ADDITIONAL HYDRAULIC DRIVE WITH VARIABLE DISPLACEMENT

DESCRIPTION OF THE INVENTION

1. TECHNICAL FIELD

The invention relates to the construction of an additional drive of the rear wheels of a car by adapting the hydraulic machines used in transmissions of mobile machines.

An example of hydraulic machines that can be used to make the invention can be found in petent GB1512358A and GB1281101A.

The aforementioned hydraulic machines are mainly used on small machines whose maximum speed does not exceed 50 km / h with precision, moving in the range of about 25 km / h.

It is an object of the present invention to allow the use of mentioned and similar machines on cars as an additional rear wheel drive. The compact design of the hydraulic machines and the fact that the connection between the machine acting as the pump and the machine acting as the motor can be made with flexible tubes, indicate that vehicles that are not designed to be fitted with all-wheel drive can be transform into a four-wheel drive vehicle at an acceptable cost.

In addition, if an electric motor is used to drive the machine, with the function of a pump, then a simple and cost-effective hybrid drive can be achieved. For standard hybrid electric drives, it is necessary to provide an inverter that adjusts the DC voltage/tension of the battery to the lelvet, and possibly frequency, of the tension required to drive the vehicle. That is, by controlling the tension, it controls the current flowing through the electric motors and thus their output torque. These converters represent about 30% of the cost of an electric hybrid drive.

In addition, the connection between the electric motor and the drive wheels, in most cases due to the control of the overall cost of such drive, is designed as a single-speed gearbox, which limits the possibility of optimizing the overall drive.

Unlike mechanical transmissons, hydraulic machines allow for a controlled change of transmission ratio from infinite to final. An infinite gear ratio, corresponds to the case when a pump, connected eg to an electric motor, rotates only to maintain pressure in the installation until the motor itself doesn’t rotates. This situation corresponds to the case when the vehicle is on a slope and torque must be generated to maintain position. By increasing the speed of the vehicle, itself, it is possible to increase the oil flow through the pump, regardless of its rotational speed. As the person skilled in the art is aware, in the previously mentioned case the pump must be of variable supply.

The described feature allows for simple drive operation, especially electric, ie electro- hydraulic, where, thanks to the possibility of controlling the supply of the pump, output speed control can be achieved, regardless of the speed of rotation of the electric motor. It turns out that it is possible to create an electro-hydraulic hybrid drive, without the need for an expensive electric converter, which opens the possibility of reducing the price.

2. TECHNICAL PROBLEM

A technical problem that should be solvedd by this invention is the reduction of mechanical; that is, hydraulic losses, especially when the vehicle is used at higher speeds, such as when the vehicle is traveling on the freeway.

If the said hydraulic machines were permanently connected to the wheels of the car, then at higher speeds, even if the said machines were idling or not transmitting, additional torque on the rear or front, actually wheels not driven by mechanical transmission, the losses that would result from the mixing of the oil would be unacceptably large. The aforementioned losses would cause the oil to overheat, which would lead to the destruction of the machines themselves. In addition, due to the increased losses, unnecessarily high fuel consumption, ie increased emissions of harmful gases, would occur.

In addition, intention of this patent application is to protect an autoregulation system tailored to this solution that enables cheaper performance of the system itself.

For the proposed solution, to be commercially viable, the cost of the technical realisation itself should not be too high. In order to reduce the total overall cost, the activation of the clutches, as well as the primary control of the pump load, ie the transmission ratio, will be solved through autoregulation, with the possibility of improving the regulation itself by using additional electrically controlled regulating mechanisms. Aditioanl technical problem, that can be solved by proposed innovation relates to the cost of existing car hybridization solutions that are to high and as such limits the wider introduction of the hybrid powertrains.

3. BACKGROUND OF THE INVENTION

In the current state of the art, hydraulic transmissions, intended for additional propulsion of the rear wheels of cars exist, as described in FR2621280A1 and WO2015032683 and US2018283371 , respectively, characterized by the use of fixed delivery pumps.

As hydraulic power transmissions show their full value only when using variable displacement machines, this is not the optimal solution. It will be shown that this also applies when the propulsion machine is an internal combustion engine and the propulsion engine is an electric motor, with or without electronic control. The use of fixed supply pumps, in the current state of the art, is a major obstacle on the use of existing solutions for affordable vehicle hybridization.

