ELECTRICALLY OPERATED CUTTING GRINDER WITH VIBRATION FUNCTION

Abstract

Electrically operated construction machine (100, 1200, 1300, 1400, 1500) with an electric motor (120) which is set up to drive an abrasive cutting tool (130) via a drive arrangement (200), wherein the abrasive cutting tool (130) comprises abrasive elements (131) arranged on a carrier (132) of the cutting tool (130), wherein the abrasive elements (131) are spaced apart from each other on the carrier (132) and follow a closed path during operation of the construction machine, wherein the construction machine (100, 1200, 1300, 1400, 1500) further comprises a vibration device (120, 300, 350, 400, 500, 600, 700, 800) which is configured to generate a controlled amount of vibration of the abrasive cutting tool (130), the vibration being generated in a frequency band below 15 kHz.

Description

TECHNICAL FIELD

[0001] This disclosure relates to handheld, electrically powered power cutters and other abrasive tools for cutting hard materials such as concrete and stone. Although the techniques discussed herein are primarily intended for use with power cutters, they may also be applied to other types of electrically powered construction equipment for cutting concrete and stone, such as core drills and wall saws. BACKGROUND

[0002] Power cutters are handheld construction machines that use a rotating cutting wheel to cut hard materials such as concrete and stone. Power cutters are traditionally powered by an internal combustion engine. However, electric machines are also available, and battery-powered machines are becoming increasingly common.

[0003] WO 2021 / 107827 A1 discloses an example of an electric-driven cut-off machine.

[0004] There is a desire to improve the cutting performance of electric cut-off machines and other electrically powered construction machines. SUMMARY

[0005] An object of the present disclosure is to increase the cutting performance of electric power cutters and other electrically powered construction machines. This object is achieved by the electrically powered construction machine disclosed herein, which comprises an electric motor configured to drive an abrasive cutting tool via a drive arrangement. The abrasive cutting tool comprises abrasive elements arranged on a carrier of the cutting tool, wherein the abrasive elements are spaced apart from one another on the carrier in order to follow a closed path during operation of the construction machine. The construction machine further comprises a vibration device configured to generate a controlled vibration of the abrasive cutting tool. The vibration is generated in a frequency band below 15 kHz, i.e.The vibration is a non-ultrasonic vibration, which in some examples mimics the vibration generated by an internal combustion engine during operation and in others is adapted for sharpening abrasive elements on the cutting tool. This vibration device generates vibrations that propagate to the abrasive elements, which positively affects the cutting performance of the cutting tool. The vibrations make the cutting process more similar to that of construction machinery with internal combustion engines, where the vibration can clean the abrasive tool as it penetrates the work object. The vibrations generated are preferably non-uniform, i.e., irregular or random. This type of randomness in the vibration pattern can improve the performance of the construction machine.

[0006] In some examples, the vibration is generated at frequencies below 5 kHz or even below 1 kHz. This type of vibration is a type of mechanical vibration that mimics the vibration generated by an internal combustion engine during operation.

[0007] The vibration device can be configured to be activated and deactivated in response to a user input signal, e.g., an input signal from a control button or the like. This allows the user to activate the vibration function or optionally operate the tool without vibration, depending on their preference and / or the cutting task being performed. The function can also be advantageously used to temporarily activate vibration to sharpen the abrasive elements of the abrasive cutting tool. Automatic activation and deactivation of the vibration device are also discussed here.

[0008] The vibration device can optionally also be configured to generate vibrations with a configurable amplitude and / or frequency. The amplitude and / or frequency can be optimized, for example, for a specific work task or according to the user's wishes, which is an advantage. The vibration device can also be configured to generate vibrations in the radial and / or axial direction relative to the tool axis, depending on the work task and / or user requirements. Certain machine types also benefit from vibrations in different directions. The vibration characteristics can be preconfigured or adjusted during operation in response to user inputs. Please note that the vibration does not have to be generated at a fixed frequency and / or amplitude.In some cases, advantages can be achieved by varying the frequency composition and / or amplitude of the generated vibration in a non-uniform manner over time, i.e., by adding a degree of randomness to the generated vibration. A pseudo-noise sequence can be used to generate such non-uniform or random vibration.

[0009] The vibration device is preferably arranged in conjunction with a tool axis of the construction machine and spaced from other parts of the construction machine, such as the handles. The main purpose of supplying vibration is to improve cutting performance by supplying a controlled amount of vibration to the cutting tool during operation. The vibration is intended to promote vibration within the tool itself, which can be achieved by arranging the vibration device near the tool axis. At the same time, vibrations may be undesirable in other parts of the equipment, such as handles and in conjunction with sensitive control circuits, and the like. Therefore, it may be desirable to suppress vibrations in parts of the equipment other than the tool, which can be achieved by arranging the vibration device near the tool axis.

