CN114673769A - Coaxial reciprocating mechanism and device - Google Patents

Abstract

The invention discloses a coaxial reciprocating mechanism and a device, comprising an inner rotating shaft, an output shaft and an outer sleeve, wherein the inner rotating shaft and the output shaft are positioned on the same axis, and the outer sleeve is sleeved outside the output shaft; the inner rotating shaft is provided with at least one annular groove which surrounds the surface of the shaft, the annular groove has a certain inclination angle relative to the cross section of the shaft, and the annular groove is provided with a positioning steel ball; the output shaft comprises a shaft part and a shaft sleeve at the rear end of the shaft part; the shaft sleeve is provided with a cavity for accommodating the inner rotating shaft; the wall of the shaft sleeve is provided with a positioning hole; the inner wall of the outer sleeve is provided with at least one straight line groove extending axially; the positioning steel balls pass through the positioning holes and fall into the linear grooves; the inner rotating shaft rotates, the positioning steel balls roll along the annular groove and are constrained by the linear groove on the inner wall of the outer sleeve to slide along the linear direction, and the positioning steel balls drive the output shaft to do reciprocating motion of stretching back and forth through the positioning holes; the coaxial reciprocating mechanism and the appliance have the advantages of long service life, small volume and low noise.

Description

Coaxial reciprocating mechanism and apparatus

technical field

The invention relates to a reciprocating motion mechanism, in particular to a coaxial reciprocating motion mechanism and an appliance using the mechanism.

Background technique

Existing electric tools (reciprocating saws, electric files), fascia guns, electric toothbrushes, etc. all use reciprocating motion mechanisms.

The fascia gun of CN112263459A includes a reciprocating motion mechanism, which adopts an eccentric wheel to drive a sliding block to reciprocate through a sliding rod.

The electric toothbrush of CN200957117Y includes a rotatable transmission shaft arranged in the brush head, an eccentric shaft is installed on the transmission shaft, and the eccentric shaft rotates around the transmission shaft.

The reciprocating motion mechanism of CN104096910A for a reciprocating saw machine, the reciprocating motion mechanism includes a first driving part, a second driving part, a guiding part and a moving part, and the moving part is driven by the first and second driving parts so as to perform the movement in the first direction. The reciprocating motion and the oscillating motion along a second direction, the second direction being the cutting advancing direction of the reciprocating saw machine and perpendicular to the first direction.

In summary, the link-type reciprocating mechanism, the angle between the input end and the output end is 90°, and the required volume of the equipment is relatively large;

The swash plate type reciprocating mechanism has a relatively large friction force, and the output end cannot automatically return to the original position. It is necessary to add a rebound mechanism, and the working noise is large.

In the eccentric wheel type reciprocating mechanism, the volume of the pendulum bearing is large and cannot form a coaxial output.

SUMMARY OF THE INVENTION

Based on the deficiencies of the existing reciprocating mechanism, the technical problem to be solved by the present invention is to provide a coaxial reciprocating mechanism and an appliance, the reciprocating mechanism has the characteristics of long life and low noise; further, the reciprocating mechanism and Appliances are miniaturized.

The technical solution adopted by the present invention to solve the above technical problems is as follows: a coaxial reciprocating motion mechanism includes an inner rotating shaft, an output shaft and an outer casing, the inner rotating shaft and the output shaft are on the same axis, and the outer casing is sleeved on the output shaft off-axis;

The inner rotating shaft is provided with at least one annular groove surrounding the surface of the shaft, the annular groove has a certain inclination angle relative to the cross section of the shaft, and a positioning steel ball is arranged on the annular groove;

the output shaft comprises a shaft part and a shaft sleeve at the rear end of the shaft part; the shaft sleeve has a cavity for accommodating the inner rotating shaft; the wall of the shaft sleeve is provided with a positioning hole;

The inner wall of the outer casing is provided with at least one linear groove extending axially; the positioning steel ball falls into the linear groove through the positioning hole;

When the inner shaft rotates, the positioning steel ball rolls along the annular groove and is bound by the linear groove on the inner wall of the outer casing to slide in a linear direction.

