DE102017107485A1 - Oscillably drivable hand tool and method for operating such - Google Patents

Abstract

The invention relates to an oscillating drivable hand tool with a drive (28) for the oscillating drive of a tool, with at least one vibration sensor (32) for monitoring vibrations in at least one plane whose output signal (v, v, v) of a control unit (30). which is adapted to derive a vibration characteristic value (vk) from the output signal (v, v, v) of the vibration sensor (32) and, when the vibration characteristic value (vk) exceeds a limit value (vk), the drive (28) switch off and then restart automatically.

Description

The invention relates to an oscillating drivable hand tool, with a drive for oscillating drive of a tool, and with at least one vibration sensor for monitoring vibrations whose output signals are fed to a control unit.

Such a hand tool is from the DE 10 2007 014 891 A1 known.

In this case, the accelerations occurring are to be determined to determine the vibration load of persons by means of a measuring device and, if necessary, a shutdown of the hand tool are performed after exceeding a predetermined limit.

However, this is essentially done by detecting and summing the vibrations over a longer operating life of the tool, and then, when a time-weighted predetermined limit is reached, a shutdown is performed.

It is not intended to shut down during operation if a certain vibration limit is exceeded.

According to the WO 2015/197753 A1 It is also known to use in a hand tool in the form of a hammer drill a sensor for detecting vibration values in order to reduce the output power of the hand tool when a predetermined limit value is exceeded.

Against this background, the invention has the object to provide an oscillating drivable hand tool and a method for operating such, wherein a monitoring of the vibrations occurring during operation is performed and a short-term shutdown occurs when a predetermined limit value is exceeded to the extent of the vibrations for to reduce a user to physiologically more favorable levels.

This object is achieved in an oscillating drivable hand tool with a drive for oscillating drive a tool, with at least one vibration sensor for monitoring vibrations in at least one plane whose output signals are fed to a control unit, characterized in that the control unit is adapted to from the output signals derive a vibration characteristic of the vibration sensor and then, if the vibration characteristic exceeds a maximum value, turn off the drive and then restart automatically.

• - Starten eines oszillierenden Antriebs;
• - zyklische Messung der Beschleunigung in drei Raumrichtungen;
• - Berechnen eines Vibrationskennwertes aus den Beschleunigungswerten in drei Raumrichtungen;
• - Anhalten des Antriebs, sofern der Vibrationskennwert einen vorgegebenen Grenzwert überschreitet; und
• - erneutes Starten des oszillierenden Antriebs nach Ablauf einer vorgegebenen Zeit.

With regard to the method, the object of the invention is further achieved by a method for operating an oscillatingly handleable hand tool with the following steps:

• - starting an oscillating drive;
• - Cyclic measurement of acceleration in three spatial directions;
• Calculating a vibration characteristic from the acceleration values in three spatial directions;
• - stopping the drive if the vibration characteristic exceeds a given limit; and
• - Restart the oscillating drive after a predetermined time.

The object of the invention is achieved in this way.

According to the invention a careful monitoring is ensured that the hand tool is not operated with excessive vibration exceeding a physiologically harmless limit. Since the drive is automatically restarted after being turned off, the limitation of the vibrations to some extent can be imperceptible to the user.

For this purpose, the control unit may be designed, for example, to have the drive after a switch-off within a time span which is in the range from 2 seconds to 0.1 seconds, preferably between 1.5 and 0.5 seconds, particularly preferably between 1.2 and 0.8 seconds, to restart, preferably in soft start, preferably up to a preset oscillation frequency of up to 25000 1 / min.

If the automatic restart of the drive takes place after such a short period of time, the restart can be largely unnoticed by the user, especially if the startup is carried out in soft start, i. with increasing speed over time.

In an advantageous embodiment of the invention, the sampling rate for determining the vibration characteristic value is greater than the maximum oscillation frequency of the drive, wherein the ratio between the sampling rate and the maximum oscillation frequency is preferably greater than 2.

In this way, a sufficiently frequent sampling to determine the vibration characteristic is guaranteed, even at different sizes maximum oscillation frequencies to ensure the detection of the vibration characteristic.