[0010] The controlled vibration intensity is a non-ultrasonic vibration in a frequency band below 15 kHz, and in most examples, below 5 kHz or even below 1 kHz. This type of non-ultrasonic vibration has been shown to improve the cutting performance of the abrasive cutting tool 130, at least in part because the vibration cleans the abrasive elements 131 during operation, and often also because the vibration improves the interaction between the abrasive elements 131 and the work object being machined by the construction machine. Thus, the controlled amount of vibration generated by the vibration device of the present disclosure is fundamentally different from the ultrasonic vibration generated by the tool in JPH0482609A, which has a much higher frequency.The purpose of the ultrasonic vibrations generated by the tool in JPH0482609A is to pulverize workpiece residues in the cut and not to improve the performance of the tool, hence the difference in the vibration frequency band.

[0011] The vibration device can be configured to be driven by the main electric motor of the construction machine or by a motor and / or a magnetic device separate from the main electric motor of the construction machine. Combinations of drive arrangements for the vibration device are also possible. One advantage of using a separate electric motor and / or a magnetic device to generate vibration is that the vibration can be controlled independently of the operation of the main motor.

[0012] The vibration device can be simple in design, e.g., consisting of a mass and spring arrangement. These arrangements are robust and also cost-effective.

[0013] The main electric motor of the construction machine can also serve as the vibration device. In other words, the main drive motor itself can be used to generate a controlled amount of vibration. This is advantageous because it eliminates the need for additional hardware to generate vibration. A control unit configured to control the main electric motor to a target speed (also known as target rpm) can, for example, be programmed to vary the target speed over time. This makes it possible to control the frequency of the vibration by modulating an axle speed command over time. The control unit can also be configured to control the amplitude of the vibration by modulating the axle speed command over time, which is an advantage.

[0014] In some aspects, the electrically powered construction machine includes an inertial measurement unit (IMU) configured to output a signal indicative of vibration. The control unit can then be configured to control the main electric motor based on the IMU output signal to achieve a desired frequency and / or amplitude of vibration. This is a feedback system in which the effects of a particular applied vibration in the tool are measured and fed back to the control unit. The control unit can then modulate the vibration, for example, in terms of amplitude and frequency composition, to achieve a desired vibration pattern near the tool, which is an advantage. The feedback signal can also be used to ensure that the vibration intensity does not exceed a maximum allowable value.

[0015] The electrically powered construction machine may also include a user interface configured or designed to activate and deactivate the vibration device. This user interface may be either a digital interface with a menu system through which the function can be activated, or a simpler button or knob that can be operated by a user to activate and deactivate the vibration function. The interface may, of course, also be used to control the frequency and / or strength of the generated vibration. For example, a user may operate a knob to increase the strength and / or frequency of the vibration, similar to the volume control on a stereo system.

[0016] In general, all terms used in the claims should be construed according to their ordinary meaning in the art, unless expressly defined otherwise herein. All references to "an element, device, component, means, step, etc." should be interpreted openly and refer to at least one instance of the element, device, component, means, step, etc., unless expressly stated otherwise. The steps of a method disclosed herein need not be performed in the exact order unless expressly stated otherwise. Other features and advantages of the present invention will become apparent upon studying the appended claims and the following description.Those skilled in the art will recognize that various features of the present invention may be combined to create embodiments other than those described below without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present disclosure will now be described in more detail with reference to the accompanying drawings, in which Fig. 1 shows an example of an electrically powered cutting machine; Fig. 2 shows an exemplary drive arrangement for a cutting machine; Fig. 3A-C illustrate exemplary cam arrangements for generating vibrations; Fig. 4-7 show exemplary mechanisms for generating vibrations; Fig. 8A schematically illustrates a control system for an electric motor; Fig. 8B-C show exemplary change patterns of the target speed of an electric motor; Fig. Figure 9 is a flow chart illustrating the procedures; Fig. 10 shows a control unit with processing circuits; Fig. 11 represents a computer program product; Fig. 12 shows an example of a wall saw; Fig. 13 shows an example of a core drill; Fig. 14 shows an exemplary ring cutter; and Fig. 15 shows a chainsaw with abrasive. DETAILED DESCRIPTION

[0018] The invention will now be described in more detail with reference to the accompanying drawings, in which certain aspects of the invention are illustrated. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments and aspects set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout this specification.

[0019] It is to be understood that the present invention is not limited to the embodiments described herein and illustrated in the drawings; rather, those skilled in the art will recognize that many changes and modifications may be made within the scope of the appended claims.

