A reverse interlocking automatic differential

Abstract

The application discloses a reverse interlocking automatic differential, belongs to the field of vehicle pure mechanical transmission technology, and is an optimization and improvement of a prior bidirectional self-locking planetary mechanism. The differential comprises a power input unit, a fixed inner ring gear unit, an integrated movable inner ring gear interconnecting piece and left and right planetary mechanisms, and the core relies on the fixed inner ring gear and the movable inner ring gear to form reverse torque mutual offset and torque balance on double planetary gears, so that the self-rotation torque of the double planetary gears is completely offset, pure mechanical rigid self-locking is realized, and when a speed difference occurs, torque balance is broken, and the differential state is automatically switched. The application discloses discarding electric control, hydraulic pressure and friction auxiliary structures, canceling a through interlocking shaft and a locking tooth disc, and having an extremely simple structure, instantaneous locking, high bearing capacity and high reliability, solves the problems of power loss, complex structure and unstable locking of the existing differential, can be widely matched with various vehicles and multi-shaft driving equipment, and has excellent industrial practicability.

Description

Technical Field

[0001] This application relates to the field of vehicle transmission system technology, specifically to a purely mechanical automatic differential for vehicle drive axles, and more particularly to a reverse interlocking automatic differential that achieves self-locking by counteracting reverse torque. Background Technology

[0002] The differential is a core component of a car's drive axle. Its function is to transmit power to the left and right wheels while allowing them to rotate at different speeds to ensure smooth cornering. However, traditional bevel gear differentials have an inherent characteristic of "differential speed but not torque," meaning torque is preferentially distributed to the wheel with less resistance. This means that when one drive wheel gets stuck in mud or ice and slips, the other drive wheel with traction cannot receive effective torque, significantly reducing the vehicle's traction.

[0003] To address this issue, existing technologies often employ differential lock devices, such as friction plate type, electronically controlled multi-plate clutch type, pneumatic or hydraulic drive type, etc. However, these solutions generally rely on sensors, controllers, and actuators, resulting in drawbacks such as complex structure, high manufacturing cost, response delay, and susceptibility to environmental influences on reliability. From a structural mechanics perspective, the aforementioned existing self-locking differential mechanisms generally suffer from an inherent defect of unbalanced force arms. Under heavy load, reverse pressure, and alternating start-stop conditions, the unbalanced force arm generates a continuous reverse overturning torque, leading to problems such as slippage, lateral movement, and locking failure.

[0004] The applicant previously filed a patent application for a "shaft-type" self-locking automatic differential (application numbers: 202522228807.7, 202511510218.6, published on December 23, 2025). This differential uses external gear transmission and consists of a sun gear, fixed gear, locking disc, planetary carrier, double planetary gears, and pins, achieving reverse interlocking between the left and right units through a through-type interlocking shaft.

[0005] This application is a further optimization and improvement based on the aforementioned prior disclosed technology, aiming to simplify the structure and optimize the force distribution while retaining the core self-locking advantage. The core improvement lies in changing the external meshing transmission to the internal meshing transmission, and realizing direct reverse interlocking of the left and right units through an integrated movable internal gear ring interconnection, thereby eliminating the locking disc and the through-type interlocking shaft, solving the lever arm imbalance problem from the root of the geometric structure, and providing a more compact, stronger, and faster-responding pure mechanical self-locking differential. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] This application aims to address the problems of delayed response, complex structure, and reliance on external control in existing differential lock technologies, while also overcoming industry pain points such as unreliable locking and easy slippage and loosening caused by lever arm geometric imbalance.

[0008] The specific technical problems to be solved include:

[0009] 1. A purely mechanical self-locking differential is provided, which can instantly and seamlessly switch between rigid locking and free differential according to the driving conditions, without the need for any sensors, controllers or external actuators.

[0010] 2. While maintaining the core self-locking principle, the structure is further simplified, the number of parts is reduced, the radial and axial dimensions of the differential are decreased, and the ease of layout is improved.

[0011] 3. By optimizing the geometric configuration to achieve center-to-center balance of the lever arm, ineffective overturning moments are eliminated at the source, thereby improving overall rigidity and load-bearing capacity.

[0012] 4. Ensures 100% traction distribution when locked, flexible and stable steering in differential mode, and requires no manual intervention from the driver throughout the process.

