Method for actuating a travel drive

Abstract

The invention relates to a method for actuating a travel drive of a mobile working machine, said travel drive comprising an electric drive machine and a transmission arrangement with a shift transmission which has at least two transmission gears and is coupled to the drive machine via an input shaft in such a way that a torque can be transmitted, the shifting transmission mechanism is connected with an output device of the mobile working machine through an output shaft, and the method is characterized by comprising the following steps; a, a command for switching the gear shifting transmission mechanism from the first transmission mechanism gear to the second transmission mechanism gear is obtained; b. Detecting a variable as the current travel speed of the mobile working machine or dependent on the travel speed; c, calculating the gradient of the parameters detected in the step b; d, calculating a rotating speed deviation based on the gradient calculated in the step c; e, the target rotating speed of the electric driver is obtained based on the rotating speed deviation calculated in the step b; and f, under the condition that the target rotating speed obtained in the step e is considered, switching of the gear shifting transmission mechanism from the first transmission mechanism gear to the second transmission mechanism gear is executed.

Description

Field of the Invention

[0001] The present invention relates to a method for controlling a drive of a work machine. Furthermore, the present invention relates to a control unit, a work machine including the control unit, and a computer program. Background Art

[0002] In the development of shift transmissions, especially those operating without a friction clutch and especially those using active synchronization in an electric drive, speed synchronization plays an important role. The shifting process requires precise coordination of speeds to ensure a frictionless transition between gears.

[0003] The process flow of this process includes different important steps.

[0004] First, the speed at the output of the transmission is continuously measured, which serves as the basis for the entire synchronization process. This measurement is crucial to obtain real-time data on the instantaneous speed at the output of the transmission.

[0005] Subsequently, the measured speed at the output of the transmission is precisely converted into the target speed of the transmission drive in the desired gear. This conversion is very important because it determines the speed required for a frictionless transition to the gear to be achieved.

[0006] Subsequently, this calculated target speed is transmitted to the drive motor. The motor thus receives a corresponding command to adjust the speed in order to achieve the required speed for the desired gear.

[0007] The gear is engaged only when the measured speed difference between the drive and the output of the transmission reaches a pre-given target range. This ensures that the gear is engaged only when the speeds are correspondingly synchronized in order to ensure a frictionless shift.

[0008] This precise and strictly regulated process enables efficient power transmission and helps to minimize wear and damage at the transmission. Using such a synchronization mechanism not only ensures comfortable driving comfort, but also contributes to the durability and optimal functionality of the transmission.

[0009] There is usually a time offset between the measured output speed and the set drive speed, which can be problematic in the context of a shift transmission. This problem occurs due to driving resistances that accelerate or brake the vehicle and thus change the output speed.

[0010] During this time window, speed changes cause the speeds to deviate from each other. This again makes the speed difference greater or less than the speed difference required for a frictionless gear shift. This difference poses a challenge during engagement.

[0011] However, it is feasible to at least partially mitigate this problem. The feasible solution lies in compensating for the acceleration or braking that depends on the driving resistance. This compensation mechanism aims to predict and compensate for the changes in the output speed that occur due to the driving resistance.

[0012] However, currently, it is not possible to completely prevent the said problem through the prediction of such compensation because different operating states are very difficult to predict.

[0013] Therefore, the object of the present invention is to improve a method that can achieve the elimination of this difference during connection and always ensure that the switching can be implemented without problems during speed synchronization. Summary of the Invention

[0014] According to an embodiment of the present invention, a method for controlling a travel drive (1) of a mobile working machine is proposed, wherein the travel drive includes an electric drive motor (4) and a transmission assembly (3), wherein the transmission assembly (3) includes a shift transmission (6) that has at least two transmission gear positions (46, 48), wherein the shift transmission is coupled or can be coupled to the drive motor (4) via an input shaft (18) so as to be able to transmit torque, and wherein the shift transmission is connected or can be connected to an output device of the mobile working machine via an output shaft (22), characterized in that the method includes the following steps:

[0015] a. Obtain a command to switch the shift transmission from a first transmission gear position to a second transmission gear position (this command can be generated automatically or by the driver) (it is not important for the present invention whether the first transmission gear position or the second transmission gear position results in a higher or lower transmission ratio);

[0016] b. Detect a parameter that is the current travel speed of the mobile working machine or depends on the travel speed (such as the rotational speed of the output shaft, the rotational speed of the wheels, etc.);

[0017] c. Calculate the gradient of the parameter detected in step b;

[0018] d. Calculate a speed deviation based on the gradient calculated in step c;

[0019] e. Obtain the target speed of the electric drive motor (4) based on the speed deviation calculated in step b;

[0020] f. Taking into account the target rotational speed obtained in step e., shift the shift transmission mechanism from the first transmission gear to the second transmission gear (the rotational speed of the electric drive motor actually does not have to reach the target rotational speed because it can be determined that a specific difference between the target rotational speed and the actual rotational speed is acceptable, and in such a case the electric drive motor can even not be controlled, or can be controlled until the difference between the target rotational speed and the actual rotational speed is less than a pre-given threshold).

