Percussive hand-held power tool with contact-pressure-adapted power control

Abstract

The invention relates to a percussive hand-held power tool, preferably a hammer drill or chipping hammer, having an electromotive drive unit (4) for producing a rotary drive movement which a downstream striking-mechanism unit (5) converts into an alternatingly linear striking movement that acts on a percussive drilling or chipping tool (8) detachably locked in a downstream tool holding unit (6), wherein a housing arrangement consisting of an outer housing (1) having a handle (2) and of a base housing (3) resiliently mounted in the striking-force direction (FA) relative thereto for accommodating at least the striking-mechanism unit (5) is provided, wherein an electronic control unit (10) is provided for contact-pressure-adaptive power control of the electromotive drive unit (4) starting from a current contact pressure, determined by means of a sensor (11), on the hammer drill or chipping hammer (8) when machining a workpiece, wherein the sensor (11) is located on an electronic circuit board (12) which at least partially forms the electronic control unit (10) and which is accommodated within the outer housing (1) such that the sensor (11) is positioned next to a detection element (13) located to the side of the base housing (3).

Description

[0001] IMPACT POWER HAND TOOL WITH A CONTACT FORCE

[0002] ADAPTED POWER CONTROL

[0003] DESCRIPTION

[0004] The present invention relates to a percussive electric hand tool, such as a hammer drill or chisel hammer, with an electromotive drive unit for generating a rotary drive movement which converts a subsequent impact unit into an alternating linear impact movement which acts on an impact drilling or chiseling tool releasably locked in a subsequent tool holder unit, wherein a housing arrangement composed of an outer housing with a handle and a base housing spring-mounted relative to the handle in the direction of impact for accommodating at least the impact unit is provided, wherein an electronic control unit is further provided for contact force-adapted power control of the electromotive drive unit based on a current contact force on the impact drilling or chiseling tool when machining a workpiece, determined by means of a sensor.

[0005] The field of application of the invention extends primarily to handheld rotary hammers or chisel hammers equipped with an electric motor drive unit. Such electric hand tools generate a linearly alternating working movement via a mechanical percussion mechanism, i.e., a back-and-forth movement to actuate the tool, which in the case of a chisel hammer is designed as a chisel and in the case of a hammer drill as an impact drill for machining preferably mineral materials - such as stone, concrete, and the like. An electric hand tool that drives a tool by impact usually exhibits complex vibration behavior due to interaction with the workpiece and the operator's hand-arm system, as well as the internal mass and stiffness distribution. This vibration behavior must be suppressed as far as possible.For this reason, composite housing arrangements of interest are used here. Their outer housing is equipped with a molded-on handle and is combined with a spring-mounted base housing. The base housing houses at least the impact mechanism unit with the attached tool holder extending from the base housing, as well as usually the electric drive unit. This composite housing concept serves to reduce vibration by not fully transmitting the working movement generated by the impact mechanism unit to the handle and thus to the operator, but dampening it via the spring elements arranged between the housing parts.

[0006] A contact force-adapted power control of the electric motor drive unit, usually created in addition to this, ensures that the power of the drive unit is increased with increasing contact force, which is carried out automatically via an electronic control unit.

[0007] State of the art

[0008] Percussive power tools with contact force-adapted impact performance are known from the generally known state of the art. These tools utilize various concepts for detecting the contact force currently exerted by an operator on the workpiece. Particularly in the case of composite housing assemblies consisting of a base and outer housing, which are preloaded against each other by spring means, it is advisable to infer the contact force from the relative movement between the base and outer housing, knowing the spring characteristic, for example, using a displacement sensor.

[0009] In previously known sensor arrangements for detecting this relative movement, both the sensor and the corresponding detection element are usually arranged as separate components in the power tool. The sensor is assigned electronics for processing the measurement data and transmitting it in digital or analog form to the power tool's electronic control unit.

[0010] DE 10 2012 005 803 A1 discloses a generic percussive electric hand tool comprising a percussion unit driven by a drive unit and a handle for an operator formed on the housing. A force detection device can detect the operator's pressing force on the handle. If the detected pressing force exceeds a predefined working impact force limit, the impact frequency of the percussion mechanism can be increased to a predefined working frequency. If the detected pressing force of the operator falls below a predefined idle impact force limit, the impact frequency can be reduced to a predefined idle speed.For this purpose, the force detection device comprises a force sensor arranged in the force flow between a contact surface provided on the holding device for the operator's hand, on the one hand, and the drive unit and / or the impact mechanism unit and / or the tool holder unit, on the other hand, and generates a signal depending on the operator's pressing force. The force sensor is preferably a displacement sensor with which a relative movement of the handle relative to the drive unit and / or the impact mechanism unit can be detected, wherein the relative movement depends on the operator's pressing force.

