JP2009024502A - Exhaust bypass valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust bypass valve provided in a bypass flow passage for bypassing a turbine of a turbocharger and capable of preventing any thermal damage of a diaphragm caused by the heat conduction from high-temperature exhaust gas. <P>SOLUTION: In the exhaust bypass valve comprising a housing 22 having an exhaust gas flow passage 21 for distributing exhaust gas from an engine, a valve element 24 for opening/closing the exhaust gas flow passage 21, and an actuator 31 having a diaphragm 33 connected to the valve element 24 via a valve stem 26 to adjust the opening of the valve element 24, a cooling casing 38 having a cooling chamber 39 for distributing a cooling medium to cool the valve stem 26 is interposed between the housing 22 and the actuator 31, and a packing member 42 for sealing a shaft penetration part of the cooling casing 38 is provided on the cooling casing 38. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust bypass valve provided in a bypass flow path that bypasses a turbine of a supercharger.

  In recent years, research on premixed compression ignition combustion (PCI combustion) that enables NOx (nitrogen oxide) and smoke to be simultaneously reduced in a diesel engine has been actively conducted. In PCI combustion, a uniform and lean mixture is generated earlier than the compression top dead center of the piston and then burned. When the engine load increases, pre-ignition occurs and it becomes difficult to control the ignition timing, so that there is a problem that the operating range in which PCI combustion can be performed is limited to the low load range.

  As a method of expanding the operating range for PCI combustion, high EGR (exhaust gas recirculation) is used to reduce the oxygen concentration in the air-fuel mixture to control the ignition timing of combustion and ensure a high A / F (air-fuel ratio) It is known to be effective. As a specific countermeasure, it is conceivable to use a two-stage turbocharger and obtain a high boost from a low-speed and low-load region by using a high-pressure small turbocharger to ensure high EGR and high A / F.

  In addition, the use of a two-stage turbocharger reduces fuel consumption during city driving (low, medium, and low and medium loads) with a small high-pressure turbocharger, and increases output at the output point of a large-scale turbocharger with low pressure. It is effective as a means to achieve both.

  In the two-stage supercharging device, when the high-pressure supercharger and the low-pressure supercharger are connected in series to the engine, it is necessary to switch the supercharger to be used in a predetermined operation region. In order to switch the supercharger, a bypass valve is required for both the intake system and the exhaust system. In general, a butterfly valve having a diaphragm / actuator is used as a bypass valve for the exhaust system.

  Patent Documents 1 to 3 describe a poppet type valve having a diaphragm actuator and used as an EGR valve.

JP-A-9-68108 Japanese Patent Laid-Open No. 11-22562 JP-A-8-145221

  Here, when only the high-pressure supercharger is operated, it is difficult to ensure high gas sealing performance in the valve portion of the mechanism even if the flow path can be switched with the butterfly valve. If a gas leak occurs in the valve section, there is a concern that the high-pressure supercharger cannot be operated efficiently.

  Therefore, as an exhaust system bypass valve, it is considered that a poppet type valve having a self-sealing property and already used for an EGR valve is suitable.

  However, when a poppet valve having a diaphragm / actuator is used as an exhaust system bypass valve, the actuator diaphragm is connected to the shaft of the valve. Due to heat conduction from the diaphragm, heat damage of a diaphragm made of an elastic body having relatively poor heat resistance such as rubber becomes a problem.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an exhaust bypass valve that can prevent thermal damage to a diaphragm due to heat conduction from high-temperature exhaust gas in an exhaust bypass valve provided in a bypass flow path that bypasses a turbocharger turbine. It is in.

  In order to achieve the above object, the present invention provides a housing having an exhaust gas flow path for circulating exhaust gas from an engine, a valve body for opening and closing the exhaust gas flow path, and a valve shaft connected to the valve body. An exhaust bypass valve provided with an actuator having a diaphragm connected to adjust the opening of the valve body, and a cooling chamber in which a cooling medium is circulated between the housing and the actuator to cool the valve shaft And a packing member for sealing the shaft penetrating portion of the cooling casing is provided on the cooling casing.

  Here, a cooling hole may be provided in the valve shaft so as to penetrate the valve shaft in a radial direction of the valve shaft.

  The packing member may have an annular member made of ethylene tetrafluoride resin attached to the outer periphery of the valve shaft, and an O-ring made of fluorine-based rubber attached to the outer periphery of the annular member.

