Hydrostatic drive for a utility vehicle and method for operating a hydrostatic drive of a utility vehicle

Abstract

The present disclosure relates to a hydrostatic drive (200) for a utility vehicle (10), comprising at least one hydraulic motor (230) which is configured to drive at least one axle (A) of the utility vehicle (10); at least one hydraulic pump (210) which is connected to the at least one hydraulic motor (230) via a fluid circuit (202), in order to drive the at least one hydraulic motor (230); at least one auxiliary pump (220) which is connected to the fluid circuit (202), in order to feed fluid to the fluid circuit (202); and at least one electric drive (240) which is configured to drive the at least one auxiliary pump (220).

Description

Hydrostatic drive for a commercial vehicle and method for operating a hydrostatic drive of a commercial vehicle

[0001] The present disclosure relates to a hydrostatic drive for a commercial vehicle, a commercial vehicle with such a hydrostatic drive, and a method for operating a hydrostatic drive of a commercial vehicle. The present disclosure relates in particular to an electrified auxiliary pump of a hydrostatic drive for commercial vehicles, especially heavy commercial vehicles. State of the art

[0002] Commercial vehicles can optionally use a hydrostatic drive for temporary traction support, which, when needed, drives an axle hydrostatically in addition to a main drive, such as an internal combustion engine. The hydrostatic drive can be designed as a closed hydraulic circuit, in which fluid flows from a hydraulic pump to at least one hydraulic motor and back to the hydraulic pump.

[0003] During operation of the hydrostatic drive, friction losses cause the fluid to heat up. To protect the system from overheating, a portion of the fluid is continuously diverted from a low-pressure side of the closed hydraulic circuit when the auxiliary drive is active. Furthermore, the fluid volume of the closed hydraulic circuit can decrease due to internal leakage, for example, into the hydraulic pump and motor. To compensate for this fluid loss, an auxiliary pump connected to a low-pressure branch of the closed hydraulic circuit can supply fresh fluid to the circuit.

[0004] The energy balance of the auxiliary pump is rarely considered nowadays, meaning this potential remains largely untapped in the overall efficiency of the hydrostatic drive. Furthermore, auxiliary pumps in hydrostatic drives require considerable installation space. For example, the auxiliary pump can be connected to the internal combustion engine or integrated into the high-pressure pump, requiring a specific volume in close proximity to the drive components – this space is often limited due to its position within the vehicle. Moreover, since the available installation space in commercial vehicles is becoming increasingly scarce, for example, due to the use of batteries in electric vehicles, flexible integration of hydrostatic drives is advantageous.

[0005] Disclosure of the invention

[0006] It is an object of the present disclosure to specify a hydrostatic drive for a commercial vehicle, a commercial vehicle with such a hydrostatic drive, and a method for operating a hydrostatic drive of a commercial vehicle, which can improve the efficiency of the hydrostatic drive and reduce the energy consumption of the commercial vehicle. Furthermore, it is an object of the present disclosure to enable the flexible integration of hydrostatic drives in commercial vehicles.

[0007] This problem is solved by the subject matter of the independent claims. Advantageous embodiments are specified in the dependent claims.

[0008] According to an independent aspect of the present disclosure, a hydrostatic drive for a commercial vehicle, in particular a heavy commercial vehicle and / or a truck, is specified. The hydrostatic drive comprises at least one hydraulic motor which is equipped to drive at least one (hydraulic) axle of the commercial vehicle; at least one hydraulic pump (main pump) connected to the at least one hydraulic motor via a fluid circuit to drive the at least one hydraulic motor; at least one auxiliary pump connected to the fluid circuit to supply fluid to the fluid circuit; and at least one electric drive equipped to drive the at least one auxiliary pump.

