Mechanical automatic tightening differential device

Abstract

To provide a mechanical automatic tightening type differential device that prevents wheels from spinning when a vehicle turns. The system includes a case with at least two planetary gears F, G connected to respective shafts D, E, a planet gear carrier or carrier axle, and a set of planetary gears H, the operation of which is characterized by actively controlling the torque differential between the inner and outer wheels, allowing the two half shafts to rotate simultaneously in opposite directions with the differential case fixed while maintaining drive to all wheels. In contrast, attempting to rotate only one half shaft with the differential case fixed would cause the system to lock up and become inoperable.

Description

[Technical field]

[0001] The present invention relates to self-tightening differentials, particularly for use in engine and pedal driven vehicles. [Background technology]

[0002] [Prior Art] A differential in an automotive transmission typically functions to drive two output shafts from a single input shaft, with the two output shafts driven at different rotational speeds but with equal torque, half that of the input shaft.

[0003] The problem with conventional differentials is that the torque transmitted to both shafts is limited to the smaller of the wheel resistance torques, i.e. if one wheel loses significant ground contact, the torque transmitted to that wheel is reduced and it tends to spin while the other wheel maintains contact with the ground.

[0004] In a conventional differential, the torque transmitted to each wheel cannot exceed the torque that the lost wheel can tolerate: if the torque is too small, the wheel that has ground contact will not rotate and the vehicle will remain stationary or come to a stop.

[0005] A known publication discloses a self-tightening differential having an input device, two output devices, two output shafts associated with each output device, and axially movable integration means for axially moving the input device to integrate with one of the output devices.

[0006] The coupling system consists of two independent multi-plate couplings, the coupling means being preloaded by a spring, and the clamping force of the multi-plates is generated by the axial thrust from the opposing planetary gears, which is transmitted through a reaction sleeve interposed between the two planetary gears.

[0007] The clamping force is obtained as the difference between two axial thrust forces generated at the inclined cam surface connection between the planetary gear connection and the output shaft. The inclined cam surface detects the reaction force of each wheel, i.e., the contact force with the road surface.

[0008] When the two axial reaction forces are equal, the two multi-plate discs remain in a disengaged state. This means that no clamping forces are generated. The differential exhibits a conventional free differential action. This condition requires sufficient ground contact, or an equal level of ground contact, at each wheel. It also requires that the wheels rotate at the same speed, i.e. the vehicle moves in a straight line.

[0009] On the other hand, when the vehicle is turning and has sufficient ground contact, the wheels follow a different path: the wheel on the inside of the curve travels a shorter distance than the wheel on the outside, so it rotates slower than the differential speed and the wheel on the outside rotates faster.

[0010] The torque to each wheel varies due to internal friction in the planetary gear shafts and bearings, planetary gear bearings, output shaft bearings, etc. This causes a torque transfer from the faster wheel to the slower wheel. The slower wheel receives half the engine torque increased by half the faster friction torque, and the faster wheel receives half the engine torque decreased by half the friction torque.

[0011] Preloading one of the discs further increases the axial force imbalance at the support. Due to the self-amplification effect, the total torque is transferred from the faster wheel to the slower wheel. In this condition, the differential loses the operating freedom required to properly control the vehicle's turning trajectory. The torque transfer to the inside wheel during turning gives the vehicle a noticeable understeer characteristic.

[0012] Furthermore, when one wheel loses traction, the axial reaction force at the cam surface connection between the planetary gear and the corresponding output shaft drops suddenly, causing a difference in the axial thrust forces of the two planetary gears, which causes a clamping force to act on the disk assembly on the side of the wheel that has lost traction. The friction torque of this disk assembly replaces the torque that the wheel cannot accept and allows it to transmit an equal torque to the opposing wheel that still has traction, sufficient to ensure the vehicle's movement.

[0013] In this state, the friction torque of the disk assembly is transmitted through the central mechanism (planetary gears and planetary gears) which ultimately imparts a torque twice that of the motor torque.

