阅读说明：本技术 控制发动机限扭的方法、装置及系统 (Method, device and system for controlling torque limit of engine ) 是由 王通 孙国治 宋茜 吴速超 孙树矗 于 2020-05-08 设计创作，主要内容包括：本发明涉及车辆技术领域,具体涉及一种控制发动机限扭的方法、装置及系统。该方法包括获取SCR转换效率值；根据SCR转换效率值小于预设转换效率值时获取的第一时间和第二时间的SCR箱上游NOX质量流量的瞬时值计算出SCR箱上游NOX质量流量变化率值；根据SCR箱上游NOX质量流量变化率值大于预设变化值暂停对SCR转换效率值监测。本方案中,通过SCR上游NOX质量流量变化率值过大即出现突增或突减现象时,暂停ECU对SCR转换效率的监测,解决由于发动机负荷突变,使上游原排NOX质量流量变化率过大导致发动机限扭的问题和NOX排放超标影响发动机动力性的问题。(The invention relates to the technical field of vehicles, in particular to a method, a device and a system for controlling torque limit of an engine. The method comprises the steps of obtaining an SCR conversion efficiency value; calculating an upstream NOx mass flow rate change value of the SCR box according to instantaneous values of the upstream NOx mass flow of the SCR box at a first time and a second time, which are acquired when the SCR conversion efficiency value is smaller than a preset conversion efficiency value; and suspending monitoring of the SCR conversion efficiency value according to the fact that the upstream NOx mass flow rate change value of the SCR box is larger than a preset change value. In the scheme, when the mass flow rate of NOx at the upstream of the SCR is too large, namely, the SCR is suddenly increased or decreased, the monitoring of the SCR conversion efficiency by the ECU is suspended, and the problems that the mass flow rate of the NOx at the upstream is too large to cause the torque limitation of an engine and the power performance of the engine is influenced by the excessive NOx emission due to sudden change of the load of the engine are solved.)

1. A method of controlling an engine torque limit, the method comprising the steps of:

acquiring an SCR conversion efficiency value;

acquiring an instantaneous value of the upstream NOx mass flow of the SCR box at a first time and an instantaneous value of the upstream NOx mass flow of the SCR box at a second time when the SCR conversion efficiency value is smaller than a preset conversion efficiency value;

calculating the mass flow rate change value of the NOx at the upstream of the SCR box according to the acquired instantaneous value of the mass flow of the NOx at the upstream of the SCR box at the first time and the acquired instantaneous value of the mass flow of the NOx at the upstream of the SCR box at the second time;

judging the fault of the engine according to the condition that the change rate value of the mass flow of the NOx at the upstream of the SCR box is smaller than or equal to a preset change rate value, and controlling the engine to enter a torque limiting mode; or

And suspending monitoring of the SCR conversion efficiency value according to the fact that the upstream NOx mass flow rate change value of the SCR box is larger than a preset change value.

2. The method of controlling engine torque limit of claim 1, wherein said obtaining an SCR conversion efficiency value comprises;

acquiring a concentration value of NOx gas at the upstream of the SCR and a concentration value of NOx gas at the downstream of the SCR;

calculating the SCR conversion efficiency value according to the SCR upstream NOx gas concentration value and the SCR downstream NOx gas concentration value;

k is (n-n1)/n, where k is the SCR conversion efficiency value, n is the SCR upstream NOx gas concentration value, and n1 is the SCR downstream NOx gas concentration value.

3. The method of controlling engine torque limiting as set forth in claim 1 further comprising the step of, after said suspending monitoring of the SCR conversion efficiency value based on said SCR tank upstream NOX mass flow rate change value being greater than a preset change value:

obtaining an engine rotating speed value;

obtaining a detection time value according to the mass flow rate of NOx at the upstream of the SCR box and the engine rotating speed value;

and starting timing according to the monitoring of the SCR conversion efficiency value suspended to obtain a suspended time value, and re-obtaining the SCR conversion efficiency value according to the suspended time value larger than the detection time value.

