CN101046420A - On-line detection method for transmission torque required by PFC (Power factor correction) of mechanical press - Google Patents

Abstract

The present invention discloses an online detection method for the torque required to be transmitted by a mechanical press PFC. The method adopts a slider force range indirect measurement method to detect the torque _Ma required to be transmitted by the PFC. According to the relevant information of the actual processing of the mechanical press, a method for obtaining the value of _Ma by using the slider force range characteristics is studied. After the required torque M _Ra of the crankshaft is obtained by the force range characteristics on the slider, the value of _Ma can be conveniently determined by a formula. The deformation force value and its time are measured online by using a force sensor, an A/D board, a computer, etc., and the torque M _Ra at different times in the deformation stage of the workpiece can be automatically calculated by using software, and the M _Ra values at different times and the maximum value M _Rm are output. The method has good characteristics such as rapidity and reliability, and can be promoted and applied in production.

Description

On-line detection method of transmission torque required by mechanical press PFC

                    

The invention belongs to a transmission torque detection method in the field of mechanical presses of forging equipment, and in particular relates to an online detection method and device for PFC required transmission torque.

Background technique

When the mechanical press performs forging work, the friction pair of the pneumatic friction clutch (PFC) needs to be able to output a large enough torque M _q ≥ _{M a} , otherwise the PFC friction surface will slip and cause a stuffy car accident. Provide proper air pressure to the PFC cylinder through the electric proportional pressure valve to meet the normal working requirements of M _q ≥ _{M a} , obviously the size of M _a must be known in advance.

At present, in all mechanical presses at home and abroad, no matter how much torque M _a needs to be transmitted by the PFC each time the workpiece is deformed (for example, the upsetting force of the first step of the gear hot die forging is often only 100% of the final forging force of the second step 1/3, the corresponding M _a1 required for the first working step is less than 1/2 of the second working step), but each time the PFC cylinder enters the maximum air pressure p _max , correspondingly the torque that the PFC can provide is always The maximum value M _qmax not only causes the waste of compressed air energy but also increases the exhaust noise of the PFC and aggravates the pollution of the environment. Therefore, the present invention provides a method for online measurement of the torque required to be transmitted by the PFC. It also discusses in detail _{how to detect the torque Ma required by PFC through the measurement device, and how PFC provides enough torque M q to meet} the needs of working deformation according to the size of Ma.

Due to the complexity of the plastic deformation process and the mechanical press, it brings considerable difficulty to the theoretical calculation. Therefore, the online actual measurement method is used to determine the size of _Ma . Usually, the actual torque test method on the PFC shaft is useful. Torque sensor There are four methods: direct measurement, indirect measurement using load cell, indirect measurement using motor current and indirect measurement using slider force distance. This paper first discusses these four methods respectively.

1. Torque sensor direct measurement method

Transducers that directly measure torque on a rotating shaft are of two types:

a. Strain torque sensor:

The mechanical strain is converted into an electrical signal proportional to the torque by using a resistance strain gauge. Because it outputs signals from the rotating shaft, the device is complicated, or the reliability is poor, or the cost is too high, and it is inconvenient to use.

b. Torsion angle phase difference torque sensor

For example, the torque measurement principle of the JCZ torque speed sensor is the principle of phase difference, that is, two signal gears are installed at both ends of the elastic shaft, and a set of signal coils are respectively installed above the two gears. The magnetic cylinder and the signal gear form a magnetoelectric signal generator. When the signal gear rotates with the elastic shaft, since the tooth top and tooth valley of the signal gear alternately sweep across the bottom of the magnetic cylinder, the air-gap permeability will change periodically, and the magnetic flux inside the coil will also change periodically, making the coil The medium induction produces an alternating current signal that approximates a sine wave. When the elastic shaft is twisted, it will produce torsional deformation, which will cause the phase difference between the two sets of AC signals to change. Within the elastic deformation range, the absolute value of the phase difference change is proportional to the magnitude of the torque.

The industrial site environment of forging production is harsh, and it is not suitable for destructive treatment of the crankshaft of the mechanical press (such as grinding, drilling, etc.) , the above-mentioned method of directly measuring the torque on the rotating shaft is difficult to apply in the FPC torque test of the mechanical press.

