CN104884756A - 内燃机的排气净化装置 - Google Patents

内燃机的排气净化装置 Download PDF

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CN104884756A
CN104884756A CN201380067870.4A CN201380067870A CN104884756A CN 104884756 A CN104884756 A CN 104884756A CN 201380067870 A CN201380067870 A CN 201380067870A CN 104884756 A CN104884756 A CN 104884756A
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fuel
temperature range
temperature
addition valve
injection amount
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CN104884756B (zh
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岩谷一树
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Abstract

本发明涉及一种内燃机的排气净化装置,其目的在于,抑制在实施对还原剂添加阀的堵塞进行抑制的添加时的、NOX净化率的下降。在内燃机的排气通道上依次设置有燃料添加阀、具有氧化能力的催化剂、选择还原型NOX催化剂,并在从燃料添加阀喷射燃料的预定的条件成立了的情况下,在选择还原型NOX催化剂的温度在预定的温度范围内时,与在预定的温度范围外时相比而减少从燃料添加阀喷射的燃料量。

Description

内燃机的排气净化装置
技术领域
本发明涉及内燃机的排气净化装置。
背景技术
有时在内燃机的排气通道上设置用于添加还原剂的还原剂添加阀。在该还原剂添加阀上,附着有排气中的粒状物质。而且,在还原剂添加阀的温度较高的情况下,附着在还原剂添加阀上的粒状物质因受热而固化,从而有可能会堵塞该还原剂喷射阀的喷孔。即,可能会在还原剂添加阀中产生堵塞。对此,通过使还原剂添加阀的温度下降,从而能够抑制在该还原剂添加阀中产生堵塞。而且,通过从还原剂添加阀定期性地喷射还原剂,从而能够使该还原剂添加阀的温度降低。以下,将这种用于对还原剂的堵塞进行抑制的还原剂的添加,称为“堵塞抑制喷射”。
而且,已知有如下的技术(参照专利文献1),即,在内燃机的排气通道上从上游侧起依次设置有对燃料进行喷射的燃料添加阀、和氧化催化剂,并在氧化催化剂的活化之前,对燃料添加阀的堵塞抑制喷射时的添加量进行限制的技术。
并且,具有在氧化催化剂的下游侧处设置选择还原型NOX催化剂(以下,也称为SCR催化剂)的情况。SCR催化剂的NOX净化率具有根据NO2量在流入SCR催化剂的排气中的NOX量中所占的比例(以下,称为NO2比率)而改变的情况。在此,在实施堵塞抑制喷射时,氧化催化剂的氧化能力将降低。因此,由于从NO向NO2的氧化被抑制,因此NO2的比率降低。在以这种方式使NO2的比率降低时,SCR催化剂的NOX净化率可能会降低。即,通过实施堵塞抑制喷射而有可能导致NOX净化率降低。
在先技术文献
专利文献
专利文献1:日本特开2007-064183号公报
专利文献2:日本特开2004-060515号公报
专利文献3:日本特开2007-071175号公报
专利文献4:日本特开2009-138731号公报
发明内容
发明所要解决的课题
本发明是鉴于上述是问题点而完成的发明,其目的在于,抑制在实施对还原剂添加阀的堵塞进行抑制的添加时的、NOX净化率的降低。
