JP6503742B2 - Urea injector - Google Patents

Description

  The present invention relates to a urea injection device of an exhaust gas post-treatment device.

  Urea SCR (Selective Catalytic Reduction; hereinafter abbreviated as SCR) has been put to practical use as one of the devices for harming NOx (nitrogen oxide) contained in diesel exhaust gas.

  After-treatment device for diesel exhaust using SCR, DOC (oxidation catalyst), DPF (diesel particulate filter), and SCR are connected in order to the exhaust pipe of diesel engine, and urea injection nozzle is provided on the upstream side of the SCR Is configured.

  The exhaust gas from the diesel engine is oxidized in the unburned fuel (HC) and carbon monoxide (CO) in the exhaust gas in the DOC, and then PM (particulate matter) in the exhaust gas is collected by the DPF The urea water injected from the urea injection nozzle on the inlet side of the SCR is hydrolyzed by the heat of the exhaust gas to become ammonia, and the ammonia and NOx in the exhaust gas react with the catalyst in the SCR (selective reduction catalyst) It is reduced to nitrogen and water and detoxified.

  The urea water injected by this urea injection nozzle is a supply pump, sucks the urea water in the urea water tank, supplies this to the urea water injection nozzle, and injects urea water directly from the urea injection nozzle. Since the nozzle is exposed to a high temperature, urea water adhering to the tip of the nozzle crystallizes and a white product derived from urea adheres, which may clog the nozzle and cause a problem that urea water can not be injected.

  Then, the urea water injection nozzle which consists of a two fluid nozzle which injects urea water and air simultaneously is proposed.

  The urea injection device including the urea water injection nozzle supplies the urea water injection nozzle with an amount necessary for the injection of urea water in the urea water tank using a solenoid pump, and the urea water supplied to the urea water injection nozzle is By injecting it into the exhaust pipe while sucking it with air supplied from the air pump, it is not necessary to return excess urea water to the urea water tank as in the past, and moreover linear control is performed by controlling the drive frequency of the solenoid pump. Has the advantage of being able to vary the flow rate.

JP, 2006-122878, A JP, 2014-005744, A

  However, the supply amount of urea water by the solenoid pump is at most 150 ml / min, and the urea water injection nozzle and its piping system are easily affected by the temperature of the exhaust gas, and the urea water is in the urea water injection nozzle and piping system. There is an inevitable problem of becoming easy to crystallize.

  Then, the object of the present invention solves the above-mentioned subject, and when urea water is injected using a urea water injection nozzle which simultaneously injects urea water and air, a urea injection device capable of avoiding clogging due to crystallization of urea water To provide.

Provided in the exhaust pipe, through a urea water injection nozzle for morphism injection of urea water and the air, the urea water discharge pipe to the urea water injection nozzle is connected via a urea water suction pipe to the aqueous urea tank connection A urea pump for suctioning urea water from the urea water tank through the urea water suction pipe and supplying the urea water to the urea water injection nozzle through the urea water discharge pipe; and urea provided in the urea water suction pipe a valve, is connected via the air supply pipe to the urea water injection nozzle, and an air pump for supplying air to the urea water injection nozzle through the air supply pipe, which is connected with the air supply pipe and the urea water discharge pipe and an air sweep-out pipe, and the air valve provided in the air sweep tube, when the engine is stopped, a state of driving the urea pump, closed the air valve, and the Eapon After the urea valve is closed and the urea water is drawn from the air pump to the tip of the urea water injection nozzle in a driving state, the urea pump is stopped and the air valve is opened to discharge the urea water from the urea water tank sweeping the urea water to the tip of the injection nozzle, and thereafter, to provide a urea injection device and a control device for stopping the air pump.

The control device determines whether to stop the injection of urea water during engine operation based on the operating state of the vehicle, and when it is determined that the injection of urea water is stopped during engine operation, the state where the urea pump is driven The urea valve is closed in a state in which the air valve is closed and the air pump is driven, and after the urea water is drawn from the air pump to the tip of the urea water injection nozzle, the urea pump is stopped and the air is stopped. Preferably, the valve is opened to sweep urea water from the urea water tank to the tip of the urea water injection nozzle, and then the air pump is stopped after the air valve is closed .

The controller opens the urea valve and closes the air valve at the time of engine start, and then starts the air pump to supply air from the air pump to the urea water injection nozzle, and then the urea pump It is preferable to start and supply urea water from the urea water tank to the urea water injection nozzle .

After stopping the injection of urea water during engine operation , the control device determines from the driving state of the vehicle whether to resume the injection of urea water during engine operation and determines that the injection of urea water is to be resumed. Sometimes, the air pump is started to supply air from the air pump to the urea water injection nozzle, and then the urea pump is started to supply urea water from the urea water tank to the urea water injection nozzle. preferable.

