A flow-induced vibration collaborative energy harvesting device based on dual mechanical transmission mechanisms

Abstract

The present invention relates to a flow-induced vibration collaborative energy capture device based on a dual mechanical transmission mechanism, which belongs to the fields of clean new energy power generation technology and marine engineering. The device includes a high-speed energy capture module and a low-speed energy capture module coupled to both ends of the vibrator. Through collaborative work, the device completes flow-induced vibration energy capture under different working conditions and converts the captured energy into electrical energy for transmission to the load. When the vibrator vibrates at a low speed, the low-speed energy capture module is used as the main component, and the high-speed energy capture module is used as the auxiliary component to perform flow-induced vibration energy capture. When the vibrator vibrates at a high speed, the high-speed energy capture module is used as the main component, and the low-speed energy capture module is used as the auxiliary component to perform flow-induced vibration energy capture. The present invention solves the problem of uncoordinated electromechanical systems of energy capture devices in actual working environments, and can achieve efficient energy capture of the energy capture device under complex factors such as low flow velocity and variable flow environment.

Description

Technical Field

[0001] The present invention belongs to the field of clean new energy power generation technology and marine engineering, and specifically relates to a flow-induced vibration collaborative energy capture device based on a dual mechanical transmission mechanism. Background Art

[0002] Energy, as the core driving force for economic and social development, faces the dual pressures of dwindling mineral resources and global environmental challenges. Therefore, exploring and utilizing new, clean, and renewable energy sources has become a key path to sustainable development. Compared to traditional energy sources, ocean current energy offers lower electricity costs. Compared to renewable wind and solar energy, ocean current energy boasts a higher energy density and a lifetime of over 90%. Therefore, fully developing and utilizing ocean current energy could generate substantial economic benefits.

[0003] Currently, energy capture based on flow-induced vibration is an effective means of energy conversion. Flow-induced vibration refers to the alternating fluid forces exerted on the surface of a solid when a fluid flows through it, causing the solid to reciprocate. This reciprocating motion of the solid changes the fluid flow pattern, which in turn changes the fluid forces acting on the solid surface. This interaction between fluid and solid is called flow-induced vibration. Studies have shown that when flow-induced vibration occurs, the structure also absorbs some of the fluid energy. The energy generated by flow-induced vibration has potential for utilization. Therefore, current work is focused on the research and development of power generation devices that can capture flow-induced vibration energy. Common flow-induced vibrations mainly include vortex-induced vibration and galloping. Vortex-induced vibration has a high amplitude when resonance occurs. Galloping can also be used for vibration energy capture, but a single smooth cylindrical oscillator is generally not considered to experience galloping.

[0004] The main methods of flow-induced vibration energy harvesting include: piezoelectric, electromagnetic and electrostatic. Electromagnetic is a common energy conversion method for flow-induced vibration energy harvesting devices. For the current research on flow-induced vibration energy harvesting, most of the focus is on the impact of changes in the structure and number of vibrators on the energy harvesting efficiency. Among them, the vibrator structure can change the vibration type. For example, the cylindrical vibrator corresponds to vortex-induced vibration, while the triangular prism structure vibrator corresponds to galloping vibration. The change in the number of vibrators involves the impact of the spacing between the vibrators on the energy harvesting efficiency, and traditional flow-induced vibration energy harvesting devices often have the problem of poor environmental adaptability of the electromechanical system. When the vibration speed is slow, the energy harvesting efficiency is reduced due to the slow transmission response; when the vibration speed is fast, stress will be generated on the transmission components, thereby reducing the energy conversion efficiency, which is not conducive to energy harvesting.

[0005] Therefore, the present invention proposes a flow-induced vibration collaborative energy capture device based on a dual mechanical transmission mechanism. Summary of the Invention

[0006] Technical issues to be solved:

[0007] In order to avoid the shortcomings of the existing technology, the present invention provides a flow-induced vibration collaborative energy capture device based on a dual mechanical transmission mechanism, which obtains energy under different vibration states through different energy capture modules, and adopts a modular design to rationally layout the device; the present invention solves the problem of poor environmental adaptability of the electromechanical system of the energy capture device in the actual working environment, and can realize efficient energy capture of the energy capture device under complex factors such as low flow velocity and changeable flow environment.