  A plurality of the packing members may be provided at intervals in the longitudinal direction of the valve shaft via a packing guide having a notch for exposing the valve shaft to the cooling chamber.

  Moreover, the inlet / outlet of the cooling medium to the cooling chamber may be provided above the outlet.

  The cooling medium may be cooling oil.

  ADVANTAGE OF THE INVENTION According to this invention, the exhaust bypass valve provided in the bypass flow path which bypasses the turbine of a supercharger can provide the exhaust bypass valve which can prevent the thermal damage of a diaphragm by the heat conduction from high temperature exhaust gas. There is an excellent effect.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  First, the two-stage supercharging device will be described with reference to FIG.

  FIG. 5 is a schematic view of an engine to which the two-stage supercharging device is applied.

  In FIG. 5, reference numeral 1 is an engine body (diesel engine), 2 is an intake manifold, 3 is an intake pipe, 4 is an exhaust manifold, 5 is an exhaust pipe, 6 is an EGR pipe, 7 is an EGR valve, and 8 is an EGR cooler. .

  A small-capacity high-pressure supercharger HTC and a large-capacity low-pressure supercharger LTC are connected to the engine body 1 in series from the side closer to the engine body 1.

  The exhaust pipe 5 connected to the engine main body 1 is connected in series with the high-pressure stage turbine HT of the high-pressure supercharger HTC and the low-pressure stage turbine LT of the low-pressure supercharger LTC from the side closer to the engine main body 1. The high-pressure turbine HT is connected to the exhaust pipe 5 and is provided in the exhaust bypass pipe 9 as an exhaust bypass flow path that bypasses the high-pressure turbine HT. The exhaust bypass pipe 9 can open and close the exhaust bypass pipe 9. And a valve 10.

  On the other hand, to the intake pipe 3 connected to the engine body 1, a high-pressure stage compressor HC of the high-pressure supercharger HTC and a low-pressure stage compressor LC of the low-pressure supercharger LTC are connected in series from the side closer to the engine body 1. ing. The high-pressure compressor HC is connected to the intake pipe 3 and is provided in the intake bypass pipe 11 as an intake bypass flow path that bypasses the high-pressure compressor HC, and the intake bypass pipe 11 that can open and close the intake bypass pipe 11. And a valve 12.

  The intake pipe 3 is provided with an intercooler 13 that cools the intake air boosted by the high-pressure compressor HC and the low-pressure compressor LC.

  In such a two-stage turbocharging device, in the low, medium and low middle load region of the engine, the exhaust bypass valve 9 is closed by the exhaust bypass valve 10 to supply the exhaust gas from the engine body 1 to the high pressure turbine HT. The high-pressure supercharger HTC is mainly operated. By doing so, the high-pressure turbine HT is mainly operated in the low-medium-speed low-medium load region of the engine, and supercharging is performed by the high-pressure compressor HC.

  On the other hand, in the high-speed and high-load region of the engine, the exhaust bypass pipe 9 is opened by the exhaust bypass valve 10 to bypass the exhaust gas from the engine body 1 and supply the low-pressure turbine LT to the low-pressure turbocharger LTC. Is to be activated. By doing so, the low-pressure turbine LT is operated in the high-speed and high-load region of the engine, and supercharging is performed by the low-pressure compressor LC.

  Further, in the transition region where the low, medium, low and medium load regions and the high speed and high load region of the engine transition to each other, the high pressure supercharger HTC and the low pressure supercharger are adjusted by adjusting the opening of the exhaust bypass valve 10. The LTC is activated. By doing so, in the transition region, the high-pressure turbine HT and the low-pressure turbine LT are operated, and supercharging is performed by the high-pressure compressor HC and the low-pressure compressor LC.

  Next, the exhaust bypass valve 10 according to the present embodiment will be described with reference to FIG.

  FIG. 1 is a longitudinal sectional view of an exhaust bypass valve according to an embodiment of the present invention.

  As shown in FIG. 1, an exhaust bypass valve 10 according to the present embodiment is disposed in the middle of an exhaust bypass pipe 9 (see FIG. 5), and includes a housing 22 having an exhaust gas passage 21 through which exhaust gas flows. And a poppet valve 23 supported by the housing 22 so as to be movable up and down.

