JP5342288B2 - Engine intake control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an intake control device for an engine capable of preventing an inlet of a bypass from being intake resistance in the output operation of the engine, and preventing the penetration of water droplets into the bypass even if the water droplets flow on the inner surface of an intake air passage. <P>SOLUTION: The intake control device for the engine includes: the bypass 30 formed at a throttle body 1 having the intake air passage 7 bypassing a throttle valve 8, and communicating with the intake air passage 7; and a valve means 31 provided at the bypass 30 for opening and closing the bypass. In the device, the inlet of the bypass 30 is composed of a recessed groove 32 formed at the inner surface of the intake air passage 7 so that the inlet starts from the upstream end of the throttle body 1 and stops before the throttle valve 8. The other passage 33 of the bypass 30 reaching the recessed groove 32 is formed in a stepped portion 32c raised from the inner surface 32b of the recessed groove 32 by one stage. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention provides a throttle body having an intake passage that is opened and closed by a throttle valve, with a bypass that bypasses the throttle valve and communicates with the intake passage, and in which the valve means for opening and closing the engine is provided. It is related with improvement of a control device.

Such an intake control device for an engine is already known as disclosed in Patent Documents 1 and 2.
Japanese Utility Model Publication No.59-88236 Japanese Utility Model Publication No. 63-151965

  In the conventional engine intake control system, the bypass inlet is formed in a pipe shape from the inner surface of the intake passage, so that when the engine is operated with the throttle valve opened, the protruding bypass inlet is the intake resistance. This adversely affects the engine output performance. Therefore, it is conceivable that the inlet of the bypass is directly opened on the inner surface of the intake passage without protruding into the intake passage. In such a case, water droplets generated due to condensation have flowed along the inner surface of the intake passage. Sometimes, the water droplets can enter the bypass.

  The present invention has been made in view of such circumstances, and when the engine is operated for output, the inlet of the bypass does not serve as an intake resistance, and even if water drops flow on the inner surface of the intake passage, An object of the present invention is to provide an intake control device for an engine that can prevent intrusion.

  In order to achieve the above object, the present invention provides a throttle body having an intake passage that is opened and closed by a throttle valve, with a bypass that bypasses the throttle valve and communicates with the intake passage, and the bypass opens and closes the valve. In the intake control device for an engine provided with means, the inlet of the bypass is configured by a concave groove formed on the inner surface of the intake passage so as to start from the upstream end of the throttle body and stop before the throttle valve, The first feature is that another passage of the bypass following the concave groove is opened to a step portion raised one step from the inner surface of the concave groove. The valve means corresponds to an idle adjustment valve 31 in an embodiment of the present invention described later, and the other passage corresponds to a valve hole 33.

  Moreover, in addition to the 1st characteristic, this invention sets it as the 2nd characteristic that the opening part to the said step part of the said other channel | path was arrange | positioned away from the periphery of the said step part.

Furthermore, in addition to the first or the second feature, the present invention further includes forming the concave groove downward on an upper inner surface of the intake passage, and the step portion , the step portion being a ceiling surface of the concave groove. The third feature is that the terminal is formed continuously with the dead end portion.

  Furthermore, in addition to any of the first to third features, the present invention provides an intake passage in the cylinder portion of the throttle body, and is orthogonal to the valve shaft of the throttle valve with respect to the center of the outer shape of the cylinder portion. A fourth feature is that the concave groove is formed in the thick portion of the cylindrical portion opposite to the eccentric direction of the intake passage.

  According to the first feature of the present invention, since the bypass inlet is a concave groove recessed from the inner surface of the intake passage, the concave groove does not reduce the flow passage area of the intake passage, and the engine load is reduced. During operation, it does not hinder the flow of intake air going straight through the intake passage, thereby reducing the intake resistance of the engine and contributing to the improvement of its output.

  In addition, since the other passageway of the bypass following the concave groove opens to a stepped portion raised from the inner surface of the concave groove, even if there is a water droplet flowing on the inner surface of the concave groove, the water droplet does not flow. The inertia flows around the step portion and avoids the opening portion of the other passage, so that the ingress of water droplets downstream of the bypass can be prevented.

  According to the second feature of the present invention, the opening to the step portion of the other passage is arranged away from the periphery of the step portion, so that water droplets flow around the step portion and enter the other passage. It becomes more difficult to enter, and water droplets can be further prevented from entering downstream of the bypass.

