JP2022003237A - EGR valve - Google Patents

Abstract

To provide an inward opening type EGR valve capable of preventing opening of a valve element regardless of existence of backlash between a male screw and a female screw even when an intake negative pressure or an exhaust pressure acts on the valve element when being fully closed.SOLUTION: An EGR valve 31 includes a valve seat 34 provided in a flow passage 32 of a housing 33, a valve element 35 positioned in an upstream side of the valve seat 34, a valve stem 36 having the valve element 35, a male screw 38 provided on the valve stem 36, a step motor 37 for reciprocating the valve stem 36, a female screw 61 provided on a rotor 53 of the step motor 37 and screwed with the male screw 38, and a valve element spring 62 for energizing the valve element 35 and the valve stem 36 to a direction separating from the valve seat 34. A male thread includes a first male thread surface facing the valve seat 34 and a second male thread surface on an opposite side, and a female thread includes a first female thread surface facing the valve seat 34 and a second female thread surface on an opposite side.SELECTED DRAWING: Figure 1

Description

The technique disclosed herein relates to an internally open EGR valve provided in an EGR passage for refluxing EGR gas.

Conventionally, as a technique of this kind, for example, an internally open type EGR valve described in Patent Document 1 below is known. This EGR valve includes a housing having a flow path, a valve seat provided in the flow path, a valve body provided so as to be seated on the valve seat, and a valve shaft provided with a valve body at one end. It is provided with an actuator for reciprocating the valve shaft in the axial direction thereof. The flow path is divided into an upstream side flow path and a downstream side flow path with the valve seat as a boundary, and the valve body is arranged so as to be seatable on the valve seat in the downstream side flow path. The actuator includes a drive shaft having a male screw, a rotor having a female screw screwed into the male screw to reciprocate the drive shaft in the axial direction, and a coil for rotating the rotor. A predetermined backlash is provided between the male screw and the female screw in the axial direction of the drive shaft. The drive shaft is provided with a valve closing spring that urges the valve body in the valve closing direction. An electromagnetic clutch is provided between the valve shaft and the drive shaft. In this EGR valve, when the intake negative pressure acts on the downstream flow path or the exhaust pressure acts on the upstream side flow path when the valve is fully closed, the valve body moves in the opening direction, so that the intake negative pressure or A valve closing spring is provided to urge the valve body in the valve closing direction against the exhaust pressure.

Here, the internal valve opening type EGR valve has the following merits as compared with the external valve opening type EGR valve because the valve shaft is separated from the valve hole of the valve seat when the valve is opened. That is, when the outer diameters of the valve bodies are made equal, the maximum flow rate of the EGR gas in the internal valve opening type increases as compared with the external valve opening type. Therefore, in the internal valve opening type, the outer diameter of the valve body for obtaining a predetermined maximum flow rate can be made smaller than that in the external valve opening type, and as a result, the flow rate resolution in the low flow rate region can be improved. Since such merits are obtained, there is an increasing demand for the use of an internally open valve type EGR valve.

Japanese Unexamined Patent Publication No. 2010-275941

However, in the internally open type EGR valve described in Patent Document 1, when the valve is fully closed, the drive shaft is pushed in the valve closing direction by the urging force of the valve closing spring, and the thread of the male thread hits the thread of the female thread. The valve body will be seated on the valve seat in this state. In this state, there is a backlash (gap) between the female screw and the male screw so that the drive shaft can move in the valve opening direction. Therefore, when intake negative pressure or exhaust pressure acts on the valve body, a force in the valve opening direction acts from the valve body to the drive shaft via the valve shaft, the male screw moves by the amount of the back pressure, and the valve body becomes minute. It will open the valve. As a result, the EGR gas may leak to the downstream flow path, and unnecessary EGR gas may flow to the intake passage.

As a countermeasure to the above problem, it is conceivable to increase the urging force (tension) of the valve closing spring to the extent that it can withstand the intake negative pressure and the exhaust pressure. It is not preferable because the wear may increase between them.

This disclosed technique was made in view of the above circumstances, and the purpose is to use a male screw in an internally open valve type EGR valve even if an intake negative pressure or an exhaust pressure acts on the valve body when the valve body is fully closed. The purpose is to prevent the valve body from opening regardless of the presence of backlash between the female screw and the female screw.

