Nut rotating type electric cylinder

Abstract

The invention belongs to the technical field of electric cylinders, and relates to a nut rotating type electric cylinder which comprises a cylinder barrel, a controller, a push rod assembly and a detection assembly, the push rod assembly comprises a frameless motor, a ball screw pair and an ejector head, the frameless motor is fixed in the cylinder barrel, and an inner rotor of the frameless motor is fixed to a nut of the ball screw pair in a sleeving mode; the top head is used for converting rotary motion of an inner rotor of the frameless motor into combination of rotation and linear motion of a lead screw of the ball screw pair, and the top head is located on the outer side of the cylinder barrel and arranged at the end of the lead screw of the ball screw pair; the detection assembly and the frameless motor are both electrically connected with the controller, and the detection assembly is used for determining the push stroke of the ejector head; and the controller controls the operation of the frameless motor according to the push stroke signal of the ejector head fed back by the detection assembly. The electric cylinder is short in transmission chain and high in precision, the characteristic of high response of the frameless motor is combined, the electric cylinder has higher acceleration and deceleration capacity, the overall structure is compact, and safety and reliability are high.

Description

Technical Field

[0001] This invention belongs to the field of electric cylinder technology, and specifically relates to a nut-rotating electric cylinder. Background Technology

[0002] Electric cylinders, as actuators that convert the rotary motion of an electric motor into linear motion, are widely used in industrial automation, aerospace, and simulation fields due to their advantages such as high control precision, fast response speed, and ease of maintenance. For applications requiring high thrust output, such as heavy-duty lifting equipment and large test benches, the performance requirements for electric cylinders are particularly stringent.

[0003] Traditional electric cylinders typically use servo motors as their power drive unit. Since servo motors are externally mounted, their power needs to be transmitted to the lead screw through a reducer, gear mechanism, or other multi-stage transmission structure. Due to backlash, elastic deformation, and efficiency loss in multi-stage transmission, the system's positioning accuracy, repeatability, and transmission efficiency are not high. In addition, the use of reducers, gear mechanisms, or other multi-stage transmission structures makes the overall structure complex, with long transmission chains, large axial dimensions, and large space requirements, making it difficult to apply in specific confined spaces or special applications, thus limiting its application. Summary of the Invention

[0004] In view of this, the present invention provides a nut-rotating electric cylinder to solve the technical problems of the prior art.

[0005] The technical solution of this invention is: A nut-rotating electric cylinder includes a cylinder barrel, a controller, a push rod assembly, and a detection assembly. The push rod assembly includes a frameless motor, a ball screw assembly, and a mandrel. The frameless motor is fixed inside the cylinder barrel, and its inner rotor is fitted and fixed to the nut of the ball screw assembly, converting the rotational motion of the inner rotor into a combination of rotational and linear motion of the ball screw assembly. The mandrel is located outside the cylinder barrel and is positioned at the end of the ball screw assembly. The detection assembly and the frameless motor are electrically connected to the controller. The detection assembly determines the stroke of the mandrel. The controller controls the operation of the frameless motor based on the mandrel stroke signal fed back by the detection assembly.

[0006] Furthermore, the cylinder includes a cylinder body, a gland, and an end cap. A positioning groove structure is provided on the inner side wall of one end of the cylinder body, and a flange is fixed on the outer side wall. The flange is positioned close to the positioning groove structure. The gland and the end cap are located at opposite ends of the cylinder body. The gland is detachably connected to the cylinder body, and the end cap is detachably connected to the flange. The ball screw of the ball screw assembly passes through the end cap.

[0007] Furthermore, the inner rotor of the frameless motor is glued to the outer circumferential surface of the nut of the ball screw pair, the stator of the frameless motor is limited and installed on the positioning groove structure, and a positioning bushing for axial positioning of the frameless motor is provided between the stator and the end cover.

[0008] Furthermore, the top head includes a bearing housing, a connecting lug, a bearing, a bushing, a bearing inner ring connecting sleeve, a lock nut, and a locking washer. The bearing inner ring connecting sleeve, bushing, locking washer, and lock nut are sequentially fitted onto the lead screw of the ball screw assembly. The lock nut and locking washer cooperate to achieve axial positioning of the bearing inner ring. The bearing inner ring connecting sleeve is fixedly fitted onto the lead screw, the bearing inner ring is fitted onto the bearing inner ring connecting sleeve, and the bearing outer ring is fitted onto the bearing housing. One end of the connecting lug has a groove for accommodating the lock nut and locking washer, and the connecting lug is fixedly connected to the bearing housing.

