Liquid jet device

Abstract

To provide a liquid jet device capable of improving convenience of a user.SOLUTION: A liquid jet device 1 includes: a nozzle 5 which is openable / closable and from which a liquid is jetted when it is opened; a pump 4 for forcibly sending the liquid pumped up from a liquid source 2 to the nozzle 5; a flow path (discharge path 45 and force-feeding path 12) in which the liquid forcibly fed by the pump 4 circulates; a return path 13 for returning the liquid circulating in the flow path to the upstream side (liquid source 2) of the pump 4; a first valve 6 for closing the return path 13, and opening the return path 13 when the liquid pressure of the flow path is higher than a first liquid pressure; a discharge path 15 for discharging the liquid circulating in the flow path to the liquid source 2; and a second valve 7 for opening the discharge path 15, and closing the discharge path 15 when the liquid pressure of the flow path is higher than a second liquid pressure lower than the first liquid pressure.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a liquid ejection apparatus. [Background technology]

[0002] The liquid ejection device described in Patent Document 1 includes a pump, a nozzle, and a flow path (hereinafter referred to as a "liquid discharge path"). The pump pumps up liquid from a liquid source and pumps it to the nozzle. The liquid pumped by the pump flows through the flow path. A user of the liquid ejection device manually opens and closes the nozzle. When the nozzle is open, liquid is ejected from the nozzle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-001002 A Summary of the Invention [Problem to be solved by the invention]

[0004] A pump pumps liquid by causing a plunger to reciprocate in response to rotational motion from a driving source such as an internal combustion engine. When the rotation speed of the driving source is high, the force with which the driving source drives the pump is large, so the pump can pump the liquid by overcoming the pressure of the liquid in the flow path (liquid pressure in the flow path). On the other hand, since the rotation speed of the drive source is low at the time of startup, there is a concern that the pump will not be able to overcome the liquid pressure in the flow path, and operation of the pump will be prevented. Therefore, the user manually opens the nozzle when starting the drive source. This reduces the liquid pressure in the flow path, allowing the pump to operate smoothly. However, this reduces the user's convenience.

[0005] An object of the present disclosure is to provide a liquid ejecting device that can improve convenience for users. [Means for solving the problem]

[0006] The liquid injection device of the present disclosure is characterized in that it comprises a nozzle that can be opened and closed and from which liquid is injected when the nozzle is open, a pump that pressure-feeds the liquid pumped from a liquid source to the nozzle, a flow path through which the liquid pressure-feed by the pump flows, a return path for returning the liquid flowing through the flow path to the upstream side of the pump, a first valve that closes the return path and opens when the liquid pressure in the flow path is higher than a first liquid pressure, a discharge path for discharging the liquid flowing through the flow path to the liquid source, and a second valve that opens the discharge path and closes when the liquid pressure in the flow path is higher than a second liquid pressure that is lower than the first liquid pressure.

[0007] In the present disclosure, a pump draws liquid from a liquid source and pumps it through a nozzle that can be opened and closed, such that liquid is ejected through the nozzle when the nozzle is open. The liquid pumped by the pump flows through a flow path. When the nozzle is closed, the liquid is not ejected from the nozzle, and the liquid pressure in the flow path may increase.

[0008] The first valve closes the return path. However, when the liquid pressure in the flow path is higher than the first liquid pressure, the first valve opens the return path, and at least a portion of the liquid flowing through the flow path is returned to the upstream side of the pump through the return path. Therefore, there is no risk of the liquid pressure in the flow path increasing excessively. This makes it possible to prevent the inconvenience of the pump being overloaded. The liquid returned to the upstream side of the pump can be pumped again to the nozzle, so there is no waste.

[0009] When the pump is not operating, the liquid pressure in the flow path is equal to or lower than the second liquid pressure. When the pump starts operating, the liquid starts to be pumped to the nozzle. In general, immediately after the pump starts operating, the force with which the pump tries to pump the liquid (pump pumping force) is small. However, because the second valve opens the discharge path, at least a portion of the liquid flowing through the flow path is discharged to the liquid source through the discharge path. Therefore, there is no risk of the liquid pressure in the flow path increasing excessively compared to the small pumping force of the pump. Therefore, the pump operates smoothly. As a result, the user does not need to manually open the nozzle to reduce the liquid pressure in the flow path when the pump starts to operate, which improves user convenience. Also, the liquid discharged through the discharge path is collected in the liquid source, so there is no waste.

