Fluid injection device and fluid injection system

Abstract

Fluid injection device (10), comprising: a valve body (20) with a cylindrical shape; a valve element (30) which is movably housed in the valve body (20) and has a valve surface section (35a) which, during operation, rests against or is separated from the valve seat section (23a) which is formed in an interior of the valve body (20), an annular fluid passage (W11, W21, W22) formed between an inner peripheral surface of the valve body (20) and an outer peripheral surface of the valve element (30), through which gas flows, wherein the valve element (30) includes the following; - an internal passage (31) formed in the interior of the valve element (30) and extending in an axial direction of the valve element (30), through which fluid flows; and - a communication port (33) to connect the inner passage to the annular fluid passage (W11, W21, W22), wherein the communication port (33) is open on the outer peripheral surface of the valve element (30) at a position which is located on an upstream side of the valve surface section (35a) in a flow direction of the gas flowing along the axial direction of the valve element (30) through the annular fluid passage (W11, W21, W22), wherein the fluid is supplied to the annular fluid passage (W11, W21, W22) from the inner passage (31) through the communication port (33), and the fluid supplied to the annular fluid passage (W11, W21, W22) from the communication port (33) is injected together with the gas flowing through the annular fluid passage (W11, W21, W22) when the valve element (30) is in a valve opening position, wherein the injection of the liquid and gas is terminated when the valve surface section (35a) abuts the valve seat section (23a) to close the annular fluid passage (W11, W21, W22), where the cross-sectional area of ​​a connecting passage section (C10) is smaller than the cross-sectional area of ​​a passage section (C20) on the upstream side, wherein the connecting passage section (C10) is a section of the annular fluid passage (W11) to which the communication port (33) is connected with the annular fluid passage (W11), and wherein the passage section (C20) on the upstream side is another section of the annular fluid passage (W11) which is located on an upstream side of the connecting passage section (C10).

Description

[0001] The present disclosure relates to a fluid injection device and a fluid injection system for a motor vehicle.

[0002] An SCR (Selective Catalytic Reduction) system is known in the art as an exhaust gas purification system for purifying nitrogen oxides (NOx) contained in the exhaust gas emitted from an internal combustion engine of a motor vehicle. The SCR system includes a liquid injection valve (a urea addition valve) provided in an exhaust pipe of the motor vehicle and a selective reduction catalyst provided on a downstream side of the urea addition valve in the exhaust pipe. In the SCR system, a liquid (for example, an aqueous urea solution) injected into the exhaust pipe is hydrolyzed into ammonia by heat from the exhaust gas. When the exhaust gas containing ammonia flows into the selective reduction catalyst, the nitrogen oxides (NOx) are reduced to nitrogen and water using ammonia as a reducing agent.A fluid injection system in which the aqueous urea solution is added to the exhaust gas is disclosed, for example, in Japanese Patent Publication JP 2015-200321 A.

[0003] The fluid injection system of the above prior art includes an injector provided in an exhaust pipe of a motor vehicle, a pump for supplying an aqueous urea solution from a tank to the injector, and a compressed air supply unit for supplying air to the injector. In the fluid injection system, the aqueous urea solution and the air are mixed together and injected from the injector, thereby atomizing the aqueous urea solution.

[0004] The fluid injection system may become complicated if the injection device is provided which has the above structure for atomizing the aqueous urea solution with the air, which is similar to the fluid injection system of the above prior art.

[0005] The problem that the fluid injection system may become complicated is a common problem not only for the fluid injection system for atomizing the aqueous urea solution with the air, but also for such a fluid injection system or fluid injection device for atomizing an optional fluid with an optional gas.

[0006] In DE 10 2018 122 192 A1, a reducing agent injector unit has an injector body, an injection hole for injecting reducing agent into an exhaust pipe of an engine, a valve for opening or closing the injection hole, and a fluid supply passage for supplying the reducing agent to the injection hole. An inner peripheral surface of the injector body includes a passage wall surface including a valve seat surface onto which the valve element is seated during operation, and an upstream surface portion extending in an upstream direction from the valve seat surface.A recessed portion is formed in the upstream-side surface portion such that a part of the upstream-side surface portion is extended outward in a radial direction of the injector body from a valve seat extension line corresponding to a virtual line extending outward from the valve seat surface.

[0007] The present disclosure is made in view of the above problem. It is an object of the present disclosure to provide a fluid injection device and a fluid injection system having a structure for atomizing and injecting fluid, and making it possible to simplify the structure.

[0008] According to one of the features of the present disclosure, a fluid injection device comprises: a valve body (20) having a cylindrical shape; a valve element (30) movably housed in the valve body and having a valve surface portion (35a) operatively abutting or separated from the valve seat portion (23a) formed in an interior of the valve body, an annular fluid passage (W11, W21, W22) formed between an inner peripheral surface of the valve body (20) and an outer peripheral surface of the valve element (30), through which gas flows.

[0009] The valve element (30) includes; an inside passage (31) formed in an interior of the valve element and extending in an axial direction of the valve element, through which liquid flows; and a communication port (33) for communicating the inside passage with the annular fluid passage, wherein the communication port is opened on the outer peripheral surface of the valve element at a position located on an upstream side of the valve surface portion (35a) in a flow direction of the gas flowing through the annular fluid passage along the axial direction of the valve element.

[0010] In the fluid injection device the liquid is supplied to the annular fluid passage (W11, W21, W21) from the inside passage (31) through the communication port (33), and the liquid supplied to the annular fluid passage from the communication port is injected together with the gas flowing through the annular fluid passage when the valve element is in a valve opening position.

[0011] In the fluid injection device the injection of the liquid and the gas is terminated when the valve surface portion (35a) abuts the valve seat portion (23a) to close the annular fluid passage, a cross-sectional passage area of ​​a connecting passage section (C10) is smaller than a cross-sectional passage area of ​​a passage section (C20) on the upstream side, the connecting passage portion (C10) is a portion of the annular fluid passage (W11) at which the communication port (33) is connected to the annular fluid passage, and the upstream side passage portion (C20) is another portion of the annular fluid passage (W11) located on an upstream side of the connecting passage portion (C10).

[0012] According to another feature of the present disclosure, a fluid injection system uses the above fluid injection device and includes a gas supply unit (11, 16, 18) for supplying the gas to the fluid injection device. The fluid injection system further comprises a pressure control section (150) for controlling an operation of the gas supply unit to regulate the pressure of the gas to be supplied to the fluid injection device.

[0013] According to the above structure, it is possible to make the flow velocity of the gas flowing through the communication passage portion of the annular fluid passage faster than the flow velocity of the gas flowing through the passage portion on the upstream side of the annular fluid passage when the valve element is in the valve-opening position. When the gas having the faster flow velocity converges with the liquid present at an opening portion of the communication port, the liquid is sucked from the inside of the communication port. According to the above operation, the liquid can be sucked from the inside of the communication port even when the pressure of the liquid is low or zero. Thus, the gas and the liquid converge with each other.Since it is possible to atomize the liquid based on the Bernoulli equation, such atomized liquid can be injected. Furthermore, since the fluid injection device has a simple structure in which the cross-sectional passage area of ​​the annular fluid passage at the connecting passage portion is made smaller than that of the passage portion on the upstream side, the structure of the fluid injection device can be simplified as a whole.

[0014] In the present disclosure, it is possible to provide the fluid injection device and the fluid injection system according to which the liquid is atomized and injected.

[0015] The above and other objects, features, and advantages of the present disclosure will become apparent from the following detailed description with reference to the accompanying drawings. Fig. 1 is a block diagram showing an outline of a fluid injection system according to a first embodiment of the present disclosure; Fig. 2 is a schematic cross-sectional view showing a fluid injection device of the first embodiment; Fig. 3 is a schematically enlarged cross-sectional view showing a front end portion of the fluid injection device of the first embodiment; Fig. 4 is a schematic cross-sectional view showing an operation of the fluid injection device of the first embodiment; Fig. 5 is another schematic cross-sectional view showing the operation of the fluid injection device of the first embodiment; Fig. 6 is a block diagram showing an outline of a fluid injection system according to a modification of the first embodiment; Fig. 7 is a schematic cross-sectional view showing a fluid injection device (a valve-open state) according to a second embodiment; Fig. 8 is a schematic cross-sectional view showing an operation (a valve-closed state) of the fluid injection device of the second embodiment; Fig. 9 is a schematic cross-sectional view showing a fluid injection device according to a third embodiment; Fig. 10 is a schematic cross-sectional view showing a fluid injection device according to a fourth embodiment; and Fig. 11 is a block diagram showing an outline of a fluid injection system according to a fifth embodiment of the present disclosure.

[0016] The present disclosure will be explained below using a plurality of embodiments and modifications with reference to the drawings. The same or similar structures and / or sections are denoted by the same reference numerals to avoid repetitive explanation. First embodiment

[0017] First, an outline of a fluid injection system 1 including a fluid injection device 10 of a first embodiment of the present disclosure will be explained. The fluid injection system 1 shown in Fig. 1 is applied to an SCR (Selective Catalytic Reduction) system of a motor vehicle (hereinafter, the vehicle) for adding a liquid (for example, an aqueous urea solution) to the exhaust gas flowing through an exhaust pipe of the vehicle having an internal combustion engine (hereinafter, the engine). The fluid injection system 1 includes the fluid injection device 10, an air pump 11, a liquid tank 12, a pressure sensor 13, a flow rate sensor 14, an electronic control unit 15 (hereinafter, the ECU 15), and so on.

