Differential device

Abstract

To provide a differential device which can improve responsiveness of a cam section.SOLUTION: A differential device 1 includes: a differential case 7; a differential gear 11; a pair of output gears 13, 15; a differential limiting section 5 which limits a differential of the pair of output gears 13, 15; a cam section 35 which operates the differential limiting section 5 by driving torque input in the output gears 13, 15; and an urging member 39 which applies a pre-load to the differential limiting section 5. Each of the output gears 13, 15 has: a gear member 25 engaged with the differential gear 11; and an operation member 27 which is arranged to be movable in an axial direction, is engaged to be integrally rotatable through the gear member 25 and the cam section 35, and operates the differential limiting section 5. The urging member 39 is arranged between the gear member 25 and the operation member 27 so as to apply a pre-load within a range in which loads are increased when a deflection amount is increased. A first load when the cam section 35 of the urging member 39 is operated is set to be lower than a second load when the cam section 35 is not operated.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, a differential device includes a rotatably arranged differential case, a differential gear supported rotatably on the differential case and revolving with the rotation of the differential case, and a pair of output gears meshing with the differential gears and rotatable relative to each other. The differential device also includes a differential limiting portion provided between the differential case and the output gears for limiting the differential between the pair of output gears, and a cam portion for operating the differential limiting portion with a driving torque input to the output gears. A differential device further including a biasing member for applying a preload to the differential limiting portion is known (see Patent Document 1).

[0003] In this differential device, the output gear has a gear member that meshes with the differential gear, and an output member that is arranged to be movable in the axial direction and engaged with the gear member via a cam portion so as to be rotatable together with the gear member and serves as an operating member that operates the differential limiting portion. The biasing member is arranged between the gear member and the output member, and biases the output member in the axial direction to apply a preload load to the differential limiting portion.

[0004] In such a differential device, when the cam portion operates, the axial distance between the gear member and the output member becomes wider, whereas when the cam portion does not operate, the axial distance between the gear member and the output member becomes narrower. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-49345 A Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, in a differential device such as the above Patent Document 1, when a biasing member such as a coned disc spring that applies a preload is disposed, the biasing member is set to a load range including the vicinity of the maximum load where the load does not change with respect to the deflection amount. For this reason, when the initial state where no driving torque is applied to the cam portion is changed to a state where the thrust force of the cam portion is increased by the driving torque applied to the cam portion, the preload load of the biasing member may pass through the maximum value. This may also occur when the state where the thrust force of the cam portion is increased is changed to the initial state. Here, the state of the deflection amount of the biasing member will be explained using a coned disc spring as an example. If the deflection amount at the initial point of disposing the coned disc spring is a predetermined value, as the driving torque is applied to the cam portion and the axial distance between the gear member and the output member (i.e., the disposing distance of the coned disc spring) becomes wider, the deflection amount of the coned disc spring gradually decreases. Conversely, as the axial distance between the gear member and the output member (i.e., the disposing distance of the coned disc spring) becomes narrower, the deflection amount of the coned disc spring gradually increases. In the conventional structure, as the deflection of the disc spring changes in this way, the preload of the disc spring as the biasing member passes through a maximum value. In such a case, the preload of the biasing member increases and then decreases as a result of the thrust force of the cam portion corresponding to the input torque to the differential device, so that the differential limiting characteristic fluctuates up and down around the maximum value of the preload of the biasing member, adversely affecting controllability.

[0007] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a differential device capable of suppressing the preload of the biasing member from adversely affecting the controllability of the differential limiting characteristic. [Means for solving the problem]

[0008] The differential device according to this embodiment includes a rotatably arranged differential case, a differential gear supported on the differential case so as to be rotatable about its axis and revolving due to the rotation of the differential case, a pair of output gears that mesh with the differential gear and can rotate relative to each other, and a differential limiting unit that is provided between the differential case and the output gear and limits the differential between the pair of output gears. A cam portion that operates the differential limiting unit with a driving torque input to the output gear, and a biasing member that applies a preload load to the differential limiting unit. The output gear has a gear member that meshes with the differential gear, and an operating member that is arranged to be movable in the axial direction and engaged with the gear member via the cam portion to rotate integrally with the differential limiting unit, and the biasing member is arranged to apply a preload load between the gear member and the operating member within a range in which the load increases when the amount of deflection increases, and the first load when the cam portion of the biasing member is operated is set to a load lower than the second load when the cam portion is not operated. Effect of the Invention

