JP6673729B2 - Flow control valve - Google Patents

Description

  The present invention relates to a flow control valve for controlling a flow rate of a fluid, for example, an EGR valve used for an exhaust gas recirculation device.

  Conventionally, an exhaust gas recirculation device has been used in an engine. This exhaust gas recirculation device recirculates part of the exhaust gas discharged from the engine to the intake system as EGR gas, mixes it with outside air, and sucks it into the combustion chamber. This lowers the combustion temperature of the combustible mixture in the combustion chamber, so that the amount of nitrogen oxide (NOx) generated in the exhaust gas can be reduced. And such an exhaust gas recirculation device has a flow control valve (EGR valve) for controlling the flow rate of the EGR gas.

  Here, as an example of such a flow control valve (EGR valve), for example, there is a fluid control valve described in Patent Document 1. In this fluid control valve, a butterfly valve is held and fixed to a valve shaft, and welds are formed at two joints between the butterfly valve and the valve shaft.

JP 2007-239667 A

  In the fluid control valve described in Patent Literature 1, a welded portion is formed at two joints between the butterfly valve and the valve shaft, but the butterfly valve and the valve shaft are welded due to heat shrinkage generated at the welded portion during welding. There is a possibility that it will be displaced by being pulled by the part.

  Therefore, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a flow control valve capable of preventing a positional displacement between a valve body and a shaft due to thermal contraction generated during welding. I do.

One embodiment of the present invention made to solve the above problem has a valve body, and a shaft that rotates the valve body by rotating about an axis, and the shaft has a through hole provided in the valve body. A flow control valve which is welded to the valve body in a state where it is inserted into the through hole and at least a part of the outer circumferential surface of the shaft in a circumferential direction and having a larger curvature than an inner circumferential surface of the through hole; At a linear contact portion where the inner peripheral surface of the hole is in linear contact with the shaft along the axial direction, a welded portion where the valve body and the shaft are welded, and the linear contact portion at both sides in the axial direction of the shaft with respect to the weld portion, and a non-welded portion in which the valve body and said shaft is not welded, have a, the weld of a predetermined in a linear direction of said linear contact portion it has a length, a And butterflies.

  According to this aspect, the non-welded portions are formed on both sides of the welded portion. Therefore, at the time of forming the welded portion, that is, at the time of welding the valve body and the shaft, even if thermal contraction due to welding occurs at the welded portion, the contact state between the valve body and the shaft is secured at the non-welded portion. Thus, the valve body and the shaft are less likely to be pulled toward the weld. Therefore, it is possible to prevent a positional displacement between the valve body and the shaft due to thermal contraction generated at the time of welding.

  Further, the valve body and the shaft are welded at a single welded portion, and only one welding operation in the axial direction of the shaft at the linear contact portion is required. Therefore, the time required for the work of welding the valve body and the shaft can be reduced.

  In the above aspect, the shaft is provided with a reference position for positioning the shaft at a predetermined position in the axial direction of the shaft in the flow control valve, and the welded portion is provided on the shaft. In the axial direction, it is preferable that a welding start portion is provided at an end portion on the reference position side, and a welding end portion is provided at an end portion opposite to the reference position.

  According to this aspect, the portion on the reference position side of the shaft is hardly affected by heat shrinkage generated by welding. Therefore, there is no displacement of the reference position of the shaft, and the shaft can be maintained at a predetermined position in the flow control valve.

  In the above aspect, it is preferable that the welded portion is laser-welded.

  According to this aspect, since heat generated during welding is relatively small, it is possible to suppress the occurrence of heat shrinkage in the welded portion. Therefore, it is difficult for the valve body and the shaft to be pulled toward the welded portion due to thermal contraction generated during welding. Therefore, it is possible to prevent a positional displacement between the valve body and the shaft due to thermal contraction generated at the time of welding.

  ADVANTAGE OF THE INVENTION According to the flow control valve of this invention, it can prevent that a positional displacement of a valve body and a shaft arises by the heat contraction which arises at the time of welding.

