JPS60168218A - Flow rate control method - Google Patents

Abstract

PURPOSE:To make it possible that a worker adjusts easily a flow rate control valve, by using the flow rate control valve, which is driven directly by a pulse motor, to correct relations of the injection speed to a degree of opening of the valve to a linear function. CONSTITUTION:A flow rate control valve 51 has such mechanism that a spool valve 55 is driven directly by a pulse motor 50. A pulse number indicating degree of valve opening of a flow rate limiting valve 51 corresponding to an optional injection speed is set to an opening degree setter 30, and a frequency indicating a gradient of the injection speed is set to an acceleration setter 31. Set values of these pulse number and frequency are corrected in accordance with pressure of a pressure supply source 11 by a corrector 29 so that relations of the injection speed to the degree of opening are a linear function. The number of pulses sent to the motor 50 and the output frequency of pulses are changed by a controller 28; and when reaching an injection speed change point set to a position setter 10, the motor 50 is driven with the pulse number and the frequency which are set by setters 30 and 31 and are corrected by the corrector 29.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a flow rate control method for compensating and controlling the control flow rate of a flow rate control valve, and mainly for compensating and controlling the injection speed of an injection cylinder of an injection molding machine or a die casting machine. The present invention relates to a flow rate control method.

[Prior art]

This will be explained according to FIGS. 1 to 3. Figure 1 shows the injection speed control mechanism of the injection cylinder of a conventional die-casting machine, and Figure 2 shows an example where the mechanism shown in Figure 1 controls the injection speed. The axis is the injection speed.

In FIG. 1, an injection plunger 4 is connected to a rod 2 of an injection cylinder l via a coupling 3, and the molten metal (hereinafter referred to as Molten metal) is cast and formed. A striker 5 is integrally attached to the coupling 3, and a so-called magnetic scale 6 is installed on the surface of the coupling 3, which has magnetized portions and non-magnetized portions alternately formed at equal intervals. The presence or absence of this magnetism is detected by a magnetic detector 7,
It is output as a pulse-like signal and counted by the position detector 8. The controller 9 is a position detector 8, and is configured to send a speed control signal to the four-way valve 16 or 17 when the measured position signal matches the position preset in the position setting device IO. To explain this with reference to the injection speed control shown in FIG. 16 is excited and the on-off valve 12
The pilot pressure is released to the tank through the throttle valve 18. Therefore, the hydraulic fluid of the pressure source 11 such as a pressure accumulator is supplied to the on-off valve 12.
and flows into the injection cylinder l via the throttle valve 14. At this time, the first stage injection speed v1 is determined by the opening degree of the throttle valve 14.
is decided. Further, by adjusting the throttle valve 18 that determines how much pilot pressure is removed from the on-off valve 12, the speed rise gradient θ1 can be changed.

Next, when the rod 2 of the injection cylinder 1 moves forward (moves to the left from the position shown in FIG. 1) and reaches the stroke S2 set in the position setting device 10, the controller 9 excites the four-way valve 17. , the pilot pressure of the on-off valve 13 is released to the tank through the throttle valve 19. Then, the working fluid from the pressure source 11 passes through the throttle valve 15 and enters the injection cylinder 1, controlling the injection speed to the second stage v2. Further, depending on the adjustment of the throttle valve 19, the rising gradient θ2 from the speed v1 to the speed V2 changes.

Moreover, S3 indicates the position at which the filling of the molten metal 24 into the cavity 23 is completed.

Each of the throttle valves 14, 15, 18, and 19 shown here independently determines, for example, the injection speed and acceleration (gradient ) has a uniquely determined locus, and the number of throttle valves used increases in proportion to the number of injection speed changes for one die-casting machine. However, with the recent demand for high-precision, high-quality molded products, there is a tendency for the number of speed steps to be changed in the injection process to double, making it difficult for operators to make adjustments using conventional throttle valves. there were. In particular, when the production format is high-mix, low-volume production, where there are many opportunities to change the settings of casting conditions, and where multiple machines are operated by one worker, individual differences between the machines become apparent and the work becomes standardized. This was a major obstacle in terms of

[Purpose and outline]

The present invention corrects the relationship between the flow rate and injection speed to a predetermined value, such as a linear function, so that an operator can easily adjust the flow rate control valve, and maintains this relationship even when the machine changes. The purpose of this design is to make it easier for the operator by keeping it unchanged, and the above setting conditions are repeated during the injection process.

