Gas engine extended-range hybrid oxygen sensor heating control strategy

Abstract

The application discloses a gas engine range-extender hybrid power oxygen sensor heating control strategy and relates to the technical field of hybrid electric vehicles. A battery SOC is collected in real time, and if the battery SOC is lower than a calibration threshold, an oxygen sensor is heated in advance; if the engine is stopped, the heating of the oxygen sensor is stopped. The application ensures that the oxygen sensor can normally work before the engine is started, avoids open-loop control of an air-fuel ratio after the engine is started, guarantees emission control, and greatly improves the reliability of oxygen sensor use.

Description

TECHNICAL FIELD

[0001] The present application relates to hybrid vehicle technology, more particularly, it relates to a gas engine extended-range hybrid oxygen sensor heating control strategy. BACKGROUND

[0002] The oxygen sensor is installed behind the supercharger exhaust pipe of the national six gas engine to monitor the exhaust oxygen concentration for feedback to the ECU for closed-loop control of air-fuel ratio. Under normal circumstances, after the engine starts, the oxygen sensor starts heating after the dew point time of calibration, and starts working after heating to a certain temperature. The oxygen sensor stops working after the engine stops, and so on. The extended-range hybrid engine is mainly used for power generation and does not participate in driving. When the power generation reaches the SOC set value of the vehicle, the engine receives the stop command of the vehicle and stops. Through actual road spectrum analysis, the engine starts and stops frequently, so the working state of the oxygen sensor also changes frequently.

[0003] The principle diagram of the extended-range hybrid engine system is shown in Figure 1 The engine 3 is connected to work and generate electricity through the clutch 4 and the generator 5 and stores in the power battery 9. The power battery 9 drives the motor 8 to drive the vehicle wheels. The oxygen sensor is generally installed behind the supercharger turbine and in front of the catalyst. The heating energy of the oxygen sensor comes from two sources, one is heating by its own heating chip, and the other is heating by the exhaust gas of the engine. According to the calibration, the start and stop of the oxygen sensor can be synchronized or unsynchronized with the engine, as shown in Figure 2

[0004] However, no matter which way is adopted, there are corresponding defects:

[0005] Method one: problems existing in the synchronization of the working state of the oxygen sensor and the engine: after the engine starts running, the oxygen sensor cannot immediately enter the working state and needs to be heated to the normal working temperature before it can work normally. This period of time cannot normally monitor the air-fuel ratio of the engine (i.e. open-loop control), and the actual air-fuel ratio control exists the problem of lean or rich conditions, causing high emissions.

[0006] Method two: problems existing in the unsynchronization of the working state of the oxygen sensor and the engine: after the engine stops, the oxygen sensor continues to heat and work. At this time, the heating energy of the oxygen sensor mainly relies on the oxygen sensor itself, and long-time heating may affect the reliability of the oxygen sensor.

[0007] Therefore, a new control strategy needs to be designed to ensure emission control and sensor reliability. SUMMARY

[0008] ​The technical problem solved by the present application is to provide a gas engine extended-range hybrid power oxygen sensor heating control strategy to ensure that the oxygen sensor can work normally before the engine starts, avoid open-loop control of the air-fuel ratio after the engine starts, and ensure emission control.

[0009] The gas engine extended-range hybrid power oxygen sensor heating control strategy of the present application collects the battery SOC in real time, and if the battery SOC is lower than the calibration threshold, the oxygen sensor is heated in advance; if the engine is stopped, the heating of the oxygen sensor is stopped.

[0010] The oxygen sensor is heated in advance, specifically including,

[0011] A minimum calibration threshold, a half-power calibration threshold, and a maximum calibration threshold are set; before the engine is started,

[0012] If the battery SOC is lower than the maximum calibration threshold, the oxygen sensor is preheated;

[0013] If the battery SOC is lower than the half-power calibration threshold, the oxygen sensor is heated to 50%-70% of the rated operating temperature;

[0014] If the battery SOC is equal to or lower than the minimum calibration threshold, the oxygen sensor is heated to the rated operating temperature.

[0015] After the oxygen sensor is preheated, the preheating temperature of the oxygen sensor is 5-20℃ higher than the temperature before the oxygen sensor is not heated, and the preheating temperature of the oxygen sensor is at least 30%-40% of the rated operating temperature.

