JP2015001291A - Hydraulic pressure control method of press cylinder, and hydraulic pressure control device of press cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep holding pressure of a press cylinder while preventing over-shoot.SOLUTION: After pressure P2 in an extrusion side pressure chamber 3b reaches holding pressure, a secondary pressure detection sensor 10 detects that the pressure P2 in the extrusion side pressure chamber 3b reaches lower limit pressure lower than the holding pressure. Then, a hydraulic pump 5 is driven until pressure P1 of a primary pressure detection sensor 9 reaches lower limit pressure. Thereafter, the hydraulic pump 5 is driven until the hydraulic pressure P1 of the primary pressure detection sensor 9 reaches the holding pressure again.

Description

  The present invention relates to a press cylinder hydraulic control method and a press cylinder hydraulic control apparatus.

  Conventionally, there has been known a hydraulic control method for controlling a press cylinder so as to mold a rubber molded product or a sintered metal molded product by holding a molding material between an upper mold and a lower mold at a constant holding pressure for a predetermined time. It has been. For example, as in the constant pressure control circuit device of Patent Document 1, there is known one that keeps the pressure on the extrusion side of a hydraulic cylinder constant by using a check valve or the like.

Japanese Utility Model Publication No. 63-25803

  However, in the conventional press cylinder hydraulic control method, if the press cylinder is held while preventing the backflow by the action of the check valve, the pressure in the extrusion side pressure chamber gradually increases due to high-pressure oil leakage or the like. Will fall.

  Then, it is necessary to repressurize and return the pressure in the extrusion side pressure chamber to the holding pressure by pressure feedback control.

  In this case, due to the action of the check valve, there is no relationship between the discharge side pressure chamber and the discharge side pressure of the hydraulic pump, and when the discharge pressure is increased from that state to the holding pressure at once, Therefore, even if the hydraulic pump is suddenly stopped when the check valve opens and the extruding side pressure reaches the holding pressure, the pressure in the extruding side pressure chamber is higher than the holding pressure. The overshoot phenomenon of rising temporarily will occur.

  If it does so, there will be a problem that the quality deteriorates, for example, an excessive load is applied to the molded product and an error occurs in the dimension of the molded product after molding.

  The present invention has been made in view of such a point, and an object thereof is to keep the holding pressure of the press cylinder within a predetermined range while preventing overshoot.

  In order to achieve the above object, according to the present invention, the hydraulic pump is driven in two stages upon re-pressurization after the holding pressure is lowered.

Specifically, in the first invention, on the premise of a hydraulic control method of a press cylinder that holds the press cylinder with a holding pressure,
The above method
An initial pressurizing step of driving a hydraulic pump to bring the pressure chamber in the extrusion side of the press cylinder into the holding pressure;
A holding step of holding the extrusion-side pressure chamber by a check valve in a state where the holding pressure is the holding pressure;
After the holding step, it is detected that the pressure in the extrusion-side pressure chamber has become a lower limit pressure lower than the holding pressure, and the hydraulic pump is driven so that the discharge pressure of the hydraulic pump becomes the lower limit pressure. A first pressurizing step to
And a second pressurizing step of driving the hydraulic pump again so that the pressure in the extrusion side pressure chamber becomes the holding pressure when the discharge pressure from the hydraulic pump becomes the lower limit pressure.

  According to the above configuration, after the discharge pressure of the hydraulic pump is increased to the lower limit pressure in the first pressurization step, the pressure in the extrusion side pressure chamber is increased from the lower limit pressure to the holding pressure in the second pressurization step. Therefore, the overshoot, which is a sudden pressure increase due to the check valve opening and high pressure oil flowing in, does not show up and does not deteriorate the quality of the molded product. The lower limit pressure is determined from the material of the molded product, the size of the mold, and the like. The discharge pressure refers to the pressure in the piping on the discharge side of the hydraulic pump.

In the second invention, in the first invention,
The first pressurizing step and the second pressurizing step are repeated within a predetermined time.