[0008] The technical solution of the present invention is: a flow-induced vibration collaborative energy harvesting device based on a dual mechanical transmission mechanism: comprising a high-speed energy harvesting module and a low-speed energy harvesting module coupled to both ends of the vibrator, which work together to achieve flow-induced vibration energy harvesting under different working conditions, and convert the harvested energy into electrical energy and transmit it to the load;

[0009] When the vibrator vibrates at a low speed, the low-speed energy harvesting module is used as the main method, and the high-speed energy harvesting module is used as the auxiliary method to perform flow-induced vibration energy harvesting.

[0010] When the vibrator vibrates at high speed, the high-speed energy harvesting module is used as the main method, and the low-speed energy harvesting module is used as the auxiliary method to carry out flow-induced vibration energy harvesting.

[0011] A further technical solution of the present invention is: it also includes two relatively arranged shells, and slide grooves are opened on the opposite surfaces of the two shells in the vertical direction. The two ends of the vibrator are suspended in the slide grooves of the two shells by springs respectively, and can move back and forth along the slide grooves; one end of the vibrator passes through the slide groove of the first shell and is connected to the low-speed energy capture module inside it, and the other end passes through the slide groove of the second shell and is connected to the high-speed energy capture module inside it.

[0012] A further technical solution of the present invention is: two sliders are respectively provided at both ends of the vibrator; one end of the first spring is fixed to the top wall of the slide groove of the first shell, and the bottom end is connected to the first slider; one end of the second spring is fixed to the top wall of the slide groove of the second shell, and the bottom end is connected to the second slider.

[0013] A further technical solution of the present invention is: the low-speed energy capture module is a gear rack mechanism assembly, including a rack fixed to one end of the vibrator, a gear set meshing with the rack, and a second motor. The rack is driven to reciprocate up and down by the vibrator, thereby driving the first gear, the second gear, and the third gear meshing in sequence in the gear set to rotate. The third gear transmits the torque to the second motor and converts it into electrical energy.

[0014] A further technical solution of the present invention is that the transmission ratio i of the first gear, the second gear and the third gear in the gear set is 9.65.

[0015] A further technical solution of the present invention is: the high-speed energy capture module is a crank slider mechanism assembly, including a connecting rod rotatably connected to the other end of the vibrator, a driven rod rotatably connected to the top end of the connecting rod, and a first motor. The vibrator drives the bottom end of the connecting rod to reciprocate up and down, and then converts the linear motion into rotational motion. The top end drives the driven rod to rotate, and the rotational torque is transmitted to the first motor and converted into electrical energy.

[0016] A further technical solution of the present invention is that the length ratio of the connecting rod and the driven rod is 2.69.

[0017] A further technical solution of the present invention is: a flywheel and a gear box are installed between the driven rod and the first motor, the flywheel is used to adjust the speed of the first motor and ensure the continuity of rotation; the gear box is used to make the first motor work at the rated speed.

[0018] A further technical solution of the present invention is that the cross-sections of the first shell and the second shell on one side of the slide groove are both V-shaped, and the two V-shaped tips are opposite to each other, so that the flow channel between the two shells is in the form of first converging and then expanding, so as to increase the fluid flow rate in the vibrator movement area.

[0019] A further technical solution of the present invention is: the first shell and the second shell are relatively installed at the bottom of the cover plate, and a rectifier and a load are provided on the cover plate. The high-speed energy capture module and the low-speed energy capture module are electrically connected to the rectifier device respectively, and the current passes through the rectifier device to power the load.

[0020] Beneficial effects

[0021] The beneficial effects of the present invention lie in the following: The device, which provides a flow-induced vibration collaborative energy harvesting device based on dual mechanical transmission mechanisms (a high-speed energy harvesting module and a low-speed energy harvesting module), achieves efficient energy harvesting in complex and changing flow environments. Different flow environments, corresponding to different vibration states, require different energy harvesting modules for efficient energy harvesting.

