Idle speed reduction control method
By performing carbon loading and regeneration mode control in preset operating conditions in diesel vehicles, the problem of incomplete coverage of idle-down tests in the prior art is solved, and the effectiveness of the test results and the service life of the particle trap are improved.
Patent Information
- Application Number
- CN202310479931.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-04-28
- Publication Date
- 2025-01-03
- Estimated Expiration
- 2043-04-28
AI Technical Summary
The existing idle-down test cannot cover the various idle-down conditions of the vehicle, resulting in low validity of the test results.
Carbon loading is performed under the preset first operating condition of the engine until the carbon load in the particle trap reaches the target carbon load, and the particle trap is controlled to enter regeneration mode under the second operating condition, and then When the idle-down condition is met, the engine is reduced to the idle operating condition until the particle trap exits the regeneration mode and completes the idle-down control process.
This method can cover the vehicle's various idle-down conditions as much as possible, improve the effectiveness of test results, ensure the accuracy of uniform carbon loading of the particle trap and the bed temperature detection, reduce regeneration frequency and fuel consumption, and extend the use of catalysts life.
Smart Images
Figure CN116447022B_ABST
Abstract
Description
Technical Field
[0001] The present application belongs to the technical field of diesel vehicles, and in particular, relates to an idle speed reduction control method. Background Art
[0002] The upgraded vehicle emission regulations not only raise the emission requirements for particulate matter (PM), but also increase the total number of particulate matter with a diameter of more than 23nm. In order to comply with current emission regulations, a particulate filter (DPF) is usually added to the exhaust system of the car to deal with particulate matter in the car exhaust and reduce the emission of particulate matter.
[0003] DPF is not only used to capture particulate matter, but also to periodically regenerate particulate matter when the particulate matter accumulates to a certain level. The regeneration process is to increase the exhaust temperature so that the particulate matter in the DPF reacts with the exhaust oxygen under the action of the catalyst, thereby achieving the purpose of removing particulate matter. After the regeneration, the DPF can continue to capture particulate matter, so that the vehicle's emissions can always meet the requirements of relevant regulations.
[0004] During the DPF regeneration process, as the exhaust temperature rises, the accumulated particulate matter will burn violently, generating a large amount of heat. If the engine drops to the idle (DTI) condition at this time, the exhaust flow rate will be reduced in vain, making it impossible to remove the generated heat in time, causing the internal temperature of the DPF to rise sharply, and there will be a large temperature difference between different parts of the DPF. Because of this, the DPF will also be regenerated under the idle condition, and will be subjected to a high heat load and thermal stress, making the DPF body very prone to melting and cracking problems, and the excessively high temperature will also easily cause the catalyst to age too quickly.
[0005] Although the control conditions for DPF regeneration under reduced idle conditions can be determined through reduced idle tests, the current reduced idle tests cannot cover a variety of reduced idle conditions of the vehicle, resulting in low validity of the test results. Summary of the invention
[0006] The present application provides an idle speed reduction control method, which can improve the effectiveness of test results.
[0007] In a first aspect, the present application provides an idle speed reduction control method, comprising:
[0008] The following steps of reduced idle speed control are performed according to the predetermined target temperature:
[0009] When the engine is in a preset first operating condition, a carbon loading operation is performed on the pretreated particulate filter until the carbon load in the particulate filter reaches a target carbon load; an exhaust outlet of the engine is connected to an exhaust inlet of the particulate filter, and the target carbon load is a limit carbon load of the particulate filter at a target temperature;
[0010] When the engine is in a preset second operating condition, the particulate filter is controlled to enter a regeneration mode; the exhaust flow rate of the engine in the second operating condition reaches a preset exhaust flow rate threshold;
[0011] In the regeneration mode, when the particulate filter meets the idle speed reduction conditions, the engine is controlled to reduce to the idle speed condition until the particulate filter exits the regeneration mode, completing the current idle speed reduction control process.
