CN113320686B

CN113320686B - Propeller active pitch-changing mechanism

Info

Publication number: CN113320686B
Application number: CN202110486698.2A
Authority: CN
Inventors: 葛文杰; 刘斌; 李树军
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2021-05-01
Filing date: 2021-05-01
Publication date: 2022-11-01
Anticipated expiration: 2041-05-01
Also published as: CN113320686A

Abstract

The invention relates to a propeller active pitch-changing mechanism, aiming at solving the problems that the propeller of an aircraft in the prior art can not realize pitch changing, hydraulic pitch-changing mechanisms have hydraulic oil leakage, volume loss and difficult guarantee of control precision, gear type structures are complex, the overall quality is difficult to guarantee on the premise of guaranteeing objective function requirements such as strength and the like, and the propeller active pitch-changing mechanism can only be used in places with low weight requirements. The function principle is that the motor is fixedly connected with the shell of the first transmission part and then connected with the worm gear mechanism, the motor transmits motion to the ball screw push rod through the worm gear mechanism with a large transmission ratio, and the push rod and the swing rod form a sine mechanism to realize accurate and controllable pitch change. The invention can realize active pitch change, has the characteristics of compact mechanism, light weight, simple and direct pitch change mode and high pneumatic efficiency, and has certain popularization.

Description

Propeller active pitch-changing mechanism

Technical Field

The invention belongs to the technical field of aviation, and particularly relates to a propeller pitch-variable mechanism.

Background

The aircraft propellers are mainly divided into two categories according to the fixing mode of the blades on the hub: fixed pitch propeller which can not change the angle of the propeller and variable pitch propeller which can change the angle of the propeller.

(1) A fixed-distance propeller: the propeller blades are arranged on the propeller hub according to a design angle, the angle of the propeller blades cannot be changed in the flight process, and the angle of the propeller can be changed only by changing the installation position after landing. Since the fixed-pitch propeller has only one angle during operation, its efficiency is not stable in different flight situations.

(2) Variable pitch propeller: the variable pitch propeller is designed to overcome the defects of fixed pitch propellers, and is characterized in that the angle of the propeller can be changed in an allowable range around the axial direction of the propeller, so that the aircraft has higher efficiency in different flight states, thereby saving energy and improving the overall function of the aircraft.

In order to reduce the number of movable parts, aircraft are mostly designed as fixed-moment propellers. Because the difference of the rotating speeds of the aircraft which need to be reached in different flight states is large, the matching of the rotating speeds of the fixed pitch propeller and the motor is very difficult, and the system efficiency is greatly influenced.

To solve the efficiency problem, the method that the 'Apollo' aircraft uses a plurality of groups of propellers for propulsion improves the overall efficiency and stability of the aircraft, but the plurality of groups of propulsion devices have high energy consumption and heavy weight which are harmful to the design of the aircraft. People at home Wang Ning and the like have invented an aircraft propeller variable pitch mechanism (patent number CN 109606648A), which comprises components such as a propeller rotating speed control module, a motor, an oil tank and the like, a high-pressure pump is driven by the motor to generate high-pressure lubricating oil, and then the propeller is indirectly controlled to rotate around the axis of the propeller to realize variable pitch, although the stepless variable pitch can be realized by adopting the hydraulic variable pitch propeller mechanism, the energy of the hydraulic variable pitch propeller mechanism needs to be converted in the transmission process, and the problems of volume loss, liquid leakage, complex hydraulic pipeline, difficult guarantee of control precision, difficult troubleshooting and the like exist. Zhang Jianxing et al invented a planetary differential pitch-variable propeller (patent No. CN 1055581 a) for wind power generation, which can adjust the position of the propeller blades with the change of natural wind to keep the blades at a stable rotation speed, but such a pitch-variable propeller using a differential mechanism has a complex structure and high maintenance cost, and the planetary gear mechanism is difficult to ensure the overall quality on the premise of ensuring objective function requirements such as strength, and can only be used in places with low requirements for weight, and cannot be applied to the environment with strict requirements for weight, such as aircrafts. Zhang Xiaoyu a pitch-variable propeller (patent No. CN 110254694 a) is invented, which utilizes the elastic force of a spring to actively resist the change of external load, and although the pitch-variable propeller can realize the pitch change, the pitch change precision is low, the degree of dependence on an elastic piece is large, the precise control cannot be realized, and the long-term realization of the target function of the aircraft is difficult to ensure. In view of the above, it is necessary to provide a pitch-variable propeller mechanism with high precision, light weight and high efficiency.

