Transmission and braking system

Abstract

A transmission and braking system (10) comprises a differential gear mechanism (20) having an outer housing (21) with a first inner chamber (22) containing a fluid, and a first (25) and a second (26) transmission shaft axially aligned with each other, each having a first end (25a, 26a) provided with a gear wheel (27) arranged in the first inner chamber (22). A first (30) and a second (31) magneto-rheological brake each comprise an outer stator (32) integral with the outer housing (21) and defining a second inner chamber (34) containing a magneto- rheological fluid, and a rotor (35) arranged in the second inner chamber (34) and rotationally integral with the first (25) or the second (26) transmission shaft. A control system is configured to selectively actuate the first (30) and / or the second (31) magneto-rheological brake and generate independent braking forces on at least one of the two transmission shafts (25, 26) of the differential gear mechanism (20).

Description

[0001] Transmission and braking system

[0002] Technical field

[0003] The present invention relates to transmission and braking systems for vehicles with three or more wheels and provided with at least one axle connected to a pair of wheels. In particular, it relates to transmission and braking systems applicable to electric, hybrid, or combustion vehicles.

[0004] Background art

[0005] For proper operation, vehicles are traditionally equipped with a transmission system comprising a differential gear, that is, a device capable of adjusting the rotational speed and / or torque delivered to each of the two wheels associated with the same axle.

[0006] Different types of differential gears are known in the art, including classic differential gears, also known in the field as “open” differential gears, which are transmission devices designed to distribute the driving torque equally to the two wheels associated with the same axle, allowing the two wheels to rotate at different speeds, for example when the vehicle is turning.

[0007] During vehicle operation, situations may arise in which one of the two wheels connected to the same axle loses traction with the ground. In such situations, a classic differential gear would concentrate the driving torque mainly on the wheel that has lost traction, preventing proper vehicle advancement. To overcome this limitation, limited-slip differential gears and self-locking differential gears have been introduced, which allow for the delivery of different driving torques between the two wheels connected to the same axle, thus preventing wheel slip. In the case of self-locking differential gears, the increase and / or distribution of the driving torque is achieved by inserting an additional device into the differential gear, such as a clutch or a gear, or by using a viscous fluid or a magneto-rheological fluid.

[0008] In order to ensure proper vehicle operation, considerable attention is also being given to vehicle braking systems, with the aim of minimizing the production and emission of particulate matter and other waste products such as carbon dioxide, nitrogen oxides and their mixtures, which are mainly produced during the braking phase.

[0009] To this end, some solutions have been developed that employ braking systems using magneto-rheological fluid, which are installed on the vehicle wheels. However, since such braking systems are located downstream of the vehicle’s suspension system, they increase the vibrations transmitted to the vehicle due to unsprung masses; these vibrations are therefore transmitted to the users, reducing comfort during use.

[0010] Summary of the invention

[0011] A main object of the present invention is to provide a transmission and braking system designed to minimize particulate emissions.

[0012] Another object is to provide a transmission and braking system that increases user comfort during use. In particular, an object of the invention is to reduce the vibrations perceived by users when using the vehicle.

[0013] A further object of the present invention is to provide a transmission and braking system capable of slowing down and / or stopping each wheel of the pair of wheels connected to the same axle independently of the others.

[0014] The above and other objects and advantages, which will be better understood hereinafter, are achieved according to the present invention having the features set forth in independent claim 1. Preferred embodiments of the invention are defined in the dependent claims.

[0015] In summary, a transmission and braking system for vehicles with three or more wheels comprises a differential gear mechanism, a first and a second magneto-rheological brake, and a control system. The differential gear mechanism comprises an outer housing defining a first inner chamber in which a fluid is contained, at least one pinion mounted on and rotationally integral with a drive shaft of the vehicle and housed in the first inner chamber, and a first and a second transmission shaft axially aligned with each other, wherein each transmission shaft has a first end provided with a gear wheel arranged in the first inner chamber and a second end connectable to a wheel of the vehicle. The first and second magneto-rheological brakes each comprise an outer stator provided with windings, integral with the outer housing of the differential gear mechanism and defining a second inner chamber in which a magneto-rheological fluid is contained, and a rotor arranged in the second inner chamber and rotationally integral with the first or the second transmission shaft of the differential gear mechanism. The control system is configured to selectively actuate the first and / or second magneto-rheological brake and generate independent braking forces on at least one of the two transmission shafts of the differential gear mechanism.