[0011] DE 19738092 C1 also discloses a contact force-adapted power control system for a percussive power tool, the force sensor of which is located directly beneath a casing formed by the handle. The sensor surface of the force sensor faces the casing, which has thinner walls in the area of ​​the force sensor than the housing section surrounding this area. The electronic control unit records a signal from the force sensor corresponding to an actuating force and, if constant, automatically maintains the operating parameters corresponding to this actuating force over a selectable period of time. The effective range of the force sensor can be preset to influence the operating parameters using an adjusting wheel assigned to the electronic control unit.All of these prior art sensor concepts prove to be relatively complex and / or error-prone, particularly with regard to data lines running between a sensor and the electronic control unit, which are exposed to disruptive magnetic fields of the drive unit and the like.

[0012] It is the object of the present invention to further improve a percussive electric hand tool with contact force-adapted power control of the generic type in such a way that a simple structure is achieved with, at the same time, reduced susceptibility to failure.

[0013] Disclosure of the invention

[0014] The object is achieved by means of a percussive electric hand tool according to the preamble of claim 1 in conjunction with its characterizing features. The following dependent claims reflect advantageous developments of the invention.

[0015] The invention includes the technical teaching that a sensor of a contact force-adapted power control is arranged directly on an electronic circuit board which at least partially forms the electronic control unit and which is accommodated within the outer housing of a composite housing arrangement in such a way that the sensor is positioned adjacent to a detection element arranged on the side of the base housing, specifically within the sensor-effective range thereof.

[0016] The complexity of contact force-adapted power control is advantageously reduced by placing the electronics board of the electronic control unit in the power tool in such a way that the sensor is directly integrated into the electronics board. The electronics board is located on the outer housing side, and the detection element is housed in the base housing. The electronics board is to be mounted in the outer housing in such a way that the distance to the detection element on the base housing is as small as possible. The electromotive drive unit adjacent to the sensor normally generates strong interference on data lines due to the constantly changing magnetic field of the motor.However, since the sensor is arranged directly on the electronics board according to the invention, these interference fields can only feed very low levels of interference into the data lines between the sensor and the electronic control unit, which is also arranged at least partially on the same electronics board, because the length of the data lines is reduced to a minimum. This eliminates the need for complex shielding measures for such a data line. At the same time, manufacturing costs are significantly reduced because the sensor requires no additional electronics, such as measuring amplifiers or converters, and no cable connection between the sensor and the electronic control unit. In addition to the pure component costs, assembly costs for mounting and cable routing can also be saved.This not only reduces the manufacturing effort but also the mechanical robustness of the sensor concept of the contact force-adapted power control, since additional data lines are always susceptible to mechanical damage due to the prevailing high vibration level of percussive power tools, which can lead to an interruption of the device communication and thus to device failure, which is avoided by the solution according to the invention.

[0017] According to a first preferred embodiment of the invention, the electronics board with sensor is arranged on a top side within the outer housing such that the electronics board runs parallel and spaced from the impact axis. This arrangement is suitable for housing shapes that offer sufficient space on the top side to accommodate the electronics board.

[0018] According to a second preferred embodiment, it is proposed to arrange the electronic circuit board with the sensor in a space between the base housing and the outer housing such that the electronic circuit board runs transversely to the striking axis. This arrangement is particularly suitable for housing designs with a relatively large transverse extension.

[0019] According to a third preferred embodiment, it is proposed that the electronics board with the sensor be arranged on the underside of the outer housing such that the electronics board runs parallel and spaced from the impact axis. This arrangement is particularly suitable for housing shapes that accommodate a short motor. It is also conceivable to arrange the electronics board with the sensor between the top and bottom, i.e., on the flank of the outer housing, so that the electronics board also runs parallel and spaced from the impact axis.

[0020] The sensor for detecting relative movements between the base and outer housing is preferably designed as a 3D magnetic field sensor. This type of sensor is capable of detecting distance changes in both the longitudinal and transverse directions and is therefore equally suitable for all installation positions of the electronics board. A permanent magnet element can be used as the associated detection element, which is attached to the base housing as close as possible to the sensor.

[0021] Alternatively, the sensor can also be designed as an inductive sensor and the associated detection element can also be formed by metallic / magnetic component structures of the base housing or the components accommodated therein.

[0022] If the electronic control of the power tool is to be distributed across multiple electronic circuit boards, it is proposed that at least a logic component of the electronic control unit be located on the electronic circuit board with the sensor, while the remaining power component can be placed outside the board in the outer housing or in the base housing of the power tool, close to the drive. This measure increases the flexibility of accommodating electronic components in particularly compact housing designs.

