EXHAUST GAS RECIRCULATION VALVE

Abstract

A valve that constitutes part of an exhaust gas recirculation valve is connected to a shaft, such that the valve is rotatable together with the shaft in the interior of a main body. An outer peripheral surface of the valve is formed in a substantial spherical shape, the axis (center of curvature) of the valve and the axis of the shaft being arranged eccentrically by a predetermined distance along a flow direction of the exhaust gas. In addition, a percentage between the eccentric distance between the center of curvature of the valve and the axis of the shaft, and the diameter of a gas inlet port of the main body into which the exhaust gas flows is 5.5% or greater.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-068841 filed on Mar. 26, 2012, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an exhaust gas recirculation valve, which is capable of switching between fluid passages, and whereby an exhaust gas of an internal combustion engine is recirculated from an exhaust system to an intake system.

2. Description of the Related Art

Heretofore, an exhaust gas recirculation valve has been used, for example, for eliminating harmful components that are discharged from an internal combustion engine. Such an exhaust gas recirculation valve has functions to communicate between the intake system and the exhaust system of the internal combustion engine for recirculating the exhaust gas, which has been discharged from the internal combustion engine, to an intake system, in order to reduce harmful components such as NOx or the like contained in the exhaust gas.

In Japanese Laid-Open Patent Publication No. 2010-236686, the present applicant has proposed a fluid passage valve, which is disposed in an exhaust gas recirculation passage connected between an intake passage and an exhaust passage of an internal combustion engine. The fluid passage valve includes a main body, which is connected to the exhaust gas recirculation passage, and having a spherical shaped ball valve, which is arranged rotatably in the interior of the main body. In addition, by rotating the ball valve, which is connected through a shaft to a rotary drive source, through a predetermined angle, a state of communication is switched between an exhaust gas inlet port and an exhaust gas outlet port that are formed in the main body, whereby a flow through state of the exhaust gas into the exhaust gas recirculation passage is controlled.

SUMMARY OF THE INVENTION

A general object of the present invention is to provide an exhaust gas recirculation valve, which is capable of realizing a more linear flow rate characteristic of the exhaust gas, together with enabling an increase in the flow rate of the exhaust gas.

The present invention is an exhaust gas recirculation valve including a body having a fluid passage through which an exhaust gas flows, a valve arranged in the fluid passage that switches a flow through state of the exhaust gas, at least a portion of an outer peripheral surface of the valve being spherically shaped, a seat member having a seat section, which is disposed in the fluid passage on an upstream side from the valve and on which the valve is seated, and a shaft connected to the valve and which rotates the valve, wherein a percentage of an eccentricity amount between a center of curvature of the valve when the valve is completely closed and an axis of the shaft along a direction of flow of the exhaust gas with respect to a diameter of an inlet port formed in the body and into which the exhaust gas flows is 5.5% or greater.

According to the present invention, in an exhaust gas recirculation valve having such a valve, in which at least a portion of an outer peripheral surface of the valve is spherically shaped, by setting the eccentric distance (offset distance) between the center of curvature of the outer peripheral surface and the axial center of the shaft such that the percentage thereof with respect to the diameter of the exhaust gas inlet port of the body into which the exhaust gas flows is 5.5% or greater, the flow rate characteristic of the exhaust gas that flows through the fluid passage can be made more linear, while also enabling the flow rate of the exhaust gas to be increased.

