Drive system for a work vehicle

Abstract

Drive system (1) for a work vehicle, for example a truck-mounted forklift, with at least one consumer (2), wherein the drive system (1) comprises - a hydraulic pump (3) designed to drive the at least one consumer (2), - an electric motor (4) mechanically coupled to the hydraulic pump (3) and designed to drive the hydraulic pump (3), and - a control or regulating unit (5) for controlling or regulating the electric motor (4) and / or the hydraulic pump (3), wherein the control or regulating unit (5) is designed to control or regulate a volume flow that can be generated by the hydraulic pump (3).

Description

[0001] The present invention relates to a drive system for a work vehicle, for example a truck-mounted forklift, with at least one consumer, wherein the drive system comprising a hydraulic pump designed to drive at least one consumer, an electric motor mechanically coupled to the hydraulic pump and designed to drive the hydraulic pump, and a control or regulating unit for controlling or regulating the electric motor and / or the hydraulic pump.

[0002] Furthermore, the invention relates to a work vehicle with such a drive system.

[0003] These drive systems are primarily used in compact electric work vehicles, such as forklifts, excavators, and the like, where they are specifically designed to power the lifting unit, such as a fork carriage or bucket. The lifting unit comprises at least one component, often several, each with a specific function. For example, these functions might include lifting and lowering, tilting up and down, or stabilizing the unit with outriggers. To perform their functions, these components require a certain amount of power, which is supplied by a hydraulic pump generating the necessary pressure and flow rate.

[0004] In state-of-the-art drive systems, the power requirement is typically met entirely by generating the necessary pressure. A disadvantage of this is that operating such a drive system requires a significant amount of energy, especially when multiple consumers are to be used simultaneously, e.g., for driving the work vehicle and for lifting, laterally moving, and tilting a load with the forklift.

[0005] The object of the present invention is therefore to provide a drive system by means of which energy consumption can be optimized to a minimum.

[0006] This problem is solved by the features of claim 1, namely with a drive system of the type mentioned at the outset, in which the control or regulating unit is designed to control or regulate a volume flow that can be generated by the hydraulic pump.

[0007] Controlling or regulating the volume flow rate as a control variable advantageously forms the basis for operating the drive system in a particularly energy-efficient manner. This means, in particular, that the at least one consumer receives only the maximum amount of power it actually requires, given its maximum power demand. The drive system according to the invention can therefore contribute significantly to energy savings.

[0008] The at least one consumer is in particular a hydraulic consumer, especially a hydraulic cylinder.

[0009] If the work vehicle is a truck-mounted forklift, forklift truck or the like, then the at least one consumer is preferably five consumers, which is provided for the operation of a fork carriage and a support device of the forklift truck, in particular wherein one consumer each may be responsible for the functions of lifting and lowering, increasing and reducing reach, tilting up and down, moving the fork carriage to the left and right and moving a support device down and up.

[0010] In preferred embodiments, the hydraulic pump for driving the at least one consumer is a one-way pump.

[0011] Further advantageous embodiments of the invention are defined in the dependent claims.

[0012] It is particularly preferred that the control unit is configured to control or regulate the flow rate at the request of the at least one consumer. This can mean, in particular, that the at least one consumer determines the energy consumption at the hydraulic pump to meet its power requirements. Advantageously, such a direct demand-based request enables precise and therefore energy-efficient control or regulation.

[0013] In preferred embodiments, the requirement of the at least one consumer corresponds to a defined maximum power requirement of the at least one consumer, in particular so that the at least one consumer can fulfill its assigned function in the best possible way.

[0014] It is conceivable that the requirement of at least one consumer cannot be met, for example, because the maximum flow rate achievable by the hydraulic pump may be limited by the pump's design, particularly with regard to its maximum speed. Especially when multiple consumers demand flow, it is possible that one or more of their requirements cannot be met. However, this can be accepted because it results in the advantage of low energy consumption.

