A single variable pitch coaxial counter-rotating propeller for UAV

Abstract

The present invention belongs to the field of aviation technology, and specifically discloses a single-pitch coaxial counter-rotating propeller for an unmanned aerial vehicle. The structural support includes a base column, a bottom plate, a support column, a top plate, a bearing seat, and bolts. The base column is fixed to the bottom plate by bolts, and a motor is provided at the bottom of the bottom plate. The motor and the bearing seat are fixed to the bottom plate by bolts. A top plate is provided on the top of the bottom plate, and a support column is provided between the bottom plate and the top plate. The two ends of the support column are fixedly connected to the bottom plate and the top plate respectively. A servo and a guide plate are provided on the top of the top plate, and the top plate is fixed to the servo and the guide plate by screws; a simple gear set is used to realize the driving of the coaxial counter-rotating propeller, and the structure is simple, easy to manufacture, safe and reliable; the single-pitch mechanism of the present invention performs pitch control on the rear propeller, and effectively improves the working efficiency of the entire power system, especially the rear propeller, under the premise of control system complexity and weight.

Description

Technical Field

[0001] The present invention relates to the field of aviation technology, and in particular to a single-pitch coaxial counter-rotating propeller for a drone. Background Art

[0002] Currently, lightweight, small rotary-wing UAVs are being successfully applied in scenarios such as aerial photography and entertainment, power inspections, environmental monitoring, logistics and transportation, and even manned flights, becoming a research hotspot in the civil aviation field. Their advantages include small size, low cost, and maneuverability. Rotary-wing UAVs typically use an electric drive to drive the rotor system to maintain lift and horizontal motion, which often limits their payload capacity and endurance. Coaxial counter-rotating propellers, with two sets of propellers driven by the same motor, can increase the thrust output of a single power unit compared to a single propeller. Consequently, coaxial counter-rotating propellers are increasingly being used in rotary-wing UAVs.

[0003] Light, small, and micro-rotor UAVs often use fixed-pitch propellers due to weight, complexity, and cost considerations. These propellers typically operate at low speeds and within a limited operating range. The front propeller, located upstream, operates in relatively stable conditions. The rear propeller, operating downstream, is situated in the downwash of the upstream propeller, where the velocity varies dramatically in both radial and circumferential directions. This velocity range varies significantly at different speeds. Coupled with varying ambient airflow, the downstream propeller often deviates from its optimal operating point, resulting in lower efficiency. Variable pitch propellers can effectively alter their operating state. However, conventional coaxial counter-rotating propeller variable pitch structures used in large rotorcraft such as helicopters simultaneously control the pitch of both upper and lower rotors. These complex structures, heavy weight, and complex drive methods and control logic make them unsuitable for light, small, and micro-rotor UAVs. Summary of the Invention

[0004] The object of the present invention is to provide a single variable-pitch coaxial counter-rotating propeller for a UAV to solve the problems raised in the above background technology.

[0005] To achieve the above-mentioned object, the present invention provides the following technical solution: a single variable-pitch coaxial counter-rotating propeller for a UAV, characterized by comprising a structural support, a coaxial counter-rotating drive mechanism, a variable-pitch actuator, and a variable-pitch propeller body;

[0006] The structural support includes a base column, a bottom plate, a support column, a top plate, a bearing seat, and bolts. The base column is fixed to the bottom plate by bolts. A motor is provided at the bottom of the bottom plate. The motor and the bearing seat are fixed to the bottom plate by bolts. A top plate is provided on the top of the bottom plate. A support column is provided between the bottom plate and the top plate. Both ends of the support column are fixedly connected to the bottom plate and the top plate respectively. A steering gear and a guide plate are provided on the top plate. The top plate is fixed to the steering gear and the guide plate by screws.

[0007] The pitch actuator includes a cross swash plate pull rod, a cross swash plate, a swash plate crank, and a hub rocker arm pull rod. The servo is connected to the cross swash plate through the cross swash plate pull rod. The cross swash plate is sleeved on the outside of the outer shaft. The top of the swash plate crank is hinged to the outer shaft. The ball head hinge at the lower end of the swash plate crank is connected to the ball head of the cross swash plate. The top of the cross swash plate is connected to the hub rocker arm pull rod. The top of the hub rocker arm pull rod is provided with a hub rocker arm. The hub rocker arm pull rod is connected to the hub rocker arm through a ball hinge. The top of the hub rocker arm is provided with an outer shaft hub, and the hub rocker arm is mounted and fixed to the outer shaft hub by screws.

