Drive unit for an industrial truck

Abstract

Drive unit for an industrial truck with • a reluctance machine (10) having a number n of separately energizable stator windings (L1, L2, L3), • a supply connection (16) to which an energy storage device can be connected, and • an electronic control system via which the stator windings (L1, L2, L3) can be connected to the supply connection (16), wherein • the electronic control system has a supply module and a selection module, • the supply module is connected between the supply connection (16) and a central node (18) and has a supply module semiconductor switching device whose switching state determines a voltage at the central node (18), • the selection module has a selection module semiconductor switching device for each of the separately energizable stator windings (L1, L2, L3), the switching state of which determines whether the stator winding (L1, L2, L3) assigned to the selection module semiconductor switching device is energized via the central node (18), and • the supply module semiconductor switching device comprises a first supply module semiconductor switch (M9) having a first end and a second end, and a second supply module semiconductor switch (M10) having a first end and a second end, wherein the first end of the first supply module semiconductor switch (M9) is connected to a ground connection, the second end of the first supply module semiconductor switch (M9) is connected to the first end of the second supply module semiconductor switch (M10), the second end of the second supply module semiconductor switch (M10) is connected to the supply connection (16), and the connection of the two supply module semiconductor switches (M9, M10) forms the central node (18).

Description

[0001] The invention relates to a drive unit for an industrial truck with a reluctance motor and an electronic control system. Reluctance motors with an electronic control system offer an alternative to the DC or asynchronous motors commonly used in electrically powered industrial trucks. They are characterized by their particularly simple design and great robustness. In conjunction with an electronic control system, four-quadrant operation is possible, i.e., operation in both directions of rotation, both as a drive motor and as a generator for recovering electrical energy.

[0002] Unlike magnetically excited machines, reluctance machines generate torque in a rotor through the so-called reluctance force. The rotor, made of a soft magnetic material, aligns itself in a magnetic field generated by current-carrying stator windings in such a way that the system exhibits minimal magnetic resistance. Such an arrangement with minimal magnetic resistance is particularly evident in rotational positions in which two poles of the stator and two poles of the rotor are aligned relative to each other in such a way that a ring is formed through which the magnetic flux is guided.

[0003] In order to generate a rotary motion for a mechanical drive or to generate electrical energy from a rotary motion, the stator windings must be connected to an electrical energy storage device in a suitable chronological sequence. Known electronic control devices for this purpose have four semiconductor switches for each separately energized stator winding for four-quadrant operation. MOSFET transistors or other power transistors can be used as semiconductor switches and connected in the form of an H-bridge. To control a reluctance machine with, for example, three separately energized stator windings corresponding to three phases, four such H-bridges are required, i.e., a total of twelve semiconductor switches.

[0004] The document DE 199 31 972 A1 describes a circuit arrangement for operating an electromagnetic actuator, which according to the embodiment of the Fig. 3 and Fig. 4 is a reluctance motor.

[0005] The US patent US 5 689 164 A describes a current supply to the windings of a reluctance motor in conjunction with resonant circuits connected in parallel to the individual coils.

[0006] The document GB 2 456 336A describes a circuit arrangement for connecting the coils of a starter motor in parallel or series.

[0007] The document DE 10 2012 211 043 A1 describes a device for charging and discharging an electrical device in a vehicle and discloses a drive unit for a vehicle, comprising: an electric motor having three stator windings, a supply connection to which an energy storage device can be connected, an electronic controller via which the stator windings can be connected to the supply connection, wherein the electronic controller has a supply module and a selection module, the supply module is connected between the supply connection and a central node and has a supply module switching device, the switching state of which determines a voltage at the central node, the selection module has a selection module semiconductor switching device for each of the stator windings, the switching state of which determines,how the stator winding associated with the selection module semiconductor switching device is energized via the central node, and the supply module switching device comprises a contactor connected to the supply terminal and the central node, and a switch connected to the central node and a resistor.

