Reciprocating motion power tool

Abstract

The present application relates to a reciprocating electric tool, belonging to the technical field of electric tools. The tool comprises a motor arranged in a housing and a reciprocating output shaft extending from one end of the housing, the motor is in transmission connection with a crank wheel with a biased crank pin, the crank pin is hinged with one end of a connecting rod, the other end of the connecting rod is hinged with the output shaft; further comprising a support with a rotating center coaxial with the crank wheel and a counterweight with a rotating center eccentric to the rotating center of the support, the support has a hinged hole, the counterweight has a radial guide groove, the crank pin is hinged with the hinged hole and forms a moving pair with the radial guide groove. The present application can make the electric tool absorb more rotational inertia energy during the idle stroke, release some rotational inertia energy during the resistance stroke, and as a result, the resistance stroke and the idle stroke are considered, the inertia of the reciprocating electric tool is better through the crank dead point and the resistance stroke, and at the same time, it is more conducive to suppress vibration.

Description

TECHNICAL FIELD

[0001] The present application relates to a hand-held electric power tool, in particular a reciprocating electric power tool, and belongs to the technical field of electric power tools. BACKGROUND

[0002] The reciprocating electric power tool converts the rotary motion of a power source such as a motor into the reciprocating motion required for workpiece machining through a mechanism such as a crank slider. In order to suppress the vibration and noise caused by the mass imbalance of the reciprocating transmission mechanism, a counterbalance device is usually configured.

[0003] A Chinese patent with patent number 201420301516.5 discloses an electric power tool with a counterbalance device, which includes a housing, a motor, and a transmission mechanism. The transmission mechanism includes a driven gear driven by the motor. The driven gear is positioned vertically in the housing and has an upper portion and a lower portion. The transmission mechanism further includes a connecting rod connected to the driven gear to convert the rotary motion of the driven gear into reciprocating motion, and an output shaft connected to the connecting rod to reciprocate relative to the housing to complete a cutting stroke and a return stroke. The transmission mechanism further includes a counterweight connected to the driven gear to rotate with the driven gear. During the cutting stroke of the output shaft, the counterweight moves through the upper portion of the driven gear, and during the return stroke of the output shaft, the counterweight moves through the lower portion of the driven gear.

[0004] The counterbalance devices so far are designed according to the no-load balance of the reciprocating mechanism, without considering the actual situation that the reciprocating electric power tool often only has work resistance in one-way operation. As a result, since the resistance stroke and the no-load stroke are balanced by the same counterweight, it is inevitable that one aspect is compromised for the other, which not only unbalances the vibration suppression effect, but also is not conducive to overcoming the work resistance. SUMMARY

[0005] The present application aims to address the shortcomings of the prior art by improving the structure and providing a reciprocating electric power tool that balances the counterbalance effect of the resistance stroke and the no-load stroke, so as to make the reciprocating electric power tool more convenient to operate and have better work performance.

[0006] To achieve the above purpose, the basic technical scheme of the reciprocating electric power tool of the present application is as follows: it includes a motor arranged in a housing and a reciprocating output shaft extending from one end of the housing, the motor is in transmission connection with a crank wheel with a biased crank pin, the crank pin is hinged to one end of a connecting rod, the other end of the connecting rod is hinged to the output shaft; it further includes a bracket with a rotating center coaxial with the crank wheel and a counterweight with a rotating center eccentric to the rotating center of the bracket, the bracket has a hinge hole, the counterweight has a radial guide groove, the crank pin is hinged to the hinge hole and forms a moving pair with the radial guide groove.

[0007] Since the present application breaks the traditional structure of the counterweight and the crank coaxial rotation, the angular velocity and the center of mass of the counterweight relative to the crank and the support are changed due to the eccentric and radial guide slot mechanism, thus causing the change of the inertial kinetic energy of the counterweight. As long as the angular position of the eccentric is properly set on the side deviated from the return direction of the output shaft, the reciprocating electric tool can absorb more rotational inertia energy during the no-load stroke, and release some rotational inertia energy during the resistance stroke. As a result, the resistance stroke and the no-load stroke are considered, the performance of the inertial reciprocating electric tool through the crank dead point and the resistance stroke is better, and the vibration is also inhibited. BRIEF DESCRIPTION OF DRAWINGS

[0008] The present application will be further described below in conjunction with the drawings.

[0009] Figure 1 is a structural schematic diagram of the embodiment one of the present application.

[0010] Figure 2 is Figure 1 A-A cross-sectional structural schematic diagram of

[0011] Figure 3 is Figure 1 the three-dimensional exploded structural schematic diagram of the reciprocating mechanism part in the embodiment.

