Open type fan engine and variable pitch mechanism thereof

Abstract

The invention provides an open type fan engine and a variable pitch mechanism thereof, and relates to the technical field of open type fan engines. The open type fan engine variable pitch mechanism comprises an actuating cylinder, a shifting fork, a first-stage lead screw mechanism and a second-stage lead screw mechanism, the first-stage lead screw mechanism is connected with a piston rod of the actuating cylinder, and the first-stage lead screw mechanism is used for being driven by the piston rod to rotate; the second-stage lead screw mechanism is in transmission connection with the first-stage lead screw mechanism, and the second-stage lead screw mechanism is used for driving the shifting fork to move under the condition that the first-stage lead screw mechanism rotates, so that the fan blades are driven to rotate through the shifting fork, and propeller pitch adjustment is achieved. The first-stage lead screw mechanism is provided with first matching teeth, the second-stage lead screw mechanism is provided with second matching teeth, and the screw pitch of the first matching teeth is larger than that of the second matching teeth, so that the output load of the actuator cylinder is amplified according to the design multiple. Therefore, enough torque can be provided under the condition that the actuator cylinder provides small load so as to meet the requirement for adjusting the propeller pitch of the fan blade.

Description

Technical Field

[0001] This invention relates to the field of open fan engine technology, and more specifically, to an open fan engine and its variable pitch mechanism. Background Technology

[0002] Open-type fan engines adjust the pitch of the fan blades through a pitch control mechanism, allowing the fan blades to operate at the appropriate angle of attack of the incoming flow under different operating conditions, thereby improving efficiency. During operation, the fan blades are subjected to centrifugal torque, aerodynamic torque, and frictional torque, requiring the pitch control mechanism to have sufficient power to overcome these external loads and drive the fan blades to change pitch.

[0003] Current open-fan engine pitch control mechanisms primarily reference turboprop engine design experience, typically employing a hydraulically actuated actuator. The pitch control mechanism rotates around the engine axis along with the fan blades, supplied with oil via a rotary joint, and the adjustment mechanism utilizes a fork and eccentric pin. However, due to the greater number, thinner blade profile, sharper leading edge, and larger sweep angle of open-fan engine fan blades compared to propeller blades, the total torque experienced by the fan blades during operation is greater than that of the propeller blades. When directly applying propeller pitch control mechanisms, the increased number of fan blades and the increased load on each blade necessitate a larger hydraulic pressure to balance the load within a limited space. This increased hydraulic pressure presents challenges for both the actuator design and the rotary joint oil supply design. Summary of the Invention

[0004] The following provides a brief overview of one or more aspects to offer a basic understanding of them. This overview is not an exhaustive summary of all conceived aspects, nor is it intended to identify key or decisive elements of all aspects, nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form to prepare for the more detailed descriptions that follow.

[0005] The purpose of this invention is to provide a variable pitch mechanism for an open-type fan engine, which can meet the pitch adjustment requirements of the open-type fan blades while the actuator provides a relatively small load.

[0006] Another objective of this invention is to provide an open-type fan engine that can meet the requirements for open-type fan blade pitch adjustment while the actuator provides a relatively small load.

[0007] Embodiments of the present invention can be implemented in the following ways:

[0008] An open-type fan engine pitch control mechanism includes an actuator and a shift fork. The actuator drives the shift fork to move, and the shift fork drives the fan blades to rotate, thereby adjusting the pitch. The open-type fan engine pitch control mechanism also includes:

[0009] A first-stage lead screw mechanism and a second-stage lead screw mechanism are connected to the piston rod of the actuating cylinder, and the first-stage lead screw mechanism is used to rotate under the drive of the piston rod; the second-stage lead screw mechanism is driven to the first-stage lead screw mechanism, and the second-stage lead screw mechanism is used to drive the shift fork to move when the first-stage lead screw mechanism rotates.

[0010] The first-stage lead screw mechanism has a first mating tooth, and the second-stage lead screw mechanism has a second mating tooth, wherein the pitch of the first mating tooth is greater than the pitch of the second mating tooth.

[0011] Optionally, the open fan engine pitch mechanism further includes a load amplification shaft, which is sleeved on the piston rod; the first mating tooth includes a first internal thread provided on the load amplification shaft and a first external thread provided on the piston rod, wherein the first internal thread and the first external thread mate.

