JPS6023452Y2 - Secondary air supply system for internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a secondary air supply device for supplying secondary air to the exhaust system of an internal combustion engine, in particular with a negative pressure responsive secondary air control valve.

BACKGROUND OF THE INVENTION In order to treat harmful components in the exhaust gas of an internal combustion engine in the engine exhaust system, for example by means of a catalytic converter, it is common practice to supply secondary air to the exhaust system.

A secondary air control valve that responds to intake negative pressure is used to control supply cutoff of secondary air depending on the operating state of the engine.

This secondary air control valve is generally connected to the intake manifold or intake system via a temperature-sensitive negative pressure switching valve that is sensitive to a predetermined engine temperature, thereby cutting off the supply of secondary air, for example, before and after warming up the engine. This system protects the catalytic converter (prevents overheating) and reduces harmful components in the exhaust gas.

Problems to be Solved by the Invention However, with such simple conventional control, it has not been possible to deal with the problem of afterfire, especially during deceleration.

In other words, in order to prevent afterfire during deceleration, it is necessary to temporarily cut off the supply of secondary air at the start of deceleration, but the required cut time also needs to satisfy the requirement to purify the exhaust gas. It is desirable to make the difference when the engine is warmed up.

That is, if the secondary air is cut for a long period of time when the engine is hot, as in the case when the engine is cold, harmful substances in the exhaust gas will increase, so it is necessary to make the cut time not short or zero, depending on the temperature state of the engine.

Further, when the engine is cold, it is desirable to stop the supply of secondary air, for example, to prevent overheating and melting of the catalytic converter.

In the prior art, no consideration was given to satisfying such a request.

In view of the above points, the purpose of the present invention is to variably control the cut-off time of secondary air according to the engine temperature, thereby effectively preventing afterfire during deceleration without increasing the harmful components of exhaust gas. Next is to provide an air supply device.

Means for Solving the Problems In order to achieve the above object, the present invention provides a secondary air control valve that controls supply and cutoff of secondary air to the exhaust system in response to intake negative pressure. In the secondary air supply device for an internal combustion engine, the secondary air control valve is provided with two negative pressure operating chambers bordering each other via a diaphragm, one of which has a first negative pressure chamber.
The negative pressure working chamber is directly connected to the intake negative pressure system, and the other second negative pressure working chamber opens and closes at a set temperature T□, which is representative of the engine's low temperature. A temperature-sensitive negative pressure switching valve is connected in series with the temperature-sensitive negative pressure switching valve to switch communication with one of the pressure regions, and a set temperature T2 (T2>T1), which represents the time when engine warm-up is completed, is reached. It is connected to the intake negative pressure system via a temperature-sensitive negative pressure switching valve with a delay orifice that opens and closes.

The above-mentioned temperature-sensitive negative pressure switching valve opens when the temperature is lower than its set temperature and opens the second negative pressure operating chamber of the secondary air control valve to the atmosphere, thereby setting the secondary air control valve to the closed position. At the same time, when the set temperature T is reached, the valve closes and the second
The secondary air control valve is brought to the open position by connecting the negative pressure operating chamber to the intake negative pressure system via the temperature-sensitive negative pressure switching valve.

The temperature-sensitive negative pressure switching valve closes when the temperature is lower than the set temperature T2, and the delay orifice delays the negative pressure in the intake negative pressure system by a predetermined time and transmits it to the second negative pressure working chamber. At the same time, when the set temperature T2 is reached, the valve opens and the delay effect by the delay orifice is nullified.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

A secondary air control valve 1, which is known per se, supplies secondary air from an air cleaner (not shown) via a valve opening passage 11, as indicated by the arrow, to an exhaust manifold or exhaust pipe (Ex).

Reference numeral 17 denotes a reed valve for preventing backflow of exhaust gas, which opens and closes in response to exhaust pulsation to supply secondary air.

The valve stem 9 of the valve body 13, which controls the passage area of the valve port passage 11 and therefore the flow rate of secondary air, is fixed to a diaphragm 4 that partitions two negative pressure working chambers 3 and 5, and moves up and down according to the movement of the diaphragm. move.

The first negative pressure working chamber 5 is directly connected via a passage 21 to an intake negative pressure system such as an intake pipe manifold or an intake pipe (not shown).

The second negative pressure chamber 3 is connected to a bimetallic temperature-sensitive negative pressure switching valve 31 via a passage 19 .

