JPH0652490B2 - Pressure control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure control device, and more specifically, to a flow path for supplying a fluid from a pump to a hydraulic device (actuator) such as an injection molding machine operated by a pressure fluid. The present invention relates to a pressure control device having an electromagnetic proportional pressure control valve interposed therein and operating the electromagnetic proportional pressure control valve to control the pressure of a fluid supplied to an actuator.

2. Description of the Related Art As a pressure control device of this type, the present inventor configures an open loop control circuit as a whole to eliminate an overshoot phenomenon caused by closed loop feedback control, and eliminates a pressure difference to achieve a static accuracy. We newly proposed the one shown in FIG. The pressure control device of FIG. 3 controls the pressure of the flow path 3 for supplying fluid from the pump 2 which is a source of pressure fluid to the actuator 1 which is a load of hydraulic equipment by an electromagnetic proportional pressure control valve 4 such as a relief valve. In this case, the control signal to the electromagnetic proportional pressure control valve 4 is picked up (b) at a constant timing (b) and the pressure P _{2 of the} flow path and the pressure P _{1 of} the fluid which is a preset target (c) are set. And are obtained by performing a comparison operation (d) (ε = P ₁ −P ₂ ). That is, by the timing control signal,
While the pressure P _{2 in the} flow path 3 is picked up and stored, the stored pressure P ₂ in the previous cycle and the target pressure P ₁ are extracted, and the difference between them (ε = P ₁ −
P ₂ ) is multiplied by the gain α (ε · α) (e), and the target pressure P ₁ is added to the resulting value (PA = P ₁ + αε) (f), and then the amplifier and the valve or the amplifier itself The value obtained by multiplying the disturbance factor β including the temperature drift of (β) (PA) (g) is transmitted to the solenoid proportional pressure valve 4 as a control signal, and this value is sequentially repeated every predetermined cycle. Road 3
The pressure P ₂ of the fluid supplied to the actuator 1 from the above is close to the target pressure P ₁ . (Japanese Patent Laid-Open No. 59-12391
However, in the device shown in FIG. 3, the relationship between the final pressure P ₂ and the target pressure P ₁ is calculated as follows.
The deviation ε does not converge to 0. That is, P ₂ = P ₁ does not hold.

Taking this as a numerical example, if (α = 0.7) (β = 1.2), then (A≈1.11), and if there is no compensation by the pressure control mechanism as described above, that is, (P ₂ = βP ₁ =
About 45% compared to 1.2P ₁ ) Improved, but (ε = P ₁ −P ₂ = P ₁ −1.11P ₁ = −0.11P
₁ ) and (ε = 0), that is, (P ₁ = P ₂ ) does not hold.

The present invention has been made to solve the problems in the conventional pressure control device as described above, and the deviation ε converges to 0 while preventing the overshoot phenomenon.
That is, the purpose is to provide a pressure control device in which P ₁ = P ₂ .

Therefore, according to the present invention, an electromagnetic proportional pressure control valve is provided in a flow path for supplying a fluid from a pump to an actuator, and the electromagnetic proportional pressure control valve is operated at every predetermined cycle. A device for controlling the pressure of fluid supplied to an actuator, comprising: extraction means, reference signal output means, comparison means, storage means, and calculation means, wherein the extraction means corresponds to the pressure of the supply fluid. A signal is output, the reference signal output means outputs a reference signal corresponding to a target value of the pressure of the supply fluid, and the comparison means outputs a signal output from the extraction means. A comparison signal that is a difference between the reference signals output by the reference signal output means is output, and the storage means stores the control signal output by the calculation means in the previous cycle. The calculation means outputs the sum of the control signal in the previous cycle stored in the storage means and the comparison signal to the electromagnetic proportional pressure control valve as a control signal. The present invention provides a pressure control device characterized in that an electromagnetic proportional pressure control valve is controlled by the control signal.

In the pressure control device having the above-described configuration, the pressure corresponding to the pressure of the fluid supplied from the pump output by the extraction means to the actuator, that is, the signal corresponding to the pressure of the supply fluid, and the target value of the pressure of the supply fluid output from the comparison means The comparison means outputs a comparison signal which is a difference from the reference signal, and the calculation means outputs the sum of the control signal of the previous cycle stored in the storage means and the comparison signal to the electromagnetic proportional pressure control valve as a control signal. Therefore, it is possible to achieve high-precision pressure control such that the deviation between the pressure of the supply fluid and its target value converges to 0 while preventing the overshoot phenomenon.

