JPH0366522B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application 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 relates to a method for 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 for compensation control.

[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 1 via a coupling 3, and a cavity 23 formed by a fixed mold 21 and a movable mold 22 is provided with molten metal (hereinafter referred to as molten metal) in an injection sleeve 20. ) is cast and formed. A striker 5 is integrally attached to the coupling ring 3, and a so-called magnetic scale 6 is installed on the surface of the striker 5, which has magnetized portions and non-magnetized portions alternately formed at equal intervals. Magnetic detector 7 detects the presence or absence of this magnetism.
The position sensor 8 detects the signal and outputs it as a pulse-like signal, which is 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 a position preset in the position setting device 10. To explain this with reference to the injection speed control shown in FIG. 16 is energized and the pilot pressure of the on-off valve 12 is released to the tank through the throttle valve 18. Therefore, the hydraulic fluid in the pressure source 11 such as a pressure accumulator passes through the on-off valve 12 and the throttle valve 14.
Flows into the injection cylinder 1 via. At this time, the opening degree of the throttle valve 14 determines the first stage injection speed V ₁ a. Further, by adjusting the throttle valve 18 which determines the amount of relief of the pilot pressure of the on-off valve 12, the rising gradient θ ₁ a of the speed can be changed.
Next, when the rod 2 of the injection cylinder 1 moves forward (moves from right to left in FIG. 1) and reaches the stroke _S2 set in the position setting device 10, the controller 9 excites the four-way valve 17. Then, 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 enters the injection cylinder 1 through the throttle valve 15 and controls the second stage injection speed to V ₂ a. Also, depending on the adjustment of the throttle valve 19, the speed
The rising slope θ ₂ a from V ₁ a to V ₂ a changes. When the cavity 23 is filled with the molten metal 24 in this manner (stroke _S3 position in FIG. 2), the pressure applied by the plunger 4 to the molten metal 24 is equal to the pressure that the liquid pressure source 11 finally has, that is, If the pressure source 11 is a pressure accumulator, the molten metal 24 is pressurized at a pressure equal to the pressure it had before injection minus the pressure drop caused by the movement of the rod 2 of the injection cylinder 1.
This pressing force is determined by the size of the molded product, the required properties, and the force for clamping the fixed mold 21 and the movable mold 22. If the molded product changes or the mold changes, it will be applied accordingly. This will automatically change the pressing force. That is, it becomes necessary to change the pressure of the pressure source 11. Then, as shown by the broken line in FIG. 2, if the pressure is high, as shown in c, even if the throttle valve openings 14 and 15 are the same as a, the injection speed,
Both the velocity rising gradient become large as V ₁ c, V ₂ c, θ ₁ c, and θ ₂ c. Conversely, if the pressure is low, both the injection velocity and the velocity rising gradient become as shown in b.
A phenomenon in which V ₁ b, V ₂ b, θ ₁ b, and θ ₂ b become smaller appears. In Fig. 2, a,
If the pressures of b and c are Pa, Pb, and Pc, respectively,
When the pressure is Pc＞Pa＞Pb, the injection speed is V ₂ c＞
V ₂ a>V ₂ b, V ₁ c>V ₁ a>V ₁ b, and the speed rise gradient is θ ₂ c>θ ₂ a>θ ₂ b, θ ₁ c>θ ₁ a>θ ₁ b.

[Problems to be solved by the present invention]

Therefore, in the conventional method, each time the pressure of the pressure source 11 is changed, in order to compensate for the injection speed, the valve openings of the throttle valves 14 and 15 must be adjusted. In order to guarantee the gradient, the valve openings of the throttle valves 18 and 19 had to be adjusted.

Generally speaking, the characteristics of injection speed and acceleration (gradient) with respect to the valve opening of each throttle valve, for example,
Although this appears as shown in Figures a and b, it does not appear constant under all pressures, nor does it appear the same for all throttle valves, but as the pressure in the hydraulic circuit changes. For example, if a plurality of throttle valves are used, the curves shown in FIGS. 3a and 3b will naturally change depending on the throttle valves used.

Therefore, in the past, trajectories like those shown in Figure 3 a and b were required for the working pressure and for the number of throttle valves used depending on the number of injection speed change stages. .

For the above reasons, it is extremely complicated to set and manage casting conditions related to predetermined injection speeds, especially when the production mode is high-mix, low-volume production.
This was a major obstacle in standardizing work.

