CN106460608A - Reduction agent dosing system with damped reduction agent feed - Google Patents

Abstract

The invention relates to a reduction agent dosing system (10) for the injection of a reduction agent into the exhaust gas flow of an internal combustion engine for selective catalytic reduction, having a feed pump (20), by means of which a reduction agent is suctioned from a reduction agent tank (40) via a suction line (30) from the tank (40) and fed via a pressure line (50), and introduced into the exhaust gas flow of the internal combustion engine via at least one nozzle (60), wherein the suction line (30) has a bidirectional rubber valve (70).

Description

There is the reductant metering system of downtrod reducing agent conveying

The present invention relates in a kind of waste gas stream for spraying reductant into internal combustion engine so as SCR also Former dose of metering system（Reduktionsmitteldosiersystem）, it has delivery pump, by this delivery pump by reducing agent Reducing agent in storage tank suctions out from storage tank via suction channel, is conveyed via pressure pipeline, and via at least one spray Mouth is introduced in the waste gas stream of internal combustion engine.

Moreover, it relates to a kind of spray reductant in the waste gas stream of internal combustion engine so that selectivity is urged for running The method changing the reductant metering system of reduction, described metering system has the magnetic force piston-type pump as delivery pump, will by it Reducing agent in reducing agent storage tank suctions out from storage tank via suction channel, is conveyed via pressure pipeline, and via at least One nozzle is introduced in the waste gas stream of internal combustion engine, wherein causes piston movement by activating one or more cylindrical coils.

Using the catalyst for SCR, i.e. so-called SCR catalyst（English：selective Catalyic reduction, abbreviation：SCR）To reduce Diesel engine, combustion apparatus, garbage incineration equipment, industrial equipment etc. Discharged nitrous oxides.Spray into reducing agent for this using metering device to gas extraction system.As reducing agent is ammonia or ammonia solution Or other reducing agent.

Dangerous due to carrying ammonia in vehicle, therefore especially it is usually using urea concentration according to DIN 70070 standard 32.5% aqueous solution of urea.When temperature is more than 150 degrees Celsius, the carbamide in waste gas can resolve into gaseous ammonia and CO₂.Urine The parameter that element decomposes is mainly the time（Vaporization time and response time）, the droplet size of temperature and the urea liquid spraying into. In these SCR catalyst, by SCR（English selective catalyic reduction, SCR）Make The discharge of nitrogen oxides reduces by 90% about.

Known in the waste gas stream spraying reductant into internal combustion engine so that based on the reducing agent of SCR In amount system, by magnetic force piston-type pump, reductant solution is transported to nozzle.Here, it is shown that due to the conveying in magnetic force piston-type pump After stroke, the momentum in conveyance conduit creates that reducing agent is uncontrolled to be conveyed again.In addition it is also shown that due to conveying In stroke, piston speed is high, and hydraulic fluid could not flow out from cylinder body via adjustment hole as desired like that, on the contrary early in regulation Hydraulic fluid is just delivered, so because increasing of conveying thin film deflects thus delivered excessive reduction before bore closure Agent, this makes accurate measurement become difficult.

It shows furthermore that, because after delivery stroke, piston speed is high, could not as desired like that via adjustment hole by liquid Pressure fluid supplies to cylinder body and piston, also suctions out hydraulic fluid from membrane well on the contrary, has been consequently inhaled the reducing agent of excess, this Accurate measurement is made to become difficult.

The task of the present invention is, constructs the reductant metering system of aforementioned type as follows further and proposes one Plant for running the method for reductant metering system so that accurate measurement reducing agent can be possible to, and effectively stop defeated Produce unexpected excess conveying after journey of seeing off or convey again.

According to the present invention, this task is achieved by the reductant metering system described in claim 1.The present invention is favourable Improved form illustrate in the corresponding dependent claims.