  The poppet valve 23 has a valve body 24 for opening and closing the exhaust gas passage 21 in the housing 22, a valve body 24 provided at one end (lower end), and a flange 25 provided at the other end (upper end). And a valve shaft 26. The valve shaft 26 is supported by a bush 27 mounted on the housing 22 so as to be movable up and down and non-rotatable. Further, the valve shaft 26 is inserted into the bush 27 while forming a shaft seal. A return spring 29 as a biasing means for biasing the poppet valve 23 (valve shaft 26) in the closing direction (X direction) is disposed in a compressed state between the flange portion 25 and an actuator housing 28 described later. The When the poppet valve 23 is fully closed, the valve body 24 is seated on the valve seat 30 mounted on the housing 22.

  A diaphragm actuator (actuator) 31 as a driving means for driving the poppet valve 23 is provided on the upper portion of the housing 22. The diaphragm actuator 31 has an actuator housing 28 provided in the upper part of the housing 22 and having a diaphragm housing chamber 32 formed therein. A diaphragm 33 for adjusting the opening degree of the poppet valve 23 (valve body 24) is stretched in the diaphragm housing chamber 32 formed in the actuator housing 28, and the diaphragm housing chamber 32 is negatively pressured by the diaphragm 33. It is divided into a chamber 34 and an atmospheric pressure chamber 35. The diaphragm 33 is made of an elastic material such as rubber. The diaphragm 33 is connected to the flange 25 provided at the end of the valve shaft 26. The return spring 29 is accommodated in the negative pressure chamber 34, and the negative pressure chamber 34 is connected to a vacuum pump (not shown) via a suction pipe 36. The atmospheric pressure chamber 35 is opened to the atmosphere.

  The actuator housing 28 is fixed to the housing 22 using bolts 37 or the like. A cooling casing 38 (described later) is interposed between the actuator housing 28 and the housing 22. In the present embodiment, the actuator housing 28 is fixed to the housing 22 at a plurality of locations (for example, three locations at intervals of 120 °) at regular intervals around the longitudinal axis of the valve shaft 26.

  Between the housing 22 and the actuator housing 28, a cooling casing 38 having a cooling chamber 39 through which a cooling medium flows so as to cool the intermediate portion in the longitudinal direction of the valve shaft 26 is interposed. In the present embodiment, cooling oil is used as the cooling medium, and the inlet / outlet of the cooling medium (cooling oil) into the cooling chamber 39 is an outlet (cooling oil outlet) formed by an inlet pipe 40 forming an inlet (cooling oil inlet). It is provided above the tube 41. The cooling chamber 39 is connected to an oil pump, an oil tank or the like (not shown) via an inlet pipe 40 and an outlet pipe 41. The cooling oil is appropriately introduced into the cooling chamber 39 via the inlet pipe 40 by the oil pump, and is appropriately discharged from the cooling chamber 39 via the outlet pipe 41.

  In the cooling casing 38, a packing member (combined packing) 42 mounted on the valve shaft 26 is disposed so as to seal the shaft through portion of the cooling casing 38 and keep the cooling chamber 39 airtight. The packing member 42 according to the present embodiment is attached to the outer periphery of the valve shaft 26, and is attached to the outer periphery of the annular member 43 made of a heat resistant material (for example, ethylene tetrafluoride resin) and the annular member 43, and the heat resistant material. And an O-ring 44 made of (fluorinated rubber). The annular member 43 and the O-ring 44 are arranged in the longitudinal direction of the valve shaft 26 via a cylindrical packing guide 46 (see FIG. 2) having a notch 45 for exposing the valve shaft 26 into the cooling chamber 39. It is provided above and below at intervals. In FIG. 1, reference numerals 47 and 48 denote seal rubbers mounted on the valve shaft 26 in order to keep the negative pressure chamber 34 and the cooling chamber 39 airtight, respectively.

  A predetermined gap 49 forming a cooling oil passage is formed between the outer periphery of the valve shaft 26 and the inner periphery of the packing guide 46 so that the cooling oil can pass through the predetermined gap 49. Further, a cooling hole 50 (see FIG. 3) that is positioned in the cooling chamber 39 and forms a cooling oil passage is provided in the middle portion in the longitudinal direction of the valve shaft 26 so as to penetrate in the radial direction of the valve shaft 26. The cooling oil can pass through the hole 50.

  In the present embodiment, the heat flow path to the cooling oil is the outer peripheral portion of the valve shaft 26, the hole 50 of the valve shaft 26, and the contact portion between the housing 22 and the cooling casing 38. That is, in this embodiment, heat transferred from the high-temperature exhaust gas to the diaphragm actuator 31 is removed by the cooling oil at the outer periphery of the valve shaft 26, the hole 50 of the valve shaft 26, and the contact portion between the housing 22 and the cooling casing 38. Like to do.

