JPS605798A - Pulse motor operation system - Google Patents

Abstract

PURPOSE:To eliminate the pulsating current due to excess output by providing an irreversible time constant circuit in which the time constants between charging and discharging are differentiated in a feedback loop, thereby preferably controlling a pulse motor by a slowup quickdown operation. CONSTITUTION:An irreversible time constant circuit provided between the output of a controller an the input of a V/F converter 4 connects in parallel a series circuits of the first diode D1 and the first resistor R7, and a series circuit of the second diode D2 and the second resistor R8 so that the direction of the diode become reverse. A capacitor C2 is connected between the input of the converter 4 and the ground. The discharging is accelerated by setting R7, R8 as a slowup quickdown operation. Accordingly, when applied to a chromatograph pump, the pulsation of a pump an be reduced, and high sensitivity analysis can be performed in the chromatograph.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a pulse motor operation method when a controlled object is operated by a pulse motor.

[Background of the invention]

In a liquid chromatograph, the liquid pump is an important part that supplies the eluent to the separation column and adds the coloring liquid to the bathing liquid from the separated separation column. In order to speed up separation analysis, a cylindrical pressure pump is required, and for highly sensitive analysis, a non-pulsating flow pump with no pulsation in the pump discharge flow is required.

The pulsating flow of the pump is indirectly detected as pressure fluctuation, but
The main cause of pulsating flow is, for example, in a reciprocating plunger pump, when the plunger moves from the suction stroke to the discharge stroke, the liquid sucked into the cylinder at atmospheric pressure suddenly switches to a high-pressure flow path. The liquid in the cylinder is compressed, its volume decreases, and the discharge flow decreases and becomes pulsating. As a result, it is detected as a pressure drop.

For this reason, a feedback circuit detects the pressure drop and accelerates the pulse motor to correct the pressure fluctuation.

However, this had the following drawbacks.

The pulse motor must be accelerated at high speed by detecting the pressure drop, but the pulse motor has the disadvantage that it cannot be accelerated for emergency relief.

A pulse motor can be accelerated arbitrarily within the self-starting frequency range, but when accelerating beyond the self-starting frequency range, the feedback loop response must be adjusted to prevent the pulse motor from stepping out, and an amplifier must be installed. I kept it low and let the pulse increase slowly. However, although this prevents step-out, when the pressure reaches a specified value and the pulse rate is lowered, the response of the feedback loop is delayed, so the pulse rate does not drop suddenly but slowly. Therefore, the pulse motor has an extra −j
As the pump rotated at a faster speed, the pump's discharge amount increased accordingly, resulting in pulsating flow due to overdischarge.

On the other hand, an optical emission analyzer measures the concentration of a sample by heating the sample to a high temperature and emitting light to measure the intensity of the spectral lines specific to that element. In order to measure the spectral intensity of each element, it is necessary to set the wavelength of the spectrometer for each element.

What is required in emission spectrometry is the spectrum of the analysis line unique to each element, and there is no need to measure any other spectra. Therefore, the wavelength drive pulse motor of the spectrometer is scanned at high speed for wavelengths near the analysis line, and at low speed for only the vicinity of the analysis line for precise measurements. The transition from low speed to high speed, and from high speed to low speed, was done using a slow-up/slow-down method with a slope in the pulse rate.

This is a common method when moving from the self-starting region to the through region when using a pulse motor at high torque and high speed.

Conos slow-up/slow-down has disadvantages in that it takes time to repeat dozens of times for dozens of elements, and requires a correspondingly large amount of sample.

[Purpose of the invention]

A first object of the present invention is to provide a pulse motor operation method that can make the operation of a controlled object beneficial by changing the driving conditions of the pulse motor.

A second object of the present invention is to provide a fluid transfer pump that achieves good pressure control by effectively utilizing an irreversible time constant circuit that matches the feedback loop response to the characteristics of a pulse motor. be.

A third object of the present invention is to provide an analyzer in which the paper analysis time is shortened by changing the driving method of the pulse motor for wavelength scanning. - [Summary of the invention] The present invention c. Focused on the fact that slowing up and slowing down the pulse motor lengthens the analysis time, and as a means to solve this problem, the time during deceleration is shortened by slowing up and quick down. It is something.

In a preferred embodiment of the present invention, the pulsating flow of the pump is in a feedback loop that controls the speed of the pulse motor, and the slow-up/slow-down commonly used in pulse motor circuits is the cause of the increased pulsating flow. We confirmed this through experiments, and as a means to eliminate this pulsating current, we added an irreversible time constant circuit in which the time constants for charging and discharging the capacitor are different in the feedback loop. Improved control to eliminate pulsating flow caused by overdischarge.

[Embodiments of the invention]

FIG. 1 is a diagram showing the operating principle of a conventionally known micro-liquid pump.

The pump 1 includes a heart cam 11, a plunger 12, a cylinder 13, a check valve 14, and the like.

The discharge side of the pump 1 passes through a pressure sensing element 2 and is connected to a separation column 7.
It is piped to.

