JP2015132335A - Hydraulic press and hydraulic driving system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform high accuracy pressure control with high energy utilization efficiency.SOLUTION: A hydraulic driving system includes: a hydraulic cylinder; a compression pump which supplies a hydraulic oil to the hydraulic cylinder; an inverter motor which drives the compression pump; a main duct line which connects the compression pump with the hydraulic cylinder; a drain duct line which is branched from a middle part of the main duct line and returns to an oil tank; a first flow regulating valve which is provided at a middle part of the drain duct line; a pressure sensor which detects an oil pressure of the main duct line; and a controller which performs feedback control of a rotation number of the inverter motor on the basis of a detection result of the pressure sensor so that the oil pressure of the main duct line corresponds with a set pressure.

Description

  The present invention relates to a hydraulic press device and a hydraulic drive system for the press device, and more particularly to a hydraulic press device that controls pressure by the number of rotations of a motor that drives a hydraulic pump and a hydraulic drive system for the press device.

  2. Description of the Related Art A hydraulic press device that drives a press panel by a hydraulic cylinder is used. In the conventional hydraulic press device described in Patent Document 1, the hydraulic pump is always operated at a rated pressure with a hydraulic pressure higher than the maximum hydraulic pressure required for driving the hydraulic cylinder, and a variable electromagnetic relief valve has a required size. Pressure reduction is adjusted to hydraulic pressure.

JP 2003-249010 A

  In the above-described press apparatus, a considerable amount of hydraulic oil supplied from the hydraulic pump is discharged from the variable electromagnetic relief valve without being used for driving the hydraulic cylinder, and thus the energy utilization efficiency is extremely low.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a hydraulic press device and a hydraulic system for the press device that have high energy use efficiency.

According to one embodiment of the present invention,
A hydraulic cylinder;
A pressurizing pump for supplying hydraulic oil to the hydraulic cylinder;
An inverter motor for driving the pressurizing pump;
A main line connecting the pressurizing pump and the hydraulic cylinder;
A drain line branching from the middle of the main line and returning to the oil tank;
A first flow rate adjusting valve provided in the middle of the drain line;
A pressure sensor for detecting the hydraulic pressure of the main pipeline;
Based on the detection result of the pressure sensor, a controller that feedback-controls the rotation speed of the inverter motor so that the hydraulic pressure of the main pipeline matches a set pressure;
A hydraulic drive system is provided.

Also, according to one embodiment of the present invention,
A pair of press plates arranged opposite to each other;
The hydraulic drive system for driving the one of the pair of press panels forward and backward toward the other;
Is provided.

  According to the present invention, hydraulic control can be performed with high energy utilization efficiency.

FIG. 1 is a diagram showing a schematic configuration of a hydraulic press apparatus according to an embodiment of the present invention. FIG. 2 is a hydraulic circuit diagram showing a schematic configuration of the hydraulic drive system according to the embodiment of the present invention. FIG. 3 is a block diagram showing a schematic configuration of the electric control system of the hydraulic control apparatus according to the embodiment of the present invention. FIG. 4 is a table summarizing the setting of the switching valve and the operation of the pump in each operation mode of the hydraulic drive system.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of a press apparatus 1 according to an embodiment of the present invention. The press apparatus 1 is a hydraulic press apparatus equipped with a hydraulic drive system H according to an embodiment of the present invention described later. The press device 1 includes a press main body 2, a control unit 3, and a hydraulic control device 5. The hydraulic control device 5 is connected to the control unit 3 and operates under the control of the control unit 3.

  The press body 2 of the hydraulic press device 1 includes a frame 2a, an upper press board 2b, a lower press board 2c, and a hydraulic cylinder S.

  The hydraulic cylinder S is connected to the common main pipeline 10 of the hydraulic control device 5 and operates according to the supply and discharge of hydraulic oil by the hydraulic control device 5. The cylinder tube Sb of the hydraulic cylinder S is fixed to the frame 2a.

  The upper press panel 2b is fixed to the frame 2a with the lower surface horizontal. Moreover, the lower press board 2c is arrange | positioned so that the upper surface may oppose the lower surface of the upper press board 2b. The lower press panel 2c is fixed to the ram Sa of the hydraulic cylinder S on the lower surface thereof, and moves up and down together with the ram Sa according to supply and discharge of hydraulic oil to and from the hydraulic cylinder S. When the hydraulic cylinder S is driven to raise the lower press machine 2c fixed to the ram Sa, the workpieces placed on the upper surface (press surface) of the lower press machine 2c become the upper press machine 2b and the lower press machine. 2c and is pressurized.

