JP2007247802A - Hydraulic control circuit with excellent pressure controllability - Google Patents

Abstract

The present invention provides a pressure control circuit that enables continuous pressure control by minimizing a pressure drop when an automatic return circuit of a pressure intensifier operates in a pressure control device using a pressure intensifier.
According to the hydraulic control circuit excellent in pressure controllability of the present invention, even when the automatic return circuit of the pressure intensifier 2 is activated due to oil leakage from a high pressure shutoff valve 8 or the like, the step-down shutoff is performed. By providing the valve 22 and the oil leakage amount setting valve 23, the pressure increases between the restart of the pressure control of the pressure booster 2 and the time when the high pressure shut-off valve 8 opens and the pressure oil on the pressure booster side and the pressure vessel side merge. Since the pressure deviation can be given so that the pressure on the pressure device reaches the pressure on the pressure vessel side, the pressure drop when the automatic return circuit of the pressure intensifier 2 is operated is minimized, and the continuous pressure of the pressure vessel Control becomes possible. Thereby, it can apply widely also to continuous pressure control apparatuses, such as a pressure vessel.
[Selection] Figure 5

Description

  The present invention relates to improvement of control accuracy of a pressure control device including an electro-hydraulic servo valve (hereinafter simply referred to as “servo valve”), and more particularly, when an automatic return circuit of a pressure intensifier of the pressure control device is operated. The present invention relates to a hydraulic control circuit that enables highly accurate continuous pressure control by minimizing the pressure drop and is optimal for a crown variable roll for a rolling mill.

  In rolling a plate material (steel plate, copper plate, aluminum plate, etc.), the rolling roll is elastically flattened or bent due to a rolling load acting between the material and the rolling roll. For this reason, the roll roll is provided with a roll crown so as to compensate for the deformed shape in advance.

  Correspondingly, a variable crown roll (hereinafter referred to as “VC roll”) is provided with a hydraulic chamber inside the rolling roll, and the rolling roll is expanded by adjusting the hydraulic pressure, so that the roll crown is variable. It is said.

  The VC roll hydraulic control circuit is provided with a main pressure circuit that boosts the pressure oil from the hydraulic pump to a several times higher pressure by a pressure intensifier and supplies it to the VC roll. It is controlled by changing the oil amount by. In a hydraulic control circuit equipped with a servo valve, a correction signal is always output to eliminate the deviation between the command signal for increasing the pressure oil to the pressure intensifier and the feedback signal obtained by converting the high pressure of the VC roll into an electrical signal. (Hereinafter referred to as “feedback control”). As a result, the VC roll hydraulic control circuit can accurately maintain a predetermined high pressure.

  On the other hand, the hydraulic control circuit of the VC roll is provided with the following four limit switches for detecting the stroke of the intensifier for the purpose of enabling pressure control by using the intensifier continuously. .

  FIG. 1 is a view for explaining the mounting position of a pressure intensifier limit switch provided in the hydraulic control circuit of the VC roll and its operation. The pressure intensifier 2 shown in the figure has four limit switches. The limit switch 16 (hereinafter also referred to as “LS1”) is installed to detect the upper limit of the piston 4, and when the piston detection unit 4a reaches LS1, the pressure intensifier 2 enters the forced lowering mode (dead zone state). The piston 4 descends. The limit switch 18 (hereinafter also referred to as “LS2”) is installed to detect the intermediate position of the piston 4, and when the piston detector 4a reaches LS2, it stops at that position, and the pressure intensifier 2 is normal. Return to normal pressure control. A limit switch 19 (hereinafter also referred to as “LS3”) is installed to detect the lower limit of the piston 4 and serves as a starting point when pressure control is started. The limit switch 17 (hereinafter also referred to as “LS4”) is for a signal before the upper limit of the piston 4, and when the detection unit 4a of the piston reaches LS4, a warning signal that the pressure booster 2 will soon reach the upper limit by a buzzer or the like. Control is continued.

  In the VC roll hydraulic control circuit, the pressure booster automatic return circuit when the pressure booster reaches the upper limit switch is sequenced so that the above limit switch and the shutoff valve as the switching valve operate in conjunction with each other. It is controlled.

  FIG. 2 is a diagram illustrating an example of an operation sequence (S1 to S8) of an automatic return circuit for a pressure booster provided in a conventional hydraulic control circuit. In the following description, the high-pressure shut-off valve means a shut-off valve that switches between a supply valve for the pressure generated by the pressure intensifier to the pressure vessel side and a check valve that shuts back the reverse flow. It means a shut-off valve that switches between a pressure oil supply valve to the pressure intensifier and a check valve that shuts off the supply.

