Power-split continuously variable transmission system

Abstract

Power-split continuously variable transmission system for stepless transmission of drive power for an agricultural vehicle, with an input element for introducing torque and speed at least two switchable output elements for outputting torque and speed, an electromagnetic gear stage with an inner and a middle rotor and an outer stationary ring element, which are mounted concentrically to each other, a mechanical gear stage connected to the electromagnetic gear stage, wherein the outer ring element of the electromagnetic gear stage has electromagnetic coils to generate an electromagnetic field, and an output element is actuated solely by the electromagnetic gear stage, and a further output element is actuated by the electromagnetic gear stage and the mechanical gear stage, wherein the continuously variable transmission system is designed such that the same rotational speed is present between two output elements at a switching point in order to carry out a switching between them synchronously.

Description

[0001] The invention relates to a power-split continuously variable transmission in the drive train for agricultural vehicles, which converts an input power in the form of torque and speed through transmission stages and introduces it into at least two switchable output elements.

[0002] This application is based on DE 10 2016 210 333.4, which serves as the basis and is fully incorporated herein.

[0003] Power-split continuously variable transmissions (CVTs) are typically implemented using two electric machines. The first electric machine operates as a generator, converting mechanical energy into electrical energy. This electrical energy is then used by a second electric machine, operating as a motor, to generate more mechanical energy. This strategy, known as an electric variator, is particularly common in CVTs and serves to split power in engine-driven vehicles. The second electric machine is located in a transmission stage, allowing it to add mechanical power, previously extracted by the first electric machine, to the drivetrain as needed. This enables the transmission to adapt its power output to the driving requirements.This division allows part of the drive power to be converted mechanically with high efficiency, while a variable part can be converted with lower efficiency but higher variability.

[0004] EP 2 644 946 B1 demonstrates a method for using a magnetic gear stage to modify input power. This method, employing rotors each containing magnets, eliminates the need for gearing. Furthermore, it also demonstrates the use of an electric machine to generate electrical energy by driving it with the magnetic gear stage.

[0005] However, using a magnetic gear stage results in increased costs due to the materials used. Furthermore, the magnetic gear stage from EP 2 644 946 B1 requires an external electric motor for control.

[0006] Additionally, such a transmission with a variable ratio should be able to cover all mechanical driving ranges, ideally with a high level of driver comfort. This also includes relative speed differences within the transmission, which occur during output shifts due to brief, strong accelerations or decelerations caused by interruptions in traction, and which are perceived as disruptive.

[0007] It is therefore an object of the present invention to provide a cost-effective design for a power-split continuously variable transmission. Furthermore, it is an object to increase comfort. Another object is to provide a compact system to enable increased use of installation space.

[0008] The problem is solved according to the invention by the teaching of claim 1. Further advantageous embodiments and developments of the invention are set forth in the dependent claims.

[0009] One embodiment of the invention comprises a power-split continuously variable transmission system for the stepless transmission of drive power for an agricultural vehicle, with an input element for introducing torque and speed, at least two switchable output elements for outputting torque and speed, an electromagnetic transmission stage with an inner and a middle rotor and an outer stationary ring element, which are mounted concentrically to each other.A mechanical gear stage is connected to the electromagnetic gear stage, wherein the outer ring element of the electromagnetic gear stage has electromagnetic coils to generate an electromagnetic field, and one output element is acted upon only by the electromagnetic gear stage, and another output element is acted upon by the electromagnetic gear stage and the mechanical gear stage, wherein the continuously variable transmission system is designed such that at a switching point between two output elements the same rotational speed is present in order to perform a switching between them synchronously.

[0010] By incorporating an electrically controllable coil, in the form of a highly integrated electrical machine, an electromagnetic field can be controlled within the electromagnetic gear stage. No additional rotating components are required; torque and speed are introduced by the controlled, freely adjustable electromagnetic field.

[0011] Both gear stages according to the invention operate interdependently, so that controlling one gear stage controls the other in turn. A connecting control element, such as that used in DE 10 2016 210 333.4, can be avoided. Simultaneously, the control allows the use of a speed range in which the speeds of the two output elements are matched, thus enabling seamless switching.

[0012] Furthermore, by using a mechanical gear stage, the number of gear stages in mechanical engagement can be reduced and an increased gear efficiency can be achieved.

[0013] In a further embodiment of the invention, the electromagnetic gear stage is an electromagnetic three-shaft rotary gear.

[0014] In contrast to conventional converter designs, this reduces the proportion of mechanically meshed gears. The design according to the invention eliminates the need for complex force-supporting bearings for the gear shafts. Consequently, the assembly and design of the housings used can be simplified.

[0015] In a preferred design, the mechanical transmission stage is a three-shaft rotary transmission.

