Pump unit

Abstract

By allowing liquid to flow smoothly into the detection passage without increasing the size of the pump unit, the accuracy of moisture level detection is improved. [Solution] The pump unit 11 is equipped with a guide member 37 that guides the fuel flowing from the fuel passage 13 into the communication chamber 24 toward the inlet 30A of the detection passage 30. Therefore, the fuel flowing from the fuel passage 13 into the communication chamber 24 can be guided toward the inlet 30A of the detection passage 30 by the guide member 37.

Description

Technical Field

[0001] The present disclosure relates to a pump unit applied to a liquid supply device that supplies a liquid such as fuel.

Background Art

[0002] In a pump unit of a fuel supply device such as Patent Document 1, there are a casing, a fuel passage provided in the casing through which fuel flows, a fuel pump provided in the casing that discharges fuel into the fuel passage, a sensor unit chamber and a filter chamber provided in communication with the fuel passage, and a water detection sensor provided in the sensor unit chamber. The fuel discharged from the fuel pump flows out of the pump unit through an outflow passage after passing through the sensor unit chamber and the filter chamber.

[0003] The water detection sensor detects the amount of moisture contained in the fuel flowing into a detection passage formed in a holder. Specifically, the water detection sensor arranges a transmitter and a receiver so as to sandwich the detection passage in a direction orthogonal to the flow direction of the detection passage, transmits terahertz waves from the transmitter to the fuel flowing through the detection passage, and detects the amount of moisture (concentration) based on the terahertz waves received by the receiver.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Because the pump unit houses many components, the position and orientation of the fuel passage, the communication chamber equipped with the sensor unit and filter, and the water detection sensor (detection passage) are restricted. In other words, depending on the position and orientation of the fuel passage, communication chamber, and water detection sensor (detection passage), stagnation may occur in the flow of fuel from the communication chamber to the outlet passage, and fuel flowing from the fuel passage into the communication chamber may flow out of the communication chamber without entering the detection passage, potentially reducing detection accuracy. On the other hand, it is conceivable to change the position and orientation of the fuel passage, communication chamber, and water detection sensor (detection passage) to ensure smooth flow of fuel from the fuel passage into the communication chamber and into the detection passage, but this would require a large space, resulting in the problem of increasing the size of the pump unit.

[0006] An objective of one embodiment of the present invention is to provide a pump unit that can smoothly flow liquid into the detection passage without increasing the overall size, thereby improving the accuracy of moisture level detection. [Means for solving the problem]

[0007] The present invention relates to a pump unit provided within the housing of a liquid supply device for supplying liquid, comprising: a casing; a liquid passage provided in the casing through which liquid flows; a liquid pump provided in the casing for discharging liquid into the liquid passage; a communication chamber provided in communication with the liquid passage; and a water detection sensor provided in the communication chamber for detecting the amount of water contained in the liquid flowing through a detection passage, wherein the pump unit is further provided with a guide member for guiding the liquid flowing from the liquid passage into the communication chamber toward the entrance of the detection passage. [Effects of the Invention]

[0008] According to the present invention, it is possible to improve the accuracy of moisture content detection by smoothly flowing liquid into the detection passage without increasing the size of the pump unit. [Brief explanation of the drawing]

[0009] [Figure 1]This is an overall configuration diagram showing a fuel supply device as a liquid supply device according to an embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view of the pump unit in Figure 1. [Figure 3] This is a perspective view of the pump unit. [Figure 4] This is a front view showing the inlet, sensor holder, detection passage, guide member, etc. [Figure 5] This is a cross-sectional view showing the inlet, sensor holder, detection passage, water detection sensor, guide member, etc., from the direction of arrow VV in Figure 4. [Modes for carrying out the invention]

[0010] The following will describe in detail, with reference to Figures 1 to 5, an example of a pump unit according to an embodiment of the present invention being installed in a fuel supply device as a liquid supply device.

[0011] Figure 1 schematically shows a gas station equipped with a fuel supply device 1 as a liquid supply device. In Figure 1, the gas station is equipped with one or more ground-mounted fuel supply devices 1 (only one is shown). The fuel supply device 1 supplies fuel such as gasoline or diesel fuel in liquid form to the fuel tank of a vehicle such as an automobile.

