JP2020033897A - EGR valve - Google Patents

Abstract

To suppress deterioration of sealing performance of a lip seal provided in an EGR valve.SOLUTION: An EGR valve includes a valve housing 11 in which a gas passage having EGR gas flowing therein is formed. The EGR valve includes a valve shaft 20 displaced in the valve housing 11. The valve shaft 20 includes: a valve part seated on a valve seat provided in the gas passage to enable closing of the gas passage; and a stem part 21 to which the valve part is coupled. The EGR valve also includes a lip seal 30 for sealing between the valve housing 11 and the stem part 21. In the EGR valve, a rough surface 17A is provided in an abutment portion to the lip seal 30 of the valve housing 11.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an EGR valve applied to an EGR passage that connects an exhaust passage and an intake passage of an internal combustion engine.

  Patent Literature 1 discloses an EGR valve applied to an EGR passage that connects an exhaust passage and an intake passage of an internal combustion engine. The EGR valve includes a valve shaft having a valve portion capable of closing a gas passage by sitting on a valve seat, and an actuator for driving the valve shaft. The EGR valve opens and closes a gas passage by displacing a valve shaft by an actuator, and adjusts a flow rate of EGR gas flowing from an exhaust passage to an intake passage. A lip seal that seals between the housing of the EGR valve and the valve shaft is used for the EGR valve. The lip seal suppresses the EGR gas and the condensed water generated by condensing the moisture contained in the EGR gas from entering the actuator.

  In Patent Literature 1, a drain passage for discharging condensed water is formed in the housing of the EGR valve in order to suppress generated condensed water from remaining near the lip seal.

JP 2018-80584 A

  When the lip seal is exposed to EGR gas, dew condensation may occur. That is, condensed water may be generated on the surface of the lip seal. When the lip seal and the condensed water are in contact with each other, the condensed water is absorbed by the lip seal, and the lip seal may swell. When the lip seal is deformed due to swelling, a gap is generated, and the sealing property of the lip seal deteriorates.

  Even if the condensed water generated is discharged as in Patent Literature 1, there is a problem that if the lip seal swells due to dew condensation on the lip seal, the sealing performance is reduced.

  An EGR valve for solving the above problem is applied to an EGR passage that connects an exhaust passage and an intake passage of an internal combustion engine, and is an EGR valve that adjusts a flow rate of EGR gas flowing from the exhaust passage into the intake passage. A valve housing in which a gas passage through which the EGR gas flows is formed, a valve portion capable of closing the gas passage by sitting on a valve seat provided in the gas passage, and a shaft connected to the valve portion. A valve shaft that opens and closes the gas passage by displacing the valve portion by displacing the valve portion; and a lip seal that seals between the valve housing and the shaft portion. The gist of the present invention is to have a rough surface in a contact portion with the seal.

  When the lip seal is exposed to the EGR gas, the lower the temperature of the lip seal, the more easily dew condensation occurs. According to the configuration described above, the contact area between the valve housing and the lip seal can be increased as compared with a case where a rough surface is not formed at a contact portion of the valve housing with the lip seal. For this reason, the heat of the valve housing is easily transmitted to the lip seal, and the temperature of the lip seal tends to increase. Thereby, it is possible to suppress the occurrence of dew condensation when the lip seal is exposed to the EGR gas. That is, it is possible to suppress the deformation of the lip seal due to the swelling of the lip seal, and to suppress the deterioration of the sealing property.

FIG. 1 is a schematic diagram showing an internal combustion engine to which an embodiment of an EGR valve is applied. FIG. 2 is a cross-sectional view of the EGR valve according to the embodiment. FIG. 2 is a cross-sectional view showing the periphery of a lip seal of the EGR valve according to the embodiment.

Hereinafter, an embodiment of the EGR valve will be described with reference to FIGS.
The internal combustion engine 90 shown in FIG. 1 is an in-line four-cylinder internal combustion engine having cylinders # 1 to # 4. The internal combustion engine 90 includes an intake passage 91 that supplies air to a combustion chamber 93 of each cylinder. A throttle valve 92 is provided in the intake passage 91. The combustion chamber 93 is provided with a fuel injection valve 94 for injecting fuel and an ignition device 95 for generating spark discharge. In the combustion chamber 93, a mixture of air and fuel is burned. The internal combustion engine 90 includes an exhaust passage 96 that discharges the burned air-fuel mixture from the combustion chamber 93 as exhaust gas.

