A bidirectional self-locking motor for a height-adjustable desk

Abstract

This utility model discloses a bidirectional self-locking motor for a height-adjustable desk, including a front cover (1) and a rear cover (2). A stator (3) is provided between the front cover (1) and the rear cover (2). Multiple coils (4) are provided in the stator (3). A rotor (5) is provided inside the stator (3). Multiple permanent magnets (6) are provided on the outside of the rotor (5). A rotating shaft (7) is provided on the axis of the rotor (5). A first ball bearing (8) is provided between the rotating shaft (7) and the rear cover (2). A spring washer (9) and a friction plate (10) are provided in sequence on the rear side of the first ball bearing (8). A screw (11) is provided on the rear side of the friction plate (10). A screw groove is opened at the front end of the rotating shaft (7) to form a worm (12). A worm wheel (13) is provided on one side of the worm (12). The worm wheel (13) is connected to the front cover (1) through a bracket (14). This utility model has the advantages of convenient installation, low failure rate, low noise, and bidirectional self-locking function.

Description

Technical Field

[0001] This utility model belongs to the field of height-adjustable table motors, and particularly relates to a bidirectional self-locking motor for height-adjustable tables. Background Technology

[0002] The lifting power of an adjustable desk comes from a motor. Currently, most motors used in adjustable desks are brushed motors. Their structure includes the motor body, within which coils are fixed to the rotor, permanent magnets are fixed to the stator, and a worm gear is located at the output end of the motor body. A bracket is mounted on the outer shell of the motor body, and a worm wheel that meshes with the worm gear rotates on the bracket. The motor body drives the worm gear to rotate, which in turn drives the worm wheel. The rotational force of the worm wheel is converted into a vertical force through another mechanism, thus raising or lowering the desk. Customers use a controller on the adjustable desk to start the motor and control the height adjustment range.

[0003] In practice, it has been found that existing motors, due to their compact structure and externally mounted drive board, present inconvenience for installation. Brushed motors generally produce significant noise (around 56 dB) due to brush friction during operation. To increase the lifting speed of the table, the worm gear has a large helix angle, preventing self-locking between the worm and worm wheel. This results in low friction between them, causing relative movement even under heavy loads on the table. This leads to an unintended decrease in table height, altering the set operating height and resulting in poor performance. Furthermore, in certain situations, when moving the table, the lack of self-locking between the worm and worm wheel means that if the lifting part of the table rests on the tabletop, movement between them will also occur, causing an unintended increase in table height, again altering the set operating height and leading to poor performance. Utility Model Content

[0004] The purpose of this invention is to provide a bidirectional self-locking motor for height-adjustable desks. This invention has the advantages of easy installation, low failure rate, low noise, and bidirectional self-locking function.

[0005] The technical solution of this utility model is as follows: A bidirectional self-locking motor for a height-adjustable desk includes a front cover and a rear cover. A stator is provided between the front cover and the rear cover. The stator has multiple circumferentially distributed coils. A rotor is provided inside the stator. Multiple circumferentially distributed permanent magnets are provided on the outer side of the rotor. A rotating shaft is provided on the axis of the rotor. A first ball bearing is provided between the rotating shaft and the rear cover. A spring washer and a friction plate are provided in sequence on the rear side of the first ball bearing. A screw for connecting the rear cover is provided on the rear side of the friction plate. The front end of the rotating shaft extends out of the front cover and has a threaded groove to form a worm. A worm wheel is provided on one side of the worm. The worm wheel is connected to the front cover through a bracket. The worm wheel and the bracket are rotatably connected.

[0006] In the aforementioned bidirectional self-locking motor for lifting tables, the stator includes multiple stacked first steel sheets, and at least two channels are provided on the outer side of the stator. A screw is provided in the channel, and the screw passes through the rear cover and the channel in sequence and then connects to the front cover.

[0007] In the aforementioned bidirectional self-locking motor for lifting tables, the rotor includes multiple second steel plates stacked together and tightly fitted through by a rotating shaft. Multiple through slots are provided on the outer circumferential surface of the rotor, and permanent magnets are provided in the through slots.

[0008] In the aforementioned bidirectional self-locking motor for lifting tables, the inner diameter of the stator is 18-22mm, and multiple wire grooves are provided on the inner wall of the stator. Ribs are formed between adjacent wire grooves, and the coil is wound on the corresponding ribs.