[0023] If sufficient installation space is available, preference should be given to an electronic control unit that is completely arranged on the electronics board in order to maximize the functional reliability of the electronics and reduce assembly effort.

[0024] Preferably, the sensor should be soldered directly onto the electronics board. This applies not only to the electrical connection of the sensor terminals, but also to the sensor housing, which can then be securely mounted on the electronics board. The electronics board itself can be detachably and thus replaceably attached to suitable support structures using a conventional screw connection inside the outer housing.

[0025] Detailed description based on drawing

[0026] Further measures improving the invention are described in more detail below, together with the description of preferred embodiments of the invention, with reference to the figures. It shows:

[0027] Fig. 1 is a schematic side view of a first embodiment of a percussive electric hand tool with contact force-adapted power control according to the invention,

[0028] Fig. 2 is a schematic side view of a second embodiment of a percussive electric hand tool with contact force-adapted power control according to the invention,

[0029] Fig. 3 is a schematic side view of a third embodiment of a percussive electric hand tool with contact force-adapted power control according to the invention, and

[0030] Fig. 4 is a schematic side view of a fourth embodiment of a percussive electric hand tool with contact force-adapted power control according to the invention. According to Fig. 1, a hammer drill has an assembled housing arrangement consisting of an outer housing 1 with handle 2 and a base housing 3 spring-mounted relative to the outer housing in the direction of impact force FA, in which an electromotive drive unit 4 and a subsequent impact unit 5 are housed, on which an outwardly projecting tool holder unit 6 is arranged. A percussion drilling tool 8 is releasably locked in the tool holder unit 6 along an impact axis 7. While the impact unit 5, the tool holder unit 6 and the percussion drilling tool 8 lie on the common impact axis 7, the electromotive drive unit 4 is arranged transversely thereto and is connected to the impact unit 5 via gear means.Overall, the overall arrangement of the various functional units forms the focal point.

[0031] Furthermore, a manually operable switch 9 for switching the electric motor drive unit 4 on and off is arranged on the handle 2 of the outer housing 1, which switch is located on the side of the base housing 3. When the power tool is not in use, a distance L exists between the outer housing 1 and the base housing 3, which determines the spring stroke.

[0032] The hammer drill is equipped with an electronic control unit 10 for contact force-adapted power control of the electric motor drive unit 4. A sensor 11 determines the distance between the outer housing 1 and the base housing 3, which is spring-mounted relative to the outer housing in the direction of impact force FA. This sensor, in a conventional manner, represents a measure of the contact force currently exerted on the impact drilling tool 8 during machining of a workpiece.

[0033] The sensor 11, designed here as a 3D magnetic field sensor, is firmly arranged by soldering on an electronic circuit board 12 forming the electronic control unit 10. The electronic circuit board 12 with the sensor 11 is arranged on an upper side 14 within the outer housing 1, parallel to the striking axis 7, and positioned such that the sensor 11 is adjacent to a detection element 13 arranged on the side of the base housing 3. The detection element 13 is designed as a permanent magnet element that is embedded in the wall of the base housing 3 close to the sensor 11. Fig. 2 shows an embodiment in which the electronic circuit board 12' with the sensor 11' attached thereto is arranged in a gap 15 between the base housing 3 and the spring housing 1. The gap 15 is formed by the spring travel of the vibration decoupling, which corresponds to the spring stroke L. The electronic board 12' runs transversely to the striking axis 7.The sensor 11' arranged on the side of the outer housing 1 is positioned opposite the detection element 13', whereby the two components, sensor 11' and detection element 13', do not come into contact even in the retracted end position of the base housing 3 with respect to the outer housing 1. The remaining structure of the power tool according to the second embodiment corresponds to the first embodiment described above.

[0034] According to Fig. 3, in the third embodiment of an electric hand tool, the electronic circuit board 12" with sensor 11" is arranged on the inside of the underside 16 of the outer housing 1 such that the electronic circuit board 12" runs parallel and spaced from the impact axis 7. This design is particularly suitable for short electric motors, since there is still sufficient space below them for the arrangement of the sensor 11" with the corresponding detection element 13", which is positioned below the electromotive drive unit 4. Here, too, the remaining components of the electric hand tool correspond to the first embodiment.

[0035] According to the fourth embodiment illustrated in Fig. 4, the electronic circuit board 12"' is arranged on the flank side 17 of the outer housing 1 running between the top side 14 and the bottom side 16, so that the electronic circuit board 12"' here also runs parallel and spaced from the striking axis 7.

[0036] Alternatively, the 12" electronic board can of course also be arranged inside the housing on the flank side opposite the flank side 17 (without reference symbol).