[0016] Three-shaft rotary gearboxes allow for high power density with simultaneous power splitting or summation. This solution enables the use of a small installation space, particularly due to its reduced length.

[0017] In a further development of the invention, both gear stages are connected to the input element by a differential shaft of the electromagnetic gear stage and by a summing shaft of the mechanical gear stage.

[0018] The configuration allows for free adaptation to the drive conditions. The use of a common shaft connection between the electromagnetic and mechanical gear stages ensures optimal dependent control.

[0019] In one embodiment of the invention, an output element is formed with a differential shaft of the mechanical gear stage and a further output element is formed with a summing shaft of the electromagnetic gear stage, which is connected to a further differential shaft of the mechanical gear stage.

[0020] This configuration allows switching between the first and second output elements, so that different paths within the system are used for each. The switching occurs optimally at the point when both output elements reach the same rotational speed.

[0021] In a further preferred embodiment, both gear stages are connected to the input element by a summing shaft of the electromagnetic gear stage and by a summing shaft of the mechanical gear stage.

[0022] When the electromagnetic gear stage is driven by the electromagnetic coils and the resulting rotating field, as well as by the input element, both the electromagnetic and mechanical gear stages are subject to positive guidance. The rotational speeds of the connected sum shafts of both gear stages are determined by the input of drive power. This eliminates the need for a control element between the two gear stages, which would otherwise be required.

[0023] In one embodiment, an output element is formed with a differential shaft of the mechanical gear stage, and another output element is formed with a differential shaft of the electromagnetic gear stage and is connected to another differential shaft of the mechanical gear stage.

[0024] When the electromagnetic gear stage is driven by the electromagnetic coils and the resulting rotating field, as well as by the input element, the electromagnetic and mechanical gear stages form a positive-weighted transmission. The degree of freedom of the transmission system is fixed at one. Therefore, the otherwise necessary control element between the two gear stages is unnecessary.

[0025] The invention is further described with reference to the following figures. These show: Fig. 1. A schematic diagram of a continuously variable transmission system; Fig. 2 a schematic diagram of the continuously variable transmission system according to the Wolf scheme; Fig. 3 an embodiment of the invention according to the Wolf scheme with the power flow shown; Fig. 4 a further embodiment of the invention according to the Wolf scheme with the power flow shown; Fig. 5 a further embodiment of the invention according to the Wolf scheme with the power flow shown; Fig. 6 a further embodiment of the invention according to the Wolf scheme with the power flow shown; Fig. 7 an embodiment of the invention in a sectional view; Fig. 8. A schematic overview of the invention.

[0026] The continuously variable transmission system 10 in Fig. Figure 1 shows the system architecture. The continuously variable transmission system consists of an electromagnetic transmission stage 12 and a mechanical transmission stage 14. On the left side in Fig. Figure 1 shows that the continuously variable transmission system 10 has an input element 16. The input element 16 can be a shaft, a hollow shaft, or a component suitable for transmitting input power in the form of torque and speed. On the right side in Fig. The continuously variable transmission system 10 comprises a first output element 18 and a second output element 20. Like the input element 16, the output elements can also be a shaft, a hollow shaft, or another component suitable for transmitting output power in the form of torque and speed. An input power 22 is introduced into the continuously variable transmission system 10 through the input element 16, transformed and converted within the system, and then discharged from the continuously variable transmission system 10 through the output elements 18 and 20.

[0027] The continuously variable transmission system 10 can consist of one or more housings containing the transmission stages. The system can also have multiple input elements and three or more output elements. The input and output elements can be arranged coaxially or parallel to each other. It is also possible to arrange them at an angle to each other. The output elements can be used to drive vehicle components or to drive trailer functions. The input elements can be driven by an internal combustion engine, electrically, or hydraulically.

[0028] In Fig. Figure 2 shows the continuously variable transmission system 10 in a diagram according to the Wolf diagram. The continuously variable transmission system 10, in particular the electromagnetic gear stage 12 and the mechanical gear stage 14, is represented in abstract form, each as a three-shaft rotary transmission. A rotary transmission is characterized by a circle with three outward-pointing lines, which represent three connecting shafts. These symbols, their type, and their use are defined in the VDI guideline [VDI 672]. The sum shaft, the shaft with the greatest torque, is indicated by a double line. The shafts can be solid or hollow. The Wolf diagram represents the system structure in abstract form, so the embodiments can vary and are not fixed by the diagram.