[0018] The air pump 11 pressurizes gas (in the present embodiment, air) to a predetermined value necessary for injection and supplies such pressurized gas to the fluid injection device 10. In the present embodiment, the air pump 11 serves as a gas supply unit for regulating a pressure of the gas and supplying such gas at a regulated pressure to the fluid injection device 10. In addition to the gas (air) from the air pump 11, the liquid (urea aqueous solution) is supplied from the liquid tank 12 that stores the urea aqueous solution. The fluid injection device 10 atomizes the urea aqueous solution from the liquid tank 12 by the air from the air pump 11 and injects such atomized fluid into the exhaust pipe of the vehicle.The fluid injection device 10 is used as a urea addition valve for adding the aqueous urea solution to the exhaust gas flowing through the exhaust pipe.

[0019] The pressure sensor 13 detects the pressure of the air supplied to the fluid injection device 10 from the air pump 11 and outputs an electrical signal corresponding to the detected air pressure. The flow rate sensor 14 detects the flow rate of the air supplied to the fluid injection device 10 from the air pump 11 and outputs an electrical signal corresponding to the detected air flow rate. Each of the electrical signals from the pressure sensor 13 and the flow rate sensor 14 is transmitted to the ECU 15.

[0020] The ECU 15 is composed of a microcomputer including a CPU, memory devices, and so on. The ECU 15 detects the pressure and flow rate of the air supplied to the fluid injection device 10 based on respective output signals of the pressure sensor 13 and the flow rate sensor 14. The ECU 15 controls operation of the air pump 11 in accordance with the detected pressure and flow rate of the air.

[0021] A structure of the fluid injection device 10 will be explained.

[0022] As in Fig. As shown in Figure 2, the fluid injection device 10 includes a valve body 20 and a valve element 30. The valve body 20 is formed in a cylindrical shape having a center point of an axis line ml. In the present disclosure, a direction of the axis line ml is referred to as an axial direction. In addition, an upward direction Z1, which is parallel to the axis line ml, is referred to as an upward axial direction, while a downward direction Z2, which is also parallel to the axis line ml, is referred to as a downward axial direction.

[0023] A first valve element accommodation hole 21 and a second valve element accommodation hole 22, each extending in the axial direction of the axis line ml, are formed in the valve body 20. The valve element 30 is movably accommodated in the first and second valve element accommodation holes 21 and 22. The first and second valve element accommodation holes 21 and 22 are formed coaxially with each other around the axis line ml. A cross-sectional shape of each of the first and second valve element accommodation holes 21 and 22, which has the center point at the axis line ml, is circular. The first and second valve element accommodation holes 21 and 22 are arranged in this order from a lower-side end and an upper-side end of the valve body 20 upward in the axial direction Z1.The second valve element accommodating hole 22 has an inner diameter larger than that of the first valve element accommodating hole 21.

[0024] An annular fluid passage W11 is formed in a space formed between an inner peripheral surface of the first valve element accommodation hole 21 and an outer peripheral surface of the valve element 30. The annular fluid passage W11 is formed in a ring shape having a center point at the axial line ml. An air supply passage W12 is formed along a left-side wall of the valve body 20 in the axial direction and is connected to the annular fluid passage W11. The air is supplied to the air supply passage W12 from the air pump 11 (which is shown in Fig. 1). As above, air is supplied at high pressure to the annular fluid passage W11 through the air supply passage W12. A check valve 50, also referred to as a flow restricting device, is provided in the air supply passage W12 to restrict a reverse flow of air in the upward axial direction Z1 from the annular fluid passage W11 to the air supply passage W12 and the air pump 11.

[0025] An injection port 24 is formed at a center point of the lower-side end of the valve body 20, the injection port 24 penetrating the valve body 20 in the axial direction from an inside of the first valve element accommodating hole 21 to an outside of the valve body 20. A part of the inner peripheral surface of the first valve element accommodating hole 21, which is located at the lower-side end of the valve body 20, is formed with a tapered surface 23. In other words, the inner peripheral surface at the lower-side end of the valve body 20 is formed into a tapered shape having a center point at the axial line ml.The conical surface 23 is formed such that an inner diameter of the conical surface 23 in the axial direction Z2 becomes smaller downwards with each point at which the respective point of the conical surface 23 approaches the injection port 24.

[0026] An interior of the second valve element accommodating hole 22 forms a fluid supply passage W13. A fluid supply port W14 is formed in the valve body 20 and communicates with the fluid supply passage W13. As shown in Fig. 1, the liquid supply port W14 is connected to the liquid tank 12. The liquid (the aqueous urea solution) is supplied to the liquid supply passage W13 from the liquid tank 12 through the liquid supply port W14.

[0027] The valve element 30 is formed in a cylindrical shape having a center point at the axis line ml. In the present disclosure, the axis line ml corresponds to a center line of the valve element 30. A flanged portion 32 is formed at one end on the upper side of the valve element 30. An outer peripheral surface of the flanged portion 32 is in sliding contact with the inner peripheral surface of the first valve element accommodating hole 21. The valve element 30 is movably supported by and in the valve body 20 due to the sliding contact, so that the valve element 30 is movable relative to the valve body 20 in the axial direction of the axis line ml. The annular fluid passage W11 is fluid-tightly separated from the liquid supply passage W13 by this sliding contact between the first valve element accommodating hole 21 and the flanged portion 32 of the valve element 30.

[0028] The lower end of the valve element 30 is formed in a conical shape having a center point on the axial line ml. A conical surface 35 formed at the lower end of the valve element 30 is arranged opposite the conical surface 23 of the valve body 20 in the axial direction. An annular groove 34 having a center point on the axial line ml is formed in the conical surface 35. The conical surface 35 of the valve element 30 is composed of a first conical surface portion 35a and a second conical surface portion 35b on both axial sides of the annular groove 34. The first conical surface portion 35a is also referred to as a valve surface portion 35a, while the second conical surface portion 35b is also referred to as a passage reducing portion 35b.A part of the conical surface 23 of the valve body 20, which is arranged opposite to the valve surface portion 35a, is referred to as a valve seat portion 23a.

[0029] As in Fig. As shown in Fig. 3, a gap formed between the valve seat portion 23a of the valve body 20 and the valve surface portion 35a of the valve element 30 serves as a first injection passage W21. A gap formed between the tapered surface 23 of the valve body 20 and the passage reducing portion 35b of the valve element 30 serves as a second injection passage W22. A passage width of the first injection passage W21 is smaller than a passage width of the second injection passage W22. Both the first and second injection passages W21 and W22 are part of the annular fluid passage W11.

[0030] As in Fig. 2, an inside passage 31 is formed in the valve element 30 such that the inside passage 31 extends in an interior of the valve element 30 along the axis line ml. One end on the upper side of the inside passage 31 is opened at an end surface on the upper side of the valve element 30 to the fluid supply passage W13 of the valve body 20. A plurality of communication ports 33 are formed in a front end portion of the valve element 30 such that the plurality of communication ports 33 extend in a radial manner, and each of the communication ports 33 extends from the inside passage 31 to the annular fluid passage W11.According to the above structure, the aqueous urea solution flows into the fluid supply passage W13 of the valve body 20, and the aqueous urea solution is supplied through the inside passage 31 and the plurality of communication ports 33 of the annular groove 34. In the present embodiment, each of the communication ports 33 is opened at the annular groove 34. A portion C10 of the annular fluid passage W11 to which the annular groove 34 is connected corresponds to a connection passage portion C10 at which each of the communication ports 33 is connected to the annular fluid passage W11.

[0031] A spring 40 is housed in the second valve element housing hole 22. The spring 40 biases the valve element 30 in a direction toward the tapered surface 23 of the valve body 20 (downward in the axial direction Z2), that is, in a valve closing direction. The valve closing direction is a direction in which the valve surface portion 35a of the valve element 30 approaches the valve seat portion 23a of the valve body 20. In the present embodiment, the spring 40 is also referred to as a biasing element.

[0032] An electrical structure of the fluid injection system 1 will be explained.

[0033] As in Fig. 1, the ECU 15 includes a pressure control section 150, a pressure detection section 151, a flow rate detection section 152, and so on. The pressure detection section 151 detects the pressure of the air supplied to the fluid injection device 10 from the air pump 11 based on the output signal of the pressure sensor 13. The flow rate detection section 152 detects the flow rate of the air supplied to the fluid injection device 10 from the air pump 11 based on the output signal of the flow rate sensor 14.The pressure control section 150 controls an opening and closing operation of the fluid injection device 10 based on the pressure and flow rate of the air detected by the pressure detection section 151 and the flow rate detection section 152, such that the pressure control section 150 changes the pressure and flow rate of the air to be supplied to the fluid injection device 10 from the air pump 11.

[0034] Specifically, the pressure control section 150 performs normal liquid injection control in a predetermined cycle so that the urea aqueous solution is injected from the fluid injection device 10. In the normal liquid injection control, the urea aqueous solution is injected from the fluid injection device 10, or the injection of the urea aqueous solution from the fluid injection device 10 is stopped depending on a valve position of the valve element 30, and the valve element 30 is moved to a valve-opening position or a valve-closing position using the pressure of the air supplied to the fluid injection device 10 from the air pump 11.