[0022] The two mechanical structures can cope with different vibration conditions. When the vibration speed is high, the transmission mechanism is prone to instability. Therefore, a crank-slider mechanism with high stability and quick return characteristics is adopted. By adjusting the relative length of the cranks, different motion patterns can be obtained to improve the mechanical transmission efficiency and thus the energy capture efficiency. When the vibration speed is low, a highly sensitive transmission mechanism is required. Therefore, a gear rack assembly with fast speed response is adopted. The gear rack assembly can ensure a constant instantaneous transmission ratio. When the oscillator vibrates at low speed and the speed is unstable, it can also respond quickly and obtain stable transmission efficiency, thereby improving the mechanical transmission efficiency and thus the energy capture efficiency.

[0023] In addition, the present invention designs the cross-sections of the two shells to have an hourglass-like structural feature (i.e., the fluid flow path is a structure that first converges and then expands). The flow velocity will increase in the vibrator movement area, which can achieve passive flow control and enhance the amplitude of the vibrator, which means that the mechanical energy of the vibrator is increased, and the mechanical energy can be converted into more electrical energy, thereby improving the energy capture power.

[0024] The energy-harvesting modules at both ends of the oscillator are relatively independent, and have a simple structure, high feasibility, and strong adaptability. The invention can be applied to electrical devices such as marine observation equipment and offshore light buoys, as well as to marine ranching, marine chemical industry, and seawater desalination. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the overall three-dimensional structure of the flow-induced vibration coordinated energy capture device based on dual mechanical transmission mechanisms according to an embodiment of the present invention;

[0026] Figure 2 A schematic structural diagram of two sets of mechanical transmission device components according to an embodiment of the present invention;

[0027] Figure 3 Schematic diagram of the structure of the first housing, the second housing and the vibrator according to an embodiment of the present invention;

[0028] Figure 4 This is a schematic structural diagram of a cover plate, a rectifier device, and an electrical device according to an embodiment of the present invention;

[0029] Figure 5 Schematic diagram of the structure of the first support member and the second support member according to an embodiment of the present invention.

[0030] Explanation of the accompanying drawings: 1. electrical device; 2. rectifier; 3. cover plate; 31. wire hole; 4. first shell; 41. first support plate; 42. first V-shaped structure; 43. first rectangular slide; 5. vibrator; 51. first slider; 52. second slider; 6. second shell; 61. second V-shaped structure; 62. second rectangular slide; 7. crank slider mechanism assembly; 71. first motor; 72. gear box; 73. connecting shaft; 74. flywheel; 75. driven rod; 76. connecting rod; 77. first spring; 8. rack and pinion mechanism assembly; 81. second spring; 82. first gear; 83. second gear; 84. second pin; 85. third gear; 86. second motor; 87. third pin; 88. rack; 89. first pin; 9. support assembly; 91. first support member; 92. second support member; 921. second support plate. DETAILED DESCRIPTION

[0031] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0032] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0033] Based on the fact that traditional flow-induced vibration energy harvesting devices often have poor adaptability to the electromechanical system environment, when the vibration speed is slow, the energy harvesting efficiency is reduced due to the slow transmission response; when the vibration speed is fast, stress will be generated on the transmission components, thereby reducing the energy conversion efficiency, which is not conducive to energy harvesting. The present invention provides a flow-induced vibration collaborative energy harvesting device based on a dual mechanical transmission mechanism, including a high-speed energy harvesting module and a low-speed energy harvesting module coupled to the two ends of the vibrator, which completes flow-induced vibration energy harvesting under different working conditions through collaborative work, and converts the acquired energy into electrical energy and transmits it to the load; when the vibrator vibrates at low speed, the low-speed energy harvesting module is used as the main method and the high-speed energy harvesting module is used as the auxiliary method to carry out flow-induced vibration energy harvesting; when the vibrator vibrates at high speed, the high-speed energy harvesting module is used as the main method and the low-speed energy harvesting module is used as the auxiliary method to carry out flow-induced vibration energy harvesting.

