JP2024040101A - Sprocket and chain transmission mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sprocket which can stabilize a chain behavior while suppressing noise and vibration by reducing an influence of a tension variation corresponding to a load torque variation, and can suppress the lowering of the durability of the sprocket and the generation of a rotation order tone, and a chain transmission mechanism.

SOLUTION: A sprocket includes a tooth bottom formed between adjacent teeth having a tooth-bottom displacement amount at which the tooth bottom is separated in a radial direction from a tooth bottom circle of a standard tooth form which is set within a prescribed numerical value range corresponding to a pitch of teeth, and an amplitude of a waveform of a phase variation pattern which is formed by changing a tooth bottom radius according to an angle position is set so as to be changed within a range of (1/7)Amax with respect to a maximum amplitude Amax. In a chain transmission mechanism, at least one of a plurality of sprockets bridged by a chain is constituted of the sprocket.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a sprocket formed with a plurality of teeth that mesh with a chain, and a chain transmission mechanism using this sprocket.

As a transmission mechanism that reliably transmits rotation, a transmission mechanism in which a chain is passed around a sprocket having a plurality of teeth formed on the circumferential surface is commonly used.
When the sprocket teeth mesh with the chain, timing and rotational force are reliably transmitted between the multiple sprockets, but it is inevitable that noise and vibration will occur as the sprocket teeth mesh with the chain. .

To address this problem, in the case of a chain transmission mechanism in which the load torque fluctuates periodically with rotation, multiple teeth are installed on each tooth to synchronize with the periodic fluctuations in the load torque and reduce tension fluctuations. When the phase of meshing with the chain at equal intervals is set to zero, the effect of tension fluctuations corresponding to load torque fluctuations is reduced by arranging them to form a phase fluctuation pattern in which the phases alternately fluctuate to the positive and negative sides. However, sprockets that suppress noise and vibration are known.

For example, Patent Document 1 discloses that between adjacent teeth, a plurality of A sprocket is disclosed that has a phase variation pattern in which the radial position of the no-load seating point increases or decreases depending on the angular position.

JP2020-085041A

As with the sprocket described in Patent Document 1 above, even when the tooth root radius is varied while keeping the pitch of the teeth constant, the load transmitted between the chain and the sprocket is evenly distributed among the multiple teeth. As long as you do this, the durability of the sprocket will not decrease.
However, depending on the amplitude and period of the waveform of the phase fluctuation pattern, the polygonal momentum of the chain increases and the kinetic energy is amplified. As a result, chain behavior becomes unstable and load sharing deteriorates, resulting in a decrease in the strength of the sprocket.
As described above, the reality is that it is difficult to suppress noise and vibration while maintaining the durability of chains and sprockets. Furthermore, if the load distribution deteriorates, the teeth of the sprocket will wear out quickly, and there is also the problem that the noise reduction effect will be lost early.

The present invention solves these problems, and is capable of stabilizing chain behavior while reducing noise and vibration by reducing the effects of tension fluctuations in response to load torque fluctuations, and improving sprocket performance. It is an object of the present invention to provide a sprocket and a chain transmission mechanism capable of suppressing a decrease in durability and generation of rotational order noise.

The sprocket according to the present invention is a sprocket in which a plurality of teeth are formed to mesh with a chain, and the plurality of teeth are arranged on the positive side and the negative side when the phase in which each tooth meshes with the chain at equal intervals is set to zero. The teeth are arranged so as to form a phase variation pattern of a waveform whose phase varies, and the tooth roots formed between adjacent teeth have a root shift amount that radially deviates from the root circle of the standard tooth profile. The maximum value of the tooth root shift amount is set within a range of 2 to 7% of the pitch of the teeth, and the phase variation pattern is created by changing the root radius according to the angular position. The above problem is solved by having a configuration in which the amplitude of the waveform of the phase fluctuation pattern is set to vary within a range of (1/7) Amax with respect to the maximum amplitude Amax.
Here, a standard tooth profile is one in which the root circle radius of each tooth is constant and the tooth angle from the shaft center is constant (the tooth profile pitch indicated by the distance between the centers of circumferentially adjacent teeth is constant). Let's say something.

