Title of Invention

A SPROCKET COUPLING DEVICE

Abstract

A sproker device furnished with a cup-shaped joint having an engaging concave portion for engaging a sprocket of an engine output shaft, characterized in that a plurality of tapered tooth fixing portions of which surface are shaped to incline to an axial line of the sprocket, to be in close contact with tooth portions of the sprocket are provided in said engaging concave portion of said joint, at equal distance in the peripheral direction.

Full Text

The present invention relates to a sprocket coupling device for use in a firing apparatus of an engine or the like. Description of the prior Art A firing apparatus to be used for load test of an engine (as an example, refer to Japanese Patent Laid-Open Publication No. SHO58-18140) is designed to combine a sprocket provided on an output shaft of an engine with a joint provided on an input shaft of a measuring apparatus. In this combination structure, a corrugated concave portion lying along an outer peripheral contour of the sprocket is provided on the joint and the sprocket is engaged with the concave. By the way, in the above prior art, a wall of the joint facing the concave portion is corrugated, wherein some clearance is inevitably required between the wall and the tooth part of the sprocket. For this reason, when the sprocket rotation becomes irregular, noise is to be generated between the sprocket and the joint, and reduction of such noise has been desired. Especially, as the firing apparatus has a role to discover the abnormal sound of the engine for the inspection purpose, there is an imminent demand for reduction of such noise. SUMMARY OF THE INVENTION In order to solve the above subject, according to the first aspect of the present invention, a sprocket coupling device furnished with a cup-shaped joint having an engaging concave portion for engaging a sprocket, is characterized in that a plurality of tapered tooth fixing portions to be in close contact with tooth portions of the sprocket are provided in the engaging concave portion of the joint, at equal distance in the peripheral direction. In the second aspect of the invention, each of the tooth fixing portions has a tapered head portion. In the third aspect of the invention, the tooth fixing portion is formed in a shape of rod which is fitted to the joint and which has an inclined axial line with respect to a rotary axis of the sprocket. In the fourth aspect of the invention, the tooth fixing portion is a taper-shaped wall integrally formed within the engaging concave portion of the joint. In further aspect of the invention, the joint is provided in a firing apparatus. According to the first invention, when the sprocket is engaged in the coupling concave portion, some of the tooth portions thereof come into close contact with the tooth fixing portions provided at a moderate distance in a peripheral direction. However, as the tooth fixing portion has a tapered shape, the tooth portion is to be in dense contact, with the result that the sprocket and the joint are coupled without rattling. Consequently, even if the sprocket rotation becomes irregular, less noise is apt to be generated with the joint, and the noise at the coupling portion can be reduced. According to the second invention, because the tooth fixing portion comprises a member having a tapered head, it can be fitted to the joint in parallel with the rotary shaft of the sprocket, whereby fitting of the tooth fixing portion is facilitated. In the third invention, since the rod-shaped member is fitted to the joint in a manner that the axial line of the rod-shaped member is inclined to the rotary shaft of the sprocket, the tooth fixing portion having a tapered portion can be easily provided, and the shape of the rod-like member can be simplified. In the fourth invention, since the tapered wall is formed in one-piece with the wall surface facing the engaging concave portion of the joint, the wall is made into a tapered tooth fixing portion and the tooth portion can be densely set in contact with the sprocket when being engaged. Moreover, by forming the tapered wall integral with the joint, the number of parts can be curtailed to make the joint manufacture easier. In the fifth invention, the tooth fixing portion is provided on the joint of the firing apparatus, so that it is possible to obtain a coupling device suited to the firing apparatus so as to evade occurrence of noise in the coupling portion between the sprocket and the joint. BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a sectional view showing a coupling structure between a joint and a sprocket according to the first embodiment of the present invention; Fig. 2 is an elevational view showing a measuring device side in a firing apparatus according to the first embodiment; Fig. 3 is a sectional view taken along line 3-3 in Fig. 1; Fig. 4 is a sectional view similar to Fig. 1 according to the second embodiment of the invention; Fig. 5 is a sectional view similar to Fig. 1 according to the third embodiment of the invention; and Fig. 6 is a sectional view taken along line 6-6 in Fig. 5. DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention will be described with reference to the accompanying drawings. Figs. 1 to 3 are concerned with the first embodiment applied to a firing apparatus, wherein Fig. 1 is a sectional view showing a coupling structure between a joint and a sprocket; Fig. 2 is a view showing