An electric screwdriver with adjustable clutch and torque protection

Abstract

The present invention belongs to the field of mechanical transmission technology, and specifically relates to an adjustable clutch and torque protection electric screwdriver. The clutch includes a first rotating shaft, a first friction plate, a second friction plate, a thermal expansion unit, and a second rotating shaft, which are coaxially arranged in sequence, and also includes a bracket that can limit the distance between the first rotating shaft and the second rotating shaft; the first rotating shaft and the second rotating shaft are each rotatably mounted on the bracket, the first friction plate is fixedly connected to the first rotating shaft, and the second friction plate and the second rotating shaft are respectively fixedly connected to the two ends of the thermal expansion unit; when the thermal expansion unit is heated, the axial dimension increases, forcing the first friction plate and the second friction plate to contact and squeeze each other. The clutch structure has a small volume, can transmit a large torque, and the maximum torque transmitted can be continuously adjusted within a wide range. It has low vibration and low noise during operation, and has high reliability and good controllability.

Description

Technical Field

[0001] The invention belongs to the technical field of mechanical transmission, and in particular relates to an electric screwdriver with adjustable clutch and torque protection. Background Art

[0002] The clutch is a type of transmission device that can be connected in series in the power transmission path to change or limit the power connection relationship between the upstream and downstream. The mechanical clutch is the most widely used type of clutch. It relies on a purely mechanical structure for switching. The structure is reliable and the power transmission is direct. However, due to the inherent characteristics of the mechanical structure, it is easy to generate noise and vibration when switching the clutch state, and there is a relatively obvious sense of stagnation. In addition, the mechanical clutch has a small degree of freedom in regulating the clutch force, and it is difficult to achieve multi-level regulation and continuous regulation. The electromagnetic clutch is a type of clutch that has been used more and more in recent years. It controls the friction plate separation and the pressure between the friction plates by changing the coil magnetic field to achieve the regulation of the power connection state. This regulation method is smoother than the mechanical clutch, with lower noise and vibration, but the electromagnetic clutch is more expensive and less reliable. In addition, the electromagnetic clutch relies on electromagnetic induction to generate the clutch force, and the size of the clutch force is limited, making it difficult to transmit large torque. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides an adjustable clutch, and on this basis further provides a torque protection electric screwdriver.

[0004] The adjustable clutch provided by the present invention comprises a first rotating shaft, a first friction plate, a second friction plate, a thermal expansion unit, and a second rotating shaft which are coaxially arranged in sequence, and also comprises a bracket which can limit the distance between the first rotating shaft and the second rotating shaft; the first rotating shaft and the second rotating shaft are each rotatably mounted on the bracket, the first friction plate is fixedly connected to the first rotating shaft, and the second friction plate and the second rotating shaft are respectively fixedly connected to the two ends of the thermal expansion unit; when the thermal expansion unit is not heated, the first friction plate and the second friction plate are separated from each other; when the thermal expansion unit is heated, the axial dimension increases, forcing the first friction plate and the second friction plate to contact and squeeze each other.

[0005] Furthermore, the thermal expansion unit includes a cylinder body, a piston slidingly fitted in the cylinder body, a heating component capable of heating the cylinder body, and a thermal expansion medium filled in a cavity between the cylinder body and the piston; the heating component causes the thermal expansion medium to expand due to heat, thereby pushing the piston to move in a direction away from the cylinder body.

[0006] Furthermore, the thermal expansion medium is a liquid thermal expansion medium.

[0007] Furthermore, the heating assembly includes an electric heating film wrapped around the circumference of the cylinder body and rotating with the cylinder body, a first annular electrode and a second annular electrode fixed at both ends of the electric heating film, a first brush elastically contacting the first annular electrode, and a second brush elastically contacting the second annular electrode; the electric heating film is heated by supplying power between the first brush and the second brush.

[0008] Furthermore, the piston is fixed on the back of the second friction disk, and the closed end of the cylinder body is fixed on the second rotating shaft; a group of protrusions are provided at the opening of the cylinder body, and a group of recesses are provided on the back of the second friction disk; the protrusions are embedded in the recesses to transmit torque.

[0009] Furthermore, the outer ring of the piston is provided with one or more sealing rings.

