Mobile machine tool

Abstract

The invention discloses a mobile machine tool having an electric motor and a controller, the electric motor having an integer number of stator windings, characterized in that the electric motor contains the same number of contacts as stator windings, which contacts are connected alternately in a ring circuit, each contact being individually electrically connected to a connection of the controller which is assigned to said contact, and the controller being configured to apply electrical current in phase in pairs to two contacts located opposite one another in the ring circuit.

Description

[0001] 2021 ID00176

[0002] Hilti Aktiengesellschaft in Schaan

[0003] Principality of Liechtenstein

[0004] Mobile machine tool

[0005] AREA OF INVENTION

[0006] The present invention relates to a mobile machine tool. The machine tool has an electric motor and a control unit. The electric motor has an integer number of stator windings.

[0007] In machine tools of the type mentioned above, a rotating magnetic field can be generated by applying electric current to the stator windings in a known manner in order to exert a torque on a rotor in order to rotate the rotor in order to drive a tool of the machine tool.

[0008] One example of this is the double-delta connection shown in Fig. 5. In this connection, a stator has three contacts A, B, and C. Two stator windings are connected in parallel between each pair of contacts. These parallel stator windings are arranged opposite each other within the stator with respect to a rotor axis of the electric motor. This results in a reduction ratio of 1:2 (i.e., a slower speed) between the rotation of an electrical phase and the rotation of a rotor around the rotor axis. Conversely, a correspondingly high torque is achieved. Each of the three contacts is connected to a terminal of the control unit via a separate cable.

[0009] If you want to increase the deliverable torque, you need to increase the current, which would require a larger cable cross-section. However, for manufacturing reasons, it is either impossible or extremely difficult to solder even thicker cables than before to a control unit. This would mean that with current electric motors for mobile machine tools, a different type of connection between the cable and the terminal would have to be used. 20211 DO0176

[0010] - 2 -

[0011] Against this background, one object of the present invention is to provide an improved mobile machine tool.

[0012] REVELATION OF THE INVENTION

[0013] Accordingly, a mobile machine tool is proposed. The proposed mobile machine tool has an electric motor and a control unit. The electric motor has an integer number of stator windings. Furthermore, the electric motor has the same number of contacts as stator windings. The contacts and stator windings are alternately connected in a ring circuit. Each contact is individually electrically connected to a terminal of the control unit, with the respective terminal assigned to that contact. The control unit is configured to supply current in phase to any pair of contacts opposite each other in the ring circuit.

[0014] A stator winding is preferably formed by an insulated wire wound around a stator core, stator core section, or the like. Both ends of the wire are electrically connected to a contact. By applying different voltages to the two ends of the wire, a current is induced through the stator winding, which, together with the winding, generates a magnetic field. The fact that the windings are connected in a ring circuit means that the stator windings and contacts alternate. In other words, the ring circuit forms a closed loop, with each stator winding followed by a contact and each contact followed by a stator winding along the loop.

[0015] The proposed ring circuit therefore has twice as many contacts as the double-delta circuit described at the beginning. By connecting each contact individually to a terminal of the control unit, the conductor cross-sectional area from the control unit to the stator windings can be effectively doubled. Since the stator windings opposite each other in the ring circuit can be energized in pairs, an even higher torque can be achieved, as described at the beginning. Therefore, the proposed mobile machine tool is superior to previously known mobile 20211 DO0176

[0016] - 3 -

[0017] Machine tools improved. The term "opposite in the ring circuit" is ambiguous: on the one hand, the corresponding contacts or stator windings are opposite each other in the circuit diagram, on the other hand, the corresponding contacts or stator windings are spatially opposite each other.

[0018] The control unit may be configured to apply different phases to different contact pairs. In other words, the control unit may be configured to apply the same electrical phase to the contacts within each contact pair, while the contact pairs themselves are applied different phases to each other. This allows for particularly precise control of the rotor's movement.

