FR2889895A1 - TORQUE CONTROL DEVICE FOR ELECTRIC TOOLS - Google Patents

Abstract

A torque control device for a power tool has a switching circuit (10), a voltage sensing circuit (30), a torque sensing circuit (40), and a processor (20). The switching circuit (10) is connected between a motor of the power tool and a DC voltage source. The voltage detection circuit (30) detects a change in voltage or current of the motor. The torque detection circuit (40) based on the detected voltage or current variation data outputs a real torque value of the motor. The processor (20) compares the actual torque value with a default value to determine whether or not the actual torque is greater than the default. If this is the case, the switching circuit (10) is closed by the processor (20) to prevent the motor from being damaged.

Description

TORQUE CONTROL DEVICE FOR TOOLS

ELECTRICAL

  The present invention relates to a torque control device, and more particularly to a torque control device for power tools, wherein the control device can automatically interrupt power supply of the power tools if a detected actual torque is greater than one. default torque value.

  Power tools commonly have an electric motor for driving a tool head, thereby helping an operator to easily perform operations such as screwing or drilling. Each kind of tool head can support a particular torque corresponding to a target object to be driven. Therefore, the torque generated by the power tools must be adjustable to suit different target objects. If the torque exceeds a tolerable range that the tool head can withstand, this tool head will be temporarily disengaged from the motor to prevent possible damage to the tool head and motor.

  The default torque setting can be made by mechanically varying the compression range of a spring installed in power tools. The tool head is driven by the motor as long as the torque is within the default value. However, the use of the spring to adjust the torque mechanically and to obtain a precise default value are both very difficult. In addition, even when the tool head has been temporarily disengaged under the motor, the motor running empty consumes power continuously.

  Therefore, in accordance with the present invention, there is provided a torque control device for power tools to limit or overcome the problem mentioned above.

  An object of the present invention is to provide a torque control device for power tools, in which a default torque can be accurately adjusted. If the actual torque value of a power tool motor is greater than the default value, the motor power supply may be interrupted to protect the motor.

  To achieve the above object, the present invention relates to a torque control device for a power tool having a motor powered by a DC voltage source, the torque control device being characterized in that it comprises: a switching circuit connected between the motor and the DC voltage source; a processor with an output terminal connected to the switching circuit for switching on / off the switching circuit; a voltage detection circuit having an input terminal connected between the motor and the DC voltage source for detecting voltage variation data of the motor; a torque detection circuit connected between the voltage detection circuit and the processor, wherein the torque detection circuit produces a motor torque value on the basis of the voltage variation data, the motor torque value. being issued to the processor; and - a torque control unit connected to the processor, in which a default torque is set in the processor by the torque control unit.

  A torque control device for a power tool according to the invention therefore has a switching circuit, a voltage detection circuit, a torque detection circuit and a processor. The switching circuit is connected between a motor of the power tool and a DC voltage source. The voltage detection circuit detects a variation in voltage or current of the motor. The torque detection circuit based on the detected voltage or current variation data outputs a real torque value of the motor. The processor compares the actual torque value with a default value to determine whether or not the actual torque is greater than the default. If this is the case, the switching circuit is closed by the processor to prevent the motor from being damaged.

  A torque control device according to the invention may comprise: a switching circuit which is connected between the motor and the DC voltage source; a processor with an output terminal which is connected to the switching circuit to turn on or off the switching circuit; a voltage detection circuit having an input terminal connected between the motor and the DC voltage source for detecting motor voltage change data; a torque detection circuit connected between the voltage detection circuit and the processor for producing a motor torque value to be transmitted to the processor based on the voltage change data; a torque setting unit which is connected to the processor to provide a default torque value to the processor; a high voltage protection circuit connected between the voltage detection circuit and the processor and comprising a second operational amplifier having: two input terminals which are respectively connected to the voltage detection circuit and to a reference high voltage; and an output terminal which is connected to the processor; a low voltage protection circuit connected between the voltage detection circuit and the processor and comprising an operational amplifier having: two input terminals which are respectively connected to the voltage detection circuit and to a reference low voltage ; and - an output terminal connected to the processor; and a display device connected to the processor to show the default torque.

  The switching circuit may comprise: - a control transistor having a base connected to the processor through a resistor, a collector and an emitter; and a switching transistor having a gate connected to the collector, a source and a drain with the source and the drain respectively connected to the motor and the DC voltage source.

