Power tool

Abstract

Power tool (2) comprising: a motor (8); an output torque calculation unit configured to calculate an output torque of the motor (8) based on a current (i) flowing through the motor (8); a friction torque calculation unit configured to calculate a friction torque of the motor (8) based on a rotational speed (ω) of the motor (8); a load torque estimation unit (16) configured to estimate a load torque (τ) acting on the motor (8); an inertial torque calculation unit configured to calculate an inertial torque based on the output torque, the friction torque, and the load torque (τ); and a motor braking unit configured to stop or decelerate the motor (8) when the inertial torque is greater than an inertial torque reference value (τir).

Description

[0001] This application claims priority over Japanese patent application JP 2013-241199, which was filed on November 21, 2013, and the contents of which are hereby incorporated into the present application by reference.

[0002] The teachings revealed herein relate to power tools.

[0003] WO 2012 / 108246 A1 discloses a power tool comprising a motor and a load torque estimation unit configured to estimate a load torque acting on the motor. This power tool makes it possible to estimate a load torque acting on the motor without using a torque sensor.

[0004] In the event of a sudden increase in load, such as a kickback occurring while working with a power tool, it is preferable to stop or decelerate the motor to ensure user safety. This document discloses a technology that makes it possible to stop or decelerate the motor in the event of a sudden increase in load.

[0005] A power tool according to the present invention is specified in claim 1. Further developments of the invention are specified in the dependent claims.

[0006] In this power tool, the motor's inertial torque increases significantly when the load rises abruptly. Therefore, if the inertial torque exceeds the reference value, the motor will stop or decelerate. This ensures user safety. Furthermore, the motor will not stop or decelerate when the load torque is high but the inertial torque is low, such as during normal heavy-duty work. This prevents a decrease in work efficiency.

[0007] Further features and advantages will become apparent from the following description of embodiments based on the figures, of which:

[0008] Fig. 1. Schematic representation of a power tool 2 shows one embodiment;

[0009] Fig. 2 schematically a design of a voltage detection unit 32 the embodiment shows;

[0010] Fig. 3 is a block diagram that is an example of a design for a load torque estimation circuit 16 the embodiment shows;

[0011] Fig. 4 is a block diagram that shows a configuration of a combination of the load torque estimation circuit 16 from Fig. 3 and one engine 8 shows;

[0012] Fig. 5 is a block diagram that represents a control system equivalent to a control system of Fig. 3 shows;

[0013] Fig. 6 is a block diagram, which is another example of a design for a load torque estimation circuit. 16 the embodiment shows;

[0014] Fig. 7 is a block diagram, which is yet another example of a design for a load torque estimation circuit.16 the embodiment shows;

[0015] Fig. 8 is a block diagram, which is yet another example of a design for a load torque estimation circuit. 16 the embodiment shows;

[0016] Fig. 9 is a flowchart that explains an example of a process controlled by a controller 18 the embodiment is carried out; and

[0017] Fig. 10 is a flowchart that explains another example of a process controlled by the system. 18 the embodiment is carried out.

[0018] In a power tool according to some embodiments, the load torque estimation unit can be configured to estimate the load torque based on at least two measurements: a measurement of the current flowing through the motor, a measurement of the motor's terminal voltage, and a measurement of the motor's rotational speed. The current flowing through the motor, the motor's terminal voltage, and the motor's rotational speed can be measured using a conventionally used, small-format, and inexpensive sensing device. This power tool makes it possible to estimate the load torque acting on the motor without increasing its size or cost.

[0019] A power tool according to some embodiments can further comprise a speed estimation unit configured to estimate the motor's speed based on a measured value of the current flowing through the motor and a measured value of the motor's terminal voltage. This power tool makes it possible to calculate the motor's frictional torque by estimating the motor's speed without using a speed sensor configured to detect the motor's speed.

[0020] In a power tool according to some embodiments, the motor braking unit can be configured not to stop or decelerate the motor when the load torque is less than a load torque reference value, or when the output torque is less than a load torque reference value, even if the inertial torque is greater than the inertial torque reference value. During light-load work, where the load torque or output torque is low, an abrupt increase in load while working with the power tool is, if anything, less of a problem for user safety. The power tool will not stop or decelerate the motor when the load torque or output torque is low, even if the inertial torque increases due to an abrupt increase in load. This design makes it possible to suppress a decrease in work efficiency.

[0021] The power tool can be designed such that a user can select a combination of the load torque reference value or the output torque reference value and the inertial torque reference value from a plurality of predetermined combinations. This design allows the user to modify the settings for the power tool to the extent appropriate for the purpose for which the power tool is used.

[0022] A power tool according to some embodiments may also be designed to have a removable side handle. A power tool with a removable side handle is typically used for heavy-duty work involving high load torque. During heavy-duty work, ensuring the user's safety is of paramount importance, especially in the event of a sudden increase in load. This power tool makes it possible to guarantee the user's safety during heavy-duty work.

[0023] A power tool, according to some embodiments, can be designed such that the motor is a brushless motor. Normally, a brushless motor can be quickly decelerated or stopped because its rotor has a low moment of inertia. This power tool allows the motor to be quickly decelerated or stopped in the event of a sudden increase in load.

