Torque wrench overcurrent protection circuit based on sampling resistor

Abstract

The utility model relates to a torque wrench overcurrent protection circuit based on a sampling resistor, which utilizes a comparator to detect the working current of a motor, when the working current of the motor is larger, the voltage drop of the sampling resistor is larger, and the voltage of the normal phase input end of the comparator is larger, and when the voltage of the normal phase input end of the comparator is larger than the reference voltage, the voltage drop of the sampling resistor is smaller. The comparator outputs high level to conduct the third triode and further conduct the second triode, and after the second triode is conducted, the base voltage of the first triode is pulled down, so that the first triode is disconnected, a driving circuit of the motor is disconnected, and the motor stops rotating, and therefore overcurrent protection is achieved, a switch is not disconnected, and the protection state is not relieved. The protection state is automatically released after the switch is disconnected. No control chip is needed in the whole control process, the overcurrent protection response speed can be effectively improved, and the manufacturing cost of the control circuit is reduced.

Description

TECHNICAL FIELD

[0001] The utility model belongs to current detection technical field, concretely relates to a torsion wrench overcurrent protection circuit based on sampling resistance. BACKGROUND

[0002] The torsion detection of the torsion wrench is realized by detecting the motor working current, when the motor working current reaches the set value, the torsion of the motor reaches the target value, at this time, the motor is controlled to stop. The main component for control is MCU and other data processing chips. Because the processing of the data processing chip is needed, the control feedback speed is slow, the problem of excessive torsion is prone to appear, at the same time, the cost of the torsion wrench is high due to the chip control, the parameter setting when the torsion is adjusted is also more troublesome, and the user of older age is not very friendly. UTILITARY MODEL CONTENTS

[0003] The utility model solves the technical problems of slow feedback speed and high manufacturing cost caused by MCU processing sampling current and then feeding back output control signal.

[0004] In order to solve the above technical problems, the utility model adopts the technical scheme of a torsion wrench overcurrent protection circuit based on sampling resistance, which comprises a switch and a motor connected in series on a power supply circuit, the switch is connected between the positive electrode of the power supply and the motor, the negative electrode of the motor is connected with a sampling resistance, the other end of the sampling resistance is grounded, a first triode is connected in series between the sampling resistance and the motor, a driving voltage and a second triode are connected in parallel to the base of the first triode, the collector of the second triode is connected with the first triode, the emitter is grounded, and the base is connected with the emitter of the third triode, the collector of the third triode is connected between the motor and the switch, a comparator is connected in parallel between the sampling resistance and the first triode, the output end of the comparator is connected with the base of the third triode, the positive input end of the comparator is connected between the sampling resistance and the first triode, and the negative input end of the comparator is connected with a reference voltage.

[0005] As a preferred scheme, the sampling resistance is an adjustable resistance.

[0006] As a preferred scheme, the collector of the third triode is connected in series with a voltage regulating part between the switch, and the voltage regulating part is a voltage regulating chip or a resistance.

[0007] The utility model discloses beneficial effect is: the utility model discloses utilize the comparator to the working current of motor carries out the detection, when the working current of motor is bigger, the voltage drop of sampling resistance is bigger, the positive phase input voltage of comparator is bigger, when the positive phase input voltage of comparator is greater than reference voltage, and the comparator will output high level and turn on the third triode, and then turn on the second triode, and the second triode turns on and pulls down the first triode base voltage and makes the first triode break, and the drive circuit of motor breaks, and the motor stops, thereby realizes the overcurrent protection, and the switch does not open, and the protection state is not removed, and the protection state is automatically removed after the switch opens. The whole control process does not need control chip to participate, can effectively improve overcurrent protection reaction speed, and reduce the manufacturing cost of control circuit.

[0008] The utility model discloses further through setting up sampling resistance as resistance adjustable resistance, make the overcurrent protection circuit of the utility model can adjust the current size of overcurrent protection through the resistance of sampling resistance, thereby realize the adjustment of the maximum torsion value of torsion wrench, need not through interface setting, greatly reduced the difficulty of torsion value adjustment, improve user use convenience. DRAWINGS

[0009] The utility model discloses further through setting up sampling resistance as resistance adjustable resistance, make the overcurrent protection circuit of the utility model can adjust the current size of overcurrent protection through the resistance of sampling resistance, thereby realize the adjustment of the maximum torsion value of torsion wrench, need not through interface setting, greatly reduced the difficulty of torsion value adjustment, improve user use convenience.

[0010] Figure 1 It is the circuit diagram of the overcurrent protection circuit of the utility model. CONCRETE IMPLEMENTING METHOD

[0011] The utility model discloses further through setting up sampling resistance as resistance adjustable resistance, make the overcurrent protection circuit of the utility model can adjust the current size of overcurrent protection through the resistance of sampling resistance, thereby realize the adjustment of the maximum torsion value of torsion wrench, need not through interface setting, greatly reduced the difficulty of torsion value adjustment, improve user use convenience.

