JP2712355B2 - Drive control device for liquid feed pump - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an apparatus for controlling the driving of a liquid feed pump of a liquid crographograph, and in particular, uses a pulse motor as a driving motor and controls the pulse motor by a micro-step driving method. The present invention relates to a control device for driving.

(Prior Art) As a liquid feed pump of a liquid crographograph, a pump that converts the rotational movement of a pulse motor into a reciprocating movement of a plunger by a cam and thereby feeds a liquid is used.
When a pulse motor is used as the driving motor, it is necessary to reduce the vibration of the pulse motor and improve the position resolution in order to improve the liquid sending performance. Although liquid chromatographs of high-end models use a five-phase pulse motor or the like to improve the liquid sending performance, the pulse motor is complicated and expensive.

Therefore, an inexpensive two- or four-layer pulse motor is used. In order to increase the position resolution by a two-layer or four-layer pulse motor, micro-step driving for controlling a phase current pattern is performed.

(Problems to be Solved by the Invention) In the micro-step drive, when the phase current is small, the position accuracy becomes poor in a low flow rate region such as several μl / min to several hundred μl / min, and the liquid transmission becomes uneven. Occurs. Conversely, if the phase current is increased, the vibration increases in the middle flow rate range, adversely affecting the operation of the check valve, and may deteriorate the liquid sending performance.

SUMMARY OF THE INVENTION An object of the present invention is to provide a control device for driving a liquid feed pump by driving a pulse motor by micro-step driving, and to improve positional accuracy and liquid transfer performance.

(Means for Solving the Problems) In the present invention, the magnitude of the phase current of the pulse motor can be changed according to the flow rate. The phase current is increased in a low flow rate region where positional accuracy is required, the phase current is decreased in a medium flow rate region where vibration is a problem, and the phase current is increased in a high flow rate region where power is required.

According to the present invention, the pressure of the liquid being supplied is measured, and the magnitude of the phase current can be controlled by the pressure.

According to the present invention, the magnitude of the phase current can be controlled depending on whether the rotation of the pulse motor is acceleration, constant speed, or deceleration.

 FIG. 1 illustrates the present invention.

A setting unit 3 sets a flow rate and a flow rate program at that time. Reference numeral 4 denotes an operation flow value calculation unit that inputs a set value from the setting unit 3 and calculates an operation flow amount of the liquid feed pump 1. Reference numeral 5 denotes a motor drive current pattern generator that generates a current pattern of the motor drive current according to the flow value from the operation flow value calculator 4. Reference numeral 7 denotes a low flow region and a high flow region according to the flow value from the operation flow value calculator 4. A flow rate correction unit that outputs a correction value for correcting the magnitude of the phase current to the motor drive current output unit 8 so that the phase current in the motor is larger than the phase current in the medium flow rate region. This is a motor drive current output unit that determines the magnitude of the drive current. 6 is a pulse motor 2 according to the current pattern from the motor drive current pattern generator 5 and the current value from the motor drive current output unit 8.
Is a pulse motor drive circuit for driving the motor.

In order to further optimize the control, the pressure correction unit 10
And / or both of the acceleration / deceleration state correction units 11 are further provided. The pressure correction unit 10 receives the load pressure from the pressure sensor 9 provided in the discharge flow path of the liquid feed pump 1 and outputs a correction value for correcting the magnitude of the phase current based on the load pressure to the motor drive current output unit 8. I do. The acceleration / deceleration state correction unit 11 determines the acceleration, constant velocity, or deceleration state from the flow rate value from the operation flow rate calculation unit 4, and outputs a correction value for correcting the magnitude of the phase current according to the acceleration / deceleration state to the motor drive. Output to the current output unit 8.

(Operation) The motor drive current pattern generator 5 outputs a control waveform of a pulse speed and a phase current according to the flow rate.

When the flow rate calculated by the operation flow rate calculation section 4 based on the signal from the setting section 3 is in the low flow rate range, a signal for increasing the phase current is output from the flow rate correction section 7, and the motor drive current output section 8 outputs the signal. The magnitude of the phase current is largely determined. As a result, in the low flow rate region, the pulse motor 2 is driven by the phase current having a large amplitude, and the position accuracy of the pulse motor is improved.

