Patent Publication Number: US-7213557-B2

Title: Air intake control system

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an air intake control system provided in an air intake line of an internal combustion engine. 
   2. Description of the Background Art 
   Generally, an air intake control system of an internal combustion engine employs an air intake control apparatus which includes an intake air control valve disposed in an inlet pipe connected to cylinders, the intake air control valve including a valve shaft and a valve element mounted pivotably about the valve shaft. The valve shaft is turned in a controlled fashion by an actuator, such as a motor, whereby the valve element is pivoted between a fully opened position and a completely closed position to adjust intake passage cross section of the inlet pipe. 
   For example, Japanese Patent Application Publication No. 2004-124933 discloses a variable air intake control apparatus including a valve element mounted on a valve shaft disposed in an intake passage within an intake manifold which is connected to engine cylinders. The valve element is mounted pivotably about the valve shaft which is supported by the intake manifold. A gear is fixedly mounted on the valve shaft and the valve element is controllably opened and closed by a driving force produced by a motor of which rotary shaft is fitted with a pinion that meshes with the gear of the valve shaft. 
   In the variable air intake control apparatus thus structured, the valve element goes into contact with a stopper at a fully opened position and at a completely closed position. One problem of this variable air intake control apparatus is that an impact load acts on the valve element due to inertia of the motor and of the gear fitted on the valve shaft when the valve element goes into contact with the stopper, causing an impact on meshing teeth of the gear fitted on the valve shaft and the pinion fitted on the motor shaft. Since contact areas of the meshing teeth carry the entirety of the impact load, the teeth of the gear and the pinion are likely to break. 
   One approach to reducing this impact load for overcoming the aforementioned problem is introduced in Japanese Patent Application Publication No. 1999-173116, which discloses an air intake control apparatus in which a gear (motor gear) fitted on a rotary shaft of a motor and a gear (throttle gear) fitted on a valve shaft carrying a valve element are helical gears, and the motor gear fitted on the rotary shaft is sandwiched by a pair of spring washers. The motor gear is mounted on the rotary shaft in such a manner that the motor gear can move along an axial direction of the rotary shaft but does not rotate relative to the rotary shaft. When the throttle gear goes into contact with a stopper and stops at a fully opened position or at a completely closed position, one of the spring washers is compressed and the other extends, whereby the motor gear moves along the axial direction of the rotary shaft and an impact load caused by inertia is alleviated. 
   The air intake control apparatus of Japanese Patent Application Publication No. 1999-173116 however poses the following problems: 
   (1) The helical gears are complicated in structure and are difficult to manufacture; 
   (2) The structure of the Publication, in which one of the helical gears sandwiched by the spring washers is mounted movably along the rotary shaft but unturnably around the rotary shaft, requires a larger number of components including the spring washers and stoppers therefor as well as a complex assembly process; and 
   (3) Foreign matter may intrude between sliding areas of the helical gear and the rotary shaft when the helical gear moves along the rotary shaft, or the spring washers may be damaged by repeated stress over the course of time, resulting in poor reliability of the air intake control apparatus. 
   SUMMARY OF THE INVENTION 
   The present invention is intended to overcome the aforementioned problems of the prior art. Accordingly, it is an object of the invention to provide a highly reliable air intake control system which can alleviate an impact load exerted on gears mounted on a motor shaft and a valve shaft with a minimum number of components without using helical gears which are difficult to manufacture. 
   An air intake control system of the invention includes an intake passage for supplying intake air to an internal combustion engine, a valve element disposed in the intake passage for varying the cross-sectional area of the intake passage by pivoting between fully opened and completely closed positions, a valve shaft for transmitting a driving force for pivoting the valve element to the valve element, an actuator including a prime mover (motor) for supplying the driving force for pivoting the valve element, a driving force transmission gear (worm gear) which is fitted to the motor and rotated thereby, and a housing accommodating the motor and the worm gear, and a driving gear which is mounted on the valve shaft and meshes with the worm gear to transmit the driving force supplied from the actuator to the valve shaft. 
   The driving gear includes a boss portion, a tooth portion which meshes with the worm gear to receive the driving force supplied from the actuator, and an elastic member which is sandwiched between and bonded to the boss portion and the tooth portion and elastically deforms when twisted. 
   The boss portion has a hole into which the valve shaft is inserted in such a manner that the boss portion rotates together with the valve shaft. The tooth portion and the elastic member have holes into which the valve shaft is inserted in such a manner that the tooth portion and the elastic member can rotate relative to the valve shaft. An impact load caused by opening and closing motion of the valve element is alleviated by torsional deformation of the elastic member in a turning direction of the valve shaft. 
