Hydraulic pump unit and work machine provided with hydraulic pump unit

Abstract

A hydraulic pump unit (17) comprises: a pump body (34) having an air vent port (52) for discharging air accumulated in an internal space to the outside; an electric motor (32) disposed vertically above the pump body (34) and connected to the pump body (34) so as to be capable of transmitting power; a tank (38) connected to the pump body (34) via a suction pipe (44); and an external pipe (56) directly connecting the air vent port (52) and the suction pipe (44).

Description

Hydraulic pump unit and work machine equipped with said hydraulic pump unit

[0001] The present invention relates to a hydraulic pump unit equipped with an air bleeding structure, and a work machine equipped with the hydraulic pump unit.

[0002] Hydraulic equipment, such as hydraulic actuators, is supplied with hydraulic oil discharged from a hydraulic pump unit. The hydraulic pump unit includes a pump body, a pump power source that drives the pump body, and a tank that stores the hydraulic oil supplied to the pump body. A hydraulic pump unit structure has also been proposed in which the pump power source is disposed vertically above the pump body. For example, the hydraulic pump unit (hydraulic drive unit) disclosed in Patent Document 1 corresponds to this structure. Patent Document 1 discloses an air vent structure that vents air that accumulates inside a hydraulic pump. Specifically, an air vent port is formed that communicates with the internal space of the hydraulic pump, and the air vent port is connected to a tank via a communication line. Patent Document 1 also discloses a structure in which a gas-liquid separator that separates air and hydraulic oil is provided on the communication line.

[0003] Patent No. 6446103 Patent No. 7001951

[0004] In the air vent structure for a hydraulic pump unit disclosed in Patent Document 1, air accumulated inside is separated from hydraulic oil by a gas-liquid separator and then released to the outside through an air passage and an air vent valve, but the need for a gas-liquid separator, air passage, and air vent valve makes the structure complicated. In contrast, Patent Document 2 discloses an integrated pump structure including a pump body, a tank, and a head formed between the pump body and the tank, in which air accumulated inside the hydraulic pump is sucked into the pump body through an air vent pipe formed in the head. However, the structure disclosed in Patent Document 2 requires a tank to be located vertically above the pump body, making it difficult to apply to a structure in which a pump power source is located vertically above the pump body.

[0005] An object of the present invention is to provide a hydraulic pump unit that can realize an air bleeding structure with a simple configuration when bleeding air that accumulates inside the pump body in a structure in which the pump power source is located vertically above the pump body, and a work machine equipped with such a hydraulic pump unit.

[0006] A hydraulic pump unit according to one embodiment of the present invention comprises a pump body having an air vent port for discharging air that accumulates in an internal space to the outside, a pump power source that is disposed vertically above the pump body and is connected to the pump body so as to be capable of transmitting power, a tank that is connected to the pump body via a suction pipe, and an external pipe that directly connects the air vent port and the suction pipe.

[0007] A work machine according to another aspect of the present invention includes a hydraulic pump unit including: a pump body having an air vent port for discharging air that accumulates in an internal space to the outside; a pump power source that is arranged vertically above the pump body and is connected to the pump body so as to be able to transmit power; a tank that is connected to the pump body via a suction pipe; and external piping that directly connects the air vent port and the suction pipe, wherein the pump power source is an electric motor that is driven by power supplied from a battery.

[0008] Fig. 1 is a side view showing a hydraulic excavator to which one embodiment of the present invention is applied. Fig. 2 is a view of an upper rotating body of the hydraulic excavator of Fig. 1 as seen vertically from above. Fig. 3 is a perspective view of an electric motor and a pump body of Fig. 2. Fig. 4 is a cross-sectional view showing a part of the pump body of Fig. 3. Fig. 5 is a hydraulic circuit diagram that controls the operation of an actuator driven by hydraulic oil discharged from the pump body.

[0009] 1 is a side view of a hydraulic excavator 1, which is a work machine equipped with a hydraulic pump unit 17 according to one embodiment of the present invention. The hydraulic excavator 1 includes a lower traveling body 10 (lower main body) capable of traveling on the ground G, an upper rotating body 12 (machine body) mounted on the lower traveling body 10 so as to be rotatable about a rotation center axis extending in the vertical direction, and a working device 14 mounted on the upper rotating body 12.