  The internal combustion engine 90 includes an EGR passage 81 that recirculates exhaust gas into the intake passage 91 as EGR gas. The EGR passage 81 connects a portion of the intake passage 91 downstream of the throttle valve 92 with the exhaust passage 96. The EGR passage 81 is provided with an EGR valve 10 for adjusting the cross-sectional area of the passage. The flow rate of the EGR gas flowing from the exhaust passage 96 into the intake passage 91 is adjusted by the opening degree of the EGR valve 10.

  The EGR valve 10 will be described with reference to FIG. A gas passage 12 through which EGR gas flows is formed in a valve housing 11 of the EGR valve 10. The gas passage 12 is formed to bend from the inlet 13 on the exhaust passage 96 side to the outlet 14 on the intake passage 91 side. An annular valve seat 15 is attached to the inlet 13 side of the gas passage 12.

  The EGR valve 10 includes a valve portion 23 that can close the gas passage 12 by sitting on the valve seat 15 from the inlet 13 side. FIG. 2 shows a state in which the valve portion 23 is seated on the valve seat 15 and the gas passage 12 is closed. The gas passage 12 is communicated when the valve portion 23 is separated from the valve seat 15. The EGR valve 10 includes a valve shaft 20 having a valve portion 23 and a shaft portion 21. The valve portion 23 is attached to one end of the shaft portion 21 of the valve shaft 20.

  The valve shaft 20 is housed in the valve housing 11. The valve housing 11 is formed with a shaft housing 16 which is a cylindrical hole for housing the shaft 21 of the valve shaft 20. The shaft housing 16 communicates with the gas passage 12. The shaft portion 21 of the valve shaft 20 is supported via a first cylindrical bearing 41 and a second cylindrical bearing 43 disposed in the shaft housing portion 16 so as to be vertically displaceable in the drawing. . The first cylindrical bearing 41 and the second cylindrical bearing 43 are arranged side by side in the axial direction of the valve shaft 20. The second cylindrical bearing 43 partially projects from the valve housing 11. The first cylindrical bearing 41 is disposed closer to the gas passage 12 than the second cylindrical bearing 43 is.

  In the shaft housing portion 16 of the valve housing 11, on the gas passage 12 side of the first cylindrical bearing 41, there is provided a seal housing portion 17 in which a hole is wider in a radial direction than a portion where the first cylindrical bearing 41 is arranged. Is formed. An annular lip seal 30 is arranged in the seal accommodating portion 17. The shaft 21 of the valve shaft 20 is inserted into a hole of the lip seal 30. When the valve shaft 20 is displaced, the shaft portion 21 slides on the inner peripheral surface of the lip seal 30. The lip seal 30 seals between the shaft portion 21 and the valve housing 11.

  An annular guard ring 42 is attached to the shaft passage 16 on the gas passage 12 side of the lip seal 30. The portion of the shaft housing 16 to which the guard ring 42 is attached has a hole that extends more radially than the seal housing 17. The guard ring 42 is formed of a metal material. The guard ring 42 is located at an end of the shaft housing 16 on the gas passage 12 side. The shaft 21 of the valve shaft 20 is inserted into a hole of the guard ring 42. The diameter of the hole of the guard ring 42 is made larger than the diameter of the shaft portion 21, and the shaft portion 21 is inserted so as not to contact the guard ring 42.

  The EGR valve 10 includes an actuator 50 for displacing the valve shaft 20. The actuator 50 is attached to the valve housing 11. The actuator 50 includes a coil 52 housed in a case 51. The case 51 is provided with a connector 53 having a terminal 53A for energizing the coil 52.

  A magnet rotor 54 is disposed inside the coil 52. The magnet rotor 54 has a rotor main body 54A connected to the valve shaft 20, and a cylindrical magnet portion 54B covering the outer periphery of the rotor main body 54A. The end of the shaft portion 21 on the side opposite to the valve portion 23 of the valve shaft 20 is connected to the rotor main body 54A. The rotor body 54 </ b> A and the shaft 21 are connected by a screw mechanism 55. A first ball bearing 56 is mounted between the rotor body 54A and the case 51. A second ball bearing 58 is provided inside the magnet portion 54B. The second ball bearing 58 is attached to the second cylindrical bearing 43 projecting from the valve housing 11 at the end of the magnet rotor 54 opposite to the rotor body 54A. The magnet rotor 54 is rotatably supported in the case 51 by a first ball bearing 56 and a second ball bearing 58.

  A first spring 57 and a second spring 59 are provided inside the magnet portion 54B. The first spring 57 urges the magnet rotor 54 toward the first ball bearing 56. The second spring 59 urges the valve shaft 20 in a direction in which the valve portion 23 is pressed against the valve seat 15.

