POWER TOOL AND METHOD FOR DETECTING AN EVENT AND / OR CONDITION OF A POWER TOOL

Description

[0001] The invention relates to a power tool according to the preamble of claim 1, comprising a rotatable tool designed as a saw blade or milling cutter, a sensor device for detecting a mechanical variable which depends on a force emanating from the tool, and a control device communicatively coupled to the sensor device, which control device is designed to detect an event of the power tool according to the detected mechanical variable.

[0002] WO 2014 / 105935 describes a table saw with a kickback detection system comprising a sensor configured to detect a shaft deflection as a scalar value. A controller compares the detected deflection with a scalar threshold to determine whether a kickback is present.

[0003] US 2014 / 166323 A1 relates to a power tool with a 3-axis acceleration sensor. The sensor can be used to detect the acceleration of a handle of the power tool. The sensor provides acceleration information for the tool, and in particular, the acceleration of the handle should it rotate in a direction opposite to the direction of the bit, indicating a stuck bit, or in the same direction as the bit, indicating a broken bit.

[0004] WO 01 / 26064 A2 relates to a table saw with a detection system for detecting a kickback. In response to the detection, the saw blade movement is stopped.

[0005] DE 10 2015 211584 A1 relates to a diagnostic device for a handheld power tool. An acceleration sensor detects vibration and uses the vibration value to determine wear.

[0006] US Pat. No. 4,802,095 A describes a system for measuring tool wear of a rotary end mill. The system measures wear by monitoring side load forces on the tool during cutting. The resulting side load forces FRES have tangential FT and radial FR components. The radial component FR increases accordingly with tool wear. FRES and FT are measured directly, and based on these measurements, FR is mathematically determined to provide an indication of tool wear.

[0007] An object of the invention is to modify the power tool mentioned at the outset in such a way that the detection carried out by the control device is improved.

[0008] This object is achieved by a power tool according to claim 1. According to the invention, the sensor device serves to detect a mechanical vector variable that depends on a force emanating from the tool. The direction of the detected vector variable corresponds to the direction in which the tool pushes relative to another component of the power tool. The mechanical vector variable is, for example, a force, an acceleration, a speed, a deflection, a deformation, and / or a mechanical stress. The control device is designed to detect an event and / or a state of the power tool according to a change in direction of the mechanical vector variable detected by the sensor device. The control device is designed to detect a kickback, forward sawing, backward sawing, and / or plunging of the tool into a workpiece as the event and / or state to be detected.

[0009] According to the invention, a vector variable is thus detected and the event and / or the state of the power tool is recognized based on the change in direction (and optionally the direction) of this vector variable. This approach is based on the realization that the tool pushes in certain directions during certain events and / or states of the power tool and that, for this reason, the change in direction (and optionally the direction) of a mechanical vector variable, which depends on the force emanating from the tool, is a good indicator for detecting these events and / or states. By taking the change in direction (and optionally the direction) of the mechanical vector variable into account according to the invention, an earlier event and / or state detection can occur than if the detection were based solely on a scalar variable.This is because, as a rule, a certain direction is present and / or a certain change of direction occurs before a certain scalar threshold is exceeded. The power tool according to the invention therefore enables particularly early—and thus improved—event and / or condition detection.

[0010] The recorded mechanical vector quantity represents a force, acceleration, velocity, deflection, deformation, or mechanical stress and is preferably two-dimensional. The mechanical vector quantity depends on a force emanating from the tool. The direction of the recorded vector quantity corresponds to the direction of the force emanating from the tool or the direction in which the tool is pushing, relative to another component of the power tool. The vector quantity is expediently recorded in a force flow emanating from the tool.

[0011] The condition to be determined by the control device is, in particular, a so-called "kickback" of the power tool. The term "kickback" typically refers to an event in which, while the power tool is processing a workpiece, a sudden and unexpected force occurs between the power tool and the workpiece, which then accelerates the power tool or the workpiece and sets it in motion. In table saws, a kickback usually results in an unexpected acceleration of the workpiece toward the user. In hand-held circular saws, a kickback can cause unexpected movement of the tool. Kickbacks can lead to injury to the user and therefore impair operational safety.

