# Patent

## Title
Hand-held power tool

## Abstract

The invention is based on a hand-held power tool, in particular a cordless screwdriver, having a drivable output shaft, a supporting element, and a roller bearing unit that is provided to transmit a supporting force of the output shaft to the supporting element. According to the invention, the output shaft and/or the supporting element constitutes at least one roller element running surface of the roller bearing unit.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
This application is based on German Patent Application 10 2009 001 657.1 filed Mar. 19, 2009.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is based on a hand-held power tool, in particular a cordless screwdriver.
2. Description of the Prior Art
A hand-held power tool, in particular a cordless screwdriver, has already been proposed, which has a drivable output shaft, a supporting element, and a roller bearing unit that is provided to transmit a supporting force of the output shaft to the supporting element.
ADVANTAGES AND SUMMARY OF THE INVENTION
The invention is based on a hand-held power tool, in particular a cordless screwdriver, which has a drivable output shaft, a supporting element, and a roller bearing unit that is provided to transmit a supporting force of the output shaft to the supporting element.
As proposed by the invention, the output shaft and/or the supporting element constitutes at least one roller element running surface of the roller bearing unit. In this context, an “output shaft” should be understood in particular to mean a shaft such as a working spindle that transmits a torque from a motor, in particular an electric motor, indirectly or more precisely stated, via a transmission, to a tool such as a screwdriver bit. A “supporting element” should be understood in particular to mean an element that is provided to absorb bearing forces of the output shaft and/or to transmit them to a housing of the hand-held power tool and/or that in particular represents a component of the housing and/or of a transmission housing of the hand-held power tool. In addition, a “roller bearing unit” should be understood in particular to mean a unit that has at least one roller element in the form of a barrel, a needle, and/or a ball and/or that is situated spatially between the output shaft and the supporting element and/or absorbs the bearing forces of the output shaft and transmits them to the supporting element. In this context, a “roller element running surface” should be understood in particular to be a surface against which the roller elements roll and/or to be part of a roller bearing. The roller element running surface particularly extends around the output shaft in the circumference direction. The expression “the output shaft and/or the supporting element constitutes at least one roller element running surface of the roller bearing unit” should be understood in particular to mean that the roller element running surface is integral with the output shaft and/or the supporting element; “integral with” should be understood in particular here to mean of one piece with and/or composed of a single casting and/or composed of a single component. In addition, “provided” should be understood to mean especially equipped and/or designed. The embodiment according to the invention advantageously makes it possible to implement a reduced overall radial length of the hand-held power tool in the region of the output shaft. Furthermore, the integral embodiment makes it possible to achieve savings in terms of parts, space, and costs in a structurally simple way.
According to another proposal, the output shaft constitutes an inner roller element running surface of the roller bearing unit. This should be understood in particular to mean the embodiment of the roller element running surface as integral with the output spindle; the inner roller element running surface is preferably situated on an outer surface of the output shaft oriented toward the supporting surface and extends along its circumference. The implementation of the inner roller element running surface makes it possible in a particularly effective manner to transmit powerful forces from a tool, which is operatively connected to the output shaft, to a housing of the hand-held power tool. This also achieves a good quality of concentricity for the output shaft.
The roller element running surface advantageously has at least one supporting surface in the axial direction of the output shaft. An “axial direction” is defined here in particular as a direction extending in a main span direction of the output shaft. A “supporting surface” should be understood in particular to mean a surface that confines and/or limits a movement freedom of the roller element rolling against the roller element running surface at least in the axial direction. The supporting surface can be advantageously embodied to provide a good axial guidance of the roller elements along the roller element running surface.
It is also advantageous if, in the axial direction of the output shaft, the roller element running surface has at least one second supporting surface that allows for further improvement of the axial guidance. The two supporting surfaces are preferably situated on two axially opposite sides of the roller element running surface.
In another proposed embodiment of the invention, the roller element running surface is embodied in the form of a segment of a circle. The expression “in the form of a segment of a circle” should be understood in particular here to mean a form that is adapted to at least one outer contour of a roller element of the roller bearing unit and/or that is constituted by an external radius or arc of a segment of a circle; a “segment of a circle” is a part of a circular area that is divided into two unequal segments by a chord. Due to its embodiment in the form of a segment of a circle, the roller element running surface is able to guide the roller element with a particularly small amount of play.
In another proposed embodiment, the roller bearing unit constitutes a ball bearing, making it possible to use a roller bearing unit with particularly material-friendly properties.
