阅读说明：本技术 基于scr温度梯度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 based on SCR temperature gradient ) 是由 王通 孙树矗 孙国治 吴速超 高古祥 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,具体涉及一种基于SCR温度梯度控制发动机限扭的方法、装置及系统。本发明的基于SCR温度梯度控制发动机限扭的方法包括获取SCR转换效率值；根据所述SCR转换效率值小于预设转换效率值获取SCR箱上游阶跃的温差值；根据所述SCR箱上游阶跃的温差值小于等于预设温度值判断出发动机故障,控制发动进入限扭模式；或根据所述SCR箱上游阶跃的温差值大于预设温度值暂停对SCR转换效率值监测。本方案中,通过监测SCR上游温度阶跃的偏差值来决定是否暂停ECU对NOX经过SCR转换效率的监控,避免出现“误报”导致的发动机限扭状况,影响驾驶员的驾驶体验,避免扭矩限制一刀切问题,最大程度保证功率输出。(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 temperature gradient. The method for controlling the torque limit of the engine based on the SCR temperature gradient comprises the steps of obtaining an SCR conversion efficiency value; acquiring a temperature difference value of an upstream step of an SCR box according to the condition that the SCR conversion efficiency value is smaller than a preset conversion efficiency value; judging the fault of the engine according to the condition that the temperature difference value of the upstream step of the SCR box is less than or equal to a preset temperature value, and controlling the engine to enter a torque limiting mode; or the monitoring of the SCR conversion efficiency value is suspended according to the fact that the temperature difference value of the upstream step of the SCR box is larger than the preset temperature value. In this scheme, whether suspend ECU to NOX through SCR conversion efficiency's control through the deviation value of monitoring SCR upstream temperature step, avoid appearing "wrong report" the engine limit that leads to turn round the situation, influence driver's driving experience, avoid moment of torsion restriction one cutting the problem, the maximum power output of guaranteeing.)

1. A method for controlling engine torque limit based on SCR temperature gradient, characterized in that the method comprises the following steps:

acquiring an SCR conversion efficiency value;

acquiring a temperature difference value of an upstream step of an SCR box according to the condition that the SCR conversion efficiency value is smaller than a preset conversion efficiency value;

judging the fault of the engine according to the condition that the temperature difference value of the upstream step of the SCR box is less than or equal to a preset temperature value, and controlling the engine to enter a torque limiting mode; or

And pausing the monitoring of the SCR conversion efficiency value according to the fact that the temperature difference value of the upstream step of the SCR box is larger than a preset temperature value.

2. The method of controlling engine torque limits based on an SCR temperature gradient 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 limit based on an SCR temperature gradient of claim 1, wherein the temperature difference value of the step upstream of the SCR tank is obtained as a difference between intake temperature values of the SCR tank respectively obtained at adjacent specified time periods.

4. The method of claim 1, further comprising the following steps after the monitoring of the SCR conversion efficiency value is suspended according to the temperature difference value of the SCR tank upstream step is larger than a preset temperature value:

obtaining an engine rotating speed value;

obtaining a detection time value according to the temperature difference value of the step at the upstream of the SCR box and the rotating speed value of the engine;

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.

5. An apparatus for controlling torque limit of an engine based on an SCR temperature gradient, the apparatus for controlling torque limit of an engine based on an SCR temperature gradient being used to perform the method for controlling torque limit of an engine based on an SCR temperature gradient according to any one of claims 1 to 3, the apparatus for controlling torque limit of an engine based on an SCR temperature gradient 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 a temperature difference value of an upstream step of the SCR tank;

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 the temperature difference value of the upstream step of the SCR box is smaller than or equal to a preset temperature 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 temperature difference value of the upstream step of the SCR box is larger than a preset temperature value.

6. The SCR temperature gradient-based control engine torque limit apparatus of claim 5, wherein the first acquisition 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.

7. The SCR temperature gradient-based control engine torque limit apparatus of claim 6, wherein the second acquisition unit comprises; an SCR box upstream temperature acquisition subunit and a difference value calculation subunit;

the SCR box upstream temperature acquisition subunit is used for respectively acquiring the intake temperature values of the SCR boxes in adjacent specified time periods;

and the difference value operator unit is used for calculating the temperature difference value of the upstream step of the SCR box according to the obtained inlet air temperature values of the SCR boxes in the adjacent specified time periods.

8. The apparatus for controlling engine torque limit based on SCR temperature gradient of claim 7, 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 the control unit pauses monitoring the SCR conversion efficiency value;

the control unit is used for obtaining a detection time value according to the temperature difference value of the step 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.

