A supercharger cooling control method

Abstract

The present invention discloses a supercharger cooling control method. The specific steps include that before the medium-temperature system conducts the cooling process, the engine's EMS needs to perform a self-check first; if the system is normal, the EMS needs to judge whether the engine speed is higher than the idle threshold; if the engine speed is higher than the idle threshold, it is necessary to determine the electronic water pump speed required to meet the target intake air temperature under different engine operating conditions and the electronic water pump speed required for the supercharger not to overheat under different operating conditions; perform a lower limit constraint on the output of the electronic water pump speed in the previous step; if the engine speed is lower than the idle threshold, observe whether the change rate of the engine speed is less than 0 to judge whether the supercharger needs to perform post-cooling treatment and other steps. The present invention does not require adding a high-power electronic water pump, avoiding the increase in cost, and can also avoid the boiling phenomenon in the expansion water tank after the vehicle turns off and stops.

Description

Technical Field

[0001] The present invention relates to the technical field of engine superchargers, and particularly relates to a supercharger cooling control method. Background Art

[0002] Currently, the cooling system solutions used in vehicles on the market are usually mechanical water pumps + thermostats, and the thermostats are used to adjust the two branches of the radiator large cycle and the bypass small cycle. The thermostat is generally designed to gradually open the large cycle when it reaches 80 - 90°C, so that the flow enters the radiator for heat dissipation. In such a cooling system, since the rotational speed of the mechanical water pump is related to the engine speed, and the thermostat only realizes physical control by melting paraffin, neither of them can actively control the cooling system too much.

[0003] Turbocharging and intercooling are very common as mainstream technologies nowadays. Generally speaking, this technology involves two sets of cooling systems. One is the high-temperature cooling system, that is, the engine cooling system. The other is the medium-temperature cooling system, that is, the intake air intercooling system, the purpose of which is to reduce the intake air temperature. Since the turbine of the supercharger endures exhaust gas as high as 700 - 900°C for a long time, there are reliability problems of thermal fatigue of the metal, so it needs to be cooled. According to the mainstream design, generally the supercharger is connected to the high-temperature cooling system of the engine, and ordinary mechanical water pumps and thermostats are used for cooling control.

[0004] In this case, although the high-temperature cooling water of the engine is 90 - 110°C, it is still very low compared with the exhaust gas as high as 700 - 900°C, and it can be cooled under normal conditions. However, when the vehicle shuts off and the power is cut off, after the mechanical water pump stops working, the coolant inside the cooling water pipe near the supercharger turbine stops flowing, and will be heated to boiling by the metal wall surface of the turbine in a short time. At this time, heat transfer to the metal wall surface cannot be effectively carried out, and if this continues for a long time, the turbine will fail. In addition, after the liquid boils, pressure will be quickly built up in the expansion water tank and the pressure relief valve will be pushed open to relieve pressure, resulting in some water vapor overflowing. If this continues for a long time, the coolant will decrease and the engine cooling effect will become worse. Summary of the Invention

[0005] In view of this, the present invention provides a supercharger cooling control method. The cooling of the supercharger is realized by the medium-temperature cooling system. Through the control of the electronic water pump, on the premise of ensuring that the intake air temperature meets the engine requirements, it is ensured that the supercharger does not overheat, and post-cooling can be realized after the vehicle shuts off, avoiding turbine overheating and solving the problem that the coolant in the expansion water tank is prone to boiling after shutting off in the past.

[0006] A supercharger cooling control method provided by the present invention includes: determining whether the engine is in a normal operating state; if the engine is in a normal operating state, further determining the electronic water pump speed required to meet the engine target intake air temperature and the electronic water pump speed required to meet the supercharger cooling under the current working condition, and controlling the electronic water pump with the larger value of the electronic water pump speed required to meet the target intake air temperature and the electronic water pump speed required to meet the supercharger cooling; if the engine is in an abnormal operating state, further determining whether the supercharger needs post-cooling treatment; if the supercharger needs post-cooling treatment, further determining the electronic water pump speed required to meet the supercharger post-cooling treatment.

