JP2007051645A - Electric metering pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metering pump provided with a rotary drive motor and an oscillating piston. <P>SOLUTION: A rotary motion of the drive motor is transformed into an oscillatory motion of a connecting rod by means of a gear arrangement and a displacement means activated thereby executes an oscillating linear motion on continuous rotation of the drive motor, which results in transfer of a medium to be metered in a metering head 12 arranged in a longitudinal axis of the connecting rod 19 cooperating alternately with an outlet valve and an inlet valve to produce a pump stroke (pressure stroke) and a priming stroke. In such a metering pump, a reference element 35 is associated with the connecting rod, the position of which is detected by a positional sensor, wherein the positional sensor provides an actual signal x1 which is in a fixed relationship to the position of the reference element and thus to that of the displacement means and provides information regarding the motion executed by the displacement means, so that an electronic control system of the metering pump can react to the conditions of a metering circuit and the pump. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric metering pump according to the preamble of claim 1.

  Such electric metering pumps are generally known and are adapted to the requirements by means of add-ons. The electric metering pump operates with quantitative analysis, and metering is performed by transferring a closed volume via the displacement means. Therefore, the measurement volume for each stroke corresponds to the difference in volume due to the movement of the displacement means.

  Generally, such an electric metering pump converts a continuous rotational motion of a drive motor into a vibrating linear motion of a displacement means via a gear unit. The rotational speed and torque of the motor are reduced in the gear unit and adapted to the speed and power requirements of the displacement means. The take-out shaft of the gear drives a device that converts the rotational movement laterally, ie perpendicular to the rotational axis, such as a spring / fitting or cam drive. Due to the lateral deflection, a connecting rod is slidably guided by a bearing in the deflection direction. As a result, movement and power move to the displacement means, and in the metering head arranged on the longitudinal axis of the connecting rod, the displacement means cooperates with the outlet valve and the inlet valve alternately while pump stroke (pressing stroke). ) And a priming stroke. As a result, the medium to be weighed moves.

  In the various embodiments, first the type of motor is different. Usually, an asynchronous motor, a synchronous motor, or a step motor is mounted outside or inside the actual pump chamber. The type of the metering pump varies depending on the type of the metering pump, and is a worm gear, a spur gear, or a belt driving unit. The drive unit that drives the connecting rod via the deflection device is forcibly guided or locked completely only in the forward direction of the deflection device. The connecting rod is driven by the deflecting device in the pressing stroke, but in the latter priming case, it is driven by a recovery spring and the connecting rod approaches the reversing deflecting device. The recovery spring is dimensioned to be compressed with a pressing stroke to provide the necessary force during priming. Depending on the type of pump, the power for connecting the connecting rod to the diaphragm as the displacement means via either a rigid link mechanism or a hydraulic intermediate circuit varies. The hydraulic fluid is usually oil, but is not compressible, so the hydraulic coupling mechanism operates in the same way as a rigid coupling mechanism. In addition to systems with metering heads described herein, pump structures are also known to operate with two or more metering heads driven by a common drive. According to one embodiment, two opposing connecting rods are arranged on one side of a common longitudinal cam and are driven in opposite directions, each connecting rod having a metering head with displacement means. According to another embodiment, a camshaft supporting several co-driven cams is extended and operated with a number of metering heads, each cam being arranged to extend over the camshaft It is also known to drive a unit formed by a metering head with displacement means lying in the direction of the rod and the connecting rod axis.

  In the simplest example, all moving parts are mounted on ball bearings or friction bearings in a common pump chamber. In another example, each functional group is further collected in a chamber or mount, some filled with oil, and mounted as a module. As a specific example of the present case, there is a unit mounted outside the pump chamber, which is formed by a reduction gear having a motor and a mounting flange and a take-out shaft attached in advance.

  In the simplest example, the drive motor is turned on continuously for continuous metering or is turned on for a specific period for each metering stroke. In another type, the drive motor is controlled via a frequency converter according to a predetermined time profile. As a result, the rotational speed of the motor, and thus the metering power, becomes more reproducible and does not depend on electrical parameters such as the frequency of the mains voltage or the actual voltage level.

  The motor rotation speed is determined in advance by the electric frequency of the motor drive unit, and is determined in combination with the gear speed characteristic of the cam gear and the sine curve and each stroke period. When continuously driven, one stroke period is determined by the effective motor rotation speed and the gear reduction in a state where a load is applied. In the on / off operation, when a single stroke or a plurality of strokes are executed, and the motor itself stops at, for example, a priming dead center, the start and deceleration times are taken into consideration. Therefore, the period of one stroke must be extended as appropriate. In continuous operation, the number of strokes is determined by the period of one stroke, and in on / off operation, the number of strokes is determined by the motor switching repetition rate, but the repetition rate may be faster than the time required to execute one stroke. Of course not.

  The stroke length is adjusted by limiting the lateral deflection. This may be done, for example, by adjusting the eccentric using a wobble cylinder operating on two slopes that can rotate in opposite directions. One possibility is to use an adjustment buffer that can be used with a spontaneous deflection system. This buffer is adjusted in the form of a mechanically adjustable spindle that limits the reverse movement of the connecting rod back to the adjustable point before reaching the rear dead center of the deflector during priming . The buffer determines the starting point of the stroke motion, and the end point is the completion point of the deflection operation. According to one possible embodiment, the stroke adjustment pin is screwed into a thread in the pump chamber and is provided with a calibration knob accessible from the outside to constitute a buffer for the connecting rod during priming. In the case of a hydraulic system, stroke adjustment is performed, for example, by screwing a slidable sleeve, which can be positioned using a calibration knob accessible by the operator, into a thread in the pump chamber. This sleeve covers the relief hole of the connecting rod, opens the shunt of the oil circuit after moving a certain distance, and increases the power to connect the connecting rod to the diaphragm.

  The movement of the displacement means is caused by a combination of gears and other mechanical parts. During forward movement, the drive unit operates against the force of the recovery spring acting on the connecting rod via the displacement means. In the reverse movement, in the case of a forced displacement system, the connecting rod is pulled back by the drive, and in the case of one-way operation, the recovery spring pushes back the connecting rod to generate power for priming the metering medium. The movement of the connecting rod thus follows the characteristics of the deflection device. For example, in the case of a cam, the movement is represented by a sinusoid and is performed between two dead points of the cam stroke for the entire stroke length. When the stroke length is shortened, the movement when adjusting the cam is represented as a complete sinusoid with reduced amplitude, and in a tightly connected system with an adjustment buffer or hydraulic system with a relief hole, The original motion and amplitude of the deflecting device is maintained but is no longer fully implemented. Moreover, the movements of the connecting rods intersect at the start or end area (step-off), depending on the adjusted stroke length and the connection system. The forward movement for executing the pressing stroke is executed in less than 1 second (for example, 200 ms) depending on the motor drive unit. The priming stroke is carried out as set by the deflection device for a time similar to the time of the pressing stroke. This achieves a relatively high instantaneous speed for the metering medium in both stroke stages, and in the case of an eccentric drive, the maximum speed is achieved in the middle of the movement.

  In an embodiment consisting of several units consisting of a connecting rod and a metering head driven by a common camshaft operating with several cams, the cam can be arranged on the shaft with the phase displaced. Good. This distributes the necessary peak power to the individual metering heads during a complete revolution of the camshaft, making the best use of the available power of the motor.

  According to a particular embodiment, the so-called diaphragm metering pump uses a partially flexible diaphragm as the displacement means. This diaphragm is not stiff and elastically deforms by a certain amount in the bending region when the pressure of the metering medium is activated. The amount of deformation occurs in the first part of the stroke motion that is not used for metering, but is lost due to the effective stroke motion, resulting in an increase in operating pressure and a decrease in the measured amount. This reduction characteristic is much more pronounced in normal use than allowed by metering accuracy. Normally, the electric metering pump cannot be adjusted over a wide range of operating pressures while maintaining the desired accuracy. Also, the error due to calibration gets worse with each repeated calculation. However, in use under actual operating conditions, the above-described calibration measurement must be performed, especially when using strong chemicals, which is a very difficult step.

  Current general-purpose electric metering pumps are useful and exhibit favorable metering characteristics for many processes, but have a deficiency with respect to the hydraulic characteristics of the metering process compared to the ideal one. For example, the measured quantity is relatively strongly dependent on the operating pressure of the measuring circuit, and problems such as flow noise and pressure drop due to the high instantaneous flow rate of the measuring medium occur.

  A particular object of the present invention is to provide a variable and wide range of operation of an electric metering pump without adversely affecting manufacturing costs by overcoming known deficiencies related to the hydraulic characteristics of the metering process. In addition, the operation of the connecting rod and the connected displacement means are adapted to the standards, making it possible to adjust the weighing process itself, and defects due to manufacturing and unfavorable characteristics of the module (eg elastic diaphragms if present) are electronically controlled. To be considered by. These means prevent or detect defects in operating conditions and correct defects in manufacturing and / or use with on-board electronics, thereby reducing the predetermined volume of the weighing medium in the weighing process. It must be possible to measure accurately and reliably.

The problem is solved by a reference element connected to a connecting rod whose position is detected by a position sensor. Here, the position sensor has a fixed relationship with the position of the reference element and thus the position of the displacement means, and provides an actual signal (x ₁ ) that provides information on the movement of the displacement means. This allows the electronic control system of the metering pump to react to the metering circuit and the operating conditions of the pump.