[0012] Optionally, the actuator further includes an actuator housing and an actuator end cap. The actuator end cap is fixed to the end of the actuator housing to define a movable cavity. The piston rod passes through the actuator end cap, with one end of the piston rod located inside the movable cavity and the other end of the piston rod located outside the movable cavity and provided with the first external thread.

[0013] A guide shaft extending axially along the actuator housing is also fixedly connected to the actuator housing. The guide shaft is located inside the movable cavity and cooperates with the piston rod through a first key structure to restrict the piston rod from rotating relative to the guide shaft.

[0014] Optionally, the first-stage screw mechanism is a ball screw, and the first-stage screw mechanism further includes balls disposed between the first internal thread and the first external thread.

[0015] Optionally, the open fan engine pitch mechanism further includes a load amplification shaft, and the shift fork is sleeved on the load amplification shaft; the second mating tooth includes a second external thread disposed on the load amplification shaft and a second internal thread disposed on the shift fork, wherein the second external thread and the second internal thread mate.

[0016] Optionally, the second-stage screw mechanism is a ball screw, and the second-stage screw mechanism further includes balls disposed between the second internal thread and the second external thread.

[0017] Optionally, the open fan engine pitch control mechanism further includes a bearing housing and a first bearing, the load amplification shaft being rotatably supported on the bearing housing via the first bearing; the shift fork has a mating tube portion, the mating tube portion being sleeved outside the bearing housing, and the bearing housing engaging with the shift fork via a second key structure to restrict the shift fork from rotating relative to the bearing housing.

[0018] Optionally, the open fan engine pitch mechanism further includes a displacement adjusting nut screwed onto the load amplification shaft. The displacement adjusting nut is used to stop the shift fork, so as to adjust the translation range of the shift fork relative to the load amplification shaft when the screwing depth of the displacement adjusting nut changes.

[0019] Optionally, both the first-stage lead screw mechanism and the second-stage lead screw mechanism are arranged along the axis of the actuating cylinder.

[0020] Optionally, the open fan engine pitch control mechanism further includes multiple rocker arms distributed circumferentially along the shift fork; the shift fork has a groove extending circumferentially, one end of the rocker arm is fixedly connected to the fan blade, and the other end of the rocker arm is equipped with a second bearing, which is rolled within the groove; the shift fork is used to drive the rocker arm to rotate via the second bearing when translating along the engine axis.

[0021] An open-type fan engine includes fan blades, a hub, and the aforementioned open-type fan engine pitch control mechanism. The fork of the open-type fan engine pitch control mechanism is used to drive the fan blades to rotate. The fan blades are mounted on the hub via support bearings.

[0022] The beneficial effects of the open-type fan engine and its variable pitch mechanism provided by the embodiments of the present invention include:

[0023] An embodiment of the present invention provides a variable pitch mechanism for an open-type fan engine, comprising an actuator, a shift fork, a first-stage screw mechanism, and a second-stage screw mechanism. The first-stage screw mechanism is connected to the piston rod of the actuator and is used to rotate under the drive of the piston rod. The second-stage screw mechanism is driven by the first-stage screw mechanism and is used to drive the shift fork to move when the first-stage screw mechanism rotates, thereby driving the fan blades to rotate and achieving pitch adjustment. The first-stage screw mechanism has a first mating tooth, and the second-stage screw mechanism has a second mating tooth. The pitch of the first mating tooth is greater than the pitch of the second mating tooth, thus amplifying the output load of the actuator by a design multiple, thereby helping to provide sufficient torque to meet the pitch adjustment requirements of the fan blades when the actuator provides a relatively small load.

[0024] Embodiments of the present invention also provide an open-type fan engine, which includes the aforementioned open-type fan engine pitch adjustment mechanism. Since this open-type fan engine includes the aforementioned open-type fan engine pitch adjustment mechanism, it also has the beneficial effect of providing sufficient torque to meet the pitch adjustment requirements of the fan blades while the actuator provides a relatively small load. Attached Figure Description

[0025] The above-described features and advantages of the present invention will be better understood after reading the following detailed description of embodiments of the present disclosure in conjunction with the accompanying drawings. In the drawings, components are not necessarily drawn to scale, and components having similar related characteristics or features may have the same or similar reference numerals.

[0026] Figure 1 A partial structural schematic diagram of an open-fan engine according to one aspect of the present invention is shown;

[0027] Figure 2 A schematic diagram of the structure of an open fan engine pitch control mechanism according to one aspect of the present invention is shown.