  When the detector of the piston reaches LS1 (S1), the high pressure shut-off valve is closed, the backflow from the pressure vessel is shut off, and the pressure on the VC roll side is maintained (S2). After the high-pressure shut-off valve is closed, the replenishment shut-off valve is opened after the timer set value, and the supply of pressure oil to the pressure intensifier is started (S3). After the replenishment shutoff valve is opened, the piston is lowered by a servo valve reverse command after a timer set value (S4).

  When the piston detector reaches LS2, it stops at that position (S5), and the servo valve returns to normal pressure control (S6). After the pressure control of the servo valve is resumed, the replenishment shutoff valve is closed after the timer set value, and the supply of pressure oil to the pressure intensifier is shut off (S7). After the replenishment shutoff valve is closed, the high pressure shutoff valve is opened after the set value of the timer (S8), the VC roll side pressure oil held by the high pressure shutoff valve and the timer after the servo valve pressure control is restored The pressure oil increased in pressure between the set values merges to obtain a normal state.

  In this way, the hydraulic control circuit of the VC roll is continuously maintained by maintaining a high pressure by feedback control in a normal state and by operating a sequence-controlled automatic return circuit when the pressure intensifier reaches the upper limit switch. And pressure control is performed.

  As an example of the prior art, Japanese Patent Application Laid-Open No. 2004-228867 discloses that a high pressure generating operation, a control operation, and a holding operation can be performed by one pressure intensifier and one hydraulic power source, and circuit damage is prevented when an abnormal high pressure occurs. A hydraulic control circuit with a space-saving and low-cost design has been disclosed that is configured so that the pressure release operation is automatically performed, and the number of parts such as piping and switching valves is greatly reduced compared to the same type of conventional circuit. Has been. Patent Document 2 proposes a control circuit that uses an electromagnetic relief valve in place of a servo valve, with the object of further space saving and low cost.

No. 03-36725 Japanese Utility Model Publication No. 05-79003

  The hydraulic control circuit proposed in Patent Document 1 and Patent Document 2 described above is an excellent hydraulic control circuit that realizes space saving and low cost, but the VC roll hydraulic control circuit has the following regarding continuous pressure control. There's a problem.

  The booster piston may reach the upper limit LS1 due to circuit oil leakage. The locations where oil leakage that causes the piston to rise are as follows: the high pressure shut-off valve, the pressure relief shut-off valve that switches the pressure oil feed valve toward the hydraulic pump and the check valve that shuts off the feed There is an off-valve and a VC roll rotary joint.

  When oil leaks from the above location, the booster piston rises by the amount of oil leaked. At this time, since no change occurs in the pressure on the VC roll side, only the increase of the piston of the intensifier proceeds without being output as a feedback signal. When the amount of oil leakage increases with time and exceeds the expected amount of oil leakage (volume corresponding to the stroke of LS1 and LS2 in FIG. 1), the piston of the pressure booster reaches the upper limit LS1, and the pressure booster The automatic return circuit of is activated.

  As described above, when the automatic return circuit of the intensifier is activated due to oil leakage, the pressures on the VC roll side and the intensifier side separated by the high pressure shutoff valve were measured, and the results are shown below.

  FIG. 3 is a diagram schematically showing the pressure waveforms on the VC roll side and the intensifier side separated by the high-pressure shutoff valve when a conventional hydraulic control circuit is used. In the figure, ΔP1 represents the pressure control deviation on the VC roll side from when the booster automatic return circuit is activated until the high pressure shutoff valve is opened, and θ1 represents the pressure increase speed of the pressure booster after the pressure control is resumed.

  As shown in the figure, when the piston of the pressure booster reaches the upper limit LS1, the automatic return circuit of the pressure booster operates to close the high pressure shutoff valve. At this time, on the VC roll side, the pressure is maintained by closing the high-pressure shut-off valve, but a minute pressure deviation ΔP1 due to oil leakage occurs. On the intensifier side, when the intensifier is lowered by the set value of the pressure reducing valve and reaches the intermediate LS2, the pressure control is resumed and the pressure oil is increased at the pressure increase rate θ1. Thus, it can be confirmed that the automatic return circuit of the pressure intensifier is operating as controlled in sequence.

