JP2746844B2 - Overload protector for hydraulically driven link press machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overload protector for preventing an overload in a molding process of a hydraulically driven link press.

[0002]

2. Description of the Related Art Conventionally, when a material to be drawn is drawn into an arbitrary shape by a hydraulically driven link press machine, or when a resin is formed, when a die height is set incorrectly or when the thickness of the formed material is incorrectly press-formed. May be overloaded.

[0003]

In the case of drawing or resin molding using the above-mentioned conventional hydraulically driven link press machine, if an overload occurs as described above, the quality of the product is deteriorated and the press machine itself is deteriorated. It also has an adverse effect. Therefore, it is necessary to avoid the above-mentioned overload.

Accordingly, in the present invention, an overload of a hydraulically driven link press for preventing the above-mentioned overload condition is provided.
The problem to be solved is to provide a protector.

[0005]

In order to solve the above-mentioned problems, according to the first aspect of the present invention, a hydraulically driven link press machine is provided.
-The bar load protector is driven by the pressurizing cylinder.
Links and slides that move up and down in conjunction with the links
And a small stroke hydraulic chamber installed inside
A movable piston connected to the link and the oil
The accumulator connected to the pressure chamber via the hydraulic circuit
In the hydraulically driven link press provided,
A variable displacement hydraulic pump for discharging pressure oil to the
A pressure sensor for detecting a hydraulic pressure of the chamber, and the variable displacement hydraulic pressure.
A pressure control valve for controlling the discharge pressure of the pump;
When the movable piston is driven by driving the cylinder
Before the hydraulic pressure of the hydraulic chamber becomes a preset value,
The pressure control based on a pressure detection signal from the pressure sensor.
And a control circuit for controlling the control valve.

[0006]

The overdrive of the hydraulically driven link press having the above construction is described.
According to the load protector, the link is made by the pressurized cylinder.
Is driven to start the press operation, and the movable
When the ton is driven, the control circuit
The pressure control valve is controlled based on the detection signal,
Variable displacement hydraulic pump so that force becomes a preset value
The discharge pressure is controlled. Therefore, the hydraulic pressure in the hydraulic chamber
Prevents overload during press operation without exceeding the fixed value
can do.

[0007]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing a hydraulic control circuit of an overload protector of the hydraulic drive link press 1, and FIG. 2 is a hydraulic drive circuit diagram of a pressurizing cylinder.

As shown in FIGS. 1 and 2, a frame 2 of the hydraulically driven link press 1 is formed in a substantially C shape, and an upper frame 5 opposed to a bolster 4 mounted on a bed 3 is provided.
A support shaft 6 is provided on one side, and one end of a substantially triangular operating lever 7 is pivotally mounted on the supporting shaft 6.
An upper end of a link 9 having a predetermined length is pivotally connected to a corner of the link 9 via a connecting pin 8.
Are connected via connecting pins 11, and an upper die (not shown) is detachably attached to the lower surface of the slide 10, and a lower die (not shown) is attached to and detachable from the upper surface of the bolster 4. Mounted on

A mounting shaft (not shown) of the pressure cylinder 15 is provided at a predetermined position on the rear side of the upper frame 5 so that the base of the pressure cylinder 15 is pivotally mounted.
The tip of the rod 16 of the pressurizing cylinder 15 is the operating lever 7
Are pivotally connected to the corners of the by connecting pins 17. The slide 10 is moved up and down by the expansion and contraction operation of the pressurizing cylinder 15 provided as described above.

