Differential mechanism

Abstract

To provide a differential mechanism capable of suppressing reduction of strength and deterioration of NV.SOLUTION: A differential mechanism 1 comprises a differential case 2 having a pillar part 11 and a window part 12, and a differential ring gear 3 composed of a helical gear and rotating integrally with the differential case 2. In the differential ring gear 3, in one of a phase of the pillar part 11 and a phase of the window part 12 with which a tooth part 21 of the differential ring gear 3 comes into partial contact, a base part 22 of the tooth part 21 is formed so as to be thinner on a side where the tooth part 21 comes into strong contact than on a side where the tooth part 21 comes into weak contact.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a differential mechanism. [Background technology]

[0002] Patent Document 1 discloses a differential mechanism having a structure in which the shell portion of the differential case is made thicker only in the necessary phase in order to suppress the rigidity difference caused by the difference in shape between the window portion and the pillar portion of the differential case. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-220361 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a differential mechanism, the differential case and the differential ring gear are integrated, and the differential ring gear is supported by the differential case. The support rigidity of the differential ring gear differs between the phase of the pillars and the phase of the windows in the differential case. In addition, because the differential ring gear is a helical gear, thrust forces are generated at the meshing parts when transmitting torque, causing misalignment. If the teeth come into one-sided contact due to this misalignment, it may result in a decrease in strength and a deterioration of NV.

[0005] The present invention has been made in consideration of the above circumstances, and has an object to provide a differential mechanism capable of suppressing a decrease in strength and an increase in NV. [Means for solving the problem]

[0006] The present invention is a differential mechanism comprising a differential case having a pillar portion and a window portion, and a differential ring gear composed of a helical gear and rotating integrally with the differential case, wherein in the differential ring gear, in a phase between the pillar portion and the window portion in which the teeth of the differential ring gear make one-sided contact, the base portion of the teeth is formed thinner on the side where the contact of the teeth is stronger than on the side where the contact of the teeth is weaker. Effect of the Invention

[0007] In the present invention, taking into consideration that the shape of the differential case differs depending on the phase, the base portion of the differential ring gear is made to have a different thickness depending on the phase, and the base portion is formed thinner on the side where the teeth contact is stronger than on the side where the teeth contact is weaker. This makes it possible to suppress one-sided contact of the teeth in the differential ring gear. As a result, it is possible to suppress a decrease in strength and a deterioration in NV. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing a differential mechanism according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram for explaining a support structure for the differential ring gear. [Diagram 3] FIG. 3 is a diagram for explaining that the misalignment occurring in the differential ring gear varies in magnitude depending on the phase. [Figure 4] FIG. 4 is a diagram for explaining the thickness of the base portion according to the phase. [Diagram 5] FIG. 5 is a diagram for explaining that the thickness of the base portion differs between the side where the teeth contact is strong and the side where the teeth contact is weak. [Figure 6] FIG. 6(a) is a diagram illustrating the T-shape of the differential ring gear in the first modified example, and FIG. 6(b) is a diagram illustrating the L-shape of the differential ring gear in the first modified example. [Figure 7] FIG. 7 is a view for explaining a thin-walled portion of a differential ring gear in the second modified example. [Figure 8] FIG. 8(a) is a diagram for explaining a phase in which the structure of the third modified example has a support structure, and FIG. 8(b) is a diagram for explaining a phase in which the structure of the third modified example does not have a support structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The differential mechanism according to the embodiment of the present invention will be specifically described below, however, the present invention is not limited to the embodiment described below.

[0010] 1 is a perspective view showing a differential mechanism in an embodiment. The differential mechanism 1 includes a differential case 2 and a differential ring gear 3. In the differential mechanism 1, the differential case 2 and the differential ring gear 3 rotate integrally.

