JP6743493B2 - Urea water addition system for internal combustion engine - Google Patents

Description

The present invention relates to a urea water addition system for an internal combustion engine, and more particularly to a urea water addition system for adding urea water to a NOx selective reduction catalyst in a diesel engine.

An SCR system using a selective reduction type NOx catalyst (SCR: Selective Catalytic Reduction) has been developed as a system for purifying NOx in exhaust gas of a diesel engine.

In this SCR system, urea water is added to the upstream side of the SCR in the exhaust flow direction, ammonia is generated by the heat of the exhaust gas, and NOx is reduced in the SCR by this ammonia to purify it. The urea water is added from a urea water addition valve provided on the upstream side of the SCR.

JP-A-6-118177

In the urea water addition system (including the urea water addition valve) for performing such urea water addition, a tank for storing the urea water and a sensor arranged in the tank for detecting the concentration of the urea water are provided. May be provided.

In this case, bubbles may adhere to the sensor, and the bubbles may interfere with accurate concentration detection.

Therefore, the present invention has been devised in view of the above problems, and an object thereof is to provide a urea water addition system for an internal combustion engine that can suppress a decrease in the detection performance of the sensor due to bubbles adhering to the sensor.

According to one aspect of the invention,
A tank for storing the urea water,
A sensor arranged in the tank for detecting the concentration of urea water, the sensor having a pair of sensor surfaces arranged to face each other,
A bubble outlet that is disposed below at least one of the sensor surfaces and blows bubbles toward the sensor surface,
A urea water addition system for an internal combustion engine is provided.

Preferably, the urea water addition system,
A bubble supply port that is arranged at a position lower than the bubble outlet and supplies bubbles blown from the bubble outlet,
A guide member that is disposed at a height position between the bubble outlet and the bubble supply port and that guides the bubble supplied from the bubble supply port to the bubble outlet.

Preferably, the guide member is a guide cover that covers the bubble supply port from above,
The bubble outlet comprises a hole provided in the guide cover.

Preferably, the bubble outlet is formed in a nozzle shape.

Preferably, the urea water addition system,
A urea water addition valve arranged in the exhaust pipe of the internal combustion engine,
A urea water suction port for sucking the urea water in the tank,
A urea water supply device that supplies urea water sucked from the urea water suction port toward the urea water addition valve,
Further comprising a control unit that controls the urea water addition valve and the urea water supply device,
The control unit is
When the internal combustion engine is stopped, the urea water supply device is reversely operated so as to recover the urea water in the urea water addition valve to the tank, and the urea water supply device is reversely operated even after completion of the recovery, and the urea The water addition valve is opened, and the gas sucked from the urea water addition valve is configured to be blown out from the urea water suction port.
The urea water suction port serves as the bubble supply port.

Preferably, the urea water addition system,
A urea water addition valve disposed in the exhaust passage of the internal combustion engine,
A urea water suction port for sucking the urea water in the tank,
A urea water supply device that supplies urea water sucked from the urea water suction port toward the urea water addition valve,
Further comprising a control unit that controls the urea water addition valve and the urea water supply device,
The control unit is
When the internal combustion engine is stopped, the urea water supply device is reversely operated so as to recover the urea water in the urea water addition valve to the tank, and the urea water supply device is reversely operated even after completion of the recovery, and the urea The water addition valve is opened, and the gas sucked from the urea water addition valve is configured to be blown out from the urea water suction port.
The urea water suction port forms the bubble outlet.

According to the present invention, it is possible to suppress the deterioration of the detection performance of the sensor due to the bubbles attached to the sensor.

It is a schematic diagram showing the whole composition of this embodiment. It is the schematic which shows the mode at the time of normal rotation operation of a urea water supply apparatus. It is a schematic diagram showing a situation at the time of reverse operation of a urea water supply device. It is a schematic plan view which shows the structure of a density sensor periphery. It is a schematic front view which shows the structure of a density sensor periphery. FIG. 5 is a VI-VI cross-sectional view of FIG. 4 showing a cross section of the guide cover. It is a schematic front view which shows the effect|action of this embodiment. It is a schematic side view which shows the structure of a 1st modification. It is a schematic side view which shows the effect|action of a 1st modification. It is a schematic side view which shows the structure and operation of a 2nd modification.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First, the overall configuration of this embodiment will be described with reference to FIG.

