Improved electric cylinder and intelligent press-fitting device with same

Abstract

This invention relates to an improved electric cylinder and an intelligent pressing device incorporating the electric cylinder, belonging to the field of linear drive devices. It comprises: a stator assembly, with a ring-shaped structure, having stator windings for transmitting direct current to generate a driving magnetic field; a rotor assembly, coaxially integrated inside the stator assembly, including a lead screw nut and magnets circumferentially attached to the outer wall of the lead screw nut, the magnets cooperating with the stator windings to form a driving force, driving the lead screw nut to rotate; a roller screw drive mechanism, coaxially integrated inside the rotor assembly, including a push rod with external threads passing through the lead screw nut, and roller screws distributed between the lead screw nut and the push rod, the roller screws converting the rotational motion of the lead screw nut into the linear extension and retraction motion of the push rod; and a detection feedback component, integrated at the end of the electric cylinder, including an encoder for detecting motor speed and push rod displacement. This invention improves the overall integration of the equipment and space utilization.

Description

Technical Field

[0001] This invention relates to the field of linear drive devices, and more particularly to an improved electric cylinder and an intelligent pressing device incorporating the electric cylinder. Background Technology

[0002] As a core linear drive component in automated equipment, electric cylinders are widely used in automotive parts assembly, electronic component pressing, precision machining and other fields due to their advantages of high precision, high stability and strong controllability. Their structural design and performance directly determine the precision, efficiency and overall maintenance cost of automated pressing processes.

[0003] Currently, most traditional electric cylinders on the market adopt a split layout of "drive motor + cylinder body". The drive motor, as an independent component, needs to be connected to the lead screw transmission mechanism of the electric cylinder through intermediate transmission structures such as couplings and reducers to realize the conversion of rotary motion into linear motion. This split design not only results in a large overall size and redundant structure of the electric cylinder, occupying more equipment installation space, but also makes it particularly difficult to adapt to the installation requirements of miniaturized and compact automated equipment, leading to low overall equipment integration and poor space utilization, which needs to be improved. Summary of the Invention

[0004] To improve the overall integration and space utilization of the equipment, this invention provides an improved electric cylinder and an intelligent pressing device with the electric cylinder.

[0005] In a first aspect, the present invention provides an improved electric cylinder, which adopts the following technical solution: An improved electric cylinder, with an integrated coaxial structure, includes: The stator assembly has a ring-shaped structure and is equipped with stator windings for passing direct current to generate a driving magnetic field; The rotor assembly is coaxially integrated inside the stator assembly and includes a lead screw nut and a magnet circumferentially attached to the outer wall of the lead screw nut. The magnet cooperates with the stator winding to form a driving force, driving the lead screw nut to rotate. The roller screw drive mechanism is coaxially integrated inside the rotor assembly, including a push rod with external threads that passes through the screw nut and a roller screw distributed between the screw nut and the push rod. The roller screw converts the rotational motion of the screw nut into the linear extension and retraction motion of the push rod. The detection feedback component, integrated at the end of the electric cylinder, includes an encoder for detecting the motor speed and the displacement of the push rod.

[0006] By adopting the above technical solution, the stator assembly, rotor assembly, and roller screw transmission mechanism are designed as an integrated coaxial structure, eliminating the need for independent drive motors, couplings, reducers, and other intermediate transmission components required in traditional electric cylinders, thus achieving integrated motor and electric cylinder. This reduces the overall size of the electric cylinder, avoids the structural redundancy of a split layout, effectively improves the overall integration and space utilization of the equipment, and can adapt to the installation requirements of miniaturized and compact automated equipment, solving the problem of high space occupancy in traditional electric cylinders.

[0007] Optionally, the roller screw is evenly distributed along the internal thread groove of the screw nut, and the internal thread of the screw nut is adapted to the external thread of the push rod.

[0008] By adopting the above technical solution, and by evenly distributing the roller screw along the internal thread groove of the screw nut, the force exerted by the rotation of the screw nut can be evenly transmitted to the push rod, avoiding transmission jamming or component wear caused by localized force concentration, and extending the service life of the core transmission components of the electric cylinder. Simultaneously, the precise thread fit between the screw nut and the push rod, combined with the evenly distributed roller screw, reduces frictional resistance during transmission, improves power transmission efficiency, reduces energy loss, and makes the linear extension and retraction motion of the push rod smoother and more stable, further enhancing the positioning accuracy and motion stability of the electric cylinder.

[0009] Optionally, the encoder is electrically connected to an external servo driver. The encoder calculates the displacement of the push rod by detecting the number of rotations of the motor. The speed and displacement data fed back by the encoder are transmitted to the external servo driver in real time.

[0010] By adopting the above technical solution, the direct electrical connection between the encoder and the external servo driver allows for the synchronous feedback of the push rod displacement data calculated from the detected motor rotation count, along with real-time speed data, to the servo driver. This provides precise data support for the motion control of the electric cylinder. Based on this real-time feedback data, the servo driver can quickly adjust the motor's operating state, achieving closed-loop control of the push rod's extension and retraction motion. This effectively avoids situations where the push rod experiences displacement errors or motion jamming, improving the positioning accuracy and response speed of the electric cylinder.

