Rotary drive mechanism, boom and engineering machine

Abstract

This invention relates to the field of booms, and discloses a rotary drive mechanism, a boom, and engineering machinery. The rotary drive mechanism includes an annular piston (10) and a stator. The annular piston (10) is provided with piston teeth having protruding curved tooth surfaces and piston teeth having inclined flat tooth surfaces. The stator is provided with stator teeth having protruding curved tooth surfaces and stator teeth having inclined flat tooth surfaces. The annular piston (10) can be driven to move axially relative to the stator. Through the above-described technical solution, the combination of the meshing of curved tooth surfaces and the meshing of flat tooth surfaces can ensure smooth transmission in the initial meshing stage, reduce noise, and allow the subsequent meshing stage to convert axial movement into uniform rotation, providing a more stable torque output.

Description

Technical Field

[0001] This invention relates to the field of booms, specifically to a rotary drive mechanism, to a boom, and to a type of engineering machinery. Background Technology

[0002] A boom is usually made up of multiple boom sections hinged together and is extended and retracted by the hydraulic cylinders of each boom section. The relative angle between two adjacent boom sections is a key factor affecting the boom's flexibility and working range. The larger the relative angle between two adjacent boom sections, the greater the boom's flexibility and working range, and vice versa.

[0003] Currently, most boom systems have a maximum relative angle of no more than 220° between adjacent boom sections. This is sometimes insufficient to meet the material placement requirements in complex construction environments, especially when the boom system needs to avoid obstacles. The limited relative angle makes it difficult to deploy the boom system into the required posture. Furthermore, the boom section connection method, which uses hydraulic cylinders and hinged plates, results in a very limited range of motion during boom deployment; the boom sections can only be deployed clockwise or counterclockwise. Moreover, when the relative angle of the boom sections is large, retracting the boom requires rotating a very large angle in the opposite direction, significantly reducing the boom's flexibility and work efficiency.

[0004] In addition, the relative angular velocity of the boom segments is not proportional to the stroke of the cylinder. As the relative rotation angle changes, the angular velocity of the boom segments also changes. Furthermore, due to the long boom segments, a "magnification" effect is formed at the end. This fluctuation will significantly reduce the stability and accuracy of the boom end. Summary of the Invention

[0005] The purpose of this invention is to provide a rotary drive mechanism to solve the problems of uneven torque output and inconsistent rotational speed.

[0006] To achieve the above objectives, the present invention provides a rotary drive mechanism comprising an annular piston and a stator. The annular piston is provided with piston teeth having protruding curved tooth surfaces and piston teeth having inclined flat tooth surfaces. The stator is provided with stator teeth having protruding curved tooth surfaces and stator teeth having inclined flat tooth surfaces. The annular piston can be driven to move axially relative to the stator. The annular piston first engages with the stator teeth having protruding curved tooth surfaces via the piston teeth having protruding curved tooth surfaces, and then engages with the stator teeth having inclined flat tooth surfaces via the piston teeth having inclined flat tooth surfaces, thereby driving the annular piston to rotate circumferentially.

[0007] Optionally, the stator includes an annular first stator and a second stator, with the annular piston disposed between the first stator and the second stator.

[0008] Optionally, the annular piston has a first piston tooth and a second piston tooth at its axial first end, and a third piston tooth and a fourth piston tooth at its axial second end. The first stator has a first stator tooth capable of meshing with the first piston tooth and a second stator tooth capable of meshing with the second piston tooth. The second stator has a third stator tooth capable of meshing with the third piston tooth and a fourth stator tooth capable of meshing with the fourth piston tooth. The first piston tooth and the first stator tooth each have protruding curved tooth surfaces. The second piston tooth and the second stator tooth each have inclined flat tooth surfaces. The third piston tooth and the third stator tooth each have protruding curved tooth surfaces. The fourth piston tooth and the fourth stator tooth each have inclined flat tooth surfaces.

[0009] The annular piston can be driven to reciprocate axially. The first piston tooth first engages with the first stator tooth, then the second piston tooth engages with the second stator tooth, the third piston tooth first engages with the third stator tooth, and then the fourth piston tooth engages with the fourth stator tooth, thereby driving the annular piston to rotate.

