JP2010014205A - Sealing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing device capable of retaining a sealing function even if pressure is accumulated in a space between a first seal part and a second seal part. <P>SOLUTION: The sealing device is characterized in that a communication hole 20 having a membrane part 23 provided to block a gap between a first opening 21 opened into a sealed space S and a second opening 22 opened into a low pressure side L and connecting the first opening 21 to the second opening before a pressure of the sealed space S rises to a pressure of a degree causing breakage of the seal lips, when the pressure of the sealed space S rises with respect to a pressure of the low pressure side L, and capable of connecting the sealed space S with the low pressure side L by connecting the first opening 21 to the second opening by the membrane part 23, is provided in a second seal part 12 disposed in the low pressure side L of a first seal part 11 of the sealing device 1 for a fuel pump and having the seal lips 16, 17 slidably contacting a surface 301 of a shaft 300. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sealing device for a fuel pump, for example, for pressurizing fuel to a high pressure.

  2. Description of the Related Art In recent years, internal combustion engines such as diesel engines and gasoline engines have often employed a method in which high pressure fuel is directly injected into a cylinder and burned in order to improve performance such as low fuel consumption and high output. . Such an internal combustion engine is equipped with a pump for increasing the pressure of the fuel, and a sealing device as shown in FIG. 3 is used for a plunger (shaft) portion of the high-pressure fuel pump. FIG. 3 is a schematic half sectional view of a sealing device according to the prior art.

  The sealing device 101 is used to prevent the fuel from flowing out from the sliding portion side of the plunger (shaft) to the cam side and to prevent oil from entering the plunger sliding portion side from the cam side. It is.

  The sealing device 101 is installed at the end of the housing 111, and high pressure fuel (gasoline, alcohol, light oil, etc.) is supplied to the high pressure side H that is the sealing target side, and the low pressure side L that is the anti sealing target side. Is sealed with oil for lubrication and cooling purposes.

  The sealing device 101 includes a metal ring 102 having a cylindrical portion 102a fitted to the outer periphery of the end portion of the housing 111, and an inward flange portion 102b provided at the low pressure side L end of the cylindrical portion 102a of the metal ring 102. And first and second seal lips 103, 104 made of rubber-like elastic material that extend to the low-pressure side L and slidably contact the shaft 110, respectively.

  However, in such a sealing device, there is a risk of excessive wear and damage of the seal lip made of a thin rubber elastic body. It is necessary to keep the fuel pressure within the range of 0 to 0.6 MPa. This complicates the pump structure and increases the cost.

  On the other hand, as a sealing device that can be used under high pressure without requiring addition of a drain port or the like, Patent Document 1 proposes a sealing device as shown in FIG. FIG. 4 is a schematic half sectional view of another sealing device according to the prior art.

  As shown in FIG. 4, the sealing device 201 is attached to the end portion of the housing 111 whose inner diameter is enlarged from the high-pressure side H in the order of the first seal portion 202 and the second seal portion 203.

  The first seal portion 202 includes a resin ring 221 as a resin seal member that slidably seals with the shaft 110 and an O-ring 222 as an urging member that urges the resin ring 221 toward the shaft 110. Is done.

  The second seal portion 203 is fitted into the mounting groove of the seal retainer 204, and the second seal portion 203 abuts and slides on the shaft 110 to seal the low pressure side L. The second seal portion 203 uses an X ring 231 that is a squeeze packing.

However, since this sealing device 201 does not include a mechanism for avoiding the occurrence of pressure accumulation in the sealed space between the first seal portion 202 and the second seal portion 203, sliding resistance is generated by the occurrence of pressure accumulation. May increase, resulting in seal breakage or the like, and the seal function may not be maintained.

Patent Document 1 also discloses a configuration in which a lip packing having a substantially U-shaped cross section is used as the second seal portion. In this configuration, the seal lip of the second seal portion is a low pressure of the lip packing. Since only the seal lip extending to the side L is provided, there is a possibility that the liquid on the high pressure side H is pumped out to the low pressure side L depending on the operating conditions. Therefore, although there is little risk of damage to the seal, many leaks will occur, and the operating conditions will be restricted in order to maintain the sealing function.
WO2002 / 099320

  The present invention has been made in order to solve the above-described problems of the prior art, and an object of the present invention is to provide a sealing function even if pressure accumulation occurs in the sealed space between the first seal portion and the second seal portion. An object of the present invention is to provide a sealing device capable of maintaining the above.

