gear mechanism

Abstract

A gear device capable of more reliably suppressing vibration noise is provided. [Solution] The gear device (10) comprises a first gear (30) that rotates about a first axis (12), a second gear (32) that rotates about a second axis (14) and meshes with the first gear (30), and a third gear (34) that rotates about a third axis (16) and meshes with the second gear (32). An inter-axis angle γ, which is the angle between a first line (L1) connecting the axial center points of the first axis (12) and the second axis (14) and a second line (L2) connecting the axial center points of the second axis (14) and the third axis (16), is a half-integer multiple of a pitch angle α, which is 360° divided by the number of teeth (z2) of the second gear (32).

Description

[Technical Field]

[0001] This specification discloses a gear train having three intermeshing gears. [Background technology]

[0002] Gear devices having three gears meshing with each other to transmit driving force have been widely known. However, vibration noise generated during operation of such gear devices has been a problem. Therefore, techniques for suppressing vibration noise of gear devices have been proposed.

[0003] For example, Patent Document 1 discloses a three-shaft gear including an input gear mounted on an input shaft, an output gear mounted on an output shaft, and an intermediate gear mounted on an intermediate shaft that meshes with both the input gear and the output gear. In Patent Document 1, the input shaft, output shaft, and intermediate shaft are arranged so that the angle formed by a first center line connecting the axial center of the input shaft and the axial center of the intermediate shaft and a second center line connecting the axial center of the intermediate shaft and the axial center of the output shaft is an integer multiple of 360° divided by the number of teeth of the intermediate gear. With this configuration, the meshing transmission error between the input gear and the intermediate gear and the meshing transmission error between the intermediate gear and the output gear advance in opposite phases. The phase reversal cancels out the vibratory forces, thereby suppressing the generation of vibration noise to some extent. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-322225 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in order to sufficiently suppress vibration noise using the technology of Patent Document 1, it is necessary to make the two mesh transmission error levels equivalent. However, it is not easy to meet this condition, and there is a risk that the technology of Patent Document 1 may not be able to sufficiently suppress vibration noise.

[0006] The technology in Patent Document 1 is somewhat effective in reducing vibration noise in the low frequency band. However, when mesh transmission error occurs in the intermediate shaft in the opposite phase, the vibratory force increases in the mid- to high frequency band compared to when the mesh transmission error is not in the opposite phase. In other words, it was difficult to sufficiently reduce vibration noise in the gear device using the technology in Patent Document 1.

[0007] Therefore, this specification discloses a gear device that can more reliably suppress vibration noise in the mid- to high-frequency band. [Means for solving the problem]

[0008] The gear device disclosed in this specification comprises a first gear that rotates about a first axis, a second gear that rotates about a second axis and meshes with the first gear, and a third gear that rotates about a third axis and meshes with the second gear, and is characterized in that an inter-axis angle, which is the angle between a first line connecting the axis point of the first axis and the axis point of the second axis and a second line connecting the axis point of the second axis and the axis point of the third axis, is a half-integer multiple of a pitch angle obtained by dividing 360° by the number of teeth of the second gear.

[0009] In this case, the first shaft may be an input shaft, and the third shaft may be an output shaft.

[0010] Furthermore, the rotational speed control device may further include a fourth gear that rotates together with the third gear around the third axis, and a fifth gear that meshes with the fourth gear around a fifth axis, wherein the first axis is an input shaft, the fifth shaft is an output shaft, and the number of teeth of the fourth gear may be different from the number of teeth of the third gear.

[0011] Furthermore, the number of teeth of the first gear may be smaller than the number of teeth of the third gear, the number of teeth of the fourth gear may be smaller than the number of teeth of the fifth gear, and the number of teeth of the third gear and the number of teeth of the fourth gear may have no common divisor other than 1.

