JP3055441B2 - Control method of injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling an injection molding machine suitable for use in controlling an actuator for, for example, injecting a resin or opening and closing a mold.

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine, for example, an actuator for injecting a resin, opening and closing a mold, etc.
It is operated by hydraulic oil supplied from the pump, and the flow rate of oil supplied from the pump is adjusted according to the required operating speed of the actuator, such as the injection speed of the resin and the opening and closing speed of the mold. By adjusting with a valve, the operating speed is adjusted. At this time, the flow control valve adjusts the opening degree of the valve based on a flow command corresponding to the required operation speed of the actuator, and supplies a desired flow rate of hydraulic oil to the actuator.

Some of such actuators have a structure including a plurality of pumps. When the operating speed is high, the plurality of pumps are operated simultaneously, and when the operating speed is low, only one pump is operated. Unnecessary pumps are unloaded (no load state), and control is performed so that the supply flow rate from the pumps is reduced more than necessary.

[0004]

However, the conventional method of controlling an injection molding machine as described above has the following problems. For example, when two pumps, a large pump and a small pump, are provided to operate the actuator, the relationship between the flow command and the flow rate at the flow control valve when both the large pump and the small pump are operated is shown in FIG. 6
It becomes as shown in. FIG. 7 shows the relationship between the flow rate command and the flow rate at the flow rate control valve when only the large pump is operated. Then, as shown in FIG. 8, the load state of the two pumps is switched at a predetermined threshold value A, and only the large pump is operated when the threshold value is equal to or less than the threshold value A. When the two pumps are controlled to operate, the flow rate supplied from the pump to the primary side of the flow regulating valve and the primary side of the pressure compensating valve controlling the primary pressure of the flow regulating valve before and after the threshold value A And the relationship between the flow rate command and the flow rate is discontinuous due to an increase in the differential pressure (valve differential pressure) between the primary side and the secondary side of the flow control valve, which should be kept constant. turn into.

For this reason, in order to change the operation speed of the actuator, when the flow rate command is changed before and after the threshold value A, for example, from the threshold value A or less to the threshold value A or more, the large pump 1 operates. The state is switched from the single pump to the large pump and the small pump, and the flow rate actually controlled by the flow control valve is increased at a stretch even though the opening of the flow control valve is slightly changed. As a result, there is a problem that the operation speed of the actuator changes abruptly.

Further, for example, when the operation speed required by the actuator is a speed corresponding to the flow rate indicated by reference numeral B in the drawing, a flow rate command for controlling the flow rate of the hydraulic oil by the flow rate control valve is issued. There is also the problem that you cannot do that.

The present invention has been made in view of the above points, and provides a control method of an injection molding machine capable of smoothly controlling the operation speed of an actuator over the entire flow rate range from a pump. With the goal.

[0008]

The invention according to claim 1 is
A plurality of pumps for operating the actuator are connected to an actuator provided in the injection molding machine via a flow control valve, and adjust the flow rate from the flow control valve and selectively operate the plurality of pumps. A control method for an injection molding machine comprising control means for controlling the operation speed of the actuator by switching to the control means, wherein the control means sets an operation speed set value of the actuator based on a stroke position of the actuator. Setting, and a first process of setting a flow command value at the flow control valve corresponding to the operating speed set value, and the flow command value set in the first process is out of a predetermined range. After correcting the flow rate command value, it is output to the flow rate regulating valve, and when the flow rate command value is within the range, the flow rate Performing a second process to output to the valve regulation, while switching the operation of the plurality of pumps based on the flow command value determined in the first process, the flow command output in the second process It is characterized in that the flow rate from the flow control valve to the actuator is controlled based on the value.

According to a second aspect of the present invention, in the control method of the injection molding machine according to the first aspect, the actuator causes the screw to advance in the axial direction in the cylinder to inject the resin into the mold from the injection nozzle. It is characterized by being for driving a cylinder.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Here, the control method of the injection molding machine according to the present invention will be described using an example in which the injection speed is controlled by applying the method to an actuator for injecting resin, for example.

FIG. 1 shows an injection speed control circuit of an injection molding machine. In this figure, reference numeral 1 denotes an actuator for an injection cylinder. The actuator 1 is driven by hydraulic pressure of hydraulic oil supplied from, for example, an electric small pump (pump) 2 and a large pump (pump) 3.