4. An apparatus for controlling an engine torque limit, which is used to perform the method for controlling an engine torque limit of claim 1 or 2, comprising: the device comprises a first acquisition unit, a second acquisition unit and a control unit;

the first acquisition unit is used for acquiring an SCR conversion efficiency value;

the second acquisition unit is used for acquiring the instantaneous value of the mass flow of the NOx at the upstream of the SCR box at a first time and the instantaneous value of the mass flow of the NOx at the upstream of the SCR box at a second time;

the control unit judges the fault of the engine according to the condition that the SCR conversion efficiency value is smaller than a preset conversion efficiency value and according to the condition that the NOx mass flow rate change value at the upstream of the SCR box is smaller than or equal to a preset change rate value, and controls the engine to enter a torque limiting mode; or

And the control unit suspends the monitoring of the SCR conversion efficiency value according to the condition that the SCR conversion efficiency value is smaller than a preset conversion efficiency value and according to the condition that the upstream NOx mass flow rate change value of the SCR tank is smaller than or equal to a preset change rate value.

5. The apparatus of controlling engine torque limit according to claim 4, wherein the first acquisition unit includes: the system comprises an upstream acquisition subunit, a downstream acquisition subunit and an SCR conversion efficiency calculation subunit;

the upstream acquiring subunit is used for acquiring a concentration value of the SCR upstream NOx gas;

the downstream acquiring subunit is used for acquiring a concentration value of NOx gas at the downstream of the SCR;

the SCR conversion efficiency calculation subunit is used for calculating the SCR conversion efficiency value according to the SCR upstream NOx gas concentration value and the SCR downstream NOx gas concentration value.

6. The apparatus of controlling engine torque limit according to claim 5, characterized in that the second acquisition unit includes; an SCR box upstream acquisition subunit and a change rate calculation subunit;

the SCR box upstream acquiring subunit is used for respectively acquiring an instantaneous value of the SCR box upstream NOx mass flow at a first time and an instantaneous value of the SCR box upstream NOx mass flow at a second time;

and the change rate calculating subunit is used for calculating the change rate value of the mass flow of the NOx at the upstream of the SCR box according to the obtained instantaneous value of the mass flow of the NOx at the upstream of the SCR box at the first time and the obtained instantaneous value of the mass flow of the NOx at the upstream of the SCR box at the second time.

7. The apparatus of controlling engine torque limit of claim 6, further comprising: a third acquisition unit and a fourth acquisition unit;

the third acquisition unit is used for acquiring an engine rotating speed value;

the fourth acquisition unit is used for acquiring a pause time value when monitoring of the SCR conversion efficiency value is paused;

the control unit is used for obtaining a detection time value according to the NOx mass flow rate change value at the upstream of the SCR box and the engine speed value, and controlling the first acquisition unit to restart according to the fact that the pause time value obtained by the fourth acquisition unit is larger than the detection time value.

8. A system for controlling engine torque limit, the system comprising a memory and an apparatus for controlling engine torque limit as claimed in claim 7, the memory having stored therein instructions for a method for controlling engine torque limit as claimed in claim 1 or 2;

the system also comprises a controller, an engine, an SCR box, a rotating speed sensor, an upstream NOx sensor and a downstream NOx sensor;

the rotating speed sensor is connected with the engine and the controller;

the upstream NOx sensor is arranged at the upstream of the SCR box and is connected with the controller;

the downstream NOx sensor is disposed downstream of the SCR tank and is connected to the controller.

Technical Field

The invention relates to the technical field of vehicles, in particular to a method, a device and a system for controlling engine torque limit based on SCR (selective catalytic reduction) box upstream NOx mass flow.