[0019] It's possible that in the control unit, the two terminals assigned to each contact pair are connected by a conductor. This is a particularly simple and robust way to supply a contact pair with the same phase. For example, the terminals can be formed on a circuit board, with the conductors forming traces on or within the board.

[0020] The control unit may have a switching element, particularly a MOSFET switching element, assigned to each terminal and connected to supply electrical current to the respective terminal. Preferably, the terminals can be supplied with electrical current independently of each other. By allowing each terminal to be supplied with current via a switching element (preferably independently), the control of the electric motor can be particularly variable. For example, different speeds can be achieved, and / or energy-saving modes can be implemented.

[0021] Each contact may be configured as a separate busbar, which contacts one end of each conductor from both stator windings connected to that contact. Such a busbar could, for example, consist of a contact section for connecting a cable, two conductor connection sections for each connecting one conductor of a stator winding, and one or two busbar sections for connecting the 20211 DO0176

[0022] - 4 -

[0023] The contact section consists of the conductor connection sections. In combination with the ring circuit, this results in particularly simple and space-saving busbars, which ensure an efficient distribution of the electrical current from each contact to the two associated stator windings.

[0024] The connections may be distributed across at least two spatially separate connection areas of the control unit. This is a particularly important option because it allows for a more efficient and advantageous distribution of the wiring. In a preferred configuration, there are two connection areas, each with exactly one connection for each contact pair. This allows, for example, for planning the cable routing to improve installation and / or maintenance. It also allows for planning the cable routing to improve airflow. Furthermore, the connection areas can be distributed to dissipate heat during soldering.

[0025] It is possible that at least two connection areas are located on the side of the control unit facing the stator, with a heat sink of the control unit situated between the two connection areas. Therefore, an airflow may be directed between the cables and over the heat sink.

[0026] The cooler may be located in line with the rotor axis of the electric motor. This represents a particularly advantageous relative arrangement for utilizing the cooling airflow through the electric motor to cool the control unit.

[0027] The electric motor may have a fan located axially along the rotor axis between the stator windings and the control unit. This proximity allows for a particularly strong airflow to be generated, which also helps cool the control unit.

[0028] It is possible that a cable is soldered to each terminal, suitable or configured to connect the terminal to the respective contact. 2021 IDO0176

[0029] - 5 -

[0030] Other possible implementations of the invention also include those not explicitly mentioned.

[0031] Combinations of features or embodiments described previously or subsequently with regard to the exemplary embodiments. In doing so, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0032] 20211 DO0176

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[0034] Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the exemplary embodiments of the invention described below. The invention will be explained in more detail below with reference to preferred embodiments and the accompanying figures.

[0035] BRIEF DESCRIPTION OF THE FIGURES

[0036] Fig. 1 schematically shows a mobile machine tool according to one embodiment of the invention;

[0037] Fig. 2 schematically shows a perspective view of an electric motor and a control unit of the mobile machine tool, which are interconnected according to the embodiment of the invention;

[0038] Fig. 3 shows a schematic and perspective-figurative representation of a ring circuit in which six stator windings and six contacts alternate, the contacts being designed as busbars, according to the embodiment of the invention;

[0039] Fig. 4 schematically shows the ring circuit of Fig. 3 in circuit diagram representation, according to the embodiment of the invention; and

[0040] Fig. 5 schematically shows a double delta circuit in circuit diagram representation according to a prior art.

[0041] 20211 DO0176

[0042] - 7 -

[0043] In the figures, identical or functionally equivalent elements have been given the same reference symbols, unless otherwise indicated.

[0044] Figure 1 shows a mobile machine tool 1. The machine tool 1 is, by way of example, a hand-held machine tool, more precisely a drilling machine. Other preferred embodiments include a grinding machine or a sawing machine.

[0045] The machine tool 1 has a tool holder 2 for holding a tool 3. The tool 3 can be rotated via the tool holder 2 by a rotor 4 of an electric motor 5.