[0008] Preferably, the coaxial reversing drive mechanism includes a driving helical gear, a reversing helical gear, an outer shaft driven helical gear, an inner shaft driven helical gear, a bearing, a flange bearing, an outer shaft, and an inner shaft, and the motor power shaft passes through the bottom plate to connect the driving helical gear; the side of the driving helical gear is meshed and connected with the outer shaft driven helical gear and the reversing helical gear, and the side of the reversing helical gear is meshed and connected with the inner shaft driven helical gear; a flange bearing is provided on the top of the outer shaft driven helical gear, and a bearing is provided at the bottom of the inner shaft driven helical gear, and a flange seat is provided on the flange bearing, and the flange bearing is fixed to the top plate through the flange seat; the outer shaft and the inner shaft are provided on the top of the flange bearing, and the top of the inner shaft passes through the outer shaft and extends to the top of the outer shaft.

[0009] Preferably, the variable pitch propeller body includes an outer shaft sleeve, a rear propeller fixing bolt, a rear propeller, an inner shaft sleeve, an inner shaft hub, a front propeller fixing bolt, and a front propeller. The outer shaft hub fixes the rear propeller through a fixing bolt; the inner shaft and the sleeve are punched with holes, the inner shaft is fixed to the sleeve by screws, an outer shaft sleeve is provided on the outside of the outer shaft, and the front propeller is fixed to the inner shaft hub by the front propeller fixing bolt.

[0010] The structural support mechanism is used to support and connect the coaxial reversing drive mechanism and the pitch changing mechanism, wherein the coaxial reversing drive mechanism is mainly fixed to the bottom plate of the support mechanism, and the pitch changing mechanism is mainly fixed to the top plate. The coaxial reversing drive mechanism is used to drive the gear set to drive the inner and outer rotating shafts to rotate in opposite directions through the motor. The motor drives the active helical gear, and the active helical gear drives the outer shaft driven helical gear to rotate, and at the same time drives the reversing helical gear, and the reversing helical gear drives the inner shaft driven helical gear. The pitch changing mechanism is used to execute the pitch changing instruction. The servo is connected through the cross swash plate pull rod and drives the cross swash plate to move up and down along the axial direction. The cross swash plate is connected to the propeller hub rocker arm pull rod, and the propeller hub rocker arm pull rod pulls the propeller hub rocker arm to rotate the propeller hub along the axial direction to achieve the pitch changing purpose.

[0011] The pitch mechanism adopts real-time control mode, with the real-time speed of the propeller as the main input parameter. The speed signal sensor obtains the real-time speed, calculates the optimal pitch angle and the corresponding cross swash plate movement stroke at this speed according to the pre-stored speed-stroke-pitch relationship curve, and outputs the execution signal to the servo line instruction. The servo drives the swash plate pull rod to drive the cross swash plate up and down, and adjusts the rear propeller to the optimal pitch angle according to the current speed; when the swash plate moves upward, the hub rocker arm pull rod pushes the hub rocker arm upward, and the propeller pitch is reduced; when the swash plate moves downward, the hub rocker arm pull rod pulls the hub rocker arm downward, and the propeller pitch is increased.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] A simple gear set is used to drive the coaxial counter-rotating propeller, which has a simple structure, is easy to manufacture, and is safe and reliable. The single pitch-changing mechanism of the present invention performs pitch control on the rear propeller, effectively improving the working efficiency of the entire power system, especially the rear propeller, under the premise of control system complexity and weight. Pitch control is performed according to a pre-stored speed-stroke-pitch relationship curve, and the control method is simple and easy to execute. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention;

[0015] Figure 2 It is a schematic diagram of the side structure of the present invention;

[0016] Figure 3 This is a schematic structural diagram of the coaxial reverse drive mechanism of the present invention;

[0017] Figure 4 Schematic diagram of the variable pitch actuator of the present invention.

[0018] In the figure: 101, base column; 102, bottom plate; 103, support column; 104, top plate; 105, bearing seat; 106, bolt; 201, motor; 202, driving helical gear; 203, reversing helical gear; 204, outer shaft driven helical gear; 205, inner shaft driven helical gear; 206, bearing; 207, flange bearing; 208, outer shaft; 209, inner shaft; 301, rudder Engine; 302, cross swash plate pull rod; 303, cross swash plate; 304, swash plate crank; 305, hub rocker arm pull rod; 306, guide plate; 401, hub rocker arm; 402, outer shaft sleeve; 403, outer shaft hub; 404, rear propeller fixing bolt; 405, rear propeller; 501, inner shaft sleeve; 502, inner shaft hub; 503, front propeller fixing bolt; 504, front propeller. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] In the description of the present invention, it should be noted that the terms "vertical", "up", "down", "horizontal", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limiting the present invention.