[0035] The pressure control section 150 performs liquid discharge control and air supply stop control (gas supply stop control) to stop the liquid injection operation of the fluid injection device 10 after the urea aqueous solution is injected from the fluid injection device 10 by executing the normal liquid injection control. In the liquid discharge control, the valve element 30 is in the valve-closed position. In addition, the urea aqueous solution remaining in the fluid injection device 10 is returned to the liquid tank 12 using the pressure of the air supplied to the fluid injection device 10 from the air pump 11.In the air supply termination control, the supply of air from the air pump 11 to the fluid injection device 10 is stopped to completely terminate the operation (injection of liquid) of the fluid injection device 10.

[0036] The pressure control section 150 then executes liquid suction control to start the operation (liquid injection) of the fluid injection device 10 when a next injection timing is reached. In the liquid suction control, the injection of the urea aqueous solution is prepared by supplying the urea aqueous solution to the fluid injection device 10 from the liquid tank 12. The pressure control section 150 starts the injection of the urea aqueous solution from the fluid injection device 10 through the normal liquid injection control when the preparation for injection by the liquid suction control is completed.

[0037] The operation of the fluid injection device 10, which is carried out by the pressure control section 150, will be further explained.

[0038] The pressure control section 150 controls the air pump 11 such that the supply of air to the fluid injection device 10 is stopped so that the valve element 30 is moved to the valve closing position in the normal liquid injection control. As shown in Fig. 4, the check valve 50 is closed when the supply of air is stopped. In addition, because the valve element 30 is biased downward in the axial direction Z2, that is, in the valve closing direction, by the biasing force of the spring 40, the valve surface portion 35a of the valve element 30 abuts against the valve seat portion 23a of the valve body 20. When the valve element 30 is moved to the valve closing position, the first injection passage W21 is closed. Therefore, the injection of the urea aqueous solution and the air from the fluid injection device 10 is terminated.

[0039] In the normal liquid injection control, the pressure control section 150 further controls the air pump 11 such that the air having an air pressure higher than a first preset value is supplied to the fluid injection device 10 so that the valve element 30 is opened from the valve closing position of Fig. 4 is moved to a valve opening position. The first preset value corresponds to an air pressure that can move both the check valve 50 and the valve element 30 to the respective valve opening positions. When the air supply passage W12 of the fluid injection device 10 is supplied with air having the pressure at the first preset value (or higher than this), the check valve 50 is opened, as shown in Fig. 2, so that the air at the high pressure (higher than or equal to the first preset value) is supplied to the annular fluid passage W11. When the pressure of the air supplied to the annular fluid passage W11 is applied to a surface 320 on the lower side of the flanged portion 32 of the valve element 30 and the passage reducing portion 35b, an air pressure force for pressing the valve element 30 upward in the axial direction Z1 (that is, in the valve opening direction) is applied to the valve element 30. In the present embodiment, the surface 320 on the lower side of the flanged portion 32 of the valve element 30 and the passage reducing portion 35b correspond to a pressure receiving surface to which the pressure of the air in the annular fluid passage W11 is applied.The valve opening direction is a direction in which the valve surface portion 35a of the valve element 30 is separated from the valve seat portion 23a of the valve body 20. When the valve element 30 is moved upward in the axial direction Z1 by the air pressure force in the valve opening direction against the biasing force of the spring 40, the injection port 24 is opened. A valve-open state is maintained in which the valve surface portion 35a of the valve element 30 is separated from the valve seat portion 23a of the valve body 20.

[0040] As in Fig. 3, a cross-sectional passage area of ​​the annular fluid passage W11 at the communication passage portion C10 is a cross-sectional area of ​​a portion indicated by a two-dot chain line L10 when the fluid injection device 10 is in the valve-open state. Thus, the cross-sectional passage area of ​​the annular fluid passage W11 at the communication passage portion C10 is equal to a cross-sectional passage area of ​​the second injection passage W22. A cross-sectional passage area of ​​the annular fluid passage W11 at a passage portion C20 on the upstream side of the second injection passage W22 is a cross-sectional area of ​​a portion indicated by a two-dot chain line L20.The cross-sectional passage area of ​​the annular fluid passage W11 at the connecting passage portion C10 is smaller than the cross-sectional passage area of ​​the annular fluid passage W11 at the passage portion C20 on the upstream side. A flow velocity of the air in the connecting passage portion C10 of the annular fluid passage W11 is higher than that of the air in the passage portion C20 on the upstream side of the annular fluid passage W11. When the air at a higher flow velocity merges with the urea aqueous solution in the annular groove 34, the urea aqueous solution is sucked from the annular groove 34 and merges with the air. According to the above structure and operation, it is possible to atomize the urea aqueous solution based on the Bernoulli equation.The aqueous urea solution, which is atomized by the air, is injected from the injection port 24 through the first injection passage W21.

[0041] In the fluid injection device 10, the aqueous urea solution is sucked from the annular groove 34 by the air flowing through the communication passage portion C10 of the annular fluid passage W11. Although no pump is provided between the liquid tank 12 and the fluid injection device 10 for the aqueous urea solution in the present embodiment, it is possible to supply the fluid injection device 10 with water from the liquid tank 12 ( Fig. 1) Supply the aqueous urea solution by applying a suction force to the aqueous urea solution. According to the structure of the present embodiment, it is possible to supply the aqueous urea solution to the fluid injection device 10 from the liquid tank 12 even when the pressure of the aqueous urea solution is low or zero.

[0042] The pressure control section 150 executes the air supply (gas supply) termination control after the liquid discharge control when the operation (normal liquid injection control) of the fluid injection device 10 is terminated. First, the pressure control section 150 controls the air pump 11 during the liquid discharge control such that the air having a pressure of a second preset value is supplied to the fluid injection device 10. The second preset value is smaller than the first preset value. The second preset value corresponds to a pressure at which the check valve 50 can be opened but the valve element 30 cannot be opened. In other words, the second preset value corresponds to the pressure at which the valve element 30 is maintained in a valve-closed state. As shown in Fig. As shown in Fig. 5, when the valve element 30 is maintained in the valve-closing position while the check valve 50 is maintained in the valve-open state, the air in the annular fluid passage W11 pushes the urea aqueous solution in the annular groove 34 of the valve element 30, so that the urea aqueous solution flows back from the annular groove 34 into the communication ports 33. Therefore, the urea aqueous solution remaining in the communication ports 33, the inside passage 31 of the valve element 30, the liquid supply passage W13, and the liquid supply port W14 flows back toward the liquid tank 12. As a result, the urea aqueous solution is substantially discharged from the fluid injection device 10.

[0043] The pressure control section 150 determines whether the aqueous urea solution has been discharged from the fluid injection device 10 to the liquid tank 12 based on the air flow rate detected by the flow rate detection section 152. When the pressure control section 150 determines that the aqueous urea solution has been substantially discharged from the fluid injection device 10 to the liquid tank 12, the pressure control section 150 terminates the liquid discharge control. Thus, the pressure control section 150 stops the operation of the air pump 11 as the air supply termination control.

[0044] Specifically, when the discharge of the urea aqueous solution from the fluid injection device 10 to the liquid tank 12 is completed, the air supplied to the fluid injection device 10 from the air pump 11 is also discharged to the liquid tank 12. When the air from the air pump 11 reaches the liquid tank 12, an air supply load (a gas supply load) to the air pump 11 is rapidly reduced. As a result, an air discharge pressure at the air pump 11 is temporarily reduced. Since the air discharge pressure of the air pump 11 is controlled at the second preset value during the liquid discharge control, the air pump 11 is controlled to increase an air discharge amount, so that the air discharge pressure is increased again to the second preset value. Accordingly, the flow rate of air to be supplied to the fluid injection device 10 from the air pump 11 is rapidly increased.The pressure control section 150 uses the above phenomenon to determine whether the air from the air pump 11 has reached the liquid tank 12. Therefore, the pressure control section 150 determines that the air from the air pump 11 has reached the liquid tank 12 based on the phenomenon that the air pressure detected by the pressure detection section 151 is temporarily reduced or the phenomenon that the air flow rate detected by the flow rate detection section 152 becomes greater than a predetermined value.The pressure control section 150 controls the air pump 11 for a period from the time the liquid discharge control is started until the time the pressure control section 150 determines that the air from the air pump 11 has reached the liquid tank 12, such that the pressure of the air supplied to the fluid injection device 10 is maintained at the second preset value. The pressure control section 150 terminates the liquid discharge control when it determines that the air from the air pump 11 has reached the liquid tank 12 and stops the operation of the air pump 11 as the air supply termination control. As above, it is possible to stop the air pump 11 after the urea aqueous solution has been safely discharged from the fluid injection device 10 to the liquid tank 12.

[0045] The pressure control section 150 executes the liquid suction control when the operation (liquid injection) of the fluid injection device 10 is started. The pressure control section 150 controls the air pump 11 during the liquid suction control such that the air having the pressure at the first preset value is supplied to the fluid injection device 10. When the air at the first preset value is supplied to the fluid injection device 10, both the check valve 50 and the valve element 30 are moved to their valve opening positions, as shown in Fig. 2. Therefore, the air supplied to the fluid injection device 10 from the air pump 11 is injected from the injection port 24 via the air supply passage W12, the annular fluid passage W11, the second injection passage W22, and the first injection passage W21.

