JP2008202516A - Exhaust gas recirculation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas recirculation device stably ensuring arrangement position accuracy of a stopper and reducing the number of parts and the number of manufacturing processes. <P>SOLUTION: An EGR valve 10 has an actuator 30 which can move a valve 20, through a rod 21 of which one end is attached to the valve 20, disposed to a communicating passage 13 connecting an inlet port 12 with an exhaust port 13, and is abutted with or separated from a seat 15. The actuator 30 has a coil 31, a rotor 32 rotary driven by the energization to the coil 31, and a conversion mechanism 33 converting rotary motion of the rotor 32 into stroke motion of the rod 21. The conversion mechanism 32 includes a male screw part 22 formed to the rod 21, and a female screw part 42 formed at the center of the rotor 32 and screwed with the male screw part 22. A stopper 25 restricting an initial position of the rod 20 itself is molded integrally with the rod 21. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas recirculation device that opens and closes a valve by an actuator to return a part of exhaust gas discharged from an engine to an intake system.

  Conventionally, in an engine system, part of exhaust gas discharged from the engine is returned to the intake system. An exhaust gas recirculation device is used to control the amount of exhaust gas recirculation to the intake system. In such an exhaust gas recirculation device, for example, a valve is provided at one end of a drive shaft formed with a male screw portion that is screwed into a female screw portion of the actuator, and the drive of the actuator is controlled. The provided valve is moved up and down, and the opening degree is adjusted to control the recirculation amount of exhaust gas returned to the intake system (Patent Document 1).

In this type of exhaust gas recirculation device, it is necessary to provide a stopper for regulating the initial position of the drive shaft. For example, when the stopper is attached to the drive shaft, the stopper portion formed with the stopper on the drive shaft Is pressed and fixed, or a stopper is welded to the drive shaft.
JP-A-7-310605

However, as described above, when the stopper portion is fixed to the drive shaft by press-fitting or welding, it is difficult to stably secure the stopper mounting accuracy (positioning accuracy of the stopper) with respect to the drive shaft. There was a problem that there was. If the stopper is displaced, the vertical movement of the valve may not be accurately controlled. This is because the valve opening degree (stroke amount of the drive shaft) is controlled based on the initial position of the drive shaft. As described above, if the position of the stopper is shifted, the exhaust gas recirculation amount control may be poor and the engine performance may be deteriorated.
Further, when the stopper portion is attached to the drive shaft, the male screw portion formed on the drive shaft may be damaged.

  Further, in the conventional exhaust gas recirculation device, the drive shaft and the stopper portion are configured separately, and thus a process for fixing the stopper portion to the drive shaft is necessary. And in such a process, since the mounting accuracy of the stopper portion is required, it has been one of the factors that prevent improvement in production efficiency and cost reduction.

  Here, it is possible to stably secure the stopper placement position accuracy by cutting the drive shaft material to produce the stopper portion. However, in order to cut out the stopper portion, a complicated processing step is required, which lowers the production efficiency as compared with press-fitting or welding and is very disadvantageous in terms of cost.

  Therefore, the present invention has been made to solve the above-described problems, and it is possible to stably secure the placement position accuracy of the stopper, and to reduce the number of parts and the manufacturing process. It is an object to provide a reflux device.

  An exhaust gas recirculation apparatus according to the present invention, which has been made to solve the above problems, includes an inlet for introducing exhaust gas discharged from an engine, and an intake air of the engine for mixing a part of the exhaust gas into the intake air. A housing formed with a discharge port for discharging to the system, a communication path that communicates the introduction port and the discharge port, a seat provided in the communication path, and a valve that contacts or separates from the sheet In the exhaust gas recirculation device having a drive shaft attached to the actuator and an actuator that moves the valve via the drive shaft, the actuator includes a coil, a rotor that is rotationally driven by energization of the coil, A conversion mechanism that converts the rotational movement of the rotor into a stroke movement of the drive shaft to abut or separate the valve from the seat, and the conversion mechanism comprises: A male screw portion formed on the drive shaft, and a female screw portion formed at the center of the rotor and screwed into the male screw portion, the drive shaft for restricting an initial position of the drive shaft. The stopper is integrally formed.

  In this exhaust gas recirculation device, the actuator moves the valve via the drive shaft, and the valve is brought into contact with or separated from the seat to block or open the communication path. Thereby, the exhaust gas introduced from the introduction port is discharged from the discharge port to the intake system. At this time, the exhaust gas recirculation control is performed by controlling the opening / closing timing and opening degree of the valve by controlling the operation of the actuator.