2. Load sensor indirect torque measurement method

It is more convenient to install and use the load sensor on the mechanical press. In the PFCB-82 mechanical press pneumatic friction clutch and brake comprehensive intelligent test bench of the Mold and Plastic Processing Research Institute of Xi'an Jiaotong University (as shown in Figure 1) The load sensor installed on the PFC shaft can measure the relationship between the torque on the PFC shaft and the time. Figure 2 shows the installation of the load cell on the test bench. The fixed seat of the brake has two bosses on the left and right, and the load cell is installed on one side. By measuring the output force of the load cell, the torque calculation formula M _a =F×L is used indirectly Calculate the torque acting on the PFC shaft.

3. Method of indirect measurement of shaft torque by motor current

The mechanical press is generally driven by a three-phase asynchronous motor. When the torque required on the PFC shaft is greater, the corresponding output torque of the motor is also greater. In this way, the measurement of the output torque of the motor can be indirectly obtained. Calculate _Ma on the PFC axis. According to the operating principle of the asynchronous motor, the current in the rotor winding produces an electromagnetic torque acting on the rotor of the motor under the action of the rotating magnetic field. According to electromechanics, the average electromagnetic torque M of the motor is:

M＝K·Φ _m ·I ₂ ·cosΦ ₂ (N·m) (1)

In the formula: K-coefficient related to the structural parameters of the motor, called the torque coefficient;

Φ _m - magnetic flux per pole of the air gap (Wb);

I ₂ - rotor winding phase current (A);

_cosΦ2 - power factor of the rotor winding

转子折合电流

与电动机的励磁电流 的关系：It can be seen from formula (1) that the magnitude of the electromagnetic torque M of the asynchronous motor is proportional to the magnetic flux Φ _m of each pole of the air gap, the rotor phase current I ₂ and the power factor cos Φ ₂ of the rotor. But because this relationship is more complicated, and in actual production, the slip rate of the motor is very small when the motor is running in the normal range, its air gap flux Φ _m can be regarded as the rated value, and the power factor cosΦ ₂ ≈ 1, so the electromagnetic The magnitude of the torque M is only proportional to the rotor current _I2 . But because the rotor current is not easy to measure, according to the equivalent circuit of the motor, the stator current can be obtained after converting the rotor quantities into the number of turns, the number of phases and the position of the rotor

Rotor equivalent current

With the field current of the motor Relationship:

${\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>{\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

的变化也非常小，基本上可视为定值。因此由式(1)和(2)可知，电动机的电磁转矩与定子电流有一定的比例关系，可以通过测量电动机定子中的某一相的电流，来间接测得电动机的电磁输出转矩。经在实验台上的大量实验发现，电动机的电流大小不但与其输出转矩有关，而且与工艺类型有关，故本发明不采用此方法获得M_a的值。In the formula ${\stackrel{\&Center\; Dot;}{I}}_2^{\&prime;}=\frac{{\stackrel{\&Center\; Dot;}{I}}_1}{k_i},$ k _i is the electrorheological ratio, which can be obtained by calculation or experiment. In the normal operating range of an asynchronous motor from no load to rated load, the excitation current

The change of is also very small and can basically be regarded as a constant value. Therefore, it can be seen from formulas (1) and (2) that the electromagnetic torque of the motor has a certain proportional relationship with the stator current, and the electromagnetic output torque of the motor can be indirectly measured by measuring the current of a certain phase in the motor stator. A large number of experiments on the test bench have found that the current of the motor is not only related to its output torque, but also related to the type of process, so the present invention does not use this method to obtain the value of _Ma .

4. Indirect measurement method of slider force distance:

In practice, the torque M _a required to be transmitted by the PFC of the mechanical press is determined by the force and deformation height required when the slider passes through the mold to deform the workpiece. In actual industrial production, some mechanical presses are equipped with automatic detection forging punches. The device of deformation force and deformation height, so that the torque M _Ra acting on the crankshaft can be obtained by using the magnitude of these two signals

M _Ra = Pm _q (3)

In the formula, P is the workpiece deformation force (N) acting on the slider, and m _q is the equivalent force arm (m) of the crank linkage mechanism.

