JP2009197765A - Valve driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small sized valve driving device having good mountability to an engine by suitably setting an arrangement relation between a motor and a valve shaft. <P>SOLUTION: The valve driving device 1 includes a housing 2 including a fluid channel therein, a valve seat 3 provided in the fluid channel in the housing 2, a valve element 4 controlling flow rate of exhaust gas by being seated on and separated from the vale seat 3, the valve shaft 5 fixed on the valve element 4 at one end and capable of reciprocating linear motion, a motor 6 moving the valve shaft 5 in reciprocating linear motion, conversion mechanisms 16, 17 converting rotary motion of the motor 6 to reciprocating linear motion of the valve shaft 5, and transmission mechanisms 14, 15 transmitting the rotary motion of the motor 6 to the conversion mechanisms 16, 17. The motor 6 is provided in parallel with the reciprocating linear motion direction of the valve shaft 5, and is provided at a position in a same direction as the valve element 4 with respect to the transmission mechanism 15. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a valve drive device that is installed in an exhaust gas recirculation device (EGR device) that returns a part of exhaust gas discharged from an engine to an intake system and that drives a valve member that opens and closes a fluid passage by a motor.

  In an EGR (Exhaust Gas Recirculation) device installed in an exhaust gas recirculation system, a part of the exhaust gas discharged from the combustion chamber of the engine to the exhaust passage is recirculated to the intake passage through the EGR passage. In the engine, a part of this exhaust gas is introduced into the intake passage as EGR gas, mixed with the outside air, and sucked into the combustion chamber, thereby lowering the combustion temperature of the combustible air-fuel mixture in the combustion chamber and reducing the nitrogen in the exhaust gas. The amount of oxide (NOx) produced can be reduced. The EGR device is provided with a valve body for opening and closing the EGR passage, and the valve body is opened and closed by a valve driving device. The inflow amount of exhaust gas is controlled by the valve opening amount of the EGR passage by the valve body. A general valve drive device installed in an EGR device includes a housing having a fluid passage as an EGR passage therein, a valve seat provided in the fluid passage in the housing, and a seat (valve closing) on the valve seat. A valve body that controls the flow rate of exhaust gas by separating (opening), a valve shaft that is fixed at one end to the valve body and capable of reciprocating linear motion, a motor that reciprocates linearly the valve shaft, and the motor A conversion mechanism that converts the rotational motion of the motor into a reciprocating linear motion of the valve shaft, and a transmission mechanism that transmits the rotational motion of the motor to the conversion mechanism.

As this type of valve drive device, there are Patent Documents 1 to 3. In the valve drive device of Patent Document 1, a motor for reciprocating linear movement of the valve shaft is provided in series at the rear end of the valve shaft having a valve body at the tip. The valve drive device of Patent Document 2 is also provided with a stepping motor in series at the rear end of the valve shaft. The conversion mechanism here consists of a female screw and a female screw provided on the rotor and valve shaft of the stepping motor. By rotating the rotor, the valve shaft reciprocates linearly in its axial direction due to the relationship between the male screw and the female screw. By doing so, the valve body is opened and closed. When the valve body is fully closed, play is provided between the thread of the male screw and the thread of the female screw. Can be absorbed by play. In addition, in order to restrict the rotation of the rotor when the valve element is fully closed, the rotation is composed of a pin protruding outward in the radial direction of the valve shaft and a stopper provided on the rotor that can come into contact with the pin. Regulatory means are also provided. In the valve drive device of Patent Document 3, the motor is in a right angle relationship with the reciprocating linear motion direction of the valve shaft. Here, a spur gear that meshes with a pinion gear provided on the rotation shaft of the motor is used as a transmission mechanism that transmits the rotation motion of the motor to the valve shaft via the conversion mechanism. As a conversion mechanism for converting into a reciprocating linear motion, a cam plate that rotates coaxially with a spur gear is used.
JP 2007-255583 A JP 2002-34228 A JP 2006-292009 A

  In the valve drive devices of Patent Document 1 and Patent Document 2, since the motor and the valve shaft are arranged in series, the dimension of the valve shaft in the reciprocating linear motion direction in the valve drive device is the length of the valve shaft + the valve shaft. The valve opening amount (linear momentum) + the motor length is the minimum required, and the valve drive device becomes large. If the overall length of the valve drive device is large, the mountability on the engine also deteriorates. In the valve drive device of Patent Document 3, since the motor and the valve shaft are in a right angle relationship, it is not as large as the valve drive devices of Patent Document 1 and Patent Document 2, but in addition to the reciprocating linear motion direction of the valve shaft. Since a certain dimension is required also in the direction in which the motor is arranged, it is not suitable for downsizing the apparatus.