[0010] The lower traveling structure 10 includes a pair of right crawlers 11R and left crawlers 11L disposed on the right and left, respectively. The right crawlers 11R and left crawlers 11L are each operated to cause the lower traveling structure 10 to travel on the ground G.

[0011] The upper rotating body 12 includes a rotating frame 16 and a plurality of elements mounted thereon. The plurality of elements include various devices that constitute a hydraulic pump unit 17, a cab 18 that serves as an operator's room, and a counterweight 19 that constitutes the rear end of the upper rotating body 12.

[0012] The work implement 14 includes a boom 21, an arm 22, and a bucket 24. The boom 21 is supported on the front end of the revolving frame 16 so as to be able to be raised and lowered. The arm 22 is connected to the tip of the boom 21 so as to be able to rotate up and down relative to the boom 21. The bucket 24 is a tip attachment used for excavation work and the like, and is attached to the tip of the arm 22 so as to be able to rotate up and down relative to the arm 22. The cab 18 is located at the front end of the upper revolving body 12, on the left side of the work implement 14. However, the cab 18 may also be located on the right side of the work implement 14.

[0013] The hydraulic excavator 1 further has a boom cylinder 26, an arm cylinder 27, and a bucket cylinder 28. The boom cylinder 26 extends and retracts to rotate the boom 21 in the hoisting direction. The arm cylinder 27 extends and retracts to rotate the arm 22 in the up and down direction. The bucket cylinder 28 extends and retracts to rotate the bucket 24 in the up and down direction relative to the arm 22. These cylinders are hydraulic cylinders.

[0014] [Structure of Hydraulic Pump Unit] Next, we will explain the hydraulic pump unit 17 provided in the hydraulic excavator 1. The hydraulic pump unit 17 is a hydraulic pressure generating device provided in the hydraulic excavator 1 and supplies hydraulic oil to various actuators that are operated by hydraulic pressure. The hydraulic pump unit 17 includes an electric motor 32, a pump main body 34, a battery 36, and a tank 38.

[0015] Figure 2 is a view of the upper rotating body 12 of Figure 1 as seen from vertically above. In Figure 2, the up-down direction on the paper surface corresponds to the front-rear direction of the hydraulic excavator 1, and the left-right direction on the paper surface corresponds to the left-right direction of the hydraulic excavator 1. As shown in Figure 2, the rear part of the upper rotating body 12 is formed in a semicircular shape, and a counterweight 19 is arranged in an arc shape along the periphery of the semicircular shape.

[0016] The electric motor 32, pump body 34, battery 36, and tank 38 that constitute the hydraulic pump unit 17 are disposed in a space surrounded by the counterweight 19 at the rear of the revolving frame 16. In this embodiment, the rear of the upper revolving body 12 is formed in a semicircular shape, so the space on the rear side of the revolving frame 16 is smaller than when the rear is formed in a rectangular shape. The battery 36 is disposed between the electric motor 32 and pump body 34 and the tank 38. In other words, the tank 38 is disposed at a position separated from the pump body 34 by the battery 36.

[0017] The electric motor 32 functions as a pump power source that drives the pump body 34, and is connected to the pump body 34 so as to be capable of transmitting power thereto. The electric motor 32 is driven by electric power supplied from a battery 36.

[0018] The pump body 34 draws hydraulic oil stored in a tank 38 and discharges the hydraulic oil to a delivery pipe 46 (see FIG. 3) connected to various actuators. The pump body 34 of this embodiment is configured as a swash plate type piston pump. Since swash plate type piston pumps are well known technology, detailed description of the pump body 34 will be omitted.

[0019] The battery 36 corresponds to a power supply device that supplies power to the electric motor 32 and the like. The electric motor 32 is a pump power source that drives the pump body 34. The battery 36 has a large capacity to ensure the operating time of the hydraulic excavator 1. In connection with this, the volume of the battery 36 is large, and the battery 36 occupies most of the space formed at the rear of the revolving frame 16. As a result, the space is limited, and in order to make effective use of the limited space, in this embodiment, the electric motor 32 is disposed vertically above the pump body 34 (see FIG. 3 ).

[0020] The tank 38 is provided with an air breather 58 on a wall located vertically above the tank 38. The air breather 58 is configured to be able to open and close in response to changes in the internal pressure of the tank 38. The air breather 58 is a known technique, and therefore a description thereof will be omitted.