[0020] Fig. 1 shows an exemplary power cutter 100, i.e., a hand-held cutting tool for cutting workpieces made of hard material such as concrete and stone. The power cutter 100 consists of a housing of a power cutter 110 with a motor 120, which is connected to a rotatable abrasive cutting tool 130 via a drive arrangement in an arm of the driven tool. The abrasive cutting tool 130 comprises abrasive elements 131 arranged on a carrier 132 of the cutting tool 130, which in this case is a disk. The abrasive elements 131 are arranged spaced apart from one another on the carrier 132 and, in a known manner, follow a closed circular path during operation of the construction machine. The power cutter is actuated by a trigger device 180.

[0021] This particular example of a power cutter is a battery-powered electric machine with an electric motor that draws its power from a rechargeable battery 140. Electric power cutters that are powered by a power cable from the mains are also known.

[0022] The 100 power cutter is an example of an electrically powered construction machine. Other examples of electrically powered construction machines are 1200 wall saws, 1300 core drills, 1400 abrasive ring saws, and 1500 abrasive chain saws, as shown in the Fig. 12 to 15. These tools all comprise abrasive cutting tools 130, in which abrasive elements 131 are arranged on corresponding supports 132 of the cutting tools 130. The abrasive elements 131 are arranged spaced apart from one another on the support 132 and follow a closed path during operation of the construction machine. The wall saw 1200 in Fig. 12 has a carrier in the form of a circular saw blade (in Fig. 12 not visible), similar to that of the cut-off machine 100, on which abrasive elements are arranged along the circumference of the saw blade. The core drilling machine 1300 has a cylindrical support 132 on which abrasive elements 131 are arranged along the lower edge of the drill bit, as in Fig. 13. The ring saw 1400 has an annular, rotatable support 132, in which the abrasive elements 131 are arranged along the circumference of the ring. The chain saw 1500 has a saw blade that carries a chain forming the support 132. Abrasive elements 131 are attached to the chain, which is slidably supported by the saw blade in a known manner. The abrasive cutting tool 130 comprises, in all examples 100, 1200, 1300, 1400, 1500, abrasive elements 131 arranged on a support 132 of the cutting tool 130. The abrasive elements 131 are arranged spaced apart from one another on the support 132 and follow a closed path during operation of the construction machine, i.e., a path that begins and ends at the same point. Along this closed path, the abrasive elements engage the work object to be ground or cut.

[0023] The abrasive elements preferably consist of diamonds or grains of another hard material such as carbide.

[0024] Some of the construction machines discussed here are designed to cut into the work piece using abrasive elements arranged along the circumference of a rotating, circular cutting tool such as a saw blade, core bit, or power cutter. In other examples of construction machines, a chain is used instead to carry the abrasive elements. The power cutter 100, the wall saw 1200, the ring saw 1400, and the abrasive chain saw 1500 all have saw blades that create a cut (sometimes called a kerf) whose length substantially exceeds the width of the cut. The width of this cut is determined by the axially measured width of the abrasive elements. The length of the cut depends on how the blade is moved relative to the workpiece and is not dependent on the shape of the tool.The 1300 core drill also creates a cut or kerf whose length is substantially greater than its width, unlike the circular hole created by a normal rotary drill. The width of the cut is again determined by the width of the abrasive elements, while the length of the cut corresponds to the circumference of the core bit. The construction machine discussed here is fundamentally different from normal twist drills, which create circular holes through a cutting rather than a grinding action. One factor that distinguishes the construction machine discussed here from normal twist drills is that the multiple abrasive elements follow a closed path in a plane—that is, a path that begins and ends at the same point on the plane, with the abrasive elements being separated from each other as they move along the path.

[0025] The abrasive elements on the saw blade of a power cutter 100 or a wall saw 1200 or the abrasive elements on a core drill bit 1300 or the abrasive elements on the ring of the ring cutter 1400 follow a circular closed path centered on and spaced from the axis of rotation of the tool, while the abrasive elements on the saw chain of the chain saw 1500 follow an elliptical closed path in a plane of the saw blade, as in Fig. 15 shown.

[0026] The cut-off machine 100, the wall saw 1200, the core drill 1300 and the ring saw 1400 consist of abrasive elements that engage with the workpiece at a distance from the axis of rotation of the rotating circular tools.

[0027] As in Fig. As shown in Figure 1, the power cutter 100 includes a user interface 150 with an input / output device (I / O) and a display device through which an operator of the tool 100 can enter various types of configuration data for the operation of the machine and also receive status messages and the like. The I / O device may include buttons, light-emitting diode (LED) indicators, a buzzer, and also a radio transceiver circuit configured to communicate with a remote device such as a server or an external wireless device such as a tablet or smartphone. The term "I / O device" should be interpreted broadly and include any type of interface to a user or a remote device.

