JP2021124161A - Chain tensioner - Google Patents

Abstract

To shorten the whole length while maintaining preferable spring characteristics across the whole stroke range by ensuring a stroke of a plunger.SOLUTION: A chain tensioner (30) includes: a tensioner body (31) formed with a cylindrical space (36) extending between one end opening (34) and the other end opening (35); a plunger (41) accommodated in the cylindrical space so as to project from one end opening; a bolt (51) fixed to the tensioner body so as to block the other end opening; and a spring (61) for causing a spring force to act on the plunger in a pressing direction. The bolt is formed with an accommodation space (52) which the plunger enters. The spring is installed in the accommodation space.SELECTED DRAWING: Figure 3

Description

The present invention relates to a chain tensioner.

A ratchet type chain tensioner that holds the tension of the cam chain of an engine is known (see, for example, Patent Document 1). A tubular through hole is formed in the tensioner body of the chain tensioner described in Patent Document 1, and one end of the through hole is closed by a bolt. A coil spring and a plunger are housed in the through hole, and the plunger is pushed out from the other end of the through hole by the coil spring. Ratchet teeth are formed on the outer peripheral surface of the plunger, and ratchet claws are provided on the tensioner body so as to be swingable. With the tip of the plunger pressed against the cam chain, the ratchet teeth and ratchet claws regulate the push back of the plunger by the cam chain.

Jikkensho 59-036768 Gazette

By the way, the plunger needs a stroke that can loosen the cam chain when the cam chain is attached and detached, and the coil spring needs a spring length that can obtain good spring characteristics over the entire stroke of the plunger. .. In the chain tensioner described in Patent Document 1, since the plunger, the coil spring, and the bolt are linearly arranged, the total length of the chain tensioner becomes long if the stroke of the plunger and the spring length of the coil spring are sufficiently secured. Therefore, there is a problem that the vehicle becomes large in order to avoid interference between the chain tensioner and peripheral parts.

The present invention has been made in view of this point, and an object of the present invention is to provide a chain tensioner capable of shortening the total length while ensuring the stroke of the plunger and maintaining good spring characteristics over the entire stroke. And.

The chain tensioner according to one aspect of the present invention includes a tensioner body in which a tubular space extending from an opening at one end to an opening at the other end is formed, and a plunger housed in the tubular space so as to project from the opening at one end. A bolt fixed to the tensioner body so as to close the opening at the other end, and a spring that exerts a spring force on the plunger in the pushing direction, and the bolt has a storage space for the plunger to enter. The above problem is solved by being formed and the spring being installed in the accommodation space.

According to the chain tensioner of one aspect of the present invention, the tension of the chain is maintained by pressing the plunger against the chain by the spring force of the spring. Further, when the plunger enters the bolt accommodation space, the stroke of the plunger is secured while the total length of the chain tensioner is shortened. Further, by installing the spring in the accommodation space, the spring length required to obtain good spring characteristics over the entire stroke of the plunger is secured while the overall length of the chain tensioner is shortened. By shortening the total length of the chain tensioner, it is possible to suppress interference between the chain tensioner and peripheral parts.

It is a vertical sectional view of the engine of this embodiment. It is sectional drawing of the chain tensioner of this Example. It is an exploded sectional view of the chain tensioner of this Example. It is a figure which shows the tension adjustment of the cam chain of the comparative example. It is a figure which shows the tension adjustment of the cam chain of this Example. It is a schematic diagram of the expansion and contraction mechanism of another embodiment.

The chain tensioner according to one aspect of the present invention includes a tensioner body in which a tubular space extending from an opening at one end to an opening at the other end is formed. A plunger is housed in the tubular space of the tensioner body, and the plunger protrudes from an opening at one end of the tensioner body. A bolt is fixed to the tensioner body, and the bolt closes the opening at the other end of the tensioner body. A storage space for the plunger to enter is formed in the bolt, and a spring that exerts a spring force on the plunger in the pushing direction is installed in the storage space. The tension of the chain is maintained by pressing the plunger against the chain by the spring force of the spring. Further, when the plunger enters the bolt accommodation space, the stroke of the plunger is secured while the total length of the chain tensioner is shortened. Further, by installing the spring in the accommodation space, the spring length required to obtain good spring characteristics over the entire stroke of the plunger is secured while the overall length of the chain tensioner is shortened. By shortening the total length of the chain tensioner, it is possible to suppress interference between the chain tensioner and peripheral parts.

