JP5787082B2 - Additive valve seal structure - Google Patents

Description

  The present invention relates to a seal structure between an addition valve that adds an ammonia-based reducing agent into an exhaust pipe of an internal combustion engine and a cooling mechanism that connects the addition valve to the exhaust pipe in a cooled state.

  An SCR (Selective Catalytic Reduction) system is known as a nitrogen oxide purification device that reduces NOx (nitrogen oxide) discharged from an internal combustion engine (see, for example, Patent Document 1). An exhaust purification device using this SCR system includes a catalyst for purifying nitrogen oxides, and, for example, an aqueous urea solution, ammonia gas, or the like is injected into the exhaust pipe as a reducing agent, so that it is included in the exhaust by its reducing action. NOx is selectively reduced to nitrogen or water.

JP 2010-14083 A (7th to 8th pages, FIG. 7)

  In Patent Document 1, as an addition valve, an injection device is attached to an exhaust pipe of an internal combustion engine, and a tip thereof is inserted into an internal space of the exhaust pipe. However, in order to prevent heat damage to the addition valve, it is necessary to connect the addition valve to the exhaust pipe through a cooling mechanism.

  In this case, an addition valve storage space is formed in the cooling mechanism, and the addition valve is disposed therein. In such an addition valve mounting structure, in order to prevent exhaust from leaking to the outside from between the inner peripheral surface of the addition valve storage space and the outer peripheral surface of the addition valve, or water from entering from the outside. Usually, an O-ring is arranged by forming a smooth seating surface on the inner peripheral surface and the outer peripheral surface.

  However, due to restrictions on the inner peripheral surface shape of the storage space and the outer peripheral surface shape of the addition valve, a seat surface having a shape sufficient for the O-ring arrangement may not be ensured. If an O-ring is arranged on a seating surface that does not have a sufficient shape, the O-ring may drop to the small diameter side, or the corner of the seating surface may bite into the O-ring and damage the O-ring. is there. This creates a problem with the durability of the seal.

  An object of the present invention is to provide a seal structure that can seal a gap between an inner peripheral surface of an addition valve storage space having a shape restriction and an outer peripheral surface of an addition valve without causing a problem in durability. To do.

In the following, means for achieving the above-mentioned purpose, and its operation and effect are described.
The addition valve seal structure according to claim 1 is a seal structure between an addition valve for adding an ammonia-based reducing agent into an exhaust pipe of an internal combustion engine and a cooling mechanism for connecting the addition valve to the exhaust pipe in a cooled state. An expansion graphite seal and a resin seal are sequentially disposed from the exhaust pipe side between the inner peripheral surface of the addition valve storage space formed in the cooling mechanism and the outer peripheral surface of the addition valve, and the expansion The graphite seal is in contact with the resin seal .

  By using the resin seal, it is not necessary to specially form a seating surface shape for the seal on the inner peripheral surface of the addition valve storage space and the outer peripheral surface of the addition valve. By molding the resin seal itself into a shape that matches the shape of the gap between the inner peripheral surface of the addition valve storage space and the outer peripheral surface of the addition valve, the shape of the inner peripheral surface and the outer peripheral surface is restricted. Even so, the restricted shape itself can be used as a seating surface that can be sufficiently sealed.

In addition, the gap between the inner peripheral surface of the addition valve storage space and the outer peripheral surface of the addition valve is a passage of heat from the exhaust pipe side, and the temperature of the resin seal can be raised within a range not subject to heat damage. . The resin seal that expands due to the temperature rise and has increased flexibility fills the gap and is in close contact with the inner and outer peripheral surfaces, thereby achieving a more reliable sealing effect.
In addition, by placing an expanded graphite seal closer to the exhaust pipe than the resin seal between the inner peripheral surface of the addition valve storage space and the outer peripheral surface of the addition valve, the resin seal does not receive heat directly from the exhaust. Can be. Furthermore, the expanded graphite seal can quickly release the heat received from the exhaust on the tip of the addition valve to the air cooling mechanism so that the addition valve is not damaged by heat.
The resin seal is in contact with the expanded graphite seal. Due to heat transfer from the expanded graphite seal due to this contact, the temperature of the resin seal can be quickly raised to such an extent that no thermal damage is caused. With this temperature rise, the resin seal expands and the flexibility increases. Accordingly, the resin seal can achieve a more reliable sealing effect by filling the gap and closely contacting the inner and outer peripheral surfaces.