[0028] Fig. 2 shows an exemplary drive assembly 200 for driving a saw blade, such as saw blade 130. Drive assembly 200 includes a first pulley 210 configured to be driven by a motor shaft 125 of an electric motor 120. Torque applied to motor shaft 125 is transmitted via first pulley 210 to a drive belt 230, which in turn drives a second pulley 220. Second pulley 220 is connected to a tool shaft 135, causing circular cutting tool 130 to rotate due to the torque applied to motor shaft 125 by electric motor 120.

[0029] Construction machines with internal combustion engines, such as power cutters, generate a certain amount of vibration from the engine, which is transmitted to the various parts of the machine. Vibrations at the tool handles 160, 170 are undesirable because they can be harmful to the operator. Vibrations at the control unit 101 or the battery 140 can also be undesirable, as severe vibrations can reduce the service life of these components.

[0030] However, for certain jobs, the vibration of the internal combustion engine transmitted to the tool 130 can improve the efficiency of the cutting operation by the tool 130. It has been observed that electrically powered construction equipment sometimes has lower cutting performance than machines powered by an internal combustion engine. For some jobs, the internal combustion engine-powered machine performs better than the electrically powered one, even though the two machines have identical abrasive tools and the same drive power. The reason for the lower cutting performance sometimes observed with electrically powered equipment is, at least in part, due to the lower vibration of an electrically powered machine, which does not have internal combustion engine vibration.

[0031] This deficiency of electrically powered construction machines such as electric power cutters, wall saws, and core drills can be addressed by incorporating a vibration device into the machine that generates a controlled vibration of the cutting tool 130. This vibration device "emulates" the vibration that would have been present if the machine were powered by an internal combustion engine and, in some cases, can improve the cutting performance of the tool. The vibration device is preferably configured to be activated and deactivated in response to a user input signal, e.g., via a user interface 150 configured or arranged to trigger the activation and deactivation of the vibration device.For example, the machine 100, 1200, 1300 may include a vibration activation button or a menu selection option that allows a user to activate the vibration function to evaluate whether cutting performance improves as a result of the vibration. This activation and deactivation function can be advantageously used to temporarily activate the generation of the controlled amount of vibration to sharpen the abrasive elements 131 of the cutting tool 130, which can be particularly advantageous when using a core drill. It is also possible to implement an automatic vibration activation mechanism that automatically activates the vibration device, e.g., by the control unit 101 in response to a trigger signal. The trigger signal can, for example, be a signal from a configured or designed timer that results in periodic activation and deactivation of the vibration device.The trigger signal can also be generated based on an output signal from an inertial measurement unit (IMU) or a microphone configured or adapted to measure an operating characteristic of the abrasive cutting tool and activate the vibration device if the operating characteristic deviates from an expected or desired operating characteristic. The operating characteristic can, for example, be associated with an expected amount of noise and / or vibration from the tool in use. This expected noise and / or vibration exposure from the tool can be determined through laboratory tests or computer simulations. It can also be configured by the user of the device. The expected operating characteristic can include an amplitude and / or frequency characteristic of a detected vibration or generated sound in use.The expected operating characteristic may also include a measured amount of dust from the construction machine, which may be measured using a scale or a dust sensor connected to a dust collector connected to the construction machine. A reduction in the amount of dust generated may indicate that the abrasive elements 131 need sharpening. The expected operating characteristic may further include an expected torque of the motor 120 during operation. The expected torque may also be preconfigured through practical tests in a laboratory or in the field during use of the construction machine.

[0032] The vibration device can also be configured or designed so that it is only activated in a high speed range of the rotating tool, i.e. the vibration function only becomes active when the tool approaches its working speed and remains deactivated at idle or low speeds and when accelerating to the working speed. This range in which the vibration function becomes active can be above 70% of the full tool speed. Alternatively, the speed range in which the vibration device is activated can be set to, for example, 40-80% of full speed. In this way, the vibration function starts when the tool has reached a certain working speed and then stops again when it is close to full speed. Alternatively, the vibration function can also only be activated at full throttle, i.e. when the user presses the trigger 180° fully.The vibration function can also be activated manually using some type of input control device, such as a button or a rotary knob. The user can then activate the vibration function when and if desired. The user can also use the input control means to control one or more properties of the vibration, such as its frequency or amplitude. It is also possible to employ one or more predefined vibration properties that have been previously optimized for different work tasks. The user can then choose between a range of options, possibly depending on personal preference and / or the work task to be performed.