[0014] In the above prior art differential, the planetary gears and their shafts are fixed relative to the casing. However, the transmission of axial thrust from one planetary gear to the other through the central reaction sleeve and the locking of the disks requires axial displacement of the planetary gears. In this differential, the amount of movement depends on the backlash between the planetary gears and the planetary gears. Excessive backlash is detrimental.

[0015] However, too much backlash reduces the strength of the teeth, while too little backlash limits the clearance between the discs and the wear margin of the discs, and also carries the risk of gear noise. These constraints therefore hinder the proper operation of the mechanism.

[0016] In summary, the applicant has found that differentials of this type known in the prior art have three main drawbacks: - Torque transfer phenomenon caused by - Excessive load on planetary gears compared to conventional differentials - Axial and relative displacement of planetary gear with respect to planetary gear - Loss of wheel grip and traction when cornering or driving on rough terrain

[0017] In light of this, the applicant focused on the technical challenge of realizing a differential that enables the inner and outer wheels to rotate at different speeds when the vehicle turns, and that can prevent wheels from spinning when they have lost or reduced driving force, even in situations where ground contact is insufficient, such as on ice.

[0018] Another object of the invention is to provide a differential in which both half shafts can rotate simultaneously in opposite directions when the differential case is stationary, whereas if an attempt is made to rotate only one half shaft when the differential case is stationary, the system will lock up and become inoperable.

[0019] A further object of the present invention is to realize a differential that can continuously ensure the vehicle's ground contact stability and driving force by controlling the driving force of the inner and outer wheels while avoiding the above-mentioned drawbacks. Summary of the Invention

[0020] The invention relates to a mechanical self-tightening differential as claimed in claim 1.

[0021] The applicant of the present application has surprisingly found that the technical problems identified above can be effectively and reliably solved by a mechanical self-tightening differential, which comprises a case including the following elements: - Multiple planetary gears at least one support element supporting said plurality of planetary gears; at least two planetary gears each having a shaft and rotatable integrally with the plurality of planetary gears; - a locking element for locking the axial position of said planetary gear, characterized in that:

[0022] The first planetary gear has internal teeth having a helical or spiral thread with a first rotational direction, and the second planetary gear has internal teeth having a helical or spiral thread with a second rotational direction opposite the first rotational direction.

[0023] Due to the structural features of the present invention, the planetary gears move in response to the rotation of the planetary gears, and conversely, when a rotational force is applied from the planetary gears, the planetary gears do not move due to the configuration of the opposing helical threads of each planetary gear.

[0024] This allows the self-tightening mechanical differential to actively control the torque differential between the inside and outside wheels of a vehicle.

[0025] Specifically, the planetary gear shafts are configured to transmit torque to each associated wheel in response to the axial thrust of the corresponding planetary gear.

[0026] These structural features allow the vehicle to turn by allowing the inside wheels to rotate slower and the outside wheels to rotate faster, taking into account the rotational movement of the differential case. At the same time, even if the wheels lose grip on the road, this system can prevent the wheels from spinning.

[0027] According to a preferred embodiment, said at least one support element is an annular element.

[0028] According to a preferred embodiment, the first planetary gear and the second planetary gear are disposed symmetrically with respect to the plurality of planetary gears.

[0029] According to a preferred embodiment, the first planetary gear and the second planetary gear each rotate about their own shaft.

[0030] According to a preferred embodiment, the mechanical self-tightening differential further comprises a plurality of pins, each pin configured to secure a corresponding planetary gear to the support element.

[0031] According to a preferred embodiment, each of the planetary gears has a tooth profile configured such that both ends of each tooth are lower than the center.

[0032] According to a preferred embodiment, the tooth profile of the plurality of planetary gears is configured to follow the movement of the helical tooth profile of the first and second planetary gears.

