Throttle device of engine

Abstract

To provide a throttle device of an engine which achieves reduction of an outer dimension of a throttle shaft in an axial direction and positions the throttle shaft in the axial direction to enable smooth opening / closing of a throttle valve.SOLUTION: One end of a throttle shaft 4 supporting a throttle valve 7 in an openable and closable manner protrudes into a gear case 18 fixed to a side part of a throttle body 2 through shaft holes 20, 21 and a throttle device of an engine is driven through gear trains 22, 26, 29. The throttle device of the engine includes: an annular fitting part 42 formed adjacent to the shaft hole 21; a bearing 6 which rotatably supports the throttle shaft 4 with an outer ring 6b fitted in the annular fitting part 42 and an inner ring 6a fitted in the throttle shaft 4; a positioning ring 45 which is press-fitted into the annular fitting part 42, contacts with the outer ring 6b, and restricts displacement of the outer ring 6b along an axis C of the throttle shaft 4; and a fixing nut 39 which is threadedly engaged with one end of the throttle shaft 4 in the gear case 18 and contacts with the inner ring 6a from the one end side to restrict the displacement.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to an engine throttle device. [Background technology]

[0002] In this type of throttle device, a throttle shaft is disposed so as to pass through the throttle bore of the throttle body and both ends are supported by bearings, and the throttle valve opens and closes within the throttle bore as the throttle shaft rotates. If the throttle shaft is displaced in the axial direction, i.e., in the thrust direction, both sides of the throttle valve come into sliding contact with the inner peripheral surface of the throttle bore, causing problems such as an impediment to smooth opening and closing operations. Therefore, as described in Patent Document 1, for example, a shaft support structure has been proposed that positions the throttle shaft in the axial direction.

[0003] In the throttle device of Patent Document 1, the outer rings of each bearing supporting both ends of the throttle shaft are press-fitted into annular fittings formed in the throttle body, and the inner ring of one bearing is sandwiched between the step surface of the throttle shaft by a fixing nut. The inner ring of the other bearing is biased in one direction by a compression spring via a receiving member, while allowing for positional displacement in the axial direction of the throttle shaft. This eliminates backlash between the inner and outer rings of each bearing and the balls, and positions the throttle valve in the axial direction together with the throttle shaft. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-293581 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the throttle device of the above-mentioned Patent Document 1, a compression spring that biases the inner ring of the other bearing must be provided on the throttle shaft, which causes a problem that the external dimensions of the throttle device in the axial direction of the throttle shaft increase by an amount equivalent to the full length of the compression spring. Therefore, a throttle shaft support structure that does not use the compression spring is sometimes adopted, but this results in the loss of the axial positioning effect provided by the compression spring.

[0006] For this reason, when the throttle shaft is subjected to some kind of external force and tries to displace along its axis, for example, the inner ring of one of the bearings, which is positioned by a fixing nut, begins to displace in the same direction as the throttle shaft, and this force acts on the outer ring via the balls. If the outer ring is firmly positioned in the axial direction, the balls and the inner ring act to restrict the positional displacement of the throttle shaft. However, the outer ring may move in the axial direction simply by being pressed into the annular fitting portion. In that case, not only is it not possible to restrict the positional displacement of the throttle shaft, but there is also a possibility that the bearing's function as a normal bearing may be impaired, and so a countermeasure has been demanded for some time.

[0007] The present invention has been made to solve these problems, and its object is to provide an engine throttle device which reduces the axial outer dimensions of the throttle shaft and can position the throttle shaft in the axial direction to achieve smooth opening and closing of the throttle valve. [Means for solving the problem]

[0008] In order to achieve the above object, the engine throttle device of the present invention supports a throttle valve in a throttle bore of a throttle body so that it can be opened and closed by a throttle shaft, and has a gear case accommodating a gear train fixed to the side of the throttle body, with one end of the throttle shaft protruding into the gear case through a shaft hole to drive it via the gear train, and is characterized in that it comprises an annular fitting portion formed adjacent to the shaft hole, a bearing for rotatably supporting the throttle shaft by fitting an outer ring into the annular fitting portion and fitting an inner ring on the throttle shaft, a positioning ring press-fitted into the annular fitting portion and abutting the outer ring to regulate positional displacement of the outer ring along the axis of the throttle shaft, and a fixing nut screwed onto one end of the throttle shaft within the gear case and abutting the inner ring from one end side to regulate positional displacement of the inner ring towards one end side.