Background

At present, in a diesel engine aftertreatment system, an SCR (Selective Catalytic Reduction) is an important link for controlling the NOx value emission of an engine, however, when the engine has small rotation speed fluctuation and large load change, the upstream original NOx value can suddenly increase or suddenly decrease, and due to aftertreatment reaction lag, the urea injection quantity of the SCR system is insufficient or excessive, NOx or NH3 in tail gas cannot timely and sufficiently react, so that an emission standard exceeding is monitored by a SCR downstream sensor, and then an ECU reports corresponding aftertreatment faults, so that the power influence effects such as torque limitation, limping home and the like of the engine are caused.

Disclosure of Invention

The invention aims to at least solve the problems that in the prior art, the emission of a downstream sensor exceeds the standard, an ECU reports a corresponding fault, and an engine enters a torque-limiting mode to influence the driving experience because the original NOx is suddenly increased or reduced when the working condition of the engine suddenly changes and the SCR system cannot respond quickly. The purpose is realized by the following technical scheme:

a first aspect of the invention proposes a method of controlling an engine torque limit, the method comprising the steps of:

acquiring an SCR conversion efficiency value;

acquiring an instantaneous value of the upstream NOx mass flow of the SCR box at a first time and an instantaneous value of the upstream NOx mass flow of the SCR box at a second time when the SCR conversion efficiency value is smaller than a preset conversion efficiency value;

calculating the mass flow rate change value of the NOx at the upstream of the SCR box according to the acquired instantaneous value of the mass flow of the NOx at the upstream of the SCR box at the first time and the acquired instantaneous value of the mass flow of the NOx at the upstream of the SCR box at the second time;

judging the fault of the engine according to the condition that the change rate value of the mass flow of the NOx at the upstream of the SCR box is smaller than or equal to a preset change rate value, and controlling the engine to enter a torque limiting mode; or

And suspending monitoring of the SCR conversion efficiency value according to the fact that the upstream NOx mass flow rate change value of the SCR box is larger than a preset change value.

According to the method for controlling the engine torque limit, the mass flow rate change value of the original NOx discharged at the upstream of the SCR is monitored, when the mass flow rate change value of the NOx discharged at the upstream of the SCR is too large, namely, a sudden increase or a sudden decrease phenomenon occurs, the monitoring of the SCR conversion efficiency by the ECU is suspended, and the problems that the engine torque limit is caused by the fact that the mass flow rate of the original NOx discharged at the upstream is too large due to sudden change of engine load and the dynamic performance of the engine is influenced by the excessive NOx emission are solved.

In addition, the method for controlling the torque limit of the engine can also have the following additional technical characteristics:

in some embodiments of the invention, said obtaining an SCR conversion efficiency value comprises;

acquiring a concentration value of NOx gas at the upstream of the SCR and a concentration value of NOx gas at the downstream of the SCR;

calculating the SCR conversion efficiency value according to the SCR upstream NOx gas concentration value and the SCR downstream NOx gas concentration value;

k is (n-n1)/n, where k is the SCR conversion efficiency value, n is the SCR upstream NOx gas concentration value, and n1 is the SCR downstream NOx gas concentration value.

In some embodiments of the invention, after suspending monitoring the SCR conversion efficiency value according to the value of the rate of change of the NOX mass flow upstream of the SCR tank being greater than a preset change value, the method further comprises the following steps:

obtaining an engine rotating speed value;

obtaining a detection time value according to the mass flow rate of NOx at the upstream of the SCR box and the engine rotating speed value;

and starting timing according to the monitoring of the SCR conversion efficiency value suspended to obtain a suspended time value, and re-obtaining the SCR conversion efficiency value according to the suspended time value larger than the detection time value.

