JP6119532B2 - Hydraulic device and press machine provided with the same - Google Patents

Description

  The present invention relates to a hydraulic device and a press machine including the same.

  Conventionally, in a press machine, a hydraulic device using a servo valve is used to obtain a molded product with high dimensional accuracy.

  Examples of this type of hydraulic device include those described in Japanese Patent Application Laid-Open No. 2011-11521 (Patent Document 1), Japanese Patent Application Laid-Open No. 2010-208124 (Patent Document 2), and the like. This hydraulic apparatus includes a hydraulic pump, a hydraulic cylinder, and a servo valve, and the position of the hydraulic cylinder is controlled with high accuracy by the servo valve to obtain a molded product with high dimensional accuracy.

JP 2011-11521 A JP 2010-208124 A

  However, since the conventional hydraulic device uses a servo valve, there is a problem that the cost is inevitably increased.

  On the other hand, in a press machine that performs powder molding or the like, a hydraulic device that does not use a servo valve or a servo motor is also used to reduce the cost. In this press machine, after the hydraulic cylinder that drives the upper die of the upper die and the lower die reaches the target position, the pressure of the oil is controlled by the pressure control with priority to the density of the powder in the pressure holding process. Is controlled to a predetermined constant pressure to press the powder at a constant pressure. As described above, conventionally, the pressure at the time of holding pressure is controlled to a constant pressure that is determined in advance with density priority.

  However, recently, the demand for dimensional accuracy of molded products has become stricter, and for example, dimensional accuracy of the order of 20 μm has been required. However, an inexpensive conventional hydraulic device that does not use a servo valve or a servo motor cannot satisfy this requirement.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a hydraulic apparatus capable of obtaining extremely high positional accuracy of an actuator and a press machine capable of obtaining a molded product having extremely high dimensional accuracy with a simple and inexpensive configuration.

In order to solve the above problems, the hydraulic device of the present invention is:
A hydraulic pump;
A motor for driving the hydraulic pump;
An actuator to which oil is supplied from the hydraulic pump;
A position sensor for detecting the position of the actuator;
A pressure sensor for detecting the pressure of the oil;
And a controller for controlling the pressure of the oil using the detected pressure of the pressure sensor when the actuator reaches a target position as a target pressure in response to the output of the position sensor.

  According to the hydraulic apparatus having the above configuration, the controller receives the output of the position sensor, and the pressure of oil supplied to the actuator using the detected pressure of the pressure sensor when the actuator reaches the target position as the target pressure. To control.

  When this hydraulic device is used in, for example, a pressing machine that targets an elastic molding material that generates a reaction force such as powder, the controller detects a pressure detected by the pressure sensor when the actuator reaches a target position. Since the pressure of the oil supplied to the actuator is controlled using as a target pressure, for example, it is possible to obtain a molded product that satisfies the requirement of dimensional accuracy of the order of 20 μm.

  Further, this hydraulic device does not use a servo valve or a servo motor, so that the structure is simple and inexpensive.

In one embodiment,
The controller controls the oil pressure by controlling the rotational speed of the hydraulic pump.

  In the embodiment, the controller controls the rotation speed of the hydraulic pump to control the pressure of the oil. Therefore, the controller has a surplus as compared with a hydraulic device using a servo valve and a fixed displacement hydraulic pump having a constant speed. Since the amount of oil is small, energy saving is excellent.

  In addition, this embodiment is superior in maintainability because it does not use an accumulator with poor maintainability compared to a hydraulic device using a servo valve, a variable displacement hydraulic pump, and an accumulator.

One embodiment is:
With pressure control valve,
The controller controls the pressure of the oil by controlling the pressure control valve.

  In the above embodiment, the controller controls the pressure control valve to control the pressure of the oil, thereby simplifying the pressure control.

In one embodiment,
The actuator is a single rod hydraulic cylinder.

  In this embodiment, the actuator is a single rod hydraulic cylinder that is cheaper and easier to obtain than the double rod hydraulic cylinder, and therefore can be manufactured inexpensively and easily.

  In a hydraulic device using a servo valve and a servo motor, a double rod hydraulic cylinder is generally used in order to make the oil amount relative to the unit movement amount on the going side and the returning side of the hydraulic cylinder, but in the present invention, the servo valve, Since a servo motor is not used, a single rod hydraulic cylinder that is inexpensive and easily available can be used.

In one embodiment,
The controller performs proportional integral derivative control (PID control), receives the output of the position sensor, and clears the integral term when the actuator reaches a target position.

