JP2010151094A - Device and method for detecting leak of reducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reducer leak detection device and a leak detection method capable of detecting leak of a reducing agent in a storage tank. <P>SOLUTION: This leak detection device of reducer from a storage tank of an exhaust emission control device purifying exhaust gas of an internal combustion engine by supplying the reducer stored in the storage tank from a reducer supply part to the exhaust gas passage of the internal combustion engine, includes a reduced quantity detection part detecting reduced quantity of the reducer in the storage tank, a supply quantity detection part capable of detecting supply quantity of the reducer into the exhaust gas passage from the reducer supply part, and a leak decision part deciding existence of leak by operating difference between reduced quantity detected by the reduced quantity detection part and supply quantity detected by the supply quantity detection part, and comparing the result with a predetermined reference value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reducing agent leakage detection device and a leakage detection method for detecting leakage of a reducing agent from a storage tank. In particular, the present invention relates to a reducing agent leakage detection device and a leakage detection method for detecting leakage of a reducing agent from a storage tank provided in an exhaust emission control device of a vehicle.

  2. Description of the Related Art Conventionally, there has been known an exhaust purification device that performs exhaust gas purification processing by supplying a reducing agent into an exhaust passage of an internal combustion engine. For example, a reduction catalyst such as an SCR catalyst is disposed in the exhaust passage of an internal combustion engine, an aqueous urea solution is supplied as a reducing agent into the exhaust passage upstream of the reduction catalyst, and ammonia and exhaust gas generated from the aqueous urea solution are reduced. There is an exhaust emission control device that reduces and discharges nitrogen oxides in exhaust gas by contacting with a catalyst.

Such an exhaust purification device stores a storage tank in which a reducing agent such as an aqueous urea solution is stored, a reducing agent supply unit such as an injection valve for supplying the reducing agent into the exhaust passage of the internal combustion engine, and a storage tank. And a control unit (hereinafter referred to as “DCU: Dosing Control Unit”) for controlling the reducing agent supply device, as well as including a reducing agent supply device including a pump for sending the reduced agent to the injection valve. It is configured with.
The reducing agent stored in the storage tank is controlled by the DCU according to various conditions such as the operating state of the internal combustion engine, the concentration of nitrogen oxides in the exhaust gas, and the temperature of the reducing catalyst. Is supplied from the reducing agent supply section into the exhaust passage at an appropriate supply amount, and nitrogen oxides in the exhaust gas are purified and released to the outside.

  In such an exhaust purification device, when the reducing agent in the storage tank becomes empty, nitrogen oxides are released to the outside without being purified. Therefore, the remaining amount of the reducing agent in the storage tank is constantly detected using a level sensor or the like (for example, see Patent Document 1 below).

JP 2008-248708 A

  However, the storage tank may expand due to, for example, freezing of the reducing agent, or unexpected stress may be applied from the outside, causing damage such as cracks, and reducing agent leakage may occur. is there. When leakage of the reducing agent occurs due to damage to the storage tank, etc., the reducing agent flows out and is useless, and the reducing agent adheres and stays around the storage tank, causing various problems. There is a possibility. In particular, when the leaked reducing agent is heated to a high temperature to generate ammonia, the ammonia is released into the atmosphere. Therefore, it is desirable that the leakage of the reducing agent be detected early.

  Therefore, the inventors of the present invention have found that such a problem can be solved by comparing the amount of reducing agent in the storage tank with the amount of reducing agent supplied, and completed the present invention. Is. That is, an object of the present invention is to provide a reducing agent leakage detecting device and a leakage detecting method capable of detecting reducing agent leakage from a storage tank.

  According to the present invention, the reducing agent stored in the storage tank is supplied from the reducing agent supply unit into the exhaust passage of the internal combustion engine, whereby the reduction from the storage tank in the exhaust purification device that purifies the exhaust gas of the internal combustion engine. In the agent leakage detection device, a reduction amount detection unit capable of detecting a reduction amount of the reducing agent in the storage tank, and a supply amount detection unit capable of detecting the supply amount of the reducing agent from the reducing agent supply unit into the exhaust passage, A leak determination unit that calculates a difference between the decrease amount detected by the decrease amount detection unit and the supply amount detected by the supply amount detection unit, and compares the preset amount with a preset reference value; There is provided a reducing agent leakage detection device characterized in that the above-described problems can be solved.

