JPH0970700A - Pressure controlling method of hydraulic press device and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the quality of pressing article and to improve the safety by restricting the action of a controlling valve in a hydraulic press device which executes the flow rate control of a hydraulic cylinder and the pressure control with a single controlling valve. SOLUTION: In a hydraulic press device to execute controlling the flow rate and the pressure of a hydraulic cylinder with a single controlling valve, the restriction against an electric command to control the spool position of a controlling valve 1 in a time of increasing the pressure and acting is given and the moving range of the spool is restricted. In this case, one of the restriction is to prevent the action to the decreasing side of the pressure against the load of a piston rod in the hydraulic cylinder 11 and another one is to prevent the hydraulic cylinder 11 from generating the excess large output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanical device such as a high pressure casting machine, a die casting machine, an injection molding machine, a press machine, and a powder molding machine, and particularly to a single control of a flow rate control and a pressure control of a hydraulic cylinder used for a press. More particularly, the present invention relates to a control method and a control device for controlling the pressure of a hydraulic press device.

[0002]

2. Description of the Related Art As a typical prior art relating to a high-pressure casting machine in a mechanical device of this type, for example, Japanese Patent Laid-Open No. 4-134.
No. 65 publication is cited. As is apparent from this prior art, the conventional high-pressure casting machine operates the flow control valve during the injection operation, while operating the pressure control valve during the pressure increasing operation. However, in such a control method, since two control valves are used, the number of parts is large and the cost is high, and the control means is complicated because the controlled object covers two systems. There was a problem that switching to boosting control could not be made smoothly and surge pressure was generated, and the operation time delay was increased. Therefore, in order to improve the above problems, the applicant of the present invention has proposed a control method and a device capable of controlling the flow rate and the pressure with a single control valve in Japanese Patent Application No. 5-88689. Flat 6−
It was proposed earlier by 161380 and Japanese Patent Application No. 6-275152.

[0003]

The fluid pressure control valve used in each of the above-mentioned inventions, that is, the control valve for performing flow rate control and pressure control with a single valve structure has its opening characteristic ( The opening area diagram) is as shown in FIG. Referring to FIG. 7, this control valve mainly uses position (b) and its vicinity for pressure control, and cylinder extension side positions (c) to (e) or cylinder contraction for flow control. Side position
In each of (f) to (g), a range of large opening is used.

Due to the opening characteristic as described above, for example, when the target pressure is considerably lower than the actual pressure, feedback control for rapidly reducing the pressure is applied. It happens that the valve spool moves out of the vicinity of the pressure control position (b) and moves to the position of large opening in the cylinder reduction side positions (f) to (g). This operation causes the pressure to drop quickly, but due to the delay in valve operation, it cannot immediately return to the range of the small opening position near the pressure control position (b) even after the pressure drops. Sometimes.
Therefore, the injection cylinder as a hydraulic cylinder momentarily contracts and the mold cavity expands. As a result, the molten metal in the mold becomes a negative pressure, causing shrinkage cavities, which may reduce the strength of the product. Can be considered.

On the contrary, when the target pressure is higher than the actual pressure, feedback is applied for the purpose of rapidly increasing the pressure, and the spool has a large opening range in the extension side positions (c) to (e). Move up to. This operation causes the pressure to rise, but due to the delay in valve operation, the pressure control position is immediately increased even after the pressure rises.
It becomes impossible to return to the range of the small opening position near (b). Therefore, the pressure on the cylinder head side increases excessively. That is, the pressure of the molten metal in the mold pushed through the sleeve of the cylinder rises excessively, and in the worst case, the pressure exceeds the mold clamping force of the mold,
The molten metal may blow out of the mold and impair the quality of the product.

The present invention has been made in order to solve the above problems, and an object of the present invention is to control the flow rate and pressure of a hydraulic cylinder for pressing in a hydraulic system of the cylinder. In a hydraulic press device such as a high-pressure casting machine that can be operated by a single control valve provided, the control valve is used when pressurizing the product while making the most of the advantages of the device and control of this hydraulic press device. It is intended to maintain the strength of the product, improve the quality, and enhance the safety by preventing the occurrence of the disturbance caused by the operation delay of.

[0007]

The present invention has the following configuration to achieve the above object. That is, the present invention relates to a hydraulic press device in which flow control and pressure control of a hydraulic cylinder for pressing are performed by a single control valve provided in a hydraulic system of the cylinder, in which the control valve is operated during pressure increasing operation of the hydraulic cylinder. Is a pressure control method for a hydraulic press device, which restricts an electric command for controlling the spool position to regulate the moving range of the spool.

According to the present invention, in the pressure control method, the above-mentioned restriction given to the electric command is for preventing the operation of the piston rod in the hydraulic cylinder to the side that reduces the pressure against the load. It is a method of controlling the pressure of the apparatus, and is a method of controlling the pressure of the hydraulic press apparatus in which the above-mentioned limitation given to the electric command is to prevent excessive output of the hydraulic cylinder.

In the pressure control method according to the present invention, when controlling the control valve during the pressure increasing operation of the hydraulic cylinder, the integrated value of the pressure deviation between the target value and the measured value is fed back to the pressure chamber of the hydraulic cylinder or A feedback value including a feedback control method for controlling the pressure in the hydraulic piping and including an integral value of the pressure deviation from the limit given to the electric command in the calculation process for determining the electric command for controlling the spool position of the control valve. When the deviation is out of the range, this is a pressure control method for the hydraulic press device in which the integral value of the pressure deviation is feedback-controlled while being held at the value before the deviation.