[0015] The hydraulic pump is preferably designed to come to a standstill without a demand from a consumer. In a variable displacement pump, this can be achieved primarily by a swivel angle in the neutral position, or by the motor coming to a standstill, which is mandatory for a constant displacement pump to reach a standstill state. In other words, the hydraulic pump is advantageously only active if at least one function is being activated.

[0016] It may be provided that the electric motor is designed to be controlled or regulated by at least one signal generated by the request of at least one consumer.

[0017] At least one of the signals can be a mechanical, electrical, or hydraulic signal.

[0018] At least one signal can be converted and / or obtained by means of signal conversion.

[0019] It may be provided that the control or regulating unit is designed to generate a proportional and / or constant volume flow depending on a function of the consumer.

[0020] Preferably, the control or regulating unit is designed to control or regulate the hydraulic pump and / or the electric motor in such a way that a proportional and / or constant volume flow is generated.

[0021] It is possible that only a proportional volume flow or only a constant volume flow is generated.

[0022] It is also possible that the volume flow is a superposition of a proportional and a constant volume flow and / or that a proportional and a constant volume flow are generated alternately.

[0023] In the case of a truck-mounted forklift, forklift or the like, for example, the lifting and lowering function and the increasing and decreasing reach function are proportional in their power requirements, so that the consumers demand a proportional volume flow to fulfill these functions, especially when they are operated.

[0024] The control or regulating unit is preferably designed to control or regulate the volume flow based on a speed of the hydraulic pump and / or a displacement volume per revolution of the hydraulic pump.

[0025] In particularly preferred embodiments, the hydraulic pump is a constant displacement pump with a constant displacement volume per revolution of the hydraulic pump, preferably wherein the control or regulating unit is designed to control or regulate the volume flow based on the speed of the hydraulic pump.

[0026] The control or regulating unit is particularly preferably designed to control or regulate the electric motor, preferably a speed of the electric motor and / or on the basis of at least one request from one or more consumers.

[0027] In other embodiments, the hydraulic pump is a variable displacement pump, and the control or regulating unit is preferably designed to control or regulate the volume flow based on an adjustment parameter such as a swivel angle and / or a speed of the hydraulic pump.

[0028] In preferred embodiments, the control or regulating unit is designed to control or regulate the volume flow by means of at least one functional request to the at least one consumer by an operator, preferably in real time.

[0029] At least one functional requirement can be fulfilled, for example, by an operator operating a lever, button, etc., whereby the operation can be carried out in or on the work vehicle and / or remotely.

[0030] It is also conceivable that the functional requirement could be fulfilled by an autonomous system, etc.

[0031] It is preferably provided that at least the electric motor and the hydraulic pump form a first hydraulic drive train for driving the at least one consumer, preferably wherein the at least one consumer comprises at least two, for example four or five, consumers.

[0032] In the first drive train, at least one pressure relief valve can be provided, in particular wherein the at least one pressure relief valve is located upstream of at least one consumer.

[0033] In the first drive train, at least one multi-way valve is provided, which can be operated, for example, by means of a lever, and in particular by means of which the at least one consumer can be activated.

[0034] The first drive train is preferably an open hydraulic circuit.

[0035] In particularly preferred embodiments, the control or regulating device is designed to control or regulate the volume flow based on a sum of the individual requirements of the at least two consumers.

[0036] As mentioned above, it is conceivable, and preferably intended for energy-saving purposes, that the sum of the requirements exceeds the maximum power of the hydraulic pump, so that one or more consumers are not operated according to their respective maximum power requirements.

[0037] For example, a hydraulic pump with a maximum speed of 3000 revolutions per minute might be available. One function requires 1000 revolutions per minute, a second 600 revolutions per minute, and a third 1500 revolutions per minute. This would result in a demand of 3100 revolutions per minute, leading to an insufficient supply for one function. To benefit from lower energy consumption, it is acceptable to operate, for example, only one function at 2000 revolutions per minute.