  A position sensor captures the movement of the connecting rod and an electronic control system evaluates it. In this regard, the control system begins by limiting the conditions, examines the motion by comparing characteristics, and reacts to the motion by influencing the motor drive. In this way, the weighing is performed in the best condition, and for example, the precision failure caused by the characteristics of the diaphragm is eliminated.

  If the position sensor operates according to the non-contact principle, the non-wearing operation of the sensor is guaranteed, but this is convenient and practically necessary because of the high number of strokes during the lifetime of the metering pump.

  If the position element associated with the connecting rod is installed outside the metering head, the flexibility is increased with respect to the space for the precursor.

  When the reference element affects the optical path of the light source and the cooperating position sensor is fixed to the pump chamber or other fixed part and operates as a light receiving part, non-wearing operation is guaranteed, but the lifetime of the metering pump This is extremely important as the number of strokes in it is large, and the moving parts pass through without contact. Such an arrangement is further advantageous in that the structure of such a position sensor is essentially insensitive to stray magnetic fields.

  If the reference element is a shadow generator or shadow defining edge and the cooperating position sensor fixed to the pump chamber or other fixed part is composed of a series of photo-coupled charge coupled devices (CCD), such an arrangement is Has important optical properties that must be satisfied by the position sensor. First, this arrangement operates on the principle of non-wear optical function and is insensitive to stray magnetic fields. Second, such sensors are substantially free of linear defects.

  If the position sensor is placed on its own sensor carrier fixed to the pump chamber or other fixed part, such an arrangement is pre-assembled and tested as a module, which facilitates assembly. To do. When the sensor carrier is formed as a non-insulating plastic part, it is easy to electrically insulate the sensor element from the metal parts and gears of the chamber.

  If the light source, shadow generator or shadow-defining contour, and receiver constitute a light box-like arrangement and the measurement values are fed continuously or stepwise to the electronic control system, such an arrangement The electronic control system is provided with location data at an appropriate frequency.

  If the light receiving part of the position sensor is composed of a plurality of receivers (pixels) arranged in a straight line, preferably 128 pixels, such an arrangement can be achieved with illuminated and unilluminated cells. By determining the shadow edge between the two, the position can be readily determined, and a resolution equal to the cell spacing of the receiver module can be clearly provided.

  If the light source is a light emitting diode (LED), the light emitting diode is arranged opposite the light receiving part of the position sensor and the light beam directed to the light receiving part is not blocked by the connecting rod, the cheap LED is high Convenient because it has a nearly point light source that is essential for obtaining optical resolution and has an almost infinite lifetime. By disposing the LED opposite the position sensor on the other side of the connecting rod, it is possible to increase the distance between the light source and the light receiving unit, thereby making the light emission angle relatively to the element mounting position. No longer depend on it.

  If the start value of the position sensor is generated by interpolating the luminance values of several pixels present in the shadow transition region, the resolution of the start signal of the position sensor is determined by the mechanical pitch (interval of the cells of the CCD receiver). ) Will be finer than that determined by.

  When filtering means are used to process the signal from the position sensor, the resistance of the position sensor to interference is improved.

  If the zero position error of the position sensor is eliminated by the reference memory and the scaling error of the position sensor is eliminated by including one or more reference positions, assembly fluctuations during operation, for example during heating or bearing wear, The sensitivity of the position sensor with respect to mechanical displacement is reduced.

  When the illumination variation of the position sensor is made constant by controlling or adjusting the light source using the luminance value obtained by the pixel, the sensitivity to the module parameter variation of the position sensor is lowered.

  When the luminance variation between individual pixels of the light receiving unit is corrected by providing a reference memory for each pixel sensitivity, the influence of contamination on the light receiving unit is reduced.

  If the setpoint of the stroke adjustment pin is determined by measuring directly during weighing via a position sensor, no additional sensor is required to mechanically position the associated mounting element.

  If the electronic control system detects a blockage or incomplete stroke in the displacement means by evaluating the position sensor signal, the reliability of the metering can be increased. In the case of prior art metering pumps that do not have a position sensor, a sensor is often added to monitor the metering movement, for example by sending a test signal to the electronic control system through a reference mark for each stroke. Thus, the stroke period is measured and it can be estimated whether the weighing process has been carried out correctly. In contrast to such sensors, the position sensor can be used as described above to obtain the desired information at any point during the metering stroke, not only when passing the fiducial mark, without additional sensors. It is easy to finish and is convenient.

  When the drive motor is operated with slip, for example an asynchronous motor is employed, and the electronic control system determines the nominal number of strokes or the nominal stroke duration of the displacement means from the nominal rotational speed of the drive motor and known gear characteristics The position of the displacement means by evaluating the position sensor signal to determine the slip of the drive motor by comparing the actual stroke count with the nominal stroke count or by comparing the actual stroke period with the nominal stroke duration of the displacement means. When determining the actual number of strokes or the actual stroke period, and finally changing the nominal rotational speed of the drive motor so that the displacement means operates at the desired number of strokes, the stroke caused by the slip of the drive motor Weighing accuracy is improved by eliminating the error of times That. Prior art metering pumps that do not include a position sensor often employ sensors that monitor metering movement, for example, by passing a reference mark every stroke and sending an inspection impulse to an electronic control system. Makes it possible to measure and correct the stroke period and to dispense with such additional sensors when using position sensors.

  If the drive motor is operated with slip, for example an asynchronous motor is employed, and the electronic control system determines the nominal number of strokes or nominal stroke duration of the displacement means from the nominal rotational speed of the drive motor and the known gear characteristics of the piston Displacement by evaluating the position sensor signal to determine the slippage of the drive motor by comparing the actual stroke number with the nominal stroke number or comparing the actual stroke period with the nominal stroke period of the displacement means When determining the actual number of strokes or the actual stroke period of the means, the electronic control system also determines the force applied to the displacement means from the observed drive motor slip and known gear characteristics to reduce the operating pressure of the metering medium This information can be used to improve the reliability and accuracy of weighing. And means that it is possible to perform the compensation function. An electronic control system determines the nominal speed of the displacement means from the nominal rotational speed of the drive motor and known gear characteristics at every moment of the metering process, and further compares the actual instantaneous speed with the nominal speed of the displacement means, By calculating the instantaneous slip of the drive motor, thereby reassociating the known gear characteristics and relating it to the instantaneous energy profile of the displacement means, by evaluating from the position sensor signal When determining the nominal speed of the displacement means, the desired information can be obtained with respect to the energy at any point in the weighing process, the desired monitoring and compensation functions can be performed at different times, and thus the reliability and accuracy of the weighing can be improved. improves.

  If the electronic control system reduces the working pressure of the metering medium from the observed power profile of the displacement means, the adverse effect of the working pressure on the metering process can be offset.

  The electronic control system detects movement of the metering medium outside the specified pressure range from the observed working pressure and exceeds a predetermined maximum allowable pressure specified by the metering pump or operator or falls below a predetermined minimum pressure Sometimes when an electronic control system adjusts the metering, it can detect problematic operating conditions such as overpressure conditions or pressure loss due to defective piping and take safety measures such as adjusting the metering, which makes it lighter Can improve the reliability. As long as the metering pump is the only pressure increase system in the process, other operating means such as an overpressure limiter can be dispensed with. If it is possible to control the operating pressure to a value within a specific pressure range of the metering pump, even in situations where it is not possible to use a prior art metering pump monitoring system that begins to operate only when the metering pump is blocked, Monitoring becomes possible.

  The displacement means is a partially elastic diaphragm, which is caused by the elastic deformation of the diaphragm and is known to the possible weighing error and weighing effectiveness working pressure determined from the measured working pressure of the weighing medium When notifying the electronic control system of the dependency, and when the displacement means affects the rotational speed of the drive motor and thus the number of strokes, and the expected measurement error is compensated, the measurement accuracy is improved.

The rotational speed of the drive motor is influenced by the signal (x ₁ ) read by the position sensor which detects the position of the connecting rod via the control circuit in the control accuracy, so that the linear movement of the connecting rod and the displacement means When influencing linear motion to follow a given nominal profile, the intended effect on the motion of the displacement means is used to take advantage of favorable metering hydraulic properties, such as low speed metering properties, and / or Can achieve or improve weighing accuracy for partial strokes.

Metering pump, or have a control device in addition to the position sensor and by or by varying the rotational speed of the drive motor, the position of the displacement means via a control unit (hereinafter, indicated by x _1), the speed (hereinafter, v indicated by ₁₎ or it is advantageous if affects the alternating acceleration. By controlling the speed, for example, it is possible to directly control the actual flow rate of the measuring medium necessary to avoid the occurrence of cavitation when priming is performed at a low speed. On the other hand, it is possible to control almost the deadlock situation by controlling the position, but this situation is that information about the speed is generated by the difference of the displacement signal, but it is very small and cannot be processed efficiently by the control device. It is. By controlling the position, this problem can be avoided. For example, the position control can be advantageously employed by electronically limiting the stroke or suppressing the measuring speed. Since the acceleration of the mass to be moved directly reflects the power of the motor for high-speed processing, controlling the acceleration is convenient for controlling the adjustment easily.