用于解决课题的方法
为了达成上述课题,在本发明中提供一种内燃机的排气净化装置,所述内燃机的排气净化装置具备:第一排气净化装置,其被设置在内燃机的排气通道上,并具有氧化能力;第二排气净化装置,其被设置在与所述第一排气净化装置相比靠下游的排气通道上,并具有NOX的选择还原功能;燃料添加阀,其被设置在与所述第一排气净化装置相比靠上游的排气通道上,并向排气中喷射燃料,其中,所述内燃机的排气净化装置具备:控制装置,其在从所述燃料添加阀喷射燃料的预定的条件成立了的情况下,在所述第二排气净化装置的温度在预定的温度范围内时,与在预定的范围外时相比而减少从所述燃料添加阀喷射的燃料量。
第一排气净化装置例如具备具有氧化能力的催化剂。该催化剂可以被负载在过滤器中。此外,也可以将在与具有氧化能力的催化剂相比靠下游处设置了过滤器的装置设为第一排气净化装置。第二排气净化装置例如具备选择还原型NOX催化剂。该NOX催化剂可以负载在过滤器中。
燃料添加阀向第一排气净化装置供给燃料。当该燃料在第一排气净化装置中发生反应时,使该第一排气净化装置的氧化能力下降。在SCR催化剂的温度在预定的温度的范围内的情况下,控制装置减少从燃料添加阀喷射的燃料喷射量。另外,该预定的温度范围可以设为,如果从燃料添加阀喷射燃料时不减少燃料喷射量则会使NOX净化率降低的温度范围。在此,根据SCR催化剂的温度,由于NO2比率发生变化,因而NOX净化率会发生变化。当在这样的温度范围内从燃料添加阀喷射燃料时,NOX净化率可能会下降。另一方面,当减少来自燃料添加阀的燃料喷射量时,由于能够抑制第一排气净化装置的氧化能力的下降,因此能够抑制NOX净化率的下降。另外,从燃料添加阀喷射燃料的预定的条件可以设为执行堵塞抑制喷射的条件。堵塞抑制喷射能够以规定间隔而实施。即,可以设为以规定间隔而使预定的条件成立。此外,“从燃料添加阀喷射燃料的预定的条件成立的情况”可以设为,实施堵塞抑制喷射的情况。
在本发明中可以采用如下方式,即,所述预定的温度范围,当NO2量在流入所述第二排气净化装置的排气中的NOX量中所占的比例发生变化时,所述第二排气净化装置中的NOX净化率发生变化的温度范围。
通过使来自燃料添加阀的燃料喷射量减少,从而使NO2比率的减少程度变小。由此,由于能够使更多的NO2流入SCR催化剂,因此能够抑制NOX净化率的下降。此外,通过仅在NO2比率发生变化时SCR催化剂的NOX净化率也发生变化的温度范围内使来自燃料添加阀的燃料喷射量减少,从而能够在处于预定的温度范围外时抑制燃料添加阀的温度上升。此外,在预定的温度范围外时,即使减少来自燃料添加阀的燃料喷射量从而提高了NO2比率,但由于对NOX净化率没有影响,因此无需使燃料喷射量减少。另外,在NO2比率发生了变化时的NOX催化剂的变化量为,被认为是非常小的预定量以下的情况下,也可以认为NOX净化率没有发生变化。
在本发明中可以采用如下方式,即,所述控制装置在从所述燃料添加阀喷射燃料的预定的条件成立了的情况下,对在所述燃料添加阀中成为基准的燃料喷射量进行计算,并在所述第二排气净化装置的温度在预定的温度范围内时,与所述成为基准的燃料喷射量相比而减少实际的燃料喷射量,而在所述第二排气净化装置的温度为,与所述预定的温度范围相比而较低的温度范围且与所述预定的温度范围相邻的温度范围、或者与所述预定的温度范围相比而较高的温度范围且与所述预定的温度范围相邻的温度范围的情况下,与所述成为基准的燃料喷射量相比而增加实际的燃料喷射量。
成为基准的燃料喷射量(以下,也称为基准喷射量)为,例如根据内燃机的运行状态而被计算出的燃料喷射量,且为为了抑制燃料添加阀的堵塞而必需的燃料喷射量。另外,当基准喷射量过少时,对燃料添加阀的堵塞进行抑制会变得困难,而当基准喷射量过多时,燃料的消耗量会变多从而导致耗油率的恶化。因此,基准喷射量可以设为,为了对燃料添加阀的堵塞进行抑制所需要的燃料添加量的下限值。
