Patent Publication Number: US-6334430-B1

Title: Intake air amount control system for engine

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an intake air amount control system for an engine, including a plurality of throttle devices each of which comprises a butterfly-type throttle valve rotatably carried in an intake passage body defining an intake passage for controlling the opening degree of the intake passage, the throttle devices being disposed in a pair at each of two points spaced from each other in a direction perpendicular to rotational axes of the throttle valves, the intake passage bodies of the throttle devices disposed at the two points being connected to each other by at least one connecting member. 
     2. Description of the Related Art 
     Such intake air amount control system is conventionally known, for example, from Japanese Patent Application Laid-open No. 10-176637 and the like, and designed such that the throttle valves of the pair of throttle devices are driven in operative association with each other by an interlocking mechanism. 
     In the above intake air amount control system, the pair of throttle valves are operated in association with each other so that they are opened slightly upon starting of the engine. Thus, the opening degree of each of the throttle valves is small and for this reason, there is a possibility that the amount of air at the start of the engine may be unstable, whereby the idling rotational speed of the engine becomes unstable. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an intake air amount control system including a plurality of throttle devices, wherein the idling rotational speed of an engine can be stabilized, while avoiding an increase in size of the intake air amount control system. 
     To achieve the above object, according to a first aspect and feature of the present invention, there is provided an intake air amount control system for an engine, comprising a plurality of throttle devices each of which comprises a butterfly-type throttle valve rotatably carried in an intake passage body defining an intake passage for controlling the opening degree of the intake passage, the throttle devices being disposed in a pair at each of two points spaced from each other in a direction perpendicular to rotational axes of the throttle valves, the intake passage bodies of the throttle devices disposed at the two points being connected to each other by at least one connecting member, the intake air amount control system further including bypass air passages mounted on opposed sides of the intake passage bodies forming a pair so as to extend around the throttle valves, respectively, air control valves mounted on the opposed sides of the intake passage bodies for controlling the opening degrees of the bypass air passages, respectively, and a synchronizing mechanism disposed between the pair of the throttle devices for synchronizing the operations of the air control valves. 
     With such arrangement, the bypass air passage is provided in the intake passage body of each of the throttle devices to extend around the throttle valve, and the amount of air flowing through the bypass air passage can be controlled by the air control valve. Therefore, the control of the small amount of air at the start of the engine can be carried out stably, whereby the idling rotational speed can be stabilized, as compared with the prior art in which the amount of air at the start of the engine is controlled by decreasing the opening degree of the throttle valve. In addition, the bypass air passages provided in the intake passage bodies and the air control valves mounted to the intake passage bodies are disposed on opposed sides of the intake passage bodies forming the pair. Therefore, it is possible to avoid an increase in size of the entire intake air amount control system, in spite of the provision of the bypass air passages and the air control valves. Moreover, since the synchronizing mechanism for synchronously operating the air control valves is disposed between the throttle devices forming the pair, the size of the entire intake air amount control system cannot be increased due to the provision of the synchronizing mechanism. 
     According to a second aspect and feature of the present invention, in addition to the first feature, the intake passage bodies forming the pair and having an identical shape, and the air control valves mounted to the intake passage bodies and having an identical shape are disposed symmetrically with respect to a center lying between both the intake passages and established on a straight line passing through axes of the intake passages in the intake passage bodies. With such arrangement, the preparation of a plurality of types of throttle devices is not needed, thereby enabling a reduction in cost and a simplification of the construction of the synchronizing mechanism. 
     According to a third aspect and feature of the present invention, in addition to the second feature, the connecting member is formed into a flat plate-shape. With such arrangement, the shape of the connecting member can be simplified, thereby providing a reduction in cost. 
     According to a fourth aspect and feature of the present invention, in addition to any of the first to third features, the synchronizing mechanism is supported on the connecting member. With such arrangement, an exclusive part for supporting the synchronizing mechanism is not required, whereby the number of parts can be reduced. 
     According to a fifth aspect and feature of the present invention, in addition to the second or third feature, the throttle passage bodies of the pair of throttle devices are disposed at a distance from each other in a direction parallel to the rotational axes of the throttle valves included in the throttle devices, and are connected to each other by a pair of the connecting members which form a substantially right-angled tetragon by cooperation with the intake passage bodies, and the synchronizing mechanism includes a first lever supported on an inner surface of one of the connecting members and connected to the air control valve of one of the throttle devices, a second lever supported on an inner surface of the other connecting member and connected to the air control valve of the other throttle device, and a synchronizing member disposed on a diagonal line of the substantially right-angled tetragon and connecting the first and second levers to each other. With such arrangement, sufficient strengths of the pair of throttle devices can be ensured and moreover, it is possible to protect the synchronizing mechanism by the connecting members and to simplify the synchronizing mechanism. 