The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view shown partially in cross section of an exhaust gas recirculation valve according to an embodiment of the present invention;

FIG. 2 is a cross sectional view taken along line II-II of FIG. 1;

FIG. 3 is a characteristic line diagram showing a relationship between an eccentric distance between an axis of a shaft and an axis of the valve along a direction of flow of the exhaust gas, and the flow rate of an exhaust gas when the valve is completely open, in the exhaust gas recirculation valve of FIG. 1;

FIG. 4A is a characteristic line diagram with respect to the exhaust gas recirculation valve of FIG. 1, showing a relationship between the eccentric distance of the shaft and the exhaust gas flow rate when the valve is completely open, for a case in which the diameter of a gas inlet port is small; and

FIG. 4B is a characteristic line diagram with respect to the exhaust gas recirculation valve of FIG. 1, showing a relationship between the eccentric distance of the shaft and the exhaust gas flow rate when the valve is completely open, for a case in which the diameter of a gas inlet port is large.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIGS. 1 and 2, an exhaust gas recirculation valve 10 includes a main body (body) 12, a valve 14 disposed rotatably in the interior of the main body 12, a valve seat (seat member) 16 with which an outer peripheral surface of the valve 14 is in abutment (contact), and a drive force transmission mechanism 18 disposed in an upper portion of the main body 12 and which imparts a rotary drive force to the valve 14.

The main body 12 is formed from a metallic material, for example. On the lower side of the main body 12, there are provided a gas inlet port (inlet port) 20 to which the exhaust gas is supplied, and a gas outlet port 22 disposed on an opposite side from the gas inlet port 20 through which the exhaust gas is directed out and circulated to an internal combustion engine (not shown). In the main body 12, the gas inlet port 20 and the gas outlet port 22 are disposed substantially on a straight line. Further, a communication chamber (fluid passage) 24 is formed in the main body 12 between the gas inlet port 20 and the gas outlet port 22, and the substantially disk-shaped valve 14 is arranged rotatably in the interior of the communication chamber 24.

Between the communication chamber 24 and the gas inlet port 20, an installation opening 26 is formed, which is expanded in diameter with respect to the gas inlet port 20. The valve seat 16, which slides on the outer peripheral surface of the valve 14, is disposed in the installation opening 26. The valve seat 16, for example, is formed from a metallic material, and is equipped with a communication hole 28 that penetrates therethrough in an axial direction (the direction of arrows A1 and A2), and a tapered seat section 30, which gradually expands in diameter from the interior of the communication hole 28. In the installation opening 26, the communication hole 28 is arranged on the side of the gas inlet port 20 of the main body 12 (in the direction of the arrow A2), whereas the seat section 30 is arranged on the side of the communication chamber 24 (in the direction of the arrow A1). In addition, the gas inlet port 20 and the communication chamber 24 are placed in communication through the communication hole 28 of the valve seat 16.

Further, the valve seat 16 is movably disposed in the installation opening 26 both in an axial direction (the direction of arrows A1 and A2) and in a radial direction. A spring 34 is interposed between the valve seat 16 and a ring-shaped stopper 32 provided on the communication chamber 24 side of the installation opening 26. The valve seat 16 is urged by the spring 34 toward the side of the gas inlet port 20 (in the direction of the arrow A2).

On the other hand, as shown in FIG. 1, in a substantially central portion of the main body 12, a shaft hole 36 is formed, which penetrates in a vertical upward direction from the communication chamber 24. A later-described shaft 38 of the drive force transmission mechanism 18 is inserted through the shaft hole 36.

The valve 14 comprises a substantially disk-shaped main body portion 40 having a hemispherical shaped outer peripheral surface, and an axial portion 42, which projects in the axial direction (the direction of the arrow A2) from an end of the main body portion 40 and is connected to the shaft 38.

The drive force transmission mechanism 18 includes the shaft 38, which is connected to the valve 14, a valve gear 44 connected to an upper end of the shaft. 38, and a drive source 46 connected to an upper part of the main body 12 and which drives the shaft 38 rotatably through the valve gear 44.

The upper end of the shaft 38 is inserted through a substantially central portion of the valve gear 44, and the shaft 38 is fixed to the valve gear 44 by tightening a nut 48 thereon. In addition, the shaft 38 is rotatably supported by a pair of bearings 50a, 50b, which are mounted in the main body 12 respectively above and below the valve 14.