For spraying reductant in the waste gas stream of internal combustion engine so that the reductant metering system of SCR, tool There is delivery pump, by this delivery pump, the reducing agent in reducing agent storage tank is suctioned out via suction channel from storage tank, via pressure Pipeline is conveyed, and is introduced in the waste gas stream of internal combustion engine via at least one nozzle, in such reductant metering system It is particularly preferred that suction channel has two-way rubber valve.

Especially, reductant metering system can have the pump unit comprising delivery pump.Except delivery pump, this pump unit is also Can have other components, particularly there is reversal valve and/or sensor.

Here represents the conveyance conduit from reducing agent storage tank to the pump orifice of delivery pump with term suction channel.Here is taken out Two-way rubber valve is arranged in suction pipe road.Described two-way rubber valve is passive component, and it is in the both sides of two-way rubber valve Between occur during corresponding pressure differential, automatically opening up and discharge fluid course, in turn, in the both sides less than two-way rubber valve It is automatically switched off fluid course during desirable pressure difference again.Thus effectively stop due to after the conveying stroke of delivery pump in delivery pipe Momentum in road and the unexpected conveying reducing agent again that causes.

Here represented with term pressure pipeline the on the pressure side remittance of delivery pump wherein and via its by reducing agent from pump It is transported to the conveyance conduit of nozzle.

Term reductant metering system or metering system are in the present invention by synonymous use.Term reductant solution or reduction Agent includes the various reducing agents being suitable for SCR, and here preferably uses the urea liquid according to DIN 70070. But the present invention is not limited to this.

In preferred form of implementation, pressure pipeline has choke valve.Result shows, two-way rubber valve in suction channel The arrangement being combined with the choke valve in pressure pipeline is made particularly precisely to measure reducing agent and is possibly realized, and effectively stops Produce undesirable excessive conveying after conveying stroke or convey again.

Preferably, system has part stent, and delivery pump is mounted thereto, and wherein leads to the suction channel of pump intake It is integrated with the pressure channel being connected to pump discharge that in this part stent, wherein part stent has assembly area, in this assembling In region, rubber valve is fluidlyIntegrated installation is in suction channel.

Pump and two-way rubber valve particularly advantageously can be arranged in by suction channel by such part stent In.Here is possible to, and the part assembled in advance being arranged at part stent and/or be arranged in part stent is become assembly.By This make metering system assembling simpler, and due to multiple parts are merged into the assembly of save space thus saving Necessary installing space.

In preferred integral arrangement, reductant metering system has storage tank, is connected to suction channel thereon.Here will be also Former agent solution is filled in storage tank and is stored in the operation for system in storage tank.In order to measure, by reductant solution from storage tank Middle taking-up, is conveyed by delivery pump, and is introduced in the waste gas stream of internal combustion engine via at least one nozzle.

It is particularly preferred that system has compressed air supply unit and will be gone back in nozzle interior or nozzle exterior with compressed air Former dose of atomization.Compressed air supply unit here can have reversal valve and/or pressure regulator valve.Reversal valve is used for controlling, that is, be used for be Metering system switches on and off compressed air supply unit all or in part.

Alternative or can supplement, compressed air supply unit can have pressure regulator valve.Thus compressed air can be arranged Become for reducing agent being atomized desired pressure stage by compressed air.Compressed air itself can derive from such as commercial car Vehicle-mounted compressed air system, the exhaust duct of this commerial vehicle arranges metering system, accounts in compressed air system Most system pressures does not cause to limit, because can be by the reduced pressure of compressed air to desired pressure.