The present embodiment is applied to an internal combustion engine (engine) mounted on a vehicle, particularly a diesel engine 10. An intake pipe 12 is connected to the intake manifold 11 of the diesel engine 10, and an exhaust pipe 14 is connected to the exhaust manifold 13. The intake pipe 12 is provided with an air flow sensor 15 for measuring the intake flow rate and an intake throttle valve 16.

The exhaust manifold 13 and the intake manifold 11 are connected by an EGR pipe 17 for circulating a part of exhaust gas to the intake side, and the EGR pipe 17 is provided with an EGR cooler 18 and an EGR valve 19.

An exhaust brake valve 20 and an exhaust throttle valve 21 are provided in the exhaust pipe 14, and a filter device 22 and an SCR device 32 are provided downstream thereof.

The filter device 22 includes a front-stage oxidation catalyst (DOC) 24 that oxidizes unburned components (HC, CO) and a rear-stage particulate filter (DPF) 25 that traps particulate matter (PM) in exhaust gas. Prepare

The SCR device 32 includes a pre-stage selective reduction NOx catalyst (SCR) 23 that reduces NOx in the exhaust gas, and a post-stage oxidation catalyst (DOC) 33 that treats ammonia that has leaked to the downstream side of the SCR 23. ..

The electronic control unit (ECU) 30 is input with detection values of a rotation sensor 31 that detects the engine speed and an accelerator opening sensor 34 that detects the accelerator opening.

The ECU 30 controls the fuel injection amount injected from the in-cylinder injector 35 according to the rotation speed and the accelerator opening degree while the vehicle is traveling, and also appropriately controls the intake throttle valve 16, the exhaust brake valve 20, and the exhaust throttle valve 21. At the same time, the EGR valve 19 is opened and closed to control the EGR amount.

Next, a urea water addition system 40 for adding urea water into the exhaust pipe 14 will be described.

The urea water addition system 40 includes an addition module 60 including a urea water addition valve 41 for adding (or injecting or supplying) urea water into the exhaust pipe 14 on the upstream side in the exhaust flow direction of the SCR 23, and for storing the urea water. A urea water tank 42, a urea water supply device 43 for supplying the urea water in the urea water tank 42 to the urea water addition valve 41, and an addition control unit for controlling the urea water addition valve 41 and the urea water supply device 43 ( DCU) 44. The addition module 60 is a unit in which the urea water addition valve 41 is integrated with the housing.

The urea water supply device 43 includes a urea water pump that sucks urea water from the urea water tank 42 and discharges the urea water toward the urea water addition valve 41, and a urea water valve that switches the direction of the urea water between the forward and reverse directions.

The DCU 44 and the ECU 30 are communicatively connected and form a control unit or controller that is configured and programmed to perform the control and arithmetic processing described below. The ECU 30 outputs information necessary for urea water addition control to the DCU 44. Specifically, the ECU 30 determines the amount of urea water added from the urea water addition valve 41, that is, urea based on the engine operating state, particularly the engine speed and the accelerator opening detected by the rotation sensor 31 and the accelerator opening sensor 34, respectively. The amount of water added is determined and this information is output to the DCU 44. The DCU 44 controls the urea water addition valve 41 to open so that the determined urea water addition amount is actually added. The DCU 44 and the ECU 30 may be integrated to form a control unit or controller.

A concentration sensor 100, which will be described later, is arranged in the urea water tank 42, and information regarding the concentration of the urea water stored in the urea water tank 42 is output from the concentration sensor to the DCU 44 and thus the ECU 30. The ECU 30 or the DCU 44 determines whether or not appropriate urea water is added based on this information. Further, the ECU 30 or the DCU 44 may correct the urea water addition amount.

In the urea water addition system 40, the urea water tank 42, the urea water supply device 43, and the addition module 60 are connected to each other by a urea water line 61 shown by a broken line and a hot water line 62 shown by a solid line. Here, the hot water specifically means the engine cooling water that has been used for cooling the engine 10 and has reached a high temperature, and serves as a heat fluid that heats the urea water to prevent freezing of the urea water. In this embodiment, hot water is used as the heat fluid. However, it is possible to use various thermal fluids such as engine exhaust gas and engine oil.

