Title of Invention

SLOW ADJUST SCREW FOR CARBURETOR

Abstract

The present invention provides a slow adjust screw for a carburetor which can accurately adjust an amount of a low speed air or an amount of a low speed mixture and has an excellent reproducibility, wherein adjust passage (B) formed in a carburetor main body (1) is structured such that a female hole (B1), a spring receiving hole (B2), a guide hole (B3) and a control hole (B4) are continuously connected from an inlet toward a front end in an coaxial manner and slow adjust screw (J) being provided with a male screw portion (J1) threadedly engaged with the female hole (B1), a guide rod (J3) and a taper portion (J2) moving forward within the control hole (B4) from a rear end toward a front end, and in a state of engaging the male screw portion (j1) of the slow adjust screw (J) with the female screw hole (B1) so as to move forward the taper portion (J2) within the control hole (B4), an annular ring (R) made of an elastic material being arranged in an annular gap (X) formed by the guide hole (B3) and the guide rod (J3) in a compressed state.

Full Text

SPECIFICATION BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a carburetor which adjusts and controls an amount and a concentration of a mixture supplied to an engine, and particularly to a slow adjust screw which adjusts an amount of a low speed air or an amount of a low speed mixture in the carburetor. THE PRIOR ART The conventional slow adjust screw for the carburetor is shown in Fig. 2. Reference numeral 1 denotes a main body of the carburetor in which a suction passage 2 laterally passes through an inner portion thereof, and a float chamber 4 is formed by a lower recess portion of the carburetor main body 1 and a float chamber main body 3. Reference numeral 5 denotes a throttle valve which opens and closes the suction passage 2, which is movably arranged within a throttle valve guiding cylinder 6 connected to the suction passage 2. The throttle valve 5 is opened and closed in by an acceleration wire operation by a driver. A fixed fuel liquid surface is formed within the float chamber 4 by a fixed liquid surface control mechanism mentioned below. The fixed liquid surface control mechanism is constituted by a valve seat 7 which is communicated with a fuel passage 19, a float valve 8 which opens and closes the valve seat 7 and a float 9. In the case that the fuel liquid surface within the flat chamber 4 is low in the drawing, the float 9 rotates in a counterclockwise direction 1A and the float valve 8 opens the valve seat 7, thereby allowing the fuel to flow from the fuel passage 19 into the float chamber 4. When the fuel within the float chamber 4 reaches a fixed liquid surface height, the float 9 rotates in a clockwise direction and the float valve 8 closes the valve seat 7, thereby preventing the fuel flowing from the fuel passage 19 from flowing into the float chamber 4. Accordingly, a fuel liquid surface having a fixed height is formed within the float chamber 4. A fuel system of the carburetor is mainly constituted by a main system M and a slow system S. The main system M is constituted by the following elements. Reference numeral 18 denotes a main fuel jet, in which a controlled fuel is supplied toward a bleed pipe 10, a main fuel passing within the bleed pipe 10 is mixed with a main air sucked from a main air passage 11 so as to form a main mixture, and the main mixture reaches a needle jet 12. A jet needle 13 attached to the throttle valve 5 is inserted into the needle jet 12, and the mixture within the needle jet 12 is controlled by an annular gap which is formed by the jet needle 13 and the needle jet 12 so as to be sucked out within the suction pipe 2. The slow system S is constituted by the following elements. Reference numeral 14 denotes a slow fuel jet, in which a controlled fuel is supplied toward a bleed pipe 15, while a slow air is supplied to the bleed pipe 15 from a slow air passage 16. Accordingly, in the bleed pipe 15, the slow fuel which is controlled in the slow fuel jet 14 and the slow air which is supplied from the slow air passage 16 are mixed to form a slow mixture. Then, the slow mixture is sucked out within the suction pipe 2 via a slow injection hole. Further, an amount of the slow air which flows through the slow 2 air passage 16 is controlled by a slow adjust screw A. The slow adjust screw A is formed from a rear end to a front end in the following manner. Reference symbol Al denotes a male screw portion which is formed in the rear end, in which a taper portion A3 is formed in the front end via a guide rod A2. At this time, a minus groove A4 is formed on a rear end surface A5 of the male screw portion Al, and a step portion D1 which faces downward is formed in a connecting portion between a front end surface A6 and the guide rod A2 in the male screw portion A1. That is, a diameter of the guide rod A2 is smaller than a diameter of the male screw portion A1. Further, the male screw portion Al, the guide rod A2 and the tape portion A3 are concentrically formed. The slow adjust screw A structured in the manner mentioned above is engaged with an adjust passage B in the carburetor main body 1 so as to be inserted therein. The adjust passage B is structured such that a female screw hole B1 with which the male screw portion Al of the slow adjust screw A is engaged, a spring receiving hole B2, a guide hole B3 and a control hole B4 are continuously connected from an inlet toward the front end so as to have the same axis. The spring receiving hole B2 and the guide hole B3 are formed so that these holes have a diameter larger than at least the diameter of the guide rod A2, and a step portion D2 which faces upward is formed in a connecting portion between a lower end of the spring receiving hole B2 and an upper end of the guide hole B3. The female screw hole B1, the spring receiving hole B2, the guide hole B3 and the controlhole B4 are concentrically formed. Further, a primary flow passage B5 which is communicated with an ambient air is opened to the guide hole B3, and a downstream side of the control hole B4 is communicated 3 with the slow air passage 16. That is, the slow air passage 16 is opened to the atmosphere via the control hole B4, the guide hole B3 and the primary flow passage B5. (Opening to the atmosphere means opening to a state of the atmospheric pressure.) The slow adjust screw A is arranged so as to be engaged with the adjust passage B, in which the female screw hole B1 is engaged threadedly with