  According to said structure, since the pressure in an extrusion side pressure chamber can be kept more than a minimum pressure, preventing an overshoot, a high quality molded product can be shape | molded efficiently.

Further, in the third invention, on the premise of a hydraulic control device of a press cylinder that holds the press cylinder with a holding pressure,
The hydraulic control device
A hydraulic pump that discharges high-pressure oil into the pressure-side chamber of the press cylinder;
An electric motor for driving the hydraulic pump;
An inverter for controlling rotation of the electric motor;
A primary pressure detection sensor for detecting the discharge pressure of the hydraulic pump;
A check valve disposed between the discharge side of the hydraulic pump and the extrusion side pressure chamber;
A secondary pressure detection sensor for detecting the pressure in the extrusion side pressure chamber;
A control unit that receives the signal from the secondary pressure detection sensor and controls the inverter;
The control unit
After maintaining the pressure in the extrusion side pressure chamber at the holding pressure, the secondary pressure detection sensor detects that the pressure in the extrusion side pressure chamber has become a lower limit pressure lower than the holding pressure, and The hydraulic pump is driven until the pressure of the primary pressure detection sensor reaches the lower limit pressure, and then the hydraulic pump is driven again until the pressure of the primary pressure detection sensor reaches the holding pressure again.

  According to the above configuration, since the discharge pressure of the hydraulic pump is increased to the lower limit pressure and then increased again from the lower limit pressure to the holding pressure, the overshoot is a sudden pressure increase when the check valve is opened. Does not show any dew and does not degrade the quality of the molded product.

  As described above, according to the present invention, it is detected that the pressure in the extrusion side pressure chamber has become the lower limit pressure lower than the holding pressure, and the hydraulic pump is driven so that the discharge pressure becomes the lower limit pressure. After that, since the hydraulic pump is driven so as to become the holding pressure again, a high-quality mold can be obtained while maintaining the holding pressure of the press cylinder while preventing overshoot.

It is a graph which shows the mode of the pressure change in the hydraulic control apparatus of the press cylinder which concerns on embodiment of this invention. It is a hydraulic circuit diagram of the hydraulic control apparatus of a press cylinder. It is a flowchart which shows operation | movement of a press. FIG. 2 is a view corresponding to FIG. 1 according to a comparative example.

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

  FIG. 2 is a hydraulic circuit diagram of the hydraulic control device for the press cylinder 3 according to the embodiment of the present invention. Although not shown in detail, for example, the press cylinder 3 is used in a rubber seal molding apparatus. A rubber material before heating is inserted between the upper mold 1 and the lower mold 2, and the rubber material is inserted into the press cylinder 3. It is configured to be sandwiched between the pushed up lower die 2 and the upper die 1 and molded by applying a certain pressure while heating. On the rubber seal molding device side, the lower die 2 is connected to the tip of the cylinder rod 3a of the press cylinder 3.

  The hydraulic control device for the press cylinder 3 according to the embodiment of the present invention includes a power unit 4 in which a series of parts are combined into one. The power unit 4 includes a hydraulic pump 5 that discharges high-pressure oil into the extrusion-side pressure chamber 3 b of the press cylinder 3. Although this hydraulic pump 5 is not specifically limited, For example, it consists of an internal gear pump. The electric motor 6 that drives the hydraulic pump 5 is not particularly limited, and is composed of, for example, a three-phase induction motor, and is integrally coupled to the hydraulic pump 5. For this reason, there is no need for a coupling or the like, resulting in a compact configuration.

  The rotation of the electric motor 6 is controlled by an inverter 7 provided outside the power unit 4. Similarly, the inverter 7 can be controlled by a control unit 8 provided outside the power unit 4 and provided with a sequencer or the like. The structure of the control part 8 is not specifically limited, The controller which controls the whole rubber seal molding apparatus may be sufficient.

