Electromagnetic pump anomaly detection device

Abstract

The present invention provides an electromagnetic pump malfunction detection device that can accurately determine whether or not there is a malfunction in the pump without being affected by external vibrations. [Solution] The electromagnetic drive pump abnormality detection device 200 according to the present invention is an electromagnetic drive pump abnormality detection device 200 that pumps fluid by causing a plunger 140 to reciprocate using an electromagnetic coil 120, and comprises a drive circuit 202 that drives the electromagnetic drive pump by applying a sawtooth wave voltage to the electromagnetic coil, an ammeter 210 arranged on the drive circuit, and a determination unit 220 that determines an abnormality from the current value acquired by the ammeter, wherein the determination unit measures the current while voltage is applied to the electromagnetic coil, differentiates the measured current value to calculate a derivative value, and determines that the plunger is in a normal state and is not locked if the peak Imax that appears in the calculated derivative value exceeds a predetermined threshold I0.

Description

Technical Field

[0001] The present invention relates to an abnormality determination device for an electromagnetic drive pump that reciprocates a plunger by an electromagnetic coil to pump fluid.

Background Art

[0002] Conventionally, as a pump for transferring fluid, an electromagnetic drive pump that uses an electromagnetic coil as power is known. The electromagnetic drive pump reciprocates a plunger inside a housing by switching ON / OFF of the voltage applied to the electromagnetic coil. At this time, the electromagnetic drive pump sucks fluid from the suction port and discharges it from the discharge port, thereby pumping (transferring) the fluid. As a method for detecting an abnormality in the discharge flow rate of the pump, a flow rate sensor disposed on the flow path for detecting the flow rate of the fluid and a pressure sensor for detecting the pressure inside the flow path are generally used.

[0003] However, when the target flow rate is minute, the detection accuracy of the flow rate and pressure becomes low. Therefore, a vibration detection device may be used instead of the flow rate sensor and the pressure sensor (for example, Patent Document 1). The fuel cell system of Patent Document 1 includes "a plunger-type reformed water pump that is reciprocally housed in a cylinder, moves when a coil is energized, and has a plunger that collides with a collision portion, and supplies reformed water to an evaporation portion", a vibration detection device that detects vibration of the reformed water pump generated during the reciprocating movement of the plunger, and a control device that controls at least the reformed water pump.

[0004] Further, the control device of Patent Document 1 includes "an abnormality determination unit that determines that a reformed water supply abnormality has occurred in which reformed water is not supplied to the reformed water pump when the amplitude of the vibration detected by the vibration detection device is equal to or greater than a first determination value within a first time period during which the plunger is moving from the start time of energization of the coil to the collision time when the plunger collides with the collision portion". According to Patent Document 1, it is stated that the occurrence of a reformed water supply abnormality in which reformed water is not supplied to the pump that supplies reformed water can be surely detected with such a configuration.

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2017-147182 [Overview of the project] [Problems that the invention aims to solve]

[0006] When a vibration detection device is used to determine a pump malfunction, as described in Patent Document 1, if there is external vibration in the pump's mounting environment, for example, the vibration detection device may detect this external vibration and mistakenly determine that a pump malfunction has occurred (for example, the pump is running when it should be stopped). Therefore, while the method using a vibration detection device as described in Patent Document 1 is useful as one method for determining a pump malfunction, there is room for further improvement in order to more accurately determine whether or not a pump malfunction has occurred.

[0007] In view of these problems, the present invention aims to provide an electromagnetic pump abnormality detection device that can accurately determine whether or not there is an abnormality in the pump without being affected by external vibrations. [Means for solving the problem]

[0008] To solve the above problems, a typical configuration of the electromagnetic drive pump abnormality detection device according to the present invention is an electromagnetic drive pump abnormality detection device that pumps fluid by causing a plunger to reciprocate using an electromagnetic coil, comprising: a drive circuit that drives the electromagnetic drive pump by applying a sawtooth wave voltage to the electromagnetic coil; an ammeter arranged on the drive circuit; and a determination unit that determines an abnormality from the current value acquired by the ammeter. The determination unit measures the current while voltage is applied to the electromagnetic coil, differentiates the measured current value to calculate a derivative value, and determines that the plunger is in a normal state and is not locked if the peak appearing in the calculated derivative value exceeds a predetermined threshold.

