JP2012219890A - Valve unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a valve unit that can suppress valve leakage occurring when a butterfly valve 4 is held at a full closing position.SOLUTION: A valve leakage prevention means comprises: a nozzle (first nozzle 16 and second nozzle 17) pressed in and fixed to an inner circumference of a valve passage 2a; two seal rings 19 and 20 which are disposed in a circumferential groove 18 formed in the nozzle; and a backup ring 21 disposed between both seal rings 19 and 20. When the butterfly valve 4 is held at a full closing position, ring inner circumferential surfaces of the two seal rings 19 and 20 are pressed and adhered onto an outer circumferential surface of the butterfly valve 4 with own elastic restoration force of the seal rings acting in a diameter reduction direction. The backup ring 21 shuts off a closed gap formed between both seal rings 19 and 20. Even if the full closing position is varied a little, the outer circumferential surface of the butterfly valve 4 in a radial direction is formed in a spherical surface shape so as not to generate a gap between the seal rings 19 and 20.

Description

  The present invention relates to a valve unit that adjusts a flow rate of a fluid flowing through a fluid passage by a butterfly valve, and can be suitably used particularly for an exhaust gas recirculation device of an internal combustion engine.

Conventionally, as means for suppressing NOx (nitrogen oxides) contained in engine exhaust, an exhaust gas recirculation device that recirculates part of the exhaust as EGR gas to the intake system of the engine is known. Although this exhaust gas recirculation device can reduce the amount of NOx by increasing the amount of EGR gas, if the EGR gas is excessively recirculated, graphite (PM), which is a particulate matter, is likely to be generated. . For this reason, it is necessary to appropriately control the flow rate of the EGR gas according to the operating state of the engine, and an EGR valve capable of adjusting the flow rate of the EGR gas is provided.
For example, as disclosed in Patent Document 1, the EGR valve includes a valve shaft that is rotatably supported by a housing via a bearing, and an end of the valve shaft that is inclined at a predetermined angle with respect to the valve shaft. A butterfly valve fixed to the section, and the flow rate of the EGR gas is adjusted according to the opening of the butterfly valve.

Moreover, in patent document 1, the valve leak prevention means for ensuring the sealing performance when a butterfly valve fully closes the channel | path (a part of EGR channel | path) formed in a housing is provided.
As shown in FIG. 8, the valve leakage prevention means includes a seal ring 130 that is provided with a circumferential groove 120 recessed in the inner circumferential surface of the passage 110 formed in the housing 100, and is disposed inside the circumferential groove 120. A holding ring 140 disposed on one side (the left side in the figure) of the seal ring 130 inside the circumferential groove 120 and a leaf spring 150 that presses the seal ring 130 toward the holding ring 140 are provided. When the butterfly valve 160 that opens and closes the passage 110 is held in the fully closed position, the seal ring 130 is pressed against and closely contacts the outer peripheral edge of the butterfly valve 160 by its own elastic restoring force. Sealing performance is secured.

Japanese National Patent Publication No. 11-502582 (FIG. 2)

  However, in the prior art disclosed in Patent Document 1, when the butterfly valve 160 is fully closed, the air flow from the right side to the left side in FIG. 8 can be sealed, but the reverse flow is sealed. Insufficient sex. That is, when air flows from the left side to the right side in FIG. 8, the seal ring 130 is pushed away from the holding ring 140 against the urging force of the leaf spring 150 due to the pressure of the air flow. It is conceivable that a gap is formed between the seal ring 130 and the holding ring 140 and air leakage occurs through the gap.

Further, the butterfly valve 160 shown in FIG. 8 has an arc shape in which the cross-sectional shape of the outer peripheral end in contact with the seal ring 130 when fully closed is a large curvature (judging from FIG. 8, approximately 1/2 the plate thickness of the butterfly valve 160. Therefore, if the fully closed position of the butterfly valve 160 varies, a gap may be formed between the butterfly valve 160 and the valve may leak.
The present invention has been made based on the above circumstances, and an object of the present invention is to provide a valve unit capable of suppressing valve leakage when the butterfly valve is held in a fully closed position where the passage is fully closed. .