A chain transmission mechanism according to the present invention includes a plurality of sprockets including a driving sprocket provided on a crankshaft and a driven sprocket provided on a camshaft, and a chain suspended over the plurality of sprockets. This mechanism solves the above problem by configuring at least one of the driving sprocket and the driven sprocket with the sprocket described above.

According to the sprocket according to claim 1, basically, a plurality of teeth are arranged to form a phase variation pattern, thereby dynamically responding to load torque variations and reducing the influence of chain tension variations. It is possible to reduce noise and vibration.
Moreover, by forming the phase variation pattern by changing the root radius of each tooth according to the angular position and changing the amplitude of the waveform of the phase variation pattern within a predetermined range, the chain wraps around the sprocket better. Therefore, the number of teeth on the sprocket that takes care of chain tension increases, making it possible to stabilize the behavior of the chain during running. As a result, it is possible to suppress the occurrence of meshing order sounds, and it is also possible to disperse the orders of meshing sounds. Further, since excessive contact force is not generated and it is possible to equalize the load sharing, it is possible to reduce wear of the meshing portion and suppress a decrease in durability.

According to the configuration according to the second aspect of the present invention, it is possible to suppress the occurrence of waviness of the chain during running of the chain, so that the behavior of the chain can be further stabilized.

According to the configuration according to claim 3, since the polygonal momentum of the chain can be reduced, the speed in the vertical direction of the chain is reduced, the kinetic energy is reduced, and the noise (overall sound) of the entire chain transmission mechanism is reduced. It is possible to reduce the Additionally, the pitch of the sprocket teeth relative to the chain pitch increases, reducing chain play, which prevents imbalances in load sharing and increases the strength of the sprocket and chain. Become. Here, "play" refers to a state in which the teeth of the sprocket around which the chain is wrapped do not receive any load due to the loss of periodicity in the teeth of the sprocket.

According to the configuration according to claim 4, by increasing or decreasing the polygonal momentum of the chain, it becomes possible to reduce the meshing order noise that occurs periodically.
According to the configuration according to the fifth aspect of the present invention, harmonic sound reduction can be effectively obtained while preventing the occurrence of imbalance in load sharing.

According to the configuration of claim 6, it is possible to reduce wear by increasing the lubrication area of the contact area with the chain through improved oil retention on the tooth surface of the sprocket, and it is also possible to obtain a noise reduction effect by damping air vibrations through porosity. In addition, it is possible to shift the resonance point during meshing by controlling the mass through sintering density.

According to the chain transmission mechanism according to claim 7, by configuring at least one of the driving side sprocket and the driven side sprocket with the above-mentioned sprocket, the influence of tension fluctuation corresponding to load torque fluctuation is reduced and noise is reduced. It is possible to stabilize the chain behavior while suppressing vibration, and it is also possible to suppress deterioration in sprocket durability and generation of meshing order noise.

According to the structure according to claim 8, the driven sprocket is configured to have a phase fluctuation pattern that is opposite in phase to the phase fluctuation pattern of the driving sprocket, and the magnitude of the inter-axle distance due to the variation in the tooth bottom radius is determined by two axes. By combining the above, it becomes possible to disperse the order of the meshing sound. Furthermore, since fluctuations in the distance between the shafts can be suppressed, chain tension can be reduced. This reduces changes in the sprocket tooth profile, making it possible to maintain the effect of reducing overall noise (OA) and meshing order noise (specific frequency noise) for a long time.

According to the configuration according to the ninth aspect of the present invention, it is possible to reduce the influence of tension fluctuations in the chain corresponding to fluctuations in the crankshaft, and to suppress noise and vibration.

According to the configuration according to the tenth aspect of the present invention, it is possible to effectively reduce the influence on torque fluctuation, which is a main cause of noise and vibration.

