Power systems for construction machinery and corresponding operating methods

Abstract

The present invention relates to a power system (1) for a working machine (100), comprising: a prime mover (2) and a main shaft (3), wherein the prime mover (2) is drivably connected to the main shaft (3); a planetary gear set (4) comprising: a rotatable first member (41) drivably connected to the main shaft (3); a rotatable second member (42); and a rotatable third member (43) for propelling the working machine; a hydraulic system (5) comprising at least one hydraulic actuator (160) for performing working functions of the working machine during use; an energy storage system (ES); and a first hydraulic... The system comprises: a first hydraulic press (HM1) mechanically connected to a spindle (3) and hydraulically connected to a hydraulic system (5); a first motor (EM1) mechanically connected to the spindle (3); and a second motor (EM2) mechanically connected to a rotatable second component (42), wherein the first motor (EM1) and the second motor (EM2) are electrically connected, and wherein an energy storage system (ES) is electrically connected to the first motor (EM1) and the second motor (EM2), and wherein the power system further comprises: a second hydraulic press (HM2) mechanically connected to the rotatable second component (42) and hydraulically connected to the hydraulic system (5). This disclosure also relates to a method, a control unit (170), and a working machine (100).

Description

Technical Field

[0001] The present invention relates to a power system for a work machine, a method for operating the power system for the work machine, a control unit and / or a work machine.

[0002] This invention applies to construction machinery or equipment in the field of industrial construction machinery, such as wheel loaders. Although the invention will be described with respect to wheel loaders, it is not limited to this specific machine, but can also be used with other construction machinery, such as articulated conveyors, excavators, and backhoe loaders. Background Technology

[0003] Construction machinery (such as wheel loaders) is rapidly becoming more electrified. For example, construction machinery can be electric hybrid machinery, such as "plug-in" electric hybrid machinery, in which the construction machinery operates by using an internal combustion engine and by using one or more electric motors combined with an energy storage system that can be charged by plugging into the power grid.

[0004] Operating machinery typically includes a drivetrain for propelling the machinery and one or more operating functions. These operating functions can be any of the following: wheel loader function, reach stacker function, telescopic forklift function, forestry machinery function, forklift loader function, or any other operating function requiring a hydraulic system.

[0005] In light of the above, efforts are underway to develop more cost-effective and energy-efficient work machinery, powered by an engine and one or more additional power sources in the form of an electric motor. Summary of the Invention

[0006] The object of this invention is to provide an improved power system for working machinery that is cost-effective and energy-efficient, or at least provides a suitable alternative to known power systems for working machinery. Another object of this invention is to provide an improved method for operating a power system for working machinery that is cost-effective and energy-efficient. Yet another object of this invention is to provide working machinery comprising an improved power system that is cost-effective and energy-efficient, or at least provides a suitable alternative to known working machinery.

[0007] According to a first aspect of the invention, the objective is achieved by a power system according to the invention. According to a second aspect of the invention, the objective is achieved by a method according to the invention. According to a third aspect of the invention, the objective is achieved by a control unit according to the invention. According to a fourth aspect of the invention, the objective is achieved by a working machine according to the invention.

[0008] According to the first aspect, the objective is achieved by a power system for operating machinery, the power system comprising:

[0009] A prime mover and a main shaft, wherein the prime mover is drivably connected to the main shaft;

[0010] A planetary gear set, the planetary gear set comprising: a rotatable first member drivably connected to the main shaft; a rotatable second member; and a rotatable third member for propelling the working machinery;

[0011] A hydraulic system, the hydraulic system including at least one hydraulic actuator, the at least one hydraulic actuator being used to perform the working function of the working machinery during use of the working machinery;

[0012] Energy storage system;

[0013] A first hydraulic press, which is mechanically connected to the spindle and hydraulically connected to the hydraulic system;

[0014] A first motor is mechanically connected to the main shaft;

[0015] A second motor is mechanically coupled to the rotatable second component, wherein the first motor and the second motor are electrically connected, and wherein the energy storage system is electrically connected to the first motor and the second motor, and wherein the power system further includes:

[0016] The second hydraulic press is mechanically connected to the rotatable second component and hydraulically connected to the hydraulic system.

[0017] By providing the power system disclosed herein, a highly efficient and low-cost power system for operating machinery is achieved. More specifically, the construction of said power system (particularly the way the motor and hydraulic press are connected to the planetary gear set and the spindle) enables sufficient performance to be provided with a relatively low installed power. Furthermore, the power system disclosed herein allows for fewer and more efficient power conversions.