Further, as shown in FIG. 2, the axis B1 of the shaft 38 is connected so as to be positioned eccentrically (i.e., offset) with respect to an axis B2 through which the center of curvature of the outer peripheral surface on the valve 14 when the valve 14 is completely closed passes. More specifically, the axis B1 is set to be parallel with the axis B2 of the valve 14, and is separated therefrom by a predetermined distance.

For this reason, the valve 14 is arranged within the communication chamber 24 so as to be rotatable (swingable) about the axis B1, which is set at a position eccentric (offset) from the axis B2.

The axis B1 of the shaft 38 is arranged so as to be eccentric with respect to the axis B2 of the valve 14 by a predetermined distance (eccentric distance L) toward the downstream side (in the direction of the arrow A1) along the direction of flow of the exhaust gas.

More specifically, the percentage of the eccentric distance L with respect to the diameter D of the gas inlet port 20 in the main body 12 is set to be equal to or greater than 5.5% (L/D×100≧5.5). Stated otherwise, the value obtained by dividing the eccentric distance L by the diameter D is equal to or greater than 0.055.

The drive source 46 is constituted, for example, from a stepping motor or a rotary actuator, which is driven rotatably by supply of electric current thereto. By transmitting the rotary drive force of the drive source 46 to the shaft 38 via the valve gear 44, the valve 14, which is connected to the shaft 38, is moved or actuated rotatably about the axis B1.

The exhaust gas recirculation valve 10 according to the embodiment of the present invention is constructed basically as described above. Next, operations and advantages thereof shall be explained. A valve-closed state, as shown in FIGS. 1 and 2, will be described as an initial position, in which the outer peripheral surface of the valve 14 is seated on the seat section 30 of the valve seat 16, and communication between the gas inlet port 20 and the gas outlet port 22 is blocked.

From the initial position, which is the valve-closed state as described above, by driving the drive source 46 of the drive force transmission mechanism 18, a rotary drive force of the drive source 46 is transmitted to the shaft 38 through the valve gear 44. The shaft 38 rotates the valve 14, which is connected to the shaft 38, counterclockwise a predetermined angle about the axis B1, which is located at a position eccentric (offset) from the axis B2. Consequently, the valve 14 is displaced in a direction to gradually separate away from the valve seat 16.

In addition, as a result of the outer peripheral surface of the valve 14 separating away from the seat section 30 of the valve seat 16, a valve-open state is brought about, and the exhaust gas, which is supplied to the gas inlet port 20 through a gap between the outer peripheral surface and the seat section 30, is introduced to the interior of the communication chamber 24. By further rotation of the valve 14 under a driving action of the drive source 46, the valve 14 is gradually separated away from the seat section 30, whereby a fully valve-open state is brought about in which the valve 14 is rotated from the initial position, for example, by about 90°.

In the valve-open state, the exhaust gas supplied to the gas inlet port 20 flows through the communication hole 28 of the valve seat 16, passes through the communication chamber 24, and then flows to the gas outlet port 22, whereupon the exhaust gas is supplied to a non-illustrated internal combustion engine.

Next, with reference to FIGS. 3, 4A and 4B, explanations shall be given of the relationship between the diameter D of the gas inlet port 20 in the main body 12, the eccentric distance L, and the flow rate at a time of full opening when the valve 14 is in a fully open state.

FIG. 3 is a characteristic line diagram showing a relationship between the eccentric distance L and the flow rate of the exhaust gas when the valve 14 is completely open, for a case in which the diameter D of the gas inlet port 20 is 18 mm. FIG. 4A is a characteristic line diagram showing a relationship between the eccentric distance L and the flow rate of the exhaust gas, for a case in which the diameter D of the gas inlet port 20 is 9 mm and thus is smaller in diameter than the aforementioned gas inlet port 20 of FIG. 3. FIG. 4B is a characteristic line diagram showing a relationship between the eccentric distance L and the flow rate of the exhaust gas, for a case in which the diameter D of the gas inlet port 20 is 27 mm and thus is larger in diameter than the aforementioned gas inlet port 20 of FIG. 3.