(Invention of Claim 1)
The valve unit of the present invention includes a valve housing that forms a passage through which a fluid flows, a valve shaft that is rotatably supported by the valve housing via a bearing, and an axial direction of the valve shaft that is disposed inside the passage. Flow control valve that has a disk-like butterfly valve that is attached to the end of the valve shaft in an inclined state relative to the valve shaft, and adjusts the flow rate of the fluid that flows through the passage when the butterfly valve rotates integrally with the valve shaft And valve leakage prevention means for preventing fluid leakage when the butterfly valve is held in a fully closed position for fully closing the passage.
The valve leakage prevention means has an annular nozzle that is press-fitted and fixed to the inner periphery of the passage, and a ring assembly that is held by the nozzle, and the nozzle is upstream of the flow direction of the fluid that flows through the passage. The first nozzle disposed on the second nozzle and the second nozzle disposed on the downstream side, and having a circumferential groove formed in cooperation with the first nozzle and the second nozzle, This circumferential groove is formed in the entire circumference by opening inward in the radial direction.

  The ring assembly includes a first seal ring that is accommodated in the circumferential groove and disposed on the first nozzle side, and a second seal ring that is accommodated in the circumferential groove and disposed on the second nozzle side. And a backup ring that is accommodated in the circumferential groove and disposed between the first seal ring and the second seal ring, each of the first and second seal rings being part of the circumferential direction. When the butterfly valve is held in the fully closed position, the outer peripheral surface of the butterfly valve is pressed and brought into close contact with the butterfly valve by its own elastic restoring force acting in the diameter reducing direction. The backup ring forms a ring surface that is continuous in the circumferential direction, and includes a joint gap formed in the first seal ring and a joint gap formed in the second seal ring. Block the gap with the ring surface And wherein the Rukoto.

According to the present invention, by arranging the backup ring between the first seal ring and the second seal ring, when the butterfly valve is held in the fully closed position for fully closing the passage, Fluid leakage from the joint gap formed in the second seal ring can be reduced.
Further, since the gap between the abutment gap formed in the first seal ring and the abutment gap formed in the second seal ring is blocked by the ring surface of the backup ring, regardless of the flow direction of the fluid flowing through the passage. , Valve leakage when fully closed can be suppressed.
Furthermore, since the outer periphery of the butterfly valve can be sealed with the first seal ring and the second seal ring, that is, a multistage seal structure can be achieved, the effect of reducing valve leakage when fully closed is increased.

(Invention of Claim 2)
The valve unit according to claim 1, wherein the butterfly valve has a radially outer peripheral surface formed in a spherical shape.
In this case, even if the fully closed position varies somewhat due to the inclination of the butterfly valve or the like, the outer peripheral surface of the butterfly valve is spherical, so that valve leakage can be prevented. That is, if the outer peripheral surface of the butterfly valve is spherical, a flow rate dead zone can be created for variations in the fully closed position. Therefore, even if the fully closed position of the butterfly valve varies somewhat, there is no gap between the seal surfaces of the first and second seal rings and the outer peripheral surface of the butterfly valve, so that sealing performance can be ensured, Valve leakage can be prevented.

(Invention of Claim 3)
The valve unit according to claim 1 or 2 is used in an exhaust gas recirculation device that recirculates a part of exhaust gas discharged from an internal combustion engine to an intake passage as EGR gas. The EGR passage is a part of the EGR passage that recirculates the EGR gas to the intake passage, and the flow rate control valve is an EGR control valve that adjusts the flow rate of the EGR gas flowing through the EGR passage.
According to the present invention, since the valve leakage can be reduced when the butterfly valve of the EGR control valve is held at the fully closed position where the EGR passage is fully closed, the flow rate of the EGR gas recirculated to the intake passage can be reduced. It is possible to control appropriately according to the driving state.

It is sectional drawing which shows the structure of an EGR control valve and a valve leak prevention means. It is sectional drawing of a valve unit. It is a side view of a valve unit. (A) It is sectional drawing of a 1st nozzle, (b) It is a top view of the nozzle. (A) It is sectional drawing of a 2nd nozzle, (b) It is a top view of the same nozzle. (A) It is sectional drawing of a seal ring, (b) It is a top view of the ring. (A) Sectional view of backup ring, (b) Plan view of the ring. It is sectional drawing of the valve leak prevention means based on a prior art.

  The best mode for carrying out the present invention will be described in detail with reference to the following examples.

Example 1
In Example 1, an example in which the valve unit of the present invention is used in an exhaust gas recirculation device for an internal combustion engine will be described.
The exhaust gas recirculation device has, for example, an EGR passage that connects an exhaust passage and an intake passage of an internal combustion engine mounted on an automobile, and a part of the exhaust gas (EGR gas) discharged from the internal combustion engine through the EGR passage. This is a device that recirculates the air in the intake passage. The internal combustion engine is, for example, a diesel engine that uses light oil as a fuel or a gasoline engine that uses gasoline.
As shown in FIG. 2, the valve unit 1 includes a valve housing 2 that forms a part of the EGR passage, an EGR control valve that adjusts the flow rate of EGR gas that flows through the EGR passage, and a drive for driving the EGR control valve. An electric actuator (not shown) that generates a driving force, a power transmission device that transmits the driving force of the electric actuator to the EGR control valve, and a rotation angle of the EGR control valve are detected to control the operating state of the internal combustion engine. It is comprised from the rotation angle detection means etc. which are output to ECU (not shown) which is an electronic controller for performing.

