Linear drive apparatus and method of controlling and using same for solar energy tracking

Abstract

A linear drive apparatus is provided. The linear drive apparatus may include an outer tube, a sealing end cap provided at the end of the outer tube, a screw provided in the outer tube, a drive nut provided on the screw in a threaded fit, an extension rod provided between the outer tube and the screw, a sealing assembly provided between the extension rod and the sealing end cap, and a waterproof and oil-proof ventilation stopper provided on the outer tube. One end of the screw may be connected to a drive mechanism. One end of the extension rod may be connected to the drive nut. The other end of the extension rod may pass through the sealing end cap.

Claims

1. A linear drive apparatus, comprising: an outer tube with a first tube end and a second tube end, the outer tube including a front section extending from the second tube end and a back section extending from the first tube end; a sealing end cap provided at the first tube end; a screw provided in the outer tube, a first end of the screw connected to a drive mechanism; a drive nut provided on the screw in a threaded fit therewith; an extension rod provided between the outer tube and the screw, one end of the extension rod connected to the drive nut and the other end thereof passing through the sealing end cap; a sealing assembly provided between the extension rod and the sealing end cap; and a waterproof and oil-proof ventilation stopper provided on the outer tube, wherein: the length-diameter ratio of the screw is 20-25; the length-diameter ratio of the drive nut is 3-5; and a wear resistant rust-proof layer is provided on a surface of the extension rod.

2. A linear drive apparatus, comprising: an outer tube with a first tube end and a second tube end, the outer tube including a front section extending from the second tube end and a back section extending from the first tube end; a sealing end cap provided at the first tube end; a screw provided in the outer tube, a first end of the screw connected to a drive mechanism; a drive nut provided on the screw in a threaded fit therewith; an extension rod provided between the outer tube and the screw, one end of the extension rod connected to the drive nut and the other end thereof passing through the sealing end cap; a sealing assembly provided between the extension rod and the sealing end cap; a waterproof and oil-proof ventilation stopper provided on the outer tube; a single-row tapered roller bearing provided in the outer tube; an outer ring of the single-row tapered roller bearing connected to an inner wall of the outer tube; an inner ring of the single-row tapered roller bearing fitted with the screw; a sliding bearing provided between the extension rod and the sealing end cap; and a dustproof ring provided at an end of the sealing end cap distal to the outer tube and between the extension rod and the sealing end cap, wherein the sealing assembly is provided between the dustproof ring and the sliding bearing.

3. The linear drive apparatus of claim 1, wherein the drive mechanism is a DC motor with a planet reduction gear and Hall signal feedback, and a power output terminal of the DC motor is connected to the first end of the screw through a coupling.

4. The linear drive apparatus of claim 2, wherein the drive mechanism is a DC motor with a planet reduction gear and Hall signal feedback, and a power output terminal of the DC motor is connected to the first end of the screw through a coupling.

5. The linear drive apparatus of claim 3, wherein: the first end of the screw is positioned in the front section of the outer tube and is in a drive connection with the DC motor through the coupling, the extension rod is positioned in the back section of the outer tube, a first O-shaped sealing ring is provided between the sealing end cap and the first tube end of the outer tube, and a sealing ring is provided between the screw and an interface of the coupling.

6. The linear drive apparatus of claim 4, wherein: the first end of the screw is positioned in the front section of the outer tube and is in a drive connection with the DC motor through the coupling, the extension rod is positioned in the back section of the outer tube, a first O-shaped sealing ring is provided between the sealing end cap and the first tube end of the outer tube, and a sealing ring is provided between the screw and an interface of the coupling.

7. The linear drive apparatus of claim 1, wherein: the extension rod is positioned in the back section of the outer tube, a first O-shaped sealing ring is provided between the sealing end cap and the first tube end of the outer tube, and a sealing ring is provided between the screw and an interface of the coupling.

8. The linear drive apparatus of claim 2, wherein: the extension rod is positioned in the back section of the outer tube, a first O-shaped sealing ring is provided between the sealing end cap and the first tube end of the outer tube, and a sealing ring is provided between the screw and an interface of the coupling.

9. The linear drive apparatus of claim 1, wherein the sealing assembly includes a group of O-shaped sealing rings.

10. The linear drive apparatus of claim 2, wherein the sealing assembly includes a group of O-shaped sealing rings.

11. The linear drive apparatus of claim 3, wherein the sealing assembly includes a group of O-shaped sealing rings.

12. The linear drive apparatus of claim 4, wherein the sealing assembly includes a group of O-shaped sealing rings.

13. The linear drive apparatus of claim 5, wherein the sealing assembly includes a group of O-shaped sealing rings.

14. The linear drive apparatus of claim 6, wherein the sealing assembly includes a group of O-shaped sealing rings.

15. The linear drive apparatus of claim 7, wherein the sealing assembly includes a group of O-shaped sealing rings.

16. The linear drive apparatus of claim 8, wherein the sealing assembly includes a group of O-shaped sealing rings.

Description

DRAWINGS OF THE INVENTION

(1) FIG. 1 is a diagram of a linear drive apparatus in the prior art applied on a solar tracker.

