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

Abstract

Control circuit (1) for detecting a rotation position (2, 3) of a control element (30) of an electrically operated hand tool that is rotatable about a rotation axis (R), with two magnetic field sensors (21, 22) for detecting a magnetic field and with a magnet (31) which can be arranged on the control 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 configured to determine the rotational position of the magnet (31) about the rotational axis (R) from a measured field strength of the magnetic field of the magnet (31) and / or to transmit the 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 rotational axis (R) from the two measured field strengths of the magnetic field of the magnet (31).

Description

[0001] The invention relates to a control circuit for detecting a rotational position of an operating element of an electrically operated hand tool that can be rotated about a particularly fixed rotational axis, and to a hand tool with such a control circuit.

[0002] A variety of methods for detecting the rotational position of a control element are known from the prior art. For example, a rotary potentiometer, a wiper rotating over contact surfaces, or spring-loaded metallic contact elements that establish electrical contact at predetermined switching positions can be used.

[0003] For example, a cost-effective solution is often used on hand tools, 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 locking positions formed by the disc spring.

[0004] However, this results in a mechanically complex structure, and the suspension is susceptible to vibration, so that the steel balls may not make any or only a permanent electrical contact at the intended locking positions.

[0005] 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 displaced relative to each other along a straight line. However, the design disclosed therein is not always optimal for rotary switches, such as those often used in hand tools to reduce installation space and facilitate operation by an operator.

[0006] The invention is therefore based on the object of overcoming the aforementioned disadvantages and providing a control circuit with which the rotational position of an operating element rotatable about a rotation axis can be detected in a simple and cost-effective manner and at the same time in an error-resistant manner even in the case of vibration and other external influences.

[0007] This problem is solved by the combination of features according to claim 1.

[0008] According to the invention, a control circuit is therefore proposed for detecting a rotational position of an operating element of an electrically operated hand tool, which operating element can be rotated about a rotational axis. On the hand tool, for example, an operating mode or a direction of rotation of a motor of the hand tool can be set or changed by means of the operating element. For this purpose, the control circuit has 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 operating element and is rotatable from a starting point to an end point along an actuation path or freely about the rotational axis, so that the control circuit can preferably be designed as a rotary switch by the rotatable operating element. The magnetic field sensors are offset from one another along iearranged on, on or adjacent to the actuation path, whereby a magnetic field formed by the magnet can be detected by the two magnetic field sensors when the magnet moves along the actuation path, but with its 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 designed to determine the rotational position of the magnet about the rotation axis from a respectively measured field strength of the magnetic field of the magnet. In a simple variant, for example, a respective threshold value or value range for a respective rotational position can be stored in the magnetic field sensors, so that it can be detected that the magnet has reached one of the predetermined rotational positions or the predetermined rotational position when the field strength lies within the value range or exceeds the threshold value.The magnetic field sensors can be magnetic field or Hall switches, which have a correspondingly predetermined switching hysteresis. Alternatively or additionally, the magnetic field sensors can be configured to transmit the respectively measured field strength of the magnet's magnetic field to an evaluation device of the control circuit, which is configured to determine the rotational position of the magnet about the rotation axis from the two measured field strengths of the magnet's magnetic field and, if necessary, a previously known relative position of the magnetic field sensors to one another, as well as, if applicable, the previously 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 provides a position along the actuation path as a result, for example also in the form of an angle of rotation around the rotation axis.

[0009] 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.

[0010] If the evaluation unit is designed to determine the rotational position, this or a higher-level control unit can switch or control a function depending on the rotational position. For example, a motor speed can be set or specified between a minimum and a maximum value depending on the rotational position.

[0011] Since a spring bearing or a mechanical interaction of components is dispensed with for detecting the rotational position, 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 ambient conditions.

[0012] According to an advantageous variant, in which essentially only exactly two rotational positions and thus three and preferably four switching states are to be detected, it is provided that the magnetic field sensors are each designed as magnetic field switches and in particular as Hall switches. Furthermore, the magnetic field sensors or switches are designed 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 minimal distance from 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 minimal distance from the respective magnetic field sensor or switch.