In order to achieve the above object, the technique according to claim 1 is a housing having a flow path, a valve seat provided in the flow path, a valve body provided so as to be seated on the valve seat, and a valve. The valve shaft provided with the body and the valve shaft include one end and the other end, the valve body is fixed to one end, a male screw is provided at the other end, and the valve shaft is oriented in the axial direction thereof. The actuator for reciprocating motion and the actuator include a rotor having a female screw screwed into a male screw, and the flow path is divided into a side closer to the rotor and a side far from the rotor with the valve seat as a boundary, and the valve is on the near side. The body is seatable on the valve seat, the male thread has a spiral thread in the axial direction of the valve axis, and the male thread has a first male thread surface facing toward the valve seat. The female thread has a female thread spirally connected in the axial direction of the valve axis, and the female thread is toward the valve seat. A predetermined bucklash in the axial direction of the valve shaft is included between the male thread and the female thread so as to include the first female thread surface facing the direction and the second female thread surface located on the opposite side of the first female thread surface. It is intended that the valve body is provided with a valve body spring for urging the valve body together with the valve shaft in a direction away from the valve seat.

According to the configuration of the above technique, by driving the actuator to rotate the rotor in order to fully close the EGR valve, the rotational movement moves the valve shaft and the valve body in the axial direction via the female screw and the male screw. , The valve body is fully closed when seated on the valve seat. At this time, due to the urging force of the valve body spring, the second male thread surface of the male thread is engaged with the first female thread surface of the female thread. In this engaged state, the valve shaft is urged in the direction away from the valve seat by the urging force of the valve body spring, so that the male screw thread comes into contact with the female screw thread without going through the backlash, and the movement of the valve shaft is prevented. .. Therefore, even if the intake negative pressure that tries to pull up the valve body acts on the downstream flow path or the exhaust pressure that tries to push up the valve body acts on the upstream side flow path, the valve body opens. Be blocked.

In order to achieve the above object, the technique according to claim 2 is the technique according to claim 1, wherein the valve seat restricts the movement of the valve body in the valve closing direction while the valve body is seated. The purpose is to function as a valve stopper.

According to the configuration of the above technique, in addition to the operation of the technique according to claim 1, since the valve seat functions as a valve closing stopper while the valve body is seated on the valve seat, a valve closing stopper is separately provided on the valve shaft or the like. There is no need to provide it.

According to the technique according to claim 1, in an internally opened EGR valve, even if an intake negative pressure or an exhaust pressure acts on the valve body when the valve is fully closed, the backlash between the male screw and the female screw is on the valve opening side. Since it is not in the state, it is possible to prevent the valve body from opening.

According to the second aspect of the present invention, in addition to the effect of the technique according to the first aspect, the configuration of the EGR valve can be simplified by the amount that the valve closing stopper is not provided.

FIG. 6 is a cross-sectional view showing an EGR valve in a fully closed state according to an embodiment. FIG. 6 is a cross-sectional view showing an EGR valve in a fully open state according to an embodiment. An enlarged cross-sectional view showing a one-dot chain line square portion of FIG. 1 in a fully closed state for an EGR valve according to an embodiment. An enlarged cross-sectional view showing a part of a screwed state of a male screw and a female screw in FIG. 3 according to an embodiment. FIG. 2 is an enlarged cross-sectional view showing a one-dot chain line square portion of FIG. 2 in a fully open state for an EGR valve according to an embodiment. An enlarged cross-sectional view showing a part of a screwed state of a male screw and a female screw in FIG. 5 according to an embodiment. FIG. 6 is an enlarged cross-sectional view showing a part of a screwed state of a male screw and a female screw in a fully closed state of an internally opened EGR valve according to a conventional example. FIG. 6 is an enlarged cross-sectional view showing a part of a screwed state of a male screw and a female screw in a state where an intake negative pressure is applied to a downstream flow path when the internally open type EGR valve is fully closed according to a conventional example.

Hereinafter, an embodiment in which the EGR valve is embodied will be described in detail with reference to the drawings.

FIG. 1 shows a fully closed EGR valve 31 in a cross-sectional view. FIG. 2 shows a cross-sectional view of the EGR valve 31 in a fully open state. As shown in FIGS. 1 and 2, the poppet-type internal valve opening type EGR valve 31 has a housing 33 having a flow path 32, a valve seat 34 provided in the flow path 32, and a valve seat 34. On the other hand, a valve body 35 provided so as to be seated, a valve shaft 36 provided with the valve body 35, and a step motor 37 for reciprocating (stroke movement) the valve shaft 36 in the axial direction thereof are provided. The step motor 37 corresponds to an example of an actuator in this disclosed technique.

