EP3913232A1

EP3913232A1 - Hybrid hydraulic arrangement for a work vehicle

Info

Publication number: EP3913232A1
Application number: EP21174960.1A
Authority: EP
Inventors: Rosario Aliperti; Francesco PINTORE
Original assignee: CNH Industrial Italia SpA
Current assignee: CNH Industrial Italia SpA
Priority date: 2020-05-20
Filing date: 2021-05-20
Publication date: 2021-11-24
Also published as: IT202000011782A1

Abstract

Hybrid hydraulic arrangement (1) for providing a flow of pressurized oil to a priority module (3) of a work vehicle configured to divide such pressurized oil between a plurality of working module of the work vehicle,
said hybrid hydraulic arrangement (1) comprising a hydro-mechanic module (4) and a hybrid module (5), the hydro-mechanic module (4) and hybrid module (5) being each separately mechanically coupled to an engine (2) of the work vehicle and both fluidly connected together to the priority module (3),
the hybrid module (5) being controlled independently with respect to the operation of said engine (2) to provide an oil flow complementary to the flow provided by the hydro-mechanic module (4).

Description

TECHNICAL FIELD

The present invention concerns a hybrid hydraulic arrangement, in particular a hybrid hydraulic arrangement for a work vehicle such as agricultural or a construction equipment vehicle.

BACKGROUND OF THE INVENTION

Work vehicles such as agricultural vehicles or construction equipment vehicles use a fluid in pressure, e.g. oil, to operate a plurality of elements of the vehicles, such as transmission, steering, brakes and auxiliary valves.
To this aim, a source of such fluid in pressure is generated by at least a pump configured to supply the fluid into a distribution circuit configured to distribute the fluid in pressure among the aforementioned elements in function of their hydraulic load.
Such distribution circuit may comprise a so-called priority valve, i.e. a valve configured to subdivide the pressurized oil flow to the different elements of the vehicle and the at least one pump is usually carried by the engine of the vehicle.
Figure 1 discloses a known hydraulic arrangement 1' configured to generate oil in pressure to feed the hydraulic needs of the work vehicle.
In particular, such hydraulic arrangement 1' comprises essentially a load sensing pump module 2' and a priority module 3'. The priority module 3' is fluidly connected to pump module 2' to subdivide the oil flow to the different elements of the work vehicle according to load sensing signals, as known in the art.
The pump module 2' is mechanically connected to an internal combustion engine (not shown) of the work vehicle, e.g. via a shaft 4'. Usually, the pump module 2' comprises at least a pump, in particular two pumps 5', 6' carried by the same shaft 4' operated by the internal combustion engine of the work vehicle.
The two pumps 5', 6' are variable displacement pump preferably controlled to vary the angle of their swashplates to modify their flow according to a load sensing signal provide by compensating valves 7', 8' , as per se known.
However, as always known, such pumps 5', 6' are configured to start their operation at different pressure level with respect to each other. In particular, the first pump 5' is be carried by shaft 4 thereby starting to flow oil towards the priority valve module 3' before the second pump 6'.
Accordingly, it is clear that the second pump 6' represents a passive load for internal combustion engine, while not working, because such second pump 6' is always carried by shaft 4' thereby forcing the internal combustion engine to provide a torque to shaft 4' greater than the torque that will be sufficient to operate only the single pump 5'.
Furthermore, according to the above configuration, it is clear that if the flow of pressurized oil that can be provided to the priority valve is directly linked to the power provided by the internal combustion engine.
Therefore, if the vehicle is at standstill or at low speed, i.e. the internal combustion engine is maintained at low speed, the quantity of pressurized oil that can be provided by pump module 2' is low. In order to increase the quantity of pressurized oil it is therefore necessary to increase the power provided by the internal combustion engine, thereby increasing fuel consumption and consequently costs and pollution linked to the use of the work vehicle.
Therefore, the need is felt to provide a hydraulic arranged configured to reduce fuel consumption and costs of the work vehicle.
An aim of the present invention is to satisfy the above mentioned needs in a cost effective and optimized way.