According to a further feature of the invention, the drive with a drive motor for generating a rotationally oscillating drive movement of a tool spindle, on which a tool can be fixed, formed around a fixed axis, wherein the drive movement of the tool spindle preferably with a small pivoting angle in the range of 0.5 ° to 5 ° and preferably with a high oscillation frequency of up to 25,000 1 / min, and wherein the drive motor for generating the rotationally oscillating drive movement is preferably coupled to an oscillating gear.

Usually, the drive consists of a combination of a drive motor and an oscillation gear, which converts the rotational movement of the motor shaft of the drive motor in the desired rotational oscillating drive movement of the tool spindle about its longitudinal axis. In principle, however, drives are conceivable in which the rotationally oscillating drive movement of the tool spindle is generated directly by a hydraulic motor, such as a rotary vane motor, which is driven by a hydraulic generator with oscillating fluid energy, as for example from WO 2015/071304 A1 is known.

According to a further embodiment of the invention, the drive is designed as an assembly which is coupled to a housing of the hand tool via at least one preferably elastic damping element.

In such an embodiment, the limitation of the vibrations to a predetermined maximum value is particularly effective. Hand tools in which the drive is vibration-decoupled from the housing are known in principle, for example WO 2015/140029 A1 , which is hereby incorporated by reference in its entirety.

According to a further embodiment of the invention, the vibration sensor is rigidly connected to the housing.

In this way, the vibrations can be detected directly, even if the drive is connected by means of elastic damping elements vibrationally decoupled with the housing.

Preferably, the vibration sensor is accommodated on an electronic board, which is rigidly connected to the housing.

More preferably, the vibration sensor is designed as an acceleration sensor, which detects three mutually perpendicular sensor directions.

In this way, as a vibration sensor, a conventional acceleration sensor can be used.

According to a further embodiment of the invention, the vibration sensor is aligned so that at least one sensor device is angularly offset, preferably arranged at 45 ° with respect to a main direction of the vibrations.

This measure has the advantage that lower-cost vibration sensors can be used, which are designed only for a lower maximum vibration. Because of the angularly offset arrangement with respect to the main vibration direction, the detected vibration values are lower. If the sensor direction is aligned at 45 ° to the main vibration direction, then only one value is detected by the assigned axes, which corresponds to the actual acceleration divided by 2, ie only about 0.7 times. Thus, more cost-effective vibration sensors can be used.

According to a further embodiment of the invention, the control device is designed to separately evaluate the output signals of the vibration sensor for the three sensor directions and preferably to smooth and filter and to calculate therefrom a sum signal which is used as a vibration characteristic.

Such an evaluation method is particularly precise, since all sensor directions are used.

According to a further embodiment of the invention, the control device is designed to first rectify and average the output signals of the vibration sensor before the vibration characteristic value is calculated therefrom.

This results in a particularly reliable determination of the vibration characteristic.

According to a further embodiment of the invention, the control device is designed to form the square for each output signal of the vibration sensor relating to each sensor direction and to use the root of the sum of the respective factor-weighted squares as the vibration characteristic value.

According to a further embodiment of the invention, a modified cut-off limit value is used which depends on the oscillation frequency of the hand tool.

In this way, the physiological relationship can be exploited that larger accelerations are tolerable at higher oscillation frequencies than at lower oscillation frequencies.

For this purpose, a means for measuring the rotational speed of the drive motor is preferably provided, wherein the control device is further adapted to calculate from the rotational speed of the drive motor, a proportionality factor, with which the limit value is weighted to obtain a speed-weighted limit, when it exceeds the shutdown and the subsequent start of the drive takes place.

In this way, a relationship between the rotational speed of the drive motor and the allowable maximum vibration value can be used.

In an additional development of this embodiment, a means for measuring the current consumption of the drive motor is further provided, preferably by measuring the phase current, wherein the control device is adapted to calculate a current consumption of the drive motor, the current consumption is used as an additional switch-off criterion for speed-weighted limit and a Shutdown only takes place when both the vibration characteristic exceeds a predetermined limit dependent on the speed limit, and the current consumption of the drive motor exceeds a predetermined dependent on the speed limit.

In this way, both a dependence of the maximum allowable vibration of the rotational speed and of the output power of the hand tool can be used.