  In the above embodiment, the controller performs PID control, receives the output of the position sensor, and clears the integral term when the actuator reaches the target position, thereby suppressing the occurrence of pressure overshoot. Can do.

In one embodiment,
The controller uses the detected pressure of the pressure sensor when the actuator reaches the target position as the target pressure during holding.

  According to the above embodiment, the pressure detected by the pressure sensor when the actuator reaches the target position is set as the target pressure at the time of holding pressure, so that the pressure at the time of holding pressure is appropriately controlled with a simple and inexpensive configuration. can do.

The press machine of this invention is
A hydraulic device as described above;
A mold driven by the actuator,
The main machine controller is characterized in that a detected pressure of the pressure sensor when the actuator reaches a target position is set as a target pressure at the time of holding pressure.

  The press machine of the present invention includes the hydraulic device, and the main machine controller uses the detected pressure of the pressure sensor when the actuator reaches the target position as the target pressure at the time of holding pressure. Thus, a molded product with extremely high dimensional accuracy can be produced.

  According to the hydraulic device of the present invention, extremely high positional accuracy of the actuator can be obtained with a simple and inexpensive configuration.

  Further, according to the press machine of the present invention, a molded product with extremely high dimensional accuracy can be made with a simple and inexpensive configuration.

1 is a schematic block diagram of a press machine according to an embodiment of the present invention. It is a flowchart of the principal part of the controller of the said embodiment. It is a graph which shows operation | movement of the press of the said embodiment. It is a graph which shows the pressure-flow rate characteristic of the hydraulic device of the press machine of the said embodiment.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

  As shown in FIG. 1, the press according to this embodiment includes a mold 10 including an upper mold 11 and a lower mold 12, and a single rod hydraulic cylinder 20 as an example of an actuator that drives the upper mold 11. The powder 13 between the upper mold 11 and the lower mold 12 is pressed by the single rod hydraulic cylinder 20 through the upper mold 11 to perform powder molding.

  The position of the rod of the single rod hydraulic cylinder 20 is detected by a position sensor 21. The head side port 23 and the rod side port 24 of the single rod hydraulic cylinder 20 are connected to load ports 31 and 32 of the proportional flow direction control valve 30. A counter balance valve 35 and a check valve 36 are connected between the rod side port 24 of the single rod hydraulic cylinder 20 and the load port 32 of the proportional flow direction control valve 30. The counter balance valve 35 and the check valve 36 are connected in parallel, and the check valve 36 has a forward flow from the load port 32 of the proportional flow direction control valve 30 to the rod side port 24 of the single rod hydraulic cylinder 20. It has become.

  A fixed displacement hydraulic pump 40 is connected to the pump port 33 of the proportional flow direction control valve 30, and a safety valve is provided between the fixed displacement hydraulic pump 40 and the pump port 33 of the proportional flow direction control valve 30. A functioning relief valve 41 and a pressure sensor 42 are connected.

  The oil discharge amount is controlled by driving the hydraulic pump 40 with a motor 50 and controlling the rotation speed (number of rotations / hour) of the motor 50. The motor 50 is provided with an encoder 51, and the rotational position or rotational speed of the motor 50 can be detected by the output of the encoder 51.

  The controller 60 receives the pressure command and flow rate command from the main machine controller 70, the output of the position sensor 21, the output of the pressure sensor 42, and the output of the encoder 51.

  In the controller 60, a flow rate deviation between the flow rate command from the main controller 70 and the feedback signal from the encoder 51 is obtained at the addition point 61, and this flow rate deviation is input to the control calculation unit 62.

  In the controller 60, the pressure command from the main machine controller 70 is input to the addition point 65 via the switch 63, and the detected pressure from the pressure sensor 42 is also input to the addition point 65. A pressure deviation between the pressure command and the detected pressure is obtained at point 65 and input to the control calculation unit 62.

  Further, the control calculation unit 62 of the controller 60 performs PID control based on the flow rate deviation and the pressure deviation, outputs the rotation speed output to the motor 50, and the state of the hydraulic circuit including the actuator from the hydraulic pump 40 It controls to discharge the oil according to.

  When the switch 63 receives a signal from the position sensor 21 indicating that the one-rod hydraulic cylinder 20 has reached the target position, the switch 63 switches from the terminal on the pressure command side to the terminal on the detection pressure side of the pressure sensor 42, and adds The detected pressure is input to both the positive and negative terminals of the point 65. A signal indicating that the pressure deviation is zero is input to the control calculation unit 62 from the addition point 65, and the control calculation unit 62 detects the pressure detected by the pressure sensor 42 when the target position is reached. PID control is performed with the target pressure as the target pressure, and a rotational speed output for controlling the oil pressure is output to the motor 50. At this time, the control calculation unit 62 receives the output of the position sensor 21 and clears the integral term of the PID control when the one-rod hydraulic cylinder 20 reaches the target position so as to suppress overshoot. Yes.