1 is a diagram schematically showing a part of a configuration example of a sprocket according to Example 1 of the present invention. FIG. 3 is a diagram showing an example of a phase variation pattern of a sprocket according to Example 1. FIG. FIG. 3 is a diagram showing changes over time in the contact force of the chain against the teeth in a sprocket with a standard tooth profile. FIG. 3 is a diagram showing changes over time in the contact force of the chain against the teeth in the sprocket according to Example 1. FIG. 3 is a diagram showing changes over time in the maximum value of the contact force of the chain against the sprocket. It is a figure which shows an example of the phase fluctuation pattern of the comparison sprocket 1. It is a figure which shows the change with time of the contact force of the chain with respect to the tooth in the comparative sprocket 1. FIG. 3 is a diagram showing changes over time in the amount of chain vibration in the sprocket according to Example 1. It is a figure which shows an example of the phase fluctuation pattern of the sprocket 2 for comparison. It is a figure which schematically shows a part of one structural example of the sprocket based on Example 2 of this invention. 7 is a diagram showing an example of a phase variation pattern of a sprocket according to Example 2. FIG. FIG. 7 is a diagram showing changes in primary component sounds of the overall sound and meshing sound of the sprocket according to Example 2, depending on the rotation speed. FIG. 3 is a diagram showing a change over time in the maximum value of the contact force of the chain with respect to the comparative sprocket 3. It is a figure which shows the change with time of the contact force of the chain with respect to the tooth in the comparative sprocket 3. FIG. 7 is a diagram showing changes over time in the contact force of the chain against the teeth in the sprocket according to Example 2. FIG. 7 is a diagram showing a change over time in the maximum value of the contact force of the chain with respect to the sprocket according to Example 2. 1 is a diagram schematically showing the configuration of an example of a chain transmission mechanism of the present invention. FIG. 3 is a diagram showing the relationship between the arrangement position of the tooth bottom of the drive side sprocket and the meshing position where the engine explosion fluctuation occurs. FIG. 3 is a diagram showing changes in primary component sounds of the overall sound and meshing sound of the chain transmission mechanism according to the present invention, depending on the rotation speed of the crankshaft. FIG. 6 is a diagram showing changes in the overall sound and the second-order component sound of the meshing sound of the chain transmission mechanism according to the present invention, depending on the rotation speed of the crankshaft. It is a figure which shows the change of chain tension according to the rotational speed of a crankshaft in the chain transmission mechanism based on this invention.

Embodiments of the present invention will be described below based on the drawings.

[Example 1]
The sprocket according to the first embodiment has a waveform whose phase fluctuates to the positive side and the negative side when, for example, a plurality of teeth meshing with the rollers of a roller chain have a phase at which each tooth meshes with the chain at equal intervals, and the phase changes to the positive side and the negative side. are arranged to form a fluctuating pattern.
As shown in FIG. 1, in the sprocket 100 according to the first embodiment, a plurality of teeth 101 are arranged at equal pitches in the circumferential direction, and the tooth bottoms 102 formed between adjacent teeth 101 have a standard tooth profile. This includes those having a root shift amount that is radially outward or radially inward from the root circle D. The maximum value of the tooth bottom shift amount is set within a range of 2 to 6.5% of the pitch of the teeth 101, thereby making it possible to equalize the load sharing among the teeth 101. rs in FIG. 1 is the radius of the root circle D.

The phase variation pattern is formed by changing the root radius (r1, r2, r3, r4, r5, . . . ) so as to continuously increase or decrease in the circumferential direction according to the angular position. An example of the waveform of the phase variation pattern of the amount of tooth bottom shift is shown in FIG. The vertical axis in FIG. 2 is the ratio [%] of the tooth bottom shift amount to the tooth pitch, and the case where the tooth root radius is smaller than the tooth root radius of the standard tooth profile is shown as a negative value. The horizontal axis in FIG. 2 is the arrangement number of the tooth bottom.
This phase variation pattern of the tooth bottom shift amount is related to a sprocket with 18 teeth, and has, for example, six periods P1 to P6, and the wavelength changes continuously from large to small in the circumferential direction. is set to. Note that the term "period" in the present invention refers to one set of fluctuations on the positive side (peak) and once on the negative side (trough) in the waveform of the phase fluctuation pattern. It is used as a concept that includes things whose wavelength changes.