  The voltage detection circuit may comprise a voltage divider circuit formed by a first resistor and a second resistor connected in series, a first terminal of the first resistor being connected to the DC voltage source and the switching circuit, and a second terminal of the first resistor connected to the second resistor being coupled to the protection circuit against a high voltage.

  The torque detection unit may comprise a first RC circuit and a first operational buffer amplifier.

  In a first embodiment of the present invention, the torque control unit may comprise: a switch having multiple nodes; and a torque setting circuit formed by multiple resistors, wherein each resistor is connected to a respective node of the switch and to a respective input terminal of the processor.

  In a second embodiment of the present invention, the torque control unit may comprise: a rheostat; and a torque control circuit formed by an RC circuit and a fourth operational amplifier, wherein the fourth operational amplifier has an input terminal connected to the RC circuit and has an output terminal connected to the processor.

  A torque control device according to the invention may comprise: a switching circuit which is connected between the motor and the DC voltage source and comprising: - a control transistor having a base, a collector and an emitter; and - a switching transistor having a gate connected to the collector, and a source and a drain respectively connected to the motor and to the DC voltage source; a processor with an output terminal which is connected to the base of the control transistor of the switching circuit to turn on or off the switching circuit; a high voltage protection circuit which is connected to the processor; a voltage detection circuit having a voltage divider circuit formed by a first resistor and a second resistor connected in series, wherein: a first terminal of the first resistor is connected to the DC voltage source and the switching circuit; and - a second terminal of the first resistor connected to the second resistor is connected to the high voltage protection circuit; a torque detection circuit which is connected between the voltage detection circuit and the processor to produce a motor torque value to be transmitted to the processor based on the voltage change data; and - a torque setting unit which is connected to the processor for providing a default torque value to the processor and comprising a first RC circuit and a first buffered operational amplifier.

  The high voltage protection circuit may comprise: - a second operational amplifier having: two input terminals respectively connected to the voltage detection circuit and to a reference high voltage; and - an output terminal connected to the processor; with the torque control device further comprising: - a low voltage protection circuit which is connected between the voltage detection circuit and the processor and comprising: a third operational amplifier having two input terminals respectively connected the voltage detection circuit and a reference low voltage; and - an output terminal connected to the processor; and a display device connected to the processor to show the default torque.

  To better illustrate the object of the present invention, will be described below, by way of indication and not limited to several particular embodiments with reference to the accompanying drawings.

On these drawings.

  Figure 1 is a block diagram of a torque control device according to the present invention; Figure 2 is a circuit diagram of the torque controller according to a first embodiment of the present invention; and - Figure 3 is a circuit diagram of the torque control device according to a second embodiment of the present invention.

  With reference to FIG. 1, a torque control device for power tools includes a switching circuit 10, a processor 20, a voltage sensing circuit 30, a torque sensing circuit 40, a circuit high voltage protection device 50, a low voltage protection circuit 60, a torque control unit 70 and a display device 80.

  The switching circuit 10 is connected between a motor and a DC voltage source, the DC voltage source being a battery.

  The processor 20 has a first output terminal 10 connected to the switching circuit 10 to control its open / closed states.

  The voltage sensing circuit 30 has an input terminal connected between the DC voltage source and the motor whereby changes in voltage or motor current can be detected.

  The torque detection circuit 40 is connected between the voltage detection circuit 30 and the processor 20. Based on the voltage variation and / or motor current data or their frequency varying in a unit of time, the Torque sensing circuit 40 may rely on the sensed data to generate a torque value of the motor and provide the torque value to the processor 20.

  The high voltage protection circuit 50 is connected between the voltage detection circuit 30 and the processor 20. The high voltage protection circuit 50 compares the detected voltage value from the voltage detection circuit 30 with a high voltage. reference voltage. If the detected voltage is higher than the reference high voltage, the high voltage protection circuit 50 outputs a signal to the processor 20 so that the switching circuit can be closed upon receipt of processor control.

  The low voltage protection circuit 60 is connected between the voltage detection circuit 30 and the processor 20. The low voltage protection circuit 60 compares the detected voltage value from the voltage detection circuit 30 with a low voltage reference voltage. If the detected voltage is lower than the low reference voltage, the low voltage protection circuit 60 sends a signal to the processor 20 so that the switching circuit 10 can be closed upon receipt of the command issued from the processor 20.

