Electric crankshaft servo press structure and control method

Abstract

The invention provides an electric crankshaft servo press structure and a control method, and belongs to the technical field of servo presses. According to the technical scheme, the acting characteristic of a flywheel in a traditional press machine is reserved, a servo motor connected with a crankshaft is added, and speed control is directly conducted on a crankshaft rotating pair, so that the speed of the crankshaft is equal to that of the flywheel when a clutch acts, and the crankshaft is in a static state in advance when a brake acts. Friction loss generated by a clutch and a brake of a traditional press machine can be completely eliminated, other attached problems such as noise, energy consumption and mechanical impact are solved, meanwhile, the productivity is improved, and the production cost is reduced. The speed of the crankshaft is directly controlled through the servo motor, so that the clutch acts when the speed of the crankshaft and the speed of the flywheel are synchronous, the brake acts when the crankshaft is static, and meanwhile shaping machining of a workpiece is completed through the inertia of the flywheel.

Description

Technical Field

[0001] The invention relates to the technical field of servo presses, and in particular to a structure and a control method of an electric crankshaft servo press. Background Art

[0002] Mechanical presses used for forging materials such as steel often use crank-connecting rod structures such as Figure 1 As shown. The main feature of this type of press is that the equipment is driven by an ordinary asynchronous motor. In the standby state, the motor drives the flywheel to rotate through the reduction mechanism, and the electrical energy is converted into kinetic energy and stored in the flywheel. When working, the clutch is closed, and the flywheel accelerates the crankshaft rotating pair through the friction force of the clutch, and drives the slider to slide up and down along the guide rail through the connecting rod mechanism to complete the extrusion process of the workpiece between the slider and the workbench. After the processing is completed, the speed is reduced because part of the kinetic energy of the flywheel acts on the workpiece. Thereafter, the crankshaft continues to rotate, driving the slider upward. During this process, the clutch is separated, and the slider is decelerated by the friction brake before reaching the top dead center and stops at the top dead center. After the clutch is separated, the motor accelerates the flywheel again, stores energy, and waits for the next work (a typical example of this type of press can be found in the Chinese utility model patent "Integral Body Hot Forging Press"; Publication No. CN201088998Y).

[0003] The main disadvantages of this type of press are: 1. The clutch generally adopts the form of friction disc. When the clutch is just closed, the flywheel rotates and the crankshaft is stationary, which causes violent sliding between the friction discs, generates a lot of heat, and causes energy loss.

[0004] 2. After the work is completed, the brake converts the remaining kinetic energy in the crankshaft rotating pair into friction heat and dissipates it, which also increases the energy loss of the equipment.

[0005] 3. The continuous friction of the clutch and brake causes wear of parts, which must be replaced regularly.

[0006] 4. The equipment runs at a fixed speed, resulting in poor process adaptability, low product yield, and rapid mold loss.

[0007] 5. The transmission mechanism has great impact and loud noise, resulting in a harsh production site environment.

[0008] In view of the shortcomings of traditional mechanical presses, the industry has proposed the concept of servo presses. Taking the Chinese utility model patent "Servo Press Transmission System" (publication number CN202283787U) as an example, the main features of this patented technology are: 1. The clutch is cancelled, and the slider is directly driven by the servo motor through the transmission system.

[0009] 2. Eliminate the flywheel, and all the energy required for the slider to process the workpiece comes directly from the electromagnetic torque of the servo motor.

[0010] 3. After the work is completed, the servo motor is used to decelerate the equipment, and the brake is commanded to operate only after it reaches a stationary state, eliminating the friction loss of the brake.

[0011] Through the above measures, the existing patented technology solves some problems of traditional mechanical presses and can be well applied to stamping processes such as deep drawing and blanking, but it is difficult to use in forging processes. The main reason is that there are important differences between forging and stamping processes. The stamping process requires that the slider is very slow in the working stroke close to the bottom dead center, or even remains stationary for a certain period of time. The servo motor only needs to output a large torque, so that the motor power is limited to an acceptable range (power = speed × torque). The forging process requires the motor to output both the maximum torque and the highest speed in the working stroke, so that the servo motor power is very large, often reaching several times or even dozens of times that of the stamping process. This makes the servo motor costly, large in size, and heavy in weight. In addition, the energy required for the equipment to work is obtained from the power grid in a short period of time, causing a huge impact.