[0018] Optionally, the second hydraulic press can be configured to operate in two opposite directions of rotation to generate hydraulic power for the hydraulic system. This means increased versatility of the power system, resulting in more efficient power conversion within the system.

[0019] Optionally, at least one of the first and second hydraulic presses may be an electro-hydraulic press. An electro-hydraulic press can provide a power system with reduced power loss. This can, for example, make it possible to control the displacement of the hydraulic press, which can be advantageous if / when a hydraulic flow is provided in parallel with the current between the motor and the hydraulic system. An electro-hydraulic press further implies increased freedom in selecting different control strategies, which in turn can further reduce power loss.

[0020] Optionally, the first and second hydraulic presses can be hydraulically coupled, allowing hydraulic power to be transmitted between them in at least one direction, preferably in either direction. This provides further improved efficiency, enabling more possible control strategies for the power system. Typically, the peak efficiencies of hydraulic presses and motors are in different operating zones. Therefore, it is possible to more efficiently transmit power hydraulically or electrically depending on the required torque and speed. For example, when the motor has poor efficiency, hydraulic power can be transmitted between the first and second hydraulic presses during low speed and high torque periods. This can further facilitate motor miniaturization, resulting in a more cost-effective power system.

[0021] Optionally, at least one of the hydraulic presses can be configured to operate at all possible combinations of positive and negative rotational speeds and positive and negative torques, i.e., a so-called four-quadrant machine. Therefore, further improved efficiency can be provided, thereby enabling more possible control strategies for the power system.

[0022] Optionally, the rotatable first component may be the sun gear of the planetary gear set. Still optionally, the rotatable second component may be the ring gear of the planetary gear set. Still optionally, the rotatable third component may be the planet carrier of the planetary gear set. However, it should be understood that although the above-described configuration of the planetary gear set has been shown to facilitate a highly efficient and low-cost power system, other configurations are also possible.

[0023] Optionally, the power system may further include a coupling member located between the prime mover and the main shaft, the coupling member being used to selectively engage and disengage the prime mover from the main shaft. This enables pure electric drive when the prime mover is disconnected.

[0024] Optionally, the power system may further include a first gear set, wherein the rotatable third member is drivably connected via the first gear set to an output shaft for propelling the working machinery. By providing the first gear set, the torque and speed to the output shaft can be fixedly adjusted. Furthermore, a geometrical drop between the main shaft and the output shaft can be provided, which facilitates the installation of the power system in the working machinery.

[0025] Optionally, the power system may further include a first gear set coupling member for selectively engaging and disengaging from the rotatable third member relative to the output shaft.

[0026] Optionally, the power system may further include a second gear set, wherein the rotatable first member is drivably connected to the output shaft via the second gear set.

[0027] Optionally, the power system may further include a second gear set coupling member for selectively engaging and disengaging from the rotatable first member relative to the output shaft. By providing a second gear set and a second gear set coupling member, an improved speed range and increased maximum drive speed can be achieved.

[0028] Optionally, the power system may further include a reverse gear set, wherein the rotatable third member is drivably connected to the output shaft via the reverse gear set for selectively providing a reverse output speed on the output shaft.

[0029] Optionally, the power system may also include the output shaft for propelling the working machinery.

[0030] Optionally, the power system may further include a first mechanical coupling and a second mechanical coupling, wherein the first hydraulic press and the first motor are directly coupled to the first mechanical coupling, and the second hydraulic press and the second motor are directly coupled to the second mechanical coupling, wherein the first mechanical coupling is directly coupled to the spindle, and the second mechanical coupling is directly coupled to the rotatable second component. Still optionally, at least one of the first and second couplings may be configured to have a fixed gear ratio. For example, the first mechanical coupling may include two or more mechanically engaged gears, and the second mechanical coupling may also include two or more mechanically engaged gears. Alternatively, at least one of the first and second mechanical couplings may be configured to provide a variable gear ratio, such as by providing gearboxes with different gear ratios, thereby providing more control options for the power system, which can provide further improved efficiency.

[0031] Optionally, the mechanical connection from the first hydraulic press to the spindle and the mechanical connection from the first motor to the spindle may have different gear ratios relative to the spindle. Still optionally, the mechanical connection from the second hydraulic press to the rotatable second component and the mechanical connection from the second motor to the rotatable second component may have different gear ratios relative to the rotatable second component. Still optionally, the mechanical connections of the first hydraulic press and the first motor may have the same gear ratio. Still optionally, the mechanical connections of the second hydraulic press and the second motor may have the same gear ratio.

