Intersecting shaft gear mechanism

Abstract

To provide an intersecting-axes type gear mechanism capable of ensuring an amount of lubrication oil to between tooth flanks.SOLUTION: For example, in a ring gear 2 of a hypoid gear 1, lubrication oil in a lubrication oil sump, which exists inside a radially inner end face 6 of a tooth 4 having a tooth trace extending in a radial direction, tends to flow toward a drive-side tooth surface 8 from a chamfered portion 12 provided at the radially inner end of a tooth flank due to the centrifugal force caused by rotation of the gear. At this time, since there is no curved portion in the region where the chamfered portion 12 and the radially inner end face 6 intersect, nor in the region where the chamfered portion 12 and the drive-side tooth surface 8 intersect, that is, since in the region where the lubrication oil flows, there is no boundary line portion (ridge line portion) intersecting with the flow direction of the lubrication oil, the lubrication oil that is about to flow from the chamfered portion 12 to the drive-side tooth flank 8 side does not flow in a direction away from the tooth flank.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gear mechanism, and more particularly to a gear mechanism in which the rotation axes of two gears that rotate while meshing with each other intersect. [Background technology]

[0002] Such intersecting-axis type gear mechanisms are generally used when transmitting power while changing the direction of rotation, and hypoid gears used in final reduction gear units in vehicles are well known. In hypoid gears, the input and output shafts are offset, so the rotation axes of the two gears are in a torsional position. However, gear mechanisms in which the rotation axes of two gears intersect, including hypoid gears, are called intersecting-axis type gear mechanisms. Another intersecting-axis type gear mechanism is a bevel gear mechanism, in which the rotation axes of two gears intersect at right angles.

[0003] A hypoid gear is composed of a pinion gear (small diameter gear) and a ring gear (large diameter gear). Hypoid gears have the characteristics of excellent noise and vibration performance during meshing rotation and large torque transmittance, as well as the characteristic that the meshing points of the gears shift in the tooth trace direction (generally, the tooth flanks slide). Regarding this characteristic, when focusing on the ring gear, on the tooth flank of the ring gear, where the tooth trace curves and extends in a roughly radial direction, the meshing points with the pinion gear teeth at the inner end in the radial direction are considered to be the most stressed.

[0004] Therefore, in the following Patent Document 1, the portions (corners) where the tooth flanks of the ring gear teeth intersect with the radially inner end faces of the teeth are chamfered to avoid stress concentration at these corners. The chamfered portions described in this prior art are provided on both the drive-side and coast-side tooth flanks of the ring gear teeth, and are configured by removing the corners obliquely and flatly, a so-called C-chamfer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-162745 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in response to the recent demand for increased transmission torque in vehicles, a decrease in transmission efficiency in hypoid gears has become a problem. This is thought to be due to the fact that, for example, when the lubrication state between the tooth surfaces of a hypoid gear is the same, the greater the transmission torque, the smaller the lubricating oil thickness between the tooth surfaces, and the greater the friction coefficient between the tooth surfaces. In other words, as the transmission torque increases, the lubrication state between the tooth surfaces decreases (thinner) in oil film thickness in the order of hydrodynamic lubrication, mixed lubrication, and boundary lubrication. In particular, in the region from mixed lubrication to boundary lubrication, almost no lubricating oil is present between the tooth surfaces, and the friction coefficient between the tooth surfaces increases.

[0007] When hypoid gears are lubricated by oil bath lubrication, the amount of lubricating oil supplied between the tooth surfaces can be increased by increasing the amount of lubricating oil in the gear case that houses the hypoid gear. However, doing so comes with a trade-off: increased resistance due to stirring and splashing of the lubricating oil in the lubricating oil reservoir.

[0008] As described in Patent Document 1, it has been confirmed that in a hypoid gear ring gear having chamfered portions formed by C-chamfering at the corners of the tooth flank and the radially inner end face, it is not possible to supply sufficient lubricating oil between the tooth flank and the pinion teeth.

