JP7468019B2 - Thrust generating device - Google Patents

Description

The present invention relates to a thrust generating device.

A technology for electrically changing the pitch of a propeller (rotor blades) without using hydraulics is disclosed, for example, in Patent Document 1. In this technology, the main rotating shaft is formed to be hollow, and an operating rod is arranged concentrically within this main rotating shaft so that it can move only in the axial direction, and an arm fixed to the lower end of the operating rod is connected to each support shaft of the blades via a link and lever mechanism. Then, by moving the operating rod back and forth in the axial direction, the mounting angle of each blade is changed via the link and lever mechanism.

Japanese Patent Application Laid-Open No. 5-87037

The thrust required for thrust generating devices mounted on flyable flying objects such as multicopters, airplanes, rotorcraft, and flyable automobiles varies depending on the weight of the flying object. When changing the thrust, it is possible to change the entire propeller. However, manufacturing many different types of propellers with different complex internal mechanisms increases manufacturing costs.

The present invention aims to provide a thrust generating device that allows propeller components to be changed according to the required thrust while minimizing increases in manufacturing costs.

A thrust generating device according to an aspect of the present invention includes a thrust generating motor that generates thrust by rotating a plurality of rotors, a pitch angle changing motor that changes the pitch angle of the rotors, a rotation transmission unit connected to the pitch angle changing motor, a linear shaft, a first motion conversion unit that is connected to the rotation transmission unit and the linear shaft and has a first motion conversion mechanism that converts the rotation of the rotation transmission unit into linear motion of the linear shaft, and a second motion conversion unit that converts the linear motion of the linear shaft into rotational motion to change the pitch angle of the rotors. The second motion conversion unit includes a hub that is rotated by the thrust generating motor, a plurality of grips that are attached to the hub and support the rotors, a second motion conversion mechanism that converts the linear motion of the linear shaft into rotational motion of the grips, and a plurality of radial bearings that rotatably support inner ends of the grips. The hub has a case that houses the inner ends of the grips, the second motion conversion mechanism, and the radial bearings. The grips can be modified while the second motion conversion mechanism and radial bearings remain on the hub.
In this embodiment, each grip is changeable. Therefore, a grip suitable for the thrust can be attached to the hub according to the weight of the flying object to which the thrust generating device is attached and the thrust required for the thrust generating device. While each grip is changeable, each radial bearing and the complicated second motion conversion mechanism can be used without modification, so that an increase in manufacturing costs can be minimized.

Preferably, each grip is changeable depending on the type of rotor.
Therefore, once an appropriate rotor is selected depending on the weight of the flying object to which the thrust generating device is attached and thus the thrust required for the thrust generating device, a grip suitable for that rotor can be attached to the hub.

Preferably, the second motion converter further includes a plurality of cylinders into which the inner ends of the grips are inserted and which are inserted into the radial bearings. Each cylinder can be divided along a plane including the longitudinal axis of the grip. The case is indivisible, and has a plurality of openings into which the inner ends of the grips can be inserted with the outer ends of the grips disposed outside the case.
In this case, the inner end of the grip is inserted through the opening of the case and disposed inside the case. Inside the case, the radial bearing is disposed around the inner end of the grip so as to rotatably support the grip. Specifically, the inner end of the grip is inserted into a tube, and the tube is inserted into the radial bearing. Each tube can be divided with a plane including the longitudinal axis of the grip as a boundary, and can be easily disposed around the inner end of the grip and easily inserted into the radial bearing in a combined state. Therefore, even if the case cannot be divided, it is possible to easily dispose the radial bearing around the inner end of the grip inside the case. Therefore, each grip can be easily changed.

Preferably, the outer circumferential surface of the inner end of the grip has a portion having a smaller diameter radially outward from the hub. The tube has a sleeve and a flange disposed radially outward from the sleeve, and the inner circumferential surface of the sleeve has a smaller diameter radially outward from the hub. When a force toward the radially outward side of the hub is applied to the tube, the tube is supported by the inner surface of the outer end wall of the case.
In this case, when the grip is pulled radially outward from the hub by the centrifugal force acting on the rotor, the outer peripheral surface of the grip's inner end fits against the inner peripheral surface of the sleeve of the cylinder. When a force toward the radially outward direction of the hub is applied to the cylinder, the cylinder is supported by the inner surface of the outer end wall of the case, so that the cylinder functions as a retainer for the grip that is subjected to the centrifugal force. Also, when the centrifugal force increases to a certain extent, the outer peripheral surface of the grip's inner end fits against the inner peripheral surface of the sleeve of the cylinder, so that the longitudinal axis of the grip is adjusted to an ideal direction.

Preferably, the radial bearing is a double row angular contact ball bearing and is arranged radially outward of the hub relative to the second motion conversion mechanism.
In this case, when centrifugal force is applied to the second motion conversion mechanism that rotates the grip through the grip, an axial load is applied to the radial bearing on the radial outside of the second motion conversion mechanism. The radial bearing is a double row angular contact ball bearing, and can withstand a large axial load.

Preferably, when a force directed radially outward from the hub is applied to the cylinder, the cylinder is supported on an inner surface of an outer end wall of the case via a thrust bearing.
In this case, the axial load of the cylinder, to which centrifugal force is applied via the grip, can be firmly supported by the outer end wall of the case.

FIG. 1 is a perspective view showing a thrust generating device according to an embodiment to which rotors are attached. FIG. 2 is a side view showing a thrust generating device according to an embodiment having rotors attached thereto. FIG. 3 is a side view showing a thrust generating device according to an embodiment having rotors attached thereto. FIG. 4 is an exploded perspective view of the thrust generating device according to the embodiment. FIG. 5 is an exploded perspective view of the thrust generating device according to the embodiment as viewed from another direction. FIG. 6 is a plan view of the thrust generating device according to the embodiment. 7 is a cross-sectional view taken along line VII-VII of FIG. FIG. 8 is a plan view of the rotation transmission unit and the rotary-to-linear conversion unit of the thrust generating device according to the embodiment. FIG. 9 is a cross-sectional view taken along line IX-IX of FIG. FIG. 10 is a cross-sectional view taken along line X-X of FIG. FIG. 11 is a perspective view of a rotation transmission unit and a rotary-to-linear conversion unit of the thrust generating device according to the embodiment. FIG. 12 is a perspective view of the linear motion transmission shaft and the ball screw nut of the rotary-linear motion conversion portion. FIG. 13 is a perspective view showing a linear body of the linear motion-rotation converting unit of the thrust generating device according to the embodiment, and the position of the linear body corresponds to the pitch angle of the rotor in FIG. FIG. 14 is a perspective view showing a linear moving body, the position of which corresponds to the pitch angle of the rotor blades in FIG. FIG. 15 is an exploded perspective view of a hub of the thrust generating device according to the embodiment. FIG. 16 is an enlarged cross-sectional view of a portion of the hub. FIG. 17 is a cross-sectional view of the grip and its vicinity of the thrust generating device according to the embodiment. FIG. 18 is an exploded perspective view of the components shown in FIG. FIG. 19 is a cross-sectional view of another type of grip and its vicinity in the thrust generating device according to the embodiment. FIG. 20 is an exploded perspective view of the components shown in FIG.