[0032] According to the second aspect, the objective is achieved by a method for operating a power system for working machinery, wherein the power system comprises:

[0033] A prime mover and a main shaft, wherein the prime mover is drivably connected to the main shaft;

[0034] A planetary gear set, the planetary gear set comprising: a rotatable first member drivably connected to the main shaft; a rotatable second member; and a rotatable third member for propelling the working machinery;

[0035] A hydraulic system, the hydraulic system including at least one hydraulic actuator, the at least one hydraulic actuator being used to perform the working function of the working machinery during use of the working machinery;

[0036] Energy storage system;

[0037] A first hydraulic press, which is mechanically connected to the spindle and hydraulically connected to the hydraulic system;

[0038] A first motor is mechanically connected to the main shaft;

[0039] A second motor is mechanically coupled to the rotatable second component, wherein the first motor and the second motor are electrically connected, and wherein the energy storage system is electrically connected to the first motor and the second motor, and wherein the power system further includes a second hydraulic press, which is mechanically coupled to the rotatable second component and hydraulically coupled to the hydraulic system.

[0040] The method includes operating the second hydraulic press as a pump or as a motor.

[0041] The advantages and effects of the second aspect of the invention are largely similar to those of the first aspect. More specifically, by using the construction of the power system as disclosed herein, it has been achieved that the power system can be operated more efficiently. In fact, operating the second hydraulic press as a pump or as a motor in the power system disclosed herein contributes to fewer and more efficient power conversions in the power system. It should also be noted that all embodiments of the first aspect of the invention are applicable to all embodiments of the second aspect of the invention, and vice versa.

[0042] Optionally, the method may further include:

[0043] The second hydraulic press is driven as a pump by using mechanical power supplied from the main shaft to the rotatable second component, and

[0044] When there is residual mechanical power supplied from the main shaft to the rotatable second component:

[0045] The second motor is operated as a generator by using the remaining mechanical power.

[0046] Therefore, surplus mechanical power can be effectively obtained through a second motor, in which the generated electrical power can be used directly or later for other purposes in the power system. This can also mean lower required torque in the second motor and / or a lower amount of recycle energy in the power system.

[0047] Optionally, the method may further include charging the energy storage system using electrical energy generated by the second motor. Thus, excess mechanical power can be effectively converted into electrical power, which is stored in the energy storage system for later use, implying increased mechanical efficiency over time.

[0048] Optionally, the method may further include operating the first motor as a motor using electrical energy generated by the second motor. Thus, the mechanical power obtained by the second motor (such as the residual mechanical power mentioned above) can be efficiently converted into electrical power and transferred to the first motor without any further power conversion.

[0049] Optionally, as described above, the first hydraulic press and the second hydraulic press can be hydraulically connected, such that hydraulic power can be transmitted between the first hydraulic press and the second hydraulic press in at least one direction, preferably in either direction, wherein the method may further include:

[0050] Hydraulic power is transferred from one of the first and second hydraulic presses to the other of the first and second hydraulic presses.

[0051] Therefore, as mentioned above, this can contribute to the miniaturization of motors, which in turn means more cost-effective power systems. Furthermore, as mentioned above, it is possible to more efficiently transmit power selectively, either hydraulically or electrically, depending on the required torque and speed.

[0052] Optionally, the method may further include:

[0053] The first hydraulic press is driven as a pump by using mechanical power from the main shaft; and simultaneously:

[0054] The second motor is operated as a motor by using electrical energy stored in the energy storage system. This can mean further improved efficiency, reduced power conversion, and lower power losses.

[0055] Optionally, the method may further include:

[0056] The second hydraulic press is driven by the second motor as a pump.

[0057] This is particularly advantageous when the rotatable second component of the planetary gear set rotates freely. Thus, the second motor can drive the hydraulic press as a pump at an optimized rotational speed, independent of other rotational speeds in the power system. Consequently, the hydraulic power from the second hydraulic press can be transmitted, for example, to at least one hydraulic actuator in the hydraulic system.

[0058] According to the third aspect, the objective is achieved by a control unit for a working machine, wherein the control unit is configured to perform the steps of any of the embodiments of the second aspect of the invention.

[0059] According to the fourth aspect, the objective is achieved by a working machine comprising a power system according to any embodiment of the first aspect of the invention.

[0060] Optionally, the operating machinery may include a control unit according to any embodiment of the third aspect of the present invention.

[0061] Other advantages and beneficial features of the invention are disclosed in the following description. Attached Figure Description

[0062] Referring to the accompanying drawings, the following is a more detailed description of embodiments of the invention cited by way of example.

