Wing tip folding mechanism, wing and wing tip folding method

Abstract

The present invention discloses a wingtip folding mechanism, a wing and a wingtip folding method, and relates to the technical field of wingtip folding. The wingtip folding mechanism comprises a rotating assembly, a telescopic driving device, a motor, a worm gear mechanism, a first friction disc and a second friction disc. The rotating assembly is configured to connect the wing body and the wingtip and enable the wingtip to rotate relative to the wing body. The telescopic driving device is fixedly connected to the wingtip; the motor is fixedly connected to the wing body; the worm gear mechanism comprises a meshing worm wheel and a worm, the worm wheel is connected to the wing body, and the worm is transmission-connected to the driving end of the motor; the first friction disc is connected to the telescopic end of the telescopic driving device; the second friction disc is relatively fixedly connected to the worm wheel in the circumferential direction, and the second friction disc and the first friction disc are arranged relative to each other. The present invention has a simple structure, precise control and can realize multi-mode folding.

Description

Technical Field

[0001] The present invention relates to the technical field of wingtip folding, and in particular to a wingtip folding mechanism, a wing and a wingtip folding method. Background Art

[0002] Although the wingtip only occupies a small part of the wing, it has a great impact on the overall performance of the aircraft. Folding wingtip wing technology is a multifunctional, partial variant technology that can be used to improve wing aerodynamic performance, improve fuel efficiency, reduce gust loads, and enhance control performance. Folding wingtips can reduce induced drag and improve the aircraft's lift-to-drag ratio by improving wingtip vortices. Folding wingtips can significantly reduce fuel consumption by improving the aircraft's aerodynamic efficiency. In addition, the design of the folding wingtip can adjust the angle and shape of the wingtip according to flight conditions (such as takeoff, cruising, landing, etc.), thereby optimizing flight control and improving flight stability and efficiency.

[0003] Folding wings usually consist of a wing body and a wing tip. The wing body is connected to the fuselage as a whole, and the internal actuator of the wing drives the wing tip to move around the hinge through the folding mechanism. From the perspective of drive form, folding wing tips include two categories: active folding and passive folding. Active folding technology is mainly used to reduce fuel consumption and control aircraft flight. During takeoff and landing, the active folding system can adjust the wing tip angle to optimize aerodynamic performance. When taxiing on the ground or entering the hangar, the wing tip can be folded to adapt to a small space. Compared with active folding technology, passive folding wing tip technology has the advantages of simple system composition and easy structure implementation. Passive folding is suitable for specific flight conditions, such as automatic unfolding during high-speed cruising and automatic folding during low-speed takeoff or landing. Folding wing tips usually have a wing tip self-locking mechanism, which helps the wing tip maintain the stability of the wing tip structure during flight or ground operation. This structure plays an important role in both active folding or passive folding systems, ensuring that the wing tip can be firmly maintained in the predetermined position after unfolding or folding, avoiding accidental folding or unfolding during flight.

[0004] Currently, active folding technology relies on mechanical devices, transmission systems and control systems to achieve the folding and unfolding of the wingtips. This usually includes electric motors, hydraulic systems or other power sources, which are precisely controlled by sensors and control units. Passive folding relies on aerodynamic design and natural forces to achieve the folding and unfolding of the wingtips. This usually includes springs, hinges and aerodynamic shape designs, which drive the folding through the forces generated by wind and aircraft movement. The implementation of the self-locking mechanism generally includes mechanical self-locking devices (structural elements such as locking pins, locking hooks and locking slots), hydraulic or pneumatic systems.

[0005] The existing folding wingtip mechanism, the active folding mechanism requires complex mechanical devices and control systems, and is prone to failure; the passive folding mechanism relies on natural forces, has low control accuracy and flexibility, and cannot accurately adjust the wingtip angle. Most of the folding wingtip mechanisms today are single-mode folding wingtips, that is, they only have one mode of active folding or passive folding. Single-mode folding wingtips are difficult to provide optimal performance under various flight conditions.

