JP2012154285A - Reducing agent supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reducing agent supply device capable of preventing inconvenience of respective parts by flowing-in of foreign matter collected in a filter.SOLUTION: This reducing agent supply device includes a reducing agent tank for storing a reducing agent of liquid, a pump for forcibly feeding the reducing agent, a reducing agent injection valve for injecting the reducing agent forcibly fed by the pump into an exhaust pipe of an internal combustion engine, and the filter arranged in the middle of a reducing agent passage to the reducing agent injection valve from the reducing agent tank and collecting the foreign matter in the reducing agent, and performs purge control for collecting the reducing agent in the reducing agent passage and the reducing agent injection valve in the reducing agent tank in response to stopping of the internal combustion engine. The passing direction of the reducing agent passing through the filter in injection control of the reducing agent and the passing direction of the reducing agent passing through the filter in the purge control, are set in the specific direction.

Description

  The present invention relates to a reducing agent supply device that injects a reducing agent for purifying exhaust gas discharged from an internal combustion engine into an exhaust pipe.

Conventionally, as an aspect of an exhaust gas purification device for removing nitrogen oxides (hereinafter referred to as “NO _X ”) in exhaust gas discharged from an internal combustion engine mounted on a vehicle or the like, NO _X provided in an exhaust passage is provided. and NO _X purification catalyst to promote the reduction reaction with a reducing agent, a device that includes a reducing agent supply device for injecting a reducing agent in the liquid such as an aqueous urea solution at the upstream side of the NO _X purification catalyst has been put to practical use and .

  A reducing agent supply device used in such an exhaust purification device includes a reducing agent tank that stores a liquid reducing agent, a pump that sucks and pumps the reducing agent in the reducing agent tank, and a reducing agent that is pumped by the pump. And a reducing agent injection valve that injects the exhaust pipe into the exhaust pipe. The reducing agent passage through which the reducing agent flows is provided with a filter for collecting foreign substances in the reducing agent.

  Here, when a urea aqueous solution is used as the reducing agent, the concentration of the urea aqueous solution is adjusted to a concentration at which the freezing point is lowest (for example, 32.5% concentration, freezing point≈-11 ° C.). However, in cold districts and the like, if the outside air temperature falls below the freezing point while the internal combustion engine is stopped, the reducing agent may solidify in the reducing agent supply path. In particular, since the moisture evaporates due to exhaust heat or the like, the concentration of the reducing agent increases, and the freezing point of the reducing agent may increase.

  When solidification of the reducing agent occurs, the volume of the reducing agent expands, and there is a possibility that the piping and the reducing agent injection valve are damaged. For this reason, when the internal combustion engine is stopped, purge control for collecting the reducing agent remaining in the reducing agent supply path in the reducing agent tank is performed (see, for example, Patent Document 1).

JP 2008-101564 A

  By the way, the filter provided in the reducing agent supply device plays a role of collecting foreign substances in the reducing agent supplied from the reducing agent tank to the reducing agent injection valve during the reducing agent injection control. The foreign matter collected during the injection control of the reducing agent includes dust mixed in the reducing agent in the storage tank, pump abrasion powder, and the like depending on the position of the filter. Further, the filter plays a role of collecting foreign substances in the reducing agent recovered from the reducing agent injection valve and the reducing agent passage to the reducing agent tank during the purge control. The foreign matter collected during the purge control includes incombustibles and exhaust particulates in the exhaust pipe, wear powder of the reducing agent injection valve, and pump wear powder depending on the position of the filter.

  In the conventional reducing agent supply device, the filtering surface of the filter is different between the reducing agent injection control and the purge control. That is, during the reducing agent injection control, it is assumed that the reducing agent passes from the first surface side to the second surface side of the first surface and the second surface that are opposite to each other in the filter. During the control, the reducing agent passes from the second surface side to the first surface side.

  For this reason, the foreign matter adhering to the first surface during the reducing agent injection control may flow into the reducing agent tank, the pump, or other components during the purge control. Further, the foreign matter adhering to the second surface side during the purge control may flow into the reducing agent injection valve and other parts during the reducing agent injection control.

  If foreign substances flow into the reducing agent tank all together, there is a risk of contamination of the reducing agent in the tank. If foreign substances flow into the pump all at once, there is a risk of pump seizure or abnormal wear. In addition, if foreign substances collectively flow into the reducing agent injection valve, there is a risk of clogging the nozzle holes, poor sliding of the valve body, and abnormal wear of the seat surface. In addition, there is a possibility that defects of the respective parts may be caused by the inflow of foreign matters.

  Further, if the reducing agent passes through the filter in different directions, the deflection of the filter itself tends to increase due to the flow, and the filter may be damaged.

In view of such a problem, the inventor of the present invention solves such a problem by making the passage direction of the reducing agent passing through the filter constant during the injection control and the purge control of the reducing agent. The present invention has been completed by finding out that it can be solved.
That is, an object of the present invention is to provide a reducing agent supply device that can prevent problems of each component due to inflow of foreign matter collected by a filter.

  According to the present invention, a reducing agent tank that contains a liquid reducing agent, a pump that pumps the reducing agent, and a reducing agent injection valve that injects the reducing agent pumped by the pump into an exhaust pipe of an internal combustion engine; A filter that is disposed in the middle of the reducing agent passage from the reducing agent tank to the reducing agent injection valve and collects foreign matter in the reducing agent, and when the internal combustion engine is stopped, the reducing agent passage and In the reducing agent supply device in which purge control for recovering the reducing agent in the reducing agent injection valve to the reducing agent tank is executed, the reducing agent passing direction passing through the filter during the injection control of the reducing agent; A reducing agent supply device is provided in which the direction of passage of the reducing agent passing through the filter during the purge control is set to a fixed direction, and the above-described problems can be solved.