[0012] Compared with the prior art, the present application has the beneficial effect that after the target temperature is determined, the idle speed reduction control step can be performed according to the target temperature. Specifically, carbon loading is performed first, that is, when the engine is in the preset first working condition, the exhaust gas of the engine can flow through the pre-treated particulate trap, that is, the exhaust outlet of the engine is connected to the exhaust inlet of the particulate trap, so that the carbon particles in the exhaust gas can be accumulated in the particulate trap; when the carbon load in the particulate trap reaches the target carbon load, it indicates that the carbon loading is over. In order to improve the harshness of the idle speed reduction control, the target carbon load here is the limit carbon load at the target temperature. At the same time, in order to cover the idle speed reduction working condition of the vehicle as comprehensively as possible, before triggering the particulate trap to enter the regeneration mode, the working condition in which the exhaust flow rate of the engine is large enough can be selected as the initial working condition of the idle speed reduction control. Specifically, the initial working condition can be set to the second working condition. When the engine is in the preset second working condition, that is, when the exhaust flow rate of the engine reaches the preset exhaust flow rate threshold, the particulate trap that has completed carbon loading can be controlled to enter the regeneration mode. During the regeneration of the particulate filter, when the particulate filter meets the idle speed reduction control condition, the engine can be controlled to enter the idle speed condition from the second working condition until the particulate filter exits the regeneration mode, marking the completion of the current idle speed reduction control process. It can be understood that the exhaust flow rate of the engine in the second working condition is much greater than the exhaust flow rate in the idle speed condition, that is, the present application is to expand the exhaust flow rate difference of the engine in the two working conditions, thereby covering as many idle speed reduction conditions of the vehicle as possible and improving the validity of the test results. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0014] Figure 1 is a schematic diagram of the arrangement of thermocouples in a particle collector provided in an embodiment of the present application;
[0015] Figure 2 is a schematic diagram of the arrangement of thermocouples in a cross section provided in an embodiment of the present application;
[0016] Figure 3 It is a flow chart of the idle speed reduction control steps provided in an embodiment of the present application. DETAILED DESCRIPTION
[0017] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.
[0018] In the related art, the current idle reduction test cannot cover various idle reduction conditions of the vehicle, resulting in low validity of the test results.
[0019] In order to solve this problem, the present application proposes an idle speed reduction control method, which can cover a variety of idle speed reduction conditions of the vehicle as much as possible and improve the effectiveness of the test results. The idle speed reduction control method proposed in the present application will be described below through specific embodiments.
[0020] The idle speed reduction control method provided in the embodiment of the present application can be implemented by an idle speed reduction control device. The idle speed reduction control device includes an engine pedestal / vehicle hub, a diesel oxidation catalytic converter, and a particulate filter connected in sequence. The engine pedestal / vehicle hub is used to collect the exhaust temperature of the engine, the pressure difference at both ends of the particulate filter, and the temperature information of each thermocouple set in the particulate filter.
[0021] In some embodiments, in order to reduce the impact of the packaging design of the idle speed reduction control device on the uniformity of carbon loading, the exhaust system can be designed according to the computational fluid dynamics (CFD) simulation results of the exhaust system of the engine. Specifically, it can be determined first that uniform carbon loading requires the exhaust system to meet a preset condition. As an example only, it is assumed that the preset condition is that the fluid velocity uniformity coefficient UI at 10 mm from the exhaust inlet of the particulate trap is greater than 0.95, and the eccentricity VI is less than 0.5. Then, when it is determined that the CFD simulation results of the exhaust system meet the preset conditions, it is considered that uniform carbon loading can be achieved based on the current idle speed reduction control device, that is, experiments can be conducted based on such an idle speed reduction control device.
[0022] In some embodiments, the particle trap may be provided with multiple thermocouples. By properly setting the placement of the thermocouples, the bed temperature at different positions of the particle trap may be accurately determined. Specifically, the particle trap may include N thermocouples, where N is a positive integer greater than or equal to 9. The arrangement of the N thermocouples is as follows:
[0023] Step A1: n thermocouples are arranged in a cross section at a first preset depth from an exhaust outlet of a particulate trap according to a preset rule.
[0024] In order to accurately determine the highest temperature that may occur in the particulate filter in the regeneration mode, the airflow distribution of the engine exhaust in the particulate filter can be determined based on the CFD simulation results of the exhaust system, and then the position where the highest temperature can be detected can be determined based on the airflow distribution. When setting the thermocouple, it is necessary to extend the thermocouple from the exhaust outlet of the particulate filter; therefore, in order to accurately set the thermocouple that can detect the highest temperature, the first preset depth from the exhaust outlet of the particulate filter can be determined based on the position where the highest temperature can be detected.
[0025] In order to further improve the accuracy of the maximum temperature detection, multiple thermocouples can be set to detect the maximum temperature. Specifically, n thermocouples can be set according to a preset rule within a cross section at a first preset depth from the exhaust outlet of the particulate trap, where n is a positive integer and 7≤n<N.
[0026] Step A2: m thermocouples are arranged at equal intervals on a central axis extending from the center point of the cross section to the exhaust inlet of the particulate trap.
[0027] In addition to detecting the highest temperature, it is also necessary to detect the bed temperature of the particle collector at different positions. Therefore, m thermocouples can be set to the exhaust inlet starting from the location of the cross section, where m+n=N. For these m thermocouples, they can be equidistantly set on the central axis extending from the center point of the cross section to the exhaust inlet of the particle collector. Of course, they can also be set non-equidistantly according to the airflow characteristics.
[0028] In some embodiments, the setting rules of n thermocouples, that is, the preset rules, may include: setting one thermocouple at the center point of the cross-section; dividing the cross-section into four sectors according to the exhaust gas concentration area; setting one thermocouple at a specified position of each sector that does not include the exhaust gas concentration area; and concentrating n-4 thermocouples in the sector that includes the exhaust gas concentration area.