As a result, the gap between the inner peripheral surface of the addition valve storage space having a shape restriction and the outer peripheral surface of the addition valve can be sealed without causing a problem in durability.
The addition valve seal structure according to claim 2 is the addition valve seal structure according to claim 1, wherein the ammonia-based reducing agent is an aqueous urea solution.

Examples of the ammonia-based reducing agent include an aqueous urea solution in which urea is hydrolyzed by heating in the exhaust pipe to generate ammonia.
The addition valve seal structure according to claim 3 is the addition valve seal structure according to claim 1, wherein the ammonia-based reducing agent is ammonia gas.

As the ammonia-based reducing agent, ammonia gas itself may be used.
In the addition valve seal structure according to claim 4, in the addition valve seal structure according to any one of claims 1 to 3, the cooling mechanism cools the addition valve by air. .

  An example in which the cooling mechanism is air-cooled. Since the structure of the cooling mechanism by air cooling is simplified, this simplified structure can be applied to a resin seal even if the structure cannot be applied by O-ring, and a reliable sealing effect can be achieved. As a result, the gap between the inner peripheral surface of the addition valve storage space having a shape restriction and the outer peripheral surface of the addition valve can be sealed without causing a problem in durability.

In addition valve seal structure according to 請 Motomeko 5, wherein said additive in addition valve seal structure according to any one of claims 1 to 4, the inner peripheral surface of the cooling mechanism which is formed on the addition valve housing and Between the outer peripheral surface of the valve, a thermal expansion space for the resin seal is provided on the side opposite to the expanded graphite seal.

  The presence of the thermal expansion space does not cause unnecessary deformation or distortion in the thermally expanded resin seal. For this reason, the durability of the addition valve seal structure can be maintained.

The addition valve seal structure according to claim 6 , wherein in the addition valve seal structure according to any one of claims 1 to 5 , the exhaust pipe has a nitrogen oxide purification catalyst disposed downstream of the addition valve. In the nitrogen oxide purifying catalyst, the ammonia reducing agent produces a reducing action.

  Examples of the ammonia-based reducing agent include those added to the exhaust gas in order to cause a reducing action in the catalyst for purifying nitrogen oxides.

1 is a configuration diagram illustrating an outline of an exhaust emission control device according to a first embodiment. FIG. 3 is a cross-sectional view of the mounting structure of the urea water addition valve according to the first embodiment. Sectional drawing of the mounting structure of the urea water addition valve of the second embodiment.

[Embodiment 1]
<Configuration of Embodiment 1> FIG. 1 is a configuration diagram showing an outline of an exhaust emission control device 2 to which the above-described invention is applied. The exhaust purification device 2 is configured as a urea SCR system that purifies NOx in exhaust using a catalyst.

The exhaust purification device 2 includes an SCR catalyst 4, a urea water addition valve 6, a urea water tank 8, and a pressure feed pump 10.
The SCR catalyst 4 is a selective reduction catalyst that is connected to an exhaust pipe 12 of an internal combustion engine mounted on a vehicle and purifies NOx in the exhaust by a reduction reaction.

  The urea water addition valve 6 is attached to the upstream side of the SCR catalyst 4 in the exhaust pipe 12 via an air cooling mechanism 24 described later. The urea water (corresponding to the urea aqueous solution) stored in the urea water tank 8 is pressure-fed through the filter 14 to the urea water addition valve 6 by the pressure-feed pump 10. As a result, urea water can be added from the urea water addition valve 6 to the internal space of the exhaust pipe 12.

  This urea water is an ammonia-based reducing agent that generates ammonia by hydrolysis of urea when heated in exhaust gas. The ammonia generated in this manner exhibits a reducing action on NOx in the SCR catalyst 4, and NOx is reduced to nitrogen and water. This purifies the exhaust.

