JP5801767B2 - Reducing agent supply device - Google Patents

Description

  The present invention relates to a reducing agent supply device that sprays a reducing agent on the exhaust of a construction machine.

  From the viewpoint of environmental protection, in recent years, it has been required to purify NOx of exhaust gas from internal combustion engines such as diesel engines. As one of devices that meet this requirement, an exhaust purification device (SCR system) that purifies exhaust gas by reducing NOx is known. As an aspect of the SCR system, there is a system in which a reducing agent injection valve is provided in an exhaust pipe and a liquid reducing agent (urea solution or the like) is injected into the exhaust pipe. However, in the case of an SCR system that injects a liquid reducing agent into the exhaust, there is a concern about thermal damage of a reducing agent injection valve installed in a high temperature environment. On the other hand, there has been proposed one in which a part of the engine cooling water is circulated to the reducing agent injection valve and the temperature of the reducing agent injection valve is adjusted by the opening degree of the flow rate adjusting valve (see Patent Document 1, etc.).

International Publication No. 2009/050948

  Here, for example, in a passenger car, exhaust gas is usually discharged from the lower part of the vehicle body. Therefore, when the apparatus of Patent Document 1 is applied, the cooling water flow path of the reducing agent injection valve is connected to the engine cooling water flow. The overall position relative to the connection with the road can be lowered. Therefore, even if air is mixed into the cooling water flow path of the reducing agent injection valve, the air can be pushed out into the engine cooling water flow path relatively easily by the flow of the cooling water. The air discharged to the engine cooling water flow path is discharged out of the system through the radiator cap.

  However, in the case of construction machinery, the engine room has a limited size in the horizontal and height directions in order to achieve a small turning diameter and secure a rear view from the driver's seat, as well as radiators, engines, and hydraulic pumps. There are also restrictions on the layout of each equipment such as counterweights. Under such circumstances, the exhaust pipe is often installed so as to protrude from the upper surface of the engine room, and the reduction catalyst and the reducing agent injection valve may be installed in the upper space of the engine room. Therefore, when the apparatus of Patent Document 1 is applied to a construction machine, all or part of the cooling water flow path of the reducing agent injection valve can inevitably be positioned higher than the engine and its cooling water flow path. In the course of arranging the cooling water flow path in the engine room, an inverted U-shaped part may be formed in a part of the flow path. For this reason, if air enters the cooling water flow path of the reducing agent injection valve, air accumulates in this inverted U-shaped portion, obstructing water flow through the cooling water flow path, and increasing the opening of the flow rate adjustment valve as required. However, the amount of cooling water does not increase and the reducing agent injection valve may not be cooled properly. In severe cases, the water flow itself can be delayed.

  This invention is made | formed in view of the said situation, and it aims at providing the reducing agent supply apparatus which can suppress the fall of the cooling capability of the reducing agent injection valve by mixing of the air to a cooling water flow path.

In order to achieve the above object, a first aspect of the present invention is a reducing agent supply device that sprays a reducing agent on the exhaust of an engine of a construction machine including a traveling body and a working device, and the upstream of the reduction catalyst in the exhaust pipe of the engine. A cooling water passage that circulates cooling water between the reducing agent injection valve installed at a position, the engine cooling water passage and the reducing agent injection valve, and an inverted U-shaped portion in a part of the cooling water passage The injection valve cooling water flow path at least a part of which is higher than the highest part of the engine cooling water flow path, the circulation pump that circulates the cooling water in the injection valve cooling water flow path, and the setting device And a control device for controlling the circulation pump, wherein the control device is more than a reference rotational speed calculated based on the setting of the setting device until a set time elapses after the engine is started. For high air extrusion And drives the circulation pump at a rotation speed.

