Reducing agent supply device, reducing agent supply device control method, and control device

Abstract

A reducing agent supply device is provided with: a tank for storing a reducing agent to be supplied into an exhaust pipe of an engine; a pressure feed mechanism for pressure-feeding the reducing agent in the tank; a reducing agent supply passage for supplying the pressure-fed reducing agent; a nozzle that injects the reducing agent supplied by the reducing agent supply passage into the exhaust pipe; a back-suction mechanism that sucks back the reducing agent in the reducing agent supply passage to the tank side; and a control device that controls the operation of the pressure feed mechanism, the nozzle, and the suction-back mechanism, and that repeatedly opens and closes the nozzle at a prescribed cycle while the suction-back mechanism is being operated.

Description

Technical Field

[0001] The present disclosure relates to a reducing agent supply device, a control method for the reducing agent supply device, and a control device.

[0002] This application claims priority based on Japanese Patent Application No. 2022-140701 filed in Japan on September 5, 2022, the contents of which are incorporated herein by reference. Background Art

[0003] Patent document 1 discloses a reducing agent supply device. In order to prevent urea water from sticking in a urea injection device, a high-pressure gas is filled in a path between the urea water injection device and a pump, and the urea water remaining in the urea water injection device is blown away and removed by releasing the compressed gas. In the reducing agent supply device described in Patent document 1, it is necessary to close the valve of the urea water injection device before the compressed gas is released and urea water is supplied to the urea water injection device. In the reducing agent supply device described in Patent document 1, control is performed such as opening and closing the valve at a preset timing or opening and closing the valve when the pressure in the path reaches a preset value.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2016 / 092665 (Patent No. 6564393) Summary of the invention

[0007] Problems to be solved by the invention

[0008] In the reducing agent supply device described in Patent Document 1, adhesion of urea water in the urea injection device can be prevented by pressure fluctuations. However, precise control of the opening and closing of the valve based on timing or pressure is required.

[0009] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a reducing agent supply device, a control method of the reducing agent supply device, and a control device that can prevent adhesion of urea water in a urea injection device through simple control.

[0010] Technical solutions to solve problems

[0011] One embodiment of the present disclosure provides a reducing agent supply device, which includes: a tank that stores the reducing agent supplied to the exhaust pipe of the engine; a pressure-feeding mechanism that pressure-feeds the reducing agent in the tank; a reducing agent supply passage that supplies the pressure-feeding reducing agent; a nozzle that sprays the reducing agent supplied by the reducing agent supply passage into the exhaust pipe; a back-suction mechanism that sucks the reducing agent in the reducing agent supply passage back to the tank side; and a control device that controls the operation of the pressure-feeding mechanism, the nozzle, and the back-suction mechanism, and the control device repeatedly opens and closes the nozzle at a specified period while the back-suction mechanism is in operation.

[0012] One aspect of the present disclosure provides a control method for a reducing agent supply device, wherein the reducing agent supply device comprises: a tank that stores the reducing agent to be supplied to an exhaust pipe of an engine; a pressure-feeding mechanism that pressure-feeds the reducing agent in the tank; a reducing agent supply passage that supplies the pressure-feeding reducing agent; a nozzle that sprays the reducing agent supplied by the reducing agent supply passage into the exhaust pipe; a back-suction mechanism that back-suctions the reducing agent in the reducing agent supply passage to the tank side; and a control device that controls the operation of the pressure-feeding mechanism, the nozzle, and the back-suction mechanism, wherein the control method includes the step of repeatedly opening and closing the nozzle at a specified period while the back-suction mechanism is in operation.

[0013] One embodiment of the present disclosure provides a control device, wherein the reducing agent supply device comprises: a tank that stores the reducing agent supplied to the exhaust pipe of the engine; a pressure-feeding mechanism that pressure-feeds the reducing agent in the tank; a reducing agent supply passage that supplies the pressure-feeding reducing agent; a nozzle that sprays the reducing agent supplied by the reducing agent supply passage into the exhaust pipe; and a suction mechanism that sucks the reducing agent in the reducing agent supply passage back to the tank side, wherein the control device controls the operation of the pressure-feeding mechanism, the nozzle and the suction mechanism in the reducing agent supply device, wherein the nozzle is repeatedly opened and closed at a specified period while the suction mechanism is in operation.

[0014] Effects of the Invention

[0015] According to each aspect of the present disclosure, it is possible to prevent the urea water in the urea injection device from adhering by simple control. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 1 is a structural diagram showing a structural example of an exhaust gas post-treatment device including the reducing agent supply device according to the embodiment of the present disclosure.