[0010] When the pumping force of the pump increases and the liquid pressure in the flow path becomes higher than the second liquid pressure, the second valve closes the discharge path. Since the second liquid pressure is lower than the first liquid pressure, the liquid pressure in the flow path can be maintained higher than the second liquid pressure but lower than the first liquid pressure (a liquid pressure suitable for ejecting liquid from the nozzle).

[0011] The liquid injection device disclosed herein is characterized by comprising a nozzle that can be opened and closed and from which liquid is injected when the nozzle is open, a pump that pressurizes the liquid pumped from a liquid source to the nozzle, a drive source that drives the pump by imparting rotational motion to the pump, a flow path through which the liquid pressurized by the pump flows, a return path for returning the liquid flowing through the flow path to the upstream side of the pump, a first valve that closes the return path when the liquid pressure in the flow path is low and opens when the liquid pressure is high, a discharge path for discharging the liquid flowing through the flow path to the liquid source, and a second valve that opens the discharge path when the rotation speed of the drive source is low and closes it when the rotation speed is high.

[0012] In the present disclosure, a pump pumps up liquid from a liquid source and pumps it to a nozzle. The pump pumps the liquid by being given a rotational motion from a drive source. The nozzle can be opened and closed, and when the nozzle is open, the liquid is sprayed from the nozzle. The liquid pumped by the pump flows through a flow path. When the nozzle is closed, the liquid is not ejected from the nozzle, and the liquid pressure in the flow path may increase.

[0013] When the liquid pressure in the flow path is low, the first valve closes the return path. However, when the liquid pressure in the flow path is high, the first valve opens the return path, so that at least a portion of the liquid flowing through the flow path is returned to the upstream side of the pump through the return path. Therefore, there is no risk of the liquid pressure in the flow path increasing excessively. This makes it possible to prevent the inconvenience of the pump being overloaded. The liquid returned to the upstream side of the pump can be pumped again to the nozzle, so there is no waste.

[0014] When the rotation speed of the drive source is low, the pumping force of the pump is small. However, because the second valve opens the drain passage, at least a portion of the liquid flowing through the flow passage is discharged to the liquid source through the drain passage. Therefore, there is no risk of the liquid pressure in the flow passage increasing excessively compared to the small pumping force of the pump. Therefore, the pump operates smoothly. As a result, when the rotation speed of the drive source is low, the user does not need to manually open the nozzle in order to reduce the liquid pressure in the flow path, which improves user convenience. In addition, the liquid discharged through the discharge path is collected in the liquid source, so there is no waste. When the rotation speed of the drive source is high, the second valve closes the discharge passage, so that the liquid pressure in the passage can be increased to a level suitable for ejecting the liquid from the nozzle.

[0015] The liquid injection device according to the present disclosure is characterized in that the second valve includes a valve seat and a valve body, and is configured to open the discharge passage when the valve body is away from the valve seat due to its own weight or the biasing force of a biasing member that biases the valve body in a direction away from the valve seat, and to close the discharge passage when the valve body is seated on the valve seat due to the hydraulic pressure in the flow path, and to complete seating of the valve body on the valve seat after the liquid has flowed from the flow path into the discharge path.

[0016] In the present disclosure, the second valve includes a valve seat and a valve body. The second valve opens the discharge passage when the valve disc is separated from the valve seat, and closes the discharge passage when the valve disc is seated on the valve disc. The valve element leaves the valve seat due to its own weight or the biasing force of a biasing member that biases the valve element in a direction away from the valve seat, and the valve element seats on the valve element when the hydraulic pressure in the flow path overcomes the valve element's own weight and / or the biasing force of the biasing member. In other words, the second valve naturally opens and closes depending on the level of the fluid pressure in the flow path. The structure of such a second valve is simple.