[0063] In the attached diagram:

[0064] Figure 1 A schematic perspective view of a working machine according to an exemplary embodiment of the present invention is shown;

[0065] Figure 2 A schematic diagram of a power system according to an exemplary embodiment of the present invention is shown; and

[0066] Figure 3 A schematic diagram of a power system according to another example embodiment of the present invention is shown. Detailed Implementation

[0067] exist Figure 1 The diagram shows a schematic perspective view of a work machine 100 in the form of a wheeled loader. The wheeled loader 100 includes a power system 1 (not shown) according to any embodiment of the first aspect of the invention. As shown, the wheeled loader 100 may also include a control unit 170 configured to perform any step of the method according to the second aspect of the invention.

[0068] Control unit 170 may include a microprocessor, microcontroller, programmable digital signal processor, or other programmable device. The control unit may also include, or alternatively may include, an application-specific integrated circuit (ASIC), a programmable gate array (FPGA) or programmable array logic, a programmable logic device, or a digital signal processor. Where control unit 170 includes a programmable device (such as a microprocessor, microcontroller, or programmable digital signal processor as described above), the processor may also include computer-executable code that controls the operation of the programmable device. Control unit 170 may include embedded hardware (sometimes with integrated software) exhibiting a close physical relationship. Examples of such physical relationships are shared housings and components mounted on one or more circuit boards. It should also be noted that control unit 170 may be a combination of several communicatively connected control units.

[0069] like Figure 1 The wheel loader 100 shown includes four wheels 110, 120, 130, and 140. The wheel loader 100 also includes a front bucket 150. The front bucket 150 can be actuated using at least one hydraulic actuator 160, which is operated and powered by a hydraulic system 5 (see, for example, [link to relevant documentation]). Figure 2 ).

[0070] Despite Figure 1 A wheeled loader 100 is shown, but it should be noted that the invention disclosed herein can be used with and includes any other type of work machinery and / or vehicle with a hydraulic system having at least one hydraulic actuator for performing work functions. Additionally, instead of wheels, the work machinery 100 may include, for example, track components for moving the work machinery 100. Therefore, the work machinery 100 may include any type of ground engagement device or any combination of different types of ground engagement devices.

[0071] about Figure 2 A schematic diagram of a power system 1 according to an exemplary embodiment of the present invention is shown. The power system 1 includes a prime mover 2 and a main shaft 3, wherein the prime mover 2 is drivably connected to the main shaft 3. In the illustrated embodiment, the prime mover 2 is an internal combustion engine, such as a diesel engine. However, it should be noted that any type of prime mover, such as a main electric motor, can be advantageously used. Therefore, according to an exemplary embodiment of the present invention, the working machinery 100 can be a fully electric working machinery.

[0072] The power system 1 also includes a planetary gear set 4, which comprises: a rotatable first member 41 drivenly connected to the main shaft 3; a rotatable second member 42; and a rotatable third member 43 for propelling the working machine 100. In the illustrated embodiment, the rotatable first member 41 is the sun gear of the planetary gear set 4, the rotatable second member 42 is the ring gear of the planetary gear set 4, and the rotatable third member 43 is the planet carrier of the planetary gear set 4. However, it should be understood that although this configuration has been shown to provide beneficial torque transmission and speed conversion, other configurations are possible. The rotatable third member 43 is further capable of being connected to an output shaft (not shown) for propelling the working machine 100.

[0073] Power system 1 also includes:

[0074] Hydraulic system 5, which includes at least one hydraulic actuator 160 (see...) Figure 1 The at least one hydraulic actuator 160 is used to perform the operating functions of the operating machinery 100 during use of the operating machinery 100;

[0075] Energy storage system (ES);

[0076] The first hydraulic press HM1 is mechanically connected to the main shaft 3 and hydraulically connected to the hydraulic system 5;

[0077] A first motor EM1 is mechanically connected to the main shaft 3; and

[0078] The second motor EM2 is mechanically connected to the rotatable second component 42.

[0079] The energy storage system ES can be any type of energy storage system (such as a battery or multiple battery packs), which may include, for example, individual lithium-ion battery cells. Alternatively or additionally, the energy storage system ES may include capacitors.

[0080] A first motor EM1 and a second motor EM2 are electrically connected, and an energy storage system ES is also electrically connected to the first motor EM1 and the second motor EM2. Motors EM1 and EM2 and the energy storage system ES can be electrically connected, for example, via a junction box (not shown). By using this electrical connection, electrical power can be directly transferred between motors EM1 and EM2 (meaning improved efficiency), and can also be transferred through the energy storage system. Therefore, the electrical energy generated by either motor EM1 or EM2 can also be stored for later use, which means improved efficiency over time. Furthermore, either motor EM1 or EM2 can also function as a motor driven by the electrical power stored in the energy storage system ES.