[0008] The document DE 10 2012 204 866 A1 describes a device for diagnosing a discharge circuit which is provided for discharging an electrically driven vehicle and discloses a drive unit for a vehicle which has the following: an electric motor which has three stator windings and can be designed as a reluctance machine, a supply connection to which an energy storage device can be connected, an electronic control via which the stator windings can be connected to the supply connection, wherein the electronic control has a supply module and a selection module, the supply module is connected between the supply connection and a central node and has a supply module switching device whose switching state determines a voltage at the central node, and the selection module has a selection module switching device for each of the stator windings, whose switching state determines,how the stator winding associated with the selection module switching device is energized via the central node, and the supply module switching device comprises a switch connected to the supply terminal and the central node, and a switch connected to the central node and a resistor.

[0009] The patent specification DE 10 2004 030 460 B3 describes a drive for a vehicle as a main drive or hybrid drive and discloses: an electric motor having three stator windings, a supply connection to which an energy storage device can be connected, an electronic control via which the stator windings can be connected to the supply connection, wherein the electronic control has a supply module and a selection module, the supply module is connected between the supply connection and a central node and has a supply module switching device whose switching state determines a voltage at the central node, the selection module has a selection module semiconductor switching device for each of the stator windings, the switching state of which determines how the stator winding assigned to the selection module semiconductor switching device is energized via the central node,and the supply module switching device comprises a relay connected to the supply terminal and a fuse connected to the central node, and a thyristor connected to the central node and a ground terminal.

[0010] Based on this, the object of the invention is to provide a drive unit for an industrial truck which is characterized by a particularly simple design.

[0011] This object is achieved by the drive unit having the features of claim 1. Advantageous embodiments are specified in the subsequent subclaims.

[0012] The drive unit is intended for an industrial truck and has the following features: • a reluctance machine having a number n of separately energizable stator windings, • a supply connection to which an energy storage device can be connected, • an electronic control system through which the stator windings can be connected to the supply terminal, whereby • the electronic control system has a supply module and a selection module, • the supply module is connected between the supply connection and a central node and has a supply module semiconductor switching device whose switching state determines a voltage at the central node, and • the selection module has a selection module semiconductor switching device for each of the separately energizable stator windings, the switching state of which determines whether the stator winding assigned to the selection module semiconductor switching device is energized via the central node, and • the supply module semiconductor switching device comprises a first supply module semiconductor switch having a first end and a second end, and a second supply module semiconductor switch having a first end and a second end, wherein the first end of the first supply module semiconductor switch is connected to a ground terminal, the second end of the first supply module semiconductor switch is connected to the first end of the second supply module semiconductor switch, the second end of the second semiconductor switch is connected to the supply terminal, and the connection of the two supply module semiconductor switches forms the central node.

[0013] The drive unit is particularly suitable for an electric drive of an industrial truck, but can also be used for any other drive of an industrial truck, in particular for a hydraulic unit.

[0014] The reluctance machine has a number of stator poles, each of which is assigned a stator winding. In principle, each of these stator windings can have two externally accessible terminals, allowing it to be energized separately. Typically, however, several stator windings are interconnected within the reluctance machine, so that the stator windings combined in this way can only be energized together. For example, the stator windings of two oppositely arranged stator poles are often connected in series and thus can only be energized together.

[0015] For example, the reluctance machine can have six stator poles, each with a stator winding. Two oppositely arranged stator windings are connected in series and can only be energized together. Such a reluctance machine has three separately energizable stator windings.

[0016] The reluctance machine also has a rotor with a number of rotor poles. This number can, in particular, be smaller than the number of stator poles. For example, many reluctance machines with six stator poles have four rotor poles and three separately energizable stator windings.

[0017] The supply connection is used to connect the drive unit to an electrical energy storage device, in particular a battery. Using an electronic control system, the supply connection can be connected to the stator windings of the reluctance machine in the desired manner to control the energy flow between the energy storage device and the reluctance machine.

[0018] In the invention, the electronic control unit comprises a supply module and a selection module. The supply module is located (relative to the energy flow) between the supply connection and a central node of the drive unit. It comprises a supply module semiconductor switching device whose switching state determines a voltage at the central node. For example, the central node can be connected to a positive connection of the energy storage device via the supply module, so that, possibly apart from voltage drops on the lines and elements of the electronic control unit, the same potential is present at the central node as at the positive connection of the energy storage device. In a different switching state of the supply module, the central node can, for example, be connected to ground potential.