  That is, the reducing agent supply device of the present invention is configured so that the reducing agent passing direction through the filter is constant during the reducing agent injection control and the purge control. Foreign matter is collected on a certain surface side. Accordingly, the foreign matter collected by the filter at the time of injection control or purge control of the reducing agent is prevented from flowing back, and it is possible to prevent the occurrence of problems in each component due to the inflow of foreign matter collected by the filter. It becomes possible to reduce the damage of the.

  Moreover, in the reducing agent supply apparatus of the present invention, the filter has a first surface and a second surface that are opposite to each other, and the reducing agent passage closer to the reducing agent tank than the filter is the first. The first branch path is connected to the first surface side of the filter, while the second branch path is connected to the second branch path of the filter. The reducing agent passage which is connected to the surface side and is closer to the reducing agent injection valve than the filter branches into a third branch path and a fourth branch path, and the third branch path is the first branch of the filter. The first branch path, the filter, and the fourth branch path are connected to the second face side of the filter while the reducing agent is being controlled to be injected. The reducing agent is supplied to the reducing agent injection valve via the fourth branch path. On the other hand, during the purge control, the reducing agent is collected in the reducing agent tank via the third branch path, the filter, and the second branch path, thereby reducing the reducing agent. Is preferably passed from the first surface side of the filter to the second surface side.

  By configuring the reducing agent supply device in this way, the reducing agent can be guided to the first surface side of the filter and pass through the filter regardless of whether the reducing agent is being injected or purged. It becomes possible to guide the reducing agent thus obtained from the second surface side of the filter to the reducing agent tank side or the reducing agent injection valve side.

  In the reducing agent supply device of the present invention, the first branch path and the third branch path are unidirectional to block the flow of the reducing agent to the reducing agent tank side or the reducing agent injection valve side. While providing a valve, it is preferable that the said 2nd branch path and the said 4th branch path are provided with the one-way valve which interrupts | blocks the flow to the said filter side of the said reducing agent.

  By configuring the reducing agent supply device in this way, the flow path through which the reducing agent flows is switched between the reducing agent injection control and the purge control by a mechanical one-way valve not controlled by the control device or the like. Is possible.

  Moreover, in the reducing agent supply apparatus of the present invention, the reducing agent tank side and the first branch path or the second branch path are arranged at a branch portion between the first branch path and the second branch path. A flow path switching control valve for switching the connection between the third branch path and the fourth branch path, the reducing agent injection valve side and the third branch path or the second branch path. It is preferable to provide a flow path switching control valve for switching the connection with the four branch paths.

  By configuring the reducing agent supply device in this way, it is possible to switch the flow path through which the reducing agent flows between the reducing agent injection control and the purge control by controlling the switching control valve with a control device or the like. Become.

  In the reducing agent supply apparatus of the present invention, it is preferable that the filter is configured as a filter unit including at least the one-way valve or the flow path switching control valve.

  By configuring the reducing agent supply device in this way, it is possible to easily configure the reducing agent supply device of the present invention by replacing the filter portion.

  In the reducing agent supply apparatus of the present invention, it is preferable that the second branch path is connected to a lowermost portion of the second surface side region of the filter.

  By configuring the reducing agent supply device in this way, the amount of reducing agent remaining on the filter during purge control can be reduced as much as possible.

It is a figure which shows roughly an example of the whole structure of the exhaust gas purification apparatus provided with the reducing agent supply apparatus which concerns on 1st Embodiment. It is a figure shown in order to demonstrate the structure of the reducing agent supply apparatus which concerns on 1st Embodiment. It is a figure shown in order to demonstrate the flow direction of a reducing agent. It is a figure which shows roughly an example of the whole structure of the exhaust gas purification apparatus provided with the reducing agent supply apparatus which concerns on 2nd Embodiment. It is a figure shown in order to demonstrate the structure of the reducing agent supply apparatus which concerns on 2nd Embodiment. It is a figure shown in order to demonstrate the flow direction of a reducing agent. It is a figure shown in order to demonstrate the structure of the reducing agent supply apparatus which concerns on the modification 1. As shown in FIG. It is a figure shown in order to demonstrate the structure of the reducing agent supply apparatus which concerns on the modification 2. As shown in FIG. It is a figure shown in order to demonstrate the structure of the reducing agent supply apparatus which concerns on the modification 3. FIG. It is a figure shown in order to demonstrate the structure of the reducing agent supply apparatus which concerns on the modification 4. FIG. It is a figure shown in order to demonstrate the structure of the reducing agent supply apparatus which concerns on the modification 5. FIG. It is a figure shown in order to demonstrate the structure of the reducing agent supply apparatus which concerns on the modification 6. FIG.

  Hereinafter, an embodiment relating to a reducing agent supply apparatus according to the present invention will be specifically described with reference to the drawings. In addition, in each figure, what has attached the same code | symbol has shown the same member, and description is abbreviate | omitted suitably.

[First Embodiment]
FIG. 1 is a diagram schematically illustrating an example of an overall configuration of an exhaust purification device 10A including a reducing agent supply device 20A according to the first embodiment. FIG. 2 is a diagram for explaining the configuration of the reducing agent supply apparatus 20A according to the first embodiment. 3A and 3B are diagrams for explaining the flow direction of the reducing agent. FIG. 3A shows the flow direction of the reducing agent during the injection control of the reducing agent, and FIG. 3B shows the purge control. The flow direction of the reducing agent is shown.