According to a second aspect of the present invention, there is provided a reducing agent supply device for spraying a reducing agent on an exhaust gas of an engine of a construction machine having a traveling body and a working device , wherein the reducing agent injection is installed upstream of the reduction catalyst in the exhaust pipe of the engine. A cooling water flow path for circulating cooling water between the valve, the engine cooling water flow path and the reducing agent injection valve, wherein an inverted U-shaped portion is formed in a part of the cooling water flow path , at least a part of which is An injection valve cooling water flow path that is higher than the highest part of the engine cooling water flow path, a circulation pump that circulates the cooling water in the injection valve cooling water flow path, and a flow of cooling water in the injection valve cooling water flow path are detected. And a control device that controls the circulation pump according to the setting by the setting device, and the control device flows the cooling water in the injection valve cooling water flow path based on a signal from the flow detector. When it is judged that there is an abnormality Will the rotation speed of the circulation pump until the rotational speed of the air extruded increases continuously or stepwise from the reference rotation speed which is calculated based on the settings of the setter, and reaches the rotation speed for the air extruded Until it is determined that the flow of the cooling water in the injection valve cooling water flow path has been normalized based on the signal from the flow detector, the rotational speed of the circulation pump is determined as the reference rotation at that time. It is characterized by returning to a number .

In a third aspect based on the second aspect , the control device drives the circulation pump at the rotation speed for pushing out the air and then controls the flow path of the injection valve cooling water flow path based on a signal from the flow detector. When it is determined that there is an abnormality in the flow of the cooling water, a warning device is activated to stop the engine.

According to a fourth invention, in any one of the first to third inventions, an air bleeding device provided in the injection valve cooling water flow path is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of the cooling capacity of the reducing agent injection valve by mixing of the air to a cooling water flow path can be suppressed.

1 is an external view of an example of a construction machine to which a reducing agent supply device according to a first embodiment of the present invention is applied. 1 is a circuit diagram of an exhaust purification device including a reducing agent supply device according to a first embodiment of the present invention. It is the schematic diagram seen from the horizontal direction of the exhaust gas purification apparatus provided with the reducing agent supply apparatus which concerns on the 1st Embodiment of this invention. It is a functional block diagram of the control apparatus with which the reducing agent supply apparatus which concerns on the 1st Embodiment of this invention was equipped. It is a flow church showing the control procedure of the circulation pump by the control apparatus with which the reducing agent supply apparatus which concerns on the 1st Embodiment of this invention was equipped. It is a flow church showing the control procedure of the circulation pump by the control apparatus with which the reducing agent supply apparatus which concerns on the 2nd Embodiment of this invention was equipped. It is a figure explaining the 3rd Embodiment of this invention, Comprising: It is the figure which illustrated the variation of the control system of the circulation pump of a reducing agent supply apparatus.

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

(First embodiment)
1. Applicable object FIG. 1 is an external view of an example of a construction machine to which a reducing agent supply apparatus according to a first embodiment of the present invention is applied. As shown in FIG. 1, in the present embodiment, a hydraulic excavator is illustrated as an example of an application target of the reducing agent supply device of the present embodiment. In the present embodiment, unless otherwise specified, the left and right in FIG.

  The hydraulic excavator shown in FIG. 1 includes a traveling body 101, a revolving body 102 that is turnably mounted on the traveling body 101, and a work device 108.

  The traveling body 101 includes left and right crawlers having endless track tracks, and travels by driving the left and right crawlers by left and right traveling motors 133 respectively. The travel motor 133 is, for example, a hydraulic motor.

  The swivel body 102 has a swivel frame 103. The swivel frame 103 has a cab box 104 on which an operator gets on the front side, and a building cover 105 that defines an engine room on the rear side of the cab box 104. A counterweight 106 for adjusting the balance in the front-rear direction of the aircraft is mounted. The turning frame 103 is provided with a turning motor (not shown), and the turning body 102 is driven to turn by this turning motor. The turning motor is, for example, a hydraulic motor.

  The work device 108 is provided at the front portion of the revolving structure 102 (right side of the cab box 104 in this example) and moves up and down with respect to the revolving structure 102. The working device 108 includes a boom 109 that is pin-coupled to the revolving frame 103 of the revolving structure 102, an arm 110 that is pin-coupled to the distal end side of the boom 109, and a work tool (bucket that is pin-coupled to the distal end side of the arm 110. 111). The boom 109, the arm 110, and the bucket 111 are driven by the boom cylinder 134, the arm cylinder 135, and the bucket cylinder 136. The cylinders 134 to 136 are, for example, hydraulic cylinders.

2. FIG. 2 is a circuit diagram of an exhaust purification device provided with the reducing agent supply device according to the first embodiment of the present invention, and FIG. 3 is a schematic view seen from the horizontal direction.