In the pressure control method according to the present invention, when the target value at the final point is 0 kgf / cm ² , the pressure detector determines the substantial target value at the final point of the pressure control. Is a pressure control method for a hydraulic press device in which the value is automatically or manually reset to an appropriately low value corresponding to the offset amount.

The present invention also provides a hydraulic press device in which the flow rate control and the pressure control of a hydraulic cylinder for pressing are performed by a single control valve provided in the hydraulic system of the cylinder, in the pressure increasing operation of the hydraulic cylinder. Command control means for restricting the moving range of the spool by restricting the electric command for controlling the spool position of the control valve so that the value does not deviate from the set region is provided in the electric control system of the control valve. It is a pressure control device of a hydraulic press device characterized by the following.

The present invention is also the pressure control device, wherein the command control means is for preventing the operation of the piston rod in the hydraulic cylinder toward the side that reduces the pressure with respect to the load. The device is a pressure control device of a hydraulic press device, wherein the command control means is for preventing an excessive output of the injection cylinder.

In the pressure control device of the present invention, when controlling the control valve during the pressure increasing operation of the hydraulic cylinder, the integrated value of the pressure deviation between the target value and the measured value is fed back to the pressure chamber of the hydraulic cylinder or In the process of determining the feedback control means for controlling the pressure in the hydraulic pipe and the electrical command for controlling the spool position of the control valve, the feedback value including the integral value of the pressure deviation from the limit given to this electrical command is If it comes off,
The command control means for performing feedback control while maintaining the integrated value of the pressure deviation at the value before it deviates from the region is the pressure control device of the hydraulic press device provided in the electric control system of the control valve.

According to the present invention, in the pressure control device, when the pressure control in which the target value at the final point is 0 kgf / cm ² is performed, the substantial target value at the final point of the pressure control is set to the pressure detector. The setting control means for automatically or manually resetting to an appropriately low value corresponding to the offset amount is the pressure control device of the hydraulic press device provided in the electric control system of the control valve.

[0015]

According to the present invention, which is characterized by each of the above-mentioned means, a restriction is imposed on an electric command for controlling the spool position of the control valve during a pressure increasing operation of a hydraulic cylinder for pressing, for example, an injection cylinder. By restricting the moving range of the spool by giving a negative pressure inside the mold, which is the load of the injection cylinder, it is possible to prevent the occurrence of shrinkage cavities in the product. It is possible to prevent the molten metal from being blown out. For example, referring to FIGS. 3 and 4, in the range of the cylinder expansion side positions (c) to (e) or the cylinder contraction side positions (f) to (of the hydraulic control valve 1 for controlling the injection cylinder 11 in FIG. Stroke is restricted to a range near the pressure control position (b) or a small opening range on the cylinder extension side and contraction side so that the spool does not move greatly to the range of g). Therefore, the output voltage is limited to a certain range.

Therefore, even if the spool stroke [mm] and the command voltage [V] correspond to 1: 1 and there is a delay in the operation of the hydraulic control valve 1, the injection cylinder 11 shrinks or an excessive output is generated. The range of command voltage to prevent the occurrence of
Assuming a value of 3 to 1V, -3V is output when a command less than -3V is fed back, and 1V is output when a command exceeding 1V is fed back, -3V
If a command of 1V or less is fed back, programming is performed so that the voltage according to the command is output. This is because, for example, in FIG. 7, the range in which the injection cylinder 11 does not shrink is the range until P → B starts to open (up to the position (h) in the figure), and the range in which excessive output does not occur is B
It is a range up to a point (position (d) in the figure) where the opening degree between → D and P → A starts to suddenly increase.

By doing so, even if the command fed back during the pressure increase control is a command to reduce the injection cylinder (expand the mold cavity), the spool will not move beyond a certain range. Injection cylinder 1 for controlling electric commands
1 is prevented from shrinking so that the product does not shrink.

Further, by doing so, the command fed back at the time of pressure increase control is given to the injection cylinder 11
Even if it is a command to generate an excessive output, the electric command is controlled so that the spool does not move beyond a certain range, so that the injection cylinder 11 is prevented from generating an excessive output. As a result, the pressure inside the mold will not rise excessively and the molten metal will not blow out of the mold.

By applying the method of the present invention having the above-mentioned structure and functioning, the above-mentioned problem to be solved is basically solved. Under the condition that the feedback control of the control valve 1 includes an I (integration) control method which has been widely used in the past, the electrical control according to claim 1 to claim 3 and claim 6 to claim 8 is performed. The limitation may cause problems as shown below.

The I (integration) control is ideally a feedback control of the cumulative value of the deviation between the target value and the actual measurement value according to the following equation (A) so that the steady deviation between the target value and the actual measurement value is achieved. Has a function of setting 0 to 0.

V (t) = KI × SumI (t) + α = KI × (SumI (t-dt) + e (t)) + α (A) where V (t): electrical command at time t e (t): Deviation between target pressure at time t and actual pressure detected by pressure detector SumI (t): Integrated value of deviation at time t KI: Coefficient of integrated value of deviation dt: Time step (analog control Then dt →
0) α: Change in electric command when other control methods are simultaneously performed (for example, P (proportional) control)

For example, as shown in FIG. 9, the first pressure P1
When the I (integral) control is used for the set target that changes from the second pressure P2 to the second pressure P2 within the fixed time T, there is a delay in the operation of the hydraulic control valve 1 at the time of starting, so the measured value is the target. The integral value SumI (t) of the deviation continues to increase until the time Ta exceeds the value.