[0021] Through this compensation, the rotational speed change dependent on the driving resistance caused by the driving resistance is automatically compensated, so that the rotational speed can be led back into an acceptable target range again. Since the rotational speed of the drive and the rotational speed of the transmission output device are synchronized, a more frictionless connection can thus be achieved. Steps a. to f. do not have to be carried out one after another. In particular, step a. can be carried out after one of steps b. to e.

[0022] This compensation mechanism is crucial in order to overcome the challenges arising from the time delay between the rotational speed measurement and the adaptation of the drive rotational speed. This compensation mechanism thus helps to improve the shifting accuracy and efficiency in the shift transmission mechanism, especially in the case of an electric drive without a friction clutch. Description of the Drawings

[0023] The present invention is described with reference to the accompanying drawings, in which the same reference numerals refer to the same and / or similar and / or corresponding components of the system. Regarding the drawings:

[0024] Figure 1 A circuit diagram of a traveling drive according to the prior art is shown,

[0025] Figure 2 A method for controlling a traveling drive of a mobile working machine according to an embodiment of the present invention is shown. Detailed Embodiment

[0026] The present invention is described below with reference to specific embodiments as shown in the drawings. Nevertheless, the present invention is not limited to the specific embodiments described in the following detailed description and shown in the drawings, but the described embodiments only show some aspects of the present invention, and the protection scope of the present invention is defined by the claims.

[0027] Further variations and modifications of the present invention will be clear to those skilled in the art. Therefore, this specification includes all variations and / or modifications of the present invention, and the protection scope of the present invention is defined by the claims.

[0028] According to Figure 1, a travel drive 1, for example a travel drive of a mobile working machine, has a transmission assembly 3 which has a drive machine 2 configured as an electric motor and a two-stage shift transmission 6 in the embodiment. The drive shaft 18 of the drive machine is coupled to the input shaft 20 of the shift transmission 6. The output shaft 22 of the shift transmission 6 is coupled to the differential 24 of the double-wheel shaft 26 of the travel drive 1.

[0029] Furthermore, the transmission assembly 3 has a control device 28. A shift request device 30, a gear selection device 32, a travel direction selection device 34, an accelerator pedal 36, a creep gear selection device 38, a brake pedal 40 and an automatic selection device 42 are signal-connected to the control device 28. All the mentioned devices 30 to 42 are signal-connected via a CAN bus.

[0030] The shift transmission 6 has a first transmission gear 46 and a second transmission gear 48. The first transmission gear has a small transmission ratio, and the second transmission gear has a larger transmission ratio of the rotational speed nA of the output shaft 22 relative to the rotational speed nE of the input shaft 18.

[0031] Furthermore, the shift transmission 6 has a claw coupling 50 which is designed without a synchronizing ring. The actuator 52 of the claw coupling 50 is rigidly coupled to the piston 54 of the adjusting cylinder 56. The adjusting cylinder has two identical pressure medium chambers 58, 60 separated by the piston 54, and these two pressure medium chambers are connected to an electromagnetically actuable three-position four-way (4 / 3-) switching valve 66 via control lines 62, 64.

[0032] The switching valve has a first switching position 66a in which the first pressure chamber 58 is connected to the pressure medium line 68 and the second pressure chamber 60 is connected to the reservoir line 70. In the second switching position 66b, the second pressure medium chamber 60 is connected to the pressure medium line 68 and the first pressure medium chamber 58 is connected to the reservoir line 70. The first switching position 66a causes the piston 54 to be displaced in such a way that the first transmission gear 46 is engaged via the claw coupling 50, and the second switching position 66b causes the second transmission gear 48 to be engaged via the piston 54 and the claw coupling 50.

[0033] The three-position four-way switching valve 66 and the adjusting cylinder 56 are combined into a unit. This unit furthermore has two end position switches 72, 74, and based on the position of the piston 54, the successful switching of the corresponding transmission gears 46, 48 can be identified via these end position switches. The two end position switches 72, 74 are respectively connected to the control device 28 via signal lines. The three-position four-way switching valve 66 is connected to a pressure source 88 (such as a feed pump for example) via the pressure medium line 68.

