JP4473990B2 - Press brake - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ram moving method in a press brake that performs bending by relatively moving an upper table or a lower table up and down, and a press brake using the ram moving method.
[0002]
[Prior art]
As shown in FIG. 4, in the hydraulic cylinder 103 that moves up and down, for example, the upper table 101 </ b> U as a ram in a conventional press brake, the upper cylinder chamber 105 </ b> U of the hydraulic cylinder 103 is connected by a pipe 107, and the lower cylinder chamber 105 </ b> L is The pipe 109 is connected to the switching valve 111.
[0003]
The switching valve 111 is connected to the oil tank 115 via a pipe 113 and to the oil tank 115 via a hydraulic pump 119 via a pipe 117. The hydraulic pump 119 is driven by an AC servo motor 121, for example.
[0004]
With the above configuration, when the piston 123 is raised, the hydraulic pump 119 is rotated by the AC servo motor 121 and the switching valve 111 is moved leftward from the state shown in FIG. Thus, the hydraulic oil is discharged from the oil tank 115 by the hydraulic pump 119 and supplied to the lower cylinder chamber 105L, and the hydraulic oil in the upper cylinder chamber 105U is returned to the oil tank 115 through the switching valve 111.
[0005]
On the other hand, when lowering the piston 123, the hydraulic pump 119 is rotated by the AC servo motor 121, and the switching valve 111 is moved rightward from the state shown in FIG. As a result, the flow of the hydraulic oil is reversed, so that the hydraulic oil discharged from the oil tank 115 is supplied to the upper cylinder chamber 105U, and the hydraulic oil in the lower cylinder chamber 105L passes through the switching valve 111 and the oil tank 115. Returned to
[0006]
[Problems to be solved by the invention]
However, in such a conventional technique, the hydraulic oil in the upper cylinder chamber 105U and the hydraulic oil in the lower cylinder chamber 105L are discharged to the oil tank 115 through the switching valve 111, and thus are discharged at a high pressure. At that time, a strong fluid force acts on the switching valve 111. For this reason, an actuator with a large capacity is required to move the switching valve 111, which causes a problem of increasing the cost and increasing the size of the switching valve 111.
[0007]
Further, when the hydraulic oil is discharged at a high pressure, the switching valve 111 may vibrate due to a strong external force, and vibration may occur in the upper table 101U that is a ram. Further, as shown in FIG. 5, since the “opening-flow rate” characteristic of the switching valve 111 differs between no load (low pressure) and high pressure, the ram operating gain changes to cause vibration. May occur. For this reason, since the ram speed at the time of depressurization is reduced to reduce the occurrence of vibration, there is a problem that productivity is deteriorated.
[0008]
The object of the present invention has been made by paying attention to the problems of the prior art as described above, and reduces the shock at the time of depressurization to prevent vibration, and increases the ram speed to improve the productivity. An object of the present invention is to provide a press brake that can handle the above.
[0011]
[ Means for Solving the Problems ]
The present invention has been made in view of the above-described problems. In a press brake having a plurality of hydraulic cylinders for moving the ram up and down, the press brake is provided corresponding to each of the plurality of hydraulic cylinders. A bidirectional fluid pump connected to the cylinder chamber and the lower cylinder chamber; a servomotor that drives each bidirectional fluid pump to supply hydraulic oil to the upper cylinder chamber or the lower cylinder chamber; and a vertical position of the ram. A position detector for detecting, and a control device for controlling the servo motor, wherein the control device determines whether or not the bending process is completed based on a signal from the position detector; When the determination unit determines that the bending process has been completed, the servo motor is instructed to reverse the servo motor to reverse the bidirectional fluid pump. It is provided with a command unit giving the bidirectional piping that connects the on cylinder chamber with the fluid pump, between the pipe that connects the lower cylinder chamber and the bidirectional fluid pump, a high pressure priority A type shuttle valve is provided, and a relief valve is connected to the discharge side of the high-pressure priority type shuttle valve .
[0012]
Therefore, a bidirectional fluid pump provided corresponding to each hydraulic cylinder is operated by a servo motor, and hydraulic oil is supplied to one cylinder chamber of each hydraulic cylinder in the upper cylinder chamber or the lower cylinder chamber, so that the ram is supplied. Bend by moving up and down. Then, the vertical position of the ram is detected by the position detector, and from the detected ram position, the determination unit determines whether or not the bending process is completed. Gives a reverse rotation command to the servo motor, reverses the servo motor to reverse the bidirectional fluid pump, supplies the hydraulic oil in the one cylinder chamber to the other cylinder chamber, and moves the ram up and down.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0014]
2 and 3 show the entire press brake 1 according to the present invention. The press brake 1 has side plates 3L and 3R which are erected on the left and right sides, and has an upper table 5U as a ram that can be moved up and down on the upper front end surface of the side plates 3L and 3R, and a lower portion of the side plates 3L and 3R. A lower table 5L is provided on the front surface.
