An upsetting die for cold forging of motor shafts

Abstract

This invention relates to the field of motor shaft machining technology, and more particularly to an upsetting die for cold forging of motor shafts, comprising: an upsetting unit for upsetting the motor shaft into a predetermined shape; a detection unit for detecting the downward speed of the upper die, the amount of remaining debris on the contact surface of the die, and the volume of gas discharged from the die; and a control unit for determining the flow rate of hydraulic oil based on the change in the downward speed of the upper die, estimating the amount of debris attracted by the magnetic field generated on the motor shaft based on the variance of the downward speed of the upper die after contact with the motor shaft, determining the upsetting ambient temperature based on the difference between the amount of debris and the amount of remaining debris on the contact surface of the die, calculating the amount of lubricant loss based on the difference, and determining the pressure relief pause duration before holding pressure based on the amount of lubricant loss and the volume of gas discharged from the die. This invention effectively improves the forming accuracy of motor shafts and is suitable for high-precision motor shaft manufacturing.

Description

Technical Field

[0001] This invention relates to the field of motor shaft machining technology, and in particular to an upsetting die for cold forging of motor shafts. Background Technology

[0002] In existing technologies, the motor shaft is a core transmission component of motors (including industrial motors, servo motors, and drive motors for new energy vehicles). Its main function is to support the rotation of the rotor and transmit torque. The machining quality of the motor shaft directly determines the motor's operating accuracy, vibration and noise level, energy efficiency ratio, and service life. With the rapid development of high-end equipment manufacturing and the new energy vehicle industry, the market has placed increasingly stringent requirements on the dimensional accuracy, surface integrity, mechanical properties (such as fatigue strength), and magnetic properties (such as remanence) of motor shafts. Traditional motor shaft manufacturing often adopts the process route of "bar cutting + heat treatment." However, cutting processing has disadvantages such as low material utilization, strength reduction due to metal fiber cutting, and limited production efficiency. In contrast, cold forging has become the mainstream trend in mass production of motor shafts because it can maintain the continuity of metal fibers, improve material utilization, and achieve no or little cutting processing.

[0003] Chinese Patent Application Publication No. CN121571595A discloses a cold forging step-by-step extrusion and stretching method for motor shaft preparation. This method involves obtaining an approximate average force for forward extrusion, adjusting the initial deformation resistance of the workpiece based on the approximate average force, obtaining the target parameter increment of the reverse extrusion process and the average inner diameter of the target hollow part of the reverse extrusion to determine the target volume deformation, and determining a process difficulty evaluation index based on the initial deformation resistance and the target volume deformation; obtaining the adjustment intensity of the set value of the stamping force, determining the correlation between the process difficulty evaluation index and the subsequent process adjustment intensity based on several adjustment intensities of the current batch of workpieces and the process difficulty evaluation index; and adjusting the difficulty threshold of the workpiece processing difficulty state determined based on the process difficulty evaluation index in response to the correlation. Therefore, this cold forging step-by-step extrusion and stretching method for motor shaft preparation suffers from problems such as the hydraulic oil temperature rise affecting the downward speed control accuracy of the upper die, and the stick-slip motion between the die and the motor shaft causing charge separation and current generation. The resulting magnetic field attracts debris, leading to porosity, delamination, or surface pits inside the workpiece. Summary of the Invention

[0004] Therefore, the present invention provides an upsetting die for cold forging of motor shafts, which overcomes the problems in the prior art where the rise in hydraulic oil temperature affects the control accuracy of the downward speed of the upper die, and the stick-slip motion between the die and the motor shaft causes charge separation and current generation, resulting in the magnetic field that attracts debris, causing pores, delamination or surface pits inside the workpiece.

