EP1727650A1

EP1727650A1 - Hand-held machine tool

Info

Publication number: EP1727650A1
Application number: EP05707914A
Authority: EP
Inventors: Andreas Strasser; Markus Leupert
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2004-03-13
Filing date: 2005-02-02
Publication date: 2006-12-06
Anticipated expiration: 2025-02-02
Also published as: DE102004012433A1; US7497272B2; US20070074883A1; WO2005087446A1; JP2007529327A; JP4340316B2; CN1929959A; EP1727650B1; CN100522502C

Abstract

The invention concerns a hand-held machine tool, more particularly a hammer drill, comprising a machine housing (10) with a tool holder (12) integrated therein, it being possible to drive said tool holder so that it rotates in a first operating mode and to secure it to the machine housing (10) so that it cannot rotate in a second operating mode, and also comprising a switch (20) for switching between the two operating modes, said switch comprising a coupling element (21) which can be moved in order to activate the operating modes and an actuating member (22) that effects said movement. In order to prevent an operator from making an operating error when switching between operating modes and thus the damage to the machine associated therewith, the actuating member (22) is an electric actuator (23), preferably an electromagnet (25), which is controlled by an electronic control unit (24).

Description

Handwerkzeuqmaschine

State of the art

The invention relates to a hand tool, in particular a rotary hammer, according to the preamble of claim 1.

In a known hand-held power tool designed as a rotary / chisel hammer, the tool holder is rigidly connected to a rotary or drive sleeve, which in turn can be rotatably carried by an output gear of a drive gear seated on the rotary sleeve. The axially displaceable tool held in the tool holder is acted upon in the axial direction by a striking mechanism, which impulses on the shaft end of the tool via a racket or striker. The handheld power tool can be operated either in the "hammer drilling" mode or in the "chiseling" mode. The tool is acted upon by the striking mechanism in both operating modes. In the "hammer drilling" operating mode, in which a hammer drill is inserted into the tool holder, the tool holder and thus the tool are driven in rotation. In the "chiseling" operating mode, in which a chisel tool is inserted into the tool holder, the tool holder is fixed to the assembly housing in a non-rotatable manner, and the chisel tool only executes an axial hammer movement under the action of the striking mechanism. An operating mode switch is used to switch the operating modes, which has a manually operated rotary knob and a shift fork that can be displaced by the rotary knob. The shift fork carries a coupling ring which rigidly couples the rotary sleeve to the driven gear of the drive transmission in a first displacement position and rigidly connects it to the machine housing in a second displacement position. In an intermediate position, the coupling ring does not engage either the driven wheel or the machine housing, so that the rotating sleeve and thus the tool holder can be freely rotated without a drive. In the case of hand-held machine tools with a rotating tool, operating or workpiece defects or the destruction of the tool mean that forces act on the hand-held machine tool which can no longer be controlled by the operator and which can lead to injuries to the operator.

In a known hand-held power tool with rotating tool (EP 0 771 619 B1), a system is installed with which such a so-called uncontrolled blocking situation is recognized and the resulting rotary movement of the machine housing is braked and limited. The system comprises a sensor which detects a movement quantity which characterizes the spatial dimensioning of the hand machine tool as a whole, e.g. the acceleration, the rotational speed or a rotational path of the machine housing, an operator that generates a control signal after reaching or exceeding a predetermined threshold value by the movement quantity supplied by the sensor, and an actuator that, based on the control signal of the operator, the drive for the rotating Tool interrupts. The actuator is designed as a disconnect clutch in the drive train of the tool and / or as a switch for switching off the drive motor and / or as a clutch for suddenly connecting the drive train to the machine housing. Advantages of the invention

The handheld power tool according to the invention with the features of claim 1 has the advantage that by switching the operating mode switch from a manual rotary knob to an electronically controlled actuator, the operator can switch between the operating modes independently of one another, which precludes switching during operation of the machine and thus Incorrect operation and wear on the components are reduced, which leads to a longer service life of the machine. In the simplest case, the operating mode is selected by the operator via an

Machine casing arranged keyboard selected, in a more luxurious The operating mode setting is carried out automatically in that a sensor senses the type of tool present in the tool holder and sends a corresponding identification signal to the electronic control unit, which in turn sets the associated operating mode. In the latter case, there is also an increased safety aspect, since accident risks are avoided, which arise from the fact that the hand-held power tool is set to an operating mode that does not match the machining tool inserted in the tool holder, for example the "percussion drilling" operating mode with a tool holder imported chisel tool.

Advantageous further developments and improvements of the hand-held power tool specified in claim 1 are possible through the measures listed in the further claims.

