JP2005195041A - Power transmission mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power transmission mechanism capable of easily performing mounting of a timing belt and dramatically reducing a burden on an operator. <P>SOLUTION: In this power transmission mechanism, the timing belt 41 is bridged between a timing-belt pulley 31 provided for a crankshaft 15 and a timing-belt pulley 35 provided for a camshaft 23. Flanges 37, 38 shaped to have enlarged diameter are formed in both sides of a pulley main body 36 having external teeth 36a engaged with the timing belt 41 of the timing-belt pulley 35. Notch parts 39 for locking the timing belt 41 engaged with the external teeth 36a and guiding the timing belt 41 to a lateral direction are formed on the flange 37. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a power transmission mechanism, and more particularly to a power transmission mechanism in which a timing belt is stretched between a timing belt pulley provided on a driving side shaft and a timing belt pulley provided on a driven side shaft.

  For example, as a power transmission mechanism that transmits the rotation of the drive side shaft to the driven side shaft, there is a type that uses a timing belt called a toothed belt, a synchronous belt, or a cog belt. The timing belt has inner teeth integrally formed with the belt body at a constant pitch inside the endless belt body, and the timing belt is provided with the inner teeth on the drive shaft side shaft and the driven side shaft, respectively. The belt is stretched over while being engaged with the external teeth of the timing belt pulley.

  Such a power transmission mechanism including a timing belt and a timing belt pulley is also used for an OHC (overhead camshaft) engine. The OHC engine is an engine in which the camshaft of the intake / exhaust valve is arranged at the upper part of the cylinder head, and is a rocker arm type having a rocker arm provided between the camshaft and the valve, Alternatively, there is a direct acting type in which the intake / exhaust valve is directly driven by a camshaft.

  In an engine equipped with such a valve operating mechanism, the camshaft is configured to be driven by the crankshaft. For example, in order to transmit the rotation of the crankshaft to the camshaft, FIG. As shown in the side view of FIG. 9B, the timing belt 110 is interposed between the timing belt pulley 101 attached to the crankshaft of the driving side shaft and the timing belt pulley 105 attached to the camshaft of the driven side shaft. Is over.

  The timing belt pulley 101 is integrally formed with flanges 103 and 104 having enlarged diameters on both sides of a pulley body 102 on which external teeth 102a are formed at a constant pitch. Similarly, the timing belt pulley 105 has external teeth 106a at a constant pitch. Expanded flanges 107 and 108 are integrally formed on both sides of the formed pulley body 106. On the other hand, in the timing belt 110, a large number of internal teeth 112 called cog portions are integrally formed at an equal pitch inside an endless belt body 111 formed in a loop shape, and extends in the width direction of the timing belt 110. A tooth groove 113 that meshes with the external teeth 102a and 106a of the timing belt pulleys 101 and 105 is formed between the internal teeth 112 (see, for example, Patent Document 1).

  Further, the belt main body 111 and the respective internal teeth 112 of the timing belt 110 are integrally formed of rubber such as acrylonitrile butadiene rubber (NBR), and the belt main body 111 includes a plurality of glass fibers or the like in the longitudinal direction. A core of the book is embedded, and a cloth layer made of polyamide or the like is laminated on the inner surface of the timing belt 110. Further, a resin-made reinforcing liner is embedded inside the cloth layer of each tooth groove 113 portion that meshes with the external teeth 102a and 106a of the timing belt pulleys 101 and 105. The load at the time of meshing with the external teeth 102a and 106a of the timing belt pulleys 101 and 105 is distributed to the internal teeth 112 and the belt main body 111 by these reinforcing liners, and the tooth profile of the internal teeth 112 is maintained over a long period of time. Is ensured and the life of the timing belt 110 under severe use conditions is extended to improve durability (see, for example, Patent Document 2).