[0009] Advantageous Effects of Invention According to the present invention, it is possible to provide a differential device capable of suppressing the preload of the biasing member from adversely affecting the controllability of the differential limiting characteristic. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a cross-sectional view of the differential device according to the embodiment. [Diagram 2] FIG. 2 is a front view of the biasing member of the differential device according to the embodiment. [Diagram 3] FIG. 2 is a side view, with a portion thereof in cross section, of the biasing member of the differential device according to the embodiment. [Figure 4] 4 is a schematic diagram of the differential device according to the embodiment when the cam portion is not in operation. FIG. [Diagram 5] 5 is a schematic diagram of a cam portion of the differential device according to the embodiment when the cam portion is actuated. FIG. [Figure 6]11 is a diagram showing load settings in relation to load changes with respect to the amount of deflection of the biasing member of the differential device according to the embodiment; FIG. [Figure 7] 13 is a diagram showing load settings in a comparative example in which the load changes with respect to the amount of deflection of a biasing member. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The differential device according to the present embodiment will be described in detail below with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for the convenience of explanation and may differ from the actual ratios.

[0012] 1, a differential device 1 according to this embodiment is disposed between a drive source (not shown), such as an engine or an electric motor, and left and right wheels (not shown). Driving force from the drive source is transmitted to the differential device 1 via a transmission (not shown), and the driving force is distributed to the left and right wheels via a pair of output shafts (not shown).

[0013] As shown in FIGS. 1 to 5, the differential device 1 includes a differential mechanism 3 and a differential limiting section 5. The differential mechanism 3 and the differential limiting section 5 include a differential lock section 5a and a differential lock section 5b.

[0014] The differential mechanism 3 includes a differential case 7, a pinion shaft 9, a differential gear 11, and a pair of output gears 13 and 15. As an example, in this embodiment, a bevel gear set is used for meshing between the differential gear 11 and the pair of output gears 13 and 15.

[0015] The differential case 7 is rotatably supported by a stationary member (not shown) such as a carrier via bearings (not shown) at the outer periphery of each of bosses 17, 19 formed on both axial sides. The differential case 7 is formed with a flange portion 21 to which a ring gear (not shown) is fixed. The ring gear fixed to the flange portion 21 meshes with a power transmission gear (not shown) that transmits a driving force, and the driving force is transmitted to rotate the differential case 7. A pinion shaft 9, a differential gear 11, a pair of output gears 13, 15, etc. are housed and arranged inside the differential case 7.

[0016] The pinion shaft 9 has an end engaged with a hole formed in the differential case 7 and is prevented from coming off and rotating by a pin 23, and is rotated integrally with the differential case 7. Differential gears 11 are supported on both axial ends of the pinion shaft 9, respectively.

[0017] A plurality of differential gears 11 (two in this example) are arranged at equal intervals in the circumferential direction of the differential case 7, each supported on the shaft end side of the pinion shaft 9 and revolving with the rotation of the differential case 7. The differential gear 11 transmits driving force to the pair of output gears 13, 15, and is rotatably supported by the pinion shaft 9 so as to be rotationally driven when a differential rotation occurs between the pair of meshed output gears 13, 15.

[0018] The pair of output gears 13, 15 are accommodated in the differential case 7 so as to be capable of relative rotation. Each of the pair of output gears 13, 15 includes a gear member 25 and an operating member 27. In the pair of output gears 13, 15, the gear member 25 and the operating member 27 are formed symmetrically, so that only one of them will be mainly described below, and a description of the other will be omitted.

[0019] The gear member 25 is formed in an annular shape, and a gear portion that meshes with the differential gear 11 is formed on the outer circumferential side. The gear member 25 meshes with the differential gear 11, thereby transmitting driving force from the differential gear 11 to the pair of output gears 13, 15. In addition, when a differential rotation occurs between the pair of output gears 13, 15, the gear member 25 rotates the differential gear 11.

[0020] The actuating member 27 is formed in a concave ring shape capable of accommodating a part of the gear member 25 in the axial direction so that the actuating member 27 can be arranged close to the gear member 25 in the axial direction. A sliding surface 29 inclined conically in the axial direction is provided on a portion of the actuating member 27 located radially outward of the gear member 25. On the inner peripheral side of the actuating member 27, spline-shaped output portions 31, 33 are formed in the pair of output gears 13, 15, which can be connected to the pair of output shafts so as to be rotatable together. The actuating member 27 outputs the driving force input from the differential case 7 to the pair of output gears 13, 15 to the left and right wheels via the pair of output shafts.

