Limited slip differential
By dividing the planetary gears into outer and inner zones with different inclination angles, the meshing area contradiction of the helical gear limited slip differential is resolved, achieving a more efficient limited slip effect and a longer service life.
Patent Information
- Application Number
- CN202422250003.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-12
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2034-09-12
AI Technical Summary
The existing helical gear limited slip differential has conflicting tooth surface slopes in the meshing area between the planetary gears and the side gears, which cannot be taken into account, resulting in low transmission efficiency, high noise, rapid wear, short service life, and poor limited slip effect.
The planetary gears are divided into an outer zone and an inner zone with different inclination angles. The outer zone meshes with the half-shaft gears, and the inner zone meshes with other planetary gears. The inner zone gears with a larger inclination angle have the opposite rotation direction, and the axial force of the tooth surface is offset to reduce the deformation of the end cover and enhance the limited slip effect.
The maximum torque distribution ratio is improved, the transmission efficiency is higher, the noise is lower, the wear is reduced, the service life is extended, and the cost does not increase.
Smart Images
Figure CN223399182U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of differentials, in particular to a limited slip differential. Background Art
[0002] A limited-slip differential is an advanced type of automotive differential. Compared to an open differential, it uses a variety of operating principles to limit the speed difference between the left and right wheels to a certain range. When the tires on one side of the differential lose grip and resistance decreases, the gears inside the open differential will spin and accelerate the rotation of the idle wheel on that side, causing the vehicle to lose traction as a whole. A limited-slip differential, on the other hand, uses this limitation to continue distributing a certain amount of drive torque to the wheels that still have grip, preserving some or all of the vehicle's traction and allowing it to continue moving forward. Depending on their operating principles, limited-slip differentials can be divided into several categories: torque-sensing, speed-sensing, and electronically controlled mechanical.
[0003] The planetary gears used in a helical limited-slip differential can be divided into two meshing areas: one meshing with the side gears, and the other meshing with the other planetary gears in a separate group. These two areas operate independently and do not overlap. As helical gears, existing technology uses the same tooth slope in both areas. This creates a contradiction: a certain amount of axial force can exist between the planetary gears and the side gears, but it cannot be too large. In actual use, the power transmission path is from the differential gears to the differential housing to the planetary gears to the side gears to the side gears to the wheels. During frequent acceleration and deceleration, excessive alternating axial forces on the side gears can cause deformation of the differential housing end cover, shortening the differential's service life over time. Therefore, the tooth slope in this meshing area cannot be too large.
[0004] However, as mentioned above, the operating principle of a helical gear limited-slip differential dictates that the tooth slope in the meshing area between planetary gears cannot be too small. To generate sufficient friction to limit forced rotation between the planetary gears, the tooth slope should be as large as possible. A larger tilt angle distributes more torque to the tooth surfaces, increasing pressure between the tooth surfaces and, in turn, friction, thereby achieving a better limited-slip effect. Theoretically, when the tilt angle is just large enough to cause self-locking, the limited-slip differential can achieve a maximum torque distribution of 100:0, achieving the most perfect limited-slip effect.
[0005] In practice, to balance these two contradictions, the helical gear's tilt angle often fluctuates around 45 degrees. This angle is not self-locking and generally only achieves a maximum torque distribution of around 70:30. This means that wheels that lose grip still receive some power, which is wasted in the form of idling. Furthermore, the redundant work performed by the gears inside the differential causes unnecessary wear and tear, shortening its service life. Utility Model Content
[0006] The purpose of the present utility model is to provide a limited slip differential that can solve the above technical problems.
[0007] The utility model provides a limited slip differential, comprising a housing and:
[0008] A left end gear set, the left end gear set comprising a left side gear and a left planetary gear, the left side gear being coaxially arranged with the housing, the left planetary gear being arranged around the axis of the left side gear and meshing with the left side gear;
[0009] a right end gear set, the right end gear set comprising a right side gear and a right planetary gear, the right side gear being coaxially arranged with the housing, the right planetary gear being arranged around the axis of the right side gear and meshing with the right side gear;
[0010] The left planetary gear is meshed with the right planetary gear. The section where the left planetary gear and the right planetary gear are far away from each other is called an outer zone, and the section where the left planetary gear and the right planetary gear are close to each other is called an inner zone. The inclination angle of the inner zone gear is greater than the inclination angle of the outer zone gear. The outer zone of the left planetary gear is meshed with the left half-shaft gear, the outer zone of the right planetary gear is meshed with the right half-shaft gear, and the left planetary gear is meshed with the inner zone of the right planetary gear.