[0029] As can be seen from the above embodiments, the airflow has agglomeration property. In order to accurately detect the highest temperature in the particulate filter based on fewer thermocouples, a thermocouple can be set at the center point of the cross section first; then, the exhaust gas aggregation area in the cross section is determined according to the CFD simulation results of the exhaust system, and n-1 thermocouples are set in the exhaust gas aggregation area as much as possible.
[0030] Specifically, the cross section can be divided into four sectors by dividing the sectors, one of which includes the exhaust gas gathering area. Although n-1 thermocouples can be directly set in the sector including the exhaust gas gathering area, in order to avoid inaccurate CFD simulation results of the exhaust system, one thermocouple can be set at each designated position in the other three sectors; and n-4 thermocouples can be set in the sector including the exhaust gas gathering area.
[0031] In some embodiments, the locations of the m thermocouples may also correspond to exhaust gas gathering areas.
[0032] For example only, see Figure 1 , Figure 1 The figure shows an arrangement of thermocouples in a particle trap. The first preset depth is 15 mm as determined by the CFD simulation results of the exhaust system. The particle trap has 17 thermocouples, with n being 12 and m being 5.
[0033] Among them, n thermocouples are set: No. 1 to No. 9 and No. 13 to No. 15 thermocouples are concentrated in the cross section of 15mm away from the exhaust outlet. Figure 2 , Figure 2 The schematic diagram of the arrangement of 12 thermocouples in the cross section is shown. Obviously, the exhaust gas concentration area is in sector a, so the thermocouples in sector a are arranged more concentratedly.
[0034] m thermocouples are set: Thermocouples No. 10 to No. 12 and No. 17 are set according to the airflow gathering area and airflow characteristics of the cross section, and the setting positions are all corresponding to thermocouple No. 2. Among them, thermocouple No. 17 is 10mm away from the cross section; thermocouple No. 12 is 49mm away from the cross section; thermocouple No. 11 is 99mm away from the cross section; thermocouple No. 10 is 198mm away from the cross section. Because the exhaust gas gathering area is closer to thermocouple No. 15, a thermocouple, namely thermocouple No. 16, can also be set at the position corresponding to thermocouple No. 15.
[0035] The idle speed reduction control device provided in the present application can achieve uniform carbon loading and improve the accuracy of bed temperature detection at various positions of the particulate trap.
[0036] Next, the idle speed reduction control method proposed in the present application will be described based on the above-mentioned idle speed reduction control device.
[0037] The idle speed reduction control method proposed in the present application may include at least one idle speed reduction control process, and the idle speed reduction control process can be understood as an idle speed reduction control cycle. Each idle speed reduction control cycle may correspond to a target temperature. The target temperature is the temperature that the exhaust inlet of the particulate filter needs to reach in the regeneration mode, which determines the target carbon load in the idle speed reduction control cycle. The carbon load is a very critical indicator for the particulate filter in the regeneration mode. Too low a carbon load will make it difficult for the carbon particles in the particulate filter to ignite each other in the regeneration mode, that is, the regeneration is incomplete; at the same time, it will also cause frequent regeneration and increase fuel consumption. However, too high a carbon load will cause the temperature inside the particulate filter in the regeneration mode to be too high and / or the temperature difference of the bed temperature at different positions is too large, which may easily cause damage to the particulate filter body. Therefore, in order to achieve safe and active regeneration of the particulate filter, a safe and appropriate carbon load can be set according to different temperatures.
[0038] In some embodiments, under the premise of ensuring that the particle trap body is not damaged, in order to reduce the regeneration frequency and reduce fuel consumption, at each temperature, the maximum carbon load (also called the limit carbon load) at which the particle trap can achieve safe active regeneration can be determined as the safe and appropriate carbon load at the corresponding temperature. That is, the target carbon load can be set according to the limit carbon load of the particle trap at the target temperature.
[0039] In some embodiments, the target temperature can be determined from a preset idle speed reduction matrix. The idle speed reduction matrix records the corresponding relationship between each benchmark test temperature and the carbon load, and the benchmark test temperature is determined according to the temperature resistance boundary of the body of the particulate trap and the temperature resistance boundary of the catalyst. The carbon load corresponding to each benchmark test temperature is the limit carbon load of the particulate trap at the benchmark test temperature.
[0040] In some embodiments, in addition to recording the baseline test temperature, the idle reduction test matrix can also record the extended test temperature, that is, each baseline test temperature is expanded to obtain more testable temperatures, which helps to explore the harsh working conditions under each carbon loading.
[0041] Specifically, for each benchmark test temperature, at least two extended test temperatures may be determined according to the benchmark test temperature and a preset temperature value, and the benchmark test temperature is a median value of the corresponding extended test temperatures.