[0011] The differential case 2 has a pillar portion 11 and a window portion 12. As shown in FIG. 2, a differential pinion gear 13 and a differential side gear 14 are accommodated in the inside of the differential case 2 in a meshed state. The pillar portion 11 is a shell-shaped portion that forms the accommodation space. The pillar portion 11 connects between a flange portion 15 and a boss portion 16 of the differential case 2. The differential case 2 is provided with two pillar portions 11, and a pinion shaft 17 is attached to the two pillar portions 11. The window portion 12 is a window formed between the two pillar portions 11. The differential case 2 is provided with two pillar portions 11 and two window portions 12. The phase of the differential case 2 can be divided into a phase in which the pillar portion 11 is provided and a phase in which the window portion 12 is provided. In the differential case 2, a rigidity difference occurs due to a difference in shape between the phase in which the pillar portion 11 is provided and the phase in which the window portion 12 is provided.

[0012] The differential ring gear 3 has a tooth portion 21 and a base portion 22. The differential ring gear 3 is configured by a helical gear. The tooth portion 21 is an external tooth with an oblique tooth trace. The base portion 22 is an annular portion formed on the inner periphery of the tooth portion 21. The base portion 22 is formed over the entire circumference of the differential ring gear 3. The disk portion 23 is a disk-shaped portion formed on the inner periphery of the base portion 22. The disk portion 23 is formed at the same axial position as the center position of the tooth portion 21, and is a flat portion protruding radially inward from the inner periphery of the base portion 22.

[0013] In the differential mechanism 1, the flange portion 15 of the differential case 2 and the disk portion 23 of the differential ring gear 3 are fastened by a bolt 31. The differential ring gear 3 is supported by the differential case 2. The support rigidity of the differential ring gear 3 is different between the phase of the column portion 11 and the phase of the window portion 12. Since the differential ring gear 3 is a helical gear, a thrust force is generated by the meshing of the teeth portion 21 during torque transmission, causing misalignment. Misalignment refers to a phenomenon in which the gear posture changes, and the meshing position of the gears is shifted. Misalignment includes parallelism error and misalignment error. The parallelism error is the inclination of the gears when the meshing portion of the gear pair is viewed from a direction perpendicular to a plane including both rotation axes when a gear pair whose rotation axes are arranged parallel to each other meshes. The misalignment error is the inclination of the gears when the meshing portion of the gear pair is viewed in a direction parallel to a plane including both rotation axes when the gear pairs mesh with each other and the meshing portion is viewed from the rotation axis of the gears toward the meshing position of the gear pair. This misalignment causes the teeth 21 of the differential ring gear 3 to contact only one side. For example, if the misalignment is large, the teeth 21 of the differential ring gear 3 may contact only one side, and if the misalignment is small, the teeth 21 may contact only the center.

[0014] The inventors' findings have revealed that the magnitude of misalignment occurring in the phase of the pillar portion 11 differs from that in the phase of the window portion 12, as shown in FIG. 3. It has been found that the misalignment may be greater in the phase of the pillar portion 11 than in the phase of the window portion 12. Also, the tooth portion 21 corresponding to the phase of the pillar portion 11 experiences one-sided contact during meshing. Since the misalignment is small in the phase of the window portion 12, the tooth portion 21 corresponding to the phase of the window portion 12 experiences central contact during meshing. In this way, the phase of the pillar portion 11 is a phase in which the tooth portion 21 experiences one-sided contact, and the phase of the window portion 12 is a phase in which the tooth portion 21 experiences central contact.

[0015] In addition, when the tooth portion 21 comes into partial contact during meshing, there are strong and weak contact sides at different axial positions of the tooth portion 21 in the meshing portion. When the tooth portion 21 comes into partial contact, one of the axial sides of the tooth portion 21 is the strong contact side and the other is the weak contact side. As shown in FIG. 3, when the tooth portion 21 comes into partial contact on the right side, it can be expressed as right contact. When the support portion of the differential ring gear 3 has a phase shape difference such as the pillar portion 11 and the window portion 12 as in the differential case 2, a rigidity difference occurs due to the phase, and the gear posture changes in the tilt direction. For the gear pair, the more partial the tooth contact, the worse the strength and NV (noise and vibration) become.