9. A system for controlling engine torque limit based on SCR temperature gradient, comprising a memory and the device for controlling engine torque limit based on SCR temperature gradient as described in claim 8, the memory having stored therein instructions of the method for controlling engine torque limit based on SCR temperature gradient as described in any one of claims 1 to 4;

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

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

the temperature sensor is arranged at the upstream of the SCR box and is connected with 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 temperature gradient.

Background

At present, in a diesel engine aftertreatment system, an SCR is an important link for controlling the NOX value emission of an engine, however, the engine is often in a complex working condition, when the temperature in an SCR box rises sharply in a short time (for example, the temperature step is too large due to rapid acceleration), NH3 attached to a carrier in the SCR box is released, so that an SCR downstream NOX sensor monitors excessive NOX, an ECU reports a corresponding aftertreatment fault, and then the engine has power-affecting results such as torque limitation, limping home and the like, and when the temperature in the SCR rises for a period of time, NH3 is stored less, and the NOX value is also reduced correspondingly until the NOX value is lower than a fault threshold value.

Disclosure of Invention

The invention aims to at least solve the problem that the dynamic property of an engine and the driving experience of a driver are influenced due to the false alarm phenomenon caused by ammonia leakage in a short time due to sudden change of the working condition of the engine in the prior art. The purpose is realized by the following technical scheme:

the first aspect of the invention provides a method for controlling the torque limit of an engine based on an SCR temperature gradient, which comprises the following steps:

acquiring an SCR conversion efficiency value;

acquiring a temperature difference value of an upstream step of an SCR box according to the condition that the SCR conversion efficiency value is smaller than a preset conversion efficiency value;

judging the fault of the engine according to the condition that the temperature difference value of the upstream step of the SCR box is less than or equal to a preset temperature value, and controlling the engine to enter a torque limiting mode; or

And pausing the monitoring of the SCR conversion efficiency value according to the fact that the temperature difference value of the upstream step of the SCR box is larger than a preset temperature value.

According to the method for controlling the engine torque limit based on the SCR temperature gradient, whether the ECU monitors the SCR conversion efficiency of NOX or not is determined by monitoring the deviation value of the SCR upstream temperature step, and the influence on the driving experience of a driver due to the engine torque limit condition caused by 'false alarm' is avoided.

In addition, the method for controlling the torque limit of the engine based on the SCR temperature gradient 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, the step temperature difference value obtained upstream of the SCR boxes is a difference between intake air temperature values of the SCR boxes respectively obtained at adjacent specified time periods.

In some embodiments of the present invention, after the monitoring of the SCR conversion efficiency value is suspended according to the temperature difference value of the step upstream of the SCR tank being greater than the preset temperature value, the method further comprises the following steps:

obtaining an engine rotating speed value;

obtaining a detection time value according to the temperature difference value of the step at the upstream of the SCR box and the rotating speed value of the engine;

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 torque limit of an engine based on an SCR temperature gradient is further provided, where the apparatus is configured to perform the method for controlling torque limit of the engine based on the SCR temperature gradient, and the apparatus includes: 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 a temperature difference value of an upstream step of the SCR tank;

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 the temperature difference value of the upstream step of the SCR box is smaller than or equal to a preset temperature 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 temperature difference value of the upstream step of the SCR box is larger than a preset temperature 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 temperature acquisition subunit and a difference value calculation subunit;

the SCR box upstream temperature acquisition subunit is used for respectively acquiring the intake temperature values of the SCR boxes in adjacent specified time periods;

and the difference value operator unit is used for calculating the temperature difference value of the upstream step of the SCR box according to the obtained inlet air temperature values of the SCR boxes in the adjacent specified time periods.

In some embodiments of the present invention, the apparatus for controlling engine torque limit based on SCR temperature gradient 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 the control unit pauses monitoring the SCR conversion efficiency value;

the control unit is used for obtaining a detection time value according to the temperature difference value of the step 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 based on the SCR temperature gradient, which comprises a memory and the device for controlling the torque limit of the engine based on the SCR temperature gradient, wherein the memory stores the instruction of the method for controlling the torque limit of the engine based on the SCR temperature gradient;

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

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

the temperature sensor is arranged at the upstream of the SCR box and is connected with 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 based on an SCR temperature gradient, according to an embodiment of the invention;

FIG. 2 schematically illustrates a schematic diagram of a method of controlling engine torque limit based on an SCR temperature gradient, according to another embodiment of the present disclosure;