[0038] It is particularly preferred that a primary consumer with a defined power requirement is arranged upstream of the at least one consumer in the first drive train, preferably wherein the drive system is designed to supply the primary consumer with a quantity of hydraulic fluid to meet its defined power requirement. This advantageously ensures that the primary consumer can be operated optimally at all times according to its required power demand and that an undersupply of the primary consumer is reliably avoided.

[0039] Preferably, the primary consumer is a hydraulic cylinder of the steering system of the work vehicle. This means, in particular, that the work vehicle can always be steered reliably and safely.

[0040] It may be provided that the drive system has at least a second hydraulic drive train with a second electric motor and a second hydraulic pump mechanically coupled to the second electric motor.

[0041] Particularly preferred are the first drive train and the at least one second drive train designed separately from each other, i.e., in particular hydraulically unconnected.

[0042] However, it is also conceivable that the first drive train and at least one second drive train are hydraulically connected, for example for the purpose of pressure equalization.

[0043] In preferred embodiments, the second drive train comprises at least one hydraulic motor, preferably for driving at least one wheel of the working vehicle, preferably wherein the second hydraulic pump is designed to drive the at least one hydraulic motor.

[0044] It is preferably intended that the second drive train is a closed hydraulic circuit.

[0045] Preferably, the second hydraulic pump is a two-way pump, in particular with a variable delivery volume.

[0046] Protection is also sought for a work vehicle, in particular a truck-mounted forklift, with a drive system according to the invention and at least one consumer that can be driven by the drive system.

[0047] The at least one consumer is in particular a hydraulic consumer, preferably a hydraulic cylinder.

[0048] Particularly preferred is a forklift with several, preferably five, consumers for operating a fork carriage and a support device of the forklift, in particular wherein one consumer is provided for the functions of lifting and lowering, increasing and reducing reach, tilting upwards and downwards, moving the fork carriage to the left and right and moving the support device downwards and upwards.

[0049] Further advantages of the invention become apparent from the figures and the accompanying figure description. These show: Figs. 1-3 each show a section of a preferred embodiment of a drive system according to the invention.

[0050] The in the Fig. 1-3 The sections shown together form the preferred embodiment of a drive system 1 according to the invention. Essentially, in Fig. 1 a main section of the drive system 1 with a first drive train 7 and in Fig. 2 A primary consumer 8 provided in the first drive train 7 is shown. In the Fig. 3 An optional second powertrain is shown in Figure 9.

[0051] The Fig. 1 This shows a section of a preferred embodiment of a drive system 1 for a work vehicle, for example a truck-mounted forklift, with at least one consumer 2, wherein the drive system 1 a hydraulic pump 3, which is designed to drive at least one consumer 2, an electric motor 4 mechanically coupled to the hydraulic pump 3, which is designed to drive the hydraulic pump 3, and a control or regulating unit 5 for controlling or regulating the electric motor 4 and / or the hydraulic pump 3 comprising, wherein the control or regulating unit 5 is designed to control or regulate a volume flow that can be generated by the hydraulic pump 3.

[0052] In this preferred embodiment, the control or regulating unit 5 is designed to control or regulate the electric motor 4.

[0053] Furthermore, in this example, at least the electric motor 4 and the hydraulic pump 3 form a first hydraulic drive train 7, which is designed to drive at least one consumer 2, here by way of example five consumers 2.

[0054] The consumers 2, preferably hydraulic cylinders, are not shown; these would connect to the upward-extending hydraulic lines. However, a total of five exemplary functions 6 that can be realized by the consumers 2 are shown. These five functions 6 are, from left to right: raising and lowering a fork carriage of a work vehicle, tilting the fork carriage up and down, moving the fork carriage left and right, increasing and decreasing the reach of the fork carriage, and moving a support device up and down.

[0055] In this embodiment, the control or regulating unit 5 is designed to control or regulate the volume flow at the request of at least one consumer 2, i.e., in particular at the request of one or more consumers 2 of the five existing consumers 2.

