Control circuit for sensing a rotational position of an operating element of a hand-held tool, and hand-held tool having such a control circuit

Abstract

The invention relates to a control circuit (1) for sensing a rotational position of an operating element (30) of an electrically operated hand-held tool, which operating element can be rotated about a fixed axis of rotation (R), the control circuit comprising: two magnetic field sensors (21, 22) for sensing a magnetic field; and a magnet (31) which can be arranged on the operating element (30) and can be rotated from a starting point (11) to an end point (12) along an actuation path (10) or freely along the actuation path (10) about the axis of rotation (R), wherein the magnetic field sensors (21, 22) are offset to one another along the actuation path (10) and are designed to each determine, from its own measured field intensity of the magnetic field of the magnet (31), the rotational position of the magnet (31) about the axis of rotation (R) and / or to each transmit its own measured field intensity of the magnetic field of the magnet (31) to an evaluation device (23) which is designed to determine the rotational position of the magnet (31) about the axis of rotation (R).

Description

[0001] Marquardt GmbH

[0002] P 592 PCT KN

[0003] Control circuit for detecting the rotational position of an operating element of a hand tool and hand tool with such a control circuit

[0004] Description:

[0005] The invention relates to a control circuit for detecting the rotational position of a control element of an electrically operated hand tool, which is rotatable about a rotational axis, in particular a fixed axis, and to a hand tool with such a control circuit. Numerous methods for detecting the rotational position of a control element are known in the prior art. For example, a rotary potentiometer, a wiper rotating over contact surfaces, or spring-loaded metallic contact elements can be used, which establish an electrical contact at predetermined switching positions.For hand tools, a cost-effective solution is often used which is based on two steel balls pushed apart by a spring, which are guided along a disc spring and create a conductive contact between the conductive disc spring and an adjacent contact surface on a circuit board at predetermined detent positions formed by the disc spring.

[0006] However, this results in a mechanically complex design, and the suspension is also susceptible to vibration, so that the steel balls may not make electrical contact at the intended detent positions, or may not make a lasting electrical contact.

[0007] Document US 10,414,033 B2 also discloses a control circuit that can be used to set an operating mode. The control circuit disclosed in this document is based on the use of several magnets and a magnetic field sensor, which are moved relative to each other along a straight line. However, the design disclosed there is not always optimal for rotary switches, such as those often used in hand tools to reduce installation space and facilitate easy operation by a single user.

[0008] The invention is therefore based on the objective of overcoming the aforementioned disadvantages and providing a control circuit with which the rotational position of a control element rotatable around a rotational axis can be detected in a simple and cost-effective manner and at the same time in a fault-resistant manner even in the presence of vibration and other external influences.

[0009] This problem is solved by the combination of features according to claim 1.

[0010] According to the invention, a control circuit is therefore used to detect a

[0011] A rotational position of a control element of an electrically operated hand tool, rotatable about a rotational axis, is proposed. The control element allows, for example, the setting or changing of an operating mode or the direction of rotation of the hand tool's motor. For this purpose, the control circuit comprises two, and in particular exactly two, magnetic field sensors for detecting a magnetic field, as well as one, and in particular exactly one, magnet, which can be arranged on the control element and rotated from a starting point to an endpoint along an actuation path or freely about the rotational axis, so that the control circuit can preferably be designed as a rotary switch via the rotatable control element. The magnetic field sensors are offset from each other along the...The magnets are arranged on, along, or adjacent to the actuation path, whereby the magnetic field generated by the magnet can be detected by the two magnetic field sensors as the magnet moves along the actuation path, with the field strength depending on the distance of the magnet from the respective magnetic field sensor. According to the invention, the magnetic field sensors are each configured to determine the rotational position of the magnet about the axis of rotation from the measured field strength of the magnet's magnetic field. In a simple embodiment, for example, a threshold value or range of values ​​for a respective rotational position can be stored in the magnetic field sensors, so that it can be recognized that the magnet has reached one of the predetermined rotational positions or the predetermined rotational position when the field strength is within the range of values ​​or exceeds the threshold value.The magnetic field sensors can be magnetic field or Hall switches with a predetermined switching hysteresis. Alternatively or additionally, the magnetic field sensors can be configured to transmit the measured field strength of the magnet's magnetic field to an evaluation unit of the control circuit. This evaluation unit is designed to determine the magnet's rotational position around its axis of rotation from the two measured field strengths of the magnet's magnetic field, and, if necessary, a known relative position of the magnetic field sensors to each other, as well as, if applicable, the known actuation path and its relative position to the magnetic field sensors.For this purpose, a function can be stored in the evaluation unit, for example, which has the two field strengths detected by the magnetic field sensors as variables and delivers as a result a position along the actuation path, for example also in the form of a rotation angle around the rotation axis.