When the torque M _Ra acting on the crankshaft is known on the line, the corresponding torque _Ma that needs to be transmitted on the PFC shaft should be

${\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}}{\mathrm{<span\; class="notranslate">\; i\&eta;</span>}}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

In the formula, i is the transmission ratio from the shaft of the PFC to the crankshaft, and η is the transmission efficiency between the PFC shaft and the crankshaft. For one-stage gear transmission, η=0.97, and for two-stage gear transmission, η=0.94.

Contents of invention

The object of the present invention is to provide an online detection method for the required transmission torque of the PFC of a mechanical press, which uses the above fourth method to online test the actual torque on the PFC shaft to determine the size of _Ma .

In order to realize above-mentioned task, the present invention takes following technical solution:

An on-line detection method for the torque required to be transmitted by the PFC of a mechanical press, the method adopts the indirect measurement method of the slider force distance to detect the torque M _a required to be transmitted by the PFC, and is characterized in that it specifically includes the following steps:

1) With the torque M _q that can be provided by the PFC = βM _a and M _q has a good linear relationship with the cylinder air pressure M _qC = kp, the control of the torque that can be generated by the PFC is achieved by adjusting the air pressure p entering the PFC cylinder;

2) The method of determining the required transmission torque M _Ra on the PFC friction surface by using the force-distance curve of the slider includes two methods: the maximum deformation force P _m of the process type and the online actual measurement of the Pt numerical relationship;

A. When the torque M _Ra is determined by the method of the process type and the maximum deformation force P _m , the mathematical expression of the more accurate working load characteristics of the completed process should be established first, and then the maximum torque M of each section during the deformation process of the workpiece should be calculated _Raim , and finally calculate the maximum torque M _Rm in the whole deformation process through the comparison of each section;

B. The online measured value of Pt is used to measure the deformation force value and its time online by using the force sensor, A/D board and computer. The computer controls the data acquisition and output card, and the software can automatically calculate the workpiece deformation stage. Torque M _Ra at different moments, and output M _Ra value and maximum value M _Rm at different moments.

In order to verify the correctness of the relevant procedures of the method of the present invention, the typical process of the cold extrusion of the JH23-63 type mechanical press produced by Shanghai No. 2 Forging Machine Tool Factory was selected for research. Assume that P _m =3×10 ⁵ N, α ₀ =30° in a cold extrusion process, the parameters of the mechanical press are slider stroke s ₀ =100mm, crank radius R=s ₀ /2=50mm, d _o = 115mm, d _A = 155mm, d _B = 120mm, μ = 0.045, λ = 0.1, Δα = 1°, ε = 0.5°, transmission ratio I = 5.353 (in order to facilitate the difference from i in the angle increase, the formula (4) The transmission ratio i between the crankshaft and the PFC shaft is replaced by letter I here), the first-stage gear transmission efficiency η=0.97, the number of strokes of the slider n=50 times/min, and the corresponding crank rotation angular velocity is ω =2πn/60=5.236(rad/s), the calculated result is shown in Figure 3, for the sake of intuition, the abscissa is represented by the pressure angle α (angle), and M′ _l and M′ _μ in the figure are converted Desired and resistive torque to the PFC shaft.

Description of drawings

Figure 1 is a schematic diagram of the structure of the PFC-B-82 mechanical press pneumatic friction clutch and brake comprehensive intelligent test bench. The labels in the figure respectively indicate: 1. Brake air pressure proportional valve 2. Load sensor 3. Air pressure transmitter on the brake cylinder 4. Brake housing 5. Brake piston 6. Brake piston displacement sensor 7. Brake moving disc 8. Brake friction Block 9. Rolling bearing 10. Braking end support frame and bearing 11. Moment of inertia adjustment plate 12. Driven shaft speed measuring plate 13. Driven shaft speed measuring photoelectric sensor and bracket 14. Driven inertia plate 15. Clutch end supporting frame and bearing 16. Flywheel 17. Rolling bearing 18. Clutch piston displacement sensor 19. Piston 20. Flywheel speed measuring disc 21. Flywheel speed measuring photoelectric sensor and bracket 22. Clutch intake and exhaust pipe air pressure transmitter 23. Clutch air pressure proportional valve 24. Ground 25. Friction block 26. V-belt groove 27. Driven shaft;