[0015]
A punch P is replaceably provided at the lower end of the upper table 5U via an intermediate plate 7. A die D is provided on the die base 9 so as to be replaceable at the upper end of the lower table 5L.
[0016]
Note that an example linear scale 11 as a position detector for measuring the height position of the upper table 5U is provided. The distance from the die D is obtained from the height of the punch P, and the bending process is completed. Whether or not, detection of the bending angle, ensuring safety, etc. are performed.
[0017]
Hydraulic cylinders 13L and 13R are respectively provided on the upper front surfaces of the left and right side plates 3L and 3R. The above-described upper table 5U is attached to the piston rods 17L and 17R attached to the pistons 15L and 15R of the hydraulic cylinders 13L and 13R. Is attached.
[0018]
Next, a hydraulic circuit for the hydraulic cylinders 13L and 13R will be described with reference to FIG. Since the left and right hydraulic cylinders 13L and 13R are provided with exactly the same hydraulic circuit, only the right hydraulic cylinder 13R and the hydraulic circuit will be described below.
[0019]
The upper cylinder chamber 19U of the hydraulic cylinder 13R that moves the upper table 5U as a ram up and down is connected to the prefill valve 23 by a pipe 21 and further connected to an oil tank 27 by a pipe 25.
[0020]
The upper cylinder chamber 19U is connected to one side of a bidirectional piston pump 31 as a bidirectional fluid pump that can rotate bidirectionally by a pipe 29. A pipe 33 is connected to the pipe 29 on the way, and is connected to the oil tank 27 via a check valve 35 and a suction filter 37. The bidirectional piston pump 31 is rotationally driven by an AC servo motor 39 as a servo motor.
[0021]
On the other hand, a pipe 41 is connected to the lower cylinder chamber 19L of the hydraulic cylinder 13R, and a counter balance valve 43 and a sequence switching valve 45 that is an electromagnetic poppet valve are provided in parallel. The counter balance valve 43 and the sequence switching valve 45 are connected to the other side of the bidirectional piston pump 31 by a pipe 47. In addition, a pipe 49 is connected to the pipe 47 on the way, and this pipe 49 is connected to the oil tank 27 via a check valve 51 and a suction filter 53.
[0022]
In addition, a throttle valve 55 and a high-pressure priority type shuttle valve 57 are provided between the pipe 41 and the pipe 29. A piping 59 is connected to the discharge side of the high-pressure priority type shuttle valve 57, and a piping 63 connected to the relief valve 61 and the oil tank 27 is provided in the piping 59.
[0023]
An AC servo motor 39 that rotationally drives the bidirectional piston pump 31 is controlled by a control device 65. The control device 65 receives the position signal 67 of the upper table 5U sent from the linear scale 11 and determines whether or not the bending process is completed. And a command unit 73 that issues a forward or reverse command signal 71 to the AC servo motor 39.
[0024]
With the above configuration, the upper cylinder chamber 19U and the lower cylinder chamber 19L are filled with hydraulic oil, the bidirectional piston pump 31 is stopped, and the piston 15R is at the top dead center. When the table 5U is rapidly lowered, the sequence switching valve 45 is switched to connect the piping 41 and the piping 47, and the bidirectional piston pump 31 is rotated by the AC servo motor 39.
[0025]
In the case of further lowering and bending, the sequence switching valve 45 is set to the state shown in FIG. 1 and the hydraulic oil from the lower cylinder chamber 19L passes through the pipe 41, the counter balance valve 43 and the pipe 47 in both directions. It returns to the piston pump 31 and is further supplied from the pipe 29 to the upper cylinder chamber 19U of the hydraulic cylinder 13R. As a result, the piston 15R descends and the upper table 5U descends, and bending is performed.
[0026]
Since the cross-sectional area on the lower surface side of the piston 15R is smaller than that on the upper surface side, the hydraulic oil returning from the lower cylinder chamber 19L to the bidirectional piston pump 31 compared to the amount of hydraulic oil injected into the upper cylinder chamber 19U. Therefore, hydraulic oil is replenished from the oil tank 27 via the check valve 51.