     According to a sixth aspect and feature of the present invention, in addition to the first feature, a choke wire assembly is supported on the connecting member and connected to the synchronizing mechanism. With such arrangement, the structure of interconnection of the synchronizing mechanism and the choke wire assembly can be simplified, while increasing the degree of freedom of disposition of the choke wire assembly. 
     The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 to  8  show an embodiment of the present invention, wherein 
     FIG. 1 is a plan view of the entire arrangement of an intake air amount control system; 
     FIG. 2 is a side view taken in the direction of an arrow  2  in FIG. 1; 
     FIG. 3 is a plan view similar to FIG. 1, except for a fuel supply system and throttle valves; 
     FIG. 4 is a side view of an intake passage body taken in a direction of an arrow  4  in FIG. 3; 
     FIG. 5 is an enlarged sectional view taken along a line  5 — 5  in FIG. 4; 
     FIG. 6 is an enlarged sectional view taken along a line  6 — 6  in FIG. 4; 
     FIG. 7 is an enlarged sectional view taken along a line  7 — 7  in FIG. 4; and 
     FIG. 8 is an enlarged sectional view taken along a line  8 — 8  in FIG.  7 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will now be described by way of an embodiment with reference to FIGS. 1 to  8 . Referring first to FIGS. 1 and 2, an intake air amount control system is used in a V-shaped 2-cylinder engine, and includes first and second throttle devices  11 A and  11 B individually corresponding to cylinders of the engine. 
     Each of the first and second throttle devices  11 A and  11 B comprises a butterfly valve  14  which is rotatably carried in an intake passage body  13  defining an intake passage  12  connected to an intake port in each of the cylinders in the engine, and which is capable of controlling the opening degree of the intake passage  12 . The first and second throttle devices  11 A and  11 B are disposed in a pair at two places spaced apart from each other in a direction perpendicular to rotational axes of the throttle valves  14 . 
     The intake passage bodies  13  of the throttle devices  11 A and  11 B have an identical shape, and are disposed symmetrically with each other with respect to a center C lying between both the intake passages  12  and established on a straight line L passing through the axes of the intake passages  12  provided respectively in the intake passage bodies  13 . The intake passage bodies  13  are disposed at a distance from each other in a direction parallel to the rotational axes of the throttle valves  14 , and connected to each other by a pair of connecting members  15  and  16  forming a substantially right-angled tetragon together with both the intake passage bodies  13 . Each of the connecting members  15  and  16  is formed into a flat plate-shape parallel to the straight line L. 
     The throttle valves  14  are secured to valve stems  17  rotatably supported in the intake passage bodies  13 , respectively. A throttle drum  18 A is secured at one end of the valve stem  17  protruding from the intake passage body  13  of the first throttle device  11 A, and a throttle drum  18 B is secured at one end of the valve stem  17  protruding from the intake passage body  13  of the second throttle device  11 B. Moreover, the throttle drums  18 A and  18 B are connected to each other by a connecting member  19 , so that the drums  18 A and  18 B, that is, the valve stems  17  are rotated in operative association with each other by rotating the second throttle drum  18 B by a throttle wire (not shown), whereby the opening degrees of the throttle valves  14  are controlled in operative association with each other. An opening degree sensor  20  for detecting an opening degree of the throttle valve  14  is mounted to the intake passage body  13  of the second throttle device  11 B and connected to the other end of the valve stem  17  on the side opposite to the second throttle drum  18 B. 
     Pairs of fuel injection valves  21  and  22  for injecting fuel into the intake passages  12  at locations downstream of throttle valves  14  included in the throttle devices  11 A and  11 B are mounted on opposite sides of the intake passage bodies  13  in the throttle devices  11 A and  11 B, respectively such that their axes are disposed in a plane perpendicular to axes of the valve stems  17 . 
     The fuel injection valves  21  and  22  are clamped between the intake passage bodies  13  and valve support members  23  mounted to the intake passage bodies  13 . 
     The valve support member  23  is fastened to the intake passage body  13  and has a fuel passage leading to a rear end of each of the fuel injection valves  21  and  22 . Substantially U-shaped pipes  24  leading to the fuel passages are connected at their opposite ends to the pair of valve support members  23  for each of the throttle devices  11 A and  11 B, and substantially U-shaped pipes  25  leading to the fuel passages are connected at their opposite ends to the valve support members  23  for mounting the fuel injection valves  22  to the first and second throttle devices  11 A and  11 B. A fuel inlet joint  26  for connecting the injection valve  21  to a fuel supply pump (not shown) is mounted to the valve support member  23  for mounting the fuel injection valve  21  to the second throttle device  11 B, and a regulator  27  for returning a surplus amount of fuel to a fuel tank (not shown) is connected to the valve support member  23  for mounting the fuel injection valve  21  to the first throttle device  11 A. 
