GB2539325A

GB2539325A - Hand held machine tool

Info

Publication number: GB2539325A
Application number: GB1609328.8A
Authority: GB
Inventors: Braun Willy
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2015-06-01
Filing date: 2016-05-26
Publication date: 2016-12-14
Anticipated expiration: 2036-05-26
Also published as: DE102015210070A1; GB2539325B; GB201609328D0

Abstract

The tool (10, Figure 1) such as a drill and/or chisel hammer includes a fixed bearing device 50 which is arranged in a plastic motor housing 24. At least one antifriction bearing 54 is provided for rotatably supporting an armature shaft 46. The bearing has at least one outer ring 56, and an inner ring 58 is connected in a fixed manner to the armature shaft. A first part 64 of the at least one antifriction bearing is pressed in the axial direction 52 of the armature shaft into a bearing seat 62 provided in the motor housing. A second part 68 of the at least one antifriction bearing is fixed radially and/or axially by means of a rubber bearing bush 66 made from an elastomeric plastic material.

Description

Hand-held machine tool

Prior art

Hand-held machine tools having a fixed bearing device for rotatably supporting an armature shaft are known.

Disclosure of the invention

The invention starts with a hand-held machine tool, in particular a drill and/or chisel hammer, having a fixed bearing device which is arranged in a plastic motor housing and comprises at least one antifriction bearing which is provided for rotatably supporting an armature shaft and, to this end, comprises at least an outer ring and an inner ring, wherein the inner ring is connected in fixed manner to the armature shaft.

It is proposed that a first part of the at least one antifriction bearing be pressed in the axial direction of the armature shaft into a bearing seat provided in the motor housing and a second part of the at least one antifriction bearing be fixed radially and/or axially by means of a rubber bearing bush made from an elastomeric plastic material.

The term hand-held machine tool is intended to refer to all hand-held machine tools which appear useful to a person skilled in the art, in particular impact drilling machines, demolition hammers, drill hammers, impact hammers, impact screwdrivers and/or preferably drill hammers and/or chisel hammers.

The hand-held machine tool has a fixed bearing device which is arranged in a plastic motor housing and is provided to rotatably support an armature shaft of the motor. In an exemplary embodiment of the hand-held machine tool, the armature shaft serves to drive a functional component of the hand-held machine tool, for example a connecting rod which in turn drives a striking mechanism or a rotating tool holder of the hand-held machine tool.

The term fixed bearing device of the hand-held machine tool is intended to refer in particular to a radial bearing device or a pivot bearing device, which is provided to support an armature shaft of the motor such that it is able to rotate or pivot about its own longitudinal axis, which armature shaft is arranged in particular axially to the fixed bearing device. The fixed bearing device is moreover provided to counteract a translatory movement of the armature shaft in the direction of its axial extent, preferably to prevent a translatory movement of the armature shaft in the direction of its axial extent.

The fixed bearing device therefore enables a rotation of the armature shaft about its own longitudinal axis, but prevents a translatory movability of the armature shaft in the direction of its longitudinal axis. All further degrees of freedom, in particular a translatory movement of the armature shaft in the radial direction of a circular cross-section of the armature shaft, for example, are furthermore preferably greatly restricted, preferably prevented. To realise this support of the armature shaft, the fixed bearing device has at least one antifriction bearing.

At this point, it should be noted that the expression "axially" or "in the axial direction" means in particular "in the direction of the axial extent of the armature shaft". In contrast, "radially" or "in the radial direction" refers to a radial direction which is perpendicular to the axial direction.

In the case of the at least one antifriction bearing, rolling elements rolling between an inner ring and an outer ring reduce a frictional resistance upon a relative movement of the outer ring and the inner ring. The at least one antifriction bearing on the armature shaft here is implemented in such a way that the inner ring of the radial antifriction bearing is connected in fixed manner to the armature shaft or is provided to be connected in fixed manner to the armature shaft, in particular also to be connectable in fixed manner to the armature shaft. "In fixed manner" means in particular "in rotationally fixed manner" and "non-displaceably" in the axial direction. In this connection, "in rotationally fixed manner" means that the inner ring is not supported such that it can be displaced or slide in the direction of the circumference of the inner ring with respect to the armature shaft, but is connected to rotate with the rotational movement of the armature shaft. In this connection, "non-displaceably" means that the inner ring is not supported such that it can be displaced or slide with respect to the armature shaft in the direction of its axial extent. In a preferred embodiment of the fixed bearing device, a rotationally fixed and non-displaceable connection can be realised for example by screwing, adhesion, welding or by any other connection technique which appears expedient to a person skilled in the art and which enables a rotationally fixed, non-displaceable, preferably material-fitting, force-fitting and/or form-fitting connection of the armature shaft and antifriction bearing, in particular the armature shaft and inner ring of the antifriction bearing.