  Therefore, the present invention solves the above-described problems, and provides a valve drive device that is small and has good mountability to an engine by suitably setting the positional relationship between the motor and the valve shaft.

  The present invention includes a housing having a fluid passage therein, a valve seat provided in the fluid passage in the housing, a valve body that controls the flow rate of exhaust gas by being seated on and separated from the valve seat, and one end thereof A valve shaft fixed to the valve body and capable of reciprocating linear motion; a motor for reciprocating linear motion of the valve shaft; a conversion mechanism for converting rotational motion of the motor into reciprocating linear motion of the valve shaft; And a transmission mechanism that transmits rotational motion to the conversion mechanism, wherein the motor is provided in parallel with a reciprocating linear motion direction of the valve shaft, and the valve body with respect to the transmission mechanism It is provided in the position of the same direction.

  A sensor that detects the reciprocating linear momentum of the valve shaft is provided at a position opposite to the valve body with the transmission mechanism interposed therebetween.

  The transmission mechanism is constituted by a pinion gear provided on a rotating shaft of the motor, and a spur gear in which the valve shaft is inserted in a central portion in a radial direction meshing with the pinion gear, and the conversion mechanism is configured by the flat gear. It can be set as the thread part provided in the said valve stem which can be screwed together with the thread part provided in the gearwheel, and the screw part of this spur gear. In this case, when the valve body is seated on the valve seat, a clearance is provided between the screw portion of the spur gear and the screw portion of the valve shaft so as to allow the spur gear to rotate. preferable.

  Alternatively, the transmission mechanism is constituted by a pinion gear provided on the rotation shaft of the motor and a spur gear meshing with the pinion gear, and the conversion mechanism is provided in an arc shape on the lower surface of the spur gear, It can also be set as the cam converted into a linear motion by pressing the other end of the valve shaft. In this case, when the valve body is seated on the valve seat, it is preferable to provide a gap between the cam and the other end of the valve shaft.

  The valve drive device of the present invention includes a rotation preventing mechanism that reciprocates and linearly moves the valve shaft, and a linear movement preventing mechanism that rotates the spur gear but does not linearly rotate it.

  According to the present invention, the motor is provided in parallel with the reciprocating linear motion direction of the valve shaft, and is provided at a position in the same direction as the valve body with respect to the transmission mechanism. The length of the motor can be omitted from the dimension (length dimension) of the valve shaft in the reciprocating linear motion direction, and the valve drive device can be downsized. Further, since the motor and the valve shaft are in a parallel relationship, the direction perpendicular to the reciprocating linear mobility direction of the valve shaft, that is, the dimension in the planar direction of the valve drive device is not unnecessarily increased. Since the overall length of the valve drive device is reduced, the mountability to the engine is also improved.

  Currently, in order to meet the exhaust gas regulations of automobiles, it is obliged to install on-board diagnosis (OBD) system that detects the failure of various devices by means of sensors on the vehicle. It is becoming necessary to detect it. The OBD system is a device in which the vehicle itself detects and monitors an abnormality (sudden failure) of the exhaust gas countermeasure device, displays an alarm to notify the driver when the abnormality occurs, and stores and stores the details of the failure. Therefore, if a sensor for detecting the reciprocating linear momentum of the valve shaft is provided, it is possible to detect an operation failure of the valve body and cope with emission OBD. The sensor can also be used for feedback control when the motor is used. That is, by detecting the movement amount of the valve shaft by the sensor, the rotation direction, rotation amount, stop timing, etc. of the motor can be controlled.

  The transmission mechanism is composed of pinion gears and spur gears, and the conversion mechanism is a screw part provided on the spur gears and the valve shaft, so that the rotation output of the motor can be transmitted and converted with a compact configuration, and the rotation of the motor The output can be small. In addition, if a clearance is provided between the screw portion of the spur gear and the screw portion of the valve shaft when the valve body is seated on the valve seat, the motor stop timing can be reduced. It is possible to avoid a malfunction due to the spur gear and the valve shaft being firmly meshed with each other when the inertia rotates after shifting or stopping. Further, this play can absorb dimensional errors of the spur gear and the valve shaft.

  The transmission mechanism is composed of pinion gears and spur gears, and the conversion mechanism is a cam provided on the lower surface of the spur gear, so that the rotational output of the motor can be transmitted and converted with a compact configuration, and the rotational output of the motor is also small. Tesumu. In addition, when the valve element is seated on the valve seat, a dimensional error of the valve shaft can be absorbed by providing a gap between the cam and the valve shaft.