[0007] Further, determining whether the engine is in a normal operating state includes: determining whether the engine speed is higher than the idle threshold; if the engine speed is higher than the idle threshold, confirming that the engine is in a normal operating state; if the engine speed is lower than the idle threshold, confirming that the engine is in an abnormal operating state.

[0008] Further, determining whether the supercharger needs post-cooling treatment includes: determining whether the change rate of the engine speed is less than 0; if the change rate of the engine speed is greater than 0, determining that the supercharger does not need post-cooling treatment; if the change rate of the engine speed is less than 0, continue to observe until the change rate of the engine speed is equal to 0; if the change rate of the engine speed is equal to 0, further determining whether the engine water temperature at this moment is higher than the post-operation threshold; if the engine water temperature at this moment is lower than the post-operation threshold, the electronic water pump stops; if the engine water temperature at this moment is higher than the post-operation threshold, determining that the supercharger needs post-cooling treatment.

[0009] Further, before determining whether the engine is in a normal operating state, it also includes: system self-check, and the self-check objects include sensors and actuators of each system of the engine; if the system is normal, supercharger cooling control is performed, if the system is abnormal, an alarm is given and the engine is torque-limited.

[0010] Further, determining the electronic water pump speed required to meet the target intake air temperature under different working conditions of the engine includes: determining the current working condition of the engine according to the current engine speed and engine load; obtaining the target intake air temperature and the initial electronic water pump speed corresponding to the current working condition by looking up the table based on the current working condition; performing PID closed-loop control on the speed of the electronic water pump based on the temperature difference between the actual intake air temperature and the target intake air temperature until the actual intake air temperature coincides with the target intake air temperature.

[0011] Further, when performing PID closed-loop control on the rotational speed of the electric water pump based on the temperature difference between the actual intake air temperature and the target intake air temperature, the calculation formula used is: the rotational speed of the electric water pump required to meet the target intake air temperature under the current working condition = the initial rotational speed of the electric water pump + P + I * t, where the P correction amount is the single correction amount, and the I correction amount gradually accumulates over time t.

[0012] Further, the current working condition includes three working conditions: high, medium, and low.

[0013] Further, determining the rotational speed of the electric water pump required for turbocharger cooling under the current working condition includes: obtaining the working condition of the current turbocharger based on the engine speed and the engine load; looking up the table based on the turbocharger load and the actual intake air temperature to obtain the minimum rotational speed of the electric water pump required for turbocharger cooling under the current working condition, and this rotational speed is the rotational speed of the electric water pump required for the turbocharger not to overheat under the current working condition.

[0014] Further, set time points t1 and t2, and observe the change trend of the engine speed at set time points t1 and t2 at a fixed frequency. Then, the change rate of the engine speed = (engine speed at time point t2 - engine speed at time point t1) / (t2 - t1), and this is continuously monitored three times.

[0015] Further, the rotational speed of the electric water pump when meeting the post-cooling treatment of the turbocharger is determined by looking up the table based on the water temperature of the current engine. When the working duration of the engine reaches the set value, the post-cooling mode ends, and the working duration of the engine is determined by looking up the table based on the water temperature of the current engine.

[0016] Compared with the existing technology, the present invention has the following beneficial technical effects:

[0017] A turbocharger cooling control method provided by the present invention, based on the characteristics of the engine cooling system design, connects the turbocharger cooling system to the medium-temperature cooling system of the engine instead of remaining in the high-temperature cooling system. A small-power electric water pump in the medium-temperature cooling system provides cooling for the turbocharger, eliminating the need to add a high-power electric water pump, avoiding cost increase, and also being able to prevent boiling in the expansion water tank after the vehicle shuts off. In addition, through the control method of the present invention, when controlling the electric water pump in the medium-temperature cooling system, different working conditions of the turbocharger are distinguished, and the allowable lower limit of the electric water pump is restricted. Without necessity, there is no need to increase the power of the electric water pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a system diagram of a turbocharger cooling control method of the present invention;