[0011] Optionally, the magnet is fixed to the outer wall of the lead screw nut by adhesive bonding. The roller screw is rolled and embedded in the receiving space formed by the internal thread groove of the screw nut and the external thread groove of the push rod, and the outer peripheral surface of the roller screw is respectively in contact with the groove walls of the internal thread groove and the external thread groove.

[0012] By adopting the above technical solution, the magnet is fixed to the outer wall of the lead screw nut by bonding, avoiding structural redundancy caused by the space occupied by the fixing parts, reducing the risk of the magnet shifting or falling off during high-speed rotation, and ensuring stable transmission of the driving force generated by the stator and rotor. The roller lead screw is embedded in the receiving space formed by the thread grooves of both and fits against the groove wall, which can limit the movement trajectory of the roller lead screw, avoid deviation and shaking during transmission, and maximize the contact area to ensure uniform force transmission, further reducing transmission gap and frictional resistance, so that the rotational motion of the lead screw nut can be smoothly and efficiently converted into the linear motion of the push rod, reducing power loss.

[0013] In a second aspect, an intelligent pressing device with an improved electric cylinder is provided, comprising the improved electric cylinder of the first aspect, and further comprising a pressing host unit and an independently configured electrical control unit, wherein the pressing host unit and the electrical control unit are connected by a cable; The press-fitting host unit includes a frame, an industrial control computer, and a human-machine interaction module; The frame includes a bottom base, two perforated side plates, a top platform, and vertical columns. The improved electric cylinder is installed above the top platform and is coaxially connected to the motor.

[0014] By adopting the above technical solution, the improved electric cylinder is combined with the intelligent pressing equipment. Leveraging the advantages of the integrated coaxial structure of the electric cylinder, the overall integration of the equipment is further enhanced. Furthermore, the improved coaxial connection between the electric cylinder and the motor continues the advantages of integrated transmission, eliminating additional connection gaps and ensuring precise and efficient power transmission, thus meeting the needs of precision pressing. The pressing main unit and the electrical control unit are independently set up and connected by cables, simplifying the structural layout of the main unit and reducing space occupation.

[0015] Optionally, it also includes a tooling mounting platform disposed within the frame, the tooling mounting platform being horizontally disposed between the vertical columns and coaxially corresponding to the push rod; The human-computer interaction module is installed above the top platform and is rotatably connected to the top platform.

[0016] By adopting the above technical solution, the tooling mounting platform is horizontally positioned between the columns and coaxially aligned with the push rod. This ensures that during the pressing process, the force of the improved electric cylinder's push rod is applied vertically along the coaxial direction to the tooling and the workpiece to be pressed, avoiding pressing deviations caused by eccentric forces and guaranteeing pressing accuracy and product consistency. Simultaneously, the frame columns provide stable support for the tooling mounting platform, improving the structural rigidity of the equipment during operation. The human-machine interface module is rotatably connected to the top platform, allowing operators to flexibly adjust the module angle according to their actual standing position requirements. This facilitates viewing pressing parameters and the operating interface without needing to adjust their own standing position or posture, enhancing operational convenience.

[0017] Optionally, the electrical control unit is an independent cabinet structure, and the improved electric cylinder is equipped with a servo driver and is located inside the electrical control unit. The servo driver has a built-in PCAN communication module and a current loop detection unit. The current loop detection unit is used to detect the motor operating current and calculate the pressing force based on the current value to achieve pressure feedback. The industrial control computer is directly connected to the servo driver via a PCAN communication module.

[0018] By adopting the above technical solution, the servo drive integrates a PCAN communication module and a current loop detection unit, eliminating the need for additional independent detection and communication components. This simplifies the electrical link structure of the equipment and reduces potential failure points. Furthermore, the current loop detection unit calculates the pressing force by detecting the motor's operating current, replacing the traditional external pressure sensor design. This avoids issues such as sensor installation deviation and signal delay, achieving accurate and real-time pressure feedback. Combined with encoder displacement detection, this forms a dual closed-loop control, improving the accuracy and stability of the pressing process.

[0019] Optionally, the table surface of the tooling mounting platform is provided with a plurality of arrayed mounting holes for fixing the press-fit tooling. It also includes electrical closed-loop control methods during the pressing process: Receive pressing parameters set through the human-machine interaction module; Based on the press-fit parameters, drive commands are generated and sent to the servo driver via the PCAN communication module; It responds to drive commands to control and improve the operation of the electric cylinder, and acquires the motor operating current in real time based on the current loop detection unit and the push rod displacement in real time based on the encoder. The motor operating current and push rod displacement are fed back to the industrial control computer via the PCAN communication module. The motor operating current is converted into real-time pressing force based on a pre-stored current-pressure conversion model. Dynamic adjustment commands are generated based on real-time pressing force, push rod displacement, and pressing parameters. In response to dynamic adjustment commands, the servo driver is controlled via the PCAN communication module to adjust the output and complete the pressing process.