The diaphragm 4 is always pressed toward the second negative pressure chamber 3 by a spring 7 placed in the first negative pressure chamber 5 .

The configuration of the bimetallic temperature-sensitive negative pressure switching valve (BVSV) 3i is also well known and will not be described in detail.

In the negative pressure switching valve 31, the valve body 35 closes the valve port 39 when the temperature reaches a predetermined temperature or higher due to the action of the bimetal 37.

Therefore, until this predetermined temperature is reached, the valve body 35 remains open and the valve port 39 is exposed to the atmosphere via the port 33.

The temperature that the negative pressure switching valve 31 should sense is the engine temperature, and examples thereof include cylinder block temperature and radiator water temperature.

Since the negative pressure switching valve 31 is for sensing that the engine temperature is low, its set temperature T1 is approximately 10°C.
It is.

In this way, the negative pressure switching valve 31 connects the second negative pressure chamber 3 of the secondary air control valve 1 to the negative pressure region or opens it to the atmosphere via the negative pressure delay valve 51, which will be described later, depending on the engine temperature. , second
It switches and controls communication between the negative pressure chamber 3 and the atmosphere.

The negative pressure switching valve 31 is connected in series via a passage 41 to a port 65 of a temperature-sensitive negative pressure switching valve (TVTV) 51, which is known per se.

Similarly, the valve port 57 of the negative pressure delay valve 51 is made of bimetal 6, for example.
It is opened and closed by a valve body 59 operated by 1.

A small orifice or throttle passage 55 and a check valve 52 are also formed in the wall 58 forming the valve port 57 .

The negative pressure delay valve 51 is connected via a passage 43 to an intake negative pressure system such as an intake manifold or an intake pipe.

Since the negative pressure delay valve 51 is for sensing the completion of warming up the engine, the set operating temperature T2 is, for example, about 50°C.

That is, the valve port 57 of the negative pressure delay valve 51 opens when the temperature reaches a predetermined temperature of 50° C. or higher, for example.

Further, as the operating temperature of the negative pressure delay valve 51, for example, the temperature of the riser portion may be suitable.

Alternatively, the temperature at the same location as the temperature sensed by the negative pressure switching valve 31 may be sensed.

The secondary air supply device configured as described above operates as follows.

■ When the engine temperature is low, the set temperature T of the negative pressure switching valve 31 (for example, T
= 10°C) or lower, the negative pressure switching valve 31 is in the open position, so atmospheric pressure acts on the second negative pressure working chamber 3 of the secondary air control valve 1, and the valve body 13 is brought to the closed position. It will be done.

That is, the valve port 11 is closed and the supply of secondary air is completely cut off.

In this way, the requirement to stop the supply of secondary air when the engine temperature is low to prevent overheating of the exhaust gas purification device such as the catalytic converter is satisfied.

@ When the engine is warmed up during engine warm-up and the engine temperature exceeds the set temperature T (for example, 10°C) of the negative pressure switching valve 31, the negative pressure switching valve 3
1 is closed.

On the other hand, the engine temperature is still the set temperature T of the negative pressure switching valve 31.
Since the pressure is lower than 2, the negative pressure delay valve 51 remains closed.

Therefore, the intake negative pressure is transferred to the passage 43, the negative pressure delay valve 51, the passage 41
, and is transmitted to the second negative pressure working chamber 3 of the secondary air control valve 1 via the passage 19.

At this time, since the negative pressure delay valve 51 is provided with a throttle 55, the intake negative pressure is delayed by the presence of the throttle 55 and is transmitted to the second negative pressure working chamber 3.

On the other hand, since the intake negative pressure is directly transmitted to the first negative pressure working chamber 5 of the secondary air control valve 1, the valve body 13 is closed only for a period corresponding to the delay time caused by the throttle 55, and the secondary air is Cut the supply.

After the delay time elapses, the first negative pressure working chamber 5 and the second negative pressure working chamber 3
The negative pressures become equal, the valve body 13 is lifted by the force of the spring 7, and secondary air is supplied.

That is, the supply of secondary air is temporarily cut off immediately after the intake negative pressure increases during deceleration, and it is possible to effectively prevent afterfire, which occurs frequently immediately after deceleration.

Since secondary air is then supplied again, an increase in harmful components of the exhaust gas is also substantially prevented.