[0009] Furthermore, a dustproof structure is provided between the connecting lug and the end cap. The dustproof structure includes a skin connecting plate and a skin stretching cylinder. The skin connecting plate is fitted and fixed around the connecting lug. One end of the skin stretching cylinder is detachably connected to the end cap, and the other end is detachably connected to the skin connecting plate.

[0010] Furthermore, the ball screw assembly is provided with a self-locking unit for locking the position of the screw.

[0011] Furthermore, the self-locking unit is a brake.

[0012] Furthermore, the detection component is one of a magnetic grating ruler, an optical grating ruler, a linear displacement sensor, or a rotary encoder.

[0013] Furthermore, it also includes a stroke protection unit, which includes an extreme trigger, a first limit switch, and a second limit switch. The first limit switch and the second limit switch are electrically connected to the controller, wherein the first limit switch and the second limit switch are both fixed on the inner wall of the cylinder and correspond to the extreme positions of the fully retracted and fully extended head, respectively. The extreme trigger is a metal ring and is fixed on the lead screw, used to trigger the first limit switch or the second limit switch to form electrical limit protection.

[0014] Compared with the prior art, the nut-rotating electric cylinder provided by the present invention has the following beneficial effects: 1. Extremely compact structure and high thrust density: The frameless motor is directly integrated with the nut, eliminating all intermediate transmission components, significantly shortening the axial dimension and reducing the moment of inertia, so that it can output greater thrust with the same external dimensions, or smaller volume with the same thrust requirements.

[0015] 2. High transmission accuracy and efficiency: The direct drive method avoids backlash, elastic deformation and efficiency loss caused by multi-stage transmission, and improves the positioning accuracy, repeatability and transmission efficiency of the system.

[0016] 3. Fast dynamic response: The short transmission chain and high rigidity, combined with the high response characteristics of the frameless motor, enable the electric cylinder to have faster acceleration and deceleration capabilities. The overall structure is compact, with a wide range of applications and strong practicality. Attached Figure Description

[0017] Figure 1 This is a cross-sectional view of the overall structure of the present invention. Figure 2 This is a schematic diagram of the structure of the present invention in the extended state.

[0018] Figure 3 This is a schematic diagram of the external structure of the present invention.

[0019] Figure label: 1-Glander cap, 2-Rotary encoder, 3-First limit switch, 4-Limit trigger, 5-Connecting column, 6-Cylinder, 7-Lead screw, 8-Second limit switch, 9-Nut, 10-Frameless motor, 11-Positioning bushing, 12-End cover, 13-Brake, 14-Skin tensioning cylinder, 15-Bearing seat, 16-Connecting lug, 17-Bearing, 18-Bushing bushing, 19-Bearing inner ring connecting sleeve, 20-Locking nut, 21-Stop washer, 22-Skin connecting plate. Detailed Implementation

[0020] This invention provides a nut-rotating electric cylinder to solve the above-mentioned problems. In order to enable those skilled in the art to better understand the technical solution of this invention and to implement it, the technical solution of this invention will be clearly and thoroughly described below with reference to the accompanying drawings.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to 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 invention.

[0022] Furthermore, it should be further explained that in the description of the embodiments of the present invention, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present invention, "multiple" means two or more.

[0023] The terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Thus, a feature defined as "first," "second," "third," or "fourth" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0024] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0025] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0026] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this invention are for illustrative purposes only and do not represent the only possible implementation.

[0027] Example 1 A nut-rotating electric cylinder, its structure is as follows: Figures 1 to 3 As shown, the structure includes cylinder 6, push rod assembly, self-locking unit, position detection unit and stroke protection unit.

[0028] The cylinder 6 is the main structure, including the cylinder body, the pressure cap 1 and the end cap 12. Specifically, the pressure cap 1 and the end cap 12 are used to seal the ends of the cylinder body and are located at both ends of the cylinder body respectively.

[0029] Furthermore, a positioning groove structure is provided on the inner side wall of one end of the cylinder, and a flange for connecting with the end cover 12 is fixed on the outer side wall. The end cover 12 is connected to the flange on the cylinder by screws, and the pressure cover 1 is connected to the cylinder by screws.

[0030] As one embodiment, the pressure cap 1 may be provided with a lug structure with a pin hole for connecting the electric cylinder to other equipment.