The outer ring of the antifriction bearing preferably serves for guiding and/or aligning the at least one antifriction bearing with respect to a component surrounding the at least one antifriction bearing, in particular with respect to a motor housing of the hand-held machine tool, preferably with respect to a bearing seat provided in the motor housing of the hand-held machine tool. In this way, the outer ring of the at least one antifriction bearing serves for guiding and aligning the armature shaft which is rotatably supported by means of the at least one antifriction bearing. Furthermore, in an advantageous embodiment, the outer ring of the at least one antifriction bearing is provided to enable the at least one antifriction bearing to be fixed in or on a component surrounding the at least one antifriction bearing, in particular in or on the motor housing of the hand-held machine tool, preferably in or on the bearing seat provided in the motor housing. It is therefore possible to realise a free rotation of the armature shaft with respect to the motor housing, preferably with respect to the bearing seat of the motor housing.

The at least one antifriction bearing is therefore provided to enable the rotation of the armature shaft in the handheld machine tool, to furthermore advantageously reduce a frictional resistance during the rotation of the armature shaft, and to enable an attachment of the armature shaft in or to a further component of the hand-held machine tool, in particular in or to the motor housing of the hand-held machine tool.

In a preferred embodiment, the at least one antifriction bearing is realised as a radial ball bearing or a radial roller bearing. Using radial ball bearings or roller bearings advantageously enables the realisation of a particularly smooth, in particular virtually frictionless rotational movement of the armature shaft about its own longitudinal axis.

The hand-held machine tool has a motor housing made from a plastic material, which is provided to surround a motor of the hand-held machine tool and to protect it from external influences, for example from the penetration of dust or moisture or the like.

According to the invention, a first part of the at least one antifriction bearing is pressed in the axial direction of the armature shaft into the bearing seat provided in the motor housing and a second part of the at least one antifriction bearing is fixed radially and/or axially by means of a rubber bearing bush made from an elastomeric plastic material.

The bearing seat, in particular the bearing seat of the fixed bearing device, is provided to receive the at least one antifriction bearing and, in particular, to surround it in the direction of the circumference of its outer ring. The bearing seat is integrated in the plastic motor housing of the hand-held machine tool, preferably in the housing shell of the motor housing.

A first part of the at least one antifriction bearing is pressed into the bearing seat in the axial direction of the armature shaft, in particular pressed into full contact with interference fit, and therefore fixed in the bearing seat and advantageously in the motor housing. In particular, the at least one antifriction bearing is supported and arranged in the bearing seat with a "press fit" or "force fit". The bearing seat therefore serves to attach and fix the at least one antifriction bearing, in particular its outer ring, in the motor housing. The bearing seat forms the connection between the at least one antifriction bearing and the motor housing of the hand-held machine tool and thus fastens the armature shaft, which is supported in the at least one antifriction bearing, in the motor housing of the hand-held machine tool. The bearing seat of the fixed bearing device further serves for guiding the at least one antifriction bearing in the radial direction and preferably also in the axial direction. The use of the bearing seat, the at least one antifriction bearing and the armature shaft supported in the at least one antifriction bearing enables a stable arrangement and fixation of the armature shaft in the motor housing of the hand-held machine tool to be realised whilst at the same time enabling an unrestricted rotation of the armature shaft in relation to the motor housing.

Radial forces, which are transmitted from the armature shaft to the bearing seat by way of the at least one antifriction bearing, are advantageously absorbed by the bearing seat and/or transferred to the motor housing so that a movement of the armature shaft in a direction corresponding to the effective direction of the force, in particular a radial direction, is prevented.

By pressing the at least one antifriction bearing into the bearing seat in the axial direction, it is possible to position the at least one antifriction bearing in particularly simple manner and therefore facilitate the ease of assembly of the fixed bearing device. In an advantageous embodiment of the hand-held machine tool, the fixed bearing device including the armature shaft can be introduced into the motor housing of the hand-held machine tool in the axial direction in particularly simple and economically favourable manner.

A second part of the at least one antifriction bearing is fixed radially and/or axially by means of a rubber bearing bush made from an elastomeric plastic material. The rubber bearing bush is preferably made from an elastomeric plastic material and is therefore a stable component which is still elastically deformable under a force effect. The term elastomeric plastic material preferably refers to vulcanisates of natural rubber and/or silicone rubber. It is therefore advantageously possible to realise a compact, cost-effective rubber bearing bush which can be manufactured simply and economically. A different plastic material which appears expedient to a person skilled in the art can also alternatively be used for manufacturing the rubber bearing bush so long as the plastic material has the necessary properties in terms of dimensional stability and elastic deformability.

According to the invention, the rubber bearing bush serves to fix the at least one antifriction bearing in the radial and/or axial direction, preferably to fix the at least one antifriction bearing in the bearing seat in the radial and/or axial direction. Therefore, in addition to the fixation of the at least one antifriction bearing by pressing it into the bearing seat, a fixation in the radial and/or axial direction is realised by using the rubber bearing bush.