Therefore, be provided with compressed air supply unit in the preferred form of implementation of reductant metering system, wherein by Compressed air is atomized reducing agent in nozzle interior or nozzle exterior.Mixing chamber can be arranged be used for being atomized reducing agent, early in introducing Just to implement the atomization of reducing agent in the indoor compressed air of mixing before exhaust duct.However, will in preferred form of implementation Nozzle structure becomes the double nozzle of external mix, and wherein reductant solution flows out from first jet opening and compressed air is from second Nozzle opening is discharged, and two of which nozzle opening is aligned with each other as follows, that is, compressed air in nozzle exterior by reducing agent Atomization is so that nozzle is configured to the double nozzle of external mix, and realizes forming aerosol in nozzle exterior.Especially, Second opening of nozzle positions as follows, the particularly injection direction placement at an angle with the first opening of nozzle, makes Obtain to be atomized, by the compressed air discharged from the second opening, the reducing agent flowing out from the first opening.

Preferably, pressure pipeline is connected to compressed air supply unit via reversal valve or regulating valve, to terminate in metering Remove the reducing agent of pressure pipeline and nozzle afterwards by compressed air.

Therefore, the preferred form of implementation of reductant metering system arranges compressed air supply unit, wherein conveying also Former dose of pressure pipeline, thus nozzle is also connected to compressed air supply unit via reversal valve, so as after metering to terminate by Compressed air removes the reducing agent of pressure pipeline and nozzle.

Pressure pipeline and nozzle and/or the meter of conveying reducing agent thus can be removed after metering terminates by compressed air Amount room and/or the reductant solution of metering conduit, to prevent reductant solution from freezing or to crystallize.Thus can effectively prevent Freezing and blocking.

Alternative or can supplement for this, it is atomized the reducing agent in gas extraction system using compressed air, and in meter Amount uses it to after terminating clean the pipeline of conveying reducing agent.

Preferably, detected with pressure transducer and monitor the pressure in pressure pipeline.By the pressure to conveying reducing agent Pressure in hydraulic piping carries out described detection and monitoring can also constantly monitor correct operation and the metering of delivery pump.

Preferably, system has the heater for heating reductant solution.Going back according to DIN 70070 standard common Former agent solution can freeze when -11 DEG C about because of its water content.Therefore, it is necessary to and/or lead to suction for example in storage tank Pipeline and/or the thermal coupling of pressure pipeline（thermischer Kopplung）Middle setting heater is used for non-in ambient temperature Heat reductant solution in the case of often low.

Preferably, delivery pump is piston pump, particularly magnetic force piston-type pump.One or many is arranged in described magnetic force piston-type pump Individual cylindrical coil, produces magnetic field by means of it.The piston movement of magnetic force piston is controlled by the magnetic field producing by coil.

In magnetic force piston-type pump particularly advantageously, it can be carried out accurately by correspondingly controlling the coil producing magnetic field Operation and control.

Therefore there is this probability, that is, for running in the waste gas stream spraying reductant into internal combustion engine so that selectivity In the method for reductant metering system of catalysis reduction, described metering system has the magnetic force piston-type pump as delivery pump, by The reducing agent of reducing agent storage tank is suctioned out from storage tank by it via suction channel, is conveyed via pressure pipeline, and via extremely A few nozzle is introduced in the waste gas stream of internal combustion engine, wherein produces magnetic field by cylindrical coil, one or more by controlling Cylindrical coil causing piston movement, is so arranged, that is, according to the existing position of piston, speed and the direction of motion to one or Multiple cylindrical coils implement the control of pulse width modulation.

Here, term controls cylindrical coil to refer to carry out power supply variable in time to coil, thus produce respectively and close Become magnetic field, this magnetic field applies the power of synthesis to magnetic force piston.The magnetic force of synthesis makes piston upper in the cylinder body of magnetic force piston-type pump Move back and forth between stop and lower dead center and thereby speed up or brake piston.

Dutycycle（The Lifetime powered to cylindrical coil during a circulation and disconnection The ratio of time）It is changed by controlling with carrying out pulse width modulation to cylindrical coil, thus produce anaplasia at any time The resultant magnetic field of the cylindrical coil changed.Thus, subsequently produce again and change over the synthesis magnetic force acting on piston, and And produce the variable piston acceleration thus causing or piston speed.By duty ratio（Tastgrad）Change can change electricity The arithmetic average of pressure.To control with therefore, it can the pulse width modulation of the cylindrical coil by magnetic force piston-type pump Act on the synthesis magnetic force on piston.