[0013] (II) Technical Solution

[0014] The core of this application lies in realizing pure mechanical self-locking by utilizing the mechanical principle of torque balance. By constructing the geometric prerequisite of lever arm center-balanced, and cooperating with the integrated movable internal gear ring interconnection component, direct reverse interlocking of the left and right units is realized, providing a compact "shaftless" design scheme.

[0015] 2.1 Core Principle – Self-locking Mechanism Based on “Torque Balance and Lever Arm Centering Balance”

[0016] The core mechanical principle of this application is the counterbalancing of opposing torques and torque equilibrium: the fixed and movable internal gear rings in this differential are equivalent to two opposing crowbars, simultaneously applying opposing forces to the double planetary gears. The forces on both sides are equal in magnitude and opposite in direction, counteracting each other and creating a torque equilibrium state. At this time, the effective rotational torque of the double planetary gears around their own axes is completely canceled out, preventing the generation of rotational driving torque, thus achieving rigid self-locking. When a speed difference occurs between the left and right wheels, the left and right output ends reverse direction. This reversing motion releases the internal gear wedging, breaking the torque equilibrium state, allowing the double planetary gears to rotate freely, and restoring the differential's differential function.

[0017] The theoretical basis of this application stems from the classical torque principle: the torque that causes an object to rotate about an axis is equal to the force multiplied by the lever arm (M = F × L). Here, a zero lever arm is the final mechanical result in the locked state, and the key structural prerequisite for achieving this result is a geometric configuration where the lever arm is centrally balanced.

[0018] This application constructs the key geometric conditions for the center-balanced lever arm by precisely setting the minute tooth number difference (1-4 teeth, preferably 1-2 teeth) between the fixed internal gear ring and the movable internal gear ring within the same unit, and the tooth number difference of the matching double planetary gears.

[0019] Locking Mechanism (Passive Rotation of Planetary Carrier): When an external torque attempts to reverse the rotation of the movable internal gear ring, the double planetary gears are forcibly pushed to a specific position. In this position, the line of action of the resultant force of the meshing forces exerted by the fixed and movable internal gear rings on the double planetary gears passes precisely through the center of rotation of the planetary gears, creating a balance of lever arms. At this point, the lever arm of this resultant force about the planetary gear's rotation axis is zero (M = F × 0 = 0). The planetary gears cannot obtain any torque to cause their rotation and are kinematically completely locked, becoming a rigid "wedge" firmly wedged between the movable and fixed internal gear rings, generating enormous normal pressure and static friction, exhibiting a strong mechanical self-locking capability.

[0020] Unlocking Mechanism (Active Rotation of Planetary Carrier): When power is input from the planetary carrier, its rotation drives the double planetary gears to revolve. Since the double planetary gears mesh simultaneously with both the fixed and movable internal gear rings, their revolving motion forces them to rotate. This rotational motion breaks the geometric constraint of the center-of-center balance of the lever arm, causing the line of action of the resultant force to deviate from the center of rotation. The lever arm L≠0, and the planetary gears acquire rotational torque, allowing the differential to smoothly switch from the locked state to the differential state.

[0021] 2.2 Summary of Overall Machine Operating Conditions – Three States of Passive / Active Rotation of the Planetary Carrier

[0022] Based on the above principles, this application defines: "passive rotation of the planetary carrier" (locked state) means that when an external torque attempts to drive the movable internal gear ring, the system is locked due to the centering balance of the lever arm, and the planetary carrier and differential housing are forced to rotate synchronously; "active rotation of the planetary carrier" (locked-out state) means that when power is input from the planetary carrier, the centering balance constraint of the lever arm is automatically released, and the planetary carrier can rotate relative to the housing.

[0023] Based on this, the overall operating modes of the differential can be summarized into the following three conditions:

[0024] First, the left and right planetary carriers rotate passively at the same time. At this time, both units are in a state of equilibrium with the lever arm aligned, and the lever arm is zero, thus realizing rigid transmission, which corresponds to the straight-line driving condition of the vehicle.

[0025] Second, one planetary carrier rotates passively while the other planetary carrier rotates actively. At this time, the unit on the passively rotating side transmits the locking state to the actively rotating side through an integrated interconnection, so that the entire differential is locked. When the vehicle's single wheel slips, the self-locking effect of the lever arm center-to-center balance takes effect quickly, preventing power loss.

[0026] Third, the left and right planetary carriers rotate actively at the same time. At this time, the geometric condition of the center-to-center balance of the lever arm is broken, the lever arm is not zero, the differential enters the differential state, which corresponds to the vehicle turning driving condition.