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a gear mechanism of an intersecting axis type that can ensure the supply of lubricating oil between the tooth surfaces. [Means for solving the problem]

[0010] The intersecting shaft type gear mechanism for achieving the above object is as follows: In a gear mechanism of the intersecting-axis type, the rotation axes of two gears that rotate while meshing with each other are intersecting-axis type, and at least one of the gears has teeth whose tooth traces extend in a substantially radial direction and the teeth have radially inner end faces, A chamfered portion is formed only at the portion where the radially inner end surface of the tooth and the tooth flank of the tooth intersect, over the entire length of the intersection, and at least the region where the chamfered portion intersects with the radially inner end surface and the region where the chamfered portion intersects with the tooth flank are formed by curved surfaces over their entire lengths.

[0011] Another configuration of the intersecting-axis type gear mechanism is characterized in that the chamfered portion is formed of a curved surface.

[0012] A further configuration of the above-mentioned intersecting-axis type gear mechanism is characterized in that the two gears are hypoid gears, and the chamfered portion is formed only on the drive-side tooth flank of the ring gear of the hypoid gear. [Effects of the Invention]

[0013] As described above, according to the present invention, the lubricating oil present inside the radially inner end faces of the teeth whose tooth traces extend radially flows from the chamfers to the tooth flanks due to the centrifugal force that accompanies the rotation of the gears, and this flow is not obstructed, so that a sufficient amount of lubricating oil can be supplied between the meshing tooth flanks, thereby improving the transmission efficiency of the intersecting-axis gear mechanism. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a perspective view showing an embodiment of a ring gear of a hypoid gear to which a gear mechanism of an intersecting axis type according to the present invention is applied; FIG. [Figure 2] FIG. 2 is an explanatory diagram of the flow of lubricating oil in the ring gear of FIG. [Figure 3] FIG. 1 is a perspective view showing an example of a ring gear of a conventional hypoid gear. [Figure 4] FIG. 4 is an explanatory diagram of the flow of lubricating oil in the ring gear of FIG. 3. [Figure 5]FIG. 1 is a perspective view of a ring gear of a hypoid gear showing a first comparative example of the present invention. [Figure 6] FIG. 6 is an explanatory diagram of the flow of lubricating oil in the ring gear of FIG. 5. [Figure 7] FIG. 10 is a perspective view of a ring gear of a hypoid gear showing a second comparative example of the present invention. [Figure 8] FIG. 8 is an explanatory diagram of the flow of lubricating oil in the ring gear of FIG. 7. [Figure 9] FIG. 2 is an explanatory diagram of the transmission efficiency of a hypoid gear using the ring gear of FIG. 1. [Figure 10] FIG. 1 is an explanatory diagram illustrating an example of a hypoid gear. DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the intersecting-axes gear mechanism of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of a ring gear 2 of a hypoid gear 1 to which the intersecting-axes gear mechanism of the present invention is applied, and FIG. 10 is an explanatory diagram showing an example of the hypoid gear 1. First, a brief description of the hypoid gear 1 will be given. The hypoid gear 1 is composed of a ring-shaped ring gear (large-diameter gear) 2 and a truncated conical pinion gear (small-diameter gear) 3. A shaft member (not shown) is integrally connected to the large-diameter side of the truncated cone of the pinion gear 3. The rotational axis of the pinion gear 3 and the rotational axis of the ring gear 2 are offset in the vertical direction of the drawing, so that these rotational axes are in a twisted position.