[0009] According to the invention, at least one electric drive is provided for operating the at least one auxiliary pump, enabling demand-based operation of the at least one auxiliary pump both during hydrostatic ferry operation and when the hydrostatic ferry operation is switched off. This reduces energy losses from the operation of the at least one auxiliary pump and improves the efficiency of the hydrostatic drive. As a result, the overall energy input for operating the commercial vehicle is reduced, thus conserving energy resources.

[0010] Furthermore, the service life of the hydrostatic drive increases due to its improved efficiency; in particular, because of reduced heat loss, a critical shutdown temperature for the hydrostatic drive is not reached, or at least not reached, more quickly. The inclusion of at least one electric drive also simplifies the overall system, for example by eliminating valves, thus reducing the installation space required for the hydrostatic drive and enabling flexible integration into the commercial vehicle.

[0011] Additionally, the at least one electric drive of the at least one auxiliary pump allows conclusions to be drawn about the operating status of the hydrostatic drive. For example, by recording and evaluating the power consumption of the at least one electric drive, critical situations and / or signs of wear (e.g., cable breakage, filter clogging, etc.) can be detected and used for planning maintenance tasks.

[0012] In some embodiments, which can be combined with other embodiments described here, the fluid is an oil, in particular a hydraulic oil.

[0013] In some embodiments, which can be combined with other embodiments described here, the at least one electric drive is at least one electric motor.

[0014] In some embodiments, which can be combined with other embodiments described herein, the at least one electric drive is configured for operation at 24 volts or 48 volts. For example, the at least one electric drive can be integrated into a 24 V or 48 V electrical system of the commercial vehicle. Alternatively, integration into an AC electrical system of the commercial vehicle is also possible, for example in purely electric commercial vehicles.

[0015] In some embodiments, which can be combined with other embodiments described herein, the at least one electric drive is configured to drive the at least one auxiliary pump independently of the at least one hydraulic pump and / or a main drive of the commercial vehicle (e.g., internal combustion engine) and / or a hydrostatic ferry operation. In other words, the at least one auxiliary pump can be operated as needed, independently of the further operation of the commercial vehicle.

[0016] In some embodiments, the at least one electric drive can be configured to operate the at least one auxiliary pump independently of the at least one hydraulic drive. to drive the pump and / or the mechanical force generated by the main drive of the commercial vehicle and / or in hydrostatic ferry operation. In particular, there can be no mechanical interface between the at least one auxiliary pump and the at least one hydraulic pump and / or the main drive. In other words, the mechanical interface can be omitted. This allows the at least one auxiliary pump to be operated as required, independently of an axis and / or the rotational speed of the at least one hydraulic pump or the main drive. In other words, the delivery rate of the at least one auxiliary pump is independent of an axis and / or the rotational speed of the at least one hydraulic pump or the main drive.

[0017] In some embodiments, which can be combined with other embodiments described herein, the at least one auxiliary pump has a substantially constant displacement volume. Displacement volume or flow rate of the at least one auxiliary pump refers to the quantity of fluid that the at least one auxiliary pump delivers or consumes per revolution. Due to the constant displacement volume, the at least one auxiliary pump can be simply configured and cost-effective.

[0018] In some embodiments, which can be combined with other embodiments described herein, the hydrostatic drive further comprises at least one control module configured to control the at least one electric drive. In some embodiments, the at least one control module can be configured to control the at least one electric drive by adjusting the current supplied to the at least one electric drive. The higher the current, the higher the rotational speed and thus the delivery rate of the at least one auxiliary pump can be.

[0019] In some embodiments, which can be combined with other embodiments described herein, the at least one control module is configured to variably adjust the delivery rate of the at least one auxiliary pump by actuating the at least one electric drive. The at least one electric drive thus enables demand-based adjustment of the delivery rate. When the hydrostatic drive is deactivated, there is no oil requirement, meaning the at least one auxiliary pump can be switched off or remain stationary. When the hydrostatic drive is activated, the at least one electric drive can adjust itself precisely to the required delivery rate or flow rate, independent of the main drive or the main pump speed. This eliminates the need for additional fluid handling components, such as lossy flow control valves.

