EP1907172B1 - Electric tool in particular battery-driven thread-cutting machine - Google Patents

Description

The invention relates to a method for operating a power tool according to the preamble of patent claim 1.

Such a procedure is known from US 2005/01 035 10

Such power tools are used as a thread cutting machine, drill, screwdriver o. The like., Which may be in particular a cordless power tool.

Battery and / or mains operated power tools, which from the WO 02/078416 A1 , of the US 2005/0103510 A1 or the US 5 014 793 A are known, have an electric motor for driving a tool holder. Furthermore, the power tool is equipped with an actuator having a switch for switching on and / or off the power supply for the electric motor and a switch for the clockwise / counterclockwise rotation of the electric motor. In advanced equipment, the power tool has electronics for speed control and / or regulation of the electric motor and short-circuit braking for the electric motor.

Such cordless screwdrivers are very often used for cutting threads. For this purpose, a tap is then inserted into the tool holder. Especially with larger workpieces that can not be edited with a stand or bench drill with adapted tapping, the use of such a cordless screwdriver offers.

In the US 2005/0103510 A1 is further described the use of the cordless screwdriver for threading. After actuation of the actuator, the electric motor runs in the clockwise direction, wherein the thread is cut by screwing the tap. Once the thread depth has been reached, the electric motor is switched over to counterclockwise rotation. Thereafter, the tap is again unscrewed from the thread.

However, this use of cordless screwdrivers for tapping has the disadvantage that the life of the switch for the clockwise / counterclockwise rotation due to wear of the electrical changeover contacts is achieved quickly by the frequent switching between clockwise and counterclockwise rotation of the electric motor. In chord mode, it may also happen that even then switched by the user when the electric motor is still rotating. This also leads to premature wear of the changeover contacts. Furthermore, the mechanical torque coupling is too inaccurate, which can lead to breakage of the tap by jamming or seizure. Conventional cordless screwdrivers are therefore only partially suitable for the Cutting threads. In particular, the life of the motor and the switching contacts of this cordless screwdriver is limited. The same disadvantages can also be observed with mains operated screwdrivers when they are used for thread cutting.

The invention has for its object to make the thread cutting with the battery and / or mains powered power tool more effective and safer. In particular, the battery and / or mains-powered power tool suitable for threading should be further developed with regard to its service life.

This object is achieved in a generic method for operating the power tool by the characterizing features of claim 1.

Such a power tool forms a completely new generation of devices for the niche market of thread cutting. The invention is based on a battery-operated power tool that has various electronic functions. Ideally, this is a power tool, which also functions as a conventional cordless screwdriver, namely screwing, drilling, right / left switching; Brake, speed control, shutdown o. The like. Has.

The power tool can be switched between manual and / or automatic operation. Such a switching function offers the user the comfortable Possibility to operate the power tool automatically according to a given program. If desired, however, the user can also intervene manually in the process.

The automatic operation with regard to thread cutting proceeds as follows. As soon as the actuator on the power tool is pressed by the user, the motor runs forward in the pitch mode according to a preset characteristic, that is with a kind of ramp function, up to the ideal speed. This predefinable ideal speed varies, for example, according to the thread diameter and / or the material to be machined. Then the thread is cut by turning the tap in the clockwise direction with this ideal speed. When screwing in the number n of threads is counted, which is possible in a simple manner by means of the electronics. Once the desired thread depth has been reached, or if the thread cutter is running in a blind hole, or if the user releases the actuating member, or if another condition is met, then the electric motor is automatically switched over to counterclockwise rotation. As a result, the tap is turned out of the thread in the reverse direction, with the tap being moved at a higher speed in the left-hand rotation than in the clockwise rotation in order to increase the performance of the power tool for tapping. When unscrewing the tap is then counted on at least the number of threads. For safety's sake, however, it can be counted a little further, for example to n + 3 threads. If this number is reached, the electronics switch the Electric motor off automatically. This process ensures a fast yet safe and high quality automatic working cycle.

Manual operation is as follows. The user switches on and / or off the motor in this mode via the actuator. The speed is controlled by the user in the right direction over the actuation path of the actuator. Once the thread depth has been reached, the user switches to anti-clockwise rotation. If the preselected torque is exceeded, the machine switches off.

Further embodiments of the invention are the subject of the dependent claims.

Extending is also an automatic chip breaking function by alternately forward and backward rotation according to the clockwise and counterclockwise rotation of the electric motor feasible. For this purpose, the electric motor rotates, for example, one revolution forward, and then a little more than one revolution backwards. In tests, a reverse rotation of about 1.4 turns has proven to be particularly effective. Hereby the chip is surely broken. The acceleration and / or deceleration of the electric motor is expediently carried out with a suitable characteristic in the manner of a ramp function.