  However, as shown in the figure, the pressure oil on the pressure vessel side and the pressure intensifier side separated by the high pressure shutoff valve is mixed at the moment when the high pressure shutoff valve is opened, and a certain pressure drop is detected. When such a sudden pressure drop occurs during rolling work using a VC roll, depending on the amount of pressure drop and the rolled material, it may cause a deterioration in the quality of the plate material that is the rolled material, and is continuously stable. There is a possibility that the rolling operation cannot be performed, and the productivity of the plate material rolling is lowered.

  The present invention has been made in view of the above-described problems, and provides a hydraulic control circuit for a pressure vessel capable of minimizing a pressure drop when an automatic return circuit for a pressure intensifier operates. It is aimed.

  First, the present inventors investigated the cause of the pressure drop shown in FIG. As a result, it was found that the pressure drop was caused by the pressure on the intensifier side being lower than that on the VC roll side, because the pressure on the VC roll side and the intensifier side were not the same pressure. did. Furthermore, when the pressure on the VC roll side is maintained by closing the high-pressure shut-off valve, the amount of oil leakage from the high-pressure shut-off valve or the like is smaller than the predicted amount, so that the pressure intensifier is normal. It took Δt1 + Δt2 until the high pressure shut-off valve opened after returning to the pressure control, and during that time, the pressure deviation sufficient to increase the pressure on the intensifier side to the pressure on the VC roll side was not obtained. It has been found that this is the cause of the pressure difference between the VC roll side and the intensifier side.

  In order to eliminate the above-mentioned causes, the present inventors have a viewpoint that it is effective to use the characteristic of a servo valve that always outputs a correction signal in order to eliminate a deviation between a command signal and a feedback signal. ,Study was carried out. As a result, when the pressure intensifier resumes pressure control, the speed at which the pressure is increased is proportional to the pressure control deviation due to minute oil leakage from the high pressure shutoff valve, etc., due to the characteristics of feedback control. It has been found that the above hydraulic control circuit can be realized by adding a valve and forcibly setting the amount of oil leakage.

The present invention has been completed on the basis of the above findings, and the gist of the following hydraulic control circuits (1) to (7).
(1) a hydraulic pump, a pressure booster that boosts the pressure oil discharged from the hydraulic pump, variable control means for controlling the pressure generated by the pressure booster, and pressure holding means for holding pressure on the pressure vessel side; A hydraulic control circuit comprising a pressure reducing means for lowering the pressure on the pressure vessel side, wherein the pressure intensifier comprises a piston and a detecting means for detecting a stroke, and the automatic return circuit of the pressure intensifier operates. At this time, the pressure control means forcibly gives a pressure deviation to the pressure oil on the pressure vessel side held by the pressure holding means.
(2) In the hydraulic control circuit with excellent pressure controllability described in (1) above, the pressure-lowering means opens and closes so as to reduce the pressure on the pressure vessel side in a relationship that is in conflict with the pressure holding by the pressure-holding means. With a circuit configuration comprising a pressure-down shut-off valve and an oil leakage amount setting valve that forcibly lowers the pressure on the pressure vessel held by the pressure-holding means, while exhibiting a reliable pressure drop function, This is desirable because it requires fewer maintenance inspections and a smaller circuit.
(3) In the hydraulic control circuit excellent in pressure controllability described in (1) or (2) above, the pressure holding means interrupts the supply valve of the generated pressure by the pressure intensifier to the pressure vessel side and the backflow thereof. A circuit configuration including a high pressure shut-off valve that switches between the check valve and the check valve is desirable because a simple and reliable pressure holding function can be expected.
(4) In the hydraulic control circuit with excellent pressure controllability described in (1) to (3) above, the variable control means controls the servo valve so that the pressure generated by the pressure intensifier becomes a target set value; If the circuit configuration includes a pressure transducer that converts the high pressure of the pressure vessel into a feedback signal for driving the servovalve, a command signal for boosting operation can be quickly generated with respect to the pressure deviation given by the stepping-down means. This is desirable because it is sent to the servo valve.
(5) In the hydraulic control circuit excellent in pressure controllability described in (1) to (4) above, the detection means includes a limit switch 1 that detects an upper limit of the piston, and a limit that detects an intermediate position of the piston. A circuit configuration including the switch 2, the limit switch 3 for detecting the lower limit of the piston, and the limit switch 4 for the upper limit signal for the piston is desirable because the boosted state of the pressure intensifier can be directly detected.
(6) In the hydraulic control circuit excellent in pressure controllability described in (1) to (5) above, when the automatic return circuit reaches the upper limit of the piston of the pressure booster, the pressure booster is forced down mode (dead zone state) At the same time, when the pressure holding means holds the pressure vessel side pressure, the piston is lowered by the reverse command of the variable control means, and when the piston reaches the intermediate position, the pressure intensifier is again in the control mode. If the circuit configuration is such that the pressure holding means releases the pressure on the pressure vessel side and performs sequence control so as to perform pressure control, it is desirable because a reliable and quick continuous control function can be exhibited.
(7) Since the hydraulic control circuit excellent in pressure controllability described in the above (1) to (6) is applied to the VC roll, it is desirable because continuous operation of the rolling mill becomes possible.

