Electric hydraulic tool

Abstract

An electric hydraulic tool, comprising: a hydraulic system (1), comprising a cylinder body (11), the cylinder body (11) having one end provided with an oil reservoir (12) and the other end provided with a piston chamber (111), a piston assembly (13) being provided in the piston chamber (111), an oil intake channel (112) being provided between the piston chamber (111) and the oil reservoir (12), and an oil intake check valve (14), a plunger assembly (15) and an oil output check valve (16) being sequentially provided on the oil intake channel (112); a drive control system (2), comprising a brushless direct-current electric motor (21) for driving the plunger assembly (15) to move and having no displacement sensor, a main control module (22) for controlling the operation of the brushless direct-current electric motor (21), and an electric-motor drive module (23); and a power supply system (3) for supplying power to the drive control system (2).

Description

Electric hydraulic tools Technical Field

[0001] The utility model belongs to the technical field of electric tools, in particular to an electric hydraulic tool. Background Art

[0002] Electric hydraulic tools include electric hydraulic crimping pliers, electric hydraulic wire cutters, electric hydraulic reaming pliers, electric hydraulic pipe crimping pliers, etc.

[0003] An electric hydraulic tool typically consists of a hydraulic cylinder, a piston assembly, an oil bag, a motor, a plunger assembly, oil inlet and outlet control valves, and a pressure relief valve. The piston assembly is located within the piston chamber of the hydraulic cylinder, and the outer end of the piston assembly is fixedly connected to a working component. During operation, the electric hydraulic tool drives the plunger assembly via a motor, forcing the hydraulic oil in the oil bag into the piston chamber, pushing the piston assembly and the working component to move, achieving the desired action. When the working component completes its operation, the motor stops, and the pressure relief valve opens. The piston assembly's return spring then forces the hydraulic oil back into the oil bag.

[0004] Currently, the motors used in electric hydraulic tools are all brushless DC motors with position sensors such as Hall elements. These sensors detect the position of the rotor magnetic poles relative to the stator windings, providing the driver with correct commutation information. However, brushless DC motors using position sensors have the following drawbacks:

[0005] 1. The circuit layout is complicated and there are many parts, which increases the size and cost of the motor.

[0006] 2. In high-power hydraulic tools, a lot of heat is generated, and the position sensor is prone to failure, which reduces the reliability of the brushless DC motor and affects the life of the hydraulic tool.

[0007] 3. The installation accuracy of the position sensor will also affect the performance of the brushless DC motor.

[0008] Summary of the Invention

[0009] The purpose of the utility model is to provide an electric hydraulic tool with simple structure, low cost and long service life.

[0010] The purpose of this utility model is achieved in this way:

[0011] An electric hydraulic tool comprising:

[0012] The hydraulic system comprises a cylinder body, an oil bag is provided at one end of the cylinder body, a piston chamber is provided at the other end, a piston assembly is provided in the piston chamber, an oil inlet channel is provided between the piston chamber and the oil bag, and an oil inlet check valve, a plunger assembly and an oil outlet check valve are provided in sequence on the oil inlet channel;

[0013] A drive control system comprising a brushless DC motor without a displacement sensor for driving the plunger assembly, a main control module and a motor drive module for controlling the operation of the brushless DC motor; and

[0014] A power supply system is used to supply power to the drive control system.

[0015] The utility model is further provided with that the motor drive module includes a MOS pre-drive chip and a drive circuit composed of six MOS tubes.

[0016] The utility model is further provided with that the drive control system further includes a current detection module, which is used to detect the output current of the drive circuit in real time and feed it back to the main control module;

[0017] When the output current exceeds the current setting value, the main control module controls the brushless DC motor to stop working.

[0018] The utility model is further provided with that the drive control system also includes a voltage detection module, which is used to detect the voltage of the U / V / W phase in the brushless DC motor in real time and feed it back to the main control module;

[0019] When the actual voltage does not match the voltage setting value or the actual voltage of the non-connected phase does not change, the main control module controls the brushless DC motor to stop working.