The preferred technical solution adopted by the present invention to solve the above technical problem is: a linear bearing is arranged between the shaft portion and the outer casing.

The preferred technical solution adopted by the present invention to solve the above technical problems is: the inner rotating shaft is fixed in the shaft sleeve through a bearing and a retaining spring.

The preferred technical solution adopted by the present invention to solve the above-mentioned technical problems is: further comprising a motor, and the motor drives the inner rotating shaft to rotate.

The preferred technical solution adopted by the present invention to solve the above-mentioned technical problems is: the center of the inner rotating shaft is provided with a shaft hole, and the rotating shaft of the motor is butted with the shaft hole.

The preferred technical solution adopted by the present invention to solve the above technical problems is as follows: the annular groove is further provided with movable steel balls, the wall of the shaft sleeve is provided with axially extending waist-shaped holes, and the movable steel balls are arranged in the A waist-shaped hole, the movable steel ball is located in the straight groove of the outer casing.

The preferred technical solution adopted by the present invention to solve the above technical problems is as follows: the inner rotating shaft is provided with a first annular groove and a second annular groove distributed in the front and rear, the first annular groove is provided with a first positioning steel ball, and the second annular groove is provided with a first positioning steel ball. A second positioning steel ball is arranged on the groove;

The wall of the shaft sleeve is provided with a first positioning hole matched with the first positioning steel ball and a second positioning hole matched with the second positioning steel ball, and the inner wall of the sleeve is provided with a first linear groove matched with the first positioning steel ball and a second straight groove matched with the second positioning steel ball;

The difference between the first positioning steel ball and the second positioning steel ball is 180 degrees on the circumferential surface of the inner rotating shaft.

The preferred technical solution adopted by the present invention to solve the above technical problems is as follows: the first annular groove is provided with three movable steel balls, and the wall of the shaft sleeve is provided with three waist-shaped holes which are respectively matched with the three movable steel balls; The three movable steel balls differ by 90 degrees on the circumferential surface of the inner rotating shaft.

The preferred technical solution adopted by the present invention to solve the above technical problems is: a reduction gear is arranged between the motor and the inner rotating shaft.

Another technical solution adopted by the present invention to solve the above-mentioned technical problems is: a coaxial reciprocating motion mechanism includes a motor, an inner rotating shaft, an output shaft and an outer casing, the inner rotating shaft and the output shaft are on the same axis, and the outer casing is on the same axis. Outside the output shaft, the motor drives the inner shaft to rotate;

The inner rotating shaft is provided with at least one annular groove surrounding the surface of the shaft, the annular groove has a certain inclination angle relative to the cross section of the shaft, and a positioning steel ball is arranged on the annular groove;

The output shaft includes a shaft portion and a shaft sleeve at the rear end of the shaft portion, the shaft sleeve has a cavity for accommodating the inner rotating shaft, and a linear bearing is arranged between the shaft portion and the outer sleeve; the shaft sleeve There are positioning holes on the wall;

The inner wall of the outer casing is provided with at least one linear groove extending axially; the positioning steel ball falls into the linear groove through the positioning hole;

When the inner shaft rotates, the positioning steel ball rolls along the annular groove and is bound by the linear groove on the inner wall of the outer casing to slide in a linear direction.

Another technical solution adopted by the present invention to solve the above-mentioned technical problem is preferably as follows: the annular groove is further provided with movable steel balls, the wall of the shaft sleeve is provided with axially extending waist-shaped holes, and the movable steel balls are provided in the The waist-shaped hole and the movable steel ball are located in the straight groove of the outer casing.

Another technical solution adopted by the present invention to solve the above technical problem is preferably: a reduction gear is arranged between the motor and the inner rotating shaft.

Another subject of the present invention is: an appliance comprising a housing and the coaxial reciprocating mechanism within the housing.