[0028] Figure 3 A schematic diagram of the connection structure between the rocker arm and the shift fork in a pitch control mechanism provided according to one aspect of the present invention is shown.

[0029] Figure label:

[0030] 10-Open fan engine; 100-Pitch control mechanism; 110-Actuator cylinder; 111-Actuator cylinder housing; 112-Actuator cylinder end cap; 113-Moving chamber; 114-Guide shaft; 115-Piston rod; 116-Piston head; 120-First stage screw mechanism; 121-First internal thread; 122-First external thread; 123-First ball bearing; 130-Second stage screw mechanism; 131-Second internal thread; 1 32-Second external thread; 133-Second ball; 141-Load amplifying shaft; 142-Bearing housing; 143-First seat; 144-Second seat; 145-First bearing; 146-Locking nut; 147-Displacement adjusting nut; 150-Shift fork; 151-Inner ring; 152-Connecting part; 153-Outer ring; 154-Matching tube; 155-Channel; 160-Rock arm; 161-Second bearing;

[0031] 21-First axis; 22-Second axis; 23-Hub; 24-Support bearing; 25-Fan blade; 26-Hollow shaft; 27-Intake cone. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should be noted that the aspects described below with reference to the accompanying drawings and specific embodiments are merely exemplary and should not be construed as limiting the scope of protection of the present invention in any way.

[0033] In the description of this invention, it should be noted that if terms such as "upper," "lower," "inner," "outer," or "vertical" appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed when in use, and does not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0034] At the same time, it should be noted that the terms "first" and "second" are used only for distinguishing descriptions and should not be interpreted as indicating or implying relative importance.

[0035] In the description of this invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an integral connection, or a detachable connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or a connection within two components, etc. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0036] The following is an explanation of the relevant terms that may appear in the description of this invention:

[0037] Hub ratio: The ratio of the hub diameter to the outer diameter of the fan blades in an open-fan engine.

[0038] Figure 1 This diagram shows a partial structural schematic of the open-fan engine 10 provided in this embodiment. Figure 2 A schematic diagram of the pitch control mechanism 100 for an open-fan engine provided in this embodiment is shown. Please refer to the attached diagram. Figure 1 and Figure 2 This embodiment provides an open fan engine pitch mechanism 100, hereinafter referred to as pitch mechanism 100, and also provides an open fan engine 10.

[0039] Please refer to Figure 1 The open-fan engine 10 includes a pitch control mechanism 100, a hub 23, and multiple fan blades 25. The fan blades 25 are mounted on the hub 23 via support bearings 24. The hub 23 is connected to a hollow shaft 26 via a ring of flange bolts. This hollow shaft 26 can be a gearbox output shaft or a low-power turbine shaft. A fork 150 of the pitch control mechanism 100 drives the fan blades 25 to rotate about the axis of the support bearings 24, which is the first axis 21. Further, the open-fan engine 10 also includes an intake cone 27, which is bolted to the hub 23. Specifically, the hub 23, intake cone 27, and hollow shaft 26 are coaxially arranged, with this axis being the second axis 22.

[0040] The pitch adjustment mechanism 100 includes an actuator 110, a shift fork 150, a first-stage lead screw mechanism 120, and a second-stage lead screw mechanism 130. The first-stage lead screw mechanism 120 is connected to the piston rod 115 of the actuator 110 and is used to rotate under the drive of the piston rod 115. The second-stage lead screw mechanism 130 is driven by the first-stage lead screw mechanism 120 and is used to drive the shift fork 150 to move when the first-stage lead screw mechanism 120 rotates, thereby driving the fan blades 25 to rotate through the shift fork 150 to achieve pitch adjustment. The first-stage lead screw mechanism 120 has a first mating tooth, and the second-stage lead screw mechanism 130 has a second mating tooth. The pitch of the first mating tooth is greater than the pitch of the second mating tooth. Optionally, in this embodiment, the actuator 110 is mounted on a hollow shaft 26 and rotates with the hollow shaft 26. Specifically, the actuator 110 is installed in the inner hole of the hollow shaft 26 and is coaxially arranged with the hollow shaft 26.