In another aspect of the present invention, an apparatus for controlling an engine torque limit is provided, which is used for executing the method for controlling the engine torque limit described above, and comprises: the device comprises a first acquisition unit, a second acquisition unit and a control unit;

the first acquisition unit is used for acquiring an SCR conversion efficiency value;

the second acquisition unit is used for acquiring the instantaneous value of the mass flow of the NOx at the upstream of the SCR box at a first time and the instantaneous value of the mass flow of the NOx at the upstream of the SCR box at a second time;

the control unit judges the fault of the engine according to the condition that the SCR conversion efficiency value is smaller than a preset conversion efficiency value and according to the condition that the NOx mass flow rate change value at the upstream of the SCR box is smaller than or equal to a preset change rate value, and controls the engine to enter a torque limiting mode; or

And the control unit suspends the monitoring of the SCR conversion efficiency value according to the condition that the SCR conversion efficiency value is smaller than a preset conversion efficiency value and according to the condition that the upstream NOx mass flow rate change value of the SCR tank is smaller than or equal to a preset change rate value.

In some embodiments of the invention, the first obtaining unit comprises: the system comprises an upstream acquisition subunit, a downstream acquisition subunit and an SCR conversion efficiency calculation subunit;

the upstream acquiring subunit is used for acquiring a concentration value of the SCR upstream NOx gas;

the downstream acquiring subunit is used for acquiring a concentration value of NOx gas at the downstream of the SCR;

the SCR conversion efficiency calculation subunit is used for calculating the SCR conversion efficiency value according to the SCR upstream NOx gas concentration value and the SCR downstream NOx gas concentration value.

In some embodiments of the invention, the second obtaining unit comprises; an SCR box upstream acquisition subunit and a change rate calculation subunit;

the SCR box upstream acquiring subunit is used for respectively acquiring an instantaneous value of the SCR box upstream NOx mass flow at a first time and an instantaneous value of the SCR box upstream NOx mass flow at a second time;

and the change rate calculating subunit is used for calculating the change rate value of the mass flow of the NOx at the upstream of the SCR box according to the obtained instantaneous value of the mass flow of the NOx at the upstream of the SCR box at the first time and the obtained instantaneous value of the mass flow of the NOx at the upstream of the SCR box at the second time.

In some embodiments of the invention, the means for controlling engine torque limit further comprises: a third acquisition unit and a fourth acquisition unit;

the third acquisition unit is used for acquiring an engine rotating speed value;

the fourth acquisition unit is used for acquiring a pause time value when monitoring of the SCR conversion efficiency value is paused;

the control unit is used for obtaining a detection time value according to the NOx mass flow rate change value at the upstream of the SCR box and the engine speed value, and controlling the first acquisition unit to restart according to the fact that the pause time value obtained by the fourth acquisition unit is larger than the detection time value.

The invention also provides a system for controlling the torque limit of the engine, which comprises a memory and the device for controlling the torque limit of the engine, wherein the memory stores instructions of the method for controlling the torque limit of the engine;

the system also comprises a controller, an engine, an SCR box, a rotating speed sensor, an upstream NOx sensor and a downstream NOx sensor;

the rotating speed sensor is connected with the engine and the controller;

the upstream NOx sensor is arranged at the upstream of the SCR box and is connected with the controller;

the downstream NOx sensor is disposed downstream of the SCR tank and is connected to the controller.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like parts are designated by like reference numerals throughout the drawings. In the drawings:

FIG. 1 schematically illustrates a schematic diagram of a method of controlling engine torque limit, according to an embodiment of the invention;

FIG. 2 schematically illustrates a schematic diagram of a method of controlling engine torque limit according to another embodiment of the present disclosure;

FIG. 3 schematically illustrates a MAP data plot of a method of controlling engine torque limit according to an embodiment of the present disclosure;

FIG. 4 schematically illustrates a logic diagram for a method of controlling engine torque limit in accordance with an embodiment of the present invention;

FIG. 5 schematically illustrates a functional block diagram of an apparatus for controlling engine torque limit according to an embodiment of the present invention;

FIG. 6 schematically illustrates a functional block diagram of a first acquisition unit of an apparatus for controlling engine torque limit, according to an embodiment of the present invention;

fig. 7 schematically shows a functional block diagram of a second acquisition unit of the apparatus for controlling the engine torque limit according to the embodiment of the present invention.