[0019] Figure 2 It is a flowchart of a turbocharger cooling control method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] The following further describes in detail the specific implementation manners of the present invention in conjunction with the accompanying drawings and embodiments. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0021] In the description of the present invention, it should be noted that the orientation or positional relationship indicated in this description is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0022] Please refer Figure 1 to a supercharger cooling control method provided by the present invention. The cooling system of the supercharger is connected to the medium-temperature cooling system of the engine. The coolant inlet of the supercharger is connected between the electronic water pump and the intercooler, and the coolant outlet of the supercharger is connected to the auxiliary expansion tank of the intercooler, so that the supercharger can be cooled by relying on the electronic water pump existing in the medium-temperature cooling system itself. The cooling process of the entire system includes the control of the intake air temperature when the engine is operating normally, the cooling of the supercharger when the engine is operating normally, and the post-cooling treatment of the supercharger after shutdown. When the engine is operating normally, the rotational speed of the electronic water pump needs to meet both the intake air temperature control requirement and the supercharger cooling requirement. Because when cooling the intake air temperature, the electronic water pump itself needs to consume work. If the supercharger cooling requirement is added, its power consumption will be further increased, and ultimately it will be reflected in the increase of the engine fuel consumption. Therefore, on the premise of meeting the intake air temperature and supercharger cooling requirements, the power of the electronic water pump should be reduced as much as possible.

[0023] It should be noted that the main reason for controlling the intake air temperature is that the gas density changes greatly with temperature. When the temperature is higher, for the gas with the same volume flow rate, the mass is less. Then, after entering the engine, it is difficult to match the corresponding fuel mass, which has a greater impact on the engine performance. The reason for the post-cooling treatment of the supercharger after shutdown is that in addition to the normal working state, when the vehicle is driven violently for a long time and suddenly shuts down when the temperature is high, due to the coupling of the mechanical water pump and the rotational speed, it will also shut down immediately. At this time, there is no flow in the system, which will cause the heat of the supercharger to accumulate in a short time, resulting in the boiling phenomenon of the coolant. Therefore, after the supercharger is connected to the medium-temperature cooling system, post-cooling treatment after shutdown is still required.

[0024] Please refer Figure 2 to a supercharger cooling control method provided by the present invention, which specifically includes the following steps:

[0025] S1. The engine's EMS performs a self-check on the system. If the system is normal, supercharger cooling control is carried out. If the system is abnormal, an alarm is given and the engine is torque-limited.

[0026] Specifically, after the vehicle is powered on, the Engine Management System (EMS) of the engine needs to first perform a system self-check to determine whether there is a fault in the system. If there is no fault in the system, it enters the cooling control process of the present invention. If there is a fault in the system, the EMS reports the fault and limits the torque of the engine. The objects of the self-check include sensors (such as temperature sensors) and actuators (such as radiators and electric water pumps) of each system of the engine. If individual sensors or actuators report faults during the self-check process, it may involve the inability to carry out subsequent control normally and the engine cannot enter the normal working state. Therefore, in this case, the EMS needs to report the fault and limit the torque of the engine to prevent the engine from reaching a high power in an unexpected state and causing more serious mechanical damage.

[0027] S2. Before performing the turbocharger cooling control, the EMS determines whether the engine speed is higher than the idle threshold value, and confirms whether the engine is in the normal working state according to the judgment result.

[0028] Specifically, the engine speed is obtained by internal acquisition of the EMS, and the idle threshold value is a preset value obtained through tests and can be obtained by looking up a table. If the engine speed is higher than the idle threshold value, it indicates that the engine is in the normal working state and it is necessary to control the intake air temperature and cool the turbocharger. If the engine speed is lower than the idle threshold value, it indicates that the engine is in the abnormal working state, starting or preparing to stop. If the engine is starting, no additional processing is required. If the engine is preparing to stop, it is necessary to continue to judge whether to perform post-cooling processing.

[0029] S3. If the engine speed is higher than the idle threshold value, determine the electric water pump speed required to meet the target intake air temperature under different engine operating conditions and the electric water pump speed required for turbocharger cooling.