而且,在有可能因燃料喷射而使NOX净化率下降的情况下,在从燃料添加阀喷射燃料时,喷射与基准喷射量相比而较少量的燃料。虽然通过喷射与基准喷射量相比而较少量的燃料,能够抑制NOX催化剂的下降,但是有可能会因燃料添加阀的温度升高而发生堵塞。因此,通过在进入预定的温度范围内之前,预先喷射与基准喷射量相比而较多量的燃料,从而预先使燃料添加阀的温度以所需以上的程度而下降。由此,即使在预定的温度范围内燃料添加阀的温度上升了,但由于距达到发生堵塞的温度还有余量,因此能够对发生堵塞的情况进行抑制。
在本发明中可以采用如下方式,即,所述控制装置在从实际的燃料喷射量中减去所述成为基准的燃料喷射量而得的值的累计值成为了预定值以下的情况下,将从所述燃料添加阀喷射的燃料量设为所述成为基准的燃料喷射量。
从实际的燃料喷射量中减去基准喷射量而得的值的累计值与燃料添加阀的温度相关。即,在喷射了多于基准喷射量的燃料的情况下,燃料添加阀的温度将以所需以上的程度而下降,而在喷射了少于基准喷射量的燃料的情况下,燃料添加阀的温度将变得高于为了抑制堵塞所需要的温度。燃料添加阀的温度的下降量与上升量根据从基准喷射量的增减量而决定,该增减量与燃料添加阀的温度存在相关关系。而且,从实际的燃料喷射量减去基准喷射量而得的值的累计值表示燃料添加阀的温度的过高与不足的状态,可以说累计值越增大,则燃料添加阀的温度就越低。然而,当SCR催化剂的温度成为所述预定的温度范围内的时间较长地持续时,燃料添加阀的温度将升高,从而有可能发生堵塞。在这种情况下,从实际的燃料喷射量减去基准喷射量而得的值的累计值变小。因此,将从实际的燃料喷射量减去基准喷射量而得的值的累计值、即可能使燃料添加阀中产生堵塞的累计值设定为预定值。而且,在该累计值成为了预定值以下的情况下,通过将来自燃料添加阀的燃料喷射量设为基准喷射量,从而能够将燃料添加阀的温度维持在不发生堵塞的温度上。
另外,即使具有燃料喷射量的增减,但在经过较长的时间时,由于施加到当前时间点的燃料添加阀的温度上的影响变小,因此所述累计值可以设为预定期间内的累计值。
发明的效果
根据本发明,能够抑制在实施对还原剂添加阀的堵塞进行抑制的添加时的、NOX净化率的降低。
附图说明
图1为表示实施例所涉及的内燃机及其排气系统的概要结构的图。
图2为表示SCR催化剂的温度与SCR催化剂的NOX净化率之间的关系的图。
图3为表示SCR催化剂的温度与堵塞抑制喷射时的燃料喷射量之间的关系的图。
图4为表示确定堵塞抑制喷射时的燃料喷射量的程序的流程图。
图5为表示SCR催化剂的温度与基准喷射量的补正系数之间的关系的图。
图6为例示在实施了图4所示的程序的情况下的、与内燃机相关的各参数的推移的时序图。
具体实施方式
以下,参照附图并基于实施例而对用于实施该发明的方式进行详细说明。然而,该实施例中记载的构成部件的尺寸、材质、形状、部件及其相对配置等,只要未特别地记载,则并不表示该发明的范围仅限定于此的含义。
<实施例1>
图1为表示本实施例所涉及的内燃机及其排气系统的概要结构的图。虽然图1所示的内燃机1是柴油机,但也可以是汽油机。内燃机1例如被搭载于车辆上。
在内燃机1上连接有排气通道2。在该排气通道2的路径上从上游侧起依次设置有氧化催化剂3、过滤器4、选择还原型NOX催化剂(以下,称为SCR催化剂5)。
氧化催化剂3为具有氧化能力的催化剂,并使排气中的例如HC或CO氧化。另外,氧化催化剂3也可以为具有氧化能力的其他的催化剂(例如三元催化剂或吸留还原型NOX催化剂)。而且,在本实施例中,氧化催化剂3相当于本发明中的第一排气净化装置。
过滤器4对排气中的粒状物质(PM)进行捕集。另外,氧化催化剂3也可以被负载在过滤器4中。
