Machine tool and method for operating the machine tool

Abstract

The present invention relates to a motor of a machine tool that is operated at a speed range of 2,000 to 30,000 rpm and has an inertia of 20·10 -6 ~750·10 -6 kg m 2 In a second aspect, the invention relates to a method for operating said machine tool, which is characterized by a series of selected parameters that are specified to characterize the motor of the machine tool, so that the machine tool can be designed and operated without the use of a mechanical slip clutch. In particular, the motor parameters "speed" and "inertia" are selected in particular such that the maximum torque in the gear mechanism of the power tool is always below a predefined upper limit. In addition, tests have shown that the invention allows a particularly productive work with the power tool, and that the omission of a mechanical slip clutch advantageously extends the service intervals.

Description

[Technical Field]

[0001] The present invention relates to a power tool motor that is operated at a speed range of 2,000 to 30,000 rpm and has an inertia of 20.10 -6 ~750·10 -6 kg m 2 In a second aspect, the present invention relates to a power tool having a tool and a motor in the range of 2,000 to 30,000 rpm, and an inertia of the motor in the range of 20·10 -6 ~750·10 -6 kg m 2 The present invention relates to a method for operating a power tool in a range of 100-200°C (120-240°F) and 150-200°C (160-180°F) by selecting and specifying a set of parameters that characterize the power tool's motor, thereby enabling the power tool to be designed and operated without the use of a mechanical slip clutch. The motor parameters "speed" and "inertia" are selected, among other things, so that the maximum torque at the power tool's transmission is always below a predetermined upper limit. Additionally, the present invention allows for particularly productive operation of the power tool, and tests have shown that the elimination of the mechanical slip clutch advantageously extends service intervals. [Background technology]

[0002] In the prior art, power tools capable of performing different types of work are known, such as hammer drills, chisels, cutting or angle grinders, screwdrivers or core drills, each of which is driven by a motor, which can be supplied with power via a mains connection or by means of a battery or accumulator.

[0003] Devices known from the prior art may attempt to limit the maximum torque in the driveline if the device or its tool becomes blocked. This is particularly to protect the user of the device, preventing injuries to the user's arm, shoulder, or wrist caused by the device continuing to rotate when the tool becomes blocked. To date, mechanical slip clutches have been used to provide such maximum torque and power tool deflection limits and protect the power tool user from excessive loads. However, such mechanical slip clutches are costly. In addition, mechanical slip clutches require maintenance and short service intervals. Furthermore, high trip speeds have been observed in some slip clutches, which can negatively affect productivity when working with the power tool.

[0004] Therefore, in order to protect the user, the prior art has proposed mechanical solutions that can, in particular, limit the recoil of the device against the user. However, no satisfactory solution exists for limiting the short-term torque peaks that occur in the power tool or its drive train when the tool is blocked. As a result, currently available power tools, and in particular their mechanical components, must be designed to be very robust in order to withstand the extreme loads that can occur during torque peaks when the tool is blocked or jammed. Therefore, the mechanisms of conventional power tools known from the prior art are oversized for most applications. Such torque peaks can be exceptionally high, especially in the case of core drills that can cut cylindrical drill cores from substrates. This is due in particular to the torsional rigidity of the drill bit, which is the tool used in core drills.

[0005] It is therefore an object of the present invention to provide an improved power tool and method of operating a power tool that overcomes the above-mentioned deficiencies and shortcomings of the prior art and that is capable of limiting torque peaks in the event of a blockage or jam of the tool. A further concern of the present invention is that the power tool should be managed without a mechanical slip clutch and that no compromise should be made in terms of protecting the power tool user. In addition, it is intended to make available a compact and lightweight power tool that allows convenient handling and, in particular, requires little maintenance.

