JP2757682B2 - Press machine using toggle mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a press apparatus using a toggle mechanism which can increase the speed of a press and improve safety.

[0002]

2. Description of the Related Art FIG. 10 is a view showing a conventional press apparatus using a toggle mechanism. In the drawing, 1 is an upper fixed platen, 2 is an upper mold attached to the upper fixed platen 1, 3 is a movable platen, 4 is a lower mold attached to the movable platen 3, 5a and 5b are upper fixed. Columns (stays) 7 supported by the platen 1 and the lower fixed platen 6 are ball screws (drive screws) having left and right reversed screws.

[0003] 8a and 8b are toggle mechanism links that are moved by the ball screw 7, 9a and 9b are load cells (strain gauges), 10 is a gear box that meshes with the ball screw 7, 11 is a drive motor (M), and 12 is this drive motor (M). ) A tachogenerator (TG) connected to the rotating shaft of 11, and 13 a tachogenerator (TG)
It is an encoder (EC) connected to twelve rotating shafts.
14 is an input terminal 1 to which a mold clamping torque command pulse 15 is input.
4a, input terminal 14 to which position command pulse 16 is input
b, motor drive output terminal 14c, TG feedback input terminal 14
d and an encoder feedback pulse input terminal 14e,
FIG. 11 shows a detailed block diagram of the press control circuit.

In the press control circuit 14 shown in FIG. 11, a pulse processing circuit 17 receives a position command pulse 16 input to an input terminal 14b, discriminates a moving amount and a moving direction, and outputs the pulse processing circuit. Consists of
A difference counter for holding a difference between a command value and a pulse fed back from the encoder (EC) 13, that is, a position error pulse. A D / A converter 19 converts a digital amount of position error (deviation) into an analog amount. It is.

Reference numeral 20 designates a position loop gain and a servo band, and a position loop operational amplifier (forward transfer function) for outputting a position error signal, 21 a subtractor, 22 a speed loop gain and a servo band. A speed loop operational amplifier (forward transfer function), 23 is a changeover switch, and 24 is a subtractor that outputs a difference between an input command and a motor current negatively fed back from a current detector described below.

Reference numeral 25 denotes a torque loop (current loop) operational amplifier (forward transfer function) for determining a gain and a servo band of the torque loop, and reference numeral 26 denotes a current detector for detecting a current flowing through the drive motor 11 and applying negative feedback. C ・ T),
Reference numeral 27 denotes a waveform shaping circuit for shaping an encoder pulse output from the encoder 13. Reference numeral 28 denotes a toggle link mechanism that is moved by a ball screw (drive screw) 7.
Let the output torque be T _L.

Next, the operation of the press apparatus using the toggle mechanism having the above configuration and the control method thereof will be described. First, the position command pulse 16 is transmitted to the press control circuit 14.
The pulse processing circuit 17 receives the position command pulse 16, determines the amount and direction of the movement, and outputs it to the deviation counter 18. The deviation counter 18 holds the difference between the command value and the encoder pulse waveform shaped by the waveform shaping circuit 27 fed back from the encoder 13, that is, the position error pulse. And
The D / A converter 19 converts the digital amount of the position error (deviation) into an analog value, and converts it into an operational amplifier 20 for the position loop.
Send to

Therefore, the position loop operational amplifier 20
Determines the position loop gain and servo band bandwidth,
Outputs a position error signal. This position error signal becomes an input signal (speed command value) of the speed loop, and the difference between the position error signal and the output of the tacho generator 12 of the drive motor 11 is used as a speed loop error so as to rotate at a speed corresponding to the magnitude of this signal. It is input to the speed loop operational amplifier 22.

The speed loop operational amplifier 22 determines the gain and the servo band of the speed loop, and outputs an amplified speed error signal. The output signal is transmitted via a changeover switch 23 and a subtractor 24 to a torque (current). It becomes an input command for the loop operational amplifier 25. In this case, the current detector 26 detects the current flowing through the drive motor (M) 11 and applies a negative feedback to create a difference from the input command, which is input to the torque (current) loop operational amplifier 25.

The gain and servo band of the torque loop are determined by the torque (current) loop operational amplifier 25. Thus, in order to control the position loop more stably, the current loop (torque loop)
And a minor loop of the speed loop is provided. The position loop is controlled up to the mold clamping position, and the mold clamping position is set to be larger than the position where the movable platen 3 hits the upper fixed platen 1 (to a position where the movable platen 3 extends at a predetermined torque by the spring constant of the columns 5a and 5b). The mold clamping can be performed by switching to the mold clamping torque command by closing the mold or by switching the changeover switch 23 and controlling the motor current only by the torque loop.