the male screw portion Al, the guide rod A2 is arranged within the spring receiving hole B2 and the guide hole B3, and the taper portion A3 is arranged within the control hole B4. And a coil spring Cp is arranged on an outer periphery of the connecting rod A2. The coil spring Cp is arranged within the spring receiving hole B2, in which a lower end thereof is locked with the step portion D2 of the adjust passage B and a lower end thereof is locked with the step portion D1 of the adjust screw A so as to press the slow adjust screw A outward. Then, an amount of the slow air which flows within the slow air passage 16 is adjusted in the following manner. When screwing the slow adjust screw A so that it may move in a direction that the taper portion A3 moves forward within the control hole B4, thereby making an annular gap P formed between the taper portion A3 and the control hole B4 small, it is possible to reduce the amount of the slow air which flows from the control hole B4 into the slow air passage 16. On the contrary, when screwing the slow adjust screw A so that it may move in a direction that the taper portion A3 moves apart from the control hole B4, thereby making the annular gap P formed between the taper portion A3 and the control hole B4 large, it is possible to increase the amount of the slow air which flows from the control hole B4 into the slow air passage 16. 4 Fig. 3 shows another embodiment of the slow adjust screw A. (This corresponds to a structure disclosed in Japanese Utility Model Laid-Open No. 56-63836.) In this case, the reference numerals used in Fig . 2 are used in Fig. 3 to denote the corresponding portions and a description thereof will be omitted. In this embodiment, an annular flange portion A7 is formed in the connecting rod A2, in which an outer periphery of the annular flange portion A7 is guided in a state of being arranged near the guide hole. That is, an outer diameter of the annular flange portion A7 is slightly smaller than the diameter of the guide hole B3. In the structure shown in the conventional slow adjust screwmentioned above, it is hard to accurately and stably supply the amount of the low speed air which is adjusted by the slow adjust screw A. This is because of the following reasons. (1) The amount of the low speed air which is supplied to the slow air passage 16 is adjusted by inserting a minus screwdriver into the minus groove A4 of the slow adjust screw A so as to rotate in a fastening direction, thereby moving forward the taper portion A3 within the control hole B4 and setting a suitable annular gap P, and thereafter stopping the rotation. In this case, at a time of rotating the slow adjust screw A in the fastening direction, the slow adjust screw A moves toward the control hole B4 (in a downward direction in Fig. 2) against a pressing force of the coil spring Cp, and when the rotation in the fastening direction is stopped and the forward movement thereof is stopped, the slow adjust screw A moves in a returning direction (to a side of a backward movement in an upward direction in Fig. 2) by the pressing force of the coil spring Cp at a degree corresponding 5 to a backlash between the male screw portion Al and the female screw hole B1. More particularly describing with reference to Fig. 2, the slow adjust screw A displaces upward at a degree corresponding to the backlash of the screw after screwing the slow adjust screw A downward so as to adjust the position thereof. (2) It is impossible to accurately center and arrange the taper portion A3 and the control hole B4. This is mainly because the male screw portion Al at the rear end of the slow adjust screw A is threadedly engaged only with the female screw hole B1. In the structure mentioned above, it is hard to form the annular gap P formed by the taper portion A3 and the control hole B4 in an uniform concentric circle, thereby causing the problem mentioned above. (3) On the contrary, in the structure shown in Fig. 3, in centering the taper portion A3 and the control hole B4, they are guided by the male screw portion Al and the annular flange portion A7, so that it is effective in comparison with the structure shown in Fig. 2, however, it is significantly hard to manufacture the structure. That is, the following reasons exist. It is necessary to increase an accuracy of concentricity between the female hole B1 and the guide hole B3. It is necessary to increase an accuracy of concentricity between the male screw portion Al and the annular flange portion A7. It is necessary to increase an accuracy of the inner diameter of the guide hole B3 and the outer diameter of the annular flange portion A7. If the inner diameter of the guide hole B3 and the outer diameter of the annular flange portion A7 are brought into contact with each other, it is impossible to insert and arrange the slow adjust screw A within the 6 adjust passage B, and if an interval is generated between the inner diameter of the guide hole B3 and the annular flange portion A7, no centering function can be obtained. SUMMARY OF INVENTION A slow adjust screw for a carburetor in accordance with the present invention is made by taking the problems mentioned above into consideration, and a main object of the present invention is to accurately adjust an amount of a low speed air or an amount of a low speed mixture by means of a slow adjust screw , and to improve a reproducibility Accordingly the present invention provides for a slow adjust screw for a carburetor which adjusts an amount of a low speed air or an amount of a low sped mixture in the carburetor, wherein an adjust passage formed in a carburetor main body is structured such that a female hole, a spring receiving hole, a guide hole and a control hole are continuously connected from an inlet toward a front end in an coaxial manner, a primary flow passage is opened to the guide hole and the control hole is connected to the slow passage, a slow adjust screw is provided with a male screw portion threadedly engaged with the female hole, a guide rod and a taper portion moving forward within the control hole from a rear end toward a front end, and in a state of engaging the male screw portion of the slow adjust screw with the female screw hole so as to move forward the taper portion within the control hole, the slow adjust screw is urged to the rear end side by a spring which is contracted within the spring receiving hole and an annular ring made of an elastic material is arranged in an annular gap formed by the guide hole and the guide rod in a