[0030] Specifically, the control of the engine intake air temperature is related to the engine operating conditions. In the present invention, the engine operating conditions are divided into three types: low, medium, and high loads. The high load condition is the condition close to the engine's external characteristic, with relatively high performance requirements. Generally, it is required that the turbocharger works at full load. At this time, a higher exhaust gas flow is required, and due to the high thermal load, the exhaust gas temperature is relatively high, which is the working condition with the most severe temperature resistance of the turbocharger. When the load is medium or low, the turbocharger does not work at full load, and the exhaust gas bypasses through the wastegate valve and does not all flow through the turbocharger. Moreover, the engine thermal load is relatively low, the exhaust gas temperature is not high, and the temperature resistance of the turbocharger is relatively good. Therefore, the EMS needs to determine the electric water pump speed required to meet the target intake air temperature under each operating condition based on the engine operating conditions.

[0031] Further, the EMS internally acquires the current engine speed and load, and then the EMS can obtain what working condition the engine is in currently based on the engine speed and load by looking up a table. Then, based on the current working condition, it looks up another table to obtain the target intake air temperature and the initial speed of the electric water pump corresponding to the current working condition. However, generally, the actual intake air temperature and the target intake air temperature do not immediately match, and there is a temperature difference = actual intake air temperature - target intake air temperature. Therefore, the EMS system needs to perform PID closed-loop control on the speed of the electric water pump based on this difference until the actual intake air temperature and the target intake air temperature match. After the EMS looks up the P correction amount and the I correction amount based on the temperature difference between the actual intake air temperature and the target intake air temperature, it corrects the speed of the electric water pump. The P correction amount is the single correction amount, and the I correction amount gradually accumulates with time t, that is: the speed of the electric water pump required to meet the target intake air temperature under the current working condition = initial speed of the electric water pump + P + I * t.

[0032] As described above, during actual control, it is necessary to take into account both the intake air temperature and the power consumption of the electric water pump. In this combination, the engine will achieve the lowest intake air temperature at the lowest power consumption cost, thereby achieving the optimal fuel consumption. Therefore, the EMS can obtain the current working state of the turbocharger by looking up a table based on the engine speed and the engine load. In the present invention, based on the calibration test in the initial design stage, the working state of the turbocharger is divided into three states: BIT = 0, 1, 2. 0 represents the low load of the turbocharger, 1 represents the medium load, and 2 represents the full load. The essence of these three types of working conditions is the cooling requirements at three levels: low, medium, and high. Based on the low, medium, and high load levels of the turbocharger, that is, the three states of BIT = 0, 1, 2, the minimum speed of the electric water pump that matches them is set respectively. The minimum speed of the electric water pump in each state can be obtained by looking up a table based on the engine load and the actual intake air temperature to get the minimum speed of the electric water pump required for turbocharger cooling under the current working condition (the turbocharger load state and the intake air temperature are the preset values of the test). This minimum speed of the electric water pump is the speed of the electric water pump required to meet the turbocharger cooling.

[0033] S4, perform a lower limit constraint on the output of the speed of the electric water pump required to meet the target intake air temperature and the speed of the electric water pump required to meet the turbocharger cooling in S3.

[0034] When the electric water pump is working, before optimizing the intake air temperature, it is necessary to first meet the minimum cooling requirement of the turbocharger. Therefore, it is necessary to perform a lower limit constraint on the speed of the electric water pump required to meet the target intake air temperature and the speed of the electric water pump required to meet the turbocharger cooling in S3 and S4, and take the larger value for output to control the electric water pump.

[0035] S5, if the engine speed is lower than the idle threshold, then observe whether the change rate of the engine speed at the set moment is less than 0 to determine whether the turbocharger needs post-cooling treatment.