  Next, the hydraulic drive system H according to the embodiment of the present invention will be described. FIG. 2 is a hydraulic circuit diagram showing a schematic configuration of the hydraulic drive system H. The hydraulic drive system H according to the present embodiment includes a hydraulic control device 5 and a hydraulic cylinder S. FIG. 3 is a block diagram showing a schematic configuration of the electric control system of the hydraulic control device 5.

  The hydraulic control device 5 of the present embodiment includes two hydraulic pumps. One is a moving pump P1 for moving the hydraulic cylinder S with a low load for a long distance, and the other is a pressurizing pump P2 for driving the hydraulic cylinder S with a high load. In a state where the upper press panel 2b and the lower press panel 2c are not in contact with each other, the hydraulic cylinder S is driven relatively fast mainly by the moving pump P1, and the upper press panel 2b and the lower press panel 2c are in contact with each other. The hydraulic cylinder S is driven with a hydraulic pressure controlled to a constant pressure by the pressurizing pump P2 so that a stable press pressure can be obtained.

  The moving pump P1 is driven by a motor M1. For the motor M1, for example, a general-purpose three-phase induction motor that is directly driven by a commercial power source (three-phase AC power source) is used. Therefore, the motor M1 operates at a constant rotational speed, and the discharge amount of the moving pump P1 becomes substantially constant. The motor M1 is connected to a driver D that supplies voltage-adjusted driving power. The driver D is connected to the controller C through a signal line, and the controller C performs drive control (ON / OFF control) of the motor M1.

  On the other hand, the pressurizing pump P2 is driven by an inverter motor M2 having a variable rotation speed. The hydraulic control device 5 includes an inverter I that generates variable AC power for driving the inverter motor M2. By controlling the rotational speed of the inverter motor M2 with the variable AC power generated by the inverter I, the discharge amount of the pressurizing pump P2 is controlled. The inverter I is connected to the controller C through a signal line, and the controller C performs drive control (rotational speed control) of the inverter motor M2. The drive control of the inverter motor M2 is performed by, for example, a variable voltage variable frequency control (VVVF) method.

  The discharge port of the movement pump P1 is connected to the hydraulic cylinder S through the movement main pipeline 11, the check valve 31, and the common main pipeline 10. The moving pump P1 pumps up the hydraulic oil stored in the tank 90 and supplies it to the hydraulic cylinder S. As described above, the movement pump P1 is driven by the motor M1 that operates at a constant rotational speed, and therefore supplies hydraulic oil to the hydraulic cylinder S with a substantially constant discharge amount. Accordingly, the hydraulic cylinder S operates at a substantially constant speed while being driven mainly by the movement pump P1.

  A drain line 19 that returns to the tank 90 is connected to the moving main line 11 via a relief valve 71 for preventing overpressure.

  A pressure sensor 20 that detects the hydraulic pressure applied to the hydraulic cylinder S is attached to the common main pipeline 10. The pressure sensor 20 is connected to the controller C via a signal line, and supplies a hydraulic pressure signal indicating the detected hydraulic pressure to the controller C. In the pressurizing mode described later, the controller feedback-controls the drive of the inverter motor M2 based on the hydraulic signal from the pressure sensor 20. Specifically, the rotational speed of the inverter motor M2 is controlled so that the deviation between the set value of the hydraulic pressure and the value measured by the pressure sensor 20 is eliminated.

  Further, a drain line 18 for returning the hydraulic oil in the hydraulic cylinder S to the tank 90 when the lower press panel 2c is lowered is connected to the common main line 10. A pilot check valve 35 for controlling the opening and closing of the drain line 18 is provided in the middle of the drain line 18.

  The discharge port of the pressurizing pump P2 is connected to the hydraulic cylinder S via the pressurizing main pipeline 12, the 4-port switching valve 41, the pressurizing main pipeline 13, the switching valve 51, and the common main pipeline 10. Check valves 32 and 33 are provided in the middle of the pressurizing main pipelines 12 and 13, respectively. The 4-port switching valve 41 and the switching valve 51 are connected to the controller C via signal lines, respectively, and the switching of the 4-port switching valve 41 and the switching valve 51 is controlled by the controller C.

  The pressurizing pump P <b> 2 pumps up the hydraulic oil stored in the tank 90 and supplies it to the hydraulic cylinder S. As described above, the discharge amount of the pressurizing pump P2 is controlled by controlling the rotation speed of the inverter motor M2. Therefore, while being driven by the pressurizing pump P2, the driving force (that is, the press pressure) of the hydraulic cylinder S can be controlled by controlling the rotation speed of the inverter motor M2.