In this way, by arranging the plurality of teeth 101 to form a phase fluctuation pattern, it is possible to dynamically respond to load torque fluctuations, reduce the influence of chain tension fluctuations, and suppress noise and vibration. It becomes possible.

Further, the phase variation pattern of the tooth bottom shift amount is set so that the amplitude of the waveform is changed within the range of (1/7) Amax with respect to the maximum amplitude Amax. That is, the minimum amplitude Amin of the waveform is set smaller than (1/7) Amax.
By changing the root radius of the sprocket 100, for example, the seating position of a roller in a roller chain changes in the radial direction according to the size of the tooth root radius. By regulating and changing the polygonal momentum of the chain, it becomes possible to suppress the polygonal momentum of the chain to a small value. Therefore, the number of teeth 101 on the sprocket that handles chain tension increases, so the winding ability of the chain around the sprocket 100 improves, making it possible to stabilize the behavior of the running chain. As a result, it is possible to suppress the generation of meshing order sounds, and it is also possible to disperse the meshing order sounds.

Further, since excessive contact force is not generated and it is possible to equalize the load sharing, it is possible to reduce wear of the meshing portion and suppress a decrease in durability. That is, when focusing on individual teeth, the contact force of the chain against the teeth of the sprocket tends to increase over time, reach a peak value, and then gradually decrease over time. In a sprocket with a standard tooth profile, a plurality of teeth mesh sequentially at predetermined time intervals, so that each tooth shares substantially the same load as shown in FIG. 3A. As shown by the curve, when looking at the sprocket as a whole, there is no sudden change in contact force or increase in chain tension when the maximum value of contact force changes over time. In FIGS. 3A and 4, for convenience, only the contact forces of the chain with respect to three arbitrary mutually adjacent teeth t1 to t3 that sequentially mesh with the chain are shown.

In the sprocket 100 according to the first embodiment, although the timing of the start of meshing changes depending on the size of the root radius, the amount of tooth root shift is set according to the pitch of the teeth 101, and the phase fluctuation is By changing the amplitude of the pattern waveform within a predetermined range, as shown in FIG. 3B, while maintaining a state in which the load distribution of each tooth is substantially equal, as shown by the solid curve in FIG. , it is possible to suppress sudden changes in contact force and increases in chain tension when the maximum value of contact force changes over time. This makes it possible to suppress an increase in chain tension, and also to reduce the stress generated, making it possible to avoid a decrease in durability. In FIG. 3B, for convenience, only the contact force of the chain with respect to three arbitrary mutually adjacent teeth t1 to t3 that sequentially mesh with the chain is shown.

On the other hand, as shown in FIG. 5, in the comparative sprocket 1 in which the minimum amplitude Amin is set smaller than 1/7 Amax, the load sharing among each tooth becomes uneven as shown in FIG. As shown by the broken line curve in , when the maximum value of the contact force changes over time, a sudden change in the contact force occurs, which deteriorates the load sharing. As a result, the teeth of the sprocket wear quickly, and the noise reduction effect is quickly lost. In FIG. 6, for convenience, only the contact force of the chain with respect to three arbitrary mutually adjacent teeth t1 to t3 that sequentially mesh with the chain is shown.

In the above, the phase variation pattern is set so that the period of the teeth changes continuously from small to large in the circumferential direction. Here, the term "tooth period" refers to the period of the sine curve (A sin (Bx)) (sine curve equivalent period) with which the tooth bottom shift amounts match. For example, the amount of root shift of the n-th tooth bottom located on the downstream side of the sprocket rotation direction of the n-th tooth is the tooth of the n-th tooth bottom in a variation pattern shown by a sine curve with a period of "a". When it matches the bottom shift amount, the period of the nth tooth becomes "a".

The minimum value of the tooth period is preferably set within the range of 2 to 10, for example, and the tooth period variation range, which is indicated by the difference between the maximum value and the minimum value of the tooth period, is 21 or less. It is preferable that this is set. As a result, as shown by the solid curve in Fig. 7, it is possible to suppress the amount of chain vibration to a small level and suppress the occurrence of chain waviness when the chain is running, thereby further stabilizing the chain behavior. It becomes possible. Here, the amount of vibration of the chain is obtained by measuring the position of the chain with a gap sensor using the position of the chain under no load as a reference (vibration amount 0 mm).