[0012] A kickback can occur particularly when the tool is inserted into the workpiece jerkily or too quickly, when sawing backwards, when the tool jams in the workpiece, when certain workpiece properties (e.g. inhomogeneous wood, tensions) and / or when the tool is blunt. The event detection described above based on the change in direction (and optionally the direction) of the detected mechanical vector variable makes it particularly easy to detect a kickback event. The kickback or kickback event to be detected here also refers in particular to an imminent kickback, i.e. an event in which the causes of the kickback are already present, but no or no significant acceleration of the power tool and / or the workpiece has yet occurred. Before the power tool 10 or the workpiece is set in motion or stopped by the kickback.If the tool is significantly accelerated, the kickback is already signaled by the force vector emanating from the tool changing direction. Thus, shortly before or at the beginning of a kickback, the tool pushes in a different direction than during normal operation. This push in a different direction can be detected by measuring the mechanical vector quantity, thus concluding that a kickback condition is present.

[0013] Furthermore, the event to be detected can be a plunge of the tool into the workpiece, forward sawing or backward sawing.

[0014] Advantageous further training is the subject of the subclaims.

[0015] The invention further relates to a method, according to claim 13, for detecting an event and / or a state of a power tool with a rotatable tool designed as a saw blade or milling cutter. The method comprises the steps of: detecting a mechanical vector quantity, namely a force, an acceleration, a speed, a deflection, a deformation, and / or a mechanical stress, which depends on a force emanating from the tool, wherein the direction of the detected vector quantity corresponds to the direction in which the tool is pushing, and detecting the event and / or state of the power tool according to a change in direction of the detected mechanical vector quantity. The event and / or state includes a kickback, forward sawing, backward sawing, and / or plunging of the tool into a workpiece.

[0016] The procedure is conveniently carried out using a power tool as described here.

[0017] Further exemplary details and exemplary embodiments are explained below with reference to the drawing. Figure 1 shows a schematic representation of a power tool according to a first embodiment, Figure 2 shows a diagram to illustrate an event and / or state detection based on a direction or change in direction of a mechanical vector variable, Figure 3 shows a sectional representation of a power tool according to a second embodiment, Figure 4 shows a sectional representation of a power tool according to a third embodiment, Figure 5 shows a sectional representation of a power tool according to a fourth embodiment, Figure 6 shows a sectional representation of a power tool according to a fifth embodiment, Figure 7 shows a sectional representation of an output shaft and two bearings of the power tool according to the fifth embodiment, Figure 8 shows a schematic representation of a power tool according to a sixth embodiment and Figure 9 shows a block diagram of a method.

[0018] The Figure 1 shows a power tool 10 according to a first embodiment.

[0019] The power tool 10 has a rotatable tool 1 designed as a saw blade or milling cutter, a sensor device 2, and a control device 4. The sensor device 2 is designed to detect a mechanical vector variable 3. The mechanical vector variable 3 is a force, an acceleration, a speed, a deflection, a deformation, and / or a mechanical stress. Furthermore, the mechanical vector variable 3 depends on a force emanating from the tool 1. The control device 4 is communicatively connected to the sensor device 2 and is designed to detect an event and / or a state of the power tool 10 according to a change in direction (and optionally a direction) of the mechanical vector variable 3 detected by the sensor device 2.

[0020] Because the event and / or state detection of the power tool 10 is based on a change in direction (and optionally a direction) of a detected mechanical vector variable 3, an event or a change in state of the power tool 10 can be detected at a very early point in time. Event and / or state detection is thus improved.

[0021] In the following, exemplary details of the power tool 10 and further exemplary embodiments are explained.

[0022] The power tool 10 is preferably a saw, in particular a hand-held circular saw or a plunge-cut saw. The power tool 10 can also be designed as a biscuit joiner. The tool 1 is particularly circular and rotates clockwise during operation.

[0023] By way of example, the power tool 10 has a housing 6, in which, in particular, the sensor device 2 and the control device 4 are arranged. A support surface 9 is provided on the housing 6, with which the power tool 10 can be placed on a workpiece 11 to be machined.

[0024] The power tool 10 has a drive device 7. The drive device 7 comprises, for example, an electric motor and a gear. The drive device 7 is preferably controlled by the control device 4. The power tool 10 further has an output shaft 8, which can be driven by the drive device 7. The tool 1 is mechanically coupled to the output shaft 8. The tool 1 is expediently attached to the output shaft 8.

[0025] The power tool 10 further comprises a support structure 21, which is expediently arranged in the housing 6. The output shaft 8, for example, is mounted on the support structure 21. Furthermore, the support structure 21 can be designed as a housing for the drive device 7. The support structure 21 can, for example, represent or comprise a drive housing, in particular a gear housing.

[0026] By way of example, the power tool 10 further comprises a user interface 5. The user interface 5 comprises, for example, an input device with which the user can switch the power tool 10 on and off and / or configure and / or calibrate it.

