EP1425770A1

EP1425770A1 - Electric switch

Info

Publication number: EP1425770A1
Application number: EP02776666A
Authority: EP
Inventors: Daniel Hafen; Michael Bufe; Peter Broghammer
Original assignee: Marquardt GmbH
Current assignee: Marquardt GmbH
Priority date: 2001-09-11
Filing date: 2002-09-10
Publication date: 2004-06-09
Anticipated expiration: 2022-09-10
Also published as: EP1425770B1; WO2003023802A1; DE50205838D1; DE10241868A1; ATE318008T1

Abstract

The invention relates to an electric switch (1), especially for an electric tool with an electric motor (2), e.g. an electric drilling machine, a hammer drill, an electric screwdriver or the like, comprising an actuating element (4) which can be adjusted between an initial and a final position. A set-point value device (6) actively cooperates with the actuating element (4) for the production of a set-point value associated with the adjustment path of the actuating element (4). The switch (1) also comprises a control device (8) for operating, especially for controlling and/or regulating, the electric motor (2) according to the set-point value. The adjustment path is divided into several sections, particularly into at least two sections, between the initial and final position in a step-like manner, each section being associated with a different digital code. The set-point value device (7) produces the digital code associated with the adjustment path of the actuating element (4) as a set-point value. The control device (8) subsequently processes the digital code so that the electric motor (2) can be operated accordingly.

Description

Electrical switch

The invention relates to an electrical switch according to the preamble of claim 1.

Such switches are used for power tools, such as electric drills, rotary hammers, electric screwdrivers or the like.

From DE 19708 939 AI an electrical switch with a manually adjustable between an initial and an end position actuator is known. The actuating member is operatively connected to a potentiometer which outputs an electrical voltage corresponding to the actuating member's travel range. The potentiometer thus serves as a setpoint device for generating an assigned setpoint, which in this case is represented by the electrical voltage. This setpoint is fed to a control device in the switch, the control device operating, controlling and / or regulating an electric motor as a function of this setpoint. For example, the control device adjusts the speed of the power tool in accordance with the adjustment of the actuating member made by the user.

The potentiometer in the switch consists of a slider and a resistance track, the slider sliding through the operative connection with the actuating element on the resistance track. The resistance track is usually produced by printing a resistance paste on a printed circuit board. The manufacture of the resistance track is complex and sensitive to tolerance. The potentiometer is therefore, on the one hand, an expensive component and, on the other hand, this can disadvantageously also lead to increased rejects. Furthermore, from GB 2 314 980 A an electrical switch for a power tool has become known, in which the resistance track for the potentiometer is replaced by individual discrete resistors. In addition to the resulting higher costs due to the large number of resistors, which ultimately require an even more complex manufacture of the setpoint device, the problem of tolerance sensitivity is also present here.

Starting from DE 197 08 939 AI, the invention is based on the object of further developing the electrical switch in such a way that it is less sensitive to tolerances. In particular, the use of a resistance track and / or resistors in the setpoint device should be avoided.

This object is achieved in a generic electrical switch by the characterizing features of claim 1.

In the switch according to the invention, the travel distance for the actuating member between the starting and the end position is divided into several sections in the manner of stages, each of these sections being assigned a different digital code. The setpoint device is designed in such a way that it generates this digital code assigned to the actuating member's travel path as the setpoint. This digital code is then processed in the control device for the corresponding operation of the electric motor. Since, in contrast to an analog resistance value, the digital code is not subject to any tolerances, the switch according to the invention does not have the disadvantages inherent in the prior art. Further embodiments of the invention are the subject of the dependent claims.

The digital code generated by the setpoint device can be fed directly and directly to the control device. A preprocessing or further processing in the setpoint device is not necessary, so that the setpoint device according to the invention represents an overall cost-effective solution. With regard to the customary processing methods used in digital technology, it makes sense to count the number of sections Powers of two to choose. In order to achieve a sufficiently large resolution of the setpoint device without great effort, it has proven to be advantageous to divide the adjustment path into eight sections.

