Planetary system differential mechanism for transfer case and torque dividing ratio adjusting method of transfer case

Abstract

According to the planetary system differential mechanism for the transfer case, the torque ratio of the front output shaft to the rear output shaft can be equal to the outer diameter ratio of the corresponding sun gears, the outer diameter ratio of the large sun gear to the small sun gear is designed to be 1-2, the torque dividing ratio of the rear output shaft to the front output shaft can be adjusted to be 1-2, and when the planetary system differential mechanism is applied to an articulated mine truck, the rear output shaft is connected with a rear axle of a vehicle; the front output shaft is connected with the front axle of the vehicle, the torque distribution ratio of the rear axle to the front axle of the vehicle can be adjusted to be 1-2, the torque distribution ratio is only related to the outer diameter ratio of the large sun gear and the small sun gear, the outer diameter ratio of the large sun gear and the small sun gear can be designed according to different torque distribution requirements of the vehicle, and therefore the torque distribution requirements of the front axle and the rear axle of the hinged mine truck are met. The operation stability at high rotating speed is ensured, the load stress in the transmission process is reduced, the abrasion of gears and bearings when the front output shaft and the rear output shaft form high differential is reduced, the use reliability of the differential mechanism is improved, and the service life of the differential mechanism is prolonged.

Description

Technical Field

[0001] This invention relates to a planetary system differential for a transfer case, belonging to the field of transfer case technology. This invention also relates to a method for adjusting the torque ratio of a transfer case. Background Technology

[0002] Articulated mining trucks are multi-axle drive vehicles, mostly employing a 6x6 drive structure. A transfer case distributes the power output from the transmission to each drive axle. The basic structure of the transfer case is a gear transmission system. Its input shaft is connected to the output end of the transmission, while its output shafts have several connections, each to a drive axle. Currently, bevel gear differentials are commonly used in articulated mining truck transfer cases to achieve coaxial input and output. A bevel gear differential includes a planetary gear shaft connected to the input shaft, planetary gears mounted on the planetary gear shaft, and half-shaft gears meshing on either side of the planetary gears. One half-shaft gear connects to the rear output shaft, and the other connects to the front output shaft, forming a symmetrical differential structure. However, bevel gear differentials can only achieve a 1:1 torque distribution between the front and rear output shafts. Furthermore, the planetary gears and half-shaft gears are perpendicular to each other. Given the limited load-bearing capacity of the differential housing support structure, excessively large differences between the front and rear output shafts can cause internal gears or bearings to overheat, posing a risk of the differential burning out. To improve torque distribution and extend service life, heavy-duty vehicle transfer cases often use planetary differentials instead of bevel gear differentials. Planetary differentials use a planetary carrier as the input, with the front and rear outputs connected to the sun gear and internal ring gear, respectively. This allows for a torque distribution of 1:1 front and ≥2:2 rear, resulting in a torque distribution ratio between the rear and front axles greater than or equal to 2. However, for articulated mining trucks, to ensure the stability of the articulated structure and considering different load conditions, a more reasonable torque distribution ratio is 40% for the front axle and 60% for the middle and rear axles, requiring a rear-to-front torque distribution ratio of approximately 1.5. This solution aims to improve existing planetary differentials to adjust the torque distribution ratio between the rear and front axles, meeting the torque distribution requirements of articulated mining trucks. Summary of the Invention

