JP7758930B2 - Abnormality detection device for electromagnetically driven pump - Google Patents

Description

The present invention relates to an abnormality detection device for an electromagnetically driven pump that pumps fluid by reciprocating a plunger using an electromagnetic coil.

Electromagnetically driven pumps, which use an electromagnetic coil as a power source, have been known for some time as pumps for transporting fluids. In an electromagnetically driven pump, a plunger reciprocates inside a housing by switching the voltage applied to the electromagnetic coil on and off. The electromagnetically driven pump pumps (transports) the fluid by drawing it in through an intake port and discharging it through an outlet port. Methods commonly used to detect abnormalities in the pump's discharge flow rate include a flow sensor located in the flow path that detects the fluid flow rate, and a pressure sensor that detects the pressure within the flow path.

However, when the target flow rate is very small, the accuracy of detecting the flow rate and pressure decreases. For this reason, a vibration detection device may be used instead of a flow rate sensor or pressure sensor (see, for example, Patent Document 1). The fuel cell system in Patent Document 1 includes "a plunger-type reforming water pump that is housed in a cylinder and is capable of reciprocating motion, moves when a coil is energized, and has a plunger that collides with a collision target, and supplies reforming water to an evaporation section; a vibration detection device that detects vibrations of the reforming water pump that occur when the plunger reciprocates; and a control device that controls at least the reforming water pump."

The control device in Patent Document 1 also includes an "abnormality determination unit that determines that a reforming water supply abnormality has occurred, in which reforming water is not supplied to the reforming water pump, if the amplitude of vibration detected by the vibration detection device is equal to or greater than a first determination value during a first period of time during which the plunger is moving, from the time when current begins to be applied to the coil until the time when the plunger collides with the impact target." Patent Document 1 claims that this configuration makes it possible to reliably detect the occurrence of a reforming water supply abnormality, in which reforming water is not supplied to the pump that supplies the reforming water.

JP 2017-147182 A

When using a vibration detection device to determine whether a pump is malfunctioning, as in Patent Document 1, if there is a disturbance vibration in the pump's installation environment, the vibration detection device may detect the disturbance vibration and determine that a pump malfunction has occurred (for example, a pump that should be stopped is still operating). For this reason, while the method of using a vibration detection device, as in Patent Document 1, is useful as one method for determining whether a pump is malfunctioning, there is room for further improvement in order to more accurately determine whether a pump malfunction exists.

In light of these issues, the present invention aims to provide an abnormality detection device for an electromagnetically driven pump that can accurately determine whether or not a pump is abnormal without being affected by external disturbances.

A typical configuration of an abnormality determination device for an electromagnetically driven pump according to the present invention, which solves the above problems, is an abnormality determination device for an electromagnetically driven pump that pumps fluid by reciprocating a plunger using an electromagnetic coil, and is characterized by including an ammeter located on a drive circuit that supplies power to the electromagnetic coil, and a determination unit that determines an abnormality based on the current value acquired by the ammeter, where the determination unit acquires the minimum current value within a predetermined time from the fall of the drive voltage, and determines that the plunger is locked if the minimum value falls below a threshold. It is also preferable that the abnormality determination device for an electromagnetically driven pump includes a flywheel diode located on the drive circuit.

This invention provides an abnormality detection device for an electromagnetically driven pump that can accurately determine whether or not a pump is abnormal without being affected by external disturbances.

1 is a diagram illustrating an abnormality determination device for an electromagnetically driven pump according to an embodiment of the present invention; 5A and 5B are diagrams illustrating the operation of a plunger of an electromagnetically driven pump. 4A and 4B are diagrams illustrating waveforms of current and voltage values of an electromagnetically driven pump in normal and abnormal states;

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Dimensions, materials, and other specific values shown in these embodiments are merely examples intended to facilitate understanding of the invention and, unless otherwise specified, do not limit the present invention. Furthermore, in this specification and drawings, elements having substantially the same function and configuration are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present invention will not be illustrated or described.

Figure 1 is a diagram illustrating an abnormality determination device 200 for an electromagnetically driven pump 100 according to this embodiment. The electromagnetically driven pump 100 shown in Figure 1 is a device that pumps a fluid (not shown) by reciprocating a plunger 140 using an electromagnetic coil 120.