It is thereby particularly advantageously possible to overcome disadvantages known from the prior art. By means of the fixed bearing device according to the invention, it is possible to overcome disadvantages which arise when a fixed bearing device for the armature shaft is realised merely by implementing a press fit of the at least one antifriction bearing in the bearing seat -i.e. without using a rubber bearing bush. In particular, tolerances caused by manufacture, for example precision deficits in the injection-moulding manufacture of the plastic motor housing and therefore also precision deficits in the bearing seat, can be at least partially countered or compensated by using the rubber bearing bush. A more precise guidance of the at least one antifriction bearing and therefore the armature shaft can be advantageously achieved. It is likewise possible to at least partially counter or compensate material-related expansions or contractions, in particular expansions or contractions of the bearing seat, by using the rubber bearing bush. Such material-related expansions or contractions can be induced for example through temperature fluctuations and/or mechanical deformations of the fixed bearing device. By using the rubber bearing bush according to the invention, it is readily possible for the at least one antifriction bearing of the fixed bearing device to be arranged, aligned, guided and preferably fixed in the radial and/or axial direction in the bearing seat in particularly precise and stable manner, irrespective of manufacturing tolerances, temperature-induced size changes or the like.

Furthermore, the fixed bearing device according to the invention can be used to overcome disadvantages which arise when a fixed bearing device of the armature shaft is only realised using a rubber component for fixing the at least one antifriction bearing in the motor housing. It is therefore known that rubber components of this type still have a low flexibility, even in the installed and tensioned state, which means that the bearing is able to execute 5 undesired movements within the motor housing during operation of the hand-held machine tool which, amongst other things, can have negative consequences on the useful life of the motor, gearings, bearing points and the like and therefore also on the useful life of the hand-held 10 machine tool.

In contrast to this, in the case of the proposed fixed bearing device, the first part of the at least one antifriction bearing has a press fit in the bearing seat, whilst the second part of the at least one antifriction bearing is fixed radially and axially by means of the rubber bearing bush. The at least one antifriction bearing is therefore fixed in the bearing seat both with press fit -i.e. with a particularly precise guidance in the bearing seat -as well as elastically by means of the rubber bearing bush -and therefore in a manner which is independent of tolerances or compensates tolerances. It can therefore be ensured that the fixed bearing is guided and fixed in the bearing seat of the motor vehicle in a manner which continues to remain precise and stable, in particular unyielding. Dimensional changes as a result of manufacturing tolerances and/or temperature fluctuations are advantageously compensated by the rubber bearing bush. The tensioning of the bearing by the rubber bearing bush is preferably so strong that the press fit of the at least one antifriction bearing in the bearing seat of the motor housing is maintained over the useful life of the hand-held machine tool. It is advantageously possible to permanently prevent a deflection and/or wobbling of the fixed bearing device in the bearing seat.

The direct, precisely fitting radial support of the at least one antifriction bearing by means of the bearing seat moreover makes it possible to dispense with further components, in particular components which are relatively complex and affected by tolerances, to realise the precise radial guidance and/or alignment of the at least one antifriction bearing. A particularly simple, economical and at the same time particularly precise guidance, alignment and fixation of the at least one antifriction bearing in the bearing seat, in particular in the motor housing, is therefore furthermore possible without the use of further components which are affected by tolerances.

In addition to the at least one antifriction bearing, it is furthermore possible to provide further antifriction bearings for more stable, in particular more tilt-resistant, support of the armature shaft. These further antifriction bearings, in particular a second antifriction bearing, are preferably at least non-rotatably connected to the armature shaft. In particular, further antifriction bearings can be realised analogously in the form of a fixed bearing device and/or in the form of a floating bearing device for rotatably supporting the armature shaft.

The invention therefore furthermore relates to a hand-held machine tool, in particular a drill and/or chisel hammer, having a double bearing device for rotatably supporting an armature shaft, comprising at least one fixed bearing device according to the invention and a floating bearing device.

The double bearing device according to the invention can preferably be used for supporting armature shafts in electric tools. In an exemplary embodiment of a double bearing device here, a fixed bearing device according to the invention is combined with a floating bearing device. The fixed bearing device serves here for locking the armature shaft on one side in the axial direction, whilst the floating bearing device permits the length of the armature shaft, which is locked on one side by the fixed bearing device, to change freely as a result of a sliding fit. It is thus advantageously possible to realise a support of the armature shaft in the double bearing device which does not permit an axial movement of the armature shaft relative to the double bearing device as a whole, for example as a result of an alternating load upon a rotation of the armature shaft, in particular during operation of the gear device. However, a one-sided movement of the armature shaft in the floating bearing device of the double bearing device, in particular as a result of a thermal expansion of the armature shaft, is possible.

Using at least one fixed bearing device according to the invention and a floating bearing device, it is thus possible to realise a double bearing device for rotatably supporting an armature shaft for hand-held machine tools, which is particularly favourable in terms of cost and can be easily assembled.