When the flow rate is in the middle flow rate range, the amplitude of the phase current is reduced, and the vibration of the pulse motor is suppressed.

In the high flow rate range, the amplitude of the phase current is increased, and the pulse motor is driven with a large power.

As described above, it is possible to supply a drive current to the pulse motor so as to generate an optimal torque for the operation state according to the flow rate.

In order to further optimize the magnitude of the phase current, the motor drive current output unit 8 is provided with one of a correction value according to the pressure from the correction unit 10 based on the pressure and a correction value from the correction unit 11 according to the acceleration / deceleration state. By inputting both, the magnitude of the phase current is determined together with the correction value of the correction unit 7 based on the flow rate.

(Embodiment) FIG. 2 shows an overall configuration of a liquid feed pump and a drive control device.

The pump 1 has a plunger 1a supported reciprocally.
Is provided. The plunger 1a is in contact with a cam 1b rotated by the pulse motor 2, and the rotation of the pulse motor 2 is converted into a reciprocating motion of the plunger 1a. Reference numeral 20 denotes a liquid sent by the pump 1, and a pressure sensor 9 is provided in a discharge channel of the pump 1.

A CPU 22 is provided for driving and controlling the pulse motor 2. The CPU 22 outputs to the pulse motor drive circuit 6 a current pattern including the pulse speed and the control waveform, a current value indicating the magnitude of the phase current, and a polarity switching signal. CPU2
A RAM 24 and a ROM 26 are connected to the RAM 2 in addition to the setting unit 3 for setting a liquid flow rate program and a flow rate at a certain point. For example, an EPROM is used as the RPM 26, and a control waveform pattern, a table, and the like are stored in order to realize the motor drive current pattern generation unit 5, the flow rate correction unit 7, and the pressure correction unit 10 of FIG. .

The load pressure is also input from the pressure sensor 9 to the CPU 22. Although not shown in the figure, the output of the pressure sensor 9 is amplified to an appropriate size, converted into a digital signal, and
Read by U22.

FIG. 3 is a circuit diagram embodying the configurations of the pulse motor 2 and the pulse motor drive circuit 6 in the present embodiment.

30A and 30 are the A phase of the stator of the pulse motor 2, respectively.
A phase winding for a phase, and switching transistors 32A and 32 for polarity switching are connected in series, respectively, and these two series circuits are connected in parallel with each other. 30B and 30 are the stator B of the pulse motor 2 respectively.
The phase windings are phase windings, and switching transistors 32B and 32 for polarity switching are connected in series, respectively, and these two series circuits are connected in parallel with each other.

An A-phase current control transistor 34A is connected between the connection point of the phase windings 30A and 30 and the power supply + V, and an A-phase current detection is provided between the connection point of the emitters of the transistors 32A and 32 and the ground. Resistor 36A is connected. Phase winding 30B, 3
A B-phase current control transistor 34B is connected between the connection point 0 and the power supply + V, and a B-phase current detection resistor 36B is connected between the connection point of the emitters of the transistors 32B and 32 and the ground. It is connected.

To switch the polarity between the A phase and the phase, a polarity switching signal F is applied to the transistor 32A from the CPU 22, and the signal F is applied to the transistor 32 via the inverter 38A. Transistors 32A and 32 are turned on by signal F
Turn off to switch the polarity of A phase and phase. To switch the polarity between the B phase and the phase, the transistor 32B has C
The polarity switching signal G is applied from PU22, and the transistor 32
Is applied through an inverter 38B. The transistors 32B and 32 are turned on / off by the signal G to switch the polarity of the B phase and the phase.

A multiplication type D / A converter 40A is supplied with a pulse pattern corresponding to the flow rate and a current pattern signal a including a motor drive current control waveform from the CPU 22. 40B is also a multiplying D / A converter, and receives a pulse pattern corresponding to the flow rate and a current pattern signal b including a motor drive current control waveform from the CPU 22.