[0006] This object is achieved by the subject matter of the independent claims. Advantageous embodiments of the subject matter according to the invention are set forth in the dependent claims. Summary of the Invention [Means for solving the problem]

[0007] In a first aspect, the object is to provide a motor that can be operated in a speed range of 2,000 to 30,000 rpm and whose inertia is 20 10 -6 ~750·10 -6 kg m 2This is achieved by a power tool having a tool and a motor in the range of 1 / 4000 rpm. The abbreviation rpm stands for revolutions per minute, i.e., revolutions per minute. The inventors recognized that the level of a torque peak occurring when the tool of the power tool jams or blocks depends on the inertial conditions within the power tool. The present invention is based on the idea that the level of the maximum torque can be set and limited by skillfully selecting motor parameters so that the maximum torque does not exceed a predetermined upper limit. In the sense of the present invention, the upper limit preferably represents the maximum torque that can be achieved by the power tool or its motor. In this case, the maximum torque in the power tool's drive train is reached, in particular, when the tool of the power tool jams or blocks. The high torque value occurring at this time is preferably referred to as a "torque peak" in the sense of the present invention. In particular, the inventors recognized that the maximum torque depends on the inertia ratio between the power tool and its motor, as well as the tool's blocking speed and the stiffness of the power tool's drive train. When a power tool is operated at a motor speed range of 2,000 to 30,000 rpm and the inertia of the power tool's motor is 20·10 -6 ~750·10 -6 kg m 2 The basic idea of ​​the present invention is that when the torque is in the range of 0.1 V, the maximum torque that is generated can be limited to keep it below the upper limit value.

[0008] The present invention includes, inter alia, specifying defined parameter ranges for motor speed and motor inertia so that the maximum torque of the power tool motor is always below a predetermined upper limit. This allows the power tool user to operate the power tool in a particularly safe manner. The time during which the power tool stalls in the event of a jam or blockage is typically very short. The corresponding period may be, for example, in the range of 5 milliseconds (ms). After a blockage event, the power tool preferably continues to rotate at a predetermined initial speed. This action is perceived by the power tool user as a deflection of the power tool. Tests have shown that this deflection of the power tool, which in the past often led to injuries in the user's arms, shoulders, and hands, can be significantly reduced using the present invention.

[0009] The proposed power tool may in particular be a core drill. The tool of the power tool is then preferably designed as a drill bit. The drill bit is used to cut out a cylindrical drill core from a solid substrate. However, the proposed power tool may also be, for example, a hammer drill or a drill driver.

[0010] In particular, in the context of the present invention, a range of motor inertia is described that allows slip-clutch-free operation of the power tool in a similarly specified speed range. Therefore, thanks to the present invention, a mechanical slip clutch can be dispensed with, resulting in a more cost-effectively manufactured and more compactly designed power tool. This advantageously leads to particularly convenient and simplified handling of the power tool. In particular, at motor speeds of 2,000 to 30,000 rpm, and above 20-10 -6 ~750·10 -6 kg m 2 Operating the power tool with an inertia in the range of 0.5 can provide a power tool with increased productivity, easier maintenance, and longer service intervals.

[0011] In the sense of the present invention, the term "motor inertia" is preferably understood as the mass moment of inertia of the motor, in particular as the mass moment of inertia of a rotating component of the motor about the rotation axis of the motor shaft. The rotating component of the motor, which preferably rotates about the rotation axis of the motor shaft, is preferably the motor rotor. Similarly, in the sense of the present invention, the term "power tool inertia" is preferably understood as the mass moment of inertia of the power tool, which preferably rotates about the tool's rotation axis.

[0012] In the context of the present invention, it is preferred that the upper torque limit is in the range of 500 to 1,500 Nm, preferably in the range of 700 to 1,200 Nm, particularly preferably in the range of 850 to 950 Nm, and most preferably 900 Nm. In the context of the present invention, the level of the permissible maximum torque value is preferably based on the robustness of the power tool's transmission. The inventors have recognized that the tangential component of the acceleration of the power tool's side handle also plays a role in determining the maximum torque. In the context of the present invention, this tangential component of acceleration is referred to as the "level of pain" (LOP). In the context of the present invention, this acceleration component is preferably used as a measure of the comfort of operating the power tool when the tool is blocked. The inventors have recognized that the level of pain is related to the maximum torque or its torque peak. This relationship arises, inter alia, from the inertia of the power tool. Therefore, a relationship exists between the maximum permissible speed in a power tool and the torque peak. Therefore, limiting the torque to a value below the upper limit advantageously also limits the pain level and improves comfort when operating the power tool compared to conventional power tools as known from the prior art.