[0046] In this liquid suction control operation, the air flowing through the second injection passage W22 and the first injection passage W21 is injected from the injection port 24, while the above air pump sucks the air from the annular groove 34. This creates negative pressure in the annular groove 34. The air present in the liquid supply passage W13 of the valve body 20, the inside passage 31 of the valve element 30, and the communication ports 33 is gradually discharged to the outside of the fluid injection device 10. The urea aqueous solution is then sucked from the liquid tank 12 to the fluid injection device 10 due to the above air flow (the negative pressure in the liquid supply passage W13), and thereby the urea aqueous solution is supplied to the fluid injection device 10.

[0047] Thereafter, the pressure control section 150 determines whether the urea aqueous solution has reached the annular groove 34 of the valve element 30 based on the air flow rate detected by the flow rate detection section 152. If it determines that the urea aqueous solution has reached the annular groove 34, the pressure control section 150 terminates the liquid suction control.

[0048] Specifically, when the urea aqueous solution reaches the annular groove 34, not only the air but also the urea aqueous solution flows through the first injection passage W21. Since the urea aqueous solution serves as an obstacle to the flow of air, the air supply load of the air pump 11 is rapidly increased. As a result, the air discharge pressure of the air pump 11 is temporarily increased. Since the air discharge pressure of the air pump 11 is controlled at the first preset value during the liquid suction control, the air pump 11 is controlled to reduce the air discharge pressure to the first preset value. Thus, the air pump 11 is controlled to reduce the air discharge amount from the air pump 11. Subsequently, the flow rate of the air supplied from the air pump 11 to the fluid injection device 10 is rapidly reduced.The pressure control section 150 determines that the urea aqueous solution has reached the annular groove 34 based on the detection by the pressure detection section 151 (the detection that the pressure of the air is temporarily increased) or the detection by the flow rate detection section 152 (the detection that the flow rate of the air becomes lower than the predetermined amount).

[0049] When the pressure control section 150 determines that the urea aqueous solution has reached the annular groove 34, it controls the air pump 11 to stop the supply of air to the fluid injection device 10. The pressure control section 150 then stops the liquid suction control. The valve element 30 is thereby moved to the valve closing position. Preparation for injecting the urea aqueous solution from the fluid injection device 10 is completed. Thereafter, the pressure control section 150 executes the normal liquid injection control to inject the urea aqueous solution from the fluid injection device 10.

[0050] The fluid injection system 1 and the fluid injection device 10 of the present embodiment have the following advantages (A1) to (A9).

[0051] (A1) In the present embodiment, the portion of the annular fluid passage W11 connected to the communication ports 33 of the valve element 30 is defined as the communication passage portion C10. The cross-sectional passage area of ​​the annular fluid passage W11 at the communication passage portion C10 is made smaller than the cross-sectional passage area of ​​the annular fluid passage W11 at the passage portion C20 on the upstream side. According to the above structure, the urea aqueous solution flowing through the communication ports 33 can be atomized by the air flowing through the annular fluid passage W11. Therefore, the fluid injection device 10 can inject the atomized urea aqueous solution.Since the fluid injection device 10 has the structure according to which the cross-sectional passage area of ​​the communication passage portion C10 of the annular fluid passage W11 is made smaller than that of the passage portion C20 on the upstream side, it is possible to simplify the structure of the fluid injection device 10.

[0052] (A2) In the liquid discharge control, the urea aqueous solution remaining in the annular groove 34 and the communication ports 33 is returned to the liquid tank 12 by the pressure of the air flowing in the annular fluid passage W11. In the above operation, it is difficult to completely return the urea aqueous solution remaining in a part of the annular fluid passage W11 to the annular groove 34 and the liquid tank 12 from a valve contact portion between the valve surface portion 35a and the valve seat portion 23a.

[0053] In a case where the communication ports 33 are provided at positions located on an upstream side of the valve surface portion 35a in the air flow direction and separated from the valve surface portion 35a, the valve contacting portion between the valve surface portion 35a and the valve seat portion 23a is separated from the annular groove 34. In such a case, the urea aqueous solution remaining in the portion of the annular fluid passage W11 between the valve contacting portion and the annular groove 34 cannot be completely returned to the liquid tank 12 when the liquid discharge control is executed.

[0054] However, in the fluid injection device 10 of the present embodiment, the annular groove 34 is formed on the outer peripheral surface of the valve element 30 at a position adjacent to (not separated from but close to) the valve surface portion 35a. According to such a structure, it is possible to form the annular groove 34 at the position close to the valve contacting portion between the valve surface portion 35a and the valve seat portion 23a. This makes it possible to avoid a situation that the urea aqueous solution may remain in the annular fluid passage W11 when the liquid discharge control is executed. In addition, the first injection passage W21 has a cross-sectional passage area when the valve element 30 is opened, which is the smallest among the cross-sectional passage areas of the annular fluid passage W11.Since the flow velocity of the air in the first injection passage W21 is increased, the aqueous urea solution can be suitably atomized.

[0055] (A3) The plurality of communication ports 33 are formed in the valve element 30. The annular groove 34 is formed on the outer peripheral surface of the valve element 30 such that opened portions of each communication port 33 are connected to each other via the annular groove 34. According to the above structure, since the urea aqueous solution stays in the annular groove 34 from the opened portion of each communication port 33, it is possible to supply the urea aqueous solution not only to a passage area of ​​the annular fluid passage W11 around the opened portion of each communication port 33, but also to an entire passage area of ​​the annular fluid passage W11. This makes it possible to uniformly inject the urea aqueous solution from an entire circumference of the injection port 24.When the valve element 30 is in the valve closing position during the normal liquid injection control, it is preferable that a boundary surface between the air and the aqueous urea solution is located at a position between the annular groove 34 and the annular fluid passage W11.

[0056] (A4) When the valve element 30 is in the valve-closing position, the air pressure is applied to the surface 320 on the lower side of the flanged portion 32 and the passage-reducing portion 35b of the valve element 30. The valve element 30 is moved in the valve-opening direction by the above air pressure against the biasing force of the spring 40. The valve surface portion 35a of the valve element 30 is separated from the valve seat portion 23a of the valve body 20, and the valve element 30 is opened. According to the above structure, the valve element 30 can be moved to the valve-closing position or the valve-opening position simply by adjusting the pressure of the air to be supplied to the fluid injection device 10. In other words, it is not necessary to provide a drive device such as an electromagnetic valve or the like to open and close the valve element 30.As a result, it is possible to simplify the structure of the fluid injection device 10.

[0057] (A5) In a case where the liquid tank 12 is located at a position higher in a vertical direction than the fluid injection device 10, a pressure difference is generated by a difference in liquid levels between the aqueous urea solution in the liquid tank 12 and the aqueous urea solution inside the fluid injection device 10. The fluid pressure generated by the pressure difference is applied to the aqueous urea solution in the fluid injection device 10.

[0058] If the fluid injection device 10 has a structure such that the air can flow from the annular fluid passage W11 back to the air supply passage W12, the air is forced from the annular fluid passage W11 back to the air supply passage W12 by the fluid pressure exerted on the urea aqueous solution in the fluid injection device 10. Subsequently, the urea aqueous solution can flow into the fluid injection device 10, although this is not the time for injecting the urea aqueous solution.

[0059] However, according to the present embodiment, the check valve 50 is provided in the valve body 20 as the flow restriction device that restricts the flow of air from the annular fluid passage W11 to the air supply passage W12. According to the above structure, even if the fluid pressure generated by the liquid level difference is exerted on the urea aqueous solution in the fluid injection device 10, it is possible to avoid a situation in which the air flows back from the annular fluid passage W11 to the air supply passage W12. As a result, it is possible to avoid a situation in which the urea aqueous solution flows from the liquid tank 12 to the fluid injection device 10 during the period in which the urea aqueous solution is not to be injected.

[0060] (A6) The pressure control section 150 controls the air pump 11 such that the air having the pressure of the second preset value is supplied to the fluid injection device 10 when the valve element 30 is in the valve-closed state. Then, the air is supplied to the communication ports 33 and the inside passage 31 of the valve element 30 from the annular fluid passage W11, thereby executing the liquid discharge control, according to which the urea aqueous solution present in the communication ports 33 and the inside passage 31 is discharged to the liquid tank 12. The second preset value is the pressure lower than the predetermined pressure (for example, the first preset value) for moving the valve element 30 in the valve-opening direction.

[0061] According to the above structure, it is possible to discharge the urea aqueous solution from the fluid injection device 10 to the outside thereof when the injection operation of the fluid injection device 10 is stopped. This makes it possible to prevent a situation where the urea aqueous solution in the fluid injection device 10 may be frozen and the fluid injection device 10 may be broken due to such freezing of the urea aqueous solution when the fluid injection device 10 is not in operation.

[0062] In addition, even in a case where the urea aqueous solution cannot be completely discharged from the fluid injection device 10 by the liquid discharge control, it is possible to reduce the amount of the urea aqueous solution that may remain in the fluid injection device 10. Therefore, even in a case where a small amount of the urea aqueous solution is frozen in the fluid injection device 10, it is possible to shorten a time required to thaw the frozen urea aqueous solution. This makes it possible to improve starting performance of the fluid injection device 10. Furthermore, it is possible to avoid a situation where the urea aqueous solution may deteriorate in the fluid injection device 10 due to heat transferred from the exhaust pipe of the engine to the fluid injection device 10.