[0012] The gear device may also be a gear device that transmits power from a traction motor mounted on an electric vehicle. [Effects of the Invention]

[0013] According to the gear device disclosed in this specification, the meshing between the first gear and the second gear proceeds in the same phase as the meshing between the second gear and the third gear. This makes it easier for the second shaft to displace in the mid- to high-frequency range, reducing the gear vibratory force. As a result, vibration noise in the mid- to high-frequency range can be reduced. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 2 is a diagram showing the configuration of a gear device. [Figure 2] FIG. 2 is a diagram showing how gears mesh. [Figure 3] FIG. 10 is a diagram showing the configuration of another gear device. DETAILED DESCRIPTION OF THE INVENTION

[0015] The configuration of the gear device 10 will be described below with reference to the drawings. Fig. 1 is a diagram showing the gear device 10. This gear device 10 transmits power input to an input shaft 22 to an output shaft 24 and outputs the power. For example, in an electric vehicle, such a gear device 10 is disposed in a power transmission path that transmits power from a driving motor to wheels.

[0016] 1, the gear device 10 includes a first gear 30, a second gear 32, and a third gear 34. The first gear 30 is a gear that rotates around a first shaft 12 together with the first shaft 12. In this example, the first shaft 12 is an input shaft 22 to which power is input.

[0017] The second gear 32 rotates about the second shaft 14 and meshes with the first gear 30. The second shaft 14 is disposed parallel to the first shaft 12. Because the second gear 32 meshes with the first gear 30, it rotates in the opposite direction to the first gear 30. For example, when the first gear 30 rotates counterclockwise, the second gear 32 rotates clockwise. Hereinafter, the value obtained by dividing 360° by the number of teeth z2 of the second gear 32 will be referred to as the "pitch angle α" (i.e., α = 360 / z2). In other words, the "pitch angle α" is the angle formed by the circular pitch (i.e., the distance between teeth) of the second gear 32. Hereinafter, the line connecting the center point of the first shaft 12 and the center point of the second shaft 14 will be referred to as the "first line L1."

[0018] The third gear 34 is a gear that rotates together with the third shaft 16 around the third gear 34. This third gear 34 meshes with the second gear 32. Therefore, the third gear 34 and the third shaft 16 rotate in the opposite direction to the second gear 32 and in the same direction as the first gear 30 and the first shaft 12. The third shaft 16 is also disposed parallel to the first shaft 12 and the second shaft 14. In this example, the third shaft 16 is the output shaft 24 that outputs power. Hereinafter, the line connecting the axial center of the second shaft 14 and the axial center of the third shaft 16 will be referred to as the "second line L2." Note that in the example of FIG. 1, the number of teeth z1 of the first gear 30 is smaller than the number of teeth z3 of the third gear 34, so the gear device 10 functions as a reducer that decelerates the input.

[0019] In this example, if the angle between the first line L1 and the second line L2 is defined as the "axis angle γ," the third shaft 16 and the third gear 34 are disposed at a position where the axis angle γ is a half-integer multiple of the pitch angle α. In other words, where i is an integer greater than or equal to 0, γ = α × (i + 0.5).

[0020] In this configuration, the meshing between the first gear 30 and the second gear 32 and the meshing between the second gear 32 and the third gear 34 advance in the same phase. This will be explained with reference to FIG. 2. FIG. 2 is a diagram showing how the drive gear 50 and the driven gear 52 rotate in the direction of the white arrows. In FIG. 2, black circles indicate locations where teeth mesh. As shown in FIG. 2, during the rotation of the meshing gears, for example, a "single-tooth meshing" occurs in which the drive gear 50 and the driven gear 52 mesh with one tooth, as shown in the upper part of FIG. 2, and a "two-tooth meshing" occurs in which the drive gear 50 and the driven gear 52 mesh with two teeth, as shown in the lower part of FIG. 2. In the case of the first gear 30 and the second gear 32, the first gear 30 is the drive gear 50, and the second gear 32 is the driven gear 52. In addition, in the case of the second gear 32 and the third gear 34, the second gear 32 is the driving gear 50 and the third gear 34 is the driven gear 52.