The small pump 2 and the large pump 3 are connected to a small pump load solenoid valve 4 and a large pump load solenoid valve 5 for switching between supply and cutoff of hydraulic pressure from the respective pumps to the primary side of the flow proportional valve 6. Have been. By operating the small pump load solenoid valve 4 and the large pump load solenoid valve 5, the load of the small pump 2 and the large pump 3 can be selected.

The small pump load solenoid valve 4 and the large pump load solenoid valve 5 are connected on the secondary side to a flow proportional valve (flow control valve) 6. In the flow proportional valve 6, the hydraulic oil supplied from the small pump 2 and the large pump 3 connected by the small pump load solenoid valve 4 and the large pump load solenoid valve 5 by changing the opening of the valve (not shown). The flow rate is adjusted.

Further, a pressure compensating valve 7 is provided in a bypass circuit of the flow proportional valve 6, and a pressure proportional valve 8 is connected to a vent line side of the pressure compensating valve 7.

The secondary side of the flow proportional valve 6 is connected to an electromagnetic valve 9.
Is connected to the actuator 1 through the solenoid valve 9.
To switch the operation direction of the actuator 1.

Such a hydraulic circuit is controlled by a control unit (control means) 10. In the control section 10, the stroke position of the actuator 1 is detected by the pulse encoder 11, and the CPU 12 performs the processing described later based on the detected data, and the small pump load solenoid valve 4, the large pump load solenoid valve 5, the flow proportional valve 6 , The operation of the solenoid valve 9 is controlled.

As shown in FIG. 2, an injection cylinder 13 driven by an actuator 1 having such a hydraulic circuit (see FIG. 1) injects resin by advancing an injection screw 15 in a heating cylinder 14. It is supposed to. That is, the pulse encoder 1 shown in FIG.
1, the stroke position of the actuator 1 is detected.
This means that the position of No. 5 has been detected.

Next, a method of controlling the actuator 1 of the injection molding machine by the control unit 10 will be described. In advance, as shown in FIG. 2, the injection speed at the time of operating the injection cylinder 13 is accelerated from the stroke start end side of the injection cylinder and then arbitrarily changed as it approaches the stroke end side. Hereinafter, this is referred to as a “speed setting value”, and is set so as to be changed to, for example, four stages of V1 to V4. Distance; hereinafter referred to as "switching position"
) Are set as S1 to S3. The speed setting values V1 to V4, the switching positions S1 to S3, and the predetermined first and second threshold values L and H of the flow rate command are input by the KEY 16 shown in FIG. (Memory) 17.

After the initial setting has been performed, the injection cylinder 13 is operated. FIG. 3 is a flowchart showing a control method in the control unit 10 when the injection cylinder 13 is operated, and will be described below with reference to FIGS.

(STEP 1) When the injection cylinder 13 is operated, detection data of the stroke position of the actuator 1 from the pulse encoder 11 is input to an input unit (DI in the figure) 18.
And converts it into a screw position by the CPU 12 and substitutes it as a variable X.

Next, the variable X is compared with the switching positions S1 to S3 input in advance (first processing). (STEP 2) When the variable X is larger than the switching position S1, a digital value corresponding to the speed set value V1 (the CPU internal amount corresponding to the flow proportional valve opening required to operate the actuator 1 at the speed set value V1) Digital value: 0
(A dimensionless number of 1000) is set as the flow rate command value Vout. (STEP 3) When the variable X is equal to or less than the switching position S1 and greater than the switching position S2, a digital value corresponding to the speed set value V2 is set as the flow command value Vout. (STEP 4) When the variable X is equal to or smaller than the switching position S2 and larger than the switching position S3, a digital value corresponding to the speed set value V3 is set as the flow command value Vout. When the variable X is equal to or less than the switching position S3, a digital value corresponding to the speed set value V4 is set as the flow command value Vout.

Next, the flow command value Vout set in the above-mentioned STEPs 2 to 4 is compared with the preset first threshold L and second threshold H (second processing). (STEP 5) When the flow command value Vout is less than the first threshold value L (Vout <L), the flow command value Vout is corrected by a predetermined correction coefficient α (> 1), and this is corrected to a new flow command value. Update as Vout.

The updated flow command value Vout is converted from a digital value to an analog voltage value via a D / A converter (D / A in the figure) 19 and output to the flow proportional valve 6. The valve is opened by the opening corresponding to the flow rate command value Vout. Further, a signal for switching the small pump load solenoid valve 4 and the solenoid valve 9 for switching the operation direction is output via an output unit (DO in the figure) 20, so that the small pump 2 is turned on and the large pump 3 is turned on.
FF (unload) state. Then, in this case, the actuator 1 is supplied only from the small pump 2, and the flow command value V after correction (by the correction value α) by the flow proportional valve 6.
It is driven by hydraulic oil adjusted to the flow rate according to out.