The reference numerals in the drawings denote the following:

1: a first acquisition unit; 101: an upstream acquisition subunit; 102: a downstream acquisition subunit; 103: an SCR conversion efficiency calculation subunit; 2: a second acquisition unit; 201: an SCR tank upstream acquisition subunit; 202: a change rate calculation subunit; 3: a control unit; 4: a third acquisition unit; 5: and a fourth acquisition unit.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

It is to be understood that the terminology used herein is for the purpose of describing particular example embodiments only, and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "including," and "having" are inclusive and therefore specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order described or illustrated, unless specifically identified as an order of performance. It should also be understood that additional or alternative steps may be used.

Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as "first," "second," and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

For convenience of description, spatially relative terms, such as "inner", "outer", "lower", "below", "upper", "above", and the like, may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" or "over" the other elements or features. Thus, the example term "below … …" can include both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The invention provides a method for controlling the torque limit of an engine, which can overcome the resistance of a low-pressure oil circuit system to meet the requirement of the capacity of a high-pressure oil pump, so that the engine can normally work, the problem that the engine cannot be normally used due to overlarge resistance is avoided, the problem that the capacity of the self-carried oil delivery pump of the high-pressure oil pump is insufficient is solved, and the fuel resistance of a low-pressure system is effectively overcome.

As shown in fig. 1 to 3, the method of controlling the engine torque limit in the present embodiment includes the steps of:

s1, acquiring an SCR conversion efficiency value k;

s2, acquiring an instantaneous value M1 of the mass flow of the NOx at the upstream of the SCR tank at a first time t1 and an instantaneous value M2 of the mass flow of the NOx at the upstream of the SCR tank at a second time when the SCR conversion efficiency value k is smaller than a preset conversion efficiency value k 1;

s3, calculating an upstream NOx mass flow rate change value x of the SCR box according to the acquired instantaneous value M1 of the upstream NOx mass flow of the SCR box at the first time t1 and the acquired instantaneous value M2 of the upstream NOx mass flow of the SCR box at the second time t 2;

s4, judging the fault of the engine according to the fact that the change rate value x of the mass flow of the NOx at the upstream of the SCR box is smaller than or equal to a preset change rate value delta M, and controlling the engine to enter a torque limiting mode; or

S5, suspending the monitoring of the SCR conversion efficiency value according to the fact that the NOx mass flow rate change value x on the upstream of the SCR box is larger than a preset change value delta M.

The specific operation steps are as follows: as shown in fig. 1 and 4, S1, acquiring an SCR conversion efficiency value k through ECU monitoring;

s2, acquiring an instantaneous value M1 of the mass flow of the NOx at the upstream of the SCR tank at a first time t1 and an instantaneous value M2 of the mass flow of the NOx at the upstream of the SCR tank at a second time t2 when the SCR conversion efficiency value k is smaller than a preset conversion efficiency value k 1;

s3, calculating an upstream NOx mass flow rate change value x of the SCR box according to the acquired instantaneous value M1 of the upstream NOx mass flow of the SCR box at the first time t1 and the acquired instantaneous value M2 of the upstream NOx mass flow of the SCR box at the second time t 2;

s4, judging the fault of the engine according to the fact that the change rate value x of the mass flow of the NOx at the upstream of the SCR box is smaller than or equal to a preset change rate value delta M, controlling the engine to enter a torque limiting mode, and ending the control;

if the SCR conversion efficiency value is larger than the preset conversion efficiency value k1, the ECU monitors and acquires the SCR conversion efficiency value k again.