[0021] A cam portion 35 that converts rotational torque into an axial thrust force is provided between the gear member 25 and the operating member 27. The cam portion 35 is composed of a plurality of engaging recesses provided on the inner peripheral side of the gear member 25 and a plurality of engaging protrusions that are provided on the outer peripheral side of the operating member 27 and can engage with the plurality of engaging recesses. The cam portion 35 enables the gear member 25 and the operating member 27 to rotate integrally by engaging the plurality of engaging recesses with the plurality of engaging protrusions.

[0022] On the other hand, in cam portion 35, the engagement surface in the rotational direction between the multiple engagement recesses and the multiple engagement protrusions is a cam surface inclined at a predetermined angle. When a driving force (driving torque) is input to differential case 7, the cam surface in cam portion 35 is actuated by the driving force branched from differential gear 11 and input to the pair of output gears 13, 15, causing cam portion 35 to move operating member 27 outward in the axial direction. The axial movement of operating member 27 by cam portion 35 can increase and strengthen the differential limiting force in differential limiting unit 5 arranged between differential case 7 and the pair of output gears 13, 15.

[0023] The differential limiting unit 5 is disposed between the differential case 7 and the pair of output gears 13, 15. The differential limiting unit 5 has a tapered ring 37 and an operating member 27 which slide against each other.

[0024] The tapered rings 37 are disposed on the differential case 7 at positions corresponding to the sliding surfaces 29 of the operating members 27 of the pair of output gears 13, 15. The tapered ring 37 rotates integrally with the differential case 7 by engaging a plurality of protrusions 40 formed in the circumferential direction on the inner peripheral side with recesses 42 formed on the inner wall surface of the differential case 7.

[0025] The tapered ring 37 slides against the sliding surface 29 of the operating member 27 of the pair of output gears 13, 15 that is moved axially by a meshing reaction force with the differential gear 11 according to the magnitude of the driving force (driving torque) input to the differential case 7. At this time, the sliding friction between the tapered ring 37 and the sliding surface 29, which is the differential limiting force of the differential limiting unit 5, is increased and strengthened by the cam thrust force of the cam unit 35.

[0026] The differential limiting unit 5 transmits friction torque between the differential case 7 and the pair of output gears 13, 15 in response to the magnitude of the cam thrust force, thereby limiting the differential of the differential mechanism 3. Such a differential limiting unit 5 is a cone clutch type among torque-sensitive friction clutches. A preload is applied to the differential limiting unit 5 by a biasing member 39.

[0027] The biasing member 39 is made of a coned disc spring, and applies a load acting as a biasing force to the target member in accordance with the amount of elastic deformation in the axial direction. The biasing member 39 is disposed between the gear member 25 and the operating member 27 in the axial direction. The biasing member 39 biases the gear member 25 inward in the axial direction (toward the differential gear 11), and biases the operating member 27 outward in the axial direction (toward the differential limiting unit 5). By disposing the biasing member 39 between the gear member 25 and the operating member 27, a preload is applied to the differential limiting unit 5. By using a coned disc spring as the biasing member 39, a uniform load in the axial direction can be obtained in a well-balanced manner on the circumference, and a preload can be applied stably to the differential limiting unit 5.

[0028] 4, when there is no driving torque to turn off the accelerator or when the driving torque is small and the cam portion 35 is not operating, the biasing member 39 is deflected to a large extent and the preload is large.

[0029] 5, when the cam portion 35 operates, such as when the accelerator is turned on and the driving torque is applied until it reaches its maximum, the amount of deflection of the biasing member 39 decreases and the preload is reduced. At this time, the preload applied to the differential limiting portion 5 by the biasing member 39 is reduced or released.

[0030] Here, the "deflection amount" of the urging member will be explained. In general, the urging member is disposed between two members (gear member 25 and operating member 27 in this embodiment) in an assembled state. When the arrangement gap (or the arrangement height) between the two members changes, the urging member applies a load while elastically deforming in the arrangement gap between the two members. The deflection amount is the stroke amount of the elastic deformation of the urging member in the arrangement gap between the two members, and means the expansion and contraction stroke amount of the urging member. An increase in the deflection amount means that the urging member is elastically deformed in the contracting side. This embodiment is characterized by using a urging member having a characteristic that the urging load increases as the deflection amount of the urging member increases, or a urging member that utilizes a characteristic portion where the urging load increases as the deflection amount of the urging member increases.

