Sprocket and transmission mechanism

Abstract

To provide a sprocket capable of reducing influence of tension fluctuation corresponding to load torque fluctuation, suppressing generation of order sound corresponding to a cycle while suppressing noise and vibration, and preventing increase of tension fluctuation due to resonance and increase of noise and vibration.SOLUTION: A plurality of teeth meshing with the chain are arranged such that adjacent angular phases θ n of the teeth are not uniform, and when an angular phase in a case where all the teeth are arranged at a uniform angular phase is θ (360 ° / the number of teeth), the adjacent angular phases θ n of the teeth include a location where θ + 1.5 ° ≥ θ n ≥ θ + 0.1 ° and a location where θ - 0.1 ° ≥ θ n ≥ θ - 1.5 °.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sprocket having a plurality of teeth formed thereon for meshing with a chain, and to a power transmission mechanism. [Background technology]

[0002] 2. Description of the Related Art A commonly used transmission mechanism for reliably transmitting rotation is one in which a chain is looped around a sprocket having a plurality of teeth formed on the circumferential surface of a main body. The teeth of the sprockets mesh with the chain, ensuring that timing and rotational force are transmitted between multiple sprockets, but noise and vibration are inevitably generated as the sprockets mesh. In the case of a power transmission mechanism in which the load torque fluctuates periodically with rotation, a sprocket is known that reduces the effects of tension fluctuations corresponding to load torque fluctuations and suppresses noise and vibration by arranging multiple teeth so that, when the phase in which each tooth meshes with the chain at equal intervals is set to zero, the phase fluctuates alternately between positive and negative sides, thereby synchronizing with the cyclic fluctuations of the load torque to reduce tension fluctuations (see, for example, Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-156320 Summary of the Invention [Problem to be solved by the invention]

[0004] With known sprockets, it is possible to suppress noise caused by chain vibration by reducing tension fluctuations, but because load torque fluctuations are periodic, the generation of harmonic sounds corresponding to those periods is unavoidable. Furthermore, if the load torque fluctuations are out of phase or if there is resonance between the sprocket rotation speed and the chain's natural frequency, there is a possibility that tension fluctuations will increase, or that noise and vibration will increase.

[0005] The present invention aims to solve these problems by providing a sprocket that reduces the effects of tension fluctuations corresponding to load torque fluctuations, suppresses noise and vibration, and also suppresses the generation of harmonic sounds corresponding to the period of the load torque fluctuations, thereby preventing an increase in tension fluctuations and an increase in noise and vibration due to phase shifts and resonance of the load torque fluctuations. [Means for solving the problem]

[0006] The sprocket of the present invention is a sprocket having a plurality of teeth that mesh with a chain, and the plurality of teeth are arranged so that the adjacent angular phase θn of each tooth is not uniform.If the angular phase when each tooth is arranged with a uniform angular phase is θ (360° / number of teeth), the adjacent angular phase θn of each tooth (n is 1 to number of teeth) includes points where θ+1.5°≧θn≧θ+0.1° and points where θ-0.1°≧θn≧θ-1.5°, thereby solving the above problem. [Effects of the Invention]

[0007] According to the sprocket of claim 1 and the power transmission mechanism of claim 7, the multiple teeth are arranged so that the adjacent angular phase θn of each tooth is not uniform. If the angular phase when each tooth is arranged with a uniform angular phase is θ (360° / number of teeth), the adjacent angular phase θn of each tooth (n is 1 to number of teeth) includes a portion where θ+1.5°≧θn≧θ+0.1° and a portion where θ-0.1°≧θn≧θ-1.5°. This makes it possible to set the portion where the fluctuation period of the load torque and the periods of the multiple phase fluctuations are shifted, suppressing the generation of harmonic sounds corresponding to the fluctuation period of the load torque and resonance, and preventing increased tension fluctuations and increases in noise and vibration due to phase shifts in the load torque fluctuations, resonance, etc. When the adjacent angular phase θn of each tooth is in the range of θ-0.1°<θn<θ+0.1°, the tooth phase variation is small and the influence of load torque variation cannot be effectively eliminated. Furthermore, when θ+1.5°<θn and θn<θ-1.5°, the effects of load torque fluctuations can be eliminated, but the effects of harmonic sounds caused by tension fluctuations resulting from tooth phase fluctuations become greater, resulting in increased noise and vibration.