The valve shaft 36 is arranged so as to vertically penetrate the housing 33. The valve shaft 36 includes one end (lower end) and the other end (upper end), the valve body 35 is fixed to the lower end, and the male screw 38 is provided at the upper end. The valve shaft 36 is provided with a flange-shaped spring receiver 39 adjacent to the male screw 38 on the lower side thereof. Below the spring receiver 39 of the valve shaft 36, a two-sided width portion 36a having a substantially oval cross section is provided.

In the housing 33, both ends of the flow path 32 are an inlet 32a into which the EGR gas is introduced and an outlet 32b from which the EGR gas is led out. The inlet 32a is connected to the upstream EGR passage 22, and the outlet 32b is connected to the downstream EGR passage 22. The valve seat 34 has a valve hole 34a communicating with the flow path 32. The valve hole 34a has a tapered shape whose diameter increases toward the lower side (upstream side). The flow path 32 is divided into an upstream side flow path 32c on the lower side (upstream side) and a downstream side flow path 32d on the upper side (downstream side) with the valve seat 34 as a boundary. In this embodiment, the valve body 35 is arranged so as to be seatable on the valve seat 34 in the downstream flow path 32d. In other words, the flow path 32 is divided into a side closer to the step motor 37 (downstream side) and a far side (upstream side) with the valve seat 34 as a boundary, and the valve body 35 is the valve seat 34 on the near side (downstream side). It is placed so that it can be seated in.

The valve body 35 has a substantially truncated cone shape, and is provided so as to be seatable and separable to the valve seat 34 so that the small diameter portion thereof is fitted into the valve hole 34a. The housing 33 is provided with a first thrust bearing 41 and a second thrust bearing 42 for supporting and guiding the valve shaft 36 so as to be able to stroke in the axial direction. On the inner circumference of the first thrust bearing 41, a rotation restricting portion 41a having a substantially oval cross section and engaging with the width across flat portion 36a of the valve shaft 36 is formed. By aligning the width across flats 36a and the rotation restricting portion 41a, the stroke motion of the valve shaft 36 is guided and the rotation of the valve shaft 36 is regulated.

The step motor 37 includes a stator 52 having a coil 51 and a magnet rotor 53 as a rotor provided inside the stator 52. These members 51 to 53 and the like are molded and covered with a resin casing 54. A connector 55 projecting laterally is formed in the casing 54. The connector 55 is provided with a terminal 56 extending from the coil 51.

The magnet rotor 53 includes a rotor main body 57 and a cylindrical plastic magnet 58 integrally provided on the outside of the rotor main body 57. A first radial bearing 59 is provided between the rotor main body 57 and the casing 54 on the outer periphery of the upper end portion. A second radial bearing 60 is provided between the first thrust bearing 41 and the inner circumference of the lower end portion of the plastic magnet 58. The magnet rotor 53 is rotatably supported inside the stator 52 by the first and second radial bearings 59 and 60. At the center of the rotor body 57, a female screw 61 screwed into the male screw 38 of the valve shaft 36 is provided.

FIG. 3 shows an enlarged cross-sectional view of the portion of the one-dot chain line square S1 in FIG. 1 in the fully closed state of the EGR valve 31. FIG. 4 shows a part of the screwed state of the male screw 38 and the female screw 61 in FIG. 3 by an enlarged cross-sectional view. FIG. 5 shows an enlarged cross-sectional view of the portion of the one-dot chain line square S2 in FIG. 2 in the fully open state of the EGR valve 31. FIG. 6 shows a part of the screwed state of the male screw 38 and the female screw 61 in FIG. 5 by an enlarged cross-sectional view. As shown in FIGS. 3 to 6, the male screw 38 has a male screw thread 38a spirally connected in the axial direction of the valve shaft 36. The male thread 38a includes a first male thread surface 38aa facing toward the valve seat 34 (downward) and a second male thread surface 38ab located on the opposite side (upper side) of the first male thread surface 38aa. Further, the female thread 61 has a female thread 61a spirally connected in the axial direction of the valve shaft 36. The female thread 61a includes a first female thread surface 61aa facing toward the valve seat 34 (downward) and a second female thread surface 61ab located on the opposite side (upper side) of the first female thread surface 61aa. Then, as shown in FIGS. 4 and 6, a predetermined backlash 65 (play) is provided between the male screw 38 and the female screw 61 in the axial direction of the valve shaft 36.

Here, the valve body 35 is moved away from the valve seat 34 together with the valve shaft 36 between the spring receiver 39 of the valve shaft 36 and the lower second radial bearing 60, that is, between the spring receiver 39 and the housing 33. A valve body spring 62 for urging in the direction (upper of FIGS. 1 to 6) is provided. Further, a rotor spring 63 for urging the magnet rotor 53 in a direction away from the valve seat 34 is provided between the magnet rotor 53 (plastic magnet 58) and the second radial bearing 60.