  According to the third feature of the present invention, when the throttle body is molded, the mold can be removed from the intake passage and the recessed groove without being interfered by the stepped portion.

  According to the fourth aspect of the present invention, the flow path area of the groove can be sufficiently obtained without reducing the strength of the throttle body, and the other part of the bypass following the groove is used as the valve shaft. It can be easily formed without being disturbed.

1 is a longitudinal side view of a motorcycle engine intake control apparatus according to an embodiment of the present invention (a cross-sectional view taken along line 1-1 of FIG. 3). FIG. 2 is a view taken along arrow 2-2 in FIG. 1. FIG. 3 is a sectional view taken along line 3-3 in FIG. 1. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. FIG. 5 is a sectional view taken along line 5-5 of FIG. FIG. 6 is a sectional view taken along line 6-6 of FIG. FIG. 7 is an enlarged sectional view taken along line 7-7 in FIG. 2 (idle intake air amount minimum adjustment state). FIG. 8 is an operation explanatory diagram corresponding to FIG. 7 (idle intake air amount maximum adjustment state). FIG. 9 is a sectional view taken along line 9-9 in FIG. 3. The diagram which shows the relationship between the rotation angle of an idle adjustment valve, and idle intake air quantity.

  Embodiments of the present invention will be described below on the basis of preferred embodiments of the present invention shown in the accompanying drawings.

  First, in FIGS. 1 to 4, the throttle body 1 is made of a die casting made of a light alloy, and includes a cylindrical portion 1a and a flange portion 1b projecting from one end of the cylindrical portion 1a to the outer periphery. Is done. The flange portion 1b has a substantially square shape when viewed from the front (see FIG. 3), and a pair of upper and lower first and second fastening bosses 2 and 2 'are formed at corners on one of the diagonal lines. The second fastening bosses 2 and 2 'are coupled to the joint flange portion of the intake pipe 5 of the engine by a pair of fastening bolts 3 and 3. An inlet tube 6 connected to the air cleaner is fitted and connected to the outer periphery of the cylindrical portion 1a.

  The throttle body 1 has a cylindrical intake passage 7 that communicates between the inlet tube 6 and the intake pipe 5, and the intake passage 7 is valved with respect to the outer center of the cylindrical portion 1 a of the throttle body 1. It is formed eccentrically downward below the axis 8a. A valve shaft 8 a of a butterfly throttle valve 8 that opens and closes the intake passage 7 is rotatably supported by a pair of first and second bearing bosses 9 and 9 ′ formed on the throttle body 1. The first and second bearing bosses 9 and 9 ′ are formed integrally with the cylindrical portion 1 a at one half circumference and the flange portion 1 b at the other half circumference. At that time, it is desirable to arrange the first and second bearing bosses 9 and 9 'so that one side surface thereof is substantially flush with the end surface of the flange portion 1b as shown in the drawing.

  Thus, by forming the first and second bearing bosses 9, 9 'from the cylindrical portion 1a to the flange portion 1b, the throttle valve 8 can be disposed close to the downstream end of the intake passage 7, and the throttle body 1 Can be greatly reduced, in particular, the axial dimension of the throttle body 1 can be greatly shortened.

  As shown in FIGS. 2 to 4, a throttle drum 10 is fixed to one end of the valve shaft 8a, and an operation wire 11 for opening and closing the throttle valve 8 (see FIG. 4) is attached to the throttle drum 10. Is connected.

  The upper first fastening boss 2 is arranged so that a part thereof overlaps with the cylindrical body 1a in a plan view, and a stay boss 15 is integrally connected to the outside of the first fastening boss 2. A guide tube stay 13 that supports the end portion of the guide tube 12 of the operation wire 11 is fixed to the stay boss 15 with a screw 16 on the end surface of the stay boss 15 on the cylindrical portion 1a side. At that time, a positioning pin 18 projecting from the end surface of the stay boss 15 on the side of the cylindrical portion 1a is fitted into the positioning hole 17 which is formed in the guide tube stay 13 and is adjacent to the lower side of the screw 16. Accordingly, the rotation of the guide tube stay 13 around the screw 16 is prevented. As a result, the guide tube stay 13 can be fixed to the stay boss 15 with a single screw 16. The distal end portion of the positioning pin 18 passes through the positioning hole 17 and protrudes from the outer surface of the guide tube stay 13, and a stopper arm 10 a that abuts against the distal end portion and regulates the fully open position of the throttle valve 8 serves as a throttle drum. 10 integrally formed. That is, since the positioning pin 18 also serves as a stopper pin that restricts the fully open position of the throttle valve 8, a dedicated stopper pin is not required, and the structure can be simplified.