  Further, when configuring the reducing agent leakage detection device of the present invention, the storage tank is provided with level detection means for detecting the liquid level of the reducing agent in the storage tank, and the decrease amount detection unit is detected by the level detection means. It is preferable to calculate the amount of decrease based on the liquid level level displacement range and the horizontal cross-sectional area of the storage tank stored in advance.

  Further, in configuring the reducing agent leakage detection device of the present invention, the storage tank is mounted on the vehicle, the vehicle is provided with acceleration detecting means capable of detecting acceleration, and the reduction amount detection unit is an acceleration detection unit. It is preferable to calculate the amount of decrease using the displacement of the liquid level when the acceleration detected by the means is equal to or less than a predetermined value.

  Further, in configuring the reducing agent leakage detection apparatus of the present invention, the storage tank is provided with freezing detection means capable of detecting the frozen state of the stored reducing agent, and the decrease amount detection unit is reduced by the freezing detection means. Preferably, the amount of decrease is calculated using the liquid level when it is detected that the fluid is in a flow state other than the frozen state.

  Another aspect of the present invention is a storage in an exhaust purification device that purifies exhaust gas of an internal combustion engine by supplying the reducing agent stored in the storage tank from the reducing agent supply unit into the exhaust passage of the internal combustion engine. In the method for detecting leakage of reducing agent from the tank, the amount of reduction of reducing agent in the storage tank is detected, and the amount of reducing agent supplied from the reducing agent supply unit to the exhaust passage is detected. It is a reducing agent leakage detection method characterized by determining the presence or absence of leakage in the storage tank by comparing the difference between the two and a reference value.

  In carrying out the reducing agent leakage detection method of the present invention, the reduction amount is the amount of reducing agent reduced from the storage tank during a predetermined period, and the supply amount is the reduction supplied from the reducing agent supply unit during the predetermined period. It preferably consists of an integrated value of the amount of the agent.

  Further, in carrying out the reducing agent leakage detection method of the present invention, the amount of decrease is determined by the liquid level level displacement range of the reducing agent in the storage tank and the horizontal cross-sectional area of the storage tank stored in advance. It is preferable to calculate based on this.

  In carrying out the reducing agent leakage detection method of the present invention, the supply amount is preferably an integrated value of the target supply amount set to control the reducing agent supply unit.

  According to the reducing agent leakage detection apparatus of the present invention, the reduction amount detection unit capable of detecting the reduction amount of the reducing agent in the storage tank, and the supply amount of the reducing agent supplied from the reducing agent supply unit into the exhaust passage. A pre-stored reference by calculating a difference between the decrease amount detected by the decrease amount detection unit and the supply amount detected by the supply amount detection unit in the leak determination unit. Since the presence or absence of leakage is determined by comparing with the value, it is easily grasped whether or not the reducing agent in the storage tank is reduced to a quantity other than the amount supplied from the reducing agent supply unit. Therefore, when leakage of the reducing agent from the storage tank occurs, it is possible to easily detect the leakage.

  Further, in the reducing agent leakage detection device of the present invention, the storage tank includes level detecting means for detecting the liquid level of the reducing agent, and the reduction amount detecting unit detects the liquid level level displacement range and the horizontal direction of the storage tank. If the amount of decrease is calculated based on the cross-sectional area, the amount of reduction of the reducing agent in the storage tank can be easily detected.

  Further, in the reducing agent leakage detection device of the present invention, when the storage tank is mounted on the vehicle and the vehicle is provided with the acceleration detection means, the reduction amount detection unit detects the acceleration by the acceleration detection means. If the amount of decrease is calculated using the displacement of the liquid level when the applied acceleration is less than or equal to a predetermined value, the amount of decrease detected by the vibration generated on the liquid surface of the reducing agent in the storage tank when acceleration is given to the vehicle Therefore, it is easy to prevent errors that occur in the above, and the leakage of the reducing agent is accurately determined.

  Further, in the reducing agent leakage detection device of the present invention, the storage tank is provided with a freezing detecting means capable of detecting the freezing state of the reducing agent, and is reduced by using the liquid level when the reducing agent is in a fluid state other than the frozen state. If the amount is calculated, it is easy to prevent an error that occurs in the amount of decrease detected by freezing of the reducing agent, and the leakage of the reducing agent is accurately determined.