If the metering pump is equipped with a control device in addition to the position sensor, and if the displacement means v ₁ is reduced during the priming and / or pressing phase, the pressure loss caused by the resistance to flow and the occurrence of cavitation I can deal with it. When metering a highly viscous medium, such as lecithin, if the flow rate is too high, a large pressure drop occurs in a confined area, such as in a valve. Such a pressure drop must be overcome in the form of additional power from the drive and can be kept low by controlling v ₁ of the displacement means. Furthermore, the flow noise when the flow velocity is reduced can also be effectively reduced. When weigh a medium that easily generates gas, such as chlorine bleach, cavitation frequently occurs especially during priming where the flow rate is too high, and mechanical wear is reduced by lowering it below the vapor pressure of the weighing medium. becomes terrible. By controlling the displacement means v ₁ during the priming stage and / or the pressing stage, this phenomenon can be successfully avoided.

  When the metering pump has a control device in addition to the position sensor, and the desired stroke length is transmitted to the control device, and the movement of the displacement means is electronically limited to the stroke length to be executed by the control device. The control device, after executing the desired stroke length, stops the drive motor, reverses the rotation, executes the priming stroke, stops the motor or executes the next pressing stroke, and the mechanical adjustment element is large. The part becomes unnecessary.

  If the metering pump is equipped with a control device in addition to the position sensor, the control device also distributes the forward movement of the displacement means during the pressing phase by driving the motor for a period determined by the repetition rate of the metering stroke. Thus, if the metering medium is to be distributed as smoothly as possible, for example even during a slow metering stroke of several minutes, the density variation of the metering medium can be substantially avoided.

  The displacement means is a partially elastic diaphragm, and the electronic control system detects the opening of the outlet valve from the instantaneous power profile and measures the immovable region due to the elastic deformation of the diaphragm from this observation value. If the actual stroke path is influenced by deliberately stopping the stroke movement as a function of the deformation, the measurement accuracy is improved when the dependence of the measured quantity on the back pressure is substantially reduced. This improvement is achieved by eliminating errors due to the elastic deformation of the diaphragm due to operating pressure so that the aforementioned deformation does not contribute to weighing. The reduced dependence of the measured amount on the operating pressure eliminates the need for subsequent calibration that would otherwise be required when operating parameters such as operating pressure are changed significantly. Compensating for diaphragm deformation by observing the power profile is particularly advantageous when evaluating motor slip as it reflects the actual power requirements. Therefore no further measurements are necessary.

  If the metering pump is equipped with a control device in addition to the position sensor, and if the displacement means is a partially elastic diaphragm and the actual stroke path is affected by the deformation of the diaphragm, the control device After the desired stroke length is released, the drive motor is stopped, the drive motor is rotated in reverse, the priming stroke is executed, the motor is stopped, or the next pressing stroke is executed, resulting from the deformation of the diaphragm The error (related to the stroke path or the measurement volume) is eliminated, the deformation amount does not contribute to the measurement, and the measurement accuracy is improved. The reduced dependence of the measurand on the working pressure eliminates the need for subsequent calibrations that would otherwise be necessary when changing operating parameters such as operating pressure, and the stroke length setting and weighing medium. This means that the linearity of the relationship between the actual measured quantity and the actual measured quantity is improved. Determining the deflection of diaphragm deformation from power profile observations is particularly advantageous when evaluating motor slip as it reflects actual power requirements. Therefore no further measurements are necessary.

  If the displacement means is a partially elastic diaphragm and the metering pump is equipped with a control device in addition to the position sensor, and the actual number of strokes is affected by the deformation of the diaphragm, the control device is due to the deformation of the diaphragm Determine the correction value of the error (related to the stroke path or measurement volume), and the rated rotation speed of the drive motor will change greatly due to the above-mentioned correction, so the error caused by the deformation of the diaphragm is eliminated and the operation of the measured quantity The dependence on pressure is reduced.

  Embodiments of the invention and various uses of an electric diaphragm metering pump with a cam drive will be described in detail. The drawings are as follows.

  FIG. 1 shows the structure of an electric metering pump (part of which can be seen inside). As is generally known, the electric metering pump basically includes three groups of parts, that is, a drive motor 2 having a gear unit, a cam drive unit in the cam chamber 1, and an electronic control system. The electronic device housing 28 is mounted with modules and the like. A foot plate 4 having a fixing hole is disposed on the lower side of the electronic device housing 28, and the cam chamber 1 installed and fixed on the electronic device housing includes, for example, a gear unit fixed to the cam chamber with a screw. The drive motor 2 provided is supported.

  The housing formed from the cam chamber 1 and the electronic device housing 28 is mounted with the components of the cam drive unit on the upper portion thereof, that is, the cam chamber 1. The components of the cam drive are housed in a cam receiver 22 which ensures that the individual parts are correctly positioned and secured within the cam chamber 1. The three-phase asynchronous motor 2 is formed as a square gear and is flanged from the outside as a module on the cam chamber 1 together with a reduction gear 11 fixed with screws. The take-out shaft of the motor is perpendicular to the shaft center line of the motor, and directly forms the drive shaft of the cam drive unit, or is fixed coaxially through a coupler as in this embodiment. . The drive shaft of the cam drive portion, that is, the cam shaft 17 is rotatably mounted on the cam receiver 22 and supports a cam fixed thereto. The cam shaft passes with the cam through the appropriately cut push arm 20. The cam shaft 17 is rotated by a motor / gear unit via a shaft coupler for the drive motor 2 to drive the push arm 20 together with the outer surface of the cam to the inner surface of the cutout portion, that is, the stop surface. The push arm 20 drives the connecting rod 19 that is inserted and fixed in this specific example. The unit formed by the push arm 20 and the connecting rod 19 can be displaced in the longitudinal direction by two guide bushes. The shaft of the cam shaft 17, the longitudinal axis 18 of the push arm 20 and the connecting rod 19 are on the same horizontal plane and are perpendicular to each other. One of the two guide bushes 26 for the connecting rod 19 is located on the bearing plate 24 fixed to the cam receiver 22 on the pressing head side. A further guide bushing 27 occupying the plug-in part of the push arm 20 directed towards the measuring head is located on the stroke adjusting pin 8. Coaxial to the longitudinal axis 18 of the connecting rod 19 is a manually actuable adjusting means 7, which limits the axial movement of the push arm 20 during priming and thus the stroke of the metering pump. The stroke adjusting pin 8 screwed into the thread of the cam receiver 22 is adjusted.

  There is also an electronics housing 28 or electronic control system at the bottom of the sealed chamber of the housing. Since metering pumps are often used in conjunction with chemically strong media, the housing is sealed to prevent splashing, protecting the cam drive and electronic control system from moisture and corrosion. The electronic control system is a horizontal control electronic element 34 provided with a controller for the motor control unit 29, the horizontal control electronic element 34 formed as an integrated frequency converter, and an input element necessary for operating the metering pump. And an electronic device 6 disposed on a housing cover 5 that supports the display element. The control element is protected by a cover 9. Under the cover 9, there is a control wire 10 or a connecting portion for power supply.

  Next to the connecting portion of the control wire 10 or the power source, there is a measuring head 12 coaxially with the longitudinal axis 18 of the connecting rod. In the measuring head 12, a diaphragm made of, for example, plastic is fixed to the circumference thereof. Functions as a means. Metering head 12 also supports inlet valve 14 and outlet valve 15, metering through metering chamber 16 through inlet valve 14 between the diaphragm and metering head 12, and metering tube through outlet valve 15. Let the media prime. The electric metering pump operates in a quantitative analysis, i.e. priming a predetermined volume and pushing through the outlet valve 15 for each stroke. The diaphragm 13 is moved by a vibrating motion by a cam drive unit that moves the connecting rod 19 back and forth in the vertical axis direction. On the side of the stroke adjusting pin 8, the unit formed by the push arm 20 and the connecting rod 19 operates together with the adjusting means 7 as a manually adjustable stroke adjusting device. At the opposite end, the portion of the connecting rod 19 that faces the measuring head 12 is fixed to the core 30 of the diaphragm 13 and is moved by a vibrating motion.

  Between the push arm 20 and the joint ring 25 of the bearing sleeve 24 is a compression spring 23, such as a spiral spring, that allows the push arm 20 to constantly withstand the cam. In the forward phase of the cam action, i.e. in the phase where the connecting rod moves towards the metering head, the push arm moves with the connecting rod towards the compression spring and at the same time the diaphragm 13 is pushed forward into the measuring chamber 16. However, this means that excess pressure is generated in the metering chamber, the outlet valve 15, for example a ball valve with a spring, is opened and the metering medium is pushed into the metering tube. In the reverse movement stage of the cam movement, i.e. in the stage in which the connecting rod moves away from the metering head, the push arm 20 is stroke-adjusted by a compression spring 23 which is formed, for example, as a spiral spring after the cam movement. Moving in the opposite direction toward the pin 8, this is because the connecting rod 19 moves the diaphragm 13, an underpressure is generated in the metering chamber 16, the inlet valve 14 is opened and the metering medium is primed one more time. To be sent to the weighing room. The metering medium is driven to the metering tube by the alternating vibration motion by the cam drive portion of the diaphragm 13. The cam drive generates a sinusoidal movement of the unit formed from the push arm 20, the connecting rod 19 and the diaphragm 13 during the metering stroke. If a shortened stroke length is set using the stroke adjustment pin 8, the priming phase movement is prematurely braked before the adjustable buffer of the stroke adjustment pin 8 reaches dead center, thereby Paths that draw a sinusoidal curve of movement intersect, changing the stage of stroke movement.