The urea water line 61 connects the urea water tank 42 and the urea water supply device 43 to connect the first urea water pipe 64U for sending the urea water from the former to the latter, the urea water supply device 43 and the urea water addition valve 41. Then, a second urea water pipe 65U for sending the urea water from the former to the latter and a third urea water pipe 66U for connecting the urea water supply device 43 and the urea water tank 42 to return the urea water from the former to the latter are provided. Have. Each of these tubes consists of a relatively flexible hose.

The hot water line 62 connects the engine 10 and the urea water tank 42 to the first hot water pipe 68W for sending hot water from the former to the latter, and connects the urea water tank 42 and the urea water supply device 43 to the former to the latter. The second hot water pipe 64W for sending hot water, the heater pipe 78 that connects the first hot water pipe 68W and the second hot water pipe 64W in the urea water tank 42, the urea water supply device 43, and the engine 10 are connected to each other. To the latter from the third hot water pipe 69W for returning hot water. Each of these tubes also consists of a relatively flexible hose. The first warm water pipe 68W is provided with a tank heater valve 50 that switches between sending and stopping hot water. The tank heater valve 50 is controlled by the DCU 44. In addition, the hot water line 62 connects the engine 10 and the addition module 60 to send hot water from the former to the latter by a fourth hot water pipe 65W, and connects the addition module 60 and the engine 10 to return hot water from the former to the latter. And the fifth warm water pipe 67W. Each of these tubes also consists of a relatively flexible hose.

During operation of the engine, the urea water pump of the urea water supply device 43 is operated, the urea water valve is switched to the normal rotation side, and the urea water supply device 43 is normally rotated. At this time, the urea water is supplied to the urea water addition valve 41 of the addition module 60 from the urea water tank 42 through the first urea water pipe 64U, the urea water supply device 43, and the second urea water pipe 65U in this order as shown by the arrow on the broken line. To be done. Excess urea water that is not supplied for addition is returned from the urea water supply device 43 to the urea water tank 42 through the third urea water pipe 66U. The flow direction of such urea water is called a forward flow direction.

Further, the hot water pump of the urea water supply device 43 is also operated, and hot water is supplied from the engine 10 to the first hot water pipe 68W, the heater pipe 78, the second hot water pipe 64W, the urea water supply device 43, and the third hot water pipe 69W. It is returned to the engine 10 through the order. At the same time, the hot water is returned from the engine 10 to the engine 10 through the fourth hot water pipe 65W, the addition module 60, and the fifth hot water pipe 67W in this order. The flow direction of this warm water is called the forward flow direction. In this way, the warm water is made to flow through the entire route in which the urea water flows, and the freezing of the urea water due to a decrease in the outside temperature is reliably suppressed.

On the other hand, when the engine is stopped, immediately after that, the urea water pump of the urea water supply device 43 is continuously operated for a short time. Then, the urea water valve of the urea water supply device 43 is switched to the reverse rotation side, and the urea water supply device 43 is reversely operated. As a result, all urea water remaining in each device and pipe is collected in the urea water tank 42. The flow direction of the urea water at this time is referred to as a reverse flow direction, and is indicated by a parenthesized arrow in the figure. The flow directions of the urea water in the first urea water pipe 64U, the second urea water pipe 65U, and the third urea water pipe 66U are opposite to those in the normal rotation operation. The urea water that has flowed backward through the third urea water pipe 66U is sent to the first urea water pipe 64U in the urea water supply device 43 and then collected in the urea water tank 42 through the first urea water pipe 64U.

FIG. 2 schematically shows the state of the urea water supply device 43 during the normal rotation operation. The urea water supply device 43 includes a urea water pump 51 and a urea water valve 52, which are controlled by the DCU 44. When an engine operation signal indicating that the engine is operating is sent from the ECU 30 to the DCU 44, the DCU 44 basically operates the urea water pump 51 and also sets the urea water valve 52 to the normal rotation side as illustrated. Or switch to the forward rotation position. Then, the first urea water pipe 64U is connected to the suction port 53 of the urea water pump 51, the second urea water pipe 65U and the third urea water pipe 66U are connected to the discharge port 54 of the urea water pump 51, and the above-described forward flow direction is obtained. The flow of is realized.

