JPH08312470A - Flow control valve - Google Patents

Abstract

PURPOSE: To execute control for both a low flow rate and a high flow rate by letting the valve be equipped with first valve provided with a circular ring shaped valve part, and with a second valve which is provided with a small diameter valve part being coaxial with the first valve in the flow control valve used for the EGR control of an internal combustion engine and the like. CONSTITUTION: In the high loading range of engine, when action air in excess of the force of a return spring 9 is supplied to a control pressure chamber 38 by actuators such as cylinders and the like, a piston member 34 is slid downward, and the valve part of a second valve 7 is parted from the valve part 4 of a first valve 5, so that the valve is thereby opened. Following which, in a low loading range of engine, when acting pressure by the actuators is raised, and when the piston member 34 is furthermore lowered downward while the acting pressure overcomes the forces of the return springs 8 and 9, the retainer 33 of the second valve 7 abuts against the upper end 32 of the first valve 5, the first valve 5 is lifted together with the second valve 7 so as to be in a full lifted condition, and a high flow rate of exhaust gas G is thereby circulated through an EGR passage 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow control valve used for EGR control of an internal combustion engine.

[0002]

2. Description of the Related Art As a method for reducing NOx in exhaust gas of an internal combustion engine, a method (EGR) of recirculating a part of exhaust gas to an intake system is widely known. The amount of recirculation (EGR
It is necessary to determine and finely control the amount) so that the target NOx level and the engine stability are compatible. The valve (EGR valve) used for this control operates the air cylinder or the diaphragm by the positive pressure or the negative pressure to lift the poppet valve connected to the air cylinder or the diaphragm to adjust the gas flow rate.

[0003]

By the way, in the EGR control of a diesel engine, when a high EGR rate at a low load and a low EGR rate at a high load are used, there is a problem that a conventional EGR valve cannot perform desired gas control. It was That is, as shown in FIG. 3, fine lift control is required on the high load side, but since the amplitude of the exhaust gas pulsation in the exhaust manifold at this time is large, the valve cannot maintain a stable lift and the desired EGR is performed. Very difficult to rate.

As a countermeasure against this, it is conceivable to reduce the valve diameter and increase the lift, but on the contrary, there is a possibility that the required flow rate cannot be secured when the load is low. It is also conceivable that two large and small EGR valves are provided and each is driven, but this complicates the configuration, increases the cost, and makes the layout difficult.

Therefore, the present invention was devised to provide a flow control valve having a simple structure capable of stably controlling a minute flow rate and securing a large flow rate.

[0006]

According to the present invention, there is provided a first valve having an annular valve portion and a valve portion having a small diameter seated on the valve portion and provided coaxially with the first valve. It is provided with two valves and a drive means for appropriately opening and closing these valves.

[0007]

With the above structure, the drive means drives the second valve to control the minute flow rate by the lift amount and the opening area corresponding to the valve portion, and further drives the first valve to increase the large flow rate. Control.

[0008]

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

FIG. 1 shows an embodiment of the flow control valve of the present invention. This flow control valve is used for the EG of an internal combustion engine.
The valve body 2 is configured as an R valve, has an EGR passage 1 for guiding a part of the exhaust gas G (EGR gas) to the intake system, and has an annular valve portion 4 having a shaft hole 3. The first valve 5 and the second valve 7 having the valve portion 6 having a diameter smaller than that of the valve portion 4 are provided.
Return springs 8 and 9 are provided as driving means for appropriately opening and closing each of the two.

The valve body 2 has a bottom portion attached to a flange 12 of an opening 11 formed in the exhaust pipe 10. An EGR passage 1 is formed at a right angle from the bottom to the side, and an intake manifold (not shown) is formed at this side.
The pipe line 13 leading to is connected. The upper part of the valve body 2 is covered with a cylinder cup 14 having a bottomed cylindrical shape,
The flange portion 15 and the valve body 2 formed on the periphery thereof
Is fastened to the upper part 16 of the with bolts 17. An intermediate plate 18 having the same diameter and a predetermined thickness is interposed between the flange portion 15 and the upper portion 16.