[0012] For example, for a servo forging press with a nominal force of 1,000 tons and a rated work energy of 100 kJ, if the above-mentioned existing patented technology is used, the peak power of the motor is required to exceed 3 MW. Even if the torque is increased by a reduction mechanism, the motor size is still huge. In addition, if calculated based on the conventional 30 times of work per minute, the average power of the motor is only 55 kW. The impact current (instantaneous power) generated during work is more than 50 times the average value, which will have a huge impact on the power grid. And this also requires the factory power equipment to be equipped with a 3 MW capacity specifically for this press, which will also cause a huge economic burden.

[0013] It can be seen that using the idea of ​​stamping servo press to solve the problems of forging press is difficult to accept from both technical and economic perspectives. This is the key obstacle to the application of servo press in the forging industry. Summary of the invention

[0014] The present invention aims to address the technical defects of the prior art and provide an electric crankshaft servo press structure and control method to solve the problems of high energy consumption caused by clutches and brakes in traditional mechanical presses.

[0015] Another technical problem to be solved by the present invention is that the existing servo press technology is difficult to use in forging process.

[0016] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: A structure of an electric crankshaft servo press comprises a flywheel motor, a flywheel, a clutch, a crankshaft, a brake, a crank, a connecting rod, a slider, a guide rail, a crankshaft motor, a first encoder, a second encoder, a controller, a first driver and a second driver, wherein the flywheel motor is connected to the flywheel, a clutch is provided between the flywheel and the crankshaft, a brake is provided on the crankshaft, a crank is provided on the crankshaft, a connecting rod is connected to the crank, a slider is connected to the connecting rod, the slider is slidably matched with the guide rail, the crankshaft motor is connected to the crankshaft, a first encoder is installed on the flywheel motor, a second encoder is installed on the crankshaft motor, the first encoder and the second encoder are respectively connected to the controller for communication, the controller is connected to the flywheel motor for communication via the first driver, and the controller is connected to the crankshaft motor for communication via the second driver.

[0017] Preferably, the first encoder and the second encoder are rotary encoders.

[0018] Preferably, the first encoder measures the rotational speed of the flywheel, and the second encoder measures the rotational angle of the crankshaft.

[0019] Preferably, the first driver is electrically connected to the second driver.

[0020] Preferably, the clutch and the brake are respectively communicatively connected to the controller.

[0021] Preferably, an interface is provided on the controller, and the interface receives control instructions from the user and inputs them into the controller.

[0022] Preferably, the connection between the flywheel motor and the flywheel is a direct drive transmission connection or a non-direct drive transmission connection; the connection between the crankshaft motor and the crankshaft is a direct drive transmission connection or a non-direct drive transmission connection. When the non-direct drive form is adopted, the motor torque can be transmitted to the flywheel and the crankshaft respectively through the transmission and reduction mechanism, thereby achieving the same technical characteristics. For example, the technical solution of the present invention can be realized by simply adding a crankshaft motor on the basis of the existing traditional crank connecting rod press.

[0023] As a preference, the crank is replaced by an eccentric wheel, and the connecting rod is replaced by a toggle lever. In addition, the connecting rod can be a single connecting rod structure or a multi-connecting rod structure.

[0024] In the above technical scheme, the transmission system of the equipment includes a flywheel, a clutch, a crankshaft, a crank, a connecting rod, a slider, a guide rail, and a brake. When the clutch is disengaged, the flywheel is driven by the flywheel motor and rotates at a constant speed. When the clutch is closed and the brake is released, the flywheel drives the crankshaft to rotate, and the rotational motion is converted into linear motion through the crank-connecting rod mechanism, so that the slider moves up and down along the guide rail. The workpiece to be processed is located between the slider and the workbench, and extrusion molding is completed through the mold.

