CN100462534C - Diesel engine - Google Patents
Diesel engine Download PDFInfo
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- CN100462534C CN100462534C CNB200580033450XA CN200580033450A CN100462534C CN 100462534 C CN100462534 C CN 100462534C CN B200580033450X A CNB200580033450X A CN B200580033450XA CN 200580033450 A CN200580033450 A CN 200580033450A CN 100462534 C CN100462534 C CN 100462534C
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Abstract
A diesel engine having a reentrant cavity (11) provided in the top section of a piston (4), a fuel injection means (9) for injecting fuel toward the cavity (11), an exhaust gas recirculation means (19) for recirculating a part of exhaust gas into a combustion chamber, and a control device (26) for controlling fuel injection timing set by the fuel injection means (9) and also controlling an EGR rate or EGR amount set by the exhaust gas recirculation means (19). In a predetermined operation region, the control device (26) controls the timing of fuel injection set by the fuel injection means (9) so that the injection of the fuel is completed before the compression upper dead end of the piston (4) and that the entire injected fuel enters into the cavity (11), and also controls an EGR rate or EGR amount set by the exhaust gas recirculation means (19) so that the fuel injected by the fuel injection means (9) is ignited near the compression upper dead end of the piston (4) after the completion of the fuel injection. The control device (26) thus realizes premix combustion. Favorable premix combustion is realized, and, even if the combustion is switched to diffuse combustion, favorable combustion can be achieved.
Description
Technical field
The present invention relates to a kind of diesel engine of realizing pre-mixing combustion in the operation area of regulation.
Background technique
In the diesel engine of cylinder inner direct fuel, near the burner oil compression top dead center of the piston of the high pressure that in cylinder, reaches a high temperature usually.In this case, the starting point formation flame of fighting in the injection of fuel, and by supplying with follow-up fuel and sustained combustion to this flame.Like this, the combustion manner that begins to light a fire in the injection of fuel is commonly called diffusive combustion, but the problem of generation NOx or cigarette etc. is pointed out in this diffusive combustion.
Therefore in recent years, following scheme is proposed: the combustion manner of realizing being called as pre-mixing combustion, so-called pre-mixing combustion is, make the time for spraying of fuel more Zao than the compression top dead center of piston, and the fuel AEI After End of Injection light premixed gas (with reference to the spy open the 2003-83119 communique, the spy opens the 2002-227650 communique).
In pre-mixing combustion because at the fuel AEI After End of Injection, refire premixed gas through to a certain degree time, therefore before igniting premixed gas by thin homogenization fully.Therefore, local combustion temperature descends and the discharge capacity of NOx reduces, and owing to the burning that can avoid under the lack of air state, therefore also suppresses the generation of cigarette.
But, since in pre-mixing combustion when piston position is low burner oil, therefore in the time will in the common diesel engine that designs for prerequisite with the realization diffusive combustion, realizing pre-mixing combustion, the fuel deposition that the fuel deposition that may make injection is rebounded at the top of the sidewall of cylinder or collision piston causes not firing the generation of HC below cylinder head.
Therefore, following scheme is proposed: as shown in Figure 7, in the diesel engine of realizing pre-mixing combustion, make the cavity C A at the top that is formed on piston P become the style of opening that enlarges towards opening portion (topmost), and the fuel injection angle degree α that makes nozzle I than common little (with reference to the spy open the 2003-83119 communique, the spy opens the 2002-227650 communique).Like this because the fuel F that sprays enters in the cavity C A, be not attached to the sidewall of cylinder CL or cylinder head CH below, the therefore generation that can suppress not fire HC.
But, in the diesel engine of this nozzle I that has used opening cavity C A and shallow angle degree α, have following problem.
1) because cavity C A is opening, therefore the eddy current (swirl) that is difficult to be formed in the cavity C A remains in the cavity C A.Its result, the thin homogenization of the mixing of premixed gas may become insufficient, and causes the reduction of output power and the deterioration of exhaust.
2) because when when the many high load area of fuel injection amount realize pre-mixing combustion, detonation may take place, therefore need convert diffusive combustion in high load area, but because the spray angle α of nozzle I is little, so when near burner oil for the compression top dead center of the piston P that realizes diffusive combustion, the bottom surface of fuel that is sprayed and cavity C A (center side) collision, and produce cigarette.That is to say, used the diesel engine of the nozzle I of opening cavity C A and shallow angle degree α to be designed to pay attention to pre-mixing combustion, and will realize that diffusive combustion is as problem.
Summary of the invention
The purpose of this invention is to provide a kind of diesel engine, can realize good pre-mixing combustion, even and also can guarantee good burning being transformed under the situation of diffusive combustion.
In order to achieve the above object, the diesel engine of technological scheme 1 is, possesses: the cavity of spill (reentrant) is arranged with in piston head, and for eddy current is remained on inside, the opening portion on this cavity top shrinks and is formed with the protuberance of protuberance upward in the bottom center of this cavity; Fuel injection mechanism, to above-mentioned cavity burner oil, and spray angle is set in 140 °～165 ° the scope, so that near the compression top dead center of piston during burner oil, this fuel arrives than the protuberance of the above-mentioned cavity inwall by radial outside; Exhaust gas recirculation mechanism is back to the part of exhaust in the firing chamber; And control gear, control the fuel injection time of above-mentioned fuel injection mechanism and the EGR of above-mentioned exhaust gas recirculation mechanism and lead; Above-mentioned control gear, when the operating condition of motor is in low load area, in the scope of 14 °～30 ° of BTDC, begin the injection of fuel by above-mentioned fuel injection mechanism, make the fuel of this injection and the opening portion on above-mentioned cavity top collide and import in this cavity, and before the compression top dead center of piston, finish the injection of this fuel, on the other hand, lead the exhaust gas recirculation that carries out above-mentioned exhaust gas recirculation mechanism with the EGR more than 50%, by the exhaust of the eddy current in the above-mentioned cavity to this backflow, air inlet and the fuel that imports in the above-mentioned cavity have carried out after the premixing, near the ignition by compression compression top dead center of piston and carry out pre-mixing combustion.