[0046] The electric motor 5, for example, is a brushless AC motor. It has a stator 6 which can be supplied with an electric current to generate a torque between the stator 6 and the rotor 4.

[0047] The rotor 4 and the tool holder 2 are rotationally coupled with a reduction gear 7, which can be switched or not switched.

[0048] The tool holder 2, the electric motor 5, the reduction gear 7, a receptacle 8 for a replaceable accumulator 9, at least one actuating element 10 and a control unit 11 are mounted by a housing 12 and functionally interconnected in the usual manner. The actuating element 10 is preferably a push button.

[0049] Machine tool 1 can be operated wirelessly. Battery 9 contains lithium.

[0050] The machine tool 1 is designed as a portable device. It weighs between 0.5 and 15 kg, and generally less than 25 kg.

[0051] The control device includes, for example, a Hall sensor 13, which is designed and arranged to detect a rotation angle and angular velocity of the rotor 4 relative to the housing 12. 20211 DO0176

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[0053] The tool holder 2 has a radially outwardly arranged handle 14, which is part of the tool holder 2. From the perspective of the electric motor 5, a spindle 15 is connected downstream of the reduction gear 7, which is suitable for transmitting rotary power to the tool holder 2.

[0054] By twisting the handle 14 relative to the spindle 15, a (not shown) chuck of the tool holder 2 can be opened and / or closed.

[0055] The joint structure of the electric motor 5 and the control unit 11 will now be described in more detail with reference to Figs. 2 to 4.

[0056] The stator 6, for example, has 6 stator windings W1-W6. The stator windings W1-W6 are connected in a ring circuit 16, with a contact A1, A2, B1, B2, C1, O2 arranged and connected between each pair of windings W1-W6. The ring circuit 16 can be described as a series circuit closed into a ring. The ring circuit 16 is shown schematically in Fig. 3 and as a circuit diagram in Fig. 4.

[0057] Contacts A1-02 are configured as busbars 17. Each busbar 17 has a contact section 18, two conductor connection sections 19, and a connecting section 20 that connects the two conductor connection sections 19 to the contact section 18. Each conductor connection section 19 holds one end 21 of a conductor, which forms the respective winding W1-W6.

[0058] As can be seen in Fig. 2, the control unit 11 has a circuit board design. On a circuit board 22, three terminals 24 are arranged and interconnected in each of two spatially separated connection areas 23. A heat sink 25 is located between the connection areas 23, which is thermally coupled to MOSFET switching elements. The MOSFET switching elements are interconnected to allow individual control and / or regulation of the current and voltage at each terminal 24. The heat sink 25 is a 20211 DO0176

[0059] - 9 - preferred cooler design. For example, further active and / or passive components are installed on circuit board 22, such as a set of battery contacts 26.

[0060] Each of the contacts A1 - C2 is electrically connected to an assigned terminal 24 by means of a single cable 27.

[0061] The MOSFET switching elements of the circuit board 22 are designed to apply an individually adjustable voltage profile to each terminal 24.

[0062] In the first operating mode, contact pair A1, A2 is energized with a first phase, contact pair B1, B2 with a second phase, and contact pair C1, C2 with a third phase. The phases are offset by 120°. Thus, in the first operating mode, a slow rotation of rotor 4 with high torque is achieved.

[0063] In a second operating mode, contact A1 is energized with a first phase, contact B2 with a second phase, and contact C1 with a third phase. The phases are also offset by 120°. Thus, in the second operating mode, two stator windings W1–W6 are simultaneously energized. This results in a faster rotation of rotor 4, albeit with lower torque.

[0064] Figure 2 does not show a rotor 4 or the rotor-mounted fan coupled to it. The rotor 4 runs concentrically within the stator 6. The fan is located between the stator 6 and the heat sink 25. Thus, during operation, the fan generates an airflow to cool the heat sink 25 and the stator 6. This improves the efficiency of the cooled components.