[0025] The control system of the equipment includes two encoders, whose signals are input to the controller. The first encoder is used to measure the speed of the flywheel, and the second encoder is used to measure the angle of the crankshaft. The controller uses the angular derivative of the second encoder to calculate the speed. The controller sends commands to the first and second drivers to control the flywheel motor and the crankshaft motor to generate the required torque and speed, respectively, thereby driving the flywheel and crankshaft to rotate respectively. The first and second drivers are electrically connected to each other, and direct energy exchange between them can be completed under the control of the controller. The control signals of the clutch and brake are also generated by the controller to complete the required actions according to the process requirements. The controller also has other interfaces to receive user commands and complete other functions of the equipment.

[0026] On the basis of the above technical solution, the present invention further provides a control method for the above electric crankshaft servo press structure, comprising: 1) In the standby state, the controller sends a standby command, so that the brake is closed, the clutch is released, the crankshaft is stationary, the angle is equal to 0, the slider is at the top dead center, and the flywheel speed is equal to the set value nf; 2) The controller checks the user interface to see if there is a start command; if not, it returns to step 1) and remains in standby mode; if yes, it proceeds to the next step and enters the acceleration stage; 3) The controller outputs the brake release and crankshaft motor acceleration command, and the crankshaft target speed is equal to nf; 4) During the crankshaft acceleration process, the controller checks the crankshaft speed in real time; when it is equal to the flywheel speed, it proceeds to the next step and the equipment enters the power stage; otherwise, it returns to step 3) and continues to accelerate; 5) The controller issues a clutch closing command, causing the crankshaft to engage with the flywheel, and the equipment to perform work on the workpiece; 6) During the power stage, the controller continuously checks the crankshaft angle; when the angle exceeds 180 degrees, it proceeds to the next step and the device enters the return stage; otherwise, it returns to step 5) and continues to power; 7) During the return phase, the controller issues a clutch release command to control the flywheel motor to accelerate to the target speed nf, and at the same time controls the crankshaft motor to decelerate so that the crankshaft stops at the 360-degree position.

[0027] Preferably, after completing step 7), the controller returns to step 1), with steps 1) to 7) as one forging stroke, and the method cyclically executes several forging strokes.

[0028] In the above control method, the press enters the standby state after starting. In standby state, the brake is closed, the clutch is disengaged, the crank angle is equal to 0, the slider is at the top dead center, and the flywheel rotates at a given speed. At this point, the equipment is ready for forging. The processing technology is divided into three stages according to the process of one crank rotation.

[0029] Phase 1: Acceleration phase. After receiving the start command, the controller issues a brake release and crankshaft acceleration command. The crankshaft motor drives the crankshaft to accelerate and accelerate to the same speed as the flywheel before the crank angle enters the power phase. At this time, the controller issues a clutch closing command to connect the flywheel to the crankshaft, and the equipment enters the power phase. Because the clutch closing requires a certain amount of time, the issuance time of the clutch closing command should be calculated in advance to ensure that the clutch is reliably closed before the slider contacts the workpiece. During the acceleration process, the crankshaft motor outputs a large power. In order to reduce the impact on the power grid, the flywheel motor can be operated in an electric energy regeneration state after the required power exceeds the rated value, that is, by slightly braking the flywheel to generate electric energy to supply the crankshaft motor, reducing the electric energy obtained from the power grid.

[0030] Phase 2: Power phase. The range from the crank angle when the slider contacts the workpiece to 180 degrees is the power phase. The device uses the kinetic energy in the entire transmission mechanism including the flywheel, crankshaft rotating pair, connecting rod and slider to work on the workpiece. In addition, the two motors also generate electromagnetic torque to assist in the work. In the power phase, the kinetic energy of the device decreases and the speed decreases. When the crankshaft angle reaches 180 degrees, the flywheel speed drops to the lowest point.

[0031] Phase 3: Return phase. After the crankshaft angle exceeds 180 degrees, the clutch is disengaged. After that, the crankshaft motor generates braking torque, forcing the crankshaft to decelerate and stop when the slider reaches the top dead center, that is, the crankshaft reaches 360 degrees. The brake is then closed to prevent the crankshaft from moving. After the clutch is disengaged, the flywheel motor outputs driving torque to accelerate the flywheel and reach a given speed before the next start. During the crankshaft braking process, the kinetic energy in the crankshaft, connecting rod and slider is converted into electrical energy by the crankshaft motor and transmitted to the first drive by the second drive to assist the acceleration of the flywheel. In order to shorten the return time as quickly as possible, the crankshaft can also be accelerated first, and then braked to stop after approaching the top dead center at the fastest speed.

