Machine tools and methods for operating machine tools

Abstract

A machine tool and method for fastening a screw, the machine tool comprising: a motor having a shaft; a controller configured to supply an electric current to the motor to rotationally drive the shaft, continuously determine a first parameter characterizing the fastening process, recognize a screw engagement start point when the first parameter satisfies a predefined set of conditions, determine a second parameter that affects a time difference between the recognized screw engagement start point and an actual screw engagement start point, calculate a target rotational speed to be performed by the motor after the recognized screw engagement start point depending on the second parameter, and stop the motor when the motor has performed a rotation of the target number after the recognized screw engagement start point.

Description

Technical Field

[0001] A machine tool for fastening a screw and a method of operating the machine tool are described herein. A handheld power tool for enabling such screw fastening is also described. Generally, such handheld tools are widely used in the construction industry. Typical handheld tools within the technical scope of the present invention include, but are not limited to, an automatic screwdriver for screwing a screw onto a workpiece, thereby fastening the workpiece such as a metal plate with the screw.

Background Art

[0002] A handheld power tool for enabling screw fastening is known. This tool includes a machine tool housing that includes a motor that provides at least a rotational movement to a rotating shaft. The rotating shaft then finally transmits a specific torque at a specific rotational speed to a workpiece fastening element such as a drill or a screw. The tool may also include a controller for controlling the motor and continuously determining some parameters of the drilling or fastening process, such as the transmitted torque and rotational speed of the rotating shaft, during the use of the tool.

[0003] One possible application field is the fastening of self-tapping and self-sealing screws into pre-drilled holes. The sealing performance may depend on the fastening depth of the fastening element into the pre-drilled hole. Such an operation is usually performed using a depth gauge that needs to be calibrated under specific circumstances, which can be cumbersome and / or time-consuming.

Summary of the Invention

Means for Solving the Problems

[0004] One aspect of the present invention is a method for operating a machine tool for fastening a screw to a workpiece along a fastening axis, the machine tool comprising a motor having a shaft, the method comprising supplying current to the motor to rotationally drive the shaft; continuously determining a first parameter characterizing the fastening process; recognizing a screw engagement start time if the first parameter satisfies a set of predefined conditions; determining a second parameter affecting the time difference between the recognized screw engagement start time and the actual screw engagement start time; calculating a target number of rotations performed by the motor after the recognized screw engagement start time based on the second parameter; and stopping the motor when it has performed the target number of rotations after the recognized screw engagement start time.

[0005] In another embodiment, a machine tool for drilling holes in a workpiece and / or fastening screws along a fastening shaft includes a motor having a shaft, a switch, and a controller configured to supply current to the motor to rotationally drive the shaft, to continuously determine a first parameter characterizing the fastening process, to recognize a screw engagement start time if the first parameter satisfies a set of predefined conditions, to determine or continuously determine a second parameter that affects the time difference between the recognized screw engagement start time and the actual screw engagement start time, to calculate a target number of rotations performed by the motor after the recognized screw engagement start time based on the second parameter, and to stop the motor when the motor has performed the target number of rotations after the recognized screw engagement start time.

[0006] In another embodiment, the first parameter includes at least one of the voltage of the current supplied to the motor, the amperage of the current supplied to the motor, the power consumption of the current supplied to the motor, the rotational speed of the motor, the changes of these over time, and combinations thereof.

[0007] In a preferred embodiment, the determination of the second parameter is performed before the recognized start of screw engagement. In an alternative or additional embodiment, the determination of the second parameter is performed after the recognized start of screw engagement.

[0008] In another embodiment, the second parameter includes at least one of the force applied to the shaft toward the tool along the fastening axis, the torque applied to the shaft about the fastening axis, the voltage of the current supplied to the motor, the amperage of the current supplied to the motor, the power consumption of the current supplied to the motor, the rotational speed of the motor, the acceleration of the tool along the fastening axis, the acceleration of the tool across the fastening axis, the rotation of the tool about the fastening axis, the yaw rate of the tool, the temperature of the tool, the changes of these over time, and combinations thereof.

