CN114473967A - Electric tool - Google Patents

Electric tool Download PDF

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Publication number
CN114473967A
CN114473967A CN202210073360.9A CN202210073360A CN114473967A CN 114473967 A CN114473967 A CN 114473967A CN 202210073360 A CN202210073360 A CN 202210073360A CN 114473967 A CN114473967 A CN 114473967A
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CN
China
Prior art keywords
torque
clutch
motor
power tool
transmission gear
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Pending
Application number
CN202210073360.9A
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Chinese (zh)
Inventor
肖胜强
赵殿虎
朱爱民
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Yongkang Crown Power Tools Manufacture Co ltd
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Yongkang Crown Power Tools Manufacture Co ltd
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Publication date
Application filed by Yongkang Crown Power Tools Manufacture Co ltd filed Critical Yongkang Crown Power Tools Manufacture Co ltd
Priority to CN202210073360.9A priority Critical patent/CN114473967A/en
Publication of CN114473967A publication Critical patent/CN114473967A/en
Pending legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25F—COMBINATION OR MULTI-PURPOSE TOOLS NOT OTHERWISE PROVIDED FOR; DETAILS OR COMPONENTS OF PORTABLE POWER-DRIVEN TOOLS NOT PARTICULARLY RELATED TO THE OPERATIONS PERFORMED AND NOT OTHERWISE PROVIDED FOR
    • B25F5/00—Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
    • B25F5/001—Gearings, speed selectors, clutches or the like specially adapted for rotary tools
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B45/00—Hand-held or like portable drilling machines, e.g. drill guns; Equipment therefor
    • B23B45/02—Hand-held or like portable drilling machines, e.g. drill guns; Equipment therefor driven by electric power
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25D—PERCUSSIVE TOOLS
    • B25D16/00—Portable percussive machines with superimposed rotation, the rotational movement of the output shaft of a motor being modified to generate axial impacts on the tool bit
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D43/00—Automatic clutches
    • F16D43/02—Automatic clutches actuated entirely mechanically
    • F16D43/20—Automatic clutches actuated entirely mechanically controlled by torque, e.g. overload-release clutches, slip-clutches with means by which torque varies the clutching pressure
    • F16D43/202—Automatic clutches actuated entirely mechanically controlled by torque, e.g. overload-release clutches, slip-clutches with means by which torque varies the clutching pressure of the ratchet type
    • F16D43/2028—Automatic clutches actuated entirely mechanically controlled by torque, e.g. overload-release clutches, slip-clutches with means by which torque varies the clutching pressure of the ratchet type with at least one part moving radially between engagement and disengagement

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Portable Power Tools In General (AREA)
  • One-Way And Automatic Clutches, And Combinations Of Different Clutches (AREA)
  • Percussive Tools And Related Accessories (AREA)

Abstract

The application provides an electric tool, through set up the concave part on drive gear, set up the clutch piece in the recess of clutch disc, a clutch piece is connected with an elastic component, when electric tool needs overload protection, adopts the elastic component to connect and can give the stroke space of certain buffering of clutch piece, like this first moment of torsion transmission face on the concave part with when second moment of torsion transmission face on the slider breaks away from each other, can not produce huge frictional force, leads to its wearing and tearing. Further, the gradient of the first torque transmission surface and the second torque transmission surface satisfies the formula: 90-0.5 arcsin2W1/F<α<90°‑arctan mu, so that the electric tool can be ensured to normally work, and easy overload protection is not easy to occur.

Description

Electric tool
Technical Field
The invention relates to the technical field of electric tools, in particular to an electric tool with overload protection.
Background
In torque transmission, a mechanical torque transmission device that is provided as a torque limiter (overload protection device) for protecting a machine when an excessive torque is generated due to some cause, in particular, performs torque transmission by engagement of a protrusion and a recess.