[0020] The utility model is further provided with an oil return channel between the piston cavity and the oil bag, and a pressure relief valve is provided on the oil return channel;

[0021] When the pressure of the piston chamber exceeds the set value of the pressure relief valve, the pressure relief valve opens, the load of the brushless DC motor decreases, and its speed suddenly increases. At this time, the main control module controls the brushless DC motor to stop working.

[0022] The present invention is further provided with that the main control module includes an MCU chip connected to the MOS pre-driver chip.

[0023] The present invention is further provided with that the power supply system includes a lithium battery pack and a main switch for controlling the lithium battery pack to supply power to the drive control system.

[0024] The utility model is further provided with an execution system, which includes a clamp head installed at one end of the cylinder body, a fixed mold base provided on the clamp head, and a movable mold base provided at the front end of the piston assembly, the fixed mold base is provided with a fixed mold for disassembly, and the movable mold base is provided with a movable mold that is compatible with the fixed mold for disassembly.

[0025] Compared with the prior art, the present invention has the following outstanding and beneficial technical effects:

[0026] 1. The electric hydraulic tool of the utility model is driven by a brushless DC motor without a displacement sensor, which has the advantages of low cost, small size, high reliability and long service life.

[0027] 2. The utility model is equipped with a current detection module and a voltage detection module, which can realize functions such as overcurrent protection, phase loss protection, and MOS tube fault protection, greatly improving the reliability of the product.

[0028] 3. The utility model realizes pressure relief detection by detecting the rotation speed of the motor. When a pressure relief event occurs, the MCU chip controls the brushless DC motor to automatically cut off the power supply, which can effectively save the power consumption of the lithium battery pack and increase the number of times the lithium battery pack is used. At the same time, it reminds the operator that the operation is completed, thereby increasing work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG1 is a schematic structural diagram of the present utility model.

[0030] FIG2 is a schematic diagram of the structure inside the housing of the present invention.

[0031] FIG3 is one of the cross-sectional views of the present invention.

[0032] FIG4 is a second cross-sectional view of the present invention.

[0033] FIG5 is a circuit diagram of the drive control system of the present utility model.

[0034] FIG6 is a circuit diagram of the drive control system of the present utility model.

[0035] FIG7 is a waveform diagram of the back electromotive force of the brushless DC motor of the present invention.

[0036] FIG8 is a diagram showing the motor speed of the electric hydraulic tool of the present invention during one working cycle.

[0037] The symbols in the figure represent the following: hydraulic system 1; drive control system 2; power supply system 3; execution system 4; housing 5; cylinder body 11; piston chamber 111; oil inlet channel 112; oil return channel 113; oil bag 12; piston assembly 13; oil inlet check valve 14; plunger assembly 15; oil outlet check valve 16; filter 17; pressure relief valve 18; pressure relief button 19; reducer 20; brushless DC motor 21; main control module 22; MCU chip 221; motor drive module 23; MOS pre-driver chip 231; MOS transistor 232; current detection module 24; current sampling resistor 241; voltage detection module 25; first voltage sampling resistor 251; second voltage sampling resistor 252; lithium battery pack 31; main switch 32; clamp head 41; fixed die base 42; movable die base 43; fixed die 44; movable die 45; mounting portion 51; handle portion 52. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with specific embodiments:

[0039] As shown in Figures 1 and 2, an electric hydraulic tool includes a hydraulic system 1, a drive control system 2, a power supply system 3, an execution system 4 and a housing 5.

[0040] The housing 5 has a mounting portion 51 and a handle portion 52 . The inner cavity of the mounting portion 51 is used for mounting the hydraulic system 1 and other components, and the handle portion 52 is used for an operator to hold.