[0011]

The conventional press device using the toggle mechanism performs only the current value control for detecting the current flowing through the drive motor and applying negative feedback. Therefore, the press mechanism uses the toggle link angle of the toggle mechanism. The true loop gain of the torque loop fluctuates significantly.

This is because, at an angle between 85 ° and 89 ° where the mold is clamped at the toggle link angle TANθ (tangent value), a slight difference in the toggle link angle causes a large change in the mold clamping torque,
Control becomes unstable, and oscillation may occur. In addition, every time a mold or the like is put into the mold to adjust the uniformity of the mold surface pressure, a slight difference in the toggle link angle appears, and TANθ
(Tangent value) changes, and the mold clamping pressure changes. Further, there has been another problem that the press rising speed changes in the same manner as the torque depending on the toggle link angle, and the press cannot be raised at a constant speed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. It is desirable to provide a correction means for detecting a toggle link angle and canceling the influence of the toggle link angle, thereby stabilizing a control loop. With the goal.

[0014]

According to the present invention, there is provided a press apparatus using a toggle mechanism according to the present invention.
A correction means for adding a transfer function of (inverse tangent value) to the control system is provided. Moreover, TAN is added to the current value of the drive motor.
A torque correction means is provided which multiplies by θ (tangent value) to obtain a negative torque feedback signal. Further, a speed correction means is provided which corrects the speed command value of the output of the error amplifier of the position loop by COTθ and uses this signal as a speed command value.

[0015]

According to the present invention , the correction means is provided for controlling the change of the toggle link angle θ.
Since the mechanical gain fluctuation due to is canceled, the control loop can be stabilized, and the push-up force of the press can be prevented from being affected by the toggle link angle.
Further, the press moving speed can be made constant.

[0016]

FIG. 1 is a structural view showing an embodiment of a press device using a toggle mechanism according to the present invention. In the figure,
Reference numeral 29 denotes a link encoder for detecting the toggle link angle θ of the toggle mechanism. The link encoder 29 may be either an increment type or an absolute type, but is an increment type in this embodiment. Reference numeral 30 denotes an input terminal 30a to which the clamping torque command pulse 15 is input, and an input terminal 3 to which the position command pulse 16 is input.
0b, an output terminal 30c, and feedback input terminals 30d and 30e. A detailed block diagram of the press control circuit shown in FIG.

In the press control circuit 30 shown in FIG. 2, 31 is a speed command limiter, and 32 is a speed command COT.
A .theta. (inverse tangent) multiplier, 33 is a torque limiter, 34 is a COT.theta. (inverse tangent) multiplier whose detailed block diagram is shown in FIG. 4, and 35 is a TAN .theta. (tangent) whose detailed block diagram is also shown in FIG. A multiplier, 36 is a torque loop feedback transfer function (H), 37 is a brake, 38 is a toggle link mechanism having a link angle encoder 29 (FIG. 1) and having a transfer function of TANθ.

FIGS. 3A and 3B are conceptual diagrams for explaining the output torque and the speed change (TANθ) of the movable platen 3 depending on the toggle link angle θ. In this case, the motor drive torque is T _M, and the force for pushing up the press is T _L
Then, the following expression is obtained. _{T L = TANθ · T M (} 1) V L = TANθ · V M (2) V M = (1 / TANθ) V L = COTθ · V L (3)

According to the equation (2), the press rising speed V _L
Is a function of TANθ, and after passing through the speed command limiter 31, the speed command is converted to the speed command COTθ multiplier 3
2 and input as a speed command value to the speed loop to make the press ascending speed constant. The speed command value is compared with the output of the tach generator 12, and an operational amplifier (G _V ) 22 forms a forward transfer function of the speed loop.

In the position loop, the pulse processing circuit 17 determines the reversible direction of the command pulse, and also determines the reversible direction of the pulse fed back via the encoder 13 and the waveform shaping circuit 27, and sends it to the deviation counter 18. And
The content of the deviation counter 18 is the difference between the command value and the current value. This is connected to the operational amplifier 2 via the D / A converter 19.
0 constitutes the forward transfer function of the position loop. From the viewpoint of the position loop, the torque control loop and the speed loop are minor loops for stabilizing the control.