[0016] The teeth 4, 5 formed on the ring gear 2 and pinion gear 3 of the hypoid gear 1 are so-called spiral teeth, and the tooth 4 of the ring gear 2 extends in a substantially radial direction with a curved tooth trace, with the tooth 4 having a radially inner end face 6 and a radially outer end face 7. Of these teeth 4, 5, the convex tooth flank of the ring gear 2 and the concave tooth flank of the pinion gear 3 form the respective drive-side (driving side) tooth flanks 8, 9, while the concave tooth flank of the ring gear 2 and the convex tooth flank of the pinion gear 3 form the respective coast-side (driven side) tooth flanks 10, 11. Due to this tooth flank configuration and offset of the rotation axis, the meshing point (mesh line) between the tooth flanks of the hypoid gear 1 shifts in the tooth trace direction, and this is called tooth flank sliding. In this example, the engagement point of the drive-side tooth flank (convex tooth flank) 8 of the ring gear 2 shifts from the tooth tip side on the radially outer side to the tooth base side on the radially inner side during meshing rotation with the pinion gear 3. In this embodiment, the rotation axis of the pinion gear 3 is positioned above the rotation axis of the ring gear 2. Therefore, in the case of oil-bath lubrication, the amount of lubricating oil at the engagement point tends to be insufficient because the pinion gear 3 is high.

[0017] In this embodiment, as shown in FIG. 1 , a chamfered portion 12 is formed only at the intersection between the radially inner end surface 6 of the tooth 4 of the ring gear 2 and its drive-side tooth flank 8, over the entire length of the intersection. This chamfered portion 12 is a so-called R-chamfered shape formed by a circular arc surface. Because this chamfered portion 12 is a circular arc surface formed by a R-chamfer, there is no bend in the area of ​​this chamfered portion 12. Note that the "bend" refers to the portion where two surfaces intersect in a bent state, resulting in a clear boundary (ridge) at the intersection of the surfaces. Furthermore, in this embodiment, because the chamfered portion 12 is a R-chamfer, there is no bend in the area where this chamfered portion 12 intersects with the radially inner end surface 6 of the tooth 4, nor in the area where the chamfered portion 12 intersects with the drive-side tooth flank 8 of the tooth 4. In other words, the area where the chamfered portion 12 intersects with the radially inner end face 6 of the tooth 4 and the area where the chamfered portion 12 intersects with the drive side tooth face 8 of the tooth 4 are both formed by arcuate curved surfaces.

[0018] Figure 2 is a schematic diagram of the lubricating oil flow in the teeth 4 of the ring gear 2 in Figure 1. In this embodiment, the lubricating oil flow was analyzed using a particle method. As is well known, the particle method treats a fluid as an array of particles, calculates the acceleration of each particle using the Navier-Stokes equations, and then calculates the fluid movement, i.e., flow, by successively updating the velocity of the particles moved by that acceleration. However, particles do not represent substances such as water droplets, but rather represent calculation points, similar to the grid points in a grid method. This particle method has several advantages, particularly in tracking conditions in which fluid droplets are widely dispersed, and allows intuitive visualization of analysis results. In this specification, the lubricating fluid in a gear mechanism is referred to as lubricating "oil." However, it is clear that this lubricating oil also includes lubricating fluids other than oils and fats, such as petroleum.

[0019] For example, if the hypoid gear 1 shown in FIG. 10 is immersed in a lubricating oil bath within the gear case, a lubricating oil reservoir will be formed on the inner side of the radially inner end of the tooth 4 of the ring gear 2, which is moved upward from the oil bath as the ring gear 2 rotates. In FIG. 2, this lubricating oil reservoir is indicated by a two-dot chain line, and the flow of lubricating oil is indicated by arrows. As is clear from the figure, the lubricating oil in the lubricating oil reservoir tends to move radially outward due to the centrifugal force (inertial force) associated with the rotation of the ring gear 2. At this time, the lubricating oil is transferred to the chamfered portion 12, which is a rounded chamfer formed at the intersection of the radially inner end surface 6 of the tooth 4 and the drive-side tooth flank 8, and then from the chamfered portion 12 to the drive-side tooth flank 8. This flow of lubricating oil does not deviate from the tooth flank, as will be described later, and a sufficient amount of lubricating oil can be supplied between the tooth flank of the pinion gear 3 and the tooth 5. Furthermore, as in this example, the meshing point with the teeth 5 of the pinion gear 3 transitions from the radially outer side to the radially inner side, while the lubricating oil flows (supplied) from the radially inner side to the radially outer side, so that the lubricating oil can be supplied reliably and without interruption between the tooth surfaces of the teeth 5 of the pinion gear 3.