(2) FIG. 2 is a structure diagram of the invention.

(3) FIG. 3 is an enlarged drawing of part A in FIG. 2.

(4) FIG. 4 is an enlarged drawing of part B in FIG. 2.

(5) FIG. 5 is a diagram of a linear drive apparatus of the invention applied on a solar tracker.

(6) FIG. 6 is a connection relation drawing of a linear drive apparatus of the invention.

(7) Reference Signs: 1: Outer Tube, 2: Sealing End Cap, 3: Screw, 4: Drive Nut, 5: Extension Rod, 6: Waterproof And Oil-Proof Ventilation Stopper, 7: Tapered Roller Bearing, 8: Sliding Bearing, 9: Dustproof Ring, 10: DC Motor, 11: Coupling, 12: O-Shaped Sealing Ring, 13: Sealing Ring, 14: Mounting Supporting Lug, 15: Linear Drive Apparatus In Prior Art, 16: Connection Rod, 17 Solar-Energy Panel, 18: Mounting Base:

EMBODIMENTS OF THE INVENTION

(8) With the combination of the following drawings, the invention is described in details.

(9) The invention will be further described in more details and the purposes, the technical solution and the advantages of the invention will be more apparent with the combination of the following drawings and embodiments. It shall be understood that the embodiments described herein are only used for explaining the invention but do not limit the invention.

(10) As shown I FIGS. 1, 2, a linear drive apparatus comprises an outer tube 1 and a sealing end cap 2 provided at the end of the outer tube 1, a mounting support lug 14 is provided on the outer tube, a screw 3 is provided in the outer tube 1, the length-diameter ratio of the screw 3 is 2025, one end of the screw 3 is connected to a drive mechanism, a single-row tapered roller bearing 7 is provided correspondingly in the outer tube 1 and at connection ends between the screw 3 and the drive mechanism, an outer ring of the single-row tapered roller bearing 7 is connected to an inner wall of the outer pipe 1, an inner ring thereof is closely fitted with the screw 3, the drive mechanism is a DC motor 10 with a planet reduction gear and Hall signal feedback, a power output terminal of the DC motor 10 is connected to one end of the screw 3 through a coupling 11, and the sealing ring 13 is provided between the screw 3 and an interface of the coupling 11,

(11) a drive nut 4 is provided on the screw 3 in a threaded fit therewith, an extension rod 5 is provided between the outer tube 1 and the screw 3, a wear-resistant rust-proof layer is provided on a surface of the extension rod 5, one end of the extension rod 5 is connected to the drive nut 4 and the other end thereof passes through the sealing end cap 2, a sealing assembly and a sliding bearing 8 are provided between the extension rod 5 and the sealing end cap 2, a dustproof ring 9 is provided at the end of the sealing end cap 2 and between the extension rod 5 and the sealing end cap 2, the sealing assembly is provided between the dustproof ring 9 and the sliding bearing 8, and the sealing assembly consists of two groups of O-shape sealing rings 12,
wherein the outer tube 1 is in a threaded connection with the front and the back sections thereof and welded into one integral structure, a waterproof and oil-proof ventilation stopper 6 is provided on the back section of the outer tube 1, the front end of the screw 3 is positioned at the front section of the outer tube 1 and is in a drive connection with the DC motor 10 through the coupling 11, the sealing end cap 2 is provided at the end of the back section of the outer tube 1, the extension rod 5 is positioned in the back section of the outer tube 1, and the O-shaped sealing ring 12 is provided between the sealing end cap 2 and the end of the back section of the outer tube 1.

(12) A method for controlling solar tracking with the above linear drive apparatus comprises the following steps: a) determining solar tracking orientation through a controller of a solar tracker firstly, and then determining the current solar angles P1 in different periods through the solar tracking orientation; b) comparing the current solar angle PI with the initial angle P0 of the solar tracker to judge whether the current linear drive apparatus is needed to act, wherein the initial angle of the solar tracker is determined by structure design; c) calculating the number M of pulses tracked this time with a processor according to the current solar angle P1 and the initial angle P0 of the solar tracker, and controlling a motor in the linear drive apparatus to rotate according to the number M of the pulses, if the linear drive apparatus is needed to act; and d) sending to a driver a signal tracked and rotated this time with the processor, driving the motor in the linear drive apparatus to act with the driver after the driver receives a control signal, and determining whether the linear drive apparatus extends or shortens based on the positive-negative voltage of the motor input by the driver. the step c) has a following concrete calculation method: the reduction speed ratio of a planet reduction gear in the linear drive apparatus is firstly determined to be 1:T, an encoder produces N orthogonal coded signals if the motor rotates one circle, the extension rod extends by S after the screw rotates one circle, wherein T is determined based on the adopted planet reduction gear, the number of N of the orthogonal coded signals is determined by the encoder, the extension amount of S of the extension rod obtained through one circle of rotation of the screw is the thread pitch value of the screw, that is to say, when the motor outputs T*N signals, the extension rod extends S mm, each millimeter corresponds to T*N/S pulses. If the reduction speed ratio of the planet reduction gear of the linear drive apparatus is 1:135; two orthogonal coded signals is produced if the motor rotates one circle, and the extension rod extends by 5 mm for each circle, when the DC motor outputs 135*2 signals, the extension tube extends 5 mm, each millimeter corresponds to 54 pulses.