   In the air intake control system thus structured, the impact load acting on the tooth portion of the driving gear and the worm gear is absorbed by torsional deformation of the elastic member so that damage to the tooth portion of the driving gear and the worm gear is avoided. It will be appreciated that the invention provides a highly reliable air intake control system built with a minimum number of components without using helical gears. 
   These and other objects, features and advantages of the invention will become more apparent upon reading the following detailed description along with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-sectional view showing an actuator, a driving gear and components in surrounding areas thereof of an air intake control apparatus according to a first embodiment of the invention; 
       FIG. 2  is a cross-sectional view formed by a plane cutting through an intake passage along a centerline thereof showing the air intake control apparatus installed on an internal combustion engine; 
       FIG. 3  is a cross-sectional view showing how valve elements are connected to the actuator of the air intake control apparatus of the first embodiment; 
       FIG. 4  is a perspective view showing a gear mechanism of the air intake control apparatus of the first embodiment. 
       FIG. 5  is a cross-sectional view showing an actuator, a driving gear and components in surrounding areas thereof of an air intake control apparatus according to a second embodiment of the invention; 
       FIG. 6  is a cross-sectional view showing an actuator, a driving gear and components in surrounding areas thereof of an air intake control apparatus according to a third embodiment of the invention; 
       FIG. 7  is a cross-sectional view showing an actuator, a driving gear and components in surrounding areas thereof of an air intake control apparatus according to a fourth embodiment of the invention; and 
       FIG. 8  is a cross-sectional view showing an actuator, a driving gear and components in surrounding areas thereof of an air intake control apparatus according to a fifth embodiment of the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An air intake control apparatus and an intake vortex generator are examples of air intake control systems provided in an air intake line of an internal combustion engine. The invention is hereinafter described with reference to specific embodiments thereof in which the invention is implemented in an air intake control apparatus. 
   FIRST EMBODIMENT 
     FIG. 1  is a cross-sectional view showing an actuator  50 , a driving gear  60  and components in surrounding areas thereof of an air intake control apparatus  1  according to a first embodiment of the invention,  FIG. 2  is a cross-sectional view formed by a plane cutting through an intake passage along a centerline thereof showing the air intake control apparatus  1  installed on an internal combustion engine,  FIG. 3  is a cross-sectional view showing how valve elements  30  are linked to the actuator  50  of the air intake control apparatus  1  of the first embodiment, and  FIG. 4  is a perspective view showing a gear mechanism of the air intake control apparatus  1  of the first embodiment. 
   As shown in  FIG. 1 , the actuator  50  includes a motor  54  serving as a prime mover for producing a driving force for turning a valve shaft  40 , a worm gear (driving force transmission gear)  55  which is fixedly mounted on a rotary shaft of the motor  54  and meshes with teeth cut around a tooth portion  63  of the driving gear  60  to transmit the driving force of the motor  54  to the tooth portion  63  of the driving gear  60 , and a housing  51  fixing and enclosing the motor  54 . The housing  51  is fixed to an intake manifold (inlet pipe)  10  by a plurality of screws  71 . The driving gear  60  includes the aforementioned tooth portion  63 , a boss portion  61  and an elastic member  62  disposed between the tooth portion  63  and the boss portion  61 . The boss portion  61  and the elastic member  62 , and the elastic member  62  and the tooth portion  63 , are bonded at contact surfaces thereof with an adhesive agent, whereby the boss portion  61 , the elastic member  62  and the tooth portion  63  are joined into a single structure. 
   The valve shaft  40  has a noncircular cross section as viewed along a central axis thereof (refer to  FIG. 4 ). One end portion of the valve shaft  40  forms a cylindrical projecting part  41  extending from a noncircular portion of the valve shaft  40 . In the boss portion  61  of the driving gear  60 , there is formed a hole having the same noncircular cross-sectional shape as the valve shaft  40  as viewed along a central axis of the boss portion  61 . In the elastic member  62  and the tooth portion  63  there are formed holes of which diameter is slightly larger than the diameter of the projecting part  41  of the valve shaft  40  as viewed along a central axis of the elastic member  62  and the tooth portion  63 . 