[0013] Building on this, Hall switches with a predetermined switching hysteresis can be used as the two magnetic field sensors, which form an overlap region between them through their respective switching hysteresis and positioning relative to each other. If the magnet is located exclusively in the range of the first magnetic field sensor, only this one is actuated and a first switching state, for example, "clockwise rotation", is present. If the magnet is located exclusively in the range of the second magnetic field sensor, only this one is actuated and a second switching state, for example, "counterclockwise rotation", is present. If the magnet is located in the overlap region along the actuation path between the two magnetic field sensors, both magnetic field sensors are actuated and a third switching state, for example, "off" or "not rotating", is present.

[0014] Furthermore, it can additionally be provided that a fourth switching state exists when none of the magnetic field sensors is actuated, i.e. the magnet is located along the actuation path outside the exclusive areas and the overlap area of ​​the magnetic field sensors.

[0015] If switching states are possible in which none of the magnetic field sensors is actuated, a distinction can be made between a fourth and fifth switching state using a stop and / or an additional evaluation unit. 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 be used to determine which magnetic field sensor was actuated before no magnetic field sensor was actuated. If initially only the first magnetic field sensor was actuated and immediately afterwards no magnetic field sensor, a fourth switching state exists. If initially only the second magnetic field sensor was actuated and immediately afterwards no magnetic field sensor, a fifth switching state exists.

[0016] Furthermore, the rotatable operating element can also be part of the control circuit, whereby the control circuit can also be referred to as a control device. In such a variant, the control circuit further comprises the operating element rotatable about the rotation axis, wherein the magnet is embedded in the operating element and / or fixed to the operating element.

[0017] The operating element preferably has a front side facing the magnetic field sensors, wherein the magnet is fixed to the front side in particular offset to the axis of rotation and lying on the actuation path or is embedded in the operating element and / or fixed in the operating element forming part of the front side.

[0018] In order to make the control circuit interference-proof, it can also be provided that a shielding element, in particular a metal 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 shielding element 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.

[0019] Such a shielding element can, for example, be integrated into the operating element as a film or the operating element itself can be made of a shielding material so that the operating element integrally forms the shielding element.

[0020] Furthermore, the control circuit can have 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 in a predetermined relative position to one another.

[0021] If the rotatable operating element is part of the invention, at least one locking element can be fixed to it or formed integrally with the operating element. Preferably, two opposing locking elements are provided, each of which, in particular, has a spring portion extending parallel to the rotational axis and an adjoining locking portion extending orthogonally to the rotational axis and away from it.

[0022] At least one locking element can fulfil several functions.

[0023] Thus, it can be provided that the at least one locking element is designed to hold the operating element relative to the circuit carrier concentrically to the rotational axis and rotatable about the rotational axis. For this purpose, the at least one locking element can, for example, engage in a circular guideway arranged on the circuit carrier as a counter-body.

[0024] Furthermore or alternatively, the at least one locking element can be designed to hold the operating element along the rotation axis at a predetermined distance from the circuit carrier, which can also be realized by such a counter-body if it forms two and preferably also annular stops in the axial direction, ie parallel to the rotation axis, so that the operating element locked into the counter-body is held in its axial position by the stops.

[0025] In addition, the at least one locking element can alternatively or additionally be designed to engage into a corresponding counter-body at at least one predetermined locking position along the actuation path by means of a predetermined force, and to be haptically perceptible for an operator.

[0026] For this purpose, the locking element or the locking section of the locking element can, for example, be convex and the counter body can be concave at the locking positions corresponding to the locking section, wherein the force required to release the locking can be predetermined from the convex and corresponding concave shape.

[0027] Preferably, a plurality of locking positions are formed on the counter body, which are arranged evenly or are provided only at predetermined switching positions, so that a locking or predetermined locking points, which may serve as switching points, are haptically perceptible to the operator during rotation.

[0028] If a limited number of switching states is 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, whereby, for example, an additional switching state can also be provided.

[0029] For example, a first detent position can be selected such that the magnet lies in an exclusive area of ​​the first magnetic field sensor designed as a Hall switch, which is thereby actuated and triggers the "clockwise rotation" switching state. Furthermore, a second detent position can be selected such that the magnet lies in an exclusive area of ​​the second magnetic field sensor designed as a Hall switch, which is thereby actuated and triggers the "counterclockwise rotation" switching state. Furthermore, a third detent position can be selected such that the magnet lies in an overlap area between the two magnetic field sensors designed as Hall switches, which are each actuated and triggers the "off" or "non-rotating" switching state.