First, from the characteristic line diagram shown in FIG. 3, it can be understood that, from a condition in which the eccentric distance L is nonexistent (L=0) until the eccentric distance L reaches in the neighborhood of roughly 1 mm, the flow rate of the exhaust gas increases rapidly, and then as the eccentric distance L becomes equal to and exceeds 1 mm, the rise in the flow rate slows down or levels off. Stated otherwise, the rate of change at which the flow rate of the exhaust gas increases continues to rise and becomes greatest when the eccentric distance L reaches about 1 mm. More specifically, the flow rate characteristic undergoes a change in the vicinity of where the eccentric distance L is about 1 mm.

For this reason, since the increase in the flow rate of the exhaust gas continues to become larger until reaching an eccentric distance L at which the percentage (L/D×100) between the diameter D of the gas inlet port 20 and the eccentric distance L is roughly 5.5%, at least the percentage of the eccentric distance L with respect to the diameter D of the gas inlet port 20 should be set to 5.5% or greater.

Further, from the characteristic line diagram shown in FIG. 4A, it can be understood that, from a condition in which the eccentric distance L is nonexistent (L=0) until the eccentric distance L reaches in the neighborhood of roughly 0.5 mm, the flow rate of the exhaust gas increases rapidly, and then as the eccentric distance L becomes equal to and exceeds 0.5 mm, the rise in the flow rate lessens and rises more slowly. More specifically, the flow rate characteristic undergoes a change in the vicinity of where the eccentric distance L is about 0.5 mm. In this case as well, the relationship between the eccentric distance L and the diameter D of the gas inlet port 20 is such that 0.5/9×100≈5.5%.

Furthermore, from the characteristic line diagram shown in FIG. 4B, it can be understood that, from a condition in which the eccentric distance L is nonexistent (L=0) until the eccentric distance L reaches in the neighborhood of roughly 1.5 mm, the flow rate of the exhaust gas increases rapidly, and then as the eccentric distance L becomes equal to and exceeds 1.5 mm, the rise in the flow rate lessens and rises more slowly. More specifically, the flow rate characteristic undergoes a change in the vicinity of where the eccentric distance L is about 1.5 mm. In this case as well, the relationship between the eccentric distance L and the diameter D of the gas inlet port 20 is such that 1.5/27×100≈5.5%.

In the foregoing manner, according to the present embodiment, in an exhaust gas recirculation valve 10 in which the center of curvature (axis) B2 of the valve 14 and the axis B1 of the shaft 38 that rotates the valve 14 are eccentric, by setting the relationship between the diameter D of the gas inlet port 20, which is formed in the main body 12 and through which the exhaust gas flows into the main body 12, and the eccentric distance L between the center of curvature (axis) B2 of the valve 14 and the axis B1 of the shaft 38 along the flow direction of the exhaust gas, such that the eccentric distance L is 5.5% or greater than the diameter D, the flow rate characteristic of the exhaust gas can be made more linear, while the flow rate of the exhaust gas can also be increased.

The exhaust gas recirculation valve according to the present invention is not limited to the above-described embodiment, and it is a matter of course that various additional or modified structures could be adopted therein without deviating from the essential gist of the present invention.

Claims

1. An exhaust gas recirculation valve comprising a body having a fluid passage through which an exhaust gas flows, a valve arranged in the fluid passage that switches a flow through state of the exhaust gas, at least a portion of an outer peripheral surface of the valve being spherically shaped, a seat member having a seat section, which is disposed in the fluid passage on an upstream side from the valve and on which the valve is seated, and a shaft connected to the valve and which rotates the valve,

wherein a percentage of an eccentricity amount between a center of curvature of the valve when the valve is completely closed and an axis of the shaft along a direction of flow of the exhaust gas with respect to a diameter of an inlet port formed in the body and into which the exhaust gas flows is 5.5% or greater.