[0027] As in the Figure 1As shown, the power tool 10 typically rests with its support surface 9 on the workpiece 11 during machining and is moved in a feed direction 12 relative to the workpiece 11. For example, the saw teeth of the tool 1 saw into the workpiece 11 from bottom to top. In this configuration, the tool 1 pushes relative to the rest of the power tool 10 in the direction of the mechanical vector quantity 3 shown, i.e., diagonally downward. The force emanating from the tool 1 points in particular in the direction of the mechanical vector quantity 3.

[0028] In the Figure 1 the sensor device 2 is exemplarily coupled to the output shaft 8 and designed to detect the mechanical vector variable 3 - namely a force, acceleration, speed, deflection, deformation and / or mechanical stress - of the output shaft 8.

[0029] Preferably, the sensor device 2 is designed to continuously detect the mechanical vector quantity 3 so that a change, in particular a change in direction of the mechanical vector quantity 3 can be detected.

[0030] The control device 4 is embodied, for example, as a microcontroller. The control device 4 is configured to determine an event and / or a state of the power tool 10 based on the mechanical vector variable 3. For example, the control device 4 is configured to determine whether the direction of the detected mechanical vector variable 3 lies within or outside a specific directional range and, based on this determination, to decide whether or not a specific state exists.

[0031] Based on the Figure 2 The following will explain in detail how the detection of a specific event and / or condition can be carried out.

[0032] The Figure 2 shows a diagram with different direction ranges 14, 15 and 16, two direction thresholds 17, 18 and the recorded mechanical vector quantity 3.

[0033] The diagram is divided into four quadrants. Each quadrant covers 90 degrees. Reference numeral 19 indicates the zero-degree line. The angular coordinates and degrees mentioned below are to be understood in the mathematically positive direction of rotation (counterclockwise). The zero-degree line conveniently runs parallel to the support surface 9 and / or the feed direction 12.

[0034] The directional ranges 14, 15, and 16 are exemplary two-dimensional directional ranges. The directional ranges 14, 15, and 16 can also be referred to as angular ranges.

[0035] The directional areas 14, 15, and 16 are expediently located in one plane. This plane is expediently aligned parallel to the plane of the tool 1 or perpendicular to the axial direction of the output shaft 8. The directional areas 14, 15, and 16 preferably do not overlap.

[0036] The control device 4 is configured to provide at least one directional range 14, 15, or 16. For example, the at least one directional range is stored in a memory in the control device 4. Alternatively or additionally, the control device 4 can also be configured to generate the at least one directional range itself. The control device 4 is further configured to determine whether the detected mechanical vector variable 3 lies within or outside the directional range 14, 15, or 16, and to detect the state of the power tool 10 based on this determination.

[0037] Conveniently, the control device 4 is configured to provide a plurality of directional ranges 14, 15, 16 and to detect various events and / or states based on which of the directional ranges 14, 15, 16 the direction of the mechanical vector quantity 3 lies in. In particular, a respective event and / or state is assigned to each of the directional ranges 14, 15, 16.

[0038] The first directional range 14 represents a directional range in which the mechanical vector quantity 3 lies when the tool 1 is immersed in the workpiece 1 and the power tool 10 is moved relative to the workpiece 1 in the feed direction 12. For example, the first directional range 14 is located in the two lower quadrants, i.e., within a range between 180 degrees and 360 degrees. In the example shown, the first directional range 14 extends from 220 degrees to 330 degrees.

[0039] A mechanical vector quantity 3 that lies within the first directional range 14 is an indicator that the event or state exists that the power tool 10 is sawing forward in the feed direction 12. Accordingly, the control device 4 is configured to detect that a "forward sawing event" or "forward sawing state" exists when the mechanical vector quantity 3 lies within the first directional range 14.

[0040] The second directional range 15 represents a directional range in which the mechanical vector variable lies when the tool 1 is immersed in the workpiece 11 and the power tool 10 is moved relative to the workpiece 11 opposite to the normal feed direction 12—i.e., in the reverse direction. Furthermore, the second directional range 15 represents a directional range in which the mechanical vector variable 3 lies when the tool 1 is immersed in the workpiece 11. For example, the second directional range 15 is located in the two left-hand quadrants, i.e., within a range between 90 degrees and 270 degrees. In the example shown, the second directional range 14 extends from 125 degrees to 220 degrees.