For example, the torque transmission device is configured as follows: torque transmission is performed by engaging a protrusion provided on a clutch surface (engagement surface) of one of a driving-side clutch disc and a driven-side clutch disc disposed on the same axis with each other and a recess provided on the other clutch surface, and torque transmission is interrupted by disengaging the engagement. The clutch disc has a protrusion side engagement surface and a recess side engagement surface formed as torque transmission surfaces on the protrusion and the recess, and extends linearly in a radial direction on a normal line of the clutch disc while being inclined at a predetermined angle in a rotational axis direction.
When an excessive torque is generated, the protrusion and the recess of the torque limiter are engaged with each other with an elastic force that defines a maximum transmission force, and the protrusion and the recess slide relative to each other in the axial direction against the elastic force by an axial force acting between the protrusion-side engagement surface and the recess-side engagement surface (inclined surface in the rotational axial direction), thereby releasing the engagement. In particular, when the torque limiter is used, since the engaging and disengaging operation of the engaging surfaces is performed with receiving a large load, it is easy to wear, and there is a need for improvement in this point.
Disclosure of Invention
The invention aims to provide an electric tool, which aims to solve the technical problem that gears are easily abraded due to overload protection in the conventional electric tool.
To achieve the above object, the present application provides an electric power tool including:
a housing;
a motor including a motor shaft, the motor disposed within the housing;
the transmission mechanism comprises a transmission gear and an output shaft, the transmission gear is meshed with the motor shaft, and the transmission gear is in clearance fit with the output shaft; a plurality of concave parts are arranged on the end surface of the inner ring of the transmission gear, and each concave part is provided with a first torque transmission surface;
the clutch mechanism comprises a clutch disc, at least two clutch blocks and at least two elastic pieces, wherein one end face of the clutch disc is provided with at least two grooves, one elastic piece is arranged in one groove, one clutch block is arranged on one elastic piece and is partially arranged in the groove, the elastic piece is provided with a pre-tightening force capable of driving the clutch blocks to reciprocate along the radial direction of the clutch disc, and the clutch blocks can be matched with or separated from the concave parts; the clutch disc is fixedly connected with the output shaft; wherein the clutch plate has a second torque transmitting surface and the first and second torque transmitting surfaces have the same slope;
and, the gradient satisfies the formula: 90-0.5 arcsin2W1/F <α<90-arctan mu; wherein α is a slope of the first torque transfer surface or the second torque transfer surface; mu is a friction coefficient; w is a group of1The elastic force of the elastic piece when the elastic piece is deformed maximally; f is the force of the transmission gear on the clutch block in the vertical direction.
Optionally, in the power tool, the power tool is configured to: when the instantaneous torque of the motor satisfies the formula: t is<T0≤0.8TmaxWhen the clutch plate is disengaged from the recess, there is relative movement between the first torque transmitting surface and the second torque transmitting surface; wherein, T0Is the instantaneous torque of the motor; t is the overload protection torque of the motor; t ismaxIs the maximum torque of the motor.
Optionally, in the power tool, the power tool is configured to: when the instantaneous torque of the motor satisfies the formula: t is a unit of0When the torque is less than or equal to T, the first torque transmission surface and the second torque transmission surface are matched without relative movement; wherein, T0Is the instantaneous torque of the motor; and T is the overload protection torque of the motor.
Optionally, in the electric tool, the number of the grooves satisfies a formula: n = F sin α cos α/W1(ii) a n is the number of the grooves and is an integer; f is the force in the vertical direction generated by the transmission gear to the clutch block; w1The elastic force of the elastic piece when the elastic piece is deformed maximally; α is a gradient of the first torque transmission surface or the second torque transmission surface.
Optionally, in the electric tool, the elastic member is a spring or an elastic sheet.
Optionally, in the electric tool, when the elastic member is a spring, the width of the groove satisfies the formula S > D +1.5 mm; wherein S is the width of the groove; d is the pitch diameter of the spring; d is the wire diameter of the spring.
Optionally, in the electric tool, the transmission gear and the clutch block are made of steel.