[0021] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0022] See also Figure 1-4 , the present invention provides a technical solution: a single variable pitch coaxial counter-rotating propeller for a UAV, comprising a structural support, a coaxial counter-rotating drive mechanism, a variable pitch actuator, and a variable pitch propeller body;

[0023] The structural support includes a base column 101, a bottom plate 102, a support column 103, a top plate 104, a bearing seat 105, and bolts 106. The base column 101 is fixed to the bottom plate 102 by bolts 106. A motor 201 is provided at the bottom of the bottom plate 102. The motor 201 and the bearing seat 105 are fixed to the bottom plate 102 by bolts 106. A top plate 104 is provided on the top of the bottom plate 102. A support column 103 is provided between the bottom plate 102 and the top plate 104. Both ends of the support column 103 are fixedly connected to the bottom plate 102 and the top plate 104 respectively. A servo 301 and a guide plate 306 are provided on the top of the top plate 104. The top plate 104 is fixed to the servo 301 and the guide plate 306 by screws.

[0024] The variable pitch actuator includes a cross swash plate rod 302, a cross swash plate 303, a swash plate crank 304, and a hub rocker arm rod 305. The servo 301 is connected to the cross swash plate 303 through the cross swash plate rod 302. The cross swash plate 303 is sleeved on the outside of the outer shaft 208. The top of the swash plate crank 304 is hinged to the outer shaft 208. The ball hinge at the lower end of the swash plate crank 304 is connected to the ball head of the cross swash plate 303. The top of the cross swash plate 303 is connected to the hub rocker arm rod 305. The top of the hub rocker arm rod 305 is provided with a hub rocker arm 401. The hub rocker arm rod 305 is connected to the hub rocker arm 401 through a ball hinge. The top of the hub rocker arm 401 is provided with an outer shaft hub 403. The hub rocker arm 401 is mounted and fixed to the outer shaft hub 403 by screws.

[0025] Furthermore, the coaxial reverse drive mechanism includes a driving helical gear 202, a reversing helical gear 203, an outer shaft driven helical gear 204, an inner shaft driven helical gear 205, a bearing 206, a flange bearing 207, an outer shaft 208, and an inner shaft 209. The power shaft of the motor 201 passes through the bottom plate 102 and is connected to the driving helical gear 202; the side of the driving helical gear 202 is meshed with the outer shaft driven helical gear 204 and the reversing helical gear 203, and the reversing helical gear The side of 203 is meshedly connected with the inner shaft driven helical gear 205; the top of the outer shaft driven helical gear 204 is provided with a flange bearing 207, and the bottom of the inner shaft driven helical gear 205 is provided with a bearing 206, and the flange bearing 207 is provided with a flange seat, and the flange bearing 207 is installed and fixed to the top plate 104 through the flange seat; the top of the flange bearing 207 is provided with an outer shaft 208 and an inner shaft 209, and the top of the inner shaft 209 passes through the outer shaft 208 and extends to the top of the outer shaft 208.

[0026] Furthermore, the variable pitch propeller body includes an outer shaft sleeve 402, a rear propeller fixing bolt 404, a rear propeller 405, an inner shaft sleeve 501, an inner shaft hub 502, a front propeller fixing bolt 503, and a front propeller 504. The outer shaft hub 403 fixes the rear propeller 405 through the fixing bolt 404; the inner shaft 209 and the sleeve 501 are punched with holes, and the inner shaft 209 is installed and fixed to the sleeve 501 through screws. The outer side of the outer shaft 208 is provided with an outer shaft sleeve 402, and the front propeller 504 is installed and fixed to the inner shaft hub 502 through the front propeller fixing bolt 503.

[0027] The structural support can be connected to the UAV fuselage or power system test bench through the base column 101; the base column is connected to the bottom plate 102 by bolts, and the bottom plate 102 uses bolts to fix the motor 201 and the bearing seat 105 of the coaxial reversing drive system. The bottom plate 102 and the top plate 104 are connected through the support column 103, and the top plate 104 is fixed with bolts to the servo 301 and the guide plate 306 of the variable pitch actuator.