Here is in addition to the improved form according to the present invention it is also possible in the such reducing agent according to prior art Using the method running reductant metering system in metering system.But there is also this probability, changed according to the present invention Increase using the method for running reductant metering system in the reductant metering system entered.

Preferably, realize the control of cylindrical coil as follows, that is, conveying stroke during make piston decelerate to through The height of the adjustment hole of hydraulic fluid is introduced by it.

Preferably, realize the control of cylindrical coil as follows, make during intake stroke piston decelerate to through The height of the adjustment hole of hydraulic fluid is introduced by it.

Preferably, realize the control of cylindrical coil as follows, that is, brake piston is defeated to terminate before top dead center See off journey.

Hydraulic fluid is introduced or derivation cylinder body via it by decelerating to piston（Introduce piston in this cylinder body） Adjustment hole height, optimize the desired flowing via adjustment hole of hydraulic fluid, because in the too high situation of piston speed Under can observe in aspiration stroke during intake stroke and undesirably to suck excessive hydraulic fluid from membrane well, and defeated Can produce because piston speed is too high in pumping strokes and undesirably hydraulic fluid be delivered in membrane well.In intake stroke and defeated These the undesirable effects seen off in journey can control cylindrical coil and braking by corresponding pulse width modulation Adjust the piston in bore region and significantly reduce.

Piston does not collide in the pressure pipeline causing metering system on the impingement plate at conveying stroke end end and produces with braking The huge momentum of life, its consequence is, due to this momentum, inlet valve is opened and produced uncontrolled and undesirably conveying reduction Agent.This unexpected effect can be suppressed by brake piston before closing on top dead centre.Firmly touched by avoiding piston Bump against the momentum occurring in pressure pipeline to be reduced on impingement plate so that will not occur undesirably after conveying stroke terminates Continue conveying reducing agent.The realization duty ratio that correspondingly reduction cylindrical coil is powered is with brake piston.

Embodiments of the invention illustrate in figure and are illustrated in more detail below.In figure illustrates：

Fig. 1 shows the schematic illustration of reductant metering system；

Fig. 2 shows the zoomed-in view of the metering system according to Fig. 1 in sectional view；

Fig. 3 shows the two-way rubber valve according to Fig. 1 and Fig. 2 with different views；

Fig. 4 shows the schematic illustration of the delivery pump in sectional view according to Fig. 2；

Fig. 5 shows the sectional view of the delivery pump during the stage B according to the conveying stroke of Fig. 9；

Fig. 6 shows the sectional view of the delivery pump during the stage C according to the conveying stroke of Fig. 9；

Fig. 7 shows the sectional view of the delivery pump during the stage D according to the conveying stroke of Fig. 9；

Fig. 8 shows the sectional view of the delivery pump during the stage E according to the conveying stroke of Fig. 9；

Fig. 9 shows that elapsed time t controls piston stroke s of delivery pump and PWM to account for during the delivery stroke of delivery pump The curve of empty ratio.

Fig. 1 show for spray reductant into unshowned internal combustion engine waste gas stream in so that SCR The schematic illustration of reductant metering system 10.Reductant solution is inhaled from storage tank 40 via suction channel 30 by delivery pump 20 Go out and be delivered to nozzle 60 via pressure pipeline 50.Inject a reductant in the waste gas stream of internal combustion engine via nozzle 60.According to The present invention, arranges two-way rubber valve 70 in suction channel 30.

Fig. 2 illustrates the zoomed-in view of the metering system according to Fig. 1 with section view.Pump 20 here is arranged in part stent 15 On.Integrated suction channel 30 ' and integrated pressure pipeline 50 ' are integrated in part stent 15.Pump 20 and part stent 15 Match each other as follows, that is, the suction channel 30 ' being integrated in part stent 15 is directly pooled to the pump intake of pump 20, this The pump discharge of outer pump 20 is also directly pooled to the pressure pipeline 50 ' being integrated in part stent 15.

