JPH06101460A - Exhaust gas purifying device for engine - Google Patents

Abstract

PURPOSE:To control a secondary air amount to a proper value according to an operation condition, in an exhaust gas purifying device having a motor- operated air pump serving as a secondary air feed source. CONSTITUTION:An exhaust gas purifying device for an engine comprises a secondary air feed passage 5 though which a motor-operated air pump 6 is communicated to an exhaust gas passage 3 located upper stream from a catalyst converter 4, a diaphragm chamber 23 which has a diaphragm type flow rate control valve 8 located in the middle of a secondary air feed passage 5 and causes the increase of the opening area of the secondary air feed passage 5, and a signal passage 25 through which a diaphragm chamber 23 is communicated to the exhaust gas passage 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust gas purification apparatus for supplying secondary air to an exhaust system.

[0002]

2. Description of the Related Art In an engine in which a catalytic converter is installed in an exhaust passage to prevent air pollution of an automobile or the like, secondary air is supplied to the upstream side of the catalytic converter to generate HC, C
Some promote the oxidation reaction of O (Japanese Patent Laid-Open No. 55-1993).
No. 2, gazette).

In order to activate the catalytic converter, it is necessary to increase the amount of secondary air in accordance with the amount of exhaust gas and to keep the flow rate ratio of the secondary air mixed with the exhaust gas proper.

Conventionally, there are a secondary air supply source equipped with a mechanically driven air pump driven by an engine via a belt and the like, and an electrical power pump driven by an electric motor.

When a mechanically driven air pump is provided as a secondary air supply source, the discharge air amount of the air pump automatically increases as the engine speed rises, so that the flow rate ratio of the secondary air mixed with the exhaust gas is appropriate. Can be easily achieved.

[0006]

However, when an electric air pump driven by a constant current is provided as the secondary air supply source, the flow rate ratio of the secondary air to the exhaust gas decreases as the exhaust pressure increases. However, there is a problem that the amount of secondary air is insufficient when the engine has a high load.

As a countermeasure against this, controlling the rotational speed of the electric air pump by using a modulator or the like can be considered, but in this case, the cost is increased.

In view of the above problems, the present invention has an object of properly controlling the amount of secondary air in an exhaust gas purification apparatus having an electric air pump as a secondary air supply source in accordance with operating conditions.

[0009]

According to the present invention, there is provided an exhaust gas purifying apparatus for an engine, which guides air discharged from an electric air pump to an exhaust passage upstream of a catalytic converter through a secondary air supply passage. A diaphragm type flow rate control valve is provided in the middle of the valve, and the flow rate control valve is provided with a diaphragm chamber for increasing the opening area of the secondary air supply passage in accordance with the pressure of the diaphragm type flow control valve. Provide a passage.

[0010]

In the flow rate control valve, the exhaust pressure of the exhaust passage is introduced into the diaphragm chamber through the signal passage, and the opening area of the secondary air supply passage is increased according to the exhaust pressure. As a result, the amount of secondary air mixed with the exhaust gas can be appropriately increased in response to the increase in exhaust pressure, and activation of the catalytic converter can be promoted under a wide range of engine operating conditions.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, a catalytic converter 4 is interposed in the exhaust passage 3 of the engine 1, and a secondary air supply passage 5 for supplying secondary air to the upstream side of the catalytic converter 4.
Are connected. In FIG. 1, 2 is an intake passage, 1
Reference numeral 1 is a piston, 12 is an intake valve, and 13 is an exhaust valve.

An electric air pump 6, a cut valve 7 and a flow rate control valve 8 are provided in the middle of the secondary air supply passage 5. The air pump 6 is driven by an electric motor at a constant current, sucks air taken in from an air cleaner (not shown), and discharges air from the air flow control valve 8
The gas is supplied to the exhaust passage 3 through the cut valve 7.

In the diaphragm type cut valve 7, the diaphragm chamber 15 communicates with the intake passage 2 on the downstream side of the throttle valve 10 through a signal passage 16, and an electromagnetic valve 17 is interposed in the signal passage 16. It

The control unit 18 closes the solenoid valve 17 under the operating condition of stopping the supply of the secondary air, and the diaphragm chamber 15 of the cut valve 7 guides the atmospheric pressure, whereby the cut valve 7 is provided with the spring 19. The secondary air supply passage 5 is closed by the force. On the other hand, the control unit 18 opens the solenoid valve 17 under the operating condition that requires the supply of the secondary air, and reduces the suction negative pressure generated on the downstream side of the throttle valve 10 to the diaphragm chamber 1 of the cut valve 7.
5, which causes the cut valve 7 to move to the spring 19
The secondary air supply passage 5 is opened while compressing.

The cut valve 7 is provided with a reed valve 31 which prevents exhaust gas from flowing backward through the secondary air supply passage 5.

