A constant torque electric power tool

Abstract

The utility model relates to a fixed torque electric tool and belongs to the electric tool technical field. The tool is composed of a handle with a shell and a handlebar extending downward from the handle, the handle includes a driving clutch end driven by a motor through a transmission mechanism and an output shaft with a tool head installed at the extending end, the inner section of the output shaft is sleeved with a passive clutch end constrained in the circumferential direction, the passive clutch end tends to be close to the driving clutch end, a wedge piece is installed between the driving clutch end and the passive clutch end, the inner end of a sensing lever hinged in the shell is connected to the passive clutch end, the outer end of the sensing lever is installed with a magnetic body adjacent to a Hall device, the Hall device is located on a circuit board arranged in the shell, and the lever ratio of the sensing lever makes the axial displacement of the magnetic body greater than that of the passive clutch end. The utility model can amplify the axial displacement of the Hall device, thereby more reliably and effectively sensing, sending a signal that the predetermined torque has been reached, controlling power-off stop, and ensuring consistent screwing operation torque and stable quality.

Description

Technical Field

[0001] This utility model relates to a constant torque power tool, and more particularly to a constant torque wrench, belonging to the field of power tool technology. Background Technology

[0002] A torque-controlled wrench features a mechanism that limits the output torque via an end-face clutch, thus avoiding variations in force applied during human operation. Its basic structure can be found in US Patent No. 10,357,871 and Chinese Patent Applications Nos. 201790001479.8 and 201822216777.8. The power tool disclosed in 201790001479.8 includes: a brushless motor; a main body housing the brushless motor and extending in the front-rear direction; and a grip connected to the main body and extending downwards. When the predetermined torque is reached, it can detect the axial displacement of the clutch slider in the end-face clutch mechanism using a sensor, and through a control circuit, output an luminous notification signal or even a stop function, thus further preventing adverse consequences caused by improper human operation.

[0003] However, due to the small travel of the clutch slider, directly sensing its displacement using Hall effect devices is not sensitive enough and is prone to errors. As a result, it is impossible to reliably control the machine to stop and display, which is not conducive to ensuring the quality of wrench tightening operations and operational safety. Utility Model Content

[0004] The purpose of this utility model is to address the shortcomings of the existing technology by improving the structure and proposing a constant torque electric tool that can be reliably controlled when the predetermined output torque is achieved.

[0005] To achieve the above objectives, the basic technical solution of the constant torque electric tool of this utility model is as follows: it consists of a head with a housing and a handle extending downward from the head. The head includes an active clutch end driven by a motor through a transmission mechanism and an output shaft with a tool head mounted on its extended end. The inner section of the output shaft is fitted with a passive clutch end that is circumferentially constrained thereto. The passive clutch end tends to be closer to the active clutch end. A wedge is installed between the active clutch end and the passive clutch end. The improvement is that the passive clutch end is connected to the inner end of a sensing lever hinged in the middle of the housing. A magnetic body adjacent to a Hall effect device is installed at the outer end of the sensing lever. The Hall effect device is located on a circuit board mounted on the housing. The lever ratio of the sensing lever makes the axial displacement of the magnetic body greater than that of the passive clutch end.

[0006] It is easy to understand that, due to the addition of the sensing lever structure, when the predetermined output torque is reached and the passive clutch end moves axially away from the active clutch end, its displacement is amplified, so that the Hall device can sense more reliably and effectively, send a signal that the predetermined torque has been reached, control the power-off and stop the machine, ensure consistent torque and stable quality in the twisting operation, and issue an indication signal when necessary.

[0007] Further: the active clutch end is composed of an end face ratchet, and the passive clutch end is composed of a clutch slider; the end faces of the end face ratchet and the clutch slider adjacent to each other have ratchet teeth distributed at intervals, and a clutch steel ball as a wedging element is installed between the end face ratchet and the clutch slider.