SUMMARY OF THE INVENTION

The aforementioned aim is reached by a hybrid hydraulic arrangement and a work vehicle as claimed in the appended independent claims.
Preferred embodiments of the invention are realized according to the claims dependent or related to the aforementioned independent claims.

BRIEF DESCRIPTION OF DRAWINGS

For a better understanding of the present invention, a preferred embodiment is described in the following, by way of a non-limiting example, with reference to the attached drawings wherein:

Figure 1 is a hydraulic scheme of a hydraulic arrangement for a work vehicle as known in the prior art;
Figure 2 is a hydraulic scheme of a hybrid hydraulic arrangement for a work vehicle according to the present invention; and
Figures 3 to 5 are hydraulic schemes of the hybrid hydraulic arrangement of figure 2 each representing a different operational condition

DETAILED DESCRIPTION OF THE INVENTION

Figure 2 discloses a hybrid hydraulic arrangement 1 for a work vehicle (not shown) configured to use the power provided by an engine 2 of such work vehicle to provide pressurized oil to different elements of the work vehicle such as a priority valve module 3.
In particular, the engine 2 is advantageously an internal combustion engine and the priority valve module 3 is configured to subdivide the pressurized oil flow to different hydraulic power modules (e.g. steering, brakes, power beyond modules) of the vehicle and not described in the present application for sake of brevity.
In detail, the hydraulic arrangement 1 comprises hydro-mechanic module 4 and a hybrid module 5 each separately mechanically coupled to the engine 2 and both fluidly connected together to priority valve module 3 as detailed below.
In particular, the hydro-mechanic module 4 comprises a variable displacement pump 6 and a compensator module 7 configured to vary the pressure of the flow pumped by such variable displacement pump 6. This latter is mechanically coupled to engine 2, e.g. via a dedicated shaft 8.
Variable displacement pump 6 comprises an inlet 6a fluidly connected to a source of oil 9 and an outlet 6b fluidly connected to priority valve module 3 via a conduit 11. Variable displacement pump 6 is configured to increase the pressure of the aspired oil to a preset value between the inlet 6a and the outlet 6b.
As per se known and therefore not described in detail, the compensator module 7 comprise valve means 12 configured to regulate the flow of a hydraulic signal 13 spilled by conduit 11 downstream to pump 6.
Such hydraulic signal 13 is used to control a swashplate control piston 14 configured to vary the angle of the swash plates of the pump 6 between a minimum and a maximum value.
In greater particular, the disclosed embodiment comprises two proportional valves 12', 12" as valve means 12. The quantity of oil sent to swashplate control piston 14, i.e. configured to vary the flow pressure provided by pump 6 is regulated by moving valves 12', 12'' e.g. by varying the stiffness of elastic means 15 configured to maintain the valves 12', 12'' in a first set position.
Furthermore, it is noticed that valves 12', 12" are furthermore fluidly connected to discharge 16 and that swashplate control piston 14 is itself connected to both valves 12', 12" and to discharge 16.
According to the invention, the hybrid module 5 comprises a fixed displacement pump 20 and a motor/generator module 21 operationally interposed between the engine 2 and the fixed displacement pump 20 to use apportion of the torque provided by engine 2 to operate fixed displacement pump 20.
In particular, motor/generator module 21 comprises essentially a generator 22 mechanically coupled to engine 2 and a motor 23 mechanically coupled to pump 20 and electrically coupled to generator 22.
In addition, the motor/generator module 21 comprises an electronic control unit 24 electrically connected to both the generator 22 and the motor 23 and accumulator means 25 electrically connected to both the generator 22 and the motor 23.
The electronic control unit 24 is configured to control the operation of the generator 22 and of motor 23 according to the operation of the work vehicle and the accumulator means 25 are configured to store the electrical energy provided by generator 22 so as to be used by motor 23, if needed, in addition or in substitution of the action of generator 22. Accumulator means 25 may comprise a battery and/or an inverter or equivalent devices.
The generator 22 is mechanically coupled to shaft 8 via a mechanical transmission unit 26, preferably comprising a gearing 27 configured to define a transmission ratio between shaft 8 and an input shaft 28 coupled to generator 22. In an essential embodiment, such gearing 27 comprises a first gear 27' carried by shaft 8 configured to cooperated with a second gear 27" carried by input shaft 28. It is clear that further gearing may be provided instead of the above described, such as a planetary gearing.
The pump 20 is operated thanks to an output shaft 29 connecting the pump 20 to the motor 23. In the disclosed embodiment, such connection is a direct connection, however it may be envisaged a transmission unit or a decoupling unit between the motor 23 and the pump 20 to adjust in the most optimized way the transmission of torque between motor 23 and pump 20.
Fixed displacement pump 20 comprises an inlet 20a fluidly connected to a source of oil 9 and an outlet 20b fluidly connected to priority valve module 3 via a conduit 31. Pump 20 is configured to increase the pressure of the aspired oil to a preset between the inlet 20a and the outlet 20b, thereby increasing the maximum flow directed to priority valve module 3.
Conduit 31 is fluidly connected to priority valve module 3, preferably by a fluidly connection with conduit 11 and hydraulic circuit 1 can further comprises a check valve 32 configured to allow the motion of fluid only from pump 20 towards priority valve module 3.
The operation of motor 23 is controlled by electronic unit 24 that is configured to receive a plurality of electric signals representing different quantities related to the operation of the wok vehicle to consequently control the motor 23.
In particular, the electronic control unit 24 comprises elaboration means configured to elaborate the electric signals to provide a suitable control signal for managing the operation of motor 23.
Such electric signals are generated by a plurality of sensor means configured to detect quantities related to the operation of the work vehicle. Such electric signals may also be input signals representative of an operational condition requested by the user, e.g. thanks to a joystick, for requesting a particular operation that involves the use of hydraulic actuators.
In particular, the hydraulic arrangement 1 essentially comprises:

an engine speed sensor configured to detect the rotational speed (e.g. in rpm) of the engine 2; and
a pressure sensor configured to detect the pressure of the oil fluid flowing into priority valve module, i.e. on conduit 11 downstream to the junction with conduit 31.

Furthermore, the hydraulic arrangement 1 can furthermore comprise the following sensor means:

a torque sensor configured to detect the torque provided by said engine 2, i.e. at shaft 8; and
a speed sensor configured to detect the rotational speed of the output shaft of said electrical motor 21, i.e. on shaft 29.

Furthermore, the electronic control unit 24 is electrically connected to accumulator means 25 to detect the their threshold of charge.
Clearly, the electric connection of electronic control unit 24 with the aforementioned elements may be realized by wire or wireless thanks to electromagnetic signals.
The operation of the hydraulic arrangement 1 according to the invention and described as above is the following.
In a first mode of operation, shown in figure 3, only variable displacement pump 6 pumps fluid towards priority valve module 3. Such condition may be representative of an operational condition of work vehicle 1 in which the engine 2 provide sufficient power to provide the oil thanks to only variable displacement pump 6.
In such mode of operation, engine 2 provides torque to shaft 8 that starts rotate thereby leading pump 6 to aspire oil from source 9 and direct the latter, pressurized, to the priority mode. Thanks to check valve 32, such oil cannot flow via conduit 31 towards pump 20. The swashplate angle of the pump 6 is regulated via hydraulic signal 13, spilled downstream to pump 6, and compensator module 7. A portion of the torque provided by the engine 2 to shaft 8 is transferred via gearing 27 to input shaft 28 and then to generator 22 that recharges the accumulator means 25.
In a second mode of operation, shown in figure 4, both pumps 6 and 20 pump fluid towards priority valve module 3.
In such mode of operation, engine 2 provides torque to shaft 8 that starts rotate thereby leading pump 6 to aspire oil from source 9 and direct the latter, pressurized, to the priority valve module 3. The swashplate angle of the pump 6 is regulated via hydraulic signal 13, spilled downstream to pump 6, and compensator module 7. A portion of the torque provided by the engine 2 to shaft 8 is transferred via gearing 27 to input shaft 28 and then to generator 22 that recharges the accumulator means 25. In the meantime, the control unit 24 controls motor 23 that used the power stored in accumulator means 25 to make rotating shaft 29 thereby leading pump 20 that aspires oil from source 9 and direct the latter, pressurized, to the priority valve module 3.
Such condition may be representative of a plurality operational condition of work vehicle 1 as detailed below.
In a first operational condition, it is requested an oil flow to priority valve module 3 while engine 2 is at idle.