[0034] Preferably, it also includes two oppositely arranged shells, with slide grooves opened in the vertical direction on the opposite surfaces of the two shells, and the two ends of the vibrator are suspended in the slide grooves of the two shells by springs respectively, and can move back and forth along the slide grooves; one end of the vibrator passes through the slide groove of the first shell and is connected to the low-speed energy capture module inside it, and the other end passes through the slide groove of the second shell and is connected to the high-speed energy capture module inside it.

[0035] Preferably, two sliders are respectively provided at both ends of the vibrator; one end of the first spring is fixed to the top wall of the slide groove of the first shell, and the bottom end is connected to the first slider; the other end of the second spring is fixed to the top wall of the slide groove of the second shell, and the bottom end is connected to the second slider.

[0036] Preferably, the low-speed energy capture module is a gear rack mechanism assembly, including a rack fixed to one end of the vibrator, a gear set meshing with the rack, and a second motor. The rack is driven to move up and down by the vibrator, thereby driving the first gear, the second gear, and the third gear meshing in sequence in the gear set to rotate, and the third gear transmits the torque to the second motor and converts it into electrical energy. The transmission ratio of the first gear, the second gear, and the third gear in the gear set is 9.65, and the vibrator speed is v. When the vibrator movement speed is 0.1m / s, it is known from the formula v=wr that the first gear speed is 112 rpm. After the secondary gear acceleration, the third gear speed is 1083 rpm. The third gear is fixedly connected to the motor, so the motor shaft speed is also 1083 rpm.

[0037] Preferably, the high-speed energy capture module is a slider-crank mechanism assembly, comprising a connecting rod rotatably connected to the other end of the oscillator, a driven rod rotatably connected to the top of the connecting rod, and a first motor. The oscillator drives the bottom end of the connecting rod to reciprocate up and down, thereby converting linear motion into rotational motion. The top of the connecting rod then rotates the driven rod, transmitting the rotational torque to the first motor and converting it into electrical energy. The length ratio of the connecting rod to the driven rod is 2.69.

[0038] Preferably, a flywheel and a gear box are installed between the driven rod and the first motor, and the flywheel is used to adjust the rotation speed of the first motor and ensure the continuity of rotation; the gear box is used to make the first motor work at the rated speed.

[0039] Preferably, the cross-sections of the first and second shells on one side of the slide groove are both V-shaped, and the two V-shaped tips are opposite, so that the flow channel between the two shells is in the form of first converging and then expanding, so as to increase the fluid flow rate in the vibrator movement area.

[0040] Preferably, the first shell and the second shell are relatively installed at the bottom of the cover plate, and a rectifier and a load are provided on the cover plate. The high-speed energy capture module and the low-speed energy capture module are electrically connected to the rectifier respectively, and the current passes through the rectifier to supply power to the load.

[0041] The above technical solution is further described below with reference to the accompanying drawings:

[0042] Reference Figure 1As shown, in this embodiment, a flow-induced vibration collaborative energy capture device based on a dual mechanical transmission mechanism includes a first shell 4, a second shell 6, a vibrator 5, a cover plate 3, a crank slider mechanism assembly 7, a gear rack mechanism assembly 8, a support assembly 9, a rectifier 2 and an electrical device 1; the first shell 4 and the second shell 6 are arranged opposite to each other, and are both fixedly connected to the cover plate 3 through connecting holes and screws; one end of the vibrator 5 is placed on the first shell 4, and the other end is placed on the second shell 6. When the fluid passes through, the vibrator 5 generates flow-induced vibration in the area between the first shell 4 and the second shell 6; the crank slider mechanism assembly 7 is connected to one end of the vibrator 5, and the gear rack mechanism assembly 8 is connected to the other end of the vibrator 5. When the fluid passes through, the single degree of freedom motion of the vibrator 5 drives the crank slider mechanism assembly 7 and the gear rack mechanism assembly 8 to move; the rectifier 2 and the electrical device 1 are fixedly arranged on the cover plate 3; the crank slider mechanism assembly 7 and the gear rack mechanism assembly 8 are both circuit-connected to the rectifier 2, and the current passes through the rectifier 2 to power the electrical device 1.

[0043] Reference Figure 2 As shown, a first slider 51 and a second slider 52 are respectively provided at both ends of the vibrator 5 .