(1) Overall Configuration of Exhaust Purification Device The exhaust purification device 10A purifies NO _X in the exhaust discharged from the internal combustion engine 1 mounted on a vehicle or the like on the NO _X purification catalyst 11 using a reducing agent. It is the apparatus comprised as follows. The exhaust purification device 10 </ b> A includes a NO _X purification catalyst 11 disposed in the middle of the exhaust pipe 3 connected to the exhaust system of the internal combustion engine 1, and a reducing agent in the exhaust pipe 3 upstream of the NO _X purification catalyst 11. The main components are a reducing agent supply device 20A for supplying the fuel and a control device 40A that controls the operation of the reducing agent supply device 20A.

The NO _x purification catalyst 11 has a function of promoting a reaction between the reducing agent injected into the exhaust pipe 3 or a reducing component generated from the reducing agent and NO _{x in} the exhaust. As the NO _x purification catalyst 11, a NO _x selective reduction catalyst or a NO _x storage catalyst is used.

The NO _X selective reduction catalyst is a catalyst that has a function of adsorbing a reducing agent and selectively purifying NO _X in exhaust gas flowing into the catalyst using the reducing agent. In the case of using a NO _x selective reduction catalyst, an aqueous urea solution or unburned fuel is used as a reducing agent. When an aqueous urea solution is used as the reducing agent, ammonia (NH ₃ ) produced by the decomposition of urea in the aqueous urea solution reacts with NO _x , so that NO _x becomes nitrogen (N ₂ ) and water (H Decomposed into ₂ O). When unburned fuel is used as the reducing agent, the hydrocarbon (HC) in the unburned fuel reacts with NO _x , so that NO _x is nitrogen (N ₂ ), carbon dioxide (CO ₂ ), and water. Decomposed into (H ₂ O).

Further, NO _X storage catalyst, while the air-fuel ratio of the exhaust gas flowing in the catalyst occludes NO _X in the lean state (fuel-lean state), release the NO _X when the air-fuel ratio is switched to a state rich and a catalyst that functions to purify NO _X with hydrocarbons in the exhaust gas (HC). NO _{x that} has reacted with the hydrocarbon (HC) is decomposed into nitrogen (N ₂ ), carbon dioxide (CO ₂ ), and water (H ₂ O). When the NO _x storage catalyst is used, unburned fuel as a reducing agent is injected and supplied into the exhaust pipe 3 in order to make the air-fuel ratio of the exhaust rich.

(2) Reducing agent supply device The reducing agent supply device 20A includes a reducing agent tank 21 that contains a liquid reducing agent, a pump 23 that pumps the reducing agent, and a reducing agent that is pumped by the pump 23 into the exhaust pipe 3. The reductant injection valve 25 to inject, the reverting valve 24 which switches the flow direction of the reductant pumped by the pump 23, and the filter part 50A for collecting the foreign material in a reductant are provided.

  The reducing agent tank 21 and the pump 23 are connected by a first reducing agent passage 31 via a reverting valve 24, and the pump 23 and the filter unit 50 </ b> A are connected by a second reducing agent passage via the reverting valve 24. 32, and the filter unit 50A and the reducing agent injection valve 25 are connected by a third reducing agent passage 33. A return passage 35 whose other end is connected to the reducing agent tank 21 is connected to the filter portion 50A, and a relief valve 37 is provided in the return passage 35.

  The third reducing agent passage 33 is provided with a pressure sensor 27 for detecting the pressure in the third reducing agent passage 33. However, the pressure sensor 27 only needs to be able to detect the pressure of the reducing agent supplied to the reducing agent injection valve 25, and may not be provided directly in the third reducing agent passage 33.

  The reducing agent injection valve 25 is controlled by the control device 40A, and the reducing agent injection valve 25 that can be used is not particularly limited. For example, it is possible to use an electromagnetic valve that is switched between open / close by switching between energization / non-energization.

  The pump 23 is controlled by the control device 40A, and the pump 23 that can be used is not particularly limited. For example, an electric pump in which the discharge amount is adjusted by adjusting the duty ratio of ON / OFF of energization per unit time can be used.

  The reverting valve 24 is driven and controlled by the control device 40, and the flow direction of the reducing agent is the forward direction from the reducing agent tank 21 side to the reducing agent injection valve 25 side, and the reducing agent injection valve 25. It is configured to be switchable in the reverse direction that flows from the side to the reducing agent tank 21 side. The reverting valve 24 that can be used is not particularly limited. For example, an electromagnetic switching valve capable of switching the flow direction of the reducing agent to the forward direction or the reverse direction by turning on / off the current can be used.

  In the reducing agent supply apparatus 20A according to the present embodiment, when injection control of the reducing agent into the exhaust pipe 3 is performed, the energization to the reverting valve 24 is stopped so that the reducing agent flows in the forward direction. It has become. On the other hand, when performing purge control to collect the reducing agent in the reducing agent tank 21, the reverting valve 24 is energized and the flow path is switched so that the reducing agent flows in the reverse direction. .

  As shown in FIG. 2, the filter unit 50 </ b> A includes a casing 54 and a filter 51 accommodated in the casing 54. In the reducing agent supply apparatus 20A of the present embodiment, a cylindrical filter 51 is used, and the filter 51 includes a first surface 51a positioned outside the cylindrical shape, and a second surface 51b positioned inside. have. In FIG. 2, only the cross section of the filter 51 is shown.

