JP2009264504A - Valve driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve driving device enabling to control the valve opening of a valve element with high accuracy while avoiding an increase in the size of the device by efficiently assembling an internal mechanism. <P>SOLUTION: The valve driving device comprises the valve element 4 to be seated on/off a valve seat 3 provided on a housing 2 having a fluid passage 7, to control the flow of exhaust gas, a valve shaft 5 having reciprocating linear motion, a motor 6 as a power source for the valve shaft 5, and a transmission mechanism for transmitting the rotating speed of the motor 6 to the valve shaft 5 while reducing the speed. The motor 6 is provided in parallel to the direction of the reciprocating linear motion of the valve shaft 5, and located on the transmission mechanism in the same direction as the valve element 4. The transmission mechanism consists of a first gear 11 provided on the rotating shaft of the motor 6, a second gear 12 engaging with the first gear 11 and having a diameter larger than the first gear 11, a third gear 13 coaxially integrated with the second gear 12 and having a diameter smaller than the second gear 12, and a fourth gear 14 engaging with the third gear 13 for driving the valve shaft 5 and having a diameter larger than the third gear 13. <P>COPYRIGHT: (C)2010,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 (intake manifold) 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. Generally, an EGR device includes a housing having a fluid passage as an EGR passage therein, and a valve seat provided in the fluid passage in the housing. A general valve driving device installed in the EGR device includes a valve body that controls the flow rate of exhaust gas by seating (closing) and separating (opening) the valve seat, and one end of the valve driving apparatus is a valve body. A valve shaft that is fixed and capable of reciprocating linear motion, a motor that is a power source for reciprocating linear motion of the valve shaft, and a transmission mechanism that transmits the rotational motion of the motor to the valve shaft.

As this type of valve drive device, there are, for example, Patent Document 1 and Patent Document 2. In the valve drive device of Patent Document 1, a stepping motor is provided in series in the axial direction at the rear end of a valve shaft having a valve body at the tip. The transmission mechanism here consists of a female screw and a female screw provided on the rotor of the stepping motor and the valve shaft. 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. In the valve drive device of Patent Document 2, the motor is in a right angle relationship with the reciprocating linear motion direction of the valve shaft. The transmission mechanism includes a pinion gear provided on the rotation shaft of the motor, a conversion gear that receives the rotation output of the motor and linearly moves the valve shaft, and an intermediate gear that is interposed between the pinion gear and the conversion gear. The valve opening amount by the valve element is controlled while reducing the rotational speed of the motor in two stages.
JP 2002-34228 A JP 2006-292009 A

  However, in Patent Document 1, a female screw is directly provided on the rotor of the stepping motor, and the rotation output from the motor is directly transmitted to the valve shaft. In this case, since the reduction ratio of the motor speed is not sufficient, the axial movement of the valve body relative to the motor speed is relatively large, the resolution of the valve body opening control is poor, and the exhaust gas flow rate is highly accurate. There is a limit to the control.

  In contrast, in Patent Document 2, an intermediate gear is provided to reduce the rotational speed of the motor in two stages. However, in Patent Document 3, since the motor shaft and the valve shaft are in a right angle relationship, in addition to the reciprocating linear motion direction of the valve shaft, a certain dimension is required in the motor arrangement direction, and the apparatus becomes large. Further, since the motor shaft and the valve shaft are in a right angle relationship, the internal structure becomes complicated, and it is difficult to effectively use the space formed by providing the intermediate gear.

  Here, this type of valve drive apparatus may be provided with a sensor that detects the opening degree of the valve body in accordance with the rotation angle of the gear. However, this type of sensor is not provided in Patent Documents 1 and 2. For example, even if it is going to arrange | position a sensor to the valve drive apparatus of patent document 2, the specific mechanism in which it arrange | positions efficiently is unknown.

  Therefore, the present invention solves the above-mentioned problems, and the object of the present invention is to increase the valve opening amount of the valve body with high accuracy while avoiding an increase in the size of the apparatus by efficiently assembling the internal mechanism. Provided is a valve drive that can be controlled.