Additionally, being used for receiving the valve seat of two-way rubber valve 70 it can also be seen that being integrated in part stent 15 in fig. 2 16.Two-way rubber valve 70 is fixed in valve seat by valve support 31, and this valve support is requisite group of suction channel 30 again Become part.Suction channel 30 is connected with the storage tank not shown in Fig. 2.Valve support 31 by two-way rubber valve sealing surface and In addition also seal off with the valve seat 16 in part stent 15 by O-ring seal 35.

Fig. 3 illustrates two-way rubber valve 70 and cross section A-A to overlook.The top view of rubber valve 70 can be seen To aperture slots 71.When applying corresponding pressure differential on two-way rubber valve 70, aperture slots 71 automatically open up.On the contrary, working as On two-way rubber valve 70, necessary pressure differential is less than necessary when opening pressure, and aperture slots 71 can be closed automatically because of its restoring force Close.

Two-way rubber valve 70 is arranged in the suction channel 30 of metering system 10 reducing agent conveying can be led to be pressed down System, particularly when conveying stroke end, if because do not have integrated two-way rubber valve 70, the pressure pipeline of metering system Momentum in 50 may cause the reducing agent undesirably conveying again from storage tank.By being integrated in the suction side of pump 20 Valve 70 in suction channel 30 stops this undesirable convey again effectively.

Fig. 4 shows the sectional view of delivery pump 20.Delivery pump 20 is electromagnetic force piston pump, lives in this electromagnetic force delivery pump Plug 21 pass through set up corresponding magnetic field by solenoid 22, that is, pass through by cylindrical coil 22 produce magnetic field and thus produce The magnetic force acting on piston 21 moving.

By correspondingly controlling cylindrical coil 22 in the discharge stroke direction of piston 21, that is, in the conveying stroke of piston 21 Period, in the direction towards top dead centre, is realized driving piston 21.As can be seen in Figure 4, piston 21 resets by spring 23.

The space around piston with cylindrical coil is filled with hydraulic fluid, the wherein lubrication of piston and stroke sky Between wadding warp realized by corresponding adjustment hole 24.The actual fed volume of pump 20 is set up by cylinder body volume 25.

Suction to be realized via access road 26.Discharge to be realized via exit passageway 27.Thin film 28 covers access road 26 and exit passageway 27.

Control cylindrical coil 22 being carried out according to piston position, piston speed and the direction of motion is below according to other Accompanying drawing is described.

Each piston position during conveying circulation can be seen in Fig. 4 to Fig. 8, they correspond to each according to Fig. 9 Stage A to G.

A is when the lower dead center of piston absolutely controls cylindrical coil in the first stage, by absolutely Ground controls cylindrical coil to realize premagnetization and to set up high-intensity magnetic field.Piston is thus led to convey when stroke starts from lower dead center UT starts to produce big acceleration, and this point can be seen by the position of the piston 21 shown in Fig. 4.When stage A starts, live Plug 21 is located at lower dead center UT.By improving control by the alive pulse width modulation of institute, the stage A that figure 9 illustrates Required electric current i is only provided with now by big pulse width modulation, to arrange magnetic field as follows, even if piston 21 is only With less acceleration movement.