[0017] Figure 21 is a structural diagram showing a structural example of an exhaust gas post-treatment device including the reducing agent supply device according to the embodiment of the present disclosure.

[0018] Figure 3 It is a diagram showing the structure of a nozzle in the reducing agent supply device.

[0019] Figure 4 It is a diagram showing the structure of a nozzle in the reducing agent supply device.

[0020] Figure 5 It is a diagram showing the structure of a nozzle in the reducing agent supply device.

[0021] Figure 6 It is a block diagram showing a configuration example of a control device according to an embodiment of the present disclosure.

[0022] Figure 7 This is a flowchart showing an operation example of the reducing agent supply device according to the embodiment of the present disclosure.

[0023] Figure 8 It is a timing chart showing an operation example of the reducing agent supply device according to the embodiment of the present disclosure. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Figure 1 and Figure 2 1 is a structural diagram showing a structural example of an exhaust gas post-treatment device including the reducing agent supply device according to the embodiment of the present disclosure. Figure 3 to Figure 5 It is a diagram showing the structure of a nozzle in the reducing agent supply device. Figure 6 It is a block diagram showing a configuration example of a control device according to an embodiment of the present disclosure. Figure 7 This is a flowchart showing an operation example of the reducing agent supply device according to the embodiment of the present disclosure. Figure 8 It is a timing chart showing an operation example of the reducing agent supply device according to the embodiment of the present disclosure. It should be noted that in each figure, the same reference numerals are used for the same or corresponding structures, and the description thereof is appropriately omitted.

[0025] [Schematic structure of exhaust gas purification device]

[0026] Figure 1 and Figure 2The schematic diagram shows the general structure of an engineering vehicle 1 equipped with the exhaust gas purification device 10 of the present embodiment. Here, the engineering vehicle 1 is, for example, an engineering machine that performs excavation, land leveling and other operations or transports sand and soil at construction sites such as mines or roads, and is equivalent to, for example, construction machinery such as hydraulic excavators, wheel loaders, bulldozers, motor graders, cranes, and transport vehicles such as dump trucks and forklifts. It should be noted that the exhaust gas purification device 10 of the present embodiment is a device for purifying the exhaust gas of a diesel engine, so it is not limited to the engineering vehicle 1, and can also be used for various vehicles or equipment equipped with an engine. The engineering vehicle 1 is equipped with a diesel engine 2 (hereinafter also referred to as the engine), a turbocharger 3 that utilizes the exhaust gas of the diesel engine 2 to rotate a turbine to compress the air supplied to the diesel engine 2, a control device 8, a monitor 9, and an exhaust gas purification device 10. It should be noted that, Figure 1 and Figure 2 Indicates that the directional switching valve 42 (also referred to as the pump internal directional switching valve) described later is in the drive OFF (disconnected) state ( Figure 1 ) and the drive ON state ( Figure 2 ), the direction of flow of the urea water 7 is indicated by arrow u.

[0027] The diesel engine 2 is provided with an engine speed detection device 6 for detecting the engine speed and a fuel injection device (not shown) for injecting fuel into the engine 2. The detection data of the engine speed detection device 6 is output to the control device 8. The control device 8 controls the fuel injection device (not shown) according to the accelerator operation and the like.

[0028] [Monitor]

[0029] The monitor 9 includes a display unit and an input unit. The display unit is composed of a liquid crystal display, etc. The display unit displays various information such as cooling water temperature and remaining fuel amount, warnings, etc.

[0030] [Exhaust gas purification device]

[0031] The exhaust gas purification device 10 performs processing such as capturing or reducing residual substances such as particulate matter (Particulate Matter; hereinafter referred to as "PM") and NOx (nitrogen oxides) in the exhaust gas, and is controlled by the control device 8. The exhaust gas purification device 10 is equipped with a fuel injection device 172, a DPF device 171, a reducing agent supply device 4, and a selective reduction catalyst (hereinafter referred to as "SCR") device 175 in order from the upstream side of the flow direction of the exhaust gas discharged from the diesel engine 2. The DPF device 171 is equipped with a diesel oxidation catalyst (Diesel Oxidation Catalyst; hereinafter referred to as "DOC") device 30 and a DPF (Diesel Particulate Filter: diesel particulate filter) 170. These DPF device 171, the reducing agent supply device 4, and the SCR device 175 are arranged in the middle of the path 11 where the exhaust gas from the diesel engine 2 flows. The path 11 includes an inlet pipe 12 for introducing the exhaust gas from the turbocharger 3 connected to the diesel engine 2 into the DPF device 171, an outlet pipe 13 for connecting the DPF device 171 and the SCR device 175, and an outlet pipe 14 connected to the outlet of the SCR device 175. In addition, the outlet pipe 13 includes a mechanism for diffusing urea water supplied from the reducing agent supply device 4. The path 11 corresponds to the exhaust pipe of the engine 2 of the present disclosure.