Here, the deviation integral value SumI (t) increases, the electric command V (t) (= KI × SumI (t) + α) exceeds the maximum value Vmax of the electric control range, and the sprawl stroke is increased. Even if it is limited to the maximum value of the limit range, SumI (t) continues to increase. SumI (t) continues to monotonically increase, and the measured value exceeds the target value, e (t)
At time Ta when <0, KI × SumI (t) exceeds the maximum value Vmax by ΔV. SumI at the time of Ta
(T) reaches the maximum value, and thereafter, SumI (t) decreases in accordance with the calculation of SumI (t) = SumI (t-dt) + e (t).

It takes a time of ΔT (= Tb-Ta) until the electric command V (t) starts to fall within the range of KI × SumI (t) <Vmax (hatched range in FIG. 9). Requires. During this period, the output V (t) should be decreased so as to reduce the pressure, but it takes time for SumI (t) to decrease, so that the output V (t) requires a voltage Vmax. Continues to output for ΔT. As a result, the pressure largely overshoots, an excessively large pressure is generated more than intended, and an excessive force is applied to the machine, which greatly impairs the life of the machine. Further, if the overshoot is large, it takes time for the pressure to settle, and stable operation cannot be performed.

Therefore, in order to solve such a problem, according to the present invention, in the process of determining the electric command for controlling the spool position of the hydraulic control valve 1, the electric command causes the electric limit range to be set. In the case of deviation, feedback control is performed while maintaining the integrated value of the pressure deviation at the value before it deviates from the region.

By using such a control method, even if the output V (t) increases, the integrated value SumI (t) does not increase, and the integrated value SumI (t) does not increase. SumI (t) can be suppressed to a necessary minimum value. Therefore, as shown in FIG. 10, when the deviation e (t) <0, the electric command V
(T) begins to decrease, and the effect of reducing the overshoot is achieved.

Since the overshoot is reduced in this way, it is possible to prevent excessive pressure from being generated and reduce the load on the mechanical device. Further, in the case of a high-pressure casting machine or the like, it is possible to prevent the risk that a pressure exceeding the mold clamping force of the mold is applied to the molten metal, the mold opens, and the molten metal spouts out of the mold. Further, since the overshoot is reduced, the settling time is shortened, stable operation is possible, and the quality of the product is improved.

Incidentally, there is a prior art relating to a mechanical device for compressing a rubber mold by a pressing force of a hydraulic cylinder and press-molding a powder such as a magnetic material by pseudo isotropic pressure.
It is known from Japanese Patent No. 363010, and this prior art also performs flow rate control and pressure control of a hydraulic cylinder by a single control valve, similarly to the control means of the above-mentioned high-pressure casting machine. It can be expected that a solution similar to the present invention can be used with the conventional device. However, in such a device, since the obtained product is a brittle molded product obtained by compacting a powder body, in order to prevent cracking, the pressing force is 0 kgf / It is necessary to smoothly lower it to cm ² .

However, when controlling the pressing force, the pressure detector used for detecting the pressure of the hydraulic cylinder generally has a temperature drift and other offset values, and the pressure value indicated by the pressure detector is 0 kgf / cm ^2. However, the true pressure value may not be 0 kgf / cm ² . When the final target value of pressure control is set to 0 kgf / cm ² when the pressure value indicated by the pressure detector is smaller than the true pressure value, the pressure controlled by the pressure control means is indicated by the pressure detector. 0 kgf / c
m ² . However, the true pressure at this time is higher than 0 kgf / cm ² by the offset value (Fig. 11).
reference).

When the pressure control operation is completed and the hydraulic cylinder is contracted, the hydraulic cylinder is contracted regardless of the pressure indicated by the pressure detector, and the true pressure becomes 0 kgf / cm ² as the pressure is reduced. Since the reduction speed at this time affects the cycle time, set it as fast as possible. Therefore, the pressure change from the pressure value higher than 0 kgf / cm ² by the offset amount to the true pressure value of 0 kgf / cm ² becomes a sudden pressure change, and the force applied to the entire rubber mold until then suddenly changes. Depending on the shape of the molded product, asymmetrical force may be applied instantaneously, causing cracking.

In order to solve such a problem, the present invention provides a substantial target at the final point of pressure control when the target value at the final point of pressure control is 0 kgf / cm ^2. The value is automatically or manually reset to an appropriately low value corresponding to the offset amount of the pressure detector. The offset value at this time is determined by allowing a margin for error in the maximum value of the temperature drift of the pressure detector.

By adopting the above-mentioned solution, the true pressure value deviates from the target value by the offset value until the true pressure reaches 0 kgf / cm ² , as shown in FIG. It smoothly drops to 0 kgf / cm ² according to the set slope of pressure change. It remains true pressure from reduced to 0 kgf / cm ^2, the true pressure is kept 0 kgf / cm ^2,
The spool is stroked, and the spool is stroked.
Move to the limit on the low pressure side (position (h) in the case of FIG. 7) of the electrical limit range of the spool stroke set in.
During this time, the pressure is 0 kgf / cm ² regardless of the target value. Moreover, since the spool stroke is electrically limited, the hydraulic cylinder does not shrink. Due to such an operation, the pressure can be smoothly dropped to 0 kgf / cm ² without causing a sudden pressure change, and there is no fear of cracking of the molded product.