[0041] As shown in Figure 3, the hydraulic system 1 comprises a cylinder 11, with an oil bag 12 disposed at one end and a piston chamber 111 at the other. A piston assembly 13 is disposed within the piston chamber 111. The piston assembly 13 comprises a piston rod, a return spring, and a piston. An oil inlet passage 112 is disposed between the piston chamber 111 and the oil bag 12. This oil inlet passage 112 is sequentially provided with a filter 17, an oil inlet check valve 14, a plunger assembly 15, and an oil outlet check valve 16. When the plunger assembly 15 reciprocates, hydraulic oil in the oil bag 12 enters the piston chamber 111 through the oil inlet passage 112, pushing the piston assembly 13 out.

[0042] As shown in Figure 4 , an oil return channel 113 is provided between the piston chamber 111 and the oil bag 12. A pressure relief valve 18 is installed in this channel. When the pressure in the piston chamber 111 exceeds the set value of the pressure relief valve 18, the pressure relief valve 18 opens, automatically releasing the pressure. A pressure relief button 19 is also provided on the handle 52, connected to the operating end of the pressure relief valve 18. When the operation is completed, the operator presses the pressure relief button 19, and the pressure relief valve 18 can be manually released under the action of the return spring of the piston assembly 13.

[0043] The execution system 4 has a clamp head 41 installed at one end of the cylinder body 11, a fixed mold base 42 arranged on the clamp head 41, and a movable mold base 43 arranged at the front end of the piston assembly 13. The fixed mold base 42 is disassembled and provided with a fixed mold 44, and the movable mold base 43 is disassembled and provided with a movable mold 45 adapted to the fixed mold 44.

[0044] In this embodiment, the movable die holder 43 is disposed at the outer end of the piston rod of the piston assembly 13 and can be integrally mounted or separately fixed. The movement of the piston assembly 13 enables the movable die 45 and the fixed die 44 to be joined together for processing. The movable die 45 and the fixed die 44 can be a crimping die, a thread trimming die, a punching die, or other molds. In this embodiment, a crimping die is used.

[0045] The drive control system 2 includes a sensorless brushless DC motor 21 for driving the plunger assembly 15, a main control module 22 for controlling the operation of the brushless DC motor 21, and a motor drive module 23. Both the main control module 22 and the motor drive module 23 are integrated on a PCB. The brushless DC motor 21 is connected to the plunger assembly 15 via a speed reducer 20 and is used to drive the plunger assembly 15 to reciprocate.

[0046] The power supply system 3 is used to supply power to the drive control system 2 , and includes a lithium battery pack 31 detachably mounted below the handle portion 52 and a main switch 32 for controlling the lithium battery pack 31 to supply power to the drive control system 2 . The main switch 32 is disposed at the upper end of the handle portion 52 .

[0047] As shown in Figures 5-6, the motor drive module 23 includes a MOS pre-driver chip 231 and a drive circuit consisting of six MOS transistors 232. The U / V / W output terminals of the drive circuit are connected to the brushless DC motor 21. The drive circuit converts DC power into AC power and modulates the amplitude and frequency of the AC power to control the operation of the brushless DC motor 21. The drive circuit changes the output phase sequence based on the motor rotor position to control the operation of the brushless DC motor 21.

[0048] The main control module 22 includes an MCU chip 221 connected to the MOS pre-driver chip 231. When the main switch 32 is pressed, the MCU chip 221 sends a working instruction to the MOS pre-driver chip 231, and the MOS pre-driver chip 231 controls the driving circuit to start the brushless DC motor 21.

[0049] Preferably, the drive control system 2 further includes a current detection module 24, which is used to detect the output current of the drive circuit in real time and feed it back to the main control module 22. When the output current exceeds the current set value, the main control module 22 controls the brushless DC motor 21 to stop working, thereby achieving overcurrent protection.

[0050] Specifically, the current detection module 24 includes a current sampling resistor 241, which is arranged at the ground end of the drive circuit. One end of the current sampling resistor 241 is connected to the MCU chip 221 through a current signal transmission unit, and the current of the current sampling resistor 241 is collected and fed back to the main control module 22.

