Hammer drill or chipping hammer having a vibration-reduced hammer-mechanism unit

Abstract

The invention relates to a hammer drill or chipping hammer comprising a hammer-mechanism unit having a drive motor (1) with a motor axis (AM) which is arranged transversely to a hammer-mechanism axis (As) for generating a rotary driving motion which a downstream eccentric gear (5) converts into a linearly alternating working motion along the hammer-mechanism axis (As), which working motion can be transmitted to a coaxially adjacent tool via a hammer mechanism (9) connected to the eccentric gear. For the purpose of reducing vibrations, the center of gravity (SM) of the drive motor (1) is arranged at a radial distance (sM) from the hammer-mechanism axis (As), and the center of gravity (SG) of the eccentric gear (5) is arranged at an opposite radial distance (sM) from the hammer-mechanism axis (As), wherein the radial distance (sM) of the drive motor (1) and the radial distance (sG) of the eccentric gear (5) are dimensioned in such a way that a balanced mass distribution with respect to the hammer-mechanism axis (As) results.

Description

[0001] DRILL OR CHISEL HAMMER WITH A VIBRATION-REDUCED IMPACT UNIT

[0002] DESCRIPTION

[0003] The present invention relates to a drilling or chisel hammer with a percussion unit, comprising a drive motor with a motor axis arranged transversely to a percussion axis for generating a rotary drive movement, which converts a subsequent eccentric gear into a linearly alternating working movement along the percussion axis, which can be transmitted to a coaxially adjacent tool via a percussion mechanism connected thereto, wherein, to reduce vibration, the center of gravity of the drive motor is arranged at a radial distance from the percussion axis and the center of gravity of the eccentric gear is arranged at an opposite radial distance from the percussion axis.

[0004] The field of application of the invention extends primarily to handheld rotary hammers or chisel hammers, which are primarily equipped with an electric motor drive. Such electric hand tools generate a linearly alternating working movement via a mechanical percussion unit, 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 has a complex self-excitation due to the interaction with the workpiece and the operator's hand-arm system, as well as the internal mass and stiffness distribution. The resulting self-vibration, particularly in the handle area, must be suppressed as far as possible.The technical complexity of passively dampening or actively controlled vibration suppression increases with the complexity of the self-excitation to be compensated. To ensure the most controlled and fatigue-free handling of such power tools, the impact mechanism unit should be as vibration-free as possible.

[0005] State of the art

[0006] EP 1 431 005 A2 discloses a generic electric hand-held power tool equipped with an electric motor with a rotor shaft arranged transversely to the impact axis, as well as with a rotor lamination stack and a motor pinion, which drives an impact mechanism by means of an eccentric gear via a spur gear stage, wherein the rotor lamination stack is arranged completely diametrically to the impact mechanism gear with respect to the impact axis. As a result, the core area of ​​the impact axis is only penetrated by the rotor shaft. This not only ensures a radial mass distribution opposite the impact mechanism axis, but also ensures that the electric motor is arranged close to the eccentric, thus generating fewer vibration-causing bending moments. The arrangement of the eccentric gear with spur gear stage on the one hand and the drive motor on the other hand, opposite the impact mechanism axis, achieves a certain reduction in vibration.

[0007] Since the mass of the drive motor increases disproportionately with increasing power class of a rotary hammer or chisel hammer, the vibration reduction effect explained above is correspondingly weakened, which impairs the handling, particularly in the case of heavy electric hand tools of the type in question here.

[0008] It is therefore the object of the present invention to further improve a generic drilling or chisel hammer in such a way that effective vibration reduction is achieved across all performance classes using simple technical means.

[0009] Disclosure of the Invention: This object is achieved by a hammer drill or chisel according to the preamble of claim 1 in conjunction with its characterizing features. The following dependent claims describe advantageous developments of the invention.

[0010] The invention includes the technical teaching that the radial distance of the drive motor and the radial distance of the eccentric gear of the percussion unit from the percussion axis is dimensioned such that a balanced mass distribution is achieved with respect to the percussion axis. This means that the relative distance of the respective components is selected according to their mass, so that the overall center of gravity of the percussion unit lies on the percussion axis.

[0011] The advantage of the solution according to the invention lies in the fact that a balanced mass distribution relative to the percussion mechanism axis can be achieved simply by optimizing the radial distances mentioned. Since, as a result, acceleration of the percussion mechanism unit in the transverse direction does not occur, minimal vibration is achieved.

[0012] According to a first preferred design, the drive motor is arranged completely behind an eccentric unit of the eccentric gear, as seen along the percussion mechanism axis. This eliminates the inherent mass of the drive motor, as it can be freely positioned transversely to achieve the desired mass balance compared to the normally lighter eccentric gear. This is because the eccentric gear does not interfere with the transverse positioning of the drive motor, and vibration reduction can be achieved using this design even with relatively heavy drive motors.