[0021] When γ = α×(i+0.5), one tooth meshing between the first gear 30 and the second gear 32 occurs at the same timing as one tooth meshing between the second gear 32 and the third gear 34. Also, two teeth meshing between the first gear 30 and the second gear 32 occurs at the same timing as two teeth meshing between the second gear 32 and the third gear 34. In other words, the meshing between the first gear 30 and the second gear 32 and the meshing between the second gear 32 and the third gear 34 advance in the same phase. As a result, the first transmission error E1 generated by the meshing between the first gear 30 and the second gear 32 and the second transmission error E2 generated by the meshing between the second gear 32 and the third gear 34 also advance in the same phase.

[0022] Here, the effects of the gear train 10 shown in FIG. 1 will be explained in comparison with a comparative example. First, consider a comparative example in which γ = α×i and the first transmission error E1 and the second transmission error E2 progress in opposite phase. In this case, gear excitation forces act on the first shaft 12 and the third shaft 16 in opposite phases. Therefore, in the low-frequency band (e.g., below 1 kHz) where the entire gear train vibrates rigidly, the gear excitation forces of the entire gear train are canceled out, thereby suppressing the generation of vibration noise. However, to cancel out the gear excitation forces in this way, the levels of the two mesh transmission errors E1 and E2 must be equalized. However, the levels of the mesh transmission errors E1 and E2 depend on the structure and characteristics (misalignment) of the gears and shafts. Therefore, to equalize the levels of the mesh transmission errors E1 and E2, the gears and shafts must be designed taking into account characteristics other than vibration noise, which is extremely difficult.

[0023] Furthermore, when the two meshing motions proceed in opposite phases, vibration noise is reduced in the low frequency band. However, in the mid- to high frequency band (e.g., 1 kHz to 2 kHz), individual mechanical elements tend to vibrate independently. This makes it difficult to achieve a reduction in vibration noise by canceling out the gear excitation forces. In addition, the mid- to high frequency band contains many resonance frequencies of the covers and cases that cover the gear device, making it easy for loud noise to be generated. In other words, when γ = α×i, vibration noise can be suppressed to some extent in the low frequency band, but it cannot be sufficiently suppressed in the mid- to high frequency band.

[0024] On the other hand, as mentioned previously, in the gear train 10 of this example, γ = α×(i+0.5), and the first transmission error E1 and the second transmission error E2 progress in the same phase. In this case, the second gear 32 is subjected to a first gear vibratory force F1, which fluctuates in the same phase as the transmission error E1, and a second gear vibratory force F2, which fluctuates in the same phase as the transmission error E2. When the two gear vibratory forces F1 and F2 act on the second gear 32 in the same phase, a natural vibration mode of the second shaft 14, which exists in the mid-to-high frequency band, is excited, making the second shaft 14 more likely to displace. Furthermore, because the gear vibratory force is inversely proportional to the ease of displacement of the second shaft 14, the ease of displacement of the second shaft 14 reduces the gear vibratory force. The reduced gear vibratory force effectively suppresses vibration noise associated with the operation of the gear train 10.

[0025] Furthermore, as is clear from the above explanation, in the gear device 10 of this example, it is not necessary to strictly control the levels of the two transmission errors E1 and E2 in order to suppress the gear excitation force; it is sufficient to mainly control the inter-axis angle γ. This simplifies the design of the gears and shafts, and also reduces the precision required for their manufacture. As a result, the costs required for designing and manufacturing the gear device 10 can be reduced.

[0026] Furthermore, since the gear device 10 of this example can suppress vibration noise in the mid-to-high frequency band, the amount of structures (such as ribs) for vibration and noise control on the case or cover that covers the gear device 10 can be reduced, further reducing the cost required for the gear device 10. Furthermore, reducing these structures can reduce the mass of the gear device 10. As a result, the fuel efficiency and electricity efficiency of an electric vehicle equipped with the gear device 10 can be improved.