  According to the reducing agent leakage detection method of the present invention, the reduction amount of the reducing agent in the storage tank and the supply amount of the reducing agent supplied into the exhaust passage from the reducing agent supply unit are detected, and the reduction amount and the supply amount are detected. Since the presence or absence of leakage of reducing agent from the storage tank is determined by comparing the difference with the reference value, whether the reducing agent in the storage tank has decreased other than the amount supplied from the reducing agent supply unit Whether or not it is easily grasped and leakage of the reducing agent occurs, it is possible to easily detect the leakage.

  Further, in the reducing agent leakage detection method of the present invention, the amount of reduction of the reducing agent in the storage tank is the amount reduced in a predetermined period, and the supply amount from the reducing agent supply unit is supplied from the reducing agent supply unit in the predetermined period. The amount of reducing agent accumulated in the storage tank and the amount of reducing agent supplied from the reducing agent supply unit can be obtained easily and accurately, and leakage can be accurately determined. Done.

  Further, in the reducing agent leakage detection method of the present invention, the amount of decrease is calculated based on the liquid level level displacement range of the reducing agent in the storage tank and the horizontal sectional area of the storage tank stored in advance. Then, the reduction amount of the reducing agent in the storage tank can be acquired based on the liquid level, so that the reduction amount can be easily detected.

  In the reducing agent leakage detection method of the present invention, if the supply amount is an integrated value of the target supply amount set to control the reducing agent supply unit, the supply amount can be easily detected.

  Hereinafter, embodiments of the reducing agent leakage detection apparatus and leakage detection method of the present invention will be specifically described with reference to the drawings. However, this embodiment 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. In addition, in each figure, what has attached | subjected the same code | symbol has shown the same member, and description is abbreviate | omitted suitably.

1. FIG. 1 shows an example in which a reducing agent leakage detection device (control device) 50 of this embodiment is mounted on an exhaust purification device 10 provided in an exhaust system of an internal combustion engine mounted on a vehicle. 1 is a schematic diagram showing an overall configuration of a purification device 10.
The exhaust purification device 10 includes a reduction catalyst unit 20 in which a reduction catalyst 21 such as an SCR catalyst is disposed in an exhaust passage 11 through which exhaust gas of the internal combustion engine 5 flows, and a storage tank 30 that stores a urea aqueous solution or the like as a reducing agent. And the operation of the reducing agent supply device 40 capable of supplying the reducing agent stored in the storage tank 30 to the upstream side of the reduction catalyst unit 20 in the exhaust passage 11, the internal combustion engine 5, the reducing agent supply device 40, and the like. And a control device 50. The control device 50 includes a leak detection unit 60, and the control device 50 has a function as a leak detection device that detects leakage of the reducing agent from the storage tank 30.

The reduction catalyst 21 of the reduction catalyst unit 20 is a catalyst that reduces and purifies NO _x contained in the exhaust gas by bringing the exhaust gas into contact with the reducing agent supplied from the reducing agent supply device 40. Sensors 23 and 25 for measuring the temperature of the reduction catalyst unit 20 and a sensor 27 for measuring the nitrogen oxide concentration in the exhaust gas are provided on the upstream side and the downstream side of the reduction catalyst 21. An oxidation catalyst, a particulate filter, etc. (not shown) may be disposed on the upstream side and / or downstream side of the reduction catalyst 21.

The reducing agent supply device 40 includes a storage tank 30 in which the reducing agent is stored, a liquid feeding unit 43 that pumps the reducing agent in the storage tank 30 through the supply paths 41 and 42, and the supply paths 41 and 42. A reducing agent injection valve 45 capable of injecting the pumped reducing agent upstream of the reduction catalyst 21 in the exhaust passage 11 is provided.
The storage tank 30 is a liquid container formed of, for example, resin, and has a structure that cannot be substantially deformed. Although the shape is not particularly limited, the horizontal cross-sectional area at each position in the vertical direction is grasped in advance and stored in the control device 50. The change in the cross-sectional area in the horizontal direction with respect to the vertical direction need not be constant or have a predetermined correlation, and is arbitrary.