A preferred technical solution of another subject of the present invention is that: a storage battery is arranged in the casing, and the storage battery provides electric power for the motor in the coaxial reciprocating mechanism.

Compared with the prior art, the advantages of the present invention are:

First: the inner shaft and the output end are coaxial to realize coaxial output, and the diameter of the equipment can be made smaller, avoiding the situation that the volume of the equipment is forced to increase due to the angular connection or eccentric connection between the output shaft and the input shaft;

Second: The positioning steel ball is a rolling mechanism, the sliding friction force is small, and the noise generated by its own activity is small. And the arrangement of the annular groove makes the movement of the positioning steel ball consistent, and there is no need to set up a rebound mechanism, which not only simplifies the structure, reduces the volume required by the mechanism, but also avoids the rebound mechanism. The extra noise further realizes the miniaturization and muteness of the coaxial reciprocating mechanism;

Third, because of its simple structure, small friction and smooth operation, the service life of the coaxial reciprocating mechanism of this embodiment is also longer than that of the traditional swash plate type reciprocating mechanism, eccentric wheel type reciprocating mechanism or link type reciprocating mechanism Institutions come a long way.

Description of drawings

The present invention will be described in further detail below with reference to the accompanying drawings and preferred embodiments, but those skilled in the art will appreciate that these drawings are drawn for the purpose of explaining the preferred embodiments only and should therefore not be taken as a Limitation of the scope of the invention. Furthermore, unless otherwise indicated, the drawings are merely schematic representations of the composition or construction of the described objects and may contain exaggerated representations and are not necessarily drawn to scale.

Fig. 1 is the schematic diagram of the electric file of a preferred embodiment of the present invention;

2 is a cross-sectional view of an electric file according to a preferred embodiment of the present invention;

3 is an exploded view of an electric file according to a preferred embodiment of the present invention;

4 is a schematic diagram of a coaxial reciprocating mechanism of a preferred embodiment of the present invention;

FIG. 5 is a cross-sectional view of a coaxial reciprocating mechanism according to a preferred embodiment of the present invention (without movable steel balls);

6 is an exploded view of a coaxial reciprocating mechanism of a preferred embodiment of the present invention;

Fig. 7 is the internal structure diagram 1 of the coaxial reciprocating mechanism of a preferred embodiment of the present invention;

8 is a second internal structure diagram of a coaxial reciprocating mechanism according to a preferred embodiment of the present invention;

FIG. 9 is a schematic diagram of a casing of a coaxial reciprocating mechanism according to a preferred embodiment of the present invention.

Detailed ways

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Those skilled in the art will appreciate that these descriptions are descriptive, exemplary only, and should not be construed as limiting the scope of protection of the present invention.

It should be noted that like numerals refer to like items in the following figures, so once an item is defined in one figure, it may not be further defined and explained in subsequent figures.

As shown in FIGS. 1-3 , the present embodiment provides an electric file including a casing 100 , a coaxial reciprocating mechanism 200 located in the casing 100 , and a front end connected to the coaxial reciprocating mechanism 200 and exposed from the casing 100 File head 300 on the front. The movement of the coaxial reciprocating mechanism 200 makes the file head 300 move back and forth, so as to realize a straight line operation to file the surface of the object to be processed.

Of course, it should be specially noted that the electric file of this embodiment is only a representative of one type of appliance. The coaxial reciprocating mechanism 200 can be used in similar appliances, such as saber saws, jigsaws, fascia guns, electric toothbrushes, etc. The coaxial reciprocating mechanism 200 drives the working part or other components of the appliance to perform the same operation. The shaft reciprocates to achieve the working effect.

Specifically, as shown in FIGS. 2-6 , in this embodiment, the coaxial reciprocating mechanism 200 includes an inner shaft 1, an output shaft 2 and an outer casing 3, the inner shaft 1 and the output shaft 2 are arranged along the same axis, and the outer casing 3 is sleeved on the output shaft 3. Outside axis 2.