Reference numeral 42 denotes a D / A converter, which receives a signal indicating the current value of the phase current from the CPU 22, and outputs a signal to the D / A converters 40A and 40B as a signal for controlling the phase current span. This gives D /
The A converters 40A and 40B respectively convert the motor drive current control waveforms A and B, whose amplitudes are controlled, into respective pulse width modulation circuits 44A and 44B.
Output to The pulse width modulation circuit 44A modulates the pulse width so that the motor drive current control waveform A becomes equal to the voltage corresponding to the phase current input from the resistor 36A, and the transistor 34
Control the on-time of A. The pulse width modulation circuit 44B modulates the pulse width so that the motor drive current control waveform B becomes equal to the voltage corresponding to the phase current input from the resistor 36B, and controls the ON time of the transistor 34B. Thus, the pulse width modulation circuits 44A and 44B minimize the error between the motor drive current control waveform and the current value actually flowing to the motor.

FIG. 4 shows motor drive current control waveforms A and B output from the D / A converters 40A and 40B, and polarity switching signals F and G. The amplitudes of the motor drive current control waveforms A and B are corrected depending on the flow rate, the load pressure, and the acceleration / deceleration state, for example, as indicated by a solid line, a one-dot chain line, and a two-dot chain line in A. These signals A, B,
The pulse motor 2 is operated by F and G.

The torque of the pulse motor 2 is controlled by the value output from the CPU 22 to the D / A converter 42. The relationship between the set flow rate and the appropriate torque is small in the middle flow rate range as shown in FIG. , Low and high flow areas. This pattern is written in the ROM 26 using a table or the like. The CPU 22 reads the value at that time according to the read set flow rate value, and outputs the value to the D / A converter 42.
That is, when the set flow rate value is small, a large value is output to the D / A converter 42, and in the D / A converters 40A and 40B, the span of the motor drive current control waveforms A and B is increased and the pulse motor 2 is driven. When the set flow rate value is in the middle flow rate range, a small value is output to the D / A converter 42, and the D / A converter 40
In A and 40B, the pulse motor 2 is driven with a small torque by reducing the span of the motor drive current control waveforms A and B. When the set flow rate value is in the high flow rate range, a large value is output to the D / A converter 42, and in the D / A converters 40A and 40B, the span of the motor drive current control waveforms A and B is increased so that a pulse is generated at a large torque. The motor 2 is driven.

Here, as an example of the flow rate range, the low flow rate range is about 1 μm.
l / min ~ 100μl / min, medium flow range is about 100μl / min ~ 3ml / min,
The high flow rate region indicates about 3 ml / min or more.

It is desirable that the optimum motor torque value is also corrected by the load pressure, that is, the liquid sending pressure. So, ROM26
Further, a correction pattern of the load pressure and the current correction value as shown in FIG. 6 is stored in a table or the like. The CPU 22 reads the correction value from the pressure value input from the pressure sensor 9, and determines the span of the motor drive current control waveforms A and B in addition to the correction value based on the flow rate shown in FIG.

Further, the CPU 22 determines whether the rotation speed of the pulse motor 2 is accelerated, constant, or decelerated from the flow rate. In the case of acceleration or deceleration, it is desirable to make correction so as to increase the motor torque as shown in FIG. The CPU 22 reads the correction value from the acceleration / deceleration state at that time, and determines the span of the motor drive current control waveforms A and B together with the correction value based on the flow rate or the correction value based on the flow rate and the correction value based on the pressure.

The relationship between the flow rate f and the correction value f ′ shown in FIG. 5 is stored in the ROM 26 as a conversion table T ₂ (f), and the relationship between the load pressure P and the correction value P ′ shown in FIG.
The operation of determining the span of the motor drive current control waveforms A and B when T ₁ (P) has been written in the ROM 26 will be described with reference to FIG.

The value output to the D / A converter 42 is K, and K = 0 and X = 0 as initial settings (step S1). X is a correction value according to the acceleration / deceleration state.

The pressure data is read from the pressure sensor 9 (step S
2), P ′ is obtained by referring to the conversion table (step S)
3). F 'is obtained from the flow rate by referring to the conversion table (step S4). It is determined from the flow rate whether the vehicle is accelerating or decelerating (step S5). If the vehicle is accelerating or decelerating, X = N (constant value) (step S6). As it is, K = P '+ f' + X is calculated (step S7). The calculated K is output to the D / A converter 42.

