Submersible geared servo motor

Abstract

To provide a submerged type geared servo motor that enables contact work of a robot in water.SOLUTION: A submerged type geared servo motor 1 requires no need to use a sealing material, and includes: a brushless DC motor 2 subjected to waterproof treatment; a reduction gear 3 provided on a rotary shaft 22 of the brushless DC motor 2; a bearing 5 for rotatably supporting the rotary shaft 22 of the brushless DC motor 2; and a detection sensor 4 for detecting at least an angle of the brushless DC motor 2. The detection sensor 4 is subjected to waterproof treatment. The reduction gear 3 and the bearing 5 are formed of a material requiring no lubrication oil and capable of being immersed in water.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a submerged geared servo motor.

Background Art

[0002] In recent years, expectations for underwater robots have been increasing, and research and development of autonomous unmanned submersibles called AUVs (Autonomous Underwater Vehicles) and underwater drones called ROVs (Remotely operated vehicles) have been actively conducted. Many of these robots use a thruster that combines an electric brushless DC motor and a screw, and are configured to move while generating water flow by rotating infinitely. The magnet part and copper wire coil part of this thruster motor are subjected to rust prevention treatment to enable submersion (see, for example, Non-Patent Document 1). Therefore, there is an advantage that the motor part can be allowed to be immersed in water and there is no need to use a sealing material such as an O-ring or a V-ring.

[0003] By the way, many inexpensive submerged motors have been sold so far and their use has been expanding due to the following advantages.

[0004] (1) Not only is the structure simple, but since the electric motor can be directly immersed in water for cooling, it is possible to pass a large current. (2) Since there is no frictional loss of the sealing material, there is an advantage that the back drivability is high and it is easy to estimate the output torque from the motor current.

[0005] Thus, typical brushless DC motors used in such submersible motors can be easily submerged if their rotor and stator are protected from rust and galvanic corrosion, as the rotor and stator do not come into contact. However, the rotor's rotation angle must be detected by some sensor, and the appropriate current must be supplied to the multiphase coils accordingly in order to make it rotate. This is called commutation, and sensorless commutation technology, which utilizes the induced voltage generated in the coils, is commonly implemented in underwater drones and other applications. Many submersible motors are intended for use as high-speed, infinitely rotating motors, like those in drones, and are designed to have their speed controlled by an ESC (Electric Speed ​​Controller) that incorporates this sensorless commutation technology.

[0006] On the other hand, when manipulating an object underwater, such as with a robotic arm or gripper, joint movement within a certain angular range is required, rather than infinite rotation (see, for example, Non-Patent Document 2). [Prior art documents] [Patent Documents]

[0007] [Non-Patent Document 1] Naoki Sumitomo, Norimitsu Sakagami, and Sadao Kawamura, "Development of a small underwater robotic arm using a submersible motor," Proceedings of the 36th Annual Conference of the Robotics Society of Japan, AC1D2-06, 2018. [Non-Patent Document 2] Sakagami, N., Shibata, M., Hashizume, H., Hagiwara, Y., Ishimaru,K., Ueda, T., Saitou, T., Fujita, K., Kawamura, S., Inoue,T., , Murakami, S., “Development of a HumansizedROV with Dual-arm,” in Proc. the IEEE OCEANS, pp.1-6, 2010 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, the submersible motors described above, like those in typical aerial drones, are high-speed, low-torque types. For this application, they tend to suffer from insufficient torque and their rotational speed is too high. Therefore, a gearbox with a high reduction ratio is required. In addition, because angle sensors must be built into the robot's joints, sealant must be placed in the gaps of the relative motion parts of the gearbox to prevent water ingress. As a result, the joints become stiff due to the friction between the waterproof sealant and the gearbox, which makes contact work underwater difficult.

[0009] Therefore, in view of the above problems, the present invention aims to provide a submersible geared servo motor that enables robots to perform contact operations underwater. [Means for solving the problem]

[0010] The object of the present invention described above is achieved by the following means. The reference numerals in parentheses indicate the embodiments described later, but the present invention is not limited thereto.

