JPS6139105Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an exhaust gas recirculation device for an engine.

Generally, as an engine exhaust gas recirculation device,
An exhaust gas recirculation flow control valve is installed in the middle of the exhaust gas recirculation passage that communicates the exhaust system and the intake system, and the port negative pressure (so-called VC negative pressure) around the throttle valve of the carburetor is controlled when the throttle valve of the carburetor is closed. The operating state of the engine is detected by a negative pressure signal based on the control valve, and an orifice is provided upstream of the control valve to form a constant pressure chamber between the control valve and the orifice, and the pressure in the constant pressure chamber is sensed. The negative pressure signal sent to the control valve is adjusted to keep the pressure constant, thereby recirculating exhaust gas in proportion to the amount of exhaust gas corresponding to the amount of intake air, over almost the entire operating range. There are known methods for controlling the exhaust gas recirculation rate to a constant value.

However, with this type of device, it is not possible to accurately control the signal negative pressure of the exhaust gas recirculation amount control valve to follow engine temperature changes, and in particular, the exhaust gas recirculation rate does not decrease much even during warm-up operation. Without,
There were problems with poor drivability and backfire.

Therefore, in order to eliminate such problems,
For example, as described in Japanese Utility Model Application Publication No. 53-36620, an exhaust gas recirculation control device has been proposed which is characterized by being provided with a temperature control valve that controls the opening area of the orifice according to the engine temperature.

However, when the opening area of the orifice is directly controlled in this way, the opening area itself increases continuously as the temperature rises, so it is difficult to accurately set the maximum opening area of the orifice in the warm-up state. This resulted in a problem in which the amount of exhaust gas recirculation was insufficiently controlled.

The present invention has been made in view of the above points, and includes a temperature-sensitive valve that is interposed in the exhaust gas recirculation passage and continuously controls the amount of exhaust gas recirculation according to the engine temperature.
The main object of the present invention is to provide an exhaust gas recirculation device for an engine that eliminates the above-mentioned conventional problems by arranging in series an orifice that limits the maximum recirculation amount in the exhaust gas recirculation passage.

The present invention provides a device in which a temperature-sensitive valve that continuously controls the amount of exhaust gas recirculated according to the engine temperature is interposed in an exhaust gas recirculation passage that recirculates a part of engine exhaust gas to the intake system. An orifice is disposed in the gas recirculation passage in series with the temperature-sensitive valve, and the opening area of the orifice is set smaller than the passage cross-sectional area of the exhaust gas recirculation passage when the temperature-sensing valve is at its maximum lift. This is an exhaust gas recirculation device for an engine that

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is an exhaust gas recirculation device, 2 is an intake pipe having first and second throttle valves 3, 4, and 5 is an exhaust gas recirculation device.
is an intake manifold connected to the intake pipe 2. A connecting member 7 is connected to the intake manifold 5 via a gasket 6 to form an exhaust gas recirculation passage 9 that recirculates a portion of engine exhaust gas to the gathering portion 8a of the intake passage 8.

An exhaust gas recirculation amount control valve 10 is interposed in the exhaust gas recirculation passage 9, and a valve body 10a of the control valve 10 is seated on a valve seat 11 in the middle of the recirculation passage 9 so that the opening area can be adjusted. A fixed orifice 6a formed by a gasket 6 is disposed at the upstream side of the control valve 10, and a constant pressure chamber 19 is formed between the two orifices 10 and 6a.

The exhaust gas recirculation control valve 10 has a casing 1 formed by joining a lower casing integrally formed with the connecting member 7 and a cover-shaped upper casing.
0b is the negative pressure chamber 10d at the diaphragm 10c.
and an atmospheric chamber 10e. The valve body 1
0a is connected to one end of the valve shaft 10f whose moving direction is regulated by the guide member 12, and the valve shaft 1
The other end of Of is connected to the diaphragm 10c. Thereby, the valve body 10a is moved to the valve seat 11 by the spring 10g compressed in the negative pressure chamber 10d (via the diaphragm 10c and the valve shaft 10f).
In other words, the exhaust gas recirculation passage 9 is constantly biased so that the opening area of the exhaust gas recirculation passage 9 is reduced. Note that an atmospheric hole 10h is provided in the atmospheric chamber 10e.

13 is a first negative pressure passage, which is connected to the exhaust gas recirculation control valve 1;
0 negative pressure chamber 10d and a first negative pressure outlet 1 that opens near the first throttle valve 3 when fully closed (so-called VC position).
It communicates with 4.

