JPH07197881A - Pump unit - Google Patents

Abstract

PURPOSE:To improve gas liquid separation capacity as much as possible and to reduce the size of the whole of a device by a method wherein a gas liquid separating device to separate fluid delivered from a pump into revolved liquid and gas enriched liquid consists of a vertical type cyclone the lower end of which is opened. CONSTITUTION:In a pump unit arranged at an oil feeder used in a service station, a vane type pump 19, a gas liquid separating device 31, and a filter chamber 40 are continuously arranged in a casing 10. In this case, the gas liquid separating device 31 comprises a vertical cyclone 32, the lower end of which is released, consisting of a cylindrical introduction part 33; a truncated conical drum part 34; and a conical ceiling part 35. Liquid delivered from the pump 19 is introduced through a flow passage 30 to generate a swirl flow. By utilizing a centrifugal force difference, liquid and air enriched liquid are radially separated from each other and vertically separated away from each other by utilizing a gravity difference. The separated liquid is fed through a filter 41 to an outflow port and the air enriched liquid is fed in an air separating chamber through the hole 37a of the ceiling part 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pump unit equipped in an oil supply device or the like.

[0002]

2. Description of the Related Art For example, a refueling device used in a gas station is
Due to space constraints, it is required that the pump unit be as small as possible, and accordingly, the pump unit is also required to be small. On the other hand, gas is often mixed in gasoline or the like handled at a gas station, and a pump unit having a gas-liquid separating means is required.

Therefore, conventionally, in order to meet the above-mentioned requirements,
A casing having an inflow port and an outflow port, and a pump for sucking fluid from the inflow port in the casing;
A gas-liquid separator that swirls the fluid discharged from the pump to separate it into a liquid and a gas-enriched liquid; and a gas separation chamber that separates the gas from the gas-enriched liquid separated by the gas-liquid separator. A pump unit has been developed in which the liquid separated by the gas-liquid separation device is caused to flow out from the outflow port and the liquid separated in the gas separation chamber is returned to the suction port side of the pump. It is disclosed in Japanese Patent Publication No. 4-19389. According to such a pump unit, 1
Not only can the components be arranged in one casing to achieve miniaturization, but it is also possible to supply a liquid containing very little gas by the double gas-liquid separation by the gas-liquid separator and the gas separation chamber.

[0004]

However, according to the above-mentioned conventional pump unit, the gas-liquid separating device for separating the liquid and the gas-enriched liquid is insufficient in separation capacity, and the gas separation chamber is correspondingly insufficient. There is a problem that the burden on the side is increased and the gas separation chamber has to be formed in a large size, and the increase in size of the whole is inevitable.

The present invention has been made in view of the above problems of the prior art, and its problem is to enhance the gas-liquid separation capacity of the gas-liquid separation device as much as possible, thereby contributing to downsizing of the entire device. It is to provide a pump unit that operates.

[0006]

In order to solve the above problems, the present invention provides a casing having an inlet and an outlet for sucking fluid from the inlet and swirling the fluid discharged from the pump. A gas-liquid separator for separating the liquid and the gas-enriched liquid is provided, and a gas separation chamber for separating the gas from the gas-enriched liquid separated by the gas-liquid separator is provided, and the gas-liquid separator is used for the separation. In the pump unit configured to cause the liquid to flow out from the outflow port and to return the liquid separated in the gas separation chamber to the suction port side of the pump, the gas-liquid separation device is formed by a vertical cyclone having an open lower end. Then, one end of a flow path connected to the discharge port of the pump is opened so as to guide the fluid in the tangential direction to the peripheral wall of the cyclone, and the gas separation chamber is connected to the center of the ceiling of the cyclone. Characterized by being configured to open one end of the channel.

In the present invention, the cyclone may have a shape in which the lower side thereof is gradually narrowed toward the lower end opening. In addition, in the present invention, the ceiling of the cyclone can be formed in a conical shape, and one end of the flow path connected to the discharge port of the pump can be partially opened in the ceiling formed in the conical shape.