[0024] In a power tool according to some embodiments, the motor braking unit can further be configured to stop or decelerate the motor when the load torque exceeds an upper limit. This power tool makes it possible to achieve the effect of a screwdriver that stops tightening a screw at a predetermined torque, as in the case where a mechanical clutch is used. Compared to the mechanical clutch, the resulting electric clutch neither generates noise during operation nor deteriorates due to wear.

[0025] The power tool may be configured to include a mode-switching unit designed to select an operating mode of the power tool from a plurality of operating modes, and the motor braking unit may be configured not to stop or decelerate the motor when a particular operating mode is selected, even if the load torque exceeds the upper limit of the load torque. This configuration allows the user to select whether or not to engage the electric clutch, depending on the purpose for which the power tool is used.

[0026] The power tool can also be equipped with a notification unit designed to alert a user when the motor braking unit stops or decelerates the motor. This design allows the user to recognize that the motor is being decelerated or stopped to ensure safety.

[0027] Representative, non-limiting examples of the present invention are now described in further detail with reference to the accompanying drawings. This detailed description is intended solely to provide a person skilled in the art with further details on carrying out preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed below can be used, individually or in combination with other features and teachings, to specify improved power tools and methods for their use and manufacture.

[0028] Furthermore, combinations of features and steps disclosed in the following detailed description need not be necessary for carrying out the invention in the broadest sense and are instead taught merely to accurately describe representative examples of the invention. Moreover, various features of the representative examples described above and below, as well as the various independent and dependent claims, can be combined to specify additional useful embodiments of the present teachings in ways that are not specifically and expressly enumerated.

[0029] All features disclosed in the description and / or claims are intended to be disclosed individually and independently of one another for the purpose of the original written disclosure and for the purpose of limiting the claimed subject matter, irrespective of the combinations of features in the embodiments and / or claims. Furthermore, all ranges of values ​​or indications of groups of structures are intended to disclose any possible intermediate value or any possible intermediate structure for the purpose of the original written disclosure and for the purpose of limiting the claimed subject matter.

[0030] As in Fig. As shown in 1, a power tool 2 in the present embodiment a tool unit 4 , a power transmission unit 6 , an engine 8 , a battery 10 , a speed sensor 12, a motor drive circuit 14 , a load torque estimation circuit 16 , a control system 18 (or control), a mode switching unit 20 , a torque setting unit 22 , a notification unit 24 , a drive switch 26 and a side handle 28 up. The power tool 2 The present embodiment is, for example, a drill / driver.

[0031] With the power tool 2 is the motor drive circuit 14 trained, the engine 8 to drive it to rotate, and the power transmission unit 6 is trained to control the rotation of the engine 8 on the tool unit 4 to transmit. The speed sensor 12 is designed to achieve a rotational speed ω of the motor 8 to detect. If the engine 8 If it is a brushless DC motor, the speed sensor can 12a speed sensor that the engine 8 structurally exhibits the following: The motor drive circuit 14 It features a current sensing unit 30 , which is trained to conduct a current through the motor 8 flows, to detect, and a voltage detection unit 32 on, which is designed to supply a connection voltage to the motor 8 to capture.

[0032] Fig. 2 shows an example of how the voltage detection unit works. 32 is trained when the engine 8 It is a brushless three-phase DC motor. The voltage sensing unit 32 exhibits differential circuits 34a , 34b and 34c , resistors 36a , 36b , 36c , 36d , 36e and 36f and an adder 38 on. The differential circuit 34a is formed, a voltage between a U-phase of the motor 8and a V-phase of the engine 8 to output. The output from the differential circuit 34a is caused by the resistances 36a and 36b divided and into the adder 38 entered. The differential circuit 34b is formed, a voltage between the V-phase of the motor 8 and a W-phase of the motor 8 to output. The output from the differential circuit 34b is caused by the resistances 36c and 36d divided and into the adder 38 entered. The differential circuit 34c is formed, a voltage between the W-phase of the motor 8 and the U-phase of the engine 8 to output. The output from the differential circuit 34c is caused by the resistances 36e and 36f divided and into the adder 38 entered. The adder 38 is trained to process the inputs from the differential circuits 34a ,34b and 34c to add the inputs together and output the sum of the inputs. In the present embodiment, the output is taken from the adder. 38 as a measured value V m the motor's connection voltage 8 used. It should be noted that the differential circuits 34a , 34b and 34c , the resistances 36a , 36b , 36c , 36d , 36e and 36f and the adder 38 as circuits that are controlled by the controller 18 are separate, can be mounted, or are integrated into the control system 18 They may be built in.

[0033] The load torque estimation circuit 16 from Fig. 1 is designed to estimate a load torque applied by the tool unit 4 through the power transmission unit 6 on the engine 8 It works.

[0034] Fig. Figure 3 shows an example of a design of the load torque estimation circuit. 16 The load torque estimation circuit 16 from Fig. 3 is formed, an estimated value τ e of the load torque applied to the engine 8 acts, based on a measured value of the current flowing through the motor 8 flows, as from the current sensing unit 30 recorded, and the measured value V m the motor's connection voltage 8 , as from the voltage detection unit 32 The load torque estimation circuit is recorded and output. 16 one engine model 40 , a comparison tool 42 and an amplifier 44 on.

[0035] The engine model 40 is a model of the engine's characteristic data 8 as a transmission system with two inputs and two outputs. The motor model 40 It specifies a motor connection voltage V as its input.8 and a load torque τ applied to the motor 8 acts, and exhibits as its outputs a current i, which is driven by the motor 8 flows, and the rotational speed ω of the motor 8 It should be noted that the motor's connection voltage V is important. 8 , the load torque τ, which is applied to the motor 8 acts, the current i, which flows through the motor 8 flows, and the rotational speed ω of the motor 8 hereinafter also referred to as state variables of the engine. 8 Reference is made to this.