The following describes in detail the embodiments of the present invention with reference to the accompanying drawings. The following embodiments do not limit the present invention, and not all of the combinations of features described in the embodiments are necessarily essential to the configuration of the present invention. The configuration of the embodiments may be modified or changed as appropriate depending on the specifications of the device to which the present invention is applied and various conditions (conditions of use, environment of use, etc.). The technical scope of the present invention is determined by the claims and is not limited by the individual embodiments below. The drawings are not necessarily drawn to scale, and some features may be exaggerated or omitted.

In the following explanation, we will use an example in which the rotor driven by the thrust generating device has three blades, but the number of blades driven by the thrust generating device is not necessarily limited to three, and may be N (N is a positive integer).

Figure 1 is a perspective view showing a thrust generating device according to an embodiment in which rotors are attached. Figures 2 and 3 are side views showing thrust generating devices according to an embodiment in which rotors are attached, with the rotors having different pitch angles.

As shown in Figures 1 to 3, the thrust generating device 1 rotates a rotor or propeller R having multiple rotors H1 to H3. The propeller R is disposed directly below the thrust generating device 1. The propeller R has grips P1 to P3, which support the rotors H1 to H3 so that they extend radially in the horizontal direction from the thrust generating device 1.

The thrust generating device 1 is attached to the airframe of the flying object via the upper mounting part 1A. The flying object to which the thrust generating device 1 is attached is, for example, a flying object or vehicle such as a motor-driven multicopter, an airplane, a rotorcraft, or an automobile with flying capabilities. Although not shown, multiple thrust generating devices 1 with propellers R attached may be attached to the airframe of the flying object.

The thrust generating device 1 comprises a thrust generating motor 2, a pitch angle changing motor 5A, and a motion transmission unit 6. The thrust generating motor 2 rotates the propeller R to generate thrust to be applied to the flying object. Each of the pitch angle changing motors 5A changes the pitch angles θ1 to θ3 of the rotors H1 to H3. By changing the pitch angles θ1 to θ3 of the rotors H1 to H3, it is possible to change the thrust to be applied to the flying object. The motion transmission unit 6 transmits the rotational motion of the pitch angle changing motor 5A to the rotors H1 to H3.

Figures 4 and 5 are exploded perspective views of the thrust generating device 1. Figure 6 is a plan view of the thrust generating device 1, and Figure 7 is a cross-sectional view taken along line VII-VII in Figure 6. As shown in Figures 4 to 7, the thrust generating motor 2 comprises a stator 2A, a rotor 2B, and a frame 2C. The rotor 2B comprises a rotor shaft 4 and hollow portions 3A and 3C on the radially inner side.

The stator 2A is composed of an electromagnetic steel plate and windings, and is located outside the rotor 2B. The stator 2A is fixed to the annular portion of the frame 2C, which is arranged outside the stator 2A. The mounting portion 1A of the thrust generating device 1 can be provided in the center of the frame 2C. The mounting portion 1A has an opening 1B, into which the motion transmission unit 6 is inserted. The mounting portion 1A is connected to the annular portion via a plurality of spokes 1C extending radially. The frame 2C is formed with an inner cylindrical portion 1D, which rotatably supports the rotor shaft 4 via a bearing U1. The frame 2C, including the annular portion, the mounting portion 1A, the spokes 1C, and the inner cylindrical portion 1D, can be formed, for example, by cutting an alloy such as duralumin.

The rotor 2B of the thrust generating motor 2 is connected to the rotor shaft 4 via multiple spokes 2D extending radially. The rotor 2B rotates together with the rotor shaft 4 about the central axis S0 (see Figures 2 and 3). The rotor 2B and the rotor shaft 4 are rotatably supported by the frame 2C via the bearing U1.

The hollow portion 3A is provided between the rotor 2B and the rotor shaft 4. The pitch angle change motor 5A is disposed in the hollow portion 3A. The pitch angle change motor 5A is fixed to the frame 2C.

The hollow portion 3C is the central hole of the rotor shaft 4 and extends along the axial direction of the rotor shaft 4. A part of the motion transmission unit 6 is inserted into the hollow portion 3C.

A hollow cylindrical extension 9 is fixed to the lower end surface of the rotor shaft 4 of the thrust generating motor 2, and the extension 9 is fixed to the hub 10 of the rotor R. The hub 10 is therefore supported by the frame 2C in a state in which it can rotate around the central axis S0. Grips P1-P3 that support the rotor blades H1-H3 are attached to the hub 10. In this way, the thrust generating motor 2 rotates the propeller R having the rotor blades H1-H3. That is, when the thrust generating motor 2 operates and the rotor 2B rotates, the rotor shaft 4 rotates, and the rotor blades H1-H3 rotate around the central axis S0. As the rotor blades H1-H3 rotate, thrust is generated and applied to the flying object.

The extension 9 is a spacer that maintains a gap between the thrust generating motor 2 and the rotors H1 to H3 in the axial direction of the thrust generating device 1, and prevents the rotors H1 to H3 from colliding with the thrust generating motor 2. The material of the extension 9 is, for example, duralumin.

The pitch angle changing motor 5A, which changes the pitch angle of the rotor blades H1 to H3, is fixed to the frame 2C of the thrust generating motor 2 and is disposed inside the thrust generating motor 2, specifically in the hollow portion 3A. The rotation shaft of the pitch angle changing motor 5A extends vertically, just like the rotor shaft 4 of the thrust generating motor 2. In other words, the rotation shaft of the pitch angle changing motor 5A and the rotor shaft 4 are different parallel shafts.