15 is a temperature-sensitive valve (thermo valve), and orifice 6a
The valve body 15a is interposed in the exhaust gas recirculation passage 9 on the upstream side, and the valve body 15a is connected to another valve seat 16 in the middle of the recirculation passage 9.
The opening amount is adjustable. Valve body 15a
is connected to a valve shaft 15d that is slidably inserted through the upper and lower casings 15b and 15c that are screwed together, and the plate member 15e and the lower casing 1 are fixed to the valve shaft 15d.
At the spring 15f interposed between the spring 5c and the
It is constantly biased so as to come into contact with the valve seat 16, that is, to close off the exhaust gas recirculation passage 9. Further, a part of the upper casing 15b, that is, a part in which the wax 15g is sealed, is provided to protrude into the cooling water passage 17 formed in the intake manifold 5,
As a result, the wax 15g gradually expands due to the rise in the temperature of the cooling water in the cooling water passage 17, and the rod 15h biases the valve body 15a (valve shaft 15d) downward against the elastic force of the spring 15f. The structure is such that a force that causes the opening to move is applied to increase the opening area.

A negative pressure regulating valve 18 is defined by a diaphragm 18a into a first pressure chamber 18b and a second pressure chamber 18c. The first pressure chamber 18b includes the pressure passage 2
0 to the constant pressure chamber 19. On the other hand, the second pressure chamber 18c is communicated with the first negative pressure passage 13 through the negative pressure port 18d, and has a spring 18e compressed therein. Also,
A valve body 18f is fixed to the surface of the diaphragm 18a on the second pressure chamber 18c side, facing the negative pressure port 18d, and as the pressure in the first pressure chamber 18b increases, the valve body 18f opens to the negative pressure port. 18d is configured to be able to be closed. 18g is the large hole, the second pressure chamber 1
8c is open to the atmosphere.

20 is a second negative pressure passage in which a three-way valve 21 is interposed, which includes a second negative pressure outlet 22 that opens slightly upstream of the first negative pressure outlet 14, and a negative pressure regulating valve 18.
The second pressure chamber 18c is connected to the second pressure chamber 18c. This three-way valve 21 communicates the second pressure chamber 18c with the atmosphere when the engine speed is 2100 rpm or less or when the intake negative pressure is -370 mmHg or more, and in other cases communicates the second pressure chamber 18c with the atmosphere. It is configured to be switched so as to communicate with the intake passage 8.

Next, the operation of the above device will be explained.

First, the temperature of the cooling water is almost constant, and the exhaust gas recirculation passage 9 is closed by the temperature-sensitive valve 15 at the valve seat 16.
When the opening area of the constant pressure chamber 1 is almost constant,
When the pressure inside 9 increases above a certain value, the pressure in the first pressure chamber 18b of the negative pressure regulating valve 18 increases, and the valve body 18f (diaphragm 18a) is deflected to regulate the negative pressure port 18d. As a result, the negative pressure introduced into the negative pressure chamber 10d of the control valve 10 through the first negative pressure passage 13 increases, and the upward deviation of the diaphragm 10c displaces the valve body 10a and increases the valve opening. , increasing the amount of exhaust gas recirculation. As a result, the pressure within the constant pressure chamber 19 decreases.

Conversely, if the pressure in the constant pressure chamber 19 decreases below a certain value, the negative pressure introduced into the negative pressure chamber 10d of the control valve 10 through the first negative pressure passage 13 in the negative pressure regulating valve 18 is reduced to atmospheric pressure. It is opened to and decreases. As a result, the opening degree of the control valve 10 becomes smaller, reducing the amount of exhaust gas recirculation. Thereby, constant pressure chamber 19
The pressure inside increases.

By repeating these operations, constant pressure chamber 1
Since the pressure in control valve 9 is controlled to a constant value,
The amount of recirculation controlled by 0 is proportional to the amount of exhaust gas corresponding to the amount of intake air. the result,
The exhaust gas recirculation rate is controlled to be substantially constant.