compressed state 7 Further, in accordance with a second aspect of the present invention, there is provided a slow adjust screw for a carburetor as stated in the first aspect, wherein the annular ring is arranged within an annular groove which is formed on an outer periphery of the guide rod. In accordance with the first aspect of the present invention, since the annular ring is arranged between the guide rod and the guide hole in a compressed state and the pressing force is applied to all the periphery of the guide rod by this annular ring, it is possible to prevent the slow adjust screw from moving at a degree of the backlash at a time of releasing an operating force applied to the slow adjust screw after adjusting the slow adjust screw. Further, it is possible to accurately center and arrange the taper portion within the control hole. In accordance with the second aspect of the present invention the annular groove of the guide rod can be formed at the same time of performing a lathe turning of the slow adjust screw, and it is not necessary to widely increase the accuracy of the outer diameter and the inner diameter thereof. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig. 1 is a vertical cross sectional view which shows an embodiment of a slow adjust screw for a carburetor in accordance with the present invention; Fig. 2 is a vertical cross sectional view of a slow adjust screw for a carburetor in accordance with the conventional art; and Fig. 3 is a vertical cross sectional view of a main portion which 8 shows another embodiment of a slow adjust screw for a carburetor in accordance with the conventional art DESCRIPTION OF THE PREFERRED EMBODIMENT A description will be given below of an embodiment of a slow adjuster for a carburetor in accordance with the present invention with reference to Fig. 1. In this case, the same reference numerals used in Fig. 2 are used in Fig. 3 to denote the corresponding portions and a description thereof will be omitted. A slow adjust screw is different from that shown in the embodiment in accordance with the present invention and that of the conventional embodiment shown in Fig. 2. A slow adjust screw J is constituted by a male screw portion J1 which is engaged with the female screw hole B1 from a rear end toward a front end, a taper portion J2 which moves forward within the control hole B4, and a guide rod J3 which connects the male screw portion J1 and the taper portion J2, and the guide rod J3 is constituted by a large diameter guide rod J3a which is connected to the male screw portion J1 and a small diameter guide rod J3b which is connected to the taper portion J2. Then, an annular groove J4 is formed in the large diameter guide rod J3a of the guide rod J3, and an annular ring R such as an 0 ring, a rectangular ring or the like which is made of an elastic material such as a rubber material or the like is mounted to the annular ring J4. In this case, a minus groove J5 is formed on a rear end surface of the slow adjust screw J, and a step portion D1 is formed between the front end surface of the male screw portion J1 and the guide rod J3. The structure is made such that the slow adjust screw J is porivded threadedly to the adjust passage B, in which the male screw portion J1 9 is engaged threadedly with the female screw hole B1, the guide rod J3 is arranged within the spring receiving hole B2 and the guide hole B3, and the taper portion J2 is arranged within the control hole B4. In this case, in the guide rod J3, the annular ring R attached to the annular groove J4 is arranged within the guide hole B3 in a compressed state, and the small diameter guide rod J3b is arranged within the guide hole B3. Further, the primary flow passage B5 is arranged within the guide hole B3 and is faced and opened to the small diameter guide rod J3b. Further, the coil spring Cp is arranged on the outer periphery of the large diameter guide rod J3a of the guide rod J3, and the coil spring Cp is arranged within the spring receiving hole B2, a lower end of which is locked to the step portion D2 in the adjust passage B and an upper end of which is locked to the step portion D1 in the slow adjust screw J, thereby pressing the slow adjust screw J outward. Next, a description will be given of an adjustment of the amount of the low speed air by means of the slow adjust screw J. The amount of the low speed air which flows within the slow air passage 16 via the primary flow passage B5, the guide hole B3 and the control hole B4 is adjusted by engaging a minus screwdriver (not shown) within the minus groove J5 in the slow adjust screw J so as to rotate the slow adjust screw J in a fastening direction and moving forward the taper portion J2 within the control hole B4 so as to adjust the annular gap P. In a state that a suitable amount of the low speed air is adjusted in accordance with the adjustment, mentioned above, the rotation of the slow adjust screw J is stopped and the pressing force applied to the slow adjust screw J by the minus screwdriver 10 is cancelled, and in this state, the slow adjust screw J in accordance with the present invention can accurately keep the adjusted position with generating no positional change. That is, in accordance with the slow adjust screw J in accordance with the present invention, since an annular ring R made of an elastic material is arranged in an annular gap X formed between the guide rod J3 of the slow adjust screw J and the guide hole B3 in a compressed state, the slow adjust screw J always receives a uniform pressing force applied by the annular ring R toward a center from all the outer periphery. In the structure mentioned above, since the slow adjust screw J is not displaced outward at a degree corresponding to the backlash between the male screw portion J1 and the female screw hole B1 even in the state that the adjustment with respect to the slow adjust screw J is completed and the force of the adjusting operation with respect to the slow adjust screw J is cancelled, the annular gap P between the taper portion J2 and the control hole B4 which is set at a time of the adjustment can be accurately kept. In other words, a substantially uniform pressing force can be applied from a direction perpendicular to a longitudinal direction of the slow adjust screw J (corresponding to a direction of the positional change of the slow adjust screw), and a force of keeping the position of the slow adjust screw J can be secured. Accordingly, it is possible to completely solve the problem that the slow adjust