The valve portion 4 of the first valve 5 is a valve body 2
Has an outer diameter slightly larger than the bottom opening 19 of the valve seat 20, and the outer peripheral end surface 21 cut out in a truncated cone shape is seated on the exhaust pipe 10 side (lower surface) of the valve seat 20 provided at the opening edge. Has become. A shaft portion 23 is integrally attached to the valve portion 4 at a shaft center position via a stay 22. The shaft portion 23 has an insertion hole 2 formed in the valve body 2.
4 and extends inwardly of the cylinder cup 14. A pipe-shaped valve guide 25 is fitted in the insertion hole 24, and the shaft portion 23 is slidably held by the valve guide 25. A retainer 26 for holding the upper end of the first return spring 8 is fitted near the upper end 32 of the shaft portion 23. That is, the first return spring 8 is stretched between the retainer 26 and the intermediate plate 18, and biases the first valve 5 in the valve closing direction (upward).

The second valve 7 is provided coaxially with the first valve 5. The valve portion 6 of the second valve 7 has a disc shape having an outer diameter slightly larger than the inner diameter of the shaft hole 3 of the valve portion 4 of the first valve 5, and the outer peripheral edge 27 thereof is the exhaust pipe of the shaft hole 3. 10
The seat portion 28 formed on the side (lower surface) is seated. A small-diameter shaft portion 29 integrally formed with the valve portion 6 is attached to the valve portion 6 of the second valve 7.
The shaft 29 is slidably inserted into a shaft hole 30 formed in the shaft 23 of the first valve 5. The upper end 31 of the shaft portion 29 extends further upward from the upper end 32 of the shaft portion 23 of the first valve 5, and a retainer 33 for holding the upper end of the second return spring 9 is attached. The second return spring 9 is stretched between the retainer 33 and the intermediate plate 18 so as to surround the first return spring 8 and biases the second valve 7 in the valve closing direction (upward).

Inside the cylinder cup 14, there is provided a bottomed cylindrical piston member 34 which is formed so as to surround the return springs 8 and 9 above and laterally. The peripheral side portion 35 of the piston member 34 is slidably joined to a liner 36 formed on the inner wall of the cylinder cup 14, and the disc-shaped pressure receiving surface portion 37 has an outer diameter substantially equal to the inner diameter of the cylinder cup 14. ing. That is, the inside of the cylinder cup 14 is vertically divided by the piston member 34, and the control pressure chamber 38 for lifting the valves 5 and 7 in the valve opening direction is defined. The back surface (lower surface side) of the pressure receiving surface portion 37 is in contact with the upper end 31 of the shaft portion 23 of the first valve 5. The upper surface of the pressure receiving surface portion 37 (upper surface side) is in contact with a convex portion 39 formed on the inner wall of the cylinder cup 14 to regulate the upper limit of sliding. The lower end of the circumferential side portion 35 of the piston member 34 is located at a predetermined distance H from the intermediate plate 18 when the first valve 5 is closed. That is, the downward stroke (maximum lift) of the piston member 34 is defined by this distance H. Furthermore, the lower surface of the retainer 33 of the second valve 7 and the upper end 32 of the shaft portion 23 of the first valve 5 are located at a distance h smaller than the above-mentioned distance H (h <H). Therefore, when the piston member 34 descends beyond the predetermined distance h, the first valve 5 is pushed via the retainer 33.

In addition, the flow rate control valve is provided with an actuator (air cylinder or the like) which operates by positive pressure, and the compressed air is supplied to the control pressure chamber 38 via a regulator for pressure adjustment. There is. The actuator may be any actuator as long as it supplies compressed air according to the load of the engine. In the present embodiment, a high operating pressure is supplied in the low load region and a low operating pressure is supplied in the high load region so that a lift approximately inversely proportional to the increase in the load is obtained. The mechanism that supplies the operating pressure to the control pressure chamber 38 may include a diaphragm that operates by negative pressure.