[0009] Further embodiments and advantages of the machine tool, related parts, and methods of use thereof will become apparent from the following description, which is given solely as an example and with reference to the accompanying drawings. [Brief explanation of the drawing]

[0010] [Figure 1] This diagram shows a mechanical tool for drilling holes and fastening screws. [Modes for carrying out the invention]

[0011] Figure 1 shows a machine tool 100 for drilling holes and / or fastening screws. In the illustrated embodiment, the machine tool 100 is a handheld work tool such as an automatic screwdriver. The machine tool 100 includes a housing 105, a motor 110 having a shaft 120 enclosed by the housing 105, a switch 130 formed as a trigger switch, a controller 140 formed as a microcomputer and having data storage 145 formed as computer memory, a battery 150, and a communication unit 155 formed as a wireless transmitter. The controller 140 supplies current from the battery 150 to the motor 110 to rotate the shaft 120. The machine tool 100 further includes a gear 160 and a spindle 170 having a screw drive device 175 such as a hexagonal drive device, which is driven by the shaft 120 via the gear 160.

[0012] Furthermore, the machine tool 100 includes a rotational speed sensor 180 for detecting the rotational speed of the motor 110, and an ampere / voltage sensor 190 for detecting the amperage and / or voltage of the current supplied to the motor 110. Furthermore, the machine tool 100 includes several acceleration sensors for detecting the force applied to the shaft toward the machine tool along the fastening axis, the acceleration of the machine tool along the fastening axis, the acceleration of the machine tool across the fastening axis, the rotation of the machine tool about the fastening axis, and the yaw rate of the machine tool, i.e., the rotation of the machine tool about an axis perpendicular to the fastening axis.

[0013] Furthermore, the machine tool 100 includes a line 195 connecting the controller 140 to the motor 110, the switch 130, and the sensors 180, 190 in order to supply current to the motor 110 and / or to collect electrical signals from the switch 130 and / or the sensors 180, 190. Additionally or alternatively, to obtain data on the rotational speed, amperage, or voltage of the motor 110, the controller 140 may use information already present from controlling the rotational operation of the motor 110, such as the number of electrical rectifications over time relative to the rotational speed. The housing 105 includes a grip portion 106 for the user to hold the machine tool 100 by hand so that the switch 130 can be pressed by the user's index finger. The switch 130 can notify the controller 140 of its switch position via the line 195.

[0014] During use, the machine tool 100 can be set up, for example, by selecting the appropriate clutch settings and gears to activate a specific screw fastening mode. During this fastening process, the controller 140 monitors several parameters, including the voltage, amperage, and power consumption of the current supplied to the motor, the motor's rotational speed, the force applied to the shaft toward the machine tool along the fastening axis, the torque applied to the shaft about the fastening axis, the acceleration of the machine tool along the fastening axis, the acceleration of the machine tool across the fastening axis, the rotation of the machine tool about the fastening axis, the yaw rate of the machine tool, and the temperature of the machine tool. Furthermore, the controller 140 monitors the changes in these parameters over time.

[0015] The controller 140 recognizes the screw engagement start time when a first parameter, such as the power consumption of the current supplied to the motor, satisfies a set of predefined conditions, such as a minimum time after the start-up phase of the machine tool, which is followed by an increase. The controller 140 then calculates a target rotational speed to be performed by the motor after the recognized screw engagement start time in order to complete the screw fastening process at the appropriate location, and stops the motor when it has performed the target number of rotations after the recognized screw engagement start time. However, the recognized screw engagement start time may not exactly coincide with the actual screw engagement start time. To compensate for the time difference between the recognized screw engagement start time and the actual screw engagement start time, the controller 140 takes into account one or more second parameters that may affect the aforementioned time difference when calculating the target rotational speed. For this purpose, a nonlinear model equation derived using well-known statistical methods during the development or testing of the machine tool may be used. The controller 140 may determine the second parameter before and / or after the recognized screw engagement start time.

[0016] In summary, when the screw threads begin tapping into the holes in the base structure, the controller 140 recognizes the specific behavior of several parameters that affect the time difference between the recognized screw engagement start time and the actual screw engagement start time. The controller then stops the motor after a target number of rotations. This ensures that the screw fastening process is stopped at the appropriate point, thus resulting in more precise compression of, for example, the sealing element.