  If an anti-rotation mechanism for the valve shaft is provided, the valve shaft does not rotate together with the spur gear, and the valve shaft can be reliably reciprocated linearly. Further, if a linear motion prevention mechanism for the spur gear is provided, the spur gear does not move linearly with the valve shaft, and the valve shaft can be reliably reciprocated linearly.

Example 1
Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. However, the present invention is not limited thereto, and various modifications can be made without departing from the gist of the present invention. 1 to 11 show a first embodiment of the present invention. FIG. 1 is a cross-sectional view of the valve drive device according to the first embodiment. FIG. 2 is a plan view of the valve drive device according to the first embodiment. FIG. 3 is a front view of the valve stem. FIG. 4 is a side view of the valve shaft. FIG. 5 is a plan view of the valve shaft. FIG. 6 is a bottom view of the valve shaft. FIG. 7 is a plan view of the rotation preventing body. FIG. 8 is a longitudinal sectional view of the rotation preventing body. FIG. 9 is a longitudinal sectional view of a spur gear. FIG. 10 is a bottom view of the spur gear. FIG. 11 is an enlarged vertical cross-sectional view of a main part of the screw part.

  The valve drive device 1 of the present invention is installed to control the flow rate of exhaust gas when a part of exhaust gas from an engine is recirculated to an intake passage as EGR gas in an automobile exhaust gas recirculation system. The As shown in FIG. 1, the valve drive device 1 includes a housing 2 having a fluid passage therein, a valve seat 3 provided in the fluid passage in the housing 2, and a seating / separating operation on the valve seat 3. The valve body 4 for controlling the flow rate of the exhaust gas, the valve shaft 5 capable of reciprocating linear motion, the motor 6 for reciprocating linear motion of the valve shaft 5, and the reciprocating linear motion of the valve shaft 5 by rotating the motor 6 And a transmission mechanism for transmitting the rotational motion of the motor 6 to the conversion mechanism.

  The housing 2 accommodates various members such as a valve body 4, a valve shaft 5, a motor 6, a conversion mechanism, and a transmission mechanism in addition to a fluid passage. The fluid passage is provided as an EGR passage, and includes an introduction portion 10 that communicates with an exhaust passage (not shown) from the engine, and an exhaust portion 11 that communicates with an intake passage (not shown) connected to the combustion chamber of the engine. The communication part 12 communicates the introduction part 10 and the discharge part 11. The valve seat 3 is provided between the introduction part 10 and the communication part 12, and the fluid passage is opened and closed by the valve body 4 being seated and separated from the introduction part 10 side. The valve body 4 is a poppet valve having a substantially conical shape, and a lower end (one end) of a valve shaft 5 extending in the vertical direction in the housing 2 is fixed to the valve body 4 by welding. That is, the valve shaft 5 reciprocates linearly in the vertical direction. A DC motor is used as the motor 6.

  A pinion gear 14 is provided on the rotating shaft of the motor 6, and a spur gear 15 is arranged so as to mesh with the pinion gear 14. The diameter of the spur gear 15 is at least twice the diameter of the pinion gear 14. The valve shaft 5 is inserted through the central portion of the spur gear 15 in the radial direction, and the rotational output of the motor 6 is transmitted to the valve shaft 5 via the spur gear 15. That is, a transmission mechanism is constituted by the pinion gear 14 and the spur gear 15 of the motor 6. A female screw 16 is provided on the inner peripheral surface of the valve shaft insertion hole of the spur gear 15. On the other hand, a male screw 17 screwed with the female screw 16 is provided on the upper outer peripheral surface of the valve shaft 5. By rotating the female screw 16 of the spur gear 15 and the male screw 17 of the valve shaft 5, the rotational motion of the spur gear 15 around the valve shaft 5 is converted into the reciprocating linear motion of the valve shaft 5. That is, the female screw 16 of the spur gear 15 and the male screw 17 of the valve shaft 5 constitute a conversion mechanism. The female screw 16 of the spur gear 15 and the male screw 17 of the valve shaft 5 correspond to the screw portion of the present invention.

  The motor 6 is provided in the vertical direction parallel to the reciprocating linear motion direction of the valve shaft 5 and is in the same direction as the valve body 4 with respect to the spur gear 15 constituting the transmission mechanism, that is, more than the spur gear 15. It is provided in the lower position. Thereby, as shown well in FIG. 1, the vertical dimension of the valve drive device 1 is short, and as shown in FIG. It has become.

