The present invention relates to an improvement of an air intake device for an engine, the air intake device including a throttle body having an air intake path, a throttle valve that is supported on the throttle body and that opens and closes the air intake path, a bypass connected to the air intake path while bypassing the throttle valve, and a bypass valve for controlling the degree of opening of the bypass, the bypass valve being formed from a tubular valve chamber having an interior thereof opening on the upstream side of the bypass and having an inner face with a metering hole opening toward the downstream side of the bypass, and a valve body that is slidably but non-rotatably fitted into the valve chamber and that opens and closes the metering hole.
Such an air intake device for an engine is already known, as disclosed in Patent Publication 1.
[Patent Publication 1] Japanese Patent Application Laid-open No. 2003-74444
In recent years, accompanying an increase in the output of engines mounted in automobiles and motorcycles, there is a requirement for a high flow rate of fast idle air, and there is therefore a trend towards enlargement of a metering hole that is controlled so as to open and close by a bypass valve.
However, in the case of a large metering hole, when the valve body is drawn to the metering hole side by engine air intake negative pressure, there is a possibility of an end part of the valve body being forced out toward the metering hole, thus preventing a smooth opening and closing movement of the valve body.
The present invention has been accomplished in the light of such circumstances, and it is an object thereof to provide an air intake device for an engine of the above type that can prevent any hindrance to the closing movement of the valve body even when a large metering hole is employed.
In order to attain the above object, according to a first aspect of the present invention, there is provided an air intake device for an engine, comprising a throttle body having an air intake path, a throttle valve that is supported on the throttle body and that opens and closes the air intake path, a bypass connected to the air intake path while bypassing the throttle valve, and a bypass valve for controlling the degree of opening of the bypass, the bypass valve being formed from a tubular valve chamber having an interior thereof opening on the upstream side of the bypass and having an inner face with a metering hole opening toward the downstream side of the bypass, and a valve body that is slidably but non-rotatably fitted into the valve chamber and that opens and closes the metering hole, characterized in that the valve chamber and the metering hole are formed in a bypass valve holder provided so as to be connected to the throttle body, and a dividing wall that divides the metering hole into a plurality of small metering holes arranged in the peripheral direction of the valve chamber is formed in the bypass valve holder so as to be continuous with an inner peripheral face of the valve chamber.
According to a second aspect of the present invention, in addition to the first aspect, the small metering holes are each formed as a rectangle having two sides parallel to a sliding direction of the valve body.
According to a third aspect of the present invention, in addition to the first or second aspect, the valve body is given a normal idle adjustment stroke for moving from a fully closed position thereof to a position at which the metering holes start to open, the valve body is provided with a slit for providing communication between the valve chamber and at least one of the small metering holes, and the slit is formed so that the area of the slit opening to the small metering hole increases as the valve body moves through the normal idle adjustment stroke from the fully closed position.
According to a fourth aspect of the present invention, in addition to the third aspect, the small metering hole in which the slit opens is positioned on the upstream side, relative to the other small metering hole, of the bypass, and a labyrinth wall is provided so as to be connected to the dividing wall, the labyrinth wall trapping carbon flowing backward in the bypass and preventing carbon from entering the small metering hole in which the slit opens.
In accordance with the first aspect of the present invention, even when the valve body is drawn toward the plurality of small metering holes due to engine air intake negative pressure, since the valve body is supported by the dividing wall between the small metering holes, it is possible to prevent the end part of the valve body from being forced out toward the small metering hole, thereby enabling the valve body to always open and close well. This enables the small metering holes to be enlarged so that they can match a higher output for the engine.
In accordance with the second aspect of the present invention, it is possible to control a large fast idle air volume and to make the fast idle air volume linearly proportional to the stroke of the valve body.
In accordance with the third aspect of the present invention, since, before the valve body opens the small metering holes, the area of the slit of the valve body opening to the small metering hole increases in response to movement through the normal idle adjustment stroke from the fully closed position, it is possible to easily carry out fine adjustment of the normal idle air volume by movement of the valve body within the normal idle adjustment stroke.
In accordance with the fourth aspect of the present invention, even when blow back gas from the engine flows backward in the bypass, carbon contained in the gas can be trapped in the labyrinth wall, thus preventing carbon from entering the small metering hole, in which the slit opens, and it is therefore possible to prevent the slit from being blocked by carbon, thereby stabilizing the adjusted normal idle air volume and consequently stabilizing engine idling.