And then the first stage A being related to absolutely control is second stage B with larger piston speed.? During stage B, should realize in the adjustment hole 24 that hydraulic fluid is squeezed the pump pre-setting for this, this as shown in Figure 5 and uses Arrow 24 ' schematically shows.During motion stage B when conveying stroke, hydraulic fluid is generally not only by setting in advance The adjustment hole 24 put flows out, and some also flows to membrane well.In order to avoid hydraulic fluid is driven to before piston, and It is not to flow out in the adjustment hole 24 arranging for this, using the pulse width modulation reducing in the motion stage B that figure 9 illustrates Dutycycle maintain the piston in less speed, this point is in fig .9 by the piston stroke curve s of elapsed time t more Little slope can be seen that.During stage B, the position of the height in adjustment hole 24 for piston phase in the sectional view according to Fig. 5 Illustrate with answering.Equally also have recorded the elevation plane 25 ' at the regulation edge 25 ' according to adjustment hole 24 in Figure 5, piston pump true Positive actual cylinder body volume initiates in this elevation plane, and is pressed to membrane well as delivered volume.

Exceed after adjustment hole 24 adjusts edge 25 ' with it in piston and reach the reality on the height of plane 25 ' During the section start of cylinder body volume 25, as shown in fig. 6, being the stage C according to Fig. 9 then in ensuing time graph.In rank Achieve in section C again and control cylindrical coil using higher duty ratio so that piston is again speeded up, this point is from piston Learn in the dutycycle that can read in the stroke-time diagram of Fig. 9 of motion and equally also can record from Fig. 9.In motion rank The real conveying of the cylinder body volume 25 of pump 20 is achieved during section C.

Can cause on the impingement plate that piston 21 does not collide in top dead centre OT with braking in the pressure pipeline 50 of metering system Produce huge momentum.This collision and the same momentum producing are possible in metering conduit again can be so big, cause into Mouth valve opens and reducing agent flows through pump sidewards, until momentum eliminates.This is possible to cause unexpected conveying again, and thus draws Play uncontrolled metering.

In order to suppress this effect, stop the impingement plate in top dead centre OT for piston 21 hard collision as follows, that is, exist During motion stage C when convey stroke end when brake piston, this point is in the stroke-time diagram of the piston movement according to Fig. 9 In it can be seen that.Before top dead centre OT, brake piston 21 to be realized when motion stage C terminates, that is, in warp again as follows Duty ratio extreme is reduced to minima when controlling cylindrical coil by extra pulse width modulated ground.This time marked and drawed from Fig. 9 Can learn in the curve of the duty ratio during interval T4.

After reaching top dead centre OT, piston 21 returns to lower dead center by spring 23, is achieved in via suction channel 30 phase Reducing agent should be suctioned out in ground.

When piston reaches top dead centre OT, the stage, D started, and was shown in the position of top dead centre OT by the piston 21 according to Fig. 7 Go out or figure 9 illustrates.

When piston is returned due to the spring force of back-moving spring in stage E, hydraulic fluid is in the swept volume stroke phase Between from membrane well suction out.Because the piston movement too fast in the region of adjustment hole 24 when being back to lower dead center UT leads to hydraulic pressure Fluid continues to suction out from thin film and be more than suctioning out from adjustment hole 24, and this is in fig. 8 with arrow 24 " illustrate, this is according to Fig. 9 Stage E and F in, piston is during it is due to the backhaul of back-moving spring spring force also by correspondingly through pulse width modulation Ground control cylindrical coil is braked in adjustment hole 24 region, and this can see in fig .9 during motion stage E and F. Fig. 9 can substantially read, and from the lower regulation edge 25 ' of adjustment hole, the height upper piston speed in adjustment hole 24 is less.One Denier piston has exceeded adjustment hole, then slow down piston speed to realize from adjustment hole 24 by using less dutycycle in stage F Swimmingly suction out hydraulic fluid, this is in fig. 8 with arrow 24 " schematically show.

Complete motion cycle is illustrated with general overview in fig .9.Fig. 9 upper partly in show elapsed time t Stroke-the time diagram of piston stroke s during whole conveying circulation and suction circulation.Have recorded lower dead center UT, top dead centre OT And the regulation edge 25 ' of the adjustment hole 24 of pump.In stroke-time diagram it can be seen that conveying stroke during section A to D with And followed by correspond to the stage E to G of the aspiration stroke of pump.