[0041] A mechanical vector quantity 3 lying within the second directional range 15 is an indicator that the event or condition exists that the power tool 10 is sawing backwards or that the tool 1 is plunging into the workpiece 11. Accordingly, the control device 4 is configured to detect that a "backward sawing event" or "backward sawing condition" or a "plunging event" is present when the mechanical vector quantity 3 lies within the second directional range 15.

[0042] The first directional range 14 and the second directional range 15 together represent a normal range. As long as the mechanical vector variable 3 is within the normal range, the control device 4 can assume that the power tool 10 is operating safely and, for example, provide a corresponding signal.

[0043] The third directional range 16 represents a directional range in which the mechanical vector variable lies when a kickback event occurs. For example, the third directional range 16 is located in the two upper quadrants, i.e., within a range between 0 degrees and 180 degrees. In the example shown, the third directional range 16 extends from 5 degrees to 100 degrees. The control device 4 is expediently configured to detect the kickback event when the mechanical vector variable 3 lies within the third directional range 16.

[0044] The directional range within which the control device 4 concludes a kickback event can also be defined larger. For example, the boundaries of this directional range can be placed between the boundaries of the normal range and the boundaries of the third directional range 16.

[0045] This is in the Figure 2by the two directional thresholds 17, 18. For example, the directional thresholds 17, 18 adjoin the boundaries of the normal range. Alternatively, the directional thresholds can also be located at the boundaries of the normal range.

[0046] Conveniently, the directional range extending clockwise from the second directional threshold value 18 to the first directional threshold value 17 can be used instead of the third directional range 16. The (in the Figure 2 shown) third direction area 16 is optional in this case.

[0047] The control device 4 is expediently designed to detect the kickback event when the mechanical vector variable 3 lies between the two directional threshold values ​​17, 18 - that is to say counterclockwise behind the first directional threshold value 17 and before the second directional threshold value 18. The kickback event can thus be detected at a time when the cause of the kickback has already occurred, but the power tool 10 or the workpiece 11 have not yet been significantly accelerated or have not yet exerted a recoil or kickback. The control device 4 can expediently be designed to detect the kickback event 50 ms to 100 ms before an acceleration of the power tool 10 relative to the workpiece 11 occurring (without detection of and reaction to the kickback). The acceleration is, for example, an acceleration with an upward or downward component.a component in the 90-degree direction in the diagram shown.

[0048] The event and / or state detection is performed based on a change in the direction of the mechanical vector quantity 3. Optionally, this event and / or state detection can be performed based on the change in the direction of the mechanical vector quantity 3 in addition to the event and / or state detection based on the direction of the detected mechanical vector quantity 3 described above.

[0049] If, for example, a kickback is imminent, the mechanical vector variable 3 rotates in the direction towards the third directional range 16. The control device 4 can be designed accordingly to recognize an event and / or state based on a detected rotation of the mechanical vector variable 3. For example, the control device 4 is designed to compare the angular velocity of the mechanical vector variable with a velocity threshold value and, if the velocity threshold value is exceeded, to recognize the event and / or state. Furthermore, the control device 4 can be designed to determine by which angle of change the mechanical vector variable 3 has changed, in particular within a specific time window, and to compare this angle of change with an angular threshold value in order to recognize the event and / or state.

[0050] During kickback detection, the control device 4 can further be configured to distinguish between different types of kickbacks. For example, if a kickback is imminent, which occurs during reverse sawing or plunging, the mechanical vector variable 3 rotates counterclockwise (starting from the second directional range 15), whereas the mechanical vector variable 3 rotates clockwise in the case of a kickback caused by the tool 1 becoming jammed in the workpiece 11. Accordingly, the control device 4 can be configured to consider the direction of rotation of the mechanical vector variable 3 when detecting the event and / or condition.

[0051] Furthermore, the control device 4 can be configured to also consider a magnitude of the detected mechanical vector variable 3 during state and / or event detection. For example, the control device 4 can be configured to detect the state and / or event only if the magnitude of the mechanical vector variable 3 is greater than a threshold value. In this way, weak shocks occurring during operation can be prevented from being mistakenly detected as kickbacks.

[0052] In addition, the control device 4 can be configured to take into account the duration of time for which the mechanical vector variable 3 lies within a specific directional range 14, 15, 16. For example, the control device 4 can be configured to detect the state and / or event only if the mechanical vector variable lies within a specific directional range 14, 15, 16 for longer than a specific time threshold.