In FIG. 2, a discharge line 22 from a hydraulic pump 21 driven by a drive motor 20 is connected to a first port of an electromagnetic switching valve 23 for switching the pressurizing cylinder 15, and this electromagnetic switching valve The second port 23 and the piston rod chamber 15a of the pressurizing cylinder 15
The third port of the electromagnetic switching valve 23 and the piston chamber 15b of the pressurizing cylinder 15 are connected by a high-pressure line 25. The high-pressure line 25 has a pilot check valve 26 Further, a proportional electromagnetic flow control valve 27 for controlling the extension speed when the pressurizing cylinder 15 performs the extension operation is provided. In addition, pilot check valve 2
6 is connected to an electromagnetic direction switching valve 26A. Also,
A safety valve 29 for the hydraulic pump 21 is provided between the discharge pipe 22 and the tank 28.

The slide 10 is provided with a hydraulic chamber 30 for a small stroke, and the hydraulic chamber 30 has a movable piston 3 connected to the link 9 via a connecting pin 11.
1 is provided internally. As shown in FIG.
0 is connected to a pipe 32, and at an end of the pipe 32,
A gas pressure type accumulator (pressure accumulator) 33 is attached. On the other hand, a variable displacement hydraulic pump 36 is provided via a check valve 35 at an end of a pipe 34 branched from the middle of the pipe 32. The variable displacement hydraulic pump 36 is driven by a motor 37,
8. Pump oil from tank 39 through 8.

When the pressure of the closed circuit between the hydraulic chamber 30 and the accumulator 33 reaches the maximum working pressure, the above-described pressurizing cylinder 15 is provided at the end of the pipe 40 branched from the pipe 32.
A pressure switch 41 for stopping the driving of the motor is mounted. Further, a non-leak type relief valve 42 is attached to the pipe 40, and when the pressure of the accumulator 33 exceeds a predetermined value, it operates so as to decrease to a predetermined pressure.

A pressure sensor 43 for detecting the pressure of a closed circuit between the hydraulic chamber 30 and the accumulator 33 is attached to the pipe 40, and outputs an electric signal corresponding to the detected pressure. This electric signal is fed back to the pressure controller 44 to check for abnormal pressure.

The pressure controller 44 receives an electric signal from the pressure sensor 43 so that the discharge pressure of the variable displacement hydraulic pump 36 becomes a set pressure set by a press operation panel (not shown). Then, the electromagnetic proportional pressure control valve 45 is controlled. The variable displacement hydraulic pump 3
An electromagnetic directional control valve 46 is provided between the sixth pilot valve 36P and the electromagnetic proportional pressure control valve 45. Also,
When the pressure switch 41 is operated, the stop valve 47
It is provided to perform pressure relief.

In the overload protector of the hydraulically driven link press having the above structure, when the press pressure is set by a press operation panel (not shown), the electromagnetic directional control valve 46 is turned on. And pressure control
The controller 44 supplies a control current to the electromagnetic proportional pressure control valve 45 based on an electric signal from the pressure sensor 43, and controls the discharge pressure of the variable displacement hydraulic pump 36 to a set pressure. Therefore, when an electric signal corresponding to a pressure equal to or lower than the set pressure is output from the pressure sensor 43, the pressure controller 44 increases the pressure of the closed circuit between the hydraulic chamber 30 and the accumulator 33 to the set pressure. As described above, by controlling the control current for the electromagnetic proportional pressure control valve 45 and controlling the discharge pressure of the variable displacement hydraulic pump 36, the press forming pressure is maintained.

The capacity of the accumulator (accumulator) 33 is about three times the oil quantity corresponding to the stroke quantity of the movable piston 31 of the small stroke hydraulic chamber 30. The reason for this is that the difference between the minimum operating pressure and the maximum operating pressure of the accumulator (pressure accumulator) 33 is reduced, and the load pressure at the time of press molding is made uniform, so that the hydraulically driven link press 1 and the mold can be connected. This is because the burden is reduced.