In a preferred embodiment of the hand-held machine tool, the rubber bearing bush is elastically pre-tensioned radially and/or axially by means of a counter-mounting as a result of an elastic deformation of the rubber bearing bush, in particular a squeezing of the rubber bearing bush.

The term counter-mounting is used to refer to a device which is provided to elastically pre-tension the rubber bearing bush in that it produces an external force acting on the rubber bearing bush. A counter-mounting can advantageously be realised as a component which compresses, tensions, presses, squeezes, shears or twists the rubber bearing bush, or exerts some other force on the rubber bearing bush as appears expedient to the person skilled in the art.

The rubber bearing bush is preferably made from an elastomeric plastic material and is therefore a dimensionally stable, but still elastically deformable, component. In particular, the rubber bearing bush can deform elastically under the effect of an external force, for example in the event of a tensile and/or pressure load. The elastomeric plastic material advantageously counteracts a mechanical effect, in particular a deformation, compression, squeezing, shearing, torsion or the like. In this case, as a result of the external force effect, the rubber bearing bush exerts an elastic expansion force directed against the external force effect. This elastic expansion force advantageously acts on those components of the fixed bearing device which act on the rubber bearing bush to produce a compressing, squeezing, shearing or twisting effect on the rubber bearing bush. The surface of the rubber bearing bush can therefore be used as an elastic stop and/or as a contact point and/or supporting point for components adjoining the rubber bearing bush. The rubber bearing bush advantageously exerts an elastic expansion force on components which adjoin the rubber bearing bush, in particular components which are pressed against the rubber bearing bush.

In a preferred embodiment of the hand-held machine tool, the rubber bearing bush is elastically pre-tensioned radially and/or axially by means of the counter-mounting, and thereby exerts an expansion force in the radial and/or axial direction on components adjoining the rubber bearing bush, preferably the at least one antifriction bearing.

In a preferred embodiment of the hand-held machine tool, the second part of the at least one antifriction bearing is fixed radially and/or axially in the bearing seat by means of the rubber bearing bush as a result of an elastic, in particular homogeneously acting, expansion force of the rubber bearing bush.

In powerful hand-held machine tools, it is not sufficient to guide, stabilise and support the at least one antifriction bearing, and therefore the armature shaft, merely in the bearing seat of the motor housing, which is realised from plastic material. The motor, the armature shaft and the at least one antifriction bearing heat up significantly as a result of the high power input of the motor, which means that the plastic material of the motor housing -and therefore also the bearing seat -are subject to thermal expansion. As a result of the expansion, it is not possible to guide the at least one antifriction bearing, and therefore the armature shaft, in precise and stable manner, and the armature shaft is at risk of deflection and/or wobbling. This effect is substantially increased in the case of percussive hand-held machine tools, for example in the case of drill hammers and chisel hammers, owing to a high mechanical vibrational load.

To still ensure that the at least one antifriction bearing is fixed permanently, the rubber bearing bush according to the invention is provided for fixing the at least one antifriction bearing in the bearing seat in the radial and/or axial direction. In particular, the rubber bearing bush serves to fix the outer ring of the at least one antifriction bearing in the bearing seat. By fixing the outer ring of the at least one antifriction bearing, in particular by fixing the outer ring of the at least one antifriction bearing relative to the bearing seat, in addition to a non-rotatable arrangement of the outer ring of the at least one antifriction bearing in the bearing seat, it is also possible to realise an arrangement of the outer ring of the at least one antifriction bearing in the bearing seat which is non-displaceable in the radial and/or axial direction and therefore to realise a fixation of the outer ring of the at least one antifriction bearing in the bearing seat.

In one embodiment, the expansion force of the rubber bearing bush acts homogeneously in the radial direction on the at least one antifriction bearing, in particular on its outer ring. By using the rubber bearing bush, it is therefore advantageously possible to realise a permanent radial fixation, which preferably acts on the outer ring over the entire length of the circumference of the outer ring of the at least one antifriction bearing. As a result of the homogeneously acting expansion force of the rubber bearing bush, the at least one antifriction bearing is preferably arranged and fixed in the bearing seat in mechanically stable manner, in particular such that it is resistant to torsion and/or bending in the radial direction. It is thus possible to achieve a particularly stable and non-rotatable interconnection of the outer ring of the at least one antifriction bearing and the bearing seat, in which the outer ring of the at least one antifriction bearing cannot rotate and displace relative to the bearing seat. Moreover, with the high torsional and/or bending rigidity of the at least one antifriction bearing, it is advantageously possible to realise a torsion-and/or bending-resistant fixed bearing devices. Forces, in particular forces acting in the radial direction, which are transmitted from the armature shaft to the at least one antifriction bearing -and therefore to the fixed bearing device -can therefore be advantageously taken up and absorbed. The rubber bearing bush therefore serves to fix the armature shaft, which is supported in rotatable or pivotable manner by means of the at least one antifriction bearing, in stable manner in the radial direction without restricting the pivotal movement or rotation of the armature shaft. The stability of the fixed bearing device also has an advantageous effect on the armature shaft as a whole and therefore on the hand-held machine tool as a whole and therefore has a decisive influence on the quality and stability thereof.