  The second reducing agent passage 32 that connects the pump 23 and the filter unit 50A is branched into a first branch passage 32a and a second branch passage 32b. The first branch passage 32a is connected to the region A on the first surface 51a side of the filter 51, and the first one-way valve 52a that blocks the flow of the reducing agent from the filter unit 50A side to the pump 23 side. It has. The second branch path 32b is connected to the region B on the second surface 51b side of the filter 51, and a second one-way valve 52b that blocks the flow of the reducing agent from the pump 23 side to the filter unit 50A side. It has.

  The third reducing agent passage 33 that connects the filter unit 50A and the reducing agent injection valve 25 is branched into a third branch passage 33a and a fourth branch passage 33b on the way. The third branch path 33a is connected to the region A on the first surface 51a side of the filter 51 and is configured to block the flow of the reducing agent from the filter unit 50A side to the reducing agent injection valve 25 side. A directional valve 53a is provided. The fourth branch path 33b is connected to the region B on the second surface 51b side of the filter 51 and is configured to block the flow of the reducing agent from the reducing agent injection valve 25 side to the filter unit 50A side. A directional valve 53b is provided.

  The return passage 35 connecting the filter unit 50A and the reducing agent tank 21 is connected to the region B on the second surface 51b side of the filter 51, and the reducing agent from the reducing agent tank 21 side to the filter unit 50A side. A relief valve 37 for blocking the flow is provided.

  The first to fourth one-way valves 52a, 52b, 53a, 53b and the relief valve 37 are configured as mechanical valves using a valve body and a spring. The first one-way valve 52a, the fourth one-way valve 53b, and the relief valve 37 are opened during the injection control of the reducing agent. The second one-way valve 52b and the third one-way valve 53a are opened during the purge control.

  Specifically, as shown in FIG. 3 (a), during the reducing agent injection control, the reducing agent is pumped in the forward direction by driving the pump 23, and the second reducing agent passage 32, the first branch passage. As the pressure in 32a and the second branch path 32b rises, the second one-way valve 52b closes, while the first one-way valve 52a opens. When the first branch path 32a is opened, the reducing agent flows into the area A on the first surface 51a side of the filter 51.

  Further, when the reducing agent flows into the filter unit 50A and the pressure in the filter unit 50A increases, the third one-way valve 53a is closed, while the fourth one-way valve 53b is opened. Therefore, the reducing agent that has flowed into the filter unit 50A passes through the filter 51 from the first surface 51a side to the second surface 51b side. At this time, foreign matter mixed in the reducing agent adheres to the first surface 51 a side of the filter 51.

  The reducing agent that has passed through the filter 51 flows through the fourth branch passage 33b via the fourth one-way valve 53b, and further flows through the third reducing agent passage 33 to be supplied to the reducing agent injection valve 25. At this time, if the supply amount of the reducing agent becomes excessive and the pressure of the reducing agent exceeds the opening pressure of the relief valve 37, the relief valve 37 is opened, and excess reducing agent passes through the return passage 35. Returned to the tank 21. Since the return passage 35 is connected to the region B on the second surface 51 b side of the filter 51, foreign matter adhering to the filter 51 does not flow into the reducing agent tank 21 through the return passage 35.

  Further, as shown in FIG. 3B, during the purge control, the pump 23 is driven and the reducing agent is pumped in the reverse direction so that the second reducing agent passage 32, the first branch passage 32a, and the second By depressurizing the inside of the branch path 32b, the first one-way valve 52a is closed, while the second one-way valve 52b is opened. When the second one-way valve 52b is opened, the reducing agent in the filter unit 50A is sucked back to the pump 23 side.

  Further, the reducing agent in the filter unit 50A is sucked back and the pressure in the filter unit 50A is reduced, whereby the fourth one-way valve 53b and the relief valve 37 are closed, while the third one-way valve 53a is Open the valve. Therefore, the reducing agent in the reducing agent injection valve 25 and the third reducing agent passage 33 flows into the first surface 51a side of the filter 51 through the third one-way valve 53a, and further, the filter 51 passes through the first 51a. Passes from the surface 51a side to the second surface 51b side. At this time, foreign matter mixed in the reducing agent adheres to the first surface 51 a side of the filter 51.

  The reducing agent that has passed through the filter 51 is sucked back by the pump 23 via the second branch passage 32 b and the second reducing agent passage 32 and is collected in the reducing agent tank 21. At this time, since the second branch path 32b is connected to the lowermost part of the casing 54 of the filter unit 50A, the reducing agent is less likely to remain in the filter unit 50A.

  That is, during the reducing agent injection control, the reducing agent pumped by the pump 23 is the second reducing agent passage 32, the first branch passage 32a, the region A on the first surface 51a side, the filter 51, the second reducing agent. Are sequentially supplied to the reducing agent injection valve 25 through the region B on the surface 51b side, the fourth branch passage 33b, and the third reducing agent passage 33. Further, during the purge control, the reducing agent sucked back by the pump 23 is the third reducing agent passage 33, the third branch passage 33a, the region A on the first surface 51a side, the filter 51, and the second surface 51b. Side region B, second branch passage 32b, and second reducing agent passage 32 are sequentially passed through and collected in the reducing agent tank 21.

  Therefore, in the reducing agent supply apparatus 20A of the present embodiment, the reducing agent passes through the filter 51 because the reducing agent passes from the first surface 51a side to the second surface 51b side during both the reducing agent injection control and the purge control. The direction of passage of the reducing agent is the same so that the foreign matter adhering to the filter 51 does not flow backward.

