Method and drive system for driving a vehicle

Abstract

The invention relates to a method for regulating constant slow travel of a vehicle. The vehicle has a drive system (1) which has a stepped automatic transmission (3) with a hydrodynamic torque converter (5) and a plurality of shift elements (A, B, D, E, F) for adjusting different transmission ratio steps. A first transmission ratio step is adjusted in the stepped automatic transmission (3) by at least partial closure of at least one first and second shift element (A, F). Furthermore, at least one further third shift element (E) which is configured as a frictional shift element is actuated in dependence on an output rotational speed. Furthermore, a fourth shift element (D) which is configured as a frictional shift element is actuated in alternation with or simultaneously with the third shift element (E) in dependence on the output rotational speed. Furthermore, a drive system (1) and a computer program product for carrying out the method are proposed.

Description

Technical Field

[0001] The present invention relates to a method for driving a vehicle at low speeds and a drive system for driving vehicles, especially rail vehicles. Background Technology

[0002] Vehicles are known to be driven at sustained low speeds (i.e., slow travel) for extended periods, in addition to their usual travel and cruising speeds. Therefore, track construction vehicles, such as those used for rail construction or overhead line construction, must also be driven at constant speeds for extended periods to perform operations at very low speeds (e.g., 3 km / h, 5 km / h, 7 km / h, or 9 km / h). To travel a certain distance more quickly, these track vehicles should also be able to be driven at significantly higher speeds. For example, higher speeds are needed to quickly move from one construction site to another. For this purpose, a drive system or drive train with a planetary gear structure and a graded automatic transmission can be used.

[0003] In vehicles equipped with graded automatic transmissions in the form of planetary structures with hydraulic torque converters, it is impossible to go below a constant minimum speed without additional measures. Because the transmission is hydraulically mechanical, when the motor is at idle speed, a balance is formed by the idle speed regulator, torque converter, and driving resistance, resulting in a minimum constant speed that cannot be lowered. Furthermore, due to inaccurate motor speed regulation at slow speeds, the high precision requirement of a constant speed involving + / - 1 km / h is often unattainable.

[0004] Solutions for driving vehicles at very low, constant speeds are known, and these solutions incorporate an additional hydrostatic drive for slow travel. Thus, a drive system for driving at least one wheel axle of a rail vehicle is known from EP 3 434 550 A1, comprising a mechanical drive system and a hydrostatic drive system. Both drive systems are connected to the rail vehicle's drive motor on the drive side. On the output side, the mechanical and hydrostatic drive systems are combined in a wheel drive arranged on the wheel axle to drive the wheel axle. Such drive systems are typically used in track construction vehicles. These track construction vehicles can be driven at very low operating speeds via the hydrostatic drive system in operating mode, while being driven via the mechanical drive system for faster travel over certain sections. However, the additional hydrostatic drive system requires considerable additional cost.

[0005] DE 10 2009 001 799 A1 also discloses a method for regulating a constant slow speed of a vehicle having a drive system with a graded automatic transmission having a hydraulic torque converter and multiple switching elements for adjusting different gear ratio levels. In this method, for slow speed operation, the first and second switching elements in the graded automatic transmission are closed, while a third switching element, configured as a friction-type switching element (which is closed during normal operation), slips and adjusts. Summary of the Invention

[0006] The objective of this invention is to provide a method for driving a vehicle with a graded automatic transmission having a planetary structure at a constant low speed, and a drive system suitable for this purpose, wherein the drive system should have a structure as simple as possible.

[0007] A method for regulating a vehicle to a constant, slow speed is proposed. The method is configured for a vehicle having a drive system including a graded automatic transmission with a hydraulic torque converter and multiple switching elements for adjusting different gear ratio levels. A first gear ratio level is adjusted within the graded automatic transmission by at least partially closing at least one first and second switching element. These switching elements can be configured, in particular, as friction-type switching elements in the form of diaphragm clutches or diaphragm brakes. Preferably, for constant, slow speed, the first and second switching elements are fully closed, thereby preventing slippage between the shafts to be connected within the graded automatic transmission.