[0012] The housing 2 of the fuel supply device 1 contains a pump unit 11, which is driven by a motor 3 (described later), a flow meter 4 for measuring the flow rate of fuel discharged from the pump unit 11, and the like. An internal pipe 5 is connected to the outlet side of the flow meter 4, and a fuel nozzle 7 is connected to the end of the internal pipe 5 via a fuel hose 6. The suction side of the pump unit 11 is connected to an underground tank 9 for storing fuel via an underground pipe 8.

[0013] The fuel supply device 1 inserts the refueling nozzle 7 into the fuel filler of the vehicle. In this state, the pump unit 11 draws fuel from the underground tank 9 and supplies it to the refueling nozzle 7 via the internal piping 5 and refueling hose 6. This allows the fuel supply device 1 to refuel the vehicle's fuel tank from the underground tank 9. During this refueling operation, the amount of fuel supplied is measured by the flow meter 4.

[0014] Next, the configuration and function of the pump unit 11, which is a characteristic feature of this embodiment, will be described.

[0015] The pump unit 11 is installed inside the housing 2 of the fuel supply device 1 and supplies fuel drawn up from the underground tank 9 to the internal piping 5. As shown in Figure 2, the pump unit 11 consists of a casing 12, a fuel passage 13, a fuel pump 19, a communication chamber 24, and a water detection sensor 31. Note that Figure 2 schematically shows the arrangement of various parts to make the overall configuration of the pump unit 11 easy to understand, and the actual arrangement of some parts may differ in the front-to-back, left-to-right, and up-and-down directions.

[0016] The casing 12 is formed, for example, as a box-shaped container. The underground piping 8 and the internal piping 5 are connected to the casing 12. Inside the casing 12, in order from the upstream side of the fuel passage 13 (described later), a strainer housing chamber 14, a check valve housing chamber 16, a rotor chamber 18, a communication chamber 24, and an outlet passage 35 are arranged.

[0017] The fuel passage 13, which serves as a liquid passage, extends within the casing 12. Liquid fuel flows through the fuel passage 13. The fuel passage 13 forms a flow path from the suction port 13A to the fuel pump 19 on the upstream side, and a flow path from the fuel pump 19 to the separation cylinder 25, which will be described later, on the downstream side. The outflow passage 35 forms a flow path from the communication chamber 24 to the discharge port 13B. The underground piping 8 is connected to the suction port 13A, and the internal piping 5 is connected to the discharge port 13B.

[0018] The strainer housing chamber 14 is formed as a space in the middle of the fuel passage 13 following the downstream side of the suction port 13A.

[0019] The strainer (filter) 15 is housed in the strainer housing chamber 14. The strainer 15 captures foreign matters contained in the fuel sucked in from the suction port 13A of the fuel passage 13 and flowing in. The strainer 15 is formed in a bottomed cylindrical shape from a mesh member.

[0020] The check valve housing chamber 16 is provided in the middle of the fuel passage 13 following the downstream side of the strainer housing chamber 14.

[0021] The suction side check valve 17 is housed in the check valve housing chamber 16. The suction side check valve 17 permits the fuel that has passed through the strainer 15 to flow toward the rotor chamber 18 and restricts the reverse flow. The suction side check valve 17 is biased in the valve closing direction by the spring force of the spring member 17A, opens when the suction pressure (negative pressure) during pump driving exceeds a predetermined pressure, and closes when the pump is stopped or otherwise.

[0022] The rotor chamber 18 is provided in the middle of the fuel passage 13 following the downstream side of the check valve housing chamber 16. A fuel pump 19 is provided in the rotor chamber 18. Specifically, the rotor chamber 18 is formed as a circular space in which the rotor 20 can rotate and fit.

[0023] The fuel pump 19 as a liquid pump is housed in the rotor chamber 18. The fuel pump 19 is configured as a gear pump that continuously sends out the fuel housed in the space between the teeth by rotating a gear. The fuel pump 19 includes a rotor 20 rotated by the motor 3 and a pinion 21 rotated by the rotor 20.

[0024] The rotor 20 is formed as a disk body having an outer diameter corresponding to the inner diameter of the rotor chamber 18. Further, on the outer peripheral side of the rotor 20, engagement portions 20A protruding semi-circularly in the plate thickness direction are provided. A plurality of these engagement portions 20A are provided at a predetermined pitch in the circumferential direction that is the rotation direction of the rotor 20.

[0025] The pinion 21 is rotatably supported in the casing 12 by a rotating shaft 22. Multiple semicircular recesses 21A corresponding to the engaging portion 20A of the rotor 20 are provided on the outer circumference of the pinion 21 at predetermined pitches.