[0033] Preferably, the vibration device is also designed to generate vibrations with configurable amplitude and / or frequency. This allows a specific machine type to be adapted or even optimized for a specific cutting task, i.e., for cutting into a specific type of material. The amplitude and / or frequency of the generated vibration can be configured during assembly in the factory. Alternatively or additionally, the amplitude and / or frequency of the vibration can be configured by the user, e.g., via a menu selection in the user interface 150. The control can then comprise controlling a frequency of the vibration and / or controlling a magnitude or amplitude of the generated vibration. The amplitude or magnitude of the vibration refers to the strength of the generated vibration, i.e., how strong the vibration is compared to a specific reference value of the vibration.The frequency of a vibration refers to the frequency composition of the generated vibration. The frequency of the vibration can, for example, refer to a maximum frequency of the generated vibration or to the width of a frequency band that encompasses a major portion of the generated vibration, e.g., a 3 dB bandwidth of the power spectrum of the vibration frequency. The following describes methods for implementing a vibration device that allow for configuration of the vibration amplitude and / or frequency.

[0034] In Fig. 2, the vibration device is preferably arranged in conjunction with the tool axis 135 of the construction machine, as represented by the bracket 240. It is advantageous to arrange the vibration device near the tool where vibration is desired and away from the handles of the machine where vibration is undesirable. In some aspects, the vibration device is configured to be driven directly by the tool axis 135, or via the pulley 220, or via the belt 230. The vibration element may also be driven indirectly by the tool axis 135 via some type of transmission, such as a gear transmission or a separate drive belt arrangement. The advantage of a transmission, such as a gear transmission, between the power source and the vibration device is that the frequency can be adjusted depending on the speed of the power source, such as the speed of the tool axis 135.

[0035] The vibration device can be driven directly or indirectly by the main electric motor 120 of the construction machine, i.e., by the electric motor that also drives the tool 130. A toothed belt can bring additional advantages to the design, as a toothed belt is better able to transmit abrupt changes in torque to the tool than a non-toothed belt, such as a V-belt or similar, which is more likely to slip. A toothed belt is also less sensitive to suboptimal belt tension. However, a motor and / or a magnetic device separate from the electric motor 120 of the construction machine can also be mounted to drive the vibration device. This has the advantage that the frequency of the generated vibration can be fully controlled by controlling the axis speed of the separate electric motor. A separate electric motor can, for example,can be used to generate a controlled amount of vibration by placing an eccentrically configured weight on the motor shaft in a known manner. A magnetic device can be used to "pulse" a weight, thereby generating a controlled vibration. Individual motors and magnetic devices can be combined to enhance the effect. Multiple magnetic devices can also be used to move the respective weights back and forth, thus generating different vibration patterns. A non-uniform rotating element, such as a ring gear or similar, can also be attached to the motor shaft or the tool shaft. This rotating element generates vibration when it comes into contact with some type of cooperating element. By axially shifting the cooperating element and / or the rotating element, the vibration can be activated and deactivated.

[0036] The vibration device can be configured to generate vibrations in a radial and / or axial direction relative to the tool axis 135. The vibration direction can also be configured or designed by the user, and some vibration directions may be better for certain machining tasks than others. A machine may also include more than one vibration device. For example, one vibration device may be primarily dedicated to generating vibrations in a radial direction, while another vibration device may be primarily dedicated to generating vibrations in an axial direction.

[0037] The Fig. Figures 3A-C and 4-7 illustrate some example mechanisms that can be used to generate controlled vibration intensity.

[0038] Fig. 3A shows an example of a vibration device 300 consisting of a mass 320 and a spring 330. A cam 310 is set in a rotational motion R about a rotational axis 315. The cam then engages a mass 320 suspended by one or more springs 330 or other elastic elements, such as a rubber bearing or the like. The mass 320 is set in a reciprocating motion M by the cam 310. The weight of the mass and the properties of the spring arrangement, together with the speed at which the cam is rotated and the design of the cam, determine the amplitude and frequency of the vibration generated. The cam 310 can be mounted directly on the tool axis 135 or directly on the motor axis 125, or it can be driven via some type of gearing.The gearbox can then also be used to translate an axle speed into a desired cam speed by adding an appropriate gear ratio.

[0039] A cam arrangement with more than one cam can also be used to adjust the frequency of the vibration. Fig. Figure 3B shows an example of a double cam 340. These cams 310, 340 are also set in a rotational movement R about a rotation axis 315.

[0040] More than one mass 320 may also be used to adjust the amplitude and / or frequency of the vibration generated by the vibration device. Fig. Figure 3C shows an example of a mass-spring system in which two masses 320 are driven into a reciprocating motion M by a single cam element.

[0041] Fig. 4 and Fig. 5 show further examples 400, 500 of mechanisms that can be used to generate controlled vibration. These mechanisms consist of a first gear 410 that meshes with a second gear 420. The second gear 420 includes a pin 430 or pivot pin that meshes with a lever 450 that rotates about a pivot point 440. A mass 320 is attached to the lever 450, which, through interaction with the lever 450, is caused to move M, thereby generating a controlled amount of vibration. The mass 320 can be moved along the lever 450 to adjust the characteristics of the vibration generated by the vibrating device.

