Hydraulic tool and method for operating the hydraulic tool

Abstract

The presented invention relates to a method (100) for operating a hydraulic device (200) comprising a plurality of valves (203) for adjusting partial volume flows of hydraulic fluid through a plurality of hydraulic subsystems (201). The method (100) comprises determining (101) respective partial volume flows for several valves (203) of the plurality of valves (203), determining (103) a total volume flow based on the determined partial volume flows, determining (105) a target delivery volume to be supplied by a modulating hydraulic pump (205) for pumping the hydraulic fluid based on the determined total volume flow, and adjusting (107) the target delivery volume for the hydraulic pump (205).

Description

[0001] The presented invention relates to a method for operating a hydraulic device, a control unit for a hydraulic device, a hydraulic device and a program product according to the appended claims.

[0002] In a conventional hydraulic drive (open-center), a hydraulic pump is driven by a drive motor at a constant speed. This creates a constant flow rate in the hydraulic circuit. A control block with proportional valves and / or binary-acting valves, such as black / white directional control valves, then directs portions of the flow rate to individual hydraulic functions. The excess flow rate is returned to the hydraulic tank.

[0003] Due to the operation described above, the hydraulic pump is constantly at the highest pressure required to operate all hydraulic functions in parallel. Since the volume flow delivered by the pump is constant, the drive motor must deliver high power, even if the pressure required by the respective active hydraulic functions is very low. This results in significantly more energy being consumed, particularly converted into heat, than necessary to operate such a hydraulic system.

[0004] Furthermore, operation with high volume flows results in loud flow noises, which can be particularly disturbing if the hydraulic pump is driven by a quiet electric motor.

[0005] Therefore, it is an object of the invention presented to provide a possibility for energy-efficient and quiet operation of a hydraulic working device.

[0006] Thus, according to a first aspect of the invention presented, a method for operating a hydraulic device is presented, which comprises a plurality of valves for adjusting partial volume flows of hydraulic fluid through a plurality of hydraulic subsystems.

[0007] The presented method comprises determining respective partial volume flows for a plurality of valves of the plurality of valves, particularly preferably each valve of the plurality of valves, determining a total volume flow based on the determined partial volume flows, determining a target delivery volume to be delivered by a modulating hydraulic pump for pumping the hydraulic fluid based on the determined total volume flow and setting the target delivery volume for the hydraulic pump.

[0008] In the context of the invention presented, a hydraulic subsystem is understood to be a part of a hydraulic system that is supplied, for example, with a predetermined volume flow of hydraulic fluid via a number of valves. A hydraulic subsystem comprises, in particular, a number of hydraulic lines or subcircuits that are pressurized with a predetermined pressure by hydraulic fluid to implement a respective function, such as telescoping the boom of a work platform or the like. The volume flow of hydraulic fluid required to set the predetermined pressure is adjusted by the number of valves, in particular throttled relative to a pressure in a supply line for supplying the subsystem with hydraulic fluid.

[0009] In the context of the invention presented, a modulating hydraulic pump is understood to be a hydraulic pump whose delivery volume can be adjusted, i.e., changed. For this purpose, the hydraulic pump can comprise a drive, such as a motor, whose speed can be adjusted, i.e., dynamically changed, for example, by a corresponding control unit.

[0010] To adjust the hydraulic fluid flow rate, for example, a back pressure on a valve plate and / or the degree of valve opening can be adjusted. For this purpose, corresponding control parameters can be transmitted from a control unit to the valve and adjusted by a control system integrated into the valve.

[0011] The presented invention is based on determining planned or set partial volume flows for several of the plurality of valves, particularly preferably for each of the plurality of valves. This means that for an individual valve, a specific partial volume flow that is or should be set by the valve is determined. Accordingly, the partial volume flow refers to a volume flow that flows or should flow through the valve or downstream of the valve.

[0012] Based on the determined partial volume flows, a total volume flow is calculated, which is required to provide all partial volume flows. Accordingly, the total volume flow is composed of at least the sum of the partial volume flows, optionally supplemented by a safety margin.