[0026] Here, the axis of rotation of the rotor 20 and the axis of rotation shaft 22, which is the rotation center of the pinion 21, are eccentric in the diametrical direction of the rotor chamber 18. A crescent-shaped partition portion 23 is provided in the gap between the outer edge of the pinion 21 and the inner edge of the rotor 20, which is formed by the inscribed circles of the multiple engagement portions 20A, corresponding to the amount of eccentricity of the rotation center. The inner surface of the partition portion 23 slides against the outer surface of the pinion 21, and the outer surface slides against the engagement portions 20A of the rotor 20.

[0027] Then, with the engaging portion 20A of the rotor 20 engaged with the recess 21A of the pinion 21, when the rotor 20 is rotated by the motor 3, the pinion 21 also rotates in the same direction as the rotor 20. At this time, the fuel pump 19 generates negative pressure on the suction side of the rotor chamber 18 based on the rotation of the rotor 20 and the pinion 21. As a result, the suction side check valve 17 opens, and the fuel that has passed through the strainer 15 is drawn into the suction side of the rotor chamber 18.

[0028] As the rotor 20 and pinion 21 rotate counterclockwise, the fuel pump 19 directs the drawn-in fuel into the gap between the recess 21A of the pinion 21 and the engagement portion 20A of the rotor 20, and the rotation of the rotor 20 and pinion 21 discharges the fuel to the discharge side of the rotor chamber 18. Consequently, the fuel discharged from the fuel pump 19 is supplied to the air separation chamber 26 located further downstream.

[0029] The communication chamber 24 is provided downstream of the fuel pump 19, specifically to connect the separation cylinder 25 (inlet 25A), which will be described later, with the outlet passage 35. The communication chamber 24 is equipped with the separation cylinder 25 (inlet 25A), sensor holder 29 (water detection sensor 31), filter 34, etc. When the fuel pump 19 is running, the communication chamber 24 is filled with fuel. The communication chamber 24, in which the water detection sensor 31 will be described later, may also be provided upstream of the fuel pump 19 (for example, in the strainer housing chamber 14), but by providing it downstream of the fuel pump 19, the water detection sensor 31 can determine the presence or absence of water in fuel in a state where the fuel and water have been mixed and the water has been uniformly dispersed, thereby improving detection accuracy.

[0030] The separation cylinder 25 is formed as a circular cylinder extending horizontally. The downstream side of the separation cylinder 25 is an inlet 25A that opens into the communication chamber 24. More specifically, the separation cylinder 25 is positioned upstream in the flow direction when fuel flows through the communication chamber 24. The inlet 25A is an open end that allows fuel to flow from the fuel passage 13 into the communication chamber 24.

[0031] The air separation chamber 26 is located in the middle of the fuel passage 13, which is downstream of the rotor chamber 18, that is, inside the separation cylinder 25. Fuel discharged from the fuel pump 19 and flowing through the fuel passage 13 flows into the air separation chamber 26. At this time, the air separation chamber 26 separates the fuel into a gas-enriched liquid containing gas and a supply fuel containing only a minimum amount of gas by circulating the fuel in a swirling motion along the inner surface of the cylindrical chamber, utilizing centrifugal force and gravity caused by the swirling motion.

[0032] At the top, where the separated gas-enriched liquid tends to collect, a gas-enriched liquid outlet 27 is provided for recovering the separated gas-enriched liquid into the gas-liquid separation chamber 38. The gas-enriched liquid outlet 27 connects the top where the gas-enriched liquid collects with the gas-liquid separation chamber 38. Meanwhile, the separated supply fuel flows from the inlet 25A into the communication chamber 24 and flows toward the filter 34. At this time, the fuel that flows into the communication chamber 24 passes through the detection passage 30 before flowing toward the filter 34.

[0033] The sensor unit 28 is located in the communication chamber 24 together with the separation cylinder 25. More specifically, it is located within the communication chamber 24. The sensor unit 28 is positioned downstream in the flow direction when fuel flows through the communication chamber 24, that is, downstream of the separation cylinder 25. The sensor unit 28 consists of a sensor holder 29, a detection passage 30, and a water detection sensor 31, which will be described later.