[0010] Optionally, the first piston tooth, the first stator tooth, the third piston tooth, and the third stator tooth each have an involute tooth surface.

[0011] Optionally, the first piston teeth and the second piston teeth are located radially inner and outer, respectively, and the third piston teeth and the fourth piston teeth are located radially inner and outer, respectively.

[0012] Optionally, the first piston teeth and the second piston teeth correspond one-to-one and are aligned on their center lines; the first stator teeth and the second stator teeth correspond one-to-one and are aligned on their center lines; the third piston teeth and the fourth piston teeth correspond one-to-one and are aligned on their center lines; and the third stator teeth and the fourth stator teeth correspond one-to-one and are aligned on their center lines.

[0013] Optionally, the center lines of the first stator teeth and the second stator teeth are offset from the center lines of the third stator teeth and the fourth stator teeth, and the center lines of the first piston teeth and the second piston teeth are aligned with the center lines of the third piston teeth and the fourth piston teeth.

[0014] Optionally, the distance between the tips of the first and second piston teeth and the tips of the third and fourth piston teeth is greater than the distance between the tips of the first and second stator teeth and the tips of the third and fourth stator teeth, and less than the distance between the tips of the first and second stator teeth and the roots of the third and fourth stator teeth, and less than the distance between the roots of the first and second stator teeth and the tips of the third and fourth stator teeth.

[0015] Optionally, the rotary drive mechanism includes two sets of first stators, second stators, and annular pistons arranged axially, the first stators and second stators of the two sets being relatively fixed, the two annular pistons being circumferentially fixed and capable of axial relative movement.

[0016] Optionally, the center lines of the first piston teeth of the two annular pistons are staggered.

[0017] Alternatively, the rotary drive mechanism includes an inner ring, on which two annular pistons are axially slidably mounted, and which are circumferentially fixed relative to the inner ring.

[0018] In addition, the present invention also provides a boom, wherein the boom is provided with the rotary drive mechanism described in the above solution.

[0019] In addition, the present invention also provides an engineering machine, wherein the engineering machine is equipped with the boom described in the above solution.

[0020] The above-described technical solution combines the meshing of curved tooth surfaces with the meshing of flat tooth surfaces, ensuring smooth transmission during the initial meshing stage with less noise. Furthermore, it allows the subsequent meshing stage to convert axial movement into uniform rotation, providing a more stable torque output. Attached Figure Description

[0021] Figure 1 This is a partial schematic diagram of the rotary drive mechanism described in an embodiment of the present invention;

[0022] Figure 2 It is an explosion of the rotary drive mechanism described in the embodiments of the present invention;

[0023] Figure 3 This is a perspective view of the annular piston according to an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the structure of the annular piston and stator as described in an embodiment of the present invention;

[0025] Figure 5This is a diagram illustrating the process of the engagement between the teeth of the annular piston and the teeth of the stator according to an embodiment of the present invention.

[0026] Figure 6 and Figure 7 These are diagrams showing the process of the annular piston rotating in two different directions relative to the stator.

[0027] Explanation of reference numerals in the attached figures

[0028] 10-Annular piston, 11-First piston tooth, 12-Second piston tooth, 13-Third piston tooth, 14-Fourth piston tooth, 20-Second stator, 21-First stator tooth, 22-Second stator tooth, 30-Second stator, 31-Third stator tooth, 32-Fourth stator tooth, 40-Inner ring, 50-End cap. Detailed Implementation

[0029] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0030] The present invention provides a rotary drive mechanism, wherein the rotary drive mechanism includes an annular piston 10 and a stator. The annular piston 10 is provided with piston teeth having protruding curved tooth surfaces and piston teeth having inclined flat tooth surfaces. The stator is provided with stator teeth having protruding curved tooth surfaces and stator teeth having inclined flat tooth surfaces. The annular piston 10 can be driven to move axially relative to the stator. The annular piston 10 first engages with the stator teeth having protruding curved tooth surfaces through the piston teeth having protruding curved tooth surfaces, and then engages with the stator teeth having inclined flat tooth surfaces through the piston teeth having inclined flat tooth surfaces, thereby driving the annular piston 10 to rotate circumferentially.