  The valve drive device of the present invention includes a valve body that controls the flow rate of exhaust gas by seating and separating from a valve seat provided in a housing having a fluid passage therein, and a reciprocating straight line with one end fixed to the valve body. A valve shaft that moves, a motor that is a power source for the reciprocating linear motion of the valve shaft, and a transmission mechanism that transmits the rotational speed of the motor to the valve shaft while reducing the rotational speed at the other end of the valve shaft. That is, it is a valve drive device installed in an EGR device having an exhaust gas flow passage inside. The valve body closes when the valve shaft is seated on the valve seat as the valve shaft reciprocates linearly, and the valve body opens when the valve body moves away from the valve seat. A transmission mechanism (transmission) that transmits the driving force to the valve shaft while decelerating the rotational speed of the motor can also be called a deceleration mechanism. Here, the motor is provided in parallel with the reciprocating linear motion direction (axial 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. That is, the valve shaft reciprocates linearly in the direction of the rotation axis (center axis) of the motor on the side of the motor. The transmission mechanism is integrated with a first gear provided on the rotation shaft of the motor, a second gear meshing with the first gear and having a larger diameter than the first gear, and coaxially integrated with the second gear. A third gear having a smaller diameter than that of the second gear and a fourth gear having a larger diameter than that of the third gear, which meshes with the third gear and drives the valve shaft. That is, an intermediate gear composed of the second gear and the third gear is interposed between the first gear provided on the rotating shaft of the motor and the fourth gear that drives the valve shaft. The second gear and the third gear may be integrated by bonding or the like, or may be integrally formed.

  At this time, the rotation shafts of the second and third gears are preferably arranged between the rotation shaft of the first gear and the rotation shaft of the fourth gear. If the rotation shafts of the second and third gears are between the rotation shaft of the first gear and the rotation shaft of the fourth gear, the first to fourth gears do not necessarily have to be aligned.

  Further, it is preferable that a gear ratio between the first gear and the second gear is larger than a gear ratio between the third gear and the fourth gear. In other words, the gear ratio between the third gear and the fourth gear is made smaller than the gear ratio between the first gear and the second gear. Here, the gear ratio is the ratio of the number of teeth of the drive-side gear to the passive-side gear, and is obtained by a calculation formula of (number of teeth of the passive gear / number of teeth of the drive gear). For example, (the gear ratio between the first gear and the second gear = the number of teeth of the second gear / the number of teeth of the first gear).

  In the case of providing a sensor for detecting and controlling the opening degree of the valve body in this valve drive device, a fifth gear that is integrated coaxially above the fourth gear and has a smaller diameter than the fourth gear, and meshes with the fifth gear. And a sixth gear capable of accommodating the sensor in the central portion in the radial direction. At this time, the third gear is integrated below the second gear, and the second gear is positioned between the fourth gear and the sixth gear in the rotation axis direction of each gear. It is preferable to assemble to.

  At the same time, it is preferable that the sixth gear is provided coaxially above the second and third gears so as to be rotatable independently of the second and third gears.

  Further, the gear ratio between the fifth gear and the sixth gear is changed from a fully closed state (a state where the valve body is seated on the valve seat) to a fully opened state (a state where the valve body is separated from the valve seat to the maximum extent). It is preferable that the rotation angle of the sixth gear be designed to be 90 degrees or less. Accordingly, the tooth portion of the sixth gear can be formed into a ¼ to 円 circle, that is, a fan shape having a spread of 90 to 120 degrees in the circumferential direction around the central axis.

  Generally, a predetermined clearance (meshing backlash) is provided between the gears so that smooth meshing rotation is possible. In addition, it is preferable to provide an elastic body that biases the sixth gear in the circumferential direction (rotation direction). Here, the direction in which the sixth gear is urged by the elastic body is not particularly limited, and may be the same direction as the rotation direction of the sixth gear or the opposite direction.

  According to the present invention, the motor is provided in parallel with the reciprocating linear motion direction (axial 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. In the length of the valve shaft in the device in the axial direction, the length of the motor can be omitted, and the valve drive device becomes small. Further, since the motor and the valve shaft are in a parallel relationship, the dimension perpendicular to the axial direction of the valve shaft, that is, the planar dimension of the valve drive device does not increase more than necessary. Since the valve drive device can be reduced in size, it can be mounted on the engine.