[0030] The aforementioned fourth switching state, in which none of the magnetic field sensors is activated, can also be assigned a detent position, although this is preferably not assigned a detent position. Instead, stops can also be provided that prevent the magnet from rotating into the fourth switching state.

[0031] Furthermore, a track extending circumferentially around the rotation axis can be provided in the counter body, in particular on a side facing away from the magnetic field sensors. This track forms two stops in the circumferential direction, so that the actuation path extends along the track between the stops, and the stops are designed to limit the rotation of the operating element about the rotation axis. Correspondingly, at least one counter-stop can be provided on the operating element, which is designed to be guided along the track and to engage the stops.

[0032] Based on the use of a circuit carrier, contact surfaces corresponding to the magnetic field sensors can be formed on the circuit carrier. The magnetic field sensors are designed as surface-mounted components (SMDs) and are fixed to the circuit carrier and electrically contacted via the contact surfaces. This not only reduces costs but also minimizes the influence of vibrations.

[0033] The magnet is preferably a ferrite magnet, which can additionally or alternatively be sintered.

[0034] A further aspect of the invention also 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.

[0035] The features disclosed above can be combined as desired, as long as this is technically possible and they do not contradict each other.

[0036] Other advantageous developments of the invention are characterized in the subclaims or are presented in more detail below, together with the description of the preferred embodiment of the invention, with reference to the figures. They show: Fig. 1 a control circuit; Fig. 2 a control element with a magnet embedded in it.

[0037] The figures are schematic examples. Identical reference numerals in the figures indicate identical functional and / or structural features.

[0038] In Fig. 1 shows a variant of a control circuit 1 according to the invention, wherein a magnet 31 which can be arranged on an operating element 30, as shown in Fig. 2, can be rotated by an operator along an actuating path 10 about the rotation axis R.

[0039] The rotation can be free, ie not limited by a stop, so that the magnet 31 can be rotated around the rotation axis R as often as desired and in any direction.

[0040] 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 operating element 30 can only be rotated from the starting position 11 about the rotation axis R to the end position 12, wherein the rotation can take place over the smaller circular arc section or over the larger circular arc section of the actuating path 10 depending on the positioning of the stop or the positioning of several stops.

[0041] Two magnetic field sensors 21, 22 are arranged on a circuit carrier 20 along and, in the present case, directly adjacent to the actuation path 10, 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 one another.

[0042] According to a simple variant, it is provided that the magnetic field sensors 21, 22 are each magnetic field switches or Hall switches based on the Hall effect, 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.

[0043] If the magnet 31 is in the starting position 11 and thereby overlaps with the first magnetic field sensor 21, a first rotational position 2 is detected by the first magnetic field sensor 21. If the magnet 31 is rotated about the rotation axis R to the end position 12 and thereby overlaps with the second magnetic field sensor 22, a second rotational position 3 of the magnet 31 is detected by the second magnetic field sensor 22.

[0044] The magnetic field sensors 21, 22 can each generate an associated switching signal or switching state, so that no additional evaluation device 23 is required.

[0045] If the magnet 31 is neither in the start position 11 nor in 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 in an indeterminate rotational position between the start and end point 11, 12.

[0046] From the representation of the Fig. 1, however, it can also be provided that Hall switches are selected as magnetic field sensors 21, 22, which, due to their respective predetermined switching hysteresis along the actuation path 10, form an overlap region between them in addition to a respective exclusive region in which both the first magnetic field sensor 21 and the second magnetic field sensor 22 are actuated. This allows four switching states to be detected, wherein in a first switching state only the first magnetic field sensor 21, in a second switching state only the second magnetic field sensor 22, in a third switching state both the first and the second magnetic field sensor 21, 22 are actuated, and in a fourth switching state none of the magnetic field sensors 21, 22 are actuated. The fourth switching state can also be excluded by a corresponding arrangement of the stops already mentioned.

[0047] However, if the rotation 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 which can only generate a switching signal, but that they transmit the value measured by them for the field strength of the magnetic field of the magnet 31 to a common evaluation device 23, as shown in Fig. 2 can optionally be the case. The evaluation device 23 can be provided directly on the circuit carrier 20 or separately therefrom. 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 one another and to the actuation path 10 stored in the evaluation device 23, as well as the course of the actuation path 10 stored in the evaluation device 23, the position of the magnet 31 on the actuation path 10 and thus the rotational position about the rotation axis R can be determined safely and reliably, for example by triangulation.