Aiming at the problems, the invention provides the variable pitch propeller mechanism with light weight, high efficiency and high control precision, and experiments prove that the variable pitch propeller mechanism can adapt to complex environments with different heights, different flight rotating speeds and the like and has excellent performance.

Disclosure of Invention

The technical problems solved by the invention are as follows: the invention discloses a propeller active pitch-changing mechanism, which aims to solve the problems that hydraulic oil leakage, volume loss and control precision of a hydraulic pitch-changing propeller are difficult to guarantee in the prior art, the existing aircraft is light in weight, the aircraft is stressed greatly in the operation process, and an active motor can not bear other loads when driving the propeller to rotate at a high speed, and the design of the pitch-changing propeller has the defects of complex mechanism and part number.

The technical scheme of the invention is as follows: a propeller active pitch-changing mechanism comprises a propeller part and a main pushing motor, wherein the main pushing motor drives the propeller part to rotate circumferentially; the device is characterized by also comprising an actuating mechanism, a main pushing motor, a transmission mechanism and a variable pitch motor; the actuating mechanism is respectively connected with the two propeller parts;

a worm gear structure and a lead screw nut structure are arranged in the transmission mechanism, and the lead screw is connected with the worm gear in a matching way and the axes of the lead screw and the worm gear are overlapped; one end of the screw rod is connected with the actuating mechanism;

the output end of the variable pitch motor is connected with the worm;

the actuating mechanism comprises a shifting fork, a connecting piece, a guide post and a force release sleeve; the middle part of the shifting fork is fixedly connected with the screw rod, and two ends of the shifting fork are respectively hinged with a connecting piece which is fixedly connected with the blade; the force-releasing sleeve is coaxially sleeved on the lead screw and does not interfere with the lead screw, and is finally and indirectly fixedly connected with the support frame and in a relatively static state. The other end of the force-releasing sleeve is connected with the transmission mechanism; the pneumatic load borne by the propeller is transmitted to the support frame through the force-releasing sleeve;

the transmission mechanism converts the rotary motion of the variable pitch motor into the linear motion of the screw rod through the characteristics of the worm gear and the worm, and the screw rod drives the shifting fork to move axially, so that the connecting piece is driven to rotate around the axis of the propeller hub of the propeller, and the pitch angle of the blade is changed.

The further technical scheme of the invention is as follows: the middle main body of the shifting fork is a columnar body, a through hole is axially formed, a step is arranged in the through hole and used for mounting a bearing and a lead screw, and the lead screw is fixedly connected with the shifting fork and can bear a larger axial load; the outer wall extends outwards along the axis to form two bulges, wherein the outwards extending directions of the two bulges are opposite, and the two bulges are not on the same plane; the protruding end is provided with a through hole as a mounting hole.

The further technical scheme of the invention is as follows: the whole connecting piece is a water drop-shaped plate, a through hole is formed in the small-diameter end, and a special-shaped hole is formed in the large-diameter end; after the roller is assembled in the through hole of the small diameter end, the roller is hinged with the mounting hole of the shifting fork protrusion through a pin shaft; the special-shaped hole at the large-diameter end is fixedly connected with the paddle root.

The further technical scheme of the invention is as follows: the actuating mechanism further comprises a hub upper cover, a guide column and a hub lower cover; the upper hub cover and the lower hub cover are connected with each other to form an actuating mechanism outer shell with a cavity inside, one end of the guide post is fixedly connected with the lower hub cover, and the other end of the guide post is in nested fit with the columnar body in the middle of the shifting fork; the upper end of the force release sleeve is provided with a stepped shaft which is fixedly connected with the guide post through a bearing so as to form indirect fixed connection with the lower cover of the hub, and the lower end of the force release sleeve is provided with a key groove which is fixedly connected with the two shells of the transmission mechanism through two specially processed non-standard keys; the inside hollow structure that is of power release sleeve, the lead screw can have noninterference linear motion about power release sleeve is inside.

The further technical scheme of the invention is as follows: the transmission mechanism comprises a lead screw, a first transmission mechanism bearing, a worm wheel, a second transmission mechanism bearing, a first transmission mechanism shell, a second transmission mechanism shell, a lead screw nut, a worm, a shaft and a sleeve; the worm wheel and the worm are vertically installed, a round hole with the same diameter as the smaller diameter of the screw nut stepped shaft and a threaded hole are machined in the middle of the worm wheel and used for installing the screw nut, the round hole and the threaded hole are fixedly connected with the screw nut, and the axes of the worm wheel and the worm are ensured to coincide. The lead screw is divided into an optical axis part and a thread part, the thread part is matched with a lead screw nut, low-friction motion is realized by means of internal balls, the optical axis part of the lead screw is arranged to be a stepped shaft, and the large-shaft-diameter part is provided with two sliding key grooves which are symmetrically arranged. The two shells of the transmission mechanism are of a symmetrical structure and are connected through bolts, and the nonstandard keys are in interference fit with the key slots on the two shells of the transmission mechanism and then form clearance fit with the sliding key slots on the lead screw, so that the degree of freedom of the lead screw in rotation along the axis of the lead screw is limited, and the lead screw can only realize linear motion with single degree of freedom.