  The storage tank 30 includes a level sensor 31 as a level detection unit capable of detecting the liquid level L of the stored reducing agent, a temperature sensor 33 as a freezing detection unit capable of detecting the liquid temperature Tu of the reducing agent, And a concentration sensor 35 capable of detecting the concentration Q of the reducing agent.

The level sensor 31 is an area where the reducing agent in the storage tank 30 is stored, and always detects the liquid level L which is the height from the bottom. A typical level sensor is a capacitance type sensor, but a sensor of another type may be used. The method for detecting the liquid level L is not particularly limited, but in the present embodiment, a level sensor that continuously detects the liquid level at a predetermined detection cycle is used.
Further, since the horizontal sectional area of the storage tank 30 is stored in the control device 50 in advance, the volume of the reducing agent stored in the storage tank 30 is determined by the liquid level L detected by the level sensor 31. I can grasp it. Further, since the horizontal sectional area of the storage tank 30 is stored in the control device 50 in advance, it depends on the range in which the liquid level L detected before and after the predetermined time changes, that is, the displacement range of the liquid level L. The volume of the reducing agent decreased in the storage tank 30 can be grasped.

  The temperature sensor 33 may be any sensor that can detect the freezing state of the reducing agent by detecting the liquid temperature Tu of the reducing agent in the storage tank 30. For example, the temperature sensor 33 may detect only a predetermined temperature that is equal to or higher than the melting point of the reducing agent or higher than the melting point, and can always detect the temperature of the reducing agent stored in the storage tank 30. It may be anything.

  The concentration sensor 35 detects the concentration Q of the reducing component or its precursor in the reducing agent. As a typical concentration sensor 35, a sensor capable of detecting a voltage change at both ends of a heating resistor due to energization for a predetermined time to detect a liquid concentration can be cited. Also good.

  Although not shown in detail in the liquid feeding unit 43, a pump for pumping the reducing agent, a switching valve for controlling the flow direction of the reducing agent, and a pressure detection means for detecting the pressure of the reducing agent in the supply path 42 Etc. are provided. As the reducing agent injection valve 45, for example, an ON-OFF valve in which ON / OFF of the valve opening is controlled is used.

The control device 50 is configured to be able to control the operation of each part such as the pump and switching valve of the liquid feeding unit 43 and the reducing agent injection valve 45, and the injection amount, injection pressure, injection timing, injection time, etc. of the reducing agent. To control. The control device 50 of the present embodiment has various conditions such as the operating state of the internal combustion engine 5, the temperature of the exhaust passage 11, the temperature of the reduction catalyst 21, the ammonia adsorption amount in the reduction catalyst 21, the nitrogen oxide concentration, and the reducing agent concentration. Based on the above, the target supply amount based on the mass of the reducing agent is calculated, and the reducing agent is injected from the reducing agent injection valve 45.
In addition, the control device 50 is configured to be able to control the operation of each part of the internal combustion engine 5 based on various detection amounts transmitted from each part of the vehicle and the internal combustion engine 5. The control device 50 according to the present embodiment calculates the acceleration of the vehicle based on the vehicle speed transmitted from the vehicle speed sensor.

2. Leak detection device (control device)
FIG. 2 shows a configuration example in which the leak detection unit 60 provided in the control device 50 is represented by functional blocks. The leak detection unit 60 includes a reduction amount detection unit 61 that can detect the reduction amount of the reducing agent in the storage tank 30 and a supply that can detect the supply amount of the reducing agent from the reducing agent supply device 40 into the exhaust passage 11. Based on the detection results of the amount detection unit 63, the decrease amount detection unit 61, and the supply amount detection unit 63, a leakage determination unit 65 capable of determining leakage of the reducing agent from the storage tank 30, and various types of information are stored. RAM 67. Specifically, each of these units is realized by executing a program by a microcomputer.

  Various setting values are stored in the RAM 67 in advance. For example, the RAM 67 is set with the detection period td of the reduction amount Mn of the reducing agent in the storage tank 30 and the supply amount Qn from the reducing agent supply device 40 together with the detection period, and is horizontal along the vertical direction of the storage tank 30. A change S (L) in the directional cross-sectional area and a leakage allowable value k as a reference value for comparing the difference between the decrease amount Mn and the supply amount Qn are stored. Furthermore, the RAM 67 stores various other set values such as the freezing temperature TF of the reducing agent and the acceleration allowable value am.