Correspondingly control cylindrical coil through pulse width modulation, convert duty ratio every time, by with respect to each Individual motion stage A to G phase shift is realizing, because on the one hand must be magnetized accordingly, and also needs to certain anti-in addition Between seasonable, until piston makes corresponding response to the magnetic field changing.For this Fig. 9 lower partly in it can be seen that control circle Each duty ratio during cylindrical solenoid, that is, show when the cylindrical coil of piston pump is powered turn-on time or turn-off time Curve.

Realize necessary magnetization using high duty ratio during the first period T1, cause piston to produce phase during stage A Should less acceleration and relatively low movement velocity.And then by using subtracting during the second period T2 in motion stage B Little duty ratio is controlled realizing the constant low velocity of piston.Then the period T3 in for example corresponding motion stage C Period, it is controlled using the duty ratio of somewhat raising during real conveying reducing agent, afterwards profit during period T4 Control cylindrical coil to be used for the braking work when motion stage C terminates before reaching top dead centre OT with minimum duty ratio Plug.In the period T5 of stage D, improve dutycycle at top dead centre OT again, collided with preventing and guarantee firmly to keep piston. From top dead centre OT, the spring force that piston passes through back-moving spring is returning towards the direction of lower dead center UT, wherein subsequent Almost inhibit the magnetic influence to piston using minimum duty ratio during period T6, thus only about limit the speed of piston Degree.In subsequent period T7, caused using the duty ratio improving and originating in the adjustment hole 24 on the height adjusting edge 25 ' Height upper piston braking.Followed by another period T8, in this period, make piston using the duty ratio of somewhat reduction again Keep less speed, and return to lower dead center UT.When piston will encounter lower dead center UT, using raising in period T9 Dutycycle brake piston again, also to stop collision here.After loop ends, after that is, period T9 terminates, according to metering Require to start anew conveying circulation after corresponding time out again.

By the solenoid of piston pump is carried out with the control of variable pulse width modulation, piston is lentamente guided into regulation Hole 24 simultaneously passes therethrough.Thus a small amount of hydraulic fluid is transported to thin film and sucks back from thin film.Thus create antagonism pump back-pressure More straight Flow characteristics curve, that is, system is more uncorrelated to back-pressure.Because this control makes piston slow down, so piston stroke Cycle time than constant unmodulated control long during cylindrical coil.Thus reduce the possible frequency of delivery of maximum. Because result shows in altofrequency, high conveying capacity can form back-pressure in the pressure pipeline of metering system, therefore exists this Probability, reduces corresponding dutycycle in each period when close to the maximum delivery frequency of pump.Thus can reach Big frequency of delivery.The numerical value of the dutycycle, time and the stroke that illustrate is only symbolistic.

The metering precision of membrane pump or piston pump is improved by the specific control through pulse width modulation.This Outward, reduce reducing agent also by the specific control through pulse width modulation during the conveying stroke of membrane pump or piston pump Transporting velocity, and thus be considered to form thinner spraying by double nozzle.

Claims (according to the 19th article of modification of treaty)

1. a kind of reductant metering system (10), for spray reductant in the waste gas stream of internal combustion engine in case selective catalysis also Former, described reductant metering system (10) has delivery pump (20), by described delivery pump by the reduction of reducing agent storage tank (40) Agent suctions out from described storage tank (40) via suction channel (30), is conveyed via pressure pipeline (50), and via at least one Individual nozzle (60) is introduced in the waste gas stream of described internal combustion engine it is characterised in that described suction channel (30) has two-way rubber Valve (70), and described delivery pump (20) is piston pump, particularly magnetic force piston-type pump.

2. metering system (10) according to claim 1 is it is characterised in that described pressure pipeline (50) has choke valve.