[0056] Preferably, the requirement of the respective consumer 2 corresponds to a defined maximum power requirement of this consumer 2.

[0057] Since there are several consumers 2 present, the control or regulating device 5 is preferably designed to control or regulate the volume flow based on a sum of the individual requirements of the at least two consumers 2.

[0058] In this embodiment, the control or regulating unit 5 is designed to generate a proportional and / or constant volume flow depending on the respective function 6 of the respective consumer 2.

[0059] Preferably, the hydraulic pump 3 is a constant displacement pump with a constant displacement volume per revolution of the hydraulic pump 3, wherein the control or regulating unit 5 is designed to control or regulate the volume flow based on the speed of the hydraulic pump 3.

[0060] It is also conceivable that the control or regulating unit 5 is designed to control or regulate the volume flow based on a displacement volume per revolution of the hydraulic pump 3.

[0061] In this embodiment, the control unit 5 is designed to control or regulate the volume flow by means of at least one functional request to the at least one consumer 2 by an operator. For example, an operator can actuate a lever of a work vehicle to perform one or more functions 6, e.g., raising and / or tilting a fork carriage, whereupon the associated consumer(s) 2 request a volume flow required for the function(s) 6.

[0062] In particular, the control or regulation and the subsequent processes take place in real time, i.e., in particular directly as a result of at least one functional requirement.

[0063] In Fig. 1 In a preferred variant, a valve 13 is arranged adjacent to the hydraulic pump 3, from which a primary consumer 8 (shown in Fig. 2 ) is provided, preferably wherein the primary consumer 8 is upstream of the at least one consumer 2 in the first drive train 7.

[0064] The valve 13 is preferably a switching valve, in particular a load-sensing valve functioning as a priority valve, which is designed in particular to ensure that the defined power requirement of the primary consumer 8 is always met.

[0065] In Fig. 1 As a preferred variant, a control line is shown extending from the control unit 5 to the preferably provided second drive train 9, in particular to the second electric motor 10 of the second drive train 9 (see Fig. 3 ).

[0066] The Fig. 2 shows a second section of the preferred embodiment of a drive system 1, wherein here the Fig. 1 The primary consumer 8 mentioned above is shown, which is upstream of at least one consumer 2 in the first drive train 7.

[0067] In this embodiment, the drive system 1 is designed to provide the primary consumer 8 with a quantity of hydraulic fluid to cover the defined power requirement of the primary consumer 8, in particular by means of the valve 13.

[0068] The primary consumer 8 is, in particular, a hydraulic cylinder for a steering system, preferably wherein a rack is provided on the hydraulic cylinder for performing a rotary movement. In particular, the function 6 of this primary consumer 8 is the steering of the work vehicle.

[0069] The Fig. 3 Figure 1 shows a third section of the preferred embodiment of a drive system 1, wherein at least a second hydraulic drive train 9 with a second electric motor 10 and with a second hydraulic pump 11 mechanically coupled to the second electric motor 10 is shown.

[0070] Starting from the second electric motor 10, a control line is shown which connects to the control or regulating unit 5 (see Fig. 1 ) is connected.

[0071] The control or regulating unit 5 is specifically designed to control or regulate the first drive train 7 and the second drive train 9.

[0072] In this preferred embodiment, the first drive train 7 and the second drive train 5 are not hydraulically connected to each other.

[0073] In this example, the second drive train 9 has at least one hydraulic motor 12, in particular three hydraulic motors 12.

[0074] Each hydraulic motor 12 is specifically designed to drive one wheel of the work vehicle, preferably wherein the second hydraulic pump 11 is designed to drive the at least one hydraulic motor 12.