The inner rotating shaft 1 is provided with at least one annular groove 10 surrounding the surface of the shaft. The annular groove 10 has a certain inclination angle relative to the cross section of the shaft. Adaptation, the positioning steel ball 4 moves along the extending direction of the annular groove 10 during the rotation of the inner shaft 1 .

As shown in FIGS. 5 and 6 , the output shaft 2 includes a shaft portion 21 and a shaft sleeve 22 at the rear end of the shaft portion 21 . The shaft portion 21 and the shaft sleeve 22 are arranged along the same axis. The shaft sleeve 22 has a cavity L for accommodating the inner rotating shaft 1 , and the cavity L is opened to the rear for the inner rotating shaft 1 to be assembled therein. The wall of the shaft sleeve 22 is provided with a positioning hole a, and the positioning steel ball 4 passes through the positioning hole a, so that the movement of the positioning steel ball 4 is associated with the output shaft 2 .

As shown in Figures 5 and 9, the inner wall of the outer casing 3 is provided with at least one axially extending linear groove b. The linear groove b corresponds to the position of the positioning hole a. The positioning steel ball 4 passes through the positioning hole a and falls into the linear groove b. and the movement of the positioning steel ball 4 in the radial direction of the outer casing 3 is restricted, and can only move linearly along the linear groove b. That is to say, the position of the positioning steel ball 4 in the radial angle is fixed, but the axial direction is movable.

When the inner shaft 1 rotates, it means that the position of the annular groove 10 has changed, which makes the axial position of the annular groove 10 change at a fixed radial angle, so that the positioning steel ball 4 is caught by the straight line of the inner wall of the outer casing 3. The groove b is bound and forced to roll along the annular groove 10, thereby sliding in a linear direction and changing the axial position.

It should be noted that the positioning hole a is a hole that matches the diameter of the positioning steel ball 4, that is, the gap between the spherical surface of the positioning steel ball 4 and the positioning hole a can be ignored, and the linear movement of the positioning steel ball 4 is bound to exert a force on the hole wall of the positioning hole a. , so as to push the output shaft 2 to move in the same direction.

And, because the annular groove 10 is a closed ring, and has a certain inclination angle with respect to the cross section of the shaft. This means that when the inner rotating shaft 1 rotates 180 degrees, the positioning steel ball 4 pushes the output shaft 2 to reach an axial distance extreme value, and then rotates 180 degrees, that is, after one rotation, the positioning steel ball 4 drives the output shaft 2 back to the other shaft. To the extreme value of the distance, so that the output shaft 2 reciprocates forward and backward.

To sum up, in this embodiment, the circular groove 10 , the positioning steel ball 4 , the positioning hole a, and the linear groove b cooperate with each other to convert the circumferential rotational motion of the inner shaft 1 into the linear reciprocating motion of the output shaft 2 . Compared with the connecting rod type and eccentric wheel type reciprocating mechanism, in this embodiment, the inner rotating shaft 1 and the output end are coaxially arranged, so that the mechanism is in a coaxial extension state, and the diameter of the equipment can be made smaller, to avoid the output shaft 2 and the output end. The case where the input shaft is connected at an angle or eccentrically, forcing the device to increase in size.

Moreover, in this embodiment, the positioning steel ball 4 is a rolling mechanism. During the whole reciprocating motion, its rolling is always driving the movement of the output shaft 2, so the sliding friction force is small, and the noise generated by the movement itself is small. More importantly, because of the arrangement of the annular groove 10, the movement of the positioning steel ball 4 is continuous, that is, the output shaft 2 can be automatically returned after one rotation, and there is no need to provide an additional rebound mechanism, which not only simplifies the structure, but also further The volume required by the mechanism is reduced, the extra noise generated during the movement of the rebound mechanism is avoided, and the miniaturization and muteness of the coaxial reciprocating mechanism 200 are further realized.