[0036] When the vehicle is driven violently for a long time and the temperature is high, and then suddenly stops, since the electronic water pump is coupled with the rotational speed, it will also stop immediately. At this time, there is no flow in the system, which will cause the heat of the supercharger to accumulate in a short time, resulting in the boiling phenomenon of the coolant. Therefore, after the supercharger is connected to the medium-temperature cooling system, it is also necessary to deal with the hot soak condition. If the EMS determines that the engine speed is lower than the idle threshold, it is considered that the engine is starting or preparing to shut down. If the engine is starting, no additional treatment is required. If the engine is preparing to shut down, it is necessary to determine whether to perform post-cooling treatment. The judgment method is as follows: At this time, the EMS continues to observe the change trend of the engine speed at the set time at a fixed frequency. For example, at the set times t1 and t2, then the set change rate = (engine speed at time t2 - engine speed at time t1) / (t2 - t1), and it is continuously monitored three times.

[0037] S6, if the change rate of the engine speed at the set time is greater than 0, the supercharger does not need to perform post-cooling treatment and is in the normal start state. If the change rate of the engine speed at the set time is less than 0, the engine is in the state of preparing to stop and needs to be continuously observed until the change rate of the engine speed at the set time is equal to 0.

[0038] If the change rates monitored three times are all less than 0, it is considered that the engine speed is continuously decreasing and preparing to stop. At this time, the set stop status bit is equal to 1, otherwise it is 0. Also, in any state, when the EMS monitors that it has been equal to 0, it is also considered that the shutdown is complete and the set stop status bit is equal to 1. When the stop status bit is equal to 1, it is necessary to determine whether the engine is in a hot state or a cold state, that is, to determine whether it is necessary to perform post-cooling on the supercharger.

[0039] S7, when the change rate of the engine speed at the set time is equal to 0, judge whether the engine water temperature at this moment is higher than the post-operation threshold. If it is lower than the post-operation threshold, the electronic water pump stops. If it is higher than the post-operation threshold, the supercharger needs to perform post-cooling treatment to determine the required rotational speed of the electronic water pump for the supercharger at this time.

[0040] Since generally the water temperature sensor is only arranged in the high-temperature cooling system, it can only be judged based on the sensor in the high-temperature cooling system at this time. Therefore, the EMS continues to judge whether the engine water temperature is higher than the post-operation threshold (the engine water temperature is collected by the temperature sensor, and the post-operation threshold is a test preset value). If it is lower than the threshold, the electronic water pump stops. If it is higher, it is determined that the supercharger needs to perform post-cooling treatment, and the post-cooling demand bit is equal to 1, otherwise it is 0.

[0041] When the supercharger undergoes aftercooling treatment, regardless of other situations, the EMS maintains the electronic water pump to continue operating, but at this time its speed no longer depends on the engine operating conditions. Its speed and operating duration are both set based on the engine water temperature, obtained by looking up a table, and the operating duration generally does not exceed the allowable after-running duration of the EMS. When the after-running duration reaches the set value, or when there is no aftercooling requirement, the electronic water pump stops and the aftercooling mode ends.

[0042] It should be noted that the above-mentioned engine speed, engine load, actual intake air temperature, and engine water temperature are all signals collected or calculated inside the EMS; the table is obtained based on the corresponding calibration experiments and pre-stored in the EMS. The idle threshold, initial speed of the electronic water pump, target intake air temperature, P correction amount, I correction amount, engine operating conditions, supercharger operating conditions, after-running threshold, after-running speed, and operating duration can all be obtained by querying the preset table.

[0043] In summary, a supercharger cooling control method provided by the present invention, based on the characteristics of the engine cooling system design, connects the supercharger cooling system to the medium-temperature cooling system of the engine instead of remaining in the high-temperature cooling system. The small-power electronic water pump in the medium-temperature cooling system is used to provide cooling for the supercharger. Under non-essential conditions, there is no need to add a high-power electronic water pump, which avoids cost increase and can also prevent the boiling phenomenon in the expansion water tank after the vehicle shuts off and stops. In addition, through the control method of the present invention, when the electronic water pump is controlled in the medium-temperature cooling system, different operating conditions of the supercharger are distinguished, and the allowable lower limit of the electronic water pump is restricted. Under non-essential conditions, there is no need to increase the power of the electronic water pump.