  The position of the unit formed by the push arm 20, the connecting rod 19, and the diaphragm 13 is detected by a position sensor 36, and the signal from the position sensor has a predetermined relationship with the position of the unit, for example, a strictly proportional relationship. Etc. The signal of the position sensor 36 is constantly related to the position of the part of the movable unit where it is employed. This fixed point is formed by the reference element and is abstract in this example. Depending on the requirements of the position sensor, it may be formed as an additional element that is actually built in, but it is composed of one of the necessary components, for example, a characteristic shape such as the edge or surface of the push arm 20 There may be only.

  In the present embodiment, the cam receiver 22 includes a sensor carrier 31 (shown in FIG. 6) fixed thereto, and supports a vertical light receiving CCD cell 32 (charge coupled device) on one side of the sensor carrier, On the other side, a light source 33, for example a light emitting diode, is supported.

  The sensor carrier 31 fixed to the cam receiver and the components fixed thereto form a light box, and the light beam from the light box is partially blocked by the push arm. The reference element is formed by the shadow defining edge 35 of the push arm 20 in the region of the light box arrangement. When the connecting rod 19 vibrates, the shadow defining edge 35 passes through the light receiving cell 32 without contact. As can be seen in particular from FIG. 5, which is an axial top view, the light source 33 must be arranged in such a way that light rays are not blocked by the connecting rod 19 on the way to the light receiving cell 32. That is, for example, this means that the matrix of the light source 33 and the light receiving CCD cell 32 is arranged above or below the connecting rod 19, for example. As can be seen in particular in FIG. 7, the light-receiving cell 32 is shaded by the shadow-defining edge of the light source 33, whereby the cell is divided into an illuminated cell (h) and a non-illuminated cell (d). The light-receiving cell row, for example 128 pixels, oriented parallel to the long axis 18 spans a distance of approximately 8 mm, but is only partially illuminated or shaded in the transition region, The transition situation SV shown in FIG. 8 occurs. The height of the perpendicular surface shown in FIG. 8 represents the luminance of the pixel. The special process described below with reference to FIG. 10 utilizes this transition situation to accurately determine the position of the shadow defining edge and thus the position of the connecting rod or diaphragm. This measuring device consists of a light receiving CCD cell on the sensor carrier side with a shadow demarcating edge on the push arm side and an opposite light source, which serves to measure the actual position or speed of the oscillating connecting rod and utilizes this information And fulfill the above functions.

  The connecting rods that cause the diaphragm to vibrate span the distance of each stroke that matches the mechanical stroke length. In order to allow assembly variation, the vertical extent of the light receiving CCD cell must be somewhat increased. The same applies to all other possible position sensors.

The following mechanical and electronic components are required when the diaphragm, and more generally, the displacement motion is controlled using position sensor signals, particularly as described in FIGS. . The meanings of the ellipsis used in the two drawings are as follows.
the actual value v _s1 displacement representing the velocity of the nominal value v ₁ displacement means representing the speed of the error vs displacement means positions the actual values x _s1 displacement means representing the position of the nominal value x ₁ displacement means for indicating a position of x _s displacement means Deviation in speed of means SG Control unit output KSG Correction control unit output MA (U, f) Electric drive unit (voltage or frequency)

  The movable part of the drive unit is controlled in its movement, but is composed of a push arm 20 with a connecting rod 19, and a diaphragm core 30 is fixed to the sush arm 20. The recovery spring 23 returns the push arm to the original position after the working stroke, whereby priming is activated. The outer ring of the diaphragm 13 is mounted on and fixed to the measuring head 12, but a metal diaphragm core 30 inserted into the diaphragm moves the center plane of the diaphragm in the measuring head as a displacement means. The inlet valve 14 is closed on the priming side and the outlet valve 15 is closed on the pressing side of the metering head. This completes the connecting portion for external piping. The reference element is connected to, for example, an end facing the measuring head in a state where the connecting rod 19 or the module is connected. In this case, the position of the push arm 20 is, for example, a position sensor that operates without contact. 36. In the illustrated embodiment, the reference element is the shadow defining edge 35 of the push arm 20 and the position sensor is like a light box consisting of a light source 33 cooperating with a series of light receiving cells 32 as described above. It is a configuration, and the position of the shadow defining edge 35 is optically determined based on the shadow formation without contact. The connecting rod 19 is actually a connecting portion and a power coupler to the diaphragm 13, and in this embodiment, the push arm and the connecting rod are fixed to each other, so the following description relates to the movement of the connecting rod 19. In practice, however, it is the motion of the shadow defining edge 35 of the push arm 20 that is measured.

The position sensor 36 generates an actual signal x ₁ that is proportional to the position of the reference element 35. In the case of the speed controller, in this embodiment, the real signal is fed through the time differentiator 37 (dx ₁ / dt), and further generates the real signal v ₁ proportional to the speed. There are other methods suitable for the control phase, and it is possible to generate a signal proportional to the diaphragm speed. The type and metering requirements of the control, the time-dependent profile representing a nominal value 38 position x _s or velocity v _s is created. In the variance comparison 39, the variance is determined as position variance x _s1 = (x _s -x ₁ ) or velocity variance v _s1 = (v _s -v ₁ ), and the result is a PID control unit (proportional, integral and derivative control unit) ). The output, that is, the control unit output SG coincides with the value to the driving unit. In order to improve the stability of the control unit, the control unit output SG is processed using the position correction 41. The position correction takes into account the fact that the motor rotation speed depends on the cam rotation angle (deflection from the connecting rod position) according to the sinusoidal characteristics of the cam drive, and the motor rotation speed is changed to the connecting rod speed. Convert. Thereafter, in the position correction 41, the start signal for the PID control unit 40 is converted into the correction control unit output KSG in accordance with the reverse characteristics of the cam drive unit, but the correction control unit output matches the desired control unit output SG. It is necessary to obtain the movement of the connecting rod 19 by the output from the section. The amplifier 42 is formed as a frequency converter, but maintains the power level and uses the voltage and frequency to drive the motor at the desired rotational speed. The deflection constant for the position dependent correction amount, the conversion of the correction controller output KSG to the actual rotational speed of the frequency converter and, if necessary, the generation of the overall speed signal v ₁ has three proportional coefficients k1, k2. , K3. The position dependent correction coefficient k1 is selected according to the characteristics of the cam drive. Two coefficients, the coefficient k2 for the amplifying unit and the coefficient k3 related to the speed signal deviation, are selected in consideration of actual conditions such as operation in the best use size range.

FIG. 3 shows a control circuit of the position adjustment unit, and FIG. 4 shows a control circuit when the speed control unit is used. The control circuit communicates a predetermined time-dependent profile of the nominal position value x _s or the nominal speed value v _s in the context of possible control adjustments.

  Creating an actual profile of position, velocity, or acceleration and switching between these operating modes is done as described below, but limits the functional limits of the controller, such as control speed and achievable accuracy, for example. Done in consideration.

  By such control, it is possible to determine in advance the desired speed of the diaphragm 13, generally the displacement means, using the electric metering pump, and to control the effective flow rate of the measuring medium.

  The diaphragm position is directly controlled in this way. This function allows the position to be determined at selected stages of the metering procedure and, if necessary, at rest.

  By controlling the operation by the position display unit, it is possible to cope with the change of the operating parameter as opposed to the uncontrolled operation. However, this change suddenly occurs over time, or environmental factors or environmental changes, that is, in the manufacturing process. It can be caused by statistical deviation, and adverse effects can be reduced. Specific examples cited are diaphragm stiffness or metering medium viscosity. Both require a driving force that is in addition to the force to apply operating pressure to the surface of the diaphragm. By determining this effect and then adjusting the motor drive, adverse effects can be compensated. An unadjusted metering pump with a preset motor speed will continue to be adversely affected, even if controlled and kept stable. Moreover, it is impossible to accurately predict the instantaneous speed of the displacement means without knowing the connecting rod position, that is, the cam angle, due to the sinusoidal characteristics of the cam drive unit.

  Further, by controlling the operation by the position display unit, in response to the internal and external influences described below, in contrast to the voluntary measurement process for the unadjusted operation, the specific hydraulic state during measurement is utilized or It is possible to establish an operating state that can be avoided. A specific example is a cavitation protection function during priming described below.

  Individual embodiments of the electric metering pump of the above kind will be described. The pump is provided with a position sensor, and the operation condition of the metering circuit is lowered by evaluating the position signal, or the operation of the diaphragm is affected by controlling and adjusting the motor driving unit.

Detection of the position of the adjustment control with respect to the stroke length The metering pump according to the prior art operates such that a metering stroke is carried out and the dispensed volume (stroke length) of the piston chamber is converted into a metered total volume. Often, the volume is indicated, for example, as a volumetric flow rate in liters per hour. For such a function, it is necessary to know the stroke set by the operator, since the volume measured for each stroke depends on the set value. For this reason, the position of the stroke adjusting device in the metering pump according to the prior art must be converted into an electrical signal by another sensor and read out to the control system. A specific example is a linear potentiometer on the stroke adjusting means 7, which detects the adjustment value via a needle.