[0034] As shown in Figures 3 and 5, the sensor holder 29 is formed in a cylindrical shape. The sensor holder 29 is located downstream of the separation cylinder 25 and is provided in the casing 12. As shown in Figure 4, the sensor holder 29 is positioned close to the separation cylinder 25 and aligned horizontally. In other words, the cylindrical sensor holder 29 and the cylindrical separation cylinder 25 are positioned so that their respective axes are parallel in the horizontal direction.

[0035] The detection passage 30 is provided in the sensor holder 29. More specifically, the detection passage 30 is positioned in the axial direction of the sensor holder 29 at a location corresponding to the inlet 25A of the separation cylinder 25. The detection passage 30 extends laterally and passes through in a straight line, with the inlet 30A on the side of the separation cylinder 25 and the outlet 30B on the opposite side of the separation cylinder 25. By orienting the inlet 30A towards the separation cylinder 25, the detection passage 30 can efficiently take in fuel that has flowed into the communication chamber 24 from the inlet 25A (fuel that remains in the communication chamber 24 or before it flows out of the communication chamber 24 (outlet passage 35)). Furthermore, the fuel can be introduced into the detection passage 30 even more efficiently by the guide member 37, which will be described later.

[0036] Furthermore, as shown in Figure 5, the inlet 30A of the detection passage 30 is formed in a funnel shape that widens toward the upstream inlet 25A. As a result, the funnel-shaped inlet 30A can collect the fuel flowing from the inlet 25A toward the detection passage 30 and allow a larger amount of fuel to flow into the detection passage 30.

[0037] The water detection sensor 31 is located in the communication chamber 24. The water detection sensor 31 consists of a sensor board (not shown), a transmitter 32, and a receiver 33. The sensor board is a board to which the transmitter 32 and receiver 33 are connected for communication, and it constitutes a control unit that controls the transmission timing and transmission strength (intensity of electromagnetic waves) of signals (electromagnetic waves) output from the transmitter 32, calculates the water content (moisture content) of the fuel from the signals received by the receiver 33, and determines the presence or absence of water.

[0038] The transmitter 32 and receiver 33 are mounted on the sensor holder 29 and are positioned opposite each other, straddling the detection passage 30 in a direction perpendicular to the longitudinal direction of the detection passage 30. The transmitter 32 transmits a terahertz wave (electromagnetic wave) signal (or terahertz wave) to the fuel flowing through the detection passage 30, and the receiver 33 receives the electromagnetic wave transmitted from the transmitter 32 and passed through the fuel.

[0039] Furthermore, terahertz waves have the characteristic of being easily absorbed by water. Therefore, the terahertz waves transmitted from the transmitter 32 are attenuated by the moisture in the fuel flowing through the detection passage 30, and the attenuated terahertz waves are received by the receiver 33. The sensor substrate calculates the amount of moisture in the fuel from the attenuation rate of the electromagnetic waves received by the receiver 33. In other words, the water detection sensor 31 can detect the amount of moisture contained in the fuel as the fuel discharged from the fuel pump 19 flows through the detection passage 30 which is connected to the fuel passage 13.

[0040] As shown in Figure 2, the filter 34 is located on the lower vertical side of the communication chamber 24. The downstream side of the filter 34 is connected to the outlet passage 35. The filter 34 comprises, for example, a cylindrical filter element. The filter 34 filters out foreign matter from the fuel that flows into the communication chamber 24 from the fuel passage 13. As a result, the filter 34 allows only clean fuel to flow through the outlet passage 35 to the discharge port 13B.

[0041] The discharge-side check valve 36 is located at the discharge port 13B. The discharge-side check valve 36 receives the pressure of the fuel discharged by the fuel pump 19 and opens to prevent fuel from returning from the flow meter 4 side. The discharge-side check valve 36 is biased in the closing direction by the spring force of the spring member 36A, and opens when the suction pressure (negative pressure) during pump operation exceeds a predetermined pressure, and closes at other times, such as when the pump is stopped.

[0042] Next, the configuration and effects of the guide member 37, which is a characteristic feature of this embodiment, will be described.

[0043] As shown in Figures 2 and 3, the guide member 37 is provided in the communication chamber 24. The guide member 37 guides the fuel flowing from the fuel passage 13 into the communication chamber 24 toward the inlet 30A of the detection passage 30. The guide member 37 surrounds the inlet 25A of the separation cylinder 25 and extends toward the inlet 30A of the detection passage 30, and is formed as a curved plate with a cutout on the inlet 30A side. Also, as shown in Figure 5, the guide member 37 is made of a wide plate in the axial direction of the separation cylinder 25 and protrudes beyond the open end of the inlet 25A.