[0006] Based on this, a new solution is urgently needed to at least solve some of the above problems. Summary of the invention

[0007] The object of the present invention is to provide a wingtip folding mechanism, a wing and a wingtip folding method to solve the problems existing in the above-mentioned prior art, with a simple structure, precise control and multi-mode folding.

[0008] To achieve the above object, the present invention provides the following solutions:

[0009] The present invention provides a wingtip folding mechanism, comprising a rotating assembly, a telescopic driving device, a motor, a worm gear mechanism, a first friction disc and a second friction disc, wherein the rotating assembly is constructed to connect a wing body and a wingtip and enable the wingtip to rotate relative to the wing body, the telescopic driving device is fixedly connected to the wingtip; the motor is fixedly connected to the wing body; the worm gear mechanism comprises a meshing worm wheel and a worm, the worm wheel is connected to the wing body, and the worm is transmission-connected to the driving end of the motor; the first friction disc is connected to the telescopic end of the telescopic driving device; the second friction disc is relatively fixedly connected to the worm wheel in the circumferential direction, and the second friction disc and the first friction disc are arranged opposite to each other.

[0010] Preferably, the rotating assembly includes two fixed supports and two connecting shafts, the two fixed supports are both arranged between the wing body and the wing tip, the two fixed supports are both fixedly connected to the wing body, the two connecting shafts are both fixedly connected to the wing tip, and the connecting shafts are rotatably connected to the fixed supports via bearings.

[0011] Preferably, it also includes a torsion spring and a wingtip connecting shaft, the wing body and the wingtip can rotate around a first rotating shaft, the axis of the torsion spring coincides with the first rotating shaft, one end of the torsion spring is fixedly connected to the fixed support, and the other end is fixedly connected to the wingtip connecting shaft, the wingtip connecting shaft is fixedly connected to the wingtip, and under normal conditions, the surfaces of the wingtip and the wing body are on the same curved surface or streamlined surface.

[0012] Preferably, the wingtip connecting axis is one of the connecting axes.

[0013] Preferably, the two fixed supports are respectively a first fixed support and a second fixed support, one end of the torsion spring is fixedly connected to the first fixed support, and the wingtip connecting shaft is rotatably connected to the second fixed support via a bearing.

[0014] Preferably, the portion of the wingtip connecting shaft between the torsion spring and the second fixed support is bent toward one side of the first rotating shaft to form an accommodating space, the first rotating shaft passes through the accommodating space, and the telescopic drive device is fixedly arranged on the wingtip connecting shaft and is located in the accommodating space; the telescopic end of the telescopic drive device can be telescoped along the direction of the first rotating shaft.

[0015] Preferably, the telescopic drive device is an electric push rod.

[0016] Preferably, it also includes an angle encoder and a controller, the rotating body of the angle encoder is fixedly connected to the wingtip connecting shaft, the fixed body is fixedly connected to the second fixed support, and the controller is communicatively connected to the angle encoder, the motor, and the telescopic drive device.

[0017] The present invention also provides a wing, comprising the wingtip folding mechanism as described above.

[0018] The present invention also provides a wingtip folding method, wherein the wingtip is connected to the wing body through the wingtip folding mechanism as described above; comprising:

[0019] Passive folding: the telescopic drive device does not work, the first friction disc and the second friction disc do not engage, and when the aircraft encounters a gust of wind, the wing tip rotates under the action of the gust of wind, resulting in folding and deformation;

[0020] Active folding: The telescopic drive device drives the first friction disc to move toward the second friction disc until it engages. At the same time, the motor drives the worm to rotate, the worm is meshed with the worm wheel, and the worm drives the worm wheel to rotate. Due to the friction force, the first friction disc and the second friction disc transmit the torque to the second friction disc and drive the wing tip to rotate. By controlling the motor speed, the wing folding speed is controlled. Similarly, when there is a need to fold the wing tip downward, the motor reverses to drive the wing tip to fold downward.

[0021] Self-locking: When the wing is in the passive folding mode, the telescopic drive device works to drive the first friction disk to move toward the second friction disk until it engages, the motor does not work, and friction is generated between the first friction disk and the second friction disk. Since the worm gear mechanism has the characteristic of one-way transmission, the worm gear cannot drive the worm to move, thereby causing the wing tip to self-lock; when the wing is in the active folding mode, self-locking can be achieved by stopping the motor.