Hereinafter, this embodiment will be described in detail with reference to the accompanying drawings. In the following description, a chain tensioner that adjusts the tension of the cam chain that transmits the rotation of the crankshaft of the engine to the cam shaft will be described. However, the chain tensioner of this embodiment can be applied to other chains such as a chain that transmits the rotation of the crankshaft to an auxiliary machine such as an oil pump. FIG. 1 is a vertical cross-sectional view of the engine of this embodiment.

As shown in FIG. 1, the engine 10 is a multi-cylinder engine of a motorcycle in which a cylinder block 12 is installed above a crankcase 11. A cylinder head 13 is attached to the upper part of the cylinder block 12, and a head cover 14 is attached to the upper part of the cylinder head 13. A crankshaft 15 is supported on the crankcase 11, and a drive sprocket 16 is attached to the crankshaft 15. A cap 18 is attached to the journal wall 17 of the cylinder head 13, and a camshaft 19 is supported by the journal wall 17 and the cap 18. A driven sprocket 21 is attached to the camshaft 19.

The crankshaft 15 and the camshaft 19 extend in parallel, and the cam chain 22 is wound around the drive sprocket 16 and the driven sprocket 21. A chain transmission mechanism is formed by the drive sprocket 16, the driven sprocket 21, and the cam chain 22. The rotation of the crankshaft 15 is decelerated and transmitted to the camshaft 19 via this chain transmission mechanism. Inside the crankcase 11, the cylinder block 12, and the cylinder head 13, chain guides 23 and 24 are provided between the drive sprocket 16 and the driven sprocket 21 to guide the orbital movement of the cam chain 22.

The chain guide 23 is formed with a guide surface having a linear side view, and the cam chain 22 drawn from the driven sprocket 21 into the drive sprocket 16 is guided by the chain guide 23. A side view arch-shaped guide surface is formed on the chain guide 24, and the cam chain 22 sent from the drive sprocket 16 to the driven sprocket 21 is guided by the chain guide 24. Since the cam chain 22 from the driving sprocket 16 to the driven sprocket 21 is slackened, the chain guide 24 is pressed against the cam chain 22 by the chain tensioner 30 so that the tension of the cam chain 22 is maintained.

By the way, various parts are installed inside the engine 10, and it is difficult to secure a sufficient installation space for the chain tensioner 30. It is preferable to take a long stroke of the chain tensioner 30, but when the stroke of the chain tensioner 30 becomes long, the total length of the chain tensioner 30 becomes long. Therefore, if the chain tensioner 30 is installed in a narrow installation space, the chain tensioner 30 may interfere with peripheral parts. Further, if the chain tensioner 30 is miniaturized by using a short spring, the spring constant of the spring becomes high, and it is difficult to obtain good spring characteristics over the entire stroke.

Therefore, in the chain tensioner 30 of the present embodiment, the plunger 41 is inserted into the bolt 51 that closes the hollow tensioner body 31, so that the stroke of the plunger 41 is secured in a state where the total length of the chain tensioner 30 is shortened (). (See FIG. 2). Further, the chain tensioner 30 uses a combination spring 61 in which the large-diameter spring 62 and the small-diameter spring 63 partially overlap each other (see FIG. 2). Due to the large-diameter spring 62 and the small-diameter spring 63, good spring characteristics are obtained over the entire stroke of the plunger 41 in a state where the total length of the chain tensioner 30 is shortened.

The chain tensioner will be described with reference to FIGS. 2 and 3. FIG. 2 is a cross-sectional view of the chain tensioner of this embodiment. FIG. 3 is an exploded cross-sectional view of the chain tensioner of this embodiment. Note that FIG. 2 shows a state in which the chain tensioner is contracted.

As shown in FIGS. 2 and 3, the tensioner body 31 of the chain tensioner 30 has a hollow tubular portion 32 that enters the inside of the cylinder block 12 and a flange portion 33 that is fixed to the outer surface of the cylinder block 12. ing. The tubular portion 32 is formed with a tubular space 36 extending on the axis C from the opening 34 at one end to the opening 35 at the other end, and the flange portion 33 has a female screw hole 37 having a diameter larger than that of the tubular space 36. Is formed. The tubular space 36 and the female screw hole 37 are aligned coaxially and communicate with each other through the opening 35 at the other end of the tensioner body 31. In this way, the tensioner body 31 has a hole along the axis C penetrated by the tubular space 36 and the female screw hole 37.