  In addition, the second gear is provided between the first gear provided on the rotating shaft of the motor and the fourth gear for driving the valve shaft to the transmission mechanism that transmits the driving force to the valve shaft while reducing the rotational speed of the motor. And the intermediate gear made up of the third gear reduces the rotational speed of the motor in two steps, improves the resolution of the opening control of the valve body, and controls the flow rate of the exhaust gas with high accuracy. it can. In addition, a new space is formed below the intermediate gear as a result of newly providing the intermediate gear. Therefore, a new function can be added to the EGR device by effectively using the space below the intermediate gear, for example, by flowing cooling water in the space below the intermediate gear.

  If the rotation shaft of the intermediate gear composed of the second gear or the like is provided outside the first gear or the fourth gear, it is necessary to enlarge the valve driving device in the plane direction. However, if the rotation shaft of the intermediate gear is arranged between the rotation shaft of the first gear and the rotation shaft of the fourth gear, the second and third gears are efficiently meshed with the first and fourth gears, respectively. Therefore, it is possible to minimize the increase in the size of the valve driving device in the plane direction.

  The reduction ratio design in the transmission mechanism is performed by first determining the final reduction ratio from the first gear provided on the rotating shaft of the motor to the fourth gear for driving the valve shaft, and then between the first gear and the second gear. The relationship between the gear ratio and the gear ratio between the third gear and the fourth gear is determined. At this time, the relative relationship between the gear ratio between the first gear and the second gear and the gear ratio between the third gear and the fourth gear is mutually contradictory. In other words, assuming the final reduction ratio, if the gear ratio between the first gear and the second gear is relatively large, the gear ratio between the third gear and the fourth gear is relatively small. There is a need to. Conversely, if the gear ratio between the first gear and the second gear is relatively small, the gear ratio between the third gear and the fourth gear needs to be relatively large. When the gear ratio between the third gear and the fourth gear is increased, the diameter of the third gear inevitably decreases, but the diameter of the fourth gear located on the outermost side in the plane direction increases. In this case, since the fourth gear greatly protrudes in the plane direction, the dimension in the plane direction of the entire apparatus is increased. Therefore, the final reduction ratio from the first gear to the fourth gear is determined, and the gear ratio between the first gear and the second gear is made larger than the gear ratio between the third gear and the fourth gear. Thus, the diameter of the fourth gear can be reduced by reducing the gear ratio between the third gear and the fourth gear as much as possible. Thereby, it can avoid that the dimension of the plane direction of an apparatus expands significantly.

  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 and controlling the opening degree of the valve body (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, the rotation direction, rotation amount, stop timing, and the like of the motor can be controlled by detecting the opening degree of the valve body by the sensor.

  Since the gear ratio between the first gear and the second gear is larger than the gear ratio between the third gear and the fourth gear, the second gear inevitably overlaps with the fourth gear. On the other hand, since the fifth gear has a smaller diameter than the fourth gear, the sixth gear that inevitably meshes with the fifth gear has a relatively large diameter. In such a relationship, if the third gear is integrated below the second gear, and the second gear is positioned between the fourth gear and the sixth gear in the rotation axis direction of each gear, Since the transmission mechanism can be assembled efficiently in space, the size of the apparatus in the length direction (gear axis direction) can be made as small as possible.

  At this time, if the sixth gear is arranged coaxially with the second and third gears, it is more efficient in terms of space, and it is more accurate that the apparatus is enlarged not only in the longitudinal direction but also in the plane direction. can avoid. At this time, if the sixth gear can be rotated independently of the second and third gears, detection of the opening degree of the valve body by the sensor is not hindered.

  If the gear ratio between the fifth gear and the sixth gear is designed so that the rotation angle of the sixth gear during the valve body from the fully closed state to the fully open state is 90 degrees or less, for example, the intake passage It can also be used as a valve opening degree detection sensor for other products such as a throttle valve, and the cost can be reduced. For example, an intake passage for introducing air into the internal combustion engine is provided downstream of the EGR device. A butterfly valve is generally used as the throttle valve for the intake passage, and its operating angle is 90 degrees or less. Therefore, the rotation angle of the sixth gear for detecting the opening degree of the valve body in the valve drive device is also set to 90 degrees or less, so that the mass production amount of butterfly valve opening degree detection device for controlling the intake air amount is shared. become able to.

