EP4461470A1 - Machine-outil et procédé de freinage d'une machine-outil - Google Patents

Machine-outil et procédé de freinage d'une machine-outil Download PDF

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Publication number
EP4461470A1
EP4461470A1 EP23173190.2A EP23173190A EP4461470A1 EP 4461470 A1 EP4461470 A1 EP 4461470A1 EP 23173190 A EP23173190 A EP 23173190A EP 4461470 A1 EP4461470 A1 EP 4461470A1
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EP
European Patent Office
Prior art keywords
machine tool
braking
electrical energy
motor
supply
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP23173190.2A
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German (de)
English (en)
Inventor
Markus Scherbaum
Qin Liu
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hilti AG
Original Assignee
Hilti AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hilti AG filed Critical Hilti AG
Priority to EP23173190.2A priority Critical patent/EP4461470A1/fr
Publication of EP4461470A1 publication Critical patent/EP4461470A1/fr
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25F—COMBINATION OR MULTI-PURPOSE TOOLS NOT OTHERWISE PROVIDED FOR; DETAILS OR COMPONENTS OF PORTABLE POWER-DRIVEN TOOLS NOT PARTICULARLY RELATED TO THE OPERATIONS PERFORMED AND NOT OTHERWISE PROVIDED FOR
    • B25F5/00—Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for