[0008] In motor vehicles equipped with a graded automatic transmission with a planetary gear structure, the gear ratio stages are automatically engaged or switched by closing at least one friction-type switching element (however, usually two friction-type switching elements). To start the vehicle from a standstill and while traveling at low speed, the relevant friction-type switching element can be closed to switch to a gear with the starting gear ratio, i.e., the starting gear. The starting gear can exist in two directions of travel, such as a first forward gear and a reverse gear, or, for vehicles traveling in two equivalent directions (e.g., rail vehicles), a starting gear with the same gear ratio in each direction of travel.

[0009] According to the present invention, for constant slow driving, at least one additional third switching element, configured as a friction-type switching element, is operated depending on the output rotational speed. The operation of the third switching element does not need to drive the vehicle. Instead, the operation of the third switching element is for targeted braking of the vehicle and thus achieving a constant speed during slow driving. In other words, by targeted engagement of the third switching element, braking of the transmission or vehicle is achieved, thereby ensuring constant slow driving under varying driving resistance conditions. This is particularly necessary when driving slowly in inertial mode (i.e., downhill) to maintain a constant, slow speed with high precision. The operation of the third switching element as a brake is achieved by temporarily closing the friction-type switching element. The third switching element can be operated, in particular, in a slippery manner.

[0010] To this end, the motor speed of the drive motor connected to the input shaft of the automated transmission can be adjusted so that there is always a power surplus within the automated transmission during slow travel. This power surplus enables constant slow travel by a third switching element that acts as a brake. For this purpose, the third switching element is at least temporarily partially closed depending on the output speed.

[0011] Furthermore, the first and / or second switching elements can also be implemented as friction-type switching elements and can operate in a slippery manner during slow travel. This is particularly advantageous when the speed obtained at the desired motor speed and the gear ratio in the starting gear of the corresponding drive system is higher than the desired slow travel speed. Then, by adjusting the slippery first and / or second switching elements, a desired speed lower than the speed obtained from the motor speed and the gear ratio in the drive system can also be achieved. Therefore, as the differential speed at the slippery first or second switching element increases, the output speed can be reduced while keeping the input speed constant.

[0012] A driving speed of up to 10 km / h is considered slow driving. In particular, a driving speed deviating from the target speed by less than 2 km / h, preferably less than 1 km / h, within the observed time period is considered a constant speed. Therefore, constant slow driving is driving at a target speed of up to 10 km / h, where the actual speed deviates from the target speed by no more than 2 km / h, preferably no more than 1 km / h. The speed during slow driving can be lower than the creep speed obtained from the drive motor's idle speed and the transmission ratio in first forward or reverse gear.

[0013] The torque converter lock-up clutch on the hydraulic torque converter should preferably be disengaged during constant slow driving.

[0014] According to the invention, a fourth switching element, configured as a friction-type switching element, is operated alternately or simultaneously with the third switching element at the output rotational speed. Overheating of the third switching element can be avoided in this manner, as the heat generated by the brake is distributed to both the third and fourth switching elements.

[0015] Alternatively, the reducer can be attached as a braking element and used alternately or simultaneously with the third switching element to prevent the third switching element from overheating. To identify overheating of the third switching element, temperature monitoring can be used, where, for example, when the temperature threshold of the switching element is exceeded, the load on the third switching element can be reduced by using a fourth switching element or a reducer.

[0016] The present invention also relates to a drive system for driving a vehicle, the drive system being adapted to perform the method. This drive system includes a graded automatic transmission, wherein the graded automatic transmission includes an input shaft connectable to a drive motor, a torque converter, multiple planetary gear sets, multiple friction-type switching elements for selecting different gear ratio stages, an output shaft, a speed sensor for detecting the output speed of the output shaft, and a control device. The control device is configured to enable it to implement the method. The control device may include at least one processor, at least one data memory, at least one piece of software in the form of a computer program, and at least one interface for communication. The control device may, for example, be configured as a transmission control device or as part of such a transmission control device. The control device is connected to the speed sensor for detecting the output speed in terms of signal transmission. In an alternative embodiment, the control device may also obtain information about the output speed from other control devices of the vehicle via a suitable data connection. Furthermore, the control device is connected to the drive motor or a control device for the drive motor to enable regulation of the drive motor speed so that there is excess power in the graded automatic transmission during slow driving. The control device is also connected to the actuating device for the switching elements within the graded automatic transmission and thus controls or regulates the opening and closing of the switching elements based on the output speed. Furthermore, the control device may also be connected to at least one temperature sensor to monitor the temperature of at least the third switching element, which operates in a slip-operated manner. This prevents damage due to overheating of the third switching element by promptly taking the aforementioned measures to reduce the load on the third switching element.