[0041] When it is necessary to adjust the pitch of the fan blades 25, the actuator 110 is activated and drives the shift fork 150 to move through the first-stage lead screw mechanism 120 and the second-stage lead screw mechanism 130. Since the pitch of the first mating tooth of the first-stage lead screw mechanism 120 is greater than the pitch of the second mating tooth of the second-stage lead screw mechanism 130, the output load of the actuator 110 is amplified by the design multiple. This ensures that the aerodynamic torque and centrifugal torque on each fan blade 25 along the axial direction of the support bearing 24 can be overcome when the actuator 110 provides a small load, thereby driving the fan blades 25 to rotate around the first axis 21 and realizing the pitch adjustment.

[0042] It should be noted that in this embodiment, the pitch mechanism 100 is provided with a first-stage lead screw mechanism 120 and a second-stage lead screw mechanism 130, which together constitute two stages of lead screw mechanism. It is understood that in some other embodiments, more than two stages of lead screw mechanism may also be provided.

[0043] The pitch control mechanism 100 provided in this embodiment will be further described below:

[0044] Figure 3 This is a schematic diagram of the connection structure between the rocker arm 160 and the shift fork 150 in the pitch control mechanism 100 provided in this embodiment. Please refer to the attached diagram. Figure 1 and Figure 3 In this embodiment, the pitch-changing mechanism 100 further includes multiple rocker arms 160. The multiple rocker arms 160 are distributed circumferentially along the shift fork 150, and the multiple rocker arms 160 are connected one-to-one with the multiple fan blades 25. The shift fork 150 drives the multiple rocker arms 160 to rotate synchronously, thereby driving the multiple fan blades 25 to rotate synchronously, so as to realize the synchronous adjustment of the pitch of the multiple fan blades 25.

[0045] Specifically, the shift fork 150 includes an inner ring portion 151, an outer ring portion 153, and a connecting portion 152 extending radially along the shift fork 150. Both ends of the connecting portion 152 are fixedly connected to the inner ring portion 151 and the outer ring portion 153, respectively. The outer ring portion 153 is provided with a groove 155 extending circumferentially along the shift fork 150 itself. One end of the rocker arm 160 is fixedly connected to the fan blade 25, and the other end of the rocker arm 160 is equipped with a second bearing 161, which is rolled within the groove 155. Please refer to... Figure 3 , Figure 3 The arrows in the diagram indicate the translational direction of the shift fork 150 and the rotational direction of the rocker arm 160. When the shift fork 150 translates along the axis of the engine (i.e., the second axis 22), the second bearing 161 rolls in the channel 155, which, together with the support bearing 24, limits the movement of the fan blade 25, causing the rocker arm 160 and the fan blade 25 to rotate around the axis of the support bearing 24, thereby achieving pitch adjustment.

[0046] Please refer to the reference again. Figure 1 and Figure 2 In this embodiment, both the first-stage lead screw mechanism 120 and the second-stage lead screw mechanism 130 are arranged along the axis of the actuating cylinder 110, which is arranged along the second axis 22. That is, the direction of extension and retraction of the piston rod 115 is the direction of the second axis 22. By setting both the first-stage lead screw mechanism 120 and the second-stage lead screw mechanism 130 to be arranged along the axis of the actuating cylinder 110, the first-stage lead screw mechanism 120 and the second-stage lead screw mechanism 130 mainly occupy axial space and occupy less radial space, which helps to reduce the hub ratio and thus reduce the mass of the open-circuit fan engine 10.

[0047] In this embodiment, the pitch control mechanism 100 further includes a load amplification shaft 141, which is sleeved on the piston rod 115. The first mating tooth includes a first internal thread 121 provided on the load amplification shaft 141 and a first external thread 122 provided on the piston rod 115. The first internal thread 121 and the first external thread 122 engage to form a screw mechanism, which can drive the load amplification shaft 141 to rotate when the piston rod 115 moves axially.

[0048] Specifically, the load amplification shaft 141 is a tubular shaft with an inner circumferential surface defining an inner hole. The first internal thread 121 is a threaded structure provided on this inner circumferential surface. The actuator cylinder 110 also includes an actuator cylinder housing 111 and an actuator cylinder end cap 112. The actuator cylinder housing 111 is a cylindrical structure with one end closed and the other end open. The actuator cylinder end cap 112 is fixedly connected to the open end of the actuator cylinder housing 111, thereby defining the movable cavity 113 through the actuator cylinder housing 111 and the actuator cylinder end cap 112. The piston rod 115 is disposed through the actuator cylinder end cap 112, such that one end of the piston rod 115 is located inside the movable cavity 113, and the other end is located outside the movable cavity 113. The piston head 116 is provided at the end of the piston rod 115 located inside the movable cavity 113. The movable cavity is divided into two independent chambers by the piston cylinder, thereby driving the piston rod 115 to move axially and extend and retract under the action of the hydraulic difference between the two independent chambers. In other words, in the pitch-changing mechanism 100 provided in this embodiment, the hydraulic cylinder of the actuator 110 can also be understood to be another power cylinder structure as the actuator 110 in some other embodiments. The piston rod 115 is provided with a first external thread 122 at one end located outside the movable cavity 113.