  The power unit 4 is provided with a primary pressure detection sensor 9 that detects the discharge pressure P1 of the hydraulic pump 5. By feeding back the value P1 of the primary pressure detection sensor 9 to the control unit 8, the rotational speed or torque of the electric motor 6 can be controlled to control the discharge pressure P1 of the hydraulic pump 5.

  On the other hand, a secondary pressure detection sensor 10 is provided in the hydraulic piping reaching the extrusion side pressure chamber 3 b of the press cylinder 3. Maintaining the value P2 of the secondary pressure detection sensor 10 accurately is important in maintaining the finished quality of the product to be pressurized.

  For example, a 4-port 2-position switching valve 11 is arranged between the discharge side of the hydraulic pump 5 in the power unit 4 and the extrusion-side pressure chamber 3b. The 4-port 2-position switching valve 11 may be a 4-port 3-position switching valve. A pilot check valve 12 as a check valve is provided between the 4-port 2-position switching valve 11 and the extrusion-side pressure chamber 3b. The hydraulic piping on the press side pressure chamber 3 c side of the press cylinder 3 is directly connected to the 4-port 2-position switching valve 11. The pilot check valve 12 is automatically closed to prevent backflow when the discharge pressure P1 of the hydraulic pump 5 becomes lower than the extrusion side pressure (value P2 of the secondary pressure detection sensor 10). Yes. When the pilot check valve 12 is closed, the connection between the hydraulic pump 5 and the press cylinder 3 is disconnected, so that the relationship between the value P2 of the secondary pressure detection sensor 10 and the value P1 of the primary pressure detection sensor 9 is lost.

  After the pressure P2 in the extrusion side pressure chamber 3b becomes the holding pressure and the pilot check valve 12 is closed, the control unit 8 determines that the secondary pressure detection sensor 10 detects that the pressure P2 in the extrusion side pressure chamber 3b is the holding pressure. The hydraulic pump 5 is driven until the pressure P1 of the primary pressure detection sensor 9 reaches the lower limit pressure, and then the pressure P1 of the primary pressure detection sensor 9 is maintained at the holding pressure. It is comprised so that the hydraulic pump 5 may be driven until it becomes.

-Hydraulic control method for press cylinders-
Next, the hydraulic control method for the press cylinder 3 according to the present embodiment will be specifically described.

  As shown in FIG. 3, first, in step S01, a rubber material before heating (vulcanization) is placed on the lower mold 2.

  Next, in the initial pressurizing step of step S02, the hydraulic pump 5 is driven to bring the inside of the extrusion side pressure chamber 3b of the press cylinder 3 to a holding pressure. As shown in FIG. 1, the value P <b> 1 of the primary pressure detection sensor 9 and the value P <b> 2 of the secondary pressure detection sensor 10 are increased in two stages. This is because the time pressure does not increase. Thus, in the situation where the press cylinder 3 is operated, since the discharge pressure and the extrusion side pressure are the same, the pilot check valve 12 is in an open state, and it is easy to perform control without causing overshoot. It becomes.

  Next, in the holding step of Step S03, the extrusion side pressure chamber 3b is held for a predetermined time in a state where the holding pressure (for example, 21 MPa) is maintained. Thereafter, the rotation of the electric motor 6 is stopped. In this state, the molding material is heated at the holding pressure. Theoretically, the pilot check valve 12 is closed to prevent backflow, so that the pressure P2 in the extrusion side pressure chamber 3b is kept at the holding pressure.

  However, as indicated by a broken line in FIG. 1, high pressure oil leaks from the pilot check valve 12 or the like, and the value P2 of the secondary pressure detection sensor 10 gradually decreases.

  In step S04, when the secondary pressure detection sensor 10 detects that the pressure P2 in the extrusion-side pressure chamber 3b has become a lower limit pressure (for example, 19.5 MPa) lower than the holding pressure, the control unit 8 Send a signal.