Fig. 2 is the structure of utilizing the load cell to test the torque on the shaft;

Fig. 3 is the torque change characteristic curve obtained from P _m for the cold extrusion process, wherein curve a is M _a , curve b is M′ _l , and curve c is M′ _μ ;

Fig. 4 is the computer online monitoring and control system of the required transmission torque of mechanical press PFC;

Figure 5 is the deformation force characteristic curve measured online;

Fig. 6 is the torque variation curve of the drawing process calculated online;

Figure 7 is the deformation curve of the drawing process.

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Detailed ways

As mentioned above, in order to make the torque M _q output by the PFC friction pair meet the requirements of workpiece deformation, it is necessary to know the torque M _a transmitted by the PFC friction surface when the workpiece is deformed, so as to realize the M _a , through the intelligent pneumatic system, the torque output by the PFC friction pair can satisfy: M _q ≥ M _a , and the reliable, high-efficiency, and low-pollution forging process can be adaptively realized. The present invention determines the value of _Ma according to the relevant information of the actual processing of the mechanical press. There are many ways to obtain _Ma , and the present invention only studies the method of obtaining the value of _Ma by using the force characteristic of the slider. After the required torque M _Ra of the crankshaft is obtained from the force characteristic on the slider, the value of _Ma can be easily determined by the formula. For this reason, the present invention only studies how M _Ra is determined.

In some mechanical presses in industrial practice, a device that can automatically detect and display the deformation force of the workpiece acting on the slider (hereinafter referred to as the force measuring device) is installed. At present, this kind of force measuring device has two output methods, one is only able to output and display the maximum workpiece deformation force P _m , the other is to output the size of deformation force P at different moments, and give the maximum value, that is, Output and display Pt value and curve. For this reason, the present invention first studies how to obtain M _Ra when the process type is known but the force measuring device can only output the maximum workpiece deformation force P _m , and then discusses the value of M _Ra obtained under the known Pt .

1. The relationship between PFC torque and air pressure

The foregoing describes how to obtain the torque _Ma on the PFC shaft online during the working process of the mechanical press. After the size of _Ma is known, the next problem is to make the friction pair of PFC provide enough torque M _q so that M _q ≥ M _a , otherwise the friction surface will slip during the deformation of the workpiece. The friction material wears out, overheats, and even serious "stuffy car" accidents occur. However, if the maximum value M _qmax is taken every time regardless of the size of _Ma , although the work is reliable, it will cause a huge waste of compressed air energy as mentioned above, which is the deficiency of the current PFC air circuit system , which is exactly what the present invention will improve.

Considering the existence of friction motion resistance torque in the working process, in order to work normally M _q ≥ _{M a} , but in order to save energy and can not be much larger, the definition here is taken when performing torque intelligent control:

M _q =βM _a (5)

where β is defined as the PFC torque reserve coefficient. It is obtained by considering that the torque M _q that can be transmitted between the PFC friction pairs is affected by the fluctuation of the air pressure in the PFC cylinder, the stability of the friction coefficient, and the change of the real friction contact area, etc., so that the PFC can still work normally. Here, β=1.1-1.3 is taken, and in this application, β=1.2.