Since the valve housing 2 is used in a thermally severe environment, the valve housing 2 is die-cast using a heat resistant material resistant to high temperatures, such as an aluminum alloy. In the following description, a passage formed in the valve housing 2 (a part of the EGR passage) is referred to as a valve passage 2a.
The EGR control valve includes a valve shaft 3 to which the driving force of the electric actuator is transmitted via a power transmission device, and a disc-shaped butterfly valve 4 fixed to the end of the valve shaft 3 by welding or the like. The
In the valve passage 2a, as shown in FIG. 1, when the butterfly valve 4 is held in a fully closed position where the valve passage 2a is fully closed, valve leakage prevention means for preventing EGR gas from leaking to the intake side ( (Described later) is provided.

The valve shaft 3 is rotatably supported by the valve housing 2 via a metal bearing 5 and a ball bearing 6, and has the other shaft end portion opposite to one shaft end portion to which the driving force of the electric actuator is transmitted. It protrudes into the valve passage 2a. An oil seal 7 is disposed between the metal bearing 5 and the ball bearing 6.
As shown in FIG. 2, the butterfly valve 4 is disposed inside the valve passage 2 a and is attached to the shaft end of the valve shaft 3 in a state inclined by a predetermined angle with respect to the axial direction of the valve shaft 3. By rotating integrally with the valve shaft 3, the flow rate of the EGR gas flowing through the EGR passage is adjusted. The butterfly valve 4 and the valve shaft 3 are made of a heat resistant material resistant to high temperatures, for example, stainless steel such as SUS304. Moreover, the outer peripheral surface of the radial direction of the butterfly valve 4 is formed in the spherical shape (refer FIG. 1).

The electric actuator is, for example, a DC motor, and a control target value in which the rotation angle of the EGR control valve detected by the rotation angle detection means, that is, the opening degree of the butterfly valve 4 is set according to the operating state of the internal combustion engine. The electric power supplied to the DC motor by the ECU is feedback-controlled so as to match the above.
The power transmission device is constituted by a gear train that reduces the rotational speed of the DC motor and transmits it to the valve shaft 3. This gear train has a pinion gear (not shown) attached to the output shaft (armature shaft) of the DC motor, an intermediate reduction gear (not shown) meshing with the pinion gear, and a central axis common to the intermediate reduction gear. A small-diameter gear (not shown) that is supported and rotates integrally with the intermediate reduction gear, and a valve gear 8 (see FIG. 2) that meshes with the small-diameter gear, this valve gear 8 is one shaft end of the valve shaft 3. It is connected to.

As shown in FIG. 2, the rotation angle detection means includes a rotor 9 fixed to one end of the valve shaft 3, two magnets 10 held by the rotor 9, and the two magnets 10. A yoke (not shown) that forms a magnetic circuit in an annular shape with a pin in between, a Hall IC 11 that generates an electrical signal according to the magnetic flux density of the magnetic field generated by the two magnets 10, and a magnetic flux focused on the Hall IC 11 For example, a stator 12 for causing the
The Hall IC 11 is an IC circuit in which a Hall element that outputs a voltage (Hall voltage) according to the magnetic flux density and an amplifier circuit that amplifies the output voltage of the Hall element are integrated on a semiconductor chip. It has been.
As shown in FIG. 3, the sensor cover 13 is attached to the upper end surface of the valve housing 2 and is fixed to the valve housing 2 by a screw 14. Further, the sensor cover 13 is provided with a connector 15 for connection with the ECU by a cable (not shown).

Subsequently, the valve leakage prevention means will be described.
The valve leakage prevention means includes a nozzle that is press-fitted and fixed to the inner periphery of the valve passage 2a and a ring assembly that is held by the nozzle.
As shown in FIG. 1, the nozzle includes a first nozzle 16 disposed on the upstream side (exhaust side) with respect to the flow direction of EGR gas flowing from the exhaust side to the intake side through the valve passage 2a, and a downstream side. It has a circumferential groove 18 that is divided into the second nozzle 17 arranged on the (intake side) and that is formed in cooperation with the first nozzle 16 and the second nozzle 17. 18 is formed on the entire circumference of the nozzle by opening inward in the radial direction.