Even if there are several changes, the characteristic is that it can be handled using only unique characteristic information, instead of having to have separate information because each of them has different characteristics as in the past.

To accomplish this, the present invention uses a pulse motor directly driven flow control valve. The water flow control valve is
Since it is possible to accurately control from a very small flow rate to a large flow rate with a single unit, it can be handled without having to prepare separate ones according to the size of the injection speed like conventional throttle valves. Therefore, even if the injection speed is changed in multiple steps within the injection process, the characteristics can be made uniform.

〔Example〕

Next, the present invention will be explained in detail with reference to an embodiment shown in the drawings.

FIG. 4 shows the structure of a digital direct-acting type flow control valve 51 having a mechanism for directly driving a spool valve with a pulse motor applied in the present invention.

In the flow control valve 51 shown in FIG. 4, 52 is a valve body having a hydraulic oil inlet 53 from the axial direction and a hydraulic oil outlet 54 from the axis in a direction perpendicular to the axis, and 55 is a valve body having a hydraulic oil inlet 53 extending in the axial direction in the valve body 52. A moving spool, 56 is a nut shaft integrally provided at the rear of the spool 55, 57 is a screw shaft screwed into the inner shaft center of the nut shaft 56 by a ball screw 58, and 59 is a screw shaft 57 and a pulse motor. A joint 60 connects the nut shaft 56 with the shaft 56, and a key 60 prevents the rotation of the nut shaft 56 and guides its movement in the axial direction.

The spool 55 moves back and forth in the axial direction in response to the rotation of the pulse motor 50 to instantaneously open and close the valve and adjust the opening degree to control the flow rate. As described above, this flow rate control valve 51 has a spool 55 connected to a pulse motor 50 within a cylindrical valve body 52 having a hydraulic oil inlet 53 at the end face in the axial direction and a hydraulic oil outlet 54 at the side surface. This device controls the flow rate by driving the spool 55 in the axial direction by the action of Reduces the required driving force,
This allows the flow rate control valve 51 to further improve the performance of changing the flow rate at high speed and reduce the driving force.

In this flow rate control valve 51, the opening amount of the spool 55 is determined by the rotation amount, that is, the rotation angle, of the pulse motor 50 by a control pulse train from a control pulse generator not shown in this figure, and the flow rate to the injection cylinder l is determined. The rate of change of the flow rate, that is, the rising state of the speed, is determined by the magnitude of the rotational speed of the pulse motor 50 during the rotation.

Note that the flow control valve 5 having such a structure and operation
1, it is now possible to keep the time until the spool 55 actually begins to open after receiving a speed change command to less than 1 millisecond at maximum, and the response is extremely responsive compared to conventional normal flow control valves. Furthermore, the operability and operational precision of opening and closing the valve have also been extremely improved. A permanent magnet 61 is fixed to a part of the surface of the nut shaft 56, and a part of the opposing casing 62 is connected to the permanent magnet 61. For example, a magnetic position detector 63 called a zero cross sensor is attached. The position detector 63 is constituted by a proximity switch that is sensitive to the movement of the permanent magnet 61, and can accurately detect the moving distance of the nut shaft 56 and the spool 55 in the axial direction and feed it back to the control device. Further, the zero position of the spool 55 is electrically detected by the action of the permanent magnet 61 and the position detector 63, and the pulse motor 50 is accurately moved to that position via a control pulse generator not shown in this figure. It can also be made so that it can be stopped. Note that as the position detector 63, one with an accuracy of 0.01 mm can be used.

In this embodiment, since the flow rate control valve 51 driven by such a pulse motor 50 is used, the inertia is reduced, the responsiveness is improved, and control can be performed reliably and easily. Furthermore, an increase in spool thrust force can also be suppressed.

FIG. 5 shows an embodiment in which the pulse motor directly driven flow control valve 51 shown in FIG. The explanation is omitted. Further, (b) in the valve opening degree (number of pulses) vs. injection speed diagram in FIG. 6 is a diagram showing the injection speed with respect to the valve opening degree of the flow control valve 51 in the injection mechanism shown in FIG. It is.