[0042] As an example only, assuming that the base test temperature is 570°C and the preset temperature value is 10°C, the extended test temperature can be determined based on 570°C and 10°C. For example, a pair of extended test temperatures can be determined by 570±a10°C, and when a=1, a pair of extended test temperatures of 560°C and 580°C can be determined.
[0043] Among them, the smaller the preset temperature value, the more extended test temperatures can be determined, which is helpful to explore the harsh working conditions under each carbon loading, but the corresponding test time is longer. The larger the setting of a, the more extended test temperatures can be determined, and the longer the test time. And it should be noted that if the value of a is too large, the determined extended test temperature may far exceed the temperature corresponding to the harsh working conditions under the carbon loading, so the value of a is not the larger the better. In general, whether it is the setting of the preset temperature value or the setting of a, it can be determined according to their respective characteristics and actual conditions, and is not limited in this application.
[0044] After obtaining the extended test temperature corresponding to each benchmark test temperature, the idle speed reduction test matrix can be updated according to the extended test temperature corresponding to each benchmark test temperature to obtain a new idle speed reduction test matrix. That is, the extended test temperature is used as a new benchmark test temperature and added to the original idle speed reduction test matrix to obtain an idle speed reduction test matrix including the new benchmark test temperature (extended test temperature) and the originally set benchmark test temperature.
[0045] As an example only, the idle speed reduction test matrix may be as shown in Table 1:
[0046] Table 1 Idle speed reduction test matrix
[0047]
[0048]
[0049] In Table 1, "√" indicates the base test temperature, and + indicates the new base test temperature (extended test temperature). When each base test temperature is extended, the preset temperature value is 10°C, and a = 1. Of course, if there are unnecessary test temperatures in each extended test temperature, they can be removed.
[0050] As an example only, assume that the extended test temperature is 550°C at a carbon loading of 7 g / L. Since the temperature of 550°C is relatively low, the test is not necessary. In this case, it can be removed to shorten the time required for the test method of this application.
[0051] In some embodiments, the rule for determining the target temperature based on the idle speed reduction test matrix may be: for multiple benchmark test temperatures (including newly added and original) of the idle speed reduction test matrix, the benchmark test temperature with the lowest temperature without the idle speed reduction control step may be sequentially determined as the target temperature. The reason for using this rule to determine the target temperature is to perform the test at the low temperature in the idle speed reduction test matrix, which is conducive to the multiple use of the particulate filter and reduces the test cost.
[0052] As an example, taking the idle speed reduction test matrix in Table 1 as an example, for the first idle speed reduction control cycle, 550°C can be used as the target temperature; for the second idle speed reduction control cycle, 560°C can be used as the target temperature; for the third idle speed reduction control cycle, 560°C can be used as the target temperature. And so on, until 630°C is used as the target temperature.
[0053] It can be considered that there are several reference test temperatures (including newly added and original) corresponding to several idle speed reduction control cycles. In this example, there are twelve idle speed reduction control cycles.
[0054] In some embodiments, in addition to determining the test temperature based on the temperature, the initial reference test temperature may be tested first, and then the target temperature may be determined from a plurality of newly added reference test temperatures (i.e., extended test temperatures) in turn according to the target temperature determination rule in the aforementioned embodiment for testing. In short, when determining the target temperature, the principle of reusing the particle trap may be adhered to, thereby reducing the test cost.
[0055] In some embodiments, in each idle speed reduction control cycle, the idle speed reduction control step executed can refer to Figure 3 The idle speed reduction control step may be performed according to a predetermined target temperature, and specifically includes:
[0056] Step 110 : performing a carbon loading operation on the pretreated particulate filter until the carbon loading in the particulate filter reaches a target carbon loading.
[0057] In order to avoid the influence of carbon components accumulated by rapid carbon accumulation methods such as adjusting the engine's fuel injection amount or adjusting the intake volume on the test results, the embodiment of the present application adopts a normal carbon accumulation method for carbon loading, that is, the preset first operating condition is selected as the operating condition of the engine during carbon accumulation.
[0058] In some embodiments, the first operating condition is a steady-state operating condition, which refers to an operating condition in which the engine can make the carbon accumulation rate of the particulate trap reach a preset rate threshold, and the temperature of the first designated thermocouple in the particulate trap is less than a preset first temperature threshold, for example, less than 330° C. The first designated thermocouple refers to a thermocouple used to detect the exhaust inlet temperature T4 of the diesel oxidation catalytic converter and the exhaust inlet temperature T5 of the particulate trap.
[0059] As an example only, assuming that the rate threshold is 4 g / h, the specific parameters of the first working condition may be as shown in Table 2:
[0060] Table 2 Parameters of the first working condition
[0061]
[0062] When the engine is in the first operating condition, the carbon loading operation can be performed on the pretreated particulate filter, that is, the engine being in the first operating condition can be used as a sign of starting the carbon loading operation. The purpose of pre-treating the particulate filter is to clear impurities in the particulate filter, thereby reducing the difference in axial carbon distribution in the particulate filter during the carbon loading process and improving the reliability of the carbon loading.