[0036] The engine model's specifications 40 can be determined based on the input and output characteristics of the actual motor. 8 can be determined. For example, if the engine 8 a DC motor, the specifications of the motor model 40 can be determined in the following way.

[0037] For the electrical system of the motor 8If L is the inductance, i is the current, V is the connection voltage, R is the resistance, KB is the generator constant (current generation constant / power generation constant), and ω is the rotational speed, the following comparative expression applies: L di dt = V – Ri – KBω (1)

[0038] For the mechanical system of the engine 8 On the other hand, if J is the moment of inertia of the rotor, KT is the torque constant, B is the friction constant, and τ is the load torque, the following comparative expression applies: J dω dt = KTi – Bω – τ (2)

[0039] It should be noted that in this specification, the left side of mathematical expression (2) refers to the inertial torque, and the first, second and third expressions of the right side of mathematical expression (2) refer to the output torque, the friction torque and the load torque respectively.

[0040] Integrating both sides of mathematical expressions (1) and (2) with respect to time yields the following two comparison expressions: i = ∫( 1 L V – R L i – KB L ω)dt (3) ω = ∫( KT J i – B J ω – 1 J τ)dt (4)

[0041] Performing numerical calculations using mathematical expressions (3) and (4) yields two outputs i and ω with respect to two inputs V and τ. As can be seen from the above, each of the outputs can be, if the motor model 40 is trained when its inputs determine the motor's connection voltage V 8 and the load torque τ, which is applied to the motor 8 acts, to demonstrate and as its expenditure the current i, which flows through the motor 8 flows, and the rotational speed ω of the motor 8 to demonstrate, by integral calculus without performing differential calculus. In general, it is difficult when the load torque estimation circuit 16For example, a microcomputer mounted on a single chip can perform differential calculations with high accuracy when there is an abrupt change in the state variable of the motor. 8 However, such a design of the engine model can... 40 that the outputs are obtained by integral calculus, as stated above, the behavior of the motor 8 can be simulated with high accuracy, even if there is an abrupt change in the state variable of the motor. 8 gives.

[0042] As in Fig. As shown in section 3, a power output from the motor model is displayed. 40 , i.e., an estimated value i e of the current flowing through the motor 8 flows, the comparator 42 provided. The comparison tool 42 calculates a difference Δi between the measured value of the current flowing through the motor. 8 flows, and the power output i e from the engine model40 The calculated difference Δi is then applied to the amplifier by a predetermined gain factor G. 44 amplified and then connected to the torque input of the motor model 40 than the estimated value τ e of the load torque applied to the engine 8 The input takes effect. In this way, the load torque estimation circuit 16 This represents a feedback loop. It should be noted that this is a voltage input for the motor model. 40 the measured value V m the motor's connection voltage 8 is entered.

[0043] In a feedback loop, a sufficiently high preset gain factor G in the amplifier is used. 44 the input torque of the motor model 40 , i.e., the order of magnitude of the estimated value τ e of the load torque applied to the engine 8 It is adapted so that the power output from the motor model 40, i.e., the estimated value i e of the current flowing through the motor 8 flows, to the measured value of the current flowing through the motor 8 It flows, converges. This design makes it possible to use the engine model. 40 then to calculate the load torque τ e , which is on the engine 8 acts, and at a rotational speed ω e of the engine 8 to use that the current in the motor 8 flows, is obtained when the connection voltage V m to the engine 8 is created.

[0044] The principle of estimating the load torque τ, which is applied to the motor 8 This is achieved through the load torque estimation circuit. 16 is based on Fig. 4 explained. In Fig. 4 will be the actual engine 8 expressed as a transfer function M1, and the engine model 40 , which is a virtual realization of the engine 8in the load torque estimation circuit 16 This is expressed as a transfer function M2. The relationship between an input τ1 (i.e., the value of the load torque applied to the actual motor) and the input τ1 (i.e., the value of the load torque applied to the motor) is defined as follows: 8 (acts) to the control system, which is in Fig. 3 is shown, and an output τ2 (i.e., an estimated value of a torque obtained from the load torque estimation circuit). 16 is output) from the control system, which is in Fig. The 3 shown is as follows:

[0045] Therefore, it allows the preset of the engine model. 40 in the load torque estimation circuit 16 , so that it is in key data relating to the actual engine 8 equivalent is to replace M1 = M2 = M in mathematical expression (5), which yields the following comparison expression: τ 2 = GM 1+GM τ 1 (6)

[0046] As can be seen from mathematical expression (6), a transfer function from the input τ1 to the output τ2 of the control system of Fig. 4 equivalent to that of a feedback control system, such as the one used in Fig. Figure 5 shows where the forward transfer function is GM and the backward transfer function is GM. 1 Therefore, the output τ2 changes according to the input τ1. The sufficiently high preset gain factor G in the amplifier... 44 This causes the output τ2 to converge to the input τ1. Therefore, the load torque τ1 applied to the motor can 8 acts, from the estimated value τ2 of the torque, which is determined by the load torque estimation circuit 16 The output will be found.