According to an advantageous embodiment of the invention,

A manually operated electrical switch for switching the machine on and off is arranged in the machine housing and is designed as a so-called "dead man switch" for additional safety for the operators during drilling operation, i.e. irj. the operating mode "impact drilling" must be held manually in its closed position with the rotating tool against the force of a return spring. at

When the switch is released, the switch is opened and the machine is stopped. Since such a "dead man's switch" is not required in the "chiseling" operating mode with the tool holder fixed on the machine housing, according to an advantageous embodiment of the invention, an electrical magnet controlled by the control device is assigned to the electrical switch, the magnetic force of which is greater than the spring force of the return spring , The control unit is designed such that it provides an excitation current for the electromagnet during the operating mode with a non-rotating tool, which keeps the electrical switch in the closed position even if the operator does not operate the switch. According to an advantageous embodiment of the invention, the electrical switch is designed in such a way that it can be lifted manually from the energized electromagnet in order to transfer it to its open position, so that the machine can be switched off at any time even in pure impact operation. Since the power supply for the electromagnet is also interrupted when the electrical switch is opened, it can only be energized again when the electrical switch is subsequently closed.

In a further embodiment of the invention, the electronic signal for switching the operating modes can also additionally be used to activate the booster function known per se in the handheld power tool. Such a booster function regulates the electric drive motor when switching to pure blow operation.

According to an advantageous embodiment of the invention,

Machine housing, a sensor connected to the control unit for detecting a tool block in the operating mode with a rotating tool holder, and the control unit is designed such that, on the one hand, it disconnects the electric motor when a sensor signal occurs and, on the other hand, the actuator for switching to the operating mode with am

Controlled machine housing fixed tool holder or to set a freewheel of the tool holder. This constructive measure easily integrates a safety function for the uncontrolled blocking situation in the handheld power tool, which accesses existing components and does not require any additional hardware apart from the sensor to detect the blocking situation. Appropriate control of the actuator makes it possible to fix the drive sleeve, which sets the tool in rotation, to the machine housing or to let it rotate freely without a drive.

drawing The invention is described below with reference to an embodiment shown in the drawing. Show it:

1 is a schematic side view of a hand machine tool, partially in section,

2 is an enlarged view of section II in FIG. 1st

Description of the embodiment

The hand-held power tool shown schematically in FIG. 1 is designed as a hammer drill, which can be operated optionally in an "impact drilling" operating mode and in a "chiseling" operating mode. The handheld power tool has a machine housing 10, on which a bow handle 11 is formed for holding the machine. At the end of the machine housing 10 facing away from the bow handle 11, a tool holder 12 is integrated in the machine housing 10, in which an exchangeable tool 13 can be received in a rotationally fixed and axially displaceable manner. In the percussion drilling operation, the tool 13 is a percussion drill and in the hammer or chisel operation, a chisel tool. As is not shown further, the tool holder 12 is rigidly attached to an

Machine housing 10 rotatably mounted drive sleeve 14, which can be driven in rotation by an electric motor 19 shown schematically here via a gear transmission 15 designed here as a bevel gear. The gear transmission 15 has an output gear 16 rotatably received on the drive sleeve 14 and a bevel pinion 17 which meshes with the output gear 16. The bevel pinion 17 sits in a rotationally fixed manner on an output shaft 18, which is driven either directly or via an intermediate gear 43 by the electric motor 19. As is not shown further here, the electric motor 19 also drives a percussion mechanism, which is driven by a percussion piston and striker or striker axially displaceably in the drive sleeve 14 with the interposition of an air cushion Impacts on the front end of the tool 13 held in the tool holder 12. An exemplary structure of the striking mechanism is described in DE 2820 128 A1.