Modes for carrying out the present invention are explained below by reference to a preferred embodiment of the present invention shown in the attached drawings.
First, in
As shown in
A lower end part of the valve chamber 15 communicates with the air intake path 2 on the upstream side of the throttle valve 5 via an inlet port 18 (see
The inlet port 18, the valve chamber 15, the metering hole 16, the recesses 13 and 14, and the outlet port 19 thereby form a bypass 20 connected to the air intake path 2 while surrounding the first bearing boss 3 so as to bypass the throttle valve 5. A seal 21 is provided between the opposing faces 1f and 10f of the throttle body 1 and the bypass valve holder 10 so as to surround the recesses 13 and 14, the inlet port 18, and the outlet port 19.
As clearly shown in
Formed in the bypass valve holder 10 is a mounting hole 29 communicating with the upper end of the valve chamber 15, and mounted in this mounting hole 29 is an electric actuator 28 for moving the valve body 25 for opening and closing. This electric actuator 28 has a downwardly projecting output shaft 28a screwed into a screw hole 25a in a center part of the valve body 25, and rotating the output shaft 28a forward and backward enables the valve body 25 to move up and down (open and close). A plate-shaped seal 30 is provided between a lower end face of the electric actuator 28 and a base face of the mounting hole 29, the seal 30 making intimate contact with an outer peripheral face of the output shaft 28a.
As shown in
As shown in
The valve body 25 is given a normal idle adjustment stroke S for moving from a fully closed position (see
In
Formed integrally with the bypass valve holder 10 is a tubular wall 39 surrounding the throttle drum 8 and being integrally equipped with a support boss 40 on one side, linked to the throttle drum 8 is a connection terminal 41a at one end of a throttle wire 41 running through the support boss 40, and linked to a throttle operation member such as a throttle grip (not illustrated) is a connection terminal at the other end of the throttle wire 41. A hollow bolt 43 through which the throttle wire 41 runs is adjustably screwed into the support boss 40, and an end part of a guide tube 42 slidably covering the throttle wire 41 is supported by a head portion 43a of the hollow bolt 43.
Pulling the throttle wire 41 by the throttle operation member enables the throttle valve 5 to be opened via the throttle drum 8, and releasing the pulling enables the throttle valve 5 to be closed by the urging force of the return spring 35.
A cover 45 for closing an open face of the tubular wall 39 is detachably retained on the tubular wall 39 by a screw.
Referring again to
The operation of this embodiment is now explained.
When the engine is running, the electronic control unit 54 supplies to the electric actuator 28 a current corresponding to an air intake temperature detected by the temperature sensor 53, thus operating the electric actuator 25 and thereby controlling the opening and closing of the valve body 25. When the engine is at a low temperature, that is, the engine is warming up, the valve body 25 is pulled up by a large amount, thus controlling the degree of opening of the small metering holes 16a and 16b so that it is large (see
When the engine temperature increases as warming up progresses, since the electric actuator 28 accordingly makes the valve body 25 descend, thus decreasing the degree of opening of the small metering holes 16a and 16b, the amount of fast idle air supplied to the engine through the bypass 20 decreases, and the engine fast idling rotational speed decreases. When the engine temperature attains a predetermined high temperature, since the electric actuator 28 makes the valve body 25 descend to a position at which it closes the small metering holes 16a and 16b (see
Since the small metering holes 16a and 16b have a rectangular shape, it is possible to control a large fast idle air volume by opening and closing the small metering holes 16a and 16b by the valve body 25 (see section b-c in
Furthermore, since the dividing wall 17 continuous with the inner peripheral face of the valve chamber 15 is present between the plurality of small metering holes 16a and 16b, even when the valve body 25 is drawn toward the plurality of small metering holes due to engine air intake negative pressure, since the valve body 25 is supported by the dividing wall 17, it is possible to prevent the end part of the valve body 25 from being forced out toward the small metering holes 16a and 16b, thereby guaranteeing a smooth opening and closing movement of the valve body 25. This enables the small metering holes 16a and 16b to be set sufficiently large and a large fast idle air volume to be controlled, thus enabling a higher output for the engine to be matched.