[0008]

In the pump unit configured as described above, the liquid mixed with the gas sent from the pump causes a swirling motion in the cyclone, so that the centrifugal force acting on the liquid is different from that on the liquid. As the gas gathers radially outward and the gas gathers radially inward, the separated liquid flows down from the bottom opening of the cyclone, while the gas-enriched liquid containing gas is discharged from the opening in the ceiling of the cyclone to the gas separation chamber. To be done. Since the cyclone has a vertical shape, the liquid and the gas are vertically separated due to the difference in specific gravity, and the gas-liquid separation ability is improved in combination with the centrifugal separation. Further, when the lower side of the cyclone is narrowed toward the lower end opening, the flow velocity of the swirling flow increases as it goes downward, and the gas-liquid separation capacity is further improved. Further, when the cyclone ceiling is formed in a conical shape, a downward swirling flow is easily formed, the gas-liquid separation capacity is further improved, and the separated gas-enriched liquid is easily discharged. Further, when the one end of the flow path connected to the discharge port of the pump is partially opened in the ceiling portion formed in the conical shape, the swirling flow velocity is increased even in the initial stage where the fluid flows into the cyclone, The gas-liquid separation capacity is further improved.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIGS. 1 to 9, 10 is a casing having an inflow port 11 in the lower part and an outflow port 12 in the upper part, which are integrally cast from an aluminum alloy. A suction chamber 13 is formed on the lower side of the casing 10 so as to face the inflow port 11, and the suction chamber 13 includes a strainer 14 and a suction side check valve 15. A valve assembly 16 described in detail later. Is provided. On the other hand, on the upper side in the casing 10, a pump chamber 18 communicating with the suction chamber 13 via a flow path 17 (FIG. 4).
A vane pump (rotary pump) 19 is arranged in the pump chamber 18. The pump 19 includes a bottomed cylindrical main body 20 fitted in the pump chamber 18.
The main body 20 is provided with a suction port 21 connected to the flow channel 17 and a discharge port 22 connected to another flow channel 30 described later.

A rotor 23 is arranged in the main body 20 of the pump 19, and the rotor 23 is fixedly attached to a rotary shaft 24 extending from the eccentric position of the main body 20. The rotating shaft 24 includes a bearing portion 25 integrally formed inside the casing 10 and the casing 10.
It is rotatably supported by a bearing portion 26a formed integrally with a lid body 26 covered on the outer wall of the. The pump chamber 18 and the main body 20 are
By closing the opening 10a of the casing 10 with the lid 26, a closed chamber is defined. A plurality of vanes 27 are radially mounted on the rotor 23 so as to be slidable in the radial direction. Each vane 27 is a recess provided on both side surfaces of the rotor 23.
Each proximal end is supported by a ring 28 arranged in 23a. In addition, the rotary shaft 24 extended outside the casing 10
A pulley 29, which is driven to rotate by a motor (not shown), is attached to one end of the.

In such a pump 19, when a pulley 29 is rotated by the operation of a motor (not shown), the rotation is transmitted to the rotor 23 via the rotary shaft 24, and each vane 27 has its tip end of the main body 20. Rotates while sliding on the inner surface. At this time, since the rotor 23 rotates around an eccentric position with respect to the main body 20, the volume of each chamber partitioned by the vanes 27 is repeatedly expanded and contracted, and thereby negative pressure is generated on the suction side in the main body 20. Therefore, if you connect the inlet 11 to the tank,
The rotation of the rotor 23 causes the fluid in the tank to flow from the inflow port 11 to the strainer 14, the suction side check valve 15, the flow path 17, and the suction port.
It is sucked into the pump 19 via 21 and flows from the discharge port 22.
It will be discharged to 30.

Also, on the upper side of the casing 10 and at the pump
A gas-liquid separating device 31 is arranged at a portion located on the side opposite to 19. The gas-liquid separation device 31 is composed of a vertical cyclone 32 having an open lower end, and the cyclone 32 has an upper cylindrical introduction portion 33 and a downwardly extended portion extending from the introduction portion 33 toward the lower end opening. A gradually constricted frusto-conical body 34 and a conical ceiling 35 covering the upper side of the introduction portion 33 are provided. The body part 34 of the cyclone 32 is formed such that a lower part 34a corresponding to approximately half the length thereof protrudes into the filter chamber 40, which will be described later, and has a protruding part 34a that intersects with the highest ceiling part of the filter chamber 40. A slit 36 extending in the vertical direction is formed in the peripheral wall portion.