In an alternative or additional embodiment, the rubber bearing bush serves for axially tensioning or fixing the at least one antifriction bearing in the bearing seat. As a result of pressing the at least one antifriction bearing into the bearing seat of the fixed bearing device, a displaceability of the at least one antifriction bearing in the axial direction in the bearing seat is not envisaged in principle, although it is fundamentally possible, for example as a result of continuous vibrations of the hand-held machine tool. The rubber bearing bush forms a fixing element of the fixed bearing device, which is provided to prevent an axial movability of the at least one antifriction bearing of the fixed bearing device and therefore to fix the at least one antifriction bearing in the bearing seat. In a preferred embodiment of the fixed bearing device according to the invention, an elastically homogeneous expansion force which is exerted on the at least one antifriction bearing by the rubber bearing bush results in a tensioning of the at least one antifriction bearing being realised in the axial direction. In particular, a tensioning force which is exerted as a result of the elastic expansion force of the ring therefore acts on the at least one antifriction bearing in the axial 10 direction.

In a preferred embodiment of the hand-held machine tool, the rubber bearing bush is incorporated at least partially between the at least one antifriction bearing and the 15 bearing seat in the motor housing.

Incorporating the rubber bearing bush at least partially between the at least one antifriction bearing and the bearing seat in the motor housing enables a particularly compact and therefore space-saving arrangement of the rubber bearing bush to be realised. It is therefore furthermore possible to increase the supporting surface of the rubber bearing bush on the at least one antifriction bearing, in particular its outer ring. A more uniform and stable fixation of the at least one antifriction bearing, both in the radial and in the axial direction, can be achieved and consequently reduces the risk of a deflection and/or wobbling of the at least one antifriction bearing in the bearing seat. The risk of a deflection and/or wobbling of the armature shaft which is rotatably supported by the fixed bearing device is therefore also advantageously reduced.

The at least partial incorporation of the rubber bearing bush between the at least one antifriction bearing and the bearing seat in the motor housing moreover enables a particularly uniform, in particular homogeneous distribution of the expansion force exerted by the rubber bearing bush. A division of the expansion force into an axial and a radial component can advantageously be achieved and results in the at least one antifriction bearing being fixed more effectively.

In a preferred embodiment of the hand-held machine tool, the rubber bearing bush abuts against the second part of the at least one antifriction bearing in the radial and/or axial direction.

It is thus possible to realise a particularly uniform expansion force of the rubber bearing bush, in particular an expansion force acting homogeneously in the radial and/or axial direction. A continuous, particularly long-lasting and stable radial and or axial fixation can be realised, which preferably acts in the radial and/or axial direction on the outer ring of the at least one antifriction bearing over the entire length of the circumference of the outer ring. A division of the expansion force into an axial and a radial component can be advantageously achieved and results in a more effective fixation of the at least one antifriction bearing so that at least one antifriction bearing is fixed in mechanically stable manner by the homogeneously acting radial and/or axial expansion force of the rubber bearing bush.

In a preferred embodiment of the hand-held machine tool, the first and the second part of the at least one antifriction bearing each form 50% of the axial extent of the at least one antifriction bearing.

A particularly stable fixation of the at least one antifriction bearing in the bearing seat can therefore be achieved. In relation to its axial extent, half of the at least one antifriction bearing thus serves for the mechanically stable guidance of the at least one antifriction bearing in the bearing seat and is fixed in the bearing seat with press fit. This part serves for the particularly precise and preferably stable and unyielding guidance of the at least one antifriction bearing in the bearing seat, in particular for taking up and absorbing forces which are transmitted from the armature shaft to the at least one antifriction bearing. The second half of the at least one antifriction bearing in relation to its extent in the axial direction serves for elastically fixing and pressing the at least one antifriction bearing in the radial and/or axial direction by means of the rubber bearing bush. This part effects the pressing, fixation and guidance of the at least one antifriction bearing in the bearing seat in a manner which is independent of tolerances or compensates tolerances and therefore brings about a compensation of dimensional changes due to manufacturing tolerances and/or temperature fluctuations.

The division into equal components enables a particularly stable and therefore continuously acting distribution of forces to be achieved. However, it should be noted that deviations from this equal distribution can also be applied. The preferred ratios here depend in particular on the precise shaping of the bearing seat, the rubber bearing bush and the capacity of the motor.

In a preferred embodiment of the hand-held machine tool, the rubber bearing bush has a rotationally symmetrical form.

The rotationally symmetrical construction of the rubber bearing bush enables the assembly of the rubber bearing bush in the fixed bearing device to be simplified and an incorrect arrangement, in particular a twisted arrangement, of the rubber bearing bush to be avoided. It is thus possible to eliminate a source of error when assembling the rubber bearing bush of the fixed bearing device. It is furthermore possible to achieve a radial and/or axial expansion force of the rubber bearing bush, which acts particularly homogenously on the at least one antifriction bearing.