On the other hand, as shown in Fig. 8, in the comparison sprocket having a phase variation pattern in which the minimum value of the tooth period is set to less than 2, the behavior of the chain is unstable, as shown by the dashed curve in Fig. 7. This causes excessive vibration. As a result, chain tension increases and durability decreases. Additionally, if the phase variation pattern is set so that the minimum tooth period exceeds 10, the strength of the chain will become unstable, excessive vibration will occur, the chain tension will increase, and durability will decrease. This problem occurs.
Furthermore, if the phase fluctuation pattern is set so that the tooth period fluctuation width exceeds 21, it becomes difficult to set the waveform of the phase fluctuation pattern so that the minimum value of the tooth period is 2 or more. This causes problems such as the strength of the chain becomes unstable, excessive vibration occurs, the chain tension increases, and durability decreases.

The sprocket 100 described above is formed of a sintered body having a porous structure capable of impregnating and retaining lubricating oil.
This makes it possible to increase the lubrication area of the contact area with the chain, improving oil retention on the tooth surface of the sprocket 100, reducing wear, and attenuating air vibrations due to the porous structure. This makes it possible to obtain a noise reduction effect. Furthermore, by controlling the mass by sintering density, it is possible to shift the resonance point during meshing.

In the above, a configuration in which a plurality of teeth are arranged so that the tooth profile pitch is constant in the circumferential direction has been described. There may be.
For example, the tooth profile pitch is set to vary according to the angular position in accordance with the phase variation pattern of the tooth root shift amount, and the variation amount of the tooth profile pitch with respect to the tooth profile pitch of the standard tooth profile is within a range of ±1%. Preferably, it is sized. Thereby, by increasing or decreasing the polygonal momentum of the chain, it becomes possible to further reduce the meshing order noise that occurs periodically.

[Example 2]
FIG. 9 is a plan view schematically showing a part of the configuration of a sprocket according to Example 2 of the present invention.
In the sprocket 100 according to the second embodiment, all the tooth bottoms 102 have root radii (r1, r2, r3, r4, r5, . . . ) larger than the radius rs of the root circle D of the standard tooth profile. The sprocket has the same configuration as the sprocket according to the first embodiment except that it is formed. That is, each of the tooth bottoms 102 in the sprocket 100 according to Example 2 has a radius rs of the root circle D of the standard tooth profile (as shown by the square plot in FIG. 10), as shown by the solid curve in FIG. This excludes tooth bottoms that have a shift amount that is radially inward.

As shown by the broken line curve in FIG. 10, even if the comparative sprocket 3 has a root shift amount that is radially inward from the radius rs of the root circle D of the standard tooth profile, the overall sound (see FIG. It is possible to reduce the noise of the first-order component of meshing sound (shown by the broken line curve B1 in FIG. 11) compared to the standard tooth profile sprocket. In FIG. 11, the overall sound of a sprocket with a standard tooth profile is shown by a dashed-dotted curve C0, and the sound of the primary component of meshing noise is shown by a dashed-dotted curve C1.
However, if the phase variation pattern is set within a range in which the maximum value of the tooth bottom shift amount is less than 2% of the pitch of the teeth 101, as shown in FIG. A change in the maximum value over time does not cause a sudden change in the contact force of the chain against the sprocket, but as shown in FIG. 13, an imbalance occurs in the load sharing of each tooth. Note that in FIGS. 12 and 13, for convenience, only the contact force of the chain with respect to three arbitrary mutually adjacent teeth t1 to t3 that sequentially mesh with the chain is shown.