Next, we will explain the motion transmission unit 6 that transmits the rotational motion of the pitch angle change motor 5A to the rotors H1 to H3. The motion transmission unit 6 includes a rotation transmission section 6A, a rotary-to-linear motion conversion section 7, and a linear-to-rotary motion conversion section 8.

The rotation transmission unit 6A transmits the rotation of the rotating shaft of the pitch angle change motor 5A to the ball screw shaft 7F of the rotary-linear conversion unit 7. The ball screw shaft 7F extends vertically along the central axis S0 of the thrust generating device 1 and is disposed within the hollow portion 3C, which is the central hole of the rotor shaft 4. Therefore, the rotation transmission unit 6A transmits the rotational motion of the pitch angle change motor 5A to the shaft on the central axis S0. Each rotation transmission unit has a rotating member that rotates in conjunction with the rotation of the rotating shaft of the pitch angle change motor. The rotation transmission unit 6A is fixed to the frame 2C.

The rotary-linear converter (first motion converter) 7 has a linear transmission shaft (linear shaft) 7D that extends vertically along the central axis S0 of the thrust generating device 1, and a motion conversion mechanism that converts the rotation of the rotary transmission unit 6A into linear motion of the linear transmission shaft 7D. The motion conversion mechanism (first motion conversion mechanism) of the rotary-linear converter 7 is connected to the rotary transmission unit 6A and the linear transmission shaft 7D. This motion conversion mechanism has a ball screw shaft 7F that is coaxially arranged above the linear transmission shaft 7D. The upper part of the rotary-linear converter 7 is housed within the thrust generating motor 2, but the lower part of the rotary-linear converter 7 protrudes downward from the thrust generating motor 2. The rotary-linear converter 7 is fixed to the frame 2C.

The linear motion-rotation conversion unit (second motion conversion unit) 8 converts the linear motion of the linear motion transmission shaft 7D of the rotary-linear motion conversion unit 7 into rotational motion to change the pitch angle of the rotors H1 to H3. The linear motion-rotation conversion unit 8 is located below the thrust generating motor 2.

The pitch angle change motor 5A, the rotation transmission unit 6A, and the rotary-linear conversion unit 7 are fixed to the frame 2C of the thrust generating motor 2. Therefore, even if the rotor shaft 4 rotates, the pitch angle change motor 5A, the rotation transmission unit 6A, and the rotary-linear conversion unit 7 do not rotate around the rotor shaft 4. On the other hand, the linear-rotation conversion unit 8 is supported by the rotor shaft 4. Therefore, the linear-rotation conversion unit 8 rotates around the rotor shaft 4 as the rotor shaft 4 rotates.

As shown in Figures 8 to 11, gear G1 is fixed to the upper end of the ball screw shaft 7F of the rotary-linear conversion unit 7. The rotation transmission unit 6A has gears G2 and G3, with gear G3 fixed to the rotating shaft of the pitch angle change motor 5A and gear G2 meshing with gears G3 and G1. Therefore, in the rotation transmission unit 6A, gears G3 and G2 can transmit the rotational motion of the pitch angle change motor 5A to the ball screw shaft 7F fixed to gear G1. The material of the gears G1 to G3 is, for example, carbon steel.

The rotary-linear converter 7 is supported by a support member F1. As shown in Figures 4, 6 and 7, the support member F1 is disposed in an opening 1B of the mounting portion 1A of the frame 2C of the thrust generating motor 2. The support member F1 is supported on the frame 2C by, for example, four bolts J1 (see Figures 8 to 11). The bolts J1 can be disposed, for example, at the four corners of the support member F1. A support member F3 is disposed in the hollow portion 3A of the thrust generating motor 2. The support member F3 is also supported on the frame 2C by bolts J3 (see Figures 8, 9 and 11). The pitch angle changing motor 5A is fixed to the support member F3 in the hollow portion 3A by bolts J4 (see Figures 8 to 11).

As shown in Figures 8 to 11, support member F2 is supported by bolt J2 on support member F1, and support member F1 and support member F2 rotatably support gear G2 of rotation transmission unit 6A. Support members F1 to F3 are made of a material such as an aluminum alloy.

In this embodiment, in the rotation transmission unit 6A, a gear transmits the rotational motion of the pitch angle change motor 5A to the ball screw shaft 7F of the rotary-linear conversion unit 7. However, each rotation transmission unit may have a belt-pulley mechanism or a chain-sprocket. Specifically, a pulley may be fixed to the ball screw shaft 7F, and a belt may be wound around this pulley and a pulley fixed to the rotating shaft of the pitch angle change motor 5A. A timing belt may be used as the belt. A sprocket may be fixed to the ball screw shaft 7F, and a chain may be wound around this sprocket and a sprocket fixed to the rotating shaft of the pitch angle change motor 5A.

In this embodiment, the rotary-linear conversion unit 7 uses a ball screw as a motion conversion mechanism to convert the rotary motion of the ball screw shaft 7F into linear motion of the linear transmission shaft 7D. The motion conversion mechanism includes a ball screw shaft 7F, a ball screw nut 7G, and a pair of linear guides 7E. However, a sliding screw or other feed screw may be used instead of the ball screw. In this embodiment, by using a ball screw as the motion conversion mechanism of the rotary-linear conversion unit 7, the drive torque can be reduced compared to when a sliding screw is used, and power consumption of the pitch angle change motor 5A can be reduced.

The ball screw shaft 7F extends vertically. As shown in FIG. 7, the ball screw shaft 7F is rotatably supported by a bearing U2 fixed to the cylindrical portion F1a of the support member F1, and rotates about the longitudinal axis of the ball screw shaft 7F as the gear G1 rotates.

As shown in Figures 9 and 10, the ball screw nut 7G is engaged with the ball screw shaft 7F. The ball screw nut 7G also extends vertically and is fixed to a linear motion transmission shaft 7D that extends vertically and is located below the ball screw nut 7G.

As shown in Figures 9 to 11, the ball screw nut 7G and the linear transmission shaft 7D are sandwiched between linear guides 7E, which are a pair of parallel long plate walls protruding from the cylindrical portion F1a of the support member F1, and are restricted from rotating by the pair of linear guides 7E. As the ball screw shaft 7F rotates, the ball screw nut 7G and the linear transmission shaft 7D move linearly in the vertical direction along the axial direction of the ball screw shaft 7F. The linear guides 7E allow the linear motion of the ball screw nut 7G and the linear transmission shaft 7D. In other words, the linear guides 7E guide the ball screw nut 7G and the linear transmission shaft 7D to move linearly. Therefore, when the ball screw shaft 7F rotates together with the gear G1, the ball screw nut 7G and the linear transmission shaft 7D move linearly in the vertical direction, guided by the linear guides 7E. The linear guides 7E can be provided integrally with the support member F1.