  A metering pump that uses the integrated position sensor 36 to detect the actual diaphragm path during a stroke does not require an additional sensor. The difference between the two position values at the end position is measured after reaching the mechanical buffer as soon as the operation stops, but is used to directly calculate the stroke length and can be used for further processing.

Detection of blockage or incomplete strokes Prior art metering pumps that do not have a position sensor often employ sensors that provide an impulse to the electronic control system to monitor the metering action for each stroke. In a known embodiment, for example, a small permanent magnet fixed to the output shaft of the gear, fixed on the cam shaft 17 outside the shaft and rotating with the output shaft is connected to the stationary Hall sensor, and the stationary Hall sensor is connected to the cam shaft. A signal is generated when passing through the magnet at a certain angle. The electronic control system measures the same stroke period as the camshaft speed from this signal and estimates whether the metering process is being performed correctly. If an obstruction occurs during the execution of a metering stroke due to an overpressure situation, for example by an obstructing means that is unintentionally closed in the metering tube, the Hall sensor signal is turned off and an alarm is issued when the monitoring period has passed, and further Operation such as stopping the metering pump is performed. In such prior art systems, the desired information cannot be obtained until the monitoring period has elapsed.

  The use of the position sensor 36 means that the speed of the connecting rod 19 for driving the motor 2 can be set at any time during the metering stroke, and the blockage can also be determined basically at any time.

Slip compensation When the drive motor 2 is a synchronous motor, for example, the effective mechanical rotational speed of the loaded motor take-out shaft is always slightly lower than that determined by the frequency of the electronic control system. The difference between the two rotational speeds, the so-called slip, depends on the motor parameters and is approximately proportional to the torque in the loaded state if the load is within a reasonable range. Slip is measured in various ways as described below. Based on the slip, the frequency converter can calculate a correction value that is incorporated into the motor rotational speed as an increase in frequency, thus compensating for the slip.

  Slip is determined, for example, by comparing the measured stroke duration with that provided by the electronic control system. This method is also applied to a metering pump according to the prior art by measuring the time difference between two Hall sensor impulses. In the case of a metering pump with a position sensor, a characteristic point of the stroke path, for example an intermediate point, is defined for measuring the time period, and the time of passing through this point is recorded for a series of metering processes. That is, the difference between the two times is a desired period.

  In the electric metering pump provided with the position sensor 36, the slip is determined by observing the instantaneous speed of the connecting rod 19 using the direct method. From the motor rotation speed obtained from the electronic control system, an ideal connecting rod speed is calculated using known gear characteristics and cam characteristics. By comparing the ideal with the measured speed, a slip at any time during the cam cycle can be generated and the slip corrected by re-adjusting the motor drive frequency.

Pressure Determination When an asynchronous motor is used, the force applied to the displacement means is determined using the slip measured by one of the above methods to reduce the operating pressure of the metering medium. However, the cam changes the force acting on the connecting rod 19 in a sinusoidal manner, in which case the force acting depends on the instantaneous angle with respect to the motor 2 via the gear 11. At the two dead points, the turning point of the stroke movement, the motor is disconnected from the connecting rod force, in other words, released from the load, and at two points just between them, the cam transmits the maximum load moment to the motor. To do. As described above, assuming that the force of the connecting rod is constant, the torque on the motor take-out shaft shows the same pattern, and the slip fluctuates so as to draw a substantially sinusoidal curve. Thus, the variation reflects the force of the connecting rod.

When the deviation from the ideal value of the stroke duration is determined as described above, it represents the slip transmitted through the cam sinusoidal pattern and is also a measure of the average stroke force or operating pressure. If slip is continuously determined from a comparison of the motor rotation speed provided by the electronic control system and the connecting rod speed, the connection is based on known cam characteristics and knowledge of the cam instantaneous angle from the connecting rod position. The force profile of the bar 19 can be calculated. The connecting rod force profile is also used to estimate the operating pressure.
If the deflection mechanism is provided by something other than a cam, this property can be applied as appropriate.

Pressure limit, pressure drop recognition When the operating pressure is determined according to the above method, it is monitored to be within certain limits, triggers an alarm upon query of the monitoring system, and performs actions such as stopping the metering pump. Let it be done. By monitoring over-limits, the pump and other components can be protected, and in some cases, 130% of the maximum pressure of the metering pump can be set and monitored as an operating limit. However, the monitoring limit may be set within certain operating limits of the metering pump, for example when protecting sensitive parts, in which case the operator can set it. It is also possible to monitor whether pre-set operating requirements are observed, in which case, for example, an alarm is issued if the operating pressure set as a reference increases or decreases by 1 percentage point. When monitoring the operating pressure to see if the minimum pressure of 1 bar is being observed, it is possible to detect leaks caused by piping damage.

Pressure Compensation The application volume of the electric metering pump is influenced by the operating pressure in different ways depending on the embodiment employed. On the other hand, when the drive motor 2 is an asynchronous motor, there is a problem that slip increases with an increase in operating pressure. This causes a decrease in rotational speed, and accordingly, a decrease in the number of strokes. Let On the other hand, the diaphragm used as the displacement means 13 experiences elastic deformation under the influence of the operating pressure. If the outlet valve 15 is closed at the start of the metering stroke, the internal pressure of the metering chamber 16 will rise continuously, and the diaphragm core 30 will move to the metering chamber by the connecting rod 19 as the pressure increases. . The elastic deformation region of the diaphragm 13 yields to a pressure that opposes the operation of the diaphragm core 30. Although the diaphragm 13 deforms, in general, no volume change actually occurs, since the metering medium is not actually compressed and at this point both valves are closed. At the end of this deformation phase, the chamber pressure coincides with the external operating pressure. The execution path of the connecting rod 19 coincides with the diaphragm deformation and coincides with the immovable area at the start of measurement. And it does not contribute to the measurement substantially. The deformation or immobility region is typically in the range of about 0.1 to 0.5 mm depending on the size of the diaphragm and the operating pressure. The operating side outlet valve 15 opens at the pressure equilibrium point. The pressure on the diaphragm 13 is then the same as the external operating pressure and is substantially constant during the remainder of the metering stroke, as is the diaphragm deformation. The pressure equilibrium point at which the working outlet valve opens is an indication of the actual start of metering and the diaphragm deformation is not affected by the metering stroke, which means that the effective stroke length is a mechanical length with less diaphragm deformation. It is determined from. Since the diaphragm deformation itself is substantially proportional to the operating pressure, the metering curve typically falls with increasing operating pressure. Therefore, minus deviation is remarkable for a short stroke length.

In the case of electric metering pumps according to the prior art, metering is not only dependent on pressure, but is not strictly proportional to the mechanical stroke length under partial stroke conditions. Further, effective metering starts with a stroke only after the initial stationary region from the point in time when the diaphragm deformation becomes maximum when the outlet valve 15 is opened. If the steady state characteristic is represented by a metric profile as a function of mechanical stroke length, a linear ascending curve is created, which can be expressed as x _T1 , x _T2 , x _T3 ... x _Tn (see FIG. 12). It only shows the actual application amount after the stroke corresponding to the minimum stroke length corresponding to the immobile area. Since this minimum stroke length corresponds to the diaphragm deformation, it depends on the operating pressures p ₁ , p ₂ , p ₃ ... _Pn .

The steady state characteristic deviations x _T1 , x _T2 , x _T3 ... X _Tn in this prior art mean that recalibration is necessary under actual working conditions as long as the current stroke length is substantially changed. However, the new metering performance cannot be determined with sufficient accuracy by calculating the current stroke length and the new stroke length in proportion.

  When the operating pressure is determined by one of the above methods, the above-mentioned dependency that can be quantitatively determined in advance for each type of device is used to preliminarily determine the effect of causing an error in the measuring performance of the operating pressure. Can be determined and compensated. For this reason, the determined operating pressure and the adopted stroke length are measured by the position sensor as described above, but this is a correction calculated from the known error dependence added to the number of adopted strokes. Used to calculate a value. For practical and economic reasons, only the systematic part of the impact is eliminated. Pressure dependent metrological performance errors are primarily determined by material properties and measurements performed on the components employed, but they may vary to some extent due to modifications or may be caused by manufacturing variations. These variations are taken into account in the methods described herein, which use predefined module parameters or a series of measurements to correct errors due to diaphragm deformation. Further, in this specific example, a new actual relationship must be defined at a predetermined interval or at each stroke.

  If the effects causing the diaphragm deformation error are compensated as described above, the operating pressure is determined using one of the above methods, and the number of strokes is changed by the correction value, which is proportional in the partial stroke operating mode. Errors are also eliminated. Therefore, the metering pump operates within a useful stroke length range of 20% to 100%, so in a prior art metering pump that needs to adjust the stroke length longer than 10% in order to maintain a specific metering accuracy. Does not have to perform the recalibration that is still necessary.