[0019] The electronic control system also has a selection module that has a selection module semiconductor switching device for each of the separately energizable stator windings. The switching state of this selection module semiconductor switching device determines whether the stator winding assigned to this selection module semiconductor switching device is energized via the central node. The selection module thus uses the switching states of the associated selection module semiconductor switching devices to determine which of the separately energizable stator windings is connected to the central node at a specific time. At any given time, an exchange of electrical energy between the energy storage device and the reluctance machine via the central node and the supply module is only possible for those stator windings that can currently be energized via the central node by the selection module and its assigned selection module semiconductor switching device.

[0020] A special feature of the invention is the functional separation of the electronic control system into a supply module and a selection module. Unlike conventional electronic controls for reluctance machines, in which each individual, separately energizable stator winding is assigned an H-bridge via which the respective stator winding can be directly connected to an energy storage device, in the invention the supply module assumes part of the control function for all separately energizable stator windings simultaneously by specifying the voltage at the central node. This functionality therefore does not have to be set up separately for each separately energizable stator winding. Instead, a selection module is sufficient to supplement the supply module, with the aid of which the stator winding to be energized is essentially selected.This results in a simplification of the circuit design, particularly with regard to the number of semiconductor switches required.

[0021] In the invention, the supply module semiconductor switching device has two supply module semiconductor switches connected in series between the supply connection and a ground connection, wherein the connection of these two supply module semiconductor switches forms the central node. The two semiconductor switches thus form a half-bridge and, depending on the switching state, enable the central node to be set to the potential of the supply connection or the ground connection. Each of the semiconductor switches can have two ends, for example, a source and a drain connection in the case of a MOSFET transistor. The series connection is then configured as follows: The first end of the first semiconductor switch is connected to the ground connection. The second end of the first semiconductor switch is connected to the first end of the second semiconductor switch. This connection also forms the central node.The second end of the second semiconductor switch is connected to the supply terminal.

[0022] In one embodiment, the separately energizable stator windings are connected in series, and each of the separately energizable stator windings is bridged by the selection module semiconductor switching device assigned to it. Energizing an individual one of the separately energizable stator windings via the central node is then possible by keeping only the selection module semiconductor switching device assigned to this stator winding in an open / non-conducted state, while all other selection module semiconductor switching devices are closed / conducted. The current then flows via the central node, which is connected to one end of the series connection of the separately energizable stator windings, through all of the connected selection module semiconductor switching devices, and through the stator winding to be energized. Simultaneous energization of several of the separately energizable stator windings is also possible.Exactly those stator windings are excluded from the current flow which are bridged or short-circuited by the selection module semiconductor switching device assigned to them.

[0023] In an alternative embodiment, each of the separately energizable stator windings is connected in series with its associated selection module semiconductor switching device, and each of these series connections forms a branch of a star connection. This arrangement also allows individual or multiple stator windings to be selected for energization via the central node by switching through the selection module semiconductor switching devices associated with the respective stator windings.

[0024] In one embodiment, the star point of the star connection is connected to ground or to the central node. If the star point is connected to ground, the other ends of the series circuits forming each branch of the star connection can be connected to the central node. If the star point is connected to the central node, the other ends of the series circuits forming each branch can be connected to ground. In both cases, the relevant, separately energizable stator windings can be energized via the central node.

[0025] In one embodiment, each of the selection module semiconductor switching devices comprises two semiconductor switches connected in series. Together, the two series-connected semiconductor switches form a bidirectional switch that can block current flow in both directions. This enables four-quadrant operation.