[0013] Since the valves of the hydraulic device are adjusted depending on their function, i.e., for example, only a portion of the numerous valves is opened, the sum of the partial flow rates is smaller than the maximum possible total flow rate, depending on the activated function of the hydraulic device. Accordingly, the flow rate to be delivered by the hydraulic pump of the hydraulic device can be dynamically adjusted depending on the total flow rate required for each currently activated function of the hydraulic device.

[0014] Dynamically adjusting the flow rate reduces the load on the hydraulic pump, especially on the hydraulic pump drive. As a result, the hydraulic pump operates energy-efficiently and quietly.

[0015] Furthermore, the dynamic adjustment of the flow volume minimizes flow noise in the hydraulic device, since less hydraulic fluid is circulated at lower pressure than is usual with conventional hydraulic devices operating at constant pressure.

[0016] It can be provided that a selection of valves from the plurality of valves is assigned to a respective hydraulic function of the hydraulic device, and a partial volume flow assigned to the respective hydraulic function is determined on the basis of respective partial volume flows of the selected valves.

[0017] By assigning respective valves to a hydraulic function, a logical unit of valves is formed which together set a partial volume flow required to execute the hydraulic function. Accordingly, a partial volume flow required for a respective hydraulic function can be determined so that when the respective function is activated, the partial volume flow required by the activated hydraulic function can be taken into account when determining the required delivery volume. In particular, when a respective function is activated, a partial volume flow required by the activated hydraulic function can be initially determined or learned and saved with the respective function. Accordingly, the saved partial volume flow can be retrieved from the memory when the respective function is activated and used directly to determine the target delivery volume.

[0018] Furthermore, it can be provided that the total volume flow is determined only on the basis of partial volume flows determined for the respective activated functions of the hydraulic device.

[0019] By determining the total flow rate based solely on partial flow rates determined for the respective activated functions of the hydraulic device, fast control with low computational load is possible. For example, partial flow rates already stored for the respective activated functions of the hydraulic device can be retrieved and used directly to determine the target flow rate.

[0020] It can further be provided that the determination of the partial volume flows, the determination of the total volume flow, the determination of the target delivery volume and the setting of the target delivery volume are repeated if at least one partial volume flow changes and / or a predetermined time has passed since the setting of the target delivery volume.

[0021] By repeatedly performing the presented procedure, a dynamic control of the hydraulic device is achieved, so that a safe operation of the hydraulic device with at least a total volume flow required for each currently activated function is ensured.

[0022] It can further be provided that the partial volume flows determined for respective valves are determined on the basis of control parameters specified by a control unit for adjusting the valves.

[0023] The respective control parameters for adjusting the valves are usually determined by a central control unit of the hydraulic device and transmitted to the valves. By querying the control parameters determined by the central control unit, a planned state of the hydraulic device can be determined by the central control unit and implemented by selecting the appropriate delivery volume to be set with a minimum total flow rate for the planned state.

[0024] It can further be provided that the target delivery volume is selected such that the hydraulic pump delivers a delivery volume that differs from the total volume flow by at most a predetermined threshold value.

[0025] To allow the flow rate to stabilize at the target flow rate, a threshold value or tolerance range can be specified within which a given flow rate is considered or accepted as the target flow rate. Accordingly, the hydraulic pump is only readjusted or adjusted when the hydraulic pump delivers a flow rate that differs from the total flow rate by more than the specified threshold value.

[0026] It can further be provided that the hydraulic pump is driven by a drive and the target delivery volume is specified by a target speed of the drive, and to determine the target speed, the target speed is selected using an allocation scheme, wherein the allocation scheme assigns a respective target speed to a respective total volume flow, by means of which a respective delivery volume is set.

[0027] To set a specific target flow rate, a hydraulic pump drive can be set to a target speed corresponding to the target flow rate or achieving the target flow rate. An allocation scheme that assigns a specific target speed to a specific total flow rate can be implemented, for example, as an allocation table, a characteristic map, or a mathematical model.