[0027] Next, another example of the gear device 10 will be described with reference to FIG. 3. FIG. 3 is a diagram showing the configuration of the other gear device 10. Like the gear device 10 in FIG. 1, this gear device 10 has a first gear 30, a second gear 32, and a third gear 34. The gear device 10 shown in FIG. 3 also has a fourth gear 36 and a fifth gear 38. The fourth gear 36 is a gear that rotates together with the third gear 34 around the third shaft 16. The fifth gear 38 is a gear that rotates together with the fifth shaft 20 around the fifth shaft 20. The fifth gear 38 meshes with the fourth gear 36. The fifth shaft 20 is an axis parallel to the first shaft 12, the second shaft 14, and the third shaft 16. In this example, the first shaft 12 is the input shaft 22, and the fifth shaft 20 is the output shaft 24.

[0028] 3, the inter-shaft angle γ formed by the first line L1 connecting the axial center point of the first shaft 12 and the axial center point of the second shaft 14 and the second line L2 connecting the axial center point of the second shaft 14 and the axial center point of the third shaft 16 is a half-integer multiple of the pitch angle α of the second shaft 14. With this configuration, the second shaft 14 becomes more easily displaced, reducing gear vibratory force and, ultimately, vibration noise.

[0029] 3, the number of teeth z4 of the fourth gear 36 is smaller than the number of teeth z5 of the fifth gear 38. With this configuration, the gear device 10 of FIG. 3 can increase the output torque of the output shaft 24 by an amount equivalent to the reduction ratio of the fourth gear 36 and the fifth gear 38, compared to the gear device 10 of FIG.

[0030] 3, the number of teeth of the fourth gear 36 is different from the number of teeth of the third gear 34. With this configuration, the gear excitation force caused by the meshing of the fourth gear 36 and the fifth gear 38 is less likely to be superimposed on the gear excitation forces of other meshing gears. In particular, by configuring the number of teeth of the fourth gear 36 and the number of teeth of the third gear 34 to have no common denominators other than 1, the gear excitation forces are hardly superimposed. This makes it possible to maintain the ease of displacement of the second shaft 14, and ultimately to reduce vibration noise.

[0031] The configuration described above is merely an example, and other configurations may be changed as appropriate as long as the configuration described in claim 1 is included. For example, the diameter and number of teeth of each of the multiple gears may be changed as appropriate. Therefore, for example, instead of a configuration in which the speed is reduced from the input shaft 22 to the output shaft 24, a configuration in which the speed is increased from the input shaft 22 to the output shaft 24 may be used. [Explanation of symbols]

[0032] 10 gear device, 12 first shaft, 14 second shaft, 16 third shaft, 20 fifth shaft, 22 input shaft, 24 output shaft, 30 first gear, 32 second gear, 34 third gear, 36 fourth gear, 38 fifth gear, 50 driving side gear, 52 driven side gear, α pitch angle, γ inter-axis angle.

Claims

1. a first gear rotating about a first axis; a second gear that rotates about a second axis and meshes with the first gear; a third gear that rotates about a third axis and meshes with the second gear; an inter-axis angle, which is an angle between a first line connecting an axis point of the first axis and an axis point of the second axis, and a second line connecting an axis point of the second axis and an axis point of the third axis, is a half-integer multiple of a pitch angle obtained by dividing 360° by the number of teeth of the second gear; A gear device characterized by:

2. 2. The gear device of claim 1, A gear device, characterized in that the first shaft is an input shaft and the third shaft is an output shaft.

3. 2. The gear device of claim 1, further comprising: a fourth gear that rotates together with the third gear around the third axis; a fifth gear that meshes with the fourth gear around a fifth axis; Equipped with The first shaft is an input shaft, and the fifth shaft is an output shaft, The number of teeth of the fourth gear is different from the number of teeth of the third gear. A gear device characterized by:

4. 4. The gear device according to claim 3, the number of teeth of the first gear is smaller than the number of teeth of the third gear, the number of teeth of the fourth gear is smaller than the number of teeth of the fifth gear, the number of teeth of the third gear and the number of teeth of the fourth gear have no common divisor other than 1; A gear device characterized by:

5. 5. A gear device according to claim 1, wherein: The gear device is characterized in that the gear device is a gear device that transmits power from a traction motor mounted on an electric vehicle.

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