[0011] Submersible geared servo motor according to claim 1 In, A motor case (20) that allows water to enter, The stator (21) is fixed inside the motor case (20) and has a configuration in which a rust-proofed coil is wound around it. A rotor (23) is provided with a permanent magnet that has been treated to prevent rust, and is positioned within the motor case (20) in a non-contact manner with the stator (21), and is further rotated by the rotating magnetic field formed by the stator (21), A rotating shaft (22) is fitted onto the rotor (23) and rotates integrally with the rotor (23), A brushless DC motor (2) equipped with, A reduction gear (3) is provided on one end (front end 22a) of the rotating shaft (22) of the brushless DC motor (2), and is made of a material that does not require lubrication and is waterproof. The rotating shaft (22) of the brushless DC motor (2) is rotatably supported by a bearing (5) made of a material that does not require lubrication and is waterproof, The system includes a detection sensor (4) positioned on the other end (rear end 22b) side of the rotating shaft (22), The aforementioned detection sensor (4) is A rust-proofed magnet (40) is attached and fixed to the other end (rear end 22b) of the rotating shaft (22), and further rotates together with the rotating shaft (22). The system includes an encoder IC (41) that detects the angular position of the brushless DC motor (2) by detecting the direction of the magnetic field that changes due to the rotation of the magnet (40), and is capable of deriving an offset value between the electrical angle and mechanical angle of the brushless DC motor (2) for use in commutating the brushless DC motor (2). It is characterized by the following. [Effects of the Invention]

[0013] Next, the effects of the present invention will be described with reference numerals in the drawings. In the parentheses are the reference numerals of the embodiments described later, but the present invention is not limited thereto.

[0014] According to the invention of claim 1, the brushless DC motor (2) is subjected to a waterproof treatment, and further, the detection sensor (4) is also subjected to a waterproof treatment. The speed reducer (2) and the bearing (5) are formed of a material that does not require lubricating oil and can be immersed in water. Therefore, it is possible to immerse the submerged gear servo motor (1) in water without using a waterproof sealing material such as an O-ring or a V-ring. As a result, since the waterproof sealing material is not required, the accuracy of the torque estimated from the current of the brushless DC motor (2) is increased, and further, the frictional loss is reduced. Therefore, if the submerged gear servo motor (1) is applied to a robot, it is possible to prevent a situation where the joints of the robot become rigid due to the influence of the friction of both the waterproof sealing material and the speed reducer as in the conventional case. Therefore, contact work of the robot in water becomes possible. Furthermore, since the stator (21) and rotor (23) of the brushless DC motor (2) are arranged in a non-contact manner, water resistance can be easily and simply made water-resistant by applying rust-preventive treatment to the coils of the stator (21) and the permanent magnets of the rotor (23).

[0015] moreover, Claim 1 According to the invention related to Since the commutation and angle control of the brushless DC motor (2) can be performed with only one encoder IC (41), the number of components can be minimized.

Brief Description of the Drawings

[0016] [Figure 1] It is a perspective longitudinal sectional view of a submerged gear servo motor according to an embodiment of the present invention. [Figure 2] (a) is a perspective view of the substrate on the side where the encoder IC according to the embodiment is arranged and fixed, and (b) is a perspective view of the substrate on the side where the encoder IC according to the embodiment is not arranged and fixed.

Modes for Carrying Out the Invention

[0017] Hereinafter, a submerged gear servo motor according to an embodiment of the present invention will be specifically described with reference to the drawings. In the following description, when indicating the up, down, left, and right directions, the up, down, left, and right as viewed from the front shown in the drawing shall be referred to.

[0018] <Overview of a submersible geared servo motor> The submersible geared servo motor according to this embodiment does not require the use of waterproof sealing materials such as O-rings or V-rings. Specifically, as shown in Figure 1, the submersible geared servo motor 1 mainly consists of a brushless DC motor 2, a reduction gear 3, and a detection sensor 4. Each component will be described in detail below.

[0019] <Explanation of Brushless DC Motor> As shown in Figure 1, the brushless DC motor 2 consists of a motor case 20, a stator 21 fixed inside the motor case 20, a rotating shaft 22, and a rotor 23 fitted onto the rotating shaft 22 and rotating integrally with the rotating shaft 22. The stator 21 has three phase windings of U-phase, V-phase, and W-phase with coils wound around an iron core, and the rotor 23 has permanent magnets. As a result, when current flows through the three phase windings of U-phase, V-phase, and W-phase, the rotor 23 rotates due to the rotating magnetic field formed by this current. Therefore, the rotating shaft 22 fitted onto the rotor 23 also rotates.

[0020] Incidentally, in the brushless DC motor 2 configured as described above, the stator 21 and rotor 23 are non-contact, so water resistance can be easily made possible simply by applying rust-preventive treatment to the coils of the stator 21 and the permanent magnets of the rotor 23. Also, since the stator 21 has coils wound around an iron core, if the submersible geared servo motor 1 is submerged in water, this iron core will rust. Therefore, in this embodiment, rust-preventive treatment (for example, applying waterproof spray to this iron core) is applied to prevent this iron core from rusting.

