Hand-operated, motor-driven tool with motor control circuit

Abstract

Hand-operated, motor-driven tool with motor control circuit. The invention relates to a hand-operated motor-driven working device having a user-operated control unit and a motor control circuit. According to the invention, the motor control circuit comprises a control unit which is configured to receive a motor operating signal (BS) from the operating unit and to generate a motor control signal (SS) as a function thereof, a motor function enabling unit which is configured to generate a motor function enabling signal as a function of a supplied enabling control signal (FS), and a redundancy control circuit (4) designed as a discrete electrical circuit which is configured to receive the motor operating signal (BS) and the motor control signal (SS) and to generate the enabling control signal (FS) as a function thereof. Use e.g. for ground-guided or hand-carried garden or forestry equipment with battery-powered electric motor or with combustion engine.

Description

The present invention relates to a manually operated power tool having a user operated operation unit and a motor control circuit. The working device can be, in particular, a ground-guided or hand-carried garden or forest device with an electric motor with battery power or with an internal combustion engine, for example a power saw, a grinder, a motor snow or a hedge trimmer.In working tools of this type, as in many other devices, redundant design of certain device components plays an important role, for example for increasing functional or operational safety and / or as a protective measure against undesired consequences of a malfunction of the relevant device component. The redundant design of a device component is often also a rule and thus a necessary measure for putting the device into traffic or putting the device into operation.For example, for such redundancy measures, mention may be made of laid-open specification EP 2 292 383 A2, which discloses redundant overspeed protection for a power tool, laid-open specification DE 10 2015 212 934 A1, which discloses redundant sensor signal evaluation by means of corresponding comparator circuits, and laid-open specification DE 10 2013 102 785 A1, which discloses a redundant embodiment of a vehicle collision determination apparatus.Patent specification EP 3 310 534 B1 discloses a hand-held machine tool having an electric motor, a user-operated main switch, a motor controller sensing the latter and a start-up lock which determines the chronological sequence of the provision of a power supply and the actuation of the main switch and, depending on this, outputs an unlocking signal or a locking signal to the motor controller. The motor controller activates the electric motor only when the main switch is operated and receives the unlock signal.The patent specification DE 101 39 616 B4 discloses an electronic control module having an emergency redundancy function, in particular for use in a vehicle computer, having a microcontroller, a monitoring microcontroller and a control circuit. If the monitoring microcontroller detects a failure of the microcontroller, it sends an emergency signal to the control circuit, which thereupon no longer allows control signals of the microcontroller to pass through to a load, but instead signals input externally via switches.The invention is based as a technical problem on the provision of a manually operated, motor-operated working device of the type mentioned at the beginning, which contains an embodiment of the motor control circuit which is advantageous compared to the prior art, in particular with regard to implementation complexity and / or functionality.The invention solves this problem by providing a manually operated power tool with the features of claim 1. This also includes in particular all embodiments of the invention which result from the combinations of features defined by the references in the dependent claims.In the working device according to the invention, the motor control circuit comprises a control unit, a motor function enabling unit and a redundancy control circuit. The control unit is configured to receive a motor control signal from the control unit and to generate a motor control signal depending thereon. The control unit is usually embodied in integrated circuit technology or as a microchip or microcontroller module and functions, for example, as a central engine control unit of the working device. The motor function enabling unit is configured to generate a motor function enabling signal in response to a supplied enabling control signal. The redundancy control circuit is designed as a discrete electrical circuit and is configured to receive the motor control signal and the motor control signal and to generate the enable control signal depending thereon.It is evident that, in particular, the discrete embodiment of the redundancy control circuit makes it possible to