Engine throttle device

Abstract

The present invention provides an engine throttle device that prevents foreign matter from entering the slit formed in the throttle shaft, thereby preventing adverse effects caused by foreign matter. [Solution] In an engine throttle device 1 comprising a throttle body 2 through which a throttle bore 2a having a circular cross-section is provided, a throttle shaft 3 that is rotatably supported in axial holes 4L and 4R of the throttle body 2 while penetrating the throttle bore 2a, and having a slit 7 formed along the axis C in the portion exposed inside the throttle bore 2a, and a throttle valve 8 that is disc-shaped and inserted and fixed into the slit 7 inside the throttle bore 2a, the throttle valve 8 has expanded portions 15 formed on both sides along the axial direction of the throttle shaft 3, each expanded in the axial direction.

Description

Technical Field

[0001] The present invention relates to a throttle device for an engine.

Background Art

[0002] For example, Patent Document 1 discloses a butterfly-type throttle device mounted on an engine. A pair of throttle bores having a circular cross-section are formed through a throttle body, and a throttle shaft is rotatably supported in a state of passing through these throttle bores. Slits along the axis are formed at portions of the throttle shaft exposed in each throttle bore, and a throttle valve in the shape of a disk is inserted and fixed in the slits.

[0003] For example, the driving force of a motor is transmitted to the throttle shaft via a gear train, and the throttle shaft rotates according to the rotation direction to open and close the throttle valve in the throttle bore. Thereby, the intake air amount flowing through the throttle bore, and thus the intake air amount supplied into the cylinder of the engine, is adjusted.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The slit of the throttle shaft is formed by, for example, grooving using a metal saw. However, due to processing constraints in cutting at the outer peripheral portion rather than the axis of the metal saw, for example, a metal saw having a diameter considerably larger than the diameter of the throttle valve has to be used. As a result, when cutting with a metal saw in the cutting direction A in FIG. 7, a slit having the cross-sectional shape shown by the solid line is formed, and when cutting with a metal saw in the cutting direction A and the cutting direction B, respectively, a slit having the cross-sectional shape shown by the two-dot chain line is formed.

[0006] A typical throttle valve is disc-shaped, as shown by the dashed line in Figure 7. Therefore, when the throttle valve is in the fully open position, the outer edge of the throttle valve separates from the inner surface of the throttle bore in the axial direction at four points where its outer edge intersects with the outer surface of the throttle shaft (two of these points on one side are shown as region E in Figure 7). In these separated regions, a slit opens into the throttle bore.

[0007] Foreign matter may be present in the intake air circulating within the throttle bore. For example, rubber fragments detached from the upstream air cleaner element may enter the intake air as foreign matter. If such foreign matter enters the slit through the opening, it can increase the sliding resistance of the bearing supporting the throttle shaft in close proximity, potentially adversely affecting the smooth operation of the throttle valve.

[0008] The present invention was made to solve these problems, and its objective is to provide an engine throttle device that can prevent foreign matter from entering the slit formed in the throttle shaft, thereby preventing adverse effects caused by foreign matter. [Means for solving the problem]

[0009] To achieve the above objective, the present invention provides an engine throttle device comprising: a throttle body through which a throttle bore having a circular cross-section is provided; a throttle shaft rotatably supported in the axial hole of the throttle body while penetrating the throttle bore, with a slit formed along the axis in the portion exposed to the throttle bore; and a throttle valve having a disc shape and being inserted into and fixed in the slit within the throttle bore, wherein the throttle valve is characterized in that expanded portions are formed on both sides of the throttle shaft along the axial direction, each expanding in the axial direction.

[0010] In other embodiments, the extension may be formed to have a length approximately equal to the diameter of the throttle shaft. In other embodiments, the expansion portion may have a straight section that faces the slit and is perpendicular to the axis of the throttle shaft.