[0009] In another aspect, the gear case may have an axial hole formed therein and a case side annular fitting portion formed as an annular fitting portion on the other end side of the axial hole, and the positioning ring may abut against the outer ring from the other end side within the case side annular fitting portion to regulate positional displacement of the outer ring toward the other end side.

[0010] In another aspect, the gear case may have a movement restricting surface facing the other end between the shaft hole and the case side annular fitting portion, and the positioning ring may be positioned in the axial direction of the throttle shaft by clamping the outer ring between the positioning ring and the movement restricting surface.

[0011] In another aspect, the throttle body may have a body side annular fitting portion formed adjacent to the other end side of the case side annular fitting portion, and the positioning ring may be press-fitted into the case side annular fitting portion and also inserted into the body side annular fitting portion.

[0012] In another aspect, the throttle shaft may be formed with a stepped surface facing one end side, and the fixing nut may sandwich the inner ring of the bearing between the fixing nut and the stepped surface to position the throttle shaft in the axial direction.

[0013] In another aspect, the throttle valve may further include a cylindrical collar that is fitted onto the throttle shaft and abuts against the inner ring from one end, and the fixing nut may clamp the inner ring of the bearing between the collar and the step surface.

[0014] In another aspect, a gap may be formed between the inner peripheral surface of the shaft hole and the outer peripheral surface of the throttle shaft, and the collar may abut against the inner ring through the gap.

[0015] In another aspect, the throttle body may have an axial hole formed therein and a body side annular fitting portion formed as an annular fitting portion on one end side of the axial hole, and the positioning ring may abut against the outer ring from one end side within the body side annular fitting portion to regulate positional displacement of the outer ring towards the one end side. Effect of the Invention

[0016] According to the engine throttle device of the present invention, the outer dimensions of the throttle shaft in the axial direction can be reduced, and the throttle shaft can be positioned in the axial direction to achieve smooth opening and closing of the throttle valve. [Brief description of the drawings]

[0017] [Figure 1] 1 is a perspective view showing a throttle device of an engine according to an embodiment; [Diagram 2] FIG. 2 is a front view showing the throttle device. [Diagram 3] FIG. 2 is a plan view showing the throttle device. [Figure 4] FIG. [Diagram 5] FIG. 4 is a right side view showing the gear train in the gear case. [Figure 6] 6 is a cross-sectional view taken along line VI-VI in FIG. 5. [Figure 7] FIG. 4 is an exploded perspective view showing a pivot support location at the right end of the throttle shaft. [Figure 8] 7 is an enlarged cross-sectional view of part A in FIG. 6, showing a pivot support location at the right end of the throttle shaft. [Figure 9]9 is a cross-sectional view corresponding to FIG. 8 and showing another example in which the positional relationship between the bearing and the positioning ring is reversed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an engine throttle device embodying the present invention will now be described. FIG. 1 is a perspective view showing the throttle device of the engine of this embodiment, FIG. 2 is a front view showing the throttle device, FIG. 3 is a plan view showing the throttle device, FIG. 4 is a right side view showing the throttle device, FIG. 5 is a right side view showing the gear train in the gear case, and FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5.

[0019] The throttle device 1 of this embodiment is applied to a two-cylinder engine mounted on a motorcycle. When the throttle device 1 is attached to an engine mounted on a vehicle, the engine is located diagonally to the upper right side of FIG. 1, and the driver sits on the vehicle facing in the same direction. Therefore, in the following description, the front-rear, left-right, and up-down directions are expressed with the driver as the subject. In this embodiment, the right side corresponds to one end side of the present invention, and the left side corresponds to the other end side of the present invention.

[0020] As shown in Figures 1 to 3, a pair of left and right throttle bores 3 are formed in the throttle body 2 of the throttle device 1 in the front-rear direction. For example, the throttle body 2 is manufactured by injection molding a synthetic resin material. Although not shown, when the throttle device 1 is mounted on a vehicle, the front ends of the throttle bores 3 are connected to the intake manifold of the engine, and the rear ends are connected to an air cleaner.