  Since the rotation angle of the sixth gear is designed to be 90 degrees or less, the tooth portion of the sixth gear is sufficient to be ¼ to ３. As a result, the space for installing the sixth gear can be reduced, and the rotation trajectory can be reduced, so that the apparatus can be further downsized more efficiently.

  If the sixth gear is always urged in the circumferential direction (rotation direction) by the elastic body, the engagement backlash between the fifth gear and the sixth gear and the gears in the rotation direction is Always stable in one direction. As a result, when the valve shaft moves forward and backward with forward and reverse rotation of the motor, it is possible to eliminate the deviation of the rotation timing due to the backlash, so that the valve opening detection system by the sensor is stabilized. At the same time, accuracy is improved. In addition, by selecting the urging direction, it is possible to accurately cope with a malfunction of the valve drive device due to a motor failure or the like.

  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 scope of the present invention. FIG. 1 is a cross-sectional view of the valve drive device. FIG. 2 is a plan view of the valve drive device with the bracket 24, the housing cover 26, the upper bearing 27, and the torsion coil spring 34 removed. FIG. 3 is an enlarged plan view of a main part of the sixth gear 16. FIG. 4 is a bottom view of the valve shaft 5.

  The valve drive device is an exhaust gas recirculation device (EGR) that recirculates a part of the exhaust gas from the engine as EGR gas to the intake passage (intake manifold) while controlling the flow rate in the exhaust gas recirculation system of the automobile. Device) 1 is installed. As shown in FIG. 1, the EGR device 1 includes a housing 2 having a fluid passage 7 therein, a valve seat 3 provided in the fluid passage 7 in the housing 2, and a housing cover that closes an upper surface opening of the housing 2. 26. The housing 2 can be made of aluminum die casting or synthetic resin such as polyethylene terephthalate (PET). The housing cover 26 is made of a synthetic resin such as polyethylene terephthalate (PET). The housing 2 and the housing cover 26 are fixed by rivets at their peripheral edges. The valve drive device is constructed in the housing 2, and is configured to reciprocate linearly with a valve body 4 that controls the flow rate of exhaust gas by being seated and separated from the valve seat 3, a valve shaft 5 that can reciprocate linearly. It has a motor 6 to be moved and a transmission mechanism for transmitting to the valve shaft 5 while reducing the rotational speed of the motor 6.

  The fluid passage 7 is provided as an EGR passage and communicates from an exhaust passage through which exhaust gas generated in the combustion chamber of the engine is discharged to an intake passage for introducing air into the combustion chamber of the engine. Although not shown, the lower end of the fluid passage 7 in FIG. 1 communicates with the exhaust passage, and the front end of the fluid passage 7 extending in the rear in FIG. 1 communicates with the intake passage. Then, the EGR passage 7 is opened and closed by the valve body 4 being seated and separated from below the valve seat 3. 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. The valve shaft 5 is arranged to reciprocate linearly in the vertical direction.

  As shown in FIGS. 1 and 2, in the transmission mechanism, an intermediate gear 10 is interposed between a first gear 11 provided on the rotating shaft of the motor 6 and a fourth gear 14 that drives the valve shaft 5. ing. Thereby, the rotational output of the motor 6 is transmitted to the valve body 4 while the rotational speed of the motor 6 is decelerated in two stages by the intermediate gear 10 and the fourth gear 14. The first gear 11 is made of a pinion gear made of iron or brass, and the fourth gear 14 has a spur gear shape. The intermediate gear 10 is made of fiber reinforced plastic (FRP) in which 30% by weight of glass fiber and 10% by weight of polytetrafluoroethylene (PTFE) are mixed with polyamide resin (nylon 46). It is a two-stage spur gear comprising two gears 12 and a third gear 13 that is coaxially integrated with the second gear 12 on the lower surface of the second gear 12. The second gear 12 has a larger diameter than the first gear 11, and the third gear 13 has a smaller diameter than the second gear 12. The fourth gear 14 meshes with the third gear 13 and has a larger diameter than the third gear 13. Specifically, the first gear 11 has 11 teeth, the second gear 12 has 57 teeth, the third gear 13 has 20 teeth, and the fourth gear 14 has teeth. The number is 29 teeth. That is, the gear ratio between the first gear 11 and the second gear 12 (the number of teeth of the second gear 12 / the number of teeth of the first gear = 5.18) is the gear ratio between the third gear 13 and the fourth gear 14. (The number of teeth of the fourth gear 14 / the number of teeth of the third gear 13: 1.45). Thereby, the diameter of the 4th gearwheel 14 is restrained as small as possible, and the expansion of the planar direction of the EGR apparatus 1 is avoided.