[0020] FIG. 3 is a perspective view of the ring gear 2 of a conventional hypoid gear 1, in which no part of the teeth has a chamfered portion. The results of analyzing the lubricant flow on the teeth of this ring gear 2, similarly using the particle method, are shown in FIG. 4. As described above, the lubricant in the lubricant reservoir inside the radially inner end face 6 of the teeth 4 of the ring gear 2 tends to move radially outward due to centrifugal force generated by the rotation of the ring gear 2. However, in this example, as shown in FIG. 3, the lubricant flows toward the tip of the tooth along the corner (edge) where the radially inner end face 6 of the tooth intersects with the drive-side tooth flank 8, i.e., the bent portion. Furthermore, the lubricant then flows radially outward along the corner (edge) of the tip of the drive-side tooth flank 8, i.e., the bent portion, resulting in a small amount of lubricant flowing to the drive-side tooth flank 8. Therefore, the teeth 4 of the conventional ring gear 2 do not receive sufficient lubricant between the tooth flanks of the teeth 5 of the pinion gear 3.

[0021] FIG. 5 is a perspective view of the ring gear 2 of the hypoid gear 1 of the first comparative example, in which a chamfered portion 13 formed by a C-chamfer is formed only at the intersection of the radially inner end surface 6 of the tooth 4 of the ring gear 2 and the drive-side tooth flank 8, along the entire length of the intersection (the chamfered portion described in the aforementioned Patent Document 1 is provided only on the drive-side tooth flank). That is, in this first comparative example, a bend (ridge portion) exists in the region where the chamfered portion 13 formed by a C-chamfer intersects with the radially inner end surface 6 of the tooth 4 and in the region where the chamfered portion 13 intersects with the drive-side tooth flank 8. The flow of lubricant in the tooth 4 of this ring gear 2 was analyzed using the particle method in the same way. As described above, the lubricant in the lubricant reservoir inside the radially inner end surface 6 of the tooth 4 of the ring gear 2 tends to move radially outward due to the centrifugal force generated by the rotation of the ring gear 2. However, in this example, as shown in the figure, the lubricating oil flows toward the tooth tip mainly along the bend (ridge) where the chamfered portion 13 intersects with the radially inner end surface 6 of the tooth 4 and the bend (ridge) where the chamfered portion 13 intersects with the drive-side tooth flank 8. Furthermore, the lubricating oil then flows radially outward along the corner (edge) of the tip of the drive-side tooth flank 8, i.e., the bend, and only a small amount of lubricating oil flows to the drive-side tooth flank 8. Therefore, in the tooth 4 of the ring gear 2 of this first comparative example, sufficient lubricating oil is not supplied between the tooth flank of the tooth 5 of the pinion gear 3.

[0022] The lubricant flow in the conventional tooth 4 of the ring gear 2 of FIG. 3 (FIG. 4) and the lubricant flow in the drive-side tooth flank 8 of the tooth 4 of the ring gear 2 of FIG. 6 (FIG. 5) where a chamfered portion 13 consisting of a C-chamfer is provided on the drive-side tooth flank 8 of the tooth 4 of the ring gear 2 share a common element. Specifically, the lubricant flow from the lubricant reservoir on the radially inner end face 6 of the tooth 4 of the ring gear 2 to the drive-side tooth flank 8 due to centrifugal force caused by gear rotation has a boundary (ridge) extending in a direction intersecting the flow direction. When a boundary (ridge) extending in a direction intersecting the direction of the lubricant flow is present, the lubricant flows along the boundary (ridge) in a direction away from the tooth flank. Therefore, in a ring gear 2 where such a boundary (ridge) exists on the radially inner end face 6 of the tooth 4, the drive-side tooth flank 8, or the chamfered portion 13, lubricant is not sufficiently supplied between the tooth flank and the tooth 5 of the pinion gear 3.