[0017] Throughout this application, "current supplied to the motor" means that, in the case of a handheld power tool being a battery-operated tool, the current measured within a power supply device such as a battery.

[0018] The above description of embodiments of the present invention is presented for illustrative and explanatory purposes. This description is not intended to be exhaustive or to limit the invention to any specific embodiment disclosed, and modifications and variations may be possible in light of the above teachings or obtained from the practice of the invention. The functionalities described may be distributed across modules that differ in the number and distribution of functionalities from those described herein. In addition, the order in which the functionalities are performed may be changed depending on the embodiment. The embodiments have been selected and described as practical applications of the invention to illustrate the principles of the invention and to enable those skilled in the art to utilize the invention in various embodiments and with various modifications to suit specific intended uses. The technical scope of the invention is defined by the claims and equivalents appended herein.

Claims

1. A method for operating a machine tool for fastening a screw to a workpiece along a fastening shaft, wherein the machine tool includes a motor having a shaft, and the method is - Supplying current to the motor in order to rotate the shaft, - Continuously determine the first parameter that characterizes the fastening process, - If the first parameter satisfies a predefined set of conditions, the start time of screw engagement is recognized. - A second parameter that affects the time difference between the recognized screw engagement start time and the actual screw engagement start time is determined after the recognized screw engagement start time. - Based on the second parameter, calculate the target rotational speed performed by the motor after the recognized start of screw engagement, and - After the recognized start of screw engagement, the motor is stopped when it rotates at the target rotational speed. Methods that include...

2. The method according to claim 1, wherein the first parameter includes at least one of the voltage of the current supplied to the motor, the amperage of the current supplied to the motor, the power consumption of the current supplied to the motor, the rotational speed of the motor, the changes of these over time, and combinations thereof.

3. The method according to claim 1 or 2, wherein determining the second parameter includes continuously determining the second parameter.

4. The method according to claim 1 or 2, wherein the second parameter includes at least one of the force applied to the shaft toward the machine tool along the fastening axis, the torque applied to the shaft about the fastening axis, the voltage of the current supplied to the motor, the amperage of the current supplied to the motor, the power consumption of the current supplied to the motor, the rotational speed of the motor, the acceleration of the machine tool along the fastening axis, the acceleration of the machine tool across the fastening axis, the rotation of the machine tool about the fastening axis, the yaw rate of the machine tool, the temperature of the machine tool, changes of these over time, and combinations thereof.

5. A mechanical tool for drilling holes in a workpiece and / or fastening screws along a fastening shaft, - A motor having a shaft, -switch, - A controller configured to supply current to the motor to rotate the shaft, continuously determine a first parameter characterizing the fastening process, recognize the screw engagement start time if the first parameter satisfies a set of predefined conditions, determine a second parameter after the recognized screw engagement start time that affects the time difference between the recognized screw engagement start time and the actual screw engagement start time, calculate a target rotation speed performed by the motor after the recognized screw engagement start time based on the second parameter, and stop the motor when the motor rotates at the target rotation speed after the recognized screw engagement start time. Machine tools including those mentioned.

6. The machine tool according to claim 5, wherein the first parameter includes at least one of the voltage of the current supplied to the motor, the amperage of the current supplied to the motor, the power consumption of the current supplied to the motor, the rotational speed of the motor, the changes of these over time, and combinations thereof.

7. The machine tool according to claim 5 or 6, wherein the controller is configured to continuously determine the second parameter.

8. The machine tool according to claim 5 or 6, wherein the second parameter includes at least one of the force applied to the shaft toward the machine tool along the fastening axis, the torque applied to the shaft about the fastening axis, the voltage of the current supplied to the motor, the amperage of the current supplied to the motor, the power consumption of the current supplied to the motor, the rotational speed of the motor, the acceleration of the machine tool along the fastening axis, the acceleration of the machine tool across the fastening axis, the rotation of the machine tool about the fastening axis, the yaw rate of the machine tool, the temperature of the machine tool, changes of these over time, and combinations thereof.

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