  Further, a full-closed stopper boss 20 is integrally formed on the flange portion 1b on the opposite side of the stay boss 15 with the first bearing boss 9 interposed therebetween. The full-closed stopper boss 20 receives the stopper arm 10a and receives a throttle. A fully closed stopper bolt 21 for restricting the fully closed position of the valve 8 is screwed.

  In the above, the first and second fastening bosses 2, 2 ′, the holes of the stay boss 15, the positioning pins 18, and the holes of the fully closed stopper boss 20 are arranged in parallel with the intake passage 7. By doing so, it is possible to perform mold forming and drilling for the intake passage 7, the first and second fastening bosses 2, 2 ′, the stay boss 15, the positioning pin 18, and the fully closed stopper boss 20 all at once. Good properties.

  A space 22 is formed around the first bearing boss 9 so as to separate the stay boss 15 and the fully-closed stopper boss 20. The space 22 is used to urge the throttle drum 10 in the closing direction of the throttle valve 8. A torsion coil type return spring 23 is disposed on the outer periphery of the bearing boss 9.

  Thus, the stay boss 15, the first bearing boss 9, the return spring 23, and the fully closed stopper boss 20 can be aligned on one side of the flange portion 1 b, which can contribute to making the throttle body 1 compact. At this time, in particular, the stay boss 15 from one side of the flange portion 1b is provided by integrally connecting the stay boss 15 to the outside of the first fastening boss 2 disposed so as to partially overlap the cylindrical portion 1a in plan view. The projection length of the fully-closed stopper boss 20 aligned with the stay boss 15 from the flange portion 1b can be kept short, and the throttle body 1 can be made more compact. Can contribute.

  As shown in FIGS. 1 and 3, a casing 25 of a throttle sensor 25 that detects the opening of the throttle valve 8 is fitted to the outer periphery of the second bearing boss 9 ′. On the other hand, a sensor support boss 27 aligned with the second fastening boss 2 ′ is formed integrally with the flange portion 1 b so as to sandwich the second bearing boss 9, and a bolt 28 to which the casing 25 is fastened is attached to the sensor support boss 27. It is concluded by. The sensor support boss 27 is arranged in parallel with the second bearing boss 9. According to such an arrangement, the second bearing boss 9 and the sensor support boss 27 can be molded and drilled at once, and the workability is good.

  Thus, the second fastening boss 2 ', the second bearing boss 9', and the sensor support boss 27 can be aligned with the other side of the flange portion 1b, and the stay boss 15, the first bearing boss 9, the return spring 23, and the fully closed state. Combined with the arrangement of the stopper boss 20 on one side of the flange portion 1b, the overall throttle body 1 can be greatly reduced in size.

  2, 3, and 5 to 8, the throttle body 1 is formed with a bypass 30 that bypasses the throttle valve 8 and communicates with the intake passage 7. The bypass 30 is provided to supply idling intake air (hereinafter referred to as idle intake air) to the engine, and an idle adjustment valve 31 for adjusting the idle intake air amount is screwed to the throttle body 1. . The bypass 30 and the idle adjustment valve 31 will be described in detail below.

The bypass 30 is a concave groove 32 (FIGS. 2, 5, and 6 ) formed downward on the upper side surface (that is, the upper inner surface) of the intake passage 7 in the range from the upstream end of the throttle body 1 to the front of the throttle valve 8. A cylindrical valve hole 33 (see FIG. 7) extending in a direction that bends at right angles from the concave groove 32, and a measurement hole 34 extending from the middle of the valve hole 33 toward the downstream end of the throttle body 1. The notch 35 (see FIG. 3) formed on the end surface of the flange portion 1b of the throttle body 1 joined to the intake pipe 5 so as to communicate the measuring hole 34 with the downstream end portion of the intake passage 7. Composed.