It is a front view of an electric EGR valve. FIG. 2 is a top view of the electric EGR valve. FIG. 4 is a perspective view showing a partially broken valve portion in a fully closed state in which a valve body is seated on a valve seat. FIG. 5 is a perspective view showing a partially broken valve portion in a fully opened state in which a valve body is farthest from a valve seat. It is a side view showing a valve seat, a valve element, and a shaft of a fully closed state. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG. It is CC sectional drawing of FIG. FIG. 4 is a diagram when the valve element and the shaft are viewed from the tip end side of a pin of the shaft. It is the figure at the time of seeing a valve element and a shaft from the drawing upper side of FIG. It is DD sectional drawing of FIG. It is the figure which showed typically the curvature of the inner peripheral surface of the through-hole of a valve body, and the curvature of the outer peripheral surface of the pin of a shaft. It is a figure showing the influence of heat contraction generated by welding progress direction and welding in this embodiment. FIG. 4 is a diagram illustrating the influence of the welding progress direction and the heat shrinkage generated by welding in a comparative example.

  The EGR valve 1, which is an example of the flow control valve of the present invention, will be described below.

  As shown in FIGS. 1 and 2, the EGR valve 1 includes a valve unit 2 configured by a double eccentric valve, and a drive mechanism unit 3. The valve section 2 includes a pipe section 12 (see FIG. 7) having a flow path 11 through which EGR gas as a fluid flows. Inside the flow path 11, a valve seat 13, a valve body 14, and a shaft 15 (rotating shaft) are provided. ) (See FIGS. 7 and 8). A driving force (rotational force) is transmitted to the shaft 15 from the driving mechanism 3. The drive mechanism 3 includes a motor 32 and a speed reduction mechanism 33 (see FIGS. 7 and 8).

  As shown in FIGS. 3 and 4, a step portion 10 is formed in the flow path 11, and a valve seat 13 is incorporated in the step portion 10. The valve seat 13 has an annular shape and has a valve hole 16 at the center. An annular seat surface 17 is formed at the edge of the valve hole 16. The valve body 14 has a disk-shaped portion, and an annular sealing surface 18 corresponding to the seat surface 17 is formed on the outer periphery of the disk-shaped portion. The valve body 14 is provided integrally with the shaft 15 and rotates integrally with the shaft 15. 3 and 4, the flow path 11 below the valve element 14 indicates the upstream side of the flow of the EGR gas, and the flow path 11 above the valve seat 13 indicates the downstream side of the flow of the EGR gas. That is, the valve element 14 in the flow path 11 is disposed on the upstream side of the flow of the EGR gas with respect to the valve seat 13.

  As shown in FIGS. 5 and 6, the central axis Ls of the shaft 15 extends in parallel with the radial direction of the valve element 14, and extends from the central axis Lv of the valve element 14 in the radial direction of the valve element 14 (the center P1 of the valve hole 16). And a radial direction of the valve hole 16), and the sealing surface 18 of the valve element 14 is eccentrically disposed in a direction in which the central axis Lv of the valve element 14 extends from the central axis Ls of the shaft 15. Thus, the valve part 2 is constituted by a double eccentric valve. Further, by rotating the valve body 14 about the central axis Ls of the shaft 15, the seat surface 18 of the valve body 14 comes into contact with the seat surface 17 of the valve seat 13 in a fully closed position (see FIG. 3). It is movable between a fully open position (see FIG. 4) farthest from the surface 17.

  As shown in FIGS. 7 and 8, the valve housing 35 made of metal or synthetic resin includes the flow path 11 and the pipe 12. An end frame 36 made of metal or synthetic resin closes an open end of the valve housing 35. The valve body 14 and the shaft 15 are provided on a valve housing 35. The shaft 15 has a pin 15a protruding from the tip. Thus, the pin 15a is provided at one end (on the valve element 14 side) in the direction of the center axis Ls (see FIG. 8) of the shaft 15. A base end 15b is provided at the other end of the shaft 15 in the direction of the center axis Ls (on the side of the main gear 41).

  The distal end of the shaft 15 where the pin 15 a is located is a free end, and the distal end of the shaft 15 is inserted into the flow path 11 of the tube 12 and arranged. Further, the shaft 15 is rotatably cantilevered with respect to the valve housing 35 via a first bearing 37 and a second bearing 38, which are two bearings arranged apart from each other. The first bearing 37 and the second bearing 38 are both constituted by ball bearings. The first bearing 37 and the second bearing 38 are arranged at a position between the valve body 14 and the main gear 41 in the direction of the center axis Ls of the shaft 15 and rotatably support the shaft 15. The valve element 14 is fixed by welding to a pin 15 a formed at the tip of the shaft 15, and is arranged in the flow path 11. The details of the joint between the valve element 14 and the pin 15a of the shaft 15 will be described later.