The further technical scheme of the invention is as follows: the device also comprises a supporting frame and a flange plate; the supporting frame is provided with a mounting through hole and a threaded hole; the stator of the main pushing motor is fixedly connected with the support frame; the flange plate is positioned below the lower cover of the propeller hub, one surface of the flange plate is fixedly connected with an inner rotor of the main pushing motor, and the other surface of the flange plate is fixedly connected with the lower cover of the propeller hub.

The further technical scheme of the invention is as follows: still include the semicircle ring subassembly, the semicircle ring subassembly comprises a plurality of high strength wear-resisting material's semicircle ring, imbeds respectively that actuating mechanism propeller hub lower cover is opened in having corresponding annular, converts big normal pressure into little frictional force through smooth surface, can fix a position the screw and produce centrifugal force with the high rotational speed of transmission screw and make it offset each other.

Effects of the invention

The invention has the technical effects that: the propeller pitch-changing mechanism can realize active pitch changing, has the characteristics of compact structure, light weight, simple and direct pitch changing mode and high pneumatic efficiency, and has certain popularization. Specifically, the beneficial effects of the invention are as follows:

(1) The propeller pitch-changing mechanism of the invention changes the angle of the blade through devices such as a servo pitch-changing motor, a worm gear, a lead screw, a shifting fork and the like, thereby realizing active pitch changing. Experiments prove that the mechanism can realize the change of the pitch angle of 30 degrees at the temperature of 65 ℃ below zero and under the environment of 4kpa, and the change precision can reach 0.2 degree. Continuous positive and negative pitch angle changes can be achieved. The variable-pitch hydraulic control system has the advantages of high control precision, simple and direct variable-pitch mode, no need of carrying hydraulic oil, direct transmission, light weight and the like.

(2) The invention combines software such as ANSYS, solidworks and the like for verification for many times, adopts the semicircular ring made of special materials to bear larger centrifugal force generated by the propeller in the rotating process, adopts materials made of different materials to manufacture the hub cover, has good stress performance, and can ensure that all moving parts can move strictly according to a set route by combining with a specially designed guide mechanism. The inventive hub can bear 48000N centrifugal force and 1093 N.m torque under the condition that the overall mass is 12.88kg and the total weight of the upper hub and the lower hub is 3.2 kg.

(3) The propeller hub and the connecting piece matched with the propeller hub are provided with the profiles which are completely matched, the connection can bear larger load, additional fixing parts are not needed, and the installation is convenient.

(4) The small-diameter end of the connecting piece is provided with the slotted hole, in the variable pitch process, the slotted hole can realize force transmission and rolling motion with small friction coefficient through the roller matched with the slotted hole, and the length of the larger slotted hole can adapt to a large variable pitch range and cannot be blocked in the motion process.

(5) According to the invention, the force-releasing sleeve is skillfully designed with a set of connecting and mounting structure, so that most of force borne by the propeller in the motion process is successfully transferred to the mounting frame, and the problems of overlarge friction force and low efficiency caused by the large pressure borne by the main pushing motor are avoided.

(6) According to the invention, the worm gear and the ball screw transmission mechanism are combined together, double guarantee is carried out by utilizing the characteristics of large transmission ratio and good self-locking performance of the worm gear and the ball screw transmission mechanism, a self-locking structure is not required to be specially designed, the requirement on the performance of the variable pitch motor is reduced by the transmission mechanism with the large transmission ratio, and the variable pitch motor can provide 0.5 N.m of torque to realize variable pitch under the conditions of 20km high altitude and the rotating speed of the propeller being 500r/min through calculation.

(7) The non-standard key designed by the invention not only can play a role in bearing and positioning, but also can be matched with a sliding key groove on the lead screw to play a role in a guide key.

Drawings

FIG. 1 is a schematic diagram of the active pitch-changing mechanism of the propeller of the present invention

Fig. 2 is a schematic structural diagram of the propeller active pitch-changing mechanism of the invention.

Fig. 3 is a sectional view of the structure of the propeller active pitch mechanism of the present invention (only the root is shown here).