  The decrease amount detection unit 61 is configured to be able to detect the decrease amount of the reducing agent in the storage tank 30 based on the signal from the level sensor 31. Since the cross-sectional area S (L) in the horizontal direction at each position in the vertical direction of the storage tank 30 is stored in the RAM 67 in advance, the decrease amount detection unit 61 uses the level sensor 31 to determine the volume of the displacement range of the liquid level L. The decrease amount Mn is detected by obtaining.

  The decrease amount detection unit 61 detects the liquid level L1 at the start time t1 of the detection period td by the level sensor 31, and detects the liquid level Ln at the end time tn of the detection period td, thereby detecting the detection period td. The displacement range in which the liquid level L is displaced is specified. And, as shown in the following formula (1), it is specified based on the displacement range of the specified liquid level L and the horizontal sectional area S (L) in the storage tank 30 stored in the RAM 67. The volume of the reducing agent corresponding to the displacement range is calculated, and the reducing agent reduction amount Mn in the storage tank 30 is detected. In the present embodiment, since the supply amount of the reducing agent from the reducing agent supply device 40 to the exhaust passage 11 is set on a mass basis, the mass basis reduction amount Mn is calculated using the reducing agent density ρ. The density ρ can be calculated based on a signal from the density sensor 35.

Mn = ρ · ∫ _L1 ^Ln S (L) dL (1)
(In formula (1), Mn is the amount of decrease, ρ is the reducing agent density, L1 and Ln are the liquid level, and S (L) is the horizontal cross-sectional area at each height position of the storage tank.)

  The decrease amount detection unit 61 detects the decrease amount Mn based on the change in the liquid level L of the reducing agent in the storage tank 30, so that the change in the liquid level L of the reducing agent can be accurately detected. It is required to be. Therefore, the present embodiment is configured not to detect the decrease amount Mn when the stored reducing agent is in a frozen state and when the liquid level of the reducing agent is greatly shaken.

  Specifically, a freezing temperature TF higher than the melting point of the reducing agent that can be determined that the reducing agent in the storage tank 30 is reliably maintained in a fluid state is stored in the RAM 67. When the temperature Tu of the reducing agent detected by the temperature sensor 33 is equal to or lower than the freezing temperature TF, the decrease amount detection unit 61 stops detecting the decrease amount Mn until the temperature Tu becomes higher than the freezing temperature TF. It is configured.

  In addition, the RAM 67 stores an allowable acceleration value am at which the liquid level of the reducing agent in the storage tank 30 is so large that it cannot be determined. The decrease amount detection unit 61 detects the detected liquid level L until the acceleration a becomes smaller than the allowable value am when the acceleration a calculated from the change in the vehicle speed is equal to or greater than the allowable acceleration value am. It is configured to stop entering values.

The supply amount detection unit 63 is configured to be able to detect the supply amount of the reducing agent from the reducing agent supply device 40. Here, during the same detection period td as the period during which the decrease amount detector 61 detects the displacement of the liquid level L, the reductant injection valve 45 of the reductant supply device 40 enters the exhaust passage 11 one or more times. The supply amount Qn can be detected by integrating the supply amount of the reducing agent that is repeatedly injected.
Specifically, in the supply amount detection unit 63, the control device 50 uses the reducing agent mass-based target supply amount D (t) calculated based on various conditions to control the reducing agent supply device 40. Is used to accumulate the target supply amounts D (1), D (2),... D (n) that are repeatedly set during the predetermined detection period td as shown in the following equation (2). To detect the supply amount Qn.

Qn = ∫ _t1 ^tn D (t) dt (2)
(In formula (2), Qn represents the supply amount, and D (t) represents the target supply amount at each time point.)

Whether the leakage determination unit 65 has leaked the reducing agent from the storage tank 30 based on the decrease amount Mn detected by the decrease amount detection unit 61 and the supply amount Qn detected by the supply amount detection unit 63. Whether or not can be determined. Here, by comparing the decrease amount Mn with the supply amount Qn, the presence or absence of leakage of the reducing agent is determined based on whether or not the material balance is established.
Specifically, in the leakage determination unit 65, as shown in the following equation (3), the supply amount Qn is subtracted from the decrease amount Mn, and the supply paths 41 and 42 of the reducing agent supply device 40 and the liquid feeding unit 43 are further subtracted. If the result of adding the stationary detection error E (positive or negative value) due to deterioration with time of the reducing agent injection valve 45 or the like is 0, there is no leakage of the reducing agent from the storage tank 30. If the result is not 0, it is determined that a leak exists or a failure exists.