[0017] The control device or transmission device has a suitable communication interface for the connection, which can be configured not only for wireless communication but also for cable connection.

[0018] In drive systems particularly suitable for applications in rail vehicles, the graded automatic transmission is implemented as a planetary transmission and includes first, second, and third planetary gear sets for adjusting different gear ratios, and a fourth planetary gear set for reversing the direction of travel. Here, the fourth planetary gear set serves as a reversing gear set to provide two equivalent directions of travel for the rail vehicle. This means that all gear ratios adjustable by means of the first, second, and third planetary gear sets within the graded automatic transmission are available in both directions of travel, allowing the rail vehicle to be driven in the same speed range in both directions. Specifically, the four mentioned planetary gear sets can be configured as negative planetary gear sets. A negative planetary gear set is a single planetary gear set having exactly one cage on which planetary gears are rotatably supported, exactly one sun gear, and exactly one ring gear, wherein the teeth of each planetary gear mesh not only with the teeth of the sun gear but also with the teeth of the ring gear, so that when the sun gear rotates while the cage remains stationary, the ring gear and the sun gear rotate in opposite directions of rotation.

[0019] In one embodiment of the drive system, it has proven advantageous in terms of appropriate gear ratios and speed ranges to provide a graded automatic transmission in which the first, second, third, and fourth planetary gear sets are each configured as negative planetary gear sets. In this graded automatic transmission, a first switching element connects the drive shaft to the sun gear of the third planetary gear set, a second switching element connects the ring gear of the third planetary gear set to the housing of the graded automatic transmission, and a third switching element connects the ring gear of the second planetary gear set to the housing. The first, second, and third switching elements are preferably configured as friction-type switching elements. The friction-type switching element connecting the ring gear of the first planetary gear set to the housing can also be configured as the fourth switching element.

[0020] Finally, the present invention also includes a computer program product having a computer program that can be loaded into the storage unit of a vehicle's control device so that, when the computer program is implemented within the control device, all steps of the method are executed. The computer program product achieves the aforementioned inventive technical effects if the relevant computer program is used in a computer or a vehicle's control device. The computer program product proposed herein includes a sequence of instructions that causes the drive system to execute the method, thereby driving the vehicle at a slow speed. Attached Figure Description

[0021] The invention is illustrated in the following embodiments. In the figures: Figure 1 An embodiment of the drive system according to the invention is shown schematically in an adjusted state while driving in the first gear; and Figure 2 The basis for showing the adjustment state of constant slow driving is shown. Figure 1 The drive system. Detailed Implementation

[0022] The drive system 1 for driving the vehicle includes a drive motor 2 and a stepped automatic transmission 3. The stepped automatic transmission 3 has an input shaft 4, which is connected to or can be connected to the drive motor 2. This means that the output shaft of the drive motor 2 is connected to the input shaft 4 in terms of torque transmission. The stepped automatic transmission 3 also has a hydraulic torque converter 5. The impeller of the torque converter 5 is connected to the input shaft 4. The turbine of the torque converter 5 is connected to a drive shaft 6, which is in turn connected to or can be connected to the various elements of planetary gear sets P1, P2, P3, and P4. The first planetary gear set P1, the second planetary gear set P2, and the third planetary gear set P3 are configured to adjust different gear ratio stages, and the fourth planetary gear set P4 is configured to reverse the direction of travel.