The urea water supply pressure of the pressure pump 10 is adjusted by the pressure adjustment valve 16, and excess urea water is returned from the pressure adjustment valve 16 to the urea water tank 8 side.
The urea water addition amount by the urea water addition valve 6 and drive control of the pressure feed pump 10 are executed by an ECU (electronic control unit) 18. For this control, the ECU 18 detects the supply pressure of urea water from various data, for example, a pressure sensor 20 provided in the urea water supply path to the urea water addition valve 6.

  FIG. 2 shows a cross section of a structure for attaching the urea water addition valve 6 to the exhaust pipe 12. The urea water addition valve 6 is not directly connected to the exhaust pipe 12 but is connected to the exhaust pipe 12 via the air cooling mechanism 24.

  The air cooling mechanism 24 is made of a metal such as an aluminum alloy. The housing 24a has a substantially cylindrical shape, and disc-like cooling fins 24b are formed on the outer peripheral portion by integral molding or bonding.

  The interior of the housing 24a forms an addition valve storage space 24c, and the nozzle portion 6a of the urea water addition valve 6 is stored in the center. The urea water addition valve 6 is inserted from the insertion port 24d of the air cooling mechanism 24, and the stepped portion 6b existing at the base of the urea water addition valve 6 comes into contact with the ring-shaped stopper 24e disposed at the insertion port 24d. The positioning is performed in the axial direction.

  Between the inner peripheral surface 24 f of the addition valve storage space 24 c and the outer peripheral surface 6 c of the urea water addition valve 6, a cylindrical expanded graphite seal 26 and a ring-shaped resin seal 28 are arranged. The expanded graphite seal 26 is disposed closer to the exhaust pipe 12 than the resin seal 28. Thus, the urea water addition valve 6 is positioned at the central axis position without directly contacting the inner peripheral surface 24f of the addition valve storage space 24c.

The expanded graphite seal 26 is formed by processing expanded graphite into a cylindrical shape. Besides the expanded graphite alone, it may be a composite material of expanded graphite and a metal foil or a metal net.
The resin seal 28 is formed by molding a resin in a ring shape so as to correspond to the gap shape between the outer peripheral surface 6c of the urea water addition valve 6 and the inner peripheral surface 24f of the addition valve storage space 24c. The resin seal 28 is disposed on the opposite side to the exhaust pipe 12 with respect to the expanded graphite seal 26, and is separated from the internal space 12a of the exhaust pipe 12 through which exhaust flows. A resin seal 28 is arranged in contact with the expanded graphite seal 26.

  <Operation of Embodiment 1> The expanded graphite seal 26 is disposed closer to the exhaust pipe 12 than the resin seal 28, so that the tip of the nozzle portion 6a is as shown by the broken arrow line. The heat received from the exhaust is immediately transferred to the housing 24a through the expanded graphite seal 26. Then, heat is radiated from the cooling fins 24b to the outside air side. That is, the urea water addition valve 6 is cooled by the air cooling mechanism 24. For this reason, the whole urea water addition valve 6 does not become high temperature.

  As for the resin seal 28, a heat flow is generated as indicated by the broken arrow line before heat is transferred from the nozzle portion 6a, the expanded graphite seal 26, or the housing 24a, so that most of the heat is released from the cooling fin 24b. The made seal 28 does not reach an excessively high temperature that degrades.

  Thus, although the resin seal 28 does not become excessively high temperature, it is in contact with the outer end of the expanded graphite seal 26, so that the heat transferred to the expanded graphite seal 26 from the nozzle portion 6 a or the exhaust gas. However, it quickly conducts the expanded graphite seal 26 in the axial direction and reaches the resin seal 28. In response to this heat, the temperature of the resin seal 28 rises early.