[0021] As shown in Fig. 6, one throttle shaft 4 is disposed in the throttle body 2 so as to penetrate each throttle bore 3 in the left-right direction, and the left end of the throttle shaft 4 is rotatably supported by a bearing 5, and the right end is rotatably supported by a bearing 6. Each of the bearings 5, 6 may be, for example, a deep groove ball bearing. A throttle valve 7 is fixed to the throttle shaft 4 in each throttle bore 3 by a screw 8, and each throttle valve 7 opens and closes in response to the rotation of the throttle shaft 4. The rotation angle of the throttle shaft 4 is detected as the throttle opening by a throttle sensor 9 connected to the left end of the throttle shaft 4.

[0022] 1 to 3, injectors 10 are attached to the throttle body 2 in correspondence with each throttle bore 3, and although not shown, the tip of each injector 10 protrudes into the throttle bore 3. The base end of each injector 10 is connected to a common delivery pipe 11, which is supported from above the throttle body 2 via a pair of left and right bracket portions 11a. Although not shown, when mounted on a vehicle, a fuel hose extending from a fuel pump on the vehicle body is connected to a nipple portion 11b provided on the delivery pipe 11, and couplers of a harness extending from an engine control controller on the vehicle body are connected to a connector 9a provided on the throttle sensor 9 and a connector 10a provided on each injector 10, respectively.

[0023] Fuel supplied through a fuel hose is distributed by a delivery pipe 11 and supplied to each injector 10. A detection signal relating to the throttle opening detected by the throttle sensor 9 is input to the controller via a harness. Based on various information including this detection signal, the controller controls various devices attached to the engine, and as part of that, outputs a drive signal to each injector 10 via the harness to drive it. Fuel is injected into the throttle bore 3 in response to the opening and closing of each injector 10 and mixed with the intake air, and the mixture is supplied to each cylinder of the engine for combustion.

[0024] 2, 5 and 6, three bracket portions 12a, 12b and 12c are integrally formed on the right side of the throttle body 2, and a left case member 13 is fastened to the left case member 13 by bolts (not shown) via the bracket portions 12a, 12b and 12c. A right case member 14 is fastened to the left case member 13 from the right side by screws 16 with a waterproof packing 15 sandwiched therebetween, and these case members 13 and 14 form a gear case 18 having a gear storage chamber 17 therein. For example, the left and right case members 13 and 14 are manufactured by injection molding a synthetic resin material.

[0025] FIG. 7 is an exploded perspective view showing the support location of the right end of the throttle shaft 4. In the following description, the portion of the throttle shaft 4 to the right of the right throttle valve 7 is referred to as the right end. As shown in Figs. 5 to 7, the right end of the throttle shaft 4 is inserted through a shaft hole 20 formed in the throttle body 2 and a shaft hole 21 formed in the left case member 13, and the right end of the throttle shaft 4 protrudes into the gear accommodating chamber 17 to have a sector-type driven gear 22 fixed thereto. The driven gear 22 is manufactured by injection molding using a flat core metal 22a as an insert material. A return spring 23 is wound around the throttle shaft 4, one end of which is hooked to the left case member 13 and the other end of which is hooked to the driven gear 22, thereby biasing the throttle valve 7 together with the driven gear 22 and the throttle shaft 4 in the closing direction. The support structure of the right end of the throttle shaft 4 will be described in detail later as it is related to the gist of the present invention.

[0026] The upper part of the right case member 14 is cylindrical and bulges to the right. A motor housing chamber 24 is formed inside the motor housing chamber 24 and communicates with the gear housing chamber 17. A motor 25 is housed in the motor housing chamber 24, and its output shaft 25a protrudes into the gear housing chamber 17 and a drive gear 26 is fixed to the motor 25. A gear shaft 27 is disposed in the middle between the drive gear 26 and the driven gear 22, and its base end is embedded in the left case member 13 and its tip is inserted into a shaft hole 28 formed in the right case member 14. An intermediate gear 29 consisting of a large diameter portion 29a and a small diameter portion 29b is rotatably supported on the gear shaft 27, and the large diameter portion 29a meshes with the drive gear 26 and the small diameter portion 29b meshes with the driven gear 22. The driven gear 22, the drive gear 26 and the intermediate gear 29 correspond to a gear train of the present invention.