The setpoint device can have a grinder and contact areas assigned to the respective section of the adjustment path. The grinder then interacts electrically with the respective contact surfaces in accordance with its adjustment path, so that the respective digital code can be tapped off from the electrically contacted contact surfaces in a simple manner. For this purpose, a contacted contact area is expediently rated as logical "one" and a non-contacted contact area as logical "zero".

In a further embodiment, the switch has a housing. A plunger reaching into the housing is attached to the actuator. An attachment for fastening the grinder is arranged on the tappet inside the housing. The exterior of this switch is thus designed essentially in a conventional manner, so that the switch according to the invention can be used in place of a conventional switch without further changes in the power tool.

The contact areas are expediently located on a printed circuit board. The contact areas can be designed in the manner of conductor tracks, in particular in a different arrangement and / or length, as a result of which the setpoint device can be implemented in a small space. The circuit board is protected from harmful influences and is arranged in the switch housing in such a way that the grinder can be moved on the contact surfaces along the adjustment path in the manner of a grinder track. With regard to a compact design, it is furthermore favorable to equip the grinder with a plurality of grinder fingers, one grinder finger interacting with one contact surface.

Furthermore, it is advisable to also arrange the control device on the circuit board, which in turn contributes to the compact design of the switch. The control device can be an electronic and / or electrical circuit for controlling and / or regulating the Electric motor be formed. The circuit for the control device is designed as an electronic digital and / or analog circuit. The control device is preferably a microprocessor and / or a microcontroller, in particular a single-chip microprocessor. For the purpose of good resolution, the microprocessor and / or microcontroller is equipped with at least three inputs for the digital code, so that the adjustment path can be divided into at least eight sections. Since the microprocessor and / or microcontroller is also located on the circuit board, the inputs can be electrically connected directly to one contact surface each, which saves installation space and costs. With the help of the microprocessor and / or microcontroller, on the one hand the haptics of the switch can be easily adapted to the wishes of the user, and on the other hand additional functions of the control device can be implemented without additional effort.

In particular, the control device is used to control and / or regulate the speed and / or the torque of the electric motor as a function of the digital code generated by the setpoint device. The switch according to the invention then contains, as a control device, a pulse width modulation control for an electric motor operated with direct voltage or a phase control for an electric motor operated with alternating voltage.

The digital code can be a binary or dual code. This code is preferably designed in one step. For example, it can be a Gray code, which advantageously has a particularly high level of error security.

In addition, the setpoint device can not only be used in electrical switches, but can also be used independently. Such a setpoint device is in turn in operative connection with an actuating member which can be adjusted between a starting and an end position in such a way that a setpoint assigned to the adjustment path of the actuating member can be generated. The setpoint device has an electrical output for providing the setpoint. Again, the adjustment path between the starting and end positions is several Sections, in particular divided into at least two sections, in the manner of stages, each section being assigned a different digital code. The digital code assigned to the adjustment path of the actuating member is generated as the setpoint and is made available at an output consisting of electrical connections. The setpoint device can of course also be provided with the configurations described.

The advantages achieved with the invention consist in particular in the fact that the large tolerances which conventionally occur when printing the resistance track and / or with individual discrete resistors need not be taken into account further. The control device, such as a pulse width modulation circuit which is customary per se, no longer has series spreading of the duty cycle and the operating frequency. There are also no fluctuations in the course of the operating time of the switch. In addition, the service life of the setpoint device is increased compared to the potentiometer previously used. The manufacture of the setpoint device, in particular the circuit board used here, is simplified. In addition, the proportion of the setpoint device on the printed circuit board takes up less space, so that additional functions that could previously only be implemented with great effort due to the limited space available in the switch can now be integrated into the switch according to the invention with little effort and largely without additional costs.

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

1 is a basic circuit diagram for the arrangement of the electrical switch in a power tool,

2 the electrical switch in side view,

3 shows a section along the line 3-3 from FIG. 2,

4 shows a schematic top view of the circuit board located in the switch, 5 a perspective view of a part of the switch containing the setpoint device,

6 the setpoint device in a perspective view

Fig. 7 is a diagram of the dependence between the adjustment of the actuator and the speed of the electric motor.