  The valve drive device 1 will be described in more detail. The motor 6 is fixed to the housing 2 on both sides of the valve shaft 5 by two bolts 20. The motor 6 is fixed in a floating manner so as not to come into direct contact with the housing 2, and the bottom surface thereof is elastic by a wave washer 21 having a circular ring shape interposed between the motor 6 and the housing 2 and having a central portion curved upward. Is supported. Thereby, it is avoided that the drive vibration of the motor 6 is directly transmitted to the housing 2. The valve shaft 5 is supported by a bearing 22 made of a thrust bearing so as to be able to reciprocate linearly in the vertical direction. The body 23 is arranged.

  The lower surface of the spur gear 15 is integrally formed with a cylindrical portion 15a having an open lower surface, and the cylindrical portion 15a surrounds the outer periphery of the lower bearing 25 formed of a ball bearing provided on the outer periphery of the rotation preventing body 23. Yes. A housing cover 26 is bolted above the housing 2, and the upper portion of the spur gear 15 is rotatably supported by an upper bearing 27 formed of a ball bearing provided on the housing cover 26. The valve shaft 5 is always urged upward (in the valve closing direction) by a first spring 29 provided between the circular plate 28 provided immediately below the male screw 17 and the lower bearing 25. The spur gear 15 is also always urged upward by the second spring 30 provided on the outer periphery of the first spring 29 between the upper surface of the cylindrical portion 15 a and the lower bearing 25.

  The upper part of the valve shaft 5 extends to the inside of the housing cover 26, and an inductive sensor for detecting the reciprocating linear momentum of the valve shaft 5 is provided in this portion. That is, an inductive sensor is provided at a position opposite to the valve body 4 with the spur gear 15 constituting the transmission mechanism interposed therebetween. The inductive sensor is composed of a sensor main body 32 provided on the housing cover 26 so as to be located on the side of the valve shaft 5 and a metal cursor 33 fitted to the upper end (the other end) of the valve shaft 5. Has been. Although not shown, the sensor body 32 is provided with an excitation coil and a plurality of search coils for detecting voltage, and the capacitance change when the cursor 33 moves up and down in the electric field by the excitation coil. By detecting the sensor main body 32, the reciprocating linear momentum of the valve shaft 5 can be detected. The housing 2 is provided with a connector 34 connected to a power source, and the sensor main body 32 is energized through a terminal 35 passing through the housing 2 from the connector 34. Although not shown, the motor 6 is also energized through a power supply terminal connected to the terminal 35. Reference numeral 36 denotes a seal that ensures airtightness between the housing 2 and the housing cover 26.

  The valve shaft 5 is basically cylindrical from the lower end to the upper end, but as shown in FIGS. 4 and 6, the left and right sides of a large-diameter circle are cut off at a part thereof. As described above, there is an oval shaft portion 5a that is wide in the front and rear direction. The oval shaft portion 5a is formed below the circular plate 28 over a predetermined dimension. As shown in FIGS. 3 and 5, two stopper pieces 38 and 38 are integrally formed on the left and right sides of the upper surface of the circular plate 28. As shown well in FIG. 5, the left and right stopper pieces 38, 38 are slightly misaligned with respect to the center line L passing through the center of the circular plate 28. As shown in FIGS. 7 and 8, the rotation preventing body 23 has a cylindrical shape, and receives the lower bearing 25 at a step portion 23 a formed at the upper and lower intermediate portions of the outer peripheral surface. The insertion hole 39 through which the valve shaft 5 is inserted is also an oval shape having the same shape and size as the oval shaft portion 5 a of the valve shaft 5. FIG. 7 shows the rotation preventing body 23 and the insertion hole 39 in an enlarged state in relation to the dimensions of the oval shaft portion 5a shown in FIG. The oval shaft portion 5 a of the valve shaft 5 has a vertical dimension that reaches at least below the upper end of the anti-rotation body 23 when the valve body 4 is in a closed state in which the valve body 4 is seated on the valve seat 3. The anti-rotation body 23 and the oval shaft portion 5a constitute the anti-rotation mechanism of the present invention.

  As shown in FIGS. 9 and 10, two stoppers 41 and 41 that are in contact with the stopper pieces 38 of the circular plate 28 are integrally formed on the top surface of the cylindrical portion 15 a (the central portion of the lower surface of the spur gear 15). Is formed. Each stopper 41 is formed in a circular arc shape with the female screw 16 as the center, a stopper portion 41a having substantially the same height as the stopper piece 38, and the reverse rotation direction (forward rotation direction) of the spur gear 15 from the stopper portion 41a. And an inclined portion 41b extending to the downstream side. Further, as shown in FIG. 11, a gap S having a predetermined dimension is provided between the female screw 16 of the spur gear 15 and the male screw 17 of the valve shaft 5. The stopper piece 38 of the circular plate 28 and the stopper 41 of the spur gear 15 serve as an over-rotation preventing mechanism that defines the rotation limit of the spur gear 15.