(STEP 6) The flow command value Vout is equal to or more than the first threshold value L and less than the second threshold value H (Vou
When t <H), the flow rate command value Vout is corrected by a predetermined correction coefficient β (> 1), and this is updated as a new flow rate command value Vout, and then the D / A converter (D / A in FIG.
A) The digital value is converted into an analog voltage value via 19, and is output to the flow proportional valve 6.

The flow proportional valve 6 is opened by an opening corresponding to the flow command value Vout. Further, a signal for switching the large pump load solenoid valve 5 and the solenoid valve 9 for switching the operation direction is output via an output unit (DA in the figure) 20, and the small pump 2 is turned off (unloaded) and the large pump 3 is turned on. State. Then, in this case, the actuator 1 is supplied only from the large pump 3 and is operated by the flow proportional valve 6 (correction value β
Driven by hydraulic fluid adjusted to a flow rate corresponding to the corrected flow rate command value Vout.

When the flow command value Vout is equal to the second threshold value H,
When Vout ≧ H, the flow rate command value Vout
D / A converter (D / A in the figure) 19 without directly correcting
After converting the digital value into an analog voltage value via the, it is output to the flow proportional valve 6.

The flow proportional valve 6 is opened by an opening corresponding to the flow command value Vout. Further, a signal for switching the small pump load solenoid valve 4, the large pump load solenoid valve 5, and the solenoid valve 9 for switching the operation direction is output through an output unit (DO in the figure) 20, so that the small pump 2 is turned on and the large pump is turned on. 3 to O
N state. Then, in this case, the actuator 1
Is driven by hydraulic oil supplied from both the small pump 2 and the large pump 3 and adjusted by the flow proportional valve 6 to a flow rate corresponding to the flow rate command value Vout.

Here, the correction values α and β are before and after the first threshold value L and the second threshold value H, respectively. When switching from 3 to two pumps, small pump 2 and large pump 3,
In order to obtain the opening of the flow proportional valve 6 in which the flow rate of the hydraulic oil supplied to the actuator 1 is continuous, the flow command value Vout corresponding thereto is set in advance to correct the flow command value Vout. FIG. 4 shows a flow rate command value after the processing in STEPs 2 to 4 (first processing) when the first threshold value L is 300 and the second threshold value H is 600 (solid line in the figure). And S
5 shows the flow rate command values (dotted lines in the figure) after the processing of TEPs 5 and 6 (second processing).

As described above, by correcting the flow command value Vout and controlling the flow proportional valve 6, the flow rate of the supplied working oil is continuous over the entire speed set value as shown in FIG. (In FIG. 5, the dotted line indicates the flow rate based on the speed set value before correction).

In the control method of the actuator 1 of the injection molding machine described above, the stroke position of the actuator 1 is detected, and the flow rate command value Vout corresponding to the speed set values V1 to V4 determined based on the stroke position is determined (STEP2 to STEP4).
4) and when the flow command value Vout deviates from the predetermined first threshold value L and second threshold value H, the flow command value Vout is corrected by the correction values α and β (STEP 5,
6), and the flow rate command value V set in STEPs 2 to 4
out, the operation of the small pump 2 and the large pump 3 is switched, and the speed set value V corrected in STEPs 5 and 6 is changed.
The control is performed to adjust the opening of the flow proportional valve 6 based on out. Thus, the flow rate command value Vout
Is corrected and the flow proportional valve 6 is controlled, whereby the flow rate of the working oil supplied to the actuator 1 can be made continuous over the entire speed set value. As a result, even when the pumps to be operated are switched from the small pump 2 to the large pump 3 and from the large pump 3 to the two small pumps 2 and 3, respectively, the operating speed of the actuator 1 rapidly changes. Therefore, the injection speed of the injection cylinder 13 can be smoothly controlled over the entire control range. Of course, it is possible to issue a flow rate command corresponding to a flow rate required by the actuator 1 to obtain a desired operation speed of the injection cylinder 13 over the entire range.