  In this exhaust gas recirculation device, a female screw portion that is screwed into a male screw portion formed on the drive shaft is formed at the center of the rotor provided in the actuator. A valve is disposed at one end of the drive shaft. Thereby, since the rotational motion of the rotor can be directly converted into the stroke motion of the drive shaft, it is possible to suppress a decrease in position accuracy and operation accuracy during the conversion. As a result, the valve position with respect to the seat, that is, the valve opening degree can be controlled with high accuracy.

The drive shaft is integrally formed with a stopper for regulating the initial position of the drive shaft (in other words, the initial position of the valve). That is, when manufacturing the drive shaft, the male screw portion and the stopper are integrally formed. For this reason, it is possible to stably ensure the placement position accuracy of the stopper with respect to the drive shaft. Accordingly, since the initial position of the drive shaft, which serves as a reference for controlling the valve opening (stroke amount of the drive shaft), is accurately determined, the valve opening can be controlled with high accuracy.
In this way, in this exhaust gas recirculation device, the valve opening degree can be controlled with high accuracy, and therefore, the exhaust gas recirculation amount can be controlled with high accuracy and the engine performance is not deteriorated.

  Further, in this exhaust gas recirculation device, since the stopper is integrally formed with the drive shaft, a step for fixing the stopper to the drive shaft as in the conventional case is not required. For this reason, the number of parts and the manufacturing process can be reduced. Further, since the stopper is integrally formed with the male screw portion, there is no possibility that the male screw portion is damaged.

  In the exhaust gas recirculation device according to the present invention, it is desirable that a receiving portion for receiving an elastic body for urging the valve in the valve closing direction is integrally formed on the drive shaft.

  Thus, the receiving part for receiving the elastic body for urging the valve in the valve closing direction is also integrally formed with the drive shaft, whereby the number of parts and the manufacturing process can be reduced. Further, since the receiving portion can be formed without being inclined (perpendicular to the drive shaft), smooth movement of the drive shaft can be ensured.

  In the exhaust gas recirculation device according to the present invention, the drive shaft is preferably formed by precision cold forging.

  In this way, by forming the drive shaft by precision cold forging, the male screw and the stopper (in some cases, the receiving portion) can be integrally formed on the drive shaft, thereby reducing the number of parts and the manufacturing process. be able to. In addition, the dimensional accuracy of the drive shaft can be improved.

  Moreover, in the exhaust gas recirculation device according to the present invention, it is desirable that the stopper abuts in a state of surface contact with the counterpart member when the valve is fully closed.

  By doing so, the initial position of the drive shaft can always be kept the same when the valve is fully closed, so that the valve opening can be controlled with high accuracy. This is because the valve opening degree control is performed based on the initial position of the drive shaft when the valve is fully closed.

  In the exhaust gas recirculation device according to the present invention, it is preferable that the counterpart member is a convex portion formed on a part of the rotor.

  By doing so, when the valve is fully closed, the mutual positional relationship between the initial position of the drive shaft and the initial position of the rotor can always be the same, so that the valve opening degree can be controlled with high accuracy. This is because the valve opening degree control is performed based on the mutual positional relationship between the initial position of the drive shaft and the initial position of the rotor when the valve is fully closed.

  According to the exhaust gas recirculation device of the present invention, as described above, the stopper placement position accuracy can be stably secured, and the number of parts and the manufacturing process can be reduced.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a most preferred embodiment embodying an exhaust gas recirculation device of the present invention will be described in detail based on the drawings. The exhaust gas recirculation device according to the present embodiment is an EGR valve for returning EGR gas to the intake system of the engine.

  Therefore, the EGR valve according to the embodiment will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing a schematic configuration of an EGR valve according to an embodiment. FIG. 2 is a front view showing a schematic configuration of the rod. FIG. 3 is a top view showing a schematic configuration of the rod. FIG. 4 is a cross-sectional view showing a schematic configuration of the magnet rotor. FIG. 5 is a bottom view of the magnet rotor. FIG. 6 is a top view showing a schematic configuration of the rotor body. FIG. 7 is a view showing the positional relationship between the rotor body and the rod when the valve is fully closed.