[0032] [DPF device]

[0033] The DPF device 171 includes the DOC device 30 and the DPF 170 . The DPF 170 captures PM, and the PM captured downstream is oxidized into carbon dioxide using nitrogen dioxide converted by the DOC device 30 , thereby removing the PM.

[0034] [DOC device]

[0035] The DOC device 30 includes a housing, and a diesel oxidation catalyst is accommodated inside the housing. The DOC device 30 is a catalyst that oxidizes the fuel (hereinafter referred to as metered fuel. In addition, the supplied metered fuel is referred to as fuel metering) supplied to the exhaust gas as needed, generates heat, and raises the exhaust gas temperature to a predetermined high temperature range. By utilizing the exhaust gas with the increased temperature, urea deposits accumulated on the outlet pipe 13, etc., which will be described later, are decomposed and removed, and regenerated. The metered fuel is, for example, the same light oil as the engine fuel. When the metered fuel is supplied to the engine cylinder, the metered fuel is supplied by post-injection using a fuel injection device for injection into the engine cylinder. In addition, in the present embodiment, by means of a metered fuel injection device 172 provided on the inlet pipe 12, fuel can be supplied to the exhaust gas so that it flows into the DOC device 30 together with the exhaust gas.

[0036] [Reducing agent supply device]

[0037] The reducing agent supply device 4 is a device that sprays urea water 7 as a reducing agent aqueous solution into the exhaust gas, and includes a pump unit 40 that pressurizes the urea water 7, a tank 50 that stores the urea water 7, a nozzle 60 that sprays the urea water 7 into the path 11 (outlet pipe 13), and a reducing agent supply passage 70 through which the urea water 7 supplied from the tank 50 to the nozzle 60 by the pump unit 40 flows. It should be noted that the reducing agent supply device 4 may include the control device 8, or may not include the control device 8.

[0038] [Pump unit]

[0039] The pump unit 40 includes a pump 41 for pressurizing the urea water 7, a direction switching valve 42, a pressure gauge 43, a check valve 44, and an orifice 46. The pump unit 40 includes three ports 451, 452, and 453. The port 451 is an inlet port of the pump unit 40, and the port 451 and the direction switching valve 42 are connected by a first passage 471. The port 452 is an outlet port of the pump unit 40, and the direction switching valve 42 and the port 452 are connected by a second passage 472. The port 453 is a return port for returning the urea water 7 to the tank 50, and the port 453 is connected to a third passage 473 branched from the second passage 472. A filter 461 for the pump inlet is provided on the port 451 to prevent foreign matter from entering the pump 41. A filter 462 is provided in the middle of the second passage 472 to prevent foreign matter from flowing out. A filter 463, a check valve 44, and an orifice 46 are provided on the port 453. The pressure gauge 43 is disposed in the third passage 473. Since the third passage 473 communicates with the second passage 472, the pressure gauge 43 detects the system pressure P of the second passage 472 and the second reducing agent supply passage 72.

[0040] [Reducing agent supply passage]

[0041] The tank 50 and the port 451 are connected by a first reducing agent supply passage 71. The port 452 and the nozzle 60 are connected by a second reducing agent supply passage 72. Therefore, the first reducing agent supply passage 71 and the second reducing agent supply passage 72 constitute the reducing agent supply passage 70 for supplying urea water 7 as a reducing agent from the tank 50 to the nozzle 60. In addition, the port 453 and the tank 50 are connected by a bypass passage 73. Moreover, the first reducing agent supply passage 71, the second reducing agent supply passage 72, and the bypass passage 73 are specifically constituted by hoses.

[0042] The end of the first reducing agent supply passage 71 on the tank 50 side is arranged near the bottom surface of the tank 50 so as to be able to suck the urea water 7. In addition, a tank suction port filter 75 is provided at the end of the first reducing agent supply passage 71 to prevent foreign matter from being sucked into the reducing agent supply passage 70. The end of the bypass passage 73 on the tank 50 side is arranged at a position higher than the liquid level of the urea water 7 in the tank 50. Furthermore, a ventilator or the like is provided in the tank 50 for maintaining the internal pressure at atmospheric pressure.