[0020] In some embodiments, which can be combined with other embodiments described herein, the at least one control module is configured to determine a torque of the at least one auxiliary pump and / or a fluid pressure of the at least one auxiliary pump and / or an auxiliary circuit based on the current consumption of the at least one electric drive. This allows conclusions to be drawn about the operating parameters of the hydrostatic drive.

[0021] In some embodiments, which can be combined with other embodiments described herein, the at least one control module is configured to adjust the fluid pressure of the at least one auxiliary pump and / or the auxiliary circuit, for example by adjusting the current supplied to the at least one electrical actuator. Instead of a single fixed pressure value, which is regulated by a pressure relief valve, Low pressure is defined in the closed hydraulic circuit; at least one electric drive enables adjustment of the pressure level by means of pressure control.

[0022] In some embodiments, the pressure in the closed hydraulic circuit can be adjusted by varying the current, depending on the situation. This allows the drive torque of the hydrostatic drive to be optimized by changing the pressure differential across the at least one hydraulic motor. Furthermore, losses can be minimized, as the at least one auxiliary pump only generates as much pressure as required.

[0023] In some embodiments, which can be combined with other embodiments described herein, the at least one control module is configured to control the at least one electric drive based on the ambient temperature of the commercial vehicle. The ambient temperature can be the vehicle's outside temperature. If the ambient temperature falls below a defined threshold, the at least one auxiliary pump can, for example, be operated in a warm-up mode.

[0024] In some embodiments, which can be combined with other embodiments described herein, the at least one control module is configured to perform preconditioning of the hydrostatic drive by operating the at least one auxiliary pump before the start of hydrostatic ferry operation. For example, the at least one control module can be configured to perform preconditioning when the ambient temperature is equal to or less than a threshold temperature. The threshold temperature can be, for example, 10°C or less, 5°C or less, or 0°C or less.

[0025] Preferably, the preconditioning of the hydrostatic drive is a thermal preconditioning of the hydrostatic drive, such as a thermal preconditioning of the fluid and / or the at least one hydraulic motor and / or the at least one main pump and / or the at least one auxiliary pump.

[0026] Preferably, the at least one auxiliary pump is operated in a warm-up mode during preconditioning. In warm-up mode, the at least one auxiliary pump can circulate fluid up to a defined capacity, for example, from a fluid reservoir to one or more main components (e.g., valve block, hydraulic pump, and / or wheel motor(s)) and back to the fluid reservoir. The flow rate and the resulting pressure level (as a result of the flow rate and flow resistance) determine the heat input into the system. Once a certain temperature is reached after a certain period, the at least one auxiliary pump switches off again.

[0027] In some embodiments, which can be combined with other embodiments described herein, the at least one control module is configured to perform post-conditioning of the hydrostatic drive after the end of hydrostatic ferry operation by operating the at least one auxiliary pump. For example, the at least one control module can be configured to perform post-conditioning in order to lower a system temperature.

[0028] This allows the conditioning to be extended to a period of time after the traction support has been engaged. For example, if the auxiliary drive has been operated up to a certain shutdown temperature, the auxiliary pump can continue to run afterward at a low flow rate. From an energy perspective, this does introduce energy, but this amount is significantly less than the amount of heat in the system at the time of the temperature shutdown. Through the The volume flow through the main components, and especially a cooler (the cooler's fan is running), can thus quickly lower the system temperature below a threshold of, for example, 50°C or 60°C.

[0029] In some embodiments, the same procedure can be used to safeguard the drive system at very cold ambient temperatures, i.e., the hydrostatic drive is only allowed to be engaged after a certain minimum temperature has been exceeded.

[0030] In some embodiments, which can be combined with other embodiments described herein, the hydrostatic drive further comprises at least one monitoring module configured to determine at least one state of the hydrostatic drive based on at least one operating parameter of the at least one auxiliary pump and / or the at least one electric drive. By continuously evaluating the operating parameters of the at least one auxiliary pump and / or the at least one electric drive, optionally in combination with at least one other external parameter, such as ambient temperature and / or parameters or operating parameters of other components of the hydrostatic drive, state monitoring of the hydrostatic drive is thus possible.

