Method for Operating a Variable-Speed Electrohydraulic Pump, Computing Unit and Variable-Speed Electrohydraulic Pump

Abstract

A system and method of operating a variable-speed electrohydraulic pump, in which a pump delivery mechanism having an adjustable control volume is driven by an electric machine, includes activating the variable-speed electrohydraulic pump with a specific control volume and a specific speed, such that a specific volume flow is provided. The method includes obtaining control information for an actuator which indicates an increase in the volume flow and increasing the speed and reducing the control volume in response to the obtained control information. The method includes activating the variable-speed electrohydraulic pump to increase the volume flow after increasing the speed and reducing the control volume.

Claims

1. A method of operating a variable-speed electrohydraulic pump, in which a pump delivery mechanism having an adjustable control volume is driven by an electric machine, comprising: activating the variable-speed electrohydraulic pump with a specific control volume and a specific speed, such that a specific volume flow is provided; obtaining control information for an actuator which indicates an increase in the volume flow; increasing the speed and reducing the control volume in response to the obtained control information; and activating the variable-speed electrohydraulic pump to increase the volume flow after increasing the speed and reducing the control volume.

2. The method according to claim 1, wherein increasing the speed and reducing the control volume comprises: increasing the speed and reducing the control volume such that the volume flow remains at least substantially constant.

3. The method according to claim 1, wherein activating the variable-speed electrohydraulic pump comprises: activating the variable-speed electrohydraulic pump using speed control.

4. The method according to claim 3, wherein the electric machine is operated by means of a converter, and wherein increasing the speed comprises: using an additive term to form a setpoint for the converter.

5. The method according to claim 1, wherein the control information comprises or is derived from control information transmitted from an input unit to the actuator.

6. The method according to claim 5, wherein the variable-speed electrohydraulic pump is used to operate at least one component of a mobile machine.

7. The method according to claim 6, wherein: the input unit is used to control the at least one component via the actuator (142, 152); and the at least one component is one of a dynamic working unit, a steering system, and a traction unit.

8. The method according to claim 1, wherein: the speed is increased and the control volume is reduced before the actuator has reacted to the control information; and the variable-speed electrohydraulic pump is activated to increase the volume flow as soon as the actuator has reacted to the control information.

9. A system, comprising: a control unit configured to activate a variable-speed electrohydraulic pump with a specific control volume and a specific speed, such that a specific volume flow is provided; obtain control information for an actuator which indicates an increase in the volume flow; increase the speed and reduce the control volume in response to the obtained control information; and activate the variable-speed electrohydraulic pump to increase the volume flow after increasing the speed and reducing the control volume.

10. The system of claim 9, further comprising: the variable-speed electrohydraulic pump, the variable-speed electrohydraulic pump including a pump delivery mechanism with an adjustable control volume driven by an electric machine.

11. The system of claim 10, wherein the system is a mobile machine system, the mobile machine system further comprising: at least one component configured to be driven by the variable-speed electrohydraulic pump; and an input unit configured to control the at least one component via the actuator.

12. The system of claim 9, further comprising: a memory including program instructions stored therein, wherein the control unit is configured to execute the program instructions to activate the variable-speed electrohydraulic pump with the specific control volume and the specific speed, such that the specific volume flow is provided; obtain the control information for the actuator which indicates the increase in the volume flow; increase the speed and reduce the control volume in response to the obtained control information; and activate the variable-speed electrohydraulic pump to increase the volume flow after increasing the speed and reducing the control volume.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 shows, schematically, a machine having a variable-speed electrohydraulic pump in which a method according to the disclosure can be used.

[0023] FIG. 2 shows, schematically, a sequence of a method according to the disclosure in a preferred embodiment.

DETAILED DESCRIPTION

[0024] FIG. 1 illustrates, schematically, a machine 100 having a variable-speed electrohydraulic pump 110, in which a method according to the disclosure can be used or carried out. The machine 100, which is illustrated here only purely schematically with the relevant components, can in particular be a mobile working machine such as, for example, a telehandler.

