JPH0549400B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to electric presses, and in particular, to small and
This invention relates to a method for reducing excessive pressing force of an electric press that presses small-volume workpieces precisely and accurately.

[Conventional technology]

Since conventional electric presses convert the rotational force of the electric motor into linear motion, the inertia of the drive system including the electric motor is inevitably converted into linear motion, which is applied as an impact to the pressurized object. , which was added to the original output of the motor, resulting in a large pressing force.

[Problem to be solved by the invention]

There was no electric press that could control such pressure. Particularly, when the impact force is added to the original output of the electric motor, there is a problem in that the appropriate pressing force cannot be used for the work.

[Means to solve the problem]

Therefore, as a result of intensive research in order to solve the above problem, the inventor applied the invention to a control method for an electric press equipped with a mechanism that converts the rotational force of an electric motor into linear motion using a screw mechanism. It is equipped with a means for detecting and storing the height position of a ram that can be raised and lowered to pressurize a pressurized object, and a rotation speed detection means for detecting the rotation speed of the electric motor. A current setting circuit is provided to control the current, and the approach stroke of the ram is lowered at high speed with a current that allows high speed, and the ram is operated at low speed with a current that only allows lowering just before the object to be pressurized, so that the ram is pressed. After confirming that the object has come into contact with the rotation speed detection means, the electric press supplies a current necessary for a set pressure sufficient to pressurize the object. By using the reduction method, the load current of the motor can be controlled based on the ram position stored in the central processing unit.The ram is lowered at high speed until it reaches the pressurizing point, and the object to be pressurized is The above-mentioned problem is solved by supplying power to the motor at a low speed from immediately before reaching the contact point, and supplying the current necessary for the set pressing force after the contact is made.

〔Example〕

Hereinafter, embodiments of the present invention will be described based on the drawings. First, the names and functions of the constituent parts of the present invention will be explained using the block diagram shown in FIG.
is an operation panel, and has each switch from A to J, each button, and each knob on its surface.

A is an electric switch, and B is a memory point setting button, which is used to set and change various memories.

C ₁ and C ₂ are operation buttons, and their function is to press the C ₁ and C ₂ buttons to lower the ram 5, and to release only the C ₂ button to temporarily stop. Furthermore, C ₁ and C ₂
The ram 5 is configured to rise when the button is released.

D is an open height setting button, E is a pressure point setting button, F is a stop point setting button, and G uses a digital switch as a code generator, which is used to correct the fixed position stopping point. For example, how to use it is to set a correction value on the digital switch G and instruct addition or subtraction using the sign changeover switch H.
The central processing unit 2 performs calculations and the set point by the stop point setting button F is changed.

I is an upper limit pressure setting knob, and J is a lower limit pressure setting knob.

2 is a central processing unit (CPU) that stores the open height set point, high speed to low speed switching point, set pressure generation point, and fixed position stop point of the ram 5, and moves the ram to each of these positions. 5 has been reached, and has a function of instructing the electric motor 4 to change the settings of the rotational speed and current value, as well as to intermittent and reverse the rotational speed and current value.

Reference numeral 3 denotes a motor driver, which drives the electric motor 4 according to instructions from the central processing unit 2.

The electric motor 4 drives the ram 5. The ram 5
has the function of pressurizing the pressurized object by vertical movement.

6 is a limit switch A that detects the upper limit point of the ram 5.

An encoder 7 is connected to the electric motor 4 and detects the amount of movement and speed of the ram 5.

8 is a current setting circuit which has the function of converting the signal from the central processing unit 2 from digital to analog and sending it to the motor driver 3.

Reference numeral 9 denotes a limit switch B, which is used to define the lowering limit point of the ram 5. When the protrusion 5b fixed to the ram 5 presses the switch lever 9a of the limit switch B9, the central processing unit 2 activates the motor driver 3. so that the ram 5
will rise to the open height set point and stop. This prevents the ram 5 from descending too much and causing the ball screw and feed screw to become disengaged.

The means for converting the rotational force of the electric motor 4 into linear motion can be achieved by using a ball screw, a feed screw, or the like.