[0043] [Pump]

[0044] The pump 41 is typically an electric pump, and is driven and controlled by the control device 8 . The inlet-side passage 411 and the outlet-side passage 412 of the pump 41 are connected to the direction switching valve 42 .

[0045] [Directional switching valve]

[0046] The direction switching valve 42 switches the direction of the urea water 7 pumped by the pump 41 to the downstream direction from the tank 50 toward the nozzle 60 according to the control signal from the control device 8. Figure 1 ) and the reverse flow direction from the nozzle 60 toward the tank 50 ( Figure 2 ) electromagnetic directional control valve. Figure 1 As shown, when the control signal is not output from the control device 8 and the solenoid is not energized, the direction switching valve 42 connects the first passage 471 with the inlet side passage 411 and connects the second passage 472 with the outlet side passage 412, and sets the flow direction of the urea water 7 to the downstream direction. In this case, when the pump 41 is operated, the urea water 7 is sucked from the first reducing agent supply passage 71 to the inlet side passage 411 via the first passage 471, and the urea water 7 is discharged from the outlet side passage 412 to the second reducing agent supply passage 72 via the second passage 472. Therefore, the pump 41 and the direction switching valve 42 set to the downstream direction constitute the pressure feeding mechanism of the present disclosure.

[0047] On the other hand, Figure 2 As shown, when the control signal is output from the control device 8 to energize the solenoid, the direction switching valve 42 connects the first passage 471 with the outlet side passage 412 and connects the second passage 472 with the inlet side passage 411, and switches the flow direction of the urea water 7 to the reverse flow direction. In this case, when the pump 41 is operated, the urea water 7 is sucked from the second reducing agent supply passage 72 to the inlet side passage 411 via the second passage 472, and the urea water 7 is returned from the outlet side passage 412 to the tank 50 side via the first passage 471 and the first reducing agent supply passage 71. Therefore, the pump 41 and the direction switching valve 42 set to the reverse flow direction constitute the back suction mechanism of the present disclosure.

[0048] It should be noted that the structure for switching the flow direction of the urea water 7 is not limited to the structure using the direction switching valve 42 as in the present embodiment. For example, two pumps may be provided to share the discharge and the back-suction. In this case, the urea water 7 is sprayed in the downstream direction by operating the ejection pump and stopping the back-suction pump, and the urea water 7 is back-suctioned in the upstream direction by stopping the ejection pump and operating the back-suction pump.

[0049] [nozzle]

[0050] The nozzle 60 is controlled by the control device 8 to be driven on (energized) or driven off (non-energized) to inject the urea water 7 pumped by the pump 41 into the path 11 (outlet pipe 13) (hereinafter, the nozzle 60 is also referred to as the urea injection device). Figure 3 and Figure 4 As shown, the needle valve 62 disposed axially movably in the housing 61 is moved forward and backward relative to the valve seat 64 communicating with the injection hole 63 by using an electromagnet 65 and a spring 66 to control the valve opening and closing states. Figure 4 As shown in FIG. 1 , when a control signal is output from the control device 8 and the electromagnet 65 is energized, the needle valve 62 is separated from the valve seat 64 by the magnetic force generated by the electromagnet 65, and the urea water 7 inside the needle valve 62 flows between the needle valve 62 and the valve seat 64, and the nozzle 60 is in an open valve state capable of injecting the urea water 7 from the injection hole 63. Figure 3 As shown in FIG. 1 , when the control signal is not output from the control device 8 and the electromagnet 65 is not energized, the needle valve 62 abuts against the valve seat 64 by the spring 66 and the pressure of the urea water 7, and the nozzle 60 is in a closed valve state where the urea water cannot be injected from the injection hole 63. In addition, the nozzle 60 is in an open valve state, and the urea water 7 injected into the exhaust pipe 11 from the injection hole 63 is hydrolyzed by the heat of the exhaust gas to become ammonia, and the nitrogen oxides are reduced and purified by the SCR 31.