[0025] The variable-speed electrohydraulic pump 110 has a variable-speed electric machine 112 (e.g. an electric motor), which can be activated and operated via a frequency converter 114 by a computing unit 116 designed as a control unit. The electric machine 112 is coupled to a pump delivery mechanism 118 with an adjustable control volume (indicated by the arrow). The control volume can, for example, likewise be set via the control unit 116 (depending on the type of pump, this is done, for example, by setting a pivot angle, as already mentioned). In this way, via the control unit 116, via the setting or predefinition of the speed (via a frequency on the frequency converter) and the control volume, the variable-speed electrohydraulic pump 110 can be activated and operated such that it provides a specific volume flow.

[0026] By way of example, the machine 100 has two components 140 and 150, which are driven by means of or via the variable speed electrohydraulic pump 110. The component 140 is, for example, a dynamic working unit (for example a shovel arm) having a hydraulic cylinder 141. The component 150 is, for example, a traction drive with a hydraulic motor 151. Also provided is an input unit 160 designed as a joystick by means of which, by way of example, both the components 140 and the component 150 can be activated, for example by the joystick being moved to the left or right or forward or backward. It goes without saying that further input units can also be provided, for example an accelerator pedal for activating the component 150. Likewise, further components which are driven via the variable-speed electrohydraulic pump 110 can be provided.

[0027] In order then to be able to activate the components 140, 150 by means of the input unit 160, actuators 142, 152 formed as valves are provided, which can be actuated by a control signal S from the input unit 160 in order to supply the hydraulic cylinder 141 and the hydraulic motor 151 (as part of the components 140, 150) with hydraulic fluid 132 provided by the variable-speed electrohydraulic pump 110 and, for example, taken from a tank 130. It goes without saying that a plurality of valves can also be integrated in a valve block (it is precisely in mobile working machines that there are often many different hydraulically operated components, which can also be activated separately).

[0028] If one of the components 140, 150 is to be actuated or moved, an increase in load occurs and an increased volume flow is required from the pump 110 in order to compensate for the pressure dip. The control unit 116 then detects the control signal S, for example continuously, in order to be able to determine whether an increase in the volume flow is impending because of an actuation of the input unit 160.

[0029] FIG. 2 illustrates, schematically, a sequence of a method according to the disclosure in a preferred embodiment, such as can be carried out, for example, in the machine shown in FIG. 1.

[0030] Here, to begin with in an operating phase 200, for example idling, the variable-speed electrohydraulic pump is operated with a specific value for the speed n of the electric machine and for the control volume V.sub.s, so that a specific volume flow V is established. Here, the speed n is chosen to be (as far as possible) low, the control volume V.sub.s is relatively high, on the other hand, so that a high efficiency is achieved.

[0031] During this, according to step 210, the control signal (cf. FIG. 1) is monitored for control information I for an actuator (or else for a plurality of actuators). If this control information I then indicates an (impending) increase in the volume flow, since the input unit is actuated in order, for example, to move the dynamic working unit, the speed n is reduced and the control volume V.sub.s is increased (without delay) while the volume flow {dot over (V)} which is produced thereby more remains the same or unchanged (since the actuator has not yet reacted). The increase in the speed and the reduction in the control volume are therefore carried out in particular during a latency or dead time of the actuator.

[0032] Only after that, according to step 220, is the variable-speed electrohydraulic pump activated to increase the volume flow {dot over (V)}, for example by increasing the control volume. This can be done as a result of the actuation of the actuator, for example within the context of control which is carried out in any case. Because of a high speed but low control volume which are present during the increase in load which then has to be managed, the dynamics of the variable-speed electrohydraulic pump, that is to say the speed with which the volume flow can be increased—and therefore the dynamic working unit is moved or set moving—are considerably higher than without this previous adaptation of speed and control volume. The manipulated variable for the control is therefore preferably the speed of the pump.