     Referring to FIGS. 3 to  7 , a bypass passage  30  is provided in each of opposed sides of the intake passage bodies  13  to extend around the throttle valve  14 , and comprises an upstream passage portion  30   a  which opens at its upstream end into the intake passage  12  at a location upstream of the throttle valve  14 , and a downstream passage portion  30   b  which opens at its downstream end into the intake passage  12  at a location downstream of the throttle valve  14 . An air control valve  31  is mounted on each of the opposite sides of the intake passage bodies and disposed between the upstream passage portion  30   a  and the downstream passage portion  30   b  of the bypass air passage  30  to control the opening degree of the bypass air passage  30 . Thus, the upstream passage portion  30   a  and the downstream passage portion  30   b  of the bypass air passage  30  are defined in the intake passage body  13  in such a manner that they are bent at a plurality of points. 
     Referring further to FIG. 8, the air control valve  31  includes a columnar valve member  32  slidably fitted in the intake passage body  13 , a rod  33  coaxially connected to the valve member  32  and protruding outwards from the intake passage body  13 , a guide member  34  screwed into the intake passage body  13  for guiding the axial movement of the rod  33 , and a return spring  35  mounted between the guide member  34  and the valve member  32 . 
     A slide bore  36  having a substantially horizontal axis is provided in the intake passage body  13  and connected to a downstream end of the upstream passage portion  30   a  of the bypass air passage  30 , and the valve member  32  is slidably received in the slide bore  36 . A plurality of, for example, three valve bores  37  are provided in parallel and in a partially lapped manner in a direction along an axis of the slide bore  36 . The valve bores  37  are connected to an upstream end of the downstream passage portion  30   b  of the bypass air passage  30  and open into an inner surface of the slide bore  36 . With such arrangement of the valve bores  37 , the opening area of a path between the upstream passage portion  30   a  and the downstream passage portion  30   b  of the bypass air passage  30  is varied proportionally by the sliding movement of the valve member  32  within the slide bore  36 . 
     The return spring  35  is mounted between the guide member  34  and the valve member  32  to exhibit a spring force for biasing the valve member  32  in a direction to decrease the opening area of a path between the upstream passage portion  30   a  and the downstream passage portion  30   b  of the bypass air passage  30 . Mounted at an outer end of the guide member  34  screwed into the intake passage body  13  to occlude an outer end of the slide bore  36  is a boot  38  for sealing the guide  34  and the rod  33  axially movably passed through the guide member  34  from each other. 
     Such bypass air passages  30  are provided in an identical shape in the opposed sides of the intake passage bodies  13 , respectively, and the air control valves  31  having an identical shape are mounted to the intake passage bodies  13 , respectively. Moreover, the air control valves  31  are disposed symmetrically with respect to the center C established on the straight line L. 
     Referring especially to FIG. 3, the air control valves  31  are operated synchronously by the operation of a synchronizing mechanism  40  disposed between the throttle devices  11 A and  11 B forming the pair. The synchronizing mechanism  40  includes a first lever  41  supported on an inner surface of the connecting member  15  and connected to the air control valve  31  of the first throttle device  11 A, a second lever  42  supported on an inner surface of the connecting member  16  and connected to the air control valve  31  of the second throttle device  11 B, and a synchronizing member  43  which connects the first and second levers  41  and  42  to each other. 
     The first lever  41  is turnably supported by a support shaft  44  mounted in an inner surface of the connecting member  15 , and is engaged and connected at one end thereof to an end of the rod  33  included in the air control valve  31  of the first throttle device  11 A. A spring  45  is mounted between the first lever  41  and the connecting member  15  for biasing the first lever  41  in a direction to maintain the engagement and connection between the first lever  41  and the rod  33 . 
     The second lever  42  is turnably supported by a support shaft  46  mounted in an inner surface of the connecting member  16 , and is engaged and connected at one end thereof to an end of the rod  33  included in the air control valve  31  of the second throttle device  11 B. A spring  47  is mounted between the second lever  41  and the connecting member  16  for biasing the second lever  42  in a direction to maintain the engagement and connection between the second lever  42  and the rod  33 . Moreover, a regulating member  48  for regulating the position of engagement and connection of the second lever  42  to the rod  33  is threadedly engaged for advancing and retracting movements with the rod  33  included in the air control valve  31  of the second throttle device  11 B. 
     The pair of intake passage bodies  13  are connected to each other by the pair of connecting members  15  and  16  so as to form a substantially right-angled tetragon by cooperation of the intake passage bodies  13 , and the synchronizing member  43  connects the first and second levers  41  and  42  to each other to extend on a diagonal line of the right-angled tetragon. 