Fig. 4 is an exploded view of the active pitch mechanism of the propeller of the present invention.

Fig. 5 is a schematic view of the connection of the propeller part of the active pitch mechanism of the propeller of the present invention.

Fig. 6 is a schematic view of the connection structure of the actuator of the propeller active pitch-changing mechanism of the present invention.

Fig. 7 is a schematic structural view of a fork and a connecting piece part of the active pitch-changing mechanism of the propeller.

FIG. 8 is a schematic view of the connection between the force-releasing sleeve and the support seat of the active pitch-varying mechanism of the propeller of the present invention

FIG. 9 is a schematic view of the transmission part of the propeller active pitch-changing mechanism of the present invention

Description of the reference numerals:

a, a motor 1; b, a worm; c, a worm wheel; d, a motor 2; e, a push rod; f (g) a swing rod; h (i) a paddle; 1, a propeller part; 2, an actuating mechanism; 3, a main push motor; 4, supporting the frame; 5, a transmission mechanism; 6, a variable pitch motor; 1-1, a paddle root; 1-2, propeller: 1-3, an outer semicircular ring; 1-4, inner semicircular ring; 1-5, connecting pieces; 1.1, a first molded surface; 1.2, a second molded surface; 1.3, an inner ring groove; 1.4, an outer ring groove; 1.5, a slotted hole; 2-1, mounting a hub cover; 2-2, a shifting fork; 2-3, bearing end cover; 2-4, a first actuator bearing; 2-5, a guide post; 2-6, a second actuating mechanism bearing; 2-7, a paddle hub seat; 2-8, a force-releasing sleeve; 2-9, pin roll; 2-10 parts of a cylindrical roller; 2.1 key slots; 3-1, a flange plate; 3-2, inner rotor; 3-3, stator; 5-1, a lead screw; 5-2, a first transmission mechanism bearing; 5-3, bearing sleeve; 5-4, a worm wheel; 5-5, a second transmission mechanism bearing; 5-6, a first transmission mechanism shell; 5-7, a second transmission mechanism shell; 5-8, a screw nut; 5-9, a worm; 5-10, a third transmission mechanism bearing; 5-11 is a bond; 5-12, sleeve; 5-13, round nuts; 5.1 key slots;

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "left", "right", "top", "bottom", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are used only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the referred orientations or positional relationships must have specific orientations, be constructed in specific orientations, and be operated; for ease of viewing the details of the invention, FIG. 2 of the present invention does not include a propeller and therefore should not be construed as limiting the invention.

Referring to fig. 1-9, the present invention provides an active pitch-changing mechanism for propellers during rotation, so as to solve the problem that pitch-changing of fixed-pitch propellers of prior art aircrafts cannot be realized; the hydraulic variable-pitch propeller has large weight and low precision; gear formula weight is big, passive form control accuracy low grade problem to improve the pneumatic efficiency of aircraft, improve the comprehensive properties of aircraft, reduce cost.

The technical scheme of the invention is as follows: a propeller active pitch-changing mechanism comprises six parts, namely a propeller part 1, an actuating mechanism 2, a main pushing motor 3, a supporting frame 4, a transmission mechanism 5 and a pitch-changing motor 6. The propeller comprises a pair of propellers 1-2, a shifting fork 2-2, a connecting piece 1-5, a propeller hub upper cover 2-1, a propeller hub base 2-7, a main pushing motor 3, a variable pitch motor 6, a force-releasing sleeve 2-8, a flange plate 3-1, a support frame 4, a worm wheel 5-4, a worm 5-9, a ball screw 5-1 and the like. The principle diagram of the invention is shown in figure 1, and the invention comprises a motor 1a, a worm b, a worm wheel c, a motor 2d, a push rod e, swing rods f and g and blades h and i. The rotation of the motor 1a is transmitted to a ball screw push rod (e) through a worm gear large transmission ratio mechanism, and the push rod e drives two swing rods f and g to move to form a sine mechanism. According to the large transmission ratio of the worm and the gear, the torque conversion of the ball screw with high transmission efficiency level is realized, and the high-efficiency controllable pitch change of the propeller can be realized by controlling the motion of the motor. The motor transmits motion to the ball screw push rod through the worm gear large transmission ratio mechanism, and the push rod and the swing rod form a sine mechanism to realize stable distance change.