[0047] The load torque estimation circuit 16The present embodiment makes it possible to determine the load torque τ applied to the motor without providing a dedicated sensor for detecting torque. 8 It acts with high accuracy based on the motor's connection voltage V. 8 and the current i, which flows through the motor 8 It flows, to estimate.

[0048] The load torque estimation circuit 16 In the present embodiment, the feedback loop that the motor model is designed 40 exhibits that, as its inputs, is the connection voltage V of the motor. 8 and the load torque τ, which is applied to the motor 8 acts, exhibits, and as its outputs the current i, which flows through the motor 8 flows, and the rotational speed ω of the motor 8 exhibits, to use for convergence of the current output i c from the engine model 40 to the current in the motor 8This design makes it possible to determine the load torque τ applied to the motor without using differential calculus. 8 its effect can be estimated with high accuracy.

[0049] Fig. Figure 6 shows another example of a design for a load torque estimation circuit. 16 The load torque estimation circuit 16 from Fig. 6 is formed, an estimated value τ c of the load torque applied to the engine 8 its effect is based on a measured value ω m the engine speed 8 , as through the speed sensor 12 recorded, and the measured value V m the motor's connection voltage 8 , as from the voltage detection unit 32 The load torque estimation circuit is recorded and output. 16 from Fig. 6 features an engine model 40 , a comparison tool 46 and an amplifier 48 on.

[0050] The engine model 40 the load torque estimation circuit 16 from Fig. 6 is identical to the engine model 40 the load torque estimation circuit 16 from Fig. 3. In the load torque estimation circuit 16 from Fig. 6 will provide a speed output from the engine model 40 , i.e., an estimated value ω e the engine speed 8 , the comparator 46 provided. The comparison tool 46 calculates a difference Δω between the rotational speed output ω e from the engine model 40 and the measured value ω m the engine speed 8 The calculated difference Δω is then replaced by a predetermined gain factor H in the amplifier. 48 amplified and then connected to the torque input of the motor model 40 than the estimated value τ e of the load torque applied to the engine 8It works, entered. As the voltage input of the motor model 40 will the measured value V m the motor's connection voltage 8 entered.

[0051] In the feedback loop of the load torque estimation circuit 16 from Fig. 6 is achieved by a sufficiently high preset gain factor H in the amplifier. 48 the input torque to the motor model 40 , i.e., the order of magnitude of the estimated value τ e of the load torque applied to the engine 8 It is adapted so that the speed output is derived from the engine model. 40 , i.e., the estimated value ω e the engine speed 8 to the measured value ω m the engine speed 8 converges. This design makes it possible to configure the engine model. 40 to use for this purpose, the load torque τ e , which is on the engine 8 It acts to estimate that the rotational speed ω mof the engine 8 is obtained when the connection voltage V m to the engine 8 is created.

[0052] Fig. Figure 7 shows another example of a design for a load torque estimation circuit. 16 The load torque estimation circuit 16 from Fig. 7 is formed, an estimated value τ e of the load torque applied to the engine 8 It acts, based on the measured value of the current flowing through the motor. 8 flows, as from the current sensing unit 30 recorded, of the measured value ω m the engine speed 8 , as from the speed sensor 12 recorded, and the measured value V m the motor's connection voltage 8 , as from the voltage detection unit 32 The load torque estimation circuit is recorded and output. 16 from Fig. 7 features an engine model 40 , Comparator 50 and52 and amplifier 54 and 56 and an adder 58 on.

[0053] The engine model 40 the load torque estimation circuit 16 from Fig. 7 is identical to the engine model 40 the load torque estimation circuit 16 from Fig. 3. In the load torque estimation circuit 16 from Fig. 7 will be the speed output from the engine model 40 , i.e., the estimated value ω e the engine speed 8 , the comparator 50 provided. The comparison tool 50 calculates the difference Δω between the rotational speed output ω e from the engine model 40 and the measured value ω m the engine speed 8 The difference Δ calculated in this way ω is increased by a predetermined amplification factor G ω in the amplifier 54 amplified and then the adder 58provided. Furthermore, the load torque estimation circuit 16 from Fig. 7 the current output from the motor model 40 , i.e., the estimated value i e of the current flowing through the motor 8 flows, the comparator 52 provided. The comparison tool 52 calculates the difference Δi between the measured value of the current flowing through the motor. 8 flows, and the power output i e from the engine model 40 The difference Δi calculated in this way is multiplied by a predetermined amplification factor G. i in the amplifier 56 amplified and then the adder 58 provided. The adder 58 adds the output from the amplifier 54 and the output from the amplifier 56 together. The output from the adder 58 is connected to the torque input of the motor model 40 than the estimated value τ eof the load torque applied to the engine 8 The input is active. At the voltage input of the motor model. 40 will the measured value V m the motor's connection voltage 8 entered.

[0054] In the feedback loop of the load torque estimation circuit 16 from Fig. 7 is achieved by a sufficiently high preset gain factor G ω in the amplifier 54 and the amplification factor G i in the amplifier 56 the input torque of the motor model 40 , i.e., the order of magnitude of the estimated value τ e of the load torque applied to the engine 8 It is adapted so that the speed output is derived from the engine model. 40 , i.e., the estimated value ω e the engine speed 8 to the measured value ω m the engine speed 8 converges, and that the power output from the motor model 40, i.e., the estimated value i e of the current flowing through the motor 8 flows, to the measured value of the current flowing through the motor 8 It flows, converges. This design makes it possible to use the engine model. 40 to use for this purpose, the load torque τ e , which is on the engine 8 It works, so as to estimate that the current in the motor 8 flows, and the rotational speed ω m of the engine 8 will be obtained if the connection voltage V m to the engine 8 is created.