[0017] The second valve is configured so that the valve disc seats on the valve seat after the liquid flows from the flow path into the discharge path, so that even if gas is accumulated in the flow path before the pump starts to operate, there is no risk that the second valve will close the discharge path just by discharging the gas from the flow path through the discharge path. Effect of the Invention

[0018] According to the liquid ejecting device of the present disclosure, it is possible to improve convenience for the user. [Brief description of the drawings]

[0019] [Figure 1] 1 is a block diagram showing a configuration of a liquid ejecting apparatus according to an embodiment; [Diagram 2] 2 is a diagram showing the appearance of a pump and cross sections of a first valve and a second valve. FIG. [Diagram 3] FIG. 4 is a cross-sectional view of the second valve. [Figure 4] FIG. 4 is a diagram for explaining the flow of liquid when the nozzle is closed during normal operation. [Diagram 5] FIG. 13 is a diagram for explaining the flow of liquid at the time of start-up. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, embodiments of the present disclosure will be described.

[0021] FIG. 1 is a block diagram showing a configuration of a liquid ejecting apparatus according to an embodiment. In the figure, reference numeral 1 denotes a liquid ejection device, which is used together with a liquid source 2 . The liquid source 2 is a tank that stores a liquid such as tap water, a chemical solution, etc. The liquid pressure of the liquid source 2 is equal to atmospheric pressure. Note that the liquid source 2 is not limited to a tank, and may be a river, a reservoir, etc.

[0022] The liquid ejection device 1 includes a drive source 3, a pump 4, and a nozzle 5. The drive source 3 includes an engine 31 and a starter 32. The engine 31 drives the pump 4 by providing rotational motion of an output shaft of the engine 31 to the pump 4. The engine 31 is, for example, a gasoline engine. The starter 32 assists in starting the engine 31 by providing rotational motion to the stopped engine 31. The starter 32 is, for example, a motor. The rotation speed of the engine 31 at the time of starting is a low rotation speed R1 (e.g., 500 rpm) corresponding to the rotation speed of the starter 32. If the engine 31 is successfully started, the rotation speed increases. The engine 31 is normally operated at a rotation speed R2 (e.g., 3000 rpm) higher than the rotation speed R1.

[0023] The pump 4 includes an intake port 41, an intake passage 42, a liquid chamber 43, a plunger 44, a discharge passage 45, a discharge port 46, and a discharge port 47. The intake port 41 is connected to the liquid source 2 via the liquid supply passage 11. The intake passage 42 extends from the intake port 41 to the liquid chamber 43. The plunger 44 is disposed in the liquid chamber 43 and is linked to the output shaft of the engine 31. The plunger 44 reciprocates in response to the rotational motion provided by the drive source 3, thereby generating positive and negative pressures alternately in the liquid chamber 43. The discharge passage 45 extends from the liquid chamber 43 to the discharge port 46 and the discharge port 47, respectively.

[0024] A check valve 431 is provided between the suction passage 42 and the liquid chamber 43. Normally, the check valve 431 is closed, and opens when negative pressure occurs in the liquid chamber 43. When the check valve 431 is open, liquid can flow from the suction passage 42 toward the liquid chamber 43. When the check valve 431 is closed, liquid does not flow between the suction passage 42 and the liquid chamber 43. A check valve 432 is provided between the liquid chamber 43 and the discharge passage 45. Normally, the check valve 432 is closed, and opens when a positive pressure is generated in the liquid chamber 43. When the check valve 432 is open, liquid can flow from the liquid chamber 43 toward the discharge passage 45. When the check valve 432 is closed, liquid does not flow between the liquid chamber 43 and the discharge passage 45.

[0025] The nozzle 5 includes an inlet 51 and an ejection port 52. The inlet 51 is connected to the ejection port 46 of the pump 4 via the pressure feed path 12. The ejection port 52 opens and closes in response to manual operation of a trigger (not shown) by a user. The discharge path 45 and the pressure-feed path 12 function as a path (hereinafter referred to as the pressure-feed path) through which the liquid pumped by the pump 4 flows. The appropriate liquid pressure of the pressure-feed path (the liquid pressure suitable for ejecting the liquid from the nozzle 5) is equal to or lower than the first liquid pressure P1 and higher than the second liquid pressure P2. Here, the second liquid pressure P2 is lower than the first liquid pressure P1 and higher than the atmospheric pressure.

[0026] The middle of the pumping path 12 and the liquid source 2 are connected to each other via a return path 13. The liquid flowing through the pumping path 12 can flow into the return path 13. The discharge port 47 of the pump 4 is connected midway through the return path 13 via the relay path 14 and the discharge path 15. The relay path 14 is directly connected to the discharge port 47 and one end of the discharge path 15. The other end of the discharge path 15 is directly connected to the return path 13, so that the discharge path 15 is indirectly connected to the liquid source 2.