[0012] Figure 4 is Figure 2 the three-dimensional exploded structural schematic diagram of another perspective.

[0013] Figure 5 is Figure 1 the force analysis schematic diagram of the counterweight mechanism in the embodiment.

[0014] Figure 6 is Figure 5 the local enlarged structural schematic diagram.

[0015] Figure 7 is the three-dimensional exploded structural schematic diagram of the reciprocating mechanism part in the embodiment two of the present application.

[0016] Figure 8 is the cross-sectional structural schematic diagram of the embodiment two of the present application. DETAILED DESCRIPTION

[0017] Embodiment one

[0018] The reciprocating electric tool in the embodiment is actually a reciprocating saw, and its structure is as follows Figures 1 to 4As shown, the housing is composed of a rear handle housing 1 and a front gear box 2, the gear box 2 is composed of a left box 2-L and a right box 2-R. The handle housing 1 is equipped with a motor 3, the gear box 2 is fixed with a shaft sleeve 2-1 and an axial sliding groove 9, the front end of which extends out of the output shaft 5 supported by the shaft sleeve 2-1. The main shaft 3-2 of the motor 3 is connected with the large gear 4 as a crank wheel through the end cone gear 3-1, the large gear 4 is hinged with one end of the connecting rod 7 and one end of the "8" shaped bracket 8 through the crank pin 6. The other end of the connecting rod 7 is hinged with the output shaft 5 constrained by the sliding groove 9, thus forming a crank slider mechanism to make the output shaft reciprocate.

[0019] The bracket shaft 11 as the rotation center of the bracket 8 is coaxial with the crank shaft 4-1 as the rotation center of the large gear 4, the bracket shaft 11 is supported in the inner hole of the eccentric boss 1-1 of the housing 1 through the needle bearing, the mounting hole of the counterweight 10 is sleeved on the outer circle of the eccentric boss 1-1 through the inner lining roller sleeve 10-2, since the outer circle of the eccentric boss 1-1 has an eccentricity of 0.5mm to the side of the return direction of the output shaft relative to its inner hole, thus making the rotation center of the counterweight 10 eccentric to the rotation center of the bracket 8.

[0020] The bracket 8 has a hinged hole 8-2, the counterweight 10 has a radial guide groove 10-1, the crank pin 6 passes through the hinged hole 8-2 and is hinged therewith, and is inserted into the radial guide groove 10-1 to form a moving pair.

[0021] In operation, as shown in Figure 5 and Figure 6 , C1 is the rotation center of the counterweight 10, C2 is the rotation center of the large gear 4, the distance between C1 and C2 is the eccentricity e, and the center distance between the crank pin 6 and C2 is R2. When the large gear 4 is driven by the motor to rotate at a constant speed, since the crank pin 6 is hinged to the large gear 4, its linear velocity at any time is V, and the direction is perpendicular to R2. At this time, the contact point on the large gear 4 with the crank pin 6 moves synchronously with the crank pin 6, and the velocity of the contact point is also V, which is the same in size and direction as the crank pin 6. The velocity V of the contact point is actually composed of two vector velocities: the linear velocity V1 perpendicular to R1 rotating with the counterweight 10 around the center C1, and the linear velocity V2 sliding along the radial guide groove 10-1. According to vector analysis, the linear velocity V1 of the counterweight 10 is V*cosβ=R2*ω2*cosβ, where β is a function of α, α is the included angle between R2 and the line connecting C1 and C2, and ω2 is the angular velocity of the large gear 4. Thus the angular velocity ω1 of the counterweight 10 is ω1=V1 / R1=R2*ω2*cosβ / R1, where R1 2 =e 2 +R2 2-2*e*R2*cos(pi-a). Based on the above analysis, the counterweight 10 does not rotate at a constant speed with the gear 4, but rotates at a variable speed with the change of the angle a. The kinetic energy of the counterweight J=1 / 2*I*ω2 is known from the energy formula 2 where I is the rotational inertia of the counterweight, and this structure causes the kinetic energy of the counterweight to change with the change of the angular velocity ω2, and the energy storage and release are completed under the driving action of the force of the crank pin 6. Referring to Figure 1 The saw blade reciprocatingly moves in the return stroke to cut the material, and the cutting resistance is large, requiring a large power; and in the opposite direction, the saw blade moves in the idle stroke without cutting the material. The structure of the embodiment realizes that in the idle stroke, the actual load of the motor is light, the rotational speed of the counterweight 10 is increased, and the kinetic energy is increased, thereby accumulating the excess energy of the motor; and in the cutting stroke, the rotational speed of the counterweight 10 is decreased, and the accumulated energy is released, thereby improving the cutting efficiency. For a long time, due to the neglect of the difference between the two strokes, a simple balance structure is adopted in which the counterweight and the gear are coaxial and rotate synchronously, and scientific energy distribution cannot be realized, which is not conducive to reducing the load of the motor and increasing the cutting efficiency.