[0065] Although the present invention has been described with reference to exemplary embodiments, it can be modified in many ways. 20211 DO0176

[0066] - IQ -

[0067] REFERENCE MARK LIST

[0068] 1 machine tool

[0069] 2 Tool holder

[0070] 3 tools

[0071] 4 Rotor

[0072] 5 electric motor

[0073] 6 Stator

[0074] 7 reduction gears

[0075] 8 slots for a replaceable battery

[0076] 9 Accumulator

[0077] 10 Actuating elements

[0078] 11 Control unit

[0079] 12 cases

[0080] 13 Hall sensor

[0081] 14 handle

[0082] 15 spindles

[0083] 16 ring circuit

[0084] 17 busbar

[0085] 18 Contact section

[0086] 19 conductor connection section

[0087] 20 Connecting section

[0088] 21 End of a conductor of a winding

[0089] 22 circuit boards

[0090] 23 Connection area

[0091] 24 connection

[0092] 25 heat sinks

[0093] 26 Battery contact 20211 DO0176

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[0095] 27 cables

[0096] A1, A2 contacts, contact pair

[0097] B1, B2 contacts, contact pair

[0098] C1, C2 contacts, contact pair W1-W6 stator winding

Claims

20211 DO0176 - 12 - PATENT CLAIMS 1. Mobile machine tool (1) comprising an electric motor (5) and a control unit (11), wherein the electric motor (5) has an integer number of stator windings (W1 - W6), characterized in that the electric motor (11) has the same number of contacts (A1, A2, B1, B2, C1, C2) as stator windings (W1 - W6), which are alternately connected in a ring circuit (16), wherein each contact (A1, A2, B1, B2, C1, C2) is individually electrically connected to a terminal (24) of the control unit (11) assigned to that contact (A1, A2, B1, B2, C1, C2), and wherein the control unit (11) is configured to supply current in phase to pairs of opposite contacts (A1, A2; B1, B2; C1, C2) in the ring circuit (16). to impose.

2. Mobile machine tool according to claim 1, characterized in that the control unit (11) is configured to apply different phases to different contact pairs (A1 , A2; B1 , B2; C1 , C2).

3. Mobile machine tool according to one of the preceding claims, characterized in that in the control unit (11) the two respective connections (24) which are assigned to each contact pair (A1 , A2; B1 , B2; C1 , C2) are connected to a conductor.

4. Mobile machine tool according to one of the preceding claims, characterized in that in the control unit (11) a switching element, in particular a MOSFET switching element, is assigned to each terminal and is connected to actuate the respective terminal.

5. Mobile machine tool according to one of the preceding claims, characterized in that each contact (A1, A2; B1, B2; C1, C2) is designed as a respective busbar (17), each of which connects one end (21) of a respective conductor of both 20211 DO0176 - 13 - contacted with this contact (A1 , A2; B1 , B2; C1 , C2) stator windings (W1 - W6) connected.

6. Mobile machine tool according to one of the preceding claims, characterized in that the connections (24) are distributed on at least two spatially separate connection areas (23) of the control unit (11).

7. Mobile machine tool according to claim 6, characterized in that the at least two connection areas (23) are located on a side of the control unit (11) facing the stator (6), wherein a cooler (25) of the control unit (11) is located between the two connection areas (23).

8. Mobile machine tool according to claim 7, characterized in that the cooler (25) is located in extension of a rotor axis of the electric motor (5).

9. Mobile machine tool according to claim 7 or 8, characterized in that the electric motor (5) has a fan which is located axially along the rotor axis or a rotor axis of the electric motor (5) between the stator windings (W1 - W6) and the control unit (11).

10. Mobile machine tool according to one of the preceding claims, characterized in that a cable (27) for connecting the connection (24) to the respective contact (A1 , A2; B1 , B2; C1 , C2) is soldered to each connection (24).

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