For the PFC friction pair, its output torque M _q should be

M _q ＝mμqF ₀ R _μ (6)

In the formula, m is the number of friction surfaces, μ is the friction coefficient, and for the friction materials and anti-wear elements usually used in mechanical presses, μ=0.3~0.4. R _μ is the equivalent friction radius, F ₀ is the single-sided friction area, q is the specific pressure on the friction surface, and the total pressing force Q acting on the friction surface is

Q＝qF ₀ (7)

Q is usually generated by the piston in the cylinder, and the piston is driven by compressed air. In this way, if the area of the PFC piston is S and the pressure of the compressed air is p, when the friction between the piston and the cylinder is neglected, we can get:

Q＝pS

Because μ, F, R _μ and S in formulas (6) and (8) are difficult to adjust artificially, it can be seen from formula (5) that in order to make M _q change with _Ma , only by adjusting the air pressure p the size of. The size of the air pressure p in this application, in this paper, the air pressure p is adjusted online by the electric proportional solenoid valve, and the air pressure sensor is used to feedback and detect the debugging results to form a closed-loop system.

Generally, there are two types of friction pairs of PFC: disc type and floating insert type. The PFC-B-82 test bench in this application adopts the floating insert type structure, and the friction torque it can produce is

M _q ＝2μqzF _i R _μ (9)

In the formula: z is the number of floating inserts;

F _i is the unilateral friction area of a floating insert.

That is to say, for this kind of floating fast structure, there is the following formula

F ₀ =zF _i (10)

m=2 m=2 (11)

From formula (7) ~ (11) can get:

M _q = 2μpSR _μ (12)

In the experiment of the present invention, the size of the friction surface of PFC and PFB is z=10, R _μ =0.210m, μ=0.3～0.35, F _i =7.7117×10 ^-3 m ² , S _B =0.2366m ² , S _C = 0.2686m ² . Where S _B , S _C are the areas of the PFC and PFB pistons, respectively.

Substitute the above data into formula (12) and take μ=0.31 to get:

M _qB ＝0.0308p(N·m) (13)

M _qC ＝0.0350p(N·m) (14)

It can be seen that PFCs of other sizes still exist

M _qC = kp (15)

That is to say, the friction torque that the friction clutch can produce is directly proportional to the air pressure in the cylinder, so it can be seen from formula (5) and formula (15) that under the condition that the friction torque M _a required to be transmitted by the PFC has been directly detected , the air pressure in the cylinder can be adjusted according to _Ma , so as to achieve the purpose of saving compressed air.

2. Determine M _a using the online measured force-range characteristics of the slider

It can be seen from the literature that when the deformation force P of the workpiece is known, the torque M _Ra acting on the crankshaft cannot be determined. The size of the moment arm must be known. The moment arm may not always take the maximum value at the maximum deformation force P _m . There are great differences in the relationship between different processes. In order to obtain the value of M _Ra , the deformation force P under any arm length m _q must be known, and the value of M _Ra can be obtained by multiplying the two together, and then _Ma on the PFC axis can be obtained from formula (4). Now the value of M _Ra at any time cannot be known but only the value of P _m , how to calculate M _Ra ?

Although P cannot be obtained at any time, the types of processes actually completed by mechanical presses such as blanking, deep drawing, hot die forging, and cold extrusion are determined. Each process has its unique force characteristics, especially in When the P _m and the deformation height are known, the deformation law of the force at other times can be calculated, and the deformation height of the workpiece here is also known to the determined processing blank and mold, so that when the process type, P _m and h are known , the M _Ra value at any time can be obtained, which shows that there is a certain approximation in this method.

For this reason, the present invention first discusses the law of deformation force ranges of different process types, and then studies how to determine M _Ra from the deformation force ranges of known processes. As mentioned above, since M _Ra is known, it can be known from formula (4), that M _a can be obtained, so the following only studies how to obtain M _Ra .

According to the literature, after considering the friction effect, the torque required to be transmitted by the crankshaft (or eccentric wheel) of the mechanical press can be expressed as:

M _Ra (α)＝M _l (α)+M _μ (a) (16)

${\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="sin"\; filenames="A20071001776000161.png"\; state="\{\{state\}\}">sin</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; sin</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 17</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&mu;</span>}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="sin"\; filenames="A20071001776000161.png"\; state="\{\{state\}\}">sin</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}{\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; sin</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 18</span>}<span\; class="notranslate">\; )</span>$