However, by making the root radius (r1, r2, r3, r4, r5, . . .) larger than the radius rs of the root circle D of the standard tooth profile, the polygonal momentum of the chain is reduced. For this reason, the speed in the vertical direction of the chain decreases and the kinetic energy decreases, resulting in the overall sound (shown by the solid curve A0 in Figure 11) and the first-order component of the meshing sound (shown by the solid curve A1 in Figure 11). ) can be further reduced.
Moreover, by enlarging the root radius, the pitch of the sprocket teeth relative to the chain pitch is increased, reducing chain play. Thereby, as shown in FIG. 14, it becomes possible to suppress imbalance in load sharing among the teeth. Furthermore, as shown in Fig. 15, when looking at the sprocket as a whole, there is no sudden change in contact force or increase in chain tension when the maximum value of contact force changes over time. This leads to increased strength. Note that "play" refers to the loss of periodicity in the teeth of the sprocket, and refers to a state in which the teeth of the sprocket around which the chain is wound do not receive any load. Further, in FIGS. 14 and 15, for convenience, only the contact force of the chain with respect to three arbitrary mutually adjacent teeth t1 to t3 that sequentially mesh with the chain is shown.

Hereinafter, a chain transmission mechanism according to the present invention using the above sprocket will be described, taking as an example a case in which it is applied as a timing system in an engine whose cylinder head is equipped with two camshafts that drive intake and exhaust valves.

As shown in FIG. 16, this chain transmission mechanism 110 includes a driving sprocket 111 provided on the crankshaft, two driven sprockets 112 provided on the camshaft, and the driving sprocket 111 and the driven sprocket 112. and a chain 115 suspended between the two. Reference numeral T in FIG. 16 is a tensioner that applies appropriate tension to the slack side of the chain 115 via a tensioner lever G to suppress vibrations that occur during running.

In this embodiment, each of the driving side sprocket 111 and the driven side sprocket 112 has a phase fluctuation pattern formed by changing the tooth root radius so that it continuously increases or decreases in the circumferential direction according to the angular position. The driven sprocket 112 is configured to have a phase fluctuation pattern that is opposite in phase to the phase fluctuation pattern of the driving sprocket 111.

As shown in FIG. 17, the driving side sprocket 111 has a tooth root radius larger than the tooth root radius of the standard tooth profile (indicated by the dashed-dotted curve in FIG. 17). It is formed so that it is not located at the position (the position indicated by the broken line in FIG. 17). In this example, engine explosion fluctuations occur at tooth bottom positions (for example, No. 4, No. 10, and No. 16) that have a root shift amount that shows a peak on the negative side with respect to the tooth root radius of a sprocket with a standard tooth profile. This corresponds to the position of engagement when it occurs.
This makes it possible to reduce the effects of chain tension fluctuations in response to crankshaft fluctuations, and to suppress noise and vibration. FIG. 17 is a radar graph in which the values of the root radius of each tooth root 102 are arranged radially from a common origin, and the arrow indicates the rotation direction of the drive side sprocket 111.

Further, it is preferable that the phase variation pattern of the driving sprocket 111 is formed to match the phase with the periodic load variation of the camshaft. This makes it possible to effectively reduce the influence of torque fluctuations, which are the main cause of noise and vibration.

In the chain transmission mechanism 110 described above, the influence of chain tension fluctuations corresponding to load torque fluctuations can be reduced, so as shown in FIGS. 18A and 18B, an overall sound (indicated by a solid line in FIGS. Curve A0), the sound of the first-order component of the meshing sound (curve A1 shown by the solid line in FIG. 18A), and the sound of the second-order component of the meshing sound (curve A2 shown by the solid line in FIG. 18B) from the driving sprocket and the driven sprocket. This makes it possible to reduce the noise compared to a comparative chain transmission mechanism using a sprocket with a standard tooth profile, and also to disperse meshing order noise. Curve B0 shown by a broken line in FIGS. 18A and 18B is the overall sound in the comparison chain transmission mechanism, and curve B1 shown by the broken line in FIG. 18A is the first-order component of meshing sound in the comparison chain transmission mechanism. A curve B2 indicated by a broken line is the second-order component sound of the meshing sound in the comparative chain transmission mechanism.