[0031] In another embodiment, a connecting post 5 fixed to the cylinder can be provided on the cylinder body for connecting the electric cylinder to other equipment.

[0032] The push rod assembly includes a frameless motor 10, a ball screw pair, and a push head. Specifically, the frameless motor 10 is the core power source, used to drive the ball screw pair to move, thereby converting the rotation of the frameless motor 10 into the linear movement of the push head while rotating, thus achieving the position adjustment of the push head.

[0033] Specifically, the stator limiter of the frameless motor 10 is installed in the positioning groove structure opened on the inner side wall of the cylinder, realizing the axial limit of the first end. The other end is axially limited by the positioning bushing 11 installed between the frameless motor 10 and the end cover 12. The positioning groove and the positioning bushing 11 cooperate to realize the axial positioning of the frameless motor 10. The frameless motor 10 is circumferentially limited by connecting the frameless motor 10 and the cylinder with screws.

[0034] The ball screw assembly includes a nut 9 and a screw 7. The screw 7 is mounted on the end cover 12. The screw 7 includes a first cylindrical section, a threaded section, a second cylindrical section, and a third cylindrical section connected in sequence. The diameters of the first and third cylindrical sections are smaller than the diameter of the second cylindrical section. The nut 9 is fitted onto the threaded section of the screw 7. The nut 9 is fixedly connected to the inner rotor of the frameless motor 10. Thus, when the frameless motor 10 is energized, the inner rotor of the frameless motor 10 directly drives the nut 9 to rotate. Since the nut 9 is fixedly connected to the inner rotor of the frameless motor 10, the nut 9 only performs rotational motion, thereby forcing the screw 7, which meshes with the nut 9, to perform axial linear motion along the cylinder while rotating.

[0035] The top end includes a connecting lug 16, a bearing housing 15, a bearing 17, a bushing 18, a bearing inner ring connecting sleeve 19, a locking nut 20, and a locking washer 21. Specifically, in this embodiment, the bearing inner ring connecting sleeve 19, the bushing 18, the locking washer 21, and the locking nut 20 are sequentially fitted onto the third cylindrical section of the lead screw 7. The bearing inner ring connecting sleeve 19 is fixed to the third cylindrical section of the lead screw 7 by an interference fit. The inner ring of the bearing 17... The outer ring of the bearing 17 is fitted onto the bearing housing 15, and the bushing 18 is fitted onto the third cylindrical section of the lead screw 7 and located on the side of the bearing 17 away from the frameless motor 10 to position the inner ring of the bearing 17. The locking nut 20 and the stop washer 21 cooperate to axially position the inner ring of the bearing 17. One end of the connecting lug 16 has a groove to accommodate the locking nut 20 and the stop washer 21. The connecting lug 16 is fixedly connected to the bearing housing 15.

[0036] In this structure, the inner rotor of the frameless motor 10 drives the nut 9 to rotate. Since the nut 9 is fixedly connected to the inner rotor of the frameless motor 10, the nut 9 only performs rotational motion, thereby forcing the lead screw 7, which meshes with the nut 9, to rotate while also making axial linear motion along the cylinder, thereby driving the top head to achieve position adjustment.

[0037] Specifically, for load-bearing capacity considerations, bearing 17 can be selected as an angular contact ball bearing (such as model 7018C / DB) to withstand bidirectional axial force and part of radial force generated during operation.

[0038] Specifically, to prevent dust from entering, a dustproof structure is added to the top. This dustproof structure includes a skin connecting plate 22 and a skin tension cylinder 14. The skin connecting plate 22 is fitted and fixed around the connecting lug 16. One end of the skin tension cylinder 14 is connected to the end cap 12 with screws, and the other end is connected to the skin connecting plate 22 with screws. Because the skin tension cylinder 14 is a threaded tube structure, it can adapt to changes in the top's position while providing dust protection for the top.

[0039] In practice, the skin connecting plate 22 can be welded to the connecting lug 16, or it can be processed as a whole during manufacturing.

[0040] In one embodiment, a self-locking unit is used to lock the position of the lead screw 7 to prevent it from retracting during use. The self-locking unit can reliably lock at any position, preventing accidental load drops, providing high safety, and is simple and durable in structure. Specifically, as shown... Figure 1 and Figure 2As shown, the self-locking unit is implemented using a brake 13, which is mounted on the second cylindrical section of the lead screw 7. The flange of the brake 13 is fixedly connected to the bearing housing 15 via bolts. When the preset position is reached, the brake 13 is activated to clamp the lead screw 7, achieving reliable self-locking and preventing the lead screw 7 from retracting. Since the brake 13 is a readily available component, this invention does not involve any improvement to its structure, but merely its application; therefore, it will not be described in detail here.