[0003] The planetary differential for transfer cases provided by this invention has a torque distribution ratio that is only related to the ratio of the outer diameters of the large and small sun gears. The ratio of the outer diameters of the large and small sun gears can be designed according to the different torque distribution requirements of the vehicle to meet the torque distribution needs of the front and rear axles of articulated mining trucks. This reduces wear on gears and bearings when the front and rear output shafts form a high differential, improves the reliability of the differential, and extends its service life. This invention also provides a method for adjusting the torque distribution ratio of the transfer case.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A planetary differential for a transfer case includes an input shaft, a rear output shaft coaxially aligned with the input shaft, a front output shaft, and a planetary gear set. The front output shaft is rotatably mounted on the rear output shaft. The planetary gear set includes a planet carrier fixed coaxially with the input shaft, large planetary gears mounted on the planet carrier, small planetary gears mounted on the planet carrier, a small sun gear splined and mounted on the front output shaft, and a large sun gear splined and mounted on the rear output shaft. The large planetary gear meshes with the small sun gear, and the small planetary gear meshes with the large sun gear. The outer diameter of the small planetary gear is smaller than that of the large planetary gear, and the outer diameter of the small sun gear is smaller than that of the large sun gear, with each small sun gear meshing with the large sun gear in a one-to-one correspondence.

[0005] Preferably, the input shaft is integrally formed with the planetary carrier, the rear output shaft is clearance-fitted with the front output shaft, the front end of the rear output shaft extends out of the front output shaft and into the planetary carrier, and the large sun gear is assembled at the front end of the rear output shaft.

[0006] Preferably, the planet carrier has a short planetary gear shaft corresponding to the large planetary gear and a long planetary gear shaft corresponding to the small planetary gear. The large planetary gear is mounted on the short planetary gear shaft via a needle roller bearing, and the small planetary gear is mounted on the long planetary gear shaft via a needle roller bearing. The front half of the small planetary gear meshes with the large sun gear, and the rear half meshes with the corresponding large planetary gear.

[0007] Preferably, the rear end of the long planetary shaft is flush with the rear end of the short planetary shaft, the planetary carrier cover is coaxially fixed to the rear side of the planetary carrier, the front ends of the long planetary shaft and the short planetary shaft are respectively pressed into the planetary carrier, and the rear ends are respectively pressed into the planetary carrier cover.

[0008] Preferably, the planet carrier has spacers evenly distributed circumferentially, and a short planetary gear shaft and a long planetary gear shaft are installed between adjacent spacers, with the planet carrier cover fixedly connected to the spacers.

[0009] Preferably, the rear end of the rear output shaft extends from the front output shaft, and the rear end of the rear output shaft is fitted with a differential lock sleeve that can slide axially. The rear output shaft and the front output shaft are integrated as the differential lock sleeve slides forward.

[0010] Preferably, a front output gear corresponding to the differential lock sleeve is fixed on the front output shaft. The rear end face of the front output gear and the front end face of the differential lock sleeve are both mating tooth surfaces. The differential lock sleeve slides forward and engages with the front output gear, thus combining the front output shaft and the rear output shaft into a whole.

[0011] Preferably, the outer diameter of the large sun gear does not exceed twice the outer diameter of the small sun gear.

[0012] The method for adjusting the torque ratio of the transfer case involves using the planetary differential system described above, connecting the front output shaft to the front axle of the vehicle, and connecting the rear output shaft to the rear axle of the vehicle. The ratio of the outer diameter of the large sun gear to the small sun gear is adjusted to 1~2, so that the torque ratio between the rear axle and the front axle of the vehicle is 1~2.