[0009] In the aforementioned bidirectional self-locking motor for lifting tables, the outer diameter of the rotor is 1.5-3.5mm smaller than the inner diameter of the stator. Multiple permanent magnets are provided on the outer circumferential surface of the rotor. The outer circumferential surface of the permanent magnets is composed of a bottom surface, a top surface, and two side surfaces. The bottom surface and the two side surfaces are both planes. The bottom surface is located inside the rotor, and the top surface is located outside the rotor. The inner ends of the two side surfaces are connected through the bottom surface, and the outer ends of the two side surfaces are connected through the top surface. The bottom surface is 5.0-5.4mm wide, the included angle between the two side surfaces is 40-50°, the top surface protrudes outward in the middle, the radius of the top surface is 5.5-7.2mm, and the distance between the permanent magnets and the stator is 0.3-0.9mm.

[0010] In the aforementioned bidirectional self-locking motor for lifting tables, there are six coils, the inner diameter of the stator is 20mm, and six wire slots are provided on the inner wall of the stator.

[0011] The rotor has an outer diameter of 17.5 mm, eight permanent magnets on its outer circumference, a bottom width of 5.2 mm, an included angle of 45° between the two sides, a top radius of 6.0-6.7 mm, a maximum thickness of 1.8 mm for the permanent magnets, and a distance of 0.6 mm between the permanent magnets and the stator.

[0012] In the aforementioned bidirectional self-locking motor for a height-adjustable table, the middle of the rear cover protrudes outward to form a mounting cavity, a first ball bearing is provided in the mounting cavity, the rear end of the rotating shaft is inserted into the first ball bearing, and a second ball bearing is provided between the front cover and the rotating shaft.

[0013] In the aforementioned bidirectional self-locking motor for a height-adjustable table, an annular drive plate is fixed on the inner side of the front cover, and the rotating shaft passes through the drive plate. The drive plate is equipped with a brushless motor drive circuit and a Hall integrated circuit, and the brushless motor drive circuit is connected to a coil.

[0014] Compared with the prior art, the main improvements made by this utility model on the basis of existing motors include the following:

[0015] First, the change from a brushed motor to a brushless motor reduces the friction noise of the brushes. Since brushless motors have the characteristic of high output torque, the axial dimensions of the rotor and stator of this invention can be reduced while maintaining the same output torque. Under the premise of keeping the motor's external dimensions basically unchanged and not affecting the universal installation and use of the motor on the lifting table, a certain amount of space can be left inside the motor to realize the built-in drive ring. This reduces the installation steps of the drive ring on the lifting table, making the motor easier to install. At the same time, the drive ring is better protected to avoid external impact damage, thus reducing the failure rate.

[0016] Secondly, the stator is located between the front and rear covers, and the outer circumferential surface of the stator can be aligned with the outer circumferential surfaces of the front and rear covers, which increases the radial dimension of the stator. Under the premise of keeping the motor output torque unchanged, the axial dimensions of the stator and rotor can be further shortened, leaving more space inside the motor, making it easier to install the drive ring, and improving heat dissipation performance. At the same time, the installed drive ring can be further away from the rotor, reducing heat radiation and further reducing the failure rate of the motor.

[0017] Third, spring washers and friction plates are installed on the bearing side of the rear cover. By tightening the friction plates with screws, the spring washers simultaneously contact the inner and outer rings of the bearing, increasing the rotational resistance of the shaft. This rotational resistance, combined with the friction between the worm gear and worm, achieves bidirectional self-locking of the motor, preventing the height of the lifting table from changing under external force and improving the usability.

[0018] Fourth, by adopting a specific cross-sectional shape of the permanent magnet, the airflow deformation pattern between the stator and rotor is optimized, which has a better effect on noise reduction. Under the condition of background noise of 36dB and distance of 30cm, the motor noise is reduced to 45.4dB, and the noise reduction effect is obvious.

[0019] In summary, this utility model has the advantages of convenient installation, low failure rate, low noise, and bidirectional self-locking function. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of Example 1.

[0021] Figure 2 This is a wiring diagram of the coil in Example 1.

[0022] Figure 3 This is a cross-sectional schematic diagram of the rotor.

[0023] Figure 4 This is a schematic diagram of the cross-sectional dimensions of the permanent magnet in Example 1.

[0024] Figure 5 This is a schematic diagram of the cross-sectional dimensions of the permanent magnet in Example 5.