[0027] The liquid ejection device 1 further comprises a first valve 6 and a second valve 7 . FIG. 2 is a diagram showing the appearance of the pump 4, and a cross section of the first valve 6. As shown in Figures 1 and 2, the first valve 6 is provided at the branch point of the pressure-feeding path 12 and the return path 13. The first valve 6 closes the return path 13 when the hydraulic pressure in the pressure-feeding path 12 is low, and opens the return path 13 when the hydraulic pressure in the pressure-feeding path 12 is high. For example, an unloader valve is used as the first valve 6. The first valve 6 shown in Figure 2 closes the return path 13.

[0028] The first valve 6 includes a first flow path 61, a second flow path 62, and a valve body 63. The first flow path 61 constitutes a part of the pressure-feed path 12. The second flow path 62 branches off from the middle of the first flow path 61, and constitutes a part of the return path 13. The valve body 63 is biased to close the second flow path 62, and opens the second flow path 62 when the fluid pressure in the first flow path 61 is higher than the first fluid pressure P1.

[0029] 1 and 2, the second valve 7 is provided at a connection portion between the relay passage 14 and the discharge passage 15. The second valve 7 opens the discharge passage 15 when the rotation speed of the engine 31 is low, and closes the discharge passage 15 when the rotation speed of the engine 31 is high. 2, the second valve 7 includes a first flow path 71, a second flow path 72, and a valve body 73. The first flow path 71 constitutes a part of the relay path 14 and extends vertically. The second flow path 72 constitutes a part of the discharge path 15 and has one end connected to the upper end of the first flow path 71.

[0030] Figure 3 is a cross-sectional view of the second valve 7. Figure 3A shows the second valve 7 in a state where the discharge passage 15 is open, and Figure 3B shows the second valve 7 in a state where the discharge passage 15 is closed. The first flow path 71 is a space surrounded by the inner circumferential surface of the vertical cylinder 701. The vertical cylinder 701 has a cylindrical shape. The axial direction of the vertical cylinder 701 faces up and down.

[0031] The second flow path 72 is a space surrounded by the inner surface of the bottomed cylinder 702 and the inner peripheral surface of the horizontal cylinder 703. The bottomed cylinder 702 has a cylindrical shape with a bottom. The lower end of the bottomed cylinder 702 is liquid-tightly connected to the upper end of the vertical cylinder 701 by inserting the upper end of the vertical cylinder 701 into the bottomed cylinder 702 with the opening of the bottomed cylinder 702 facing downward. A cylindrical sheet member 704 is coaxially and liquid-tightly fitted into the bottomed cylinder 702 midway in the axial direction of the bottomed cylinder 702. The lower end surface of the sheet member 704 contacts the upper end surface of the vertical cylinder 701. The inner peripheral edge of the lower opening of the sheet member 704 is chamfered.

[0032] A through hole 705 is provided in the peripheral wall of the bottomed cylinder 702. The through hole 705 is located between the inner bottom surface of the bottomed cylinder 702 and the upper end surface of the sheet member 704. One end of the horizontal cylinder 703 in the axial direction is inserted into the through hole 705, and thereby is liquid-tightly connected to the upper end of the bottomed cylinder 702.

[0033] The second valve 7 includes a valve seat 74 and a biasing member 75 . The valve seat 74 is provided at the boundary between the first flow path 71 and the second flow path 72. Specifically, the inner peripheral edge (the chamfered portion) of the lower opening of the seat member 704 functions as the valve seat 74.

[0034] The valve element 73 is spherical. The outer diameter of the valve element 73 is larger than the inner diameter of the seat member 704. The valve element 73 is disposed in the first flow passage 71 so as to be movable in the vertical direction. The valve element 73 rises to seat on the valve seat 74 and descends to leave the valve seat 74. When the valve element 73 sits on the valve seat 74, the second flow passage 72 is closed. When the valve element 73 leaves the valve seat 74, the second flow passage 72 is opened. A step 706 that receives the valve element 73 when it is not seated is provided on the inner peripheral surface of the vertical cylinder 701.