[0016] Therefore, in the differential mechanism 1, in order to suppress the tooth portion 21 from contacting one side during meshing, the base portion 22 of the differential ring gear 3 is formed to have different thicknesses in consideration of the phase of the differential case 2 and the side where the tooth portion 21 contacts strongly. Since the shape of the differential case 2 supporting the differential ring gear 3 differs depending on the phase, the rigidity changes, and the rigidity changes between the column portion 11 and the window portion 12. Therefore, the rigidity of the base portion 22 of the differential ring gear 3 is configured to be reduced for the phase where the tooth contact is one-sided due to the large misalignment. The rigidity of the base portion 22 is reduced to allow the strong contact portion to escape. In a structure in which the support rigidity changes between the column portion 11 and the window portion 12 as in the differential case 2, when the rigidity is low in the phase of the column portion 11 and deformation is large and the tooth contact is one-sided, the base portion 22 on the side where the contact is strong in the phase of the column portion 11 is made thin.

[0017] Specifically, in the phase where the tooth portion 21 comes into one-sided contact, the thickness of the base portion 22 is formed to be thinner. As shown in FIG. 4, in the phase of the column portion 11, the thickness of the base portion 22 is thinner than that of the window portion 12. Furthermore, in the base portion 22 corresponding to this phase, the side where the tooth portion 21 comes into strong contact is formed thinner than the side where the tooth portion 21 comes into weak contact. In other words, even in the portion corresponding to the phase of the column portion 11, the entire base portion 22 is not thinned, but only the side where the tooth portion 21 comes into strong contact is formed thin. For example, as shown in FIG. 5, one side of the base portion 22 relative to the disk portion 23 in the axial direction is formed thin, and the other side is formed to the same thickness as the phase of the window portion 12. In the phase where the tooth portion 21 comes into right contact as shown in FIG. 3, the right side of the base portion 22 is made thinner than the disk portion 23 as shown in FIG. 5. In the base portion 22, the side where the tooth portion 21 comes into strong contact is made thinner. In this way, the thickness of the base portion 22 is made thinner on the side where the tooth portion 21 comes into strong contact. This reduces the rigidity of the thinly formed base portion 22, making it easier to deform in a direction that alleviates tooth contact. As a result, misalignment in the tooth portion 21 can be reduced, and uneven contact of the tooth portion 21 can be suppressed.

[0018] As described above, according to the embodiment, the shape of the differential case 2 differs depending on the phase, and the base portion 22 of the differential ring gear 3 is made to have a different thickness depending on the phase of the differential case 2, and the base portion 22 is formed so that the side where the tooth portion 21 contacts strongly is thinner than the side where the tooth portion 21 contacts weakly. This makes it possible to suppress one-sided contact of the tooth portion 21 during torque transmission. As a result, it is possible to suppress a decrease in strength and a deterioration in NV.

[0019] The tooth contact will be either center contact or one-sided contact depending on the balance between the parallelism error and the misalignment error, not just the parallelism error. For example, in the case of one-sided contact, if the parallelism error component is right contact and the misalignment error component is left contact, if the parallelism error component is stronger, it will be right contact, and if the misalignment error component is stronger, it will be left contact.

[0020] Even if the misalignment due to the support rigidity of the differential ring gear 3 is to the left, if the misalignment error is such that the left contact is stronger, the teeth portion 21 may contact on the left. In other words, in the differential mechanism 1, the teeth portion 21 may contact only on one side, resulting in a left contact. In such a case, the side where the contact of the teeth portion 21 is stronger is the left side, and therefore the left side of the base portion 22 is formed thin in that phase.

[0021] Also, when the misalignment is large, it does not necessarily mean that the bearing will hit on one side.Similarly, when the misalignment is small, it does not necessarily mean that the bearing will hit on the center.In other words, even when the misalignment is large, the bearing may hit on the center, and even when the misalignment is small, the bearing may hit on one side.

[0022] 4 are shown with a boundary line for ease of explanation, and such clear boundaries do not have to be provided. In short, it is sufficient for the base portion 22 to include a portion formed so that the column portion 11 side is relatively thinner than the window portion 12 side, and the entire phase of the column portion 11 does not have to be thicker than the phase of the window portion 12. Furthermore, the thickness of the base portion 22 may change gradually or stepwise depending on the phase.