Next, to explain the operating principle using press-fitting work as an example, in Fig. 1, when the power switch A on the operation panel 1 is turned on, a rising signal for setting the origin is sent from the central processing unit 2 to the motor driver 3.
The electric motor 4 is driven and the ram 5 begins to rise.
When the protrusion 5a fixed to the ram 5 presses the switch lever 6a of the limit switch A6 to detect the upper limit point of the ram 5, the central processing unit 2 stops the electric motor 4, and then reverses and
As the ram 5 is driven, the ram 5 begins to descend by the number of pulses stored in the central processing unit 2 while being confirmed by the encoder 7 connected to the electric motor 4. When the ram 5 reaches the set number of pulses, the central processing unit 2
stops the electric motor 4.

Thereafter, various functions are performed using this point as a reference point. Next, after pressing the memory point setting button B to bring the central processing unit 2 into a state of loading various memory points, the operation buttons C ₁ and C ₂ are pressed simultaneously to lower the ram 5, and only the operation button C ₂ is pressed. is released to temporarily stop the ram 5, and when the open height setting button D is pressed, the open height setting point is stored in the central processing unit 2. Thereafter, even if the operating buttons _C1 and _C2 are released at the same time, the ram 5 will not rise above the open height setting point, so that the idle stroke can be eliminated.

Furthermore, the pressurization point can be set using the operation buttons _C1 and
Press C ₂ to lower the ram 5, and when you reach the position where you should apply the pressure necessary for press-fitting, press operation button C _2.
When the pressurizing point setting button E is pressed, the central processing unit 2 memorizes the position at which the pressurizing force necessary for the press-fitting is to be applied.

Further, press the operation buttons _C1 and _C2 to lower the ram 5, temporarily stop the ram 5 at the press-fitting stop point, press the stop point setting button F, this point will be stored in the central processing unit 2, and the above-mentioned Ram 5 automatically rises to the open height set point and stops.

Furthermore, regarding the fixed position stopping point, if the set position is inconvenient, a correction value can be set on the digital switch G on the operation panel 1, and the fixed position stopping point can be changed by the necessary dimension.

This means that the memory settings for the actions necessary for the pressurization work have been made.

When the operator presses the operation buttons C ₁ and C ₂ according to the setting operations described above, the current set at high speed from the central processing unit 2 to the current setting circuit 8 is supplied to the electric motor 4 through the motor driver 3. A ram 5 connected to the electric motor 4 descends at high speed, and when it reaches a set pressurizing point, the ram 5 is connected to the central processing unit 2.
Then, the electric motor 4 is driven with a preset minimum current and rotational speed necessary for the ram 5 to descend, and the ram 5 descends at a low speed.

When the ram 5 reaches the object to be pressurized, the rotational force of the electric motor 4 is overcome by the resistance of the object to be pressurized, and the ram 5 stops. At this time, when the central processing unit 2 confirms that the ram 5 has stopped using the encoder 7, it instantly supplies the electric current necessary for the set pressing force to the electric motor 4 with a constant rising slope, and then The ram 5 descends at a constant speed set in the processing device 2.

Through these series of operations, excessive pressurizing force on the electric motor 4 and the transmission mechanism is removed.

Further, when the ram 5 reaches just before the fixed position stopping point stored in the central processing unit 2, a deceleration braking command is transmitted from the central processing unit 2 to the control unit, and the electric motor 4 descends at a constant low speed and reaches the fixed position. At the stop point, the power is cut off and the machine stops.

Furthermore, after stopping for a certain period of time programmed into the central processing unit 2, the ram 5 rises to the open height set point and stops.

As mentioned above, the ram 5 reaches the pressurized object,
After the ram 5 is stopped due to the resistance of the pressurized object, the current necessary for the set pressurizing force is supplied to the electric motor 4,
Since press-fitting is performed at a constant speed, highly accurate press-fitting with less excessive pressure is possible.

Here, a method for removing excessive pressurizing force of the electric motor will be further explained in detail based on FIG. 2.

First, we will explain the names and functions of each component.
COMP1, COMP2, COMP3 are power comparators,
It compares the difference in voltage between the + side input and the - side input, and if the + side is even slightly larger, the output will be positive, and if it is smaller, the output will be negative.

VR ₁ is a variable resistor for setting pressure force, and R is a resistor for current detection.