[0021] Fig. 3 is a perspective view of the electric motor 32 and the pump body 34. Fig. 4 is a cross-sectional view of a portion of the pump body 34 located vertically above. As shown in Fig. 3, the electric motor 32 and the pump body 34 are arranged one above the other, separated by a fixed base 40. In this embodiment, the electric motor 32 is arranged vertically above the pump body 34. As shown in Fig. 4, the pump body 34 is arranged vertically with its drive shaft 34A parallel to the vertical line. The drive shaft 34A of the pump body 34 is connected to the electric motor 32 so as to be able to transmit power, and the pump body 34 is driven by the power of the electric motor 32.

[0022] As shown in FIG. 4 , the drive shaft 34A is rotatably supported by a bearing 39. A seal member 41 is provided vertically above the bearing 39. The seal member 41 is provided between the casing 34C of the pump body 34 and the drive shaft 34A, sealing the gap between the internal space of the casing 34C and the external space. In relation to this, air generated in the internal space of the pump body 34 may move upward but continue to accumulate within the internal space without being discharged, which may result in an insufficient filling state of the hydraulic oil in the pump body 34 and cause poor lubrication. To discharge air accumulated in the internal space of the pump body 34 to the outside, an air vent port 52 is formed in the casing 34C. The air vent port 52 is connected to an upper position in the internal space of the pump body 34. Specifically, the air vent port 52 is connected to a position facing the seal member 41, which is located at the topmost position in the vertical direction within the pump body 34.

[0023] Returning to FIG. 3, the electric motor 32 is connected to the battery 36 via wiring 42 and an inverter (not shown) or the like.

[0024] The pump body 34 has a suction port 48, a discharge port 50, and an air bleed port 52. The suction port 48 is connected to the suction pipe 44, and the discharge port 50 is connected to the delivery pipe 46. The suction pipe 44 is connected to the tank 38. That is, the pump body 34 is connected to the tank 38 via the suction pipe 44. As a result, the hydraulic oil stored in the tank 38 is supplied to the pump body 34 via the suction pipe 44.

[0025] The delivery pipe 46 is connected to an actuator 54 (see FIG. 5) described later via a control valve 64 and the like described later.

[0026] The air vent port 52 is connected to an external pipe 56. The external pipe 56 is also connected to the suction pipe 44. That is, the external pipe 56 directly connects the air vent port 52 and the suction pipe 44. Here, the direct connection of the external pipe 56 means that the external pipe 56 is connected only to the air vent port 52 and the suction pipe 44, and that the external pipe 56 does not branch off along its path and is not connected to any other location. In this embodiment, no filter or the like for removing foreign matter is provided along the path of the external pipe 56.

[0027] FIG. 5 is a hydraulic circuit diagram that controls the operation of the actuator 54. In the hydraulic circuit of FIG. 5, the hydraulic pump unit 17 that supplies hydraulic oil to the actuator 54 includes the electric motor 32, the pump main body 34, the tank 38, the suction pipe 44, the delivery pipe 46, and the external pipe 56. The actuator 54 in this embodiment corresponds to various actuators such as a swing motor for swinging the upper swing structure 12, the boom cylinder 26, the arm cylinder 27, and the bucket cylinder 28. For convenience, these various actuators are shown as a single actuator 54 in FIG. 5. The following description will be given taking as an example an example in which the actuator 54 is a swing motor for swinging the upper swing structure 12.

[0028] The actuator 54 is supplied with hydraulic oil discharged from the pump main body 34 (hydraulic pump unit 17). A control valve 64, a relief valve 69, and a brake valve 71 are provided between the actuator 54 and the pump main body 34. The pump main body 34 and the control valve 64 are connected by a delivery pipe 46. The control valve 64 and the actuator 54 are connected by a first supply line 65A and a second supply line 65B. A bleed-off line 65C is also provided, connecting the control valve 64 and the tank 38. The bleed-off line 65C is connected to the first supply line 65A and the second supply line 65B depending on the switching position of the control valve 64, and is an oil passage that guides return oil discharged from the actuator 54 to the tank 38. A brake line 65D is also provided as part of the bleed-off line 65C. The brake line 65D is capable of communicating with openings A3, B3, and C3 of the control valve 64.