[0020] By adopting the above technical solution, pressing parameters are set through the human-machine interface module, and the PCAN communication module ensures rapid transmission of control commands and data. This is combined with a current loop detection unit to collect the motor's operating current in real time, and an encoder to collect the push rod displacement in real time. Based on a pre-stored model, the current is converted into pressing force, eliminating the need for an external pressure sensor and effectively avoiding detection errors caused by sensor installation deviations. Furthermore, dynamic adjustment commands correct the servo driver output in real time, preventing pressing force or displacement from exceeding tolerances, thus improving the automation level and operational reliability of the pressing process.

[0021] Optionally, methods for constructing and dynamically calibrating the current-pressure conversion model are also included: During the equipment initialization phase, a known standard pressure is applied to the improved electric cylinder, and in response to the known standard pressure, the corresponding motor operating current value is collected through the current loop detection unit. An initial current-pressure mapping relationship is established based on the motor's operating current value; Based on the initial current-pressure mapping relationship, the preset current sampling accuracy, and the transmission efficiency parameters, a reference current-pressure conversion model is generated and stored in the industrial control computer. During the press-fitting process, the internal temperature data of the servo drive is collected; Dynamic temperature compensation is performed on the real-time collected motor operating current value based on internal temperature data and preset current sampling temperature drift curve to update the real-time output accuracy of the reference current pressure conversion model.

[0022] By adopting the above technical solution, a mapping relationship is established by collecting the motor's operating current based on the known standard pressure. A benchmark model is generated by combining sampling accuracy and transmission efficiency parameters to replace the theoretical calculation model, ensuring the initial accuracy of the current-pressure conversion and solving the problem of large deviations between traditional models and actual working conditions. During press-fitting, temperature data is collected and dynamically compensated using drift curves to avoid current detection deviations caused by motor heating, ensuring stable model output accuracy. This improves the accuracy of press-fitting force detection and ensures the reliability of subsequent operations.

[0023] Optional, also includes: After a single press-fit cycle is completed, the actual current value during the steady-state holding phase is collected. The actual steady-state pressure value is obtained based on the actual current value; Calculate the deviation between the actual steady-state pressure value and the target pressure value set in the press-fitting parameters to obtain the pressure deviation value; The pressure deviation value is used to determine whether the reference current-pressure conversion model needs parameter calibration. If calibration is required, the parameters of the reference current-pressure conversion model are optimized based on the pressure deviation value, and the optimized model is stored in the industrial control computer for subsequent press-fitting tasks.

[0024] By adopting the above technical solution, after a single pressing cycle, the actual steady-state pressure value can be obtained by collecting the actual current value during the steady-state holding phase. By comparing the actual steady-state pressure with the target pressure to obtain the deviation value, the accuracy degradation of the reference model can be determined. If calibration is required, the model parameters are optimized and updated based on the deviation value, eliminating the need for manual model adjustment, simplifying the calibration process, reducing human error, and allowing the model to adapt to performance changes after long-term equipment operation, continuously ensuring the accuracy of pressure conversion.

[0025] In summary, this application includes at least one of the following beneficial technical effects: 1. By designing the stator assembly, rotor assembly, and roller screw transmission mechanism as an integrated coaxial structure, the independent drive motor, coupling, reducer, and other intermediate transmission components required by traditional electric cylinders are eliminated, achieving integrated motor and electric cylinder. This reduces the overall size of the electric cylinder, avoids the structural redundancy of a split layout, effectively improves the overall integration and space utilization of the equipment, and can adapt to the installation requirements of miniaturized and compact automated equipment, solving the problem of high space occupancy of traditional electric cylinders; 2. By integrating the PCAN communication module and current loop detection unit into the servo driver, the electrical link structure of the equipment is simplified, reducing the number of fault points, eliminating the need for additional independent detection and communication components. Furthermore, the current loop detection unit calculates the pressing force by detecting the motor's operating current, replacing the traditional external pressure sensor design. This avoids problems such as sensor installation deviation and signal delay, achieving accurate and real-time pressure feedback. Combined with encoder displacement detection, this forms a dual closed-loop control, improving the accuracy and stability of the pressing process. 3. Pressing parameters are set via the human-machine interface module, and the PCAN communication module ensures rapid transmission of control commands and data. This, combined with a current loop detection unit to collect the motor's operating current in real time and an encoder to collect the push rod displacement in real time, allows for the conversion of current into pressing force based on a pre-stored model. This eliminates the need for an external pressure sensor, effectively avoiding detection errors caused by sensor installation deviations. Furthermore, dynamic adjustment commands correct the servo driver output in real time, preventing pressing force or displacement from exceeding tolerances and improving the automation level and operational reliability of the pressing process. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the improved electric cylinder; Figure 2 This is a cross-sectional view of an improved electric cylinder; Figure 3 This is an overall schematic diagram of the intelligent pressing equipment; Figure 4 This is a flowchart of the electrical closed-loop control method during the press-fitting process.