[0049] Furthermore, a guide shaft 114 extending axially along the actuator housing 111 is fixedly connected to the actuator housing 111. The guide shaft 114 is located in the movable cavity 113 and cooperates with the piston rod 115 through a first key structure to restrict the piston rod 115 from rotating relative to the guide shaft 114.

[0050] Specifically, the piston rod 115 is provided with a mounting hole, into which the guide shaft 114 is inserted. The first key structure includes an external spline or a flat key provided on the guide shaft 114. Correspondingly, the first key structure also includes an internal spline or a flat keyway provided on the piston rod 115. The cooperation of the two restricts the rotational movement of the piston rod 115, so that the piston rod 115 can only translate along the axis of the actuator cylinder 110.

[0051] Furthermore, the first-stage screw mechanism 120 is a ball screw, and the first-stage screw mechanism 120 also includes a ball disposed between the first internal thread 121 and the first external thread 122, which is a first ball 123. Correspondingly, the first internal thread 121 and the first external thread 122 are arc-shaped helical grooves. Furthermore, a return ball tube (not shown in the figure) is also provided on the piston rod 115 or the load amplification shaft 141, through which the first ball 123 is guided from one end to the other end to form a closed loop.

[0052] It should be noted that the specific structure of the first-stage lead screw mechanism 120 is not limited here. It is understood that in some other embodiments, the first internal thread 121 and the first external thread 122 can also be configured as a direct meshing structure.

[0053] In this embodiment, the shift fork 150 is sleeved on the load amplification shaft 141, and the second mating tooth includes a second external thread 132 disposed on the load amplification shaft 141 and a second internal thread 131 disposed on the shift fork 150, wherein the second external thread 132 and the second internal thread 131 are mated.

[0054] Specifically, the second external thread 132 is disposed on the outer circumferential surface of the load amplifying shaft 141, and the inner ring portion 151 of the shift fork 150 is sleeved on the load amplifying shaft 141, with the shift fork 150 and the load amplifying shaft 141 coaxially arranged. The second internal thread 131 is disposed on the inner circumferential surface of the inner ring portion 151. The load is transmitted between the load amplifying shaft 141 and the shift fork 150 through the cooperation of the second internal thread 131 and the second external thread 132. When the load amplifying shaft 141 rotates under the action of the piston rod 115, it drives the shift fork 150 to translate along the second axis 22. Moreover, since the pitch of the first mating tooth is greater than the pitch of the second mating tooth, the load obtained by the shift fork 150 is increased by a multiple relative to the load generated by the actuator cylinder 110. This helps to generate a load sufficient to drive the pitch adjustment of multiple fan blades 25 when the oil pressure of the actuator cylinder 110 is relatively low, reducing the requirements on the oil supply system and the actuator cylinder 110 itself.

[0055] Furthermore, since the load amplification shaft 141 serves as a component of both the first-stage lead screw mechanism 120 and the second-stage lead screw mechanism 130, it helps to reduce the mass of the pitch mechanism 100.

[0056] It should be noted that the positional relationship and structure of the first-stage lead screw mechanism 120 and the second-stage lead screw mechanism 130 are not limited here. It is understood that in some other embodiments, the first-stage lead screw mechanism 120 and the second-stage lead screw mechanism 130 can be set as two independent parts and connected by an intermediate transmission structure. Alternatively, the second external thread 132 and the first internal thread 121 can be set at different axial positions of the load amplification shaft 141.

[0057] Furthermore, the pitch control mechanism 100 also includes a bearing housing 142 and a first bearing 145, with the load amplification shaft 141 rotatably supported on the bearing housing 142 via the first bearing 145. The shift fork 150 has a mating tube 154, which is sleeved on the bearing housing 142, and the bearing housing 142 engages with the shift fork 150 via a second key structure to restrict the rotation of the shift fork 150 relative to the bearing housing 142.