[0081] The power system 1 also includes a second hydraulic press HM2, which is mechanically connected to the rotatable second component 42 and hydraulically connected to the hydraulic system 5.

[0082] In view of the above, a highly efficient and low-cost power system 1 for the operating machinery 100 has been realized. For example, by constructing as follows: Figure 2 The power system 1 shown (in which the first hydraulic press HM1 and the first motor EM1 are mechanically coupled to the spindle 3, and the second hydraulic press HM2 and the second motor EM2 are mechanically coupled to the rotatable second component 42) is capable of providing beneficial performance with a lower amount of installed power (such as electrical power). The power system 1 also enables less and more efficient power conversion.

[0083] like Figure 2The power system 1 shown also includes a first mechanical coupling 11 and a second mechanical coupling 12. A first hydraulic press HM1 and a first motor EM1 are directly connected to the first mechanical coupling 11, and a second hydraulic press HM2 and a second motor EM2 are directly connected to the second mechanical coupling 12. The first mechanical coupling 11 is directly connected to the spindle 3, and the second mechanical coupling 12 is directly connected to the rotatable second member 42. The first mechanical coupling 11 and the second mechanical coupling 12 are separate from each other. Therefore, according to an exemplary embodiment of the invention, hydraulic presses HM1 and HM2 are mechanically separated from each other, and motors EM1 and EM2 are also mechanically separated from each other, thus forming corresponding pairs of one hydraulic press and one motor, namely HM1+EM1 and HM2+EM2. In the illustrated embodiment, the first coupling 11 and the second coupling 12 are configured to have a fixed gear ratio, but a variable gear ratio is also possible, such as by providing gearboxes with different gear ratios. As shown, a fixed gear ratio is provided from the first hydraulic press HM1 and the first motor EM1 to the spindle 3. Furthermore, a fixed gear ratio is provided from the second hydraulic press HM2 and the second motor EM2 to the rotatable second component 42. In the illustrated embodiment, the first mechanical coupling device 11 is in the form of two mechanically engaged gears 111 and 112, and the second mechanical coupling device is also in the form of two mechanically engaged gears 121 and 122. Further, according to another embodiment, the first motor EM1 can be mechanically coupled to the spindle 3 at a first gear ratio, and the first hydraulic press HM1 can be mechanically coupled to the spindle 3 at a second gear ratio different from the first gear ratio. The second hydraulic press HM2 and the second motor EM2 can also have a similar configuration with respect to the rotatable second component 42.

[0084] Furthermore, such as Figure 2 The second hydraulic press HM2 shown can be configured such that it can be operated in two opposite rotational directions to generate hydraulic power for the hydraulic system 5 in either of those directions. Furthermore, the first hydraulic press HM1 can also be configured such that it can be operated in two opposite rotational directions to generate hydraulic power for the hydraulic system 5 in either of those directions. At least one of the first hydraulic press HM1 and the second hydraulic press HM2 can also be an electro-hydraulic press. By way of example only, the first hydraulic press HM1 can be a conventional mechanical load induction pump, and the second hydraulic press HM2 can be electro-hydraulic. Therefore, the second hydraulic press HM2 can increase hydraulic power during certain operating modes to minimize power loss.

[0085] Furthermore, such as Figure 2The first hydraulic press HM1 and the second hydraulic press HM2 shown can be hydraulically coupled, allowing hydraulic power to be transmitted between the first hydraulic press HM1 and the second hydraulic press HM2 in at least one direction, preferably in either direction. In the illustrated embodiment, at least one of the hydraulic presses HM1 and HM2 is configured to operate at all possible combinations of positive and negative rotational speeds and positive and negative torques. This functionality allows for the implementation of a hydraulic transmission. Therefore, power can be transmitted hydraulically in parallel with the possibility of transmitting electrical power between motors EM1 and EM2. Typically, the peak efficiencies of the hydraulic press and the motor are in different operating regions. Therefore, it is possible to transmit power more efficiently, either hydraulically or electrically, depending on the required torque and speed. When motors EM1 and EM2 have poor efficiency, the hydraulic power path can be used, for example, during periods of lower speed and higher torque. By using the above configuration, it is possible to further miniaturize motors EM1 and EM2.