Or the following steps are carried out;

as shown in fig. 2 and 4, S1, acquiring an SCR conversion efficiency value k through ECU monitoring;

s2, acquiring an instantaneous value M1 of the mass flow of the NOx at the upstream of the SCR tank at a first time t1 and an instantaneous value M2 of the mass flow of the NOx at the upstream of the SCR tank at a second time when the SCR conversion efficiency value k is smaller than a preset conversion efficiency value k 1;

s3, calculating an upstream NOx mass flow rate change value x of the SCR box according to the acquired instantaneous value M1 of the upstream NOx mass flow of the SCR box at the first time t1 and the acquired instantaneous value M2 of the upstream NOx mass flow of the SCR box at the second time t 2;

s5, suspending the monitoring of the SCR conversion efficiency value according to the fact that the NOx mass flow rate change value x on the upstream of the SCR box is larger than a preset change value delta M.

The calculation formula of the upstream NOx mass flow rate change value x of the SCR box is as follows:

x＝|M2-M1|/(t2-t1),

where t1 is the first time, t2 is the second time, M1 is the instantaneous value of the SCR tank upstream NOx mass flow at the first time t1, and M2 is the instantaneous value of the SCR tank upstream NOx mass flow at the second time t 2.

According to the method for controlling the engine torque limit, the mass flow rate change value of the original NOx discharged at the upstream of the SCR is monitored, when the mass flow rate change value of the NOx discharged at the upstream of the SCR is too large, namely, a sudden increase or a sudden decrease phenomenon occurs, the monitoring of the SCR conversion efficiency by the ECU is suspended, the problem that the engine torque limit is caused by the too large mass flow rate change value of the original NOx discharged at the upstream due to sudden change of engine load and the problem that the engine dynamic performance is influenced by the excessive NOx discharge are solved, and the driving experience of a driver is improved.

In some embodiments of the invention, said obtaining an SCR conversion efficiency value comprises;

step S101, acquiring a concentration value n of NOx gas at the upstream of SCR and a concentration value n1 of NOx gas at the downstream of SCR;

step S102, calculating the SCR conversion efficiency value k according to the SCR upstream NOx gas concentration value n and the SCR downstream NOx gas concentration value n 1;

namely, calculating to obtain an SCR conversion efficiency value k by the formula k-n 1/n, wherein k is the SCR conversion efficiency value, n is the SCR upstream NOx gas concentration value, and n1 is the SCR downstream NOx gas concentration value.

In some embodiments of the invention, after suspending monitoring the SCR conversion efficiency value according to the value of the rate of change of the NOX mass flow upstream of the SCR tank being greater than a preset change value, the method further comprises the following steps:

that is, in step 5, the following steps are also included:

s501, obtaining an engine rotating speed value y;

s502, obtaining a detection time value t according to the upstream NOx mass flow rate change value x of the SCR box and the engine rotating speed value y;

s503, according to the SCR conversion efficiency value k which is monitored and started to be timed, a pause time value is obtained, and according to the fact that the pause time value is larger than the detection time value t, the SCR conversion efficiency value is obtained again.

As shown in fig. 3, the detection time value t is obtained by looking up from the MAP, and when x is 10 and y is 600, t is 50s, for example.

In the embodiment, during the normal running process of the vehicle, the upstream and downstream nitrogen oxygen sensors feed back upstream and downstream NOx concentration monitoring values C in real time₁、C₂(ii) a Suppose t-th under a certain working condition_iThe mass flow of the exhaust gas of the engine is M at the moment_iThen t is_iThe mass flow of the NOx at the upstream and the downstream at the moment is the product of the mass flow of the exhaust gas and the concentration values of the NOx at the upstream and the downstream, namely M_1i＝M_i*C_1i，M_2i＝M_i*C_2iIn the same way as the t_i+1Time of day, upstream and downstream NOX mass flowAre respectively M_1(i+1)＝M_i+1*C_1(i+1)，M_2(i+1)＝M_i+1*C_2(i+1)The ECU begins to calculate the upstream NOx mass flow rate change rate, with change x ═ M_1(i+1)-M_1i)/(t_i+1-t_i) If the change x is larger than or equal to △ M, the ECU conversion efficiency monitoring is suspended, the time for shielding the ECU monitoring function is determined according to the rotating speed and the upstream NOx mass flow rate, the monitoring function is recovered after the interval time, the situation that the engine torque limit condition is caused by the fact that the aftertreatment cannot respond quickly due to the fact that the load change is too large is avoided, the situation that the engine power degrades in a one-time mode due to the fact that the emission exceeds the standard is avoided, the driving experience of a driver is improved, meanwhile, the monitoring of the NOx conversion efficiency by the ECU is suspended within a period of time after the load change is suddenly changed, the special situation that the NOx emission exceeds the standard when the aftertreatment does not fail is effectively distinguished, the power output is guaranteed to the maximum degree, and the situation that the engine torque limit condition is caused by the fact that the aftertreatment cannot respond quickly due to the fact that the.