A cylindrical plunger 41 is housed in the tubular space 36 of the tensioner body 31 so as to be able to advance and retreat. The tip of the plunger 41 projects from the opening 34 at one end to the inside of the cylinder block 12, and the base end of the plunger 41 protrudes from the opening 35 at the other end into the female screw hole 37. A cap 42 that comes into contact with the chain guide 24 (see FIG. 1) is attached to the tip of the plunger 41, and a small diameter space 43 is formed at the base end of the plunger 41. Further, a part of the outer peripheral surface of the plunger 41 is recessed along the advancing / retreating direction, and a large number of ratchet teeth 45 arranged in the advancing / retreating direction are formed on the bottom surface of the recess.

A bolt 51 through which a washer 53 is inserted is fixed to the female screw hole 37 of the tensioner body 31 so as to close the opening 35 at the other end. A large-diameter space (accommodation space) 52 is formed from the tip of the bolt 51 toward the head. The large-diameter space 52 of the bolt 51 is formed to have a larger diameter than the base end portion of the plunger 41, and the total length of the chain tensioner 30 is shortened by inserting the base end portion of the plunger 41 into the large-diameter space 52. Further, the small diameter space 43 of the plunger 41 communicates with the large diameter space 52 of the bolt 51, and a combination spring 61 that exerts a spring force on the plunger 41 in the pushing direction is installed in the large diameter space 52 and the small diameter space 43. Has been done.

The combination spring 61 connects the large-diameter spring 62 installed in the large-diameter space 52 of the bolt 51, the small-diameter spring 63 installed in the small-diameter space 43 of the plunger 41, and the large-diameter spring 62 and the small-diameter spring 63 in series. It has a connecting member 64. The inner diameter of the large-diameter spring 62 is formed to be larger than the outer diameter of the small-diameter spring 63, and the free length of the large-diameter spring 62 is formed to be shorter than the free length of the small-diameter spring 63. The wire diameter, coil diameter, and number of turns are adjusted so that the large-diameter spring 62 and the small-diameter spring 63 have the same spring constant. It should be noted that the same spring constant includes a case where there is an error that can be regarded as substantially the same.

The connecting member 64 is formed in a cross-sectional view hat shape, and has a bottomed cylinder portion 65 that enters the inside of the large-diameter spring 62 and a flange portion 66 that extends radially outward from the bottomed cylinder portion 65. .. The outer diameter of the bottomed cylinder portion 65 is formed according to the inner diameter of the large-diameter spring 62, and the inner diameter of the bottomed cylinder portion 65 is formed according to the outer diameter of the base end portion of the plunger 41. A large-diameter spring 62 is installed on the outside of the bottomed tubular portion 65, and the end portion of the large-diameter spring 62 is in contact with the flange portion 66. A small-diameter spring 63 is inserted together with the plunger 41 inside the bottomed cylinder portion 65, and the end portion of the small-diameter spring 63 is in contact with the bottom portion of the bottomed cylinder portion 65.

The large-diameter spring 62 and the small-diameter spring 63 are integrated by the connecting member 64 in a state where a part of the small-diameter spring 63 is inserted inside the large-diameter spring 62. By connecting the small-diameter spring 63 in series with the large-diameter spring 62 in a partially overlapped state, even if the combined spring 61 is installed in a narrow installation space consisting of the large-diameter space 52 and the small-diameter space 43, it can withstand the load. A sufficient amount of spring displacement can be secured. The large-diameter spring 62 and the small-diameter spring 63 are integrally expanded and contracted via the connecting member 64, and good spring characteristics can be obtained over the entire stroke of the plunger 41.

A ratchet claw 38 is swingably supported on the tubular portion 32 of the tensioner body 31. Further, the tensioner body 31 is provided with a spring 39, and the ratchet claw 38 is pulled counterclockwise by the spring 39. In the chain tensioner 30, a ratchet mechanism is formed by meshing the ratchet claw 38 of the tensioner body 31 and the ratchet teeth 45 of the plunger 41. The forward movement of the plunger 41 is permitted when the ratchet claw 38 gets over the ratchet tooth 45, and the backward movement of the plunger 41 is regulated by the engagement between the ratchet claw 38 and the ratchet tooth 45.