  The valve shaft 5 is inserted through the central portion of the fourth gear 14 in the radial direction, and a female screw 18 is provided on the inner peripheral surface of the valve shaft insertion hole. On the other hand, a male screw 17 screwed with the female screw 18 is provided on the upper outer peripheral surface of the valve shaft 5. The rotational movement of the fourth gear 14 around the valve shaft 5 is converted into the reciprocating linear motion of the valve shaft 5 by screwing the female screw 18 of the fourth gear 14 and the male screw 17 of the valve shaft 5. . The rotation shaft 19 serving as the rotation center of the intermediate gear 10 is made of an iron alloy, and is between the rotation shaft of the first gear 11 (rotation shaft of the motor 6) and the rotation shaft of the fourth gear 14 (valve shaft 5). The first gear 11, the intermediate gear 10, and the fourth gear 14 are arranged in a substantially straight line in the left-right direction in this order. The space below the intermediate gear 10 formed by providing the intermediate gear 10 is effectively used to provide a cooling water passage 35 through which cooling water is conducted. Thereby, the temperature rise of the EGR device 1 due to the high-temperature exhaust gas flowing in the fluid passage 7 or the driving heat of the motor 6 is suppressed. Further, it is possible to prevent malfunction due to icing of the drive part at low temperatures.

  A DC motor is used as the motor 6, and is provided in the vertical direction in parallel with the reciprocating linear motion direction (rotational axis direction of each gear) of the valve shaft 5, and the gears 11 to 14 constituting the transmission mechanism. On the other hand, it is provided in the same direction as the valve body 4, that is, at a position lower than the gears 11-14. The motor 6 is fixed to the housing 2 by bolts 20 on the side of the valve shaft 5. Reference numeral 32 denotes a caulking fixing portion of the motor 6. The motor 6 is fixed in a floating manner so as not to directly contact the housing 2. Specifically, between the bottom surface of the motor 6 and the housing 2, a steel wave washer 21 having a circular ring shape and a center portion curved upward is interposed. Elastically supported. Thereby, it is avoided that the drive vibration of the motor 6 is directly transmitted to the housing 2. The valve shaft 5 can reciprocate linearly in the vertical direction, and an anti-rotation body 23 is disposed immediately above the bearing 22 as a rotation preventing mechanism that causes the valve shaft 5 to reciprocate linearly but does not rotate.

  The valve shaft 5 is basically cylindrical from the lower end to the upper end, but as shown in FIGS. 1 and 4, the left and right sides of a large-diameter perfect circle are cut off at a part thereof. The oval-shaped shaft portion 5a is widened such that both ends of two opposing flat surfaces are connected by a curved surface. The oval shaft portion 5a is formed below the circular plate 28 over a predetermined dimension. The insertion hole of the anti-rotation body 23 through which the valve shaft 5 is inserted also has an oval shape having the same cross-sectional shape and dimensions as the oval shaft portion 5a of the valve shaft 5. That is, the oval shaft portion 5 a of the valve shaft 5 and the rotation preventing body 23 constitute a rotation preventing mechanism for the valve shaft 5. 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. A gap having a predetermined size is provided between the female screw 18 of the fourth gear 14 and the male screw 17 of the valve shaft 5.

  Returning to FIGS. 1 and 2, a cylindrical portion 14 a having an open lower surface is integrally formed at the radial center portion of the fourth gear 14, and the cylindrical portion 14 a is provided on the outer periphery of the rotation preventing body 23. The outer periphery of the lower bearing 25 which consists of a ball bearing is enclosed. The upper portion of the cylindrical portion 14a is rotatably supported by an upper bearing 27 formed of a ball bearing provided on an aluminum die cast or a synthetic resin bracket 24 fixed to the housing 2 by bolts. 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 fourth gear 14 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 cavity in the cylindrical portion 14 a and the lower bearing 25. The second spring 30 suppresses vertical play of the fourth gear 14 and a fifth gear 15 described later.