4. OBJECT OF THE INVENTION

It is an object of the present invention to provide an additional drive solution, for the wheels of the vehicule that are not driven directly by mechanical transmission, driven by internal combusion engine. The proposed solution is based on a hydraulic transmission comprising at least one variable displacement machine and at least one clutch, where a variable displacement pump is used in each embodiment.

Using the machine, with variable delivery, enables the optimization of the power transmission, whether propulsion machine is an internal combustion enginel and / or electric motor. In addition, by relying on the possibilities of self-regulating variable displacement hydraulic machines, it is possible to offer a cost-effective solution to this problem, especially when the drive machine is an electric motor. In the known solutions of electric transmissions, electronic converters are used to adjust the torque of the electric motor, which represent a considerable share in the final/overall cost. Using the aftrementioned possibility of selfregulating hydraulic transmission, it is possible to omit the electronic converter or to install an electronic converter that controls only the amounts of current that are only one third of the amount controlled by the transducers for single-speed electric transmissions. By reducing the intensity of the current, which is controlled by the electronic converter, or by completely omitting the said electric converter, the cost of the final solution is significantly reduced.

In addition, the essence of the present invention is that it is based on high-speed hydraulic machines with radial pistons. This should be emphasized as in the prior art similar solution with slow hydraulic machines with radial pistons are known. The difference between fast and slow hydraulic machines, with radial pistons is that for fast machines, the piston makes only one stroke per turn, while for slow machines the piston makes more strokes during one turn. It follows that for fast machines the piston moves along a curve which is actually a circle, while for slow machines the pistons move along a wavy circular curve. The important difference, between fast and slow machines, is that in the present state of art ther are existing industrial designs of the fast-rotating machines with variable displacement, while ther is no known existing industrial designs of the slow-rotating machines design of variable displacement machines. That is, solutions that are proposed as slow variable delivery machines are much more complicated for technical realization than fast variable delivery machines.

By using variable displacement motors, technical charactersistis can be further improved as the combination of the pump and motor, of variable delivery increases the possible transmission ratio. In addition, if two motors, with variable delivery, are used, it is possible to independently control the torque transmitted to the wheels, driven by said motors, in order to improve the handling of the vehicle. Due to the use of a variable displacement pump, simple hybridization can be achieved also by using a flywheel directly or indirectly connected to the variable displacement pump.

It is known, from the prior art, that the driving torque is transmitted to the wheels via a differential assembly. To clarify the scope of the present invention, it has to be expalioend what is meant by the term; differential assembly within this application. The function of the differential assembly is to allow smooth distribution of the torque, regardless of the differential speed of the wheels themselves. This is desirable when cornering when the wheels that are further from the center of the turning radius rotate faster than the wheels that are closer to the center of the turning radius. It is known, in present state of the art, that this feature may be undesirable when the vehicle is on slippery ground and / or uneven ground such that one wheel can go 'in the air' i.e. contacts with the ground is lost. Due to the unobstructed distribution of the torque, the wheel that has lost contact with the ground will allow the differential assembly to rotate freely. The free rotation of the differential assembly limits the development of the reactive torque required to achieve active torque on the non-slip wheel that isn't lost the contact with the road, and as it is known in the art, a wheel that has not lost contact with the ground can develop a torque corresponding only to the reactive torque of the wheel that has lost contact with the ground.

There are various solutions that try to solve this problem. One group of the solutions aims to limit the freedom of rotation, within the differential assembly, until it is completely locked. In the case of a locked differential assembly, the full drive torque may be transmitted to any wheel connected to said differential assembly.

The second group of solutions uses the brakes in such a way as to break a wheel that has lost contact with the road, thereby developing a reactive torque in the differential assembly required to create a torque on the wheel that has not lost contact with the ground. The disadvantage of these aproach is that the control of the torque distribution is performed by braking, which dissipates energy.

One method of constructing a differential assembly, particularly suitable when using hydraulic machines as a source of driving torque, as is the case in the present invention, is to connect each wheel to a separate hydraulic machine. By using the valves, it is possible to control the flow of oil to each hydraulic machine and thus to generate the torque at wheels associated with the mentioned machines, thereby controlling the creation of drive torque separately for each wheel. The problem of controlling torque, through valves, is that in this case, as in the case of brakes, the control of torque transmitted to the wheels is associated with losses.

It is particularly advantageous, if variable-displacement hydraulic machines are used, to control the transmission of drive torque to the wheels by changing the displacment of said machines. This enables independent control of the torque, transmisted to the wheels without loss. This type of control is particularly suitable when it is desired to improve vehicle driving performance in turns, which is known in the area as vector torque control. This kind of control is already known on those electric vehicles where each wheel is powered by its own motor.