On the other hand, when the engine stop signal indicating that the engine has been stopped is sent from the ECU 30 to the DCU 44, the DCU 44 causes the urea water supply device 43 to reversely operate for a short time after the engine is stopped. At this time, as shown in FIG. 3, the DCU 44 continuously operates the urea water pump 51 for a short period of time and switches the urea water valve 52 to the reverse rotation side or the reverse rotation position as shown. Then, the second urea water pipe 65U and the third urea water pipe 66U are connected to the suction port 53 of the urea water pump 51, the first urea water pipe 64U is connected to the discharge port 54 of the urea water pump 51, and the above-described reverse flow direction is used. The flow of is realized. In this way, all the urea water in the urea water path is collected in the urea water tank 42, but in the present embodiment, as described later in detail, the above state is maintained even after the collection is completed, and the gas is blown into the urea water tank 42. , The bubbles formed by this gas are used to remove the bubbles adhering to the concentration sensor.

Returning to FIG. 1, the urea water tank 42 is made of resin in the present embodiment, but the material thereof is arbitrary and may be made of metal, for example. The urea water tank 42 includes a lid body 71 that closes an opening formed on the upper surface of the urea water tank 42. The heater pipe 78 is suspended and supported by the lid body 71, and is disposed in the urea water tank 42. In addition to the heater pipe 78, various parts are arranged in the urea water tank 42 in a state of being directly or indirectly supported by the lid 71. The heater pipe 78 is made of a metal U-shaped tube, extends in the up-down direction, and has a lower end portion that is bent 90° at the bottom portion of the urea water tank 42 (referred to as the tank bottom portion).

Inside the urea water tank 42, a metal suction pipe 72 and a return pipe 73 extending in the vertical direction are arranged. The suction pipe 72 is a pipe for sucking urea water from the inside of the urea water tank 42, and has a urea water suction port 74 serving as an inlet of urea water at the lower end thereof. The urea water suction port 74 is arranged at the bottom of the tank. The upper end of the suction pipe 72 is supported by the lid 71, and is connected to the first urea water pipe 64U via a passage and a pipe joint in the lid 71 not shown. The suction pipe 72 is also supported at an appropriate position in the tank by a tank supporting member (not shown) suspended and supported by the lid 71. The heater pipe 78 may also serve as the in-tank support member.

The return pipe 73 is a pipe for returning the urea water into the urea water tank 42, and has a urea water discharge port at its lower end. The urea water discharge port is arranged at the upper end of the urea water tank 42. The upper end of the return pipe 73 is supported by the lid 71, and is connected to the third urea water pipe 66U via a passage and a pipe joint inside the lid 71 not shown. The return pipe 73 may be further supported by the in-tank support member. The urea water flowing in the forward flow direction through the third urea water pipe 66U is returned to the urea water tank 42 through the return pipe 73.

In addition, a sensor for detecting the concentration of urea water, that is, a concentration sensor 100 is arranged at the bottom of the tank. The concentration sensor 100 is supported by an in-tank support member.

In addition, the urea water tank 42 is also provided with a level sensor (residual amount sensor), a temperature sensor, a breather, a water level gauge, a filler cap, a drain cap, etc., but these are not characteristic parts of the present embodiment, and therefore description thereof is omitted.

Next, the configuration around the density sensor 100 will be described with reference to FIGS. 4 is a plan view when viewed from above, FIG. 5 is a front view when viewed from the front, and FIG. 6 is a VI-VI sectional view of FIG. 4 showing a cross section of the guide cover.

The density sensor 100 is composed of an optical sensor, and includes a sensor body 101, and a light emitting portion 102 and a light receiving portion 103 that project horizontally from the sensor body 101. The light emitting unit 102 and the light receiving unit 103 have a light emitting surface 104 and a light receiving surface 105 that are arranged to face each other and are spaced apart in the horizontal direction. The light emitting surface 104 and the light receiving surface 105 form a pair of sensor surfaces. A light emitting element is provided inside the sensor body 101, and light emitted from this light emitting element is bent at a right angle by a prism incorporated in the light emitting section 102 and then emitted from the light emitting surface 104 toward the light receiving surface 105. To be done. The emitted light (indicated by L in the figure) passes through the urea water located between the light emitting surface 104 and the light receiving surface 105, and then is received by the light receiving surface 105. The received light is bent at a right angle by a prism built in the light receiving unit 103, and then sensed by a light receiving element provided inside the sensor body 101.

Note that the method of detecting the concentration of urea water by the optical concentration sensor 100 is already known, and therefore its explanation is omitted. The sensor body 101 is electrically connected to the DCU 44 via a wire harness (not shown). The DCU 44 receives a detection signal corresponding to the urea concentration or the urea component concentration from the sensor body 101, and sends it to the ECU 30.