In another aspect of the present invention, an apparatus for controlling an engine torque limit is provided, which is used for executing the method for controlling the engine torque limit described above, and comprises: a first acquiring unit 1, a second acquiring unit 2 and a control unit 3;

the first obtaining unit 1 is used for obtaining an SCR conversion efficiency value;

the second acquiring unit 2 is used for acquiring the instantaneous value of the mass flow of the NOx at the upstream of the SCR box at a first time and the instantaneous value of the mass flow of the NOx at the upstream of the SCR box at a second time;

the control unit 3 judges the fault of the engine according to the condition that the SCR conversion efficiency value is smaller than a preset conversion efficiency value and according to the condition that the NOx mass flow rate change value at the upstream of the SCR box is smaller than or equal to a preset change rate value, and controls the engine to enter a torque limiting mode; or

And the control unit 3 suspends the monitoring of the SCR conversion efficiency value according to the condition that the SCR conversion efficiency value is smaller than a preset conversion efficiency value and according to the condition that the upstream NOx mass flow rate change value of the SCR tank is smaller than or equal to a preset change rate value.

In some embodiments of the present invention, the first obtaining unit 1 comprises: an upstream acquisition subunit 101, a downstream acquisition subunit 102, and an SCR conversion efficiency calculation subunit 103;

the upstream acquiring subunit 101 is used for acquiring an SCR upstream NOX gas concentration value;

the downstream acquiring subunit 102 is used for acquiring a concentration value of the SCR downstream NOx gas;

the SCR conversion efficiency calculation subunit 103 is configured to calculate the SCR conversion efficiency value according to the SCR upstream NOX gas concentration value and the SCR downstream NOX gas concentration value.

Namely, calculating to obtain an SCR conversion efficiency value k by the formula k-n 1/n, wherein k is the SCR conversion efficiency value, n is the SCR upstream NOx gas concentration value, and n1 is the SCR downstream NOx gas concentration value.

In some embodiments of the invention, said second acquisition unit 2 comprises; an SCR tank upstream acquisition subunit 202 and a rate of change calculation subunit;

the SCR tank upstream acquisition subunit 202 is configured to acquire an instantaneous value of the SCR tank upstream NOX mass flow at a first time and an instantaneous value of the SCR tank upstream NOX mass flow at a second time, respectively;

and the change rate calculating subunit is used for calculating the change rate value of the mass flow of the NOx at the upstream of the SCR box according to the obtained instantaneous value of the mass flow of the NOx at the upstream of the SCR box at the first time and the obtained instantaneous value of the mass flow of the NOx at the upstream of the SCR box at the second time.

The calculation formula of the upstream NOx mass flow rate change value x of the SCR box is as follows:

x＝|M2-M1|/(t2-t1),

where t1 is the first time, t2 is the second time, M1 is the instantaneous value of the SCR tank upstream NOx mass flow at the first time t1, and M2 is the instantaneous value of the SCR tank upstream NOx mass flow at the second time t 2.