[Means to solve the problem]

In view of this, the present invention eliminates the need to change injection speed-related setting conditions each time the pressure of the pressure supply source changes, and automatically performs compensation control according to changes in pressure within the circuit. In this way, the injection speed and the rising gradient of the speed are always set to the desired value, which is the same as the set value.

To this end, in the present invention, a flow control valve having a mechanism for directly driving the spool valve with a pulse motor is provided between the pressure source and the injection cylinder, and a pressure detector is provided to detect the pressure of the pressure supply source and output an output signal. In a hydraulic circuit system, when the pressure source pressure changes with respect to the reference pressure, the number of pulses that drive the pulse motor is corrected according to the pressure, and the opening degree of the flow rate control valve is corrected to adjust the flow rate characteristics. In addition to compensating for
Even if the valve opening, that is, the number of pulses, is corrected due to a change in pressure, the time required to change the valve opening will be the same as the time required to change the valve opening under the standard pressure. Second, the frequency of the pulses that drive the pulse motor is corrected to compensate for the flow rate increase/decrease characteristics of the flow rate control valve.

[Effect]

When setting the injection speed of the injection cylinder and operating the injection cylinder at that injection speed, the speed setting is performed by controlling the valve opening of the flow control valve depending on the number of pulses input to the pulse motor. When setting the rate of rise of the speed, the time required to change the valve opening speed or valve opening degree of the flow control valve is controlled by the magnitude of the frequency of the pulse input to the pulse motor.

In this case, if the pressure supply source pressure changes with respect to the reference pressure, the injection speed will change if the valve opening degree (number of pulses) and valve opening speed (pulse frequency) are constant.

For example, if the pressure of the pressure supply source becomes lower than the reference pressure, the number of pulses input to the pulse motor is increased according to the amount, thereby keeping the flow rate, that is, the speed of the injection cylinder constant. As a result, the time required to open the valve increases, so the pulse frequency is increased so that the time required to change the valve opening does not change.

On the other hand, if the pressure of the pressure supply source becomes higher than the reference pressure, the number of pulses input to the pulse motor is reduced according to the amount, thereby keeping the flow rate, that is, the speed of the injection cylinder constant. As a result, the time required to open the valve becomes shorter, so the frequency of the pulse is made smaller so that the time required to change the valve opening does not change.

Therefore, even if the pressure changes, the same injection speed and speed rise as the injection speed and speed rise under the standard pressure can be obtained.

In addition, in the present invention, by using a pulse motor directly driven flow rate control valve, it is possible to accurately control from a minimum flow rate to a large flow rate by itself.
Unlike conventional throttle valves, there is no need to prepare individual ones depending on the magnitude of the injection speed. Therefore,
Even if multiple stages or injection speeds are changed during the injection process,
Since there is only one flow control valve, characteristics can be made uniform. In addition, compensation control for pressure detects the pressure of the pressure supply source and changes the correction amount of the valve opening of the flow control valve calculated based on it and the acceleration characteristic to reach the valve opening, thereby controlling the injection. Compensate control of speed and slope when changing injection speed.

〔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 perpendicular to the axis, and 55 moves in the axial direction in the valve body 52. A 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. 50
60 is the nut shaft 5.
This key prevents rotation of 6 and guides movement in the axial direction.

The spool 55 rotates according to the rotation of the pulse motor 50.
moves back and forth in the axial direction 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 hydraulic oil inlet 53 on the end face in the axial direction, and a hydraulic oil outlet 5 on the side surface.
In a cylindrical valve body 52 with 4,
The spool 55 is driven in the axial direction by the action of the pulse motor 50 to control the flow rate, and the axial thrust of the spool 55 due to the hydraulic oil is rapidly reduced as the opening amount and movement speed of the spool 55 increases. By doing so, the driving force required for high-speed flow rate switching is reduced, and the flow rate control valve 51 can further improve the performance of high-speed flow rate switching 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 1 is determined. is controlled, and the rate of change of the flow rate, that is, the rising state of the speed, is determined by the magnitude of the rotation speed of the pulse motor 50 during the rotation.

In addition, the flow control valve 51 having such a structure and operation can suppress the time required for the spool 55 to actually start opening after receiving a speed change command to a maximum of 1 millisecond or less. Compared to conventional flow rate control valves, the response is extremely good, and the valve opening/closing operability and operational accuracy are also extremely improved.

A permanent magnet 61 is fixed to a part of the surface of the nut shaft 56, and a magnetic position detector 63 called a zero cross sensor is attached to the permanent magnet 61 and a part of the opposing casing 62, for example. The position detector 63 is constituted by a proximity switch 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 provide feedback 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 moved to that position via a control pulse generator not shown in this figure. It can also be made to be able to be stopped accurately. 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. 4 is used in the injection mechanism of a die-casting machine, and parts having the same structure and function as those in FIG. 1 are given the same numbers. The explanation is omitted.