  An exhaust purification device 1 shown in FIG. 2 includes a reduction catalyst 3 provided in the middle of an exhaust pipe 2 of an engine (internal combustion engine) 14 and a liquid reducing agent (for example, an aqueous urea solution) in the exhaust of the engine 14 that flows through the exhaust pipe 2. And a reducing agent supply device 5 for spraying NOx, and selectively reducing and purifying NOx in the exhaust gas of the engine 14. The reducing agent supply device 5 is a main component of the exhaust purification device 1. The components shown in FIGS. 2 and 3 including the engine 14 and the radiator 15 are accommodated inside the building cover 105 (see FIG. 1) in the engine room. The radiator 15 is known and includes a radiator cap. The radiator 15 and the engine 14 are connected by an engine cooling water channel 16, and the engine cooling water channel 16 is provided with a circulation pump 8 that is driven by the power of the engine 14. The engine cooling water flow path 16 is stretched around the engine 14 in order to ensure a wide contact area with the engine 14. Further, a thermostat 22 (see FIG. 3) is provided in a pipe line for sending cooling water from the engine 14 to the radiator 15 in the engine cooling water flow path 16. The thermostat 22 is an on-off valve that mechanically opens and closes depending on the cooling water temperature by a bimetal or the like. The thermostat 22 opens when the cooling water temperature reaches a set temperature, and closes when the temperature does not reach the set temperature. In addition, a fan 30 is connected to the engine 14, and the engine coolant is cooled when circulating through the radiator 15 by the cooling air induced by the fan 30.

  With the above configuration, the engine 14 is cooled by driving the circulation pump 8 and circulating the engine cooling water around the engine 14 through the engine cooling water flow path 16 of the engine 14. Thereafter, when the temperature of the engine 14 is raised to a certain temperature and the thermostat 22 is opened, the engine cooling water 16 that has cooled the engine 14 flows into the radiator 15, and the engine cooling water radiated by the radiator 15 returns to the engine 14 to Cooling.

  At this time, in addition to the engine 14 and the radiator 15, various hydraulic-related devices such as a hydraulic pump and a hydraulic oil tank that supply hydraulic oil to the above-described hydraulic actuators are accommodated in the engine chamber, although not particularly illustrated. Nevertheless, a counterweight 106 (see FIG. 1) is provided at the rear of the engine compartment, and a small turning diameter of the turning body 102 is desired, so that the dimensions are limited in the horizontal direction. In addition, in order to secure a rear view from the cab box 104, the upper surface of the engine compartment is desired to be as low as possible from the line of sight of the operator who is in the cab box 104. Therefore, the engine room is narrow with respect to the contents, and due to space constraints, the exhaust pipe 2 of the engine 14 has a terminal (exhaust tube) protruding from the upper surface of the building cover 105 to the outside as shown in FIG. There are times when it crawls. In this case, since the exhaust pipe 2 extends to a position higher than the engine 14 and the radiator 15 as schematically shown in FIG. 3, the reduction catalyst 3 is disposed using the upper space in the engine chamber. is there.

3. Reducing agent supply device The reducing agent supply device 5 includes a reducing agent supply system 100 that sprays the reducing agent on the exhaust of the engine 14, an injection valve cooling system 200 that cools the reducing agent injection valve 4 of the reducing agent supply system 100, and these reductions. A control device 18 for controlling the agent supply system 100 and the injection valve cooling system 200 is provided.

  The reducing agent supply system 100 includes a reducing agent tank 6 in which the reducing agent is stored, a reducing agent injection valve 4 that sprays the reducing agent on exhaust, and a pump module that pumps the reducing agent in the reducing agent tank 6 to the reducing agent injection valve 4. 7 is provided. The reducing agent injection valve 4 is installed upstream of the reduction catalyst 3 in the exhaust pipe 2 (upstream in the exhaust flow direction), and its injection hole faces the internal space of the exhaust pipe 2. In the present embodiment, the reducing agent injection valve 4 is arranged with respect to the exhaust pipe 2 by utilizing the upper space in the engine room, as with the above-described reduction catalyst 3, and as schematically shown in FIG. It is higher than the engine 14 and the radiator 15. The pump module 7 is connected to the reducing agent injection valve 4 and the reducing agent tank 6 through supply passages 9 and 10, respectively, and is further connected to the reducing agent tank 6 through a circulation passage 11.