[0023] 7 is a perspective view of the ring gear 2 of the hypoid gear 1 of a second comparative example, in which, like FIG. 1 , a chamfered portion (hereinafter referred to as the first chamfered portion) 12 is formed by R-chamfering along the entire length of the intersection between the drive-side tooth flank 8 and the radially inner end surface 6 of the tooth 4 of the ring gear 2, and a second chamfered portion 14 is formed by R-chamfering at the tooth tip corner (edge) of the drive-side tooth flank 8. That is, in this second comparative example, there are no bends (ridges) in the two chamfered portions 12, 14, the area where the first chamfered portion 12 intersects with the radially inner end surface 6 of the tooth 4, the area where the first chamfered portion 12 intersects with the drive-side tooth flank 8, or the area where the second chamfered portion 14 intersects with the drive-side tooth flank 8. The flow of lubricant in the tooth 4 of this ring gear 2 was analyzed using a particle method in the same way, and the results are shown in FIG. 8. As described above, the lubricating oil in the lubricating oil reservoir inside the radially inner end surface 6 of the tooth tends to move radially outward due to the centrifugal force generated by the rotation of the ring gear 2. However, in this example, as shown in the figure, the lubricating oil flows toward the tooth tip through the first chamfered portion 12, and then flows radially outward through the second chamfered portion 14, resulting in a small amount of lubricating oil flowing to the drive-side tooth surface 8. Therefore, in the second comparative example, tooth 4 of the ring gear 2 does not receive enough lubricating oil between the tooth surface and tooth 5 of the pinion gear 3.

[0024] Figure 9 shows the results of measuring the actual transmission efficiency (gear efficiency in the figure) of the hypoid gear 1 using the ring gear 2 of Figure 1 and the hypoid gear 1 using the ring gear 2 of Figure 3 (both pinion gears 3 have the same shape). The torque on the horizontal axis is the torque on the rotational axis of the pinion gear 3. As mentioned above, the greater the load (torque), the smaller the oil film thickness between the tooth flanks. Furthermore, the higher the rotation speed, the easier the lubricating oil is to splash, resulting in a smaller oil film thickness. As is clear from the figure, the hypoid gear 1 using the ring gear 2 of this embodiment has better transmission efficiency, especially at high rotation speeds and high loads, than the hypoid gear 1 using a conventional ring gear 2. This is thought to be due to the sufficient supply of lubricating oil between the tooth flanks, which reduces the friction coefficient between the meshing tooth flanks. Therefore, the hypoid gear 1 using the ring gear 2 of this embodiment can be effectively used in today's high-speed, high-load vehicles.

[0025] As described above, in the intersecting-axis gear mechanism of this embodiment, in an intersecting-axis gear mechanism in which the rotation axes of two gears are at torsional positions, such as the ring gear 2 of the hypoid gear 1, the lubricating oil in the lubricating oil reservoir located inside the radially inner end surface 6 of the tooth 4, whose tooth trace extends radially, tends to flow from the chamfered portion 12 toward the drive-side tooth flank 8 due to centrifugal force caused by the rotation of the gear. At this time, at least the area where the chamfered portion 12 intersects with the radially inner end surface 6 and the area where the chamfered portion 12 intersects with the drive-side tooth flank 8 are formed as curved surfaces. As a result, there are no boundary lines (ridges) that intersect with the flow direction of the lubricating oil in the area where the lubricating oil flows. Therefore, the lubricating oil that attempts to flow from the chamfered portion 12 toward the drive-side tooth flank 8 does not flow in a direction deviating from the tooth flank. As a result, the amount of lubricating oil supplied to the tooth flank that meshes with the tooth 5 of the pinion gear 3 is ensured, improving transmission efficiency.