The diesel engine of technological scheme 2 is, when above-mentioned control gear is in middle and high load area in the operating condition of motor, the fuel injection time of above-mentioned fuel injection mechanism is controlled near the compression top dead center of piston, to realize diffusive combustion.
The diesel engine of technological scheme 3 is, technique scheme 1 or 2 described diesel engines also possess exhaust gas post-treatment device and additive remaining amount detection mechanism, and exhaust gas post-treatment device has: be arranged on the catalyzer in the exhaust passageway; The additive agent adding machine structure is used for the upstream side at this catalyzer, and additive is added in the exhaust that above-mentioned exhaust passageway flows through; And additive accommodation structure, be used to deposit the additive of supplying with this additive agent adding machine structure, the additive remaining amount detection mechanism is used to detect the amount of the additive that leaves above-mentioned additive accommodation structure in, above-mentioned control gear is that the 1st specified value is when following at the checkout value of above-mentioned additive remaining amount detection mechanism, even the operating condition of motor is in middle and high load area, also realize above-mentioned pre-mixing combustion.
The diesel engine of technological scheme 4 is, above-mentioned control gear is that the 1st specified value is when following at the checkout value of above-mentioned additive remaining amount detection mechanism, will be according to the torque that requires of engine speed and accelerator open degree decision, the maximum that is limited in above-mentioned low load area requires below the torque.
The diesel engine of technological scheme 5 is, above-mentioned control gear is that the 1st specified value is when following at the checkout value of above-mentioned additive remaining amount detection mechanism, to be limited in below the maximum fuel emitted dose of above-mentioned low load area according to the fuel injection amount of engine speed and accelerator open degree decision.
The diesel engine of technological scheme 6 is, also possessing can be by the alert mechanism of above-mentioned control gear action, when the checkout value of above-mentioned additive remaining amount detection mechanism becomes the 2nd specified value that is set to the value more than above-mentioned the 1st specified value when following, above-mentioned control gear makes above-mentioned alert mechanism action.
The diesel engine of technological scheme 7 is, the catalyzer of above-mentioned exhaust gas post-treatment device is for selecting the contact reducing catalyst, and above-mentioned additive is ammonia spirit, aqueous solution of urea or liquid ammonia.
According to the present invention, can realize good pre-mixing combustion, even and being converted under the situation of diffusive combustion, also can guarantee good burning.
Description of drawings
Fig. 1 is the skeleton diagram of the diesel engine of an embodiment of the invention.
Fig. 2 is the IGNITION CONTROL plotted curve (MAP figure) of the conversion line of decision mixed combustion and diffusive combustion.
Fig. 3 a is the figure of expression from nozzle ejection fuel position of piston before.
Fig. 3 b has passed through the figure of stipulated time from Fig. 3 (a), is the figure of expression from the relation of the fuel of nozzle ejection and piston.
Fig. 3 c has passed through the figure of stipulated time from Fig. 3 (b), is the figure of expression from the relation of the fuel of nozzle ejection and piston.
Fig. 4 is used to determine the injection beginning time of fuel and the MAP figure of emitted dose.
Fig. 5 is in the diesel engine and opening motor of expression an embodiment of the invention, the plotted curve of the measurement result of mean effective pressure Pmi, THC discharge capacity, cigarette discharge capacity.
Fig. 6 is illustrated in the diesel engine of an embodiment of the invention the fuel injection beginning time is carried out three kinds of settings, and chien shih EGR leads the plotted curve of measurement result when changing, THC discharge capacity, NOx discharge capacity, cigarette discharge capacity, clean mean effective pressure BMEP between about 40～60% when each injection beginning.
Fig. 7 is the figure of the summary of the opening motor of expression.
Fig. 8 is the control flow chart that ECU (control gear) carries out.
Fig. 9 a according in the normal state, engine speed and accelerator open degree determined to require the skeleton diagram of the MAP figure of torque.
Fig. 9 b be according under the state after the step S5 by Fig. 8 has changed the full load characteristic, engine speed and accelerator open degree determined to require the skeleton diagram of the MAP figure of torque.
Embodiment
Below, describe preferred implementation of the present invention with reference to the accompanying drawings in detail.
Fig. 1 is the skeleton diagram of the diesel engine (below, only be called motor) of present embodiment.In addition, only representing a cylinder in Fig. 1, can certainly be a plurality of cylinders.
Among the figure, 1 is engine main body, and it is by cylinder 2, cylinder head 3, piston 4, suction port 5, relief opening 6, suction valve 7, outlet valve 8, nozzle 9 formations such as (fuel injection mechanism).In the space that surrounds by cylinder 2, cylinder head 3 and piston 4, form firing chamber 10.Be concaved with cavity 11 at the top of piston 4, from the nozzles 9 that are provided with in 10 towards the firing chamber to cavity 11 direct fuel injections.
The cavity 11 of the motor of present embodiment and nozzle 9 with to realize the identical of common diesel engine that diffusive combustion designs for prerequisite.