[0025] The labels in the attached diagram are as follows: 1-Front cover, 2-Rear cover, 3-Stator, 4-Coil, 5-Rotor, 6-Permanent magnet, 7-Shaft, 8-First ball bearing, 9-Spring pad, 10-Friction plate, 11-Screw, 12-Worm, 13-Worm wheel, 14-Bracket, 15-Screw, 16-Firming plate, 17-Mounting cavity, 18-Second ball bearing, 19-Drive plate. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0027] Example 1: A bidirectional self-locking motor for a height-adjustable desk, such as... Figures 1 to 4 As shown, it includes a front cover 1 and a rear cover 2, with a stator 3 located between the front cover 1 and the rear cover 2, and six circumferentially distributed coils 4 located in the stator 3.

[0028] The stator 3 has a rotor 5 inside, and eight circumferentially distributed permanent magnets 6 on the outside of the rotor 5. A rotating shaft 7 is provided on the axis of the rotor 5. A first ball bearing 8 is provided between the rotating shaft 7 and the rear cover 2. A spring pad 9 and a friction plate 10 (made of iron-based powder alloy) are provided in sequence on the rear side of the first ball bearing 8. The spring pad 9 has a flared cross section. A screw 11 for connecting the rear cover 2 is provided on the rear side of the friction plate 10. The front end of the rotating shaft 7 extends out of the front cover 1 and has a screw groove to form a worm 12. A worm wheel 13 is provided on one side of the worm 12. The worm wheel 13 is connected to the front cover 1 through a bracket 14. The worm wheel 13 is rotatably connected to the bracket 14.

[0029] The stator 3 includes multiple stacked first steel sheets, the first steel sheets are made of silicon steel, and the outer side of the stator 3 is provided with at least two channels. The channels can be through holes or slots connecting the outer periphery of the stator 3. A screw 15 is provided in the channel, and the screw 15 passes through the rear cover 2 and the channel in sequence and then connects to the front cover 1.

[0030] The rotor 5 includes multiple second steel sheets stacked together and tightly fitted through the rotating shaft 7. The second steel sheets are made of silicon steel. Multiple through slots are provided on the outer circumferential surface of the rotor 5, and permanent magnets 6 are provided in the through slots.

[0031] The stator 3 has an inner diameter of 20mm. Six wire grooves are provided on the inner wall of the stator 3, and ribs 16 are formed between adjacent wire grooves. The coil 4 is wound on the corresponding ribs 16.

[0032] The outer diameter of the rotor 5 is 17.5 mm. The outer peripheral surface of the permanent magnet 4 is composed of a bottom surface, a top surface, and two side surfaces. The bottom surface and the two side surfaces are both planes. The bottom surface is located inside the rotor 11, and the top surface is located outside the rotor 11. The inner ends of the two side surfaces are connected through the bottom surface, and the outer ends of the two side surfaces are connected through the top surface. The bottom surface is 5.2 mm wide, the included angle between the two side surfaces is 45°, the top surface protrudes outward in the middle, the radius of the top surface is 6.35 mm, the thickest part of the permanent magnet 4 is 1.8 mm, and the distance between the permanent magnet 4 and the stator 10 is 0.6 mm.

[0033] The rear cover 2 protrudes outward in the middle to form a mounting cavity 17. A first ball bearing 8 is provided in the mounting cavity 17. The rear end of the rotating shaft 7 is inserted into the first ball bearing 8. A second ball bearing 18 is provided between the front cover 1 and the rotating shaft 7. The front side of the first ball bearing 8 and the front and rear sides of the second ball bearing 18 are provided with retaining rings for connecting the rotating shaft 7. The retaining rings are used to restrict the axial movement of the rotating shaft 5.

[0034] An annular drive plate 22 is fixed to the inner side of the front cover 1. The rotating shaft 5 passes through the drive plate 22. The drive plate 22 is equipped with a brushless motor drive circuit (existing circuit) and a Hall integrated circuit (existing circuit). The brushless motor drive circuit is connected to the coil 3. The motor in Embodiment 1 is a brushless motor, driven by the brushless motor drive circuit. The Hall integrated circuit is used to detect the motor's speed and direction, which can be fed back to the original controller of the lifting platform. The controller can know the motor's operating status and thus the lifting stroke of the lifting platform. After reaching the set height, the motor stops. The method for the Hall integrated circuit to detect the motor's direction and speed is described in patent application document No. 202411299088.1. The external wiring harness of the brushless motor drive circuit and the external wiring harness of the Hall integrated circuit are combined and extend out of the front cover 1 to connect to the controller of the lifting table.