[0033]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 is a structural view showing a cross section of a main part of a hydraulic control valve used in a high pressure casting machine according to a first embodiment of the present invention, and FIG. 2 is an enlarged view of a spool part in FIG. A hydraulic control valve (hereinafter abbreviated as a control valve) 1 shown in FIG. 1 includes a main body valve part 2, left and right cover parts 3, 4, an adapter plate part 5, a pilot valve part 6, and a differential transformer part. 7 and. A main spool 8 is slidably inserted in the valve hole portion of the main body valve portion 2. Pilot chambers 3a and 4a are provided in the left and right cover portions 3 and 4, respectively. As the pilot valve portion 6 integrally attached to the main body portion 2 via the adapter plate portion 5, a high response, for example, a torque motor driven two-stage servo valve is used, and the pilot valve portion 6 allows the pilot chamber 3a or the pilot chamber 3a to operate. The pilot pressure is introduced into the chamber 4a, the position of the main spool 8 is detected by the differential transformer unit 7, and the spool position is controlled by (minor) feedback control by the amplifier.

In the valve hole portion of the main body valve portion 2, as shown in FIG. 2, from the left side close to the pilot chamber 3a to the right side, the differential port D, one actuator port B, the pressure source port P, and the other Five ports, an actuator port A and a tank port T, are provided adjacent to each other. On the other hand, the main spool 8 has a small diameter portion 8A at the center, large diameter portions 8B and 8C on the left and right sides thereof, and small diameter portions 8D on the left and right sides thereof.
8E are provided respectively, and a vertical hole 8F is provided in the main spool 8 so as to extend in the axial direction, and horizontal holes 8G and 8H communicating with the vertical hole 8F are provided at the spool body. Has been. The lateral hole 8G is opened across the boundary between the large diameter portion 8B and the small diameter portion 8D, and the lateral hole 8H is opened on the right side of the small diameter portion 8E. Also,
The large-diameter portion 8B has a notch (notch) 8I formed in the end edge portion on the small-diameter portion 8A side, and the left and right end edges of the large-diameter portion 8C are
Notches 8J and 8K are cut respectively. The vertical hole 8F is closed at the right end of the spool in a liquid-tight manner by a plug.

When used in an injection hydraulic cylinder circuit, the control valve 1 having the above structure has the following seven positions (a) to (g) as shown in the symbol diagram of FIG. The one having the function represented by is used. That is, (a) the pressure source port P is closed, the differential port D is connected to the tank port T through the throttle, the A port is connected to the tank port T through the throttle, and the B port is connected to the tank port T. Neutral position to be connected, (b) A port is connected to pressure source port P and tank port T via throttles respectively, and differential port D is B port and tank port T via throttles
(C) A meter-in meter in which the A port is connected to the pressure source port P via the throttle and the B port is connected to the differential port D and the tank port T via the throttle respectively. Out control position, (d) A
A differential throttle control position in which the port is connected to the pressure source port P through the throttle, the B port is connected to the differential port D through the throttle, and the tank port T is closed, (e) A port is the pressure source port The differential control position is connected to P, the B port is connected to the differential D port, and the tank port T is closed. (F) The B port is connected to the pressure source port P via the throttle and is differential with the A port. The return throttle control position where the port D is connected to the tank port T through each throttle, (g) The A port is connected to the tank port T, the B port is connected to the pressure source port P, and the differential port D is The return control position that is connected to the tank port T through the throttle.

FIG. 3 shows an injection hydraulic cylinder circuit of a high-pressure casting machine according to the first embodiment of the present invention. The hydraulic cylinder 11 shown in FIG. 3 is used, for example, as an injection cylinder of a device that injects and presses molten metal into a die of a high-pressure casting machine. The injection cylinder 11 performs an injection operation and then
The hydraulic circuit for performing the pressing operation includes an injection cylinder 11, a hydraulic line 12, a tank line 13, a pilot check valve 14, and an injection control valve realized by the control valve 1. , A hydraulic circuit including a differential check valve 16, a controller 10 for controlling the operation of the hydraulic circuit, a hydraulic circuit for detecting hydraulic pressure in the hydraulic circuit, an operating state of the valve, etc., and transmitting a signal to the controller 10. It is composed of a detector.

The injection cylinder 11 is composed of a single-rod double-acting hydraulic cylinder. A pilot check valve 14 is connected to the cylinder port of the head side chamber whose volume increases during the injection operation, and the cylinder of the rod side chamber whose volume decreases during the injection operation. The injection control valve 1 is connected to the port via the B port. A pressure sensor 26 for detecting the pressure in the head side chamber and a position sensor 27 for detecting the position and speed of the rod are attached to the injection cylinder 11. The hydraulic line 12 includes a hydraulic pump 15, a check valve 17 that allows the flow of pressure oil from the hydraulic pump 15 to the load side, a relief valve 20 having a solenoid valve 21, and a high pressure accumulator 2
2 and the oil feed pipe 23, the oil of a predetermined pressure is supplied to the oil feed pipe 23. The injection control valve 1 is connected to the oil feed pipe 23 via a pressure source port P.

The tank line 13 is provided with an oil tank 24 and an oil return pipe 25 so that the pressure oil after operating with the injection cylinder 11 and each valve is returned to the oil tank 24 through the oil return pipe 25. ing. The injection control valve 1 is connected to the oil return pipe 25 via a tank port T. On the other hand, the injection control valve 1 has a pilot check valve 1 whose A port is a pipe line.
4 and the differential port D and the A port are connected by a conduit provided with a differential check valve 16. The pilot check valve 14 is opened and closed by a solenoid valve 19. In addition, the differential check valve 16
Is provided to allow the flow of pressure oil from the differential port D to the same conduit as the A port.