JP 10-89444 A JP-A-11-190398

  Timing belt pulley 101 in which flanges 103 and 104 are integrally formed on both sides of pulley body 102 on which external teeth 102a are formed, and flanges 107 and 108 are integrally formed on both sides of pulley body 106 in which external teeth 106a are formed. The operation of laying and attaching the timing belt 110 between the timing belt pulley 105 and the timing belt pulley 105 involves engaging the tooth groove 113 of the timing belt 110 with the external teeth 102a formed between the flanges 103 and 104 of one timing belt pulley 101. In the combined state, the timing belt 110 is stretched while overcoming the flange 107 or 108 of the other timing belt pulley 105 and engaging the tooth groove 113 between the inner teeth 112 with the outer teeth 106a. However, since the timing belt 110 is extremely restrained from being stretched by a plurality of core wires embedded along the longitudinal direction of the belt main body 111, the installation work requires the skill and burden of the operator.

  Accordingly, an object of the present invention made in view of such a point is to provide a power transmission mechanism in which a timing belt can be easily mounted in a power transmission mechanism using a timing belt, and the burden on an operator can be greatly reduced.

  The invention of the power transmission mechanism according to claim 1, which achieves the above object, includes a timing between a driving side timing belt pulley provided on the driving side shaft and a driven side timing belt pulley provided on the driven side shaft. In the power transmission mechanism over which the belt is stretched, one of the timing belt pulleys is formed with an enlarged flange on one side of the pulley body having external teeth with which the timing belt engages, and faces the flange. The timing belt is locked to the other side of the pulley body, and one side of the timing belt is held in engagement with the external teeth from the locking portion, and the other side of the timing belt is connected to the timing from the locking portion. It has a belt guide that guides to the side of the belt pulley, and the other timing belt pulley has external teeth that engage with the timing belt. Characterized in that each expanded shaped flange on either side of the pulley body is formed.

  According to a second aspect of the present invention, in the power transmission mechanism according to the first aspect, the belt guide portion is a notch that is recessed along the outer peripheral edge of an enlarged-diameter flange formed on the other side of the pulley body. It is a part.

  According to a third aspect of the present invention, in the power transmission mechanism of the second aspect, along the notch, the other side of the timing belt guided from the notch to the side of the timing belt pulley is connected to the periphery of the timing belt pulley. A belt guiding portion for guiding in a direction is formed.

  According to a fourth aspect of the present invention, in the power transmission mechanism of the first aspect, the belt guide portion is a belt locking member that protrudes on the other side of the pulley body so as to face the flange. And

  According to the first aspect of the present invention, when the timing belt is mounted, the timing belt is locked to the belt guide portion provided on one timing belt pulley while the timing belt is wound around the other timing belt pulley. Enhancing the timing belt by engaging one side of the belt with external teeth and guiding the other side of the timing belt to the side of the timing belt pulley and rotating one timing belt pulley in that state With no or very little stretching, the timing belt can be completely stretched over and mounted on both timing belt pulleys, and the timing belt can be easily attached and the burden on the operator can be greatly reduced.

  According to the invention of claim 2, the belt guide portion can be easily formed by forming the notch portion in the flange of the timing belt pulley. As a result, the timing belt can be locked to the end of the notch, and one of the timing belts can be engaged with the external teeth between the flanges, and the other of the timing belt can be guided from the notch to the side of the timing belt pulley. The mounting workability can be further improved.

  According to the invention of claim 3, the timing belt guided to the side of the timing belt pulley from the notch is guided in the circumferential direction, that is, the rotational direction of the timing belt pulley by the belt guiding portion. Thereby, the bending of the timing belt when the timing belt is attached and detached is suppressed, and damage to the timing belt can be avoided.

  According to the invention of claim 4, the belt guide portion can be formed by projecting the belt locking member on the pulley body, and in contrast to the inventions of claim 2 and claim 3, the tooth of the timing belt can be obtained by omitting the flange. The groove can be engaged with the external teeth from the side of the timing belt pulley, so that the timing belt can be easily attached and detached.