In addition, because of the simple structure, low friction and smooth operation, the service life of the coaxial reciprocating mechanism 200 of this embodiment is also longer than that of the traditional swash plate type reciprocating mechanism, eccentric wheel type reciprocating mechanism or link type reciprocating mechanism Institutions come a long way.

It should be noted that the annular grooves 10 can be inclined from front to back or from back to front, and the plurality of annular grooves 10 can be parallel to each other, or the inclination angles of the two can be complementary angles to each other. However, no matter how the annular groove 10 is set, the positioning steel balls 4 on it should be set to move synchronously and in the same direction.

As shown in Figures 5-8, the inner shaft 1 is provided with a first annular groove 101 and a second annular groove 102 distributed in the front and rear, the first annular groove 101 is provided with a first positioning steel ball 4a, and the second annular groove 102 is provided with There is a second positioning steel ball 4b, the wall of the shaft sleeve 22 is provided with a first positioning hole a1 matched with the first positioning steel ball 4a and a second positioning hole a2 matched with the second positioning steel ball 4b, and the inner wall of the outer casing 3 is provided with a The first straight groove b1 matched with the first positioning steel ball 4a and the second straight groove b2 matched with the second positioning steel ball 4b.

In this embodiment, the inclination angles of the first annular groove 101 and the second annular groove 102 are complementary. The first positioning steel ball 4a and the second positioning steel ball 4b differ by 180 degrees on the circumferential surface of the inner rotating shaft 1 . First of all, it should be clear that this arrangement enables the first positioning steel ball 4a and the second positioning steel ball 4b to push the output shaft 2 synchronously and in the same direction when the inner shaft 1 rotates, and there is no interference between the two, which is a synergistic effect. In addition, in this way, both sides of the output shaft 2 have guided sliding structures to avoid deflection due to uneven force during axial movement, further ensuring the smooth movement of the entire coaxial reciprocating mechanism 200, and also It further avoids the generation of extra friction and provides a guarantee for the muteness of the equipment.

Further, as shown in Figures 6-8, the annular groove 10 is also provided with movable steel balls 5, and the movable steel balls 5 are also adapted to the annular groove 10. During the rotation of the inner shaft 1, the movable steel balls 5 also roll along the annular groove 10. . But unlike the positioning steel ball 4 , the movable steel ball 5 does not push the output shaft 2 . This is because an axially extending waist-shaped hole c is provided on the wall of the shaft sleeve 22 , and the length of the waist-shaped hole c is the stroke length of the reciprocating motion of the output shaft 2 , that is, the axial direction of the annular groove 10 on the axis of the inner rotating shaft 1 . distance.

The movable steel ball 5 passes from the annular groove 10 of the inner rotating shaft 1 inside the shaft sleeve 22 , passes through the waist-shaped hole c, and is accommodated in the linear groove b of the outer casing 3 . It should be noted that, according to the different installation positions of the movable steel balls 5, the linear groove b here can be the linear groove b where the positioning steel balls 4 are located, or an additional linear groove b for avoiding the movable steel balls 5.

When the inner shaft 1 rotates, the positioning steel ball 4 pushes the shaft sleeve 22, and the movable steel ball 5 moves in the waist-shaped hole c without exerting force on the hole wall of the waist-shaped hole c.

The reason why the movable steel ball 5 is provided is to further eliminate the gap between the shaft sleeve 22 and the outer sleeve 3, so that the movement of the output shaft 2 is smoother and more stable. Therefore, preferably, four movable steel balls 5 are arranged on the first annular groove 101 and the second annular groove 102 in total, and the difference between each movable steel ball 5 on the circumferential surface of the inner shaft 1 is 90 degrees.

As shown in Figures 7-8, preferably, in this embodiment, the first annular groove 101 is provided with three first movable steel balls 5a, a first positioning steel ball 4a, and the first annular groove 101 is provided with a second positioning steel ball 4b and a second movable steel ball 5b. The wall of the shaft sleeve 22 is provided with three first waist-shaped holes c1 which are respectively matched with the three first movable steel balls 5a. The two are 90 degrees apart. The wall of the shaft sleeve 22 is provided with a second waist-shaped hole c2 which is matched with the second movable steel ball 5b. The second positioning steel ball 4b is 180 degrees from the first positioning steel ball 4a. ipsilateral.