FIG. 3 schematically illustrates a MAP data plot of a method of controlling engine torque limit based on an SCR temperature gradient, according to an embodiment of the present disclosure;

FIG. 4 schematically illustrates a logic diagram for a method of controlling engine torque limit based on SCR temperature gradients, in accordance with an embodiment of the present disclosure;

FIG. 5 schematically illustrates a functional block diagram of an apparatus for controlling engine torque limit based on SCR temperature gradients, in accordance with an embodiment of the present invention;

FIG. 6 schematically shows a functional block diagram of a first acquisition unit of an apparatus for controlling engine torque limit based on SCR temperature gradients, according to an embodiment of the present invention;

fig. 7 schematically shows a functional block diagram of a second acquisition unit of an apparatus for controlling an engine torque limit based on an SCR temperature gradient according to an 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 temperature acquisition subunit; 202: a difference value calculating 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 based on an SCR temperature gradient, which can avoid the influence on the driving experience of a driver due to the torque limit condition of the engine caused by 'false alarm'.

As shown in fig. 1 to 4, the method for controlling the torque limit of the engine based on the SCR temperature gradient in the present embodiment includes the following steps:

s1, acquiring an SCR conversion efficiency value k;

s2, acquiring a temperature difference value x of an upstream step of the SCR tank according to the condition that the SCR conversion efficiency value k is smaller than a preset conversion efficiency value k 1;

s3, judging the fault of the engine according to the fact that the temperature difference value x of the upstream step of the SCR box is smaller than or equal to a preset temperature value delta T, and controlling the engine to enter a torque limiting mode; or

S4, monitoring the SCR conversion efficiency value is suspended according to the fact that the temperature difference value x of the upstream step of the SCR box is larger than a preset temperature value delta T.

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 a temperature difference value x of an upstream step of the SCR tank according to the condition that the SCR conversion efficiency value k is smaller than a preset conversion efficiency value k 1;

s3, judging the fault of the engine according to the fact that the temperature difference value x of the upstream step of the SCR box is smaller than or equal to a preset temperature value delta T, 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 a temperature difference value x of an upstream step of the SCR tank according to the condition that the SCR conversion efficiency value k is smaller than a preset conversion efficiency value k 1;

s4, monitoring the SCR conversion efficiency value k is suspended according to the fact that the temperature difference value x of the upstream step of the SCR box is larger than a preset temperature value delta T.

In some embodiments of the present invention, after the monitoring of the SCR conversion efficiency value is suspended according to the temperature difference value x of the SCR tank upstream step is greater than the preset temperature value Δ T, the method further includes the following steps:

that is, when the SCR conversion efficiency monitoring is suspended in step S4, the method further includes the steps of:

s401, obtaining an engine rotating speed value y;

s402, obtaining a detection time value t according to the temperature difference value x of the upstream step of the SCR box and the engine rotating speed value y;

s403, according to the SCR conversion efficiency value k which is monitored and started to be timed, obtaining a pause time value, and according to the fact that the pause time value is larger than the detection time value t, obtaining the SCR conversion efficiency value again.

As shown in fig. 3, the detection time value t is obtained by looking up from the MAP, and when x is 20 and y is 800, t is 70 s.

In the embodiment, when the time interval exceeds the detection time t, the ECU monitors the SCR conversion efficiency again to ensure that the engine torque limit condition caused by the excessive emission due to the ammonia leakage after the sudden change of the working condition can not occur.

According to the method for controlling the torque limitation of the engine based on the SCR temperature gradient, whether the ECU monitors the SCR conversion efficiency of NOX or not is determined by monitoring the deviation value of the SCR upstream temperature step, the situation that the engine torque limitation is caused by 'false alarm' and the driving experience of a driver is influenced is avoided, the sudden change of the working condition of the engine is determined by the SCR temperature gradient, the function of monitoring the conversion efficiency is suspended within a period of time after the sudden change, the problem of torque limitation and cutting is avoided, and the power output is ensured to the maximum extent.

In some embodiments of the present invention, in step S1, the obtaining the SCR conversion efficiency value includes;

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, the step temperature difference value obtained upstream of the SCR boxes is a difference between intake air temperature values of the SCR boxes respectively obtained at adjacent specified time periods.

