JP7108498B2 - Reductant tank and exhaust purification device - Google Patents

Description

The present invention relates to a reducing agent tank and an exhaust purification device.

Exhaust gas from an internal combustion engine such as a diesel engine mounted on a mobile object such as a vehicle contains NO _x (nitrogen oxide). A urea SCR (Selective Catalytic Reduction) system has been put into practical use as a device for purifying exhaust gas by reducing such _NOx and decomposing it into nitrogen, water, and the like.

The urea SCR system is a system that uses an aqueous urea solution as a liquid reducing agent, and decomposes NO _x by reacting NO _x in the exhaust gas with ammonia produced by decomposition of the aqueous urea solution. The urea aqueous solution is stored in the reducing agent tank. The urea aqueous solution in the reducing agent tank is pressure-fed by a pump, and is supplied to the exhaust passage after being metered by a control valve such as an electromagnetic valve.

JP 2017-122391 A

However, due to layout restrictions when the reducing agent tank is mounted on the moving body, there are cases where the suction port of the liquid reducing agent by the pump is located on the horizontal end side of the reducing agent tank. In this case, if the vehicle body is tilted such that the height of the side where the suction port of the liquid reducing agent is located is higher than the height of the opposite side due to the inclination of the road surface, etc., the liquid reducing agent around the suction port will decrease. Prone. As a result, the liquid reducing agent cannot be supplied to the exhaust passage, and purification of the exhaust gas may become insufficient.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a reducing agent tank and an exhaust emission control device that can continue to supply a liquid reducing agent even when the vehicle body is tilted.

In order to solve the above problems, according to one aspect of the present invention, there is provided a reducing agent tank that is mounted on a vehicle equipped with an internal combustion engine and stores a liquid reducing agent that is used to purify exhaust gas discharged from the internal combustion engine. It is provided in contact with the bottom of the reducing agent tank and is formed so as to surround the suction area where the suction port of the pump for pumping the liquid reducing agent is located, and the liquid reducing agent can flow through a part of the peripheral wall. A reductant tank is provided that includes a wall member having an opening.

In order to solve the above-described problems, according to another aspect of the present invention, there are provided a reducing agent tank for storing a liquid reducing agent, a reducing agent supply device for supplying the liquid reducing agent to an exhaust passage of an internal combustion engine, and an exhaust gas passage. a selective reduction catalyst that is disposed in the passage and uses a liquid reducing agent to reduce nitrogen oxides in the exhaust gas discharged from the internal combustion engine, wherein the reducing agent tank contains the reducing agent A wall that is provided in contact with the bottom of the tank and is formed so as to surround a suction area where a suction port of a pump that pumps the liquid reducing agent is located, and has an opening that allows the liquid reducing agent to flow through a part of the peripheral wall. An exhaust purification device is provided that includes a member.

As described above, according to the present invention, it is possible to continue supplying the liquid reducing agent even when the vehicle body is tilted.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the structural example of the exhaust gas purification device which concerns on embodiment of this invention. FIG. 3 is a schematic diagram of a reducing agent tank according to the same embodiment as viewed from above; FIG. 3 is a schematic diagram of the reducing agent tank according to the same embodiment as viewed from the side; FIG. 3 is a schematic diagram of the reducing agent tank of FIG. 2 viewed from the left side; FIG. 3 is a schematic diagram of the reducing agent tank of FIG. 2 as viewed from the right side; It is a perspective view which shows an example of a wall member. FIG. 4 is an explanatory view showing a state in which a reducing agent tank without wall members is maintained horizontally; FIG. 4 is an explanatory diagram showing a state in which a reducing agent tank having no wall member is tilted; FIG. 5 is an explanatory diagram showing a state in which the reducing agent tank according to the same embodiment is maintained horizontally; FIG. 4 is an explanatory diagram showing a state in which a reducing agent tank according to the same embodiment is tilted; FIG. 4 is an explanatory diagram showing an example in which a pump unit is equipped with a level sensor;

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and drawings, constituent elements having substantially the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description.

<1. Configuration example of urea SCR system>
First, a configuration example of the urea SCR system 10 will be described. FIG. 1 is a schematic diagram showing a configuration example of a urea SCR system 10. As shown in FIG.