[0027] The parts referred to by the numbers in the above attached diagrams are as follows: 1. Improved electric cylinder; 11. Stator assembly; 111. Stator winding; 12. Rotor assembly; 121. Lead screw nut; 122. Magnet; 13. Roller lead screw transmission mechanism; 131. Push rod; 132. Roller lead screw; 14. Detection feedback component; 2. Intelligent pressing equipment; 21. Pressing main unit; 211. Frame; 2111. Bottom base; 2112. Side plate; 2113. Top platform; 2114. Vertical column; 2115. Tooling mounting table; 212. Human-machine interaction module; 22. Electrical control unit; 3. Mounting lug. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0029] This application discloses an improved electric cylinder and an intelligent pressing device with the improved electric cylinder.

[0030] Reference Figure 1 , Figure 2 and Figure 3 The improved electric cylinder 1 is an integrated coaxial structure with a compact structure and high transmission accuracy. It includes a stator assembly 11, a rotor assembly 12, a ball screw transmission mechanism 13, and a detection feedback component 14. The components are arranged coaxially and nested in sequence. The rotor assembly 12 is located inside the stator assembly 11, the ball screw transmission mechanism 13 is located inside the rotor assembly 12, and the detection feedback component 14 is integrated at the end of the electric cylinder.

[0031] The intelligent pressing equipment 2 with the improved electric cylinder 1 includes the improved electric cylinder 1, the pressing host unit 21, and the independently set electrical control unit 22. All the actuators are connected to the electrical control unit 22 by signal. The pressing host unit 21 and the electrical control unit 22 are connected by cables.

[0032] During the press-fitting operation, the workpiece to be press-fitted is first fixed on the tooling mounting table 2115 of the press-fitting host unit 21. Press-fitting parameters are input through the human-machine interaction module 212. After the parameter signals are transmitted to the industrial control computer, the industrial control computer sends instructions to the servo driver through the PCAN communication module. The servo driver drives the motor to rotate, and the motor drives the lead screw nut 121 of the improved electric cylinder 1 to rotate. The rotational motion of the lead screw nut 121 is converted into the linear extension and retraction motion of the push rod 131 through the roller lead screw 132. The push rod 131 feeds towards the workpiece and completes the press-fitting action.

[0033] During the pressing process, the encoder of the detection feedback component 14 collects the speed and displacement data of the push rod 131 in real time and transmits it to the servo driver. At the same time, the current loop detection unit built into the servo driver collects the motor operating current and calculates the real-time pressing force through the current value, realizing dual closed-loop control of displacement and pressure during the pressing process, without the need for additional pressure sensors.

[0034] In this embodiment, the stator assembly 11 is a ring structure, integrally formed from aluminum alloy. Its inner ring surface has a winding mounting groove, within which a stator winding 111 for transmitting direct current is wound. When energized, the stator winding 111 generates a stable driving magnetic field. Two sets of mounting lugs 3 are symmetrically machined on the outer wall of the stator assembly 11. The mounting lugs 3 have threaded holes for fixing the electric cylinder to the top platform 2113 of the press-fitting main unit 21.

[0035] The rotor assembly 12 is coaxially integrated inside the stator assembly 11, with a 0.5mm air gap between them to prevent interference during operation. The rotor assembly 12 includes a lead screw nut 121 and magnets 122. The lead screw nut 121 is made of stainless steel, and eight magnet mounting slots are evenly distributed around its outer circumference. The magnets 122 are circumferentially attached to the magnet mounting slots. The magnets 122 cooperate with the stator winding 111 to form a driving force, driving the lead screw nut 121 to rotate around its own axis.

[0036] The roller screw drive mechanism 13 is coaxially integrated inside the rotor assembly 12, including a push rod 131 and a roller screw 132. The push rod 131 is made of high-strength alloy steel, and its outer circumferential surface is machined with a trapezoidal external thread. The push rod 131 passes through the inner hole of the screw nut 121. The inner hole of the screw nut 121 is machined with a trapezoidal internal thread that matches the external thread of the push rod 131. The thread grooves of the two mesh with each other to form a receiving space. The roller screw 132 is distributed in the receiving space, converting the rotational motion of the screw nut 121 into the linear extension and retraction motion of the push rod 131.

[0037] The detection feedback component 14 is integrated into the end of the electric cylinder that extends away from the push rod 131, and includes an encoder for detecting the motor speed and the displacement of the push rod 131. The encoder is connected to the end of the push rod 131 via a coupling, and the encoder housing is fixed to the end face of the stator assembly 11 via a bracket. The encoder is electrically connected to an external servo drive, and the displacement of the push rod 131 is calculated by detecting the number of rotations of the motor. The speed and displacement data fed back by the encoder are transmitted to the external servo drive in real time.

[0038] Furthermore, the roller screws 132 are evenly distributed along the internal thread groove of the screw nut 121, and the distance between two adjacent roller screws 132 is 5mm to ensure uniform force during transmission; the internal thread of the screw nut 121 and the external thread pitch of the push rod 131 are consistent, which improves the smoothness of transmission.

[0039] Furthermore, the magnet 122 is fixed to the inner wall of the lead screw nut 121 by epoxy resin adhesive; the roller lead screw 132 is rolled and embedded in the receiving space formed by the inner thread groove of the lead screw nut 121 and the outer thread groove of the push rod 131, and the outer peripheral surface of the roller lead screw 132 is in close contact with the groove walls of the inner thread groove and the outer thread groove, respectively.