[0035] The biasing member 75 is placed on the upper part of the valve body 73 in the second flow passage 72, and is, for example, a coil spring. The level of the fluid pressure in the first flow path 71 is affected by the level of the fluid pressure in the discharge path 45. When the fluid pressure in the discharge path 45 is equal to or lower than the second fluid pressure P2, the fluid pressure in the first flow path 71 is low, and therefore the valve body 73 is separated from the valve seat 74 by its own weight and the weight of the biasing member 75 (see FIG. 3A).

[0036] When the liquid pressure in the first flow path 71 is very low and the step 706 is supporting the valve body 73, the liquid flows through a gap (not shown) formed between the valve body 73 supported by the step 706 and the vertical cylinder body 701. As the liquid pressure in the first flow path 71 increases, the valve disc 73 separates from the step portion 706 and starts to rise. However, before the raised valve disc 73 seats on the valve seat 74, the biasing member 75 is sandwiched between the valve disc 73 and the inner bottom surface of the bottomed cylindrical body 702 and compressed. At this time, the biasing member 75 biases the valve disc 73 in a direction in which it leaves the valve seat 74, so that the valve disc 73 does not seat on the valve seat 74.

[0037] When the fluid pressure in the discharge passage 45 is higher than the second fluid pressure P2, the fluid pressure in the first flow passage 71 is high, and thus overcomes both the weight of the valve body 73 and the biasing force of the biasing member 75, pushing the valve body 73 up and seating it on the valve seat 74 (see FIG. 3B).

[0038] According to the liquid ejection device 1 as described above, the pump 4 pumps up the liquid from the liquid source 2 and pumps it to the nozzle 5. More specifically, when the driving source 3 drives the pump 4 to generate negative pressure in the liquid chamber 43, the liquid from the liquid source 2 is sucked into the liquid chamber 43 through the liquid supply path 11 and the suction path 42 in this order. When the driving source 3 drives the pump 4 to generate positive pressure in the liquid chamber 43, the liquid from the liquid chamber 43 is ejected (pumped) to the nozzle 5 through the ejection path 45 and the pumping path 12 in this order.

[0039] 1 is also a diagram for explaining the flow of liquid when the nozzle 5 is open during normal operation. The direction of liquid flow is indicated by the dashed double-dashed line. The liquid pumped to the nozzle 5 is received in the internal space of the nozzle 5 through the receiving port 51 . When the nozzle 52 is open, the liquid is sprayed from the nozzle 5 through the nozzle 52. The form of the liquid sprayed from the nozzle 52 is not limited, and may be, for example, a straight form, a shower form, or a mist form. When the outlet 52 is closed, no liquid is ejected from the nozzle 5 .

[0040] 4 is a diagram for explaining the flow of liquid when the nozzle 5 is closed during normal operation. The direction of the liquid flow is indicated by a two-dot chain line. It is necessary to switch between operation and stop of the engine 31 in order to switch between operation and stop of the pump 4. Since it is inefficient to switch between operation and stop of the engine 31 in response to the opening and closing of the nozzle 5 while the liquid injection device 1 is in use, the engine 31 and the pump 4 continue to operate regardless of the opening and closing of the nozzle 5. Therefore, when the nozzle 5 is closed after ejection of liquid from the nozzle 5, the liquid pressure in the nozzle 5 and the pressure-feeding passage increases.

[0041] The liquid pressure in the liquid chamber 43 is affected by the liquid pressure in the pressure-feeding passage when the check valve 432 of the pump 4 is opened. Therefore, if the liquid pressure in the pressure-feeding passage rises excessively, the liquid pressure in the liquid chamber 43 becomes excessively high. This inhibits the reciprocating motion of the plunger 44, and overloads the pump 4. However, when the fluid pressure in the first flow path 61, which is a part of the pumping flow path, is higher than the first fluid pressure P1, the first valve 6 opens the return path 13, so that at least a part of the liquid flowing through the pumping flow path is returned to the upstream side of the pump 4 through the return path 13. Therefore, there is no risk of the fluid pressure in the pumping flow path excessively increasing beyond the first fluid pressure P1. This makes it possible to prevent the pump 4 from being overloaded. In this embodiment, the liquid is returned to the liquid source 2 via the return passage 13, so that no liquid is wasted.

[0042] For example, when the nozzle 5 is reopened and the liquid pressure in the first flow path 61 drops, and falls to or below the first liquid pressure P1, the first valve 6 closes the return path 13 (see FIG. 1). Therefore, there is no risk of the pressure of the liquid sprayed from the nozzle 5 being unnecessarily reduced due to the liquid being returned to the liquid source 2. Therefore, the liquid can be effectively sprayed or washed with the liquid.