[0053] Furthermore, the control device 4 can be designed to determine whether a wear condition exists based on the direction of the detected mechanical vector variable 3. The wear condition can, in particular, be a wear condition of the tool 1. The control device 4 can be designed to provide a directional range and, based on whether the mechanical vector variable 3 is within or outside the directional range, to determine a wear condition. For example, the control device 4 can detect a reversal of direction, for example a reversal of the direction of force, of the mechanical vector variable 3 and use this to infer the wear condition. The control device 4 can then output an acoustic or visual signal via a corresponding signaling means, which indicates that the wear condition exists.

[0054] The specific angle specifications of the directional ranges 14, 15, and 16 explained above are purely exemplary. Depending on the type and design of the power tool 10, the actual angles may vary. The actual angles of the directional ranges 14, 15, and 16 can be determined by calibration. Calibration can be performed, for example, during the development or manufacture of the power tool and / or by the user.

[0055] The control device 4 is expediently designed to calibrate one or more directional ranges 14, 15, 16. For example, the calibration can be initiated via the user interface 5. The control device 4 can then drive the tool 1 via the drive device 7 and, in doing so, detect the mechanical vector variable 3 via the sensor device 2. Based on the detected mechanical vector variable 3, the control device 4 can then create a directional range and / or one or more threshold values ​​and store them in a memory of the control device 2. This process can be performed, for example, when a new tool 1 is mounted. The wear detection of the tool 1 can thus be improved.

[0056] The following describes the sensor device 2 and the detection of the mechanical vector quantity 3 in detail.

[0057] The sensor device 2 is expediently designed to detect the mechanical vector quantity 3 as at least a two-dimensional vector. For this purpose, the sensor device 2 is designed to measure the mechanical quantity underlying the mechanical vector quantity 3 in at least two different spatial directions. The two spatial directions are, for example, a spatial direction that runs parallel to the feed direction 12 and a spatial direction that runs perpendicular to the feed direction 12. Both spatial directions are expediently perpendicular to the axial direction of the output shaft 8. For example, the sensor device 2 has at least two sensor elements 25, 26. Each of the sensor elements 25, 26 expediently serves to measure the underlying mechanical quantity - i.e., a force, an acceleration, a speed, a deflection, a deformation, and / or a mechanical stress - in a different spatial direction.

[0058] The mechanical vector quantity 3 is, in particular, a force vector, an acceleration vector, a velocity vector, a displacement vector, a deformation vector, and / or a mechanical stress vector or stress tensor. Accordingly, the sensor device 2 can be configured to measure a force, an acceleration, a velocity, a displacement, a deformation, and / or a mechanical stress in at least two spatial directions.

[0059] The sensor device 2 can, in particular, comprise a radial measuring bearing 28, with which, for example, the output shaft 8 is mounted. The radial measuring bearing 28 can be designed to detect the force between the output shaft 8 and the measuring bearing 28 as the mechanical vector variable 3 using force or voltage sensors, for example piezoresistive sensors.

[0060] Alternatively or additionally, the sensor device 2 may comprise distance sensors spaced from the output shaft 8, which are designed to detect the deflection of the output shaft 8 as the mechanical vector variable 8.

[0061] Furthermore, the sensor device 2 can comprise stress sensors, in particular strain gauges (DMS), fastened to the support structure 21.

[0062] In principle, the sensor device 2 can be configured to measure the mechanical vector variable 3 at any part within the force flow emanating from the tool 1. The force flow runs, for example, from the tool 1 via the output shaft 8, a bearing device 27, the support structure 21, the housing 6, and the support surface 9 to the workpiece 11. In particular, the sensor device 2 is configured to measure the mechanical vector variable 3 between two parts located one behind the other in the force flow.

[0063] The Figures 3 to 6show a second, third, fourth, and fifth exemplary embodiment, in which the detection of the mechanical vector quantity 3 is carried out in a different manner. Except for the design and arrangement of the support structure 21 and the sensor device 2, the second to fifth embodiments correspond to the first embodiment discussed above. The features already explained above in connection with the first embodiment also apply to the second, third, fourth, and fifth embodiments.

[0064] The Figure 3 shows a power tool 20 according to the second embodiment. In the second embodiment, the sensor device 2 comprises two sensor elements 25, 26, both of which are arranged on the support structure 21. For example, the sensor elements 25, 26 are glued to the support structure 21.

[0065] The sensor elements 25, 26 are, in particular, sensors for detecting a deformation of the support structure 21 caused by a force exerted on the support structure 21 by the output shaft 8. The sensor elements 25, 26 are, for example, force-stress sensors, in particular strain gauges (SGs), piezo elements, and / or fiber optic sensors.