[0031] As a comparative example, FIG. 7 shows the setting of the preload of a conventional urging member 39 (here, a coned disc spring is shown as a representative) in the load change with respect to the deflection amount. In the conventional load setting of the urging member 39, the load is set to be applied in a load setting range 41 that is almost unchanged (almost constant) in the vicinity of the maximum value of the urging member 39 with respect to the deflection amount. For this reason, when the cam portion 35 is shifted from an initial state in which no driving torque is applied to the cam portion 35 to a state in which the thrust force of the cam portion is increased by the driving torque being applied to the cam portion 35, the preload of the urging member 39 may pass through the maximum value 44. This is because the preload of the urging member 39 may pass through the maximum value 44 even when the cam portion 35 is shifted from a state in which the thrust force of the cam portion 35 is increased to the initial state. In such a case, the preload of the urging member 39 is added to the thrust force of the cam portion 35 corresponding to the input torque to the differential device 1 so as to increase and then decrease. As a result, the differential limiting characteristic fluctuates up and down around the maximum value 44 of the preload of the biasing member 39, adversely affecting controllability.

[0032] In contrast, the setting of the preload of the biasing member 39 of this embodiment in relation to the change in the preload relative to the amount of deflection is shown in Fig. 6. The load of the biasing member 39 of this embodiment is set so as to apply a preload within a load setting range 43 in which the preload increases as the amount of deflection increases. In other words, the dimension in the axial direction between the gear member 25 and the operating member 27 is set so that the maximum value 44 of the preload is not used within the utilization range of the differential limiting characteristic of the differential device 1, or does not exceed the utilization range.

[0033] As an example of setting the preload of the biasing member 39 in this embodiment, in the load setting range 43, the first load when the cam portion 35 is activated is set to be lower than the second load when the cam portion 35 is not activated.

[0034] The first load of the biasing member 39 is set so that, in a preload load setting range 43, the load increases as the deflection amount increases when the cam portion 35 is operating, and a preload load is applied within a first load setting range 45 lower than a maximum value 44. As shown in FIG. 5, the first load of the biasing member 39 is applied to the gear member 25 and the operating member 27 when the cam portion 35 operates and the deflection amount of the biasing member 39 decreases. Note that a configuration is also possible in which the arrangement interval between the gear member 25 and the operating member 27 is equal to or exceeds the free length of the biasing member 39 when the cam portion 35 operates. In this case, the first load is set to zero (0) or as small as possible, but the technical idea of ​​this embodiment is enjoyed.

[0035] The second load of the biasing member 39 is set so as to apply a preload load within a second load setting range 47, which is higher than the first load setting range 45 and lower than the maximum value 44, when the cam portion 35 is not operating and the deflection amount increases, in a preload setting range 43. The second load of the biasing member 39 is applied to the gear member 25 and the operating member 27 when the cam portion 35 is not operating or the cam portion 35 is in an initial state and the deflection amount of the biasing member 39 increases, as shown in FIG. 4. Therefore, the second load of the biasing member 39 becomes the upper limit value of the load of the biasing member 39 in the initial state in which the cam portion 35 is not operating and no driving torque is input or a small driving torque is input. The upper limit value of the second load setting range 47 (load setting range 43) may be set as the maximum value 44 of the load of the biasing member 39.

[0036] The biasing member 39 applies a preload within a load setting range 43 in which the load increases as the deflection amount increases, so that the load of the biasing member 39 does not exceed the maximum value 44 of the biasing member 39. By setting the first load of the biasing member 39 lower than the second load, when the cam portion 35 is returned to the initial state after it is actuated, the preload load of the maximum value 44 of the biasing member 39 is not applied between the gear member 25 and the operating member 27. Therefore, the cam portion 35 is easily returned to the initial state, and the responsiveness of the cam portion 35 can be improved. Therefore, it is possible to suppress the preload load of the biasing member 39 from adversely affecting the controllability of the differential limiting characteristic. In addition, by setting the second load as the upper limit value when the cam portion 35 is not actuated, the first load does not approach the maximum value 44 of the load of the biasing member 39, and the responsiveness of the cam portion 35 can be stably improved.