Optionally, in the electric tool, the number of the concave parts is not less than the number of the clutch blocks.
Optionally, in the power tool, a shape of an end of the clutch block near the transmission gear matches a shape of the recess.
Optionally, in the electric tool, the electric tool is a hammer drill.
Compared with the prior art, the electric tool that this application provided sets up the separation and reunion piece through setting up the concave part on drive gear, in the recess of clutch disc, and a separation and reunion piece is connected with an elastic component, when electric tool needs overload protection, adopts the elastic component to connect and can give the stroke space of certain buffering of separation and reunion piece, like this first moment transmission face on the concave part with when second moment transmission face on the slider breaks away from each other, can not produce huge frictional force, lead to its wearing and tearing. Further, the gradient of the first torque transmission surface and the second torque transmission surface satisfies the formula: 90-0.5 arcsin2W1/F <α<90-arctan mu, so that the normal operation of the electric tool can be ensured, and easy overload protection is not easy to occur.
Drawings
Fig. 1 is an exploded view of a power tool according to an embodiment of the present application;
FIG. 2 is a block diagram illustrating normal operation of a transmission gear and a clutch plate according to an embodiment of the present disclosure;
FIG. 3 is a block diagram of an initial overload protection transient of the transmission gear and clutch plate provided by an embodiment of the present application;
FIG. 4 is a block diagram illustrating an exemplary embodiment of the present invention for providing initial overload protection of the transmission gear and the clutch plate;
FIG. 5 is a schematic view of an assembly of a transmission gear and a clutch mechanism provided by an embodiment of the present application;
FIG. 6 is a schematic assembly view of yet another drive gear and clutch mechanism provided by an embodiment of the present application;
fig. 7 is an assembly schematic diagram of a transmission gear and a clutch mechanism provided by an embodiment of the application.
Wherein the reference numerals of figures 1-7 are as follows:
10-a housing; 20-a motor; 21-a motor shaft; 30-a transmission gear; 31-a recess; 32-a first torque transfer surface; 40-an output shaft; 50-a clutch mechanism; 51-clutch disc; 52-a clutch block; 53-a spring; 511-grooves; 521-a second torque-transmitting surface.
Detailed Description
To further clarify the objects, advantages and features of the present invention, a power tool according to the present invention will be described in further detail with reference to the accompanying drawings 1 to 7. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
As used in this specification, the singular forms "a", "an" and "the" include plural referents, and the plural forms "a plurality" includes more than two referents unless the content clearly dictates otherwise. As used in this specification, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise, and the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either fixedly connected, detachably connected, or integrally connected. Either directly or indirectly through intervening media, either internally or in any other relationship. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.
Referring to fig. 1, a power tool includes: the casing 10, the motor 20, the transmission mechanism and the clutch mechanism 50. The motor 20 includes a motor shaft 21, and the motor 20 is disposed in the housing 10. The transmission mechanism comprises a transmission gear 30 and an output shaft 40, the transmission gear 30 is meshed with the motor shaft 21, and the transmission gear 30 is in clearance fit with the output shaft 40; a plurality of recesses 31 are formed on the inner ring end surface of the transmission gear 30, and the recesses 31 have a first torque transmission surface 32. The clutch mechanism 50 comprises a clutch disc 51, at least two clutch blocks 52 and at least two elastic members, wherein one end face of the clutch disc 51 is provided with at least two grooves 511, one elastic member is arranged in one groove 511, and one clutch block 52 is arranged on one elastic member and is partially arranged in the groove 511. Wherein the number of the grooves 511, the springs 53 and the clutch pieces 52 is the same. The elastic piece has a pre-tightening force capable of driving the clutch block 52 to reciprocate along the radial direction of the clutch disc 51, and the clutch block 52 can be matched with the concave part 31 or separated from the concave part 31; the clutch disc 51 is fixedly connected with the output shaft 40; wherein the clutch plate 52 has a second torque transmitting surface 521, and the first torque transmitting surface 32 and the second torque transmitting surface 521 have the same slope.