  With the above configuration, the pump module 7 is driven and the reducing agent stored in the reducing agent tank 6 is pumped to the reducing agent injection valve 4 to reduce the engine exhaust flowing through the exhaust pipe 2 via the reducing agent injection valve 4. The agent is sprayed.

4). Injection valve cooling system 200
The injection valve cooling system 200 includes an injection valve cooling water passage 13 that circulates cooling water that exchanges heat with the reducing agent injection valve 4, and a circulation pump 8 that circulates the cooling water through the injection valve cooling water passage 13.

  The circulation pump 8 is provided between the thermostat 22 and the radiator 15 in the middle of the engine cooling water flow path 16, for example, upstream of the thermostat 22 (see FIG. 3).

  The injection valve cooling water flow path 13 is a part for diverting a part of the engine cooling water flowing through the engine cooling water flow path 16 as the injection valve cooling water and leading it to the reducing agent injection valve 4. The injection valve cooling water flow path 13 branches and merges with the engine cooling water flow path 16 around the engine 14, and a part of the middle is constituted by the cooling water passage 12 of the reducing agent injection valve 4. The cooling water passage 12 is a part that cools the reducing agent injection valve 4 by exchanging heat with the reducing agent injection valve 4. Further, the inlet 40 (upstream end portion) of the injection valve cooling water flow path 13 is, for example, in a portion between the thermostat 22 and the circulation pump 8 on the upstream side of the thermostat 22 (see FIG. 3) in the engine cooling water flow path 16. Connected. On the other hand, the outlet 41 (downstream end) of the injection valve cooling water flow path 13 is connected to a portion between the circulation pump and the radiator 15 on the upstream side of the circulation pump 8 in the engine cooling water flow path 16, for example. Further, an inverted U-shaped portion 13 a that protrudes upward is formed in a part of the path of the injection valve cooling water flow path 13, in the present embodiment, in the upstream portion of the cooling water passage 12.

  In order to make it difficult for air to enter the injection valve cooling water flow path 13 from the engine cooling water flow path 16, the most upstream portion of the injection valve cooling water flow path 13 is downstream from the inlet 40 connected to the engine cooling water flow path 16. It is preferable to extend a certain distance downward (downwardly inclined or vertically downward) toward the side. On the other hand, in order to make it easy for the air mixed in the injection valve cooling water flow path 13 to be discharged to the engine cooling water flow path 16, the most downstream portion of the injection valve cooling water flow path 13 is an outlet 41 connected to the engine cooling water flow path 16. It is preferable to extend a certain distance upward (upwardly inclined or vertically upward). As described above, since the reducing agent injection valve 4 is positioned higher than the engine 14 and the radiator 15, at least a part of the injection valve cooling water flow path 13 is the engine cooling water flow path 16 as shown in FIG. 3. Inevitably higher than the highest part. In other words, at least a part of the injection valve cooling flow path 13 is higher than the inlet 40. The engine cooling water flow path 16 and the injection valve cooling water flow path 13 are entirely filled with cooling water.

  With the above configuration, when the circulation pump 8 is driven, the cooling water in the injection valve cooling water flow channel 13 communicating with the engine cooling water flow channel 16 flows from the inlet 40 toward the outlet 41 and passes through the cooling water passage 12 on the way. At this time, after the reducing agent injection valve 4 is cooled, the flow returns to the engine coolant flow path 16.

  An air venting device 42 (see FIG. 3) capable of discharging mixed air is installed in the middle of the injection valve cooling water flow path 13. A known air vent valve or the like can be used for the air vent device 42. Further, the injection valve cooling water flow path 13 is provided with a flow detector 17 for detecting the presence or absence of the flow of cooling water in order to determine whether or not there is an abnormality in the flow in the flow path. The state in which the cooling water flows in a state where the injection valve cooling water flow passage 13 is filled with the cooling water is a normal flow state, and the “abnormality” of the flow mentioned here means that the flow is not in a normal flow state. . The abnormality in flow may occur due to the mixing of air into the injection valve cooling water flow path 13. As the flow detector 17, for example, a detector that determines whether or not a predetermined flow rate is obtained by directly measuring the flow rate with a differential pressure type flow meter that detects the flow rate from the difference between the dynamic pressure and the static pressure of the fluid is used. Can do. Moreover, what distinguishes whether the substance which exists in the injection valve cooling water flow path 13 is air or cooling water using the property of temperature, a pressure, and an ultrasonic wave can also be used. However, the type of the flow detector 17 is not particularly limited as long as an abnormality in flow can be determined.