Definitions

  • the present invention relates to a machine tool that can be connected to a tool to carry out work, the machine tool comprising a motor and a control device.
  • the control device is designed to control a supply of electrical energy to the motor, a movement of the tool being able to be slowed down by reducing a supply of electrical energy to the motor by the control device.
  • the supply of electrical energy to the motor is reduced in at least two steps, the supply of electrical energy being reduced more in a second step than in a first step.
  • the invention relates to a method for braking a machine tool, the braking of the machine tool taking place in at least two steps, the machine tool being braked more in a second step than in a first step. In this way, a particularly gentle braking of the machine tool can be provided, which prevents the tool from becoming undesirably detached from the machine tool.
  • Machine tools are known in the state of the art that can be connected to a tool in order to carry out work. These can be, for example, drills, rotary hammers, grinding, chiseling or cutting devices or core drilling devices, but are not limited to these.
  • the machine tool should generally be switched off. Ideally, the machine tool should not continue to run for long after being switched off in order not to endanger the user or other people when putting the device down with the tool still running. By actively braking, the tool of the machine tool can be brought to a standstill more quickly. This can reduce the time during which there is a risk to the environment.
  • the clamping nut or the grinding wheel that is still rotating can unintentionally loosen.
  • the unintentional loosening of the clamping nut and grinding wheel or the tool and its fastening device can also depend on how tightly the user tightened the clamping nut when mounting the wheel.
  • the object underlying the present invention is to overcome the deficiencies and disadvantages of the prior art and to provide an optimized braking method for a machine tool, with which a rapid braking of a machine tool can be made possible while simultaneously using a standard tool which, in the case of a cutting or grinding wheel, for example, has a round holder.
  • the new braking method is also intended in particular to reduce the risk of the tool or its fastening means becoming unintentionally detached from the machine tool.
  • a machine tool which can be connected to a tool in order to carry out work.
  • the machine tool comprises a motor and a control device, wherein the control device is designed to control a supply of electrical energy to the motor.
  • a movement of the tool can be slowed down by reducing a supply of electrical energy to the motor by the control device, wherein the supply of electrical energy to the motor is reduced in at least two steps.
  • the supply of electrical Energy is reduced more in a second step than in a first step.
  • the invention can advantageously provide an optimized braking method for a machine tool, the machine tool or the braking method being characterized by a multi-stage, in particular two-stage braking trajectory.
  • the invention advantageously makes it possible to use standardized tools, in the case of grinding or cutting disks, for example disks with a central round holder for fastening.
  • the machine tool or its tool can be braked safely, with unintentional detachment of the tool from the machine tool being effectively prevented by the gentle braking made possible by the two-stage braking trajectory.
  • the stronger braking in the second braking stage means that the braking time for the entire braking process can be significantly reduced.
  • the electrical energy that can be supplied to or withdrawn from the motor of the machine tool to carry out the work is preferably also referred to as "motor current" in the sense of the invention. It is preferred in the sense of the invention that the control device of the machine tool is set up to control the supply of motor current to the motor. In other words, the control device can check whether and if so how much electrical energy, i.e. "motor current", the motor of the machine tool receives.
  • the basic idea of the present invention is that the machine tool can be braked if the supply of motor current to the motor is reduced.
  • a positive motor current preferably means that the machine tool, its motor or the tool of the machine tool is driven, while a negative motor current means that the machine tool, its motor or the tool of the machine tool is braked.
  • the torque of the motor is approximately directly proportional to the motor current, so that the following explanations advantageously also apply analogously to the torque curve.
  • a positive supply of electrical energy means driving the machine tool, its motor or the tool of the machine tool, while a negative supply of electrical energy means braking the machine tool, its motor or the tool of the machine tool.
  • a change from a positive supply of electrical energy to a negative supply of electrical energy can preferably be referred to as a zero crossing.
  • a positive motor current means driving the machine tool, its motor or the tool of the machine tool, while a negative motor current means braking the machine tool, its motor or the tool of the machine tool.
  • the change from positive motor current to negative motor current can be referred to as a zero crossing.
  • control device is designed to control a supply of motor current to the motor, wherein a movement of the tool can be braked by reducing a supply of motor current to the motor by the control device, wherein the supply of motor current to the motor is reduced in at least two steps, wherein the supply of motor current is reduced more in a second step than in a first step.
  • a torque pulse can be generated when the machine tool is braked quickly due to the gear backlash, which can have an adverse effect on the fastening of the machine tool's tool.
  • this torque pulse can act on the clamping nut with which the cut-off or grinding wheel is fastened to the angle grinder or cut-off machine. If the torque of the torque pulse is greater than the holding torque, the clamping nut or the fastening of the tool can come loose and thus become a danger for the machine tool operator.
  • the torque pulse can arise in particular when the gear tooth flanks change, i.e. when different teeth of different gears of the gearbox engage with one another and there may be play between the teeth of these gears of the gearbox ("gear backlash").
  • the machine tool is braked in at least two steps, with the machine tool being braked more strongly in a second step than in a first step.
  • This formulation is essentially equivalent to the fact that a supply of electrical energy is reduced more strongly in a second step than in a first step or that a motor current is reduced more strongly in a second step than in a first step.
  • a reduction of the electrical energy in the first step is described by a first gradient dl1/dt and a reduction of the electrical energy in the second step is described by a second gradient dl2/dt, wherein an amount of the second gradient is greater than an amount of the first gradient:
  • a reduction in the motor current in the first step is described by a first gradient dl1/dt and a reduction in the motor current in the second step is described by a second gradient dl2/dt, wherein an amount of the second gradient is greater than an amount of the first gradient:
  • the smaller gradient in the first interval or first step causes a smoother gear flank change with a smaller torque pulse.
  • the motor current is then guided more quickly to a braking current limit, which shortens the braking time.
  • a braking current limit which shortens the braking time.
  • an optimized braking process can be provided for a machine tool, for example an angle grinder, which is characterized by a multi-stage braking trajectory, whereby the multi- or two-stage braking trajectory can lead to a reduced torque pulse due to the gear play.
  • a particularly smooth gear flank change can be made possible and the risk of the machine tool's tool becoming unintentionally loosened can be significantly reduced.
  • the change from a positive supply of electrical energy to a negative supply of electrical energy is referred to as a zero crossing.
  • the motor current changes its sign, from positive to negative or vice versa.
  • a change from a positive to a negative motor current occurs, or vice versa.
  • the change from the first step to the second step of the braking process occurs at the zero crossing of the supply of electrical energy or the motor current. It has been shown that the change between the first and the second step of the braking process at the zero crossing of the motor current is advantageous, since the gear edge change is completed in this interval .
  • the gear edge change takes place in the interval with the flatter gradient of the motor current.
  • the change from the first step to the second step of the braking process can take place with a positive or a negative supply of electrical energy, ie in particular when the motor current is not "zero" but assumes a positive or negative value.
  • the change between the first and the second step of the braking process can advantageously also take place with a motor current that is not equal to zero, ie with an offset.
  • the time of the tooth or gear flank change depends on a distribution of the friction losses in the drive system between the motor and the spindle output
  • the friction losses on the motor side can be higher than on the spindle output side, so it is advantageous to change between the first and second interval of the braking process at a positive motor current offset in order to achieve a shorter braking time. If the friction losses on the spindle side are greater than on the motor side, it may be preferable to change the interval later at a negative motor current value.