It can also be advantageous if the roller bearing unit is situated at an end oriented toward an output end of the output shaft. An “output end of the output shaft” should be understood in particular to mean an end that is oriented toward a tool holder of the output shaft. This arrangement makes it possible to support not only radial but also axial bearing forces, permitting a bearing force of the output shaft to be transmitted to a housing of the hand-held power tool spatially close to a tool holder in a manner that is gentle to the output shaft. A reliable and stable support of the output shaft can be advantageously achieved if the hand-held power tool has at least one additional bearing unit that is provided to support the output shaft.
According to another proposal, the additional bearing unit is situated at an end oriented away from an output end of the output shaft, thus making it possible to achieve a balanced support of the output shaft.
A preferred modification proposes that the at least one additional bearing unit is constituted by a slide bearing or an additional roller bearing unit. An embodiment in the form of a slide bearing makes it possible to implement the additional bearing unit in a way that is inexpensive and also saves on space and parts. By means of an additional roller bearing unit, it is also possible in a structurally simple fashion to support powerful bearing forces, thus also making it possible to achieve an advantageously material-friendly distribution of force.
According to another proposal, the roller bearing unit is partially integral with the additional roller bearing unit. In this context, “integral with” should be understood in particular to mean that the two roller bearing units can only be separated from each other with the loss of function of at least one of the roller bearing units and/or that the roller bearing unit has at least one component that is also a component of the additional roller bearing unit. The integral embodiment makes it possible to embody a support in a way that provides particular savings in terms of parts and costs.
According to another proposed embodiment of the invention, the roller element running surface is let into the output shaft and/or the supporting element by means of a material-removing method. In this context a “material-removing method” should be understood in particular to mean a cutting process and/or a grinding process and/or particularly advantageously, a turning process. In general, it would also be conceivable to use another method that appears suitable for the purpose to the person skilled in the art. By means of the material-removing method, the roller element running surface can be inexpensively let into the output shaft by means of a simple manufacturing process.
According to another proposal, the hand-held power tool has a stop collar for a tool holder and the axial width of this stop collar is greater than 80% of an axial width of the roller bearing unit. In general, an axial width of greater than 100% would also be conceivable. A “stop collar” should be understood in particular here to mean a shape, in particular of the output shaft, which extends in a radial direction toward the supporting element and/or constitutes an axial stop for the tool holder in an assembly procedure, e.g. a screw-mounting, of a tool holder such as a drill chuck. Basically, it would also be conceivable to embody the stop collar as a part that is separate from the output shaft. The wide stop collar makes it possible to implement or ensure a good support of prestressing forces during assembly and when holding the tool holder.
According to another proposal, an outer diameter of the output shaft in a region of the roller element running surface is at least 55% of an outer diameter of the output shaft in a region of a stop collar of a tool holder. In general, an outer diameter of greater than 75% would also be conceivable. This is possible because a space that is occupied by an inner ring of the roller bearing in roller bearing units that are currently the standard can be filled by the working shaft in the embodiment according to the invention. Embodying the output shaft with a large outer diameter permits a particularly stable embodiment of the output shaft. In general, though, it would also be possible to maintain the dimensions of the output shaft in accordance with the currently standard embodiment, which would conversely permit an advantageous reduction of a radial distance of the supporting element or the housing of the hand-held power tool from the output shaft, which immediately yields a smaller and lighter-weight hand-held power tool.
The output shaft is advantageously embodied as a hollow shaft, at least in a subregion in which the roller bearing unit is situated. A “hollow shaft” should be understood in particular here to mean a shaft with a central opening extending in the axial direction. In this case, the subregion preferably extends from the output end of the output shaft toward the region in which the roller element running surface is situated and extends beyond this in the axial direction toward the additional healing unit. Embodying the subregion as a hollow shaft permits the output shaft to be embodied in a structurally simple fashion in the form of a socket for a tool holder such as a drill chuck and/or directly as a tool holder. In connection with the possibility of embodying the output shaft with a broad outer diameter, this yields a particularly rugged socket or tool holder. Basically, however, it would also be conceivable to embody the output shaft in the form of a hollow shaft over its entire axial length.
In another proposed embodiment of the invention, the output shaft is embodied with a constant outer diameter in a subregion that extends from an end of the output shaft situated at an output end to the roller element running surface of the roller bearing unit. An “end of the output shaft situated at an output end” should be understood in particular to mean an end at which a tool can be fastened directly to the output shaft. A “constant outer diameter” should be understood in particular to mean an outer diameter that is embodied as continuous. By means of the embodiment according to the invention, the output shaft can be produced in a manner that saves material and costs and is also structurally simple.
It is also advantageous if the hand-held power tool has a planetary gear that makes it possible to transmit a torque from a motor to the output shaft in a good and variable fashion.



BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of preferred embodiments taken in conjunction with the drawings, in which:
FIG. 1 shows a hand-held power tool according to the invention, embodied in the form of a cordless screwdriver;
FIG. 2 shows a tool holder region of the hand-held power tool from FIG. 1;
FIG. 3 is a detailed depiction of a bearing region of the tool holder region from FIG. 2;
FIG. 4 shows an alternative embodiment of a bearing region in a detailed depiction; and
FIG. 5 shows an alternative tool holder region of a hand-held power tool.



DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a hand-held power tool 10a according to the invention, embodied in the form of a cordless screwdriver 12a. FIG. 2 shows a tool holder region 64a of the hand-held power tool 10a. In this tool holder region 64a, the hand-held power tool 10a has a steel output shaft 14a that can be driven by an electric motor 66a, a supporting element 16a embodied as integral with a transmission housing 68a, and a roller bearing unit 18a, which comprises a roller bearing 30a and is provided to transmit a supporting force of the output shaft 14a to the supporting element 16a. The roller bearing unit 18a is also a part of a bearing arrangement 70a of the output shaft 14a. 
A torque generated by the electric motor 66a is transmitted via a three-stage planetary gear 62a to the output shaft 14a; by means of a gearing 76a, a planet carrier 72a of a third planetary stage 74a of the planetary gear 62a engages with a gearing 78a of the output shaft 14a. The output shaft 14a is embodied in the form of a hollow shaft 60a in a subregion 58a in which the roller bearing unit 18a is situated and which extends from an output end 32a of the output shaft 14a in an axial direction 24a toward the planetary gear 62a. The hollow shaft 60a has an internal thread via which a tool holder 44a, schematically depicted here, in the form of a drill chuck 94a can be fastened by means of a screw, not shown here, to the output shaft 14a, as a result of which the torque in a screwdriving operation of the hand-held power tool 10a is transmitted from the output shaft 14a to a schematically depicted tool 80a in the form of a screwdriver bit fastened in the drill chuck 94a. 
The output shaft 14a extends in the axial direction 24a along the supporting element 16a and is supported by the latter against the transmission housing 68a. For this purpose, the bearing arrangement 70a is equipped with the roller bearing unit 18a, which is situated at an end 34a closer to the output end 32a of the output shaft 14a in order to support axial and radial forces of the output shaft 14a. The hand-held power tool 10a or more precisely stated, the bearing arrangement 70a, also has an additional bearing unit 36a that is provided to support the output shaft 14a and is situated at an end 38a remote from the output end 32a of the output shaft 14a or toward the end closer to the planetary gear 62a. The additional bearing unit 36a is composed of a slide bearing 40a and serves to support radial forces.
In addition, the output shaft 14a constitutes at least one roller element running surface 20a of the roller bearing unit 18a, which surface is embodied in the form of an inner roller element running surface 22a. The roller element running surface 20a is let into the output shaft 14a by means of a material-removing method and in particular by means of a turning process and is consequently integral with the output shaft. In addition, the roller element running surface 20a extends in a circumference direction 82a on an outer surface 84a of the output shaft 14a. The roller element running surface 20a has a first supporting surface 26a on the side closer to the output end 32a in the axial direction 24a of the output shaft 14a (FIG. 3). In addition, a second supporting surface 28a is situated on the end 38a remote from the output end 32a in the axial direction 24a of the output shaft 14a. The supporting surfaces 26a, 28a are thus situated on two axially opposite sides of the roller element running surface 20a and serve to axially fix roller elements 86a in the form of balls as they roll along the roller element running surface 20a. The roller element running surface 20a is embodied in the form of a segment of a circle and is thus adapted to a ball-shaped outer contour 88a of the roller elements 86a. An outer ring 90a of the roller bearing unit 18a, which ring is situated between the roller elements 86a and the supporting element 16a in a radial direction 92a, transmits bearing forces of the output shaft 14a to the supporting element 16a and to the transmission housing 68a. To facilitate an assembly of the ball bearing 30a, the outer ring 90a is embodied in a two-piece fashion and is composed of two half-shells (not shown).
The hand-held power tool 10a or more precisely stated, the output shaft 14a, has a stop collar 42a for the tool holder 44a, in this case for the drill chuck 94a. In the axial direction 24a, the stop collar 42a adjoins the roller bearing unit 18a at the output end 32a or at an end of the tool holder 44a and extends in the radial direction 92a toward the supporting element 16a. It serves as an axial stop for the drill chuck 94a when it is screwed onto an end region 96a of the output shaft 14a situated at the output end 32a in an assembly process or more precisely, a screw-mounting procedure.
As shown in the detailed depiction in FIG. 3, which shows a bearing region 98a of the hand-held power tool 10a, the stop collar 42a has an axial width 46a that corresponds to 80% of an axial width 48a of the roller bearing unit 18a. In addition, in a region 52a in which the roller element running surface 20a is situated, an outer radius 50a of the output shaft 14a corresponds to 55% of an outer radius 54a of the output shaft 14a in a region 56a in which the stop collar 42a is situated (also see FIG. 2).