[0027] When the motor 25 rotates in either the forward or reverse direction, the rotation is reduced in speed through the drive gear 26, the large diameter portion 29a and the small diameter portion 29b of the intermediate gear 29, and the driven gear 22, and is transmitted to the throttle shaft 4, which rotates while receiving the biasing force of the return spring 23 to open and close the throttle valve 7. Although not shown, when mounted on a vehicle, a coupler of a harness extending from a controller on the vehicle body side is connected to the connector 13b provided on the left case member 13. The controller outputs a drive signal to the motor 25 via the harness to drive it, and opens and closes the throttle valve 7 in response to the driver's accelerator operation.

[0028] Next, the support structure for the right end of the throttle shaft 4 will be described in detail. FIG. 8 is an enlarged cross-sectional view of a portion A in FIG. As described above, the right end of the throttle shaft 4 protrudes into the gear accommodating chamber 17 through the shaft hole 20 of the throttle body 2 and the shaft hole 21 of the left case member 13. As shown in Figures 7 and 8, a boss portion 2a having an annular shape centered on the throttle shaft 4 protrudes from the right side of the throttle body 2, and an annular protrusion 13a protruding from the left side of the left case member 13 is fitted onto this boss portion 2a via an O-ring 30. A small gap is formed between the boss portion 2a and the annular protrusion 13a in a direction perpendicular to the axis C of the throttle shaft 4, i.e., in the radial direction, to allow relative positional displacement.

[0029] The right end of the throttle shaft 4 is stepped to form an annular stepped surface 32 facing right, and an O-ring groove 33 is formed on the right side of the stepped surface 32 into which an O-ring 34 is fitted. The bearing 6 consists of an inner ring 6a, an outer ring 6b, balls 6c, and a cage (not shown). The inner ring 6a fits onto the throttle shaft 4 from the right and abuts against the stepped surface 32, and the gap between the inner peripheral surface of the inner ring 6a and the outer peripheral surface of the throttle shaft 4 is kept airtight by the O-ring 34.

[0030] A cylindrical collar 35 is fitted onto the throttle shaft 4 from the right. A male thread 36 and a pair of flat surfaces 37 that are 180° opposed to each other are formed on the right side of the collar 35 on the throttle shaft 4. A chamfered hole 22b formed in the core metal 22a of the driven gear 22 is fitted into this portion from the right, and the engagement between the chamfered hole 22b and each flat surface 37 prevents the driven gear 22 from rotating together with the core metal 22a relative to the throttle shaft 4. A fixing nut 39 is screwed onto the male thread 36 via a washer 38, and the inner ring 6a of the bearing 6 is sandwiched between the step surface 32 via the washer 38, the core metal 22a and the collar 35 under the fastening force of the fixing nut 39. As a result, the driven gear 22 is fixed to the right end of the throttle shaft 4, and the inner ring 6a is positioned in the direction along the axis C of the throttle shaft 4, i.e., in the thrust direction.

[0031] A body-side annular fitting portion 41 is formed adjacent to the right side of the shaft hole 20 of the throttle body 2 and has an annular shape centered on the throttle shaft 4. A case-side annular fitting portion 42 is formed adjacent to the left side of the shaft hole 21 of the left case member 13 and has an annular shape centered on the throttle shaft 4. A leftward-facing annular movement restricting surface 43 is formed between the shaft hole 21 and the case-side annular fitting portion 42. The inner peripheral surface of the shaft hole 21 is spaced from the outer peripheral surface of the throttle shaft 4 to form a gap 44, and the above-mentioned collar 35 abuts against the inner ring 6a of the bearing 6 from the right side through this gap 44. The body-side annular fitting portion 41 and the case-side annular fitting portion 42 are set to the same inner diameter and are adjacent to each other and continuous in the left-right direction.

[0032] The outer ring 6b of the bearing 6 is press-fitted into the case-side annular fitting portion 42 and abuts against the movement restriction surface 43 from the left. A cylindrical positioning ring 45 is disposed on the left side of the outer ring 6b, and about half of the left side of the positioning ring 45 is fitted into the body-side annular fitting portion 41, and about half of the right side is fitted into the case-side annular fitting portion 42. The radial thickness of the positioning ring 45 is slightly thicker than the thickness of the outer ring 6b of the bearing 6, and its right end face abuts against the left end face of the outer ring 6b. As described above, the body-side annular fitting portion 41 and the case-side annular fitting portion 42 have the same inner diameter, but the body-side annular fitting portion 41 has a tolerance corresponding to a so-called clearance fit with respect to the outer diameter of the positioning ring 45, and the case-side annular fitting portion 42 has a tolerance corresponding to a so-called interference fit. For this reason, the positioning ring 45 is inserted into the body side annular fitting portion 41 with almost no clearance, whereas it is pressed into the case side annular fitting portion 42, requiring a large force to insert or remove it.