In FIG. 5, a flow control valve 51 having a mechanism for directly driving a spool valve with a pulse motor 50 is provided between the pressure supply source 11 and the injection cylinder 1. 30 is an opening setting device, and pressure supply source 1
The valve opening degree of the flow rate control valve 51 is set such that 1 corresponds to an arbitrary injection speed under a reference pressure. 31
is an acceleration setting device, which similarly sets the rising slope of the injection speed under the standard pressure. To explain the structure of the set value here, the flow control valve 51
is directly driven by the pulse motor 50, so to increase or decrease the injection speed, increase or decrease the valve opening,
That is, the number of pulses sent to the pulse motor 50 is set. 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 10 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 are determined by the corrector 2.
9, the value is corrected according to the pressure of the pressure supply source 11. A pressure detector 25 has a function of inputting pressure information of the pressure supply source 11 to the corrector 29. 26 is a check valve type on-off valve, and 27 is a four-way valve. However, it is not necessary to provide this on-off valve 26, and the flow rate control valve 51 can also have the function of this on-off valve 26.

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 in FIG. 6, the pressure supply source 11 is at the reference pressure.
It is assumed that there is a relationship between the valve opening degree of the flow control valve 51 under _P0 , that is, the number of pulses, and the injection speed. 1st
The speed of the stage is v ₁ m/sec, and the speed of the second stage is v 1 m/sec.
If v ₂ m/sec is required, the operator reads n ₁ and n ₂ as the number of pulses from the locus diagram in FIG. 6, and sets these in the opening setting device 30. Also, the first
m ₁ as the rising slope to the stage velocity v ₁ m/sec,
Assume that a value m ₂ is set in the acceleration setter 31 as the rising gradient to the second stage speed v m/sec. Then, the reference clock pulses in the controller 28 are counted, and after counting the set value, the drive pulse is outputted to the pulse motor 50 by one pulse. For example, the period of the reference clock pulse is t sec/1 pulse (fHz).
If so, m ₁ times in the first stage and m ₂ times in the second stage
After counting the number of times, the pulse for driving the pulse motor 50 will be output, so the first stage is t×m ₁
= t ₁ sec (f ₁ Hz), and the second stage outputs a pulse at a frequency of t×m ₂ =t ₂ sec (f ₂ Hz). This time chart is shown in FIG. Now, actually, the injection speed related information n ₁ , which has been set as above,
n ₂ , m ₁ , and m ₂ are not kept as they are, but are converted by the corrector 29 as described below to become n ₁ ′, n ₂ ′, respectively.
m ₁ ′, m ₂ ′ are input to the controller 28.

In this state, when an injection command is received from the sequencer S, etc., the four-way valve 27 is switched, and the check valve type on-off valve 2
6 is opened to bring the pressure supply source 11 and flow rate control valve 51 into communication. At the same time, the injection command is issued by the controller 28.
up to the number of pulses n ₁ ' in the first stage,
Pulse motor 50 at a frequency of m ₁ ′=t ₁ ′sec (f ₁ ′Hz)
is driven, the injection speed increases according to the frequency of f ₁ ′, and reaches the injection speed v ₁ corresponding to the valve opening of the number of pulses n ₁ ′. When the position setting device 10 reaches the speed change point, follow the same process,
The pulse motor 50 is driven at a frequency of t×m ₂ ′=t ₂ ′sec (f ₂ ′Hz) up to the number of pulses n ₂ ′, and the injection speed is
It becomes v ₂ and the injection is completed in that state.

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

The current pressure P of the pressure supply source 11 is detected by the pressure detector 2.
5 and inputs the value to the corrector 29, the corrector 29 adjusts the reference pressure of the pressure source 11.
From the relationship between P ₀ and the current pressure P, the flow control valve 5
The correction amount is calculated according to a correction formula regarding the valve opening degree, that is, the number of pulses, and the change characteristic of the valve opening degree, that is, the pulse frequency. An example of the correction formula is shown below.