Be specifically described, the cavity 11 of present embodiment is the cavity of the spill shown in Fig. 3 a, axial area the best part perpendicular to piston 4, be positioned at upper end portion than piston 4 part of the axial area minimum of piston 4 (in the present embodiment perpendicular to) by downside, and be formed with the protuberance 11a of protuberance upward in its bottom center.Nozzle 9 and roughly configuration coaxially of cylinder 2, and from a plurality of spray orifices with spray angle β (with reference to Fig. 3 (c)) burner oil.The spray angle β of nozzle 9 equates with the spray angle of common (realization diffusive combustion) motor, is set in the present embodiment in 140 °～165 ° the scope.
Return Fig. 1, nozzle 9 rail 24 together connects, and the fuel under high pressure that is stored in this common rail 24 is by supply nozzle 9 often.Undertaken by high voltage supply pump 25 to the fuel pressurized delivered that is total to rail 24.Suction port 5 is connected with outlet pipe 13 with suction tude 12 respectively with relief opening 6.
The motor of present embodiment also possesses EGR device 19 (exhaust gas recirculation mechanism), and the part of the exhaust in the outlet pipe 13 is back in the firing chamber 10.
In suction tude 12, be provided with intake-air throttle valve 23, be used for the more upstream side of the joint of EGR pipe 20, suitably throttling sucks air.Also can be by this intake-air throttle valve 23 of switch, the amount of the suction air (new gas) to air inlet in all or ratio are regulated EGR with regulating and are led.That is, become big, can increase suction air quantity (ratio) by the valve opening that makes intake-air throttle valve 23, and the EGR that makes air inlet leads and the EGR amount reduces, on the contrary, diminish, can reduce the suction air quantity and the EGR of air inlet is led and the increase of EGR amount by the valve opening that makes intake-air throttle valve 23.
Be provided for this motor is carried out electronically controlled electronic control unit (hereinafter referred to as ECU) 26.ECU26 (control gear) reads the operating condition of motor from various sensor classes, and according to these engine operating status control nozzle 9, EGR valve 21 and intake-air throttle valve 23 etc.As the sensor class, comprising: the accelerator open degree sensor 14 that is used to detect accelerator open degree; Be used for the bent axle (not shown) of detection of engine phase place, be the CKP 16 of crank angle; Be used to detect the common rail pressure sensor 17 of the fuel pressure in the common rail 24 etc., ECU26 is according to the actual accelerator open degree of this each signal of sensor decision, crank angle, rail pressure etc. altogether.In addition, ECU26 is according to the load (requiring torque) of accelerator open degree value decision motor, and calculates with respect to the increase ratio of the crank angle of time and determine the rotational speed N E of motor.
In addition, also carrying out altogether, rail pressure is the feedback control of jet pressure.Promptly, ECU26 is according to parameter, especially the engine speed NE of the expression engine operating status that is detected by the sensor class and require torque (engine loading), decision is the desired value of rail pressure altogether, and the aperture ground of controlling not shown amount adjusting valve is controlled from high voltage supply pump 25 to the fuel feed that is total to rail 24, so that make actual common rail pressure near this desired value.
The motor of present embodiment is realized as the illustrated pre-mixing combustion of " background technique " part in the operation range of regulation.Be specifically described, as shown in Figure 2, operating condition according to the motor that is determined by engine speed NE and fuel injection amount Q, the conversion line A that will be used to change pre-mixing combustion and diffusive combustion imports ECU26 in advance, the ECU26 basis is by the operating condition (engine speed NE and fuel injection amount Q) of the motor of the checkout value decision of the sensor class, control nozzle 9, EGR valve 21, intake-air throttle valve 23 are so that any one combustion manner in realization pre-mixing combustion and the diffusive combustion.As mentioned above, because fuel injection amount Q is torque as requested decision, operating condition that therefore also we can say motor is according to engine speed NE and require the torque decision.According to Fig. 2 as can be known, in the motor of present embodiment, realize pre-mixing combustion at the low load area of fuel injection amount Q less (require torque less), and in fuel injection amount Q more (require torque bigger)/high load area realizes diffusive combustion.
So the motor of present embodiment uses the cavity 11 of spill and the nozzle 9 with common spray angle β to realize pre-mixing combustions.Below, the implementation method of pre-mixing combustion of the motor of present embodiment is described.
In the operation range that realizes pre-mixing combustion, ECU26 is controlled to the following injection beginning time with the injection beginning time of the fuel of nozzle 9: finished the injection of fuel before piston 4 arrives compression top dead center, and the fuel that is sprayed enters all in the cavity 11.Such injection beginning time for example is upper dead center 5～35 ° scope before.That is,, have advance angle, all enter scope in the cavity 11 but this advance angle scope is limited in the fuel that is sprayed than the compression upper dead center for the discharge time of the fuel of realizing pre-mixing combustion.
Here, utilize Fig. 3 to specify fuel and all enter injection beginning time in the cavity 11.
The state of (when the energising of nozzle 9 is begun) during the injection beginning of Fig. 3 (a) expression fuel, this moment piston 4 be positioned at compression top dead center below, fuel is from nozzle 9 injections.Afterwards, shown in Fig. 3 (b), follow the passing piston 4 of time to rise, fuel F begins to disperse to radial outside from nozzle 9.But fuel F does not arrive the cavity 11 of piston 4 in this moment.And, shown in Fig. 3 c, behind the injection beginning of fuel, when having passed through the stipulated time, the side wall upper part of fuel F collision cavity 11.At this moment, then such as shown if the position of collision of fuel F is correct, whole fuel F of injection flow into cavity 11 inboards.Like this, all fuel F is fed into the discharge time of cavity 11 inboards, is the discharge time that sets in the present embodiment.On the contrary, a part of having collided the fuel of cavity 11 rebounds upward and attached to the following discharge time of cylinder head 3, does not set in the present embodiment.In addition, in the moment that the injection of fuel is all over, piston 4 is positioned at the below of compression top dead center.