In FIG. 5, reference numeral 30 denotes an opening degree setting device, which sets the valve opening degree of the flow rate control valve 51 corresponding to an arbitrary injection speed. 31 is an acceleration setter, which sets the rising slope of the injection speed. To explain the structure of the set value here, since the flow rate control valve 51 is directly driven by the pulse motor 50, in order to increase or decrease the injection speed, the valve opening degree must be increased or decreased, that is, the pulse motor Set the number of pulses to be sent to 50. Furthermore, in order to increase or decrease the rising slope of the injection speed, it is sufficient to change the time interval of pulses sent to the pulse motor 50, that is, the output frequency of the pulses. The controller 28 does this, and when the injection speed change point set in the position setting device 1O is reached, the number of pulses set in the opening setting device 30 is increased to the number of pulses set in the acceleration setting device 31. The pulse motor 50 is driven at the specified frequency. However, at this time, both the above-mentioned pulse number and frequency have been corrected by the corrector 29 according to the pressure of the pressure supply source 11. 26 is a check valve type on-off valve, 27 is a four-way valve, and S is a sequencer.

Next, each function will be explained in detail according to a series of injection strokes. - As an example, a case will be described in which the two-step injection speed change shown in FIG. 2 is performed.

As shown by (&) in FIG. 6, if the characteristics of the hydraulic circuit including the flow control valve 51 are given to have a linear relationship, for example, the speed of the first stage is v 1 m 1 sec.
, if y2-/sea is required as the speed of the second stage, then
The operator reads each nl+nz as the number of pulses and sets it in the opening setting device 30. Also, the operator reads ml as the rising slope to the first stage speed y 1ml1sec, and sets it to the second stage speed V2Lm/sea. m as the rising slope
Assume that a value l is set in the acceleration setting device 31. Then, the reference clock pulses in the controller 28 are counted, and after counting the set number of pulses, the drive pulse is outputted to the pulse motor 50 by one pulse. and,
For example, if the period of the reference clock pulse is tsec/1 pulse (f Hz), the first stage is m1 times, the second
In the first stage, after counting m2 times, the pulse for driving the pulse motor 50 is output, so the first stage is tXm1=
t1sec (f+Hz), second stage is t Xm2 = t
Pulses will be output at a frequency of 25 ec (f 2 Hz). This time chart is shown in FIG. 8. Actually, the injection speed-related information nl, n2. ml, ml is not the same,
After being converted by the corrector 29 as described below, the values of (b) in FIG. 6 are respectively nl'+n2Z ml'.

m2' and is input to the controller 28.

In this state, when an injection command is received from the sequencer S or the like, the four-way valve 27 is switched, the check valve type on-off valve 26 is opened, and the pressure supply source 11 and the flow rate control valve 51 are brought into communication with each other. At the same time, the injection command is also input to the controller 28, and up to the number of pulses n1' in the first stage, t X m +' = t I'5ec
Since the pulse motor 50 is driven at the (f1'Hz) cr) frequency, the injection speed increases according to the frequency of fl', and reaches the injection speed v1 corresponding to the number of pulses and the valve opening degree of F. When the speed change point of the 0 position setter 10 is reached, the same process is followed until the number of pulses n2' is reached.
The pulse motor 50 is driven at a frequency of tXm2'=t2'5ec (f2'Hz), and the injection speed is v2.
, and the injection is completed in that state.

Next, the function of the corrector 29 and its correction method will be explained.

In a flow rate control valve having the flow rate characteristics with respect to the valve opening as shown in (b) in Fig. 6, (a) in Fig. 6 is used.
In order to achieve the characteristics shown in , proceed as follows.

First of all, according to actual measurements, the 6th v! Based on the characteristic (b) at J, the deviation valve opening amount from the desired characteristic (a) is obtained as shown in (C) in FIG. Specifically, in order to obtain the injection speed v1 at the valve opening n1, the actual flow! Since the control valve has the characteristics as shown in FIG. 6(b), the injection speed v1 cannot be achieved unless the opening is n1', so the deviation valve opening amount Δn1=nl'-nl
If expressed as the number of 5g for the set valve opening n1, it will be as shown in Figure 6 (e), and if the valve opening is corrected according to this, the characteristics shown in Figure 6 (a) will be obtained. Become. In other words, if the valve opening set to obtain the injection speed V is generally n and the deviation valve opening is Δn, then the corrected valve opening n', which is the output of the corrector 29, is n' =n+Δn =n+func (n)□ ■.