  The 4-port switching valve 41 is an open center type 4-port electromagnetic switching valve to which all ports are connected in a neutral state. The P port of the 4-port switching valve 41 is connected to the pressurizing pump P2 via the pressurizing main line 12, and the A port is connected to the hydraulic cylinder S via the pressurizing main line 13, the switching valve 51, and the common main line 10. It is connected. The T port of the 4-port switching valve 41 is connected to the tank 90 via the drain line 14, and the B port is connected to the pilot port of the pilot check valve 35 via the pilot line 15. A branch pipe communicating with the drain line 14 is connected to the pressurizing main line 13 via a relief valve 72 for preventing overpressure. Further, a branch pipe connected to the drain pipe line 14 is connected to the pilot pipe line 15 through a relief valve 73 for preventing overpressure.

  A drain line 16 returning to the tank 90 is connected between the check valve 33 and the switching valve 51 of the pressurizing main line 13. A one-way throttle valve 61 for leak is provided in the middle of the drain line 16. The one-way throttle valve 61 is a variable throttle valve (flow rate adjusting valve) and a check valve connected in parallel, and performs flow rate control only in one direction (the direction from the pressurizing main pipe 13 to the tank 90). The one-way throttle valve 61 for leak is set such that when the pressurizing pump P2 is operated near the minimum number of cycles, an amount of hydraulic oil corresponding to the discharge amount of the pressurizing pump P2 flows. Prevent overpressure.

  The minimum cycle number of the pressurizing pump P2 is a lower limit value of the normal cycle number at which the pressurizing pump P2 can operate normally. If the pressurizing pump P2 is operated at a cycle number that is less than the minimum cycle number, the discharge pressure and the discharge amount become unstable and the pressure control accuracy of the hydraulic cylinder S decreases, and the pressurization pump P2 fails. Cause. Therefore, it is necessary to always operate the pressurizing pump P2 at a minimum cycle number or more.

  Further, in the middle of the drain line 16, a bypass line 17 that bypasses the one-way throttle valve 61 is connected. In the middle of the bypass pipe line 17, a variable throttle valve (flow rate adjusting valve) 62 for adjusting the pressure reduction speed and a switching valve 52 are provided in series. The switching valve 52 is also connected to the controller C via a signal line, and switching of the switching valve 52 is controlled by the controller C. The switching valve 52 is a valve that switches opening and closing of the bypass pipe line 17. When the switching valve 52 is set to “open”, the operation amount is leaked from the variable throttle valve 62 in addition to the one-way throttle valve 61, so that the leakage amount can be increased.

  The hydraulic pressure applied to the hydraulic cylinder S during pressurization is determined by the balance between the supply of hydraulic oil by the inverter motor M2 and the leakage of hydraulic oil from the one-way throttle valve 61 and the like. The hydraulic pressure increase speed is determined by the amount of hydraulic oil supplied from the inverter motor M2, and the hydraulic pressure decrease speed is determined by the hydraulic oil leakage amount from the one-way throttle valve 61 and the like. Therefore, the response time of hydraulic control can be shortened by increasing the amount of hydraulic oil supplied and the amount of leakage. In particular, when the press pressure (hydraulic pressure) is set to a high pressure, sufficient speed response may not be obtained only by the leak from the one-way throttle valve 61. In such a case, by opening the switching valve 52 and increasing the leak amount, it is possible to increase the speed response of the hydraulic control. In the present embodiment, the switching of the switching valve 52 can be performed automatically by a control program of the press device 1 or by a user operation.

  Further, the hydraulic control device 5 includes a limit switch 81 and a speed sensor 82 (FIG. 3) attached to the press body 2. The limit switch 81 and the speed sensor 82 are connected to the controller C. When the limit switch 81 detects that the lower press panel 2c is at the lower limit position, the limit switch 81 transmits a detection signal to the controller C. The speed sensor 82 detects the moving speed of the lower press panel 2c in the vertical direction, and transmits a speed signal indicating the detected speed to the controller C.

  Next, the operation of the hydraulic drive system H will be described. FIG. 4 is a table summarizing the settings of the 4-port switching valve 41 and the switching valve 51 and the operations of the moving pump P1 and the pressurizing pump P2 in each operation mode of the hydraulic drive system H. The operation mode of the hydraulic drive system H includes a pause mode in which the hydraulic cylinder S is not driven, a lift mode in which the hydraulic cylinder S is raised until the lower press board 2c comes into contact with the upper press board 2b, a lower press board 2c, and an upper press. There are five modes: a pressurization mode in which a predetermined press pressure is applied between the panels 2b, a depressurization mode in which the press pressure is removed, and a lowering mode in which the lower press panel 2c is lowered to the lower limit position.