Accordingly, the flow that can be provided by pump 6, directly linked to shaft 8 rotation, is at a value that is proportional to the shaft 8 speed. Since the engine 2 is at idle, the shaft 8 speed is at minimum and therefore the flow that can be provided by pump 6 is minimum, as regulated by compensator module 7. If the user requests a particular operation that involves the use of a hydraulic actuator, e.g. via a joystick of the work vehicle, the electronic unit 24 elaborates such input signal provided by the user to determine the amount of oil needed at priority valve module 3. The electronic unit 24, thanks to pressure signal on conduit 11 and the knowledge of engine speed, can estimate the oil flow currently provided by pump 6 and estimate a difference with respect to the requested flow by the user. Therefore, knowing such difference of oil flow, the electronic unit 24 controls motor 23 to make rotate input shaft 29 thereby allowing pump 20 to provide an oil flow corresponding to such difference. In this way, even if the engine 2 is at idle, the work vehicle is provided with a sufficient quantity of oil without need of increasing engine 2 speed.
In a second operational condition, it is requested an oil flow to priority valve module 3 while engine 2 is already at its maximum speed.
Accordingly, the flow that can be provided by pump 6, directly linked to shaft 8 rotation, is at a value that is proportional to the shaft 8 speed. Since the engine 2 is at its maximum speed, the shaft 8 speed is maximal and therefore the flow that can be provided by pump 6 is maximum, as regulated by compensator module 7. If the user requests a particular operation that involves the use of a hydraulic actuator, e.g. via a joystick of the work vehicle, the electronic unit 24 elaborates such input signal provided by the user to determine the amount of oil needed at priority valve module 3. The electronic unit 24, thanks to pressure signal on conduit 11 and the knowledge of engine speed, can estimate the oil flow currently provided by pump 6 and estimate a difference with respect to the requested flow by the user. Therefore, knowing such difference of oil flow, the electronic unit 24 controls motor 23 to make rotate input shaft 29 thereby allowing pump 20 to provide an oil flow corresponding to such difference. In this way, even if the engine 2 is at maximum, the work vehicle is provided with a further quantity of oil.
In a third operational condition, it is requested an oil flow to priority valve module 3 while engine 2 is operating at an intermediate speed.
Accordingly, the flow that can be provided by pump 6, directly linked to shaft 8 rotation, is at a value that is proportional to the shaft 8 speed. Since the engine 2 is an intermediate speed, the flow that can be provided by pump 6 is comprised between its minimum and maximum value, as regulated by compensator module 7. If the user requests a particular operation that involves the use of a hydraulic actuator, e.g. via a joystick of the work vehicle, the electronic unit 24 elaborates such input signal provided by the user to determine the amount of oil needed at priority valve module 3. The electronic unit 24, thanks to pressure signal on conduit 11 and the knowledge of engine speed, can estimate the oil flow currently provided by pump 6 and estimate a difference with respect to the requested flow by the user. Therefore, knowing such difference of oil flow, the electronic unit 24 controls motor 23 to make rotate input shaft 29 thereby allowing pump 20 to provide an oil flow corresponding to such difference.
In particular, at least two control law of electric motor 23 may be envisaged. In mathematical terms the base equation related to the control of the flow of oil is the following: $Q_{F} \approx {k Q}_{U} / ω_{F}$
wherein:

Q_F is the flow provided by fixed displacement pump 20;
Q_U is the flow needed at the priority valve module 3;
ω_F is the speed of fixed displacement pump 20;
k is a proportional factor.