In the formula, M _l (α) is the ideal torque, M _μ (α) is the friction torque, P (α) is the deformation force of the workpiece, μ is the friction coefficient of the mechanical rotation system, the split press μ=0.04～0.05, and the closed press Type press μ = 0.045 ~ 0.055, d _A , d _B and d _o are the diameters of the connecting rod big end, small end and crankshaft bearing journal respectively. Considering that the aforementioned five typical processes are all composed of broken lines with different slopes, in order to make the expression of P(α) more general, referring to the discussion of the force characteristic equations of the aforementioned processes, P(α) can be written as:

P(α)=k(α-a ₀ )+P ₀ (19)

In the formula, k=(P ₁ -P ₀ )/(a ₁ - a ₀ ) is the slope of the load line segment; (a ₀ , P ₀ ) and (a ₁ , P ₁ ) are the coordinates of the two ends of the line segment respectively, which The coordinates of the two points are determined by the parameters of each typical process. In the specific solution process, the coordinates of the two points need to be determined according to the process parameters before further solution.

For the convenience of calculation later, it can be ordered:

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="sin"\; filenames="A20071001776000161.png"\; state="\{\{state\}\}">sin</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; arcsin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 20</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&mu;</span>}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="sin"\; filenames="A20071001776000161.png"\; state="\{\{state\}\}">sin</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}{\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; arcsin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; twenty\; one</span>}<span\; class="notranslate">\; )</span>$

In this way, equations (17) and (18) can be written as:

M _l (α)=P(α)f ₁ (α) (22)

M _μ (α)＝P(α)f ₂ (α) (23)

Combined with formula (16), it can be seen that M _Ra (α) is a function of α, so from formulas (16) and (19) to (23), it is convenient to use a computer to find the value of M _Ra (α) and obtain its maximum value. In addition, it can be seen from the force diagrams of typical processes in relevant literature that for each section of the force diagram, M _q (α) is continuous, that is, each section has an extreme value, and this extreme value is the maximum torque of this section value.

Because the intelligent control of the PFC output torque M _q is online and real-time, it is required to output the value of M _Ra quickly and automatically according to the online measured P _m value and the completed process type, so as to facilitate the control of the system. Therefore, the value of M _Ra must be obtained online by programming, and then the value of _Ma is obtained from formula (4).

According to the above technical solution, the online monitoring system of the mechanical press PFC required transmission torque of the present invention uses a computer to collect deformation force sensor signals through data, and determines M _Ra by using the online measured Pt numerical relationship. Figure 4 is a schematic diagram of the computer on-line monitoring and control system for the transmission torque required by the PFC of the mechanical press.

As mentioned above, the deformation force sensor installed on some mechanical presses can output the analog signal of the deformation force P value at any time, and the Pt data relationship can be obtained through A/D data acquisition and computer. Considering α=ωt, the P-α relationship and value shown in Figure 5 can be obtained after converting the time t into the crank angle relationship α and digital filtering. Let's discuss how to determine the size of M _Ra from Figure 5.

3. Selection of corner step size Δα

Firstly, for the micro-interval [α _i , α _i+1 ] as shown in Figure 5, α _i+1 = α _i + Δα, Δα is the step size for calculating M _Ra , in this micro-interval, it is possible to assume that the change of P is small Negligible, so it can be regarded as a constant, and taken as the value P _i on the left side of the micro-interval, that is, P=P(α _i )(α _i ≤α≤α _i +Δα). In this way, the continuous curve in Figure 5 can be replaced by steps (α _i , P _i ) with different heights. In fact, when the computer obtains the curve in Figure 5 through the A/D card, it is also smoothed by very dense discrete points . Therefore, in order to improve the calculation speed, it is not necessary to obtain the curve in Fig. 5 first (except in the case of the control system with P-α display function, of course), when the sampling period Δt of the A/D card is known, the torque M _Ra when calculating The corner step size Δα can be selected according to the following formula:

                          

Obviously, the smaller Δα is, the higher the accuracy is, but the real-time performance of online torque control will be affected to a certain extent, so the selection of Δα should take into account the above two aspects.