[0027] Based on the bidirectional principle characteristics of "passive locking" and "active constraint release" revealed by the above three working conditions, this application designs the following specific structural scheme.

[0028] 2.3 Core Structural Scheme – Compact Design Based on Reverse Interlocking

[0029] The self-locking automatic differential of this application is equivalent to two sets of bidirectional self-locking planetary reduction mechanisms with the same speed ratio but opposite output rotation directions, arranged coaxially and symmetrically and interlocked. The bidirectional self-locking planetary reduction mechanism consists of a fixed internal gear ring, a movable internal gear ring, and a planetary mechanism, wherein the planetary mechanism includes a planet carrier, double planetary gears, and a pin shaft. Its characteristic is that it includes:

[0030] Power input end: includes ring bevel gear (1) and differential housing (2); ring bevel gear (1) is fixedly connected to differential housing (2).

[0031] Fixed internal gear ring unit: includes a left unit fixed internal gear ring (2b) and a right unit fixed internal gear ring (3) which are fixedly connected to the differential housing (2), and both rotate synchronously with the differential housing.

[0032] Reverse interlock component: It is an integral movable internal gear ring interconnect (4) made by rigidly fixing the left movable internal gear ring (4a) and the right movable internal gear ring (4b) coaxially. The interconnect is rotatably supported in the differential housing (2) and located between the left and right fixed internal gear rings.

[0033] Left unit planetary mechanism (5): includes a left unit planetary carrier (5a), at least one left unit double planetary gear (5b), and a corresponding number of left unit pins (5d). The output shaft (5c) of the left unit planetary carrier (5a) is used to connect the left half shaft; the double planetary gear (5b) is rotatably mounted on the fork of the planetary carrier (5a) via the pins (5d); after installation, the pinion (5b2) meshes with the left movable internal gear ring (4a), and the large gear (5b1) meshes with the left fixed internal gear ring (2b).

[0034] The right unit planetary mechanism (6) includes a right unit planetary carrier (6a), at least one right unit double planetary gear (6b), and a corresponding number of right unit pins (6d). The output shaft (6c) of the right unit planetary carrier (6a) is used to connect the right half shaft; the double planetary gear (6b) is rotatably mounted on the fork of the planetary carrier (6a) via the pins (6d); after installation, the large gear (6b1) meshes with the right movable internal gear ring (4b), and the small gear (6b2) meshes with the right fixed internal gear ring (3).

[0035] The double planetary gear is made of two external gears, one large and one small, with a difference of 1-4 teeth (preferably 1 or 2 teeth), which are coaxially integrated. According to the rotation direction requirements of the unit, the installation direction of the large and small gears is changed to make the output rotation direction of the left and right units opposite, forming a reverse interlock.

[0036] 2.4 Tooth Number Difference Design and Meshing Relationship

[0037] The key to achieving the self-locking function lies in the specific geometric matching and tooth number difference design, which is also the core prerequisite for ensuring the center-aligned balance geometry of the lever arm:

[0038] Size matching: Within each unit, the tip circle diameter of the pinion of the double planetary gear must be greater than or equal to (preferably greater than) the root circle diameter of its large gear; correspondingly, regardless of whether the large or small internal gear ring is used as the fixed internal gear ring, the root circle diameter of the small internal gear ring must be greater than or equal to (preferably greater than) the tip circle diameter of the large internal gear ring. If this matching relationship is not met, a stable lever arm concentric balance cannot be formed, resulting in insufficient locking force or even failure to lock.

[0039] Tooth difference: The number of teeth of the large and small gears of the double planetary gears in each unit differs by 1-4 teeth (preferably 1 or 2 teeth); the difference in the number of teeth between the fixed internal gear ring and the movable internal gear ring must match the difference in the number of teeth of the large and small double planetary gears in the corresponding unit to ensure correct meshing and reliable locking.

[0040] Rotation direction configuration: The left unit fixed internal gear ring (2b) has more teeth than the left movable internal gear ring (4a); the right unit fixed internal gear ring (3) has fewer teeth than the right movable internal gear ring (4b). This configuration ensures that the output rotation directions of the two planetary mechanisms are opposite, creating conditions for reverse interlocking, while ensuring the elimination of motion interference under differential speed conditions.

[0041] (III) Beneficial Effects

[0042] Compared with existing technologies and prior applications, this application has the following significant technical advantages:

[0043] 1. Superior Reverse Interlocking Structure: Direct reverse interlocking between left and right units is achieved through an integrated movable internal gear ring interconnection component. The interlocking path is shorter, the rigidity is better, and the synchronization is higher. It eliminates the problems of long shaft torsional vibration and deformation. Combined with the centering balance of the lever arm, the self-locking response is faster and more reliable.