(13) Secondly, as shown in FIGS. 5, 6, the linear drive apparatus, when being in the initial place, has the length of H, the length of the connection between the end of the extension rod and a rotation point of a solar-energy panel through a connection rod is B, the distance between the lower part of the linear drive apparatus and a connection point of a mounting base is Z, the length from the lower part of the linear drive apparatus and the mounting base to the rotation point of the solar-energy panel is A, the length from the lower part of the linear drive apparatus and the connection point of the mounting base 18 to the connection points of the connection rod and the connection rod 16 is C, In an HZC triangle, the change of H directly influences the change of C, in an ABC triangle, A and B are fixed, and the change of C directly influences the angle between A and B, according to the above-mentioned triangle relation, the following relations can be obtained: in the ABC triangle,
C.sup.2=A.sup.2+B.sup.22ABC0S(P), wherein P is the angle of AB,Formula 1 in the HCZ triangle,
C.sup.2=H.sup.2+Z.sup.2,Formula 2 in
H.sup.2=A.sup.2+B.sup.2Z.sup.22ABC0S(P),Formula 3 the structure design determines to track the initial angle, according to the initial angle P0, the initial H0 can be obtained.

(14) If the extension amount is assumed to be y, and the rotating angle of the solar-energy panel is X, the following relation can be obtained:
y=HH0=A.sup.2+B.sup.2Z.sup.22AB COS(X)HO,Formula 4 in Formula 4, A, B, Z and HO are all determined, the arbitrarily given X directly determines the value of y, the positive-negative y determines the tracking direction; if the current solar angle obtained by a controller is P1, and the current angle of the tracker is P0, according to Formula 4: y(p1)y(p)=d, d is the drive amount of the linear drive apparatus this time; finally, M=d*T*N/S is the pulse number of the drive this time, the number of the rotation circles of the motor is obtained according to the pulse number of the drive this time, so that the motor is controlled to be rotated by the driver, so as to obtain the needed amount of the extension or shortening of the extension rod of the linear drive apparatus.

(15) After the controller informs the driver to output drive voltage, it starts to calculate feedback signals of the motor of the linear drive apparatus. When the counting number reaches the number of the pulses driven this time, the controller stops the driver to output the drive voltage, thus completing the tracking task of this time. After the driver receives a stopping signal, the driver stops supplying electricity for the DC motor of the linear drive apparatus. Meanwhile, the driver also starts a brake apparatus in the inner part thereof to rapidly stop the rotation of the DC motor of the linear drive apparatus, so as to avoid the influence on tracking accuracy due to overthrow produced by inertia of the motor.

(16) In the practical application of the solar tracker, as it is operated outdoors for a long time, beside the linear drive apparatus needs higher reliability itself, its control system shall have necessary protection function when the linear drive apparatus is used. A drive control system is provided in the linear drive apparatus. During the operation of the linear drive apparatus, according to its property that its rotation speed (the frequency of a feedback pulse signal) is also changed with the change of the load of the DC motor, the drive control system carries out real-time monitoring for the frequency of the feedback pulse signal, and controls the linear stroke of the extension rod according to the number of the feedback pulse signals. In the practical engineering application, the controller starts a monitoring module while driving the driver. When the controller detects that the frequency of the pulse signal generated by Hall element during the rotation of the motor is decreased, the rotation speed of the motor is indicated to be decreased. When the rotation speed (embodied by pulse frequency) of the motor is lower than the rated value (the rated value can be determined by the frequency of the corresponding feedback signal under the different loads of the driver according to the parameters of the motor), the controller starts the protection module to prevent the driver from overload operation and damage, to realize the timely effective protection for the driver. This function is completed totally by a control program, which neither needs any outer monitoring circuitry nor occupies resources of system hardware.

(17) Moreover, the control system is provided with remote monitoring and controlling functions. The technical and maintenance personnel can monitor the operation state of the linear drive apparatus remotely or on site at any time, and predict and dispose its potential fault, thus greatly reducing the failure rate of the solar tracker.

(18) As to a method for solar tracking with the above linear drive apparatus, when the linear drive apparatus is used, the linear drive apparatus, corresponding to a rotation part of a solar tracker, is mounted at a rotation axis with center-of-gravity shift. With the action of the gravity, the rotation part of the solar tracker, during its whole tracking process, always maintains a pulling or pressing force on the linear drive apparatus. During the tracking, when the linear drive apparatus carries out reversal drive, the method totally eliminates the fabrication tolerance of a transmission of a drive nut of a screw and the impact on tracking precision due to abrasion produced by long-term operation, and decreases the accuracy requirements for processing the drive nut of the screw, so that the linear drive apparatus can keep stabler tracking accuracy for long term.

(19) The above-mentioned are only preferred embodiments of the invention and do not limit the invention. Any modification, equal replacement and improvement made within the spirit and the principle of the invention shall be comprised in the protection scope of the invention.