[0051] [SCR device]

[0052] The SCR device 175 uses ammonia obtained by decomposing the urea water 7 injected from the reducing agent supply device 4 into the exhaust gas as a reducing agent to reduce and purify nitrogen oxides (NOx) in the exhaust gas. It should be noted that the SCR device 175 is provided with various sensors omitted in the figure, such as the temperature sensor 51 for measuring the outlet temperature of the SCR device 175, the temperature sensor not shown for measuring the inlet temperature of the SCR device 175, and the ammonia sensor for measuring the ammonia concentration. However, some of these sensors can be omitted. The measurement data of each of these sensors is output to the control device 8, and the control device 8 controls the reducing agent supply device 4 to perform the spray control of the urea water based on each measurement data. When the urea water 7 is injected from the nozzle 60, urea may crystallize and precipitate in the outlet pipe 13. Therefore, it is necessary to perform a regeneration process by making the exhaust gas temperature high to decompose the precipitate (urea deposit) in the outlet pipe 13. As the regeneration process, there are, for example, automatic regeneration control automatically performed when the engineering vehicle is working and fixed manual regeneration performed by manual operation of the operator, which are switched and selected and controlled by the control device 8.

[0053] [Example of adhesion of urea water]

[0054] The urea water 7 freezes below a certain temperature. Therefore, in order to avoid damage to the reducing agent supply device 4 (the nozzle (urea water injection device) 60, the pump 41, the first reducing agent supply passage 71, the second reducing agent supply passage 72 and other hoses) due to expansion when freezing, it is necessary to implement control to return the urea water 7 between the tank 50 and the nozzle 60 to the tank 50 after the engine 2 stops (hereinafter referred to as urea water return control). In the urea water return control, in particular, since the flow path in the nozzle 60 forms a complex shape, the urea water 7 may not be completely recovered and the urea water 7 may remain in the nozzle 60. In addition, if Figure 5 As shown, in the urea water return control, since the exhaust gas e from the outlet pipe 13 flows into the housing 61 from the injection hole 63 during the back suction of the urea water 7, the urea water 7 changes into crystals C1 between the needle valve 62 and the valve seat 64, or changes into crystals C2 in the gap between the needle valve 62 and the housing 61. Crystals C1, C2, etc. may cause blockage in the flow path of the urea water 7. If blockage occurs, the nozzle 60 may not be able to inject the urea water 7 until the blockage is eliminated. Although the blockage can be eliminated by the above-mentioned regeneration process, the regeneration process is accompanied by the deterioration of the fuel efficiency and the generation of a notification in the monitor 9. Therefore, it is desirable to prevent the blockage regardless of the regeneration process. Therefore, in the present embodiment, as described later, during the urea water return control, control is performed to prevent the generation of crystals C1 between the needle valve 62 and the valve seat 64 or crystals C2 in the housing 61.

[0055] [sensor]

[0056] Various sensors for detecting the conditions of the diesel engine 2 and the exhaust gas purification device 10 are provided in the exhaust gas purification device 10. That is, a NOx sensor (not shown) for detecting the concentration of nitrogen oxides (NOx) contained in the exhaust gas is arranged at the inlet pipe 12 or the inlet or outlet of the DPF device 171, the outlet pipe 13, the inlet of the SCR device 175, etc. An inlet temperature sensor 31 for measuring the inlet temperature of the DOC device 30, an outlet temperature sensor 45 for measuring the outlet temperature of the DOC device 30, and an outlet temperature sensor 174 for measuring the outlet temperature of the DPF 170 are arranged in the DPF device 171. An SCR outlet temperature sensor 51 for measuring the outlet temperature of the SCR device 175 as described above is provided in the SCR device 175. A NOx sensor 52 for detecting the concentration of nitrogen oxides contained in the exhaust gas discharged from the SCR device 175 is arranged on the outlet pipe 14 connected to the SCR device 175. These sensors are connected to the control device 8 via a Controller Area Network (CAN) 18 , and output measurement data to the control device 8 .

[0057] [Control device]

[0058] Next, the structure of the control device 8 is described. The control device 8 can be formed by using a computer such as a microcomputer, and is a functional structure composed of a combination of hardware such as a computer, peripheral circuits, and peripheral devices, and software such as a program executed by the computer. Figure 6 As shown, a data acquisition unit 81 and a reducing agent supply device control unit 82 are provided.

[0059] [Data Acquisition Department]

[0060] The data acquisition unit 81 repeatedly acquires measurement data of sensors such as the engine speed detection device 6 , the inlet temperature sensor 31 , the outlet temperature sensor 45 , the NOx sensor 52 , and the pressure gauge 43 at a predetermined cycle.