  In the actuator 50, the magnet rotor 54 can be rotated by energizing the coil 52. The rotational movement of the magnet rotor 54 is converted into a linear movement along the axial direction of the valve shaft 20 via the screw mechanism 55. As a result, the valve shaft 20 is displaced vertically in the drawing. As described above, the valve shaft 20 can be displaced by the actuator 50, and the displacement of the valve shaft 20 causes the valve portion 23 to be separated from the valve seat 15 and the valve portion 23 to be seated on the valve seat 15. Can be.

The structure around the lip seal 30 will be described in detail with reference to FIG.
The lip seal 30 has an annular core portion 31 formed of a metal material, and a seal portion 32 held by the core portion 31. The seal portion 32 is made of rubber or the like having elasticity.

  In the cross-section shown in FIG. 3, the shape of the annular core portion 31 on one side of the shaft portion 21 is U-shaped. The length of the core portion 31 in the axial direction of the valve shaft 20 is longer on the valve housing 11 side than on the shaft portion 21 side. The core portion 31 of the lip seal 30 is covered by the seal portion 32, but a part thereof is exposed on the outer surface of the lip seal 30. The core portion 31 has a first exposed portion 31A exposed on the side surface of the lip seal 30 and a second exposed portion 31B exposed on the top surface of the lip seal 30 on the first cylindrical bearing 41 side. The first exposed portion 31 </ b> A is located on the gas passage 12 side of the side surface of the lip seal 30.

  The wall surface of the seal accommodating portion 17, which is the inner peripheral surface of the valve housing 11, has a rough surface 17A having a large surface roughness in order to increase the contact area between the valve housing 11 and the lip seal 30. The rough surface 17 </ b> A is formed on a wall surface facing the side surface of the lip seal 30 and a wall surface facing the top surface of the lip seal 30. The lip seal 30 housed in the seal housing part 17 is in contact with the rough surface 17A. The rough surface 17A shown in FIG. 3 is a schematic one, and does not impair the sealing property of the lip seal 30 by the rough surface 17A.

  Further, the shaft portion 21 of the valve shaft 20 is formed hollow. A heat conductive material 22 having a higher thermal conductivity than the material of the shaft portion 21 is sealed in the shaft portion 21. As the heat conductive material 22, for example, sodium can be adopted. The heat conductive material 22 is sealed in a range from a position where the valve portion 23 of the valve shaft 20 is in contact with the valve seat 15 to a position where the valve portion 23 contacts the lip seal 30 on the valve portion 23 side.

The operation and effect of the present embodiment will be described.
In the EGR valve 10, the seal accommodating portion 17 accommodating the lip seal 30 has a rough surface 17A. For this reason, the contact area between the valve housing 11 and the lip seal 30 is larger than when the rough surface 17A is not formed in the seal housing portion 17. Thereby, the heat of the valve housing 11 is easily transmitted to the lip seal 30, and the temperature of the seal portion 32 of the lip seal 30 is easily increased. When the temperature of the lip seal 30 is low, dew condensation may occur on the surface of the lip seal 30 when the lip seal 30 is exposed to the EGR gas. According to this, it is possible to suppress the occurrence of dew condensation when the lip seal 30 is exposed to the EGR gas. For this reason, swelling of the seal portion 32 due to the condensation water being absorbed by the seal portion 32 due to the occurrence of dew condensation can be suppressed. Since the deformation of the seal portion 32 caused by the swelling can be suppressed, a decrease in the sealing performance of the lip seal 30 can be suppressed.

  Further, the lip seal 30 of the EGR valve 10 has a first exposed portion 31A and a second exposed portion 31B where the core portion 31 is exposed. The heat of the valve housing 11 can be transmitted to the core 31 from the direction orthogonal to the axial direction of the valve shaft 20 by the first exposed portion 31A. The heat of the valve housing 11 can be transmitted to the core 31 from the axial direction of the valve shaft 20 by the second exposed portion 31B. By increasing the temperature of the core 31 in this way, the temperature of the seal 32 held by the core 31 can be increased. That is, the temperature of the seal portion 32 can be increased by the heat directly transmitted from the valve housing 11 to the seal portion 32 and the heat transmitted from the valve housing 11 to the inside of the seal portion 32 via the core portion 31. Thereby, the temperature of the seal portion 32 of the lip seal 30 can be increased more quickly. By increasing the temperature of the seal portion 32 more quickly, the occurrence of dew can be suppressed, and the swelling of the seal portion 32 due to the occurrence of dew can be suppressed. Since the deformation of the seal portion 32 caused by the swelling can be suppressed, a decrease in the sealing performance of the lip seal 30 can be suppressed.