The controller 10 is provided with a well-known microcomputer including a central processing unit CPU and a memory as control elements, and the CPU has a pressure sensor 26, a position sensor 27 and an injection control valve 1 according to a preset program. The external data corresponding to the displacement of the main spool 8 is fetched from the differential transformer section 7, data is exchanged with the memory to perform arithmetic processing, and the digital output signal is converted into an analog for control as necessary. The signal is converted into a signal and output to the pilot valve section 6 of the injection control valve 1. The controller unit 100 in the controller 10 includes a pressure control unit, an injection speed control unit, and a command control unit. The control modes of these units will be described below with reference to the injection operation and the pressing operation. Revealed by

The injection control valve 1 has a highly responsive two-stage servo valve driven by a torque motor as a pilot valve portion 6,
This controls the switching direction and the opening degree of the main valve of the main body valve unit 2. With respect to the position of the main valve, the spool position is detected by the differential transformer unit 7, and feedback control is performed by the amplifier 30 via the amplifier 29, whereby spool stroke control, that is, valve opening control is performed. (1) Injection control, neutral position: The pressure source port P is closed, the A port is connected to the tank port T via the notch 8K (throttle), and the B port is connected via a partial opening (throttle) of the lateral hole 8G. Port D
Further, it is connected to the tank port T through the horizontal hole 8G, the vertical hole 8F, and the horizontal hole 8H. Pilot check valve 14
Is closed, and the rod of the injection cylinder 11 is stopped without expanding or contracting. Switching from pressure control position (b) to meter-in / meter-out control position (c): The main spool 8 moves slightly to the right, and the pressure source port P has a notch 8J (throttle).
Is connected to the A port via the pressure control, and then the B port is connected to the tank port T through a partial opening (throttle) of the horizontal hole 8G, vertical hole 8F, and horizontal hole 8H, and the A port is connected to the notch 8J (throttle). ) To the pressure source port P via
It becomes meter-in / meter-out control. The opening area on the meter-in side is determined in consideration of the pressure control characteristics and the meter-in flow rate control characteristics.The opening area on the meter-out side is the area ratio of the head side and rod side of the cylinder to the opening area on the meter-in side. Also, it can be determined in consideration of how much damping is desired or how much pressure is desired to be applied to the rod side during deceleration.

While the area of B port → tank port T is large, most of the oil on the rod side flows into the oil tank 24 to form a double-action circuit, and as the B port → tank port T is throttled, the pressure of B port increases. The flow rate rises and the flow rate from the B port to the differential port D increases and flows into the head side through the differential check valve 16 to increase the extension speed while forming a differential circuit.

Differential throttle control position (d): A port is connected to pressure source port P via notch 8J (throttle), and B port is differential port D via partial opening (throttle) of lateral hole 8G. , And the tank port T is closed,
Although it is a completely differential circuit, the pressure on the rod side is higher than the pressure on the head side by the pressure loss due to the restriction between B port → differential port D, and damping is effective.

Differential control position (e): Since the A port is connected to the pressure source port P, the B port is connected to the differential D port, and the tank port T is closed, both meter-in side and meter-out side throttling effects The valve pressure loss is minimized. During deceleration, not only the differential throttle control position (d) → meter-in / meter-out control position (c) and the valve is closed, but the oil supplied from the pressure source is throttled by the meter-in throttle, and B port → differential port D, Since the outflow amount from the rod side is throttled by the meter-out throttle of B port → tank port T, the pressure rises on the rod side, and the deceleration can be surely performed by the meter-out control.

A mode of speed control of the injection cylinder 11 using the injection control valve 1 is shown in a block circuit in FIG. The speed command value that has entered the injection speed control means in the controller unit 100 is converted into a voltage and output to the amplifier 30. The injection control valve 1 is controlled by the output of the amplifier, and the speed of the injection cylinder 11 is controlled by the output flow rate of the valve 1.
The speed pattern of the injection cylinder 11 is set with respect to, for example, the cylinder stroke position.
Detecting the rod position of No. 1 by the position sensor 27, and further creating a speed signal by the differential value of the output of the position sensor 27, and comparing the speed signal for each stroke position with the speed command value in the injection speed control means. Thus, normally, the real-time feedback control of the speed is performed by the difference from the command value to match the actual speed with the target speed.

(2) Pressure increase control, injection is decelerated immediately before the filling of the molten metal into the mold is completed, and the injection control valve 1 is set to the pressure control position near the neutral position.
Switch to (b) and perform pressure increase control. A pressing circuit (pressure increase) control mode of the injection cylinder 11 in this case is shown by a block circuit in FIG. A pressure command is input to the pressure control means in the controller unit 100, detected by the pressure sensor 26 in the head side chamber of the injection cylinder 11, and fed back to the pressure control means to perform feedback control based on the difference from the target value. Real-time feedback control of pressure is possible.