[0032] The present invention adds a crankshaft motor to the original traditional press. Before starting the forging action each time, the crankshaft is first driven by the crankshaft motor to rotate first, and the clutch is closed after reaching the same speed as the flywheel. In addition, after the forging is completed, the crankshaft is first electrically braked by the crankshaft motor, and the brake is closed after the crankshaft is stationary. This method still uses the flywheel to store energy when in standby mode and release energy when working.

[0033] The present invention retains the flywheel work characteristics of the traditional press, adds a servo motor connected to the crankshaft, and directly controls the speed of the crankshaft rotating pair, so that the speed of the crankshaft and the flywheel are equal when the clutch is actuated, and the crankshaft is put into a static state in advance when the brake is actuated. This can not only completely eliminate the friction loss generated by the clutch and brake of the traditional press, but also solve other incidental problems such as noise, energy consumption and mechanical impact. At the same time, the present invention improves productivity and reduces production costs.

[0034] The key point of the present invention is to use a servo motor to directly control the speed of the crankshaft, so that the clutch is activated when the crankshaft and the flywheel speed are synchronized, and the brake is activated when the crankshaft is stationary, and the flywheel inertia is used to complete the shaping of the workpiece. The present invention uses a servo motor directly connected to the crankshaft to realize the electric crankshaft structure, uses a flywheel to realize an efficient and energy-saving servo forging process control method, and uses electronic equipment and software such as a controller, a driver, and an encoder to realize the joint control of the electric crankshaft and the flywheel.

[0035] Compared with the prior art, the present invention has the following beneficial effects: 1. Compared with the traditional non-servo forging press, the present invention eliminates the relative sliding of the parts in the clutch and brake, thereby eliminating friction loss. This significantly improves the energy utilization rate of the equipment, greatly reduces mechanical impact and noise, extends the maintenance and replacement cycle of parts, and reduces production costs.

[0036] 2. Compared with the traditional non-servo forging press, the present invention eliminates the relative sliding of the components in the clutch and the brake, so the flywheel can rotate at a higher speed, so that a smaller flywheel can be used to store sufficient energy, which greatly reduces the weight of the flywheel, the largest component in such equipment, thereby reducing material usage and reducing equipment costs.

[0037] 3. Compared with the traditional non-servo forging press, the present invention can significantly shorten the travel time due to the use of a higher flywheel speed, which can directly improve productivity.

[0038] 4. Compared with the traditional non-servo forging press, the present invention can significantly shorten the contact time between the die and the workpiece when the equipment is working due to the higher flywheel speed, which is conducive to extending the life of the die. This advantage reduces the frequency of die replacement, increases the effective production time, and reduces the cost of die use.

[0039] 5. Compared with the existing servo press technology, the present invention can greatly reduce the equipment's requirements for servo motor power, which not only makes the cost of the servo forging press within an acceptable range, but also because the motor volume and weight are greatly reduced, the overall structure of the press is reasonable, the center of gravity is lowered, and the overall stability is achieved, making the servo forging press technically feasible. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a structural diagram of the drive and transmission system of a traditional crank-connecting rod press; Figure 2 It is a structural diagram of the transmission and drive system of the electric crankshaft servo press of the present invention; Figure 3 It is a schematic diagram of the crank movement of the forging process of the electric crankshaft servo press of the present invention; Figure 4 It is a control flow chart of the electric crankshaft servo press of the present invention; Figure 5 It is a schematic diagram of the crank-connecting rod structure used for calculating technical parameters in the present invention; In the figure: 1. Flywheel motor 2. Flywheel 3. Clutch 4. Crankshaft 5. Brake 6. Crank 7. Connecting rod 8. Sliders 9. Guide rail 10. Crankshaft motor 11. First Encoder 12. Second encoder 13. Controller 14. First Drive 15. Second Driver 16. Workbench 17. Belt. DETAILED DESCRIPTION

[0041] The specific embodiments of the present invention will be described in detail below. In order to avoid too much unnecessary details, the well-known structures or functions will not be described in detail in the following examples. The approximate language used in the following examples can be used for quantitative expression, indicating that the quantity can be allowed to have a certain change without changing the basic function. Unless otherwise defined, the technical and scientific terms used in the following examples have the same meaning as those generally understood by those skilled in the art to which the present invention belongs.