In the electromagnetically driven pump 100, an electromagnetic coil 120 is disposed inside the housing 110. Inside the electromagnetic coil 120 are disposed 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 disposed inside the electromagnetic coil 120. The plunger 140 is guided by the guide 142 and can move within the housing 110.

Figure 2 is a diagram explaining the operation of the plunger 140 of the electromagnetically driven pump 100. As shown in Figures 1 and 2, an intake valve 150 is disposed inside the fixed core 130, and a discharge valve 160 is disposed inside the plunger 140. The intake valve 150 draws fluid into the plunger 140, and the discharge valve 160 discharges the fluid inside the plunger 140.

By alternately turning the current to the electromagnetic coil 120 on and off, the plunger 140 reciprocates within the housing 110. As a result, as shown in Figure 2(a), when the plunger 140 is driven (moves in the direction of arrow A), the fluid (e.g., water) in the pump chamber 112 is discharged from the discharge valve 160.

On the other hand, as shown in Figure 2(b), when the plunger 140 is returned by the spring 144 (when it moves in the direction of arrow B), fluid is sucked into the pump chamber 112 through the suction valve 150. The discharge valve 160 communicates with the discharge port 172 of the discharge port body 170 and seals one end of the cylindrical guide 142 (the end on the discharge valve 160 side). As a result, the fluid discharged from the discharge valve 160 is transported outside the electromagnetically driven pump 100 through the discharge port 172.

As a feature of this embodiment, as shown in FIG. 1, an abnormality determination device 200 is connected to the electromagnetically driven pump 100. The abnormality determination device 200 includes an ammeter 210 and a determination unit 220. A power supply 204, a switch 206, a flywheel diode 208 (also called a freewheel diode), and an ammeter 210 are arranged on a drive circuit 202 that supplies power to the electromagnetic coil 120 of the electromagnetically driven pump 100.

When switch 206 on drive circuit 202 is turned ON, power is supplied from power supply 204 to electromagnetic coil 120. On the other hand, when switch 206 on drive circuit 202 is turned OFF, the supply of power from power supply 204 to electromagnetic coil 120 is stopped. At this time, the placement of flywheel diode 208 on drive circuit 202 prevents damage to switch 206 due to flyback voltage (also known as surge voltage).

The ammeter 210 acquires the current in the drive circuit 202. Connected to this ammeter 210 is a determination unit 220 which determines whether there is an abnormality in the electromagnetically driven pump 100 by referring to the current value acquired by the ammeter 210. In more detail, the determination unit 220 acquires the minimum current value within a predetermined time from the falling edge of the drive voltage (pulse wave), and determines that the plunger 140 is locked if the minimum value falls below a threshold. Specifically, the determination unit 220 can be implemented by a program running on a computer or an embedded CPU.

However, when a vibration detection device is used to determine an abnormality in an electromagnetically driven pump as in the past, if there is a disturbance vibration in the installation environment of the electromagnetically driven pump, the vibration detection device may detect the disturbance vibration and falsely detect an abnormality. For this reason, the inventors investigated whether it would be possible to accurately detect an abnormality in an electromagnetically driven pump using factors other than vibration, and focused on the current value at a predetermined time T after the electromagnetically driven pump 100 has stopped.

Figure 3 is a diagram illustrating the waveforms of the current and voltage values of the electromagnetically driven pump 100 under normal and abnormal conditions. Figure 3(a) is a diagram illustrating the waveforms of the current and voltage values of the electromagnetically driven pump 100 under normal conditions. Figures 3(b) and (c) are diagrams illustrating the waveforms of the current and voltage values of the electromagnetically driven pump 100 under abnormal conditions.

The waveform of the voltage value (drive voltage) of the electromagnetically driven pump 100 is a square wave, and as shown in Figures 3(a)-(c), when the electromagnetically driven pump 100 is driven (driving time t1), the voltage value rises (increases) from 0 V to 24 V, and when the electromagnetically driven pump 100 is stopped (stopping time t2), the voltage value falls (drops) from 24 V to 0 V. In contrast, as shown in Figures 3(a)-(c), when the electromagnetically driven pump 100 is driven (driving time t1), the current value of the electromagnetically driven pump 100 rises in a curved manner and then remains approximately constant, and when the electromagnetically driven pump 100 is stopped (stopping time t2), the current value drops sharply and then gradually drops again.