Because the suitable position of collision of fuel F is by the shape of cavity 11 and the decisions such as spray angle β of nozzle 9, therefore according to this suitable position of collision and piston stroke etc., in advance the operating condition of each motor is obtained the suitable injection beginning time, and store among the ECU26 as MAP figure in advance.
Fig. 4 is that concrete expression is used to determine the injection beginning time of fuel and the MAP figure of emitted dose.Transverse axis is engine speed (rpm), and the longitudinal axis is fuel injection amount (mm
3/ st), than the zone of the conversion line more close low load side of A (downside) for the realization pre-mixing combustion.And, in practicality, because fuel injection amount can not be 0 during except fuel shutoff etc., so use the fuel injection amount suitable (5mm in the present embodiment with idle running
3/ st) above zone.According to figure as can be known, in realizing the zone of pre-mixing combustion, the combustion jet time set in 5 °～35 ° the scope, along with engine speed and fuel injection amount (being equivalent to engine loading) increase, had tendency in advance before upper dead center.And under the stable situation of engine speed, load increases discharge time more and shifts to an earlier date more.This is need increase the premixing time because of the increase along with emitted dose.On the other hand, under the stable situation of fuel injection amount, the high more discharge time of rotating speed shifts to an earlier date more.This is also to increase because of the increase velocity of piston along with rotating speed, need earlier begin to spray in order to ensure the premixing time.
But, in the motor of the present embodiment of the nozzle 9 that has used general spray angle β (in 140 °～165 ° the scope), the scope that the injection beginning time of fuel can shift to an earlier date, little than the motor that has reduced spray angle (with reference to Fig. 7) certainly becomes.Therefore, in the motor of present embodiment, carry out fuel under the state of pressure and the temperature in fuel chambers 10 higher (motor that reduces with spray angle compares) and spray.Thus, premixed gas was lighted a fire before the compression top dead center of piston, may not make the thin fully homogenization of premixed gas.
Therefore, the motor of present embodiment is carried out the EGR of volume that compares with EGR device 19, thereby is avoided this problem when realizing pre-mixing combustion.
Promptly, in realizing the operation range of pre-mixing combustion, ECU26 leads the EGR of the premixed gas of EGR device 19 decisions or the EGR amount is controlled to that following EGR leads or the EGR amount: the fuel that is sprayed by nozzle 9 is at the fuel AEI After End of Injection, light a fire near the compression top dead center of piston 4.That is to say, reduce, guarantee the premixing time fully, and realize the accuracy of firing time by the air concentration that makes premixed gas by EGR.In the present embodiment, MAP figure to the suitable valve opening of the EGR valve 21 of each engine operating status decision and intake-air throttle valve 23, imported ECU26 in advance, ECU26 is according to this MAP figure control EGR valve 21 and intake-air throttle valve 23, and the EGR of control premixed gas leads or the EGR amount.In the present embodiment, in the operation range that realizes pre-mixing combustion, setting the valve opening MAP figure of EGR valve 21 and intake-air throttle valve 23, is more than 50% so that the EGR of premixed gas is led.
Like this, by carrying out the EGR of more amount by EGR device 19 and the oxygen concentration of premixed gas being reduced, can guarantee the premixing time fully and promote the thin homogenization of premixed gas.Therefore, in the motor of the present embodiment that extremely shifts to an earlier date in the injection beginning time that can not make fuel, pre-mixing combustion is realized well.And, owing to regulate that EGR leads or EGR amount ground is controlled near reasonable time (compression top dead center of piston) with firing time of premixed gas, so specific fuel consumption and also raising of output.And, make the oxygen concentration reduction of premixed gas by the EGR ground of carrying out volume, can reduce the NOx in the exhaust.
Fig. 5 be illustrated in the motor of present embodiment and used opening cavity C A shown in Figure 7 and the motor of the nozzle I of shallow angle degree α (below, be called opening motor) in, an example of the measurement result of mean effective pressure Pmi, THC (total hydrocarbons) discharge capacity, cigarette discharge capacity.
The transverse axis of figure is the injection beginning time (ATDC) of fuel, and the line of connecting part's form point represents that the motor of present embodiment, the line that connects the triangle form point represent the measurement result of opening motor among the figure.In addition, the line of connection Diamond spot is represented the measurement result of the common diesel engine that carries out diffusive combustion as a reference.
According to figure as can be known, the motor of present embodiment is that mean effective pressure Pmi (being equivalent to motor output) surpasses opening motor in all injection beginning times.
And,, identical with opening motor or below it in all injection beginning times about THC and cigarette discharge capacity.The point that should particularly point out is, the motor of present embodiment long injection beginning in the time cigarette discharge capacity little.This just means the degrees of freedom height of the setting of injection beginning time.That is to say, in opening motor, since the scope of little injection beginning time of cigarette discharge capacity little (in this embodiment approximately-26 °～approximately-18ATDC), therefore the setting possible range of injection beginning time is just little, but in the motor of present embodiment, because the scope of the injection beginning time that the cigarette discharge capacity is little big (about-30 ° in this embodiment～about-14 ° of ATDC) therefore can freely be set the injection beginning time on a large scale at this.