The propeller part is arranged in the inner cavity of the actuating mechanism, and the propeller can rotate around the axis of the propeller in the inner cavity of the actuating mechanism; an inner rotor 3-2 of the main pushing motor is fixedly connected with the actuating mechanism, a stator 3-3 is fixedly connected with the supporting frame, and the main pushing motor rotates to drive the actuating mechanism to rotate so as to drive the propeller to rotate around the axis of the main pushing motor; the transmission mechanism is fixedly connected with the support frame, and transmission parts are contained in the transmission mechanism; the variable pitch motor is fixedly arranged on a shell of the transmission mechanism, and the variable pitch motor drives components in the transmission mechanism to move, so that the movement is transmitted to the actuating mechanism, and then the variable pitch of the propeller is realized.

The upper cover of the propeller hub and the hub seat are both hollow semicylinders, an inner annular groove 1.3 and an outer annular groove 1.4 are specially designed in the middle cavity for functions of installation, positioning, stress and the like, positioning bosses are arranged on the upper cover of the propeller hub and the hub seat to ensure the upper cover of the propeller hub and the hub seat to be concentric, and the upper cover of the propeller hub and the hub seat are fixedly connected through bolts to form a cylindrical cavity for installing a propeller; the propeller root 1-1 is designed with inner and outer annular grooves 1.3, 1.4 with corresponding size and position, and the actual contact relation in the installation cavity formed by the upper cover of the propeller hub and the hub seat is as follows: the upper cover and the hub seat of the propeller hub are contacted with inner and outer semicircular rings 1-3 and 1-4 made of special materials, and the inner and outer semicircular rings are contacted with the propeller root; the connecting piece 1-5 is a water-drop-shaped plane piece, a profile 1.1 is arranged in the big end hole and is accurately matched with the profile 1.2 on the propeller root, so that the propeller is fixedly connected with the connecting piece; the propeller hub seat is fixedly connected with the flange plate, and an inner rotor 3-2 of the main push motor is fixedly connected with the flange plate, so that the propeller hub seat is fixedly connected with the main push motor; the middle main body of the shifting fork 2-2 is a cylinder, a through hole is axially formed, and steps are arranged in the through hole and used for mounting the first actuating mechanism bearings 2-4 and the second actuating mechanism bearings 2-6 and the lead screw 5-1, so that the lead screw is fixedly connected with the shifting fork; two bulges extend out of the outer wall of the middle cylinder, the two bulges extend outwards in opposite directions and are not on the same plane, and through holes are arranged at the bulge ends and are used as mounting holes to be matched with the cylindrical rollers 2-10, the cylindrical pins 2-9 and the like, and finally, hinging is formed at the connecting piece. The guide column is fixedly connected with the propeller hub seat through a bolt; the inner cavity of the cylindrical part of the shifting fork main body is sleeved on the guide post, so that the cylinder of the shifting fork main body is concentric with the guide post and can move up and down; the guide post is also internally provided with a through hole and a step which are fixedly connected with the force release sleeve. The first and second transmission mechanism shells 5-6 and 5-7 are designed to be of a symmetrical structure, the upper parts of the shells are designed to be two semicircular discs which are concentrically matched with an inner disc on the support frame, and the first and second transmission mechanism shells are fixedly connected with the support frame through bolts. The force-releasing sleeve is provided with a key groove 2.1 which is in interference fit with a non-standard key, so that the first transmission part shell, the second transmission part shell and the force-releasing sleeve are fixedly connected through the non-standard key. And a through hole is processed in the center of the worm gear 5-4 and matched with a screw nut 5-8 in the ball screw, and the worm gear and the ball screw are fixedly connected through a bolt. The first transmission mechanism shell and the second transmission mechanism shell are symmetrically designed, the first transmission mechanism shell and the second transmission mechanism shell are fixedly connected through bolts, one end of an internal worm 5-9 is provided with a key groove, and the two ends of the internal worm are fixedly connected with the first transmission mechanism shell and the second transmission mechanism shell through a pair of third transmission mechanism bearings 5-10. The variable pitch motor 6 is fixedly connected with the first transmission mechanism shell through a bolt and is connected with the worm through a key connection.

The main pushing motor drives the propeller hub base and the propeller blades to rotate in a rotating mode, and when the aircraft hopes to keep high-efficiency flight in different environments, the pitch angle of the propeller blades needs to be changed.

When the variable pitch motor rotates clockwise, clockwise rotation motion is changed into upward linear motion through the worm gear and the ball screw, the shifting fork moves upwards, and the connecting piece drives the paddle to rotate clockwise, so that the paddle pitch of the paddle is increased. When the variable pitch motor rotates anticlockwise, anticlockwise rotation motion is changed into downward linear motion through the worm gear and the ball screw, the shifting fork moves downwards, and the connecting piece drives the paddle to rotate anticlockwise, so that the paddle pitch of the paddle is reduced.