The output voltage of pressure sensing element 2 is connected to switch S11 and amplifier A2 via resistors R,+ and R2.

It is assumed that the amplifier Al is a hold amplifier and functions as an inverting amplifier of the amplifier 1 when the switch sl is on the a-contact side, and as a hold amplifier when the switch 81 is on the b-contact side.

The amplifier A2 is a comparator that compares and amplifies the voltage of the pressure sensing element 2 and the output voltage of the amplifier A2.

When R1=R2=R3''R4, amplifier AI becomes an inverse amplifier of amplifier 1, so the voltage of the pressure sensing element is V.
When , the output voltage of the amplifier Al is 1 and the output voltage of the comparator is zero.

Amplifier A3 is a summing amplifier that adds the voltage of flow rate setting device 3 and the voltage of switch S2. When the switch S2 is on the a-contact side, the added voltage is zero, and when the switch S2 is on the b-contact side, the output voltage of the comparator is added.

The output voltage of the amplifier A3 passes through a filter circuit of a resistor R7% and a capacitor C2, and is then converted to a voltage-frequency converter 4 (hereinafter referred to as VF).
input terminal of the converter).

The pulse motor 5 advances in proportion to the number of pulses of the VF converter 4.

The pulse motor 5 drives the vert cam 11 of the pump 1 and simultaneously drives the cam 6. A switch S is attached to the cam 6, and the switch S constitutes a switch 5lsS2.

To explain the operation, the displacement of the cam 11 (7%-) is shown in Figure 2 (
As in a), half a rotation is a discharge stroke, a half rotation is a suction stroke, and when one plunger is in a discharge stroke, the other plunger is in a suction stroke.

If the discharge pressure is zero, the liquid sucked into the cylinder 13 at atmospheric pressure will be discharged without pulsation, but if there is back pressure on the discharge side, the note cam will move through the discharge stroke as shown in Figure 2(b). Even if it moves, do not spit it out immediately.

This is due to the compressibility of the liquid, and the liquid with a high compressibility takes a long time to discharge.

Since a decrease in the discharge amount of the pump is detected as a decrease in pressure, it is sufficient to detect the decrease in pressure and rotate the pump's nozzle motor at high speed until a predetermined pressure is reached.

Switch S is operated by cam 6, but in this section...-
The tocam 11 operates before and after moving to the discharge stroke. Figure 2 (
C) is a state diagram of switch S. The switch is made before the note cam 11 moves to the discharge stroke. This is to hold the pressure during normal discharge. When the switch 81 is moved to the b contact side, the amplifier Al operates as a hold amplifier. In this state, the pressure is stable, so if the pressure signal is ■, the input to the amplifier A2 is 1■, which is applied to the resistor R4, and +■ is applied to the resistor R2, so the input of the amplifier A2 is If the input sum is zero, the output will also be zero. The switch S2 has also moved to the b contact side, but since the voltage at the b contact is zero, there is no change in the output of the amplifier A3. Therefore, the Nockles motor continues to rotate normally.

Next, the heart cam 11 detects the inhalation/discharge change point (θ=06
), the discharge pressure begins to decrease due to the compressibility of the liquid. When the pressure decreases, the output voltage of the pressure conversion element also decreases, and only the voltage applied to the resistor 2 side of the amplifier A2 decreases, so the amplifier A2, which operates as a comparator, outputs a voltage close to the power supply voltage at the output terminal. do.

When voltage is applied to the bi point of the switch S2, the amplifier A3
The input voltages are added and output as shown in FIG. 3(a).

The output voltage of amplifier A3 is input to VF converter 4 via resistor R7 and capacitor Czk.

The resistor R7 and the capacitor C2 cause the voltage to rise slowly as shown in FIG. 3(b) until the pulse motor 5 is unable to fully respond when the input voltage of the VF converter suddenly increases and the output frequency suddenly increases. This is because the pulse motor is the fourth
As shown in the figure, there is a case where the motor is driven with pulses within the self-starting frequency range A, and a so-called slow-up case where the motor is first driven within the self-starting frequency range and then slowly accelerated to drive within the through range B.

There is no problem when accelerating within self-starting frequency region A, but
This is because when operating at high torque and high speed like this pump, a circuit for slowing up is required when operating across the above two regions.

The pulse motor 5 rotates at a high speed, the pressure increases, and when the output of the pressure conversion element reaches V from v', the output voltage of the amplifier A2 becomes zero.

Since the added voltage from the switch S2 of the amplifier A3 becomes zero, the input voltage of the amplifier A3 becomes only the voltage of the flow rate setting device 3, and the output voltage of the amplifier A3 also becomes only the voltage of the flow rate setting device 3.

However, the problem here is that the voltage charged in the capacitor C2 slows down over time t via the resistor R7 as shown in Figure 3b.
Discharge at s't. In the trench where the input voltage of VF converter 4 drops to the output voltage of amplifier A3, the excess voltage is transferred to VF'
Since this means that an extra pulse is added to the converter, the discharge amount of the pump increases, resulting in a pulsating flow.

FIG. 5 is a diagram showing the principle of the micro-liquid pump according to the present invention.