[0033] The positioning ring 45 is manufactured by cutting a material such as free-cutting brass steel. However, the material and manufacturing method are not limited to this, and can be changed as desired. The outer ring 6b of the bearing 6 is sandwiched between the movement restricting surface 43 and the positioning ring 45, and is thereby positioned in the direction along the axis C of the throttle shaft 4, i.e., in the thrust direction.

[0034] Additionally, the right side of the positioning ring 45 is press-fitted into the case-side annular fitting portion 42, and the left side is inserted into the body-side annular fitting portion 41. As described above, a gap is formed between the boss portion 2a and the annular protrusion 13a to allow positional displacement, and therefore the throttle body 2 and the left case member 13 are positioned via the positioning ring 45 in the direction perpendicular to the axis C, i.e., in the radial direction.

[0035] Next, the effects of the throttle device 1 described above, and in particular the effects of the support structure for the right end of the throttle shaft 4, will be described. First, the inner ring 6a of the bearing 6 is sandwiched between the stepped surface 32 of the throttle shaft 4 and the fixing nut 39, and is positioned in the direction of the axis C of the throttle shaft 4. Therefore, when the throttle shaft 4 is subjected to some external force and attempts to displace along the axis C, the inner ring 6a of the bearing 6 begins to displace in the same direction as the throttle shaft 4, and this force acts on the outer ring 6b via the balls 6c.

[0036] On the other hand, the outer ring 6b of the bearing 6 is sandwiched between the movement restricting surface 43 of the left case member 13 and the positioning ring 45 to be positioned in the axial direction C. In detail, the outer ring 6b is not only restricted from being displaced by friction with the inner peripheral surface of the case-side annular fitting portion 42, but also restricted from being displaced to the right by the movement restricting surface 43 and from being displaced to the left by the positioning ring 45. Since the outer ring 6b is firmly positioned in the axial direction C in this way, even if the positional displacement of the throttle shaft 4 in the axial direction C is transmitted via the inner ring 6a and the ball 6c, the outer ring 6b is kept in a desired position without being displaced. In other words, the outer ring 6b is kept in a desired position, so that the positional displacement of the throttle shaft 4 in the axial direction C is restricted via the ball 6c and the inner ring 6a. If the throttle valve 7 is displaced in the axial direction C, both sides of the throttle valve 7 will come into sliding contact with the inner peripheral surface of the throttle bore 3, causing problems such as the throttle valve 7 being unable to open and close smoothly. Since such troubles can be prevented, the reliability of the throttle device 1 can be improved.

[0037] In particular, the positioning ring 45 of this embodiment has a longer contact length in the left-right direction with each of the annular fitting portions 41, 42 than the outer ring 6b, and therefore comes into contact with the inner peripheral surfaces of the annular fitting portions 41, 42 over a wider area, and the mutual friction more firmly restricts positional displacement. Inevitably, just as the movement restriction surface 43 restricts the rightward positional displacement of the outer ring 6b, the positioning ring 45 also reliably restricts the leftward positional displacement of the outer ring 6b. Therefore, the outer ring 6b can be more firmly positioned, and thus the positional displacement of the throttle valve 7 in the direction of the axis C can be more reliably restricted.

[0038] In this way, unlike the technology of Patent Document 1, the throttle device 1 of this embodiment achieves positioning of the throttle shaft 4 in the direction of axis C without providing a compression spring on the throttle shaft 4. Therefore, the external dimensions of the throttle device 1, particularly the external dimensions of the throttle shaft 4 in the direction of axis C, can be reduced, thereby improving the ease of mounting on the engine.

[0039] On the other hand, in this embodiment, the throttle body 2 and the left case member 13 are separate members. This is because the two members 2, 13 are injection molded separately to achieve a compact mold and a simple mold shape. However, in this case, it becomes necessary to ensure coaxial accuracy when joining the throttle body 2 and the left case member 13. The coaxial accuracy refers to the accuracy regarding the positional relationship between the throttle body 2 and the left case member 13 in the direction perpendicular to the axis C of the throttle shaft 4.

