Construction machine

Abstract

The present invention relates to a construction machine (1) comprising a first electric motor (2.1) and a second electric motor (2.2), a first inverter (3.1) and a second inverter (3.2), two independently exchangeable rechargeable batteries (4.1, 4.2), namely a first rechargeable battery (4.1) and a second rechargeable battery (4.2), and a common controller (5) suitable for controlling the first electric motor (2.1) and the second electric motor (2.2). The first electric motor (2.1) can be supplied with electrical current via the first inverter (3.1) by the first rechargeable battery (4.1). The second electric motor (2.2) can be supplied with electrical current via the second inverter (3.2) by the second rechargeable battery (4.2). The first electric motor (2.1) cannot be supplied with electrical current by the second rechargeable battery (4.1). The second electric motor (2.2) cannot be supplied with electrical power by the first removable battery (4.1).

Description

[0001] The present invention relates to a construction machine with an electric motor and a replaceable battery that supplies the electric motor with electrical power.

[0002] Such construction machines, which are typically mobile and can be operated wirelessly, are being used on more and more construction sites worldwide, replacing conventional gasoline- or diesel-powered construction machines in order to reduce or completely avoid local emissions of exhaust gases, CO2 and noise.

[0003] Particularly when such a construction machine is a relatively large soil compaction machine with a correspondingly high power requirement, the power storage is typically divided into several separate interchangeable batteries that can be replaced and recharged independently of one another in order to keep the weight and dimensions of the individual interchangeable batteries within limits and to avoid making their handling too cumbersome.

[0004] In construction machinery with two or more removable batteries, these are typically connected in parallel or in series. In both cases, the energy content of the individual removable batteries adds up to a total energy content of the power storage unit available to the construction machinery.

[0005] If the interchangeable batteries are connected in parallel, the discharge currents of the individual batteries add up to a maximum discharge current that can be drawn.

[0006] In a series connection, however, the discharge voltage (terminal voltages) of the individual batteries add up to a maximum discharge voltage that can be drawn.

[0007] In practice, connecting multiple removable batteries in series is often avoided because the resulting relatively high maximum system voltage would require extensive and costly safety precautions. For this reason, connecting removable batteries in parallel is often preferred.

[0008] In practice, it must be taken into account that the interchangeable batteries typically have different states of charge (SoC), different states of health (SoH) and (consequently) different terminal voltages and internal resistances.

[0009] This must be taken into account when connecting the replaceable batteries in series and especially in parallel in order to prevent uncontrolled current flows that are harmful to the service life of the batteries.

[0010] Against this background, with batteries connected in parallel, a battery management system that controls and regulates the batteries individually often initially discharges only the fuller battery, i.e., the one with the higher SoC, until the terminal voltages of the two parallel-connected batteries have equalized (the equalization phase). Only then is the parallel-connected spare battery with the initially lower SoC connected.

[0011] During this equalization phase, the maximum discharge current is limited by the maximum discharge current of a single battery. This maximum discharge current during the equalization phase typically also represents the general power limitation for normal operation, upon which the construction machine is designed and operated. Ultimately, it cannot be guaranteed that a higher discharge power can be provided for all operating conditions.

[0012] In this way, by connecting two similar interchangeable batteries in parallel, a doubling of the capacity and thus the running time can be achieved, but not a doubling of the available discharge current.

[0013] The German patent application DE 10 2017 121 177 A1 discloses a vibrating plate for soil compaction with two BLDC electric motors that can be supplied with power by at least one energy storage element.

[0014] WO 2022 265 556 A1, GB 2 604 349 A and DE 11 2021 007 871 T5 each describe an electrically powered soil compactor with two separate replaceable batteries.

[0015] DE 10 2021 130 987 A1 describes an electric drive system for a work machine with two independently controllable electric motors.

[0016] DE 10 2022 127 864 A1 discloses an electrically driven vibration generator with four electric motors, each carrying an unbalanced weight, for a soil compactor with a ground contact plate.

[0017] Based on this prior art, the object of the present invention is to provide a construction machine of the type mentioned at the outset which is characterized by improved practical suitability, in particular with regard to the provision of a higher discharge power or a higher discharge current while at the same time preserving the service life of the battery.