  Although the controller 60 is shown in a schematic block diagram in FIG. 1, it may be an analog circuit or a digital circuit.

  The controller 60 can be constituted by, for example, a DSP (digital signal processor). In this case, as shown in FIG. 2, the configuration of the pressure control at the time of holding pressure of the DSP captures the output of the position sensor 21 in step S1, and the one-rod hydraulic cylinder 20 reaches the target position in step S2. It is determined whether or not. If not, the determination in step S2 is repeated. If yes, the process proceeds to step S3, and the pressure detected by the pressure sensor 42 is taken in. In step S4, the detected pressure of the pressure sensor 42 is set as the target pressure, the integral term of PID control is cleared, and the rotation speed of the motor 50 is controlled.

  The press machine having the above-described configuration operates as follows.

  In FIG. 1, it is now assumed that the single rod hydraulic cylinder 20 is at the top dead center and the powder 13 is filled between the lower mold 12 and the upper mold 11.

  In this state, the controller 60 first places the proportional flow direction control valve 30 in the right switching position, and then, based on the flow command from the main controller 70 and the feedback signal from the encoder 51, As shown in FIGS. 3A and 3B, the rotational speed is PID-controlled, and the one-rod hydraulic cylinder 20 is first lowered at a high speed, then at a low speed, and further at a speed slower than this low speed. Then, the rotational speed of the motor 50 is controlled so as to cause the speed to gradually decrease so that the discharge amount of the hydraulic pump 40 is controlled. At this time, the detected pressure (load pressure) detected by the pressure sensor 42 changes as shown in FIG.

  At this time, the single rod hydraulic cylinder 20 is subjected to speed control with high accuracy because a constant back pressure is applied by the counterbalance valve 35.

  Then, when the controller 60 determines that the one-rod hydraulic cylinder 20 has reached the target position in the state where the one-rod hydraulic cylinder 20 is descending at the above-mentioned slow speed, based on the output from the position sensor 21, the controller 60 is instantly The rotational speed is controlled so that the motor 50 and the hydraulic pump 40 are stopped, the rod of the single rod hydraulic cylinder 20 is stopped, and the detected pressure of the pressure sensor 42 at the moment when the target position is reached, The motor 50 is controlled so as to control the holding pressure as the target pressure. At this time, the controller 60 sets the detected pressure of the pressure sensor 42 as the target pressure, clears the integral term of the PID control in the control calculation unit 62, and controls the rotation speed of the motor 51. As shown in FIG. Pressure control overshoot can be suppressed.

  After that, the pressure control of the holding pressure is continued for a predetermined period of time using the detected pressure of the pressure sensor 42 at the moment of reaching the target position as the target pressure. Then, the single rod hydraulic cylinder 20 balances the reaction force from the powder 13 and maintains the target position.

  Thereafter, as shown in FIGS. 3A and 3C, after performing pressure relief, in FIG. 1, the proportional flow direction control valve 30 is switched to the left position, and as shown in FIG. The rod hydraulic cylinder 20 is raised at high speed. At this time, the oil passes through the check valve 36 and is supplied to the rod side port 24 of the single rod hydraulic cylinder 20 at a high speed.

  Thereafter, the molded product of the powder 13 is taken out from the mold 10 with an ejector (not shown).

  In the press machine of the above embodiment, the controller 60 uses the detected pressure of the pressure sensor 42 when the rod of the single rod hydraulic cylinder 20 reaches the target position as the target pressure, Since control is performed via the rotational speed, a molded product with high dimensional accuracy of, for example, the order of 20 μm can be obtained from an elastic molding material that generates a reaction force such as the powder 13.

  Further, the hydraulic device and the press of this embodiment do not use a servo valve, a servo motor, or an accumulator, so that the structure is simple and inexpensive.

  In the hydraulic apparatus of this embodiment, the controller 60 controls the rotational speed of the motor 50 and the rotational speed of the fixed displacement hydraulic pump 40 to control the oil pressure. Compared to a hydraulic device using a fixed displacement hydraulic pump, the amount of surplus oil is small, so energy saving is excellent.