The predetermined limit value for the vibration index or the speed-weighted limit value is preferably at least 10 g (i.e., 10 times the acceleration of gravity), preferably at least 12 g.

If a speed-weighted limit is used for shutdown, it may tend to be slightly higher, for example in the range between 14 g and 16 g.

The limit value or speed-weighted limit value relating to the maximum permissible vibration as well as the limit value relating to the maximum permissible current consumption are preferably read from a look-up table.

It is understood that the features mentioned above in connection with the hand tool can also be used in connection with the above-mentioned method for operating an oscillatingly drivable hand tool. It is further understood that the features of the invention mentioned above and those yet to be explained below can be used not only in the respectively indicated combination but also in other combinations or alone, without departing from the scope of the invention.

• 1 eine perspektivische Darstellung eines erfindungsgemäßen Handwerkzeugs;
• 2 eine Darstellung des Handwerkzeugs gemäß 1 nach Abnahme eines Teils des das Handwerkzeug umschließenden Gehäuses;
• 3 eine Seitenansicht des Handwerkzeugs gemäß 1;
• 4 einen Schnitt durch das Handwerkzeug gemäß 3 längs der Linie IV-IV;
• 5 eine perspektivische Ansicht des Vibrationssensors in vergrößerter Darstellung;
• 6 ein Ablaufdiagramm (Flow-Chart), das den grundsätzlichen Aufbau des Verfahrens zum Erfassen der Vibrationen mittels des Vibrationssensors und zur Berechnung des Vibrationskennwertes nebst Abschalten und Wiederanfahren im Falle einer Überschreitung des Grenzwertes zeigt;
• 7 ein Ablaufdiagramm, das die Berechnung des Vibrationskennwertes aus den einzelnen Beschleunigungswerten im Detail erläutert; und
• 8 ein Ablaufdiagramm für eine alternative Ausführung der Erfindung, bei welcher ein modifizierter Vibrationskennwert ermittelt und zur Abschaltung verwendet wird.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the drawings. Show it:

• 1 a perspective view of a hand tool according to the invention;
• 2 a representation of the hand tool according to 1 after removal of a part of the housing enclosing the hand tool;
• 3 a side view of the hand tool according to 1 ;
• 4 a section through the hand tool according to 3 along the line IV-IV;
• 5 a perspective view of the vibration sensor in an enlarged view;
• 6 a flow chart, which shows the basic structure of the method for detecting the vibrations by means of the vibration sensor and for calculating the vibration characteristic plus shutdown and restarting in case of exceeding the limit value;
• 7 a flowchart illustrating the calculation of the vibration characteristic of the individual acceleration values in detail; and
• 8th a flow chart for an alternative embodiment of the invention, in which a modified vibration characteristic is determined and used for shutdown.

In 1 is a perspective view of a hand tool according to the invention shown, which is designed for the oscillating drive of a tool, such as in the form of a grinding cutting or sawing tool.

The total with the numeral 10 designated hand tool has a housing 12 on, whose back area 14 can be grasped by a hand to the hand tool 10 to be able to comfortably hold in one hand. At the top of the housing is an on / off switch 16 recognizable, for switching on and off of the hand tool 10 serves. At the left longitudinal side of the grip area 14 is a wheel 26 recognizable, that to adjust the oscillation frequency is used. Thus, the oscillation frequency can be infinitely adjusted between 10,000 and about 20,000 oscillations per minute.

At the grip area 14 facing away from the front area is a tension lever at the top 18 taken for fast clamping a tool (not shown) at the outer end of a tool spindle 20 Serves at an angle from the front end of the hand tool 10 protrudes downwards. The tool spindle 20 can around its longitudinal axis 22 are rotationally driven driven, as by a double arrow 24 is indicated. The pivoting angle here is relatively low (between about 0.5 ° and 5 °), while the oscillation frequency, as already mentioned above, can be up to about 20,000 oscillations per minute.

2 shows the closer structure of the hand tool 10 after removal of the rear housing part 14 in the grip area 14 , In the middle area of the hand tool 10 is a drive 28 taken, which is designed as a self-supporting unit and includes a drive motor and an oscillating gear, as described below with reference to 4 will be described in more detail.