[0011] Furthermore, the number of the left planetary gears and the number of the right planetary gears are both four, the left planetary gears are evenly distributed circumferentially around the axis of the left side shaft gear, and the right planetary gears are evenly distributed circumferentially around the axis of the right side shaft gear.
[0012] Furthermore, one side of the left half-shaft gear is cross-shaped with four left planetary gears of the same rotation direction arranged on the upper, lower, left and right sides, and one side of the right half-shaft gear is X-shaped with four right planetary gears of another rotation direction arranged on the upper left, upper right, lower left and lower right sides.
[0013] Furthermore, a tooth root cylindrical surface is retained between the outer area and the inner area as a tool relief groove.
[0014] Furthermore, the housing has mounting holes adapted to the left planetary gear and the right planetary gear.
[0015] Furthermore, it also includes a left end cover and a right end cover, which are respectively arranged on the left and right sides of the shell and are detachably connected to the shell.
[0016] Furthermore, the left end cover and the right end cover are both detachably connected to the shell by bolts.
[0017] Furthermore, there are multiple bolts, and the bolts are evenly distributed circumferentially around the axis of the shell.
[0018] Furthermore, the left half-shaft gear and the right half-shaft gear are both transmission-connected to the wheels.
[0019] The utility model also provides a vehicle, comprising the above-mentioned limited slip differential.
[0020] Beneficial effects:
[0021] Compared to a helical gear limited-slip differential, this new design overcomes the conflicting requirements for the two meshing areas of the planetary gears, requiring different tilt angles. By using the same operating principle, the maximum torque distribution ratio, previously around 70:30, can be significantly increased to nearly 100:0. This means that when implementing the limited-slip function, the limited-slip differential offers greater responsiveness, higher transmission efficiency, quieter operation, lower heat generation, less gear wear, less maintenance, and a longer service life, all without significantly increasing manufacturing costs. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0023] Figure 1 This is a schematic diagram of the overall structure of the utility model;
[0024] Figure 2 This is a schematic diagram of the internal structure of the utility model;
[0025] Figure 3 This is a schematic diagram of the left half-shaft gear structure in the present utility model;
[0026] Figure 4 This is a schematic diagram of the left planetary gear structure in the utility model;
[0027] Figure 5 This is a schematic diagram of the right half-shaft gear structure in the present invention;
[0028] Figure 6 This is a schematic diagram of the right planetary gear structure in the utility model;
[0029] Figure 7 It is a structural schematic diagram of the shell in the utility model.
[0030] Explanation of the reference numerals: 1-housing, 2-left half-shaft gear, 3-left planetary gear, 4-right half-shaft gear, 5-right planetary gear, 6-outer area, 7-inner area, 8-recess, 9-mounting hole, 10-threaded hole. DETAILED DESCRIPTION
[0031] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.
[0032] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.
[0033] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present utility model, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be a communication between the two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.
[0034] The contradiction mentioned in the background art above can be summarized as follows: the tooth surface slope in the meshing area between the planetary gears and the side gears cannot be too large, but the tooth surface slope in the meshing area between the planetary gears and other planetary gears should be as large as possible. To this end, the present invention splits the planetary gears into two components (an outer region and an inner region) based on these two regions. Specifically, two helical gears with different inclination angles are integrated into a single unit: the gear with the smaller inclination angle meshes with the side gears, while the gear with the larger inclination angle meshes with the same region of the other planetary gears. These two inclination angles can be arranged in a herringbone pattern with opposite rotational directions. In this case, the axial forces on the two tooth surfaces of the planetary gears are always directed in opposite directions. Considering the planetary gears as a whole, their forces offset each other, reducing pressure between the end faces of the planetary gears and the differential end cover, minimizing deformation, and further extending service life. Furthermore, the pressure at the meshing point between any tooth surface is unaffected, and the limited slip effect of the differential is not weakened.
[0035] Theoretically, these two types of helical gears only need to meet the meshing teeth and size conditions of their respective areas. Except for the direction of rotation, their number of teeth, module, pressure angle, tooth top height coefficient, etc. can be different, and there is huge room for expansion.
