JPH0767607B2 - Cylinder position control method and device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and a device for position control of a cylinder piston of a cylinder device used for a hydraulic mechanism, for example, molten resin or molten metal in a mold. And method for controlling the position of a cylinder piston such as an injection cylinder and a pressurizing cylinder of an injection molding machine or a die casting machine for injecting and filling the above material and an extruder cylinder for extruding the material through a die. .

[Prior Art] Conventionally, a method of controlling a cylinder piston of an injection cylinder of an injection molding machine or a die casting machine is as shown in FIG. This is a system in which the position of the cylinder piston 2 of the injection cylinder 1 is detected by the position detector 3 and the cylinder piston 2 is controlled to reach a predetermined speed when it reaches a predetermined position. Usually uses a servo valve 25 and is configured as follows.

As shown in the figure, the speed setter 20 is preset with a desired speed v with respect to the position st of the cylinder piston 2 detected by the position detector 3, and this speed command value v is set by an external command. Output to the servo valve controller 22. Here, at the position st, the cylinder piston 2 is the most cylinder 1
The state of pulling in is 0, and the operation in the illustrated fwd direction is represented by a positive symbol and the operation in the bwd direction by a negative symbol. The servo valve controller 22 uses the speed command value v and the speed measurement value vm obtained by time-differentiating the position st detected by the position detector 3 with the speed detector 21 to determine the servo valve.
An opening signal vo for driving 25 is calculated and output. The illustrated servo valve 25 is of a flow rate control type and controls the speed of the cylinder piston 2 to a predetermined value by increasing or decreasing the flow rate of the hydraulic oil from the hydraulic pressure source 24 in accordance with the opening signal vo. There is. Reference numeral 23 is a direction switching valve, which functions to switch the moving direction of the cylinder piston 2 by exciting the solenoid 23a or 23b.

As shown in the figure, the speed setter 20 is set to the speed v with respect to the position st of the cylinder piston 2, and the speed is only the target v1, v2, v3, ... −
> V2, v2−> v3, ... The shift process was basically stepwise adjustment, which is not the target of control. Further, the transient characteristics such as the overshoot amount ovs and the acceleration / deceleration adjustment acc as shown in FIG. 3 which appear at the time of shifting are controlled by the fixed gain adjustment of the servo valve controller 22.

[Problems to be Solved by the Present Invention] In the conventional method of setting the speed with respect to the stroke, the opening amount of the servo valve, which is the control amount, is basically equivalent to the speed value of the cylinder piston. Therefore, there is an advantage that the control device can be easily configured by setting this speed value. However, particularly in the process of filling and pressurizing the molding material into the mold cavity, it may be desirable to be able to control the change in the volume of the molding material with respect to time, that is, the stroke of the injection cylinder piston, as molding conditions. . In particular, as precision molding and high-quality molding are aimed at, conventional stepwise adjustment of speed has a limit in stably satisfying delicate molding conditions in the case of a large change in load.

[Means for Solving the Problems] In the present invention, the moving stroke amount of the cylinder piston is predetermined as a target locus with respect to time, and when the cylinder piston is operated so as to follow the target locus, Depending on the amount of deviation between the movement stroke of the cylinder piston that is the target trajectory and the actual movement stroke,
The cylinder head chamber pressure and the rod chamber pressure that actuate the cylinder piston are independently changed to control the movement stroke amount of the cylinder piston.

Further, as a control device therefor, a cylinder device in which the head chamber and the rod chamber are respectively connected to independent pressure sources, and an independent device capable of controlling the pressure acting on the head chamber and the rod chamber according to the magnitude of the input signal are provided. A pressure control valve, a position detector that detects the position of the cylinder piston and outputs an electrical signal according to that position, and a command signal setting unit that sets and commands the stroke stroke of the cylinder piston with respect to time as a target trajectory. The pressure control valve via an independent gain setting device for the head chamber and the rod chamber according to the deviation amount between the output signal from the command signal setting unit and the output signal from the position detector. And a feedback controller that outputs a drive signal to the pressure adjustment drive unit.

[Operation] The movement stroke amount of the cylinder piston is set in advance as a target locus with reference to the time from the start of operation of the cylinder piston, and the movement stroke amount of the cylinder piston and the actual movement stroke of the cylinder piston are set as the target locus. By independently changing the pressure acting on the cylinder head chamber and the rod chamber that drive the cylinder piston in accordance with the amount of deviation from the amount, the cylinder stroke so that the movement stroke amount of the cylinder piston with respect to time follows the target locus. Controls piston operation. That is,
If the actual movement stroke amount has not reached the target trajectory,
The pressure on the cylinder chamber side that contributes to the moving direction of the cylinder piston is increased according to the deviation amount, and conversely, the pressure on the other cylinder chamber side is decreased according to the deviation amount. If the actual movement stroke amount is too large with respect to the target locus, the pressure on the cylinder chamber side that contributes to the movement direction of the cylinder piston is reduced according to the deviation amount, and conversely the pressure on the other cylinder chamber side is reduced. Increase according to the amount of deviation. By repeating such an operation at every minute time interval, it becomes possible to control so that the movement stroke amount of the cylinder piston with respect to time follows the target locus.