[0075] In this embodiment, the second hydraulic pump 11 is a two-way pump, preferably with a variable delivery volume. Reference symbol list:

[0076] 1. Drive system 2. Consumer 3. Hydraulic pump 4. Electric motor 5. Control unit 6. Function 7. First drive train 8. Primary consumer 9. Second drive train 10. Second electric motor 11. Second hydraulic pump 12. Hydraulic motor 13. Priority valve

Claims

1. Drive system (1) for a work vehicle, for example a truck-mounted forklift, with at least one consumer (2), wherein the drive system (1) comprises: - a hydraulic pump (3) designed to drive the at least one consumer (2), - an electric motor (4) mechanically coupled to the hydraulic pump (3) and designed to drive the hydraulic pump (3), and - a control or regulating unit (5) for controlling or regulating the electric motor (4) and / or the hydraulic pump (3), characterized by the fact that the control or regulating unit (5) is designed to control or regulate a volume flow that can be generated by the hydraulic pump (3).

2. Drive system (1) according to claim 1, wherein the control or regulating unit (5) is configured to control or regulate the volume flow at the request of the at least one consumer (2).

3. Drive system (2) according to claim 2, wherein the requirement of the at least one consumer (2) corresponds to a defined maximum power requirement of the at least one consumer (2).

4. Drive system (2) according to claim 2 or 3, wherein the electric motor (4) is configured to be controlled or regulated by at least one signal, preferably mechanical, electrical or hydraulic, generated by the request of the at least one consumer (2).

5. Drive system (1) according to one of the preceding claims, wherein the control or regulating unit (5) is configured to generate a proportional and / or constant volume flow depending on a function (6) of the consumer (2).

6. Drive system (1) according to one of the preceding claims, wherein the control or regulating unit (5) is configured to control or regulate the volume flow based on a speed of the hydraulic pump (3) and / or a displacement volume per revolution of the hydraulic pump (3).

7. Drive system (3) according to one of the preceding claims, wherein the hydraulic pump (3) is a constant displacement pump with a constant displacement volume per revolution of the hydraulic pump (3), preferably wherein the control or regulating unit (5) is configured to control or regulate the volume flow based on the rotational speed of the hydraulic pump (3).

8. Drive system (3) according to one of claims 1 to 6, wherein the hydraulic pump (3) is a variable displacement pump, preferably wherein the control or regulating unit (5) is configured to control or regulate the volume flow based on an adjustment parameter such as a swivel angle and / or a speed of the hydraulic pump (3).

9. Drive system (3) according to one of the preceding claims, wherein the control or regulating unit (5) is configured to control or regulate the electric motor (4), and / or to control or regulate the volume flow by means of at least one functional request to the at least one consumer (2) by an operator, preferably in real time.

10. Drive system (1) according to one of the preceding claims, wherein at least the electric motor (4) and the hydraulic pump (3) form a first hydraulic drive train (7) for driving the at least one consumer (2), preferably wherein the at least one consumer (2) comprises at least two, for example five, consumers (2).

11. Drive system (1) according to claim 10, wherein the control or regulating device (5) is configured to control or regulate the volume flow based on a sum of individual requirements of the at least two consumers (2).

12. Drive system (1) according to claim 10 or 11, wherein the at least one consumer (2) in the first drive train (7) is preceded by a primary consumer (8) with a defined power requirement, preferably wherein the drive system (1) is configured to provide the primary consumer (8) with a quantity of hydraulic oil to cover the defined power requirement by means of a device for controlling the prioritized energy supply.

13. Drive system (1) according to one of claims 10 to 12, wherein the drive system (1) comprises at least a second hydraulic drive train (9) with a second electric motor (10) and a second hydraulic pump (11) mechanically coupled to the second electric motor (10).

14. Drive system (1) according to claim 13, wherein the second drive train (9) comprises at least one hydraulic motor (12), preferably for driving at least one wheel of the work vehicle, preferably wherein the second hydraulic pump (11) is designed to drive the at least one hydraulic motor (12) and / or wherein the second hydraulic pump (11) is a two-way pump.

15. Work vehicle, in particular a truck-mounted forklift, with a drive system (1) according to one of the preceding claims and at least one consumer (2) that can be driven by the drive system (1).

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