[0086] further, Figure 2 A connecting member 6 between the engine 2 and the main shaft 3 is shown. This connecting member 6 is used to selectively engage the engine 2 to the main shaft 3 and disengage the engine 2 from the main shaft 3. Therefore, the engine 2 can be temporarily disengaged, thereby enabling fully electric operation.

[0087] Figure 3 The embodiments illustrate the relationship with Figure 2 A similar configuration is shown, except that the power system 1 also includes a first gear set 8, a second gear set 9, and a reverse gear set 10. Furthermore, an output shaft 7 is also shown.

[0088] More specifically, in addition to Figure 2 In addition to the embodiments described herein, the power system 1 also includes a first gear set 8, wherein the rotatable third member 43 is drivably connected via the first gear set 8 to an output shaft 7 for driving the working machine 100. The power system 1 also includes a first gear set coupling member F1 for selectively engaging and disengaging the rotatable third member 43 relative to the output shaft 7. It should be understood that the output shaft 7 may be formed as part of the power system 1 disclosed herein.

[0089] Additionally, the rotatable first member 41 is drivably connected to the output shaft 7 via the second gear set 9. The power system 1 also includes a second gear set coupling member F2, which is used to selectively engage and disengage the rotatable first member 41 relative to the output shaft (7).

[0090] Furthermore, the rotatable third member 43 is drivably connected to the output shaft 7 via the reverse gear set 10 for selectively providing a reverse transmission speed on the output shaft 7. For this purpose, the reverse gear set connecting member R1 is used to selectively engage the rotatable third member 43 to and disengage it from the output shaft 7.

[0091] The operating mode when the first gear set connecting member F1 is engaged alone (and connecting members F2 and R1 are disengaged) is called mode F1. The operating mode when the second gear set connecting member F2 is engaged alone is called mode F2. The operating mode when the reverse gear set connecting member R1 is engaged alone is called mode R1.

[0092] With the above configuration, the first gear set connecting member F1 and the second gear set connecting member F2 can also be engaged, thereby providing an additional mode F1F2 for the power system 1. For electric operation, F1F2 can provide an additional torque / speed range for the power system 1 (i.e., when the connecting member 6 is disengaged).

[0093] In mode F2, only motor EM1 can be used for propulsion of the work machine 100. This results in a lower maximum output power. On the other hand, the second hydraulic press EM2 can drive the second hydraulic press HM2. In modes F1 and F1F2, both motors EM1 and EM2 can be used for propulsion of the work machine 100. However, since the planetary gear set 4 is locked in the additional mechanical modes F1F2, the torque / speed range is offset. This can be used when determining the scale of the power system 1 to obtain optimal operation between F1, F1F2, and F2. All three modes can also be used in reverse when purely electrically driven, because according to the example embodiment, motors EM1 and EM2 can be controlled at negative speeds. This requires the first hydraulic press HM1 to be able to rotate in both directions.

[0094] exist Figure 3 In the embodiment shown, the hydraulic presses HM1 and HM2 can also be advantageously electrically controlled. This can provide higher output power for mode F2 (if the power required by the hydraulic operation function is not too high). Then, both the first motor EM1 and the first hydraulic press HM1 can be used to provide torque to the spindle 3.

[0095] For example Figure 2 and Figure 3The power system 1 shown can be operated according to an example embodiment of the method disclosed herein. The method may include the step of operating the second hydraulic press HM2 as a pump or motor. Furthermore, the method may also include driving the second hydraulic press HM2 as a pump by using mechanical power supplied from the spindle 3 to the rotatable second member 42, and, when there is residual mechanical power supplied from the spindle 3 to the rotatable second member 42, using the residual mechanical power to operate as a generator.

[0096] The power system 1 disclosed herein can typically operate in three power flow modes (negative cycle power, additional power, and full mechanical power). With the power system 1 disclosed herein, negative cycle power can occur at lower speeds (e.g., 0 to 10 km / h of the working machine 100, depending on the selection of the gear ratio)), full mechanical power can occur at higher speeds (e.g., 10 km / h of the working machine 100) and additional power can occur at even higher speeds (e.g., 10 to 20 km / h of the working machine 100).

[0097] In negative circulation mode, the second motor EM2 can operate as a generator. When the hydraulic operation function requires hydraulic power, the second hydraulic press HM2 can be used primarily. This reduces the torque required by the second motor EM2 and the amount of recirculated energy. This is expected to occur, for example, during the filling operation of the front bucket 150 of the work machine 100, in which the work hydraulic device is used and the work machine 100 operates at a lower speed.