[0051] Preferably, the drive control system 2 also includes a voltage detection module 25, which is used to detect the voltage of the U / V / W phase in the brushless DC motor 21 in real time and feed it back to the main control module 22; when the actual voltage does not match the voltage set value or the actual voltage of the non-connected phase has not changed, the main control module 22 controls the brushless DC motor 21 to stop working.

[0052] Specifically, the voltage detection module 25 includes an ADC sampling circuit electrically connected to the U / V / W phase output terminals of the drive circuit. The ADC sampling circuit includes a first voltage sampling resistor 251 and a second voltage sampling resistor 252 connected to the U / V / W phase output terminals, respectively. The other end of the second voltage sampling resistor 252 is grounded. A voltage signal transmission unit connected to the MCU chip 221 is provided between the first voltage sampling resistor 251 and the second voltage sampling resistor 252.

[0053] When the actual voltage of the non-connected phase remains unchanged, it can be considered that the motor is in phase loss, and the main control module 22 controls the brushless DC motor 21 to stop working to achieve phase loss protection.

[0054] When the actual voltage does not match the voltage setting value, that is, when the actual voltage sampled by any one of the MOS tubes 232 in the U / V / W phase is not within ±10% of the voltage setting value when it is turned on, the system considers that the MOS tube 232 is faulty, and the main control module 22 controls the brushless DC motor 21 to stop working to prevent the problem from further deteriorating, thereby realizing MOS tube fault protection.

[0055] FIG8 is a diagram showing the motor speed of the electric hydraulic tool of the present invention during one working cycle.

[0056] By calculating the sensorless brushless commutation time, the MCU chip 221 can obtain the real-time speed of the motor. When the main switch 32 is pressed, the brushless DC motor 21 starts quickly and reaches the rated speed. The hydraulic system 1 works normally, the hydraulic oil enters the piston chamber 111, the execution system 4 closes the mold, and the pressure in the piston chamber 111 gradually increases, resulting in an increase in load. At this time, the torque of the brushless DC motor 21 gradually increases, the motor current gradually increases, and the speed gradually decreases. When the pressure in the piston chamber 111 exceeds the set value of the pressure relief valve 18, the pressure relief valve 18 opens, the load of the brushless DC motor 21 decreases, and its speed suddenly increases. At this time, the execution system 4 completes its work.

[0057] Based on this, when the MCU chip 221 detects a change in motor speed from a gradual decrease to a sudden increase, it deems a hydraulic system pressure relief event and issues a motor shutdown command, thereby stopping the brushless DC motor 21. In this embodiment, the MCU chip 221 automatically powers off the brushless DC motor 21, effectively conserving power from the lithium battery pack 31 and increasing its usability. It also reminds the operator that the operation is complete, improving work efficiency.

[0058] Furthermore, this embodiment uses the back electromotive force method (BEM) to detect the rotor position of the brushless DC motor 21. The principle is to detect the terminal voltage of the non-conducting phase and compare it with the neutral-point voltage of the brushless DC motor to determine the rotor position. Specifically, this embodiment uses an ADC sampling circuit to convert the voltage of the brushless DC motor 21 into a digital signal, which is then compared with the analog neutral-point voltage to determine the rotor position.

[0059] As shown in Figure 7, the horizontal axis represents the rotor position, and the vertical left side represents the voltage of the U / V / W phases. The rotor's rotation area is divided into six sectors, with each sector having an angle of 60°. The three wave lines correspond to the voltages of the U / V / W phases in different sectors, with those below zero representing low voltage, those above zero representing high voltage, and the oblique lines representing no voltage. Within each sector, the U / V / W phases correspond to low voltage, high voltage, and no voltage, respectively. The above voltage combinations are used to determine the rotor sector and, therefore, the rotor position.