When assembling the chain tensioner 30 like this, the tensioner body 31 into which the plunger 41 is inserted is attached to the cylinder block 12. The cap 42 of the plunger 41 is in contact with the chain guide 24 (see FIG. 1), and the chain guide 24 is in contact with the cam chain 22. At this time, the tip end portion of the plunger 41 protrudes from the opening 34 at one end, and the base end portion of the plunger 41 protrudes from the opening 35 at the other end. A small-diameter spring 63 is installed in the small-diameter space 43 at the base end of the plunger 41, and the bottomed tubular portion 65 of the connecting member 64 is placed on the small-diameter spring 63 protruding from the plunger 41.

A large-diameter spring 62 is attached to the outside of the bottomed tubular portion 65, and a bolt 51 is screwed to the flange portion 33 of the tensioner body 31 via a washer 53. The large-diameter spring 62 and the small-diameter spring 63 are compressed by screwing the bolt 51, and the plunger 41 is pushed out by the spring force of the large-diameter spring 62 and the small-diameter spring 63. The plunger 41 strongly presses the chain guide 24 (see FIG. 1) against the cam chain 22 to maintain the tension of the cam chain 22. At this time, the meshing of the ratchet claw 38 and the ratchet tooth 45 regulates the backward movement of the plunger 41 due to the pushback of the cam chain 22.

Subsequently, the tension adjustment of the cam chain by the chain tensioner will be described with reference to FIGS. 4 and 5. FIG. 4 is a diagram showing tension adjustment of a cam chain of a comparative example. FIG. 5 is a diagram showing tension adjustment of the cam chain of this embodiment. 4 (A) and 5 (A) show the state before tightening the bolt, and FIGS. 4 (B) and 5 (B) show the state after tightening the bolt.

As shown in the comparative example of FIG. 4A, in the chain tensioner 70 of the comparative example, a tubular space 74 extending on the axis C is formed in the tensioner body 71 from the opening 72 at one end to the opening 73 at the other end. .. The tip of the plunger 76 protrudes from the opening 72 at one end, and a cap 77 that comes into contact with the chain guide 24 (see FIG. 1) is attached to the tip of the plunger 76. The opening 73 side at the other end has a female screw hole, and the bolt 79 through which the washer 78 is inserted is attached to the opening 73 at the other end. Spaces 81 and 82 are formed at the base end of the plunger 76 and the shaft of the bolt 79, respectively, and a long spring 83 is installed inside the spaces 81 and 82, respectively.

The chain tensioner 70 of the comparative example also has a ratchet mechanism similar to that of the chain tensioner 30 of the present embodiment. A ratchet claw 86 pulled counterclockwise by a spring 84 is swingably supported on the tensioner body 71. The ratchet claw 86 of the tensioner body 71 meshes with the ratchet teeth 87 on the outer peripheral surface of the plunger 76, and the retracting movement of the plunger 76 is restricted by the meshing of the ratchet claw 86 and the ratchet teeth 87. As described above, the chain tensioner 70 of the comparative example is different from the chain tensioner 30 of the present embodiment in that a long spring 83 is mainly interposed between the bolt 79 and the plunger 76.

In this initial state, the long spring 83 is not sufficiently compressed by the bolt 79. Therefore, the plunger 76 is not strongly pushed by the spring 83, the plunger 76 is retracted from the chain guide 24, and the cam chain 22 (see FIG. 1) is detachably loosened. The plunger 76 must have a sufficient stroke to loosen the cam chain 22, and a long spring 83 is used to obtain good spring characteristics over the entire stroke of the plunger 76. Therefore, the plunger 76, the spring 83, and the bolt 79 are arranged on the axis C, so that the total length of the chain tensioner 70 is increased.

As shown in FIG. 4B, when the bolt 79 is tightened into the female screw hole of the tensioner body 71, the long spring 83 contracts and the plunger 76 is pushed out by the spring force of the spring 83. In the chain tensioner 70 of the comparative example, the bolt 79 and the plunger 76 are separated from each other, and a long spring 83 is used. Although the stroke of the plunger 76 can be secured and good spring characteristics can be obtained over the entire stroke of the plunger 76, the total length L1 of the chain tensioner 70 from the head of the bolt 79 to the tip of the cap 77 is long. Therefore, the vehicle becomes large in order to avoid interference between the chain tensioner 70 and peripheral parts.