3. metering system (10) according to claim 1 and 2 is it is characterised in that described system (10) has part stent (15), described delivery pump (20) is arranged in described part stent, and wherein leads to the suction channel (30 ') of pump intake and connect The pressure channel (50 ') being connected to pump discharge is integrated in described part stent (15), and wherein said part stent (15) has dress Join region (16), valve (70) described in described assembly area fluidly integrated installation in described suction channel (30 ').

4. according to metering system in any one of the preceding claims wherein (10) it is characterised in that described system (10) has Reducing agent storage tank (40), described suction channel (30) is connected to described reducing agent storage tank.

5. according to metering system in any one of the preceding claims wherein (10) it is characterised in that described system has compression Air supply unit, and reducing agent is atomized by compressed air in described nozzle interior or outside, particularly described compression is empty Gas supply unit has reversal valve and/or pressure regulator valve.

6. according to metering system in any one of the preceding claims wherein (10) it is characterised in that described nozzle (60) is outer Portion mixing double nozzle, in described nozzle, reducing agent flows out from least one first opening, and compressed air to Discharge in few second opening, wherein said second opening positions as follows, especially with respect to described first opening Injection direction placement at an angle, that is, by from described second opening discharge described compressed air will be from described first opening The reducing agent atomization flowed out.

7. according to metering system in any one of the preceding claims wherein (10) it is characterised in that described pressure pipeline (50) It is connected to compressed air supply unit via reversal valve or regulating valve, to make described pressure by compressed air after metering terminates Pipeline (50) and described nozzle (60) remove reducing agent.

8. according to metering system in any one of the preceding claims wherein (10) it is characterised in that suction is via access road (26) to realize, discharge to realize via exit passageway (27), and described access road (26) and described exit passageway (27) Covered by thin film (28).

Claims (8)

1. a kind of reductant metering system (10), for spray reductant in the waste gas stream of internal combustion engine in case selective catalysis also Former, described reductant metering system (10) has delivery pump (20), by described delivery pump by the reduction of reducing agent storage tank (40) Agent suctions out from described storage tank (40) via suction channel (30), is conveyed via pressure pipeline (50), and via at least one Individual nozzle (60) is introduced in the waste gas stream of described internal combustion engine it is characterised in that described suction channel (30) has two-way rubber Valve (70).

2. metering system (10) according to claim 1 is it is characterised in that described pressure pipeline (50) has choke valve.

3. metering system (10) according to claim 1 and 2 is it is characterised in that described system (10) has part stent (15), described delivery pump (20) is arranged in described part stent, and wherein leads to the suction channel (30 ') of pump intake and connect The pressure channel (50 ') being connected to pump discharge is integrated in described part stent (15), and wherein said part stent (15) has dress Join region (16), valve (70) described in described assembly area fluidly integrated installation in described suction channel (30 ').

4. according to metering system in any one of the preceding claims wherein (10) it is characterised in that described system (10) has Reducing agent storage tank (40), described suction channel (30) is connected to described reducing agent storage tank.

5. according to metering system in any one of the preceding claims wherein (10) it is characterised in that described system has compression Air supply unit, and reducing agent is atomized by compressed air in described nozzle interior or outside, particularly described compression is empty Gas supply unit has reversal valve and/or pressure regulator valve.

6. according to metering system in any one of the preceding claims wherein (10) it is characterised in that described nozzle (60) is outer Portion mixing double nozzle, in described nozzle, reducing agent flows out from least one first opening, and compressed air to Discharge in few second opening, wherein said second opening positions as follows, especially with respect to described first opening Injection direction placement at an angle, that is, by from described second opening discharge described compressed air will be from described first opening The reducing agent atomization flowed out.

7. according to metering system in any one of the preceding claims wherein (10) it is characterised in that described pressure pipeline (50) It is connected to compressed air supply unit via reversal valve or regulating valve, to make described pressure by compressed air after metering terminates Pipeline (50) and described nozzle (60) remove reducing agent.

8. according to metering system in any one of the preceding claims wherein (10) it is characterised in that described delivery pump (20) is Piston pump, particularly magnetic force piston-type pump.