[0022] Compared with the prior art, the present invention has achieved the following technical effects:

[0023] The present invention drives the first friction disk to engage with the second friction disk through a telescopic drive device so that the motor can transmit torque to the wing tip, thereby realizing active folding; drives the first friction disk away from the second friction disk through the telescopic drive device to disconnect the transmission relationship between the wing tip and the motor, thereby realizing passive folding; and locks the folded state of the wing tip by driving the first friction disk to engage with the second friction disk and turning off the motor through the telescopic drive device. Therefore, the present application can realize the conversion of the three modes of the wing tip only by setting up a telescopic drive device, a friction disk, a motor and a worm gear mechanism, and its structure is simple and flexible.

[0024] In addition, the present application is provided with an angle encoder to monitor the rotation angle of the wing tip, and then the motor and the telescopic drive device are controlled by a controller to improve the control accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 A schematic diagram of the structure of a wing provided by an embodiment of the present invention;

[0027] Figure 2 for Figure 1 A front view of

[0028] Figure 3 for Figure 1 Schematic diagram of the structure of the mid-wing tip folding mechanism;

[0029] Figure 4 for Figure 1 An exploded view of the vertical setting, showing only part of the wing body and wingtips;

[0030] Figure 5 for Figure 3 Schematic diagram of the setting method of the worm gear;

[0031] Figure 6 for Figure 5 Schematic diagram of the arrangement of the middle worm gear and the second friction disc;

[0032] Figure 7 for Figure 3 A schematic diagram of the structure of the middle telescopic drive device, the wing tip connecting shaft and the first friction disc thereon;

[0033] Figure 8is a schematic diagram of the structure of the first friction disc and the second friction disc in a separated state;

[0034] In the figure: 1-wing body; 2-wingtip; 3-wingtip folding mechanism; 4-second fixed support; 5-telescopic drive device; 6-first friction disc; 7-angle encoder; 8-wingtip connecting shaft; 9-torsion spring; 10-connecting shaft; 11-first fixed support; 12-motor; 13-second friction disc bracket; 14-worm gear; 15-bearing; 16-first friction disc adapter; 17-worm; 18-second friction disc. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] like Figures 1 to 8 As shown, the present invention provides a wingtip folding mechanism 3, comprising a rotating assembly, a telescopic drive device 5, a motor 12, a worm gear mechanism, a first friction disc 6 and a second friction disc 18, the rotating assembly is constructed to connect the wing body 1 and the wing tip 2 and enable the wing tip 2 to rotate relative to the wing body 1, the telescopic drive device 5 is fixedly connected to the wing tip 2; the motor 12 is fixedly connected to the wing body 1; the worm gear mechanism comprises a meshing worm wheel 14 and a worm 17, the worm wheel 14 is connected to the wing body 1, and the worm 17 is transmission-connected to the driving end of the motor 12; the first friction disc 6 is connected to the telescopic end of the telescopic drive device 5; the second friction disc 18 is relatively fixedly connected to the worm wheel 14 in the circumferential direction, and the second friction disc 18 and the first friction disc 6 are arranged relatively.

[0038] The present invention drives the first friction disk 6 to engage with the second friction disk 18 by the telescopic drive device 5 so that the motor 12 can transmit the torque to the wing tip 2, thereby realizing active folding; drives the first friction disk 6 away from the second friction disk 18 by the telescopic drive device 5 to disconnect the transmission relationship between the wing tip 2 and the motor 12, thereby realizing passive folding; and locks the folded state of the wing tip 2 by driving the first friction disk 6 to engage with the second friction disk 18 and turning off the motor 12 by the telescopic drive device 5. Therefore, the present application can realize the conversion of the three modes of the wing tip 2 only by setting the telescopic drive device 5, the friction disk, the motor 12 and the worm gear mechanism, and its structure is simple and flexible.