  Next, the operation of the valve drive device 1 will be described. In the stop state of the valve drive device 1, the circular plate 28 fitted to the valve shaft 5 is biased upward by the first spring 29, so that the valve body 4 is seated on the valve seat 3 from below. In addition, the introduction part 10 and the communication part 12 constituting the fluid passage are closed in a non-communication manner. When the engine is driven and exhaust gas is generated, a part of the exhaust gas is introduced into the intake passage as EGR gas as necessary, so that the valve drive device 1 is operated and the fluid passage is opened. Specifically, when the motor 6 is energized through the terminal 35 extending from the connector 34 and the motor 6 rotates forward, the spur gear 15 that meshes with the pinion gear 14 also rotates forward, and the rotation output of the motor 6 serves as a conversion mechanism. Are transmitted to the female screw 16 and the male screw 17. When the spur gear 15 rotates forward, the valve shaft 5 linearly moves downward against the biasing force of the first spring 29 due to the relationship between the female screw 16 and the male screw 17. As the valve shaft 5 moves downward while rotating, each stopper piece 38 also moves below each stopper 41 while rotating. At this time, the stopper 41 is provided with the inclined portion 41b, so that one stopper piece 38 can be prevented from coming into contact with the other stopper 41 with rotation. The valve shaft 5 is designed to move once when the spur gear 15 rotates 240 ° forward.

  When the valve shaft 5 linearly moves in the vertical direction, the oval shaft portion 5a of the valve shaft 5 slides up and down in the oval insertion hole 39 of the rotation preventing body 23 fixed in a stationary manner. The valve shaft 5 does not rotate in the circumferential direction. Further, since the spur gear 15 is always urged upward by the second spring 30, the step portion 15 b (see FIG. 9) provided at the upper portion thereof is firmly in contact with the lower surface of the upper bearing 27. Therefore, it does not move up and down carelessly. That is, the second spring 30, the upper bearing 27, and the step portion 15 b of the spur gear 15 constitute a linear motion prevention mechanism that rotates the spur gear 15 but does not linearly move it. The elastic pressure (biasing force) of the second spring 30 is larger than the elastic force of the first spring 29. Further, since the spur gear 15 has a diameter more than twice that of the pinion gear 14, the gear ratio between both gears 14 and 15 is large, and the torque acting on the pinion gear 14 is small. In addition, the DC motor has a larger driving force than the stepping motor. Therefore, a relatively small motor can be used as the motor 6, thereby further reducing the size of the valve drive device 1.

  As the valve shaft 5 moves downward, the valve body 4 also moves downward, so that the valve body 4 is separated from the valve seat 3 and opened. When the valve body 4 is opened, the introduction portion 10 and the communication portion 12 are in communication with each other, and a part of the exhaust gas flowing through the exhaust passage is passed through the introduction portion 10, the communication portion 12, and the discharge portion 11. It flows in the housing 2 in order, and is recirculated to the intake passage as EGR gas. The valve opening amount (vertical linear momentum) of the valve body 4 is detected and controlled by an inductive sensor. That is, the sensor body 32 detects the downward movement amount of the cursor 33 based on the change in capacitance, and the motor 6 is controlled to stop when the cursor 33 moves downward by a predetermined amount. At the same time, even when the motor 6 is energized, even if the valve shaft 5 does not move linearly due to a failure or the like, it can be detected by the inductive sensor, so that the OBD system can be accurately handled.