As shown in this embodiment of FIG. 5A, in the initial state, the large-diameter spring 62 and the small-diameter spring 63 are not sufficiently compressed by the bolt 51, and the plunger 41 is moved from the chain guide 24 (see FIG. 1). The cam chain 22 is retracted and loosened so that it can be attached and detached. A large-diameter space 52 into which the plunger 41 enters is formed in the bolt 51, and the stroke of the plunger 41 is secured by the large-diameter space 52. The combined spring 61 of the large-diameter spring 62 and the small-diameter spring 63 provides good spring characteristics over the entire stroke of the plunger 41. Therefore, even if the plunger 41, the large-diameter spring 62, the small-diameter spring 63, and the bolt 51 are lined up on the axis C, the total length of the chain tensioner 30 does not increase.

As shown in FIG. 5B, when the bolt 51 is tightened into the female screw hole 37 of the tensioner body 31, the large-diameter spring 62 and the small-diameter spring 63 contract, and the springs of the large-diameter spring 62 and the small-diameter spring 63. The plunger 41 is pushed out by the force. In the chain tensioner 30 of this embodiment, a combination spring 61 is used in which the base end portion of the plunger 41 is inserted inside the bolt 51 and the large-diameter spring 62 and the small-diameter spring 63 overlap. Compared with the total length L1 of the chain tensioner 70 of the comparative example, the total length L2 of the chain tensioner 30 from the head of the bolt 51 to the tip of the cap 18 is shorter. Therefore, the vehicle does not become large in order to avoid interference between the chain tensioner 30 and peripheral parts.

As described above, when the cam chain 22 is assembled, the stroke of the plunger 41 can be sufficiently secured in order to loosen the cam chain 22 (see FIG. 1). Further, it is possible to obtain good spring characteristics over the entire stroke of the plunger 41 by the large diameter spring 62 and the small diameter spring 63 without using the long spring 83 as in the chain tensioner 70 of the comparative example. .. Since the spring constants of the large-diameter spring 62 and the small-diameter spring 63 are the same, the spring characteristics of the large-diameter spring 62 and the small-diameter spring 63 are linearly displaced with respect to the load. Therefore, the tension of the cam chain 22 can be stably adjusted by the chain tensioner 30.

As described above, according to the present embodiment, the tension of the cam chain 22 is maintained by pressing the plunger 41 against the cam chain 22 by the spring force of the large diameter spring 62 and the small diameter spring 63. Further, since the plunger 41 enters the large diameter space 52 of the bolt 51, the stroke of the plunger 41 is secured in a state where the total length of the chain tensioner 30 is shortened. Further, by installing the large-diameter spring 62 and the small-diameter spring 63 in the large-diameter space 52 and the small-diameter space 43, good spring characteristics can be obtained over the entire stroke of the plunger 41 while the overall length of the chain tensioner 30 is shortened. The spring length required to obtain it is secured. By shortening the total length of the chain tensioner 30, interference between the chain tensioner 30 and peripheral parts can be suppressed.

In this embodiment, a configuration in which a combination spring in which a part of the small diameter spring is inserted inside the large diameter spring is applied to the chain tensioner has been described, but such a configuration is also applied to an expansion / contraction mechanism other than the chain tensioner. It is possible. Hereinafter, the expansion / contraction mechanism of another embodiment will be described with reference to FIG. FIG. 6 is a schematic view of the expansion / contraction mechanism of another embodiment.

As shown in FIG. 6, the expansion / contraction mechanism 90 is configured by connecting two members by a combination spring, similarly to the chain tensioner 30 described above. That is, the expansion / contraction mechanism 90 has a large-diameter spring 93 installed between the first member 91 and the second member 92, which can move relatively in a predetermined direction, and the first member 91 and the second member 92. A small-diameter spring 94 installed between the first member 91 and the second member 92, and a connecting member 95 for connecting the large-diameter spring 93 and the small-diameter spring 94 in series. Further, a part of the small diameter spring 94 enters the inside of the large diameter spring 93 via the connecting member 95, and the small diameter spring 94 and the large diameter spring 93 have the same spring constant.

More specifically, a part of the cylindrical first member 91 is housed in one end of the tubular guide 97, and a part of the cylindrical second member 92 is housed in the other end of the cylindrical guide 97. There is. The first member 91 is fixed to a base or the like, and the second member 92 is slidably housed along the tubular guide 97. The first member 91 and the second member 92 are connected via a large-diameter spring 93 and a small-diameter spring 94. The large-diameter spring 93 is in contact with the first member 91, and the small-diameter spring 94 is in contact with the second member 92. The large-diameter spring 93 and the small-diameter spring 94 are connected in series via a connecting member 95 having a cross-sectional view.