[0098] For additional power modes, the present invention can freely select whether the first hydraulic press HM1 or the second hydraulic press HM2 should supply hydraulic power to optimize efficiency. For example, when the energy storage system ES is discharging, a portion of the power can be supplied by the second hydraulic press HM2 to operate at the optimal efficiency point of the engine 2 and the first hydraulic press HM1.

[0099] Near the fully mechanical point, the speed of the second rotatable member 42 approaches zero. If the second hydraulic press HM2 is electrically controlled, it can then assist the second motor EM2 in supplying torque to the second rotatable member 42. This reduces the total losses (hydraulic presses HM1 and HM2 are generally more efficient than motors EM1 and EM2 at lower speeds and higher torques).

[0100] The method may also include charging the energy storage system ES by using electrical energy generated by the second motor EM2.

[0101] The method may also include operating the first motor EM1 as a motor by using electrical energy generated by the second motor EM2.

[0102] The method may also include transferring hydraulic power from one of the first hydraulic press HM1 and the second hydraulic press HM2 to the other hydraulic press in the first hydraulic press HM1 and the second hydraulic press HM2.

[0103] The method may also include driving the first hydraulic press as a pump by using mechanical power from the spindle; and simultaneously operating the second motor EM2 as a motor by using electrical energy stored in the electrical energy storage system ES.

[0104] The method may also include driving the second hydraulic press HM2 as a pump by the second motor EM2.

[0105] It will be understood that the invention is not limited to the embodiments described above and shown in the accompanying drawings; rather, those skilled in the art will recognize that many modifications and variations can be made within the scope of the appended claims.

Claims

1. A power system (1) for a work machinery (100), comprising: A prime mover (2) and a main shaft (3), wherein the prime mover (2) is drivably connected to the main shaft (3); A planetary gear set (4) comprising: a rotatable first component (41) drivably connected to the main shaft (3); a rotatable second component (42); and a rotatable third component (43) for propelling the working machine; A hydraulic system (5) includes at least one hydraulic actuator (160) for performing the working functions of the working machinery during use of the working machinery; Energy storage system (ES); The first hydraulic press (HM1) is mechanically connected to the spindle (3) and hydraulically connected to the hydraulic system (5); The first motor (EM1) is mechanically connected to the main shaft (3); A second motor (EM2) is mechanically coupled to the rotatable second component (42), wherein the first motor (EM1) and the second motor (EM2) are electrically connected, and wherein the energy storage system (ES) is electrically connected to the first motor (EM1) and the second motor (EM2), and wherein the power system further includes: A second hydraulic press (HM2) is mechanically connected to the rotatable second component (42) and hydraulically connected to the hydraulic system (5), wherein the second hydraulic press (HM2) is configured such that the second hydraulic press (HM2) can be operated in two opposite rotational directions in order to generate hydraulic power for the hydraulic system (5).

2. The power system (1) according to claim 1, wherein, At least one of the first hydraulic press (HM1) and the second hydraulic press (HM2) is an electro-hydraulic press.

3. The power system (1) according to claim 1 or 2, wherein, The first hydraulic press (HM1) and the second hydraulic press (HM2) are hydraulically connected such that hydraulic power can be transmitted between the first hydraulic press (HM1) and the second hydraulic press (HM2) in at least one direction.

4. The power system (1) according to claim 1 or 2, wherein, At least one of the first hydraulic press (HM1) and the second hydraulic press (HM2) is configured to operate at all possible combinations of positive and negative rotational speeds and positive and negative torques.

5. The power system (1) according to claim 1 or 2, wherein, The rotatable first component (41) is the sun gear of the planetary gear set.

6. The power system (1) according to claim 1 or 2, wherein, The rotatable second component (42) is the ring gear of the planetary gear set.

7. The power system (1) according to claim 1 or 2, wherein, The rotatable third component (43) is the planet carrier of the planetary gear set.

8. The power system (1) according to claim 1 or 2 further includes a connecting member (6) located between the prime mover (2) and the main shaft (3), the connecting member (6) being used to selectively engage and disengage the prime mover (2) from the main shaft (3).

9. The power system (1) according to claim 1 or 2 further includes a first gear set (8), wherein the rotatable third member (43) is drivably connected via the first gear set (8) to an output shaft (7) for propelling the working machinery.

10. The power system (1) according to claim 9 further includes a first gear set coupling member (F1) for selectively engaging and disengaging from the rotatable third member (43) relative to the output shaft (7).

11. The power system (1) according to claim 9 further includes a second gear set (9), wherein the rotatable first member (41) is drivably connected to the output shaft (7) via the second gear set (9).

12. The power system (1) according to claim 11 further includes a second gear set coupling member (F2) for selectively engaging and disengaging from the rotatable first member (41) relative to the output shaft (7).