SCR催化剂5吸附有还原剂,并在NOX穿过时通过所吸附着的还原剂而对NOX进行选择还原。在向SCR催化剂5供给的还原剂中,能够利用NH3。另外,SCR催化剂5也可以负载在过滤器4中。例如,也可以在与氧化催化剂3相比靠下游处设置负载了SCR催化剂5的过滤器4。此外,也可以在与负载了氧化催化剂3的过滤器4相比靠下游处设置SCR催化剂5。而且,在本实施例中,SCR催化剂5相当于本发明中的第二排气净化装置。
在与氧化催化剂3相比靠上游的排气通道2上,设置有向在该排气通道2中流通的排气中喷射燃料(HC)的燃料添加阀7。通过从燃料添加阀7向排气中添加HC,从而能够利用氧化催化剂3使HC发生反应,并利用该反应热而使排气的温度上升。例如,在使氧化催化剂3、过滤器4、SCR催化剂5的温度上升时,从燃料添加阀7添加HC。
此外,在与过滤器4相比靠下游且与SCR催化剂5相比靠上游处的排气通道2上,设置有向排气中添加尿素水或氨(NH3)的氨添加阀8。尿素水通过排气的热量而被水解并成为氨。另外,氨添加阀8也可以设置在与氧化催化剂3相比靠上游处,或者还可以设置在与氧化催化剂3相比靠下游且与过滤器4相比靠上游处。氨在SCR催化剂5中作为还原剂而被使用。
此外,在与氧化催化剂3相比靠下游且与过滤器4相比靠上游的排气通道2上,安装有对排气的温度进行检测的第一温度传感器11以及对排气的空燃比进行检测的空燃比传感器12。另外,通过第一温度传感器11,能够对氧化催化剂3的温度或过滤器4的温度进行检测。此外,通过空燃比传感器12,能够对从氧化催化剂3流出的排气的空燃比或流入过滤器4的排气的空燃比进行检测。此外,在与过滤器4相比靠下游且与氨添加阀8相比靠上游的排气通道2上,安装有对排气的温度进行检测的第二温度传感器13。通过该第二温度传感器13,能够对过滤器4的温度或SCR催化剂5的温度进行检测。另外,也可以在氧化催化剂3、过滤器4、SCR催化剂5上分别安装温度传感器,并直接检测各部件的温度。
另外,上述传感器无需全部安装,也可以适当地选择安装。
在以上述的方式而构成的内燃机1中,同时设置有用于对该内燃机1进行控制的作为电子控制单元的ECU10。该ECU10根据内燃机1的运行条件或驾驶员的要求而对该内燃机1进行控制。
ECU10经由电子配线而与上述传感器连接,并且这些传感器的输出信号被输入至ECU10中。此外,燃料添加阀7、氨添加阀8经由电子配线而与ECU10连接,且通过该ECU10而对这些设备进行控制。
并且,ECU10通过对氧化催化剂3供给HC,从而使氧化催化剂3及排气的温度上升。例如,在由于SCR催化剂5的温度较低从而NOX净化率较低的情况下,能够通过向氧化催化剂3供给HC而使SCR催化剂5的温度上升。此外,在欲使氧化催化剂3的温度上升而提高净化率时,也能够通过向氧化催化剂3供给HC而使该氧化催化剂3的温度上升。
此外,ECU10在被捕集到过滤器4中的PM量达到阈值时,向氧化催化剂3供给HC从而使排气的温度上升。如此一来,由于过滤器4的温度上升,因此使PM被氧化。由此,能够从过滤器4中去除PM。通过这种方式,实施了过滤器4的再生。另外,在与氧化催化剂3相比靠下游处设置有吸留还原型NOX催化剂的情况下,能够通过向该氧化催化剂3供给HC而使该吸留还原型NOX催化剂的温度上升,并使硫磺中毒恢复。
为了如此向氧化催化剂3供给HC,从而ECU10从燃料添加阀7添加燃料。
此外,为了使燃料添加阀7的温度降低,ECU10实施从该燃料添加阀7喷射燃料的堵塞抑制喷射。堵塞抑制喷射在内燃机1正在进行工作的情况下以规定间隔而实施,该规定间隔以燃料添加阀7的温度成为抑制堵塞的温度即规定温度的方式而被预先确定。此外,ECU10计算出在燃料添加阀7的温度成为抑制堵塞的温度的条件下的燃料喷射量、即基准喷射量,并依据该基准喷射量而实施堵塞抑制喷射。
然而,通过实施堵塞抑制喷射,从而使氧化催化剂3的氧化能力下降,进而使得在该氧化催化剂3及过滤器4中被氧化成NO2的NO的量减少。因此,流入SCR催化剂5中的NO2量相对于NOX量之比(NO2比率)下降。另外,NOX量也可以设为NO与NO2总计的量。而且,根据SCR催化剂5的温度,使得NO2比率下降,从而使NOX净化率下降。