   The valve shaft  40  is inserted into the central holes of the boss portion  61 , the elastic member  62  and the tooth portion  63  in this order. The valve shaft  40  is forcibly fitted into the central hole of the boss portion  61  so that the boss portion  61  does not rotate relative to the valve shaft  40 . The elastic member  62  and the tooth portion  63  are fitted on the cylindrical projecting part  41  at one end portion of the valve shaft  40  having a slightly smaller diameter than the diameter of the central holes of the elastic member  62  and the tooth portion  63  so that the elastic member  62  and the tooth portion  63  can rotate relative to the valve shaft  40 . The boss portion  61  of the driving gear  60  is rotatably supported by a bearing  70 , and a seal member  72  is fitted between the housing  51  and the intake manifold  10  to seal off a gap therebetween. The tooth portion  63  of the driving gear  60  is precisely positioned in the aforementioned structure so that the teeth of the tooth portion  63  correctly mesh with teeth of the worm gear  55 . 
   The tooth portion  63  and the boss portion  61  are formed by molding polyamide resin and the elastic member  62  is formed by molding vulcanized synthetic nitrile rubber, for example. The elastic member  62  may be formed by a vulcanizing process between the tooth portion  63  and the boss portion  61  which are formed in advance such that the boss portion  61 , the elastic member  62  and the tooth portion  63  are joined into a single structure without using any adhesive agent. 
   As shown in  FIG. 2 , the intake manifold  10  of the air intake control apparatus  1  interconnects a surge tank  11  and an engine body  20 . Intake air drawn in through an intake duct (not shown) is introduced into the surge tank  11  through an air cleaner (not shown) and a throttle body in which a throttle valve  15  ( FIG. 2 ) is disposed and distributed to individual tubes (or intake runners) which are formed in the intake manifold  10 , as if branching out from the surge tank  11 . The intake runners formed in the intake manifold  10  lead to individual cylinders formed in the engine body  20 , each of the intake runners including an low-speed intake passage  12  used in low-speed ranges and an high-speed intake passage  13  used in high-speed ranges. The overall length of the low-speed intake passage  12  as measured up to the engine body  20  is made larger than that of the high-speed intake passage  13 . The low-speed intake passage  12  and the high-speed intake passage  13  branch out from the surge tank  11  and join downstream at an engine body side. 
   The aforementioned valve elements  30  which are mounted on the valve shaft  40  are disposed in a plurality of high-speed intake passages  13  of the individual intake runners as illustrated in  FIG. 3  so that the high-speed intake passages  13  can be opened and closed by pivot action of the valve elements  30  to permit and interrupt intake air flow through the intake passages  13 . The actuator  50  turns the valve shaft  40  to open and close the valve elements  30  according to engine speed. Specifically, the valve elements  30  are closed to form intake passageways having an increased overall length when the engine speed is low, whereas the valve elements  30  are opened to form intake passageways having a reduced overall length when the engine speed is high. It is possible to improve engine torque performance regardless of engine speed by closing the valve elements  30  to increase the overall length of the intake passageways in low engine speed ranges and by opening the valve elements  30  to decrease the overall length of the intake passageways at high engine speed ranges. 
   Referring to  FIG. 3 , the intake manifold  10  includes the plurality of high-speed intake passages  13  branching out to the individual cylinders, and the individual valve elements  30  are disposed in the high-speed intake passages  13 . Each of the valve elements  30  includes a flat valve plate  31  and sleeves  32  extending from both sides of the valve plate  31 . A noncircular valve shaft hole  33  is formed in each valve element  30 , passing through the valve plate  31  and the sleeves  32  thereof. The valve shaft hole  33  has the same noncircular cross-sectional shape as the valve shaft  40  as viewed along the central axis of the valve shaft  40 , so that the valve elements  30  do not rotate relative to the valve shaft  40  when the valve shaft  40  is inserted into the valve shaft holes  33  formed in the valve elements  30 . 
   The valve plate  31  and the sleeves  32  of each valve element  30  are made of polyamide resin, for instance, together forming a single structure, while the valve shaft  40  is made of metallic material, such as steel. 
   As previously mentioned, the boss portion  61  of the driving gear  60  fixed at one end portion of the valve shaft  40  is rotatably supported by the bearing  70 . A middle portion and the opposite end portion of the valve shaft  40  are rotatably supported by the intake manifold  10  via shaft guide bearings  43  fitted therein. The end portion of the valve shaft  40  opposite to the aforementioned projecting part  41  forms a cylindrical part which is slidably held by a bushing  42  fitted in an end of the intake manifold  10 , the bushing  42  having a sealing function. 