[0063] In some embodiments, the particle collector is pre-treated by the following steps:
[0064] Step B1: When it is determined that the particulate filter is not damaged, remove impurities in the particulate filter.
[0065] Step B2: When it is determined that the particulate filter is damaged, replace the particulate filter with one of the same type, and remove impurities in the particulate filter of the same type.
[0066] It can be seen from the above content that more than one idle reduction control cycle can be set. Therefore, when the idle reduction control cycle exceeds one, in order to reduce the test cost, the test can be carried out based on the same particulate filter within more than two idle reduction control cycles.
[0067] Inevitably, if the control conditions in the first idle speed reduction control cycle are relatively harsh, it is very easy to cause the particulate filter to be damaged in the first idle speed reduction control cycle. In this case, it is not appropriate to continue to use the same particulate filter for the control steps in the subsequent idle speed reduction control cycles.
[0068] In order to solve the above problems, before each pretreatment, it is possible to determine whether the particulate filter is damaged. If it is not damaged, it means that the control steps in the subsequent idle speed reduction control cycle can still be performed based on the current particulate filter; but if it is damaged, it means that the particulate filter should be replaced to ensure the accuracy and effectiveness of the test results. When replacing the particulate filter, in order to minimize the variables in subsequent tests, the particulate filter of the same model can be replaced.
[0069] Whether it is an intact particulate filter or a replaced particulate filter, there are inevitably impurities, such as carbon particles, moisture or organic matter, etc. In order to reduce the impact of impurities on the test results, the impurities in the particulate filter can be removed.
[0070] In some embodiments, the pretreatment may be performed on an engine bench / vehicle hub or in a muffle furnace. Specifically, in order to effectively remove impurities, the pretreatment may be: heating the particle collector to 600 degrees Celsius for two hours.
[0071] During the process of carbon loading the particulate trap after pretreatment, if the carbon loading in the particulate trap reaches the target carbon loading, the current carbon loading operation may be terminated.
[0072] In some embodiments, in order to accurately measure whether the carbon loading operation is completed, the weight of the particulate trap before and after the carbon loading may be determined to determine whether the carbon loading reaches the target carbon loading.
[0073] Among them, the first weight of the particulate filter before carbon loading is m 1 , is the weight of the particle collector after pretreatment, when the temperature drops to 200℃~300℃, measured by an electronic balance. The second weight of the particle collector after weighing carbon loading, m 2 It is the weight obtained by using an electronic balance after carbon loading, removing the moisture in the particulate filter (the carrier, catalyst and carbon easily absorb water), and maintaining the temperature of the particulate filter at 200℃~300℃ for 2h.
[0074] In order to improve the accuracy of the target carbon loading determination, the temperature of the particulate trap when the two weights are measured may be the same, for example, 300° C.
[0075] In some embodiments, since the thermocouple is easily damaged, in order to ensure the validity of the subsequent test results, 1 Before weighing, a handheld temperature measuring device can be used to detect the benchmark test temperature inside the particle collector; when the temperature difference between the thermocouple and the benchmark test temperature is greater than the preset temperature difference threshold, the thermocouple is considered damaged. At this time, the thermocouple should be replaced and weighed to obtain m 1 .
[0076] This method can not only ensure the accuracy of temperature detection, but also ensure m 1 In summary, this method can improve the accuracy of test results from aspects such as temperature detection accuracy, weighing accuracy and loading reliability.
[0077] Accordingly, the structure of the particulate collector may also be improved. For example, the exhaust outlet of the particulate collector may adopt an end cone with a detachable clamp to facilitate replacement of the thermocouple.
[0078] In some embodiments, it should be noted that the weighing m 2 The timing can be when the current carbon accumulation of the particulate filter is predicted to reach the target carbon accumulation based on the current carbon accumulation rate. 2 After that, if m 2 If the target carbon loading has not been reached, carbon loading can be continued. 2Approaching the target carbon loading. In the best case, m 2 Equal to the target carbon load, but this condition is obviously too harsh, so a reasonable carbon load fluctuation range can be determined based on the target carbon load. 2 If the carbon load falls within the carbon load fluctuation range, it is considered that the current carbon load in the particulate filter reaches the target carbon load, and the subsequent experimental steps can be performed.
[0079] Step 120: When the engine is in a preset second operating condition, control the particulate filter to enter a regeneration mode.
[0080] In order to cover the vehicle's idle speed reduction conditions as comprehensively as possible, before triggering the regeneration mode, a condition in which the exhaust flow rate of the engine is large enough can be selected as the initial condition.
[0081] Specifically, a preset exhaust flow rate threshold value may be determined first, and whether the engine is in the initial operating condition may be determined based on whether the scheduled flow rate of the engine reaches the preset exhaust flow rate threshold value. In order to facilitate the distinction from the operating condition in the aforementioned carbon loading step, this operating condition may be recorded as the second operating condition. The preset exhaust flow rate threshold value may be determined based on the maximum exhaust flow rate of the engine, for example, the preset exhaust flow rate threshold value may be determined based on 75% of the maximum exhaust flow rate.