Examples Hereinafter, the present invention will be described in detail based on the examples shown in the drawings.

In FIG. 1, a flow path 3 is provided for supplying a fluid from a pump 2 which is a pressure fluid source to an actuator 1 which is a load of hydraulic equipment or the like. An electromagnetic proportional pressure control valve 4 such as a relief valve is provided in a branch path branched from the flow path 3, and the electromagnetic proportional pressure control valve 4 is operated every predetermined cycle to control the pressure of the fluid supplied to the actuator 1. The control signal to the electromagnetic proportional pressure control valve 4 is sequentially changed for each cycle to adjust the pressure of the fluid supplied to the actuator 1.

The take-out means b, which is a pickup, at the constant timing defined by the timing control circuit a, the previous cycle, the current cycle, the next cycle, ...
The pressure of the fluid supplied to the actuator 1 is sequentially detected via, and a signal (P ₂ j) corresponding to the detected pressure of the supplied fluid is output to the comparator e.

The memory circuit c and the take-out circuit d constitute a reference signal output means for outputting a reference signal (P _{1 1 to n} ) corresponding to the target value of the pressure of the supply fluid. That is, the storage circuit c stores a reference signal (P _{1 1 to n} ) corresponding to the target value of the pressure of the supply fluid, and the reference signal (P ₁ i) is stored in the timing control circuit a. At the specified timing, the signal is taken out by the take-out circuit d, and at the same time with the signal (P ₂ j) corresponding to the pressure of the supply fluid, the comparator e
Is output to.

The comparator e and the amplifier circuit f form a comparison means. Comparator e
Calculates the difference ε (ε = P ₁ i−P ₂ j) between the signal (P ₂ j) output by the extraction means b and the reference signal (P ₁ i), and this value is timely increased. The comparison signal (α
Output ε) to the calculating means g. Here, α is a loop gain.

The calculation means g consisting of an adder or an integrator has a control signal (αεi) in the previous cycle stored in a memory k described later.
_-1 = PAj _-1 ) and the comparison signal (α
・ Control signal (PAj = PAj _-1 + α ・) which is the sum of ε)
ε) is calculated.

This control signal (PAj) is amplified (βP
Aj) is inputted to the electromagnetic proportional pressure control valve 4, and at the same time, it is outputted to the memory k through the A / D converter h. Here, β is a disturbance factor and may be a constant value or a variable value.

The memory k and the register 1 constitute a storage means. The memory k is provided with a control signal (PA
j) is once memorized. Then, the control signal (PAj) in the memory k calculates the control signal (PAj) in the next cycle at an appropriate time until the pressure control timing of one cycle passes and the next cycle is started. It is transferred to the register 1 as the control signal (PAj ₋₁ ) of the previous cycle when performing. The control signal (PA
j ₋₁ ), after being taken out, is converted into an analog quantity through the D / A converter m and output to the calculating means g. The timing of taking out is controlled by the timing control circuit a.

When the control as described above is repeated at the next cycle, the cycle after the next, and the predetermined timing defined by the timing control circuit a, the actuator 1 is supplied to the actuator 1 through the flow path 3 represented by the signal (P ₂ i). The pressure of the supplied fluid gradually approximates to the target value represented by the reference signal (P ₁ i).

That is, in the above pressure control device, (P ₂ j) and (P ₂ j)
_{1 When} the relationship of i) is calculated Becomes For example, if P ₁ i = 1, α = 1, β = 1.2, and P ₂ in the first, second, third, and fourth cycles is calculated from the initial state, as shown in Table 1. Become, P ₂₄
Is 0.998, which is very close to 1.

As described above, in the pressure control device of the present invention, the comparison value (ε = P ₁ −P ₂ ) between the pressure (signal P ₂ ) of the fluid supplied to the actuator 1 and its target value (reference signal P ₁ ) is set. The deviation converges to 0, and the pressure of the fluid supplied to the actuator 1 can be approximated to the target value with high accuracy.

Further, in the present invention, as described above, the pressure state of the previous cycle, that is, the control signal PAj _-1 output to the electromagnetic proportional control valve 4 in the previous cycle is stored, and the error of the previous cycle is corrected. Since the pressure control is performed in an open loop as described above, it is possible to prevent the above-mentioned overshoot phenomenon.

That is, the pressure control device of the present invention can surely perform highly accurate control such that the pressure of the fluid supplied to the actuator approaches the target value while preventing the overshoot phenomenon.