  Next, in the first pressurizing step of step S05, the control unit 8 rotates the electric motor 6 again to drive the hydraulic pump 5, and the discharge pressure P1 of the hydraulic pump 5 detected by the primary pressure detection sensor 9 is the lower limit pressure. The inverter 7 is controlled to be equal to Then, when the value P1 of the primary pressure detection sensor 9 approaches the lower limit pressure under the control of the control unit 8, the rotational speed of the electric motor 6 decreases. At this time, the rotation of the electric motor 6 may be completely stopped or may be rotated.

  Next, in step S06, the control unit 8 receives that the value P1 of the primary pressure detection sensor 9 has reached the lower limit pressure. When the lower limit pressure is exceeded, the pilot check valve 12 opens naturally and the high pressure oil flows into the extrusion side pressure chamber 3b.

  Next, in the second pressurizing step in step S07, the controller 8 rotates the electric motor 6 to drive the hydraulic pump 5 so that the value P1 of the primary pressure detection sensor 9 becomes the holding pressure. When high-pressure oil flows through the pilot check valve 12, the value P1 of the primary pressure detection sensor 9 and the value P2 of the secondary pressure detection sensor 10 already indicate substantially the same value. Since the pressures P1 and P2 increase from there to the holding pressure, the overshoot does not appear as shown in FIG. 4, and the pressure changes as shown in FIG. The upper limit of the lower limit pressure is preferably 97% or less of the holding pressure. If the lower limit pressure is too high, the difference from the holding pressure is reduced, and overshoot may occur.

  Next, in step S08, it is determined whether a predetermined time has elapsed. If the predetermined time has not elapsed, the process returns to step S03, and the first pressurization process and the second pressurization process are repeated.

  On the other hand, when a predetermined time has elapsed in step S08, the unloading step is performed in the next step S09. In this unloading step, the 4-port 2-position switching valve 11 is switched to send high-pressure oil into the pressing-side pressure chamber 3c, and the press cylinder 3 is reduced to release the gas generated in the molded product.

  Next, in step S10, it is determined whether the unloading has been performed a predetermined number of times. If the predetermined number of times has not been performed, the process returns to step S02 and repressurization is performed. If it has been performed a predetermined number of times, mold opening is performed in step S11.

  Thus, according to the hydraulic control method for the press cylinder 3 according to the present embodiment, it is detected that the pressure P2 in the extrusion side pressure chamber 3b has become the lower limit pressure lower than the holding pressure, and the hydraulic pump 5 is driven. After the discharge pressure P1 is set to the lower limit pressure, the hydraulic pump 5 is driven so that the pressure P1 becomes the holding pressure again, so that the holding pressure of the press cylinder 3 is maintained while preventing overshoot. be able to.

-Comparative example-
On the other hand, in the comparative example shown in FIG. 4, in step S <b> 05, the electric motor 6 is rotated so that the value P <b> 1 of the primary pressure detection sensor 9 suddenly becomes equal to the holding pressure, and high-pressure oil is discharged from the hydraulic pump 5.

  When the value P1 of the primary pressure detection sensor 9 exceeds the lower limit pressure, the check valve opens and high pressure oil flows into the extruding side pressure chamber 3b all at once. Then, when the value P1 of the primary pressure detection sensor 9 becomes the holding pressure, the rotation of the electric motor 6 is completely stopped.

  However, the rotation control of the electric motor 6 is performed by feeding back the value P1 of the primary pressure detection sensor 9, and when the electric motor 6 starts to rotate, the value P2 of the secondary pressure detection sensor 10 is near the lower limit pressure. From there, the check valve suddenly opens and rises to the holding pressure. For this reason, an overshoot occurs, and the value P2 of the secondary pressure detection sensor 10 temporarily rises above the holding pressure. Once the pressure P2 in the extruding side pressure chamber 3b rises, it is not immediately reduced but gradually decreases as shown by the broken line.

  Then, a load larger than a desired load is applied to the molded product, and the quality of the molded product is deteriorated.

  Therefore, the press cylinder hydraulic control method and the press cylinder hydraulic control device according to the embodiment of the present invention can reliably prevent overshoot as in the comparative example, and can mold an extremely high-quality molded product.