The switch of the power tool according to the invention is in another embodiment to an electronic switch, in particular a Power semiconductor for contactless switching the polarity of the power supply for the electric motor has. The switching on and switching of the power supply for the electric motor thus happens electronically, so that no contact wear can occur as before, which in turn increases the life of the power tool.

In an advantageous embodiment of the power semiconductor can be controlled via an electronic circuit or electronics for switching, which can be done manually by the user and / or automatically in the presence of certain conditions. The electronics can thus advantageously operate the power tool programmatically in automatic operation. The switching can be triggered by means of a switching signal to the electronics. In manual operation, it makes sense that the switching signal is generated by a leading only a signal current auxiliary contact, which in turn can be actuated by means of an actuating element on the power tool by the user.

The electronic circuit for switching can additionally serve as electronics for controlling the electric motor, so that there are no additional costs. Conveniently, the electronics have a microprocessor, which results in a very compact design control for the electric motor in the manner of a microprocessor control. Preferably, the electric motor is a brushless, electronically commutated (EC) electric motor that is particularly sturdy and durable. In addition, such EC electric motor is low maintenance, since an exchange of carbon brushes is eliminated. However, if desired, a brushed motor may also be used for the power tool. However, a power tool with a brushless DC (DC) motor is particularly suitable for the special thread cutting functions, since even a large part of the electronic components of the existing control can be used simultaneously for the electronics and / or the switch, so that a particularly cost-effective Solution is provided.

The system, consisting of EC motor and EC control electronics, can be easily provided with both conventional punctures and with an extension to the auxiliary functions for threading. Thus, the power tool on the one hand have a means for speed detection. On the other hand, the power tool may have a means for torque detection. Appropriately, the torque detection takes place by means of a current measurement. It is then possible to predetermine a maximum torque that can be set, for example, via an external switch, via a potentiometer or the like. Upon reaching the maximum torque then the electric motor is turned off. In a simple way, this adaptation to small or larger taps, different materials to be machined o. The like. Enables.

The advantages achieved by the invention are in particular that the on / off switching of Power tool and the switching between clockwise and counterclockwise for the power tool is made electronically. Therefore, no contact wear can occur, so that the life of the power tool is increased. In particular, as a further advantage when using an EC motor results in an additional increase in the life, since no brush wear occurs. Due to the very long service life of all components, the power tool can be used in multi-shift operation for a very long time as well as reliably and especially in the professional field.

In general, in such power tools electronic and / or electrical components for speed detection, current measurement, control by means of a microprocessor o. The like. Already exist anyway. These electronic and / or electrical components may be used at least in part for electronic switching and / or switching. Thus result at best slightly higher

Cost of implementing the invention. At least a possibly higher price compared to conventional power tools is quickly compensated by the high life and high efficiency for the power tool.

If the power tool according to the invention is used as a threading tool, very short cycle times can be achieved in automatic mode. In addition, the service life of the taps is increased. This allows the introduction of new cordless power tools on the market for the threading specialty.

By eliminating a mechanical torque clutch due to the electronic torque detection, the power tool is shorter ausgestaltbar. Furthermore, the tap can also be used directly in the spindle, for example by means of a magnetic square recording, without using the drill chuck. This leads to a further shortening of the power tool, so that its handling is improved for the user.

• Fig. 1 ein Elektrowerkzeug zum Gewindeschneiden,
• Fig. 2 das Elektrowerkzeug aus Fig. 1 in Draufsicht und
• Fig. 3 ein Blockschaltbild für die Ansteuerung des Elektrowerkzeugs.

An embodiment of the invention with various developments and refinements is shown in the drawings and will be described in more detail below. Show it

• Fig. 1 a power tool for threading,
• Fig. 2 the power tool off Fig. 1 in plan view and
• Fig. 3 a block diagram for the control of the power tool.

In Fig. 1 is a power tool 1 to see a housing 2, which in a known manner as a drill, screwdriver o. The like. Is used. In the present case, the power tool 1 is a cordless power tool which can be operated by means of a rechargeable battery 4 which can be inserted into the handle 3 on the housing 2. In a novel way that is Power tool 1 can be used as a thread cutting machine by a thread cutter 6 can be used in the tool holder 5 of the power tool 1.

As in Fig. 3 can be seen, the power tool 1 has an electric motor 7 for driving the tool holder 5 via a transmission 14. For switching on and / or off the power supply for the electric motor 7, the power tool 1 has an on / off switch 8 with a user operable, in Fig. 1 visible actuator 9. The electric motor 7 is by means of an electronic circuit 12, hereinafter also referred to as electronics 12, operated. The electronics 12, which includes a microprocessor and / or consists of a microprocessor, controls for the desired operation of the electric motor 7, an array of power semiconductors 13 for powering the electric motor 7 in the manner of a microprocessor control accordingly.