[0042] In Fig. Figure 5 shows a more compact version 500 of the vibration device 400. The operating principle is the same as that of the device 400.

[0043] Fig. Figure 6 shows an exemplary vibration device 600 based on a rotating element 610 eccentrically attached to a lever 630 via a pin 620. The lever engages a mass 320 suspended from one or more elastic elements, such as springs 330. When the rotating element 610 is set in a rotational motion R, the mass M performs a reciprocating motion M, producing a controlled vibration.

[0044] The rotations R of the rotating elements 410, 610, 710 in the Fig. 4-7 are carried out around the respective rotation axes 315, as indicated in the respective figures.

[0045] Fig. Figure 7 shows another example 700 of a vibration device. This device comprises a rotating element 710 with pins 720 distributed over the circumference of the rotating element 710, which pins 720 engage one after the other with a lever 730 that is rotatably mounted about a pivot point 740. A mass 320 is set into a reciprocating motion M by the rotation R of the rotating element 710.

[0046] In the Fig. 3A-C, 4, 5, 6, and 7 illustrate examples of mechanical vibration devices suitable for generating controlled vibration. These vibration devices can be driven directly by the main electric motor 120 of the construction machine 100, 1200, 1300 or by a separate motor for actuating the vibration device. A clutch mechanism can be arranged between the main electric motor 120 and the vibration device to enable activation and deactivation of the vibration device by a user, e.g., via the user interface 150. This clutch can be a mechanical clutch, e.g., a spring-loaded clutch, that can be actuated, e.g., by a lever or other user-operable control mechanism. The clutch can also be an electrically actuated clutch, e.g., an electromagnetic clutch that can be actuated automatically, e.g.,by the control unit 101. The basic principles of clutch mechanisms are generally known and will therefore not be discussed in detail here.

[0047] Vibrations can also be generated directly by an electric motor by controlling the motor currents to drive the motor. A converter is often used to generate currents in the motor windings to control the motor to operate at a desired setpoint speed and / or axle torque. When a disturbance is added to these currents, vibrations occur. The magnitude and temporal characteristics of the disturbance determine the amplitude and frequency of the generated vibration. It is understood that the vibration device can also consist of the electric motor 120 of the construction machine, which can be used to generate controlled vibration. The amplitude and / or frequency of the generated vibration can advantageously be controlled by the control unit 101.

[0048] Further advantages arise when the vibration can be configured independently of the rotational speed of the tool axis. This can be achieved, for example, if the vibration is generated by a separate electric motor with an eccentrically arranged weight on its motor axis. The separate electric motor is then preferably located near the tool 130 and away from the handles 160, 170 that serve to guide the machine. By arranging a separate motor for vibration generation in this way, both the frequency and amplitude of the vibration can be controlled. A pulsating magnet arrangement can also be used with a similar effect.

[0049] Fig. 8A schematically shows a control system for electric motors 800 that can be used, for example, with the power cutter 100, the wall saw 1200, or the core drill 1300. A control unit 101 receives a speed command and a vibration activation command, which is not required if vibration is always activated. The speed command can be received, for example, from the trigger 180 of the power cutter 100, from a remote control device 1210 of the wall saw 1200, or from a control interface of the core drill 1300. The command indicates whether or not the user wants to activate the vibration function. It can be generated based on user input via the user interface 150. The control unit 101 then controls an inverter 810, which generates motor currents so that the axis of the electric motor strives to rotate at the configured or designed speed.

[0050] If the vibration command indicates that the vibration function should be activated, the control unit 101 adds a "perturbation" to the current command to the inverter 810 to generate vibration through the electric motor. In this case, the motor itself is the vibration device. For example, the control unit 101 can be configured to generate a command to control the electric motor 120 corresponding to a target motor speed with a variance over time, e.g., a pulsed speed or a sequence of abrupt speed changes with an amplitude and frequency depending on the type of desired vibration.

[0051] The control unit 101 is optionally configured to control a frequency and / or an amplitude of the vibration by modulating the axle speed command, ie, the control of the electric motor speed, over time. Fig. 8B-C show exemplary variation patterns of the motor target speed 820, 830. The amplitude of the pulses in Fig. 8B affects the strength of the generated vibration. A pulse with a small amplitude A produces a weaker vibration than one with a larger amplitude. The duration D between pulses, i.e., the pulse repetition interval, influences the frequency of the generated vibrations. A shorter duration between pulses results in a higher-frequency vibration, and vice versa. The pulse amplitude A and the pulse repetition interval do not need to be constant but can be varied over time to produce a more complex vibration pattern. For example, a pseudo-noise (PN) sequence might be suitable for modulating the pulse amplitude and / or the pulse repetition interval over time.