[0044] 2. The structure is greatly simplified and the volume is more compact: the through-type interlocking shaft and locking disc parts are completely eliminated, reducing the number of parts and assembly steps. Both radial and axial dimensions can be reduced, which is beneficial for layout in limited space.

[0045] 3. Significantly improved rigidity and load-bearing capacity: The fixed internal gear ring is integrated with the housing, resulting in high rigidity; the movable internal gear ring adopts internal meshing transmission, with a large number of meshing teeth, low contact stress, and uniform load distribution; the integrated interconnection component has high rigidity, accurately ensuring the centering balance of the lever arm and greatly improving locking stability.

[0046] 4. Superior and more reliable self-locking performance: The multi-tooth internal meshing increases the contact area, and the self-locking logic with zero lever arm is achieved based on the center-alignment balance of the lever arm, eliminating invalid torque from the root. The pressure and friction generated by the wedge tightening effect are more widely and evenly distributed, eliminating the risk of slippage and loosening.

[0047] 5. Easier manufacturing and maintenance: Eliminating precision parts such as long shafts and locking gear discs reduces machining difficulty and assembly errors; the internal gear ring can be manufactured using mature gear shaping or grinding processes; the shaftless structure reduces dynamic balance issues and simplifies maintenance.

[0048] 6. Wide range of applications: It is not only suitable for conventional automobile drive axles, but can also be used as a central differential for four-wheel drive vehicles and multi-axle drive vehicles, with flexible installation; it can be widely used in military vehicles, special vehicles, off-road vehicles and various engineering vehicles, and has excellent industrial practicality and industrialization promotion value. Attached Figure Description

[0049] Figure 1 This is a cross-sectional schematic diagram of the reverse interlocking automatic differential of this application; Figure 2 This is an exploded view of the overall structure of the reverse interlocking automatic differential of this application; Figure 3 This is a three-dimensional external view of the reverse interlocking automatic differential of this application; Figure 4 This is a schematic diagram of the differential housing (2) formed by the left fixed internal gear ring and the differential housing in this application; Figure 5 This is a structural schematic diagram of the fixed internal gear ring (3) of the right unit in this application; Figure 6 This is a schematic diagram of the structure of the internal gear ring interconnect (4) of this application; Figure 7This is a schematic diagram of the assembly structure of the left unit planetary mechanism (5) and the right unit planetary mechanism (6) of this application.

[0050] The part numbers of the main components in the attached diagram are explained below: Part Number Name 1. Ring bevel gear 2 Differential housing (where: 2a-hollow shaft hole, 2b-left unit fixing internal gear ring, 2c-bolt hole, 2d-housing flange, 2e-oil passage hole) 3. Right unit fixed internal gear ring (where: 3a-hollow shaft hole, 3b-right unit fixed internal gear ring flange, 3c-bolt hole) 4 Integrated movable internal gear ring interconnection (where: 4a - left movable internal gear ring, 4b - right movable internal gear ring) 5. Left unit planetary mechanism (including: 5a-left unit planetary carrier, 5b-left unit double planetary gear, 5b1-large gear, 5b2-small gear, 5c-output shaft, 5d-pin) 6. Right Unit Planetary Mechanism (including: 6a-Right Unit Planetary Carrier, 6b-Right Unit Double Planetary Gear, 6b1-Large Gear, 6b2-Small Gear, 6c-Output Shaft, 6d-Pin Shaft) 7 bolts Detailed Implementation

[0051] The present application will be further described in detail below with reference to specific embodiments and the accompanying drawings. Example

[0052] like Figures 1 to 7 As shown, the reverse interlocking automatic differential in this embodiment mainly includes: a ring bevel gear 1, a differential housing 2, a right unit fixed internal gear ring 3, a movable internal gear ring interconnection 4, a left unit planetary mechanism 5, a right unit planetary mechanism 6, and bolts 7.

[0053] The ring bevel gear 1 is the power input end, and its inner diameter fits with the outer circle of the differential housing 2. Several blind threaded holes are evenly distributed on the back of the teeth of the ring bevel gear 1, which are used to fix it to the differential housing flange 2d and the right unit fixing internal gear ring flange 3b by bolts 7.