[0043] Meanwhile, the rotation speed of the engine 31 during normal operation is high (rotation speed R2). Therefore, the force with which the engine 31 drives the pump 4 is large, so that the plunger 44 smoothly reciprocates, overcoming the liquid pressure in the liquid chamber 43 (and therefore the liquid pressure in the pumping flow path). As a result, the pump 4 has a large pumping force, so that the pump 4 can pump the liquid by overcoming the liquid pressure in the pumping flow path.

[0044] On the other hand, the rotation speed of the engine 31 at the time of starting is low (rotation speed R1). Therefore, the force with which the engine 31 drives the pump 4 is small, and there is a concern that the plunger 44 will not be able to overcome the liquid pressure in the liquid chamber 43 and will stop (or remain stationary). Since the plunger 44 and the output shaft of the engine 31 are linked to each other, if the plunger 44 does not reciprocate, the output shaft of the engine 31 will not rotate, and starting of the engine 31 will end in failure. Therefore, the pump 4 cannot be operated.

[0045] If the return path 13 is opened, the hydraulic pressure in the pumping path can be lowered. However, since the pumping force of the pump 4 is small when the engine 31 is started, it is not expected that the hydraulic pressure in the first path 61 will exceed the first hydraulic pressure P1 and the return path 13 will be opened. If the user opens the nozzle 5, the hydraulic pressure in the pressure-feeding passage can be reduced. However, if the user is forced to open the nozzle 5 when starting the engine 31, convenience for the user is impaired.

[0046] Fig. 5 is a diagram for explaining the flow of liquid at the time of start-up. In Fig. 5 (and Fig. 3), the direction of the liquid flow is indicated by a two-dot chain line. The second valve 7 opens the discharge passage 15 when the engine 31 is at a low speed and the fluid pressure in the discharge passage 45 is equal to or lower than the second fluid pressure P2 (see FIG. 3A). The discharge passage 45 is connected to the liquid source 2 via the relay passage 14, the discharge passage 15, and the return passage 13, so that the fluid pressure in the pumping passage is equal to atmospheric pressure when the engine 31 is started. Therefore, even if the force with which the engine 31 drives the pump 4 is small, the plunger 44 overcomes the fluid pressure in the fluid chamber 43 and smoothly reciprocates. Therefore, the engine 31 can be started successfully. Also, even if the pumping force of the pump 4 is small, the pump 4 can overcome the fluid pressure in the pumping passage and pump the liquid.

[0047] While the discharge passage 15 is open, at least a part of the liquid flowing through the pumping passage is discharged to the liquid source 2 through the relay passage 14, the discharge passage 15, and the return passage 13 in this order. Therefore, there is no risk of the liquid pressure in the pumping passage increasing excessively compared to the small pumping force of the pump 4. Therefore, the pump 4 operates smoothly. As a result of the above, when the engine 31 is started (when the engine 31 rotation speed is low and the fluid pressure in the discharge passage 45 is equal to or lower than the second fluid pressure P2), the user does not need to manually open the nozzle 5 in order to lower the fluid pressure in the pressure-feed passage 12. This improves user convenience. In addition, the liquid discharged through the relay passage 14, the discharge passage 15, and the return passage 13 is collected in the liquid source 2, so there is no waste.

[0048] When the engine 31 is successfully started, the engine 31 speed increases, and the pumping force of the pump 4 increases, causing the hydraulic pressure in the first flow path 61 to become higher than the second hydraulic pressure P2, the second valve 7 opens the drain path 15 (see Figure 3B). As a result of the above, the fluid pressure in the pressure-feeding passage can be maintained at an appropriate level.

[0049] When gas has accumulated in the liquid chamber 43 or the discharge passage 45 etc. before the start of the engine 31, the relay passage 14, the discharge passage 15, and the return passage 13 also function as gas flow paths for so-called air bleeding. Specifically, the gas accumulated in the liquid chamber 43 or the discharge passage 45 etc. is pushed out of the liquid chamber 43 or the discharge passage 45 etc. by the liquid, and is discharged to the liquid source 2 through the relay passage 14, the discharge passage 15, and the return passage 13 in this order. The spring constant of the biasing member 75 and the orifice diameter of the valve seat 74 are designed so that the valve body 73 is seated on the valve seat 74 after the liquid flows from the pressure-feeding flow path into the discharge path 15. Therefore, the second valve 7 does not close the discharge path 15 before the liquid flows from the pressure-feeding flow path into the discharge path 15. In other words, the second valve 7 is different from a valve that is dedicated to bleeding air.