  As described above, the reducing agent injection device 20A according to the first embodiment has the reducing agent passing direction through the filter 51 during the reducing agent injection control and the reducing agent passing through the filter 51 during the purge control. It is comprised so that the passage direction of an agent may become a fixed direction. Therefore, foreign matters are always collected on the first surface 51 a side of the filter 51. Therefore, the foreign matter collected by the filter 51 during the reducing agent injection control or purge control is prevented from flowing back, and the foreign matter collected by the filter 51 flows in, so that the pump 23, the reducing agent injection valve 25, the first The fourth one-way valve 52a, 52b, 53a, 53b, the relief valve 37, the reducing agent tank 21 and the like can be prevented from malfunctioning and the filter 51 itself can be prevented from being damaged. Become.

  Further, according to the reducing agent supply device 20A according to the first embodiment, the second reducing agent passage 32 connecting the pump 23 and the filter unit 50A is branched, and the filter unit 50A and the reducing agent injection valve 25 are branched. The third reducing agent passage 33 that connects the two is branched, and each branch passage is provided with a one-way valve to be connected to a predetermined location. Even in this case, the reducing agent can be guided to the first surface 51a side of the filter 51, and the reducing agent that has passed through the filter 51 can be passed from the second surface 51b side of the filter 51 to the reducing agent tank 21 side or the reducing agent. It becomes possible to guide to the injection valve 25 side.

  Moreover, according to the reducing agent supply apparatus 20A according to the first embodiment, the mechanical type that blocks the flow of the reducing agent in a predetermined direction in the first to fourth branch paths 32a, 32b, 33a, and 33b. Since the first to fourth one-way valves 52a, 52b, 53a, and 53b are provided, the flow path through which the reducing agent flows can be switched without requiring control by the control device 40.

  Further, according to the reducing agent supply apparatus 20A of the first embodiment, the return passage 35 is connected to the region B on the second surface 51b side of the filter 51, so that foreign matter adhering to the filter 51 is returned to the return passage. It is possible not to flow into the reducing agent tank 21 via 35.

  Furthermore, according to the reducing agent supply apparatus 20A according to the first embodiment, the second branch path 32b through which the reducing agent in the filter unit 50A flows during the purge control is disposed in the region on the second surface 51b side of the filter 51. Since it is connected to the lowermost part of B, the amount of reducing agent remaining in the filter unit 50A during purge control can be reduced as much as possible.

[Second Embodiment]
FIG. 4 is a diagram schematically illustrating an example of an overall configuration of an exhaust purification device 10B including the reducing agent supply device 20B according to the second embodiment. FIG. 5 is a diagram shown for explaining the configuration of the reducing agent supply apparatus 20B according to the second embodiment. 6A and 6B are diagrams for explaining the flow direction of the reducing agent. FIG. 6A illustrates the flow direction of the reducing agent during the injection control of the reducing agent, and FIG. 6B illustrates the purge control. The flow direction of the reducing agent is shown.

  The overall configuration of the exhaust emission control device 10B is basically the same as that of the first embodiment, but the configuration of the reducing agent supply device 20B is the reducing agent supply device 20A according to the first embodiment. And different. Hereinafter, the configuration of the reducing agent supply device 20B will be mainly described.

  The reducing agent supply apparatus 20B according to the present embodiment injects the reducing agent tank 21 that stores the liquid reducing agent, the pump 23 that pumps the reducing agent, and the reducing agent that is pumped by the pump 23 into the exhaust pipe 3. A reducing agent injection valve 25, a reverting valve 24 for switching the flow direction of the reducing agent pumped by the pump 23, and a filter unit 50B for collecting foreign substances in the reducing agent are provided.

  The reducing agent tank 21 and the pump 23 are connected by a first reducing agent passage 31 via a reverting valve 24, and the pump 23 and the filter unit 50 </ b> B are connected by a second reducing agent passage via the reverting valve 24. 72, and the filter unit 50B and the reducing agent injection valve 25 are connected by a third reducing agent passage 73. A return passage 35 having the other end connected to the reducing agent tank 21 is connected to the filter portion 50B, and the return passage 35 is provided with a relief valve 37. The third reducing agent passage 73 is provided with a pressure sensor 27 for detecting the pressure in the third reducing agent passage 73.

  The reducing agent injection valve 25, the pump 23, the reverting valve 24, the pressure sensor 27, the filter unit 50B, the return passage 35, and the relief valve 37 are configured in the same manner as in the reducing agent supply device 20A according to the first embodiment. can do.

  The second reducing agent passage 72 that connects the pump 23 and the filter unit 50B is branched into a first branch path 72a and a second branch path 72b on the way. The first branch path 72 a is connected to the region A on the first surface 51 a side of the filter 51. The second branch path 72 b is connected to the region B on the second surface 51 b side of the filter 51.

  A first switching control valve 75 is provided at a branch portion between the first branch path 72a and the second branch path 72b. The first switching control valve 75 is controlled by the control device 40B. Whether the second reducing agent passage 72 is connected to the first branch path 72a or the second branch path 72b. Can be switched. In the reducing agent supply apparatus 20B according to the present embodiment, while the energization to the first switching control valve 75 is stopped, the second reducing agent passage 72 and the first branch passage 72a are connected, While the first switching control valve 75 is energized, an electromagnetic control valve that connects the second reducing agent passage 72 and the second branch passage 72b is used. However, the first switching control valve 75 that can be used is not particularly limited.

  The third reducing agent passage 73 connecting the filter unit 50B and the reducing agent injection valve 25 is branched into a third branch path 73a and a fourth branch path 73b. The third branch path 73 a is connected to the region A on the first surface 51 a side of the filter 51. The fourth branch path 73 b is connected to the region B on the second surface 51 b side of the filter 51.