[0031] Of the two teeth of the annular piston 10, one tooth surface is curved and protruding, while the other tooth surface is flat. Correspondingly, one tooth surface of the stator is curved and protrudes outward, while the other tooth surface is flat. The curved tooth surface of the annular piston 10 mates with the curved tooth surface of the stator, and the flat tooth surface of the annular piston 10 mates with the flat tooth surface of the stator.

[0032] Here, the tooth surface refers to the surface where two teeth mesh together. The axial direction refers to the axial direction of the annular piston 10, and the circumferential direction is also the circumferential direction of the annular piston 10.

[0033] Specifically, the annular piston 10 can be driven to move axially, for example, by hydraulic or pneumatic pressure, so that the teeth at both ends of the piston engage and disengage with the teeth of the stator, respectively. During the engagement of the two teeth, the tips of the stator teeth are slightly misaligned with the tips of the annular piston 10 teeth. The teeth on the stator can guide the teeth on the annular piston 10 to move circumferentially relative to each other, so that the tips of the annular piston 10 teeth move to align with the roots of the stator teeth, thereby realizing the rotation of the annular piston 10 relative to the stator.

[0034] refer to Figure 5 As shown, when the annular piston 10 meshes with the stator (e.g., the first stator 20), the initial meshing between the annular piston 10 and the first stator 20 is achieved through the meshing of the curved tooth surface. The curved tooth surface is a conventional tooth structure. This design can reduce wear between the teeth, make the transmission smooth, and has the advantages of saving effort, durability and low noise. Of course, even if the axial relative movement between the two is uniform, the circumferential relative movement caused by meshing is non-uniform. Then, the second piston tooth 12 meshes with the second stator tooth 22. These two teeth are non-conventional tooth structures, that is, the tooth surface is a plane. This plane forms an angle with the axial direction (or the center line of the tooth). When the axial relative movement is uniform, the circumferential movement of the annular piston 10 relative to the first stator 20 is also uniform, that is, uniform rotation is achieved.

[0035] The stator includes an annular first stator 20 and a second stator 30, and an annular piston 10 is disposed between the first stator 20 and the second stator 30. The annular piston 10 can move axially between the first stator 20 and the second stator 30, and through the meshing of its teeth, it is driven to rotate circumferentially to achieve continuous rotation.

[0036] Specifically, the annular piston 10 has a first piston tooth 11 and a second piston tooth 12 at its first axial end, and a third piston tooth 13 and a fourth piston tooth 14 at its second axial end. The first stator 20 has a first stator tooth 21 that meshes with the first piston tooth 11 and a second stator tooth 22 that meshes with the second piston tooth 12. The second stator 30 has a third stator tooth 31 that meshes with the third piston tooth 13 and a fourth stator tooth 32 that meshes with the fourth piston tooth 14. The first piston tooth 11 and the first stator tooth 21 each have protruding curved tooth surfaces, the second piston tooth 12 and the second stator tooth 22 each have inclined flat tooth surfaces, the third piston tooth 13 and the third stator tooth 31 each have protruding curved tooth surfaces, and the fourth piston tooth 14 and the fourth stator tooth 32 each have inclined flat tooth surfaces.

[0037] The annular piston 10 is driven to reciprocate axially. The first piston tooth 11 first engages with the first stator tooth 21, then the second piston tooth 12 engages with the second stator tooth 22, the third piston tooth 13 first engages with the third stator tooth 31, and then the fourth piston tooth 14 engages with the fourth stator tooth 32, thereby driving the annular piston 10 to rotate.

[0038] The annular piston 10, the first stator 20, and the second stator 30 can each be generally formed as tubular structures, and the three are arranged coaxially. The rotation of the annular piston 10 is a rotation about its central axis.

[0039] refer to Figure 5 As shown, when the annular piston 10 meshes with the first stator 20, the first piston tooth 11 first meshes with the first stator tooth 21, that is, the annular piston 10 and the first stator 20 are initially meshed through the meshing of the curved tooth surface. The curved tooth surface is a conventional tooth structure. This design can reduce wear between the teeth, make the transmission smooth, and has the advantages of saving effort, durability and low noise. Of course, even if the axial relative movement of the two is uniform, the circumferential relative movement caused by meshing is non-uniform. Then, the second piston tooth 12 meshes with the second stator tooth 22. These two teeth are non-conventional tooth structures, that is, the tooth surface is a plane. This plane forms an angle with the axial direction (or the center line of the tooth). When the axial relative movement is uniform, the circumferential movement of the annular piston 10 relative to the first stator 20 is also uniform, that is, uniform rotation is achieved.