[0029] In Fig. 2 The continuously variable transmission system 10 consists of a mechanical transmission stage 14 on the left side in Fig. 2 and the electromagnetic gear stage 12 on the right side in Fig. 2, each represented by a circle. Power is introduced into the continuously variable transmission system 10 by a drive 28, which can be an internal combustion engine or an electric motor. The introduction occurs via the input element 16, which is represented by a small circle. The input element 16 transmits the input power to the mechanical transmission stage 14 or the electromagnetic transmission stage 12. Both stages can also be supplied with power simultaneously. The electromagnetic transmission stage 12 has an electromagnetic coil 26 and is connected to the second output element 20. One embodiment of the electromagnetic transmission stage 12 is shown in Fig. Figure 7 is shown and further described there. The electromagnetic coil 26 generates a rotating field in the electromagnetic gear stage 12. This rotating field induces a rotational movement in one of the magnetic rings of the electromagnetic gear stage 12, which initiates and transmits the rotational movement within the continuously variable transmission system 10.

[0030] The mechanical gear stage 14 is connected to the input element 16, as well as to the first output element 18 and the second output element 20. This is achieved through the Wolf diagram in Fig. 2 it can be seen that the input element 16 in one embodiment is connected via a summing shaft to both the mechanical gear stage 14 and the electromagnetic gear stage 12, and thereby power is directed to both gear stages 12, 14.

[0031] Fig. Figure 3 shows the representation of the continuously variable transmission system 10 according to Fig. 2, however, with a modified power flow through the continuously variable transmission system 10 in a further embodiment. Due to the power input from a drive 28 and by a power input from the electrical coil 26 through the electromagnetic gear stage 12, an output power 24 is provided at the first output element 18.

[0032] By introducing drive power 30 through the drive 28, power at the input element 16 is directed through the continuously variable transmission system 10 into both the electromagnetic gear stage 12 and the mechanical gear stage 14. This is illustrated by the arrows 34, which each show a power component and path.

[0033] In the electromagnetic gear stage 12, additional power is introduced into the electromagnetic gear stage 12 by the electromagnetic coil 26. A power component 34 from the electromagnetic gear stage 12 is then transferred to the mechanical gear stage 14. This power is output at the first output element 18, so that output power 24 is available. The flow of the power components 34 in Fig. Figure 3 shows that the power distribution within the continuously variable transmission system 10 takes place via both the electromagnetic transmission stage 12 and the mechanical transmission stage 14. In the embodiment according to Fig. No power is output at the second output element 20. This implementation is illustrated in the following figure.

[0034] In Fig. Figure 4 shows an embodiment in which the electromagnetic coil 26 is used in generator operation, so that power 32 is extracted from the continuously variable transmission system 10 by the electromagnetic coil 26.

[0035] The power flow of the electromagnetic coil 26 differs from the representation in Fig. 3. Both the flow of the power component 34 and the output of power at the first output element 18 are identical to Fig. 3, so that a description is once again omitted.

[0036] Through the operation after Fig. 4 of the electromagnetic coil 26, a portion of the power 30, which is introduced into the continuously variable transmission system 10 by the drive 28, can be extracted by means of the continuously variable transmission system 10 in order to be available for further uses within the vehicle system.

[0037] In Fig. Figure 5 shows the continuously variable transmission system 10 with power transmission from the input element 16 to the second output element 20. Arrows 34 indicate the portion of power that is routed through the continuously variable transmission system 10 from the input element 16 to the second output element 20. The electromagnetic coil 26 is operating in motor mode, so that power 32 is introduced into the continuously variable transmission system 10 at the electromagnetic transmission stage 12. It is evident that the mechanical transmission stage 14 is not included in the power path, and therefore the first output element 18 does not output any power. The torque and speed of the power at the second output element 20 differ from those at the first output element 18. Switching between the different output elements 18 and 20 can be accomplished by a clutch.Due to the system's design and the resulting forced coupling, the output elements 18 and 20 exhibit synchronous (identical) rotational speeds at any given time. Switching can occur at this point, thus preventing the drive train from decelerating or accelerating.

[0038] Fig. Figure 6 shows the same setup as Fig. 5 with a power output at the second output element 20. In contrast to Fig. However, in position 5 the electromagnetic coil 26 is in generator mode. This allows power 32 to be drawn from the continuously variable transmission system 10 in the electromagnetic transmission stage 12.

[0039] Fig. Figure 7 shows a cross-sectional view of an embodiment of the electromagnetic gear stage 12 and the mechanical gear stage 14. The input element 16 has a hollow shaft. The electromagnetic gear stage 12 comprises an outer ring 26 containing electromagnetic coils. The coils can be controlled by a control system known in principle, so that the coils generate a rotating electric field. The outer ring 26 can be stationary, thus eliminating the need for bearings and lubrication of the ring. The electromagnetic gear stage 12 further comprises a middle ring, which is positioned between the outer coils 26 and another inner ring. The middle ring comprises several pole bars, is rotatably mounted, and rotates relative to both the coil 26 and the inner ring. This allows the middle ring to interact with the rotating field generated by the outer coils 26 and be set into rotation.