Between the housing 33 and the valve shaft 36, a lip seal 43 having a substantially cylindrical shape for sealing between the housing 33 and the valve shaft 36 is provided adjacent to the second thrust bearing 42. Further, between the housing 33 and the valve shaft 36, a depot guard plug 44 having a substantially cylindrical shape for guarding the space between the housing 33 and the valve shaft 36 from the deposit is provided adjacent to the lip seal 43. ..

By driving the step motor 37 to rotate the magnet rotor 53, the EGR valve 31 converts the rotational movement into the stroke movement of the valve shaft 36 and the valve body 35 via the female screw 61 and the male screw 38, and the valve seat. The opening degree of the valve body 35 with respect to 34 is adjusted. That is, the EGR valve 31 is fully formed by using the step motor 37 to stroke the valve shaft 36 together with the valve body 35 to seat the valve body 35 on the valve seat 34 against the urging force of the valve body spring 62. It will be closed. Then, when the magnet rotor 53 rotates in one direction from the fully closed state, the valve shaft 36 moves in the thrust direction together with the valve body 35 together with the urging force of the valve body spring 62 due to the screwing relationship between the male screw 38 and the female screw 61. It makes a stroke movement in the upward direction of FIG. As a result, the valve body 35 is separated from the valve seat 34 and the valve is opened, and the valve body 35 is further fully opened.

On the other hand, as shown in FIG. 2, the valve body spring is caused by the screwing relationship between the male screw 38 and the female screw 61 due to the rotation of the magnet rotor 53 in the opposite direction from the fully open state where the valve body 35 is farthest from the valve seat 34. Against the urging force of 62, the valve shaft 36 makes a stroke movement in the downward direction of FIG. 2, which is the thrust direction, together with the valve body 35. As a result, the valve body 35 is seated on the valve seat 34 and is fully closed, and further, the fully closed state is maintained. At this time, the valve seat 34 functions as a valve closing stopper of the valve body 35, the rotation of the rotor main body 57 is restricted, and the stroke movement of the valve shaft 36 and the valve body 35 is restricted. The position of the valve shaft 36 at this time is defined as the initial position.

[About the action and effect of EGR valve]
According to the configuration of the EGR valve 31 of this embodiment described above, the step motor 37 is driven to rotate the magnet rotor 53 in order to fully close the EGR valve 31, so that the rotational movement is a female screw 61 and a male screw. The valve shaft 36 and the valve body 35 move in the axial direction via the 38, and the valve body 35 is seated on the valve seat 34 in a fully closed state. At this time, due to the urging force of the valve body spring 62, the second male thread surface 38ab of the male thread 38 is engaged with the first female thread surface 61aa of the female thread 61. As shown in FIG. 4, in this engaged state, the valve shaft 36 is urged by the urging force F1 of the valve body spring 62 in the direction away from the valve seat 34 (upward in FIG. 4), so that the valve shaft 36 is urged via the backlash 65. The male thread 38a abuts on the female thread 61a without any problem, and the valve shaft 36 is prevented from moving upward. Therefore, even if the intake negative pressure for pulling up the valve body 35 acts on the downstream side flow path 32d or the exhaust pressure for pushing up the valve body 35 acts on the upstream side flow path 32c, the valve body The valve opening of 35 is blocked. Therefore, in the internal valve opening type EGR valve 31, even if the intake negative pressure or the exhaust pressure acts on the valve body 35 when the valve body 35 is fully closed, the backlash 65 between the male screw 38 and the female screw 61 is not on the valve opening side. Therefore, it is possible to prevent the valve body 35 from opening. As a result, the valve body 35 can be held in the fully closed state without particularly increasing the output and the size of the step motor 37 (actuator).

Here, FIG. 7 shows a part of the screwed state of the male screw 138 and the female screw 161 when the internally open type EGR valve is fully closed according to the conventional example by an enlarged cross-sectional view. FIG. 8 shows a part of the screwed state of the male screw 138 and the female screw 161 in the state where the intake negative pressure is applied to the downstream flow path when the internally open type EGR valve is fully closed according to the conventional example. It is shown by an enlarged cross-sectional view. In the conventional internally open type EGR valve, when the valve body is seated on the valve seat and fully closed, as shown in FIG. 7, the first male thread surface 138a of the male thread 138a is the second female thread of the female thread 161a. It is in a state of engaging with the mountain surface 161ab. The first male thread surface 138a of the male thread 138a engages with the second female thread surface 161ab of the female thread 161a because the valve body is in the direction of the valve seat together with the valve shaft due to the urging force F2 of the valve closing spring (FIG. 7). By being urged downward).