Like this, the motor of present embodiment is compared with opening motor, exports and all good reason of exhaust, can be speculated as the effect of the cavity 11 of spill.That is to say, in the cavity 11 of spill,, therefore cause the raising of exporting in cavity 11 owing to burning almost all can be carried out.And,, therefore can make the mixing of premixed gas realize thin more fully homogenization because the cavity 11 of spill can remain on the eddy current that forms in the cavity 11 energetically in cavity 11.This causes the improvement of exhaust.And as the formation of the high squish of other advantage of re-entrant cavity 11, also the improvement to exhaust has contribution.
Fig. 6 is illustrated in the motor of present embodiment the fuel injection beginning time is carried out three kinds of settings, and when each injection beginning chien shih EGR lead when between about 40～60%, changing, THC discharge capacity, NOx discharge capacity, cigarette discharge capacity, clean mean effective pressure BMEP (with motor output quite) an example of measurement result.
The transverse axis of figure is represented the air fuel ratio (A/F) of premixed gas, and the EGR of premixed gas leads that high air-fuel ratio is low more more, and it is high more that EGR leads low more air fuel ratio.The line that connects circular point among the figure is that injection beginning time 20 ° of BTDC, the line that connects the triangle form point are that injection beginning time 30 ° of BTDC, the line that connects Diamond spot are injection beginning time 40 ° of BTDC.In addition, the line of connecting part's form point is represented the measurement result of common diesel engine as a reference, that carry out diffusive combustion.
According to figure as can be known, the THC discharge capacity about equally, and is significantly to increase under the situation of 40 ° of BTDC in the injection beginning time only under the situation of injection beginning time 20 ° of BTDC and 30 ° of BTDC.And, for clean mean effective pressure BMEP, also be under the situation of injection beginning time 20 ° of BTDC and 30 ° of BTDC about equally, and be significantly to reduce under the situation of 40 ° of BTDC only in the injection beginning time.
Like this, the injection beginning time is that the situation of 40 ° of BTDC is that 20 ° of BTDC compare with the situation of 30 ° of BTDC with the injection beginning time, and THC discharge capacity, output all worsen, and its reason is that the part of the fuel of injection is dispersed to the reason in the outside from cavity 11.
That is to say, in the injection beginning time is under the situation of 20 ° of BTDC and 30 ° of BTDC, because the fuel that is sprayed all enters in the cavity 11, therefore THC discharge capacity, output are all good, both do not have big difference, but are under the situation of 40 ° of BTDC in the injection beginning time, and the injection beginning time too early, the part of fuel disperses outside cavity 11, and following etc. attached to cylinder head 3, thereby cause the discharge of THC.And, because therefore the fuel that disperses outside cavity 11 can not cause the reduction of exporting in cavity 11 internal combustion.
Then, in Fig. 6, be conceived to that EGR leads and exhaust and output between concern the time, as can be known at all injection beginnings in the time, it is low more that EGR leads high more NOx discharge capacity.Its reason is to have reduced the oxygen concentration of premixed gas by a large amount of EGR.According to figure as can be known, be under the situation of 20 ° of BTDC and 30 ° of BTDC in the injection beginning time of fuel, be about more than 50% if EGR is led, then the NOx discharge capacity can be reduced to almost 0 level.In addition, for THC discharge capacity, cigarette discharge capacity and clean mean effective pressure BMEP, can not find the clear and definite dependency relation that leads with EGR.
According to the measurement result of Fig. 6 as can be known, according to making fuel all enter the motor that cavity 11 ground are set the injection beginning time and carried out the present embodiment of a large amount of EGR (EGR leads more than 50%), can obtain good discharge characteristic and output.
As mentioned above, the motor of present embodiment, in middle high load area, realize diffusive combustion, but the motor of present embodiment uses the common nozzle 9 of big (about 140 °～165 °) of the cavity 11 of the spill be suitable for diffusive combustion and spray angle β, therefore also can guarantee good burning when realizing diffusive combustion.That is to say, when in order to realize that diffusive combustion during burner oil, because the fuel that is sprayed collides the sidewall of cavity 11 in the same manner with common diesel engine, so can not produce cigarette etc. in a large number near compression top dead center.In addition, by the cavity 11 of spill,, therefore can obtain good discharge characteristic in cavity 11 owing to the eddy current that forms can be remained in the cavity 11.
Therefore,, can realize good pre-mixing combustion at low load area, and be transformed in middle high load area under the situation of diffusive combustion, also can guarantee good burning according to the motor of present embodiment.
Here, in order positively to realize good diffusive combustion, be preferably as follows the fuel injection angle degree β that sets nozzle 9.That is, this angle is, makes near the fuel in order to realize that diffusive combustion sprays the compression top dead center of piston 4, arrives than the extreme lower position B (with reference to Fig. 3 (a)) of cavity 11 more by the cavity inner wall of radial outside.Therefore,, then can guarantee good diffusive combustion, and when realizing pre-mixing combustion, shifted to an earlier date the combustion jet elapsed time significantly if the spray angle β of nozzle 9 is diminished.
In addition, in the diesel engine of present embodiment,, preferably use high-eddy type cylinder head 3 or suction port 5 in order further to promote the mixing of premixed gas.For example also can vortex generator be set at suction port 5.
In addition, in the above-described embodiment as the EGR device, illustrated that a part with the exhaust in the outlet pipe 13 is back to the outside EGR device in the suction tude 12, but the invention is not restricted to this, also can use by open and close controlling outlet valve 8 or suction valve 7 make exhaust gas recirculation to the firing chamber internal EGR device in 10.