The electrical switch 1 is used in an electrical device that is supplied by a voltage source. The electrical switch 1 is preferably used in an electric tool, such as an electric drill, a rotary hammer, an electric screwdriver or the like. 1 shows the basic circuit diagram for the arrangement of the electrical switch 1 in a power tool, which is supplied by the AC line voltage U, in more detail.

The power tool has an electric motor 2 with field windings 3. The electric motor 2 is switched on and off by the user by actuating the switch 1, which is located, for example, in the handle of the power tool, and its speed is set by means of the switch 1. For this purpose, the switch 1 has an actuating element 4 designed as a pusher, which serves as a handle for the user and is manually adjustable between an initial and an end position. When moving, the actuating member 4 is on the one hand in operative connection with a setpoint device 7 and on the other hand has a switching action in certain positions on two contact systems 5, 6. The actual control and / or regulation for operating the electric motor 2 takes place by means of a control device 8 connected to a power semiconductor 9, such as a triac or the like. The control device 8 and the power semiconductor 9 operate in the manner of a phase control.

Through the manual movement of the actuator 4 from the initial position, the contact system 5 is first closed and the AC line voltage U is applied to the electric motor 2 via the power semiconductor 9. Next is from the setpoint device 7 generates a setpoint value which is assigned to the adjustment path of the actuating member 4 starting from the starting position. This setpoint is then fed to the control device 8. The control device 8 ignites the power semiconductor 9 at the corresponding phase or current flow angle of the AC line voltage U, depending on the desired value, so that ultimately the speed of the electric motor 2 corresponding to the position of the actuating member 4 is set and optionally regulated. If the actuating member 4 is in its end position, which corresponds to the maximum adjustment path starting from the starting position, the contact system 6 is closed, as a result of which the control device 8 and the power semiconductor 9 are bridged. The full AC line voltage U is thus present at the electric motor 2 and the latter moves at the maximum speed.

According to the invention, in the electrical switch 1, the adjustment path between the starting position and the end position is divided into several sections, but at least two sections. In practice, the division into eight sections has proven to be expedient. A different digital code is assigned to each section. The respective digital code is generated by the setpoint device 7 as a setpoint when the actuator 4 is moved into the corresponding section. This digital code is then processed by the control device 8 for the corresponding operation of the electric motor 2, the electric motor 2 being controlled as described so as to be operated at the speed which is functionally dependent on the setpoint. Since each section is assigned to a digital code, these sections are designed in the manner of stages with regard to the corresponding speed. This step-like division of the sections can be seen in more detail in FIG. 7, in which the speed n of the electric motor 2 is shown in connection with the adjustment path s of the actuating member 4 for a specific functional dependency between setpoint and speed.

The further configuration of the switch 1 will now be described in more detail below.

The switch 1 has for receiving the electrical components, such as the contact systems 5, 6 u. Like., A housing 10, as shown in more detail in FIG. 2. A plunger 11 reaching into the housing 10 is fastened to the actuating member 4. As in Fig. 3 can be seen, the setpoint device 7 has a grinder 12 and contact surfaces 15. The grinder 12 is attached to an extension 13 arranged in the interior of the housing 10 on the plunger 11. The contact surfaces 15 are located on a printed circuit board 14. The printed circuit board 14 is arranged in the housing 10 such that the grinder 12 can interact with the contact surfaces 15, which can be seen in particular in the perspective view according to FIG. 5. As can also be seen in the enlarged illustration according to FIG. 6, the grinder 12 now interacts electrically with the contact surfaces 15 assigned to the respective section of the adjustment path, so that the digital code can be tapped from the electrically contacted contact surfaces 15. The digital code is then fed directly and directly from the setpoint device 7 to the control device 8.

As can be seen from FIG. 6, the contact surfaces 15 are designed in particular in the manner of conductor tracks on the printed circuit board 14. The contact surfaces 15 consist of individual contact surfaces 15a, 15b, 15c, 15d, which are arranged next to one another differently and have a different length, as can be clearly seen in FIG. 4. The contact surfaces 15a, 15b, 15c, 15d are provided with electrical connections 16, which serve as an output for the desired value device 7. The corresponding input of the control device 8 is then in electrical connection with the electrical connections 16 of the output of the setpoint device 7.