By the way, many fine bubbles may adhere to at least one of the light emitting surface 104 and the light receiving surface 105 due to surface tension. When the bubbles adhere, the light is diffused by the bubbles, and the light may not be accurately detected. Then, the urea component concentration of the urea water may not be accurately detected.

Therefore, in the present embodiment, air bubbles are blown to both the light emitting surface 104 and the light receiving surface 105, and the air bubbles remove the air bubbles attached to the light emitting surface 104 and the light receiving surface 105. The structure for removing bubbles will be described below.

The urea water addition system 40 of the present embodiment is provided below the light emitting surface 104 and the light receiving surface 105, and includes a bubble outlet 81 that blows bubbles toward the light emitting surface 104 and the light receiving surface 105. Further, the urea water addition system 40 is arranged at a position lower than the bubble outlet 81, and the bubble supply port 82 for supplying the bubbles blown out from the bubble outlet 81, and between the bubble outlet 81 and the bubble supply port 82. And a guide member 83 which is disposed at the height position and guides the bubbles supplied from the bubble supply port 82 to the bubble outlet 81. For the sake of convenience, the guide member 83 is shown transparently in FIG. 5 and 6, the guide member 83 is shown in cross section.

Specifically, a guide cover 84 that forms a guide member 83 is arranged at a position below the light emitting surface 104 and the light receiving surface 105. The urea water suction port 74 of the suction pipe 72 is arranged at a position below the guide cover 84. Holes, that is, cover holes 85 are provided in the guide cover 84 just below the light emitting surface 104 and the light receiving surface 105, and these cover holes 85 form the bubble outlet 81. The urea water suction port 74 forms the bubble supply port 82.

The lower end of the suction pipe 72 is bent at a right angle in the horizontal direction and has a urea water suction port 74 at its tip. Urea water is sucked into the suction pipe 72 from the urea water suction port 74 during engine operation, but at the time of removing bubbles, bubbles are blown out from the urea water suction port 74 as described later. A filter having a large number of fine holes, that is, a filter tube 75 is attached to the urea water suction port 74 to prevent suction of foreign matter. A filter may be provided in a place other than the urea water suction port 74.

The urea water suction port 74 is horizontally separated from the light emitting surface 104 and the light receiving surface 105 when seen in a plan view (FIG. 4 ). Therefore, in order to guide the bubbles blown out from the urea water suction port 74 to the position directly below the light emitting surface 104 and the light receiving surface 105, a guide cover 84 as a guide member 83 is provided.

The guide cover 84 covers the urea water suction port 74 and the entire filter tube 75 from above, and extends horizontally to a position below the sensor body 101. The guide cover 84 of the present embodiment has a substantially trapezoidal shape in plan view, but the shape is arbitrary. Bubbles blown out from the urea water suction port 74 must be reliably captured by the lower surface of the guide cover 84 and smoothly guided to the cover hole 85. Therefore, the outer peripheral edge portion of the guide cover 84 is bent downward, so that the downward flange portion 89 is formed. Further, the guide cover 84 is provided with an inclination that increases toward the cover hole 85.

The cover hole 85 has an elliptical shape whose major axis Z is longer than the width W of the light emitting surface 104 and the light receiving surface 105 in a plan view so that bubbles can be efficiently blown over the entire light emitting surface 104 and the light receiving surface 105. However, the shape of the cover hole 85 is not limited to this.

In the present embodiment, the guide cover 84 is integrally formed with a nozzle portion 86 whose diameter decreases toward the upper side, and a cover hole 85 is formed at the upper end of the nozzle portion 86. That is, the bubble outlet 81 of this embodiment is formed in a nozzle shape. As a result, bubbles can be efficiently blown from the cover hole 85 to the light emitting surface 104 and the light receiving surface 105. Further, even when the vehicle is inclined when removing the bubbles, the bubbles can be collected in the cover hole 85 by the nozzle portion 86 and blown out from the cover hole 85.

Next, the operation of this embodiment will be described.