[0022] Embodiment Two

[0023] The embodiment is also a reciprocating saw, and the basic structure is the same as that of Embodiment One. The difference is as shown in Figure 7 and Figure 8 The two ends of the support shaft 11 are coaxial sections 11-1 and 11-2, which are supported on the left box body 2-L and support the rotational center hole of the support 8 through the needle bearing. The middle part of the support shaft 11 is an eccentric section 11-M, and the mounting hole of the counterweight 10 is sleeved on the eccentric section 11-M through the inner lining roller sleeve 10-2. Since the outer circle of the eccentric section 11-M has an eccentricity of 0.5 mm to the side of the return direction of the output shaft relative to the coaxial sections 11-1 and 11-2 at the two ends, the rotational center of the counterweight 10 is eccentric relative to the rotational center of the support 8.

[0024] The working principle and effect of the embodiment are the same as those of Embodiment One, and are not described again.

[0025] In addition to the above embodiments, the present application can also have other implementation manners. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope of the present application.

Claims

1. A reciprocating electric tool, comprising a motor arranged in a housing and a reciprocating output shaft extending from one end of the housing, the motor being in driving connection with a crank wheel with a biased crank pin, the crank pin being hinged to one end of a connecting rod, the other end of the connecting rod being hinged to the output shaft; characterized in that further comprising a bracket with a rotating center coaxial with the crank wheel and a counterweight with a rotating center eccentric to the rotating center of the bracket, the bracket having a hinge hole, the counterweight having a radial guide slot, the crank pin being hinged to the hinge hole and forming a moving pair with the radial guide slot; the bracket having a bracket shaft as the rotating center, the bracket shaft being supported in a eccentric boss inner hole of the housing, the mounting hole of the counterweight being sleeved on the outer circle of the eccentric boss, the outer circle of the eccentric boss having an eccentricity relative to the inner hole.

2. The reciprocating power tool according to claim 1, characterized by: the bracket shaft being supported in the eccentric boss inner hole of the housing through a bearing, the mounting hole of the counterweight being sleeved on the outer circle of the eccentric boss through an inner lining roller sleeve.

3. A reciprocating electric tool, comprising a motor arranged in a housing and a reciprocating output shaft extending from one end of the housing, the motor being in driving connection with a crank wheel with a biased crank pin, the crank pin being hinged to one end of a connecting rod, the other end of the connecting rod being hinged to the output shaft; characterized in that further comprising a bracket with a rotating center coaxial with the crank wheel and a counterweight with a rotating center eccentric to the rotating center of the bracket, the bracket having a hinge hole, the counterweight having a radial guide slot, the crank pin being hinged to the hinge hole and forming a moving pair with the radial guide slot; the bracket having a bracket shaft as the rotating center, both ends of the bracket shaft being coaxial segments supported by the housing and a eccentric segment in the middle, the mounting hole of the counterweight being sleeved on the eccentric segment, the outer circle of the eccentric segment having an eccentricity relative to the coaxial segments at both ends.

4. The reciprocating power tool according to claim 3, characterized by: both ends of the bracket shaft being respectively supported in the rotating center hole of the housing and the bracket through a bearing, the mounting hole of the counterweight being sleeved on the eccentric segment through an inner lining roller sleeve.

5. The reciprocating power tool according to claim 1 or 3, wherein: the eccentricity being biased to one side of the return direction of the output shaft.

6. The reciprocating power tool according to claim 5, wherein: the crank pin being hinged to the hinge hole of the bracket and inserted into the radial guide slot to form a moving pair.

7. The reciprocating power tool of claim 5, wherein: the housing being composed of a handle shell at the rear and a gear box at the front, the gear box being composed of a left box and a right box that are closed together.

8. The reciprocating power tool according to claim 7, wherein: the handle shell being internally provided with the motor, the gear box being internally provided with a shaft sleeve and an axial sliding slot, and the output shaft supported by the shaft sleeve extending out of the front end of the gear box; the main shaft of the motor being in driving connection with the crank wheel through the bevel gear at the end, the crank wheel being hinged to one end of the connecting rod and one end of the "8" shaped bracket through the crank pin; the other end of the connecting rod being hinged to the output shaft constrained by the sliding slot, forming a crank slider mechanism for reciprocating the output shaft.

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