[0037] Such a differential device 1 includes a rotatably arranged differential case 7, a differential gear 11 supported rotatably on the differential case 7 and revolving with the rotation of the differential case 7, and a pair of output gears 13, 15 meshing with the differential gear 11 and capable of relative rotation. A differential limiting unit 5 is provided between the differential case 7 and the output gears 13, 15 to limit the differential between the pair of output gears 13, 15. The differential limiting unit 5 further includes a cam portion 35 that operates the differential limiting unit 5 with the driving torque input to the output gears 13, 15, and a biasing member 39 that applies a preload to the differential limiting unit 5. The output gears 13, 15 also include a gear member 25 that meshes with the differential gear 11, and an operating member 27 that is arranged axially movable and engaged with the gear member 25 via the cam portion 35 to rotate together with the gear member 25, thereby operating the differential limiting unit 5. Furthermore, the biasing member 39 is disposed so as to apply a preload between the gear member 25 and the operating member 27 within a range in which the load increases as the amount of deflection increases. The first load when the cam portion 35 of the biasing member 39 operates is set to a load lower than the second load when the cam portion 35 does not operate.

[0038] Since the biasing member 39 applies a preload within a range in which the load increases when the amount of deflection increases, the load of the biasing member 39 does not exceed the maximum value 44 of the biasing member 39. By setting the first load of the biasing member 39 lower than the second load, when the cam portion 35 attempts to return to the initial state after being actuated, the load of the maximum value 44 of the biasing member 39 is not applied between the gear member 25 and the operating member 27. This makes it easier for the cam portion 35 to return to the initial state, and the responsiveness of the cam portion 35 can be improved.

[0039] Therefore, in such a differential device 1, it is possible to suppress the preload of the biasing member 39 from adversely affecting the controllability of the differential limiting characteristic.

[0040] Moreover, the biasing member 39 is set so that the second load becomes the upper limit value in the initial state where the driving torque is not input and the cam portion 35 is not actuated.

[0041] Therefore, the first load, which is lower than the upper limit value of the second load of the urging member 39, does not approach the maximum load value 44 of the urging member 39, and the responsiveness of the cam portion 35 can be stably improved.

[0042] Moreover, the biasing member 39 is a disc spring.

[0043] For this reason, a well-balanced and uniform load in the axial direction can be obtained on the circumference of the biasing member 39, and a stable preload can be applied to the differential limiting unit 5. In addition, by obtaining a uniform preload in the circumferential direction of the biasing member 39, the setting of the preload of the biasing member 39 can be stabilized.

[0044] Although the present embodiment has been described above, the present embodiment is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment.

[0045] For example, in the differential device according to the present embodiment, the differential limiting portion has a tapered ring arranged so as to be able to rotate integrally with the differential case, but this is not limiting, and the operating member may slide on the inner wall surface of the differential case without using a tapered ring. Alternatively, the differential limiting portion may use a flat disc-shaped single plate or multiple plates arranged alternately, or the operating member of the output gear may be directly frictionally slid against the differential case.

[0046] In addition, various combinations can be used for the meshing combination of the differential gear and the pair of output gears, such as a face gear set, a parallel shaft set with parallel shafts, etc. In any case, at least the output gear includes a gear member and an operating member.

[0047] Furthermore, the biasing member is not limited to a disc spring, and may be of various shapes such as a coil, plate, or wave shape, selected based on the arrangement space and preload characteristics.

[0048] The first load and the second load may be set so that their load ranges partially overlap. [Explanation of symbols]

[0049] 1 Differential device 5. Limited slip differential 7 Differential Case 11 Differential gear 13,15 Output gear 25 Gear Materials 27 Actuating member 35 Cam section 39 Pressing member

Claims

1. A rotatably disposed differential case; A differential gear that is rotatably supported by the differential case and revolves with the rotation of the differential case; a pair of output gears meshing with the differential gear and relatively rotatable; A differential limiting unit provided between the differential case and the output gears to limit a differential between the pair of output gears; a cam portion that operates the differential limiting portion by a driving torque input to the output gear; a biasing member that applies a preload to the differential limiting portion; Equipped with the output gear has a gear member that meshes with the differential gear, and an operating member that is arranged to be movable in the axial direction, is engaged with the gear member via the cam portion so as to be integrally rotatable, and operates the differential limiting portion, the biasing member is disposed between the gear member and the operating member so as to apply a preload within a range in which the load increases as the deflection amount increases, A differential device, wherein a first load applied when the cam portion of the biasing member is actuated is set to a load lower than a second load applied when the cam portion is not actuated.

2. 2. The differential device according to claim 1, wherein the biasing member is set so that the second load is an upper limit value in an initial state in which no driving torque is input and the cam portion is not actuated.

3. 3. The differential device according to claim 1, wherein the biasing member is a disc spring.

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