[0013] The beneficial effects of the invention are: The planetary differential for the transfer case of this invention has a large planetary gear and a small planetary gear respectively mounted on a planet carrier. The planet carrier rotates synchronously with the input shaft, driving the large and small planetary gears to revolve around the sun gear. The large sun gear drives the rear output shaft to rotate, and the small sun gear drives the front output shaft to rotate. The large and small planetary gears mesh one-to-one. The rotation of the large and small planetary gears on the planet carrier allows the large and small sun gears to rotate at different speeds, thereby forming a differential between the front and rear output shafts and realizing the differential function. During transmission, the planetary carrier drives the large and small planetary gears to revolve synchronously. The torque of the large and small sun gears along the circumference is equal, but their outer diameters are different. Therefore, the torque ratio of the large and small sun gears will be equal to the ratio of their outer diameters. In other words, the torque ratio of the front and rear output shafts will be equal to the ratio of the outer diameters of the corresponding sun gears. By designing the outer diameter ratio of the large and small sun gears to be 1~2, the torque distribution ratio between the rear and front output shafts can be adjusted to 1~2. In articulated mining trucks, the rear output shaft is connected to the rear axle of the vehicle, and the front output shaft is connected to the front axle. This allows the torque distribution ratio between the rear and front axles to be adjusted to 1~2. The torque distribution ratio is only related to the outer diameter ratio of the large and small sun gears. The outer diameter ratio of the large and small sun gears can be designed according to the different torque distribution requirements of the vehicle to meet the torque distribution requirements of the front and rear axles of the articulated mining truck. The large sun gear can float on the rear output shaft, and the small sun gear can float on the front output shaft, so that the large and small planetary gears can bear the load evenly, ensuring the stability of operation at high speeds, reducing the load stress during transmission, reducing the wear of gears and bearings when the front and rear output shafts form a high differential, improving the reliability of the differential and extending its service life. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the planetary system differential for the transfer case of the present invention.

[0015] Figure 2 This is a schematic diagram of the combination of the planetary carrier, the large sun gear, the small sun gear, the large planet gear, and the small planet gear. Detailed Implementation

[0016] The following is combined with Figures 1-2 The embodiments of the present invention will be described in detail below.

[0017] A planetary differential for a transfer case includes an input shaft 1, a rear output shaft 2 coaxially aligned with the input shaft 1, a front output shaft 3, and a planetary gear set. The front output shaft 3 is rotatably mounted on the rear output shaft 2. The planetary gear set includes a planet carrier 4 coaxially fixed to the input shaft 1, a large planetary gear 5 mounted on the planet carrier 4, a small planetary gear 6 mounted on the planet carrier, a small sun gear 7 splinedly mounted on the front output shaft 3, and a large sun gear 8 splinedly mounted on the rear output shaft 2. The large planetary gear 5 meshes with the small sun gear 7, and the small planetary gear 6 meshes with the large sun gear 8. The outer diameter of the small planetary gear 6 is smaller than the outer diameter of the large planetary gear 5, and the outer diameter of the small sun gear 7 is smaller than the outer diameter of the large sun gear 8, with each small sun gear 7 and large sun gear 8 meshing in a one-to-one correspondence.

[0018] The planetary differential for the transfer case described above has a large planetary gear 5 and a small planetary gear 6 mounted on a planetary carrier 4. The planetary carrier 4 rotates synchronously with the input shaft 1, causing the large planetary gear 5 and the small planetary gear 6 to revolve, which in turn causes the large sun gear 8 and the small sun gear 7 to rotate. The large sun gear 8 drives the rear output shaft 2 to rotate, and the small sun gear 7 drives the front output shaft 3 to rotate. The large planetary gear 5 and the small planetary gear 6 mesh one-to-one. The rotation of the large and small planetary gears on the planetary carrier 4 allows the large and small sun gears to rotate at different speeds, thereby forming a differential between the front output shaft 3 and the rear output shaft 2, and realizing the differential function. During transmission, the planetary carrier 4 drives the large planetary gear 5 and the small planetary gear 6 to revolve synchronously. The torque of the large and small sun gears along the circumferential direction is equal, but the outer diameters of the large and small sun gears are different. Therefore, the torque ratio of the large and small sun gears will be equal to the ratio of their outer diameters. That is, the torque ratio of the front and rear output shafts will be equal to the ratio of the outer diameters of the corresponding sun gears. By designing the outer diameter ratio of the large sun gear to the small sun gear to be 1~2, the torque distribution ratio between the rear output shaft and the front output shaft can be adjusted to 1~2. When used in articulated mining trucks, the rear output shaft is connected to the rear axle of the vehicle, and the front output shaft is connected to the front axle of the vehicle. This allows the torque distribution ratio between the rear axle and the front axle of the vehicle to be adjusted to 1~2. The torque distribution ratio is only related to the outer diameter ratio of the large and small sun gears. The outer diameter ratio of the large and small sun gears can be designed according to the different torque distribution requirements of the vehicle to meet the torque distribution requirements of the front and rear axles of the articulated mining truck. The large sun gear 8 can float on the rear output shaft 2, and the small sun gear 7 can float on the front output shaft 3, so that the large and small planetary gears can bear the load evenly, ensuring the stability of operation at high speeds, reducing the load stress during transmission, reducing the wear of gears and bearings when the front and rear output shafts form a high differential, improving the reliability of the differential and extending its service life.