[0028] According to a second aspect, the presented invention relates to a control unit for a hydraulic device comprising a plurality of valves for adjusting a volume flow of hydraulic fluid through a plurality of hydraulic subsystems, wherein the control unit comprises a computing unit configured to carry out a possible embodiment of the presented method.

[0029] In the context of the invention presented, a computing unit is understood to mean a processor, a subprocessor or any other programmable circuit.

[0030] The proposed control unit can, for example, be connected to a central control unit of a hydraulic device to expand the functionality of the hydraulic device using the proposed method. For this purpose, the control unit can include a communication interface, such as a wired or wireless communication interface.

[0031] According to a third aspect, the presented invention relates to a hydraulic device, wherein the hydraulic device comprises a plurality of hydraulic subsystems, a plurality of valves for adjusting a volume flow of hydraulic fluid through the plurality of hydraulic subsystems, a modulating hydraulic pump for pumping the hydraulic fluid and a computing unit configured to carry out a possible embodiment of the presented method.

[0032] The computing unit of the hydraulic device presented can, for example, be a possible embodiment of the control unit presented. Alternatively, the computing unit of the hydraulic device presented can be a control unit, in particular a central control unit of the hydraulic device.

[0033] The hydraulic device may be a telescopic working device.

[0034] A telescopic work device, such as a mobile crane or a lifting platform, usually comprises several working circuits to which the respective functions are assigned, so that the presented method is particularly advantageous for the energy-efficient and low-noise operation of a telescopic work device.

[0035] Accordingly, the hydraulic device may be a mobile crane or a lifting platform.

[0036] According to a fourth aspect, the presented invention relates to a program product, wherein the program product comprises program code means that configure a computing unit to carry out a possible embodiment of the presented method when the program product is executed on the computing unit.

[0037] Further features, details, and advantages of the invention will become apparent from the wording of the claims and from the following description of exemplary embodiments with reference to the drawings. They show: Fig. 1 shows a possible embodiment of the method presented, and Fig. 2 shows a possible embodiment of the hydraulic device presented.

[0038] In Fig. 1 is a method 100 for operating a hydraulic device 200 according to Fig. 2 , which comprises a plurality of valves 203 for adjusting partial volume flows of hydraulic fluid through a plurality of hydraulic subsystems 201.

[0039] The method 100 comprises a first determination step 101 in which respective partial volume flows are determined for a plurality of valves of the plurality of valves 203, particularly preferably for each valve of the plurality of valves 203, a second determination step 103 in which a total volume flow is determined on the basis of the partial volume flows determined in the first determination step 101, a determination step 105 in which a target delivery volume to be delivered by a modulating hydraulic pump 205 for pumping the hydraulic fluid is determined on the basis of the total volume flow determined in the second determination step 103 and a setting step 107 in which the target delivery volume determined in the determination step 105 is set for the hydraulic pump 205.

[0040] To set the target delivery volume for the hydraulic pump 205, for example, a drive of the hydraulic pump 205 can be set to a target speed corresponding to the target delivery volume or assigned to the target delivery volume.

[0041] In Fig. 2 is a hydraulic device 200, such as a telescopic mobile crane.

[0042] The hydraulic device 200 comprises a plurality of hydraulic subsystems 201, a plurality of valves 203 for adjusting a volume flow of hydraulic fluid through the plurality of hydraulic subsystems 201, a modulating hydraulic pump 205 for pumping the hydraulic fluid, and a computing unit 207 configured to carry out the method 100 according to Fig. 1 to execute.

[0043] The computing unit 207 is in communicative connection with a control unit 209 of an electric motor 211 for driving the hydraulic pump 205. To set a target delivery volume on the hydraulic pump 205, the computing unit 207 transmits a target speed selected as a function of a currently required total volume flow to the control unit 209, so that the control unit 209 adjusts the electric motor 211 accordingly and the hydraulic pump 205 delivers the target delivery volume corresponding to the required total volume flow from a hydraulic fluid tank 213.