5. Control device 18
The control device 18 controls the circulation pump 8 by changing, for example, the engine speed or the transmission ratio of the power transmission mechanism from the engine 14 to the circulation pump 8 to control the reducing agent supply system 100 and the injection valve cooling system 200. Control. In addition to the flow detector 17, a signal from a key switch 19 for instructing start of the engine 14 and a signal from an engine controller dial (encon dial) 20 as a setting device are input to the control device 18. The encon dial 20 is a setting device for setting the target rotational speed of the engine 14. Further, the control device 18 outputs a signal to the warning device 21 (warning light or the like) and the circulation pump 8. The control device 18 normally controls the circulation pump 8 according to the setting of the encon dial 20 and drives the circulation pump 8 at the number of revolutions according to the setting of the encon dial 20. When the engine is started, the control device 18 increases the number of revolutions of the circulation pump 8 for a certain period of time, and pushes out air that may be mixed in the injection valve cooling water flow path 13 from the injection valve cooling water flow path 13 to cool the engine. It discharges to the water channel 16.

  FIG. 4 is a functional block diagram of the control device 18.

  The control device 18 is configured around a known microcomputer, and includes an engine operation time calculation unit 18a and a pump rotation speed control unit 18b. The engine operating time calculation unit 18a determines whether or not the engine 14 is in an operating state based on the signal S1 from the key switch 19, and when the engine 14 is in an operating state, an elapsed time ( Operating time). The calculation method of the operating time of the engine 14 is not particularly limited, and for example, a configuration in which the calculation is performed from timekeeping information of a timer (not shown) provided in the control device 18 is sufficient.

  The pump rotation speed control unit 18b outputs a control signal for the rotation speed of the circulation pump 8 based on the command value S2 which is a signal from the encon dial 20 and the flow rate detection information S3 which is a signal from the flow detector 17. . Further, the pump rotation speed control unit 18b stores the relationship information between the cooling water flow rate in the injection valve cooling water flow path 13 and the rotation speed of the circulation pump 8 obtained in advance by a test or the like. Deviation between the coolant flow rate (F1) calculated from the flow rate detection information S3 and the normal coolant flow rate (F0) corresponding to the number of revolutions of the circulation pump 8 (for example, a command value to the circulation pump 8) in the relationship information. When (ΔF) exceeds a preset threshold value Fs (ΔF = F0−F1> Fs), a warning device 21 is used to prevent thermal damage to the reducing agent injection valve 4 due to a decrease in cooling water flow rate (decrease in cooling capacity). To output a signal. The warning device 21 that has input the signal notifies the driver by turning on a warning lamp or the like.

6). Control of Circulation Pump 8 FIG. 5 is a flow church showing a control procedure of the circulation pump 8 by the control device 18 in the present embodiment.

  The control procedure shown in FIG. 5 is to increase the rotational speed of the circulation pump 8 for a predetermined time when the engine is started. In the procedure shown in the figure, first, in step S11, a signal S1 from the key switch 19 is input, and the process proceeds to step S12 to determine whether the engine 14 is in an operating state. If it is determined that the engine 14 is moving based on the signal S1, the control device 18 moves the procedure to step S13, and if it is determined that the engine 14 is not moving, the flow of FIG. When the engine 14 is in an operating state, an operation time t that is a time during which the engine 14 continues to operate continuously from the most recent start is calculated in step S13, and the operation time t is a preset threshold value t1 in step S14. It is judged whether it is less than. If it is determined that the operation time t is less than t1 (that is, before t1 elapses after starting), the procedure proceeds to step S15, and if it is determined that the operation time t is equal to or longer than t1 (that is, after t1 elapses from start), step S17 (described later). Move the procedure to.