[0055] Fig. Figure 8 shows another example of a design for a load torque estimation circuit. 16 The load torque estimation circuit 16 from Fig. 8 is formed, an estimated value τ e of the load torque applied to the engine 8 It acts, based on the measured value of the current flowing through the motor. 8flows, as from the current sensing unit 30 recorded, and the measured value ω m the engine speed 8 , as from the speed sensor 12 The load torque estimation circuit is recorded and output. 16 from Fig. 8 features an engine model 40 , Comparator 50 and 52 and amplifier 54 and 56 , an adder 58 , amplifier 60 and 62 and an adder 64 on.

[0056] The load torque estimation circuit 16 from Fig. 8 essentially has the same components as that of the load torque estimation circuit. 16 from Fig. 7. In the load torque estimation circuit 16 from Fig. 8 becomes the measured value V m the motor's connection voltage 8 not connected to the voltage input of the motor model 40 Instead, an estimated value V is entered.e the motor's connection voltage 8 , as from the measured value of the current flowing through the motor 8 flows, and the measured value ω m the engine speed 8 calculated, at the voltage input of the motor model 40 entered. In the load torque estimation circuit 16 from Fig. 8 becomes the estimated value V e the motor's connection voltage 8 calculated by approaching Ldi / dt on the left side of mathematical expression (1) towards zero. That is, in the load torque estimation circuit 16 from Fig. 8 becomes the estimated value V e the motor's connection voltage 8 by adding together a value obtained by multiplying the measured value in the current flowing through the motor 8 flows, with the resistance R of the motor. 8 is obtained, and a value obtained by multiplying the measured value ω m the engine speed8 with the generator constant KB of the motor 8 The amount received is calculated.

[0057] It should be noted that the load torque estimation circuit 16 as a circuit that can be mounted by the controller 18 is separated, or in the control system 18 can be installed.

[0058] The mode switching unit 20 from Fig. 1 allows the user to perform a switching operation from one operating mode of the power tool to another. 2 to execute in another. The power tool 2 In the present embodiment, it is switchable between a screwdriver mode, a drill mode, and a percussion drill mode (vibration drill mode). The mode switching unit 20 It can, for example, be in the form of a rotary switch, a slide switch, or the like. The mode switching unit 20 can, for example, be located near the tool unit 4It may be located near a rear surface of the power tool. 2 (the tool unit 4 opposite side) or can be located near the battery 10 be planned.

[0059] The torque setting unit 22 allows the user to switch between activating and deactivating a torque limiting function and to adjust the inertial torque reference value τ mentioned below. ir , of the load torque reference value τ mentioned below lr and the upper limit of the load torque τ mentioned below lu to execute. The torque setting unit 22 It can, for example, be in the form of a rotary switch, a slide switch, or the like. Regarding the torque setting unit... 22 can the inertial torque reference value τ ir , the load torque reference value τlr and the upper limit of the load torque τ lu be separately adjustable, or a combination of the inertial torque reference value τ ir , of the load torque reference value τ lr and the upper limit of the load torque τ lu The torque setting unit can be selected by the user from a number of combinations that are predetermined before the product is delivered. 22 can, for example, be located near the tool unit 4 It may be located near the rear surface of the power tool. 2 (the tool unit 4 opposite side) or can be located near the battery 10 be planned.

[0060] The notification unit 24 is trained to notify the user when the control 18 the engine 8 stops or slows down. The notification unit 24This could be, for example, an LED or similar device designed to notify the user by emitting light. Alternatively, the notification unit could be... 24 It should be a buzzer or similar device designed to notify the user by producing a sound. Regarding the power tool 2 In the present embodiment, the notification unit 24 an LED. The notification unit 24 can, for example, be located near the tool unit 4 It may be located near the rear surface of the power tool. 2 (the tool unit 4 opposite side) or can be located near the battery 10 be planned.

[0061] The drive switch 26 is operated by the user. During normal operation, the motor 8 stopped when the drive switch 26 is switched off, and the engine8 is driven to rotate when the drive switch 26 is switched on.

[0062] The side handle 28 It can be solved with the power tool. 2 fastened. Even when work is performed under such a heavy load that a kickback torque from a workpiece onto the power tool occurs. 2 If the torque is greater than, for example, 40 Nm, the user can stably perform the work by gripping the power tool. 2 with both hands by using the side handle 28 carry out.

[0063] The control 18 is trained in the operation of the power tool 2 based on the measured value ω m the engine speed 8 , as from the speed sensor 12 recorded, the measured value i m of the current flowing through the motor 8 flows, as from the current sensing unit 30 recorded, and the estimated value τ eof the load torque applied to the engine 8 It acts as if by the load torque estimation circuit 16 calculated, to control. A process that is controlled by the control system. 18 The procedure is described below. Fig. 9 described.

[0064] In step S2, the control determines 18 , whether the drive switch 26 is switched on or not. When the drive switch 26 If the controller is switched off (if NO in step S2), the process proceeds to step S4. In step S4, the controller pauses. 18 , if the engine 8 is driven, the engine 8 After step S4, the process returns to step S2.