[0044] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claimed rights.

Claims

1. A supercharger cooling control method, characterized in that, it includes: judging whether the engine is in a normal working state; if the engine is in a normal working state, determining the electronic water pump speed required to meet the engine target intake air temperature under the current working condition and the electronic water pump speed required to meet the supercharger cooling under the current working condition, and controlling the electronic water pump with the larger value of the electronic water pump speed required to meet the engine target intake air temperature and the electronic water pump speed required to meet the supercharger cooling; if the engine is in an abnormal working state, judging whether the supercharger needs post-cooling treatment; if the supercharger needs post-cooling treatment, determining the electronic water pump speed required to meet the supercharger post-cooling treatment; judging whether the supercharger needs post-cooling treatment includes: judging whether the change rate of the engine speed is less than 0; if the change rate of the engine speed is greater than 0, it is determined that the supercharger does not need post-cooling treatment; when the change rate of the engine speed is equal to 0, judging whether the engine water temperature is higher than the post-operation threshold; if the engine water temperature is lower than the post-operation threshold, the electronic water pump stops; if the engine water temperature is higher than the post-operation threshold, it is determined that the supercharger needs post-cooling treatment.

2. The supercharger cooling control method according to claim 1, characterized in that, judging whether the engine is in a normal working state includes: judging whether the engine speed is higher than the idle threshold; if the engine speed is higher than the idle threshold, it is confirmed that the engine is in a normal working state; if the engine speed is lower than the idle threshold, it is confirmed that the engine is in an abnormal working state.

3. The supercharger cooling control method according to claim 1, characterized in that, before judging whether the engine is in a normal working state, it further includes: system self-check, and the self-check objects include sensors and actuators of each system of the engine; if the system is normal, supercharger cooling control is carried out, if the system is abnormal, an alarm is given and the engine is torque-limited.

4. The supercharger cooling control method according to claim 1, characterized in that, determining the electronic water pump speed required to meet the target intake air temperature under different working conditions of the engine includes: determining the current working condition of the engine according to the current engine speed and engine load; obtaining the target intake air temperature and the initial electronic water pump speed corresponding to the current working condition by looking up a table based on the current working condition; performing PID closed-loop control on the speed of the electronic water pump based on the temperature difference between the actual intake air temperature and the target intake air temperature until the actual intake air temperature coincides with the target intake air temperature.

5. The supercharger cooling control method according to claim 4, characterized in that, when performing PID closed-loop control on the speed of the electronic water pump based on the temperature difference between the actual intake air temperature and the target intake air temperature, the calculation formula is: the electronic water pump speed required to meet the target intake air temperature under the current working condition = the initial electronic water pump speed + P + I*t, where the P correction amount is the single correction amount, and the I correction amount gradually accumulates with time t.

6. The supercharger cooling control method according to claim 4, characterized in that, the current working condition includes three working conditions: high, medium, and low.

7. The supercharger cooling control method according to claim 1, characterized in that, Determining the rotational speed of the electric water pump required for turbocharger cooling under the current operating conditions includes: Obtaining the operating conditions of the current turbocharger based on the engine speed and engine load; Looking up the table based on the turbocharger load and the actual intake air temperature to obtain the minimum rotational speed of the electric water pump required for turbocharger cooling under the current operating conditions, and this rotational speed is the rotational speed of the electric water pump required for the turbocharger not to overheat under the current operating conditions.

8. The turbocharger cooling control method according to claim 1, characterized in that, Set times t1 and t2, and observe the change trend of the engine speed at set times t1 and t2 at a fixed frequency. Then, the change rate of the engine speed = (engine speed at time t2 - engine speed at time t1) / (t2 - t1), and this is continuously monitored three times.

9. The turbocharger cooling control method according to claim 1, characterized in that, The rotational speed of the electric water pump when post-cooling treatment of the turbocharger is satisfied is determined by looking up the table based on the current engine water temperature. When the working duration of the engine reaches the set value, the post-cooling mode ends, and the working duration of the engine is determined by looking up the table based on the current engine water temperature.

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