In the present embodiment, removal of bubbles from the light emitting surface 104 and the light receiving surface 105 is performed when the engine is stopped. That is, as described above, immediately after the engine is stopped, the urea water supply device 43 is reversely operated as shown in FIG. 3, the urea water pump 51 of the urea water supply device 43 is continuously operated, and the urea water valve 52 is moved to the reverse rotation side. Can be switched. Further, the urea water addition valve 41 is opened (turned on). Then, the urea water in the urea water addition valve 41 flows back through the illustrated route and is collected in the urea water tank 42. Further, the urea water in the third urea water pipe 66U and the return pipe 73 also flows backward through the illustrated route and is collected in the urea water tank 42. During this recovery, the urea water flows backward through the suction pipe 72 and is blown out into the urea water tank 42 through the urea water suction port 74. By performing such urea water recovery, it is possible to suppress or prevent the urea water from freezing or crystallizing in the urea water passage while the engine is stopped.

Next, even after this urea water recovery is completed, the urea water supply device 43 is continuously operated in the reverse direction, and the urea water addition valve 41 is opened. Then, the gas in the exhaust pipe 14 (exhaust gas, air, or a mixed gas thereof) is sucked from the urea water addition valve 41, and the sucked gas passes through the above-described backflow path and the urea water suction port 74 of the suction pipe 72. Is blown into the urea water in the urea water tank 42. Further, the gas (air) located above the liquid surface of the urea water in the urea water tank 42 is also sucked into the return pipe 73, passes through the above-described backflow path, and is discharged from the urea water suction port 74 of the suction pipe 72 to the urea water. It is blown out into the urea water in the water tank 42.

Then, as shown in FIG. 7, the gas blown out from the urea water suction port 74 generates micro bubbles B1 while passing through the filter tube 75. The fine bubbles B1 gradually merge with each other in the process of floating in the urea water and become larger. The bubble lump B2 thus formed is captured by the lower surface portion of the guide cover 84 and floats along the lower surface portion of the guide cover 84 and toward the cover hole 85. Even in this process of progress, the bubble lumps B2 gradually merge and become larger. Further, the bubble lump B2 is efficiently guided to the cover hole 85 by the nozzle portion 86.

Finally, the bubble lump B2 floats above the cover hole 85 and is blown out. At this time, the bubble lump B2 is relatively strongly blown out by utilizing its large buoyancy, and at the same time, the large number of minute bubbles B attached to the light emitting surface 104 and the light receiving surface 105 by surface tension are peeled off, and the minute bubbles B2 are removed. Surface in the state of capturing. Since the bubble lump B2 is much larger than the minute bubbles B, the minute bubbles B attached to the light emitting surface 104 and the light receiving surface 105 can be reliably peeled off and removed. Therefore, the minute bubbles B are removed from the light emitting surface 104 and the light receiving surface 105, and the deterioration of the detection performance of the concentration sensor 100 due to the minute bubbles B can be suppressed.

When a predetermined time sufficient to remove the minute bubbles B has elapsed since the engine was stopped, the urea water pump 51 is stopped, the urea water valve 52 is switched to the normal rotation side as shown in FIG. The addition valve 41 is closed (OFF). The vehicle and engine are then put to a standstill.

Next, when the engine is restarted, the density detection by the density sensor 100 is performed. For example, the density detection by the density sensor 100 is performed at the timing when the ignition switch is turned on for restarting the engine. At this time, since the minute bubbles B have already been removed from the light emitting surface 104 and the light receiving surface 105, the urea water concentration can be detected with high accuracy.

The timing of density detection is not limited to the timing of turning on the ignition switch. For example, it may be the timing of turning the starter on or off, or the timing immediately after the engine is restarted. Further, the timing of density detection does not necessarily have to be when the engine is restarted.

As described above, according to the present embodiment, since the bubble outlet 81 that blows out the bubble lump B2 toward the light emitting surface 104 and the light receiving surface 105 is provided, the minute bubbles B attached to the light emitting surface 104 and the light receiving surface 105 are removed. It can be peeled off and removed by B2. Therefore, it is possible to suppress the deterioration of the detection performance of the concentration sensor 100 due to the minute bubbles B.

Further, according to this embodiment, since the guide member 83 for guiding the bubbles supplied from the bubble supply port 82 to the bubble outlet 81 is provided, even if the bubble supply port 82 is located away from the bubble outlet 81. Also, the supplied bubbles can be reliably guided to the bubble outlet 81. Therefore, it is possible to increase the degree of freedom in installing the bubble supply port 82 and improve the layout.

In particular, when the guide member 83 is formed of the guide cover 84 and the bubble outlet 81 is formed of the cover hole 85 as in the present embodiment, the bubbles can be accurately guided to the bubble outlet 81 with a simple configuration. it can. Further, when the bubble outlet 81 is formed in a nozzle shape, even if the vehicle is tilted, the bubble can be surely guided to the bubble outlet 81 without deviating on the way.