  Next, the operation of this embodiment will be described.

  When the air in the negative pressure chamber 34 is sucked by a vacuum pump (not shown) and the pressure in the negative pressure chamber 34 is set to a predetermined negative pressure, the diaphragm 33 resists the urging force of the return spring 29 to the negative pressure chamber 34 side. Transforms into Thereby, the valve shaft 26 and the valve body 24 are moved in the opening direction (Y direction), and the poppet valve 23 is lifted in the opening direction (Y direction).

  Here, in this embodiment, a cooling housing having a cooling chamber 39 for circulating a cooling medium between a housing 22 having an exhaust gas passage 21 formed therein and an actuator housing 28 having a diaphragm housing chamber 32 formed therein. 28 is provided, heat transmitted from the high-temperature exhaust gas flowing through the exhaust gas passage 21 to the diaphragm actuator 31 (diaphragm 33) via the valve shaft 26 is positively confined in the narrow space between the housing 22 and the actuator housing 28. The diaphragm actuator 31 (diaphragm 33) can be kept at a low temperature. Therefore, heat of the high-temperature exhaust gas flowing through the exhaust gas passage 21 is suppressed from being transmitted to the diaphragm 33 connected to the end of the valve shaft 26 via the valve shaft 26, and heat conduction from the high-temperature exhaust gas. The heat damage of the diaphragm 33 due to can be prevented.

  Further, since the packing member 42 is disposed in the shaft through portion of the cooling casing 38, the exhaust gas from the shaft through portion (valve shaft 26) of the cooling casing 38 is sealed to keep the cooling chamber 39 airtight. it can. Further, the cooling oil flowing through the cooling chamber 39 formed in the cooling casing 38 is prevented from leaking out of the cooling chamber 39 through the shaft penetration portion of the cooling casing 38, and the cooling chamber 39 can be kept airtight.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various other embodiments can be adopted.

  For example, as shown in FIG. 4, a plurality of cooling holes 50 may be provided in the valve shaft 26 so as to intersect each other.

  In the above embodiment, the cooling medium is cooling oil. However, the present invention is not limited to this, and the cooling medium may be cooling water.

1 is a longitudinal sectional view of an exhaust bypass valve according to an embodiment of the present invention. It is a perspective view of a packing guide. It is a cross-sectional view of a valve shaft. It is a cross-sectional view of the valve stem which concerns on a modification. It is a schematic diagram of an engine to which a two-stage supercharging device is applied.

Explanation of symbols

10 Exhaust bypass valve 21 Exhaust gas flow path 22 Housing 24 Valve body 26 Valve shaft 31 Diaphragm actuator (actuator)
33 Diaphragm 38 Cooling casing 39 Cooling chamber 42 Packing member 43 Ring member 44 O-ring 45 Notch 46 Packing guide 50 Hole

Claims (6)

  A housing having an exhaust gas flow path for circulating exhaust gas from the engine, a valve body for opening and closing the exhaust gas flow path, and a valve body connected to the valve body via a valve shaft to adjust the opening of the valve body An exhaust bypass valve comprising an actuator having a diaphragm, wherein a cooling casing having a cooling chamber for circulating a cooling medium for cooling the valve shaft is interposed between the housing and the actuator, and the cooling casing An exhaust bypass valve characterized in that a packing member for sealing the shaft penetration portion of the cooling casing is provided.   The exhaust bypass valve according to claim 1, wherein a cooling hole is provided in the valve shaft so as to be positioned in the cooling chamber and penetrate in a radial direction of the valve shaft.   3. The packing member according to claim 1 or 2, wherein the packing member includes an annular member made of ethylene tetrafluoride resin attached to an outer periphery of the valve shaft, and an O-ring made of fluorine-based rubber attached to the outer periphery of the annular member. Exhaust bypass valve.   The said packing member is provided with two or more in the longitudinal direction of the said valve shaft through the packing guide which has a notch part for exposing the said valve shaft in the said cooling chamber at intervals. The exhaust bypass valve described.   The exhaust bypass valve according to any one of claims 1 to 4, wherein an inlet / outlet of the cooling medium to the cooling chamber is provided above the outlet.   The exhaust bypass valve according to any one of claims 1 to 5, wherein the cooling medium is cooling oil.

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