For the setting of the operating modes, an operating mode switch 20 is provided, which has an axially displaceable coupling element 21 and an actuating element 22 causing its displacement. The coupling element 21 is designed such that in a first displacement position it rigidly couples the driven wheel 16 of the gear transmission 15 to the drive sleeve 14 and in a second displacement position it fixes the drive sleeve 14 on the machine housing 10 in a rotationally fixed manner. For this purpose, the actuator 22 has an electrical actuator 23 and an electronic control unit 24 which controls the actuator 23. In the exemplary embodiment in FIG. 1, the electrical actuator 23 is designed as an electromagnet 25. Alternatively, the electric actuator 23 can also be an electric servomotor. The clutch element 21 actuated by the actuator 23 comprises a shift fork 26 and an intermediate ring 27 with internal teeth 271 fastened to the shift fork 26 (FIG. 2). The shift fork 26 is displaceable against the force of a return spring 28 when the electromagnet 25 is energized. The return spring 28 formed here as a compression spring is supported on the one hand on the shift fork 26 and on the other hand on a holder 29 fixed on the machine housing 10. The holder 29 encloses the drive sleeve 14 with an integrally molded holder sleeve 291. The holder sleeve 291 has an outer, ring-shaped tooth section 30 on its end section facing the driven wheel 16 corresponds to the tooth pitch of the tooth section 30 on the holder sleeve 291. Between the holder sleeve 291 and the driven gear 16, a gear 32 with external teeth is arranged in a rotationally fixed manner on the drive sleeve 14, the tooth pitch of which in turn corresponds to the tooth pitch of the tooth section 30 and the ring gear 31. The gear 32 lies on the end face on the holder sleeve 291 and on the driven wheel 16 and has an axial width which is somewhat larger than the axial width of the intermediate ring 27. The intermediate ring 27 engages with its internal toothing 271 in the external toothing of the gear wheel 32 and, depending on the displacement, can also be immersed in the ring gear 31 on the driven gear 16 or in the tooth section 30 on the holder sleeve 291. In the first-mentioned shift position of the intermediate ring 27, which it assumes when the electromagnet 25 is not energized under the action of the return spring 28, the driven wheel 16 is connected in a rotationally fixed manner to the gear 32 via the intermediate ring 27, so that the driven wheel 16 is connected in a rotationally fixed manner to the drive sleeve 14 , In the second displacement position, into which the intermediate ring 27 is moved when the electromagnet 25 is energized by moving the shift fork 26 against the force of the return spring 28, the gear wheel 32 is rigidly connected to the tooth section 30, so that the drive sleeve, which supports the gear wheel 32 in a rotationally fixed manner 14 is held non-rotatably on the holder 29. In the first displacement position of the intermediate ring 27, the hand tool operates in the "percussion drilling" mode, in which both the rotary drive and the striking mechanism are effective, and in the second displacement position of the intermediate ring 27, the hand tool operates in the "chiseling" mode, in which Tool 13 is driven exclusively by the striking mechanism.

The operating mode switch 20 also includes a keyboard 33 arranged on the machine housing 10, with which the desired operating mode can be preselected manually by the operator. The keyboard 33 is connected to the control unit 24 via a connecting line 34 indicated by a broken line in FIG. 1. The connecting line between the control unit 24 and the electromagnet 25 is identified by 35.

To switch the electric motor 19 of the hand-held power tool on and off, which here, like the control unit 24, is supplied with power from an accumulator (rechargeable battery) 44, an electrical switch 36 is used, which can be actuated manually via a toggle button 37, in such a way that the switch 36 is closed by pressing the toggle button 37 and the switch 36 opens when the toggle button 37 is released. The The toggle button 37 is reset by means of a compression spring 38. This design of the electrical switch 36 as a so-called dead man's switch serves for the safety of the operator in order to switch the hand-held power tool to be idle when the toggle button 37 is released.

When the electrical switch 36 is closed, the control unit 24 is also supplied with power. The preselection signal fed in by the keyboard 33 for the desired operating mode of the hand-held power tool is processed in the control unit 24 and, depending on the specification, leads to energization or de-energization of the electromagnet 25. Is the operating mode " Chisel "is selected, the electromagnet 25 is energized, and this transfers the shift fork 26 with the intermediate ring 27 against the force of the return spring 28 into the displacement position shown in FIGS. 1 and 2, in which the intermediate ring 27, the drive sleeve 14 on the holder sleeve 291 is non-rotatable sets. The switched on electric motor 19 only drives the striking mechanism, while the driven wheel 16, which is also set in rotation by the electric motor 19, rotates freely on the drive sleeve 14. If the operating mode "percussion drilling" is selected, the control unit 24 switches the electromagnet 25 to be de-energized, and the return spring 28 pushes the shift fork 26 with the intermediate ring 27 in FIGS. 1 and 2 to the right until the internal toothing 271 of the intermediate ring 27 into the ring gear 31 immersed in the driven gear 16. The driven wheel 16 is now connected in a rotationally fixed manner to the drive sleeve 14 via the intermediate ring 27 and toothed ring 32, and the tool 13 is now also driven in rotation via the drive sleeve 14 and the tool holder 12.