[0052] Fig. 8C shows another example of a motor target speed 830 with a variation over time. In this case, the target speed is changed in a random pattern around an average target speed S, e.g., according to a PN sequence with a configurable amplitude and frequency characteristic. In general, the magnitude of the changes and the distribution of the time periods between the changes in the target speed determine the amplitude and frequency of the generated vibration. In both examples 820, 830, the control unit 101 is configured to control an amplitude and / or a frequency of the vibration by modulating the axis speed command over time.

[0053] The electrically powered construction machine 100, 1200, 1300 may further comprise an inertial measurement unit (IMU) configured to output a signal indicative of the currently generated vibration. The control unit 101 may then be configured to control the main electric motor 120 based on the IMU output signal to achieve a desired frequency and / or amplitude of the vibration. For example, the temporal variation of the rotational speed command may be adjusted to generate a desired vibration frequency and / or amplitude. If the IMU signal indicates that the frequency composition of the currently generated vibration is below a desired frequency, the disturbance to the target rotational speed may be adjusted to increase the frequency of the vibration generated by the electric motor, e.g.by reducing the time between pulses or the average time between command speed changes in a sequence of speed changes as in . Fig. 8C. The same type of adjustment can also be made for the vibration amplitude. If the generated vibration is weaker than a desired vibration level, the amplitude of the disturbance added to the target speed can be increased, and vice versa.

[0054] Fig. 9 is a flowchart illustrating a method performed in a control unit 101 for controlling an electric motor 120. The method includes receiving a speed command S1 and controlling the electric motor S2 to operate at a desired speed in response to the speed command. The method further includes, in response to a vibration activation command, adding a disturbance S3 to the speed control of the electric motor 120 to generate a controlled vibration by the electric motor 120.

[0055] In Fig. 10, the components of a control unit 101 according to the embodiments described herein are schematically illustrated in the form of a series of functional units. This control unit may be located in the machines 100, 1200, 1300, or elsewhere, e.g., in a remote device 1210. The processing circuitry 1010, which may be distributed across multiple units, is provided using any combination of one or more suitable central processing units (CPUs), multiprocessors, microcontrollers, digital signal processors (DSPs), etc., capable of executing software instructions stored in a computer program product, e.g., in the form of a storage medium 1030.The processing circuit 1010 may further be provided as at least one application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA).

[0056] In particular, the processing circuit 1010 is configured or arranged to cause the control unit 1000 to perform a series of operations or steps, such as those associated with Fig. 9 and the procedures discussed elsewhere herein.

[0057] For example, the storage medium 1030 may store the set of operations, and the processing circuit 1010 may be configured or arranged to retrieve the set of operations from the storage medium 1030 to cause the control unit 1000 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus, the processing circuit 1010 is arranged to perform the methods disclosed herein. The control unit comprises a processing circuit 1010, an interface 1020 coupled to the processing circuit 1010, and a memory 1030 coupled to the processing circuit 1010, wherein the memory comprises machine-readable computer program instructions that, when executed by the processing circuit, cause the control unit to perform the operations described above in connection with Fig. 9 procedures discussed.

[0058] The storage medium 1030 may also include persistent storage, which may, for example, consist of a single or combination of magnetic storage, optical storage, solid-state storage, or even remotely mounted storage.

[0059] The control unit 1000 may further include an interface 1020 for communication with at least one external device. As such, the interface 1020 may include one or more transmitters and receivers with analog and digital components and a suitable number of ports for wired or wireless communication.

[0060] The processing circuit 1010 controls the general operation of the control unit 1000, e.g., by sending data and control signals to the interface 1020 and the storage medium 1030, by receiving data and reports from the interface 1020, and by retrieving data and instructions from the storage medium 1030. Other components, as well as the associated functionality of the control node, are omitted to avoid obscuring the concepts presented here.

[0061] Fig. 11 shows a computer-readable medium 1110 containing a computer program with program code means 1120 for performing the Fig. 9 when the program product is executed on a computer. The computer-readable medium and the code means may together form a computer program product 1100. 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] WO 2021 / 107827 A1

[0003] JPH0482609A

[0010]