[0034] The transmission assembly 3 is designed such that the shift transmission 6 can be switched during driving operation. The switching or changing of the transmission gears 46, 48 can be automatically controlled by the control device 28. For this purpose, the transmission assembly 3 has a rotational speed sensor 76 that can detect the rotational speed nA of the output shaft 22. In addition, the transmission assembly has a rotational speed sensor 78 for detecting the rotational speed nE of the input shaft 18.

[0035] The first transmission gear 46 has a gear 80 that is firmly coupled to the input shaft 20 and is in permanent mesh with an idle gear 82 that can be coupled to the output shaft 22 by a claw coupling 50. Correspondingly, the second transmission gear 48 has a gear 84 that is firmly coupled to the input shaft 20 and an idle gear 86 that is in permanent mesh with this gear and can be coupled to the output shaft 22 by a claw coupling 50.

[0036] As can be seen in Figure 1 , the control unit 28 can additionally include a plurality of input or output terminals that can be respectively connected to additional sensors or actuators.

[0037] It should be noted that Figure 1 is only one embodiment, and the present invention (as is clear from the description) can also be applied to other types of shift transmissions. In particular, an actuator can be used that operates electrically and is used to manipulate the shift fork by the movement of a screw or nut. In this case, the movement of the shift fork is achieved by a screw or nut driven by an electric actuator.

[0038] Now refer to Figure 1 and Figure 2 to describe a method for controlling the Figure 1 shown travel drive of a mobile working machine.

[0039] In a first step, a command to switch the shift transmission from the first transmission gear to the second transmission gear is obtained (in this case, the first transmission gear can be denoted by reference numeral 46 and the second transmission gear by reference numeral 48). The method of course also operates properly for the case where the first transmission gear is 48 and the second transmission gear is 46.

[0040] It should be noted that the command can be created automatically, for example, by the control unit required for the independent (atomistische) switching between the first transmission gear and the second transmission gear, or manually, for example, by the driver.

[0041] In a second step 100, the current travel speed of the mobile working machine or a parameter dependent on the travel speed is detected. This parameter can for example be the rotational speed nA of the output shaft 22 or of the wheels of the double-wheeled shaft 26. Preferably, after the detection (or measurement), the parameter is smoothed by a filter 101 in order to enable a clearer gradient formation.

[0042] In a further step 102, the gradient of the detected parameter (output rotational speed) is calculated. In particular, a first-order difference quotient is calculated.

[0043] In parallel, an estimated dead time between the measurement and the setting is acquired 103. This acquisition can be carried out online or offline. This dead time (also known as "delay") describes how much time the travel drive needs until it actually switches the transmission gear. The reason for this is that there are specific components that come into play during the switch. For example, it first takes a specific time until the electromagnetic three-way four-way switching valve 66 receives a control signal. In particular, since the electric drive motor 4 is controlled according to an embodiment of the invention, it takes a specific time window until the actual control takes place, because different components come into play here: the inverter, the electric motor, the control unit.

[0044] As an example, a first time window can be taken into account for the control unit 28 (or the transmission controller). This first time window can for example be 10 ms. A second time window can be taken into account for the inverter-control message. This second time window can also for example be 10 ms. A third time window can be taken into account for the inverter communication module. This third time window can also for example be 10 ms. In addition, the reaction time of the electric drive unit 4 (for example 3 ms) can also be taken into account.

[0045] In step 105, the information from steps 102 and 103 is then combined. In particular, the rotational speed deviation is calculated by multiplying the gradient calculated in step 102 by the estimated dead time in step 103.

[0046] In parallel, in step 104, the current rotational speed of the output shaft 22 and the change in the transmission ratio due to the second transmission gear are taken into account in order to calculate the unadapted target rotational speed for the electric drive motor. Specifically, step 104 corresponds to a method according to the prior art.

[0047] Now in step 106 the unadapted target rotational speed is combined with the rotational speed deviation, so that the actual target rotational speed of the electric drive motor 4 is obtained based on the rotational speed deviation calculated in step 105 and the unadapted target rotational speed calculated in step 104. In particular, the actual target rotational speed is obtained according to the sum of the unadapted target rotational speed and the rotational speed deviation.

[0048] Finally, a shift transmission mechanism is switched from a first transmission gear to a second transmission gear while taking into account the target rotational speed obtained in step 106.