Drawings The invention is explained in more detail in the description below, with reference to exemplary embodiments illustrated in the drawings. The drawings, the description and the claims contain numerous features in combination. The person skilled in the art will also expediently examine individual features and combine them into useful further combinations. Similar reference numerals in the figures denote similar elements.

The drawings show: Figure 1 a schematic side view of a hand-held machine tool in the form of a drill hammer Figure 2 a schematic sectional illustration of the handheld machine tool according to Figure 1 Figure 3 an enlarged schematic sectional illustration of an inventive fixed bearing device of the handheld machine tool Figure 1 shows a hand-held machine tool 10, which is constructed for example as a drill and/or chisel hammer 10'. It should be pointed out that the embodiments should not be seen as being restricted to a drill hammer and/or chisel hammer 10'. Rather, the technical teaching forming the basis of the embodiments can, in principle, also be transferred to any other hand-held machine tools 10 which appear expedient to a person skilled in the art, in particular, for example, impact drilling machines, demolition hammers, impact screwdrivers or the like.

The drill and/or chisel hammer 10' has a machine housing 12 which encloses an interior space 14 of the drill hammer 10' in which at least one drive mechanism 16 is arranged. The hand-held machine tool 10 furthermore has a main handle 18, an additional handle 20, a tool holder 22, in particular a chuck, and a motor housing 24 for receiving a motor (not illustrated in more detail), in particular an electric motor. The main handle 18 is connected to the machine housing 12 and the motor housing 24 on a side of the machine housing 12 which is remote from the tool holder 22. The additional handle 20 is connected to the machine housing 12 on a side of the drill hammer 10' which faces the tool holder 22. Both handles serve for stable and safe handling and guidance of the drill hammer 10' during operation. The tool holder 22 serves to receive a drilling and/or a chiselling tool.

The hand-held machine tool 10, in particular the drill and/or chisel hammer 10' has a mains connection 26 for its energy supply. In an alternative or additional embodiment of the hand-held machine tool 10, it is also possible to provide for mains-independent operation of the hand-held machine tool 10 by means of a battery.

Figure 2 shows a detail of the drill and/or chisel hammer 10' in a schematic section through the machine housing 12 and the motor housing 24. Both housing components have a housing shell 28. The drive mechanics 16 are arranged in the interior space 14 of the machine housing 12. The interior space 14 has a lubricant so that all-round permanent lubrication of the mechanical components, in particular the drive mechanics 16, is ensured in the interior space 14.

The drive mechanics 16 have at least one striking mechanism as well as a first gear device 32 and a second gear device 34 for a drilling and a hammer operation of the drill and/or chisel hammer 10'. The striking mechanism 30 of the drill and/or chisel hammer 10' is advantageously constructed as a hammer striking mechanism. The first gear device 32 is constructed as a gear device for driving the striking mechanism 30. The striking mechanism 30 furthermore has a piston 36, a hammer tube 38 and a striker (not illustrated in more detail) as well as a rivet set (not illustrated in more detail). The mode of operation of a striking mechanism 30 of this type is known to the person skilled in the art. The piston 36 is mechanically movably connected to the gear device 32, in particular to a cam gear 42 of the gear device 32.

In conjunction with the striking mechanism 30 of the handheld machine tool 10, in particular the hammer striking mechanism, the gear device 32 is provided to realise a drive of the connecting rod 40 which in turn drives the striking mechanism 30 of the hand-held machine tool 10. In this way, a drill bit (not illustrated in more detail) moves during operation of the drill and/or chisel hammer 10' at least in the direction of its axial extent 44, during which a striking energy generated by means of the striking mechanism 30 is transmitted by way of the drill bit to a material to be machined. A rotational movement of the armature shaft 46 of the motor is converted by means of the gear device 32 here into a stroke movement of the piston 36, striker and hammer pin in an axial direction 44 of the hammer tube 38. The striker, which is moved periodically forwards here, strikes the hammer pin and thereby transfers its kinetic energy, during which the pulse of the striker is transmitted from the hammer pin to a drill bit or chisel inserted into the tool holder 22.

The second gear device 34 drives the hammer tube 38 in preferably rotational manner in order to rotate the drill bit inserted in the tool holder 22 during operation of the drill and/or chisel hammer 10'. The rotational movement of the hammer tube 38 can be activated and/or adjusted and/or deactivated in a manner which appears expedient to the person skilled in the art by means of a switch mechanism. In particular, the second gear device is coupled to the armature shaft 46 by way of a coupling device (not illustrated in more detail).

Figure 3 shows a region marked in Figure 2 as a section through the drill and/or chisel hammer 10', in particular its motor housing 24, which illustrates an inventive fixed bearing device 50 of the armature shaft 46 of the motor of the drill hammer and/or chisel hammer 10' in detail.