The urea SCR system 10 is an exhaust purification device provided in an exhaust system of an internal combustion engine 5 such as a diesel engine. The urea SCR system 10 is mounted on a mobile object such as a vehicle, construction machine, or agricultural machine equipped with an internal combustion engine 5, or equipment such as a power generator. The urea SCR system 10 uses a urea aqueous solution as a liquid reducing agent to decompose NO _x in the exhaust gas discharged from the internal combustion engine 5 to purify the exhaust gas. As the urea aqueous solution, for example, an approximately 32.5% concentration urea aqueous solution having the lowest freezing temperature is used.

The urea SCR system 10 includes a selective reduction catalyst 13 disposed in the middle of the exhaust pipe 11 and a reducing agent supply device 30 that supplies an aqueous urea solution into the exhaust passage upstream of the selective reduction catalyst 13 .

The selective reduction catalyst 13 selectively reduces NO _x contained in the exhaust gas of the internal combustion engine 5 using ammonia. The selective reduction catalyst 13 adsorbs ammonia generated by decomposition of the urea aqueous solution supplied by the reducing agent supply device 30 . The selective reduction catalyst 13 decomposes NO _X in the inflowing exhaust gas by reacting it with ammonia.

The reducing agent supply device 30 supplies the urea aqueous solution into the exhaust passage upstream of the selective reduction catalyst 13 . The reducing agent supply device 30 is controlled by the control device 100 . The injection amount of the aqueous urea solution is controlled so that the concentration of NO _x and the concentration of ammonia flowing downstream from the selective reduction catalyst 13 are equal to or lower than reference values.

Exhaust temperature sensors 21 and 23 that detect the exhaust temperature at respective positions are provided in the exhaust pipe 11 upstream and downstream of the selective reduction catalyst 13 . Sensor signals from the exhaust temperature sensors 21 and 23 are output to the control device 100 . The exhaust temperature detected by the exhaust temperature sensors 21 and 23 is also used for estimating the temperature of the selective reduction catalyst 13 . The exhaust temperature sensor 23 provided downstream of the selective reduction catalyst 13 may be omitted. In addition to this, the exhaust pipe 11 may be provided with a NO _X concentration sensor, an ammonia sensor, and the like (not shown).

The reducing agent supply device 30 includes an injection valve 31 and a pump 41 . The pump 41 pressure-feeds the urea aqueous solution in the reducing agent tank 60 toward the injection valve 31 . The injection valve 31 is fixed to the exhaust pipe 11 at a position upstream of the selective reduction catalyst 13 . The injection valve 31 measures and injects the liquid reducing agent into the exhaust passage. Pump 41 and injection valve 31 are controlled by control device 100 .

In this embodiment, the pump 41 is attached to the bottom of the reducing agent tank 60 . A reducing agent supply passage 57 having the other end connected to the injection valve 31 is connected to the pump 41 . The pump 41 sucks the urea aqueous solution in the reducing agent tank 60 and supplies it to the injection valve 31 through the reducing agent supply passage 57 . As the pump 41, for example, an electromagnetically driven diaphragm pump or gear pump is used. As the injection valve 31, for example, an electromagnetically driven injection valve that is switched between opening and closing by energization control is used. The pump 41 and the injection valves 31 are controlled by the control device 100 .

For example, the control device 100 controls the output of the pump 41 so that the pressure of the urea aqueous solution supplied to the injection valve 31 is maintained at a predetermined target value. Further, the control device 100 adjusts the valve opening time according to the target injection amount of the aqueous urea solution. For example, the control device 100 controls the injection amount of the aqueous urea solution by adjusting the duty ratio, which is the ratio of the energization time to the entire time of the injection cycle, for each fixed injection cycle.

<2. Reducing agent tank>
Next, the configuration of the reducing agent tank 60 that stores the urea aqueous solution as the liquid reducing agent will be described.

2 to 5 are schematic diagrams showing the reducing agent tank 60. FIG. 2 is a schematic diagram of the reducing agent tank 60 viewed from above, and FIG. 3 is a schematic diagram of the reducing agent tank 60 viewed from the side. 4 is a schematic diagram of the reducing agent tank 60 of FIG. 2 as seen from the left side, and FIG. 5 is a schematic diagram of the reducing agent tank 60 of FIG. 2 as seen from the right side.

The reducing agent tank 60 according to the present embodiment has a length in a first direction (Y direction in the drawing; hereinafter also referred to as a “longitudinal direction”) in a second direction ( has a planar shape longer than the length in the X direction). For example, when the reducing agent tank 60 mounted on a passenger car is arranged below the trunk room at the rear part of the vehicle body, the reducing agent tank 60 can be installed in the space where the tire house, auxiliary tires, fuel tank, etc. are arranged. As such, it can be a shape having a longitudinal direction.