Claims

[1] Electrically operated construction machine (100, 1200, 1300, 1400, 1500) with an electric motor (120) which is arranged to drive an abrasive cutting tool (130) via a drive arrangement (200), wherein the abrasive cutting tool (130) comprises abrasive elements (131) arranged on a carrier (132) of the cutting tool (130), wherein the abrasive elements (131) are arranged spaced apart from one another on the carrier (132) and follow a closed path during operation of the construction machine, wherein the construction machine (100, 1200, 1300, 1400, 1500) further comprises a vibration device (120, 300, 350, 400, 500, 600, 700, 800) configured to generate a controlled amount of vibration of the abrasive cutting tool (130), the vibration being generated in a frequency band below 15 kHz. [2] An electrically powered construction machine (100, 1200, 1300, 1400, 1500) according to claim 1, wherein the vibration device is configured to be activated and deactivated in response to a user input signal. [3] Electrically powered construction machine (100, 1200, 1300, 1400, 1500) according to claim 1 or 2, wherein the vibration device is arranged to generate vibrations with configurable amplitude and / or frequency. [4] Electrically operated construction machine (100, 1200, 1300, 1400, 1500) according to one of the preceding claims, wherein the vibration device is arranged in connection with a tool axis (135) of the construction machine. [5] Electrically operated construction machine (100, 1200, 1300, 1400, 1500) according to one of the preceding claims, wherein the vibration device is arranged to generate vibrations in a radial and / or axial direction with respect to the tool axis (135). [6] Electrically powered construction machine (100, 1200, 1300, 1400, 1500) according to one of the preceding claims, wherein the vibration device is arranged to be driven by a main electric motor (120) of the construction machine. [7] Electrically powered construction machine (100, 1200, 1300, 1400, 1500) according to one of claims 1 to 6, wherein the vibration device is arranged to be driven by a motor and / or a magnetic device which is / are separate from the main electric motor (120) of the construction machine. [8] Electrically operated construction machine (100, 1200, 1300, 1400, 1500) according to one of the preceding claims, wherein the vibration device comprises a mass (320) and spring (330) arrangement (300, 350, 600). [9] Electrically operated construction machine (100, 1200, 1300, 1400, 1500) according to one of claims 1 to 3, wherein the main electric motor (120) of the construction machine forms the vibration device. [10] An electrically powered construction machine (100, 1200, 1300, 1400, 1500) according to claim 9, comprising a control unit (101) arranged to control the main electric motor (120) to a target speed with a change over time. [11] An electrically powered construction machine (100, 1200, 1300, 1400, 1500) according to claim 10, wherein the control unit (101) is arranged to control a frequency of the vibration by modulating the axle speed command over time. [12] An electrically powered construction machine (100, 1200, 1300, 1400, 1500) according to claim 10 or 11, wherein the control unit (101) is arranged to control an amplitude of the vibration by modulating the axle speed command over time. [13] An electrically powered construction machine (100, 1200, 1300, 1400, 1500) according to any one of claims 9 to 12, comprising an inertial measurement unit (IMU) arranged to output a signal indicative of the vibration, wherein the control unit (101) is arranged to control the main electric motor (120) on the basis of the IMU output signal to achieve a desired frequency and / or amplitude of the vibration. [14] Electrically powered construction machine (100, 1200, 1300, 1400, 1500) according to one of the preceding claims, comprising a user interface (150) configured or arranged to trigger the activation and deactivation of the vibration device. [15] Electrically powered construction machine (100, 1200, 1300, 1400, 1500) according to one of the preceding claims, wherein the control unit (101) is arranged to generate a non-uniform, random or pseudo-random vibration pattern over time. [16] Electrically operated construction machine (100, 1200, 1300, 1400, 1500) according to one of the preceding claims, wherein the construction machine is a cut-off machine (100), a wall saw (1200), a core drilling machine (1300), an abrasive ring saw (1400) or an abrasive chain saw (1500). [17] Electrically operated construction machine (100, 1200, 1300, 1400, 1500) according to one of the preceding claims, wherein the vibration is generated in a frequency band below 5 kHz or in a frequency band below 1 kHz. [18] An electrically powered construction machine (100, 1200, 1300, 1400, 1500) according to any one of the preceding claims, comprising an automatic vibration activation mechanism, wherein the vibration device is arranged to be automatically activated and deactivated in response to a signal from the automatic vibration activation mechanism. [19] The electrically powered construction machine (100, 1200, 1300, 1400, 1500) of claim 18, wherein the automatic vibration activation mechanism comprises a control unit (101) and one of the following elements: a timer, an inertial measurement unit (IMU), a microphone and / or a dust sensor configured or arranged to measure an amount of dust generated by the construction machine. [20] An electrically powered construction machine (100, 1200, 1300, 1400, 1500) according to claim 18 or 19, wherein the signal of the automatic vibration activation mechanism is connected to a torque output by a motor (120) of the electrically powered construction machine used. [21] Method which is carried out in a control unit (101) for controlling an electric motor (120), the method comprising Receiving (S1) a speed command, Controlling (S2) the electric motor to operate at a target speed depending on the speed command, and, in response to a vibration activation command, Adding (S3) a disturbance to the speed control of the electric motor (120) to generate a controlled vibration by the electric motor (120).

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