FIG. 8 shows the valve opening when the flow rate control valve 50 is actually installed in the hydraulic circuit system of the injection cylinder 1, that is, the injection speed _v and the plurality of pressures P ₁ , P ₂ , ..., shows an actual measurement example at Pn. In the illustrated example, P ₀ is the reference pressure of this hydraulic circuit system, and for example, the reference pressure is taken as the highest working pressure of the hydraulic circuit. Also, the pressure Pi (i=
1 to n), the larger the attached number, the lower the pressure. Fig. 8. In order to obtain an arbitrary injection speed v _i , an opening degree of V ₀ i is required at the reference pressure P ₀ , and even when the pressure changes to P ₁ , P ₂ , ..., Pn, each ΔV ₀ i ₁ , ΔV ₀ i ₂ , ..., ΔV ₀ in, the same injection speed v _i can be obtained by adding an extra pulse.

Therefore, over the entire range of injection speed v, the above v _i
by moving the valve opening, that is, the number of pulses.
FIG. 9 shows the relationship between V ₀ and the number of pulses ΔV ₀ that must be added. All symbols in the figure are the same as those in Figure 8, and the reference pressure
Since the number of additional pulses ΔV ₀ at P ₀ is always zero, it coincides with the horizontal axis in the figure.

As is clear from the above explanation, if you try to keep the injection speed constant when the pressure in the hydraulic circuit system changes, the number of additional pulses ΔV ₀ = f unc (V ₀ , P ₀ , Pi)
It is sufficient to drive the pulse motor 50 according to the result of the function. Here, in the above explanation, the pressure Pi is considered as a plurality of values, that is, a finite number of values, but since this is interpolated by converting it into a function, for any pressure P, ΔV ₀ = f unc (V ₀ ,
This means that the relationship P ₀ , P) can be obtained.
Therefore, as a correction formula for the valve opening degree of the flow rate control valve 51, the following function may be set in the corrector 29.

V ₀ '=V ₀ +ΔV ₀ =V ₀ +f unc (V ₀ , P ₀ , P) ... V ₀ ; Valve opening at reference pressure P ₀ , which is input by the operator P ₀ ; Reference pressure P; Current circuit system pressure V ₀ ′: The corrected valve opening is actually:
The pulse motor 50 is driven accordingly.

In addition, the correction regarding the change characteristics of the valve opening, that is, the pulse frequency, is the difference in valve opening caused by the result of the above correction formula, that is, the number of pulses at the reference pressure of the difference in the number of pulses after the correction. The frequency can be proportionally converted by the difference ratio. for example,
To explain using the example shown in Fig. 8, in order to obtain the same injection speed v _i from a state where the injection speed is zero, a pulse of V ₀ i at the reference pressure P ₀ and a pulse of V ₀ i + ΔV ₀ in at the pressure Pn. A number is required. This means that if the pulse frequency is output without changing, it will take (V ₀ i + ΔV ₀ in)/V ₀ i times the time to reach the same injection speed v _i . To compensate for this, the pressure Pn
When , the pulse frequency is (V ₀ i + ΔVin)/V ₀ i
By doubling it, it is possible to prevent changes in the injection speed change time.

Also, regarding the speed change from v ₁ to v ₂ shown in Fig. 6, the actual valve openings n ₁ ′, n ₂ ′ at the current pressure P are the input valve openings n ₁ , n ₁ In the input setting example where n ₁ ′=n ₁ +f unc (n ₁ , P ₀ , P) n ₂ ′=n ₂ +f unc (n ₂ , P ₀ , P) from the formula, the opening degree n Since one pulse is to be output every time the reference clock pulse t sec (fHz) is counted from ₁ to n ₂ m ₂ times, the change time is t × m ₂ × (n ₂ − n ₁ ) sec. . However, in reality, the correction is made as described above, and unless the set value m ₂ of the pulse frequency is changed, a time of t×m ₂ ×(n ₂ ′−n ₁ ′) sec is required. Therefore, if it is desired to make both of them the same time, the count number m ₂ ' of the reference clock pulses corrected with respect to m ₂ can be determined as follows.

t×m ₂ ×(n ₂ −n ₁ ) =t×m ₂ ′×(n ₂ ′−n ₁ ′) Therefore, m ₂ ′=n ₂ −n ₁ /n ₂ ′−n ₁ ′m ₂ … Therefore, the reference clock pulse shown in FIG.
Instead of counting m ₂ , just count m ₂ ′. In other words, this is nothing but multiplying the frequency by _n2' - _n1 '/ _n2 - _n1 , and the equation may be set in the corrector 29 to correct the pulse frequency.

Although this embodiment shows an example in which the injection speed is compensated and controlled by the flow rate control valve 51, it 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 degree when filling a molding material into a cavity and pressurizing it, as shown in Japanese Patent Publication No. 99470.