In addition, when the first throttle valve 3 is opened and is located upstream of the second negative pressure outlet 22, the intake negative pressure downstream of the first throttle valve 3 acts on the second negative pressure outlet 22. In this state, when the engine speed is 2100 rpm or more, or when the intake negative pressure is -370 mmHg or less, the three-way valve 21 communicates with the second negative pressure passage 20 and stops introducing atmospheric air, so that the second pressure chamber 18c
Intake negative pressure is applied to the second negative pressure passage 20. As a result, the diaphragm 18a is deflected upward, and the valve body 18f resists the biasing force of the spring 18e to nearly close the negative pressure port 18d, thereby increasing the negative pressure in the negative pressure chamber 10d of the exhaust gas recirculation control valve 10. As a result, the opening degree of the valve body 10a increases. As a result, the pressure in the constant pressure chamber 19 decreases, and the pressure in the constant pressure chamber 19 is controlled so that the pressures in the first pressure chamber 18b and the second pressure chamber 18c of the negative pressure regulating valve 18 are balanced. That is, when the engine load increases as described above, the amount of exhaust gas recirculation increases. On the other hand, when the first throttle valve 3 is located upstream of the second negative pressure outlet 22 and the engine speed is 2100 rpm or less, or when the intake negative pressure is -370 mmHg or more, the three-way valve 21 is connected to the second negative pressure passage. 20 to the atmosphere, the negative pressure regulating valve 18 is operated by the pressure of the constant pressure chamber 19 as described above, and the negative pressure chamber 10 of the exhaust gas recirculation control valve 10 is
Control the negative pressure acting on d. Furthermore, when the first throttle valve 3 is located downstream of the second negative pressure outlet 22,
As described above, the negative pressure regulating valve 18 is operated by the pressure in the constant pressure chamber 19.

On the other hand, in the temperature-sensitive valve 15, since the wax 15g is contracted during warm-up operation when the cooling water temperature is low, the elastic force of the spring 15f causes the valve body 15 to
a comes into contact with the valve seat 16 and tends to block the exhaust gas recirculation passage 9. As a result, the amount of exhaust gas recirculation is either no or very small, and the exhaust gas recirculation rate is low.

When the cooling water temperature rises, the wax 15g expands and the rod 15h moves the valve body 15a (valve shaft 15d) to the spring 1.
The temperature-sensitive valve 1 is deflected downward against the elastic force of 5f.
The opening area of the exhaust gas recirculation passage 9 due to the exhaust gas recirculation passage 9 gradually increases. As a result, as shown in FIG. 2, the amount of exhaust gas recirculation gradually increases, and the exhaust gas recirculation rate also increases.

The characteristic of the temperature-sensitive valve 15 is that, as shown in A in Fig. 2, the exhaust gas recirculation amount increases in proportion to the increase in the cooling water temperature from, for example, 40°C to 70°C until the warm-up is completed. 15g of wax will expand even if the cooling water temperature is 70°C or higher.

Therefore, even when warm-up is completed (when the cooling water temperature reaches 70°C or higher), the wax 15g expands as the cooling water temperature rises, and the exhaust gas recirculation amount (the 2A), the opening area of the fixed orifice 6a is set smaller than the passage cross-sectional area of the exhaust gas recirculation passage at the maximum lift of the temperature-sensitive valve 15, so the amount regulated by the fixed orifice 6a. (Fig. 2B), so the orifice 6 is fixed at the maximum exhaust gas recirculation amount that does not deteriorate the fuel condition of the engine.
It is regulated by a.

Note that in the above embodiment, the temperature-sensitive valve 15 is arranged upstream of the fixed orifice 16a;
Needless to say, it may be arranged on the downstream side.

Since the present invention is configured as described above, the opening area of the orifice is constant regardless of the amount of exhaust gas recirculated by the temperature-sensitive valve, so that the orifice can effectively recirculate the exhaust gas even in the warm-up state. The flow rate is accurately regulated and the fuel condition of the engine is good throughout the entire operating range, which is a practical advantage.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an exhaust gas recirculation system for an engine according to the present invention, and FIG. 2 is a graph showing the relationship between the cooling water temperature and the amount of exhaust gas recirculated by the temperature-sensitive valve. 1...Exhaust gas recirculation device, 2...Intake pipe, 3,
4... Throttle valve, 5... Intake manifold, 6...
Gasket, 8...Intake passage, 8a...Collection part,
6a... Fixed orifice, 10... Exhaust gas recirculation control valve, 15... Temperature sensing valve, 18... Negative pressure regulating valve,
19... Constant pressure chamber.

Claims (1)

[Scope of utility model registration request] In a device in which a temperature-sensitive valve that continuously controls the amount of exhaust gas recirculation according to the engine temperature is interposed in the exhaust gas recirculation passage that recirculates a part of the exhaust gas of the engine to the intake system, the exhaust gas recirculation passage An engine exhaust system, characterized in that an orifice is arranged in series with the temperature-sensitive valve, and the opening area of the orifice is set smaller than the cross-sectional area of the exhaust gas recirculation passage when the temperature-sensing valve is at its maximum lift. Gas reflux device.