Wherein, because the transmission gear 30 is in clearance fit with the output shaft 40, the clutch disc 51 is in interference fit with the output shaft 40, when the electric tool works normally, the second torque transmission surface 521 of the clutch block 52 is abutted with the first torque transmission surface 32 of the concave portion 31, the torque of the motor 20 is transmitted to the output shaft 40 through the clutch disc 51, when the electric tool is overload-protected, the second torque transmission surface 521 of the clutch block 52 and the first torque transmission surface 32 of the concave portion 31 move relatively and depart from each other, so that when the motor 20 rotates, the torque is transmitted to the transmission gear 30, because the transmission gear 30 is in clearance fit with the output shaft 40, the transmission gear 30 does not directly transmit the torque to the output shaft 40, and only does circular motion along the output shaft 40, at this time, the transmission gear 30 and the clutch disc 51 are always in a slipping state, so that the torque of the motor 20 is not transmitted to the output shaft 40 through the clutch disc 51. This ensures both normal operation of the power tool and overload protection when the output shaft 40 is stuck.
And, the gradient satisfies the formula: 90-0.5 arcsin2W1/F <α<90-arctan mu; wherein α is the slope of the first torque transfer surface 32 or the second torque transfer surface 521; mu is a friction coefficient; w1The elastic force of the elastic piece when the elastic piece is deformed maximally; f is the vertical force of the drive gear 30 against the clutch block 52.
The research shows that when the gradient alpha of the first torque transmission surface 32 or the second torque transmission surface 521 is less than or equal to 90-0.5 arcsin2W1at/F, overload protection is easily generated, that is, when the output shaft 40 is not locked, since the slope α of the first torque transmission surface 32 or the second torque transmission surface 521 is too small, relative movement between the first torque transmission surface 32 and the second torque transmission surface 521 is easily generated, which may cause difficulty in transmitting the torque of the motor 20 to the output shaft 40 by the transmission gear, and thus, normal operation of the electric power tool may be affected. When the slope α of the first torque transmission surface 32 or the second torque transmission surface 521 is greater than or equal to 90 ° -arctan μ, the overload is easily unprotected, that is, when the output shaft 40 is stuck, because the slope α of the first torque transmission surface 32 or the second torque transmission surface 521 is too large, the first torque transmission surface 32 and the second torque transmission surface 521 are not easily moved relative to each other, which may cause the transmission gear to be difficult to separate from the output shaft 40, and when the output shaft 40 is stuck, the overload protection is difficult to occur, which may cause the motor 20 to be burned out. The gradient of the first torque transmission surface 32 or the second torque transmission surface 521 is set so as to satisfy the following equation: 90-0.5 arcsin2W1/F <α<90-arctan mu, and can effectively achieve overload protection.
By providing the transmission gear 30 with the recess 31, the clutch plate 51 is engagedThe recess 511 is provided with a clutch piece 52, and a clutch piece 52 is connected with an elastic member, so that when the electric tool needs overload protection, the elastic member is connected to give a certain buffering stroke space to the clutch piece 52, so that when the first torque transmission surface 32 on the concave part 31 and the second torque transmission surface 521 on the sliding block are separated from each other, great friction force is not generated, and the electric tool is not worn. Further, the slopes of the first torque transmission surface 32 and the second torque transmission surface 521 satisfy the formula: 90-0.5 arcsin2W1/F <α<90-arctan mu, so that the normal operation of the electric tool can be ensured, and easy overload protection is not easy to occur.