[0011] In another embodiment, the straight portion may be formed as a tangent to the outer edge of a disc-shaped throttle valve. In other embodiments, the corner between the outer edge of the throttle valve and the straight section may be formed in an arc shape.

[0012] In other embodiments, bearings are provided on both sides of the throttle bore within the shaft hole, each supporting the throttle shaft so as to be rotatable, and a gap is formed between the outer surface of the throttle shaft and the inner surface of the shaft hole in the region between the throttle bore and each bearing in the axial direction of the throttle shaft, with the outer surface of the throttle shaft and the inner surface of the shaft hole being separated. In other embodiments, the expansion portion may be formed to have a length approximately equal to the outer diameter of the gap. [Effects of the Invention]

[0013] According to the engine throttle device of the present invention, it is possible to prevent foreign matter from entering the slit formed in the throttle shaft, thereby preventing adverse effects caused by foreign matter. [Brief explanation of the drawing]

[0014] [Figure 1] This is a perspective view showing the throttle device of an engine according to an embodiment. [Figure 2] This is a cross-sectional view taken along line II-II in Figure 1, with the throttle valve in the fully open position. [Figure 3] This is a cross-sectional view taken along line III-III in Figure 2. [Figure 4] This is a cross-sectional view taken along line IV-IV in Figure 2. [Figure 5] This is a partial cross-sectional view of the VV line in Figure 4 when the throttle valve is in the fully closed position. [Figure 6] This is an exploded perspective view showing the throttle shaft and throttle valve. [Figure 7] This is a detailed view of section A1 in Figure 3. [Figure 8] It is a detailed view of part A2 in FIG. 7. [Figure 9] It is a detailed view of part B in FIG. 5. [Figure 10] It is a cross-sectional perspective view corresponding to the X-X line in FIG. 9. [Figure 11] It is a cross-sectional perspective view corresponding to the XI-XI line in FIG. 9. [Figure 12] It is a cross-sectional perspective view corresponding to FIG. 11 showing a general throttle device.

Mode for Carrying Out the Invention

[0015] [[ID=二十]] Hereinafter, an embodiment in which the present invention is embodied in a throttle device for a single-cylinder engine will be described. FIG. 1 is a perspective view showing the throttle device of the engine of this embodiment, FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1 when the throttle valve is in the fully open position, FIG. 3 is a cross-sectional view taken along line III-III of FIG. 2, FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 2, and FIG. 5 is a partial cross-sectional view taken along line V-V of FIG. 4 when the throttle valve is in the fully closed position. As an example, in each figure, the front-back, left-right, and up-down directions are shown mainly with respect to the driver riding in the vehicle. In the vehicle-mounted state where the throttle device 1 is assembled to the engine mounted on the vehicle, the throttle device 1 is maintained in the posture shown in each figure. In the following description, assuming that the throttle device 1 is in the vehicle-mounted state, the front-back, left-right, and up-down directions are expressed.

[0016] [[ID=二十八]]<0OO0098>The throttle body 2 of the throttle device 1 is manufactured as a die-cast aluminum part, and a throttle bore 2a with a circular cross-section is provided extending through it in the front-to-back direction. A single throttle shaft 3 is rotatably supported in the throttle body 2 so as to pass through the throttle bore 2a from left to right. Specifically, shaft holes 4L and 4R extending in the left-to-right direction are formed on both the left and right sides of the throttle bore 2a, respectively. A rolling bearing 5 is fitted into the left shaft hole 4L, and a sliding bearing 6 is fitted into the right shaft hole 4R. The throttle shaft 3 is inserted into the respective shaft holes 4L and 4R and is rotatably supported by the respective bearings 5 ​​and 6 so as to be about axis C. Note that the types of the bearings 5 ​​and 6 are not limited to these and can be changed as desired.