[0021] <Explanation of the gear reducer> As shown in Figure 1, the speed reducer 3 is a speed reducer using planetary gears attached to the front end 22a side (left side in the figure) of the rotating shaft 22, and is configured to reduce the output of the brushless DC motor 2 by a predetermined reduction ratio. Specifically, as shown in Figure 1, the speed reducer 3 has a sun gear 30, which is press-fitted into the front end 22a side (left side in the figure) of the rotating shaft 22. Multiple planetary gears (not shown) mesh with this sun gear 30, and multiple planetary gears (not shown) mesh with an internal gear (not shown). This internal gear (not shown) is provided inside the speed reducer case 31 and is fixed. Therefore, when the multiple planetary gears (not shown) revolve around the sun gear 30 due to the rotation of the rotating shaft 22, the rotation of the multiple planetary gears (not shown) is reduced because the internal gear (not shown) is fixed. Therefore, by connecting planetary carriers to the rotation axes of these multiple planetary gears (not shown), the output of the brushless DC motor 2 can be reduced and output from the output shaft 32 of these planetary carriers at a predetermined reduction ratio. The reducer case 31 and the motor case 20 are fastened together axially by screw members N.

[0022] By the way, when submerging the reduction gear 3 as described above, it is necessary to use waterproof sealing materials such as O-rings or V-rings in the gaps with the outside to prevent water from entering the interior. However, in this embodiment, the reduction gear 3 is made of a resin made of a polymer material so that it is not a problem even if water enters the interior. As a result, it will not rust even if water enters the interior, and thus water resistance is made possible. Furthermore, this reduces the sliding friction of the sun gear 30, planetary gears (not shown), and internal gears (not shown), so lubricating oil is not required.

[0023] By the way, when using the reduction gear 3 described above, a bearing is required. Therefore, in this embodiment, as shown in Figure 1, a bearing 5 is provided on the rear side (right side in the figure) of the rotating shaft 22 to rotatably support the rotating shaft 22. This bearing 5 is made of ceramic so that it is not affected even if water enters it. As a result, it will not rust even if water enters the interior, thereby making it water-resistant. Furthermore, this reduces the sliding friction between the rotating shaft 22 and the bearing 5, so lubricating oil is not required.

[0024] <Description of detection sensor> As shown in Figure 1, the detection sensor 4 consists of a magnet 40 and an encoder IC 41. The magnet 40 is attached and fixed to the rear end 22b of the rotating shaft 22, and as the rotating shaft 22 rotates, the magnet 40 also rotates.

[0025] On the other hand, the encoder IC 41 is positioned and fixed in the central part of the rectangular resin substrate 42 (see Figure 2(a)), as shown in Figure 2. This encoder IC 41 is positioned opposite the magnet 40 so that it can receive the magnetic field created by the magnet 40. As a result, when the magnet 40 attached and fixed to the rotating shaft 22 rotates, the direction of the magnetic field changes, and the encoder IC 41 detects this change in the direction of the magnetic field and detects the angular position of the brushless DC motor 2. The detected angular position data is output to a drive device (not shown) that drives the brushless DC motor 2 via a connector 43 positioned and fixed on the back of the substrate 42 (the side opposite to the side on which the encoder IC 41 is located), as shown in Figure 2(b), and further via a connector 6 attached to the connector 43, as shown in Figure 1.

[0026] Furthermore, the encoder IC41 can also perform offset detection necessary when commutating the brushless DC motor 2 using a drive device (not shown). To explain this in more detail, when commutating the brushless DC motor 2, it is assumed that the number of poles of the permanent magnets of the rotor 23 is known, and that the stator 21 and the rotor 23 are stationary at the point where they are magnetically balanced. In this case, a drive device (not shown) is used to input a rectangular wave current (or sine wave) with a constant electrical angle to the three-phase windings of the U-phase, V-phase, and W-phase of the stator 21 for one, two, or three cycles. By reading the mechanical angle of the brushless DC motor 2 at this time with the encoder IC41, an offset value between the electrical angle and the mechanical angle can be derived, which can then be used for commutation.

[0027] Incidentally, this offset value is output to a drive unit (not shown) that drives the brushless DC motor 2 via connector 43, and further via connector 6 attached to connector 43, as shown in Figure 1. As a result, the drive unit (not shown) correctly resets the origins of the U-phase, V-phase, and W-phase according to this offset value and drives the brushless DC motor 2 with a sine wave. This causes the brushless DC motor 2 to rotate.

[0028] Thus, since the commutation and angle control of the brushless DC motor 2 can be performed with only one encoder IC 41, the number of components can be minimized.

[0029] Incidentally, if the detection sensor 4 configured as described above is submerged in water, the magnet 40 may rust, potentially causing a change in its magnetic force and direction. Therefore, in this embodiment, the magnet 40 is treated with a rust-preventive coating, and the encoder IC 41 is waterproofed by covering it with a silicone resin S, as shown in Figures 2(a) and (b), to prevent the electrical circuit from getting wet and short-circuiting. This prevents the magnet 40 from rusting and the encoder IC 41 from short-circuiting even if the detection sensor 4 is submerged in water. Note that the rust-preventive coating on the magnet 40 may be applied before the magnetization of the magnet 40, or it may be applied after the magnetization of the magnet 40.