  In the rest mode, the 4-port switching valve 41 is set to a neutral position where all ports are connected to each other, and the switching valve 51 is set to “open”. Further, the driving of the moving pump P1 and the pressurizing pump P2 is stopped. At this time, since each pipe line is connected to the drain pipe line 14 directly connected to the tank 90, almost no hydraulic pressure is applied to each pipe line. Therefore, the lower press panel 2c stops at the lower limit position. At this time, the switching valve 52 may be automatically switched to “closed” to reduce the leak amount.

  When the start of pressing is commanded, the operation mode is switched from the pause mode to the ascending mode. In the ascending mode, the 4-port switching valve 41 is switched to a straight connection in which the P port and the A port, and the T port and the B port are respectively connected. Further, the switching valve 51 is kept in the “open” state. Accordingly, the moving main pipeline 11 and the pressurizing main pipelines 12 and 13 are both connected to the common main pipeline 10. Then, the operation of the moving pump P1 and the pressurizing pump P2 is started. In the ascending mode, the rotational speed control (speed control) of the inverter motor M2 is performed so that the ascending speed of the lower press panel 2c detected by the speed sensor 82 matches the set speed. In addition, the set value of the rising speed of the lower press panel 2c can be set as a constant value or a fluctuation value (a function of time). In the present embodiment, the moving pump P1 supplies the same amount of hydraulic oil that should be supplied to the hydraulic cylinder S in order to raise the lower press panel 2c at the set speed, and the one-way throttle valve 61 and the variable throttle valve 62. The hydraulic oil leaking from the hydraulic pump is configured to be supplied from the pressurizing pump P2 in the same amount. Accordingly, the hydraulic cylinder S is driven by the hydraulic oil supplied from the movement pump P1, and the lower press panel 2c is raised at a relatively high speed. At this time, since the pilot line 15 is connected to the drain line 14, no pilot pressure acts on the pilot check valve 35, and the pilot check valve 35 remains closed.

  When the lower press board 2c eventually comes into contact with the upper press board 2b, the lower press board 2c (that is, the ram Sa of the hydraulic cylinder S) is prevented from rising. To rise. When the measured value of the pressure sensor 20 exceeds a predetermined value, the controller C determines that the lower press board 2c has contacted the upper press board 2b, and switches the operation mode from the ascending mode to the pressurizing mode. The contact (or proximity) between the lower press board 2c and the upper press board 2b may be detected using a proximity sensor or the like provided on the main body 2. In addition, it is good also as a structure which provides a pressure switch separately from the pressure sensor 20, and detects the contact with the lower press board 2c and the upper press board 2b with a pressure switch.

  In the pressurization mode, the controller C stops the movement pump P1 and starts the rotational speed control (pressure control) of the pressurization pump P2 (inverter motor M2). Specifically, the controller C feedback-controls the rotation speed of the inverter motor M2 so that the measured value of the pressure sensor 20 matches the set value of the hydraulic pressure. In the pressurization mode, since the drive amount of the hydraulic cylinder S is small, the inverter motor M2 is driven at a low rotational speed close to the minimum cycle number of the pressurization pump P2, and the hydraulic oil discharged from the pressurization pump P2 is discharged. Almost the entire amount is leaked from the one-way throttle valve 61 (and the variable throttle valve 62). The set value of the hydraulic pressure can be set as a constant value or a fluctuation value (a function of time). Further, the set value of the hydraulic pressure is set to a value equal to or higher than the minimum pressure necessary for maintaining the height of the lower press panel 2c.

  When the pressurization by the hydraulic cylinder S is completed, the controller C switches the operation mode from the pressurization mode to the pressure reduction mode. In the decompression mode, the rotational speed control of the inverter motor M2 is performed so that the hydraulic pressure decreases at the set speed. Further, when the decompression speed does not reach the set value in the decompression mode, the controller C switches the switching valve 52 to “open” to increase the leak amount and increase the decompression speed.