[0017] A straight slit 7 is formed along axis C in the portion of the throttle shaft 3 exposed within the throttle bore 2a, and a disc-shaped throttle valve 8 is inserted and fixed into this slit 7. As the throttle shaft 3 rotates, the throttle valve 8 opens and closes between the fully open position shown by the solid line and the fully closed position shown by the dashed line in Figure 4, and is always biased to the closed position by a return spring (not shown). The structure around the throttle valve 8 is related to the essence of the present invention, and its details will be described later.

[0018] A motor housing chamber 2b is integrally molded on the lower side of the throttle bore 2a, and a flange portion 2c is integrally molded on the left side of both the throttle bore 2a and the motor housing chamber 2b. A gear cover 10 is detachably attached to the flange portion 2c from the left, and the flange portion 2c and the gear cover 10 form the gear case 11. Although not shown in the diagram, the left end of the throttle shaft 3 and the output shaft of the motor 12 housed in the motor housing chamber 2b protrude from the gear case 11, and these output shafts are connected to the left end of the throttle shaft 3 via a gear train. The driving force of the motor 12 is transmitted to the throttle shaft 3 via the gear train, and the throttle valve 8 opens in response to an increase in driving force, resisting the biasing force of the return spring, and closes in response to a decrease in driving force, receiving the biasing force of the return spring.

[0019] The gear cover 10 is provided with a connector 10a that is electrically connected to the motor 12. When the throttle device 1 is installed in a vehicle, a coupler of a harness (not shown) extending from the engine control controller on the vehicle side is connected to the connector 10a. As a result, a drive signal from the controller is input to the motor 12, and the throttle valve 8 is opened and closed by the motor 12 in accordance with the drive signal as described above.

[0020] Next, we will explain the structure surrounding the throttle valve 8. Figure 6 is an exploded perspective view showing the throttle shaft 3 and throttle valve 8, and Figure 7 is a detailed view of part A1 of Figure 3. As shown in Figure 6, the throttle valve 8 is inserted into the slit 7 of the throttle shaft 3 and secured by two screws 13. This assembly of the throttle valve 8 is not performed on the throttle shaft 3 alone, but on the throttle shaft 3 that has already been assembled to the throttle body 2. Specifically, first, the throttle shaft 3 is inserted through the shaft holes 4L and 4R of the throttle body 2 and supported so as to be rotatable by the bearings 5 ​​and 6, and the throttle valve 8 is angle-adjusted to keep the throttle valve 8 fully open. The slit 7 opens upstream and downstream within the throttle bore 2a, and the throttle valve 8 is inserted into the slit 7 from either the upstream or downstream side via the throttle bore 2a. After that, the throttle shaft 3 is angle-adjusted to keep the throttle valve 8 fully closed, and the throttle valve 8 is secured to the throttle shaft 3 with screws 13 from the upstream side.

[0021] In order to enable the above assembly work and to operate the throttle valve 8 smoothly, the dimensions of each component surrounding the throttle valve 8 are set as follows. First, the thickness of the throttle valve 8 and the width of the slit 7 are set to be approximately equal so that the throttle valve 8 can be inserted and fixed into the slit 7 without any rattle.

[0022] Furthermore, as shown in Figure 7, the throttle bore 2a has a circular cross-section with a diameter of φ, while the throttle valve 8 has an elliptical shape with its minor axis running in the left-right direction along the throttle shaft 3. By setting the length of the minor axis L ≤ diameter φ, the throttle valve 8 can be positioned within the throttle bore 2a during assembly, and by making the length L as close as possible to the diameter φ, airtightness is maintained in the fully closed position. With these dimensions, when the throttle valve 8 changes its position to the closed position as shown by the dashed line in Figure 4, its entire outer edge comes into close contact with the inner surface of the throttle bore 2a, as shown in Figure 5, thus blocking the upstream and downstream sides. If the angle of the throttle valve 8 in the position facing the intake air flow direction is defined as 0 degrees, then the angle of the throttle valve 8 in the fully closed position in this embodiment is set to 10 degrees. As a result, the throttle valve 8 opens and closes between 10 degrees, which corresponds to the fully closed position, and 90 degrees, which corresponds to the fully open position.