From this description it is clear that there are a number of ways of making a differential assembly already known in the art. The following description starts from the point of view of which it will be apparent to one of ordinary skill in the art that the essence of the present invention can be applied to all variants of known differential circuits in which the driving torque is achieved using hydrostatic machine and it is considered to be sufficient to mention, in the claims, that the hydraulic machine, according to the present invention is coupled to the wheels of the vehicle by means of a differential assembly, and it will be clear that this invention relates to all possible embodiments, of a differential assembly, based on rapid radial hydraulic a ball piston machine characterized in that only one piston stroke is performed per revolution.

In this description, emphasis is placed on high-speed radial hydraulic machines, although it will be apparent to one of ordinary skill in the art that the prior art knows a wide variety of hydraulic technologies that can be used.

What is common to all designs is that in each embodiment there is one variable supply pump and one motor that can be either variable or fixed supply. Regardless of the type of motor, it is always connected to the wheels of the car via a clutch which allows the motor conection to the rear wheels when it is necessary to secure the drive or to disconnect it when no additional drive is needed. The clutch allows the motor and drive design to be optimized for speed ranges from 0 to 50 km / h.

This eliminates the restriction on existing hydraulic transmissions that, due to the limiting speed of their hydraulic machines.limit the speed of the vehicle itself. Due to the introduced clutch, which is automatically actuated when pressure is applied, hydraulic machines will connect to the wheels when additional torque is required in the low speed area, and will automatically be deactivated in the higher speed range so that the maximum speed of the vehicle will not be limited by the maximum allowable speed of rotation of the hydraulic machines themselves. Already with this characteristic, the present invention is separate from the invention FR2621280A1 which uses a toothed clutch that needs to be actuated by a separate actuator.

The present invention differs from the inventions WO2015032683 and US2018283371 , in that clutch activation forces are not transmitted to the housing of the machine itself, thereby obtaining a substantially easier and less costly embodiment.

This invention is further separated from the inventions FR2621280A1 , WO2015032683 and US2018283371 because it uses a variable supply pump in all variants, which significantly improves the controllability of the system itself and thus of the entire vehicle. In addition, in the aforementioned inventions, the pump is mounted at the output of the differential, which means that the pump must absorb mechanical energy in the form of high torque and low speed, which affects the performance of the pump, which must be adapted to the size of the torque itself. According to the embodiment described in this patent application, mechanical energy is taken before exiting the differential, which means at higher speed, which means that both the pump and the coupler can be significantly smaller or cheaper because the torque they take is much smaller than is the case for patents FR2621280A1 , WO2015032683 and US2018283371 .

This invention is separate from the inventions FR2621280A1 and US2018283371 because it uses a variable supply pump in all variants, which significantly improves the controllability of the system itself and thus of the entire vehicle. In addition, the variable supply pump allows the use of flywheels as an energy reservoir, which is favorable for the introduction of cost-effective hybridization.

5. BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, that are part of the description and invention itself, ilustrates what, at the moment, seems as the best way of the invertion realization, and assist in explaining the basic principles of the invention.

Fig.1 . Schematic representation of a front-wheel drive vehicle platform and mechanical additional rear drive.

Fig. 2. Schematic illustration of a front-drive vehicle platform and hydraulic additional rear drive, where power is obtained from an internal combustion engine.

Fig. 3. Schematic representation of a front-wheel drive platform and a hydraulic additional rear drive, where power is obtained from an electric motor located in the internal combustion engine compartment;

Fig. 4.. Schematic representation of a front-wheel drive platform and hydraulic additional rear-wheel drive, where power is obtained from an electric motor integrated into the rear- drive assembly.

Fig. 5.. Schematic representation of a front-wheel drive platform and hydraulic additional rear-wheel drive, where power is supplied by an electric motor integrated into the rear-drive assembly, and where the differential function is achieved by the parallel coupling of two hydraulic motors.

Fig. 6.. Schematic representation of a front-wheel drive platform and hydraulic additional rear-wheel drive, where power is obtained from an electric motor integrated into the rear- drive assembly, and where differential function is achieved with two mechanically independent hydraulic clutches, which transmit the drive torque of the hydraulic motor to the wheels.