Next, the operation of this embodiment will be described.

In the high load region of the engine, when the actuator is supplied with working air having a pressure exceeding the urging force of the second return spring 9, the piston member 34 slides downward in the cylinder cup 14. The second valve 7 is lifted. That is, by this initial lift, the valve portion 6 of the second valve 7 is opened apart from the valve portion 4 of the first valve 5. With this, as shown in FIG. 2, a part of the exhaust gas G becomes the EGR gas and the first valve 5
Through the shaft hole 3 of the valve portion 4, and is returned to the intake manifold through the EGR passage 1 of the valve body 2 by an amount corresponding to the opening area and the lift amount. Then, in the low load region, when the operating pressure by the actuator is increased and exceeds the biasing force of the return springs 8 and 9, and the piston member 34 is further pushed down, the retainer 33 of the second valve 7 moves to the upper end 32 of the first valve 5. Upon contact, the first valve 5 is lifted together with the second valve 7 to be in a full lift state. That is, the first valve 5 is opened in addition to the second valve 7, and the exhaust gas G corresponding to the opening area and the lift amount is recirculated through the EGR passage 1.

As described above, the first valve 5 having the large-diameter annular valve portion 4 and the second valve 7 having the smaller-diameter valve portion 6 are coaxially provided to control the pressure chamber 38. Since the gas flow rate is controlled by opening the valve in two steps by supplying the operating pressure to the valve and the biasing force of the return springs 8 and 9, it is possible to finely control the minute flow rate in the initial lift and to control the gas flow rate fully in the full lift. It can be a flow rate. That is, the EGR control as shown in FIG. 3 can be achieved with a stable lift characteristic that is not affected by the pulsation in the exhaust manifold. In addition, the present invention has a compact structure in which large and small valves 5 and 7 are incorporated in a common valve body 2, and is low cost and easy in layout.
It can be an R valve. Since the valve pressure receiving surface (the area of the valve portion 6) in the initial stage of opening the valve is small, the pushing force in the initial stage of the lift is small, and the compressed air supplied to the control pressure chamber 38 ensures the resistance against the exhaust pressure of the engine. Can be operated.

As a prior art to be compared with the present invention, there is Japanese Utility Model Laid-Open No. 4-129866. This proposal is to provide double coil springs in the negative pressure introducing chamber to obtain a two-step flow rate characteristic. However, in this configuration, since the control is performed by one valve, the opening area is the same during both the small lift and the large lift, and the change amount of the flow rate is determined only by the lift amount. Therefore, the flow rate change amount cannot be determined and controlled in detail. On the other hand, according to the present invention, since the opening area itself changes according to the valve lift, the desired flow rate control can be surely obtained.

Further, in the present embodiment, the valve portion 6 of the second valve 7
Is seated in the shaft hole 3 of the first valve 5, but may be seated on the lower surface of the valve portion 4 of the first valve 5 to open and close the shaft hole 3. Further, the flow rate control valve of the present invention is not limited to the EGR valve of the above-described embodiment, but can be widely applied to those that control the flow rate in two stages.

[0020]

In summary, according to the present invention, it is possible to stably control a minute flow rate and to secure a large flow rate with a simple structure.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of a flow control valve of the present invention.

FIG. 2 is a partially cutaway perspective view of the first valve of FIG.

FIG. 3 is a relationship diagram showing a load and a lift showing an EGR control characteristic of an internal combustion engine.

[Explanation of symbols]

 1 EGR passage 2 Valve body 3 Shaft hole 4 Valve part 5 First valve 6 Valve part (small diameter valve part) 7 Second valve 8, 9 Return spring (driving means) 34 Piston member (driving means) 38 Control pressure chamber ( Drive means)

Claims (1)

[Claims] 1. A first valve having an annular valve portion, a second valve having a small-diameter valve portion seated on the valve portion and provided coaxially with the first valve, and these valves. A flow control valve comprising: a drive unit for appropriately opening and closing.