[0005] To achieve the above objectives, the present invention provides an upsetting die for cold forging of motor shafts, comprising: An upsetting unit is used to upset a motor shaft into a predetermined shape. It includes a mold consisting of an upper mold and a lower mold, an ejector assembly connected to the lower mold to eject the upset motor shaft formed in the mold out of the mold, and a stamping constraint assembly sleeved on the outer ring of the ejector assembly to constrain the spatial position of the ejector assembly. The top material assembly includes a top material ring, a top material rod disposed below the top material ring, a pad disposed below the top material rod, and a lower top rod disposed below the pad. The top material ring is disposed above the top material rod, and a lower punch is disposed inside the top material ring. The detection unit is connected to the upsetting unit and is used to detect the downward speed of the upper die, the amount of remaining debris on the contact surface of the die, and the volume of gas discharged from the die, respectively. The control unit is connected to both the upsetting unit and the detection unit. It is used to determine the hydraulic oil flow rate based on the change in the downward speed of the upper die, estimate the amount of debris attracted by the magnetic field generated on the motor shaft based on the variance of the downward speed of the upper die after contacting the motor shaft, determine the upsetting ambient temperature based on the difference between the amount of debris and the amount of debris remaining on the contact surface of the die, calculate the amount of lubricant loss based on the difference, and determine the pressure relief pause time before pressure holding based on the amount of lubricant loss and the volume of gas discharged from the die.

[0006] Furthermore, the detection unit includes: A displacement sensor is installed on the workshop sidewall corresponding to the outer side of the upper mold to detect the downward speed of the upper mold; A vision sensor, positioned below the displacement sensor, is used to detect the amount of remaining debris on the contact surface of the mold. A gas flow sensor is disposed between the displacement sensor and the vision sensor to detect the gas flow rate discharged from the mold.

[0007] Furthermore, the control unit is connected to the displacement sensor and is used to determine that the influence of the hydraulic oil viscosity change on the pressing process does not meet the requirements if the change in the downward speed of the upper mold is greater than a preset change, and to reduce the flow rate of the hydraulic oil. The flow rate of the hydraulic oil is negatively correlated with the change in the downward speed of the upper mold. The change in the downward speed of the upper mold is the difference between the downward speed of the upper mold at the beginning and the downward speed of the upper mold at the end of the monitoring period.

[0008] Furthermore, the control unit is connected to the vision sensor and the centrifugal fan respectively, and is used to determine whether the degree of magnetic field influence on the motor shaft meets the requirements based on the difference being greater than a preset difference, and to control the centrifugal fan to reduce the upsetting environment temperature.

[0009] Furthermore, the amount of debris attracted by the magnetic field generated on the motor shaft is the product of the variance of the downward speed of the upper mold after contacting the motor shaft and the debris amount conversion coefficient.

[0010] Furthermore, the upsetting ambient temperature is negatively correlated with the difference.

[0011] Furthermore, the control unit is connected to the gas flow sensor and the hydraulic station respectively, and is used to determine that the influence of the air cushion between the motor shaft and the mold on upsetting does not meet the requirements if the gas volume difference is greater than the preset volume difference, and to control the hydraulic station to increase the pressure relief pause time before holding pressure.

[0012] Furthermore, the duration of the pressure relief pause before pressure holding is positively correlated with the gas volume difference.

[0013] Furthermore, the gas volume difference is the difference between the amount of pyrolysis gas and the volume of gas discharged from the mold.

[0014] Furthermore, the amount of pyrolysis gas is the product of the amount of lubricant loss and the loss conversion coefficient, and the amount of lubricant loss is the product of the difference and the difference conversion coefficient.