[0066] The sensor elements 25, 26 are expediently arranged on two sections 24 of the support structure 21 that extend radially outward relative to the output shaft 8. For example, the sensor element 25 is arranged on a horizontally extending section 24, and the sensor element 26 is arranged on a vertically extending section 24. The sections 24 are, in particular, web-shaped.

[0067] The sections 24 expediently connect a first subsection 22 and a second subsection 23 of the support structure 21. For example, the first subsection 22 surrounds the output shaft 8. In particular, the first subsection 22 represents or comprises a gear housing. The output shaft 8 is preferably mounted on the first subsection 22. The second subsection 23 is expediently located behind—i.e., downstream of—the first subsection 22 in the power flow emanating from the tool 1.

[0068] The Figure 4 shows a power tool 30 according to the third embodiment. The support structure 21 is expediently designed as in the second embodiment discussed above.

[0069] In the third embodiment, the sensor device 2 comprises two sensor elements 25, 26, which are designed to detect the deflection of the output shaft 8 in two different spatial directions. Preferably, the sensor element 25 detects the deflection of the output shaft 8 in a first spatial direction, and the sensor element 26 detects the deflection in a second spatial direction, in particular rotated by 90 degrees relative to the output shaft 8.

[0070] The sensor elements 25, 26 are expediently distance sensors, for example, eddy current sensors, capacitive sensors, and / or inductive sensors. If they are inductive sensors, magnetic particles can be arranged in or on the output shaft 8.

[0071] By way of example, the two sensor elements 25, 26 are arranged on the support structure 21. The sensor elements 25, 26 are expediently arranged, in particular screwed, in bores that are preferably provided on the support structure 21. By way of example, the two sensor elements 25, 26 are arranged on the inner section 22 of the support structure 21.

[0072] The Figure 5 shows a power tool 40 according to a fourth embodiment. The fourth embodiment is based on a support structure 21 as described above in connection with the second embodiment, but has, in particular, the following modifications compared to the second embodiment.

[0073] Thus, in the fourth embodiment, the sensor elements 25, 26 are arranged between the first subsection 22 and the second subsection 23 of the support structure 21. In particular, the sensor elements 25, 26 represent connecting elements that mechanically connect the second subsection 23 to the first subsection 22. By way of example, the sensor elements 25, 26 replace the sections 24 discussed above in connection with the second embodiment.

[0074] The sensor elements 25, 26 are expediently designed as force sensors and measure the force present between the first subsection 22 and the second subsection 23 in two different spatial directions. The two spatial directions are expediently aligned orthogonally to each other. In particular, the first spatial direction runs parallel to the support surface 9 and / or feed direction 12, and the second spatial direction runs perpendicular thereto.

[0075] According to a preferred embodiment, the first subsection 22 represents a gear housing and is suspended from the second subsection 23 and / or the remaining support structure 21 via the sensor elements 25, 26, preferably exclusively via the sensor elements 25, 26.

[0076] The Figure 6 shows a power tool 50 according to a fifth embodiment. The support structure 21 is expediently designed as in the second embodiment explained above.

[0077] The Figure 6 shows an example of a bearing device 27. The bearing device 27 is expediently provided on the support structure 21 and supports the output shaft 8 relative to the support structure 21. The bearing device 27 expediently comprises one or more bearings 31, 32, in particular radial and / or radial axial bearings, preferably ball bearings.

[0078] Conveniently, at least one bearing 31, 32 of the bearing device 27 is designed as a measuring bearing 28, in particular a radial measuring bearing, and thus represents the sensor device 2. The measuring bearing 28 is preferably designed to measure a force present between the output shaft 8 and the support structure 21 in at least two different spatial directions. For example, the measuring bearing 28 has a plurality of sensor elements, for example piezoresistive sensor elements, in particular piezoresistive thin-film sensor elements, which are conveniently arranged in the circumferential direction around the output shaft 8. In particular, the sensor elements are arranged on an outer bearing component of the measuring bearing 28—that is, a bearing component that is stationary relative to the support structure 21 or a bearing component that does not rotate with the output shaft 8, such as an outer ring.As an example, eight sensor elements are provided, each arranged offset by 45 degrees from each other.

[0079] The Figure 6 shows the output shaft 8 together with two bearings 31, 32 of the bearing device 27. By way of example, the first bearing 31 is arranged in the region of a distal end of the output shaft 8 assigned to the tool 1 and the second bearing 32 is arranged in the region of a distal end of the output shaft 8 facing away from the tool 1.