[0050] The driving source 3 is not limited to a configuration including the engine 31 and the starter 32, and may be, for example, a motor that provides rotational motion to the pump 4. However, since the engine 31 increases in rotation speed more slowly at start-up than a motor, the liquid injection device 1 of the present disclosure is particularly suitable for a case in which the driving source 3 includes the engine 31. The engine 31 is not limited to a gasoline engine, and may be a hydrogen engine. The engine 31 is not limited to an internal combustion engine, and may be an external combustion engine. The pump 4 is not limited to a configuration that can be imparted with rotational motion.

[0051] In this embodiment, one end of the return path 13 is connected to the middle of the pumping path 12, and the other end of the return path 13 is connected to the liquid source 2. However, the location to which the return path 13 is connected is not limited to this. For example, the other end of the return path 13 may be connected to the middle of the liquid supply path 11. When the return path 13 is not connected to the liquid source 2, it is desirable to connect the discharge path 15 directly or indirectly to the liquid source 2 rather than to the return path 13. The second valve 7 in this embodiment naturally closes / opens the discharge passage 15 depending on whether the hydraulic pressure in the pressure-feed passage is high / low, which corresponds to whether the rotation speed of the engine 31 is high / low. However, for example, an electromagnetic valve may be used as the second valve 7. In this case, the rotation speed of the engine 31 is detected, and the opening / closing of the second valve 7 is controlled in accordance with the detection result.

[0052] The embodiments disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is intended to include not only the above-mentioned meaning, but also the meaning equivalent to the claims and all modifications within the scope of the claims. Independent claims and dependent claims described in the claims may be combined with each other in any and all combinations, regardless of the reference format. Furthermore, the claims may be written in a format in which a claim references two or more other claims (multiple claim format), but this is not limited to this format. A multiple claim that references at least one other multiple claim (multiple multiple claim format) may also be written. [Explanation of symbols]

[0053] 1 Liquid injection device 12 Pressure passage (flow path) 13 Return Route 15 Exhaust channel 2 Fluid source (upstream of the pump) 3. Power Source 4. Pump 45 Discharge passage (flow path) 5 Nozzles 6 First valve 7 Second valve 73 Valve body 74 Valve seat 75 Pressing member

Claims

1. a nozzle that can be opened and closed and that ejects liquid when opened; a pump for pumping the liquid from a liquid source to the nozzle; a flow path through which the liquid pumped by the pump flows; a return path for returning the liquid flowing through the flow path to the upstream side of the pump; a first valve that closes the return passage and opens when the hydraulic pressure in the passage is higher than a first hydraulic pressure; a discharge passage for discharging the liquid flowing through the flow path to the liquid source; a second valve that opens the drain passage and closes when the hydraulic pressure in the passage is greater than a second hydraulic pressure that is lower than the first hydraulic pressure; A liquid ejection apparatus comprising:

2. a nozzle that can be opened and closed and that ejects liquid when opened; a pump for pumping the liquid from a liquid source to the nozzle; a drive source that drives the pump by imparting a rotational motion to the pump; a flow path through which the liquid pumped by the pump flows; a return path for returning the liquid flowing through the flow path to the upstream side of the pump; a first valve that closes the return passage when the hydraulic pressure in the passage is low and opens the return passage when the hydraulic pressure in the passage is high; a discharge passage for discharging the liquid flowing through the flow path to the liquid source; a second valve that opens the discharge passage when the rotation speed of the drive source is low and closes the discharge passage when the rotation speed is high; A liquid ejection apparatus comprising:

3. The second valve is A valve seat and a valve body are provided, opening the discharge passage when the valve body is separated from the valve seat due to its own weight or due to a biasing force of a biasing member that biases the valve body in a direction in which the valve body is separated from the valve seat; the valve body closes the discharge passage when the valve body is seated on the valve seat by a hydraulic pressure in the passage; 3. The liquid ejection device according to claim 1, wherein the valve body is configured to completely seat on the valve seat after the liquid has flowed from the flow path into the discharge path.

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