[0040] It should be noted that during the stage when the first piston tooth 11 is engaged with the first stator tooth 21, the second piston tooth 12 is not engaged with the second stator tooth 22. When the second piston tooth 12 begins to engage with the second stator tooth 22, the first piston tooth 11 begins to disengage from the first stator tooth 21.

[0041] The way in which the third piston tooth 13 and the fourth piston tooth 14 of the annular piston 10 are engaged with the second stator 30 is basically the same as the way in which the annular piston 10 is engaged with the first stator as described above, and will not be repeated here.

[0042] Optionally, the first piston tooth 11, the first stator tooth 21, the third piston tooth 13, and the third stator tooth 31 each have an involute tooth surface. That is, the curved tooth surface is an involute tooth surface, which is the tooth surface structure of a conventional gear.

[0043] Wherein, the first piston tooth 11 and the second piston tooth 12 are located radially inner and outer, respectively, and the third piston tooth 13 and the fourth piston tooth 14 are located radially inner and outer, respectively. Figures 1-4As shown, the annular piston 10 has teeth at both axial ends, and each end has two layers of teeth, inner and outer. Correspondingly, the two stators that mate with the annular piston 10 also have inner and outer layers of teeth, respectively. It should be noted that both curved and flat tooth surfaces can be provided in the outer or inner layer.

[0044] In this configuration, the first piston teeth 11 and the second piston teeth 12 correspond one-to-one and are aligned along their center lines; the first stator teeth 21 and the second stator teeth 22 correspond one-to-one and are aligned along their center lines; the third piston teeth 13 and the fourth piston teeth 14 correspond one-to-one and are aligned along their center lines; and the third stator teeth 31 and the fourth stator teeth 32 correspond one-to-one and are aligned along their center lines. The teeth on the annular piston 10, the first stator 20, and the second stator 30 can be axially symmetrical, and the number of radially outer teeth and radially inner teeth are the same and aligned along their center lines. This structure is easier to manufacture. Of course, in other embodiments, the outer and inner teeth of the annular piston 10, the first stator 20, and the second stator 30 can be staggered, as long as the engagement is first through the teeth with curved tooth surfaces and then through the teeth with flat tooth surfaces.

[0045] In this configuration, the centerlines of the first stator teeth 21 and the second stator teeth 22 are offset from the centerlines of the third stator teeth 31 and the fourth stator teeth 32. The centerlines of the first piston teeth 11 and the second piston teeth 12 are aligned with the centerlines of the third piston teeth 13 and the fourth piston teeth 14. In this structure, when the annular piston 10 is fully engaged with the first stator 20, the centerline of the first piston teeth 11 is aligned with the root of the first stator teeth 21, while the centerline of the third piston teeth 13 is offset from the root of the third stator teeth 31. Therefore, when the annular piston 10 disengages from the first stator 20 and engages with the second stator 30, it inevitably leads to circumferential relative movement between the third piston teeth 13 and the third stator teeth 31. This prevents the centerline of the third piston teeth 13 from aligning with the root of the third stator teeth 31, thus preventing circumferential relative movement between the annular piston 10 and the second stator 30 during engagement. This structural design allows the annular piston 10 to rotate continuously as it reciprocates axially.

[0046] In other embodiments, the center lines of the first piston teeth 11 and the second piston teeth 12 may be offset from the center lines of the third piston teeth 13 and the fourth piston teeth 14. The relative positional relationship between the center lines of the first stator teeth 21 and the second stator teeth 22 and the center lines of the third stator teeth 31 and the fourth stator teeth 32 needs to be adjusted accordingly to ensure that when the teeth at one end of the annular piston 10 are aligned with the root of the corresponding stator tooth, the teeth at the other end are offset from the root of the corresponding stator tooth.