[0063] (A7) During the liquid discharge control, the pressure control section 150 determines that the air has reached the liquid tank 12 when it detects the increase in the air flow rate based on the output signal from the flow rate detection section 152. Then, the pressure control section 150 terminates the liquid discharge control.

[0064] According to the above operation, the liquid discharge control is continuously executed until the urea aqueous solution is substantially discharged from the fluid injection device 10. Therefore, it is possible to safely discharge the urea aqueous solution from the fluid injection device 10. In addition, since the liquid discharge control is terminated when the urea aqueous solution has been discharged from the fluid injection device 10, it is possible to avoid a situation where air is wastefully supplied to the fluid injection device 10.

[0065] (A8) The pressure control section 150 executes the liquid suction control, according to which the pressure control section 150 controls the air pump 11 at the start of the injection operation of the fluid injection device 10 so that the air having the pressure of the first preset value is supplied to the fluid injection device 10 when the urea aqueous solution has not yet been filled into the inside passage 31 and the communication ports 33 of the valve element 30. Subsequently, the negative pressure is generated in the annular groove 34, and the urea aqueous solution is sucked from the liquid tank 12 to the annular groove 34.

[0066] According to the above operation, it is possible to supply the aqueous urea solution to the fluid injection device 10 from the liquid tank 12 without using any kind of liquid pump for supplying the aqueous urea solution from the liquid tank 12 to the fluid injection device 10. This makes it possible to simplify the fluid injection system 1 to such an extent that the liquid pump is not necessary.

[0067] (A9) During the liquid suction control, the pressure control section 150 determines that the urea aqueous solution has reached the annular groove 34 when the flow rate detection section 152 detects the decrease in air. Subsequently, the pressure control section 150 terminates the liquid suction control and determines that the preparation for the injection of the urea aqueous solution and air in the fluid injection device 10 is completed.

[0068] According to the above operation, in the case where the aqueous urea solution is not filled in the fluid injection device 10, it is possible to surely determine whether the preparation for injection in the fluid injection device 10 is completed. First modification

[0069] A first modification of the fluid injection device 10 of the first embodiment will be explained.

[0070] In the ECU 15 of the first modification, instead of (or in addition to) the flow rate detecting section 152, a pump-out pressure detecting section 153 is provided as shown by a dotted line in Fig. 1. The discharge load detecting section 153 detects a discharge load (equal to the air supply load) of the air pump 11 for the air to be supplied to the fluid injection device 10 from the air pump 11 based on a drive current to the air pump 11. More specifically, the discharge load detecting section 153 detects the drive current to the air pump 11. Then, the discharge load detecting section 153 determines that the discharge load for the air is high when the detected drive current is large, while determining that the discharge load for the air is low when the detected drive current is small.

[0071] A relationship between the drive current of the air pump 11 and the air discharge rate of the air pump 11 is obtained in advance based on experiments or the like, and the relationship is stored in a storage device of the ECU 15. The air discharge rate is quantified. If such a quantified value is high, it indicates that the air discharge rate is high.

[0072] When the discharge air from the air pump 11 reaches the liquid tank 12 during the operation of the liquid discharge control, the discharge pressure of the air by the air pump 11 is temporarily reduced, and the discharge capacity is rapidly reduced. During the liquid discharge control, pressure compensation control is executed, according to which the air pump 11 is controlled so that the discharge pressure of the air is controlled at the second preset value. Therefore, it is possible to increase the discharge amount of the air when the discharge pressure is temporarily reduced because the discharge pressure of the air is increased to the second preset value by the pressure compensation control. As a result, the discharge capacity of the air pump 11 is increased.

[0073] According to the first modification, during the liquid discharge control, the pressure control section 150 determines that the air has reached the liquid tank 12 when the pressure control section 150 determines that the discharge pressure of the air detected by the discharge pressure detecting section 153 is increased. Subsequently, the pressure control section 150 stops supplying the air to the fluid injection device 10.

[0074] The discharge pressure for the air pump 11 is transiently reduced immediately after the air discharged from the air pump 11 reaches the liquid tank 12. Therefore, the pressure control section 150 may alternatively detect the above transient reduction in the discharge pressure, determine that the air has reached the liquid tank 12, and stop supplying the air to the fluid injection device 10.

[0075] As explained above, when the aqueous urea solution from the liquid tank 12 reaches the annular groove 34 during the operation of the liquid suction control, the pumping pressure of the air from the air pump 11 is temporarily increased and thereby the pumping capacity of the air pump 11 is rapidly increased.

[0076] The pressure compensation control is also performed during the operation of the liquid suction control such that the air discharge pressure for the air pump 11 is controlled at the first preset value. Therefore, the air discharge amount is controlled to be reduced so that the air discharge pressure is reduced to the first preset value when the discharge pressure is temporarily increased. As a result, the discharge amount for the air pump 11 is reduced.

[0077] During the operation of the liquid suction control, the pressure control section 150 determines that the aqueous urea solution has reached the annular groove 34 when the pressure control section 150 determines that the discharge pressure of the air detected by the discharge pressure detection section 153 is decreasing. The pressure control section 150 ends the liquid suction control and determines that the preparation for the injection of the aqueous urea solution in the fluid injection device 10 is completed.

[0078] The pumping pressure for the air pump 11 is transiently increased immediately after the aqueous urea solution from the liquid tank 12 reaches the annular groove 34. Alternatively, the pressure control section 150 may detect the above transient increase in the pumping pressure, determine that the aqueous urea solution has reached the annular groove 34, terminate the liquid suction control, and determine that the preparation for the injection of the aqueous urea solution in the fluid injection device 10 has been completed.

[0079] According to the fluid injection system 1 of the above first modification, the same advantages as those of the first embodiment can be achieved. In addition, the structure of the fluid injection system 1 can be simplified because the flow rate sensor 14 is not always necessary. Second modification

[0080] The fluid injection system 1 according to a second modification of the first embodiment will be explained.

[0081] As in Fig. 6, in the fluid injection system 1 of the second modification, a pressure regulating valve 16 and an air tank 18 are provided between the fluid injection device 10 and the air pump 11. In this second modification, the air pump 11, the pressure regulating valve 16, and the air tank 18 constitute the gas supply unit. The air having a predetermined pressure and supplied from the air pump 11 is stored in the air tank 18. The pressure regulating valve 16 regulates the pressure of the air in the air tank 18 and supplies such air at a regulated pressure to the fluid injection device 10. The pressure regulating valve 16 is controlled by the pressure control section 150 (which is shown in Fig. 1) of the ECU 15. The pressure control valve or pressure regulating valve 16 corresponds to a pressure control section or pressure regulating section.

[0082] According to the above structure, the air tank 18 absorbs pulsation of the air to be supplied to the fluid injection device 10 from the air pump 11. In other words, it is possible to stably supply the air to the fluid injection device 10. As a result, it is possible to inject the aqueous urea solution from the fluid injection device 10 more uniformly. Second embodiment

[0083] The fluid injection system 1 and the fluid injection device 10 of a second embodiment will be explained with a focus on differences between the first embodiment and the second embodiment.

[0084] As in Fig. 7, in the fluid injection device 10 of the present embodiment, an outwardly extended portion 36 is formed at a central portion of the valve element 30. The outwardly extended portion 36 is extended outward of the valve element 30 in a radial direction. Furthermore, the outwardly extended portion 36 is a cylindrical portion formed at an outer periphery of the valve element 30 and has a central axis coinciding with the axial line ml of the valve element 30. The outwardly extended portion 36 is formed at a position separated from the front end portion (the lower-side end) of the valve element 30 in the axial direction by a predetermined distance between the front end portion and the outwardly extended portion 36.A passage reducing portion 37 is formed at an outer periphery of the outwardly extended portion 36, which is different from the structure of the first embodiment.

[0085] Specifically, the passage reducing portion 37 protrudes outward in the radial direction toward the inner peripheral surface of the first valve element accommodation hole 21 of the valve body 20. A radially outer surface of the passage reducing portion 37 is formed by a cylindrical surface having a straight line extending in the axial direction of the valve element 30. In other words, the radially outer surface is parallel to the inner peripheral surface of the valve body 20 in the axial direction. The annular groove 34 is formed on the radially outer surface of the passage reducing portion 37. Each of the plurality of communication ports 33 is opened at the annular groove 34, so that the inside passage 31 of the valve element 30 communicates with the annular groove 34 through the plurality of communication ports 33.

[0086] In the present disclosure, a portion of the valve element 30 located at a position above the passage reducing portion 37 is referred to as an upstream-side cylindrical portion 36a. A portion of the valve element 30 located at a position below the passage reducing portion 37 is referred to as a downstream-side cylindrical portion 36b. A portion of the annular fluid passage W11 formed between an outer peripheral surface of the upstream-side cylindrical portion 36a and an inner peripheral surface of the first valve element accommodating hole 21 of the valve body 20 is referred to as an upstream-side fluid passage portion W11a (equivalent to an upstream-side passage portion C20).A portion of the annular fluid passage W11 formed between an outer peripheral surface of the downstream-side cylindrical portion 36b and an inner peripheral surface of the first valve element accommodating hole 21 of the valve body 20 is referred to as a downstream-side fluid passage portion W11b.

