Differential gear assembly and method of assembling the same
A differential gear assembly, and method for assembling such an assembly are provided. The differential gear assembly comprises a housing constructed of substantially identically shaped and sized housing plates, which each have an outer flange of a same diameter. The assembly further comprises an outer helical ring gear that is fixed to the housing, wherein outer helical ring gear comprises an inner flange for mounting to the outer flange of the first or second housing plate, wherein an inner diameter of the inner flange is smaller than the outer diameter of the housing plates. The inner flange of the helical ring gear can thus be held, e.g. clamped, between the outer flanges of the housing plates. In an alternative embodiment, the outer flange of one of the housing plates is held between the inner flange of the ring gear and the outer flange of the other of the housing plates.
1. A differential gear assembly comprising:
a housing comprising a first housing plate and a second housing plate, wherein the first housing plate and the second housing plate have a substantially identical shape and size, and each of the first housing plate and the second housing plate comprise a respective outer flange having substantially a same outer diameter;
a first pair of gears mounted within the housing, wherein each gear of the first pair of gears is mounted rotatably around a first axis of rotation (A1);
a second pair of gears mounted within the housing, wherein each gear of the second pair of gears is mounted rotatably around a second axis of rotation (A2), wherein the second pair of gears engage with the first pair of gears, and wherein the second axis of rotation (A2) is normal to the first axis of rotation (A1); and
an outer helical ring gear that is fixed to the housing, wherein the outer helical ring gear comprises an inner flange for mounting to the respective outer flange of at least one of the first housing plate or the second housing plate, wherein an inner diameter of the inner flange is smaller than the outer diameter of the first housing plate and the second housing plate, wherein each gear of the second pair of gears is rotatably mounted on a gear shaft, wherein the gear shaft comprises a shaft portion with a non-circular cross-section having two flat surfaces in respective planes parallel to a longitudinal axis of the gear shaft, wherein at least one of the first housing plate or the second housing plate comprises a receiving portion that directly mounts to the shaft portion with some play in such a manner that rotation of the gear shaft around the second axis of rotation with respect to the housing is substantially blocked by the two flat surfaces, wherein the respective outer flanges of the first housing plate and the second housing plate are provided with a circumferential ridge that is raised in a normal direction from respective surfaces of the respective outer flanges, wherein the circumferential ridge has an outer circumferential side surface for aligning the inner flange of the outer helical ring gear with the respective outer flanges, wherein the outer circumferential side surface has an outer diameter that is less than the inner diameter of the inner flange of the outer helical ring gear, wherein the circumferential ridge has an inner circumferential side surface that engages with the shaft portion of the gear shaft with the non-circular cross-section, and wherein a first height of the outer circumferential side surface in the normal direction from the respective surfaces of the respective outer flanges is less than a second height of the inner circumferential side surface in the normal direction from the respective surfaces of the respective outer flanges.
2. The differential gear assembly of claim 1 , wherein the gear shaft is arranged completely within an interior of the housing between facing sides of the first housing plate and the second housing plate.
3. The differential gear assembly of claim 1 , wherein the second axis of rotation (A2) intersects an external gear mesh of the outer helical ring gear.
4. The differential gear assembly of claim 3 , wherein a plane (P) through the second axis of rotation (A2) and normal to the first axis of rotation (A1) divides the external gear mesh of the outer helical ring gear into two mesh portions of having substantially equal heights along the first axis of rotation (A1).
5. The differential gear assembly of claim 1 , wherein the inner flange of the outer helical ring gear is held between the respective outer flanges of the first housing plate and the second housing plate, and wherein the inner flange is clamped between the respective outer flanges.
6. The differential gear assembly of claim 1 , wherein the inner flange is provided with openings, wherein the respective outer flanges are provided with a number of through openings for bolts to connect the first housing plate and the second housing plate together, and wherein the through openings of the respective outer flanges are aligned with the openings in the inner flange of the outer helical ring gear.
7. The differential gear assembly of claim 1 , wherein at least one of the first housing plate or the second housing plate are formed from a material comprising a ceramic material.
8. The differential gear assembly of claim 1 , wherein facing sides of the first housing plate and the second housing plate are spaced apart from each other at a distance (h) by the inner flange of the outer helical ring gear.