In this embodiment, the stepped temperature difference value upstream of the SCR box, i.e. the difference between the intake air temperature values of the SCR box obtained twice in the same specified time period, is obtained, for example, in 2s, the intake air temperature value of the SCR box obtained in the first 2s is 70 ℃, the intake air temperature value of the SCR box obtained in the second 2s (i.e. in 2s after the previous 2s is 4s) is 80 ℃, and the stepped temperature difference value upstream of the SCR box is equal to 80-70 which is equal to 10 ℃, and the time value of the specific specified time period is set according to actual needs.

As shown in fig. 5 to 7, another aspect of the present invention also provides an apparatus for controlling torque limit of an engine based on an SCR temperature gradient, which is used for executing the above method for controlling torque limit of an engine based on an SCR temperature gradient, and the apparatus for controlling torque limit of an engine based on an SCR temperature gradient 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 obtaining unit 2 is used for obtaining a temperature difference value of an upstream step of the SCR tank;

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 the temperature difference value of the upstream step of the SCR box is smaller than or equal to a preset temperature 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 temperature difference value of the upstream step of the SCR box is larger than a preset temperature value.

In some embodiments of the present invention, as shown in fig. 6, the first obtaining unit 1 includes: 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 n;

the downstream acquiring subunit 102 is used for acquiring an SCR downstream NOx gas concentration value n 1;

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 present invention, as shown in fig. 7, the second obtaining unit 2 includes; an SCR tank upstream temperature acquisition subunit 201 and a difference calculation subunit 202;

the SCR box upstream temperature acquiring subunit 201 is configured to acquire intake temperature values of the SCR boxes in adjacent specified time periods, respectively;

the difference value operator unit 202 is configured to calculate a temperature difference value of an upstream step of the SCR box according to the obtained intake air temperature values of the SCR boxes in the adjacent specified time periods.

In the embodiment, for example, the specified time period is 2s, the intake air temperature value of the SCR box obtained at the first 2s is 70 ℃, the intake air temperature value of the SCR box obtained at the second 2s (i.e. 2s after the previous 2s is the 4 th s) is 80 ℃, the temperature difference value of the step at the upstream of the SCR box is equal to 80-70-10 ℃, and the time value of the specific specified time period is set according to actual needs.

As shown in fig. 3 and 5, in some embodiments of the present invention, the apparatus for controlling torque limit of an engine based on an SCR temperature gradient further includes: a third acquiring unit 4 and a fourth acquiring unit 5;

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

the fourth obtaining unit 5 is configured to obtain a pause time value when the control unit 3 suspends monitoring of the SCR conversion efficiency value, that is, when the control unit 3 suspends monitoring of the SCR conversion efficiency value, a time value in the period of time, that is, a pause time value, is obtained by the fourth obtaining unit 5;

the control unit 3 is configured to obtain a detection time value t according to the temperature difference value x of the step upstream of the SCR tank and the engine speed value y, and control the first obtaining unit 1 to restart according to the fact that the pause time value obtained by the fourth obtaining unit 5 is greater than the detection time value t.

The invention also provides a system for controlling the torque limit of the engine based on the SCR temperature gradient, which comprises a memory and the device for controlling the torque limit of the engine based on the SCR temperature gradient, wherein the memory stores the instruction of the method for controlling the torque limit of the engine based on the SCR temperature gradient;

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

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

the temperature sensor is arranged at the upstream of the SCR box and is connected with 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 a value k1, the temperature sensor is controlled to measure an intake air temperature value within a specified time period according to the condition that the SCR conversion efficiency value k is smaller than a preset conversion efficiency value k1, the controller calculates a temperature difference value x of an upstream step of an SCR box, the controller judges an engine fault according to the condition that the temperature difference value x of the upstream step of the SCR box is smaller than or equal to a preset temperature value delta T, the engine is controlled to enter a torque limiting mode, and control is; or after the controller calculates the temperature difference value x of the SCR box upstream step, the SCR conversion efficiency value k is monitored in a suspending mode according to the fact that the temperature difference value x of the SCR box upstream step is larger than a preset temperature value delta T, the rotating speed value of the engine is monitored through the rotating speed sensor, a detection time value T is obtained according to the temperature difference value x of the SCR box upstream step 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, according to the method for controlling the torque limit of the engine based on the SCR temperature gradient, whether the ECU suspends monitoring of the SCR conversion efficiency of NOX is determined by monitoring the deviation value of the SCR upstream temperature step, thereby avoiding the occurrence of the engine torque limit condition caused by "false alarm" and affecting the driving experience of the driver, determining the sudden change of the engine working condition by the SCR temperature gradient, suspending the conversion efficiency monitoring function within a period of time after the sudden change, avoiding the torque limit-one-off problem, and ensuring the power output to the maximum extent.

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.