  Embodiments of a power transmission mechanism according to the present invention will be described below with reference to the drawings, taking an engine as an example.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing an outline of an OHC engine 1 having a power transmission mechanism, and FIG. 2 is a cross-sectional view taken along the line II of FIG.

  The engine 1 is a general-purpose air-cooled engine. A cylinder part 11 is provided in a cylinder case 12, and a piston 13 is reciprocally mounted in a cylinder bore formed in the cylinder part 11. A crankcase 14 is coupled to the lower portion of the cylinder case 12. A crankshaft 15 rotatably attached to a joint portion between the cylinder case 12 and the crankcase 14 via a bearing 15 a is connected to the piston 13 via a connecting rod 16, and the crankshaft 15 is reciprocated by the piston 13. Is driven to rotate. A flywheel 17 for smooth rotation is attached to the end of the crankshaft 15.

  The cylinder portion 11 is provided with an intake valve 19 for opening and closing the intake port 18, an exhaust valve (none of which is shown) for opening and closing the exhaust port, and a spark plug 20. A carburetor 21 for supplying air-fuel mixture into the cylinder bore via the intake port 18 is attached to the cylinder case 12, and a muffler 22 for silencing exhaust gas from an exhaust port (not shown) and discharging it to the outside is provided in the cylinder case. 12 is attached to the opposite side.

  A camshaft 23 having a cam 24 that opens and closes an intake valve 19 and an exhaust valve is arranged in parallel with the crankshaft 15 and is rotatably provided on the upper part of the cylinder case 12. The cam of the cam 24 attached to the camshaft 23 A rocker arm 26 that contacts the surface and swings around the rocker shaft 25 is connected to the intake valve 19. The opening / closing operation of the exhaust valve is performed by a rocker arm 27 attached to the camshaft 23 out of phase with the cam 24. A head cover 28 is detachably provided on the upper portion of the cylinder case 12 so as to cover the rocker arms 26 and 27 and the like.

  The power transmission mechanism that transmits the rotation of the crankshaft 15 to the camshaft 23 uses the crankshaft 15 as a driving side shaft to drive the camshaft 23 of the driven side shaft by the rotation thereof, so that the driving side timing belt pulley is connected to the crankshaft 15. 31 is attached, a timing belt pulley 35 on the driven side of the camshaft 23 is attached, and a timing belt 41 is stretched between the timing belt pulleys 31 and 35.

  The drive-side timing belt pulley 31 attached to the crankshaft 15 is formed by integrally forming enlarged flanges 33 and 34 on both sides of a disk-shaped pulley body 32 having a large number of external teeth 32a formed at a constant pitch. Yes. A timing mark M, which serves as a positioning mark when the timing belt 41 is mounted on one flange 33, is attached by stamping or the like.

  On the other hand, the driven timing belt pulley 35 attached to the camshaft 23 is larger in diameter than the timing belt pulley 31 as shown in the top view in FIG. 3A and in the front view in FIG. An enlarged flange 37 is formed on one side of the disk-shaped pulley body 36 in which the external teeth 36a are formed at a constant pitch, and the flange 38 is integrally formed on the other side facing the flange 37 of the pulley body 36. Is formed. A notch 39 serving as a belt guide portion is formed in a notch along the outer peripheral edge of the flange 37 on the side opposite to the cam 24 to expose the side end of the external tooth 36a. The notch 39 recessed along the outer peripheral edge of the flange 37 has a width L where, for example, three to four external teeth 36a are exposed, and the position of one end 39a is when the timing belt 41 is mounted. The end 39a has a function as a timing mark.

  The timing belt 41 fitted between the flanges 33 and 35 facing the timing belt pulley 31 and the flanges 37 and 38 facing the timing belt pulley 35 is an endless belt body having a loop shape. A large number of internal teeth 43 are integrally formed at an equal pitch inside 42, and tooth grooves 44 that mesh with the external teeth 32 a and 36 a of the timing belt pulleys 31 and 35 are formed between the internal teeth 43 extending in the width direction of the timing belt 41. Has been. Further, timing marks ma and mb (not shown) for aligning the timing mark M attached to the timing belt pulley 31 on the belt main body 42 of the timing belt 41 and the end 39a of the notch 39 of the timing belt pulley 35. Is attached.