Fig. 7. Schematic illustration of the simplest version of the transmission torque control, in the case when the required power is obtained directly from the electric motor or from a gearbox where the direction of rotation of the pump changes with the direction of movement of the vehicle.

Fig. 8. Schematic illustration of the simplest version of the torque control, for the case where required power is obtained from the electric drive with a flywheel or directly from the drive group 2, by the side of additional devices such as water pump, alternator... that is, the pump always rotates in the same direction regardless of the direction of motion of the vehicle.

Fig. 9. Schematic representation of a more advanced torque control platform when a proportional electric valve is used to control the torque.

Fig, 10. Shows a possible embodiment of a pump and motor module in an integrated embodiment where the novelty details of the present invention are shown, the selector and the clutch integrated into the construction of the hydraulic machine

Fig. 1 1. Like figure 10 but with emphasis on the details of the control mechanism.

5. BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, that are part of the description and invention itself, ilustrates what, at the moment, seems as the best way of the invertion realization, and assist in explaining the basic principles of the invention.

Fig.1 . Schematic representation of a front-wheel drive vehicle platform and mechanical additional rear drive.

Fig. 2. Schematic illustration of a front-drive vehicle platform and hydraulic additional rear drive, where power is obtained from a thermal engine.

Fig. 3. Schematic representation of a front-wheel drive platform and a hydraulic additional rear drive, where power is obtained from an electric motor located in the thermal engine compartment; Fig. 4.. Schematic representation of a front-wheel drive platform and hydraulic additional rear-wheel drive, where power is obtained from an electric motor integrated into the rear- drive assembly.

Fig. 5.. Schematic representation of a front-wheel drive platform and hydraulic additional rear-wheel drive, where power is supplied by an electric motor integrated into the rear-drive assembly, and where the differential function is achieved by the parallel coupling of two hydraulic motors.

Fig. 6.. Schematic representation of a front-wheel drive platform and hydraulic additional rear-wheel drive, where power is obtained from an electric motor integrated into the rear- drive assembly, and where differential function is achieved with two mechanically independent hydraulic clutches, which transmit the drive torque of the hydraulic motor to the wheels.

Fig. 7. Schematic illustration of the simplest version of the transmission torque control, in the case when the required power is obtained directly from the electric motor or from a gearbox where the direction of rotation of the pump changes with the direction of movement of the vehicle.

Fig. 8. Schematic illustration of the simplest version of the torque control, in case the required power is obtained from the electric drive with a flywheel or directly from the drive group 2, by the side of additional devices such as water pump, alternator... that is, the pump always rotates in the same direction regardless of the direction of motion of the vehicle.

Fig. 9. Schematic representation of a more advanced torque control platform when a proportional electric valve is used to control the torque.

Fig, 10. Shows a possible embodiment of a pump and motor module in an integrated embodiment where the novelty details of the present invention are shown, the selector and the clutch integrated into the construction of the hydraulic machine

Fig. 11. Like Figure 10 but with emphasis on the details of the control mechanism.

6. DESCRIPTION OF THE INVENTION AND METHOD OF FUNCTIONING OF THE INVENTION WITH LEGEND

1 Front-wheel drive and rear-drive capability 2 Main drive group in the form of thermal/internal combustion engine and / or electric motor, with or without gearbox