[0026] Furthermore, by using a so-called R-chamfer, in which the chamfered portion 12 itself is composed of a curved surface, there are no bends in the area of ​​the chamfered portion 12 itself or in the area where the chamfered portion 12 intersects with the radially inner end surface 6 of the tooth 4 or the drive-side tooth surface 8, and the amount of lubricating oil supplied to the gap between the tooth surfaces can be ensured with a relatively simple configuration.

[0027] Furthermore, in the ring gear 2 of the hypoid gear 1, where the meshing point with the pinion gear 3 transitions in the tooth trace direction, lubricating oil is supplied from the radially inner side to the radially outer side, particularly at the drive side tooth surface 8, where the meshing point transitions from the radially outer side to the radially inner side, thereby enabling lubricating oil to be supplied reliably and without interruption between the tooth surface with the teeth 5 of the pinion gear 3.

[0028] Although the intersecting-axis gear mechanism according to the embodiment has been described above, the present invention is not limited to the configuration described in the above embodiment and various modifications are possible within the scope of the present invention. For example, in the above embodiment, the chamfered portion 12, i.e., the chamfered portion 12 formed by a rounded chamfer, i.e., a circular arc, is provided at the intersection of the radially inner end surface 6 of the tooth 4 of the ring gear 2 and the drive-side tooth flank 8. However, this chamfered portion 12 may have other curved surface configurations. Furthermore, a part of the chamfered portion 12 may have a flat surface. As mentioned above, when lubricating oil accumulated inside the radially inner end surface 6 of the tooth 4 of the ring gear 2 flows from the chamfered portion 12 to the drive-side tooth flank 8, if there is a boundary portion (ridge portion) extending in a direction intersecting the flow direction, the amount of lubricating oil supplied to the tooth flank is reduced. Therefore, an important constituent element of the present invention is that at least the area where the chamfered portion 12 intersects with the radially inner end surface 6 of the tooth 4 and the area where the chamfered portion 12 intersects with the drive side tooth surface 8 are both constructed of curved surfaces over their entire length.

[0029] In the above embodiment, the chamfered portion 12 is provided at the intersection of the radially inner end surface 6 of the tooth of the ring gear 2 of the hypoid gear 1 and the drive-side tooth flank, but it can also be provided on the coast-side tooth flank. Also, as long as the tooth traces of the teeth extend in the approximately radial direction and the teeth have radially inner end surfaces 6, the present invention can be similarly applied to gears such as bevel gears (straight teeth, spiral teeth). [Explanation of symbols]

[0030] 1 Hypoid gear (intersecting axis type gear mechanism) 2 ring gears 4 teeth (on ring gear) 6 Radial inner end surface 8 (drive side) tooth surface 12 Chamfered part

Claims

1. In a gear mechanism of the intersecting-axis type, the rotation axes of two gears that rotate while meshing with each other are intersecting-axis type, and at least one of the gears has teeth whose tooth traces extend in a substantially radial direction, and the teeth have radially inner end faces, a chamfered portion is formed only at a portion where a radially inner end surface of the tooth and a tooth surface of the tooth intersect, over the entire length of the intersection; an intersecting-axis type gear mechanism, wherein at least an area where the chamfered portion intersects with the radially inner end surface and an area where the chamfered portion intersects with the tooth surface are formed by curved surfaces over their entire lengths;

2. 2. The intersecting-axis type gear mechanism according to claim 1, wherein the chamfered portion is formed of a curved surface.

3. 3. The intersecting-axis type gear mechanism according to claim 1, wherein the two gears are hypoid gears, and the chamfered portion is formed only on the drive-side tooth surface of the ring gear of the hypoid gear.

Images