[0040] For example, the driven gear 22 is supported from the throttle body 2 side via the throttle shaft 4, and the intermediate gear 29 meshing with it is supported from the left case member 13 side via the gear shaft 27. Therefore, if the coaxial accuracy of the throttle body 2 and the left case member 13 is reduced, the meshing state between the driven gear 22 and the small diameter portion 29b of the intermediate gear 29 will deteriorate, causing problems such as noise generation and accelerated wear. In addition, the function of the waterproof packing 15 may be impaired due to the reduced coaxial accuracy, in which case rainwater, etc. will enter the gear housing chamber 17.

[0041] In this embodiment, the positioning ring 45 not only has its right side pressed into the case side annular fitting portion 42 to position the outer ring 6b of the bearing 6, but also has its left side inserted into the body side annular fitting portion 41. As a result, the throttle body 2 and the left case member 13 are maintained in a regular positional relationship in a direction perpendicular to the axis C via the positioning ring 45, thereby achieving high coaxial accuracy and preventing the above-mentioned problems.

[0042] In addition, the positioning ring 45 performs two functions: positioning the outer ring 6b of the bearing 6 in the direction of the axis C, and positioning the throttle body 2 and the left case member 13 in a direction perpendicular to the axis C. It is possible to achieve each function with separate members, but in that case, a large space would be required to install each member and the structure around the bearing would become complicated. As both functions can be achieved with a single positioning ring 45, this contributes to the miniaturization of the throttle device 1 and the reduction of manufacturing costs.

[0043] In this embodiment, the fastening force of the fixed nut 39 is applied to the inner ring 6a of the bearing 6 via the cylindrical collar 35. As shown in FIG. 8, the bearing 6 is disposed at the joint between the throttle body 2 and the left case member 13, in other words, at the fitting position between the boss portion 2a and the annular protrusion 13a. On the other hand, the fixed nut 39 is disposed in the gear accommodating chamber 17 to fasten the driven gear 22 to the right end of the throttle shaft 4, and as a result, the bearing 6 and the fixed nut 39 are separated in the left-right direction. For example, it is possible to add a portion corresponding to the cross-sectional shape of the collar 35 to the core metal 22a of the driven gear 22 and abut against the inner ring 6a, but this would cause the core metal 22a to have a complex cross-sectional shape instead of a flat plate shape, which would increase costs. By simply adding the collar 35 having a simple cylindrical shape between the inner ring 6a and the driven gear 22, the fastening force of the fixed nut 39 can be applied to the inner ring 6a, which contributes to reducing the cost of the throttle device 1.

[0044] The left case member 13 is also formed with a shaft hole 21 through which the throttle shaft 4 is inserted, and a case-side annular fitting portion 42 into which the outer ring 6b of the bearing 6 and a positioning ring 45 are press-fitted is formed on the left side of the shaft hole 21, and a movement restriction surface 43 is formed between the shaft hole 21 and the case-side annular fitting portion 42 to restrict the rightward positional displacement of the outer ring 6b, and further, a gap 44 is formed between the inner peripheral surface of the shaft hole 21 and the outer peripheral surface of the throttle shaft 4 to allow the collar 35 to abut against the inner ring 6a of the bearing 6. In this way, four parts having different functions are provided in the left case member 13 in a positional relationship adjacent to each other. This contributes to the miniaturization of the throttle device 1.

[0045] The aspects of the present invention are not limited to this embodiment. For example, in the above embodiment, the throttle device 1 is applied to a two-cylinder engine mounted on a motorcycle, but the present invention is not limited to this. For example, the vehicle on which the engine is mounted may be a passenger car, a motorized bicycle, or a so-called ATV (All Terrain Vehicle) such as a four-wheeled buggy, and the type of engine may also be changed as desired.

[0046] In addition, in the above embodiment, the positioning ring 45 is disposed on the throttle body 2 side, and the bearing 6 is disposed on the left case member 13 side, but this is not limited to this. For example, the positional relationship between the bearing 6 and the positioning ring 45 may be reversed. Figure 9 is a cross-sectional view corresponding to Figure 8 showing this alternative example, and the following description will focus on the differences from the above embodiment.