  • the machine tool Before starting the braking process, the machine tool can be operated with a positive, preferably essentially constant motor current, for example.
  • the motor of the machine tool can be at an operating point, for example idle.
  • the motor current that is required for the machine tool to rotate at idle is referred to as idle current I_L in the sense of the invention.
  • the braking process can be initiated, for example, by a switch-off command from the user. To do this, the user can use a switch or another interface to enter operating commands for the machine tool. Alternatively or additionally, the braking process can be started by another event, such as a switch-off command through a kickback event.
  • the braking process begins by reducing the motor current in a first time interval or first step t1, followed by a second time interval or second step of the braking process t2 in which the motor current is reduced more quickly until the braking current limit is reached at the end of the second interval t2.
  • the braking current limit I_B can preferably also be referred to as a "predetermined braking value for the electrical energy" or "braking current” in the sense of the invention.
  • the gradient in the second interval t2 is greater in magnitude than in the first interval t1. In the second interval t2, the motor current therefore falls faster than in the first interval t1.
  • the change between the first interval t1 and the second interval t2 when the motor current passes through zero is advantageous, since in a machine tool the gear flank change is usually completed in the first interval t1.
  • the change between the first interval t1 and the second interval t2 can also take place with a motor current that is not equal to zero, i.e. with an offset.
  • the smaller gradient in magnitude in the first interval t1 causes a smoother gear flank change with a smaller torque pulse.
  • the motor current is then guided more quickly to the braking current limit, so that the braking time can be shortened. This also advantageously reduces the period of time during which a user of the machine tool may be exposed to a danger caused by the tool running on.
  • a third interval t3 the motor is braked to a standstill using a constant braking current, i.e. preferably with a maximum permissible braking torque.
  • a constant braking current i.e. preferably with a maximum permissible braking torque.
  • the second step or the second interval t2 ends when a predetermined braking value for the electrical energy that is supplied to the motor of the machine tool is reached, whereby the second step of the braking process can be followed by a third step.
  • the predetermined braking value for the electrical energy that is supplied to the motor of the machine tool preferably corresponds to the braking current limit or the braking current with which the machine tool is operated essentially constantly following the second interval t2 of the braking process in order to achieve braking of the machine tool, its tool or the motor of the machine tool.
  • the machine tool in the third step of the braking process is operated with the predetermined braking value for the electrical energy until the machine tool, its tool or the motor of the machine tool is braked.
  • the predetermined braking value for the electrical energy can preferably correspond essentially to a maximum permissible braking torque.
  • the machine tool motor can be braked to a standstill with a constant braking current, i.e. with the maximum permissible braking torque.
  • the braking process is advantageously completed.
  • the invention in a second aspect, relates to a method for braking a machine tool.
  • the terms, definitions and technical advantages introduced for the machine tool preferably apply analogously to the braking method.
  • the braking method is characterized in that the braking of the machine tool takes place in at least two steps, with the machine tool being braked more strongly in a second step than in a first step.
  • this preferably means that a supply of electrical energy is reduced more strongly in a second step than in a first step or that the motor current is reduced more strongly in a second step of the braking method than in a first step.
  • the proposed method can also comprise more than two stages, for example three, four, five, seven or ten stages, without being limited to this.
  • the braking process has at least two steps or stages, whereby the machine tool is braked to different degrees in the at least two stages.
  • a first step of the braking process the machine tool is initially braked less strongly than in a second step of the braking process.
  • This can advantageously prevent the tool of the machine tool from becoming detached from the machine tool or its tool holder during braking and becoming a danger to the user of the machine tool.
  • the total time for the braking process can be reduced so that the period of time in which there is a possible danger to the user due to the tool running on can be kept as short as possible.
  • the setting of the different gradients of the motor current in the first and second steps of the braking process can preferably be carried out by a control device of the machine tool.
  • the control device of the machine tool is therefore set up to set a gradient for the motor current that is smaller in magnitude in a first step of the braking process than in a second step of the braking process.
  • which is preferably set by the control device during the first step of the braking process, is smaller than the amount of the second gradient
  • the braking of the machine tool takes place by reducing the supply of electrical energy to a motor of the machine tool.
  • the braking of the machine tool can preferably take place by reducing the motor current of the machine tool.
  • the different gradients dl/dt of the motor current can achieve a smooth gear flank change (especially in the first stage of the braking process) while at the same time achieving a short braking time (especially due to the stronger braking of the machine tool in the second stage of the braking process).
  • an optimized braking process for the machine tool can advantageously be provided, which can enable a machine tool to be braked quickly while simultaneously using a standard tool which, in the case of a cutting or grinding wheel, for example, has a round holder.
  • the new braking process can also advantageously reduce the risk of the tool or its fastening means becoming unintentionally loose, thus reducing the danger for a user of the machine tool.
  • Figure 1 shows an example plot of the motor current I against time t in the context of the proposed braking method.
  • the motor current I is plotted on the y-axis, while the time t is plotted on the x-axis.
  • Figure 1 is divided into four time intervals t0, t1, t2 and t3.
  • the motor is at an operating point, for example idling.
  • the machine tool is operated with the motor current I, whereby the Figure 1 the motor current I shown in interval t0 is essentially constant and is in the positive range.
  • the braking process begins, for example initiated by a switch-off command from the user using a switch or by another event, such as a switch-off command due to a kickback event.
  • the change in the motor current I is described by the gradient dl1/dt
  • the change in the motor current I in the second interval t2 which preferably corresponds to the second step of the braking process, is described by the gradient dl2/dt.
  • the motor current I is essentially constant, whereby the machine tool can be operated with the idle motor current I_L, for example, in the zeroth interval t0.
  • the machine tool can be operated with the braking current I_B, for example.
  • the no-load motor current I_L has a positive sign
  • the braking current I_B has a negative sign.
  • the change from a positive sign of the motor current I to a negative sign of the motor current I (or vice versa) preferably takes place at the zero crossing, which is in Figure 1 marked with the letter «N».
  • the start or beginning of the braking process is indicated in Figure 1 marked with the letter "S”, while the end of the braking process is marked in Figure 1 is designated by the letter "E”.
  • the start S of the braking process is preferably between the zeroth interval t0 and the first interval t1, while the end E of the braking process marks the end of interval t3.
  • the braking process begins by reducing the motor current I in a first time interval t1, followed by a second time interval t2, in which the motor current I is reduced more quickly until the braking current limit I_B is reached at the end of the second interval t2.
  • the gradient dl2/dt in the second interval t2 is greater in magnitude than the gradient dl1/dt in the first interval t1.
  • the motor current I therefore drops more quickly than in the first interval t1. It has been shown that the change between the first interval t1 and the second interval t2 at the zero crossing N of the motor current I is advantageous, since in a machine tool the gear flank change is completed in the interval t1.
  • the change between the first Interval t1 and the second interval t2 can also be carried out with a motor current I that is not equal to zero, ie with an offset.
  • in the first interval t1 causes a smoother gear edge change with a smaller torque pulse.
  • the motor current I is then guided more quickly to the braking current limit I_B, ie a specified value for the braking current, which can shorten the total braking time.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Turning (AREA)
EP23173190.2A 2023-05-12 2023-05-12 Machine-outil et procédé de freinage d'une machine-outil Withdrawn EP4461470A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP23173190.2A EP4461470A1 (fr) 2023-05-12 2023-05-12 Machine-outil et procédé de freinage d'une machine-outil