[0054] The differential housing 2 is a cylindrical shape closed at one end. A hollow shaft hole 2a is provided in the central area of ​​its closed end for the output shaft 5c of the left unit planetary carrier 5a to pass through. Near the closed end, the inner circumference of the housing 2 is integrally formed with a left unit fixed internal gear ring 2b. Several oil passage holes 2e for lubricating the internal gears are also provided on its closed end. A flange 2d is integrally formed on the open end face of the housing 2. Several bolt holes 2c, corresponding to the ring bevel gear, are evenly distributed on the flange 2d for connection with the ring bevel gear 1 and the flange 3b of the right unit fixed internal gear ring 3.

[0055] The right unit fixed internal gear ring 3 is a fixed internal gear ring with an end cap. Its outer circumference is integrally fixed with a flange 3b, which also functions as a differential end cap. The central area of ​​its end cap has a hollow shaft hole 3a for the output shaft 6c of the right unit planetary carrier 6a to pass through. Several bolt holes 3c corresponding to the ring bevel gear are evenly distributed along the edge of its flange. During assembly, the right unit fixed internal gear ring 3 is inserted into the open end of the differential housing 2, and the ring bevel gear 1, the flange 2d of the differential housing 2, and the flange 3b of the right unit fixed internal gear ring 3 are locked together as a whole by bolts 7.

[0056] The movable internal gear ring interconnection 4 is an integral component, formed by coaxially connecting the left unit movable internal gear ring 4a and the right unit movable internal gear ring 4b. This interconnection 4 is rotatably supported inside the differential housing 2 and axially positioned between the left unit fixed internal gear ring 2b and the right unit fixed internal gear ring 3, ensuring the coaxial symmetry of the left and right unit lever arms' centering balance condition.

[0057] The left unit planetary mechanism 5 includes a left unit planetary carrier 5a, at least one left unit double planetary gear 5b, and a left unit pin (5d) matching the number of left unit double planetary gears. One end of the left unit planetary carrier 5a extends integrally with a half-shaft connecting shaft 5c with internal splines, and the other end is a planetary gear mounting fork. The double planetary gear 5b is coaxially fixedly connected by a large gear 5b1 and a small gear 5b2. During installation, the double planetary gear 5b is rotated and adjusted to ensure that its large and small gears 5b1 and 5b2 are correctly aligned and meshed with the fixed internal gear ring 2b and the movable internal gear ring 4a. Then, it is rotated and mounted on the fork of the planetary carrier 5a via the pin 5d. After installation, the small gear 5b2 meshes with the movable internal gear ring 4a of the left unit, and the large gear 5b1 meshes with the fixed internal gear ring 2b of the left unit. The output shaft 5c of the left unit planetary carrier 5a passes through the hollow shaft hole 2a of the differential housing 2, is supported in the axle housing by bearings, and is connected to the left half-shaft.

[0058] The right unit planetary mechanism 6 is basically the same in structure as the left unit planetary mechanism 5, including the right unit planetary carrier 6a and the right unit double planetary gear 6b. The key difference is that the installation direction and meshing relationship of the double planetary gears are opposite: the large gear 6b1 meshes with the right unit movable internal gear ring 4b, and the small gear 6b2 meshes with the right unit fixed internal gear ring 3, ensuring that the left and right units rotate in opposite directions and are reliably interlocked, strictly meeting the symmetrical design requirements of the center-balanced force arms on both sides. The output shaft 6c of the right unit planetary carrier 6a passes through the hollow shaft hole 3a of the right unit fixed internal gear ring 3, is supported in the axle housing by bearings, and is connected to the right half shaft.

[0059] The gear tooth configuration in this embodiment is as follows: Left side unit: Fixed internal gear ring (2b) 40 teeth, movable internal gear ring (4a) 38 teeth, small gear (5b2) of double planetary gear (5b) 13 teeth, large gear (5b1) 15 teeth; Right side unit: fixed internal gear ring (3) 38 teeth, movable internal gear ring (4b) 40 teeth, small gear (6b2) of double planetary gear (6b) 13 teeth, large gear (6b1) 15 teeth.

[0060] The above parameters are for illustrative purposes only and are not all embodiments. Those skilled in the art can make adaptive adjustments to the number of teeth, module, number of planetary gears, etc., according to the specific vehicle model parameters without departing from the principle of this application. Such adjustments all fall within the protection scope of this application.