[Example] An explanation will be given with reference to FIG. 1 is an injection cylinder of an injection molding machine or a die casting machine, which has a cylinder piston 2.
A cylinder head chamber 1a and a cylinder rod chamber 1b are formed. The cylinder head chamber 1a is connected to a pump 5a and a pressure control valve 6a which are independent hydraulic sources by a hydraulic circuit, and the cylinder rod chamber 1b is also a pump 5b and a pressure control valve which are independent hydraulic sources by a hydraulic circuit. It is connected to 6b. Reference numeral 4 is an electric motor that drives the pumps 5a and 5b. Here, the pressure control valves 6a, 6b are electromagnetic relief valves that are so-called electromagnetic proportional automatic pressure control valves, and can arbitrarily control the pressure of each hydraulic pressure source by a predetermined electric signal.
That is, the pressure control valves 6a and 6b control the operating force of the cylinder piston 2 according to the magnitude of the input signal, and, for example, increase the control pressure of the pressure control valve 6a and increase the control pressure of the pressure control valve 6b. If lowered, the pressure oil from the pump 5a enters the cylinder head chamber 1a, and the hydraulic oil from the cylinder rod chamber 1b and the pump 5b is released to the tank 7 via the pressure control valve 6b. Outgoing direction (fwd
Direction). On the contrary, if the control pressure of the pressure control valve 6b is increased and the control pressure of the pressure control valve 6a is decreased, the operation opposite to the above is performed, and the cylinder piston 2 operates in the return direction (bwd direction). . Further, 3 is a position detector composed of a potentiometer, which can detect the stroke position of the cylinder piston 2 and output an electric signal corresponding to the position.

Reference numeral 9 is a model portion created in the microcomputer for setting and instructing the change amount of the movement stroke of the cylinder piston 2 with respect to time as a target locus, that is, a command signal setting portion, and 10 is an input signal from the position detector 3 and It is a deviation detection unit that compares the input signal from the command signal setting unit 9 and outputs an output signal according to the deviation amount of these two input signals. 8a, 8
Reference numeral b denotes a gain setting unit that receives a signal from the deviation detection unit 10 and appropriately processes the signal, and outputs a predetermined output signal corresponding to the signal, which corresponds to the pressure control valves 6a and 6b, respectively. These command signal setting unit 9, deviation detection unit 10 and gain setting unit 8
Feedback controllers 11 are constituted by a and 8b. 12a, 12
Reference numeral b denotes a driver that controls the pressures of the pressure control valves 6a and 6b according to the magnitudes of the output signals from the gain setting units 8a and 8b, respectively, and constitutes a pressure adjustment drive unit.

Now, when a controller (not shown) gives an operation command for the injection cylinder 1 to the feedback controller 11, as shown in FIG. 1, the command signal setting unit 9 of the feedback controller 11 causes the cylinder piston 2 for the time t. The desired locus of the moving stroke st is pre-programmed, and the target moving stroke st is time-divisionally processed, for example, every few milliseconds upon receiving the operation command, and is input to the deviation detecting unit 10. Here, the movement stroke st is 0 when the cylinder piston 2 is most retracted into the cylinder 1.
The illustrated operation in the fwd direction is represented by a positive symbol, and the operation in the bwd direction is represented by a negative symbol. The deviation detector 10 uses the position detector 3
The deviation amount e (e = st-stb) from the actual position stb of the cylinder piston 2 detected by is calculated, and this is calculated as the gain setting unit 8a,
Type in 8b. Here, the gain setting units 8a and 8b are configured to adjust the deviation e
Based on the result of, a predetermined P (proportional) I (integral) gain k1, k
By multiplying by 2, the deviation amount e of the stroke is converted into pressure command values v1 and v2 which are control amounts. Here, the characteristics of the gains k1 and k2 basically have opposite sign characteristics with respect to the deviation amount e as shown in the figure, and the magnitude of the inclination is actually operated, and experience is utilized, So that the tracking ability is the highest,
Normally, each is determined, but in order to maintain the force balance of the cylinder piston 2, a value that roughly considers the area difference between the cylinder head chamber 1a and the rod chamber 1b, that is, the distribution of the inverse ratio of both areas is distributed. Becomes Drivers 12a, 12b use pressure command values v1, v2
Signal p1, which actually drives the electromagnetic relief valves 6a, 6b
The pressure in the cylinder head chamber 1a and the rod chamber 1b is controlled by converting to p2.

As an example, when the cylinder piston 2 is moved in the fwd direction, the deviation amount e is defined as above (e = st).
According to −stb), the fact that e has a positive value is nothing but the fact that the actual movement stroke amount stb has not reached the target locus st. Therefore, the feedback controller 11 determines the pressure v1 (p1) on the cylinder chamber (head chamber in this example) side that contributes to the moving direction of the Linda piston 2 according to the deviation amount e from the characteristics of the gains k1 and k2. The pressure v2 (p2) on the other cylinder chamber (rod chamber in this example) side is decreased in accordance with the deviation amount e, so that the cylinder piston 2 is pushed out in the fwd direction. do. If the actual movement stroke amount stb is over the target locus st, the deviation amount e takes a negative value.
The feedback controller 11 reduces the pressure v1 (p1) on the cylinder chamber (head chamber in this example) side that contributes to the moving direction of the cylinder piston 2 according to the deviation e from the characteristics of the gains k1 and k2. On the contrary, since the pressure v2 (p2) on the other cylinder chamber (rod chamber in this example) side is increased in accordance with the deviation amount e, the cylinder piston 2 is pushed back in the bwd direction. . As described above, the actual movement of the cylinder piston is made to follow the target locus st.