As shown in Figures 9 and 10, a vertically extending cavity is formed at the top of the linear motion transmission shaft 7D, and a ball screw nut 7G meshed with the ball screw shaft 7F is inserted into this cavity.

As shown in Figures 10 and 11, two guided flat surfaces 7C are formed on the outer peripheral surface of the upper part of the linear motion transmission shaft 7D. The two guided flat surfaces 7C are parallel to each other. On the other hand, the two linear motion guide parts 7E each have a guide flat surface 7E1, and these guide flat surfaces 7E1 are parallel to each other. The two guided flat surfaces 7C each face the guide flat surfaces 7E1 of the two linear motion guide parts 7E. However, the guided flat surfaces 7C do not contact the guide flat surfaces 7E1, and a small clearance is provided between the guided flat surfaces 7C and the guide flat surfaces 7E1.

As shown in Figures 10 and 12, a recess is formed in each of the guided flat surfaces 7C, and a sliding member 7H made of a low-friction material, such as fluororesin, is fitted into the recess. A part of the sliding member 7H protrudes from the recess and slidably contacts the guide flat surface 7E1 of the linear guide part 7E. Therefore, when the ball screw nut 7G and the linear transmission shaft 7D move linearly in the vertical direction, the sliding member 7H reduces friction with the linear guide part 7E. The sliding member 7H may be fixed to the recess with an adhesive or the like. To further reduce friction, a lubricant such as grease may be coated on the clearance between the guided flat surface 7C and the guide flat surface 7E1.

As shown in Figures 9 to 12, a flange 7A is formed at the upper end of the ball screw nut 7G, and a flange 7B is also formed at the upper end of the linear motion transmission shaft 7D. The flanges 7A and 7B are shaped like a cylinder cut by two parallel planes, with the flange 7A having two arc-shaped protruding portions 7A1 and two flat portions 7A2, and the flange 7B having two arc-shaped protruding portions 7B1 and two flat portions 7B2.

The arc-shaped protruding portions 7A1 and 7B1 of the flanges 7A and 7B are exposed between the pair of linear guides 7E. The protruding portions 7A1 and 7B1 of the flanges 7A and 7B are fixed by the bolt J5, and therefore the linear transmission shaft 7D is fixed to the ball screw nut 7G.

On the other hand, as shown in FIG. 10, the flat portions 7A2 and 7B2 of the flanges 7A and 7B face the guide flat surfaces 7E1 of the two linear guide parts 7E, respectively. The flat portion 7A2 of the flange 7A does not contact the guide flat surface 7E1 of the linear guide part 7E. The flat portion 7B2 of the flange 7B is part of the guided flat surface 7C, and the sliding member 7H is fitted into the recess formed therein. In this way, by providing the flat portions 7A2 and 7B2 on the flanges 7A and 7B, the outer diameter of the pair of linear guide parts 7E can be reduced, and the rotary-linear conversion part 7 can be housed within the rotor shaft 4 while suppressing an increase in the diameter of the rotor shaft 4. Therefore, the thrust generating device 1 can be further reduced in size and weight.

As shown in FIG. 7, most of the rotary-linear converter 7, including the upper part of the linear transmission shaft 7D, is disposed inside the thrust generating motor 2, while the lower part of the linear transmission shaft 7D passes through the internal space of the extension 9, which is a hollow cylinder, and further reaches the inside of the hub 10 of the propeller R.

The lower part of the linear motion transmission shaft 7D is connected to a linear motion rotation conversion unit 8 that converts the linear motion of the rotary-linear motion conversion unit 7 into rotational motion in order to change the pitch angle of the rotors H1 to H3. In this embodiment, the linear motion rotation conversion unit 8 uses a rack and pinion as a motion conversion mechanism (second motion conversion mechanism) to convert the linear motion of the linear motion transmission shaft 7D of the rotary-linear motion conversion unit 7 into rotational motion.

As shown in Figures 4 and 5, the linear motion rotation conversion unit 8 includes a linear body 11, racks A1 to A3, a case 21, support shafts M1 to M3, bearings E1 to E3, shaft adapters D1 to D3, and pinions B1 to B3.

The linear body 11 has a regular triangular prism shape with a cavity formed in its center. As shown in FIG. 7, the lower end of the linear transmission shaft 7D is fitted into the inner ring of the bearing U3, and the outer ring of the bearing U3 is fitted into the cavity of the linear body 11. Therefore, the linear body 11 can rotate around the linear transmission shaft 7D and moves linearly in the vertical direction together with the linear transmission shaft 7D. For example, a double row angular ball bearing can be used as the bearing U3.

The racks A1 to A3 are fixed to three corners of the linear body 11 and move linearly together with the linear body 11. The racks A1 to A3 are meshed with the pinions B1 to B3, respectively, and the pinions B1 to B3 are rotated simultaneously with the linear motion of the linear body 11 and the racks A1 to A3.

The support shafts M1 to M3 are arranged on the extensions of the grips P1 to P3 that support the rotors H1 to H3 of the propeller R. That is, the support shafts M1 to M3 support the grips P1 to P3 so as to extend horizontally radially from the thrust generating device 1. The grip P1 and the support shaft M1 can be provided integrally, the grip P2 and the support shaft M2 can be provided integrally, and the grip P3 and the support shaft M3 can be provided integrally. The material of the grips P1 to P3 and the support shafts M1 to M3 is, for example, duralumin. However, to increase the durability of the grips P1 to P3 and the support shafts M1 to M3, the material of the grips P1 to P3 and the support shafts M1 to M3 can be, for example, titanium.

The support shafts M1 to M3 are supported by bearings E1 to E3 fixed to the case 21 so that they can rotate around their own axes. For example, thrust bearings, preferably double row angular contact ball bearings, can be used as E1 to E3.

The pinions B1 to B3 are fixed to the tips of the support shafts M1 to M3, respectively. Therefore, when the pinions B1 to B3 rotate in accordance with the linear motion of the linear body 11 and the racks A1 to A3, the support shafts M1 to M3 also rotate together with the grips P1 to P3. The material of the pinions B1 to B3 and the racks A1 to A3 is, for example, chrome molybdenum steel.