[0061] This embodiment features a compact structure and flexible layout. It is not only suitable for conventional vehicle drive axles, but can also be used as a central differential for four-wheel drive vehicles and multi-axle drive vehicles, meeting the requirements of high-load and high-reliability vehicles such as military vehicles, special vehicles, and off-road vehicles.

[0062] Core working principle and overall machine operating conditions

[0063] This differential is divided into three core operating conditions: straight driving / single wheel slippage (rigid self-locking mode), turning driving (differential mode), and turning straight (automatic recovery of lock).

[0064] The overall core logic is unified as follows: Reverse interlocking forms a pre-limiting position → lever arm aligned with the center of rotation, resulting force passes through the center of rotation → lever arm is zero, torque is zero → rigid self-locking. The speed difference breaks the centering structure → the lever arm is not zero → an effective rotational torque is generated → the differential is unlocked. The following is a detailed description of each working condition in conjunction with the accompanying drawings.

[0065] 1. Straight-line driving and single-wheel slippage – Rigid self-locking mode

[0066] Power is input from the ring bevel gear 1, which drives the differential housing 2, the left unit fixed internal gear ring 2b, and the right unit fixed internal gear ring 3 to rotate synchronously.

[0067] (1) Formation of reverse interlocking - creating the locking condition

[0068] In the left unit, the fixed internal gear ring 2b drives the large gear 5b1 of the double planetary gear 5b, causing the small gear 5b2 to tend to drive the left movable internal gear ring 4a to rotate in a certain direction.

[0069] In the right unit, the fixed internal gear ring 3 drives the pinion 6b2 of the double planetary gear 6b, causing the large gear 6b1 to tend to drive the right movable internal gear ring 4b to rotate in the opposite direction.

[0070] Because the left and right movable internal gear rings are rigidly connected by an integrated interconnect 4, these two opposing rotational trends create a direct and intense kinematic resistance. As a result, the movable internal gear ring interconnect 4 cannot produce any relative rotation, effectively being forcibly "locked" in its current position. At this point, the left and right units have completed their reverse interlocking, and the entire differential enters a ready-to-lock state.

[0071] (2) The lever arm is balanced to the center → The lever arm is zero, and the mechanical self-locking is completed. Taking the left wheel of the vehicle as an example (slipping) and the right wheel as having adhesion. At this time, the left unit is in the "passive rotation of the planetary carrier" state and the right unit is in the "active rotation of the planetary carrier" state.

[0072] The wheel with traction on the right side attempts to drive the right unit planetary carrier 6a in the opposite direction via the half-shaft, causing its rotational speed to be lower than that of the differential housing 2 (or even approaching a standstill). Power is continuously input from the ring bevel gear 1, which drives the housing and the fixed internal gear ring to rotate. The fixed internal gear ring 3 of the right unit drives the right unit double planetary gear 6b ​​to revolve.

[0073] Because the right unit planetary carrier 6a is delayed by the reverse drive, the right unit double planetary gear 6b ​​is forced to rotate. This rotation drives the right movable internal gear ring 4b through the large gear 6b1, and is transmitted to the left movable internal gear ring 4a through the integrated interconnect 4.

[0074] The rotational tendency of the left movable internal gear ring 4a drives the pinion 5b2 of the left unit double planetary gear 5b. At this time, the left unit double planetary gear 5b is wedged between the movable internal gear ring 4a and the fixed internal gear ring 2b.

[0075] Key geometric effect: At this position, the line of action of the resultant force of the meshing forces of the fixed and movable internal gear rings acting on the planetary gears passes precisely through the center of rotation of the planetary gears, forming a center-aligned balance of lever arms. The effective lever arm L = 0, and the rotational torque M = F × 0 = 0. The planetary gears receive no effective torque and cannot rotate at all, becoming a rigid "wedge" that firmly weds the fixed internal gear ring, movable internal gear ring, and planetary carrier together, forming a rigid whole that cannot move relative to each other. Power is directly and without slippage transmitted from the differential housing 2 to the left and right half-shafts, achieving 100% traction force distribution.

[0076] The principle is the same as the above situation when the right wheel is suspended in the air and the left wheel has traction.

[0077] 2. Turning – Disengage the centering, release the lock, and enter differential mode.

[0078] When the left and right output ends produce opposing and equal-speed reverse rotation (for example, when a vehicle turns, the outer wheel speed increases and the inner wheel speed decreases, causing the left and right planetary carriers 5a and 6a to rotate at equal speeds in opposite directions), this opposing and equal-speed reverse motion relationship is exactly the key to releasing the internal gear wedging, which can break the geometric condition of the lever arm's center-to-center balance.