In addition, the change characteristic of the valve opening degree, that is, the frequency of the pulse output, is shown only in the case of a constant value in this embodiment.
As shown in Publication No. 70454), with respect to frequency,
The same can be applied to the case where the valve opening degree is changed by providing a certain pattern.

Further, in this embodiment, when correcting the frequency of the pulse output, the count of the reference clock pulses is 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 example, the correction formula for calculating the additional pulse was made a function of the reference pressure, the current pressure, and the valve opening at the reference pressure. Since there is a one-to-one correspondence with the state quantity, for example, the injection speed as in this embodiment, it is also possible to directly set the injection speed in place of the valve opening.

Further, in this embodiment, the reference pressure is the maximum working pressure of the hydraulic circuit system, but it is not limited to that. There is no change in the basic form of the correction formula at the lowest pressure or at the intermediate pressure.

〔Effect of the invention〕

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

(1) Even if the pressure in the hydraulic circuit system changes, the flow rate control valve is compensated, so the flow rate relative to the valve opening (equivalent to the injection speed) does not change, so the valve opening for each pressure - flow rate There is no need to prepare many line diagrams; just one is sufficient.

(2) Even if the pressure in the hydraulic circuit system changes, the flow rate control valve is compensated, so the time required to change the valve opening is the same as the time required to change the valve opening under the standard pressure. It can always be kept the same, and there is no need to adjust the flow rate increase/decrease characteristics (equivalent to the injection speed acceleration/deceleration characteristics) for each pressure.

(3) In order to cover the entire injection speed range with one flow control valve, the above
The characteristic information of (1) and (2) is not required, and the injection speed can be changed arbitrarily in any number of steps, which greatly contributes to the standardization of condition setting work.

(4) Therefore, the flow rate can be controlled reliably and easily under the optimum injection conditions at all times, 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 at all times, resulting in consistently high quality. injection products become easier to obtain.

[Brief explanation of drawings]

Fig. 1 is a hydraulic circuit diagram showing an example of a device similar to the device for carrying out 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. 3a is a Diagram showing the relationship between throttle valve opening and injection speed, Figure 3b shows throttle valve opening and acceleration (gradient)
FIG. 4 is a longitudinal sectional view showing an embodiment of a flow control valve used in carrying out the method of the present invention, and FIG. 5 is a diagram showing an embodiment of a device carrying out the method of the present invention. Fig. 6 is a diagram showing the relationship between valve opening (number of pulses) and injection speed under standard pressure, Fig. 7 is a time chart showing the pulse output state, and Fig. 8 is the pressure change state. The diagram below shows the relationship between the valve opening (number of pulses) and injection speed, and Figure 9 is a diagram showing the relationship between the valve opening (number of pulses) to be added to the predetermined valve opening (number of pulses). be. 1... Injection cylinder, 4... Injection plunger,
8... Position detector, 9... Controller, 10... Position setter, 11... Pressure source, 20... Injection sleeve, 21... Fixed type, 22... Movable type, 25...
Pressure detector, 26... Check valve type on-off valve, 27...
... Four-way valve, 28 ... Controller, 29 ... Compensator, 3
0... Opening setting device, 31... Acceleration setting device, 50...
...Pulse motor, 51...Flow control valve.

Claims (1)

[Claims] 1. A flow control valve having a mechanism for directly driving a spool valve with a pulse motor is provided between the pressure source and the injection cylinder, and a pressure detector is provided that detects the pressure of the pressure supply source and outputs an output signal. In a hydraulic circuit system, if the pressure source pressure changes with respect to the reference pressure,
The number of pulses that drive the pulse motor is corrected according to the pressure, and the valve opening of the flow control valve is corrected to compensate for the flow characteristics. Even if the number is corrected, the time required to change the valve opening is the same as the time required to change the valve opening under the standard pressure.
A flow rate control method comprising: correcting the frequency of pulses that drive the pulse motor to compensate for flow rate increase/decrease characteristics of the flow control valve. 2. The flow rate control method according to claim 1, wherein the correction amount of the number of pulses is expressed as a function of a reference pressure, the current pressure, and the valve opening degree (number of pulses) under the reference pressure. 3. To correct the pulse frequency by changing the ratio of the difference in the corrected change valve opening (number of pulses) to the difference in the change valve opening (number of pulses) at the reference pressure, and by changing the count of the reference clock pulses. A flow rate control method according to claim 1, characterized in that: 4. The flow rate according to claim 1, 2, or 3, characterized in that 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. Control method.