  According to the present invention, when stopping the injection of urea aqueous solution by the urea aqueous solution injection nozzle for injecting two fluids, after the urea aqueous solution remaining in the urea aqueous solution injection nozzle and the piping thereof is sucked out with air, By stopping after being swept out, an excellent effect of preventing clogging of the nozzle is exhibited.

It is a schematic diagram showing an exhaust gas post-treatment device to which a urea injection device of the present invention is applied. It is a figure showing the urea injection device of the present invention. It is a figure which shows the relationship between the instruction | indication voltage in the urea injection apparatus of this invention, and the urea injection quantity. In the urea injection device of the present invention, a control flow at the time of start and stop of the vehicle is shown, and (a) shows a flow at key-on and (b) shows a flow at key-off. In the urea injection device of the present invention, it is a diagram showing a control flow of urea injection stop at the time of vehicle operation. FIG. 6 is a diagram showing a control flow from the urea injection stop to the injection resumption at the time of vehicle operation in the urea injection device of the present invention.

  Hereinafter, a preferred embodiment of the present invention will be described in detail based on the attached drawings.

  First, an exhaust gas post-treatment device will be described with reference to FIG.

  A turbocharger 11 including a turbine 12 and a compressor 13 is connected to an intake / exhaust system of the engine 10, and an exhaust pipe 14 connected to the turbine 12 is provided with a DOC (oxidation catalyst) 15, a DPF (diesel particulate filter) An exhaust gas post-treatment device 18 is configured by sequentially connecting the SCRs 17 and 16.

  The urea injection device 20 of the present invention is provided on the upstream side of the SCR 17 and supplies urea water from the urea water tank 22 to the urea water injection nozzle 21 that simultaneously jets air and urea water and the urea water injection nozzle 21. The air pump 24 supplies air to the urea pump 23 and the urea water injection nozzle 21 and sucks and injects the urea water supplied by the urea pump 23. The urea pump 23 controls driving of the air pump 24 and the air pump 24. And a control device 30 comprising an ECU for controlling the opening and closing of the air valve 26.

  The control device 30 controls the flow rate of urea from the urea pump 23 in accordance with the concentration of NOx in the exhaust gas, and the operation information of the vehicle and the temperature sensor provided near the urea water injection nozzle 21 and the temperature of the exhaust gas The operation state of is determined, and control of urea solution injection and stop is performed. That is, for example, when the idling operation or the exhaust gas temperature is as low as 200 ° C. or lower and the urea injection can not be performed, the control device 30 stops the urea injection, and when the exhaust gas temperature exceeds 200 ° C. in the operating condition of the vehicle The urea pump 23 is driven to control urea aqueous solution injection.

  FIG. 2 shows the details of the urea injection device 20. The urea water tank 22 and the urea pump 23 are connected via the urea water suction pipe 31, and the urea pump 23 and the urea water injection nozzle 21 are It is connected via the urea water discharge pipe 32. A urea valve 25 composed of a solenoid valve is connected to the urea water suction pipe 31.

  The air pump 24 is connected to the urea water injection nozzle 21 through the air supply pipe 33, the air supply pipe 33 and the urea water discharge pipe 32 are connected by the air sweep pipe 34, and the air sweep pipe 34 is composed of a solenoid valve. An air valve 26 is connected.

  The urea pump 23 is a solenoid pump, and a cylinder chamber 36 is formed in the pump casing 35, and an inlet side valve 37i and an outlet side valve 37o are provided on the inlet / outlet side of the cylinder chamber 36. At the time of suction, the piston of the plunger is moved in the suction direction by the electromagnetic force of the electromagnetic coil 39 by reciprocating the plunger (not shown) having the piston by the biasing force of the spring 38 and the electromagnetic force of the electromagnetic coil 39 Urea water is sucked into the cylinder chamber 36 via the inlet valve 37i, and at the time of discharge, the piston is moved in the discharge direction by the biasing force of the spring 38, and the urea water sucked in the cylinder chamber 36 is the outlet valve It discharges via 37o.

  As shown in FIG. 3, the urea pump 23 changes the flow rate to 0 to 150 ml / min by changing the output frequency for energizing the electromagnetic coil 39 at 1 to 100 Hz (adjusting at the command voltage 1 to 5 V). Can be changed.

  The urea water injection nozzle 21 has, at the center, a urea water injection passage 40 connected to the urea water discharge pipe 32 for injecting urea water, and has an air passage 41 on the outer periphery of the urea water injection passage 40. , 41 are opened at the tip 21 a of the urea water injection nozzle 21.