[0008] According to the configuration of claim 2, the adjacent angle phase θn of each tooth is set to repeatedly increase and decrease in a cycle of 3 to 9 times per rotation, which makes it possible to smoothly change the timing of the phase shift between the load torque fluctuation cycle and the tooth phase fluctuation cycle, and further suppress the generation of harmonic sounds. If the cycle of increase and decrease is less than 3 per rotation, it becomes difficult to eliminate the effects of load torque fluctuations. If the frequency of increase and decrease exceeds 9 per rotation, the effect of the generation of harmonic sounds due to tension fluctuations caused by tooth phase fluctuations becomes greater, resulting in increased noise and vibration.

[0009] According to the configuration of claim 3, the valleys of the increase / decrease cycle of the adjacent angular phase θn of each tooth are positioned corresponding to the teeth at which the chain tension due to the periodically fluctuating load torque reaches a maximum. This makes it possible to reduce the maximum value of the actual chain tension, thereby more effectively reducing the impact of load torque fluctuations. According to the configuration of claim 4, the increase / decrease cycle of the adjacent angular phase θn of each tooth is different from the fluctuation cycle of the largest load torque generation source among the multiple load torque generation sources, thereby making it possible to more effectively reduce the influence of load torque fluctuations. For example, when used in a transmission mechanism that transmits output from an engine crankshaft, there are multiple load torque generating sources with different cycles, such as crankshaft load, camshaft load, oil pump load, and balancer shaft load, and by making the cycle different from the cycle of fluctuation of the crankshaft load, which is the largest load torque generating source, and further from the cycle of fluctuation of the torque that is dominant in generating tension among these torque loads, or the cycle of fluctuation of the composite torque load, it is possible to effectively reduce the impact of load torque fluctuation.