[0029] The actuator 54 has a first port 54A and a second port 54B, with the first port 54A connected to a first supply line 65A and the second port 54B connected to a second supply line 65B. The actuator 54 is configured to rotate the upper rotating body 12 in one direction when hydraulic oil is supplied from the first port 54A, and to rotate the upper rotating body 12 in the other direction when hydraulic oil is supplied from the second port 54B.

[0030] The control valve 64 is configured as an electromagnetic switching type directional control valve (solenoid valve) and operates to switch the direction of supply of hydraulic oil to the actuator 54 and adjust the flow rate of hydraulic oil in response to a switching signal input to the control valve 64. Specifically, the control valve 64 has a pair of first and second pilot ports 63A and 63B, and operates to switch the control valve 64 between a one-way rotation position, a neutral position, and an other-way rotation position in response to pilot pressure input to these pilot ports 63A and 63B. The control valve 64 also opens with an opening area corresponding to the pilot pressure, thereby changing the flow rate of hydraulic oil.

[0031] Openings A1, A2, and A3 are formed in the one-way pivot position of the control valve 64. In the one-way pivot position, the control valve 64 receives hydraulic oil discharged from the pump body 34 through the opening A1 and supplies the hydraulic oil to the first port 54A via the first supply line 65A, and receives hydraulic oil discharged from the second port 54B through the opening A2, forming an oil passage that guides the hydraulic oil to the tank 38 via the bleed-off line 65C.

[0032] Openings C1, C2, and C3 are formed in the other pivotal position of the control valve 64. In the other pivotal position, the control valve 64 receives hydraulic oil discharged from the pump body 34 through the opening C2 and supplies the hydraulic oil to the second port 54B via the second supply line 65B, and also receives hydraulic oil discharged from the first port 54A through the opening C1 and forms an oil passage that guides the hydraulic oil to the tank 38 via the bleed-off line 65C.

[0033] Openings B1, B2, and B3 are formed in the intermediate position of the control valve 64. In the intermediate position, the control valve 64 forms an oil passage that connects the first supply line 65A and the second supply line 65B to each other via the openings B1 and B2, thereby allowing the hydraulic oil to circulate between the first port 54A and the second port 54B.

[0034] The control valve 64 is switched depending on the operating position of an operating lever 66 operated by an operator. The operating lever 66 is disposed inside the cab 18 and is operated by the operator to rotate the upper rotating body 12. The operating lever 66 is configured to be operable in a first operating area S1 for rotating the upper rotating body 12 in one direction, a second operating area S2 for rotating the upper rotating body 12 in the other direction, and a neutral operating area SS between the first operating area S1 and the second operating area S2.

[0035] When the control lever 66 is operated to the first operation range S1, a pilot pressure corresponding to the operation amount is input to the first pilot port 63A. When the control lever 66 is operated to the second operation range S2, a pilot pressure corresponding to the operation amount is input to the second pilot port 63B.

[0036] The relief valve 69 operates to prevent the hydraulic pressure of the hydraulic oil flowing through the delivery pipe 46 from exceeding a predetermined value. More specifically, the relief valve 69 opens when the hydraulic pressure of the hydraulic oil in the delivery pipe 46 reaches a predetermined value, thereby reducing the hydraulic pressure in the delivery pipe 46.

[0037] The brake valve 71 is a flow control valve disposed on the brake line 65D. The brake valve 71 cuts off the flow of hydraulic oil in the brake line 65D when the actuator 54 rotates the upper rotating body 12. On the other hand, when a braking operation is performed on the upper rotating body 12, the brake valve 71 adjusts the flow rate of hydraulic oil in the brake line 65D to adjust the brake pressure applied to the actuator 54.

[0038] [Function, etc.] As described above, the hydraulic pump unit 17 is formed with the air vent port 52 for discharging air accumulated in the internal space of the pump body 34 to the outside. The air vent port 52 is directly connected to the suction pipe 44 via the external pipe 56. Therefore, when the pump body 34 is driven by the electric motor 32, a flow of hydraulic oil is generated that guides the hydraulic oil flowing through the suction pipe 44 to the pump body 34. At the same time, a flow of hydraulic oil is generated that guides the hydraulic oil from the air vent port 52 to the suction pipe 44 via the external pipe 56. As a result, hydraulic oil containing air accumulated inside the pump body 34 is sucked into the pump body 34 via the external pipe 56 and the suction pipe 44, and then discharged from the discharge port 50 to the suction pipe 44. As a result, air is prevented from accumulating inside the pump body 34. The air discharged to the delivery pipe 46 moves dissolved in the hydraulic oil to the tank 38 via the actuator 54, etc., where it turns into bubbles and is released from the liquid surface at the top of the tank. Furthermore, the air released from the liquid surface is exhausted to the outside of the tank 38 through an air breather 58 provided in the tank 38 .