[0047] Optionally, the distance between the tips of the first piston teeth 11 and the second piston teeth 12 and the tips of the third piston teeth 13 and the fourth piston teeth 14 is greater than the distance between the tips of the first stator teeth 21 and the second stator teeth 22 and the tips of the third stator teeth 31 and the fourth stator teeth 32, and less than the distance between the tips of the first stator teeth 21 and the second stator teeth 22 and the roots of the third stator teeth 31 and the fourth stator teeth 32, and less than the distance between the roots of the first stator teeth 21 and the second stator teeth 22 and the tips of the third stator teeth 31 and the fourth stator teeth 32. The distance between the tips of the teeth at both ends of the annular piston 10 is less than the distance between the tips of the teeth of the two stators. This means that when the teeth at one end of the annular piston 10 are about to disengage from the corresponding stator teeth, the teeth at the other end have already begun to engage with the corresponding stator teeth. That is, at least one end of the annular piston 10 maintains engagement with the corresponding stator teeth. This engagement allows the annular piston 10 to maintain circumferential movement, thus ensuring that circumferential movement always exists when the annular piston 10 moves axially, i.e., rotation is continuous. In addition, the distance between the tips of the teeth at both ends of the annular piston 10 is less than the distance between the tip of any stator tooth and the root of another stator tooth. This means that when the annular piston 10 is fully engaged with one stator (the tip of the piston tooth engages with the root of the stator tooth), the piston teeth at the other end disengage from the tip of the other stator tooth, thus allowing the annular piston 10 to rotate circumferentially to pass over the tip of the other stator tooth.

[0048] like Figure 5 The diagram illustrates the meshing process between the first piston teeth 11 and 12 and the first stator teeth 21 and 22. Initially, the first piston teeth 11, each with curved tooth surfaces, mesh with the first stator teeth 21. However, the second piston teeth 12 and 22 disengage and cease meshing. Figure 5 In step 3, the second piston tooth 12 and the second stator tooth 22 begin to mesh, while the first piston tooth 11 and the first stator tooth 21 begin to disengage.

[0049] It should be noted that for curved tooth surfaces, the profile is a smooth curve, and the angle between the tangent of this profile and the central axis of the tooth gradually decreases from the tooth tip to the tooth root. The tangent at each point on this profile corresponds to the relative movement direction of the teeth when meshing at that point. Similarly, for flat tooth surfaces, the profile is a straight line, and the angle between the straight line and the central axis of the tooth remains constant. When the first piston tooth 11 and the first stator tooth 21 begin to disengage, and the second piston tooth 12 and the second stator tooth 22 begin to mesh, at the meshing point of the first piston tooth 11 and the first stator tooth 21, the tangent direction of the tooth surface is the same as the tangent direction of the tooth surface of the first piston tooth 11 and the first stator tooth 21 (which is actually the direction of the tooth surface profile), achieving a smooth transition. The mating structure of the third piston tooth 13 and the fourth piston tooth 14 at the other end of the annular piston 10 with the third stator tooth 31 and the fourth stator tooth 32 is also the same, and will not be described in detail here.

[0050] The rotary drive mechanism includes two sets of axially arranged first stators 20, second stators 30, and annular pistons 10. The first stators 20 and second stators 30 are relatively fixed, while the two annular pistons 10 are circumferentially fixed but axially movable relative to each other. Figure 1 and Figure 2 As shown, two sets of first stators 20, second stators 30, and annular pistons 10 are arranged axially. In particular, the second stators 30 of one set and the first stators 20 of the other set are connected to each other and can be integrally formed. The two sets of structures have essentially the same function, which can improve the overall reliability. If one set fails, the other set can be used.

[0051] Specifically, the center lines of the first piston teeth 11 of the two annular pistons 10 are staggered. When the rotary drive mechanism stops, one annular piston 10 can be moved to fully engage with a stator to achieve self-locking. That is, when an external torque is applied to the annular piston 10, it will not rotate. In other words, when the rotary drive mechanism is in the unengaged state, if the piston teeth at one end of the first annular piston 10 are fully engaged with the stator teeth, the axial movement of the annular piston 10 and the engagement of the piston teeth at the other end with the stator teeth mean that the annular piston 10 can only rotate in one direction. At the same time, the second annular piston 10 is in a partially engaged state, and it can be driven to move in the opposite axial direction. Its rotation direction is exactly opposite, that is, the rotation direction can be determined by selecting the axial movement direction of the annular piston 10. The second annular piston 10 can drive the first annular piston 10 to rotate, thus achieving rotation through the axial movement of the two annular pistons.