The principle of the embodiment of the invention is shown in figure 1, and the invention comprises a motor 1,b worm, a worm gear c, a motor d, a push rod e, a swing rod f and a paddle h. The function principle of the variable-pitch drive mechanism is that a motor 1 is fixedly connected with a first transmission part shell 5-6 and then connected with a worm gear mechanism, the motor 1 transmits motion to a ball screw push rod e through a worm gear large transmission ratio mechanism, and the push rod e and a swing rod f (g) form a sine mechanism, so that accurate and controllable variable pitch is realized.

Based on the arrangement, according to the propeller active pitch-changing mechanism, the main pushing motor rotates to drive the propeller hub seat and the blades to rotate, and when the aircraft wants to keep a fixed flight attitude in different environments, the pitch angle of the blades needs to be changed.

When high altitude vehicle need adapt to the environment and reduce specific quantity pitch, the appointed number of turns of pitch motor clockwise rotation, through worm gear, ball become rotary motion linear motion, the shift fork shifts up the appointed distance, the accurate angle of connecting piece clockwise rotation, the pitch motor passes through transmission makes the required numerical value of pitch grow of paddle. When the aircraft need initiatively increase the pitch for adaptation environment, the appointed number of turns of displacement motor anticlockwise rotation, through worm gear, ball become rotary motion linear motion, the shift fork moves down the appointed distance, the connecting piece anticlockwise rotation, the displacement motor passes through transmission makes the pitch of paddle diminishes appointed numerical value.

In the embodiment, as shown in fig. 1 to 9, in the flying process of the aircraft, the high rotating speed of the propeller generates a large centrifugal force, and the large propeller generates a large overturning moment at the hub due to an overlarge force arm, and the embodiment of the invention is provided with an outer semicircular ring 1-3 and an inner semicircular ring 1-4 which are made of wear-resistant materials. The semicircular ring can be processed with high precision on the surface, and bears large positive pressure in the process of propeller pitch changing, but generates small resistance due to small friction coefficient. The semicircular ring can transmit centrifugal force generated by the propeller in the rotating process to the upper hub cover and the hub seat, and the left cavity and the right cavity of the upper hub cover and the hub seat are connected through the connecting part to form a whole body, so that the centrifugal force generated in the rotating process of the propeller is mutually offset and is not loaded into other parts, and the propeller rotating mechanism is very beneficial to an aircraft whole machine and a variable pitch mechanism.

The invention relates to a propeller active pitch-varying mechanism of a propeller, wherein a propeller of an aircraft is subjected to larger aerodynamic force in high-altitude flight, in order to improve the mechanical property of the aircraft, avoid a main pushing motor from bearing larger additional load and facilitate the pitch variation of the propeller 1, the upper end of a force-releasing sleeve 2-8 in the propeller active pitch-varying mechanism is fixedly connected with a propeller hub seat 2-7 through a bearing and a guide column 2-5, a key groove 2.1 is arranged on the force-releasing sleeve 2-8 and is in interference fit with a non-standard key, a first transmission part shell, a second transmission part shell and the force-releasing sleeve are fixedly connected through the non-standard key, the first transmission mechanism shell and the second transmission part shell are designed into symmetrical structures, the upper part of the shells are designed into two semicircular discs which are in concentric fit with an inner disc on a support frame, and the first transmission mechanism shell and the second transmission mechanism shell are fixedly connected with the support frame through bolts. In the flying process of the aircraft, the pneumatic load borne by the propeller is transmitted to the propeller hub seat 2-7 and then transmitted to the support frame 4 through the force release sleeve 2-8, and finally the pneumatic load borne by the propeller 1 is transmitted to the support frame.

As shown in figures 1-9, in order to reduce the weight of the aircraft, in the embodiment of the invention, a hollowed weight reduction design is carried out on a hub upper cover 2-1, a hub seat 2-7 and a shifting fork 2-2. The worm and gear mechanism with large transmission ratio is designed to be in transmission with the combination of the ball screw, the shifting fork 2-2 with the force arm is designed, large torque borne by the propeller is changed into small force through the force arm to be transmitted to the screw rod 5-1, the weight of the variable pitch motor is finally reduced, and the transmission mechanism 5 is designed to have self-locking performance.

As shown in fig. 1 to 9, in order to prevent the screw from rotating along with the main push motor 3 when the propeller rotates, the large-diameter optical axis portion of the screw is provided with a sliding key groove which is matched with the non-standard part keys 5 to 11, so that the ball screw is ensured not to move circumferentially but only to move linearly.