screw J is displaced due to the backlash in the screw portion and the amount of the low speed air is changed after the adjustment, after rotating the slow adjust screw J so as to adjust the amount of the low speed air, so that it is possible to supply the low speed mixture which 11 is controlled in a significantly accurate manner in comparison with the slow system S in the carburetor, to the engine, thereby improving an operability of the engine and effectively preventing a harmful exhaust gas component from being discharged. Further, since the slow adjust screw J is structured such that the rear end thereof is engaged threadedly with the female screw hole B1 and the guide rod J3 in the middle thereof is held by the guide hole B3 via the annular ring R in a compressed state, it is possible to accurately center and arrange the taper portion J2 of the slow adjust screw J toward the control hole B4 so as to form the concentric annular gap P, and further, since the centering and supporting state is not changed even at a time of rotating and adjusting the slow adjust screw J, it is possible to particularly increase a reproducibility of the amount of the low speed air. For example, in the case that the centering and supporting state mentioned above is incomplete so as not to form the concentric annular gap P, the flow of the low speed air which flows through the gap becomes uneven and the amount of the low speed air always changes at a time of adjusting the slow adjust screw J, so that there is a risk that an improved reproducibility of the amount of the low speed air can not be obtained. Further, since the slow adjust screw J is supported by the annular ring R made of the elastic material in a compressed manner, the slow adjust screw J and the adjust passage B are not mechanically brought into contact with each other, so that no specially high accuracy is not required in the outer diameter of the guide rod J3 and the inner diameter of the guide hole B3 and there is no problem in increasing a manufacturing cost. 12 In this case, in the embodiment mentioned above, a description is given of the slow adjust screw for controlling the amount of the low speed air corresponding to the so-called air screw, however, the structure may be used for a slow adjust screw for adjusting an amount of a low speed mixture flowing within the slowmixture passage corresponding to a so-called pilot screw. As mentioned above, in accordance with the slow adjust screw for the carburetor of the present invention, since the slow adjust screw is urged to the rear end side by the spring which is contracted within the spring receiving hole and the annular ring made of the elastic material is arranged in the annular gap formed by the guide hole and the guide rod in a compressed state; the uniform pressing force can be always applied to the slow adjust screw toward the center by the annular ring so as to increase the force of holding the position of the slow adjust screw, so that it is possible to control the amount of the low speed air or the amount of the low speedmixture which is supplied to the carburetor in a significantly accurate manner. Further, since the slow adjust screw is structured such that the rear end thereof is engaged with the female screw hole and the middle portion is held by the annular ring, it is possible to accurately center and arrange the taper portion of the slow adjust screw toward the control hole, thereby increasing a reproducibility of the amount of the low speed air and the amount of the low speed mixture. Further, since the centering of the slow adjust screw is performed by the annular ring, it is not necessary to increase the accuracy of manufacturing the outer diameter of the guide rod and the inner diameter of the guide hole, thereby not 13 increasing the manufacturing cost. 14 WE CLAIM 1. A slow adjust screw for a carburetor which adjusts an amount of a low speed air or an amount of a low speed mixture in the carburetor, wherein an adjust passage (B) formed in a carburetor main body (1) is structured such that a female hole (B1), a spring receiving hole (B2), a guide hole (B3) and a control hole (B4) are continuously connected from an inlet toward a front end in an coaxial manner, a primary flow passage (B5) is opened to the guide hole (B3) and the control hole (B4) is connected to the slow passage, a slow adjust screw (J) is provided with a male screw portion (J1) threadedly engaged with the female hole (B1), a guide rod (J3) and a taper portion (J2) moving forward within the control hole (B4) from a rear end toward a front end, and in a state of engaging the male screw portion (j1) of the slow adjust screw (J) with the female screw hole (B1) so as to move forward the taper portion (02) within the control hole (B4), the slow adjust screw (J) is urged to the rear end side by a spring (Cp) which is contracted within the spring receiving hole (B2) and an annular ring (R) made of an elastic material is arranged in an annular gap (X) formed by the guide hole (B3) and the guide rod (J3) in a compressed state. 2. A slow adjust screw for a carburetor as claimed in claim 1, wherein said annular ring (R) is arranged within an annular groove (J4) which is formed on an outer periphery of the guide rod (J3) . 15 3. Slow adjust screw for a carburetor, substantially as herein described, particularly with reference to the accompanying drawings Dated this 19th day of April, 2000 (S MUKHERJEE) of D P AHUJA & CO APPLICANTS' AGENT 16 The present invention provides a slow adjust screw for a carburetor which can accurately adjust an amount of a low speed air or an amount of a low speed mixture and has an excellent reproducibility, wherein adjust passage (B) formed in a carburetor main body (1) is structured such that a female hole (B1), a spring receiving hole (B2), a guide hole (B3) and a control hole (B4) are continuously connected from an inlet toward a front end in an coaxial manner and slow adjust screw (J) being provided with a male screw portion (J1) threadedly engaged with the female hole (B1), a guide rod (J3) and a taper portion (J2) moving forward within the control hole (B4) from a rear end toward a front end, and in a state of engaging the male screw portion (j1) of the slow adjust screw (J) with the female screw hole (B1) so as to move forward the taper portion (J2) within the control hole (B4), an annular ring (R) made of an elastic material being arranged in an annular gap (X) formed by the guide hole (B3) and the guide rod (J3) in a compressed state.