[0015] Compared with the prior art, the beneficial effect of the present invention is that by setting up a hydraulic station, an upsetting unit, a detection unit and a control unit, the present invention reduces the flow rate of hydraulic oil according to the change in the downward speed of the upper die. During the operation of the upper die and the hydraulic station, the temperature of the hydraulic oil rises due to the change in workshop temperature and the continuous operation of the hydraulic station for a long time, resulting in a decrease in viscosity, which in turn changes the damping characteristics of the servo valve, thereby affecting the control accuracy of the downward speed of the upper die. By reducing the flow rate of hydraulic oil, the sensitivity of the hydraulic oil to changes in temperature and viscosity decreases, thereby reducing the impact of viscosity changes on the damping characteristics of the hydraulic oil. This reduces the influence of viscosity changes on the downward pressing process, thus solving the problem of fluctuations in the cohesive force of oil molecules and a decrease in viscosity caused by hydraulic oil temperature changes, which in turn leads to abnormal changes in the damping characteristics of the servo valve and fluctuations in the downward speed of the slider. The upsetting ambient temperature is reduced based on the difference between the amount of debris and the amount of debris remaining on the contact surface of the die. During the upsetting process, the motor shaft and the die undergo microscopic stick-slip motion, leading to charge separation. Electron transitions at the metal-metal interface generate instantaneous currents. When this current pulses... When the flow passes through the shaft in a punching motion, a brief but strong magnetic field is induced, causing some magnetic domains to rearrange. By lowering the ambient temperature, the adsorption capacity of debris for lubricant decreases, thereby weakening the separating effect of the lubricant and allowing it to function better. This also reduces the conduction of charges generated by friction. The pressure relief pause time before holding pressure is determined based on the amount of lubricant loss and the volume of gas discharged from the mold. Due to the gas pressure generated by the high-temperature decomposition of the lubricant, the decomposed gas cannot escape from the mold cavity in time, resulting in an air cushion effect. This leads to changes in the friction boundary and obstruction of metal flow. By increasing the pressure relief pause time before holding pressure, the gas forming the air cushion is discharged.

[0016] Furthermore, this invention reduces the flow rate of hydraulic oil by adjusting the downward speed of the upper mold to a predetermined value. When the temperature of the hydraulic oil rises, its viscosity changes, leading to a change in its damping characteristics and consequently a decrease in its hydraulic pressure transmission. Therefore, the change in the downward speed of the upper mold characterizes the degree of change in the hydraulic oil's damping characteristics, and by reducing the flow rate, the influence of the change in hydraulic oil viscosity on the transmission of hydraulic pressure is weakened.

[0017] Furthermore, this invention calculates the amount of debris attracted by the magnetic field generated on the motor shaft by setting a formula based on the product of the variance of the downward speed of the upper die after contacting the motor shaft and the debris amount conversion coefficient. After the upper die contacts the motor shaft, it undergoes microscopic stick-slip motion with the motor shaft, resulting in charge separation. This causes the charge on the motor shaft to generate a magnetic field, which attracts debris. Thus, the amount of debris attracted by the magnetic field generated on the motor shaft is estimated by the variance of the downward speed of the upper die after contacting the motor shaft, thereby determining the attraction of debris by the magnetic field generated by the charge on the motor shaft. The amount of debris remaining on the die is the amount of debris remaining on the surface of the die during the previous upsetting process. This amount of debris is the debris that adheres to the surface of the die after being attracted by the magnetic field of the motor shaft. Therefore, the difference between the amount of debris attracted and the amount of debris remaining on the die characterizes the actual magnetic field influence on the motor shaft. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the upsetting die for cold forging of motor shafts according to an embodiment of the present invention; Figure 2 This is an overall structural block diagram of an upsetting die for cold forging of a motor shaft according to an embodiment of the present invention; Figure 3 This is a detailed structural block diagram of the upsetting unit of the upsetting die for cold forging of motor shafts according to an embodiment of the present invention; Figure 4 This is a block diagram showing the connection structure between the upsetting unit and the control unit of the upsetting die for cold forging of motor shafts according to an embodiment of the present invention. Figure descriptions: 1-Upper liner plate; 2-Upper pad plate; 3-Upper pad block; 4-Upper die; 5-Lower die; 6-Lower die plate; 7-Lower punch; 8-Ejector ring; 9-Punch plate; 10-Punch pad; 11-First transition bushing; 12-Second transition bushing; 13-Lower die sleeve; 14-Ejector rod; 15-First lower bushing; 16-Second lower bushing; 17-Lower ejector rod; 18-Lower liner plate; 19-Lower pad block; 20-Pad block. Detailed Implementation