The pressure source port P → A port and the A port → tank port T are notched 8J in the main spool 8,
The flow rate is controlled with a small area of 8K. As described above, the pressure on the cylinder head side, that is, the A port is detected, and the controller 100 performs feedback control to automatically control the flow rate of at least one of the pressure source port P → A port and the A port → tank port T. As a result, the pressure on the head side is controlled to the target pressure. At the time of this pressure control, the B port → tank port T is opened wider than the P → A port and the A port → tank port T, and pressure loss does not occur and the double-action circuit is meter-in control. Here, by the arithmetic processing in the controller unit 100,
The command voltage to the amplifier 31 is limited to a certain range. This operation will be described below with reference to the flowchart of FIG.

FIG. 8 is a flow chart for explaining the operation mode of the command control means provided in the controller section 100 for limiting the electric command at the time of boosting pressure. When the command control means starts, first, stepS1 With controller section 100
Receives the pressure signal from the pressure sensor 26. Then
In step S2, this pressure signal is compared with the value of a predetermined pressing force command, and feedback such as PID control is performed to calculate the command voltage VF. The command voltage VF after this feedback is compared with the minimum value Vmin and the maximum value Vmax in steps S3 and S4.

Here, the minimum value Vmin is the minimum value in the range of the command voltage that does not cause the injection cylinder 11 to shrink or generate an excessive output even if there is an operation delay in the injection control valve 1. The maximum value Vmax is the maximum value of the range of the command voltage that does not cause the injection cylinder 11 to shrink or generate an excessive output even if there is an operation delay in the injection control valve 1. In step S3, if the command voltage V
If F is greater than the minimum value Vmin and is greater than the maximum value Vmax, the process proceeds to step S4. If the command voltage VF is less than the maximum value Vmax, the process proceeds to step S5 and the command voltage is reached. VF is converted into an analog signal as it is and output to the injection control valve 1 as a command.

On the other hand, in step S3, if the command voltage VF is smaller than the minimum value Vmin, the process proceeds to step S6, where the minimum value Vmin is replaced with the command voltage VF and converted into an analog signal. It is output to the injection control valve 1 as a command. If the command voltage VF is larger than the maximum value Vmax at step S4, the process proceeds to step S7, where the maximum value Vmax is replaced with the command voltage VF and converted into an analog signal, which is passed through the amplifier 31 and the injection control valve. It outputs to 1 as a command.

Here, when the feedback control executed during the pressure increasing control includes I (integration) control, the upper limit of the integral value is limited by the arithmetic processing in the controller section 100. The operation in this case will be described below with reference to the flowchart of FIG. FIG. 13 shows an operation mode of the command control means provided in the controller section 100 for limiting the upper limit of the integrated value in the I (integration) control. The deviation e (t) between the target pressure and the measured pressure is calculated in the step of.

Next, in the stage of processing 2, if VV
(t) = KI × (SumI (t−dt) + e (t)) + α
Is calculated, and as a result, when the expression in conditional branch 1 of the next stage is satisfied, that is, VV (t) is Vmax or less, or Vmi
In the case of n or more, the calculation of the stage of processing 3 is executed, that is, VF (t) = VV (t) SumI (t) = SumI (t-dt) + e (t) VF (t) according to the control procedure
Is output.

On the other hand, when the expression in conditional branch 1 is not satisfied, that is, VV (t) is larger than Vmax, or V
If it is smaller than min, VV (t) obtained in process 1
Without adopting the above, the process newly moves to the stage of processing 4 and the operation of the following equation is executed, that is, VF (t) = KI × (SumI (t-dt)) + α SumI (t) = SumI (t -Dt) is output as VF (t). Here, processing 3, processing 4
The lower expression in the table prepares SumI to be used in the next process, that is, the process at time t + dt.

The operation on the rod contracting side (returning side) performed after the pressure increasing control is completed is performed by the main spool 8 of the control valve 1.
3 is moved from the neutral position to the left in FIG. 3, the B port is connected to the pressure source port P via the notch 8I (throttle), and the A port and the differential port D are the notches 8K and the lateral holes 8 which are throttles.
The return throttle control position (f) connected to the tank port T through a part of the opening of G, the A port is connected to the tank port T, the B port is connected to the pressure source port P, and the differential port D is connected. Is a return control position (g) where is connected to the tank port T through a part (opening) of the lateral hole 8G.
The pilot check valve 14 is kept open at that time.

FIG. 14 shows a hydraulic circuit for the press hydraulic cylinder of the powder molding machine according to the second embodiment of the present invention. This hydraulic circuit is similar to the hydraulic circuit shown in FIG.
Corresponding parts are provided with the same reference numerals. Hydraulic cylinder 11 for press for powder molding, flow rate pressure control valve for controlling flow rate and pressure (abbreviated as control valve)
1, a pressure sensor 26 for detecting the pressure on the head side of the hydraulic cylinder 11, a no-leak valve 3 used for the purpose of stopping and holding
7. A hydraulic circuit is configured to include a switching valve 36 for surely reducing the rod side pressure of the hydraulic cylinder 11 to the tank pressure (≈0 kgf / cm ² ) during pressure control. The pressure source is composed of pumps 15A, 15B and relief valves 20, 32, 35, and the pressure is set by a combination of excitation of switching valves 21, 33, 34.

In the above hydraulic circuit, the control valve 1 constitutes a single control valve used for speed control and pressure control, which is similar to the control valve 1 in the hydraulic circuit shown in FIG. The mode of pressure control will be described below with reference to FIG. Lowering operation: A speed pattern is set for the position of the hydraulic cylinder 11, the no-leak valve 37 and the switching valves 21, 34 are switched, and the control valve 1 is moved to the position (b) → (c) → (d).
The pressure source pressure is applied to the head side of the hydraulic cylinder 11 by opening in this order. The pressure oil discharged from the rod side returns to the tank through the no-leak valve 37 and the B → T line of the control valve 1.
The speed of the hydraulic cylinder 11 is P → A, B → T of the control valve 1.
It is controlled by the opening area of the line stop.