achieve advantages with regard to implementation complexity and functionality of the motor control circuit having the redundancy control circuit, especially also in comparison with an alternative embodiment of a functionally similar redundancy control circuit as an integrated circuit or as a chip-integrated control circuit and / or in parts or completely in software. This comparatively simple and cost-effective design of the redundancy control circuit as a discrete electrical circuit can be used advantageously, for example, in ground-guided or hand-carried garden or forest devices with an electric motor powered by an accumulator, such as for power saws, hedge trimmers and motors, but also for other manually operated power tools, such as grinders, etc.In particular, the redundancy control circuit is used in the present case to provide a redundant and thus safety-enhancing evaluation of the motor control signal generated by the control unit as a function of the received motor control signal. In other words, the redundancy control circuit provides redundancy for the control unit specifically with respect to the evaluation of the motor control signal. The redundancy control circuit accordingly supplies the motor function enabling unit with the enabling control signal as a function of this redundant and thus safety-enhancing evaluation of the motor control signal on the basis of the motor control signal supplied to it in parallel with the control unit of the motor control circuit. The motor function enabling unit generates the motor function enabling signal in dependence on the enabling control signal generated in such a redundantly safety-enhancing manner, which initiates the enabling of a predefined motor function. This motor function can be, for example, a switching-on or a power setting of the battery-powered electric motor or internal combustion engine of the working device, alternatively another function for this motor.The redundancy control circuit comprises a comparator circuit part which receives the motor control signal on the input side, a threshold circuit part which is connected downstream of the comparator circuit part and receives an output signal of the comparator circuit part, and a logic circuit part which receives the motor control signal and an output signal of the threshold circuit part and outputs the enable control signal. This represents a favorable embodiment of the redundancy control circuit with regard to minimizing the circuit realization cost. The redundancy control circuit can use the comparator circuit part to assess the input motor control signal on the input side, the downstream threshold circuit part enables advantageous further processing of the output signal supplied by the comparator circuit part, for example also for implementing a suitable hysteresis behavior, and the output logic circuit part enables simple production of the enable control signal in terms of circuitry, assessing the motor control signal on the basis of the output signal supplied by the threshold circuit part.In a further development of the invention, the comparator circuit part has an operational amplifier. Such use of an operational amplifier for a comparator circuit is a measure typically advantageous for many applications.In one embodiment of the invention, the motor control signal is an active high signal applied to an inverting input of the operational amplifier or an active low signal applied to a non-inverting input of the operational amplifier. The motor operating signal, which is embodied, for example, as a binary digital signal, can thus be fed on the input side to the operational amplifier in a fitting manner.In one embodiment of the invention, the redundancy control circuit has a level hysteresis circuit path between an input side of the operational amplifier and an output side of the threshold circuit part. This represents an embodiment of the redundancy control circuit which is advantageous for a desired hysteresis behavior with respect to the signal levels involved.In one embodiment of the invention, the comparator circuit part comprises a prefilter circuit connected upstream of the operational amplifier. The prefilter circuit can fulfil a debouncing function for the motor control signal supplied to the operational amplifier in a manner known per se.In one embodiment of the invention, the comparator circuit part comprises a time delay circuit connected downstream of the operational amplifier. The time delay circuit provides a desired time delay for the processed motor control signal as needed.In a further embodiment of the invention, the time delay circuit has an activation delay part with a predefinable activation time constant and / or a deactivation delay part with a predefinable deactivation time constant. Depending on the need and application, the corresponding embodiment of the time delay circuit enables a desired time delay for the processed motor control signal in the case of