But because the motor of present embodiment is realized diffusive combustion during high load area in the operating condition of motor is in, so some NOx are discharged in the exhaust when middle high load area is travelled (running).
Therefore, as shown in Figure 1, in the motor of present embodiment, be provided with and be used for reducing the exhaust gas post-treatment device 40 of the NOx that purifying exhaust gas contains.
Exhaust gas post-treatment device 40 possesses: be arranged on the catalyzer 41 in the outlet pipe 13 (exhaust passageway); Additive agent adding machine structure 42 (additive nozzle) at the upstream side of this catalyzer 41, is used for adding additive to flow through exhaust in outlet pipe 13; Be used to deposit and supply with the additive accommodating mechanism 43 (additive tank) of this additive, in additive tank 43, be provided with additive remaining amount detection mechanism 44, be used to detect the amount that leaves the additive in the case 43 in nozzle 42.
The catalyzer 41 of the exhaust gas post-treatment device 40 of present embodiment uses ammonia spirit, aqueous solution of urea or liquid ammonia etc. for selecting contact reducing catalyst (SCR catalyzer) as additive.Can use following catalyzer as SCR catalyzer 41: will form granular or cellular alumina (aluminium oxide: Al
2O
3), titanium white (titanium dioxide: TiO
2) wait as carrier, and with platinum (Pt), vanadium oxide (V
2O
5), iron oxide (Fe
2O
3), cupric oxide (CuO), manganese oxide (Mn
2O
3), chromium oxide (Cr
2O
3), molybdenum oxide (MoO
3) wait as active body.
Can use various mechanisms as additive remaining amount detection mechanism 44, use the float type level instrument here.
When the operating condition of motor is in middle high load area and realizes diffusive combustion, when the additive by exhaust gas post-treatment device 40 sprays (interpolation) ammonia (NH with nozzle 42 in exhaust
3) time, by SCR catalyzer 41 ammonia (NH
3) with exhaust in NOx reaction, and it is reduced into harmless nitrogen (N
2) and water (H
2O).In addition, as mentioned above,, therefore when the operating condition of motor is in the zone (low load area) of realizing pre-mixing combustion, there is no need to make exhaust gas post-treatment device 40 actions because the NOx discharge capacity is almost 0 in pre-mixing combustion.
But, in the exhaust gas post-treatment device 40 that utilizes additive, when the additive in the additive tank 43 is used up, just can not obtain the purifying effect of exhaust certainly.Therefore, in the diesel engine of present embodiment, study, so that the additive in additive tank 43 is few or when using up fully, with its driver and urge replenishing of additive.
Be specifically described, in the diesel engine of present embodiment, the quantitative change of the additive in the additive tank 43 that is detected by additive remaining amount detection mechanism 44 is specified value when following, and the alert mechanism 45 (with reference to Fig. 1) that is arranged on driver's seat etc. is moved driver.In addition, mechanism 45 uses lamps by way of caution in the present embodiment, but also can use other mechanism such as buzzer, also can a plurality of mechanisms and use.
And, in the diesel engine of present embodiment, the quantitative change of the additive in the additive tank 43 that is detected by additive remaining amount detection mechanism 44 is specified value when following, even the operating condition of motor is in beyond the zone of above-mentioned realization pre-mixing combustion, also realizes pre-mixing combustion.Be specifically described, the quantitative change of the additive in additive tank 43 is that specified value is when following, will be according to the CLV ceiling limit value that requires torque and fuel injection amount of decisions such as engine speed and accelerator open degree, the maximum that is limited in the zone of realizing pre-mixing combustion requires torque and below the maximum fuel emitted dose, can irrespectively realize pre-mixing combustion with accelerator open degree thus.
Like this, owing to tail off or realize pre-mixing combustion when using up by residual volume at additive, can make the discharge capacity of NOx be almost 0 level, even, also in atmosphere, do not discharge NOx therefore because the additive deficiency can not get the purifying effect of exhaust gas post-treatment device 40.In addition, because therefore requirement for restriction torque and fuel injection amount can not turn round by driver's intention and travel, and can urge driver's supplemented by additives as early as possible.And, because the running of shutting engine down fully, but so can arrive the position of supplemented by additives voluntarily.
Because the control of above explanation is carried out by ECU26, therefore use the object lesson of the content of the control that the flowchart text ECU26 of Fig. 8 carries out.This control flow is carried out in each stipulated time by ECU26.
At first, in step S1, read residual volume (level) L of the additive in the additive tank 43 that detects by additive remaining amount detection mechanism 44.
Secondly, in step S2, judge whether the residual volume L of the additive that reads at step S1 is bigger than the specified value of importing ECU26 in advance (owing to the 2nd specified value that is equivalent in claims, so hereinafter referred to as the 2nd specified value).
(YES judgement) returns step S1 when the residual volume L that is judged as additive is bigger than the 2nd specified value, carries out the reading of residual volume L of additive once more.
In step S2, be the 2nd specified value when following (NO judgement) at the residual volume L that is judged as additive, advance to step S3, make alert mechanism action (lighting lamp 45 in the present embodiment).Thus, can notify additive to tail off or use up to the driver.
Then, advance to step S4, judge whether the residual volume L of the additive that reads at step S1 is bigger than the specified value of importing ECU26 in advance (owing to the 1st specified value that is equivalent in claims, so hereinafter referred to as the 1st specified value).It is identical or than its little value that the 1st specified value is configured to the 2nd specified value with step S2.
(YES judgement) returns step S1 when the residual volume L that is judged as additive is bigger than the 1st specified value, carries out the reading of residual volume L of additive once more.