[0023] In this embodiment, the throttle bore 2a has a circular cross-section and the throttle valve 8 has an elliptical cross-section, but this is not the only possible configuration. The throttle bore 2a can be arbitrarily changed to any shape that has a circular cross-section, including a circular cross-section, and the throttle valve 8 can be arbitrarily changed to any shape that has a disc-like shape, including an elliptical cross-section.

[0024] On the other hand, the slit 7 extends not only to the area in which the throttle valve 8 is inserted and fixed, but also to both the left and right sides thereof. This is due to the constraints of the slitting process using a metal saw. Specifically, the slitting process forms a straight slit 7 along the axis C on the throttle shaft 3, but because it is necessary to cut with the outer circumference of the metal saw rather than the axis, a metal saw with a considerably larger diameter than the diameter of the throttle valve 8 is used. In the slitting process, cutting is performed with a metal saw from cutting direction A as shown in Figure 7, or from cutting direction A and cutting direction B as shown in Figure 7. The slit 7 formed by the former method has the cross-sectional shape shown by the solid line, and the slit 7 formed by the latter method has the cross-sectional shape shown by the dashed line.

[0025] Note that Figure 7 shows the portion of the slit 7 corresponding to the right side of the throttle valve 8, but the left side also has a symmetrical shape. As a result, in either slotting method, the slits 7 on both the left and right sides of the throttle valve 8 form cavities with a circular arc cross-section that follows the outer circumference of the metal saw.

[0026] Furthermore, in order to allow the insertion of the throttle valve 8, the length of the slit 7 in the axial direction C must be set to be greater than or equal to the length L of the short axis of the throttle valve 8. As a result, as shown in Figure 7, the slit 7 is formed deeper than the inner circumferential surface of the throttle bore 2a by an amount corresponding to dimensions La1 to La3 in the axial direction C.

[0027] Furthermore, as shown in Figures 3 and 7, the sliding bearing 6 is spaced to the right of the throttle bore 2a, and in the region between them, the outer surface of the throttle shaft 3 and the inner surface of the shaft hole 4R are spaced apart, forming an annular gap 14R when viewed from the direction of axis C. Similarly, as shown in Figure 3, the rolling bearing 5 is spaced to the left of the throttle bore 2a, and in the region between them, the outer surface of the throttle shaft 3 and the inner surface of the shaft hole 4L are spaced apart, forming an annular gap 14L when viewed from the direction of axis C. These gaps 14L and 14R function as clearances, allowing the throttle shaft 3 to be supported by each bearing 5 and 6 and rotate smoothly without contact with the inner surface of the shaft hole 4R.

[0028] On the other hand, as shown by the dashed line in Figure 7, a typical throttle valve 8 has a simple elliptical shape without the expansion portion 15 described below. In the fully closed position of the throttle valve 8 shown in Figure 5, the outer edge of the elliptical throttle valve 8 is in close contact with the inner surface of the circular cross-section throttle bore 2a. However, as the throttle valve 8 changes its orientation toward the open side, the outer edge of the throttle valve 8 gradually moves away from the inner surface of the throttle bore 2a in the direction of axis C at a total of four points where the outer edge of the throttle valve 8 intersects with the outer surface of the throttle shaft 3 (in Figure 7, the two on the right are shown as region E).

[0029] This separation distance is maximized when the throttle valve 8 is fully open, as shown in Figures 3 and 7. The slit 7 opens widely into the throttle bore 2a through the region of the slit 7 corresponding to the dimensions La1 to La3 described above, and through the gap formed around the throttle shaft 3. This condition occurs every time the throttle valve 8 opens, and foreign matter mixed in with the intake air flowing through the throttle bore 2a can enter the slit 7 through the opening, potentially increasing the sliding resistance of the bearings 5 ​​and 6 that support the throttle shaft 3 in close proximity to the slit 7.