[0058] Specifically, the bearing housing 142 includes a first seat portion 143 and a second seat portion 144 connected to each other, wherein the outer diameter of the first seat portion 143 is smaller than the outer diameter of the second seat portion 144. In this embodiment, the second seat portion 144 is fixedly connected to the actuator cylinder end cover 112 by bolts or other fastening structures. It is understood that in some other embodiments, the second seat portion 144 may also be directly fixedly connected to the hollow shaft 26 by bolts or other fastening structures. The first seat portion 143 has a front cavity of the bearing housing 142, and a first bearing 145 is installed in the front cavity of the bearing housing 142 and is located between the first seat portion 143 and the load amplifying shaft 141, thereby rotatably supporting the load amplifying shaft 141 on the bearing housing 142.

[0059] The shift fork 150 has a mating tube 154 located at the connecting portion 152. The mating tube 154 is a tubular component extending axially toward the bearing housing 142 and is sleeved on the outside of the first seat portion 143 of the bearing housing 142. The second key structure includes an external spline located outside the first seat portion 143 and an internal spline located at the mating tube 154. Through the engagement of the internal spline and the external spline, the rotation of the shift fork 150 relative to the bearing housing 142 is limited, so that the shift fork 150 can only translate relative to the bearing housing 142 along the second axis 22. Thus, when the load amplification shaft 141 rotates, the shift fork 150 can be driven to move smoothly along the second axis 22, thereby driving the fan blades 25 to rotate and achieve pitch adjustment.

[0060] Furthermore, the pitch mechanism 100 also includes a locking nut 146, which is screwed onto the outside of the load amplification shaft 141 and used to lock the first bearing 145, thereby fixing the inner ring of the first bearing 145 to the load amplification shaft 141.

[0061] In this embodiment, the second-stage lead screw mechanism 130 is a ball screw, and the second-stage lead screw mechanism 130 also includes a ball disposed between the second internal thread 131 and the second external thread 132, which is a second ball 133. Correspondingly, the second internal thread 131 and the second external thread 132 are arc-shaped helical grooves. Further, a ball return tube (not shown) is provided on the inner ring portion 151 of the shift fork 150 or the load amplification shaft 141, through which the second ball 133 is guided from one end to the other end to form a closed loop.

[0062] It should be noted that the specific structure of the second-stage lead screw mechanism 130 is not limited here. It is understood that in some other embodiments, the second internal thread 131 and the second external thread 132 can also be configured as a direct meshing structure.

[0063] In this embodiment, the pitch adjustment mechanism 100 also includes a displacement adjusting nut 147 screwed onto the load amplification shaft 141. The displacement adjusting nut 147 uses a stop fork 150 to limit the movement limit position of the fork 150 relative to the load amplification shaft 141. Moreover, since the displacement adjusting nut 147 is screwed onto the load amplification shaft 141, the screwing depth of the displacement adjusting nut 147 can be changed by rotating the displacement adjusting nut 147, thereby changing the movement limit position of the fork 150 relative to the load amplification shaft. That is, the translation range of the fork 150 relative to the load amplification shaft 141 is adjusted, so that the pitch adjustment range of the fan blades 25 can be adjusted according to requirements.

[0064] The open-type fan engine 10 and its variable pitch mechanism 100 provided in the embodiments of the present invention, by setting a two-stage lead screw mechanism, the first-stage lead screw mechanism 120 converts the axial motion of the actuator cylinder 110 into rotational motion, and the second-stage lead screw mechanism 130 converts the rotational motion of the first-stage lead screw mechanism 120 into linear motion. At the same time, the pitch of the first mating tooth of the first-stage lead screw mechanism 120 is greater than the pitch of the second mating tooth of the second-stage lead screw mechanism 130, so that the power output by the actuator cylinder 110 can be increased by the designed multiple during the transmission process of the first-stage lead screw mechanism 120 and the second-stage lead screw mechanism 130. Moreover, the first-stage lead screw mechanism 120 and the second-stage lead screw mechanism 130 are arranged along the axis of the actuator cylinder 110, and the nut of the first-stage lead screw mechanism 120 serves as the lead screw of the second-stage lead screw mechanism 130 (i.e., sharing the load amplification shaft 141). This makes full use of the axial space of the open-type fan engine 10, occupies a small volume, and helps to reduce the hub ratio, thereby reducing the mass of the open-type fan engine 10. Meanwhile, a displacement adjusting nut 147 is provided to make the pitch adjustment range controllable.