The case 21 is a part of the hub 10 of the propeller R. The case 21 houses the linear body 11, racks A1 to A3, support shafts M1 to M3, bearings E1 to E3, shaft adapters D1 to D3, and pinions B1 to B3. Therefore, the case 21 can also be considered as the case of the linear motion rotation conversion unit 8.

The upper part of the case 21 is fixed to the lower end of the extension 9, which is a hollow cylinder, and the upper end of the extension 9 is fixed to the rotor shaft 4 of the thrust generating motor 2. Therefore, the case 21 rotates around the axis of the thrust generating device 1 together with the rotor 2B and the rotor shaft 4.

The bearings E1 to E3 fixed to the case 21 can support the support shafts M1 to M3 against the centrifugal force acting on the rotors H1 to H3 when the thrust generating device 1 rotates around its axis.

The shaft adapters D1 to D3 are disposed outside the support shafts M1 to M3 and inside the bearings E1 to E3, respectively, and are supported by the support shafts M1 to M3. The inner circumferential surface of each shaft adapter D1 to D3 is formed to fit the outer circumferential surface of the support shafts M1 to M3, which vary in diameter, and the outer circumferential surface of each shaft adapter D1 to D3 is formed to fit the inner circumferential surface of the cylindrical bearings E1 to E3. The shaft adapters D1 to D3 allow the bearings E1 to E3 to support the support shafts M1 to M3 while accommodating changes in the diameter of each support shaft M1 to M3. The case 21 and the shaft adapters D1 to D3 are made of a material such as duralumin.

The linear body 11, racks A1-A3, support shafts M1-M3, bearings E1-E3, shaft adapters D1-D3, and pinions B1-B3 housed in the case 21 rotate together with the case 21 around the axis of the thrust generator 1. As described above, the linear body 11 is fixed to the outer ring of the bearing U3, and can rotate around the axis of the thrust generator 1 independently of the linear transmission shaft 7D fixed to the inner ring of the bearing U3. As shown in FIG. 7, the inner ring of the bearing U3 can be fixed to the lower end of the linear transmission shaft 7D by, for example, a nut 15, and the outer ring of the bearing U3 can be fixed to the linear body 11 by, for example, a C-shaped retaining ring 16.

Figure 13 shows the position of the linear body 11 corresponding to the pitch angle of the rotor blade in Figure 2, and Figure 14 shows the position of the linear body 11 corresponding to the pitch angle of the rotor blade in Figure 3. As shown in Figures 13 and 14, the linear motion rotation conversion unit 8 includes a base 13, lift guides T1-T3, and nuts S1-S3 to limit the range of movement of the linear body 11 in the linear direction. The base 13 is an equilateral triangular plate with the same outline as the linear body 11, and a through opening 14 is formed in the center of the base 13 through which the lower end of the linear transmission shaft 7D can pass. The base 13 supports parallel lift guides T1-T3, which are rods extending vertically. The lift guides T1-T3 can be provided integrally with the base 13.

The linear body 11, which has the shape of a regular triangular prism, has three side faces Z1 to Z3. Racks A1 to A3 are fixed to the side faces Z1 to Z3, respectively. A cavity 12 is formed in the center of the linear body 11, and a bearing U3 (see Figure 7) is disposed in the cavity 12.

Openings V1 to V3 are formed at the three corners of the linear body 11. Lift guides T1 to T3 fixed to the base 13 are inserted into the openings V1 to V3, respectively. Nuts S1 to S3 are attached to the lower ends of the lift guides T1 to T3, respectively.

Figure 15 is an exploded perspective view of the hub 10. The hub 10 comprises a case 21, an outer lid 22, and an inner lid 23. The case 21 comprises a storage section 21A, an opening 21B, hollow sections Q1 to Q3, and openings K1 to K3 (see Figures 4 and 5).

The accommodation section 21A is formed in the center of the case 21, and accommodates the linear body 11 to which the racks A1 to A3 are attached together with the base 13. The accommodation section 21A is, for example, a hollow or recessed section provided in the case 21. The planar shape of the accommodation section 21A corresponds to the planar shape of the base 13, and can be a substantially equilateral triangle. The opening 21B is formed so that the linear body 11 to which the racks A1 to A3 are attached and the base 13 can be placed in the accommodation section 21A through the opening 21B.

The hollow sections Q1 to Q3 are arranged at angular intervals of 120 degrees outside the housing section 21A and communicate with the housing section 21A. The support shaft M1, pinion B1, bearing E1 and shaft adapter D1 are arranged in the hollow section Q1, the support shaft M2, pinion B2, bearing E2 and shaft adapter D2 are arranged in the hollow section Q2, and the support shaft M3, pinion B3, bearing E3 and shaft adapter D3 are arranged in the hollow section Q3. The pinions B1 to B3, bearings E1 to E3 and shaft adapters D1 to D3 can be arranged in these hollow sections Q1 to Q3 through the opening 21B and the housing section 21A.

Openings K1 to K3 are formed on the outer surface of case 21 at angular intervals of 120 degrees, and communicate with hollow portions Q1 to Q3, respectively. Support shafts M1 to M3 can be placed in storage portion 21A by inserting them into openings K1 to K3, respectively.

The inner lid 23 is fixed to the case 21 by a number of bolts J7. Furthermore, the outer lid 22, which covers the inner lid 23, is fixed to the inner lid 23. The material of the inner lid 23 is, for example, duralumin, and the material of the outer lid 22 is, for example, resin.

The inner lid 23 has multiple through holes 23A formed in it. The lower ends of the lift guides T1 to T3 (see Figures 13 and 14) are inserted into the through holes 23A of the inner lid 23, respectively, and protrude to the outside of the inner lid 23. On the outside of the inner lid 23, nuts S1 to S3 are attached to the lower ends of the lift guides T1 to T3. This allows the base 13 to be positioned within the storage section 21A of the case 21.

When the pitch angle change motor 5A rotates under the above configuration, the gears G3 and G2 in the rotation transmission section 6A transmit the rotational motion of the pitch angle change motor 5A to the gear G1 (see Figures 8 to 11). Since the gear G1 is fixed to the ball screw shaft 7F of the rotary-linear conversion section 7, the rotational motion of the pitch angle change motor 5A is transmitted to the ball screw shaft 7F. When the ball screw shaft 7F rotates, the ball screw nut 7G and the linear transmission shaft 7D are guided by the linear guide section 7E and move linearly in the vertical direction (see Figures 9 to 11).