[0044] Reference Figure 1 and Figure 2 The crank slider mechanism assembly 7 includes a first motor 71, a gear box 72, a connecting shaft 73, a flywheel 74, a driven rod 75, a connecting rod 76, and a first spring 77; one end of the first spring 77 can be fixed to the first slider 51 of the vibrator 5 by a screw, and the other end can also be fixed to the first housing 4 by a screw. The first spring 77 provides the restoring force required for the vibrator movement. The connecting rod 76 and the vibrator 5 can be rotatably connected by a bearing, and the connecting rod 76 and the driven rod 75 can also be rotatably connected by a bearing. One end of the connecting shaft 73 is fixedly connected to the driven rod 75, and the other end is connected to the gear box 72 through a connecting piece. The gear box 72 is connected to the first motor 71 through the connecting piece. The flywheel 74 can also be fixedly installed on the connecting shaft 73 by a key block. The flywheel 74 can not only be used for speed regulation, but also help the motion mechanism to break through the dead point and ensure the continuity of motion.

[0045] Reference Figure 1 and Figure 2The rack and pinion mechanism assembly 8 includes a second motor 86, a second spring 81, a rack 88, a first gear 82, a second gear 83, a third gear 85, a first pin 89, a second pin 84, and a third pin 87; the support assembly 9 includes a first support member 91 and a second support member 92; one end of the second spring 81 can be fixedly connected to the second slider 52 of the vibrator 5 by a screw, and the other end can also be fixedly connected to the second housing 6 by a screw. The second spring 81 provides the vibrator 5 with the restoring force required for movement. The first pin 89 and the second pin 84 are both fixed between the first support member 91 and the second support member 92, the third pin 87 is fixed on the first support member 91, the first pin 89 and the first gear 82 can be rotatably connected via a bearing, the second pin 84 and the second gear 83 can be rotatably connected via a bearing, the third pin 87 and the third gear 85 can be rotatably connected via a bearing, the third gear 85 is fixedly connected to the main shaft of the second motor 86, and transmits the rotational torque to the second motor 86; the first support member 91 and the second support member 92 are both fixedly connected to the second housing 6 via screws.

[0046] Reference Figure 4 As shown, a wire hole 31 is provided on the cover plate 3.

[0047] Furthermore, the cover plate 3 is provided with a connection hole.

[0048] Reference Figure 3 As shown, the V-shaped structure 42 of the first housing 4 and the V-shaped structure 61 of the second housing 6 form a narrow channel between the two housings, with wide sides and a cross-section similar to an hourglass. Therefore, when fluid passes through, it inevitably undergoes a process of acceleration, which enhances the interaction between the fluid and the structure, thereby increasing the total energy capture power. The first housing 4 and the second housing 6 are both equipped with rectangular chute structures 43 and 62 for accommodating the vibrator 5. The first and second sliders 51 and 52 at the ends of the vibrator 5 move within the rectangular chute 43 and 62, respectively.

[0049] Furthermore, a connecting hole is provided on the side wall of the first shell 4, and the first shell 4 and the cover plate 3 are fixedly connected through the connecting hole and screws.

[0050] Furthermore, a first support plate 41 is provided in the first housing 4 . The first support plate 41 is provided with connection holes. The first motor 71 and the gear box 72 are fixedly connected to the first support plate 41 through the connection holes and screws.

[0051] Furthermore, a connecting hole is provided on the side wall of the second shell 6, and the cover plate 3 and the second shell 6 are fixedly connected through the connecting hole and screws.

[0052] Reference Figure 5As shown, a connecting hole is provided on the first support member 91, a second support plate 921 and a connecting hole are provided on the second support member 92, a connecting hole is provided at the bottom of the second shell 6, the first support member 91 is fixedly connected to the second shell 6 through the connecting hole and screws, and the second support member 92 is fixedly connected to the second shell 6 through the connecting hole and screws.

[0053] Furthermore, a connecting hole is provided on the second support plate 921 , and the second motor 86 is fixedly connected to the second support plate 921 via the connecting hole and screws.

[0054] Furthermore, the wire hole 31 can pass wires from the first motor 71 and the second motor 86 , and the wires are all connected to the rectifier device 2 .