[0065] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An open fan engine variable pitch mechanism comprising an actuating cylinder for actuating a fork for rotating a fan blade to achieve pitch adjustment; characterized in that, The open fan engine variable pitch mechanism further comprises: a first-stage screw mechanism connected with the piston rod of the actuator cylinder and used to rotate under the driving of the piston rod; and a second-stage screw mechanism in transmission connection with the first-stage screw mechanism and used to drive the shift fork to move under the rotation of the first-stage screw mechanism. The first-stage screw mechanism has first matching teeth, and the second-stage screw mechanism has second matching teeth, the pitch of the first matching teeth being greater than the pitch of the second matching teeth.

2. The open fan engine variable pitch mechanism according to claim 1, wherein The open fan engine variable pitch mechanism further comprises a load amplification shaft sleeved on the piston rod, the first matching teeth comprise a first internal thread arranged on the load amplification shaft and a first external thread arranged on the piston rod, and the first internal thread and the first external thread are in matching.

3. The open fan engine variable pitch mechanism according to claim 2, wherein The actuator cylinder further comprises an actuator cylinder shell and an actuator cylinder end cover fixed at the end of the actuator cylinder shell to define a movable cavity through the actuator cylinder shell and the actuator cylinder end cover, the piston rod is arranged through the actuator cylinder end cover, one end of the piston rod is located in the movable cavity, and the other end of the piston rod is located outside the movable cavity and is provided with the first external thread; a guide shaft extending along the axial direction of the actuator cylinder shell is further fixedly connected to the actuator cylinder shell, the guide shaft is located in the movable cavity, and the guide shaft is matched with the piston rod through a first key structure to limit the rotation of the piston rod relative to the guide shaft.

4. The open fan engine variable pitch mechanism according to claim 2, wherein The first-stage screw mechanism is a ball screw, and the first-stage screw mechanism further comprises balls arranged between the first internal thread and the first external thread.

5. The open fan engine variable pitch mechanism according to claim 1, wherein The open fan engine variable pitch mechanism further comprises a load amplification shaft, the shift fork is sleeved on the load amplification shaft, the second matching teeth comprise a second external thread arranged on the load amplification shaft and a second internal thread arranged on the shift fork, and the second external thread and the second internal thread are in matching.

6. The open fan engine variable pitch mechanism according to claim 5, wherein The second-stage screw mechanism is a ball screw, and the second-stage screw mechanism further comprises balls arranged between the second internal thread and the second external thread.

7. The open fan engine variable pitch mechanism according to claim 5, wherein The open fan engine variable pitch mechanism further comprises a bearing seat and a first bearing, the load amplification shaft is rotatably supported on the bearing seat through the first bearing; the shift fork has a matching tube portion, the matching tube portion is sleeved outside the bearing seat, and the bearing seat is matched with the shift fork through a second key structure to limit rotation of the shift fork relative to the bearing seat.

8. The open fan engine variable pitch mechanism according to claim 5, characterized in that, The open fan engine variable pitch mechanism further comprises a displacement adjusting nut screwed on the load amplification shaft, the displacement adjusting nut is used to stop the shift fork, so as to adjust a translation range of the shift fork relative to the load amplification shaft when a screwing depth of the displacement adjusting nut is changed.

9. The open fan engine variable pitch mechanism according to claim 1, characterized in that, The first-stage screw rod mechanism and the second-stage screw rod mechanism are arranged along an axis of the actuating cylinder.

10. The open fan engine variable pitch mechanism according to claim 1, characterized in that, The open fan engine variable pitch mechanism further comprises a plurality of rocker arms, the plurality of rocker arms are distributed along a circumference of the shift fork; the shift fork has a groove extending along a circumference of the shift fork, one end of the rocker arm is used to be fixedly connected with a fan blade, and the other end of the rocker arm is provided with a second bearing, the second bearing is rotatably installed in the groove; the shift fork is used to drive the rocker arm to rotate through the second bearing when the shift fork is translated along an axis of an engine.

11. An open fan engine, characterized in that, The open fan engine comprises a fan blade, a hub, and the open fan engine variable pitch mechanism according to any one of claims 1-10, the shift fork of the open fan engine variable pitch mechanism is used to drive the fan blade to rotate; and the fan blade is installed on the hub through a support bearing.

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