[0028] like Figure 3As shown, the coaxial reversing drive mechanism 2 is connected to the driving helical gear 202 through the flat key on the shaft through the power shaft of the motor 201; the driving helical gear 202 drives the outer shaft driven helical gear 204 to rotate by meshing, and at the same time meshes to drive the reversing helical gear 203, and the reversing helical gear 203 meshes to drive the inner shaft driven helical gear 205; the bearing seats 105 are fixed to the upper end surface of the bottom plate 102 and the lower end surface of the top plate 104 by bolts, and the flange bearing 207 provides the bearing required for the rotation of the outer shaft and provides a flange seat, which is bolted to the top plate 104 through the flange seat; the outer shaft driven helical gear 204 and the inner shaft driven helical gear 205 respectively drive the outer shaft 208 and the inner shaft to rotate 209, the gear center hole and the outer shaft have an interference fit, the top screw is pressed against the flat key on the shaft through the side internal thread of the gear, and the inner and outer shafts are determined by the axial limit of the retaining spring.

[0029] like Figure 4 As shown, the servo 301 and the guide plate 306 are fixed to the top plate 104 by bolts. The servo 301 is connected to and drives the cross swash plate 303 through the cross swash plate pull rod 302. The cross swash plate 303 is externally mounted on the outer shaft 208 and moves up and down along the axial direction. The upper end of the swash plate crank 304 is hinged to the outer shaft 208, and the crank arm can rotate in a direction perpendicular to the axial direction of the outer shaft. The ball joint hinge at the lower end of the crank is connected to the ball joint of the cross swash plate 303. The cross swash plate 303 is connected to the hub rocker arm pull rod 305. The rocker arm pull rod 305 is linked to the hub rocker arm 401 through a ball joint. The hub rocker arm pull rod 305 that moves up and down with the cross swash plate pulls the hub rocker arm 401. The hub rocker arm 401 is fixed to the outer shaft hub 403 by bolts.

[0030] like Figure 1 As shown, the outer shaft hub 403 uses a fixing bolt 404 to fix the rear propeller 405. The outer shaft hub 403 deflects to achieve a change in the pitch angle of the rear propeller 405. The outer shaft 208 is hollow and the inner shaft 209 is located inside the outer shaft; the inner shaft is connected to the sleeve 501 by punching screws, and the front propeller 504 is fixed to the inner shaft hub 502 by the front rotor fixing bolt 503.

[0031] Working principle: The structural support mechanism is used to support and connect the coaxial reversing drive mechanism and the pitch changing mechanism, wherein the coaxial reversing drive mechanism is mainly fixed to the bottom plate 102 of the support mechanism, and the pitch changing mechanism is mainly fixed to the top plate 104. The coaxial reversing drive mechanism is used to drive the gear set to drive the inner and outer rotating shafts to rotate in opposite directions through the motor 201. The motor 201 drives the active bevel gear 202, and the active bevel gear 202 drives the outer shaft 208 and the driven bevel gear 204 to rotate, and at the same time drives the reversing bevel gear 203, and the reversing bevel gear 203 drives the inner shaft 209 and the driven bevel gear 205. The pitch changing mechanism is used to execute the pitch changing instruction. The servo 301 is connected through the cross swash plate 303 pull rod 302 and drives the cross swash plate 303 to move up and down along the axial direction. The cross swash plate 303 is connected to the hub rocker arm 401 pull rod 305. The hub rocker arm 401 pull rod 305 pulls the hub rocker arm 401 to rotate the hub along the axial direction to achieve the pitch changing purpose.

[0032] The pitch mechanism adopts a real-time control mode, with the real-time speed of the propeller as the main input parameter. The speed signal sensor obtains the real-time speed, calculates the optimal pitch angle and the corresponding cross swash plate 303 movement stroke at this speed based on the pre-stored speed-stroke-pitch relationship curve, outputs the execution signal to the servo 301 line instruction, and drives the swash plate pull rod through the servo 301 to drive the cross swash plate 303 to move up and down, and adjusts the rear propeller to the optimal pitch angle according to the current speed; when the swash plate moves upward, the hub rocker arm 401 pull rod 305 pushes the hub rocker arm 401 upward, and the propeller pitch is reduced; when the swash plate moves downward, the hub rocker arm 401 pull rod 305 pulls the hub rocker arm 401 downward, and the propeller pitch is increased;

[0033] Furthermore, the calculation process of the speed-stroke-variable pitch relationship is as follows:

[0034] The pitch of a variable-pitch propeller is usually represented by the pitch at 0.7R (R represents the propeller radius). Therefore, in order to make the control law simple and easy to operate, the performance of the cross-sectional airfoil at 0.7R of the rear propeller is optimized. In order to obtain the optimal pitch angle at this location, the speed-stroke-variable pitch relationship is established.