In order to achieve the above object, a sealing device according to the present invention comprises:
A first seal on one side in the axial direction is formed in an annular gap formed between a shaft provided so as to reciprocate relatively in the axial direction in the fuel pump and a housing having a shaft hole through which the shaft is inserted. In order to prevent the fuel existing in the region from entering the second sealed region on the other side in the axial direction, and to prevent the oil present in the second sealed region from entering the first sealed region. A sealing device comprising: a first seal portion disposed on a sealed region side; and a second seal portion disposed on a second sealed region side,
The second seal portion is
A seal lip that slidably contacts one surface of the shaft and the shaft hole;
A first opening that opens into a sealed space between the first seal portion and the second seal portion; a second opening that opens into the second sealing region; and the first opening and the second opening. And when the pressure in the sealed space rises relative to the pressure in the second sealed region, the pressure in the sealed space rises to a height that causes damage to the seal lip. A membrane portion that communicates between the first opening and the second opening, and the membrane portion communicates between the first opening and the second opening to thereby provide the sealed space. And a communication hole capable of communicating with the second sealing region,
It is characterized by providing.

  According to such a configuration, even if pressure accumulation occurs in the sealed space between the first seal portion and the second seal portion, the membrane portion has the communication hole before the seal lip is damaged due to an increase in sliding resistance or the like. By communicating between the first opening and the second opening, the space between the first seal part and the second seal part and the second sealing region communicate with each other. Thereby, the rise in the pressure of the sealed space between the first seal portion and the second seal portion is suppressed, and damage to the seal lip can be prevented.

  When pressure builds up in the sealed space between the first seal part and the second seal part, the film part communicates between the first opening part and the second opening part of the communication hole. It is good to have such a configuration.

  That is, when the pressure in the sealed space rises with respect to the pressure in the second sealed region, the membrane portion has the first opening and the second opening before the seal lip is damaged. It is good to have a thickness that causes breakage so that it can communicate.

  In this case, it is preferable that the thickness of the film portion is smaller than the thickness of the seal lip.

Alternatively, the membrane part is
The oil has a small hole that is blocked by being held by surface tension,
When the pressure in the sealed space rises with respect to the pressure in the second sealed region, the first opening portion is deformed so that the small hole expands before the seal lip is damaged. You may make it communicate with the said 2nd opening part.

  According to such a configuration, when pressure accumulation occurs in the sealed space between the first seal portion and the second seal portion, the first opening portion and the second opening portion of the communication hole are preferably communicated. Can do.

  As described above, according to the present invention, it is possible to maintain the sealing function even if pressure accumulation occurs in the sealed space between the first seal portion and the second seal portion.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. .

(Example)
With reference to FIG.1 and FIG.2, the sealing device based on the Example of this invention is demonstrated. FIG. 1 is a schematic cross-sectional view of a sealing device according to the present embodiment. FIG. 2 is a schematic diagram for explaining the configuration of the second seal portion of the sealing device according to the present embodiment, where (a) is a half sectional view of the second seal portion, and (b) is an arrow A in (a). FIG. 4C is a perspective view of the second seal portion.

  The sealing device 1 according to this embodiment is used as a plunger seal of a fuel pump provided in an internal combustion engine such as a gasoline direct injection engine, and prevents fuel from flowing out from the sliding portion side of the plunger (shaft) to the cam side. In addition, it is a so-called two-liquid seal that prevents oil from entering from the cam side to the plunger sliding portion side.

  As shown in FIG. 1, the sealing device 1 seals an annular gap between the housing 200 and the shaft 300 inserted through the shaft hole 201 of the housing 200. Fuel (gasoline, alcohol, light oil, etc.) that is a fluid to be pressurized in the fuel pump is present on the high-pressure side H that is the first sealing region on the one axial side of the annular gap. In addition, oil for lubrication and cooling is sealed in the low pressure side L which is the second sealing region on the other side in the axial direction.