  In step S15, the control device 18 drives the circulation pump 8 at the set rotational speed N1. The set rotation speed N1 is a rotation speed for air extrusion that is higher than the reference rotation speed N0 calculated based on the setting of the encon dial 20. The “reference rotational speed N0” here is a value determined according to the engine rotational speed in accordance with the setting of the encon dial 20 during normal operation, and varies depending on the engine rotational speed. On the other hand, the rotation speed N1 for air extrusion is a fixed value that is set. In a succeeding step S16, it is determined whether or not the operation time t is equal to or greater than a threshold value t1. If it is determined that the operation time t is less than t1, the procedure returns to step S15. On the other hand, if it is determined that the operation time t is equal to or greater than the threshold value t1, the control device 18 moves the procedure to step S17, drives the circulation pump 8 at the reference rotational speed N0 calculated from the command value S2 from the encon dial 20, The flow in FIG. 5 ends. By executing the above procedure, when the engine 14 is started, until the set time t1 elapses from the start, the set rotational speed N1 for air extrusion that is higher than the reference rotational speed N0 regardless of the setting of the encon dial 20. Thus, the circulation pump 8 is driven.

7). As described above, according to the present embodiment, even if air is mixed into the injection valve cooling water flow path 13 when the engine is stopped, the rotation speed N1 for pushing out air is higher during the set time t1 when starting the engine than during normal operation. By driving the circulation pump 8 at this time, air can be discharged from the cooling water circulation passage 13 during the set time t1. By discharging the air that hinders the flow of the cooling water in the injection valve cooling water flow path 13 in this way, the required amount of cooling water can be passed through the injection valve cooling water flow path 13. A decrease in cooling capacity can be suppressed.

(Second Embodiment)
FIG. 6 is a flow chart showing a control procedure of the circulation pump 8 by the control device 18 in the second embodiment.

  This embodiment is different from the first embodiment in the control procedure of the circulation pump 8 by the control device 18. That is, in the first embodiment, the circulation pump 8 is driven unconditionally for the set time t1 at the rotation speed N1 for pushing out the air at the time of starting the engine, whereas in the present embodiment, the injection valve cooling water flow is caused by air mixing. The difference is that the speed of the circulation pump 8 is increased to the speed N1 for pushing out air when an abnormality (flow rate decrease or the like) in the flow of the cooling water in the passage 13 is detected. Since the hardware configuration is basically the same as that of the first embodiment, description thereof is omitted.

  As shown in FIG. 6, the control device 18 inputs the signal S3 from the flow detector 17 in step S21, and moves the procedure to step S22. In step S22, it is determined whether or not the cooling water flow rate F calculated based on the signal S3 has fallen below a threshold value F1 determined in advance from a test or the like. Although the threshold value F1 can be a constant value, the flow rate corresponding to the rotation speed of the circulation pump 8 is set as the reference flow rate based on the relationship information between the rotation speed of the circulation pump 8 and the cooling water flow rate described above. The value can also be lowered by a predetermined value. If it determines with the cooling water flow volume F being less than the threshold value F1 in step S22, the control apparatus 18 will transfer a procedure to step S23, and if it determines with the cooling water flow volume F being more than the threshold value F1, a procedure will be returned to step S21.

  In step S23, the control device 18 drives the circulation pump 8 at a set rotational speed N1 for a predetermined time. The set rotation speed N1 is a rotation speed for air extrusion that is higher than the reference rotation speed N0 calculated based on the setting of the encon dial 20. The time for increasing the rotational speed of the circulation pump 8 to N1 is a preset time. In the subsequent step S24, the signal S3 is input again from the flow detector 17, and it is determined whether or not the coolant flow rate F calculated based on the step S25 signal S3 has returned to the threshold value F1 or more. Here, if the cooling water flow rate F has returned to the threshold value F1 or more, the control device 18 assumes that the air has been discharged and the flow of the cooling water has been normalized, and the procedure proceeds to step S26, where the circulation pump 8 And the procedure is returned to step S21. On the other hand, if the cooling water flow rate F is still less than the threshold value F1, the control device 18 moves the procedure to step S27 to operate the warning device 21 to urge the driver to warn, and further in step S28 the reducing agent injection valve 4. In order to prevent thermal damage, the engine 14 is stopped and the procedure is terminated.

  As described above, according to the present embodiment, even if air is mixed into the injection valve cooling water flow path 13 during engine operation, an abnormality in the flow of the cooling water in the injection valve cooling water flow path 13 is detected due to the air mixing. Then, by increasing the rotational speed of the circulation pump 8 to the rotational speed N1 for pushing out the air, the air can be discharged from the cooling water circulation passage 13 to normalize the flow of the cooling water. By discharging the air that hinders the flow of the cooling water in the injection valve cooling water flow path 13 in this way, the required flow rate of cooling water can be passed through the injection valve cooling water flow path 13 also in the present embodiment. And the fall of the cooling capacity of the reducing agent injection valve 4 can be suppressed.