  Next, the mounting operation of the timing belt 41 for mounting the timing belt 41 between the timing belt pulleys 31 and 35 configured as described above will be described with reference to FIGS.

  When the timing belt 41 is mounted, as shown in FIG. 4A and a front view in FIG. 4A and FIG. 4B, the timing mark ma attached to the timing belt 41 is set to the timing belt pulley 31 on the driving side. The timing belt 41 is wound around the timing belt pulley 31 in accordance with the timing mark M attached to the flange 33 and the tooth groove 44 of the timing belt 41 is engaged with the external teeth 32a. While maintaining the state where the tooth groove 44 and the external tooth 32a are engaged, the timing mark mb attached to the timing belt 41 is aligned with the end 39a of the notch 39 formed in the timing belt pulley 35 on the driven side. The timing belt 41 is wound around the timing belt pulley 35 via the notch 39, and the timing belt 41 is locked to the end 39a. Then, the portion of the timing belt 41 on the timing belt pulley 31 side, which is one side of the timing belt 41 from the locking portion locked to the end 39a, is fitted between the flanges 37 and 38, and The tooth groove 44 is engaged and held with the external tooth 36a. In this state, the portion of the timing belt 41 that is not engaged with the timing belt pulley 35 on the other side of the engaging portion that is engaged with the end portion 39 a of the notch 39 is bent to the outside of the timing belt pulley 35. It will be in the state induced | guided | derived to the outward of the flange 37 from the notch 39.

  The timing belt 41 is stretched by winding the timing belt 41 around the timing belt pulley 35 from the notch 39 of the timing belt pulley 35, so that the portion of the timing belt 41 that is guided outward from the flange 37 is bent. This can be easily performed without applying tension, i.e., stretching, to the belt 41 or with very little stretching.

  As shown in FIG. 4, the operator rotates the timing belt pulley 35 as shown by the arrow F from the state where the timing belt 41 is stretched over the timing belt pulleys 31 and 35. As shown in (b), the inner teeth 43 of the timing belt 41 engaged with the outer teeth 36 a of the timing belt pulley 35 are pulled, and the timing belt 41 rotates together with the timing belt pulley 31. At this time, the external teeth 36 a of the timing belt pulley 35 and the tooth groove 44 of the timing belt 41 that are engaged with each other gradually increase, and the timing belt 41 is wound around the timing belt pulley 35.

  Further, by continuously rotating the timing belt pulley 35 in the direction of arrow F, the timing belt 41 is completely wound around the timing belt pulleys 31 and 35 as shown in FIGS. 6 (a) and 6 (b). The installation work of the timing belt 41 is completed.

  Therefore, the mounting operation for passing the timing belt 41 between the timing belt pulleys 31 and 35 is performed on the external teeth 32a and 36a of the timing belt pulleys 31 and 35 without the timing belt 41 getting over the flanges 37 and 38 of the timing belt pulley 35. The tooth groove 44 can be engaged, the application of stretching to the timing belt 41 is extremely reduced, the work is facilitated, and the work load on the operator can be greatly reduced.

  Further, the operation of removing the timing belt 41 that is stretched over the timing belt pulleys 31 and 35 is a part of the timing belt 41 in the state where the timing belt 41 shown in FIGS. 6A and 6B is attached. 5 is pulled out from the cutout portion 39 and locked to the other edge 39b of the cutout portion 39, and the timing belt pulley 35 is rotated in the reverse direction, that is, in the direction of the arrow R, as shown in FIG. 5B, 4A, and 4B, the timing belt 41 can be easily detached from the timing belt pulleys 31 and 35, and the timing belt 41 can be easily attached and detached. As a result, the work burden on the worker can be greatly reduced.