[0033] According to a preferred embodiment, two or four of said planetary gears are provided.

[0034] According to a preferred embodiment, the distance between the center of the planetary gear and the tooth profile of each planet gear is variable. [Brief description of the drawings]

[0035] Further features and advantages of the invention will become apparent from the following detailed description of preferred embodiments, given for illustrative and non-limiting purposes with reference to the accompanying drawings, in which:

[0036] [Figure 1] 1 illustrates an embodiment of a differential according to the present invention;

[0037] [Diagram 2] FIG. 2 is a perspective view showing in detail the positional relationship of a planetary gear with respect to the planetary gear of FIG. 1.

[0038] [Diagram 3] FIG. 2 is a side view showing in detail the positional relationship of a planetary gear with respect to the planetary gear of FIG. 1.

[0039] [Figure 4] 4 shows a cross-sectional view taken along line AA in FIG.

[0040] [Diagram 5] BB line cross-sectional view of FIG. 3 is shown.

[0041] [Figure 6] FIG. 2 shows a detailed view of the first planetary gear shown in FIG.

[0042] [Figure 7] FIG. 7 shows a view of the first planetary gear shown in FIG. 6 from another angle.

[0043] [Figure 8] FIG. 2 shows a detailed view of the second planetary gear shown in FIG.

[0044] [Figure 9] FIG. 9 shows a view of the second planetary gear shown in FIG. 8 from another angle.

[0045] [Figure 10] FIG. 2 is a detailed perspective view of the planetary gear shown in FIG. 1 .

[0046] [Figure 11] FIG. 11 shows a plan view of the planetary gear shown in FIG.

[0047] [Figure 12] 11 shows details of the teeth of the planetary gear shown in FIG. 10.

[0048] [Figure 13] 11 shows a detail of the helical pitch of the planetary gear shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] An embodiment of a differential K according to the present invention will be described with reference to FIGS.

[0050] FIG. 1 shows a differential K and its components, including a motor pinion A, a differential ring gear B and a differential case C which houses a right planetary gear shaft D, a left planetary gear shaft E, a left planetary gear F, a right planetary gear G, a plurality of planetary gears H, pins I of the planetary gears H, pin shafts L of the planetary gears F and G, and an annular support member M for the planetary gears H.

[0051] The planetary gears H are integrally fixed to a central annular support member M via pins I.

[0052] A first planetary gear F and a second planetary gear G are disposed on either side of the central annular support member M, and the planetary gears F, G rotate about shafts E and D, respectively. The shafts E and D of the planetary gears F, G are held in the center by a predetermined connecting structure. The planetary gears F, G rotate integrally with the planetary gear H.

[0053] An inner pin L disposed at the center of the differential K constitutes a support pin for the planetary gears F, G and maintains the axial position of the planetary gears themselves.

[0054] The central annular support member M, the planetary gear H, the planetary gears F, G, their respective shafts E and D, and the pin I are housed and sealed within a case C of the differential K.

[0055] FIG. 2 shows details of a first planetary gear F and a second planetary gear G that are arranged symmetrically with respect to a plurality of planetary gears H.

[0056] 3 is a side view showing in detail the four planetary gears H that protrude from the outer circumferential ends of the planetary gears F and G and are arranged at 90 degree intervals from each other. In this embodiment, four planetary gears H are provided, but the object of the present invention and the operation of the differential K in this embodiment can also be achieved with two planetary gears H.

[0057] 4 and 5 are cross-sectional views of the planetary gear H of FIG. 3 taken along lines AA and BB, respectively.

[0058] The unique operation of the mechanical self-tightening differential K according to the present invention is based on the unique mechanical structure of the planetary gears F, G and the planetary gear H, which structure constitutes the characteristic and functional elements for the purposes of the present invention.