The four-angle movable steel balls 5 support the shaft sleeve 22 and the outer casing 3 at four angles, thereby ensuring the coaxiality of the shaft sleeve 22 and the outer casing 3, and further ensuring the flexibility of the output shaft 2 to move.

As shown in Figures 2, 3, and 6, a linear bearing 6 is provided between the shaft portion 21 and the outer casing 3, and the linear bearing 6 is tightly fitted with the outer casing 3 or a retaining spring is provided at both ends to prevent back and forth movement. The axially arranged ball g on the inner wall of the linear bearing 6 acts on the shaft portion 21 of the output shaft 2, so that the output shaft 2 can be directly loosely matched with the inner hole of the outer casing 3 and grease is used. In addition, the ball g can reduce the forward and backward movement. resistance to further ensure the smooth reciprocation of the output shaft 2.

As shown in Figures 3 and 5, the inner shaft 1 extends into the cavity of the shaft sleeve 22 from the back to the front, and a bearing 7 is provided between the inner shaft 1 and the inner wall of the shaft sleeve 22. The setting of the bearing 7 not only affects the inner shaft 1 It has a supporting effect, and is also more conducive to the circumferential rotation of the inner rotating shaft 1 . And the rear side of the bearing is fixed with a retaining spring 8 , so that the inner shaft 1 is rotatably limited in the shaft sleeve 22 .

As shown in FIGS. 3 and 5 , the coaxial reciprocating motion mechanism 200 further includes a motor 9 . The rotating shaft of the motor 9 is coaxially connected to the inner rotating shaft 1 , and the motor 9 rotates and drives the inner rotating shaft 1 to rotate. Preferably, a reduction gear is provided between the motor 9 and the inner rotating shaft 1 .

Preferably, the center of the inner rotating shaft 1 is provided with a shaft hole f, and the rotating shaft r of the motor 9 is abutted with the shaft hole. The two are preferably matched in a pluggable manner, and the shaft hole is a non-circular hole, that is, there must be a limiting surface in the shaft hole that restricts the circumferential rotation of the rotating shaft and the shaft hole. Preferably, the shaft hole is a pentagonal hole, a square hole and other regular polygonal holes.

As shown in FIG. 2 , because the movement of the motor 9 requires power support, in order to realize wireless operation and improve the portability of the appliance application, the housing 100 of the appliance provided in this embodiment is also provided with a battery compartment for installing the battery 400 and related Connect the circuit. The battery 400 is assembled in the battery compartment, and provides electrical support for the motor 9 in the coaxial reciprocating mechanism 200 through the connection circuit.

The coaxial reciprocating motion mechanism and the apparatus provided by the present invention are introduced above. Specific examples are used to illustrate the principles and implementations of the present invention. The descriptions of the above embodiments are only used to help understand the present invention and its core ideas. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can also be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims (14)