[0040] The press-fitting main unit 21 includes a frame 211, an industrial computer, and a human-machine interface module 212. The frame 211 is a welded frame structure, including a bottom base 2111, two perforated side plates 2112, a top platform 2113, and vertical columns 2114. The bottom base 2111 supports the entire equipment; the side plates 2112 are evenly provided with heat dissipation perforations for heat dissipation of the internal components of the frame 211; the vertical columns 2114 are four stainless steel round tubes, vertically connected between the bottom base 2111 and the top platform 2113 to ensure the structural strength of the frame 211.

[0041] The improved electric cylinder 1 is fixedly installed on the top platform 2113 by bolts. The improved electric cylinder 1 is coaxially connected to the motor, which is a servo motor, to provide stable driving force for the operation of the electric cylinder. The industrial control computer is an embedded industrial control computer, installed on the mounting plate inside the frame 211, used to receive instructions from the human-machine interaction module 212 and send control signals. The human-machine interaction module 212 is a touch screen, installed on the top platform 2113 and rotatably connected to the top platform 2113. The rotation angle range is 0 to 90°, which is convenient for operators to operate from different perspectives.

[0042] In this embodiment, the frame 211 of the press-fitting main unit 21 also includes a tooling mounting table 2115. The tooling mounting table 2115 is an aluminum alloy plate with a thickness of 15mm, horizontally arranged between the vertical columns 2114, and coaxially corresponding to the push rod 131 of the improved electric cylinder 1, ensuring that the push rod 131 and the workpiece are coaxially stressed during the press-fitting process. The table surface of the tooling mounting table 2115 has multiple arrayed mounting holes for fixing press-fitting tooling of different specifications, adapting to the press-fitting requirements of various workpieces.

[0043] The electrical control unit 22 is an independent cabinet structure, made of cold-rolled steel plate, with an anti-static coating sprayed on the surface. The improved electric cylinder 1 is equipped with a servo driver, which is located inside the electrical control unit 22. The servo driver has a built-in PCAN communication module and a current loop detection unit.

[0044] The current loop detection unit is used to detect the motor operating current. Since the motor output torque is directly proportional to the input current, and the pressing force and the motor torque can be established through the transmission ratio of the lead screw nut 121, there is no need to set up an additional pressure sensor. The real-time pressing force can be accurately calculated from the current value to achieve pressure feedback.

[0045] The industrial control computer is directly connected to the servo driver via the PCAN communication module. The intelligent pressing equipment 2 eliminates the need for a PLC relay control unit, reducing control link nodes and improving signal transmission efficiency.

[0046] In this embodiment, the PCAN communication module adopts the CAN2.0B protocol, and the communication link includes a PCAN communication card, shielded twisted pair cable, and terminating resistor, with a maximum transmission rate of 1Mbps. In other embodiments, the PCAN communication module can also adopt the CANFD protocol to further improve the transmission rate. The cabinet of the electrical control unit 22 is equipped with a cabinet door, ventilation holes, and an emergency stop button. The cabinet door is hinged to the cabinet body, and the ventilation holes are located on both sides of the cabinet body to ensure heat dissipation of heat-generating components such as the servo driver. The emergency stop button is signal-connected to the servo driver; pressing it can immediately cut off the motor power supply and achieve emergency stop.

[0047] Reference Figure 2 , Figure 3 and Figure 4 Based on the same inventive concept, embodiments of the present invention provide an electrical closed-loop control method for the pressing process, including: S10: Receive the pressing parameters set through the human-machine interaction module 212.

[0048] Pressing parameters refer to the control target values ​​input by the operator through the human-machine interaction module 212 according to the process requirements of the workpiece to be pressed. These parameters include at least the target pressing force, target displacement, feed speed at each stage, and holding time.

[0049] S11: Generate drive commands based on press-fit parameters and send them to the servo driver via the PCAN communication module.

[0050] Drive commands refer to the specific motion control commands calculated and generated by the motion control module inside the industrial control computer based on pressing parameters (such as target displacement and segmented speed). These commands are encapsulated into data frames according to the CAN bus protocol through the industrial control computer's PCAN communication interface and sent directly to the PCAN communication module of the servo driver via the PCAN communication link (including the PCAN communication card and shielded twisted pair cable).

[0051] The driving instructions are calculated using an internal trajectory planning algorithm (such as S-curve or trapezoidal curve planning). This internal trajectory planning algorithm is common knowledge in the field and will not be elaborated upon here.

[0052] S12: Responds to drive commands to control the operation of the improved electric cylinder 1, and acquires the motor operating current in real time based on the current loop detection unit and the push rod displacement in real time based on the encoder.

[0053] The servo driver parses and executes drive commands, controlling the power module to output corresponding voltage and current to the motor stator winding 111, driving the motor to rotate. The motor directly drives the lead screw nut 121 of the improved electric cylinder 1 to rotate via a coupling. Simultaneously, the servo driver's built-in current loop detection unit samples and digitizes the motor's operating current in real time; the encoder integrated at the end of the electric cylinder detects the number of rotations and angle of the lead screw nut 121 in real time and feeds it back to the servo driver. Based on the pre-stored lead screw lead parameters (i.e., the linear displacement of the push rod 131 corresponding to one rotation of the lead screw), the servo driver converts the number of rotations into the real-time linear displacement of the push rod 131 for subsequent steps.