   Referring to  FIG. 4 , the worm gear  55  fixedly mounted on the rotary shaft of the motor  54  meshes with the tooth portion  63  of the driving gear  60 . Actuated by an unillustrated control device, the motor  54  turns the worm gear  55  in a controlled fashion and this rotary motion of the worm gear  55  is transmitted to the valve shaft  40  through the tooth portion  63  of the driving gear  60 , causing the valve elements  30  to open and close the respective high-speed intake passages  13 . The valve elements  30  go into contact with stoppers (not shown) at a fully opened position and at a completely closed position. Although an impact load acts on the valve elements  30  when the valve elements  30  go into contact with the stoppers due to inertia of the motor  54  and of the valve elements  30  themselves, the impact load is absorbed by torsional deformation of the elastic member  62  so that a resultant impact load on the tooth portion  63  of the driving gear  60  is reduced. Therefore, the above-described air intake control apparatus  1  of the first embodiment does not require difficult-to-manufacture helical gears or a large number of components unlike the earlier-mentioned structure of Japanese Patent Application Publication No. 1999-173116. 
   According to the aforementioned structure of the first embodiment, the tooth portion  63  and the boss portion  61  of the driving gear  60  are joined by the elastic member  62  so that the impact load acting on the valve elements  30  due to the inertia of the motor  54  and of the valve elements  30  is absorbed and the resultant impact load on the teeth of the tooth portion  63  is alleviated without the need for helical gears or a large number of components. It is appreciated from the foregoing that the structure of the first embodiment serves to prevent damage to the tooth portion  63  and the worm gear  55  and provide a highly reliable air intake control system. 
   SECOND EMBODIMENT 
     FIG. 5  is a cross-sectional view showing an actuator  50 , a driving gear  60  and components in surrounding areas thereof of an air intake control apparatus  1  according to a second embodiment of the invention, in which elements identical or similar to those of the first embodiment ( FIG. 1 ) are designated by the same reference numerals. 
   Referring to  FIG. 5 , there is not provided the bearing  70  (refer to  FIG. 1 ) for rotatably supporting the boss portion  61  of the driving gear  60  in the air intake control apparatus  1  of the second embodiment. Instead, there is formed a bearing hole  52  in the housing  51  for rotatably supporting the projecting part  41  of the valve shaft  40 . The bearing hole  52  has a slightly larger diameter than the projecting part  41  of the valve shaft  40  so that the valve shaft  40  can rotate. 
   According to the second embodiment, there is no need for the bearing  70  for supporting the valve shaft  40 . 
   In the structure of the first embodiment, the bearing  70  for rotatably supporting the boss portion  61  of the driving gear  60  fixed at one end portion of the valve shaft  40  is fitted in the intake manifold  10 , so that accuracy of mesh between the tooth portion  63  of the driving gear  60  and the worm gear  55  mounted on the rotary shaft of the motor  54  is affected by assembling position accuracy of the actuator  50  with respect to the intake manifold  10 . In the aforementioned structure of the second embodiment, however, the bearing hole  52  for rotatably supporting the valve shaft  40  is formed in the housing  51  which constitutes part of the actuator  50 , so that accuracy of mesh between the tooth portion  63  of the driving gear  60  and the worm gear  55  mounted on the rotary shaft of the motor  54  is not affected by assembling position accuracy of the actuator  50  with respect to the intake manifold  10 . Consequently, the accuracy of mesh between the tooth portion  63  and the worm gear  55  increases in the structure of the second embodiment. 
   THIRD EMBODIMENT 
     FIG. 6  is a cross-sectional view showing an actuator  50 , a driving gear  60  and components in surrounding areas thereof of an air intake control apparatus  1  according to a third embodiment of the invention, in which elements identical or similar to those of the first embodiment ( FIG. 1 ) are designated by the same reference numerals. 
   Referring to  FIG. 6 , the air intake control apparatus  1  of the third embodiment has essentially the same structure as that of the second embodiment except that a bushing  80  made of a low-friction sliding member is fitted in the bearing hole  52  formed in the housing  51  or on the projecting part  41  of the valve shaft  40  by press fit, for instance, so that the valve shaft  40  can smoothly rotate with low friction. 
   The aforementioned structure of the third embodiment serves to lessen frictional resistance exerted on the projecting part  41  of the valve shaft  40  from the bearing hole  52  and reduce the amount of torque needed for rotating the valve shaft  40 . 
   FOURTH EMBODIMENT 
     FIG. 7  is a cross-sectional view showing an actuator  50 , a driving gear  60  and components in surrounding areas thereof of an air intake control apparatus  1  according to a fourth embodiment of the invention, in which elements identical or similar to those of the first embodiment ( FIG. 1 ) are designated by the same reference numerals. 
   Referring to  FIG. 7 , a bushing  80  made of a low-friction sliding member is disposed between the projecting part  41  of the valve shaft  40  and the tooth portion  63  of the driving gear  60  in the fourth embodiment. The bushing  80  may be fitted in the central hole of the tooth portion  63  or on the projecting part  41  of the valve shaft  40 . 