[0012] If only two rotation positions are to be recorded anyway, a function can be switched depending on the recorded rotation positions, for example by the evaluation unit or by the magnetic field sensors themselves.

[0013] If the evaluation unit is designed to determine the rotational position, it or a higher-level control unit can perform a switching or control of a function depending on the rotational position. For example, the speed of a motor can be set or specified between a minimum and a maximum value depending on the rotational position.

[0014] Since the detection of the rotational position does not require a spring bearing or a mechanical interaction of components, the control circuit proposed according to the invention is extremely fault-tolerant with regard to vibrations and, for example, contamination, so that the rotational position can be reliably detected even under unfavorable environmental conditions.

[0015] According to an advantageous embodiment, in which essentially only two rotational positions, and thus three and preferably four switching states, are to be detected, the magnetic field sensors are each designed as magnetic field switches, and in particular as Hall effect switches. Furthermore, the magnetic field sensors or switches are configured to generate a switching signal, and preferably only a switching signal, when the magnet is in a rotational position along the actuation path in which it has a minimum distance to the respective magnetic field sensor. A tolerance can be taken into account here, so that the respective magnetic field sensor generates a switching signal when the magnet is within a predetermined range around the rotational position in which it has a minimum distance to the respective magnetic field sensor or switch.

[0016] Building on this, Hall effect switches with predetermined switching hysteresis can be used as the two magnetic field sensors, which, due to their respective switching hysteresis and relative positioning, form an overlapping area between them. If the magnet is located exclusively within the area of ​​the first magnetic field sensor, only this sensor is activated, and a first switching state, for example, "clockwise rotation," is present. If the magnet is located exclusively within the area of ​​the second magnetic field sensor, only this sensor is activated, and a second switching state, for example, "counterclockwise rotation," is present. If the magnet is located along the actuation path between the two magnetic field sensors in the overlapping area, both magnetic field sensors are activated, and a third switching state, for example, "off" or "do not rotate," is present.

[0017] Furthermore, it may be additionally provided that a fourth switching state exists when none of the magnetic field sensors are actuated, i.e., the magnet is located along the actuation path outside the exclusive areas and the overlap area of ​​the magnetic field sensors.

[0018] If switching states are possible in which none of the magnetic field sensors are activated, a stop and / or an additional evaluation unit can be used to distinguish between a fourth and fifth switching state. If a stop is provided along the actuation path outside the overlap area and outside the exclusive areas, which blocks the free rotation of the magnet along the actuation path, the evaluation unit can detect which magnetic field sensor was activated before no magnetic field sensor was activated. If initially only the first magnetic field sensor was activated and immediately afterwards no magnetic field sensor was activated, a fourth switching state exists. If initially only the second magnetic field sensor was activated and immediately afterwards no magnetic field sensor was activated, a fifth switching state exists.

[0019] Furthermore, the rotatable control element can also be part of the control circuit, which in this case can also be referred to as a control device. In such a variant, the control circuit is provided to also include the control element rotatable about the axis of rotation, with the magnet being embedded in and / or fixed to the control element.

[0020] The control element preferably has an end face facing the magnetic field sensors, wherein the magnet is fixed to the end face, in particular offset to the axis of rotation and lying on the actuation path, or is embedded in the control element and / or is fixed in the control element forming part of the end face.

[0021] To make the control circuit interference-resistant, it may also be provided that a shielding element, in particular a metallic one, is provided on a side of the magnetic field sensors facing away from the magnet and / or on a side of the magnet facing away from the magnetic field sensors, which is designed to block a magnetic field not generated by the magnet and to shield the magnetic field of the magnet acting on the magnetic field sensors from interference.

[0022] Such a shielding element can, for example, be integrated into the control element as a film, or the control element itself can be made of a shielding material, so that the control element integrally forms the shielding element.

[0023] Furthermore, the control circuit can include a circuit carrier, which is in particular a printed circuit board. The magnetic field sensors are arranged and fixed on the circuit carrier in a predetermined position and relative to each other.