An opening 30a which constitutes one end of the flow channel 30 is provided above the cyclone 32. This opening 30a
Is provided so that the fluid from the pump 19 flows out in the tangential direction of the cyclone 32, and the introduction portion 33 and the ceiling portion 35 are provided.
It is provided vertically across the and. A plug member 37 having a through hole 37a is fitted in the center of the ceiling portion 35 of the cyclone 32. The through hole 37a of the plug member 37 is provided with a gas separation chamber 60, which will be described later, via a channel 39 in a lid 38 attached to the casing 10.
Is in communication with. In such a gas-liquid separator 31, the liquid mixed with the gas, which has been pumped from the pump 19 through the flow path 30, flows into the cyclone 32 through the opening 30a and causes a swirling motion to separate the liquid and the gas. Due to the different centrifugal forces acting, the liquid gathers radially outward and the gas gathers radially inward. Then, the separated liquid flows down into the filter chamber 40 from the lower end opening of the body portion 34, while the gas-enriched liquid containing gas is introduced into the lid 38 from the through hole 37a of the plug member 37 of the ceiling portion 35. It is discharged to the flow path 39 and further discharged to the gas separation chamber 60.

A filter 41 is arranged in the filter chamber 40. The filter 41 has a filter chamber 40 at its tip.
42a provided in the vertical partition wall 42 in the casing 10 for partitioning the
Is fitted to. Behind the filter 41 is a casing 10
A compression spring 44, one end of which is in contact with a lid 43 covered with the filter 41, is provided, and the filter 41 is pressed against the vertical partition wall 42 by the compression spring 44. The opening 10b of the casing 10 closed by the lid 43 has a size large enough to allow the filter 41 to be taken in and out, so that the filter 41 can be replaced as appropriate by removing the lid 43. become able to.

In front of the filter 41, the casing 10
End part of the flow path 46 leading to the outlet side check valve 45 (FIGS. 4 and 6) provided on the upper side of the suction side check valve 15 and the secondary side flow path 17 of the suction side check valve 15.
One end of a flow path 47 communicating with the vertical partition wall 48 is disposed so as to sandwich the vertical partition wall 48. The outlet check valve 45 is a horizontal partition of the casing 10.
A valve seat 51 fitted in a through hole 50 formed in the valve seat 49;
A valve spring that makes one end abut against the valve body 52 which is seated on and away from the lid body 53 of the casing 10 and normally urges the valve body 52 in the closing direction.
54 and. The outlet side check valve 45 has a flow path on the secondary side.
It is connected to the outlet 12 via 55 (FIG. 9). Therefore, the liquid separated by the gas-liquid separator 31 and flowing down to the filter chamber 40 opens the outlet side check valve 45 from the filter 41 through the flow path 46, and further flows from the flow path 55 to the outside through the flow outlet 12. Is sent under pressure. Then, a relief valve 56, which will be described later, is bolted to the side wall of the casing 10 on the vertical partition wall 48.
When the pump 19 is driven and the outlet side is closed or squeezed, the relief valve 56 is opened and the liquid flows from the flow passage 47 and the flow passage 17 into the pump 19 and It will be returned to the suction port 21.

On the other hand, the casing forming the gas separation chamber 60.
As shown in FIG. 7, a through hole 61 is formed in the upper wall of the upper wall 10 so as to face the flow path 39 from the gas-liquid separating device 31, and the gas-liquid separating device 31 is formed in the through hole 61. A pipe member 62 for supplying the gas-enriched liquid separated in step 1 to the gas separation chamber 60 is press-fitted. The lower end of the pipe member 62 extends into a small-volume liquid pool 64 provided near the lowest liquid level in the gas separation chamber 60. The liquid pool 64 is formed in a U-shaped groove from a vertical partition wall 63 of the casing 10, a stepped portion 63a of this partition wall and a vertical wall 64a parallel to the partition wall 63, and one end thereof is opened as shown in FIG. There is. As a result, the gas-enriched liquid supplied into the gas separation chamber 60 through the pipe member 62 once accumulates in the liquid pool 64, and then flows from one end thereof to the bottom side of the gas separation chamber 60 to accumulate. During this time, the gas is separated from the gas-enriched liquid, and this gas is discharged to the outside from the air vent 65 (FIG. 9) provided on the upper wall of the casing 10.