  It will be as follows if the concrete structural example of the hydraulic control circuit of this invention prescribed | regulated to said (1)-(6) is explained.

  First, as shown in FIG. 5 described later, control is performed so that the hydraulic pump 1, the pressure booster 2 that boosts the pressure oil discharged from the hydraulic pump 1 to a high pressure, and the generated pressure of the pressure booster 2 become a target set value. A servo valve 7 for pressure, a pressure transducer 9 for converting the high pressure of the pressure vessel into a feedback signal for driving the servo valve 7, a supply valve for the generated pressure by the pressure intensifier 2 to the pressure vessel side, and its reverse flow A high pressure shut-off valve 8 for switching between a check valve to be shut off, a pressure relief shut-off valve 14 for switching between a pressure oil feed valve in the direction of the hydraulic pump and a check valve for shutting off the feed, and a pressure intensifier 2 A replenishment shutoff valve 12 for switching between a pressure oil supply valve and a check valve that cuts off the supply, a pressure-reducing shutoff valve 22 that opens and closes in a relationship opposite to the high-pressure shutoff valve 8, and a high-pressure shutoff By valve 8 The hydraulic control circuit comprising an oil leak amount setting valve 23 to forcibly lower the pressure in the lifting and the pressure vessel side assumed.

  Next, as a detection means, the pressure booster 2 has the piston 4, the limit switch (1) 16 for detecting the upper limit of the piston 4, the limit switch (2) 18 for detecting the intermediate position of the piston 4, and the lower limit of the piston 4. A limit switch (3) 19 for detection and a limit switch (4) 17 for a signal before the upper limit of the piston 4 are provided.

  Furthermore, in the present invention, when the piston 4 of the intensifier 2 reaches the upper limit, the intensifier 2 enters the forced lowering mode (dead zone state), and at the same time, the high pressure shutoff valve 8 is closed to maintain the pressure vessel side pressure, and the servo valve When the piston 4 descends by the reverse command 7 and the piston 4 reaches the intermediate position, the pressure intensifier 2 enters the control mode again, and the pressure intensifier is sequence-controlled so that the high pressure shut-off valve 8 is opened and pressure control is performed. When the automatic return circuit 2 operates, a pressure deviation is forcibly given to the pressure oil on the pressure vessel side held by the high pressure shutoff valve 8 by the pressure reducing shutoff valve 22 and the oil leakage amount setting valve 23. It is characterized by comprising.

  In the present invention, “excellent in pressure controllability” means that, as described above, continuous pressure control of the pressure vessel is enabled by minimizing the pressure drop when the automatic return circuit of the intensifier operates. Means.

  The “dead zone state” defined in the present invention means a state in which the variable control means does not respond to the feedback signal and does not perform pressure control of the intensifier.

  FIG. 4 is a diagram showing an example of the operation sequence (S1 to S10) of the automatic return circuit of the pressure booster provided in the hydraulic control circuit of the present invention. In the same figure, S1-S8 shows the same operation | movement order as the said FIG. The operation sequence of the automatic return circuit of the pressure booster provided in the hydraulic control circuit described in the above specific configuration example will be described with reference to FIG. In the following description, the pressure-reducing shut-off valve is opened and closed in a relationship opposite to that of the high-pressure shut-off valve, and switches between the supply valve and the check valve when forcibly giving a pressure deviation to the pressure oil on the pressure vessel side. The shut-off valve means an oil leak amount setting valve, which means a valve that promotes an oil leak of a set amount in order to forcibly lower the pressure on the pressure vessel held by the high pressure shut-off valve.