The switch 10 is designed as an electronic switch and has a power semiconductor for contactless switching the polarity of the power supply for the electric motor 7, wherein for this purpose the power semiconductor 13 for the Voltage supply of the electric motor 7 is used. For manual operation of the electronic switch 10 by the user is used in Fig. 1 visible actuator 11, which acts on a right / left switch 22.

Similarly, the power semiconductor 13 is also used for switching on the electric motor 7. The on / off switch 8 and the right / left switch 22 thus each comprise an auxiliary contact, which is connected to an input of the microprocessor 12. By operating the actuating member 9 and / or the actuating element 11, the auxiliary contact 8, 22 is switched, thereby generating an on / off switching signal and / or a switching signal, so that the electronic circuit 12, the power semiconductor 13 for switching on / off and / or switching over. Since the switching on / off and / or the switching of the load current to the electric motor 7 is carried out electronically, therefore, no contact wear can occur. At the auxiliary contacts 8, 22, however, only a small, no significant wear causing signal current occurs.

The power tool 1 is further equipped with electronics for speed control and / or regulation of the electric motor 7, this electronics in turn being formed by the microprocessor 12. For this purpose, the power tool 1 has a means for speed detection, wherein the detected at the electric motor 7 actual speed n is supplied to an input 15 of the microprocessor 12. The target speed is specified in a known manner by the path of movement of the actuator 9 designed as a pusher by the user. Furthermore, a short-circuit braking for the electric motor 7 is realized in the power tool 1.

The power tool 1 has a means for torque detection. The torque detection can be done by means of a current measurement on the electric motor 7. The measured current, which corresponds to the actual torque, is supplied to an input 16 on the microprocessor 12. The desired maximum torque can be specified by the user by means of an external switch, a potentiometer 17 or the like. On the housing 2 is to adjust the potentiometer 17 is operated by the user, in Fig. 2 visible knob 18. When the maximum torque is reached, the electric motor 7 is then switched off by the microprocessor 12 via the power semiconductor 13. The knob 18 thus allows an adaptation to small or larger taps, different materials o. The like., To achieve an optimal result when tapping. It is preferred that the electric motor 7 is a brushless, electronically commutated (EC) electric motor which ensures a long-lasting, functionally reliable and low-maintenance power tool 1.

The power tool 1 has a switching function between manual and automatic operation, which are explained in more detail below. For this switching function, a switch 19 is arranged on the housing 2, as based on Fig. 2 you can see. Another switch 20 is used to switch between drilling / screwing and tapping. Yet another switch 21 is used to switch on the also discussed below chipbreaking function.

In automatic operation of the electric tool 1 for the thread cutting runs after actuation of the actuator 9 by the user of the electric motor 7 in the clockwise direction to the ideal speed. The predefinable ideal speed depends on various circumstances, such as the diameter of the thread to be cut. Appropriately, the run-up takes place with a kind of ramp function, that is, according to a predetermined characteristic, in order to avoid an overload. Then, the thread is cut by screwing the tap 6 in the clockwise direction of the electric motor 7. As soon as the desired thread depth is reached, it automatically switches over to the counterclockwise rotation of the electric motor 7. Of course, this also other conditions, for example, as soon as the tap 6 runs in a blind hole, as soon as the user releases the actuator 9 o. The like., Are used. Thereafter, the tap 6 is rotated out of the thread again in reverse. To save time, this can be done at a higher speed. In manual operation of the power tool 1, however, the user switches by means of the actuating element 11 manually between clockwise and counterclockwise rotation of the electric motor 7.

In addition, the subsequent process ensures a particularly fast and nevertheless safe working cycle. When screwing in the tap 6, the number n of threads is counted, to which the microprocessor of the electronics 12 can be advantageously used. When unscrewing the tap 6 is counted on at least the number of threads. However, it can also be counted, for example, n + 3 threads, so that the thread cutter 6 is certainly completely unscrewed. Upon reaching this number n or n + 3 in reverse, then the electronics 12 is automatically switched off together with the electric motor 7.

An automatic chip breaking function, which is particularly suitable for automatic operation, is realized in that the electric motor 7 is rotated alternately back and forth in accordance with its right and left rotation. For example, the electric motor 7 is rotated one revolution forward and then slightly more than one revolution backwards. The chip is then certainly broken. According to experiments carried out are particularly good results for the chipbreaker function achieved when the electric motor 7 is rotated in about 1.4 turns backwards. The acceleration and / or deceleration of the electric motor 7 can in turn be carried out with a suitable ramp function or according to another characteristic in order to prevent an overload of the tap 6. This makes it possible to produce threads of particularly good quality.