On the other hand, in step S4, be the 1st specified value when following (NO judgement) at the residual volume L that is judged as additive, advance to step S5, the full load characteristic of change motor.In addition, be configured in step S4, must judge into NO when identical at the 1st specified value with the 2nd specified value.
Here, with reference to Fig. 9 the change of the full load characteristic carried out at step S5 is described.
Fig. 9 represents to formulate the MAP figure that requires torque (motor output) according to engine speed and accelerator open degree, and Fig. 9 (a) represents the state when common, and Fig. 9 (b) is illustrated in by step S5 and has changed state after the full load characteristic.
At first, describe, the operating condition decision of motor is 1 point on the MAP figure by engine speed and accelerator open degree with reference to the MAP figure of Fig. 9 (a) when common.Then, from MAP figure, determine to require torque according to its operating condition.As mentioned above, require torque to determine fuel injection amount, and in pre-mixing combustion and the diffusive combustion which decision realize according to this.According to figure as can be known, accelerator open degree is big more to require torque to be set greatly more.In addition, realizing that the zone of pre-mixing combustion is set at the zone that requires torque lower, is the zone of realizing diffusive combustion in the zone of this zone upside.
In Fig. 9 (a), when representing accelerator open degree maximum (100%), the line that is positioned at the top side requires torque, and be the full load characteristic.Dotting the example that the speed of a motor vehicle changes in the drawings, is that 100% o'clock speed of a motor vehicle reaches the most at a high speed at accelerator open degree.
Below, the state that has changed after the full load characteristic is described with reference to Fig. 9 (b).
In the step S4 of Fig. 8, be the 1st specified value when following being judged as additive residual volume L, ECU26 is altered to the full load characteristic of motor as Fig. 9 (b) from Fig. 9 (a).
That is, according to figure as can be known, make full load characteristic (accelerator open degree is 100% o'clock the characteristic that requires torque) consistent with the maximum value in pre-mixing combustion zone.Thus, the torque that requires according to accelerator open degree and engine speed decision is restricted to the value in the pre-mixing combustion zone.Be specifically described, under the situation of 1 point (operating condition) in the pre-mixing combustion zone according to engine speed and accelerator open degree decision, by determining the requirement torque usually like that, but under the extra-regional situation of pre-mixing combustion, the torque that requires that is determined is that maximum engine speed, the pre-mixing combustion zone requires torque at this moment at above-mentioned 1 point (operating condition).Therefore, even the driver is operating as any aperture of 0～100% with accelerator open degree, require an also value that is decided to be in the pre-mixing combustion zone of torque according to the decision of engine speed and accelerator open degree.And, requiring below the torque by requiring the maximum of torque limit in the pre-mixing combustion zone, the fuel injection amount of torque decision also is limited in below the maximum fuel emitted dose in pre-mixing combustion zone as requested.
So, in the diesel engine of above-mentioned present embodiment, the residual volume of the additive in additive tank 43 becomes the 1st specified value when following, irrespectively realizes pre-mixing combustion with accelerator open degree, requires the CLV ceiling limit value of torque and fuel injection amount to be restricted to low (little) when common.Thus because the NOx discharge capacity is almost 0, even therefore because of the additive deficiency, can not get the exhaust gas purification effect of exhaust gas post-treatment device 40, in atmosphere, do not discharge NOx yet.In addition, because limiting engine output, so can not travel according to driver's intention, and can urge replenishing as early as possible of additive.That is to say, shown in Fig. 9 (b), because comparing when common the most at a high speed of vehicle is limited extremely lowly, so driver's supplemented by additives of having to.
In addition, in the above-described embodiment, as the exhaust gas post-treatment device 40 that utilizes Active agent the SCR catalyzer being described, but having the invention is not restricted to this, so long as utilize by the exhaust gas post-treatment device of the Active agent of supplying with to exhaust independently, also can be other type.For example, also can use oxidation of NOx catalyzer that utilizes carbon hydride (HC) or the DPF that has catalyzer that utilizes carbon hydride (diesel oil particulate fluidization filter cleaner) etc. as the Active agent that adds to exhaust.
In addition, in the above-described embodiment, become the 1st specified value when following at the residual volume of additive, only change the full load characteristic, promptly require the CLV ceiling limit value of torque, but the invention is not restricted to this, also can with the MAP figure shown in Fig. 9 (a) require torque characteristics integral body with the requirement ratio compresses, and to make the torque that requires according to the decision of engine speed and accelerator open degree be that the maximum that realizes the zone of pre-mixing combustion requires below the torque.
In addition, in the above-described embodiment, the example of carrying out according to the control of torque has been described, require torque and require torque decision fuel injection amount according to being controlled to be of torque according to this according to engine speed and accelerator open degree decision, but the invention is not restricted to this, also go for carrying out type, directly determine fuel injection amount according to being controlled to be of emitted dose according to engine speed and accelerator open degree according to the control of emitted dose.In this case, become the 1st specified value when following, also the CLV ceiling limit value according to the fuel injection amount of engine speed and accelerator open degree decision can be limited in below the maximum fuel emitted dose in the zone of realizing pre-mixing combustion at the residual volume of additive.