a measuring device side in the firing apparatus; and Fig. 3 is a sectional view taken along the line 3-3 in Fig. 1. Firstly, as shown in Fig. 2, in the measuring device of this firing apparatus, an input shaft 2 an end of which is fitted to a joint 1 is coupled to a torque meter 3, and further connected to a pump motor 4. The input shaft 2 projects from a cover 5 so as to mount the joint 1 thereon. A plurality of position setting rods 6 project in parallel with the input shaft 2. The position setting rods 6 are inserted into a fitting hole 8 for engine mounting (Fig. 3) in an engine 7 thereby setting the joint 1 and the engine 7 in position for example for an motor bicycle. Under this condition, the joint 1 is combined with a sprocket 10 fitted to an output shaft 9. The engine 7 is fixed to a supporting stand (not shown) of the firing apparatus. To an air suction side of the engine 7, an air supply apparatus which is throttle-controlled is connected, and to an air exhaust side thereof, an air exhaust duct is connected. Accordingly, by having the input shaft 2 cooperatively coupled with a brake apparatus, inspections of engine starting and brake performance by load test and the like can be performed. Fig. 1 and Fig. 3 show details of the coupling structure between the joint 1 and the sprocket 10, wherein the joint 1 is in the form of a cup, and a plurality of (in this embodiment, three at 120"" distance) tooth fixing portion fitting holes 13 are provided on a concentric circle at equal distance along the inside of a peripheral wall 12 surrounding an engaging concave portion 11 for engaging the sprocket 10. The tooth fixing portion fitting holes 13 are formed in parallel with the center axis C of the output shaft 9 which is a rotary shaft of the sprocket 10. The fitting hole 13 are engraved to a bottom 14 so as to communicate with a bolt head accommodating concave portion 16 which is formed on a step 15 provided on the outer periphery of the bottom 14. Also, an input shaft fitting hole 17 extends at the center of the bottom 14, and the axis of the input shaft fitting hole 17 is formed coaxial with the center axis C of the output shaft 9. A spline groove is formed on an inner peripheral surface of the fitting hole 17. To the fitting holes 13 there are fixed a plurality of tooth fixing portions 20 having a tapered head of generally a mushroom shape. The number of tooth fixing portions is optional but corresponds to the fitting holes 13. In the present embodiment, three tooth fixing portions are provided at a distance of 120 degrees. The tooth fixing portion 20 is provided with a mushroom shaped tapered head 21 and a shaft 22 continued to it. By inserting the shaft 22 into the fitting hole 13 and screwing a bolt 24, inserted from the accommodating concave portion 16 of the bolt head, into a screw hole 23, the tooth fixing portion 20 is formed into one-piece with the bottom part 14. The tapered head 21 has an inclination at an angle Of to the center axis C of the output shaft 9 in such a direction as to engage the sprocket 10 so as to cross with the centerline C of the output shaft 9. Thje head 21 is received at the top side in the tooth groove 10b of the tooth 10a. The base side of the head 21 is larger than the tooth groove 10b, and is in close contact with a part of the tooth 10a, e.g., a tooth bottom 10c. A spline part 30 formed at an end of the input shaft 2 is engaged into the input shaft fitting hole 17 at the bottom part 14 and the input shaft 2 is anchored by the circlip 31. Further, an axial slot 32 is formed on the spline part 30, and a pin 33 is inserted thereinto from the side of the joint 1. Thus, the joint 1 is integrally rotatable with the input shaft 2 and is freely movable in the axial direction along the input shaft 2 in the range of the length of the slot 32. A coil spring 35 is provided in compression between a flange 34, which is provided in integrally rotatable state around the input shaft 2, and the step 15. The joint 1 is forced by the coil spring 35 to move to an axial end of the input shaft 2. Next, the action of the present embodiment will be explained. When a sprocket 10 is engaged into the engaging concave part 11 of the joint 1, the tapered head 21 of the tooth fixing portion 20 enters into the tooth groove 10b. In addition, because the joint 1 is forced to move in the direction of the sprocket 10 by the coil spring 35, the tapered head 21 is pushed to the tooth 10a of the sprocket 10. Then, because the surface of the tapered head 21 has inclination at an inclination angle α in a manner to cross with the center axis C of the output shaft 9 in the direction to engage the sprocket 10, the tapered head 21 comes into direct contact at any portion on the base side surface thereof with a part of the tooth portion 10a e.g., tooth bottom 10a, and is pushed densely at the portion to the latter. Moreover, as apparent from Fig. 3, as the tooth fixing portion 20 is provided at a distance of 120 degrees, the sprocket 10 is steadily fixed to and combined without clearance with the joint 1 at the three points. Thus, the input shaft 2 and the output shaft 9 are centered in coaxial manner, so that, even if the rotation of the sprocket 10 becomes irregular, it may be less likely for noise to be generated with the joint 1 and that noise at such combined part can be reduced. Also, as the tooth fixing portion 20 is formed into approximately a headed mushroom shape, it can be fitted in