As shown in figures 1-9, in order to avoid the problems of difficult manufacturing and installation, responsible structure and the like caused by a large number of mechanism parts, the connecting piece 1-5 designed by the invention skillfully utilizes the profile connection characteristic, has no redundant connecting parts, has simple structure, convenient installation and good stress characteristic, has the load capacity determined by the characteristics of materials only, and does not need to consider the problems of looseness prevention, expansion and contraction of the materials due to environmental change and the like.

In conclusion, the propeller active pitch-changing mechanism has the advantages of capability of accurately and actively changing the pitch, compact structure, light weight, self-locking property and simple and convenient pitch-changing mode, thereby having certain popularization.

Experiments prove that the propeller active pitch-changing mechanism can realize 150r/min pitch change of a main push motor under the ground condition, the pitch change precision is 0.2 degrees, and the pitch change amplitude is 30 degrees; can work normally under the environment of high temperature, low temperature, high pressure and low pressure.

In conclusion, aiming at the problems that hydraulic oil leakage, volume loss and control precision are difficult to guarantee in a hydraulic variable-pitch propeller, the invention designs and uses power which can realize accurate control of a servo motor to realize pitch angle change for the propeller, and adopts a skillfully designed sine mechanism to realize transmission of motor motion; aiming at the problem of light weight which is a troublesome problem of the design of the prior aircraft, the invention specially designs the split type hub, and carries out hollow design on the split type hub, solves the stress problem of the hub by bearing larger centrifugal force through a plurality of semicircular rings made of special materials, realizes small stress of the upper hub cover, and can use low-density materials such as aluminum alloy and the like. Unique parts such as a shifting fork, a guide sleeve and the like are designed, so that the single stress condition and the non-deviation motion of each moving part in the motion process are realized; aiming at the problems that the aircraft is stressed greatly in the operation process, and the driving motor cannot bear other loads when driving the propeller to rotate at a high speed, the invention designs the force release mechanism, so that most of the force borne by the propeller can be successfully transmitted to the mounting frame, and the driving motor only needs to overcome the resistance in the flight process and does not bear additional pressure; aiming at the problems of complex mechanism, more parts and the like which are difficult to avoid in the design of the conventional variable pitch propeller, the invention successfully realizes high-transmission-ratio transmission variable pitch by only utilizing worm and gear and ball screw transmission parts, and greatly reduces the number of parts. Through calculation, under the condition that the rotating speed of a propeller is 500r/min at 20km high altitude, the variable-pitch motor provides 0.5 N.m of torque to realize variable pitch.

The foregoing is directed to the preferred embodiment of the present invention, and it is understood that various changes and modifications may be made by one skilled in the art without departing from the spirit of the invention, and it is intended that such changes and modifications be considered as within the scope of the invention.

Claims

1. A propeller active pitch-changing mechanism comprises a propeller part (1) and a main pushing motor (3), wherein the main pushing motor (3) drives the propeller part (1) to rotate circumferentially; the device is characterized by also comprising an actuating mechanism (2), a main pushing motor (3), a transmission mechanism (5) and a variable pitch motor (6); the actuating mechanism (2) is respectively connected with the two propeller parts (1);

a worm gear structure and a lead screw nut structure are arranged in the transmission mechanism (5), and the lead screw is connected with the worm gear in a matching way and the axes of the lead screw and the worm gear are overlapped; one end of the screw rod is connected with the actuating mechanism (2);

the output end of the variable pitch motor (6) is connected with the worm;

the actuating mechanism (2) comprises a shifting fork (2-2), a connecting piece (1-5), a guide post (2-5) and a force release sleeve (2-8); the middle part of the shifting fork (2-2) is fixedly connected with the screw rod, two ends of the shifting fork are respectively hinged with a connecting piece, and the connecting piece is fixedly connected with the paddle; the force-releasing sleeve (2-8) is coaxially sleeved on the screw rod and does not interfere with the screw rod, and the force-releasing sleeve (2-8) is finally and indirectly fixedly connected with the support frame (4) and is in a relatively static state; the other end of the force release sleeve (2-8) is connected with a transmission mechanism (5); the pneumatic load borne by the propeller is transmitted to the support frame (4) through the force release sleeve (2-8);

the transmission mechanism (5) converts the rotary motion of the variable pitch motor (6) into the linear motion of a lead screw through the characteristics of a worm gear and a worm, when the variable pitch motor rotates clockwise, the clockwise rotary motion is converted into the upward linear motion through the worm gear and the ball lead screw, the shifting fork moves upwards, and the connecting piece drives the paddle to rotate clockwise; when the variable pitch motor rotates anticlockwise, anticlockwise rotation is changed into downward linear motion through the worm gear and the ball screw, the shifting fork moves downwards, and the connecting piece drives the paddle to rotate anticlockwise.