The minimum operating pressure of the accumulator (accumulator) 33 is about 50% of the nominal capacity of the press, and pressurized oil is supplied to the accumulator (accumulator) 33 so that the pressure matches the nominal capacity of the press. In this case, the residual gas amount of the accumulator (pressure accumulator) 33 is 45% of the initial value from the gas state equation (considered as an isothermal change). That is, the capacity of the accumulator (accumulator) 33 in the original state is V0, the pressure is P0, and the capacity in the minimum operating pressure state is V0.
1, the pressure is P1, the capacity in the press nominal capacity pressure state is V2, the pressure is P2, the capacity in the 5% overload state is V3, and the pressure is P3, V1 = 0. 9V0. Also, does V0 · P0 = V1 · P1 hold? P1 = V0 · P0 / V1 = P0 / 0.9 holds. Further, since P2 = 2P1 and V0.P0 = V2.P2 hold, V2 = P0.V0 / 2P1 = P0.V0 / (2 / 0.9) P0 Therefore, V2 = 0.45V0 holds, so the accumulation The residual gas amount of the negative pressure (accumulator) 33 becomes 45% of the initial gas amount.

The capacity of the accumulator (pressure accumulator) 33 is three times the oil amount corresponding to the stroke amount of the movable piston 31 of the small stroke hydraulic chamber 30. , 5% pressure increase of press nominal capacity pressure
When the pressure switch 41 is set to operate, the stroke amount of the movable piston 31 in the hydraulic chamber 30 at that time is calculated as follows.

P0 · V0 = P3 · V3 = 1.05P2 · V3, and P2 = 2P1 = 2P0 / 0.9 = 20P0 / 9. Therefore, V3 = P0.V0 / 1.05P2 = P0.V0 / 1.05 * (20/9) = 9V0 / 21 = 0.429V0. Therefore, V2 -V3 = 0.45V0 -0.429V0 = 0.021V0. Assuming that the volume of the hydraulic chamber 30 is v, V0 = 3v, so that 0.021V0 = 0.021 × 3v = 0.063v.

The above value is the value of the movable piston 31 of the hydraulic chamber 30.
Corresponds to 6.3% of the total stroke amount.
If the total stroke amount is 20 mm, then 20 × 0.0
63 = 1.26 mm, which is an excessive amount when viewed from the precision of the product due to the variation in the thickness of the material at the time of resin molding, and the variation in the thickness is extremely small in a metal plate or the like. In the press operation, overload is hardly generated, so that the set pressure of the pressure switch 41 for detecting overload can be set very close to the nominal capacity of the press. The bar load protector is extremely significant also in terms of security between the hydraulically driven link press 1 and the mold.

Next, the features of the hydraulic circuit shown in FIG. 2 will be described. The pressurizing cylinder 15 moves forward and slide 10
Is lowered, the electromagnetic directional control valve 26A of the pilot check valve 26 is turned on, and when the slide 10 is pressurized, the electromagnetic directional control valve 23 is turned off to unload the hydraulic pump 21. Then, the pressurized side of the pressurized cylinder 15 is kept oil-tight by the pilot check valve 26, and can be pressurized and held. In resin molding and the like, the pressure holding time varies depending on the size and thickness of the product, but is generally 20 to 60 seconds.

During this time, since the hydraulic pump 21 is in the unloaded state, the longer the pressurization holding time is, the less power is consumed, and as a result, the pump noise and the oil temperature are also reduced. This pressure holding operation is applied to a hydraulically driven link press machine 1 using a toggle mechanism as compared to a general hydraulic press.
In the vicinity where the lever 7 is fully extended, that is, in the vicinity of the so-called bottom dead center, the output of the pressurizing cylinder 15 may be very small, so that the output loss due to oil leakage is extremely small.

In the case of molding that is desirably performed at a high speed, such as a thermoplastic resin, the pressure holding function of the hydraulically driven link press 1 and the speed of the slide 10 at a position higher than the bottom dead center can be effectively controlled. By using it, flexible molding according to the product is enabled. Hereinafter, the relationship between the pressing force and the slide speed will be described. The pressure is the discharge pressure of the hydraulic pump 21, and the slide speed is the maximum speed that can be obtained at the die height position.