   When the valve elements  30  go into contact with the stoppers (not shown) at the fully opened position or at the completely closed position, the impact load acting on the valve elements  30  due to the inertia of the motor  54  and of the valve elements  30  is absorbed by the elastic member  62  as mentioned earlier. At this moment, there occurs a torque which causes relative rotation of the projecting part  41  of the valve shaft  40  and the tooth portion  63  of the driving gear  60 . If the amount of frictional resistance occurring between the projecting part  41  of the valve shaft  40  and the central hole of the tooth portion  63  is large, the projecting part  41  of the valve shaft  40  will not smoothly rotate relative to the tooth portion  63  and the impact load acting on the valve elements  30  will be transmitted to the tooth portion  63 , eventually diminishing the aforementioned effect of reducing the impact load on the tooth portion  63  of the driving gear  60 . 
   In the aforementioned structure of the fourth embodiment, the low-friction bushing  80  is fitted between the projecting part  41  of the valve shaft  40  and the tooth portion  63  in the central hole formed therein, so that the amount of frictional resistance caused by relative rotary motion of the projecting part  41  of the valve shaft  40  and the tooth portion  63  of the driving gear  60  is reduced. As a result, the projecting part  41  of the valve shaft  40  can smoothly rotate relative to the tooth portion  63  and the impact load is less likely to be transmitted to the tooth portion  63  of the driving gear  60 . 
   While the fourth embodiment has been described with reference to an example in which one end portion of the valve shaft  40  is supported by the bearing hole  52  formed in the housing  51  as illustrated in  FIG. 7 , the boss portion  61  of the driving gear  60  fixed at one end portion of the valve shaft  40  may be rotatably supported by a bearing as in the first embodiment. 
   FIFTH EMBODIMENT 
     FIG. 8  is a cross-sectional view showing an actuator  50 , a driving gear  60  and components in surrounding areas thereof of an air intake control apparatus  1  according to a fifth embodiment of the invention, in which elements identical or similar to those of the first embodiment ( FIG. 1 ) are designated by the same reference numerals. 
   Referring to  FIG. 8 , the noncircular hole formed in the boss portion  61  of the driving gear  60  is made slightly larger than the noncircular portion of the valve shaft  40  in cross section so that the driving gear  60  can be smoothly moved along an axial direction of the valve shaft  40  in the fifth embodiment. Additionally, there is formed a protrusion  53  which goes into contact with a side surface of the tooth portion  63  of the driving gear  60  inside the housing  51  and there is provided a stopper (not shown) for limiting movement of the driving gear  60  along the axial direction of the valve shaft  40  in a direction opposite to the protrusion  53 . 
   In the aforementioned structure of the fifth embodiment, the driving gear  60  can be smoothly moved along the axial direction of the valve shaft  40 , so that the driving gear  60  can be fitted on the valve shaft  40  by hand without using a press fitting process or the like. Therefore, the fifth embodiment provides ease of assembly. 
   The protrusion  53  which goes into contact with the side surface of the tooth portion  63  and the aforementioned stopper for limiting movement of the driving gear  60  along the axial direction of the valve shaft  40  in the direction opposite to the protrusion  53  together constitute a movement restrictor for limiting the distance of movement of the driving gear  60  along the axial direction of the valve shaft  40 . This structure of the fifth embodiment serves to ensure that the worm gear  55  and the tooth portion  63  of the driving gear  60  mesh over proper dimensions. 
   While the fifth embodiment has been described with reference to an example in which one end portion of the valve shaft  40  is supported by the bearing hole  52  formed in the housing  51  as illustrated in  FIG. 8 , the boss portion  61  of the driving gear  60  fixed at one end portion of the valve shaft  40  may be rotatably supported by a bearing as in the first embodiment. 
   While the invention has thus far been described as being implemented in the air intake control apparatus  1  which is an example of an air intake control system provided in an air intake line of an internal combustion engine in the foregoing first to fifth embodiments, the above-described structures of the first to fifth embodiments can also be applied to an intake vortex generator provided in the air intake line of the internal combustion engine. 
   The aforementioned intake vortex generator is a system provided in the air intake line of the internal combustion engine for producing swirl in a combustion chamber of each cylinder by reducing the cross-sectional area of an intake passageway by means of a swirl valve (valve element) in low engine speed ranges. The intake vortex generator increases burn rate (i.e., mixture burning velocity) to improve combustion efficiency and fuel economy and thereby reduces noxious emissions. 
   It is appreciated from the foregoing that the air intake control system of the invention can be effectively applied either as an air intake control apparatus or as an intake vortex generator provided in the air intake line of the internal combustion engine of a motor vehicle, for example.