[0035] First, it is necessary to determine the axial distance D between the front and rear propellers and the optimal angle of attack α of the rear propeller 0.7R cross-section airfoil opt ; The front propeller speed ω, the axial spacing D downstream of the front propeller rotation plane and the axial induced velocity V at the rear propeller 0.7R position a and the circumferential induced velocity V c The relationship between the induced speed and the speed ω needs to be calibrated in advance by experiments; the induced speeds in the two directions are fitted as a quadratic function of the speed ω, that is, V a =f1·ω2+f2·ω+f3, V c =g1·ω 2 +g2·ω+g3;

[0036] The optimal pitch angle The relationship with the speed ω is as follows:

[0037] The horizontal distance between the center axis of the hub rocker arm 401 and the center axis of the outer shaft hub 403 is C; the initial state pitch angle is The initial stroke of the cross swash plate 303 is 0. When the rotation speed ω is set, in order to ensure the optimal pitch angle, the relationship between the stroke h of the cross swash plate 303 and the rotation speed ω is as follows:

[0038]

[0039] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A single variable pitch coaxial counter-rotating propeller for a UAV, characterized by: It includes structural support, coaxial reverse drive mechanism, variable pitch actuator, and variable pitch propeller body; The structural support comprises a base column (101), a bottom plate (102), a support column (103), a top plate (104), a bearing seat (105), and bolts (106). The base column (101) is fixed to the bottom plate (102) by means of bolts (106). A motor (201) is provided at the bottom of the bottom plate (102). The motor (201) and the bearing seat (105) are fixed to the bottom plate (102) by means of bolts (106). A top plate (104) is provided on the top of the bottom plate (102), a support column (103) is provided between the bottom plate (102) and the top plate (104), two ends of the support column (103) are fixedly connected to the bottom plate (102) and the top plate (104), a steering gear (301) and a guide plate (306) are provided on the top of the top plate (104), and the top plate (104) is fixed to the steering gear (301) and the guide plate (306) by screws; The variable pitch actuator comprises a cross swash plate pull rod (302), a cross swash plate (303), a swash plate crank (304), and a propeller hub rocker arm pull rod (305); the servo (301) is connected to the cross swash plate (303) via the cross swash plate pull rod (302); the cross swash plate (303) is sleeved on the outside of the outer shaft (208); the top of the swash plate crank (304) is hinged to the outer shaft (208); the ball head hinge at the lower end of the swash plate crank (304) is hinged to the cross swash plate (303); The cross swash plate (303) is connected to the ball head, the top of the cross swash plate (303) is connected to the propeller hub rocker arm pull rod (305), the top of the propeller hub rocker arm pull rod (305) is provided with a propeller hub rocker arm (401), the propeller hub rocker arm pull rod (305) is connected to the propeller hub rocker arm (401) through a ball hinge, the top of the propeller hub rocker arm (401) is provided with an outer shaft propeller hub (403), and the propeller hub rocker arm (401) is fixed to the outer shaft propeller hub (403) through screws.

2. The single variable pitch coaxial counter-rotating propeller for a UAV according to claim 1, characterized in that: The coaxial reverse drive mechanism comprises a driving helical gear (202), a reversing helical gear (203), an outer shaft driven helical gear (204), an inner shaft driven helical gear (205), a bearing (206), a flange bearing (207), an outer shaft (208), and an inner shaft (209); a power shaft of the motor (201) passes through the bottom plate (102) and is connected to the driving helical gear (202); a side surface of the driving helical gear (202) is meshedly connected to the outer shaft driven helical gear (204) and the reversing helical gear (203); and the reversing helical gear (203) is meshedly connected to the outer shaft driven helical gear (204). ) is meshedly connected to the side of the outer shaft driven helical gear (205); a flange bearing (207) is provided on the top of the outer shaft driven helical gear (204), a bearing (206) is provided on the bottom of the inner shaft driven helical gear (205), a flange seat is provided on the flange bearing (207), and the flange bearing (207) is fixed to the top plate (104) through the flange seat; an outer shaft (208) and an inner shaft (209) are provided on the top of the flange bearing (207), and the top of the inner shaft (209) passes through the outer shaft (208) and extends to the top of the outer shaft (208).

3. The single variable pitch coaxial counter-rotating propeller for a UAV according to claim 1, characterized in that: The variable pitch propeller body comprises an outer shaft sleeve (402), a rear propeller fixing bolt (404), a rear propeller (405), an inner shaft sleeve (501), an inner shaft hub (502), a front propeller fixing bolt (503), and a front propeller (504); the outer shaft hub (403) fixes the rear propeller (405) via the fixing bolt (404); the inner shaft (209) and the sleeve (501) are punched with holes, the inner shaft (209) is fixed to the sleeve (501) via screws, the outer side of the outer shaft (208) is provided with an outer shaft sleeve (402), and the front propeller (504) is fixed to the inner shaft hub (502) via the front propeller fixing bolt (503).

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