[0019] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0020] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0021] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0022] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] Please see Figure 1 , Figure 2 , Figure 3 as well as Figure 4 The figures shown are, respectively, a schematic diagram of the overall structure of the upsetting die for cold forging of motor shafts according to an embodiment of the present invention, an overall structural block diagram, a specific structural block diagram of the upsetting unit, and a connection structural block diagram of the upsetting unit and the control unit; an upsetting die for cold forging of motor shafts according to an embodiment of the present invention includes: An upsetting unit for upsetting a motor shaft into a predetermined shape includes a mold consisting of an upper mold 4 and a lower mold 5, an ejector assembly connected to the lower mold 5 for ejecting the upset motor shaft formed in the mold out of the mold, and a stamping constraint assembly fitted around the outer ring of the ejector assembly for constraining the spatial position of the ejector assembly. The top material assembly includes a top material ring 8, a top material rod 14 disposed below the top material ring 8, a pad block 20 disposed below the top material rod, and a lower top rod 17 disposed below the pad block. The top material ring 8 is disposed above the top material rod 14, and a lower punch 7 is disposed on the inner side of the top material ring 8. The detection unit is connected to the upsetting unit and is used to detect the downward speed of the upper die 4, the amount of remaining debris on the contact surface of the die, and the volume of gas discharged from the die, respectively. The control unit is connected to both the upsetting unit and the detection unit. It is used to determine the hydraulic oil flow rate based on the change in the downward speed of the upper die 4, to estimate the amount of debris attracted by the magnetic field generated on the motor shaft based on the variance of the downward speed of the upper die 4 after contacting the motor shaft, to determine the upsetting ambient temperature based on the difference between the amount of debris and the amount of debris remaining on the contact surface of the die, to calculate the amount of lubricant loss based on the difference, and to determine the pressure relief pause time before pressure holding based on the amount of lubricant loss and the volume of gas discharged from the die.

[0024] Specifically, a hydraulic station (not shown in the figure) is also provided above the upsetting unit to provide upsetting power to the upsetting unit.

[0025] Specifically, the flow rate of hydraulic oil is controlled and adjusted by a hydraulic station. The specific flow rate change process is existing technology and will not be described in detail here.

[0026] It will be understood by those skilled in the art that the specific structure of the hydraulic station is prior art and is not specifically limited here.

[0027] Specifically, the upper die 4, the lower die 5, and the lower punch 7 work together to form a stamping space, which is used to place the motor shaft to be upset.

[0028] Specifically, the lower mold 5 is also connected to a lower mold pressure plate 6.

[0029] Specifically, the stamping constraint assembly includes a punch pressure plate 9, a punch pad 10, a first lower bushing 15, a second lower bushing 16 disposed below the first lower bushing 15, a lower pad block 19 disposed below the second lower bushing 16, a first transition bushing 11 disposed outside the punch pressure plate 9 assembly, a second transition bushing 12 disposed below the first transition bushing 11, a lower die sleeve 13 disposed below the second transition bushing 12, and a lower bushing 18 disposed below the lower die sleeve 13.

[0030] Specifically, pin holes in the same vertical direction are provided on the punch pressure plate 9, the punch pad 10 and the first lower bushing 15, and positioning pins are provided in the pin holes. The positioning pins connect the punch pressure plate 9, the punch pad 10 and the first lower bushing 15.

[0031] Specifically, an upper pad block 3 is connected above the upper mold 4, an upper pad block pressure plate 2 is sleeved on the outside of the upper pad block 3, and an upper liner plate 1 is provided above the upper pad block pressure plate 2.