  As shown in FIG. 1, the EGR valve 10 according to the present embodiment includes a housing 11, a valve 20 movably provided in the housing 11, and an actuator 30 that moves (vertically moves) the valve 20. ing. The housing 11 is formed with an introduction port 12 through which EGR gas is introduced, a discharge port 13 through which EGR gas is discharged, and a communication path 14 that connects the introduction port 12 and the discharge port 13. A seat 15 with which the valve 20 abuts or separates is formed in the middle of the communication path 14.

  The valve 20 has a rod 21 extending to the actuator 30 side (upward). This rod 21 corresponds to the drive shaft of the present invention. As shown in FIG. 2, a male screw portion 22 is formed at the upper end of the rod 21. A spring receiver 23 is formed in the middle of the rod 21 (near the lower end of the male screw portion 22). The lower surface of the spring receiver 23 is a receiving surface of the spring 24, and a stopper 25 is formed on the upper surface as shown in FIG. The stopper 25 is for restricting the initial position of the rod 21.

  The rod 21 is an integrally formed product formed by precision cold forging. For this reason, when the rod 21 is manufactured, the male screw portion 22, the spring receiver 23, and the stopper 25 are integrally formed at the same time. Thereby, the position accuracy of the stopper 25 with respect to the rod 21 can be stably secured. Accordingly, since the initial position of the rod 21 that serves as a reference for valve opening (stroke amount of the rod 21) is accurately determined, the opening of the valve 20 can be controlled with high accuracy. Further, since the rod 21 is formed by precision cold forging, the dimensional accuracy of the rod 21 itself can be improved.

Further, since the stopper 25 is integrally formed with the rod 21 (more precisely, with the spring receiver 23 integrally formed with the rod 21), there is no need for a step for fixing the stopper to the rod as in the prior art. Become. Thereby, the number of parts and a manufacturing process can be reduced. Further, when the rod 21 is manufactured, the male screw portion 22, the spring receiver 23, and the stopper 25 are integrally formed at the same time, so that the male screw portion 22 is not damaged.
Further, since the spring receiver 23 is integrally formed with the rod 21, the spring receiver 23 can be formed without being inclined (in a state orthogonal to the rod 21), so that the smooth movement of the rod 21 can be ensured. it can.

  Returning to FIG. 1, the valve 20 has a conical shape, and this conical surface comes into contact with or separates from the seat 15. Such a valve 20 is biased toward the actuator 30 (upward) by a spring 24 that is contracted between the spring receiver 23 and the housing 11, and is driven (vertically moved) by the actuator 30. ing. As a result, the valve 20 contacts or separates from the seat 15 so that the communication path 14 is blocked or opened.

  Here, the actuator 30 includes a coil 31, a magnet rotor 32, and a conversion mechanism 33. As a result, when the coil 30 is energized, the actuator 30 rotates the magnet rotor 32 by a predetermined number of steps and converts the rotational motion of the magnet rotor 32 into the stroke motion of the rod 21 by the conversion mechanism 33. Is driven (moved up and down).

  As shown in FIG. 4, the magnet rotor 32 includes a resin rotor main body 40 and an annular plastic magnet 41. In the center of the rotor body 40, a female screw portion 42 that is screwed into the male screw portion 22 of the rod 21 is formed. As a result, the rotational motion of the rotor body 40 is converted into the stroke motion of the rod 21 in a state where the female thread portion 42 of the rotor body 40 and the male thread portion 22 of the rod 21 are screwed together. That is, the conversion mechanism 33 is configured by the male screw portion 22 of the rod 21 and the female screw portion 42 of the rotor body 40. Thereby, since the rotational motion of the rotor main body 40 can be directly converted into the stroke motion of the rod 21, the positional relationship between the rotor main body 40 and the rod 21 and the deviation of the operation timing at the time of conversion are minimized. be able to. Therefore, the actuator 30 can accurately control the position (opening degree) of the valve 20.