[0048] In Fig.2 shows an operating element 30, which can be part of the control circuit. The magnet 31 is embedded in the operating element 30 and forms part of an end face of the operating element 30, which, in the assembled state, faces the circuit carrier 20. As can be seen, the magnet 31 is arranged outside the rotation axis R, so that the magnet 31 is not rotated in, but around, the rotation axis R.

[0049] In order to ensure that the magnet 31 can only be moved along the actuation path 10 and not, for example, towards or away from the circuit carrier 20 and thus the magnetic field sensors 21, 22, two locking elements 32 are formed on the operating element 30, which are opposite one another with respect to the rotation axis R and each consist of a spring section 33 and a locking section 34.

[0050] Due to the elasticity created by the spring portion 33, the locking elements 32 can deflect toward the rotation axis R into a free space 35 and thereby engage with a counter element (not shown), which forms a circular guide rail corresponding to the actuation path 10. The guide rail encompasses the locking portion 34 on both sides in the axial direction, so that the operating element 30 is thereby held in a predetermined position in the axial direction.

[0051] Although the locking elements 32 are engaged with the locking sections 34 in the guide rail of the counter element, they can still be deflected elastically inwardly in the radial direction relative to the rotation axis R. If concave recesses are provided in the guide rail, the locking section 34 can engage with its convex contour extending outward in the radial direction into the concave recesses and thus provide a locking action at one or more predetermined positions and thus provide haptic feedback for the operator.

[0052] Furthermore, in the counter body and in particular on a side facing away from the magnetic field sensors, a track running in the circumferential direction around the rotation axis R can be provided, which track forms two stops in the circumferential direction, so that the actuation path 10 extends on the track between the stops and the stops are designed to limit the rotation of the operating element 30 about the rotation axis R. Correspondingly, two counter stops 36 are provided on the operating element 30, which are designed to be guided along the track and to come into contact with the stops. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 10,414,033 B2

[0005]

Claims

[1] Control circuit (1) for detecting a rotational position (2, 3) of an operating element (30) of an electrically operated hand tool that can rotate about a rotational axis (R), with two magnetic field sensors (21, 22) for detecting a magnetic field and with 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 actuating path (10) or freely along the actuating path (10) about the rotation axis (R), wherein the magnetic field sensors (21, 22) are arranged offset from one another 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) during a movement of the magnet (31) along the actuating path (10) and the magnetic field sensors (21, 22) are designed to determine the rotational position of the magnet (31) about the rotational axis (R) from a respectively measured field strength of the magnetic field of the magnet (31) and / or to transmit the respectively measured field strength 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 rotational axis (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 designed as magnetic field switches and in particular as Hall switches and are further designed to generate a switching signal when the magnet (31) is in a rotational position (2, 3) along the actuating path (10) in which it has a minimum distance from the respective magnetic field sensor (21, 22). [3] Control circuit according to claim 2, wherein the magnetic field sensors (21, 22) along the actuation path each determine an exclusive area in which exclusively the respective magnetic field sensor (21, 22) is actuated, and determine 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 operating element (30) rotatable about the rotation axis (R), wherein the magnet (31) is embedded in the operating element (30) and / or fixed to the operating 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 in a predetermined positioning and the predetermined relative position to one another on the circuit carrier (20). [6] Control circuit according to the two preceding claims, wherein at least one locking element (32) is fixed to the operating element (30) or is formed integrally by the operating element (30). [7] Control circuit according to the preceding claim, wherein the at least one locking element (32) is designed to hold the operating element (30) relative to the circuit carrier (20) concentrically to the rotation axis (R) and rotatable about the rotation axis (R). [8] Control circuit according to one of the two preceding claims, wherein the at least one locking element (32) is designed to hold the operating element (30) along the rotation axis (R) at a predetermined distance from the circuit carrier (20). [9] Control circuit according to one of the three preceding claims, wherein the at least one latching element (32) is designed to latch into a corresponding counter-body along the actuation path (10) at at least one predetermined latching position by a predetermined force in a manner that is releasable and haptically 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 to 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.

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