Further, as in the above example, correction regarding the change characteristic of the pulp opening degree, that is, the pulse frequency, is performed using the opening degree n shown in FIG.
If the change is from 1 to nl with a slope of m2, then l < the difference in lube opening caused by the result of the above correction formula (■), that is, the pulse number difference after correction is the set pulse of 6/2'. Number difference Δ
The frequency may be proportionally converted by the ratio of n12.

In other words, for the set valve opening n1ln2, in the input setting example where nl' = n1 + func (nl) nl' = n2 + func (nl) from the formula (■), the reference clock pulse t sec (f Hz) is applied from the opening n1 to nl. ) is to be output m2 times, so the change time is tXm2X(nl-nl) sea. However, in reality, it is corrected as described above, and unless the set value m2 of the pulse frequency is changed, a time of tXm2X(n2'-rz') sec is required. Therefore, if we try to make both of them the same time, m2
The count number m of reference clock pulses corrected for
2' may be determined as follows.

t Xm2 X (nl-nl) = t
11. Therefore, instead of counting m2 of the reference clock pulse shown in FIG. 8, it is sufficient to count m2', which is all that is required, and the 0 formula may be set in the corrector 29 to correct the pulse frequency.

In addition, in the characteristics shown in FIG. 6 (b), the injection speed difference, that is, the flow rate difference with respect to the difference in the opening degree of the valve, does not become constant depending on the opening degree at which opening and closing of the valve is started. As shown in Figure 6 (a), by approximating a linear shape and using this as the basic shape, the relationship between the pulp opening difference and the control flow rate difference becomes constant. Therefore, Figure 9 (&) As shown in the figure, if it opens and closes at a certain frequency,
Regardless of the flow rate difference, the slope θ will be constant,
Furthermore, if the same frequency conversion as in equation 0 is performed for the desired flow rate difference, as shown in FIG. 9(b), the time Δt or stroke Δ required to change the injection speed or flow rate
It is also easy to keep st constant.

In other words, specifically expressed by the symbols (a) and (b) in FIG. 6, the injection speed vI (opening n+) to vl
If the standard clock count m2 is used for opening nz), the time required to change the opening is tXm2X (nl-nl) sec In the same time, change from vl (opening n+) to v3 (opening n3), the reference clock count number m3
tXm2X (nl-nl) = tXm3X (n3-nl) However, since the corrector 29 further includes correction from (a) to (b) in Fig. 6, take this into consideration. The count number m3' of the reference clock may be tXm2X (nl-nl) = tXm3'X (n3'-n+').

In this embodiment, an example is shown in which the injection speed is compensated and controlled by the flow rate control valve 51, but the injection speed is not limited to the injection speed. It goes without saying that the present invention is equally applicable to flow rate control, such as setting the valve opening when applying pressure.

In addition, although the change characteristics of the valve opening degree, that is, the frequency of the pulse output, are shown only when constant in this example, for example,
As shown in Japanese Patent Application No. 57-179151, the same approach can be taken in the case where the valve opening degree is changed by providing a certain pattern with respect to the frequency.

Furthermore, in this embodiment, when correcting the frequency of the pulse output, the count of the reference clock pulses was changed, but it goes without saying that this can also be done by changing the oscillation frequency of the reference clock pulses themselves.

Furthermore, in this embodiment, the correction formula for calculating the additional pulse is a function of the valve opening, but the valve opening and the state quantity when it is incorporated into the hydraulic circuit system, for example, Since there is a one-to-one correspondence with the injection speed, it is also possible to directly set the injection speed in place of the valve opening.

Further, in this embodiment, a linear function is exemplified as the target flow rate characteristic with respect to the valve opening degree, but the present invention is not limited to this and may be a quadratic function or an exponential function, for example.

Further, in this embodiment, the speed of the -injection stroke is controlled in two stages, but as is clear from the above explanation, even if the injection stroke is changed to incineration, it can be handled in exactly the same way with one flow rate control valve.

〔Effect of the invention〕

Since the present invention is configured as described above, it has the following effects.