[0031] Preferably, the at least one state of the hydrostatic drive comprises an operating state of the hydrostatic drive. If, for example, implausible conditions occur, such as insufficient auxiliary pump drive torque for a given flow rate, for example due to a line break in the closed hydraulic circuit or auxiliary circuit, the system can output an error and optionally transition to a safe state.

[0032] Additionally or alternatively, at least one state of the hydrostatic drive can include a fluid filter state of the hydrostatic drive. Generally, the flow resistance of filter elements increases with increasing filter loading. Based on at least one operating parameter of the at least one auxiliary pump and / or the at least one electric drive, a change in the flow resistance can be detected. If the flow resistance exceeds a certain threshold, the system can output corresponding information, for example, to a driver and / or maintenance personnel and / or an electronic device (e.g., a server).

[0033] In some embodiments, which can be combined with other embodiments described here, the fluid filter is arranged in an (e.g. open) auxiliary circuit of the at least one auxiliary pump.

[0034] In some embodiments, which can be combined with other embodiments described herein, an algorithm is implemented in at least one monitoring module. This algorithm is designed to analyze at least one operating parameter of the at least one auxiliary pump and / or the at least one electric drive. For example, the algorithm can compensate for the influence of temperature on the flow resistance of the fluid filter. Additionally or alternatively, the algorithm can compare the current consumption of the at least one auxiliary pump with historical values ​​recorded under the same or similar environmental conditions (e.g., fluid temperature in the fluid reservoir). The algorithm can learn and develop itself and independently detect critical operating conditions when a defined degree of deviation is exceeded.

[0035] In some embodiments, which can be combined with other embodiments described here, the hydrostatic drive further comprises a fluid container or reservoir, such as an oil tank or reservoir. The at least one auxiliary pump can be arranged in or on the fluid container or reservoir. This allows for a flexible arrangement of the hydrostatic drive components, thus reducing the installation space required for the hydrostatic drive.

[0036] According to another independent aspect of the present disclosure, a commercial vehicle, in particular a heavy commercial vehicle and / or truck, is specified. The commercial vehicle includes the hydrostatic drive according to the embodiments of the present disclosure.

[0037] The term commercial vehicle includes heavy commercial vehicles, trucks, buses, etc., used for the transport of people, goods, etc. In particular, the term includes commercial vehicles for the transport of goods and / or passengers with a maximum permissible speed of 60 km / h or greater.

[0038] In some embodiments, which can be combined with other embodiments described herein, the commercial vehicle is a hybrid or electric vehicle. Depending on the embodiment, the hybrid or electric vehicle can be a battery electric vehicle (BEV) or a plug-in hybrid electric vehicle (PHEV). Vehicles with electric drive (especially hybrid or electric vehicles) include electrical energy storage devices (e.g., batteries) that can be connected to a charging station and recharged via a charging device on the vehicle.

[0039] According to a further independent aspect of the present disclosure, a method for operating a hydrostatic drive of a commercial vehicle, in particular a heavy commercial vehicle and / or truck, is disclosed. The method comprises driving at least one electric drive of at least one auxiliary pump to operate the at least one auxiliary pump; and supplying a fluid to a fluid circuit by operating the at least one auxiliary pump, wherein the fluid circuit connects at least one hydraulic motor configured to drive at least one axle of the commercial vehicle and at least one hydraulic pump configured to drive the at least one hydraulic motor.

[0040] According to another independent aspect of the present disclosure, a software (SW) program is specified. The SW program can be configured to run on one or more processors and thereby execute the method described in this document for operating a hydrostatic drive of a commercial vehicle.