[0012] As Figure 1 The utility model discloses a kind of torsion wrench overcurrent protection circuit based on sampling resistance, including series connection in power supply circuit on switch S and motor M, the switch S is connected between power supply positive pole B+ and motor M, the motor M negative pole has a sampling resistance R in series connection, sampling resistance R other end ground connection, sampling resistance R and motor M between series connection have a first triode Q1, the base of first triode Q1 is parallel with a drive voltage V+ and a second triode Q2, the collector of second triode Q2 is connected with first triode Q1, emitter ground connection, base connects the emitter of third triode Q3, the collector of third triode Q3 is connected between motor M and switch S, the sampling resistance R and first triode Q1 between parallel have a comparator U1, the output terminal Vo of comparator U1 is connected with the base of third triode Q3, the positive phase input terminal vi of comparator U1 is connected between sampling resistance R and first triode Q1, the opposite phase input terminal er of comparator U1 is connected with a reference voltage Vb.

[0013] The user first calculates the design maximum working current of the motor according to the torque extreme value of the torque wrench, and then calculates the positive electrode end voltage of the sampling resistor R when the motor is at the design maximum working current according to the resistance value of the sampling resistor R, and sets the voltage as the reference voltage Vb. When the actual working voltage of the motor is greater than the design maximum working voltage, the positive electrode voltage of the sampling resistor R will exceed the reference voltage Vb, so that the output end Vo of the comparator U1 outputs a high level to turn on the third triode Q3, and then turn on the second triode Q2. After the second triode Q2 is turned on, the base voltage of the first triode Q1 is pulled low to make the first triode Q1 be turned off, the driving circuit of the motor M is turned off, and the motor M is stopped, so that the overcurrent protection is realized. The switch S is not turned on, and the protection state is not released. When the switch S is turned off, the protection state is automatically released.

[0014] The sampling resistor R in the embodiment is preferably an adjustable resistor. The user can adjust the torque extreme value of the torque wrench by adjusting the resistance value of the sampling resistor R. For example, when the resistance value of the sampling resistor R is adjusted to be smaller, a larger motor working voltage is needed to make the voltage value of the positive electrode end of the sampling resistor R greater than the reference voltage Vb, so that the torque extreme value of the torque wrench can be adjusted to be larger. Conversely, the torque extreme value of the torque wrench can be adjusted to be smaller.

[0015] The collector of the third triode Q3 is connected in series with the switch S, and a voltage regulating component W is connected in series between the collector of the third triode Q3 and the switch S, and the voltage regulating component W is a voltage regulating chip or a resistor.

[0016] The working process of the utility model is: the user first calculates the design maximum working current of the motor according to the torque extreme value of the torque wrench, and then calculates the positive electrode end voltage of the sampling resistor R when the motor is at the design maximum working current according to the resistance value of the sampling resistor R, and sets the voltage as the reference voltage Vb. When the actual working voltage of the motor is greater than the design maximum working voltage, the positive electrode voltage of the sampling resistor R will exceed the reference voltage Vb, so that the output end Vo of the comparator U1 outputs a high level to turn on the third triode Q3, and then turn on the second triode Q2. After the second triode Q2 is turned on, the base voltage of the first triode Q1 is pulled low to make the first triode Q1 be turned off, the driving circuit of the motor M is turned off, and the motor M is stopped, so that the overcurrent protection is realized. The switch S is not turned on, and the protection state is not released. When the switch S is turned off, the protection state is automatically released.

[0017] When the user needs to adjust the torque extreme value of the torque wrench to be larger, the user can adjust the resistance value of the sampling resistor R to be smaller, and adjusting the resistance value of the sampling resistor R to be larger can adjust the torque extreme value of the torque wrench to be smaller.

[0018] The above embodiment only illustrates the principle and effect of the present application, and part of the applied embodiments, and is not used to limit the present application; it should be pointed out that, for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application.

Claims

1. A torque wrench overcurrent protection circuit based on sampling resistance, comprising a switch and a motor connected in series on a power supply circuit, characterized in that, The switch is connected between the positive pole of the power supply and the motor, the negative pole of the motor is connected with a sampling resistor in series, the other end of the sampling resistor is connected with the ground, a first triode is connected in series between the sampling resistor and the motor, the base of the first triode is connected with a driving voltage and a second triode in parallel, the collector of the second triode is connected with the first triode, the emitter of the second triode is connected with the ground, the base of the second triode is connected with the emitter of a third triode, the collector of the third triode is connected between the motor and the switch, a comparator is connected in parallel between the sampling resistor and the first triode, the output of the comparator is connected with the base of the third triode, the positive input of the comparator is connected between the sampling resistor and the first triode, and the negative input of the comparator is connected with a reference voltage.

2. The sampling resistance based torque wrench overcurrent protection circuit of claim 1, wherein, The sampling resistor is an adjustable resistor.

3. The sampling resistor based torque wrench overcurrent protection circuit of claim 1, wherein, The collector of the third triode is connected in series with the switch, and a voltage regulator is connected between the collector of the third triode and the switch, wherein the voltage regulator is a voltage regulator chip or a resistor.

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