As shown in FIGS. 4 and 5, the first nozzle 16 and the second nozzle 17 are provided in an annular shape in which round holes 16 a and 17 a are opened on the inner periphery, and the diameters of the round holes 16 a and 17 a, that is, The inner diameters of the first nozzle 16 and the second nozzle 17 are set to be slightly larger than the outer diameter of the butterfly valve 4.
As shown in FIG. 4A, the first nozzle 16 has both side surfaces in the plate thickness direction (the left-right direction in the figure), that is, the intake side surface and the exhaust side surface are formed in parallel, and the intake side. The inner diameter (diameter of the round hole 16a) is constant between the side surface on the side and the side surface on the exhaust side.
As shown in FIG. 5A, the second nozzle 17 has an enlarged inner diameter portion formed by enlarging the inner diameter on the exhaust side (the left side in the drawing) in the plate thickness direction. The enlarged inner diameter portion is formed by a cylindrical inner peripheral surface 17b that opens to the exhaust side of the second nozzle 17, and a radial side surface 17c that is orthogonal to the cylindrical inner peripheral surface 17b. The above-mentioned circumferential groove 18 is formed between the side surfaces of the two. That is, the circumferential groove 18 is formed on both side surfaces in the groove width direction by the intake side surface of the first nozzle 16 (the right side surface shown in FIG. 4A) and the radial side surface 17c of the second nozzle 17. In addition, the bottom surface of the circumferential groove 18 is formed by the cylindrical inner circumferential surface 17 b of the second nozzle 17.

The ring assembly consists of two seal rings 19 and 20 and one backup ring 21. As shown in FIG. 1, the two seal rings 19 and 20 include a first seal ring 19 disposed on the first nozzle 16 side inside the circumferential groove 18 formed in the nozzle, and the circumferential groove 18. It is the 2nd seal ring 20 arrange | positioned inside the 2nd nozzle 17 side inside.
As shown in FIG. 6B, the two seal rings 19 and 20 are each formed in a C shape having joint gaps 19a and 20a in a part of the circumferential direction. The two seal rings 19 and 20 are formed so that the inner diameter of the ring is slightly smaller than the outer diameter of the butterfly valve 4, and when the butterfly valve 4 is held in the fully closed position shown in FIG. The inner peripheral surface of the ring is pressed against and closely contacts the outer peripheral surface of the butterfly valve 4 by its own elastic restoring force. That is, the inner peripheral surface of the ring shown in FIG. 6A forms seal surfaces 19b and 20b that seal the entire periphery with the butterfly valve 4.

As shown in FIG. 1, the backup ring 21 is disposed between the first seal ring 19 and the second seal ring 20 inside the circumferential groove 18. As shown in FIG. 7B, the backup ring 21 is a complete ring body having no joint gap, and forms a ring surface 21a continuous in the circumferential direction.
The backup ring 21 is formed slightly small so that the inner diameter of the ring does not interfere with the outer diameter of the butterfly valve 4, and is disposed between the first seal ring 19 and the second seal ring 20, so that both seals The gaps 19a and 20a formed in the rings 19 and 20 are blocked by the ring surface 21a.

The first nozzle 16, the second nozzle 17, the two seal rings 19, 20 and the backup ring 21 are each formed of a heat resistant material resistant to high temperatures, for example, stainless steel such as SUS304. .
Further, the width dimension of the ring aggregate obtained by adding the plate thicknesses of the two seal rings 19 and 20 and the backup ring 21 is set slightly smaller than the width dimension of the circumferential groove 18 formed in the nozzle. On the other hand, when the butterfly valve 4 is held in the fully closed position, the outer peripheral surface formed in a spherical shape has a plate thickness dimension that allows the seal surfaces 19b and 20b of the two seal rings 19 and 20 to be in close contact with each other. Have. That is, as shown in FIG. 1, the plate thickness dimension t of the butterfly valve 4 is formed larger than the width dimension of the ring assembly.

(Effect of Example 1)
In the valve unit 1 shown in the first embodiment, since the two seal rings 19 and 20 are arranged inside the circumferential groove 18 formed in the nozzle, the butterfly valve 4 is in a fully closed position where the valve passage 2a is fully closed. The outer periphery of the butterfly valve 4 can be sealed with the first seal ring 19 and the second seal ring 20, that is, a multi-stage seal structure can be used, thereby preventing EGR gas leakage when the valve is fully closed. The effect that can be achieved is great, and EGR gas can be prevented from being mixed into the intake air.