  As described above, the concave groove 32 is formed in the upper portion of the cylindrical portion 1a by decentering the intake passage 7 downward perpendicular to the valve shaft 8a with respect to the outer shape center of the cylindrical portion 1a of the throttle body 1. The thick portion 36 is formed. Thereby, the flow passage area of the concave groove 32 can be sufficiently obtained without reducing the strength of the throttle body 1, and the other part of the bypass 30 following the concave groove 32 is obstructed by the valve shaft 8a. It can form easily, without.

  On the outer end side of the valve hole 33, a screw hole 38 and a guide hole 39, which gradually increase in diameter, are connected in a coaxial manner, and the guide hole 39 opens on the outer surface of the throttle body 1. The guide hole 39, the screw hole 38 and the valve hole 33 are formed in parallel with the second bearing boss 9 ′ similarly to the sensor support boss 27. By doing so, it is possible to perform mold forming and drilling for each of the holes, the sensor support boss 27 and the second bearing boss 9 'all at once, and the workability is good.

As shown in FIGS. 2 and 5 to 7 , the concave groove 32 has a dead end portion 32a on the downstream side thereof, and the valve hole 33 is bent at a right angle from the front of the dead end portion 32a. It is arrange | positioned so that it may extend. Further, the opening 33a of the valve hole 33 to the concave groove 32 is narrowed, and the opening 33a opens to a step 32c raised by one step from the inner side surface 32b of the concave groove 32, and The opening 33a is arranged away from the peripheral edge of the step 32c.

The step 32c is formed to be continuous with the ceiling surface of the groove 32 and the dead end 32a. According to this, at the time of mold forming of the throttle body 1, it is possible to perform die removal from the intake passage 7 and the concave groove 32 without being interfered by the step portion 32 c.

  On the other hand, the idle adjustment valve 31 is configured by integrally connecting the main shaft 41, the screw shaft 42, and the adjustment valve shaft 43 in a coaxial manner so that the diameter gradually decreases, and the main shaft 41 has a huge head with a tool groove 44. 41a is provided at the outer end, and an O-ring 45 is mounted on the outer periphery. The adjusting valve shaft 43 is fitted to the valve hole 33 so as to be rotatable and slidable, the screw shaft 42 is screwed into the screw hole 38, and the main shaft 41 is inserted into the guide hole 39 via the O-ring 45. A coil spring 46 for preventing rotation of the idle adjustment valve 31 is provided between the outer surface of the throttle body 1 and the enormous head portion 41a so as to be rotatably and slidable.

  The adjusting valve shaft 43 has a dead end hole 48 that opens at its end surface and communicates with the valve hole 33, an annular measuring groove 49 that surrounds the outer periphery of the adjusting valve shaft 43 and communicates with the measuring hole 34, and a dead end hole 48. Are provided with a plurality of through holes 50, 50... Communicating with the measuring groove 49. The groove width of the measuring groove 49 is set sufficiently longer than the inner diameter of the measuring hole 34. Further, the dead end portion of the dead end hole 48 beyond the through holes 50, 50.

  The measuring hole 34 and the through holes 50, 50... Are always arranged so as to be offset from each other along the axial direction of the adjusting valve shaft 43 at any adjustment position of the adjusting valve shaft 43.

  As shown in FIG. 1, the number of the plurality of through holes 50, 50... Is preferably four that are arranged at equal intervals in the circumferential direction of the adjustment valve shaft 43. One or a plurality of annular grooves 52 (see FIG. 6) constituting a labyrinth seal are formed on the outer peripheral surface of the tip portion of the adjustment valve shaft 43.

  Thus, during idling of the engine with the throttle valve 8 fully closed, the air flowing into the intake passage 7 is bypass 30, that is, the concave groove 32, the valve hole 33, the dead end hole 48, the plurality of through holes 50, 50,. After passing through the measuring groove 49 and the cutout portion 35 in sequence, it moves to the downstream side of the intake passage 7 and is further supplied to the engine as idle intake through the intake pipe 5. The amount of idle intake can be adjusted by adjusting the communication width w of the measurement groove 49 with the measurement hole 34 by adjusting the advancement / retraction of the adjustment adjustment valve shaft 43 by screwing the screw in and adjusting the idle adjustment valve 31. That is, as shown in FIG. 7, if the communication width w is narrowed, the idle intake air amount can be reduced. As shown in FIG. 8, if the communication width w is widened, the idle intake air amount can be increased.