[0018] This object is achieved by the construction machine according to the invention according to claim 1 and its preferred embodiments according to claims 2 to 4.

[0019] The construction machine according to the invention comprises - a first and a second electric motor, - a first and a second inverter, suitable for converting direct current into alternating current, - two independently replaceable batteries, namely a first and a second battery, - a common control system suitable for controlling the first and second electric motors, wherein - the first electric motor can be supplied with electrical power via the first inverter by the first removable battery, and - the second electric motor can be supplied with electrical power via the second inverter using the second removable battery.

[0020] The invention is based on the finding that higher discharge powers can be achieved while simultaneously preserving the service life of the battery by connecting the interchangeable batteries neither in parallel nor in series, but by choosing a configuration in which each interchangeable battery supplies a separate electric motor with electrical energy via a separate inverter.

[0021] In this way, each removable battery can deliver its maximum discharge current (discharge rate, discharge power) to the construction machine without having to take a "weaker" battery into account. The maximum discharge power available to the construction machine at any given time of operation is thus the sum of the discharge powers of the individual removable batteries.

[0022] It is obvious that the invention can only be used if the construction machine has (at least) two consumers, in particular electric motors, which are to be supplied with electrical current.

[0023] If the construction machine has more than two electric motors (e.g. 3, 4, n), the same number (3, 4, n) of interchangeable batteries and inverters is advantageously provided according to the invention, so that in this configuration too it can be achieved that each interchangeable battery supplies a separate electric motor with electrical energy via a separate inverter.

[0024] According to the invention, the operation of the electric motors is controlled and / or synchronized via a common control system.

[0025] A synchronized operation of (at least) two electric motors as per specifications is particularly important when the construction machine is designed as a soil compactor and the electric motors each drive a separate unbalance exciter.

[0026] Such soil compactors are described in more detail, for example, in the applicant's subsequently published patent application DE 10 2023 114 869 B3. As explained therein, the precise, specified synchronization of the two electric motors with regard to their speed and phase separation (phase difference, phase offset) leads to a desired, specific superposition of the oscillating horizontal and vertical forces of the two unbalance exciters, whereby the soil compaction characteristics as well as the direction of travel and the travel speed of the soil compactor can be controlled. Such control or synchronization of the (at least) two electric motors can be achieved by the shared control system. Such a shared control system can be implemented, in particular, as part of one of the inverters or as separate hardware. The electric motors can be controlled directly by the control system or via the inverters.

[0027] The invention furthermore enables the interchangeable batteries to be protected and thus their service life to be extended, since different states of charge (SoC) and states of health (SoH) of the interchangeable batteries do not have a negative influence on the other interchangeable battery and the battery management can be individually adapted to the respective interchangeable battery.

[0028] In the following, some terms and features of the construction machine according to the invention will be explained in more detail: The formulation that an electric motor can be supplied with electrical current (via an inverter) by a removable battery expresses that a rotor and / or stator coil winding of the electric motor can be supplied with or flowed through with electrical current originating from the removable battery, so that the rotor of the electric motor is set in rotation.

[0029] The wording that a controller is suitable for controlling an electric motor expresses that the controller is capable of specifying, for example, the speed and / or torque of the electric motor.

[0030] According to the construction machine according to the invention - the first electric motor cannot be supplied with electrical power by the second removable battery, and - the second electric motor cannot be supplied with electrical power from the first removable battery.

[0031] Preferably, the first and the second electric motor can be controlled by the common control in such a way that they - with the same speed, and / or - rotate with a defined phase difference from each other.

[0032] The advantages according to the invention are particularly evident when the construction machine is designed as a soil compaction machine, in particular as a rammer, a roller or a vibrating plate, and in particular the first and the second electric motor each drive an unbalance exciter.

[0033] In the following, an embodiment of the invention is explained in more detail in comparison with typical solutions of the prior art. Fig. 1 and Fig. 2 shows a functional diagram of a construction machine according to the state of the art with two interchangeable batteries connected in parallel ( Fig. 1) and two interchangeable batteries connected in series ( Fig. 2), and Fig. 3 a functional diagram of a construction machine according to the invention.