  Further, as shown in FIGS. 4 and 5, an abutting portion 44 with which the stopper 25 formed on the spring receiver 23 of the rod 21 abuts is formed at the lower portion of the rotor body 40. When the valve is fully closed, as shown in FIG. 7, the end face of the stopper 25 comes into contact with the end face of the contact portion 44 in a state of surface contact. Thereby, since the contact strength between the stopper 25 and the contact portion 44 is improved, deformation of the contact portion between the stopper 25 and the contact portion 44 can be prevented. Accordingly, the mutual positional relationship between the rotational position (initial position) of the rod 21 and the rotational position (initial position) of the rotor body 40 when the valve is fully closed, which is a reference for valve opening control by the actuator 30, is always kept in the same state. Therefore, the valve opening can be controlled with high accuracy over a long period of time. This is because the opening degree control of the valve 20 is performed based on the mutual positional relationship between the initial position of the rod 21 and the initial position of the rotor body 40 when the valve is fully closed. Thus, as a result of being able to control the valve opening with high accuracy over a long period of time, the control reliability of the EGR valve 10 can be improved.

Further, as shown in FIGS. 4 and 6, an anti-rotation portion 43 having a protruding shape toward the outside is formed on the outer periphery of the rotor body 40. In the present embodiment, six rotation preventing portions 43 are formed at equal intervals in the rotor body 40.
An annular plastic magnet 41 is integrated with the outside of the rotor body 40 by insert molding to constitute a magnet rotor 32.

  Here, a polyphenylene sulfide (PPS) resin is used as the material of the rotor body 40, and a polyamide resin having a melting point lower than that of the PPS resin is used as the material of the plastic magnet 41. Then, the magnet rotor 32 sets a preformed rotor body 40 in an insert mold, and injects the molten material of the plastic magnet 41 into a mold having a space shape that matches the shape of the plastic magnet 41. The rotor main body 40 and the plastic magnet 41 are integrally molded.

Therefore, when the rotor main body 40 and the plastic magnet 41 are integrally formed, the rotation preventing portion 43 formed in the rotor main body 40 is deteriorated or burned out by the heat of the molten material of the plastic magnet 41 injected into the mold. This can be surely prevented. For this reason, in the magnet rotor 32, the joining strength between the rotor body 40 and the plastic magnet 41 does not decrease. Furthermore, since the six anti-rotation portions 43 are formed at equal intervals, the stress acting on each anti-rotation portion 43 can be made uniform, and the bonding strength between the rotor body 40 and the plastic magnet 41 can be improved. Can do.
Further, since the plastic magnet 41 is not heated after being cured, the heat damage to the plastic magnet 41 does not occur. Therefore, the performance of the plastic magnet is not lowered, and the performance of the magnet rotor 32 is not lowered.

Subsequently, the operation of the EGR valve 10 having the above-described configuration will be described. First, part of the exhaust gas discharged from the engine is introduced into the EGR valve 10 from the inlet 12 as EGR gas.
When the EGR gas is recirculated to the engine intake system, when the magnet rotor 32 is rotated counterclockwise, the rod 21 is rotated clockwise via the male screw portion 22 screwed into the female screw portion 42 of the rotor body 40. Move downward while rotating. As a result, the valve 20 moves downward and is separated from the seat 15. As a result, the communication passage 14 is opened and the introduction port 12 and the discharge port 13 communicate with each other, so that EGR gas is discharged from the EGR valve 10 and returned to the intake system of the engine.

  Here, the flow rate of the EGR gas returning to the intake system of the engine is controlled by the distance (valve opening) between the valve 20 and the seat 15. That is, the valve opening degree is controlled by changing the stroke amount of the rod 21. In the EGR valve 10, the rotational movement of the rotor main body 40 is directly converted into the stroke movement of the rod 21 by the conversion mechanism 33, so that the mutual positional relationship and operation timing between the rotor main body 40 and the rod 21 at the time of conversion. Can be minimized. In the EGR valve 10, when the rod 21 is manufactured, the male screw portion 22, the spring receiver 23, and the stopper 25 are integrally formed at the same time, so that the placement position accuracy of the stopper 25 with respect to the rod 21 is stably secured. Has been. For this reason, the initial position of the rod 21 serving as a reference for controlling the valve opening (stroke amount of the rod 21) is accurately determined. Therefore, in the EGR valve 10, the position (opening degree) of the valve 20 can be controlled with high accuracy, and the recirculation amount control of the exhaust gas can be performed with high accuracy.

  Thereafter, when the recirculation of EGR gas to the intake system of the engine is stopped, the magnet rotor 32 is rotated clockwise. Then, the rod 21 rotates counterclockwise via the male screw portion 22 screwed into the female screw portion 42 of the rotor body 40. The rod 21 moves upward by the counterclockwise rotation of the rod 21 and the urging force of the spring 24. As a result, the valve 20 moves upward and comes into contact with the seat 15. As a result, the communication path 14 is blocked and the introduction port 12 and the discharge port 13 are not communicated with each other, so that EGR gas is not discharged from the EGR valve 10 and the recirculation to the intake system of the engine is stopped.