3 Differential

4 Front final gears

5 Transmission shafts

6 Electromagnetic clutches with transmission mometer multiplier

7 Rear conical gears

8 Differential assembly

9 Rear half axles

10 Rear wheels

1 1 Pump modules

12 Variable displacement hydraulic pump

13 Direct Electromagnetic Coupling

14 Non-return valves

15 Filter

16 Oil tank

17 Pressure line

18 Return line

19 Drive modules

20 Fix displacement hydraulic motor

21 Hydraulically actuated multidisc coupling

22 Pressure selectors

23 Clutch Hydraulic Cylinder with Reverse Spring

24 Gearing

25 Electric motor

26 Flywheel

27 Variable Displacement Hydraulic Motor

28 Control spring assembly

29 Control cylinders

30 Electronically controlled maximum pressure limiter

31 Directional electro-valves

32 Electrically operated proportional electro valve

33 Auxiliary system pumps

34 Cylinder block 35 Clutch housing

36 Transmission housing

37 Battery

38 Clutch

39 Electronic converters

40 Control mechanism feedback

41 Pressure sensors

42 Temperature sensors

43 Electronic control unit

44 Information collected by car sensors

45 Pulley

46 Acessory Belt transmission

47 Spring Actuated clutches

48 Electromagnetic actuators for deactivating spring actuated clutch

49 Hydraulic actuators for deactivating the spring actuated clutch

50 Electric motor actuators for deactivating the spring-actuated clutch

51 Belt

Figure 1 is a schematic illustration of a front-mounted vehicle platform 1 and a mechanical additional rear-wheel drive. Where the front drive is achieved by using the main drive group 2 which transmits the drive torque to the front wheels via the front differential 3. By using the conical gears 4 and the transmission shaft 5 it is possible to transfer the driving torque to the rear drive. The rear drive consists of an electromagnetic clutch with a torque multiplier 6, conical gears of the rear drive 7 and a rear differential assembly 8, with a differential 3. By activating the electromagnetic clutch with a torque multiplier 6, the driving torque is transmitted via the conical gears 7 to the rear differential 8 and through rear flat shafts 9 finally to rear wheels 10.

Figure 2 is a schematic illustration of a front-wheel drive platform and a hydraulic rear drive, where power is obtained from the main drive group 2. In this embodiment, the front conical gears 4 are replaced by the pump module 1 1 , and the rear conical gears are replaced by the rear drive module 19, which now has an integrated rear differential 8. In the embodiment shown, the front pump module 1 1 connects to the main drive group 2 via a simple direct electromagnetic clutch 13. The advantage of the design according to this patent application, in relation to the existing solutions, relates to introduction of a variable displacement hydraulic pump 12.. Using variable displacement pump it is possible to control the flow, independently of the rotational speed of the elements of the main drive group 2 which further enables the required power to be taken at a higher rotational speed of the variable displacement pump 12. It follows that for the same power transmitted to the rear wheels 10, the input torques will be smaller than it is the case in the current state of the art, so that the pump, as well as its associated electromagnetic couplings 13, may be reduced. Additionally, due to the variable delivery, or the variable transmission ratio between the front and rear wheels, this feature allows much better adaptation to the requirements / needs of the driver. It will be evident, to one of the ordinary skill in the art that this schematic representation provides the basic elements encountered in closed-type hydraulic transmissions of the prior art, characterized in that the pump and the motor are directly connected by pressure lines 17, that is, the output from the motor 20 returns directly to pump 12, and that part of the oil which has been leaked and / or discharged by the control mechanism flows through the oil reservoir 16. Therefore, there are elements in the circuit, such as non-return valves 14, which allow, in the event of a pressure drop in the pressure lines 17, the oil from the tank 16, filtered by the filter 15, been introduced into said pressure lines 17, in order to avoid cavitation in the the pump 12 itself. In said tank 16, oil leaked from the pump 12 and the motor 20 is collected. In the simplest embodiment, the crankcase of the pump module has a function of the tank that directly collects oil losses from the pump 12, while the oil collected in the crankcase of the motor 20. returns to the sump pump or tank 16 with return line 18. It will be apparent to one of ordinary skill in the art that such systems are almost as a rule equipped with an auxiliary pump that allows more efficient passage of oil through the filter and increases the limits of cavitation safety and are as a rule, integrated onto the shaft of the pump 12 itself, this is also implied in the present description, so that in order to simplify the view, special emphasis is placed on the placement of the auxiliary pump in this view. In addition, this omition underline that there are variants of transmissions in which, thanks to the successful optimization of the whole system, auxiliary pumps are not even needed.

Further, the following schematic shows that the pressure lines 17 have replaced the transmission shaft 5. The flexibility of the pressure lines gives great freedom to adapt to the vehicle platform itself, which is not the case with mechanical design. This is an advantage of all hydraulic systems, including the one proposed for patent protection.

The following illustration provides a rear drive module 19. The base of the drive module 19 is a fixed-supply hydraulic motor 20, with an integrated, hydraulically actuated, multi-discs clutch 21. The selector 22 connects said clutch 21 to that pressure line 17 in which there is greater pressure. Said pressure enables the hydraulic cylinder 23 to activate said; multi-dicsc clutch 21 thereby transferring the driving torque of said motor 20 via a gear train 24 to a differential assembly 8 with a differential 3, and by means of the axles 9 on to the rear wheels 10.