[0023] Also, as shown in Figs. 6 to 8, it is possible to configure modified versions of the differential mechanism 1. In the differential mechanism 1 of the first modified version, as shown in Figs. 6(a) and 6(b), in a phase where the tooth contact is one-sided due to a difference in the rigidity of the support structure, the base portion 22 is connected to the disk portion 23 on the side opposite to the side where the tooth contact is strong. Since the phase where the tooth portion 21 is in center contact is a phase where the tooth contact is good, in this phase, as shown in Fig. 6(a), the shape of the connection portion between the base portion 22 and the disk portion 23 of the differential ring gear 3 is formed in a T-shape, and the disk portion 23 is supported by the flange portion 15. On the other hand, in a phase where the tooth portion 21 is in right contact (one-sided contact), is a phase where the tooth contact is poor, in this phase, as shown in Fig. 6(b), the shape of the connection portion between the base portion 22 and the disk portion 23 of the differential ring gear 3 is formed in an L-shape, and the disk portion 23 is supported by the flange portion 15. When the tooth portion 21 contacts on the right, the disk portion 23 extends radially inward from the left end side of the base portion 22. The connection portion between the base portion 22 and the disk portion 23 is formed in an L-shape so that the side connected to the disk portion 23 is opposite the side with strong tooth contact. This L-shape structure reduces the rigidity of the tooth portion 21 and the base portion 22 on the side where the disk portion 23 is not provided (the right side), making it easier to deform to the side that alleviates the tooth contact.

[0024] In the differential mechanism 1 of the second modification, as shown in FIG. 7, in a phase where the tooth contact is one-sided due to the difference in the rigidity of the support structure, if the direction in which the differential ring gear 3 tilts due to the rigidity of the support structure is the same as the side with strong tooth contact, the disk portion 23, which is the support structure, is made thinner. In the example shown in FIG. 7, in a state where a posture change occurs in which gear tilt occurs on the left side, the left side of the tooth portion 21 is the side with strong tooth contact (left contact occurs). The disk portion 23 has a thin portion 23a at a position corresponding to that phase. By partially thinning the thickness of the disk portion 23 according to the phase, the rigidity is partially reduced, and in that phase, in addition to the original posture change (gear tilt), a posture change (gear tilt) occurs. This structure having the thin portion 23a reduces the rigidity of the disk portion 23, making it easier to deform to the side that alleviates the tooth contact.

[0025] The structure of the third modified example is applicable to a driven gear. For example, the counter driven gear 100 has a tooth portion 101, a base portion 102, a disk portion 103, and a hole portion 104, as shown in Fig. 8(a) and Fig. 8(b). The counter driven gear 100 has a structure in which the hole portion 104 is provided in the disk portion 103 in a part of the circumferential direction. The hole portion 104 is a through hole that penetrates a part of the disk portion 103 in the axial direction, and has a shape that extends along the circumferential direction of the counter driven gear 100. For example, the hole portion 104 is provided in three places in the entire counter driven gear 100. The counter driven gear 100 includes a phase supported by the disk portion 103, as shown in Fig. 8(a), and a phase that is not supported because the disk portion 103 has a hole portion 104 provided therein, as shown in Fig. 8(b). This counter driven gear 100 has a structure having a phase that is not supported partially. 8(b), the thickness of the base portion 102 is increased in the portion not supported by the hole portion 104. The thickness of the base portion 102 in the phase in which the hole portion 104 is provided is greater than the thickness of the base portion 102 in the phase in which the hole portion 104 is supported by the disk portion 103. [Explanation of symbols]

[0026] 1 Differential mechanism 2 Differential case 3 Differential ring gear 11 Pillar section 12 Window section 15 Flange 21 Teeth 22 Base 23 Disc Club

Claims

[Claim 1] A differential case having a pillar portion and a window portion; A differential ring gear that is configured by a helical gear and rotates integrally with the differential case; A differential mechanism comprising: In the differential ring gear, in a phase in which the teeth of the differential ring gear come into one-sided contact among a phase of the pillar portion and a phase of the window portion, a base portion of the teeth is formed thinner on a side where the teeth come into strong contact than on a side where the teeth come into weak contact. A differential mechanism characterized by:

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