  When the valve body 4 is closed, the motor 6 is rotated in the reverse direction. By rotating the motor 6 in the reverse direction, the pinion gear 14, the spur gear 15, the female screw 16, and the male screw 17 are also rotated in the reverse direction, so that the valve shaft 5 linearly moves upward. When the sensor body 32 detects that the valve body 4 is seated on the valve seat 3 and is closed based on the upward movement amount of the cursor 33, the motor 6 is stopped. However, in reality, a slight time lag may occur in the control of the motor 6 by the inductive sensor, or the spur gear 15 may further rotate due to inertia. Thus, when the valve shaft 5 is at the upper movement limit position, the spur gear 15 is further rotated, so that the female screw 16 and the male screw 17 are firmly meshed with each other, and the motor 6 is rotated forward again. In other words, there are problems such as requiring a large amount of force, shifting the start timing of the motor 6, and in the worst case, the motor 6 cannot be re-driven. However, when the valve shaft 5 with the valve body 4 seated on the valve seat 3 is at the upper movement limit position, a gap is provided between the female screw 16 of the spur gear 15 and the male screw 17 of the valve shaft 5. Further, the play that allows the spur gear 15 to rotate is secured, and the above problem does not occur. In addition, as the valve shaft 5 moves upward while rotating, each stopper piece 38 also approaches each stopper 41 from below while rotating. One stopper piece 38 passes along the inclined portion 41 b of the other stopper 41, and comes into contact with the stopper portion 41 a of the one stopper 41 when the valve body 4 is seated on the valve seat 3. Similarly, the other stopper piece 38 passes along the inclined portion 41 b of the one stopper 41 and contacts the stopper portion 41 a of the other stopper 41 when the valve body 4 is seated on the valve seat 3. This restricts the spur gear 15 from rotating further.

(Example 2)
FIG. 12 shows a second embodiment of the present invention. FIG. 12 is a cross-sectional view of the valve drive device 1 according to the second embodiment. The second embodiment is a modification of the first embodiment, and a rotary non-contact sensor is used instead of the induction sensor as a sensor for detecting the reciprocating linear momentum of the valve shaft 5. As shown in FIG. 12, the rotary non-contact sensor includes a sensor main body 45 incorporating a calculation unit, and a plurality of (three in this embodiment) detection terminals 46 protruding outward from the sensor main body 45. And is fixed immovably in a sensor chamber 47 integrally formed from the lower surface of the housing cover 26. On the other hand, a pair of left and right magnets 48 and 48 are fitted to the upper end of the spur gear 15, and both magnets 48 and 48 circulate around the detection terminal 46 as the spur gear 15 rotates. The detection terminal 46 detects the direction of the magnetic field generated between the magnets 48 and 48. By detecting the rotation amount of the magnets 48 and 48, the rotation amount of the spur gear 15 and thus the valve shaft 5 is detected. The linear momentum can be detected. Although not shown in FIG. 12, the rotary non-contact sensor is also energized from the connector 34 through the terminal. The other parts are the same as those in the first embodiment, and thus the same members are denoted by the same reference numerals and the description thereof is omitted.

(Example 3)
13 to 16 show a third embodiment of the present invention. FIG. 13 is a cross-sectional view of the valve drive device 1 according to the third embodiment. FIG. 14 is a bottom view of the spur gear 50. FIG. 15 is a schematic configuration diagram showing a linear motion mechanism of the valve shaft 5 as the spur gear 50 rotates. FIG. 16 is an enlarged view of a main part showing the positional relationship between the cam 51 and the valve shaft 5 when the valve body 4 is seated on the valve seat 3. The third embodiment is a modification of the second embodiment, and is different in a conversion mechanism for converting the rotational motion of the motor 6 into the reciprocating linear motion of the valve shaft 5. Specifically, the conversion mechanism includes a cam 51 provided in an arc shape on the lower surface of the spur gear 50.

  As shown in FIG. 13, the spur gear 50 is disposed so as to be rotatable around a rotating shaft 53 erected in the housing 52. The lower surface of the spur gear 50 is supported by a gear support surface 52 a of the housing 52, and the upper portion of the spur gear 50 is supported by the upper bearing 27. Thus, the spur gear 50 is restricted from moving in the vertical direction, and the gear support surface 52a and the upper bearing 27 constitute a linear motion preventing mechanism that rotates the spur gear 50 but does not linearly move. The third embodiment is not provided with a spring that constantly biases the spur gear 50 upward.

  As shown in FIG. 14, the cam 51 is formed in an arc shape having a length of 240 ° with the central hole through which the rotary shaft 53 is inserted as the center, and the first flat portion 51 a and the first inclination are formed. The shape which has the part 51b, the 2nd plane part 51c, the 2nd inclination part 51d, and the 3rd plane part 51e continuously in this order is exhibited. As well shown in FIG. 15A, the amount of protrusion from the lower surface of the spur gear 50 is stepwise (in three steps) in the order of the first plane portion 51a, the second plane portion 51c, and the third plane portion 51e. The flat portions 51a, 51c, 51e have a predetermined length dimension in the circumferential direction.