In the above-described example, an example in which the injection amount is controlled by controlling the actuator 1 that operates the injection cylinder 13 is used. However, the present invention is applied to another actuator, for example, an actuator that opens and closes a mold. It is also possible to control the opening / closing speed of the mold, and in this case, the same configuration as in the above example may be employed. In the above example, two pumps (small pump 2 and large pump 3) are provided for operating the actuator 1. However, the present invention can be applied to a case where two or more pumps are provided. It is. Furthermore, the configuration is such that the two pumps are sequentially switched so that only the small pump 2, the large pump 3, and both the small pump 2 and the large pump 3 are driven as the required flow rate gradually increases from a small state. Other than this, the combination of pumps in use is not limited, for example, only the large pump 3 is driven when the required flow rate is small, and both the small pump 2 and the large pump 3 are driven when the required flow rate is large.

[0032]

As described above, according to the control method of the injection molding machine according to the first aspect, the flow rate command value corresponding to the operation speed set value determined based on the stroke position of the actuator is set. When the flow rate command value set in the first processing is out of the predetermined range, the flow rate correction value is corrected, D / A converted and output to the flow rate regulating valve, and the flow rate command value is within the above range. Sometimes D
A / A conversion and a second process of outputting to the flow control valve are performed, the operation of the plurality of pumps is switched based on the flow command value determined in the first process, and the flow rate output in the second process is performed. The configuration is such that the flow regulating valve is controlled based on the command value. Thus, by correcting the flow command value and controlling the flow control valve, the flow rate of the working oil supplied to the actuator can be made continuous over the entire flow command range. As a result, even when the pump operated to change the operation speed of the actuator is switched, the operation speed of the actuator does not suddenly change, so that the operation of the injection molding machine by this actuator can be smoothly controlled. . of course,
A flow rate command corresponding to a flow rate required by the actuator to obtain a desired operation speed of the injection molding machine can be issued over the entire command range.

According to the control method of the injection molding machine of the second aspect, the actuator is applied to a device for driving an injection cylinder for injecting a resin into a mold. This makes it possible to smoothly and finely control the injection speed of the injection molding machine.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a control circuit of an actuator to which a control method of an injection molding machine according to the present invention is applied.

FIG. 2 is a vertical sectional view showing an injection cylinder operated by the actuator.

FIG. 3 is a flowchart of the control method.

FIG. 4 is a diagram showing a flow rate command value corrected by the control method.

FIG. 5 is a diagram showing a speed set value to an actuator and an actual control flow rate when a small pump and a large pump are switched and operated in the control method.

FIG. 6 is a diagram showing a flow rate command value to an actuator and an actual control flow rate when both a large pump and a small pump are operated in a conventional method of controlling an injection molding machine.

FIG. 7 is a diagram showing a flow command value to an actuator and an actual control flow when only a large pump is operated in a conventional method of controlling an injection molding machine.

FIG. 8 is a diagram showing a flow command to an actuator and an actual control flow when a large pump alone and a small pump and a large pump are switched and operated in a conventional method of controlling an injection molding machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Actuator 2 Small pump (pump) 3 Large pump (pump) 6 Flow proportional valve (flow regulating valve) 7 Pressure compensation valve 10 Control part (control means)

Continuation of front page (56) References JP-A-4-78305 (JP, A) JP-A-6-312256 (JP, A) JP-A-56-49236 (JP, A) JP-A-62-27125 (JP) , A) Jikken 63-53002 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/46-45/82

Claims (2)

(57) [Claims] 1. An actuator provided in an injection molding machine, a plurality of pumps for operating the actuator are connected via a flow control valve, and the plurality of pumps adjust the flow rate from the flow control valve. A control method for an injection molding machine, comprising a control means for controlling an operation speed of the actuator by selectively switching an operation of the actuator, wherein the control means controls the operation speed of the actuator based on a stroke position of the actuator. A first process of setting an operation speed set value, and setting a flow command value at the flow control valve corresponding to the operation speed set value, wherein the flow command value set in the first process is predetermined. When the flow rate command value is out of the range, the flow rate command value is corrected and then output to the flow rate regulating valve. Performing a second process to output to the flow control valve as it is, switching the operation of the plurality of pumps based on the flow command value determined in the first process, and outputting the second process. A control method for an injection molding machine, comprising controlling a flow rate from the flow control valve to an actuator based on the flow command value. 2. The control method for an injection molding machine according to claim 1, wherein the actuator drives an injection cylinder for injecting a resin into a mold from an injection nozzle by advancing a screw in the cylinder in an axial direction. A method for controlling an injection molding machine.