JPH066991B2 - Fluid control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device that controls a flow rate and a control amount related to pressure by performing PWM modulation (pulse width modulation) on an electromagnetic on / off valve.

(Prior Art) A conventional device shown in FIG. 3 has an oscillating unit 1 that oscillates a constant rectangular wave signal, and a sawtooth wave or a triangular wave (hereinafter referred to as a reference signal wave) by integrating the rectangular wave signal of the oscillating unit 1. The output signal of the integrator 2 is input to the comparator 3, and the target signal Vr output from the target signal generator 4 is also input to the comparator 3. I am trying.

Then, the output signal of the comparison unit 4 is transmitted to the electromagnetic on / off valve 6 via the amplification unit 5, and its operation is as follows.

That is, as shown in FIG. 4, the comparison unit 3 compares the reference signal wave signal Ve from the integration unit 2 with the target signal Vr from the target signal generation unit 4, and the comparison result is (Vr−Ve )> 0
When, the modulation signal becomes high level and (Vr−Ve) ≦ 0
At this time, the modulation signal is set to the low level.
Then, the output signal of the comparison unit 3 is amplified by the amplification unit 5 and applied to the solenoid of the electromagnetic on / off valve 6.

Therefore, the modulation rate of the voltage applied to the solenoid (the ratio between the modulation synchronization and the time when the voltage is applied) is controlled according to the target signal Vr, and the flow rate is controlled according to the modulation rate. Controlled by value.

(Problems to be Solved by the Present Invention) However, the electromagnetic on / off valve 6 has a delay time τ _ON from when a voltage is applied to its solenoid until the electromagnetic on / off valve 6 is opened. Generally, there is a delay time τ _OFF from when the application is cut off until the electromagnetic on / off valve 6 is closed. Since there is a delay in the opening / closing operation of the electromagnetic on / off valve 6 as described above, the modulation rate of the modulation signal and the modulation rate of the on / off valve (ratio between the modulation cycle and the time when the electromagnetic on / off valve is open) are as described above. It will not change proportionally.

Therefore, as shown in FIG. 5, when the modulation rate of the modulation signal is equal to or less than the constant value η _ON , there is no time for the electromagnetic on / off valve to open, so that it does not open. Further, when the modulation rate is higher than the constant value η _OFF , there is no time to close the valve, so that the on / off valve 6 continues to be fully opened. Therefore, the flow rate changes according to the modulation rate of the applied voltage because the modulation rate is η _ON
Only it becomes, the eta _ON below and eta _OFF region between eta _OFF
In the above case, the actual control becomes impossible and the control area becomes narrower accordingly.

Also, in order to improve the response of the control system, the modulation frequency must be increased, but if the modulation frequency is increased, the above η _ON increases and η _OFF decreases, so
Its control area becomes smaller and smaller.

Further, the flow rate also changes due to disturbance such as pressure fluctuation of the hydraulic pressure source.

Therefore, the above-mentioned conventional device has a problem that its control area is limited, high-speed response cannot be realized, and it is vulnerable to disturbance.

Although the present invention is premised on the response delay of the solenoid of the electromagnetic on / off valve, it improves the response by improving the control system to maintain the linearity between the input signal and the output signal, The purpose is to secure a wide control area and to be strong against external disturbances.

(Means for Solving Problems) In order to achieve the above object, the present invention has the following configuration.

That is, a control amount detection unit that detects the output control amount and outputs a signal according to the control amount, a target signal generation unit that outputs a signal according to the target control amount, and the target signal generation unit. From the signal from the control amount detector, an adder / subtractor that calculates a deviation between the signal from the control amount detector, an integral unit that integrates the deviation output from the adder / subtractor, and a sample hold unit that samples and holds the integrated value for each modulation cycle. A reference signal wave generator that oscillates a predetermined reference signal wave for each modulation cycle,
A comparison unit that compares the magnitudes of the sample hold value and the reference signal wave, and outputs a modulation signal according to the comparison value,
An electromagnetic on / off valve that operates according to the modulation signal is provided.

(Operation of the present invention) As described above, the flow rate and pressure output from the electromagnetic on / off valve are detected, the deviation between the target value and the detected value is calculated, and the deviation is integrated to output the control signal. Therefore, when the actual control amount does not reach the target control amount, the modulation rate of the modulation signal is controlled until the target control amount is reached.