The same symbols as in FIG. 1 have the same functions.

Diode D+ is connected in series with resistor R7 and amplifier A3
A diode D2 and a resistor R8 are further connected in parallel between the output terminal of the VP converter 4 and the input terminal of the VP converter 4.

Now, if the voltage of amplifier A3 increases as shown in 11 in Figure 3(a), capacitor C has diode Dt and resistor R.
7, and the voltage increases slowly as shown in FIG. 3(b).

Next, when the voltage decreases as shown at t2 in FIG. 3(a), the voltage of the capacitor C2 is discharged through the resistor Rs% die and the ode D2. If the discharge speed is R8-9, then the discharge speed is shown in Figure 3 (
As in b), the discharge occurs slowly, but if Rs>Re, the discharge becomes faster, as shown in FIG. 3(C).

Therefore, the extra voltage applied to the VF converter is reduced and the extra pulses are also reduced, which reduces overdischarge of the pump and has the effect of reducing pulsating flow.

In this example, the irreversible time constant circuit provided between the output of the control circuit and the input of the VF converter includes a series circuit of a first diode and a first resistor between the output of the control circuit and the input of the VF converter. Further, a series circuit of a second diode and a second resistor are connected in parallel so that the directions of the diodes are reversed. A capacitor is connected between the input of the VF converter and ground.

In FIG. 5, if R7>>R8, the discharge time constant is determined by resistor R8 and capacitor C2, so the effect is the same even without diode D1.

FIG. 6 is a diagram showing the principle of a conventional optical emission analyzer.

A sample 101 emits light by a light emitting auxiliary device 102 and a light source 10
It becomes 3. The light from the light source 103 is made monochromatic by the diffraction grating 104 and measured by the photoelectric conversion device 105. The one-envelopment grating 104 is driven by a pulse motor 106, and the pulse motor 106 is pulse-controlled by a controller 107.

FIG. 7(a) is a diagram of a scan pattern. Wavelength scanning is performed at low speed in the vicinity of the analysis line, and high-speed scanning with slow-up and slow-down is performed before and after the analysis line. Figure 7 (
b) is a diagram showing the relationship between wavelength and signal, and shows the spectrum of the analysis line recorded in a low speed range. In FIG. 7(a), Tt is a high-speed section, Ta is a slow-down section, T is a low-speed section, and Tm is a slow-up section.

Here, the slow-up section T is an unavoidable section due to the characteristics of the pulse motor, but in the past, TD was also set to be the same as T. For this reason, slowdown also takes time, and in an optical emission spectrometer or the like that repeats the slope drop and slowdown dozens of times, this has the disadvantage that the total analysis time becomes longer.

FIG. 8 is a scan pattern diagram based on another embodiment of the present invention.

The difference from FIG. 7 is that the slowdown T- is shortened. In other words, the time of the high-speed section Tt is lengthened and the time of the slowdown T4 is shortened, thereby reducing the scan time.

〔Effect of the invention〕

If the present invention is applied to a liquid sending pump for a liquid chromatograph, it is possible to reduce the pulsating flow of the pump, which has the effect of enabling highly sensitive analysis in the liquid chromatograph. Furthermore, if applied to a photometer, the pulse motor can be slowed up and quick-downed, thereby shortening the analysis time and reducing the amount of sample consumed.

[Brief explanation of drawings]

Fig. 1 is a diagram of the operating principle of a conventional micro-liquid pump, Figs. 2 and 3 are explanatory diagrams of pump operation, Fig. 4 is an illustration of the operating status of a pulse motor, and Fig. 5 is an embodiment of the present invention. A diagram showing a schematic configuration of an example, FIG. 6 is an explanatory diagram of a conventional emission spectrometer,
Figure 7 is a diagram of the velocity pattern in a conventional photometer, Figure 8
The figure is a speed pattern diagram of an embodiment in which the present invention is applied to a photometer. ■... Pump, 2... Pressure conversion element, 3... Flow rate setting device, 4... VF converter, 5... Pulse motor, 7... Column, R7, R8... Resistor, Dl, D
2...Diode, C2...Capacitor, 102...
...Light emitting device, 104...Diffraction grating, 106...Pulse motor, 107...Controlling 2nd eye (ku) θ l and θ 36θ □ Certain 3 Kukuhisa) it is t3 (C) t, tz Z'J Figure 6 $7 Solid (+2) Wavelength

Claims (1)

[Scope of Claims] 1. A pulse motor operating system characterized by having different pulse rates during speed increase and deceleration. 2. A pump driven by a pulse motor, a pressure sensing element piped to the discharge side of the pump, a control circuit that controls the output of the pressure sensing element to be constant, and a pulse motor that controls the output of the control circuit. The pulse motor operation method of the device consisting of the VP converter to be converted is characterized by the pulse rate of the VF converter being fast and quick down. 3. In the method of driving the diffraction grating of a photometer with a pulse motor, a pulse motor driving method is characterized in that a preset rotation speed is set by the number of pulses, and the rotation is performed in multiple stages of low speed and high speed.