  The torque adjusting unit 70 is connected to the processor 20. An operator can set a default torque in the processor 20 through the torque adjusting unit 70.

  Display device 80 is connected to an output terminal of processor 20 to display the default torque level set by the operator.

  With reference to FIG. 2, the switching circuit 10 comprises a control transistor 11 and a switching transistor 12. The control transistor 11 comprises a bipolar junction transistor (BJT) with a base , a collector and a transmitter. The switching transistor 12 is a MOSFET with a gate, a source and a drain. The control transistor 11 provides its base connecting to the processor 20 through a resistor, and its collector is connected to the gate of the switching transistor 12. The drain and the source of the switching transistor 12 are respectively connected to the voltage source continuous and engine.

  When the processor 20 transmits a signal with a high voltage level to activate the control transistor 11, the switching transistor 12 is subsequently turned on, which allows the DC voltage source to supply power to the motor. . Otherwise, when the control transistor 11 is turned off, the switching transistor 12 is therefore turned off, whereby the power supply to the motor can be terminated.

  The voltage detection circuit 30 is composed of a voltage divider circuit with two resistors (R1), (R2) connected in series. A terminal of the resistor (R1) is connected to the DC voltage source and to the switching circuit 10. The other terminal of the resistor (R1) to which the resistor (R2) is connected is coupled to the protection circuit against a negative voltage. high voltage 50.

  The torque detection circuit 40 comprises an operational amplifier (U2B) and an RC circuit formed by a resistor (R3) and a capacitor (C1).

  The operational amplifier is buffered, the negative terminal and the output terminal of the operational amplifier being connected together to form a negative feedback loop.

  The high voltage protection circuit 50 is formed by an operational amplifier (U1B) which serves as a comparator. The comparator has a positive input terminal and a negative input terminal which are respectively coupled to the reference high voltage and the voltage detection circuit 30. If the output voltage of the voltage detection circuit 30 is greater than the reference high voltage, the comparator emits a signal with a low level to warn the processor 20. The processor 20 can subsequently close the switching circuit 10 to avoid possible damage.

  The low voltage protection circuit 60 is also formed by an operational amplifier (U3B) serving as a comparator. The comparator has a positive input terminal and a negative input terminal which are respectively coupled to the voltage sense circuit 30 and a reference low voltage. If the output voltage of the voltage detection circuit 30 is lower than the low reference voltage, the comparator outputs a signal with a low level to warn the processor 20. The processor 20 may subsequently close the switching circuit 10.

  The torque adjusting unit 70 includes a switch 71 having multiple nodes and a torque adjusting circuit 72. The torque adjusting circuit 72 is formed by multiple resistors. When a node in the switch 71 is selected, a respective input terminal of the processor 20 corresponding to the node represents a voltage. The processor 20 according to the voltage shown determines the torque value.

  The display device 80 is preferably a seven-segment display element with multiple input terminals connected to the processor 20.

  Referring to Fig. 3, the second embodiment is substantially similar to the first embodiment of Fig. 2. The modification in this embodiment is directed to the torque control unit 70 '. The torque adjusting unit 70 'comprises a rheostat 73 and a torque control circuit 72', in which the torque control circuit 72 'consists of a resistor (R6), a capacitor (C2) and an operational amplifier (U4B). The operational amplifier (U4B) is configured to form a buffer.

  The voltage detection circuit accompanying the torque detection circuit can acquire the instantaneous torque value of an engine according to the voltage and / or current variation data between the motor and the DC voltage source, or the frequency of the voltage and / or current varying in a unit of time. The processor further compares the torque value with a default torque to determine whether or not the motor should be turned off. If the torque value of the motor is higher than the default value, the motor power supply is interrupted. Thus, the default value can be precisely set by a torque control unit.

Claims (6)