[0008] Furthermore, the clutch slider and the output shaft form an axially moving pair with circumferential constraints through torsion transmission steel balls that are respectively embedded in the inner groove of the clutch slider and the corresponding groove on the outer circle of the output shaft.

[0009] Furthermore: the clutch slider and the output shaft are connected by a slide key to form an axial moving pair with circumferential constraint.

[0010] Furthermore, the clutch slider tends to move towards the end face ratchet under the action of the clutch spring fitted on the output shaft.

[0011] Furthermore, the inner hole of the end face ratchet forms a rotating pair with it through the bearing steel ball embedded in the output shaft.

[0012] Furthermore: the transmission mechanism is a planetary gear reduction mechanism with an output planetary carrier, and the end of the end face ratchet adjacent to the transmission mechanism has a reduced diameter section that inserts into the recess of the output planetary carrier end face to form a circumferential constraint.

[0013] Further: The outer section of the sensing lever abuts against the free end of the compression spring constrained to the housing at one end. Attached Figure Description

[0014] The present invention will be further described below with reference to the accompanying drawings.

[0015] Figure 1 This is a structural schematic diagram of Embodiment 1 of the present invention.

[0016] Figure 2 yes Figure 1 A schematic diagram of the sensing lever in the clutch engagement position in the embodiment.

[0017] Figure 3 yes Figure 1 A schematic diagram of the sensor lever in the disengaged position according to the embodiment.

[0018] Figure 4 yes Figure 1 An exploded view of the sensing amplification component in the embodiment. Detailed Implementation

[0019] Example

[0020] This embodiment is a constant torque electric wrench, the structure of which is as follows: Figure 1 As shown, the device consists of a head 2 located within a housing 1 and a handle 3 extending downward from the head. The head 2 includes a ratchet 2-3 driven by a motor 2-1 via a transmission mechanism 2-2, serving as the active clutch end, and an output shaft 2-5 with a wrench head 4 mounted on its extended end. A clutch slider 2-4, serving as the passive clutch end, is fitted inside the output shaft 2-5. The clutch slider 2-4 and the output shaft 2-5 form a circumferentially constrained axial movement pair via torque-transmitting steel balls 2-6 embedded in the inner groove of the clutch slider 2-4 and the corresponding groove on the outer circumference of the output shaft 2-5, respectively. Under the action of a clutch spring 2-7 fitted onto the output shaft, the clutch slider 2-4 tends to move towards the ratchet 2-3. The end faces of the ratchet 2-3 and the clutch slider 2-4 adjacent to each other have spaced ratchet teeth 2-3.1 (see [reference]). Figure 4 The end face ratchet 2-3 and the clutch slider 2-4 are equipped with a clutch steel ball 2-8 as a wedge, so that torque can be transmitted when the adjacent end faces of the two are close together.

[0021] The transmission mechanism 2-2 is a two-stage planetary gear reduction transmission mechanism mainly composed of a first-stage planetary gear 2.1, a first-stage sun gear 2.3, a second-stage planetary gear 2.2, a second-stage sun gear 2.4, an internal gear ring 2.5, and an output planetary carrier 2.7 (similar to existing technology, not detailed here). The inner hole of the end-face ratchet 2-3 forms a rotating pair with it through the bearing steel ball 2.6 embedded in the output shaft 2-5, and one end adjacent to this transmission mechanism has a reduced diameter section that inserts into the end face recess of the output planetary carrier 2.7 to form a circumferential constraint, thus forming a stable and reliable clutch transmission structure.

[0022] like Figure 2 , 3 As shown in Figure 4, the clutch slider 2-4 is connected to the inner end hook of the sensing lever 5, which is hinged in the middle of the housing. The outer end of the sensing lever 5 is equipped with a magnetic body adjacent to the Hall device 7. The Hall device 7 is located on the circuit board 6 placed on the housing. Since the outer section of the sensing lever 5 abuts against the free end of the compression spring 8, which is constrained by the housing at one end, its inner end hook is always in close contact with the end face of the clutch slider 2-4. The ratio of the inner section to the outer section lever on both sides of the hinge point of the sensing lever 5 is 1:2, so the axial displacement of the magnetic body relative to the clutch slider 2-4 can be amplified by one time.