[0079] Decoupling path:

[0080] When the vehicle turns, the speed difference between the left and right wheels forces the left and right planetary carriers (5a, 6a) to rotate in opposite directions at the same speed through the half-shafts. This opposite rotational motion drives the double planetary gears (5b, 6b) of their respective units to revolve. Since the double planetary gears mesh with both the fixed internal gear ring and the movable internal gear ring at the same time, the revolution forces the planetary gears to rotate on their own axis.

[0081] This rotational motion precisely breaks the geometric condition of "the line of action of the resultant force passing through the center of rotation" in the locked state, causing the line of action of the resultant force acting on the planetary gears to deviate from the center of rotation, and the lever arm L ≠ 0. The planetary gears thus obtain effective rotational torque and begin to rotate freely around their own pivot pins, providing an adjustment channel for the speed difference between the left and right planetary carriers.

[0082] In this state, the motion resistance that originally caused the reverse interlock is canceled out by the rotational motion. The integrated movable internal gear ring interconnect (4) can rotate slightly adaptively with the planetary gear rotation, thereby releasing the rigid constraint on the left and right half shafts. The differential fully enters the free differential state, ensuring smooth steering without interference.

[0083] 3. Turning back to straight – automatic reset, instantaneous return to self-locking mode. When the vehicle exits the curve and resumes straight driving:

[0084] The rotational speeds of the left and right wheels returned to the same level, and the left and right planetary carriers 5a and 6a resumed synchronous rotation.

[0085] The external speed difference that forced the double planetary gears to rotate completely disappeared.

[0086] Under the inherent geometric constraint of the difference in the number of teeth between the fixed and movable internal gear rings, the double planetary gears will automatically and precisely return to the critical locking position where the lever arm is aligned centrally. At this point, the resultant force returns to the center of rotation, the lever arm is zero, the torque instantly returns to zero, and the planetary gears are re-wedged into a rigid body.

[0087] Without any external intervention, delay, or impact, the entire differential instantly returns to a rigid locking state of torque balance, regaining its ability to cope with single-wheel slippage.

[0088] This design scheme is only a partial embodiment covered by this application and not all possible embodiments. Besides this embodiment, other structural forms may also be adopted in this application. Any technical solution formed through equivalent substitution or equivalent transformation should be considered to fall within the protection scope of this application.

Claims

1. A reverse interlocking automatic differential, characterized in that, It includes a power input unit, a fixed internal gear ring unit, an integrated movable internal gear ring interconnection, a left unit planetary mechanism, and a right unit planetary mechanism; The power input unit includes a ring bevel gear (1) and a differential housing (2), wherein the ring bevel gear (1) is fixedly connected to the differential housing (2); The fixed internal gear unit includes a left unit fixed internal gear ring (2b) and a right unit fixed internal gear ring (3). The left unit fixed internal gear ring (2b) is integrally formed with the differential housing (2). The right unit fixed internal gear ring (3) is coaxially fixedly connected to the open end of the differential housing (2). The two rotate synchronously with the differential housing (2). The integrated movable internal gear ring interconnect (4) is formed by the coaxial rigid connection of the left movable internal gear ring (4a) and the right movable internal gear ring (4b). The integrated movable internal gear ring interconnect (4) is rotatably supported in the differential housing (2) and located between the left unit fixed internal gear ring (2b) and the right unit fixed internal gear ring (3). The left unit planetary mechanism (5) includes a left unit planetary carrier (5a), at least one left unit double planetary gear (5b), and a left unit pin (5d) matching the number of the left unit double planetary gear (5b). The output shaft (5c) of the left unit planetary carrier (5a) is used to connect the left half shaft. The left unit double planetary gear (5b) meshes with the left unit fixed internal gear ring (2b) and the left movable internal gear ring (4a) simultaneously. The right unit planetary mechanism (6) includes a right unit planetary carrier (6a), at least one right unit double planetary gear (6b), and a right unit pin (6d) matching the number of the right unit double planetary gear (6b). The output shaft (6c) of the right unit planetary carrier (6a) is used to connect the right half shaft. The right unit double planetary gear (6b) meshes with the right unit fixed internal gear ring (3) and the right movable internal gear ring (4b) simultaneously. The double planetary gears (5b, 6b) of the left and right units are rotatably mounted on the forks of the corresponding planetary carriers (5a, 6a) via corresponding pins (5d, 6d); In the locking condition, the fixed internal gear ring and the corresponding movable internal gear ring are equivalent to two opposing force arms, which pry the double planetary gears in opposite directions. The forces on both sides are equal in magnitude and opposite in direction, forming opposing torques and torque balance. This completely cancels out the effective rotational torque of the double planetary gears around their own axes, making it impossible to obtain rotational driving torque, thus achieving pure mechanical rigid self-locking. When there is a speed difference, when the left and right output ends produce opposing constant speed reverse rotation, the opposing constant speed reverse rotation motion relationship releases the internal gear wedging, the torque balance state is broken, the double planetary gears can rotate freely, and the differential smoothly enters the differential state.