[0052] refer to Figure 6 and Figure 7 The figures shown are planar development diagrams of the teeth, with the numbers indicating the sequence of steps. When the initial positions of the two annular pistons 10 (hereinafter distinguished as left annular piston 10 and right annular piston 10) are the same, the left annular piston 10 is in the self-locking position, and the teeth at both ends of the right annular piston 10 are engaged with the corresponding stator teeth. Figure 6 In the middle, the left and right annular pistons 10 are simultaneously driven to move to the right. Guided by the second stator 30, the right annular piston 10 rotates "upward," thereby causing the left annular piston 10 to also rotate "upward." Then, the two annular pistons 10 continue to move axially back and forth, achieving continuous "upward" rotation. Figure 7 In the middle, the right annular piston 10 is driven to move axially to the left, and the left annular piston 10 is driven to move axially to the right. Under the guidance of the first stator 20, the right annular piston 10 rotates "downward", which can drive the left annular piston 10 to rotate "downward" as well. Then, the two annular pistons 10 continue to be driven to move axially back and forth, realizing continuous "downward" rotation.

[0053] Additionally, the rotary drive mechanism includes an inner ring 40, on which two annular pistons 10 are axially slidably mounted, and the two annular pistons 10 are circumferentially fixed relative to the inner ring 40. The annular pistons 10 can be mounted on the inner ring 40 via splines and spline grooves, thus allowing axial movement relative to the inner ring 40, but not circumferential rotation. The inner ring 40 restricts its direction of movement through a relatively fixed structure, meaning it can only rotate relative to each stator, and cannot move axially relative to the stators. For example, structures guiding the inner ring 40 can be provided on multiple stators. Figure 2 As shown, the inner ring 40 passes through the stator and the annular piston, and an end cap 50 can be provided at its other end. The end cap 50 can restrict the axial movement of the inner ring 40 and achieve a seal. The end cap 50 can be annular, and the overall rotary drive mechanism is provided with a central hole to allow pipelines to pass through.

[0054] In a structure in which the first stator 20 and the second stator 30 are integrally connected, a cavity can be provided to accommodate the movement of the two annular pistons 10. By providing hydraulic power to the cavity, the annular pistons 10 can be driven to move axially.

[0055] In addition, the present invention also provides a boom, wherein the boom is provided with the rotary drive mechanism described in the above embodiments. The stator portion can be fixed relative to one boom segment, and the annular piston 10, particularly the inner ring 40, can cooperate with another adjacent boom segment to drive the other boom segment to rotate.

[0056] In addition, the present invention also provides an engineering machine, wherein the engineering machine is equipped with the boom described in the above-described scheme. The engineering machine can be a concrete pump truck, a crane, etc.

[0057] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. However, these simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A rotary drive mechanism, characterized by, The rotating driving mechanism comprises an annular piston (10) and a stator, the annular piston (10) is provided with piston teeth with protruding curved tooth surface and piston teeth with inclined flat tooth surface, the stator is provided with stator teeth with protruding curved tooth surface and stator teeth with inclined flat tooth surface, one of the piston teeth with protruding curved tooth surface and the piston teeth with inclined flat tooth surface is located at the outer layer, and the other is located at the inner layer; and the number of the piston teeth with protruding curved tooth surface and the piston teeth with inclined flat tooth surface is the same; one of the stator teeth with protruding curved tooth surface and the stator teeth with inclined flat tooth surface is located at the outer layer, and the other is located at the inner layer; and the number of the stator teeth with protruding curved tooth surface and the stator teeth with inclined flat tooth surface is the same; the annular piston (10) can be driven to move axially relative to the stator, and the annular piston (10) is first engaged with the stator teeth with protruding curved tooth surface through the piston teeth with protruding curved tooth surface, and then engaged with the stator teeth with inclined flat tooth surface through the piston teeth with inclined flat tooth surface, so as to drive the annular piston (10) to rotate circumferentially.

2. The rotational drive mechanism of claim 1, wherein, The stator comprises a first stator (20) and a second stator (30), and the annular piston (10) is arranged between the first stator (20) and the second stator (30).