1. Determination of M _Ra

According to equations (16), (17) and (18), the torque M _Rai required to be transmitted on the crankshaft at any rotation angle α _i is

M _Rai =M _l (α _i )+M _μ (α _i ) (25)

M _l (α _i )＝P(α _i )f ₁ (α _i ) (26)

M _μ (α _i )＝P(α _i )f ₂ (α _i ) (27)

Then add a Δα, calculate the value of M _Ra(i+1) at the next corner α _i+1 =α _i +Δα, and proceed in turn until the value of M _Ra in the entire (0～α ₀ ) range is calculated , and then compare to obtain the maximum value M _Rm . The value of the torque M _Rai at different times t _i can be obtained by using the formula ωt _i =α _i . Compiling the above calculation steps into a program can realize online calculation and quickly provide data for the subsequent control system. In order to verify the correctness of the program, the JH23-63 mechanical press used in the previous example is still used to simulate the force deformation diagram of an approximate half sine wave with a typical drawing process, namely

P(α)＝4×10 ⁵ sin 2α(N) (0≤α≤90°) (28)

As mentioned above, for the mechanical press because of its slider stroke s ₀ =100mm, crank radius R=s ₀ /2=50mm, d ₀ =115mm, d _A =155mm, d _B =120mm, μ=0.045, λ = 0.1, Δα = 1°, transmission ratio I = 5.353, primary gear transmission efficiency η = 0.97, slider stroke times n = 50 times/min, corresponding crank rotation angular velocity ω = 2πn/60 = 5.236 (rad/s ). Input the above known data into the compiled program, and the simulation results shown in Figure 6 and Figure 7 can be obtained, Figure 6 is the torque change curve, and Figure 7 is the deformation force curve. From Fig. 6, it can be obtained that the maximum torque _Ma = 3493 (N·m) required to obtain the PFC shaft at the pressure angle α = 53.1° (t = 0.177s). It can be seen from Figure 6 and Figure 7 that the maximum value of _Ma and the maximum value of force P appear at different times (deformation force P takes the maximum value at 45), so it cannot be simply considered that the maximum deformation force P _m where the torque is greatest.

Using the force sensor, A/D board and computer to measure the deformation force value and its time on-line, the software can automatically calculate the torque M _Ra at different times in the deformation stage of the workpiece, and output the M _Ra value and the maximum value M _Rm at different times , this method has good characteristics such as rapidity and reliability, and it is worth popularizing and applying in production.

The applicant has completed a series of tests according to the above technical solution, and the results prove that the object of the present invention has been achieved.

Claims (1)

1. the online test method of the required transmission moment of torsion of punching machine air operated friction clutch, this method adopt the slide block range indirect method of measurement to detect the moment of torsion M of the required transmission of air operated friction clutch _a, it is characterized in that, specifically comprise the following steps:

1) defines the moment of torsion M that air operated friction clutch can provide _q=β M _a, and M _qBecome good linear relationship with PFC cylinder air pressure, promptly the interior air pressure size of the air operated friction clutch friction torque size that can produce and cylinder is directly proportional, i.e. M _q=kp, wherein, M _aThe moment of torsion of the required transmission of air operated friction clutch during for the punching machine operate as normal; β is the PFC coefficient of torque reserve, and β=1.1～1.3, and the air pressure p that enters the air operated friction clutch cylinder by adjusting reaches the control of the moment of torsion that can produce air operated friction clutch;

2) utilize slide block range curve to determine required transmission moment of torsion M on the rubbing surface _Ra, comprise maximum distortion power P by technology type _mWith online actual measurement P-t numerical relation dual mode;

A. adopt by technology type and maximum distortion power P _mMode be, at first set up the mathematic(al) representation of the workload characteristics of the technology of finishing, calculate the peak torque M of each section in the workpiece deformation process then _Raim, obtain moment of torsion maximal value M in the whole deformation process by the contrast of each section at last _Rm

B. adopt online actual measurement P-t numerical relation to be, utilize force transducer, A/D plate and computing machine online actual measurement deformation force numerical value and the moment thereof, computing machine is controlled by data acquisition and output card, adopts software to calculate workpiece deformation different moment of torsion M constantly in the stage automatically _Ra, and the different M constantly of output _RaValue and maximal value M _Rm

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