[0041] According to another independent aspect of the present disclosure, a storage medium is specified. The storage medium may comprise a software program configured to run on one or more processors and thereby execute the method described in this document for operating a hydrostatic drive of a commercial vehicle.

[0042] According to another independent aspect of the present disclosure, software with program code for carrying out the method for operating a hydrostatic drive of a commercial vehicle is to be executed if the software runs on one or more software-controlled devices.

[0043] According to another independent aspect of the present disclosure, a system for operating a hydrostatic drive of a commercial vehicle is specified. The system comprises one or more processors; and at least one memory connected to the one or more processors and containing instructions that can be executed by the one or more processors to carry out the method described in this document for operating a hydrostatic drive of a commercial vehicle.

[0044] A processor or processor module is a programmable computing unit, i.e., a machine or an electronic circuit that controls other elements according to given instructions and thereby advances an algorithm (process). Brief description of the drawings

[0045] Examples of the manifestation of the revelation are shown in the figures and are described in more detail below. They show: Figure 1 shows a known hydrostatic drive for a commercial vehicle, Figure 2 shows a hydrostatic drive for a commercial vehicle according to embodiments of the present disclosure, Figure 3 shows the heating of a hydrostatic drive by a flow through control and leakage lines. Figure 4 shows an evaluation of a fluid filter loading according to embodiments of the present disclosure, and Figure 5 shows a flowchart of a method for operating a hydrostatic drive of a commercial vehicle according to embodiments of the present disclosure. Implementations of the revelation

[0046] Unless otherwise noted, the same reference symbols are used for identical and equivalent elements in the following.

[0047] Figure 1 shows a known hydrostatic drive 100 for a commercial vehicle 10, in which an auxiliary pump 120 is arranged on a shaft 112 of a hydraulic pump (main pump) 110. Fluid power symbols according to DIN ISO 1219 are used in Figure 1.

[0048] The commercial vehicle 10 can use the hydrostatic drive 100 for temporary traction support, which, if required, hydrostatically drives an axle A in addition to a main drive 20, such as an internal combustion engine. The hydrostatic drive 100 can be designed as a closed hydraulic circuit 102, in which fluid flows from the hydraulic pump 110 to at least one hydraulic motor 130 and back to the hydraulic pump 110.

[0049] During operation of the hydrostatic drive 100, the fluid heats up due to friction losses. To protect the system from overheating, a portion of the fluid is continuously discharged from a low-pressure side of the closed hydraulic circuit 102 when the auxiliary drive is active. Furthermore, the volume of the closed hydraulic circuit 102 can decrease due to internal leakage, for example, into the hydraulic pump 110 and the hydraulic motor 130. To compensate for this fluid loss, an auxiliary pump 120 connected to a low-pressure branch of the closed hydraulic circuit 102 can supply new fluid to the closed hydraulic circuit 102.

[0050] The auxiliary pump 120 can be connected to the shaft 112 of the hydraulic pump 110 via a mechanical interface, as shown in Figure 1. Alternatively, the auxiliary pump can 120 can be directly connected via a mechanical interface to an auxiliary drive 22 of the main drive 20 to drive the auxiliary pump 120 (not shown).

[0051] For cost reasons, auxiliary pumps for hydrostatic drives are preferably designed as pumps with a constant displacement. Due to the mechanical coupling to the shaft 112 of the hydraulic pump 110 (or the main drive 20), a fluid delivery volume proportional to the rotational speed of the hydraulic pump 110 (or the main drive 20) is established. Additional valves in the open low-pressure circuit, such as flow control valves and / or pressure relief valves (exemplarily indicated by reference numerals 30 and 32 in Figure 1), ensure that the fluid supplied to the closed hydraulic circuit 102 does not exceed maximum values ​​that would be detrimental to the overall system.