[0080] Advantageously, one or both bearings 1, 2 are designed as the measuring bearing 28 explained above.

[0081] Alternatively or in addition to the embodiment explained above, in which the sensor device 2 is integrated internally in one or more bearings 31, 32, the sensor device 2 can also be arranged between one or more bearings 31, 32 and the support structure 21.

[0082] The Figure 8shows a power tool 60 according to a sixth embodiment. The power tool 60 is embodied here, by way of example, as a stationary saw, in particular as a circular table saw. The power tool 60 includes the features already discussed above in connection with the power tool 10. Furthermore, the sensor device 2 and / or support structure 21 of the power tool 60 can be configured in accordance with the second to fifth embodiments.

[0083] For example, tool 1 rotates counterclockwise here. For practical purposes, the workpiece 11 is pushed into the tool 1, which is designed as a saw blade, during machining in such a way that the saw teeth saw into the workpiece 11 from top to bottom. Figure 8 a corresponding feed direction 12 is shown. The direction ranges 14, 15, 16 and / or direction threshold values ​​17, 18 are adjusted accordingly in the power tool 60. For example, the Figure 2shown directional ranges 14, 15, 16 and / or directional thresholds 17, 18 are point-mirrored around the center of the diagram.

[0084] The following discusses various options for responding to a detected event and / or condition. Each of these options can be conveniently provided for each of the power tools discussed above.

[0085] Preferably, the control device 4 is configured to provide a corresponding signal in response to the detected event and / or condition. The control device 4 can, for example, be configured to store the signal in a memory and / or output it via a signal output means of the power tool, in particular an acoustic or visual signal. The stored signal can, in particular, be a data recording in which data detected by the sensor device 2 is recorded. For example, it is a data recording for the purpose of recording the course of an accident.

[0086] Furthermore, the control device 4 can be configured to perform a specific control of the drive device 7 in response to the detected event and / or state, for example, to cause the tool 1 to stop being driven and / or to decelerate, in particular to decelerate completely. This is particularly useful if the detected event is a kickback event. The deceleration can be effected, in particular, with the same electric motor that otherwise drives the tool 1.

[0087] Alternatively or additionally, the power tool may comprise a braking means and the control device may be designed to control the braking means in response to the detected event and / or signal such that the tool 1 is braked.

[0088] The control device 4 is expediently designed, in the event of a detected kickback event, to decelerate the tool 1 via the drive device 7 and / or the braking means at a time in which no recoil or kickback of the power tool and / or the workpiece 11 has yet occurred. For example, the deceleration can take place at a time in which, returning to the Figure 2 , the directional threshold value 17 or 18 has already been exceeded, but the mechanical vector quantity 3 is preferably not yet in the third directional range 16. In this way, the recoil or recoil caused by the kickback can be reduced or completely prevented.

[0089] Furthermore, the power tool 10, 60 can comprise a positioning device 29, which is designed to selectively position the tool 1 in an operating position or a safety position. The control device 4 can be designed to control the positioning device 29 in response to the detected event and / or the detected state, so that the tool 1 is positioned in the operating position or the safety position. The positioning device 29 is designed, for example, to move and / or pivot the tool 1 between the operating position and the safety position. Expediently, the tool 1 is positioned further into the housing 6 in the safety position than in the operating position. Expediently, the tool 1 is positioned in the safety position in response to a kickback event.

[0090] The Figure 9shows a flowchart of a method for detecting an event and / or a state of a power tool 10, 20, 30, 40, 50, 60 with a rotatable tool 1 designed as a saw blade or milling cutter. The method comprises the steps of: detecting, S1, a mechanical vector quantity 3, namely a force, an acceleration, a speed, a deflection, a deformation and / or a mechanical stress that depends on a force emanating from the tool 1, and detecting the event and / or state of the power tool according to a change in direction (and optionally a direction) of the detected mechanical vector quantity 3.

[0091] The method is expediently carried out using one of the power tools 10; 20; 30; 40; 50; 60 explained above.

[0092] Preferably, the method comprises a further step in which one of the reactions discussed above is carried out to the detected event and / or the detected condition.