[0037] The figure illustrates in one image all of the above-described possibilities for a space-saving arrangement of the electronic circuit board 12, 12', 12", 12'", 12"". The invention is not limited to the three exemplary embodiments described above. Rather, modifications thereof are also conceivable, which are also covered by the scope of protection of the following claims. For example, it is also possible to use an inductive sensor instead of a 3D magnetic field sensor, provided that this can deliver sufficiently reliable measured values ​​about the current distance situation between the outer housing 1 and the base housing 2 with regard to the installation position and detection environment.

[0038] List of reference symbols

[0039] 1 outer casing

[0040] 2 handles

[0041] 3 base housings

[0042] 4 Drive unit

[0043] 5 percussion unit

[0044] 6 Tool holder unit

[0045] 7 Impact axis

[0046] 8 Impact drill or chisel tool

[0047] 9 switches

[0048] 10 electronic control unit

[0049] 11 Sensor

[0050] 12 Electronic board

[0051] 13 Detection element

[0052] 14 Top

[0053] 15 space

[0054] 16 Subpage

[0055] 17 flank side

[0056] FA impact force direction

[0057] S Focus

[0058] L distance

Claims

CLAIMS 1. Percussive electric hand tool, preferably a hammer drill or chisel hammer, with an electromotive drive unit (4) for generating a rotary drive movement which converts a subsequent impact mechanism unit (5) into an alternating linear impact movement which acts on an impact drilling or chiseling tool (8) releasably locked in a subsequent tool holder unit (6), wherein a housing arrangement composed of an outer housing (1) with a handle (2) and a base housing (3) which is resiliently mounted relative to the handle in the direction of impact force (FA) for accommodating at least the impact mechanism unit (5) is provided, wherein an electronic control unit (10) is also provided for the power control of the electromotive drive unit (4) which is adaptive to the contact force and starts from a signal transmitted by a sensor (11; 1 T;11") is provided for detecting the current contact pressure on the percussion drilling or chiseling tool (8) during the machining of a workpiece, characterized in that the sensor (11; 11'; 11") is arranged on an electronic circuit board (12; 12'; 12"; 12'"; 12"") which at least partially forms the electronic control unit (10) and which is accommodated within the outer housing (1) in such a way that the sensor (11) is positioned adjacent to a detection element (13, 13', 13") arranged on the side of the base housing (3).

2. Percussive electric hand tool according to claim 1, characterized in that the electronic circuit board (12) with sensor (11) is arranged in an upper side (14) of the outer housing (1) in such a way that the electronic circuit board (12) runs parallel and spaced from the percussion axis (7).

3. Percussive electric hand tool according to claim 1, characterized in that the electronic circuit board (12') with sensor (11') is arranged in or on an intermediate space (15) between the base housing (3) and the outer housing (1) in such a way that the electronic circuit board (12') runs transversely to the percussion axis (7).

4. Percussive electric hand tool according to claim 1, characterized in that the electronic circuit board (12") with sensor (11") is arranged on an underside (16) of the outer housing (1) in such a way that the electronic circuit board (12") runs parallel and spaced from the percussion axis (7).

5. Percussive electric hand tool according to claim 1, characterized in that the electronic circuit board (12"'; 12"") with sensor (11") is arranged on one of the flank sides (17) of the outer housing (1) running between the top side (14) and the bottom side (16) in such a way that the electronic circuit board (12") runs parallel and spaced from the percussion axis (7).

6. Percussive electric hand tool according to claim 1, characterized in that the sensor (11; 11 11") is designed as a 3D magnetic field sensor and the associated detection element (13, 13', 13") is designed as a permanent magnet element.

7. Percussive electric hand tool according to claim 1, characterized in that the sensor (11; 11 '; 11") is designed as an inductive sensor and the associated detection element is formed by component structures of the base housing (3) or the components accommodated therein.

8. Percussive electric hand tool according to one of the preceding claims, characterized in that the electromotive drive unit (4) is also accommodated in the base housing (3).

9. Percussive electric hand tool according to one of the preceding claims, characterized in that a logic part of the electronic control unit (10) is arranged on the electronic circuit board (12, 12', 12"; 12'"; 12""), whereas a power part is accommodated outside the same in the outer housing (1) or in the base housing (3).

10. Percussive electric hand tool according to one of the preceding claims 1 to 8, characterized in that the electronic control unit (10) is arranged entirely on the electronic circuit board (12, 12', 12"; 12'"; 12"") of the outer housing (1).

11. Percussive electric hand tool according to one of the preceding claims, characterized in that the sensor (11; 11 '; 11") is firmly attached to the electronic circuit board by soldering.

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