在此,图2为表示SCR催化剂5的温度与SCR催化剂5中的NOX净化率之间的关系的图。实线表示NOX净化率为30%的情况,单点划线表示NO2比率为40%的情况,虚线表示NO2比率为50%的情况。
如图2所示,SCR催化剂5的温度越升高,则NOX净化率越升高。而且,SCR催化剂5的温度在例如从150℃到200℃的范围内时,NO2比率越接近50%,则NOX净化率越升高。在该温度范围内,由于在NOX被还原时只需要NO与NO2为相同数量,因此在NO2比率为50%时,NOX净化率变为最高。另一方面,在SCR催化剂5的温度例如低于150℃的情况下、以及例如高于200℃的情况下,由于NOX净化率基本根据温度而决定,因此几乎对NO2比率没有影响。
然而,虽然刚刚从内燃机1中被排出的气体中的NO2比率低于50%,但能够通过在氧化催化剂3中使NO氧化而使NO2比率接近50%。另外,也可以预先使氧化催化剂3具有使NO2比率接近于50%这样的氧化能力。
即使在排气通道2上设置以这种方式将NO2比率调节为接近于50%的氧化催化剂3,但在实施了堵塞抑制喷射的情况下,由于氧化催化剂3的氧化能力下降,因此NO2比率也将下降。因此,SCR催化剂5中的NOX净化率将会下降。
因此在本实施例中,在NO2比率改变时NOX净化率也将改变的预定的温度范围内的情况下,为了抑制氧化催化剂3的氧化能力下降,使在堵塞抑制喷射时所喷射的燃料量与其他的温度时相比而减少。此时的燃料喷射量与基准喷射量相比而较少。由于通过减少从燃料添加阀7喷射的燃料喷射量能够抑制氧化催化剂3的氧化能力的下降,因此能够促进NO的氧化。另外,在堵塞抑制喷射时所喷射的燃料量越多,则氧化催化剂3的氧化能力越降低。
如此,在SCR催化剂5的温度为预定的温度范围内的情况下,能够通过使在堵塞抑制喷射时所喷射的燃料量减少而提高NOX净化率。
然而,通过将在堵塞抑制喷射时所喷射的燃料量设为少于基准喷射量,从而有可能使燃料添加阀7的温度变得高于抑制堵塞的温度、即规定温度。即,有可能发生燃料添加阀7的堵塞。
因此在本实施例中,SCR催化剂5的温度处于与所述预定的温度范围相比而较低的温度范围或较高的温度范围,并处于与所述预定的温度相邻的温度范围内的情况下,可以使在堵塞抑制喷射时所喷射的燃料量与基准喷射量相比而增加。
在此,图3为图示了SCR催化剂5的温度与堵塞抑制喷射时的燃料喷射量之间的关系的图。在处于与所述预定的温度范围相邻的温度范围内时,通过将堵塞抑制喷射时的燃料喷射量设为与基准喷射量相比而较多,从而使燃料添加阀7的温度与抑制堵塞的温度即规定温度相比而进一步降低。由此,在SCR催化剂5的温度成为了所述预定的温度范围内时,由于燃料添加阀7的温度成为了以所需以上的程度而下降了的状态,因此即使减少在堵塞抑制喷射时所喷射的燃料量,也能够抑制燃料添加阀7的温度变得高于规定温度的情况。另外,使在堵塞抑制喷射时所喷射的燃料量与基准喷射量相比而增加的情况可以为,SCR催化剂5的温度为与所述预定的温度范围相比而较低的温度的情况、或者为与所述预定的温度范围相比而较高的温度的情况中的至少一方。
此外,使堵塞抑制喷射时的燃料喷射量多于基准喷射量的温度范围可以在考虑耗油率的恶化等的条件下决定。在此,虽然通过扩大使堵塞抑制喷射时的燃料喷射量多于基准喷射量的温度范围,能够进一步抑制发生堵塞的情况,但存在耗油率恶化的可能性。此外,如果过度地缩小使堵塞抑制喷射时的燃料喷射量多于基准喷射量的温度范围,则发生堵塞的概率会升高。因此,可以在考虑抑制耗油率的恶化和抑制堵塞的发生的基础上,通过实验或模拟而预先求得使堵塞抑制喷射时的燃料喷射量多于基准喷射量的温度范围。此外,此时的燃料喷射量也能够同样地进行求取。