FIG. 4 shows, in another embodiment, an example in which the method and apparatus of the present invention are applied to a pressurizing cylinder 31 of a die casting machine for disk wheel molding. As shown in the figure, the upper mold 33, the lower mold 35 that can be opened and closed in the vertical direction, and the four cores 34 that can be moved in the horizontal direction are combined, and the mold clamping mechanism (not shown) allows The molten metal 37 in the injection sleeve 39 is clamped in the cavity 38 formed thereby.
Is filled with the ascending action of the injection plunger 36 and the plunger tip 36a by the action of an injection cylinder (not shown) (the state in which the molten metal 37 is completely filled in the cavity 38 is shown). Cylinder piston 32 of pressurizing cylinder 31 after a predetermined time (pressurizing time lag) has elapsed from the completion of filling molten metal 37
A pressurizing plunger 40 attached to the cavity is projected into the cavity 38 to pressurize the molten metal 37 in the cavity 38 to perform a feeder operation.

At this time, it is best to control the operation of the pressurizing plunger 40 so that the history of the protrusion stroke amount into the cavity 38 follows the predetermined target locus with the lapse of time from the start of the operation. To achieve this, the applicants have previously presented the method and apparatus in Japanese Patent Application No. 63-244552. At this time, the pressure control valve controls only the operating pressure of the head chamber 31a of the pressurizing cylinder 31, that is, fwd
The movement in the bwd direction was due to the acting force of the injection plunger 36. By configuring this as the present invention, the head chamber of the pressure cylinder 31
The pressures of 31a and rod chamber 31b were controlled at the same time, and the response was remarkably improved, and the followability was improved to a deviation width of less than half of the conventional one.

In the embodiment, the injection cylinder of the injection molding machine or the die casting machine, and the position control of the cylinder piston of the pressurizing cylinder 31 of the die casting machine for disc wheel molding are shown. It can also be used to control the position of the cylinder piston of the cylinder or other cylinders.

[Effect of the Invention] Like the injection cylinder of an injection molding machine or die casting machine, the load is relatively light during the injection of the molding material into the mold cavity, and the load increases as soon as the filling is completed. Even when the pressure varies greatly during the stroke, or when the sliding resistance of the pressure cylinder varies over time, the position of the cylinder piston with respect to time can be ensured with good responsiveness. Can be controlled to follow.

[Brief description of drawings]

FIG. 1 is a control circuit diagram showing one embodiment of an apparatus for carrying out the method of the present invention, and FIG. 2 is a control circuit diagram showing one example of an apparatus for carrying out a method similar to the present invention. 3, FIG. 3 is a stroke-speed diagram showing a state at the time of shifting, and FIG. 4 is a control circuit diagram showing another embodiment of the apparatus for carrying out the method of the present invention. 1 ... Injection cylinder, 2 ... Cylinder piston, 1a ... Cylinder head chamber, 1b ... Cylinder rod chamber, 3 ... Position detector, 5a, 5b ... Pump, 6a, 6b ... Electromagnetic relief valve, 8a , 8b …… Gain setting section, 9 …… Model section (command signal setting section), 10 …… Deviation detection section, 11 …… Feedback controller, 12a, 12b …… Driver (pressure adjustment drive section), 31 …… Pressurized silane, 36 ... Injection plunger, 38 ... Cavity, 40 ... Pressurized plunger.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B30B 15/18 F 8718-4E

Claims (2)

[Claims] 1. A moving stroke of a cylinder piston which is set as the target locus when a moving stroke of the cylinder piston is predetermined as a target locus with respect to time and the cylinder piston is operated so as to follow the target locus. The cylinder head chamber pressure and the rod chamber pressure that actuate the cylinder piston independently according to the amount of deviation between the amount and the actual movement stroke amount, thereby controlling the movement stroke amount of the cylinder piston. A cylinder position control method characterized by the above. 2. A cylinder device in which the head chamber and the rod chamber are respectively connected to independent pressure sources, and an independent pressure control valve capable of controlling the pressure acting on the head chamber and the rod chamber according to the magnitude of an input signal. It also has a position detector that detects the position of the cylinder piston and outputs an electrical signal according to that position, and a command signal setting unit that sets and commands the movement stroke of the cylinder piston as a target locus with respect to time. Adjusting the pressure of the pressure control valve via an independent gain setting device for the head chamber and the rod chamber according to the deviation amount between the output signal from the command signal setting unit and the output signal from the position detector. A cylinder position control device comprising: a feedback controller that outputs a drive signal to a drive unit.