[0054] S13: Responds to the motor operating current and push rod displacement to feed back to the industrial control computer via the PCAN communication module.

[0055] The servo driver encapsulates the collected real-time motor operating current data and real-time push rod displacement data, along with timestamps and device status information, into a feedback data frame, and uploads it to the industrial control computer in real time via the PCAN communication link through its PCAN communication module.

[0056] S14: Convert motor operating current into real-time pressing force based on a pre-stored current-pressure conversion model.

[0057] The current-pressure conversion model refers to a mathematical model that is pre-established through calibration experiments and stored in an industrial control computer, used to characterize the mapping relationship between the motor's operating current and the electric cylinder's output pressure. The current-pressure conversion model is established in advance by those skilled in the art and will not be elaborated upon here.

[0058] Real-time pressing force refers to the real-time force value that the electric cylinder push rod 131 is currently applying to the workpiece, calculated instantly by the industrial control computer by substituting the received real-time motor operating current value into the current-pressure conversion model.

[0059] S15: Generates dynamic adjustment commands based on real-time pressing force, push rod displacement, and pressing parameters.

[0060] The dynamic adjustment command refers to the industrial control computer comparing the real-time pressing force with the target pressing force in the pressing parameters, comparing the real-time push rod displacement with the preset displacement-time curve generated based on the target displacement and speed, and then performing calculations using a built-in closed-loop control algorithm (such as a PID algorithm) to generate a correction command for real-time adjustment of the servo drive's output torque and speed. This command is used to eliminate tracking errors in force and displacement.

[0061] S16: Responds to the dynamic adjustment command to control the servo driver to adjust the output via the PCAN communication module to complete the pressing process.

[0062] The industrial control computer sends dynamic adjustment commands to the servo driver via the PCAN communication module. The servo driver adjusts the output of its power module according to these commands, thereby changing the motor's torque and speed, achieving precise adjustment of the output force and movement speed of the push rod 131. This feedback-comparison-adjustment process continues in a loop until the push rod displacement reaches the target value and the real-time pressing force reaches and stabilizes at the target value, and the set holding time is completed. The pressing cycle then ends. Subsequently, the push rod 131 returns to its initial position according to the command, the data of this pressing process is stored, and the equipment prepares to execute the next task.

[0063] It also includes the construction and dynamic calibration methods for the current-pressure conversion model: S20: During the equipment initialization phase, a known standard pressure is applied to the improved electric cylinder 1, and in response to the known standard pressure, the corresponding motor operating current value is acquired through the current loop detection unit.

[0064] The equipment initialization phase refers to a standard force calibration working mode that is actively triggered when the equipment is first put into use, after regular maintenance, or when the system detects that the model accuracy may drift. In this mode, the system controls the push rod 131 of the improved electric cylinder 1 to press against a metrologically certified standard force gauge.

[0065] The known standard pressure refers to the accurately known force value measured and fed back by a standard force gauge. The system controls the improved electric cylinder 1 to output a series of forces of different magnitudes according to a preset program (for example, from 10% to 100% of the rated pressure, increasing in 10% increments). Each force value is accurately measured by a standard force gauge and provided to the industrial control computer as the known standard pressure.

[0066] The motor operating current value refers to the average current value flowing through the motor windings, synchronously collected and recorded by the current loop detection unit built into the servo driver during the application and stable maintenance of each known standard pressure. Each known standard pressure value corresponds to a collected motor operating current value, thus forming a set of calibration data pairs.

[0067] S21: Establish an initial current-pressure mapping relationship based on the motor operating current value.

[0068] The initial current-pressure mapping relationship refers to the system performing a preliminary mathematical correlation between multiple sets of known standard pressure-motor operating current value pairs obtained in step S20, with current as the independent variable and pressure as the dependent variable. This correlation manifests as a preliminary fitting curve, which directly reflects the original correspondence between current and pressure under the current test conditions.

[0069] S22: Based on the initial current-pressure mapping relationship, the preset current sampling accuracy, and the transmission efficiency parameters, a reference current-pressure conversion model is generated and stored in the industrial control computer.

[0070] Current sampling accuracy refers to the inherent error range (e.g., ±0.5% of FS) of the current loop sensing unit when performing analog-to-digital conversion (ADC), as specified in the servo driver product datasheet. This is a known, fixed device performance parameter.

[0071] The transmission efficiency parameter refers to the average efficiency value of the improved electric cylinder 1 as a mechanical transmission component in converting the motor's rotational torque into the linear thrust of the push rod 131. This parameter takes into account factors such as the frictional loss of the roller screw 132 and bearing friction, and is a known performance parameter (e.g., 92%) determined by both electric cylinder design theory calculations and factory testing.

