Hammer drill or chisel with vibration-reducing strike mechanism

Abstract

The invention relates to a hammer drill or chisel having a striking mechanism unit, which comprises a drive motor (1), which has a motor axis (AM), which is arranged transversely to a striking mechanism axis (AS), for generating a rotary drive movement, a subsequent eccentric gear (5) converts the rotary drive movement into a linear alternating working movement along the strike mechanism axis (AS), which movement can be transmitted to a coaxially adjacent tool via a strike mechanism (9) connected to the eccentric gear, the centre of gravity (SM) of the drive motor (1) being arranged at a radial distance (sM) from the strike mechanism axis (AS), the center of gravity (SG) of the eccentric gear (5) is arranged at an opposite radial distance (sG) from the strike mechanism axis (AS) in order to reduce vibrations, the radial distance (sM) of the drive motor (1) and the radial distance (sG) of the eccentric gear (5) being dimensioned such that a balanced mass distribution is established with respect to the strike mechanism axis (AS).

Description

Technical Field

[0001] The invention relates to a hammer drill or a hammer chisel, which has a striking mechanism unit, which includes a drive motor, the drive motor having a motor axis, which is arranged transversely to the striking mechanism axis for generating a rotary drive motion, and a subsequent eccentric gear converts the rotary drive motion into a linear alternating working motion along the striking mechanism axis, which motion can be transmitted to a coaxially adjacent tool via a striking mechanism connected to the eccentric gear, wherein the center of gravity of the drive motor is arranged at a radial distance from the striking mechanism axis, and the center of gravity of the eccentric gear is arranged at an opposite radial distance from the striking mechanism axis in order to reduce vibration.

[0002] The field of application of the invention extends primarily to hand-held hammer drills or hammer chisels, which are primarily provided with an electric motor drive. Such electric hand tools generate a linear alternating working motion via a mechanical striking mechanism unit, i.e. a reciprocating motion for an impact tool, which in the case of a hammer chisel is designed as a mortise chisel and in the case of a hammer drill is designed as an impact drill, for preferably working on mineral materials such as stone, concrete, etc. Due to the interaction with the workpiece and the operator's arm system as well as the internal mass and stiffness distribution, the electric hand tool driving the tool has complex self-excitation, the natural vibrations generated by which, in particular in the handle area, must be suppressed as much as possible. The technical complexity of such passively damped or actively controlled vibration suppression increases with the complexity of the self-excitation to be compensated.

[0003] In order to ensure the most controlled and fatigue-free operation of such electric machine tools, the striking mechanism should therefore be as vibration-free as possible. Background Art

[0004] EP 1 431 005 A2 discloses a universal electric hand tool, which is provided with an electric motor, the electric motor having a rotor shaft arranged transversely to the striking axis, a rotor laminated core and a motor pinion, the motor pinion driving a striking mechanism via an eccentric gear via a spur gear stage, wherein the rotor laminated core is completely arranged to the striking mechanism gear in diameter relative to the striking axis. Therefore, only the rotor shaft passes through the core area of ​​the striking axis, which, in addition to the mass distribution acting radially opposite to the striking mechanism axis, also means that the electric motor is arranged close to the eccentric and therefore induces less bending moments that cause vibrations. By arranging the eccentric gear with the spur gear stage on the one hand and the drive motor on the other hand relative to the striking mechanism axis relative to each other, vibrations are reduced to a certain extent.

[0005] Since the mass of the drive motor increases disproportionately with increasing power level of the drill hammer or chisel hammer, the above-mentioned vibration-damping effect is correspondingly weakened, which impairs manageability in particular in the case of heavy electric hand tools of the type of interest here.

[0006] The object of the present invention is therefore to further develop a universal drill hammer or chisel hammer in such a way that effective vibration damping can be achieved at all power levels by simple technical means. Summary of the invention

[0007] This object is achieved by a drill hammer or a chisel hammer in combination with its characterizing features according to the preamble of claim 1. The following dependent claims describe advantageous developments of the invention.

[0008] The present invention includes such technical teaching that the radial distance of the drive motor and the radial distance of the eccentric gear of the striking mechanism unit from the striking mechanism axis are dimensioned so that a balanced mass distribution is established relative to the striking mechanism axis. This means that the relative distances of the corresponding components are selected according to their masses so that the overall center of gravity of the striking mechanism unit is located on the striking mechanism axis.

[0009] The advantage of the solution according to the invention is that a balanced mass distribution relative to the striking mechanism axis can be achieved simply by optimizing the radial distance, since the striking mechanism unit is not accelerated in the transverse direction, thereby achieving minimal vibrations.

[0010] According to a first preferred design, the drive motor is arranged completely behind the eccentric unit of the eccentric gear, as viewed along the axis of the striking mechanism. As a result, the deadweight of the drive motor no longer plays a limiting role, since the drive motor can be freely positioned in the lateral direction to produce the desired mass balance associated with the generally light eccentric gear. This is because in this design, the eccentric gear does not prevent the drive motor from being positioned in the lateral direction, and when using this design, vibration reduction can also be achieved with a relatively heavy drive motor.