  When the detector of the piston reaches LS1 (S1), the high pressure shut-off valve is closed, the backflow from the pressure vessel is shut off, and the pressure on the VC roll side is maintained (S2). At the same time, the step-down shut-off valve is opened, and the oil pressure on the pressure vessel side maintained by the high-pressure shut-off valve is forcibly reduced by the oil leakage amount setting valve (S9). After the high-pressure shut-off valve is closed, the replenishment shut-off valve is opened after the timer set value, and the supply of pressure oil to the pressure intensifier is started (S3). After the replenishment shutoff valve is opened, the piston is lowered by a servo valve reverse command after a timer set value (S4).

  When the piston detector reaches LS2, it stops at that position (S5), and the servo valve returns to normal pressure control, but the forced pressure reduction amount by the pressure reduction shutoff valve and oil leakage amount setting valve is a feedback signal. And is sent to the servo valve (S6). The supply shutoff valve is closed Δt1 after the pressure control of the servo valve is resumed, and the supply of pressure oil to the pressure intensifier is shut off (S7). After Δt2 after the replenishment shut-off valve is closed, the high-pressure shut-off valve is opened (S8), and at the same time, the pressure-decreasing shut-off valve is closed (S10). After the pressure control of the servo valve is restored, the pressure oil increased to a pressure equivalent to the pressure oil on the pressure vessel side during Δt1 + Δt2 merges and becomes a normal state.

  When the pressure reached between Δt1 and Δt2 is lower than the pressure vessel side in the above-described automatic return circuit of the pressure intensifier, the pressure drops by a value calculated from the pressure difference and the capacity difference between the intensifier side and the pressure vessel side. However, when the pressure reached between Δt1 + Δt2 is higher than that on the pressure vessel side, no pressure drop occurs.

  The reason why the above pressure drop does not occur is that when the pressure on the intensifier side becomes higher than the pressure vessel side, a pressure deviation occurs immediately after the pressure rises, and the servo valve reduces the pressure due to the minute deviation. However, since the deviation is small, the speed at which the piston of the intensifier descends is very slow, and the high-pressure shutoff valve opens while the pressure is not lowered.

  According to the hydraulic control circuit excellent in pressure controllability of the present invention, when the pressure-reducing shutoff valve and the oil leakage amount setting valve are provided, when the pressure booster automatic return circuit is activated, the pressure control of the pressure booster is resumed. Since the high pressure shut-off valve opens and the pressure oil on the intensifier side and the pressure vessel side merges, a pressure deviation can be given so that the pressure on the intensifier side reaches the pressure on the pressure vessel side. The pressure drop when the automatic return circuit of the pressure device is operated is minimized, and the continuous pressure control of the pressure vessel becomes possible.

  For this reason, if the hydraulic control circuit excellent in pressure controllability of the present invention is used for the VC roll, the pressure drop caused by oil leakage can be reduced even when the rolling operation by the rolling mill using the VC roll is continuously performed. Since it can prevent, board materials (copper material, iron material, aluminum material, stainless steel material, copper foil material, aluminum foil material, other plate materials), such as a steel plate with good quality, can be manufactured.

  Hereinafter, a circuit configuration of a hydraulic control circuit excellent in pressure controllability of the present invention will be described with reference to the drawings.

  FIG. 5 is a diagram showing an example when the hydraulic control circuit of the present invention is used for a VC roll. In the hydraulic control circuit shown in the figure, a circuit that boosts the pressure oil from the hydraulic pump 1 to a high pressure by the pressure intensifier 2 and supplies it to the VC roll 3 is referred to as a main pressure circuit A. The main pressure circuit A includes a high-pressure side circuit A2, a return circuit B, a pressure release circuit C, a replenishment circuit D, a relief circuit E, an accumulator circuit F, a cooling and cleaning circuit G, and a step-down circuit H. Is done.

  The low-pressure side circuit A1 is a circuit for supplying the pressure oil from the hydraulic pump 1 to the pressure intensifier 2, and removes contaminants from the unload relief valve 5 that switches between supply of pressure oil and return to the tank 26, and the circuit. A line filter 6 and a servo valve 7 that is operated so that the pressure intensifier 2 generates a high pressure are provided.

  The high-pressure side circuit A2 is a circuit that supplies the pressure oil boosted to a high pressure to the VC roll 3 by the pressure intensifier 2, and switches between a supply valve for the generated pressure by the pressure intensifier 2 and a check valve for blocking the backflow. A shut-off valve 8 and a pressure transducer 9 that detects the pressure generated by the pressure booster 2 and converts it into a feedback signal for driving the servo valve 7 are provided.