the switching on or switching off of this signal with the aid of the relevant switching-on delay part or switching-off delay part. In the present case, activation is understood to mean a signal state of the motor control signal requesting activation of the relevant motor function, while deactivation is understood to mean the signal state of the motor control signal requesting deactivation of this motor function.In a further embodiment of the invention, the switch-on time constant is less than 100 ms, in particular less than 6 ms. It is found that this selection of the switch-on time constant for many applications results in an optimum switch-on delay time for the motor control signal.In a further embodiment of the invention, the switch-off time constant is greater than 100 ms, in particular greater than 180 ms and less than 220 ms. It is found that this selection of the shutdown time constant results in an optimal delay of the motor control signal in its shutdown signal state for many applications.In a further embodiment of the invention, the switch-on time constant is smaller than the switch-off time constant. This selection of the time delay for the connection which is shorter than the disconnection has proven to be favorable for many applications.In a development of the invention, the motor control circuit comprises a status information circuit path which leads from an output side of the redundancy control circuit to an input side of the control unit. This measure enables a status feedback to be provided from the redundancy control circuit to the control unit, so that the control unit can use this status feedback as required.Advantageous embodiments of the invention are illustrated in the drawings. These and other embodiments of the invention will be explained in more detail below. The following are shown: FIG. 1 shows a side view of a power saw as an example of a manually operated power tool according to the invention, which has a user-operated operating unit and a motor control circuit with a discrete redundancy control circuit, FIG. 2 is a block diagram of the operating unit and the motor control circuit, FIG. 3 is a circuit diagram of a first embodiment of the discrete redundancy control circuit, FIG. 4 is a circuit diagram of a second embodiment of the discrete redundancy control circuit, FIG. 5 is a circuit diagram of a third embodiment of the discrete redundancy control circuit, FIG. 6 is a circuit diagram of a fourth embodiment of the discrete redundancy control circuit; and FIG. 7 is a circuit diagram of a fifth embodiment of the discrete redundancy control circuit.As illustrated in the figures on the basis of the embodiments shown there, the manually operated power-operated working device according to the invention comprises a user-operated operating unit 1 and a motor control circuit. The motor control circuit comprises, as illustrated in the block diagram of FIG. 2, a control unit 2, a motor function enabling unit 3 and a redundancy control circuit 4. the control unit 2 is configured to receive a motor control signal BS from the control unit 1 and to generate a motor control signal SS depending thereon. The motor function enabling unit 3 is configured to generate a motor function enabling signal MS in dependence on a supplied enabling control signal FS. The redundancy control circuit 4 is designed as a discrete electrical circuit and is configured to receive the motor control signal BS and the motor control signal SS and to generate the enable control signal FS as a function of the received motor control signal BS and the received motor control signal SS.As representative of many other working tools according to the invention, FIG. 1 shows a power saw 15 with an electric motor fed by an accumulator as working tool. In this case, the operating unit 1 can comprise, in a manner known per se, for example a throttle lever switch or engine power switch and optionally additionally an on / off switch or engine start switch and / or an unlocking switch which is to be actuated in order to cancel a lock for the engine power switch. The engine operation signal BS may accordingly be, for example, an engine start signal from the engine start switch or a power setting signal from the engine power switch in this case.FIGS. 3 to 7 illustrate various circuit-related implementations for the discrete redundancy control circuit 4 by way of example, these implementations being chosen differently depending on the type of motor control signal BS supplied and depending on optional functions desired in each case.The redundancy control circuit 4 comprises an input-side comparator circuit part 5, a threshold value circuit part 6 connected downstream thereof and an output-side logic circuit part 7. The threshold circuit part 6 receives an output signal KA of the comparator circuit part 5. the logic circuit part 7 receives the motor control signal SS and an output signal SA of the threshold circuit part 6, and