  Furthermore, since the belt guide part is formed by the notch part 39 recessed in the flange 37, the belt guide part can be easily formed with a simple configuration and without greatly changing the existing timing belt pulley.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIG. The present embodiment is different from the first embodiment in that the shape of the timing belt pulley on the driven side is different and the other configurations are the same. Therefore, this portion will be mainly described.

  FIGS. 7A, 7B, and 7C are explanatory diagrams in the present embodiment corresponding to FIGS. 3A, 5A, and 5B, respectively. In addition, the detailed description of this part is abbreviate | omitted by attaching | subjecting the same code | symbol to a corresponding site | part.

  The timing belt pulley 45 on the driven side is the same as the timing belt pulley 31 in the first embodiment, further from the bottom edge of the notch 39 in the circumferential direction, that is, the end 39a side of the notch 39 along the rotation direction of the timing belt pulley 45. The belt guiding portion 46 is formed by a substantially triangular bottom 47 that gradually protrudes in the axial direction as it moves from the edge 39b toward the end 39b, and a side portion 48 that continues to the flange 37 along the edge of the bottom 47 and rises in the outer circumferential direction. Integrally formed.

  In addition to the first embodiment, the portion of the timing belt 41 guided outward from the notch 39 by the belt guiding portion 46 is guided and held in the circumferential direction, that is, the rotational direction of the timing belt pulley 45, When the timing belt 41 is attached or detached, the timing belt 41 can be prevented from being bent when the timing belt 41 is attached or detached, or the bending can be suppressed and damage to the timing belt 41 can be avoided.

(Third embodiment)
A third embodiment of the present invention will be described with reference to FIG. The present embodiment is different from the first embodiment in that the shape of the timing belt pulley on the driven side is different and the other configurations are the same. Therefore, this portion will be mainly described.

  FIGS. 8A, 8B, and 8C are explanatory diagrams in the present embodiment corresponding to FIGS. 3A, 5A, and 5B, respectively. In addition, the detailed description of this part is abbreviate | omitted by attaching | subjecting the same code | symbol to a corresponding site | part.

  In the timing belt pulley 50, one flange 37 of the timing belt pulley 35 in the first embodiment is omitted, and instead of the flange 37, the side surface of the pulley body 36, that is, the other side, is opposed to the flange 38 in the radial direction. A belt guide member is formed by attaching a belt locking member 51 formed of a projecting sheet metal band member with a bolt 52 or the like.

  When the timing belt 41 is attached to the timing belt pulley 50, the tooth belt 44 of the timing belt 41 is engaged with the external teeth 32a and the timing belt 41 is wound around the timing belt pulley 31 as in the first embodiment. . In this state, the timing belt 41 is locked to the belt locking member 51 of the timing belt pulley 50, and the timing belt 41 portion on the timing belt pulley 31 side that is one side of the timing belt 41 from the locking portion. The tooth groove 44 is engaged with and held by the external teeth 36a, and the portion on the other side of the engagement portion by the belt engagement member 51 is bent outward of the timing belt pulley 50 and guided outward. Then, as indicated by an arrow F, when the operator rotates the timing belt pulley 50, the internal teeth 43 of the timing belt 41 that engages with the external teeth 36 a of the timing belt pulley 50 are pulled, and together with the timing belt pulley 31. The timing belt 41 rotates. At this time, the external teeth 36 a of the timing pulley 50 and the tooth grooves 44 of the timing belt 41 that are engaged with each other gradually increase, and the timing belt 41 is wound around the timing belt pulley 50.

  The timing belt 41 is stretched by locking the timing belt 41 to the belt locking member 51 and locking the tooth groove 44 to the external teeth 36a from the side of the timing belt pulley 50. Stretching is extremely reduced, the work is facilitated, and the work burden on the operator can be greatly reduced.