The linear motion of the linear transmission shaft 7D is transmitted to the linear body 11. In response to the linear motion of the linear transmission shaft 7D, the racks A1 to A3 fixed to the linear body 11 move linearly in the vertical direction together with the linear body 11. When the racks A1 to A3 move linearly together with the linear body 11, the lift guides T1 to T3 guide the linear body 11 (see Figures 13 and 14). The range of movement of the linear body 11 is limited by the base 13 and nuts S1 to S3. The racks A1 to A3 are engaged with pinions B1 to B3, respectively, and when the racks A1 to A3 move linearly, the pinions B1 to B3 fixed to the support shafts M1 to M3 rotate at the same time (see Figures 4 and 5). Therefore, in response to the rotational motion of the pinions B1 to B3, the support shafts M1 to M3 rotate around their respective axes. Grips P1 to P3 that support the rotors H1 to H3 are attached to the support shafts M1 to M3, and the rotational motion of the support shafts M1 to M3 is transmitted to the rotors H1 to H3. Therefore, the pitch angles of the rotors H1 to H3 are changed at the same time. For example, when the linear body 11 is in the position shown in FIG. 13, the pitch angles of the rotors H1 to H3 are set as shown in FIG. 2, and when the linear body 11 is in the position shown in FIG. 14, the pitch angles of the rotors H1 to H3 are set as shown in FIG. 3.

The thrust generating device 1 can change the thrust given to the flying object by changing the rotation angle of the pitch angle changing motor 5A and therefore the pitch angle of the rotors H1 to H3. By changing the thrust by changing the pitch angle, the response speed of the thrust change can be increased and the stability of the flying object can be improved compared to a method of changing the thrust by changing the rotation speed of the thrust generating motor 2. In addition, since the thrust given to the flying object can be changed by changing the pitch angle of the rotors H1 to H3, there is no need to enlarge the rotors H1 to H3, and there is no need to excessively increase the rotation speed of the thrust generating motor 2. Since there is no need to enlarge the rotors H1 to H3, it is possible to suppress the size and weight of the flying object. In addition, since the increase in the rotation speed of the thrust generating motor 2 is suppressed, noise dependent on the rotation speed can be suppressed.

In addition, in the thrust generating device 1, the pitch angle of the rotors H1 to H3 can be changed electrically, eliminating the need to use hydraulics. This eliminates the need to provide a hydraulic control unit that controls the supply and discharge of oil, and a complex rotary seal mechanism for oil sealing the rotor, making it possible to prevent the thrust generating device 1 from becoming too large, and also facilitating the maintenance and repair of the thrust generating device 1.

In this embodiment, by using a rack and pinion as the motion conversion mechanism of the linear motion rotation conversion unit 8, it is possible to align the longitudinal direction of each of the racks A1 to A3 with the linear motion direction of the linear body 11, and it is possible to align each of the pinions B1 to B3 concentrically with the support shaft. This allows the arrangement of the three rack and pinions to be compact, and it is possible to house the linear motion rotation conversion unit 8 within the hub 10 while preventing the hub 10 from becoming larger.

In this embodiment, the grips P1-P3 and thus the rotors H1-H3 can be changed according to the weight of the flying object and thus the required thrust. Below, we will explain the mechanism that makes it easy to change the rotors H1-H3.

Figure 16 is an enlarged cross-sectional view of a portion of the hub 10 that supports the grip P1. Figure 17 is a cross-sectional view of the grip P1 and its surroundings. Figure 18 is an exploded perspective view of the components shown in Figure 17.

As shown in FIG. 16, the case 21 of the hub 10 houses the linear motion transmission shaft 7D and the motion conversion mechanism of the linear motion rotation conversion unit 8 that converts the linear motion of the linear motion transmission shaft 7D into the rotational motion of the multiple grips P1-P3 (particularly the linear body 11, racks A1-A3, and pinions B1-B3). The case 21 further houses the support shafts M1-M3 and the bearings E1-E3 that rotatably support the support shafts M1-M3. The support shafts M1-M3 can be considered to be the inner ends of the grips P1-P3, respectively. With the linear body 11, racks A1-A3, pinions B1-B3, and bearings E1-E3 remaining on the hub 10, the grips including the support shafts can be changed depending on the type of rotor.

The hub 10 can be disassembled into a case 21, an outer lid 22, and an inner lid 23, but the case 21 itself cannot be separated. The case 21 has multiple openings K1-K3 into which the support shafts M1-M3, which are the inner ends of the grips P1-P3, can be inserted when the outer ends of the grips P1-P3 are positioned outside the case 21.

Below, the mechanism supporting grip P1 and rotor H1 will be described in detail, but the mechanisms supporting the other grips P2, P3 and rotors H2-H3 are similar (grips P1-P3 are the same type, with the same shape and size).

As shown in Figures 16 to 18, a rubber ring 30, a thrust washer 31, a needle-shaped thrust bearing 32, a thrust washer 33, a shaft adapter D1, a bearing E1, a pinion B1, a C-shaped retaining ring 34, and a fastening ring 35 are arranged around the support shaft M1.

The support shaft M1 is inserted into the rubber ring 30. As shown in FIG. 16, the rubber ring 30 is interposed between the outer surface of the outer end wall Q1a of the hollow portion Q1 of the case 21 and the outer end of the grip P1, closing the opening K1 and preventing the bearing grease from scattering while suppressing the intrusion of dust into the inside of the case 21. The grip P1 including the support shaft M1 is rotatable relative to the rubber ring 30.

Thrust washers 31 and 33 are in contact with both end faces of needle-shaped thrust bearing 32. Thrust washers 31 and 33 are raceways, or rings, and are in contact with the multiple needles of needle-shaped thrust bearing 32. A support shaft M1 is inserted into thrust washer 31, needle-shaped thrust bearing 32, and thrust washer 33. Support shaft M1 does not contact the inner circumferential surfaces of thrust washer 31, needle-shaped thrust bearing 32, and thrust washer 33, and grip P1 including support shaft M1 can rotate relative to them.