FIG. 4 shows a tan θ multiplier 35 corresponding to the toggle link angle θ using the link encoder 29.
FIG. 3 is a diagram showing multipliers and COTθ multipliers 32 and 34. In the figure, reference numeral 39 denotes a pulse shaping / direction judging circuit which receives a signal output from the link encoder 29, performs pulse shaping, determines a direction, and outputs a rising (UP) signal and a falling (DOWN) signal. is there. Numeral 40 denotes a counter composed of a pulse shaping / direction determining circuit 39, a counter 41 and an address buffer 42, which converts the toggle link angle θ into binary data and
43, which are output as addresses of the ROM 44 for COTθ.

Reference numeral 45 denotes an analog multiplier which is a binary weight adder. The analog multiplier 45 applies a binary weight to the input resistance value of the operational amplifier 46, and the analog switch operates according to the contents of the ROM data. Input value X (TANθ or COTθ)
Is performed. FIG. 4 shows the ROM 43 for TANθ.
Is used to constitute the TANθ multiplier 35, but the COT
If the θ ROM 44 is used, the COT θ multipliers 32 and 34 are configured. In the analog multiplier 45, the relationship between the input voltage _Ei and the output voltage _Eo can be expressed by the following equation (5).

[0023] _{E o = - (R f /} 2 0 R + R f / 2 1 R + ··· R f / 2 n R) E i (4) = -R f / R (1 + 1/2 ··· 1/2 ⁿ ) E _i (5)

With this configuration, the TANθ multiplier 35, CO
Multipliers 32 and 34 convert the toggle link angle θ output from the link angle encoder 29 into binary data by the counter 40, and convert the TAN θ ROM 43 and COT θ
Address of the ROM 44. If the effective angle of the toggle link is, for example, 45 degrees to 89 degrees, the variable angle is 44 degrees and the counter is 12 bits (that is, 2 ¹² = 409).
In the case of 6), the resolution is almost 1/100, which is sufficient for control. Binary data of TANθ and COTθ corresponding to the angle of the contents of the counter is TAN
Write to the ROM 43 for θ and the ROM 44 for COTθ. TAN corresponding to the toggle link angle by this means
Binary data of θ and COTθ are obtained. Table 1 shows a specific example of the ROM data.

[0025]

[Table 1]

Next, the stabilization means of the torque loop, i.e. cancel the effect of the toggle link angle, to become a linearly proportional relationship to the output torque T _L is a torque command (current loop input) T _C of the toggle link mechanism Will be described. FIG.
(A), the the G _T torque (current loop) forward transfer function, the K _tm motor torque conversion constant, the L _S load cell conversion constant, H ₁ is a negative feedback transfer function. A typical transfer function by the toggle link function is TANθ, and a loop transfer function G ₀ of this loop can be expressed by the following equation (6).

G ₀ = G _T ＫK _tm ＴＡTA Nθ ＬL _S ＨH ₁ (6) In the expression (6), feedback is applied from the final output shaft using a load cell, a strain gauge, or the like.

FIG. 5B is a block diagram showing an embodiment in which FIG. 5A is improved to stabilize the torque loop.
In this embodiment, the torque feedback is the same as when the link drive motor torque is detected and feedback is performed from the final shaft. FIG. 5C is a block diagram showing an embodiment for stabilizing the torque loop. In the figure, H ₂ = L _S · H ₁ , and by inserting COTθ (inverse tangent) into the forward transmission, the closed-loop loop transfer function G _(T0) can be expressed by the following equation (7).

[0029] _{G (T0) = G T ·} COTθ · K tm · TANθ · H 2 = G T · K tm · H 2 (7) T L ≒ (1 / (H 2 · TANθ)) TANθ · T C ≒ (1 / H ₂ ) T _C (8)

From the equation (8), the output torque _TL can cancel the influence of the toggle link angle θ, and the torque command T
_It is linearly proportional to _C. And this FIG. 5 (C)
The block diagram shown in the embodiment shown in FIG.
Rewriting using COTθ is shown in FIG. 6, and it is possible to correct TANθ and COTθ by the toggle link angle.

FIG. 7 is a block diagram showing another embodiment of the press control circuit 30. In the case of this embodiment, a load cell or a strain gauge is used as a torque converter 47 for compressing the toggle link shaft or pulling the support shaft (stay) in order to return the press-up force (mold clamping force) itself as the torque feedback. Convert the force and return. Also at this time, the loop gain of TANθ changes due to the toggle link mechanism. Therefore, by incorporating the transfer function of the COTθ multiplier 34, the loop gain becomes constant and the torque control can be stabilized.