[0044] Furthermore, the computing unit 207 is in communicative connection with the plurality of valves 203 in order to read out a state, ie respective control parameters set on the valves 203 and to determine partial volume flows for respective valves or corresponding subsystems, to determine a total volume flow based on the respective partial volume flows and to determine a desired delivery volume to be delivered by the modulating hydraulic pump 205 based on the total volume flow.

[0045] The invention is not limited to one of the embodiments described above, but can be modified in many ways.

[0046] All features and advantages arising from the claims, the description and the drawings, including design details, spatial arrangements and method steps, can be essential to the invention both individually and in a wide variety of combinations. Reference symbol:

[0047] 100Procedure 101First determination step 103Second determination step 105Determination step 107Setting step 200Hydraulic device 201Hydraulic subsystems 203Valves 205Hydraulic pump 207CPU 209Control unit 211Electric motor 213Hydraulic fluid tank

Claims

1. Method (100) for operating a hydraulic device (200) comprising a plurality of valves (203) for adjusting partial volume flows of hydraulic fluid through a plurality of hydraulic subsystems (201), the method (100) comprising: - determining (101) respective partial volume flows for a plurality of valves (203) of the plurality of valves (203), - determining (103) a total volume flow based on the determined partial volume flows, - determining (105) a target delivery volume to be delivered by a modulating hydraulic pump (205) for pumping the hydraulic fluid based on the determined total volume flow, - setting (107) the target delivery volume for the hydraulic pump (205).

2. Method (100) according to claim 1, characterized by thata selection of valves (203) from the plurality of valves (203) is assigned to a respective hydraulic function of the hydraulic device (200), and a partial volume flow assigned to the respective hydraulic function is determined on the basis of respective partial volume flows of the selected valves (203).

3. Method (100) according to claim 2, characterized by that the total volume flow is determined only on the basis of partial volume flows determined for the respective activated functions of the hydraulic device (200).

4. Method (100) according to one of the preceding claims, characterized by that the determination (101) of the partial volume flows, the determination (103) of the total volume flow, the determination (105) of the target delivery volume and the setting (107) of the target delivery volume are repeated if at least one partial volume flow changes and / or a predetermined time has passed since the setting of the target delivery volume.

5. Method (100) according to one of the preceding claims, characterized by that the partial volume flows determined for respective valves (103) are determined on the basis of control parameters specified by a control unit for adjusting the valves (203).

6. Method (100) according to one of the preceding claims, characterized by that the partial volume flows determined for respective valves (203) are determined on the basis of control parameters set on the respective valves (203).

7. Method (100) according to one of the preceding claims, characterized by that the target delivery volume is selected such that the hydraulic pump (205) delivers a delivery volume that differs from the total volume flow by at most a predetermined threshold value.

8. Method (100) according to one of the preceding claims, characterized by thatthe hydraulic pump (205) is driven by a drive (211) and the target delivery volume is specified by a target speed of the drive (211), and to determine the target speed, the target speed is selected using an allocation scheme, wherein the allocation scheme assigns a respective target speed to a respective total volume flow, by means of which a respective delivery volume is set.

9. A control unit (207) for a hydraulic device comprising a plurality of valves for adjusting a volume flow of hydraulic fluid through a plurality of hydraulic subsystems (201), wherein the control unit (207) comprises a computing unit (207) configured to carry out a method (100) according to any one of claims 1 to 8.

10. Hydraulic device (200), the hydraulic device (200) comprising: - a plurality of hydraulic subsystems (201), - a plurality of valves (203) for adjusting a volume flow of hydraulic fluid through the plurality of hydraulic subsystems (201), - a modulating hydraulic pump (205) for pumping the hydraulic fluid, and - a computing unit (207) configured to carry out a method (100) according to any one of claims 1 to 8.

11. Hydraulic device (200) according to claim 10, wherein the hydraulic device (200) is a telescopic working device.

12. Hydraulic device (200) according to claim 10 or 11, wherein the hydraulic device (200) is a mobile crane or an aerial work platform.

13. A program product, wherein the program product comprises program code means that configure a computing unit (207) to perform a method (100) according to any one of claims 1 to 8 when the program product is executed on the computing unit (107).

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