  Mn−Qn + E = 0 (3)

The leak detection unit 60 of the control device 50 according to the present embodiment is configured to repeatedly and continuously detect the leakage of the reducing agent from the storage tank 30, and includes a decrease amount detection unit 61, a supply amount detection unit 63, The leak determination unit 65 repeats such detection and determination every detection period td of each cycle.
Further, in the leak detection unit 60, when the leak determination unit 65 determines that there is a leakage of the reducing agent from the storage tank 30, the leak detection unit 60 outputs an abnormal signal to the warning display unit 68 provided in the vehicle. A lamp indicating a warning is turned on on the display unit 68.

3. Leak Detection Method Next, a reducing agent leak detection method executed by the control device 50 including the leak detection unit 60 having the above-described configuration will be described.
The leak detection method of the present embodiment performs leak detection by comparing the reducing agent supply amount Qn from the reducing agent supply device 40 with the reducing agent decrease amount Mn in the storage tank 30. In the embodiment, the leak detection unit 60 of the control device 50 performs leak detection when an ignition switch (not shown) is in an ON state and the internal combustion engine 5 is in an operating state. Once leak detection is started, the leak detector 60 continuously detects leaks until the ignition switch is turned off.

Further, during operation of the internal combustion engine 5, in the reducing agent supply device 40, the control device 50 controls the pump of the liquid feeding unit 43 and the reducing agent stored in the storage tank 30 passes through the supply path 42 at a predetermined pressure. To the reducing agent injection valve 45. In this state, the controller 50 controls the opening and closing of the reducing agent injection valve 45 so that the reducing agent is supplied to the upstream side of the reduction catalyst 21 in the exhaust passage 11. At this time, the reducing agent for the target supply amount D (t) set by the control device 50 is supplied into the exhaust passage 11. Thereby, the exhaust gas from the internal combustion engine 5 comes into contact with the reduction catalyst 21 together with the reducing agent, and the reduction treatment of nitrogen oxide in the exhaust gas is performed.
While the reducing agent is supplied to the exhaust passage 11 as described above, detection of leakage of the reducing agent from the storage tank 30 is performed.

FIG. 3 is a flowchart showing an example of a reducing agent leakage detection method performed by the leakage detection device (control device) 50 of the present embodiment.
First, in step S <b> 11, the temperature sensor 33 detects the temperature Tu of the reducing agent in the storage tank 30 and transmits it to the decrease amount detection unit 61. Next, in step S12, the temperature Tu is compared with the freezing temperature TF. If the reducing agent temperature Tu is equal to or lower than the freezing temperature TF, the reducing agent temperature Tu exceeds the freezing temperature TF. This step S12 is repeated until it is confirmed that the reducing agent is not in a frozen state.

  When it is confirmed that the reducing agent is not in a frozen state, in step S13, an acceleration a1 is calculated based on a change in the speed of the vehicle, and in step S14, the acceleration a1 is compared with the allowable acceleration value am. . When the acceleration a1 exceeds the allowable acceleration value am, this step S14 is repeated until the acceleration a1 becomes equal to or less than the allowable acceleration value am.

  When the acceleration a1 falls below the allowable acceleration value am, the timer count is started in step S15, then the detection of the liquid level L is started in step S16, and the liquid level L1 at the start t1 of the detection period td is decreased. It is transmitted to and stored in the quantity detector 61.

  Next, in step S17, after the target supply amount D (t) (D (1) for the first time) set in the control device 50 is acquired and stored in the supply amount detection unit 63, in step S18, in step S15. It is determined whether or not the timer value for which counting has started has passed the detection period td. When the timer value is before the detection period td, the process returns to step S17, and the target supply amount D (t) set in the control device 50 is acquired and stored in the supply amount detection unit 63. Thereafter, until it is determined in step S18 that the timer value has passed the detection period td, the target supply amounts D (2), D (3), D (4), ... D (n) is sequentially acquired and stored.