  In the valve shaft 20 of the EGR valve 10, a heat conductive material 22 is sealed in a shaft portion 21. Therefore, the thermal conductivity of the shaft portion 21 is high. That is, the heat transmitted to the shaft portion 21 is easily transmitted to the lip seal 30 in contact with the shaft portion 21. Thus, the temperature of the lip seal 30 can be increased also from the shaft portion 21 side. By increasing the temperature of the seal portion 32 of the lip seal 30 more quickly, the occurrence of dew condensation can be suppressed, and the swelling of the seal portion 32 due to the occurrence of dew condensation can be suppressed. Since the deformation of the seal portion 32 caused by the swelling can be suppressed, a decrease in the sealing performance of the lip seal 30 can be suppressed.

This embodiment can be implemented with the following modifications. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
In the above embodiment, the heat conductive material 22 is sealed in the hollow shaft portion 21, but the heat conductive material 22 does not always have to be sealed. Further, the solid shaft portion may be formed of a single material.

  In the above embodiment, the core portion 31 of the lip seal 30 has the first exposed portion 31A and the second exposed portion 31B, but the position where the core portion 31 is exposed in the lip seal 30 can be changed. . The position where the core 31 is exposed in the lip seal 30 is preferably a position where heat generated by combustion in the combustion chamber of the internal combustion engine 90 is easily transmitted.

In the above embodiment, the core portion 31 of the lip seal 30 has the first exposed portion 31A and the second exposed portion 31B, but the entire core portion 31 may be covered by the seal portion 32.
In the above embodiment, the rough surface 17 </ b> A may be formed on a part of the wall surface of the seal housing 17. For example, the surface roughness may be increased only on the wall surface in the direction orthogonal to the axial direction of the valve shaft 20 with respect to the lip seal 30 housed in the seal housing portion 17, that is, the wall surface facing the side surface of the lip seal 30. .

  In the above embodiment, the configuration is adopted in which the seating of the valve portion 23 on the valve seat 15 and the separation of the valve portion 23 from the valve seat 15 are performed by displacement of the valve shaft 20 in the axial direction. As the EGR valve 10, for example, a butterfly valve that displaces the valve portion by rotating the valve shaft around the central axis of the valve shaft to perform seating and separation of the valve portion can also be employed. Even in this case, by applying the lip seal 30 and the seal accommodating portion 17 in the above embodiment, the same effects as in the above embodiment can be obtained.

  In the above embodiment, the internal combustion engine 90 to which the EGR valve 10 is applied is an in-line four-cylinder internal combustion engine. However, the EGR valve 10 can be applied to an internal combustion engine having an EGR passage 81.

  DESCRIPTION OF SYMBOLS 10 ... EGR valve, 11 ... Valve housing, 12 ... Gas passage, 13 ... Inlet, 14 ... Outlet, 15 ... Valve seat, 16 ... Shaft accommodation part, 17 ... Seal accommodation part, 17A ... Rough surface, 20 ... Valve shaft, Reference numeral 21: shaft portion, 22: heat conductive material, 23: valve portion, 30: lip seal, 31: core portion, 31A: first exposed portion, 31B: second exposed portion, 32: seal portion, 41: first cylinder 42, guard ring, 43, second cylindrical bearing, 50, actuator, 51, case, 52, coil, 53, connector, 53A, terminal, 54, magnet rotor, 54A, rotor body, 54B, magnet part 55, a screw mechanism, 56, a first ball bearing, 57, a first spring, 58, a second ball bearing, 59, a second spring, 81, an EGR passage, 90, an internal combustion engine, 91, an intake passage , 92 ... throttle valve, 93 ... combustion chamber, 94 ... Fuel injection valve 95 ... ignition device, 96 ... exhaust passage.

Claims (1)

An EGR valve that is applied to an EGR passage that connects an exhaust passage and an intake passage of an internal combustion engine, and adjusts a flow rate of EGR gas flowing from the exhaust passage to the intake passage,
A valve housing in which a gas passage through which the EGR gas flows is formed;
The valve includes a valve portion that can close the gas passage by seating on a valve seat provided in the gas passage, and a shaft portion to which the valve portion is connected. A valve shaft to open and close the
A lip seal for sealing between the valve housing and the shaft portion,
An EGR valve having a rough surface at a contact portion of the valve housing with the lip seal.