[0052] The operation of the auxiliary pump 120 is therefore not adapted to the actual demand, but rather delivers its flow rate depending on the rotational speed of the hydraulic pump 110 (or the main drive 20). When the hydraulic drive 100 is engaged, a significant portion of the flow rate is throttled back under supply pressure (e.g., 20 to 30 bar), and when the hydraulic drive 100 is disengaged, the entire auxiliary pump flow rate is throttled back at a pressure typically between 4 and 10 bar. This results in considerable energy losses.

[0053] Figure 2 shows a hydrostatic drive 200 for a commercial vehicle 10 according to embodiments of the present disclosure, which avoids the disadvantages of the known hydrostatic drive described with reference to Figure 1. In Figure 2, fluid power symbols according to DIN ISO 1219 are again used.

[0054] The hydrostatic drive 200 comprises at least one hydraulic motor 230, which is configured to drive at least one axle A of the commercial vehicle 10; at least one hydraulic pump (main pump) 210, which is connected to the at least one hydraulic motor 230 via a fluid circuit 202 in order to drive the at least one hydraulic motor 230; at least one auxiliary pump 220, which is connected to the fluid circuit 202 in order to supply a fluid to the fluid circuit 202; and at least one electric drive 240, which is configured to drive the at least one auxiliary pump 220.

[0055] Instead of being coupled to the at least one hydraulic pump 210 or the main drive 20, such as an internal combustion engine, the at least one auxiliary pump 220 has an electric drive. In other words, such a decentralized drive eliminates the mechanical interface to the at least one hydraulic pump 210 or the main drive 20. This allows the at least one auxiliary pump 220, including its associated electric drive, to be flexibly positioned within the commercial vehicle 10.

[0056] In some embodiments, the at least one auxiliary pump 220 can be integrated directly into a fluid reservoir 250, such as an oil reservoir, thereby avoiding suction losses and also reducing the need for piping.

[0057] The electric drive of at least one auxiliary pump 220 also enables demand-based adjustment of the pump delivery rate. With the hydrostatic drive 100 deactivated, there is no oil requirement, meaning that at least one auxiliary pump 220 can be switched off or remain stationary. During operation, i.e., when the hydrostatic axle A is providing support, the auxiliary pump drive can adjust precisely to the required delivery rate. This occurs independently of the internal combustion engine and / or the main pump speed. Accordingly, For example, lossy flow control valves are eliminated (e.g., valves 30 and 32 shown in Figure 1).

[0058] Furthermore, the electrification of the auxiliary pump drive provides additional degrees of freedom for operating the hydrostatic drive 100. For example, the current draw of the at least one electric drive 240 of the at least one auxiliary pump 220 can be used to determine the torque of the at least one auxiliary pump 220 and thus the system pressure in the auxiliary circuit 204. Instead of a single fixed pressure value that defines the low pressure in the closed hydraulic circuit 202 by means of a pressure relief valve, the electric operation of the at least one auxiliary pump 220 allows for adjustment of the pressure level by means of pressure control.

[0059] In some embodiments, for example, a higher or lower pressure can be set depending on the situation via the current intensity. This allows the drive torque of the hydrostatic drive 200 to be optimized by changing the pressure delta via the hydraulic motors 230. Furthermore, losses can be minimized, since at least one auxiliary pump 220 only generates as much pressure as necessary.

[0060] In some embodiments, the at least one electric drive 240 can be used to precondition the hydrostatic drive 200, for example by means of demand-based oil conditioning, before the hydrostatic drive 200 is switched on. If, for example, an ambient temperature falls below a defined threshold, the at least one auxiliary pump 220 can be operated in a warm-up mode.

[0061] Figure 3 shows an exemplary preconditioning or heating of the hydrostatic drive 200 by a flow through control and leakage lines.

[0062] Typically, during preconditioning, at least one auxiliary pump 220 circulates fluid up to a defined capacity, i.e., from the oil reservoir 250 to the main components (valve block, main pump 210 and / or wheel motor(s) 230), and back to the oil reservoir 250. The flow rate and the resulting pressure level determine the heat input into the overall system. Once a desired temperature is reached after a certain period, the at least one auxiliary pump 220 can switch off.