[0072] The reference current-pressure conversion model refers to the mathematical model generated by the industrial control computer using the initial current-pressure mapping relationship as a basis, and incorporating current sampling accuracy (used to evaluate and compensate for measurement noise and zero-point drift) and transmission efficiency parameters (used to convert the motor shaft torque into the output thrust of push rod 131). After theoretical correction and data processing (such as data smoothing and error compensation), the final model is used for online calculation. This model is permanently stored in the non-volatile memory of the industrial control computer for use in the real-time pressing process.

[0073] S23: During the press-fitting process, the internal temperature data of the servo drive is collected.

[0074] Internal temperature data refers to the temperature value detected in real time by a temperature sensor installed on the servo driver power module. This data reflects the operating ambient temperature inside the driver, and its changes affect the characteristics of the current sampling element.

[0075] S24: Based on internal temperature data and preset current sampling temperature drift curve, perform dynamic temperature compensation on the real-time collected motor operating current value to update the real-time output accuracy of the reference current pressure conversion model.

[0076] The current sampling temperature drift curve refers to a correction curve that describes the drift of the current sampling value as the internal temperature changes, which is determined and stored in advance through high and low temperature tests before the driver leaves the factory.

[0077] Once the system obtains internal temperature data during the pressing process, it queries this curve to obtain the compensation amount at the current temperature and corrects the real-time collected motor operating current value to eliminate sampling errors introduced by temperature changes. This ensures that the current value input to the reference current-pressure conversion model has been temperature normalized, thereby maintaining the long-term output accuracy of the model across the entire temperature range.

[0078] Also includes: S30: After a single press-fit cycle is completed, the actual current value during the steady-state holding phase is collected.

[0079] The actual current value refers to the average value of the motor operating current that remains relatively stable over a period of time (e.g., the latter half of the pressure holding phase, which is collected by the servo drive through its current loop detection unit during a complete pressing process, when the push rod 131 reaches the target displacement and enters the preset pressure holding phase). This current value directly reflects the electrical signal corresponding to the motor torque required to maintain the target pressure under steady-state holding conditions.

[0080] S31: Obtain the actual steady-state pressure value based on the actual current value.

[0081] The actual steady-state pressure value refers to the estimated pressure value corresponding to this steady-state current, calculated and output by the reference current-pressure conversion model currently stored in the industrial control computer, using the actual current value collected in step S30 as input. This value represents the estimated force actually applied to the workpiece by the electric cylinder during the pressure holding stage, obtained by back-calculation based on the electrical signal.

[0082] S32: Calculate the deviation between the actual steady-state pressure value and the target pressure value set in the press-fitting parameters to obtain the pressure deviation value.

[0083] The target pressure value refers to the force value that the operator sets and issues through the human-machine interaction module 212 before the start of this round of pressing task, which is expected to be reached and maintained during the pressure holding stage. It is the target pressing force in the pressing parameters.

[0084] The pressure deviation value is the algebraic difference obtained by subtracting the target pressure value from the actual steady-state pressure value. This value quantifies the magnitude and direction of the error between the model-calculated pressure and the expected pressure (a positive deviation indicates that the calculated pressure is too high, and a negative deviation indicates that it is too low).

[0085] S33: Determine whether the reference current-pressure conversion model requires parameter calibration based on the pressure deviation value.

[0086] The determination of whether calibration is needed is based on comparing the absolute value of the calculated pressure deviation with a preset allowable deviation threshold. This threshold is pre-set based on process requirements and the need for press-fit accuracy (e.g., ±1% of the target pressure). If the absolute value of the pressure deviation consistently exceeds this threshold, the accuracy of the reference current-pressure conversion model is considered to have drifted considerably, requiring parameter calibration. Otherwise, the model is considered to be in good condition and does not require immediate adjustment.

[0087] S34: If calibration is required, optimize the parameters of the reference current-pressure conversion model based on the pressure deviation value, and store the optimized model in the industrial control computer for subsequent press-fitting tasks.

[0088] Parameter optimization refers to the process where, when calibration is deemed necessary, the industrial control computer's software uses the pressure deviation sequence obtained from the current and recent historical pressing cycles as feedback signals. It then calls upon built-in adaptive algorithms (such as recursive least squares or Kalman filters) to iteratively adjust one or more key parameters (e.g., slope coefficients and intercepts of the fitting formula) of the reference current-pressure conversion model. The optimization objective is to minimize the deviation between the model's calculated pressure value and the target pressure value under similar or identical future operating conditions. After optimization, the new model parameters overwrite the old parameters, are stored in the industrial control computer's non-volatile memory, and immediately take effect for real-time pressure conversion in the next pressing task, thus achieving online, adaptive learning and accuracy maintenance of the model.

[0089] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. An improved electric cylinder characterized by, The integrated coaxial structure includes: The stator assembly (11) has a ring structure and is provided with stator windings (111) for passing in direct current to generate a driving magnetic field; The rotor assembly (12) is coaxially integrated inside the stator assembly (11) and includes a lead screw nut (121) and a magnet (122) circumferentially attached to the outer wall of the lead screw nut (121). The magnet (122) cooperates with the stator winding (111) to form a driving force, driving the lead screw nut (121) to rotate. The roller screw drive mechanism (13) is coaxially integrated inside the rotor assembly (12), including a push rod (131) with external threads that passes through the screw nut (121) and a roller screw (132) distributed between the screw nut (121) and the push rod (131). The roller screw (132) converts the rotational motion of the screw nut (121) into the linear extension and retraction motion of the push rod (131). The detection feedback component (14), integrated at the end of the electric cylinder, includes an encoder for detecting the motor speed and the displacement of the push rod (131).