[0039] In a conventional air vent structure in which the air vent port is connected to the tank, there is a risk that hydraulic oil contaminated with air or foreign matter from the tank may be sucked in through the air vent port, so a filter or the like must be provided to remove foreign matter. Furthermore, the air vent piping connected to the air vent port must be routed above the air vent port so that air can be vented when the pump is stopped. Furthermore, when the tank is located across from the battery from the pump body, as in this embodiment, the piping to the tank becomes long and the shape becomes complex.

[0040] In contrast, in the air vent structure of the present embodiment, the air vent port 52 is simply connected directly to the suction piping 44 via the external piping 56, and therefore, all that is required is to add the external piping 56, thereby simplifying the air vent structure. Furthermore, in the air vent structure of the present embodiment, air or foreign matter that has entered the tank 38 is not sucked in through the air vent port 52, and therefore, there is no need to provide a filter or the like in the external piping 56 to remove foreign matter. Furthermore, because the external piping 56 is connected to the suction piping 44, the length of the external piping 56 can be shortened, and the shape of the external piping 56 is prevented from becoming complicated, even if the tank 38 is located away from the battery 36 with respect to the pump body 34.

[0041] Furthermore, in this embodiment, the electric motor 32 is driven by the battery 36, and therefore the capacity of the battery 36 must be increased to ensure the operating time of the hydraulic excavator 1, which results in the battery 36 becoming larger and limiting the space available for arranging the hydraulic pump unit 17. In contrast, by arranging the electric motor 32 vertically above the pump body 34, the space can be used effectively. Furthermore, the air bleed structure of the hydraulic pump unit 17 is simply configured by directly connecting the air bleed port 52 and the suction pipe 44, and therefore the air bleed structure can be simply configured, allowing the unit to be mounted on the hydraulic excavator 1 even when the space is limited.

[0042] [Variations] In the above embodiment, there is no risk of foreign matter flowing into the pump body 34 from the tank 38 side, so no filter or the like for removing foreign matter is provided in the external piping 56. However, the present invention does not exclude an embodiment in which a filter or the like is provided in the external piping 56, and a filter or the like may be provided on the path of the external piping 56.

[0043] In the above embodiment, the electric motor 32 serving as the pump power source is driven by electric power from the battery 36. However, the pump power source of the present invention is not necessarily limited to an electric motor. For example, the pump power source may be constituted by an engine.

[0044] In the above embodiment, the pump body 34 is a swash plate type piston pump, but the present invention is not necessarily limited to a swash plate type piston pump. For example, the pump body may be a bent axis type piston pump. The present invention can be applied as appropriate as long as the pump body is arranged so that air accumulates inside (at the top of) the pump body.

[0045] In the above embodiment, the drive shaft 34A of the pump body 34 is arranged parallel to the vertical line, but the present invention is not limited to an embodiment in which the drive shaft 34A is arranged parallel to the vertical line. For example, the drive shaft 34A may be arranged at an angle to the vertical line, and an embodiment in which the drive shaft 34A is arranged at an angle to the vertical line is also acceptable as long as the drive shaft 34A is arranged in a direction along the vertical line.

[0046] In the above embodiment, the hydraulic pump unit 17 is applied to the swing motor, boom cylinder 26, arm cylinder 27, and bucket cylinder 28 of the hydraulic excavator 1, but the present invention is not limited to these and may be applied as appropriate to any hydraulic equipment that is driven by the hydraulic pressure of hydraulic oil. In the above embodiment, the hydraulic excavator 1 is applied as one aspect of the work machine, but the present invention is not limited to the hydraulic excavator 1 and may be applied as appropriate to any work machine that is equipped with hydraulic equipment, such as a crane.

[0047] In the above embodiment, the upper rotating body 12 is a small rotating body whose longitudinal width falls within the range of the longitudinal width of the crawlers 11R, 11L, but the upper rotating body 12 is not necessarily limited to the small rotating body and may be applied to various machines. For example, the rear end of the upper rotating body may be located rearward of the rear ends of the crawlers 11R, 11L.