  For this reason, when the operation of the internal combustion engine is started, the resin seal 28 rapidly expands in heat and increases in flexibility. Thus, the resin seal 28 quickly fills the gap between the inner peripheral surface 24f of the addition valve storage space 24c and the outer peripheral surface 6c of the urea water addition valve 6, and comes into close contact with the inner peripheral surface 24f and the outer peripheral surface 6c. . Therefore, even when the resin seal 28 is not properly adhered to the inner peripheral surface 24f of the addition valve storage space 24c and the outer peripheral surface 6c of the urea water addition valve 6 due to creep deformation at room temperature, the resin seal 28 is rapidly heated during operation of the internal combustion engine. The filling property and the adhesiveness are improved at an early stage, and the function as a seal can be sufficiently achieved.

In the resin seal 28, an empty space 24 g exists on the side opposite to the side in contact with the expanded graphite seal 26. From this, for the thermal expansion of the resin seal 28 more than necessary, the empty space 24g serves as the thermal expansion space and absorbs the surplus volume that has been thermally expanded.
<Effects of Embodiment 1> (1) In this embodiment, a resin seal 28 is used instead of an O-ring as a seal structure for preventing leakage of exhaust gas and intrusion of water. In this way, the resin seal 28 can be formed into a shape adapted to the shapes of the inner peripheral surface 24f of the addition valve storage space 24c and the outer peripheral surface 6c of the urea water addition valve 6, unlike the O-ring.

  As a result, even if the shape of the inner peripheral surface 24f of the addition valve storage space 24c and the shape of the outer peripheral surface 6c of the urea water addition valve 6 are restricted, the restricted shape itself is sufficient as shown in FIG. It can be used as a sealable seating surface.

  As a result, the gap between the inner peripheral surface 24f of the addition valve storage space 24c having a shape restriction and the outer peripheral surface 6c of the urea water addition valve 6 can be sealed without causing a problem in durability.

  (2) Between the inner peripheral surface 24f of the addition valve storage space 24c and the outer peripheral surface 6c of the urea water addition valve 6, an expanded graphite seal 26 is disposed on the exhaust pipe 12 side of the resin seal 28. This prevents the resin seal 28 from receiving heat directly from the high-temperature exhaust.

Furthermore, the heat received from the exhaust at the front end side of the urea water addition valve 6 can be quickly released to the air cooling mechanism 24 by the expanded graphite seal 26, and the urea water addition valve 6 can be prevented from being damaged by heat.
(3) The resin seal 28 is in contact with the expanded graphite seal 26. As a result, the temperature of the resin seal 28 can be quickly increased to such an extent that heat transfer from the expanded graphite seal 26 does not cause thermal damage. With this temperature increase, the resin seal expands and the flexibility increases.

  As a result, the resin seal 28 fills and closely contacts the gap between the inner peripheral surface 24f of the addition valve storage space 24c and the outer peripheral surface 6c of the urea water addition valve 6. A reliable sealing effect can be achieved by this.

  (4) With respect to the resin seal 28, an empty space 24 g is provided on the side opposite to the expanded graphite seal 26. Since the empty space 24g exists in this manner, the empty space 24g becomes a thermal expansion space, and the resin seal 28 that has been thermally expanded does not cause excessive deformation or distortion. For this reason, the durability of the sealing structure by the resin seal 28 can be maintained.

[Embodiment 2]
<Configuration of Embodiment 2> In the present embodiment, as shown in FIG. 3, the inner peripheral surfaces 124f and 124i of the housing 124a of the air cooling mechanism 124 are portions where the one-step diameter is large, except for the insertion port 124d. The (inner peripheral surface 124i) exists at a position adjacent to the insertion port 124d.

A resin seal 128 corresponding to the shape of the inner peripheral surface 124 i and the outer peripheral surface 106 c of the urea water addition valve 106 is disposed at the position of the inner peripheral surface 124 i.
Since the step 124j exists between the two inner peripheral surfaces 124f and 124i, the resin seal 128 is supported by the step 124j without contacting the expanded graphite seal 126. As a result, a gap 124k exists between the resin seal 128 and the expanded graphite seal 126.

Other configurations of the air cooling mechanism 124 and the configurations of the urea water addition valve 106 and the exhaust pipe 112 are the same as those in the first embodiment.
<Operation of Second Embodiment> The cooling operation of the urea water addition valve 106 by the expanded graphite seal 126 is as described in the first embodiment.