  The end frame 36 is fixed to the valve housing 35 by a plurality of clips 39 (see FIGS. 1 and 2). As shown in FIGS. 7 and 8, a main gear 41 is fixed to the base end 15 b of the shaft 15. A return spring 40 is provided between the valve housing 35 and the main gear 41.

  As shown in FIG. 7, the motor 32 is housed and fixed in a housing recess 35 a formed in the valve housing 35. The motor 32 is drivingly connected to the shaft 15 via a speed reduction mechanism 33 to open and close the valve element 14. That is, the motor gear 43 is fixed to the output shaft of the motor 32. The motor gear 43 is drivingly connected to the main gear 41 via the intermediate gear 42. The motor 32 generates a driving force for rotating the shaft 15 in the valve opening and valve closing directions.

  The intermediate gear 42 is a two-stage gear, and is rotatably supported by the valve housing 35 via a pin shaft 44. The motor gear 43 and the main gear 41 are drivingly connected to the intermediate gear 42. In the present embodiment, the main gear 41, the intermediate gear 42, and the motor gear 43 are formed of a resin material for weight reduction.

  In the EGR valve 1 having such a configuration, when the motor 32 is energized from the fully closed state of the valve element 14 as shown in FIG. 3, the motor gear 43 causes the motor gear 43 to move in the forward direction (the direction in which the valve element 14 is opened). ), And the rotation is reduced by the intermediate gear 42 and transmitted to the main gear 41. Then, the shaft 15 fixed to the main gear 41 rotates about the central axis Ls against the return spring force, which is generated by the return spring 40 and urges in the valve closing direction, as shown in FIG. As shown by the arrow, the valve element 14 rotates and the flow path 11 is opened. Then, when the drive voltage applied to the motor 32 is maintained constant during the rotation of the valve body 14, the motor driving force and the return spring force balance at the rotation position of the valve body 14 at that time. The valve body 14 is maintained at a predetermined opening.

  Next, a joint portion between the valve body 14 and the pin 15a of the shaft 15 will be described.

  In the present embodiment, as shown in FIGS. 9 to 11, the valve body 14 has a through hole 21. The through hole 21 is formed through the valve body 14 in the radial direction of the valve body 14 (the left-right direction in FIG. 10). The valve body 14 and the pin 15a of the shaft 15 are welded together with the pin 15a of the shaft 15 inserted into the through hole 21. Specifically, a welded portion 51 and a non-welded portion 52 are formed at a joint portion between the valve body 14 and the pin 15 a of the shaft 15. In the present embodiment, the inner peripheral surface 21a of the through hole 21 is formed, for example, in a circular shape. Further, the outer peripheral surface 22 of the pin 15a of the shaft 15 is formed in, for example, a circular shape or a circular shape with a part cut off.

  The welded portion 51 is a portion where the valve body 14 and the pin 15a of the shaft 15 are welded. The welded portion 51 is formed at the position of the linear contact portion 53 as shown in FIG.

  Here, as shown in FIG. 12, the linear contact portion 53 is at least a part of the outer peripheral surface 22 of the shaft 15 in the circumferential direction and has a large curvature portion 22a having a larger curvature than the inner peripheral surface 21a of the through hole 21. And the inner peripheral surface 21a of the through hole 21. Then, the linear contact portion 53 is formed linearly along the center axis Ls direction of the shaft 15, as shown in FIG. That is, the linear contact portion 53 is a portion where the large curvature portion 22a on the outer peripheral surface 22 of the shaft 15 and the inner peripheral surface 21a of the through hole 21 are in linear contact with each other in the direction of the center axis Ls of the shaft 15.

  The large curvature portion 22a may be formed on a part of the outer circumferential surface 22 of the shaft 15 in the circumferential direction, or may be formed on the entire outer circumferential surface 22 of the shaft 15 in the circumferential direction. That is, the curvature of the outer peripheral surface 22 of the shaft 15 is smaller than the curvature of the inner peripheral surface 21 a of the through hole 21 over only a part of the outer peripheral surface 22 in the circumferential direction or over the entire circumference of the outer peripheral surface 22 in the circumferential direction. large.

  FIG. 12 schematically shows the large curvature portion 22a on the outer peripheral surface 22 of the shaft 15 and the magnitude of the curvature on the inner peripheral surface 21a of the through hole 21 for convenience of explanation, and is particularly illustrated. It is not limited to a suitable curvature.