Referring to fig. 2, in conjunction with fig. 1 and 3-4. Wherein the power tool is configured to: when the instantaneous torque of the motor 20 satisfies the formula: t is<T0≤0.8TmaxWhen so, there is relative movement between the first torque transmitting surface 32 and the second torque transmitting surface 521, and the clutch plate 52 disengages from the recess 31; wherein, T0Is the instantaneous torque of the motor 20; t is the overload protection torque of the motor 20; t ismaxIs the maximum torque of the motor 20. That is, when the instantaneous torque of the motor 20 satisfies the formula: t is<T0≤0.8TmaxWhen the first torque transmission surface 32 and the second torque transmission surface 521 have relative movement, the electric tool immediately starts overload protection, so that the motor 20 can be effectively prevented from being burnt out.
Meanwhile, the electric tool is configured to: when the instantaneous torque of the motor 20 satisfies the formula: t is0At T or less, the first torque transmitting surface 32 and the second torque transmitting surface 521 are engaged without relative movement; wherein, T0Is the instantaneous torque of the motor 20; t is the overload protection torque of the motor 20. That is, when the instantaneous torque of the motor 20 satisfies the formula: t is0When T is less than or equal to T, the first torque transmission surface 32 and the second torque transmission surface 521 are matched without relative movement, so that the electric tool can be ensured to normally work, and the easy overload protection is not easy to occur.
In one of the two casesIn the embodiment, the number of the grooves 511 satisfies the formula: n = F sin α cos α/W1(ii) a n is the number of the grooves 511, and n is an integer; f is the vertical force of the transmission gear 30 on the clutch block 52; w1The elastic force of the elastic piece when the elastic piece is deformed maximally; α is the slope of the first torque transfer surface 32 or the second torque transfer surface 521. That is, the number of the grooves 511 is proportional to the vertical force of the transmission gear 30 on the clutch piece 52. That is, the greater the number of recesses 511 and the vertical force applied to clutch block 52 by drive gear 30, the greater the number of recesses 511, that is, the greater the number of clutch blocks 52 required. The number of the grooves 511 is inversely proportional to the elastic force of the elastic member at the maximum deformation, that is, the larger the number of the grooves 511 and the elastic force of the elastic member at the maximum deformation are, the smaller the number of the grooves 511 is, that is, the smaller the required clutch piece 52 is. The elastic member having a high elastic force at the time of maximum deformation can be selected as much as possible from the viewpoint of compactness and cost saving while ensuring reasonable overload protection of the clutch mechanism 50.
Wherein, the elastic member is a spring 53 or an elastic sheet. Taking the elastic member as the spring 53 as an example, the maximum deformation amount of the spring 53 satisfies the formula: x = R1-R2 ，R2＜R1. Wherein, X is the maximum deformation of the spring 53; r is1Is the inner ring radius of the drive gear 30; r2Is the radius of the clutch disc 51. The maximum deformation of the spring 53, that is, the maximum stroke of the clutch plate 52, is to be described.
And the width of the groove 511 and the parameters of the spring 53 satisfy the formula S > D + D +1.5 mm; wherein S is the width of the groove 511; d is the pitch diameter of the spring 53; d is the wire diameter of the spring 53. Therefore, the spring 53 can be ensured to move smoothly in the deformation process, and the smooth deformation caused by the influence of the width of the groove 511 is avoided.
The transmission gear 30 and the clutch block 52 are made of steel. This ensures rigidity of the transmission gear 30 and the clutch block 52, while satisfying the requirement of the friction coefficient required for the overload protection.
Wherein the number of the concave parts 31 is not less than the number of the clutch blocks 52. In this embodiment, the number of the recesses 31 does not need to be the same as the number of the clutch pieces 52, and when the number of the recesses 31 is larger than the number of the clutch pieces 52, when an overload occurs during the operation of the electric power tool, the obstruction in the overload protection process can be reduced appropriately.
The shape of the end of the clutch block 52 close to the transmission gear 30 matches the shape of the recess 31. That is, when the cross section of the recess 31 has a trapezoidal shape, the cross section of the end of the clutch block 52 near the transmission gear 30 and the trapezoidal shape of the cross section of the recess 31 are similar to a trapezoidal shape, and preferably, the cross section of the recess 31 and the cross section of the end of the clutch block 52 near the transmission gear 30 have an isosceles trapezoidal shape.