[0010] According to the configuration of claim 5, multiple teeth are made of sintered material, which gives the sintered surface a moderate roughness and the ability to retain oil impregnated into the pores, so that when the chain and sprocket come into contact, the pores dampen air vibrations, leading to a noise reduction effect. It is also possible to control the mass by changing the sintering density, thereby shifting the resonance point during meshing. According to the configuration of claim 6, the teeth include some with actual pitch circle diameters larger and some smaller than the pitch circle diameter of the standard tooth profile, thereby reducing the vertical kinetic energy of the chain caused by its polygonal motion, making it possible to further reduce noise and vibration overall. According to the configuration of claim 8, by including a plurality of sprockets in which the arrangement of the adjacent angular phase θn of each tooth over the entire circumference is reversed, it is possible to finely set the portion of the transmission mechanism as a whole where the fluctuation period of the load torque and the periods of the multiple phase fluctuations shift, without increasing the period of increase / decrease per rotation of the adjacent angular phase θn of each tooth of a single sprocket, and further suppress the generation of harmonic sounds. Furthermore, by matching the phase of the valleys of the increase / decrease cycles of adjacent sprockets when the chain is looped around, it is possible to make the valleys even deeper. According to the configuration of claim 9, the multiple sprockets are arranged so that when the phase in which each tooth meshes with the chain at equal intervals is set to zero, the phase fluctuates to the positive and negative sides to form a phase fluctuation pattern with different wavelengths, so that tension fluctuations are reduced by synchronizing with the periodic fluctuations of the load torque.By including sprockets set so that the wavelength of the phase fluctuation pattern changes continuously in the circumferential direction from large to small or small to large, it is possible to reduce the effects of tension fluctuations corresponding to load torque fluctuations and suppress noise and vibration. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is an explanatory diagram of adjacent angular phases θn of each tooth of a sprocket according to an embodiment of the present invention. [Figure 2] FIG. 4 is an explanatory diagram showing the phase relationship between the adjacent angular phase θn of each tooth of a sprocket and the load torque according to an embodiment of the present invention. [Figure 3] FIG. 10 is an explanatory diagram showing the phase relationship between the adjacent angular phase θn of each tooth of a sprocket adjusted in a direction in which tension increases and the load torque. [Figure 4] FIG. 4 is an explanatory diagram showing the relationship between the rotation speed and tension of a sprocket according to an embodiment of the present invention. [Figure 5] FIG. 4 is an explanatory diagram showing the relationship between the rotation speed of a sprocket and noise according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] The sprocket of the present invention is a sprocket having a plurality of teeth that mesh with a chain, the plurality of teeth being arranged so that the adjacent angular phase θn of each tooth is not uniform, and if the angular phase when all the teeth are arranged with a uniform angular phase is θ (360° / number of teeth), the adjacent angular phase θn of each tooth includes points where θ+1.5°≧θn≧θ+0.1° and points where θ-0.1°≧θn≧θ-1.5°, and the sprocket may have any specific configuration as long as it reduces the effects of tension fluctuations corresponding to load torque fluctuations, suppresses noise and vibration, suppresses the generation of harmonic sounds corresponding to the period, and prevents phase shifts in load torque fluctuations, increases in tension fluctuations due to resonance, etc., and increases in noise and vibration. The chain that is wound around the sprocket may be any type, such as a silent chain, roller chain, or bushing chain, and may also be a flexible transmission member such as a timing belt, as long as it is designed to mesh with the teeth of the sprocket.

[0013] An example of a sprocket of the present invention having 20 teeth and fixed to the crankshaft of an in-line four-cylinder four-cycle engine will be described. As shown in Figure 1, if the angular phase when all teeth are arranged at a uniform angular phase is θ (360° / number of teeth), the adjacent angular phases θn of the sprocket are set as θ + α', θ + β', θ + γ'... in that order in a counterclockwise direction from the top tooth shown (see the diagram in the upper right of the table), and this is graphed for 20 teeth in the bottom right of the table. The cumulative angular phase of each tooth is, in order, θ + α, 2θ + β, 3θ + γ (α = α', β = α' + β', γ = α' + β' + γ': see the diagram at the top left of the table), and the difference in angular phase between each tooth and the case where all teeth are arranged with a uniform angular phase is α, β, γ... in that order, counterclockwise from the top tooth in the diagram. The graph for 20 teeth is shown in the bottom left of the table. In this embodiment, there are eight locations where θ+1.5°≧θn≧θ+0.1°, and eight locations where θ−0.1°≧θn≧θ−1.5°. The adjacent angular phase θn of each tooth is set to repeatedly increase and decrease in a cycle of five times per rotation.

[0014] The crankshaft of an inline four-cylinder four-stroke engine experiences two cycles of torque fluctuation per revolution, and the camshafts (each of two in the case of a DOHC) also experience two cycles of torque fluctuation per revolution of the crankshaft. The torque fluctuations that dominate tension depend on the conditions, but there are at least two locations on the teeth where the chain tension is maximized due to the periodically fluctuating load torque. In this embodiment, as shown in FIG. 2, the valleys of the increase / decrease cycle of the adjacent angular phase θn of each tooth are arranged to correspond to the positions of the teeth where the chain tension due to the load torque at two locations becomes maximum, thereby dispersing tension fluctuations and reducing their peak values.