[0011] According to an alternative design, as observed along the striking mechanism axis, in addition to the motor shaft, the drive motor is arranged next to the eccentric gear in a completely radially offset manner. This design is suitable for a striking mechanism unit that is as short as possible. Since in this case, the range of variation of the radial distance of the drive motor from the striking mechanism axis is very small, this variant is particularly suitable for a relatively light drive motor. However, in this case, the eccentric gear can also have a further impact on the balanced mass distribution. In particular, for the purpose of mass balance, the transmission gear of the eccentric gear can have a relatively heavy design. On the other hand, this design allows a transmission gear with a relatively small gear, because the axis-center distance to be bridged is less than the axis-center distance in the above-mentioned design, which in particular also reduces the overall width of the electric hand tool. This optimal value depends on the design goals and depends on the above-mentioned influencing parameters.

[0012] According to a preferred embodiment of the present invention, when using the above-mentioned first design, the radial distance between the center of gravity of the motor and the axis of the striking mechanism is less than the radial distance between the center of gravity of the eccentric gear and the axis of the striking mechanism. This means that a drive motor that is usually higher in mass than a normal eccentric gear can be used. In this regard, it is not necessary to influence the design of the drive motor or the eccentric gear itself by making certain components particularly light or heavy in order to achieve a desired balanced mass distribution in the entire framework of the striking mechanism unit.

[0013] This does not affect the fact that these components are also designed to be weight-optimized in order to achieve a balanced mass distribution not only through distance control. The drive motor is preferably designed as an electric motor and its mass is essentially determined by the power class. However, the deadweight can be influenced by using a brushless electric motor, which is usually relatively light in the same power class.

[0014] With regard to the eccentric gear, a single-stage transmission gear is preferably used for transmission to a low speed, and is very preferably designed as a spur gear stage. In order to achieve the highest possible transmission ratio, it is sufficient if the motor shaft is designed at the distal end as a toothed pinion preferably having more than ten teeth. The diameter of the corresponding spur gear of the transmission gear depends on the axis-center distance between the motor axis and the main axis of the eccentric gear, and substantially depends on the stroke of the eccentric connecting rod and the motor diameter. However, as already mentioned, this is only applicable when the aforementioned first design of the striking mechanism unit is realized. In order to change the mass of the eccentric gear, the spur gear of the transmission gear can be made of heavy steel material or lightweight plastic material. Since the spur gear is arranged outside in the radial direction, its deadweight has a significant effect on the mass distribution relative to the axis of the striking mechanism.

[0015] Preferably, the striking mechanism unit of the hammer drill or hammer chisel according to the present invention is designed so that in the desired working position maintained by the operator, the drive motor has a ground clearance, i.e., a distance from the ground, smaller than the eccentric gear. Since the drive motor protrudes further from the striking mechanism axis in the radial direction, this lower positioning is more convenient for the operator than the lateral or upper positioning. The entire striking mechanism unit is surrounded by a device housing with a handle and has a tool holder for a chisel or impact drill at the distal end. The entire striking mechanism unit is surrounded by a device housing with a handle and has a tool holder for a chisel or impact drill at the distal end. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Further measures for improving the invention are explained in more detail below together with the description of preferred exemplary embodiments of the invention with reference to the accompanying drawings. In the drawings:

[0017] Figure 1 shows a schematic side view of a striking mechanism unit according to a first design, and

[0018] Figure 2 A schematic side view of a striking mechanism unit according to a second design is shown. DETAILED DESCRIPTION

[0019] according to Figure 1 The striking mechanism unit of the hammer chisel according to the first preferred design is composed of a drive motor 1, which has a shaft transverse to the striking mechanism axis A. S A motor axis A arranged to generate a rotational drive motion M The drive motor 1 is designed as an electric motor and has a pinion tooth system at the distal end of a motor shaft 2 , which meshes with a spur gear 3 of a single-stage transmission gear 4 .

[0020] The single-stage transmission gear 4 is part of an eccentric gear 5 connected downstream of the drive motor 1. In order to generate the linear alternating working movement, the eccentric gear 5 has an eccentric wheel 6, which is connected downstream of the transmission gear 4 and has a connecting rod 7 and an exciter piston 8 arranged on the striking mechanism side. The exciter piston 8 is also part of a striking mechanism 9, which transmits the working movement to a coaxially arranged tool (not shown in further detail).

[0021] In order to reduce the vibration of the striking mechanism unit, the center of gravity S of the driving motor 1 is M Arranged at a distance A from the striking mechanism axis S The radial distance s M and the center of gravity S of the eccentric gear 5 G Arranged at a distance A from the striking mechanism axis S The opposite radial distance s G In this case, the radial distance s of the drive motor 1M and the radial distance s of the eccentric gear 5 G The dimensions are set so that the balanced mass distribution is relative to the striking mechanism axis A S Established.