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP23173190.2A EP4461470A1 (fr) 2023-05-12 2023-05-12 Machine-outil et procédé de freinage d'une machine-outil

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EP4461470A1 true EP4461470A1 (fr) 2024-11-13

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EP23173190.2A Withdrawn EP4461470A1 (fr) 2023-05-12 2023-05-12 Machine-outil et procédé de freinage d'une machine-outil

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1318596B1 (fr) * 2001-12-05 2006-09-27 Matsushita Electric Industrial Co., Ltd. Dispositif et méthode d'entraînement d'un moteur
DE102010001030A1 (de) * 2010-01-19 2011-07-21 Robert Bosch GmbH, 70469 Akku-Handwerkzeugmaschine und Verfahren zum Betreiben einer Akku-Handwerkzeugmaschine
EP2410650A2 (fr) * 2010-07-20 2012-01-25 C. & E. Fein GmbH Outil manuel
DE102018122837A1 (de) * 2017-09-19 2019-03-21 Makita Corporation Elektrisches Drehwerkzeug mit Bremse
EP4092905A1 (fr) * 2021-05-17 2022-11-23 Hilti Aktiengesellschaft Procédé de commande destiné au freinage d'un moteur électrique

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1318596B1 (fr) * 2001-12-05 2006-09-27 Matsushita Electric Industrial Co., Ltd. Dispositif et méthode d'entraînement d'un moteur
DE102010001030A1 (de) * 2010-01-19 2011-07-21 Robert Bosch GmbH, 70469 Akku-Handwerkzeugmaschine und Verfahren zum Betreiben einer Akku-Handwerkzeugmaschine
EP2410650A2 (fr) * 2010-07-20 2012-01-25 C. & E. Fein GmbH Outil manuel
DE102018122837A1 (de) * 2017-09-19 2019-03-21 Makita Corporation Elektrisches Drehwerkzeug mit Bremse
EP4092905A1 (fr) * 2021-05-17 2022-11-23 Hilti Aktiengesellschaft Procédé de commande destiné au freinage d'un moteur électrique

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