A float 67 is arranged on the bottom side of the gas separation chamber 60. The float 67 has a lid body 68 in which a tip portion of a shaft portion 67a extending from one surface thereof is bolted to the casing 10.
It can be rotated in the up and down direction by being pivotally attached to. The lid 68 has a first boss portion protruding from the front and back surfaces thereof.
69 is provided, and a shaft hole 70 is formed in the first boss portion 69. An opening 71 is formed at the tip of the boss 69 located in the gas separation chamber 60 so that the shaft hole 70 communicates with the gas separation chamber 60. Around this opening 71 is formed as a valve seat of the return valve 72, and a valve element (poppet valve) 74 axially attached to the shaft portion 67a of the float 67 using a pin 73 is fitted into this opening 71. Has been done. This return valve 72
Moves the valve element 74 upward in response to the rise of the float 67,
Open 71. The float 67 and the valve body 74 are integrated with the lid 68 in advance, and can be taken in and out of the gas separation chamber 60 through the opening 10c of the casing 10 closed by the lid 68. A plug 75 that closes the shaft hole 70 is screwed onto one end of the first boss 69 on the outside of the lid 68.

On the other hand, in the lower part of the casing 10, there is formed a return flow passage 76 (FIGS. 4, 5 and 7) which communicates with the flow passage 47 on the secondary side of the relief valve 56 from the side surface of the casing 10. . The return passage 76 and the shaft hole 70 in the first boss portion 69.
Are connected to each other through a communication hole (not shown) in the second boss portion 77 provided in the casing 10, and the connection portion has the first
A check valve (flapper valve) 78 for restricting the reverse flow of the liquid to the shaft hole 70 in the boss portion 69 is provided (FIG. 5). As a result, when the liquid is accumulated in the gas separation chamber 60 and the float 67 rises, the return valve 72 is opened so that the liquid in the gas separation chamber 60 has the shaft hole 70 in the first boss portion 69 and the second boss portion. Communication hole in 77, return flow path
76, the secondary side flow passage 47 of the relief valve 56, and the secondary flow passage 17 of the suction side check valve 15 to be returned to the suction port 21 of the pump 19.

As shown in FIGS. 10 and 11, the valve assembly 16 arranged in the suction chamber 13 on the side of the inlet 11 is mainly composed of a bottomed cylindrical valve seat 80, and this valve seat 80 The strainer 14 is fitted and fixed to one end of the valve seat 80, and the lid 81 is attached to the other end of the valve seat 80. The lid 81 is composed of a plate-shaped portion 82 having a mounting hole 82a for the casing 10, and a plurality of leg portions 83 extending from the plate-shaped portion 82. The leg portions 83 are screwed onto the outer periphery of the valve seat 80. It is integrated with the valve seat 80 by combining them. A through hole 80a is provided at the center of the bottom of the valve seat 80, and a valve shaft 84 is slidably fitted in the through hole 80a. The valve body 85 is screwed to one end of the valve shaft 84 extended into the lid 81, while the valve spring 86 is attached to the other end of the valve shaft 84 extended into the strainer 14. It is wrapped. Both ends of the valve spring 86 are brought into contact with a back surface of the valve seat 80 and a spring receiver 87 fixed to the other end of the valve shaft 84, so that the valve shaft 84 is normally strained.
The valve element 85 is normally urged toward the 14 side so that the valve element 85 always maintains the closed state in which it is seated on the open end of the valve seat 80.
A flow path 88 is also formed at the bottom of the valve seat 80, and the fluid that has passed through the strainer 14 flows into the valve seat 80 through the flow path 88. The valve body 85 includes a support plate 85a connected to the valve shaft 84 and a nut on the support plate 85.
It consists of a rubber valve member 85c which is clamped and fixed using 85b.

The valve assembly 16 is inserted into the casing through the opening 10d provided in the casing 10, and the lid 81 thereof is provided.
It is bolted to the casing 10 using the mounting hole 82a. At this time, the valve seat 80 is fitted into the hole 89 (FIG. 2) provided in the partition wall in the casing 10 via the seal member, and the suction chamber
Divide 13 into two rooms, front and rear. When the pump 19 is operated in this assembled state, the valve body 85 opens against the biasing force of the valve spring 86 due to the generation of negative pressure in the pump 19, and the valve seat 80 from the strainer 14 through the flow path 88. The fluid flowing in flows into the flow path 17 communicating with the suction port 21 of the pump 19.