FIG. 3 is a characteristic diagram showing the relationship between the pressing force (press output) and the die height position, and FIG. 4 is a characteristic diagram showing the relationship between the slide speed and the die height position. When pressurizing at a high speed, such as with a thermoplastic resin, the die height is set to a position higher than the capacity generating position, and the set pressure of the pressure switch 41 for detecting overload is set to the press nominal capacity pressure. When the required molding pressure of the molded article is set in the above state, the die height is set according to the pressure capability diagram, and the maximum sliding speed according to the die height is determined. When it is desired to reduce the molding speed, the proportional electromagnetic flow regulating valve 27 is controlled so as to achieve the molding speed.

[0025]

As described above, according to the present invention, a pressurized silicon
Link that is driven by the
A hydraulic chamber for a small stroke provided in a slide that moves up and down,
A movable pin disposed in the hydraulic chamber and connected to the link.
And an air communicating with the hydraulic chamber through a hydraulic circuit.
Hydraulic link press machine equipped with a cumulator
And a variable displacement hydraulic port for discharging pressure oil to the hydraulic chamber.
A pressure sensor for detecting a hydraulic pressure of the hydraulic chamber,
Pressure control for controlling the discharge pressure of the variable displacement hydraulic pump
A movable piston by driving the valve and the pressurizing cylinder
Is driven, the hydraulic pressure of the hydraulic chamber is set in advance.
Value based on the pressure detection signal from the pressure sensor.
And a control circuit for controlling the pressure control valve.
Hydraulic chamber that changes according to the stroke of the movable piston
Of the variable displacement hydraulic pump so that the oil pressure of
Since the discharge pressure can be controlled, press molding
To prevent product overload and prevent product quality degradation
In addition, prevent adverse effects on the press machine itself due to overload.
There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of an overload protector of a hydraulic drive link press machine.

FIG. 2 is a drive hydraulic circuit diagram of a pressurizing cylinder of the hydraulic drive link press machine.

FIG. 3 is a characteristic diagram of a hydraulic drive link press machine.

FIG. 4 is a characteristic diagram of a hydraulic drive link press machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic drive link press machine 7 Lever 9 Link 10 Slide 15 Pressure cylinder 30 Hydraulic chamber 31 Movable piston 33 Accumulator 36 Variable displacement hydraulic pump 41 Pressure switch 42 Relief valve 43 Pressure sensor 44 Pressure controller 45 Electromagnetic proportional Pressure control valve 46 Solenoid directional switching valve

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-57-4343 (JP, A) JP-A-61-259900 (JP, A) JP-A-62-61800 (JP, A) 116300 (JP, U) Fully open Showa 24-24500 (JP, U) Really open Showa 47-13776 (JP, U)

Claims (2)

(57) [Claims] A link driven by a pressure cylinder
And a slide that moves up and down in conjunction with the link
A small-stroke hydraulic chamber and the hydraulic chamber
A movable piston connected to a link, the hydraulic chamber and hydraulic pressure
Hydraulic pressure provided with an accumulator communicated through a circuit
In the drive link press machine, the hydraulic chamber
And a variable displacement hydraulic pump for discharging hydraulic pressure in the hydraulic chamber
Pressure sensor for detecting pressure and discharge of the variable displacement hydraulic pump.
A pressure control valve for controlling the output pressure;
When the movable piston is driven by movement,
Pressure sensor so that the oil pressure of the
Control the pressure control valve based on a pressure detection signal from the
And a control circuit for controlling the hydraulic pressure.
Overload protector for cup press machine. 2. A pressure switch for stopping the driving of the pressurizing cylinder when the pressure in the hydraulic chamber reaches the maximum working pressure;
2. An overload protector for a hydraulically driven link press according to claim 1, further comprising a relief valve for reducing the pressure of the hydraulic chamber to a predetermined pressure.