A support shaft M1 is inserted into the shaft adapter (cylinder) D1, and the shaft adapter D1 is rotatably inserted into the bearing E1. The bearing E1 is, for example, a radial bearing, preferably a double-row angular contact ball bearing. The shaft adapter D1 can be divided at a plane including the longitudinal axes of the grips P1-P3, and has two segments D1a and D1b. The segments D1a and D1b are combined to form the shaft adapter D1, which is a single stepped cylinder.

The shaft adapter D1, which is composed of segments D1a and D1b, has a sleeve 40 and a flange 41. The flange 41 is disposed radially outward of the hub 10 from the sleeve 40. The sleeve 40 is inserted into the inner ring of the bearing E1. The end face of the bearing E1 faces the flange 41.

A fastening ring 35 is wound around the flange 41 of the shaft adapter D1. The fastening ring 35 is a ring with ends, and uses elastic restoring force to restrain the flange 41 and prevent the combined segments D1a and D1b from separating.

The end M1a of the support shaft M1 is formed in a substantially elliptical cylindrical shape and is inserted into the substantially elliptical cylindrical central hole of the pinion B1. Therefore, the pinion B1 does not rotate with respect to the support shaft M1. A groove M1b is formed in the end M1a of the support shaft M1, and a C-shaped retaining ring 34 is fitted into the groove M1b. The C-shaped retaining ring 34 restricts the axial movement of the pinion B1 and fixes the pinion B1 to the end M1a of the support shaft M1.

The outer end of the grip P1 is bifurcated into two parallel flat plate sections. Although not shown, the base of the rotor H1 is sandwiched between these flat plate sections. These flat plate sections have multiple through holes, and the base of the rotor H1 is fixed to the outer end of the grip P1 by bolts 36 that pass through the through holes and nuts 37 that engage with the bolts 36. Countersunk holes are formed around the through holes in the flat plate sections, and washers 38 are placed in these countersunk holes. Bolts 36 are inserted into the washers 38.

As shown in FIG. 16, the hollow portion Q1 of the case 21 has a small diameter hole portion Q1b and a large diameter hole portion Q1c. The small diameter hole portion Q1b and the large diameter hole portion Q1c are coaxial circular holes, and the small diameter hole portion Q1b located on the radial outside of the hub 10 has a smaller diameter than the large diameter hole portion Q1c located on the radial inside of the hub 10. A step wall Q1d is provided between the small diameter hole portion Q1b and the large diameter hole portion Q1c.

The thrust washer 31, needle-shaped thrust bearing 32, and thrust washer 33 are disposed in the small diameter hole Q1b of the hollow portion Q1 of the case 21, and the thrust washer 31 is brought into contact with the inner surface of the outer end wall Q1a of the hollow portion Q1. The flange 41 of the shaft adapter D1 is brought into contact with the thrust washer 33 on the opposite side. The fastening ring 35 and flange 41 are also disposed in the small diameter hole Q1b.

The bearing E1 with the sleeve 40 of the shaft adapter D1 inserted is placed in the large diameter hole Q1c of the hollow Q1 of the case 21, and the end face of the outer ring of the bearing E1 is brought into contact with the step wall Q1d of the hollow Q1. The other end face of the inner ring of the bearing E1 is brought into contact with the end face of the pinion B1 fixed to the end M1a of the support shaft M1, and the sleeve 40 is also brought into contact with this end face of the pinion B1.

Therefore, in the axial direction of the support shaft M1, the thrust washer 31, the needle-shaped thrust bearing 32, the thrust washer 33, and the shaft adapter D1 are sandwiched between the pinion B1 and the inner surface of the outer end wall Q1a of the hollow portion Q1 of the case 21. When a force toward the radially outward direction of the hub 10 is applied to the shaft adapters D1 to D3, the flanges 41 of the shaft adapters D1 to D3 transmit the centrifugal force to the thrust washer 31, the needle-shaped thrust bearing 32, and the thrust washer 33, and the thrust washer 31 comes into contact with the inner surface of the outer end wall Q1a of the case 21, and the needle-shaped thrust bearing 32 is supported by the inner surface of the outer end wall Q1a of the case 21. Also, in the axial direction of the support shaft M1, the bearing E1 is sandwiched between the pinion B1 and the step wall Q1d of the hollow portion Q1 of the case 21.

In the shaft adapter D1, the inner circumferential surface of the sleeve 40 has a smaller diameter toward the radial outside of the hub 10. On the other hand, in the outer circumferential surface of the support shaft M1, the portion M1c that is inserted into the shaft adapter D1 has a smaller diameter toward the radial outside of the hub 10.

As described above, in this embodiment, the grip including the support shaft can be changed depending on the type of rotor. Figure 19 is a cross-sectional view of grip P4, another type different from grips P1 to P3, and its surrounding area. Figure 20 is an exploded perspective view of the components shown in Figure 19.

The outer end of grip P4, which is located on the outside of case 21, is larger than the outer end of grip P1 and is suitable for supporting a rotor (not shown) that is larger and heavier than rotors H1 to H3. Therefore, once an appropriate rotor is selected according to the weight of the flying object to which the thrust generating device is attached, and thus the thrust required for the thrust generating device, a grip suitable for that rotor can be attached to hub 10.

The outer end of the grip P4 is bifurcated and has two parallel flat plate sections. Although not shown, the base of the rotor is sandwiched between these flat plate sections. These flat plate sections have multiple through holes, and the base of the rotor is fixed to the outer end of the grip P4 by bolts 36a that pass through the through holes and nuts 37a that engage with the bolts 36a.

On the other hand, the support shaft M1, which is the inner end of the grip P4, has the same shape and size as the support shaft M1 of the grip P1. Therefore, the grip including the support shaft can be changed according to the type of rotor while the linear body 11, racks A1-A3, pinions B1-B3, bearings E1-E3, and other components remain on the hub 10. While the grip can be changed, the radial bearings E1-E3 and the complex linear body 11, racks A1-A3, pinions B1-B3, and other components can be used without modification, minimizing increases in manufacturing costs.