[0036] In the most extreme case of the tilt angle difference, the gear with the smaller tilt angle is a spur gear, and the gear with the larger tilt angle is a single-start involute worm. The latter can be regarded as a helical gear with a single tooth, which can mesh with another involute worm with the opposite rotation direction. Due to the limitations of gear processing conditions, the combination of the two different gears requires a certain length of the root cylindrical surface to serve as a tool relief groove. In addition, the phase difference between the two gears must strictly meet certain geometric relationships determined by dimensional factors such as the number of teeth and center distance, and they must be assembled in the correct position. Otherwise, interference with each other is likely, which will not be discussed in detail here.
[0037] Example 1
[0038] Next, we introduce an application example using the above improved technology:
[0039] A limited slip differential, such as Figure 1-7As shown, it includes a housing 1, in which a left end gear set and a right end gear set are arranged. The left end gear set includes a left half-shaft gear 2 and a left planetary gear 3. The left half-shaft gear 2 is coaxially arranged with the housing 1, and the left planetary gear 3 is arranged around the axis of the left half-shaft gear 2 and meshes with the left half-shaft gear 2; the right end gear set includes a right half-shaft gear 4 and a right planetary gear 5. The right half-shaft gear 4 is coaxially arranged with the housing 1, and the right planetary gear 5 is arranged around the axis of the right half-shaft gear 4 and meshes with the right half-shaft gear 4; the left planetary gear 3 meshes with the right planetary gear 5. The section where the left planetary gear 3 and the right planetary gear 5 are separated from each other is called the outer section 6, and the section where the left planetary gear 3 and the right planetary gear 5 are close to each other is called the inner section 7. The inclination angle of the inner section gear is greater than the inclination angle of the outer section gear. The outer section 6 of the left planetary gear 3 meshes with the left half-shaft gear 2, the outer section 6 of the right planetary gear 5 meshes with the right half-shaft gear 4, and the left planetary gear 3 meshes with the inner section 7 of the right planetary gear 5. Both the left half-shaft gear 2 and the right half-shaft gear 4 are transmission connected to the wheels.
[0040] The housing 1 has mounting holes 9 adapted to the left planetary gear 3 and the right planetary gear 5. The left end cover and the right end cover are respectively arranged on the left and right sides of the housing 1 and are detachably connected to the housing 1 by bolts. Corresponding threaded holes 10 are provided on the housing 1.
[0041] Specifically, there are four left planetary gears 3 and four right planetary gears 5. The left planetary gears 3 are evenly distributed around the axis of the left side gear 2, while the right planetary gears 5 are evenly distributed around the axis of the right side gear 4. Four left planetary gears 3 with the same rotation direction are arranged in a cross pattern on one side of the left side gear 2, at the top, bottom, left, and right. Four right planetary gears 5 with a different rotation direction are arranged in an X pattern on the top left, top right, bottom left, and bottom right of the right side gear 4. Furthermore, a cylindrical tooth root surface is retained between the outer area 6 and the inner area 7 as a tool relief groove 8.
[0042] Taking the most extreme case of tilt angle discrepancy, the meshing area of the split planetary gears (left planetary gear 3 and right planetary gear 5) and the side gears (left side gear 2 and right side gear 4) is a 10t standard spur gear (i.e., the outer area). The meshing area with the other planetary gears is a single-start standard involute worm with a lead angle of 5.739° (i.e., the inner area). Both have the same module. The worm rotation is divided into left-hand and right-hand, and the planetary gears with the same rotation mesh with the same side gear. The side gears are 16t positive displacement spur gears with a displacement coefficient of approximately +0.0082 to match the center distance. The module is the same as that of the planetary gears.
[0043] A differential requires four left-handed split planetary gears (i.e., left planetary gear 3), four right-handed split planetary gears (i.e., right planetary gear 5), and two side gears (i.e., left side gear 2 and right side gear 4). Their arrangement is as follows: the side gears are centered on both sides, with four planetary gears of the same rotation arranged in a cross pattern on one side (top, bottom, left, and right), and four planetary gears of opposite rotation arranged in an X pattern on the other side (top, right, bottom, left, and bottom). Any planetary gear can fully mesh with its two adjacent planetary gears and the side gears.
[0044] Furthermore, this differential can replace the planetary gears with eight standard 10t spur gears with longer tooth flanks, which can be directly matched with the original side gears and differential housing without modifying their dimensions. In this case, the entire differential can be used as a normal open differential.