[0047] A body-side annular fitting portion 101 is formed on the right side of the shaft hole 20 of the throttle body 2, and a movement restricting surface 103 facing right is formed between the bearing 6 and the body-side annular fitting portion 101. A case-side annular fitting portion 102 is formed on the left side of the shaft hole 21 of the left case member 13, and a gap 104 is formed between the inner peripheral surface of the shaft hole 21 and the outer peripheral surface of the throttle shaft 4. The inner ring 6a of the bearing 6 is fitted onto the throttle shaft 4 from the right, and the collar 35 is fitted through the gap 104, so that the inner ring 6a of the bearing 6 is sandwiched between the stepped surface 32 via the washer 38, the core metal 22a, and the collar 35.

[0048] The outer ring 6b of the bearing 6 is press-fitted into the body-side annular fitting portion 101, and approximately the left half of the positioning ring 45 is press-fitted, and approximately the right half of the positioning ring 45 is inserted into the case-side annular fitting portion 102. In the throttle device 1 of the other example configured as described above, the same effects as those of the above embodiment can be achieved, although a duplicated description will not be given. [Explanation of symbols]

[0049] 1 Throttle device 2 Throttle body 3 Throttle bore 4 Throttle shaft 6 Bearings 6a Inner Circle 6b Outer ring 7 Throttle valve 18 Gear case 20,21 Shaft hole 22 Driven gear (gear train) 26 Drive gear (gear train) 29 Intermediate gear (gear train) 32 Step surface 35 Color 39 Fixing nut 41,101 Body side annular fitting 42,102 Case side annular fitting 43,103 Movement restriction surface 44,104 gap 45 Positioning ring

Claims

1. A throttle device for an engine in which a throttle valve is supported by a throttle shaft in a throttle bore of a throttle body so as to be openable and closable, a gear case accommodating a gear train is fixed to a side of the throttle body, and one end of the throttle shaft is projected into the gear case through a shaft hole and driven via the gear train, an annular fitting portion formed adjacent to the shaft hole; a bearing having an outer ring fitted to the annular fitting portion and an inner ring fitted to the throttle shaft, the bearing rotatably supporting the throttle shaft; a positioning ring that is press-fitted into the annular fitting portion to come into contact with the outer ring and restricts positional displacement of the outer ring along the axis of the throttle shaft; a fixing nut that is screwed onto one end of the throttle shaft in the gear case and abuts against the inner ring from one end side to restrict a positional displacement of the inner ring toward the one end side; A throttle device for an engine comprising:

2. The gear case has the shaft hole formed therein, and a case side annular fitting portion is formed as the annular fitting portion on the other end side of the shaft hole, The positioning ring abuts against the outer ring from the other end side within the case-side annular fitting portion to restrict positional displacement of the outer ring toward the other end side.

2. The engine throttle device according to claim 1.

3. The gear case has a movement restriction surface formed between the shaft hole and the case-side annular fitting portion, the movement restriction surface facing the other end side, The positioning ring sandwiches the outer ring between itself and the movement restricting surface to position the outer ring in the axial direction of the throttle shaft.

3. The engine throttle device according to claim 2.

4. The throttle body has a body-side annular fitting portion formed adjacent to the other end side of the case-side annular fitting portion, The positioning ring is press-fitted into the case-side annular fitting portion and inserted into the body-side annular fitting portion.

3. The engine throttle device according to claim 2.

5. The throttle shaft has a stepped surface facing one end thereof, The fixing nut sandwiches the inner ring of the bearing between itself and the stepped surface to position the inner ring in the axial direction of the throttle shaft.

5. An engine throttle device according to claim 1, wherein the throttle device is a valve for regulating a throttle of the engine.

6. The throttle valve further includes a cylindrical collar that is fitted onto the throttle shaft and abuts against the inner ring from one end side, The fixing nut sandwiches the inner ring of the bearing between the collar and the step surface.

6. The engine throttle device according to claim 5.

7. a gap is formed between an inner peripheral surface of the shaft hole and an outer peripheral surface of the throttle shaft, The collar abuts against the inner ring through the gap.

7. The engine throttle device according to claim 6.

8. The throttle body has the shaft hole formed therein, and a body side annular fitting portion is formed as the annular fitting portion on one end side of the shaft hole, The positioning ring abuts against the outer ring from one end side within the body side annular fitting portion to restrict positional displacement of the outer ring toward the one end side.

2. The engine throttle device according to claim 1.

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