9. The differential gear assembly of claim 1 , wherein each of the first housing plate and the second housing plate comprises a first through-opening for passage of an axle for rotation fixed connection to one of the first pair of gears, and a second through-opening, wherein the first through-opening has a circumferential edge comprising a first diameter and the second through-opening has a circumferential edge comprising a second diameter which is larger than the first diameter, wherein the housing, when assembled, comprises an outward facing side and an opposite inward facing side which faces the first pair of gears and the second pair of gears, and wherein no other through-opening than the second through-opening has a dimension that allows passage of the first pair of gears and the second pair of gears from the outward facing side to the opposite inward facing side.
10. The differential gear assembly of claim 9 , wherein the first housing plate, the second housing plate, and the inner flange of the outer helical ring gear together substantially seal off an interior of the housing except for at the first through-opening and the second through-opening.
11. The differential gear assembly of claim 1 , wherein the outer helical ring gear comprises an external gear mesh with teeth, and wherein the teeth have tips which point radially outwards from the first axis of rotation (A1).
12. The differential gear assembly of claim 1 , wherein teeth of the outer helical ring gear are machined from a monolithic block of material.
13. The differential gear assembly of claim 1 , wherein a center of mass of the differential gear assembly substantially coincides with an intersection of the first axis of rotation (A1) and the second axis of rotation (A2).
14. Method for assembling a differential gear assembly, comprising:
providing a first housing plate and a second housing plate having a substantially identical shape and size, wherein the first housing plate and the second housing plate comprise respective outer flanges having a substantially same outer diameter;
providing a helical gear comprising an inner flange having a diameter that is smaller than the outer diameter of the respective outer flanges of the first housing plate and the second housing plate;
arranging a first pair of gears and a second pair of gears in the first housing plate or the second housing plate in such a manner that each gear of the first pair of gears engages each gear of the second pair of gears;
fixing the respective outer flanges of the first housing plate and the second housing plate relative to the inner flange of the helical gear to form a housing of the differential gear assembly, wherein each gear of the second pair of gears is rotatably mounted on a gear shaft, wherein the gear shaft comprises a shaft portion with a non-circular cross-section having two flat surfaces in respective planes parallel to a longitudinal axis of the gear shaft, wherein at least one of the first housing plate or the second housing plate comprises a receiving portion that directly mounts to the shaft portion with some play in such a manner that rotation of the gear shaft around the second axis of rotation with respect to the housing is substantially blocked by the two flat surfaces, wherein the respective outer flanges of the first housing plate and the second housing plate are provided with a circumferential ridge that is raised in a normal direction from respective surfaces of the respective outer flanges, wherein the circumferential ridge has an outer circumferential side surface for aligning the inner flange of the helical gear with the respective outer flanges, wherein the outer circumferential side surface has an outer diameter that is less than the inner diameter of the inner flange of the helical gear, wherein the circumferential ridge has an inner circumferential side surface that engages with the shaft portion of the gear shaft with the non-circular cross-section, and wherein a first height of the outer circumferential side surface in the normal direction from the respective surfaces of the respective outer flanges is less than a second height of the inner circumferential side surface in the normal direction from the respective surfaces of the respective outer flanges.
15. The method of claim 14 , wherein the gear shaft is arranged completely within an interior of the housing between facing sides of the first housing plate and the second housing plate.
16. The method of claim 14 , wherein the inner flange of the helical gear is held between the respective outer flanges of the first housing plate and the second housing plate, and wherein the inner flange is clamped between the respective outer flanges.
17. The method of claim 14 , wherein the inner flange is provided with openings, wherein the respective outer flanges are provided with a number of through openings for bolts to connect the first housing plate and the second housing plate together, and wherein the through openings of the respective outer flanges are aligned with the openings in the inner flange of the helical gear.
18. The method of claim 14 , wherein at least one of the first housing plate or the second housing plate are formed from a material comprising a ceramic material.
19. The method of claim 14 , wherein facing sides of the first housing plate and the second housing plate are spaced apart from each other at a distance (h) by the inner flange of the helical gear.
20. The method of claim 14 , wherein each of the first housing plate and the second housing plate comprises a first through-opening for passage of an axle for rotation fixed connection to one of the first pair of gears, and an opposite second through-opening, wherein the first through-opening has a circumferential edge comprising a first diameter and the second through-opening has a circumferential edge comprising a second diameter which is larger than the first diameter, wherein the housing, when assembled, comprises an outward facing side and an opposite inward facing side which faces the first pair of gears and the second pair of gears, and wherein no other through-opening than the second through-opening has a dimension that allows passage of the first pair of gears and the second pair of gears from the outward facing side to the opposite inward facing side.