[0082] As an example only, the second operating condition parameters may be as shown in Table 3:
[0083] Table 3 Parameters of the second working condition
[0084]
[0085] When the engine is in the second operating condition, the particulate filter is controlled to enter the regeneration mode, which can cover the various idle speed reduction conditions of the vehicle as comprehensively as possible. Specifically, the engine can be controlled to warm up for 5 minutes at a steady-state condition of 2500rpm@20N·m, and then transition to a steady-state condition of 2500rpmm@330N·m within 30 seconds, and after stabilization for 30 seconds, the particulate filter is controlled to enter the regeneration mode.
[0086] Step 130: In the regeneration mode, when the particulate filter meets the idle speed reduction condition, the engine is controlled to reduce to the idle speed condition until the particulate filter exits the regeneration mode, thereby completing the control steps in the current idle speed reduction control cycle.
[0087] After the particulate filter enters the regeneration mode, it can be determined whether the particulate filter meets the corresponding idle speed reduction condition to accurately determine the timing of controlling the engine to enter the idle speed condition from the second working condition. When the timing is right, the engine can be reduced to the idle speed condition until the particulate filter completes regeneration and exits the regeneration mode. This also marks the completion of the control steps of a idle speed reduction control cycle. Among them, controlling the engine to reduce to the idle speed condition refers to controlling the engine to enter the idle speed condition from the second working condition.
[0088] In some embodiments, after the particulate filter is controlled to enter the regeneration mode, the exhaust gas inlet temperature can be raised to the target temperature in order to complete the regeneration. In the process of raising the temperature, if the heating rate is too fast, it is easy to cause the bed temperature of the particulate filter to be low, and the temperature of the thermocouple at the rear end of the particulate filter 15mm cannot be made equal to the target temperature (the temperature rises too fast, and the temperature conduction at each position of the particulate filter is uneven); but if the heating rate is too low, the heating time will be long, resulting in the carbon particles in the particulate filter being burned too quickly. Obviously, whether the heating rate is too high or too low, it will affect the validity of the test results.
[0089] In order to solve the above problem, different heating rates may be set for different exhaust inlet temperature ranges, so that the temperature can be raised in a shorter time while ensuring the accuracy of bed temperature detection at various positions of the particulate filter.
[0090] Just as an example, when the target temperature is less than 450°C, the heating rate is set to 5°C / s; when the target temperature is ≥450°C, the heating rate is set to 2°C / s. In other words, the heating rate is inversely proportional to the average temperature value of the exhaust inlet temperature range. For exhaust inlet temperature ranges with lower average temperature values, the possibility of uneven temperatures at various locations of the particulate filter is lower; based on this, in order to reduce the heating time, a higher heating rate can be set. For exhaust inlet temperature ranges with higher average temperature values, the possibility of uneven temperatures at various locations of the particulate filter is higher; based on this, in order to allow each thermocouple to accurately detect the bed temperature at each location, a relatively low heating rate can be set to reduce the temperature difference at various locations in the particulate filter.
[0091] In some embodiments, when increasing the exhaust gas inlet temperature of the temperature collector, the following steps may be performed to increase the exhaust gas inlet temperature:
[0092] Step C1: determining a heating rate in a current exhaust gas inlet temperature range based on a current exhaust gas inlet temperature of a particulate trap.
[0093] Step C2: within the current exhaust gas inlet temperature range, controlling the temperature of the particulate filter based on the corresponding temperature increase rate.
[0094] Step C3: when the current exhaust gas inlet temperature is greater than the highest temperature in the current exhaust gas inlet temperature range, return to execute step C1 and subsequent steps until the current exhaust gas inlet temperature reaches the target temperature.
[0095] That is to say, the heating rate is determined according to the current exhaust inlet temperature range within which the current exhaust inlet temperature falls, thereby achieving rapid heating in a lower temperature range and shortening the time required for heating; and stable heating in a higher temperature range to ensure the accuracy of bed temperature detection at various positions of the particulate filter.
[0096] Just as an example, referring to the above example, if the current exhaust inlet temperature is 300°C and the target temperature is 600°C; it can be determined that the current exhaust inlet temperature range of the current exhaust inlet temperature is within the temperature range of 300°C to 450°C, and the temperature can be increased at a rate of 5°C / s; if the current exhaust inlet temperature rises to 460°C, it is determined that the current exhaust inlet temperature is greater than the highest temperature within the current exhaust inlet temperature range; the current exhaust inlet temperature range is re-determined to be 451°C to 600°C, and the temperature can be increased at a rate of 2°C / s until the current exhaust inlet temperature rises to 600°C, and the temperature increase is ended.