outputs the enable control signal FS.In advantageous embodiments, the comparator circuit part 5, as in the embodiments shown, has an operational amplifier 8.In corresponding implementations, the motor control signal BS is an active high signal applied to an inverting input of the operational amplifier 8, i.e. a preferably binary signal requesting motor function activation when it is at a high level. In FIGS. 3, 4 and 7, a motor operating signal BS1 is shown, which is such an active high signal applied to the inverting input of the operational amplifier 8.In alternative embodiments, the motor control signal BS is a preferably binary active low signal which is applied to a non-inverting input of the operational amplifier 8. FIGS. 5 to 7 show a motor control signal BS2 which is an active low signal of this kind which is applied to the noninverting input of the operational amplifier 8.As FIGS. 3 to 7 illustrate, the discrete redundancy control circuit 4 is in each case suitably adapted in its design to whether the supplied motor control signal BS is an active high signal, in this case the signal BS 1, or an active low signal, in this case the signal BS 2, wherein FIG. 7 shows a circuit realization in which both motor control signals, the active high signal BS 1 and the active low signal BS 2, are supplied to the redundancy control circuit 4.In advantageous embodiments, the redundancy control circuit 4 has a level hysteresis circuit path 13 between an input side of the operational amplifier 8 and an output side of the threshold value circuit part 6. Such a level hysteresis circuit path 13 is provided in the circuit realizations according to FIGS. 4, 6 and 7.In corresponding implementations, the comparator circuit part 5, as in the embodiments shown, comprises a prefilter circuit 8 connected upstream of the operational amplifier 8. in FIG. 7, the prefilter circuit 9 is explicitly marked with dashed lines; in FIGS. 3 to 6, it is likewise present in different circuit implementations.In advantageous implementations, the comparator circuit part 5 comprises a time delay circuit 10 connected downstream of the operational amplifier 8, which is also present in each of the embodiments of the redundancy control circuit 4 according to FIGS. 3 to 7 and is marked explicitly framed by dashed lines only in FIG. 7 for the sake of simplicity.In corresponding implementations, the time delay circuit 10, as in the examples shown, has an activation delay part 11 with a predefinable activation time constant. In FIG. 7, the switch-on delay part 11 is again marked with dashed lines in a boxed manner.In corresponding implementations, the time delay circuit 10, as in the examples shown, has a switch-off delay part 12 with a predefinable switch-off time constant. In FIG. 7, the shutdown delay part 12 is again marked with dashed lines in a box.In corresponding circuit-related designs, the switch-on time constant provided by the switch-on delay part 11 is smaller than the switch-off time constant provided by the switch-off delay part 12. Specifically, the switch-on time constant is less than 100 ms, preferably less than 6 ms, in corresponding implementations. In preferred implementations, the switch-off time constant is greater than 100 ms, wherein it can be in particular between 180 ms and 220 ms.In advantageous embodiments, the motor control circuit has a status information circuit path 14 which leads from an output side of the redundancy control circuit 4 to an input side of the control unit 2. This status information circuit path 14 is present, for example, in the circuit-related embodiments of the redundancy control circuit 4 according to FIGS. 4, 6 and 7.FIGS. 3 to 7 show the circuit configuration of the redundancy control circuit 4 in various exemplary embodiments, which will be discussed in more detail below.FIG. 3 shows the redundancy control circuit 4 in a basic version as is suitable for the active high motor control signal BS 1. The motor operating signal BS1 is applied via an input resistor R1 to the inverting input of the operational amplifier 8, which is connected via a resistor R2 to a ground potential GND.The noninverting input of the operational amplifier 8 is connected to the center tap of a voltage divider having two resistors R3 and R4, which is looped in between the ground potential GND and a supply voltage VCC. The three resistors R 1, R 2, R 3 are in this case components of the prefilter circuit 9.The operational amplifier 8 is connected for power supply to the ground potential GND and a voltage terminal VCCLS, as usual. An output signal of the operational amplifier 8 fed via a resistor R5 forms the output signal KA of the comparator circuit part 5; a capacitor C1 looped between the output of the comparator circuit part 5 and the supply voltage VCC forms, together with the resistor R5, the turn-on delay part 11 of the time delay circuit 10; in parallel with the capacitor C1, a resistor R6 is looped between the