[0041] The position detection unit is preferably one of a magnetic grating ruler, an optical grating ruler, or a linear displacement sensor, used to determine the absolute linear position of the top head, i.e., the push stroke of the top head.

[0042] Specifically, another implementation method given in this embodiment is to use a rotary encoder 2, which is threadedly connected to the first cylindrical section of the lead screw 7. The rotary encoder 2 detects the precise rotation angle of the lead screw 7 in real time, and the controller can calculate the push stroke of the pusher based on the lead, thereby achieving high-precision closed-loop control.

[0043] Specifically, the rotary encoder 2 is electrically connected to the controller. The rotary encoder 2 is used to detect the circumferential rotation angle of the lead screw 7 and send the circumferential rotation angle of the lead screw 7 to the controller. Based on the circumferential rotation angle of the lead screw 7 detected by the rotary encoder 2 and the lead screw 7, the controller can determine the linear displacement of a specific position of the lead screw 7 within a predetermined time. The linear displacement of the push stroke of the top end of the lead screw 7 is the same as the linear displacement of the specific position of the lead screw 7. Based on this, the controller can control the operation of the frameless motor 10, thereby realizing the control of the push stroke of the top end.

[0044] Specifically, the linear displacement of the aforementioned top head = the circumferential rotation angle of the lead screw 7 × the lead of the lead screw 7. Since the lead screw 7 rotates continuously, the circumferential rotation angle of the lead screw 7 obtained during the detection is an angle value calculated cumulatively starting from 0. The 0th position of the angle value is at the starting position of the lead screw 7, and the starting position of the nut is close to the lower limit position of the stroke protection unit.

[0045] The travel protection unit includes an limit trigger 4, a first limit switch 3, and a second limit switch 8. The first limit switch 3 and the second limit switch 8 are electrically connected to the controller. Both the first limit switch 3 and the second limit switch 8 are fixed to the inner wall of the cylinder with screws and correspond to the limit positions of the fully retracted and fully extended mandrels, respectively. The limit trigger 4 is a metal ring fixed to the first cylindrical section of the lead screw 7. When the mandrel moves to its limit position, the metal ring approaches the corresponding proximity switch, which sends a signal to the controller. The controller immediately cuts off the power to the frameless motor 10, forming electrical limit protection, which, together with the mechanical structure, constitutes dual protection.

[0046] It should be noted that the driver built into the frameless motor 10 of this invention is electrically connected to the controller. The controller controls the driver to control the frameless motor 10. When the frameless motor 10 starts, the inner rotor of the frameless motor 10 drives the nut 9 to rotate, so that the rotation of the nut 9 is converted into the rotation of the lead screw 7 while it also makes axial linear motion along the cylinder. The movement of the top head is synchronized with the lead screw 7. While the lead screw 7 is moving, the rotary encoder 2 detects the circumferential rotation angle of the lead screw 7 in real time and sends the circumferential rotation angle of the lead screw 7 to the controller. Based on the circumferential rotation angle of the lead screw 7 detected by the rotary encoder 2 and the lead of the lead screw 7, the controller determines the linear displacement of the top head using the formula: linear displacement of the top head = circumferential rotation angle of the lead screw 7 × lead of the lead screw 7. When the linear displacement of the top head reaches the preset requirement, the controller sends a control command to the driver built into the frameless motor 10, so that the frameless motor 10 stops moving. At this time, in order to prevent the lead screw 7 from retracting and causing a safety accident, a self-locking unit is used to limit the position of the lead screw 7. The self-locking unit uses brake 13 to clamp the lead screw 7, achieving reliable self-locking. When the lead screw 7 needs to retract, brake 13 releases the lead screw 7, allowing it to rise or retract freely. During this process, the controller plays a timing coordination role. It sends control commands to the driver built into the frameless motor 10, stopping the motor, and simultaneously sends control commands to brake 13, stopping the lead screw 7 while brake 13 clamps it, achieving reliable self-locking. Furthermore, when the lead screw 7 needs to rise or retract freely, an unlocking control command is input to the controller, allowing the controller to control brake 13, releasing the lead screw 7, which can then rise or retract freely under the action of the frameless motor 10.