13. The power system (1) according to claim 9 further includes a reverse gear set (10), wherein the rotatable third member (43) is drivably connected to the output shaft (7) via the reverse gear set (10) for selectively providing an output speed in the reverse direction on the output shaft (7).

14. The power system (1) according to claim 1 or 2 further includes a first mechanical coupling device (11) and a second mechanical coupling device (12), wherein the first hydraulic press (HM1) and the first motor (EM1) are directly connected to the first mechanical coupling device (11), and the second hydraulic press (HM2) and the second motor (EM2) are directly connected to the second mechanical coupling device (12), wherein the first mechanical coupling device (11) is directly connected to the spindle (3), and the second mechanical coupling device (12) is directly connected to the rotatable second component (42).

15. The power system (1) according to claim 3, wherein, The first hydraulic press (HM1) and the second hydraulic press (HM2) are hydraulically connected, so that hydraulic power can be transmitted in either direction between the first hydraulic press (HM1) and the second hydraulic press (HM2).

16. A method for operating a power system (1) for a work machine (100), wherein, The power system includes: A prime mover (2) and a main shaft (3), wherein the prime mover (2) is drivably connected to the main shaft (3); A planetary gear set (4) comprising: a rotatable first component (41) drivably connected to the main shaft (3); a rotatable second component (42); and a rotatable third component (43) for propelling the working machine; A hydraulic system (5) includes at least one hydraulic actuator (160) for performing the working functions of the working machine during use of the working machine; Energy storage system (ES); The first hydraulic press (HM1) is mechanically connected to the spindle (3) and hydraulically connected to the hydraulic system (5); The first motor (EM1) is mechanically connected to the main shaft (3); A second motor (EM2) is mechanically coupled to the rotatable second component (42), wherein the first motor (EM1) and the second motor (EM2) are electrically connected, and wherein the energy storage system (ES) is electrically connected to the first motor (EM1) and the second motor (EM2), and wherein the power system further includes a second hydraulic press (HM2), which is mechanically coupled to the rotatable second component (42) and hydraulically coupled to the hydraulic system (5), wherein the second hydraulic press (HM2) is configured such that the second hydraulic press (HM2) can be operated in two opposite rotational directions to generate hydraulic power for the hydraulic system (5); The method includes operating the second hydraulic press (HM2) as a pump or as a motor.

17. The method of claim 16, further comprising: The second hydraulic press (HM2) is driven as a pump by using the mechanical power supplied from the main shaft (3) to the rotatable second component (42), and When there is residual mechanical power supplied from the main shaft (3) to the rotatable second component (42): The second motor (EM2) is operated as a generator by using the remaining mechanical power.

18. The method of claim 16 or 17 further comprises charging the energy storage system (ES) by using electrical energy generated by the second motor (EM2).

19. The method of claim 16 or 17 further comprises operating the first motor (EM1) as a motor by using electrical energy generated by the second motor (EM2).

20. The method according to claim 16 or 17, wherein, The first hydraulic press (HM1) and the second hydraulic press (HM2) are hydraulically connected, such that hydraulic power can be transmitted between the first hydraulic press (HM1) and the second hydraulic press (HM2) in at least one direction. The method further includes: Hydraulic power is transferred from one of the first hydraulic press (HM1) and the second hydraulic press (HM2) to the other of the first hydraulic press (HM1) and the second hydraulic press (HM2).

21. The method according to claim 16 or 17, further comprising: The first hydraulic press (HM1) is driven as a pump by using mechanical power from the main shaft (3); and simultaneously: The second motor (EM2) is operated as a motor by using electrical energy stored in the energy storage system (ES).

22. The method according to claim 16 or 17, further comprising: The second hydraulic press (HM2) is driven by the second motor (EM2) as a pump.

23. The method of claim 20, wherein, The first hydraulic press (HM1) and the second hydraulic press (HM2) are hydraulically connected, enabling hydraulic power to be transmitted in either direction between the first hydraulic press (HM1) and the second hydraulic press (HM2). The method further includes: Hydraulic power is transferred from one of the first hydraulic press (HM1) and the second hydraulic press (HM2) to the other of the first hydraulic press (HM1) and the second hydraulic press (HM2).

24. A control unit (170) for a work machine (100), the control unit being configured to perform the steps of the method according to any one of claims 16 to 23.

25. A working machine (100) comprising a power system (1) according to any one of claims 1 to 15.

26. The working machine (100) according to claim 25, comprising the control unit (170) according to claim 24.

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