[0016] Brief description of the drawings

[0017] The features and advantages of the present invention will be apparent from the following description, provided by way of non-limiting example, with reference to the accompanying drawings, in which:

[0018] Figure 1 is a perspective view of a transmission and braking system according to the present invention,

[0019] Figure 2 is a sectional view of a transmission and braking system in which a first chamber of the differential gear mechanism and second chambers of the magneto- rheological brakes are separated,

[0020] Figure 3 is a sectional view of a transmission and braking system in which a first chamber of the differential gear mechanism and second chambers of the magneto- rheological brakes are in communication, allowing fluid passage and forming a single inner chamber,

[0021] Figure 4 is a sectional view of a transmission and braking system in which a porous wall is interposed between a first chamber of the differential gear mechanism and second chambers of the magneto-rheological brakes, and

[0022] Figure 5 is a sectional view of a transmission and braking system comprising a third brake associated with a drive shaft.

[0023] Detailed description The present invention relates to a transmission and braking system 10 for vehicles with three or more wheels and provided with at least one axle associated with a pair of wheels. For example, such vehicles may be cars with an electric, hybrid, or combustion engine, or vehicles with a greater number of axles, such as trucks or articulated vehicles. In particular, the transmission and braking system of the present invention is configured for adjusting the braking torque applied to the vehicle wheels.

[0024] As shown in figure 1, the system comprises a differential gear mechanism 20, a first 30 and a second 31 magneto-rheological brake, i.e., containing a magneto-rheological fluid, and a control system for actuating each magneto-rheological brake 30, 31 of the vehicle.

[0025] A magneto-rheological fluid is a fluid comprising a carrier fluid, such as a mineral, silicone or synthetic oil, and magnetic particles, such as carbonyl iron particles, dispersed in the carrier fluid. The magneto-rheological fluid is capable of varying its apparent viscosity when subjected to a magnetic field. In the absence of a magnetic field, the magneto-rheological fluid has a low apparent viscosity and behaves like an oil, whereas in the presence of a magnetic field, the magneto-rheological fluid has a high apparent viscosity and behaves like a semi- solid.

[0026] The differential gear mechanism 20 comprises an outer housing 21, at least one pinion 23, a first transmission shaft 25 and a second transmission shaft 26. The outer housing 21 defines a first inner chamber 22 configured to contain a fluid, for example a lubricating oil or a magneto-rheological fluid.

[0027] The pinion 23 is mounted on a drive shaft 24 of the vehicle, preferably at one end of the drive shaft 24, and is rotationally integral with the drive shaft 24. For example, the pinion 23 and the drive shaft 24 may rotate about an axis denoted by the letter E in the figures. The pinion 23 is housed in the first inner chamber 22 and immersed in the fluid contained therein.

[0028] The first transmission shaft 25 and the second transmission shaft 26 each have a first end 25a, 26a provided with a gear wheel or planetary gear 27 located in the first inner chamber 22, immersed in the fluid contained therein, and a second end, opposite to the first end 25a, 26a, connectable to a wheel of the vehicle, for example to a wheel hub. The transmission shafts 25, 26 are axially aligned with each other and preferably extend outward from the inner chamber 22 of the transmission mechanism 20 in opposite directions, i.e., toward the hub of a respective vehicle wheel. For example, the transmission shafts 25, 26 may rotate about an axis indicated by the letter F in the figures.

[0029] The figures illustrate a differential gear mechanism of a classic type; in other words, the differential gear mechanism shown by way of example in the figures also comprises a carrier 28 and a planet gear 29. The planet gear 29 is configured to rotate about the rotational axis F defined by the transmission shafts 25, 26 and also about its own axis, perpendicular to the axis F of the transmission shafts 25, 26, so as to transfer the rotational motion and, therefore, power from the drive shaft to the vehicle wheels. However, the present invention is not intended to be limited to a classic type differential gear, but may also be applied to a different type of differential gear, for example a limited- slip differential gear or a self-locking differential gear.

[0030] The transmission and braking system 10 also comprises a first magneto-rheological brake 30 and a second magneto-rheological brake 31, associated with the differential gear and configured to be used as vehicle brakes in order to obtain a compact transmission and braking system.

[0031] Preferably, the first magneto-rheological brake 30 is configured to generate a braking force on the first transmission shaft 25, and the second magneto-rheological brake 31 is configured to generate a braking force on the second transmission shaft 26.