[0042] An electric crankshaft servo press structure, such as Figure 2As shown, it includes a flywheel motor 1, a flywheel 2, a clutch 3, a crankshaft 4, a brake 5, a crank 6, a connecting rod 7, a slider 8, a guide rail 9, a crankshaft motor 10, a first encoder 11, a second encoder 12, a controller 13, a first driver 14, and a second driver 15, wherein the flywheel motor 1 is connected to the flywheel 2, a clutch 3 is provided between the flywheel 2 and the crankshaft 4, a brake 5 is provided on the crankshaft 4, a crank 6 is provided on the crankshaft 4, a connecting rod 7 is connected to the crank 6, a slider 8 is connected to the connecting rod 7, the slider 8 is slidably matched with the guide rail 9, the crankshaft motor 10 is connected to the crankshaft 4, a first encoder 11 is installed on the flywheel motor 1, a second encoder 12 is installed on the crankshaft motor 10, the first encoder 11 and the second encoder 12 are respectively connected to the controller 13 for communication, the controller 13 is connected to the flywheel motor 1 for communication via the first driver 14, and the controller 13 is connected to the crankshaft motor 10 for communication via the second driver 15. The first encoder 11 and the second encoder 12 are rotary encoders. The first encoder 11 measures the rotation speed of the flywheel 2, and the second encoder 12 measures the rotation angle of the crankshaft 4. The first driver 14 is electrically connected to the second driver 15. The clutch 3 and the brake 5 are respectively connected to the controller 13 for communication. The controller 13 is provided with an interface, which receives control instructions from the user and inputs them into the controller 13.

[0043] The press is used for the control process of the forging process through Figure 3 Provide explanation.

[0044] After the press is turned on, it first enters the standby state. In standby mode, the brake is closed, the clutch is disengaged, the crank angle is equal to 0, the slider is at the top dead center, and the flywheel rotates at a given speed. At this point, the equipment is ready for forging. The processing technology is divided into three stages according to the process of one crank rotation.

[0045] Phase 1: Acceleration phase. After receiving the start command, the controller issues a brake release and crankshaft acceleration command. The crankshaft motor drives the crankshaft to accelerate and accelerate to the same speed as the flywheel before the crank angle enters the power phase. At this time, the controller issues a clutch closing command to connect the flywheel to the crankshaft, and the equipment enters the power phase. Because the clutch closing requires a certain amount of time, the issuance time of the clutch closing command should be calculated in advance to ensure that the clutch is reliably closed before the slider contacts the workpiece. During the acceleration process, the crankshaft motor outputs a large power. In order to reduce the impact on the power grid, the flywheel motor can be operated in an electric energy regeneration state after the required power exceeds the rated value, that is, by slightly braking the flywheel to generate electric energy to supply the crankshaft motor, reducing the electric energy obtained from the power grid.

[0046] Phase 2: Power phase. The range from the crank angle when the slider contacts the workpiece to 180 degrees is the power phase. The device uses the kinetic energy in the entire transmission mechanism including the flywheel, crankshaft rotating pair, connecting rod and slider to work on the workpiece. In addition, the two motors also generate electromagnetic torque to assist in the work. In the power phase, the kinetic energy of the device decreases and the speed decreases. When the crankshaft angle reaches 180 degrees, the flywheel speed drops to the lowest point.

[0047] Phase 3: Return phase. After the crankshaft angle exceeds 180 degrees, the clutch is disengaged. After that, the crankshaft motor generates braking torque, forcing the crankshaft to decelerate and stop when the slider reaches the top dead center, that is, the crankshaft reaches 360 degrees. The brake is then closed to prevent the crankshaft from moving. After the clutch is disengaged, the flywheel motor outputs driving torque to accelerate the flywheel and reach a given speed before the next start. During the crankshaft braking process, the kinetic energy in the crankshaft, connecting rod and slider is converted into electrical energy by the crankshaft motor and transmitted to the first drive by the second drive to assist the acceleration of the flywheel. In order to shorten the return time as quickly as possible, the crankshaft can also be accelerated first, and then braked to stop after approaching the top dead center at the fastest speed.