[0035] When screw 11 is tightened, the spring washer 9 simultaneously contacts the inner and outer rings of the first ball bearing 8, establishing a frictional connection between them. The tighter screw 11 is tightened, the greater the friction, making it less likely for the first ball bearing 8 to roll, and consequently, less likely for the shaft 7 to rotate. The rotational resistance of the shaft 7, combined with the self-locking force of the worm gear, achieves bidirectional self-locking of the motor. While ensuring the motor's self-locking capability, excessive tightening of screw 11 should be avoided to prevent excessive rolling resistance in the first ball bearing 8. The degree of tightening can be determined through a simple experiment.

[0036] The main differences between Example 1 and existing motors are as follows:

[0037] First, replace the brushed motor with a brushless motor.

[0038] Second, the motor is built into the drive board 22.

[0039] Third, spring pads and friction plates are set to achieve bidirectional self-locking of the motor.

[0040] Example 2: Compared with Example 1, the drive board 22 is located outside the motor.

[0041] Example 3: Compared with Example 1, the Hall integrated circuit on the driver board 22 is removed. In this case, the controller can be removed from the lifting table, and a switch is used to control the motor start-up state and forward and reverse rotation state.

[0042] Example 4: Compared to Example 1, the driver board 22 is equipped with an XH2.54 (1x5p) socket. The brushless motor drive circuit and Hall effect integrated circuit are both connected to the XH2.54 (1x5p) socket. This socket is small in size and suitable for use in confined spaces. It includes five pins: 29V, GND, 5V, serial port Tx, and serial port Rx. The controller has an MX4.2 (2x3p) socket, and the wiring harness connects the X4.2 (2x3p) socket and the XH2.54 (1x5p) socket.

[0043] The MX4.2 (2x3p) is used in many height-adjustable desk controllers, but it hasn't been used in conjunction with the XH2.54 yet, mainly due to concerns about potentially excessive current draw. This application uses it in conjunction with the XH2.54 because the motor in this application is a brushless motor. This interface is used as an input for brushless motors, while it's used as an output for brushed motors. For example, if the input is 29V 2A, and the output voltage is only 14.5V, a 4A output is required. The output voltage will vary depending on the motor speed, while the input voltage is fixed. When used with a brushed motor, the 4A current draw of the XH2.54 is too high, while with a brushless motor, the 2A current draw of the XH2.54 is not excessive. By using the XH2.54, the number of interface positions on the driver board 22 is reduced, better meeting the needs of confined spaces.

[0044] The power line (29V) and 5V, Tx, Rx are separated by GND, which isolates the power supply and signal, improving anti-interference and EMC performance.

[0045] Example 4 primarily addresses the challenge of integrating the driver board 22 into the motor while maintaining a similar size and output torque to existing motors. Integrating the driver board 22 within the motor provides better protection and reduces installation difficulty. The primary goal is to reduce the size of the driver board 22, which can be achieved through methods such as using an XH2.54 socket, external power supply, using a pre-driven chip in the brushless motor drive circuit, employing a single-resistor sampling algorithm, and implementing sensorless control. Considering heat dissipation in a confined environment, the drive power supply and 5V MCU power supply included on the driver board 22 can be externally powered, and larger MOSFETs (TO-252) can be used to reduce losses and increase heat dissipation.

[0046] Example 5: Compared with Example 1, the cross-sectional dimensions of the permanent magnet are changed as follows. Figure 5 As shown, the radius of the top surface is changed to 9.35mm.

[0047] Noise tests were conducted on Examples 1 and 5 under the following conditions: ambient noise level of 36 dB and a distance of 30 cm from the motor. Example 5 had a noise level of 50.6 dB, while Example 1 had a noise level of 45.4 dB. Both are quieter than existing motors, with Example 1 being superior.

[0048] In other comparative experiments, one or more cross-sectional dimensions of the permanent magnet were adjusted multiple times. The final tests revealed that Example 1 had the best noise reduction effect, with the top surface radius having the greatest impact on noise. For example, when the top surface radius was changed to 20mm, 8.5mm, 7.2mm, and 5.5mm, the noise levels were 50.1db, 48.4db, and 48.2db, respectively. Excluding the noise reduction caused by converting a brushed motor to a brushless motor, the actual range for further noise reduction due to improvements in the top surface radius should be between 5.5 and 7.2mm.