  A second switching control valve 76 is provided at a branch portion between the third branch path 73a and the fourth branch path 73b. The second switching control valve 76 is controlled by the control device 40B, and connects the third reducing agent passage 73 to the third branch passage 73a or the fourth branch passage 73b. Can be switched. In the reducing agent supply device 20B according to the present embodiment, while the energization to the second switching control valve 76 is stopped, the third reducing agent passage 73 and the fourth branch passage 73b are connected, While the second switching control valve 76 is energized, an electromagnetic control valve that connects the third reducing agent passage 73 and the third branch passage 73a is used. However, the second switching control valve 76 that can be used is not particularly limited.

  In the reducing agent supply apparatus 20B according to the present embodiment, the energization of the first switching control valve 75 and the second switching control valve 76 is stopped during the reducing agent injection control, and the second reducing agent passage 72 is stopped. And the first branch path 72a, the fourth branch path 73b, and the third reducing agent path 73 are connected to each other. On the other hand, during the purge control, both the first switching control valve 75 and the second switching control valve 76 are energized, and the second reducing agent passage 72, the second branch path 72b, and the third branch path 73a. And the third reducing agent passage 73 are connected to each other.

  Specifically, as shown in FIG. 6A, during the reducing agent injection control, the energization of both the first switching control valve 75 and the second switching control valve 76 is stopped and the second switching control valve 76 is stopped. The reducing agent passage 72 and the first branch passage 72a are connected, and the fourth branch passage 73b and the third reducing agent passage 73 are connected to each other. When the pump 23 is driven in this state and the reducing agent is pumped in the forward direction, the reducing agent flows into the region A on the first surface 51a side of the filter 51 through the first branch path 72a.

  The reducing agent that has flowed into the filter unit 50B passes through the filter 51 from the first surface 51a side to the second surface 51b side, and further passes through the fourth branch path 73b to form a third reducing agent passage. It flows through 73 and is supplied to the reducing agent injection valve 25. At this time, foreign matter mixed in the reducing agent adheres to the first surface 51 a side of the filter 51.

  Further, when the supply amount of the reducing agent becomes excessive and the pressure of the reducing agent exceeds the opening pressure of the relief valve 37, the relief valve 37 is opened, and excess reducing agent passes through the return passage 35 and the reducing agent tank. 21 is returned. At this time, since the return passage 35 is connected to the region B on the second surface 51 b side of the filter 51, foreign matter attached to the filter 51 does not flow into the reducing agent tank 21 via the return passage 35.

  Further, as shown in FIG. 6B, during the purge control, both the first switching control valve 75 and the second switching control valve 76 are energized, and the second reducing agent passage 72 and the second branch are supplied. The path 72b is connected to the third branch path 73a and the third reducing agent path 73, respectively. When the pump 23 is driven in this state and the reducing agent is pumped in the reverse direction, the inside of the second reducing agent passage 72 and the second branch passage 72b is depressurized, whereby the reducing agent in the filter unit 50B is pumped. Sucked back to the side.

  Further, the reducing agent in the filter unit 50B is sucked back and the inside of the filter unit 50B is decompressed, whereby the relief valve 37 is closed, while the third branch path 73a and the third reducing agent path 73 are decompressed. Is done. Therefore, the reducing agent in the reducing agent injection valve 25 and the third reducing agent passage 73 flows into the first surface 51a side of the filter 51 through the third branch passage 73a, and further the filter 51 is moved to the first surface. It passes from the 51a side to the second surface 51b side. At this time, foreign matter mixed in the reducing agent adheres to the first surface 51 a side of the filter 51.

  The reducing agent that has passed through the filter 51 is sucked back by the pump 23 via the second branch path 72 b and the second reducing agent path 72 and is collected in the reducing agent tank 21. At this time, since the second branch path 72b is connected to the lowermost part of the casing 54 of the filter unit 50B, the reducing agent is less likely to remain in the filter unit 50B.

  That is, during the reducing agent injection control, the reducing agent pumped by the pump 23 is the second reducing agent passage 72, the first branch passage 72a, the region A on the first surface 51a side, the filter 51, the second reducing agent. Are sequentially passed through the region B on the surface 51b side, the fourth branch path 73b, and the third reducing agent passage 73 and supplied to the reducing agent injection valve 25. Further, during the purge control, the reducing agent sucked back by the pump 23 is the third reducing agent passage 73, the third branch passage 73a, the region A on the first surface 51a side, the filter 51, and the second surface 51b. Side region B, second branch passage 72b, and second reducing agent passage 72 are sequentially passed through and collected in the reducing agent tank 21.

  Therefore, in the reducing agent supply apparatus 20B of the present embodiment, the reducing agent passes through the filter 51 because the reducing agent passes from the first surface 51a side to the second surface 51b side during both of the reducing agent injection control and the purge control. The direction of passage of the reducing agent is the same so that the foreign matter adhering to the filter 51 does not flow backward.

  As described above, the reducing agent injection device 20B according to the second embodiment has the reducing agent passing direction through the filter 51 during the reducing agent injection control and the reducing agent passing through the filter 51 during the purge control. It is comprised so that the passage direction of an agent may become a fixed direction. Therefore, foreign matters are always collected on the first surface 51 a side of the filter 51. Accordingly, the foreign matter collected by the filter 51 during the reducing agent injection control or purge control is prevented from flowing back, and the inflow of the foreign matter collected by the filter 51 causes the pump 23, the reducing agent injection valve 25, the relief valve. 37, it is possible to prevent the occurrence of problems in each component such as the reducing agent tank 21 and to reduce the breakage of the filter 51 itself.