Further, according to the present embodiment, the reverse rotation operation of the urea water supply device 43 when the engine is stopped is used to suck the gas in the exhaust pipe 14 and blow it out into the urea water tank 42. Bubbles can be removed with a simple and low-cost configuration without separately providing a gas source.

Next, a modified example will be described.

In the first modified example shown in FIG. 8, the lower end of the suction pipe 72 is bent at a right angle in the horizontal direction, and then bifurcated toward the light-emitting surface 104 and the light-receiving surface 105. Each has a urea water suction port 74. The urea water suction ports 74 are arranged below the light-emitting surface 104 and the light-receiving surface 105, particularly just below and in the vicinity thereof, and as shown in FIG. 9, the bubbles B3 are directed toward the light-emitting surface 104 and the light-receiving surface 105. It is designed to blow out directly. This also makes it possible to remove the minute bubbles B adhering to the light emitting surface 104 and the light receiving surface 105 by peeling them off with the larger bubbles B3, and to suppress the deterioration of the detection performance of the concentration sensor 100 due to the minute bubbles B.

In this first modification, the urea water suction port 74 forms the bubble outlet 81. The guide cover 84 described above is omitted. Further, the filter tube 75 is also omitted, and an alternative filter is installed at a position not shown. Other points are almost the same as those of the basic embodiment. The same applies to the generation of the bubble B3 by utilizing the reverse operation of the urea water supply device 43 when the engine is stopped.

The second modification shown in FIG. 10 is obtained by adding a nozzle tube 87 to the configuration of the first modification. The nozzle tube 87 is a short tube having a tapered shape whose diameter decreases toward the upper side, and is arranged at a height position between the light emitting surface 104 and the light receiving surface 105 and the urea water suction port 74. The nozzle pipe 87 is supported by an in-tank support member (not shown).

By providing the nozzle tube 87, the bubble B3 blown out from the urea water suction port 74 can be guided more accurately toward the light emitting surface 104 and the light receiving surface 105. In particular, even when the vehicle leans, the blown-out bubble B3 can be more accurately guided toward the light emitting surface 104 and the light receiving surface 105 without deviating from the way.

In addition, regarding the second modified example, from a different point of view, the urea water suction port 74 forms the bubble supply port 82, the nozzle pipe 87 forms the guide member 83, and the upper end opening of the nozzle pipe 87 forms the bubble outlet 81. It is also possible to interpret that the bubble outlet 81 is formed in a nozzle shape.

The configurations of the above-described basic embodiment and each modified example can be partially or wholly combined as long as there is no contradiction. The urea water tank 42 and the concentration sensor 100 of this embodiment correspond to the tank and the sensor in the claims, respectively.

Although the embodiments of the present invention have been described above in detail, the present invention can be applied to other embodiments as described below, for example.

(1) In the above embodiment, the bubble outlet 81 is provided on both the light emitting surface 104 and the light receiving surface 105, but the bubble outlet 81 may be provided on only one of them.

(2) The concentration sensor 100 may be of any type, and may be, for example, an ultrasonic sensor. As is well known, an ultrasonic sensor has a transmitting/receiving surface and a reflecting surface that form a pair of sensor surfaces, and ultrasonic waves emitted from the transmitting/receiving surface are reflected by the reflecting surface and received by the transmitting/receiving surface. The urea concentration of the urea water is detected based on the time required for the round trip. If the microbubbles B adhere to at least one of the transmitting/receiving surface and the reflecting surface, the propagation of ultrasonic waves is hindered and the detection performance of the sensor deteriorates. Therefore, if the bubble outlet 81 is provided for at least one of the transmitting/receiving surface and the reflecting surface, it is possible to suppress deterioration of the detection performance of the sensor. The ultrasonic sensor may be one that receives the reflected waves from the plurality of reflectors and detects the urea concentration based on the time difference between the receptions.

(3) In the above-described embodiment, the bubbles are blown toward the light emitting surface 104 and the light receiving surface 105 when the urea water supply device 43 is rotated in the reverse direction when the engine is stopped, but the bubbles may be blown at another timing. .. For example, when the engine is in operation and the urea water is not added to the SCR 23 (for example, the timing when the SCR 23 is at the inactive temperature), the urea water supply device 43 may be intentionally operated in the reverse direction to blow bubbles. In this case, the urea water addition valve 41 does not have to be opened. Alternatively, when the engine is restarted and before the urea concentration is detected (particularly immediately before), the urea water supply device 43 may be reversely operated and bubbles may be blown out.