FIGS. 8A and 8B show control blocks at this time. In particular, FIG. 8A shows a case without any countermeasure, and FIG. 8B shows a case where a forward transfer function of COTθ is inserted to stabilize control. Note that FIG.
In (B), H ₂ = L _S · H ₁ . In the above description, the multiplication of TANθ and COTθ is described as the case where the operational amplifier having the input resistance of the ROM data and the binary weight is turned on / off by the analog switch. However, the present invention is not limited to this.
The SIN and COS potentiometers are attached to the toggle link angles, and the TANθ and COTθ are multiplied using the divider shown in FIG. 9A or 9B.
In this figure, 48 is a SIN potentiometer, 49
Is a COS potentiometer and 50 is a divider.

Then, the input voltage E _i in FIG.
And the output voltage E _o can be expressed by E _o = TAN θ · E _i . The relationship between the input voltage E _i and the output voltage E _o in FIG. 9 (B) can be represented by E _o = COTθ · E _i.

[0034]

As described in detail above, according to the press apparatus using the toggle mechanism according to the present invention, by adding the transfer function of the toggle link angle θ to the COT θ in the position loop control system, It is possible to remove the bad influence of performing the mold clamping with the TAN characteristic of the mechanism, and to perform stable mold clamping control. In addition, the motor current is set to TAN.
By returning the value corrected by θ to the torque loop,
The gain fluctuation of the torque loop due to the toggle link angle can be suppressed, the torque control can be stabilized, and the torque command value and the output torque have a linear relationship regardless of the toggle link angle. Regardless, torque control can be reliably performed. Further, by correcting the speed command value with COTθ, the moving speed of the moving platen or the like can be made constant, and the device can be stabilized. Further, the functions of TANθ and COTθ can be easily configured, and there are effects such as cost reduction.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a press device using a toggle mechanism according to the present invention.

FIG. 2 is a block diagram illustrating a press control circuit of FIG. 1;

FIG. 3 is a conceptual diagram showing changes in output torque and moving platen speed depending on a toggle link angle.

FIG. 4 is a block diagram showing a TANθ multiplier and a COTθ multiplier of FIG. 2;

FIG. 5 is a block diagram showing a transfer function of the torque loop of FIG. 2;

FIG. 6 is a block diagram when TANθ and COTθ are corrected in the torque loop.

FIG. 7 is a block diagram showing another example of the press control circuit shown in FIG. 2;

FIG. 8 is a block diagram illustrating a control loop when feedback is performed from an output shaft.

FIG. 9 is a block diagram showing another example of the TANθ, COTθ multiplier.

FIG. 10 is a configuration diagram showing a conventional press device using a toggle mechanism.

FIG. 11 is a block diagram showing the press control circuit of FIG. 10;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper fixed platen 2, 4 Die 3 Moving platen 5a, 5b Column 6 Lower fixed platen 7 Ball screw 8a, 8b Toggle mechanism link 9a, 9b Load cell 10 Gear box 11 Drive motor 12 Tachogenerator 13 Encoder 29 Link encoder 30 Press control Circuit 31 Speed command limiter 32 Speed command COTθ multiplier 33 Torque limiter 34 COTθ multiplier 35 TANθ multiplier 36 Torque loop feedback transfer function (H) 37 Brake 38 Toggle link mechanism

Claims (3)

(57) [Claims] 1. A link angle detecting means for detecting a toggle link angle .theta., A motor for driving a toggle mechanism, a motor driving means for feeding back the rotational position of the motor to control the motor at a predetermined position, and for driving the motor. wherein the control system means toggling
Cancels mechanical gain fluctuation due to change in lurink angle θ
The gain variation is added by adding the transfer function of COTθ as follows.
A press apparatus using a toggle mechanism, comprising: a correction unit for performing correction. 2. A link angle detecting means for detecting a toggle link angle .theta., A motor for driving a toggle mechanism, a motor driving means for feeding back the rotational position of the motor to control the motor at a predetermined position, and driving the motor. Current detecting means for detecting a current, and TANθ being added to the current value detected by the current detecting means.
A press device using a toggle mechanism, comprising: a torque correction unit that calculates a multiplied value and feeds back the calculated value to a control system of the motor driving unit. 3. A link angle detecting means for detecting a toggle link angle θ, a motor for driving a toggle mechanism, a motor driving means for feeding back the rotational position of the motor to control the motor at a predetermined position, and A press device using a toggle mechanism , comprising: a speed control unit for calculating a value obtained by multiplying a speed command value for the motor by COTθ in the control system of the means, and using the calculated value as a speed command value for the motor. .