[0024] If the rotatable control element is part of the invention, at least one detent element can be fixed to it or be integrally formed by the control element. Preferably, two opposing detent elements are provided, each of which in particular has a spring section extending parallel to the axis of rotation and a subsequent detent section extending orthogonally to and away from the axis of rotation.

[0025] In this way, at least one locking element can fulfill several functions.

[0026] It can be provided that at least one locking element is designed to hold the operating element concentric with the axis of rotation relative to the circuit carrier and rotatable around the axis of rotation. For this purpose, the at least one locking element can, for example, engage as a counter-body in a circular guide track arranged on the circuit carrier.

[0027] Alternatively, at least one detent element can be designed to hold the control element along the axis of rotation at a predetermined distance from the circuit carrier, which can also be achieved by such a counterbody if it forms two and preferably also annular stops in the axial direction, i.e., parallel to the axis of rotation, so that the control element detented into the counterbody is held in its axial position by the stops.

[0028] In addition, at least one locking element can be designed to engage in a corresponding counterbody at at least one predetermined locking position along the actuation path by a predetermined force and in a way that is haptically perceptible to an operator.

[0029] For this purpose, the locking element or the locking section of the locking element can, for example, be convex and the counter body at the locking positions can be concave corresponding to the locking section, whereby the force required to release the locking mechanism can be predetermined from the convex and corresponding concave shape.

[0030] Preferably, a multitude of uniformly arranged detent positions or detent positions provided only at predetermined switching positions are formed on the counter body, so that the operator can haptically perceive a detent pattern or predetermined detent points, which may serve as switching points, during rotation.

[0031] If a limited number of switching states are provided, each detent position can correspond to exactly one switching state. For example, three detent positions can be provided, each corresponding to exactly one switching state, and an additional switching state may also be provided.

[0032] For example, a first detent position can be selected such that the magnet lies exclusively within the area of ​​the first magnetic field sensor, which is designed as a Hall effect switch, thereby actuating it and triggering the "clockwise" switching state. Furthermore, a second detent position can be selected such that the magnet lies exclusively within the area of ​​the second magnetic field sensor, which is designed as a Hall effect switch, thereby actuating it and triggering the "counterclockwise" switching state. Finally, a third detent position can be selected such that the magnet lies in an overlapping area between the two magnetic field sensors, which are each actuated thereby, triggering the "off" or "no rotation" switching state.

[0033] The aforementioned fourth switching state, in which none of the magnetic field sensors are actuated, can also be assigned a detent position, although preferably no detent position is assigned to it. Instead, stops can also be provided that block the magnet from rotating into the fourth switching state.

[0034] Furthermore, a circumferential track extending around the axis of rotation can be provided in the counterbody, and in particular on a side facing away from the magnetic field sensors. This track forms two stops in the circumferential direction, such that the actuation path extends along the track between the stops. The stops are designed to limit the rotation of the control element around the axis of rotation. Correspondingly, at least one counter-stop can be provided on the control element, which is designed to be guided along the track and to engage the stops.

[0035] Starting with the use of a circuit carrier, corresponding contact surfaces for the magnetic field sensors can be formed on the circuit carrier. The magnetic field sensors are designed as surface-mount devices (SMDs) and are fixed and electrically connected to the circuit carrier via these contact surfaces. This not only reduces costs but also minimizes the influence of vibrations.

[0036] The magnet is preferably a ferrite magnet, which may additionally or alternatively be sintered.

[0037] A further aspect of the invention relates to an electrically operated hand tool with an actuator and a control circuit according to one of the preceding claims, wherein the actuator is controlled by the magnetic field sensors or a respective output signal of the magnetic field sensors or, if present, the evaluation device or an output signal of the evaluation device.

[0038] The features disclosed above can be combined in any way, provided that this is technically possible and they do not contradict each other.

[0039] Other advantageous embodiments of the invention are characterized in the dependent claims or are described in more detail below together with the description of the preferred embodiment of the invention with reference to the figures. The figures show:

[0040] Fig. 1 shows a control circuit;

[0041] Fig. 2 shows a control element with a magnet embedded in it.

[0042] The figures are schematic examples. Identical reference symbols in the figures indicate identical functional and / or structural features.