  As shown in FIGS. 10 and 11, the non-welded portion 52 is formed adjacent to the welded portion 51 at positions on both sides of the linear contact portion 53 in the direction of the center axis Ls of the shaft 15 with respect to the welded portion 51. ing. In the non-welded portion 52, as shown in FIG. 11, the valve body 14 and the pin 15a of the shaft 15 are in contact with each other, but are not welded.

  Thus, in the present embodiment, the non-welded portions 52 are formed on both sides of the welded portion 51. Therefore, when the welded portion 51 is formed, that is, when the pin 15a of the valve body 14 and the shaft 15 is welded, even if the heat shrinkage due to welding occurs in the welded portion 51, the valve body 14 and the shaft Since the contact state of the 15 pins 15a is ensured, the valve body 14 and the pins 15a of the shaft 15 are hardly affected by the heat shrinkage, and are hardly pulled toward the welded portion 51 side. Therefore, the (relative) positional deviation and inclination of the valve element 14 and the shaft 15 are unlikely to occur. The length of the non-welded portion 52 is, for example, 1/3 to 1/4 of the length of the welded portion 51. By defining the length of the non-welded portion 52 in this manner, the length of the welded portion 51 is sufficiently ensured, so that the joint strength between the valve body 14 and the pin 15a of the shaft 15 is ensured.

  In the present embodiment, the valve body 14 and the pin 15a of the shaft 15 are welded at only one location of the welded portion 51, and the linear contact portion 53 is used only once in the direction of the center axis Ls of the shaft 15. It is only necessary to perform the welding work. As described above, in the present embodiment, the length of the welding portion is reduced, and the number of times of performing the welding operation is reduced. Therefore, the time required for welding the valve body 14 and the pin 15a of the shaft 15 can be reduced. Further, the stress acting on the valve body 14 and the pin 15a of the shaft 15 due to thermal contraction generated during welding can be reduced.

  In the present embodiment, as shown in FIG. 13, a reference position X for positioning is defined for the shaft 15 in the direction of the center axis Ls of the shaft 15. The reference position X is a reference position for positioning the shaft 15 at a predetermined position in the direction of the central axis Ls in the EGR valve 1. Here, for example, in the EGR valve 1, the shaft 15 is positioned such that the reference position X is located at the position of the surface of the first bearing 37 on the pin 15 a side of the shaft 15.

  In the present embodiment, when the welding portion 51 performs welding of the valve body 14 and the pin 15 a of the shaft 15 at the end of the welding portion 51 on the reference position X side in the direction of the center axis Ls of the shaft 15. Is provided with a welding start portion 51a which is a portion where welding has been started. On the other hand, the welded portion 51 has a valve at an end of the welded portion 51 opposite to the reference position X in the direction of the center axis Ls of the shaft 15, that is, at an end of the shaft 15 on the side of the tip 15 c of the pin 15 a. A welding end portion 51b, which is a portion where welding is completed when welding the body 14 and the pin 15a of the shaft 15, is provided.

  As described above, in the present embodiment, at the time of welding the valve body 14 and the pin 15 a of the shaft 15, welding is started from the reference position X side in the direction of the center axis Ls of the shaft 15, That is, welding is performed toward the tip 15c side of the pin 15a of the shaft 15. That is, in the present embodiment, the welding progress direction at the time of welding the valve body 14 and the pin 15a of the shaft 15 is a direction from the reference position X side toward the tip 15c side of the pin 15a of the shaft 15, that is, the reference position X side. Away from you.

  Here, as shown in FIG. 14, the welding progress direction at the time of welding the valve body 14 and the pin 15 a of the shaft 15 is opposite to that in the present embodiment, that is, from the tip 15 c side of the pin 15 a of the shaft 15. Consider a comparative example in which the direction is toward the position X. At this time, it is assumed that welding is performed in a state where the valve body 14 is in contact with the valve seat 13.

  Then, in this comparative example, since the welded portion advances toward the reference position X side, thermal contraction due to welding gradually occurs toward the reference position X side. Therefore, as shown in FIG. 14, the portion of the shaft 15 on the reference position X side, that is, the portion of the shaft 15 on the base end portion 15 b side is heated by heat shrinkage caused by welding, so that the distal end portion 15 c It is pulled to the side. Therefore, the reference position X is shifted from the position of the first bearing 37 toward the tip 15c of the pin 15a. As described above, in the comparative example, the position shift of the reference position X of the shaft 15 occurs, and the shaft 15 is not disposed at a predetermined position in the EGR valve 1.