[0016] The power-down duration required for the battery SOC to drop from the maximum calibration threshold to the half-power calibration threshold is obtained, and 40%-60% of the power-down duration is taken as the calibration duration; the temperature rise step distance is obtained according to the preheating temperature, the temperature before the oxygen sensor is not heated, and the calibration duration, so that the oxygen sensor is gradually heated in increments with the temperature rise step distance.

[0017] The temperature rise step distance is determined by the following formula,

[0018]

[0019] In the above formula, ΔT is the temperature rise step distance; T1 is the preheating temperature; T0 is the temperature before the oxygen sensor is not heated; and t is the calibration duration.

[0020] Advantages

[0021] The present application has the advantages that: by calibrating the battery SOC, the oxygen sensor is heated in advance when the battery SOC is lower than the calibration threshold, ensuring that the oxygen sensor can work normally before the engine starts, avoiding open-loop control of the air-fuel ratio after the engine starts, and ensuring emission control. When the engine is stopped, the heating of the oxygen sensor is stopped, avoiding the reliability problems caused by long-time heating of the oxygen sensor. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A schematic diagram of a range-extending hybrid engine system;

[0023] Figure 2 An operating timing diagram of the synchronization and asynchronization of the oxygen sensor and the engine start-stop;

[0024] Figure 3 An operating timing diagram of the oxygen sensor and the engine start-stop of the present application.

[0025] 1-pressor compressor; 2-intake pipe; 3-engine; 4-clutch; 5-generator; 6-exhaust pipe; 7-vehicle driving wheels; 8-driving motor; 9-power battery; 10-vehicle VCU; 11-engine ECU; 12-pressor turbine; 13-oxygen sensor. DETAILED DESCRIPTION

[0026] The present application will be further described below in conjunction with the embodiments, but does not constitute any limitation on the present application, and any limited number of modifications made by anyone within the scope of the claims of the present application is still within the scope of the claims of the present application.

[0027] Referring to Figure 1 and Figure 3 , a range-extending hybrid oxygen sensor heating control strategy for a gas machine, when the engine ECU 11 receives the battery SOC lower than the calibration threshold sent by the vehicle VCU 10, the engine ECU 11 sends instructions to the oxygen sensor 13 to heat it in advance, ensuring that the oxygen sensor 13 can work normally before the engine 3 starts, avoiding open-loop control of the air-fuel ratio after the engine 3 starts, and ensuring emission control. In the present application, the engine ECU 11 and the vehicle VCU 10 are connected through CAN communication, and the battery SOC of the power battery 9 is sent to the engine ECU 11 by the vehicle VCU 10.

[0028] When the engine ECU 11 receives the stop command from the vehicle VCU 10, the engine 3 executes the stop, and at the same time, the engine ECU 11 sends instructions to the oxygen sensor 13 to stop heating the oxygen sensor 13, avoiding the reliability problems caused by long-time heating of the oxygen sensor 13.

[0029] The range-extended hybrid oxygen sensor heating control strategy of the application, on the basis of the original control strategy, does not increase system components, and only needs to develop a new control strategy to meet the functional requirements, and is easy to implement.

[0030] In the embodiment, the oxygen sensor is preheated, specifically including,

[0031] A minimum calibration threshold, a half-power calibration threshold and a maximum calibration threshold are set. For example, the minimum calibration threshold is 20%, that is, when the battery SOC is 20%, the engine 3 needs to be started to charge the power battery 9. The maximum calibration threshold can be set to 25%, and the half-power calibration threshold can be set to 22%.

[0032] Before the minimum calibration threshold arrives, the engine 3 is in a non-starting state. If the battery SOC is lower than the maximum calibration threshold, the oxygen sensor is preheated. If the battery SOC is lower than the half-power calibration threshold, the oxygen sensor is heated to 60% of the rated working temperature. If the battery SOC is equal to or lower than the minimum calibration threshold, the oxygen sensor is heated to the rated working temperature.

[0033] The application adopts a three-step method to heat the oxygen sensor, that is, first preheat it, then raise its temperature to 60% of the rated working temperature, and finally heat it to the rated working temperature, which not only meets the synchronous working of the oxygen sensor and the engine 3, but also saves energy. In addition, the preheating function of the oxygen sensor can make the oxygen sensor better adapt to the use of low temperature environment, and prevent the phenomenon of damage to components caused by the too fast thermal expansion speed of components due to the too fast temperature rise when directly heating at full power.