[0048] The above control process can be further represented by a flow chart. After the press is powered on, the standby state is first established, so that the crankshaft is stationary, the angle is equal to zero, and the flywheel speed is equal to the set value nf. Then enter Figure 4 The control flow shown is as follows: 1. In the standby state, the controller sends a standby command, so that the brake is closed, the clutch is released, the crankshaft is stationary, the angle is equal to 0, the slider is at the top dead center, and the flywheel speed is equal to the set value nf.

[0049] 2. The controller checks the user interface to see if there is a start command. If not, it returns to step 1 and remains in standby mode; if yes, it proceeds to the next step and enters the acceleration phase.

[0050] 3. The controller outputs the brake release and crankshaft motor acceleration command, and the crankshaft target speed is equal to nf.

[0051] 4. During the crankshaft acceleration process, the controller checks the crankshaft speed in real time. When it is equal to the flywheel speed, the next step is taken and the equipment enters the power stage; otherwise, it returns to step 3 and continues to accelerate.

[0052] 5. The controller issues a clutch closing command, causing the crankshaft to engage with the flywheel, and the equipment to perform work on the workpiece.

[0053] 6. During the power stage, the controller continuously checks the crankshaft angle. When the angle exceeds 180 degrees, the next step is taken and the device enters the return stage; otherwise, it returns to step 5 and continues to power.

[0054] 7. In the return phase, the controller issues a clutch release command to control the flywheel motor to accelerate to the target speed nf, and at the same time controls the crankshaft motor to decelerate so that the crankshaft stops at the 360-degree position. At this point, a complete forging stroke is completed, and the controller returns to step 1 to continue the next cycle.

[0055] The following takes a crank-connecting rod forging press with a nominal force of 1000 tons (10000 kN) as an example to explain in detail the design method of the main parameters of the motor.

[0056] The main technical parameters of this type of traditional forging press are: crankshaft acceleration angle θa = 150 degrees (5π / 6); flywheel rated speed nf = 90 rpm; production efficiency is 30 work operations per minute; work energy Wwk = 100 kJ; flywheel moment of inertia Jf = 7000 kg.m^2; crank length Rc = 140 mm (0.14 m); connecting rod length L = 900 mm (0.9 m); the average value of the equivalent moment of inertia of the crankshaft-connecting rod-slider on the crankshaft is Jc = 300 kg.m^2 (due to the nonlinear characteristics of the crankshaft-connecting rod structure, the moment of inertia of the connecting rod and slider converted to the crankshaft depends on the crankshaft angle. Because the inertia of the connecting rod and slider is small, the accuracy of the average value meets the engineering needs and does not affect the description of the design method).

[0057] As mentioned above, the flywheel in the present invention can run at a relatively fast speed. Based on actual working conditions, the rated speed of the flywheel is increased to nf = 120 rpm (4π rad / s); after the speed is increased, the flywheel can store the same kinetic energy with a smaller inertia, so the flywheel inertia can be reduced to Jf = 4000 kg.m^2. Other parameters remain unchanged.

[0058] References Figure 5 The calculation is performed based on the crank-connecting rod structure schematic diagram shown.

[0059] The crankshaft should accelerate from zero speed to the flywheel speed during the acceleration phase, and its acceleration is:

[0060] The time required for the acceleration phase is:

[0061] The crankshaft motor drives the crankshaft to accelerate with a constant torque, and the torque is:

[0062] The crankshaft motor outputs maximum power when its speed reaches the flywheel speed under constant torque conditions:

[0063] After the work is done, the crankshaft motor needs to brake. Because its kinetic energy has been reduced and the braking angle is greater than the acceleration angle, if the braking torque is equal to the driving torque, the required braking power of the crankshaft motor is less than the above driving power. That is, the motor power and torque calculated according to the acceleration parameters must meet the braking requirements.