另外,当SCR催化剂5的温度处于所述预定的温度范围内的时间变长时,燃料添加阀7的温度有可能变得高于抑制堵塞的温度、即规定温度。因此在本实施例中,例如也可以在从实际的燃料喷射量减去基准喷射量而得的值的累计值变为了预定值以下的情况下,使堵塞抑制喷射时的燃料喷射量返回至基准喷射量。此外,例如也可以采用如下方式,即,在以与基准喷射量相比而减少的方式喷射了燃料时的燃料减少量的总量,大于以与基准喷射量相比而增加的方式喷射了燃料时的燃料增加量的总量的情况下,认为有可能在燃料添加阀7中发生堵塞,从而使在堵塞抑制喷射时所喷射的燃料量返回至基准喷射量。
图4为图示了决定堵塞抑制喷射时的燃料喷射量的程序的流程图。本程序通过ECU10而每隔预定的时间被重复执行。另外,在本实施例中,对图4所示的程序进行处理的ECU10相当于本发明中的控制装置。
在步骤S101中,计算出使燃料添加阀7的温度成为抑制堵塞的温度的条件下的燃料喷射量、即基准喷射量。在此,燃料添加阀7的温度根据内燃机转速以及内燃机负载而改变。即,内燃机转速以及内燃机负载与基准喷射量之间存在相关关系。因此,预先通过实验或模拟等而求得用于对内燃机转速以及内燃机负载与基准喷射量的关系进行求取的映射图或公式,并存储到ECU10中。
在步骤S102中,对基准喷射量进行补正,并计算出在堵塞抑制喷射时实际喷射的燃料量(补正喷射量)。在此,图5为图示了SCR催化剂5的温度与基准喷射量的补正系数之间的关系的图。图5所示的关系与图3所示的关系相对应。即,以使在步骤S101中计算出的基准喷射量乘以在步骤S102中计算出的补正系数而得到的燃料喷射量成为图3所示的燃料喷射量的方式,来设定图5的映射图。关于补正系数,预先通过实验或模拟等而求出最佳值并存储到ECU10中。
在步骤S103中,读入累计补正量。累计补正量为,对从实际的燃料喷射量减去基准喷射量而得的值进行累计而得到的累计值。即,其为对与基准喷射量相比而多出的部分的燃料喷射量进行加法运算,而对与基准喷射量相比而减少的部分的燃料喷射量进行减法运算而得到的值。另外,也可以设为距当前时间点预定期间之前为止的累计值。
在步骤S104中,判断是否实施了堵塞抑制喷射时的燃料喷射量的减量补正。即,判断补正喷射量是否少于基准喷射量。在本步骤中,也可以判断SCR催化剂5的温度是否在所述预定的温度范围内。在步骤S104中作出肯定判断的情况下进入步骤S105,另一方面,在作出否定判断的情况下进入步骤S107。
在步骤S105中,判断累计补正量是否为预定值以下。在本步骤中,判断对燃料添加阀7的堵塞进行抑制的情况是否处于可能的状态。在此所提及的预定值为,能够对燃料添加阀7的堵塞进行抑制的累计补正量,例如可以设为0。此外,也可以根据实施了实验或模拟等而得到的结果而对预定值进行设定。在本步骤中,通过长时间实施在堵塞抑制喷射时所喷射的燃料量的减量补正,从而判断是否有可能在燃料添加阀7中发生堵塞。在步骤S105中作出肯定判断的情况下,进入步骤S106,另一方面,在作出否定判断的情况下,进入步骤S107。
在步骤S106中,堵塞抑制喷射时所喷射的燃料量被设定为基准喷射量。即,由于通过长时间实施在堵塞抑制喷射时所喷射的燃料量的减量补正从而有可能会发生燃料添加阀7的堵塞,因此禁止了减量补正。
在步骤S107中,将堵塞抑制喷射时所喷射的燃料量设定为补正喷射量。由此,能够在对发生燃料添加阀7的堵塞的情况进行抑制的同时,对NOX净化率下降的情况进行抑制。
在此,图6为,例示了在实施了图4所示的程序的情况下的、与内燃机1相关的各参数的推移的时序图。在图6中,“车速”表示搭载有内燃机1的车辆的速度,“燃料喷射量”表示在堵塞抑制喷射时被喷射的燃料量,“NOX净化率”表示相对于流入SCR催化剂5的NOX量而被SCR催化剂5还原的NOX量。实线表示实施了本实施例所涉及的控制的情况,虚线表示在始终喷射基准喷射量的条件下实施了现有的堵塞抑制喷射的情况。