[0039] The above embodiments do not limit the specific structure of the rotating assembly, which means that any structure in the prior art that can achieve a rotating connection relationship between the wing tip 2 and the wing body 1 can be applied to the present application, such as an existing rotating hinge.

[0040] Although other types of wingtip folding mechanisms can achieve folding of the wingtip 2, they cannot achieve multi-mode folding of the wingtip, and the folding mechanism has a complex structure, a relatively complex control system, and is difficult to guarantee control accuracy. It is difficult for a single-mode folding wingtip to provide optimal performance under various flight conditions. The present invention can achieve wingtip folding in multiple modes, and the mechanism device has a simple structure, relatively simple control, high self-locking accuracy, and can adapt to different flight stages and mission requirements. By adopting the most suitable folding mode in different flight stages, for example, active folding is used during takeoff and landing to provide precise control; passive folding is used during cruising to optimize aerodynamic performance and save fuel. The multi-mode wingtip folding mechanism can optimize the lift-to-drag ratio, improve fuel efficiency, extend flight distance or increase load capacity. It can overcome the shortcomings of existing folding wingtip mechanisms and improve their adaptability, performance and safety.

[0041] The present invention provides a specific embodiment for the rotating assembly, as follows:

[0042] In some embodiments, the rotating assembly includes two fixed supports and two connecting shafts 10, the two fixed supports are both arranged between the wing body 1 and the wing tip, the two fixed supports are both fixedly connected to the wing body 1, the two connecting shafts 10 are both fixedly connected to the wing tip, and the connecting shafts 10 are rotatably connected to the fixed supports through bearings 15.

[0043] The connecting shaft 10 in this embodiment is not a straight shaft, and can be partially bent to facilitate fixed connection with the wing tip. The axis of the other part coincides with the axis of the bearing 15 and is fixedly arranged in the inner ring of the bearing 15 or is fixedly connected to the side of the inner ring or the outer ring by some means. For example, a fixed sleeve is arranged at the end of the connecting shaft 10, and the fixed sleeve is sleeved on the outer ring of the bearing 15 and fixedly connected. However, in the present invention, one connecting shaft 10, the wingtip connecting shaft 8 described below is passed through the bearing 15 to realize connection with one of the bearings 15, and the other connecting shaft 10 is connected to the other bearing 15 by setting a fixed sleeve.

[0044] In some embodiments, the embodiments of the present invention also include a torsion spring 9 and a wingtip connecting shaft 8, the wing body 1 and the wingtip can rotate around the first rotation axis, the axis of the torsion spring 9 coincides with the first rotation axis, one end of the torsion spring 9 is fixedly connected to the fixed support, and the other end is fixedly connected to the wingtip connecting shaft 8, the wingtip connecting shaft 8 is fixedly connected to the wingtip, and under normal conditions, the surfaces of the wingtip and the wing body 1 are on the same curved surface or streamlined surface.

[0045] The torsion spring 9 in this embodiment provides a buffer force in the opposite direction of the torque during the process of the wing tip folding upwards, and also helps the folded wing tip to return to its original position, that is, the normal state mentioned above.

[0046] In some embodiments, the wingtip connecting shaft 8 is one of the connecting shafts 10 .

[0047] In order to reduce the number of components, this embodiment uses a common component for the wingtip connecting shaft 8 and the connecting shaft 10. It is understandable that in other embodiments, the wingtip connecting shaft 8 and the connecting shaft 10 may also be provided separately, and such a setting will not affect the folding of the wingtip and the setting of the torsion spring 9.

[0048] In some embodiments, the two fixed supports are respectively a first fixed support 11 and a second fixed support 4 , one end of the torsion spring 9 is fixedly connected to the first fixed support 11 , and the wingtip connecting shaft 8 is rotatably connected to the second fixed support 4 via a bearing 15 .

[0049] In some embodiments, part of the wingtip connecting shaft 8 between the torsion spring 9 and the second fixed support 4 is bent toward one side of the first rotating shaft to form an accommodating space, and the first rotating shaft passes through the accommodating space. The telescopic drive device 5 is fixedly arranged on the wingtip connecting shaft 8 and is located in the accommodating space; the telescopic end of the telescopic drive device 5 can be telescoped along the direction of the first rotating shaft.