  Inside the EGR device 1, a rotary non-contact type magnetic sensor 45 that detects the reciprocating linear momentum of the valve shaft 5 in accordance with the rotational speed of the transmission mechanism is disposed. The magnetic sensor 45 includes a sensor main body 45 having a calculation unit and a plurality of detection terminals 46 protruding outward from the sensor main body 45, and in the sensor chamber 47 joined to the lower surface of the housing cover 26, The intermediate gear 10 is arranged coaxially and immovably with the rotary shaft 19.

  A fifth gear 15 having a smaller diameter than that of the fourth gear 14 is integrally formed on the outer peripheral surface of the cylindrical portion 14 a so as to be coaxial with the fourth gear 14. In addition, a sixth gear 16 is provided which meshes with the fifth gear 15 and in which the magnetic sensor 45 is arranged at the central portion in the radial direction. The fourth gear 14 and the fifth gear 15 formed integrally therewith are made of polyphenylene sulfide resin (PPS), and the sixth gear 16 is a fiber reinforced plastic (polyamide resin (nylon 46) mixed with 30% by weight of glass fiber ( FRP). The sixth gear 16 is provided coaxially above the intermediate gear 10 while sharing the rotation shaft 19 of the intermediate gear 10. On the other hand, the fifth gear 15 is formed at an upper position separated from the fourth gear 14 by a predetermined dimension. At this time, a gap of a predetermined height is formed between the sixth gear meshing with the fifth gear and the fourth gear 14. The height dimension of the gap is slightly larger than the thickness of the second gear 12, and the second gear 12 is just within the gap between the fourth gear 14 and the sixth gear 16. . Thereby, it is avoided that the EGR apparatus 1 expands greatly in the rotating shaft direction (axial direction of the valve shaft 5) of each gear by assembling each gear 11-16 efficiently. Further, since the sixth gear 16 shares the rotation shaft 19 of the intermediate gear 10, it is not necessary to provide a separate rotation shaft for the sixth gear 16, and the number of parts can be reduced and the cost can be reduced. Note that a washer 33 is interposed between the sixth gear 16 and the intermediate gear 10, so that the sixth gear 16 and the intermediate gear 10 can rotate independently.

  The bracket 24 extends in the left-right direction above the sixth gear 16 and surrounds the magnetic sensor 45. The sixth gear 16 is constantly urged downward simultaneously with the circumferential direction (rotation direction) by a stainless steel torsion coil spring 34 disposed between the upper surface of the sixth gear 16 and the bracket 24. Since the sixth gear 16 is biased in the circumferential direction, the backlash between the sixth gear 16 and the fifth gear 15 is eliminated. Thereby, it is possible to prevent sensor detection deviation in the fully closed state. In the present embodiment, the urging force of the sixth gear 16 in the circumferential direction is the direction in which the valve body 4 is closed (reverse rotation direction). Thereby, even if the valve driving device is stopped due to a malfunction of the motor 6 or the like, the valve body 4 is automatically closed by the synergistic effect of the urging force of the first spring 29 and the torsion coil spring 34. At the same time, since the sixth gear 16 is constantly urged downward by the torsion coil spring 34, rattling caused by vibrations in the rotation axis direction of the intermediate gear 10 and the sixth gear 16 is also suppressed. The torsion coil spring 34 is locked to an engagement protrusion 36 integrally formed on the lower surface of the bracket 24 and an engagement portion 37 provided on the upper surface of the sixth gear 16.

  As well shown in FIG. 1 and FIG. 2, a circular metal plate 40 in which an insertion hole through which the rotary shaft 19 can be inserted is formed at the bottom of the concave portion at the center of the sixth gear 16. The metal plate 40 is fixed to the upper ends of the rotary shafts 19 of the intermediate gear 10 and the sixth gear 16 by press fitting or the like. In addition, two semicircular yokes 49 and 49 are arranged to face each other on the inner peripheral surface of the central recess of the sixth gear 16, and between the ends of the pair of yokes 49 and 49, respectively. Magnets 48 and 48 are fitted to face each other. Thus, as the sixth gear 16 rotates, both magnets 48 and 48 circulate around the detection terminal 46. The metal plate 40, the magnet 48, and the yoke 49 are integrally insert-molded when the sixth gear 16 is molded. Reference numeral 41 denotes a groove that is inevitably formed by a mold for fixing the magnet 48 and the yoke 49 when the magnet 48 and the yoke 49 are inserted into the sixth gear 16.