  In the fully closed state of the valve, as shown in FIG. 7, the end surface of the stopper 25 formed on the spring receiver 23 of the rod 21 is in surface contact with the end surface of the contact portion 44 formed on the rotor body 40. Abut. Thereby, since the contact strength between the stopper 25 and the contact portion 44 is improved, deformation of the contact portion between the stopper 25 and the contact portion 44 can be prevented. Accordingly, the mutual positional relationship between the rotational position of the rod 21 and the rotational position of the rotor main body 40 when the valve is fully closed, which is a reference for valve opening control by the actuator 30, can be always kept in the same state, so The opening degree can be controlled with high accuracy. For this reason, in the EGR valve 10, the control reliability is improved.

As described above in detail, according to the EGR valve 10 according to the present embodiment, the rod 21 that transmits the driving force of the actuator 30 to the valve 20 is used as an integrally molded product formed by precision cold forging. Yes. For this reason, when manufacturing the rod 21, the male screw portion 22, the spring receiver 23, and the stopper 25 are integrally formed at the same time, so that it is possible to stably secure the positional accuracy of the stopper 25 with respect to the rod 21. . Thereby, since the initial position of the rod 21 which becomes a reference for the valve opening (stroke amount of the rod 21) is accurately determined, the opening of the valve 20 can be controlled with high accuracy.
Further, since the stopper 25 is integrally formed with the rod 21, a process for fixing the stopper to the rod is not required as in the prior art, and the number of parts and the manufacturing process are reduced. Furthermore, when the rod 21 is manufactured, the male screw portion 22, the spring receiver 23, and the stopper 25 are integrally formed at the same time, so that the male screw portion 22 is not damaged.

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

It is sectional drawing which shows schematic structure of the EGR valve which concerns on embodiment. It is a front view which shows schematic structure of a rod. It is a top view which shows schematic structure of a rod. It is sectional drawing which shows schematic structure of a magnet rotor. It is a bottom view of a magnet rotor. It is a top view which shows schematic structure of a rotor main body. It is a figure which shows the positional relationship of the rotor main body and a rod at the time of valve | bulb full closure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 EGR valve 11 Housing 12 Inlet port 13 Outlet port 14 Communication path 15 Seat 20 Valve 21 Rod 22 Male thread part 23 Spring receiver 24 Spring 25 Stopper 30 Actuator 31 Coil 32 Magnet rotor 33 Conversion mechanism 40 Rotor main body 41 Plastic magnet 42 Female thread part 43 Non-rotating part 44 Abutting part

Claims (5)

An introduction port for introducing exhaust gas discharged from the engine, an exhaust port for discharging the exhaust gas to the intake system of the engine in order to mix a part of the exhaust gas with the intake air, and communication between the introduction port and the exhaust port. A housing in which a passage is formed; a seat provided in the communication passage; a drive shaft having a valve abutting on or separating from the seat attached to one end; and an actuator that moves the valve via the drive shaft In an exhaust gas recirculation device having
The actuator includes a coil, a rotor that is rotationally driven by energization of the coil, and a conversion mechanism that converts the rotational motion of the rotor into a stroke motion of the drive shaft so that the valve contacts or separates from the seat. With
The conversion mechanism includes a male screw portion formed on the drive shaft, and a female screw portion formed at the center of the rotor and screwed into the male screw portion,
An exhaust gas recirculation device, wherein the drive shaft is integrally formed with a stopper for regulating the initial position of the drive shaft. The exhaust gas recirculation device according to claim 1,
An exhaust gas recirculation apparatus, wherein a receiving portion for receiving an elastic body that urges the valve in a valve closing direction is integrally formed on the drive shaft. In the exhaust gas recirculation device according to claim 1 or 2,
The exhaust gas recirculation device, wherein the drive shaft is formed by precision cold forging. The exhaust gas recirculation device according to any one of claims 1 to 3,
The exhaust gas recirculation device according to claim 1, wherein when the valve is in a fully closed state, the stopper contacts the counterpart member in a surface contact state. The exhaust gas recirculation device according to claim 4,
The exhaust gas recirculation device, wherein the counterpart member is a convex portion formed in a part of the rotor.

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