[0050] In some embodiments, the telescopic driving device 5 is an electric push rod.

[0051] This embodiment uses an electric push rod to achieve high-precision extension and contraction.

[0052] In some embodiments, the second friction disc 18 is fixed to one end of the second friction disc bracket 13, the second friction disc bracket 13 is fixedly connected to the wing body 1, the second friction disc bracket 13 is sleeved with a worm gear 14, the inner wall of the worm gear 14 is provided with a stop groove, and the second friction disc bracket 13 is provided with a stop protrusion that cooperates with the stop groove to realize a relatively fixed connection between the second friction disc 18 and the worm gear 14 in the circumferential direction.

[0053] In some embodiments, the present invention also includes an angle encoder 7 and a controller, the rotating body of the angle encoder 7 is fixedly connected to the wingtip connecting shaft 8, the fixed body is fixedly connected to the second fixed support 4, and the controller and the angle encoder 7, the motor 12, and the telescopic drive device 5 are all communicatively connected.

[0054] The present application is provided with an angle encoder 7 to monitor the rotation angle of the wing tip, and then the motor 12 and the telescopic drive device 5 are controlled by a controller to improve the control accuracy.

[0055] An embodiment of the present invention further provides a wing, comprising the wingtip folding mechanism 3 as described above.

[0056] The wing in this embodiment includes all the advantages of the above-mentioned multi-mode folding wingtip mechanism, which will not be described in detail here.

[0057] The embodiment of the present invention further provides a wingtip folding method, wherein the wingtip is connected to the wing body 1 through the wingtip folding mechanism 3 as described above; the method comprises:

[0058] Passive folding: the telescopic drive device 5 does not work, the first friction disc 6 and the second friction disc 18 do not engage, and when the aircraft encounters a gust of wind, the wing tip rotates under the action of the gust of wind, resulting in folding and deformation;

[0059] Active folding: The telescopic drive device 5 drives the first friction disc 6 to move toward the second friction disc 18 until it engages. At the same time, the motor 12 drives the worm 17 to rotate, and the worm 17 meshes with the worm wheel 14. The worm 17 drives the worm wheel 14 to rotate. Due to the friction force, the first friction disc 6 and the second friction disc 18 transmit the torque to the second friction disc 18 and drive the wing tip to rotate. By controlling the speed of the motor 12, the speed of wing folding is controlled. Similarly, when there is a need to fold the wing tip downward, the motor 12 reverses to drive the wing tip to fold downward.

[0060] Self-locking: When the wing is in the passive folding mode, the telescopic drive device 5 works, driving the first friction disk 6 to move toward the second friction disk 18 until it engages, the motor 12 does not work, and friction is generated between the first friction disk 6 and the second friction disk 18. Since the worm gear mechanism has the characteristic of one-way transmission, the worm gear 14 cannot drive the worm 17 to move, thereby causing the wing tip to self-lock; when the wing is in the active folding mode, self-locking can be achieved by stopping the motor 12.

[0061] In some embodiments, when an angle encoder 7 is provided, in the passive folding mode, the angle encoder 7 monitors the rotation angle of the wing tip and transmits it to the controller for storage and recording.

[0062] In the active folding mode, the angle encoder 7 records the wing tip folding angle and feeds it back to the motor 12, thereby controlling the rotation speed of the motor 12 to prevent the wing tip from being over-folded and damaged. The speed of the wing tip folding can also be controlled by controlling the rotation speed of the motor 12.

[0063] The device and method mentioned in the present invention press the first friction disc against the second friction disc through an electric push rod, and realize active folding control through the action of friction force. At the same time, the one-way transmission characteristics of the worm gear mechanism and the friction force between the friction discs are used to realize wing tip self-locking, and the hinge mechanism between the wing tip and the wing body can also realize passive folding. The design of realizing active folding and passive folding at the same time combines the advantages of the two folding methods and provides higher flexibility and reliability. Such a design can give full play to their respective advantages under different flight conditions and ground operating conditions, and improve the performance and operational convenience of the aircraft.