[0023] Each of the mentioned planetary gear sets P1, P2, P3, and P4 has three components: a sun gear, a planetary carrier, and a ring gear. Planetary gears are rotatably supported on the planetary carrier, and the teeth of the planetary gears engage with the teeth of their respective sun gears and ring gears. This means that planetary gear sets P1, P2, P3, and P4 are each constructed as negative planetary gear sets.

[0024] Here, the fourth planetary gear set P4, arranged on the output side in the power flow, is configured as a reversing gear set to reverse the direction of rotation. It has stepped planetary gears, each comprising two tooth sections with different numbers of teeth, selected such that the transmission ratios in both directions of rotation are at least almost the same. In this way, the vehicle can operate at the same speed level in both directions of travel.

[0025] To enable the connection between the shaft of the graded automatic transmission device 3 and the components of the planetary gear sets P1, P2, P3, and P4 to close and separate, multiple switching elements A, B, D, E, F, G, and H are provided. Here, switching elements A, B, D, E, and F, which correspond to planetary gear sets P1, P2, and P3, are configured as friction-type switching elements, while switching elements G and H, which correspond to planetary gear set P4, are implemented as form-locking switching elements.

[0026] The torque converter 5, planetary gear sets P1, P2, P3, P4 and switching elements A, B, D, E, F, G and H are arranged in the housing 9 of the graded automatic transmission device 3, which can also be implemented in multiple parts.

[0027] Different transmission ratio stages are adjusted by selectively closing and opening switching elements A, B, D, E, and F, while the direction of travel is selected by switching elements G and H. With the help of switching elements G and H, which are associated with the reversing gear set P4, the output shaft 7 can be torsionally connected either to the ring gear of the fourth planetary gear set P4 or to the planetary carrier of the third planetary gear set P3.

[0028] In other words, different transmission ratio levels can be selected by using the switching element, thereby adjusting the transmission ratio between the drive shaft 6 and the output shaft 7 to match the corresponding driving conditions.

[0029] A speed sensor 11 is arranged in the area of ​​the output shaft 7 to detect the output speed of the output shaft 7. The speed sensor 11 is connected to the control device 10 to transmit signals about the output speed.

[0030] The control device 10, configured to perform the method, is arranged on the graded automatic transmission device 3 in the form of a transmission control device. According to other embodiments, the control device 10 may also be arranged in other locations or include components arranged in other locations.

[0031] In this embodiment, drive shaft 6 is permanently connected to the sun gear of the first planetary gear set P1. Drive shaft 6 can also be connected to the sun gear of the third planetary gear set P3 via the closure of the first switching element A. The ring gear of the first planetary gear set P1 can be connected to the housing 9 of the graded automatic transmission device 3 via the fourth switching element D. The ring gear of the second planetary gear set P2 and the planetary carrier of the first planetary gear set P1 are permanently connected to each other. The ring gear of the second planetary gear set P2 and the planetary carrier of the first planetary gear set P1 can be connected to the housing 9 via the third switching element E. The ring gear of the third planetary gear set P3 is permanently connected to the planetary carrier of the second planetary gear set P2. The ring gear of the third planetary gear set P3 and the planetary carrier of the second planetary gear set P2 are connected to the housing 9 via the second switching element F. Finally, the planetary carrier of the second planetary gear set P2 and the ring gear of the third planetary gear set P3 can be connected to drive shaft 6 via the fifth switching element B.

[0032] Figure 1 In the automatic transmission 3, the first gear, i.e., the starting gear, is selected and is also set for constant slow speed driving. Here, the power guiding element is indicated by a bold line. The first switching element A and the second switching element F are closed in the first gear. The closed switching elements A and F... Figure 1As can be seen from the schematic diagram, no air gap is visible between the diaphragms. Furthermore, the switching element G is closed within the reversing gear set P4, thus achieving direct drive without reversing the direction of rotation. The torque converter lock-up clutch 8 is also closed, thereby disabling the hydraulic portion of the torque converter.