[0064] The kinetic energy stored in the drive train (including all moving parts such as flywheel and crankshaft) at the beginning of the power phase is:

[0065] Part of the kinetic energy stored in the transmission system during the power stage is transferred to the workpiece. The remaining kinetic energy after this stage is:

[0066] Flywheel speed after the power phase:

[0067] The time spent in the power phase is the angle during this phase divided by the average speed (assuming that the flywheel speed decreases linearly during this phase):

[0068] After the work is done, the flywheel needs to use the standby time to accelerate to the rated speed. The standby time is (where ts is the time required for a production cycle):

[0069] The flywheel is accelerated uniformly with constant torque, and the acceleration rate is equal to the increase in speed divided by the acceleration time:

[0070] The acceleration torque can be obtained based on the flywheel acceleration and inertia:

[0071] When the flywheel accelerates to rated speed, the flywheel motor reaches maximum power:

[0072] The average power of the flywheel motor and the crankshaft motor is calculated below. It is assumed that all the energy for crankshaft acceleration comes directly from the grid, and the energy for crankshaft braking is completely regenerated after work is completed and stored in the flywheel through the flywheel motor.

[0073] During the acceleration phase, the energy obtained by the crankshaft motor from the power grid is equal to the kinetic energy obtained by the crankshaft rotating pair, connecting rod and slider:

[0074] During the return phase, the crankshaft motor regenerates the remaining kinetic energy in the crankshaft mechanism into electrical energy:

[0075] The average power of a crankshaft motor is equal to the total energy it converts divided by the production cycle:

[0076] The flywheel motor only works in the driving mode, and its energy comes from the grid and the regenerative energy of the crankshaft motor, and its total value is equal to the work energy. Therefore, the average power of the flywheel motor is:

[0077] Summarizing the above calculation results, the main parameters of the flywheel motor and crankshaft motor are as follows: Table 1 Main parameters of flywheel motor and crankshaft motor Rated speed (rpm) Peak power (kW) Maximum torque (Nm) Average power (kW) Flywheel motor 120 66 5370 50 Crankshaft motor 120 103 8192 20.2 It should be noted that the above calculation does not take into account the efficiency of mechanical and electrical equipment. In actual work, losses should be taken into account and margin should be left.

[0078] After completing the above motor parameter design, the travel time of a single forging can be checked. The acceleration stage and the power stage time have been calculated above. Now calculate the return time. During the return stroke, the crankshaft first moves forward at a constant speed at the speed after the power is completed, and then brakes and stops at the 360-degree crankshaft position.

[0079] The crankshaft is braked according to the acceleration in the acceleration phase, and the time required for crankshaft braking can be obtained:

[0080] Braking distance:

[0081] Then calculate the time for the crankshaft to run at a constant speed:

[0082] The time required to complete a forging stroke is the sum of the time required for the acceleration phase, the power phase, and the return phase:

[0083] In order to return as quickly as possible, the return stage can also be accelerated first, then decelerated and stopped. If the speed drops significantly after the work is completed, this method can significantly shorten the return time. However, in this example, the speed does not drop much after the work is completed, so the benefits of this method are not obvious.

[0084] The present invention is compared with the existing servo press patent method below. The existing servo press patent technology does not use a flywheel, and the working pressure is completely provided by the electromagnetic torque of the motor. Assume that the nominal force stroke height is 2.5 mm, corresponding to a crankshaft angle of 170 degrees. The slider is required to generate a pressure of 1000 tons between this position and the bottom dead center. At the nominal force stroke, the motor outputs the maximum torque. According to the dynamic model of the transmission system, it is calculated that the crank torque should reach 283 kNm, corresponding to a motor power of 3.6 MW, which is more than 20 times the sum of the powers of the two motors used in the design of the present invention. Correspondingly, the weight, volume and cost of the motor are also approximately the same multiple. And it will cause a strong impact on the power grid.

[0085] In addition, the present invention is compared with a conventional non-servo forging press. After calculation, it is found that the time required for a conventional press of the same tonnage to complete a forging stroke is 1.248 s, which is 33% more than that of the present invention. The working time of the conventional press is 61 ms, which is 35% more than that of the present invention.