[0013] According to an alternative design, the drive motor, with the exception of the motor shaft, is arranged completely radially offset along the percussion mechanism axis next to the eccentric unit of the eccentric gear. This design is suitable for percussion units that should be as short as possible. Since there is little scope for varying the radial distance of the drive motor from the percussion mechanism axis, this variant is particularly suitable for relatively lightweight drive motors. In this case, however, the balanced mass distribution can also be further influenced via the eccentric gear. In particular, the transmission gear of the eccentric gear could be designed to be rather heavy-duty for the purpose of mass balance.On the other hand, this design allows for a transmission gear with relatively small gears, since the center distance to be bridged is smaller than in the design described above, thus also reducing the overall width of the hand-held power tool. The optimum choice depends on the design objectives and the influencing parameters discussed above.

[0014] According to a preferred embodiment of the invention, when applying the aforementioned first design, the radial distance between the motor center of gravity and the percussion mechanism axis is smaller than the radial distance between the eccentric gear center of gravity and the percussion mechanism axis. This allows the use of a drive motor that normally has a higher mass than a standard eccentric gear. Therefore, there is no need to influence the design of the drive motor or the eccentric gear itself by making certain components particularly light or particularly heavy in order to achieve the desired balanced mass distribution within the overall frame of the percussion unit.

[0015] This does not preclude the possibility of these components being designed with appropriate weight optimization to achieve a balanced mass distribution, not just through distance control. The drive motor is preferably designed as an electric motor, and its mass is largely determined by the power class. However, the dead mass can be influenced by using brushless electric motors, which are usually relatively lighter in the same power class.

[0016] With regard to the eccentric gear, a single-stage transmission gear is preferably used for the slow transmission, which is most preferably designed as a spur gear stage. To achieve the highest possible transmission ratio, it is sufficient if the motor shaft is designed as a toothed pinion with preferably more than ten teeth on the distal end. The diameter of the corresponding spur gear of the transmission gear depends on the center distance between the motor axis and the eccentric gear main axis and is essentially dependent on the stroke of the eccentric connecting rod and the motor diameter. As already mentioned, however, this only applies when implementing the aforementioned design of an impact mechanism unit. To vary the mass of the eccentric gear, the spur gear of the transmission gear can be made of a heavy steel material or a lightweight plastic material.Since the spur gear is arranged on the outside in the radial direction, its own mass has a significant effect on the mass distribution in relation to the percussion mechanism axis.

[0017] Preferably, a percussion unit of a rotary hammer or chisel hammer according to the invention is designed such that, in a desired working position held by an operator, the drive motor has a smaller clearance from the floor—i.e., the distance to the floor—than the eccentric gear. Since the drive motor protrudes further from the percussion mechanism axis in the radial direction, this lower positioning is more convenient for the operator than a lateral or upper positioning. Within the scope of the inventive arrangement, a lower positioning of the drive motor results in the opposite eccentric gear being arranged above the percussion mechanism axis. The entire percussion unit is enclosed by a device housing with a handle and has a tool holder for the chisel or percussion drill at the distal end.

[0018] Detailed description based on drawing

[0019] 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. Fig. 1 shows a schematic side view of a percussion unit according to the first design, and

[0020] Fig. 2 is a schematic side view of a percussion unit according to the second design.

[0021] According to Fig. 1, the impact mechanism unit of a chisel hammer according to the first, preferred design consists of a drive motor 1 with a motor axis AM arranged transversely to an impact mechanism axis As for generating a rotary drive movement. The drive motor 1 is designed as an electric motor and has a pinion gearing on the distal end of a motor shaft 2, which meshes with a spur gear 3 of a single-stage transmission gear 4.

[0022] The single-stage transmission gear 4 is a component of an eccentric gear 5 connected downstream of the drive motor 1. To generate a linearly alternating working movement, the eccentric gear 5 has an eccentric wheel 6 connected downstream of the transmission gear 4, which has a connecting rod 7, and an exciter piston 8 arranged on the impact mechanism side. The exciter piston 8 is also a component of an impact mechanism 9, which transmits the working movement to a tool (not shown) arranged coaxially thereto.

[0023] To reduce vibration of the impact mechanism unit, the center of gravity SM of the drive motor 1 is arranged at a radial distance SM from the impact mechanism axis As, and the center of gravity SG of the eccentric gear 5 is arranged at an opposite radial distance SG from the impact mechanism axis As. The radial distance SM of the drive motor 1 and the radial distance SG of the eccentric gear 5 are dimensioned such that a balanced mass distribution is achieved with respect to the impact mechanism axis As.