[0009] The above drive circuit may also apply a triangular wave or trapezoidal wave voltage to the electromagnetic coil instead of a sawtooth wave. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an electromagnetic pump abnormality detection device that can accurately determine whether or not there is an abnormality in the pump without being affected by external vibrations. [Brief explanation of the drawing]

[0011] [Figure 1] This figure illustrates an abnormality detection device for an electromagnetically driven pump in an embodiment of the present invention. [Figure 2] Figure 1 is a diagram illustrating the operation of the plunger of the electromagnetically driven pump. [Figure 3] Figure 1 illustrates the voltage waveform applied to the electromagnetic coil of the electromagnetically driven pump. [Figure 4] Figure 1 illustrates the current waveform, voltage waveform, and differential current waveform of the electromagnetically driven pump under normal operation. [Figure 5] Figure 1 illustrates the current and voltage waveforms when the electromagnetically driven pump malfunctions. [Figure 6] This figure illustrates the differential current waveform of the electromagnetically driven pump shown in Figure 1 during a malfunction. [Modes for carrying out the invention]

[0012] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. The dimensions, materials, and other specific numerical values ​​shown in these embodiments are merely examples to facilitate understanding of the invention and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to the present invention are omitted from the illustrations.

[0013] Figure 1 is a diagram illustrating an abnormality detection device 200 for an electromagnetically driven pump 100 in an embodiment of the present invention. The electromagnetically driven pump 100 shown in Figure 1 is a device that pumps fluid (not shown) by causing a plunger 140 to reciprocate using an electromagnetic coil 120.

[0014] In the electromagnetically driven pump 100, an electromagnetic coil 120 is located inside the housing 110. Inside the electromagnetic coil 120 are a fixed iron core 130, a cylindrical guide 142, and a plunger 140 guided by the guide 142. The fixed iron core 130 is molded integrally with the housing 110 and is located inside the electromagnetic coil 120. The plunger 140 is movable within the housing 110, guided by the guide 142.

[0015] Figure 2 is a diagram illustrating the operation of the plunger 140 of the electromagnetically driven pump 100 shown in Figure 1. As shown in Figures 1 and 2, a suction valve 150 is located inside the fixed iron core 130, and a discharge valve 160 is located inside the plunger 140. The suction valve 150 draws fluid into the plunger 140, and the discharge valve 160 discharges the fluid from inside the plunger 140.

[0016] The electromagnetically driven pump 100 also includes a nozzle 190 and a spring 144. The nozzle 190 is mounted in a position that contacts the discharge valve 160 side of the plunger 140. For the nozzle 190, a metal such as stainless steel can be suitably used. The spring 144 biases the plunger 140 toward the nozzle 190.

[0017] In the electromagnetically driven pump 100, the plunger 140 reciprocates within the housing 110 by alternating the ON / OFF operation of the current to the electromagnetic coil 120.

[0018] When a driving voltage is applied to the electromagnetic coil 120 (when the voltage is ON), the plunger 140 is driven in the direction of arrow A away from the base 190 against the biasing force of the spring 144 as shown in Fig. 2(a). When the plunger 140 is driven in the direction of arrow A, the fluid (e.g., water) in the pump chamber 112 is discharged from the discharge valve 160 into the gap 192 and accumulates. Note that the gap 192 communicates with the discharge port 172 of the discharge port body 170.

[0019] On the other hand, when no driving voltage is applied to the electromagnetic coil 120 (when the voltage is OFF), the plunger 140 is returned by the biasing force of the spring 144 and driven in the direction of arrow B to contact the base 190 as shown in Fig. 2(b). When the plunger 140 is driven in the direction of arrow B, the discharge valve 160 is closed and the fluid is sucked into the pump chamber 112 from the suction valve 150. At the same time, the fluid accumulated in the gap 192 is pushed out of the electromagnetic drive pump 100 through the discharge port 172.

[0020] As a feature of this embodiment, as shown in Fig. 1, an abnormality determination device 200 is connected to the electromagnetic drive pump 100. The abnormality determination device 200 includes a drive circuit 202 and a determination unit 220.

[0021] The drive circuit 202 is a circuit that supplies power to the electromagnetic coil 120 of the electromagnetic drive pump 100, and drives the electromagnetic drive pump 100 by applying a voltage such that the current in the electromagnetic coil 120 gradually increases, for example, a sawtooth wave voltage (see Fig. 3(a)). On the drive circuit 202, a power supply 204, a switch 206, a flywheel diode 208 (also referred to as a freewheeling diode), and an ammeter 210 are arranged.