2. The reverse interlock automatic differential according to claim 1, characterized in that, The large gear (5b1) of the left unit double planetary gear (5b) meshes with the left unit fixed internal gear ring (2b), and the small gear (5b2) meshes with the left movable internal gear ring (4a); the large gear (6b1) of the right unit double planetary gear (6b) meshes with the right movable internal gear ring (4b), and the small gear (6b2) meshes with the right unit fixed internal gear ring (3); by changing the installation direction of the large and small gears, the output rotation directions of the left and right unit planetary mechanisms are reversed, thereby forming a stable reverse interlocking structure.

3. The reverse interlocking automatic differential according to claim 1, characterized in that, The number of teeth on the fixed internal gear ring (2b) of the left unit is greater than the number of teeth on the movable internal gear ring (4a) of the left unit, and the number of teeth on the fixed internal gear ring (3) of the right unit is less than the number of teeth on the movable internal gear ring (4b). This ensures that the left and right units output rotation directions in opposite directions and form opposing torques, while also ensuring the elimination of motion interference under differential speed conditions.

4. The reverse interlock automatic differential according to claim 1, characterized in that, The difference in the number of teeth between the large and small gears of the left and right unit double planetary gears is 1-4 teeth, preferably 1 tooth or 2 teeth; the difference in the number of teeth between the fixed internal gear ring and the movable internal gear ring of the left and right units matches the difference in the number of teeth between the large and small gears of the corresponding unit double planetary gears, so as to ensure that torque balance is stably achieved when the reverse torque is counteracted.

5. The reverse interlocking automatic differential according to claim 1, characterized in that, The addendum circle and dedendum circle dimensions of each internal gear ring and the double planetary gear meet the following ratios: the dedendum circle diameter of the small internal gear ring is greater than or equal to the addendum circle diameter of the large internal gear ring; the addendum circle diameter of the pinion of the double planetary gear is greater than or equal to the dedendum circle diameter of its large gear; this ensures that there is no meshing interference during the counter-torque process and that the torque balance is precisely achieved.

6. The reverse interlock automatic differential according to claim 1, characterized in that, The closed end of the differential housing (2) is provided with a hollow shaft hole (2a) through which the output shaft (5c) of the left unit planetary carrier (5a) passes, and the open end of the differential housing (2) is provided with a connecting flange (2d); the right unit fixed internal gear ring (3) is an internal gear ring structure with an end cover, with a flange on its outer circle and a hollow shaft hole (3a) in its middle part through which the output shaft (6c) of the right unit planetary carrier (6a) passes, and the outer end of the right unit fixed internal gear ring (3) also functions as a differential end cover.

7. The reverse interlock automatic differential according to claim 1, characterized in that, The right unit fixed internal gear ring (3) is embedded in the opening end of the differential housing (2) and is fixedly connected to the flange (2d) of the differential housing (2) through its flange (3b). The two rotate synchronously with the differential housing (2).

8. The reverse interlock automatic differential according to claim 1, characterized in that, When the vehicle is traveling in a straight line or one wheel is slipping, the differential achieves torque balance by counteracting the opposing torques, preventing the double planetary gears from rotating and achieving rigid synchronous rotation of the left and right half shafts. When the vehicle is turning, the torque balance is broken based on the speed difference between the left and right wheels, allowing the double planetary gears to obtain rotational torque, and the differential automatically enters a free differential state to achieve flexible and interference-free steering.

9. The reverse interlocking automatic differential according to any one of claims 1-8, characterized in that, The integrated movable internal gear ring interconnect (4) is an integral rigid component that directly realizes synchronous reverse interlocking of the left and right movable internal gear rings, completely eliminating the through-type interlocking shaft and locking disc, and simplifying the overall structure.

10. A vehicle, characterized in that, It is equipped with a reverse interlocking automatic differential as described in any one of claims 1-8.

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