Avoiding Flow Loss in Highly Viscous Media By adjusting the speed of the displacement means, such as diaphragm 13, especially when using high viscosity media (eg lecithin), flow loss at valves and other tight points can be limited. High flow rates in such media negatively impact metering accuracy due to the additional pressure drop as a result of flow resistance. Furthermore, this is advantageous when the valve is slow to open and close due to speed limitations. Both effects improve the weighing accuracy of the highly viscous medium. To achieve this, the diaphragm speed is limited to the maximum selectable value during the entire weighing process. This maximum speed depends inter alia on the viscosity of the actual medium to be measured and is provided as several predetermined values, for example by an application selected by the operator or provided directly. Adjustment of the speed of the position sensor and the displacement means can be used to ensure that the desired limit of diaphragm speed is maintained.

Cavitation protection In the case of gas-prone media (eg chlorinated bleach), especially if the flow rate is too high, especially during priming and metering strokes, a local drop in vapor pressure, which depends in particular on the chemical composition of the metering medium and its temperature As a result, cavitation occurs at the restriction point and wear increases. By limiting the speed by adjustment or setting the rotational speed to a value substantially below the critical flow velocity, cavitation can be avoided both during the pressing stroke and during priming, that is, when the diaphragm 13 returns. The speed requirement of the control circuit, or in the simplest case, the motor rotation speed is set, for example, to limit the corresponding diaphragm speed to 1 mm / 50 ms.

  Particularly for the priming procedure, cavitation is likely to occur because the static pressure is particularly low and the safety margin against dropping below the vapor pressure is very small. To improve the method, the diaphragm speed during priming should be limited to a value less than that used during the pressing stroke. Specific examples of reasonable values are 1 mm / 50 ms for the press stroke and 1 mm / 100 ms for the priming, but other values are clearly possible. Underlying the individual treatments of the metering phase is the fact that the position sensor can determine the exact position of the diaphragm at any point in time, so that the start of the (particularly important) priming phase can be reliably determined.

Electronic stroke length adjustment According to the present invention, a mechanical device (adjustment means 7 and stroke adjustment pin 8) for adjusting the stroke length is unnecessary. For this reason, a desired stroke length is notified to the control device electronically, for example, by an operator's input. When a stroke corresponding to a desired stroke length is executed, the motor 2 is braked to stop the diaphragm 13 at a position where it has reached, and reverse the motor at the priming stage. The next stroke can be performed by passing the priming dead center in the opposite direction (pressing step in reverse movement, priming in normal operation) or rotating the motor in the same order as the previous stroke. it can. In the first case example, the motor braking and starting procedure between strokes saves time and energy. It should be noted that the direction changing constantly means that the blower fixed to the motor shaft is no longer functioning sufficiently. Therefore, in this case, the use of an externally driven blower is extremely important for the motor when cooling is required.

Low speed metering to avoid concentration fluctuations In applications where it is necessary to mix well with the processing medium stream, the distribution of the metering medium should be made as even as possible. In certain applications, it is necessary for a nearly continuous metering to measure very small quantities as uniformly as possible over a very long period of time. In this case, in the prior art, for example, an electric metering pump including a step motor and a self-locking gear is employed. In such a metering pump, the rotation speed is reduced or distributed in several stages with a stop period in between, and a complete stroke is performed once, at the end of this stroke A (fast) priming phase is carried out, after which the metering process continues in the manner described above.

  In the case of a motion-regulating motor metering pump, the available time determined by the number of repetitions of the metering stroke can be distributed so that the remaining part after priming can be utilized to the maximum for forward movement to a short stop stage. The adjustment speed is calculated from the movement route (the set value of the stroke length) and the available time. In contrast to the prior art motor metering pumps, the position sensor 36 and the adjusting device can be used to determine the instantaneous angle of the cam drive incorporated in the motor speed from the position of the connecting rod 19 that is always known. When the cam is used, the characteristics of the deflecting device, represented by a sinusoidal curve, are compensated, and the metering stroke is a precise linear motion that distributes the metering medium uniformly. The speed falls within a very wide range, for example from 1 mm / min to 1 mm / sec.

  As can be seen from the above application of the position provider and part of the control means, the position sensor on the connecting rod is used during the full stroke and priming procedure to reveal and monitor the exact position of the displacement means. it can. The positioning and monitoring means for controlling the parameters depending on the situation leading to the above advantageous features can be precisely configured by measuring the actual values.

Position Sensor As already described, the reference element for the position display unit in the above-described embodiment is the shadow defining edge 35 of the push arm 20 for detecting the position, and this shadow is the CCD cell 32 (charge coupled device). Take the procession. The active sensor element, which is described in more detail in the specific example, detects the position, but is located beside the push arm 20 that is pointed at the metering head. The light source 33 is an LED, and the light receiving unit is an electronic module, that is, a sensor carrier 31 having a CCD cell 32. In this example, the light source 33 is mounted on an intermediate portion. By mounting the position sensor 36 on the sensor carrier 31, it is treated as an independent module in the manufacturing process, and is pre-assembled and tested separately, for example, at a location away from the final construction site. Furthermore, the light box-like arrangement is composed of non-contact and thus non-wear sensors.

  Regarding the basic function, it is not important to position the sensor at the movable unit formed by the push arm 20 and the connecting rod 19. The position can be determined based on a structural point of view such as space and assembly order. Further, the parts moving together with the parts (the light source 33 and the receiving part 32) and the connecting rod (the shadow defining edge 35) described as being fixedly mounted in this specification can exchange functions.

  In this specific example, the CCD module 32 includes a microprocessor and is controlled by an evaluation unit that generates necessary control signals. Instead of a microprocessor, a DSP (digital signal processing unit) or a separate technique can be used to manufacture the evaluation unit.

  Any element can be used for the light source 33 as long as a sufficiently narrow light spot can be generated. The shadow area SV (see also FIG. 8) is determined by the geometrical arrangement and the width shown in FIG.

  The light source 33 can also be composed of several elements or a matrix source, and the shadow region SV is created so as to satisfy specific requirements. One example is to achieve high brightness so as not to affect the sharpness of the direction of motion.

  The CCD matrix 32 is a linear arrangement of M light-receiving portions (hereinafter referred to as pixels) regularly arranged at a pitch R of several micrometers. As a specific example, 128 pixels are arranged at intervals of 64 μm over a total length of about 8 mm, that is, M = 128 and R = 64 μm.

  The control signal generated by the evaluation unit sets the illumination time for the individual pixels of the CCD matrix 32 to collect the incident light of the amplification unit in the CCD module and stores it for later processing. Condensation occurs on the light receiving surface of each pixel as well as the illumination period. After the illumination, the luminance value of the pixel is sequentially read as an analog value from the CCD module by a control signal, and is taken into the evaluation unit.

  Illumination and reading of luminance values are alternated in the simplest example. Some commercially available CCD matrix structures have the potential to perform both procedures simultaneously, storing the collected illumination measurements and immediately releasing the integrator for the next measurement. . By simultaneously outputting the measurement results during the illumination phase for subsequent procedures, the measurement speed can be increased.

  The diagram of FIG. 8 shows the actual shadow integrated luminance value H over the area of the affected pixel in the example. In this example, the shadow area SV extends from pixel 60 to 63.

As a simple evaluation procedure, a determination threshold value H _v (shown by a broken line in FIG. 8) is set to a half value of the maximum luminance, and a pixel whose luminance value H first falls below the threshold value H _v is searched in the shadow transition region. In this example, the pixel number is 62.

  According to another embodiment, the luminance is reversed as the pixel number increases from the unilluminated CCD cell to the illuminated CCD cell, but this depends on the arrangement of the light source 33, CCD module 32, and shadow generator 35 elements. , Depending on the internal structure of the CCD module 32. In this case, the pixel whose luminance first exceeds the threshold value is the desired pixel.

After three phases, an illumination phase, a reading phase, and a processing phase, position values are generated. The total time required for the three stages determines the number of times the position value is determined. The measurement resolution is the pixel pitch R of the CCD cell, corrected with a geometric relationship determined by the mounting spacing between the individual components.
About the ratio A (see FIG. 9) A = s ′ / s = x ₃ / x ₂
here,
s = actual operation of shadow defining edge s ′ = projecting operation of shadow defining edge in CCD plane x ₂ = distance between optical shadow defining edge and light source x ₃ = distance between CCD plane and light source

This procedure is a digital procedure because the position is determined by counting the number of pixels in this procedure. Deviations and deviations in linear parameters such as module sensitivity do not actually affect the results when compared to analog procedures. When the ratio A is determined by an actual value, the influence of assembly variation is small. In a specific example, when X ₃ = 21 mm and X ₂ = 20 mm, a nominal value of 1.05 for ratio A is obtained. In other words, the shift of the shadow area SV in the plane of the CCD cell 32 becomes 1.05 times higher with the movement of the shadow defining edge 35 by a specific distance. Assuming that the assembly variation coefficient of X ₃ , that is, the variation of the distance from the light source 33 of the CCD cell 32 is ± 0.3 mm, the upper limit of the allowable range is obtained when X ₃ = 21.3 mm and X ₂ = 20 mm. The ratio A is 1.065. The ratio in this example varies by 1.065 / 1.05 = 1.014 or + 1.4%. This deviation is eliminated by one calibration at the time of manufacture, for example. Linearity is almost exclusively determined by the accuracy of the pixel pitch in the chip geometry, and the deviation is small enough to be zero.