FIG. 4 shows an alternative exemplary embodiment of the roller bearing unit 18a and FIG. 5 shows an alternative exemplary embodiment of the tool holder region 64a. Parts, features, and functions that remain essentially the same have basically been provided with the same reference numerals. In order to differentiate among the exemplary embodiments, though, the letters a through c have been added to the reference numerals of the exemplary embodiments. The description below is essentially limited to the differences from the exemplary embodiment shown in FIGS. 1 through 3; for parts, features, and functions that remain the same, the reader should refer to the description of the exemplary embodiment in FIGS. 1 through 3.
FIG. 4 shows a detail of an alternative hand-held power tool 10b in the form of a cordless screwdriver 12b, in a detailed depiction of a bearing region 98b. The hand-held power tool 10b has a drivable output shaft 14b, a supporting element 16b embodied as integral with a transmission housing 68b, and a roller bearing unit 18b, which is embodied in the form of a ball bearing 30b and is situated at an end 34b closer to an output end 32b of the output shaft 14b. The supporting element 16b constitutes a roller element running surface 20b, which is embodied in the form of a segment of a circle and is part of the roller bearing unit 18b; the roller element running surface 20b is constituted by an outer roller element running surface 102b, which is let into an inner surface 100b of the supporting element 16b in the circumference direction 82b by means of a turning process. In addition, roller elements 86b are guided in the roller element running surface 20b and their movement in the axial direction 24b is limited by two supporting surfaces 26b, 28b of the roller element running surface 20b that are situated opposite from each other in the axial direction 24b. An inner ring 104b of the roller bearing unit 18b, which ring is situated between the output shaft 14b and the roller elements 86b in a radial direction 92b, transmits bearing forces of the output shaft 14b via the roller elements 86b to the supporting element 16b and to the transmission housing 68b. To facilitate an assembly of the ball bearing 30b, the transmission housing 68b is embodied of two parts or two half-shells (not shown).
Alternatively, however, it would also be possible to embody both an output shaft and a supporting element with an integrally embodied roller element running surface. It would thus be possible to eliminate an inner ring and an outer ring of a roller bearing unit, which would achieve particular savings in terms of space (not shown in detail).
FIG. 5 shows a tool holder region 64c of an alternative hand-held power tool 10c in the form of a cordless screwdriver 12c, having an output shaft 14c that can be driven by an electric motor, not shown, via a planet carrier 72c of a planetary gear 62c and having a supporting element 16c embodied as integral with a transmission housing 68c. The hand-held power tool 10c or more precisely stated, the tool holder region 64c, also has a roller bearing unit 18c that is situated at an end 34c closer to an output end 32c of the output shaft 14c, is composed of a roller bearing 30c, and is provided to transmit a supporting force of the output shaft 14c to the supporting element 16c. The output shaft 14c constitutes a roller element running surface 20c, which is embodied in the form of a segment of a circle and is part of the roller bearing unit 18c; the roller element running surface 20c is constituted by an inner roller element running surface 22c that is let into an outer surface 84c of the supporting element 16c in the circumference direction 82c by means of a turning process. In addition, roller elements 86c are guided in the roller element running surface 20c and their movement in the axial direction 24c is limited by two supporting surfaces 26c, 28c of the roller element running surface 20c situated opposite from each other in the axial direction 24c. 
The roller bearing unit 18c is also part of a bearing arrangement 70c of the output shaft 14c, which arrangement has an additional bearing unit 36c that is for supporting the output shaft 14c and is situated at an end 38c remote from the output end 32c of the output shaft 14c or toward the end closer to the planetary gear 62c. The additional bearing unit 36c is composed of an additional roller bearing unit 106c in the form of a roller bearing 30c and consequently, is likewise equipped with a roller element running surface 20c or more precisely stated, an inner roller element running surface 22c, which is embodied in the form of a segment of a circle and is for guiding roller elements 86c. The roller bearing units 18c and 106c have a shared outer ring 90c, which is situated between the roller elements 86c and the supporting element 16c in the radial direction 92c and transmits bearing forces of the output shaft 14c to the supporting element 16c; consequently, the roller bearing unit 18c is partially integral with the additional roller bearing unit 106c. 
The output shaft 14c is embodied as a hollow shaft 60c in an end region 96c situated at the output end; the end region 96c or more precisely stated, the hollow shaft 60c, represents a tool holder 44c by means of which a tool 80c or more precisely stated, a screwdriver bit, can be fastened. In addition, the output shaft 14c is embodied with a constant outer diameter 50c in a subregion 108c that extends from an end 110c of the output shaft 14c situated at the output end 32c to the roller element running surface 20c of the roller bearing unit 18c. 
The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.