  When the measured value of the pressure sensor 20 falls below a predetermined value, the controller C determines that the lower press board 2c has moved away from the upper press board 2b, and switches the operation mode from the decompression mode to the lowering mode. In the descending mode, the controller C first releases the pressure control by the pressurizing pump P2, and drives the pressurizing pump P2 at a constant speed near the minimum number of cycles. Next, the controller C controls the switching valve 41 to switch to the cross connection in which the P port and the B port and the T port and the A port are respectively connected. As a result, the pilot line 15 is connected to the pressurizing main line 12, so that pilot pressure is applied to the pilot check valve 35 and the pilot check valve 35 is opened. As a result, the hydraulic oil in the hydraulic cylinder S is discharged to the tank 90 via the drain line 18, and the lower press panel 2 c is slowly lowered together with the ram Sa of the hydraulic cylinder S. When the pilot line 15 reaches a predetermined pressure, the relief valve 73 is opened, and the hydraulic oil supplied from the pressurizing pump P2 is returned to the tank 90 via the drain line 14.

  When the limit switch 81 detects that the lower press panel 2c is lowered to the lower limit position, the controller C switches the operation mode from the descent mode to the pause mode. Specifically, the controller C opens the switching valve 51 and switches the 4-port switching valve 41 to the neutral position (all ports “open”).

  According to the configuration of the embodiment of the present invention described above, a large amount of hydraulic oil pressurized from the variable electromagnetic relief valve for adjusting hydraulic pressure is not discharged, and the hydraulic cylinder S is controlled by the pressurizing pump P2. Since only the hydraulic pressure required for driving is supplied, it is possible to operate with much higher energy utilization efficiency than conventional hydraulic presses.

  In addition, the amount of hydraulic oil leaking from the valve is small compared to a device using a conventional variable electromagnetic relief valve, and heat generation due to fluid friction that occurs when the hydraulic oil passes through the valve can be suppressed. There is also an advantage that the rise in temperature is reduced and the life of the oil is extended.

  The above is the description of the embodiment of the present invention. However, the present invention is not limited to the configuration of the above-described embodiment, and various modifications are possible within the scope of the technical idea.

DESCRIPTION OF SYMBOLS 1 ... Press apparatus 2 ... Main body 3 ... Control part H ... Hydraulic drive system S ... Hydraulic cylinder 5 ... Hydraulic control apparatus 16 ... Drain line 17 ... Bypass line 61 ... One-way throttle valve 62 ... Flow control valve M2 ... Inverter motor P2 ... Pressure pump

Claims (5)

A hydraulic cylinder;
A pressurizing pump for supplying hydraulic oil to the hydraulic cylinder;
An inverter motor for driving the pressurizing pump;
A main line connecting the pressurizing pump and the hydraulic cylinder;
A drain line branching from the middle of the main line and returning to the oil tank;
A first flow rate adjusting valve provided in the middle of the drain line;
A pressure sensor for detecting the hydraulic pressure of the main pipeline;
Based on the detection result of the pressure sensor, a controller that feedback-controls the rotation speed of the inverter motor so that the hydraulic pressure of the main pipeline matches a set pressure;
With hydraulic drive system. When the pressurizing pump operates at a first discharge amount or more, the discharge pressure is stable,
The first flow rate adjusting valve leaks a part of the hydraulic oil supplied from the pressurizing pump so that the pressurizing pump can operate at the first discharge amount or more;
The hydraulic drive system according to claim 1. A bypass line having both ends connected to the drain line so as to bypass the first flow regulating valve;
A second flow rate adjustment valve provided in the middle of the bypass line;
A first switching valve provided in the middle of the bypass line in series with the second flow rate adjustment valve, for switching between opening and closing of the bypass line;
With
The second flow rate regulating valve leaks hydraulic oil at a larger flow rate than the first flow rate regulating valve so that the hydraulic pressure of the main line can be rapidly reduced;
The hydraulic drive system according to claim 2. A moving pump for supplying hydraulic oil to the hydraulic cylinder;
An electric motor for driving the moving pump at a constant speed;
A main line for movement connecting the pump for movement and the main line;
A check valve provided in the middle of the moving main pipeline;
A second switching valve that is provided in the middle of the pressurizing pump side with respect to the connection point of the main pipeline with the main pipeline for movement, and switches between opening and closing of the main pipeline;
With
The main pipeline is
A pressurizing main line connecting the pressurizing pump and the second switching valve;
A common main line connecting the second switching valve and the hydraulic cylinder,
The pressure sensor is connected to the common main line;
The drain line was connected to the pressurization main line,
The hydraulic drive system according to any one of claims 1 to 3, wherein the hydraulic drive system is provided. A pair of press plates arranged opposite to each other;
The hydraulic drive system according to any one of claims 1 to 4, wherein one of the pair of press panels is driven forward and backward toward the other.
Hydraulic press device equipped with.

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