  Returning to FIG. 13, the valve shaft 5 is displaced from the rotating shaft 53 by a predetermined amount to the side, and is provided at a position along the lower surface of the cam 51. When the valve body 4 shown in FIG. 15A is seated on the valve seat 3, the upper end of the valve shaft 5 faces the first flat portion 51 a of the cam 51. When the motor 6 is rotated in the forward direction, the cam 51 is also rotated in the forward direction as the spur gear 50 is rotated in the forward direction. Then, the upper end of the valve shaft 5 is pressed downward by the first inclined portion 51 b, so that the valve shaft 5 linearly moves downward against the urging force of the spring 29. When the amount of recirculation of the EGR gas may be small, the second flat portion 51c may be stopped at an angle facing the upper end of the valve shaft 5 as shown in FIG. In this case, the valve opening amount by the valve body 4 is small. When it is desired to recirculate a large amount of EGR gas, the spur gear 50 is further rotated in the forward direction, and the valve shaft 5 is further pressed downward by the second inclined portion 51d, as shown in FIG. When the third flat surface portion 51e reaches the upper end of the valve shaft 5, the motor 6 is stopped. In this case, the valve opening amount by the valve body 4 is larger than the state in which the valve shaft 5 faces the second flat portion 51c. As described above, by providing the cam 51 with a plurality of flat portions, the valve opening amount of the valve body 4 can be controlled in a plurality of stages. Further, since each plane portion has a predetermined length dimension, even if the stop timing of the motor 6 is shifted or further rotated due to inertia, the valve shaft 5 can be held at the vertical height position.

  When the motor 6 is rotated in the reverse direction from the state shown in FIG. 15B or FIG. 15C, the valve shaft 5 slides on the lower surface of the cam 51 in the opposite direction to the above, and the spring 29 biases upward. When the valve shaft 5 comes to a position where the valve shaft 5 faces the first flat portion 51a, the valve body 4 is closed. At this time, as well shown in FIG. 16, a predetermined amount of gap is provided between the cam 51 and the upper end (the other end) of the valve shaft 5. Thereby, the dimensional error of the valve shaft 5 is absorbed. The other parts are the same as those in the first and second embodiments, and the same members are denoted by the same reference numerals and the description thereof is omitted.

Example 4
17 to 18 show a fourth embodiment of the present invention. FIG. 17 is a cross-sectional view of the valve drive device 1 according to the fourth embodiment. FIG. 18 is a partially broken plan view of the valve drive device 1 according to the fourth embodiment. The fourth embodiment is another modification of the second embodiment, and the arrangement position of the rotary non-contact sensor that detects the reciprocating linear momentum of the valve shaft 5 is different. Specifically, as shown in FIGS. 17 and 18, a sensor housing chamber 58 is provided on the opposite side of the motor 6 across the spur gear 15 in the housing 56 and the housing cover 57, and the sensor housing 58 is provided. The same rotary non-contact sensor as that of the second embodiment is immovably provided in the chamber 58. A second gear 59 having a smaller diameter than the spur gear 15 is integrally formed on the upper stage of the spur gear 15. A third gear 60 that meshes with the second gear 59 is provided below the sensor chamber 47 in the sensor housing chamber 58. The third gear 60 is a fan-shaped gear of about 120 °, and is rotatable around a rotating shaft 61 provided upright in the sensor housing chamber 58. A pair of left and right magnets 48, 48 are also fitted to the upper end of the third gear 60, and both the magnets 48, 48 are integrated with the third gear 60 around the sensor body 45 and the detection terminal 46. Go around.

  When the motor 6 is driven, the rotational output of the motor 6 is transmitted to the third gear 60 via the second gear 59 that rotates integrally with the spur gear 15 in a coaxial manner. Thereby, the rotation amount of the magnet 48 is detected by the magnet 48 orbiting around the rotary non-contact sensor. In the control device of the motor 6, the gear ratio of each gear 14, 15, 59, 60 is set in advance, and the linear momentum of the valve shaft 5 is calculated according to the rotation amount of the magnet 48, and the motor 6 is driven. Be controlled. The conversion mechanism and the transmission mechanism in the fourth embodiment are the same as those in the first and second embodiments. Others are the same as those in the first and second embodiments, and thus the same members are denoted by the same reference numerals and the description thereof is omitted.