[0024] In the illustrated design of the impact mechanism unit, the drive motor 1 is arranged completely behind the eccentric gear 5, as viewed along the impact mechanism axis As. Although this results in a correspondingly long electric hand tool in this embodiment, it allows for a wide range of variation in terms of radial distances. In this embodiment, the radial distance SM is smaller than the radial distance SG, so that a drive motor 1 with a relatively high mass can be positioned in a balanced manner relative to the eccentric gear 5.

[0025] According to the alternative design illustrated in Fig. 2, the drive motor 1, with the exception of the motor shaft 2, is arranged completely radially offset next to the eccentric gear 5 along the percussion mechanism axis As. As a result, the percussion mechanism unit is more compact than the design described above, but the resulting larger radial distance SM compared to the other distance SG can be compensated for, on the one hand, by an electric motor that is as lightweight as possible and, on the other hand, by a particularly heavy-duty spur gear 3 of the transmission gear 4. The more compact design is particularly evident in a relatively small center distance SA between the motor axis and the spur gear axis.

[0026] The invention is not limited to the two preferred embodiments described above. Rather, modifications thereof are also conceivable, which are also encompassed by the scope of the following claims. For example, it is also conceivable to combine the impact mechanism with a rotary drive around the impact mechanism axis in order to equip a hammer drill with the solution according to the invention.

[0027] List of reference symbols

[0028] 1 drive motor

[0029] 2 Motor shaft 3 Spur gear

[0030] 4 transmission gears

[0031] 5 eccentric gears

[0032] 6 Eccentric wheel

[0033] 7 connecting rods 8 excitation pistons

[0034] 9 Percussion

[0035] As percussion axis

[0036] AM Motor axis SM Center of gravity of motor

[0037] SG focus eccentric gear

[0038] SM radial distance motor

[0039] SG radial distance eccentric gear

[0040] SA axle distance

Claims

CLAIMS 1. A drilling or chisel hammer with a percussion unit, comprising a drive motor (1) with a motor axis (AM) arranged transversely to a percussion mechanism axis (As) for generating a rotary drive movement which a downstream eccentric gear (5) converts into a linearly alternating working movement along the percussion mechanism axis (As), which can be transmitted to a coaxially adjacent tool via a percussion mechanism (9) connected thereto, wherein, to reduce vibration, the center of gravity (SM) of the drive motor (1) is arranged at a radial distance (SM) from the percussion mechanism axis (As) and the center of gravity (SG) of the eccentric gear (5) is arranged at an opposite radial distance (SG) from the percussion mechanism axis (As), characterized in that the radial distance (SM) of the drive motor (1) and the radial distance (SG) of the eccentric gear (5) are dimensioned such that a balanced mass distribution is achieved with respect to the percussion mechanism axis (As).

2. Drill or chisel hammer according to claim 1, characterized in that the drive motor (1) is arranged completely behind the eccentric gear (5) as seen along the percussion mechanism axis (As).

3. Drill or chisel hammer according to claim 1 or 2, characterized in that the drive motor (1), with the exception of a motor shaft (2), is arranged completely radially offset next to the eccentric gear (5) as seen along the percussion mechanism axis (As).

4. Drill or chisel hammer according to one of the preceding claims, characterized in that the drive motor (1) has a higher mass than the eccentric gear (5), so that the radial distance (SM) is smaller than the radial distance (SG).

5. Drill or chisel hammer according to one of the preceding claims, characterized in that the eccentric gear (5) comprises a single-stage transmission gear (4) for slow transmission, which is designed as a spur gear stage.

6. Drill or chisel hammer according to one of the preceding claims, characterized in that for a variation of the dead mass of the eccentric gear (5) the spur gear (3) of the spur gear stage consists of a steel or plastic material.

7. Drill or chisel hammer according to one of the preceding claims, characterized in that the eccentric gear (5) for generating the linear alternating working movement comprises an eccentric wheel (6) connected downstream of the transmission gear (4) with a connecting rod (7) and an excitation piston (8) arranged on the impact mechanism side.

8. Drill or chisel hammer according to one of the preceding claims, characterized in that the drive motor (1) is designed as an electric motor.

9. Drill or chisel hammer according to one of the preceding claims, characterized in that a motor shaft (2) is designed on the side of the distal end as a toothed pinion with more than ten teeth.

10. Drill or chisel hammer according to one of the preceding claims, characterized in that the impact unit is designed such that, in a desired working position held by an operator, the drive motor (1) has a smaller distance from the ground than the eccentric gear (5).

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