[0063] In some embodiments, the same procedure can be used to safeguard the drive system at very cold ambient temperatures, i.e., the hydrostatic drive 200 is only allowed to be switched on after a minimum temperature has been exceeded.

[0064] In some embodiments, which can be combined with other embodiments described here, condition monitoring of the hydrostatic drive 200 is possible through continuous evaluation of auxiliary pump operating parameters, optionally in combination with other external parameters such as ambient temperature and / or other components. If, for example, implausible conditions occur, such as insufficient auxiliary pump drive torque for a given flow rate, due to, for example, a line break, the system can output an error and optionally transition to a safe state.

[0065] Additionally or alternatively, monitoring of a fluid filter 260, such as a hydraulic oil filter, can be carried out in the open auxiliary circuit 204, as shown by way of example in Figure 4.

[0066] In general, the flow resistance of filter elements increases with increasing filter loading. To compensate for the temperature influence on the flow resistance, an algorithm can be implemented in a vehicle control computer 270 in some embodiments. Typically, the algorithm compares, for example, the current consumption of the at least one auxiliary pump 220 with historical values ​​recorded, for example, under the same or similar ambient conditions, such as an oil temperature in the oil reservoir 250.

[0067] In some embodiments, the system or algorithm can learn itself and independently detect critical operating conditions at a predefined deviation level (“x” in Figure 4). Typically, this check can take place as part of filter conditioning.

[0068] Figure 5 shows a flowchart of a method 500 for operating a hydrostatic drive of a commercial vehicle according to embodiments of the present disclosure. The method 500 can be implemented by appropriate software that can be executed by one or more processors (e.g., a CPU).

[0069] The method comprises in block 510 a control of at least one electric drive of at least one auxiliary pump to operate the at least one auxiliary pump; and in block 520 a supply of a fluid to a fluid circuit by operating the at least one auxiliary pump, wherein the fluid circuit connects at least one hydraulic motor, which is configured to drive at least one axle of the commercial vehicle, and at least one hydraulic pump, which is configured to drive the at least one hydraulic motor.

[0070] According to the invention, at least one electric drive is provided for operating the at least one auxiliary pump, enabling demand-based operation of the at least one auxiliary pump both during hydrostatic ferry operation and when the hydrostatic ferry operation is switched off. This reduces energy losses from the operation of the at least one auxiliary pump and improves the efficiency of the hydrostatic drive. As a result, the overall energy input for operating the commercial vehicle is reduced, thus conserving energy resources.

[0071] Furthermore, the service life of the hydrostatic drive increases due to its improved efficiency; in particular, because of reduced heat loss, a critical shutdown temperature for the hydrostatic drive is not reached, or at least not reached, more quickly. The inclusion of at least one electric drive also simplifies the overall system, for example by eliminating valves, thus reducing the installation space required for the hydrostatic drive and enabling flexible integration into the commercial vehicle.

[0072] Additionally, the at least one electric drive of the at least one auxiliary pump allows conclusions to be drawn about the operating status of the hydrostatic drive. For example, by recording and evaluating the power consumption of the at least one electric drive, critical situations and / or signs of wear (e.g., cable breakage, filter clogging, etc.) can be detected and used for planning maintenance tasks.

[0073] Although the invention has been further illustrated and explained in detail by means of preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived by a person skilled in the art without departing from the scope of protection of the invention. It is therefore clear that a multitude of possible variations exist. It is also clear that the embodiments mentioned as examples are indeed only examples. The figures do not represent limitations that should not be interpreted in any way as restricting, for example, the scope of protection, the possible applications, or the configuration of the invention. Rather, the preceding description and the description of the figures enable the person skilled in the art to implement the exemplary embodiments in concrete terms. With knowledge of the disclosed inventive concept, the person skilled in the art can make numerous modifications, for example, regarding the function or the arrangement of individual elements mentioned in an exemplary embodiment, without leaving the scope of protection defined by the claims and their legal equivalents, such as further explanations in the description.