Wherein the electric tool is a percussion drill. The impact drill will now be further described by way of example. Specifically, the rated power of the motor 20 is 800W, and the maximum torque T ismax=4.5 Nm, inner ring radius R of the transmission gear 301=20 mm; radius R of the clutch disc 512=18mm, the number of the grooves 511 is 4, and it is found that the stroke of the clutch block 52 and the maximum deformation amount of the spring 53 are X =2mm, the pitch diameter D =4mm of the spring 53, the wire diameter D =1mm of the spring 53, and the number of effective turns n of the spring 53 is X =2mm1And = 3. The spring coefficient K = Gd of the spring 53 can be known4/8n1D3=821N/m, G is the modulus of elasticity of the material of the spring 53, N1Is an effective number of turns. The instantaneous torque T of the motor 20 is known0An overload protection occurs at approximately 3.6N/m, when the resultant force F of the transmission gear 30 on the clutch piece 52 is obtainedGeneral assembly=T0/[R2+（R1-R2）/2]=189.5N, when F = FGeneral assembly/4= 47.4N. Elastic force W of the elastic member at maximum deformation1=10.41N。
And the stationThe transmission gear 30 and the clutch block 52 are made of steel materials, and the friction coefficient mu =0.15, according to the formula 90-0.5 arcsin2W1/F <α<90 ° -arctan μ, obtain 76.975 °<α<81.5 °, i.e. in the hammer drill, the slope α of the first torque transmission surface 32 or the second torque transmission surface 521 is 76.975 ° to 81.5 °, which not only ensures the normal operation of the electric tool, but also protects the electric tool from overload.
Referring specifically to fig. 5, in conjunction with fig. 1, specifically, taking the number of the clutch pieces 52 as 4 as an example, the other conditions are as above, the effect of the overload protection is verified by setting different slopes α of the first torque transmission surface 32 or the second torque transmission surface 521, and part of the experimental data is as follows:
Figure 642239DEST_PATH_IMAGE002
it is noted that 76.975 ° is satisfied when the gradient α of the first torque transmission surface 32 or the second torque transmission surface 521 is 77 °<α<81.5 deg. at this time W2≈W1As long as the instantaneous torque of the motor 20 during the operation satisfies: t is<T0≤0.8TmaxAnd if T is more than or equal to T0, the electric tool does not need overload protection and continues to work normally.
It can also be seen that 76.975 ° is not satisfied when the gradient α of the first torque transmission surface 32 or the second torque transmission surface 521 is 83 °, respectively<α<81.5 deg. at this time W2<W1So even if the instantaneous torque of the motor 20 at the time of the operation satisfies: t is<T0≤0.8TmaxIn time, overload protection cannot be realized, which easily causes the motor 20 to burn out.
It can also be seen that the slope α of the first torque transmission surface 32 or the second torque transmission surface 521 does not satisfy 76.975 ° when 75 ° is set as the slope α of the first torque transmission surface 32 or the second torque transmission surface 521<α<81.5 deg. at this time W2＞W1So that the motor 20 instantaneously generates the torque T when said operation is performed0At the moment of not more than T, the motor is operated at the moment of 20The overload protection starts to appear when the torque does not reach the load needing the overload protection, and the normal work of the electric tool is easily influenced.
Referring specifically to fig. 6, in combination with fig. 1, specifically, taking the number of the clutch blocks 52 as 6 as an example, the motor 20 has the same parameters, and the effect of overload protection is verified by setting different slopes α of the first torque transmission surface 32 or the second torque transmission surface 521, and part of the experimental data is as follows:
Figure 90538DEST_PATH_IMAGE004
it is noted that 76.975 ° is satisfied when the gradient α of the first torque transmission surface 32 or the second torque transmission surface 521 is 77.5 °<α<81.5 deg. at this time W2≈W1As long as the instantaneous torque of the motor 20 during the operation satisfies: t is<T0≤0.8TmaxAnd if T is more than or equal to T0, the electric tool does not need overload protection and continues to work normally.