In this embodiment, the support shaft, which is the inner end of the grip, is inserted, and each shaft adapter inserted into the radial bearing can be divided with a plane including the longitudinal axis of the grip as a boundary. When the grip is assembled into the hub 10, the support shafts M1 to M3 are inserted through the openings K1 to K3 of the case 21 and arranged inside the case 21. Inside the case 21, the bearings E1 to E3 are arranged around the support shafts M1 to M3 so as to rotatably support the grips P1 to P3. Specifically, the support shafts M1 to M3 are inserted into the shaft adapters D1 to D3, and the shaft adapters D1 to D3 are inserted into the bearings E1 to E3. Each of the shaft adapters D1 to D3 can be divided with a plane including the longitudinal axis of the grips P1 to P3 as a boundary, and can be easily arranged around the support shafts M1 to M3 and easily inserted into the bearings E1 to E3 in a combined state. Therefore, even if the case 21 cannot be separated, the bearings E1 to E3 can be easily arranged around the support shafts M1 to M3 inside the case 21. This makes it easy to change the grips P1 to P3.

The outer peripheral surface of the support shaft M1-M3 has a portion M1c having a smaller diameter toward the radial outside of the hub 10, and the inner peripheral surface of the sleeve 40 of the shaft adapter D1-D3 has a smaller diameter toward the radial outside of the hub 10. Therefore, when the grips P1-P3 are pulled toward the radial outside of the hub 10 by the centrifugal force acting on the rotors H1-H3, the portion M1c of the outer peripheral surface of the support shaft M1-M3 fits onto the inner peripheral surface of the sleeve 40 of the shaft adapter D1-D3. When a force toward the radial outside of the hub 10 (i.e., centrifugal force) is applied to the shaft adapter D1-D3, the shaft adapter D1-D3 is supported by the inner surface of the outer end wall Q1a of the case 21. Therefore, the shaft adapter D1-D3 functions as a retainer for the grips P1-P3 that are subjected to the centrifugal force.

In addition, when the centrifugal force increases to a certain extent, the portion M1c of the outer peripheral surface of the support shaft M1-M3 fits into the inner peripheral surface of the sleeve 40 of the shaft adapter D1-D3, so that the longitudinal axis of the grips P1-P3 is adjusted to the ideal direction.

The bearings E1 to E3 are arranged radially outward of the hub 10 relative to the linear body 11, racks A1 to A3, and pinions B1 to B3. Therefore, when centrifugal force is applied to the pinions B1 to B3, which rotate the grips P1 to P3, via the grips P1 to P3, an axial load is applied to the bearings E1 to E3, which are radially outward of the pinions B1 to B3. The bearings E1 to E3 are preferably double row angular contact ball bearings, and can withstand large axial loads.

When a force (i.e., centrifugal force) toward the radial outside of the hub 10 is applied to the shaft adapters D1-D3, the shaft adapters D1-D3 are supported on the inner surface of the outer end wall Q1a of the case 21 via the needle thrust bearing 32. Therefore, the axial load of the shaft adapters D1-D3, which is subjected to centrifugal force via the grips P1-P3, can be firmly supported by the outer end wall Q1a of the case 21.

Although the present invention has been shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that changes in form and detail may be made therein without departing from the scope of the invention as set forth in the appended claims. Such changes, modifications and alterations are intended to be within the scope of the invention.

For example, in the above embodiment, the propeller R is disposed directly below the thrust generating device 1, and the thrust generating device 1 is attached to the bottom of the airframe, but the propeller R may be disposed directly above the thrust generating device 1, and the thrust generating device 1 may be attached to the top of the airframe.

1 Thrust generating device 2 Thrust generating motor R Propeller H1 to H3 Rotor P1 to P3 Grip M1 to M3 Support shaft 4 Rotor shaft 5A Pitch angle changing motor 6 Motion transmission unit 6A Rotation transmission part 7 Rotation-linear conversion part 7A Flange 7A1 Protruding part 7A2 Plane part 7B Flange 7B1 Protruding part 7B2 Plane part 7C Guided flat surface 7D Linear transmission shaft 7E Linear guide part 7E1 Guide flat surface 7F Ball screw shaft 7G Ball screw nut 7H Sliding member 8 Linear rotation conversion part 10 Hub 11 Linear body A1 to A3 Rack B1 to B3 Pinion D1 to D3 Shaft adapter D1a Segment D1b Segment 40 Sleeve 41 Flange E1 to E3 Bearing 21 Case K1 to K3 Opening Q1 to Q3 Hollow part Q1a Outer end wall 32 Needle thrust bearing

Claims (5)

a thrust generating motor that rotates a plurality of rotors to generate thrust;
a pitch angle changing motor for changing the pitch angle of the rotor;
a rotation transmission unit connected to the pitch angle changing motor;
a first motion conversion unit having a linear motion shaft, the first motion conversion mechanism being connected to the rotation transmission unit and the linear motion shaft and converting rotation of the rotation transmission unit into linear motion of the linear motion shaft;
a second motion conversion unit that converts the linear motion of the linear motion shaft into rotational motion to change the pitch angle of the rotor,
The second motion conversion unit includes:
a hub rotated by the thrust generating motor;
A plurality of grips attached to the hub and each supporting the rotor blade;
a second motion conversion mechanism that converts the linear motion of the linear motion shaft into a rotational motion of the plurality of grips;
a plurality of radial bearings each rotatably supporting an inner end of the grip;
the hub has a case that houses the inner ends of the grips, the second motion conversion mechanism, and the radial bearings;
moreover,
a plurality of cylinders into which the inner ends of the grips are respectively inserted and which are respectively inserted into the radial bearings;
Each cylinder can be divided by a plane including the longitudinal axis of the grip,
the case is inseparable, and the case has a plurality of openings into which the inner end of the grip can be inserted with the outer end of the grip disposed outside the case;
The grips can be changed while the second motion conversion mechanism and the radial bearings remain on the hub.
A thrust generating device characterized by: 2. The thrust generating device according to claim 1, wherein each grip is changeable according to the type of rotor. The outer circumferential surface of the inner end of the grip has a diameter that decreases toward the radially outer side of the hub,
the cylinder has a sleeve and a flange disposed radially outward of the hub relative to the sleeve, and an inner circumferential surface of the sleeve has a diameter that decreases toward the radially outward side of the hub,
3. A thrust generating device according to claim 1 , wherein when a force directed radially outward from the hub is applied to the cylinder, the cylinder is supported by an inner surface of an outer end wall of the case. 4. The thrust generating device according to claim 3 , wherein the radial bearing is a double row angular contact ball bearing, and is disposed radially outward of the hub relative to the second motion conversion mechanism. 5. A thrust generating device as described in claim 3 or 4 , characterized in that when a force directed radially outward from the hub is applied to the cylinder, the cylinder is supported on the inner surface of the outer end wall of the case via a thrust bearing.

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