The reference signal P ₁ corresponding to the target value may be a constant value each time, or may be a value that gently changes in a range where the object is achieved. Further, a 2-port electromagnetic proportional pressure reducing valve may be provided in the flow path 3 instead of the electromagnetic proportional pressure control valve.

FIG. 2 shows a modified example of FIG. 1, and the same components are assigned the same reference numerals as those in FIG.

In FIG. 1, the amplification circuit f and the calculating means g are processed by analog processing, whereas in FIG. 2, these parts f and g are processed by digital processing like the memory k and the register 1. , The A / D converter h shown in FIG. 1 is provided between the comparator e and the amplification circuit f, and the D / A converter m shown in FIG. 1 is provided between the calculation means g and the amplification circuit n. There is.

The other structure of FIG. 2 and the operation and flow of each component are exactly the same as those of FIG. 1 except for the difference between the analog processing of FIG. 1 and the digital processing of FIG. 2 as described above. Therefore, the description is omitted.

Further, the A / D converter h may be provided between the extracting means b and the comparator e to digitize a, c, d and e.

In the above description, the reference signal P ₁ corresponding to the target value of the pressure of the supply fluid is set in advance, but the setting value after the actual operation is set to P ₁ via P ₂ j.
It may be played back and set. That is, a control signal is directly input to the electromagnetic proportional pressure valve 4 by manual operation in advance to extract an optimum output value, and the control signal to the electromagnetic proportional pressure valve 4 corresponding to this output value is stored in the storage circuit c. It is also possible to store it in the memory and use it as a target value to perform a correction operation due to changes such as temperature drift.

Effect As is clear from the above description, in the pressure control device according to the present invention, the signal corresponding to the pressure of the fluid supplied to the actuator output by the extraction means, and the reference signal corresponding to the target value of the pressure of the supply fluid are provided. Is calculated for each cycle by the comparison means and output as a comparison signal, and the sum of this comparison signal and the control signal output to the electromagnetic proportional pressure control valve in the previous cycle stored in the storage means is calculated as By outputting the control signal to the electromagnetic proportional pressure control valve to control the pressure of the supply fluid in an open loop, it is possible to prevent the overshoot phenomenon.

Further, since the pressure control device of the present invention is configured to sequentially repeat the above control for each cycle, the pressure difference between the pressure of the fluid supplied to the actuator and the target value is reduced, and the fluid supplied to the actuator is reduced. The pressure of can be approximated to the target value with high accuracy.

That is, the pressure control device according to the present invention controls the pressure of the supply fluid with high accuracy such that the deviation between the pressure of the supply fluid to the actuator and the target value converges to 0 while preventing the occurrence of the overshoot phenomenon. It can be performed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, FIG. 2 is a schematic diagram showing a modification of FIG. 1, and FIG. 3 is a schematic diagram showing a conventional pressure control device. 1 ... Actuator, 2 ... Pump, 3 ... Flow path, 4 ... Electromagnetic proportional pressure control valve, a ... Timing circuit, e ... Comparator, g ... Computation means, k ... Memory, l ... …register.

Claims (1)

[Claims] An electromagnetic proportional pressure control valve (4) is provided in a flow path (3) for supplying a fluid from a pump (2) to an actuator (1).
And controlling the pressure of the fluid supplied to the actuator (1) by operating the electromagnetic proportional pressure control valve (4) every predetermined cycle, the extraction means (b) and the reference signal output. Means (c, d), comparison means (e, f), storage means (k, l), and calculation means (g) are provided, and the extraction means (b) corresponds to the pressure of the supply fluid. a outputs a signal (P 2 _j) to said reference signal outputting means (c, d) is for outputting a reference signal corresponding to the target value of the pressure of the supply fluid (P 1 _i) Therefore, the comparison means (e, f) is provided with the signal (P ₂ j) output from the extraction means (b) and the reference signal output means (c, d).
Of the reference signal (P ₁ i) output by the comparison signal (α
.Epsilon.), Wherein the storage means (k, l) stores and outputs the control signal (PAj _-1 ) output by the calculation means (g) in the previous cycle. Then, the arithmetic means (g) calculates the sum of the control signal (PAj ₋₁ ) in the previous cycle stored in the storage means (k, l) and the comparison signal (α · ε) as the control signal (PAj). Is output to the electromagnetic proportional pressure control valve (4), and the electromagnetic proportional pressure control valve (4) is controlled by the control signal (PAj).