[0010] Furthermore, the bracket includes a first end panel and a second end panel arranged opposite to each other, and also includes a group of connecting rods fixedly connected between the first end panel and the second end panel; the first end panel and the second end panel are both provided with axial holes in the center, the first rotating shaft is rotatably connected to the first end panel, and the second rotating shaft is rotatably connected to the second end panel.

[0011] Furthermore, a first thrust bearing is provided on the first rotating shaft, and the first thrust bearing is located between the first end panel and the first friction plate; and a second thrust bearing is provided on the second rotating shaft, and the second thrust bearing is located between the second end panel and the cylinder body.

[0012] The torque protection electric screwdriver provided by the present invention comprises a motor at the upstream end of the power and a screwdriver shaft at the downstream end of the power, the end of the screwdriver shaft is provided with a replaceable magnetic screwdriver head, and the above-mentioned adjustable clutch is connected in series on the transmission path between the motor and the screwdriver shaft.

[0013] Furthermore, a speed change gear box is connected in series between the variable clutch and the motor or between the variable clutch and the screwdriver shaft.

[0014] Beneficial effects: Compared with the prior art, the variable clutch provided by the present invention has a small structure volume, a large transmittable torque, the maximum transmitted torque can be continuously adjusted within a wide range, has low vibration and low noise during operation, and has high reliability and good controllability. The torque protection electric screwdriver provided by the present invention can effectively prevent the occurrence of slipping damage when screwing. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the adjustable clutch.

[0016] Figure 2 This is an exploded diagram of the transmission structure in the adjustable clutch.

[0017] Figure 3 A schematic diagram of the structure of the heating component.

[0018] Figure 4 It is a schematic diagram of the cooperation between the notch and the protrusion.

[0019] In the figure, the first rotating shaft 1, the first friction plate 2, the second friction plate 3, the thermal expansion unit 4, the second rotating shaft 5, the cylinder body 41, the piston 42, the heating assembly 43, the electric heating film 431, the first annular electrode 432, the second annular electrode 433, the first brush 434, the second brush 435, the bump 411, the recess 31, the sealing ring 44, the first end panel 91, the second end panel 92, the connecting rod 93, the first thrust bearing 6, and the second thrust bearing 7. DETAILED DESCRIPTION

[0020] The present invention is further illustrated by the following examples, which are intended to more clearly illustrate the technical solution of the present invention and should not be construed as a limitation.

[0021] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood as the usual meanings understood by people with ordinary skills in the field. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0022] Example 1

[0023] like Figure 1The variable clutch shown comprises a first rotating shaft 1, a first friction plate 2, a second friction plate 3, a thermal expansion unit 4, and a second rotating shaft 5 which are coaxially arranged in sequence, and also comprises a bracket which can limit the distance between the first rotating shaft 1 and the second rotating shaft 5; the first rotating shaft 1 and the second rotating shaft 5 are rotatably mounted on the bracket, the first friction plate 2 is fixedly connected to the first rotating shaft 1, and the second friction plate 3 and the second rotating shaft 5 are respectively fixedly connected to the two ends of the thermal expansion unit 4; when the thermal expansion unit 4 is not heated, the first friction plate 2 and the second friction plate 3 are separated from each other; when the thermal expansion unit 4 is heated, the axial dimension increases, forcing the first friction plate 2 and the second friction plate 3 to contact and squeeze each other. The variable clutch controls the separation and contact of the first friction plate 2 and the second friction plate 3 through the thermal expansion unit 4, thereby conveniently controlling the power connection state between the first rotating shaft 1 and the second rotating shaft 5, and realizing the controllable clutch function. Since the extrusion force generated by the thermal expansion of the material can be very large, which can be much greater than the electromagnetic force, the torque that can be transmitted by this type of clutch is much greater than that of the electromagnetic clutch under the same volume.

[0024] like Figure 2 As shown, the thermal expansion unit 4 includes a cylinder 41, a piston 42 slidingly fitted in the cylinder 41, a heating component 43 capable of heating the cylinder 41, and a thermal expansion medium filled in the cavity between the cylinder 41 and the piston 42; when the heating component 43 is not working, the thermal expansion medium is in a cooling state, and the first friction plate 2 and the second friction plate 3 are separated from each other; when the heating component 43 is working, the thermal expansion medium is heated and expanded, thereby pushing the piston 42 to move away from the cylinder 41, so that the first friction plate 2 and the second friction plate 3 are squeezed against each other. Preferably, the thermal expansion medium is a liquid thermal expansion medium, such as a non-toxic and non-flammable liquid such as thermal conductive silicone oil and sodium sulfate solution.