(Effect of the present invention) Since the modulation rate is controlled by the integrated value of the deviation as described above, even if there is a response delay in the electromagnetic on / off valve, the actually output control amount is the target control amount. Since the modulation signal is output based on whether or not the target control amount has been reached, the target control amount can always be secured.

That is, the modulation rate corresponding to the target control amount is the constant value η _ON
Even if it is less than or equal to or more than η _OFF , the control is not disabled as in the conventional case. Also, the above constant value η _ON
Since control is possible even below or above η _OFF , high-speed response can be realized by increasing the modulation frequency.

Further, as described above, the actual control amount is fed back to obtain the deviation from the target control amount, so that even if disturbance such as pressure fluctuation of the hydraulic power source occurs, the actual value can be immediately corrected. , Will also be strong against external disturbances.

(Embodiment of the present invention) The flow rate control device of FIG. 1 shown as an embodiment is provided with a target signal generator 7 for generating an apparent target signal Vr for a required flow rate, and the target signal generator 7 The output signal of the flow rate detection unit 10 is also input to the addition / subtraction unit 8. Then, the flow rate detection unit 10 detects the control flow rate that the electromagnetic on / off valve 9 attempts to control, and outputs the flow rate signal Vo.

As described above, the addition / subtraction unit 8 to which both signals are input calculates the deviation e = (Vr−Vo) between both signals and inputs the deviation signal e to the integration unit 11. Then, the integration signal Vs which is the integration result of the integration unit 11 is input to the sample hold unit 12. The clock signal of the clock signal generation unit 13 is also input to the sample hold unit 12, but the clock signal is output at each modulation cycle.

The sample signal V _SH sampled and held by the sample and hold unit 12 as described above is input to the comparison unit 14, and the output signal Ve of the reference signal wave generation unit 15 is input to the comparison unit 14. Further, the clock signal of the clock signal generation unit 13 is also input to the reference signal wave generation unit 15, and the signal Ve is output from the reference signal wave generation unit 15 at each modulation cycle defined by the clock signal.

Then, the comparison unit 14 compares the reference signal wave signal Ve and the sample signal V _SH , and the comparison unit 14 outputs a high modulation signal until the reference signal wave Ve reaches the held sample signal V _SH. Subsequently, when the sample signal V _SH is exceeded, a low modulation signal is output, and the signal is transmitted to the electromagnetic on / off valve 10 via the amplifier 16.

A time chart of the operation of the control device is shown in FIG. 2, which shows a case where the target value Vr changes stepwise.

The clock signal generator 13 outputs a clock signal at each modulation cycle T. However, in FIG. 2, each modulation cycle is shown as 0-10T for convenience. explain. The voltage of the signal in each modulation cycle is standardized at 10V.

(Regarding the modulation cycle 1T to 2T in FIG. 2) The voltage of the target value Vr is 0 to 8 between the above modulation cycles 1T and 2T.
If it changes to V, the target flow rate at this time is
That's 80%. However, at this time, since the electromagnetic on / off valve 9 is closed and the fluid does not flow, the output signal Vo of the flow rate detection unit 10 becomes zero. Therefore, the deviation e = (Vr−Vo) calculated by the adder / subtractor 8 becomes 8V, and this 8V is integrated by the integrator 11. In this case, when the deviation of 10V continues for one cycle, the integration result is set to 10V, and the reference signal wave signal Ve is also changed to 0V to 10V in one cycle.

Then, at the time when the modulation period changes to 2T, which is the moment when the clock signal is output from the clock signal generator 13, the integrated signal
V _S is sampled and held by the sample and hold unit 12.

(Regarding the modulation periods 2T to 3T in FIG. 2) When the value at the initial point of the modulation period 2T is sample-held in this way, the reference signal wave signal Ve is sampled and held between the modulation periods 2T to 3T. The comparator 14 outputs a high modulation signal until V _SH is reached. Therefore, in reality, after the delay time τ _ON has passed from the initial point of the modulation cycle 2T, the electromagnetic on / off valve 9 opens and the fluid flows.