output of the comparator circuit part 5 and the supply voltage VCC. It constitutes together with the capacitor C1 the turn-off delay portion 12 of the time delay circuit 10 of the comparator circuit portion 5.In all the embodiments shown, the threshold value circuit part 6 contains an operational amplifier 16 which is arranged quasi cascaded to the operational amplifier 8, wherein the output signal KA of the comparator circuit part 5 is applied to the inverting input of the operational amplifier 16. The noninverting input of the operational amplifier 16 is connected to a center tap of a voltage divider made up of two resistors R7 and R8 between the ground potential GND and the supply voltage VCC.An output of the operational amplifier 16 constitutes the output SA of the threshold circuit portion 6, and the output of the operational amplifier 16 is fed back to the noninverting input of the operational amplifier 16 through a resistor R9. Furthermore, the output of the operational amplifier 16 and thus of the threshold circuit part 6 is connected to the supply voltage VCC via a resistor R 10.The logic circuit part 7 comprises in all the embodiments shown a transistor 17, which may be, for example, a bipolar transistor such as an IGBT-type one. The output signal SA of the threshold circuit part 6 is applied to a base terminal of the transistor 17. To an emitter terminal of the transistor 17, the motor control signal SS generated by the control unit 2 is applied via a resistor R11. The enable control signal FS is output at a collector terminal of the transistor 17 as an output signal of the logic circuit part 7 and thus of the redundancy control circuit 4. The transistor switch 17 forms virtually an AND logic which ensures that the enable control signal FS is provided only if this is indicated by both the supplied motor control signal SS of the control unit 2 and by the output signal SA supplied by the redundancy control circuit 4.FIG. 4 shows the redundancy control circuit 4 in an embodiment which is based on that of FIG. 3 and contains some additional, optional components. With the exception of the additional components explained below, reference can thus be made to the above explanations relating to FIG. 3 for the circuit embodiment of FIG. 4.The circuit embodiment of FIG. 4 includes, in addition to that of FIG. 3, in the input-side part of the redundancy control circuit 4, a capacitor C 2 connected in parallel with the resistor R 2 and a capacitor C 3 connected in parallel with the voltage dividing resistor R 3. The capacitors C2 and C3 form optional components for the prefilter circuit 9.Furthermore, the circuit embodiment of FIG. 4 includes a resistor R 12 which connects the noninverting input of the operational amplifier 8 to the output of the threshold circuit part 6 and thereby forms the level hysteresis circuit path 13.In addition, in the circuit configuration of FIG. 4, the threshold circuit part 6 has a lead-out from the output of the operational amplifier 16 via a resistor R13. This output functions as the status information circuit path 14, via which corresponding status information can be supplied to the control unit 2 from the redundancy control circuit 4.FIG. 5 shows the redundancy control circuit in a basic embodiment as is suitable for processing the active low motor control signal BS 2. Insofar as identical or functionally equivalent circuit components as in FIGS. 3 and 4 are used in this case, reference is made to the explanations relating to FIGS. 3 and 4 above in this regard in order to avoid repetitions.In the circuit embodiment of FIG. 5, the motor control signal BS2 is applied via a resistor R14 to the noninverting input of the operational amplifier 8. The inverting input of the operational amplifier 8 is connected in this case to the center tap of a voltage divider with two resistors R15 and R16 between the ground potential GND and the supply voltage VCC. In this respect, the prefilter circuit 9 is consequently also modified with respect to the embodiments of FIGS. 3 and 4.FIG. 6 shows a circuit embodiment based on that of FIG. 5 and having additional components analogous to those in the circuit of FIG. 4. Specifically, the circuit of FIG. 6 includes the capacitor C2 between the inverting input of the operational amplifier 8 and the ground potential GND and the capacitor C3 between the noninverting input of the operational amplifier 8 and the ground potential GND as respective constituent elements of the prefilter circuit 9.FIG. 7 shows the redundancy control circuit 4 in a circuit implementation which is suitable for processing or evaluating both the active-high motor control signal BS 1 and the active-iow motor control signal BS 2 and for this purpose combines the corresponding circuit components of the embodiments according to FIGS. 4 to 6 in a suitable manner. Starting from the circuit realization according to FIG. 6, for example, the circuit embodiment according to FIG. 