  Moreover, since the hydraulic apparatus of this embodiment does not use an accumulator with poor maintainability, it is excellent in maintainability.

  Further, the hydraulic device and the press of this embodiment use a single-rod hydraulic cylinder that is cheaper and easily available as an actuator than the double-rod hydraulic cylinder, and therefore can be manufactured inexpensively and easily.

  In the hydraulic apparatus of this embodiment, the control calculation unit 62 of the controller 60 performs PID control, receives the output of the position sensor 21, and integrates when the rod of the single rod hydraulic cylinder 20 reaches the target position. Since the term is cleared, the occurrence of pressure overshoot can be suppressed.

  In the above embodiment, the controller 60 controls the rotation speed of the motor 50 to control the pressure, but instead of this, a pressure control valve is used, and the pressure sensor 42 when the actuator reaches the target position is used. The pressure control valve may be controlled by the controller using the detected pressure as the target pressure. As this pressure control valve, the relief valve shown in FIG. 1 may be used as a pressure control valve, or a pressure reducing valve may be used as a pressure control valve.

  In the above embodiment, a single rod hydraulic cylinder is used as the actuator, but a double rod hydraulic cylinder, a hydraulic motor, or the like may be used.

  In the above embodiment, the pressure sensor 42 is provided between the hydraulic pump 40 and the proportional flow direction control valve 30, but may be provided between the proportional flow direction control valve 30 and the single rod hydraulic cylinder 20.

  Moreover, in the said embodiment, although the proportional flow direction control valve 30 was used, you may use a mere direction control valve (switching valve). Further, the counter balance valve and the check valve may be removed.

  In the above embodiment, the one-rod hydraulic cylinder 20 is detected by the output of the position sensor 21 to reach the target position, and the single-rod hydraulic cylinder 20 is stopped. The controller 60 may start the stop operation of the single rod hydraulic cylinder 20 when it can be considered that the single rod hydraulic cylinder 20 has reached the target position within the error range.

  In the above embodiment, the controller 60 in the hydraulic apparatus performs control to set the detected pressure of the pressure sensor 42 when the one-rod hydraulic cylinder 20 reaches the target position as the target pressure at the time of holding pressure. Instead of 60, the main controller 70 that receives a pressure monitor signal from the pressure sensor 42 may be used.

  Moreover, although the press machine which shape | molds powder was described in the said embodiment, of course, the hydraulic device of this invention is applicable also to the press which shape | molds the granule, elastic body, etc. which produce reaction force.

  Furthermore, the hydraulic device according to the present invention can be applied not only to a press machine but also to a clamp device for clamping an elastic body or the like, an injection molding machine, or the like.

  It goes without saying that the constituent elements described in the above-described embodiments and modifications may be combined as appropriate, and may be selected, replaced, or deleted as appropriate.

10 Mold 20 Single rod hydraulic cylinder 21 Position sensor 40 Hydraulic pump 50 Motor 42 Pressure sensor 60 Controller 70 Main machine controller

Claims (7)

A hydraulic pump (40);
A motor (50) for driving the hydraulic pump (40);
An actuator (20) to which oil is supplied from the hydraulic pump (40);
A position sensor (21) for detecting the position of the actuator (20);
A pressure sensor (42) for detecting the pressure of the oil;
A controller (60) that receives the output of the position sensor (21) and controls the oil pressure using the detected pressure of the pressure sensor (42) when the actuator (20) reaches a target position as a target pressure; A hydraulic apparatus comprising: The hydraulic device according to claim 1,
The controller (60) controls the pressure of the oil by controlling the rotational speed of the hydraulic pump (40). The hydraulic device according to claim 1,
With pressure control valve,
The controller is configured to control the pressure of the oil by controlling the pressure control valve. The hydraulic apparatus according to any one of claims 1 to 3,
The actuator (20) is a single rod hydraulic cylinder (20). The hydraulic apparatus according to any one of claims 1 to 4,
The controller (60) performs proportional-integral-derivative control, receives the output of the position sensor (21), and clears the integral term when the actuator (20) reaches a target position. Hydraulic device. The hydraulic apparatus according to any one of claims 1 to 5,
The hydraulic device according to claim 1, wherein the controller (60) sets the detected pressure of the pressure sensor (42) when the actuator (20) reaches a target position as a target pressure during holding. A hydraulic device according to any one of claims 1 to 5;
A mold (10) driven by the actuator (20),
The press machine characterized in that the main machine controller (70) sets the detected pressure of the pressure sensor (42) when the actuator (20) reaches the target position as the target pressure at the time of holding pressure.

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