[0059] Figures 6 and 7 show details of a first planetary gear F having helical or spiral-shaped internal teeth S with a first rotational direction (counterclockwise), and Figures 8 and 9 show details of a second planetary gear G having helical or spiral-shaped internal teeth N with a second rotational direction (clockwise) opposite to the rotational direction of the first planetary gear F.

[0060] 10 and 11 show details of one of the planetary gears H with a unique tooth profile O configured to follow the circular motion of the helical tooth profiles S and N of the planetary gears F and G, respectively.

[0061] Each tooth of the tooth profile O of each planetary gear H is formed such that both ends P1 and P2 are lower than the center point R in the longitudinal direction (as shown in detail in FIG. 12), so that the tooth profile O of the planetary gear H has an almond-shaped profile as a whole. Due to this unique shape, each tooth of the planetary gear H has a semicircular shape along its longitudinal direction.

[0062] This allows the planetary gear H to move due to the unique tooth profile O on the planetary gear H and the unique helical tooth profiles S and N of the planetary gears F and G.

[0063] FIG. 13 shows the characteristics of the helical pitch of planetary gear H in the example with a pitch of 1 mm.

[0064] Due to the particular shape of the helical tooth profiles S and N of the planetary gears F and G, and the distance of planet gear H to the centers of the planetary gears F and G, the distance from the centers of the planetary gears F and G to the tooth profiles S and N varies infinitesimally by 1 / 4 of a pitch every 1 / 4 revolution.

[0065] Specifically, the case where the gear pitch is 1 mm will be described as an example. The locus of the tooth profile O of the planetary gear H must follow the profile of the spiral tooth profiles S and N. For example (FIG. 13), if a position 10 mm from the center of the planetary gear is used as the starting point and a certain locus is drawn every 1 / 4 rotation, the distance is 10.25 mm at 1 / 4 rotation, 10.50 mm (1 / 2 increase of pitch) at 1 / 2 rotation, and 10.75 mm (3 / 4 increase of pitch) at 3 / 4 rotation. Therefore, the distance between the center of the planetary gear and the planetary gear H arranged on the horizontal axis is 10 mm or 10.50 mm, and the distance between the center of the planetary gear and the planetary gear H arranged on the vertical axis is 10.25 mm or 10.75 mm. In this case, the tooth profile O of the planetary gear H meshes accurately with both the right planetary gear G (spiral tooth profile N) and the left planetary gear F (spiral tooth profile S in the opposite direction to the spiral tooth profile N of the right planetary gear G).

[0066] Due to this unique configuration, in order to keep the distance between planetary gear H and the centers of planetary gears F and G constant, the tooth profile modules of planetary gears F and G and planetary gear H must be a multiple of 4 or 4, and the number of teeth of tooth profile O of planetary gear H must always be an even number.

[0067] These structural features allow the vehicle to turn by allowing the inside wheels to rotate slower and the outside wheels to rotate faster through rotation compensation in the differential case. At the same time, even if the vehicle loses contact with the road surface, the system can prevent the wheels from spinning.

[0068] As an example, it can be assumed that the differential case rotates at 20 rpm, the inner wheel rotates at 10 rpm, and the outer wheel rotates at 30 rpm. In fact, due to the unique function of the present invention, the differential will not stop, but will continue to rotate and transmit drive force to the wheels.

[0069] The basic principle of this system is to improve the grip and maneuverability of all vehicles on both paved and unpaved roads, without causing tire drag that occurs with large vehicles with two or more axles, and it can be applied to a wide range of fields, including models, transportation equipment for the disabled, leisure and sports vehicles, transportation equipment within and outside of cities, military vehicles, cargo transport vehicles, and work vehicles.

[0070] In particular, the invention enables scooters and wheelchairs for the disabled to negotiate obstacles in urban environments such as church steps and curbs, as well as mountainous terrain.

[0071] In leisure and sports vehicles, the differential of the present invention allows vehicles such as ATVs to traverse rocky terrain. In industrial applications, the differential allows vehicles to maneuver more precisely in tighter spaces. Additionally, in agriculture and forestry applications, the differential allows vehicles to reach rescue areas on steep or uneven terrain, as well as in forested areas and small settlements.