  Thereafter, when it is determined in step S18 that the timer value has passed the detection period td, in step S19, the acceleration an is calculated again based on the change in the speed of the vehicle, and in step S20, the acceleration an Comparison with the acceleration tolerance am is performed. When the acceleration an exceeds the acceleration allowable value am, the process returns to step S17 again, and the target supply amount D (t) set in the control device 50 is acquired and stored in the supply amount detection unit 63. In this case, a predetermined detection period td preset in the RAM 67 is extended.

On the other hand, when it is determined in step S20 that the acceleration an is equal to or less than the acceleration allowable value am, the process proceeds to step S21, and the liquid level Ln at the end tn of the detection period td is transmitted to the decrease amount detection unit 61. Remembered.
Thereafter, in step S22, a liquid level level displacement range is specified from the liquid level L1 at the start t1 of the detection period td and the liquid level Ln at the end tn, and the reducing agent corresponding to the volume of the displacement range. Is calculated, and the calculated value is transmitted to the leakage determination unit 65 as a decrease amount Mn.

  Next, in step S23, all target supply amounts D (1), D (2),... D (n) during the detection period td are integrated, and the exhaust passage from the reducing agent supply device 40 during the detection period td. 11 is calculated, and the calculated value is transmitted as a supply amount Qn to the leakage determination unit 65.

  Next, in step S24, a difference between the decrease amount Mn and the supply amount Qn is obtained, and this difference is compared with a leakage allowable value k stored in the RAM 67. When the difference between the decrease amount Mn and the supply amount Qn is equal to or less than the allowable leakage value k, it is determined that there is no leakage of the reducing agent from the storage tank 30 and the present routine is terminated. When the difference from the supply amount Qn exceeds the leakage allowable value k, it is determined that there is a reducing agent leakage from the storage tank 30 and an abnormal signal is transmitted from the leakage determination unit 65 to the warning display unit 68 in step S25. Then, the warning display is turned on in the warning display section 68, and this routine is finished.

  In the leak detection unit 60, the leak determination unit 65 calculates the difference between the decrease amount Mn and the supply amount Qn as an absolute value, for example, an abnormality of the level sensor 31 occurs, and the supply amount Qn is larger than the decrease amount Mn. Even in such a case, it is possible to detect an abnormality, and even in this case, a display indicating the abnormality is lit on the warning display unit 68.

  According to the leak detection unit 60 as described above, the reduction amount detection unit 61 that can detect the reduction amount Mn of the reduction agent in the storage tank 30 and the supply of the reduction agent from the reduction agent supply device 40 into the exhaust passage 11. A supply amount detection unit 63 capable of detecting the amount Qn, and the leakage determination unit 65 calculates a difference between the decrease amount Mn detected by the decrease amount detection unit 61 and the supply amount Qn detected by the supply amount detection unit 63. Since the presence or absence of leakage is determined by calculating and comparing with a preset allowable leakage value k, whether or not the reducing agent in the storage tank 30 has decreased in addition to the amount supplied from the reducing agent supply device 40 I can understand. Therefore, when a leak occurs in the storage tank 30, the leak can be easily detected.

The embodiment described so far can be appropriately changed within the scope of the present invention. For example, in the above-described embodiment, target supply amounts D (1), D (2),... D (, which are set as the supply amount detection unit 63 to control the reducing agent supply device 40 in the control device 50. Although the example of obtaining the supply amount Qn using n) has been described, the method of obtaining the supply amount Qn is not limited to such an example. For example, as shown by a one-dot chain line in FIG. 1, a flow rate detection sensor 69 capable of detecting the flow rate of the reducing agent flowing inside is provided in the middle of the supply path 42 of the reducing agent supply device 40. It is also possible to detect the supply amount Qn by integrating the detected flow rate of the reducing agent flowing during the predetermined detection period td.
In this case, since the flow rate detected by the flow rate detection sensor 69 is a volume flow rate, the decrease amount Mn may be the volume of the reducing agent decreased from the storage tank 30, and the density ρ is not necessary in the above formula (1).

  Further, in the above-described embodiment, the example using the temperature sensor that detects the liquid temperature Tu of the reducing agent stored in the storage tank 30 as the freezing detection unit has been described. For example, instead of the temperature sensor, A detection means capable of determining only the frozen state of the reducing agent can be used together with the temperature sensor. Furthermore, the freezing state of the reducing agent may be detected not by the temperature in the storage tank 30 but by the temperature around the storage tank 30, the outside air temperature, the temperature at each position of the reducing agent supply device 40, or the like.