Although the illustrated reducing agent tank 60 has a rectangular planar shape, the planar shape is not limited to a rectangular shape, and may be oval or any other shape having a longitudinal direction. In addition, although the planar shape of the reducing agent tank 60 does not have to have a longitudinal direction, if it has a longitudinal direction, the liquid level of the urea aqueous solution fluctuates greatly when the reducing agent tank 60 is tilted. It is particularly suitable as the reducing agent tank 60 according to this embodiment.

A pump 41 is attached to a bottom portion 67 of the reducing agent tank 60 at one longitudinal end (the right side in FIGS. 2 and 3). In this embodiment, the pump 41 is attached to a cylindrical recess 63 projecting downward from the bottom surface of the reducing agent tank 60 . For example, a pump unit including the pump 41 is joined to the opening formed in the cylindrical recess 63 . The joints of the pump unit are liquid-tightly joined. The pump 41 has a suction port 41a through which the urea aqueous solution in the reducing agent tank 60 is sucked and pumped. It should be noted that an opening may be formed in the bottom surface of the reducing agent tank 60 without providing the cylindrical concave portion, and the pump unit may be joined to the opening.

The reducing agent tank 60 has a wall member 61 inside. The wall member 61 is provided in contact with the bottom portion 67 of the reducing agent tank 60 . Moreover, the wall member 61 is formed so as to surround a suction area 65 where the suction port 41a of the pump 41 is located. In this embodiment, the intake area 65 generally corresponds to the area where the cylindrical recess 63 is located.

FIG. 6 is a perspective view showing an example of the wall member 61. As shown in FIG. The wall member 61 shown in FIG. 6 has a rectangular planar shape, and one longitudinal end of the reducing agent tank 60 is open to form an open portion 69 through which the urea aqueous solution can flow. That is, the peripheral wall forming the wall member 61 is formed in a U shape, and one end side in the longitudinal direction of the reducing agent tank 60 is open. Further, among the peripheral walls constituting the wall member 61, the heights of the peripheral wall portions 61b and 61c located on both sides of the reducing agent tank 60 in the second direction (X direction) are equal to one end side of the reducing agent tank 60 in the longitudinal direction. to the other end side (from the right side to the left side in FIGS. 2 and 3). Of the two peripheral wall portions 61b and 61c, the height of the position in contact with the peripheral wall portion 61a on the other end side matches the height of the peripheral wall portion 61a.

The action of the reducing agent tank 60 will be described with reference to FIGS. 7 to 10. FIG. 7 and 8 are reference examples showing a reducing agent tank 160 without wall members. FIG. 7 shows a state in which the reducing agent tank 160 is maintained horizontally, and FIG. Indicates a tilted state. 9 and 10 are examples showing a reducing agent tank 160 according to the present embodiment provided with a wall member 61. FIG. 9 shows a state in which the reducing agent tank 60 is maintained horizontally, and FIG. , the reducing agent tank 60 is tilted.

As shown in FIG. 7, in the reducing agent tank 160 according to the reference example, the liquid surface of the urea aqueous solution in the reducing agent tank 160 rises to the bottom 67 of the reducing agent tank 160 while the vehicle is running on a horizontal road surface, for example. becomes approximately parallel to At this time, the urea aqueous solution exists in the suction area 65 by the pump 41, and the pump 41 can properly suck the urea aqueous solution.

On the other hand, as shown in FIG. 8, in the reducing agent tank 160 according to the reference example, the reducing agent tank 160 is positioned so that the height of the one end side where the pump 41 is mounted increases when the vehicle runs on an inclined road surface. When tilted, the urea aqueous solution is biased toward the other end of the reducing agent tank 160 . At this time, if the liquid surface of the aqueous urea solution is positioned below the suction area 65 of the pump 41, the pump 41 cannot properly suck the aqueous urea solution.

On the other hand, as shown in FIG. 9, in the reducing agent tank 60 according to the present embodiment, for example, while the vehicle is running on a horizontal road surface, the liquid surface of the urea aqueous solution in the reducing agent tank 60 is reduced. It is substantially parallel to the bottom 67 of the agent tank 60 . At this time, the aqueous urea solution also enters the wall member 61 through the opening 69 or the upper space of the wall member 61 . Therefore, the urea aqueous solution exists in the suction area 65 by the pump 41, and the pump 41 can appropriately suck the urea aqueous solution.