  The detection terminal 46 detects the direction of the magnetic field generated between the magnets 48, 48. By detecting the amount of rotation of the magnets 48, 48 accompanying the rotation of the sixth gear 16, the detection terminal 46 The amount of rotation, that is, the linear momentum of the valve shaft 5 can be detected. Specifically, when magnetism is applied by a pair of magnets 48, 48, for example, when an N pole is generated in one yoke 49 and an S pole is generated in the other yoke 49, the pair of semicircular yokes 49, 49 are aligned. A magnetic path that flows from one yoke 49 to the other yoke 49 through the magnetic detection surfaces on both sides of the magnetic sensor 45 is formed in the magnetic sensor 45 in the sensor chamber 47 disposed inside the circular shape. The strength of the magnetic field flowing in the magnetic path crossing between the yokes 49 and 49 varies depending on the angle of the magnetic sensor 45 with respect to the yoke 49 and the magnet 48. The output voltage of the magnetic sensor 45 changes according to the strength of the detected magnetic field, and a voltage signal indicating the opening degree of the sixth gear 16, that is, the valve body 4 is output. The output side of the magnetic sensor 45 is connected to an external detection circuit and an engine control controller through a terminal (not shown) provided in the housing 2. Here, the gear ratio between the fifth gear 15 and the sixth gear 16 is such that the rotation angle of the sixth gear 16 during the valve body 4 from the fully closed state to the fully open state is 90 degrees or less, preferably 85 to 90 degrees. It is designed so that it can be shared with an intake amount control butterfly valve opening detection device that is arranged in the intake passage and is produced in large quantities. Accordingly, the tooth portion 16a of the sixth gear 16 is formed in a fan shape slightly smaller than 1/3 yen. In the present embodiment, the rotation angle of the sixth gear 16 from the fully closed state of the valve body 4 is about 86 degrees, and the tooth portion 16a of the sixth gear 16 has a fan shape having an expansion of about 110 degrees. Is formed.

  Next, the operation of the valve drive device will be described. In the stop state (initial state) of the valve drive device, the valve body 4 is seated on the valve seat 3 from below, and the fluid passage 7 is closed in a non-communication manner. When the engine is driven and exhaust gas is generated, a part of the exhaust gas is introduced as EGR gas into the fluid passage 7 as necessary, so that the valve driving device is operated and the fluid passage 7 is opened. When the driver depresses the accelerator pedal, the opening degree is detected by the accelerator opening degree sensor, and the opening degree signal is sent to the engine control controller. The engine control controller outputs a drive signal to the motor 6 so that the opening degree of the valve body 4 becomes an opening degree corresponding to the accelerator opening degree, and the motor 6 is driven. Specifically, when the motor 6 energized through the terminal 31 rotates in the forward direction, the second gear 12 that meshes with the first gear 14 and the fourth gear that meshes with the third gear that rotates integrally with the second gear 12. The gear 14 also rotates forward, and the rotational output of the motor 6 is transmitted to the female screw 18 and the male screw 17 after being decelerated in two stages. When the fourth gear 14 rotates forward, the valve shaft 5 linearly moves downward against the urging force of the first spring 29 due to the relationship between the female screw 18 and the male screw 17. The valve shaft 5 is designed to move once when the fourth gear 14 rotates forward by 250 degrees, and accordingly, the fifth gear 15 and the sixth gear 16 that rotate together with the fourth gear 14 are designed. Depending on the gear ratio, the sixth gear 16 rotates forward approximately 86 degrees.

