JPH04172200A - Preliminary acceleration controller for press die cushion - Google Patents

Abstract

PURPOSE:To surely secure a restricting quantity and to prevent a defective from being generated by comparing a position data from a die cushion stroke detector with a target value and feedback-controlling a servo valve so that a deviation is removed when it occurs. CONSTITUTION:A crank angle and a slide speed are inputted respectively from a crank angle detector 12 and a press speed detector 13 into a controller body 10. On one hand, when the crank angle indicates a preliminary acceleration starting angle, a servo valve 22 is opened by a servo opening degree commanding signal, hydraulic pressure is flowed into the upper part 7 of a hydraulic cylinder 7 and a die cushion pad 5 starts the preliminary acceleration (lowering), the acceleration stroke of the pad 5 is inputted from a die cushion stroke position detector to a comparator 19 and compared with a target position outputted by an arithmetic and control unit 18 to calculate the difference. The feedback control of the servo valve 22 is performed so that the deviation is reduced to zero.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pre-acceleration control device for a die cushion provided in a press.

[Conventional technology]

The die cushion provided in conventional presses has a structure in which a lower mold cushion pad provided near the lower mold is elastically supported via a plurality of die cushion racks.
When the upper die that descends with the slide comes into contact with the blank holder and a press load is applied to the die cushion pad,
The pressure inside the die cushion cylinder that supports the die cushion pad from below is discharged, and the blank holder as well as the upper mold are moved down by the cushion stroke.

In the press die cushion as described above, when the upper die that has descended with the slide comes into contact with the blank holder, a loud collision noise is generated.

For this reason, in the past, the die cushion pad was lowered in advance at a speed slower than the descending speed of the slide to reduce the collision noise when the upper mold contacts the blank holder, and the impact shortened the life of the upper mold and blank holder. It prevents you from doing so.

Further, the conventional pre-acceleration device adjusts the descending speed by controlling the flow rate flowing into a pre-acceleration hydraulic cylinder provided in the Gui cushion using a servo valve.

In other words, the crank angle of the press is detected, and when the crank angle reaches a preset angle, the servo valve is opened at a predetermined opening degree to start preliminary acceleration, and the angle at which the upper die comes into contact with the blank holder is reached. By the way, the servo valve is closed, and the descending speed control during preliminary acceleration is performed using oven loop control.

[Problem to be solved by the invention]

However, when the descending speed of the Gui Cushion is controlled using oven loop control as in the conventional method described above, if there are large variations in the descending speed and the relative speed with the upper mold is large, effects such as reducing collision noise may not be achieved. I can't wait.

In addition, if the descending speed of the Gui Cushion is fast, the upper die will come into contact with the blank holder after preliminary acceleration, which will not only make it impossible to achieve the intended purpose, but also cause the production of defective products because press forming will not be performed properly. However, since the setting of the angle at which preliminary acceleration should be started had to be determined through many trial moldings, there were problems such as the need for a large amount of time for adjustment.

The present invention has been made in order to improve the above-mentioned problems, and it is an object of the present invention to provide a preliminary acceleration control device for a press die cushion that can perform preliminary acceleration of the goo cushion with high accuracy.

[Means and operations for solving the problem] In order to achieve the above object, the present invention provides a press die cushion that includes a pneumatic cylinder that performs a cushioning action and a hydraulic cylinder that changes the cushioning capacity. The control device main body calculates the preliminary acceleration start angle and end angle based on the preliminary acceleration stroke and throttle stroke input to the control device main body that controls the connected servo valve, and the pre-acceleration start angle and end angle are input from the crank angle detector. The target value is output to the comparator for each crank angle, and compared with the die cushion stroke position data input from the die cushion stroke position detector, and if a deviation occurs, the servo valve is feedback-controlled so that the deviation is eliminated. This is how it was done.

As a result, it is possible to accurately control the acceleration speed of the die cushion so as to reach the target value output for each crank angle, and therefore it is possible to reduce the collision noise when the upper die comes into contact with the blank holder.

〔Example〕

An embodiment of the present invention will be described in detail with reference to the drawings.

In the figure, 1 is the press body, and the lower die 2 is placed on the bolster 1a.
A blank holder 2a provided around the lower die 2 is elastically supported by a die cushion 4 via a plurality of die cushion pins 3 provided in a bolster 1a.

The Gui cushion 4 includes a Gui cushion pad 5 that supports each die cushion pin 3 from below, a pneumatic cylinder 6 that supports the die cushion pad 5, and a hydraulic cylinder connected to the Gui cushion pad 5 via a piston rod 7a. Consists of 7.

The hydraulic cylinder 7 has an upper chamber 7 inside due to a piston 7b provided on a piston rod 7a. It is divided into 72 lower rooms,
Upper chamber 7. Hydraulic pressure is supplied from a hydraulic pump 8 through a servo valve 22, and an upper chamber 71 and a lower chamber 72 can communicate with each other through a logic valve 9.

Further, the stroke position of the die cushion pad 5 is detected by a die cushion stroke position detector 11 and inputted to the control device main body 1o.

The control device main body 10 detects the crank angle from a crank angle detector 12 connected to the main shaft (not shown) of the press 1, and the press speed from a rotation detector 13 that detects the rotation of the main motor (not shown). (spm) is input, and the drawing stroke pb and preliminary acceleration stroke fla of the work 14 to be separately molded can be input from the operation panel 15 or the like.