Figure 3 is a schematic representation of a front-wheel drive platform and a hydraulic additional rear-wheel drive, where power is obtained from an electric motor 25 located in the main drive section, In this view, the electric motor 25 is connected to the flywheel 26 directly and to the pump 12 indirectly. This is illustrated to give an insight into the full potential of this solution, although a simpler solution is possible where only the electric motor 25 is directly connected to the pump 12. The said flywheel 26 serves to optimize the electric motor 25, according to description, the electric motor 25 can. when disconnected from the system by deactivating clutch 13, store energy in the flywheel 26 and use it when it is most needed. In this way, a substantially smaller electric motor can be selected without losing the system performance seen by the driver. An additional advantage of this embodiment is the fact that the noise generated by the rotation of the motor 25 with the flywheel 26 comes from the main drive group 2 so that it would be expected that drivers would easily accept such a design as it is normal that noise cams from the main drive group 2.

Figure 4 is a schematic illustration of a front-wheel drive platform and a hydraulic additional rear drive, where power is obtained from an electric motor integrated into the rear drive assembly. In this case, integrating the pump module 11 and the rear drive module results in a compact transmission. This variant is cost-effective because the cost no longer includes parts of pressure lines 17 and return lines 18 made as steel and / or flexible pipes. In addition, from the point of view of cost, such an integrated transmission, in the range of a few kilowatts, can operate without an auxiliary pump, thereby further reducing the price of the system itself.

The problem with this design is that the noise generated by the electric motor and the rotation of the pump, and possibly the flywheel, will came from the rear side, which may be unacceptable for some drivers as thy are not used to hear noise from that direcction. Finally, a variable displacment motor 27 is introduced in this embodiment, which extends the range of speeds at which described additional tramsmission can be used. It may be noted, although it will be apparent to one of ordinary skill in the art, that in all views where a fixed delivery motor 20 is mentioned, a variable displacement motor 27 can be fitted and the reverse is also valid. Figure 5 is a schematic illustration of a front-wheel drive platform and a hydraulic additional rear-wheel drive, where power is output from an electric motor integrated into the rear-drive assembly and where the differential assembly 8 is made with two hydraulic motors 27 in parallel connexion. Presented realization uses variable displacement motors to indicate additional hydraulic capabilities, which is to precisely control the driving torque on each of the rear wheels 10 in order to optimize the quality of the vehicle's dynamic control.

FIG. 6 is a schematic representation of a front-wheel drive platform and a hydraulic additional rear drive, where power is obtained from an electric motor integrated into the rear drive assembly, and where the differential assembly 8 is realized by two mechanically independent hydraulic clutches which will pass the hydraulic motor drive torque, to each wheel. In this realization, as in the previous one, the drive torque; passed to each of the rear wheels 10 can be independently controlled. According to this description, the hydraulic clutches are controlled by the variable supply of the pump 12 and the motor 27, because the flow control indirectly controls the pressure in the cylinders 23, If the supply of the pump and the motor is adjusted so that the pressure is low then each wheel will be able to rotate virtually freelly because the torque transmitted by the wheels will also be low and the clutches 21 will slip slightly. If there is a slip of the front wheels and the need to transfer torque over the rear wheels, then the supply of the pump 12 and motor 27 should allign so that the pressure should increase, which will also increase the torque transmitted by the clutches 21 and as such differentail assembly 8 will act as a locked differential. It will be apparent to one of ordinary skill in the art that if two electrically proportional valves are provided with a pressure reduction function then it is possible to control the torque transmitted by the clutches 21 independently of the pressure exerted in the pressure lines of the system.

Figure 7 is a schematic description of an embodiment control method in which the drive power or torque is obtained directly from the electric motor 25 or through the electromagnetic clutch 13 from the main drive group 2 on the side of the gearbox where the direction of rotation changes with the direction of motion of the vehicle.