Although the above method for determining the position of the shadow defining edge 35 and thus the position of the diaphragm 13 results in a very accurate linear position value, more accurate position resolution can be obtained with interpolation. In the expanded interpretation, the pixel luminance H is evaluated to obtain a position resolution between the pixels 61 and 62 (see FIG. 10) and finer than the pixel pitch R. Pixel luminance values are interpolated in the region. The purpose is to determine the position where the luminance profile crosses a determined threshold value H _v, is to assign a value on the virtual position scale in this intersection, x value of the virtual locations graduations exactly the pixel number in pixel Correspond.

For this reason, two pixels on the left side and the right side of the determination threshold value Hv are searched, and the distance from the threshold value of the luminance value? H is determined. As shown in FIG. 10 or FIG.
? H ₁ = H ₁ -H _v
? Hr = Hr-H _v

The distance calculated by a multiple of the pixel width from the central axis of each of the two neighboring pixels, in this example, the pixels 61 and 62 to the intersection? Luminance distance for x and pixel 61 (left neighboring pixel) on the left side of the intersection? The relationship with H is expressed as follows. That is,
? x ₁ / (? x ₁ +? x _r ) =? H ₁ / (? H ₁ +? H _r )
If (? X ₁ +? X _r ) = 1 (1 pixel width),
? x ₁ =? H ₁ / (? H ₁ +? H _r )

The following relationship is established for the pixel 62 (right neighboring pixel) on the right side of the searched intersection.
? x _r / (? x ₁ +? x _r ) =? H _r / (? H ₁ +? H _r )
If (? X ₁ +? X _r ) = 1 (1 pixel width),
? x _r =? H _r / (? H ₁ +? H _r )

  In this example, the intersection is at a value of 61.7. If the luminance in the interpolation region follows an ideal straight line, the same result is obtained by both of the above calculation procedures, and therefore, in principle, one of the two calculations may be performed. However, if both calculations are executed and the results are averaged, the error caused by the inaccuracy of the brightness profile or the measurement value of the transition region of interest which is not exactly a straight line can be reduced.

  In another embodiment, the non-illuminated CCD cell and the illuminated CCD cell can be switched on either side of the intersection. In this case, the functions of the left display unit and the right display unit are exchanged appropriately, and the interpolation equation is changed. Must be changed at the same time.

  Furthermore, another embodiment is possible, where brightness values from more than two pixels are used. The position is determined by a number of redundant calculations and averaging of several results. Other possible forms may employ linear interpolation other than those described herein or interpolation using data from other than directly neighboring pixels.

  Deviations and deviations of linear parameters such as module sensitivity affect the results in the interpolation domain. The slope of the brightness profile in the shadow transition region due to the sharpness of the shadow defining edge on the CCD plane is not very important since it generally does not affect the interpolation, but only the linearity of the brightness profile is It is important to know the accuracy.

  Regardless of the interpolation method described above, further procedures for improving the sensor characteristics can be used, which build the basic principle described below. These procedures are described below.

? ? Improving resistance to interference by filtering Sensor resistance to interference is improved by filters. The filtering is applied to both the luminance value of the pixel and the position determination result. In the first case, the procedure operates with averaged luminance values for several pixels or several passes, and in the second case, several first determined position results are collected to estimate the position value. The position value is then used for further processing.

? ? Compensation for assembly variation At a defined stage, for example, at a stop stage before the actual metering stroke, the position value for that stage is determined and stored in the reference memory. In the active movement phase, the position values for the previously determined reference value are processed. Assembly variations of the stop position that occur during manufacturing and deviations that occur during operation, such as thermal expansion, are automatically compensated, thereby improving accuracy.

? ? Scaling Error Compensation In a further alternative, the position sensor is adjusted using two or more known positions called reference positions. This is performed once during manufacturing or testing procedures or repeatedly during operation.

  In the first case, the reference position is given by an external device such as a pitch position or an external measuring device. From the position value measured at these reference positions and the knowledge of the actual position of the reference position, a correction value for adjustment of the position sensor is determined and stored for further processing.

  In a second example of repeated adjustment determination, a reference signal from a known position, such as a mechanical buffer or another available device, is required for positioning. When the diaphragm is installed at a known position during operation, a correction value for adjusting the position sensor is determined from the position value measured from that position and stored for further processing.

? ? Optical Sensitivity Parameter Compensation In a further embodiment, the luminance value of a fully illuminated pixel is used to determine a value representing the illumination intensity. For this reason, for example, the average luminance is obtained using an appropriate pixel group. Lighting intensity is used to control lighting so that the available range is optimally utilized. As an example, the brightness or light source on-time is controlled so that the illumination intensity of a fully illuminated pixel is somewhat below the burnout limit of the CCD module. For each measurement, the illumination intensity is corrected using the previously obtained ratio so that the fluctuation of the illumination parameter, for example, aging, is smoothed.

? ? Dirt and Pixel Deviation Compensation In a further embodiment, in a defined phase, for example a stop phase before carrying out the actual metering stroke, the complete working pixel range or a large part of that range is illuminated. A mechanical structure is built. In a possible embodiment, for example, a shadow defining edge 35 opposite the evaluation diaphragm is used. This causes the shadow defining edge to pass quickly through the sensor during the stroke movement, darkening the CCD cell area illuminated at the previous stop position. At this stage, the brightness of all relevant pixels is determined and stored individually in the reference memory. Deviations from the measured values of the individual pixels from the ideal value are compensated, for example, in the form of correction values. In the active motion phase, the brightness of each pixel is first modified and then further processed using the reference values already determined for each measurement. This procedure can compensate for deviations in individual pixel sensitivity due to the manufacturing process and some degree of contamination, and thus can improve accuracy or operational reliability.

  Naturally, the CCD receiver cells may be arranged in two or more rows, for example, to improve safety by redundancy against dropout due to contamination or the like, or to increase accuracy of measurement values by averaging. For particularly large stroke lengths, two or more CCD matrices can be combined to extend the measurement area of an individual matrix beyond the functional limits of a single matrix.

  The motor metering pumps described in detail in the specific examples can vary in the details and arrangement of components such as motors, gears, cam drives and other structural details. However, it is essential that the vibration motion generated by the drive is detected by the position sensor, which provides a real signal that is in a fixed relationship to the position of the reference element and the displacement means. Can be used to obtain information on the operation of the displacement means.

It is sectional drawing of the electric metering pump provided with the position sensor. It is an exploded view of a position sensor (enlarged view of the cross section x of FIG. 1). The structure of a position control circuit is shown. The structure of a speed control circuit is shown. It is a top view of the axial direction of a position sensor. It is a side view of the direction perpendicular | vertical to the axis | shaft of a position sensor. The shadow area of a position sensor is shown. Indicates the luminance value of the pixel that falls into the actual shadow. The dimensions of the position sensor based on the geometry are shown. Indicates position resolution interpolation. The calculation which becomes the origin of position resolution interpolation is shown. Figure 2 shows metering performance as a function of mechanical stroke length and operating pressure.

Explanation of symbols

1 Cam chamber 2 Motor (asynchronous motor)
3 Housing rib 4 Floor plate 5 Housing cover 6 Electronic device 7 in the housing cover Adjusting means 8 Stroke adjusting pin 9 Cover 10 Control wire 11 Gear (reduction gear)
12 Weighing head 13 Diaphragm 14 Inlet valve 15 Outlet valve 16 Weighing chamber 17 Cam shaft 18 Vertical axis 19 Connecting rod 20 Push arm 21 Cam attack surface 22 Cam receiver 23 Compression spring (recovery spring)
24 Bearing plate 25 Compression spring joint 26 Bushing on bearing plate 27 Bushing on stroke adjusting pin 28 Electronic equipment housing 29 Motor drive power setting 30 Diaphragm core 31 Sensor carrier 32 Receiver, CCD module 33 Light source 34 Drive Electronic device 35 Shadow demarcation edge 36 as reference element Position sensor 37 Differentiator 38 Nominal value setting 39 Nominal-actual value comparison 40 PID adjustment 41 Position correction 42 Amplifying unit SV Shadow profile h Illumination area d Dark area # 58... # 65 CCD Cells (pixels)
H Pixel brightness H _v Comparison threshold (VS) brightness
Luminance of the pixel on the left side of the intersection of H ₁ VS (pixels near the left hand side)
? H ₁ Luminance of the pixel on the right side of the intersection of the luminance difference H _r VS between the left-hand side neighboring pixel and the luminance value of the comparison threshold (right-hand side neighboring pixel)
? Luminance difference between the luminance value of the comparison threshold value H _r right hand neighboring pixels? Positional separation by the bisector of pixels near the left hand side of the intersection of x ₁ VS? x _r VS position separation by bisector of right hand side neighboring pixels x ₁ Distance between shadow defining edge and CCD plane x ₂ Distance between shadow defining edge and light source x ₃ Distance p between CCD plane and light source ₁ working pressure p1
p ₂ working pressure p2
p ₃ working pressure p3
p ₄ working pressure p4
x immobilization region for _T1 working pressure p1 immobilization region for _T2 working pressure p2 immobilization region for _T3 working pressure p3 immovable region for _T4 working pressure p4 s actual motion of shadow defining edge s' projection operation D of shadow defining edge D measurement performance HL Mechanical stroke length SG Control unit output KSG Correction control unit output MA (U, f) Motor drive unit (voltage, frequency)
Speed control deviation v _s displacement means positions the actual values x _s1 displacement means positions the nominal value x displacement means positions of the coefficient x _s displacement means for deviation of k1 position-dependent position correction coefficient k2 performance amplifying section coefficient k3 speed signal Nominal value of v ₁ Actual speed value of the displacement means v _s1 Control deviation of the speed of the displacement means