(1) The relationship between the control flow rate and the opening degree of the flow control valve can be controlled with a predetermined functionality.

(2) Even if the valve opening is corrected due to the predetermined function approximation in (1), if the difference in opening set and input to the flow control valve is constant, then from any valve opening Even when opening and closing, the time required for the change can remain unchanged.

(3) By employing a linear function as the predetermined function approximation in (1), it is possible to keep the amount of change in flow rate unchanged with respect to the difference in change in opening degree. As a result, it is possible to obtain the effect that the flow rate control as explained in FIG. 6 can be performed more reliably and easily.

(4) Since (1) to (3) are all performed by one flow control valve, even if the display is changed during the -injection stroke, sufficient control can be achieved by using only one characteristic.

From the above, it becomes easier for operators to operate, and even if one operator is in charge of multiple machines, individual differences between machines can be eliminated, making it possible to significantly contribute to standardization.

Of course, the flow rate can always be controlled easily and reliably under optimal injection conditions, so if this is used in injection molding equipment such as a die-casting machine, injection molding can be easily performed under the same conditions and high-quality injection products can always be obtained. It becomes easier.

[Brief explanation of drawings]

Fig. 1 is a hydraulic circuit diagram showing an example of a device similar to the device for implementing the method of the present invention, Fig. 2 is a diagram showing an example of changes in the injection speed of a die-casting machine, and Fig. 3 (a ) is a diagram showing the relationship between throttle valve opening and injection speed, Figure 3 (b) is a diagram showing the relationship between throttle valve opening and acceleration (gradient), and Figure 4 is a diagram showing the relationship between throttle valve opening and acceleration (gradient).
The figure is a longitudinal cross-sectional view showing an embodiment of a flow control valve used in carrying out the method of the present invention, Fig. 5 is a hydraulic circuit diagram showing an embodiment of a device carrying out the method of the present invention, and Fig. 6 is a valve. A diagram showing the relationship between opening degree (number of pulses) and injection speed, Figure 7 is a diagram showing the relationship between valve opening degree (number of pulses) and deviation valve opening degree (number of pulses), and Figure 8 shows the pulse output. Time charts showing the state, FIGS. 9(a) and 9(b) are diagrams showing different examples of the relationship between time or stroke and injection speed (flow rate). 1... Injection cylinder, 4... Injection plunger, 8...
...Position detector, 9...Controller, 10...Position setting device, 11...Pressure source, 20...Injection three 7.21
... fixed type, 22 ... movable type, 26 ... check valve type on-off valve, 27 ... four-way valve, 28 ... controller, 29
...Corrector, 30...Opening degree setting device, 31...Acceleration setting device, 50...Pulse motor, 51...Flow control valve Patent applicant Ube Industries, Ltd. Figure 4 61 No. 6 Figure 9(a) Figure 9(b) ^tlAstl=cOr+sl

Claims (5)

[Claims] (1) In a hydraulic circuit system that includes a flow control valve that has a mechanism for directly driving a spool valve with a pulse motor, the number of pulses that drive the pulse motor is corrected so that the flow rate characteristics with respect to the opening degree of the flow control valve are determined. Even if compensation is made so that the relationship of A flow rate control method comprising: compensating for the flow rate increase/decrease characteristics of the flow rate control valve by correcting the frequency of the pulses that drive the pulse motor so that time remains unchanged. (2) The first claim characterized in that the amount of correction of the number of pulses performed so that the valve opening degree and the flow rate have a predetermined relationship is expressed as a function of the valve opening degree (pulse number).
Flow rate control method described in section. (3) Flow rate control according to claim 1, characterized in that the predetermined relationship between the valve opening degree and the flow rate is such that both are linear, and the rate of increase/decrease in the flow rate with respect to the difference in change in the valve opening degree is constant. Method. (4) The pulse frequency is corrected by the corrected change valve opening (
The ratio of the difference in valve opening (number of pulses) to the difference in valve opening (number of pulses) that changes under the specified relationship between valve opening and flow rate. 2. The flow rate control method according to claim 1, wherein the flow rate control method is performed by changing the count of clock pulses serving as a reference. (5) This flow rate control method is mainly applied to compensation control of the injection speed of an injection piston of an injection molding machine or a die casting machine. , the flow rate control method according to item 4.