In addition, as shown in FIG. 10, the reducing agent tank 60 according to the present embodiment is arranged so that, for example, when the vehicle runs on an inclined road surface, the height of the one end side where the pump 41 is mounted increases. is tilted, the urea aqueous solution is held in the suction area 65 by the wall member 61 while the urea aqueous solution is biased toward the other end of the reducing agent tank 60 . Therefore, the pump 41 can properly suck the urea aqueous solution.

When the reducing agent tank 60 is returned to the horizontal state from the tilted state, the urea aqueous solution enters the wall member 61 through the opening 69 or the upper space of the wall member 61, resulting in the state shown in FIG. becomes. In the present embodiment, the opening portion 69 of the wall member 61 opens the entire lengthwise one end side of the reducing agent tank 60 to the bottom portion 67. Therefore, even when the remaining amount of the urea aqueous solution is relatively small, , the urea aqueous solution can enter the wall member 61 when the reducing agent tank 60 is in a horizontal state.

However, the height of the peripheral wall located at one end in the longitudinal direction of the reducing agent tank 60 determines the position of the liquid surface of the urea aqueous solution held in the wall member 61 when the reducing agent tank 60 is tilted. Therefore, the height of the opening 69 provided at one end in the longitudinal direction of the reducing agent tank 60 from the bottom 67 is the height of the aqueous urea solution in the wall member 61 when the reducing agent tank 60 is tilted. is preferably set to a desired height or more.

For example, the height from the bottom portion 67 of the reducing agent tank 60 to the open portion 69 may be set in consideration of how easily the urea aqueous solution is sucked when the reducing agent tank 60 is tilted. Further, when the pump unit including the pump 41 is provided with a level sensor for detecting the remaining amount of the urea aqueous solution, the height from the bottom portion 67 of the reducing agent tank 60 to the open portion 69 is the same as when the reducing agent tank 60 is tilted. Alternatively, it may be set so that a detection signal indicating a distance equal to or greater than a predetermined level can be output.

FIG. 11 shows an example in which a pump unit 44 including the pump 41 is provided with a level sensor 45 for detecting the remaining amount of the urea aqueous solution. The level sensor 45 shown in FIG. 11 emits an ultrasonic wave 46 upward from the pump unit 44 and measures the remaining amount of the urea aqueous solution based on the time it takes to receive the ultrasonic wave 46 reflected by the liquid surface. . In such a level sensor 45, the area in which ultrasonic waves 46 can be transmitted is limited to a range 47 indicated by broken lines in FIG. Therefore, the height from the bottom portion 67 to the open portion 69 of the reducing agent tank 60 is such that the ultrasonic wave 46 is detected by the level sensor 45 even if the reducing agent tank 60 is tilted when the urea aqueous solution is present in the reducing agent tank 60 . It is set so that the urea aqueous solution stays within the transmittable range 47 .

Further, the wall member 61 is arranged so that even when the reducing agent tank 60 is tilted, the level sensor 45 detects at least the remaining amount of the aqueous urea solution that is detected when the reducing agent tank 60 is horizontal. arranged or designed.

Thereby, for example, the control condition is set so that the output of the internal combustion engine 5 is limited in order to suppress the amount of NO _X discharged from the internal combustion engine 5 when the remaining amount of the urea aqueous solution is less than a predetermined level. It is possible to reduce the possibility that the level sensor 45 detects that the remaining amount of the urea aqueous solution is less than a predetermined level even though an appropriate amount of the urea aqueous solution remains in the vehicle.

In order for the urea aqueous solution to be retained inside the wall member 61 when the reducing agent tank 60 is tilted, the height of the peripheral wall forming the wall member 61 must be constant over the entire circumference. Alternatively, a top plate may be provided on the upper portion of the wall member 61 . However, when the ratio of the urea aqueous solution surrounded by the wall member 61 is high, that is, when the ratio of the internal space of the wall member 61 being open to the outside is low, when the urea aqueous solution freezes, the frozen urea aqueous solution expands There is a risk of damaging the pump 41 . Therefore, as shown in the above embodiment, it is preferable that the upper portion of the wall member 61 is left open and the height of the peripheral wall that constitutes the wall member 61 is lowered depending on the position.