It can also be seen that the slope α of the first torque transmission surface 32 or the second torque transmission surface 521 does not satisfy 76.975 ° when 76 ° is provided as the slope α of the torque transmission surface 32 or the second torque transmission surface 521<α<81.5 deg. at this time W2＞W1So that the motor 20 instantaneously generates the torque T when said operation is performed0T is less than or equal to T, overload protection begins to appear when the instantaneous torque of the motor 20 does not reach the load needing overload protection in the working process, and the normal work of the electric tool is easily influenced.
It can also be seen that 76.975 ° < α <81.5 ° is not satisfied when the slope α of the first torque transmission surface 32 or the second torque transmission surface 521 is 83 °, at which time W2< W1, so that even if the instant torque of the motor 20 at the time of the operation satisfies: when T < T0 is not more than 0.8Tmax, overload protection cannot be realized, which easily causes burning out of the motor 20.
Of course, the number of the grooves 511 may be set to 3 according to the power of the motor 20 of the power tool, the size of the transmission gear 30, the size of the clutch disc 51 and the size of the spring 53, as shown in fig. 7.
From the above description of the present specification, those skilled in the art will also understand the terms used below, terms indicating orientation or positional relationship such as "upper", "lower", "front", "rear", "left", "right", "length", "width", "thickness", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", "central", "longitudinal", "transverse", "clockwise" or "counterclockwise" and the like are based on the orientation or positional relationship shown in the drawings of the present specification, it is used for convenience in explanation of the disclosure and for simplicity of description, and does not explicitly or implicitly indicate that the device or element concerned must be constructed and operated in the particular orientation described, therefore, the above terms of orientation or positional relationship should not be interpreted or construed as limiting the present application.
The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the appended claims.

Claims (10)

1. A power tool, comprising:
a housing;
a motor including a motor shaft, the motor disposed within the housing;
the transmission mechanism comprises a transmission gear and an output shaft, the transmission gear is meshed with the motor shaft, and the transmission gear is in clearance fit with the output shaft; a plurality of concave parts are arranged on the end surface of the inner ring of the transmission gear, and each concave part is provided with a first torque transmission surface;
the clutch mechanism comprises a clutch disc, at least two clutch blocks and at least two elastic pieces, wherein one end face of the clutch disc is provided with at least two grooves, one elastic piece is arranged in one groove, one clutch block is arranged on one elastic piece and is partially arranged in the groove, the elastic piece is provided with a pre-tightening force capable of driving the clutch blocks to reciprocate along the radial direction of the clutch disc, and the clutch blocks can be matched with or separated from the concave parts; the clutch disc is fixedly connected with the output shaft; wherein the clutch plate has a second torque transmitting surface and the first and second torque transmitting surfaces have the same slope;
and, the gradient satisfies the formula: 90-0.5 arcsin2W1/F <α<90-arctan mu; wherein α is a slope of the first torque transfer surface or the second torque transfer surface; mu is a friction coefficient; w1The elastic force of the elastic piece when the elastic piece is deformed maximally; f is the force of the transmission gear on the clutch block in the vertical direction.
2. The power tool of claim 1, wherein the power tool is configured to: when the instantaneous torque of the motor satisfies the formula: t is<T0≤0.8TmaxWhen the clutch plate is disengaged from the recess, there is relative movement between the first torque transmitting surface and the second torque transmitting surface; wherein, T0Is the instantaneous torque of the motor; t is the overload protection torque of the motor; t ismaxIs the maximum torque of the motor.
3. The power tool of claim 1, wherein the power tool is configured to: when the instantaneous torque of the motor satisfies the formula: t is0When the torque is less than or equal to T, the first torque transmission surface and the second torque transmission surface are matched without relative movement; wherein, T0Is the instantaneous torque of the motor; and T is the overload protection torque of the motor.