7 additionally includes the voltage divider having the resistors R 3 and R 4, at the center tap of which the noninverting input of the operational amplifier 8 is present, wherein the voltage divider resistor of the other voltage divider, at the center tap of which the inverting input of the operational amplifier 8 is present, corresponds to the resistor R 15 of the circuits according to FIGS. 5 and 6 and to the resistor R 2 of the circuits according to FIGS. 3 and 4.As the exemplary embodiments shown and the further exemplary embodiments explained above make clear, the invention advantageously provides a manually operated power tool in which the motor control circuit has the redundancy control circuit in redundancy with the usually complex control unit, which is embodied with a greater range of functions, as an electrical circuit advantageously embodied simply using discrete circuit technology. This can save significant production effort compared to a duplicated provision of two control units, usually implemented in an integrated design or as microchips or microcontrollers, in the manner of the single control unit in the present case. The redundancy control circuit can be designed specifically to fulfil the functions required for the redundant evaluation of the motor control signal supplied by the operating unit and can be limited thereto without having to fulfil the additional functions as are typically required for the control unit which is usually used in such working tools as a central device control unit or a controller unit manufactured in integrated circuit technology.

Claims

Manually operated power-operated working device, in particular ground-guided or hand-carried garden or forest device with an electric motor supplied with an accumulator or with an internal combustion engine, wherein the working device has a user-operated operating unit (1) and a motor control circuit, wherein the motor control circuit comprises: - a control unit (2) which is configured to receive a motor operating signal (BS) from the operating unit and to generate a motor control signal (SS) as a function thereof, - a motor function enabling unit (3) which is configured to generate a motor function enabling signal (MS) as a function of a supplied enabling control signal (FS), and - a redundancy control circuit (4) which is designed as a discrete electrical circuit, which is configured to receive the motor control signal (BS) and the motor control signal (SS) and to generate the enable control signal (FS) in a manner dependent thereon, wherein the redundancy control circuit (4) comprises a comparator circuit part (5) which receives the motor control signal (BS) on the input side, a threshold value circuit part (6) which is connected downstream of the comparator circuit part (5) and receives an output signal (KA) of the comparator circuit part (5), and a logic circuit part (7) which receives the motor control signal (SS) and an output signal (SA) of the threshold value circuit part (6) and outputs the enable control signal (FS).The working implement according to claim 1, wherein the comparator circuit part (5) includes an operational amplifier (8).Working implement according to claim 2, wherein the motor operating signal (BS) is an active high signal applied to an inverting input of the operational amplifier (8) or an active low signal applied to a non-inverting input of the operational amplifier (8).The working implement according to claim 2 or 3, wherein the redundancy control circuit (4) has a level hysteresis circuit path (13) between an input side of the operational amplifier (8) and an output side of the threshold value circuit part (6).Working implement according to one of Claims 2 to 4, wherein the comparator circuit part (5) comprises a prefilter circuit (9) connected upstream of the operational amplifier (8).Working implement according to one of Claims 2 to 5, wherein the comparator circuit part (5) comprises a time delay circuit (10) connected downstream of the operational amplifier (8).Working implement according to claim 6, wherein the time delay circuit (10) has an activation delay part (11) with a predeterminable activation time constant and / or a deactivation delay part (12) with a predeterminable deactivation time constant.Working implement according to claim 7, wherein - the switch-on time constant is smaller than the switch-off time constant and / or - the switch-on time constant is smaller than 100 ms and / or - the switch-off time constant is larger than 100 ms, in particular larger than 180 ms and smaller than 220 ms.The implement of claim 8, wherein the switch-on time constant is less than 6 ms.The working implement according to any one of claims 1 to 9, wherein the motor control circuit includes a status information circuit path (14) leading from an output side of the redundancy control circuit (4) to an input side of the control unit (2).

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