The grinder 12 can be moved on the contact surfaces 15 along the adjustment path in the manner of a grinder track. The grinder 12 has a plurality of grinder fingers 12a, 12b, 12c, 12d, so that in each case one grinder finger 12a, 12b, 12c, 12d interacts with one contact surface 15a, 15b, 15c, 15d. Depending on the adjustment path of the four-part grinder 12 in accordance with the position of the actuating member 4, the grinder 12 by means of its grinder fingers 12a, 12b, 12c, 12d bridges the contact surface 15d with one or more of the contact surfaces 15a, 15b, 15c, as a result of which contact surfaces 15a, 15b , 15c either due to the contacting the same electrical potential as at the contact surface 15d or due to the non-contacting a different electrical potential is present. The contact surfaces 15a, 15b, 15c are expediently connected to a voltage, for example 5 volts, and the contact surface 15d to ground. When bridged by the wiper fingers 12a, 12b, 12c, the corresponding contact surface 15a, 15b, 15c is then also pulled to ground. The respective electrical potential at the contact surfaces 15a, 15b, 15c thus represents a binary state according to a logical "0" or "1" (bit), so that the digital code corresponding to the adjustment path of the grinder 12 by a binary or. Dual code is represented, as is particularly clear from FIG. 4.

By means of the three contact surfaces 15a, 15b, 15c shown in FIG. 4, each corresponding to one digit of the digital code, eight (equal to 2 to the power of 3 bits) states in binary / dual code can be distinguished as a power of two, as a result of which the values shown in FIG. 7 eight sections of the adjustment path shown can be uniquely assigned to the binary / dual code. Of course, depending on the need for sections for the adjustment path, a different number of contact surfaces 15 can also be selected. In accordance with the arrangement of the contact surfaces 15a, 15b, 15c, this binary / dual code can be designed in one step, so that the digital code changes in only one bit in two successive sections. For example, the binary / dual code can be a gray code, specifically a 3-bit gray code according to the three contact areas 15a, 15b, 15c. The Gray code advantageously has a high level of error security and can be realized in an extremely space-saving manner with the four contact surfaces 15a, 15b, 15c, 15d on the printed circuit board 14.

The control device 8 is also located on the printed circuit board 14 in the housing 10. The control device 8 is designed as an electronic and / or electrical circuit, preferably in the form of a chip, as shown in FIG. 3. The control device 8 can be an electronic digital and / or analog circuit for controlling and / or regulating the electric motor 2. In particular, a microprocessor / microcontroller is suitable as the control device 8, which can expediently be a single-chip microprocessor which is equipped with at least three inputs for the digital code corresponding to the electrical connections 16 on the contact surfaces 15a, 15b, 15c. As stated, the control device 8 can control and / or regulate the speed of the electric motor 2 as a function of the digital code generated by the setpoint device 7. 7 shows, by way of example, a characteristic curve that runs disproportionately at higher speeds. Of course, another characteristic curve can also be selected, for example with an essentially linear dependency between adjustment path s and speed n. It should be emphasized that when using a microprocessor / microcontroller, the assignment between the digital code and the speed can be predefined in a simple manner by means of programming , so that advantageously an individual and simple setting is possible and the feel of the switch 1 can be adjusted in the manner desired by the user. Of course, the torque of the electric motor 2 can be controlled and / or regulated as an alternative or in addition to the speed according to the digital code, which can be desirable, for example, in an electric screwdriver.

The invention is not restricted to the exemplary embodiment described and illustrated. Rather, it also includes all professional developments within the scope of the invention defined by the claims. Such a switch can be used not only on a power tool operated with AC voltage but also on a battery-operated power tool operated with DC voltage. In this case, an FET, MOS-FET or the like is used as the power semiconductor 9 and the control device 8 operates by means of pulse width modulation. By appropriately assigning the digital code to the frequency and / or the duty cycle of the pulse width modulation, the desired functional dependency of the speed on the adjustment path is also set here. Furthermore, such a switch can also be used in other electrical devices supplied by a voltage source, such as garden tools, kitchen tools or the like. Finally, the setpoint device according to the invention can also be used independently, for example as a replacement for a potentiometer. Reference numeral list:

1: electrical switch

2: electric motor

3: field winding

4: actuator

5,6: contact system

7: Setpoint adjustment

8: control device

9: power semiconductors

10: housing

11: plunger

12: grinder

12a-d grinder fingers

13: shoulder (on the ram)

14: PCB

15

(a-d): contact area

16: electrical connection

Claims

Patent claims:

1. Electrical switch, in particular for a power tool with an electric motor (2), such as an electric drill, a hammer drill, an electric screwdriver or the like, with an actuating member (4) adjustable between a starting position and an end position, with an operative connection with the actuating member (4) has setpoint device (7) for generating a setpoint assigned to the adjustment path of the actuating member (4), and with a control device (8) for operation, in particular for controlling and / or regulating the electric motor (2), such as its speed, Torque or the like, depending on the target value, characterized in that the adjustment path between the starting and the end position is divided into several sections, in particular at least two sections, in the manner of stages that a different digital code is assigned to each section that the target value device (7) digitally assigned to the adjustment path of the actuating member (4) generated code as a setpoint, and that the control device (8) processes the digital code for the corresponding operation of the electric motor (2).

2. Electrical switch according to claim 1, characterized in that the adjustment path is divided into eight sections, and that preferably the digital code from the setpoint device (7) is fed directly and directly to the control device (8).

3. Electrical switch according to claim 1 or 2, characterized in that the setpoint device (7) has a grinder (12), and that preferably the grinder (12) with contact surfaces (15) which are assigned to the respective section of the adjustment path, electrically interacts in a contacting manner such that the respective digital code can be tapped from the contact surfaces (15), in particular as a function of their electrical contacting and non-contacting in the manner of a logical "1" or "0".

4. Electrical switch according to claim 1, 2 or 3, characterized in that the switch (1) has a housing (10) that is preferably attached to the actuating member (4) in the housing (10) extending plunger (11), and that further preferably inside of the housing (10) on the plunger (11), an attachment (13) for fastening the grinder (12) is arranged.

5. Electrical switch according to one of claims 1 to 4, characterized in that the contact surfaces (15) are on a circuit board (14), that preferably the contact surfaces (15) in the manner of conductor tracks, in particular in a different arrangement and / or Length, are configured such that the printed circuit board (14) is preferably arranged in the housing (10) in such a way that the slider (12) can be moved on the contact surfaces (15) along the adjustment path in the manner of a slider track, and that it is even more preferred the grinder (12) has a plurality of grinder fingers (12a, 12b, 12c, 12d), one grinder finger (12a, 12b, 12c, 12d) interacting with a contact surface (15a, 15b, 15c, 15d).

6. Electrical switch according to one of claims 1 to 5, characterized in that the control device (8) is designed as an electronic and / or electrical circuit for controlling and / or regulating the electric motor (2), that preferably the control device (8) as electronic digital and / or analog circuit is configured, and that further preferably the control device (8) is located on the printed circuit board (14).

7. Electrical switch according to one of claims 1 to 6, characterized in that the control device (8) is a microprocessor and / or a microcontroller, in particular a single-chip microprocessor, with at least three inputs for the digital code, and that preferably the inputs of the control device (8) are in electrical connection, in particular at an electrical connection (16), each having a contact surface (15a, 15b, 15c).

8. Electrical switch according to one of claims 1 to 7, characterized in that the control device (8) controls the speed and / or the torque of the electric motor (2) in functional dependence on the digital code generated by the setpoint device (7) and / or regulates, and that preferably the control device (8) a pulse width modulation control for an electric motor operated with DC voltage (2) or a phase control for an electric motor operated with AC voltage (2).

9. Electrical switch according to one of claims 1 to 8, characterized in that the digital code is a binary or dual code, which is designed in particular in one step, for example a Gray code.

10. Setpoint device with which an adjustable between an initial and an end position actuator (4) is operatively connected such that an adjustment path of the actuator (4) assigned setpoint can be generated, and with an electrical output for providing the setpoint, characterized that the adjustment path between the starting and the end position is divided into several sections, in particular at least two sections, in the manner of stages, that each section is assigned a different digital code, that as a setpoint the one assigned to the adjustment path of the actuating member (4) Digital code is generated, and that the digital code is provided at an output consisting of electrical connections (16).