The variable supply pump 12 is controlled by a control spring assembly 28 in such a way that the operation of said spring assembly seeks to maximize supply of the pump 12. It should be emphasized that the spring assembly 28 is represented as multiple springs to emphasize that the ideal spring assembly is realized as a nonlinear spring which adjusts the delivery of the pump so that at each operating point the power input by the pump to the system is constant, entioed spring assembly can be designed as a simple spring, that sholhd be optimal design regarding cost reduction, but not regarding overall control. Furthermore, the control cylinder 29 is opposed to the action of the said spring assembly and is itself driven by maximum pressure in the system supplied to it by the high-pressure selector 22. The principle of operation is apparent from the figure, and easiest way to explain its functioning is for the case of the vehicle starting from zero speed. When the system is not pressurized, the pump 12, under the action of the spring assembly 28, is in the maximum delivery position. Whether by actuating a direct connection to the electric grid, when the source of the torque is the electric motor 25, or by activating the solenoid clutch 13, when the source of the torque is the main drive group 2, the pump 12 will send the maximum possible amount of oil, toward motor 27. This will lead to an increase in pressure which will activate the clutch 21 via the cylinder 23 which is connected to the wheels of the vehicle and, when the vehicle is stationary, will prevent the rotation of the motor 27. This will lead to an increase in pressure which will act on the control cylinder via the selector 14. Due to the increased pressure control clinder 29, will reduce the supply of the pump to zero and will result in maximum pressure in the system. When the vehicle starts and accelerates motor 27 will seek more and more of the oil flow that will result with the pressure drop. Due to the pressure drop, the spring assembly 28 will increase pump delivery until the balance, between the force in the spring assembly 28 and the force of the control cylinder 29, is reached. As an additional drive, it must be adapted to the electric motor 25, i.e. to the main drive group 2. An electronically controlled maximum pressure limiter 30 is introduced to provide additional control and safety. Without the mentioned maximum pressure limiter 30, activation of the electric motor 25, by direct connection to the power supply or by activaitngg the direct clutch 13, would generate brutal increase in the installation pressure i.e. brutal rise of the driving torque on the rear wheels 10. This may be desirable when slipping is detected on the front wheels but may also be seen as a partial or complete loss of the control of the vehicle. In addition, in the event of a brake, the motor 27 may act as the pump. The control system described would then increase the pressure in the pressure line by which the motor 27 sends the oil to the pump 12, which could also lead to the uncontrolled braking of the rear wheels. This can be avoided by timely deactivating the clutch 13 but would leave the impression of partial or complete loss of control of the vehicle.

To avoid this, mentioned, electronically controlled maximum pressure limiter 30 is introduced. Presented embodiment can be seen as the realization that is optimized reagarding cost because only one electronically controlled maximum pressure limiter 30 is used to control the pressure in both pressure lines 17. This is achieved by connecting the inlet, of said electronically controlled maximum pressure limiter 30, to the higher-pressure line 17, using pressure selector 22, while connecting outlet line, to the lower-pressure line 17, through the non-return valves 14. In this way it is possible to regulate the maximum pressure in the system and therefore the torque at the rear wheels 10, shown on previous figures. Using appropriate algorithms, it is possible to match driver requirements with the toque level developed at the rear wheels i.e. enhancing the driving experience related to the of operating of the vehicle equipped with such additional rear wheel drive.

It will be apparent to one of ordinary skill in the art that replacing the switch 38 with an electronic converter 39 may provide additional control of the driving torque, that is, the end torque transmitted to the wheels 10 shown on previous figures.

Figure 8 is a schematic illustration of the simplest design of the torque control, in the case when the required power is obtained from a flywheel electric drive or directly from drive group 2 on the accessory side of additional devices such as a water pump, an alternator ... indicating that the pump always rotates in the same direction, regardless of the direction of the vehicle motion.

If pump 12 is made with a central bore then the alternator starter/generator can be mounted from the back of the pump 12. It will be apparent to one of ordinary skill in the art that if the alternator is connected to the internal combustion motor 2 via an additional clutch; not shown; then by disconnecting the alternator actuator from the internal combustion engine 2, said alternator starter/generatr will have the role of the motor 25, and the flywheel 26 may be dropped in this embodiment.

In this case, everything is similar to the previous description except that a directional valve 31 is required to adjust the oil flow direction to the vehicle direction. In this variant, in contrast to the previous picture, realization is shown where the pump 12 is driven by electric motor 25 with a flywheel 26. Still, introducing the symbols of the main drive group 2 and the arrow, it is shown that the same scheme is retained even if the electric motor 25 with flywheel 26 is replaced with the mentioned main drive group 2, and the drive power is taken from the belt drive used to drive the water pump, etc., i.e. the rotational speed remains the same regardless of the direction of motion of the vehicle.

Figure 9 is a schematic illustration of a more advanced displacement control of the variable dispalacement pump flow control where an electronically controlled proportional valve 32 with feedback 40 is used to control the position of control cylinder 29. In this embodiment, the control mechanism feedback is derived as a spring 40, although it will be understood by one skilled in the art, that control mechanisms feedback can also be achieved by the electronic encoder position of the control cylinder 29.

The main advantage of such a solution is that the position of the control cylinder 29, that controls pump 12 flow, i;e. motor 27 speed, is independent of one set by the control spring 28.