parallel with the output shaft 9, i.e., vertically to a rotary face of the joint 1, so that the fitting work may be facilitated. Moreover, in the case it is desired to vary the extent of tapering, the portion 20 can be readily replaced with another tapered head having the different inclination angle α . Furthermore, when this coupling structure or the coupling structure in the following embodiment is adopted in the firing apparatus, the sound of the engine 7 can be inspected without being interrupted by the noise at the coupling portion between the sprocket 10 and the joint 1. Fig. 4 is concerned with a second embodiment, being a view similar to Fig. 1 which shows a general structure of the sprocket 10 and the joint 1 to be used for the firing apparatus similar to the preceding embodiment. It is to be noted that the common figures apply to the portions having the common functions to the above embodiment, and the points of difference are mainly explained in the following paragraphs. The tooth fixing portion 20 in this embodiment is formed in the shape of a rod where axial line C1 extends at an inclination angle of Of to fix an end 40 to the bottom part 14. In this fixing structure, various known methods such as press fitting can be adopted. When such arrangement is adopted, though other free end 41 of the tooth fixing portion 20 has no tapered head, it is inclined to the center axis C to form a tapered construction, so that the joint 1 enters into the tooth groove 10b and is combined with the sprocket 10 without rattling. Consequently, the system gives the same effect as that of the previous embodiment with respect to the noise, and as the tooth fixing portion 20 is formed into a simple rod type, the configuration can be simplified. Fig. 5 and Fig. 6 relate to the third embodiment which is applicable to the firing apparatus similar to that of the previous embodiment. Fig. 5 is a view similar to Fig. 4, and Fig. 6 is a sectional view showing the portion corresponding to the part of line 6-6 in Fig. 5 (which shows the section of the whole apparatus) . In the tooth fixing portion 20 of this embodiment, a tapered wall 50 is formed integral with the inner surface 12 facing the engaging concave portion 11 at a distance of 120 degrees in the peripheral direction. This tapered wall 50 also has an inclination angle (X and forms a bottom part of a concave groove 51 to which one tooth portion engages with clearance at the entrance side. This concave groove 51 is provided on a swelling-out portion 52 which projects from the peripheral wall 12 into the engaging concave portion 11. Even if the entrance side of the concave groove 11 is wide enough to have clearance, the tip of the tooth part 10 which is entered into the concave groove 51 is in contact with the tapered wall potion 50 in pressed condition and it becomes possible to make coupling without rattling. When at least one of side walls 53 facing the concave groove 51 is made into a tapered form so as to make the width of the concave groove 51 gradually narrow in the direction of the bottom, more effective state can be obtained. The number of the concave grooves 51 is optional, provided that they are plural, and they may be provided by the number which correspond to the number of teeth 10a. According to this embodiment, a tapered wall 50 can be formed integral with the joint 1, so that the manufacture of the joint having tapered shape can be facilitated. It is to be noted that the present invention is not limited to the illustrated embodiments but may be applied in various modifications, and that the apparatus may be used any other apparatus which requires the sprocket to be coupled by engagement free of rattling. It is also possible to use, in place of the coil spring 35, other kind of elastic materials such as disc spring or rubber block. WE CLAIM: 1. A sprocket coupling device furnished with a cup-shaped joint having an engaging concave portion for engaging a sprocket of an engine output shaft, characterized in that a plurality of tapered tooth fixing portions of which surface are shaped to incline to an axial line of the sprocket, to be in close contact with tooth portions of the sprocket are provided in said engaging concave portion of said joint, at equal distance in the peripheral direction. 2. The sprocket coupling device according to claim 1, wherein each of said tooth fixing portions has a tapered head portion. 3. The sprocket coupling device according to claim 1, wherein said tooth fixing portion is formed in the shape of rod which is fitted to said joint and which has an inclined axial line with respect to a rotary axis of the sprocket. 4. The sprocket coupling device according to claim 1, wherein said tooth fixing portion is a taper-shaped wall integrally formed within said engaging concave portion of said joint. 5. The sprocket coupling device according to anyone of claims 1 to 4, wherein said joint is provided in an input shaft of a firing apparatus to be used for load test of the engine.

Documents:

054-mas-2000-abstract.pdf

054-mas-2000-claims filed.pdf

054-mas-2000-claims grand.pdf

054-mas-2000-correspondence others.pdf

054-mas-2000-correspondence po.pdf

054-mas-2000-description complete filed.pdf

054-mas-2000-description complete grand.pdf

054-mas-2000-drawings.pdf

054-mas-2000-form 1.pdf

054-mas-2000-form 19.pdf

054-mas-2000-form 26.pdf

054-mas-2000-form 3.pdf

054-mas-2000-form 5.pdf

054-mas-2000-other document.pdf