  A torque control device for a power tool having a motor powered by a DC voltage source, the torque control device being characterized by comprising: a switching circuit connected between the motor and the power source; DC voltage; a processor with an output terminal connected to the switching circuit for switching on / off the switching circuit; a voltage detection circuit having an input terminal connected between the motor and the DC voltage source for detecting motor voltage change data; a torque detection circuit connected between the voltage detection circuit and the processor, wherein the torque detection circuit produces a motor torque value on the basis of the voltage change data, the motor torque value being issued to the processor; and - a torque control unit connected to the processor, in which a default torque is set in the processor by the torque control unit.   2 - Torque control device according to claim 1, characterized in that it comprises: - a switching circuit (10) which is connected between the motor and the DC voltage source; a processor (20) with an output terminal which is connected to the switching circuit (10) for switching on or off the switching circuit (10); a voltage detection circuit (30) having an input terminal connected between the motor and the DC voltage source for detecting motor voltage variation data; a torque detecting circuit (40) connected between the voltage detection circuit (30) and the processor (20) for producing a motor torque value to be transmitted to the processor (20) based on the data of voltage variation; - a torque setting unit (70) which is connected to the processor (20) for providing a default torque value to the processor (20); a high voltage protection circuit (50) connected between the voltage detection circuit (30) and the processor (20) and comprising a second operational amplifier (U1B) having: - two input terminals which are respectively connected the voltage detection circuit (30) and a reference high voltage; and - an output terminal which is connected to the processor (20); a low voltage protection circuit (60) connected between the voltage detection circuit (30) and the processor (20) and comprising an operational amplifier (U3B) having: two input terminals which are respectively connected to the voltage sensing (30) and at a reference low voltage; and - an output terminal connected to the processor (20); And - a display device (80) connected to the processor (20) to show the default torque.   3 - torque control device according to claim 2, characterized in that: - the switching circuit (10) comprises: - a control transistor (11) having a base connected to the processor (20) through a resistor, a collector and an emitter; and - a switching transistor (12) having a gate connected to the collector, a source and a drain with the source and the drain respectively connected to the motor and to the DC voltage source; the voltage detection circuit (30) comprises a voltage divider circuit formed by a first resistor (R1) and a second resistor (R2) connected in series; a first terminal of the first resistor (R1) being connected to the DC voltage source and the switching circuit (10), and a second terminal of the first resistor (R1) connected to the second resistor (R2) being coupled to the circuit protection against high voltage (50); and the torque detection unit (40) comprises a first RC circuit (R3, C1) and a first operational amplifier (U2B) in buffer.   4 - torque control device according to one of claims 2 and 3, characterized in that the torque adjusting unit (70) comprises: - a switch (71) having multiple nodes; and - a torque setting circuit (72) formed by multiple resistors, wherein each resistor is connected to a respective node of the switch (71) and to a respective input terminal of the processor (20).   - Torque control device according to one of claims 2 and 3, characterized in that the torque control unit (70 ') comprises: a rheostat (73); and - a torque control circuit (72 ') formed by an RC circuit (R6, C2) and a fourth operational amplifier (U4B), wherein the fourth operational amplifier (U4B) has an input terminal connected to the RC circuit (R6, C2) and has an output terminal connected to the processor (20).   6 - torque control device according to claim 1, characterized in that it comprises: - a switching circuit (10) which is connected between the motor and the DC voltage source and comprising: a control transistor (11 ) having a base, a collector and an emitter; and - a switching transistor (12) having a gate connected to the collector, and a source and a drain respectively connected to the motor and the DC voltage source; a processor (20) with an output terminal which is connected to the base of the control transistor (11) of the switching circuit (10) for switching on or off the switching circuit (10); - a high voltage protection circuit (50) which is connected to the processor (20); a voltage detection circuit (30) having a voltage divider circuit formed by a first resistor (R1) and a second resistor (R2) connected in series, wherein: - a first terminal of the first resistor (R1) is connected to the DC voltage source and the switching circuit (10); and - a second terminal of the first resistor (R1) connected to the second resistor (R2) is connected to the high voltage protection circuit (50); a torque detection circuit (40) which is connected between the voltage detection circuit (30) and the processor (20) to produce a motor torque value to be transmitted to the processor (20) based on the data variation of the voltage; and - a torque setting unit (70) which is connected to the processor (20) for providing a default torque value to the processor (20) and comprising a first RC circuit (72 ') and a first operational amplifier (U4B) in buffer.   7 - torque control device according to claim 6, characterized in that the high voltage protection circuit (50) comprises: - a second operational amplifier (U1B) having: - two input terminals respectively connected to the 20 voltage detection circuit (30) and a reference high voltage; and - an output terminal connected to the processor (20); with the torque control device further comprising: - a low voltage protection circuit (60) which is connected between the voltage detection circuit (30) and the processor (20) and comprising: a third operational amplifier (U3B) having two input terminals respectively connected to the voltage detection circuit (30) and to a low reference voltage; and an output terminal connected to the processor (20); and a display device (80) connected to the processor (20) to show the default torque.