  The sealing device 1 is generally composed of a first seal portion 11 disposed on the high pressure side H and a second seal portion 12 disposed on the low pressure side L. The first seal portion 11 and the second seal portion 12 are attached to a first annular groove 211 and a second annular groove 212 provided on the inner peripheral surface of the shaft hole 201 of the housing 200, respectively.

  The first seal portion 11 is mounted between a resin-made seal ring 13 having a substantially rectangular cross section that is slidably in contact with the outer peripheral surface 301 of the shaft 300, and between the seal ring 13 and the groove bottom 213 of the first annular groove 211. The rubber ring 14 is made up of. The rubber ring 14 is mounted in a compressed state between the seal ring 13 and the groove bottom 213, and the seal ring 13 is urged toward the outer peripheral surface 301 of the shaft 300 by its elastic repulsive force. 13 sealability is improved.

  The second seal portion 12 is a seal ring having a substantially X-shaped cross section in which four seal lips extend from both inner and outer peripheral sides at both ends in the axial direction of the annular seal body 15, for example, fluorine rubber, acrylic rubber, etc. Made of rubber material. The seal lip 16 extending from the seal body 15 to the high pressure side H and the shaft 300 side and the seal lip 17 extending to the low pressure side L and the shaft 300 side slidably contact the outer peripheral surface 301 of the shaft 300. The seal lip 18 extending from the seal body 15 to the high pressure side H and the groove bottom 214 side and the seal lip 19 extending to the low pressure side L and the groove bottom 214 side are in close contact with the groove bottom 214.

  In the sealing device 1 configured as described above, the first seal portion 11 mainly serves as a fuel seal portion in the plunger seal of the fuel pump, and high-pressure fuel such as gasoline is mainly fed from the high-pressure side H to the low-pressure side L (first Intrusion into the sealed space S) between the seal part 11 and the second seal part 12 is prevented. The second seal portion 12 mainly serves as an oil seal portion to prevent oil such as engine oil from entering the high pressure side H (sealed space S) from the low pressure side L.

  In FIG. 1, the first seal portion 11 and the second seal portion 12 are sandwiched between the housing 200 and the shaft 300 and are not compressed and deformed for easy understanding of the dimensional relationship between the housing 200 and the shaft 300. It is illustrated in the state.

  Here, in the sealing device 1 according to the present embodiment, a hole 20 extending in the axial direction is provided in the seal body 15 of the second seal portion 12. The hole 20 includes a first opening 21 that opens into the sealed space S, a second opening 22 that opens to the low-pressure side L, and a film portion 23 that blocks between the first opening 21 and the second opening 22. ,have.

  When pressure accumulation is generated in the sealed space S, the film portion 23 is damaged by receiving pressure in the sealed space S, and the first opening 21 side and the second opening 22 side of the hole 20 are communicated. It is provided as follows. A plurality of holes 20 are provided on the circumference of the seal body 15.

  The sealed space S that is sealed by the first seal portion 11 and the second seal portion 12 gradually increases in internal pressure due to the reciprocating movement between the shaft 300 and the housing 200 in the axial direction, and the low pressure side L The pressure may increase with respect to the pressure (occurrence of pressure accumulation). In such a state, depending on the pressure in the sealed space S, the behavior of the seal lip becomes unstable, or the force with which the seal lip is pressed against the mating member increases, thereby causing the housing 200 and the shaft 300 to move. In some cases, the sliding resistance increases, and the seal lip may be damaged.

  The sealing device 1 according to the present embodiment is configured such that the hole 20 provided in the seal body 15 of the second seal portion 12 changes to a communication hole that connects the sealed space S and the low-pressure side L due to breakage of the membrane portion 23. It has become. Thereby, the pressure in the sealed space S can be released to the low pressure side L, and further increase in the pressure in the sealed space S is suppressed. Therefore, it is possible to prevent the seal lip from being damaged due to the occurrence of pressure accumulation. That is, even if pressure accumulation occurs in the sealed space S between the first seal portion 11 and the second seal portion 12, the sealing function can be maintained.

  Here, the film part 23 is formed with the same material as each seal lip, and is formed with a thickness sufficiently thinner than the thickness of the seal lip. Therefore, the membrane portion 23 is damaged before each seal lip is damaged due to an increase in pressure in the sealed space S.