[0019] The input shaft 1 is integrally formed with the planetary carrier 4. The rear output shaft 2 and the front output shaft 3 are clearance-fitted. The front end of the rear output shaft 2 extends out of the front output shaft 3 and into the planetary carrier 4. The large sun gear 8 is mounted on the front end of the rear output shaft 2. As shown in the attached drawings, the planetary gear set connects the input shaft 1 with the front and rear output shafts. The planetary carrier 4 is integrally formed at the rear end of the input shaft 1. The front end of the rear output shaft 2 extends into the planetary carrier 4. The large sun gear 8 is located in the planetary carrier 4 and is mounted on the front end of the rear output shaft 2 via a spline, forming a coaxial arrangement of the input shaft 1, the rear output shaft 2, and the front output shaft 3. This reduces the center distance between the front output shaft 3 and the input shaft 1, thereby reducing the radial dimension of the differential. It also makes full use of the internal space of the planetary carrier 4 to reduce the axial dimension of the differential, improving the structural compactness of the differential.

[0020] The planet carrier 4 has a short planetary gear shaft 41 corresponding to the large planetary gear 5 and a long planetary gear shaft 42 corresponding to the small planetary gear 6 fixed on it. The large planetary gear 5 is mounted on the short planetary gear shaft 41 via needle roller bearings, and the small planetary gear 6 is mounted on the long planetary gear shaft 42 via needle roller bearings. The front half of the small planetary gear 6 meshes with the large sun gear 8, and the rear half meshes with the corresponding large planetary gear 5. Figure 2 As shown, three large planetary gears 5 and three small planetary gears 6 are mounted on the planet carrier 4. The large and small planetary gears are evenly distributed around the circumference of the planet carrier 4. Each large planetary gear 5 meshes with one small planetary gear 6, forming three sets of planetary gears that mesh one-to-one. The three small planetary gears 6 mesh around the outer circumference of the large sun gear 8, and the three large planetary gears 5 mesh around the outer circumference of the small sun gear 7. The small planetary gears 6 are mounted on the long planetary gear shaft 42, and the large planetary gears 5 are mounted on the short planetary gear shaft 42. The axial length of the small planetary gears 6 is greater than the axial length of the large planetary gears 5. The front half of the small planetary gear 6 meshes with the large sun gear 8, and the rear half meshes with the corresponding large planetary gear 5, forming an alternating distribution of planetary gears and sun gears, reducing the radial dimension of the planetary gear set and improving the structural compactness.

[0021] In this configuration, the rear end of the long planetary shaft 42 is flush with the rear end of the short planetary shaft 41. The planetary carrier cover 9 is coaxially fixed to the rear side of the planetary carrier 4. The front ends of the long planetary shaft 42 and the short planetary shaft 41 are respectively press-fitted into the planetary carrier 4, and their rear ends are respectively press-fitted into the planetary carrier cover 9. The planetary carrier cover 9 and the planetary carrier 4 fix and position the long and short planetary shafts, ensuring effective support for the large and small planetary gears and improving the structural stability of the differential during transmission.