  In the case of the present embodiment, by determining whether the flow of the cooling water in the injection valve cooling water flow path 13 is normal or abnormal, the warning device 21 does not normalize even if the circulation pump 8 is accelerated at the time of abnormality. An abnormality can be notified to the driver. As a result, the driver can take appropriate measures before the reducing agent injection valve 4 is damaged.

  6 may be executed independently without executing the control procedure of FIG. 5 in the first embodiment, or may be executed in combination with the procedure of FIG. . In the case of executing together with the procedure of FIG. 5, after the circulation pump 8 is executed at N1 for the set time t1 at the time of engine start, the cooling of the injection valve cooling water flow path 13 is performed during the execution of the pump control according to the setting of the encon dial 20. When an abnormality is detected in the flow of water, the circulation pump 8 is again driven at the rotational speed N1. Further, the rotational speed for air extrusion in the present embodiment may be set to a value different from N1 in the first embodiment. For example, after the circulation pump 8 is driven with N1 at the time of engine start, The circulation pump 8 may be driven by N1 ′ different from N1. However, N1 'is limited to a value higher than the reference rotational speed N0 corresponding to the setting of the encon dial 20 as with N1.

(Third embodiment)
FIG. 7 is a diagram illustrating a variation of the control method of the driving speed of the circulation pump of the reducing agent supply apparatus according to the present invention.

  In the first and second embodiments, as indicated by the control line A in FIG. 7, the circulation pump 8 at a stroke from the reference rotational speed N0 corresponding to the setting of the encon dial 20 to the rotational speed N1 for air extrusion is performed at once. Although the example which speeds up the rotation speed of was demonstrated, it is not restricted to this. For example, the control device 18 may be configured to continuously increase the number of rotations of the circulation pump 8 from N0 to N1 as in the control line B. Although the control line B in FIG. 7 illustrates a method of linearly increasing the speed in proportion to the time from the start of the acceleration, a method of increasing the speed linearly may be used. Moreover, it can also be set as the structure increased in steps like the control line C. FIG. In this case, until the rotational speed reaches N1, (for example, when the speed is increased to the rotational speed N2 in FIG. 7), based on the signal S3 from the flow detector 17, the cooling water in the injection valve cooling water flow path 13 is supplied. If it is determined that the flow has been normalized, the rotational speed of the circulation pump 8 can be returned to the reference rotational speed N0 at that time. In this case, since the flow of the cooling water in the injection valve cooling water flow path 13 has already returned to normal, the waste of power caused by increasing the rotational speed of the circulation pump 8 to N1 can be suppressed. Efficiency is good, for example, a reduction in fuel consumption can be suppressed.

(Other)
In this embodiment, the case where the reducing agent injection valve 4 is located higher than the engine 14 and the radiator 15 is described as an example. However, the reducing agent injection valve 4 itself is the highest part of the engine 14 or the radiator 15. May be installed at a low position. Even in this case, when there is an inverted U-shaped portion in a part of the injection valve cooling water flow path 13, the same problem as described above occurs, and the same effect as described above can be obtained by applying the present invention. it can. Further, even when the injection valve cooling water passage 13 does not have a portion higher than the highest portion of the engine 14 or the radiator 15, when the reverse U-shaped portion exists in the injection valve cooling water passage 13, the same as above. There is a possibility that this problem may occur, and by applying the present invention, the same effects as described above can be obtained. Moreover, although the case where the reverse U-shaped part 13a exists in the part immediately upstream of the reducing agent injection valve 4, the position of the reverse U-shaped part 13a is not limited to this, The downstream of the reducing agent injection valve 4 Or the like, as long as it exists in a part of the path of the injection valve cooling water flow path 13. Further, the present invention can be applied even when there are a plurality of inverted U-shaped portions 13a, and corresponding effects can be obtained.