[0061] [Reducing agent supply device control unit]

[0062] The reducing agent supply device control unit 82 outputs control signals to the pump 41, the direction switching valve 42, and the nozzle 60 to control their operations. That is, the reducing agent supply device control unit 82 maintains the pressure in the second passage 472 and the second reducing agent supply passage 72 at a specified value by performing feedback control on the pump 41 based on the pressure value detected by the pressure gauge 43 during the operation of the engine 2. Specifically, the control unit 8 reduces the discharge amount of the pump 41 when the pressure value detected by the pressure gauge 43 is higher than a preset specified value when the urea water 7 is pumped by the pump 41, and increases the discharge amount of the pump 41 when the pressure value is lower than the specified value, thereby maintaining the pressure in the second passage 472 and the second reducing agent supply passage 72 at a specified value.

[0063] In addition, the reducing agent supply device control unit 82 controls the driving of the nozzle 60 based on the rotation speed of the engine 2, the sensor value of the NOx sensor 52 provided on the exhaust gas downstream side of the SCR device 175, etc. Furthermore, the control device 8 performs control to remove the urea water 7 from the nozzle 60, that is, urea water return control when the engine 2 is stopped.

[0064] [Urea water return control]

[0065] Reference Figure 7 and Figure 8 , the urea water return control is explained. It should be noted that, Figure 8 The horizontal axis is the time axis, showing an example of the time change of the operating state (ON or OFF driving state) of the pump 41, the direction switching valve 42 and the nozzle 60 and the state of the reducing agent supply passage 70 such as the second reducing agent supply passage 72. Figure 7 As shown, when the operator turns off the start key of the engine 2, the reducing agent supply device control unit 82 determines "YES" in step S101 and waits for a certain time (threshold T hours) (after repeatedly "NO" in step S102, it is "YES" in step S102). The waiting time in step S102 is for lowering the temperature of the DOC 30 to a certain extent after the engine stops. For example, the threshold T is determined using a table showing the correspondence between temperature and waiting time.

[0066] The time when "YES" is determined in step S102 is the start time of the urea water return control. The reducing agent supply device control unit 82 first drives the pump 41 and drives the direction switching valve 42 (step S103, Figure 8 It should be noted that at time t0, the nozzle 60 is in a driving OFF state.

[0067] Next, the reducing agent supply device control unit 82 waits for a predetermined time T1 ("NO" is repeatedly answered in step S104 and "YES" is answered in step S104). The predetermined time T1 is a time for driving the pump 41 for a certain period of time after the flow of the urea water 7 is switched to the reverse flow direction, thereby reducing the pressure of the second reducing agent supply passage 72 when the nozzle 60 is in the drive OFF state (valve closed state). By opening the nozzle 60 after reducing the pressure, the urea water 7 can be sucked back at a higher pressure difference than when the pressure is not reduced.

[0068] Next, the reducing agent supply device control unit 82 drives the nozzle 60 ON (opens the valve) for a time period of Ton (step S105, Figure 8The time from moment t1 to Ton time). Then, the reducing agent supply device control unit 82 drives the nozzle 60 OFF (valve closed) for Toff time (step S106). Then, the reducing agent supply device control unit 82 determines whether the number of repeated opening and closing of the nozzle 60 is greater than the threshold value N1 (step S107). The threshold value N1 is determined based on the action time required for the pump 41 in the urea water return control. In this case, (Ton+Toff)×(N1+1) is the action time. When the number of repeated opening and closing of the nozzle 60 is not greater than the threshold value N1 (step S107: NO), the reducing agent supply device control unit 82 drives the nozzle 60 ON (valve open) for Ton time again (step S105), and drives it OFF (valve closed) for Toff time (step S106), and then determines whether the number of repeated opening and closing of the nozzle 60 is greater than the threshold value N1 (step S107).

[0069] When the number of times the nozzle 60 is repeatedly opened and closed is greater than the threshold value N1 (step S107: YES), the reducing agent supply device control unit 82 stops driving the pump 41 (step S108, Figure 8 at the moment t2).

[0070] Next, the reducing agent supply device control unit 82 drives the nozzle 60 ON (opens the valve) for a time period of Ton (step S109, Figure 8 The time from moment t2 to Ton time). Then, the reducing agent supply device control unit 82 drives the nozzle 60 OFF (valve closing) for Toff time (step S110). Then, the reducing agent supply device control unit 82 determines whether the number of repeated opening and closing of the nozzle 60 is greater than the threshold value N2 (step S111). The threshold value N2 is determined based on the action time required for the direction switching valve 42 in the urea water return control. In this case, (Ton+Toff)×(N2+1) is the action time. When the number of repeated opening and closing of the nozzle 60 is not greater than the threshold value N2 (step S111: NO), the reducing agent supply device control unit 82 drives the nozzle 60 ON (valve opening) for Ton time again (step S109), and drives it OFF (valve closing) for Toff time (step S110), and then determines whether the number of repeated opening and closing of the nozzle 60 is greater than the threshold value N2 (step S111).