[0040] The inner ring also has a number of pole rods and, like the middle ring, can be driven and set into rotation by a rotating field. It is possible to adjust the desired response to the generated rotating field by carefully selecting the ratio of the poles of the middle and inner rings.

[0041] In the exemplary embodiment in Fig. 7 there is a shaft connection between the middle ring of the electromagnetic gear stage 12 and the mechanical gear stage 14 and between the inner ring of the electromagnetic gear stage 12 and the mechanical gear stage 14.

[0042] The mechanical gear stage 14 is designed as a three-shaft rotary drive. The standard configuration includes a sun gear, planet gears, and a ring gear. This is a well-known design in engineering.

[0043] The shaft connections between the electromagnetic gear stage 12 and the mechanical gear stage 14 allow the power to be distributed along two paths between the gear stages. Due to the dual shaft connection and a predetermined input power, measured by torque and speed, the continuously variable transmission system 10 is positively coupled. This advantageously eliminates the need for a control mechanism between the gear stages to adjust the speeds. The speed profiles of the output elements 18 and 20 are thus inherently determined by the design. A conventional additional speed adjustment control is therefore unnecessary.

[0044] On the right side in Fig. On the output side, the two output elements 18 and 20 are each formed by a shaft of the ring gear of the mechanical gear stage 14 and by a shaft on which both the inner ring of the electromagnetic gear stage 12 and the mechanical gear stage 14 are mounted. Both output elements are thus coaxial. In another embodiment, the output elements 18 and 20 can be parallel to each other. Depending on the embodiment, any angle between them can also be provided. Furthermore, the output elements can also be solid shafts.

[0045] Fig.Figure 8 shows a system diagram of the continuously variable transmission system 10. This is connected to a ground drive 48 of the vehicle via one of the output elements 18, 20. Another output element is connected to the power take-off (PTO) drive 46. Further output elements can be provided to connect to and supply power to additional drives, e.g., on a trailer.

[0046] On the input side, the continuously variable transmission system 10 is connected to the vehicle drive 28 via an input element 16. A connection to a secondary drive is also possible. This secondary drive can operate in parallel to the vehicle drive and, for example, exclusively drive the continuously variable transmission system 10. The drive 28 can be connected to an electric motor 40. The electric motor 40 converts the drive line into electrical current, which can be stored in an energy storage device 44 for later use. All components are controlled and networked by a vehicle control unit 42. This ensures optimal operation, particularly during transitions. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2016 210 333.4 [0002, 0011] EP 2 644 946 B1 [0004, 0005]

Claims

[1] Power-split continuously variable transmission system for stepless transmission of drive power for an agricultural vehicle, with an input element for introducing torque and speed at least two switchable output elements for outputting torque and speed, an electromagnetic gear stage with an inner and a middle rotor and an outer stationary ring element, which are mounted concentrically to each other, a mechanical gear stage connected to the electromagnetic gear stage, wherein the outer ring element of the electromagnetic gear stage has electromagnetic coils to generate an electromagnetic field, and an output element is actuated solely by the electromagnetic gear stage, and a further output element is actuated by the electromagnetic gear stage and the mechanical gear stage, wherein the continuously variable transmission system is designed such that the same rotational speed is present between two output elements at a switching point in order to carry out a synchronous switching operation between them. [2] Continuously variable transmission system according to claim 1, characterized by that the electromagnetic gear stage is an electromagnetic three-shaft rotary gear. [3] Continuously variable transmission system according to claim 1 or 2, characterized by that the mechanical transmission stage is a three-shaft rotary transmission. [4] Continuously variable transmission system according to one of the preceding claims, characterized by , that both gear stages are connected by a differential shaft of the electromagnetic gear stage and by a summation shaft of the mechanical gear stage, and with the input element. [5] Continuously variable transmission system according to one of the preceding claims, characterized by , that an output element is formed with a differential shaft of the mechanical gear stage and another output element is formed with a summation shaft of the electromagnetic gear stage, which is connected to another differential shaft of the mechanical gear stage. [6] Continuously variable transmission system according to any one of claims 1 to 3, characterized by , that both gear stages are connected by a summing shaft of the electromagnetic gear stage and by a summing shaft of the mechanical gear stage, and with the input element. [7] Continuously variable transmission system according to one of claims 1 to 3 and 6, characterized by, that an output element is formed with a differential shaft of the mechanical gear stage and another output element is formed with a differential shaft of the electromagnetic gear stage and is connected to another differential shaft of the mechanical gear stage.

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