[0015] On the other hand, as shown in Figure 3, if the peaks of the increase / decrease cycle of the adjacent angular phase θn of each tooth are positioned to correspond to the positions of the teeth where the chain tension due to the load torque is maximized at two locations, the chain tension will be even greater than that of a standard sprocket. FIG. 4 shows the relationship between the rotation speed and tension for a standard sprocket, a sprocket of this embodiment with the phase arrangement shown in FIG. 2, and a comparative example sprocket with the phase arrangement shown in FIG. 3 but with an increase or decrease in the adjacent angular phase θn similar to this embodiment. As can be seen from the graph in FIG. 4, the sprocket of this embodiment has lower tension than the standard sprocket in almost all rotation speed ranges. This reduces the influence of tension fluctuations due to load torque fluctuations, and suppresses noise and vibrations.

[0016] FIG. 5 shows the results of noise measurements when the sprocket of this embodiment is attached to a balancer shaft whose rotation is transmitted by a chain from the crankshaft of an in-line four-cylinder four-cycle engine. Both the proximity noise and the vibration noise from the bottom of the chain cover are lower than when using a standard sprocket, and the interior noise is reduced by more than 2dB in the engine's normal operating speed range.

[0017] The sprocket of the present invention may be configured so that a plurality of teeth have actual pitch circle diameters that are larger or smaller than the pitch circle diameter of the standard tooth profile. This changes the sprocket pitch relative to the chain pitch, changing the chain's "play" and changing the load distribution, which increases the strength of the inner and outer flanks of the sprocket and chain and reduces vibration and noise.

[0018] The entire sprocket may be integrally formed from a sintered material, or only a portion including a plurality of teeth may be made from a sintered material. The above-described embodiments are specific examples of the sprocket according to the present invention, but the sprocket according to the present invention is not limited to these and various modifications are possible.

Claims

1. A sprocket having a plurality of teeth formed thereon to mesh with a chain, the plurality of teeth are arranged such that the adjacent angular phases θn of the respective teeth are not uniform; If the angular phase when all teeth are arranged at a uniform angular phase is θ (360° / number of teeth), then The adjacent angular phase θn of each tooth (n is 1 to the number of teeth) is A location where θ+1.5°≧θn≧θ+0.1°; and A sprocket characterized by including a location where θ-0.1°≧θn≧θ-1.5°.

2. 2. The sprocket according to claim 1, wherein the adjacent angular phase θn of each tooth is set to repeatedly increase and decrease in a cycle of 3 to 9 times per rotation.

3. 3. The sprocket according to claim 2, wherein the valleys of the increase / decrease cycle of the adjacent angular phase θn of each tooth are arranged corresponding to the teeth at which the chain tension due to the periodically fluctuating load torque is maximized.

4. 3. The sprocket according to claim 2, wherein the period of increase and decrease of the adjacent angular phase θn of each tooth is different from the period of fluctuation of the largest load torque generating source among the plurality of load torque generating sources.

5. 2. The sprocket according to claim 1, wherein said plurality of teeth are made of sintered material.

6. 2. The sprocket according to claim 1, wherein the plurality of teeth include teeth having actual pitch diameters that differ from the pitch diameter of a standard tooth profile.

7. A transmission mechanism having a plurality of sprockets, a shaft to which the plurality of sprockets are attached, and a chain wound around the plurality of sprockets, A power transmission mechanism, wherein the plurality of sprockets include the sprocket according to any one of claims 1 to 6.

8. 8. The power transmission mechanism according to claim 7, wherein the plurality of sprockets include sprockets in which the arrangement of adjacent angular phases θn of each tooth over the entire circumference is opposite to each other.

9. 8. The power transmission mechanism according to claim 7, further comprising a sprocket arranged so that, when the phase at which each tooth is equally spaced and meshes with the chain is set to zero, the phase fluctuates positively and negatively to form a phase fluctuation pattern having portions with different wavelengths, so as to synchronize with periodic fluctuations in load torque and reduce tension fluctuations, and the wavelength of the phase fluctuation pattern is set to continuously change from large to small or small to large in the circumferential direction.

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