[0032] In implementation, this invention, by setting up an upsetting unit, a detection unit, and a control unit, reduces the flow rate of hydraulic oil based on the change in the downward speed of the upper die 4. During the operation of the upper die 4 and the hydraulic station, the temperature of the hydraulic oil rises due to changes in workshop temperature and prolonged continuous operation of the hydraulic station, leading to a decrease in viscosity. This alters the damping characteristics of the servo valve, affecting the control accuracy of the downward speed of the upper die 4. By reducing the flow rate of hydraulic oil, the hydraulic oil's ability to sense changes in temperature and viscosity decreases, thus reducing the impact of viscosity changes on the damping characteristics of the hydraulic oil. Consequently, the influence of viscosity changes on the downward pressing process is reduced, solving the problem of fluctuations in the cohesive force of oil molecules and a decrease in viscosity caused by changes in hydraulic oil temperature, which in turn leads to abnormal changes in the damping characteristics of the servo valve and fluctuations in the downward speed of the slider. The remaining debris on the contact surface of the die is also considered. The difference in quantity reduces the upsetting ambient temperature. During the upsetting process, the motor shaft and the die undergo microscopic stick-slip motion, resulting in charge separation. Electron transitions at the metal-metal interface generate instantaneous currents. When this current flows through the shaft in pulse form, it induces a brief but high-intensity magnetic field, causing some magnetic domains to rearrange. By lowering the ambient temperature, the adsorption capacity of debris on the lubricant decreases, thereby weakening the lubricant's separating effect and allowing the lubricant to function better. This also reduces the conduction of charge transfer caused by frictional electrification. The pressure relief pause time before holding pressure is determined based on the amount of lubricant loss and the volume of gas discharged from the die. Due to the gas pressure generated by the high-temperature decomposition of the lubricant, the decomposed gas cannot escape from the die cavity in time, resulting in an air cushion effect. This leads to changes in the friction boundary and obstruction of metal flow. By increasing the pressure relief pause time before holding pressure, the gas forming the air cushion is discharged.

[0033] Specifically, the detection unit includes: A displacement sensor (not shown in the figure) is installed on the workshop side wall corresponding to the outer side of the upper mold 4 to detect the downward speed of the upper mold 4. A vision sensor (not shown in the figure) is located below the displacement sensor and is used to detect the amount of remaining debris on the contact surface of the mold. A gas flow sensor (not shown in the figure) is disposed between the displacement sensor and the vision sensor to detect the gas flow rate discharged from the mold.

[0034] Specifically, the vision sensor is connected to the workshop side wall via a telescopic rod to move the vision sensor to the contact surface of the mold; the gas flow sensor is connected to the workshop side wall via a connecting metal frame and is located near the contact surface between the upper mold 4 and the lower mold 5.

[0035] Specifically, the control unit is connected to the displacement sensor and is used to determine that the influence of the hydraulic oil viscosity change on the pressing process does not meet the requirements if the change in the downward speed of the upper mold 4 is greater than a preset change, and then reduce the flow rate of the hydraulic oil. The flow rate of the hydraulic oil is negatively correlated with the change in the downward speed of the upper mold 4. The change in the downward speed of the upper mold 4 is the difference between the downward speed of the upper mold 4 at the beginning and the downward speed of the upper mold 4 at the end of the monitoring period.

[0036] Specifically, in this embodiment, the monitoring period is 40ms.

[0037] Optionally, the preset variation range is [15mm / s, 40mm / s].

[0038] Preferably, the preferred embodiment of the preset change amount is 25 mm / s.