4. The power tool of claim 1, wherein the number of grooves satisfies the formula: n = F sin α cos α/W1(ii) a n is the number of the grooves and is an integer; f is the force in the vertical direction generated by the transmission gear to the clutch block; w1Is the most elastic partElasticity at large deformation; α is a gradient of the first torque transmission surface or the second torque transmission surface.
5. The power tool of claim 1, wherein the resilient member is a spring or a resilient tab.
6. The power tool of claim 5, wherein when the elastic member is a spring, the width of the groove satisfies the formula S > D + D +1.5 mm; wherein S is the width of the groove; d is the pitch diameter of the spring; d is the wire diameter of the spring.
7. The power tool of claim 1, wherein said drive gear and said clutch block are formed of steel.
8. The power tool of claim 1, wherein the number of recesses is not less than the number of clutch blocks.
9. The power tool of claim 1, wherein an end of the clutch block proximate the drive gear has a shape that matches a shape of the recess.
10. The power tool of claim 1, wherein the power tool is a hammer drill.
CN202210073360.9A 2022-01-21 2022-01-21 Electric tool Pending CN114473967A (en)

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EP0870945A1 (en) * 1997-04-12 1998-10-14 GKN Walterscheid GmbH Torque limiting clutch
CN1833826A (en) * 2005-03-18 2006-09-20 百得有限公司 Power tool torque overload clutch
US20080214313A1 (en) * 2004-05-03 2008-09-04 Jaeger Daryl J Torque Overload Clutch
CN101561020A (en) * 2008-04-15 2009-10-21 株式会社椿艾默生 Overload protection device
CN201998147U (en) * 2010-12-16 2011-10-05 浙江通达电器有限公司 Anti-overload impact drill
CN102233565A (en) * 2010-04-23 2011-11-09 株式会社牧田 Power tool
CN103180104A (en) * 2010-10-27 2013-06-26 罗伯特·博世有限公司 Overload coupling
CN206366976U (en) * 2016-11-01 2017-08-01 苏州宝时得电动工具有限公司 Electric hammer overlond trip structure and electric hammer
CN107654534A (en) * 2017-10-19 2018-02-02 兰州万里航空机电有限责任公司 A kind of embedded clutch for aeroplane motor structure
CN208348347U (en) * 2018-05-24 2019-01-08 重庆海德世拉索系统（集团）有限公司 The mechanical overload clutch of motorcar electric strut

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* Cited by examiner, † Cited by third party
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EP0870945A1 (en) * 1997-04-12 1998-10-14 GKN Walterscheid GmbH Torque limiting clutch
US20080214313A1 (en) * 2004-05-03 2008-09-04 Jaeger Daryl J Torque Overload Clutch
CN1833826A (en) * 2005-03-18 2006-09-20 百得有限公司 Power tool torque overload clutch
CN101561020A (en) * 2008-04-15 2009-10-21 株式会社椿艾默生 Overload protection device
CN102233565A (en) * 2010-04-23 2011-11-09 株式会社牧田 Power tool
CN103180104A (en) * 2010-10-27 2013-06-26 罗伯特·博世有限公司 Overload coupling
CN201998147U (en) * 2010-12-16 2011-10-05 浙江通达电器有限公司 Anti-overload impact drill
CN206366976U (en) * 2016-11-01 2017-08-01 苏州宝时得电动工具有限公司 Electric hammer overlond trip structure and electric hammer
CN107654534A (en) * 2017-10-19 2018-02-02 兰州万里航空机电有限责任公司 A kind of embedded clutch for aeroplane motor structure
CN208348347U (en) * 2018-05-24 2019-01-08 重庆海德世拉索系统（集团）有限公司 The mechanical overload clutch of motorcar electric strut

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Title
郁志纯等: "《现代职业教育汽车类专业精品教材 汽车机械基础》", 31 May 2021, 机械工业出版社, pages: 45 *

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