[0030] In addition, depending on the details of the slotting process, the dimension La1 may be 0, and depending on the structure around the bearings 5 ​​and 6, gaps 14L and 14R may not be formed around the throttle shaft 3. However, there is no difference in that the inside of the slit 7 opens widely into the throttle bore 2a when the throttle valve 8 is in the fully open position.

[0031] As a countermeasure, the throttle device 1 of this embodiment has an expansion portion 15 formed on the throttle valve 8. As shown in Figures 3 and 7, the expansion portions 15 are formed on both sides of the throttle valve 8 along the axis C of the throttle shaft 3, and each side is formed to expand in the direction of axis C, in other words, to expand toward the adjacent slit 7. Therefore, the right side of the throttle valve 8 expands toward the right, and the resulting expansion portion 15 faces the area to the right of the slit 7, more specifically the arc-shaped cavity on the right side. Similarly, the left side of the throttle valve 8 expands toward the left, and the resulting expansion portion 15 faces the area to the left of the slit 7, more specifically the arc-shaped cavity on the left side.

[0032] Figure 8 is a detailed view of part A2 in Figure 7. The shape of the right-side extension 15 will be described in more detail below based on Figures 7 and 8, but the left-side extension 15 is also symmetrical and has the same shape. Each extension 15 consists of a straight section 15a perpendicular to the axis C of the throttle shaft 3, and a pair of stepped sections 15b connecting both ends of the straight section 15a to the elliptical outer edge of the throttle valve 8. The straight section 15a is formed as a tangent to the elliptical outer edge of the original throttle valve 8 (shown as a dashed line in Figure 7). The corners between the straight section 15a and each stepped section 15b are formed in the shape of an arc with radius r1, and the corners between each stepped section 15b and the outer edge of the throttle valve 8 are formed in the shape of an arc with radius r2.

[0033] Furthermore, the length of the extension portion 15 (the vertical dimension in Figure 7) is set to be approximately equal to the diameter of the throttle shaft 3, or in other words, the length of the slit 7 in the diametrical direction.

[0034] As a result of forming the expanded portions 15 described above on both sides of the throttle valve 8, the opening area of ​​the slit 7 into the throttle bore 2a is reduced, as shown in Figure 8. More specifically, in a typical throttle valve 8 without the expansion portion 15, the slit 7 opens over dimension Lb in Figure 8, whereas in the throttle valve 8 of this embodiment with the expansion portion 15, the opening length of the slit 7 is shortened to dimension Lc in Figure 8. In either case, the opening area of ​​the slit 7 is obtained by multiplying dimension Lb or dimension Lc by the thickness of the slit 7 (in the direction perpendicular to the plane of the paper in Figure 8). Since dimension Lc is smaller than dimension Lb, the opening area can be reduced. This prevents foreign matter from entering the slit 7, and consequently, prevents an increase in the sliding resistance of the bearings 5 ​​and 6 caused by foreign matter.

[0035] Furthermore, even when the above-mentioned dimension La1=0, or when no gaps 14L and 14R are formed around the throttle shaft 3, the expansion portion 15 performs a similar function to reduce the opening area of ​​the slit 7. Therefore, even in this case, the above-mentioned effect of preventing the intrusion of foreign matter can be achieved.

[0036] On the other hand, as described above, the extension 15 of this embodiment has the following requirements. (a) Having a length approximately equal to the diameter of the throttle shaft 3. (b) Having a straight section 15a perpendicular to the axis C of the throttle shaft 3. (c) The straight section 15a is tangent to the outer edge of the throttle valve 8.

[0037] Based on requirements (a) and (b), the extension portion 15 protrudes significantly from the outer edge of the throttle valve 8 at two locations near the outer circumference of the throttle shaft 3. This effectively shortens the opening length of the slit 7.