[0060] However, because the back EMF of the stator winding is proportional to the motor speed, it is impossible to determine the position of the rotor poles based on the back EMF signal when the motor is stationary or very small at low speeds. Therefore, the back EMF method requires a special starting technique: accelerating from a standstill until the speed is high enough to detect a zero crossing using the back EMF energy, and then switching to the brushless DC motor operating state. This process is called "three-stage" starting and mainly includes three stages: rotor pre-positioning, acceleration, and operating state switching. This allows for controllable motor steering and ensures that the motor reaches a certain speed before switching, thus ensuring reliable starting.

[0061] However, in hydraulic tools, when the hydraulic pressure is high, the motor will be subjected to very large torque. At this time, if the conventional "three-stage" starting method is used, the motor will be directly stuck due to insufficient starting torque. To solve the problem of high-torque starting, the motor rotor is positioned using a pulse current positioning method. Narrow pulses of 80us are injected into the six phases UV, VU, UW, WU, VW, and WV in sequence, and the current is sampled during the pulse. Based on the magnitude of the current in different phases, the position of the motor rotor in the initial state can be determined. After locating the initial position, high torque can be used to start the motor, thus solving the problem of hydraulic tools failing to start under high pressure.

[0062] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. An electric hydraulic tool, characterized in that: include: A hydraulic system (1) comprises a cylinder body (11), one end of the cylinder body (11) is provided with an oil bag (12), the other end of the cylinder body (11) is provided with a piston chamber (111), a piston assembly (13) is provided in the piston chamber (111), an oil inlet passage (112) is provided between the piston chamber (111) and the oil bag (12), and an oil inlet check valve (14), a plunger assembly (15) and an oil outlet check valve (16) are provided in sequence on the oil inlet passage (112); A drive control system (2) comprising a brushless DC motor (21) without a displacement sensor for driving the plunger assembly (15) to move, a main control module (22) for controlling the operation of the brushless DC motor (21), and a motor drive module (23); and A power supply system (3) for supplying power to the drive control system (2); The drive control system (2) further comprises a current detection module (24) and a voltage detection module (25), wherein the current detection module (24) is used to detect the output current of the motor drive module (23) in real time and feed it back to the main control module (22), and the voltage detection module (25) is used to detect the voltage of the U / V / W phases in the brushless DC motor (21) in real time and feed it back to the main control module (22).

2. An electric hydraulic tool according to claim 1, characterized in that: The motor drive module (23) comprises a MOS pre-drive chip (231) and a drive circuit composed of six MOS tubes (232).

3. An electric hydraulic tool according to claim 1, characterized in that: When the output current exceeds the current setting value, the main control module (22) controls the brushless DC motor (21) to stop working.

4. An electric hydraulic tool according to claim 3, characterized in that: When the actual voltage does not match the voltage setting value or the actual voltage of the non-connected phase remains unchanged, the main control module (22) controls the brushless DC motor (21) to stop working.

5. An electric hydraulic tool according to claim 2, characterized in that: The main control module (22) comprises an MCU chip (221) connected to the MOS pre-driver chip (231).

6. An electric hydraulic tool according to claim 1, characterized in that: The power supply system (3) comprises a lithium battery pack (31) and a main switch (32) for controlling the lithium battery pack (31) to supply power to the drive control system (2).

7. An electric hydraulic tool according to any one of claims 1 to 6, characterized in that: An oil return passage (113) is also provided between the piston chamber (111) and the oil bag (12), and a pressure relief valve (18) is provided on the oil return passage (113); When the pressure of the piston chamber (111) exceeds the set value of the pressure relief valve (18), the pressure relief valve (18) opens, the load of the brushless DC motor (21) decreases, and its rotation speed suddenly increases. At this time, the main control module (22) controls the brushless DC motor (21) to stop working.

8. An electric hydraulic tool according to claim 1, characterized in that: It also includes an execution system (4), which has a clamp head (41) installed at one end of the cylinder body (11), a fixed die seat (42) arranged on the clamp head (41), and a movable die seat (43) arranged at the front end of the piston assembly (13), the fixed die seat (42) being disassembled and provided with a fixed die (44), and the movable die seat (43) being disassembled and provided with a movable die (45) adapted to the fixed die (44).

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