[0049] In the description of this utility model, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

Claims

1. A bidirectional self-locking motor for a height-adjustable desk, characterized in that: The device includes a front cover (1) and a rear cover (2). A stator (3) is provided between the front cover (1) and the rear cover (2). Multiple circumferentially distributed coils (4) are provided in the stator (3). A rotor (5) is provided inside the stator (3). Multiple circumferentially distributed permanent magnets (6) are provided on the outside of the rotor (5). A rotating shaft (7) is provided on the axis of the rotor (5). A first ball bearing (8) is provided between the rotating shaft (7) and the rear cover (2). A spring washer (9) and a friction plate (10) are provided on the rear side of the first ball bearing (8). A screw (11) for connecting the rear cover (2) is provided on the rear side of the friction plate (10). The front end of the rotating shaft (7) extends out of the front cover (1) and forms a worm (12) by opening a screw groove. A worm wheel (13) is provided on one side of the worm (12). The worm wheel (13) is connected to the front cover (1) through a bracket (14). The worm wheel (13) is rotatably connected to the bracket (14).

2. The bidirectional self-locking motor for a height-adjustable desk according to claim 1, characterized in that: The stator (3) includes multiple stacked first steel sheets. The stator (3) has at least two channels on its outer side. A screw (15) is provided in the channel. The screw (15) passes through the rear cover (2) and the channel in sequence and then connects to the front cover (1).

3. The bidirectional self-locking motor for a height-adjustable desk according to claim 2, characterized in that: The rotor (5) includes multiple second steel plates stacked together and tightly fitted through by the rotating shaft (7). Multiple through slots are provided on the outer circumferential surface of the rotor (5), and permanent magnets (6) are provided in the through slots.

4. The bidirectional self-locking motor for a height-adjustable desk according to claim 3, characterized in that: The inner diameter of the stator (3) is 18-22mm. Multiple wire grooves are provided on the inner wall of the stator (3), and ribs (16) are formed between adjacent wire grooves. The coil (4) is wound on the corresponding ribs (16).

5. The bidirectional self-locking motor for a height-adjustable desk according to claim 4, characterized in that: The outer diameter of the rotor (5) is 1.5-3.5 mm smaller than the inner diameter of the stator (3). Multiple permanent magnets (6) are provided on the outer circumferential surface of the rotor (5). The outer circumferential surface of the permanent magnet (6) is composed of a bottom surface, a top surface and two side surfaces. The bottom surface and the two side surfaces are both planes. The bottom surface is located inside the rotor (5) and the top surface is located outside the rotor (5). The inner ends of the two side surfaces are connected through the bottom surface and the outer ends of the two side surfaces are connected through the top surface. The bottom surface is 5.0-5.4 mm wide and the included angle between the two side surfaces is 40-50°. The top surface protrudes outward in the middle and has a radius of 5.5-7.2 mm. The distance between the permanent magnet (6) and the stator (3) is 0.3-0.9 mm.

6. The bidirectional self-locking motor for a height-adjustable desk according to claim 5, characterized in that: There are six coils (4), the inner diameter of the stator (3) is 20mm, and the inner wall of the stator (3) is provided with six wire slots. The rotor (5) has an outer diameter of 17.5 mm, eight permanent magnets (6) are provided on the outer circumference of the rotor (5), the bottom width is 5.2 mm, the included angle between the two sides is 45°, the radius of the top surface is 6.0-6.7 mm, the thickest part of the permanent magnet (6) is 1.8 mm, and the distance between the permanent magnet (6) and the stator (3) is 0.6 mm.

7. The bidirectional self-locking motor for a height-adjustable desk according to claim 5, characterized in that: The rear cover (2) protrudes outward in the middle to form an installation cavity (17). A first ball bearing (8) is provided in the installation cavity (17). The rear end of the rotating shaft (7) is inserted into the first ball bearing (8). A second ball bearing (18) is provided between the front cover (1) and the rotating shaft (7).

8. The bidirectional self-locking motor for a height-adjustable desk according to any one of claims 1 to 7, characterized in that: The inner side of the front cover (1) is fixed with an annular drive plate (19), and the rotating shaft (7) passes through the drive plate (19). The drive plate (19) is provided with a brushless motor drive circuit and a Hall integrated circuit. The brushless motor drive circuit is connected to the coil (4).

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