[0013] In the sense of the present invention, the power tool preferably has a transmission with a gear ratio. The gear ratio preferably results from the motor characteristics, i.e., the characteristics of the power tool motor. In the sense of the present invention, the motor characteristics preferably describe the minimum speed value at which the power tool motor can provide the required power. The gear ratio also reflects the time lag between the tool's idle and the power tool's motor's idle, especially in the case of a jam or blockage of the power tool. For example, the tool's idle period may be in the range of 5 ms, while the power tool's motor's idle period may be in the range of 50 ms. The subject of the present invention is, in particular, the processing during a defined period after the power tool's tool jams. These periods are referred to as the second and third periods in FIG. 1.

[0014] In the context of the present invention, it has been particularly recognized that pain level, comfort of operation, and maximum torque may depend on the motor parameters speed, rotor inertia, and / or peak torque.

[0015] In the sense of the present invention, the inertia of the power tool is 30,000·10 -6 ~70,000 10 -6 kg m 2 Preferably in the range of 40,000 10 -6 ~60,000·10 -6 kg m 2 and more preferably in the range of 45,000 10 -6 ~55,000·10 -6 kg m 2 and most preferably in the range of 50,000 10 -6 kg m 2 Preferably, the stated values ​​for the inertia of the power tool are preferably used as input variables for determining the motor parameters speed and motor inertia.

[0016] Additionally, the power tool may have a spindle that transmits rotation of the motor to the tool of the power tool, and the speed of the spindle may be in the range of 1,000 to 1,500 rpm, preferably in the range of 1,250 to 1,350 rpm, and particularly preferably 1,300 rpm.

[0017] In the sense of the present invention, the spindle speed preferably corresponds to the tool speed of the proposed power tool. This means that the tool of the power tool preferably rotates at a speed in the range of 1,000 to 1,500 rpm, preferably in the range of 1,250 to 1,350 rpm, particularly preferably at a speed of about 1,300 rpm. The spindle speed or tool speed of the power tool is coupled to the motor speed via the transmission ratio in the gearbox, which plays an important role in the effective moment of inertia.

[0018] In a second aspect, the present invention relates to a method of operating a power tool, the power tool comprising: a motor of the power tool operated at a speed in the range of 2,000 to 30,000 rpm, the inertia of the motor being 20·10 -6 ~750·10 -6 kg m 2The definitions, technical effects and advantages discussed for the proposed power tool equally apply to the proposed method of operating.

[0019] Further advantages will become apparent from the following description of the drawings, in which various exemplary embodiments of the present invention are shown. The drawings, descriptions, and claims include numerous feature combinations. Those skilled in the art will also consider features individually and combine them as appropriate to generate useful additional combinations.

[0020] In the figures, identical and similar components are designated with the same reference numerals. [Brief explanation of the drawings]

[0021] [Figure 1] 1 illustrates exemplary curves of motor speed, tool speed, machine torque and speed versus time t. [Figure 2] 1A-1C show a preferred embodiment of a power tool, in particular a core drill. DETAILED DESCRIPTION OF THE INVENTION

[0022] FIG. 1 shows exemplary curves of motor speed (1), tool speed (2), power tool 10 torque (3), and speed (4) versus time t. Motor speed (1), tool speed (2), power tool 10 torque (3), and speed (4) are plotted from top to bottom on the y-axis, and time t is plotted on the x-axis. The overview is divided into three time periods, designated by Roman numerals I, II, and III. The first period I relates to the normal operation of the power tool 10, during which work is performed using the power tool 10. During this first period I, the values ​​1-4 shown in FIG. 1 are substantially constant, and such a substantially constant profile of the values ​​1-4 does not exclude fluctuations and deviations around the mean value.

[0023] Details of the power tool 10 are illustrated by way of example in FIG. 2. When the power tool 10 is a core drill, for example, a cylindrical drill core can be cut from a solid substrate using a drill bit 11. The drill bit, which serves as the tool 11 of the power tool 10, is driven by a motor 12 of the power tool 10. Motion from the motor 12 to the tool 11 can be transmitted by a spindle 14. The power tool 10 can also include a transmission 13. In the exemplary embodiment of the invention shown in FIG. 2, the core drill 10 is fixed to a drill stand, but the invention can also be used with handheld power tools, among others.