Pressure control: When the pressure sensor 26 detects that the tip of the hydraulic cylinder 11 has come into contact with the molded product and the pressure on the head side has risen above a preset threshold value, it is judged to be the timing for starting pressure control, and the flow rate is determined. Switch from control to pressure control. The threshold value is set to an appropriate value by comparing the head side pressure of the hydraulic cylinder 11 generated during speed control with the head side pressure of the hydraulic cylinder 11 generated during pressure control.

When the control valve 1 is switched to the pressure control, the switching valve 21 is deenergized and the switching valves 33 and 36 are excited. In this case, the control valve 1 is in the position (c). At the position (c), there are flows of P → A and A → T, and the pressure of the switching port A is controlled to an intermediate pressure between the pump pressure source and the tank by the flow rate to each. That is, the area of P → A and A → T changes depending on the stroke position of the control valve 1, so that the pressure of the switching port A is determined.

A pressure pattern is set with respect to time, and the pressure is detected by the pressure sensor 26 and is feedback-controlled to control the pressure on the head side, that is,
The pressing force of the hydraulic cylinder 11 can be controlled. At this time, in order to surely drop the pressure of the hydraulic cylinder 11 to 0 kgf / cm ² without causing a sudden pressure change, the set value at the final point of the pressure control is appropriately lower than the offset value of the pressure sensor 26. Automatically or manually. In the case of the second embodiment, the control of the control valve 1 by the command control means is the same as in the first embodiment, and the spool position of the control valve 1 is controlled during the pressure control operation of the hydraulic cylinder 11. It goes without saying that the electric command is limited to control the moving range of the spool so as to prevent excessive pressure or negative pressure.

When the I (integral) control is included in the control method, the electric command deviates from the electric limit range in the process of determining the electric command for controlling the spool position of the control valve 1. In this case, as in the first embodiment, feedback control is performed while maintaining the integrated value of the pressure deviation at the value before it deviates from the range, so that excessive pressure is prevented from occurring and stable operation is performed. Needless to say.

Ascending operation: The end point in the pressure pattern set with respect to time is determined as the rising start timing, and the pressure control is switched to the ascending operation. Simultaneously with this switching, the switching valves 33 and 36 are de-energized and the switching valve 21 is excited. Control valve 1 switches to position (a),
The pressure oil of the pressure source is caused to flow into the rod side of the hydraulic cylinder 11. The pressure oil on the head side returns to the tank via the line A → T of the control valve 1. The speed of the hydraulic cylinder 11 depends on the control valve 1
It is controlled by the aperture area of the P → A and B → T line diaphragms.

Stop: When the position of the hydraulic cylinder 11 reaches the most contracted position, the ascending operation is switched to the stopped state. When switched to the stopped state, the excitation of the switching valves 21 and 34 is released, and the pumps 15A and 15B are unloaded. The control valve 1 returns to the neutral position (b) to reduce the head pressure and rod pressure of the hydraulic cylinder 11 to the tank pressure. At that time, depending on the switching timing of the no-leak valve 37 and the control valve 1, pressure may be retained on the rod side of the hydraulic cylinder 11 and the hydraulic cylinder 11 may be reduced by the amount of compressibility. The position accuracy does not need to be so high, so there is no problem.

[0062]

As described above, according to the present invention, when a single control valve is used to perform flow rate control and pressure control for a hydraulic cylinder such as an injection cylinder for injecting molten metal, the pressure of the hydraulic cylinder is increased. Since the electric command for controlling the spool position of the control valve at the time of operation is restricted so as to restrict the moving range of the spool, feedback control for increasing or decreasing the electric command rapidly and with a large change In this case, it is possible to prevent the cylinder overrun phenomenon due to the valve operation delay.

The present invention also provides that this electrical command limitation
By preventing the operation of the piston rod in the hydraulic cylinder to the side that reduces the pressure to the load, the negative pressure generated on the load side can be avoided and the product will suffer shrinkage cavities and other phenomena that reduce strength. The product strength is maintained. Further, since the above-mentioned restriction given to the electric command is to prevent the excessive output of the hydraulic cylinder from being generated, the pressure on the load side such as the molten metal in the mold rises excessively. To prevent the deterioration of quality and enhance the safety in work.

According to the present invention, when the integrated value of the pressure deviation deviates from the limit given to the electric command in the calculation process for determining the electric command for controlling the spool position of the control valve, the pressure deviation By performing feedback control while keeping the integral value at the value before it deviates from the range, overshoot due to operation delay of the control valve is eliminated and excessive force is not applied to the machine equipment to extend the machine life. It is possible.

In the present invention, the target value at the final point is 0 kgf /
When performing pressure control that is cm ² , by setting the effective target value at the final point of pressure control to an appropriately low value corresponding to the offset amount of the pressure detector, either automatically or manually. The pressure can be smoothly and reliably reduced to 0 kgf / cm ² without causing a sudden pressure change, and the effect of preventing cracking of the molded product is exhibited.

[Brief description of drawings]

FIG. 1 is a structural view showing a cross section of a main part of a hydraulic control valve 1 used in a high pressure casting machine according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a spool unit in FIG.

FIG. 3 is a hydraulic circuit diagram of an injection hydraulic cylinder of the high-pressure casting machine according to the first embodiment of the present invention.