[0072] The present invention and its technical, structural and functional features constitute a useful improvement in terms of performance and safety of four-wheel drive vehicles as well as racing and Formula 1 vehicles. The present system is an improvement over the common and widely used torque-sensitive "Torsen" system (which has 18 gears constituting a satellite system and cannot fully lock the halfshafts) and is advantageous in terms of overall system weight and manufacturing costs over conventional systems classified as "LSD" or limited slip systems. Meanwhile, the system according to the present invention significantly reduces the number of mechanical elements and the TBR (ratio of torque transmitted to high grip wheels to torque transmitted to low grip wheels) is variable in the range of 0-100% depending on the required power of the halfshafts.

[0073] All the above devices or elements can be manufactured with the most suitable materials according to the environment in which they are used. It is also clear that they can be implemented in any shape or size without departing from the purpose of the protection of the utility model claims. The number of mechanical and technical elements, their arrangement, and the connections / combinations between each element are easily understood by those skilled in the art based on the specific requirements for assembly and function, so detailed descriptions are omitted here.

[0074] Only the basic components necessary to implement the present invention will be described here.

[0075] Thus, the system may further include complementary or finishing accessories, such as pins, locking mechanisms, lubrication systems, etc., as would be readily apparent to one skilled in the art.

[0076] Also, although the detailed description above is particularly directed to automobiles, other embodiments not described in detail herein may be within the scope of the invention, such as other types of vehicles, e.g. pedal-operated vehicles.

[0077] It should be noted that the above description of the embodiment applying the innovative principle of the present invention is described as an example of the innovative principle, and should not be interpreted as limiting the scope of the utility model right claimed herein. Therefore, while maintaining the principle of the present invention, the details of the embodiment and structure can be widely modified from what has been described and illustrated above, without departing from the scope of protection of the utility model registration claims.

Claims

1. A mechanical self-tightening differential (K) for a vehicle, comprising: - several planetary gears (H), - at least one support element (M) for supporting said planetary gears (H); - at least two planetary gears (F, G) which rotate integrally with said plurality of planetary gears (H); - a locking element (L) for maintaining the axial position of said planetary gears (F, G); a case (C) for housing said first planetary gear (F) having helical or spiral internal teeth (S) with a first rotation direction, and a second planetary gear (G) having helical or spiral internal teeth (N) with a second rotation direction opposite to the first rotation direction of the first planetary gear (F).

2. 2. The mechanical self-tightening differential according to claim 1, wherein said at least one support element (M) is an annular element.

3. 2. The mechanical self-tightening differential of claim 1, wherein the first planetary gear (F) and the second planetary gear (G) are symmetrically disposed with respect to the plurality of planetary gears (H).

4. 2. The mechanical self-tightening differential of claim 1, wherein the first planetary gear (F) and the second planetary gear (G) rotate about their own shafts (E) and (D), respectively.

5. 2. The mechanical self-tightening differential of claim 1, further comprising a plurality of pins (I) each for fixing a corresponding planetary gear (H) to said support element (M).

6. 2. The mechanical self-tightening differential according to claim 1, wherein each of the planetary gears (H) has a tooth profile in which both ends (P1, P2) of each tooth (O) are lower than its center point (R).

7. 7. The mechanical self-tightening differential according to claim 6, wherein the tooth profile of the plurality of planetary gears (H) is configured to follow the movement of the helical or sparral internal teeth (S,N) of the first planetary gear and the second planetary gear (F,G).

8. 2. The mechanical self-tightening differential according to claim 1, wherein the number of planetary gears (H) is two or four.

9. 9. A mechanical self-tightening differential according to claim 1, wherein the distance between the centre of the planetary gears (F, G) and the tooth profile (O) of each planetary gear (H) is variable.

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