Here, when the engine is operating, the intake negative pressure may act on the downstream flow path of the EGR valve from the intake passage. In this case, in the conventional internal opening type EGR valve, when the intake negative pressure is larger than the urging force of the valve closing spring, the drive shaft is driven by the backlash 165 between the male screw 138 and the female screw 161 shown in FIG. The EGR gas may leak from the upstream flow path to the downstream flow path and flow into the intake passage because the valve body is pulled up by the intake negative pressure together with the drive shaft and separated from the valve seat (valve opening). be. As a result, unnecessary EGR gas may flow to the engine, causing a misfire in the engine. The same applies to the case where an excessive exhaust pressure acts on the fully closed valve body from the upstream flow path.

On the other hand, in the EGR valve 31 of this embodiment, even if the intake negative pressure acts on the valve body 35 from the downstream flow path 32d in the fully closed state, the valve body 35 is separated from the valve seat 34 (valve opening). There is nothing to do. The reason is that the male screw 38 engages with the female screw 61 to prevent the movement in the upward direction (valve opening direction), and the movement of the valve body 35 is locked against the negative intake pressure. That is, in the EGR valve 31, as shown in FIG. 4, the urging force F1 of the valve body spring 62 urges the valve shaft 36 together with the valve body 35 in the direction away from the valve seat 34, so that the second male screw 38 is used. This is because the male thread surface 38ab engages with the first female thread surface 61aa of the female thread 61, and the movement of the valve shaft 36 toward the step motor 37 (upward) together with the valve body 35 is prevented. In this fully closed state, the valve shaft 36 does not move upward unless the magnet rotor 53 is rotated to open the valve body 35, and the EGR valve 31 eventually urges the valve body spring 62. Keeps it fully closed.

Further, in this embodiment, since the valve seat 34 functions as a valve closing stopper in a state where the valve body 35 is seated on the valve seat 34, it is not necessary to separately provide a valve closing stopper on the valve shaft 36 or the like. Therefore, the configuration of the EGR valve 31 can be simplified by the amount that the valve closing stopper is not provided.

It should be noted that this disclosure technique is not limited to the above-described embodiment, and a part of the configuration may be appropriately modified and implemented within a range that does not deviate from the purpose of the disclosure technique.

For example, the embodiment of the EGR valve 31 in the above embodiment shows an example, and the embodiment can be changed.

This disclosed technology can be used for EGR devices provided in gasoline engine systems and diesel engine systems.

31 EGR valve 32 flow path 32c upstream side flow path 32d downstream side flow path 33 housing 34 valve seat 35 valve body 36 valve shaft 37 step motor (actuator)
38 Male thread 38a Male thread 38aa 1st male thread surface 38ab 2nd male thread surface 53 Magnet rotor (rotor)
61 Female thread 61a Female thread 61aa 1st female thread surface 61ab 2nd female thread surface 62 Valve body spring 65 Backlash

Claims (2)

A housing with a flow path and
The valve seat provided in the flow path and
A valve body that can be seated on the valve seat and
The valve shaft provided with the valve body and
The valve shaft includes one end and the other end, the valve body is fixed to the one end, and a male screw is provided at the other end.
An actuator for reciprocating the valve shaft in the axial direction,
The actuator includes a rotor having a female thread screwed into the male thread.
The flow path is divided into a side closer to the rotor and a side far from the rotor with the valve seat as a boundary, and the valve body is arranged so as to be seatable on the valve seat on the near side.
The male thread has a male thread spirally connected in the axial direction of the valve shaft, and the male thread is the opposite of the first male thread surface facing the valve seat and the first male thread surface thereof. Including the second male thread surface located on the side,
The female thread has a female thread spirally connected in the axial direction of the valve shaft, and the female thread is the opposite of the first female thread surface facing the valve seat and the first female thread surface thereof. Including the second female thread surface located on the side,
A predetermined backlash is provided between the male screw and the female screw in the axial direction of the valve shaft.
An EGR valve including a valve body spring for urging the valve body together with the valve shaft in a direction away from the valve seat. In the EGR valve according to claim 1,
The EGR valve is characterized in that the valve seat functions as a valve closing stopper that regulates the movement of the valve body in the valve closing direction when the valve body is seated.

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