  Further, since the backup ring 21 is disposed between the first seal ring 19 and the second seal ring 20, the abutment gap 19 a formed in the first seal ring 19 and the second seal ring 20 are provided. The gap surface 20a formed can be blocked by the ring surface 21a of the backup ring 21. Thereby, when the butterfly valve 4 is held in the fully closed position, the intake air sucked into the internal combustion engine can be prevented from leaking to the exhaust side of the butterfly valve 4, and the EGR gas can be moved to the intake side of the butterfly valve 4. Leakage can also be prevented. That is, valve leakage when the valve is fully closed can be suppressed by both the forward flow that flows through the valve passage 2 from the exhaust side to the intake side and the reverse flow that flows back from the intake side to the exhaust side.

  Further, since the outer peripheral surface of the butterfly valve 4 is formed in a spherical shape, even when the fully closed position varies somewhat due to the inclination of the butterfly valve 4 or the like, valve leakage when the valve is fully closed can be prevented. That is, if the outer peripheral surface of the butterfly valve 4 is spherical, a flow rate dead zone can be created for variations in the fully closed position. Thereby, even if the fully closed position of the butterfly valve 4 varies somewhat, a gap is generated between the seal surfaces 19b and 20b (ring inner peripheral surface) of the two seal rings 19 and 20 and the outer peripheral surface of the butterfly valve 4. The sealing performance by the two seal rings 19 and 20 can be ensured, and valve leakage can be prevented.

(Modification)
In the first embodiment, an example in which the flow control valve of the valve unit 1 according to the present invention is used as the EGR control valve of the exhaust gas recirculation device has been described. For example, the amount of intake air taken into the internal combustion engine is adjusted. The present invention can also be applied to a throttle valve or an intake throttle valve for generating intake negative pressure in the intake passage.

1 Valve unit 2 Valve housing 2a Valve passage 3 Valve shaft (flow control valve)
4 Butterfly valve (flow control valve)
5 Metal bearing (bearing)
6 Ball bearing
16 First nozzle 17 Second nozzle 18 Circumferential groove 19 First seal ring 19a Joint gap formed in seal ring 20 Second seal ring 20a Seal ring sealing surface 21 Backup ring 21a Backup ring ring surface

Claims (3)

A valve housing forming a passage through which fluid flows;
A valve shaft that is rotatably supported by the valve housing via a bearing, and a circle that is disposed inside the passage and is attached to the end of the valve shaft in an inclined state with respect to the axial direction of the valve shaft. A flow control valve that adjusts the flow rate of the fluid flowing through the passage by rotating the butterfly valve integrally with the valve shaft;
A valve leakage prevention means for preventing fluid leakage when the butterfly valve is held in a fully closed position for fully closing the passage;
The valve leakage prevention means includes
An annular nozzle press-fitted and fixed to the inner periphery of the passage;
A ring assembly held by this nozzle,
The nozzle is divided into a first nozzle disposed on the upstream side and a second nozzle disposed on the downstream side with respect to the flow direction of the fluid flowing through the passage, and the first nozzle and the A circumferential groove formed in cooperation with the second nozzle, the circumferential groove is formed in the entire circumference by opening inward in the radial direction;
The ring assembly is
A first seal ring housed in the circumferential groove and disposed on the first nozzle side;
A second seal ring housed in the circumferential groove and disposed on the second nozzle side;
A backup ring housed in the circumferential groove and disposed between the first seal ring and the second seal ring;
Each of the first and second seal rings has an abutment gap formed in a part in the circumferential direction, and when the butterfly valve is held in a fully closed position, the first and second seal rings are self-elastically restored and act in the diameter reducing direction. Having a sealing surface that seals between the butterfly valve by pressing and pressing the outer peripheral surface of the butterfly valve with force,
The backup ring forms a ring surface that is continuous in the circumferential direction, and the ring surface provides a gap between the joint gap formed in the first seal ring and the joint gap formed in the second seal ring. A valve unit characterized by blocking. In the valve unit according to claim 1,
The butterfly valve has a radially outer peripheral surface formed in a spherical shape. The valve unit according to claim 1 or 2,
Used in an exhaust gas recirculation device that recirculates a part of the exhaust gas discharged from the internal combustion engine as EGR gas to the intake passage,
The passage formed in the valve housing is a part of an EGR passage that recirculates EGR gas to the intake passage,
The valve unit, wherein the flow rate control valve is an EGR control valve that adjusts a flow rate of EGR gas flowing through the EGR passage.

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