(Other variations)
In each embodiment, the installation position of the motor 6 is not particularly limited as long as it is parallel to the reciprocating linear motion direction of the valve shaft 5 and in the same direction as the valve body 4 with respect to the transmission mechanism. The inductive sensor of the first embodiment can be applied to the second to fourth embodiments, and the rotary non-contact sensor of the second to fourth embodiments can be applied to the first embodiment. As the rotation prevention mechanism, a part of the valve shaft 5 and the insertion hole of the rotation prevention body 23 are oval, but may be at least non-circular, and may be a polygon such as a triangle or a rectangle, or an indefinite shape. The number of the stopper pieces 38 and the stoppers 41 as the over-rotation preventing mechanism for the spur gear 15 may be one, and it is not always necessary to provide the gap S between the female screw 16 and the male screw 17. The female screw 16 may be provided on the valve shaft 5 and the male screw 17 may be provided on the spur gear 15. In the third embodiment, the number of flat portions of the cam 51 may be two, or four or more. As the number of flat portions increases, the stepwise control of the valve opening amount by the valve body 4 can be performed more finely.

It is sectional drawing of the valve drive device which concerns on Example 1. FIG. 1 is a plan view of a valve drive device according to Embodiment 1. FIG. It is a front view of a valve stem. It is a side view of a valve stem. It is a top view of a valve shaft. It is a bottom view of a valve stem. It is a top view of a rotation prevention body. It is a longitudinal cross-sectional view of a rotation prevention body. It is a longitudinal cross-sectional view of a spur gear. It is a bottom view of a spur gear. It is a principal part expansion longitudinal cross-sectional view of a screw part. It is sectional drawing of the valve drive device 1 which concerns on Example 2. FIG. It is sectional drawing of the valve drive device 1 which concerns on Example 3. FIG. It is a bottom view of a spur gear. It is a schematic block diagram which shows the linear motion mechanism of the valve shaft accompanying rotation of a spur gear. It is a principal part enlarged view which shows the positional relationship of a cam and a valve stem when a valve body is seated on the valve seat. It is sectional drawing of the valve drive device 1 which concerns on Example 4. FIG. It is a partially broken top view of the valve drive device 1 which concerns on Example 4. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Valve drive device 2 * 52 * 56 Housing 3 Valve seat 4 Valve body 5a Oval shaft part 5 Valve shaft 6 Motor 10 Introduction part 11 Discharge part 12 Communication part 14 Pinion gear 15/50 Spur gear 15a Cylindrical part 16 Female screw 17 Male screw 21 Wave washer 22 Bearing 23 Anti-rotation body 25 Lower bearing 26/57 Housing cover 27 Upper bearing 28 Circular plate 29 First spring 30 Second spring 32 Sensor body 33 Cursor 34 Connector 35 Terminal 38 Stopper piece 41 Stopper 45 Sensor body 46 Detection terminal 47 Sensor chamber 48 Magnet 51 Cam 51a / 51c / 51d Flat portion 53 Rotating shaft 59 Second gear 60 Third gear S Gap

Claims (5)

A housing having a fluid passage therein, a valve seat provided in the fluid passage in the housing, a valve body that controls the flow rate of exhaust gas by being seated and separated from the valve seat, and one end of the valve body A fixed valve shaft capable of reciprocating linear motion, a motor for reciprocating linear motion of the valve shaft, a conversion mechanism for converting rotational motion of the motor into reciprocal linear motion of the valve shaft, and rotational motion of the motor A valve drive device having a transmission mechanism for transmitting to the conversion mechanism,
The valve drive device according to claim 1, wherein the motor is provided in parallel with a reciprocating linear motion direction of the valve shaft, and is provided at a position in the same direction as the valve body with respect to the transmission mechanism.   The valve drive device according to claim 1, wherein a sensor that detects a reciprocating linear momentum of the valve shaft is provided at a position opposite to the valve body with the transmission mechanism interposed therebetween. The transmission mechanism is composed of a pinion gear provided on the rotating shaft of the motor, and a spur gear in which the valve shaft is inserted in the radial center of the pinion gear.
The conversion mechanism includes a screw portion provided on the spur gear and a screw portion provided on the valve shaft that can be screwed with the screw portion of the spur gear.
When the valve body is seated on the valve seat, a gap is provided between the screw portion of the spur gear and the screw portion of the valve shaft so as to allow the spur gear to rotate. The valve drive device according to claim 1 or 2. The transmission mechanism comprises a pinion gear provided on the rotating shaft of the motor, and a spur gear meshing with the pinion gear,
The conversion mechanism comprises a cam that is provided in an arc shape on the lower surface of the spur gear and that converts to a linear motion by pressing the other end of the valve shaft,
3. The valve drive device according to claim 1, wherein a gap is provided between the cam and the other end of the valve shaft when the valve body is seated on the valve seat. 4. An anti-rotation mechanism for reciprocating linearly moving the valve shaft but not rotating it;
The valve drive device according to any one of claims 1 to 4, further comprising a linear motion prevention mechanism that rotates the spur gear around but does not linearly move it.

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