  Further, in the above-described embodiment, the example in which the acceleration is calculated based on the sensor value of the vehicle speed sensor as the acceleration detection unit has been described. However, the acceleration detection method is not limited to such an example. Alternatively, an acceleration sensor that can directly detect acceleration in an arbitrary direction may be used.

It is the schematic which shows the whole structure of the exhaust gas purification apparatus provided with the leak detection apparatus of the reducing agent concerning embodiment of this invention. It is a block diagram which shows the structural example of the leak detection apparatus concerning embodiment of this invention. It is a figure which shows the flow of the leak detection method of the reducing agent performed with the leak detection apparatus concerning embodiment of this invention.

Explanation of symbols

5: engine, 10: exhaust gas purification device, 11: exhaust passage, 20: reducing catalyst unit, 21: reduction catalyst 23, 25: temperature sensor, 27: NO _X sensor 30: storage tank, 31: level sensor, 33: Temperature sensor, 35: Concentration sensor, 40: Reductant supply device, 41, 42: Supply path, 43: Liquid supply unit, 45: Reductant injection valve, 50: Control device, 60: Leak detection unit, 61: Decrease amount detection unit 63: Supply amount detection unit 65: Leak determination unit 67: RAM 68: Warning display unit

Claims (8)

Detection of leakage of the reducing agent from the storage tank in an exhaust purification device that purifies the exhaust gas of the internal combustion engine by supplying the reducing agent stored in the storage tank from the reducing agent supply unit into the exhaust passage of the internal combustion engine. In the device
A reduction amount detection unit capable of detecting a reduction amount of the reducing agent in the storage tank;
A supply amount detection unit capable of detecting the supply amount of the reducing agent from the reducing agent supply unit into the exhaust passage;
A leak determination unit that calculates a difference between a decrease amount detected by the decrease amount detection unit and a supply amount detected by the supply amount detection unit, and determines whether there is a leak by comparing with a preset reference value; ,
An apparatus for detecting leakage of a reducing agent, comprising: The storage tank includes level detection means for detecting a liquid level of the reducing agent in the storage tank,
The reduction amount detection unit calculates the reduction amount based on a displacement range of the liquid level detected by the level detection means and a horizontal sectional area of the storage tank stored in advance. The reducing agent leakage detection device according to claim 1, wherein The storage tank is mounted on a vehicle, and the vehicle includes acceleration detection means capable of detecting acceleration,
3. The reduction according to claim 2, wherein the decrease amount detection unit calculates the decrease amount using a displacement of the liquid level when the acceleration detected by the acceleration detection unit is a predetermined value or less. Agent leak detection device. The storage tank includes freezing detection means capable of detecting the frozen state of the stored reducing agent,
The decrease amount detection unit calculates the decrease amount using the liquid level when the freezing detection unit detects that the reducing agent is in a flow state other than a frozen state. 4. A reducing agent leakage detection apparatus according to 2 or 3. Detection of leakage of the reducing agent from the storage tank in an exhaust purification device that purifies the exhaust gas of the internal combustion engine by supplying the reducing agent stored in the storage tank from the reducing agent supply unit into the exhaust passage of the internal combustion engine. In the method
Detecting the amount of reduction of the reducing agent in the storage tank, and detecting the amount of reducing agent supplied from the reducing agent supply unit into the exhaust passage;
A method for detecting leakage of a reducing agent, wherein the presence or absence of leakage in the storage tank is determined by comparing a difference between the reduction amount and the supply amount with a reference value. The amount of reduction is the amount of the reducing agent that has been reduced from the storage tank over a predetermined period of time,
6. The reducing agent leakage detection method according to claim 5, wherein the supply amount is an integrated value of the amount of the reducing agent supplied from the reducing agent supply unit during the predetermined period.   6. The reduction amount is calculated based on a liquid level level displacement range of the reducing agent in the storage tank and a horizontal cross-sectional area of the storage tank stored in advance. Or the reducing agent leakage detection method according to 6.   The reducing agent leakage detection method according to claim 5, wherein the supply amount includes an integrated value of a target supply amount set to control the reducing agent supply unit. .

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