[0032] Each of the two magneto-rheological brakes 30, 31 comprises an outer stator 32 defining a second inner chamber 34 in which a magneto-rheological fluid is contained, and also comprises a rotor 35 arranged in the second inner chamber 34 in contact with the magneto- rheological fluid contained therein (figure 2).

[0033] The outer stator 32 is provided with windings 33, preferably arranged in a radially outer portion of the outer stator 32, and is integral with the outer housing 21 of the differential gear mechanism 20. The term “integral” means that the outer stator 32 of the magneto- rheological brake 30, 31 may be made separately from the outer housing 21 of the differential gear mechanism 20 and connected thereto, for example by welding or riveting, or that the outer stator 32 of the magneto-rheological brake 30, 31 may be made in one piece or integrally with the outer housing 21 of the differential gear mechanism.

[0034] The rotor 35 of the first magneto-rheological brake 30 and the rotor 35 of the second magneto-rheological brake 31 are rotationally integral respectively with the first transmission shaft 25 and the second transmission shaft 26 of the differential gear mechanism 20.

[0035] Optionally, each rotor 35 may be provided with a permanent magnet or with windings.

[0036] The windings 33 of the stator 32 and / or the windings of the rotor 35, if present, may be powered by the vehicle battery in the case of an electric or hybrid vehicle, or may be powered by a service battery in the case of a combustion engine vehicle.

[0037] The transmission and braking system also comprises a control system, not shown in the figures, which is configured to selectively activate or actuate the first magneto-rheological brake 30 and / or the second magneto-rheological brake 31 and to generate independent braking forces on at least one of the two transmission shafts 25, 26 of the differential gear mechanism 20 in order to slow down and / or stop at least one of the wheels connected to the corresponding axle. For example, the braking forces may be balanced between the two wheels, or the braking forces may be applied differently and independently to each transmission shaft according to the driving conditions.

[0038] The control system may be activated by the user of the vehicle through a control located inside the passenger compartment of the vehicle, for example by means of a pedal.

[0039] Alternatively, the control system may be automatically activated based on the vehicle stability conditions and / or the road conditions. For example, the control system may be activated in conditions of low adhesion between the road surface and the vehicle wheel. In such an embodiment, sensor means may also be provided, configured to detect a condition of low or lost adhesion between the wheel and the road and / or sensor means for detecting vehicle instability conditions.

[0040] In one embodiment of the transmission and braking system, the first inner chamber 22 of the differential gear mechanism 20 and the second inner chamber 34 of the first 30 and / or second 31 magneto-rheological brake may be fluidically separated from each other (figure 2). This configuration is particularly advantageous when the fluid contained in the first inner chamber 22, for example a lubricating oil, differs from the magneto-rheological fluid contained in the second inner chamber 34.

[0041] The first 22 and second 34 inner chambers may be externally delimited respectively by the outer housing 21 of the differential gear mechanism and by the outer stator 32 of the magneto-rheological brake 30, 31, and may be internally delimited by a rigid wall 38 located inside the transmission and braking system and not visible from the outside.

[0042] When the first 22 and second 34 inner chambers are fluidically separated from each other, the second inner chamber 34 may be annular and may have an overall L- shape when viewed in the axial direction (figure 2). In other words, the second inner chamber or air gap 34 for the magneto-rheological fluid may have a portion parallel to the transmission shafts 25, 26 and to the windings 33, and a portion perpendicular to the transmission shafts 25, 26. This shape of the second inner chamber 34, having axial sealing, advantageously improves the sealing of the magneto-rheological brake 30, 31.

[0043] In an embodiment not illustrated in the figures, the second inner chamber 34 may be annular and arranged entirely between the outer stator 32 and the rotor 35, i.e., parallel to the transmission shafts 25, 26, in order to maximize the exposure of the magneto-rheological fluid to the magnetic field generated between the windings 33 of the stator 32.

[0044] Regardless of its shape, no sedimentation of the magnetic particles contained in the magneto- rheological fluid occurs within the second inner chamber 34. The larger the size of the second inner chamber 34 of the magneto-rheological brake 30, 31, the greater the amount of magneto-rheological fluid contained therein, and the greater the braking torque that can be exerted on the transmission shaft 25, 26 of the wheel.

[0045] In one embodiment of the transmission and braking system, the first inner chamber 22 of the differential gear mechanism 20 and the second inner chamber 34 of the first 30 and / or second 31 magneto-rheological brake may be in fluid connection with each other (figures 3 and 4).