[0022] The planet carrier 4 has spacers 43 evenly distributed circumferentially. A short planetary gear shaft 41 and a long planetary gear shaft 42 are installed between adjacent spacers 43. The planet carrier cover 9 is fixedly connected to the spacers 43. Figure 2As can be seen, the three isolation blocks 43 divide the planet carrier 4 into three equal parts around its circumference. Between each adjacent isolation block 43, there is a short planetary gear shaft 41 and a long planetary gear shaft 42. The large planetary gear 5 is mounted on the short planetary gear shaft 41, and the small planetary gear 6 is mounted on the long planetary gear shaft 42, forming a one-to-one meshing of the large sun gear 8 and the small planetary gear 6, the small sun gear 7 and the large planetary gear 5, and the small planetary gear 6 and the large planetary gear 5. After the planetary gears are assembled, the planet carrier cover 9 is bolted to the isolation blocks 43 to form a fit between the long and short planetary gear shafts and the planet carrier cover 9. The isolation blocks 43 divide the planet carrier 4 into multiple equal parts around its circumference, forming a one-to-one installation of the long and short planetary gear shafts. This ensures the one-to-one meshing of the large and small planetary gears, provides an installation position for the planet carrier cover 9, ensures the assembly reliability of the large and small planetary gears, and improves the installation convenience and structural compactness of the planetary gear set.

[0023] The rear end of the rear output shaft 2 extends from the front output shaft 3. A differential lock sleeve 10, which can slide axially, is fitted to the rear end of the rear output shaft 2. The rear output shaft 2, along with the forward sliding of the differential lock sleeve 10, integrates with the front output shaft 3 to form a whole. The forward sliding of the differential lock sleeve 10 integrates the front and rear output shafts, locking the differential function and forming a mechanical differential lock structure. When the vehicle slips, the forward sliding of the differential lock sleeve 10 locks the differential function, improving passability.

[0024] The front output shaft 3 is fixed with a front output gear 31 corresponding to the differential lock sleeve 10. Both the rear end face of the front output gear 31 and the front end face of the differential lock sleeve 10 are mating tooth surfaces. The differential lock sleeve 10 slides forward and engages with the front output gear 31, thus combining the front output shaft 3 and the rear output shaft 2 into a single unit. The differential lock sleeve 10 slides forward, and the mating tooth surface of its front end engages with the mating tooth surface of the rear end face of the front output gear 31, further combining the front output shaft 3 and the rear output shaft 2 into a single unit. The front output gear 31 is used both for power output from the front output shaft 3 and for locking the differential with the differential lock sleeve 10, improving structural compactness.

[0025] The outer diameter of the large sun gear 8 does not exceed twice the outer diameter of the small sun gear 7. During transmission, the planetary carrier 4 drives the large planet gear 5 and the small planet gear 6 to revolve synchronously. The torque of the large and small sun gears along the circumferential direction is equal, but the outer diameters of the large and small sun gears are not equal. Therefore, the torque ratio of the large and small sun gears will be equal to the ratio of their outer diameters. That is, the torque ratio of the front and rear output shafts will be equal to the ratio of the outer diameters of the corresponding sun gears. By designing the outer diameter ratio of the large sun gear to the small sun gear to be 1~2, the torque distribution ratio between the rear output shaft and the front output shaft can be adjusted to 1~2. When applied to articulated mining trucks, the rear output shaft is connected to the rear axle of the vehicle, and the front output shaft is connected to the front axle of the vehicle. This allows the torque distribution ratio between the rear axle and the front axle of the vehicle to be adjusted to 1~2, meeting the torque distribution requirements of the front and rear axles of the articulated mining truck.

[0026] This invention also provides a method for adjusting the torque distribution ratio of a transfer case. The transfer case employs the aforementioned planetary differential system, connecting the front output shaft 3 to the front axle of the vehicle and the rear output shaft 2 to the rear axle. The ratio of the outer diameter of the large sun gear to the small sun gear is adjusted to 1-2, resulting in a torque distribution ratio of 1-2 between the rear and front axles. In this torque distribution method, the torque distribution ratio between the rear and front axles is only related to the ratio of the outer diameters of the large and small sun gears. The ratio of the outer diameters of the large and small sun gears can be designed according to the different torque distribution requirements of the vehicle to meet the torque distribution needs of the articulated mining truck's front and rear axles. The torque distribution ratio adjustment is simple and can be adjusted according to the actual operating conditions of the vehicle, making it highly targeted and practical.