[0087] An outer diameter of the upstream-side cylindrical portion 36a is larger than that of the downstream-side cylindrical portion 36b. A cross-sectional passage area of ​​the upstream-side fluid passage portion W11a is smaller than that of the downstream-side fluid passage portion W11b. An inwardly protruding portion 25 having a ring shape is formed on an inner peripheral surface of the second valve element accommodation hole 22. The outer peripheral surface of the upstream-side cylindrical portion 36a of the valve element 30 is in sliding contact with an inner peripheral surface of the inwardly protruding portion 25. The valve element 30 is movably supported by and in the valve body 20 through the sliding contact, so that the valve element 30 is movable relative to the valve body 20 in the direction along the axis line ml.can be moved while ensuring fluid tightness between the annular fluid passage W11 and the liquid supply passage W13. An upstream-side tapered surface 38a is formed on the outer peripheral surface of the valve element 30 (the outwardly extended portion 36) between the passage reducing portion 37 and the upstream-side cylindrical portion 36a. Similarly, a downstream-side tapered surface 38b is formed on the outer peripheral surface of the valve element 30 between the passage reducing portion 37 and the downstream-side cylindrical portion 36b. A surface area of ​​the downstream-side tapered surface 38b is larger than that of the upstream-side tapered surface 38a.

[0088] An operation of the fluid injection device 10 of the present embodiment will be explained.

[0089] In a similar manner to the first embodiment, the valve element 30 is biased downward in the axial direction Z2 by the biasing force of the spring 40 and thereby moved to the valve closing position when the pressure control section 150 ( Fig. 1) the normal liquid injection control starts, as in Fig. 8 is shown.

[0090] When the pressure control section 150 controls the air pump 11 such that the air having the pressure at the first preset value is supplied to the fluid injection device 10 to close the valve element 30 from the valve closing position of Fig. 8 to the valve opening position of Fig. 7, not only is the pressure of the air in the upstream-side fluid passage portion W11a exerted on the upstream-side tapered surface 38a of the valve element 30, but the pressure of the air in the downstream-side fluid passage portion W11b is also exerted on the downstream-side tapered surface 38b of the valve element 30. Since the surface area of ​​the downstream-side tapered surface 38b is larger than that of the upstream-side tapered surface 38a, the force of the air exerted on the downstream-side tapered surface 38b is greater than that exerted on the upstream-side tapered surface 38a.

[0091] A force difference between the force exerted on the tapered surface 38b on the downstream side and the tapered surface 38a on the upstream side is exerted on the valve element 30 in the valve opening direction. When the valve element 30 is moved upward in the axial direction Z1 by the force of the valve opening direction against the biasing force of the spring 40, the valve element 30 opens the injection port 24, as shown in Fig. 7. The valve-open state in which the valve surface portion 35a of the valve element 30 is separated from the valve seat portion 23a of the valve body 20 is maintained.

[0092] When the valve element 30 is in the valve opening position as shown in Fig. As shown in Fig. 7, the cross-sectional passage area at the connecting passage portion C10, at which the annular groove 34 is connected to the annular fluid passage W11, is smaller than the cross-sectional passage area at the passage portion C20 on the upstream side of the annular fluid passage W11 (that is, the cross-sectional passage area of ​​the fluid passage portion W11a on the upstream side). In a similar manner to the fluid injection device 10 of the first embodiment, since the flow velocity of the air flowing through the connecting passage portion C10 of the annular fluid passage W11 can be increased at the passage reducing portion 37, the urea aqueous solution can be sucked from the annular groove 34, and the sucked solution can be atomized when injected.

[0093] The pressure control section 150 of the present embodiment further executes the liquid discharge control, the air supply termination control, and the liquid intake control in the same or similar manner as the pressure control section 150 of the first embodiment. Since the operation of the fluid injection device 10 for these controls is basically the same as that of the fluid injection device 10 of the first embodiment, a detailed explanation thereof will be omitted.

[0094] As above, the fluid injection system 1 and the fluid injection device 10 of the second embodiment have the same or similar operations and advantages as those of the first embodiment. In addition, the second embodiment has the following additional advantage A10.

[0095] (A10) Each of the communication ports 33 is opened on the outer peripheral surface of the outwardly extended portion 36 of the valve element 30. Compared with the above structure in the fluid injection device 10 of the first embodiment, in the present embodiment, it is possible to shorten the length of the inside passage 31 formed in the valve element 30. In other words, the valve element 30 becomes easier to manufacture. Third embodiment

[0096] The fluid injection system 1 and the fluid injection device 10 of a third embodiment will be explained with a focus on differences between the first embodiment and the third embodiment.

[0097] As in Fig. 9, a plurality of spiral grooves 39 are formed on the outer peripheral surface of the outwardly extended portion 36 of the valve element 30, each of the spiral grooves 39 extending in a spiral direction having a center at the axis line ml.

[0098] The fluid injection system 1 and the fluid injection device 10 of the present embodiment have the same or similar operations and advantages as those of the first embodiment. In addition, the third embodiment has the following additional advantage A11.

[0099] (A11) As the air flows along the spiral grooves 39 in the annular fluid passage W11, a swirling flow is generated. When the urea aqueous solution is sucked from the annular groove 34 by the air of the swirling flow, the urea aqueous solution is further atomized. It becomes much easier to form the atomized urea aqueous solution when injected from the injection port 24. Fourth embodiment

[0100] The fluid injection system 1 and the fluid injection device 10 of a fourth embodiment will be explained with a focus on differences between the first embodiment and the fourth embodiment.

[0101] As in Fig. 10, in the fluid injection device 10 of the present embodiment, no structure corresponding to the annular groove 34 of the first embodiment is provided. Each of the communication ports 33 has a first opening portion 331 opened to the inside passage 31 of the valve element 30 and a second opening portion 332 opened on the outer peripheral surface of the valve element 30. Each of the communication ports 33 is inclined with respect to the axis line ml of the valve element 30 such that each portion of the communication port 33 approaches the axis line ml as each such portion moves downward in the axial direction Z2 from the first opening portion 331 to the second opening portion 332.

[0102] The tapered surface 35 of the valve element 30 is formed such that its surface portion approaches the tapered surface 23 of the valve body 20, just as the surface portion of the valve element 30 is located at a position closer to the front end of the valve element 30 downward in the axial direction Z2. As a result, each of the passage areas of the first injection passage W21 and the second injection passage W22, each of which is formed between the tapered surface 35 of the valve element 30 and the tapered surface 23 of the valve body 20, becomes smaller in the direction toward the injection port 24.

[0103] The above-described fluid injection system 1 and fluid injection device 10 of the present embodiment have the same or similar operations and advantages as those of the first embodiment. In addition, the fourth embodiment has the following additional advantage A12.

[0104] (A12) Each of the communication ports 33 is formed to approach the axis line ml of the valve element 30 in the direction from the first opening portion 331 to the second opening portion 332. The urea aqueous solution flowing through the communication ports 33 merges with the flow of air flowing through the second injection passage W22 in a direction along the air flow. Therefore, it is possible to increase the suction power for sucking the urea aqueous solution from the communication ports 33. However, the similar function and performance can be achieved even if the communication port 33 is arranged to be parallel to the axis line ml. Fifth embodiment

[0105] The fluid injection system 1 and the fluid injection device 10 of a fifth embodiment will be explained below with a focus on differences between the first embodiment and the fifth embodiment.

[0106] The fluid injection system 1 of the present embodiment differs from that of the first embodiment in that the fluid injection device 10 of the present embodiment injects a fuel into the exhaust passage of the engine instead of the aqueous urea solution. As shown in Fig. 11, the fluid injection device 10 injects the fuel into the exhaust passage to avoid a situation that a purification performance of an exhaust gas purification catalyst provided in the exhaust pipe is reduced.

[0107] Specifically, a NOx trap and a reduction catalyst are known in the art as exhaust gas purification catalysts for purifying nitrogen oxide (NOx) contained in the exhaust gas. The NOx trap and the reduction catalyst have a limit to their NOx-absorbing capacity. As a storage amount of NOx approaches its saturated level, the NOx-absorbing capacity is reduced. In the fluid injection system 1 of the present embodiment, fuel is injected from the fluid injection device 10 to temporarily enrich an air-fuel mixture disposed adjacent to the NOx trap and the reduction catalyst provided in the exhaust pipe of the vehicle. The trap and the reduction catalyst reduce the NOx absorbed in the catalyst, thereby preventing a reduction in the NOx-absorbing capacity.As above, the fluid injection device 10 is used as a fuel addition valve for adding the fuel to the exhaust gas in the exhaust pipe.

[0108] As in Fig. As shown in Fig. 11, the fluid injection system 1 of the present embodiment includes a sub-fuel tank 17 for storing fuel for the vehicle. The fuel (leakage fuel) flows from a common rail (not shown) of the vehicle into the sub-fuel tank 17 via a fuel pipe W40, and such fuel is temporarily stored therein. The fuel is returned to a main fuel tank (not shown) of the vehicle via a fuel pipe W41. In the present embodiment, the sub-fuel tank 17 corresponds to a liquid tank. The fluid injection device 10 of the present embodiment has the same structure as those of the preceding embodiments.