[0044] Specifically, the guide member 37 has a diameter larger than the inlet 25A and comprises a semi-cylindrical portion 37A cut at a position in the vertical straight line passing near the centerline of the separation cylinder 25, and a lower extension portion 37B extending from the lower end edge of the semi-cylindrical portion 37A, which is below the inlet 25A, toward the lower side of the detection passage 30. The sensor holder 29 side of the lower extension portion 37B is a curved portion 37C that curves upward toward the sensor holder 29. As a result, the guide member 37 is formed as a J-shaped (C-shape inverted horizontally) curved plate with both ends in the longitudinal direction curved.

[0045] When fuel flows into the communication chamber 24 from the inlet 25A of the separation cylinder 25, the guide member 37 prevents the fuel flowing in from the inlet 25A from flowing away from the sensor holder 29 (detection passage 30) by its semi-cylindrical portion 37A. In other words, the semi-cylindrical portion 37A guides the fuel that has flowed out of the inlet 25A in a swirling motion toward the entrance portion 30A of the detection passage 30.

[0046] Furthermore, the guide member 37 guides the fuel flowing downward from the inlet 25A due to gravity along the lower extension 37B, thereby guiding a large amount of fuel flowing downward from the inlet 25A toward the inlet 30A of the detection passage 30. Moreover, since the sensor holder 29 side of the lower extension 37B has an upwardly curved portion 37C, this curved portion 37C can direct the flow direction of the fuel flowing downward from the inlet 25A upward, that is, toward the gas enrichment liquid outlet 27 and the inlet 30A of the detection passage 30.

[0047] The gas-liquid separation chamber 38 separates gas from the gas-enriched liquid that flows in from the air separation chamber 26 through the gas-enriched liquid outlet 27. A return hole 39 is provided at the bottom of the gas-liquid separation chamber 38 to return the fuel to the suction side of the fuel pump 19, and an atmospheric vent 40 is provided at the top of the gas-liquid separation chamber 38 to release the separated gas to the outside.

[0048] The gas-liquid separation chamber 38 is equipped with a float valve 41 that opens and closes a return hole 39 according to the liquid level of the fuel containing the gas-enriched liquid in the gas-liquid separation chamber 38. In addition, the relief valve 42 opens when the fuel pressure in the fuel passage 13 downstream of the fuel pump 19 becomes excessively high, etc., to return the fuel to the suction port 13A side of the fuel passage 13.

[0049] Thus, according to this embodiment, a guide member 37 is provided to guide the fuel flowing from the fuel passage 13 through which the fuel flows into the communication chamber 24 toward the inlet 30A of the detection passage 30. Therefore, the fuel flowing from the fuel passage 13 into the communication chamber 24 can be guided toward the inlet 30A of the detection passage 30 by the guide member 37. As a result, even when the position and orientation of the separation cylinder 25, communication chamber 24, water detection sensor 31, filter 34, etc. are restricted when installing them inside the casing 12, the fuel can be allowed to flow into the inlet 30A of the detection passage 30 by providing the guide member 37. As a result, fuel can be allowed to flow smoothly into the detection passage 30 without increasing the size of the pump unit 11, and the accuracy of detecting the amount of moisture in the fuel can be improved.

[0050] Furthermore, the communication chamber 24 is provided with an inlet 25A for a separation cylinder 25 into which fuel flows from the fuel passage 13. The guide member 37 surrounds the inlet 25A and extends toward the entrance 30A of the detection passage 30, and is formed as a curved plate with a cutout on the entrance 30A side. As a result, the guide member 37 prevents the fuel that flows into the communication chamber 24 from the inlet 25A of the separation cylinder 25 from flowing toward the opposite side of the detection passage 30. In other words, the guide member 37 can guide most of the fuel that flows into the communication chamber 24 from the inlet 25A toward the entrance 30A of the detection passage 30.

[0051] Furthermore, the inlet 25A of the separation cylinder 25 is positioned horizontally aligned with the detection passage 30, and the guide member 37 is equipped with a lower extension 37B that extends from below the inlet 25A toward the lower side of the detection passage 30. Therefore, the lower extension 37B can guide the fuel flowing downward from the inlet 25A by gravity toward the inlet 30A of the detection passage 30. This increases the flow rate of fuel passing through the detection passage 30, thereby improving the accuracy of detecting the amount of moisture in the fuel.