2. The propeller active pitch-changing mechanism of claim 1, wherein the middle body of the shifting fork (2-2) is a cylindrical body, a through hole is axially formed, a step is arranged inside the through hole for mounting a bearing and a lead screw, and the lead screw is fixedly hinged with the shifting fork (2-2) and can bear larger axial load; the outer wall extends outwards along the axis to form two bulges, wherein the outwards extending directions of the two bulges are opposite, and the two bulges are not on the same plane; the protruding end is provided with a through hole as a mounting hole.

3. The propeller active pitch-changing mechanism of claim 1 or 2, wherein the connecting piece is a drop-shaped plate, the small-diameter end is provided with a through hole, and the large-diameter end is provided with a special-shaped hole; after the rollers are assembled in the through holes of the small diameter ends, the rollers are hinged with the raised mounting holes of the shifting forks (2-2) through pin shafts; the special-shaped hole at the large-diameter end is fixedly connected with the paddle root.

4. A propeller active pitch mechanism according to claim 1 or 2, wherein said actuator (2) further comprises a hub upper cover (2-1), a guide post (2-5), a hub lower cover (2-7); wherein the upper propeller hub cover (2-1) and the lower propeller hub cover (2-7) are mutually connected to form an actuating mechanism outer shell with a cavity inside, one end of the guide post (2-5) is fixedly connected with the lower propeller hub cover (2-7), and the other end of the guide post is nested and matched with a cylindrical body in the middle of the shifting fork (2-2); the upper end of the force release sleeve (2-8) is provided with a stepped shaft which is fixedly connected with a guide post (2-5) through a bearing so as to form indirect fixed connection with the lower cover of the hub, and the lower end of the force release sleeve (2-8) is provided with a key groove (2.1) which is fixedly connected with two shells (5-6,5-7) of the transmission mechanism through two specially processed non-standard keys (5-11); the inside hollow structure that is of power release sleeve, the lead screw can have noninterference linear motion about power release sleeve is inside.

5. A propeller active pitch mechanism according to claim 1, wherein the transmission mechanism (5) comprises a lead screw (5-1), a first transmission mechanism bearing (5-2), a worm gear (5-4), a second transmission mechanism bearing (5-5), a first transmission mechanism housing (5-6), a second transmission mechanism housing (5-7), a lead screw nut (5-8), a worm (5-9), a shaft (5-10) and a sleeve (5-12); the worm wheel (5-4) and the worm (5-9) are vertically arranged, a round hole with the same diameter as the smaller diameter in the stepped shaft of the screw nut (5-8) and a threaded hole are processed in the middle of the worm wheel to install the screw nut (5-8), and the worm wheel and the screw nut (5-8) are fixedly connected and ensure that the axes of the worm wheel and the screw nut coincide; the screw is divided into an optical axis part and a thread part, the thread part is matched with a screw nut (5-8), low-friction motion is realized by means of internal balls, the optical axis part of the screw is set as a stepped shaft, and the large-shaft-diameter part is provided with two sliding key grooves which are symmetrically arranged; the two shells (5-6, 5-7) of the transmission mechanism are of a symmetrical structure and are connected through bolts, and the nonstandard keys (5-11) are in interference fit with the key slot holes in the two shells (5-6, 5-7) of the transmission mechanism and then form clearance fit with the sliding key slot in the lead screw, so that the degree of freedom of the lead screw in rotation along the axis of the lead screw is limited, and the lead screw can only realize linear motion with single degree of freedom.

6. A propeller active pitch mechanism according to claim 1, further comprising a support frame (4) and a flange plate (3-1); the supporting frame (4) is provided with a mounting through hole and a threaded hole; the stator of the main push motor (3) is fixedly connected with the support frame (4); the flange plate (3-1) is positioned below the lower cover (2-7) of the propeller hub, one surface of the flange plate is fixedly connected with an inner rotor of the main pushing motor, and the other surface of the flange plate is fixedly connected with the lower cover (2-7) of the propeller hub.

7. The active pitch-changing mechanism of propeller as claimed in claim 1, further comprising a semicircular ring assembly, wherein said semicircular ring assembly is composed of a plurality of semicircular rings made of high-strength wear-resistant material, and the semicircular rings are respectively embedded into corresponding ring grooves formed on the upper and lower covers of the propeller hub of the actuator, so that the smooth surface can convert large positive pressure into small friction force, and the propeller can be positioned and the high rotation speed of the propeller can be transmitted to generate centrifugal force to be offset.