[0022] When the switch 206 on the drive circuit 202 is turned ON, power from the power supply 204 is supplied to the electromagnetic coil 120. On the other hand, when the switch 206 on the drive circuit 202 is turned OFF, the supply of power from the power supply 204 to the electromagnetic coil 120 stops. At this time, the presence of a flywheel diode 208 on the drive circuit 202 prevents damage to the switch 206 due to flyback voltage (also called surge voltage).

[0023] The ammeter 210 acquires the current in the drive circuit 202. The ammeter 210 is connected to a determination unit 220 that determines an abnormality in the electromagnetic drive pump 100 by referring to the current value acquired by the ammeter 210.

[0024] In the abnormality detection device 200, the current is measured by the ammeter 210 while the drive circuit 202 applies a sawtooth wave voltage to the electromagnetic coil 120. As the sawtooth wave voltage gradually increases (see Figure 3(a)), the current also gradually increases. As the current flowing through the electromagnetic coil 120 increases, at a certain point the plunger 140 of the electromagnetic drive pump 100 moves inside the housing 110 in the direction of arrow A shown in Figure 2(a). The movement of the plunger 140 generates a back electromotive force, causing the current to decrease (the current to fluctuate).

[0025] Therefore, the abnormality detection device 200, as will be described in detail later, monitors the current fluctuations during the voltage rise with the determination unit 220 to determine whether there is an abnormality in the electric drive pump 100, that is, whether the plunger 140 is locked or not.

[0026] In conventional methods, when using a vibration detection device to determine abnormalities in an electromagnetically driven pump, if there are external vibrations in the mounting environment of the electromagnetically driven pump, for example, the vibration detection device may detect these external vibrations and falsely detect an abnormality. Therefore, the inventor investigated whether it was possible to accurately detect abnormalities in the electromagnetically driven pump using factors other than vibration, and focused on the fluctuation of current during voltage rise in the electromagnetically driven pump 100.

[0027] Figure 3 illustrates the voltage waveform (applied voltage waveform) applied to the electromagnetic coil 120 of the electromagnetically driven pump 100 shown in Figure 1. As shown in Figure 3(a), the sawtooth voltage rises gradually from 0V to 24V when the voltage is turned ON, and falls from 24V to 0V when the power is turned OFF.

[0028] In the abnormality detection device 200, abnormalities are detected by monitoring current fluctuations during voltage rise with the detection unit 220. Therefore, the voltage applied to the electromagnetic coil 120 does not need to be a sawtooth wave voltage; any voltage that causes the current to gradually increase is acceptable. For example, instead of a sawtooth wave voltage, a triangular wave (see Figure 3(b)) or a trapezoidal wave (see Figure 3(c)) voltage may be applied to the electromagnetic coil 120.

[0029] As shown in Figure 3(b), the voltage of the triangular wave gradually rises from 0V to 24V when the voltage is turned on, and then gradually falls from 24V to 0V. As shown in Figure 3(c), the voltage of the trapezoidal wave gradually rises from 0V to 24V when the voltage is turned on, maintains at 24V, and then gradually falls from 24V to 0V.

[0030] Thus, sawtooth, triangular, or trapezoidal voltages include waveforms that rise gradually when the voltage is turned ON. This allows the determination unit 220 to monitor current fluctuations during the voltage rise.

[0031] Figure 4 illustrates the current waveform, voltage waveform, and differential current waveform of the electromagnetically driven pump 100 shown in Figure 1 under normal conditions. Figure 4(a) illustrates the current waveform (solid line in the figure) and voltage waveform (dashed line in the figure) measured by the ammeter 210 while the drive circuit 202 is applying a sawtooth wave voltage (see Figure 3(a)) to the electromagnetic coil 120.

[0032] As shown in Figure 4(a), the sawtooth wave voltage gradually increases when the voltage is turned ON, and consequently the current also gradually increases. As the current flowing through the electromagnetic coil 120 increases, the plunger 140 of the electromagnetic drive pump 100 moves inside the housing 110 at a certain point (ta when it starts moving). The movement of the plunger 140 generates a back electromotive force, and the current decreases (the current fluctuates) until the plunger 140 stops (tb when it finishes moving).

[0033] Here, the current fluctuation can be more clearly observed by differentiating the measured current value. The determination unit 220 then differentiates the measured current value and obtains the differential current waveform shown in Figure 4(b). The peak Imax appearing in the differential current waveform in Figure 4(b) corresponds to the timing when the current value suddenly returns to its original "gradually increasing slope" after tb in the current waveform in Figure 4(a).