[0052] Furthermore, the inlet 30A of the detection passage 30 is formed in a funnel shape that widens toward the upstream side. As a result, the funnel-shaped inlet 30A can collect the fuel flowing from the inlet 25A toward the detection passage 30, thereby allowing a larger amount of fuel to flow into the detection passage 30.

[0053] In this embodiment, the detection passage 30 was described as a straight passage having one inlet 30A and one outlet 30B. However, the present invention is not limited to this, and for example, the detection passage may be configured to have multiple inlets or multiple outlets. Alternatively, the detection passage may be formed as multiple parallel passages.

[0054] Furthermore, in the embodiment, the case in which the inlet 30A of the detection passage 30 is formed in a funnel shape that widens toward the upstream inlet 25A was described as an example. However, the present invention is not limited to this, and for example, the detection passage may be formed with a constant opening area from the inlet to the outlet.

[0055] Furthermore, in the embodiment, the guide member 37 is shown as having a curved portion 37C that curves upward on the lower extension portion 37B. However, the present invention is not limited to this, and the lower extension portion 37B may be formed in a straight line toward the entrance portion 30A of the detection passage 30.

[0056] Furthermore, in the embodiments, fuels such as gasoline and diesel fuel are given as examples of liquids. However, the present invention is not limited to these, and may also be applied to a pump unit for supplying liquids other than fuels.

[0057] Next, as a pump unit included in the above embodiment, for example, the following embodiment can be considered.

[0058] In a first embodiment, a pump unit provided within the housing of a liquid supply device for supplying liquid comprises a casing, a liquid passage provided in the casing through which liquid flows, a liquid pump provided in the casing for discharging liquid into the liquid passage, a communication chamber provided in communication with the liquid passage, and a water detection sensor provided in the communication chamber for detecting the amount of water contained in the liquid that flows through a detection passage communicating with the liquid passage after being discharged from the liquid pump, the pump unit being characterized by comprising a guide member for guiding the liquid that flows from the liquid passage into the communication chamber toward the entrance of the detection passage.

[0059] In a second embodiment, the communication chamber is provided with an inlet for allowing liquid to flow in from the liquid passage, and the guide member is formed as a curved plate that surrounds the inlet and extends toward the entrance portion of the detection passage, with the entrance portion side being cut out.

[0060] In a third embodiment, the inlet is positioned horizontally to the detection passage, and the guide member is provided with a lower extension that extends from below the inlet toward below the detection passage.

[0061] In a fourth embodiment, the entrance portion of the detection passage is formed in a funnel shape that widens toward the upstream side, as in the first embodiment. [Explanation of Symbols]

[0062] 1 Fuel supply device (liquid supply device) 2 cabinets 11 Pump Unit 12 Casing 13 Fuel passage (liquid passage) 19. Fuel pump (liquid pump) 24 Communication room 25 Separation cylinder 25A inlet 30 detection passages 30A entrance section 31 Water detection sensor 37 Guide Member 37A Semi-cylindrical section 37B Lower extension 37C Curved section

Claims

1. A pump unit provided within the housing of a liquid supply device for supplying liquid, Casing and, A liquid passage is provided in the casing through which the liquid flows, A liquid pump provided in the casing for discharging liquid into the liquid passage, A communication chamber provided in communication with the aforementioned liquid passage, A water detection sensor that detects the amount of water contained in the liquid flowing through the detection passage provided in the communication chamber, In the pump unit provided, A pump unit characterized by comprising a guide member that guides the liquid flowing from the liquid passage into the communication chamber toward the entrance of the detection passage.

2. A pump unit according to claim 1, The aforementioned communication chamber is provided with an inlet for allowing liquid to flow in from the aforementioned liquid passage. The pump unit is characterized in that the guide member surrounds the inlet and extends toward the inlet portion of the detection passage, and is formed as a curved plate with a cutout on the inlet side.

3. The pump unit according to claim 2, The inlet is positioned horizontally aligned with the detection passage. The pump unit is characterized in that the guide member has a lower extension portion that extends from the lower side of the inlet toward the lower side of the detection passage.

4. A pump unit according to claim 1, The pump unit is characterized in that the inlet of the detection passage is formed in a funnel shape that widens toward the upstream side.

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