  The return circuit B is a circuit that connects the servo valve 7 and the cooling and cleaning circuit G.

  The pressure release circuit C is a circuit that branches from the VC roll side of the high-pressure shut-off valve 8 of the high-pressure side circuit A2 and is connected in the middle of the return circuit B. The pressure oil supply valve in the direction of the return circuit B and its supply A pressure relief shut-off valve 14 that switches between a check valve that shuts off supply and an angle check 15 that blocks oil sealed in the VC roll 3 from returning to the tank 26 due to the height difference of the mounting position are provided. .

  The replenishment circuit D is a circuit that feeds the reduced pressure oil to the pressure booster 2, and includes a pressure reducing valve 11 that adjusts the refill pressure, a pressure oil feed valve to the pressure booster 2, and a check that shuts off the feed. A replenishment shut-off valve 12 that switches between the valves and a check valve 13 that shuts off the backflow of the low-pressure oil supplied to the pressure intensifier 2 are provided.

  The relief circuit E is a circuit that branches from the middle of the unload relief valve 5 and the line filter 6 and is connected to the tank 26, and is provided with a relief valve 10 that returns to the tank 26 as a safety valve on the hydraulic circuit.

  The accumulator circuit F is a circuit for accumulating pressure oil set by the unload relief valve 5, and is provided with an accumulator 20 and a solenoid valve 21 for operating the accumulator 20.

  The cooling and cleaning circuit G is a circuit that cools and cleans the rotary joint of the VC roll, and includes an oil cooler 24 that cools the return oil from the VC roll, and a return filter 25 that filters and cleans the return oil from the VC roll. ing.

  The step-down circuit H is a circuit that branches from the VC roll side of the pressure relief shut-off valve 14 and is connected between the pressure relief shut-off valve 14 and the angle check 15 and opens and closes in a relationship opposite to the high pressure shut-off valve 8. A shut-off valve 22 and an oil leakage amount setting valve 23 for forcibly reducing the pressure on the VC roll side held by the high-pressure shut-off valve 8 are provided.

  The pressure intensifier 2 includes a piston 4, a limit switch (LS1) 16 for detecting the upper limit of the piston 4, a limit switch (LS2) 18 for detecting an intermediate position of the piston 4, and a limit switch for detecting the lower limit of the piston 4. (LS3) 19 and an upper limit signal limit switch (LS4) 17 for the piston 4 are provided.

  Next, the operating state of the hydraulic control circuit excellent in pressure controllability of the present invention will be described.

  In the main pressure circuit A, the pressure of the oil discharged from the tank 26 through the filter by the hydraulic pump 1 is set to 16.7 to 19.6 MPa as an example by the unload relief valve 5. A part of the oil is accumulated in the accumulator 20 by operating the solenoid valve 21. On the other hand, the oil discharged from the hydraulic pump 1 is supplied to the servo valve 7 through the line filter 6, and the servo valve 7 is operated through the pressure intensifier 2 so as to generate a high pressure. The return oil from the unload relief valve 5 and the servo valve 7 is sent to the tank 26 via the return filter 25 and the oil cooler 24.

  In the main pressure circuit A <b> 2, the high pressure oil boosted by the pressure intensifier 2 is supplied to the VC roll 3 through the shutoff valve 8. The high pressure is guided to the pressure transducer 9 and becomes a feedback signal for driving the servo valve 7.

  In the cooling and cleaning circuit G, the oil discharged from the hydraulic pump 1 passes through the line filter 6 and is controlled to 1.5 to 2.5 MPa as an example by the pressure reducing valve 11, and cooling and cleaning of the rotary joint of the VC roll 3 is performed. Therefore, it is supplied to the VC roll 3. The return oil from the rotary joint returns to the tank 26 through the return filter 25 and the oil cooler 24.

  At the start of control, the pressure intensifier 2 is at the position of the limit switch (LS3) 19, and when the pressure starts to increase, the pressure intensifier 2 moves from the limit switch (LS3) 19 to the limit switch (LS2) 18, Start compressing the oil. When the control is performed for a long time, the pressure intensifier 2 moves beyond the limit switch (LS2) 18 in the direction of the limit switch (LS1) 16 due to oil leakage.