Claims

Patent claims 1. Hydrostatic drive (200) for a commercial vehicle (10), comprising: at least one hydraulic motor (230) configured to drive at least one axle (A) of the commercial vehicle (10); at least one hydraulic pump (210) connected to the at least one hydraulic motor (230) via a fluid circuit (202) to drive the at least one hydraulic motor (230); at least one auxiliary pump (220) connected to the fluid circuit (202) to supply fluid to the fluid circuit (202); and at least one electric drive (240) configured to drive the at least one auxiliary pump (220).

2. The hydrostatic drive (200) according to claim 1, wherein the at least one electric drive (240) is configured to drive the at least one auxiliary pump (220) independently of the at least one hydraulic pump (210) and / or a main drive (20) of the commercial vehicle (10) and / or a hydrostatic ferry operation, in particular wherein the at least one electric drive (240) is configured to drive the at least one auxiliary pump (220) independently of a mechanical force generated by the at least one hydraulic pump (210) and / or by the main drive (20) of the commercial vehicle (10) and / or in hydrostatic ferry operation.

3. The hydrostatic drive (200) according to claim 1 or 2, wherein the at least one auxiliary pump (220) has a substantially constant displacement volume.

4. The hydrostatic drive (200) according to one of claims 1 to 3, further comprising at least one control module configured to control the at least one electric drive (240), in particular wherein the at least one control module is configured to control the at least one electric drive (240) by adjusting a current supplied to the at least one electric drive (240).

5. The hydrostatic drive (200) according to claim 4, wherein the at least one control module is configured to: variably adjust the delivery rate of the at least one auxiliary pump (220) by actuating the at least one electric drive (240); and / or determine a torque of the at least one auxiliary pump (220) and / or a fluid pressure of the at least one auxiliary pump (220) and / or an auxiliary circuit (204) based on a current input of the at least one electric drive (240); and / or adjust the fluid pressure of the at least one auxiliary pump (220) and / or the auxiliary circuit (204), in particular by adjusting the current supplied to the at least one electric drive (240); and / or control the at least one electric drive (240) based on an ambient temperature.

6. The hydrostatic drive (200) according to claim 4 or 5, wherein the at least one control module is configured to perform preconditioning of the hydrostatic drive (200) before the start of hydrostatic ferry operation by operating the at least one auxiliary pump (220) and / or postconditioning of the hydrostatic drive (200) after the end of hydrostatic ferry operation by operating the at least one auxiliary pump (220), in particular wherein the at least one control module is configured to perform preconditioning when an ambient temperature is equal to or less than a threshold temperature and / or to perform postconditioning in order to lower a system temperature.

7. The hydrostatic drive (200) according to one of claims 1 to 6, further comprising at least one monitoring module configured to determine at least one state of the hydrostatic drive (200) based on at least one operating parameter of the at least one auxiliary pump (220) and / or the at least one electric drive (240), in particular wherein the at least one state of the hydrostatic drive (200) comprises an operating state of the hydrostatic drive (200) and / or a fluid filter state of the hydrostatic drive (200).

8. The hydrostatic drive (200) according to one of claims 1 to 7, further comprising a fluid reservoir (250), wherein the at least one auxiliary pump (220) is arranged in or on the fluid reservoir.

9. Commercial vehicle (10), in particular truck, comprising the hydrostatic drive (200) according to any one of claims 1 to 8.

10. Method (500) for operating a hydrostatic drive of a commercial vehicle, comprising: Ansteuem (510) of at least one electric drive of at least one auxiliary pump to operate the at least one auxiliary pump; and Supplying (520) a fluid to a fluid circuit by operating the at least one auxiliary pump, wherein the fluid circuit connects at least one hydraulic motor configured to drive at least one axle of the commercial vehicle and at least one hydraulic pump configured to drive the at least one hydraulic motor.

Images