The data inputted from each of the above detectors 12, 13 and the operation panel 15 is sent to the arithmetic processing unit 1 from the 110 port 17.
Preliminary acceleration start angles θa and θb are calculated based on data inputted to 8 and stored in memory ROM and RAM in advance, and output to a comparator 19.

The current die cushion position is inputted to the comparator 19 from the die cushion position detector 11, and is compared with the target value output from the arithmetic processing unit 18, and the deviation is calculated as D/
A servo valve opening command signal is outputted to the servo valve 22 via the A converter 2o and the gain setting circuit 21, and the servo valve 22 is controlled.

Next, to explain the action, the die cushion motion is the curve B in contrast to the slide motion shown in the curve A in Fig. 2.
As shown in , when preliminary acceleration of the die cushion starts at crank angle θa, slide 1a starts at crank angle θb.
The upper mold 23 attached to the blank holder 2a comes into contact with the blank holder 2a, and the preliminary acceleration ends.

Further, the preliminary acceleration stroke at this time is ga1, and the drawing stroke is nb, which are known values although they vary depending on the workpiece 14 to be formed.

In forming the workpiece 14, first, in step (2) of the flowchart shown in FIG. 3, the preliminary acceleration stroke Na and the drawing stroke fIb are input.

The control device main body 10 receives input data pa.

11b, the arithmetic processing unit 18 calculates the pre-acceleration start angle θa and the end angle θb in step ① as follows.

In other words, if the slide speed during molding is ■, μmf'
v (θ, spm) - spm - fv (θ) where spm is 7 minutes of stroke θ - fe (41) Since fv (θ) is more than the speed function at lspm, preliminary acceleration start angle θa and acceleration end angle θb When calculating, t = k-1a / sp m-f v (θb
) ・(1) θa−θb−6・spm・t −
(2) Substitute (1) into (2) θb-fil(Rb) k (1<k): The die cushion contacts the slab blank holder by the coefficient.

A table of die cushion stroke positions relative to crank angles is created in advance using the pre-acceleration acceleration start angle θa and acceleration end angle θb calculated as described above, and is stored in the memory RAM.

After that, when the press operation starts, as the slide 1a descends, the crank angle detector 12 detects the reflux angle, and the press speed detector 13 detects the slide speed.
o (step ■). The arithmetic processing unit 18 of the control device main body 1o determines θa, θ and θb,
If YES, the process proceeds to step (2), where the die cushion stroke position data for each crank angle is read out from the table stored in the memory RAM, and outputted to the comparator 19 as a target position.

On the other hand, when the crank angle reaches the pre-acceleration start angle, the servo valve 22 is opened by the servo opening command signal, and the upper chamber 7 of the hydraulic cylinder 7 is opened. Hydraulic pressure flows into the die cushion pad 5 and the die cushion pad 5 starts pre-acceleration (lowering). At the same time, the acceleration stroke of the die cushion pad 5 is inputted from the die cushion stroke position detector 11 to the comparator 19, and is inputted from the arithmetic processing unit 18 to the comparator 19. It is compared with the output target position and its deviation is calculated.

Then, the servo valve 22 is feedback-controlled so that the deviation becomes zero.

As a result, the die cushion pad 5 is always pre-accelerated according to the target position, and the pre-acceleration stroke fI
When the upper die 22 is lowered a, it comes into contact with the blank holder 2a, and the preliminary acceleration is completed.

After that, the slide 1a continues to descend and draws the workpiece 14 between the upper die 22 and the lower die 2, and when the slide 1a reaches the bottom dead center, the forming is completed, and as the slide 1a rises, the die cushion pad 5 also begins to rise.

Incidentally, if necessary, the lifting of the die cushion pad 5 can be locked by the hydraulic cylinder 7 by closing the servo valve 22.

〔Effect of the invention〕

As described in detail above, this invention outputs the pre-calculated preliminary acceleration start angle and end angle as target values for each crank angle, and uses the position data from the die cushion stroke detector that detects the acceleration stroke of the die cushion and the above Since the target values are compared and if a deviation occurs, the servo valve is controlled in feedback so that the deviation becomes 0, the preliminary acceleration of the die cushion can be performed with high accuracy.

As a result, it is possible to effectively reduce the collision noise when the upper die comes into contact with the blank holder, and also to ensure the amount of drawing accurately, thereby preventing the occurrence of defective products.

In addition, the device calculates the pre-acceleration start angle and end angle by simply inputting the pre-acceleration stroke and drawing stroke according to the mold, so no troublesome adjustments are required and operability can be improved.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, with FIG. 1 being a configuration diagram, and FIGS. 2 and 3 being action explanatory diagrams. 6 is a pneumatic cylinder, 7 is a hydraulic cylinder, 10 is a control device main body, 11 is a die cushion stroke detector, 12 is a crank angle detector, 19 is a comparator, and 22 is a servo valve.

Claims (1)

[Claims] In a press die cushion consisting of a pneumatic cylinder 6 that acts as a cushion and a hydraulic cylinder 7 that changes the cushioning capacity, preliminary acceleration input to the control device main body 10 that controls the servo valve 22 connected to the hydraulic cylinder 7 is used. The control device main body 10 calculates a pre-acceleration start angle and an end angle based on the stroke and the aperture stroke,
In addition, the target value is output to the comparator 19 for each crank angle input from the crank angle detector 12, and compared with the die cushion stroke position data input from the die cushion stroke position detector 11, and if a deviation occurs. A preliminary acceleration control device for a press die cushion, characterized in that the servo valve 22 is feedback-controlled to eliminate deviation.