[0097] It is understandable that the temperature span of each exhaust inlet temperature interval can also be determined according to the specific temperature detection accuracy. The higher the accuracy, the smaller the temperature span can be set, and the more detailed the corresponding heating rate is divided. For example, the temperature difference of each exhaust inlet temperature interval is 100 pairs, and the heating rate difference corresponding to two adjacent exhaust inlet temperature intervals is 1°C / s. The specific settings are not limited in this application.
[0098] In some embodiments, to control the exhaust gas inlet temperature of the particulate trap, the temperature rise rate of the exhaust gas inlet temperature of the particulate trap can be controlled by calibrating the post-injection amount of the engine. That is, the temperature rise rate is controlled by the injection amount of the engine. As an example only, Table 4 shows the change of the injection amount of the engine at different target temperatures.
[0099] Table 4 Fuel injection amount of the engine at different target temperatures
[0100]
[0101] In some embodiments, the idle speed reduction condition may be: the exhaust gas inlet temperature of the particulate trap reaches the target temperature; or when the target temperature is less than or equal to the preset second temperature threshold and the exhaust gas inlet temperature of the particulate trap has not yet reached the target temperature, the temperature of the second designated thermocouple in the particulate trap is greater than or equal to the target temperature; or when the target temperature is greater than the preset second temperature threshold and the exhaust gas inlet temperature of the particulate trap has not yet reached the target temperature, the pressure difference between the two ends of the particulate trap decreases. The second designated thermocouple refers to Figure 2 Medium No. 2, No. 13, No. 14 and No. 15 thermocouples.
[0102] In theory, as long as the exhaust inlet temperature of the particulate filter reaches the target temperature, the engine can be reduced to idle condition. However, considering that the exhaust flow rate is large enough before the engine is reduced to idle, the carbon particles in the exhaust accumulation area of the particulate filter may burn before the exhaust inlet temperature reaches the target temperature, making the temperature in the exhaust accumulation area close to or exceeding the target temperature. In order to avoid the carbon particles from burning too quickly, it is possible to determine whether the temperature of the second designated thermocouple in the particulate filter is greater than or equal to the target temperature, for example, to determine Figure 2 Whether the temperatures of the No. 2, No. 13, No. 14 and No. 15 thermocouples are close to or exceed the target temperature; when it is determined that the temperature of the second designated thermocouple in the particulate filter is greater than or equal to the target temperature, the engine is immediately controlled to drop to the idle condition.
[0103] In addition to the above situations, it is also possible that the test temperature is too high, for example, the target temperature is greater than 600°C, resulting in the exhaust inlet temperature not rising to the target temperature, and the carbon particles in the particulate filter are already burning violently. In order to avoid this situation, for excessively high target temperatures, the pressure difference at both ends of the particulate filter can be constantly detected during the rising process of the exhaust inlet temperature; if the pressure difference decreases, it means that the carbon particles are burning. In order to avoid the violent combustion of the particulate filter and affect the effectiveness of the test, the engine can be immediately controlled to drop to idle speed when the pressure difference decreases.
[0104] The idle condition may be a condition where the engine speed is less than 1000 rpm.
[0105] In some embodiments, in order to manage the exhaust inlet temperature of the particulate filter based on the idle reduction control method of the present application, to avoid damage to the particulate filter body (such as cracks on the body, or melting) and rapid aging of the catalyst, the idle reduction control method may also include: during each execution of the idle reduction control step, the temperature information of each thermocouple in the particulate filter can be recorded; and a temperature management table for the particulate filter is generated based on the temperature information.
[0106] For each test, the temperature information of each thermocouple in the particulate filter can be recorded until the temperature of each thermocouple shows a downward trend within the preset time period, and then the recording is stopped. Based on the temperature information corresponding to each idle speed reduction control cycle, a temperature management table for the particulate filter can be generated. By referring to this temperature management table to control the exhaust inlet temperature of the particulate filter, damage to the particulate filter body and excessive aging of the catalyst can be avoided.
[0107] As an example only, the temperature management table may be as shown in Table 5.
[0108] Table 5 Temperature management table of particle collector
[0109]
[0110]
[0111] In Table 5, T max is the maximum temperature experienced by the particle collector, TG max The maximum temperature gradient experienced by the particulate filter. The temperature resistance boundary of the particulate filter used in this example is: the maximum temperature does not exceed 950°C, and the maximum temperature gradient does not exceed 130°C. Based on this, at different carbon loadings, the temperature that does not reach the temperature resistance boundary can be determined as the optional temperature management information of the particulate filter. Among them, the bold temperature information is the preferred temperature management information. Based on the preferred temperature management information, the particulate filter can fully regenerate the carbon particles without being damaged.
[0112] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.
[0113] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.