In an electromagnetically driven pump 100 where no abnormality is occurring, the minimum current value I1 for a predetermined time T is equal to or greater than the threshold value I0, as illustrated in FIG. 3(a). In contrast, an example of an abnormality occurring in the electromagnetically driven pump 100 is when the plunger 140 is locked at its upper end, as illustrated in FIG. 2(b). In such a case, the minimum current value I1 for the predetermined time T is less than the threshold value I0, as illustrated in FIG. 3(b). Another example of an abnormality occurring in the electromagnetically driven pump 100 is when the plunger 140 is locked at its lower end, as illustrated in FIG. 2(a). Even in such a case, the minimum current value I1 for the predetermined time T is less than the threshold value I0, as illustrated in FIG. 3(c).

As described above, the abnormality determination device 200 of this embodiment determines whether an abnormality exists in the electromagnetically driven pump 100 by referencing the minimum current value I1 during the predetermined time T from the time of shutdown t2. Specifically, the abnormality determination device 200 determines whether the minimum current value I1 during the predetermined time T is below the preset current threshold value I0. If the minimum current value I1 during the predetermined time T is equal to or greater than the threshold value I0, the abnormality determination device 200 determines that the plunger 140 is not locked, i.e., the electromagnetically driven pump 100 is normal. On the other hand, if the minimum current value I1 during the predetermined time T is less than the threshold value I0, the abnormality determination device 200 determines that the plunger 140 is locked, i.e., an abnormality has occurred in the electromagnetically driven pump 100.

By using current values to determine whether an abnormality exists in the electromagnetically driven pump 100 as configured above, the influence of disturbances that would occur when determining an abnormality by referring to vibrations can be eliminated, making it possible to more accurately determine whether an abnormality exists in the electromagnetically driven pump 100. Furthermore, while conventional vibration detection devices are typically attached to the pump body, the abnormality determination device 200 of this embodiment is located on the drive circuit 202 rather than the electromagnetically driven pump 100. Therefore, there are no restrictions on the location of attachment, and it can be applied regardless of the specifications of the pump body, making it highly versatile.

As shown in Figure 3(a), when the electromagnetically driven pump 100 is not malfunctioning, the current value of the electromagnetically driven pump 100 drops sharply after stopping, then begins to rise (temporary rise), and then gradually drops again. This temporary rise in current value observed during the current value decrease is a characteristic that appears only when the electromagnetically driven pump 100 is normal (when no abnormality is occurring) in the drive circuit 202 provided with the flywheel diode 208, and does not appear when the electromagnetically driven pump 100 is malfunctioning and the plunger 140 is locked. Therefore, by providing the flywheel diode 208 in the drive circuit 202 as in this embodiment, it is possible to more accurately and reliably determine whether or not there is an abnormality in the electromagnetically driven pump 100.

While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to these examples. It is clear that a person skilled in the art could conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

The present invention can be used in an abnormality detection device for an electromagnetically driven pump that pumps fluid by reciprocating a plunger using an electromagnetic coil.

100... Electromagnetically driven pump, 110... Housing, 112... Pump chamber, 120... Electromagnetic coil, 130... Stationary core, 140... Plunger, 142... Guide, 144... Spring, 150... Intake valve, 160... Discharge valve, 170... Discharge port body, 172... Discharge port, 200... Abnormality determination device, 202... Drive circuit, 204... Power supply, 206... Switch, 208... Flywheel diode, 210... Ammeter, 220... Determination unit

Claims (1)

An abnormality determination device for an electromagnetically driven pump that pumps fluid by reciprocating a plunger using an electromagnetic coil,
an ammeter disposed on a drive circuit that supplies power to the electromagnetic coil;
a determination unit that determines an abnormality based on the current value acquired by the ammeter;
a flywheel diode disposed on the drive circuit ;
The determination unit obtains the minimum value of the current value within a predetermined time from the falling edge of the drive voltage, and determines that the plunger is locked if the minimum value falls below a threshold value , and determines that the plunger is not locked if the drive voltage suddenly decreases from the falling edge and then begins to increase once .