Claims

1. Power tool (10; 20; 30; 40; 50; 60) with a rotatable tool (1) designed as a saw blade or milling cutter, comprising a sensor device (2) for detecting a mechanical vector quantity (3), wherein the mechanical vector quantity (3) comprises a force, an acceleration, a velocity, a deflection, a deformation and / or a mechanical stress, and the mechanical vector quantity (3) depends on a force emanating from the tool (1), wherein the direction of the detected vector quantity corresponds to the direction, in which the tool (1) urges relative to another component of the power tool (10; 20; 30; 40; 50; 60), and a control device (4) communicatively coupled to the sensor device (2), characterized in that the control device (4) is adapted to recognize an event and / or a state of the power tool (10; 20; 30; 40; 50; 60) according to a change of direction of the mechanical vector quantity (3) detected by the sensor device (2), wherein the control device (4) is adapted to recognize, as the event and / or the state to be recognized, a kickback, a forward sawing, a backward sawing and / or a plunging of the tool (1) into a workpiece (11) .

2. Power tool (10; 20; 30; 40; 50; 60) according to claim 1, characterised in that the control device (4) is adapted to provide at least one directional range (14, 15, 16) and to recognize the event and / or state based on whether the direction of the mechanical vector quantity (3) is within or outside the directional range (14, 15, 16).

3. Power tool (10; 20; 30; 40; 50; 60) according to claim 1 or 2, characterized in that the control device (4) is adapted to provide a plurality of directional ranges (14, 15, 16) and to recognize different events and / or states based on which of the directional ranges (14, 15, 16) the direction of the mechanical vector quantity (3) lies in.

4. Power tool (10; 20; 30; 40; 50; 60) according to claim 2 or 3, characterized in that the control device (4) is designed to carry out a calibration of one or more directional ranges (14, 15, 16).

5. Power tool (10; 20; 30; 40; 50; 60) according to any one of claims 1 to 4, characterized in that the control device (4) is adapted to recognize the event and / or state based on an angular velocity and / or an angle of change of the mechanical vector quantity (3).

6. Power tool (20; 30; 40) according to one of claims 1 to 5, characterized in that the sensor device (2) comprises a first sensor element (25) and a second sensor element (26), the first sensor element (25) being adapted to measure a mechanical quantity underlying the mechanical vector quantity (3) in a first spatial direction and the second sensor element (26) being adapted to measure the mechanical quantity underlying the mechanical vector quantity (3) in a second spatial direction different from the first spatial direction.

7. Power tool (20; 30; 40) according to claim 6, characterized in that the power tool (20; 30; 40) further comprises a support structure (21) and an output shaft (8) mounted on the support structure (21), to which output shaft (8) the tool is coupled, wherein the sensor elements (25, 26) are arranged on the support structure (21).

8. Power tool (40) according to claim 7, characterized in that the support structure (21) comprises a first subsection (22), in particular a gear housing, and a second subsection (23), and the two sensor elements (25, 26) are each designed as connecting elements between the first subsection (22) and the second subsection (23).

9. Power tool (50) according to any one of claims 1 to 8, characterized in that the sensor device (2) comprises a measuring bearing (28).

10. Power tool (10; 20; 30; 40; 50; 60) according to any one of claims 1 to 9, characterised in that the control device (4) is adapted to provide a signal in response to the recognized event and / or state.

11. Power tool (10; 20; 30; 40; 50; 60) according to any one of claims 1 to 10, characterized in that the power tool (10; 20; 30; 40; 50; 60) comprises a drive device (7) for driving the tool (1) and the control device (4) is adapted to control the drive device (7) in response to the recognized event and / or the recognized state in order to change the driving of the tool (1), in particular to brake the tool (1).

12. Power tool (10; 60) according to any one of claims 1 to 11, characterised in that the power tool comprises a positioning device (29) which is adapted to position the tool (1) selectively in an operating position or a safety position and the control device (4) is adapted to control the positioning device (29) in response to the recognized event and / or the recognized state so that the tool (1) is positioned in the operating position or the safety position.

13. Method for recognizing an event and / or state of an power tool (10; 20; 30; 40; 50; 60) with a rotatable tool (1) designed as a saw blade or milling cutter, comprising the steps: detecting (S1) a mechanical vector quantity (3), wherein the mechanical vector quantity (3) comprises a force, an acceleration, a velocity, a deflection, a deformation and / or a mechanical stress and the mechanical vector quantity (3) depends on a force emanating from the tool (1), wherein the direction of the detected vector quantity corresponds to the direction, in which the tool (1) urges relative to another component of the power tool (10; 20; 30; 40; 50; 60), characterised by recognizing (S2) the event and / or state of the power tool (10; 20; 30; 40; 50; 60) according to a change of direction of the detected mechanical vector quantity (3), wherein the event and / or the state comprises a kickback, a forward sawing, a backward sawing and / or a plunging of the tool (1) into a workpiece (11).