[0071] When the number of repeated opening and closing of the nozzle 60 is greater than the threshold value N2 (step S111: YES), the reducing agent supply device control unit 82 stops driving the direction switching valve 42 and drives OFF (closes the valve) the nozzle 60 (step S112). Here, the urea water return control ends (step S113, Figure 8After time t3, the reducing agent supply device control unit 82 controls, for example, the pump 41, the nozzle 60, etc., to adjust the pressure of the second reducing agent supply passage 72 (until time t4). The pressure adjustment here is implemented to prevent the urea water 7 from flowing into the nozzle 60, the second reducing agent supply passage 72, etc. in the downstream direction.

[0072] It should be noted that the ratio of the opening and closing time in the repetition of the opening and closing action of the nozzle 60 is preferably set to a value of 90% to 95% or more, for example, Ton / (Ton+Toff). The repetition of the opening and closing action is to prevent the urea water 7 from crystallizing due to the vibration accompanying the opening and closing action. On the other hand, in the suction action of the urea water, the nozzle 60 can effectively suck the urea water when it is basically open. Therefore, the opening and closing action of the needle valve 62 of the nozzle 60 is preferably an action in which the time of the opening action in each cycle of the opening and closing action is at least longer than the time of the closing action.

[0073] [Effects of Embodiment]

[0074] According to the present embodiment, while the urea water 7 existing in the nozzle 60 of the reducing agent supply device 4 is returned to the urea water tank 50, the nozzle (urea water injection device) 60 is made movable (opened and closed), and crystallization at the front end and inside of the nozzle (urea water injection device) 60 can be prevented. That is, according to the present embodiment, for example, during the progress of crystallization, the crystals can be physically crushed to prevent clogging. At this time, the control of the nozzle 60 can be repeated actions of turning on (fully open) and turning off (fully closed). Therefore, according to the present embodiment, the adhesion of urea water in the urea injection device can be prevented by simple control.

[0075] The embodiments of the present disclosure are described above with reference to the accompanying drawings, but the specific structure is not limited to the above embodiments, and also includes design changes that do not deviate from the scope of the main purpose of the present disclosure. For example, the cycle of the opening and closing action of the nozzle 60 in the above-mentioned urea water return control is not necessarily the same (it can also be changed). However, in this case, the action time of the pump 41 or the directional switching valve 42 is not determined by the number of repetitions, but by time. In addition, in the above embodiments, part or all of the program executed by the computer can be released via a computer-readable recording medium or communication line.

[0076] [Note]

[0077] The reducing agent supply device 4 according to the embodiment can be understood as follows.

[0078] (1) A first aspect of the present disclosure provides a reducing agent supply device 4, comprising: a tank 50 storing a reducing agent (urea water 7) to be supplied to an exhaust pipe (path 11) of an engine 2; a pressure-feeding mechanism (a pump 41 and a directional switching valve 42 set in a downstream direction) to pressure-feed the reducing agent in the tank 50; a reducing agent supply passage 70 to supply the pressure-feeding reducing agent; a nozzle 60 to inject the reducing agent supplied from the reducing agent supply passage 70 into the exhaust pipe; a back-sucking mechanism (a pump 41 and a directional switching valve 42 set in a reverse direction) to back-suck the reducing agent in the reducing agent supply passage 70 to the tank 50; and a control device 8 to control the operation of the pressure-feeding mechanism, the nozzle, and the back-sucking mechanism, wherein the control device 8 repeatedly opens and closes the nozzle 60 at a predetermined cycle while the back-sucking mechanism is in operation. According to this embodiment and the following embodiments, adhesion of urea water in the urea injection device can be prevented by simple control of repeatedly turning the nozzle 60 on (fully open) and off (fully closed).

[0079] (2) The reducing agent supply device 4 of the second embodiment of the present disclosure is the reducing agent supply device 4 of (1), wherein the opening and closing action is an action of fully opening or fully closing the valve (needle valve 62) provided in the nozzle 60. According to this embodiment, the physical effect of the valve drive can be increased compared to the case where the opening and closing range is limited to fully open or fully closed.