[0064] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A wingtip folding mechanism, comprising a rotating assembly, wherein the rotating assembly is configured to connect a wing body and a wingtip and enable the wingtip to rotate relative to the wing body, wherein: Also includes: A telescopic drive device, fixedly connected to the wing tip; A motor, fixedly connected to the wing body; A worm gear mechanism, comprising a meshing worm wheel and a worm, wherein the worm wheel is connected to the wing body, and the worm is drivingly connected to the driving end of the motor; a first friction disc connected to the telescopic end of the telescopic drive device; as well as The second friction disk is circumferentially relatively fixedly connected to the worm gear, and the second friction disk and the first friction disk are arranged opposite to each other; the rotating assembly includes two fixed supports and two connecting shafts, the two fixed supports are arranged between the wing body and the wing tip, the two fixed supports are fixedly connected to the wing body, the two connecting shafts are fixedly connected to the wing tip, and the connecting shaft is rotatably connected to the fixed supports through bearings; it also includes a torsion spring and a wingtip connecting shaft, the wing body and the wing tip can rotate around a first rotating shaft, the axis of the torsion spring coincides with the first rotating shaft, one end of the torsion spring is fixedly connected to the fixed support, and the other end is fixedly connected to the wingtip connecting shaft, the wingtip connecting shaft is fixedly connected to the wing tip, and under normal conditions, the surfaces of the wing tip and the wing body are on the same curved surface or streamlined surface.

2. The wingtip folding mechanism according to claim 1, characterized in that: The wing tip connecting axis is one of the connecting axes.

3. The wingtip folding mechanism according to claim 1, characterized in that: The two fixed supports are respectively a first fixed support and a second fixed support, one end of the torsion spring is fixedly connected to the first fixed support, and the wing tip connecting shaft is rotatably connected to the second fixed support via a bearing.

4. The wingtip folding mechanism according to claim 3, characterized in that: The portion of the wingtip connecting shaft between the torsion spring and the second fixed support is bent toward one side of the first rotating shaft to form an accommodating space, the first rotating shaft passes through the accommodating space, and the telescopic drive device is fixedly arranged on the wingtip connecting shaft and is located in the accommodating space; the telescopic end of the telescopic drive device can be telescoped along the direction of the first rotating shaft.

5. The wingtip folding mechanism according to claim 1, characterized in that: The telescopic driving device is an electric push rod.

6. The wingtip folding mechanism according to claim 3, characterized in that: It also includes an angle encoder and a controller. The rotating body of the angle encoder is fixedly connected to the wingtip connecting shaft, and the fixed body is fixedly connected to the second fixed support. The controller is communicatively connected to the angle encoder, the motor, and the telescopic drive device.

7. A wing, characterized in that: It comprises the wingtip folding mechanism according to any one of claims 1 to 6.

8. A wing tip folding method, characterized in that: The wing tip is connected to the wing body by the wing tip folding mechanism according to any one of claims 1 to 6; comprising: Passive folding: the telescopic drive device does not work, the first friction disc and the second friction disc do not engage, and when the aircraft encounters a gust of wind, the wing tip rotates under the action of the gust of wind, resulting in folding and deformation; Active folding: The telescopic drive device drives the first friction disc to move toward the second friction disc until it engages. At the same time, the motor drives the worm to rotate, the worm is meshed with the worm wheel, and the worm drives the worm wheel to rotate. Due to the friction force, the first friction disc and the second friction disc transmit the torque to the second friction disc and drive the wing tip to rotate. By controlling the motor speed, the wing folding speed is controlled. Similarly, when there is a need to fold the wing tip downward, the motor reverses to drive the wing tip to fold downward. Self-locking: When the wing is in the passive folding mode, the telescopic drive device works to drive the first friction disk to move toward the second friction disk until it engages, the motor does not work, and friction is generated between the first friction disk and the second friction disk. Since the worm gear mechanism has the characteristic of one-way transmission, the worm gear cannot drive the worm to move, thereby causing the wing tip to self-lock; when the wing is in the active folding mode, self-locking can be achieved by stopping the motor.

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