[0038] Furthermore, in accordance with requirement (c), the length L of the short shaft of the throttle valve 8 is maintained to be less than or equal to the diameter φ of the throttle bore 2a. Therefore, the throttle valve 8 can be fixed to the throttle shaft 3, which is already assembled to the throttle body 2, without any problems.

[0039] As a result, the opening area of ​​the slit 7 into the throttle bore 2a can be effectively reduced without sacrificing the ease of assembly of the throttle valve 8, thereby more reliably preventing foreign matter from entering the slit 7.

[0040] It should be noted that requirement (a) does not necessarily need to be met. In this embodiment, the throttle device 1 has annular gaps 14L and 14R formed around the throttle shaft 3. For example, as shown by the dashed line in Figure 8, the length of the expansion portion 15 may be extended to a length approximately equal to the outer diameter of the gaps 14L and 14R. However, if the expansion portion 15 protrudes beyond the outer diameter of the gaps 14L and 14R, the expansion portion 15 will come into contact with the inner circumferential surface of the throttle bore 2a when the throttle valve 8 is in the fully closed position. Therefore, it is desirable to keep the length slightly smaller than the outer diameter of the gaps 14L and 14R. In this case, the opening length of the slit 7 is further shortened from dimension Lc to dimension Ld, thereby further reducing the opening area of ​​the slit 7 and more reliably preventing the intrusion of foreign matter.

[0041] In addition, the extension 15 of this embodiment also meets the following requirements. (d) The corners between the straight section 15a and each stepped section 15b form an arc shape with radius r1. (e) The corners between each stepped portion 15b and the outer edge of the throttle valve 8 form an arc shape with radius r2.

[0042] If expansion portions 15 are added to both sides of the elliptical throttle valve 8, the assembly of the throttle valve 8 onto the throttle shaft 3 may become somewhat more difficult. For example, when inserting the throttle valve 8 into the throttle bore 2a, the expansion portions 15 may get caught on the opening of the throttle bore 2a. By fulfilling requirements (d) and (e), the throttle valve 8 can be smoothly inserted into the throttle bore 2a without getting caught. Therefore, the effects of the expansion portions 15 described above can be achieved without worsening the ease of assembly of the throttle valve 8.

[0043] It is not necessary to satisfy both requirements (d) and (e). For example, if requirement (d) is not satisfied, a corner will be formed between the straight section 15a and each stepped section 15b, so the dimension Lc of the opening length of the slit 7 can be further shortened, and the opening area of ​​the slit 7 can be reduced even further. Therefore, it is also acceptable to satisfy only requirement (e).

[0044] On the other hand, the expansion portion 15 of the throttle valve 8 in this embodiment also contributes to improving the controllability of the throttle device 1 at minute flow rates, and this point will be explained below. In this type of throttle device 1, at the minimum opening of the throttle valve 8, it is necessary to precisely adjust the intake air volume to a minute flow rate equivalent to idle. In recent years, in order to improve exhaust gas performance, there has been a demand to expand the lower limit of the intake air volume adjustment range, and expanding the lower limit leads to improved controllability at minute flow rates. However, in a general throttle device that does not have an expansion section 15 on the throttle valve 8, such as in Patent Document 1, it has been difficult to expand the lower limit of the intake air volume adjustment range because intake air still passes through the throttle valve 8 even in the fully closed position due to the following factors.

[0045] Figure 9 is a detailed view of section B in Figure 5, Figure 10 is a perspective view corresponding to the section along line XX in Figure 9, Figure 11 is a perspective view corresponding to the section along line XI-XI in Figure 9, and Figure 12 is a cross-sectional perspective view corresponding to Figure 11 showing a typical throttle device. Note that in Figure 12, the same component numbers are used in the same locations as in Figure 11 for ease of understanding. As shown in Figure 10, when the throttle valve 8 is in the fully closed position, the outer edge of the throttle valve 8 is in close contact with the inner surface of the throttle bore 2a, but the gap 14R formed around the throttle shaft 3 opens into the throttle bore 2a. The upstream and downstream sides of the throttle valve 8 are in communication with the inside of the slit 7 through this gap 14R. Therefore, even when the throttle valve 8 is fully closed, the intake air on the upstream side of the throttle valve 8 flows into the slit 7 through the gap 14R, and then flows out from the slit 7 through the gap 14R to the downstream side of the throttle valve 8, causing intake air to leak through. The above describes the phenomenon caused by the gap 14R on the right side, but the same phenomenon occurs with the gap 14L on the left side.