Documents:

00230-cal-2000-abstract.pdf

00230-cal-2000-claims.pdf

00230-cal-2000-correspondence.pdf

00230-cal-2000-description(complete).pdf

00230-cal-2000-drawings.pdf

00230-cal-2000-form-1.pdf

00230-cal-2000-form-18.pdf

00230-cal-2000-form-2.pdf

00230-cal-2000-form-3.pdf

00230-cal-2000-form-5.pdf

00230-cal-2000-gpa.pdf

00230-cal-2000-priority document other.pdf

00230-cal-2000-priority document.pdf

230-cal-2000-granted-abstract.pdf

230-cal-2000-granted-claims.pdf

230-cal-2000-granted-correspondence.pdf

230-cal-2000-granted-description (complete).pdf

230-cal-2000-granted-drawings.pdf

230-cal-2000-granted-examination report.pdf

230-cal-2000-granted-form 1.pdf

230-cal-2000-granted-form 19.pdf

230-cal-2000-granted-form 2.pdf

230-cal-2000-granted-form 3.pdf

230-cal-2000-granted-form 5.pdf

230-cal-2000-granted-gpa.pdf

230-cal-2000-granted-letter patent.pdf

230-cal-2000-granted-priority document.pdf

230-cal-2000-granted-reply to examination report.pdf

230-cal-2000-granted-specification.pdf

230-cal-2000-granted-translated copy of priority document.pdf