On the other hand, as shown in FIGS. 12 and 13, the relief valve 56 disposed in front of the filter 41 has a cylindrical valve seat 90 with a bottom and a shaft portion in a through hole 90a provided in the bottom of the valve seat 90. 91a
A valve body 91 slidably fitted in and seated on the open end of the valve seat 90, a lid body 92 having a shaft hole 92a, and a bottomed cylinder fitted in the shaft hole 92a of the lid body 92. It is composed of a valve spring 94, one end of which is in contact with the bottom of a spring receiver 93 and which normally presses and urges the valve body 91 against the valve seat 90. The valve seat 90 is formed with a flow path 95 that communicates the inside and outside thereof, and the lid 92 is provided with a mounting hole 96. Further, an adjusting screw 97 for adjusting the biasing force of the valve spring 94 is screwed into the lid body 92 via the spring receiver 93.

The relief valve 56 is inserted into the casing through the opening 10e provided in the casing 10, and the lid 92 thereof is provided.
It is bolted to the casing 10 using the mounting hole 95 of the. At this time, the valve seat 90 is fitted into the hole 98 provided in the partition wall 48 in the casing 10, and communicates with the flow path 46 leading to the outlet side check valve 45 and the secondary side of the suction side check valve 15. Completely separates from the flow path 47. Then, in this assembled state, when the liquid pressure in the flow path 46 increases more than necessary, the valve body 91 opens against the urging force of the valve spring 94, and the liquid in the flow path 46 flows into the flow path 47. And flow path
It is returned from 17 to the suction port 21 of the pump 19.

The operation of the pump unit constructed as above will be described below. When the rotor 23 of the pump 19 is rotated by the operation of a motor (not shown), the valve body 85 of the suction side check valve 15 opens, and the strainer 14 from the inlet 11 to the suction side check valve.
The fluid in the tank is sucked into the pump 19 through the flow path 15 and the flow path 17, and is discharged from the discharge port 22 to the flow path 30.
The fluid discharged from the pump 19 is the gas-liquid separation device 31.
Flow toward the side, flow into the cyclone 32 from the opening 30a of the flow path 30 and cause a swirling motion, and due to the difference in centrifugal force, the liquid gathers radially outward and the gas gathers radially inward. At this time, by adopting the vertical cyclone 32, the liquid and the gas are vertically separated due to the difference in specific gravity, and the gas-liquid separation ability is improved in combination with the centrifugal separation.

In this embodiment, in particular, since the body portion 34 of the cyclone 32 is gradually narrowed toward the lower end opening, the swirling flow velocity increases as it goes downward, and the gas-liquid separation capacity is further improved. . In addition, since the ceiling 35 of the cyclone 32 is formed in a conical shape, it is easy to create a downward swirl flow, and the swirl flow velocity increases even at the initial stage when fluid enters the cyclone 32, and gas-liquid separation is achieved. Ability is further improved. The liquid thus separated flows down from the lower end opening of the body portion 34 into the filter chamber 40, while
The gas-enriched liquid containing gas is passed through the through hole 37 of the plug member 37 of the ceiling 35.
It is discharged from a to the flow channel 39 in the lid 38. At this time, the conical shape of the ceiling portion 35 facilitates the discharge of the gas-enriched liquid.

The liquid flowing down into the filter chamber 40 is
It is pushed out into the flow path 46 through the filter 41, the outlet side check valve 45 is opened by the pressure of the liquid, and the liquid is pressure-fed from the flow path 55 to the outflow port 12. Then, when gas remains in the liquid separated by the gas-liquid separation device 31, the gas remains in the filter chamber.
It will collect at the top of 40. This accumulated gas is pumped
Since there is a flow of liquid during the operation of 19, the water remains in the upper part of the filter chamber 40, but when the pump 19 is stopped,
It returns from the slit 36 of 34 to the inside of the cyclone 32, and is discharged from the ceiling 35 in response to the restart of the pump 19. Therefore,
No liquid containing gas is supplied to the outlet 12. In addition, when the outflow of the liquid from the outlet 12 is stopped or squeezed, the relief valve 56 is opened and the liquid is sucked into the suction port of the pump 19.
Returning to 21 is as described above.