The armature shaft 46 is supported in the motor by means of 5 the fixed bearing device 50 according to the invention. The fixed bearing device 50 is a radial bearing device or pivot bearing device by means of which the armature shaft 46 arranged axially to the fixed bearing device 50 is supported such that it can rotate or pivot about its own longitudinal axis. The fixed bearing device 50 prevents a translatory movement of the armature shaft 46 in the direction of its axial extent 52.

The fixed bearing device 50 comprises at least one antifriction bearing 54, which is constructed as a radial ball bearing. The at least one antifriction bearing 54 is provided for rotatably supporting the armature shaft 46 arranged axially to the antifriction bearing 54. To this end, the at least one antifriction bearing 54, in particular the radial ball bearing, has at least an outer ring 56 and an inner ring 58, with the inner ring 58 being screwed to the armature shaft 46 in fixed manner, in particular non-rotatably and non-displaceably, by means of a counter nut 60 or lock nut. The at least one antifriction bearing 54, in particular the at least one radial ball bearing, is therefore provided to enable the rotation of the armature shaft 46 and furthermore to advantageously reduce a frictional resistance during a rotation of the armature shaft 46.

The fixed bearing device 50 for the armature shaft 46 furthermore has a bearing seat 62 into which the at least one antifriction bearing 54, here the at least one radial ball bearing, is pressed in the axial direction 52, in particular pressed into full contact with interference fit. The bearing seat 62 is manufactured in one piece with the motor housing 24 of the hand-held machine tool 10, in particular with form fit and material fit. The bearing seat 62 surrounds the outer ring 56 of the at least one antifriction bearing 54 here in the direction of its circumference. The bearing seat 62 of the fixed bearing device 50 provides the guidance of the outer ring 56 of the at least one antifriction bearing 54 in the radial direction. The bearing seat furthermore connects the at least one antifriction bearing 54 to the motor housing 24. The armature shaft 46 is therefore arranged and fixed in the motor housing 24 using the bearing seat 62, with a free rotation of the armature shaft 46 relative to the motor housing 24 of the hand-held machine tool 10 being possible in unrestricted manner.

The motor housing 24 constitutes that part of the housing shell 28 which is provided to receive the motor of the hand-held machine tool 10. In the embodiment shown, the motor housing 24 is constructed as a single-part plastic die-cast motor housing in which the bearing seat 62 is integrated.

The at least one antifriction bearing 54 of the fixed bearing device 50 is pressed into the bearing seat 62 arranged in the motor housing 24 by means of a first part 64, as seen in relation to its extent in the axial direction 52, in particular pressed into full contact with interference fit. The first part 64 of the at least one antifriction bearing 54 corresponds here to half of the at least one antifriction bearing 54, in particular half of the depth of the component, as seen in relation to its extent in the axial direction 52. The at least one antifriction bearing 54 and therefore the fixed bearing device 50 are therefore supported and guided both radially and axially in the plastic motor housing 24 in very precise manner and directly without additional components, particularly components which are affected by tolerances. The at least one antifriction bearing 54 and therefore the fixed bearing device 50 are furthermore guided in the motor housing 24 in stable and tilt-resistant manner and therefore the entire motor is aligned with respect to the motor housing 24, and guided in the motor housing 24, in stable and tilt-resistant manner.

Radial forces, which are transmitted from the armature shaft 46 to the bearing seat 62 by way of the at least one antifriction bearing 54, are transferred from the bearing seat 62 to the motor housing 24 and absorbed there. A movement of the armature shaft 46 in a radial direction corresponding to the effective direction of the force is therefore impossible.

In the case of powerful hand-held machine tools 10, it is not sufficient to guide and stabilise or support the at least one antifriction bearing 54, and therefore the armature shaft 46, merely in the bearing seat 62 in the motor housing 24, which is realised from plastic material. On the one hand, the motor, the armature shaft 46 and the at least one antifriction bearing 54 heat up significantly as a result of the high power input of the motor, which means that the plastic material of the motor housing 24 -and therefore also the bearing seat 62 -undergo thermal deformation, in particular expansion. As a result of the deformation, it is not possible to guide the at least one antifriction bearing 54, and therefore the armature shaft 46, in precise and stable manner, and the armature shaft 46 is at risk of deflection and/or wobbling. This effect is substantially increased in the case of percussive hand-held machine tools 10, for example in the case of drill and chisel hammers 10', owing to a high vibrational load.

To ensure a permanent fixation of the at least one antifriction bearing 54, an elastically pre-tensioned rubber bearing bush 66 is incorporated for further fixation. The rubber bearing bush 66 is made from elastomeric plastic material and has a rotationally symmetrical form.