[0027] The technical solutions of the embodiments of the present invention have been fully described above with reference to the accompanying drawings. It should be noted that the described embodiments are only a part of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

Claims

1. A planetary differential for a transfer case, comprising an input shaft, a rear output shaft coaxially aligned with the input shaft, a front output shaft, and a planetary gear set, characterized in that: The front output shaft is rotatably mounted on the rear output shaft. The planetary gear set includes a planet carrier fixed coaxially with the input shaft, a large planetary gear mounted on the planet carrier, a small planetary gear mounted on the planet carrier, a small sun gear mounted on the front output shaft with a spline fit, and a large sun gear mounted on the rear output shaft with a spline fit. The large planetary gear meshes with the small sun gear, and the small planetary gear meshes with the large sun gear. The outer diameter of the small planetary gear is smaller than the outer diameter of the large planetary gear, and the outer diameter of the small sun gear is smaller than the outer diameter of the large sun gear. The small sun gear and the large sun gear mesh in a one-to-one correspondence.

2. The planetary differential for a transfer case according to claim 1, characterized in that: The input shaft is integrally formed with the planetary carrier, the rear output shaft is clearance-fitted with the front output shaft, the front end of the rear output shaft extends out of the front output shaft and into the planetary carrier, and the large sun gear is assembled at the front end of the rear output shaft.

3. The planetary differential for a transfer case according to claim 2, characterized in that: The planet carrier has a short planetary gear shaft corresponding to the large planetary gear and a long planetary gear shaft corresponding to the small planetary gear fixed on it. The large planetary gear is mounted on the short planetary gear shaft via needle roller bearings, and the small planetary gear is mounted on the long planetary gear shaft via needle roller bearings. The front half of the small planetary gear meshes with the large sun gear, and the rear half meshes with the corresponding large planetary gear.

4. The planetary differential for a transfer case according to claim 3, characterized in that: The rear end of the long planetary shaft is flush with the rear end of the short planetary shaft. The planetary carrier cover is coaxially fixed to the rear side of the planetary carrier. The front ends of the long planetary shaft and the short planetary shaft are respectively pressed into the planetary carrier, and the rear ends are respectively pressed into the planetary carrier cover.

5. The planetary differential for a transfer case according to claim 4, characterized in that: The planet carrier has spacers evenly distributed around its circumference. Between adjacent spacers are a short planetary gear shaft and a long planetary gear shaft. The planet carrier cover is fixedly connected to the spacers.

6. The planetary differential for a transfer case according to claim 1, characterized in that: The rear end of the rear output shaft extends from the front output shaft, and a differential lock sleeve that can slide axially is fitted to the rear end of the rear output shaft. The rear output shaft and the front output shaft are integrated as the differential lock sleeve slides forward.

7. The planetary differential for a transfer case according to claim 6, characterized in that: A front output gear corresponding to the differential lock sleeve is fixed on the front output shaft. The rear end face of the front output gear and the front end face of the differential lock sleeve are both mating tooth surfaces. The differential lock sleeve slides forward and engages with the front output gear, thus combining the front output shaft and the rear output shaft into a whole.

8. The planetary differential for a transfer case according to claim 1, characterized in that: The outer diameter of the large sun gear shall not exceed twice the outer diameter of the small sun gear.

9. A method for adjusting the torque ratio of a transfer case, wherein the transfer case employs a planetary differential system for a transfer case as described in any one of claims 1 to 8, the front output shaft is connected to the front axle of the vehicle, the rear output shaft is connected to the rear axle of the vehicle, and the outer diameter ratio of the large sun gear to the small sun gear is adjusted to 1 to 2, so that the torque ratio between the rear axle and the front axle of the vehicle is 1 to 2.

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