[0033] Figure 2 It shows the relationship with Figure 1 The same drive system is used, with identical components labeled as shown in the accompanying drawings. Only the switching positions of the torque converter lock-up clutch 8 and the third switching element E have changed. To achieve constant slow speed driving, the torque converter lock-up clutch 8 is disengaged, thereby activating the hydraulic torque converter 5. Furthermore, in... Figure 2 The third switching element E is closed to indicate temporary braking. This means that the third switching element E does not remain permanently closed during constant slow travel. Instead, the third switching element E is only temporarily and partially closed. It operates primarily in a slippery manner. The braking duration and intensity required to actuate the third switching element E depend on the output speed, which is detected at the output shaft 7 by means of the speed sensor 11.

[0034] List of reference numerals 1. Drive System 2. Drive motor 3. Automatic transmission device for graded transmission 4 Input Axis 5. Torque Converter 6 drive shafts 7 Output shaft 8. Torque converter lock-up clutch 9. Shell 10. Control device 11. Speed ​​sensor A First Switching Element B Fifth switching element D Fourth switching element E Third switching element F Second switching element G Sixth Switching Element H Seventh Switching Element P1 First Planetary Gear Set P2 Second Planetary Gear Set P3 Third Planetary Gear Set P4 Fourth Planetary Gear Set

Claims

1. A method for regulating a vehicle to travel at a constant slow speed, the vehicle having a drive system (1), the drive system having a graded automatic transmission device (3), the graded automatic transmission device having a hydraulic torque converter (5) and a plurality of switching elements (A, B, D, E, F) for adjusting different transmission ratio levels. in, The first transmission ratio stage is adjusted within the graded automatic transmission device (3) by at least partially closing at least one first and second switching elements (A, F), and at least one additional third switching element (E) configured as a friction switching element is operated depending on the output speed, wherein the third switching element acts as a brake, characterized in that a fourth switching element (D) configured as a friction switching element is operated alternately or simultaneously with the third switching element (E) depending on the output speed, wherein overheating of the third switching element is identified using temperature monitoring, and wherein when the temperature threshold of the third switching element is exceeded, the load of the third switching element is reduced by using the fourth switching element.

2. The method according to claim 1, characterized in that, Adjust the motor speed of the drive motor (2) connected to the input shaft (4) of the graded automatic transmission device (3) so that there is power excess in the graded automatic transmission device (3) during slow driving.

3. The method according to claim 1, characterized in that, The output speed is detected at the output shaft (7) of the graded automatic transmission device (3).

4. The method according to claim 3, characterized in that, The torque converter lock-up clutch (8) on the hydraulic torque converter (5) is disengaged during constant slow driving.

5. The method according to claim 1, characterized in that, The speed reducer is attached and used as a braking element.

6. A drive system (1) for driving a vehicle, the drive system comprising a drive motor (2) and a graded automatic transmission (3), wherein, The graded automatic transmission device (3) includes an input shaft (4) connected to the drive motor (2), a hydraulic torque converter (5), multiple planetary gear sets (P1, P2, P3, P4), multiple switching elements (A, B, D, E, F, G, H) for selecting different transmission ratio levels, an output shaft (7), a speed sensor (11) for detecting the output speed of the output shaft (7), and a control device (10), characterized in that the control device (10) is configured to perform the method according to any one of claims 1 to 5.

7. The drive system according to claim 6, characterized in that, The graded automatic transmission device includes a first planetary gear set (P1), a second planetary gear set (P2), and a third planetary gear set (P3) for adjusting different transmission ratio levels, and a fourth planetary gear set (P4) for reversing the driving direction.

8. The drive system according to claim 6 or 7, characterized in that, The first, second, third and fourth planetary gear sets (P1, P2, P3, P4) are respectively constructed as negative planetary gear sets with a sun gear, a planetary gear carrier and a ring gear. The first switching element connects the drive shaft (6) to the sun gear of the third planetary gear set, the second switching element connects the ring gear of the third planetary gear set to the housing (9) of the graded automatic transmission device (3), and the third switching element connects the ring gear of the second planetary gear set to the housing (9).

9. A computer program product having a computer program that can be loaded into a storage unit of a vehicle control device so that, when the computer program is implemented in the control device, all steps of the method according to any one of claims 1 to 5 are performed.

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