[0046] The first inner chamber 22 of the differential gear mechanism 20 and the second inner chamber 34 of the first 30 and / or second 31 magneto-rheological brake may communicate fluidically, forming a single inner chamber 37 (figure 3). This configuration is particularly advantageous because a single fluid can be used in the system 10, and the fluid contained in the single inner chamber 37 can be a magneto-rheological fluid. This configuration is also particularly advantageous because it prevents possible seal failures between the inner chambers, thereby avoiding the mixing of conventional fluid and magneto-rheological fluid.

[0047] Alternatively, between the first inner chamber 22 of the differential gear mechanism 20 and the second inner chamber 34 of the first 30 and / or second 31 magneto-rheological brake, a wall 40 may be interposed, preferably a rigid wall, at least partially porous (figure 4), so as to allow the lubricating oil component of the fluid to flow between the two chambers 22, 34 and retain the magnetic particles within the second inner chamber 34 of the magneto- rheological brake 30, 31. For example, the second inner chamber 34 may contain a magneto- rheological fluid comprising a carrier fluid and magnetic particles, while the first inner chamber 22 may contain only the carrier fluid acting as a lubricating oil.

[0048] The first 22 and second 34 inner chambers may be externally delimited respectively by the outer housing 21 of the differential gear mechanism and by the outer stator 32 of the magneto-rheological brake 30, 31, and may be internally delimited by the at least partially porous wall 40, which is located inside the transmission and braking system and is not visible from the outside.

[0049] In one embodiment, the wall 40 may comprise a porous membrane. In other words, the wall 40 between the first inner chamber 22 of the differential gear mechanism 20 and the second inner chamber 34 of the first 30 and / or second 31 magneto-rheological brake may support a membrane having elastic properties so as to be deformable and porous, allowing the fluid to pass through.

[0050] In embodiments having a wall 40 that is at least partially porous and / or a porous membrane between the inner chambers 22, 34, the pores may have a size between 1 pm and 2 pm, allowing the fluid component of the magneto-rheological fluid to pass between the chambers while retaining the magnetic particles within the second inner chamber 34 of the magneto- rheological brake 30, 31.

[0051] The transmission and braking system 10 may also comprise a third magneto-rheological brake 50 configured to be used as a vehicle brake in addition to the first 30 and second 31 magneto-rheological brakes.

[0052] The third magneto-rheological brake may comprise an outer stator 51 provided with windings 52 and a rotor 54 rotationally integral with the drive shaft 24. The outer stator 51 may be integral with the outer housing 21 of the differential gear mechanism 20 and may define, together with it, a third inner chamber 53 in which a magneto-rheological fluid may be contained. The rotor 54 may be arranged within the third inner chamber 53 and may be immersed in and / or in contact with the magneto-rheological fluid.

[0053] As with the brakes 30, 31, also for the third brake 50 the windings 52 of the stator 51 may be powered by the vehicle battery if the vehicle is electric or hybrid, or may be powered by a service battery if the vehicle has a combustion engine.

[0054] When the third magneto-rheological brake is present, the control system may be configured to actuate the first 30 and / or the second 31 and / or the third 50 magneto-rheological brake and generate independent braking forces on at least one of the first transmission shaft 25, the second transmission shaft 26, and the drive shaft 24.

[0055] In one embodiment, the first inner chamber 22 of the differential gear mechanism 20 and the third inner chamber 53 of the third magneto-rheological brake may be fluidically separated from each other (figure 5). In other words, a wall may be interposed between the first 22 and third 53 inner chambers so that the fluids contained therein do not come into contact with each other, thereby preventing mixing.

[0056] In an alternative embodiment, not illustrated in the figures, the first inner chamber 22 of the differential gear mechanism 20 and the third inner chamber 53 of the third magneto- rheological brake 50 may be in fluid connection with each other.

[0057] The first inner chamber 22 of the differential gear mechanism 20 and the third inner chamber 53 of the third magneto-rheological brake 50 may be fluidically connected to each other, forming a single inner chamber. In addition, the first inner chamber 22 of the differential gear mechanism 20, the second inner chamber 34 of the first 30 and / or second 31 magneto- rheological brake, and the third inner chamber 53 of the third magneto-rheological brake 50 may be fluidically connected to each other, forming a single inner chamber.