The delay time is arbitrarily determined depending on the diameter of the aperture 55, but normally several seconds is sufficient.

In addition, since the check valve 52 has a structure with a bulk part on the side of the secondary air control valve, even if the operating condition changes during acceleration from deceleration, the second negative pressure working chamber 3 is rapidly changed to the first negative pressure. In order to maintain the same negative pressure level as the working chamber 5, the supply of secondary air can be cut in preparation for the next deceleration state.

0 After the warm-up is completed, the engine temperature further increases and when the warm-up is completed, the engine temperature is determined by the negative pressure delay valve 51 and the set temperature T2 (for example, 50 degrees Celsius).
, the valve body 59 of the negative pressure delay valve 51 is brought to the open position, and as a result, the intake negative pressure passes through the large diameter valve port 57 of the negative pressure delay valve 51 and reaches the second negative pressure without delay. The signal is transmitted to the working chamber 3.

Therefore, the secondary air control valve 1 is in the open position and secondary air is supplied to the exhaust system.

That is, after the warm-up is completed, the exhaust gas is purified without cutting off the supply of secondary air.

Although not particularly shown in the drawings, if it is necessary to prevent afterfire during deceleration even after warm-up is completed, the valve valve 57 itself can be used as a restricting passage, so that even when the negative pressure delay valve 51 is in the open position, the secondary The transmission of negative pressure from the air control valve 1 to the second negative pressure working chamber 3 can be delayed.

As a result, it becomes possible to cut off the supply of secondary air for a period corresponding to the delay time due to the throttling of the valve port 57 and the orifice 55, as in the case during the warm-up described above.

It should be noted that the negative pressure switching valve 31 and the negative pressure delay valve 51 are not limited to the bimetallic type shown in the drawings as long as they are temperature sensing type, but may be of a type using a temperature sensitive agent such as wax.

Effects of the Invention As described above, according to the present invention, it is possible to effectively prevent afterfire, which is a problem immediately after deceleration, by temporarily cutting off the secondary air.

Furthermore, since cutting off secondary air for a long period of time is undesirable from the point of view of exhaust gas purification, it is preferable to restart the supply of secondary air immediately after the necessary cutting of secondary air is completed. Since such requirements can be met, the problem of increase in harmful components of exhaust gas can also be substantially avoided.

[Brief explanation of the drawing]

The drawing is an illustration of a secondary air supply device according to the present invention. 1... Secondary air control valve, 3... Second negative pressure working chamber, 5... First negative pressure working chamber, 31...
Negative pressure switching valve, 51... Negative pressure delay valve.

Claims (1)

[Scope of utility model registration request] In a secondary air supply device for an internal combustion engine having a secondary air control valve that controls supply and cutoff of secondary air to the exhaust system in response to intake negative pressure, the secondary air control valve is connected to the secondary air control valve via a diaphragm. Two negative pressure working chambers are provided adjacent to each other, and one of the first negative pressure working chambers is directly connected to the intake negative pressure system, and the other second negative pressure working chamber is set at a temperature T1 representative of the low temperature range of the engine.
A temperature-sensitive negative pressure switching valve is connected in series with the temperature-sensitive negative pressure switching valve, and is connected in series with the temperature-sensitive negative pressure switching valve to open and close the second negative pressure operating chamber to communicate with either the atmosphere or the negative pressure region. The temperature-sensitive negative pressure switching valve is connected to the intake negative pressure system via a temperature-sensitive negative pressure switching valve with a delay orifice that opens and closes at the set temperature T2 (T2>TI), which is representative of when the machine is completed. When the temperature is lower than the set temperature T1, the secondary air control valve is brought to the closed position by opening the valve and opening the second negative pressure working chamber of the secondary air control valve to the atmosphere, and the set temperature T
1, the valve is closed and the second negative pressure operating chamber is connected to the intake negative pressure system via the temperature-sensitive negative pressure delay valve, thereby bringing the secondary air control valve to the open position, and the temperature-sensitive negative pressure delay valve is brought to the open position. The negative pressure switching valve closes when the temperature is lower than the set temperature T2, and the delay orifice delays the negative pressure of the intake negative pressure system by a predetermined time and transmits it to the second negative pressure working chamber, and the set temperature T2. 1. A secondary air supply device for an internal combustion engine, characterized in that the delay effect by a delay orifice is nullified by opening the valve when the time is reached.