According to a first control law, the torque provided by motor 23 is optimized to minimize the load imparted to engine 2 from pump 20, i.e. to maximize the efficiency of pump 20.
According to a second control law, the torque provided by motor 23 is optimized to allow the operation of engine 2 at its maximum efficiency condition, notwithstanding the efficiency of pump 20.
According to a third control law, the torque provided by motor 23 is optimized to reach a point maximizing both the efficiency of pump 20 and engine 2.
In a third mode of operation, shown in figure 5, only pump 20 pumps fluid towards priority valve module 3. Such condition may be representative of an operational condition of work vehicle 1 into which the requested oil flow is minimal and it could be worth not using/activating engine 2.
In such mode of operation, engine 2 is disconnected to provide torque to shaft 8 or off and the control unit 24 controls motor 23 that used the power stored in accumulator means 25 to make rotating shaft 29 thereby leading pump 20 that aspires oil from source 9 and direct the latter, pressurized, to the priority valve module 3.
According to the above, the present invention also relates to a method for providing pressurized oil flow to a priority valve module 3 of a work vehicle thanks to the above hydraulic arrangement 1 comprising the following steps:

detecting the pressure of the fluid provided at the priority valve module 3;
detecting the engine 2 speed, i.e. the speed at shaft 8;
estimating the flow provided by the variable displacement pump 6;
receiving a user request of flow needed at priority module valve module 3;
calculating the difference of flow needed at priority module valve module 3 with respect to the estimated flow provided by variable displacement pump 6;
Controlling electric motor 23 in order to operate fixed displacement pump 20 to provide the such difference of flow to the priority module valve module 3.

In particular, the step of controlling electric motor 23 may comprise an optimization step, preferably a minimization of the load due to fixed displacement pump 20, i.e. the maximization of its efficiency, and/or a maximization of the efficiency of engine 2.
The aforementioned steps of the method can be executed thanks to a computer program memorized in the electronic control unit 24.
In view of the foregoing, the advantages of the hydraulic arrangement 1 according to the invention are apparent.
First, the flow of pressurized oil that can be provided at the priority module 3 is no more strictly linked to the engine 2 speed. Indeed, as demonstrated above, a plurality of different mode of control of electric motor 23 allows to achieve different oil flow condition at priority valve module 3 independently with respect to engine 2 condition.
Furthermore, it is possible to provide a greater oil flor at priority valve module 3 without the need of increasing the size of engine 2 or, at idle condition, without the need of increasing its speed.
Moreover, it is possible to optimize the use of engine 2 and/or of fixed pump 20 thereby reducing the vehicle consumption.
It is furthermore evident that the load dependency, i.e. the standard load sensing architecture, it always guarantee by the variable displacement pump 6, when used.
It is clear that modifications can be made to the described the hydraulic arrangement 1 which do not extend beyond the scope of protection defined by the claims.
For example, the pump 6, 20 may be of any size, typology and in greater number. Similar consideration may be applied to compensator module 7, transmission module 26 or motor/generator module 21.
Moreover, different control law can apply different mathematical relationships to control electric motor 23.

Claims

Hybrid hydraulic arrangement (1) for providing a flow of pressurized oil to a priority module (3) of a work vehicle configured to divide said pressurized oil between a plurality of hydraulic working module of said work vehicle,
said hybrid hydraulic arrangement (1) comprising a hydro-mechanic module (4) and a hybrid module (5), said hydro-mechanic module (4) and hybrid module (5) being each separately mechanically coupled to an engine (2) of said work vehicle and both fluidly connected together to said priority module (3),
said hydro-mechanic module (4) comprising a variable displacement pump (6) configured to aspirate fluid from a source (9), pressurize such fluid and send the latter to said priority module (3) and a compensator module (7) configured to vary the displacement of said pump (6);
said hybrid module (5) comprising a fixed displacement pump (20), an electric motor (23) and a generator (22),
said fixed displacement pump (20) being carried by said electric motor (23) to aspirate fluid from said source (9), pressurize such fluid and send the latter to said priority module (3),
said generator (22) being mechanically coupled to said engine (2) and electrically coupled to said electric motor (23),
said generator (22) being configured to transform the mechanical energy taken by said engine (2) to electrical energy configured to be used by said electric motor (23),
said electrical motor (23) being controlled independently with respect to the operation of said engine (2) .
Hybrid hydraulic arrangement according to claim 1, wherein said variable displacement pump (6) is mechanically is connected to said engine (2) via a shaft (8), said generator (22) being mechanically coupled to said shaft (8) via a mechanical transmission unit (26).
Hybrid hydraulic arrangement according to claim 2, wherein said mechanical transmission unit (26) comprises a gearing (27).
Hybrid hydraulic arrangement according to any of claims 1 to 3, wherein said hybrid module (5) comprises accumulator means (25) electrically interposed between said generator (22) and said electric motor (23), said accumulator means (25) being configured to store electrical energy produced by said generator (22) so that it can be used by said electric motor (23).
Hybrid hydraulic arrangement according to any of claims 1 to 4, wherein said hybrid module (5) comprises accumulator means (25) electrically interposed between said generator (22) and said electric motor (23), said accumulator means (25) being configured to store electrical energy produced by said generator (22) so that it can be used by said electric motor (23).
Hybrid hydraulic arrangement according to any of claims 1 to 5, wherein said hybrid module (5) comprises an electronic control unit (24) electrically interposed between said generator (22) and said electric motor (23),
said hybrid hydraulic arrangement comprising a plurality of sensor means configured to detect quantities related to the operation of said work vehicle,
said electronic unit (24) being electrically connected to said sensor means and comprising elaboration means to elaborate said quantities detected by said sensor means to control the operation of said electric motor (23).
Hybrid hydraulic arrangement according to claim 6, wherein said sensor means comprise:
• an engine speed sensor configured to detect the rotational speed of said engine (2) of said work vehicle; and