[0047] Compared with existing technologies, the present invention provides a nut-rotating electric cylinder. The motion controller of the frameless motor 10 receives instructions from the controller (such as target position and speed), combines this with the actual position feedback from the rotary encoder 2, determines the control quantity, and sends it to the motion controller of the frameless motor 10 to drive the frameless motor 10. Simultaneously, the controller monitors the first limit switch 3 and the second limit switch 8 in real time. Once the protection condition is triggered, a safety strategy is immediately executed. The electric cylinder of the present invention has a compact structure, large thrust, short transmission chain, high precision, and built-in mechanical self-locking function. It boasts high safety and reliability, strong practicality, and is worthy of promotion.

[0048] The above-disclosed embodiments are merely preferred embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A nut-rotating electric cylinder, characterized in that, The system includes a cylinder, a controller, a push rod assembly, and a detection assembly. The push rod assembly includes a frameless motor, a ball screw assembly, and a mandrel. The frameless motor is fixed inside the cylinder, and its inner rotor is fitted with a nut on the ball screw assembly to convert the rotational motion of the inner rotor into a combination of rotational and linear motion of the ball screw assembly. The mandrel is located outside the cylinder and is positioned at the end of the ball screw assembly. The detection assembly and the frameless motor are electrically connected to the controller. The detection assembly determines the stroke of the mandrel. The controller controls the operation of the frameless motor based on the stroke signal of the mandrel fed back by the detection assembly.

2. The nut-rotating electric cylinder according to claim 1, characterized in that, The cylinder includes a cylinder body, a pressure cap, and an end cap. A positioning groove structure is provided on the inner side wall of one end of the cylinder body, and a flange is fixed on the outer side wall. The flange is located close to the positioning groove structure. The pressure cap and the end cap are located at the two ends of the cylinder body, respectively. The pressure cap is detachably connected to the cylinder body, and the end cap is detachably connected to the flange. The ball screw of the ball screw pair passes through the end cap.

3. The nut-rotating electric cylinder according to claim 2, characterized in that, The inner rotor of the frameless motor is glued to the outer circumferential surface of the nut of the ball screw pair. The stator of the frameless motor is limited and installed on the positioning groove structure. A positioning bushing for axial positioning of the frameless motor is provided between the stator and the end cover.

4. The nut-rotating electric cylinder according to claim 3, characterized in that, The top end includes a bearing housing, a connecting lug, a bearing, a bushing, a bearing inner ring connecting sleeve, a lock nut, and a locking washer. The bearing inner ring connecting sleeve, bushing, locking washer, and lock nut are sequentially fitted onto the lead screw of the ball screw assembly. The lock nut and locking washer cooperate to achieve axial positioning of the bearing inner ring. The bearing inner ring connecting sleeve is fitted and fixed onto the lead screw. The bearing inner ring is fitted onto the bearing inner ring connecting sleeve, and the bearing outer ring is fitted onto the bearing housing. One end of the connecting lug has a groove for accommodating the lock nut and locking washer, and the connecting lug is fixedly connected to the bearing housing.

5. The nut-rotating electric cylinder according to claim 4, characterized in that, A dustproof structure is provided between the connecting lug and the end cap. The dustproof structure includes a skin connecting plate and a skin tensioning cylinder. The skin connecting plate is fitted and fixed around the connecting lug. One end of the skin tensioning cylinder is detachably connected to the end cap, and the other end is detachably connected to the skin connecting plate.

6. The nut-rotating electric cylinder according to claim 1, characterized in that, The ball screw assembly is equipped with a self-locking unit for locking the position of the screw.

7. The nut-rotating electric cylinder according to claim 6, characterized in that, The self-locking unit is a brake.

8. The nut-rotating electric cylinder according to claim 1, characterized in that, The detection component is one of the following: magnetic scale, optical scale, linear displacement sensor, and rotary encoder.

9. The nut-rotating electric cylinder according to claim 1, characterized in that, It also includes a stroke protection unit, which includes an extreme trigger, a first limit switch, and a second limit switch. The first limit switch and the second limit switch are electrically connected to the controller. The first limit switch and the second limit switch are both fixed on the inner wall of the cylinder and correspond to the extreme positions of the fully retracted and fully extended top, respectively. The extreme trigger is a metal ring and is fixed on the lead screw to trigger the first limit switch or the second limit switch to form an electrical limit protection.

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