Since the dead man function of the electrical switch 36 is not required for safety reasons and is also not desired in the "chiseling" operating mode, the electrical switch 36 is assigned an electromagnet 39 which is connected to the control unit 24 via a connecting line 40. The electromagnet 39 is designed such that it generates a magnetic force when energized, which is greater than the restoring force of the compression spring 38 Keyboard 33 preselected the "chiseling" operating mode, the control unit 24 initiates the energization of the electromagnet 39, which holds the electrical switch 36 in the closed position against the force of the compression spring 38, even when the toggle key 37 of the electrical switch 36 is released. In order to be able to stop the striking mechanism at any time in the "chiseling" operating mode, the toggle button 37 is designed like an angle lever with a longer lever arm 371 and a shorter lever arm 372. If the operator exerts a pressure force on the longer lever arm 71 of the toggle button 37 by means of a finger, the electrical switch 36 is transferred to its closed position, in which it is held in the "chiseling" operating mode by the energized electromagnet 39. If the operator exerts a compressive force on the shorter lever arm 372, the electrical switch 36 is returned to its open position against the magnetic force of the electromagnet 39 and the power supply to the electric motor 19 is interrupted.

In a further embodiment of the hand-held power tool, the electronic switching of the operating modes is not carried out by preselecting the operator, but rather automatically according to the type of tool 13 used in the tool holder 12. For this purpose, a sensor 41 is used in the tool holder 12, which both detects the presence of a Tool 13 in the tool holder 12 as well as the type of tool 13 recognizes, so can determine whether it is a hammer drill or a chisel tool. The sensor 41 is connected to the electronic control unit 24 via the connecting line 42. The keyboard 33 with connecting line 34 is omitted. Now the electrical

Switch 36 of the handheld power tool is closed, sensor 41 sends a tool classification signal to control unit 24. If the classification signal is characteristic of a chisel tool, the electrical control unit 24 initiates energization of the electromagnet 25 and the "chiseling" operating mode is set in the drive system, ie only the striking mechanism is driven by the electric motor 19. Is that from the sensor 41 to the Control unit 24 delivered classification signal characteristic of an impact drilling tool, so the control unit 24 does not energize the electromagnet 25. The return spring 28 ensures an adjustment of the operating mode "percussion drilling" in the drive system. Both the striking mechanism and the drive sleeve 14 are driven by the electric motor 19.

As is shown schematically in FIG. 1, the electric motor 19 is connected to the battery 44 via the switch contact 451 of an electromagnetic relay 45, which is arranged in the connecting line 46 between the electric motor 19 and the battery 44. The relay 45 is controlled by the control unit 24. As long as the electrical switch 36 is closed, the relay 45 is energized and the relay contact 451 is closed.

The operating mode switch 20 is additionally used to provide the handheld machine tool with a safety function for the uncontrolled

Equip blocking case. This blocking situation occurs when the rotating tool is extremely braked or even blocked by an operating or workpiece error and this triggers a strong rotation of the housing of the hand machine tool, which can lead to injury to the operator. For this purpose, a sensor 47 is arranged in the machine housing 10, which senses a tool blockage and outputs a corresponding output signal to the control unit 24 via a connecting line 48. For this purpose, the sensor detects a movement quantity of the machine housing 10, for example its acceleration or speed or a rotational distance. This movement variable is compared in the control unit 24 with a predetermined threshold. If the sensor signal reaches or exceeds this threshold, the control unit 24 on the one hand switches off the relay 45 so that the relay contact 451 opens and the electric motor 19 is switched off. The control unit 24, on the other hand, energizes the electromagnet 25. The energized electromagnet 25 moves the shift fork 26 against the force of the return spring 28 until the intermediate ring 27 connected to it with its internal toothing 271 except Engagement with the ring gear 31 on the output gear 16 is so that the output gear 16 rotates freely on the drive sleeve 14 and the drive train is interrupted for the rotation of the tool 13. By means of a correspondingly large current supply to the electromagnet 25, the intermediate ring 27 is either displaced until its internal toothing 271 is immersed in the toothed section 30 formed on the holder sleeve 291 and thus fixes the drive sleeve 14 in a rotationally fixed manner on the machine housing 10 via the gearwheel 32, or only moved so far that the internal toothing 271 only engages with the gear 32. In the latter case, the drive sleeve 14 and thus the tool holder 12 remain freely rotatable without a drive.

Claims

Expectations

1. hand tool, in particular hammer drill, with a machine housing (10), a tool holder (12) integrated therein, which can be rotatably driven in a first operating mode by means of an electric motor (19) and rotatably fixed on the machine housing (10) in a second operating mode, and With an operating mode switch (20) which has a coupling element (21) which can be displaced to activate the operating modes and an actuating element (22) causing its displacement, characterized in that the actuating element has an electrical actuator (23) and an actuator (23). controlling electronic control unit (24).