[0027]
On the other hand, when the determination unit 69 of the control device 65 determines that the bending process is finished based on the position signal 67 of the upper table 5U from the linear scale 11, the switching valve 45 is set in FIG. And the AC servo motor 39 is reversely rotated in the opposite direction to that described above by the reverse command from the command unit 73 to reverse the bidirectional piston pump 31 and the piston 15R is lowered. The hydraulic oil from the upper cylinder chamber 19U is supplied to the lower cylinder chamber 19L through the pipe 29, the bidirectional piston pump 31, the pipe 47, the switching valve 45, the pipe 41, and the like. As a result, the piston 15R rises and the upper table 5U rises.
[0028]
When the pressure of the hydraulic oil injected into the lower cylinder chamber 19L becomes higher than a predetermined value, the prefill valve 23 is opened by the pilot signal 75, and is sent from the upper cylinder chamber 19U to the oil tank 27 through the prefill valve 23.
[0029]
From the above results, the vertical movement of the piston 15R of the hydraulic cylinder 13R is switched by reversing the rotation of the bidirectional piston pump 31 under the control of the AC servo motor 39 having a strong driving force. It is possible to reduce the shock at the time of depressurization that occurs at the time of depressurization, and to increase the ram speed at the time of depressurization. Thereby, productivity can be improved.
[0030]
Further, since there is no switching valve for switching the vertical movement of the piston 15R, it is possible to prevent the occurrence of vibration due to the switching valve as in the prior art. Further, since the flow characteristic is not influenced by the pressure, the ram operating gain does not change so much, and vibration due to the change of the flow characteristic with respect to the pressure can be prevented.
[0031]
The present invention is not limited to the embodiment of the invention described above, and can be implemented in other modes by making appropriate modifications. That is, in the above-described embodiment, the press brake 1 that moves the upper table 5U up and down has been described, but the same applies to the press brake that moves the lower table 5L up and down.
[0032]
【The invention's effect】
As described above, the present invention contact the press brake according to information, the bidirectional fluid pump is provided in correspondence to the hydraulic cylinder is operated by a servo motor, a hydraulic fluid or on the cylinder chambers of the hydraulic cylinders perform bending by vertically moving the ram is supplied to one cylinder chamber of the lower cylinder chamber, a ram for vertical position at this time is detected by the position detector, the determination of the control device from the detected ram position parts are bent, it is judged whether the finished, if it is determined that the bending is finished, by inverting the two-way fluid pump command unit is made to reverse the servo motor provides an instruction for reverse rotation to the servo motor Since the vertical movement of the ram is switched by supplying the hydraulic oil of the one cylinder chamber to the other cylinder chamber, there is no need to use a conventional switching valve. Thereby, the shock at the time of depressurization can be reduced, and the ram speed at the time of depressurization can be increased, so that the productivity can be improved. Further, since there is no switching valve, it is possible to prevent the occurrence of vibration due to the switching valve as in the prior art. Further, since the flow characteristic is not influenced by the pressure, the ram operating gain does not change so much, and vibration due to the change of the flow characteristic with respect to the pressure can be prevented.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a hydraulic circuit of a press brake according to the present invention.
FIG. 2 is a front view of a press brake according to the present invention.
FIG. 3 is a side view seen from the direction III in FIG. 2;
FIG. 4 is a circuit diagram showing a hydraulic circuit of a conventional press brake.
FIG. 5 is a graph showing the characteristics of flow rate and opening with respect to the pressure of the switching valve.
[Explanation of symbols]
1 Press brake 5U Upper table (ram)
11 Linear scale (position detector)
13L, 13R Hydraulic cylinder 19U Upper cylinder chamber 19L Lower cylinder chamber 31 Bidirectional piston pump (bidirectional fluid pump)
33 AC servo motor (servo motor)
65 Control device 69 Judgment unit 73 Command unit

Claims (1)

In more with the press brake and the hydraulic cylinder for vertically moving the ram, the plurality of hydraulic cylinders each provided in correspondence, and connected bidirectional fluid pump to the cylinder chamber and the lower cylinder chamber on top of the hydraulic cylinder A servo motor that drives each bidirectional fluid pump to supply hydraulic oil to the upper cylinder chamber or the lower cylinder chamber, a position detector that detects the vertical position of the ram, and a control device that controls the servo motor And a determination unit that determines whether or not the bending process is completed based on a signal from the position detector, and the determination unit determines that the bending process is completed. a command unit which gives an instruction to the servo motor to allowed to reverse the servo motor bidirectional fluid pump to reverse, Ri Na and wherein the bidirectional fluid A high-pressure priority type shuttle valve is provided between a pipe connecting the pump and the upper cylinder chamber and a pipe connecting the bidirectional fluid pump and the lower cylinder chamber, and the discharge side of the high-pressure priority type shuttle valve In addition, a press brake comprising a relief valve connected thereto.

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