, and the air cut valve 6 is opened with a delay.

FIG. 2 shows an engine control unit 1.
6 is a flow chart showing the contents of control of the air cut valve 6 executed in step 5. In step 1, it is determined whether the air pump 1 is in an ON state or an OFF state, and if it is OFF, a step 2 In step 3, the timer is cleared, and in step 3, the air cut valve 6 is closed. Therefore, when the air pump 1 is switched from ON to OFF, the air cut valve 6 is immediately closed.

If the air pump 1 is ON in step 1, the process proceeds to step 4 and it is determined whether the value of the timer is equal to or more than a predetermined value. The above-mentioned predetermined value is set corresponding to the time required from the start of energization of the air pump 1 until the discharge pressure rises sufficiently. If the value is less than the predetermined value in step 4, the process proceeds to step 3 and the air cut valve 6
Keep closed. If the timer value is equal to or greater than the predetermined value, the process proceeds to step 5 and the air cut valve 6 is opened. Therefore, when the air pump 1 is switched from OFF to ON, the air cut valve 6 is opened with a delay corresponding to the predetermined value. Therefore, the air cut valve 6
At the time when is opened, the discharge pressure of the air pump 1 is sufficiently high, and the reverse flow of exhaust gas through the secondary air passage 5 is reliably prevented.

A pressure sensor for detecting the pressure in the secondary air passage 5 is provided, and the negative pressure control valve 13 is switched, that is, the air cut valve 6 is opened until the pressure in the secondary air passage 5 rises sufficiently. May be delayed.

[0016]

As is apparent from the above description, according to the secondary air supply system for an internal combustion engine of the present invention, the secondary air passage is opened by delaying the operation of the air pump by a predetermined period and opening the air cut valve. It is possible to prevent backflow of the exhaust gas through the exhaust gas and prevent malfunction of the air pump and the air cut valve due to impurities in the exhaust gas.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of a secondary air supply device according to the present invention.

FIG. 2 is a flowchart showing control of an air cut valve.

[Explanation of symbols]

 1 ... Air pump 5 ... Secondary air passage 6 ... Air cut valve

Claims (1)

[Claims] 1. An air pump for supplying secondary air, and a secondary air passage extending from the air pump to an exhaust system of an internal combustion engine,
An air cut valve interposed in the secondary air passage, a pump control means for controlling the operation of the air pump based on the operating conditions of the internal combustion engine, and the air cut valve being opened / closed in accordance with the operation / stop of the air pump. A secondary air supply device for an internal combustion engine, comprising valve control means for controlling, and delay means for delaying the opening operation of the air cut valve from the start of operation of the air pump.