Claims (7)
1. diesel engine is characterized in that possessing:
The cavity of spill is arranged with in piston head, and for eddy current is remained on inside, and the opening portion on this cavity top shrinks and is formed with the protuberance of protuberance upward in the bottom center of this cavity;
Fuel injection mechanism, to above-mentioned cavity burner oil, and spray angle is set in 140 °～165 ° the scope, so that near the compression top dead center of piston during burner oil, this fuel arrives than the protuberance of the above-mentioned cavity inwall by radial outside;
Exhaust gas recirculation mechanism is back to the part of exhaust in the firing chamber; And
Control gear is controlled the fuel injection time of above-mentioned fuel injection mechanism and the EGR of above-mentioned exhaust gas recirculation mechanism and is led;
Above-mentioned control gear, when the operating condition of motor is in low load area,
In the scope of 14 °～30 ° of BTDC, begin the injection of fuel by above-mentioned fuel injection mechanism, make the fuel of this injection and the opening portion on above-mentioned cavity top collide and import in this cavity, and before the compression top dead center of piston, finish the injection of this fuel,
On the other hand, lead the exhaust gas recirculation that carries out above-mentioned exhaust gas recirculation mechanism with the EGR more than 50%, by the eddy current in the above-mentioned cavity to exhaust, the air inlet of this backflow and import fuel in the above-mentioned cavity and carried out after the premixing, near the ignition by compression compression top dead center of piston and carry out pre-mixing combustion.
2. diesel engine as claimed in claim 1 is characterized in that,
When above-mentioned control gear is in middle and high load area in the operating condition of motor, the fuel injection time of above-mentioned fuel injection mechanism is controlled near the compression top dead center of piston, to realize diffusive combustion.
3. diesel engine as claimed in claim 1 or 2 is characterized in that also possessing:
Exhaust gas post-treatment device has: be arranged on the catalyzer in the exhaust passageway; The additive agent adding machine structure is used for the upstream side at this catalyzer, additive is added in the exhaust of flowing through in above-mentioned exhaust passageway; And the additive accommodation structure, be used to deposit the additive of supplying with to this additive agent adding machine structure; With
The additive remaining amount detection mechanism is used for detecting the amount of the additive that leaves above-mentioned additive accommodation structure in,
Above-mentioned control gear is the 1st specified value when following at the checkout value of above-mentioned additive remaining amount detection mechanism, even the operating condition of motor is in above-mentioned middle and high load area, also realizes above-mentioned pre-mixing combustion.
4. diesel engine as claimed in claim 3 is characterized in that,
Above-mentioned control gear is the 1st specified value when following at the checkout value of above-mentioned additive remaining amount detection mechanism, will be according to the torque that requires of engine speed and accelerator open degree decision, and the maximum that is limited in above-mentioned low load area requires below the torque.
5. diesel engine as claimed in claim 3 is characterized in that,
Above-mentioned control gear is the 1st specified value when following at the checkout value of above-mentioned additive remaining amount detection mechanism, will be limited in below the maximum fuel emitted dose of above-mentioned low load area according to the fuel injection amount of engine speed and accelerator open degree decision.
6. diesel engine as claimed in claim 5 is characterized in that,
Also possessing can be by the alert mechanism of above-mentioned control gear action,
When the checkout value of above-mentioned additive remaining amount detection mechanism becomes the 2nd specified value when following, above-mentioned control gear makes above-mentioned alert mechanism action, and the 2nd specified value is set to the above value of above-mentioned the 1st specified value.
7. diesel engine as claimed in claim 6 is characterized in that,
The catalyzer of above-mentioned exhaust gas post-treatment device is for selecting the contact reducing catalyst, and above-mentioned additive is ammonia spirit, aqueous solution of urea or liquid ammonia.
Applications Claiming Priority (3)
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| JP2004290332 | 2004-10-01 | ||
| JP290332/2004 | 2004-10-01 | ||
| JP334582/2004 | 2004-11-18 |
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| JP5332645B2 (en) | 2008-03-03 | 2013-11-06 | 日産自動車株式会社 | In-cylinder direct injection internal combustion engine |
| JP5839801B2 (en) | 2011-01-11 | 2016-01-06 | 日立造船株式会社 | 2-stroke engine and 4-stroke engine |
| EP3743616B1 (en) * | 2018-01-23 | 2022-03-16 | Wärtsilä Finland Oy | Fuel injection arrangement and method of operating piston engine |
| JP2020007977A (en) * | 2018-07-09 | 2020-01-16 | トヨタ自動車株式会社 | Compression self-ignition internal combustion engine |
| CN110145417B (en) * | 2019-06-28 | 2023-12-15 | 潍柴动力股份有限公司 | Pressurizing device for improving EGR rate |
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| JP2002349267A (en) * | 2001-05-28 | 2002-12-04 | Isuzu Motors Ltd | Combustion system of diesel engine |
| JP2002371831A (en) * | 2001-06-13 | 2002-12-26 | Nissan Diesel Motor Co Ltd | Exhaust emission control device of automobile |
| US20030047159A1 (en) * | 2001-09-07 | 2003-03-13 | Naoki Shimazaki | Direct injection diesel engine |
| JP2003083070A (en) * | 2001-09-10 | 2003-03-19 | Mazda Motor Corp | Fuel combustion device for diesel engine |
| CN1521394A (en) * | 2003-02-07 | 2004-08-18 | �����Զ�����ʽ���� | Combustion control device for an engine |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002349267A (en) * | 2001-05-28 | 2002-12-04 | Isuzu Motors Ltd | Combustion system of diesel engine |
| JP2002371831A (en) * | 2001-06-13 | 2002-12-26 | Nissan Diesel Motor Co Ltd | Exhaust emission control device of automobile |
| US20030047159A1 (en) * | 2001-09-07 | 2003-03-13 | Naoki Shimazaki | Direct injection diesel engine |
| JP2003083070A (en) * | 2001-09-10 | 2003-03-19 | Mazda Motor Corp | Fuel combustion device for diesel engine |
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