  Moreover, according to the reducing agent supply apparatus 20B according to the second embodiment, the second reducing agent passage 72 that connects the pump 23 and the filter unit 50B is branched, and the filter unit 50B and the reducing agent injection valve 25 are branched. The third reducing agent passage 73 that connects the two is branched and connected to a predetermined location, and a switching control valve is provided at each branch portion. Therefore, either during the reducing agent injection control or during the purge control. Even in this case, the reducing agent can be guided to the first surface 51a side of the filter 51, and the reducing agent that has passed through the filter 51 can be passed from the second surface 51b side of the filter 51 to the reducing agent tank 21 side or the reducing agent. It becomes possible to guide to the injection valve 25 side.

  Moreover, according to the reducing agent supply apparatus 20B according to the second embodiment, the first switching control valve 75 is provided at the branch portion between the first branch path 72a and the second branch path 72b, and the third Since the second switching control valve 76 is provided at the branch portion between the branch path 73a and the fourth branch path 73b, the flow path through which the reducing agent can be switched by being controlled by the control device 40. become.

  Further, according to the reducing agent supply device 20B of the second embodiment, the return passage 35 is connected to the region B on the second surface 51b side of the filter 51, so that foreign matter adhering to the filter 51 is returned to the return passage. It is possible not to flow into the reducing agent tank 21 via 35.

  Furthermore, according to the reducing agent supply device 20B according to the second embodiment, the second branch path 72b through which the reducing agent in the filter unit 50B flows during the purge control is an area on the second surface 51b side of the filter 51. Since it is connected to the lowermost part of B, the amount of reducing agent remaining in the filter unit 50B during purge control can be reduced as much as possible.

[Other embodiments]
The reducing agent supply apparatus according to the first and second embodiments described above shows one aspect of the present invention and does not limit the present invention, and can be arbitrarily changed within the scope of the present invention. It is possible. For example, the reducing agent supply apparatus according to the first and second embodiments can be modified as follows.

(1) The configuration and form of each component described in the reducing agent supply apparatus according to the first and second embodiments described above are merely examples, and can be arbitrarily changed.

  For example, in the reducing agent supply devices 20A and 20B according to the first and second embodiments described above, purge control is performed by switching the flow direction of the reducing agent by the reverting valve 24. The purge control may be performed by rotating the pump 23 in the reverse direction without using the reverting valve.

  Moreover, in the reducing agent supply apparatuses 20A and 20B according to the first and second embodiments described above, the cylindrical filter 51 is used, but the form of the filter is not limited. For example, a flat filter may be used instead of a three-dimensional filter. Also, a plurality of filters 51 can be used in an overlapping manner.

(2) In the reducing agent supply devices 20A and 20B according to the first and second embodiments described above, the reducing agent is allowed to pass from the outside of the cylindrical filter 51 toward the inside of the filter 51. However, the passing direction of the reducing agent may be reversed.

FIG. 7 is a view for explaining the reducing agent supply apparatus according to the first modification, and FIG. 8 is a view for explaining the reducing agent supply apparatus according to the second modification.
In the reducing agent supply apparatus according to the first modification, the connection point of the first branch path 32a and the second branch path 32b to the filter unit 50A is the same as that of the reducing agent supply apparatus 20A according to the first embodiment. In addition, the connection point of the third branch path 33a and the fourth branch path 33b is opposite to that of the reducing agent supply apparatus 20A according to the first embodiment. Further, in the reducing agent supply apparatus according to the second modification, the connection point of the first branch path 72a and the second branch path 72b to the filter unit 50B is the reducing agent supply apparatus 20B according to the second embodiment. The connection place of the 3rd branch path 73a and the 4th branch path 73b is contrary to the case of the reducing agent supply apparatus 20B which concerns on 2nd Embodiment. That is, in the reducing agent supply apparatus according to Modifications 1 and 2, the surface located inside the filter 51 is the first surface 51a, and the surface located outside is the second surface 51b. In the reducing agent supply apparatus according to Modifications 1 and 2, the reducing agent passing through the filter 51 passes from the inside to the outside, which is opposite to the case of the first and second embodiments, respectively. The same effects as those of the reducing agent supply device according to the first or second embodiment can be obtained.

(3) The reducing agent supply devices 20A and 20B according to the first and second embodiments described above may be configured by unitizing the filters, one-way valves, switching control valves, and the like.
FIG. 9 is a view for explaining the reducing agent supply apparatus according to the third modification, and FIG. 10 is a view for explaining the reducing agent supply apparatus according to the fourth modification. The reducing agent supply apparatus according to Modification 3 includes a filter unit 50A, first to fourth branch paths 32a, 32b, 33a, 33b, and first to fourth in the reducing agent supply apparatus 20A according to the first embodiment. The filter unit 50C is formed by unitizing the one-way valves 52a, 52b, 53a, and 53b. Further, the reducing agent supply device according to the modified example 4 includes the filter unit 50B, the first to fourth branch paths 72a, 72b, 73a, 73b, the first and the second reducing agent supply device 20B according to the first embodiment. A filter unit 50D in which the second switching control valves 75 and 76 are unitized is provided. By using the filter units 50C and 50D configured in this way, the direction of the reducing agent passing through the filter 51 is constant during the reducing agent injection control and the purge control by replacing the filter portion. It becomes possible to easily constitute the reducing agent supply apparatus.

(4) In the reducing agent supply devices 20A and 20B according to the first and second embodiments described above, the filter units 50A and 50B are disposed between the pump 23 and the reducing agent injection valve 25. Filter units 50 </ b> A and 50 </ b> B may be arranged between the reducing agent tank 21 and the pump 23. Even in the case where the filter unit is arranged in this way, the reducing agent passage located on the reducing agent tank side with respect to the filter unit and the reducing agent passage located on the pump side with respect to the filter unit are respectively branched in a predetermined direction. By providing a one-way valve that shuts off the flow of reducing agent and a switching control valve that switches the flow path, the reducing agent passage direction that passes through the filter is constant during the reducing agent injection control and purge control. Can be.