• a pressure sensor configured to detect the pressure of the oil fluid flowing into said priority module (3), coming from both said fixed and variable displacement pumps (20, 6).
Hybrid hydraulic arrangement according to claim 7, wherein said sensor means comprise:
• a torque sensor configured to detect the torque transmitted by said engine (2); and

• a speed sensor configured to detect the rotational speed provided at the output shaft of said electrical motor (23).
Hybrid hydraulic arrangement according to any of claims 6 to 8 when depending on claim 5, wherein said electronic unit (24) is electrically connected to said accumulator means (25) and is configured to control the operation of said electric motor (23) elaborating further data related to said accumulator means (25).
Hybrid hydraulic arrangement according to any of claims 6 to 9, wherein said electronic unit (24) controls said electric motor (23) on the base of the following mathematical relationship $Q_{F} \approx {k Q}_{U} / ω_{F}$
wherein:
• Q_F is the flow provided by said fixed displacement pump (20) ;

• Q_U is the flow needed by said priority module (3);

• ω_F is the speed of said fixed displacement pump (20);

• k is a proportional factor.
said electronic unit (24) controlling the said electronic motor (23) optimizing the efficiency of said fixed displacement pump (20) and/or the efficiency of said engine (2).
Hybrid hydraulic arrangement according to any of the preceding claims, comprising a check valve (32) fluid interposed between said fixed displacement pump (20) and said priority module (3), said check valve (32) allowing the passage of fluid only from said fixed displacement pump (20) to said priority module (3).
Hybrid hydraulic arrangement according to any of the preceding claims wherein said compensator module (7) comprise valve means (12) fluidly interposed between an outlet of said variable displacement pump (6) and a discharge (16) and a control piston (14) configured to control the displacement of said pump (6), said valve means (12) being fluidly connected to said control piston (14) and to generate a hydraulic signal configured to actuate said control piston (14).
Method for providing a pressurized oil flow to a priority module (3) of a work vehicle according to a hybrid hydraulic arrangement according to any of the preceding claims, said method comprising the following phases:
• detecting the pressure of the fluid provided at said priority module (3);

• detecting the speed of said engine (2);

• estimating the flow provided by said variable displacement pump (6) on the base of said engine speed;

• receiving a user request of flow needed at said priority (3);

• calculating the difference of flow needed at priority module (3) with respect to the estimated flow provided by variable displacement pump (6);

• controlling electric motor (23) in order to operate said fixed displacement pump (20) to provide the such difference of flow to said priority module (3).
Method according to claim 13, therein said control of said electric motor (23) is made to optimize the efficiency of said fixed displacement pump (20) and/or the efficiency of said engine (2).
Work vehicle comprising an engine (2), a plurality of hydraulic working module and a priority module (3) configured to divide a pressurized flow of fluid to said different working module, said working module further comprising a source (9) of oil and a hybrid hydraulic arrangement (1) according to any of the preceding claims configured to pressurize said oil from said source (9) to said priority module (3).