[0080] (3) The third embodiment of the reducing agent supply device 4 of the present disclosure is the reducing agent supply device 4 of (1) or (2), wherein the opening and closing action is an action in which the opening action time is longer than the closing action time within the cycle. According to this embodiment, the influence of the closing action time on the back-sucking action can be reduced.

[0081] (4) A reducing agent supply device 4 according to a fourth aspect of the present disclosure is the reducing agent supply device 4 according to (1) to (3), wherein the control device 8 closes the nozzle 60 after the operation of the suck-back mechanism is terminated. According to this aspect, the control device closes the nozzle 60 after the operation of the suck-back mechanism is terminated. According to this aspect, the urea water 7 can be returned to the tank 50 side more effectively than when the nozzle 60 is closed before the operation of the suck-back mechanism is terminated.

[0082] Industrial Applicability

[0083] According to the above-mentioned aspect, adhesion of urea water in the urea injection device can be prevented by simple control.

[0084] Description of Reference Numerals

[0085] 1… engineering vehicle, 2… diesel engine (engine), 3… turbocharger, 4… reducing agent supply device, 6… engine speed detection device, 7… urea water, 8… control device, 9… monitor, 10… exhaust gas purification device, 11… path (exhaust pipe), 30… diesel oxidation catalyst device (DOC device), 31… inlet temperature sensor, 40… pump unit, 41… pump, 42… direction switching valve, 43… pressure gauge, 44… check valve, 45… outlet temperature sensor, 50… tank, 52… NOx sensor, 60… nozzle, 62… needle valve, 63… injection hole, 70… reducing agent supply passage, 71… first reducing agent supply passage, 72… second reducing agent supply passage, 73… bypass passage, 81… data acquisition unit, 82… reducing agent supply device control unit, 170… DPF, 171… DPF device, 172… fuel injection device, 174… outlet temperature sensor, 175… selective reduction catalyst device (SCR device).

Claims

1. A reducing agent supply device, characterized in that: have: a tank storing a reducing agent to be supplied into an exhaust pipe of the engine; a pressure-feeding mechanism for pressure-feeding the reducing agent in the tank; a reducing agent supply passage for supplying the pressure-fed reducing agent; a nozzle for injecting the reducing agent supplied from the reducing agent supply passage into the exhaust pipe; a suction back mechanism that sucks the reducing agent in the reducing agent supply passage back to the tank side; A control device controls the actions of the pressure feeding mechanism, the nozzle and the suction mechanism, The control device repeatedly opens and closes the nozzle at a predetermined cycle while the suction mechanism is being operated.

2. The reducing agent supply device according to claim 1, characterized in that: The opening and closing operation is an operation of fully opening or fully closing a valve provided in the nozzle.

3. The reducing agent supply device according to claim 2, characterized in that: The opening and closing operation is an operation in which the time of the opening operation is longer than the time of the closing operation in the cycle.

4. The reducing agent supply device according to any one of claims 1 to 3, characterized in that: The control device closes the nozzle after the operation of the suck-back mechanism is completed.

5. A method for controlling a reducing agent supply device, the reducing agent supply device comprising: a tank storing a reducing agent to be supplied into an exhaust pipe of the engine; a pressure-feeding mechanism for pressure-feeding the reducing agent in the tank; a reducing agent supply passage for supplying the pressure-fed reducing agent; a nozzle for injecting the reducing agent supplied from the reducing agent supply passage into the exhaust pipe; a suction back mechanism that sucks the reducing agent in the reducing agent supply passage back to the tank side; A control device controls the actions of the pressure feeding mechanism, the nozzle and the sucking back mechanism. The control method of the reducing agent supply device is characterized in that: The control method includes the step of repeatedly opening and closing the nozzle at a predetermined cycle while the suction mechanism is being operated.

6. A control device, the control device controlling the operation of a pressure delivery mechanism, a nozzle and a suction mechanism in a reducing agent supply device, the reducing agent supply device comprising: a tank storing a reducing agent to be supplied into an exhaust pipe of the engine; The pressure-feeding mechanism pressure-feeds the reducing agent in the tank; a reducing agent supply passage for supplying the pressure-fed reducing agent; the nozzle injecting the reducing agent supplied from the reducing agent supply passage into the exhaust pipe; The suction back mechanism sucks the reducing agent in the reducing agent supply passage back to the tank side, The control device is characterized in that While the suction mechanism is being operated, the nozzle is repeatedly opened and closed at a predetermined cycle.

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