[0034] It should be noted that since the engine 3 needs a certain time from starting to stable output, and during the stage of battery SOC from the half-power calibration threshold to the minimum calibration threshold, the temperature of the oxygen sensor is already at 60% of the rated working temperature, and the time required for heating to the rated working temperature is also relatively short, therefore, the time difference from the starting of the engine 3 to the stable output of the engine 3 can be used to heat the oxygen sensor to the rated temperature, ensuring the synchronization of the normal working of the oxygen sensor and the normal working of the engine 3.

[0035] For the specific setting of preheating, in the embodiment, after the oxygen sensor is preheated, the preheating temperature of the oxygen sensor is 5-20℃ higher than the temperature before the oxygen sensor is heated, and the preheating temperature of the oxygen sensor is not lower than 40% of the rated working temperature.

[0036] Specifically, it can be selected according to the current ambient temperature. For example, when the air temperature is low, assuming it is 10℃, the temperature of the oxygen sensor before heating can be taken as 20℃, and if the temperature is not lower than 40% of the rated working temperature, the preheating temperature is set to 30℃. Assuming that 40% of the rated working temperature is 30℃, and the current air temperature is below zero, even if the temperature of the oxygen sensor before heating is added by 20℃, it does not meet the condition that the preheating temperature of the oxygen sensor is not lower than 40% of the rated working temperature. In this case, 30℃ should be taken as the preheating temperature. Assuming that the air temperature is 30℃, and 40% of the rated working temperature is 30℃, 30℃+5℃=35℃ can be taken as the preheating temperature.

[0037] Since the preheating process has sufficient time to proceed, the present application adopts a gradually increasing heating temperature rise to realize the preheating of the oxygen sensor. Specifically, the power-down duration required for the battery SOC from the highest calibration threshold to the half-power calibration threshold is obtained, which can be the power-down duration of the power battery 9 under normal working conditions of the vehicle. Take 50% of the power-down duration as the calibration duration, and obtain the temperature rise step according to the preheating temperature, the temperature before heating, and the calibration duration, to gradually increase the heating temperature rise of the oxygen sensor by the temperature rise step. Specifically, the temperature rise step is determined by the following formula,

[0038]

[0039] In the above formula, ΔT is the temperature rise step; T1 is the preheating temperature; T0 is the temperature before heating; and t is the calibration duration.

[0040] The gradually increasing heating temperature rise can effectively avoid the problem of damage to components caused by the rapid thermal expansion of the oxygen sensor during heating, greatly improving the service life of the oxygen sensor.

[0041] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the structure of the present application, a number of modifications and improvements can be made, which will not affect the effect of the present application and the practicality of the patent.

Claims

1. A gas engine extended-range hybrid oxygen sensor heating control strategy, characterized by, Real-time acquisition of the battery SOC, if the battery SOC is lower than a calibration threshold, pre-heating the oxygen sensor; if the engine is stopped, stopping the heating of the oxygen sensor; Pre-heating the oxygen sensor, specifically including, Setting a minimum calibration threshold, a half-power calibration threshold and a maximum calibration threshold; under the premise that the engine is not started, If the battery SOC is lower than the maximum calibration threshold, pre-heating the oxygen sensor; If the battery SOC is lower than the half-power calibration threshold, heating the oxygen sensor to 60% of the rated working temperature; If the battery SOC is equal to or lower than the minimum calibration threshold, heating the oxygen sensor to the rated working temperature; After pre-heating the oxygen sensor, the pre-heating temperature of the oxygen sensor is 5-20℃ higher than the temperature before the oxygen sensor is not heated, and the pre-heating temperature of the oxygen sensor is not lower than 40% of the rated working temperature; Acquiring the power-off duration required for the battery SOC from the maximum calibration threshold to the half-power calibration threshold, and taking 50% of the power-off duration as a calibration duration; acquiring a temperature rise step distance according to the pre-heating temperature, the temperature before the oxygen sensor is not heated and the calibration duration, so as to gradually increase the heating temperature of the oxygen sensor by the temperature rise step distance.

2. The gas engine extended-range hybrid oxygen sensor heating control strategy of claim 1, wherein, The temperature rise step distance is determined by the following formula, ； In the above formula, is the temperature rise step; is the preheating temperature; is the temperature before heating; is the calibration time.

Images