[0039] In implementation, when the change in the downward speed of the upper mold 4 exceeds the preset change by less than 10 mm / s, the hydraulic oil flow rate is adjusted to 0.95 times the current hydraulic oil flow rate. When the change in the downward speed of the upper mold 4 exceeds the preset change by more than 10 mm / s, the hydraulic oil flow rate is reduced by 0.5 L / min for every 1 mm / s exceeding the preset change. In a specific embodiment, the change in the downward speed of the upper mold 4 is 40 mm / s, and the hydraulic oil flow rate is 50 L / min. Then, the reduced hydraulic oil flow rate is 50 L / min × 0.95 - (40 mm / s - 25 mm / s - 10 mm / s) / 1 mm / s × 0.5 L / min = 45 L / min (when the calculation result is a decimal, it is rounded up).

[0040] In practice, this invention reduces the flow rate of hydraulic oil by adjusting the downward speed of the upper mold 4 to a predetermined value. When the temperature of the hydraulic oil rises, its viscosity changes, which in turn changes its damping characteristics, thus reducing its hydraulic pressure transmission capacity. Therefore, the change in the downward speed of the upper mold 4 characterizes the degree of change in the damping characteristics of the hydraulic oil, and by reducing the flow rate of the hydraulic oil, the influence of the change in the viscosity of the hydraulic oil on the hydraulic pressure transmission capacity is weakened.

[0041] Specifically, the control unit is connected to the vision sensor and the centrifugal fan respectively, and is used to determine whether the degree of magnetic field influence on the motor shaft meets the requirements based on the difference being greater than a preset difference, and to control the centrifugal fan to reduce the upsetting environment temperature.

[0042] Optionally, the preset difference can be selected within a range of [4mg, 5mg]; Preferably, the preferred embodiment of the preset difference is 4.5 mg.

[0043] In practice, when the difference in the amount of debris exceeds the preset difference by less than 1 mg, the sensing upsetting ambient temperature is adjusted to 0.9 times the current upsetting ambient temperature. When the difference exceeds the preset difference by 1 mg, the upsetting ambient temperature is reduced by 0.1℃ for every 0.1 mg difference. In a specific embodiment, the difference is 6 mg, and the current upsetting ambient temperature is 16℃. The reduced upsetting ambient temperature is 16℃×0.9-(6mg-4.5mg-1mg) / 0.1mg×0.1℃=13.9℃≈14℃ (when the calculation result is a decimal, it is rounded to the nearest integer).

[0044] Specifically, the amount of debris attracted by the magnetic field generated on the motor shaft is the product of the variance of the downward speed of the upper mold 4 after contacting the motor shaft and the debris amount conversion coefficient.

[0045] Specifically, the debris conversion coefficient means the amount of debris attracted by the magnetic field generated on the motor shaft, corresponding to the unit quantity of the variance of the downward speed of the upper mold 4 after contacting the motor shaft.

[0046] Specifically, the selectable range for the debris quantity conversion factor is [0.001 mg / (mm / s)]. 2 0.02 mg / (mm / s) 2 The preferred embodiment of the debris quantity conversion factor is 0.01 mg / (mm / s). 2 .

[0047] As will be understood by those skilled in the art, the process of obtaining the chip quantity conversion coefficient is as follows: by running the new die with standard lubrication and constant temperature for several strokes under no-load / light load conditions, the variance of the downward speed of the upper die 4 after contacting the motor shaft, the amount of chip on the surface of the upper die 4, and the amount of chip on the surface of the lower die 5 are recorded. The sum of the amount of chip on the surface of the upper die 4 and the amount of chip on the surface of the lower die 5 is calculated, and the chip quantity conversion coefficient is obtained through linear regression analysis. The specific process of linear regression analysis is known to those skilled in the art, so the specific acquisition, analysis, and calculation process will not be described in detail here.