[0109] The fuel is supplied to the fluid injection device 10 from the sub-fuel tank 17. The fuel from the sub-fuel tank 17 is atomized in the fluid injection device 10 by the air supplied from the air pump 11, and such atomized fuel is injected from the fluid injection device 10. The fuel injected from the fluid injection device 10 is supplied to the NOx trap and the reduction catalyst provided in the exhaust pipe of the vehicle.

[0110] The pressure control section 150 controls the operation of the fluid injection device 10 so that it injects fuel at a predetermined frequency. The pressure control section 150 executes normal liquid injection control. After a predetermined amount of fuel is injected from the fluid injection device 10, the pressure control section 150 executes liquid discharge control so that the fuel remaining inside the fluid injection device 10 is returned to the sub-fuel tank 17. Thereafter, the pressure control section 150 executes liquid suction control when a next injection timing is reached. Then, after the liquid suction control, the pressure control section 150 executes normal liquid injection control so that the fuel is injected from the fluid injection device 10 into the exhaust pipe.

[0111] Since the operation of the fluid injection system 1 and the fluid injection device 10 of the present embodiment is the same as that of the first embodiment, its detailed explanation is omitted.

[0112] The fluid injection system 1 and the fluid injection device 10 of the present embodiment have the following additional advantages (A13) and (A14).

[0113] (A13) In a case where the fuel remains inside the fluid injection device 10, the fuel in the fluid injection device 10 may deteriorate due to the heat transferred to the fluid injection device 10 from the exhaust gas flowing through the exhaust pipe. However, in the present embodiment, the pressure control section 150 executes the liquid discharge control, and thereby the fuel remaining in the fluid injection device 10 is returned to the sub-fuel tank 17. Therefore, the fuel in the fluid injection device 10 does not have to deteriorate. This makes it possible to prevent a situation where the fuel may be deposited. In addition, it is possible to prevent a situation where the fuel may leak from the fluid injection device 10 to the exhaust pipe.

[0114] (A14) In the fluid injection system 1, the sub-fuel tank 17 is used as the fuel tank for supplying fuel to the fluid injection device 10, and the sub-fuel tank 17 stores the leaked fuel from the common rail. According to the above structure, it is possible to store the predetermined amount of fuel at a position adjacent to the fluid injection device 10. On the other hand, in a case where the sub-fuel tank is not provided and the fuel is directly supplied to the fluid injection device 10 from the main fuel tank of the vehicle, a distance between the fluid injection device 10 and the main fuel tank may become longer.

[0115] As the distance between the fluid injection device 10 and the main fuel tank becomes longer, flexibility for a layout of the related parts and components may be reduced, a time required to discharge the fuel from the fluid injection device 10 to the main fuel tank may become longer, a time required to supply the fuel to the fluid injection device 10 from the main fuel tank may become longer, and so on.

[0116] When the sub-fuel tank is located at the position closer to the fluid injection device 10, not only can the flexibility for the layout of the related parts and components be increased, but also the fuel discharge time and / or the fuel supply time for the fluid injection device 10 can be made shorter. Further embodiments and / or modifications

[0117] The above embodiments and modifications may be further modified in the following ways: (M1) In the fluid injection device 10 of the first to fourth embodiments, the check valve 50 may be provided on the outside of the fluid injection device 10. In a case where the air pump 11 has a structure for restricting a reverse flow, it is not necessary to provide the check valve 50. In this case, the air pump 11 serves as the flow restricting device for restricting the reverse flow of air. (M2) The structure of the gas supply unit for supplying air to the fluid injection device 10 is not limited to the air pump 11. It may be modified such that a high-pressure air tank capable of storing high-pressure air is connected to the fluid injection device 10 via an air pipe, and an on-off valve is provided in the air pipe. With such a modified structure, if a pressure reducing device can be provided in the air pipe, it becomes possible to regulate the pressure of the air to be supplied to the fluid injection device 10 by controlling an on-off operation of the pressure reducing device. According to such a modification, it becomes unnecessary to provide the air pump 11, and the structure for the gas supply unit can be simplified. (M3) A liquid pump may be further provided in the fluid injection system, according to which the urea aqueous solution of the liquid tank 12 or the fuel of the sub-fuel tank 17 is pumped out by the liquid pump and supplied to the fluid injection device 10. With such a modification, the liquid (the urea aqueous solution or the fuel) can be returned to the liquid tank 12 (or the sub-fuel tank 17) by the liquid pump if the liquid pump has a function to allow the reverse flow. According to the above structure, since the liquid suction control and the liquid discharge control can be performed by the liquid pump, it becomes unnecessary to regulate the pumping pressure of the air from the air pump 11. On the other hand, in a case where the liquid pump does not have the reverse flow function, the liquid (the urea aqueous solution or the fuel) can be returned from the fluid injection device 10 to the liquid tank 12 (or the sub-fuel tank 17) by the operation of the air pump 11. According to the above structure and operation, it becomes possible for the liquid pump to perform the control for supplying the liquid (the urea aqueous solution or the fuel) from the liquid tank 12 (or the sub-fuel tank 17) to the fluid injection device 10. (M4) The operation and control of the control unit 15 may be performed by one or a plurality of dedicated computers comprising a processor and a memory device, the processor being programmed to perform one or more functions. Alternatively, the operation and control of the control unit 15 may be performed by a dedicated computer comprising a processor including one or a plurality of hardware logic circuits. Furthermore, the operation and control of the control unit 15 may be performed by one or a plurality of dedicated computers structured by a combination of a processor and a memory device programmed to perform one or more functions, and a processor including one or more hardware logic circuits.The computer program may be stored as an instruction to be executed by the computer in a machine-readable and non-volatile memory device. The dedicated hardware logic circuit or the hardware logic circuit may be structured by digital circuits and / or analog circuits that include logic circuits.

[0118] The present embodiment is not limited to the above embodiments or modifications, but can be further modified in various ways without departing from a spirit of the present disclosure.