[0065] If the drive switch is in step S2 26 If the controller is enabled (if YES), the process proceeds to step S6. In step S6, the controller refers to... 18 an operating mode from the mode switching unit 20Furthermore, in step S6 the control 18 the on / off state of the torque limiting function, the moment of inertia reference value τ ir , the load torque reference value τ lr and the upper limit of the load torque τ lu from the torque adjustment unit 22 .

[0066] In step S8, the control system drives 18 the engine 8 to turn.

[0067] In step S10 the control 18 from the current sensing unit 30 the measured value of the current flowing through the motor 8 flows. Furthermore, in step S10 the control system is used. 18 the measured value V m the motor's connection voltage 8 from the voltage detection unit 32 Furthermore, in step S10 the control 18 the measured value ω m the engine speed 8 from the speed sensor 12 .

[0068] In step S12, the control system 18 from the load torque estimation circuit 16 the estimated value τ e of the load torque applied to the engine 8 It works.

[0069] In step S14 the controller calculates 18 an output torque KTi of the motor 8 by multiplying the measured value of the current flowing through the motor 8 The flow, which is referenced in step S10, with the torque constant KT, is also calculated in step S14. 18 a frictional torque Bω of the motor 8 by multiplying the measured value ω m the engine speed 8 , which is referenced in step S10, with the friction constant B.

[0070] In step S16 the controller calculates 18 an inertial torque –Jdω / dt of the motor 8 according to mathematical expression (2) by subtracting the output torque KTi of the motor 8from the estimated value τ e of the load torque applied to the engine 8 acts, and adding the frictional torque Bω of the motor 8 It should be noted here that, since the inertial torque is a force that acts at every moment in a direction opposite to the direction of acceleration and deceleration in order to maintain velocity, a negative sign is taken into account.

[0071] In step S18, the control determines 18 The process determines whether the operating mode referenced in step S6 is the screwdriver mode or not. If the operating mode is the screwdriver mode (if YES in step S18), the process proceeds to step S20. If the operating mode is not the screwdriver mode (if NO in step S18), for example, if the operating mode is the drill mode or the impact drill mode, the process proceeds to step S22.

[0072] In step S20, the controller determines 18, whether the estimated value τ e the load torque, which is referenced in step S12, is greater than the upper limit of the load torque τ lu or not. If the estimated value τ e the load torque is greater than the upper limit of the load torque τ lu (If YES in step S20), the process proceeds to step S28. If the estimated value τ e the load torque is not greater than the upper limit of the load torque τ lu (if NO in step S20), the process proceeds to step S22.

[0073] In step S22, the control determines 18 The process determines whether the torque limiting function is enabled or not. If the torque limiting function is disabled (if NO in step S22), the process returns to step S2. If the torque limiting function is enabled (if YES in step S22), the process proceeds to step S24.

[0074] In step S24, the control determines 18 , whether the inertial torque –Jdω / dt calculated in step S16 is greater than the inertial torque reference value τ ir or not. If the inertial torque –Jdω / dt is not greater than the inertial torque reference value τ ir (If NO in step S24), the process returns to step S2. If the inertial torque –Jdω / dt is greater than the inertial torque reference value τ ir (if YES in step S24), the process proceeds to step S26.

[0075] In step S26, the control determines 18 , whether the estimated value τ e the load torque estimated in step S12 is greater than the load torque reference value τ lr or not. If the estimated value τ e the load torque is not greater than the load torque reference value τ lr(If NO in step S26), the process returns to step S2. If the estimated value τ e the load torque is greater than the load torque reference value τ lr (if YES in step S26), the process proceeds to step S28.

[0076] In step S28 the control holds 18 the engine 8 Furthermore, in step S28 the control system switches on. 18 the LED lights up, which serves as the notification unit 24 serves.

[0077] In step S30 the controller waits 18 until the drive switch 26 is switched off. When the drive switch 26 If the answer is YES in step S30, the process proceeds to step S32.

[0078] In step S32 the control system switches 18 the LED turns off, which serves as the notification unit 24 It serves this purpose. After step S32, the process returns to step S2.

[0079] With the power tool 2 will the engine 8 stopped if the inertial torque –Jdω / dt calculated in step S16 is greater than the inertial torque reference value τ ir and if the estimated value τ e the load torque obtained in step S12 is greater than the load torque reference value τ lr This allows the engine to be automatically switched on. 8 to stop if an abrupt increase in load due to the occurrence of a kickback or the like causes an increase in the moment of inertia –Jdτ / dt, thus enabling the safety of the user to be ensured.

[0080] With the power tool 2 will the engine 8 not stopped if the estimated value τ e the load torque, which is referenced in step S12, is not greater than the load torque reference value τ lr, even if the inertial torque –Jdω / dt calculated in step S16 is greater than the inertial torque reference value τ ir This makes it possible to improve work efficiency by preventing the engine from 8 during light load work, where an increase in inertial torque due to an abrupt increase in load is, if anything, less of a problem for safety.

[0081] With the power tool 2 will the engine 8 stopped when the screwdriver mode is selected as the operating mode and when the estimated value τ e the load torque is greater than the upper limit of the load torque τ luThis makes it possible to achieve the effect of a screwdriver that finishes tightening a screw at a predetermined torque, as in the case where a mechanical clutch is used. Compared to a mechanical clutch, the resulting electric clutch neither produces noise during operation nor deteriorates due to wear. It should be noted that with the power tool 2 the engine 8 It will not stop if the drilling mode or the impact drilling mode is selected as the operating mode, even if the estimated value τ e the load torque is greater than the upper limit of the load torque τ lu This makes it possible to improve work efficiency by preventing the engine from 8 stops in an operating mode where the user anticipates a high load on the motor 8 will have an effect.

