Adaptive Power Display

Abstract

A method to control a power tool, especially a core drill, including a motor as the drive for the power tool, a control unit, a power display, a transmission having at least a first gear and a second gear, a first sensor to detect the rotational speed of at least one component of the transmission and a second sensor to detect the rotational speed of the motor. The method includes the following steps: ascertaining a first rotational speed of the at least one component of the transmission when the transmission has been put into a gear, ascertaining a first rotational speed of the motor when the transmission has been put into a gear, ascertaining the selection of the gear on the basis of a first prescribed ratio of the first rotational speed of the at least one component of the transmission and of the first rotational speed of the motor on the basis of a look-up table, and setting the limit value of the power display on the basis of the look-up table as a function of the gear that has been selected. A power tool for purposes of using the method.

Claims

1-2. (canceled)

3. A method to control a power tool including a motor as a drive for the power tool; a controller; a power display; a transmission having a plurality of gears including at least a first gear and a second gear; a first sensor to detect a rotational speed of at least one component of the transmission; and a second sensor to detect a motor rotational speed of the motor, the method comprising the following steps: ascertaining a first rotational speed of the at least one component of the transmission when the transmission has been put into one of the plurality of gears, ascertaining a first rotational speed of the motor when the transmission has been put into the one gear, ascertaining a selection of the one gear as a function of a first prescribed ratio of the first rotational speed of the at least one component of the transmission and of the first rotational speed of the motor on the basis of at least one look-up table, and setting a limit value of a power display on the basis of the at least one look-up table as a function of the one gear.

4. A method to control a core drill including a motor as a drive for the core drill; a controller; a power display; a transmission having a plurality of gears including at least a first gear and a second gear; a first sensor to detect a rotational speed of at least one component of the transmission; and a second sensor to detect a motor rotational speed of the motor, the method comprising the following steps: ascertaining a first rotational speed of the at least one component of the transmission when the transmission has been put into one of the plurality of gears, ascertaining a first rotational speed of the motor when the transmission has been put into the one gear, ascertaining a selection of the one gear as a function of a first prescribed ratio of the first rotational speed of the at least one component of the transmission and of the first rotational speed of the motor on the basis of at least one look-up table, and setting a limit value of a power display on the basis of the at least one look-up table as a function of the one gear.

5. A power tool performing the method as recited in claim 2 comprising: the motor as the drive for the power tool; the controller; the power display; the transmission having at least a first gear and a second gear; the first sensor to detect the rotational speed of at least one component of the transmission; and the second sensor to detect the motor rotational speed of the motor.

6. A core drill performing the method as recited in claim 3 comprising: the motor as the drive for the core drill; the controller; the power display; the transmission having at least a first gear and a second gear; the first sensor to detect the rotational speed of at least one component of the transmission; and the second sensor to detect the motor rotational speed of the motor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Additional advantages can be gleaned from the figure description below. The figures depict various embodiments of the present invention. The figures, the description and the claims contain numerous features in combination. Whenever appropriate, the person skilled in the art will also consider the features individually and unite them to create additional meaningful combinations

[0027] The following is shown:

[0028] FIG. 1: a power tool configured as a core drill according to the invention, comprising a motor, a control unit, a transmission, a tool configured as a core bit, a first sensor and a second sensor; and

[0029] FIG. 2: a first flow chart of the method according to the invention.

DETAILED DESCRIPTION

[0030] FIG. 1 shows a power tool 1 configured as a core drill that is attached to a drill stand 2. By means of the drill stand 2, the core drill 1 can be reversibly moved along the double-arrow direction A towards as well as away from the workpiece W that is to be worked. The material W is concrete.

[0031] The core drill 1 has a housing 2, a motor 3, a control unit 4, a power display 5, a transmission 6, a driven shaft 7, a tool 8 configured as a core bit, a first sensor 10 to detect the rotational speed of the transmission 6 and a second sensor 20 to detect the rotational speed of the motor 3. Any type of electric motor can be used as the motor 3.

[0032] The motor 3 is configured as an electric motor and it serves to drive the core bit 8. The motor 3 has a drive shaft that is detachably connected to the transmission 6. This connection is established by a coupling means. The core bit 8 is made to rotate by means of the transmission 6 and the driven shaft 7. The torque generated in the motor 3 is thus correspondingly transmitted to the core bit 8 in order to cut a hole into the material W.

[0033] The transmission 6 has a first gear, a second gear as well as a no-load state, and it is positioned between the drive shaft of the motor 3 and the driven shaft 7. The individual gears can be selected manually by means of a gear-speed selector in order to thus vary the transmission of the rotational speed and of the torque from the motor 3 to the driven shaft 7 or to the core bit 8.

[0034] The first sensor 10 is positioned on the transmission 6 in such a way as to detect the rotational speed of at least one component of the transmission 6 relative to the gear that is currently selected. The at least one component of the transmission 6 can be a gear wheel or the like. The second sensor 20, in contrast, is positioned in such a way as to detect that the rotational speed of the motor 3.

[0035] The control unit 4 is connected to the first sensor 10 via a first line 11 and to the second sensor 20 via a second line 12, and this is done in such a way that that rotational speed values measured by the sensors 10, 20 are transmitted to the control unit 4. Moreover, the control unit 4 is connected to the motor 3 in such a way that the control unit 4 can vary the rotational speed of the motor 3 directly. Moreover, the control unit 4 is also connected to the power display 5 in such a way that the limit values of the power display 5 can be varied (that is to say, increased or decreased). The control unit 4 has a data memory unit where a look-up table (transmission ratio table) is stored. The gear that is currently selected can be ascertained with this look-up table on the basis of the ratio of the rotational speed of the motor 3 and of the corresponding rotational speed of the transmission 6. Thanks to the connection of the control unit 4 to the motor 3, the control unit 4 can act upon the motor 3, that is to say, it can automatically increase or decrease the rotational speed of the motor 3.

[0036] The power display 5 serves to inform the user about the current power level of the core drill 1, that is to say, especially to warn the user against an overload of the core drill 1. For this purpose, the power display 5 is visibly positioned on the housing 2 of the core drill 1 in such a way that the user can see it while working with the core drill 1. The power display 5 comprises a visual scale (graduation) with which the power range and especially the overload range pertaining to the currently selected gear is displayed. As an alternative or in addition to the visual scale, an acoustic display device can be provided which can indicate when the overload range has been reached and especially when it has been exceeded.

[0037] FIG. 2 shows the course of the adaptation of the limit value to the selected gear on the basis of the method according to the invention.

[0038] Towards this end, in step S1, the first sensor 10 ascertains the rotational speed of the transmission 6.

[0039] In step S2, the rotational speed of the motor 3 is ascertained by the second sensor 20.

[0040] In step S3, the selected gear is ascertained on the basis of the look-up table stored in the data memory unit as well as on the basis of the ascertained rotational speed of the motor 3 and of the transmission 6.

[0041] In step S4, the limit value of the power display 5 is selected on the basis of the look-up table as a function the gear that has been selected.