Claims

[1] Fluid injection device (10), comprising: a valve body (20) having a cylindrical shape; a valve element (30) movably housed in the valve body (20) and having a valve surface portion (35a) operatively abutting or separated from the valve seat portion (23a) formed in an interior of the valve body (20), an annular fluid passage (W11, W21, W22) formed between an inner peripheral surface of the valve body (20) and an outer peripheral surface of the valve element (30), through which gas flows, wherein the valve element (30) includes the following; - an inside passage (31) formed in an interior of the valve element (30) and extending in an axial direction of the valve element (30), through which liquid flows; and - a communication port (33) for connecting the inside passage with the annular fluid passage (W11, W21, W22), wherein the communication port (33) is opened on the outer peripheral surface of the valve element (30) at a position which is located on an upstream side of the valve surface portion (35a) in a flow direction of the gas flowing along the axial direction of the valve element (30) through the annular fluid passage (W11, W21, W22), wherein the liquid is supplied to the annular fluid passage (W11, W21, W22) from the inside passage (31) through the communication port (33), and the liquid supplied to the annular fluid passage (W11, W21, W22) from the communication port (33) is injected together with the gas flowing through the annular fluid passage (W11, W21, W22) when the valve element (30) is in a valve opening position, wherein the injection of the liquid and the gas is terminated when the valve surface portion (35a) abuts the valve seat portion (23a) to close the annular fluid passage (W11, W21, W22), wherein a cross-sectional passage area of a connecting passage section (C10) is smaller than a cross-sectional passage area of a passage section (C20) on the upstream side, wherein the connecting passage portion (C10) is a portion of the annular fluid passage (W11) at which the communication port (33) is connected to the annular fluid passage (W11), and wherein the upstream side passage portion (C20) is another portion of the annular fluid passage (W11) located on an upstream side of the connecting passage portion (C10). [2] The fluid injection device (10) according to claim 1, wherein the communication port (33) is opened on the outer peripheral surface of the valve element (30) at a position located adjacent to the valve surface portion (35a). [3] Fluid injection device (10) according to claim 1, wherein the valve element (30) has an outwardly extended portion (36) formed in a cylindrical shape having a center point on an axis line (ml) of the valve element (30), the inside passage (31) is formed in an interior of the outwardly extended portion (36), and the communication port (33) extends from the inside passage to an outer peripheral surface of the outwardly extended portion (36). [4] Fluid injection device (10) according to claim 1, wherein the communication port (33) extends from the inside passage to the outer peripheral surface of the valve element (30) such that; the communication port (33) is parallel to an axis line (ml) of the valve element (30), or the communication port (33) is arranged inclined with respect to the axis line and approaches the axis line in the axial direction from the inside passage (31) to the outer peripheral surface. [5] Fluid injection device (10) according to one of claims 1 to 4, wherein a spiral groove (39) is formed on the outer peripheral surface of the valve element (30) such that; the spiral groove (39) extends in an axial line (ml) of the valve element (30) from an upstream side to a downstream side, and the spiral groove (39) has a spiral center point on the axis line (ml) of the valve element (30). [6] Fluid injection device (10) according to one of claims 1 to 5, wherein a plurality of communication ports (33) are formed in the valve element (30), an annular groove (34) is formed on the outer peripheral surface of the valve element (30), and respective ends of the communication port (33) opened on the outer peripheral surface of the valve element (30) are connected to each other via the annular groove (34). [7] Fluid injection device (10) according to one of claims 1 to 6, wherein a biasing element (40) is provided in the valve body (20) to bias the valve element in the axial direction to its valve closing position, a pressure-receiving surface (35b, 38b, 320) is formed in the valve element to receive a pressure of the gas in the annular fluid passage (W11, W21, W22) so that the valve element (30) is pressed in the axial direction to its valve opening position, and the valve element (30) is moved to the valve closing position by a biasing force of the biasing element (40), or the valve element (30) is moved to the valve opening position by a pressing force of the gas exerted on the pressure receiving surface (35b, 38b, 320) against the biasing force. [8] The fluid injection device (10) according to any one of claims 1 to 7, wherein a flow restriction unit (50) is provided in the valve body (20) to restrict a flow of the gas in a reverse direction from a downstream side to an upstream side. [9] Fluid injection system, comprising; the fluid injection device (10) according to one of claims 1 to 8; a gas supply unit (11, 16, 18) for supplying the gas to the fluid injection device (10); and a pressure control section (150) for controlling an operation of the gas supply unit to regulate the pressure of the gas to be supplied to the fluid injection device (10). [10] Fluid injection system according to claim 9, wherein the valve element (30) is moved to the valve opening position when the pressure of the gas in the annular fluid passage (W11, W21, W22) becomes higher than a predetermined value, and the pressure control section (150) carries out a liquid discharge control while the valve element is in the valve closing position, according to which - a gas supply unit (11, 16, 18) is controlled so that the gas having a pressure lower than the predetermined value is supplied to the fluid injection device, - the gas flowing in the annular fluid passage (W11, W21, W22) is supplied to the communication port (33) and the inside passage (31), and - the liquid is discharged from the communication port (33) and the inside passage (31) to an externally arranged liquid tank (12, 17) which is located on an outer side of the fluid injection device (10). [11] The fluid injection system of claim 10, further comprising; a flow rate detecting section (152) for detecting a flow rate of the gas supplied to the fluid injection device (10), wherein the pressure control section (150) determines during the liquid discharge control that the gas has reached the externally arranged liquid tank (12, 17) when the pressure control section (150) detects that the flow rate of the gas detected by the flow rate detecting section (152) is increased, and the pressure control section (150) terminates the liquid discharge control when it determines that the gas has reached the externally arranged liquid tank (12, 17). [12] The fluid injection system of claim 10, further comprising; a pump-out pressure detecting section (153) for detecting a pump-out pressure of the gas supply unit (11) for the gas to be supplied to the fluid injection device (10), wherein the pressure control section (150) determines during the liquid discharge control that the gas has reached the externally arranged liquid tank (12, 17) when the pump-out pressure for the gas detected by the pump-out pressure detecting section is increased, and the pressure control section (150) terminates the liquid discharge control when it determines that the gas has reached the externally arranged liquid tank (12, 17). [13] Fluid injection system according to claim 9, wherein the valve element is moved to the valve opening position when the pressure of the gas in the annular fluid passage (W11, W21, W22) becomes higher than a predetermined value, and the pressure control section (150) executes a liquid suction control when a liquid injection operation of the fluid injection device (10) is started and when the inside passage (31) and the communication port (33) of the fluid injection device (10) are not filled with the liquid, that; - a gas supply unit (11, 16, 18) is controlled to supply the fluid injection device (10) with the gas having a pressure higher than the predetermined value, - a negative pressure is generated in the annular fluid passage (W11, W21, W22) at an opening portion at which the communication port (33) is opened to the annular fluid passage (W11, W21, W22), and - the liquid is sucked from an externally arranged liquid tank (12, 17) to the annular fluid passage (W11, W21, W22) at the opening portion at which the communication port (33) to the annular fluid passage (W11, W21, W22) is opened. [14] The fluid injection system of claim 13, further comprising; a flow rate detecting section (152) for detecting a flow rate of the gas supplied to the fluid injection device (10), wherein the pressure control section (150) determines during the liquid suction control that the liquid has reached the opening section of the communication port (33) when the pressure control section (150) detects that the flow rate of the gas detected by the flow rate detecting section (152) is reduced, the pressure control section (150) terminates the liquid suction control when it determines that the liquid has reached the opening section of the communication port (33), and the pressure control section (150) determines that preparation for injecting the gas and the liquid is completed. [15] The fluid injection system of claim 13, further comprising; a pump-out pressure detecting section (153) for detecting a pump-out pressure of the gas supply unit (11) for the gas to be supplied to the fluid injection device (10), wherein the pressure control section (150) determines during the liquid suction control that the liquid has reached the opening section of the communication port (33) when the pumping pressure for the gas detected by the pumping pressure detecting section is reduced, the pressure control section (150) terminates the liquid suction control when it determines that the liquid has reached the opening section of the communication port (33), and the pressure control section (150) determines that preparation for injecting the gas and the liquid is completed. [16] Fluid injection system according to one of claims 9 to 15, wherein an aqueous urea solution is used as the liquid to be injected from the fluid injection device (10), Air is used as the gas to be supplied to the fluid injection device (10), and the fluid injection device (10) is composed of an addition valve for adding the aqueous urea solution to the exhaust gas passing through an exhaust pipe of a vehicle. [17] Fluid injection system according to one of claims 9 to 15, further comprising; a secondary fuel tank (17) provided in a fuel pipe connecting a common rail to a main fuel tank, wherein the leakage fuel is returned from the common rail through the fuel pipe to the main fuel tank and the leakage fuel is temporarily stored in the secondary fuel tank (17), the fuel stored in the secondary fuel tank (17) is used as the liquid to be injected from the fluid injection device (10), Air is used as the gas to be supplied to the fluid injection device (10), and the fluid injection device (10) is composed of an addition valve for adding the fuel to the exhaust gas passing through an exhaust pipe of a vehicle. [18] Fluid injection device (10), comprising; a valve body (20) having a cylindrical shape and having a cylindrical accommodation space (21, 22) and an injection port (24) at its axial front end, the valve body (20) having a valve seat portion (23a) around the injection port (24); a valve element (30) movably housed in the cylindrical accommodation space (21, 22) and having a valve surface portion (35a) at its front end, wherein the valve surface portion (35a) operatively abuts against the valve seat portion (23a) of the valve body (20) when the valve element (30) is in a valve-closing position, while the valve surface portion (35a) is operatively separated from the valve seat portion (23a) of the valve body (20) when the valve element (30) is in a valve-opening position, and wherein the valve element (30) has an inside passage (31) extending in the axial direction and a communication port (33) for connecting the inside passage (31) to an outside of the valve element (30), so that the fluid can flow through the inside passage (31) and the communication port (33) to the outside of the valve element (30) flows,when the valve element (30) is in the valve opening position;, an annular fluid passage (W11, W21, W22) formed between an inner peripheral surface of the valve body (20) and an outer peripheral surface of the valve element (30), such that the annular fluid passage (W11, W21, W22) communicates with the inside passage (31) of the valve element (30) through the communication port (33), wherein gas flows in the axial direction through the annular fluid passage (W11, W21, W22) to the injection port (24) when the valve element (30) is in the valve opening position, wherein one end of the communication port (33) is opened to the annular fluid passage (W11, W22) at a position located on an upstream side of the valve surface portion (35a) in a flow direction of the gas flowing along the axial direction of the valve element (30), wherein the liquid supplied to the annular fluid passage (W11, W22) through the communication port (33) is injected together with the gas flowing through the annular fluid passage (W11, W22) from the injection port (24) when the valve element is in the valve opening position, and injection of the liquid and the gas is terminated when the valve element is moved to the valve closing position, wherein a cross-sectional passage area of a connecting passage portion (C10) of the annular fluid passage (W11, W22) is smaller than a cross-sectional passage area of a passage portion (C20) on the upstream side of the annular fluid passage (W11, W22), wherein the connecting passage portion (C10) is a portion of the annular fluid passage (W11, W22) at which the communication port (33) is connected to the annular fluid passage, and wherein the upstream side passage portion (C20) is another portion of the annular fluid passage (W11, W22) located on an upstream side of the connecting passage portion. [19] A method of operating the fluid injection device (10) according to claim 18, comprising; a step of executing liquid suction control in a state in which the valve element (30) is in the valve opening position such that; - the gas having a pressure of a first preset value is supplied to the fluid injection device (10) from a gas supply unit (11, 16, 18) so that the gas is injected through the injection port (24), thereby generating a negative pressure in the connecting passage portion (C10), and - the liquid is sucked by the negative pressure from a liquid tank (12, 17) located on an outside of the fluid injection device (10) to the communication port (33), so that an injection of the liquid is prepared; a step of executing liquid injection control such that; - the gas having the pressure of the first preset value is supplied to the fluid injection device (10), - the liquid is sucked by the gas having the pressure with the first preset value from the communication port (33) to the annular fluid passage (W11), and - the liquid is injected together with the gas from the injection port (24); a step of executing a liquid discharge control when an injection operation of the fluid injection device (10) is stopped such that; - the gas having a pressure with a second preset value is supplied to the fluid injection device (10) from the gas supply unit (11, 16, 18), wherein the second preset value is lower than the first preset value, and wherein the valve element is not moved to the valve opening position by the gas having the pressure with the second preset value, and - the liquid remaining in the fluid injection device (10) is returned to the liquid tank (12, 17) by the gas having the pressure of the second preset value; and a step of executing a gas supply termination control such that a gas supply from the gas supply unit (11, 16, 18) to the fluid injection device (10) is terminated after the liquid discharge control.

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