In the rear, the tool spindle 20 applied area is an electronic board 19 recognizable, on the wheel 26 is received, and a central control unit (not shown) and a vibration sensor 32 ,

The closer construction of the hand tool 10 is from the 3 and 4 seen.

Out 4 it can be seen that the drive 28 from the drive motor 34 and the oscillation gear 38 consists. The motor shaft 36 of the drive motor 34 drives an oscillation fork of the oscillation gear via an eccentric 38 and thus sets a rotary motion of the motor shaft 36 in a rotationally oscillating drive movement of the tool spindle 20 around its longitudinal axis.

The drive 28 is with the drive motor 34 and the oscillation gear 38 formed together as a self-supporting unit, which has several elastic damping elements 40 . 42 . 44 . 46 with the housing 12 is coupled.

Vibrations coming from the drive 28 or from the tool spindle 20 taken out tool, are thus only attenuated on the grip area 14 of the housing 12 transfer.

In 4 is still the longitudinal axis of the hand tool 10 recognizable, denoted by 48, and the main direction of the vibrations v, which are perpendicular to the longitudinal axis 48 stands.

On the electronics board 19 is the central control unit 30 recorded, which includes a microprocessor, and the vibration sensor 32 ,

The vibration sensor 32 , which may be formed, for example, as a piezoelectric sensor, is enlarged in 5 shown. The vibration sensor 32 has three sensor axes x, y, z, which are arranged at right angles to each other in a Cartesian coordinate system. Preferably, the vibration sensor 32 like that on the electronics board 29 mounted, that the sensor axes x, y are arranged at an angle of 45 ° to the main direction v of the vibrations, ie by 45 ° relative to the longitudinal axis 48 of the hand tool 10 are angularly offset.

This has the consequence that the vibrations occurring in the main direction v are detected only attenuated by the sensor axes x, y, namely by a factor of root 2 reduced. Thus, a relatively inexpensive vibration sensor 32 which does not have to be designed for very high acceleration limits.

The method used according to the invention, by means of the vibration sensor 32 measured vibrations of the hand tool 10 to capture and to the vibration of the hand tool 10 to limit to a maximum allowable level, is below using the 6 to 8th explained in more detail.

6 shows a flowchart (flow chart), from which the basic principle of the method according to the invention can be seen.

After starting at 60, the timer is set to 0 at 62 (t = 0).

Subsequently, at 64 by means of the vibration sensor 32 the acceleration is measured in all three sensor axes v _x , v _y , v _z .

From this, a resulting acceleration vector is determined at 66, which is then filtered at 68 in order to determine a vibration characteristic value vk from this.

The duty cycle at which the acceleration values are v _x, v _y v _z was added at 64, is about 1.5 kHz and is approximately twice as large as the maximum oscillation frequency of about 20,000 1 / min, which corresponds to approximately 335 Hz.

at 70 is then queried whether the elapsed time .DELTA.t is greater than a predetermined period of, for example, 1 s.

If this is the case (y), the further drive is in nominal operation, which is indicated at 78. In the subsequent query 80 is checked if the at 68 determined vibration characteristic value vk is greater than the maximum value vk _max . This may, for example, be 12.8 g (g = gravitational acceleration = 9.81 m / s ² ). If this is the case (y), a loopback occurs 82 back to initialization at 62. If this is not the case (n), then it continues at 74, ie with a speed control to one by means of the setting wheel 26 set speed or oscillation frequency. From there, a loopback takes place 76 back to the acceleration values at 64.

Is at the query 70 the elapsed time .DELTA.t less than 1 s (n), the speed at 72 is further increased (soft start / run-up) until the machine is controlled at 74 in their speed.

Out 6 It can be seen that when the calculated vibration characteristic value vk is greater than the predetermined maximum vibration characteristic value vk _max , the drive is stopped and the engine is immediately restarted.

Thus, a limitation of the vibrations to a maximum allowable value can be carried out electronically, this being largely unnoticed by the user, since the subsequent restarting takes place in a time duration which is less than 1 s.

7 shows the flowchart for the cyclic measurement and processing of the vibration characteristic vk. This is at 6 practically inserted between 64 and 68. The cyclic measurement and processing of the vibration characteristic value vk at 90 starts according to 7 at 92 with the measurement of the acceleration values v _x , v _y , v _z for the three sensor axes x, y, z.