(4) Regarding the bubble generation method, in addition to the method of using the urea water supply device 43 and the urea water addition valve 41 described above, a gas supply source such as an air pump is separately provided, and the gas supplied from the gas supply source is used. Bubbles may be generated.

(5) The guide member 83 is also deformable, and may be formed of, for example, a pipe that guides bubbles or gas from the bubble supply port 82 to the bubble outlet 81.

(6) The urea water supply device 43 may be integrated with the urea water tank 42, and the concentration sensor 100 may be integrated with the urea water supply device 43.

(7) The sucking back (backflow) of the urea water may be performed by rotating the urea water pump 51 in the reverse direction other than switching the urea water valve 52.

The embodiments of the present invention are not limited to the above-described embodiments, and all modifications, applications, and equivalents included in the concept of the present invention defined by the claims are included in the present invention. Therefore, the present invention should not be limitedly interpreted, and can be applied to other arbitrary techniques belonging to the scope of the idea of the present invention.

10 Diesel engine 14 Exhaust pipe 30 Electronic control unit (ECU)
40 Urea Water Addition System 41 Urea Water Addition Valve 43 Urea Water Supply Device 44 Addition Control Unit (DCU)
74 urea water suction port 81 bubble outlet 82 bubble supply port 83 guide member 84 guide cover 85 cover hole 86 nozzle section 87 nozzle tube 100 concentration sensor 104 light emitting surface 105 light receiving surface

Claims (5)

A tank for storing the urea water,
A sensor arranged in the tank for detecting the concentration of urea water, the sensor having a pair of sensor surfaces arranged to face each other,
A bubble outlet that is disposed below at least one of the sensor surfaces and blows bubbles toward the sensor surface,
A bubble supply port that is arranged at a position lower than the bubble outlet and supplies bubbles blown from the bubble outlet,
A guide member that is arranged at a height position between the bubble outlet and the bubble supply port and that guides the bubble supplied from the bubble supply port to the bubble outlet.
A urea water addition system for an internal combustion engine, comprising: The guide member includes a guide cover that covers the bubble supply port from above,
The urea water addition system for an internal combustion engine according to claim 1, wherein the bubble outlet comprises a hole provided in the guide cover. The urea water addition system for an internal combustion engine according to claim 1 or 2, wherein the bubble outlet is formed in a nozzle shape. A urea water addition valve arranged in the exhaust pipe of the internal combustion engine,
A urea water suction port for sucking the urea water in the tank,
A urea water supply device that supplies urea water sucked from the urea water suction port toward the urea water addition valve,
Further comprising a control unit that controls the urea water addition valve and the urea water supply device,
The control unit is
When the internal combustion engine is stopped, the urea water supply device is reversely operated so as to recover the urea water in the urea water addition valve to the tank, and the urea water supply device is reversely operated even after completion of the recovery, and the urea The water addition valve is opened, and the gas sucked from the urea water addition valve is configured to be blown out from the urea water suction port.
The urea water addition system for an internal combustion engine according to any one of claims 1 to 3, wherein the urea water suction port forms the bubble supply port. A tank for storing the urea water,
A sensor arranged in the tank for detecting the concentration of urea water, the sensor having a pair of sensor surfaces arranged to face each other,
A bubble outlet that is disposed below at least one of the sensor surfaces and blows bubbles toward the sensor surface,
A urea water addition valve arranged in the exhaust passage of the internal combustion engine ,
A urea water suction port for sucking the urea water in the tank,
A urea water supply device that supplies urea water sucked from the urea water suction port toward the urea water addition valve,
Further comprising a control unit for controlling the urea water addition valve and the urea water supply device,
The control unit is
When the internal combustion engine is stopped, the urea water supply device is reversely operated so as to recover the urea water in the urea water addition valve to the tank, and the urea water supply device is reversely operated even after completion of the recovery, and the urea The water addition valve is opened, and the gas sucked from the urea water addition valve is configured to be blown out from the urea water suction port.
A urea water addition system for an internal combustion engine, wherein the urea water suction port forms the bubble outlet.

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