  In this embodiment, by omitting the flange 37, the tooth groove 44 of the timing belt 41 can be easily locked to the external teeth 36a of the timing belt pulley 50 and can be easily removed. Efficiency improvement can be obtained.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the invention. For example, in the third embodiment, the belt locking member 51 is coupled to the pulley main body 36 by the bolt 52, but the belt locking member 51 may be integrally formed with the pulley main body 36.

  In the above embodiment, the belt guide portion is formed on the timing belt pulley provided on the driven side shaft. However, the belt guide portion may be formed on the timing belt pulley provided on the driving side shaft.

  Further, in each of the above embodiments, the case where the present invention is applied to an engine has been described as an example. However, a timing belt is stretched between a timing belt pulley provided on the driving side shaft and a timing belt pulley provided on the driven side shaft. It can be applied to other power transmission mechanisms.

1 is a cross-sectional view illustrating an outline of an OHC engine having a power transmission mechanism according to a first embodiment of the present invention. It is the II sectional view taken on the line of FIG. It is explanatory drawing of a timing belt pulley by the side of the same, (a) is a top view, (b) is a front view. It is a figure explaining a timing belt mounting | wearing operation | work similarly, (a) is a top view, (b) is a front view. It is a figure explaining a timing belt mounting | wearing operation | work similarly, (a) is a top view, (b) is a front view. It is a figure explaining a timing belt mounting | wearing operation | work similarly, (a) is a top view, (b) is a front view. It is a figure explaining a timing belt pulley and a timing belt mounting operation according to the second embodiment of the present invention, (a) is a top view of the timing belt pulley, (b) is a top view during the timing belt mounting operation, (C) is a front view at the time of timing belt mounting work. It is a figure explaining a timing belt pulley and a timing belt mounting work according to a third embodiment of the present invention, (a) is a top view of the timing belt pulley, (b) is a top view at the time of timing belt mounting work, (C) is a front view at the time of timing belt mounting work. (A) is a front view of a power transmission mechanism using a timing belt, and (b) is a side view of the power transmission mechanism using a timing belt.

Explanation of symbols

15 Crankshaft (drive side shaft)
23 Camshaft (driven shaft)
31 Timing belt pulley 32 Pulley body 32a External teeth 33 Flange 34 Flange 35 Timing belt pulley 36 Pulley body 36a External teeth 37 Flange 38 Flange 39 Notch (belt guide portion)
39a End 41 Timing belt 42 Belt body 43 Internal teeth 44 Tooth groove 45 Timing belt pulley 46 Belt guide 47 Bottom 48 Side 50 Timing belt pulley 51 Belt locking member (belt guide)

Claims (4)

In a power transmission mechanism in which a timing belt is stretched between a driving side timing belt pulley provided on a driving side shaft and a driven side timing belt pulley provided on a driven side shaft,
One of the timing belt pulleys
An enlarged-diameter flange is formed on one side of the pulley body having external teeth with which the timing belt is engaged,
The timing belt is locked to the other side of the pulley body facing the flange, and the timing belt is held in a state where one side of the timing belt is engaged with the external teeth from the locking portion, and the timing belt is A belt guide for guiding the other side to the side of the timing belt pulley;
The other timing belt pulley is
A power transmission mechanism, wherein flanges having an enlarged diameter are formed on both sides of a pulley body having external teeth with which the timing belt is engaged. The belt guide part
The power transmission mechanism according to claim 1, wherein the power transmission mechanism is a notch that is recessed along an outer peripheral edge of an enlarged-diameter flange formed on the other side of the pulley body.   The belt guide portion for guiding the other side of the timing belt guided from the notch to the side of the timing belt pulley in the circumferential direction of the timing belt pulley is formed along the notch. 2. The power transmission mechanism according to 2. The belt guide part
The power transmission mechanism according to claim 1, wherein the power transmission mechanism is a belt locking member projecting on the other side of the pulley body so as to face the flange.

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