Subsequently, the squares of the measured values v _x ² , v _y ² , v _z ^{2 are} determined at 94. These are then filtered at 96 for the individual sensor axes, so that the values av _x ² , av _y ² , av _z ² result. at 98 the vibration characteristic value is calculated from this by preferably forming the sum of the values av _x ² + av _y ² + av _z ² and from this the root is drawn. In principle, of course, only a single axis or two axes could be used. However, the measurement accuracy is highest when all sensor axes x, y, z are used.

After the calculation at 98, a loop goes 100 back to the beginning at 92.

As mentioned above, the sampling rate of the acceleration measurement is higher than the maximum vibration frequency. The ratio is greater than 2: 1.

A modification of the method described above is described below with reference to 8th explained.

8th shows the cyclical determination of a modified vibration characteristic at which is switched off, which is illustrated by 102. at 104 First, the speed n is measured. This can be done by means of a separate speed sensor (not shown). However, since the drive motor is designed as an EC motor (electronically commutated motor), the frequency of the control is already known in any case, so that an additional speed sensor can possibly be dispensed with.

at 106 the vibration characteristic value kn is determined, cf. 7 ,

at 108 In addition, the current consumption of the drive motor 34 measured, which is done by measuring the current phase current I.

at 110 Subsequently, a speed-proportional phase current cut-off value is determined therefrom, wherein the speed is preferably received with a proportionality factor p2 between 1.5 and 2.5.

A shutdown of the drive (see. 6 , Query 80 ) takes place when the vibration characteristic value vk is greater than the predetermined speed-weighted limit value vkn _max and additionally the speed-weighted current consumption I _{n is} greater than the maximum predetermined current consumption I _max .

In this case, the Phasenstromabschaltwert I _{max is} preferably determined from a look-up table.

Also, the speed-weighted limit value vkn _max for the maximum allowable vibration is preferably determined from a look-up table.

The limit value vkn _max is preferably somewhat larger than in the case of the simplified method according to FIG 6 , As a result of the speed weighting, the switch-off value vkn _{max is} preferably in the range from 14 g to 16 g.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The 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

• DE 102007014891 A1 [0002]
• WO 2015/197753 A1 [0006]
• WO 2015/071304 A1 [0017]
• WO 2015/140029 A1 [0019]

Claims (18)