## Claims

1. A hand-held power tool, in particular a cordless screwdriver, comprising:
a drivable output shaft having an input end attached to a transmission gear and an output end attached to a tool holder of the power tool;
a supporting element supporting the output shaft which is disposed therein; and
a roller bearing unit disposed radially between the supporting element and the output shaft, which transmits a supporting force of the output shaft to the supporting element,
wherein at least one roller element running surface of the roller bearing unit is provided on at least one of the output shaft and the supporting element and extends therearound in a circumferential direction.

2. The hand-held power tool as recited in claim 1, wherein the output shaft constitutes an inner roller element running surface of the roller bearing unit.

3. The hand-held power tool as recited in claim 2, wherein the roller element running surface has at least one supporting surface in an axial direction of the output shaft.

4. The hand-held power tool as recited in claim 3, wherein the roller element running surface has at least one second supporting surface in the axial direction of the output shaft.

5. The hand-held power tool as recited in claim 4, wherein the roller element running surface is embodied in the form of a segment of a circle.

6. The hand-held power tool as recited in claim 1, wherein the roller element running surface has at least one supporting surface in an axial direction of the output shaft.

7. The hand-held power tool as recited in claim 6, wherein the roller element running surface has at least one second supporting surface in the axial direction of the output shaft.

8. The hand-held power tool as recited in claim 1, wherein the roller element running surface is embodied in the form of a segment of a circle.

9. The hand-held power tool as recited in claim 1, wherein the roller bearing unit constitutes a ball bearing.

10. The hand-held power tool as recited in claim 1, wherein the roller bearing unit is situated at an end closer to an output end of the output shaft.

11. The hand-held power tool as recited in claim 1, further comprising at least one additional bearing unit that is provided to support the output shaft.

12. The hand-held power tool as recited in claim 11, wherein the at least one additional bearing unit is situated at an end remote from an output end of the output shaft.

13. The hand-held power tool as recited in claim 12, wherein the at least one additional bearing unit is constituted by a slide bearing or by an additional roller bearing unit.

14. The hand-held power tool as recited in claim 13, wherein the roller bearing unit is integral with the additional roller bearing unit.

15. The hand-held power tool as recited in claim 11, wherein the at least one additional bearing unit is constituted by a slide bearing or by an additional roller bearing unit.

16. The hand-held power tool as recited in claim 15, wherein the roller bearing unit is integral with the additional roller bearing unit.

17. The hand-held power tool as recited in claim 1, wherein the roller element running surface is let into at least one of the output shaft and the supporting element by means of a material-removing method.

18. The hand-held power tool as recited in claim 1, wherein the output shaft is embodied as a hollow shaft at least in a subregion in which the roller bearing unit is situated.

19. The hand-held power tool as recited in claim 1, further comprising a planetary gear.

20. A hand-held power tool, in particular a cordless screwdriver, comprising:
a drivable output shaft;
a supporting element;
a roller bearing unit which transmits a supporting force of the output shaft to the supporting element; and
at least one roller element running surface of the roller bearing unit provided on at least one of the output shaft and the supporting element,
wherein the output shaft is embodied with a constant outer diameter in a subregion that extends from an end of the output shaft situated at the output end to the roller element running surface of the roller bearing unit.