On the other hand, the flow path 39 from the cyclone 32 to the lid 38
The gas-enriched liquid discharged to is supplied into the gas separation chamber 60 through the pipe member 62. At this time, the gas-enriched liquid is in the gas separation chamber.
When it rapidly falls into 60, the liquid in the gas separation chamber 60 is largely stirred and foaming occurs, the float 67, that is, the return valve 72 malfunctions, and the liquid containing gas flows into the return flow path 76. . However, in this embodiment, since the tip of the pipe member 62 is positioned in the liquid in the liquid pool 64, the stored liquid in the gas-liquid separation chamber 60 is not largely stirred by the gas-enriched liquid, and therefore, Foaming of the liquid and its diffusion are suppressed. Then, gas separation proceeds in the gas separation chamber 60, and the separated gas is air vent 65 of the casing 10.
Is discharged from the outside. In this way, the gas separation chamber
The liquid from which the gas has been separated accumulates in 60, and the liquid level gradually rises. Then, the float 67 rises and the valve body 74 of the return valve 72 opens, and the liquid in the gas separation chamber 60 flows into the return flow path 76,
Furthermore, the flow path 47 on the secondary side of the relief valve 56, the check valve 15 on the suction side
Is returned to the suction port 21 of the pump 19 via the secondary side flow path 17. It goes without saying that the pump 19 can be replaced with another rotary pump, for example, a gear pump or another type of pump.

[0028]

As described above in detail, according to the pump unit of the present invention, a vertical cyclone can be used for efficient gas-liquid separation, and a gas separation chamber connected to the same. It is not necessary to form a large size, which contributes to downsizing of the whole. Further, if necessary, by improving the shape of the cyclone and the liquid inlet, the gas-liquid separation capacity of the gas-liquid separation device can be further improved, and its utility value is great.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an internal structure of a pump unit according to the present invention.

FIG. 2 shows the internal structure of the pump unit,
It is sectional drawing which follows the 2-2 arrow line of FIG.

3 is a sectional view taken along the line 3-3 of FIG.

4 is a cross-sectional view taken along the line 4-4 of FIG.

5 is a sectional view taken along the line 5-5 of FIG.

FIG. 6 is a side view showing the present pump unit as a partial cross section.

FIG. 7 is a front view showing the present pump unit as a partial cross section.

FIG. 8 is a front view of the present pump unit.

FIG. 9 is a top view of the pump unit.

FIG. 10 is a cross-sectional view showing the structure of a valve assembly that constitutes the present pump unit.

11 is a front view taken along the line A of FIG.

FIG. 12 is a cross-sectional view showing the structure of a relief valve that constitutes the present pump unit.

13 is a front view taken along the line B of FIG.

[Explanation of symbols]

 10 Casing 11 Inlet 12 Outlet 15 Suction side check valve 19 Pump 21 Pump inlet 22 Pump outlet 31 Gas-liquid separator 32 Cyclone 33 Cyclone inlet 34 Cyclone body 35 Cyclone ceiling 37a Opening (Through hole) 40 Filter chamber 41 Filter 45 Check valve on outlet side 56 Relief valve 60 Gas separation chamber 62 Pipe member 64 Liquid reservoir 67 Float 72 Return valve 76 Return flow path

Claims (4)

[Claims] 1. A pump that sucks fluid from the inlet and a gas-liquid separator that swirls the fluid discharged from the pump to separate it into a liquid and a gas-enriched liquid in a casing having an inlet and an outlet. An apparatus and a gas separation chamber for separating a gas from the gas-enriched liquid separated by the gas-liquid separation device are provided, and the liquid separated by the gas-liquid separation device is caused to flow out from the outlet and the gas separation chamber is also provided. In the pump unit configured to return the liquid separated in step 1 to the suction port side of the pump, the gas-liquid separator is formed by a vertical cyclone having an open lower end, and the fluid is guided to the peripheral wall of the cyclone in the tangential direction thereof. A pump unit characterized in that one end of a flow path connected to the discharge port of the pump is opened, and one end of a flow path connected to the gas separation chamber is opened in the central part of the ceiling of the cyclone. And 2. The pump unit according to claim 1, wherein the lower side of the cyclone is gradually narrowed toward the lower end opening. 3. The pump unit according to claim 1, wherein the cyclone has a ceiling portion formed in a conical shape. 4. The pump unit according to claim 3, wherein one end of the flow path connected to the discharge port of the pump is partially opened in the conical ceiling portion of the cyclone.