Added to the advantages of this solution is the ability to control the delivery of the pump to avoid the need for a directional valve 31.

As already expaliend on fig. 8, electronically controlled proportional electro-valve 32 is supplied, via the selector 22 with high-pressure oil, and controls its flow to the control cylinder 29 in order to reduce the flow, while to increase the flow, the oil from the control cylinder 29 is discharged into the tank 16. In this case it is advisable to install an auxiliary system pump 33 that supplies pressure lines through the non-return valves 14 to avoid cavitation. It will be apparent to one of ordinary skill in the art that an auxiliary system pump 33 may be installed on each of the solutions already described, if needed by ststem integration analyisi.

It will be apparent, to one of ordinary skill in the art, that all electronically operated valves and/or electric motors are controlled by appropriate amplifiers and/or electronic control unit 43 which are controlled by control algorithms which, based on the information 44 collected by the sensors, already installed in the car, so thy are not show specifically, and the information collected by the sensors incorporated in the the system itself, such as pressure sensors 41 and temperature 42, create the required control signal, i.e. the control voltage and / or current required to control said electronically controlled valves and / or electric motors. As many of the opportunities, opened by this control concept aren’t the subject of this patent application, they are not described in more detail.

It will be apparent to one of ordinary skill in the art that additional control can also be achieved through the electronic control of an electric motor 25, and it is also clear that the basic control strategies shown in Figures 7, 8 and 9 can be combined and upgraded without leaving the spirit of invention where the additional drive of the rear wheels is obtained by a hydraulic transmission where transmission ratio is controlled primarily by controlling the displacement of the variable displacement pump 12 and secondly by changing the displacement of the variable variable diasplacement motor 27, and in addition; the hybrid drive can be reaized where electric batteries and / or flywheels are used as energy reservoir. Figure 10 is a schematic illustration of a solution in which the alternator i.e. starter/generator is used as a propulsion electric motor 25. In this way, a cost-effective hybrid actuator is realized as the role of the hybrid actuator is added to the alternator / starter/generator component. In order to achieve this, it is sufficient to connect one of the pulleys 45 of the accessory belt drive 46 to the said internal combustion engine of the main dirve 2, via a spring-actuated clutch 47. In normal operation, a spring-actuated clutch 47, with belt 51 transmits torque to the additional devices or facilitates the start of a thermal motor. By using an actuator, which can be electromagnetic 48, or hydraulic 49, or electromotor 50, it is possible to release the spring-actuated clutch 47. Realuising clutch 47 and activating direct electromagnetic clutch 13 alternator / starter / generator will be used as electric motor 25 that will provide driving torque for the pump 12.

Fig. 11 shows the possible design of the pump and rear drive module inside the integrated design showing details that present the novelty according to the prior art. Thus, in this section, the performance of the pressure selector 22 and the hydraulically actuated multi- dics clutch 21 , with its hydraulic cylinder 23. In this case, the clutch is integrated 21 into the cylinder block 34. If the drive assembly 19 includes gears and / or planetary gears then it is possible to integrate said clutch into one of the gears and / or supports of the plater gears. What is common to all possible solutions is that the clutch 21 is integrated into one of the torque-transmitting elements to prevent the clutch actuating forces from being transmitted through the drive housing and to avoid mounting additional bearings as the piston of the hydraulic cylinder rotates together with the clutch elements.

Therefore, one of the claims will use the term rotational elements that transmit torque, and the reference code 34 will be used because the cylinder is also a block of rotational elements that transmit torque.

Naturally figure shows design of variable displacement hydraulic pump 12 and the fixed delivery hydraulic motor 20 in radial piston design with the simplest possible pistons that actually are balls used in ball bearings.

Figure 12 shows the possible design of the pump and rear drive module in an integrated version showing details of the control mechanism such as the control spring assembly 28 and the control cylinder 29. The figure shows the initial state when there is no significant pressure on the spring system and thus provides maximum displacement i.e. flow for given rotational speed. As described above, when the pressure in the pressure lines exceeds the prestress value of the spring assembly 28, the piston will move to a new equilibrium position in which the force generatedby the pressure acting on to the control cylinder 29 equals the force of the control spring assembly.

7. APPLICATION OF THE INVENTION

The use of the invention is apparent from the description. It will be apparent to those skilled in the art that the proposed solution is intended primarily for the field of technology related to the construction of additional rear-wheel drive for front-wheel drive vehicles, but does not exclude other possibilities.