[0049] For the present invention, it is not important when all the calculations are carried out to obtain the target rotational speed. For example, the calculations can be carried out permanently so that the target rotational speed has been obtained when a switch is to be made. Alternatively, it is also particularly advantageous to carry out the acquisition of the target rotational speed during the switching process, for example during the disengagement (Auslegen), so as not to have to wait for the calculations for the switch.

[0050] According to an embodiment of the present invention, when performing the mentioned execution of the switch, the electric drive motor 4 is controlled based on the target rotational speed obtained in step 106. This means that the electric drive motor 4 is first controlled and the switch is actually made preferably after the electric drive motor 4 has reached the target rotational speed (or when the difference between the target rotational speed and the actual rotational speed is less than a predefined threshold).

[0051] According to a further embodiment of the present invention, it is first observed whether the target rotational speed obtained in step 106 differs greatly from the current rotational speed. If the difference is less than a predefined value, the switch is made without the need to actively control the electric drive motor 4.

[0052] The described method is stored in a memory unit and implemented by a control unit 28.

[0053] The described method can be used in different types of work machines. The method can basically be used in all work machines with an electric drive. Application examples can be, for example, excavators, telescopic forklifts, forage harvesters, combine harvesters, snow plows, road milling machines.

[0054] The present invention has been described with reference to the above-described embodiments, and it will be clear to those skilled in the art that different modifications, variations, and improvements of the present invention can be achieved according to the teachings described above and within the scope of the appended claims without departing from the scope of protection of the present invention.

[0055] Furthermore, the fields that those skilled in the art need to be proficient in are not described here so as not to unnecessarily obscure the present invention described.

[0056] Correspondingly, the present invention should not be limited by specific illustrative embodiments, but only by the scope of protection of the appended claims.

Claims

1. A method for controlling a travel drive (1) of a mobile work machine, wherein, The travel drive includes an electric drive motor (4) and a transmission assembly (3), wherein the transmission assembly (3) includes a shift transmission (6) which has at least two transmission gears (46, 48), wherein the shift transmission is coupled or can be coupled to the drive motor (4) via an input shaft (18) so as to be able to transmit torque, and wherein the shift transmission is connected or can be connected to an output device of the mobile working machine via an output shaft (22), characterized in that the method comprises the following steps: a. Obtaining a command to switch the shift transmission from a first transmission gear to a second transmission gear; b. Detecting the current travel speed of the mobile working machine or a parameter dependent on the travel speed; c. Calculating a gradient of the parameter detected in step b.; d. Calculating a rotational speed deviation based on the gradient calculated in step c.; e. Obtaining a target rotational speed of the electric drive motor (4) based on the rotational speed deviation calculated in step b.; f. Performing a switch of the shift transmission from the first transmission gear to the second transmission gear taking into account the target rotational speed obtained in step e.

2. The method according to claim 1, wherein, Between steps e. and f., the electric drive motor is controlled based on the target rotational speed obtained in step e.

3. The method according to claim 2, wherein, After the electric drive motor (4) has reached the target rotational speed, the switch is made in step f.

4. The method according to any one of claims 1 to 3, wherein In step d., the rotational speed deviation is additionally calculated based on the estimated dead time.

5. The method according to claim 4, wherein, The estimated dead time is at least one of a time delay caused by a transmission controller, a time delay caused by an inverter, and / or a response time of the electric drive motor.

6. The method according to any one of claims 4 or 5, wherein The rotational speed deviation is calculated by multiplying the gradient calculated in step c. by the estimated dead time.

7. The method according to any one of claims 1 to 6, wherein, In step e., for obtaining the target rotational speed of the electric drive motor (4), the current rotational speed of the output shaft (22) and a change in the transmission ratio due to the second transmission gear are additionally taken into account.

8. The method according to any one of claims 1 to 7, wherein At least one of steps b. to e. is carried out before step a.

9. A control unit (68) which is configured to carry out the method according to any one of claims 1 to 8.

10. A working machine, which includes the traveling drive (1), wherein, The travel drive includes an electric drive motor (4) and a transmission assembly (3), wherein the transmission assembly (3) includes a shift transmission (6) which has at least two transmission gears (46, 48), wherein the shift transmission is coupled or can be coupled to the drive motor (4) via an input shaft (18) so as to be able to transmit torque, and wherein the shift transmission is connected or can be connected to an output device of the mobile working machine via an output shaft (22), wherein the output shaft (22) is connected or can be connected to at least one wheel to be driven or a chain or shaft to be driven, and wherein the working machine includes the control unit according to claim 9.

11. A computer program configured to implement and / or control the method according to any one of claims 1 to 9.

12. A machine-readable storage medium having stored thereon the computer program according to claim 11.

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