[0023] In use, when the output torque does not reach the predetermined threshold, the motor drives the end-face ratchet to rotate through the planetary gear reduction transmission mechanism. The end-face ratchet then drives the clutch slider, which meshes with it, through the clutch steel balls 2-8, thereby driving the output shaft to rotate and output the torque required for operation. At this time, the transmission lever is as follows: Figure 2 As shown, the magnetic body at its outer end is relatively far from the Hall device on the circuit board, so the Hall device has no induction signal output, and the torque wrench works normally. When the output torque reaches the predetermined threshold, although the motor drives the end face ratchet to rotate through the planetary gear reduction transmission mechanism, the force of the clutch springs 2-7 is insufficient to keep the clutch slider engaged with the end face of the end face ratchet through the clutch steel ball, that is, the clutch steel ball slips, and the clutch slider moves axially to the right. At this time, the transmission lever is as follows: Figure 3 As shown, the magnetic body at its outer end is close to the Hall device on the circuit board. Therefore, the Hall device outputs a sensing signal, which controls the motor to stop turning by cutting off the power through the circuit. This ensures that the torque of the twisting operation is consistent and the quality is stable, and avoids unnecessary wear caused by torque fluctuations due to excessive twisting.

[0024] In addition to the embodiments described above, this utility model may have other implementations. For example, the clutch slider and the output shaft may also be connected by a sliding key to form an axially moving pair with circumferential constraints. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by this utility model.

Claims

1. A constant torque power tool, comprising a head having a housing and a handle extending downward from the head, the head including an active clutch end driven by a motor via a transmission mechanism and an output shaft with a tool head mounted on its extended end, a passive clutch end circumferentially constrained by the inner section of the output shaft, the passive clutch end tending to approach the active clutch end, and a wedging element installed between the active clutch end and the passive clutch end, characterized in that: The passive clutch end is connected to the inner end of the sensing lever of the housing via the central hinge. The outer end of the sensing lever is equipped with a magnetic body adjacent to the Hall device. The Hall device is located on the circuit board of the housing. The lever ratio of the sensing lever makes the axial displacement of the magnetic body greater than that of the passive clutch end.

2. The constant torque power tool according to claim 1, characterized in that: The active clutch end is composed of an end face ratchet, and the passive clutch end is composed of a clutch slider; the end faces of the end face ratchet and the clutch slider adjacent to each other have ratchet teeth distributed at intervals, and a clutch steel ball as a wedging element is installed between the end face ratchet and the clutch slider.

3. The constant torque power tool according to claim 2, characterized in that: The clutch slider and the output shaft form a circumferentially constrained axial moving pair through torsion transmission steel balls that are respectively embedded in the inner groove of the clutch slider and the corresponding groove on the outer circle of the output shaft.

4. The constant torque power tool according to claim 2, characterized in that: The clutch slider and the output shaft are connected by a slide key to form a circumferentially constrained axial moving pair.

5. The constant torque power tool according to claim 3 or 4, characterized in that: The clutch slider tends to move towards the end face ratchet under the action of the clutch spring fitted on the output shaft.

6. The constant torque power tool according to claim 5, characterized in that: The inner hole of the end face ratchet forms a rotating pair with it through the bearing steel ball embedded in the output shaft.

7. The constant torque power tool according to claim 6, characterized in that: The transmission mechanism is a planetary gear reduction mechanism with an output planetary carrier. The end of the end face ratchet adjacent to the transmission mechanism has a reduced diameter section that inserts into the recess of the output planetary carrier end face to form a circumferential constraint.

8. The constant torque power tool according to claim 7, characterized in that: The outer section of the sensing lever rests against the free end of the compression spring that is constrained by the housing.

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