  The injection of urea water by the urea water injection nozzle 21 is performed by the supply of urea water to the urea water injection passage 40 by the urea pump 23 and the suction force by injecting the air from the air pump 24 into the air passage 41 and injecting it. Urea water is injected in the form of a spray. Unlike the conventional supply pump and the injector for urea injection, the urea injection device 20 using the urea water injection nozzle 21 composed of the urea pump 23 and the two-fluid nozzle can inject at low pressure and can make the device compact.

  Conventionally, when the urea is not injected, the urea water is returned to the urea water tank, and the injector is cooled by the cooling water. However, the urea water injection nozzle 21 of the present invention After the injection is stopped, the urea water injection nozzle 21 is exposed to the high temperature environment of the exhaust pipe 14 or after operation stop (key off), the state where the urea water remains in the urea water injection passage 40 It becomes.

  Therefore, according to the present invention, when the control device 30 stops the vehicle with key-off, the urea pump 23 is stopped, and after holding the state and performing suction by the jet air, the air valve 26 is opened and the air pump 24 By supplying air from the discharge pipe 34 to the urea water discharge pipe 32 and injecting the air through the urea water injection passage 40, the urea water remaining in the urea water injection passage 40 is swept out, whereby the urea water is discharged. It is intended to prevent the accumulation of the whitening product due to the residue and the clogging due to it. Further, when the vehicle starts to be operated with the key-on, the control device 30 opens the urea valve 25 and closes the air valve 26, and drives the air pump 24 to flow air from the urea water injection nozzle 21 first. Next, the urea pump 23 is started to supply urea aqueous solution to the urea aqueous solution injection nozzle 21, and urea aqueous solution is injected together with air.

  Furthermore, during operation, the control device 30 determines from the driving state of the vehicle that the urea water injection stop at the urea water injection nozzle 21 is stopped, and when it is determined that the urea water injection stop, the urea pump 23 is stopped and the state is After holding and sucking out by the jet air, the air valve 26 is opened to sweep the inside of the urea water discharge pipe 32 with air, and then the air valve 26 is closed and the air pump 24 is stopped. During the injection resumption, the air pump 24 is driven and then the urea pump 23 is started to restart the urea injection.

  Next, the control flow of the control device 30 will be described with reference to FIGS.

  FIG. 4 shows a control flow of start and stop of the vehicle.

  As shown in FIG. 4A, when the vehicle is turned on (step S1), the urea valve is opened and the air valve is closed (step S2). In this state, the air pump is started in step S3 and air is supplied to the urea water injection nozzle (step S4).

  In step S5, when the air supply time is counted for a predetermined time (a time set by the pipe length), the urea pump is started (step S6), and the urea water is supplied to the urea water injection nozzle to air and urea water. Are injected (step S7) to remove NOx by SCR.

  Thus, by flowing air first, even if solid residue remains temporarily in the urea water injection nozzle, this can be discharged.

  In order to stop the vehicle, as shown in FIG. 4B, when the key is turned off (step S8), the urea valve is closed (step S9). As a result, only air is injected from the urea water injection nozzle, and suction of urea water remaining in the urea water injection nozzle is performed (step S10). The suction time is counted for a predetermined time (the suction time set by the pipe length) (step S11), and after counting up, the urea pump is stopped (step S12).

  Next, in step S13, the air valve 26 is opened to supply air also to the urea water discharge pipe 32, and the urea water remaining in the urea water injection passage 40 is swept out and the cylinder space of the urea water discharge pipe 32 and the urea pump 23 36. Urea water remaining in the chamber 36 is swept out (step S14). This sweeping time is counted for a predetermined time (sweeping time set by piping length) (step S15), and the air pump is stopped after the count-up (step S16) to complete the stop.

  Next, the urea injection stop during vehicle operation will be described with reference to FIG. 5, and the injection resumption during the injection stop will be described with reference to FIG.

  First, during operation, as shown in FIG. 5, the control device 30 determines in step S20 whether the control unit (stop) is in the operating state as shown in FIG. In this temporary stop determination, the tip temperature of the urea water injection nozzle and exhaust gas temperature are low during idle operation or low load operation of the vehicle, and the temperature is lower than the temperature at which urea water does not hydrolyze even if urea water is injected (for example, 200 ° C. or less) If it is not necessary to stop (No), control is returned to the control unit (stop) in step S20, and if it is determined that stop is necessary (Yes), control to stop the injection is performed.

  First, in step S22, as described with reference to FIG. 4B, the urea valve is closed to suck the urea water, and the suction time is counted for a predetermined time (step S23), and then it is temporarily stopped in step S24 Determine if.

  If it is determined that the temporary stop is not necessary (No), the urea valve is opened to return to the control unit (stop) in step S20, and when the temporary stop is necessary, the urea pump is stopped (step S25).

  Next, the air valve is opened, and the urea water in the urea water discharge pipe or the urea pump is swept (step S27). The sweeping time is counted for a predetermined time (step S28), and then the air valve is closed ( Step S29).