(5) In the reducing agent supply devices 20A and 20B according to the first and second embodiments described above, the filter 51 can be held by a highly rigid opening member.
FIG. 11 is a diagram for explaining a reducing agent supply apparatus according to Modification Example 5, and shows an example in which the reducing agent supply apparatus 20A according to the first embodiment is modified. In the reducing agent supply apparatus according to Modification 5, the filter 51 is held by opening members 81a and 81b arranged on the first surface 51a side and the second surface 51b side, respectively. Therefore, it is possible to prevent deformation of the filter 51 due to the influence of the reducing agent pressure during the reducing agent injection control and the suction force of the pump 23 during the purge control. The opening members 81a and 81b can be configured using a stainless steel metal or a highly rigid resin material. Moreover, the opening members 81a and 81b can be configured in a perforated plate having a plurality of openings or in a mesh shape, for example.

(6) In the reducing agent supply apparatus according to Modification 3 described above, a space portion may be provided in the casing 54 below the filter 51.
FIG. 12 is a diagram for explaining a reducing agent supply apparatus according to Modification Example 6, and shows an example in which the reducing agent supply apparatus according to Modification Example 3 is modified. In the reducing agent supply apparatus according to Modification 6, the filter 51 is pressed upward by a spring 85, and a space portion 87 is provided below the filter 51. Therefore, even when the reducing agent remains in the casing 54 when the reducing agent in the filter unit 50F is sucked back through the second branch path 32b during the purge control, the reducing agent remains in the filter 51. It is difficult to adhere. Therefore, even when the reducing agent is frozen in the filter unit 50F while the internal combustion engine is stopped, it is possible to prevent the filter 51 from being damaged due to expansion of the volume of the reducing agent.

1: internal combustion engine, 3: exhaust pipe, 10A · 10B: exhaust purification device, 11: NO _x purification catalyst, 13: NO _x sensor, 20A / 20B: reducing agent supply device, 21: reducing agent tank, 23: pump, 24: reverting valve, 25: reducing agent injection valve, 27: pressure sensor, 31: first reducing agent passage, 32: second reducing agent passage, 32a: first branching passage, 32b: second branching Road, 33: Third reducing agent passage, 33a: Third branch passage, 33b: Fourth branch passage, 35: Return passage, 37: Relief valve, 40A, 40B: Control device, 50A, 50B, 50E, 50F: Filter section, 50C / 50D: Filter unit, 51: Filter, 51a: First surface, 51b: Second surface, 52a: First one-way valve, 52b: Second one-way valve, 53a: Third one-way valve, 53b: fourth One-way valve, 54: casing, 72: second reducing agent passage, 72a: first branching passage, 72b: second branching passage, 73: third reducing agent passage, 73a: third branching passage 73b: fourth branch path, 75: first switching control valve, 76: second switching control valve, 81a and 81b: opening member, 85: spring, 87: space portion

Claims (6)

From a reducing agent tank that stores a liquid reducing agent, a pump that pumps the reducing agent, a reducing agent injection valve that injects the reducing agent pumped by the pump into an exhaust pipe of an internal combustion engine, and the reducing agent tank A filter disposed in the middle of the reducing agent passage to the reducing agent injection valve and collecting foreign matter in the reducing agent,
In the reducing agent supply apparatus in which purge control for recovering the reducing agent in the reducing agent passage and the reducing agent injection valve to the reducing agent tank is executed with the stop of the internal combustion engine.
A direction in which the reducing agent passes through the filter during the injection control of the reducing agent and a direction in which the reducing agent passes through the filter during the purge control are set in a fixed direction. Reducing agent supply device. The filter has a first surface and a second surface that face each other;
The reducing agent passage closer to the reducing agent tank than the filter branches into a first branch path and a second branch path, and the first branch path is connected to the first surface side of the filter. On the other hand, the second branch path is connected to the second surface side of the filter,
The reducing agent passage closer to the reducing agent injection valve than the filter branches into a third branch path and a fourth branch path, and the third branch path is connected to the first surface side of the filter. On the other hand, the fourth branch path is connected to the second surface side of the filter,
During the injection control of the reducing agent, the reducing agent is supplied to the reducing agent injection valve via the first branch path, the filter, and the fourth branch path,
During the purge control, the reducing agent is collected in the reducing agent tank via the third branch path, the filter, and the second branch path, so that the reducing agent is removed from the filter. The reducing agent supply device according to claim 1, wherein the first surface side is passed from the first surface side to the second surface side. The first branch path and the third branch path include a one-way valve that blocks the flow of the reducing agent to the reducing agent tank side or the reducing agent injection valve side,
The reducing agent supply apparatus according to claim 2, wherein the second branch path and the fourth branch path include a one-way valve that blocks the flow of the reducing agent toward the filter. A flow path switching control valve for switching a connection between the reducing agent tank side and the first branch path or the second branch path at a branch portion between the first branch path and the second branch path. With
Flow path switching control for switching connection between the reducing agent injection valve side and the third branch path or the fourth branch path at a branch portion between the third branch path and the fourth branch path The reducing agent supply apparatus according to claim 2, further comprising a valve.   The reducing agent supply apparatus according to claim 3 or 4, wherein the filter is configured as a filter unit including at least the one-way valve or the flow path switching control valve. The reducing agent supply apparatus according to claim 5, wherein the second branch path is connected to a lowermost portion of the second surface side region of the filter.

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