The rubber bearing bush 66 is a dimensionally stable, but still elastically deformable, component. In particular, the rubber bearing bush 66 can deform elastically under the effect of an external force, for example under a tensile and/or pressure load, whereby the elastomeric plastic material counteracts a mechanical effect, in particular a deformation, compression, shearing, torsion or the like, and thereby exerts an elastic expansion force directed against the external force effect. In particular, the rubber bearing bush 66 serves as a stop for an adjoining component, in particular a contacting component, on which an elastic expansion force is exerted as a result of an elastic deformation, in particular a squeezing, deformation, compression, shearing and/or torsion, of the rubber bearing bush 66. The rubber bearing bush 66 is incorporated in the motor housing 24 between the at least one antifriction bearing 54 and the bearing seat 62 and surrounds the at least one antifriction bearing 54 both axially and radially on a second part 68 of the at least one antifriction bearing 54, with the second part 68 corresponding to the further half of the at least one antifriction bearing 54. A brush cover 70' screwed to the motor housing 24 acts as a counter-mounting 70 which pretensions the rubber bearing bush 66 elastically in that it compresses and squeezes, and thereby compacts, the rubber bearing bush 66. As a result of the radial and axial elastic pre-tension of the rubber bearing bush 66, this exerts a high expansion force in the radial and axial direction on the at least one antifriction bearing 54.

The rubber bearing bush 66 fixes the at least one antifriction bearing 54, in particular its outer ring 56, in the radial and axial direction in the bearing seat 62. In addition to a non-rotatable arrangement of the outer ring 56 of the at least one antifriction bearing 54 in the bearing seat 62, this also realises an arrangement of the outer ring 56 of the at least one antifriction bearing 54 in the bearing seat 62 which is non-displaceable in the radial and axial direction. The use of the rubber bearing bush 66 enables the at least one antifriction bearing 54 to be fixed permanently in the bearing seat 62. As a result of a homogenously acting expansion force of the rubber bearing bush 66, the at least one antifriction bearing 54 is therefore arranged and fixed in the bearing seat 62 in mechanically stable manner, in particular such that it is resistant to torsion and/or bending in the radial direction. In addition to the press fit, the at least one antifriction bearing 54 is therefore also elastically pre-tensioned and fixed in the radial and axial direction.

The at least one antifriction bearing 54 of the fixed bearing device 50 is fixed permanently in the axial and radial direction as a result of the contact pressure of the rubber bearing bush 66. In this arrangement, the radially and axially acting elastic expansion force effects a radial and axial pre-tensioning of the at least one antifriction bearing 54 in the bearing seat 62 of the motor housing 24, which results in a rotational resistance and a fixation of the outer ring 56 of the at least one antifriction bearing 54 in the bearing seat 62. The at least one antifriction bearing 54 is therefore mechanically stabilised by the contact pressure of the rubber bearing bush 66 and is secured in the motor housing 24 and in the bearing seat 62.

Claims

Claims 1. A hand-held machine tool (10), in particular a drill a fixed bearing plastic motor one antifriction rotatably supporting an armature shaft (46) and, to this end, comprises at least an outer ring (56) and an inner ring (58), wherein the inner ring (58) is connected in fixed manner to the armature shaft (46), characterised in that a first part (64) of the at least one antifriction bearing (54) is pressed in the axial direction of the armature shaft (46) into a bearing seat (62) provided in the motor housing (24) and a second part (68) of the at least one antifriction bearing (54) is fixed radially and/or axially by means of a rubber bearing bush (66) made from an elastomeric plastic material.
2. A hand-held machine tool (10) according to Claim 1, characterised in that the first part (64) and the second part (68) of the at least one antifriction bearing (54) each form 50% of the axial extent of the at least one antifriction bearing (54).
3. A hand-held machine tool (10) according to one of the preceding claims, characterised in that the rubber bearing bush (66) is incorporated at least partly between the at least one antifriction bearing (54) and the bearing seat (62) in the motor housing (24).and/or chisel hammer (10'), having device (50) which is arranged in a housing (24) and comprises at least bearing (54) which is provided for
4. A hand-held machine tool (10) according to one of the preceding claims, characterised in that the rubber bearing bush (66) abuts against the second part (680 of the at least one antifriction bearing (54) in the radial and/or axial direction.
5. A hand-held machine tool (10) according to one of the preceding claims, characterised in that the rubber bearing bush (66) has a rotationally symmetrical form. 10
6. A hand-held machine tool (10) according to one of the preceding claims, characterised in that the rubber bearing bush (66) is elastically pre-tensioned radially and/or axially by means of a counter-mounting (70) as a result an elastic deformation of the rubber bearing bush (66), in particular a squeezing of the rubber bearing bush (66).7 A hand-held machine tool (10) according to one of the preceding claims, characterised in that, by means of the rubber bearing bush (66), the second part (68) of the at least one antifriction bearing (54) is fixed radially and/or axially in the bearing seat (62) owing to an elastic, in particular homogeneously working, expansion force of the rubber bearing bush (66).8. A hand-held machine tool substantially as described herein with reference to, or as shown in, the drawings.