[0082] It should be noted that the control 18 The output torque KTi, which is calculated in step S14, can be configured with an output torque reference value τ. or to compare in step S26, instead of the estimated value τ e of the load torque with the load torque reference value τ lr to compare. In this case, if the output torque KTi is greater than the output torque reference value τ or In step S26, the process proceeds to step S28. If the output torque KTi is not greater than the output torque reference value τ or , the process returns to step S2. This design allows the output reference value τ to be determined. or instead of the load torque reference value τ lr via the torque setting unit 22 to adjust.

[0083] At the in Fig. The process shown in 9 involves the engine. 8automatically stopped according to the magnitude of the inertial torque or the load torque. Alternatively, the control can 18 be trained to operate the engine 8 to make it slower than normal, instead of the engine 8 to stop. A process controlled by the system. 18 In such a case, the procedure is described below. Fig. 10 described.

[0084] In step S42, the control determines 18 , whether the drive switch 26 is switched on or not. When the drive switch 26 If the controller is switched off (if NO in step S42), the process proceeds to step S44. In step S44, the controller pauses. 18 , if the engine 8 is driven, the engine 8 on. Furthermore, in step S44, if the LED, which serves as the notification unit, switches on. 24 serves, is switched on, the control 18 the LED, which serves as the notification unit24 serves its purpose. After step S44, the process returns to step S42.

[0085] If the drive switch is in step S42 26 If the controller is enabled (if YES), the process proceeds to step S46. In step S46, the controller refers to... 18 an operating mode from the mode switching unit 20 Furthermore, in step S46 the control 18 the on / off state of the torque limiting function, the inertial torque reference value τ ir , the load torque reference value τ lr and the upper limit of the load torque τ lu , from the torque setting unit 22 .

[0086] In step S48, the control system drives 18 the engine 8 to turn.

[0087] In step S50, the control system refers to 18 from the current sensing unit 30 the measured value of the current flowing through the motor 8flows. Furthermore, in step S50, the control system takes into account... 18 the measured value V m the motor's connection voltage 8 from the voltage detection unit 32 Furthermore, in step S50 the control 18 the measured value ω m the engine speed 8 from the speed sensor 12 .

[0088] In step S52, the control system refers 18 from the load torque estimation circuit 16 the estimated value τ e of the load torque applied to the engine 8 It works.

[0089] In step S54 the controller calculates 18 an output torque KTi of the motor 8 by multiplying the measured value of the current flowing through the motor 8 The flow, which is referenced in step S50, with the torque constant KT, is also calculated in step S54. Furthermore, the control system calculates the torque in step S54. 18 a frictional torque Bω of the motor 8by multiplying the measured value ω m the engine speed 8 , which is referenced in step S50, with the friction constant B.

[0090] In step S56 the controller calculates 18 an inertial torque –Jdω / dt of the motor 8 according to mathematical expression (2) by subtracting the output torque KTi of the motor 8 from the estimated value τ e of the load torque applied to the engine 8 acts, and adding the frictional torque Bω of the motor 8 It should be noted here that, because the inertial torque is a force that acts at every moment in a direction opposite to the direction of acceleration and deceleration in order to maintain velocity, a negative sign is taken into account.

[0091] In step S58, the control determines 18The process determines whether the operating mode referenced in step S46 is the screwdriver mode or not. If the operating mode is the screwdriver mode (if YES in step S58), the process proceeds to step S60. If the operating mode is not the screwdriver mode (if NO in step S58), for example, if the operating mode is the drill mode or the impact drill mode, the process proceeds to step S62.

[0092] In step S60, the controller determines 18 , whether the estimated value τ e the load torque, which is referenced in step S52, is greater than the upper limit of the load torque τ lu or not. If the estimated value τ e the load torque is greater than the upper limit of the load torque τ lu (If YES in step S60), the process proceeds to step S68. If the estimated value τ e the load torque is not greater than the upper limit of the load torque τ lu(if NO in step S60), the process proceeds to step S62.

[0093] In step S62, the controller determines 18 The process checks whether the torque limiting function is enabled or not. If the torque limiting function is disabled (if NO in step S62), the process proceeds to step S70. If the torque limiting function is enabled (if YES in step S62), the process proceeds to step S64.

[0094] In step S64, the control determines 18 , whether the inertial torque –Jdω / dt calculated in step S56 is greater than the inertial torque reference value τ ir or not. If the inertial torque –Jdω / dt is not greater than the inertial torque reference value τ ir (If NO in step S64), the process proceeds to step S70. If the inertial torque –Jdω / dt is greater than the inertial torque reference value τ ir(if YES in step S64), the process proceeds to step S66.

[0095] In step S66, the control determines 18 , whether the estimated value τ e the load torque estimated in step S52 is greater than the load torque reference value τ lr or not. If the estimated value τ e the load torque is not greater than the load torque reference value τ lr (If NO in step S66), the process proceeds to step S70. If the estimated value τ e the load torque is greater than the load torque reference value τ lr (if YES in step S66), the process proceeds to step S68.