[0034] The Fig. 1 and Fig. 2 each show a functional diagram of a construction machine 1 according to the prior art. The construction machines 1 each comprise a first electric motor 2.1 and a second electric motor 2.2, a first inverter 3.1 and a second inverter 3.2, two interchangeable batteries 4.1, 4.2, and a common controller 5.

[0035] Inverters 3.1, 3.2 are designed to convert direct current from the removable batteries 4.1, 4.2 into alternating current for operating the electric motors 2.1, 2.2. The common controller 5 is designed to control the electric motors 2.1, 2.2 (via inverters 3.1, 3.2).

[0036] According to Fig. 1, the two interchangeable batteries 4.1 and 4.2 are connected in parallel. The discharge current entering the inverters 3.1 and 3.2 is determined by adding the discharge currents of the two interchangeable batteries.

[0037] As already explained above, in practice only one of the two interchangeable batteries 4.1, 4.2, namely the one with the higher SoC, is discharged during the equalization phase, so that the discharge power supplied to the inverters 3.1, 3.2 and thus available to the construction machine 1 is limited by the discharge power of a single interchangeable battery.

[0038] According to Fig. 2, two removable batteries 4.1, 4.2 are connected in series. The discharge voltage applied to the inverters 3.1, 3.2 is calculated by adding the discharge voltages (terminal voltages) of the two removable batteries. The discharge current is largely limited by the internal resistances of the two removable batteries.

[0039] Fig.Figure 3 shows a functional diagram of a construction machine 1 according to the invention with two interchangeable batteries 4.1, 4.2, two inverters 3.1, 3.2, two electric motors 2.1, 2.2, and a common controller 5. The two interchangeable batteries 4.1, 4.2 can each supply a separate electric motor 2.1, 2.2 with electrical power via a separate inverter 3.1, 3.2. The first interchangeable battery 4.1 supplies the first electric motor 2.1 with power via the first inverter 3.1, and the second interchangeable battery 4.2 supplies the second electric motor 2.2 via the second inverter 3.2.

[0040] The common controller 5, which is suitable for controlling the first and second electric motors 2.1, 2.2 and synchronizing their speed and phase difference, can be supplied with power, for example, via the first inverter 3.1 by the first removable battery 4.1. However, the fact that the controller 5 is powered by the first removable battery 4.1 and controls the second electric motor 2.2 does not imply that the first removable battery 4.1 supplies the second electric motor 2.2 with power. This is because the current flowing through the stator and / or rotor coil winding of the second electric motor 2.2 originates from the second removable battery 4.2. List of reference symbols 1 construction machine 2.1 first electric motor 2.2 second electric motor 3 inverters 3.1 first inverter 3.2 second inverter 4.1 first removable battery 4.2 second removable battery 5 Control

Claims

[1] Construction machine (1) comprising - a first electric motor (2.1) and a second electric motor (2.2), - a first inverter (3.1) and a second inverter (3.2), each suitable for converting direct current into alternating current, - two independently replaceable batteries (4.1, 4.2), namely a first battery (4.1) and a second battery (4.2), - a common control (5) which is suitable for controlling the first electric motor (2.1) and the second electric motor (2.2), wherein - the first electric motor (2.1) can be supplied with electrical power via the first inverter (3.1) by the first replaceable battery (4.1), - the second electric motor (2.2) can be supplied with electrical power via the second inverter (3.2) by the second replaceable battery (4.2), - the first electric motor (2.1) cannot be supplied with electrical power by the second replaceable battery (4.1), and - the second electric motor (2.2) cannot be supplied with electrical power by the first replaceable battery (4.1). [2] Construction machine (1) according to claim 1, wherein the first electric motor (2.1) and the second electric motor (2.2) can be controlled by the common control (5) in such a way that they - with the same speed, and / or - rotate with a defined phase difference from each other. [3] Construction machine (1) according to one of the preceding claims, wherein the construction machine (1) is designed as a soil compaction machine, in particular as a rammer, a roller or a vibrating plate. [4] Construction machine (1) according to claim 3, wherein the first electric motor (2.1) and the second electric motor (2.2) each drive an unbalance exciter.

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