In addition, since fluctuations in the distance between the shafts can be suppressed, the chain tension is compared to that of the comparative chain transmission mechanism (indicated by the broken curve β in FIG. 19), as shown by the solid curve α in FIG. 19. This makes it possible to reduce the This reduces changes in the tooth profile of the sprocket, making it possible to maintain the effect of reducing overall noise and meshing order noise (specific frequency noise) for a long time.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various design changes may be made without departing from the scope of the present invention as set forth in the claims. is possible.
For example, the plurality of teeth on the sprocket do not need to have the same shape, and may include tooth portions with different shapes. Specifically, for example, the height of the teeth, the shape of the tooth surface of the teeth, and other configurations may be different.
Further, in the above chain transmission mechanism, each of the driving sprocket and the driven sprocket is configured to have a phase variation pattern, but in the present invention, at least one of the driving sprocket and the driven sprocket has a phase variation pattern. It suffices if it is configured to have a variation pattern. For example, the drive side sprocket in the chain transmission mechanism described above may be configured with a standard tooth profile sprocket. Furthermore, each of the two driven sprockets may be configured with a standard tooth profile sprocket, or only one of the driven sprockets may be configured with a standard tooth profile sprocket.
Furthermore, the chain that runs around the sprocket may be of any kind, such as a silent chain, roller chain, bush chain, etc., and as long as it has a structure that meshes with the teeth of the sprocket, it may be a flexible chain such as a timing belt. It may also be a transmission member.

100... Sprocket 101... Teeth 102... Tooth bottom 110... Chain transmission mechanism 111... Driving side sprocket 112... Driven side sprocket 115... Chain D... Teeth with standard tooth profile Base circle rs ... Radius of the root circle of standard tooth profile

Claims (10)

A sprocket formed with a plurality of teeth that mesh with a chain,
The plurality of teeth are arranged so as to form a waveform phase fluctuation pattern in which the phase fluctuates to the positive side and the negative side, when the phase at which each tooth meshes with the chain at equal intervals is set to zero,
The tooth root formed between adjacent teeth includes one having a root shift amount that radially moves away from the tooth root circle of the standard tooth profile,
The maximum value of the tooth bottom shift amount is set within a range of 2 to 7% of the pitch of the teeth,
The phase fluctuation pattern is formed by changing the root radius according to the angular position, and the amplitude of the waveform of the phase fluctuation pattern is changed within a range of (1/7) Amax with respect to the maximum amplitude Amax. A sprocket characterized by being set. The pitch of the teeth is constant,
The phase variation pattern is set such that the period of the teeth changes continuously from small to large in the circumferential direction,
The minimum value of the tooth period is set within the range of 2 to 10, and the tooth period fluctuation width indicated by the difference between the maximum value and the minimum value of the tooth period is set to 21 or less. The sprocket according to claim 1, characterized in that: The sprocket according to claim 1, wherein the plurality of teeth are formed so that a root radius thereof is larger than a root radius of a standard tooth profile. 2. The sprocket according to claim 1, wherein the plurality of teeth include teeth having different tooth profile pitches indicated by the distance between the centers of circumferentially adjacent teeth. The sprocket according to claim 4, wherein the amount of variation of the tooth profile pitch with respect to the tooth profile pitch of the standard tooth profile is within a range of ±1%. The sprocket according to claim 1, wherein the sprocket is formed of a sintered body having a porous structure capable of impregnating and retaining lubricating oil. A chain transmission mechanism having a driving sprocket provided on the crankshaft, a driven sprocket provided on the camshaft, and a chain suspended between the driving sprocket and the driven sprocket,
A chain transmission mechanism, wherein at least one of the driving sprocket and the driven sprocket is the sprocket according to claim 1. The drive side sprocket is the sprocket according to claim 1,
8. The chain transmission mechanism according to claim 7, wherein the driven sprocket is configured to have a phase fluctuation pattern that is opposite in phase to the phase fluctuation pattern of the driving sprocket. 8. The chain according to claim 7, wherein the drive side sprocket is formed so that a tooth bottom having a tooth root radius larger than a tooth root radius of a standard tooth profile is not located at a meshing position where an engine explosion fluctuation occurs. Transmission mechanism. 8. The chain transmission mechanism according to claim 7, wherein the phase variation pattern of the driving sprocket is formed in phase with periodic load variation of the camshaft.

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