  Moreover, normally, the viscosity of the cooling water increases at low temperatures, and the flow rate may decrease compared to normal even when the number of rotations of the circulation pump is the same. For this reason, even in a normal flow state, the flow rate may decrease due to an increase in the viscosity of the cooling water, and it may be determined as abnormal. In order to prevent such a problem, for example, the relationship information between the rotation speed of the circulation pump 8 and the cooling water flow rate of the injection valve cooling water flow path 13 described above and the threshold value for abnormality determination are set for each temperature range of the cooling water. A configuration in which the control device 18 stores the temperature sensor in advance and a temperature sensor is installed in the injection valve cooling water flow path 13 and the above determination is made based on the detected value of the temperature sensor and the flow detector 17 may be adopted. Moreover, in order to determine the flow abnormality of the cooling water of the injection valve cooling water flow path 13, the case where the flow rate of the cooling water of the injection valve cooling water flow path 13 is detected by the flow detector 17 is illustrated. Changes such as temperature caused by abnormal flow of cooling water in the injection valve cooling water flow path 13 may be used as the basis of control instead of the cooling water flow rate.

  Furthermore, the first to third embodiments described above can be combined as appropriate. For example, in the first embodiment, the case where the circulation pump 8 is driven at the rotational speed N1 for pushing out the air only for a predetermined time when the engine is started has been described. For example, the signal S3 of the flow detector 17 is driven while driving at N1. If an abnormality is detected when the circulating pump 8 is input and the circulating pump 8 is driven for a predetermined time N1, the warning can be stopped as in step S25 → step S27 in the second embodiment. . In this case, the rotational speed of the circulation pump 8 can be increased continuously or stepwise as in the third embodiment.

2 Exhaust pipe 3 Reduction catalyst 4 Reducing agent injection valve 5 Reducing agent supply device 8 Circulating pump 13 Injection valve cooling water flow path 14 Engine 16 Engine cooling water flow path 17 Flow detector 18 Control device 20 Engine controller dial (setting device)
21 Warning device 42 Air bleeding device N0 Reference rotation speed N1 Air rotation speed

Claims (4)

In a reducing agent supply device that sprays a reducing agent on the exhaust of an engine of a construction machine including a traveling body and a working device ,
A reducing agent injection valve installed upstream of the reduction catalyst in the exhaust pipe of the engine;
A cooling water flow path for circulating cooling water between the engine cooling water flow path and the reducing agent injection valve, wherein an inverted U-shaped portion is formed in a part of the cooling water flow path , and at least a part of the cooling water flow path An injection valve cooling water flow path that is higher than the highest part of the water flow path;
A circulation pump for circulating cooling water through the injection valve cooling water flow path;
A control device for controlling the circulation pump according to the setting by the setting device,
The control device drives the circulation pump at a rotation speed for air extrusion higher than a reference rotation speed calculated based on the setting of the setting device until a set time elapses after the engine is started. A reducing agent supply apparatus characterized by the above. In a reducing agent supply device that sprays a reducing agent on the exhaust of an engine of a construction machine including a traveling body and a working device,
A reducing agent injection valve installed upstream of the reduction catalyst in the exhaust pipe of the engine;
A cooling water flow path for circulating cooling water between the engine cooling water flow path and the reducing agent injection valve, wherein an inverted U-shaped portion is formed in a part of the cooling water flow path, and at least a part of the cooling water flow path An injection valve cooling water flow path that is higher than the highest part of the water flow path;
A circulation pump for circulating cooling water through the injection valve cooling water flow path;
A flow detector for detecting the flow of cooling water in the injection valve cooling water flow path;
A control device for controlling the circulation pump according to the setting by the setting device,
When the control device determines that there is an abnormality in the flow of the cooling water in the injection valve cooling water flow path based on the signal from the flow detector , the control device calculates the reference rotation speed based on the setting of the setting device . Lae until the number of revolutions for the a-extrusion will be increased continuously or stepwise the rotation speed of the circulation pump, until it reaches the rotational speed for the air extrusion, the signal from the flow detector When it is determined that the flow of the cooling water in the injection valve cooling water flow path has been normalized, the reducing agent supply device returns the rotation speed of the circulation pump to the reference rotation speed at that time. 3. The reducing agent supply device according to claim 2 , wherein the control device drives the circulating pump at the number of revolutions for pushing out the air and then cools the cooling water in the injection valve cooling water flow path based on a signal from the flow detector. When it is determined that there is an abnormality in the flow of the reducing agent, the warning agent is operated to stop the engine. The reducing agent supply apparatus according to any one of claims 1 to 3 , further comprising an air venting device provided in the injection valve cooling water flow path.

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