Further, in the fuel pump, the oil on the low pressure side L is not normally filled in a large amount in the space on the low pressure side L, and the oil that can enter the hole 20 is an amount of splash level. Only a small amount is reached (to the extent that it passes through the oil film). That is, there is a low possibility that the oil on the low pressure side L passes through the hole 20 penetrating to the sealed space S and enters the sealed space S side. Therefore, even after the membrane portion 23 is damaged, the sealing performance is not significantly lowered and it can be used continuously.

  Further, the membrane portion 23 does not need to completely close the hole 20 and is small in the membrane portion 23 as long as the fluid to be used is of a size that can be closed by being held by its surface tension. A hole may be opened. With such a small hole, when pressure accumulation has not occurred, the fluid is held by the surface tension and closed, so that the fluid does not pass through the second seal portion 12, and when pressure accumulation occurs, The accumulated pressure can be released by expanding the hole. Therefore, the initial sealing function can be maintained for a long time.

  In the above embodiment, the configuration in which the sealing device is mounted in the annular groove provided in the shaft hole of the housing has been described, but the sealing device may be mounted in the annular groove provided in the outer peripheral surface of the shaft. The present invention can be preferably applied.

  Moreover, although the said Example demonstrated only the usage example as a plunger seal in a fuel pump, as a use as a 2 liquid seal | sticker which seals between two sealing area | regions, it is not restricted to this.

  For the first seal portion, so-called U packing, SP seal, spring seal, or the like can be applied. However, in order to cope with various fuels (gasoline, alcohol, light oil, etc.), it can be said that an SP seal (combination of a seal ring and a rubber ring) having a sliding surface as a resin material is desirable. Further, the cross-sectional shape of the seal ring is not limited to the rectangular cross-section as in the above embodiment.

It is typical sectional drawing of the sealing device which concerns on an Example. It is a schematic diagram explaining the structure of the 2nd seal part of the sealing device which concerns on an Example. It is typical sectional drawing of the sealing device which concerns on a prior art. It is typical sectional drawing of the other sealing device which concerns on a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sealing device 11 1st seal part 12 2nd seal part 13 Seal ring 14 Rubber ring 15 Seal main body 16, 17, 18, 19 Seal lip 20 Hole 21 1st opening part 22 2nd opening part 23 Film | membrane part 200 Housing 201 Shaft Hole 211 First annular groove 212 Second annular groove 213, 214 Groove bottom 300 Shaft (plunger)
301 outer peripheral surface

Claims (4)

A first seal on one side in the axial direction is formed in an annular gap formed between a shaft provided so as to reciprocate relatively in the axial direction in the fuel pump and a housing having a shaft hole through which the shaft is inserted. In order to prevent the fuel existing in the region from entering the second sealed region on the other side in the axial direction, and to prevent the oil present in the second sealed region from entering the first sealed region. A sealing device comprising: a first seal portion disposed on a sealed region side; and a second seal portion disposed on a second sealed region side,
The second seal portion is
A seal lip that slidably contacts one surface of the shaft and the shaft hole;
A first opening that opens into a sealed space between the first seal portion and the second seal portion; a second opening that opens into the second sealing region; and the first opening and the second opening. And when the pressure in the sealed space rises relative to the pressure in the second sealed region, the pressure in the sealed space rises to a height that causes damage to the seal lip. A membrane portion that communicates between the first opening and the second opening, and the membrane portion communicates between the first opening and the second opening to thereby provide the sealed space. And a communication hole capable of communicating with the second sealing region,
A sealing device comprising:   When the pressure in the sealed space rises with respect to the pressure in the second sealed region, the membrane portion communicates between the first opening and the second opening before the seal lip is damaged. The sealing device according to claim 1, wherein the sealing device has a thickness that causes damage.   The sealing device according to claim 2, wherein a thickness of the film portion is smaller than a thickness of the seal lip. The membrane part is
The oil has a small hole that is blocked by being held by surface tension,
When the pressure in the sealed space rises with respect to the pressure in the second sealed region, the first opening portion is deformed so that the small hole expands before the seal lip is damaged. The sealing device according to claim 1, wherein the sealing device communicates with the second opening.

Images