[0058] Alternatively, between the first inner chamber 22 of the differential gear mechanism 20 and the third inner chamber 53 of the third magneto-rheological brake 50, a wall may be interposed that is at least partially porous, so as to allow the lubricating oil component of the fluid to flow between the inner chamber 22 of the differential gear mechanism 20 and the third inner chamber 53 of the third magneto-rheological brake, while retaining the magnetic particles within the third inner chamber 53.

[0059] Each of the inner chamber 34 of the first magneto-rheological brake 30, the inner chamber 34 of the second magneto-rheological brake 31, and the inner chamber 53 of the third magneto-rheological brake 50 may be either separated from or in fluid connection with the first inner chamber 22 of the differential gear mechanism 20 in any of the embodiments described above.

[0060] It is understood that the invention is not limited to the embodiments described and illustrated herein, which are to be regarded as examples of implementation of a transmission and braking system; rather, the invention is susceptible to modifications concerning shape, dimensions and arrangement of parts, construction details, and materials used.

Claims

CLAIMS1. A transmission and braking system (10) for vehicles with three or more wheels, comprising:- a differential gear mechanism (20) comprising:- an outer housing (21) defining a first inner chamber (22) wherein a fluid is contained,- at least a pinion (23) mounted on and rotationally integral with a drive shaft (24) of the vehicle, and housed in the first inner chamber (22),- a first transmission shaft (25) and a second transmission shaft (26) axially aligned, wherein each transmission shaft (25, 26) has a first end (25a, 26a) equipped with a gear wheel (27) arranged in the first inner chamber (22) and a second end connectable to a wheel of the vehicle,- a first (30) and a second (31) magneto-rheological brake, each comprising:- an outer stator (32) equipped with windings (33), integral with the outer housing (21) of the differential gear mechanism (20) and defining a second inner chamber (34) wherein a magneto-rheological fluid is contained,- a rotor (35) arranged in the second inner chamber (34), and rotationally integral with the first (25) or second (26) transmission shaft of the differential gear mechanism (20), and- a control system configured to selectively actuate the first (30) and / or second (31) magneto- rheological brake and generate independent braking forces on at least one of the two transmission shafts (25, 26) of the differential gear mechanism (20).

2. A transmission and braking system (10) according to claim 1, wherein the first inner chamber (22) of the differential gear mechanism (20) and the second inner chamber (34) of the first (30) and / or second (31) magneto-rheological brake are fluidically separated from each other.

3. A transmission and braking system (10) according to claim 2, wherein the second inner chamber (34) is annular and has an L-shape when viewed in an axial direction.

4. A transmission and braking system (10) according to claim 1, wherein the first inner chamber (22) of the differential gear mechanism (20) and the second inner chamber (34) of the first (30) and / or second (31) magneto -rheologic al brake are in fluid connection with each other.

5. A transmission and braking system (10) according to claim 4, wherein the first inner chamber (22) of the differential gear mechanism (20) and the second inner chamber (34) of the first (30) and / or second (31) magneto-rheological brake communicate fluidically by forming a single inner chamber (37) and the fluid contained in the single inner chamber is a magneto-rheological fluid.

6. A transmission and braking system (10) according to claim 4, wherein an at least partially porous wall (40) is interposed between the first inner chamber (22) of the differential gear mechanism (20) and the second inner chamber (34) of the first (30) and / or second (31) magneto-rheological brake.

7. A transmission and braking system (10) according to claim 6, wherein the wall (40) comprises a porous membrane.

8. A transmission and braking system (10) according to claim 6 or 7, wherein the pores of the wall (40) are between 1 pm and 2 pm in size.

9. A transmission and braking system (10) according to any of the preceding claims, comprising a third (50) magneto-rheological brake, comprising:- an outer stator (51) equipped with windings (52), integral with the outer housing (21) of the differential gear mechanism (20) and defining a third inner chamber (53) wherein a magneto-rheological fluid is contained,- a rotor (54) arranged in the third inner chamber (53) and rotationally integral with the drive shaft (24), wherein the control system is configured to actuate the first (30) and / or the second (31) and / or the third (50) magneto-rheological brake and generate independent braking forces on at least one of the first transmission shaft (25), the second transmission shaft (26) and thedrive shaft (24).

10. A transmission and braking system (10) according to claim 9, wherein the first inner chamber (22) and the third inner chamber (53) are fluidically separated from each other.

11. A transmission and braking system (10) according to claim 9, wherein the first inner chamber (22) and the third inner chamber (53) are in fluid connection with each other.

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