When the fluid is flowing from the electromagnetic on / off valve 9 as described above, the flow rate signal Vo output from the flow rate detecting unit 10 is
Since it becomes 10 V, deviation from the above target value Vr e = (Vr−Vo)
There will be -2V, the integrated value V _S of the deviation is reduced.

However, if the reference signal wave signal Ve is the sample hold value V
_When reaching _SH , the modulation signal becomes low level and the electromagnetic on / off valve 9 is closed with a delay of τ _OFF . When the electromagnetic on / off valve 9 is closed in this way, the flow rate signal Vo from the flow rate detecting unit 10 becomes zero, the deviation signal e becomes 8 V again, and the integral value of the deviation increases again.

(Regarding Modulation Cycles 3T to 4T in FIG. 2) The clock signal output from the clock signal generator 13 samples and holds the integrated value V _S of the integrator 11 at that time. Then, the modulation signal maintains a high level until the reference signal wave signal Ve reaches the sample hold value V _S. Moreover, since the sample hold value V _SH in this modulation cycle is larger than the sample hold value V _{SH in} the previous cycle, the modulation signal is maintained at the high level for a longer period than the previous cycle. That is, when the actual flow rate is smaller than the target flow rate Vr that is to be obtained, the modulation rate of the modulation signal is automatically increased to secure the target flow rate.

The actual flow rate if reached the target value Vr, since the integrated value V _S of the deviation becomes equal, is maintained thereafter the same modulation rate.

(Regarding the modulation period 5T to 6T or later in FIG. 2) The target value Vr is reduced from 8V to 4V during the modulation period 5T to 6T, but in this case as well, the predetermined period has passed. After that, the modulation rate of the modulation signal becomes constant, and its average value matches the target value.

As described above, the flow rate of the electromagnetic on / off valve 9 is fed back, the deviation between the flow rate signal Vo and the target signal Vr is detected, and the deviation is integrated to control the modulation rate of the modulation signal. For example, the apparent modulation factor is η _ON
Even if it is less than or equal to or more than η _OFF , the modulation rate is automatically changed until a predetermined flow rate is obtained. Therefore, the apparent modulation factor is below a certain value η _ON or η
_Even if the flow rate is _OFF or more, the flow rate can be controlled, and the flow rate signal Vo has a linear relationship with the target signal Vr, and the control area is widened accordingly.

Further, since the control area can be widened as described above, it is also possible to realize a high-speed response by increasing the modulation frequency of the modulation signal.

Further, since the actual flow rate output from the electromagnetic on / off valve is fed back to calculate the deviation from the target flow rate and control is performed so as to fill the deviation, for example, even if there is a disturbance such as pressure fluctuation of the hydraulic power source, Its precise control becomes possible.

In the above-described embodiment, the flow rate actually output is compared with the target flow rate, but the control mode that compares the pressure actually output with the target pressure and fills those deviations In this case, the device can also be used as a pressure control device.

[Brief description of drawings]

1 and 2 show an embodiment of the present invention.
FIG. 3 is a block diagram of a control circuit, FIG. 2 is a time chart diagram of its control operation, FIGS. 3 to 5 are conventional devices, FIG. 3 is a block diagram, FIG. 4 is a time chart diagram,
FIG. 5 is a graph showing the relationship between the modulation rate of the modulation signal and the flow rate characteristic. 7 ... Target signal generating section, 8 ... Addition / subtraction section, 9 ... Electromagnetic on / off valve, 10 ... Flow rate detecting section, 11 ... Integrating section, 12 ... Sample holding section, 14 ... Comparison section, 15 ... Reference signal wave generating section.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-3719 (JP, A) Actually developed 56-45904 (JP, U)

Claims (1)

[Claims] 1. A control amount detecting section for detecting an output control amount and outputting a signal according to the control amount, and a target signal generating section for outputting a signal according to the target control amount.
An addition / subtraction unit that calculates the deviation between the signal from the target signal generation unit and the signal from the control amount detection unit, an integration unit that integrates the deviation output from this addition / subtraction unit, and a sample hold of the integrated value for each modulation cycle. A sample and hold unit, a reference signal wave generator that oscillates a predetermined reference signal wave at each modulation cycle, and the size of the sample and hold value and the reference signal wave are compared, and the modulated signal is generated according to the comparison value. A fluid control device comprising a comparing section for outputting and an electromagnetic on / off valve which operates according to the modulated signal.