[0045] When both wheels have traction, the rotational motion of the worm gears is unaffected by each other, allowing the limited-slip differential to function effectively. When one wheel loses traction, its speed tends to accelerate, but this tendency is curbed by the difficulty in transmitting power between the worm gear portions (inner region 7) of the split planetary gears (left and right planetary gears 3 and 5). This allows the wheel still having traction to receive more torque, allowing it to escape. Compared to a helical gear-type limited-slip differential, this application example of the present invention achieves near self-locking, significantly improving the maximum torque distribution ratio while minimizing power loss.
[0046] The prototype of this utility model, the helical gear limited-slip differential, is a torque-sensing type. Its key feature is the use of helical planetary gears and side gears. The planetary gears are divided into two sets, left and right. The left planetary gears mesh with the left side gears, while the right planetary gears mesh with the right side gears. The left and right planetary gears also mesh with each other. When there is a speed difference between the left and right side gears, the left and right sets of planetary gears will rotate relative to each other. The faster-rotating set of planetary gears forces the other set of planetary gears to rotate, in turn driving the slower-rotating side gears. This transmission characteristic generates significant friction between the tooth surfaces, limiting this forced rotation and thus limiting the slip of the faster-rotating wheel. Well-known limited-slip differentials such as the Torsen T-2, Quaife, and Truetrac all operate based on this principle.
[0047] The example mentioned above uses two side gears and two sets of four split planetary gears, each with opposite rotation directions. However, there are many combinations of planetary gears, including sets of three, five, or six, and each planetary gear does not necessarily need to mesh with both adjacent planetary gears (it can mesh with only one, leaving the remaining one unengaged). Therefore, the evaluation of possible alternatives to this utility model should be based primarily on the principle of "splitting the planetary gears in a helical gear-type limited-slip differential into two components with different inclination angles, each meshing with the side gears and the other planetary gears." As long as the application example splits the planetary gears into two components with different inclination angles, it can be considered that it uses the improved technology of this patent.
[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A limited slip differential, characterized in that: The invention comprises a housing and: A left end gear set, the left end gear set comprising a left side gear and a left planetary gear, the left side gear being coaxially arranged with the housing, the left planetary gear being arranged around the axis of the left side gear and meshing with the left side gear; a right end gear set, the right end gear set comprising a right side gear and a right planetary gear, the right side gear being coaxially arranged with the housing, the right planetary gear being arranged around the axis of the right side gear and meshing with the right side gear; The left planetary gear is meshed with the right planetary gear. The section where the left planetary gear and the right planetary gear are far away from each other is called an outer zone, and the section where the left planetary gear and the right planetary gear are close to each other is called an inner zone. The inclination angle of the gears in the inner zone is greater than the inclination angle of the gears in the outer zone. The outer zone of the left planetary gear is meshed with the left half-shaft gear, the outer zone of the right planetary gear is meshed with the right half-shaft gear, and the left planetary gear is meshed with the inner zone of the right planetary gear.
2. The limited slip differential according to claim 1, characterized in that The number of the left planetary gears and the number of the right planetary gears are both four. The left planetary gears are evenly distributed circumferentially around the axis of the left side shaft gear, and the right planetary gears are evenly distributed circumferentially around the axis of the right side shaft gear.
3. The limited slip differential according to claim 2, characterized in that One side of the left half-shaft gear is cross-shaped with four left planetary gears of the same rotation direction arranged on the upper, lower, left and right sides, and one side of the right half-shaft gear is X-shaped with four right planetary gears of another rotation direction arranged on the upper left, upper right, lower left and lower right sides.
4. The limited slip differential according to claim 1, wherein: A tooth root cylindrical surface is retained between the outer area and the inner area as a tool relief groove.
5. The limited slip differential according to claim 1, wherein: The housing has mounting holes adapted to the left planetary gear and the right planetary gear.
6. The limited slip differential according to claim 1, wherein: It also includes a left end cover and a right end cover, which are respectively arranged on the left and right sides of the shell and are detachably connected to the shell.
7. The limited slip differential according to claim 6, characterized in that The left end cover and the right end cover are both detachably connected to the housing by bolts.
8. The limited slip differential according to claim 7, characterized in that There are multiple bolts, and the bolts are evenly distributed around the axis of the housing.
9. The limited slip differential according to claim 7, wherein: The left half-shaft gear and the right half-shaft gear are both drivingly connected to the wheels.