  During the adjustment of the idle intake amount, even if the offset amount along the axial direction of the adjustment valve shaft 43 between the through holes 50, 50... And the measurement hole 34 is constant, the passage in the circumferential direction of the adjustment valve shaft 43 is constant. When the positions of the holes 50, 50... Change, the distance between the measuring hole 34 and the nearest through hole 50 changes, so that the idle intake air amount slightly changes. Therefore, the change in the idle intake amount with respect to the rotation angle of the idle adjustment valve 31 is obtained when the two through holes 50 are arranged at equal intervals in the circumferential direction of the adjustment valve shaft 43 and when the four through holes 50 are provided. When the case (B) where they are arranged at equal intervals was actually examined, the result shown in FIG. 10 was obtained. As is clear from the above, in the case of (B), the idle intake amount changes more smoothly, and the idle intake amount can be adjusted easily and accurately. Moreover, in the case of (B), since the four through-holes 50 can be formed by simply drilling the adjusting valve shaft 43 from two directions, the workability is good. Therefore, it is preferable to adopt (B).

  By the way, water droplets due to condensation or the like may adhere to the inner surface of the concave groove 32, and the water droplet may flow into the concave groove 32 together with the idle intake air. In this case, the valve hole 33 communicating with the concave groove 32 is arranged in a direction that bends at a substantially right angle from the front of the dead end portion 32a of the concave groove 32, and the opening 33a of the valve hole 33 to the concave groove 32 is Since the opening 33a is spaced apart from the peripheral edge of the step portion 33a, the opening 33a is opened to the step portion 32c formed one step higher than the inner side surface 32b of the groove 32. The flowing water droplets flow around the step portion 32c as shown by the arrow a in FIG. 5 and the arrow b in FIG. 6 due to the inertia of the flow, thereby avoiding the opening 33a and preventing water droplets from entering the valve hole 33. Can do.

  If foreign matter such as water droplets or fine dust flows into the valve hole 33 together with the idle intake, the idle intake is bent in a right angle from the dead end hole 48 to the through holes 50, 50. While moving to the measurement groove 49, the foreign matter that has entered the dead end hole 48 advances straight due to the inertia of the flow, is captured by the foreign matter reservoir 51 behind the dead end hole 48, and is separated from idle intake air.

  Furthermore, even if there is a foreign object that has moved from the through holes 50, 50... To the measuring groove 49 together with idle intake, the through holes 50, 50... And the measuring hole 34 are at any adjustment position of the adjusting valve shaft 43. However, since they are always offset from each other along the axial direction of the regulating valve shaft 43, idle intake air that has moved from the through holes 50, 50... To the measuring groove 49 immediately bends the course at a right angle toward the measuring hole 34. On the other hand, the foreign matter that has passed through the through holes 50, 50... Collides with the inner peripheral surface of the valve hole 33 due to inertia, falls to the lower part of the valve hole 33, and is separated from idle intake air.

  Thus, foreign matter can be prevented from adhering to the measuring portion of the measuring groove 49 and the measuring hole 34, so that the idle intake amount once adjusted by the idle adjusting valve 31 can be stabilized for a long period of time.

  When the throttle valve 8 is opened to accelerate the engine, the intake air flowing into the intake passage 7 goes straight through the intake passage 7 while being controlled in flow rate by the opening of the throttle valve 8, and is sucked into the engine. At this time, since the inlet of the bypass 30 is a concave groove 32 that is recessed from the inner surface of the intake passage 7, the flow passage area of the intake passage 7 is not reduced, and the flow of intake air that goes straight through the intake passage 7 is hindered. Absent. As a result, the intake resistance of the engine can be reduced, which can contribute to the improvement of the output.

  Even when the engine is operated under load, even if water droplets flow along the inner surface 32b of the concave groove 32, the opening portion 33a of the valve hole 33 is formed by the step portion 32c as in the idling described above. Water droplets can be prevented from entering.