The bottomed cylinder portion 96 of the connecting member 95 is inserted inside the large diameter spring 93, and the small diameter spring 94 is inserted inside the bottomed cylinder portion 96. As described above, the large-diameter spring 93 and the small-diameter spring 94 are installed inside the tubular guide 97 in an overlapping state. By overlapping the large-diameter spring 93 and the small-diameter spring 94, the expansion / contraction mechanism 90 is shortened in the expansion / contraction direction, and good spring characteristics are provided over the entire relative movement stroke of the first and second members 91 and 92. The spring length required to obtain it is secured. By shortening the total length of the expansion / contraction mechanism 90, interference between the expansion / contraction mechanism 90 and peripheral parts can be suppressed. Further, since the spring characteristics of the large-diameter spring 93 and the small-diameter spring 94 are linearly displaced with respect to the load, the large-diameter spring 93 and the small-diameter spring 94 can be stably expanded and contracted with respect to the load applied to the expansion and contraction mechanism 90.

In the above modification, the large-diameter spring 93 is installed on the first member 91 side and the small-diameter spring 94 is installed on the second member 92 side, but the small-diameter spring 94 is installed on the first member 91 side. May be installed, and a large-diameter spring 93 may be installed on the second member 92 side. Further, the first member 91 was fixed to the base or the like, and the second member 92 was slidably housed along the tubular guide 97, but the second member 92 was fixed to the base or the like. The first member 91 may be slidably housed along the tubular guide 97. Further, both the first member 91 and the second member 92 may be slidably accommodated along the tubular guide 97.

Further, a force may act on the expansion / contraction mechanism in the compression direction, or a force may act on the expansion / contraction mechanism in the tensile direction. The expansion / contraction mechanism in which a force acts in the compression direction can be applied to a cushioning mechanism such as a shock absorber, and the expansion / contraction mechanism in which a force acts in the tension direction can be applied to, for example, a spring scale.

Further, in this embodiment, a configuration in which a large-diameter space is formed in the bolt and a small-diameter space is formed in the plunger has been described, but it suffices if a space for the plunger to enter is formed in the bolt, and a small-diameter space is formed in the plunger. It does not have to be.

Further, in this embodiment, the configuration in which the chain tensioner is provided with the large-diameter spring and the small-diameter spring has been described, but the chain tensioner may be provided with a single spring. By installing a single spring in the large diameter space of the bolt, the spring length required to obtain good spring characteristics over the entire stroke of the plunger is secured while the overall length of the chain tensioner is shortened. Is also possible.

Further, in this embodiment, the large-diameter spring is installed on the bolt side and the small-diameter spring is installed on the plunger side. However, the small-diameter spring is installed on the bolt side and the large-diameter spring is installed on the plunger side. May be good.

Further, in this embodiment, the large-diameter spring and the small-diameter spring have the same spring constant, but the spring constants of the large-diameter spring and the small-diameter spring are different as long as the adjustment of the cam chain by the chain tensioner is not adversely affected. May be.

Further, in this embodiment, the connecting member is formed in a cross-sectional view hat shape, but the connecting member may be formed in a shape capable of connecting a large-diameter spring and a small-diameter spring in series.

Further, the chain tensioner of this embodiment can be appropriately applied to a saddle-mounted vehicle, a motorcycle, a buggy-type tricycle, a personal watercraft, a lawn mower, an outboard motor, and the like.

As described above, the chain tensioner (30) of the present embodiment has a tensioner body (31) in which a tubular space (36) extending from an opening (34) at one end to an opening (35) at the other end is formed, and a tensioner body (31) at one end. A plunger (41) housed in a tubular space so as to protrude from the opening, a bolt (51) fixed to the tensioner body so as to close the opening at the other end, and a spring force acting on the plunger in the pushing direction. A spring (combination spring 61) for causing the spring is provided, and a storage space (large diameter space 52) into which the plunger enters is formed in the bolt, and the spring is installed in the storage space. According to this configuration, the tension of the chain is maintained by pressing the plunger against the chain (cam chain 22) by the spring force of the spring. Further, when the plunger enters the bolt accommodation space, the stroke of the plunger is secured while the total length of the chain tensioner is shortened. Further, by installing the spring in the accommodation space, the spring length required to obtain good spring characteristics over the entire stroke of the plunger is secured while the overall length of the chain tensioner is shortened. By shortening the total length of the chain tensioner, it is possible to suppress interference between the chain tensioner and peripheral parts.