[0043] Figure 1 shows a variant of a control circuit 1 according to the invention, wherein a magnet 31, as shown in Figure 2 and which can be arranged on a control element 30, can be rotated by an operator along an actuation path 10 about the axis of rotation R. The rotation can be free, i.e., not limited by a stop, so that the magnet 31 can be rotated any number of times and in any direction about the axis of rotation R.

[0044] Alternatively, a stop can also be provided, for example, between the magnetic field sensors 21, 22 mentioned below, so that the magnet 31 or the control element 30 can only be rotated from the starting position 11 around the axis of rotation R to the end position 12, whereby the rotation can take place via the smaller arc segment or via the larger arc segment of the actuation path 10, depending on the positioning of the stop or the positioning of several stops.

[0045] Along and immediately adjacent to the actuation path 10, two magnetic field sensors 21, 22 are arranged on a circuit carrier 20, wherein the magnetic field sensors 21, 22 are each fixed in a predetermined position on the circuit carrier 20 and thus in a predetermined relative position to each other.

[0046] According to a simple variant, the magnetic field sensors 21, 22 are each Hall effect-based magnetic field switches or Hall switches, which are set to trigger as soon as they measure a magnetic field strength or field strength at which the magnet 31 directly overlaps with the respective magnetic field sensor 21, 22.

[0047] If magnet 31 is in the starting position 11 and thus overlaps with the first magnetic field sensor 21, the first magnetic field sensor 21 detects a first rotation position 2. If magnet 31 is rotated around the rotation axis R to the end position 12 and thus overlaps with the second magnetic field sensor 22, the second magnetic field sensor 22 detects a second rotation position 3 of magnet 31. In this case, the magnetic field sensors 21 and 22 can each generate a corresponding switching signal or switching state, so that no additional evaluation unit 23 is required.

[0048] If the magnet 31 is neither at the start position 11 nor at the end position 12, so that none of the magnetic field sensors 21 , 22 generates a switching signal, it can be deduced that the magnet 31 is at an indeterminate rotational position between start and end point 11 , 12.

[0049] Starting from the representation in Figure 1, it is also possible to use Hall switches as magnetic field sensors 21, 22, which, due to their respective predetermined switching hysteresis along the actuation path 10, form an overlapping area between them in addition to their respective exclusive ranges. In this overlapping area, both the first magnetic field sensor 21 and the second magnetic field sensor 22 are actuated. This allows four switching states to be detected: in the first switching state, only the first magnetic field sensor 21 is actuated; in the second switching state, only the second magnetic field sensor 22; in the third switching state, both the first and second magnetic field sensors 21, 22 are actuated; and in the fourth switching state, neither magnetic field sensor 21, 22 is actuated. The fourth switching state can also be excluded by a corresponding arrangement of the aforementioned stops.

[0050] However, if the rotational position is to be detected independently of the start and end points 11, 12, it can alternatively be provided that the magnetic field sensors 21, 22 are not switches that can merely generate a switching signal, but that they transmit the measured value for the field strength of the magnetic field of the magnet 31 to a common evaluation unit 23, as can optionally be the case in Figure 2. The evaluation unit 23 can be provided directly on the circuit carrier 20 or separately.Based on the values ​​for the measured field strength of the magnetic field transmitted by the magnetic field sensors 21, 22 and together with a relative positioning of the magnetic field sensors 21, 22 to each other and to the actuation path 10 stored in the evaluation unit 23 as well as the course of the actuation path 10 stored in the evaluation unit 23, the position of the magnet 31 on the actuation path 10 and thus the rotation position about the rotation axis R can be determined safely and reliably, for example by triangulation.

[0051] Figure 2 shows a control element 30, which can be part of the control circuit. The magnet 31 is embedded in the control element 30 and forms part of an end face of the control element 30, which, in the assembled state, faces the circuit carrier 20. As is evident, the magnet 31 is arranged outside the axis of rotation R, so that the magnet 31 does not rotate in, but around, the axis of rotation R.

[0052] In order to ensure that the magnet 31 can only be moved along the actuation path 10 and not, for example, onto the circuit carrier 20 and thus the magnetic field sensors 21, 22 towards or away from them, two detent elements 32 opposite each other with respect to the axis of rotation R are formed on the operating element 30, each consisting of a spring section 33 and a detent section 34.