(Other embodiments)
The present invention may be configured as follows with respect to the above embodiment.

  That is, in the said embodiment, although 1st pressurization and 2nd pressurization are repeated twice, this frequency | count is not limited and may be only once or 3 times or more.

In the above embodiment, in the second pressurizing step, the control unit 8 rotates the electric motor 6 to drive the hydraulic pump 5 so that the pressure P1 of the primary pressure detection sensor 9 becomes the holding pressure. The hydraulic pump 5 may be driven so that the pressure P2 of the pressure detection sensor 10 becomes the holding pressure.
This is because the pressure P1 and the pressure P2 are the same when the check valve 12 is open.

  In the above embodiment, the press cylinder 3 used in the rubber seal molding apparatus has been described. However, a press cylinder used in the sintered metal molding apparatus may be used. Moreover, in the said embodiment, although it has the unloading process, this unloading process may not be.

  In the above embodiment, the hydraulic pump 5 is an inscribed gear pump, but may be another type of pump such as a piston pump. The electric motor 6 is a three-phase induction motor, but may be another type of electric motor such as a servo motor.

  In addition, the above embodiment is an essentially preferable illustration, Comprising: It does not intend restrict | limiting the range of this invention, its application thing, or a use.

  As described above, the present invention is useful for a press cylinder hydraulic control method and a press cylinder hydraulic control method for molding rubber molded products, sintered metal molded products, and the like.

1 Upper mold
2 Lower mold
3 Press cylinder
3a Cylinder rod
3b Extrusion side pressure chamber
3c Pressing pressure chamber
4 Power unit
5 Hydraulic pump
6 Electric motor
7 Inverter
8 Control unit
9 Primary pressure detection sensor
10 Secondary pressure detection sensor
11 4 port 2 position switching valve
12 Pilot check valve (check valve)

Claims (3)

In the hydraulic control method of the press cylinder that holds the press cylinder with the holding pressure,
An initial pressurizing step of driving a hydraulic pump to bring the pressure chamber in the extrusion side of the press cylinder into the holding pressure;
A holding step of holding the extrusion-side pressure chamber by a check valve in a state where the holding pressure is the holding pressure;
After the holding step, it is detected that the pressure in the extrusion-side pressure chamber has become a lower limit pressure lower than the holding pressure, and the hydraulic pump is driven so that the discharge pressure of the hydraulic pump becomes the lower limit pressure. A first pressurizing step to
And a second pressurizing step for driving the hydraulic pump again so that the pressure in the extrusion side pressure chamber becomes the holding pressure when the discharge pressure from the hydraulic pump becomes the lower limit pressure. Cylinder hydraulic control method. The press cylinder hydraulic control method according to claim 1,
A press cylinder hydraulic control method characterized by repeating the first pressurizing step and the second pressurizing step within a predetermined time. In the hydraulic control device of the press cylinder that holds the press cylinder with the holding pressure,
A hydraulic pump that discharges high-pressure oil into the pressure-side chamber of the press cylinder;
An electric motor for driving the hydraulic pump;
An inverter for controlling rotation of the electric motor;
A primary pressure detection sensor for detecting the discharge pressure of the hydraulic pump;
A check valve disposed between the discharge side of the hydraulic pump and the extrusion side pressure chamber;
A secondary pressure detection sensor for detecting the pressure in the extrusion side pressure chamber;
A control unit that receives the signal from the secondary pressure detection sensor and controls the inverter;
The control unit
After maintaining the pressure in the extrusion side pressure chamber at the holding pressure, the secondary pressure detection sensor detects that the pressure in the extrusion side pressure chamber has become a lower limit pressure lower than the holding pressure, and The hydraulic pump is driven until the pressure of the primary pressure detection sensor becomes the lower limit pressure, and then the hydraulic pump is driven again until the pressure of the primary pressure detection sensor becomes the holding pressure again. A hydraulic control device for a press cylinder.

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