Next, to explain the operating principle, the central processing unit 2 reads the signal from the encoder 7 that detects the position of the ram 5 using the pressurization point setting button E, and sets the pressurization point. Selecting the voltage comparator COMP2 regardless of the central processing unit 2,
Regardless of the voltage _V1 required for the set pressurizing force, the voltage _V2 drops to a value sufficient to enable high-speed rotation, and when the pressurizing point is passed, the central processing unit 2 detects a voltage comparator.
Select COMP3.

A voltage V ₃ is applied to the COMP 3 to generate the low torque necessary for the ram 5 to descend at a low speed. This voltage V ₃ causes the ram 5 to descend at low speed and with low pressure, so when the ram 5 collides with the pressurized object, the ram 5 stops, but the encoder 7 causes the central processing unit 2 to control this stop. After recognition, the voltage comparator COMP1 is selected and the object to be pressurized is pressurized with the voltage _V1 required for the set pressurizing force.

By using this method, excessive pressurizing force of the electric motor can be completely eliminated.

Next, setting of the pressurizing force and knowing the upper and lower limits of the pressurizing force will be explained. When an operator wants to manage the pressurizing force, he or she can first set the upper limit pressurizing force by adjusting the upper limit pressurizing force setting knob I on the operation panel 1 to match the required upper limit pressurizing force scale. . With this operation, the current flowing through the motor 4 does not exceed the current required to generate the upper limit pressing force.

Therefore, if a pressing force greater than the upper limit pressing force is required, the electric motor 4 will stop, and by detecting that it has stopped before the fixed position stop point, the upper limit pressing force can be managed.

On the other hand, the lower limit pressing force can be managed using the lower limit pressing force setting knob J on the operation panel 1.

In managing the lower limit pressure, if the required pressure input of the pressurized object does not reach the set lower limit pressure, press-fit is monitored within a range of 3 mm before the fixed position stopping point as shown in Figure 3. In this method, first, when the ram 5 descends to 3 mm before the fixed position stopping point, the central processing unit 2 generates the current of the electric motor 4 necessary to generate the lower limit pressing force set in the motor driver 3. The value is compared with the current value of the electric motor 4 that is actually flowing. If the electric motor 4 stops at the fixed position stop point after the current value exceeds the set current value, it is determined that press-fitting has been performed within the set press-in force range.

Also, if the current value of the motor 4 does not exceed the current value required to generate the set lower limit pressing force and stops at the fixed position stopping point, or after the current value of the motor 4 exceeds the set current value, If the current value of the motor 4 falls below the set value and stops at the fixed position stop point, it is determined that the pressing force is insufficient and a signal is issued.

FIG. 3 is intended to supplement the above explanation, and is a diagram showing the current value of the motor and the speed of the ram for each position of the ram during press work.

In the figure, 1 is a state in which press-fitting is appropriate, 2 is a state in which the press-fitting force does not reach the lower limit pressurizing force, and 3 is a state in which the press-fitting force is properly performed and then falls below the lower limit pressurizing force.

Furthermore, management of the pressurizing force will be explained in detail based on FIG. 4. First, to explain the names and functions of each component, COMP1 and COMP2 are voltage comparators that compare the voltage difference between the + side input and the - side input, and if the + side is even slightly larger, the output will be It becomes positive, and when it is small, it becomes negative.

R is a current detection resistor of the motor 4.

Next, to explain the operating principle, the electric motor 4
If the torque constant of is K _t , the generated torque T is T=K _t・I, and the pressing force is the voltage comparator COMP1,
Since the current i flowing into COMP2 is extremely small, it is proportional to the current I.

Therefore, at both ends of the current detection resistor R, V=R・I A voltage V is generated.

Since the motor driver 3 controls the voltage comparator COMP1 so that V=V ₁ , in the end,
Since the current I is proportional to V ₁ , the pressing force can be adjusted by VR ₁ .

In addition, if you press the stop point setting button F and memorize the stop point in advance in the central processing unit 2, if the electric motor 4 stops due to excessive press force and the motor 4 is not fully press-fitted, the amount of movement determined by the encoder 7 and the central processing unit 2 In device 2,
Since the stopping point stored in advance does not match, it can be determined that the press-fit is not performed.

Further, by setting the lower pressure reduction force using _VR2 and having the central processing unit 2 monitor the signal of the voltage comparator COMP2 until the end of press-fitting, it is possible to detect an insufficient press-in force.