[0024] The second period II begins with the blocking of the tool 11 of the power tool 10. The start of the blocking of the tool 11 of the power tool 10 is indicated in FIG. 1 by the first dashed vertical line. During this second period II, the motor speed 1 and the tool speed 2 decrease while the torque 3 increases sharply. The second period II lasts, for example, 5 ms. The end of the second period II is determined by the tool 11 of the power tool 10 coming to a standstill. The motor 12 of the power tool 10 requires additional time to fully brake, and the stoppage of the motor 12 of the power tool 10 determines the end of the third period III. The time lag between the stoppage of the tool 11 and the stoppage of the motor 12 is determined by the gear ratio of the transmission 13 of the power tool 10. Overall, in the context of the present invention, it is a concern of the present invention that impulse shifts from the tool 11 of the power tool 10 to the power tool 10 itself occur and that the impulse shifts and deflections of the power tool 10 are limited so that no danger to the user of the power tool 10 arises therefrom.

[0025] Approximately in the middle of the second period II, torque 3 reaches its highest value 5, which simultaneously represents the upper limit 5 of torque 3. This upper limit 5 of torque 3 is indicated in FIG. 1 by the block arrow pointing upward in the upper right corner of FIG. 1. A movement or deflection 4 of the power tool 10 itself may also occur in the middle of the second period II. In the past, this deflection has led to injuries to the arm, shoulder, or wrist of the power tool 10 user; therefore, minimizing this deflection 4 is a concern of the present invention. In the context of the present invention, impulse shifts from the tool 11 of the power tool 10 to itself are preferred, and it is a concern of the present invention that the impulse shift and the associated deflection of the power tool 10 be limited so that no danger to the power tool 10 user results therefrom. Another concern of the present invention is that the torque (3) is always below the upper limit (5) of the torque (3). According to the present invention, this is achieved when the motor (12) of the power tool (10) is operated in a speed range (1) of 2,000 to 30,000 rpm, and the inertia of the motor (12) of the power tool (10) is 20 10 -6 ~750·10 -6 kg m 2 This is achieved by being in the range of

[0026] At the transition between the second period II. and the third period III., the power tool 10 or its drive begins to brake. As a result, the torque 3 decreases significantly during the third period III. The transition between the second period II. and the third period III. is indicated in FIG. 1 by a second dashed vertical line. The speed 1 of the motor 12 of the power tool 10 also decreases during the third period III. The decrease in motor speed 1 occurs approximately linearly until the motor 12 comes to a complete stop at the end of the third period III. The deflection 4 of the power tool 10 also stops during the third period III. The third period III. may last, for example, 50 ms. [Explanation of symbols]

[0027] 1 Motor speed 2 Tool speed 3 Torque or Load 4. Power Tool Speed 5 Torque limit 10 Power tools 11 Tools 12 motors 13. Transmission 14 Spindle I. Power Tool Operation II. Tool downtime in case of blockage III. Time the motor will stop in case of blockage

Claims

1. A handheld power tool (10) having a tool (11) and a motor (12) for driving the tool (11), The motor (12) can be operated in a speed range (1) of 2,000 to 30,000 rpm, and the inertia of the motor (12) is 20.10 －６ ~750.10 －６ kg m ２ is in the range of The inertia of the power tool (10) is 30,000. －６ ~70,000.10 －６ kg m ２ is in the range of The range of rotational speed and inertia of the motor (12) is selected so that the torque (3) of the motor (12) of the power tool (10) does not exceed an upper limit (5) in the range of 500 to 1,500 Nm.

2. The power tool (10) according to claim 1, characterized in that the power tool (10) comprises a transmission (13).

3. 3. The power tool (10) according to claim 1 or 2, characterized in that the power tool (10) has a spindle (14) capable of transmitting the rotation of the motor (12) to the tool (11) of the power tool (10), and the speed of the spindle (14) is in the range of 1,000 to 1,500 rpm, preferably in the range of 1,250 to 1,350 rpm, and particularly preferably 1,300 rpm.

4. A method of operating a handheld power tool (10), comprising: The power tool (10) has a tool (11) and a motor (12) for driving the tool (11), the motor (12) of the power tool (10) is operated in a speed range (1) of 2,000 to 30,000 rpm, and the inertia of the motor (12) is 20.10 －６ ~750.10 －６ kg m ２ is in the range of The inertia of the power tool (10) is 30,000. －６ ~70,000.10 －６ kg m ２ is in the range of The range of rotational speed and inertia of the motor (12) is selected so that the torque (3) of the motor (12) of the power tool (10) does not exceed an upper limit (5) in the range of 500 to 1,500 Nm.

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