[0022] In the illustrated design of the striking mechanism unit, as shown along the striking mechanism axis A S Observe that the drive motor 1 is arranged completely behind the eccentric gear 5. Although this means that the electric hand tool of this embodiment has a correspondingly long design, there is a wide variation in the radial distance. In this embodiment, the radial distance s M Less than radial distance s G , so that the drive motor 1 with a relatively high mass can be positioned relative to the eccentric gear 5 in a correspondingly balanced manner.

[0023] according to Figure 2 The alternative design shown, such as along the striking mechanism axis A S Observe that, apart from the motor shaft 2, the drive motor 1 is arranged completely radially offset next to the eccentric gear 5. Therefore, the striking mechanism unit is more compact than the above-mentioned design, but with another distance s G Compared with the larger radial distance s M This can be compensated on the one hand by an electric motor that is as light as possible and on the other hand by a particularly heavy spur gear 3 of the transmission gear 4. Specifically, a more compact design translates into a relatively small axis-center distance s between the motor axis and the spur gear axis. A .

[0024] The invention is not limited to the two preferred exemplary embodiments described above. On the contrary, modifications thereof are also conceivable, which modifications are covered by the protection scope of the following claims. For example, it is also conceivable to combine a striking mechanism with a rotary drive device around the axis of the striking mechanism in order to provide a hammer drill with the solution according to the invention.

[0025] List of Reference Numerals

[0026] 1 Drive motor

[0027] 2 Motor shaft

[0028] 3 Spur gears

[0029] 4 Transmission gear

[0030] 5 Eccentric gear

[0031] 6 Eccentric wheel

[0032] 7 Connecting rod

[0033] 8 Actuator piston

[0034] 9. Attack agencies

[0035] A S Strike the axis of the organization

[0036] A M Motor shaft

[0037] S M Center of gravity of the motor

[0038] S G Center of gravity of eccentric gear

[0039] s M Radial distance of motor

[0040] s G Radial distance of eccentric gear

[0041] s A Axis-center distance

Claims

1. A hammer drill or hammer chisel, the hammer drill or hammer chisel having a striking mechanism unit, the striking mechanism unit comprising a drive motor (1), the drive motor having a motor axis (A M ), the motor axis is transverse to the striking mechanism axis (A S ) is arranged to generate a rotational drive motion, and a subsequent eccentric gear (5) converts the rotational drive motion into a rotational motion along the axis (A) of the striking mechanism. S ) of the drive motor (1), said motion being transferable to coaxially adjacent tools via a striking mechanism (9) connected to said eccentric gear, wherein the center of gravity (S M ) is arranged at a distance from the striking mechanism axis (A S ) radial distance (s M ) and the center of gravity (S G ) is arranged at a distance from the striking mechanism axis (A S )'s opposite radial distance (s G ) to reduce vibration, It is characterized in that The radial distance (s) of the drive motor (1) M ) and the radial distance (s) of the eccentric gear (5) G ) is dimensioned so that the mass distribution of the balance is relative to the striking mechanism axis (A S ) was established.

2. A hammer drill or hammer chisel according to claim 1, It is characterized in that Along the striking mechanism axis (A S ) observes that the drive motor (1) is arranged completely behind the eccentric gear (5).

3. A hammer drill or hammer chisel according to claim 1 or 2, It is characterized in that As along the striking mechanism axis (A S ) it can be seen that, apart from the motor shaft (2), the drive motor (1) is arranged completely radially offset next to the eccentric gear (5).

4. A hammer drill or hammer chisel according to any one of the preceding claims, It is characterized in that The drive motor (1) has a higher mass than the eccentric gear (5), so that the radial distance (s M ) is smaller than the radial distance (s G ).

5. A hammer drill or hammer chisel according to any one of the preceding claims, It is characterized in that The eccentric gear (5) comprises a single-stage transmission gear (4) for low-speed transmission, and the transmission gear is designed as a spur gear stage.

6. A hammer drill or hammer chisel according to any one of the preceding claims, It is characterized in that In view of the variation of the deadweight of the eccentric gear (5), the spur gear (3) of the spur gear stage is made of steel or plastic material.

7. A hammer drill or hammer chisel according to any one of the preceding claims, It is characterized in that The eccentric gear (5) for generating the linear alternating working motion comprises an eccentric wheel (6) which is connected downstream of the transmission gear (4) and has a connecting rod (7) and an exciter piston (8) arranged on the striking mechanism side.

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

9. A hammer drill or hammer chisel according to any one of the preceding claims, It is characterized in that The motor shaft (2) is formed at the distal end as a toothed pinion having more than ten teeth.

10. A drill hammer or a chisel hammer according to any one of the preceding claims, It is characterized in that The striking mechanism unit is designed so that in a desired working position held by an operator, the drive motor (1) has a smaller ground clearance than the eccentric gear (5).

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