[0026] In one embodiment, the reluctance machine has a housing from which exactly n+1 connections for the stator windings are led out. By externally wiring the reluctance machine with the selection module semiconductor switching devices assigned to the individual stator windings, both ends of each separately energized stator winding do not have to be led out of the housing of the reluctance machine. With a star connection of the stator windings, it is sufficient to lead the star point out of the housing as one connection and also the other ends of the individual stator windings. With a series connection of the separately energized stator windings, only one connection needs to be led out of the housing of the reluctance machine for each two interconnected ends of two stator windings. The remaining ends of the stator windings can be connected to each other within the housing.By reducing the number of connections for the stator windings, the design and assembly of the drive unit is simplified.

[0027] In one embodiment, the drive unit has an energy storage device connected to the supply connection. The energy storage device can be, for example, a battery or a high-capacity capacitor (e.g., an ultra-capacitor, a supercapacitor with a capacity of >= 100 F), but also another electrical energy storage device, such as a fuel cell.

[0028] In one embodiment, the supply module has a further supply connection, to which a further supply module semiconductor switching device and a further central node are assigned, wherein the switching state of the further supply module semiconductor switching device determines a voltage at the further central node. Via a supply module expanded in this way, the drive unit can be operated jointly with two preferably different energy storage devices, such as a battery and a high-capacity capacitor. The reluctance machine and the selection module can in particular be connected between the central node and the further central node. By suitable control of the supply module and the selection module, both motor and generator operation of the reluctance machine is then possible with each of the two energy storage devices.

[0029] In one embodiment, the additional supply module semiconductor switching device comprises two additional supply module semiconductor switches connected in series between the additional supply connection and a ground connection, with the connection of these two additional supply module semiconductor switches forming the additional central node. For an explanation, reference is made to the above statements regarding the correspondingly designed supply module semiconductor switching device.

[0030] In one embodiment, the drive unit has an additional energy storage device connected to the additional supply connection. The additional energy storage device can, in particular, be a high-capacity capacitor, as already explained above. Such a capacitor is preferably combined as an additional energy storage device with an energy storage device in the form of a battery connected to the supply connection. In this case, peak power can be absorbed or provided by the capacitor, while the battery is responsible for the continuous current draw or consumption.

[0031] In one embodiment, the electronic controller is designed to control the supply module semiconductor switching device, the additional supply module semiconductor switching device, and the selection module switching devices such that electrical energy is transported from the energy storage device to the additional energy storage device or vice versa. This possibility exists because the stator windings of the reluctance machine, due to their inductances, can store electrical energy that can be absorbed from the energy storage device and transferred to the additional energy storage device, or vice versa. In this case, the drive unit is operated as a bidirectional boost converter.

[0032] In one embodiment, the drive unit is combined with an industrial truck.

[0033] The invention is explained in more detail below with reference to exemplary embodiments illustrated in the figures. They show: Fig. 1 a circuit diagram of a particularly simple drive unit in a simplified representation, Fig. 2 a circuit diagram of another drive unit in which the selection module semiconductor switching devices bridge the series-connected, separately energizable stator windings, Fig. 3 a circuit diagram of another drive unit with a star connection.

[0034] The example of Fig. 1 is characterized by its particularly simple design, but is only suitable for relatively low power levels and only for single-quadrant operation. The drive unit comprises a reluctance machine 10 with a rotor 12 (indicated in the figure) and three separately energizable stator windings L1, L2, and L3. Furthermore, there is a battery 14 as an energy storage device, the negative terminal of which is connected to a supply terminal 16 of the drive unit. A central node 18 is also shown.

[0035] A supply module is connected between the supply terminal 16 and the central node 18, which has a supply module semiconductor switching device in the form of a single power transistor M10. When the semiconductor switch M10 is switched on, the potential of the supply terminal 16, i.e., the potential of the negative pole of the battery 14, is present at the central node 18. When the semiconductor switch M10 is switched off, the central node 18 is connected to the positive pole of the battery via the series-connected stator windings L1, L2, L3 and the internal resistance 20 of the battery 14. In this sense, the switching state of the semiconductor switch M10 determines the voltage at the central node 18.

[0036] As already mentioned, the separately energizable stator windings L1, L2 and L3 are connected in series via the two connecting lines 22, 24.