1. A coaxial reciprocating mechanism, characterized in that it comprises an inner rotating shaft, an output shaft and an outer casing, the inner rotating shaft and the output shaft are on the same axis, and the outer casing is sleeved outside the output shaft; The inner rotating shaft is provided with at least one annular groove surrounding the surface of the shaft, the annular groove has a certain inclination angle relative to the cross section of the shaft, and a positioning steel ball is arranged on the annular groove; the output shaft comprises a shaft part and a shaft sleeve at the rear end of the shaft part; the shaft sleeve has a cavity for accommodating the inner rotating shaft; the wall of the shaft sleeve is provided with a positioning hole; The inner wall of the outer casing is provided with at least one linear groove extending axially; the positioning steel ball falls into the linear groove through the positioning hole; When the inner shaft rotates, the positioning steel ball rolls along the annular groove and is bound by the linear groove on the inner wall of the outer casing to slide in a linear direction. 2 . The coaxial reciprocating mechanism according to claim 1 , wherein a linear bearing is provided between the shaft portion and the outer casing. 3 . 3 . The coaxial reciprocating mechanism according to claim 1 , wherein the inner rotating shaft is fixed in the shaft sleeve through a bearing and a retaining spring. 4 . 4 . The coaxial reciprocating mechanism according to claim 1 , further comprising a motor, and the motor drives the inner shaft to rotate. 5 . 5 . The coaxial reciprocating motion mechanism according to claim 4 , wherein a shaft hole is provided in the center of the inner rotating shaft, and the rotating shaft of the motor is abutted with the shaft hole. 6 . 6. The coaxial reciprocating motion mechanism according to claim 1, characterized in that the annular groove is further provided with movable steel balls, the wall of the shaft sleeve is provided with axially extending waist-shaped holes, and the movable steel balls are provided in the The waist-shaped hole and the movable steel ball are located in the straight groove of the outer casing. 7. The coaxial reciprocating mechanism according to claim 6, characterized in that the inner rotating shaft is provided with a first annular groove and a second annular groove distributed back and forth, and the first annular groove is provided with a first positioning steel ball, A second positioning steel ball is arranged on the two annular grooves; The wall of the shaft sleeve is provided with a first positioning hole matched with the first positioning steel ball and a second positioning hole matched with the second positioning steel ball, and the inner wall of the sleeve is provided with a first linear groove matched with the first positioning steel ball and a second straight groove matched with the second positioning steel ball; The difference between the first positioning steel ball and the second positioning steel ball is 180 degrees on the circumferential surface of the inner rotating shaft. 8 . The coaxial reciprocating motion mechanism according to claim 7 , wherein three movable steel balls are arranged on the first annular groove, and three waist-shaped holes are arranged on the wall of the shaft sleeve respectively matched with the three movable steel balls. 9 . ; The three movable steel balls differ by 90 degrees on the circumference of the inner shaft. 9 . The coaxial reciprocating mechanism according to claim 4 , wherein a reduction gear is arranged between the motor and the inner rotating shaft. 10 . 10. A coaxial reciprocating mechanism is characterized in that it includes a motor, an inner rotating shaft, an output shaft and an outer casing, the inner rotating shaft and the output shaft are on the same axis, the outer casing is sleeved outside the output shaft, and the motor driving the inner shaft to rotate; The inner rotating shaft is provided with at least one annular groove surrounding the surface of the shaft, the annular groove has a certain inclination angle relative to the cross section of the shaft, and a positioning steel ball is arranged on the annular groove; The output shaft includes a shaft portion and a shaft sleeve at the rear end of the shaft portion, the shaft sleeve has a cavity for accommodating the inner rotating shaft, and a linear bearing is arranged between the shaft portion and the outer sleeve; the shaft sleeve There are positioning holes on the wall; The inner wall of the outer sleeve is provided with at least one linear groove extending axially; the positioning steel ball falls into the linear groove through the positioning hole; When the inner shaft rotates, the positioning steel ball rolls along the annular groove and is bound by the linear groove on the inner wall of the outer casing to slide in a linear direction. 11. The coaxial reciprocating motion mechanism according to claim 10, characterized in that the annular groove is further provided with movable steel balls, the wall of the shaft sleeve is provided with axially extending waist-shaped holes, and the movable steel balls are provided in the The waist-shaped hole and the movable steel ball are located in the straight groove of the outer casing. 12 . The coaxial reciprocating mechanism according to claim 10 , wherein a reduction gear is arranged between the motor and the inner rotating shaft. 13 . 13. An appliance, characterized by comprising a housing and a coaxial reciprocating mechanism as claimed in any one of claims 1-12 in the housing. 14. The appliance according to claim 13, characterized in that a battery is provided in the housing, and the battery provides power for the motor in the coaxial reciprocating mechanism.

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