[0096] In step S68, the control system brakes. 18 , if the engine 8 rotates at normal speed, the engine 8 off. Furthermore, in step S68, if the LED, which serves as the notification unit, switches off. 24serves, is switched off, the control 18 the LED, which serves as the notification unit 24 serves a purpose. After step S68, the process returns to step S42.

[0097] In step S70, the controller initiates 18 , if the engine 8 rotates at a lower speed than normal, the engine 8 to return to the normal rotational speed. Furthermore, in step S70, if the LED, which serves as the notification unit, is lit, it switches off. 24 serves, is switched on, the control 18 the LED, which serves as the notification unit 24 serves its purpose. After step S70, the process returns to step S42.

[0098] It should be noted that the control 18 The output torque KTi, calculated in step S54, can be configured with an output torque reference value τ. or to compare in step S66, instead of the estimated value τ eof the load torque with the load torque reference value τ lr to compare.

[0099] In the embodiment described above, the measured value ω m the engine speed 8 , as from the speed sensor 12 measured, for control 18 to calculate the frictional torque Bω of the motor 8 used. Unlike the embodiment described above, the load torque estimation circuit can be used. 16 , which e.g. in Fig. As shown in section 3, the motor model should be designed so that the rotational speed output is obtained from the motor model. 40 to the control 18 than the estimated value ω e the engine speed 8 is output and the control 18 the friction torque Bω of the motor 8 from the estimated value ω e the engine speed 8 calculated.

[0100] In the embodiment described above, the measured value is of the current flowing through the motor. 8 flows, as from the current sensing unit 30 measured, for control 18 to calculate the output torque KTi of the motor 8 used. Unlike the embodiment described above, the load torque estimation circuit can be used. 16 , which e.g. in Fig. As shown in section 6, the motor model should be designed so that the current output from the motor model 40 to the control 18 than the estimated value i e of the current flowing through the motor 8 flows, is output and the control 18 the output torque KTi of the motor 8 from the estimated value i e of the current flowing through the motor 8 flows, calculated. QUOTES INCLUDED IN THE DESCRIPTION

[0101] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0102] JP 2013-241199

[0001] WO 2012 / 108246 A1

[0003]

Claims

[1] Power tool ( 2 ) with: an engine ( 8 ); an output torque calculation unit ( 18 ), which is trained to produce an output torque of the motor ( 8 ) based on a current (i) that flows through the motor ( 8 ) flows, to calculate; a friction torque calculation unit ( 18 ), which is designed to generate a frictional torque of the motor ( 8 ) based on a rotational speed (ω) of the motor ( 8 to calculate; a load torque estimation unit ( 16 ), which is designed to produce a load torque (τ) that is applied to the motor ( 8 ) to estimate; an inertial torque calculation unit ( 18 ), which is designed to calculate an inertial torque based on the output torque, the friction torque, and the load torque (τ); and a motor braking unit ( 18 ), who is trained to operate the engine (8 ) to stop or decelerate when the inertial torque is greater than an inertial torque reference value (τ ir ). [2] Power tool ( 2 ) as in claim 1, wherein the load torque estimation unit ( 16 ) is designed to determine the load torque (τ) based on at least two measurements from a single measurement (i m ) of the current (i) flowing through the motor ( 8 ) flows, a measured value (V m ) a connection voltage (V) of the motor ( 8 ) and a measured value (ω m ) the rotational speed (ω) of the motor ( 8 to estimate. [3] Power tool ( 2 ) as in claim 1 or 2, further comprising a speed estimation unit configured to measure the speed (ω) of the motor ( 8 ) based on a measured value (i m ) of the current (i) flowing through the motor ( 8 ) flows, and a measured value (V m ) a connection voltage (V) of the motor ( 8 to estimate. [4] Power tool ( 2 ) as in one of claims 1 to 3, wherein the motor braking unit ( 18 ) is trained to operate the engine ( 8 ) not to stop or decelerate when the load torque (τ) is less than a load torque reference value (τ lr ) or the output torque is less than an output torque reference value (τ) or ) is, even if the moment of inertia is greater than the reference value for the moment of inertia (τ) ir ). [5] Power tool ( 2 ) as in claim 4, wherein a combination of the load torque reference value (τ lr ) or the output torque reference value (τ or ) and the inertial torque reference value (τ ir ) can be selected by a user from a plurality of predetermined combinations. [6] Power tool ( 2 ) as in any one of claims 1 to 5, furthermore with a removable side handle ( 28 ). [7] Power tool ( 2 ) as in any one of claims 1 to 6, wherein the motor ( 8 ) is a brushless motor. [8] Power tool ( 2 ) as in any one of claims 1 to 7, wherein the motor braking unit ( 18 ) is further trained to operate the engine ( 8 ) to stop or brake if the load torque (τ) is greater than an upper limit of the load torque (τ lu ). [9] Power tool ( 2 ) as in claim 8, furthermore with a mode switching unit ( 20 ), who is trained to operate the power tool in a specific mode ( 2 ) to select from a plurality of operating modes, in which the engine braking unit ( 18 ) is trained to operate the engine ( 8 ) not to stop or decelerate when a specific operating mode is selected, even if the load torque (τ) is greater than the upper limit of the load torque (τ lu ). [10] Power tool ( 2 ) as in any one of claims 1 to 9, further comprising: a notification unit ( 24 ), which is trained to notify a user when the motor braking unit ( 18 ) the engine ( 8 ) stops or slows down.