In some embodiments of the invention, the means for controlling engine torque limit further comprises: a third acquiring unit 4 and a fourth acquiring unit 5;

the third obtaining unit 4 is used for obtaining an engine rotating speed value;

the fourth obtaining unit 5 is configured to obtain a pause time value when monitoring of the SCR conversion efficiency value is paused;

the control unit 3 is used for obtaining a detection time value according to the mass flow rate change value of the NOx upstream of the SCR box and the engine speed value, and controlling the first obtaining unit 1 to restart according to the condition that the pause time value obtained by the fourth obtaining unit 5 is larger than the detection time value.

The invention also provides a system for controlling the torque limit of the engine, which comprises a memory and the device for controlling the torque limit of the engine, wherein the memory stores instructions of the method for controlling the torque limit of the engine;

the system also comprises a controller, an engine, an SCR box, a rotating speed sensor, an upstream NOx sensor and a downstream NOx sensor;

the rotating speed sensor is connected with the engine and the controller;

the upstream NOx sensor is arranged at the upstream of the SCR box and is connected with the controller;

the downstream NOx sensor is disposed downstream of the SCR tank and is connected to the controller.

In the embodiment, an upstream NOx gas concentration value n of an SCR and a downstream NOx gas concentration value n1 of the SCR are monitored by an upstream NOx sensor and a downstream NOx sensor, an SCR conversion efficiency value k is monitored and calculated by a controller (ECU), then the controller judges the relation between the SCR conversion efficiency value k and k1, the upstream NOx sensor is controlled to monitor the instantaneous value of the upstream NOx mass flow of an SCR box at a first time and a second time according to the condition that the SCR conversion efficiency value k is smaller than a preset conversion efficiency value k1, the controller further calculates a mass flow change rate value x of the upstream NOx of the SCR box, the controller judges the engine fault according to the condition that the mass flow change rate value x of the upstream NOx of the SCR box is smaller than or equal to a preset change rate value delta M, the engine is controlled to enter a torque limiting mode, and; or after the controller calculates the upstream NOx mass flow rate change value x of the SCR box, the SCR conversion efficiency value k is monitored in a suspending mode according to the fact that the upstream NOx mass flow rate change value x of the SCR box is larger than a preset change rate value delta M, the rotating speed value of the engine is monitored through the rotating speed sensor, a detection time value t is obtained according to the upstream NOx mass flow rate change value x of the SCR box and the rotating speed value y of the engine (as shown in the figure 3, the detection time value t is obtained through inquiring from MAP), and the controller monitors again according to the fact that the timing time value when the SCR conversion efficiency value k is monitored in a suspending mode is larger than the detection time value t to obtain the SCR conversion efficiency value.

In summary, in the method for controlling the torque limit of the engine according to the invention, by monitoring the mass flow rate change value of the primary exhaust NOx upstream of the SCR, when the mass flow rate of NOx at the upstream of the SCR is too large, namely, the phenomenon of sudden increase or sudden decrease occurs, the monitoring of the SCR conversion efficiency by the ECU is suspended, the problems that the engine torque is limited due to the fact that the mass flow rate of the NOx at the upstream is too large and the engine dynamic performance is influenced due to the excessive NOx emission due to sudden change of the engine load are solved, the driving experience of a driver is improved, in addition, the time for shielding the ECU monitoring function is determined according to the rotating speed and the upstream NOx mass flow rate, and the monitoring function is recovered after the interval time, so that the condition of torque limitation of the engine caused by incapability of quick response due to excessive load change after treatment is avoided, the condition of 'one-off' of engine power degradation caused by excessive emission is avoided, and the driving experience of a driver is improved; meanwhile, the ECU is suspended from monitoring the NOX conversion efficiency within a period of time after mutation, the special condition that NOX emission exceeds the standard when aftertreatment is faultless is effectively distinguished, the power output is ensured to the maximum extent, and the situation of engine torque limitation caused by the fact that aftertreatment cannot respond quickly due to overlarge change of the original emission and the emission exceeds the standard is avoided.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.