  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 of the rotation preventing body 23 fixed in a stationary manner. The shaft 5 does not rotate in the circumferential direction. The torque output to the first gear 14 is increased by transmitting the rotational output of the motor 6 to the valve shaft 5 after being decelerated in two stages. Further, the DC motor has a larger driving force than the stepping motor. Therefore, it is possible to cope with introduction of a large flow rate of EGR gas. Further, in the case of a normal EGR gas amount that is not a large flow rate, a relatively small motor can be used as the motor 6, thereby further reducing the size of the EGR device 1. The elastic pressure (biasing force) of the second spring 30 is larger than the elastic force of the first spring 29.

  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 EGR passage 7 is in communication, a part of the exhaust gas flowing through the exhaust passage flows in, 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 the magnetic sensor 45. That is, the downward movement amount of the valve body 4 is detected by the magnetic sensor 45 according to the rotation angle of the sixth gear 16, and the motor 6 is controlled to stop. In addition, even when the motor 6 is energized, even when the valve shaft 5 does not move linearly due to a failure or the like, it can be detected by the magnetic sensor 45, 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 gears 11 to 16, the female screw 18 and the male screw 17 are also rotated in the reverse direction, so that the valve shaft 5 linearly moves upward. The fact that the valve body 4 is seated on the valve seat 3 and closed is detected by the magnetic sensor 45 when the sixth gear 16 returns to the initial position, and the motor 6 is stopped.

It is sectional drawing of a valve drive device. It is a top view of the valve drive device except a housing cover etc. It is a principal part enlarged plan view of a 6th gearwheel. It is a bottom view of a valve stem.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 EGR apparatus 2 Housing 3 Valve seat 4 Valve body 5 Valve shaft 6 Motor 7 Fluid passage 10 Intermediate gear 11 First gear 12 Second gear 13 Third number of teeth 14 Fourth gear 15 Fifth gear 16 Sixth gear 17 Male screw 18 Female thread 19 Rotating shaft 22 Bearing 23 Anti-rotation body 24 Bracket 25 Lower bearing 26 Housing cover 27 Upper bearing 29 First spring 30 Second spring 34 Torsion coil spring 35 Cooling water passage 45 Magnetic sensor 47 Sensor chamber 48 Magnet 49 Yoke

Claims (8)

A valve body that controls the flow rate of exhaust gas by seating and separating from a valve seat provided in a housing having a fluid passage therein, a valve shaft that is reciprocally linearly moved with one end fixed to the valve body, and the valve A valve drive device comprising: a motor that is a power source for reciprocating linear motion of the shaft; and a transmission mechanism that transmits the rotational speed of the motor to the valve shaft while reducing the rotational speed on the other end side of the valve shaft,
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 transmission mechanism is integrated with a first gear provided on the rotation shaft of the motor, a second gear meshing with the first gear and having a larger diameter than the first gear, and coaxially integrated with the second gear. A valve drive device comprising: a third gear having a smaller diameter than the gear; and a fourth gear having a larger diameter than the third gear and meshing with the third gear to drive the valve shaft.   2. The valve drive device according to claim 1, wherein the rotation shafts of the second gear and the third gear are arranged between the rotation shaft of the first gear and the rotation shaft of the fourth gear. .   The valve drive device according to claim 1 or 2, wherein a gear ratio between the first gear and the second gear is larger than a gear ratio between the third gear and the fourth gear. The third gear is integrated below the second gear,
Further, a fifth gear that is integrated coaxially above the fourth gear and has a smaller diameter than the fourth gear, and a sensor that meshes with the fifth gear and detects the opening degree of the valve body are provided in the central portion in the radial direction. A sixth gear is provided,
The valve according to any one of claims 1 to 3, wherein the second gear is located between the fourth gear and the sixth gear in the rotation axis direction of each gear. Drive device.   5. The sixth gear according to claim 4, wherein the sixth gear is provided coaxially above the second and third gears so as to be rotatable independently of the second and third gears. Valve drive device.   The gear ratio between the fifth gear and the sixth gear is designed so that the rotation angle of the sixth gear is 90 degrees or less while the valve body is in the fully closed state to the fully opened state. The valve drive device according to claim 4 or 5, characterized by the above.   The valve drive device according to claim 6, wherein a tooth portion of the sixth gear is formed in a ¼ circle to a 円 circle. The valve drive device according to claim 4, further comprising an elastic body that urges the sixth gear in a circumferential direction.

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