Claims (31)

In a metering pump with a rotary drive motor and a vibrating piston,
The rotational motion of the drive motor (2) is converted into the vibration motion of the connecting rod (19) by the gear arrangement, and the activated displacement means performs the vibration linear motion by the continuous rotation of the drive motor (2). As a result, the medium to be measured moves to the measuring head (12) arranged on the longitudinal axis of the connecting rod (19) that alternately cooperates with the outlet valve and the inlet valve, and the pump stroke (pressing stroke) and the priming stroke are moved. A metering pump for generating
A reference element (35) is associated with the connecting rod (19) and its position is detected by a position sensor (36),
The position sensor is a real signal (x1) that is in a fixed relationship with the position of the reference element and thus the position of the displacement means, and provides a real signal (x1) that provides information on the movement performed by the displacement means. The metering pump according to claim 1, wherein the metering pump electronic control system is responsive to metering circuit and pump operating conditions.   The metering pump according to claim 1, wherein the position sensor (36) detects the position of the reference element (35) according to a non-contact principle.   2. The metering pump according to claim 1, wherein the reference element (35) associated with the connecting rod (19) and the position sensor (36) is external to the metering head.   The reference element (35) affects the path of the light source (33), and the position sensor (36) fixed to the pump chamber or other fixed portion in cooperation with the reference element (35) operates in a light receiving manner. A metering pump according to one or more of the preceding claims.   The reference element (3) is a shadow generator or a shadow generation contour, and the position sensor (36) fixed to the pump chamber or other fixed part in cooperation with the reference element (3) is a series of light receiving charge coupled devices (CCD). A metering pump according to one or more of the preceding claims, characterized in that it comprises a light-receiving part (32) in the form of   One or more of the preceding claims, characterized in that the pre-position sensor (36) is arranged on its own sensor carrier (31) fixed to the pump chamber or other fixed part. Metering pump.   The light source (33), the shadow generator or the shadow generation contour (35), and the light receiving unit (32) constitute a light box-like arrangement, and the measured values are sent to the electronic control system continuously or intermittently. A metering pump according to one or more of the preceding claims, characterized in that it is supplied.   One of the preceding claims, wherein the light receiving part (32) of the position sensor (36) comprises a number of linearly arranged receiving parts (pixels), preferably 128 pixels. One or more metering pumps.   The light source (33) is a light emitting diode (LED) arranged with respect to the light receiving part (32) of the position sensor (36), and the light beam directed to the receiving part is transmitted to the connecting rod (19). The metering pump according to one or more of the preceding claims, characterized in that it is not hindered by   A metering pump according to one or more of the preceding claims, characterized in that the starting value of the position sensor (36) is generated by interpolating the brightness of a plurality of pixels in a shadow transition region.   Metering pump according to one or more of the preceding claims, characterized in that filtering is employed when processing the signal of the position sensor (36).   A metering pump according to one or more of the preceding claims, characterized in that the zero position error of the position sensor (36) is eliminated by a reference memory.   A metering pump according to one or more of the preceding claims, characterized in that the scaling error of the position sensor (36) is eliminated by one or more reference positions.   One or more of the preceding claims, characterized in that illumination variations of the position sensor (36) are compensated by controlling or adjusting the light source (33) using the obtained pixel luminance values. The metering pump described.   A metering pump according to one or more of the preceding claims, characterized in that brightness variations between individual pixels of the light receiving part (32) are compensated by using a reference memory for each pixel sensitivity. .   One of the preceding claims, characterized in that the determination of the value that the adjusting means (7) of the stroke has to be adjusted is obtained directly using the position sensor (36) by measurement during weighing or Metering pumps listed in multiple.   One or more of the preceding claims, characterized in that the electronic control system recognizes a blockage or incompletely performed stroke of the displacement means by evaluating the signal of the position sensor (36). The metering pump described in 1. The drive motor (2) operates with slipping when, for example, an asynchronous motor is employed, and the electronic control system determines the nominal number of strokes of the displacement means from the nominal rotational speed of the drive motor and known gear characteristics. Or defining a nominal stroke period and further determining the actual stroke number or the actual stroke period of the displacement means by evaluating the position sensor signal (36),
The slippage of the drive motor is calculated and the nominal rotational speed is changed by comparing the actual stroke number with the nominal stroke number or comparing the actual stroke period with the nominal stroke period of the displacement means. A metering pump according to one or more of the preceding claims, characterized in that the displacement means can be moved at a desired number of strokes. The drive motor (2) operates with slipping when, for example, an asynchronous motor is employed, and the electronic control system determines the nominal number of strokes of the displacement means from the nominal rotational speed of the drive motor and known gear characteristics. Or providing a nominal stroke period and further defining an actual stroke number or an actual stroke period of the displacement means by evaluating the initial position sensor signal (36),
By comparing the actual stroke number with the nominal stroke number or comparing the actual stroke period with the nominal stroke period of the displacement means, the slip of the drive motor can be calculated, and the electronic control system further comprises: One or more of the preceding claims, wherein the force applied to the displacement means can be determined from the determined slip of the drive motor and known gear characteristics, thereby reducing the operating pressure of the metering medium The metering pump described in 1. The drive motor (2) is operated with slipping when, for example, an asynchronous motor is employed, and the electronic control system performs the measurement from the nominal rotational speed of the drive motor and known gear characteristics for each weighing procedure. Determining the nominal speed of the displacement means, and further determining the actual speed of the displacement means by evaluating the position sensor signal (36);
By comparing the actual instantaneous speed with the nominal speed of the displacement means, the instantaneous slip of the drive motor can be calculated, and the instantaneous force of the displacement means can be estimated therefrom again in relation to known gear characteristics. A metering pump according to one or more of the preceding claims.   21. The metering pump according to claim 20, wherein the electronic control system reduces the operating pressure of the measuring medium using a profile obtained by observing a force applied to the displacement means.   The electronic control system recognizes operation beyond a determined pressure range from the determined operating pressure of the metering medium and exceeds the maximum allowable pressure specified in the metering pump specifications or the maximum allowable pressure provided by the operator. The metering pump according to claim 19 or 21, wherein the metering is adjusted when a predetermined minimum pressure is not reached. The displacement means is a partially elastic diaphragm (13),
The electronic control system determines the expected metering error from the determined operating pressure of the metering medium and the known dependence of the metering performance on the operating pressure, and the rotational speed of the drive motor (2) and thus the stroke. The metering pump according to claim 19 or 21, wherein the metering pump works so as not to cause an expected metering error by affecting the number of times.   A signal (x1) representing the position of the connecting rod (19) read from the position sensor (36) is sent to the control circuit in relation to control accuracy, and the rotational speed of the driving motor (2) and the connecting rod are sent. A metering pump according to one or more of the preceding claims, characterized in that it influences the linear movement of the displacement means and thus the linear movement of the displacement means, so that it follows a predetermined nominal profile (38).   The control device alternately affects the position (hereinafter denoted by x1), speed (hereinafter denoted by v1) or acceleration of the displacement means by changing the rotational speed of the drive motor (2). The metering pump according to claim 24, wherein   The control device intentionally reduces v1 of the displacement means during the priming phase and / or the pressing phase so that it can cope with a sudden pressure drop caused by resistance to flow, for example the occurrence of cavitation. The metering pump according to claim 24, wherein A desired stroke length is transmitted to the control device by an operator, and electronically restricts the movement of the displacement means to the stroke length to be performed using the control device;
After executing the desired stroke length, the control device stops the drive motor (2), switches it to reverse rotation and executes the priming stroke, and the motor stops or moves to the next pressing stroke. The metering pump according to claim 24, wherein the metering pump is performed.   The control device distributes the forward movement of the displacement means during the pressing phase by driving the drive motor (2) for a time determined by the repetition rate of the metering stroke, so that a very slow metering 25. The metering pump according to claim 24, wherein the metering medium is applied as evenly as possible even in the case of a stroke, for example a metering stroke of several minutes.   The displacement means is partly in the form of an elastic diaphragm (13), and the electronic control system detects the opening of the outlet valve (15) from the instantaneous force applied to the diaphragm (13) and uses the observation. 21. The metering pump according to claim 20, wherein a fixed region caused by elastic deformation of the diaphragm (13) is measured. The actual stroke is affected regardless of the estimated diaphragm deformation,
The controller, after reaching the desired stroke length from the opening of the outlet valve (15), stops the drive motor (2), switches it to reverse rotation, and then executes the priming stroke, Stopping the motor or performing the subsequent pressing stroke eliminates the error caused by the diaphragm deformation (with respect to the stroke or metering volume) and the dependence of the metered amount on the back pressure is substantially 30. The metering pump according to claim 29, wherein the metering pump decreases the amount of the metering pump. The actual hub speed is affected regardless of the estimated diaphragm deformation,
The controller determines a correction value for an error caused by the diaphragm deformation (with respect to the stroke or the measured volume) and uses the correction to change the nominal rotational speed of the drive motor (2); 30. The metering pump according to claim 29, wherein an error caused by the diaphragm deformation is eliminated.

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