[0037] The drive unit selection module from Fig. 1 comprises three selection module semiconductor switching devices, each comprising a single semiconductor switch M11, M12, or M13. The selection module semiconductor switching device formed by the semiconductor switch M11 is assigned to the separately energizable stator winding L1. The selection module semiconductor switching device formed by the semiconductor switch M12 is assigned to the separately energizable stator winding L3. The selection module semiconductor switching device formed by the semiconductor switch M13 is assigned to the separately energizable stator winding L3.

[0038] Each of the aforementioned selection module semiconductor switching devices bridges the stator winding L1, L2, or L3 assigned to it. For example, to supply current to the separately energizable stator winding L2 via the central node 18, the semiconductor switch M12 can be blocked and the two semiconductor switches M11 and M13 can be switched on.

[0039] The diode 26 enables a current flow in the series circuit of the separately energizable stator windings L1, L2 and L3 independently of the battery 14, in particular in order to be able to reduce a magnetic field and / or to enable freewheeling of the reluctance machine 10.

[0040] The embodiment of the Fig. 2 also has a reluctance machine 10 with a rotor 12 and three separately energizable stator windings L1, L2, and L3. There is also an energy storage device in the form of a battery 14 and another energy storage device in the form of a high-capacity capacitor 28. The positive terminal of the battery 14 is connected to a supply terminal 16 of the drive unit. The positive terminal of the capacitor 28 is connected to another supply terminal 30.

[0041] The four semiconductor switches M7, M8, M9, and M10 form the drive unit's supply module. The semiconductor switches M9 and M10 form a supply module semiconductor switching device and are connected in series between the supply terminal 16 and a ground terminal 32. The connection point of these two semiconductor switches M9, M10 forms a central node 18.

[0042] The two semiconductor switches M7, M8 are also connected in series and form another supply module semiconductor switching device, which is connected in series between the additional supply terminal 30 and a ground terminal 32. The connection point of the two semiconductor switches M7, M8 forms another central node 34.

[0043] The drive unit's selection module has a total of six semiconductor switches, namely semiconductor switches M11, M21, M12, M22, M13, and M23. The two semiconductor switches M11 and M21 are connected in series and form a selection module semiconductor switching device that is assigned to and bridges the separately energized stator winding L1. The two semiconductor switches M12 and M22 are also connected in series and form a selection module semiconductor switching device that is assigned to and bridges the separately energized stator winding L2. The two semiconductor switches M13 and M23 are also connected in series and form a selection module semiconductor switching device that is assigned to and bridges the separately energized stator winding L3.

[0044] The separately energizable stator windings L1, L2 and L3 are connected in series via the connecting lines 22, 24.

[0045] With the drive unit from Fig. 2, a four-quadrant operation of the reluctance machine 10 is possible, as is energy transport from the battery 14 to the capacitor 28 and vice versa.

[0046] It can be seen that for the n=3 separately energizable stator windings L1, L2, and L3, there are only n+1 = 4 connections for the stator windings that must be led out of a housing of the reluctance machine 10. A first of these connections is designated 36, a second 38. The two connecting lines 22, 24 can be arranged within the housing of the reluctance machine 10, so that for each of the two connecting lines 22, only one connection for the stator windings needs to be led out of the housing, corresponding to the third connection 40 and the fourth connection 42.

[0047] The embodiment of the Fig. 3 does not differ from that of the Fig. 2. The elements concerned are provided with the same reference numerals as in the Fig. 2 and will not be explained again. The reluctance machine 10 with rotor 12 and three separately energizable stator windings L1, L2 and L3 is also different from the Fig. 2 unchanged.

[0048] Deviating from the embodiment of the Fig. 2, the separately energizable stator windings L1, L2, and L3 are each connected in series with their assigned selection module semiconductor switching devices: The two semiconductor switches M11, M21 form a selection module semiconductor switching device that is connected in series with the stator winding L1 and forms one branch of a star connection. The two semiconductor switches M12, M22 form a selection module semiconductor switching device that is assigned to the stator winding L2 and, connected in series with it, forms another branch of the star connection. The two semiconductor switches M13, M23 form a selection module semiconductor switching device that is assigned to the stator winding L3 and, connected in series with it, forms a third branch of the star connection. The star point 44 is connected to the three stator windings L1, L2, and L3 and is led out of the housing of the reluctance machine 10 as the first connection 36 for the stator windings.