3. The rotary drive mechanism of claim 2, wherein, The annular piston (10) is provided with a first piston tooth (11) and a second piston tooth (12) at the axial first end and a third piston tooth (13) and a fourth piston tooth (14) at the axial second end, the first stator (20) is provided with a first stator tooth (21) capable of engaging with the first piston tooth (11) and a second stator tooth (22) capable of engaging with the second piston tooth (12), the second stator (30) is provided with a third stator tooth (31) capable of engaging with the third piston tooth (13) and a fourth stator tooth (32) capable of engaging with the fourth piston tooth (14), the first piston tooth (11) and the first stator tooth (21) have protruding curved tooth surfaces respectively, the second piston tooth (12) and the second stator tooth (22) have inclined flat tooth surfaces respectively, the third piston tooth (13) and the third stator tooth (31) have protruding curved tooth surfaces respectively, and the fourth piston tooth (14) and the fourth stator tooth (32) have inclined flat tooth surfaces respectively, Wherein, the annular piston (10) can be driven to move axially reciprocatingly, wherein the first piston tooth (11) is first engaged with the first stator tooth (21), then the second piston tooth (12) is engaged with the second stator tooth (22), the third piston tooth (13) is first engaged with the third stator tooth (31), and then the fourth piston tooth (14) is engaged with the fourth stator tooth (32), thereby pushing the annular piston (10) to rotate.

4. The rotary drive mechanism of claim 3, wherein, The first piston tooth (11), the first stator tooth (21), the third piston tooth (13) and the third stator tooth (31) have involute tooth surfaces respectively.

5. The rotational drive mechanism of claim 3, wherein, The first piston tooth (11) and the second piston tooth (12) are located at the inner and outer sides in the radial direction respectively, and the third piston tooth (13) and the fourth piston tooth (14) are located at the inner and outer sides in the radial direction respectively.

6. The rotational drive mechanism of claim 5, wherein, The first piston tooth (11) and the second piston tooth (12) are in one-to-one correspondence and aligned in the center line, the first stator tooth (21) and the second stator tooth (22) are in one-to-one correspondence and aligned in the center line, the third piston tooth (13) and the fourth piston tooth (14) are in one-to-one correspondence and aligned in the center line, and the third stator tooth (31) and the fourth stator tooth (32) are in one-to-one correspondence and aligned in the center line.

7. The rotary drive mechanism of claim 6, wherein, The center lines of the first stator tooth (21) and the second stator tooth (22) are staggered with the center lines of the third stator tooth (31) and the fourth stator tooth (32), and the center lines of the first piston tooth (11) and the second piston tooth (12) are aligned with the center lines of the third piston tooth (13) and the fourth piston tooth (14).

8. The rotational drive mechanism of claim 7, wherein, The distance between the tooth tips of the first piston tooth (11) and the second piston tooth (12) and the tooth tips of the third piston tooth (13) and the fourth piston tooth (14) is greater than the distance between the tooth tips of the first stator tooth (21) and the second stator tooth (22) and the tooth tips of the third stator tooth (31) and the fourth stator tooth (32), and is less than the distance between the tooth tips of the first stator tooth (21) and the second stator tooth (22) and the tooth roots of the third stator tooth (31) and the fourth stator tooth (32), and is less than the distance between the tooth roots of the first stator tooth (21) and the second stator tooth (22) and the tooth tips of the third stator tooth (31) and the fourth stator tooth (32).

9. The rotational drive mechanism of claim 8, wherein, The rotary drive mechanism comprises two groups of the first stator (20), the second stator (30) and the annular piston (10) arranged in the axial direction, the two groups of the first stator (20) and the second stator (30) are fixed relative to each other, and the two annular pistons (10) are fixed relative to each other in the circumferential direction and can move relative to each other in the axial direction.

10. The rotational drive mechanism of claim 9, wherein, The center lines of the first piston tooth (11) of the two annular pistons (10) are staggered.

11. The rotational drive mechanism of claim 9, wherein, The rotary drive mechanism comprises an inner ring (40), and the two annular pistons (10) are slidably mounted on the inner ring (40) in the axial direction and are fixed relative to the inner ring (40) in the circumferential direction.

12. An arm support, characterized in that The arm support is provided with the rotary drive mechanism according to any one of claims 1-11.

13. A working machine, characterized in that The engineering machine is provided with the arm support according to claim 12.

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