[0030] Incidentally, the magnet 40 described above and the encoder IC 41 are not in contact. Therefore, waterproofing the encoder IC 41 is easy. The circuit board 42 on which the encoder IC 41 is positioned and fixed is mounted and fixed inside the motor case 20.

[0031] Furthermore, since encoder IC41 can perform both commutation and angle control of the brushless DC motor 2 with just one encoder IC41, the number of sensors can be minimized, thereby minimizing the number of sensors that require waterproofing.

[0032] Therefore, according to the embodiment described above, the brushless DC motor 2 is treated to be water-resistant, the detection sensor 4 is also treated to be water-resistant, and the reducer 3 and bearing 5 are made of a material that does not require lubrication and is water-resistant. As a result, the submersible geared servo motor 1 can be submerged without using waterproof sealing materials such as O-rings or V-rings. This eliminates the need for waterproof sealing materials, which improves the accuracy of the torque estimated from the current of the brushless DC motor 2 and also reduces friction loss. Therefore, when the submersible geared servo motor 1 is applied to a robot, it is possible to prevent the robot's joints from becoming stiff due to the friction of both the waterproof sealing material and the reducer, as in the conventional case. As a result, contact work by the robot underwater becomes possible, and angle, angular velocity, and torque control of the submersible geared servo motor 1 in an underwater environment becomes possible. Furthermore, when the submersible geared servo motor 1 is applied to a robot arm, position, velocity, and force control of the end effector becomes possible.

[0033] Furthermore, according to this embodiment, since waterproof sealing material is not required, the submersible geared servo motor 1 can be made significantly smaller compared to conventional designs.

[0034] Furthermore, according to this embodiment, by submerging the submersible geared servo motor 1 in water, water enters the interior because there is no waterproof sealing material. As a result, the brushless DC motor 2 is naturally cooled, and the limit of the current that can be supplied to the brushless DC motor 2 increases significantly, thereby increasing the torque.

[0035] Furthermore, according to this embodiment, since the gearbox 3 comes into direct contact with water, the gearbox 3 is also naturally cooled, thereby preventing deformation of the gearbox 3 due to heat.

[0036] Thus, because such a submersible geared servo motor 1 can be used underwater, it can be used in a wide range of applications, including humid environments, rainy environments, kitchens, swimming pools, and factories that use water.

[0037] <Explanation of variations> It should be noted that the shapes and other features shown in this embodiment are merely examples, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. For example, in this embodiment, the reducer 3 is made of a resin made of a polymer material, but it is not limited to this, and any material that does not require lubrication and is waterproof may be used. For example, if lubrication is not required, stainless steel may be used.

[0038] Furthermore, although this embodiment shows an example in which the bearing 5 is made of ceramic, it is not limited to this, and any material that does not require lubrication and is waterproof may be used. For example, if lubrication is not required, it may be made of metal.

[0039] Furthermore, in this embodiment, an example of covering the encoder IC41 with silicone resin S for waterproofing was described, but any material that provides waterproofing will suffice; for example, epoxy resin would also be acceptable. [Explanation of symbols]

[0040] 1. Submersible geared servo motor 2 Brushless DC motors 22 Rotation axis 3 Reducer 4 detection sensors 40 magnets 41 Encoder IC 5 bearings

Claims

[Claim 1] A motor case that allows water to enter, It has a configuration in which a rust-preventively treated coil is wound around it, and a stator fixed inside the motor case, A permanent magnet treated to prevent rust is provided, and the rotor is positioned within the motor case in a non-contact manner with respect to the stator, and is further rotated by the rotating magnetic field formed by the stator, A rotating shaft fitted into the rotor and rotating integrally with the rotor, A brushless DC motor equipped with, A reduction gear is provided on one end of the rotating shaft of the brushless DC motor, and is made of a material that does not require lubrication and is waterproof. A bearing that rotatably supports the rotating shaft of the brushless DC motor and is made of a material that does not require lubrication and is waterproof, The system includes a detection sensor positioned on the other end of the aforementioned rotating shaft, The aforementioned detection sensor is A rust-proofed magnet is attached and fixed to the other end of the aforementioned rotating shaft and rotates together with the aforementioned rotating shaft, A submersible geared servo motor comprising an encoder IC capable of detecting the angular position of the brushless DC motor by detecting the direction of the magnetic field that changes due to the rotation of the magnet, and deriving an offset value between the electrical angle and mechanical angle of the brushless DC motor, which is used for commutating the brushless DC motor.

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