  On the other hand, in the present embodiment, as shown in FIG. 13 described above, the welding progress direction at the time of welding the valve body 14 and the pin 15a of the shaft 15 is such that the distal end of the pin 15a of the shaft 15 moves from the reference position X side. The direction is the direction toward the side 15c, that is, the direction away from the reference position X side. At this time, it is assumed that welding is performed in a state where the valve body 14 is in contact with the valve seat 13. Then, in the direction of the center axis Ls of the shaft 15, the welding portion advances toward the opposite side to the reference position X of the shaft 15, that is, toward the tip 15 c of the pin 15 a. Then, in the present embodiment, since the welding portion proceeds toward the tip 15c of the pin 15a, heat contraction due to welding gradually occurs toward the tip 15c of the pin 15a. Therefore, as shown in FIG. 13, heat shrinkage due to welding may occur at the portion of the pin 15 a on the distal end portion 15 c side. However, at the reference position X side, that is, at the portion of the shaft 15 at the base end portion 15 b side, welding is performed. Hardly affected by heat shrinkage that occurs. Therefore, the reference position X does not deviate from the position of the first bearing 37. As described above, in the present embodiment, since the positional shift of the reference position X does not occur, the state where the shaft 15 is arranged at a predetermined position in the EGR valve 1 can be maintained. In the present embodiment, since the tip 15c of the pin 15a is a free end, heat shrinkage due to welding is likely to occur at the portion of the pin 15a on the tip 15c side. For this reason, the portion of the shaft 15 on the base end portion 15b side is relatively less affected by the heat shrinkage generated by welding.

  13 and 14 are diagrams schematically illustrating the effect on the shaft 15 due to thermal contraction generated by welding, and are not diagrams accurately illustrating the amount of contraction of the shaft 15.

  Further, in the present embodiment, the welding portion 51 is formed by laser welding. Thereby, since the heat generated during welding is relatively small, the occurrence of heat shrinkage in the welded portion 51 can be suppressed. Therefore, the valve body 14 and the pin 15a of the shaft 15 are less likely to be pulled toward the welded portion 51 due to thermal contraction generated during welding. Therefore, displacement and inclination between the valve body 14 and the shaft 15 are unlikely to occur.

  Further, in the present embodiment, the linear contact portion 53 is formed at the position of the uppermost part 21b (part farthest from the valve seat 13, the uppermost part in FIG. 9) on the inner peripheral surface 21a of the through hole 21. Thus, the linear contact portion 53 is formed at a position on the central axis Lv of the valve element 14. As a result, even if thermal contraction occurs due to welding of the valve body 14 and the pin 15 a of the shaft 15, displacement of the valve body 14 in the radial direction (radial direction of the shaft 15) is unlikely to occur.

  It should be noted that the above-described embodiment is merely an example, and does not limit the present invention in any way. Needless to say, various improvements and modifications can be made without departing from the gist of the invention.

DESCRIPTION OF SYMBOLS 1 EGR valve 2 Valve part 3 Drive mechanism part 13 Valve seat 14 Valve body 15 Shaft 15a Pin 15c Tip part 21 Through hole 21a Inner peripheral surface 21b Uppermost part 22 Outer peripheral surface 22a Large curvature portion 37 First bearing 51 Welding part 51a Welding start Portion 51b Welding end portion 52 Non-weld portion 53 Straight contact portion Ls Central axis (of shaft)

Claims (3)

A flow control, comprising: a valve element; and a shaft that rotates the valve element by rotating about an axis, wherein the shaft is inserted into a through hole provided in the valve element and is welded to the valve element. In the valve,
At least a part of the outer circumferential surface of the shaft in the circumferential direction, where a portion having a larger curvature than the inner circumferential surface of the through-hole, and the inner circumferential surface of the through-hole linearly contact along the axial direction of the shaft. A welded portion where the valve body and the shaft are welded at a linear contact portion,
Have a, a non-welded portion on both sides in the axial direction, that said said valve body shaft is not welded of the shaft relative to the welded portion in the linear contact portion,
The welded portion has a predetermined length in a linear direction of the linear contact portion,
A flow control valve. The flow control valve according to claim 1,
A reference position for positioning the shaft at a predetermined position in the axial direction of the shaft in the flow control valve is defined in the shaft,
The welded portion, with respect to the axial direction of the shaft, includes a welding start portion at an end on the reference position side, and includes a welding end portion at an end opposite to the reference position,
A flow control valve. The flow control valve according to claim 1 or 2,
The weld is laser-welded,
A flow control valve.

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