In the chain tensioner of this embodiment, the spring has a large diameter spring (62) installed on the bolt side and a small diameter spring (63) installed on the plunger side, and a part of the small diameter spring has a large diameter. It goes inside the spring. According to this configuration, the overlap of the large-diameter spring and the small-diameter spring can shorten the spring length required to obtain good spring characteristics over the entire stroke of the plunger. Therefore, the total length of the chain tensioner can be shortened.

In the chain tensioner of this embodiment, the spring has a connecting member (64) for connecting the large-diameter spring and the small-diameter spring in series, and the connecting member has a bottomed tubular portion (65) that enters the inside of the large-diameter spring. It has a flange portion (66) extending radially outward from the bottomed cylinder portion, a large-diameter spring is attached to the outside of the bottomed cylinder portion, and a small-diameter spring is attached to the inside of the bottomed cylinder portion. According to this configuration, even if the amount of overlap between the large-diameter spring and the small-diameter spring is increased, the large-diameter spring and the small-diameter spring can be integrally expanded and contracted.

In the chain tensioner of this embodiment, the large-diameter spring and the small-diameter spring have the same spring constant. According to this configuration, the spring characteristics of the large-diameter spring and the small-diameter spring are linearly displaced with respect to the load. Therefore, the tension of the chain can be stably adjusted by the chain tensioner.

In the expansion / contraction mechanism (90) of another embodiment, between the first member (91) and the second member (92), which are relatively movable in a predetermined direction, and the first member and the second member. An installed large-diameter spring (93), a small-diameter spring (94) installed between the first member and the second member, and a connecting member (95) for connecting the large-diameter spring and the small-diameter spring in series. , A part of the small-diameter spring enters the inside of the large-diameter spring via the connecting member, and the small-diameter spring and the large-diameter spring have the same spring constant. According to this configuration, the overlap of the large-diameter spring and the small-diameter spring provides good spring characteristics over the entire relative movement stroke of the first and second members in a state where the expansion / contraction mechanism is shortened in the expansion / contraction direction. The spring length required to obtain it is secured. By shortening the total length of the telescopic mechanism, interference between the telescopic mechanism and peripheral parts can be suppressed. Further, since the spring characteristics of the large-diameter spring and the small-diameter spring are linearly displaced with respect to the load, the spring can be stably expanded and contracted with respect to the load applied to the expansion and contraction mechanism.

Although this embodiment has been described, as another embodiment, the above embodiment and the modified example may be combined in whole or in part.

Further, the technique of the present invention is not limited to the above-described embodiment, and may be variously modified, replaced, or modified without departing from the spirit of the technical idea. Furthermore, if the technical idea can be realized in another way by the advancement of the technology or another technology derived from it, it may be carried out by using that method. Therefore, the claims cover all embodiments that may be included within the scope of the technical idea.

30: Chain tensioner 31: Tensioner body 34: Opening at one end 35: Opening at the other end 36: Cylindrical space 41: Plunger 51: Bolt 52: Large diameter space (accommodation space)
61: Combination spring (spring)
62: Large diameter spring 63: Small diameter spring 64: Connecting member 65: Bottomed cylinder part 66: Flange part

Claims (4)

A tensioner body in which a tubular space extending from the opening at one end to the opening at the other end is formed.
A plunger housed in the tubular space so as to protrude from the opening at one end,
A bolt fixed to the tensioner body so as to close the opening at the other end,
A spring that exerts a spring force on the plunger in the pushing direction is provided.
A chain tensioner characterized in that a storage space into which the plunger enters is formed in the bolt, and the spring is installed in the storage space. The spring has a large-diameter spring installed on the bolt side and a small-diameter spring installed on the plunger side.
The chain tensioner according to claim 1, wherein a part of the small-diameter spring is inserted inside the large-diameter spring. The spring has a connecting member for connecting the large-diameter spring and the small-diameter spring in series.
The connecting member has a bottomed cylinder portion that enters the inside of the large-diameter spring and a flange portion that extends radially outward from the bottomed cylinder portion.
The chain tensioner according to claim 2, wherein the large-diameter spring is attached to the outside of the bottomed cylinder portion, and the small-diameter spring is attached to the inside of the bottomed cylinder portion. The chain tensioner according to claim 2 or 3, wherein the large-diameter spring and the small-diameter spring have the same spring constant.

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