As described above, it becomes possible to appropriately manage the pressurizing force. The press-fitting method according to this embodiment includes, in addition to the press-fitting operation after setting the fixed position stopping point, a method of forcibly stopping the ram by means other than the press to keep the press-fitting dimensions constant. .

For example, when working with a press-fitting jig equipped with a means for forcibly regulating the press-fit dimensions, after setting the pressure point, press operation buttons C ₁ and C ₂ to lower the ram 5. Then, by means of forcibly regulating the press-fitting dimensions of the jig, the ram 5 is lowered to a stopping position, and after this stopped position is stored in the central processing unit 2, the ram 5 is raised to the open height. Stop at set point.

In this case, the position at which the ram 5 stops depends on what is stored in the memory of the press body, and the ram 5 continues to descend until it hits the forcible stopping means and stops. From then on, by pressing operation buttons C ₁ and C ₂ , the ram 5 will descend at high speed to the pressurization point set point, and as described above, the press-fitting operation will be performed at a constant pressure and constant speed, and then it will be forced to stop. The device descends until it stops, and then rises after a certain period of time.

In this case, the central processing unit 2 determines that the press-fitting dimension is insufficient and displays an error message indicating that the press-fitting force is large.

Therefore, in order to prevent such a situation, the judgment range for error display is set to a certain distance before the storage point by an amount that takes into account the variation in the forced stopping point of the jig from the set stopping point.

This makes it possible to prevent erroneous judgments.
Further, in this case, the ram 5 is lowered until it is forcibly stopped by the jig, so the press-fitting dimensions are determined by the jig. Further, in this case, if no pressurizing point is set, the central processing unit 2 is programmed so that the set points are not stored, so the ram 5 will not descend at high speed.

Therefore, damage to the machine due to collision with the forcible stopping means can be prevented.

In the case of normal caulking work, if the lower limit pressure is set at a certain level, the upper limit pressure is applied at the same time as the ram 5 contacts the pressurized object, so the central processing unit 2 detects that the lower limit pressure is insufficient. It makes a judgment and displays an error message. Therefore, in this case, if the lower limit pressing force setting knob J is set to zero, no error display will occur. This allows the operator to perform caulking work at a constant pressure set by the upper limit pressure setting knob I by setting the open height and setting the pressure point just before the ram 5 contacts the pressurized object. can.

Even in the case of caulking work, if the caulking dimensions are more important than the caulking force, by setting a fixed position stopping point and performing the caulking work, you can manage the caulking dimensions with high accuracy and the upper and lower limits of the caulking force. I can do it.

In this case, when large crimping force is displayed, the crimping dimension is insufficient because the object to be crimped is hard and has stopped short of the fixed position stop point.

On the other hand, when the crimping force is displayed as small, it means that sufficient crimping force is not applied to the object to be crimped.

〔Effect of the invention〕

By using the method of construction as explained above, the present invention can reduce the excessive pressurizing force of the electric motor that inevitably occurs in electric presses, thereby reducing the excessive pressurizing force that has conventionally occurred. The impact force is eliminated, and the precision of press pressure in the relevant press field can be further improved, improving product precision.
This can be said to be a highly effective invention.

[Brief explanation of the drawing]

Fig. 1 is a block diagram according to an embodiment of the present invention, Fig. 2 is a block diagram regarding a method for reducing excessive pressurizing force in an electric press, and Fig. 3 shows the current value of the electric motor and the speed of the ram for each position in the press operation. The illustrated diagram, FIG. 4, is a block diagram regarding pressure force management of the electric press. 4...Electric motor, 5...Ram, 8...Current setting circuit.

Claims (1)

[Claims] 1. In a control method for an electric press equipped with a mechanism that converts rotational force from an electric motor into linear motion using a screw mechanism, a means for detecting and storing the height position of a ram that can be raised and lowered to pressurize a pressurized object, Equipped with a rotation speed detection means for detecting the rotation speed of the ram, and a current setting circuit that controls the load current of the motor according to the stored height position of the ram. The object to be pressurized is operated at low speed with a current that allows only the lowering just before the object to be pressurized, and after confirming with the rotation speed detection means that the ram has contacted the object to be pressurized, the object to be pressurized is started. A method for reducing excessive pressurizing force in an electric press, characterized by supplying current necessary for a set pressurizing force sufficient to increase pressure.