In the present embodiment, since the resin seal 128 is not in contact with the expanded graphite seal 126, direct heat transfer is not performed from the expanded graphite seal 126. With this configuration, when the air cooling mechanism 124 is disposed at a position where the temperature of the expanded graphite seal 126 is particularly high, the gap 124k can prevent the temperature of the resin seal 128 from rising more than necessary. .
<Effects of Second Embodiment> (1) Except for (3) of the effects of the first embodiment, the same effects as those of the first embodiment are produced, and as a result, the addition valve storage space is restricted in shape The gap between the inner peripheral surface 124i of 124c and the outer peripheral surface 106c of the urea water addition valve 106 can be sealed without causing a problem in durability.

  (2) The height of the gap 124k between the resin seal 128 and the expanded graphite seal 126 can be adjusted by the height of the resin seal 128. As a result, the temperature of the resin seal 128 corresponding to the heat resistance of the resin seal 128 can be adjusted. Therefore, during operation of the internal combustion engine, the temperature can be raised in accordance with the material such as heat resistance, thermal expansion and flexibility of the resin seal 128.

[Other embodiments]
In each of the embodiments described above, the ammonia reducing agent added by the urea water addition valves 6 and 106 is urea water that generates ammonia by hydrolysis, but other ammonia reducing agents include: Ammonia gas may be used.

  DESCRIPTION OF SYMBOLS 2 ... Exhaust gas purification device, 4 ... SCR catalyst, 6 ... Urea water addition valve, 6a ... Nozzle part, 6b ... Step part, 6c ... Outer peripheral surface, 8 ... Urea water tank, 10 ... Pressure pump, 12 ... Exhaust pipe, 12a ... Internal space, 14 ... Filter, 16 ... Pressure regulating valve, 18 ... ECU, 20 ... Pressure sensor, 24 ... Air cooling mechanism, 24a ... Housing, 24b ... Cooling fin, 24c ... Addition valve storage space, 24d ... Insertion port, 24e ... Ring-shaped stopper, 24f ... Inner peripheral surface, 24g ... Empty space, 26 ... Expanded graphite seal, 28 ... Resin seal, 106 ... Urea water addition valve, 106c ... Outer peripheral surface, 112 ... Exhaust pipe, 124 ... Air cooling mechanism , 124a ... housing, 124c ... addition valve storage space, 124d ... insertion port, 124f, 124i ... inner peripheral surface, 124j ... step, 124k ... gap, 126 ... expanded graphite seal, 128 ... tree Ltd. seal.

Claims (6)

A seal structure between an addition valve for adding an ammonia-based reducing agent into an exhaust pipe of an internal combustion engine and a cooling mechanism for connecting the addition valve to the exhaust pipe in a cooled state;
Between the inner peripheral surface of the addition valve storage space formed in the cooling mechanism and the outer peripheral surface of the addition valve, an expanded graphite seal and a resin seal are sequentially arranged from the exhaust pipe side , and the expanded graphite An addition valve seal structure characterized in that a seal and the resin seal are brought into contact with each other . The addition valve seal structure according to claim 1, wherein the ammonia-based reducing agent is an aqueous urea solution. The addition valve seal structure according to claim 1, wherein the ammonia-based reducing agent is ammonia gas. The addition valve seal structure as described in any one of Claims 1-3 WHEREIN: The said cooling mechanism air-cools an addition valve, The addition valve seal structure characterized by the above-mentioned. The addition valve seal structure according to any one of claims 1 to 4 , wherein the resin seal is provided between an inner peripheral surface of an addition valve storage space formed in the cooling mechanism and an outer peripheral surface of the addition valve. The addition valve seal structure is characterized in that a thermal expansion space is provided on the opposite side of the expanded graphite seal. The addition valve seal structure according to any one of claims 1 to 5 , wherein the exhaust pipe has a nitrogen oxide purification catalyst disposed downstream of the addition valve, and the nitrogen oxide purification catalyst uses the nitrogen oxide purification catalyst. An addition valve seal structure, wherein the ammonia-based reducing agent produces a reducing action.

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