[0055] Furthermore, electronic equipment such as motors and wires need to be watertight during actual use, such as adding watertight connectors and other watertight equipment to the electronic equipment to prevent electronic circuit failure and ensure the normal operation of the energy capture device.

[0056] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A flow-induced vibration collaborative energy capture device based on a dual mechanical transmission mechanism, characterized by: It includes a high-speed energy harvesting module and a low-speed energy harvesting module coupled to both ends of the vibrator. Through collaborative work, they complete flow-induced vibration energy harvesting under different working conditions and convert the harvested energy into electrical energy to transmit to the load. When the vibrator vibrates at a low speed, the low-speed energy harvesting module is used as the main method, and the high-speed energy harvesting module is used as the auxiliary method to perform flow-induced vibration energy harvesting. When the vibrator vibrates at high speed, the high-speed energy harvesting module is used as the main component and the low-speed energy harvesting module is used as the auxiliary component to perform flow-induced vibration energy harvesting; It also includes two oppositely arranged shells, with slide grooves opened in the vertical direction on the opposite surfaces of the two shells. The two ends of the vibrator are suspended in the slide grooves of the two shells by springs and can reciprocate along the slide grooves; one end of the vibrator passes through the slide groove of the first shell and is connected to the low-speed energy capture module therein, and the other end passes through the slide groove of the second shell and is connected to the high-speed energy capture module therein; The low-speed energy capture module is a rack and pinion mechanism assembly, including a rack fixed to one end of the vibrator, a gear set meshing with the rack, and a second motor. The vibrator drives the rack to reciprocate up and down, thereby driving the first gear, second gear, and third gear meshed in sequence in the gear set to rotate. The third gear transmits the rotational torque to the second motor and converts it into electrical energy. The high-speed energy capture module is a crank slider mechanism assembly, including a connecting rod rotatably connected to the other end of the vibrator, a driven rod rotatably connected to the top end of the connecting rod, and a first motor. The vibrator drives the bottom end of the connecting rod to reciprocate up and down, thereby converting the linear motion into rotational motion. The top end drives the driven rod to rotate, and the rotational torque is transmitted to the first motor and converted into electrical energy.

2. The flow-induced vibration collaborative energy capture device based on a dual mechanical transmission mechanism according to claim 1, characterized in that: Two sliders are respectively provided at both ends of the vibrator; one end of the first spring is fixed to the top wall of the slide groove of the first shell, and the bottom end is connected to the first slider; one end of the second spring is fixed to the top wall of the slide groove of the second shell, and the bottom end is connected to the second slider.

3. The flow-induced vibration coordinated energy capture device based on a dual mechanical transmission mechanism according to claim 1, characterized in that: The transmission ratio i of the first gear, the second gear and the third gear in the gear set is 9.

65.

4. The flow-induced vibration coordinated energy capture device based on a dual mechanical transmission mechanism according to claim 1, characterized in that: The length ratio of the connecting rod to the driven rod is 2.

69.

5. The flow-induced vibration coordinated energy capture device based on a dual mechanical transmission mechanism according to claim 4, characterized in that: A flywheel and a gear box are installed between the driven rod and the first motor. The flywheel is used to adjust the rotation speed of the first motor and ensure the continuity of rotation; the gear box is used to make the first motor work at the rated speed.

6. A flow-induced vibration coordinated energy capture device based on a dual mechanical transmission mechanism according to any one of claims 2 to 5, characterized in that: The cross-sections of the first and second shells on one side where the slide groove is provided are both V-shaped, and the two V-shaped tips are opposite to each other, so that the flow channel between the two shells converges first and then expands, thereby increasing the fluid flow rate in the vibrator movement area.

7. The flow-induced vibration coordinated energy capture device based on a dual mechanical transmission mechanism according to claim 6, characterized in that: The first shell and the second shell are relatively installed at the bottom of the cover plate, and a rectifier and a load are provided on the cover plate. The high-speed energy capture module and the low-speed energy capture module are electrically connected to the rectifier respectively, and the current passes through the rectifier to supply power to the load.

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