[0025] like Figure 3As shown, the heating assembly 43 includes an electric heating film 431 wrapped around the cylinder body 41 and rotating with the cylinder body 41, a first annular electrode 432 and a second annular electrode 433 fixed at both ends of the electric heating film 431, a first brush 434 elastically contacting the first annular electrode 432, and a second brush 435 elastically contacting the second annular electrode 433; the first brush 434 and the second brush 435 are fixed on an insulating seat installed on a bracket. Among them, the electric heating film 431 can be made of graphene film material, and the first annular electrode 432 and the second annular electrode 433 can be made of copper electrodes. When heating is required, the electric heating film 431 is heated by supplying power between the first brush 434 and the second brush 435, so as to be transmitted to the heat expansion medium to expand it. In addition, changing the magnitude of the current can adjust the heating power, thereby adjusting the temperature of the heat expansion medium, thereby adjusting the extrusion force between the first friction plate 2 and the second friction plate 3, and thereby adjusting the maximum torque transmitted between the first rotating shaft 1 and the second rotating shaft 5. This adjustment method has many advantages, including smooth switching of power connection and separation, extremely low vibration and noise, and the maximum torque transmitted can be continuously adjusted from zero to a large range of values.

[0026] As an alternative, the electric heating film 431 in the heating assembly 43 may also be replaced by an electric heating coil, for example, a resistance wire with an insulating sheath is spirally wound on the surface of the cylinder 41, and the two ends of the resistance wire are respectively electrically connected to the first annular electrode 432 and the second annular electrode 433. The resistance wire may be made of konstantan alloy, konstantan copper alloy, zinc white copper, nickel-chromium alloy or copper-nickel alloy, etc., and the cross-section and number of winding turns of the resistance wire may be changed to obtain different resistance values ​​to adapt to different application scenarios.

[0027] like Figure 4 As shown, the piston 42 is fixed on the back of the second friction disk 3, and the closed end of the cylinder body 41 is fixed on the second rotating shaft 5; a group of protrusions 411 are provided at the opening of the cylinder body 41, and a group of recesses 31 are provided on the back of the second friction disk 3; the protrusions 411 are embedded in the recesses 31 to transmit torque.

[0028] like Figure 2 , 4 As shown, the outer periphery of the piston 42 is provided with one or more sealing rings 44 to prevent leakage of the thermal expansion medium.

[0029] like Figure 1 As shown, the bracket includes a first end panel 91 and a second end panel 92 that are arranged opposite to each other, and also includes a group of connecting rods 93 fixedly connected between the first end panel 91 and the second end panel 92; the first end panel 91 and the second end panel 92 are both provided with axial holes in the center, the first rotating shaft 1 is rotatably connected to the first end panel 91, and the second rotating shaft 5 is rotatably connected to the second end panel 92.

[0030] like Figure 2 As shown, the first rotating shaft 1 is also provided with a first thrust bearing 6, which is located between the first end panel 91 and the first friction plate 2; the second rotating shaft 5 is also provided with a second thrust bearing 7, which is located between the second end panel 92 and the cylinder body 41. By providing the first thrust bearing 6 and the second thrust bearing 7, the rotation resistance of the first rotating shaft 1 and the second rotating shaft 5 can be reduced, and a large extrusion force can be generated between the first friction plate 2 and the second friction plate 3, ensuring that the torque can be adjusted in a wide range.