[0048] A hydraulic pump unit according to a first aspect of the present invention comprises a pump body having an air vent port for discharging air accumulated in an internal space to the outside, a pump power source disposed vertically above the pump body and connected to the pump body so as to be capable of transmitting power, a tank connected to the pump body via a suction pipe, and an external pipe directly connecting the air vent port and the suction pipe.

[0049] According to the first aspect, the air vent port provided in the pump body is directly connected to the suction pipe via the external pipe, so that when the pump body is driven, air that has accumulated inside the pump body is sucked from the air vent port through the external pipe and the suction pipe into the pump body and then discharged to the outside from the discharge port of the pump body. Furthermore, the air vent structure can be formed simply by adding an external pipe that connects the air vent port and the suction pipe, thereby simplifying the structure.

[0050] A hydraulic pump unit according to a second aspect is the hydraulic pump unit according to the first aspect, wherein the tank is located at a position separated from the pump body by a battery that supplies power to the pump power source. The configuration according to the second aspect increases the distance between the tank and the pump body. Here, in a conventional configuration in which an air bleed port is connected to the tank, the piping connecting the air bleed port and the tank becomes long. Furthermore, since the piping must be routed to avoid the battery, the shape of the piping becomes complex. In contrast, with this configuration, it is only necessary to connect the air bleed port and the suction piping with external piping, allowing for a simple air bleed structure to be configured regardless of the location of the tank.

[0051] A hydraulic pump unit according to a third aspect is the hydraulic pump unit of the first or second aspect, wherein the pump body is arranged such that its drive shaft is oriented along a vertical line. If air is mixed in or generated inside the pump body, the buoyancy of the air causes the air to move vertically upward and accumulate, which can lead to insufficient hydraulic oil filling inside the pump body and poor lubrication of the pump body. In contrast, the third aspect solves this problem by discharging air accumulated inside the pump body through the air vent port. Furthermore, because the external piping connected to the air vent port is directly connected to the suction piping, the air vent structure can be configured simply.

[0052] A work machine according to a fourth aspect of the present invention includes a hydraulic pump unit comprising: a pump body having an air vent port for discharging air that accumulates in an internal space to the outside; a pump power source that is arranged vertically above the pump body and is connected to the pump body so as to be able to transmit power; a tank that is connected to the pump body via a suction pipe; and external piping that directly connects the air vent port and the suction pipe, wherein the pump power source is an electric motor that is driven by power supplied from a battery.

[0053] If the pump power source is an electric motor driven by power supplied from a battery, a large-capacity battery must be installed to ensure the operating time of the work machine. As a result, the battery becomes larger, limiting the space available for installing the hydraulic pump unit. In contrast, in the hydraulic pump unit of the fourth aspect, the pump power source is disposed vertically above the pump body, thereby making effective use of the space. Furthermore, because the air bleed structure of the hydraulic pump unit is simply configured, a hydraulic pump unit equipped with the air bleed structure can be installed on a work machine even if the space is limited.

[0054] A work machine according to a fifth aspect is the work machine according to the fourth aspect, wherein the tank further includes an air breather.

[0055] According to the fifth aspect, air released from the liquid surface of the hydraulic oil stored in the tank can be discharged to the outside of the tank via the air breather.

Claims

1. A hydraulic pump unit comprising: a pump body having an air vent port for discharging air accumulated in an internal space to the outside; a pump power source disposed vertically above said pump body and connected to said pump body so as to be capable of transmitting power; a tank connected to said pump body via a suction piping; and an external piping that directly connects between said air vent port and said suction piping.

2. The hydraulic pump unit according to claim 1, wherein the tank is disposed at a position separated from the pump body by a battery that supplies power to the pump power source.

3. A hydraulic pump unit as set forth in claim 1 or 2, wherein the pump body is arranged such that the drive shaft of the pump body is oriented along a vertical line.

4. A working machine including a hydraulic pump unit comprising: a pump body having an air vent port for discharging air accumulated in an internal space to the outside; a pump power source arranged vertically above said pump body and connected to said pump body so as to be capable of transmitting power; a tank connected to said pump body via a suction piping; and an external piping that directly connects between said air vent port and said suction piping, wherein said pump power source is an electric motor driven by power supplied from a battery.

5. The work machine of claim 4, wherein the tank further comprises an air breather.

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