2. An improved electric cylinder according to claim 1, characterized in that, The roller screw (132) is evenly distributed along the internal thread groove of the screw nut (121), and the internal thread of the screw nut (121) is adapted to the external thread of the push rod (131).

3. An improved electric cylinder according to claim 1, characterized in that, The encoder is electrically connected to an external servo driver. The encoder calculates the displacement of the push rod (131) by detecting the number of rotations of the motor. The speed and displacement data fed back by the encoder are transmitted to the external servo driver in real time.

4. An improved electric cylinder according to claim 2, characterized in that, The magnet (122) is fixed to the outer wall of the lead screw nut (121) by adhesive bonding; The roller screw (132) is rolled and embedded in the receiving space formed by the inner thread groove of the screw nut (121) and the outer thread groove of the push rod (131), and the outer peripheral surface of the roller screw (132) is respectively in contact with the groove walls of the inner thread groove and the outer thread groove.

5. An intelligent pressing device with an improved electric cylinder, comprising the improved electric cylinder as described in claims 1 to 4, characterized in that, It also includes a press-fitting main unit (21) and an independently set electrical control unit (22), which are connected by cables; The press-fitting host unit (21) includes a frame (211), an industrial computer, and a human-machine interaction module (212). The frame (211) includes a bottom base (2111), two perforated side plates (2112), a top platform (2113), and a vertical column (2114). The improved electric cylinder (1) is installed above the top platform (2113) and is coaxially connected to the motor.

6. The intelligent pressing equipment with an improved electric cylinder according to claim 5, characterized in that, It also includes a tooling mounting table (2115) disposed within the frame (211), the tooling mounting table (2115) being horizontally disposed between the vertical columns (2114) and coaxially corresponding to the push rod (131); The human-computer interaction module (212) is installed above the top platform (2113) and is rotatably connected to the top platform (2113).

7. The intelligent pressing equipment with an improved electric cylinder according to claim 6, characterized in that, The electrical control unit (22) is an independent cabinet structure. The improved electric cylinder (1) is equipped with a servo driver and is located inside the electrical control unit (22). The servo driver has a built-in PCAN communication module and a current loop detection unit. The current loop detection unit is used to detect the motor operating current and calculate the pressing force based on the current value to achieve pressure feedback. The industrial control computer is directly connected to the servo driver via a PCAN communication module.

8. The intelligent pressing equipment with an improved electric cylinder according to claim 7, characterized in that, The tooling mounting table (2115) has multiple arrayed mounting holes on its surface for fixing the press-fit tooling. It also includes electrical closed-loop control methods during the pressing process: Receive the pressing parameters set through the human-machine interaction module (212); Based on the press-fit parameters, drive commands are generated and sent to the servo driver via the PCAN communication module; Responding to drive commands to control the operation of the improved electric cylinder (1), and based on the current loop detection unit to acquire the motor operating current in real time, and based on the encoder to acquire the push rod displacement in real time; The motor operating current and push rod displacement are fed back to the industrial control computer via the PCAN communication module. The motor operating current is converted into real-time pressing force based on a pre-stored current-pressure conversion model. Dynamic adjustment commands are generated based on real-time pressing force, push rod displacement, and pressing parameters. In response to dynamic adjustment commands, the servo driver is controlled via the PCAN communication module to adjust the output and complete the pressing process.

9. The intelligent pressing equipment with an improved electric cylinder according to claim 8, characterized in that, It also includes the construction and dynamic calibration methods for the current-pressure conversion model: During the equipment initialization phase, a known standard pressure is applied to the improved electric cylinder (1), and in response to the known standard pressure, the corresponding motor operating current value is collected through the current loop detection unit; An initial current-pressure mapping relationship is established based on the motor's operating current value; Based on the initial current-pressure mapping relationship, the preset current sampling accuracy, and the transmission efficiency parameters, a reference current-pressure conversion model is generated and stored in the industrial control computer. During the press-fitting process, the internal temperature data of the servo drive is collected; Dynamic temperature compensation is performed on the real-time collected motor operating current value based on internal temperature data and preset current sampling temperature drift curve to update the real-time output accuracy of the reference current pressure conversion model.

10. The intelligent pressing equipment with an improved electric cylinder according to claim 9, characterized in that, Also includes: After a single press-fit cycle is completed, the actual current value during the steady-state holding phase is collected. The actual steady-state pressure value is obtained based on the actual current value; Calculate the deviation between the actual steady-state pressure value and the target pressure value set in the press-fitting parameters to obtain the pressure deviation value; The pressure deviation value is used to determine whether the reference current-pressure conversion model needs parameter calibration. If calibration is required, the parameters of the reference current-pressure conversion model are optimized based on the pressure deviation value, and the optimized model is stored in the industrial control computer for subsequent press-fitting tasks.

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