[0049] The other ends of the stator windings L1, L2, L3 form the second terminal 38, the third terminal 40 and the fourth terminal 42 for the stator windings, which are led out of the housing of the reluctance machine 10.

[0050] By switching through the selection module semiconductor switching device assigned to a specific stator winding L1, L2, L3, the central node 18 is connected to the respective stator winding. The star point 44 is connected to the further central node 34. Depending on the switching states of the supply module and the selection module, a current flow in each of the stator windings is thus possible in both directions. The Fig. The circuit shown in Figure 3 enables four-quadrant operation of the reluctance machine 10.

Claims

[1] Drive unit for an industrial truck with • a reluctance machine (10) having a number n of separately energizable stator windings (L1, L2, L3), • a supply connection (16) to which an energy storage device can be connected, and • an electronic control system via which the stator windings (L1, L2, L3) can be connected to the supply connection (16), wherein • the electronic control system has a supply module and a selection module, • the supply module is connected between the supply connection (16) and a central node (18) and has a supply module semiconductor switching device whose switching state determines a voltage at the central node (18), • the selection module has a selection module semiconductor switching device for each of the separately energizable stator windings (L1, L2, L3), the switching state of which determines whether the stator winding (L1, L2, L3) assigned to the selection module semiconductor switching device is energized via the central node (18), and • the supply module semiconductor switching device comprises a first supply module semiconductor switch (M9) having a first end and a second end, and a second supply module semiconductor switch (M10) having a first end and a second end, wherein the first end of the first supply module semiconductor switch (M9) is connected to a ground connection, the second end of the first supply module semiconductor switch (M9) is connected to the first end of the second supply module semiconductor switch (M10), the second end of the second supply module semiconductor switch (M10) is connected to the supply connection (16), and the connection of the two supply module semiconductor switches (M9, M10) forms the central node (18). [2] Drive unit according to claim 1, characterized bythat the separately energizable stator windings (L1, L2, L3) are connected in series and each of the separately energizable stator windings (L1, L2, L3) is bridged by the semiconductor switching device assigned to it. [3] Drive unit according to claim 1, characterized by that each of the separately energizable stator windings (L1, L2, L3) is connected in series with the selection module semiconductor switching device assigned to it and each of these series circuits forms a branch of a star connection. [4] Drive unit according to claim 3, characterized by that the star point (44) of the star connection is connected to ground or to the central node point (16). [5] Drive unit according to one of claims 1 to 4, characterized by that each of the selection module semiconductor switching devices has two semiconductor switches (M11 / M21, M12 / M22, M13 / M23) connected in series. [6] Drive unit according to one of claims 1 to 5, characterized by that the reluctance machine (10) has a housing from which exactly n+1 connections (36, 38, 40, 429) for the stator windings (L1, L2, L3) are led out. [7] Drive unit according to one of claims 1 to 6, characterized by an energy storage device connected to the supply connection (16). [8] Drive unit according to one of claims 1 to 7, characterized by in that the supply module has a further supply connection (30) to which a further supply module semiconductor switching device and a further central node (34) are assigned, wherein the switching state of the further supply module semiconductor switching device determines a voltage at the further central node (34). [9] Drive unit according to claim 8, characterized byin that the further supply module semiconductor switching device has two further supply module semiconductor switches (M7, M8) connected in series between the further supply connection (34) and a ground connection (32), the connection of these two further supply module semiconductor switches (M7, M8) forming the further central node (34). [10] Drive unit according to claim 8 or 9, characterized by a further energy storage device which is connected to the further supply connection (30). [11] Drive unit according to one of claims 8 to 10, characterized by that the electronic control is designed to control the supply module semiconductor switching device, the further supply module semiconductor switching device and the selection module switching devices in such a way that electrical energy is transported from the energy storage device to the further energy storage device or vice versa. [12] Industrial truck with a drive unit according to one of claims 1 to 11.

Images