[0048] In implementation, this invention calculates the amount of debris attracted by the magnetic field generated on the motor shaft by setting a product of the variance of the downward speed of the upper die 4 after contacting the motor shaft and the debris amount conversion coefficient. After the upper die 4 contacts the motor shaft, it undergoes microscopic stick-slip motion with the motor shaft, resulting in charge separation. This causes the charge on the motor shaft to generate a magnetic field, which attracts debris. Therefore, the amount of debris attracted by the magnetic field generated on the motor shaft is estimated by the variance of the downward speed of the upper die 4 after contacting the motor shaft, thus determining the attraction effect of the magnetic field generated by the charge on the motor shaft on the debris. The amount of debris remaining on the die is the amount of debris remaining on the surface of the die during the previous upsetting process. This amount of debris is the debris that adheres to the surface of the die after being attracted by the magnetic field of the motor shaft. Therefore, the difference between the amount of debris attracted and the amount of debris remaining on the die characterizes the actual magnetic field influence on the motor shaft.

[0049] Specifically, the upsetting ambient temperature is negatively correlated with the difference.

[0050] Specifically, the control unit is connected to the gas flow sensor and the hydraulic station respectively, and is used to determine that the influence of the air cushion between the motor shaft and the mold on upsetting does not meet the requirements if the gas volume difference is greater than the preset volume difference, and to control the hydraulic station to increase the pressure relief pause time before holding pressure.

[0051] Specifically, the duration of the pressure relief pause before pressure holding is positively correlated with the gas volume difference.

[0052] Optionally, the preset gas volume difference value can be selected within a range of [0.2 mL, 0.6 mL].

[0053] Preferably, the preferred embodiment of the preset gas volume difference is 0.4 mL.

[0054] In practice, when the gas volume difference exceeds the preset gas volume difference by less than 0.1 mL, the pressure relief pause time is adjusted to 1.1 times the current pressure relief pause time. When the gas volume difference exceeds the preset gas volume difference by more than 0.1 mL, the pressure relief pause time is increased by 0.01 s for every 0.01 mL increase. In a specific embodiment, the gas volume difference is 0.5 mL, and the current pressure relief pause time is 0.2 s, so the increased pressure relief pause time is 0.2 s × 1.1 = 0.22 s.

[0055] Specifically, the gas volume difference is the difference between the amount of pyrolysis gas and the volume of gas discharged from the mold.

[0056] Specifically, the amount of pyrolysis gas is the product of the amount of lubricant loss and the loss conversion coefficient, and the amount of lubricant loss is the product of the difference and the difference conversion coefficient.

[0057] Specifically, the loss conversion factor means the amount of cracked gas corresponding to the unit loss of lubricant, and the difference conversion factor means the amount of lubricant loss corresponding to the unit amount of the difference between the amount of debris adsorbed by the magnetic field generated on the motor shaft and the amount of debris remaining on the contact surface of the mold.

[0058] In practice, the selectable range of the differential conversion factor is [1.2 mg / mg, 2.0 mg / mg], and the preferred embodiment of the differential conversion factor is 1.5 mg / mg.

[0059] In practice, the selectable range of the loss conversion factor is [0.4 mL / mg, 0.7 mL / mg], and the preferred embodiment of the loss conversion factor is 0.6 mL / mg.

[0060] As will be understood by those skilled in the art, the loss conversion coefficient and the difference conversion coefficient are empirical coefficients obtained through actual testing. By monitoring the loss of lubricant, including but not limited to monitoring the distribution area and concentration of lubricant, as well as monitoring the amount of debris on the mold and the amount of debris on the motor shaft, the difference conversion coefficient and the loss conversion coefficient are calculated through linear regression analysis. The specific calculation process and the process and principle of obtaining the empirical coefficients are all existing technologies known to those skilled in the art. Therefore, the specific calculation process and the specific experimental process will not be described in detail here.