[0034] The determination unit 220 then determines that the plunger 140 is in a normal state and is not locked if the peak Imax appearing in the differential value (differential current waveform), as shown in Figure 4(b), exceeds a predetermined threshold I0. The peak Imax exceeding the threshold I0 appears in the predetermined time T1 shown in Figure 4(b), for example, from the time ta when the plunger 140 starts moving to the time tb when it finishes moving in Figure 4(a), and in the interval that includes the timing when the current value returns to its original slope.

[0035] Figure 5 illustrates the current and voltage waveforms of the electromagnetically driven pump 100 in Figure 1 during an abnormal operation. Figures 5(a), 5(b), and 5(c) show the waveforms when the plunger 140 abnormally stops at the upper, middle, and lower positions, respectively. An abnormal stop refers to a state in which the plunger 140 is locked at each position.

[0036] As shown in Figures 5(a), 5(b), and 5(c), the sawtooth wave voltage gradually increases when the voltage is turned ON, and consequently the current also gradually increases. Here, the plunger 140 is in an abnormal state, locked at each position, so no back electromotive force is generated that would normally occur with the movement of the plunger 140. Therefore, the current waveforms shown in Figures 5(a), 5(b), and 5(c) are all identical, without the current fluctuations (current drops) shown in Figure 4(a).

[0037] Figure 6 illustrates the differential current waveform of the electromagnetically driven pump 100 in Figure 1 during an abnormality. The differential current waveform in the figure is obtained by the determination unit 220 differentiating the current value of the current waveform shown in Figures 5(a), 5(b), and 5(c).

[0038] The differential current waveform shown in Figure 6 does not show a clear peak in any section including the predetermined time T1. Nevertheless, even if the maximum value is detected as peak Imax, peak Imax is smaller than the predetermined threshold I0. As a result, the determination unit 220 of the abnormality determination device 200 can determine that the plunger 140 is in an abnormal state where it is locked.

[0039] As described above, by using the current fluctuation during voltage rise to determine abnormalities in the electromagnetic drive pump 100, the influence of external disturbances that would occur when determining abnormalities by referring to vibrations can be eliminated, and the presence or absence of abnormalities in the electromagnetic drive pump 100 can be determined more accurately. Furthermore, while conventionally used vibration detection devices are generally attached to the pump body, the abnormality determination device 200 in this embodiment is placed on the drive circuit 202 rather than the electromagnetic drive pump 100. Therefore, the abnormality determination device 200 is not subject to restrictions on the mounting location and can be applied regardless of the specifications of the pump body, thus achieving high versatility. Moreover, by applying the abnormality determination device 200, it is possible to suppress an increase in the size of the pump body.

[0040] Preferred embodiments of the present invention have been described above with reference to the attached drawings, but it goes without saying that the present invention is not limited to these examples. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of the present invention. [Industrial applicability]

[0041] This invention can be used as an abnormality detection device for an electromagnetically driven pump that pumps fluid by causing a plunger to reciprocate using an electromagnetic coil. [Explanation of Symbols]

[0042] 100...Electromagnetic pump, 110...Housing, 112...Pump chamber, 120...Electromagnetic coil, 130...Fixed core, 140...Plunger, 142...Guide, 144...Spring, 150...Suction valve, 160...Discharge valve, 170...Discharge port body, 172...Discharge port, 190...Fitting, 192...Gap, 200...Anomaly detection device, 202...Drive circuit, 204...Power supply, 206...Switch, 208...Flywheel diode, 210...Ammeter, 220...Detection unit, I0...Threshold, Imax...Peak of differential current value

Claims

1. An abnormality detection device for an electromagnetically driven pump that pumps fluid by causing a plunger to reciprocate using an electromagnetic coil, A drive circuit that drives the electromagnetic pump by applying a sawtooth wave voltage to the electromagnetic coil, An ammeter placed on the aforementioned drive circuit, The system includes a determination unit that determines an abnormality from the current value acquired by the ammeter, The abnormality detection device for an electromagnetically driven pump is characterized in that the determination unit measures the current while voltage is applied to the electromagnetic coil, calculates a derivative value by differentiating the measured current value, and determines that the plunger is in a normal state and is not locked if the peak appearing in the calculated derivative value exceeds a predetermined threshold.

2. The abnormality detection device for an electromagnetic drive pump according to claim 1, characterized in that the drive circuit applies a triangular wave or trapezoidal wave voltage to the electromagnetic coil instead of a sawtooth wave voltage.

Images