  Thereafter, in step S30, it is determined whether the stop preparation is completed, and when the stop preparation is completed (Yes), the air pump is stopped (step S31), and the control unit (restart) in step S34 of FIG. In step S30, when the preparation for stopping is not completed, for example, when it is preferable to prepare the injection of urea water immediately, such as when the engine speed is increased and the exhaust temperature is expected to increase, the air pump was driven. Then, the process proceeds to the restart determination of step S39 in FIG.

  In the restart control of urea water injection during driving in FIG. 6, the control unit (restart) in step S34 monitors restart conditions from the vehicle driving state, and in step S35, restart determination is performed. When the restart condition is not the restart condition (No), the process returns to step S34, and when the restart is resumed (Yes), the air pump is started (step S36), air is supplied to the urea water injection nozzle, and the supply time is predetermined time After counting (step S38), the restart determination in step S39 is performed, and if it is not restart (No), the process proceeds to step S20 of FIG. 5 and if it is restarted (Yes), the urea pump is started (step S40) Then, in step S41, the urea aqueous solution is supplied to restart the urea aqueous solution injection.

As described above, according to the present invention, by combining the urea water injection nozzle consisting of the two-fluid nozzle and the urea pump consisting of the solenoid control pump, it is possible to miniaturize the urea injection device and at the time of urea injection and stop.
(1) When stopping the urea water by key-off, with the injection of urea water from the urea water injection nozzle stopped, from the air pump to the tip of the urea water injection nozzle, or from the urea water tank to the tip of the injection nozzle Stop the air after discharging the urea solution until (2) Normally, the air always flows even when the urea solution is not injected (However, if there is no command for urea solution injection for a predetermined time, or at that time) Stop the air if the nozzle tip temperature exceeds a predetermined temperature),
(3) In the case of injecting urea water again, air is first flowed, and after air is injected from the urea water injection nozzle, urea water injection is started in the order of injecting urea water,
As a result, clogging and deposition of the nozzle tip of urea water injection start / stop can be avoided and the clogging of the nozzle tip and deposition also occur in a situation where the urea water injection interval becomes long and the nozzle tip temperature becomes high (200 ° C. or more). Can be avoided.

Reference Signs List 20 urea injection device 21 urea water injection nozzle 22 urea water tank 23 urea pump 24 air pump 25 urea valve 26 air valve 30 control device 31 urea water suction pipe 32 urea water discharge pipe 33 air supply pipe 34 air discharge pipe

Claims (4)

Provided in the exhaust pipe, and the urea water injection nozzle for morphism injection of urea water and the air,
The urea water tank is connected to the urea water tank via a urea water suction pipe and connected to the urea water injection nozzle via a urea water discharge pipe, and the urea water is sucked from the urea water tank through the urea water suction pipe and the urea is A urea pump for supplying urea water to the urea water injection nozzle through a water discharge pipe ;
A urea valve provided in the urea water suction pipe;
An air pump connected to the urea water injection nozzle via an air supply pipe and supplying air to the urea water injection nozzle through the air supply pipe ;
An air sweep pipe connected to the air supply pipe to said urea water discharge pipe,
An air valve provided in the air sweep tube,
When the engine is stopped, the urea pump is driven, the air valve is closed, and the air pump is driven, and the urea valve is closed to draw urea water from the air pump to the tip of the urea water injection nozzle After that, the control unit stops the urea pump and opens the air valve to sweep out the urea water from the urea water tank to the tip of the urea water injection nozzle, and then stops the air pump .
Urea injection device characterized by having. The control device determines whether to stop the injection of urea water during engine operation based on the operating state of the vehicle, and when it is determined that the injection of urea water is stopped during engine operation, the state where the urea pump is driven The urea valve is closed in a state in which the air valve is closed and the air pump is driven, and after the urea water is drawn from the air pump to the tip of the urea water injection nozzle, the urea pump is stopped and the air is stopped. The urea injection device according to claim 1 , wherein the valve is opened to sweep urea water from the urea water tank to the tip of the urea water injection nozzle, and then the air pump is stopped after the air valve is closed . The controller opens the urea valve and closes the air valve at the time of engine start, and then starts the air pump to supply air from the air pump to the urea water injection nozzle, and then the urea pump The urea injector according to claim 1 or 2, wherein the urea aqueous solution is supplied from the urea aqueous solution tank to the urea aqueous solution injection nozzle . After stopping the injection of urea water during engine operation , the control device determines from the driving state of the vehicle whether to resume the injection of urea water during engine operation and determines that the injection of urea water is to be resumed. At the same time, the air pump is started to supply air from the air pump to the urea water injection nozzle, and then the urea pump is started to supply urea water from the urea water tank to the urea water injection nozzle. The urea injection device according to any one of 1 to 3 .

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