[0061] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. An upsetting die for cold forging of motor shafts, characterized in that, include: An upsetting unit is used to upset a motor shaft into a predetermined shape. It includes a mold consisting of an upper mold and a lower mold, an ejector assembly connected to the lower mold to eject the upset motor shaft formed in the mold out of the mold, and a stamping constraint assembly sleeved on the outer ring of the ejector assembly to constrain the spatial position of the ejector assembly. The top material assembly includes a top material ring, a top material rod disposed below the top material ring, a pad disposed below the top material rod, and a lower top rod disposed below the pad. The top material ring is disposed above the top material rod, and a lower punch is disposed inside the top material ring. The detection unit is connected to the upsetting unit and is used to detect the downward speed of the upper die, the amount of remaining debris on the contact surface of the die, and the volume of gas discharged from the die, respectively. The control unit is connected to both the upsetting unit and the detection unit. It is used to determine the hydraulic oil flow rate based on the change in the downward speed of the upper die, estimate the amount of debris attracted by the magnetic field generated on the motor shaft based on the variance of the downward speed of the upper die after contacting the motor shaft, determine the upsetting ambient temperature based on the difference between the amount of debris and the amount of debris remaining on the contact surface of the die, calculate the amount of lubricant loss based on the difference, and determine the pressure relief pause time before pressure holding based on the amount of lubricant loss and the volume of gas discharged from the die.

2. The upsetting die for cold forging of motor shafts according to claim 1, characterized in that, The detection unit includes: A displacement sensor is installed on the workshop sidewall corresponding to the outer side of the upper mold to detect the downward speed of the upper mold; A vision sensor, positioned below the displacement sensor, is used to detect the amount of remaining debris on the contact surface of the mold. A gas flow sensor is disposed between the displacement sensor and the vision sensor to detect the gas flow rate discharged from the mold.

3. The upsetting die for cold forging of motor shafts according to claim 2, characterized in that, The control unit is connected to the displacement sensor and is used to determine that the influence of the hydraulic oil viscosity change on the pressing process does not meet the requirements if the change in the downward speed of the upper mold is greater than a preset change, and then reduce the flow rate of the hydraulic oil. The flow rate of the hydraulic oil is negatively correlated with the change in the downward speed of the upper mold. The change in the downward speed of the upper mold is the difference between the downward speed of the upper mold at the beginning and the downward speed of the upper mold at the end of the monitoring period.

4. The upsetting die for cold forging of motor shafts according to claim 3, characterized in that, The control unit is connected to the vision sensor and the centrifugal fan respectively, and is used to determine whether the degree of magnetic field influence on the motor shaft meets the requirements based on the difference being greater than a preset difference, and to control the centrifugal fan to reduce the upsetting environment temperature.

5. The upsetting die for cold forging of motor shafts according to claim 4, characterized in that, The amount of debris attracted by the magnetic field generated on the motor shaft is the product of the variance of the downward speed of the upper mold after contacting the motor shaft and the debris amount conversion coefficient.

6. The upsetting die for cold forging of motor shafts according to claim 5, characterized in that, The upsetting ambient temperature is negatively correlated with the difference.

7. The upsetting die for cold forging of motor shafts according to claim 6, characterized in that, Above the upsetting unit, a hydraulic station is also provided to provide upsetting power to the upsetting unit. The control unit is connected to the gas flow sensor and the hydraulic station respectively. It is used to determine that the influence of the air cushion between the motor shaft and the mold on upsetting does not meet the requirements if the gas volume difference is greater than the preset volume difference value, and to control the hydraulic station to increase the pressure relief pause time before holding pressure.

8. The upsetting die for cold forging of motor shafts according to claim 7, characterized in that, The duration of the pressure relief pause before pressure holding is positively correlated with the gas volume difference.

9. The upsetting die for cold forging of motor shafts according to claim 8, characterized in that, The gas volume difference is the difference between the amount of pyrolysis gas and the volume of gas discharged from the mold.

10. The upsetting die for cold forging of motor shafts according to claim 9, characterized in that, The amount of pyrolysis gas is the product of the amount of lubricant loss and the loss conversion coefficient, and the amount of lubricant loss is the product of the difference and the difference conversion coefficient.

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