  When the stroke position of the piston 4 reaches the limit switch (LS1) 16, the pressure intensifier 2 closes the high pressure shut-off valve 8 and maintains the internal pressure of the VC roll 3, and the stroke position of the piston 4 is limited to the limit switch (LS1). ) 16 automatically returns to the position of limit switch (LS2) 18. At the same time as the high-pressure shut-off valve 8 is closed, the pressure-reducing shut-off valve 22 is opened, and the oil pressure on the pressure vessel side maintained by the high-pressure shut-off valve 8 is forcibly lowered by the oil leakage amount setting valve 23.

  The oil used for automatically lowering the stroke position of the piston 4 of the intensifier 2 from the limit switch (LS1) 16 to the position of the limit switch (LS2) 18 is the same as that of the pressure reducing valve 11 by operating the replenishment shutoff valve 12. Via the check valve 13, the pressure booster 2 is replenished to the high pressure side.

  When the piston 4 reaches the position of the limit switch (LS2) 18, the piston 4 stops at that position, and the servo valve 7 returns to normal pressure control. At this time, the forced step-down amount by the step-down shut-off valve 22 and the oil leakage amount setting valve 23 is converted into a feedback signal and sent to the servo valve 7. After the pressure control of the servo valve 7 is resumed, the supply shutoff valve 12 is closed and the supply of the pressure oil to the pressure intensifier 2 is shut off.

  Servo valve that has received the feedback signal by the pressure oil on the pressure vessel side that has been held by the high pressure shutoff valve 8 and the forced pressure reduction amount, as the high pressure shutoff valve 8 is opened and the pressure drop shutoff valve 22 is closed. The pressure oil increased to a pressure equivalent to the pressure oil on the pressure vessel side by the pressure control of No. 7 is merged.

  Using the hydraulic control circuit of the VC roll shown in FIG. 5, the amount of pressure drop when the automatic return circuit of the pressure intensifier was operated was measured.

  FIG. 6 is a diagram schematically showing the pressure waveforms on the VC roll side and the intensifier side separated by the high pressure shutoff valve when the hydraulic control circuit of the present invention is used. ΔP2 in the drawing represents the pressure control deviation on the VC roll side from when the pressure booster automatic return circuit is activated until the shutoff valve is opened, and θ2 represents the pressure increase speed of the pressure booster after the pressure control is resumed.

  As shown in the figure, when the piston of the pressure booster reached the upper limit LS1, the automatic return circuit of the pressure booster was activated and the high pressure shutoff valve was closed. At this time, on the VC roll side, the pressure was maintained by closing the high-pressure shutoff valve, but a small pressure deviation ΔP2 due to oil leakage occurred. The pressure deviation ΔP2 is larger than the pressure deviation ΔP1 in FIG. 3 due to the addition of the step-down shutoff valve and the oil leakage amount setting valve.

  On the pressure intensifier side, when the pressure intensifier descends with the set value of the pressure reducing valve and reaches the intermediate LS2, the pressure control is resumed and the pressure oil is increased at the pressure increase rate θ2. The pressure increase speed θ2 is larger than the pressure increase speed θ1 of FIG. 3 due to the effect of giving a pressure deviation ΔP2 larger than the conventional pressure deviation ΔP1.

  As a result, as shown in FIG. 6, even if the pressure oil on the pressure vessel side and the pressure booster side separated by the high pressure shutoff valve is mixed at the moment when the high pressure shutoff valve is opened, the pressure drop is 0. It stopped at 5 MPa.

  As described above, it was confirmed that the pressure drop when the pressure booster is automatically restored can be reduced to 1/20 to 1/30 or less by using the hydraulic control circuit of the present invention, as compared with the conventional hydraulic control circuit. .

  According to the hydraulic control circuit excellent in pressure controllability of the present invention, when the pressure-reducing shutoff valve and the oil leakage amount setting valve are provided, when the pressure booster automatic return circuit is activated, the pressure control of the pressure booster is resumed. Since the high pressure shut-off valve opens and the pressure oil on the intensifier side and the pressure vessel side merges, a pressure deviation can be given so that the pressure on the intensifier side reaches the pressure on the pressure vessel side. The pressure drop when the automatic return circuit of the pressure device is operated is minimized, and the continuous pressure control of the pressure vessel becomes possible.

  For this reason, if the hydraulic control circuit excellent in pressure controllability of the present invention is used for the VC roll, the pressure drop caused by oil leakage can be reduced even when the rolling operation by the rolling mill using the VC roll is continuously performed. Since it can prevent, board materials (copper material, iron material, aluminum material, stainless steel material, copper foil material, aluminum foil material, other plate materials), such as a steel plate with good quality, can be manufactured.