Further, when the height of the peripheral wall constituting the wall member 61 is constant, when a top plate is provided on the upper part of the wall member 61, for example, when the reducing agent tank 60 is inclined in the second direction (X direction) In addition, the urea aqueous solution may be blocked by the peripheral wall of the wall member 61 existing in the second direction, and the residual amount (liquid level) of the urea aqueous solution may be unnecessarily high. For this reason, as shown in the above embodiment, the upper portion of the wall member 61 or a portion of the wall member 61 is released, and the height of the wall member 61 is increased from one longitudinal end of the reducing agent tank 60 to the other. It is preferable that the height gradually increases toward the end side.

As described above, the reducing agent tank 60 according to the present embodiment is provided in contact with the bottom portion 67, is formed so as to surround the suction area 65 of the urea aqueous solution by the pump 41, and has the urea aqueous solution on a part of the peripheral wall. and a wall member 61 having an opening 69 through which the liquid can flow. Therefore, even if the reducing agent tank 60 is tilted in a predetermined direction, the urea aqueous solution is retained in the suction area 65, and the supply of the urea aqueous solution can be continued.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention belongs can conceive of various modifications or modifications within the scope of the technical idea described in the claims. It is understood that these also naturally belong to the technical scope of the present invention.

For example, in the above embodiment, the wall member 61 has a rectangular planar shape, but the present invention is not limited to this example. The planar shape of the wall member 61 may be circular or other shapes. Further, in the above-described embodiment, the open portion 69 of the wall member 61 opens the front surface of the reducing agent tank 60 on one end side in the longitudinal direction, but the present invention is not limited to such an example. The opening may be one or more slits or one or more holes formed in an appropriate direction such as the height direction (Z direction) or horizontal direction.

5... Internal combustion engine, 10... Urea SCR system (exhaust purification device), 13... Selective reduction catalyst, 30... Reducing agent supply device, 41... Pump, 41a... Suction port, 45 Level sensor 60 Reducing agent tank 61 Wall member 61a, 61b, 61c Peripheral wall 65 Suction area 67 Bottom 69 opening

Claims (4)

In a reducing agent tank (60) storing a liquid reducing agent used for purifying the exhaust gas discharged from the internal combustion engine (5),
It is provided in contact with the bottom (67) of the reducing agent tank (60) and is formed to surround the suction area (65) where the suction port (41a) of the pump (41) for pumping the liquid reducing agent is located. and a wall member (61) having an opening (69) through which the liquid reducing agent can flow in a part of the peripheral wall (61a to 61c) ,
In the planar shape of the reducing agent tank (60), the length in the first direction is longer than the length in the second direction perpendicular to the first direction,
The wall member (61) is provided on one end side in the first direction,
A reducing agent tank , wherein the wall member (61) has an upper end portion whose height increases from one end side toward the other end side in the first direction . 2. Reductant tank according to claim 1 , characterized in that the pump (41) is attached to the bottom (67) of the reductant tank (61). A level sensor (45) that outputs a signal corresponding to the distance to the surface of the liquid reducing agent is provided in the inhalation area ( 65 ),
The height of the wall member (61) is such that the reducing agent tank (60) is inclined such that one end of the reducing agent tank (60) in the first direction is higher than the other end thereof. 2. The reduction according to claim 1 , wherein the urea aqueous solution is set so as to remain within a range (47) in which the level sensor (45) can transmit the ultrasonic wave (46) even when the agent tank. a reducing agent tank (60) for storing a liquid reducing agent; a reducing agent supply device (30) for supplying the liquid reducing agent to an exhaust passage of an internal combustion engine (5); and a selective reduction catalyst (13) for reducing nitrogen oxides in the exhaust gas discharged from the internal combustion engine (5) using an agent,
The reducing agent tank (60)
It is provided in contact with the bottom (67) of the reducing agent tank (60) and is formed to surround the suction area (65) where the suction port (41a) of the pump (41) for pumping the liquid reducing agent is located. and a wall member (61) having an opening (69) through which the liquid reducing agent can flow in a part of the peripheral wall (61a to 61c) ,
In the planar shape of the reducing agent tank (60), the length in the first direction is longer than the length in the second direction perpendicular to the first direction,
The wall member (61) is provided on one end side in the first direction,
An exhaust gas purification device , wherein the wall member (61) has an upper end portion whose height increases from one end side toward the other end side in the first direction .

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