[0053] Due to the elasticity formed by the spring section 33, the detent elements 32 can spring into a clearance 35 towards the axis of rotation R and thereby engage in a counter element (not shown), which forms a circular guide rail corresponding to the actuation path 10. The guide rail encompasses the detent section 34 axially on both sides, thus holding the operating element 30 in a predetermined axial position. Although the detent elements 32 with the detent sections 34 are engaged in the guide rail of the counter element, they can still be deflected inwards radially towards the axis of rotation R by spring action.If concave recesses are provided in the guide rail, the detent section 34, with its convex contour extending radially outwards, can engage in the concave recesses and thus provide detent feedback for the operator at one or more predetermined positions.

[0054] Furthermore, a circumferential track extending around the axis of rotation R can be provided in the counterbody, and in particular on a side facing away from the magnetic field sensors. This track forms two stops in the circumferential direction, such that the actuation path 10 extends along the track between the stops. The stops are designed to limit the rotation of the control element 30 around the axis of rotation R. Correspondingly, two counter-stops 36 are provided on the control element 30. These counter-stops are designed to be guided along the track and to engage the stops.

[0055] * * * * *

Claims

Patent claims 1. Control circuit (1) for detecting a rotational position (2, 3) of an operating element (30) of an electrically operated hand tool rotatable about an axis of rotation (R), comprising two magnetic field sensors (21, 22) for detecting a magnetic field and a magnet (31) which can be arranged on the operating element (30) and is rotatable from a starting point (11) to an end point (12) along an actuation path (10) or freely along the actuation path (10) about the axis of rotation (R), wherein the magnetic field sensors (21, 22) are arranged offset from each other along the actuation path (10), wherein a magnetic field formed by the magnet (31) can be detected by the two magnetic field sensors (21, 22) when the magnet (31) moves along the actuation path (10), and the magnetic field sensors (21, 22) are designedto determine the rotational position of the magnet (31) about the axis of rotation (R) from each measured field strength of the magnetic field of the magnet (31) and / or to transmit the each measured field strength of the magnetic field of the magnet (31) to an evaluation device (23) which is configured to determine the rotational position of the magnet (31) about the axis of rotation (R) from the two measured field strengths of the magnetic field of the magnet (31).

2. Control circuit according to claim 1, wherein the magnetic field sensors (21, 22) are each configured as magnetic field switches and in particular as Hall switches and are further configured to generate a switching signal when the magnet (31) is in a rotational position (2, 3) along the actuation path (10) in which it is at a minimum distance to the has the respective magnetic field sensor (21, 22).

3. Control circuit according to claim 2, wherein the magnetic field sensors (21 , 22) each define an exclusive area along the actuation path in which only the respective magnetic field sensor (21 , 22) is actuated, and an overlap area in which both magnetic field sensors (21 , 22) are actuated.

4. Control circuit according to one of the preceding claims, further comprising the control element (30) rotatable about the axis of rotation (R), wherein the magnet (31) is embedded in the control element (30) and / or fixed to the control element (30).

5. Control circuit according to one of the preceding claims, further comprising a circuit carrier (20), wherein the magnetic field sensors (21, 22) are arranged and fixed on the circuit carrier (20) in a predetermined positioning and a predetermined relative position to each other.

6. Control circuit according to the two preceding claims, wherein at least one latching element (32) is fixed to the control element (30) or is integrally formed by the control element (30).

7. Control circuit according to the preceding claim, wherein the at least one locking element (32) is designed to keep the operating element (30) concentric to the axis of rotation (R) relative to the circuit carrier (20) and rotatable about the axis of rotation (R).

8. Control circuit according to one of the two preceding claims, wherein the at least one detent element (32) is configured to move the operating element (30) along the axis of rotation (R) in a pre- agreed to maintain a distance to the circuit carrier (20).

9. Control circuit according to one of the three preceding claims, wherein the at least one detent element (32) is designed to be released along the actuation path (10) at at least one predetermined detent position by a predetermined force and to engage in a corresponding counterbody in a manner perceptible to an operator.

10. Control circuit according to one of the four preceding claims, wherein contact surfaces corresponding to the magnetic field sensors (21 , 22) are formed on the circuit carrier (20) and wherein the magnetic field sensors (21 , 22) are designed as surface-mountable components and are fixed and electrically contacted on the circuit carrier (20) via the contact surfaces.

11. Control circuit according to one of the preceding claims, wherein the magnet (31) is made of ferrite and / or sintered material. * * * * *

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