In the embodiment, in order to control the amplitude of the motor drive current control waveforms A and B, in addition to the correction based on the flow rate, the correction based on the pressure and the correction based on the acceleration / deceleration state are also performed. However, only the correction based on the flow rate may be performed, and in order to perform a more sufficient correction, one or both of the correction based on the pressure and the correction based on the acceleration / deceleration state may be performed.

In the embodiment, in order to perform the correction based on the flow rate and the correction based on the pressure, the pattern or the table is written in the ROM 26 and read by the CPU 22.However, these correction values may be realized by hardware such as a function amplifier. Alternatively, it is also possible to provide a correction value by software after giving a function.

The motor drive current control waveform of the pulse motor is such that, in terms of the drive efficiency of the pulse motor, the current at the rising portion is made larger than the current at the falling portion when the motor is accelerating or rotating at high speed, and conversely when the motor is decelerating. It is preferable to control the current at the falling part of the waveform to be larger than the current at the rising part. The pattern of such a control waveform corresponding to the operation state of the pulse motor may be stored in the ROM 26.

Since the flow rate corresponds to the rotation speed of the pulse motor,
Controlling the driving of the liquid feed pump using the rotation speed of the pulse motor as a parameter is also included in the scope of the present invention.

(Effects of the Invention) In the present invention, the magnitude of the phase current of the pulse motor can be changed in accordance with the flow rate. The phase current is reduced in the range and the phase current is increased in the high flow rate range where power is required. The liquid sending performance can be improved.

In the present invention, it is also possible to measure the pressure of the liquid being fed, control the magnitude of the phase current also by the pressure, and furthermore, whether the rotation of the pulse motor is accelerated / constant speed or decelerated. If the magnitude of the phase current can be controlled depending on whether there is, the liquid sending performance can be further improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the present invention, FIG. 2 is a schematic configuration diagram showing one embodiment, FIG. 3 is a circuit diagram of the embodiment, FIG. 4 is a waveform diagram showing a motor drive current pattern, FIG. FIG. 6 shows the relationship between the flow rate and the correction value, FIG. 6 shows the relationship between the load pressure and the correction value, FIG. 7 shows the relationship between the acceleration / deceleration state and the correction value, and FIG. It is a flowchart figure which shows operation | movement of an example. Reference Signs List 1 ... Sending pump, 2 ... Pulse motor, 3 ... Setting unit, 4 ... Operation flow value calculation unit, 5 ... Motor drive current pattern generation unit, 6 ... Pulse motor drive circuit, 7 ... Flow rate ... Correction section, 8... Motor drive current output section, 9.
Pressure sensor, 10: Correction unit based on pressure, 11: Correction unit based on acceleration / deceleration state.

Claims (3)

(57) [Claims] An operating flow rate calculating section for inputting a set value from a setting section to calculate an operating flow rate of a liquid feeding pump, and a motor for generating a current pattern of a motor driving current according to the flow rate value from the operating flow rate calculating section. The magnitude of the phase current is corrected so that the phase current in the low flow rate region and the phase current in the high flow rate region becomes larger than the phase current in the middle flow rate region according to the flow value from the driving current pattern generation unit and the operation flow value calculation unit. A correction unit based on a flow rate for outputting a correction value to a motor drive current output unit described later, a motor drive current output unit for determining the magnitude of the motor drive current from the input correction value, and a current pattern from a motor drive current pattern generation unit. A pulse motor drive circuit for driving a pulse motor according to a current value from a motor drive current output unit. 2. A pressure sensor according to claim 1, wherein a load pressure from a pressure sensor provided in a discharge passage of the liquid feed pump is input, and a correction value for correcting the magnitude of the phase current according to the load pressure is output to the motor drive current output unit. The drive control device according to claim 1, further comprising a correction unit. 3. A motor drive current output unit for judging an acceleration, constant velocity or deceleration state from a flow value from the operation flow value calculation unit and correcting a magnitude of a phase current according to an acceleration / deceleration state. The drive control device according to claim 1, further comprising a correction unit that outputs an acceleration / deceleration state to the control unit.