When the valve body 25 subsequently closes the small metering holes 16a and 16b and enters a normal idle adjustment stroke S as shown in
Since the bypass 20 is formed so as to surround the first bearing boss 3, which supports the end part of the valve shaft 5a on the throttle drum 8 side, the space around the outer periphery of the first bearing boss 3, which is conventionally considered to be dead space, is utilized effectively for formation of the bypass 20, and it is therefore possible to make the overall air intake device compact while preventing the dimensions of the area around the throttle sensor 51 on the side opposite to the throttle drum 8 from increasing.
Furthermore, since at least one part of the bypass 20 is formed from the groove-shaped recesses 13 and 14 formed in opposing faces of the throttle body 1 and the bypass valve holder 10, which are joined to each other, even if the shape of the bypass 20 is complicated, at least one part thereof can be formed easily at the same time as molding the throttle body 1 and the bypass valve holder 10.
Moreover, since the center lines of the inlet port 18 and outlet port 19 of the bypass 20, which open on the air intake path 2, are parallel to the axis of the valve shaft 5a, it is possible to machine the throttle body 1 so as to coaxially form the inlet port 18 and the outlet port 19 and the shaft hole of the bearing boss, thereby contributing to a reduction in the number of machining steps.
Furthermore, since, in order to form the bypass 20, a plurality of labyrinth walls 31 and 32 are provided on the groove-shaped recesses 13 and 14 formed in the two opposing faces 1f and 10f of the throttle body 1 and the bypass valve holder 10, the labyrinth walls 31 and 32 being arranged alternately along the direction of flow of air while traversing the recesses 13 and 14, it is possible to simply form a labyrinth in the bypass 20, and even when the engine blows back and the blown back gas flows backward in the bypass 20, carbon contained in the gas can be trapped in the labyrinth and thus prevented from entering the small metering holes 16a and 16b. In particular, since one of the labyrinth walls 31 is provided so as to be connected to the dividing wall 17 between the small metering holes 16a and 16b, and the small metering hole 16a in which the slit 33 of the valve body 25 opens is positioned on the upstream side of the dividing wall 17 in the bypass 20, it is possible to prevent effectively the carbon described above from entering the slit 33. It is therefore possible to prevent the slit 33 from being blocked by carbon, thereby stabilizing the adjusted normal idle air volume.
Furthermore, since the full closure regulation part 37 running through the bypass valve holder 10 and projecting toward the throttle drum 8 side is formed integrally with the throttle body 1, and the fully closed position of the throttle valve 5 is regulated by means of the stopper bolt 38, which is screwed into the full closure regulation part 37, receiving the stopper piece 8a of the throttle drum 8, even if the bypass valve holder 10 is displaced relative to the throttle body 1 to some degree, the fully closed position of the throttle valve 5 can always be reproduced accurately regardless of the displacement.
Moreover, since the tubular wall 39 covering the outer periphery of the throttle drum 8 is formed integrally with the bypass valve holder 10, and the cover 45 is mounted on the open end of the tubular wall 39 so as to block it, the throttle drum 8 and the area around the shaft end of the valve shaft are covered in a substantially hermetically sealed manner by the tubular wall 39 of the bypass valve holder 10 and the cover 45, thus providing protection against dust and water therefor and, moreover, since the tubular wall 39 is formed on the bypass valve holder 10, it is possible to suppress any increase in the number of components and simplify the structure.
Furthermore, since the support boss 40 supporting the guide tube 42 of the throttle wire 41 is formed integrally with the tubular wall 39, the tubular wall 39, that is, the bypass valve holder 10, functions also as a support member for supporting the end part of the guide tube 42 of the throttle wire 41, thus reducing the number of components and the number of assembly steps.
An embodiment of the present invention is explained above, but the present invention is not limited thereto and may be modified in a variety of ways as long as the modifications do not depart from the spirit and scope of the present invention. For example, the present invention may be applied to a downdraft type throttle body having its air intake path standing vertically. Furthermore, the bypass valve holder 10 may be formed integrally with the throttle body 1.
Number | Date | Country | Kind |
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2005 258140 | Sep 2005 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2006/316094 | 8/16/2006 | WO | 00 | 8/24/2009 |