2. Hand tool according to claim 1, characterized in that the operating mode switch (20) on the machine housing (10) arranged keyboard (33) for operating mode selection, which is connected to the control unit (24).

3. Hand tool according to claim 1, characterized in that the operating mode switch (20) has a sensor (41) connected to the control unit (24) for classifying a tool (13) inserted into the tool holder (12) and that the control unit ( 24) in response to the classification signal of the sensor (41) controls the actuator (23) to set the operating mode required for the tool (13) present in the tool holder (12).

4. Hand tool according to one of claims 1-3, characterized in that the actuator (23) is an electric servomotor.

5. Hand tool according to one of claims 1-3, characterized in that the actuator (23) is an electromagnet (25).

6. Hand tool according to claim 5, characterized in that the actuating member (22) has a return spring (28) with a spring force opposing the magnetic force of the electromagnet (25).

7. Hand tool according to one of claims 1-6, characterized in that the tool holder (12) is rigidly coupled to a drive sleeve (14) rotatably mounted in the machine housing (10), that on the drive sleeve (14) rotatably an output gear (16) a gear (15), preferably a bevel gear, coupled to the electric motor (19), and a gear (32) which is axially adjacent to the driven gear (16) and which is fixed against rotation, that the driven gear (16) has a ring gear (31), the tooth pitch of which that of the gearwheel (32) agrees that a toothed section (30) facing the gearwheel (32) and enclosing the drive sleeve (14) is arranged on the housing (10) with the same tooth pitch that the coupling element (21) has an axially displaceable intermediate ring ( 27) with internal toothing (271), which is designed such that it either engages with the gear (32) and the toothed section (30) on the machine housing (10) or with the tooth Rad (32) or with the gear (32) and the ring gear (31) on the driven wheel (16) can be brought.

8. Hand tool according to claim 7, characterized in that the coupling element (21) has an actuating fork (26) actuated by the actuator (23), on which the intermediate ring (27) is fastened and the return spring (28) acts.

9. Hand tool according to one of claims 1-8, characterized in that on the machine housing (10) a manually Operating electrical switch (36) for switching the machine on and off is arranged, which is designed such that it must be held manually against the force of a return spring (38) in the operating mode with a rotatingly driven tool holder (12).

10. Hand tool according to claim 9, characterized in that the electrical switch (36) is associated with an electromagnet (39) controlled by the control device (24), the magnetic force of which is greater than that of the spring force of the return spring (38), and that the control unit (24) is designed such that it provides an excitation current for the electromagnet (39) assigned to the electrical switch (36) during the operating mode with the tool holder (12) fixed to the machine housing (10).

11. Hand tool according to claim 10, characterized in that the electrical switch (36) is designed such that it can be lifted manually from the energized electromagnet (39) for transferring to its open position.

12. Hand tool according to claim 11, characterized in that the electrical switch (36) has an angle lever-like toggle button (371, 372) formed with a longer and a shorter lever arm (37) and is designed so that the switch (36) by a Compressive force on the longer lever arm (371) in its closed position and a compressive force on the shorter lever arm (372) against the magnetic force of the energized electromagnet (39) can be converted into its open position.

13. Hand tool according to one of claims 1-12, characterized in that on the machine housing (10) on the control unit (24) connected sensor (47) for detecting a tool blockage in the operating mode with rotatingly driven Tool holder (12) is arranged and the control unit (24) is designed such that when a sensor signal occurs it on the one hand switches off the electric motor (19) and on the other hand the actuator (23) for switching to the operating mode with the tool holder fixed on the machine housing (10) ( 12) controls.

14. Hand tool according to claim 7 and 13, characterized in that with actuation of the electromagnet (25) the intermediate ring (27) is transferred into a shift position in which its internal toothing (271) with the gear (32) on the drive sleeve (14) and the tooth section (30) on the machine housing (10) is in tooth engagement.

15. Hand tool according to claim 14, characterized in that the electromagnet (25) is controlled with reduced excitation current, the size of which is dimensioned such that the displacement path of the intermediate ring (27) is sufficient, the internal toothing (271) out of engagement with the ring gear (31 ) on the driven gear (16).

16. Hand tool according to claim 14, characterized in that in the operating mode with a rotatably driven tool holder (12) the electromagnet (25) is switched off and the intermediate ring (27) from the return spring (28) engaging the shift fork (26) into a Transfer position is transferred, in which its internal toothing (271) with the ring gear (31) on the driven gear (16) is engaged.