  3 and FIG. 7 again, the notch portion 35 that is the notch-like shape serving as the downstream end portion of the bypass 30 is formed obliquely above the intake passage 7 on the end surface of the flange portion 1b facing the intake pipe 5. A water-drop shaped seal groove 53 that opens and surrounds the notch 35 and the intake passage 7 is formed on the end face of the flange portion 1b. The seal groove 53 includes first and second fastening bosses 2 of the flange portion 1b. , 2 ′ are fastened to the intake pipe 5 by the fastening bolts 3, 3, an O-ring 54 that is in close contact with the end surface of the intake pipe 5 is attached. At this time, seating surfaces 2a and 2a 'slightly raised from the surface of the flange portion 1b where the seal groove 53 is formed are formed on the fastening bosses 2 and 2'. The notch 35 is disposed on one side of a straight line 55 that crosses the intake passage 7 and connects the centers of the first and second fastening bosses 2 and 2 ', and on the other side, the flange portion 1b. An arcuate contact seat 56 (see FIGS. 3 and 9) slightly raised from the seal groove 53 forming surface is formed along a part of the outer edge of the seal groove 53. The abutment seat 56 and the seat surfaces 2a and 2a 'are finished to the same plane after the throttle body 1 is cast.

  Thus, at the time of the above fastening, the three portions of the seat surfaces 2a, 2a 'and the abutment seat 56 abut against the end surface of the intake pipe 5, thereby accurately regulating the amount of compressive deformation of the O-ring 54, and the seal The function can be kept for a long time. In addition, when finishing the contact surface of the flange portion 1b with the intake pipe 5 into the same plane, the three locations of the seat surfaces 2a and 2a 'of the first and second fastening bosses 2 and 2' and the contact seat 56 are provided. It is only necessary to finish the workpiece, improving the machining efficiency and extending the life of the machining tool. Further, the notched portion 35 and the abutment seat 56 are arranged on the opposite sides across the straight line 55 connecting the centers of the fastening bosses 2 and 2 ', so that a portion having a complicated shape is dispersed. In the case of die casting, it is possible to improve the hot water resistance.

  The present invention is not limited to the above embodiments, and various design changes can be made without departing from the scope of the invention. For example, the seal groove 53 can be formed on the end surface of the intake pipe 5 facing the flange portion 1b. In the above embodiment, the present invention is applied to the horizontal throttle body 1 with the intake passage 7 horizontal, but it can also be applied to a vertical throttle body with the intake passage 7 oriented in the vertical direction. Further, instead of the manual idle adjustment valve 31, an electric or wax automatic valve can be provided in the bypass.

DESCRIPTION OF SYMBOLS 1 ... Throttle body 1a ... Circle part 7 ... Intake passage 8 ... Throttle valve 8a ... Valve shaft 30 ... Bypass 31 ... Valve means (idle adjustment valve)
32... Concave groove 32 a ... dead end portion 32 b ... inner side surface 32 c ... step portion 33 ... ... other passage (valve hole) of bypass
33a ... Opening 36 ... Thick part

Claims (4)

The throttle body (1) having an intake passage (7) opened and closed by the throttle valve (8) is provided with a bypass (30) that bypasses the throttle valve (8) and communicates with the intake passage (7). 30) In an intake control device for an engine provided with valve means (31) for opening and closing it,
The inlet of the bypass (30) starts from an upstream end of the throttle body (1), and is a concave groove (32) formed on the inner surface of the intake passage (7) so as to stop before the throttle valve (8). The other passage (33) of the bypass (30) following the concave groove (32) is configured to open to a step portion (32c) raised one step from the inner surface (32b) of the concave groove (32). An intake control device for an engine. The intake control apparatus for an engine according to claim 1,
An intake control device for an engine, wherein an opening (33a) to the stepped portion (32c) of the other passage (33) is arranged away from a peripheral edge of the stepped portion (32c). The intake control apparatus for an engine according to claim 1 or 2,
The concave groove (32) is formed downward on the upper inner surface of the intake passage (7);
An intake control device for an engine, wherein the step portion (32c) is formed so that the step portion (32c) is continuous with a ceiling surface of the concave groove (32) and a dead end portion (32a). The intake control apparatus for an engine according to any one of claims 1 to 3,
The intake passage (7) is decentered in the cylinder body (1a) of the throttle body (1) in a direction orthogonal to the valve shaft (8a) of the throttle valve (8) with respect to the center of the outer shape of the cylinder body (1a). The intake air of the engine is characterized in that the concave groove (32) is formed in the thick portion (36) of the cylindrical portion (1a) opposite to the eccentric direction of the intake passage (7). Control device.