Claims
1. A method for reducing idle speed, characterized in that: include: The following steps of reduced idle speed control are performed according to the predetermined target temperature: When the engine is in a preset first operating condition, a carbon loading operation is performed on the pretreated particulate trap until the carbon loading in the particulate trap reaches a target carbon loading; the target carbon loading is a limit carbon loading of the particulate trap at the target temperature; When the engine is in a preset second operating condition, controlling the particulate trap to enter a regeneration mode; the exhaust flow rate of the engine in the second operating condition reaches a preset exhaust flow rate threshold; In the regeneration mode, when the particulate trap meets the idle speed reduction condition, the engine is controlled to reduce to the idle speed condition until the particulate trap exits the regeneration mode, thus completing the current idle speed reduction control process; Wherein, the target temperature is determined by the following steps: For multiple benchmark test temperatures of a preset idle reduction test matrix, the benchmark test temperature at which the idle reduction control step is not performed and which has the lowest temperature is determined as the target temperature in turn; the idle reduction test matrix records the corresponding relationship between each benchmark test temperature and the carbon loading, and the benchmark test temperature is determined based on the temperature resistance boundary of the particulate filter body and the temperature resistance boundary of the catalyst.
2. The idle speed reduction control method according to claim 1, characterized in that: Before determining the reference test temperature with the lowest temperature and without idle reduction control as the target temperature in sequence for the plurality of reference test temperatures of the preset idle reduction test matrix, the method further includes: For each of the reference test temperatures, determining at least two extended test temperatures based on the reference test temperature and a preset temperature value, wherein the reference test temperature is a median value of the corresponding extended test temperatures; The idle reduction test matrix is updated according to the extended test temperatures corresponding to the respective benchmark test temperatures.
3. The idle speed reduction control method according to claim 1, characterized in that: The particle collector is pre-treated by the following steps: When determining that the particle trap is not damaged, removing impurities in the particle trap; When it is determined that the particulate trap is damaged, the particulate trap of the same model is replaced, and impurities in the particulate trap of the same model are removed.
4. The idle speed reduction control method according to claim 1, characterized in that: After controlling the particle trap to enter the regeneration mode, the method further includes: determining a heating rate of a current exhaust inlet temperature interval based on a current exhaust inlet temperature of the particulate trap, wherein different exhaust inlet temperature intervals correspond to different heating rates, and the heating rate is inversely proportional to an average temperature value of the exhaust inlet temperature interval; In the current exhaust gas inlet temperature range, controlling the particulate trap to heat up based on the corresponding heating rate; When the current exhaust inlet temperature is greater than the highest temperature in the current exhaust inlet temperature range, return to the step of determining the heating rate of the current exhaust inlet temperature range based on the current exhaust inlet temperature of the particulate trap and its subsequent steps until the current exhaust inlet temperature reaches the target temperature.
5. The idle speed reduction control method according to claim 1, characterized in that: The first operating condition is a steady-state operating condition, which refers to an operating condition in which the engine can make the carbon accumulation rate of the particulate filter reach a preset rate threshold, and the temperature of the first designated thermocouple in the particulate filter is less than a preset first temperature threshold.
6. The idle speed reduction control method according to any one of claims 1 to 5, characterized in that: The idle speed reduction control method further includes: During each execution of the idle speed reduction control step, recording the temperature information of each thermocouple in the particulate trap; A temperature management table for the particulate trap is generated based on the temperature information.
7. The idle speed reduction control method according to any one of claims 1 to 5, characterized in that: The particle collector includes N thermocouples, where N is a positive integer greater than or equal to 9, and the N thermocouples are arranged as follows: n thermocouples are arranged in a cross section at a first preset depth from the exhaust outlet of the particle trap according to a preset rule, wherein the first preset depth is determined according to the airflow distribution of the exhaust gas of the engine in the particle trap, and n is a positive integer, and 7≤n<N; On a central axis extending from the center point of the cross section to the exhaust inlet of the particulate trap, m thermocouples are equidistantly arranged, where m is a positive integer, and m+n=N.
8. The idle speed reduction control method according to claim 7, characterized in that: The preset rules include: A thermocouple is arranged at the center point of the cross section; Dividing the cross section into four sectors according to the exhaust gas concentration area, wherein one sector includes the exhaust gas concentration area, and the exhaust gas concentration area is determined by the airflow distribution; At a designated position of each of the sectors that does not include the exhaust gas gathering area, one of the thermocouples is arranged; n-4 of the thermocouples are concentratedly arranged in the sector including the exhaust gas gathering area.
9. The idle speed reduction control method according to any one of claims 1 to 5, characterized in that: The idle speed reduction condition is: The exhaust gas inlet temperature of the particulate trap reaches the target temperature; or When the target temperature is less than or equal to a preset second temperature threshold and the exhaust gas inlet temperature of the particulate trap has not yet reached the target temperature, the temperature of the second designated thermocouple in the particulate trap is greater than or equal to the target temperature; or When the target temperature is greater than a preset second temperature threshold and the exhaust gas inlet temperature of the particulate trap has not yet reached the target temperature, the pressure difference across the particulate trap decreases.