[0046] In the typical throttle device shown in Figure 12, the intake air that flows into the slit 7 through gaps 14L and 14R flows downstream without being obstructed by the outer edge of the throttle valve 8. As a result, the intake air flows through various paths as indicated by the arrows in Figure 12, causing a large amount of intake air to slip through. In contrast, in this embodiment shown in Figure 11, the expansion portion 15 is located on the intake air passage within the slit 7. As a result, as indicated by the arrows in Figure 11, the intake air is obstructed by the expansion portion 15, narrowing the passage and reducing the amount of intake air flowing downstream through the slit 7, and consequently, the amount of intake air passing from the upstream to the downstream side of the throttle valve 8. As a result, the lower limit of the intake air volume adjustment range can be expanded compared to a typical throttle device, improving controllability at minute flow rates.

[0047] The embodiments of the present invention are not limited to these embodiments. For example, in the above embodiment, the throttle device 1 is embodied as having a single throttle valve 8 and driven by a motor 12, but it is not limited to this. For example, it may be applied to a multi-throttle device having multiple throttle valves 8, or to a throttle device in which the driver's accelerator operation is mechanically transmitted to the throttle valve 8 by a wire. In any case, if an extension portion 15 is formed on the throttle valve 8, the same effects and advantages as in the above embodiment can be achieved, without repeating the explanation.

[0048] In the above embodiment, an expanded portion 15 consisting of a straight portion 15a and a pair of stepped portions 15b was formed on the throttle valve 8, but the shape of the expanded portion 15 is not limited to this. For example, an expanded portion 15 without a straight portion 15a may be formed. [Explanation of Symbols]

[0049] 1. Throttle device 2 Throttle Body 2a Throttle bore 3. Throttle shaft 4L,4R shaft hole 5 Rolling bearings 6. Plain bearing 7 slits 8. Throttle valve 14L,14R gap 15. Expansion section 15a Straight section

Claims

1. A throttle body with a throttle bore having a circular cross-section, A throttle shaft is rotatably supported in the shaft hole of the throttle body while penetrating the throttle bore, and has a slit formed along its axis in the portion exposed within the throttle bore, A disc-shaped throttle valve inserted and fixed in the slit within the throttle bore, In an engine throttle device equipped with, The throttle valve has expanded portions formed on both sides of the throttle shaft along the axial direction, each portion extending in the axial direction. An engine throttle device characterized by the following:

2. The aforementioned extension is formed to have a length approximately equal to the diameter of the throttle shaft. The throttle device for an engine according to feature 1.

3. The expanded portion has a straight section that faces the slit and is perpendicular to the axis of the throttle shaft. The throttle device for an engine according to feature 1.

4. The aforementioned straight section is formed as a tangent to the outer edge of the disc-shaped throttle valve. The throttle device for an engine according to feature 3.

5. The corner between the outer edge of the throttle valve and the straight section is formed in an arc shape. The throttle device for an engine according to feature 3.

6. Bearings are provided on both sides of the throttle bore within the shaft hole, each supporting the throttle shaft so that it can rotate. In the region between the throttle bore and each bearing in the axial direction of the throttle shaft, a gap is formed between the outer surface of the throttle shaft and the inner surface of the shaft hole, respectively. The throttle device for an engine according to feature 1.

7. The expanded portion is formed to have a length approximately equal to the outer diameter of the gap. The throttle device for an engine according to feature 6.

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