  As described above, the hydraulic control circuit having excellent pressure controllability according to the present invention is capable of continuous pressure control with a minimum pressure drop, and thus is widely applied not only to the VC roll but also to continuous pressure control devices such as various pressure vessels. it can.

It is a figure explaining the attachment position of the pressure | voltage increaser limit switch provided in the hydraulic control circuit of a VC roll, and its effect | action. It is a figure which shows an example of the operation | movement order (S1-S8) of the automatic return circuit of the pressure booster provided in the conventional hydraulic control circuit. It is a figure which shows typically the pressure waveform of the VC roll side and pressure booster side which are isolate | separated into a high pressure shut-off valve when the conventional hydraulic control circuit is used. It is a figure which shows an example of the operation | movement order (S1-S10) of the automatic return circuit of the pressure booster provided in the hydraulic control circuit of this invention. It is a figure which shows an example at the time of using the hydraulic control circuit of this invention for VC roll. It is a figure which shows typically the pressure waveform of the VC roll side and pressure booster side which are isolate | separated into a high pressure shut-off valve when the hydraulic control circuit of this invention is used.

Explanation of symbols

1. Hydraulic pump 2. Intensifier VC roll 4. Piston 4a. 4. Piston detection section Unload relief valve 6. 6. Line filter Servo valve 8. 8. High pressure shut-off valve Pressure transducer 10. Relief valve 11. Pressure reducing valve 12. Refill shutoff valve 13. Check valve 14. Pressure relief shut-off valve 15. Angle check 16. Limit switch LS1 17. Limit switch LS4
18. Limit switch LS2 19. Limit switch LS3
20. Accumulator 21. Solenoid valve 22. Step-down shut-off valve 23. Oil leakage amount setting valve 24. Oil cooler 25. Return filter 26. Tank A. Main pressure circuit A1. Low voltage side circuit A2. High side circuit B. Return circuit C.I. Pressure release circuit D. Supply circuit E. Relief circuit F. Accumulator circuit Cooling and cleaning circuit Step-down circuit S1 to S10. Operating procedure

Claims (7)

A hydraulic pump, a pressure intensifier that boosts the pressure oil discharged from the hydraulic pump, a variable control means for controlling the pressure generated by the pressure intensifier, a pressure holding means for holding pressure on the pressure vessel side, and a pressure vessel side A pressure control means for lowering the pressure of the hydraulic control circuit,
The pressure intensifier comprises a piston and detection means for detecting a stroke;
When the automatic return circuit of the pressure intensifier is operated, the pressure-decreasing means forcibly gives a pressure deviation to the pressure oil on the pressure vessel side held by the pressure-holding means. Hydraulic control circuit.   The pressure-lowering means opens and closes the pressure-vessel-side pressure to lower the pressure-vessel-side pressure in a relationship opposite to the pressure holding by the pressure-holding means, and the pressure-vessel-side pressure held by the pressure-holding means. The hydraulic control circuit according to claim 1, further comprising an oil leakage amount setting valve that forcibly descends.   3. The high pressure shut-off valve according to claim 1, wherein the pressure holding means includes a high pressure shut-off valve that switches between a supply valve for generating pressure by the pressure intensifier to the pressure vessel side and a check valve for blocking the backflow thereof. The hydraulic control circuit described.   The variable control means includes a servo valve that controls the generated pressure of the pressure intensifier to a target set value, and a pressure transducer that converts the high pressure in the pressure vessel into a feedback signal for driving the servo valve. The hydraulic control circuit according to claim 1, further comprising:   The detection means includes a limit switch 1 for detecting an upper limit of the piston, a limit switch 2 for detecting an intermediate position of the piston, a limit switch 3 for detecting a lower limit of the piston, and a limit for a signal before the upper limit of the piston. The hydraulic control circuit according to claim 1, further comprising a switch 4.   When the piston of the pressure booster reaches the upper limit, the automatic return circuit enters the forced lowering mode (dead zone state), and at the same time, the pressure holding means holds the pressure vessel side pressure, and the variable control means moves backward. When the piston is lowered by the command and the piston reaches the intermediate position, the pressure intensifier is again in the control mode, and the pressure holding means releases the pressure on the pressure vessel side and performs sequence control so as to perform pressure control. The hydraulic control circuit according to any one of claims 1 to 5. It is applied to the pressure control of the crown variable roll for rolling mills, The hydraulic control circuit in any one of Claims 1-6 characterized by the above-mentioned.

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