FIG. 4 is a symbol diagram showing a control position of the hydraulic control valve 1 shown in FIG.

5 is a block circuit diagram showing an aspect of a speed control means of the injection cylinder 11 shown in FIG.

6 is a block circuit diagram showing an aspect of pressure control means of the injection cylinder 11 shown in FIG.

7 is an opening area diagram showing an opening characteristic of the hydraulic control valve 1 shown in FIG.

FIG. 8 is a flowchart illustrating an operation mode of command control means related to the hydraulic control valve 1 shown in FIG.

FIG. 9 is a diagram illustrating control characteristics in a general I (integration) control method.

FIG. 10 is a diagram illustrating a control characteristic in the I (integration) control method according to the present invention.

FIG. 11 is a diagram illustrating a feedback control characteristic under the influence of an offset amount of a general pressure sensor.

FIG. 12 is a diagram illustrating a feedback control characteristic according to the present invention under the influence of an offset amount of a pressure sensor.

FIG. 13 is a flowchart showing an algorithm when I (integration) control is included in the feedback control according to the embodiment of the present invention.

FIG. 14 is a hydraulic circuit diagram of a press hydraulic cylinder of the powder molding machine according to the second embodiment of the present invention.

[Explanation of symbols]

1 ... Hydraulic control valve 10 ... Controller 11 ... Hydraulic cylinder 12 ... Hydraulic line 13 ... Tank line 14 ... Pilot check valve 15 ... Hydraulic pump 16 ... Differential check valve 17 ... Check valve 23 ... Oil feed pipe 25 ... Oil return pipe 26 ... Pressure sensor 27 ... Position sensor 28 ... Linear differential transformer 29 ... Amplifier 30 ... Amplifier 31 ... Amplifier 32 ... Relief valve 33 ... Switching valve 34 ... Switching valve 35 ... Relief valve 36 ... Switching valve 37 ... No leak valve A ... Actuator port B ... Actuator port D ... Differential port P ... Pressure source port T ... Tank port

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location G05D 16/20 G05D 16/20 A

Claims (10)

[Claims] 1. A hydraulic press device in which flow rate control and pressure control of a hydraulic cylinder for pressing are performed by a single control valve provided in a hydraulic system of the cylinder, wherein the control valve of the control valve is operated during a pressure increasing operation of the hydraulic cylinder. A pressure control method for a hydraulic press device, characterized in that an electric command for controlling a spool position is restricted to regulate a moving range of the spool. 2. The pressure of the hydraulic press device according to claim 1, wherein the limit given to the electric command is to prevent the operation of the piston rod in the hydraulic cylinder to the side that reduces the pressure against the load. Control method. 3. The pressure control method for a hydraulic press device according to claim 1, wherein the limit given to the electric command is to prevent excessive output of the hydraulic cylinder. 4. A feedback for controlling the pressure in the pressure chamber of the hydraulic cylinder or in the hydraulic pipe by feeding back an integrated value of a pressure deviation between a target value and an actually measured value when controlling the control valve during the pressure increasing operation of the hydraulic cylinder. When the feedback value including the integral value of pressure deviation deviates from the limit given to the electric command in the process of determining the electric command for controlling the spool position of the control valve including the control method, the pressure 4. The pressure control method for a hydraulic press device according to claim 1, 2 or 3, wherein feedback control is performed while maintaining the integrated value of the deviation at a value before it deviates from the outside of the range. 5. When performing the pressure control in which the target value at the final point is 0 kgf / cm ² , the substantial target value at the final point of the pressure control is appropriately low corresponding to the offset amount of the pressure detector. 5. The pressure control method for a hydraulic press device according to claim 1, wherein the value is automatically or manually reset. 6. A hydraulic press device in which flow rate control and pressure control of a hydraulic cylinder for pressing are performed by a single control valve provided in a hydraulic system of the cylinder, wherein the control valve of the control valve is operated during a pressure increasing operation of the hydraulic cylinder. Command control means for restricting the movement range of the spool by restricting the electric command for controlling the spool position so that the value does not deviate from the set region is provided in the electric control system of the control valve. A pressure control device for a hydraulic press device. 7. The pressure control device for a hydraulic press device according to claim 6, wherein the command control means is for preventing the operation of the piston rod in the hydraulic cylinder to reduce the pressure with respect to the load. 8. The pressure control device for a hydraulic press device according to claim 6, wherein the command control means is for preventing excessive output of the hydraulic cylinder. 9. A feedback for controlling the pressure in the pressure chamber of the hydraulic cylinder or in the hydraulic pipe by feeding back an integrated value of the pressure deviation between the target value and the measured value when controlling the control valve during the pressure increasing operation of the hydraulic cylinder. In the calculation process of determining the electric command for controlling the spool position of the control valve and the control valve, when the feedback value including the integrated value of the pressure deviation deviates from the limit given to the electric command, this pressure deviation is 9. The hydraulic press device according to claim 6, 7 or 8, further comprising: command control means for performing feedback control while maintaining the integrated value of the above value outside the range. Pressure control device. 10. When performing a pressure control in which the target value at the final point is 0 kgf / cm ² , the substantial target value at the final point of the pressure control is appropriately low corresponding to the offset amount of the pressure detector. 10. The pressure control device for a hydraulic press device according to claim 6, 7, 8 or 9, wherein setting control means for resetting the value automatically or manually is provided in the electric control system of the control valve.