Oscillably drivable hand tool, with a drive (28) for oscillating drive of a tool, with at least one vibration sensor (32) for monitoring vibrations in at least one plane whose output signal (v _x , v _y , v _z ) supplied to a control unit (30) characterized in that the control unit (30) is adapted to derive a vibration characteristic value (vk) from the output signal (v _x , v _y , v _z ) of the vibration sensor (32) and when the vibration characteristic value (vk) reaches a limit value (vk _max ), turn off the drive (28) and then restart automatically. Hand tool after Claim 1 , characterized in that the sampling rate (f _T ) for determining the vibration characteristic value (vk) is higher than the maximum oscillation frequency (f _max ) of the drive (28), the ratio between the sampling rate and the maximum oscillation frequency (f _T / f _max ) is preferably greater than 2. Hand tool after Claim 1 or 2 , characterized in that the control unit (30) is adapted to the drive (30) after a shutdown within a period of time .DELTA.t, which is in the range of 2 seconds to 0.1 seconds, preferably between 1.5 seconds and 0.5 Seconds is, more preferably between 1.2 seconds and 0.8 seconds, to restart, preferably in soft start, preferably up to a preset oscillation frequency of up to 25000 1 / min. Hand tool according to one of the preceding claims, characterized in that the drive (28) with a drive motor (34) for generating a rotationally oscillating drive movement of a tool spindle (20) on which a tool can be fixed, about a fixed axis (22) is formed, wherein the drive movement of the tool spindle (20) is preferably carried out with a small pivoting angle in the range of 0.5 ° to 5 ° and preferably with a high oscillation frequency of up to 25000 1 / min, and wherein the drive motor (34) for generating the rotationally oscillating drive movement preferably coupled to an oscillating gear (38). Hand tool after Claim 4 , characterized in that the drive (28) is designed as an assembly which is coupled to a housing (12) of the hand tool (10) via at least one preferably elastic damping element (40, 42, 44, 46). Hand tool after Claim 4 or 5 , characterized in that the vibration sensor (32) is rigidly connected to the housing (12). Hand tool after Claim 6 , characterized in that the vibration sensor (32) is received on an electronic board (30) which is rigidly connected to the housing (12). Hand tool according to one of the preceding claims, characterized in that the vibration sensor (32) is designed as an acceleration sensor which detects three mutually perpendicular sensor directions (x, y, z). Hand tool after Claim 8 , characterized in that the vibration sensor (32) is aligned so that at least one sensor direction (x, y) is angularly offset, preferably arranged at 45 ° with respect to a main direction (v) of the vibrations. Hand tool after Claim 8 or 9 , characterized in that the control device (30) is adapted to evaluate one, two or three output signals of the vibration sensor for the sensor directions (x and / or y and / or z) separately and preferably to smooth and filter, and preferably a sum signal to be calculated, which is used as a vibration characteristic (vk). Hand tool after Claim 10 , characterized in that the control device (30) is adapted to calculate the sum signal from the output signals (v _x , v _y , v _z ) for all three sensor directions (x, y, z) of the vibration sensor (32). Hand tool according to one of the preceding claims, characterized in that the control device (30) is adapted to first rectify and average the output signals (v _x , v _y , v _z ) of the vibration sensor (32) before the vibration characteristic value (vk) is derived therefrom. is calculated. Hand tool after Claim 10 . 11 or 12 , characterized in that the control device (vk) is designed to form the square for each output signal (v _x , v _y , v _z ) of the vibration sensor (32) concerning each sensor direction (x, y, z) and as a vibration characteristic value ( vk) to use the root of the sum of the respective factor-weighted squares (av _x ² + av _y ² + av _z ² ) ^1/2 . Hand tool according to one of the preceding claims, characterized in that a modified limit value is used, which depends on the oscillation frequency (f _max ) of the hand tool (10), and that a shutdown only then takes place when in addition to the vibration characteristic and the speed-rated power consumption of the drive motor (34) exceeds a limit. Hand tool after Claim 14 , characterized in that a means for measuring the rotational speed (n) of the drive motor (34) is provided, and that the control device (30) is adapted to calculate from the rotational speed (n) of the drive motor, a proportionality factor (p1), with the limit value is weighted so as to obtain a speed-weighted limit value (vkn _max ) above which switching off and subsequent starting of the drive (28) occurs, wherein the proportionality factor (p1) is preferably less than three, preferably less than two , and preferably deposited in a look-up table. Hand tool after Claim 14 or 15 , characterized in that a means for measuring the rotational speed (n) of the drive motor (34) is provided, that a means for measuring the current consumption of the drive motor (34), preferably by measuring the phase current (I) is provided, and that the Control device (30) is adapted to calculate a speed-weighted current consumption (In) of the drive motor (34), in which a of the speed (n) derived proportionality factor (p2) is used, which is preferably between 1.2 and 2.7 , preferably between 1.5 and 2.5, wherein the speed-weighted current consumption (In) is used as an additional switch-off criterion for the speed-weighted limit value and a shutdown occurs only when both the vibration characteristic value (kn) exceeds a predetermined speed-weighted limit value (vkn _max ), as well as the speed-weighted current consumption (In) of the drive motor exceeds a predetermined limit (I _max ). Hand tool according to one of the preceding claims, characterized in that the predetermined limit value (vk _max ) for the vibration characteristic value or the speed-weighted limit value (vkn _max ) is at least 10 g, preferably between 14 g and 16 g. A method of operating an oscillatory drivable hand tool comprising the steps of: - starting an oscillating drive (28); - Cyclic measurement of the acceleration (v _x , v _y , v _z ) in three spatial directions; - calculating a vibration characteristic value (CV) from the acceleration values (v _x, v _y, v _z) in the three spatial directions (x, y, z); - stopping the drive if the vibration characteristic value (vk) exceeds a predetermined limit (vk _max ); and - restarting the oscillating drive (28) before expiration of a predetermined time (Δt <t ₁ ).

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