[0031] Example 2

[0032] Based on the adjustable clutch of Example 1, a torque protection electric screwdriver is provided, including a motor at the upstream end of the power and a screwdriver shaft at the downstream end of the power, the end of the screwdriver shaft has a replaceable magnetic screwdriver head, and the adjustable clutch of Example 1 is connected in series on the transmission path between the motor and the screwdriver shaft. Further, a speed change gear box is connected in series between the adjustable clutch and the motor or between the adjustable clutch and the screwdriver shaft. When the torque protection electric screwdriver of this embodiment is in use, the heating value of the heating component 43 is adjusted according to the torque requirement of screwing the screw, that is, the power supply current between the first brush 434 and the second brush 435 is adjusted, and the power supply is increased when the torque required for screwing the screw is large, and the power supply is reduced when the torque required for screwing the screw is small. As the screw is gradually tightened, the required torque gradually increases. When it exceeds the maximum torque limited by the clutch, the first friction plate 2 and the second friction plate 3 slip, thereby protecting the screw and the screw hole and preventing the damage caused by slipping teeth.

[0033] The above embodiments are exemplary, and their purpose is to illustrate the technical concept and features of the present invention so that people familiar with the technology in this field can understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. An adjustable clutch, characterized in that: The invention comprises a first rotating shaft (1), a first friction plate (2), a second friction plate (3), a heat expansion unit (4), and a second rotating shaft (5) which are coaxially arranged in sequence, and also comprises a bracket capable of limiting the distance between the first rotating shaft (1) and the second rotating shaft (5); the first rotating shaft (1) and the second rotating shaft (5) are each rotatably mounted on the bracket, the first friction plate (2) is fixedly connected to the first rotating shaft (1), and the second friction plate (3) and the second rotating shaft (5) are respectively fixedly connected to two ends of the heat expansion unit (4); when the heat expansion unit (4) is not heated, the first friction plate (2) and the second friction plate (3) are separated from each other; when the heat expansion unit (4) is heated, the axial dimension increases, forcing the first friction plate (2) and the second friction plate (3) to contact and squeeze each other; The thermal expansion unit (4) comprises a cylinder (41), a piston (42) slidably fitted in the cylinder (41), a heating component (43) capable of heating the cylinder (41), and a thermal expansion medium filled in a cavity between the cylinder (41) and the piston (42); the heating component (43) causes the thermal expansion medium to expand due to heat, thereby pushing the piston (42) to move in a direction away from the cylinder (41); The thermal expansion medium is a liquid thermal expansion medium; The heating assembly (43) comprises an electric heating film (431) wrapped around the circumference of the cylinder body (41) and rotating with the cylinder body (41), a first annular electrode (432) and a second annular electrode (433) fixed at two ends of the electric heating film (431), a first brush (434) elastically contacting the first annular electrode (432), and a second brush (435) elastically contacting the second annular electrode (433); the electric heating film (431) is heated by supplying power between the first brush (434) and the second brush (435); The piston (42) is fixed on the back side of the second friction disk (3), and the closed end of the cylinder body (41) is fixed on the second rotating shaft (5); a group of protrusions (411) are provided at the opening of the cylinder body (41), and a group of recesses (31) are provided on the back side of the second friction disk (3); the protrusions (411) are embedded in the recesses (31) to transmit torque; The outer circumference of the piston (42) is provided with one or more sealing rings (44).

2. The variable clutch according to claim 1, characterized in that: The bracket comprises a first end panel (91) and a second end panel (92) arranged opposite to each other, and also comprises a group of connecting rods (93) fixedly connected between the first end panel (91) and the second end panel (92); the first end panel (91) and the second end panel (92) are both provided with shaft holes in the center, the first rotating shaft (1) is rotatably connected to the first end panel (91), and the second rotating shaft (5) is rotatably connected to the second end panel (92).

3. The variable clutch according to claim 2, characterized in that: The first rotating shaft (1) is also provided with a first thrust bearing (6), and the first thrust bearing (6) is located between the first end panel (91) and the first friction plate (2); the second rotating shaft (5) is also provided with a second thrust bearing (7), and the second thrust bearing (7) is located between the second end panel (92) and the cylinder body (41).

4. A torque protection electric screwdriver, comprising a motor at the upstream end of the power and a screwdriver shaft at the downstream end of the power, wherein the end of the screwdriver shaft has a replaceable magnetic screwdriver head, characterized in that: The adjustable clutch according to any one of claims 1 to 3 is connected in series on the transmission path between the motor and the screwdriver shaft.

5. The torque protection electric screwdriver according to claim 4, characterized in that: A speed change gear box is connected in series between the adjustable clutch and the motor or between the adjustable clutch and the screwdriver shaft.

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