In the diaphragm type flow control valve 8, the valve body 21 which can be seated on the valve seat 20 formed in the middle of the secondary air supply passage 5 has the exhaust passage 3 side from the valve seat 20, that is, the secondary air supply. It is arranged on the downstream side of the passage 5. A conical seat surface is formed on the valve body 21, and the valve body 21 is lifted downstream with respect to the valve seat 20 to increase the opening area of the gap defined between the two. ing.

A valve body 21 of the flow control valve 8 is connected to a diaphragm 22. A diaphragm chamber 23 is defined by the diaphragm 22, and the diaphragm chamber 23 is provided with an exhaust passage 3 upstream of the catalytic converter 4 via a signal passage 25.
Be communicated to.

The diaphragm 22 has a diaphragm chamber 23.
A predetermined spring load is applied to the valve body 21 by the spring 24 that is inserted therein in a stretched state to urge the valve body 21 in the valve closing direction. That is, as the exhaust pressure guided to the diaphragm chamber 23 increases, the diaphragm 22 lifts the valve body 21 from the valve seat 20 while extending the spring 24, and the opening area of the gap defined between the two is increased. To increase.

Next, the operation will be described.

As shown in FIG. 2c, the exhaust pressure in the exhaust passage 3 rises in proportion to the square of the exhaust gas amount. Therefore, as shown in FIG. 2b, the required secondary air amount. Increases with the exhaust pressure as the load on the engine 1 increases. However, when the electric air pump 6 that rotates at a constant rotation speed is provided as the secondary air supply source, the flow rate ratio of the secondary air to the exhaust gas has a PQ characteristic that decreases as the exhaust pressure increases, and The amount of secondary air becomes insufficient as the load increases.

According to the present invention, as shown in FIG. 2A, the opening area of the secondary air supply passage 5 is enlarged in accordance with the exhaust pressure through the flow rate control valve 8 of the diaphragm chamber.
It is possible to increase the amount of secondary air according to the exhaust pressure and bring it closer to the required secondary air amount characteristic.

Next, another embodiment shown in FIG. 3 will be described.

In the diaphragm type flow control valve 8, a valve body 21 which can be seated on a valve seat 20 formed in the middle of the secondary air supply passage 5 has a valve seat 21 closer to the air pump 6, that is, a secondary air supply passage. 5 is arranged on the upstream side. A conical seat surface is formed on the valve body 21, and the valve body 21 is lifted downstream with respect to the valve seat 20 to increase the opening area of the gap defined between the two. ing.

A valve body 21 of the flow control valve 8 is connected to a diaphragm 22. A diaphragm chamber 23 is defined by the diaphragm 22, and the diaphragm chamber 23 is provided with an exhaust passage 3 upstream of the catalytic converter 4 via a signal passage 25.
Be communicated to.

The diaphragm 22 has a diaphragm chamber 23.
A predetermined spring load is applied to the valve body 21 by a spring 24 that is interposed outside in a contracted state, and the valve body 21 is biased in the valve closing direction. That is, as the exhaust pressure guided to the diaphragm chamber 23 increases, the diaphragm 22 lifts the valve body 21 from the valve seat 20 while contracting the spring 24, and the opening area of the gap defined between the two is increased. To increase.

[0027]

As described above, according to the present invention, in the exhaust gas purifying apparatus for an engine, the air discharged from the electric air pump is introduced into the exhaust passage upstream of the catalytic converter through the secondary air supply passage. A diaphragm type flow control valve is provided in the middle of the passage, and a diaphragm chamber for increasing the opening area of the secondary air supply passage according to the pressure is provided in the flow control valve, and the diaphragm chamber and the exhaust passage are communicated with each other. Since the signal passage is provided, the amount of secondary air mixed with the exhaust gas can be appropriately increased in response to the rise in exhaust pressure, and activation of the catalytic converter can be promoted under a wide range of engine operating conditions. In addition, compared with the case where a mechanical drive type air pump is provided as a secondary air supply source,
High control accuracy is ensured, and the degree of freedom in arranging the air pump can be increased.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram of the amount of secondary air.

FIG. 3 is a configuration diagram showing another embodiment.

[Explanation of symbols]

 1 Engine 3 Exhaust Passage 4 Catalytic Converter 5 Secondary Air Supply Passage 6 Air Pump 8 Flow Control Valve 23 Diaphragm Chamber 25 Signal Passage

Claims (1)

[Claims] 1. An exhaust gas purification apparatus for an engine, which guides air discharged from an electric air pump to an exhaust passage upstream of a catalytic converter through a secondary air supply passage, wherein a diaphragm type flow control valve is provided in the middle of the secondary air supply passage. A flow path control valve is provided with a diaphragm chamber for increasing the opening area of the secondary air supply passage in accordance with the pressure of the flow control valve, and a signal passage communicating the diaphragm chamber and the exhaust passage is provided. Exhaust purification device for engine.