     A support stay  49  is secured to the inner surface of the connecting member  16 , and an outer wire portion  51  of a choke wire assembly  50  comprising an inner wire  52  movably inserted through the outer wire  51  is supported at its end on the support stay  49 . An engage piece  53  is secured to an end of the inner wire  52  protruding from the end of the outer wire  51 , and is engaged and connected to the second lever  42 . Therefore, the pulling of the choke wire assembly  50  causes the second lever  42  to be turned, whereby the air control valve  31  of the second throttle device  11 B is driven, and the air control valve  31  of the first throttle device  11 A is driven by the transmission of the turning movement of the second lever  42  to the first lever  41  through the synchronizing member  43 , whereby the air control valve  31  of the first throttle device  11 A is driven. Namely, the air control valves  31  of the first and second throttle devices  11 A and  11 B are operated synchronously by the pulling of the choke wire assembly  50 . 
     A regulating screw  54  is threadedly engaged for advancing and retracting movements with the support stay  49 , with a tip end thereof abutting against the second lever  42 , for defining the minimum opening degree of the air control valves  31 . A spring  55  is mounted between a rear end of the regulating screw  54  and the support stay  49  for preventing the loosing of the regulating screw  54 . 
     The operation of the embodiment will be described below. The bypass passages  30  extending around the throttle valve  14  in the first and second throttle devices  11 A and  11 B disposed in the pair are provided in the intake passage bodies  13  in the throttle devices  11 A and  11 B, respectively, and the air control valves  31  for controlling the opening degrees of the bypass air passages  30  are mounted to the intake passage bodies  13  in the throttle devices  11 A and  11 B, respectively. Therefore, by controlling the amounts of air flowing through the bypass air passages  30  by the air control valves  31 , the control of a small amount of air at the start of the engine can be carried out stably to stabilize the idling rotational speed, as compared with the prior art in which the amount of air at the start of the engine is controlled by decreasing the opening degrees of the throttle valves  14 . 
     In addition, the bypass air passages  30  and the air control valves  31  are disposed on the opposed sides of the intake passage bodies  13  forming the pair. Therefore, an increase in size of the entire intake air amount control system can be avoided in spite of the provision of the bypass air passages  30  and the air control valves  31 . Moreover, the synchronizing mechanism  40  for synchronously operating the air control valves  31  is also disposed between the throttle devices  11 A and  11 B forming the pair and hence, the size of the entire intake air amount control system cannot be increased due to the provision of the synchronizing mechanism  40 . 
     In addition, the intake passage bodies  13  and the air control valves  31  having the identical shape are disposed symmetrically with each other with respect to the center C lying between the intake passages  12  and established on the straight line L passing through the axes of the intake passages  12 . Therefore, the preparation of a plurality of types of throttle devices is not needed, thereby enabling a reduction in cost and a simplification of the construction of the synchronizing mechanism  40 . 
     The pair of intake passage bodies  13  are connected to each other by the pair of connecting members  14  and  16  and hence, the sufficient strength of the throttle devices  11 A and  11 B can be ensured. Moreover, since each of the connecting members  15  and  16  is formed into the flat plate-shape, the shape of the connecting members  15  and  16  can be simplified to provide a reduction in cost. Additionally, since the synchronizing mechanism  40  is supported on the connecting members  15  and  16 , an exclusive part for supporting the synchronizing mechanism  40  is not required, whereby the number of parts can be reduced. 
     The synchronizing mechanism  40  includes the first lever  41  supported on the inner surface of one of the connecting member  15  and connected to the air control valve  31  of the first throttle device  11 A, the second lever  42  supported on the inner surface of the other connecting member  16  and connected to the air control valve  31  of the second throttle device  11 B, and the synchronizing member  43  which connects the first and second levers  41  and  42  to each other. The synchronizing member  43  is disposed on the diagonal line of the substantially right-angled tetragon formed by the connecting members  15  and  16  and the intake passage bodies  13 . With such arrangement of the synchronizing mechanism, it is possible to protect the synchronizing mechanism  40  by the connecting members  15  and  16  and moreover, to simplify the synchronizing mechanism  40 . 
     Further, the choke wire assembly  50  is connected to the synchronizing mechanism  40  and supported on the connecting member  16  through the support stay  49 . Therefore, the structure of interconnection of the synchronizing mechanism  40  and the choke wire assembly  50  can be simplified, while increasing the degree of freedom of disposition of the choke wire assembly  50 . 
     Although the embodiments of the present invention have been described in detail, it will be understood that the present invention is not limited to the above-described embodiments, and various modifications in design may be made without departing from the spirit and scope of the invention defined in claims. 
     For example, the intake air amount control system including the throttle devices  11 A and  11 B disposed in the pair at each of the two points spaced from each other in the direction perpendicular to the rotational axes of the throttle valves  14  has been described in the embodiment, but the present invention is applicable to an intake air amount control system including a plurality of throttle devices disposed at each of the two points.