[0086] The embodiments of the present invention are described in detail above, but the contents are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the scope of the present invention shall be included in the protection scope of the present invention.

Claims

1. An electric crankshaft servo press structure, characterized in that: The invention comprises a flywheel motor (1), a flywheel (2), a clutch (3), a crankshaft (4), a brake (5), a crank (6), a connecting rod (7), a slider (8), a guide rail (9), a crankshaft motor (10), a first encoder (11), a second encoder (12), a controller (13), a first driver (14), and a second driver (15), wherein the flywheel motor (1) is connected to the flywheel (2), a clutch (3) is provided between the flywheel (2) and the crankshaft (4), a brake (5) is provided on the crankshaft (4), a crank (6) is provided on the crankshaft (4), and a second driver (15) is provided on the crankshaft (6). A connecting rod (7) is connected to the connecting rod (7), a slider (8) is connected to the connecting rod (7), the slider (8) and the guide rail (9) are slidably matched, a crankshaft motor (10) is connected to the crankshaft (4), a first encoder (11) is installed on the flywheel motor (1), a second encoder (12) is installed on the crankshaft motor (10), the first encoder (11) and the second encoder (12) are respectively connected to a controller (13) for communication, the controller (13) is connected to the flywheel motor (1) for communication via a first driver (14), and the controller (13) is connected to the crankshaft motor (10) for communication via a second driver (15).

2. The electric crankshaft servo press structure according to claim 1, characterized in that: The first encoder (11) and the second encoder (12) are rotary encoders.

3. The electric crankshaft servo press structure according to claim 1, characterized in that: The first encoder (11) measures the rotation speed of the flywheel (2), and the second encoder (12) measures the rotation angle of the crankshaft (4).

4. The electric crankshaft servo press structure according to claim 1, characterized in that: The first driver (14) is electrically connected to the second driver (15).

5. The electric crankshaft servo press structure according to claim 1, characterized in that: The clutch (3) and the brake (5) are respectively connected to the controller (13) for communication.

6. The electric crankshaft servo press structure according to claim 1, characterized in that: The controller (13) is provided with an interface, which receives control instructions from a user and inputs them into the controller (13).

7. The electric crankshaft servo press structure according to claim 1, characterized in that: The connection between the flywheel motor (1) and the flywheel (2) is a direct drive transmission connection or a non-direct drive transmission connection; the connection between the crankshaft motor (10) and the crankshaft (4) is a direct drive transmission connection or a non-direct drive transmission connection.

8. The electric crankshaft servo press structure according to claim 1, characterized in that: The crank (6) is replaced by an eccentric wheel; the connecting rod (7) is replaced by a toggle lever.

9. The control method of the electric crankshaft servo press structure according to claim 1, characterized in that: include: 1) In the standby state, the controller sends a standby command, so that the brake is closed, the clutch is released, the crankshaft is stationary, the angle is equal to 0, the slider is at the top dead center, and the flywheel speed is equal to the set value nf; 2) The controller checks the user interface to see if there is a start command; if not, it returns to step 1) and remains in standby mode; if yes, it proceeds to the next step and enters the acceleration stage; 3) The controller outputs the brake release and crankshaft motor acceleration command, and the crankshaft target speed is equal to nf; 4) During the crankshaft acceleration process, the controller checks the crankshaft speed in real time; when it is equal to the flywheel speed, it proceeds to the next step and the equipment enters the power stage; otherwise, it returns to step 3) and continues to accelerate; 5) The controller issues a clutch closing command, causing the crankshaft to engage with the flywheel, and the equipment to perform work on the workpiece; 6) During the power stage, the controller continuously checks the crankshaft angle; when the angle exceeds 180 degrees, it proceeds to the next step and the device enters the return stage; otherwise, it returns to step 5) and continues to power; 7) During the return phase, the controller issues a clutch release command to control the flywheel motor to accelerate to the target speed nf, and at the same time controls the crankshaft motor to decelerate so that the crankshaft stops at the 360-degree position.

10. The control method according to claim 9, characterized in that: After completing step 7), the controller returns to step 1), and steps 1) to 7) are regarded as a forging stroke. The method executes several forging strokes in a cycle.

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