The invention is not limited to the described and illustrated embodiment. Rather, it also encompasses all expert developments within the scope of the invention defined by the claims. Although the invention is described with reference to a cordless power tool, it can also be used with power tools powered by mains voltage. Furthermore, a power tool according to the invention is advantageous not only for thread cutting, especially in the professional field, but also for other machining tasks.

Reference numeral list:

1:

power tool

2:

casing

3:

handle

4:

battery pack

5:

tool holder

6:

tappers

7:

electric motor

8th:

On / off switch / auxiliary contact

9:

actuator

10:

(electronic) switch

11:

actuator

12:

Microprocessor / electronic circuit / electronics

13:

Power semiconductor

14:

transmission

15:

Input (to microprocessor for actual speed)

16:

Input (to microprocessor for actual torque)

17:

Potentiometer (for torque)

18:

knob

19:

Switch (for manual / automatic switching function)

20:

Switch (for switching function drilling / thread cutting)

21:

Switch (for chip breaking function)

22:

Right / left switch / auxiliary contact

Claims (9)

1. A method for the operation of an electric power tool (1) for thread-cutting, in particular, a battery electric power tool, with an electric motor (7) for the drive of a tool holder (5) for a thread cutter (6), with a switch (8) having an actuating member (9) for switching on and/or off the voltage supply for the electric motor (7), with a changeover switch for the right-/left-handed rotation of the electric motor (7), with an electronics (12) for the speed control and/or regulation of the electric motor (7), as well as, if necessary, having a short-circuit breaking for the electric motor (7), wherein after actuation of the actuating member (9) the electric motor (7) runs up in the right-handed rotation with a type of ramp function to the ideal speed, wherein subsequently the thread is cut by screwing in the threat cutter (6) in the right-handed rotation, wherein as soon as the thread depth is achieved, as soon as the thread cutter (6) accumulates in a blind hole, as soon as the user releases the actuating member (9) or the like, the electric motor (7) is switched over into the left-handed rotation, and wherein then the thread cutter (6) is unscrewed again in the left-handed rotation from the thread, characterized in that during the screwing in of the thread cutter (6) in the right-handed rotation the number n of threads is counted by means of the electronics (12), that the switching over of the electric motor (7) into the left-handed rotation occurs automatically, that the unscrewing of the thread cutter (6) in the left-handed rotation with a higher velocity than the screwing in in the right-handed rotation occurs, that during the unscrewing of the threat cutter (6) in the left-handed rotation at least the number of the threads, for example, at n+3 threads is counted, and that when this number is reached the electronics (12) automatically switch off the electric motor (7).
2. A method according to claim 1, characterized in that by alternately forwards and backwards rotation corresponding to the right-handed and left-handed rotation of the electric motor (7) an automatic chip breaking function is realized, for example, while the electric motor (7) rotates one revolution forwards as well as then in approximately 1.4 revolutions backwards, wherein preferably the acceleration and/or deceleration of the electric motor (7) is carried out with a suitable ramp function.
3. A method according to claim 1 or 2, characterized in that the changeover switch is an electronic changeover switch (10), which in particular has a power semiconductor (13) for contactless switching over of the polarity of the voltage supply for the electric motor (7).
4. A method according to claim 1, 2 or 3, characterized in that the power semiconductor (13) is triggered manually and/or automatically via an electronic circuit (12) for the switching over, that preferably the switching over is triggered by means of a switchover signal, and that further preferably the switchover signal is generated in the manual operation of an auxiliary contact (22), which can be actuated, in particular, by means of an actuating element (11).
5. A method according to one of claims 1 to 4, characterized in that the electric motor (7) is a brushless, electronically commutated (EC-) electric motor.
6. A method according to one of claims 1 to 5, characterized in that the electronics (12) for the switching over is used in addition to the control of the electric motor (7), and that preferably the electronics (12) has a microprocessor, such that there is a microprocessor control.
7. A method according to one of claims 1 to 6, characterized in that the electric power tool (1) has a means for speed measurement.
8. A method according to one of claims 1 to 7, characterized in that the electric power tool (1) has a means for the torque measurement, which operates in particular by means of a current measurement, that preferably a maximum torque can be provided, for example, via an external switch, via a potentiometer (17) or the like, and that further preferably the electric motor (7) is switched off when the maximum torque is attained.
9. A method according to one of claims 1 to 8, characterized in that the electric power tool (1) can be switched over between manual and/or automatic operation.

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