在本实施例中,在T1的时间点上,由于SCR催化剂5的温度与预定的温度范围相比而较低且成为与预定的温度范围相邻的温度范围,因此在堵塞抑制喷射时实施燃料喷射量的增量补正。此时,燃料添加阀7的温度与以往相比而降低。此外,在此时虽然NO2比率降低,但由于SCR催化剂5的温度较低,因此NOX净化率与以往相比几乎没有改变。
此外,在本实施例中,在T2的时间点上,由于SCR催化剂5的温度处于预定的温度范围内,因此在堵塞抑制喷射时实施燃料的减量补正。在此时,由于受到在T1的时间点上的增量补正的影响而使燃料添加阀7的温度降低,因此即使在T2的时间点上燃料添加阀7的温度上升了,但也抑制了温度与以往相比而升高的情况。而且,由于在堵塞抑制喷射时实施了燃料的减量补正,因此与以往相比,NO2比率的减少量也被抑制。因此,抑制了NOX净化率的下降。
此外,在本实施例中,在T3的时间点上,由于累计补正量减少到了预定值,因此在T4的时间点上,堵塞抑制喷射时的燃料喷射量的减量补正被禁止。由此,燃料喷射量变为与以往相同。
根据以上所说明的本实施例,在SCR催化剂5为预定的温度范围内的情况下,由于对堵塞抑制喷射时的燃料喷射量进行减量补正,因此能够抑制NOX净化率下降的情况。此外,在SCR催化剂5的温度处于预定的温度范围外的情况下且处于与该预定的温度范围相邻的温度范围内的情况下,由于对堵塞抑制喷射时的燃料喷射量进行增量补正,因此即使之后实施减量补正,也能够对燃料添加阀7的温度过度升高的情况进行抑制。由此,能够抑制发生燃料添加阀7的堵塞的情况。此外,在累计补正量成为预定值以下的情况下,由于禁止减量补正,因此能够通过使燃料添加阀7的温度升高而对发生堵塞的情况进行抑制。
符号说明
1 内燃机;
2 排气通道;
3 氧化催化剂;
4 过滤器;
5 选择还原型NOX催化剂(SCR催化剂);
7 燃料添加阀;
8 氨添加阀;
10 ECU;
11 第一温度传感器;
12 空燃比传感器;
13 第二温度传感器。

Claims (4)

1.一种内燃机的排气净化装置,具备:
第一排气净化装置,其被设置在内燃机的排气通道上,并具有氧化能力;
第二排气净化装置,其被设置在与所述第一排气净化装置相比靠下游的排气通道上,并具有NOX的选择还原功能;
燃料添加阀,其被设置在与所述第一排气净化装置相比靠上游的排气通道上,并向排气中喷射燃料,
其中,所述内燃机的排气净化装置具备:
控制装置,其在从所述燃料添加阀喷射燃料的预定的条件成立了的情况下,在所述第二排气净化装置的温度在预定的温度范围内时,与在预定的范围外时相比而减少从所述燃料添加阀喷射的燃料量。
2.如权利要求1所述的内燃机的排气净化装置,其中,
所述预定的温度范围为,当NO2量在流入所述第二排气净化装置的排气中的NOX量中所占的比例发生变化时,所述第二排气净化装置中的NOX净化率发生变化的温度范围。
3.如权利要求1或2所述的内燃机的排气净化装置,其中,
所述控制装置在从所述燃料添加阀喷射燃料的预定的条件成立了的情况下,对在所述燃料添加阀中成为基准的燃料喷射量进行计算,并在所述第二排气净化装置的温度在预定的温度范围内时,与所述成为基准的燃料喷射量相比而减少实际的燃料喷射量,而在所述第二排气净化装置的温度为,与所述预定的温度范围相比而较低的温度范围且与所述预定的温度范围相邻的温度范围、或者与所述预定的温度范围相比而较高的温度范围且与所述预定的温度范围相邻的温度范围的情况下,与所述成为基准的燃料喷射量相比而增加实际的燃料喷射量。
4.如权利要求3所述的内燃机的排气净化装置,其中,
所述控制装置在从实际的燃料喷射量中减去所述成为基准的燃料喷射量而得的值的累计值成为了预定值以下的情况下,将从所述燃料添加阀喷射的燃料量设为所述成为基准的燃料喷射量。
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